KR100202461B1 - Semi-dry electrostatic cleaner and method of removing particles from exhaust gas - Google Patents

Abstract

Provided are a semi-dry electric scrubber capable of easily purifying exhaust gas and a method for purifying exhaust gas using the same. This sprays the corona plasma reactor for the high voltage corona discharge to spray the harmful substances contained in the injected exhaust gas and the slurry and compressed air containing water and the alkaline absorbent to apply the high voltage power when spraying the corona plasma reactor and water and the alkaline absorbent to maximize the efficiency of the gas-liquid reaction. Electrostatic spray systems for miniaturizing and enhancing reactivity. The reactor body in which the discharged exhaust gas and the micronized droplets are injected to undergo a gas-liquid reaction is provided. The finely sprayed slurry droplets are brought into contact with the hot exhaust gas to cause a gas-liquid contact reaction, whereby the solidified contaminants generated are removed and the purified gas is discharged into the atmosphere. It is a simple device with high removal rate of harmful gas.

Description

Semi-dry electric cleaner and exhaust gas purification method using the same

The present invention relates to a semi-dry electric cleaner and a method for purifying exhaust gas using the same, and more particularly, a semi-dry electric cleaner for removing harmful gases and fine dust contained in the exhaust gas at the same time and purifying exhaust gas with improved removal efficiency. It is about a method.

Recently, the removal of soot and dust particles generated during combustion and drying, such as incinerators and industrial boiler collecting facilities, and sulfur oxides (SOx), nitrogen oxides (NOx), hydrogen chloride (HCl), and hydrogen fluoride (HF) contained in exhaust gases Much attention has been paid to air pollution prevention facilities to efficiently remove acid gases and heavy metals.

However, the conventional treatment method is a wet type, in which water and an absorbent are sprayed, and thus requires a separate facility for treating wastewater generated after hazardous gas treatment. Due to corrosion problems, it was not easy for small and medium-sized companies or small businesses to equip these facilities.

Therefore, the development of devices with simple structure and easy maintenance and repair is accelerating at home and abroad. According to this trend, the necessity of dry and semi-dry scrubbers to remove air pollutants such as soot particles and harmful gases is rapidly increasing, but they have a disadvantage of lower removal efficiency than wet scrubbers. As a result, high-efficiency air pollution prevention devices are required to cope with increasingly stringent environmental pollution regulations, and research on the high efficiency of existing devices is urgently needed.

The object of the present invention is to consider the above problems, and in particular, it is possible to remove the harmful gases and fine dust contained in the exhaust gas discharged in the incinerator and industrial boiler with high efficiency, the structure is simple and easy to maintain and repair It is to provide a semi-dry electric cleaner.

Another object of the present invention is to provide an exhaust gas purification method that can remove the exhaust gas and fine dust at the same time with high efficiency using the semi-dry electric cleaner.

FIG. 1 is a diagram showing an electrostatic spray system in which a mixed slurry of Ca (OH) ₂ , which is an absorbent, and water is sprayed by a nozzle, and simplifies the removal of SO ₂ gas by finely formed Ca (OH) ₂ droplets.

2 is a schematic view showing a semi-dry electric cleaner according to the present invention.

3 is a view showing a semi-dry electric cleaner in which the exhaust gas passes through a portion of an electrostatic spray system after passing through a corona plasma reactor.

FIG. 4 shows the reactor body portion of a semi-dry electric cleaner in which the exhaust gas flows directly through the corona plasma reactor and then directly into the reactor body side portion without passing through the electrostatic spray system.

5 is a partial detailed view showing a corona plasma reactor of a semi-dry electric cleaner according to the present invention.

6 is a partial detailed view showing an electrostatic spray system of a semi-dry electric cleaner according to the present invention.

7 is a graph showing the presence or absence of high voltage discharge in the semi-dry electric cleaner according to the present invention and the removal efficiency of harmful gases according to the H ₂ O inflow rate, where a is no high voltage discharge and b is a high voltage discharge.

* Explanation of symbols for main parts of the drawings

2: exhaust gas

3: Corona Plasma Reactor

4: electrostatic spray system 5: reactor body

6 Hopper 7 Back Filter

16: compressed air 17: slurry

In order to achieve the above object, the present invention is a corona plasma reactor (corona plasma reactor) for the high-voltage corona discharge to maximize the efficiency of the gas-liquid reaction of harmful substances contained in the injected exhaust gas; When spraying compressed air with a slurry containing water and an alkaline absorbent, an electrostatic spray system for refining the sprayed droplets by applying a high voltage power; And a reactor body in which the discharged exhaust gas and the micronized droplets are injected to undergo a gas-liquid reaction.

At this time, since the corona plasma reactor and the reactor body are connected and the electrostatic spray system is connected to the reactor body, the exhaust gas passing through the corona plasma reactor and the fine droplets passing through the electrostatic spray system are respectively injected into the reactor body. You can do that.

In addition, since the corona plasma reactor and the electrostatic spray system are connected and the electrostatic spray system is connected with the reactor body, exhaust gas passing through the plasma reactor is injected into the electrostatic spray system, and passes through the electrostatic spray system. Exhaust gas and fine droplets may be injected into the reactor body at the same time.

And, for example, a hopper may be installed at the lower end of the reactor body as a device for easily collecting and removing the solidified contaminants obtained as a product of the gas-liquid reaction. In addition, it is preferable to have a bag filter for removing the discharge containing the gas and dust treated in the reactor body.

The pulse interval of the corona discharge discharged in the corona plasma reactor is very short in the range of 100-500ns to induce high voltage corona discharge.

Another object of the present invention is to prepare a slurry containing water and an alkaline absorbent; Mixing the slurry with compressed air and spraying at a predetermined ratio; Miniaturizing the droplets by applying a high voltage to the sprayed droplets; Discharging the exhaust gas to a high voltage corona discharge; And gas-liquid reacting the micronized droplets with the discharged exhaust gas to solidify contaminants and evaporate moisture.

After the gas-liquid reaction, the solidified contaminants are collected and removed through a separate collection facility, and the discharged discharged after treatment is refined using a filter device such as a bag filter and then discharged into the atmosphere.

In addition, a calcium-based absorbent or a sodium-based absorbent may be used as the alkaline absorbent, and includes calcium hydroxide (Ca (OH) ₂ ), calcium carbonate (CaCO ₃ ), sodium carbonate (Na ₂ CO ₃ ), and sodium bicarbonate (NaHCO ₃ ). At least one selected from the group may be preferably used, and considering economical aspects, Ca (OH) ₂ or CaCO ₃ is more preferable.

The semi-dry electric cleaner according to the present invention installs a corona plasma reactor at the front end of the reactor to convert the harmful gas present in the exhaust gas into corona plasma to convert it into an acidic substance having a high reaction rate with the absorbent liquid, and a slurry containing the absorbent is sprayed. The nozzle part is equipped with a high-pressure corona discharger to refine the sprayed droplets, activate the harmful gas and the sprayed droplets, and accelerate the gas-liquid contact reaction between the exhaust gas and the fine droplets to maximize the removal efficiency of contaminants. It is.

Hereinafter, the exhaust gas purification method using a semi-dry electric cleaner according to the present invention and its principles will be described in detail.

In the semi-dry electric cleaner according to the present invention, the reaction rate of the harmful gas is ultimately increased by promoting the chemical reaction by the ions and the electric force by using the corona discharge and the electric field through the corona plasma reactor, and miniaturization of the slurry droplets by the electrostatic spray system and It is intended to have a synergistic effect.

In other words, the corona discharge following the spraying by the spray nozzle refines the size of the sprayed droplet and is changed into a highly reactive droplet by contact with ions generated by the corona discharge.

Finely sprayed droplets are about 110-250 Contact occurs with a range of hot exhaust gases. The alkaline absorbent in the liquid state causes a gas-liquid contact reaction with, for example, SO ₂ in the exhaust gas, and is then instantaneously dried by the heat of the exhaust gas, and the gas-liquid reaction proceeds. The spray droplets vaporize while instantaneously evaporating and the temperature of the exhaust gases drops. The reaction between the sulfur dioxide (SO ₂ ) gas in the exhaust gas and the alkaline absorbent occurs most actively near the spray nozzle, an environment where heat and mass transfer are optimal.

FIG. 1 is a simplified view showing the removal of SO ₂ gas by Ca (OH) ₂ used as an absorbent. The reaction in the spray absorption drying reactor can be classified into absorption zone and drying zone.

In the absorption zone, gas is absorbed into the slurry in the liquid phase flowing into the reactor, and the slurry dries quickly. In the drying zone, as the drying ends, the reactant and the unreacted lime particles remain in the reactor, and diffusion into the lime particles occurs.

The microdroplets containing lime particles sprayed through the spray nozzles are rapidly reduced in speed for a very short time. These lime particles move constantly in the droplets, resulting in a very high evaporation rate. When evaporation occurs, the droplets contract and the distance between each particle decreases until the surfaces of the particles touch each other. At this point about 75% of the water in the droplets is evaporated and the movement of the particles is limited. Once the surfaces of the particles approach each other, it restricts the path of moisture, making it difficult to further evaporate moisture and limiting diffusion into the particles in the secondary drying zone. The shape or size of the final product is determined in this area.

The reaction between the lime slurry and SO ₂ gas in the absorption zone is as follows.

First, SO ₂ (g) is dissolved in the slurry droplet particles, and diffusion of SO ₂ (g) through the gas film boundary layer occurs at the gas-liquid interface of the slurry spray droplets.

The dissolved gas reacts with water (H ₂ O (1)) to form sulfuric acid (H ₂ SO ₄ ).

Dissolved gases reacted with water dissociate in alkaline media and dissolve lime particles.

Dissolved dissolved gas and dissolved lime particles react to form a salt.

Most of these reactants occur at a very high rate, and the diffusion rate of dissolved gas or dissociation of lime particles is the rate step. Diffusion to the droplet surface is promoted by the high relative velocity of the droplets sprayed by the spray nozzles but controlled by evaporation from the droplet surface. The salt thus produced and dried is removed by the aftertreatment dust collector, and the exhaust gas from which noxious gas is removed is discharged into the atmosphere.

Next, the effect of the oxidation of the harmful gas by the corona plasma reactor can be obtained. In general, gaseous components and moisture in the atmosphere undergo the following reactions through the corona reactor and cause active radicals by combining with electrons and causing self dissociation.

The free ions and active radicals generated in the reaction convert nitrogen monoxide (NO) and SO ₂ into sulfuric acid and nitric acid through the following reaction.

Hazardous substances such as sulfur oxides and nitrogen oxides contained in the exhaust gas generate sulfuric acid and nitric acid by active radicals, and the sulfuric acid and nitric acid react with Ca (OH) ₂ in a hot hot air to generate solid dust particles. .

That is, the device sprays an alkaline slurry containing an alkaline absorbent to react with a hot gas containing an acidic gas such as NOx, SOx and HCl under appropriate conditions and then to dry the reaction droplets into dry removable particles. will be.

SO ₂ removal efficiency is mainly influenced by the type and concentration of absorbent. The selection of the appropriate absorbent is made in consideration of the removal efficiency and economics of the pollutant gas. The most common absorbents are Ca (OH) ₂ and CaCO ₂ . Sodium-based absorbents such as Na ₂ CO ₃ and NaHCO ₃ are also used, but their use is limited because they are more expensive than calcium-based water humectants.

The absorbent has a wider effective contact surface with gas and a higher reaction absorption efficiency when the slurry is in a slurry state than in a powder state. This is because the average particle diameter of the absorbent particles in the slurry state is much smaller than in the powder state.

Hazardous gas components, SOx and HCl, are converted into solid materials such as CaCL ₂ and CaSOx by slurry injected into the reactor, and since the moisture of the droplets is all evaporated, the reaction continues on the surface of the particles. Adsorption of heavy metals is also possible.

2 is a schematic view showing a semi-dry electric cleaner according to the present invention. Through this, the operation of each component will be described.

As illustrated, when the exhaust gas 2 including dust and harmful gas discharged during incineration or combustion of fuel is introduced in an incinerator or boiler 1 used in an industry, it first passes through the corona plasma reactor 3. do. The noxious gas converted into acid by the high voltage dustproof 9-1 flows into the reactor main body 5.

Meanwhile, water, an alkaline absorbent, and other chemicals are mixed in the mixing tank 11 to prepare a slurry 17, and the slurry 17 is supplied to the electrostatic spray system 4 using the metering pump 10.

In the air compressor 12, compressed air is supplied through the air dryer 13 to allow the slurry 17 and the compressed air 16 to be sprayed through the spray nozzle at an appropriate ratio. It is then supplied to the electrostatic spray system (4). That is, a high voltage is supplied to the discharge electrode to make the droplets fine and spray them into the reactor body 5. The sprayed droplets at this time are 110-250 It comes in contact with the hot exhaust gas of. Then, the liquid absorbent causes a gas-liquid contact reaction with SO ₂ , NOx, HCl and the like in the exhaust gas, and then the gas-liquid reaction proceeds in the process of being instantaneously dried by the heat of the exhaust gas. At this time, the sprayed droplets vaporize while instantaneously evaporating, and the temperature of the exhaust gas drops. The gas-liquid reaction occurs mostly near the spray nozzles, where heat and mass transfer are optimal.

After the reaction, the solid particles obtained are accumulated in the hopper 6 due to its own weight, and the neutralized processing gas and light dust are introduced into the bag filter 7. In the bag filter 7, fine dust is separated. After that, only the gas 18 purified by the fan 8 is discharged to the atmosphere.

The size of the reactor body, the size of the spray air nozzle, the size of the corona plasma reactor, and the mixing ratio of the slurry components are controlled according to the type of the harmful gas and the amount of dust, which are determined through experimental calculations.

In addition, the incoming exhaust gas may flow directly into the reactor body after passing through the corona plasma reactor, but may also flow into the reactor body through an electrostatic spray system, which is illustrated in FIGS. 3 and 4. It is shown in the figure.

That is, FIG. 3 shows the reactor body portion of the semi-dry scrubber in which the exhaust gas passes through the corona plasma reactor and then through the electrostatic spray system part, and FIG. 4 does not pass the electrostatic spray system after passing through the corona plasma reactor. The reactor body portion of the semi-dry scrubber is shown in detail in such a way that it flows directly into the reactor body portion side of the scrubber.

FIG. 5 shows a partial detail of a corona plasma reactor, and FIG. 6 shows a partial detail of an electrostatic spray system. Reference numerals 14-1 and 14-2 denote insulating films, and 15 denote discharge electrodes.

FIG. 7 shows the harmful gas removal efficiency according to the presence or absence of high voltage discharge when the semi-dry electric cleaner according to the present invention is used. Graph a shows a case where there is no high voltage discharge, and graph b shows a case where there is a high voltage discharge. In either case, the higher the amount of H ₂ O implanted, the higher the SO ₂ removal efficiency, but in the presence of a high voltage discharge, it can be seen that an excellent SO ₂ removal efficiency appears.

As described above, according to the present invention, by using a semi-dry electric cleaner, it is possible to easily remove harmful gases and fine dust contained in the exhaust gas through the fine droplets of the absorbent and the discharge of the gas, and the removal efficiency thereof is also high. Can be. In addition, since the scrubber of the present invention is semi-dry, there is no need for a separate after-treatment facility as in the wet type, and the apparatus is simple, so that the maintenance and repair thereof are easy.

As mentioned above, although this invention was demonstrated in detail by attached drawing, this invention is not limited by this, A deformation | transformation and improvement are possible within the normal range of a person skilled in the art.

Claims (13)

A corona plasma reactor for corona discharge to maximize the efficiency of gas-liquid reaction of harmful substances contained in the injected exhaust gas; An electrostatic spray system for refining droplets sprayed by applying electric power when spraying slurry and compressed air containing water and an alkaline absorbent; And a reactor body in which the discharged exhaust gas and the micronized droplets are injected to undergo a gas-liquid reaction. The method of claim 1, wherein the corona plasma reactor and the reactor body is connected, the electrostatic spray system is also connected to the reactor body, the exhaust gas passing through the corona plasma reactor and fine droplets passing through the electrostatic spray system. Semi-dry electric cleaner, characterized in that each is injected into the reactor body. The electrostatic spray system of claim 1, wherein the corona plasma reactor and the electrostatic spray system are connected, and the electrostatic spray system is connected with the reactor body so that exhaust gas passing through the plasma reactor is injected into the electrostatic spray system, and the electrostatic spray is applied. Semi-dry electric cleaner, characterized in that the exhaust gas and the fine droplets passed through the system to be injected into the reactor body at the same time. The semi-dry electric cleaner according to claim 1, wherein a hopper for collecting crystals obtained as a product of a gas-liquid reaction is provided at a lower end of the reactor body. 5. The semi-dry electric cleaner according to claim 4, wherein a bag filter is provided for refining the discharge including gas and light dust treated in the reactor body. The semi-dry electric cleaner according to claim 1, wherein the electrostatic spray system comprises a power source and a discharge electrode. The semi-dry electric cleaner according to claim 1, wherein the pulse interval of the corona discharge discharged in the corona plasma reactor is in the range of 100-500ns. Preparing a slurry comprising water and an alkaline absorbent; Mixing the slurry with compressed air and spraying at a predetermined ratio; Applying power to the sprayed droplet to refine the droplet; Corona discharge of the exhaust gas; And gas-liquid reacting the micronized droplets with the discharged exhaust gas to solidify contaminants and evaporate moisture. The method of claim 8, wherein the exhaust gas comprises at least one selected from the group consisting of sulfur oxides, nitrogen oxides, hydrogen chloride and hydrogen fluoride. The method of claim 9, wherein the temperature of the discharged exhaust gas is 110-250 Exhaust gas purification method characterized in that the range. The exhaust gas purification method according to claim 8, wherein the exhaust gas discharged after the gas-liquid reaction is refined using a bag filter. The exhaust gas purification method according to claim 8, wherein the alkaline absorbent is a calcium absorbent or a sodium absorbent. The method of claim 12, wherein the alkaline absorbent is at least one selected from the group consisting of calcium hydroxide (Ca (OH) ₂ ), calcium carbonate (CaCO ₃ ), sodium carbonate (Na ₂ CO ₃ ) and sodium bicarbonate (NaHCO ₃ ). Exhaust gas purification method.