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. 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!!
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
Example of gross economic analysis Reaction I: Reaction II:
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
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).
Property Estimation Methods • Bound- and Group-Contributions • UNIFAC, NRTL, UNIQUAC • Polymer Property Estimation
Project Inception (Garnett, 1/20/04) The first questions for a new product are always: • What does it do? • What will it cost?
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
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.
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
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.
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
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
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
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