Development of Predictive Thermodynamic Model for Liquefaction of Natural Gas Using the C3-Mr Refrigeration Process

This paper presents a propane precooled mixed refrigerant (C3-MR) liquefaction plant with 4 pressure levels of propane cooling operational in Nigeria and demonstrates the procedure for developing a thermodynamic model that predicts the liquefied natural gas (LNG) production rate. The model prediction was validated with plant data with a maximum deviation of 3%. The thermodynamic efficiency of the natural gas liquefaction plant was estimated to be 45.1%. Simulations reveals that LNG production rate for the C3-MR plant depends on cooling water supply temperature (1 C rise results to 92 tonnes per day of LNG loss), thermodynamic efficiency of the overall liquefaction process (1% drop results to 215 tonnes per day of LNG loss), LNG outlet temperature (1 C decrease results to 108 tonnes per day of LNG loss), LNG production to feed gas supply ratio (1% rise results to 37 tonnes per day rise in LNG), thermal efficiency of gas turbine drivers (1% drop results to 277 tonnes per day of LNG loss), ambient air temperature (1 C drop results to 67 tonnes per day of LNG increase) and feed gas supply pressure.