Integrated Optimization And Performance Analysis Of 350MWe Oxy-combustion System

In order to achieve the global carbon emissions peak as soon as possible to alleviate the global greenhouse effect,the search for feasible carbon emission reduction approach has become the focus of researchers.As an important carbon emission reduction technology,oxy-combustion will play an important role.At present,the major challenges in the process of commercialization of oxy-combustion technology are the increase of system energy consumption,resource consumption and investment and operation cost.In view of the above situation,this paper adopts Aspen Plus to simulate the process of the 350MWe oxy-combustion system,and carries out three aspects of research based on the established simulation model,including integration optimization,water consumption analysis and economic analysis,to provide data support and technical reference for the commercial operation of the oxy-combustion system.Firstly,the key equipment of oxy-combustion system is selected,and the whole system process model is established by Aspen Plus.The error between simulation data and system design parameter data is controlled within 5%.The results show that when the net power generation efficiency of the benchmark air combustion system is 41.56%,the net power generation efficiency of the wet cycle and dry cycle of the oxy-combustion system are 31.36%and 31.12%,respectively.Through the sensitivity analysis of nine operating conditions,it is found that the increase of air leakage and oxygen excess will lead to the decrease of CO₂concentration in flue gas,but the increase of O₂ purity has the opposite effect.From the perspective of energy consumption,the increase of O₂ purity,air leakage and excess oxygen will increase the energy consumption of the whole system.Based on the model,the integrated optimization of the 350MWe oxy-combustion system is carried out by combining the exergy analysis and pinch analysis.Exergy analysis shows that about 65.76%of the total exergy input of the whole oxy-ombustion system is destroyed,and boiler island and turbine island are the main exergy loss units of the system,accounting for78.89%and 9.37%of the total exergy loss,respectively.Exergy loss of CO₂ capture related air separation system and CO₂ compression purification system mainly occurs in the compression process.According to the results of exergy analysis,combined with the pinch analysis,the whole system cold and heat logistics are selected for integrated optimization.Based on the minimum temperature difference of 10℃,the system recovers 111.4MW of heat,and the net power generation efficiency of the optimized system is 33.07%,increasing by 1.95%.Finally,the 350MWe oxy-combustion system is analyzed in terms of water consumption and technical economy.The life cycle analysis water consumption of oxy-combustion system is analyzed from the aspects of fuel supply,infrastructure,power plant operation,CO₂transportation and storage.It is found that the water withdrawal and consumption of life cycle analysis are 4522.05L/MWh and 3548.53L/MWh respectively.The economic analysis results show that the cost of electricity of the 350MWe oxy-combustion system is 455.60（?）/MWh,and the CO₂ avoidance cost is 213.56（?）/t-CO₂.Moreover,coal price and ASU power consumption have significant effects on power supply cost and CO₂ emission reduction cost of oxy-combustion system.