Subject2.Introduc0ontoChemicalProcessSystemsDesign

ChemicalProcessDesign

JavierR.ViguriFuenteCHEMICALENGINEERINGANDINORGANIC

CHEMISTRYDEPARTMENTUNIVERSITYOFCANTABRIAjavier.viguri@unican.es

License:Crea0veCommonsBY‐NC‐SA3.0

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INDEX

1.- Design Characteristics

2.- Major steps in process design

- Methodology, Tools and Criteria

3.- Emphasis and Importance

4.- Case Study

5.- Further Reading and References

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1.- Design Characteristics

Based on mathematics, basic science, engineering science, and flavored by the humanities, social science and economics,

engineering design is the devising of an artifact, system, new

process or modifications to existing plants to best meet a stated objective, commonly through the use of manual, algorithmic or

computer-based tools.

Chemical Engineering Process Design ���� Our Emphasis

Product Design ���� Introduction

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2.- Major Steps in Process Design: Methodology

Engineering design involves development or specifications and criteria, and the synthesis, analysis, construction, testing, and evaluation of alternative solutions to best meet the desired criteria in light of safety, reliability, economic, aesthetic, ethical, and social considerations.

Synthesis: Put together parts. Systematic alternative representation

Analysis: Predict Behaviour. Solving Mass & Energy balances + Design variables ���� Simulation

Evaluation: Optimum $ (+ other criteria) ���� Decision

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Problem Specification ���� Concept Generation

Process Synthesis ���� Generation of AlternativesOptimization

Analysis ���� Mass and energy balances; Sizing

Evaluation ���� Design Criteria

Note: Iterative process. For improvement ���� Optimization

Memo 1

Memo 2

Memo 3

2.- Major Steps in Process Design: Methodology

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Problem Specification:

Key: Identification of needs, specifications and process technology

Challenge: Often Incomplete information (Open-ended)

Tools: Meetings, literature (web), link business (marketing)

Synthesis Process Strategy:

Define: Flowsheet structure

Challenge: Very large number of alternatives

Tools: Literature, patents

Heuristics (rules of thumb)

Hierarchical decomposition (levels)

Superstructure optimization (Mathematical programming)

Key Step

2.- Major Steps in Process Design: Methodology

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Analysis ���� Mass ans energy balances; Sizing

Key: Predict performance ���� need models (Simple – Complex)

Challenge: Complexity of models

Tools: - Rules of Thumb: Quickly understood, easily used, practical method yielding

approximate results

- Short-cut methods (EXCEL, Matlab, GAMS, FORTRAN)

- Process simulating ���� Useful to check ranges, phases, etc.

* Sequential modular (ASPEN)

* Equation oriented (gPROMS)

Evaluation: Design Criteria

Define: Evaluate “goodness” design

Challenge: Multiple criteria

Tools: Economic evaluation (NPV) Exergy analysis (energy efficiency)

Reliability analysis (IGCC) HAZOP - HAZard and OPerability- Analysis (Safety)

Environmental Impact (CO2) Controllability (Biomass not uniform)

Flexibility (Refinery) LCA (Ecoindicator-99)

2.- Major Steps in Process Design: Methodology

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3.- Emphasis and Importance of the Preliminary Process Design

Conceptual Design ���� Big picture

Means preliminary Design whit short-cut models and using economics as major

criteria

Major Goal: Economic Feasibility

[Preliminary Design Area � Decision Largest

Economical Impact]

e.g. Reactive distillation

Time project

Inve

stm

en

t

Co

st

80 %

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3.- Emphasis and Importance of the Preliminary Process Design

Why is preliminary design important ?

Decisions in preliminary design have greatest economic impact ���� With 10-15% of

the money fixed the 80% final costs (Raw materials and reaction step)

Since number of alternatives is large key decision making Process Synthesis.

Fact: Since only few processes are economically feasible major role of Process

Synthesis is screening alternatives

� e.g., Pharmaceutical Industry � from many molecules to 1 marketable product

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4.- Case Study

* Presentation of the case study: Production ethanol from ethylene

• How to generate flowsheets• Obtention of the rule to generate flowsheet (limit of costs)

* Consideration of process Alternatives

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5.- Further Reading and References

• Biegler, L., Grossmann, I., Westerberg, A., 1997, Systematic Methods of Chemical

Process Design, Prentice Hall.

• Douglas, J.M., 1988, Conceptual Design of Chemical Processes. McGraw-Hill.

• Seider, W., Seader, J., Lewin, D., Widagdo, S., 2010, Product and Process Design

Principles. Synthesis, Analysis and Evaluation. 3rd Ed. John Wiley & Sons.

• Thakore, S.B., Bhatt, B.I., 2007, Introduction to Process Engineering and Design 1st

ed. Tata McGraw Hill Education