Coal-fired boiler SNCR and SCR combined denitration system and method thereof

Abstract

The invention relates to a coal-fired boiler SNCR and SCR combined denitration system. The denitration system comprises a boiler SNCR reaction system and a SCR reactor; the boiler SNCR reaction system comprises the boiler, an urea solution distribution module and a metering module, and an urea injection system and an urea supply system which are connected with the urea solution distribution module and the metering module; the urea injection system comprises multilayer-designed short spray guns with upper elevation in a 25m to 40m scope in a boiler furnace combustion zone, and multilayer-designed porous long spray guns having an furnace arch with the boiler, wherein, in each layer, at least one porous long spray gun vertically stretches into the boiler, and extends and passes through the cross section; the SCR reactor is connected with a boiler tail through a flue gas mixer; in the SCR reactor, the multilayer cellular catalyst can be arranged at a space between a coal economizer and an air preheater. According to the method, a mol ratio of ammonia nitrogen in an inlet cross section of the SCR catalyst is uniformly distributed, and denitration efficiency of the SCR reactor is enhanced.

Description

technical field [0001] The invention relates to a denitrification system of a power plant, in particular to a coal-fired boiler SNCR and SCR combined denitrification system and method. Background technique [0002] In my country's energy structure, coal occupies a major position. A significant portion of coal consumption is used for electricity production. Nitrogen oxide (NOx) produced by coal-fired power generation is one of the main pollutants causing air pollution. [0003] The reduction of NOx emissions from coal-fired power plants can be achieved through technologies such as low NOx combustion, selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR). Low NOx combustion is based on the formation mechanism of NOx in the boiler, using technologies such as low NOx combustion method, low NOx burner and low NOx furnace to reduce the production of nitrogen oxides. Selective non-catalytic reduction denitrification technology is to spray the reducing ...

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Problems solved by technology

[0009] In the existing SNCR+SCR combined denitrification technology, such as the invention patent 201010130558.3 ​​method for realizing combined SNCR and SCR denitrification of coal-fired boilers, a single-nozzle spray gun (that is, a short wall-type spray gun) is used to spray urea solution into the furnace. The distance into the furnace is limited, and the NH produced by pyrolysis cannot be well 3 and HNCO are evenly mixed with NOx in the flue gas. Although a steam turbulence device is installed at the flue turning chamber, this steam turbulence device can only improve the NH to a certain extent. 3 and the mixing uniformity of HNCO and NOx in the flue gas

NH produced by pyrolysis of urea cannot be made due to existing technology 3 and HNCO are evenly mixed with NOx in flue gas, so the denitrification efficiency of SCR is limited to a certain extent

If the molar ratio of ammonia nitrogen entering the SCR reactor is unevenly distributed on the cross section, it is easy to cause a large amount of ammonia to escape from the SCR reactor and enter the air preheater

In the air preheater, ammonia in the flue gas meets SO 3 will generate NH 4 HSO 4 , NH 4 HSO 4 Adhering to the heating surface of the cold end of the air preheater, adhering to the dust in the flue gas, it is easy to cause the air preheater to be blocked and cause corrosion

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