KR102586253B1 - spray device comprising porous structure for providing precise controllable concentration of diluted urea-water solution inserted inside - Google Patents

Abstract

The present invention provides a porous structure-inserted diluted urea spray device capable of precisely controlling concentration; An SNCR reactor in which a diluted urea water spray device inserted into the porous structure capable of precisely controlling the concentration is installed inside, and a urea decomposition reaction of the urea water sprayed from the spray device and a NOx reduction reaction occur simultaneously by selective non-catalytic reduction (SNCR); A vaporizer that installs a diluted urea water spraying device inserted into the porous structure capable of precisely controlling the concentration therein, and causes a urea decomposition reaction of the urea water sprayed from the spraying device to form ammonia; A nitrogen oxide (NOx) reduction system including a diluted urea water spray device inserted into the porous structure capable of precisely controlling the concentration; In the nitrogen oxide reduction system, ammonia is generated by performing a urea decomposition reaction of urea water injected from a spray device, and a NOx reduction reaction of NOx-containing combustion gas is performed by ammonia generated by the urea decomposition reaction of urea water. This relates to a method of treating NOx-containing combustion gas.

Description

{spray device comprising porous structure for providing precise controllable concentration of diluted urea-water solution inserted inside}

The present invention provides a porous structure-inserted diluted urea spray device capable of precisely controlling concentration; An SNCR reactor in which a diluted urea water spray device inserted into the porous structure capable of precisely controlling the concentration is installed inside, and a urea decomposition reaction of the urea water sprayed from the spray device and a NOx reduction reaction occur simultaneously by selective non-catalytic reduction (SNCR); A vaporizer that installs a diluted urea water spraying device inserted into the porous structure capable of precisely controlling the concentration therein, and causes a urea decomposition reaction of the urea water sprayed from the spraying device to form ammonia; A nitrogen oxide (NOx) reduction system including a diluted urea water spray device inserted into the porous structure capable of precisely controlling the concentration; In the nitrogen oxide reduction system, ammonia is generated by performing a urea decomposition reaction of urea water injected from a spray device, and a NOx reduction reaction of NOx-containing combustion gas is performed by ammonia generated by the urea decomposition reaction of urea water. This relates to a method of treating NOx-containing combustion gas.

High-temperature incinerators, heating furnaces, boilers, and internal combustion engines are devices that supply fuel and oxidizer to the inside, ignite the fuel, burn the fuel, and maintain a high temperature with the combustion heat of the fuel itself. When air is used as an oxidizing agent in a combustion reaction, nitrogen in the air undergoes a combustion reaction to produce nitrogen oxides such as NO, NO ₂ , NO ₃ , N ₂ O ₃ , N ₂ O, N ₂ O ₄ , N ₂ O ₅ , etc. (NOx) is generated.

In particular, nitrogen oxides (NOx) generated during the combustion process of fossil fuel-using coal-fired power plants, industrial boilers, and internal combustion engines (diesel engines) are discharged into the air as a primary pollutant and converted into ultrafine dust, causing acid rain, photochemical smog, etc. It causes environmental problems.

Technologies for removing nitrogen oxides are divided into combustion technology improvement methods such as low NOx burners, multi-stage combustion, and exhaust gas recirculation, and post-combustion exhaust gas treatment technologies. In the case of improved combustion technology, the reduction efficiency is not high, so exhaust gas treatment technologies such as selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) are mainly used to comply with emission standards.

The SCR process can achieve a removal efficiency of over 90% in the temperature range of 300 to 450°C when using a Pt-V ₂ O ₅ /TiO ₂ catalyst. However, the reduction intensity of nitrogen oxides is relatively high due to the high cost of the catalyst and the problem of deactivation depending on reaction conditions.

The SNCR process has lower initial installation costs than the SCR process and does not require a separate installation site, so it has excellent applicability, but has the disadvantage of not being highly efficient. It shows a denitrification efficiency of 40-70% in the reaction temperature range of 850 ~ 1100℃. In the SNCR process, NOx production increases due to the oxidation reaction of the introduced reducing agent (urea solution, ammonia solution) in the temperature range above the narrow reaction temperature range, and in the low temperature range, the reducing agent does not react efficiently and ammonia leakage occurs.

Because the selectivity for NO is superior to other types of reducing agents (hydrocarbons, carbon monoxide), the reducing agent mainly used in the currently commercialized catalytic reduction process (SCR) is ammonia (NH ₃ ). However, NH ₃ has the disadvantage of being very toxic and corroding various facilities, as well as requiring a lot of costs to store and transport. In addition, a large amount of NH ₃ is required to cover the SCR equipment of current power generation and incineration facilities.

Urea ((NH ₂ ) ₂ CO) is easily decomposed into ammonia as follows.

Urea → Biuret + Ammonia (1)

Urea → Cyanuric acid + Ammonia (2)

Biuret → Cyanuric acid + Ammonia (3)

Biuret → Cyanuric acid + Amminia (4)

The DeNOx reaction of urea can be expressed as Formula 1 below.

In this way, urea, which exists as a solid at room temperature and decomposes at a relatively low temperature to produce ammonia, has little toxicity and is therefore easy to store. When ammonia is replaced with urea in the DeNOx reaction, unreacted ammonia is removed. Secondary pollution can be reduced. Additionally, urea is a colorless, odorless crystal that is highly soluble in water. Therefore, urea water can be used as a reducing agent instead of highly toxic NH ₃ .

Lugt et al. used an air-blast-nozzle to treat the exhaust gas of a lean burn engine by injecting urea (NSR=2) from the top of the reactor and mixing it well with the exhaust gas through a static mixer to form V ₂ O ₅ /TiO. A NOx conversion rate of over 90% was obtained by reacting at 325°C on a ₂ /W ₂ O ₃ monolith catalyst. Kobel et al. reported the NOx reduction reaction through a urea solution (40%) on TiO ₃ -W ₂ O ₃ -V ₂ O ₅ and the molar ratio between reducing agent and NOx after the reaction, α (molar ratio of N _{reducing agent} :N _NOx , α= As a result of examining the NOx conversion rate and ammonia slip according to the stoichiometric ratio of urea and NO (1 corresponds to 0.5 stoichiometric ratio of urea and NO), the conversion rate was over 80% in a wide temperature range (230~455℃), and the ammonia slip was higher than that of the normal ammonia SCR process. Low and secondary NOx, N ₂ O, HNCO, and HCN were not detected.

Meanwhile, Selective _Noncatalytic NO It's technology. The SNCR process has a relatively _low denitrification efficiency compared to Selective Catalytic NO The installation cost is lower than that of other _NO Therefore, this process is widely used around the world not only for denitrification of combustion gas generated from power generation boilers and industrial boilers, but also for denitrification of incineration gas.

Ammonia and urea are representative reducing agents used in the SNCR process. When urea is injected as a reducing agent into combustion gas in the SNCR process, the injected urea is decomposed into NH ₃ (Ammonia) and HNCO (Isocyanic Acid) as shown in Figure 1, and NH ₃ and HNCO are denitrified along separate reaction paths. react. The reduction reaction between urea and NO consists of about 200 to 300 basic radical reactions, and can be expressed as a single general reaction equation such as Chemical Formula 1 above.

Table 1 compares the physical properties of ammonia and urea used as a reducing agent.

division Ammonia (NH ₃ ) Element( NH ₂ CONH ₂ ) Molecular Weight( M.W. .) 17 60 color colorless colorless importance 0.817 1.335 Melting point (℃) -77.7 -33.4 Boiling point (℃ 132.7 180 Form (standard state) Gas (anhydrous ammonia) solid Storage type (standard state) 200 Psig, below 35℃ solid Standard condition means measurement at 1 atm atmospheric pressure and room temperature (20°C).

Urea is colorless, odorless, and tasteless at room temperature, and slowly hydrolyzes into ammonium carbonate ((NH ₄ ) ₂ CO ₃ ) in aqueous solution, and sublimates above the melting point to convert into ammonia (NH ₃ ) and cyanuric acid (HNCO). . Therefore, compared to ammonia, urea has a significantly higher melting point, boiling point, and solubility, making it possible to secure the ease of storage and storage of urea and the safety of transportation.

When urea is used as a reducing agent in the form of urea solution dissolved in water in a nitrogen oxide reduction system, not only thermal decomposition reaction but also thermal hydrolysis reaction occurs simultaneously, but all of these reactions are converted to ammonia and produce nitrogen oxide. It becomes possible to react with. The chemical equation for the thermal hydrolysis reaction of urea is Chemical Formula 2, and the chemical equation for the thermal decomposition reaction is Chemical Formula 3.

Meanwhile, the urea water spray device is a main accessory device of SCR or SNCR, a denitrification device for reducing nitrogen oxides (NOx), an air pollutant, and is used to generate ammonia by thermally decomposing urea water.

In the case of SCR, a urea water spray device is installed inside the vaporizer outside the SCR facility, and the generated ammonia is injected into the SCR facility through the AIG (Ammonia injection grid).

In the case of SNCR, it is operated by spraying urea water directly into the high-temperature reaction section through a spray device to generate ammonia through thermal decomposition.

Ammonia must be diluted to an appropriate concentration according to the concentration of nitrogen oxides flowing into the denitrification facility, then flowed into the vaporizer, converted to ammonia gas, and supplied to the denitrification facility. Since urea water is produced and supplied at a high concentration of 40%, urea water is diluted to a certain concentration in a separate external dilution tank according to the reaction conditions of the denitrification device and then injected through a spray device.

Existing denitrification facilities manually control and inject the amount of reducing agent only to a level that satisfies emission regulations, and are not operated under optimal conditions. This is because if the excessively injected ammonia does not react, there is a problem of corroding the downstream equipment, so ammonia is injected at a level that allows operation within legal regulations.

However, the Ministry of Environment recently revised the Enforcement Decree and Enforcement Rules of the Air Quality Conservation Act as part of special measures to manage fine dust, and took effect on January 28, 2018, strengthening the emission standards for Yeongheung Thermal Power Plant Units 3 to 6 and new coal-fired power plants. did. Accordingly, when operating a new thermal power plant, we are considering applying denitrification technology to significantly lower the nitrogen oxide emission standard and reduce NOx to 5ppm. In order to meet the strengthened NOx emission standards, the denitrification facility must be operated with the optimal ammonia injection amount required for the reaction through the measured value of the NOx concentration flowing into the denitrification facility to reduce NH ₃ Slip and obtain optimal denitrification efficiency.

A new spray system is needed that can spray an appropriate amount of urea into the vaporizer or denitrification device so that ammonia can be supplied in an optimal amount according to changes in the incoming NOx concentration.

The present invention seeks to provide a diluted urea water spray device that can spray an appropriate amount of urea water into the vaporizer or inside the denitrification device so that ammonia can be injected in an optimal amount according to changes in the NOx concentration flowing into the denitrification device. .

The first aspect of the present invention is (a1) by changing each flow rate introduced by adjusting the urea water pressure and the dilution water pressure, as the pressurized urea water fluid and the pressurized dilution water fluid flow, the urea water fluid diluted to various concentrations A liquid pipe provided to the nozzle cap for liquid;

(a2) A porous structure inserted into the fluid path inside the liquid pipe, wherein the pressurized urea water fluid and the pressurized dilution water fluid simultaneously pass through adjacent pores of the porous structure and are diluted with urea water through microvortices within the pores. A porous structure in which water is uniformly mixed to provide diluted urea water; and

(a3) Gas pipe providing gas to the gas nozzle cap

A nozzle body (a) provided with; and

A nozzle tip (b) equipped with a nozzle cap for gas and a nozzle cap for liquid that is attached to the tip of the nozzle body and allows control of the flow rate and spray form of gas and diluted urea water.

Provided with one or two or more nozzles containing,

Diluted urea water is sprayed in the form of a water column from the orifice of the nozzle cap for liquid, and the water column is pulverized and sprayed by the gas sprayed from the orifice of the nozzle cap for gas. A porous structure insert type diluted urea water spray that allows precise concentration control. Provides a device.

The second aspect of the present invention is to install a diluted urea water spray device inside the porous structure capable of precisely controlling the concentration of the first mode, and to perform a urea decomposition reaction and selective non-catalytic reduction (SNCR) of the urea water sprayed from the spray device. An SNCR reactor is provided, which is characterized by simultaneous NOx reduction reaction.

The third aspect of the present invention is characterized in that the diluted urea water spray device inserted into the porous structure capable of precisely controlling the concentration of the first mode is installed inside, and the urea water sprayed from the spray device undergoes a urea decomposition reaction to form ammonia. Provides a vaporizer.

The fourth aspect of the present invention is a nitrogen oxide (NOx) reduction system including a diluted urea water spray device inserted into the porous structure capable of precisely controlling the concentration of the first aspect,

A urea decomposition reaction is performed on the urea water sprayed from the spray device to produce ammonia,

Provided is a nitrogen oxide reduction system characterized by performing a NOx reduction reaction of NOx-containing combustion gas using ammonia generated by the urea decomposition reaction of urea water.

The fifth aspect of the present invention is the nitrogen oxide reduction system of the fourth aspect,

A urea decomposition reaction of urea water injected from a spray device is performed to produce ammonia, and the NOx-containing combustion gas is treated by performing a NOx reduction reaction of the NOx-containing combustion gas with the ammonia generated by the urea decomposition reaction. Provides a method.

Hereinafter, the present invention will be described in detail.

Existing urea water spraying devices are mainly used as two-fluid spraying devices that mix liquid and gas internally or externally and spray the liquid with the power of compressed air. An air atomizing nozzle as shown in Figure 2 creates the finest spray form by mixing gas and liquid.

The porous structure insertion type diluted urea spray device capable of precise concentration control according to the present invention is

(a1) By changing each flow rate introduced by adjusting the urea water pressure and the dilution water pressure, the pressurized urea water fluid and the pressurized dilution water fluid flow and provide urea fluid diluted to various concentrations to the nozzle cap for liquid. liquid pipe;

(a2) A porous structure inserted into the fluid path inside the liquid pipe, wherein the pressurized urea water fluid and the pressurized dilution water fluid simultaneously pass through adjacent pores of the porous structure and are diluted with urea water through microvortices within the pores. A porous structure in which water is uniformly mixed to provide diluted urea water; and

(a3) Gas pipe providing gas to the gas nozzle cap

A nozzle body (a) provided with; and

A nozzle tip (b) equipped with a nozzle cap for gas and a nozzle cap for liquid that is attached to the tip of the nozzle body and allows control of the flow rate and spray form of gas and diluted urea water.

It is provided with one or two or more nozzles including.

At this time, the diluted urea water is sprayed in the form of a water column from the orifice of the nozzle cap for liquid, and the water column is pulverized and sprayed by the gas sprayed from the orifice of the nozzle cap for gas.

The internal diameter of the liquid pipe is usually about 1/2 inch. Therefore, the pressurized urea water fluid and the pressurized dilution water fluid flow in the liquid pipe within the nozzle, and the urea water density varies depending on the concentration. Furthermore, not only are the densities of urea water and the density of dilution water different, but the urea water pressure/ Since the flow rate and dilution water pressure/flow rate are different, it is difficult to provide uniformly mixed and diluted urea fluid to the nozzle cap for liquid while the pressurized urea fluid and the pressurized dilution water fluid flow in a fixed length liquid pipe. . In addition, in order to adjust the concentration of diluted urea water provided to the liquid nozzle cap in response to changes in NOx concentration to be treated in the denitrification device and/or reaction conditions of the denitrification device, the concentration and flow rate of the urea fluid fluid as well as the dilution As the water flow rate changes, it is more difficult to provide uniformly mixed and diluted urea fluid to the liquid nozzle cap while flowing urea fluid and diluted water fluid under various conditions using a liquid pipe of a fixed length.

To solve this problem, the present invention inserts a porous structure into the fluid path inside the liquid pipe of the nozzle, so that the pressurized urea water fluid and the pressurized dilution water fluid simultaneously continuously penetrate the adjacent pores of the porous structure. As it passes, urea water and diluted water are uniformly mixed through microvortices within the pores, and the diluted urea water is provided to the liquid nozzle cap.

According to the present invention, by inserting a porous structure before the nozzle cap for the liquid in the liquid pipe of the nozzle, two fluids with different densities introduced at the same or different flow rates can be uniformly mixed. Therefore, according to the present invention, the porous structure-inserted diluted urea water spray device capable of precise concentration control can insert a porous structure inside a liquid pipe to dilute and spray diluted water and high-concentration urea water at a desired ratio, The appropriate concentration can be controlled in a short time, and the spray amount can be controlled to a specific amount. In addition, according to the present invention, the porous structure inserted before the nozzle cap for liquid in the liquid pipe of the nozzle can prevent the formation of urea salt through dilution of urea water and/or heat generation by microvortices within the pores.

The flow rates of urea water and diluted water change and the concentration of diluted urea water changes due to the balance between the concentration/pressure/flow rate of urea water and the pressure/flow rate of diluted water supplied inside the liquid pipe. /or depending on the dilution water pressure/flow rate, the minimum length of the liquid pipe for uniform mixing of the pressurized urea fluid and the pressurized dilution water fluid varies, and the NOx concentration that must be treated in the denitrification device changes and/or The length of the liquid pipe must be long in order to accommodate various minimum lengths of the liquid pipe to provide the liquid nozzle cap with uniformly mixed and diluted urea water at various adjusted concentrations in response to the reaction conditions of the denitrification device. On the other hand, when a porous structure is inserted into the fluid path inside the liquid pipe of the nozzle according to the present invention, the pressurized urea fluid and the pressurized dilution even if the difference between the urea water density/pressure and the dilution water density/pressure is large. Since the water fluid continuously passes through adjacent pores of the porous structure at the same time and the urea water and diluted water can be uniformly mixed through microvortices within the pores, the liquid pipe of the nozzle can be designed to be short.

In addition, according to the present invention, the porous structure insertable diluted urea spray device capable of precise concentration control adjusts the concentration of diluted urea water in response to changes in NOx concentration to be treated in the denitrification device and/or reaction conditions of the denitrification device to remove ammonia. The supply amount can be changed, and the concentration of the diluted urea fluid can be adjusted by changing each flow rate introduced into the liquid pipe by adjusting the urea water pressure and the dilution water pressure. Therefore, in response to changes in NOx concentration to be treated in the denitrification device and/or reaction conditions of the denitrification device, urea fluid diluted to various concentrations can be provided to the liquid nozzle cap inside the liquid pipe of the nozzle. As a result, through the measured value of NOx concentration generated or introduced into the denitrification device, urea water of an appropriate dilution concentration is supplied to the denitrification device or inside the vaporizer to provide the denitrification device with the optimal ammonia supply required for the denitrification reaction, minimizing unreacted ammonia. It can be sprayed in an appropriate amount inside the device.

According to the present invention, if a porous structure is inserted before the nozzle cap for the liquid in the liquid pipe of the nozzle, two fluids with different densities introduced at the same or different flow rates can be uniformly mixed.

For rapid and uniform mixing of fluids of various densities/flow velocities and to control the flow velocity profile (contour line) based on a cross section perpendicular to the direction of fluid flow,

There may be a pore size gradient in the porous structure based on the fluid flow direction in which the diluted urea fluid is formed as the pressurized urea fluid and the pressurized dilution water fluid flow, and/or

As the pressurized urea solution fluid and the pressurized dilution water fluid flow, there may be a pore size gradient in the porous structure based on the cross section perpendicular to the fluid flow direction in which the diluted urea solution fluid is formed.

For example, as the pressurized urea solution fluid and the pressurized diluted water fluid flow, based on the cross section perpendicular to the fluid flow direction in which the diluted urea solution fluid is formed, the larger the flow rate, the smaller the pore size to induce uniform mixing.

At this time, the pore size gradient of the porous structure can be achieved by controlling the size of a single pore, or by adjusting the density of the same or different pores.

Additionally, the pore size gradient of the porous structure is not limited to an increasing or decreasing direction as long as it forms a regular pattern.

The porous structure is different from a plate-shaped orifice with one hole in the thickness direction, and has a surface shape that corresponds to the internal shape of the inserted liquid pipe and has at least two pores that can induce microvortices in the thickness/length direction. It is connected. The porous structure may have a length greater than its width (e.g., diameter).

The material of the porous structure may be the same or different from other parts of the liquid pipe or nozzle, and non-limiting examples include nickel-plated brass, stainless steel (SUS 303), hard rubber, and acrylic resin. .

For example, as shown in FIG. 2, the air fine spray nozzle sprays gas from a gas nozzle cap disposed at a slight angle, pulverizing the diluted urea liquid stream sprayed from the liquid nozzle cap at the center of the nozzle, and spraying the liquid. spraying takes place.

The gas provided to the nozzle cap for gas through the gas pipe may be compressed gas, and preferably may be compressed cooling gas. The gas sprayed through the gas nozzle cap not only serves as a carrier gas for the sprayed urea water, but the cooling gas flowing through the gas pipe can also perform the function of cooling the nozzle.

The nozzle of the present invention is a gas-liquid two-fluid fine spray nozzle, and most liquids such as urea water and/or dilution water and/or gases such as compressed air can be sufficiently pressurized with a pump or the like and supplied to the liquid pipe and gas pipe, respectively. The pressurized urea fluid and the pressurized diluted water fluid may penetrate the porous structure in the liquid pipe by the pump pressure and reach the nozzle cap for the liquid as the diluted urea fluid.

A nozzle tip equipped with a nozzle cap for gas and a nozzle cap for liquid is attached to the tip of the nozzle body (a), making it possible to control the flow rate of gas and liquid and the spray form. Liquid flow rate, gas flow rate, and spray form can ultimately be adjusted by combining various gas nozzle caps and liquid nozzle caps. Liquid flow rate and gas flow rate can each be adjusted independently.

For example, depending on the design of the nozzle cap as illustrated in FIG. 5, a fine spray, mist, or fog can be formed, and various spray patterns are possible. Additionally, various gas and liquid mixing types are possible. Therefore, the present invention can finely adjust the flow rate, drop size, spray distribution, and coverage of diluted urea water through a gas-liquid spray nozzle.

In the body of the air fine spray nozzle of the present invention, spraying can be turned on and off automatically inside the nozzle.

The diluted urea water spray device of the present invention may be equipped with one or two or more nozzles inserted into the porous structure described above. For example, in the SNCR process, the mixing of the reducing agent and the combustion exhaust gas has a great influence on the NOx reduction efficiency, so it is desirable that the diluted urea solution, which is the reducing solution, be sprayed evenly throughout the reaction section. For this purpose, the greater the number of nozzles, the better, but it is not economical. The number of nozzles can be limited by taking this into account.

The nitrogen oxide (NOx) reduction system according to the present invention is

Ammonia is generated by performing a urea decomposition reaction of urea water injected from the spray device, and a NOx reduction reaction of NOx-containing combustion gas is performed by ammonia generated by the urea decomposition reaction of urea water,

The present invention described above is characterized by including a porous structure insertion type diluted urea spray device capable of precisely controlling the concentration.

The urea decomposition reaction of urea water may include a thermal hydrolysis reaction represented by Formula 2 and/or a thermal decomposition reaction represented by Formula 3.

[Formula 2]

[Formula 3]

Therefore, it is desirable that the temperature of the area where urea water is directly sprayed from the spray device is at or above the temperature at which urea water can be thermally decomposed.

Meanwhile, a device for producing ammonia by performing a urea decomposition reaction of urea water sprayed from the porous structure insertable diluted urea water spray device capable of precisely controlling the concentration of the present invention, and NOx content by ammonia generated by the urea decomposition reaction of urea water. The device that performs the NOx reduction reaction of combustion gas may be an integrated device or a separate device connected directly or indirectly through piping.

The NOx reduction reaction of NOx-containing combustion gas with ammonia generated by the urea decomposition reaction of urea water may be selective non-catalytic reduction (SNCR) or selective catalytic reduction (SCR).

A non-limiting example of an integrated device may be a combustion furnace in which NOx-containing combustion gas is generated through a combustion reaction, such as an incinerator, heating furnace, boiler, or internal combustion engine. In this case, urea water is directly sprayed from the spray device, and the high temperature area where urea water is pyrolyzed may be part of a combustion furnace where NOx-containing combustion gas is generated through a combustion reaction.

In addition, the present invention installs the diluted urea water spraying device inside the porous structure capable of precisely controlling the concentration of the present invention described above, and NOx An SNCR reactor in which a reduction reaction occurs simultaneously is provided.

At this time, in order for the NOx reduction reaction to occur simultaneously by selective non-catalytic reduction (SNCR), the temperature of the area where the urea water sprayed from the porous structure inserted diluted urea water spray device or the urea decomposition reaction occurs is 850 ~ 1100℃. , preferably 900 to 1000°C. At this time, ammonia is generated by thermal decomposition of urea water by directly spraying it into a high-temperature reaction area where urea water can be thermally decomposed through a diluted urea water spray device inserted into the porous structure.

In the SNCR reactor, NOx-containing combustion gas is generated or supplied through a combustion reaction, and a NOx reduction reaction can occur by selective non-catalytic reduction (SNCR).

Typically, an SNCR reactor is equipped with a combustion furnace that generates NOx-containing combustion gas through a combustion reaction and a NOx reductant injection nozzle (FIG. 6). Therefore, a combustion furnace in which NOx-containing combustion gas is generated through a combustion reaction may be an SNCR reactor in which a NOx reduction reaction by selective non-catalytic reduction (SNCR) occurs. Non-limiting examples of combustion furnaces include incinerators, furnaces, boilers, or internal combustion engines.

In the nitrogen oxide reduction system of the present invention, a device for producing ammonia by performing a urea decomposition reaction of urea water sprayed from the porous structure insertable diluted urea water spray device capable of precisely controlling the concentration of the present invention, and a urea decomposition reaction of urea water If the device that performs the NOx reduction reaction of NOx-containing combustion gas by ammonia generated by the device is a separate device connected directly or indirectly through piping,

The device that generates ammonia by performing a urea decomposition reaction of urea water sprayed from the porous structure insertable diluted urea water spray device capable of precisely controlling the concentration of the present invention may be a vaporizer, that is, a urea decomposition tank.

At this time, the temperature of the area where the urea water sprayed from the spray device is injected or the urea decomposition reaction occurs may be 200 to 500°C. Therefore, the device that performs the NOx reduction reaction of NOx-containing combustion gas by ammonia generated by the urea decomposition reaction of urea water reduces NOx at 200 to 500°C by selective catalytic reduction (SCR) while supplying NOx-containing combustion gas. It may be an SCR reactor in which a reaction can occur.

Accordingly, the present invention provides a vaporizer in which the above-described porous structure-inserted diluted urea water spray device capable of precisely controlling the concentration of the present invention is installed therein, and the urea water sprayed from the spray device undergoes a urea decomposition reaction to form ammonia.

In addition, the nitrogen oxide reduction system of the present invention, as shown in FIG. 7,

The vaporizer of the present invention described above, which installs a diluted urea water spray device inside a porous structure capable of precisely controlling concentration, and urea decomposition reaction of the urea water sprayed from the spray device to form ammonia; and

It includes an SCR reactor that performs selective catalytic reduction (SCR) on NOx-containing combustion gas and ammonia gas supplied from the vaporizer.

Vanadium oxide (V ₂ 0 ₅ ) and titanium oxide (TiO ₂ ) can be used as catalysts used to reduce nitrogen oxides by selective catalytic reduction. The SCR reactor performing the catalytic reduction process (SCR) may be a fixed bed or fluidized bed catalytic reactor.

At this time, the vaporizer may be installed outside or inside the SCR reactor.

If a vaporizer is installed outside the SCR reactor to form ammonia by causing a urea decomposition reaction of urea sprayed from an insertable diluted urea water spray device with a porous structure that allows precise concentration control, the ammonia formed in the vaporizer is sent to the SCR through the AIG (Ammonia injection grid). It can be supplied to the reactor. AIG (Ammonia injection grid) can mix ammonia and NOx-containing combustion gas formed in the vaporizer and supply it to the SCR reactor (Figure 7).

In addition, the present invention in the nitrogen oxide reduction system of the present invention described above,

A urea decomposition reaction of urea water injected from a spray device is performed to produce ammonia, and the NOx-containing combustion gas is treated by performing a NOx reduction reaction of the NOx-containing combustion gas with the ammonia generated by the urea decomposition reaction. Provides a method.

According to the present invention, the porous structure-inserted diluted urea water spray device capable of precise concentration control is capable of uniformly diluting and spraying diluted water and high-concentration urea water at a desired ratio by inserting a porous structure inside a liquid pipe, The appropriate concentration can be controlled in a short time, and the spray amount can be controlled to a specific amount.

Therefore, according to the present invention, the porous structure insertable dilution urea spray device capable of precise concentration control is designed to provide an appropriate concentration of urea water inside the vaporizer or inside the denitrification device so that ammonia can be injected in an optimal amount according to changes in the NOx concentration flowing into the denitrification device. It can be sprayed in an appropriate amount.

Figure 1 shows the NO _x reduction reaction of urea, a reducing agent.
Figure 2 is a conceptual diagram of an example of an air atomizing nozzle.
Figure 3 is a conceptual diagram of an existing diluted urea water spray device equipped with an air fine spray nozzle.
Figure 4 is a conceptual diagram of a diluted urea water spraying device equipped with a porous structure-inserted airflow fine spray nozzle according to an embodiment of the present invention.
Figure 5 is a photograph illustrating various nozzle tips of commercially available Air Atomizing Nozzles.
Figure 6 is a conceptual diagram showing a bench-scale SNCR process according to an embodiment of the present invention.
Figure 7 is a schematic process diagram of a nitrogen oxide reduction system using a selective catalytic reduction method according to an embodiment of the present invention.

A typical embodiment of the present invention is described with reference to the accompanying drawings. These examples are only for illustrating the present invention in more detail, and the scope of the present invention is not limited by these examples.

Referring to FIG. 6 showing the SNCR process, a nitrogen oxide reduction system and a NOx-containing combustion gas treatment method according to an embodiment of the present invention using urea water as a reducing agent will be described.

In the nitrogen oxide reduction system according to one embodiment of the present invention, combustion gas is generated by burning LPG, and the combustion gas is transported using a turbo blower installed at the rear of the device. Maintain the combustion gas flow rate (Nm ³ /min) constant and measure the NOx concentration contained in the generated combustion gas. A diluted urea water spraying device equipped with a porous structure-inserted two-fluid fine spray nozzle, as shown in Figure 4, to provide urea water of an appropriate concentration so that ammonia can be supplied in an optimal amount according to the change in NOx concentration in the generated combustion gas. Using , spray directly into the duct through which combustion gas flows. When manufacturing and injecting diluted urea water through a porous structure-inserted air fine spray nozzle, the spray amount of diluted urea water is kept constant, and the urea concentration of the diluted urea water is changed to change the chemical properties of urea. The standard stoichiometric ratio can be changed, for example, between 1 and 2. By keeping the spray amount of diluted urea water constant, the droplet size, spray distance, spray angle, etc. of the sprayed urea water can be kept constant, thereby keeping the hydrodynamic influence on the denitrification reaction constant. Heat-resistant and insulating castables can be installed outside the duct. In the longitudinal direction of the duct, a K-Type thermocouple to measure the temperature of combustion gas and a sampling port to measure NO, CO, O ₂ , and NH ₃ concentrations of combustion gas can be installed every 50 to 100 cm. The concentrations of NO, CO, and O ₂ can be measured by the NDIR method, and the NH ₃ concentration can be measured by the neutralization titration method using H ₃ BO ₃ as an absorbent solution.

In the nitrogen oxide reduction system of Figure 6, the NO removal reaction is almost completed before the residence time of the sprayed urea solution reaches 0.5 seconds, and even if the residence time increases to 0.5 seconds or more, the NO reduction efficiency will remain almost constant. You can.

For example, the NO reduction efficiency increases as the injection temperature of the sprayed urea solution, which is a reducing agent, increases from 840 ^o C, reaching a maximum value around 960 to 980 ° C, and the temperature of the SNCR reaction decreases when the reducing agent injection temperature increases further. Dependency appears. This temperature dependence of the SNCR reaction is such that when the injection temperature of the sprayed urea water is low, the NO removal reaction rate of the reducing agent ammonia produced by thermal decomposition of urea water is slow, and ammonia is discharged in an unreacted state, but the optimal injection temperature of the sprayed urea water is In this case, the reduction reaction between ammonia, a reducing agent produced by thermal decomposition of urea water, and NO occurs at a rapid rate, and NO is reduced to N ₂ to reach the maximum NO reduction efficiency. At higher temperatures, ammonia (NH ₃ ) undergoes an oxidation reaction with O ₂ This is because it is oxidized to NO and the NO reduction efficiency is low.

In a nitrogen oxide reduction system using urea as a reducing agent, key process variables such as reducing agent injection temperature, reducing agent normalized stoichiometric ratio (NSR), and combustion gas residence time affect NO reduction efficiency.

Below, with reference to FIG. 7 showing the SCR process, a nitrogen oxide reduction system and a NOx-containing combustion gas treatment method according to an embodiment of the present invention using urea solution as a reducing agent will be described.

Figure 7 is a schematic process diagram of a nitrogen oxide reduction system 11 through selective catalytic reduction (SCR) using sprayed diluted urea water as a reducing agent according to an embodiment of the present invention, which includes a storage tank ( 1), an improved supply module (2; chemical metering pumps module) capable of supplying the urea water flowing in from the storage tank 1 by adjusting an appropriate amount, and a porous structure insertion-type diluted urea water spray capable of precisely controlling the concentration shown in FIG. 4. A vaporizer/decomposition tank (3) equipped with a space for chemically decomposing the diluted urea water sprayed in a predetermined amount with an improved device installed inside, exhaust gas moving along the transfer pipe (no reference number) A dust collector (10) that collects dust, an AIG (6) that promotes the contact of diluted ammonia vapor discharged from the vaporizer/decomposition tank (3) with nitrogen oxides contained in the exhaust gas, a catalytic reaction tower (7), and a preheater (8) ) is provided. The nitrogen oxide reduction system 11 is based on the thermal decomposition of urea water and can be designed to reduce nitrogen oxides to a level that does not affect the atmospheric environment by using urea water as a reducing agent in the selective catalytic reduction method. .

As shown in FIG. 7, the storage tank 1 of the nitrogen oxide reduction system 11 stores urea in liquid form to facilitate the flow of the reducing agent, and the improved supply module 2 is stored in the storage tank based on the amount of nitrogen oxides discharged. From (1), a predetermined number of elements is provided in the next step. The improved supply module (2) determines the flow rate required by the catalytic reaction tower (7) by calculating the amount of nitrogen oxides contained in the exhaust gas generated from the combustion device (5) and the amount of elements required for this according to the equivalence ratio. It is supplied as an improved supply module (2). Then, the urea water is sent to the vaporizer/digestion tank (3) through the improved supply module (2) that controls the supply amount of urea water.

Preferably, the decomposition of urea into ammonia should proceed as quickly as possible to immediately respond to the emissions of nitrogen oxides generated from the combustion device 5. For this purpose, it is preferable that the urea water introduced into the vaporizer/digestion tank 3 is sprayed to a size of, for example, 80 μm or less. In the vaporizer/decomposition tank (3), liquid urea water in which urea is dissolved in water is sprayed and used, so as shown in Figure 1, urea undergoes a thermal decomposition reaction, and along with the thermal hydrolysis reaction, urea water becomes ammonia. It is converted to cyanuric acid, and then to ammonium carbamate, which is then instantly converted back to ammonia. In order to carry out these reactions, a considerable amount of heat is required. Therefore, the high-temperature exhaust gas discharged from the combustion device 5 can be recycled as a heat source for the vaporizer/decomposition tank 3. Efficiently, the decomposition reaction of urea water into ammonia can occur through contact with the high temperature heat of the exhaust gas and the sprayed urea water, and the vaporizer/decomposition tank (3) is installed in at least one stage, preferably in two stages or more. It can help with the decomposition reaction. In the vaporizer/decomposition tank 3 heated with high-temperature exhaust gas, decomposition of urea into ammonia proceeds with a fast response speed of approximately 1 to 3 seconds. The high-temperature exhaust gas (about 350°C), which is partially bypassed in the transfer pipe connecting the combustion device (5) to the AIG (6) and transporting the exhaust gas containing nitrogen oxides, is converted into urea water in the vaporizer/decomposition tank (3). It can help with thermal reactions. A dust collector 10 is provided to collect a large number of dusts contained in the exhaust gas moving along the transfer pipe. Only the purified high-temperature gas is delivered to the vaporizer/decomposer (3) and used as a heat source, and the remaining dust is collected in the dust collector (10). Through this process, clean exhaust gas with low dust content is transferred to the vaporizer/decomposer (3). ) and/or may be delivered to AIG (6). The dust collector 10 can sufficiently purify the exhaust gas, suppress unnecessary side reactions with urea, and effectively achieve the decomposition reaction of urea into ammonia. Ammonia vapor generated by thermal decomposition and hydrolysis in the vaporizer/decomposition tank (3) of the nitrogen oxide reduction system (11) according to an embodiment of the present invention flows into the AIG (6) and from the combustion device (5). It may come into mixed contact with exhaust gas moving along the transfer pipe. Sufficiently mixed mixed gases are introduced into the catalytic reaction tower (7), and the decomposed ammonia can reduce nitrogen oxides through selective catalytic reduction (SCR). Additionally, nitrogen and hydrogen generated after reaction in the catalytic reaction tower (7) can be released into the atmosphere through the chimney (9). The high-temperature steam coming out of the catalytic reaction tower (7) is transferred to the preheater (8), and the energy recycling rate can be increased by preheating the combustion air to be used in the combustion device (5). Optionally, the vaporizer/digestion tank 3 may be equipped with a separate heating device (burner, etc.) for initial process system start-up, drying of the system, or protection of the catalyst layer.

Meanwhile, due to the advantage of the Urea-SCR system being able to achieve a NOx reduction rate of more than 90% while maintaining engine output, automakers are adopting the Urea-SCR method for most of the recently developed vehicles.

The Urea-SCR system precisely injects urea-water solution into the exhaust pipe through an injection control device as shown in FIG. 4, and the injected urea solution is thermally decomposed by the heat of the exhaust gas into ammonia (NH ₃ ). The converted ammonia reacts with nitrogen oxides (NOx) in the SCR catalyst mounted at the rear and decomposes into water and nitrogen, which are harmless to the human body. In order to increase catalyst utilization in the Urea-SCR system and prevent ammonia slip, the spatial distribution of ammonia must be uniform in front of the catalyst. The spatial distribution of ammonia is greatly affected by the spray characteristics of urea water sprayed into the exhaust pipe and the mixing characteristics with exhaust gas. In most Urea-SCR systems, it is necessary to promote mixing of urea water spray and exhaust gas and to avoid collision of urea water with the wall. A mixer may be used for this purpose, and a mixer-housing assembly may be installed within the exhaust pipe.

Claims (22)

(a1) By changing each flow rate introduced by adjusting the urea water pressure and the dilution water pressure, the pressurized urea water fluid and the pressurized dilution water fluid flow and provide urea fluid diluted to various concentrations to the nozzle cap for liquid. liquid pipe;
(a2) A porous structure inserted into the fluid path inside the liquid pipe, wherein the pressurized urea water fluid and the pressurized dilution water fluid simultaneously pass through adjacent pores of the porous structure and are diluted with urea water through microvortices within the pores. A porous structure in which water is uniformly mixed to provide diluted urea water; and
(a3) Gas pipe providing gas to the gas nozzle cap
A nozzle body (a) provided with; and
A nozzle tip (b) equipped with a nozzle cap for gas and a nozzle cap for liquid that is attached to the tip of the nozzle body and allows control of the flow rate and spray form of gas and diluted urea water.
Provided with one or two or more nozzles containing,
The porous structure is different from a plate-shaped orifice, and is made up of densely connected pores that can induce molecular-level micro-vortices along the length of the liquid pipe to precisely control the concentration of diluted urea water. As the fluid and pressurized dilution water continuously pass through the dense pores of the porous structure, the urea water and dilution water are uniformly mixed through microvortices within the pores.
Diluted urea water is sprayed in the form of a water column from the orifice of the nozzle cap for liquid, and the water column is pulverized and sprayed by the gas sprayed from the orifice of the nozzle cap for gas. A porous structure insert type diluted urea water spray that allows precise concentration control. Device. The method of claim 1, wherein the ammonia supply amount can be changed by adjusting the concentration of the diluted urea water in response to changes in the NOx concentration to be treated in the denitrification device, the reaction conditions of the denitrification device, or both, and the amount of ammonia supplied can be changed. A porous structure insertable diluted urea spray device capable of precise concentration control, characterized by controlling the concentration by changing each flow rate introduced into the liquid pipe by adjusting the urea water pressure and the dilution water pressure. The concentration according to claim 1, wherein urea water whose dilution concentration is adjusted in response to changes in NOx concentration to be treated in the denitrification device, reaction conditions of the denitrification device, or both can be sprayed into the vaporizer or the inside of the denitrification device. A porous structure insertable diluted urea spray device that can be precisely controlled. The porosity of claim 1, wherein there is a pore size gradient in the porous structure based on the fluid flow direction in which the diluted urea fluid is formed as the pressurized urea fluid and the pressurized dilution water fluid flow. Porosity capable of precisely controlling concentration. Structure-inserted diluted urea spray device. The concentration of claim 1, wherein there is a pore size gradient of the porous structure based on a cross section perpendicular to the fluid flow direction in which the diluted urea fluid is formed as the pressurized urea fluid and the pressurized dilution water fluid flow. A porous structure insertable diluted urea spray device that can be precisely controlled. An insertable diluted urea water spray device is installed inside the porous structure capable of precisely controlling the concentration according to any one of claims 1 to 5, and the urea water sprayed from the spray device is subjected to urea decomposition reaction and selective non-catalytic reduction (SNCR). SNCR reactor is characterized by simultaneous NOx reduction reaction. The SNCR reactor according to claim 6, wherein NOx-containing combustion gas is generated or supplied through a combustion reaction within the SNCR reactor and a NOx reduction reaction occurs by selective non-catalytic reduction (SNCR). The SNCR reactor according to claim 6, wherein the temperature of the area where the urea water sprayed from the spray device is injected or the urea decomposition reaction of the urea water occurs is 850 to 1100°C. The SNCR reactor according to claim 6, wherein the SNCR reactor is a combustion furnace in which NOx-containing combustion gas is generated through a combustion reaction. A porous structure capable of precisely controlling the concentration according to any one of claims 1 to 5 is installed inside an insert-type diluted urea water spray device, and the urea water sprayed from the spray device undergoes a urea decomposition reaction to form ammonia. Phosphorus, carburetor. The vaporizer according to claim 10, wherein the temperature of the area where the urea water sprayed from the spray device is injected or the urea decomposition reaction occurs is 200 to 500°C. A nitrogen oxide (NOx) reduction system comprising a diluted urea water spray device inserted into a porous structure capable of precisely controlling the concentration according to any one of claims 1 to 5,
A urea decomposition reaction is performed on the urea water sprayed from the spray device to produce ammonia,
A nitrogen oxide reduction system characterized by performing a NOx reduction reaction of NOx-containing combustion gas using ammonia generated by the urea decomposition reaction of urea water. The method of claim 12, which includes a device for producing ammonia by performing a urea decomposition reaction of urea water injected from a spray device, and a NOx reduction reaction of NOx-containing combustion gas by ammonia generated by the urea decomposition reaction of urea water. A nitrogen oxide reduction system characterized in that the device is an integrated device or separate devices connected directly or indirectly through piping. The method of claim 12, wherein the NOx reduction reaction of NOx-containing combustion gas by ammonia generated by the urea decomposition reaction of urea water is characterized in that the selective non-catalytic reduction (SNCR) method or selective catalytic reduction (SCR) method is used to produce nitrogen oxides. Reduction system. The nitrogen oxide reduction system according to claim 12, wherein the temperature of the area where urea water is directly sprayed from the spray device is at or above the temperature at which urea water can be thermally decomposed. The nitrogen oxide reduction system according to claim 12, wherein urea water is directly sprayed from the spray device and the high temperature area where urea water is pyrolyzed is a part of a combustion furnace in which NOx-containing combustion gas is generated through a combustion reaction. The nitrogen oxide reduction system according to claim 16, wherein the combustion furnace is an incinerator, heating furnace, boiler, or internal combustion engine. The vaporizer according to claim 10, wherein a diluted urea water spray device inserted into a porous structure capable of precisely controlling concentration is installed therein, and the urea water sprayed from the spray device undergoes a urea decomposition reaction to form ammonia; and
A nitrogen oxide reduction system characterized by comprising an SCR reactor that performs selective catalytic reduction (SCR) on NOx-containing combustion gas and ammonia gas supplied from a vaporizer. The nitrogen oxide reduction system according to claim 18, wherein the vaporizer is installed outside or inside the SCR reactor. The nitrogen oxide reduction system according to claim 18, wherein the ammonia formed in the vaporizer is supplied to the SCR reactor through an AIG (Ammonia injection grid). The nitrogen oxide reduction system according to claim 20, wherein the ammonia and NOx-containing combustion gas formed in the vaporizer are mixed in the AIG (Ammonia injection grid) and supplied to the SCR reactor. In the nitrogen oxide reduction system of paragraph 12,
A urea decomposition reaction of urea water injected from a spray device is performed to produce ammonia, and the NOx-containing combustion gas is treated by performing a NOx reduction reaction of the NOx-containing combustion gas with the ammonia generated by the urea decomposition reaction. method.