Exergoeconomic Analysis And Optimization For Coal – Based Polygeneration System

Polygeneration system, typically involving chemicals/fuels and electricity co-production, shows more opportunities to obtain higher efficiency, lower investment and less environmental impact, which is regarded as one of the key technology for the sustainable development of coal utilization. Supported by the National key basic research and development plan(973) project, the major aim of this research is to investigate integration and optimization in aspect of techno-economy of a dual-gas polygeneration system based on coal gasification gas(CGG) and coke-oven gas(COG).A synthetical evaluation index including energy, environment and economy(3E) peformance and a method of integration and optimization based on exergoeconomic theory for polygeneration system are established firstly, on the basis of which, the technological conditions, operating parameters and system configuration can be optimized, then polygeneration system can achieve the optimal whole performance with aspects of energy, element, economy and CO2 emission reduction. Besides, an exergoeconomic cost model of the polygeneration system on the basis of the key components, technical parameters and conditions is also proposed. The effects of the unit operation parameters,products output energy, feedstocks input energy, non-energy cost and production scale on product exergoeconomic cost are investigated to reveal the relationship between product exergoeconomic cost and technical parameters and conditions.The key technology condition/parameters of the dual–gas polygenerationsystem with CO2/CH4 dry reforming technology(D–PL–DR) are optimized with taking economic performance as the prior optimization objective while considering elements conversion and greenhouse gas emission reduction to realize the whole system optimization in comprehensive performance. However,CH4/CO2 dry reforming is a strong endothermic reaction, meanwhile, carbon deposition on nickel catalysts is also a fatal problem for CH4/CO2 dry reforming,both of which are the main reason for not industrialization of CH4/CO2 dry reforming technology. In order to solve these problems, a new polygeneration system from CGG and COG partial catalytic oxidation coupling with an oxygen-permeable membrane reactor(D-PL-PCO-OPMR) is proposed on the basis of the D–PL–DR. The value increment principal of product exergoeconomic cost is disclosed by analyzing and comparing the key components streams, exergy streams and exergoeconomic cost streams of each unit in both D–PL–DR and D-PL-PCO-OPMR. The results show that the D-PL-PCO-OPMR can improve the energy utilization efficiency in CGG and COG conversion process, and reduce exergy destruction in the whole process,and realize effective components(CH4\CO2\CO\H2) reasonable conversion, thus reduce the product exergoeconomic cost. The D-PL-PCO-OPMR would be a more attractive way for highly efficient and clean use of CGG and COG.