Optimization of light hydrocarbon recovery process with LNG cold energy based on the exergy analysis method

When LNG cold energy is used for light hydrocarbon recovery process, the cold energy utilization rate is low and the energy consumption is high. In order to solve the problems, the exergy analysis method was applied to the optimization of light hydrocarbon recovery process. The exergy analysis model was established to confirm the weak links of effective energy utilization in LNG light hydrocarbon recovery process system. Then, it was optimized with exergy efficiency, comprehensive energy consumption, and ethane recovery rate as object functions and the optimal parameters were obtained, so as to improve the cold energy utilization rate of light hydrocarbon recovery process. Finally, this method was practically applied in one certain LNG receiving station to optimize its light hydrocarbon recovery which makes use of cold energy. It is shown that the cold energy utilization rate is increased by 8.14%, the comprehensive energy consumption is reduced by about 21 778.01 MJ, and the ethane recovery rate is increased by 6.18% after process optimization. Meanwhile, it is revealed from the economy analysis on the optimization process that the economic benefit after the optimization is quite considerable with the annual profit RMB 5 713.24×104, the rate of return 112.24% and the payback period about 2 years. It is indicated that the economic benefit is very considerable.