Improvements of non-uniform distribution of tube wall temperatures in circulating fluidized bed boiler’s external heat exchangers

doi:10.3785/j.issn.1008-973X.2021.03.019

Journal of ZheJiang University (Engineering Science)

2021, Vol. 55

Issue (3): 578-585 DOI: 10.3785/j.issn.1008-973X.2021.03.019

Improvements of non-uniform distribution of tube wall temperatures in circulating fluidized bed boiler’s external heat exchangers

Li NIE1,2(

),Run-xia CAI3,Jia-yi LU2,*(

),Wei CHENG2,Wen-jie ZHANG2,Li-ming GONG2,Da-yong XUE2,Man ZHANG3,Hai-rui YANG3,Jun-fu LV3

1. College of Energy Engineering, Zhejiang University, Hangzhou 310027, China
2. Clean Combustion and Flue Gas Purification Key Laboratory of Sichuan Province, Chengdu 611731, China
3. Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Tsinghua University, Beijing 100084, China

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Abstract

A wall temperature distribution of the external heat exchanger of 600 MW supercritical circulating fluidized bed boiler was reproduced by numerical calculation, in order to solve the wall temperature deviation of the external heat exchanger of 660 MW ultra supercritical circulating fluidized bed boiler. The result was applied to the calculation of wall temperature of the same size external heat exchanger of ultra-supercritical circulating fluidized bed boiler. By throttling the working medium of three tube platens near side wall, the calculated wall temperature deviation of external heat exchanger of ultra-supercritical circulating fluidized bed boiler was solved. The wall temperature deviation of heating surface could be controlled within 30°C to keep safe operation of heating surface tubes. Experimental results show that the heat transfer coefficient of the particle side presents a saddle shaped bimodal distribution along the width direction of the external heat exchanger, and the maximum value of the heat transfer coefficient appear at about 0.2 times width near the side wall. By adjusting the gas velocity in the side wall area, the heat transfer coefficient can be improved, so as to provide guidance for slowing down the local deviation in the operation process.

Key words： ultra supercritical circulating fluidized bed boiler external heat exchanger tube wall temperature deviation

Received: 10 February 2020 Published: 25 April 2021

CLC:

TK 229.6

Fund: 国家重点研发计划资助项目（2016YFB0600204）

Corresponding Authors: Jia-yi LU E-mail: niel@dbc.com.cn;lujy@dbc.com.cn

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	Li NIE
	Run-xia CAI
	Jia-yi LU
	Wei CHENG
	Wen-jie ZHANG
	Li-ming GONG
	Da-yong XUE
	Man ZHANG
	Hai-rui YANG
	Jun-fu LV

Cite this article:

Li NIE,Run-xia CAI,Jia-yi LU,Wei CHENG,Wen-jie ZHANG,Li-ming GONG,Da-yong XUE,Man ZHANG,Hai-rui YANG,Jun-fu LV. Improvements of non-uniform distribution of tube wall temperatures in circulating fluidized bed boiler’s external heat exchangers. Journal of ZheJiang University (Engineering Science), 2021, 55(3): 578-585.

URL:

http://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2021.03.019 OR http://www.zjujournals.com/eng/Y2021/V55/I3/578

循环流化床外置换热器壁温偏差改进措施

为了解决660 MW超超临界循环流化床锅炉外置换热器中受热面的壁温偏差问题，通过数值计算，复现600 MW超临界循环流化床锅炉外置换热器壁温分布，并将该方法应用到相同尺寸的超超临界循环流化床锅炉外置换热器壁温计算中. 通过对边壁区域3片管屏工质节流，从工质侧解决超超临界循环流化床锅炉外置换热器壁温偏差问题，使受热面计算壁温偏差控制在30°C以内，实现受热面管材安全运行. 通过冷态试验，发现颗粒侧传热系数沿外置换热器宽度方向呈现马鞍形的双峰分布，传热系数最大值出现在距离边壁约0.2倍宽度范围内，通过调整边壁区域气体速度可以提高该区域的传热系数，为运行过程减缓局部偏差提供参考.

关键词： 超超临界, 循环流化床, 锅炉, 外置换热器, 壁温偏差

Fig.1 Wall temperature deviation of high temperature rehearter external heat exchanger of 600 MW CFB boiler

Fig.2 Schematic diagram of external heat exchanger of CFB boiler

Fig.3 Schematic diagram of cold test rig of external heat exchanger

Fig.4 Structure diagram of external heat exchanger test device

Fig.5 Schematic diagram of test heat transfer probe

Fig.6 Comparison between calculated value and measured value of wall temperature external heat exchanger on 600 MW CFB boiler

Fig.7 Wall temperature distribution of external heat exchanger of ultra supercritical CFB boiler after throttling

Fig.8 Influence of fluidization velocity of external heat exchanger on the distribution of heat transfer coefficient

Fig.9 Curve of resistance of air distribution plate of external heat exchanger with different air speed

Fig.10 Influence of bed inventory of external heat exchanger on the distribution of heat transfer coefficient

Fig.11 Influence of adjusting air distribution on heat transfer coefficient of external heat exchanger


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