超超临界循环流化床锅炉流化床换热器热偏差形成的流动基础  

Hydrodynamic Mechanisms of Non-uniform Distribution of Heat Transfer in Fluidized Bed Heat Exchangers of Ultra-supercritical CFB Boilers

作　　者：蔡润夏 吕俊复[1] 张缦[1] 葛荣存 杨海瑞[1] CAI Runxia, LYU Junfu, ZHANG Man, GE Rongcun, YANG Hairui(Key Laboratory for Thermal Science and Power Engineering of Ministry of Education,Department of Energy and Power Engineering,Tsinghua Univers让y,Beijing 100084,China)

机构地区：[1]清华大学能源与动力工程系热科学与动力工程教育部重点实验室

出　　处：《锅炉技术》2019年第4期34-39,55,共7页Boiler Technology

基　　金：“十三五”国家重点研发计划(2016YFB0600201)

摘　　要：流化床换热器是超超临界循环流化床锅炉重要的热交换设备,其有利于灵活调节床温、汽温,提高机组的燃料适应性,降低污染物排放.运行经验表明:流化床换热器内存在严重的热偏差问题,靠近床中央区域的受热面壁温显著高于壁面区域的壁温,从而导致在超超临界循环流化床锅炉中出现爆管、停机等事故.当前缺乏从气固流动、换热角度分析流化床换热器热偏差形成机制原因.在国家重点研发计划(2016YFB0600201)支持下,开展了流化床换热器内热偏差问题产生机制的相关研究.系统讨论分析了流化床换热器内热偏差形成的流动基础,揭示了气固流动不均匀性特征及其对传热不均匀性的影响,发现受热面管排存在进一步加大了近壁区传热偏差,提出了通过优化流化床换热器结构和布风设计降低热偏差的建议,为660 MW超超临界循环流化床锅炉设计与安全运行提供依据.Fluidized bed heat exchanger(FBHE)is one o￡the most important heat-exchange equipment in large-scale circulating fluidized bed(CFB)boilers,which is beneficial to regulate the steam and bed temperature,enhance the fuel flexibility and reduce the pollutant emissions.However,industrial experience found a significant deviation of temperature distribution of tube panels in the industrial FBHEs,which was high in the bed center but low near the wall region.Such overheating issue will easily lead to tube burst or even boiler breakdown in ultra-supercritical CFB boilers.Although the heat transfer mechanisms of immersed surfaces in a traditional bubbling fluidized bed have been thoroughly investigated,few studies have been conducted to analyze the local hydrodynamics and heat transfer behaviors in a FBHE,and little is known about the cause of temperature deviation in the industrial FBHEs.With the financial support by the National Key Research and Development Program of China,the generating mechanisms of the non-uniform heat transfer phenomenon in FBHEs were investigated?This paper summarized and discussed the basic gas-solid flow causing the non-uniform distribution of heat transfer,and revealed the effects of the non-uniform gas-solid flow on the non-uniform heat transfer process.In addition,the arrangement of tube bundles intensified the non-uniform distribution of the heat transfer coefficients.Therefore,it is suggested to optimize the design of EHEs and modify the distributors to alleviate the heat transfer deviation,so as to provide the basis for the design and operation of the ultra-supercritical CFB boiler.

关 键 词：超超临界 循环流化床 流化床换热器 气固流动 传热 

分 类 号：TK221[动力工程及工程热物理—动力机械及工程]