| China is a "coal-rich,oil-poor,and gas-poor" country.Coal-fired power generation accounts for more than 60%of China’s power sources and will continue to maintain a high share.It is worth noting that coal-fired power generation has caused huge Environmental pressures,including the huge challenges of dust emissions and the release of large amounts of CO2 greenhouse gases.Therefore,achieving clean and efficient utilization of coal energy is one of the most important topics in the current energy field.In recent years,sCO2(supercritical carbon dioxide)power cycle has been intensively studied to improve the power generation efficiency of various power cycles such as nuclear energy,solar energy,waste heat recovery,fossil fuel(natural gas and coal).ORC(Organic Rankine cycle)waste heat recovery is widely used as a bottom cycle to recover industrial waste heat for power generation which further improves the system thermal efficiency.In this paper,we study the coal gasification and semiclosed direct heating sCO2 power cycle as the top cycle.ORC waste heat recovery as the bottom cycle,and establish a semi-closed sCO2/ORC combined system to improve the power generation efficiency of the system while capturing CO2.The research content is as follows:Firstly,a semi-closed sCO2 benchmark system was established.Aspen Plus was used to build a model in combination with literature data.The net efficiency was 35.84%.While achieving CO2 capture purity of 98%.Secondly,according to the low-temperature waste heat characteristics of the sCO2 system,the closed-type sCO2 subsystem was designed and studied.By comparing a variety of ORC cycle working fluids,R245fa was selected as the mechanical Rankine cycle working fluid.The bottom cycle power generation efficiency can reach a maximum of 15.5%.Accounted for 8.5%of the combined power generation system.Compared with a single system,the use of ORC waste heat recovery improves the system thermal efficiency by 6.76%.The application of ORC in the sCO2 system as the bottom-cycle recovery system waste heat clarifies the ability of ORC waste heat recovery to improve the system’s thermal efficiency performance.At the same time,according to the research results,a semi-closed sCO2/ORC combined system is proposed.Based on the parameter analysis of the inlet pressure of the sCO2 top cycle main turbine,the effect of the top cycle main turbine inlet temperature and pressure on the efficiency of the combined system is studied.And by analyzing the impact of each power consumption unit of the system on the total power generation efficiency of the system under different operating conditions,increasing the inlet temperature of the main turbine is more conducive to the improvement of system efficiency.Finally,according to the current development of materials and equipment,the inlet temperature of the main turbine is 1150℃,and the inlet pressure is 30MPa to optimize the combined cycle(reduce the temperature difference of the recuperator and adjust the distribution ratio of the bottom regenerator)and consider air separation and purification 3.The energy consumption of public works,at a 100%carbon dioxide capture ratio,achieved an overall power generation efficiency of 40.1%,and the concentration of captured carbon dioxide was higher than 98.5%.Compared with the benchmark system,the thermal efficiency is increased to 4.26%. |
PDF Full Text Request