大型燃煤机组中速磨煤机一次风流场优化及数值模拟  

Numerical simulation and optimal design on primary air flow field in medium speed mill of large scale coal-fired units

作　　者：张健 向柏祥 黄军 李燕 王鹏 ZHANG Jian;XIANG Baixiang;HUANG Jun;LI Yan;WANG Peng(Shenhua Guohua(Beijing)Electric Power Research Institute Co.,Ltd.,Beijing100024,China;CHN Energy Technology&Economics Research Institute,Beijing102211,China)

机构地区：[1]神华国华(北京)电力研究院有限公司,北京100024 [2]国家能源集团技术经济研究院,北京102211

出　　处：《洁净煤技术》2021年第5期189-195,共7页Clean Coal Technology

基　　金：国家重点研发计划资助项目(2018YFB0604203)。

摘　　要：为减小占地面积,降低单位造价成本,近20 a来国内新建的燃煤机组布置通常十分紧凑,其中侧煤仓布置成为燃煤机组常见的选择之一。侧煤仓布置存在2个问题,一是远端磨煤机管道较长,易导致风粉分配不均;二是一次风管道大幅度缩短,风量的测量装置没有合适的安装位置,一次风测量准确性下降。为避免某电厂660 MW超超临界侧煤仓布置燃煤锅炉由于中速磨煤机一次风测量失真,导致燃烧和配风发生大幅波动,磨煤机出口粉管堵粉、着火和炉膛出口NO_(x)浓度超标等事故。基于数值模拟软件Fluent对磨煤机入口一次风圆形管道的流场进行了研究,分别计算了原始设计和将风管道取直后的一次风流场分布。结果表明,随着一次风流量的提高,位于管道转弯后1~3倍直径处的一次风流速分布存在一个明显的转捩点。入口风流速在9.5 m/s时,位于该点前后的风量测量失真造成风量大幅波动。取直入口管道,一次风道流场更为规则,流场的转变趋向平缓,避免了一次风测量失真。通过安装整流装置,将风量测量装置移至风粉管底部,适当延长直管段长度等也可以在较大程度上规避风量测量失真的现象发生。若现场空间不具备条件,避免在较短的管道内出现三通、转弯、变径或阀门等容易引起流动稳定性变差的部件或结构,同样可避免一次风量测量失真对机组扰动的影响。In order to reduce the floor area and unit cost, the layout of newly-built coal-fired units in China is mostly very compact in recent 20 years. Among them, changing the front coal bunker to the side coal bunker has become one of the common choices for coal-fired units. The layout of side bunker brings two problems: one is that the pipeline of remote pulverizing system is long, which is easy to lead to uneven distribution of air and powder;Second, the primary air duct is greatly shortened, the air volume measuring device does not have a suitable installation position, and the accuracy of primary air measurement decreases. In order to solve the accidents such as large fluctuation of combustion and air distribution, powder blockage at the outlet of the pulverizer, ignition and excessive NO_(x) concentration at the outlet of the furnace of 660 MW ultra super-critical side coal bunker coal-fired boiler in a power plant due to the distortion of primary air measurement of the medium speed pulverizer, the flow field of the circular primary air pipe at the inlet of the pulverizer was studied based on the(fluent)numerical simulation software. The primary air flow distribution in the original design and after straightening the air duct were calculated, respectively. The results show that there is an obvious transition point in the primary air velocity distribution at 1 to 3 times the diameter after the pipe turns, with the increase of primary air flow. However, the air volume measurement before and after this point is distorted, resulting in large fluctuation of air volume, when the inlet air velocity is 9.5 m/s. By straightening the inlet pipe, the flow field of the primary air duct is more regular, and the transformation of the flow field tends to be gentle, avoiding the distortion of the primary air measurement. By installing rectifying device, moving the air volume measurement device to the bottom of air powder pipe and appropriately extending the length of straight pipe section, the distortion of air volume measurement

关 键 词：燃煤锅炉 磨煤机 一次风量 转捩点 风量测量 风量波动 

分 类 号：TQ53[化学工程—煤化学工程] TK114[动力工程及工程热物理—热能工程]