Abstract:Most coal-fired power plants in China have abandoned Gas-Gas-Heater, and thereof resulting in frequent rainout around stacks. Extensive samples, including flue gas, stack rainout, discharged liquid from duct and stack, and slurry, were collected and analyzed for elemental distribution using ICP and XPS. Morphology analysis on solid samples using SEM was also performed. The goal is to perform a source apportionment analysis of stack rainout.The results indicated that, even though FGD and mist eliminator were operated properly, the wet flue gas was condensed on the duct/stack inner surface. Part of the formed liquid droplet was re-entrained into the flue gas as the condensed liquid could not be effectively discharged and the flue gas local velocity was high, which is the main source of the stack rainout. Meanwhile, fly ash and gypsum that were adherent to the inner surface of duct and stack were also re-entrained with the liquid droplet into the flue gas, causing increased slurry concentration along the flue gas flow. Elemental distributions between stack rainout and stack liquid discharge were quite similar. The morphology of the undissolved in the stack rainout showed agglomerate of fly ash and gypsum scale, which have also been observed in the liquid discharge. The elemental composition of un-dissolved solid in the stack rainout is determined by combining results of fly ash collection, wet flue gas desulphurization, mist eliminator, and liquid discharge. Fly ash accounts for 63.1% of the total undissolved in the stack rainout for the testing plant. Since the main contributor to the stack rainout is the re-entrainment of condensed liquid discharge from duct and stack, optimization on duct/stack design and liquid discharge alignment is necessary to eliminate stack rainout.
庄烨, 顾鹏, 欧阳丽华, 陈振宇, 刘科伟. 燃煤电厂烟囱降雨机理分析[J]. 中国环境科学, 2015, 35(3): 714-722.
ZHUANG Ye, GU Peng, 欧Yang-Li-Hua , CHEN Zhen-Yu, LIU Ke-Wei. Experimental study of formation mechanism of stack rainout from coal-fired power plant. CHINA ENVIRONMENTAL SCIENCECE, 2015, 35(3): 714-722.