P1258830027hoyMs

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CHE 448 Chemical Engineering Design
Spring 2006. Class 11 Tuesday February 14
Look Mom what I was doing last Sunday!
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Industrial Advisory Board Friday, February 17
1130 AM at EB 207 Pizza and soft drinks
provided AIChE Student Chapter Omega Xi
Epsilon Attendance required for graduating Senior
students (Seniors not worried about graduating,
no need to show up).
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Report due March 2

• Identification of Problem and Needs. Scope and
  Organization of Project. Market assessment.
  Literature Survey, Marketing and Business
  Studies, Products and Raw Materials
  specifications. Reaction Path Studies, Gross
  Material Balance and Gross Profit Analysis.
  Safety analysis (HAZOP). Preliminary Flowsheet.

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General Report Format

• Title Page
• Identify roles
• Executive Summary (less than 2 pages).
• Discussion of findings with references to report
  sections (Page Numbers!)
• Conclusions
• Body of Report
• Well identified and numbered sections for all
  report items
• Appendices

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Writing Tips (R. Garnett, 2004)

• 1st Tip
• Good writing comes from good editing.
• Good editing comes from having time to edit.

If I had more time, I would have written a
shorter letter. -Winston Churchill
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Eliminate light/heavy endsPyrolisis reactor
Composition stream 7
P/T mVC mHCl mDC
26/? 700 700 465
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Spray quench tank
When gas cools down its volume decreases and
pressure must decrease also. Pressure can be
maintained at a given level using a back-pressure
regulating valve in the exhaust stream.
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Spray quenching operation
Spray quenching Heat Exchanger duty -50113
MJ/h - 13.9 MW Liquid comp Pure
DCEthane Temperature of liquid 132 C CP stream
0.1403 MJ/kmol K TBoiling Range of T in
heat exchanger 132 C to 107 C
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Summary of quenching conditions
T(7) C P(7) KPa T(6) C T(5) C M(5) Kmol/h DQ MW
133 2634 133 158 14400 13.9
170 2026 170 195 12710 12.38
170 1256 170 195 12435 12.11
170 1600 170 195 12435 12.14
170 1300 170 220 6232 12.14
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What are dew/bubble point of effluent after spray
quenching?
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Effluent after condensationDew versus bubble
point
Stream Quench Effluent
Temp C 133
Pressure Pa 2600000
Enthalpy MJ/h -97743
Vapor fraction 1.0
Total Flow 1865
Total flow units Kmol/h
Comp unit Kmol/h
Hydrogen Chlo 700
Vinyl Chloridr 700
Dichloroethane 465
Heavies/Lights ?
Stream Condensed effluent
Temp C 42
Pressure Pa 2600000
Enthalpy MJ/h -139300
Vapor fraction 0
Total Flow 1865
Total flow units Kmol/h
Comp unit Kmol/h
Hydrogen Chlo 700
Vinyl Chloridr 700
Dichloroethane 465
Heavies/Lights ?
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Conditions for stream entering first separation
column
Chemical Normal BP C atm atm atm Critical Constants
1.0 4.8 12 26 TC PC atm
HCl -84.8 -51.7 -26.2 0 51.4 82.1
C2H3Cl -13.8 33.1 70.5 110 159 56
C2H4Cl2 83.7 146 193 242 250 50
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Conditioning of quench-effluent

• Quench Heat exchanger cools liquid from 132 C
  to 107 C.
• Condense liquid at 26 atm Condenser temperature
  is 43 C.
• Cool liquid down to 43lt T lt 6 C Brine at 5 C.
• 4. Expand liquid down to 12 atm before entering
  distillation column.

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Chapter 7 Synthesis of separation trains

• Feed separation system
• Remove catalyst poisons or inerts not needed for
  control
• Reactor effluent system
• Vapor recovery system
• Liquid separation system

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From Block Diagram to Flowsheet
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Feed separation system
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Reactor effluent stream
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Clasification of destinations
Classification Destination
Gaseous by products and feed impurities Vent
Gas reactants, inert gases, hazardous byproducts Recycle and purge
Reactants, intermed., azeotropes, reversible Recycle
Reactants with complete conversion None
Gas reactant not recovered Vent
Liquid reactant not recovered Waste
Primary product Primary
Valuable byproduct Separate
Fuel products Fuel
Waste byproducts Waste
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The reactor effluent is a liquid

• Heuristic 9 Separate liquid mixtures using
  distillation, stripping, enhanced (extractive,
  azeotropic, reactive) distillation, liquid-liquid
  extraction, crystallization and/or adsorption.
• Liquid effluent from chlorination reactor no
  separation needed.

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The reactor effluent is a two-phase mixture

• Heuristic 10 Attempt to condense or partially
  condense vapor mixtures with cooling water or a
  refrigerant.

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Flash separations
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The reactor effluent is a vapor

• Heuristic 11 Separate vapor mixtures using
  partial condensation, cryogenic distillation,
  absorption, adsorption, membrane separation
  and/or desublimation
• Effluent from quenching cool it and separate
  phases if possible.

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Vapor recovery system

• Where will it be located?
• The purge stream
• The gas-recycle stream
• The flash vapor stream
• What type of vapor recovery system?
• Condensation
• Absorption/adsorption
• Membrane separation
• Reaction systems

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Location of vapor recovery system
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Type of vapor recovery system

• Condensation Low temperature, high pressure, or
  both.
• Adsorption Pressure-swing or heat regeneration.
• Absorption Differential solubility
• Reaction scavengers, formation of intermediate
  compounds.

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Combine vapor recovery and liquid separation
systems
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Liquid separation system

• How should light ends be removed?
• What should be the destination of light ends?
• Do we recycle components that form azeotropes
  with the reactants or do we split the azeotropes?
• What separations can be made by distillation?
• What sequence of columns we use?
• How should we accomplish separations if
  distillation is not feasible?

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Effluent from hydrogenation unit

• T100 C P 500 kPa

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Alternatives for light-end removal

• Drop pressure or increase temperature of a
  stream, and remove the light ends in a flash
  drum.
• Use a partial condenser on the product column

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Alternatives for light-end removal

• Use a pasteurization section on the product
  column.
• Use a stabilizer column before the product column

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Liquid separation system

• How should light ends be removed?
• What should be the destination of light ends?
• Do we recycle components that form azeotropes
  with the reactants or do we split the azeotropes?
• What separations can be made by distillation?
• What sequence of columns we use?
• How should we accomplish separations if
  distillation is not feasible?

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What should be the destination of light-ends?

• Vent to flare
• Light end have no value
• Can be vented to flare
• Use as fuel
• Recover fuel value
• Recycle through vapor recovery system.
• Introduces another recycle.

.
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Light-ends decision graph
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Liquid separation system

• How should light ends be removed?
• What should be the destination of light ends?
• Do we recycle components that form azeotropes
  with the reactants or do we split the azeotropes?
• What separations can be made by distillation?
• What sequence of columns we use?
• How should we accomplish separations if
  distillation is not feasible?

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Recycle azeotropes with the reactants or split
the azeotropes?

• Component makes an azeotrope with reactants?
• Recycle the
• azeotrope
• Split the
• azeotrope