A joint NOx and mercury removal process and device based on sncr-scr combination

Abstract

The invention relates to an NOx and mercury combined removal process based on combination of SNCR-SCR. The process comprises the steps of: 1) mixing urea and ammonium chloride to serve as a reducing agent in an SNCR system; 2) spraying the mixed reducing agent solution into a hearth, utilizing urea and ammonium chloride to conduct thermal decomposition to obtain NH3 for denitration; conducting heating to decompose NH4Cl to get HCl gas, thus obtaining tail gas containing HCl and unreacted NH3; 3) step 2) letting the tail gas of step 2) enter an SCR system, under the action of an SCR catalyst, oxidizing elemental mercury in flue gas into bivalent mercury by HCl; and 4) making the mixed flue gas in step 3) enter a wet desulfurization tower, and dissolving bivalent ionic mercury in a gypsum slurry in the wet desulfurization tower, thus finishing removal of elemental mercury. The invention provides an NOx and mercury combined removal device based on combination of SNCR-SCR, and the device includes a control system, and the SNCR system, the hearth, the SCR system and a flue gas treatment system that are connected in order.

Description

technical field [0001] The invention relates to the field of flue gas purification for collaborative removal of pollutants in coal-fired power plants, in particular to a NOx and mercury combined removal process and removal device based on SNCR-SCR combination. Background technique [0002] Environmental and resource issues are major issues facing human beings today. The extensive use of fossil fuels such as coal, oil, and natural gas has caused increasing pollution and ecological environment deterioration. Mercury is a highly toxic pollutant. Mercury emitted from coal combustion is one of the main sources of man-made mercury pollution. When mercury is released into the atmosphere, it will cause serious harm. Under the action of microorganisms, mercury will transform into a more toxic methylmercury, which can accumulate in the human body through the food chain. Due to the high affinity of mercury to sulfur compounds, it can destroy the function of enzymes and other proteins a...

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Problems solved by technology

On the contrary, elemental mercury is extremely volatile and insoluble in water, which makes it difficult for mercury in flue gas to be removed by desulfurization and denitrification devices. Therefore, it is impossible to rely on the pollutant control equipment installed in the post-combustion area of ​​existing coal-fired power plants ( APCDs), such as electrostatic precipitator system (ESP), bag filter system (FF), wet or dry desulfurization system (FGD), selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) equipment, etc. take off

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