湿法脱硫烟气湿排问题分析

Analysis on Corresponding Problems of WFGD Flue Gas Wet Emission

目前国内湿法烟气脱硫普遍采用烟气再热器(GGH)提高出口烟温,但加装GGH会使系统复杂化并增加投资及运行费用。为探求烟气湿排的可行性,研究解决烟气湿排中的相关问题,文中利用数值模拟技术,对烟气直接排放(取消GGH)时烟囱内的流场,烟羽扩散情况进行了数值模拟研究;对烟气湿排中的腐蚀问题、烟囱内的压力分布、烟气的抬升高度等问题进行了计算分析。数值计算与分析表明,湿烟囱排放会增强对烟囱的腐蚀性,需采用特殊的防腐处理:湿烟囱直接排放会降低烟气抬升高度,不利于扩散;为减少烟流下洗,增强扩散,应保证烟气的出口动量;湿烟气各项排放指标能满足环保要求。总之,设计合理的湿烟囱,湿烟气直接排放可大大降低WFGD系统的设备投资和运行费用,是完全可行的。

Currently, GGH（gas gas heater） is widely used in the wet flue gas desulphurization system to increase flue gas temperature of stack outlet. It, however, causes the system to be complicated together with additional operation cost to equip with GGH. To probe into the feasibility of wet stack emission and related issues for flue gas wet emission, numerical simulation technique was adopted to analyze the flow field in the stack and out of the stack （without GGH）. The corruption issue, the thermal stress of the stack and the pressure distribution in the stack and lifting height of the flue gas were also calculated and analyzed. According to numerical simulation analysis, special anticorrosive measures should be taken in abating stack corruption escalated by wet stack emission. Wet stack emission will reduce the lifting height of the flue gas, and it＇s not beneficial to gas diffusion; the momentum of the flue gas （its exit velocity） should be guaranteed to decrease the plume downwash and to promote gas diffusion; each of the＇emission index of the wet flue gas can meet the requirements for the environmental protection. In conclusion, wet stack emission can reduce the equipment investment and operation cost evidently if designed reasonably and it is absolutely feasible.