Advanced Exergy Economics Analysis Of 150MW Gas Steam Combined Cycle Power Generation System

The gas steam combined cycle(CCPP)refers to the combined power generation cycle using the high-temperature flue gas of gas turbine and the high-temperature steam of waste heat boiler.Because the mixed gas of blast furnace gas and coke oven gas is used as fuel,the power supply cost of iron and steel plants is reduced,and the emission of pollutants is reduced.At the same time,it has the advantages of high thermal efficiency,fast start-up speed and high operation reliability,and has been widely used in major iron and steel enterprises in China.In this thesis,a 150 MW steam-gas combined cycle power generation unit in an iron and steel plant is taken as a research case to establish a simulation model of the combined cycle system under design conditions,and the effectiveness of the simulation model is verified by comparison with actual data.Based on the simulation results,establish the exergy analysis model of the combined cycle system,calculate the exergy value of each logistics in the system,and obtain the exergy efficiency and exergy loss of each component of the system.Then,combine the exergy analysis with the economic analysis theory to establish the exergy economic analysis model.On this basis,the advanced exergy economic analysis and advanced exergy economic analysis models of the system are built to more intuitively and comprehensively reflect the distribution of the exergy loss/cost of the combined cycle system components,analyze the improvement potential of the system components and the impact of the interaction between the components.The research shows that the combustion chamber has the largest exergy loss of 112.86 MW and the largest internal avoidable exergy loss of37.44 MW.Therefore,the structure and combustion conditions of the combustion chamber(intake air heating,fuel preheating)should be taken as the key research and optimization object to reduce the irreversible exergy loss in the operation process and reduce the internal loss of the combustion chamber;Moreover,the sum of the corrected dissipation cost rate of the combustion chamber and the annual cost of the components is the largest,indicating that the component has great potential for improvement.If the corrected economic factor value of the low-pressure superheater and low-pressure evaporator of the system is low,the efficiency of the components should be improved by increasing the endogenous-avoidable investment cost of the components.Based on the research of CCPP system,combined with the carbon capture process of monoethanolamine(MEA)method,this thesis establishes the advanced and economic analysis model of CCPP carbon capture coupling system.The research shows that due to the need to draw a large amount of low-pressure steam to heat the reboiler,the output power of the low-pressure steam turbine is reduced,and the power generation of the coupling system is reduced from 153.5MW to 136 MW,with a loss of 17.5MW.The first three components with the largest exergy loss in the coupling system are combustion chamber,turbine and reboiler.The heat loss of reboiler is caused by excessive heat transfer temperature difference.The endogenous – avoidable exergy dissipation cost rate and the endogenous-avoidable annual cost of the coupling system are 29.9% and 23.9% respectively,indicating that the coupling system can reduce the cost of the coupling system and improve the economy of the coupling system by improving the system.