循环流化床锅炉循环流率在线测量方法研究

高温床料的循环流率是循环流化床锅炉的重要参数,但目前鲜有能应用于实际锅炉中的测量技术。为此,笔者提出了一种新型冲击式循环流率的在线测量方法,并研制了原理样机;建立了测量过程的理论模型并进行了实验室冷态试验,将新型循环流率测量方法应用于某116 MWth循环流化床锅炉中进行热态试验。测量装置具有悬臂梁式几何结构,其整体布置于循环流化床锅炉立管底部。悬臂梁型装置的一端固定于锅炉外壁面,另一端固定有靶片并伸入至立管密相区中。装置通过测量立管物料下落时冲击靶片而造成的形变来计算颗粒冲击力并反推颗粒冲击速度,进而获得循环流率。同时,通过仪表风吹扫冷却装置并防止堵塞。该方法具有耐受高温、可在线测量和不影响锅炉正常运行等优点。冷态试验测量得到不同冲击速度下的气固两相流绕流阻力和阻力系数,随着冲击速度增大,气固绕流阻力随之增大而阻力系数减小,且存在"剪切变稀"现象。在实际锅炉的热态测试中,该测量装置能较好地捕捉到锅炉起停炉、变负荷时循环流率变化趋势。通过量级分析并利用炉膛稀相区压差与炉膛截面风速之积校核测量结果,验证了该方法在实际循环流化床锅炉中在线应用的可行性。

Research on in-situ measurement method for ash circulating rate of circulating fluidized bed

The ash circulating rate of high-temperature bed material is a crucial parameter for circulating fluidized bed(CFB)boilers,while there is no measurement technology that can be applied to the industrial boiler at present.Therefore,an in-situ impact measurement method for solid particle circulation rate of CFB boilers was proposed in this paper,and its prototype equipment was built.The theoretical model of the measurement process was established and the cold state test was carried out in the laboratory.The proposed measurement method of circulating flow rate measurement was also applied to a 116 MW th CFB boiler for a hot state test.The prototype equipment had the geometry structure of cantilever,which was arranged at the bottom of standpipe in circulating fluidized bed.One end of the prototype was fixed with the outer wall surface of the boiler and the other end carrying a target piece was inserted into the dense phase area of standpipe.The device calculated the impact force of particles and reversed the impact velocity of particles by measuring the deformation caused by the impact on the target plate when the materials in the riser fell,so as to obtain the circulating flow rate.Meanwhile,instrument air is supplied to cool equipment and prevents it from blocking.This measurement method has the advantages of high-temperature resistance,the ability of in-situ measurements and no disturbances to the boiler operation.The results indicate that the resistance and resistance coefficient of gas-solid flow at different impacting velocity are measured in cold state experiment.As the increase of impact velocity,the gas-solid flow resistance increases and the resistance coefficient decreases and the phenomenon of shear shinning appears.In hot state test in real boiler,the measuring method is capable of capturing the variation of the ash circulating rate when the boiler starts,shuts-down and the load changes.Based on the magnitude analysis and the checking calculation with the product of pressure drop of dilute phase area in furnace and average velocity in furnace,the feasibility of the in-situ utilization of the proposed method in CFB boilers is verified.