Exhaust gas treatment device and method for removing mercury from exhaust gas

Abstract

An air pollution control device 10 according to the first embodiment of the present invention is an air pollution control device for reducing the amounts of NOx and Hg contained in flue gas 12 from a boiler 11. The air pollution control device includes: NH 4 Cl solution supply means 16 for spraying an NH 4 Cl solution 14 by a plurality of spray nozzles 15 into a flue gas duct 13 at the downstream of the boiler 11; a reduction-denitration device 18 including a denitration catalyst for reducing NOx in the flue gas 12 with NH 3 and for oxidizing Hg under the coexistence with HCl; and a wet desulfurization device 22 for reducing the amount of Hg oxidized in the reduction-denitration device 18 by using a limestone-gypsum slurry 21. The NH 4 Cl solution supply means 16 supplies the NH 4 Cl solution 14 from the spray nozzles 15 so as to prevent the NH 4 Cl solution 14 from being adhered to an inner wall of the flue gas duct 13 through which the flue gas 12 is flowing.

Description

technical field [0001] The present invention relates to an exhaust gas treatment device for oxidizing mercury contained in exhaust gas discharged from boilers and the like, and a method for removing mercury from exhaust gas. Background technique [0002] In addition to coal dust, sulfur oxides (SOx), and nitrogen oxides (NOx), the exhaust gas generated during coal incineration and heavy oil combustion sometimes contains metallic mercury (Hg 0 ). In recent years, various methods and devices have been proposed for treating the metallic mercury by combining a denitrification device for reducing NOx and a wet desulfurization device using an alkali absorbent as an SOx absorbent. [0003] As a method for treating metallic mercury in exhaust gas, a method of spraying ammonia (NH 3 ) solution to reduce denitrification, and spray oxidation aids such as hydrochloric acid (HCl) solution to oxidize (chloride) mercury on the denitrification catalyst to become water-soluble mercuric chl...

AI Technical Summary

Problems solved by technology

[0015] here, in Figure 29 In the exhaust gas treatment system 100 shown, as Figure 30 As shown, the spray nozzle 109 is provided with multiple along the wall surface of the flue 104, for example, considering the installation cost and maintainability, it is preferable that the number of spray nozzles is small, but if it is too small, it cannot be sprayed evenly in the flue 104. NH 4 Cl solution 103

Therefore, there exists NH 4 NH produced by Cl solution 103 3 , HCl cannot be uniformly supplied to the exhaust gas 102, resulting in NH in the exhaust gas 102 3 Concentration, uneven concentration of HCl, denitrification performance and mercury oxidation performance problems

[0016] Additionally, when NH 4 When the Cl solution 103 adheres to the wall surface of the flue 104 before gasification, there may be problems such as corrosion of the flue 104, accumulation of ash, damage due to thermal shock, etc.

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