KR100681161B1 - Apparatus for removing nitrogen oxides using peroxy radical and method thereof - Google Patents

Abstract

A system and a method for removing nitrogen oxides using peroxy radicals are provided to effectively remove nitrogen oxides contained in the exhaust gas and obtain excellent economic efficiency by injecting gas molecules of pure oxygen and fine and uniform liquid particles of hydrogen peroxide as a reaction agent onto a surface of a photocatalyst in exhaust gas, thereby inducing the generation of a large amount of peroxy radicals required to remove nitrogen oxides. A system for removing nitrogen oxides comprises: a particle removal part(10) for removing nitrogen oxides with large particles that interrupts the reaction with peroxy radicals; a hydrogen peroxide injection part(30) for supplying an aqueous hydrogen peroxide solution; an oxygen supply part(20) connected to the hydrogen peroxide injection part to supply oxygen into the hydrogen peroxide injection part; a peroxy radical generating part(40) for reacting oxygen supplied from the oxygen supply part with hydrogen peroxide supplied from the hydrogen peroxide injection part under the irradiation of ultraviolet rays to generate a large amount of peroxy radicals; a reactor(50) for reacting nitrogen oxides discharged from the particle removal part with peroxy radicals supplied through the peroxy radical generating part to produce a water-soluble material; a concentration tank(60) for concentrating water-soluble nitrogen oxides discharged from the reactor in the water; and a water treating equipment part(70) for treating the concentrated nitrogen oxides.

Description

Apparatus and method for removing nitrogen oxide using peroxy radicals {APPARATUS FOR REMOVING NITROGEN OXIDES USING PEROXY RADICAL AND METHOD THEREOF}

BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the drawings cited in the detailed description of the invention, a brief description of each drawing is provided.

1 is a schematic view showing the configuration of a nitrogen oxide treatment process system according to the present invention.

2 is a view in which the existing oxygen supply unit and the hydrogen peroxide injection unit inner tube is connected.

3 is a view showing the connection of the inner tube of the oxygen supply unit and the hydrogen peroxide injection unit according to the present invention.

4 is a view for explaining the shape of the end of the hydrogen peroxide injection unit of FIG.

5 is an exemplary view of a peroxy radical generating unit of the nitrogen oxide treatment apparatus according to the present invention.

6 is a structural diagram of the concentration tank.

7 is a graph showing the relationship between the effective Henry's constant (H *) of peroxy radicals according to pH.

8 is a view showing the shape of the reaction vessel made of a quartz material installed in the water treatment apparatus.

** Description of the main symbols in the drawings **

10: particle removal device 20: oxygen supply unit

30: hydrogen peroxide injection unit 40: peroxy radical generating unit

50: gas phase reactor 60: concentration tank

70: water treatment unit

The present invention relates to an apparatus and method for effectively removing nitrogen oxides in exhaust gas by providing hydrogen peroxide in the form of fine and uniform liquid particles as a reactant of nitrogen oxides to the peroxy radical generating unit to induce a large amount of peroxy radicals. .

In general, nitrogen oxides are produced by the combustion of fuels such as petroleum and coal, especially those produced by combustion, which are nitrogen monoxide and when released into the atmosphere are nitrogen dioxide that is harmful to the human body. It is well known as a representative air pollutant and pollutant that reacts to generate photochemical oxides such as ozone, secondary pollutants, and acid rain.

Conventional nitrogen oxides appear as a physicochemically coupled state of nitrogen atom (N) and oxygen atom (O), and NO, NO ₂ , N ₂ O, N ₂ O ₃ , N ₂ O ₄ , N ₂ O ₅ , NO _It exists in the form of _three . In general, nitrogen oxides (NO) and nitrogen dioxide (NO ₂ ), which are major components of nitrogen oxides in the atmosphere that cause pollution due to environmental effects, are collectively referred to as NOx, among which NO is 90 ~ It is known to account for 95%.

Conventionally, various techniques have been studied for removing nitrogen oxides generated when using fossil fuels in fixed locations such as thermal power plants and industrial boilers. Conventional nitrogen oxide reduction methods known to date include selective catalytic reduction (SCR) or selective non-catalytic reduction (SNCR): SNCR '), a wet redox method and the like are known. However, other technologies except SCR technology are not widely used due to economic and technical limitations.

SCR technology is a method of removing nitrogen oxides contained in exhaust gas by using a catalyst, and there are commercially available vanadia-titania catalysts that have been studied to remove nitrogen oxides.

However, the method requires high temperature processing conditions around 300 ° C. for efficient removal of nitrogen oxides, which is not only inefficient in terms of energy, but still has to be solved in terms of low specific surface area and weak mechanical strength of the catalyst. In addition, there is a significant disadvantage that the catalyst cost accounts for the overall cost of the SCR process.

On the other hand, the SNCR technology does not require a catalyst, but like the SCR technology, injection of a reducing agent such as urea or ammonia is required as well as a considerable size of a reaction tank and a reducing agent distribution device, and a time for sufficient reaction is required. It is inevitable because of unavoidable requirements.

As described above, the conventional methods for treating nitrogen oxide have been pointed out that excessive energy use, land area, and operation cost are required due to heating.

The technical problem to be achieved by the present invention is to inject a large amount of peroxy radicals required to remove nitrogen oxides (NOx) by injecting pure oxygen gas molecules and hydrogen peroxide in the form of fine and uniform liquid particles into the photocatalyst surface as a reactant to exhaust gas. The purpose of the present invention is to provide a nitrogen oxide treatment apparatus and method which is effective in treating nitrogen oxides in flue gas and at the same time excellent in economic efficiency.

The present invention has been invented to solve the above problems, the nitrogen oxide treatment apparatus according to an embodiment of the present invention is a particle removal unit, the hydrogen peroxide aqueous solution to remove the large nitrogen oxide particles that hinder the reaction with the peroxy radicals The hydrogen peroxide injection unit for supplying the hydrogen peroxide injection unit is connected to the hydrogen peroxide injection unit for supplying oxygen, and the oxygen supplied from the oxygen supply unit under irradiation of ultraviolet rays with the hydrogen peroxide supplied from the hydrogen peroxide injection unit for reacting a large amount of peroxy radicals. Peroxy radical generating unit for generating a reaction tank to make a water-soluble substance through the reaction with the peroxy radicals supplied through the peroxy radical generating unit, the nitrogen oxide discharged from the particle removal unit, the water-soluble nitrogen oxide discharged from the reaction tank Concentration tank to concentrate in water and the concentrated nitrogen oxidation The water treatment apparatus comprising a treatment for a.

The oxygen supply unit has a venturi tube structure, and the hydrogen peroxide injection unit has one end inserted into the center of the oxygen supply unit so that the movement direction of the injected hydrogen peroxide solution is not the same as the movement direction of oxygen supplied to the oxygen supply unit. do.

The hydrogen peroxide injection portion is a tube shape bent in the shape of the end "", the end is blocked and the side portion is made of a porous plate. The concentrating tank includes a plurality of stages separating the concentrated nitrogen oxides, and the outlet is configured to condense the water-soluble nitrogen oxides several times and to discharge organic gases that are not concentrated.

The water treatment device portion is disposed inside the concentration tank or outside the concentration tank.

Nitrogen oxide treatment method according to another embodiment of the present invention is a step of reacting oxygen and aqueous hydrogen peroxide solution under irradiation of ultraviolet rays to generate a large amount of peroxy radicals, oxidizing nitrogen oxides using the peroxy radicals and the It is disclosed to have a step of concentrating the water-soluble material generated in the step, and discharge the concentrated nitrogen oxide aqueous solution.

In the nitrogen oxide treatment method according to another embodiment of the present invention, before the step of generating the peroxy radicals, when the oxygen and the hydrogen peroxide aqueous solution is injected, the initial movement direction of the hydrogen peroxide aqueous solution is the same as the movement direction of the oxygen It is disclosed that the step of pulverizing the aqueous hydrogen peroxide solution into uniform particles so as not to become the direction.

In the nitrogen oxide treatment apparatus according to another embodiment of the present invention, the generating of the peroxy radicals may further include removing nitrogen oxides having large particles into nitrogen oxides having small particles.

DETAILED DESCRIPTION In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the present invention and the contents described in the drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements.

1 is a schematic view showing the configuration of a nitrogen oxide treatment process system according to the present invention.

As shown in Figure 1, in order to process the nitrogen oxide generated in the combustion or heating apparatus, particle removal unit 10, oxygen supply unit 20, hydrogen peroxide injection unit 30, peroxy radical generating unit 40, It consists of the reaction tank 50, the concentration tank 60, and the water treatment apparatus part 70. The components are preferably organically connected to react with each other in the flow of liquid or gas.

The particle removal unit 10 is connected to a generation source that discharges nitrogen oxides. In general, nitrogen oxides produced by combustion are produced by various particulate matters. In this case, large-particles generated by nitrogen oxides can interfere with direct reactions when reacting with peroxy radicals, thereby reducing nitrogen oxide removal efficiency. It is preferred to remove as much as possible before the direct reaction between the peroxyradical and peroxyradical.

To this end, the particle removal unit 10 is generally used, and various particle removal devices such as a bag filter, an electrostatic precipitator, and a gravity type device are generally used.

On the other hand, oxygen and hydrogen peroxide injected through the oxygen supply unit 20 and the hydrogen peroxide injection unit 30 react with oxygen under ultraviolet irradiation with titanium dioxide as a catalyst in the peroxy radical generating unit 40 to react with nitrogen oxides. To generate radicals. The reaction mechanism for producing the peroxy radicals is as follows.

The titanium dioxide and ultraviolet light reaction in Equation 1 below the hole (h ⁺⁾ and electrons (e ^-) of the anion of the ^cation coming from outside as shown in the following formula 2, generate, and E (e) of the anion It combines with oxygen molecules to produce peroxy radicals. The peroxyradical (HO ₂ ˚ ) forms an acid-base equilibrium (K _{HO 2} = 4.80) in an aqueous solution as shown in Equation 3 below.

[Equation 1] TiO ₂ + UV → h ^{+ +} e ^-

[Equation _{^{2] e - + O 2 →}} O 2 - ˚

[Formula 3] O ₂ ^- ˚ + H ⁺ ↔ HO ₂ ˚

On the other hand, the nitrogen oxide passed through the particle removal unit 10 and the peroxy radicals generated in the peroxy radical generating unit 40 is guided to the reaction tank 50 for inducing a gas phase reaction therebetween, through the reaction tank 50 Nitrogen oxides are rapidly oxidized by peroxyradicals to form products that are finally soluble in water.

Next, the concentration tank 60 concentrates and stores the final product generated after the reaction between the nitrogen oxide and the peroxy radical in water, and then, the water treatment apparatus unit 70 for treating the wastewater concentrated in or outside the concentration tank 60. Through this process, the cycle is cleaned periodically or continuously.

The water treatment device unit 70 is composed of an ultraviolet lamp, a quartz material reactor, a transfer pump, a fan for cooling the ultraviolet lamp, and the like. In particular, the quartz material reactor has a shape such as a radiator in the form of a coil of quartz material. . Nitrogen oxide treated through the water treatment unit 70 is finally treated, and then discharged to the atmosphere through the outlet.

2 is a configuration diagram in which the inner tube of the conventional oxygen supply unit 20 and the hydrogen peroxide injection unit 31 is connected.

As shown in Figure 2, the tube is configured using a venturi tube using the Venturi effect. The venturi tube has a larger cross-sectional area at the inlet side of the gas or liquid than the cross-sectional area of the gas inlet to be treated to finely crush particles of the aqueous solution to be treated by increasing the surface area of the microbubble by using the pressure difference to facilitate dissolution. It is. This technique is described in patent 10-0403652.

However, the technique has a limitation in producing uniform particles compared to making the particle size fine, and this non-uniform particle causes the photocatalytic reaction, which will be described later, to become unsatisfactory, or an unreacted mass of particles remains in the tube. It may also act as a factor that inhibits the photocatalytic reaction that produces peroxy radicals.

Therefore, it is important to smooth the photocatalytic reaction by producing uniform particles as well as decomposing them into fine particles.

3 is a view showing the connection of the inner tube of the oxygen supply unit 20 and the hydrogen peroxide injection unit 30 according to an embodiment of the present invention.

The above-described peroxy radical is produced by irradiating ultraviolet rays in the process of reacting oxygen with nitrogen oxide using titanium dioxide as a catalyst. At this time, the production concentration of peroxy radicals depends on the reaction between fine and uniform hydrogen peroxide particles and oxygen gas.

In the following Equation 4, radicals ( ° OH) are formed by reacting with hydrogen peroxide (H ₂ O ₂ ) into which electrons (e ⁻ ) generated by the reaction of titanium dioxide and ultraviolet rays are injected. Equation 5 below shows a reaction mechanism in which the radical hydroxide reacts with unreacted hydrogen peroxide to additionally generate peroxy radicals.

[Formula _{4] H 2 O 2 + e} - → ˚ OH + OH -

[Formula 5] H ₂ O ₂ + ˚ OH → HO ₂ ˚ + H ₂ O

Looking at the inner tube of the oxygen supply unit 20 and the hydrogen peroxide injection unit 30 according to an embodiment of the present invention, the liquid hydrogen peroxide aqueous solution injected and the flow of high-purity oxygen gas is configured not to be the same flow.

That is, conventionally (see FIG. 2), the hydrogen peroxide injection unit 31 is connected only to the outer surface of the oxygen supply unit 20, so that the liquid hydrogen peroxide aqueous solution is immediately mixed with the flow of oxygen gas as soon as it is injected into the oxygen supply unit 20 and is uniform. Particle generation was difficult.

However, in the present invention, it is possible to generate uniform particles by preventing the liquid hydrogen peroxide aqueous solution from initially joining the oxygen gas in the same moving direction as much as possible.

To this end, the hydrogen peroxide injection unit 30 is inserted into the center of the oxygen supply unit 20 having one end has a venturi tube structure. Therefore, the movement direction of the injected hydrogen peroxide aqueous solution may not be the same flow as the movement direction of oxygen supplied to the oxygen supply unit 20.

In particular, the hydrogen peroxide injection portion 30 is the end of the tube shape bent in the shape of "" ", the end is blocked and the side portion is made of a porous plate. An end description is made using FIG. 4.

4 is a view for explaining the shape of the end of the hydrogen peroxide injection unit of FIG.

As shown in FIG. 4, the end of the hydrogen peroxide injection unit 30 may include a porous plate 33, unlike conventional hydrogen peroxide aqueous solution injected directly from the hydrogen peroxide injection unit 30 into the oxygen supply unit 20, The porous plate 33 is discharged to the oxygen supply unit 20 while converting the injected hydrogen peroxide aqueous solution into fine and uniform liquid particles.

Therefore, the hydrogen peroxide aqueous solution of the uniform liquid particles is uniformly distributed in the oxygen supply unit 20, and smoothly and quickly react with the high purity oxygen gas injected into the oxygen supply unit 20.

In particular, the end of the hydrogen peroxide injection unit 30 has a porous plate 33 on the side instead of the end is blocked so that the flow of hydrogen peroxide solution discharged through the porous plate 33 is not the same as the oxygen gas flow. The porous plate 33 may be configured in a net shape.

Specifically, the operation of Figure 4, when the hydrogen peroxide aqueous solution is injected through the hydrogen peroxide injection portion 30, the hydrogen peroxide generated in a fine and uniform particle size into the oxygen injection portion 20 through the porous plate 33 at the end Particles are ejected and these hydrogen peroxide particles and oxygen gas react smoothly to generate peroxy radicals, which are several tens of times more excellent than before.

5 is a diagram showing an embodiment of the peroxy radical generating unit 40 of the nitrogen oxide processing apparatus according to the present invention. As shown, the peroxy radical generating unit 40 is a reactor for generating peroxy radicals, the inside of the reactor is composed of a lamp for irradiating ultraviolet rays and a plate coated with titanium dioxide.

An ultraviolet lamp is embedded in the inside of the plate coated with titanium dioxide, and thus all or part of the plate shape is irradiated with ultraviolet light in all directions to increase the efficiency of peroxyradical reaction.

The peroxy radical generating unit 40 is connected to the oxygen supply unit 20 to allow oxygen to flow to the surface of the titanium dioxide-coated flat plate, and at the same time to induce a fine injection of liquid hydrogen peroxide to the periphery of the oxygen supply unit 20 The hydrogen peroxide injection unit 30 is provided.

In addition, it is preferable that titanium dioxide is coated on the surface of the peroxy radical generating unit 40, that is, one side of the flat plate. It may be coated only in part. The titanium dioxide is preferably coated with nano-sized particles.

Titanium dioxide is very firmly attached and can be reused for a long time in aqueous phase as well as in the gas phase. Peroxy radicals are generated through the photochemical reactions (Equation 1 to Equation 3) by the titanium dioxide molecules introduced through the inlet.

In addition, the plate is not limited, but a material capable of transmitting ultraviolet rays is preferable, and a quartz material is preferable. The spacing between the plates is preferably 2 mm or less, but is not limited thereto. As the spacing between the plates is smaller, the size of the peroxy radical generating unit 40 may be further reduced, and a larger number of plates may be accumulated and arranged. have.

In addition, a peroxy radical generating device in which titanium dioxide is coated inside the quartz material in the form of a coil so that the irradiation area of ultraviolet rays is large instead of the flat plate may be preferable.

6 shows the structure of the thickening tank 60 according to the present invention. As shown in FIG. 6, the concentration tank 60 includes a bubble generator 61, and the bubble generator 61 generates bubbles when air is dissolved in water, and reacts the reaction between the peroxy radicals and the nitrogen oxide to the bubbles. The product generated through the adhesion to the bubble is to be removed.

The concentrating tank 60 includes a plurality of stages 62 for separating the concentrated nitrogen oxides to concentrate the water-soluble nitrogen oxides several times, and includes an outlet 63 for discharging the organic gas that is not concentrated.

In addition, the water treatment device unit 70 may be disposed inside the concentration tank 60 or may be disposed outside the concentration tank 60, and when disposed therein, the stages 62 and 62 arranged horizontally. The water to be treated is purified by the water treatment device unit 70 properly disposed therebetween.

Figure 7 shows the effective Henry constant (H ^* ), H ^* = H (1 + K / [H ⁺ ]) of the peroxy radicals according to pH: H = Henry constant value, 2.0 X 10 ^-3 M / ATM; K = acid-base equilibrium constant, 1.58 X 10 ^-5 ; H ⁺ = hydrogen ion concentration, M].

When the pH is 1 to 4, it shows a constant effective Henry's constant value, whereas when the pH is increased to 4 or more, the effective Henry's constant of peroxyradical increases with increasing pH, so that the solubility of peroxyradical in water increases. Shows. Therefore, the reaction in water with nitrogen oxides can occur very easily with increasing peroxyradical solubility.

Looking at the principle in more detail, the nitrogen oxide discharged through the particle removal unit 10 is composed of almost insoluble components. To explain this in detail, the following description is based on the Henry's constant value. NO and NO ₂ in nitrogen oxides are components that are difficult to dissolve in water with Henry constant values of about 1.9 X 10 ^-3 M / atm and about 0.7 to 1.2 X 10 ^-2 M / atm, respectively.

For example, the Henry's constant for oxygen, a typical insoluble gas, is 1.3 × 10 ⁻³ M / atm, and the maximum saturation concentration at 20 ° C. is known to be about 9 mg / L.

The reaction mechanism for producing a soluble final product in the reactor 50 is as follows. Peroxy radicals react with nitrogen monoxide to form peroxynitrous acid (ONOOH) as shown in Equations 6 and 7 below. In addition, as shown in Equations 8 and 9, peroxy radicals react with nitrogen dioxide to form perperoxynitrous acid (OONOOH).

Nitrogen oxides are dissolved in water through the process from Equation 6 to Equation 9 below. For example, the Henry's constants of peroxynitrous acid (ONOOH) and peroxynitrous acid are 0.089 to 2.4 X 10 ⁶ M / atm and 0.04 to 1.0 X 10 ⁵ M / atm, respectively. Known.

Therefore, the product formed through the direct reaction between peroxy radicals and nitrogen oxides is very soluble in water so that almost all the end product nitrogen oxides are not discharged to the atmosphere and can be separated and treated in water.

[Equation 6] HO ₂ ° + NO → HOONO

[Equation _{^{7] O 2 - ˚ + NO}} → ONOO -

[Equation 8] HO ₂ ° + NO ₂ → HOONOO

[Equation 9] O ₂ ^- DEG + NO ₂ → OONOO ^-

Preferably, the peroxy radical generating unit 40 is connected to a rapid reaction with the gaseous nitrogen oxide discharged through the particle removal unit 10 immediately so that the peroxy radicals and the nitrogen oxide directly to the concentration tank 60. It is best to connect them so that they can be transported and react quickly.

The resulting peroxyradicals are known to have an average life-time of about 1 minute in the gas phase, but may be present in the water phase for longer minutes than in the gas phase. In this case, the henry constant value of peroxy radicals is about 1.2 to 9.0 X 10 ³ M / atm, and 100% of the peroxy radicals are dissolved when injected into water.

Figure 8 shows the shape of the reaction vessel made of a quartz material installed in the water treatment device 70. This maximizes the efficiency of the UV lamp.

As described above, the present invention as described above greatly improves the conversion rate of nitrogen oxides when treating nitrogen oxides contained in the exhaust gas by the peroxy radical generating process, and ultimately reduces the amount of energy required for nitrogen oxide removal, as well as nitrogen oxides. There is an effect that can recycle resources such as nitrate produced by the treatment.

Claims (8)

Particle removal unit for removing the large nitrogen oxide particles that interfere with the reaction with the peroxy radicals; Hydrogen peroxide injection unit for supplying an aqueous hydrogen peroxide solution; An oxygen supply unit connected to the hydrogen peroxide injection unit and supplying oxygen; A peroxy radical generating unit for generating a large amount of peroxy radicals by reacting oxygen supplied from the oxygen supply unit with hydrogen peroxide supplied from the hydrogen peroxide injection unit under irradiation of ultraviolet rays; A reaction tank for making the nitrogen oxide discharged from the particle removing unit into a water-soluble substance through reaction with the peroxy radicals supplied through the peroxy radical generating unit; A concentration tank for concentrating the water-soluble nitrogen oxide discharged from the reaction tank in water; And Nitrogen oxide treatment apparatus consisting of a water treatment device unit for treating the concentrated nitrogen oxides. The method of claim 1, The oxygen supply unit has a venturi tube structure, The hydrogen peroxide injection unit, One end is inserted into the center of the oxygen supply, the nitrogen oxide processing apparatus, characterized in that the flow direction of the hydrogen peroxide solution injected is not the same flow as the movement direction of oxygen supplied to the oxygen supply. The method of claim 2, wherein the hydrogen peroxide injection unit, A nitrogen oxide removal device, characterized in that the end is a "b" shaped bent tube shape, the end is blocked and the side portion is made of a porous plate. The method of claim 1, wherein the concentration tank, And a plurality of stages for separating the concentrated nitrogen oxides, wherein the water-soluble nitrogen oxides are concentrated several times, and an outlet for discharging unconcentrated organic gas is provided. The water treatment apparatus of claim 4, wherein Nitrogen oxide removal device, characterized in that disposed in the interior of the concentration tank or outside the concentration tank. Reacting oxygen with aqueous hydrogen peroxide solution under ultraviolet irradiation to generate a large amount of peroxyradical; Oxidizing nitrogen oxides using the peroxy radicals; And Concentrating the water-soluble material generated in the oxidation step, and the nitrogen oxide removal method comprising the step of discharging the concentrated nitrogen oxide aqueous solution. The method of claim 6, prior to producing the peroxyradical, When the oxygen and the hydrogen peroxide aqueous solution is injected, nitrogen oxides, characterized in that the first movement direction of the hydrogen peroxide aqueous solution is pulverized into uniform particles so as not to the same direction as the movement direction of the oxygen How to remove. The method of claim 6, wherein generating the peroxy radicals, The method for removing nitrogen oxides further comprising the step of removing nitrogen oxides having large particles to form nitrogen oxides having small particles.

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