Optimization Of The Mass Balance Of Circulating Fluidized Bed Boiler

After decades of rapid development, our country’s circulating fluidized bed boiler technology is at the forefront of the world, however, there are still many problems among which serious wear of water-wall, high ash content carbon and high power consumption rate are three most main problems. So the research of optimal operation technology of circulating fluidized bed boiler has important theoretical and practical significance.The particle concentration distribution of circulating fluidized bed boiler is important to its design and operation. According to a large amount of tests performed under different operational conditions on a1060t/h circulating fluidized bed boiler with breeches-leg, this paper got the curves of pressure distribution in furnace under different loads. Then the particle concentration distribution regularities in dilute region of large circulating fluidized bed boiler with breeches-leg were obtained. And this paper analyzed the impact of air velocity and pressure drop on the particle concentration distribution, and gave the relation of particle concentration distribution changing with air velocity and furnace height and the relation of particle concentration distribution changing with pressure drop and furnace height. The results of this study can provide technical support for design and optimization of the same type of circulating fluidized bed boiler.This paper obtained the characteristic data of first broken, intrinsic ash formation and burnout time of four types of coal including Pinshuo coal gangue Shuozhou lean coal, Zhenzhou bitumite and Neimeng lignite, and then the experimental results were analyzed. The experimental results provided technical data for the numerical modeling of optimization of the mass balance.From the perspective of material balance, this subject studied the characters of fluid dynamics in circulating fluidized bed boiler through the mathematical modeling and tests confirmed method and developed the optimization software of material balance of circulating fluidized bed boiler. This software mainly includes three modules, namely, grain-size distribution of the bed materials module, the distribution of the material density module and optimization module. With the material density of furnace outlet(Cp) and mean detention time of material in furnace(tp) as the optimizing the object function, on the premise of guarantee of boiler loads and detention time of material in furnace, the mass portion of materials of different particle size in the furnace is adjusted through changing the particle size distribution of coal, there by the proportion between the materials of coarse particle and fine particle in furnace is changed,and finally the aim of low bed pressure operation is achieved. This thesis respectively studied the effects of particle size distribution of coal and coal type to the distribution of the material density and carbon-content of cinder of1060t/h circulating fluidized bed boiler through the optimization software of material balance. The results show that the material density in the middle-lower part of furnace of circulating fluidized bed boiler is inversely proportional to the ratio(k2) between the quality share of coarse particle and fine particle in the ash formation of different coal types and the middle-upper part is in proportional to k2.The average material density in the furnace is proportional to the ratio (ko) between the quality share of coarse particle and fine particle in the coal feed; under the condition of the same bed pressure, carbon-content of cinder is inversely proportional to k0, the ratio(k1) between the quality share of coarse particle and fine particle in the coke particles of different coal types after primary fragmentation and burning rate of coal type.