SCR inlet flue gas pre-treatment system and method

Abstract

The invention relates to an SCR inlet flue gas pre-treatment system and method, relates to boiler pollutant control technology, and are used for new construction or renovation projects of ultra-cleanNOx emission of grate-firing coal-fired boilers. The SCR inlet flue gas pre-treatment system comprises a temperature regulating system, a urea solution or ammonia water solution ejector, and a cycloneequalization system. The system adopts a heating way of extracting high-temperature flue gas from a hearth outlet and then introducing the high-temperature flue gas into a cyclone tube, and a coolingway of adding a temperature-regulating economizer or extracting low-temperature flue gas from flue gas at a boiler dust collector outlet or an air preheater outlet and then introducing the low-temperature flue gas into the cyclone tube through a cold flue, and the average temperature of SCR inlet flue gas is controlled within the working range of catalysts. A urea solution is ejected in a burnoutchamber through the urea solution ejector; an ammonia water solution is ejected at an inlet pipe of a cyclone separator through the ammonia water solution ejector; NH3 is produced under the action ofthe high-temperature flue gas and mixed into the flue gas. Under the combined action of a flow equalization board and the cyclone tube, the flue gas and NH3 are mixed uniformly to achieve the effectsof equal temperature, equal concentration field and equal velocity, thereby meeting the requirements on the temperature, concentration field and velocity field at an SCR inlet.

Description

technical field [0001] The invention relates to a method for pretreatment of flue gas at an SCR inlet by direct pyrolysis in a urea flue or direct decomposition in an ammonia flue, and relates to the technical field of pollutant control in bed-fired coal-fired boilers. Background technique [0002] In my country's energy structure, coal is the main fossil energy. Coal-fired industrial boilers are one of the major coal-consuming households. By the end of 2012, my country had 467,000 industrial boilers in use, with a total of 1.78 million steam tons. According to the data of the National Bureau of Statistics and the National Energy Administration, in 2012, the annual coal consumption of industrial boilers in the field of industrial heating was 650 million tons, accounting for about 20% of the national coal consumption. The flue gas emitted by coal-fired boilers is the main source of air pollutants NOx, and the NOx emitted by industrial boilers accounts for 15% to 20% of my c...

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Problems solved by technology

[0011] The purpose of the present invention is to provide a kind of SCR inlet flue gas pretreatment system and method, adopt a kind of spraying urea solution at the furnace burnout chamber or spray ammonia solution before the inlet pipe of cyclone separator, and adopt the uniform flow uniform temperature, uniform Concentration field and temperature adjustment method to solve the problem that the flue gas condition at the SCR inlet of the layer-fired coal-fired boiler reaches the standard, so that the layer-fired coal-fired boiler can achieve ultra-clean emission of NOx

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