Study On Performance Of Coupled System Of Compressed Carbon Dioxide Energy Storage And Carbon Capture Coal-fired Unit

Under the ’carbon peak,carbon neutrality’ goal,China will build a new type of power system with renewable energy as the main body.However,its intermittence and volatility quickly consume the flexible adjustment resources of the power system,which puts forward a huge demand for the adjustment ability of the power sy stem.This makes the traditional coal-fired units in the power system from the main power supply to stabilize the power grid supply demand and meet the flexible regulation of the power grid,while coal-fired units to reduce carbon dioxide emissions should promote carbon capture applications.Energy storage is one of the key supporting technologies to realize the transformation of power system.Compressed carbon dioxide energy storage technology has the advantages of high energy storage efficiency,long life and low emission.It is easy to couple with carbon capture system to realize the utilization of carbon dioxide in carbon capture.Based on this,this paper proposes a new energy system of coal-fired units coupled with compressed CO2 energy storage,innovatively uses the carbon capture process,establishes the thermodynamic model and economic model of the coupled system,analyzes the thermodynamic characteristics of the transcritical CO2 energy storage/supercritical CO2 energy storage coupled system,and further carries out the system peak shaving characteristics analysis and economic analysis.The results show that the peak’regulation performance of the coupled compressed CO2 energy storage system of coal-fired units will decrease with the increase of the energy storage and release time ratio and the increase of the peak regulation depth.Compared with the peak regulation of carbon capture coal-fired units,the coupled system has better peak regulation performance,and this advantage will be expanded with the increase of energy storage time ratio.The research on the coupling system of transcritical compressed CO2 energy storage shows that the optimal coupling mode of the system is to use the compressor unit of the carbon capture system directly during the valley power period,and to use the superheated steam of the steam turbine to heat the high-pressure CO2 during the peak power period.When the ratio of energy storage and release time is 2.16,the thermal efficiency and exergy efficiency of the coupled system are increased by 0.45%and 0.37%,respectively,and the coal consumption rate is reduced by 24.9g/kWh compared with the carbon capture coal-fired unit.At this time,the energy storage efficiency of the transcritical compressed carbon dioxide energy storage system is 70.7%.The research on the supercritical compressed CO2 energy storage coupling system shows that the supercritical compressed carbon dioxide energy storage system has a pure power storage mode and a power storage+heat storage mode.Both modes can optimize the peak regulation performance of the coupling system and expand the depth peak regulation range.The coupling system has better thermodynamic performance in the pure power storage mode,and the coupling system in the power storage+heat storage mode can use less working fluid to optimize the peak regulation flexibility of the coupling system.The peak shaving economy of the supercritical carbon dioxide energy storage coupling system shows that the power generation cost of the coupling system is lower than that of the carbon capture coal-fired unit,and the power generation cost is reduced by 0.0124 yuan/kWh,which is reduced by 2.1%.The CO2 emission reduction cost of the coupling system and the carbon capture coal-fired unit will decrease with the increase of the annual operation time of the unit.Compared with carbon capture coalfired units,the CO2 emission reduction cost-effectiveness and economic benefits of the coupled system under the design conditions of this paper are significant,which can reduce up to 12.473 yuan/tCO2,a decrease of 5.9%.The coupling system can achieve a maximum daily income of 63,300 yuan,an increase of 184,900 yuan compared to the income of carbon capture coal-fired units.