E D W I N Z O N D E R V A N
T U / E
J U N E 1 4 T H U V A .
Process Design; Art or Engineering?
...Pragmatism or fundamentals?
Outline
Introduction Who am I? What about TU/e and Chem. Eng? Process design
What is process design?
Process design in a nutshell (by example) Process creation/synthesis Reactor design Separations design Recycles Process simulation and optimization Heat and/or mass integration Economic evaluation
Current research Reactive distillation Biorefinery
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Process Design; Art or Engineering?
Who am I?
25-6-2012
Born February 26th 1976 in Leeuwarden Performed bachelor in Process automation in Leeuwarden (1999)
Performed master in Chemical engineering at Groningen University (Master thesis topic: System Identification for control) (2003)
Performed doctorate at Twente University/Groningen University (2007)
Works currently as assistant professor at Eindhoven University
Process Design; Art or Engineering?
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What about TU/e and Chem. Eng?
Three educational and research tracks: Chemistry
Material science
Process Engineering
Averagely 50 students enrol each year in our Bachelor and M.Sc. program (Majority moves to PE)
Averagely 15 students enrol in our post master “Process and Product Design”
Around 150 Ph.D. Students
Around 50 staff
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Process Design; Art or Engineering?
What about TU/e and Chem. Eng?
Current classes in process and product design: 6BA75 – Process design, Bachelor course, 3 ECTS (40
students)
Case: Hydroalkylation of toluene
6BO06 – Product design and process management, Bachelor course, 4 ECTS (40 Students)
Case: Micellar catalysis of propylene oxide
6PE42 – Integrated process design, M.Sc. Course, 5 ECTS, (40 students)
Case: Production of paraphenylene diamine
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Process Design; Art or Engineering?
What is process design?
In chemical engineering, process design is the design of processes for desired physical and/or chemical transformation of materials. The design starts at a conceptual level and ultimately ends in the form of fabrication and construction plants.
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Process Design; Art or Engineering?
Nano Micro Meso Macro
What is process design?
Several “process design” procedures: J.M. Douglas, Conceptual design of chemical processes, (1988)
Seider et al., Product and process design principles, (2010)
Grossmann et al, Systematic methods in chemical process design, (2004)
Bongers, Product Driven Proces Synthesis (PDPS)
All of them incorporate some kind of hierarchy with feedback. Passing through the hierarchy more level of detail is required.
Process design has many (multidisciplinary) facets; engineering, environment, business.
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Process Design; Art or Engineering?
Douglas’ Process design hierarchy 8
Batch versus continuous
Input-output structure of the flowsheet
Recycle structure of the flowsheet
• Vapor recovery system • Liquid recovery system
General structure of the separation system
Heat exchanger network
Process Design; Art or Engineering?
Steps in Design and Retrofit 9
Process Design; Art or Engineering?
Assess Primitive Problem
Detailed Process Synthesis -Algorithmic
Methods
Development of Base-case
Plant-wide Controllability
Assessment
Detailed Design, Equipment sizing, Cap.
Cost Estimation, Profitability Analysis,
Optimization
Assess Primitive design problem 10
Process design begins with a primitive design problem that expresses the current situation and provides an opportunity to satisfy a societal need.
Normally, the primitive problem is examined by a small design team, who begins to assess its possibilities, to refine the problem statement, and to generate more specific problems: Raw materials - available in-house, can be purchased or need to be
manufactured? Scale of the process (based upon a preliminary assessment of the current
production, projected market demand, and current and projected selling prices)
Location for the plant
Refined through meetings with engineering technical management, business and marketing.
Brainstorming to generate alternatives
Process Design; Art or Engineering?
Important note... 11
We have many systematic tools to start designing a process, which seems to make it an Engineering discipline...
... But during the design process, it is creativity and knowledge beyound the Engineering community that leads to novel designs, which seems to make it an Art!
... But in this talk the emphasis will be on pragmatism, so on Engineering!!
Process Design; Art or Engineering?
The beginning... 12
... Most of the time it starts with something that seems to work in the lab!
The Alchemist, Adriaan van Ostade
Process Design; Art or Engineering?
Example: The toluene hydroalkylation process
Principle path:
C7H8 + H2 C6H6 + CH4
Benzene is one of the intermediates that can be converted to cyclohexane, and cyclohexane can be used to produce nylon
Side reaction:
2C6H6 C12H10 + H2
From lab. Data: irreversible reactions, no catalyst, temp ~1200-1270oF, conversion: 75% toluene/benzene, 25% benzene/biphenyl
Process Design; Art or Engineering?
Design objective
Design a plant with a capacity of 200 MMlb/year (based on a toluene conversion of 274 lbmol/hr and 330 days of operation annually)
Process Design; Art or Engineering?
Reaction operation of the hydroalkylation
Purge methane to avoid expensive separation of H2/CH4
Excess of H2 to prevent carbon deposition and to absorb heat
Process Design; Art or Engineering?
Adding the separations
Note 1: Pressures not yet known Note 2: this is just one possible selection
Process Design; Art or Engineering?
Adding cooling and heating
Note: Heating and cooling added to alter temperature, pressure and liq./vap. Phase
Process Design; Art or Engineering?
Process simulation
After the generation of process flow-sheets you would like to analyze several things:
To solve mass/energy balances, phase equilibria, mass transfer, kinetics,
All with the aim of finding suitable operating conditions (Temperature, pressure, etc.)
P.S. Simulators are also developed and used with the aim of training operators.
Process Design; Art or Engineering?
Process simulation
For this we may use process simulators
Process simulators are mostly used for steady-state and scheduling calculations.
Process simulators can also be used for process dynamics and control;
economic evaluation and profitability analysis;
process optimization.
Process Design; Art or Engineering?
Why should we use simulators?
Solution of mass/energy balances in a simultaneous manner
Non-ideal thermodynamic models
Detailed (rigorous) unit operation models
Solve large sets of equations (typical ~10.000-100.000)
Process Design; Art or Engineering?
Software packages
There are many process simulator packages available, basically we divide them into two types:
Modular: Aspen Plus, HYSIS, CHEMCAD, PRO II, Unisim,...
Equation oriented (EO): Matlab, gproms, GAMS,...
Process Design; Art or Engineering?
Modular mode
Unit and thermodynamic models are self-contained subprograms (modules)
These flow-sheets are called at a higher level to converge the stream connectivity of the flow-sheet (e.g. Recycle streams)
Has a long history and is more popular for design work
Easy to construct and debug
however; it can be inflexible for various user specifications
Process Design; Art or Engineering?
Equation oriented mode
Process equations (unit, connectivity, thermodynamic) are assembled and solved simultaneously.
Requires sophisticated numerical methods and software engineering concepts
Is primarily applied to online modelling and optimization.
Process Design; Art or Engineering?
Historical evolution
1950s: Unit stand-alone models execution in sequence to form a flow-sheet origin of sequential modular mode.
1960s: Sequential modular in-house flow-sheeting packages (petrochemical companies). Academic research for fundamentals of EO simulators.
1970s: Advanced methods for modular flow-sheets simultaneous modular flow-sheets. More general models and advanced numerical methods. Aspen (MIT).
1980s – 1990s: Considerable industrial development for equation oriented mode. User friendly interfaces and powerful algorithms. Vendor-supported software.
2000-today: Consideration of special issues and addition of the respective features/modules (e.g. Supply chain problems, advanced economic analysis, etc.)
Process Design; Art or Engineering?
Heat integration 29
Process Design; Art or Engineering?
Some streams in the process require heating and cooling.
Heat integration is concerned with finding the best connection between hot-, cold- and utility streams
Several procedures: Pinch analysis Graphical methods Algorithmic methods (e.g. With
math. optimization)
Heat and/or mass integration 30
Process Design; Art or Engineering?
Example of ethylene production process with heat integration
Safety considerations 31
Example Disaster 1 – Flixborough: 1st June 1974 http://www.hse.gov.uk/hid/land/comah/level3/5a591f6.htm 50 tons of cyclohexane were released from Nypro’s KA plant
(oxidation of cyclohexane) leading to release of vapor cloud and its detonation. Total loss of plant and death of 28 plant personnel.
Highly reactive system - conversions low, with large inventory in plant. Process involved six, 20 ton stirred-tank reactors.
– Discharge caused by failure of temporary pipe installed to replace cracked reactor.
– The so-called “dog-leg” was not able to contain the operating conditions of the process (10 bar, 150 oC)
Process Design; Art or Engineering?
Safety considerations 32
Flixborough - What can we learn? Develop processes with low inventory, especially of flashing
fluids (“what you don’t have, can’t leak”) Before modifying process, carry out a systematic search for
possible cause of problem. Carry out HAZOP analysis Construct modifications to same standard as original plant. Use blast-resistant control rooms and buildings
Process Design; Art or Engineering?
Safety considerations 33
Example Disaster 2 – Bhopal: 3rd December 1984 http://www.bhopal.com/chrono.htm Water leakage into MIC (Methyl isocyanate) storage tank leading
to boiling and release of 25 tons of toxic MIC vapor, killing more than 3,800 civilians, and injuring tens of thousands more.
MIC vapor released because the refrigeration system intended to cool the storage tank holding 100 tons of MIC had been shut down, the scrubber was not immediately available, and the flare was not in operation.
Bhopal - What can we learn?
– Avoid use of hazardous materials. Minimize stocks of hazardous materials (“what you don’t have, can’t leak”).
– Carry out HAZOP analysis. – Train operators not to ignore unusual readings. – Keep protective equipment in working order. – Control building near major hazards.
Process Design; Art or Engineering?
Process Control 34
Process design steady state
Dynamic behaviour unfavourable process characteristics.
Control systems should keep process at desired operating level for: Safety
Product specifications (quality and safety)
Environmental regulations
Operational constraints
Economics
Account for design errors
Process Design; Art or Engineering?
Plant wide control 35
Process Design; Art or Engineering?
Example of a plant wide control scheme for production of vinyl chloride
What to control and where to control without conflicts!
Economic evaluation 36
You use economic evaluation to determine from a set of alternative process designs that you have made whether or not they are (economically) feasible.
Cost accounting and profitability becomes more accurate as the process design becomes more detailed. But mind you that numbers can be easily 20-80% off!
Process Design; Art or Engineering?
Direct costs Indirect costs
Equipment
Piping
Civil & steel
Process control
Electrical
Insulation & paint
Engineering (conceptual,
basic, detailed)
Procurement
Construction & field
Supervision
Contract fees
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Economic evaluation: Cost Accounting
Process Design; Art or Engineering?
Estimation often on basis of cost factors, e.g Lang factors Sizing often according to power laws
Economic evaluation: Manufacturing costs 38
Cost of Manufacture (COM) Feedstock
Utilities
Labor related operations
Maintanance
Process Design; Art or Engineering?
Economic evaluation: Profitability analysis
Approximate profitability measures: Return of investment (ROI)
Payback period (PBP)
Venture profit (VP)
Annualized Cost
Rigorous profitability measures Net Present value (NPV)
Time value of money
Cash Flow and Depreciation
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Process Design; Art or Engineering?
Optimization for process design
Mathematical syntax:
min ( , )
. .
( , ) 0
( , ) 0
,
L U
L U
f x d
s t
c x d
g x d
x x x
d d d
x X d D
Objective: Economic or environmental criterion
Equality constraints: Mass & Energy balance, Equilibrium relations, etc.
Bound constraints: Equipment limits
Inequality constraints: Operating limits
Set over which the variables are defined: Continuous or discrete
Process Design; Art or Engineering?
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Types of optimization problems
Optimization
Discrete Continuous
CLP MIP
MINLP
G-O
LP,QP,LCP
NLP
DFO
surrogate SA,GA
See: Biegler & Grossmann (2004) Grossmann & Biegler (2004)
Process Design; Art or Engineering?
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Applications in Chem. Eng.
See: Biegler & Grossmann (2004) Grossmann & Biegler (2004)
Process Design; Art or Engineering?
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Optimization approaches
Mathematical programming Simplex method, Lagrange multiplier method, SLP, SQP,
Branch & Bound, Disjunctive programming, constraint programming, etc.
Global optimization / Meta-heuristic Neural networks, fuzzy logic, ant colony, simulated annealing,
taboo search, genetic algorithms, etc.
Other Stochastic programming, multi-objective optimization, ...
Process Design; Art or Engineering?
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Sustainable design of a reactive distillation column
Background Fatty acid esters of use to the food- and cosmetics industry.
Traditional production: Batch wise
Reactive distillation as PI option
Objective Develop and test a framework to identify and optimize relevant
operational and design parameters of an RD system
Reactive distillation
column
Process Design; Art or Engineering?
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Sustainable design
Selected variables for multi criterion decision analysis: Number of stages
Operating pressure
Ratio
Conversion
Proposed framework by Bojarski
Simulator Optimizer Decision variables
Process variables
Ecoinvent
Pro
cess
va
ria
ble
s
Met
rics
Process Design; Art or Engineering?
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Sustainable design
z1
z2
A
B
C D
E
E
A
B
C D
Objective space
Decision space
1 2min[ ( ) ( )]
. .
( ) 0
( ) 0
L U
Z x Z x
s t
c x
g x
x x x
x X Schilling et al. (1983)
Process Design; Art or Engineering?
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Sustainable design
z1
z2
E
A
B
C
D
Objective space
Non-inferior set (Pareto Optimal, or non-dominant)
Ideal- or utopia point
Process Design; Art or Engineering?
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Sustainable design
Environmental metrics
Economic metrics
Decision space
Multi criterion decision making
Catalyst loading is major player! Optimized settings for P, N, RR and X
Process Design; Art or Engineering?
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Optimal design of a Biorefinery
Background Crude oil will deplete, alternative feedstock required, biomass
can be a renewable resource.
Objective Develop a process design optimization model that can assist in
selecting promising biomass conversion routes.
Process Design; Art or Engineering?
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Proposed model
Superstructure and transhipment model
Sources Products (Sinks)
Processing steps
Splitting
Main reaction
Side reaction
Mixing
Reactants
Feed
Waste
Main product
By-product
Papoulias & Grossmann (1983) Dunn & Halwagi (1996)
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Process Design; Art or Engineering?
Method
Mathematical program
0
0
0
1
2
1
),,(
),,(
),,,,(
..
),,(min
,,
k
ik
k
ik
k
ii
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rk
m
rk
i
k
k
n
k
ik
n
fyg
fyg
SWMWh
y
ts
fyfwZ Objective function
Logical constraints
Component balances
Structural constraints
The details of this MINLP model can be found in the proceeding, it contains 452.179 single equations and 438.693 variables (containing only 68 decision variables) nonlinear terms can be linearized out!
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Process Design; Art or Engineering?
Optimal design
Linearizations:
(1 ) (1 )
min{ , }
max{ , }
Lx z Ux
y U x z y L x
L y y
U y y
{0,1}
xy
x
y
Glover
Replace xy with z Non-convex/nonlinear
Convex/linear
... 0
L U
yF
F F F
... 0
L U
F
yF F yFStandard
Process Design; Art or Engineering?
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Optimal design
Superstructure: all possible topologies. Outcome will be different for each objective
Process Design; Art or Engineering?
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