脱硫塔顶直排烟囱湿烟气液滴生成量分析

Droplet Generation of Wet Flue Gas from Direct Discharge Stack of the Desulfurizing Absorber

国内大多燃煤电厂石灰石-石膏湿法脱硫取消烟气换热器后普遍存在“烟囱雨”“有色烟羽”问题,而这些问题产生的直接原因是烟气中的液滴.针对液滴形成的3种原因,以我国北方地区某个设置吸收塔直排烟囱的项目为例,通过对饱和湿烟气液滴生成量进行定量分析,以及通过烟囱降雨量试验进行定性分析,找出“烟囱雨”“有色烟羽”中液滴的主要来源.结果表明:冬季、夏季及年均情况下不保温烟囱散热生成的液滴量分别为394.74、200.05、307.80 kg/h,保温烟囱散热生成的液滴量分别为34.04、17.32、27.91 kg/h.结合烟囱是否保温的对比试验可知,烟囱保温对减轻“烟囱雨”效果显著.在除雾器正常运行情况下,通过除雾器夹带液滴量为95.63 kg/h.虽然烟气排出后温度下降产生的液滴量最大,但在加装消雨器以排除除雾器夹带及烟囱散热形成的液滴影响后,烟囱周边基本无降雨现象发生.研究显示,烟囱散热产生液滴对形成“烟囱雨”起主要作用,除雾器夹带液滴次之,烟气排出烟囱后产生的液滴对“烟囱雨”影响非常小,其主要形成“有色烟羽”.

Most of coal-fired power plants confront the problems of‘stack rainout’and‘colored smoke plume’after the abolishment of the gas heat exchanger in flue gas limestone lime-gypsum wet desulfurization.The direct cause of these problems is the droplets in the flue gas.For three reasons of droplet formation,a direct discharge stack of a desulfurization absorber in the northern China was taken as an example.Both quantitative analysis of the droplet generation from saturated wet flue gas and qualitative analysis of stack rainfall experiment were carried out to find out the main sources of droplets in‘stack rainout’and‘colored smoke plume’.The results show that the average amount of droplets generated by the non-insulated chimney in winter,summer and year was 394.74,200.05 and 307.80 kg/h,respectively,and the amount of droplets generated by the insulated chimney was 34.04,17.32 and 27.91 kg/h.By comparison of the results of chimneys with and without insulation,it can be seen that the chimney insulation has a significant effect on reducing the‘stack rainout’.The amount of the liquid entrainment through a demister under normal operation is 95.63 kg/h.The largest amount of droplets was generated by the discharged flue gas during cooling process.However,there was no rainfall around the chimney after adding a rain eliminator to eliminate the influence of the entrainment of demister and chimney heat dissipation.This study shows that the heat loss by the chimney plays a major role in the formation of‘stack rainout’.The second main reason is the entrainment of demister.The droplets generated by discharged flue gas has minor effect on‘stack rainout’and is the main factor to form‘colored plume’.