Energy Optimization at Westlake’s Ethylene Unit by Michael McCaulley Westlake Petrochemical Sulphur, La.

Westlake’s Petrochemical Complex u Two Ethylene Units u Three Polyethylene Units u One Styrene Unit – Petro-2 u 1 Billion Pounds per year u Start up November 1997 u Ethane - Propane Feed u Highly Integrated u Low Pressure Demethanizer with Methane Refrigeration Compressor

Propylene DeC1 C2 Splitter DeC2 DeC3 C3 Splitter C2H2 Converter MAPD Converter Recycle Ethane Recycle Propane Cold Box C4’s H2 & Methane C2RC3R Ethane E/P Mix Quench Gasoline PGC Distillation Refrigeration

Objectives u Needed Quickly before APC / RTOpt u Zero Capital u High Profit Items only u Problem Areas Examined u No need for Increased Production

Approach u Westlake defined Potential u AspenTech Reviewed and Adjusted u Contract fitted to Objectives u Scope u Area and Overall Plant Models u Confirm Fit to Actual Operation u Case Studies of Possible Changes u Proposed Changes Reviewed then Implemented

High Priority Areas High Priority Areas u Cold Box - Demethanizer u Ethane - Propane Feed Splitter u Ethylene Splitter

Feed Splitter u Overhead Propane Spec Change to 1 mol % u Feed Preheater Increase plus 2.5 mm Btu/hr u Bottoms Ethane Spec Change to 50 mol % Potential Capital Changes u Propylene to the Reboiler u Recycle Ethane to Petro-1

Cold Box - Demethanizer u Shifted Cold Box Refrigeration Loads u Optimized Methane Circulation u Lowered Methane out Bottom u Lowered Side Reboiler Duty u Increased Preheater Duty

Cold Box - Demethanizer Results u Lowered Ethylene Losses u Lowered PGC Discharge Pressure u Reduce Hydrogen to the Demeth u Reduced C2 Splitter Methane Vent u Stabilized Operation

Ethylene Splitter u Decreased Product Purity u increased methane and ethane content u decreased methane recycle vent u Decreased Green Oil Wash Rate u Minimized Ethylene in Bottoms u balance reboiler loads u optimum ethylene loss identified u maximized reboiler loads by adjusting refrigeration

Summary u Feed Splitter Savings $ 240 K u Cold Box - Demethanizer $ 220 K u Ethylene Splitter $ 80 K Done quickly, & well with a lot of documentation. Very profitable

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