Production of Nitric Acid
by
UHDE’s Medium Pressure Process
Submitted by
Hassan Faraz
2017-CH-20
Muhammad Sohail
2017-CH-22
Usama Naeem
2017-CH-32
Muhammad Waqas
2017-CH-36
Supervised by
Dr. Usman Ali
Year: 2017
Department of Chemical Engineering
University of Engineering and Technology Lahore
The Final Year Project titled, “Production of Nitric Acid by UHDE’s Medium
Pressure Process” is being submitted to the Department of Chemical
Engineering, University of Engineering and Technology Lahore in partial
fulfillment of the requirement for the Degree of
Bachelor of Science
in
Chemical Engineering
________________
________________
Internal Examiner
External Examiner
______________________________
Chairman
Department of Chemical Engineering
Department of Chemical Engineering
University of Engineering and Technology Lahore
2|Page
Declaration
We declare that the work contained in this report has been checked for similarity and the
similarity index is within acceptable limits.
Name
Registration No
Signature
Hassan Faraz
2017-CH-20
Hassan Faraz
Muhammad Sohail
2017-CH-22
Sohail
Usama Naeem
2017-CH-32
Usama
Muhammad Waqas
2017-CH-36
M. Waqas
Date:
3|Page
Contribution Statement
We, members of the FYP group, endorse the level of contribution in the project titled,
“Production of Nitric Acid by UHDE’s Medium Pressure Process” as indicated below.
Registration No.
% Contribution
Signature
2017-CH-20
25 %
Hassan Faraz
2017-CH-22
25 %
Sohail
2017-CH-32
25 %
Usama
2017-CH-36
25 %
M. Waqas
4|Page
Dedication
We Dedicate Our Project Work to
Holy Prophet Hazrat Muhammad ‫ ﷺ‬Who Taught
Us to Seek Knowledge from the
Cradle to the Grave.
5|Page
Acknowledgment
First, we are very thankful to Allah Almighty who helped us in the
effective completion of our project.
We highly appreciate our project supervisor Dr. Usman Ali for
continuous guidance, as well as for giving us their precious time,
attention, and necessary information regarding the project.
We would like to express our thankfulness toward our parents for their
kind cooperation and encouragement.
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Table of Contents
Declaration .............................................................................................................................................. 3
Contribution Statement ........................................................................................................................... 4
Dedication ............................................................................................................................................... 5
Acknowledgment .................................................................................................................................... 6
List of Figures ....................................................................................................................................... 11
Abbreviations ........................................................................................................................................ 14
Abstract ................................................................................................................................................. 17
Chapter 01: Introduction ....................................................................................................................... 18
1.1.
Define Problem and Background Information ...................................................................... 18
1.2.
Background ........................................................................................................................... 18
1.2.1.
Literature Survey........................................................................................................... 18
1.3.
Introduction ........................................................................................................................... 19
1.4.
Ammonia Oxidation Chemistry ............................................................................................ 19
1.5.
Properties of HNO3 ............................................................................................................... 21
1.5.1.
Physical Properties ........................................................................................................ 21
1.5.2.
Chemical Properties ...................................................................................................... 21
1.6.
Properties of Raw Material ................................................................................................... 22
1.6.1.
Physical Properties ........................................................................................................ 22
1.6.2.
Chemical Properties ...................................................................................................... 22
1.7.
Uses of Nitric Acid ............................................................................................................... 22
1.8.
Market Analysis .................................................................................................................... 23
1.8.1.
This survey aims to help us achieve the following goals .............................................. 23
1.8.2.
Global Analysis ............................................................................................................. 23
1.8.3.
Local Market Analysis .................................................................................................. 24
1.8.4.
Economic Assessment Conclusion ............................................................................... 24
Chapter 2: Process Selection ................................................................................................................. 25
2.1.
Process selection and Comparison ........................................................................................ 25
2.2.
Process Selection and Comparison ....................................................................................... 25
2.2.1.
Selection of Process ...................................................................................................... 25
2.2.2.
Comparison of Process.................................................................................................. 26
2.2.3.
Nitric Acid Production Process ..................................................................................... 28
2.3.
Nitric Acid Production .......................................................................................................... 28
2.3.1.
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Oxidation of Ammonia ................................................................................................. 28
2.3.2.
Oxidation of Nitrogen Monoxide .................................................................................. 30
2.3.3.
Absorption of Nitrogen Dioxide ................................................................................... 31
2.3.4.
Single Stage Pressure Process ....................................................................................... 32
2.4.
Process Description of Uhde Medium Pressure .................................................................... 34
2.4.1.
Medium Pressure Process Involves Following Equipment ........................................... 34
2.4.2.
Process Flow diagram ................................................................................................... 36
2.5.
Site Selection ........................................................................................................................ 37
2.5.1.
Plant Location ............................................................................................................... 37
2.5.2.
Ideal Plant Location ...................................................................................................... 37
2.5.3.
Local Analysis............................................................................................................... 37
2.5.4.
Selection Criteria........................................................................................................... 38
2.5.5.
Selected Site .................................................................................................................. 39
Chapter 03: Material and Energy Balance ............................................................................................ 40
3.1.
Material Balance ................................................................................................................... 40
3.1.1.
Conservation of Mass.................................................................................................... 40
3.1.2.
Methods of Material Balance ........................................................................................ 40
3.1.3.
Materials Balance Assumptions .................................................................................... 41
3.1.4.
Summary of Material Balance ...................................................................................... 41
3.2.
Energy Balance ..................................................................................................................... 46
3.2.1.
Energy Balance Assumptions ....................................................................................... 46
3.2.2.
Summary of Energy Balance ........................................................................................ 47
Chapter 04: Equipment Design ............................................................................................................. 59
4.1.
Vaporizer............................................................................................................................... 59
4.1.1.
Introduction ................................................................................................................... 59
4.1.2.
Types of Heat Exchangers ............................................................................................ 59
4.1.3.
Applications of Heat Exchangers .................................................................................. 59
4.1.4.
Comparison between Heat Exchangers ......................................................................... 60
4.1.5.
Exchanger Selection...................................................................................................... 60
4.1.6.
Design Steps.................................................................................................................. 61
4.2.
Reactor .................................................................................................................................. 66
4.2.1.
Theory of Reactors ........................................................................................................ 66
4.2.2.
Chemical reactors .......................................................................................................... 66
4.2.3.
Types of reactors ........................................................................................................... 66
4.2.4.
Fixed-bed reactors ......................................................................................................... 66
4.2.5.
Reactors with fluidized bed........................................................................................... 66
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4.2.6.
Thin or shallow bed reactors ......................................................................................... 67
4.2.7.
Type of reactor to consider ........................................................................................... 67
4.2.8.
The design challenge of reactor .................................................................................... 67
4.2.9.
Design calculation ......................................................................................................... 69
4.2.10.
Catalyst calculation ....................................................................................................... 72
4.3.
Heat Exchanger ..................................................................................................................... 75
4.3.1.
Types of heat exchangers .............................................................................................. 75
4.3.2.
Criteria of selection for heat exchangers ....................................................................... 75
4.3.3.
Shell and tube heat exchangers ..................................................................................... 76
4.3.4.
Design calculation ......................................................................................................... 76
4.4.
Absorber................................................................................................................................ 84
4.4.1.
Types of Absorption Column ........................................................................................ 84
4.4.2.
Comparison between Packed and Plate Towers............................................................ 84
4.4.3.
Column Type Selection................................................................................................. 86
4.4.4.
Types of Tray Columns................................................................................................. 87
4.4.5.
Tray Type Selection ...................................................................................................... 88
4.4.6.
Design Steps.................................................................................................................. 88
Chapter 05: Process Control and Instrumentation ................................................................................ 96
5.1
Instrumentation ..................................................................................................................... 96
5.2
Objective of Instrumentation and Control System ................................................................ 96
5.3
Components of the Control System ...................................................................................... 96
5.3.1
Process .............................................................................................................................. 96
5.3.2
Measuring Means .............................................................................................................. 97
5.3.3
Process Variables .............................................................................................................. 97
5.4
Types of Instrumentation ...................................................................................................... 99
5.4.1
Alarm instrumentation ...................................................................................................... 99
5.4.2
Recording instrumentation ................................................................................................ 99
5.4.3
Indication instrumentation ................................................................................................ 99
5.5
Control system ...................................................................................................................... 99
Classification of Controller ............................................................................................. 100
5.5.1
5.6
Supervision Loops .............................................................................................................. 100
5.6.1
Inferential Supervision Manipulation ............................................................................. 100
5.6.2
Feedback Supervision Manipulation ............................................................................... 100
5.6.3
Feedforward Supervision Manipulation.......................................................................... 101
5.7
Types of Feedback Controller ............................................................................................. 101
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5.7.1
Proportional Controller ................................................................................................... 101
5.7.2
Integral Controller ........................................................................................................... 102
5.7.3
Derivative Controller ...................................................................................................... 102
5.7.4
Proportional- Integral Controller .................................................................................... 103
5.7.5
Proportional- Derivative Controller ................................................................................ 103
5.7.6
Proportional-Integral-Derivative Controller ................................................................... 104
5.8
Control loop across Reactor ................................................................................................ 104
5.9
Control Loop Across Compressor....................................................................................... 105
Chapter 06: HAZOP Analysis ............................................................................................................ 106
6.1
Introduction ......................................................................................................................... 106
6.1.1
Hazard ............................................................................................................................. 106
6.1.2
Operability ...................................................................................................................... 107
6.1.3
History............................................................................................................................. 107
6.2
Aim ..................................................................................................................................... 107
6.3
Where Is HAZOP Used? ..................................................................................................... 107
6.3.1
HAZOP Types ................................................................................................................ 107
6.3.2
Definitions of Some Useful Terms ................................................................................. 108
6.3.3
Benefits Of HAZOP ........................................................................................................ 109
6.4
HAZOP Procedure .............................................................................................................. 109
6.5
HAZOP Group .................................................................................................................... 109
6.6
HAZOP Study of Absorber ................................................................................................. 110
Chapter 07: Cost Estimation ............................................................................................................... 112
7.1.
Plant Cost Introduction ....................................................................................................... 112
7.2.
Acceptability of Plant Costs ................................................................................................ 112
7.3.
Engineering and Plant Costs ............................................................................................... 112
7.4.
Calculation of Cost of Different Equipment ....................................................................... 112
7.4.1.
Direct Cost .................................................................................................................. 113
7.4.2.
Indirect Cost ................................................................................................................ 113
7.4.3.
Total capital investment .............................................................................................. 113
7.5.
HNO3 Product Cost ............................................................................................................ 114
References ........................................................................................................................................... 117
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List of Figures
Figure 1: Process Flow Diagram ............................................................................................................ 36
Figure 2: Design of Reactors ................................................................................................................. 68
Figure 4 Tube Side Heat Transfer Factor............................................................................................... 82
Figure 3: Proportional Controller ........................................................................................................ 101
Figure 4: Proportional Integral Controller .......................................................................................... 103
Figure 5: Proportional Derivative Controller ...................................................................................... 103
Figure 6: Proportional Integral Derivative Controller ......................................................................... 104
Figure 7: Control Loop Across Reactor................................................................................................ 104
Figure 8: Control Loop Across Compressor......................................................................................... 105
Figure 09: HAZOP Study of Absorber ................................................................................................. 110
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List of Tables
Table 1: Comparison on the basis of operating pressure ..................................................................... 27
Table 2: Process Comparison ................................................................................................................ 28
Table 3: Pressure Considerations.......................................................................................................... 30
Table 4: Summary of Material Balance ................................................................................................. 41
Table 5: Reactor .................................................................................................................................... 41
Table 6: Condenser ............................................................................................................................... 42
Table 7: Absorber .................................................................................................................................. 43
Table 8: Tail Gas Reactor....................................................................................................................... 45
Table 9: Compressor ............................................................................................................................. 47
Table 10: Interstage Cooler ................................................................................................................... 47
Table 11: 2nd Compressor...................................................................................................................... 48
Table 12: Ammonia Vaporizer .............................................................................................................. 48
Table 13: Ammonia Pre-Heater ............................................................................................................ 49
Table 14: 1st Mixer ................................................................................................................................ 49
Table 15: Reactor .................................................................................................................................. 49
Table 16: Heat of Reactions .................................................................................................................. 50
Table 17: Heat to be removed .............................................................................................................. 50
Table 18: Product Cooling ..................................................................................................................... 51
Table 19: Tail Gas Heater 01 ................................................................................................................. 51
Table 20: Tail Gas Heater 02 ................................................................................................................. 51
Table 21: Economizer ............................................................................................................................ 52
Table 22: Cooler .................................................................................................................................... 52
Table 23: Condenser ............................................................................................................................. 52
Table 24: Pump ..................................................................................................................................... 54
Table 25: Secondary Air Cooler ............................................................................................................. 54
Table 26: Heat of Reactions in Absorber .............................................................................................. 54
Table 27: Absorber ................................................................................................................................ 55
Table 28: 2nd Mixer ................................................................................................................................ 57
Table 29: Tail Gas Reactor..................................................................................................................... 57
Table 30: Tail Gas Turbine ..................................................................................................................... 58
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Table 31: Heat Exchangers Comparison ............................................................................................... 60
Table 32: Shell and Tube Properties ..................................................................................................... 61
Table 33: Calculation of LMTD .............................................................................................................. 62
Table 34: Kinetic Eqs. of Ammonia Oxidation ....................................................................................... 69
Table 35: Rate vs Conversion ................................................................................................................ 71
Table 36: Types of Tray Columns .......................................................................................................... 87
Table 37: Guide words for Absorber ................................................................................................... 111
Table 38: Cost of Equipment ............................................................................................................... 112
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Abbreviations
Aa
Active area
Ac
Total column cross-sectional arca
Ad
Downcomer cross-sectional area
Ah
Hole area, the total area of all the active holes
An
Net area for vapor-liquid disengagement
Ap
Perforated arca
Dc
Diameter of column
dh
Diameter of a hole
Eo
Overall column efficiency
ho
Shell side dry-gas coefficient
hb
Back-up in down-comer
Hc
Height of column
hd
Dry plate drop
hdc
Downcomer head loss
how
Weir liquid crest
hr
Residual head
ht
Total plate pressure drops in mm liquid
hw
Weir height hip
Kd
Diffusivity
KG
Mass diffusion coefficient
Ip
Hole pitch
It
Tray spacing
Iw
Weir length
Mm
Mean molecular weight of the vapor and non-condensable
Mv
Mean molecular weight of vapor
Na
Number of actual plates Number of holes
Nh
Number of theoretical plates
Pc
Partial pressure of vapor at condensate film
14 | P a g e
Pgf
Flowing gas pressure
Pt
Total pressure
Pv
Partial pressure of vapor in gas body
Tc
Condensate film temperature
tr
Downcomer residence time
tT
Tray thickness
tw
Water temperature
uf
Flooding vapor velocity
uh
Minimum vapor velocity
L
Liquid density
V
Vapor density

viscosity
A
Absorption factor
A
Arrhenius constant
Ar
Archimedes number
dp
Particle diameter
hf
Fluidize bed height
HG
Height of gasifier
K
Volatility of component
L
Liquid mass flow rate
N
Order of reaction
Nor
Number of orifices
R
Rate of reaction
TDH Transport disengagement height
Uo
Superficial velocity
Umf
Minimum fluidization velocity
Ut
Transport velocity
V
Vapor mass flow rate
x
Liquid mole fraction
X
Conversion
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y
Vapor mole fraction
Pb
Bed pressure drop
Pd
Distributor pressure drop
c
Bed voidage

Space time

Latent heat
g
Gas density
s
Solid density

Sphericity

Fractional entrainment
Pt
Total plate pressure drops in Pa
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Abstract
Nitric acid is a strong acid, a powerful oxidizing and a nitrating agent. Nitric acid is produced
through the oxidation of ammonia to nitrogen oxides, which are then absorbed by water to
produce nitric acid. Weak nitric acid processes produce nitric acid in the concentration range
of 50–65 wt. %. In our project we are using UHDE’s medium pressure process. The reason we
are producing nitric acid is because of emerging demand of nitric acid in Pakistan. If we look
on the uses of nitric acid, around 80% of the produced acid is used in production of fertilizers
and rest is used in making explosives and as an intermediate for other compounds.
In fertilizers low strength nitric acid is required, that is why we are producing 65 % nitric acid.
As we know, Pakistan is an agriculture country, so the need of fertilizers is increasing day by
day. In Pakistan only Fatima Fertilizer possess its own plant for nitric acid production, which
they further use in fertilizers production. There are many other plants, but producing high
concentration Nitric acid. Rest of the companies import Nitric acid for their fertilizers
production, therefore in order to compensate the need and to reduce imports, we are producing
nitric acid.
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Chapter 01: Introduction
1.1.
Define Problem and Background Information
In the initial design problem, it is necessary to examine whether or not it is both technically
and economically possible to develop a plant to produce nitric acid in Pakistan.' In addition,
the yearly growth of nitric acid in Pakistan is expected to climb by 4-5 percent over the next
three to four years. Nitric acid is primarily used in the explosives and agrochemical sectors,
and its market and growth rate are being driven by these industries. To complete this project, a
thorough examination into the uses, qualities, markets, processing technologies, and costeffectiveness of manufacturing this chemical will be conducted. A suitable plant to meet the
estimated market demands is sized and configured in accordance with these considerations and
several other factors being considered.
1.2.
Background
The original developers of nitric acid were Arab chemists in the early eighth century. Aqua
Fortis or Aqua Valens were mentioned. Following that, it was primarily made from potassium
nitrate and sulfuric acid. In the nineteenth century, sodium nitrate, which was abundant in South
America, largely displaced the preceding raw material used to manufacture nitric acid.
However, emerging innovations were introduced in the early twentieth century. In Norway,
people employed the electric arc method to produce nitrogen oxides and subsequently nitric
acid due to the low cost of electricity. Meanwhile, newer techniques have been introduced.
Wilhelm Ostwald invented the process of catalytic oxidation of ammonia with air in 1908,
which became the primary method of producing nitric acid. In 1913, the Haber-Bosch process
was successfully used to synthesize ammonia from water, air, and coal. Finally, ammonia
oxidation has developed into a viable industrial process for producing nitric acid.
1.2.1.
Literature Survey
Nitric acid, or aqua fortis and niter spirit, was made commercially by reacting alternatively
potassium nitrate or sodium nitrate to sulfuric acid until the start of the twentieth century. The
two materials have been placed in enormous retorts and cooked over a stove of up to 4 tonnes
(Kirk 1996). The volatile product was vaporized and distilled. An acid of 93-95% (wt.) was
generated (Gregory 1999).
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It was at Bochum, Germany, in 1908 that the first business facility to produce nitric acid,
employing this new catalytic oxidation technique, was put into operation (Ray et al 1989). The
Haber-Bosch ammonia synthesis method began operating in 1913, paving the way for the
ongoing development and long-term viability of the ammonia oxidation for the generation of
nitric acid in the following decades. (Ray and colleagues 1989)
In the wake of World War I, the need for pyrotechnics and synthetic dyestuffs increased
dramatically, resulting in a growth of the nitric acid industry. Many new plants were built, all
of which used the ammonia oxidation method as their primary process. It was because of this
growing demand that various improvements in process technology were made possible.
Research is continuously underway to minimize nitrogen oxide emissions from plants of nitric
acid. The nitric acid process Humphreys and Glasgow/Bolme is only one example of a novel
philosophy for the absorption systems of small acid plants (50-68 percent by weight).
Emissions of nitrogen oxide from 2000 to 5000 ppm were decreased to far less than 1000 mg/l.
Tail gases are increasingly being handled by choice or – anti catalytic combustion systems for
the creation of stronger nitric acid. These revolutionary machines lowered emissions of
nitrogen oxide to around 400 ppm.
1.3.
Introduction
Nitric acid, commonly known as Aqua Fortis, is a highly toxic mineral acid. The pure chemical
is colorless, but older traces tend to develop a yellow hue by decomposing nitrogen and water
oxides. Most available commercially nitric acid has 68% water content. When the sample
contains and over 86% HNO3, it is called fuming nitric acid. Depending on the quantity of
nitrogen dioxide, fuming nitric acid is further described as white fuming nitric acid or red
fuming nitric acid at concentrations exceeding 95%. Nitric acid is the main nitration reagent
— adding a nitro group, often to an organic molecule. While some resultant nitro compounds
are shock- and thermal-sensitive explosives, some are sufficiently stable to be employed in
ammunition and detonation, and some are still more stable and utilized as pigments in inks and
colors. Nitric acid is also utilized as a powerful oxidant.
1.4.
Ammonia Oxidation Chemistry
Particularly notable is the fact that all commercial nitric acid generation processes now in use
are based on the oxidation of ammonia. As a result, it is appropriate to explore the interaction
of this process, knowing that it is sufficiently similar to any of the industrial techniques
currently accessible.
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Although the chemistry of ammonia's oxidation appears to be complex, it is quite simple. There
are no by-products in this process because it starts with a single pure chemical, air, and water
and finishes with another compound in aqueous solution. The process may be characterized by
only six key reactions, which are depicted in the diagram below:
𝑁𝐻3(𝑔) + 2𝑂2 → 𝐻𝑁𝑂3(𝑎𝑞) + 𝐻2 𝑂(𝑙)
4𝑁𝐻3(𝑔) + 5𝑂2(𝑔) → 4𝑁𝑂(𝑔) + 6𝐻2 𝑂(𝑙)
2𝑁𝑂(𝑔) + 𝑂2 → 2𝑁𝑂2(𝑔)
2𝑁𝑂2(𝑔) ⇌ 𝑁2 𝑂4
3𝑁2 𝑂4 + 2𝐻2 𝑂(𝑙) → 4𝐻𝑁𝑂3 + 2𝑁𝑂(𝑔)
3𝑁𝑂2(𝑔) + 𝐻2 𝑂(𝑙) → 2𝐻𝑁𝑂3(𝑎𝑞) + 𝑁𝑂(𝑔)
Response 1 is the reaction that governs the entire process. This final product is the consequence
of three different and unique chemical procedures carried out in sequence. It is the first of these
reactions that causes ammonia to be converted to nitrogen monoxide (Reaction 2). It is the
second reaction that involves the additional oxidation of nitrogen monoxide to nitrogen dioxide
(Reaction 3), followed by the further reduction of nitrogen dioxide to nitrogen tetroxide
(Reaction 4). Finally, the absorption of these nitrogen-based oxides into water results in the
formation of the nitric acid product in the third and final stage (Reactions 5 and 6). In most
industrial and commercial applications, each of these 3 parts is carried out by a different unit
of the manufacturing process.
The first stage is the catalytic reaction of ammonia with oxygen in heterogeneous and
extremely exothermic gas phases (Reaction 2). Primary ammonia oxidation to nitric acid is
rapidly achieved at 900-970 °C at process temperatures. Two reactions are part of the second
stage (Reactions 3 and 4). And those are the oxidations of dioxide and tetroxide monoxide. The
balance combination is roughly called nitrogen peroxide. Both processes are homogenous gasphase catalytic reactions, which are mildly exothermic. All reactions are quite exothermic.
The third stage is the cooling of reaction gases under their dew point in order to create a fluid
of weak nitric acid. This step significantly enhances the phase of oxidation and dimerization
(reactions 3 and 4). This in turn increases the nitrogen peroxide component's partial pressure
(Chilton 1960). Nitric acid is finally produced by the water dissolved nitrogen peroxide
reaction (Reactions 5 and 6).
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1.5.
Properties of HNO3
1.5.1.
Physical Properties
o Colorless crystals of pure nitric acid.
o The boiling point is 83.1 oC
o The melting point is - 41.6 oC
o Water is totally miscible in all amounts.
o At high temperature it can be degraded.
1.5.2.
Chemical Properties
1.5.2.1.
Acidic Properties
o Reacts to the formation of salts of alkaline metals, carbonates, and basic oxides.
o It is a powerful monobasic acid.
o It is a powerful oxidant.
o Oxidizing in nature, but not the normal acidity.
1.5.2.2.
Oxidizing Properties
o Nitric acid reacts aggressively with many organic components, e.g., turpentine.
o The use of nitric acid to react with organic substances, for example furfural alcohol.
o Reactions following oxidation may occur according to nitric acid concentration and
temperature.
4HNO3 + 2e‾ → 2NO3‾ + 2H2O + 2NO2
8HNO3 + 6e ‾ → 6NO3‾ + 4H2O + 2NO
10HNO3 + 8e‾ → 8NO3‾ + 5H2O + N2O
10NO3 + 8e ‾ → 9NO3 ‾ + 3H2O + NH4+
16NO3 + 12e‾ → 14NO3‾ + 4H2O + 2NH3OH
o Strong nitric acid always promotes nitrogen dioxide (NO2) formation and low
concentration for NO formation.
o Concentrated Acid interacts with all but gold, iridium, platinum, rhodium, tanal and
titanium metals and some alloys.
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o HNO3 Nitric Concentrated acid forms metal oxides and dissolves Chrome, iron and
aluminum quickly.
1.6.
Properties of Raw Material
1.6.1.
Physical Properties
o It is a white gas.
o The odor is sparkling.
o It weighs molecularly (17.031 kg/kmol).
o It has a hot spot (-33.5 oC).
o It has got a melting point (-77.73 oC).
o The density is 0.86 kg/m3
1.6.2.
Chemical Properties
o Gas is highly stable.
o Fuel in air.
o It oxidizes metal oxides to nitrogen.
o It reacts to metal hydroxides with heavy metal ions.
Uses of Nitric Acid
1.7.
o For fertilizer manufacture, for instance ammonium nitrate, calcium nitrate and silver
nitrate.
o For the manufacturing of polymers like nylon, polyamides and polyurethane.
o It is utilized as a good nitrator (which integrates a nitro group to a compound).
o Used in liquid-fueled rockets as an oxidizer (rocket propellant) in combination with sulfuric
acid.
o It is frequently utilized for explosive manufacture such gun cotton, TNT (Tri-Nitro
Toluene), nitroglycerine and ammonal, notably in the nitric acid sector where large
quantities of nitric acid are required.
o Nitrate salts, coal tars, colors, and medicines are used.
o Used for purification of precious metals such as platinum, silver and gold.
o It was utilized as a laboratory reagent domestically.
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o It is used in woodworks to manufacture maple and pine wood.
o Used as a cleaning agent for foodstuffs and equipment.
o The colorimetric test uses nitric acid to distinguish morphine from heroin.
o Used for spotting alkaloids such as LSD.
1.8.
Market Analysis
Nitric acid is an important intermediate used for the manufacture, among other goods, of
fertilizers, explosives, polymers and resins. Because nitric acid is an intermediate good, it is
important to make those products. Therefore, the market for nitric acid is controlled by the need
for the products utilized to produce. Such, in turns, are generally transitional items, the demand
of which depends on the need for the final products used to make them. For instance, the
demand for fertilizers depends on the price for agricultural produce, the provision of other
agricultural inputs and the possibility to replace fertilizers with other inputs. Similarly,
explosives based on nitrate are employed in mining and construction (particularly coal mining).
The explosive demand therefore depends on the price for coal and other minerals and on the
demand for new constructions and infrastructure.
1.8.1.
This survey aims to help us achieve the following goals
o Production of sufficient local nitric acid.
o Supply other related businesses with nitric acid.
o Reduce imports of nitric acid all across the country if possible.
Nitric acid is in high demand to produce fertilizers, explosives and metal etching/dissolution
in agriculture and the chemical sectors, as components of water for gold purification/extraction
and in chemical synthesis. The country imports enormous amounts of nitric acid. The project
produces 600 tonnes of nitric acid per day, 300 working days per year and 3 rotations each day.
The plant's capacity does not currently satisfy the market demand due to the significant
investment necessary to set up the plant and it is more affordable to enlarge the plant after
evaluating the establishment's performance.
1.8.2.
Global Analysis
The following results were obtained at the end of 1992 from a survey on the kinds of crops still operating
in the European Community. Plants are classed by pressures of oxidation and absorption.
Dual pressure process plants
23 | P a g e
o Low/medium pressure
9 (old plants)
o Medium/High Pressure
36 (Newest plants)
Single process pressure plants
o Pressure of the medium/medium
22
o High pressure/High pressure
11
o
78
Total Plants
The data acquired from the latest dual pressure plants reveal the usual plant capacity of 1000
MTPD on average. According to the MRFR analysis, a robust CAGR of 6.3 percent is
anticipated to reach USD 17.5 billion by the end of 2025. Different agrochemicals such as
ammonium nitrate (N), ammonium nitrate and calcium ammonium nitrate are made from nitric
acid. The growing demand of fertilizers, due to the growing in need of high crop yields for
crops, would likely be a major driving force of nitric acid throughout the projection period.
Furthermore, ammonium nitrate is derived mostly from explosives, and increasing demand in
military and defense-industrial explosives is predicted to increase the growth of the worldwide
nitric acid market 5%.
1.8.3.
Local Market Analysis
Pakistan is a major nitric acid importer. Pakistan's 32nd number is among the 132 largest
importers of nitric acid. It is also imported as 60 percent nitric acid or as sulphonitric acid.
Nitric acid imports are rising on an annual basis with a little volatility. The increase in imports
to nations such as Pakistan is the reason why 80% of the nitric acid generated is being utilized
as an intermediary in the production of fertilizer, primarily in the creation of ammonium nitrate.
1.8.4.
Economic Assessment Conclusion
A careful investigation on the market for nitric acid in Pakistan and abroad showed a potential
market. We have a capability based on Uhde's maximum media pressure process capacity of
700 MTPD. And we decided 600 MTPD based on market need for Nitric Acid to make
Fertilizer. Pakistan is also a country of agriculture and 80% of nitric acid is used in agriculture.
We need to establish our plant to cut our imports and the increasing demand for fertilizers day
after day. The other reason is that Pakistan imports about 10,000 tonnes of ammonium nitrate.
So, we can meet our country's needs and export them.
24 | P a g e
Chapter 2: Process Selection
Process selection and Comparison
2.1.
There are hardly many procedures for the manufacturing of nitric acid that we'll have to choose
from. Although the manufacturing of laboratory size involves a few processes, the manufacture
of nitric acid on a commercial basis is made using two different procedures. Weak generation
of nitric acid and robust production of nitric acid. Low nitric acid is created via the nitric acid
production technique Ostwald, and includes oxidation, condensation and absorption to create
low concentrations of 30 to 70% of low nitric acid. Dehydration, bleaching, condensation and
absorption of weak nitric acid produces high strength nitric acid (90% or above). The
underlying nitric acid process technique has not altered considerably throughout time. From
the beginning of the 20th century, ammonia oxidation over platinum-rhodium alloy produces
nitric acid.
2.2.
Process Selection and Comparison
2.2.1.
Selection of Process
By comparing the two most used variants of UHDE’s Process:
In the fertilizer industry, the Moderate Pressure Process is most commonly utilized in the
manufacturing of HNO3, while the High Voltage Process is most commonly used in the
explosive sector. The following factors influenced my decision on which process to use:
o More catalyst degradation in high pressures than medium pressure.
o More high-pressure energy consumption due to the usage of compressors to supply raw
materials at the necessary pressure
o The high-pressure process leads to an explosive mixture whereas the medium pressure
process is safe, which makes it preferable to be used industrially.
o The concentration of HNO3 is normally high that in the fertilizer industry is not preferable
due to safety risks.
o The cost of capital for large machinery is larger than the cost of high-pressure equipment,
which demands initial investment in the medium pressure process, but denies the relevance
of net profit.
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The medium pressure process from UHDE was selected in the end due to its reduced catalyst
use and low energy consumption, as well as its lower danger of explosive mixture development
and preference for the fertilizer business.
2.2.2.
Comparison of Process
For comparison, we have selected three mostly used processes to produce Nitric Acid:
Thyssenkrupp Uhde’s process – Stamicarbon Process – Pintsch Bamag Process
Now comparing the processes in terms of:
o UDHE's method yields the highest Nitric Acid concentration, while the Stamicarbon and
Pintsch-Bamag processes, despite the use of two absorbers, yield the lowest Nitric Acid
concentration.
o Additionally, catalyst degradation in UDHE's process is low, at 45 mg/ton of Nitric Acid
generated, which is substantially lower than the other two processes, owing to the
differences in the processes.
o The Stamicarbon and Pintsch-Bamag processes both exhaust tail gases with a high NOx
concentration of around 1000 parts per million (ppm), but the UDHE process further reacts
the tail gas with Ammonia to lower the NOx level to 200 parts per million.
o When it comes to proper absorption of Nitrogen Dioxide in water, both the Stamicarbon
and Pintsch-Bamag procedures employed two absorbers; however, UDHE's technique used
a single absorber that was more economically efficient.
o Power consumption is considerable in the Pintsch-Bamag Process, whereas it is comparable
in both UHDE's and the Stamicarbon Process, which is an important economic
consideration to take into account.
26 | P a g e
Table 1: Comparison on the basis of operating pressure
Pressure
Catalyst
Temp.
NO
Yield
Catalyst
Loss
Energy
Recovery
Turbine
Size
NOx
Content
Medium
(1.7 - 6.7 bar)
Low
(Around
850 oC)
Low
(97%)
Less
Less
High
High
(500ppm)
High
(6.7 - 12 bar)
High
(900-950 oC)
High
(94%)
More
More
Small
Low (150200ppm)
This table provides an excellent comparison of medium-pressure and high-pressure processing
methods. The temperature of the catalyst employed in the oxidation of ammonia is determined
by the pressure applied during the process of oxidation. Although the NO yield is high at low
temperatures, the reaction rate constant is relatively small, making it uneconomical to run the
reaction for an extended period of time. In order to combat this, high temperatures are
recommended. However, when exposed to high temperatures, NO decomposes into its
constituent constituents. As a result, high pressure is employed to prevent the breakdown
reaction of NO from occurring. The yield is a tiny bit lower than that of medium pressure,
although the difference isn't that significant. However, a significant downside of high pressure
is that the catalyst loss is extremely high, which can significantly alter the economics of the
entire process. When a high-pressure method is employed, the cost of the catalyst is extremely
high in the plant. Because greater catalyst loss results in less operating time, the number of
catalyst gauzes needed annually in high-pressure facilities is higher than in medium- or lowpressure processes. The operating lifetime of a plant is determined by the type of plant. The
operating lifetime of a catalyst in a medium pressure process is between 3 and 6 months.
However, in high-pressure plants, the time is only three months. The following table compares
the operating circumstances of an ammonia converter in order to make a more informed
decision.
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Table 2: Process Comparison
2.2.3.
Features
Low
Pressure
Medium
Pressure
High
Pressure
Pressure (bar)
1-2
3-7
8-12
Ammonia content (%)
12-12.5
10.5-11.5
10-10.5
Gas Velocity
0.4-1.0
1-3
2-4
Catalyst Loading
(NH3 m-2 d-1)
2-4.5
10-40
30-70
Gauze Temperature
800-850
850-900
900-950
No. of Gauzes
3-5
6-10
20-50
Catalyst Loss
(gt-1Nin NH3) *
0.2-0.4
0.7-0.9
1.1-2.2
Operating Time
(Months)
7-12
3-6
1.5-3
Nitric Acid Production Process
The Ostwald method, which involves the high-temperature catalytic oxidation of ammonia
over a platinum-rhodium alloy composed of 90 percent platinum and 10 percent rhodium,
produces weak nitric acid. This procedure is divided into three steps:
Step 1: Oxidation of NH3 to NO.
Step 2: Oxidation of NO to NO2.
Step 3: Absorption and reaction of NO2 with water.
2.3.
Nitric Acid Production
2.3.1.
Oxidation of Ammonia
Atmospheric air is first and foremost a filter that uses a cotton technology to eliminate dust
particles from it. It is then pre-heated, then pushed to pressure and finally combined with the
evaporated ammonia. The ammonia is not compressed as it condenses during unwanted
compression. This mixture is run over a platinum/rhodium gauze that serves as a catalyst for
28 | P a g e
ammonia and air reactions. The following reactions cause ammonia and air to react and produce
nitrogen oxides (NO) with a yield of 93 to 97% and water.
4NH3 + 5O2 → 4NO + 6H2O
The catalyst for this procedure is 90% platinum alloy and 10% rhodium for improved strength.
The catalyst comprises of many woven or knitted alloy gauzes. The gauze mats are pre-heated
to immediately heat the gases when they cross the catalyst. The catalyst can be contaminated
by air pollution and ammonia contamination, which decreases its performance. The costs for
these catalysts are quite high and must be updated regularly due to their wear and tear in these
harsh conditions. There is still a cheaper alternative to develop.
o Temperature Considerations
This is a catalytic high temperature reaction. Although nitrogen oxide (NO) can be generated
at highly favorable rates at low temperatures, the reaction rate at low temperatures is quite
slow. The preferred catalyst temperature for this reaction is 800 to 9500C although the optimal
temperature is about 8500C. The high temperature provides good nitrogen oxide output (NO).
Although low catalytic temperatures favor unwanted side effects and lead to less usable
nitrogen and nitrous oxide (N2) compounds (N2O).
4NH3(g) + 3O2 (g) → 2N2(g) + 6H2O(g)
2NH3(g) + 2O2 (g) → N2O(g) + 3H2O(g)
Conditions are carefully checked by the converter to guarantee that the major product is
nitrogen monoxide (NO) and not nitrogen gas (N2) and nitrogen oxide (N2O).
o Pressure Considerations
As can be observed from the (1) reaction, the quantity of the products only changes negligibly,
the principle of Le-Chatelier does not impact the balance. This means that the change in
pressure has relatively little impact on the output of this reaction. High reaction pressure is still
beneficial (1). The reason is that the nitric oxide (NO) degrades at high temperature to generate
nitrogen and oxygen.
2NO(g) = N2 (g) + O2 (g)
To prevent this, the gas mixture is extremely quickly transferred across the catalyst (contact
time is approximately 0.003 sec). To accomplish this high flow rate, the reaction is carried out
at high pressures even if lower pressures lead to increased product yield. The resulting loss in
29 | P a g e
NO output is offset by the higher reaction rates and the grade of the produced product. The
favorable circumstances for this stage in ammonia oxidation are therefore:
o
High temperature 820 - 930 oC
o
High Pressure about 11 bar
Table 3: Pressure Considerations
Pressure (bar)
Temperature (oC)
NO Yield (%)
Low Pressure
Below 1.7
810 to 850
97
Medium Pressure
1.7 to 6.5
850 to 900
96
High Pressure
Above 6.5
900 to 940
95
o Heat Recovery
Equation (1) is an exothermic process, with a high energy contents of the process stream of this
reaction includes NO and unwanted gases, which can be used via a waste heat boiler. The steam
produced in this boiler is used to operate the steam turbine to compress the ammonia-air
mixture before ammonia oxidation is performed by the compressor. The combustion gas for
energy recovery following this heat transfer has a temperature of 100 to 200°C depending on
the method.
The ammonia air ratio or % is another key thing in this reaction. Most of the ammonia content
is between 9 and 12 percent. Because the ammonia air mixture gets explosive above this limit.
Air ammonia ratio is maintained and kept below 12 percent in order to avoid any unwanted
circumstance. It is sometimes 10 percent in the sake of protection in many plants.
2.3.2.
Oxidation of Nitrogen Monoxide
For further processing, the nitric oxide created during the ammonia oxidation stage must be
oxidized. The gases following the first phase are at high temperatures and a heat recovery
equipment like waste heat heater is placed to use hot gas heat and to generate steam that may
be used in steam turbines. The nitric oxide stream has a temperature of between 150 and 200
o
C following heat recovery, depending on the process. This stream is transmitted via a cooler
condenser to reduce its temperature further to approximately 50 oC. This is because nitric oxide
oxidation is favored at low temperatures. The water is condensed and transferred to the
30 | P a g e
absorption tower in the cooler condenser. The nitrogen oxide reacts without catalysis to
nitrogen dioxide and the liquid dimer, nitrogen tetroxide, with residual oxygen.
2NO + O2 = 2NO2
In order to boost the oxygen content to such a level, secondary air is introduced to the gas
mixture resulting from ammonia oxidation that the waste gas exiting the plant has a normal
amount of oxygen of between 2% and 4% by volume. If the condensed waters absorbed some
nitrogen dioxide during condensation and produce weak acids, they are placed in the absorption
column with the appropriate concentration.
2.3.3.
Absorption of Nitrogen Dioxide
An absorption tower is used to capture nitrogen dioxide and dimer after they've been cooled to
the proper operating temperature. It is necessary to inject liquid di-nitrogen tetroxide at a higher
point in the column, and deionized water is introduced at the top of the column. During the
absorption process, nitrogen dioxide gas is absorbed into absorption trays (sieves or bubble
caps) while oxidation occurs in the free space between the trays. The absorption tower is
comprised of absorption trays (sieves or bubble caps) where nitrogen dioxide gas is absorbed
during the absorption process. It is possible to have simultaneous absorption of nitrogen
dioxide gas and its interaction with nitric acid and nitric oxide in both the liquid and gaseous
phases.
3NO2(g) + H2O(l) → 2HNO3(aq.) + NO(g)
In order to re-oxidize the NO created by this process, a secondary air stream is supplied into
the cooling tower. Aside from removing NO2 from the product acid, this secondary air also has
another function. At the bottom of the tower, an aqueous solution of nitric acid containing 55
to 65 percent (usually) nitric acid is removed. It is possible to have a nitric acid concentration
ranging from 30 to 70 %. When it comes to acid concentration, it is determined by several
factors like temperature, pressure, the number of absorption stages, and the amount of nitrogen
oxides entering the absorber.
The temperature and pressure conditions have a significant impact on the reaction. This
reaction is exothermic; hence it necessitates the use of continual cooling. Low temperatures
aid in the conversion, and substantial reaction occurs until the gases are expelled from the
towers, at which point the conversion is complete. Nitrogen dioxide gas is injected through the
inert packing material at pressures ranging from 5 to 10 atmospheres, through which water is
trickling from above.
31 | P a g e
The reaction seen between water and the gas generates nitric acid, which dissolves in the
remaining water once the reaction has occurred. Small amounts of NO are also formed, which
interacts with oxygen from the tower's air to form NO2, which subsequently through the same
reactions as before.
In order to maintain a low temperature during the absorption reaction, a cooling mechanism
must be built. The absorption reaction is favored at low temperatures and high pressures; hence
a cooling mechanism must be implemented. A scrubber is used to inject nitric acid that has
been extracted from the bottom of the absorption column into the system. The reason for this
is that some nitrogen oxides are dissolved in the nitric acid used in the production of the
product. To do this, a secondary air stream is injected from the bottom of the scrubber, and it
takes with it dissolved oxides as well as product acid dregs from the bottom, before being
expelled. The majority of the time, a product with a concentration between 50 and 70% is
achieved. Generally speaking, the purity of weak acid ranges from 30 to 70%, depending on
the use and the requirements. In certain cases, the scrubber is not employed, and instead, the
air stream is injected straight into the absorber, where it scrubs the oxides and departs as tail
gas, which is released from of the top of the tower.
In a mist separator, acid mist (acid liquid carry over) is separated from the bleached gases (tail
gases) after they have been compressed and passed through the absorber. The waste tail gas is
heated in the ammonia oxidation heat exchanger, expanded in a power recovery turbine, and
discharged into the atmosphere through the effluent stack.
There are 2 basic types of systems used to produce weak nitric acid:
o Single-stage pressure process,
o Dual-stage pressure process
2.3.4.
Single Stage Pressure Process
During the ammonia oxidation and nitrogen oxides absorption phases of an ammonia oxidation
plant, the air that is delivered into the plant is squeezed to the process pressure, and this single
pressure is used throughout the plant.
One might further divide the single stage pressure process into twin absorption tower is used
to capture nitrogen dioxide and dimer after they've been cooled to the proper operating
temperature. It is necessary to inject liquid di-nitrogen tetroxide at a higher point in the column,
and deionized water is introduced at the top of the column. During the absorption process,
nitrogen dioxide gas is absorbed into absorption trays (sieves or bubble caps) while oxidation
32 | P a g e
occurs in the free space between the trays. The absorption tower is comprised of absorption
trays (sieves or bubble caps) where nitrogen dioxide gas is absorbed during the absorption
process. It is possible to have simultaneous absorption of nitrogen dioxide gas and its
interaction with nitric acid and nitric oxide in both the liquid and gaseous phases.
3NO2(g) + H2O(l) → 2HNO3(aq.) + NO(g)
In order to re-oxidize the NO created by this process, a secondary air stream is supplied into
the cooling tower. Aside from removing NO2 from the product acid, this secondary air also has
another function. At the bottom of the tower, an aqueous solution of nitric acid containing 55
to 65 percent (usually) nitric acid is removed. It is possible to have a nitric acid concentration
ranging from 30 to 70%. When it comes to acid concentration, it is determined by several
factors like temperature, pressure, the number of absorption stages, and the amount of nitrogen
oxides entering the absorber.
The temperature and pressure conditions have a significant impact on the reaction. This
reaction is exothermic; hence it necessitates the use of continual cooling. Low temperatures aid
in the conversion, and substantial reaction occurs until the gases are expelled from the towers,
at which point the conversion is complete. Nitrogen dioxide gas is injected through the inert
packing material at pressures ranging from 5 to 10 atmospheres, through which water is
trickling from above.
The reaction seen between water and the gas generates nitric acid, which dissolves in the
remaining water once the reaction has occurred. Small amounts of NO are also formed, which
interacts with oxygen from the tower's air to form NO2, which subsequently through the same
reactions as before.
In order to maintain a low temperature during the absorption reaction, a cooling mechanism
must be built. The absorption reaction is favored at low temperatures and high pressures; hence
a cooling mechanism must be implemented. A scrubber is used to inject nitric acid that has
been extracted from the bottom of the absorption column into the system. The reason for this
is that some nitrogen oxides are dissolved in the nitric acid used in the production of the
product. To do this, a secondary air stream is injected from the bottom of the scrubber, and it
takes with it dissolved oxides as well as product acid dregs from the bottom, before being
expelled. The majority of the time, a product with a concentration between 50 and 70% is
achieved. Generally speaking, the purity of weak acid ranges from 30 to 70%, depending on
the use and the requirements. In certain cases, the scrubber is not employed, and instead, the
33 | P a g e
air stream is injected straight into the absorber, where it scrubs the oxides and departs as tail
gas, which is released from of the top of the tower.
In a mist separator, acid mist (acid liquid carry over) is separated from the bleached gases (tail
gases) after they have been compressed and passed through the absorber. The waste tail gas is
heated in the ammonia oxidation heat exchanger, expanded in a power recovery turbine, and
discharged into the atmosphere through the effluent stack.
o groups.
o Plants with a medium level of pressure (4 - 8 atm).
o High-pressure plants (between 8 and 14 atmospheres).
2.4.
Process Description of Uhde Medium Pressure
2.4.1.
Medium Pressure Process Involves Following Equipment
The process is carried out under medium pressure. 1. the reactor; 2. the process gas cooler; 3.
the tail gas heater 3; 4. the economizer; 5. the cooler condenser and feed water preheater; 6. the
absorption unit; 7. the bleacher 8. Tail gas heaters 1 and 2; 9. Tail gas reactor; 10. Ammonia
evaporator and superheater; 11. Turbine steam condenser; 12. Ammonia evaporator and
superheater
The flowsheet for UHDE's medium-pressure process. The ammonia is vaporized and filtered
out. The air that will be used in the combustion process, on the other hand, is filtered using a
two or even three-step filtration system. In order to avoid interaction with the catalyst during
NH3 oxidation, it is assumed that the filters will remove all particles present in both the
ammonia and the air streams. The flow is then pressured at this point. The air stream has been
divided in half. During the catalytic conversion process, one stream is directed to the catalytic
converter and the other to the bleaching portion of the absorption column.
Compressed air is combined with evaporated ammonia and then passed through the catalytic reactor.
The catalytic reactor is configured to distribute the air/ammonia mixture uniformly across the catalyst
gauzes. Maintaining the working temperature of the catalyst is critical for the NO production. This is
accomplished by changing the air/ammonia ratio and ensuring that the ammonia in air does not exceed
its lower explosive limit. Typically, the catalytic reactor is housed in the upper portion of a vessel that
also contains the initial heat recovery section (steam super heater and steam generator). A series of
gas/gas heat exchangers converts the energy contained in the gas exiting the boiler set to that contained
in the tail gas.
34 | P a g e
The nitric oxide (NO)-containing gaseous mixture is then passed through a colder condenser, which
lowers the temperature even further, making it more favorable for the oxidation of NO to NO2. In this
stage, a little amount of weak nitric acid is generated, which is extracted from the gases and injected
into the absorption column.
The modern absorber design employs counter-current flow circulation in conjunction with high
efficiency trays, which are often sieve trays or bubble cap trays, to achieve maximum efficiency and
efficiency. From the bottom of the absorber to the top of the absorber, the tray spacing increases in a
graduated manner. Many of the trays are equipped with inbuilt cooling coils, which help to dissipate
the heat generated during the reaction. The absorption section is made up of a number of columns that
are connected together.
Make-up water, such as demineralized water or steam condensate, is added to the tower at the
very top. After acidification, the processing condensate from the manufacturing of ammonium
nitrate may be utilized as a fertilizer. This highly dissolved nitrogen-oxide-rich acid solution
exiting the absorption section is transported to a bleaching tower where it comes into contact
with a counter-current flow of secondary air. The secondary air and nitrogen oxides that have
been removed from the gases leaving the cooling section are mixed with the gases leaving the
cooling section and recycled to the absorption section. Tail gas is the term used to describe the
gas that exits the absorption section.
When the tail gas from the absorber is exhausted, it is transferred through the heat recovery
and expander sections for energy recovery before being discharged into the stack. The energy
generated by the expander is inadequate to drive the air compressor at full capacity. The
shortage is made up by a steam turbine that uses some of the superheated steam produced in
the plant to create electricity. The steam turbine is also employed during the initial startup of
the plant. Some plants use an electric motor to generate energy, and the steam that is produced
is then sent to the outside world.
It is possible to build plants with capacities of up to 500 MTPD utilizing a single ammonia
combustion unit and a single absorption tower. Because of the process pressure, larger
throughput of up to 1000 MTPD are possible with the addition of an additional absorption
column. It is the medium pressure technique that is preferred because it allows for the greatest
amount of energy recovery when it is needed. The air compressor is powered by the steam
turbine and tail gas turbine, with steam generated within the plant to power the turbines and
compressor. If the value for exported steam is large, the compressor is operated by a high-
35 | P a g e
voltage synchronously or asynchronously electric motor instead of a steam turbine, allowing
all of the steam produced to be exported without wasting any.
It is possible to create one form of nitric acid with a maximum concentration of 65 percent
using this type of plant, or two types of nitric acid with maximum concentrations of 60 percent
and 65 percent using this type of plant. While the NOx level can be lowered to less than 500ppm
through absorption, the ozone concentration cannot be reduced. A selective catalytic reduction
approach employing ammonia as a reduction agent and non-noble metal catalyst must be used
to further minimize NOx emissions before they can be used.
The medium pressure process is distinguished by a high overall nitrogen production of around
97.5 percent or 97.2 percent when combined with the tail gas treatment process, a low platinum
consumption rate, and a high steam export rate, among other characteristics.
2.4.2.
Process Flow diagram
Figure 1: Process Flow Diagram
36 | P a g e
2.5.
Site Selection
2.5.1.
Plant Location
Plant location includes the selection of a territory or the choosing of a specific site for the
establishment of a business or a manufacturing facility. However, the final decision is taken
only after a thorough examination of the alternatives. It is a calculated choice that can't be
reversed after it has been made, so plan accordingly. As a result, extreme caution must be
exercised prior to making a decision on the site of the plant's headquarters (Ray et al 1989).
2.5.2.
Ideal Plant Location
An ideal plant location is one in which the cost of production is kept to a bare minimum, where
there is a huge market available, where the risk is kept to a bare minimum, and where the
maximum profit may be realized. It is the location with the greatest net advantage or the
location with the cheapest unit production and delivery. Small and big scale entrepreneurs can
both benefit from and contribute to local analysis in order to achieve this goal.
2.5.3.
Local Analysis
Area analysis is a dynamic process in which the entrepreneur assesses and compares the
viability of several sites with the goal of selecting the most suitable location for a certain firm
in question. It takes into account the following:
o Demographic analysis
It entails the investigation of the local population in terms of the total number of people in the
area, the age composition of the population, the per capita income, the educational level of the
population, and the occupational patterns, among other things.
o Trade area analysis
It is a study of the geographical area that offers a steady stream of customers to the sector. The
viability of entering the economic area from alternate locations should be investigated as well,
it is recommended (Ray et al 1989).
o Competitive analysis
The type, location, scale, and degree of competition in a given trade region can all be
determined using this method.
o Traffic analysis
A rough estimate of the number of possible client program by the project location during
working hours in the industry is obtained in this manner. The goal of the traffic study is to
37 | P a g e
evaluate the major options in terms of the amount of pedestrian and vehicle traffic that passes
through the site.
o Site economics
Alternative sites are measured in terms of their setups, costs, and operational costs within this
framework of evaluation. A plant's establishment costs are mostly comprised of the
expenditures incurred for solid physical infrastructure, whereas plant operation costs are
comprised of the costs required for running the facility.
2.5.4.
Selection Criteria
The following are the most significant factors to consider when choosing a suitable location.
o Environmental or climatic conditions
o Availability of raw materials as well as proximity to their suppliers
o The third factor to examine is transportation expenses, which should be considered both for
procuring raw materials and for distributing or marketing finished products to end
customers.
o Close proximity to the projected market: The industry's warehouse should be positioned in
close proximity to densely inhabited areas in order to maximize efficiency.
o Important infrastructure facilities, such as a constructed industrial shed or site, access to a
network of link highways, proximity to railway stations, airports, or seaports, and access to
electrical and water power as well as public utilities, civil amenities, and means of
communication are available.
o Availability of skilled and non-skilled workers, as well as supervisors who are technically
qualified and trained.
o Banking and financial institutions should be positioned in close proximity to one another.
o The importance of safety and security should not be overlooked.
o Influences of the government: Tax breaks, subsidies, liberation, and other favorable
policies of the government to aid in the start-up of any industry should all be carefully
evaluated before any industry is established, whether it is for profit or not. Negative
government influences such as limits on the establishment of industries in a certain location
for the purpose of pollution control and decentralization of industries should also be taken
into consideration.
o Utility costs and availability are discussed in detail in Section X.
38 | P a g e
2.5.5.
Selected Site
Khanewal road Shahrukn-e-Alam Town Multan, Punjab, Pakistan.
o We chose our location primarily based on the availability of raw materials. Because Fauji
Fertilizers is nearby, it is quite convenient to obtain raw material ammonia from them.
o There is a large water reservoir close by, which helps to keep costs down.
o Because it is on a highway, transportation costs are kept to a bare minimum.
o Land is readily available at a reasonable price, as is labor.
o It is located in close proximity to the market.
o It is possible to find a financial institution.
o Relatively safe environment.
o The availability of social facilities and communication channels.
39 | P a g e
Chapter 03: Material and Energy Balance
3.1.
Material Balance
Material balance is one of the most important components of a process design. Overall raw
material of the entire process determines the qualities of raw materials required and the
products produced in the process.
Balance over individual process units determines the process stream flows and their
compositions and the sizes of the various process equipment used in the process.
Material balance on the plant used in the production of 300,000 tonnes of Nitric acid per year.
Mass flow rate = 300,000 tonnes/year = 38480 kg/hr
3.1.1.
Conservation of Mass
For a steady state process, the accumulation term will be zero; but if a chemical reaction takes
place, particular chemical specie may be formed or consumed in the process. When there is
chemical reaction, the material balance equation is given as:
Input + Generation = Output + Consumption
If there is no chemical reaction, the steady state balance reduces to:
Input = Output
3.1.2.
Methods of Material Balance
There are two basic methods of material balance, and they are:
3.1.2.1.
Algebraic Method
The algebraic method of material balancing is one of the simplest and most common methods
applied in balancing the materials that flow through a system. It involves the systematic and
sequential technique in identifying some variable sets which are related by some sets of linear
or non-linear equations whose solution depends on the resulting degree of freedom for the
system. This degree of freedom provides us with the limit of freedom for which we can set
values for some of the variable which is referred to as the design variables. A choice of values
for the design variables results in a corresponding value for the remaining variables. The
solutions to the equation set are obtained by the various method of solution for simultaneous
equations, most appreciably the methods of substitution and elimination. The algebraic method
40 | P a g e
is most efficient for simple system, but it may be inappropriate for complex systems involving
large number of units. The split fraction method is recommended for such systems.
3.1.2.2.
Split Fraction Method
This method is based on the theory of recycle processes published by Magier (1964). The
method is based on the realization that the basic function of most chemical processing units
(Unit Operation) is to divide the inlet flow of a component between two or more outlet streams.
This method is ideal in carrying out material balancing of complex of multi-unit plants.
Materials Balance Assumptions
3.1.3.
The following assumptions were made during the material balance calculations:
1.
The system is operating at steady state i.e., there is no accumulation of any sort in the
system.
2.
There is negligible amount of inert in the process air.
3.
Effect of side reactions is minimal.
3.1.4.
Summary of Material Balance
Table 4: Summary of Material Balance
Air
NH3
3.1.4.1.
Overall Feed
=
=
4343.02
416.719
kmol/h
kmol/h
Reactor
Table 5: Reactor
Ammonia feed to reactor
41 | P a g e
=
415
kmol
1
4NH3
398.4
+
+
5O2
498
↔
↔
4NO
398.4
+
+
6H2O
597.6
2
4NH3
16.6
+
+
3O2
12.45
↔
↔
2N2
8.3
+
+
6H2O
24.9
M.W
Input - 11
Output - 12
kg/kmol kmol
kg
kmol
kg
Comp.
O2
32
784.35 25099.2 273.9 8764.8 0.06439
N2
28
2950.7 82618.2 2959 82850.6 0.69561
NH3
17
415
7055
NO
30
398.4
11952 0.09366
NO2
46
H2O (Vapor)
18
622.5
11205 0.14634
HNO3
63
Total
234
4150
114772 4253.8 114772
1
Components
3.1.4.2.
Condenser
Table 6: Condenser
2NO
398.4
3(a)
Components
NH3
O2
N2
NO
NO2
H2O
HNO3
Total
4(a)
Basis
Actual
3NO2
150
195.44
+
+
M.W
kg/kgmol
17
32
28
30
46
18
63
234
+
+
+
O2
199.2
↔
↔
2NO2
398.4
Input - 15
kmol
kg
Output
kmol
kg
273.9
2959
398.4
8764.8
82850.6
11952
74.7
2959
2390.4
82850.6
622.5
11205
398.4
622.5
18326.4
11205
4253.8
114772
4054.6
114772
H2O
50
65.145
↔
↔
↔
2HNO3
100
130.29
+
+
+
NO
50
65.14535
Assuming, 100 kmol of 45% HNO3 in the condensate leaving the condenser.
Amount of water required to form 100 kmol of
HNO3
=
50
kmol
kg
kg
Mass of 100 kmol of HNO3
Amount of water required to dilute 100 kmol of
HNO3 as 45%
=
900
6300
=
7700
kg
Total amount of water required
=
8600
kg
HNO3 Formed
=
130.291
kmol
42 | P a g e
Components
NH3
O2
N2
NO
NO2
H2O (Liquid)
HNO3
Total
3.1.4.3.
Input
Stream
kmol
kg
M.W
kg/kgmol
17
32
28
30
46
18
63
234
74.7
2958.95
2390.4
82851
398.4
622.5
18326
11205
Output - 18
Gaseous Stream
kmol
kg
74.7
2958.95
65.1453
202.964
0
2390.4
82851
1954.4
9336.3
0
4054.55 114772 3301.76
96532
Output - 16
HNO3 (45%)
kmol
kg
557.355
130.291
687.645
Output
Total
kmol
0.000
74.700
2958.95
65.145
202.964
10032.38 557.355
8208.314 130.291
18240.7 3989.4
Absorber
Table 7: Absorber
43 | P a g e
3(b)
2NO
65.145
+
+
O2
32.573
↔
↔
2NO2
65.145
4(b)
3NO2
267.094
+
+
H2O
89.031
↔
↔
2HNO3
178.063
3(c)
2NO
89.031
+
+
O2
44.516
↔
↔
2NO2
89.031
4(c)
3NO2
89.031
+
+
H2O
29.677
↔
↔
2HNO3
59.354
3(d)
2NO
29.677
+
+
O2
14.839
↔
↔
2NO2
29.677
4(d)
3NO2
29.677
+
+
H2O
9.892
↔
↔
2HNO3
19.785
3(e)
2NO
9.892
+
+
O2
4.946
↔
↔
2NO2
9.892
4(e)
3NO2
9.892
+
+
H2O
3.297
↔
↔
2HNO3
6.595
3(f)
2NO
3.297
+
+
O2
1.649
↔
↔
2NO2
3.297
4(f)
3NO2
3.297
+
+
H2O
1.099
↔
↔
2HNO3
2.198
3(g)
2NO
1.099
+
+
O2
0.550
↔
↔
2NO2
1.099
4(g)
3NO2
1.099
+
+
H2O
0.366
↔
↔
2HNO3
0.733
+
+
NO
89.031
+
+
NO
29.677
+
+
NO
9.892
+
+
NO
3.297
+
+
NO
1.099
+
+
NO
0.366
Molality
m
mol/kg
kg
0.000
2390.400
82850.600
1954.360
9336.342
10032.384
8208.314 12.987
114772.4
Amount of secondary air
Oxygen in secondary air
Nitrogen in secondary air
O2 avialable
O2 reacted
O2 in tail gas
N2 in tail gas
NO in tail gas
NO2 in tail gas
=
=
=
=
=
=
=
=
=
608.023
127.685
480.338
202.38
99.0715
103.31
3439.29
0.36638
1.01482
kmol/h
kmol/h
kmol/h
kmol
kmol
kmol
kmol
kmol
kmol
Absorbed NO2
Absorbed NO2
Necessary stoichiometric amount of water
Amount of HNO3 formed
Amount of HNO3 in weak acid stream
=
=
=
=
=
Total HNO3 produced
=
Water required to dilute HNO3 to 65%
=
Total water required
=
400.092
18404.2
133.364
266.728
130.29
397.02
25012.18
13468.1
748.228
881.592
kmol
kg
kmol
kmol
kmol
kmol
kg
kg
kmol
kmol
Input - 17
Input - 18
HNO3 (45%)
Gases
kg/kgmol kmol/h
kg/h
Comp. kmol/h
kg/h
NH3
17.000
O2
32.000
74.70 2390.40
N2
28.000
2958.95 82850.60
NO
30.000
65.15 1954.36
NO2
46.000
202.96 9336.34
H2O
18.000 557.35 10032.38 0.55
0.00
0.00
HNO3 (45%) 63.000 130.29 8208.31 0.45
HNO3 (65%) 63.000
Total
297.000 687.65 18240.70 1.00 3301.76 96531.70
Components
M.W
Output - 21
Tail Gases
kmol/h
kg/h
Comp.
44 | P a g e
103.31 3306.03
3439.29 96300.07
0.37
10.99
1.01
46.68
0.0332
0.9662
0.0001
0.0005
3543.98 99663.78
1.00
Comp.
Input - 05
Secondary Air
kmol/h kg/h
Comp.
0.02
0.86
0.02
0.10
0.00
127.68 4085.92
480.34 13449.47
0.23
0.77
1.00
608.02 17535.39
1.00
Assumption
Assumption
Input - 19
Makeup Water
kmol/h
kg/h
Input
Total
kmol/h
kg/h
0.00
0.00
202.38 6476.32
3439.29 96300.07
65.15
1954.36
202.96 9336.34
324.24 5836.27 881.59 15868.65
130.29 8208.31
0.00
324.24 5836.27 4921.67 138144.06
Output - 20
Output
Molality
Liquid Stream
Total
m
kmol
kg
Comp. kmol/h
kg/h
mol/kg
0.00
0.00
103.31 3306.03
3439.29 96300.07
0.37
10.99
1.01
46.68
748.23 13468.10 0.35 748.23 13468.10
0.00
397.02 25012.18 0.65 397.02 25012.18 29.47846
1145.25 38480.28
4689.23 138144.06
3.1.4.4.
Tail Gas Reactor
Table 8: Tail Gas Reactor
5
4NO
0.3663
+
+
4NH3
0.36628
+
+
O2
0.09157
→
→
4N2
0.36628475
+
+
6
3NO2
1.0147
+
+
4NH3
1.353
→
→
(7/2)N2
1.18384
+
+
6H2O
2.0294
Components
NH3
O2
N2
NO
NO2
H2O
HNO3
Total
45 | P a g e
M.W
kg/kgmol
17
32
28
30
46
18
63
234
Input - 24
kmol
kg
1.7192 29.2272
103.31 3306.03
3439.29 96300.1
0.3664 10.9915
1.0148 46.6817
3545.7
99693
Output - 25
kmol
kg
103.222
3440.84
0.0001
0.0001
2.579
3303.1
96343.5
0.003
0.0046
46.4196
3546.639369
99693
6H2O
0.54943
3.2.
Energy Balance
The Energy balance gives the account of all the energy requirement of the process which is
based on the principle of conservation of energy. The principle states that energy can either be
create nor destroyed but can be transformed from one form to another. Also, energy can be
transferred from one body to another.
If a plant uses more energy than its competitor, its product could be priced out of the market.
Accountability of the energy utilization of a process plant is necessary in every design project.
The conservation of energy however differs from the mass in that energy can be generated (or
consumed) in a chemical process. Material can change form; new molecular specie can be
formed in a process unit and must be equal to the one out at steady state. The same is not true
for energy. The total enthalpy of the outlet stream will not be equal to that of the inlet stream
if energy is generated or consumed in the processes, such as that due to heat of reaction.
Energy can exist in various forms: head, mechanical, electrical energy, and it is the total energy
that is conserved. In plant operation, an energy balance on the plant will show the patterns of
energy usage and suggest area for conservation and saving.
3.2.1.
Energy Balance Assumptions
o
The process is at steady state
o
No heat is lost from the vessel and from the pipe i.e., there is proper lagging.
o
Effect of pressure on enthalpy is ignored.
o
Potential and kinetic energy changes are negligible.
46 | P a g e
3.2.2.
Summary of Energy Balance
3.2.2.1.
Compressor
Table 9: Compressor
Molar Flowrate
Inlet - 01 Temperature
Inlet Pressure
Outlet
Pressure
Assumed
Temperature
F
Ti
Pi
Po
Ta
Componentts
Air
kmol/h
oC
K
kPa
kPa
K
4343.023256
25
298.15
101.325
400
500
Calculated
Outlet
<Cp>s/R
<Cp>H/R
T'o
K
3.568272304
438.0852754
3.554417912
Compressor
Efficiency
3.2.2.2.
Corrected
Heat Capacity
Iso Entropic
Work
<Cp>H
Cp
∆Hs
kJ/kmol.K
kJ/kmol.K
kJ/kmol
29.55143052
29.55143052
4135.287569
Work
h
0.75
Iso Enthalpic
Work
Outlet - 02 Temperature
∆H
W
W
To
kJ/kmol
kJ/h
MW
oC
K
5513.716759
23946200.11
6.651722253
211.5803672
484.7303672
Interstage Cooler
Table 10: Interstage Cooler
Molar Flowrate
Components
Fi
kmol/h
Inlet Temperature
Outlet Temperature
Enthalpies
Total Heat
Ti
Ti
To
To
H
Q̇
o
C
K
o
C
K
kJ/kmol
kJ/h
Air
4343.023256
211.5803672
484.7303672
150
423.15
1,820
7903381.362
CW
6978.537102
20
293.15
35
308.15
1,133
7903381.362
47 | P a g e
2nd COMPRESSOR
3.2.2.3.
Table 11: 2nd Compressor
Molar Flowrate
Inlet Temperature
Inlet Pressure
Outlet
Pressure
Assumed
Temperature
F
Ti
Pi
Po
Ta
Componentts
Air
kmol/h
oC
K
kPa
kPa
K
4343.02
150.00
423.15
350.00
600.00
500.00
Calculated
Outlet
<Cp>s/R
<Cp>H/R
T'o
K
3.61
491.24
3.61
Compressor
Efficiency
Corrected
Heat Capacity
Iso Entropic
Work
<Cp>H
Cp
∆Hs
kJ/kmol.K
kJ/kmol.K
kJ/kmol
30.02
30.02
2043.87
Work
h
0.75
3.2.2.4.
Iso Enthalpic
Work
Outlet Temperature
∆H
W
W
To
kJ/kmol
kJ/hr
MW
oC
K
2725.17
11835456.37
3.29
240.79
513.94
Ammonia Vaporizer
Table 12: Ammonia Vaporizer
Molar Flowrate
Components
Fi
kmol/h
Inlet - 06 Temperature
Ti
Enthalpies
Latent Heat per
mole
Heat
Total Heat
To
H

Q
Q̇
C
K
kJ/kmol
kJ/kmol
kJ/kmol
kJ/h
Outlet - 07 Temperature
Ti
To
C
K
o
o
NH3
416.7192444
10
283.15
10
283.15
0
31237.8884
31,238
13017429.25
CW
11494.14525
35
308.15
20
293.15
1,133
0
1,133
13017429.3
48 | P a g e
Ammonia Pre-Heater
3.2.2.5.
Table 13: Ammonia Pre-Heater
Molar Flowrate
Component
Inlet - 07 Temperature
Fi
kmol/h
Outlet - 08 Temperature
Enthalpies
Total Heat
To
H
Q̇
C
K
kJ/kmol
kJ/h
Ti
Ti
To
o
C
K
o
NH3
416.719
10
283.15
150
423.15
5,191
2163119.974
Hot Water
563.511
155
428.15
105
378.15
3,839
2163119.974
1st MIXER
3.2.2.6.
Table 14: 1st Mixer
Inlet (04 - 09) Temperature
Components
Outlet - 11 Temperature
Ti
Ti
To
To
(kmols)/hr
oC
K
oC
K
NH₃ (Gas)
415
150
423.15
O₂
784.35
204
423.15
198.6
471.75
N₂
2950.65
204
423.15
3.2.2.7.
Reactor
Table 15: Reactor
Flowrate
Components
Inlet - 11 Temperature
Outlet Temperature
Enthalpy
Total Heat
F
Ti
Ti
To
To
∆H
Q̇
kmol/h
oC
K
oC
K
kJ/kmol
kJ/hr
NH₃ (Gas)
415
198.6
471.75
320
593.15
5189.0379
2153450.725
O₂
784.35
198.6
471.75
320
593.15
5189.0379
4070021.869
N₂
2950.65
198.6
471.75
320
593.15
5189.0379
15311034.65
21534507.25
Steam
49 | P a g e
4012.448763
400
673.15
250
523.15
5366.9239
21534507.25
3.2.2.7.1.
Heat of Reactions
Table 16: Heat of Reactions
4NH3
4NH3
+
5O2
4NO
+
6H2O
Heat of reaction
=
-906000
kJ/kmol
Extent of reaction
=
99.6
kmol/h
Total Heat of reaction
=
-90237600
kJ/h
+
↔
3O2
↔
2N2
+
6H2O
Heat of reaction
=
-1267200
kJ/kmol
Extent of reaction
=
4.15
kmol/h
Total heat of reaction
=
-5258880
kJ/h
Total heat evolved due to reactions
Q
=
-95496480
kJ/h
Rise in temperature of reactants due to continuous reaction
Component
Inlet Temperature
Outlet Temperature
Ti
Ti
To
o
C
K
o
NH₃ (Gas)
320
O₂
N₂
Total Heat
To
Q̇
C
K
kJ/h
593.15
1082.463033
1355.613033
10587107.3
320
593.15
1082.463033
1355.613033
14382867.38
320
593.15
1082.463033
1355.613033
70526505.32
Total
95496480
Table 17: Heat to be removed
Heat to be removed
Component
Flowrates
F
Inlet Temperature
Outlet Temperature
Ti
Ti
To
o
C
K
o
NH₃ (Gas)
1082.463033
O₂
N₂
kmol/h
Total Heat
To
Q̇
C
K
kJ/h
1355.613033
850
1123.15
1648306.2
1082.463033
1355.613033
850
1123.15
2643933.255
1082.463033
1355.613033
850
1123.15
22084809.14
26377048.59
BFW
50 | P a g e
42185.72875
150
423.15
158
431.15
26377074.91
Table 18: Product Cooling
Product Cooling
Components
Flowrate
Inlet - 11 Temperature
Outlet - 12 Temperature
Enthalpy
Total Heat
F
Ti
To
∆H
Q̇
kmol/h
oC
K
oC
K
kJ/kmol
kJ/h
O₂
273.9
850
1123.15
320
593.15
14,966
4099310.33
N₂
2958.95
850
1123.15
320
593.15
16,417
48577959.75
NO
398.4
850
1123.15
320
593.15
14,382
5729748.144
H₂O
622.5
850
1123.15
320
593.15
19,659
12237961.12
70644979.34
BFW
3.2.2.8.
18462.24002
100
373.15
150
423.15
3826.46
70644979.34
Tail Gas Heater 01
Table 19: Tail Gas Heater 01
Inlet Molar
Flowrate
Component
Inlet - 21 Temperature
Fi
kmol/h
Outlet - 22 Temperature
Ti
Ti
To
o
C
K
o
Heat
To
Q̇
C
K
kJ/h
Tail Gas
3543.98
25
298.15
71.0512241
344.2012241
4752118.087
Air
4343.02
240.79
513.9430504
204
477.15
4752118.087
3.2.2.9.
Tail Gas Heater 02
Table 20: Tail Gas Heater 02
Molar Flowrate
Component
Fi
kmol/h
Inlet - 12 Temperature
Outlet - 13 Temperature
Ti
Ti
To
o
C
K
o
Total Heat
To
Q̇
C
K
kJ/h
Tail Gas
3543.982954
71.0512241
344.2012241
171.6037667
444.7537667
10432818.81
NO Stream
4253.75
320
593.15
240
513.15
10432818.81
51 | P a g e
3.2.2.10. Economizer
Table 21: Economizer
Molar Flowrate
Component
Fi
kmol/h
Inlet - 13 Temperature
Outlet - 14 Temperature
Ti
Ti
To
o
C
K
o
Total Heat
To
Q̇
C
K
kJ/h
BFW
3428.903973
50
323.15
100
373.15
12892740.62
NO Stream
4253.75
240
513.15
140
413.15
12892740.62
3.2.2.11. Cooler
Table 22: Cooler
Component
Molar Flowrate
Fi
kmol/h
Inlet - 14 Temperature
Outlet - 15 Temperature
Ti
Ti
To
o
C
K
o
Total Heat
To
Q̇
C
K
kJ/h
BFW
2262.597543
20
293.15
50
323.15
5115928.265
NO Stream
4253.75
140
413.15
100
373.15
5115926.695
+
O2
↔
2NO2
Heat of reaction
=
-114140
kJ/kmol
Extent of reaction
=
199.2
kmol/h
Total Heat of reaction
=
-22736688
kJ/h
2HNO3
+
NO
Heat of reaction
=
-138180
kJ/kmol
Extent of reaction
=
65.14534884
kmol/h
Total Heat of reaction
=
-9001784.302
kJ/h
3.2.2.12. Condenser
Table 23: Condenser
2NO
3NO2
52 | P a g e
+
H2O
↔
Inlet
Reference Temperature
Inlet - 15 Temperature
Enthalpy
Tr
Ti
∆H
Q
Components
oC
K
oC
K
kJ/kmol
kJ/h
O2
25
298.15
100
373.15
2,228
610381.0749
N2
25
298.15
100
373.15
2,185
6465045.091
NO
25
298.15
100
373.15
2,248
895791.7333
H2O (Vapor)
25
298.15
100
373.15
2,539
1580658.704
Outlet
Reference Temperature
Outlet (16 - 18) Temperature
Enthalpy
Total Heat
Tr
Ti
∆H
Q
Components
oC
K
oC
K
kJ/kmol
kJ/h
O2
25
298.15
40
313.15
443
33065.29404
N2
25
298.15
40
313.15
436
1290726.699
NO
25
298.15
40
313.15
450
29286.74743
NO2
25
298.15
40
313.15
570.69
115828.6281
H2O (Liquid)
25
298.15
40
313.15
1,131
630364.19
HNO3
25
298.15
40
313.15
1666.57
217138.6796
Heat of outlet streams at reference temperature
Q̇ o
=
2316410.239
kJ/h
Heat of inlet streams at reference temperature
Q̇ i
=
9551876.603
kJ/h
=
24590343.34
kJ/h
-31738472.3
kJ/h
-5826.64
kJ/kmol
-759156.9907
kJ/h
-7907285.957
kJ/h
Latent Heat of Water
Heat added due to reactions
Q̇ rxn
=
Heat added due to acid dilution
Q̇ dil
=
Total Heat Evolved
Q̇ e
=
Cooling Water
Molar Flowrate
Component
Fi
kmol/h
CW
53 | P a g e
6981.984786
Inlet Temperature
Outlet Temperature
Enthalpies
Total Heat
To
H
Q
C
K
kJ/kmol
kJ/hr
35
308.15
1,133
7,907,286
Ti
Ti
To
o
C
K
o
20
293.15
3.2.2.13. Pump
Table 24: Pump
Density of 45% HNO3 at 40 oC
Specific Volume
Inlet Pressure
Outlet
Pressure
Isoentropic Work
Pump Efficiency
Actual Work

V
Pi
Po
Ws
h
W
kg/L
kg/m3
m3/kg
cm3/kg
kPa
kPa
cm3.kPa/kg
kJ/kg
kJ/kg
1.257
1257
0.000795545
795.5449483
500
580
63643.59586
0.063643596
60%
0.10607266
Conversion
1
kJ
=
1000000
cm3.kPa
1000
L
-
1
m3
3.2.2.14. Secondary Air Cooler
Table 25: Secondary Air Cooler
Component
Molar Flowrate
Inlet
Temperature
Inlet
Temperature
Outlet
Temperature
Outlet
Temperature
Enthalpies
Total Heat
Fi
Ti
Ti
To
To
H
Q
o
C
K
o
C
K
kJ/kmol
kJ/hr
kmol/h
O2
127.68
204
477.15
40
313.15
4910.335007
626975.5544
N2
480.34
204
477.15
40
313.15
4798.93033
2305110.382
CW
2588.976738
20
293.15
35
308.15
1,133
2,932,086
3.2.2.15. Absorber
Table 26: Heat of Reactions in Absorber
54 | P a g e
2NO
+
O2
↔
2NO2
Enthalpy of
reaction
Enthalpy of
reaction
Extent of
reaction
Hr
=
-21.92
kJ/mol
Hr
=
-21920
kJ/kmol
e
=
99.0715065
kmol/h
Heat evolved
Q̇
=
-2171647.422
kJ/h
3NO2
+
H2O
↔
2HNO3
+
Enthalpy of
reaction
Enthalpy of
reaction
Extent of
reaction
Hr
=
-45.96
kJ/mol
Hr
=
-45960
kJ/kmol
e
=
133.3640489
kmol/h
Heat evolved
Q̇
=
-6129411.688
kJ/h
NO
Table 27: Absorber
Process gas stream - 18
Reference Temperature
Inlet Temperature
Enthalpy
Total Heat
Tr
Ti
∆H
Q̇
Components
oC
K
oC
K
kJ/kmol
kJ/h
O2
25
298.15
40
313.15
443
33065.29404
N2
25
298.15
40
313.15
436
36140347.58
NO
25
298.15
40
313.15
450
878602.42
NO2
25
298.15
40
313.15
571
115828.6281
37167843.93
Weak acid inlet - 17
Reference Temperature
Inlet Temperature
Enthalpy
Total Heat
Tr
Ti
∆H
Q̇
Components
oC
K
oC
K
kJ/kmol
kJ/h
H2O (Liquid)
25
298.15
40
313.15
1,131
630364.19
HNO3
25
298.15
40
313.15
1,667
217138.6796
847502.8697
55 | P a g e
Makeup Water - 19
Outlet Temperature
Inlet Temperature
Enthalpy
Total Heat
Tr
Ti
∆H
Q̇
Components
H2O (Liquid)
oC
K
oC
K
kJ/kmol
kJ/h
25
298.15
40
313.15
1,131
366709.9107
Secondary Air - 05
Reference Temperature
Inlet Temperature
Enthalpy
Total Heat
Tr
Ti
∆H
Q̇
Components
oC
K
oC
K
kJ/kmol
kJ/h
O2
25
298.15
40
313.15
443
56518.58399
N2
25
298.15
40
313.15
436
209528.9078
266047.4917
Heat of outlet streams at reference temperature
Q̇ o
=
0
kJ/h
Heat of inlet streams at reference temperature
Q̇ i
=
38281394.29
kJ/h
Heat added due to reactions
Q̇ rxn
=
-8301059.11
kJ/h
-12229.48
kJ/kmol
Heat added due to acid dilution
Q̇ dil
=
-4855333.419
kJ/h
-13156392.53
kJ/h
Total Heat Evolved
Q̇ e
=
Cooling Water
Inlet
Temperature
Outlet
Temprature
56 | P a g e
Ti
=
293.15
K
To
=
308.15
K
Enthalpy
H
=
1.13E+03
kJ/kmol
CW Flowrate
F
=
11616.84717
kmol/h
Heat Absorbed
Q̇ a
=
13156392.53
kJ/h
Q̇ e - Q̇ a
=
0.00
3.2.2.16. 2nd MIXER
Table 28: 2nd Mixer
Inlet (04 - 09) Temperature
Components
Outlet - 11 Temperature
Ti
Ti
To
To
(kmols)/hr
oC
K
oC
K
NH₃ (Gas)
1.71924444
150
423.15
O₂
103.3133772
171.6037667
444.7537667
N₂
3439.29
171.6037667
444.7537667
174.732
447.882
NO
0.36638475
171.6037667
444.7537667
NO2
1.014819767
171.6037667
444.7537667
3.2.2.17. Tail Gas Reactor
Table 29: Tail Gas Reactor
3NO2
4NO
+
4NH3
→
(7/2)N2
+
Enthalpy of
reaction
Enthalpy of
reaction
Extent of
reaction
Hr
=
-1366
kJ/mol
Hr
=
-1366000
kJ/kmol
e
=
0.338239922
kmol/h
Heat evolved
Q̇
=
-462035.7341
kJ/h
+
4NH3
+
O2
→
4N2
Enthalpy of
reaction
Enthalpy of
reaction
Extent of
reaction
Hr
=
-1627.36
kJ/mol
Hr
=
-1627360
kJ/kmol
e
=
0.091571187
kmol/h
Heat evolved
Q̇
=
-149019.2876
kJ/h
57 | P a g e
+
Total heat of
reaction
∆Hrxn
=
-611055.0217
kJ/h
Heat Evolved
Q̇ e
=
611055.0217
kJ/h
0.0000
6H2O
6H2O
Reference Temperature
Components
Inlet - 24 Temperature
Enthalpy
Heat
Tr
Tr
Ti
Ti
∆H
Q
oC
K
oC
K
kJ/kmol
kJ/hr
NH3
25
298.15
174.732
447.882
5.68E+03
9.76E+03
O₂
25
298.15
174.732
447.882
4491.9524
464078.7690
N₂
25
298.15
174.732
447.882
4374.4431
15044971.46
NO
25
298.15
174.732
447.882
4500.4054
1648.8799
NO2
25
298.15
174.732
447.882
6000.3696
6089.2937
15526552.4313
Reference Temperature
Components
Outlet - 25 Temperature
Enthalpy
Heat
Tr
Tr
To
To
∆H
Q
oC
K
oC
K
kJ/kmol
kJ/hr
O₂
25
298.15
180.5628845
453.7128845
4670.5518
482102.7885
N₂
25
298.15
180.5628845
453.7128845
4545.9281
15641804.42
NO
25
298.15
180.5628845
453.7128845
4677.0066
0.467700662
NO2
25
298.15
180.5628845
453.7128845
6248.0668
0.624806683
H2O
25
298.15
180.5628845
453.7128845
5312.0835
13699.15508
16137607.45
3.2.2.18. Tail Gas Turbine
Table 30: Tail Gas Turbine
Inlet - 25 Temperature
components
Outlet Temperature
Ti
Ti
To
To
oC
K
oC
K
kJ/kmols
kJ/h
O2
180.5628845
453.7128845
100
373.15
2420.818632
249881.2712
N2
180.5628845
453.7128845
100
373.15
2360.394164
227408583
NO
180.5628845
453.7128845
100
373.15
2406.660537
7.219981611
NO2
180.5628845
453.7128845
100
373.15
3269.612306
0.326961231
H2o
180.5628845
453.7128845
100
373.15
2764.014431
7128.024661
Total
58 | P a g e
ΔH
Ws
227665599.9
W
W
MW
170749199.9
47.4303333
Chapter 04: Equipment Design
4.1.
Vaporizer
4.1.1.
Introduction
Heat exchangers are components that allows heat exchange from one fluid to another. No
direct contact between the fluids that are exchanging heat.
Heat exchange can simply be installed in one phase, also they can be installed in two phase heat
transfers, i.e., Phase of any fluid can be changed according to industrial requirements. High
fluid velocity, high turbulence, high surface area and a large temperature differential all
contribute to more efficient heat transfer, and this feature is necessary for selection of heat
exchanger. Most commonly used exchangers are double pipe, plate and shell and tube heat
exchangers. However, different designs are more efficient than others depending on their
specific application.
In current case, as phase change will occur for ammonia coming from the storage tank. So,
for this purpose we are using vaporizer in addition with the vaporization zones.
4.1.2.
Types of Heat Exchangers
The most common types of heat exchangers are:
o
Shell and Tube heat exchanger
o
Double pipe heat exchanger
o
Plate type heat exchanger
4.1.3.
Applications of Heat Exchangers
Heat exchangers are widely used in:
o Chemical industries
o Petroleum refineries
o Petrochemical plants
o Power stations
o Refrigeration
59 | P a g e
4.1.4.
Comparison between Heat Exchangers
Table 31: Heat Exchangers Comparison
Plate Heat Exchangers
Double Pipe Heat
Shell and Tube Heat
Exchangers
Exchangers
These are used for food
These
are
processing and for close
industrial cooling purposes
preheating,
loop to open loop water
and for low heat transfer
purposes, steam generation
cooling.
coefficients.
and vapor heat recovery.
Plate heat exchangers are
Long flow length and pure
capable of handling low
counter-current flow make
pressure fluids but at high
it
flow rates.
temperature cross
suited
used
with
for
large
Plate Heat exchangers are
preferred due to better heat
transfer,
maintenance,
easier
and
more than 50m2
4.1.5.
are
used
for
vaporizing
Suitable for all kinds of
duty, one phase or twophase heat transfer.
Can be designed for any
Can
be
designed
for
pressures up to 125 bars.
compactness.
Cannot be used for area
These
high
combination
of
temperatures and pressures
due to their aerodynamic
design.
Due to the single tube
present, there heat transfer
coefficient are small.
Can be used for area more
than 50m2
Exchanger Selection
Due to above-described benefits for larger area, more heat transfer coefficient, excessive design
expert availability and reasonable costing, shell and tube heat exchangers are mostly used. In
current case study, to vaporize and for heating purposes, shell and tube heat exchanger is best
option from all other exchangers.
For shell and tube heat exchanger, the design specification is described below, which are
finalized after iterations and according to ammonia-steam system requirements remaining
within limitations of temperatures, pressures and flow rates at shell and tube side.
o Counter-current flow of two fluids, so that maximum heat transfer can be availed.
60 | P a g e
o Shell pass is two, as it can meet heat transfer requirements.
o 0.03275 m square pitch (Pt) is used here. It is best choice for removable bundles, also have
advantage of allowing mechanical cleaning of outside surfaces of tubes.
o Impingent plates are installed to shield plates under inlet nozzle to avoid direct impact of
fluid on surfaces of tubes because here vapors-liquid stream are involved
o Pull through floating head is used. Advantage is that tube exteriors and interiors are
mechanically or chemically cleaned easily.
o TEMA Standard: BEU TEMA standard is used here. Reason is that here even number of
tube passes(n=2) exist, on tube side there is steam is used and also there is not any
temperature cross exist.
4.1.6.
Design Steps
4.1.6.1.
Fluid Allocation
o On Tube Side:
Cold fluid is Ammonia
Ti = 283 K
To = 283 K
Pressure = 6 bar
Mass flow rate= 1.967 kg/s
o
ON SHELL SIDE
Hot fluid water which is to be kept on shell side.
Table 32: Shell and Tube Properties
Dimensions
Values
Tube Side
61 | P a g e
Outer diameter
0.0254 m
Inner diameter
0.022098
Pitch(square)
0.03175 m
BWG
16
Number of passes
4
Flow area/tube
0.0005032 m2
Shell Side
o
Shell diameter
0.9398 m
Baffle spacing
0.127m
No of passes
2
Shell and Tube Data
Normally the selection of tubes is made based on availability of tubes in the inventory storage. Here
we select the tube of 0.03175 m square Pitch having 0.0254 m OD and 16 BWG. Inner diameter of
above mentioned.
4.1.6.2.
Calculation Of LMTD
Here,
𝜃1 = 𝑇1 − 𝑡2
𝜃2 = 𝑇2 − 𝑡1
Table 33: Calculation of LMTD
4.1.6.3.
T(in)
308
°K
T(out)
293
°K
t(in)
283
°K
t(out)
283
°K
LMTD
16.370
°K
Properties
Dimensions
Values
Hot Fluid
62 | P a g e
Cp
74.2095 J/mol.K

0.08642 Pa.s
K
0.609777 W/m.K

993.772 kg/m3
Dimensions
Values
Cold Fluid
4.1.6.4.
Cp
37.1498 j/molk

0.0969 pa.s
K
0.0233642 W/mk

4.576 kg/m3
Tube Side Calculation
o Flow area
𝑁𝑡×𝑎𝑡′
at =
at = 0.000532929 m2
144𝑛
o Mass Velocity
𝑤
Gt = 𝑎𝑡
Gt = 3692.42403
𝐾𝑔⁄
𝑚2 . 𝑠
o Reynold Number
Re =
𝐼.𝐷 ×𝐺𝑡
Re = 842.0555854
𝜇
From Re
JH = 2.5
o Heat Transfer Coefficient
ℎ𝑖
∅𝑡
=
𝑘 𝐶𝑝𝜇
JH ( )(
𝐷
𝑘
)1⁄3
=
135.752
Assume
∅=(
hi’
𝜇
𝜇𝑤
)0.14 = 1
= 135.7519391 W/m2.s.k
hio’
Uio’
𝐼.𝐷
= hi’ × 𝑂.𝐷 = 118.104187 W/m2.s.k
=
ℎ𝑖’
2
= 59.052 0935 W/m2.s.k
𝜇𝑤 = 0.0302 Pa.s
Now
∅
=
𝜇
(𝜇𝑤) 0.14 =
1.177292444
o Heat Transfer Coefficient
hio = hio’ × ∅ = 139.043 W/m2.s.k
o Flow area
as =
63 | P a g e
𝐼.𝐷 ×𝐶′𝐵
144𝑃𝑡
C’ = Pt - O.D = 0.00635
as = 0.00016577 m2
o Mass velocity
Ga =
𝑤
𝑎𝑠
= 346684.5853 Kg/m2.s
o Reynold Number
Re =
(𝑃𝑡2−
De =
𝐷𝑒×𝐺𝑎
𝜋×𝑂.𝐷2
)
4
𝜋×𝑂.𝐷
𝜇
= 0.000506451 m
Re = 100921.739
From Re
JH = 15
o Heat Transfer Coefficient
ℎ0
𝑘 𝐶𝑝𝜇
= JH( )(
∅𝑡
𝐷
𝑘
)1⁄3
= 796.584
Assume
ho’
= 796.583 W/m2.s.k
Uo'
=
ℎ𝑜′
2
∅=(
𝜇
𝜇𝑤
).14 = 1
= 398.293 W/m2.s.k
𝜇𝑤 = 0.02574 Pa.s
Now
∅=(
𝜇
𝜇𝑤
) 0.14 = 1.184788
o Heat Transfer Coefficient
ho = ho’ × ∅ = 943.785 W/m2.s.k
o Clean overall coefficient
Uc =
ℎ𝑖𝑜ℎ𝑖
ℎ𝑖𝑜+ℎ𝑖
= 121.1889865 W/m2.s.k
o Design overall coefficient
Ud =
𝑄
𝐴∆𝑇
= 118.0396548 W/m2.s.k
o Dirt Factor Rd
Rd
=
𝑈𝑐−𝑈𝑑
𝑈𝑐𝑈𝑑
= 0.00022 W/m2.s.k
64 | P a g e
4.1.6.5.
Pressure Drop Calculations
o Tube Side
From Re
f = 0.00065 ft2/in2
s = 3.587893994
∆𝑃𝑡 =
𝑓𝐺𝑡2𝐿𝑛
5.22×1010𝐷𝑠∅
= 1.82526E-07 psi
From Gt
𝑉2
2𝑔’
=
0.204816
4𝑛𝑉2
∆𝑃𝑟 = 𝑠 ×2𝑔’ = 2.185 psi
∆PT = ∆Pt + ∆Pr = 2.185 psi
o Shell side calculation
From Re
f = 0.0312 ft2/in2
s = 0.993772
No. of crosses
N+1 = 𝐿⁄𝐵 = 48.
∆P =
4.1.6.6.
𝑓𝐺𝑎2𝐷𝑠(𝑁+1)
5.22×1010𝐷𝑒𝑠∅
= 5.25106611 psi
Material of Construction
o Tube sheets meets both fluids, so they should be of corrosion resistant materials. High
quality electro-resistance welded tubes display good grain structures atweld joints.
o Shell is made from steel material. As there is not any chances of corrosion at shell side,so
it is best material for construction economically.
o Bonnets regulate the flow of fluid in tube-side circuit, they are typically fabricated or cast
o Baffles are usually punched or machined drilled. Material selection must be compatiblewith
shell side fluid to avoid failure due to corrosion. On shell side, there is very less probability
of corrosion, so its construction will be from same material as with which shell is
constructed.
65 | P a g e
4.2.
Reactor
4.2.1.
Theory of Reactors
Reactor theory is divided into two categories: (1) theory of reactors and (2) theory of reactors
and their applications.
Before we can proceed with the design of the reactor, we must first understand what a reactor
is. What is the total number of different types of reactors? What are the selection criteria for a
nuclear reactor and how are they determined?
4.2.2.
Chemical reactors
Chemical reactors are vessels that are used in the field of chemical engineering to contain
chemical reactions. The reactants contained within a reaction vessel, also known as a reaction
vessel, are substances that change form because of a chemical reaction.
4.2.3.
Types of reactors
There are several different types of reactors, each with its own set of characteristics. Type of
reactor based on treatment (tubular, fixed bed, stirred tank, fluidized bed), and operation mode
based on treatment (tubular, fixed bed, stirred tank, fluidized bed) (Batch, Continuous, Semi
batch). As a result, we will go over them one by one.
4.2.4.
Fixed-bed reactors
These reactors make use of solid-catalyst-containing vessels. They may result in significant
pressure drops because of their design. These units are most frequently used in heterogeneous
catalysis, in which the catalyst and reacting species are in distinct phases of the same chemical
reaction. One of the most significant advantages of these units in terms of maintenance and
regeneration is their simplicity and ease of access to the catalysts. Multiple fixed beds can
improve heat transfer and control, resulting in increased performance while retaining the
relative simplicity of this reactor configuration. Flow through fixed beds is frequently very
similar to plug flow.
4.2.5.
Reactors with fluidized bed
These reactors use a gas-phase working fluid that requires gas to fluidize through and pass fine
particles at a rate that is sufficient to fluidize the particles suspended in the interior of the
reactor. Due to the flow and suspension issues arising when fluidized reactors are operating,
there are significant operational difficulties related to initiation and operation of them.
Furthermore, due to the easy backflow in the gas, these reactor types have large residential
66 | P a g e
times and a similar behavior to that of CSTRs. Their many advantages include their ability to
process fine particles and their suitability for processes that require a high reaction rate.
4.2.6.
Thin or shallow bed reactors
These designations are reserved for reactors where the reactant fluid is forced by catalytic mesh
or fine catalyst beds. The simplicity of the reactors makes them especially suitable for fast
reactions that require accurate monitoring, when access to catalysts is critical for catalyst
reactivation or maintenance, or when high reaction heats are involved.
4.2.7.
Type of reactor to consider
When selecting the most appropriate reactor type for a given process, several important
considerations must be taken into account. Design considerations such as these, for example,
include the following:
A reaction's temperature and pressure are determined by the following factors:
o Requirement for the removal or addition of reactants and products.
o It is necessary to adhere to product delivery patterns (whether continuous or batchwise).
o For example, there are concerns about the need for solid catalyst particle replacement and
contact with fluid reactants and products when using catalysts.
o The relative cost of the reactor in terms of monetary value.
o Each type of reactor has its own set of limitations, which are listed below.
Aside from the obvious factors of cost and availability of space, there are a number of other
considerations that should not be overlooked. In many cases, the complex set of reactor
physical requirements that results can be met by employing a variety of reactor types, with
cost, safety, and other related concerns becoming the deciding factors in the choice of a reactor
type.
4.2.8.
The design challenge of reactor
4.2.8.1.
The issue at hand as follow
The reactor must be designed and constructed to produce sufficient nitric oxide by partial
oxidation of ammonia to meet the requirements of an acid plant with a daily production
capacity of 600 tons.
In the reactor, the following is a description of the process that takes place:
67 | P a g e
Nitric acid is produced by the catalytic oxidation of ammonia at high temperatures, which
accounts for a significant portion of the total nitric acid produced worldwide. There are three
major steps in this process: ammonia oxidation, nitric oxide oxidation, and absorption.
Ammonia oxidation is the first of these three steps. This procedure can be carried out under a
single or multiple pressure. Specifically, the single pressure process is the subject of this paper.
For the sake of favoring the reactions, newer processes typically operate at both low and high
pressure.
When producing nitric acid, ammonia is first vaporized in a vaporizer before being mixed
with compressed air and being sent to a shallow bed reactor, as illustrated in Figure 1. The
oxidation of ammonia will take place in the reactor, resulting in the production of nitrogen
monoxide. 840-880°C will be the temperature at which the reaction will take place in the
reactor. In the reactor, energy can be recovered by cooling it in a waste heat reboiler, which is
advantageous because of the high temperature involved.
There are three steps involved in the production of nitric acid:
o Catalytic oxidation of ammonia with atmospheric oxygen to yield nitrogen monoxide:
4NH3(g) + 502(g) → 4NO(g) + 6H2O (1)
o Oxidation of the nitrogen monoxide product to nitrogen dioxide or dinitrogen tetroxide:
2NO(g) + O2(g) → 2NO2(g)
Figure 2: Design of Reactors
68 | P a g e
4.2.8.2.
Kinetics of Ammonia Oxidation Reaction
At low temperatures or with deactivated catalyst, the chemical rate may be limited or partially
limited. With active catalyst, it is clear that high temperatures and high velocities will produce
essentially total ammonia conversion. The maximum temperature is limited by the catalyst loss,
which becomes far above 900°C. The loss per unit surface area is apparently a direct function
of feed temperature, mass flow rate, and ammonia/oxygen ratio.
The rate of ammonia oxidation can be written in terms of a mass-transfer coefficient with the
ammonia partial pressure at the catalyst surface assumed to be zero for this rapid reaction.
Table 34: Kinetic Eqs. of Ammonia Oxidation
-rA = KgA^s PA awR
Where PA is partial ammonia pressure in bulk fluid and awR is surface area per screen volume
unit.
4.2.9.
Design calculation
Assumptions:
There are following assumptions as:
o Steady State Flow.
o One Dimensional Plug Flow.
o Distribution of Concentration, Heat, Pressure and Temperature is uniform in each cross
section of the reactor.
o Isothermal Operation.
o No Side reaction is occurring in the system.
69 | P a g e
Design Calculations:
To determine the weight of the catalyst, bed volume and reactor volume, we will make use of
the following equations.
o PFR Design Equation
−𝑟𝐴 = k𝑔𝑚𝑜𝑙/kg cat.hr
R = J/gmol. K
k = k𝑔𝑚𝑜𝑙/kg cat.hr
T = 𝐾; 𝑃 = bar
By putting 𝑷𝒊= 𝒚𝒊𝑷 such as 𝑷A= 𝒚A𝑷 and so on. Further, yi= 𝒚io(𝑖 − XA) for reactant and
for products and then solving the kinetics:
yi = 𝒚io (𝑖 + XA)
I =Fi0/FA0
A=1
B=1.89
C=0
D=0
And yAO = 0.1
Assuming PFR
70 | P a g e
Table 35: Rate vs Conversion
Xa
-ra
1/-ra
0
7399.284848
0.000135148
0.096
6781.3509
0.000147463
0.192
6155.853847
0.000162447
0.288
5521.005888
0.000181126
0.384
4874.407551
0.000205153
0.48
4212.761624
0.000237374
0.576
3531.409984
0.000283173
0.672
2823.550674
0.000354164
0.768
2078.844209
0.000481037
0.864
1280.77015
0.00078078
0.96
401.1968387
0.002492542
𝑉/ 𝐹𝐴𝑂 = 𝐴𝑟𝑒𝑎 𝑢𝑛𝑑𝑒𝑟 𝑡ℎ𝑒 𝑐𝑢𝑟𝑣𝑒 =0.0003710663 𝑘𝑔𝑐𝑎𝑡. ℎ𝑟/𝑘𝑔𝑚𝑜𝑙
𝐹𝐴𝑜=4150𝑘𝑔𝑚𝑜𝑙/hr
𝑉𝑐𝑎𝑡=7.712 m3
𝜀=0.45
So, actual Volume of the reactor is,
71 | P a g e
𝑉𝑟𝑒𝑎𝑐𝑡𝑜𝑟 = Vcat/ (1− ε) =7.712 / (1−0.45) = 14.02 𝑚3
L/D=3
Length=5.43m
Diameter=1.81m
4.2.10.
Catalyst calculation
From literature
Mesh size, nw = 80 in^-1
Wire diameter, dw = 0.003 in.
Surface area per unit volume, awr = πlwnw^2
Therefore, awr = πnw^2 [(1/nw)^2 + dw^2 ]^1/2
= 258.5 in^-1
Wire area per gauze cross sectional area,
fw = awr 2dw
= (258.5)(2)(0.003)
= 1.55
o Calculating mass velocity, G:
G=Flowrate of gases/ Cross sectional area of catalyst needed
=20.7624 Kg/ (m2 * s)
o Calculating superficial velocity based on outlet conditions:
us = g/ρmixture
Average molecular weight,
M = 0.10(17) + 0.19(32) + 0.71(28)
= 27.67 kg/kmol
Operating pressure, P = 5.8 bar
Operating temperature, T = 850ºC = 1123.15K
ρ mixture = MP/RT
72 | P a g e
= 1717.788 g/m3
Therefore, us=1208.676 cm/s
=39.65 ft/s
o Number of Gauzes
From literature, at temperature, T = 800-900°C and pressure, P= 5-7 bar a quantity of 80 mesh
gauze (nw), with wire of 0.003 in. in diameter (dw), equivalent to 2 Troy oz/ton of acid
produced and a cross sectional area of 2.7547 sq ft/100 daily tons of HNO3 produced is
required. The equations below are used in calculating the number of gauzes.
where fw is the wire area per gauze cross-sectional area for one gauze, εw is porosity of mesh,
dw is wire diameter, µf is viscosity, yAo is initial gaseous mole fraction of A. Perfect plug flow
model is assumed in calculating the number of gauzes, which is approached in the unit with a
special gas distributor.
µf = (12.5 + 29.20 x 10-3T) x 10-5 g/cm.s
=0.00045296g/cm.s
Ns=12.31=13
o Height of Catalyst Bed
The height of catalyst bed needed in this detailed design project is calculated by:
hc = 2dw ns
height of catalyst bed for 13 guazes =0.198 cm
o Diameter Of Catalyst Bed
Gillespie and Kenson [3] proposed a method in determining the cross-sectional area of catalyst
bed. It is found that the area is 2.7547 sq ft/100 daily tons HNO3.
73 | P a g e
The diameter can be determined using:
From literature, cross sectional area
= 2.7547 sq ft/100 daily tons HNO3
Since daily production rate is 600 ton per Day
Area=16.5282 sq ft
So, diameter of catalyst bed=4.586ft
74 | P a g e
4.3.
Heat Exchanger
As it is evident from the term heat exchanger, we can say that these are devices used to
exchange heat between hot and cold fluid. They find wide range of applications from space
heaters to refrigerators and coolers.
4.3.1.
Types of heat exchangers
o Shell and tube heat exchangers
o Plate Heat Exchangers
o Direct Contact Heat Exchangers
o Double Pipe Heat Exchangers
o Air cooled Exchangers
o Fired heaters
4.3.2.
Criteria of selection for heat exchangers
Selection criteria of heat exchangers depend upon the field of application where to use them.
It includes the number of factors as:
o Efficiency
o Space
o Flow rate
o Heat duty
o Type of application
o Operating temperature and pressure range
o Overall cost
o Maintenance ease
o Availability
o Material Capability
o Fouling tendencies
75 | P a g e
4.3.3.
Shell and tube heat exchangers
Shell and tube heat exchangers are most widely used heat exchangers in chemical and allied
industries. They consist of number of tubes in series arrangement enclosed inside cylinder.
They have well established fabrication techniques. Shell and tube heat exchangers can operate
at high pressure conditions.
4.3.3.1.
Types of shell and tube heat exchangers
There are three basic types of shell and tube heat exchangers:
o Fixed Tube Sheet Type
o U-Tube (U-Bundle) Type
o Floating Head Type
4.3.4.
Design calculation
4.3.4.1.
Fluid allocation
o Tube side
I have placed NOx on tube side due to their corrosive nature and also there is formation of
nitric acid during cooling of gases which is too much corrosive so it is better choice to keep
gases on the tube side.
Damage to shell is avoided because it will result in loss of capital because shell is too much
costly to design.
o Shell Side
Due to small flow rate of cooling water, it is kept on shell side.
Shell Side Data
Flow rate of C.W
119.609
kg/s
Inlet Temperature of C.W
293.15
K
Outlet Temperature of CW
311.15
K
Tube Side Data
76 | P a g e
Flow rate of NOx
31.88122
kg/s
Inlet Temperature of NOx
373.15
K
outlet temperature of NOx
313.15
K
4.3.4.2.
Physical Properties
o Shell Side
Heat Capacity
=
cp
=
4.1279
KJ/Kg.K
Viscosity
=
μ
=
0.000837
Pa.s
Thermal conductivity
Density
=
=
k
ρ
=
=
0.611817
993.207
W/m.K
kg/m3
Heat Capacity
=
cp
=
1.07678
KJ/Kg.K
Viscosity
=
μ
=
0.000019706
Pa.s
Thermal conductivity
=
K
=
0.0272599
W/m.K
Density
=
ρ
=
5.27273
kg/m3
o Tube Side
LMTD Calculations
LMTD
ΔT1
ΔT2
T1-t2
T2-t1
LMTD
R
P
ΔT1-ΔT2/ln(ΔT1/ΔT2)
62
20
37.12208
T1-T2/t2-t1
t2-t1/T1-t1
3.333333
0.225
Now
For 1 shell pass and 2 tube passes
Correction Factor
Ft
Therefore
True LMTD
0.84
31.18255
o Tube Specification
Tube specifications are taken from PHT by Kern
Allowing for tube sheet thickness
77 | P a g e
L=
4.8768
m
do=
0.019
m
16
ft
4.8768
4.3.4.3.
Overall Heat Transfer Coefficient
Assumed heat transfer coefficient from table 12.1
Coulson and Richardson
U
Total Q = 9027.11
=
1050
W/m2.K
KW
Provisional Area
Q
𝐴 = U∗LMTD
=
A = 275.707 m2
Area of one tube = ᴨ*do*L
= 0.29095 m2
Number of tubes = 𝑁𝑇 =
Provisional Area
Area of one tube
NT = 948
o Heat Exchanger Layout
Type of Shell and Tube Heat Exchanger: BEM Type with 1 shell pass and 2 tube passes
Tube Layout: Triangular pitch
Baffles: Single Segmental baffles (with 25% Horizontal Baffle cut)
Number of Baffles = 20
Db
=
do(Nt/K1 )^(1/n1)
K1=0.249
n1=
Bundle diameter Db=
0.2491/2.207 =
2.207
0.796269787 m
818mm
bundle diametrical clearance=17mm
=0.017m
Shell Diameter
shell diameter
=Db+Clearance
=
0.81327
m
835
mm
32.01851
K1 and n1 are taken from Table 12.4 Coulson and Richardson
78 | P a g e
in
o Individual Heat Transfer Coefficients
Tube side coefficient
Tube cross-sectional
area=
di=
(ᴨ/4)*di2
0.015748 m
0.000195 m2
473.8055
0.09224 m2
tubes per pass=
Total flow area =
mass velocity of Nox =
Nox linear velocity
345.6324 kg/s.m2
=
5.55093 m/s
hi*di/Kf= jh*Re*pr0.33(μ/μw)0.14
Re=
Pr=
Nu
(ρ*ut*di)/μ
276211.2
(Cp*μ)/kf
0.000778
0.021*Re0.8*Pr0.33*(μ/μw)0.14
44.59739
st=
(Nu/Re*Pr)
0.207427
hi'=
ρ*Ut*Cp*St
77.19839 W/m2.K
hio'=hi*(di/do)
63.98528 W/m2.K
Uio'=
hio/2
Uio'=
79 | P a g e
31.99264 W/m2.K
For isothermal Φ=1
flow
1
Shell Side Heat Transfer
Coefficient:
Choose Baffle
Spacing=
Ds/5
De= (1.10/do)*(Pt20.917*do2)
0.013491 m
0.044262 ft
Re= 72864.72
Pr=
Tube pitch=1.25*do
0.02375 m
23.75 mm
Cross flow area
As=
0.026456 m2
0.005648
Gs
=
jh=
hs'=
Uo'=
4520.999 kg/s.m2
2.4*10-3
1436.891 W/m2.K
718.4457
Calculation of Wall Temperature and Actual Film
Coefficients
Kc = U'hfs/U'cfs-1
Kc
-0.95547
r = Δθcte/Δθhte
r
0.3
Fc = ((r/r-1)+(1/Kc)/(1+(ln(1+Kc))/(lnr)))-1/Kc
(r/r-1)+(1/Kc)
-1.47518
(1+(ln(1+Kc))/(lnr))
3.584431
Fc
0.635054
Caloric Temperature θc = θmin+Fc(θmax-θmin)
Tube Side
Shell Side
Tc
80 | P a g e
351.2533 K
tc
304.581 K
0.162654m
m
167mm
mm
6.419968in
in
Wall Temperature θw =
(hio'*Tc+ho'*tc)/(hio'+ho')
θw
306.5707 K
μw
μw
0.000626 Pa.s
0.000689 pa.s
Φ =(μ/μw)^.14
Φ = (μ/μw)^.14
Φ
Φ
0.616258
hio = hio'*Φ
hio
39.43141
1.027586
ho = ho'*Φ
ho
1476.529
Calculation of Clean Overall HT Coefficient
1/Uco = 1/hio+1/ho+do/2Kw*ln(do/di)
1/Uco =
Uco
=
0.0261
38.31392
For Steel
Kw=0.035 kJ/s.m.k Table12.6
Rfi = 0.003 m2.K/W
Rfo = 0.005 m2.K/W
Rfio = 0.00036 m2.K/W
Rdo = 0.00066 m2.K/W
Dirt Factors are taken from coulson and
Richardson Table 12.2
Overall Design Coefficient
1/Udo=1/Uco+Rdo
1/Udo=
Udo =
81 | P a g e
0.026762
37.36624
Pressure Drop Calculations
Tube Side
𝐿
𝜇
𝑢𝑡 2
∆P = 𝑁𝑝[8𝑗𝑓 ( ) ( ) + 2.5]𝜌
𝑑𝑖 𝜇𝑤
2
Where
Np=Number of tube side passes
Ut=Tube side velocity,m/s
L=Length of one tube
∆Pt=Tube side Pressure drop,Pa
Jf=Friction factor
Figure 3 Tube Side Heat Transfer Factor
Reynolds number
Re=
276211.2
Friction Factor
Specific gravity
jf=
s=
0.0022
4.304269
Putting values in formula gives
82 | P a g e
∆Pt=25.70208 Kpa
Shell Side
Re=
F=
S=
Ds =
Gs=
No. of crosses
N+1
=
=3.72764 psi
72864.7
2
0.001
0.99320
7
32.0185
1
4520.99
9
ft^2/in^2
in
kg/m^2*
s
2.66820
9 ft
3035.24 lb/ft^2*
4 s
N+1 = L/B
29.9066 29.9066
9
9
ΔPs = f*Gs^2*Ds(N+1) / 5.22*10^10*De*s*Φs
0.0083 psi
83 | P a g e
4.4.
Absorber
4.4.1.
Types of Absorption Column
There is many equipment that are used for vapor liquid mass transfer operations (absorption,
distillation etc.). Mostly there are two types of absorption columns used in the industrial applications
i.
Packed columns
ii.
Tray columns
What type of absorber is to use depends upon a number of factors? These factors are majorly classified
as following:
o Factors that depend on the system/process like scaling, foaming, corrosive nature of
components, fouling factor, pressure drop, liquid holdup
o Factor that depends upon the physical characteristics of the equipment and its
internals, e.g., size, weight, maintenance etc.
o Factors that depend upon the mode of operation, i.e. batch operation or continuous
operation.
4.4.2.
Comparison between Packed and Plate Towers
Tray columns and packed columns are two widely used equipment for distillation, absorption,
stripping and to some extent for liquid-liquid extraction. Each class has characteristic but quite
different column internals for achieving the intimate contact between the two phases. But the
mechanism by which gas-liquid contacting occurs in the tray towers is totally different that in a packed
tower. This gives rise to the difference in the operating features and the applications of these columns.
Some major differences between these two columns are presented here.
o Pressure Drop
The open area for the gas (or vapor) flow in a tray tower is typically 6 to 15% of the cross section of
tower, whereas that for a packed tower it is often greater than 50% of the tower cross section. For a
packed tower with structured packing, it is more than 90%. So, the pressure drop per theoretical stage
is much more in a tray tower than in a packed tower. It is about 3-5mm Hg per stage in a tray tower
which is more than three times the pressure drops per HETP for a tower filled with random packing
and more than ten times that of having structured packing.
84 | P a g e
o Compression Energy
The gas compression energy required for a packed tower is significantly lower than that in a tray tower.
This advantage of packed tower becomes particularly important in vacuum applications where packed
towers, particularly with structured packing, are the choice.
o Liquid holdup
For a tray tower the liquid holdup remains within 8 to 12% of tower volume against 1 to 6% in case of
a packed tower. So, the packed tower offers a smaller liquid residence time and is more suitable for
processing heat sensitive liquids.
o Corrosion
Ceramic and plastic packing materials are highly corrosion resistant. Even the shell of a packed tower
may be made of a few smaller pieced of ceramic shell with bell and spigot joints. The tray towers on
the other hand are made of metals and alloys and possess more internals. So, for a highly corrosive
service a packed tower is a choice.
o Foaming Liquids
It is difficult to process a foaming liquid in a tray tower since bubbling aggravates the problem of
foaming and flooding. The problem is less severe in a packed column.
o Suspended Solids
If the liquid has some suspended solids in it, then packing of a packed tower can chock due to
deposition of solids between the openings. A tray tower can handle a dirty liquid or a slurry with ease.
Also, it can be cleaned easily. But the cleaning of packing, particularly the structured ones, is difficult.
o Heat Removal
If there is an excessive heat generation, like in the case of reactive distillation or chemisorption,
necessitating intermediate cooling of a liquid, a tray tower is convenient. A tray can be provided with
a cooling coil without much difficulty. Sometimes a jacket around the column is installed in which
cooling media is introduced but that is a costly approach. Alternatively, the liquid from a tray may be
withdrawn, passed through an external cooler and fed to the next tray. However, the efficient cooling
can’t be achieved in a packed tower.
o High capacity
A packed tower can be operated at a low gas rate, but a tray tower is prone to weeping and liquid
dumping if the gas flow rate is insufficient.
85 | P a g e
On the other hand, a tray tower with suitable tray design can handle a large liquid rate that a packed
tower may not because of possible flooding. So, for high capacities, tray columns are preferred. A tray
tower can be made to function at a low liquid rate by using a reverse flow tray, but a packed tower
may not wet properly if the liquid rate is low. This limits the application of packed tower due to lack
of versatility.
To produce nitric acid, tray columns are widely used. The merits of the tray over the packed
columns are as follows:
o Plate columns are designed to handle a wide range of liquid flow rates without flooding
o For liquids containing suspended solids tray column are preferred choice.
o Dispersion difficulties are handled in the plate columns when flow rate of liquid is low as
compared to gas.
o For periodic cleaning a manhole is provided in a tray column, but the cleaning of a
packed tower is quite difficult.
o For non-foaming liquids tray columns are used.
o Design information of tray column is more readily available and more reliable than for
packed columns.
o For columns of large height, the weight of the packed column can be more than the plate
column.
o Inter-stage cooling is possible in tray columns
o For large temperature changes tray towers are preferred because thermal expansion or
contraction of the equipment components may crush the packing material.
4.4.3.
Column Type Selection
I have selected tray column for nitric acid production due to its:
o High capacity
o High liquid and gas flow rates
o Ease of heat removal (as absorption releases heat, so an efficient heat removal mechanism
is required to maintain the absorption column at desired constant temperature by extracting
the heat of absorption)
o Ease of cleaning
86 | P a g e
4.4.4.
Types of Tray Columns
There are three major types of tray columns.
o Bubble cap tray
o Sieve tray
o Valve tray
Selection of the type of tray column is very important. A comparison is given in “Principles of Mass
Transfer and Separation Processes” by Binay K. Dutta, which is as follows
Table 36: Types of Tray Columns
Parameter
Bubble Cap Tray
Sieve Tray
Valve Tray
Capacity
Moderate
High
High to very high
Efficiency
Moderate
High
High
Entrainment
High (about three
times that of sieve
tray)
Moderate
Moderate
Pressure Drop
High
Moderate
Moderate
Turndown
Excellent (can
operate at a low
capacity)
About 2 (not
suitable to operate
at variable loads)
4-5
Fouling
Tendency
High, tends to collect
solids
Low
Low to Moderate
Cost
High (about two to
three times that of
sieve tray)
Low
About 20% more
than sieve tray
Applications
Rarely used in new
columns, may be
used if low flow
rates are anticipated
Most applications if
turndown is not
important
Preferred is a high
turndown
is anticipated
Share of Market
About 5%
About 25%
87 | P a g e
About 70%
4.4.5.
Tray Type Selection
I have selected sieve tray column for my application due to
o High capacity
o High efficiency
o Moderate pressure drop requirement
o Low fouling
o And most importantly low cost than two others
4.4.6.
Design Steps
4.4.6.1.
Solubility Data
Components
A
B
C
D
O2
Oxygen
-171.2542 8391.24 23.24323
0
N2
Nitrogen
-181.587 8,632.13 24.7981
0
NO
Nitric Oxide
Perry Chemical Engineer's Hanbook
NO2 Nitrogen Dioxide
Nist Webbook
4.4.6.2.
x (g/ 100 g of water)
0.000019
0.000010
0.0044
0.00847
Calculation of Theoretical no. of Trays
First, Henry’s Law Constant is obtained through NIST Webbook
H = 118.064 kPa
Calculation of K-value
𝐾=
𝐻
118.064
=
= 0.204
𝑃
580
Calculation of absorption coefficient
𝐴=
𝐿
1011.88
=
= 1.271
(0.204) ∗ (3909.78)
𝐾𝑉
NO2 fraction not absorbed = 0.002
No. of theoretical trays
∅=
𝐴−1
−1
𝐴𝑛 +1
nt = 23.6
88 | P a g e
H (kPa)
4,397,505
8572095.00
227.27273
118.06375
4.4.6.3.
Tray efficiency and Actual no. of Trays
𝐾𝑀𝐿 𝜇𝐿
𝐾𝑀𝐿 𝜇𝐿 2
)] − 0.0896 [log (
)]
log 𝐸𝑜 = 1.597 − 0.199 [log (
𝜌𝐿
𝜌𝐿
Average MW of liquid = ML = 8.209 kg/kmol\
Density of liquid = L = 68.84 lb/ft3
Yaw’s Handbook
Viscosity = L = 0.877 cP
Perry’s Handbook
Tray efficiency = Eo = 47.94
Seader and Henly, 4th Ed.
𝐴𝑐𝑡𝑢𝑎𝑙 𝑛𝑜 𝑜𝑓 𝑡𝑟𝑎𝑦𝑠 = 𝑛𝑎 =
4.4.6.4.
𝑛𝑡
= 49
𝐸𝑜
Tray Spacing
Tray spacing is assumed to be 45 cm as per guidelines in Chemical Engineering Design by
R.K Sinnott.
4.4.6.5.
Height of Column
Height of trays is 22.05 m, calculated using no. of trays and tray spacing. For removal of
entrained liquid, a margin of 1.22 m is provided above top tray and to incorporate bottom liquid
surge capacity a margin of 3.048 m below the last tray is provided. All of this makes total
column height to be 26.318 m.
4.4.6.6.
Calculation of Flooding Velocity
Average MW of gas mixture = Mv = 29.175 kg/kmol
Average MW of liquid mixture = ML = 26.526 kg/kmol
Density of gas mixture = v = 6.530 kg/m3
Density of liquid mixture = L = 1102.715 kg/m3
𝐸𝑛𝑡𝑟𝑎𝑖𝑛𝑚𝑒𝑛𝑡 𝑓𝑙𝑜𝑜𝑑𝑖𝑛𝑔 𝑓𝑎𝑐𝑡𝑜𝑟 = 𝐹𝐿𝑉 =
89 | P a g e
𝐿𝑀𝐿
𝜌𝑣 0.5
∗ ( ) = 0.018
𝑉𝑀𝑉 𝜌𝐿
Flooding correction factor is calculated using above graph, with a tray spacing of 18”.
Flooding correction factor = CF = 0.280 ft/s
Surface Tension = s = 70.541 dynes/cm
𝜎 0.2
) = 1.286
20
𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑡𝑒𝑛𝑠𝑖𝑜𝑛 𝑓𝑎𝑐𝑡𝑜𝑟 = 𝐹𝑆𝑇 = (
Foaming factor = FF = 0.9
FHA = 1
𝐶 = 𝐹𝑆𝑇 𝐹𝐹 𝐹𝐻𝐴 𝐶𝐹 = 0.234
𝐹𝑙𝑜𝑜𝑑𝑖𝑛𝑔 𝑉𝑒𝑙𝑜𝑐𝑖𝑡𝑦 = 𝑢𝑓 = 𝐶 (
𝑓𝑡⁄
𝑠
1⁄
2
𝜌𝐿 − 𝜌𝑉
)
𝜌𝑉
= 4.201
𝑓𝑡⁄
𝑠
85% flooding is assumed at maximum flowrate.
𝐴𝑐𝑡𝑢𝑎𝑙 𝐹𝑙𝑜𝑜𝑑𝑖𝑛𝑔 𝑉𝑒𝑙𝑜𝑐𝑖𝑡𝑦 = 𝑢𝑎𝑓 = 𝑢𝑓 ∗ 0.85 = 3.571
4.4.6.7.
𝑓𝑡⁄
𝑚
𝑠 = 1.088 ⁄𝑠
Column Diameter
Gas volumetric flowrate = FV = 4.852 m3/s
𝑁𝑒𝑡 𝐴𝑟𝑒𝑎 = 𝐴𝑛 =
𝑢𝑎𝑓
= 4.458 𝑚2
𝐹𝑣
𝐶𝑟𝑜𝑠𝑠 𝑆𝑒𝑐𝑡𝑖𝑜𝑛𝑎𝑙 𝐴𝑟𝑒𝑎 = 𝐴𝑐 =
𝐴𝑛
= 5.245 𝑚2
0.85
𝐷𝑜𝑤𝑛𝑐𝑜𝑚𝑒𝑟 𝐴𝑟𝑒𝑎 = 𝐴𝑑 = 𝐴𝑐 ∗ 0.15 = 0.787 𝑚2
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𝐴𝑐 =
𝜋 2
𝐷
4 𝑐
𝐶𝑜𝑙𝑢𝑚𝑛 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟 = 𝐷𝑐 = 2.585 𝑚
4.4.6.8.
No. of holes/Hole pitch
𝐴𝑐𝑡𝑖𝑣𝑒 𝐴𝑟𝑒𝑎 = 𝐴𝑎 = 𝐴𝑐 − 2(𝐴𝑑 ) = 3.671 𝑚2
Hole area is 10% of active area
𝑇𝑜𝑡𝑎𝑙 𝐻𝑜𝑙𝑒 𝐴𝑟𝑒𝑎 = 𝐴ℎ = 0.1 ∗ 𝐴𝑎 = 0.367 𝑚2
Hole diameter is assumed to be 0.006 m / 0.6 cm, from Chemical Engineering Design by R.K
Sinnott.
𝐻𝑜𝑙𝑒 𝐴𝑟𝑒𝑎 = 𝑎ℎ =
𝜋 2
𝑑 = 0.0000283 𝑚2
4 ℎ
𝑇𝑜𝑡𝑎𝑙 𝑛𝑜. 𝑜𝑓 𝐻𝑜𝑙𝑒𝑠 = 𝑁ℎ =
𝐴ℎ
= 12984.711
𝑎ℎ
𝑁𝑜. 𝑜𝑓 ℎ𝑜𝑙𝑒𝑠 𝑝𝑒𝑟 𝑡𝑟𝑎𝑦 = 𝑛ℎ =
𝑁ℎ
= 265
49
Perforated area is assumed to be 3 m2 less than Active Area because of beams and rings of
column.
𝐴ℎ 0.367
=
= 0.122 = 12.2 %
𝐴𝑝
3
2
𝐴ℎ
𝑑ℎ
= 0.9 [ ]
𝐴𝑝
𝑙𝑝
𝐻𝑜𝑙𝑒 𝑃𝑖𝑡𝑐ℎ = 𝑙𝑝 = 0.0163 𝑚
Equilateral triangular pitch is selected. The hole pitch (distance between the hole centres) lp
should not be less than 2.0-hole diameters, and the normal range will be 2.5 to 4.0 diameters.
91 | P a g e
4.4.6.9.
Weir Height/Weir Length
Weir Height = hw = 65 mm
(Ad/Ac) % = 15%
lw/Dc = 0.810
lw = 2.094 m = 2094 mm
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Chemical Engineering Design by R.K Sinnott.
4.4.6.10. Entrainment
At FLV = 0.018 and 85% flooding, fractional entrainment comes to be 0.15 kg/kg of gross
liquid flow.
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4.4.6.11. Weep Point
Weir length = lw = 2.094 m
Liquid flowrate = Lw = 6.688 kg/s
2⁄
3
𝑊𝑒𝑖𝑟 𝐶𝑟𝑢𝑠𝑡 = ℎ𝑜𝑤
𝐿𝑤
)
= 750 (
𝑙𝑤 𝜌𝐿
= 15.241 𝑚𝑚
hw + how = 80.241 mm
K2 = 30.4 from graph no.
Hole diameter = dh = 6 mm
𝑀𝑖𝑛𝑖𝑚𝑢𝑚 𝑉𝑎𝑝𝑜𝑟 𝑉𝑒𝑙𝑜𝑐𝑖𝑡𝑦 = 𝑢ℎ =
[𝐾2 − 0.90(25.4 − 𝑑ℎ )]
1
(𝜌𝑣 )2
Vapor volumetric flowrate = 4.85 m3/s
Actual vapor velocity = 4.85/Ah = 13.216 m/s
Which is more than minimum vapor velocity, to prevent weeping.
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= 5.063 𝑚/𝑠
4.4.6.12. Pressure Drop Calculations
Percentage perforated area = (Ah/Ap) % = 12.237%
Orifice coefficient = Co = 0.78
𝑢ℎ 2 𝜌𝑣
𝐷𝑟𝑦 𝑝𝑙𝑎𝑡𝑒 𝑑𝑟𝑜𝑝 = ℎ𝑑 = 51 [ ]
= 14.938 𝑚𝑚 𝐿𝑖𝑞𝑢𝑖𝑑
𝐶𝑜 𝜌𝐿
12.5 ∗ 103
𝑅𝑒𝑠𝑖𝑑𝑢𝑎𝑙 ℎ𝑒𝑎𝑑 = ℎ𝑟 =
= 11.335 𝑚𝑚 𝐿𝑖𝑞𝑢𝑖𝑑
𝜌𝐿
𝑇𝑟𝑎𝑦 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑑𝑟𝑜𝑝 = ℎ𝑡 = ℎ𝑑 + (ℎ𝑤 + ℎ𝑜𝑤 ) + ℎ𝑟 = 106.515 𝑚𝑚 𝐿𝑖𝑞𝑢𝑖𝑑
𝑇𝑟𝑎𝑦 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑑𝑟𝑜𝑝 = ∆𝑃𝑡 = 9.81 ∗ 10−3 ℎ𝑡 𝜌𝐿 = 1152.241 𝑃𝑎 = 1.152 𝑘𝑃𝑎
𝑇𝑜𝑡𝑎𝑙 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑑𝑟𝑜𝑝 = ∆𝑃 = ∆𝑃𝑡 ∗ 49 = 56.45 𝑘𝑃𝑎
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Chapter 05: Process Control and Instrumentation
5.1
Instrumentation
Instruments are the measurement instruments to be used to obtain the highest feasible exact
value of the variable. Measuring process parameters is the fundamental need to govern this
process. Repeatable and precise measurement is necessary for effective and successful
handling of the process, and this is also the basis of the contemporary process industry. To
execute this measuring action, measuring equipment is used. The measurement is sometimes
carried out indirectly, i.e., one factor is expressed in terms of other values and calibrated with
the needed parameter.
For example, our control targets are sometimes not measured and fall into the class of
unconsidered outputs. It may be because the measuring instrument cannot be available, e.g. the
use of compound measuring devices is highly expensive, as it usually uses spectrometric
measuring devices and only a few enterprises can afford this. In such circumstances, we
estimate alternative variables that can be easily calculated. Such metrics are known as
secondary measures. Likewise, we must assume that the temperature parameter of any source
is measured, using the most famous and simplest equipment, when the thermometer bulb is
exposed to the source in consideration, which then causes the fluid to grow because of heat
transfer from source to bulb glass and then glass walls to mercury fluid. The expansion of the
fluid finally causes the volume to rise, which can be measured in terms of temperature. Many
examples can also be cited. The measurement is mainly carried out by transforming one energy
form into another. Pressure, level, temperature, and flow are the four most often measured
parameters in any process business. These four parameters accounted for 80 percent of
measurements. The remaining 20% comprise various factors like density, speed, etc.
5.2
Objective of Instrumentation and Control System
o Suppressing the external disturbance.
o Operate the process in stable manner.
o Optimize the process operation.
5.3
Components of the Control System
5.3.1
Process
Any operation or series of operations that produces a desired result is a process. In this
discussion the process is the CO2 recovery from reformed natural gas.
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5.3.2
Measuring Means
The measuring element is likely the most crucial of all of the components of a control system's
overall function. If the measurements are not taken correctly, the rest of the system will not be
able to function properly. The measured available quantity is a dozen to depict the intended
condition in the procedure.
5.3.3
Process Variables
A process's ability to run consistently is dependent on the ability to regulate the process's
variables.
The term "process materials" refers to circumstances in process materials or apparatuses that
are susceptible to change. It is the most common variables that are measured and recorded,
followed by a dozen or so less frequently encountered variables such as chemical composition,
viscosity and density, humidity and moisture content among other things.
An automatic control is used to measure, correct, and modify changes of the found principal
types of process variations.
o Temperature measurement
o Pressure measurement
o Flow rate measurement
o Level measurement
i.
Temperature measurement
Temperature measurement systems have been created in a variety of ways. The majority of
these rely on monitoring some physical property of a working material that varies over time
in order to function.
Important devices for measuring temperature include
o Thermocouple
o
Thermistors
o Resistance Temperature Detector
o
Pyrometer
o Infrared
o
Thermometer
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ii.
Pressure Measurement
Pressure and vacuum measurements have been made possible by the development of
numerous techniques. Pressure gauges and vacuum gauges are two terms used to describe
instruments that measure pressure.
o Manometer
o Bourdon Gauge
o Diaphragm
o Expansion Bellow
o Pirani Gauge
iii.
Flow Measurement
Flow measurement is the process of quantifying the movement of a large volume of fluid. It
can be examined in a number of different ways.
o Turbine Flow Meter
o Venturi Meter
o Orifice Flow Meter
o Vortex Flow Meter
o Magnetic Flow Meter
o Coriolis Flow Meter
iv.
Level Controller
The presence of liquid can be determined in a variety of ways. The three most prevalent are
as follows:
o Before the placement of afloat, which is lightweight than the fluid; and following the
position of afloat, which is heavier than the fluid.
o When a heavy object is buoyed up somewhat by a liquid, displacement meters can be
used to determine the apparent weight of the object on the surface of the liquid.
o Calculating the dispersion in static pressure among two fixed positions, one on the vapor
side above the liquid surface and the other on the liquid surface below the vapor side The
difference in pressure between two-level wires is directly proportional to the amount of
liquid present in the container at any one time.
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5.4
Types of Instrumentation
There are majorly three types of instrumentation:
o Alarm instrumentation
o Recording instrumentation
o Indication instrumentation
5.4.1
Alarm instrumentation
Alarm instrumentation refers to the type of equipment that is used to identify potentially
hazardous or worrisome circumstances. During normal operating settings, these devices remain
silent, however, when the parameters surpass the set limits that are considered hazardous, they
turn alarming and exhibit detection, which causes them to become silent again. Switches are
the most utilized for this form of detection because they become active when an alarm is
triggered and remain inactive when the alarm is not triggered.
5.4.2
Recording instrumentation
The type of instrument in which continuous measurements of temperature, pressure, and flow
are made, and all values of these parameters are recorded through time. Once this is done, all
the measurements will be displayed in the form of a chart that will flow continually about time
as the instrumentation is recording. Depending on their shape, these charts can be either circular
or linear, and they can be controlled by a time clock action.
5.4.3
Indication instrumentation
Indication instruments are used to measure the sort of measurement that is taken in the field
and presented somewhere in the shape of dials or something similar. Operators in the field will
find this type of equipment to be quite valuable. Even though it is a continuous measurement,
the measurements are not recorded and are only presented at the time of measurement. These
indications are now also made using digital displays, which are becoming more common.
5.5
Control system
A control system is frequently used to ensure that a plant's operation is both productive and
secure. An unintended disruption that affects the regulated variable can be avoided and tracked
using a control system. Since there are several process variables to be monitored in a system,
several control systems are needed in the industry. The open and closed-loop control systems
are the two most common control systems. A closed-loop system, also called a feedback control
system, is one in which the control operation is determined by the output. When a discrepancy
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between both the set-point value and the control signal is detected, the control action changes
automatically. ASP will be corrected by a mechanism through which the control system
changes the manipulated variable to the desired condition to reduce the error over time. The
control operation of an open-loop control system is unaffected by the performance of the
system. The manual adjustment of the open-loop system is needed. As a result, it is less
dependable since the device will be impacted if an error is not corrected.
5.5.1
Classification of Controller
In general, the process controllers can be classified as:
o Pneumatic controllers
o Electronic controllers
o Hydraulic controllers
In the CO2 recovery from natural gas the controller and the final control element may be
pneumatically operated due to the following reasons:
o The pneumatic controller is very rugged and almost free of maintenance.
o The pneumatic controller appears to be safer in a potentially explosive atmosphere which
is often present in the Petro-chemical industry.
o Transmission distances are short. Pneumatic and electronic transmission systems are
generally equal up to about 250 to 300 feet. Above this distance, electronic systems begin
to offer savings.
5.6
Supervision Loops
5.6.1
Inferential Supervision Manipulation
The control system in which the number of parameters is changed by using second-class
measurements. The primary goal of this method is to retain the unspecified variables in a
controlled state throughout the experiment.
5.6.2
Feedback Supervision Manipulation
The feedforward control system is employed when the measuring instrument detects a
disturbance and the controller then corrects them, altering the system conditions so that the
combined effect of the storm and the system remain at the point before entering the system.
100 | P a g e
5.6.3
Feedforward Supervision Manipulation
It is the supervision configuration in which the disturbance enters the system, travels through
the system, and is noticed at the system's output that is being monitored. It is known as a
feedback control method when the effect is detected and corrected by the controller through
changes in the system after it has been detected and corrected.
5.7
Types of Feedback Controller
5.7.1
Proportional Controller
A proportional controller is a form of feedback controller that corrects the control variable,
which is the difference between the set-point value and the calculated value. The
implementation of a proportional controller is subject to two requirements.
o The variance should not be significant; that is, there may not be a significant difference
between both the input and output.
o The deviation should also not be abrupt.
The output of the proportional controller is related to the error signal, in mathematics form, it is
represented as:
𝐴(𝑡) = 𝐾𝑝 𝑒(𝑡)
Figure 3: Proportional Controller
➢ Advantages
o The proportional controller aids in the reduction of steady-state error, making the system
more stable.
o It also aids in the speeding up of the sluggish output of the overdamped system.
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➢ Disadvantages
o We have some offsets in the system because of the existence of these controllers.
o proportional controllers even increase the system's overall overshoot.
5.7.2
Integral Controller
It is a controller that is used to eliminate the proportional error's steady-state error. Its output
signal is equal to the integration of the error signal and its output signal is directly
proportional to the volume of the error signal. The formula is as follows:
𝑡
𝐴(𝑡) = 𝐾𝑖 ∫ 𝑒(𝑡)𝑑𝑡
0
➢ Advantages
o Integral Controllers are referred to as reset controllers because of their special ability to
return the monitored variable to the precise set point after a disturbance.
➢ Disadvantages
o Since the system reacts slowly to the generated error, it usually makes the system
unstable.
5.7.3
Derivative Controller
It is the controller that detects the rate of change of the error signal and adds an aspect to the
output signal that is directly proportional to the derivative of the error signal. The following is
the mathematical form:
𝐴(𝑡) = 𝐾𝑑
𝑑
𝑒(𝑡)
𝑑𝑡
➢ Advantages
o The main benefit of a derivative controller is whether it increases the system's transient
response.
➢ Disadvantages
o Derivative controllers are never used by themselves. Because of its few drawbacks, which
are mentioned below, it can be used in conjunction with other types of controllers:
o The steady-state error is never improved by it.
o It generates saturation effects as well as amplifying the sound signals produced by the
device.
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5.7.4
Proportional- Integral Controller
It is also a combination of proportional and integral controllers, with the output signal
equaling the sum of both controllers' error signals. The proportional-integral controller's
actuating signal is directly proportional to both the proportional and integral signals, as seen
in the following mathematical form:
𝑡
𝐴(𝑡) = 𝐾𝑖 ∫ 𝑒(𝑡)𝑑𝑡 + 𝐾𝑝 𝑒(𝑡)
0
Figure 4: Proportional Integral Controller
5.7.5
Proportional- Derivative Controller
It is also a combination of additive and derivative controllers, with the output signal equaling
the sum of both controllers' error signals. The proportional-derivative controller's actuating
signal is directly proportional to both the proportional and derivative signals, as shown in the
following mathematical form:
𝑡
𝐴(𝑡) = 𝐾𝑖 ∫ 𝑒(𝑡)𝑑𝑡 + 𝐾𝑑
0
𝑑
𝑒(𝑡)
𝑑𝑡
Figure 5: Proportional Derivative
Controller
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5.7.6
Proportional-Integral-Derivative Controller
It's also a combination of additive, integral, and derivative controllers, with the output signal
equaling the sum of all controllers' error signals. The proportional-integral-derivative controller's
actuating signal is directly proportional to the proportional, integral, and derivative signals. It is the
most effective and appropriate closed-loop feedback controller, and its mathematical form is as
follows:
𝑡
𝐴(𝑡) = 𝐾𝑖 ∫ 𝑒(𝑡)𝑑𝑡 + 𝐾𝑑
0
𝑑
𝑒(𝑡) + 𝐾𝑝 𝑒(𝑡)
𝑑𝑡
Figure 6: Proportional Integral Derivative Controller
5.8
Control loop across Reactor
Figure 7: Control Loop Across Reactor
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5.9
Control Loop Across Compressor
Figure 8: Control Loop Across Compressor
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Chapter 06: HAZOP Analysis
Introduction
6.1
HAZOP studies are a standout amongst the well-known and generally acknowledge strategies
for orderly subjective risk investigation. It is utilized for either new or existing offices and can
be connected to an entire plant, a creation unit, or a bit of hardware it utilizes as its database
the standard kind of plant and process data and depends on the judgment of designing and
wellbeing specialists in the regions with which they are generally well-known. The final
product is in this way dependable regarding building and operational desires; however, it is not
quantitative and may not consider the outcomes of complex arrangements of human blunders.
A HAZOP study is a straightforward, organized process for identifying potential hazards. It is
an investigation methodology that is intended to stimulate innovative thinking or brainstorming
among a group of experts to identify hazards and operational problems while thoroughly and
methodically evaluating a process or system.
HAZOP studies are designed to accomplish the following goals:
o To identify the sections of the design that may pose a major hazard or possibility for failure.
o To identify and investigate design aspects that have an impact on the likelihood of a
hazardous occurrence occurring.
o To acquaint the science team with the design documentation that has been made available.
o To ensure that a systematic investigation of the area with substantial hazard potential is
carried out.
o This task entails identifying prospective design information that is not presently available
to the team.
o To create a way for the client to get detailed remarks from the study team and to submit
feedback to the team.
6.1.1
Hazard
Hazard can be defined as anything that has potential to harm like injury, damage to property
and any catastrophic effects on environment or the combination of above is termed as hazard.
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6.1.2
Operability
It is defined as the ability to keep a piece of equipment or a system in safe running condition
according to pre-defined operating rules. Operability is related to the stability and maintenance
of equipment or system.
6.1.3
History
The HAZOP study was defined by ICI (imperial chemical industries, UK) during 1960s. this
is a technique of identifying the problems and then finding their solutions for safe operation of
plant and safe operation of plant is necessary for the pre-defined quality of product and capacity
to meet the need of market. The pioneer of HAZOP does not exist today but the technique
developed by the ICI is still growing and becoming more effective and efficient day by day.
Hazard and operability study is the most integral part of chemical engineering.
Aim
6.2
Hazard and operability study is a technique for the assessment of risk that has the likelihood to
be present in an equipment or several equipment. The basic aim of this technique is to identify
the risk that has the potential to occur in an equipment caused by the deviation from design of
both new and old plants.
Where Is HAZOP Used?
6.3
HAZOP is used in several areas and industries and not limited to the following given below
o Chemicals and petrochemicals industries
o Power generation industries
o Mining and metals industries
o Oil and gas including the oil refining
o
Pharmaceutical industries
6.3.1
HAZOP Types
Following are the main types of HAZOP listed below
o Process HAZOP
o Human HAZOP
o Procedure HAZOP
o Software HAZOP
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o Greenfield
o Brownfield
6.3.2
Definitions of Some Useful Terms
o Node
A node is specific part of system in which the hazard is identified. It can be a subsystem, a
piece of equipment in the system or a function group.
o
Process Parameters:
The process parameters are defined as the related parameters for the observation of conditions
of the process. The examples of process parameters are temperature and pressure etc.
o Guide Words:
The guide words in the HAZOP are the key supporting elements that are very necessary for the
implementation of HAZOP study. Some guide words are less, more, no, reverse etc.
Guide Words + Parameters = Deviation
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6.3.3
Benefits Of HAZOP
There are many circumstances when hazard and operability study provide benefits are
o During the design of new plant are doing some modifications in the existing plant
o When the hazard is related to the environmental impact, cost, and quality of products
o When the hazard in the plant is fire or explosion because fire and and explosion are the
major incidents involved in the plant.
o It is beneficial in finding the weaknesses of the design of plant.
6.4
HAZOP Procedure
6.5
HAZOP Group
Select the HAZOP research group from the drop-down menu. To enable a successful team
interface, the team leader must be knowledgeable with HAZOP as well as personal skills.
Numerous more team members should be included to ensure that all areas of design,
operation, process chemistry, and safety are adequately covered. The HAZOP team is mostly
composed of 5 to 7 persons that have come from a variety of educational backgrounds to
provide exceptional brainstorming.
o The HAZOP chairman
o HAZOP custodian
o A process Engineer
o An instrument Engineer
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o Safety engineer
o An operation representative
o Discipline engineers as appropriate
Portion members should include professionals from the piping, electrical, mechanical, and
other departments, as well as those departments not included above.
6.6
HAZOP Study of Absorber
Figure 09: HAZOP Study of Absorber
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Table 37: Guide words for Absorber
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Chapter 07: Cost Estimation
7.1.
Plant Cost Introduction
The specific money for the purchase and installation of the equipment must be provided before
the plant is in operation. Fixed investment is the capital needed for providing the necessary
plant facilities, whilst the operation of the plant is referred to as the operating principal and the
sum of two capitals is called total investment.
7.2.
Acceptability of Plant Costs
A satisfactory proposed project must present a process which can operate in terms of
profitability. Since, net profit is equivalent to the difference between total revenue and all
expenditures.
7.3.
Engineering and Plant Costs
Understanding of various types of costs related to production of products in industry is essential
for chemical engineers. Reasonable asset should be kept in hand as direct plant cost for
acquisition of raw materials, labor costs, and certain equipment costs. Besides these expenses
there should be understanding of indirect costs which are essential to calculate total plant cost.
Indirect cost is institutional salaries, product distribution costs, and interplant communication
costs.
7.4.
Calculation of Cost of Different Equipment
Table 38: Cost of Equipment
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Equipment
Cost of equipment
Reactor
120000$
Air compressor
9000$
Steam turbine
9000$
Tail gas heater 1
2500$
Tail gas heater 2
3500$
Heat exchanger 1
3000$
Heat exchanger 2
3500$
Heat exchanger 3 (cooler)
2500$
Ammonia evaporator
2000$
7.4.1.
Air compressor 2
8000$
Tail gas turbine
8000$
Mixer
1000$
Tail gas reactor
11000$
Absorber
10000$
Bleacher
3000$
Direct Cost
Purchased equipment cost=E=188000$
Installation cost (40%E) =75200$
Instrumentation and control cost (13%E) =24440$
Piping cost (10%E) =18800$
Electric cost (10%E) =18800$
Building (including services) (29%E) =54520$
Yard improvement (10%E) =18800$
Land cost (6%E) =11280$
Total Direct Cost=409840$
7.4.2.
Indirect Cost
Engineering and supervision cost (32%E) =60160$
Construction expenses (30%E) =56400$
Contractor fee (18%E) =33840$
Contingency fee (30%E) =56400$
Total Indirect Cost=206800$
7.4.3.
Total capital investment
Fixed Capital Investment = Direct Cost + Indirect Cost
F.C.1 = D.C + I.C
F.C.I = 409840$ + 206800$
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F.C.I = 616640$
Working capital (18%F.C. I)=110995.2$C
Total capital investment=working capital=fixed capital investment
T.C. I=W.C+F.C. I
T.C. I = 727635$
7.5.
HNO3 Product Cost
Suppose that the fixed investment will be depreciating using the straight-line method over the
period of twenty years. For the purposes of this calculation, 5 % salvage value is assumed at
the end of the plant's life.
𝐷𝑒𝑝𝑟𝑒𝑐𝑖𝑎𝑡𝑖𝑜𝑛 = (𝑉 − 𝑉𝑆 )/𝑁
original value (v) = fixed capital investment
v = 616640$
salvage value = 0.05*F.C. I
VS = 30832$
N = NUMBER OF YRS. = 20
D = (616640–30832)/ 20
D = 29290.4$
Total Product Cost = Total Capital Investment - Depreciation
T.P.C = 698344.6$
Fixed charges (12%T.P.C) =83801.352$
Direct product cost(55%T.P.C) =384089.53
Plant overhead(10%T.P.C) = 69834.46$
T.C.I = 727635$
T.P.C = 698344.6$
Manufacturing cost = Direct Product Cost + Fixed Charges + Plant Overhead Cost
Manufacturing Cost = 537725.342$
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o General expenses
General Expenses = Administrative Cost + Distribution and Selling Cost + R&D Cost
o Administrative Cost
It is about 2-6% of total product cost
Let’s
Administrative Cost = 4% of of total product cost
Administrative Cost = 27933.784$
o Distribution and Selling Costs
This category includes costs associated with sales offices, sales representatives, shipping and
advertising costs.
It is about 2% and 20% of the total cost of product.
Delivery and selling costs account for 11% of the total product cost.
Costs of Distribution and Sales = 76817.906$
o R&D COST:
It is about 5% of product cost
R&D expenses=0.05*698344.6
R&D expenses = 34917.2$
o Interest:
Assume that interest represents 7% of total investment.
Interest = 0.07 multiplied by 727635
Interest is equal to 50934. 45$
So,
G.E = 139668.92 $
Total Product Cost = Manufacturing Cost + Total General Expenses
Total Product Cost = 537725.342 + 139668.92
Total product cost = 677394.262 $
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Total product cost = Manufacturing cost + General expenses total
Total product cost = $537725.342 + $139668.92
Total product cost = $677394.26
Total product cost = PKR 107,299,250.78
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Prepared by:
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
5. Best Available Techniques for Pollution Prevention and Control in the European
Fertilizer Industry, By EFMA, Booklet No. 2, Production of Nitric Acid
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Weitkamp
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16. K. Thulukkanam, “Heat exchanger design Handbook,” CRC Press, vol. 53, no. 9, p. 1260,
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