(Chemical Engineering Plant Design)

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?????????????????????????????? (Chemical
Engineering Plant Design)
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Design

• 1. Conceptual design develop a preliminary
  flowsheet using approximate methods.
• 2. Preliminary design use rigorous simulators to
  evaluate steady-state and dynamic performance of
  proposed flowsheet.
• 3. Detailed design specify type of trays, no. of
  sieve tray holes, piping, pumps etc.

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CHAPTER 1 THE NATURE OF PROCESS SYNTHESIS AND
ANALYSIS
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1.1 Creative Aspects of Process Design
The propose of engineering is to create new
material wealth.
Process and plant design is the creative activity
whereby generate idea and then translate them
into equipment and processes for producing new
materials or for significantly upgrading the
value of existing materials.
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In any particular company, we might try to
generate new idea

• To produce a purchased raw material
• To convert a waste by-product to a valuable
  product
• To create a completely new material (synthetic
  fibers, food, bioprocessing)
• To find a new way of producing an existing
  product (a new catalyst, a bioprocessing
  alternative)
• To exploit a new technology (genetic engineering,
  expert systems)
• To exploit a new material of construction (high-T
  or high-P-operation, specialty polymer)

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Level of Engineering Designs
TABLE 1.1-1 Types of design estimates Order of-magnitude (ratio estimate) base on similar previous cost data probable accuracy exceed 40 Study estimate (factored estimate) base on knowledge of major item of equipment probable accuracy up to 25 Preliminary estimate (budget authorization estimate scope estimate)based on sufficient data to permit the estimate to be budgeted probable accuracy within 12 Definition estimate (project control estimate) based on almost complete data, but before completion of drawing and specifications probable accuracy with 6 Detail estimate (contractors estimate) based on complete engineering drawings, specifications, site surveys probable accuracy with 3
Frome A. Pikulik and H.E. Diaz, Cost Estimating
Major Process Equipment, Chem. Eng., 84(21)
106(1977)
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TABLE 1.1-2 Engineering Costs to Prepare
estimates(1977)
Less than 1 million 1-5 million 5-50 million
Type of estimate Plant Plant Plant
Study ( thousands) 5-15 12-30 20-40
Preliminary( thousands) 15-35 30-60 50-90
Definitive ( thousands) 25-60 60-120 100-230
Frome A. Pikulik and H.E. Diaz, Cost Estimating
Major Process Equipment, Chem. Eng., 84(21)
106(1977)
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1.2 A Hierarchical approach to Conceptual Design
Example Hydrodealkylation of Toluene
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HDA Process
Basic information 1. Reactions take place
between 1150-1300 F. 2. Pressure is about 500
psi. 3. Excess hydrogen (5/1 ratio) prevents
coking. 4. Effluent gas must be quenched to 1150
F in order to prevent coking.
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HDA Process
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HDA Process
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HAD Process
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Vapor Recovery System
As a vapor recovery system we could use one of
these

• Condensation(high P or low T, or both)
• Absorption
• Adsorption
• A membrane process

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Simplified Flowsheet for the Separation Systems
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Recycle Structure of the Flowsheet
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Input-Output Structure of the Flowsheet
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Possible Limitation
Hierarchy of decisions______________ 1.
Batch versus continuous 2. Input-output structure
of the flowsheet 3. Recycle structure of the
flowsheet 4. General structure of the separation
system a. vapor recovery system b. liquid
recovery system 5. Heat-exchanger
network______________
The goal 0f conceptual design is to find the
best alternative
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Shortcut Solutions
Decomposition Procedures for Existing Processes

1. Remove all the heat exchangers, drums, and
   storage vessels.
2. Group all the distillation columns (liquid
   separation system block)
3. Simplify the general structure of the separation
   system (similar to fig. 1.2-5)
4. Lump (group all units in single box) the complete
   separation system (similar to fig. 1.2-6)
5. Lump the complete process.

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IPA Plant
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Ethybenzene Process
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