1/31/99 Design Methdology - Intro 1
DESIGN METHODOLOGY
GOAL -- Produce a design for a chemical plant that:
u Is economically acceptable
and
uIs operable,i.e.,
eIs safe
eIs controllable
eIs reliable,and
eIs environmentally acceptable
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What are the basic steps in
designing a chemical process?
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Determine Specifications
Generate Alternate Conceptual Designs
Design #1 Design #2 Design #3
Evaluate Design Criteria
OK?
Yes
Done
NoIterate
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DESIGN METHODOLOGY PHASES
u Phase I,Conceptual Design
eGenerate alternate designs
eSelect best based on performance indices
uPhase II,Detailed Design
eRigorous equipment design
eDevelop command and control strategy
eRigorous reliability and safety analysis
uPhase III,Mechanical Design
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GENERATION OF ALTERNATE
FLOWSHEETS BY
HIERARCHICAL DECOMPOSITION
uLevel 1,Choice of process type
uLevel 2,Input-Output Structure
uLevel 3,Recycle Structure
uLevel 4,Separation System Synthesis
uLevel 5,Heat and Power Network Synthesis
Levels 2 through 5 will depend upon the choice of process type.
(Based on J.M,Douglas,Conceptual Design of Chemical Processes,
McGraw-Hill,1988)
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DESIGN CRITERIA
uPlant Capacity
uProduct Purity or Composition
uRaw Materials or Feedstock Availability
uOperability
eSafety
eControllability
eAvailability
eEnvironmental Acceptability
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EVAULATION INDICES
uPerformance
eMake capacity
eMeet product quality specs
uProfitability
eDCFROR,ROI,Payout Time,etc.
eTransfer Price
uOperability
eMinimum holdup of hazardous chemicals
eMinimal complexity for safety and control