SNCR flue gas denitration method suitable for full load conditions of circulating fluidized bed boiler

Abstract

The invention discloses a SNCR flue gas denitration method suitable for full load conditions of a circulating fluidized bed boiler and belongs to the field of SNCR flue gas denitration. According to the SNCR flue gas denitration method, a reduction agent is injected into flue gas and the reduction agent and NOx in the flue gas undergo a reaction so that denitration is realized. When a furnace box temperature is above 850 DEG C or boiler load is higher than 50%, reducing agent jet points are necessarily arranged at a cyclone separator inlet horizontal flue, and other selectable jet points can also be used; when a furnace box temperature is greater than 800 DEG C and less than 850 DEG C or boiler load is in a range of 30-50%, reducing agent jet points are necessarily arranged at a furnace wall, and other selectable jet points can also be used; and when a furnace box temperature is less than 800 DEG C or boiler load is below 30%, reducing agent jet points are necessarily arranged at a secondary air duct, and other selectable jet points can also be used. The SNCR flue gas denitration method realizes denitration under the full load conditions of a CFB boiler so that SNCR flue gas denitration efficiency is above 85%.

Description

technical field [0001] The invention belongs to the field of SNCR flue gas denitrification. Background technique [0002] Selective non-catalytic reduction (SNCR) flue gas denitrification is a well-developed NOx control technology. The main principle of SNCR is to inject a reducing agent into the high-temperature flue gas at 850-1170 °C without the action of a catalyst, and the reducing agent reacts with NOx in the flue gas to form N 2 . Compared with the selective catalytic reduction (SCR) denitrification process, SNCR has the characteristics of simple process, low investment and operation costs, and is especially suitable for circulating fluidized bed (CFB) boilers with relatively low NOx concentration at the furnace outlet. [0003] The existing CFB-SNCR technology mainly injects reducing agent into the horizontal flue at the inlet of CFB boiler cyclone separator, and the reducing agent mixes with flue gas in the cyclone separator and reacts with NOx in the flue gas. A...

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Problems solved by technology

[0004] There are various reductant injection arrangements in the prior art, but none of them can meet the requirements of SNCR flue gas denitrification under the full load condition of the boiler

The inventor found through research on the prior art that, for example, in the furnace, the boiler primary air or / and secondary air is sprayed into the reducing agent to carry out SNCR denitrification: when the reducing agent is injected into the furnace by the primary air, due to the circulating flow The concentration of solid particles in the lower part of the bed boiler is relatively high, and the reducing agent is more likely to contain the active component Fe in the solid particles. 2 o 3 , CaO, etc. catalyzed by oxidation to NOx, the purpose of NOx removal will not be achieved, but will lead to an increase in the concentration of NOx at the furnace outlet; and it is difficult to achieve more than 70% of the SNCR denitrification reaction only by injecting the reducing agent into the secondary air. Denitrification efficiency

Therefore, if this method is adopted, it is difficult to achieve the purpose of efficiently removing NOx

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