Test Of The Heat Balance And Mass Balance On The 1025t/h Circulating Fluidized Bed Boiler In BaiMa Power Plant

Because of many advantages as wide adaptability with fuels, ideal adjustability with load and well pollutant control,circulating fluidized bed (CFB)combustion technique become the best choice of clean coal combustion technique.However,with the development of large-scale, external heat exchanger applied in CFB,Superheater and reheater are adopted staggered layout between flue tail and external heat exchanger.At the same time of the convenience of steam temperature control regulation,steam temperature control and bed temperature control coupled together,so the relationship of the mass balance and heat balance more complex.As the mass balance and the heat balance of CFB boiler in design and operation are important parameters,boiler fluid flow,heat transfer characteristics,combustion characteristics,characteristics of Variable Conditions may be great impact.Because of the constraint of circulating ash rate survey,the current research in this area is still little.Supported by the "11th Five-Year" State plan of scientific and technological, this paper do more measurement on BaiMa 300MWCFB boiler, do detailed study on mass balance and heat balance the large-scale CFB boiler, then establish each part of the boiler thermal balance and mass balance, and study their relationship with the load. Through field testing and numerical calculation method, we can study the advanced CFB combustion technology and do something for the technical storage. The main task of the study:①Do the test of heat balance on BaiMa 300MWCFB boiler,study the thermal performance under the different load.②Study the relationship of heat absorption proportions of each part of boiler (furnace, external heat exchanger,flue tail) with the load and the change of heat transfer coefficient of heating surface with load.③Calculating the circulated ash by static calculation method based on heat balance and ash balance. Simulating the separator inlet to study the relation between cyclone inlet pressure drop and wind speed,solid concentration,particle size distribution, temperature.④Establish each part of the boiler thermal balance and mass balance,study their relationship with load. The results of the study mainly include: ①The study found BaiMa 300MWCFB boiler's thermal efficiency is 91.5% in general under the normal operating condition.②With the increase of load,the heat transfer coefficient of furnace heating surface is increasing.The change is linear approximation, which reflected a good load regulation characteristics.③The proportion of furnace thermal load reduced with the increase of load,and the thermal load proportion of external heat exchanger increase with the increase of load. The change of flue Tail is not be apparent.④The boiler is characterized by low emission,desulfurization efficiency is much higher than other CFB boilers.The desulfurization efficiency could reach 94.72 % under the condition of the Ca/S molar ratio = 1.74.The NOx emission concentration is 79mg/Nm3.⑤The pressure drop of cyclone entrance is increased with the increase of materials concentration,particle size,wind speed and temperature,but the temperature on the pressure drop of little effect.⑥The circulated ratio of BaiMa CFB boiler under the load of B-ECR is about 33.⑦With the increase of load,the volume of materials within the furnace is reduced,the proportion of bed materials in furnace is ireduced,the height of the packed bed in standpipe is increased,but the cycling ash within the external heat exchanger increased faster,leading to thermal cycling reduction in the proportion of ash.