Superstructure of Cogeneration of Power, Heating, Cooling and Liquid Fuels Using Gasification of Feedstock with Primary Material of Coal for Employing in LNG Process

Abstract

Using absorption refrigeration cycles instead of vapor compression refrigeration cycles can drastically decrease energy consumption. In these systems, high level of energy consumption is reduced due to the partially elimination of vapor compression refrigeration systems. On the other hand, utilization of waste heat of the plant, which is a very good opportunity for energy saving, is possible. In the present paper, a novel mixed fluid cascade natural gas liquefaction process is investigated by exergy and exergoeconomic analysis methods. In this process, one of the vapor compression cycles is replaced by water-ammonia absorption refrigeration cycle. The simulation results show that the compressors of this plant are responsible for 43.2% of total exergy lost. Decision variables of the system are consists of mass flow ratio of the tower's bottom product (bottom feed ratio), number of trays, and compressor's pressure ratio. Choosing appropriate values for these variables will result in 12% increase in exergetic efficiency of the plant. Exergoeconomic factor of water coolers, heat exchanger no.1 and tower no.1 shows that these components respectively impose a sizable capital cost to the entire system and does not result to a reasonable capital recovery. In this paper an integrated structure of producing liquid fuels from coal using Fischer-Tropsch synthesis and some equipment such as gas and steam turbines as well as HRSG heat exchanger for recovering of heat and power has been developed. Gasification method because of high efficiency and exothermic nature from energy consumption point of view is employed for producing synthesis gas.