Description of Chemical
Processes
Chao Miao
Apr.23
Objectives
• To be able to define different streams in a process.
• To describe the meaning of standard abbreviations
and symbols used on process flowsheets.
• Write a description of a process flowsheet.
• Draw a process flowsheet from a written description.
Introduction
• What is a Process?
• A process is some operation carried out to modify input(s) to
output(s) – based on physical and/or chemical changes
Inputs
“feeds”
Process
Outputs
“products”
Process design vs. Process analysis
1.
Specification of equipment, and materials and their
subsequent arrangement into processes which control the
environment of a chemical or physical operation to achieve
a desired output.
2.
The analysis of the operation of existing chemical or
physical processes in order to alter the processing operation
to achieve a desired result.
Describing Processes
• Input – output diagram
• Block diagram
• Process Flow Diagram (PFD)
5
Input-output diagram
Products
Raw Materials
Process
6
Block Flow Diagram
• Operations shown by blocks
• Lines with arrows connect blocks and represent process streams
direction
• Raw materials enter on the left
• Products exit on the right
• Light steam (gases) toward top with heavy stream (Liquid and
solids) toward bottom
• If lines cross, horizontal line is continuous and vertical line is
broken.
• Simple material balance provided
7
Block Flow Diagram
Block Flow Diagram
Process Flow Diagram
• All the major equipments in the process are represented on the
diagram along with a description of the equipment.
• Each piece of equipment is assigned with a unique equipment
number and descriptive name.
• All the flow stream is shown and identified by a number
• A discription of the process conditions and chemical composition of
each stream will be included.
• All utility streams supplied to major equipment will be shown.
• Basic control loops, illustrating the control strategy will be shown.
Process Flow Diagram
Process Flow Diagram
Process Flow Diagram
Process Flow Diagram
• Stream Information
• Equipment Information
Stream Information
•
•
•
•
•
•
•
•
Stream number
Temperature (C)
Pressure (bar)
Vapor fraction
Composition
Total Mass flowrate (kg/h)
Total Mole flowrate (kmol/h)
Individual component flowrates (kmol/h)
Equipment Information
Process Design
• Preliminary Database Creation
– to assemble data to support the design.
• Experiments
– often necessary to supply missing database items or verify crucial
data.
• Preliminary Process Synthesis
– top-down approach.
– to generate a “synthesis tree” of design alternatives.
• Development of Base-case Design
– focusing on the most promising alternative(s) from the synthesis tree.
Preliminary Database Creation
• Thermophysical property data
– physical properties
– phase equilibria (VLE data)
– Property prediction methods
• Environmental and safety data
– toxicity data
– flammability data
• Chemical Prices
– e.g. as published in the Chemical Marketing Reporter
• Experiments
– to check on crucial items above
Literature and Information Sources
Company context - employees, company files, open literature provide :
Product info (related), thermophysical properties, transport data,
flowsheets, equipment descriptions, process models.
National Laboratories and Research Institute Reports e.g. SRI International, NIST,
NIOSH.
Encyclopedias (technical, chemical process and technology).
Handbooks and Reference Books (Perry’s Chemical Engineer’s Handbook, CRC
Handbook of Physics and Chemistry)
Journals (Book format, electronic format)
Indexes (INSPEC, COMPENDEX, SCIENCE CITATION INDEX)
Patents (U.S. Patent Office www.uspto.gov/patft )
Auxiliary Studies (e.g. technical feasibility, marketing, business related)
Innovation
Process Design
• Decide whether the process will be batch or continuous
• Identify the input/output and other major operations structure of
the process
• Identify and define the recycle structure of the process
• Identify and design the heat-exchanger network or process energy
recovery system.
Batch or Continuous
An integrated series of operations through which materials and/or energy are
converted from one form to another.
Batch process:
•has a definite end
•material is put in, processed, and discharged
•applies to more than just reactors (washing machine for example)
Continuous process
•materials enter and leave in uninterrupted streams
•periodic shutdown is required
•Garden sprinkler
Semibatch or Semicontinuous
•Some materials are charged/discharged at intervals while some enter/exit continuously
•Biotechnology industry, to add nutrients
Batch or Continuous
Continuous
Batch
Fed-batch
Input/output structure of the process
Fixing the chemical state of raw materials, products, and by-products, noting the
differences between them.
• Decide on the raw material and product specifications (states):
 Mass (flow rate)
 Composition (mole or mass fraction of each chemical species
having a unique molecular type)
 Phase (solid, liquid, or gas)
 Form (e.g., particle-size distribution and particle shape)
 Temperature
 Pressure
Process operations
Six elements of the generic block flow process diagram
Recycle
Raw
Materials
Reactor Feed
Preparation
Reactor
Separator Feed
Preparation
Products
By-product
Separator
Waste Streams
Discharge to
environment
Environment
al Controls
Process operations
Software for chemical process design and analysis
ASPEN
PROII
CHEMCAD
HYSYS
ECSS
Process design and analysis
•
•
•
•
•
Algal bio-oil production
Algal hydrothermal liquefaction
2 processes can be used
One step hydrothermal liquefaction
Two-step hydrothermal liquefaction
Two-step hydrothermal liquefaction
of algae
• First Step (To produce sugar, polysaccharide,
and protein)
• Wet algae (Biomass/water ratio=1:9) are
heated to 160C to produce
• Solid phase (Treated alage)
• Aqueous phase (WEs)
Two-step hydrothermal liquefaction
of algae
• Second Step (To produce Bio-oil)
• Treated algae (Biomass/water ratio=1:6) are
heated up to 240C to produce
• Oil phase (Bio-oil)
• Gas phase (Bio-gas)
• Solid phase (Bio-char)
• Aqueous phase (WEs)
One step hydrothermal liquefaction
Algae (Biomass/water ratio=1:9) are heated up to
240C for 20min to produce
Oil phase (Bio-oil)
Gas phase (Bio-gas)
Solid phase (Bio-char)
Aqueous phase (WEs)
Hydrothermal liquefaction of algae
•
•
•
•
•
•
•
Continuous reaction
Input: Algae
Output: Bio-oil, Bio-char, WEs, Bio-gas
Reactor: Yield is required
Reaction conditions: 1st step 160C, 2nd step 240C
Mass Balance is required
Algae composition is required
Two-step hydrothermal liquefaction
Mass balance
0.7g
10g
0.7g
5.0g
3.0g Bio-Oil
0.6g WE
1.7g Water Extractive
3.3g Polysaccharide
0.7g gas
1.7g WE
160C
10g Algae
0.6g WE
300C
5.0g TA
0.7g Char
3.3g Poly
3.0g Bio-Oil
One step hydrothermal liquefaction
Mass balance
Process Description-two step process
Target productivity of bio-oil: 1M Gallon per Year
Working days per year: 260days
Working hours per day: 8h
Times of reaction finished per hour: 3 per hour
Bio-oil production per kg biomass: 0.3
First step Biomass/water ratio: 1:9.
Second step biomass/water ratio: 1:6
Dry Algae composition:
Lipid: 25%, Sugar: 46%, Protein: 17%
One step------DHTL
Two step------SEQHTL
Input of first step of SEQHTL
Components
Flow Rate (kg/h)
Percentage (wt %)
Total
15000
100
Water
13500
90
Biomass
1500
10
(Lipids)
375
2.5
(Sugars)
690
4.6
(Protein)
255
1.7
(Others)
180
1.2
Component flow rates and fraction in feed algal biomass for SEQHTL’s first step reaction
Process Description
Output of first step of SEQHTL
Products (1st step)
Flow Rate (kg/h)
Percentage (wt %)
Water
13500
90
Bio-oil
0
0
Sugars
465
3.1
Protein
315
2.1
TA Biomass
720
4.8
Bio-gas
0
0
Component flow rates and fraction in products of SEQHTL’s first step reaction
Process Description
Input of Second step of SEQHTL
Feed In (2nd step)
Flow Rate (kg/h)
Percentage (wt %)*
Total
5040
33.6
Water
4320
28.8
Treated Biomass
720
4.8
(Lipids)
375
2.5
(Sugars)
120
0.8
(Protein)
45
0.3
(Others)
180
1.2
Component flow rates and fraction in feed treated algal biomass for SEQHTL’s
second step reaction
Process Description
Output of Second step of SEQHTL
Products (2nd step)
Flow Rate (kg/h)
Percentage (wt %)*
Water
4320
28.8
Bio-oil
450
3
WEs
84
0.56
Bio-char
150
1
Bio-gas
36
0.24
Total
5040
33.6
Component flow rates and fraction in products of SEQHTL’s second step reaction
Process
10
9
B1
B5
B4
2
B2
1
B6
B3
3
7
4
5
6
8
21
15
B10
16
B8
B13
B12
B9
B14
12
19
14
B7
B11
MIXER
17
13
18
23
20
22
Aspen Model-Define the material
Component definitions for SEQHTL in Aspen Plus
Aspen Model-material input
Feed stream data for first step SEQHTL in Aspen Plus
Aspen Model-Unit of operations
Pump
Pump parameters for first step SEQHTL in Aspen Plus
Aspen Model-Unit of operations
Heat Exchanger
Heat exchanger parameters for first step SEQHTL in Aspen Plus
Aspen Model-Unit of operations
Reactor
Reactor parameters for first step SEQHTL in Aspen Plus
Aspen Model-Unit of operations
Pressure valve
Pressure valve parameters for first step SEQHTL in Aspen Plus
Aspen Model-Unit of operations
Pump
Pump parameters for second step SEQHTL in Aspen Plus
Aspen Model-Unit of operations
Heat Exchanger
Heat exchanger parameters for second step SEQHTL in Aspen Plus
Aspen Model-Unit of operations
Reactor
Reactor parameters for second step SEQHTL in Aspen Plus
Aspen Model-Unit of operations
Pressure valve
Pressure valve parameters for second step SEQHTL in Aspen Plus
Description of each stream in SEQHTL
Stream
Composition
Flow Rate (kg/h)
1
2
3
4
Water 90%, Biomass 10%
Water 90%, Biomass 10%
Water 90%, Biomass 10%
Water 90%, Biomass 10%
Water 90%, Sugar 3.1%, WEs 2.1%,
TA Biomass 4.8%
Water 94.5%, Sugar 3.3%, WEs 2.2%
Water 94.5%, Sugar 3.3%, WEs 2.2%
Water 94.5%, Sugar 3.3%, WEs 2.2%
Water 94.5%, Sugar 3.3%, WEs 2.2%
TA Biomass 100%
Water 100%
Water 86%, TA Biomass 14%
Water 86%, TA Biomass 14%
Water 86%, TA Biomass 14%
Water 86%, TA Biomass 14%
Water 85.7%, Bio-oil 8.9%, WEs 1.7%, Biochar 3%, Bio-gas 0.7%
Water 89%, Bio-oil 9.3%, WEs 1.7%
Water 89%, Bio-oil 9.3%, WEs 1.7%
Water 89%, Bio-oil 9.3%, WEs 1.7%
Water 89%, Bio-oil 9.3%, WEs 1.7%
Bio-char 100%
Bio-gas 100%
Bio-oil 100%
Water 98%, WEs 2%
15000
15000
15000
15000
Temperature
(C)
25
25
72
115
15000
160
7
14280
14280
14280
14280
720
4320
5040
5040
5040
5040
160
139
120
77
160
25
36
38
120
180
7
3.5
3.5
3.5
7
1.01
1.01
34
34
34
5040
240
34
4854
4854
4854
4854
150
36
450
4404
240
205
190
122
240
240
122
122
34
17
17
17
34
34
17
17
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Pressure (bar)
1.01
7
7
7
Energy cost for the units of operation
in SEQHTL
Unit of Operation Energy Type Heat Input (MJ/h)
Description
Pump 1
Electricity
8.805
Pressure from 1 atm to 7 bar
Reactor 1
Fuel
3156.525
Temperature from 115 to 160C
Pump 2
Electricity
52.69
Pressure from 1 atm to 34 bar
Reactor 2
Fuel
1712.37
Temperature from 180 to 240C
4930.39
System total energy cost
Total
Process Description-one step process
Target productivity of bio-oil: 1M Gallon per Year
Working days per year: 260days
Working hours per day: 8h
Times of reaction finished per hour: 3 per hour
Bio-oil production per kg biomass: 0.23g
Biomass/water ratio: 1:9
Dry Algae composition:
Lipid: 25%, Sugar: 46%, Protein: 17%
One step------DHTL
Two step------SEQHTL
Input of first step of SEQHTL
Feed In
Flow Rate (kg/h)
Percentage
Total
19500
100
Water
17550
90
Biomass
1950
10
Lipids
487.5
2.5
Sugars
897
4.6
Protein
331.5
1.7
Others
234
1.2
Process Description-one step process
Output of DHTL
Products
Flow Rate (kg/h)
Percentage
Water
17550
90
Bio-oil
448.5
2.3
WEs
327.6
1.68
Bio-char
647.4
3.32
Bio-gas
526.5
2.7
Total
19500
100
Component flow rates and fraction in products of SEQHTL’s first step reaction
Process Description-one step process
9
7
B4
B5
B6
2
B1
B2
6
B3
1
3
12
4
5
8
Process Description-one step process
Component definitions for DHTL in Aspen Plus
Component definitions for DHTL in Aspen Plus
Process Description-one step process
Feed stream data for DHTL in Aspen Plus
Feed stream data for DHTL in Aspen Plus
Process Description-one step process
Pump
Pump parameters for DHTL in Aspen Plus
Process Description-one step process
Heat exchanger
Heat exchanger parameters for DHTL in Aspen Plus
Process Description-one step process
Reactor
Reactor parameters for DHTL in Aspen Plus
Process Description-one step process
Pressure valve
Pressure valve parameters for DHTL in Aspen Plus
Process Description-one step process
Description of each stream in DHTL
Stream
Composition
1
2
3
4
Water 90%, Biomass 10%
Water 90%, Biomass 10%
Water 90%, Biomass 10%
Water 90%, Biomass 10%
Water 90%, Bio-oil 2.3%, WEs 1.7%,
Bio-char 3.3%, Biogas 2.7%
Water 95.8%, Bio-oil 2.4%, WEs 1.8%
Water 95.8%, Bio-oil 2.4%, WEs 1.8%
Water 95.8%, Bio-oil 2.4%, WEs 1.8%
Water 95.8%, Bio-oil 2.4%, WEs 1.8%
Biogas 100%
Bio-char 100%
Bio-oil 100%
Water 99%, WEs 1%
5
6
7
8
9
10
11
12
13
Flow Rate
(kg/h)
19500
19500
19500
19500
Temperature
(C)
25
25
115
175
Pressure
(bar)
1.01
34
34
34
19500
240
34
18326.1
18326.1
18326.1
18326.1
526.5
647.4
448.5
17713.8
240
205
190
115
240
240
115
115
34
17
17
17
34
34
17
17
Process Description-one step process
Energy cost for the units of operation in DHTL
Units of Operation
Energy Type
Heat Input (MJ/h)
Description
Pump
Electricity
63.12
Pressure from 1 atm to 34 bar
Reactor
Fuel
7343.7
Temperature from 175 to 240 C
7406.82
System total energy cost
Total
Comparison between SEQHTL and DHTL
SEQHTL
DHTL
Bio-oil
Productivity
(M Gallon/year)
1.04
1.04
Biomass
Consumption
(kg/h)
1500
1950
Energy
Consumption
(MJ/h)
4930.39
7406.82
Bio-oil
HHV
(MJ/h)
16785
16683
Net Energy
Balance
(MJ/h)
11854.6
9276.2
Thermal
Efficiency
(%)
44.9
41.9