Transcript Overview of Process Design - Department of Chemical Engineering

Overview of Process Design
Chapter 4
Terry A. Ring
ChE
Where is Design used in
Industry?
Where is Design used in Industry?
• De Novo Designs
• Known Plants but different location or
larger size
• Plant Improvement
– Debottlenecking Plant
– Increase Plant Capacity
– Increase Plant Efficiency
– Decrease Costs
– Pollution Minimization
Importance of Process Design
• In Preliminary Process Design
– 98% Operating Costs Committed
– 80% Capital Costs Committed
• Less than 10% $ Spent
• Design is Very Important
• But why is this so?
How is Design Practiced
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Process Conception
Preliminary Design
– Process Concepts
– Process Economics
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Management decision to go forward
Intermediate Design
– P&ID’s
– Ask vendors for prices major pieces of equipment
• Reactor, Separators, HX, Utilities, tank farms
– Process Economics
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Management decision to go forward
Detailed Design
– Mechanical Engineering
• Equipment + Supports
– Where are all the nuts and bolts
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Piping elevation
Electrical/Power Engineering
Utilities
Process Economics
Management decision to go forward
Process Creation
• Chemical Reaction Routes
• Preliminary Database
– MSDS – (Health and safety info.)
• Raw Materials
• Reaction Products and Intermediates
– Thermo/phys properties (Expts and Predictions)
• Heats of Formation
• VLE data, solubilities, etc.
– Chemical Prices (Chemical Market Reporter)
Operating costs
• Selection of Raw Materials
• Selection of Reaction Path to Product
• Determine Gross Profitability of Process
• Examples
– Vinyl Chloride Manufacture (part of PVC plant)
• Example in your book
– Octane Manufacture (part of refinery)
Process Economics-I
• Macro View
– Possible Reactions for vinyl chloride
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1) C2H4 (ethylene) + Cl2  C2H3Cl (vinyl Chloride) + HCl
2) C2H2 (acetylene) + HCl  C2H3Cl
3) C2H4 + Cl2  C2H4Cl2  C2H3Cl + HCl
4) C2H2 + 2HCl + ½ O2 C2H4Cl2+H2O
C2H4Cl2 C2H3Cl +H2O
C2H2 + 2HCl + ½ O2C2H3Cl +H2O
(overall)
• 5) C2H4 + Cl2  C2H4Cl2
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C2H2 + 2HCl + ½ O2 C2H4Cl2+ H2O
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2 C2H4Cl2 2C2H3Cl + 2HCl
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2C2H4 + Cl2 + ½ O2 2C2H3Cl + H2O
(overall)
Gross Profitability Analysis-1
• Start With Raw Material Costs and
Product Prices
Gross Profitability Analysis-1
• For Each Reaction Determine the Profit to
be made
• Gross Profit is
– 22¢/lb(1) +18¢/lb (0.583)-18¢/lb(0.449)-11¢/lb(1.134)=11.94 ¢/lb
Gross Profitability Analysis-2
• Overview of Various Reactions
• Reaction 3 is most profitable!
• How much do we make? Market Volume?
http://nexant.ecnext.com/coms2/summary_0255-3041_ITM
Example of Market Information
http://www.ceramics.org/ASSETS/574195312DA149928805FFEA1242FECF/MaterialsReview_08_08.pdf
Process Synthesis-1
• Reaction 3
– Direct Chlorination
– Pyrolysis
Consider Separations
• VLE data
• Boiling Points
• Flash HCl from Rxn Products
Process Synthesis-1
• Separation System
Process Synthesis-3
• Task Integration
– Reactor & Condenser
• Separations
Onion Model of Process Design
Overall Process
Octane Reaction
• 2C2H4 + C4H10  C8H18
• P= 5 psi, T=93C, X=98% Conversion
Preliminary
Flow Sheet
Flash
ΔP= 2 psi
Distillation
Purge Stream
With Heat
Integration
Without Heat Integration
What else can be done?
• Where is the heat duty for the Flash vessel
coming from?
– Heat Exchanger coupling reactor feed to
reactor product.
• Do we really need the flash vessel?
– Let distillation column do all the separation.
• Reactor heat duty
– Exo or Endo reaction?
– Where does it come from?
Onion Model of Process Design
Importance of Process Design
• In Preliminary Process Design
– 98% Operating Costs Committed
– 80% Capital Costs Committed
• Less than 10% $ Spent
• Design is Very Important
• But why is this so?
Why
• In Preliminary Design
– Decide on Raw Materials
– Decide Process
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Reactor System
Separation System
Recycle System
Heat Integration Scheme
Utilities
Operating Costs
Capital Costs
Capital Costs
Capital Costs
Capital Costs
Operating Costs