辛胜伟,张缦,王君峰,贺峰,曹培庆,蔡润夏,张鹏,王虎,陈建斌,杨海瑞
XIN Shengwei,ZHANG Man,WANG Junfeng,HE Feng,CAO Peiqing,CAI Runxia,ZHANG Peng,WANG Hu,CHEN Jianbin,YANG Hairui

• 1:神华国能集团有限公司
• 2:清华大学能源与动力工程系
• 3:哈尔滨锅炉厂有限责任公司

摘要(Abstract)：

外置式换热器对于大型循环流化床锅炉的高效运行有重要意义。为全面掌握CFB锅炉外置式换热器运行特性,消除现阶段制约超超临界CFB锅炉外置式换热器管屏壁温偏差问题,系统总结了外置式换热器的研究现状和关键技术研究进展,并介绍了超超临界循环流化床锅炉外置式换热器的设计方案。研究发现,600 MW超临界CFB锅炉外置式换热器壁温偏差十分明显,壁温分布呈现马鞍形分布(中心区域管屏壁温高,边壁区域管屏壁温低),这是由气泡不均匀性分布决定。外置式换热器内传热系数与受热面布置的空间位置密切相关,外置式换热器流化风速Ug=0.4 m/s时,床中央至x/Xw≈0.6处传热系数基本一致,而靠近壁面区域,传热系数显著降低,边壁流动区占床面宽度的25%～30%。将管束远离边壁区布置可以改善传热系数空间分布的不均匀性,传热系数极值偏差从15%降至6%。660 MW超超临界CFB锅炉外置式换热器的设计计算表明,外置式换热器布置高温再热器受热面时,高温再热器管子中径壁温与汽温差可达到58℃,显著制约外置式换热器的安全运行。因此,在660 MW超超临界CFB锅炉的外置式换热器中全部布置汽温相对较低的中温过热器,受热面采用TP347H和TP347HFG材料即可满足要求,仍可保证一定的余量。将外置式换热器管排布置选择与灰流动的方向平行的方式,同时为消除边壁流造成的局部换热不均问题,设计时考虑避免管屏布置在边壁区内,管屏距离边壁的距离应由传统设计的250 mm增至500 mm以上,可改善外置式换热器内的气固流动及传热行为,以减小颗粒侧传热偏差。该设计在保证外置式换热器安全运行的同时,还可有效调控炉膛温度和蒸汽温度。
The external heat exchanger( EHE) is of great significance for the high-efficient operation of large circulating fluidized bed( CFB) boilers. In order to fully master the operation characteristics of external heat exchanger( EHE) in CFB boiler and eliminate the temperature deviation of EHE tube wall in ultra-supercritical CFB boiler at this stage,in this paper,the research status and key technology of the EHE were systematically summarized,and the design scheme of the EHE for ultra-supercritical CFB boiler was introduced. The results show that the wall temperature deviation of the EHE of 600 MW supercritical CFB boiler is very obvious,and the wall temperature distribution is saddle-shaped( the wall temperature of the tube panel in the center area is high and the wall temperature of the tube panel in the side wall area is low),which is determined by the uneven distribution of bubbles. The heat transfer coefficient of the EHE is closely related to the spatial position of the heating surface arrangement. When the speed of fluidization wind( Ug) of the EHE is 0.4 m/s,the heat transfer coefficient from the center of the bed to x/Xw≈0.6 is basically the same,while near the wall area,the heat transfer coefficient decreases significantly,and the side wall flow area accounts for about 25%-30% of the bed width. The arrangement of the tube bundle away from the side wall area can improve the inhomogeneity of the spatial distribution of the heat transfer coefficient,and the extreme deviation of the heat transfer coefficient is reduced from 15% to 6%. The design and calculation of the EHE of the 660 MW ultra-supercritical CFB boiler show that when the EHE is arranged with high reheating surface,the temperature difference between the middle diameter wall temperature of the high temperature reheater tube and the steam temperature can reach 58 ℃,which significantly restricts the safe operation of the EHE. Therefore,in the EHE of ultra-supercritical CFB boiler,all medium-temperature superheaters with relatively low steam temperature will be arranged. and TP347 H and TP347 HFG materials are used for the heating surface,which can meet the requirements and still ensure a certain margin. The arrangement of EHE tube is chosen to be parallel to the direction of ash flow in order to eliminate the local heat transfer unevenness caused by the side wall flow. In the design,it is considered to avoid the arrangement of the tube screen in the side wall area,and the distance between the tube screen and the side wall should be increased from 250 mm to more than 500 mm,which can improve the gas-solid flow and heat transfer behavior in the EHE to reduce the heat transfer deviation of the particle side. The design can control the furnace temperature and steam temperature effectively while ensuring the safe operation of the EHE.

关键词(KeyWords)： 超超临界;循环流化床;锅炉;外置式换热器;传热
ultra-supercritical;circulating fluidized bed;boiler;external heat exchanger;heat transfer

Abstract:

Keywords:

基金项目(Foundation): 国家重点研发计划资助项目(2016YFB0600201)

作者(Author): 辛胜伟,张缦,王君峰,贺峰,曹培庆,蔡润夏,张鹏,王虎,陈建斌,杨海瑞
XIN Shengwei,ZHANG Man,WANG Junfeng,HE Feng,CAO Peiqing,CAI Runxia,ZHANG Peng,WANG Hu,CHEN Jianbin,YANG Hairui

DOI: 10.13226/j.issn.1006-6772.CFB20051501

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