考虑横向物质传递的大型循环流化床锅炉动态建模研究

Dynamic Simulation Research on Large Circulating Fluidized Bed Boiler Considering Transverse Mass Transfer

为了研究大型循环流化床(CFB)锅炉运行中出现的运行参数横向分布不均匀现象,在原有一维模型基础上,将炉膛沿宽度方向划分为4个并联回路,建立了准二维小室模型,每个回路内考虑炉膛内的传热、传质和燃烧以及并联回路之间的横向物质传递,并建立了包含风机、布风板、炉膛和分离器在内的风烟系统复合压降模型。对某660 MW超超临界CFB锅炉进行动态模拟,重点研究了特定工况下的床压横向波动现象,分析了床压波动过程中的横向物质传递速率。结果表明:该准二维小室模型能够反映运行参数在炉膛内的横向分布情况;炉膛内物料横向扩散和对流的综合作用是产生床压周期性波动现象的原因。

In order to study the phenomenon of the uneven lateral distribution of operating parameters in a large circulating fluidized bed(CFB) boiler, on the basis of the original one-dimensional model, a quasi-two-dimensional compartment model was established, in which the furnace was divided into four parallel loops along the width direction while heat & mass transfer and combustion in the furnace and lateral mass transfer among parallel loops were taken into account. Besides, the compound pressure drop model of flue air system including fan, air distributor, furnace and separator was also set up. Moreover, based on the dynamic simulation of a 660 MW ultra supercritical CFB boiler, the lateral fluctuation of bed pressure under specific working conditions was mainly studied while the transverse mass transfer in the process of bed pressure fluctuation was analyzed. Results show that the lateral distribution of operating parameters in the furnace can be reflected via the quasi-two-dimensional compartment model. The comprehensive effect of transverse diffusion and convection of materials in the furnace is the reason for the periodic fluctuation of bed pressure.