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OPTIMISATION OF ETHYLENE CRACKER

OPTIMISATION OF ETHYLENE CRACKER. HEMENDRA KHAKHAR. PROJECT SUMMARY. REQUIREMENT OF SIMULATOR: PREDICTION OF CONVERSION AND YIELD OF PRODUCTS WITH CHANGE IN OPERATING CONDITIONS SUNDARAM AND FROMENT MODEL: MOLECULAR REACTION SCHEME ( 8 REACTIONS )

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OPTIMISATION OF ETHYLENE CRACKER

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  1. OPTIMISATION OF ETHYLENE CRACKER HEMENDRA KHAKHAR

  2. PROJECT SUMMARY • REQUIREMENT OF SIMULATOR: PREDICTION OF CONVERSION AND YIELD OF PRODUCTS WITH CHANGE IN OPERATING CONDITIONS • SUNDARAM AND FROMENT MODEL: MOLECULAR REACTION SCHEME ( 8 REACTIONS ) • CONCERNS OF OPTIMISATION: DOWNSTREAM PLANT CAPACITIES PLANT FEED CAPACITY PRICE OF CRUDE OIL CYCLIC FLUCTUATION IN PETROCHEMICAL PRICES AVAILABLE REACTOR TIME

  3. INTRODUCTION • FEED STOCKS FOR THERMAL CRACKING: ETHANE, PROPANE, LPG, NAPHTHA,GAS OIL, CRUDE OIL, ETC. • MAIN PRODUCTS: ETHYLENE, PROPYLENE • BY PRODUCTS: BUTENE, HYDROGEN, GAS OIL, FUEL OIL • OPERATING VARIABLEAS: TEMPERATURE PARTIAL PRESSURE OF H/C RESIDENCE TIME

  4. ETHANE CRACKING FURNACE

  5. PROBLEM DESCRIPTION • FEED: ETHANE/PROPANE/LPG • CAPACITY : 200000 lb/hr. • MAIN PRODUCTS : ETHYLENE: 100000 lb/hr. PROPYLENE:20000 lb/hr. • DOWNSTREAM PLANTS: ETHYLENE GLYCOL POLYVINYL CHLORIDE HIGH DENSITY POLYETHYLENE POLYPROPYLENE

  6. ISSUES FOR OPTIMISATION • LARGE NO. OF FEED & PRODUCT STREAMS NECESSITATING CAREFUL CHOICE OF FEEDS AND CONDITIONS • INCREASING FLEXIBILITIES OF THE REACTORS CLAIMED BOTH FOR FEEDSTOCK UTILISATION AND EFFLUENT DISTRIBUTION • RECYCLING STREAMS • RUNLENGTH OF REACTORS • RELIABLE PREDICTION OF EFFLUENT DISTRIBUTION • REVAMPING OF UNITS

  7. OPTIMISATION MODEL • THREE WAYS FOR SCALING UP : DIRECT EXPERIMENTAL SIMULATION EQUIVALENT TIME AS A DESIGN PARAMETER MATHEMATICAL MODELLING • AVAILABLE MODELS: EMPIRICAL MODEL MOLECULAR ( STOICHIOMETRIC ) MODEL MECHANISTIC MODEL

  8. ADOPTED MODEL • DIFFICULTIES ENCOUNTERED; • 1. STIFFNESS OF DIFFERENTIAL EQUATIONS • 2. UNKNOWN INITIAL VALUES OF DEQ • STOICHIOMETRIC MODEL: • SUNDARAM & FROMENT MOLECULAR MODEL • MATERIAL BALANCE: dFi/dz = -  (Siri) * dt2 /4 • ENERGY BALANCE: dT/dz = 1/ Ficpi { Q(Z)* dt + dt2/4*ri *(- Hi)

  9. REACTION SCHEME

  10. FORMULATION OF OBJECTIVE FUNCTION • OBJECTIVE FUNCTION, PROFIT, f = PRODUCT COST - FEED COST - ENERGY COST • INEQUALITY CONSTRAINTS: CRACKER CAPACITY : 200000 lb/hr. ETHYLENE PROCESSING CAPACITY : 100000 lb/hr. PROPYLENE PROCESSING CAPACITY : 20000 lb/hr. • EQUALITY CONSTRAINTS: ETHANE RECYCLE BALANCE PROPANE RECYLCE BALANCE ENERGY BALANCE

  11. RESULTS OF ACTUAL RUN

  12. SENSITIVITY ANALYSIS:RUN IV

  13. SENSITIVITY ANALYSIS:RUN II

  14. SENSITIVITY ANALYSIS:RUN III

  15. SUGGESTION FOR FUTURE WORK • RADICAL REACTION MODEL: • ETHANE CRACKING: 49 REACTIONS,11 MOLECULAR SPECIES, 9 RADICAL SPECIES • PROPANE CRACKING: 80 REACTIONS,11 MOLECULAR SPECIES, 11 RADICAL SPECIES • DEVELOPMENT OF GEAR ALGORITHM TO SOLVE STIFF DEQ • REGOROUS ENERGY BALANCE(BOTH COMBUSTION AND PROCESS SIDE ) AND MOMENTUM BALANCE REQUIRES COMPUTATIONAL FLUID DYNAMICS

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