Applying an integrated trigeneration incorporating hybrid energy systems for natural gas liquefaction

Abstract

Utilizing absorption refrigeration system as an alternative to compression refrigeration system of MFC refrigeration cycle in an integrated super structure with the main aim of reduction in required energy is investigated. High energy consumption in these units is reduced because of the removal of a stage of the compression system, while the possibility of using waste energy through the use of absorption cooling can be provided. A superstructure is composed of following items: combined cooling, heating and power (CCHP), molten carbonate fuel cell (MCFC), gas turbine, water-ammonia absorption refrigeration system as well as two mixed refrigerant refrigeration cycle for producing the required cooling and Heat recovery steam generator (HRSG) for power generation and thermal recovery. Exergy analysis shows that the highest exergy destruction is imposed by after-burner with the amount of 33.91% and the lowest exergy destruction is occurred in the valves by the amount of 0.83%. The presented integrated structure has overall thermal efficiency (LHV Base) of 70.56%, and the Specific power of 0.162 kWh/kg LNG. Sensitivity analysis of the integrated system is carried out through changing the amount of fuel utilization coefficient, oxidant mass flow rate, mass flow rates of methane and nitrogen in the natural gas. The differences in the amount of consumed power and generated power in the integrated structure can be minimized by increasing the pressure ratio in gas turbines, and the mass flow rate of LNG production can be maximized to 6778.93 kg/h.