湿法烟气脱硫过程白烟成因及防治措施分析

Analysis on the causes and prevention measures of white mist in wet flue gas desulfurization

关键词:  湿法脱硫  白烟  水含量  气/气换热  排烟温度 

Key words:  wet flue gas desulfurization  white mist  water content  gas/gas heater  exhaust gas temperature

摘要:

湿法烟气净化过程普遍采用湿法脱硫工艺,但该工艺会导致烟囱出现白烟,造成不良社会公众影响,并导致露点腐蚀。在分析白烟成因的基础上,以某炼厂硫磺回收装置烟气为例,重点探讨水含量和采用气/气换热器对烟气水露点的影响。结果 表明,在研究范围内:①烟气中水的体积分数每增加1%,烟气的水露点温度上升1.13 ℃,含硫烟气温度每下降1 ℃,排烟温度上升0.925 ℃,补水量可减少5.07 kg/h；②综合考虑设备投资和烟气换热效果,降温含硫烟气温度控制在150~180 ℃为宜；③采用高效除雾器将游离水质量分数控制在0.01%,设置气/气换热器控制降温含硫烟气温度为165 ℃,烟气中水体积分数可降低6.21%,系统补水量可减少690 kg/h,排烟温度可升高122 ℃,远高于露点温度。采取上述措施后,可在有效减少白烟的同时节约装置用水量。 

Abstract:

The Wet Flue Gas Desulfurization (WFGD) is widely used in flue gas purification, which always leads to numerous white mist causing adverse public effect and dew point corrosion of the stack. Based on the reasons analysis of forming white mist, the impact of water content and gas/gas heater (GGH) was analyzed for the sulfur recovery unit of a refinery. The results showed as follows:(1) the 1% increase of water volume fraction led to about 1.13 ℃ rise of the flue gas dew point, the 1 ℃ decrease of cooling feed gas resulted in the 0.925 ℃ increase of exhaust temperature and the decrease of 690 kg/h water consuming; (2)after comprehensively considering the equipment investment and heat transfer effect of flue gas, it was suitable to control the cooling feed gas temperature at 150-180 ℃;(3) when the free water content was controlled at 0.01 wt% by the highly efficient mist eliminator and feed gas was cooled to 165 ℃ by GGH,the water content in discharged flue was decreased by 6.21 vol%,the flow of make-up water was decreased by 690 kg/h,the flue discharge temperature was raised by 122 ℃. After taking above measures, the white mist and the water consumption was reduced simultaneously.