适应新排放标准的火电厂除尘技术

Dust Control Technologies Under the New Emission Standard for Thermal Power Plants

简要介绍历次修订《火电厂大气污染物排放标准》时,中国火电厂在开发和应用电除尘器、袋除尘器、电袋复合除尘器方面的改进;指出电除尘器按传统凭飞灰比电阻和化学成分确定驱进速度并进行电除尘器选型设计,其偏差颇大;提出应更重视飞灰物相组分,还要重视显微结构、浸润性、黏附性、粒径分布和视密度、煤的燃烧方式、炉温、燃烧气氛等的影响;推荐用满足排放浓度所需要的比集尘面积数值判别不同煤质和飞灰的电除尘难易性;比较电除尘器、袋除尘器、电袋复合除尘器的技术特点和技术经济性后,建议:①煤、灰品质较稳定,比集尘面积<160m2/(m3·s-1)就能达标者,优先选用电除尘器;②煤、灰品质多样或多变,比集尘面积≥160m2/(m3·s-1),或已运行的除尘器需大幅提高除尘效率才能达标者,优先选用电袋复合除尘器,它与袋除尘器一样能够有效地捕集PM10和PM2.5微尘;③燃煤硫分低,除尘器进口烟尘浓度较低,烟气速度场、浓度场、温度场和漏风比较均匀时,需要比集尘面积≥160m2/(m3·s-1)才能达标者,优先选用袋除尘器。

The progress of dust control technologies for thermal power plants accompanying with the successive revisions of emission standards are reviewed in this paper. Electrostatic precipitator （ESP）, Bag Filter （BF） and ESP-BF integration （COPAC） are among those technologies adopted for meeting these standards. It is pointed out that to design the ESP with a migration velocity, it is not enough to consider only the dust resistivity and the chemical composition, which would involve a large error. One has to consider the influences of dust mineral composition and other properties such as microstructure, infiltration, adhesion, particle size distribution and apparent density, as well as the coal combustion method, furnace temperature, and combustion atmosphere. It is recommended to use the Specific Collection Area （SCA） of the ESP as an index of the dust precipitability for different fly ashes, produced from different coal combustions. Based on technical and economical comparisons between ESP, BF and COPAC, the following suggestions are made. （1） In case of stable coal supply, the ESP is preferred, when SCA 〈160m^2/（m^3·s^-1） in order to meet the emission standard; （2） COPAC is preferred, when SCA ≥ 160m^2/（m^3·s^-1） is required with a variety of or changeable coal supplies or in case when it is necessary to obviously improve the existing ESP performance in order to meet the emission standard. COPAC can also collect MIO and PM2.5 fine particulates in the same manner as BF. （3） BF is preferred when SCA ≥ 160m^2/（m^3·s^-1） is required and in case of low sulfur coal, low inlet dust concentration, uniform gas/dust distribution and even air leakage.