Nitrogen oxide reduction system

Abstract

The nitrogen oxide reduction system according to exemplary embodiments of the present invention provides a system in which a selective catalytic reduction (SCR) method and a selective non-catalytic reduction (SNCR) method are linked. Accordingly, nitrogen oxides and nitrous oxides included in exhaust gas generated by ammonia combustion can be effectively removed. In particular, the removal efficiency of nitrogen oxides and nitrous oxides can be further improved by optimizing the contents of nitrogen oxides and a reducing agent.

Description

Nitrogen oxide reduction system

[0001] The present invention relates to a nitrogen oxide reduction system.

[0002] More specifically, it relates to a nitrogen oxide reduction system capable of reducing nitrogen oxides generated during ammonia combustion.

[0003] Ammonia is being considered as a carbon-free fuel to reduce carbon dioxide (CO2) emissions, and combustion technologies using ammonia as a raw material are being developed accordingly. However, the nitrogen (N) atoms contained within ammonia molecules can cause nitrogen oxides (NOx) or nitrous oxide (N2O) to be generated at higher concentrations during combustion than with conventional fossil fuel combustion.

[0004] Among nitrogen oxides, NO and NO2 are representative air pollutants that cause photochemical smog and acid rain, and have recently been attracting attention as precursors of fine dust. Furthermore, while N2O is harmless to humans, the global warming potential (GWP) of a single molecule of N2O gas is 310 times that of a single molecule of carbon dioxide (CO2). Therefore, technologies to reduce these emissions must be implemented.

[0005] (Patent Document 1) Republic of Korea Patent Publication No. 10-2022-004846.

[0006] The technical idea of ​​the present invention is to provide a nitrogen oxide reduction system that can effectively remove nitrogen oxide and nitrous oxide that may be generated during ammonia combustion.

[0007] The objectives of the present invention are not limited to the above-described content. Those skilled in the art will have no difficulty understanding the additional objectives of the present invention from the overall description of the present invention.

[0008] According to exemplary embodiments of the present invention, a nitrogen oxide reduction system is provided. The nitrogen oxide reduction system includes a combustion device configured to combust a first fluid containing ammonia and discharge a first exhaust gas containing nitrogen oxide, a first reduction device configured to inject a second fluid containing ammonia toward the first exhaust gas and provide a second exhaust gas having a reduced nitrogen oxide content than the first exhaust gas, and a second reduction device configured to receive the second exhaust gas and react a third fluid containing ammonia with the second exhaust gas over a nitrogen oxide removal catalyst to remove nitrogen oxide from the second exhaust gas; wherein a nitrogen oxide content (N1) of the first exhaust gas, an ammonia supply amount (Q1) to the first reduction device, and an ammonia supply amount (Q2) to the second reduction device satisfy the following relational expression 1.

[0009] [Relationship 1]

[0010] 0.95 ≤ (Q1+Q2) / N1 ≤ 1

[0011] The nitrogen oxide content (N2) of the second exhaust gas and the ammonia supply amount (Q2) to the second reduction device can satisfy the following relationship 2.

[0012] [Relationship 2]

[0013] 0.95 ≤ Q2 / N2 ≤ 1

[0014] The above first reduction device may be configured to perform a selective non-catalytic reduction reaction (SNCR) using the second fluid as a reducing agent.

[0015] The temperature of the first exhaust gas in contact with the sprayed second fluid may be 900 to 1,000°C.

[0016] The first reduction device may include a pipe extending into the combustion facility and a nozzle configured to spray the second fluid from the pipe.

[0017] The second reduction device may be configured to perform a selective catalytic reduction (SCR) reaction using the third fluid as a reducing agent.

[0018] The second reduction device may be configured such that the third fluid is supplied to the front end of the second reduction device based on the flow of the second exhaust gas, and the catalyst for removing nitrogen oxides may be positioned at the rear end of the second reduction device.

[0019] The above nitrogen oxide reduction system may further include a nitrous oxide decomposition catalyst that is disposed at the rear end of the first reduction device and catalyzes a reduction reaction of nitrous oxide contained in the second exhaust gas.

[0020] The above catalyst for decomposing nitrogen oxide is accommodated inside the second reduction device, and the third fluid can be supplied into the inside of the second reduction device between the catalyst for decomposing nitrogen oxide and the catalyst for removing nitrogen oxide.

[0021] Based on the flow of the second exhaust gas, a third reduction device may be further included, which is arranged between the first reduction device and the second reduction device, and which receives the second exhaust gas, but is configured to treat nitrous oxide of the second exhaust gas on a catalyst for decomposing nitrous oxide.

[0022] The internal temperature of the third reduction device may be 350 to 600°C.

[0023] The above catalyst for decomposing nitrogen oxide may include at least one of a precious metal, a transition metal, and an alloy thereof.

[0024] The above catalyst for decomposing nitrogen oxide may be supported on a support containing zeolite.

[0025] The internal temperature of the second reduction device may be 200 to 400°C.

[0026] The above catalyst for removing nitrogen oxides may include any one of vanadium (V), tungsten (W), molybdenum (Mo), and a combination thereof.

[0027] The above catalyst for removing nitrogen oxides may be in a form in which active metal particles are supported on a support containing titanium (Ti).

[0028] A nitrogen oxide reduction system according to exemplary embodiments of the present invention provides a system that combines selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR). This system effectively removes nitrogen oxides and nitrous oxides contained in exhaust gas generated by ammonia combustion. In particular, the removal efficiency of nitrogen oxides and nitrous oxides can be further improved by optimizing the nitrogen oxide and reducing agent content.

[0029] The various advantageous and beneficial effects of the present invention are not limited to the above-described contents, and will be more easily understood in the course of explaining specific embodiments of the present invention.

[0030] FIG. 1 is a process diagram illustrating a nitrogen oxide reduction system according to exemplary embodiments.

[0031] FIG. 2 is a process diagram illustrating a nitrogen oxide reduction system according to other exemplary embodiments.

[0032] FIG. 3 is a process diagram illustrating a nitrogen oxide reduction system according to further exemplary embodiments.

[0033] Figure 4 is a graph showing the conversion rate of nitrogen oxide and the amount of ammonia slip according to the amount of ammonia supplied.

[0034] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, it should be noted that the terms and words used in this specification and claims should not be construed as limited to their conventional or dictionary meanings. Based on the principle that the inventor can appropriately define the concepts of terms to best explain his or her invention, they should be interpreted in a way that aligns with the technical spirit of the present invention.

[0035] Hereinafter, when explaining with reference to drawings, identical or corresponding components are given the same drawing reference numerals and redundant descriptions thereof are omitted.

[0036] In the embodiments below, the terms first, second, etc. are not used in a limiting sense, but are used for the purpose of distinguishing one component from another.

[0037] In the following embodiments, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0038] In the examples below, terms such as “include” or “have” mean that a feature or component described in the specification is present, and do not preclude the possibility that one or more other features or components may be added.

[0039] For convenience of explanation, the sizes of components in the drawings may be exaggerated or reduced. For example, the sizes and thicknesses of each component shown in the drawings are arbitrarily indicated for convenience of explanation, and thus the present invention is not necessarily limited to what is shown.

[0040] If a particular embodiment is capable of being implemented differently, a particular process sequence may be performed in a different order than described. For example, two processes described in succession may be performed substantially simultaneously, or in a reverse order from the described order.

[0041] In addition, when describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description is omitted.

[0042]

[0043] Hereinafter, nitrogen oxide reduction systems according to exemplary embodiments of the present invention will be specifically described. The configuration of the nitrogen oxide reduction system according to each embodiment described below is intended to illustrate one of the exemplary embodiments, and those skilled in the art will be able to combine the configurations of the nitrogen oxide reduction system described below in various ways.

[0044]

[0045] (Example 1)

[0046] FIG. 1 is a process diagram illustrating a nitrogen oxide reduction system (1000) according to exemplary embodiments.

[0047] Referring to FIG. 1, a nitrogen oxide reduction system (1000) includes a combustion facility (100), a first reduction device (200), and a second reduction device (300).

[0048]

[0049] The combustion facility (100) may be configured to combust a first fluid containing ammonia and discharge a first exhaust gas. As the first fluid is combusted, the first exhaust gas may contain nitrogen oxides.

[0050] The combustion facility (100) may be supplied with a first fluid and a fossil fuel. As a non-limiting example, only the first fluid may be supplied to the combustion facility (100). The combustion facility (100) is not particularly limited as long as it is a facility that can obtain thermal energy or electrical energy by combusting a predetermined fuel. As an example, the combustion facility (100) may be any one or more of a coal boiler, a gas turbine, an industrial heating furnace, and a combination thereof.

[0051] The combustion equipment (100) may include an exhaust duct located at the top so as to discharge a first exhaust gas containing nitrogen oxides. In the present invention, nitrogen oxides are oxides that can be generated by burning a raw material containing nitrogen (N), and may be at least one of NO, NO2, and N2O.

[0052] The exhaust duct can guide the flow of the first exhaust gas by forming a negative pressure at the top of the combustion equipment (100) so that the first exhaust gas can flow to the top of the combustion equipment (100).

[0053] The combustion equipment (100) may include a sensor configured to sense the content of nitrogen oxides contained in the first exhaust gas. As one example, the sensor may be a NOx sensor. As another example, the sensor may be a nitrous oxide sensor. As yet another example, the sensor may be a NOx sensor and a nitrous oxide sensor.

[0054]

[0055] The first reduction device (200) may be configured to inject a second fluid containing ammonia toward the first exhaust gas and provide second exhaust gas having a reduced nitrogen oxide content compared to the first exhaust gas. As a result, a flow of the second exhaust gas may be formed toward the rear end of the first reduction device (200).

[0056] The first reduction device (200) may include an on-off valve (not shown) configured to control the supply amount of the second fluid. By controlling the degree of opening of the on-off valve, the supply of the second fluid can be blocked or the injection amount of the second fluid can be controlled.

[0057] As a non-limiting example, the second fluid may comprise 0.2 to 3.0% ammonia by volume, based on the total volume of the second fluid. More specifically, the second fluid may comprise 0.3 to 2.5% ammonia by volume. The second fluid may comprise 0.5 to 2.0% ammonia by volume. The ammonia content of the second fluid may be controlled by diluting the second fluid with air or water.

[0058] The second fluid may be any one of ammonia gas, urea water, ammonia water, and combinations thereof. As a non-limiting example, the second fluid may be provided to the first reduction device (200) by vaporizing at least one of urea water and ammonia water.

[0059] According to exemplary embodiments, the first reduction device (200) may be configured to perform a Selective Non-Catalytic Reduction (SNCR) using the second fluid as a reducing agent. This reduces nitrogen oxides contained in the first exhaust gas, thereby reducing the nitrogen oxide content contained in the first exhaust gas.

[0060] The reduction treatment of nitrogen oxides can follow the following reaction formulas.

[0061] [Reaction Formula 1]

[0062] 4NH3+ 4NO + O2→ 4N2+ 6H2O

[0063] [Reaction Formula 2]

[0064] 8NH3+ 6NO2+ O2→ 7N2+ 12H2O

[0065] [Reaction Formula 3]

[0066] 2NH3+ 3N2O → 4N2+ 3H2O

[0067] [Reaction Formula 4]

[0068] 2N2O → 2N2+ O2

[0069]

[0070] According to exemplary embodiments, the temperature of the first exhaust gas in contact with the sprayed second fluid may be 900 to 1,000°C.

[0071] The SNCR reaction is a process that reduces a target substance using a reducing agent without the intervention of a catalyst. The SNCR reaction of nitrogen oxides requires relatively high thermal energy. Therefore, a higher temperature of the first flue gas in contact with the second fluid is advantageous.

[0072] According to exemplary embodiments, the first reduction device (200) may be positioned adjacent to the combustion facility (100). Due to the combustion reaction within the combustion facility (100), the first exhaust gas may contain high thermal energy. Therefore, the efficiency of the nitrogen oxide reduction system (1000) may be improved by utilizing the sensible heat of the first exhaust gas for the reduction reaction of nitrogen oxide.

[0073] According to other exemplary embodiments, the first reduction device (200) may be installed inside the combustion facility (100). More specifically, the first reduction device (200) may be installed inside the combustion facility (100) to inject the second fluid countercurrently with respect to the first exhaust gas. Alternatively, the first reduction device (200) may be installed to inject the second fluid cocurrently with respect to the first exhaust gas. Accordingly, there is no need to provide a separate device or reactor for receiving the first exhaust gas from the combustion facility (100), thereby reducing the usable area of ​​the nitrogen oxide reduction system (1000). In addition, since the management items of the nitrogen oxide reduction system (1000) are reduced, maintenance of the nitrogen oxide reduction system (1000) may be simplified.

[0074] More specifically, the first reduction device (200) may include a pipe (210) extending into the interior of the combustion facility (100) and a nozzle (220) configured to spray a second fluid from the pipe. As a result, the second fluid can be directly sprayed onto the first exhaust gas flowing inside the combustion facility (100). In this case, the sensible heat of the first exhaust gas can be directly utilized as thermal energy required for the reduction reaction of nitrogen oxides. As a result, the second fluid and the first exhaust gas react, so that the nitrogen oxides contained in the first exhaust gas are reduced, and the second exhaust gas with a reduced nitrogen oxide content can be provided.

[0075] The pipe (210) and nozzle (220) of the first reduction device (200) are not particularly limited as long as they can be used in a high temperature environment.

[0076] The first reduction device (200) may include an on-off valve (not shown) configured to control the spray amount of the second fluid. By controlling the degree of opening of the on-off valve, the supply of the second fluid can be blocked or the spray amount of the second fluid can be controlled.

[0077] The first reduction device (200) may include a sensor configured to measure the ammonia content contained in the second fluid. The nitrogen oxide reduction system (1000) may receive the measured ammonia content data and control the injection amount of the second fluid.

[0078] The first reduction device (200) may include a sensor configured to measure the content of nitrogen oxides contained in the second exhaust gas. The sensor included in the first reduction device (200) may be of a different or identical type to the sensor included in the combustion equipment (100). As one example, the sensor may be a NOx sensor. As another example, the sensor may be a nitrous oxide sensor. As yet another example, the sensor may be a NOx sensor and a nitrous oxide sensor.

[0079] The content of nitrogen oxides contained in the second exhaust gas can be reduced by 30 to 60% compared to the content of nitrogen oxides contained in the first exhaust gas.

[0080]

[0081] The second reduction device (300) may be configured to receive the second exhaust gas and remove nitrogen oxides of the second exhaust gas.

[0082] According to exemplary embodiments, the second reduction device (300) can react a third fluid containing ammonia with the second exhaust gas over a catalyst for removing nitrogen oxides. As a result, nitrogen oxides contained in the second exhaust gas are reduced, thereby reducing the nitrogen oxide content.

[0083] As a non-limiting example, the third fluid may comprise 0.2 to 3.0% ammonia by volume, based on the total volume of the third fluid. More specifically, the third fluid may comprise 0.3 to 2.5% ammonia by volume. The third fluid may comprise 0.5 to 2.0% ammonia by volume. The ammonia content of the third fluid may be controlled by diluting the second fluid with air or water.

[0084] The third fluid may be any one of ammonia gas, urea water, ammonia water, and a combination thereof. As a non-limiting example, the third fluid may be provided to the second reduction device (300) by vaporizing at least one of urea water and ammonia water.

[0085] The second exhaust gas has a relatively lower nitrogen oxide content than the first exhaust gas. Therefore, reducing the second exhaust gas under high-temperature conditions to remove nitrogen oxides may be relatively inefficient. However, the nitrogen oxide reduction system (1000) according to exemplary embodiments includes a second reduction device (300) that processes the second exhaust gas on a catalyst. Therefore, nitrogen oxides in the second exhaust gas can be effectively reduced even at relatively low temperatures. The nitrogen oxide reduction reaction may follow one or more of the reaction schemes 1 to 4 described above.

[0086] The second reduction device (300) may be configured to perform a selective catalytic reduction (SCR) reaction using a third fluid as a reducing agent.

[0087] The internal temperature of the second reduction device (300) may be 200 to 400°C. The second reduction device (300) can reduce nitrogen oxides in the second exhaust gas at relatively low temperatures. This reduces the load on the device and improves the stability of the device.

[0088] If the internal temperature of the second reduction device (300) is below 200°C, the reduction treatment efficiency of the second exhaust gas may be poor. If the internal temperature of the second reduction device (300) exceeds 400°C, the active metal particles included in the catalyst of the second reduction device (300) may agglomerate and become inactivated. In addition, the ammonia included in the third fluid may react with oxygen first and be consumed. As a result, the reduction treatment efficiency of the second exhaust gas may be reduced.

[0089] According to exemplary embodiments, the second reduction device (300) may include a spray device (310) and a catalyst for removing nitrogen oxides (320).

[0090] The spray device (310) may be configured to supply the third fluid to the second reduction device (300). More specifically, the spray device (310) may provide the third fluid to the front end of the second reduction device (300). This enables uniform mixing of the third fluid and the second exhaust gas, thereby improving the reduction reaction efficiency of the second exhaust gas.

[0091] As one example, the spray device (310) may include a pipe extending into the interior of the second reduction device (300) and a nozzle configured to spray a third fluid from the pipe. As another example, the spray device (310) may be a sprinkler that sprays a third fluid into the interior of the second reduction device (300).

[0092] The spray device (310) may include an on-off valve (not shown) configured to control the supply amount of the third fluid. By controlling the degree of opening of the on-off valve, the supply of the third fluid can be blocked or the spray amount of the third fluid can be controlled.

[0093] The spray device (310) can supply the third fluid in parallel with the second exhaust gas. This allows for improving the contact efficiency between the second exhaust gas and the third fluid without impeding the flow of the second exhaust gas within the second reduction device (300).

[0094] The second reduction device (300) may include a sensor configured to measure the ammonia content contained in the third fluid. The nitrogen oxide reduction system (1000) may receive the measured ammonia content data and control the injection amount or ammonia content of the third fluid.

[0095] A catalyst (320) for removing nitrogen oxides may be placed at the rear end of the second reduction device (300). As a result, before the discharge of the second exhaust gas, the reaction speed of the second exhaust gas can be improved, thereby effectively removing nitrogen oxides contained in the second exhaust gas.

[0096] The catalyst (320) for removing nitrogen oxides may include any one of iron (Fe), copper (Cu), tin (Sn), manganese (Mn), cerium (Ce), vanadium (V), tungsten (W), molybdenum (Mo), and combinations thereof.

[0097] A catalyst for removing nitrogen oxides may be in the form of active metal particles supported on a support containing titanium (Ti). Using a supported catalyst for removing nitrogen oxides increases the surface area of ​​the active metal particles and improves the durability of the catalyst. Consequently, the activity of the catalyst for removing nitrogen oxides can be enhanced, thereby increasing the nitrogen oxide reduction efficiency.

[0098] As a non-limiting example, the catalyst (320) for removing nitrogen oxides may be provided inside the second reduction device (300) in the form of a plate. The catalyst (320) for removing nitrogen oxides may be provided inside the second reduction device (300) in the form of a honeycomb. The catalyst (320) for removing nitrogen oxides may be provided inside the second reduction device (300) in the form of a corrugated board. Such catalysts (320) for removing nitrogen oxides may be provided in multi-stages inside the second reduction device (300).

[0099] The content of nitrogen oxides contained in the treated gas that has passed through the second reduction device (300) may be 5 to 50 ppm in volume% based on the total volume of the treated gas.

[0100] The content of nitrogen oxides contained in the treated gas passing through the second reduction device (300) can be reduced by 70 to 95% compared to the content of nitrogen oxides contained in the second exhaust gas.

[0101]

[0102] The nitrogen oxide reduction system (1000) can control the ammonia supply amount (Q1) to the first reduction device (200) and the ammonia supply amount (Q2) to the second reduction device based on the nitrogen oxide content of the first exhaust gas.

[0103] According to exemplary embodiments, the nitrogen oxide reduction system (1000) can control the nitrogen oxide content (N1) of the first exhaust gas, the ammonia supply amount (Q1) to the first reduction device, and the ammonia supply amount (Q2) to the second reduction device so as to satisfy the following relationship 1.

[0104] [Relationship 1]

[0105] 0.95 ≤ (Q1+Q2) / N1 ≤ 1

[0106] If the total ammonia supply amount (Q1+Q2) fed into the nitrogen oxide reduction system (1000) is less than the nitrogen oxide content (N1) of the first exhaust gas (if it is less than 0.95 in the above relational expression 1), the conversion rate of nitrogen oxides may decrease. In this case, the exhaust gas discharged from the second reduction device (300) may contain a large amount of nitrogen oxides. As the supply amount of ammonia used as a reducing agent increases, the conversion rate of nitrogen oxides can be improved. However, if an excessive amount of ammonia is fed compared to the nitrogen oxide content (N1) of the first exhaust gas (if it exceeds 1 in the above relational expression 1), excessive ammonia slip (NH3slip), in which unreacted ammonia is discharged, may occur, which may lower the efficiency of the nitrogen oxide reduction system (1000). In addition, corrosion of the nitrogen oxide removal catalyst (320) may be caused, which may increase the maintenance cost of the second reduction device (300) and shorten its lifespan.

[0107] As a non-limiting example, the ammonia supply amount (Q1) to the first reduction device can be controlled by any one of the following methods: supply amount control of the second fluid, ammonia content control of the second fluid, and a combination thereof. The ammonia supply amount (Q2) to the second reduction device can be controlled by any one of the following methods: supply amount control of the third fluid, ammonia content control of the third fluid, and a combination thereof.

[0108]

[0109] The nitrogen oxide reduction system (1000) can control the nitrogen oxide content (N2) of the second exhaust gas and the ammonia supply amount (Q2) to the second reduction device (300) so as to satisfy the following relationship 2.

[0110] [Relationship 2]

[0111] 0.95 ≤ Q2 / N2 ≤ 1

[0112] In this way, the ammonia supply amount (Q2) to the second reduction device (300) can be determined by the nitrogen oxide content (N2) of the second exhaust gas. If the ammonia supply amount (Q2) to the second reduction device (300) is less than the nitrogen oxide content (N2) of the second exhaust gas (less than 0.95 in the above relational expression 2), the nitrogen oxide conversion rate of the second reduction device (300) may decrease. Conversely, if an excessive amount of ammonia is supplied compared to the nitrogen oxide content (N2) of the second exhaust gas (exceeding 1 in the above relational expression 2), the efficiency of the second reduction device (300) may deteriorate, resulting in excessive ammonia slip.

[0113]

[0114] As a non-limiting example, the amount of third fluid supplied to the second reduction device (300) may be determined based on the ammonia content contained in the second exhaust gas. Alternatively, the ammonia content of the third fluid may be determined based on the ammonia content contained in the second exhaust gas.

[0115] The second exhaust gas supplied to the rear end of the first reduction device (200) may contain unreacted ammonia (NH3). This unreacted ammonia may be supplied to the second reduction device (300). Accordingly, the supply amount of the third gas may be adjusted so that the ammonia supply amount (Q2) to the second reduction device (300) satisfies the above-described relational expression 2. As an example, if unreacted ammonia remains in the second exhaust gas, the supply amount of the third gas may be reduced.

[0116]

[0117] From the above, the nitrogen oxide reduction system (1000) can effectively reduce nitrogen oxides in exhaust gas generated by ammonia combustion by linking the first reduction device (200) and the second reduction device (300). In addition, the nitrogen oxide conversion rate can be improved by controlling the supply amounts of the second fluid and the third fluid so that the ammonia supply amounts to the first reduction device (200) and the second reduction device (300) satisfy the above-described relational expressions 1 and 2.

[0118]

[0119] (Example 2)

[0120] FIG. 2 is a process diagram illustrating a nitrogen oxide reduction system (2000) according to other exemplary embodiments.

[0121] Referring to FIG. 2, the nitrogen oxide reduction system (2000) may further include a nitrous oxide (N2O) decomposition catalyst that catalyzes the reduction reaction of nitrous oxide. According to exemplary embodiments, the nitrogen oxide reduction system (2000) may further include a third reduction device (400) that accommodates the nitrous oxide decomposition catalyst.

[0122] Nitrous oxide is a more stable substance than other nitrogen oxides (NOx). Therefore, removing nitrous oxide requires relatively more heat energy than other nitrogen oxides (NOx). To efficiently supply the heat required for the reduction reaction of nitrous oxide, a catalyst for decomposing nitrous oxide is placed at the rear end of the first reduction device (200) to catalyze the reduction reaction of nitrogen dioxide contained in the second exhaust gas.

[0123] The reaction temperature in the first reduction device (200) is a high temperature of 900°C or higher. Therefore, the second flue gas, which is the process gas of the first reduction device (200), can also have a high sensible heat. Accordingly, the catalyst for decomposing nitrous oxide can utilize the sensible heat of the second flue gas by being positioned adjacent to the first reduction device (200). Consequently, the efficiency of the nitrogen oxide reduction system can be improved because there is no need to separately heat the second flue gas for the reduction reaction of nitrous oxide.

[0124] The catalyst for decomposing nitrous oxide may include one or more of a noble metal, a transition metal, and an alloy thereof. As non-limiting examples, the noble metal may include one or more of ruthenium (Ru), platinum (Pt), rhodium (Rh), and an alloy thereof. The transition metal may include one or more of iron (Fe), cobalt (Co), copper (Cu), and an alloy thereof.

[0125] The catalyst for decomposing nitrogen oxides may be provided in a form supported on a support comprising a zeolite. As a non-limiting example, the zeolite may include one or more structures selected from the group consisting of FER, MFI, BEA, and FAU. More specifically, the zeolite may be a zeolite having a BEA structure. FER and MFI are mesoporous zeolites. BEA and FAU are macroporous zeolites. The pore size of a zeolite may be expressed based on the number of TO4 tetrahedra forming the smallest 'ring' that restricts molecular diffusion within the pore.

[0126] As a non-limiting example, the catalyst for decomposing nitrous oxide may be provided in a plate form. The catalyst for decomposing nitrous oxide (330) may be provided in a honeycomb form. The catalyst for decomposing nitrous oxide (330) may be provided in a corrugated form.

[0127] According to exemplary embodiments, the third reduction device (400) may be configured to treat nitrous oxide of the second exhaust gas on a catalyst for decomposing nitrous oxide.

[0128] The third reduction device (400) may be positioned between the first reduction device (200) and the second reduction device (300) based on the flow of the second exhaust gas. As a result, the second exhaust gas received by the third reduction device (400) may pass through a catalyst for decomposing nitrous oxide and be discharged to the outside of the third reduction device (400). Therefore, the third reduction device (400) may receive the second exhaust gas and reduce the nitrous oxide in the second exhaust gas. In addition, the third reduction device (400) may provide the second exhaust gas with reduced nitrous oxide to the second reduction device (300).

[0129] The internal temperature of the third reduction device (400) may be 350 to 600°C. In order to reduce stable nitrous oxide, the internal temperature of the third reduction device (400) must be 350°C or higher. However, if the internal temperature of the third reduction device (400) exceeds 600°C, the third reduction device (400) may be overloaded, which may reduce stability and may cause deactivation of the catalyst for decomposing nitrous oxide.

[0130] According to exemplary embodiments, the third reduction device (400) may not be supplied with a separate reducing agent except for the second exhaust gas. The reduction treatment of nitrous oxide may be performed through a reaction using a reducing agent (see Reaction Scheme 3 above) and a direct decomposition reaction (see Reaction Scheme 4 above). The third reduction device (400) may reduce nitrous oxide using unreacted ammonia included in the second exhaust gas as a reducing agent. Even if the second exhaust gas does not contain unreacted ammonia, the third reduction device (400) may reduce nitrous oxide through a direct decomposition reaction of nitrous oxide. However, this is only one of the exemplary embodiments of the present invention, and a person skilled in the art will be able to supply a reducing agent containing ammonia to the third reduction device (400) as needed.

[0131] In addition, since the configuration overlapping with the nitrogen oxide reduction system described in the above-described Example 1 can be equally applied to the nitrogen oxide system according to the present embodiment, a detailed description thereof will be omitted.

[0132]

[0133] (Example 3)

[0134] FIG. 3 is a process diagram illustrating a nitrogen oxide reduction system (3000) according to further exemplary embodiments.

[0135] Referring to FIG. 3, a catalyst (330) for decomposing nitrous oxide can be accommodated inside the second reduction device (301).

[0136] The catalyst (330) for decomposing nitrous oxide may be placed in front of the second reduction device (301). The catalyst (320) for removing nitrogen oxide may be placed in the rear of the second reduction device (301). The third fluid may be supplied between the catalyst (330) for decomposing nitrous oxide and the catalyst (320) for removing nitrogen oxide.

[0137] The second reduction device (301) may have a temperature distribution of 350 to 500°C at the front end where the catalyst for decomposing nitrogen oxides (330) is located, and a temperature distribution of 200 to 400°C at the rear end where the catalyst for removing nitrogen oxides (320) is located.

[0138] In this way, by including a catalyst (330) for decomposing nitrous oxide in the second reduction device (301), the nitrogen oxide treatment efficiency of the second reduction device (301) can be further improved. Furthermore, the efficiency of the nitrogen oxide reduction system (3000) can be further enhanced. In addition, since nitrous oxide can be removed together with nitrogen oxide in one reactor, there is an effect of enabling an efficient process configuration by minimizing the overall process area.

[0139] In addition, since the configuration overlapping with the nitrogen oxide reduction system described in the above-described examples 1 and 2 can be equally applied to the nitrogen oxide system according to the present embodiment, a detailed description thereof will be omitted.

[0140] Experimental Example 1: Confirming the Effect of Ammonia Supply Control

[0141] The conversion rate of nitrogen oxides according to the ammonia supply was analyzed by simulating a second reduction device. Since the nitrogen oxides generated during ammonia combustion are mostly identified as NO, the experiment was conducted targeting NO.

[0142] 1,500 ppm of NO was supplied to the reactor simulating the second reduction device. Air containing a predetermined ammonia concentration was supplied as a reducing agent. At this time, the space velocity (GHSV) of the reactor was 6,300 h-1 Controlled by .

[0143] Figure 4 is a graph showing the conversion rate of nitrogen oxide and the amount of ammonia slip according to the amount of ammonia supplied.

[0144] Referring to Fig. 4, it was confirmed that the conversion rate of NO increased as the ratio of ammonia / NO increased. In addition, it was confirmed that the conversion rate of NO decreased rapidly in the section where the ratio of ammonia / NO was less than 0.95. It was confirmed that the amount of unreacted ammonia also increased as the ratio of ammonia / NO increased. However, when the ratio of ammonia / NO was 1 or less, the amount of unreacted ammonia generated was about 1.5% of the input ammonia, and it was confirmed that the amount of ammonia slip generated was not large.

[0145] From the above, it was confirmed that when the ratio of ammonia / NO was controlled to 0.95 to 1, the nitrogen oxide conversion rate could be maximized and ammonia slip could be minimized.

[0146]

[0147] The present invention has been described in more detail through drawings and examples. However, the configurations described in the drawings or examples described in this specification are merely embodiments of the present invention and do not represent all of the technical ideas of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as of the time of this application.

[0148] (Explanation of symbols)

[0149] 1000,2000,3000: Nitrogen oxide reduction system

[0150] 100: Combustion equipment

[0151] 200: First reduction system

[0152] 300: Second reduction system

[0153] 310: Spray device

[0154] 320: Catalyst for nitrogen oxide removal

[0155] 330: Catalyst for decomposition of nitrous oxide

Claims

1. A combustion facility configured to combust a first fluid containing ammonia and discharge a first exhaust gas containing nitrogen oxide; A first reduction device configured to inject a second fluid containing ammonia toward the first exhaust gas and provide a second exhaust gas having a reduced nitrogen oxide content than the first exhaust gas; and A second reduction device configured to receive the second exhaust gas and react a third fluid containing ammonia on a catalyst for removing nitrogen oxides to remove the second exhaust gas and nitrogen oxides of the second exhaust gas; A nitrogen oxide reduction system in which the nitrogen oxide content (N1) of the first exhaust gas, the ammonia supply amount (Q1) to the first reduction device, and the ammonia supply amount (Q2) to the second reduction device satisfy the following relationship 1. [Relationship 1] 0.95 ≤ (Q1+Q2) / N1 ≤ 1 2. In paragraph 1, A nitrogen oxide reduction system in which the nitrogen oxide content (N2) of the second exhaust gas and the ammonia supply amount (Q2) to the second reduction device satisfy the following relationship 2. [Relationship 2] 0.95 ≤ Q2 / N2 ≤ 1 3. In paragraph 1, The above first reduction device is, A nitrogen oxide reduction system configured to perform a selective non-catalytic reduction reaction (SNCR) using the second fluid as a reducing agent.

4. In paragraph 1, A nitrogen oxide reduction system in which the temperature of the first exhaust gas in contact with the sprayed second fluid is 900 to 1,000°C.

5. In paragraph 1, The above first reduction device is, A nitrogen oxide reduction system comprising a pipe extending into the combustion facility and a nozzle configured to spray the second fluid from the pipe.

6. In paragraph 1, The above second reduction device is, A nitrogen oxide reduction system configured to perform a selective catalytic reduction reaction (SCR) using the third fluid as a reducing agent.

7. In paragraph 1, The above second reduction device is, A nitrogen oxide reduction system in which the third fluid is supplied to the front end of the second reduction device based on the flow of the second exhaust gas, and the nitrogen oxide removal catalyst is located at the rear end of the second reduction device.

8. In paragraph 1, The above nitrogen oxide reduction system is a nitrogen oxide reduction system further including a nitrous oxide decomposition catalyst that is arranged at the rear end of the first reduction device and catalyzes a reduction reaction of nitrous oxide contained in the second exhaust gas.

9. In paragraph 8, The above catalyst for decomposing nitrogen oxide is accommodated inside the second reduction device, A nitrogen oxide reduction system in which the third fluid is supplied into the interior of the second reduction device between the catalyst for decomposing nitrogen oxide and the catalyst for removing nitrogen oxide.

10. In paragraph 8, Based on the flow of the second exhaust gas, it is placed between the first reduction device and the second reduction device, A nitrogen oxide reduction system further comprising a third reduction device configured to receive the second exhaust gas and treat nitrous oxide of the second exhaust gas on a nitrous oxide decomposition catalyst.

11. In paragraph 10, A nitrogen oxide reduction system having an internal temperature of the third reduction device of 350 to 600°C.

12. In paragraph 8, The above-mentioned catalyst for decomposing nitrogen oxides is a nitrogen oxide reduction system comprising at least one of a precious metal, a transition metal, and an alloy thereof.

13. In paragraph 8, A nitrogen oxide reduction system in which the above-mentioned catalyst for decomposing nitrogen oxide is supported on a support containing zeolite.

14. In paragraph 1, A nitrogen oxide reduction system having an internal temperature of the second reduction device of 200 to 400°C.

15. In paragraph 1, A nitrogen oxide reduction system wherein the above nitrogen oxide removal catalyst comprises one of vanadium (V), tungsten (W), molybdenum (Mo), and a combination thereof.

16. In paragraph 1, The above nitrogen oxide removal catalyst is a nitrogen oxide reduction system in which active metal particles are supported on a support containing titanium (Ti).

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