Flue gas two-stage segmented desulfurization and denitrification system and method

Abstract

The invention discloses a flue gas two-stage segmented desulfurization and denitrification system and method, and belongs to the technical field of air pollution control. NO and SO2 in the flue gas are oxidized into NO2 and SO3 through sodium chlorite, the NO2 and SO3 are absorbed and converted into magnesium nitrate and magnesium sulfate solutions through magnesium hydroxide, the oxidation absorption process is ordered and crossed in a graded and segmented manner, and the purpose of efficient desulfurization and denitrification is achieved. By means of flue gas waste heat evaporation and purified flue gas desulfurization and denitrification liquid escape washing gas recovery, a closed-loop circulation system without solid waste and wastewater discharge and with system water balance is realized on the premise of flue gas ultra-clean discharge, and desulfurization science is combined on the basis of overcoming the technical problem of flue gas low-temperature denitrification, so that desulfurization and denitrification complement each other, and the method has great guiding significance in treating low-temperature desulfurization and denitrification flue gas.

Description

technical field [0001] The invention belongs to the technical field of air pollution control, and in particular relates to a system and method for two-stage and segmental desulfurization and denitrification of flue gas. Background technique [0002] At present, the mainstream processes of industrial flue gas denitrification are selective catalytic reduction (SCR) and selective non-catalytic high-temperature reduction (SNCR), in addition to ozone oxidation absorption method, sodium hypochlorite, sodium chlorite oxidation absorption method, etc. The mainstream flue gas desulfurization process uses the limestone-gypsum method, and there are other desulfurization processes such as the magnesium method, the ammonia method, the double-alkali method, and the dry / semi-dry method. These processes and methods are mature, and the equipment has formed a complete set, and the flue gas desulfurization and denitrification basically meet the environmental protection requirements of ultra-lo...

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Problems solved by technology

However, there are many problems, mainly as follows: most of the by-products are solid waste due to poor quality, a large amount of waste water containing soluble salts produced by desulfurization and denitrification has the hidden danger of polluting groundwater, pollution from escaping ammonia, and gas produced by desulfurization liquid entrained by flue gas Invisible pollution caused by condensable particulate matter (CPM) formed by sol discharge, high operating costs of desulfurization and denitrification, burdening enterprises and other issues

while for SO 2 and the treatment of low NOx concentration, the flue gas produced by steel plant blast furnace gas and coking gas, biomass, and low calorific value solid waste fuel heat energy recovery, etc., it is not suitable to use conventional methods such as limestone-gypsum method, and because of flue gas The low temperature cannot support the technical conditions of "SNCR" and "SCR" denitrification process and cannot be applied, etc.

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