Research On The H-ESP-SCR System Used In The Coal-fired Utility Boilers

This paper uses hot-side electrostatic precipitator--selective catalytic reduction of NOx system which is referred to H-ESP--SCR system, as the research topic.H-ESP, short for hot-side electrostatic precipitator, installed boiler between economizer and the air preheater in the coal-fired power plant.There are some applications in the United States of America and Japan.The main purpose of U.S. power plants installed H-ESP is to reduce the dust resistivity and improve collection efficiency, however in Japan it is mainly used to protect the catalyst for the SCR system. The catalyst damage mechanism is analyzed in the paper,concluding that the fly ash is a major factor in the degradation of the catalyst.Hot-side electrostatic precipitator can protect the SCR catalyst, simplify the SCR reactor, but the construction and operation cost is high, needing for high quality steels, large area, what is more,there is too much heat loss, and unstable operations, so that the H-ESP--SCR system is currently not appropriate.I compared the hot-side electrostatic precipitator with the conventional electrostatic precipitator in the removal efficiency of mercury exitting the coal-fired flue gas by experimental methods.Five typical coal-fired power plant boiler units were selected for the experimental study and ash samples were collected from them.Bahco particle size classification instrument was as the pretreatment device,and fluorescence mercury analyzer was used to determine the mercury content of fly ash. Two conclusions that the level of mercury in fly ash has a direct relationship with particle size and the conventional electrostatic precipitator is superior to the hot-side electrostatic precipitator on mercury removing.