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 ) CONCERNS OF OPTIMISATION: DOWNSTREAM PLANT CAPACITIES PLANT FEED CAPACITY PRICE OF CRUDE OIL CYCLIC FLUCTUATION IN PETROCHEMICAL PRICES AVAILABLE REACTOR TIME

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

ETHANE CRACKING FURNACE

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

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

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

ADOPTED MODEL DIFFICULTIES ENCOUNTERED; 1. STIFFNESS OF DIFFERENTIAL EQUATIONS 2. UNKNOWN INITIAL VALUES OF DEQ STOICHIOMETRIC MODEL: SUNDARAM & FROMENT MOLECULAR MODEL MATERIAL BALANCE: dF i /dz = -  (S i r i ) * d t 2 /4 ENERGY BALANCE: dT/dz = 1/  F i cp i { Q(Z)* d t + d t 2 /4*r i *(-  Hi)

REACTION SCHEME

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

RESULTS OF ACTUAL RUN

SENSITIVITY ANALYSIS:RUN IV

SENSITIVITY ANALYSIS:RUN II

SENSITIVITY ANALYSIS:RUN III

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