Process Simulation And Multi-objective Optimization Of A Combined System Based On Fuel Cell-Gas Turbine And Supercritical Carbon Dioxide Brayton Cycle

The hybrid system consists of the solid oxide fuel cell and gas turbine(SOFC-GT)is a promising distributed generation scheme.At present,recovery of waste heat from the medium-high temperature exhaust of the gas turbine is an attractive research topic.Supercritical carbon dioxide Brayton cycle(SCO2BC)is a subversive and efficient power generation system.It is very suitable to be integrated into the SOFC-GT sub-system as the bottoming cycle through system integration and process improvement to realize energy recovery and cascade utilization.The SOFC-GT combined system has many advantages,such as high efficiency,low emission,flexible power generation scale,and suitability for co-generation and co-supply.In this paper,a triple combined system consists of a SOFC,a GT,a SCO2BC is investigated.The simulation model is built with process simulation software gPROMS,and the performance calculation and sensitivity analysis of the system are carried out.Besides,multi-objective optimization and decision-making methods are employed to optimize the exergoeconomic performance and explore the optimal design and operation scheme.The main contents of this paper are as follows:Firstly,the literature review of the two-stage and three-stage integrated systems based on fuel cells and gas turbine are summarized at home and abroad.Then,the concept,characteristics,and research progress of supercritical carbon dioxide Brayton cycle are elaborated.The cut-in points and innovation of this study are put forward.Secondly,two kinds of coupling systems of SOFC-GT integrated with preheating and recompression supercritical carbon dioxide Brayton cycles are described in detail.In virtue of the gPR(OMS,a detailed process simulation and an economic model are established,and the main components and key parameters of the system are discussed.Thirdly,the sensitivity analysis of six key system parameters,including fuel cell operating temperature,fuel flowrate,fuel utilization factor,gas turbine pressure ratio,inlet pressure of carbon dioxide turbine and bottoming cycle split ratio are carried out to study the variation trend of performance parameters such as the net output power,exergy destruction,exergy efficiency and levelized cost of electricity.Finally,the optimization algorithm and decision-making methods used in this paper are introduced.The optimal thermodynamic performance and economy of the coupled system are discussed with the bi-objectives of exergy efficiency and levelized cost of electricity.The Pareto frontiers of the two kinds of combined systems are obtained by combining the single objective optimization algorithm built-in gPROMS and the e-constraint method.Then the global optimal solution is determined by Linear Programming Techniques for Multi-dimensional Analysis of Preference(LINMAP)and Technique for Order Preference by Similarity to an Ideal Solution(TOPSIS)decision-making methods.Based on this,the comprehensive performances of the two systems at the optimal solution are presented and analyzed.At last,the specific distributions of eight decision variables corresponding to the optimal solution set in Pareto frontiers are presented and compared.In summary,some new results obtained in this paper reveal the general performance characteristics of the SOFC-GT-SCO2BC combined system.The optimization criteria of key design and operation parameters are presented,which can provide theoretical guidance and reference basis for the optimization design and operation of similar integrated systems.