Environmental influence and countermeasures for high humidity flue gas discharging from power plants

The source of moisture in flue gas emissions from coal-fired power plant and the impact of high humidity flue gas on the environment were reviewed. Flue gas moisture from fired power plant mainly comes from the release of hydrogen in coal combustion process and water carried by flue gas from wet flue gas desulfurization system. High humidity flue gas emission increases the overall humidity in the lower atmosphere, which is not conducive to the pollutants diffusion in low atmosphere and even affect the local climate around the plant; high humidity flue gas emission promotes the secondary transformation of air pollutants as well, accelerating the hygroscopic aerosol growth, thus aerosol optical characteristics is changed, and atmospheric visibility reduces. As for the power plant itself, high humidity flue gas emission will cause the increase of water consumption, and take away too much latent heat of vaporization, which is adverse to water conservation and heat reuse. High humidity flue gas and other acidic gases such as SO3 cause low-temperature corrosion of flue at the end of boiler, shortening the operation span of equipment. High humidity flue gas also produces "gypsum rain" after the wet flue gas desulfurization, which is harmful to the surrounding environment. Through research and analysis for high humidity flue gas emission from domestic and foreign coal fired power plants, the authors believe that a significant increase in the relative humidity and a large number of sub-micron particles discharging due to high humidity flue gas emission throughout the lower atmosphere may contribute to continuous smog, thus the quantitative study about the contribution of high humidity to smog is the next focus for the research of high humidity flue gas emission.