Introduction to chem. eng.
Chapter 3
PROCESS DESIGN
October 09
CONTENTS:
•
Products which will require the development of a
Chemical Processes
•
Project Development Story
•
Examples of two Process Design Projects
•
Laboratory and Pilot Plant Data and Specifications
(Example)
•
Qualitative Block-type Process Flow Sheet – Figure (1)
•
Simplified Equipment Flow Diagram – Figure (2)
•
Material Balance Flow Sheet – Figure (3)
•
Energy Balance Flow Sheet – Figure (4)
•
Equipment Symbols – Figure (5)
Products which require the
development of a Chemical Processes
• A request from a customer to supply a material
with properties not covered by any product in
the market.
• A new catalyst that can reduce manufacturing
cost for a chemical our competitor produces.
• The research team may have a new monomer
whose properties look promising for producing
a polymer for car bumpers.
• Management may want us to discover a process
where we can use up the surplus feedstock the
company is currently producing.
Project Development Story
‫قصـة حياه مشـروع‬
1. Board of Director’s initiate a project
‫مجلس إدارة الشركة يبحث عن بدائل لزيادة ربحية الشركة ودعم موقف الشركة‬
‫التنافسى‬
2. Identification of New Projects
- Project ideas
- Possible sources of finance
- Possible risks
3. Market Study
- Potential customer’s reaction
- Competition analysis
4. Planning and organizational Design
‫إعداد خطة المشروع بد ًء من مرحلة التصميم – تحديد المسئوليات والمهام والتوقيتات‬
Project Development Story
‫تابـع قصـة حياه مشـروع‬
5. Preliminary Process Design:
-
Generates and evaluate alternative process flow
diagram of the process
-
Select the most promising process flow diagram
based on technical, economic and safety
considerations.
6. Layout and Three Dimensional Modeling:
- equipment selection
- equipment sizing
- conversion of the process flow diagram (PFD) into a
piping and instrumentation diagram (P&ID)
- layout design
‫‪Project Development Story‬‬
‫تابـع قصـة حياه مشـروع‬
‫‪7. Construction:‬‬
‫بناء المصنع بمعرفة شركة أو شركات متخصصة فى األعمال المدنية والكهربائية والميكانيكية وعزل‬
‫المعدات وتحديد المواسير وتمهيد الطرق وشبكات المياه والصرف الحصى والتليفونات والغاز‪...‬الخ‪.‬‬
‫إدارة المشروع وفقا ً لألصول المحددة‪:‬‬
‫• إدارة الجودة للتحقق من المواصفات الفنية‬
‫• إدارة التكلفة للتحقق من أن التنفيذ يتم وفقا للميزانية المقررة‬
‫• إدارة الزمن للتحقق من أن التنفيذ يسير وفقا للبرنامج الزمنى‬
‫‪8.Startup and commissioning:‬‬
‫‪Get the plant started‬‬
‫‪9.Plant Operation:‬‬
‫‪Get the product to the market‬‬
‫‪Project Development Story‬‬
‫تابـع قصـة حياه مشـروع‬
‫‪10. Debottlenecking:‬‬
‫‪Make changes to improve process performance‬‬
‫‪11. Decommissioning:‬‬
‫فى يوم ما – ربما بعد عقود عدة من يوم بدء تشغيله – البد وأن يتوقف المصنع‬
‫عن اإلنتاج وتبدأ عملية معقدة لتفكيكه‪...‬‬
‫وبتراكم الخبرة – أصبحنا نطلب اآلن من فريق تصميم المصنع الذى ربما يتم‬
‫إنشاؤه هذا العام أن يأخذ فى االعتبار طريقة تفكيكه بعد خمسين عاما ً – من‬
‫اآلن‪...‬‬
Example of Process Design Project
The market analysis staff of Company X, a mediumsized organic products company, has recommended
to its management group that there was some
chance to diversify their product line by developing
a pesticide. The research and development (R&D)
staff suggest that benzene hexachloride (BHC)
might be a good possibility. It can be sold in the socalled crude form which contains 12 to 15 percent
of the active pesticide,  isomer of BHC, or it can be
marketed as the concentrated product Lindane (99
percent  isomer of BHC).
Example of Process Design Project Cont’d
Market analysis showed that an annual production of
600 ton of crude BHC or up to 100 ton of Lindane
could be easily sold without undue competition.
Management would like to compare the economics
of crude BHC and Lindane production before making
the final decision to spend money in a
manufacturing plant. This requires process design
study followed by a preconstruction cost estimate
and profitability analysis.
A statement of the chemical process for the
production of crude benzene hexachloride is
specified by the research and development group as
follows:
Chemical Process Considerations:
• The production of benzene hexachloride is to involve the
reaction of gaseous chlorine with liquid benzene at the
refluxing temperature.
• The reaction is to be carried out on a continuous basis in
a glass-lined reactor fitted with a refluxing system;
conversion of the chlorine is expected to be 99 percent
and the reactor product should consist of about 33
percent benzene hexachloride dissolved in
chlorobenzenes and unreacted benzene.
• The crude product is to be continuously removed for
further processing.
• The accompanying 21.5 percent muriatic acid layer
should be decanted and further concentrated to the
salable 36 percent acid.
Chemical Process Considerations Cont’d:
•
The concentration is to be accomplished in a tripping
column which produces a bottoms of 20 percent HCl
solution.
•
Since this bottoms product is not salable as such and
since the HCl cannot be stripped farther without the use
of excessively high pressures, it is to be recycled into the
chlorinator for reconcentration.
•
The organic layer is to be neutralized with 1 percent
NaOH solution and then concentrated to 56 percent BHC
by evaporation of some of the volatile ingredients in a
flash still.
•
The overhead from this still is largely benzene and
monchlor benzene which are separated by fractionational
distillation.
•
The benzene is recycled and the monochlor benzene is to
be sold as a by-product.
Chemical Process Considerations Cont’d:
•
A large fraction of the benzene hexachloride is to be
crystallized out in a double-pipe “chiller” and the crystals
removed by means of a continuous centrifuge.
•
The filtrate is to be recycled to a flash still for
reconcentration.
•
The crystalline BHC product is to be dried in a rotary
vacuum dryer equipped with a solvent recovery system.
•
The recovered solvents from various operations are to be
combined and fractionated.
•
The overhead distillate consisting primarily of benzene is
to be reused in the process whereas the chlorobenzol
solvents in the bottoms are to be stored for sale as crude
monochlorobenzene.
Laboratory and Pilot Plant Data and
Specifications (Example)
1. Raw materials specifications:
 Benzol, purified grade, considered as 99.5% benzene,
0.5% toluene
 Chlorine considered to be 100% pure
 Water catalyst, demineralized process water
 Sodium hydroxide, flake, 98% NaOH
2. Chlorinator conditions:
 Reaction temperature: 70°C
 Chorine conversion: 99%
Laboratory and Pilot Plant Data and
Specifications (Example) Cont’d
3. Characteristics of organic product layer from chlorinator:
Composition
Weight%
Benzene
58.85
Water
0.31
Monochlorobenzene
7.08
Benzene Hexachloride
Alpha
Beta
Gamma
Delta and cogeners
23.44
2.04
4.22
3.55
Heptachlorocyclohexane
0.26
Trichlorobenzene
0.15
Hydrogen chloride
0.10
Total
100.00
Specific gravity at 70ºC: 1.034
Qualitative Block-type
Process Flow Sheet
The next step for the design engineering group is to
translate the written description of the chemical
process into a working pattern. It is important to
explain that this working pattern can be developed in
a number of ways. Each industry, each company, and
each individual designer has a somewhat different
approach to process design, particularly when it
comes to pictorial representation of the design data.
We can present only a few of the possible ways of
working out a process design.
Qualitative Block-type
Process Flow Sheet Cont’d
The main points that a student should realize are that the
design should be:
(1) technically sound,
(2) on a reasonable basis, and
(3) clearly pictured.
An examination of this process description for
manufacturing benzene hexachloride and the supporting
data shows that the principal chemical reaction is that of
chlorine addition.
C6H6(l)
Benzene
+
3Cl2(g)
Absence of actinic rays And
substitution catalysts
Chlorine
Presence of H2O, 70ºC
C6H6Cl6
Benzene hexachloride or
cyclohexane, 1,2,-3,4,5,6hexachlorine
Qualitative Block-type
Process Flow Sheet Cont’d
The working pattern for this process is put down on
paper by drawing rectangular boxes and inserting
the types of physical and/or chemical operations
that take place, together with a description of the
streams entering and leaving the box. The result is
a qualitative block-type process flow sheet or flow
diagram. Figure (1) illustrates this principle. The
process engineer now has better idea of the overall process and obtains an insight as to further data
he might require.
Qualitative Block-type
Process Flow Sheet Cont’d
Figure (2) is a simplified equipment flow diagram
of the same process. This was coded by letter for
each key operation, for example, B for chlorination,
D for acid concentration, etc. All the equipment
conveniently associated with the key operation was
numbered, for example, B-1, B-2, etc. A study of
this diagram will be helpful in following this
particular plan of execution.
The equipment pictured may not represent the final
choice as subsequent material and energy balances
could reveal that a certain type of equipment was
not technically feasible to carry out the desired
process step.
From research to practice
Research project:
Study of co composting of agricultural
residues and night soil, M. Sc. student
thesis work, Hisham Sheref,1985
From research to practice
The Practice:
1. A company specialized in delivering
turn-key sorting and composting plants
2. A second company which offer contracts
to manage and operate MSW recycling and
disposal facilities
More details about the transfer of
research to practice…
Research main objective: to design a system
for the safe disposal of human waste and
domestic solid waste
The basic idea was to combine the organic
fraction of the MSW which is high in
carbon with th night soil high in nitrogen to
produce useful product.
water courses as the ultimate disposal site of
human waste and municipal solid waste
research experimental set up
• Pilot scale experiments
• Mixtures of agricultural residues and night
soil collected from household vaults in the
village of Shosha, Mynia, upper Egypt
• Aerobic decomposition
• Operating variables:
– time
– aeration rate
– C/N ratio
Rate factors
1. Moisture content:
minimum 15% for bacterial activity
optimum 50-60%
2. Time:
it is the most important factor in
determining the compost product
quality
allowance for maturation time
Cont’d rate factors
3. Temperature:
stages of the aerobic thermophilic composting
temperature as a functioning indicator
trade off: thermophilic microbial activity vs
pathogen destruction
4. Particle size:
another trade off: Oxygen diffusion in too fine
particles vs higher rate of decomposition
optimal size: 10-50 mm
Cont’d rate factors
5. Aeration:
optimal level of oxygen required for the growth
of aerobic microorganisms
Oxygen consumption in a composting mass
depends on: stage of process, temp, degree of
mixing, composition, particle size and moisture
content
Another trade off: too much aeration will cool
down the mass, too little will result in low
oxygen content .
Cont’d rate factors
6. Nutrients:
C/N as indicator of rate of decomposition
optimal C/N ratio
7. pH control:
range 6-8
when process shift to anaerobic, organic acids
will bring pH to 4.5 level
research project main activities
• Temperature
monitoring
• Pathogens destruction
rate
• Mass and energy
balance
• Product quality
assessment
• Process design
• Economic analysis
First business opportunity
• Establishment of a limited liability
company, 1994
• Acquisition of 14,000 sq meters in the
industrial estate in Mynia, 20 km from a
major sugar factory
• Detailed process and plant design of the
first large scale production facility of
agriculture residue based compost in Egypt
Cont’d Mynia composting plant
•
•
•
•
•
Fixed capital
Labor force
Production capacity
Marketing experience
Main raw materials
– Baggasse
– Agriculture residues
Continued R&D work
• Sugar factory filter mud as an alternative
raw material
• Process and plant design of
Co- composting of MSW and agricultural
waste
Global perspective on municipal solid
waste quantities
Generation rates
kg/capita.day
Low-income
country
Middle-income
country
High-income
country
Mixed urban wastelarge city
0.50 to 0.75
0.55 to 1.1
0.75 to 2.2
Mixed urban waste –
small to medium city
0.35 to 0.65
0.45 to 0.75
0.65 to 1.5
Residential waste only
0.25 to 0.45
0.35 to 0.65
0.55 to 1.0
Global Perspective on Solid Waste
Management Costs Versus Income
Units
Low
Income
Country
Middle
Income
Country
High
Income
Country
Tons/cap. yr
0.2
0.3
0.6
$/cap.yr
370
2,400
22,000
Collection cost
$/ton
10-30
30-70
70-120
Transfer cost
$/ton
3-8
5-15
15-20
Sanitary landfill cost
$/ton
3-10
8-15
20-50
Total cost without
transfer
$/ton
13-40
38-85
90-170
Total cost with transfer
$/ton
16-48
43-100
105-190
per cent
0.7-2.6
0.5-1.3
0.2-0.5
Average waste generation
Average income from
GNP
Cost as % of income
Business opportunity is to convert this kind
of waste
To this kind of product
and to get recyclable material in addition
Municipal solid waste receiving area
The waste is then transferred to sorting
conveyors, each conveyor supporting 6 stations
Two Lines sorting system picture
Adding water for moisture content control
compost turning machine in operation
Screening of matured final product