YiranIndustrial boiler flue gas denitrificationThe equipment adopts low nitrogen combustion technology and flue gas denitrification technology (oxidation flue gas denitrification method and reduction flue gas denitrification method), such as SCR flue gas denitrification method, SNCR flue gas denitrification method, etc. Firstly, low NO combustion technology is adopted to reduce the amount of NO generated in the furnace; The second is to install a flue gas denitrification device at the tail of the flue gas, which converts NO in the flue gas into nitrogen or useful fertilizers, resulting in high flue gas denitrification efficiency.

1、 Low nitrogen combustion technology

Low nitrogen combustion technology mainly refers to the technology of reducing NO generation through combustion, and its main approach is:

1. Choose fuels with low nitrogen content and remove nitrogen from the fuel, such as using clean natural gas as the combustion fuel;

2. Reduce the excess air coefficient and organize excessive combustion to lower the oxygen concentration around the fuel, that is, low excess air combustion;

3. Reduce the peak temperature under suitable excess air conditions to minimize the generation of thermal NO;

4. Increase the residence time of combustible materials in the flame front and reaction zone at low oxygen concentrations.

5. Although adopting low NO combustion technology can reduce some NO emissions, the removal rate of NO is relatively low. If you want to further reduce NO emissions, it is advisable to use flue gas denitrification technology;

2、 Industrial boiler flue gas denitrification technology

Industrial boiler flue gas denitrification technology can be divided into two methods: oxidation method and reduction method. Oxidation method for industrial boiler flue gas denitrification mainly refers to the oxidation of NO into nitrogen dioxide, which is dissolved in water and made into HNO3 or absorbed by alkaline substances. The reduction method for industrial boiler flue gas denitrification mainly refers to the use of reducing agents (such as NH3, CH4, CO, and H2) to reduce NO and NO2 to N2, which is then discharged into the atmosphere. The reduction method does not have issues with subsequent wastewater treatment. Therefore, the reduction method is currently a commonly used method for flue gas denitrification. The main technologies for industrial boiler flue gas denitrification using reduction methods include SCR selective catalytic reduction, NSCR non selective catalytic reduction, and selective non catalytic reduction.

1. Selective Catalytic Reduction (SCR) method. The so-called selectivity refers to the reduction and removal of NH3 with NO in the presence of a catalyst, rather than the oxidation reaction with oxygen in the flue gas, thereby reducing the consumption of ammonia. The reaction equation is:

4NH3+4NO+O2→4N2+6H2O；

4NH3+2NO2+O2→3N2+6H2O；

There are also some side reactions, and their reaction formulas are as follows:

4NH3+5O2 → 4NO+6H2O (oxidation reaction of NH3);

4NH3+3O2 → 2N2+6H2O (thermal decomposition reaction of NH3);

2. Non selective catalytic reduction (NSCR) method.

The non selective catalytic reduction method uses a mixture of CH4, CO, H2 and other gases as reducing agents, which react with NOx and O2 in the flue gas at a certain temperature and under the action of a catalyst, in order to achieve the goal of removing NOx. The difference between NSCR and SCR lies in the fact that NSCR's reducing agent undergoes oxidation reaction with oxygen in the flue gas to produce CO2 and H2O. Therefore, the consumption of reducing agent is relatively high, and compared with selective denitrification methods, NSCR has higher operating costs.

3. Selective Non Catalytic Reduction (SNCR) method. In the selective non catalytic reduction method, only reducing agents such as NH3 and urea are used for selective reaction of NOx, without the use of catalysts. Therefore, the SNCR method should add reducing agents in the high-temperature zone. This temperature range is generally 900-1100 ℃. The advantage of this method is that it does not require a catalyst, has less equipment and operating costs, but due to the large amount of reducing agents such as NH3, the potential leakage is also large, making it difficult to ensure the reaction temperature and residence time, resulting in a lower denitrification rate.

4. Oxidation based denitrification technology. Oxidation based denitrification technology often requires the oxidation of NO to NO2. Generally, NO is first oxidized to NO2 through oxidants such as O3, ClO2, KMnO4, and then absorbed with water or alkaline solution for denitrification. According to the type of absorbent, it can be divided into alkali absorbent, oxidation absorption method, acid absorption method, absorption reduction method, liquid phase coordination method, etc.