Emission gas control technology in waste incineration power generation

In the process of incineration of domestic waste for power generation, the exhaust gas generated by it is usually treated to reduce the exhaust emissions. However, there are not only corresponding solid particles and dust in the exhaust, but also corresponding acidic gases, such as NO2, SO2, HCl, etc. These acidic gases have a great impact on people's life and production. Therefore, domestic waste incineration power plants need to adopt scientific and reasonable measures to strengthen reasonable control of acidic gas emissions.

Domestic waste incineration power generation technology mainly includes three links, garbage collection link, incineration power generation link, tail gas treatment link. Among them, the garbage collection link mainly collects and transports municipal garbage from various regions; The process of incineration power generation is to discharge and store domestic waste, and then remove the leachate through reasonable fermentation technology, and retain the combustible waste as the incineration power generation material. At the same time, effective measures will be taken to deal with the exhaust gas during the incineration process. During incineration, the boiler exhaust pipe is the main way of exhaust gas emission, and the exhaust gas is first discharged into the purification system, and then discharged into the air environment after the exhaust gas purification treatment to reduce exhaust pollution. The exhaust gas not only contains dust and solid particles, but also a variety of acidic gases, such as NO2, SO2, HCl and so on.

Acid gas control measures

Wet acid removal technology

The wet acid removal technology is generally used to completely remove particles in the tail gas through the filter bag dust collector, and then transported to the wet smoke washing tower. First of all, after the tail gas enters the tower, the temperature of the tail gas is gradually decreased by spraying the liquid, and when the saturation temperature is reached, the chemical reaction occurs with the alkaline absorption liquid distributed in the filler gap below, so that it absorbs the acidic gas.

Dry acid removal technique

The use of dry acid removal technology, usually spray lime powder in the absorption tower, so that the lime powder can be in contact with the acid gas in a large area, so as to absorb the acid gas, and obtain good acid removal effect. However, the acid removal efficiency of this method is often low, and the removal rate of HCL is about 60%, and the removal rate of SO2 is only about 30%. In order to effectively improve the acid removal efficiency, it is necessary to moderately increase the amount of absorbent in the application.

Semi-dry acid removal technique

The use of semi-dry acid removal technology, mainly in the application of efficient atomizer, in the absorption tower into the hydrated lime slurry, the direction of injection can be sprayed downward from the top of the tower, but also from the bottom of the tower to spray upward, so as to promote the spray into the hydrated lime slurry can be in contact with the exhaust gas in a large area, and efficiently absorb the solid particles and acid gases in the exhaust gas. The semi-dry acid removal technology has a good atomization effect in the application, and the tail gas can be fully in contact with the absorption liquid phase, which not only helps to reduce the temperature of the tail gas, but also effectively absorbs the acid gas and removes the solid particles distributed in it. After the hydrated lime slurry is sprayed in, the water contained in it is evaporated to reduce the amount of wastewater produced. In the application of semi-dry acid removal technology, the device involved is relatively simple, the amount of waste water generated is relatively small, the operation cost is not high, and good acid removal effect can be obtained. The semi-dry acid removal technology has a high acid gas removal rate, and the hydrogen chloride removal rate can exceed 90% when combined with cloth bags.

Low nitrogen combustion technology

Low NOx burners in the application stage include low NOx precombustion chamber burners, mixed promotion burners, separate flame burners, self-recirculating burners, etc. The air classification combustion technology is mainly divided into one or more stages to add air, add some air in the combustion zone, make the excess air coefficient a < 1, create a fuel-rich zone, synchronously create a reducing atmosphere, in order to inhibit the generation of NOx, and synchronously reduce the generated NOx. Then add enough air to the rear combustion zone to make a > 1, creating a fuel-poor zone to improve combustion efficiency.

Flue gas denitrification technology

At present, in the process of waste incineration power generation, because of the application of low nitrogen combustion technology and "3T" technology, effectively control the secondary pollutants in incineration treatment, while the application of SNCR technology can use ammonia water as a reaction reducing agent, and establish an efficient and fully automatic denitrification system in the incinerator, which can reduce NOx emissions again, so that the final emission situation meets the relevant standards. Flue gas denitration technology in addition to SNCR, conventional SCR, etc., while various industries have also developed some new flue gas denitration technology, such as activated carbon adsorption, liquid absorption, microbial method, electron beam method, etc., although the relevant technology is still immature, but the technical application prospect is still good.

New acid removal process

In addition to the above technologies, new acid removal processes such as NHD removal process and low temperature methanol washing process can also be applied. NHD removal process belongs to a low energy consumption, a new purification process, the main components used are made of polyethylene glycol dimethyl ether mixture, with small volatility and low vapor pressure, and the solvent does not need to be washed and recovered, the essence is to physically absorb the acid gas; The low temperature methanol washing process is a physical absorption method, which can remove a variety of acidic gases such as HCl, SO2 and NO by continuously reducing the circulation amount during the continuous increase of operating pressure. The flue gas treatment system of domestic waste incineration plant is a combination of several technologies. Through practical research, it is found that the removal rate of SO2 is more than 90%, and the removal rate of HCl is as high as 99% by combining dry and semi-dry deacidification technology.