In ONGC, Uran, India, associated gas from offshore fields is sweetened to remove Hydrogen Sulfide and Carbon Dioxide. After extracting LPG and Naphtha from the sweet gas, C2C3 (ethane-propane) fractions are separated as liquid product and sent to IPCL for petrochemical feed stock. The residual Lean Gas is compressed and sent to consumers. C2C3 separation is a cryogenic process. It uses two turboexpanders and one propane compressor for refrigeration purpose. The problems were lower speed and higher outlet temperature of turboexpanders due to higher capacity utilization (110%). As a result, production of C2C3 was less and loss of C2 in Lean Gas was higher. The paper presents an innovative approach, which increased the efficiency of the turbo-expander to its design level even at 110% capacity utilization. Production went up by about 61 tons per day. At the same time, quality of the product also improved significantly.
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