CN103768908B - What a kind of wet type integrated desulfurizing denitration demercuration took off PM2.5 removes tower and technique - Google Patents

Abstract

The invention discloses a wet-type integrated desulfurization, denitrification, mercury removal, and PM2.5 removal tower and process. The removal tower is arranged in sequence from bottom to top: a wet desulfurization section, an oxidation, denitration, and mercury removal section, and a wet electrostatic precipitator section, the flue gas inlet is set on the wet desulfurization section, and the clean flue gas outlet is set on the wet electrostatic precipitator section. The process includes the following steps: step S101, wet desulfurization stage; step S102, denitrification and mercury removal stage; step S103, PM2.5 removal stage; step S104, net flue gas discharge stage. The invention realizes successive removal of fine particles such as sulfur oxides, NO _x , Hg, PM2.5 in the flue gas in the same removal tower, which can effectively prevent the formation of "gypsum rain" and improve the efficiency of the flue gas. Excellent purification efficiency, can achieve ultra-low emission of flue gas, and greatly save the floor space and reduce operating costs.

Description

A wet-type integrated desulfurization, denitrification, demercury, and PM2.5 removal tower and process

technical field

The invention relates to the technical field of air pollution control, in particular to a wet-type integrated desulfurization, denitration, demercuration, and PM2.5 removal tower and process.

Background technique

The rapid progress of industrialization has brought rapid economic development and continuous improvement of living standards for human beings. However, while enjoying the fruits of industrialization, human beings are also suffering from various environmental pollution problems caused by fossil fuels in industrial production. Among them, air pollution is one of the most serious environmental problems facing the survival and development of human society in the 21st century. my country is a country with abundant coal reserves. Coal accounts for 75% of the primary energy. The excessive dependence of the energy consumption structure on coal has led to the aggravation of air pollution. The sulfur dioxide and nitrogen oxides emitted by coal combustion are acid rain, fine particles and smog. Mercury pollution from emissions, a major precursor to weather, also poses multiple hazards. Therefore, the pollution control of SO ₂ , NO _x , mercury and fine particles in coal-fired flue gas is the most important task in the field of air pollution control.

The increasing awareness of environmental protection has made the task of pollution control an important part of the environmental protection undertakings of various countries. In order to curb the hazards of SO ₂ , NO _x , PM2.5 and mercury and achieve sustainable development, China has continuously strengthened the control of emissions of SO ₂ , NO _x , PM2.5 and mercury from coal-fired facilities. NO _x , SO ₂ Emission standards for gaseous pollutants are becoming increasingly stringent.

Internationally, the desulfurization and denitrification integrated technology with simple development technology, low operating cost and better operating performance is regarded as one of the development directions of coal-fired flue gas treatment technology. At present, the flue gas desulfurization and denitrification technologies researched and developed in the world can be divided into two categories: one is to apply the traditional flue gas desulfurization technology (FGD) combined with selective catalytic reduction technology (SCR) to work independently to remove the pollutants in the flue gas. The combined desulfurization and denitrification technology of SO ₂ and NO _x ; the other is a new combined desulfurization and denitrification technology that uses a technology to simultaneously remove SO ₂ and NO _x in the entire system, that is, simultaneous desulfurization and denitrification technology.

In recent years, the first type of desulfurization and denitrification technology has been widely used in China, that is, the method of combining wet desulfurization technology (WFGD) and selective catalytic reduction technology (SCR) to desulfurize and denitrify. Although this method can achieve desulfurization and denitrification separately, the investment and operation costs are high, and the process is complicated. Therefore, the development of collaborative removal technology for various flue gas pollutants has become a research hotspot in the world. The Ministry of Science and Technology of my country has included the development of flue gas simultaneous desulfurization, denitrification and mercury removal technology in the "863" high-tech research plan.

At present, China's coal-fired power plants generally adopt wet desulfurization technology (WFGD), which has high desulfurization efficiency, but it is difficult to denitrify and demercurize at the same time, because more than 90% of _NOx in actual industrial flue gas is NO , NO is hardly absorbed by water or lye except for the formation of complexes. In order to achieve better wet denitrification efficiency in practical applications, oxidants can be used to oxidize NO, and oxidize mercury to high-valent mercury to form mercury salts that are soluble in water. How to increase the oxidation degree of NO _x in the process of wet absorption is the key to simultaneous wet desulfurization, denitrification and mercury removal technology.

Coal-fired flue gas desulfurization, denitrification and mercury removal integrated control technology has broad application prospects. Compared with desulfurization or denitrification process alone, the advantages of simultaneous desulfurization and denitrification in one system are obvious, such as reduced system complexity and better operation. Excellent performance, convenient management, small footprint, low investment and low cost. Therefore, it is an important direction for future air pollution control and sustainable development.

More importantly, apart from SO ₂ and NO _x , the severe air pollution caused by the combustion of fossil fuels, the adverse effects of smog are also increasing, and this pollutant is fine particulate matter (PM2.5). PM2.5 refers to fine particles with an aerodynamic diameter of less than 2.5 μm, which is an important factor leading to environmental problems such as reduced atmospheric visibility, haze weather, acid rain and global climate change.

At present, PM2.5 pollution has increasingly become another core issue of my country's outstanding atmospheric environmental problems. Due to its large specific surface area, it is easy to enrich heavy metal elements and is one of the most important pollutants that affect human health. The existing conventional dust removal technology is difficult to effectively capture fine particles of PM ₁₀ and below. The development of wet electrostatic precipitator technology will play an important role in the control of PM2.5 emissions.

However, there are few reports on the technology or equipment that combines the wet electrostatic precipitator technology with the flue gas simultaneous desulfurization, denitrification and demercuration technology. _The applicant is committed to developing this new product to realize the , NO _x , mercury and PM2.5, etc., and can effectively prevent the phenomenon of "gypsum rain" after wet desulfurization, which not only improves the effect of air pollution control, meets the ultra-low emission requirements, but also effectively reduces the operating cost. The cost and floor area, the new "flue gas treatment tower" equipment and process formed are an important progress in environmental protection technology innovation, and are of great significance for the coordinated control of various pollutants.

Contents of the invention

In view of the deficiencies in the prior art above, the present invention proposes a wet integrated desulfurization desulfurization, denitrification, mercury removal and combined removal of fine particles such as PM2.5 in the flue gas in the same tower. Tower removal and process.

In order to achieve the above object, the present invention provides a wet-type integrated desulfurization, denitrification, demercuration, and PM2.5 removal tower. The removal tower is sequentially arranged from bottom to top: a wet desulfurization section, an oxidation denitration and demercuration section and In the wet electrostatic precipitator section, the flue gas inlet is arranged on the wet desulfurization section, and the clean flue gas outlet is arranged on the wet electrostatic precipitator section.

As a further improvement of the present invention, the wet desulfurization section includes a tower bottom slurry pool and a desulfurizer slurry spray layer, the desulfurizer slurry spray layer is arranged above the tower bottom slurry pool, and the flue gas inlet channel It is arranged between the desulfurizer slurry spray layer and the tower bottom slurry pool.

The slurry tank at the bottom of the tower has an oxidation air pipe built in, and the oxidation air pipe is driven by an oxidation fan arranged outside the wet desulfurization section, and a jet agitator is arranged below the oxidation air pipe, and the jet agitator The jet pump arranged outside the wet desulfurization section is conductively connected with the upper part of the slurry tank at the bottom of the tower.

The desulfurizer slurry spray layer communicates with the circulation pump arranged outside the wet desulfurization section and the slurry tank at the bottom of the tower to form a slurry circulation loop, and the slurry in the slurry tank at the bottom of the tower is introduced into the desulfurization agent slurry spray layer.

As a further improvement of the present invention, the oxidative denitrification and demercuration section is sequentially provided with: an oxidant solution inlet, a flue gas distribution plate, a flue gas uniform distribution device, and an oxidant solution outlet, and the flue gas uniform distribution device guides The wet desulfurization section and the oxidative denitrification and demercuration section are connected through a connection. Air holes are evenly opened on the flue gas uniform distribution device, and after the flue gas enters the oxidation denitrification and demercuration section from the flue gas uniform distribution device, it is sprayed out through the air holes, and is mixed with the oxidant solution in the oxidation denitrification and demercuration section. Touch and react.

As a further improvement of the present invention, an oxidant solution storage tank is also provided outside the oxidative denitrification and mercury removal section, and the oxidant solution outlet leads out the oxidant solution after gas-liquid contact and reaction with the flue gas uniformly distributed in the tower to the oxidant solution. In the solution storage tank, the oxidant solution in the oxidant solution storage tank is led to the inlet of the oxidant solution, and then enters the oxidative denitrification and demercury section to form an oxidant circulation loop.

As a further improvement of the present invention, the smoke distribution plate has a single-layer or multi-layer structure, and air holes are evenly opened on the smoke distribution plate and the smoke distribution device.

As a further improvement of the present invention, the wet electrostatic precipitator section is provided in sequence from top to bottom: a net flue gas outlet, a plate flushing water spray device, an electric field area and a flushing water outlet, and the electric field area is composed of several vertically arranged The cathode plates and anode plates are arranged alternately and spaced apart, and the electric field area of the wet electrostatic precipitator section can be set as single-stage or multi-stage.

As a further improvement of the present invention, a demister is also provided in the wet desulfurization section, and the demister is arranged above the desulfurizer slurry spray layer, and the water inlet of the flushing water pipe of the demister is connected to the demister The outlet of the plate flushing water in the wet electrostatic precipitator section is conductively connected. After the flushing water of the demister falls into the slurry tank, and then dehydrated by the slurry dehydration system, it is reused for the plate flushing water of the wet electrostatic precipitator section, thus forming a flushing water cycle. circuit.

The present invention also proposes a wet-type integrated desulfurization, denitrification, mercury removal, and PM2.5 removal process, using the wet-type integrated desulfurization, denitrification, mercury removal, and PM2.5 removal tower to perform flue gas purification treatment, including the following steps:

Step S101, wet desulfurization stage: introduce the flue gas to be treated into the wet desulfurization section from the flue gas inlet, start the desulfurizer slurry spray layer to spray the flue gas to be treated, and complete the wet desulfurization.

Step S102, denitrification and demercuration stage: the flue gas to be treated after desulfurization enters the oxidative denitrification and demercuration section, passes through the flue gas uniform distribution device and the flue gas distribution plate, and fully contacts the oxidant solution in the oxidative denitrification and demercuration section And react, oxidize and remove NO _X and Hg in the flue gas to be treated.

Step S103, PM2.5 removal stage: the flue gas to be treated after denitrification and mercury removal enters the wet electrostatic precipitator section, passes through the high-voltage electric field area formed by the cathode and anode plates, and the PM2.5 and gypsum in the flue gas to be treated Fine particles such as microparticles are charged and migrate to the anode plate, where they are washed away by the uniform water film on the anode plate.

Step S104, the stage of discharging clean flue gas: the flue gas to be treated after removing PM2.5 is discharged through the clean flue gas discharge port.

As a further improvement of the present invention, the desulfurizing agent used in the desulfurizing agent slurry spray layer is limestone, quicklime, carbide slag or lime mud.

As a further improvement of the present invention, the oxidant solution in the oxidative denitrification and demercury section is a strong oxidizing solution such as NaClO solution, H ₂ O ₂ solution or KMnO ₄ solution.

Compared with the prior art, the wet-type integrated desulfurization, denitration, demercuration, and PM2.5 removal tower and process of the present invention have at least the following technical effects:

The wet-type integrated desulfurization, denitrification, mercury removal and PM2.5 removal tower of the present invention effectively combines the traditional wet desulfurization process with the oxidation denitrification and mercury removal technology and the wet electrostatic precipitator technology to achieve the same removal tower Sulfur oxides, NO _x , Hg, PM2.5 and other fine particles in the flue gas are successively removed inside, which can effectively prevent the formation of "gypsum rain", improve the purification efficiency of flue gas, and achieve ultra-low flue gas Emissions, and greatly save the floor area and reduce operating costs.

The wet-type integrated desulfurization, denitrification, demercury, and PM2.5 removal process of the present invention, on the basis of the existing wet flue gas desulfurization technology, fully contacts and reacts the strong oxidizing solution with the flue gas after desulfurization, so that the flue gas The NO in the gas is oxidized to NO ₂ , and the NO ₂ is absorbed by the solution to remove it. This process can simultaneously remove the heavy metal Hg, and then the flue gas enters the high-voltage electric field, and PM2.5, etc. are charged and transferred and washed away. In this way, the joint removal of multiple pollutants in the same tower is realized, and the efficiency of flue gas pollution control is improved.

Description of drawings

Figure 1 is a schematic structural view of the wet integrated desulfurization, denitrification, demercuration and PM2.5 removal tower of the present invention.

Fig. 2 is a schematic plan view of the smoke uniform distribution device of the present invention.

Explanation of main component symbols in the figure:

100. Wet desulfurization section 101, circulation pump 102, slurry circulation loop

103, jet agitator 104, jet pump 105, oxidation air pipe

106. Oxidation fan 107, tower bottom slurry tank 108, desulfurizer slurry spray layer

109. Mist eliminator 110, flushing water pipeline 200, oxidation denitrification and mercury removal section

201, smoke uniform distribution device 202, air hole 203, smoke distribution plate

204, oxidant solution 205, oxidant solution inlet 206, oxidant solution outlet

207. Oxidant solution storage tank 300, wet electrostatic precipitator section 301, anode plate

302, cathode plate 303, plate flushing water spray device 304, flushing water outlet

400, flue gas import 500, net flue gas export.

detailed description

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

Embodiment one:

Figure 1 is a schematic structural view of the wet integrated desulfurization, denitrification, demercuration and PM2.5 removal tower of the present invention. As shown in Figure 1, a wet-type integrated desulfurization, denitrification, mercury, and PM2.5 removal tower proposed in this embodiment is provided with: a wet desulfurization section 100, an oxidation denitrification and denitrification section from bottom to top in the removal tower. The mercury section 200 and the wet electrostatic precipitator section 300 , the flue gas inlet 400 is arranged on the wet desulfurization section 100 , and the clean flue gas outlet 500 is arranged on the wet electrostatic precipitator section 300 .

Specifically, the wet desulfurization section 100 includes a tower bottom slurry pool 107 and a desulfurizer slurry spray layer 108, the desulfurizer slurry spray layer 108 is arranged above the tower bottom slurry pool 107, and the flue gas inlet 400 channel is set in the desulfurizer slurry Between the spray layer 108 and the slurry tank 107 at the bottom of the tower.

An oxidation air pipe 105 is built in the middle of the slurry tank 107 at the bottom of the tower. The oxidation air pipe 105 is driven by an oxidation fan 106 arranged outside the wet desulfurization section 100. A jet agitator 103 is arranged below the oxidation air pipe 105. The jet agitator 103 The jet pump 104 arranged outside the wet desulfurization section 100 is conductively connected with the upper part of the slurry tank 107 at the bottom of the tower.

The desulfurizer slurry spray layer 108 communicates with the circulating pump 101 arranged outside the wet desulfurization section 100 and the slurry tank 107 at the bottom of the tower to form a slurry circulation loop 102, and the slurry in the slurry tank 107 at the bottom of the tower is introduced into the desulfurizer The slurry is sprayed into the layer 108 .

As mentioned above, the jet agitator 103 and the jet pump 104 are connected outside the tower, and the jet agitator 103 can stir the slurry at the bottom of the tower to prevent the slurry from agglomerating. The oxidation blower 106 provides oxidation air for the oxidation air pipe 105, which is used to improve the oxidation effect of the slurry and improve the quality of by-products. The desulfurizing agent slurry spraying layer 108 sprays the desulfurizing agent slurry downwards to contact with the flue gas in reverse to achieve the purpose of desulfurization.

Specifically, the oxidative denitrification and mercury removal section 200 is arranged in order from top to bottom: an oxidant solution inlet 205, a flue gas distribution plate 203, a flue gas uniform distribution device 201, and an oxidant solution outlet 206, and the flue gas uniform distribution device 201 is connected to The wet desulfurization section 100 and the oxidation denitrification and mercury removal section 200 are connected.

An oxidant solution storage tank 207 is also provided outside the oxidative denitrification and mercury removal section 200. The oxidant solution outlet 206 leads out the oxidant solution 204 after gas-liquid contact and reaction with the flue gas uniformly distributed in the tower to the oxidant solution storage tank 207, and the oxidant solution storage tank 207. The oxidant solution in the tank 207 is then led to the oxidant solution inlet 205, and then enters the oxidative denitrification and demercury section 200 to form an oxidant circulation loop.

As shown in FIG. 1 , the flue gas distribution plate 203 has a multi-layer structure, and air holes are evenly opened on the flue gas distribution plate 203 , and the flue gas distribution plates of each layer are interleaved in the oxidation denitrification and mercury removal section 200 . Of course, in other specific embodiments, the smoke distribution plate may also have a one-layer structure, which will not be repeated here.

As shown in Figures 1 and 2, the flue gas uniform distribution device 201 is provided with a uniform air hole 202, and the flue gas enters the oxidation denitrification and demercuration section 200 from the flue gas uniform distribution device 201 and is sprayed out through the air hole, and is combined with the oxidation denitrification and demercuration The oxidant solution 204 in section 200 contacts and reacts.

Oxidative denitrification and mercury removal section 200 is filled with oxidant solution 204, and the flue gas enters from the bottom of oxidation denitrification and mercury removal section 200, and is evenly ejected from the flue gas uniform distribution device 201 and the pores on the flue gas distribution plate 203. Dispersed into bubbles and rising, gas-liquid contact to react, NO in the flue gas is oxidized to NO ₂ by the oxidant, NO ₂ is dissolved and absorbed, and NO _x in the flue gas is removed. At the same time, the elemental mercury in the flue gas It is also oxidized to Hg2+ by the oxidizing agent solution 204 for removal.

During the use of this embodiment, due to the high smoke velocity in the oxidation denitrification and mercury removal section 200, bubbles are formed rapidly and the liquid is stirred at the same time. On the one hand, it plays a stirring role, and on the other hand, it also increases the mass transfer efficiency. The arrangement of the flue gas distribution plate 203 can make the flue gas evenly distribute in the oxidant solution 204 and improve the gas-liquid contact effect.

Specifically, the wet electrostatic precipitator section 300 is sequentially arranged from top to bottom: a net flue gas outlet 500, a plate flushing water spray device 303, an electric field area and a flushing water outlet 304, and the electric field area is a number of vertically arranged The cathode plates 302 and the anode plates 301 are arranged alternately and spaced apart.

The wet desulfurization section 100 is also provided with a mist eliminator 109 arranged above the desulfurizer slurry spray layer 108 , and the water inlet of the flushing water pipeline 110 of the mist eliminator 109 is connected to the flushing water outlet 304 . The mist droplets carried by the flue gas after desulfurization are removed by the mist eliminator 109, and the mist eliminator 109 is provided with a flushing water pipe 110, and the plate flushing water of the wet electrostatic precipitator section is repeatedly recycled to clean the mist eliminator intermittently.

As shown in Figure 1, in the wet electrostatic precipitator section 300 of this embodiment, the cathode plates 302 and the anode plates 301 are alternately stacked upright and spaced apart to form the cathode and anode plates, and a plate flushing water spray device is arranged above the cathode and anode plates 303, a flat and uniform water film is formed on the anode plate 301, and the tip of the cathode plate 302 is discharged, which can charge and move fine particles such as PM2.5 in the flue gas to the anode plate 301, where they are washed by the water film on the anode plate 301 Finally, the net flue gas is discharged from the net flue gas outlet 500 on the upper part of the wet electrostatic precipitator section 300 .

Exemplarily, the electric field of the wet electrostatic precipitator section 300 can be set as single-stage or multi-stage. The plate flushing water used to form the water film in the wet electrostatic precipitator section 300 is taken out from the lower end of the cathode and anode plates and used as the flushing water for the demister 109 of the wet desulfurization section 100. The slurry is recovered after the dehydration system, and continues to be used as the anode plate flushing water of the wet electrostatic precipitator section 300, thus forming a flushing water circulation loop.

In this embodiment, limestone is used as the desulfurizing agent, and NaClO solution is used as the denitration oxidizing agent. The flue gas to be treated enters the removal tower from the flue gas inlet 400, first contacts and desulfurizes the desulfurization agent slurry sprayed by the desulfurization agent slurry spray layer 108 in the wet desulfurization section 100, and then enters the oxidation denitrification and demercuration through the demister 109 Section 200 is then uniformly distributed by the air holes on the flue gas uniform distribution device 201 and the multi-layer flue gas distribution plate 203 provided on the upper part, and performs gas-liquid contact and reaction with the oxidant solution 204 filled in the oxidation denitrification and demercuration section 200 In order to remove _NOx , heavy metals such as Hg are also oxidized and removed at the same time; finally, the flue gas enters the wet electrostatic precipitator section 300, in which the cathode plate 302 and the anode plate 301 are arranged at intervals, and the tip of the cathode plate 302 is discharged with pierce, and the flue gas Fine particles such as PM2.5 are charged and move to the anode plate 301, and are washed away by the uniform water film on the anode plate 301, and the clean flue gas is discharged from the clean flue gas outlet 500 on the upper part of the wet electrostatic precipitator section 300.

The slurry in the tower bottom slurry pool 107 _of the wet desulfurization section 100 is dehydrated by the belt dehydration system to obtain gypsum as a by-product. Some particles, as well as new particles such as PM2.5 generated by desulfurization and denitrification, are also removed by the wet electrostatic precipitator section 300. The dust removal efficiency reaches 97%, the denitrification efficiency reaches more than 80%, and the desulfurization efficiency reaches more than 95%. , and the mercury removal efficiency is over 95%.

Embodiment two:

This example proposes a wet-type integrated desulfurization, denitrification, mercury removal, and PM2.5 removal process. The wet-type integrated desulfurization, denitrification, mercury, and PM2.5 removal tower described in Example 1 is used for flue gas purification treatment. As shown in the figure, the following steps are included:

Step S101, wet desulfurization stage: introduce the flue gas to be treated into the wet desulfurization section 100 through the flue gas inlet 400, start the desulfurizer slurry spray layer 108 to spray the flue gas to be treated, and complete the wet desulfurization process. Desulfurization.

Step S102, denitrification and demercury stage: the flue gas to be treated after desulfurization enters the oxidative denitrification and demercuration section 200, passes through the flue gas uniform distribution device 201 and the flue gas distribution plate 203, and The oxidant solution 204 fully contacts and reacts, and oxidizes and removes NO _x and Hg in the flue gas to be treated.

Step S103, PM2.5 removal stage: the flue gas to be treated after denitrification and mercury removal enters the wet electrostatic precipitator section 300, passes through the high-voltage electric field area formed by the cathode and anode plates 302, 301, and the PM2 in the flue gas to be treated .5. Fine particles such as gypsum particles are charged, and move to the anode plate 301, and are washed and removed by the uniform water film on the anode plate 301.

Step S104 , the stage of discharging clean flue gas: the flue gas to be treated after removing PM2.5 is discharged through the clean flue gas discharge port 500 .

Exemplarily, the desulfurizing agent used in the desulfurizing agent slurry spray layer in this embodiment is limestone, and the oxidizing agent solution in the oxidation denitrification and demercuration section is NaClO solution. Of course, in other specific embodiments, the desulfurizing agent used in the desulfurizing agent slurry spray layer can also be quicklime, carbide slag or lime mud, etc., and the oxidizing agent solution in the oxidation denitrification and demercuration section can also be _{H2 O2} solution or _KMnO4 solution.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also It should be regarded as the protection scope of the present invention.

Claims (4)

1. A wet-type integrated desulfurization, denitrification, demercuration, and PM _2.5 removal tower, characterized in that: The desulfurization tower is arranged sequentially from bottom to top: a wet desulfurization section, an oxidation denitrification and mercury removal section, and a wet electrostatic precipitator section. The flue gas inlet is set on the wet desulfurization section, and the net flue gas outlet is set on the On the wet electrostatic precipitator section; The oxidative denitrification and mercury removal section is arranged in order from top to bottom: an oxidant solution inlet, a flue gas distribution plate, a flue gas uniform distribution device, and an oxidant solution outlet. The flue gas uniform distribution device is connected to the wet desulfurization device. section and oxidation denitrification demercury section; Air holes are evenly opened on the flue gas uniform distribution device, and after the flue gas enters the oxidation denitrification and demercuration section from the flue gas uniform distribution device, it is sprayed out through the air holes, and is mixed with the oxidant solution in the oxidation denitrification and demercuration section. touch and react An oxidant solution storage tank is also provided outside the oxidation denitrification and mercury removal section, and the oxidant solution outlet leads out the oxidant solution after gas-liquid contact and reaction with the flue gas uniformly distributed in the tower to the oxidant solution storage tank. The oxidant solution in the oxidant solution storage tank is led to the inlet of the oxidant solution, and then enters the oxidative denitrification and demercury section to form an oxidant circulation circuit; the flue gas distribution plate is a single-layer or multi-layer structure, and the The air holes are evenly opened on the flue gas distribution plate; the wet electrostatic precipitator section is arranged in sequence from top to bottom: a net flue gas outlet, a plate flushing water spray device, an electric field area and a flushing water outlet, and the electric field area consists of A plurality of vertically arranged cathode plates and anode plates are arranged alternately and spaced apart, and the electric field area is set to be single-stage or multi-stage; The wet desulfurization section is also provided with a demister, the demister is arranged above the desulfurizer slurry spray layer, the water inlet of the flushing water pipe of the demister is connected to the pole plate of the wet electrostatic precipitator section The rinse water outlet is conductively connected, and after the rinse water of the demister falls into the slurry tank at the bottom of the tower, it is dehydrated by the slurry dehydration system and then reused for the plate rinse water in the wet electrostatic precipitator section, thus forming a rinse water circulation loop; The wet desulfurization section includes a tower bottom slurry pool and a desulfurizer slurry spray layer, the desulfurizer slurry spray layer is set above the tower bottom slurry pool, and the flue gas inlet is set at the desulfurizer slurry spray layer Between the shower layer and the slurry pool at the bottom of the tower; The slurry tank at the bottom of the tower has an oxidation air pipe built in, and the oxidation air pipe is driven by an oxidation fan arranged outside the wet desulfurization section, and a jet agitator is arranged below the oxidation air pipe, and the jet agitator connected to the upper part of the slurry tank at the bottom of the tower through a jet pump arranged outside the wet desulfurization section; The desulfurizer slurry spray layer communicates with the circulation pump arranged outside the wet desulfurization section and the slurry tank at the bottom of the tower to form a slurry circulation loop, and the slurry in the slurry tank at the bottom of the tower is introduced into the desulfurization agent slurry spray layer. 2. A wet-type integrated desulfurization, denitrification, mercury removal, and PM _2.5 removal process, characterized in that: the removal tower of wet-type integrated desulfurization, denitrification, mercury removal, and PM _2.5 described in claim 1 is used for flue gas purification treatment, including the following step: Step S101, wet desulfurization stage: introduce the flue gas to be treated into the wet desulfurization section from the flue gas inlet, start the desulfurizer slurry spray layer to spray the flue gas to be treated, and complete the wet desulfurization; Step S102, denitrification and demercuration stage: the flue gas to be treated after desulfurization enters the oxidative denitrification and demercuration section, passes through the flue gas uniform distribution device and the flue gas distribution plate, and fully contacts the oxidant solution in the oxidative denitrification and demercuration section And react, oxidize and remove NO _X and Hg in the flue gas to be treated; Step S103, PM _2.5 removal stage: the flue gas to be treated after denitrification and mercury removal enters the wet electrostatic precipitator section, passes through the high-voltage electric field area formed by the cathode and anode plates, PM _2.5 and gypsum particles in the flue gas to be treated Fine particles are charged and migrate to the anode plate, where they are washed away by a uniform water film on the anode plate; Step S104, the stage of discharging clean flue gas: the flue gas to be treated after removing PM _2.5 is discharged through the clean flue gas discharge port. 3. The wet-type integrated desulfurization, denitrification, mercury, and PM _2.5 removal process according to claim 2, wherein the desulfurizing agent used in the desulfurizing agent slurry spray layer is limestone, quicklime, carbide slag or lime mud. 4. The wet integrated desulfurization, denitrification, demercuration, and PM _2.5 removal process according to claim 2, characterized in that: the oxidant solution in the oxidative denitrification and demercuration section is NaClO solution, H ₂ O ₂ solution or KMnO ₄ solution.