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CHE 448 – Chemical Engineering Design

CHE 448 – Chemical Engineering Design. Spring 2006 . Class Nr 4, Thursday, January 19. Orchid By Dr. A. Rolla. 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.

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CHE 448 – Chemical Engineering Design

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  1. CHE 448 – Chemical Engineering Design Spring 2006 Class Nr 4, Thursday, January 19 Orchid By Dr. A. Rolla

  2. 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!!

  3. 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 $/kmol=0.349 $/kg Toluene 22.46 $/kmol (21%) =0.243 $/kg Feasible increase in production after market study: 80,000 tons/year=1.024 106 kmol/yr ~ Rev= 28 M$/yr Profit opportunity: 4.94 M$/yr

  4. Example of gross economic analysis Reaction I: Reaction II:

  5. Gross Economic Model: Revenues

  6. Block diagram analysis

  7. Process Stoichiometry

  8. Stoichiometric equations

  9. Economic Potential Model

  10. Basic flowsheet

  11. Selectivity and Flow Rates versus Conversion

  12. Conversion and Selectivity Data

  13. 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

  14. 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).

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

  16. Project Inception (Garnett, 1/20/04) The first questions for a new product are always: • What does it do? • What will it cost?

  17. 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

  18. 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.

  19. 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

  20. 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.

  21. 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

  22. First Level of Decision:Batch 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

  23. 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

  24. Capacity/size considerations • Look for characteristic stream: • F(tons/year):F(kmol/hr):F(gpm) • Assume: • Density (if not known=water) • Hours on line (8000 hr/year) • Mean velocity in pipes v = 1.5 m/s • Pressure hike in pumps dP = 3 atms = 90 ft

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