燃煤电厂湿烟囱降雨成因分析

Analysis on Mechanism of Rainout Carried by Wet Stack of Thermal Power Plant

湿烟囱周边降雨现象是许多电厂和脱硫机组运行中的常见问题,对烟囱雨成因的研究是治理烟囱雨的关键.本研究对某火电厂脱硫后湿烟气进行现场采样,分析内容包括:脱硫后净烟气携带浆液量、烟道内冷凝水和烟囱周边采集的降雨雨滴,通过液态样品和固体颗粒物的物化分析,进行烟囱雨的源解析.液态样品分析结果表明,该电厂脱硫机组除雾器运行良好,达到除雾器性能保证值,但烟气携带浆液量在湿烟道中沿程增加,烟道疏水冷凝液中硫酸盐浓度沿程增大,有明显的累积现象,发生二次夹带的可能性很大,因此该燃煤电厂主要因湿烟道/湿烟囱内疏水系统运行不佳引起湿烟气卷携内衬壁面液滴而形成烟囱雨.烟囱雨中固体颗粒物的主要成分为复合碳酸盐、硅铝酸盐,尽管飞灰浓度满足脱硫系统运行要求,但固体颗粒物源解析结果表明,飞灰对烟囱雨的贡献率达60%.由于烟囱雨与烟道/烟囱冷凝液成分最为接近,因此对湿烟道/湿烟囱改造、强化疏水、避免因饱和水蒸汽冷凝形成的冷凝液在烟道/烟囱内积累是治理烟囱雨的有效措施.

Rainout from wet-stack took placed in many thermal power plants with WFGD system. Research on causes of the rainout is important to solve the problem. The objective of this research is to analyze the mechanism of rainout. Field study was performed to collect experimental data in one thermal power plant,including the amount of desulfurization slurry carried by wet flue gas,liquor condensate from wet duct,and droplets from the wet stack. Source apportionment analysis was carried out based on physical and chemical data of liquid sample and solid sample. The result showed that mist eliminator operated well,which met the performance guarantee value. But the total amount of desulfurization slurry in flue gas and the sulfate concentration in liquid condensate discharge from the wet duct / stack increased. The liquid condensate accumulated in the wet duct / stack led to liquid re-entrainment. In conclusion,the rainout in this power plant was caused by the short of wet ductwork or liquid discharge system,the droplets caused by re-entrainment carried by the saturated gas released from the stack. The main undissolved components of the rainout were composite carbonate and aluminosilicate. Although ash concentration in this WFGD met the regulation criteria,source apportionment analysis showed that fly ash contributed to rainout was accounted for 60%. This percentage value was same as the data of solid particles in the condensate. It is important to optimize the wet ductwork,wet stack liner,liquid collectors and drainage. Avoiding the accumulation from saturated vapor thermal condensation is an effective way to solve the wet stack rainout.