Denitration | What is ammonia escape in denitration system?

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SCR系统运行中,最重要的参数是氨逃逸。“氨逃逸”指的是 SCR 脱硝反应器出口测量出的氨浓度,单位 ppm 。氨本身的易挥发的特性,只要是有氨参与反应的场所都有挥发、都有未参与反应的氨的存在,这部分的氨就是所谓的氨逃逸。

During the operation of SCR system, the most important parameter is ammonia escape. "Ammonia escape" refers to the ammonia concentration measured at the outlet of SCR denitration reactor, in ppm. Ammonia itself is volatile. As long as there is ammonia involved in the reaction, there is volatilization and there is ammonia not involved in the reaction. This part of ammonia is called ammonia escape. In SCR denitration, in order to reduce the operating cost and reduce the corrosion of ammonia escape on the downstream equipment of the boiler, the ammonia escape should be controlled within a certain range as far as possible. In order to meet the national environmental protection requirements, a certain amount of ammonia should be reached, and the design value should not be greater than 3 ppm.

However, in actual operation, there will be a greater possibility, mainly due to the following factors:

1. The influence of too high or too low temperature. If the reaction temperature is too high, ammonia will generate NO; If the reaction temperature is too low, the reaction rate of NOx and ammonia will be reduced and a large amount of ammonia will escape.

2. The ammonia flow distribution of the spray gun is uneven. The ammonia in the flue gas is distributed unevenly and the flow rate is uneven, and the amount of ammonia sprayed from the outlet of each spray gun is also different, leading to higher ammonia escape at places with high concentrations.

3. The catalyst is blocked. If the catalyst is blocked, the denitration rate will decrease. Usually, it is to meet the environmental protection standards to prevent more ammonia from being sprayed if the parameters are not up to standard. In this case, a vicious circle will be caused. The problem of catalyst blockage, aging, and reduction of catalytic efficiency will lead to increased ammonia escape.

4. Influence of ammonia concentration. The ammonia concentration cannot be controlled. If you configure it by feeling, it will lead to poor atomization and high ammonia escape.

5. The atomization effect is not good. The atomization air volume is too small, and the atomization of the spray gun is not good, resulting in the flue gas and ammonia can not be fully mixed together, which will also lead to the escape of a large amount of ammonia.