运行参数对660MW高效超超临界CFB锅炉四循环回路气固流动特性的影响研究

Study on influence of operating parameters on gas-solid flow characteristics of four-cycle loop of a 660 MW high-efficiency ultra-supercritical CFB boiler

本文随着循环流化床锅炉容量的增大,分离器个数相应增加,采用多分离器并联布置的结构会出现气固分布不均的偏流现象,由此给锅炉带来巨大的危害。为研究不同的运行参数对偏流现象的影响,采用欧拉双流体模型,对四分离器M型布置的高效超超临界循环流化床(CFB)锅炉循环回路的气固流动特性问题进行了数值模拟研究,详细探讨了布风均匀性、颗粒平均粒度及一二次风配比对多分离器间均匀性的影响规律。结果显示:相对床存量及一二次风配比等,布风均匀性对四循环回路间的气固流率分布影响最大,因此保证布风的均匀性是解决气固偏流的主要措施;同时,四分离器气固分布的不均匀性随着粒径的增大呈现出先增大后减小的趋势。

As the capacity of circulating fluidized bed(CFB)boiler increases,the number of separators increases accordingly,and the structure of parallel arrangement of multiple separators will result in uneven gas-solid distribution and bias flow phenomenon,which brings great harm to the boiler.To investigate the effects of different operating parameters on the bias flow phenomenon,an Eulerian two-fluid model was used to carry out numerical simulation on the gas-solid flow characteristics of high efficiency ultra supercritical CFB boiler with four separators arranged in M type.The effects of air distribution uniformity,average particle size and volume ratio of primary air to secondary air on the gas-solid distribution uniformity among multiple separators were discussed in detail.Compared with bed stock and the primary and secondary air ratio,the uniformity of air distribution had the greatest influence on the gas-solid flow rate distribution between the four circulation loops.Therefore,ensuring the distribution uniformity of air distribution is the main measure to solve the gas-solid bias flow.Moreover,the nonuniformity of gas-solid distribution in the four separators increases at first and then decreases with the increase of particle size.