CHE 448 Chemical Engineering Design

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CHE 448 Chemical Engineering Design
Spring 2006
Class Nr 4, Thursday, January 19
Orchid By Dr. A. Rolla
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Memo
To Chief Process Engineer From J. Dilbert,
Plant Manager
Explore the possibility of making Benzene out of
our excess Toluene production in our Baton-Rouge,
LA, site. We are selling Benzene at 1.17/gal
(fob) and we sell Toluene at 0.80 /gal. Price
per gallon is 46 higher! Currently we produce
and sell about 60 106 gal/year of each (B T) (
200,000 tons/year of each). We may be able to get
additional profits of 22 M/yr!!
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Case study Hydro-dealkylation of Toluene
Proposal Make benzene out of Toluene
Motivation Seasonal use of Benzene larger than
excess production of Toluene
Incentives Benzene 1.17 /gal 27.284
/kmol0.349 /kg Toluene
22.46 /kmol (21) 0.243 /kg Feasible increase
in production after market study
80,000 tons/year1.024 106 kmol/yr Rev 28
M/yr Profit opportunity
4.94 M/yr
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Example of gross economic analysis
Reaction I
Reaction II
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Gross Economic Model Revenues
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Block diagram analysis
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Process Stoichiometry
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Stoichiometric equations
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Economic Potential Model
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Basic flowsheet
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Selectivity and Flow Rates versus Conversion
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Conversion and Selectivity Data
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Molecular Structure Design Why?

• Polymers that have desired properties
• Refrigerants that boil and condense at desired
  temperatures
• Solvents for liquid-liquid extraction
• Solvents for azeotropic distillations

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Property Estimation Methods

• Computer Data Banks
• Reid et al Properties of Gases and Liquids
• AIChE-DIPPR (Design Institute for Physical
  Property Data)
• ASPEN PCD (Pure Component Data).

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Property Estimation Methods

• Bound- and Group-Contributions
• UNIFAC, NRTL, UNIQUAC
• Polymer Property Estimation

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Project Inception (Garnett, 1/20/04)

• The first questions for a new product are
  always
• What does it do?
• What will it cost?

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What is a Feasibility Study? (Garnett, 1/20/04)

• A Feasibility Analysis consists of three parts
• The project scope or basis
• Capacity, PFD, Preliminary Equipment List, etc
• Process Hazards Analysis
• The cost forecast
• Capital Cost
• Operating Cost, Profit, etc.
• The assumptions on which the analysis is based

The Design Report is the Key Deliverable
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Focus of First Report 02/MAR/06

• Preliminary Analysis Deliverables (Page 3 of
  General Introduction).
• Identification of Problem and Needs
• Literature Survey
• Marketing and Business Studies
• Reaction Path Studies
• Hazards evaluation
• Preliminary Flowsheet and Gross Material Balance
• Gross Profit Analysis.

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Hazards and Materials

• If you have to kill it, kill it as early as
  possible!
• MSDS for all chemicals involved
• Evaluate the need for special alloys and
  materials
• Evaluate the need for special fabrication
  techniques
• Environmental, health considerations

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Chapter 3 Process Synthesis/Creation

• Assemble data for preliminary database.
• Assemble unit operations (reactors, distillation
  columns, heat exch, etc) into a process
  flowsheet.
• Build a suitable representation (flowsheets
  material and energy balances).
• Perform experiments when needed.
• Use a simulator to evaluate alternatives.

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Assemble preliminary database

• Material Safety Data Sheets (MSDS)
• Google Search Hydrogen Sulfide MSDS.htm
• SH2MSDS.PDF
• Physicochemical Properties
• CRC Handbook of Chemistry and physics C\Program
  Files\CRC Press\CRC.exe
• Poling et al. Properties of Gases and Liquids
• Woods, Data for Process Design and Engineering
  Practice
• CHEMCAD, PRO/II

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First Level of DecisionBatch vs Continuos

• Advantages of Continuous Plants
• Equipment are smaller
• In general, easier to control
• Smaller demand for labor
• Advantages of Batch Plants
• More versatile, more than one product
• Smaller number of vessels

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Guidelines for selection

• Production rate
• Less than 10,000 ton/year Batch
• More than 100,000 ton/year Cont.
• Market Forces
• Seasonal production
• Short product lifetime
• Operational Problems
• Long reaction times
• Special problems slurries at low flow rates
• Rapidly fouling materials

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Capacity/size considerations

• Look for characteristic stream
• F(tons/year)F(kmol/hr)F(gpm)
• Assume
• Density (if not knownwater)
• Hours on line (8000 hr/year)
• Mean velocity in pipes v 1.5 m/s
• Pressure hike in pumps dP 3 atms 90 ft