An environmental protection device for desulfurization, denitrification, and dust removal with good dust removal effect

Abstract : In recent years, with the rapid development of China's economy and the increasing awareness of environmental protection among the people of air pollution control has attracted much attention. The production exhaust gases of many industries environmental protection and health From the perspective of production waste gas pollution control to a minimum. Through the use of desulfurization and denitrification technology to promote the harmonious development of society and the ecological environment. A detailed study of desulfurization and denitrification technology is presented. With the rapid development of industries, energy demand is also increasing. 技术。随着产业的快速发展，能源需求也在增加。 Coal combustion power generation 、 fuel oil vehicles 、 heavy industrial units, etc., are all generating large amounts of acidic gases and particulate matter. The large-scale emission of these gases has caused serious harm to the human environment and is one of the important atmospheric pollutants.

Keywords : Dust removal Desulfurization and denitrification Technology, Environmental protection equipment .

1. Introduction
China is one of the countries with the most thermal power units in the world. By the end of 2019, China's installed capacity had reached 119.055 million kilowatts, accounting for about 80.95% of the total power generation. China is rich in coal resources, and energy structure is a major issue in future energy construction. In addition, China's per capita energy level is at a low level in the world, and per capita coal and hydropower resources are equivalent to 50% of the world average. Therefore, saving energy and land, especially in terms of exhaust gas emissions, is particularly important. Large-scale thermal power enterprises should actively promote the integrated construction of desulfurization, denitrification, dust removal, and smoke stacks, significantly reduce the unit capacity footprint, reduce upfront investment, and increase soil and environmental protection.
2. Research Background and Significance
2.1 Desulfurization technology for power plant boilers and its development
In desulfurization of power plant boilers, waste materials are easily mixed with the filler on the surface of the furnace, but it is easy to block in actual operation. The desulfurization absorption tower is a widely used tower type at present. The flue gas flows from bottom to top, and the desulfurizing agent is vertically injected from the nozzle or injected into the tower at a certain angle. This utility model has a simple structure, low cost, the contact area between the flue gas and the absorbed sludge in the spray tower is proportional to the spray density, low desulfurization pressure, and high efficiency. The disadvantage is that the flue gas distribution is uneven. There are many special schemes for spray towers, using spray pipes to spray lime at the top, and after a complete lime bath, the smoke can dissipate. This invention has the advantages of high desulfurization efficiency, good coal adaptability, good dust removal effect, and uniform distribution of waste gas flow, but its disadvantages are high strength and complex structure.
2.2 Denitrification technology for power plant boilers and its development
At present, denitrification technology is applied to the boiler manufacturing technology of thermal power plants, and there are usually two methods to achieve this technology. One is low-nitrogen combustion technology, and the other is SCR flue gas denitrification technology. The main reason for using these two methods in the boiler manufacturing of thermal power plants is that they can burn, increase the denitrification function of thermal power plants, and effectively increase the internal pressure of the boiler. At present, a third technology—SNCR flue gas denitrification technology—can also be used for denitrification of flue gas from thermal power plant boilers. The main construction process is to add a reducing agent or urea to the flue gas, and nitrogen and water are generated through a chemical reaction. At the same time, due to the use of SNCR flue gas denitrification technology, the reaction furnace of this technology is a single furnace. When the furnace temperature is 850℃-1100℃, the denitrification reducing agent is ammonia gas decomposed from urea, which reacts with nitrogen oxides generated in the furnace to generate nitrogen gas. Due to the low denitrification efficiency, the efficiency is between 20% and 50%, and the generated N2O will seriously damage the ozone. The denitrification efficiency of SNCR and SCR combined denitrification technology is mainly 60%～80%, which is a combination of the previous two denitrification technologies. However, due to the complexity of the system, this technology is not suitable for the actual manufacturing process.
2.3 Dust removal technology for power plant boiler flue gas and its development
In the boiler production stage, dust removal technology has the characteristics of high stability and high dust removal efficiency. Therefore, in the next development stage, the use of rotary electrode dust removal technology is the development direction of dust removal technology. The principle of the rotary electrode vacuum cleaner is the same as that of the traditional vacuum cleaner. It consists of a traditional electric field and a three-phase device, and the anode part of the rotating electrode electric field uses a rotating anode and a rotating cleaning brush. When the powder attached to the rotating anode plate reaches the thickness of the top anti-corona, the configured non-vacuum component is used to brush it to increase the charging efficiency of the dust remover, reduce the emission concentration, and avoid secondary dust. The advantages of the rotary electrode vacuum cleaner are as follows. The anode is cleaned regularly, which effectively reduces secondary dust, solves the problem of high-intensity dust, reduces the sensitivity of coal and ash to electricity, and especially small vacuum cleaners can reduce the footprint. It is particularly suitable for converting traditional electrostatic dust collectors. There is one drawback: the utilization rate of rotating parts and equipment is low; secondly, the installation conditions are high. In areas where a large amount of dust is generated, only using an electric vacuum cleaner does not meet the requirements, and an electric vacuum cleaner needs to be added. The main principle of the wet electrostatic precipitator is the same as that of the dry electrostatic precipitator, that is, the dry electrostatic precipitator absorbs dust particles in the flue gas. Unlike the electric dry vacuum cleaner, it absorbs positive dust through the action of the electric field. This utility model is different from the dust caused by the filler on the plate causing the smoke ash to vibrate. It sprays wet water on the plate to collect the garbage in the dust, and disperses the water. At the same time, the fine water mist sprayed in the fog can not only collect smoke dust but also reduce resistance and help the plate move.
3. Integrated Desulfurization and Denitrification Device
3.1 Working principle of wet electrostatic precipitator
First, the wet dust removal device establishes a sustainable electric field. That is, the needle electrode cathode wires (on) form a strong electric field. They generate electrons and charges, and charged particles are detected and recovered at the anode (various cations are acquired and driven to the cathode). The upper display shows that the system operates intermittently, and the cathode and anode are cleaned by auxiliary flashing and ash deposition. The injected water enters the ash collection container of the vacuum membrane dust collector through the pipes of the wet collection system. The working principle is shown in Figure 1.
During the operation of the wet vacuum device, there are two types of dust particle processing loads. One is on-site charging. For particles larger than 1 mm in diameter, the effect of the electric field is significant, and the particles collide with charged negative ions along the energy lines. At this time, the load intensity is a factor affecting processing.

Figure 1 Working principle diagram of wet electrostatic precipitator

The dust released by flue gas desulfurization is mainly ultrafine dust, and most of the particle size distribution is below 6μm, accounting for about 90% of the dust. Concentration below 5.m, mainly distributed in units of M from 0.6-1.2μm.
When the SO3 concentration in the waste gas is 80u, the temperature field does not change much. Once modified, it will not form an aerosol, but in the form of H2SO4 droplets. The average particle size is below 0.4um, which belongs to the classification of underwater particulate matter. This is also the main reason for the low SO3 removal rate of electrostatic separators and flue gas desulfurization systems. Due to the high capture rate of submicron particles, the separation efficiency of SO3 droplets is very high.
Wet electric vacuum cleaner, particles 0.01μm can effectively remove fine particles, droplets and dust. The dust removal efficiency of the electric field is generally above 70%. After wet desulfurization, a wet electric vacuum cleaner can be configured to match the composite aerosol of particulate pollutants (such as gas, quicklime, SO3 droplets, and heavy metals) after wet desulfurization.
Under existing standards and technical conditions, Nass ESP is an ideal instrument for PM25 monitoring in coal-fired power plants and industrial boilers. It is more practical, economical, and feasible.
3.2 Working principle of desulfurization and denitrification
95% of nitrogen oxides in boiler flue gas are insoluble in water. The purpose is to make NO2 easily soluble in water and remove NO2 from the flue gas after being absorbed by a strong oxidizing agent.
Denitrification reaction formula:

Desulfurization reaction formula:

The lower part of the wet vacuum cleaner is equipped with multiple layers of spray oxidation and absorption layers. The main function of the lower spray layer in contact with the flue gas is to oxidize the lower nitrogen oxides in the flue gas to form high-quality nitrogen oxides that are easily soluble in water. The collected oxidation spray liquid enters the oxidation recovery tank and then enters the alkaline absorption spray upper layer. Here, the NO2 formed after oxidation and the SO2 in the waste gas react with the alkaline sprayer and are absorbed and removed, and the alkaline mist is also recovered in the alkaline recovery tank.
IV. Summary
In general, with the sustainable development of the economy, people's requirements for the quality of life are also gradually improving. Pollution control in thermal power plants has received great attention from relevant departments. The "Regulations on the Management of Laws and Regulations on Power Plant Pollution" have been passed successively. The design of coal-fired power plants plays an important role in increasing people's understanding of air pollutant emissions and flue gas desulfurization technology in coal-fired power plants. At the same time, innovative research and practical application of flue gas desulfurization, denitrification, and comprehensive dust removal technologies for boilers in thermal power plants have been carried out. Increase the competitiveness of large companies in the energy industry, develop environmental protection enterprises, and promote the sustainable development of thermal power plants. This utility model makes full use of raw materials, increases desulfurization efficiency, reduces pollutant emissions, and increases the quality and comprehensive utilization rate of desulfurization. In addition, the main engine downtime of the desulfurization structure is short, with social, environmental, and economic advantages. In order to increase desulfurization capacity and efficiency, there is good value.
References:
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[2] Li Wei, A Brief Discussion on the Desulfurization Process of Calcium Carbide Slag [J]. Power Technology and Environmental Protection, 2019, 27(6):33-35.
[3] Song Yanhui. Research on New Denitrification Technology for Thermal Power Plants [J]. China High-tech Enterprises. 2019(05)
[4] Research Progress on Integrated Flue Gas Desulfurization and Denitrification Technology [J]. Journal of Luoyang Vocational and Technical College. 2019(05)