Research On Experiment And Power System Design Based On CaCO₃ Energy Storage

Thermochemical energy storage based on the CaCO3/CaO cycle has the advantages of high energy storage density,low-cost energy storage materials,easy reaction conditions,easy storage of reaction products,and good coupling with concentrated solar power generation.It is a very promising solar energy storage technology.However,the development of this technology is restricted due to the problem of reduced activity of calcium-based absorbents.At present,a large number of studies have been conducted on the heat storage performance of various natural calcium-based materials and mixed calcium-based materials under different working conditions at home and abroad,and a large number of studies have also been conducted on the CSP-CaL integrated system.However,since most researches on the heat storage performance of calcium-based materials are carried out under normal pressure carbonation conditions,and the CSP-CaL integrated system research shows that pressurized carbonation condition is more advantageous,so the heat storage performance study of calcium-based materials under pressurized carbonation condition is more meaningful.In this paper,a fixed-bed reactor is used to study the circulating heat storage performance of natural calcium-based materials(limestone and dolomite)under pressurized carbonation condition.The heat storage performances of limestone and dolomite both increase with the increase of carbonation pressure.When the carbonation pressure is 7bar,the effective conversion rate of limestone after 10 cycles is 32.7%,which is 9.92%higher than that under lbar;The effective conversion rate of dolomite after 10 cycles is 40.47%,which is only 1.56%higher than that under lbar.Although the limestone shows higher heat storage performance than dolomite in the first cycle,it is not as good as dolomite in subsequent cycles,and dolomite shows more stable heat storage performance.From the SEM and pore distribution characteristics,it can be concluded that the increase of carbonation pressure can reduce the sintering phenomenon of limestone and dolomite in the calcination process,and has a larger specific surface area and pore volume;at the same time,under different pressures,the specific surface area and pore volume of dolomite are higher than that of limestone.From the perspective of environmental protection,the dolomite is a calcium-based heat storage material with more application prospects than limestone.In this paper,based on the energy balance of carbonation reactor and closed CO2 Brayton cycle proposed by Chacartegui,a new integrated heat transfer mode is proposed,a closed CO2 cycle benchmark system based on the new integrated heat transfer mode is established,and the benchmark system is optimized.The simulation results show that the optimal scheme 3 has the highest efficiency of 44.02%under the condition of 875℃,3.2bar and the minimum heat exchange temperature difference of 15℃.The effects of key parameters(system operating pressure,temperature and pressure ratio)on system performance are analyzed.Considering that the heat loss in the carbonation reactor is 10%and the heat exchanger temperature difference is 5℃,the power generation efficiency of 49.26%can be achieved when the operation temperature is 875℃ and the pressure ratio is 1.8.