CFB锅炉大型化气固流动非均匀性研究进展  

Research on non-uniformity of gas-solid flow in large-scale CFB boilers

作　　者：胡南 徐梦 张缦[2] 杨海瑞[2] 张守玉[3] 赵冰 巩太义 王家林 HU Nan;XU Meng;ZHANG Man;YANG Hairui;ZHANG Shouyu;ZHAO Bing;GONG Taiyi;WANG Jialin(Jilin Province S&T Innovation Center for Physical Simulation and Security of Water Resources and Electric Power Engineering,Changchun Institute of Technology,Changchun 130012,China;Key Laboratory for Thermal Science and Power Engineering of Ministry of Education,Tsinghua University,Beijing 100084,China;School of Energy and Power Engineering,University of Shanghai for Science and Technology,Shanghai 200093,China;Huadian Power International Co.,Ltd.TEDA Branch,Tianjin 300270,China)

机构地区：[1]长春工程学院吉林省水利电力工程物理级仿真与安全科技创新中心,吉林长春130012 [2]清华大学热科学与动力工程教育部重点实验室,北京100084 [3]上海理工大学能源与动力工程学院,上海200093 [4]华电国际电力股份有限公司天津开发区分公司,天津300270

出　　处：《洁净煤技术》2020年第3期1-8,共8页Clean Coal Technology

基　　金：吉林省产业技术研究与开发专项资助项目(2019C056-3);中国华电集团有限公司重大科技项目计划(CHDKJ19-01-88)。

摘　　要：循环流化床(CFB)锅炉大型化发展的必然结果是炉膛截面尺寸和并联回路的增加,流化床锅炉炉内燃烧和传热过程很大程度上取决于炉内气固流动特性,因此横向气固流动均匀性对锅炉的安全运行具有重要影响。笔者从静态和动态2个方面分析了大型CFB锅炉气固流动横向非均匀性问题。静态非均匀性问题包括布风均匀性和并联回路引起的气固流量沿截面的偏差以及各回路流量分配偏差,在稳定运行条件下不随时间变化。分离器的阻力特性是分离器的重要特性参数,在相同气相流量下,固体颗粒浓度对分离器压降的影响是非单调的,分离器压降随固体颗粒浓度的增加先减小后缓慢增加,理论上并联回路控制方程的解存在多值性,因此多回路并联条件下各分离器循环流率存在偏差。CFB锅炉炉内悬吊屏影响颗粒局部浓度分布,进而影响各分离器固体颗粒循环流率的分配。分离器出口烟道的形式对分离器气固两相的流量分配存在不容忽视的影响。在布风均匀性方面,两侧进风和后墙进风方式均会引起风室不同程度的布风不均。大型CFB锅炉在低负荷运行过程中,存在炉膛两侧床压大幅长周期波动的现象,该现象即为动态气固流动横向非均匀性问题,其产生的主要原因是大截面的布风系统,一次风降低导致的布风失稳以及多回路并联的不均匀性。横向波动数学模型主要是基于气固两相流系统横向波动固有频率的假设,当扰动接近系统固有频率时,会产生较大幅度的横向波动。目前动态非均匀性问题还缺少实验室尺度的深入系统研究,相关机理仍较模糊,是气固流动非均匀性问题的主要研究方向,同时布风不均和密相区气固流动的耦合作用还有待进一步研究。The inevitable result of circulating fluidized bed(CFB)boilers scale-up is the increasing of furnace cross-sectional size and the parallel circuit.The coal combustion and heat transfer in a fluidized bed boiler are determined by the characteristics of gas-solid flow in the furnace.The uniformity of gas-solid flow has an important impact on the safe operation of CFB boiler.In this paper,the static and dynamic lateral non-uniformity of gas-solid flow in large CFB boilers were analyzed.The static non-uniformity problems include the air distribution uniformity,the gas-solid flow deviation along the section caused by the parallel circuit and the flow distribution deviation of each circuit,which does not change with time under the stable operation condition.The resistance characteristic of separator is an important characteristic parameter of cyclone.Under the same gas phase flow rate,the effect of solid concentration on the pressure drop of cyclone is non-monotonic.The cyclone pressure drop decreases first and then slowly increases as the concentration of solid particles increasing.The solutions of the governing equation of multi-cyclone system are multi-velued.Therefore,the solid circulating rate of each cyclone has deviation under the condition of multi loop parallel.The hanging platen superheater in CFB boiler affects the local concentration distribution of particles and then affects the distribution of solid particle circulation flow rate of each separator.In the aspect of air distribution uniformity,the way of air inlet from both sides and the back wall will lead to uneven air distribution in different degrees.The outlet duct of the cyclones has a significant influence on gas-solid flow distribution of the cyclones.The large margin and long-term pressure fluctuation in CFB furnace is discovered during lower load operation,which is the dynamic lateral non-uniformity.The large cross-section air distribution,reduction of the primary air and the multi-circuit parallel are main reasons for this problem.The mathematica

关 键 词：大型循环流化床锅炉 气固流动 非均匀性 分离器 横向波动 循环流率 

分 类 号：TK224[动力工程及工程热物理—动力机械及工程]