Coal-fired boiler denitrification system and method coupled with overfire air and SNCR

Abstract

The invention belongs to the field of coal-fired boiler denitration and discloses a coal-fired boiler denitration system and method with over fire air and SNCR coupled. The coal-fired boiler denitration system comprises an SNCR subsystem, over fire air subsystems and a DCS control subsystem. The SNCR subsystem comprises spraying guns, thermocouples, an electric adjustment valve and an electronic flow meter, wherein the spraying guns are arranged in three layers, the thermocouples are arranged in a hearth at the height corresponding to the spraying guns in three layers, the over fire air subsystems are arranged in two layers, each layer of the over fire air subsystem comprises an over fire air pipe, an electric adjustment door and a speed tester. The DCS control subsystem is used for receiving data transmitted from the subsystems and adjusting the subsystems according to data. The method uses the system for denitration. By the method and the system, temperature window can be adjusted in a wide range, denitration efficiency is utmostly improved, usage of reducing agent is reduced, and safety and cost performance of boiler operation are improved.

Description

technical field [0001] The invention belongs to the field of denitrification of coal-fired boilers, and more specifically relates to a denitrification system and method for coal-fired boilers coupled with overfire air and SNCR. Background technique [0002] Currently, 67% of China's electricity comes from coal-fired power boilers, while 33% comes from new energy sources, including hydropower, solar energy, wind energy, and nuclear energy. Since China is a large coal mining country with abundant coal reserves and relatively low prices, coal-fired power generation will still dominate the power industry in the next few decades. However, the combustion of pulverized coal will produce pollution such as dust, sulfur dioxide, nitrogen oxides, and mercury. The NOx produced by coal-fired boilers is mainly NO, and NO will be oxidized in the air to form NO 2 , NO 2 Not only will it form acid rain, but it will also cause photochemical smog, leading to urban smog and seriously endanger...

AI Technical Summary

Problems solved by technology

However, further studies have shown that the existing boilers still have the following problems after air staging low NOx transformation or SNCR transformation: In actual operation, due to the change of coal quality and boiler load, the temperature of the SNCR injection point of the boiler often deviates from the window temperature , leading to problems such as an increase in the amount of reducing agent, an increase in nitrogen oxides emitted by the boiler, and excessive ammonia escape; the adjustment of the thermal state of the boiler only provides the opening of the damper, the amount of ammonia injection and the The position parameters of ammonia injection cannot adapt to the rapidly changing boiler working conditions; since boiler thermal state adjustment requires professionals and specific instruments, the cost of boiler thermal state adjustment is relatively high, and the factory cannot hire professionals for long-term thermal state adjustment experiments In addition, the distribution of the internal temperature field of the boiler is mainly affected by the combustion conditions in the furnace. Simply changing the position of the reducing agent injection point cannot change the furnace outlet temperature, and can only passively adapt to the changing furnace temperature distribution, and the adjustment ability is low.

[0004] In short, the above-mentioned problems have seriously affected the denitrification efficiency of the boiler, the final NOx emission of the boiler and the economical efficiency of the boiler operation.

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