Enhancement of APCI cycle efficiency with absorption chillers

Liquefied natural gas (LNG) plants consume a great amount of energy. In order to enhance the energy efficiency of the LNG plant, the potential energy efficiency enhancements of various options of utilizing the waste heat powered absorption chillers in the propane pre-cooled mixed refrigerant (APCI) liquefaction cycle were investigated in this study. After developing models of the LNG process, gas turbine and absorption chillers, eight options of gas turbine waste heat utilization were simulated. The simulation results show that by replacing 22 °C and 9 °C evaporators and cooling the condenser of propane cycle at 14 °C and inter-cooling the compressor of mixed refrigerant cycle with absorption chillers which are powered by waste heat from the gas turbine, both the compressor power and fuel consumption reduction can be achieved as much as 21.32%. This enhancement requires recovering at least 97% of gas turbine waste heat.