Configuration Design Study Of Supercritical Carbon Dioxide Coal-fired Circulating Fluidized Bed Boiler

Coal-fired power generation is China's main power generation mode.Improving coal-fired power generation efficiency is the key to saving coal resources and reducing CO₂ emissions.While continuously increasing the investment in research and development and installation of ultra-high-parameter steam power generation materials,the development of new and efficient power generation power cycle has become one of the important technical ways to improve the efficiency of coal-fired power generation.Supercritical CO₂?S-CO₂?Brayton cycle has high cycle efficiency at medium and high temperature?620⁶50°C?,small volume of key equipment and weak corrosiveness to metal,and is applied to coal combustion.Power generation has broad prospects for development.In this paper,the S-CO₂ power cycle is combined with the clean and efficient circulating fluidized bed?CFB?combustion technology,and the S-CO₂ coal-fired CFB boiler is designed and analyzed for thermodynamics.The 600 MW“reheat+two-stage compression+intermediate cooling”S-CO₂ coal-fired power generation cycle,which is suitable for CFB boiler's unique wide temperature zone distribution?920°C¹20°C?and furnace frame,is constructed to realize boiler flue gas.The heat is absorbed in the full temperature zone.The influences of key factors such as boiler main outlet parameter,reheat outlet parameter,recompression split ratio,boiler waste heat utilization pumping ratio and pre-cooler inlet pressure on cycle efficiency were analyzed,and 600MW S-CO₂ cycle coal-fired fluidization was obtained.The overall layout and main parameters of the bed power generation system.Based on the above parameters of the power generation system,the thermal design of the S-CO₂ cycle CFB boiler is completed.Through the whole field and the thermal balance of the components in the furnace and its structure and size design,the furnace structure,heating surface arrangement and heat distribution characteristics of the S-CO₂ circulating coal-fired fluidized bed boiler were obtained.Compared with the traditional steam CFB boiler,the heat-recovering area of the S-CO₂ circulating coal-fired fluidized bed boiler in the high temperature zone is significantly increased,accounting for more than 40%,and 80%of the heat absorption of the working fluid is completed in the high temperature zone.The effects of bed temperature,excess air ratio,boiler load and coal type on boiler heat distribution and boiler efficiency were analyzed.The external heat exchanger can effectively improve the performance stability of the boiler.Aiming at increaseing of the heating surface of S-CO₂ high temperature zone,the design of S-CO₂ CFB boiler and the layout of heating surface were completed.In the furnace,a screen-type heating surface,a double-sided heated partition wall,and an external heat exchanger are added to increase the amount of heating area in the high-temperature zone.Using numerical simulation method,the heating surface of the furnace is arranged,the structure and size of the boiler furnace are refined,the design scheme of the S-CO₂ three-chamber furnace is improved,and the shape furnace and the double-ring furnace coal-fired fluidized bed boiler are also proposed.The exergy analysis model was established to analyze and evaluate the available energy efficiency of the above S-CO₂ coal-fired fluidized bed power generation system.84.08%of the exergy loss of the system comes from the boiler,and 91.02%of the exergy loss of the boiler occurs in the furnace.For the boiler with similar power generation,the exergy efficiency of the S-CO₂ boiler is higher than that of the steam boiler,and the CFB boiler The heat transfer exergy efficiency is higher than that of the pulverized coal boiler,but its combustion exergy efficiency is lower than that of the pulverized coal boiler.Increasing the main and reheat temperature of the boiler can improve the heat transfer exergy efficiency of the boiler.