Denitration catalyst and method for removing nitrogen oxide from combustion exhaust gas

Abstract

Provided are a denitration catalyst having high wear resistance and peeling resistance, and a method for removing nitrogen oxide from combustion exhaust gas. A denitration catalyst according to the present disclosure has a molded body containing a catalyst component, has cracks on the surface of the molded body, has a crack width of 10 μm or more, and has four or less cracks / mm2 that have an angle formed with a gas flow direction of -90° to -45° inclusive or 45° to 90° inclusive.

Description

Denitrification catalyst and method for removing nitrogen oxides from combustion exhaust gas

[0001] The present disclosure relates to denitration catalysts and methods for removing nitrogen oxides from combustion exhaust gases.

[0002] Ammonia (NH ３ ) and a catalyst that promotes the reaction, the oxygen in NOx is separated and nitrogen (N ２ ) and water (H ２ O) is known.

[0003] For example, Patent Document 1 listed below discloses a denitration catalyst for ammonia catalytic reduction that is resistant to wear due to dust in exhaust gases and has high denitration activity, and is obtained by co-impregnating the catalyst with 0.01 to 10% by weight of a water-soluble vanadium compound and 0.1 to 20% by weight of a water-soluble binder, followed by drying and calcining.

[0004] Japanese Unexamined Patent Publication No. 58-202046

[0005] However, there has been a demand for further improvements in wear resistance and peeling resistance that exceed the performance of the denitration catalyst described in Patent Document 1.

[0006] In view of the above problems, the present disclosure aims to provide a denitration catalyst having high resistance to wear and peeling, and a method for removing nitrogen oxides from combustion exhaust gas.

[0007] In order to solve the above-mentioned problems and achieve the object, the denitration catalyst according to the present disclosure has a molded body containing a catalytic component, and the molded body has cracks on the surface, the cracks have a width of 10 μm or more, and the number of the cracks per area that form an angle with the gas flow direction of −90° to −45° or 45° to 90° is 4 / mm ２ The following is the result.

[0008] In order to solve the above-mentioned problems and achieve the object, the method for removing nitrogen oxides from combustion exhaust gas according to the present disclosure comprises the steps of treating combustion exhaust gas containing nitrogen oxides in the presence of a denitration catalyst made of a molded body containing a catalytic component and having cracks on the surface of the molded body, and the surface of the molded body has cracks with a width of 10 μm or more and a number of cracks per area of ​​4 / mm2 that form an angle with the gas flow direction of -90° to -45° or 45° to 90°. ２ The following is the result.

[0009] According to the present disclosure, it is possible to provide a denitration catalyst having high resistance to wear and peeling, and a method for removing nitrogen oxides from combustion exhaust gas.

[0010] FIG. 1 is a diagram illustrating an example application of a denitration device according to the present disclosure. FIG. 2 is a diagram illustrating a first embodiment of a denitration catalyst according to the present disclosure. FIG. 3 is a diagram illustrating a second embodiment of a denitration catalyst according to the present disclosure. FIG. 4 is a diagram illustrating an optical microscope image of a randomly selected region on the surface of Example 1 of the denitration catalyst according to the present disclosure. FIG. 5 is a diagram illustrating an optical microscope image of a randomly selected region on the surface of Example 2 of the denitration catalyst according to the present disclosure. FIG. 6 is a diagram illustrating an optical microscope image of a randomly selected region on the surface of Comparative Example 1 of the denitration catalyst according to the present disclosure. FIG. 7 is a diagram illustrating an optical microscope image of a randomly selected region on the surface of Comparative Example 2 of the denitration catalyst according to the present disclosure. FIG. 8 is a diagram illustrating the definition of the angle of cracks that occur in the denitration catalyst according to the present disclosure. FIG. 9 is a diagram illustrating the number of cracks per area at θ = 45 to 90° that occur in the denitration catalyst according to the present disclosure. Fig. 10 is a diagram showing the ratio of cracks with θ = 45 to 90° to the total number of cracks that occur in the denitration catalyst according to the present disclosure. Fig. 11 is a diagram showing the evaluation conditions for the amount of wear according to the present disclosure. Fig. 12 is a diagram showing the results of the evaluation of the amount of wear for each catalyst according to the present disclosure. Fig. 13 is a diagram explaining the mechanism by which wear or peeling occurs.

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to the embodiments described below.

[0012] (Overview of Denitration Catalyst) The denitration catalyst of the present disclosure is used as part of an exhaust gas treatment device that reduces nitrogen oxides (NOx) emitted from combustion equipment that burns fuel and emits exhaust gas containing nitrogen oxides, such as coal-fired boilers, gas turbine combined cycles (GTCC), gas turbine simple cycles (GTSC), and boilers that burn inferior fuels such as petrocoke and heavy oil, for example, various thermal power plants.

[0013] Hereinafter, the denitration catalyst of the present disclosure will be referred to as a denitration device for exhaust gas from a thermal power plant, but the denitration catalyst of the present disclosure can also be used as a denitration catalyst for denitration devices in various combustion appliances whose exhaust gas contains nitrogen oxides. The denitration catalyst of the present disclosure has excellent abrasion resistance, inhibits deterioration of denitration performance, and has a long life. The denitration catalyst of the present disclosure can be suitably used to remove nitrogen oxides from combustion exhaust gas containing a large amount of soot from coal-fired boilers, coal-biomass co-firing boilers, and the like.

[0014] In a thermal power plant, a denitration device is disposed in a flue 1 through which combustion exhaust gas flows. An example of the location of the denitration device according to the present disclosure will be described using FIG. 1 . FIG. 1 is a diagram showing an application example of the denitration device according to the present disclosure. As shown in FIG. 1 , the denitration device 10 according to the present disclosure is disposed inside the flue 1 through which the combustion exhaust gas flows, in a direction perpendicular to the gas flow direction, so as to straddle the flue. The denitration device 10 includes a denitration catalyst that promotes a reduction reaction of nitrogen oxides (NOx) in the combustion exhaust gas.

[0015] (Denitration catalyst) The denitration catalyst of the present disclosure is composed of a molded body containing a catalytic component. The molded body constituting the denitration catalyst of the present disclosure can have a shape such as a honeycomb, a plate, or a corrugated board.

[0016] FIG. 2 is a schematic diagram of the structure of a honeycomb catalyst as a first embodiment of a denitration catalyst. FIG. 2 is a diagram showing the first embodiment of a denitration catalyst according to the present disclosure. A honeycomb-shaped molded body can be obtained, for example, by extrusion molding a catalyst component. A honeycomb-shaped catalyst (honeycomb catalyst) forms a fixed bed in a denitration device with through-holes in the direction of exhaust gas flow, thereby reducing pressure loss due to gas flow and increasing the exhaust gas velocity compared to catalyst devices packed with fixed-bed catalysts of other shapes. A honeycomb catalyst can efficiently carry out gas contact reactions. Honeycomb catalysts are widely used, for example, for denitration reactions of combustion exhaust gas containing nitrogen oxides generated from boilers, etc.

[0017] FIG. 3 is a schematic diagram of the structure of a plate-shaped catalyst as a second embodiment of a denitration catalyst. FIG. 3 is a diagram showing the second embodiment of the denitration catalyst according to the present disclosure. As shown in FIG. 3, the plate-shaped catalyst has flat portions and ridge portions parallel to the gas flow direction, which regulate the gas flow direction. The plate-shaped catalyst can be obtained by impregnating or applying a catalyst component to a plate-shaped substrate. Examples of the plate-shaped molded body include those having flat portions and ridge portions. Examples of the plate-shaped molded body include those having flat portions and ridge portions. Examples of the plate-shaped molded body include those having flat portions and ridge portions. Multiple plate-shaped molded bodies can be stacked together with the ridge portions abutting the flat portions, leaving gaps between the flat portions.

[0018] A corrugated board-shaped product can be obtained, for example, by stacking a flat plate-shaped product and a corrugated plate-shaped product. A corrugated plate-shaped product or a product having a flat portion and a ridge portion can be obtained, for example, by bending and pressing a flat plate-shaped product.

[0019] Examples of denitration catalysts include those containing, as catalytic components, oxides of titanium, molybdenum, and / or tungsten, and oxides of vanadium (titanium-based catalysts), those containing primarily an aluminosilicate such as zeolite carrying metals such as copper (Cu) and iron (Fe) (zeolite-based catalysts), and those comprising a mixture of the above-mentioned titanium-based catalyst and zeolite-based catalyst, etc. Of these, titanium-based catalysts are preferred.

[0020] Examples of titanium catalysts include Ti-V-W catalysts, Ti-V-Mo catalysts, and Ti-V-W-Mo catalysts.

[0021] The ratio of V element to Ti element is V ２ O ５ / TiO ２ The weight percentage of the Mo element and / or the W element relative to the Ti element is preferably 2% by weight or less, more preferably 1% by weight or less. When an oxide of molybdenum and an oxide of tungsten are used in combination (MoO ３ +WO ３ ) / TiO ２ The weight percentage of is preferably 10% by weight or less, more preferably 5% by weight or less.

[0022] The denitration catalyst can use titanium oxide powder or a titanium oxide precursor as the raw material for the titanium oxide molded body. Examples of titanium oxide precursors include titanium oxide slurry, titanium oxide sol, titanium sulfate, titanium tetrachloride, titanate, and titanium alkoxide. In the present disclosure, a material that forms anatase titanium oxide is preferably used as the raw material for the titanium oxide.

[0023] As a raw material for vanadium oxide, vanadium compounds such as vanadium pentoxide, ammonium metavanadate, and vanadyl sulfate can be used.

[0024] Examples of raw materials for tungsten oxide include ammonium paratungstate, ammonium metatungstate, tungsten trioxide, and tungsten chloride. Examples of raw materials for molybdenum oxide include ammonium molybdate and molybdenum trioxide.

[0025] The molded body used in the denitration catalyst of the present disclosure may contain, as a promoter or additive, an oxide of phosphorus (P), an oxide of sulfur (S), an oxide of aluminum (Al) (e.g., alumina), an oxide of silicon (Si) (e.g., glass fiber), an oxide of zirconium (Zr) (e.g., zirconia), gypsum (e.g., gypsum dihydrate), zeolite, etc. These can be used in the form of powder, sol, slurry, fiber, etc. when producing the molded body.

[0026] (Regarding cracks) The molded body of the denitration catalyst of the present disclosure has cracks on its surface. In images observed with a scanning electron microscope or a digital microscope, the openings of the cracks on the surface of the molded body are darker in color than the background color. Therefore, in the present disclosure, the black areas observed when an image observed with a scanning electron microscope or a digital microscope is converted into two-tone black and white using an image processing device with a pixel size of 2 μm are considered to be cracks. Therefore, cracks smaller than the pixel size cannot be distinguished from the background color and become white in the two-tone conversion, so are excluded from the crack count. Furthermore, cracks are measured at any 10 or more points on the surface of the molded body. Furthermore, the size of one measurement point is 1 mm ２ More than 2 mm ２ The measurement points are set to be at least 5 mm apart from each other.

[0027] Here, the molded body has cracks on the surface, the crack width is 10 μm or more, and the number of cracks having an angle θ with the gas flow direction of −90° to −45° or 45° to 90° is 4 / mm. ２ In other words, the inclination angle of the cracks is such that the cracks closer to the direction perpendicular to the exhaust gas flow direction than the direction of the exhaust gas flow are 4 cracks / mm. ２The angle θ between the crack and the gas flow direction is the angle between a line approximating the crack as a straight line and a line parallel to the gas flow direction. The definition of the angle θ will be described later.

[0028] The molded body preferably has cracks on the surface, the crack width is 10 μm or more, and the number of cracks forming an angle θ of −45° or more and 45° or less with respect to the gas flow direction is 8 or less.

[0029] The molded article preferably has cracks on the surface, and the number of cracks having a width of 10 μm or more is 8 or less.

[0030] Furthermore, it is preferable that the ratio of the number of cracks having a width of 10 μm or more and an angle θ with respect to the gas flow direction of −90° or more and −45° or less, or 45° or more and 90° or less, to the total number of cracks having a width of 10 μm or more, of the molded body is 20% or less.

[0031] The crack area ratio of the molded body is preferably 1% or more and 6% or less, and more preferably 1% or more and 3% or less. Here, the crack area ratio of the molded body is the ratio of the area of ​​the openings of all cracks in one randomly selected area to the predetermined area of ​​the area of ​​the area. The predetermined area is not particularly limited, but for example, it is 1 mm ２ More than 2 mm ２ The area can be as follows:

[0032] The size, direction, and number of cracks in the molded body can be controlled by controlling the amounts of catalyst components, the amount of water, the kneading conditions, the molding conditions, the drying conditions, the calcination conditions, etc. used when preparing the molded body. The greater the variation in the amounts of catalyst components, the amount of water, the molding conditions, the drying conditions, the calcination conditions, etc., the greater the variation in the crack area. Therefore, it is preferable to mold the molded body so that there is no distribution in the amounts of catalyst components and water, and to dry or calcinate the molded body so that there is no distribution in temperature, humidity, etc. Furthermore, it is preferable that the molded body contains a sulfate. A sulfate-containing molded body is preferably produced by impregnating the molded body with an aqueous solution of a water-soluble binder containing a sulfate, followed by calcination. Furthermore, it is preferable that the molded body is produced by impregnating the molded body with an aqueous solution of a water-soluble binder containing a sulfate, followed by drying and calcination. This allows for a denitration catalyst with more suitable cracks.

[0033] During the production of the molded body, it is preferable to prevent squeezing of water due to the pressure applied when molding the catalyst component paste, and / or subsequent seepage of water, in order to reduce the distribution of the amounts of catalyst components and water. Furthermore, during the production of the molded body, it is preferable to reduce the thickness of the molded body, to slow down temperature changes due to heating, and to increase the circulation of gas within the dryer or calciner. By the above-described method, molded bodies having cracks that satisfy the ranges of the present disclosure can be efficiently obtained. The obtained molded body can then be used as is, or molded bodies having the cracks specified in the present disclosure can be selected from the obtained molded bodies and used as a denitration catalyst.

[0034] The method for removing nitrogen oxides from combustion exhaust gas according to the present disclosure includes treating combustion exhaust gas containing nitrogen oxides in the presence of the above-described denitration catalyst according to the present disclosure. The treatment of combustion exhaust gas can reduce nitrogen oxides, for example, by passing the combustion exhaust gas and a reducing agent (ammonia) through a fixed bed packed with the denitration catalyst according to the present disclosure. The denitration catalyst according to the present disclosure is resistant to wear and maintains its denitration performance over a long period of time, even when the combustion exhaust gas contains a large amount of soot. Therefore, it can be suitably used to purify gases emitted from boilers in thermal power plants, factories, and the like.

[0035] (Examples and Comparative Examples) (Example 1) Ammonium molybdate, ammonium metavanadate, phosphoric acid, and silica sol were added to titanium oxide powder, and alumina silicate fibers were further added. The mixture was kneaded while adjusting the moisture content to obtain a catalyst paste. The moisture content was adjusted so that cracks were uniformly formed. This paste was applied to an expanded metal lath and then pressed to obtain a flat molded product. This molded product was dried at 120°C for 1 hour. Next, it was placed in a calcination furnace, the temperature was increased from room temperature to 500°C over 2 hours, maintained at 500°C for 2 hours, and then cooled to room temperature over 2 hours to obtain a molded product. Figure 5 shows optical microscope images of 10 randomly selected regions on the surface of the obtained molded product. Figure 4 shows optical microscope images of randomly selected regions on the surface of the denitration catalyst Example 1 according to the present disclosure.

[0036] As shown in Figure 4, cracks in the molded body of Example 1 exist on the surface of the molded body in every region. Among the cracks in Example 1, several exist with small angles relative to the perpendicular to the gas flow direction. In other words, many of the cracks in Example 1 extend approximately parallel to the gas flow direction. The crack area ratio in Example 1 was 1.0%.

[0037] Example 2 The catalyst of Example 1 was impregnated with an aqueous binder solution containing an optimized sulfate concentration, and the molded article was again dried at 120°C for 1 hour. The molded article was then placed in a calcination furnace, the temperature was raised from room temperature to 500°C over 2 hours, maintained at 500°C for 2 hours, and then cooled to room temperature over 2 hours. A denitration catalyst was obtained in the same manner as in Example 1, except for this. Optical microscope images of 10 randomly selected regions on the surface of the obtained molded article are shown in Figure 5. Figure 5 shows optical microscope images of randomly selected regions on the surface of the denitration catalyst of Example 2 according to the present disclosure.

[0038] As shown in Figure 5, cracks in Example 2 exist on the surface of the molded body in every region. It can be seen that there are multiple cracks in Example 2 that have a small angle with respect to the perpendicular to the gas flow direction, and there are few cracks that have a large angle with respect to the gas flow direction. In other words, it can be said that many of the cracks in Example 2 extend approximately parallel to the gas flow direction. The crack area ratio in Example 2 was 1.3%.

[0039] (Comparative Example 1) A denitration catalyst was obtained in the same manner as in Example 1, except that the water content, drying conditions, and calcination conditions were changed. Observation images of 10 randomly selected regions on the surface of the obtained molded body are shown in Fig. 6. Fig. 6 shows optical microscope observation images of randomly selected regions on the surface of the denitration catalyst of Comparative Example 1 according to the present disclosure.

[0040] As shown in Figure 6, the cracks in Comparative Example 1 spread in a mesh-like pattern across the surface of the molded body in every region. Among the cracks in Comparative Example 1, several cracks were present at large angles relative to the perpendicular to the gas flow direction. In other words, it can be said that several cracks in Comparative Example 1 were present and extended approximately perpendicular to the gas flow direction.

[0041] (Comparative Example 2) A denitration catalyst was obtained in the same manner as in Example 1, except that the water content, drying conditions, and calcination conditions were changed. Observation images of 10 randomly selected regions on the surface of the obtained molded body are shown in Fig. 7. Fig. 7 shows optical microscope observation images of randomly selected regions on the surface of the denitration catalyst of Comparative Example 2 according to the present disclosure.

[0042] As shown in Figure 7, cracks were present on the surface of the compact in every region, although there were variations between regions. It can be seen that there were few cracks with a small angle relative to the perpendicular to the gas flow direction, and many with a large angle. It can also be seen that there were several cracks with large widths.

[0043] (Regarding the Mode of Cracks) The characteristics of the cracks present in the test pieces of Example 1, Comparative Example 1, and Comparative Example 2 described above will be described from the viewpoint of the angle relative to the perpendicular to the gas flow direction.

[0044] The angle θ between a crack and the gas flow direction will be explained using FIG. 8 . FIG. 8 is a diagram illustrating the definition of the angle of a crack that occurs in a denitration catalyst according to the present disclosure. As shown in FIG. 8 , assume that a crack C exists in the denitration catalyst. The crack is approximated to a straight line using the least squares method or the like. The approximated line may also be formed by connecting both ends of the crack with a straight line. The absolute value of the angle between the approximated line thus obtained and the gas flow direction GDR is defined as θ. Note that H shown in FIG. 5 is the length of the approximated line of the crack projected in a direction parallel to the gas flow direction, and W is the length of the approximated line of the crack projected in a direction perpendicular to the gas flow direction. After measuring H and W from the observation image, the angle θ can be calculated using the trigonometric function (θ = 90 - |arctan (W / H) × 180 / π|).

[0045] Next, the unit area (1 mm ) of cracks present in the test pieces of Example 1, Comparative Example 1, and Comparative Example 2, whose angle θ with the gas flow direction is −90° or more and −45° or less, or 45° or more and 90° or less, is calculated. ２ The number of cracks per unit area will be explained using FIG. 9 . FIG. 9 is a diagram showing the number of cracks per area that occur in the denitration catalyst according to the present disclosure, where θ is between -90° and -45° or between 45° and 90°. As shown in FIG. 9 , for Example 1, the number of cracks per unit area where the angle θ with the gas flow direction is between -90° and -45° or between 45° and 90° is one. Furthermore, it is shown that the number of cracks per unit area in Example 1 where the angle θ with the gas flow direction is between -90° and -45° or between 45° and 90° is significantly smaller than those in Comparative Example 1 and Comparative Example 2. Note that, although not shown in FIG. 9 , the number of cracks per unit area in Example 2 where the angle θ with the gas flow direction is between -90° and -45° or between 45° and 90° was similar to that in Example 1.

[0046] Next, the proportion of cracks with a θ of -90° or more and -45° or less, or 45° or more and 90° or less, relative to the total number of cracks present in the test pieces of Example 1, Comparative Example 1, and Comparative Example 2 will be described using FIG. 10 . FIG. 10 is a diagram showing the proportion of cracks with a θ of -90° or more and -45° or less, or 45° or more and 90° or less, relative to the total number of cracks occurring in the denitration catalyst according to the present disclosure. As shown in FIG. 10 , for Example 1, the proportion of cracks with a θ of -90° or more and -45° or less, or 45° or more and 90° or less, relative to the total number of cracks, is shown to be 20% or less. It can also be seen that the proportion of cracks with a θ of -90° or more and -45° or less, or 45° or more and 90° or less, relative to the total number of cracks in Example 1 is significantly smaller than that of Comparative Example 1 and Comparative Example 2. Although not shown in FIG. 10, the ratio of the number of cracks with θ of −90° or more and −45° or less or 45° or more and 90° or less to the total number of cracks in Example 2 was similar to that in Example 1.

[0047] (Test Conditions) Next, the conditions for the evaluation test of the wear amount of the test pieces of Example 1, Comparative Example 1, and Comparative Example 2 will be described with reference to FIG. 11 . FIG. 11 is a diagram showing the evaluation conditions for the wear amount according to the present disclosure. As shown in FIG. 11 , the size of the test piece was 100 mm. Furthermore, a grid called MGH-70 with an average particle size of 500 μm was used. The grid was allowed to fall naturally from a height of 500 mm, and a predetermined amount of grid (8 kg) was allowed to collide with the test piece. The change in weight (wear loss) before and after this collision treatment was measured.

[0048] (Test Results) Next, the results of the evaluation of the amount of wear of the test pieces of Example 1, Comparative Example 1, and Comparative Example 2 will be described with reference to Fig. 9. Fig. 12 is a diagram showing the results of the evaluation of the amount of wear of each catalyst according to the present disclosure. As shown in Fig. 9, it can be seen that the amount of wear of Example 1 and Example 2 is significantly smaller than that of Comparative Example 1 and Comparative Example 2.

[0049] (Regarding the principle) Figure 13 is a diagram illustrating the mechanism by which wear or peeling occurs. As shown in Figure 13, it is believed that when dust particles D1 and D2 contained in the combustion exhaust gas collide with the edges of cracks, they cause wear or peeling of the denitration catalyst. The average particle size of typical coal ash is said to be 10 to 30 μm, but crack widths can be 10 μm or more, so it is quite possible that they will collide with the edges of cracks. Therefore, it is believed that the fewer cracks extending perpendicular to the gas flow direction GDR, the less likely wear or peeling due to collision with coal ash will occur, resulting in a catalyst with excellent wear resistance.

[0050] (Configuration and Effects) The denitration catalyst according to the first embodiment has a molded body containing a catalytic component, and the molded body has cracks on the surface, the cracks have a width of 10 μm or more, and the number of cracks forming an angle with the gas flow direction of −90° to −45° or 45° to 90° is 4 / mm. ２ The following is the result.

[0051] According to this configuration, since there are few cracks present in the direction perpendicular to the gas flow direction, abrasion and peeling due to collision with coal ash are unlikely to occur, and the denitration catalyst has excellent abrasion resistance and peeling resistance, and the reduction in the denitration rate is suppressed, resulting in a long-life denitration catalyst. Therefore, it is possible to provide a denitration catalyst that can improve abrasion resistance and peeling resistance.

[0052] A denitration catalyst according to a second aspect is the denitration catalyst according to the first aspect, which comprises a molded body containing a catalytic component, and the molded body has cracks on the surface, and the ratio of the number of cracks having a width of 10 μm or more and forming an angle with the gas flow direction of −90° or more and −45° or more, or 45° or more and 90° or less, to the total number of cracks having a width of 10 μm or more is 20% or less.

[0053] According to this configuration, since there are few cracks present in the direction perpendicular to the gas flow direction, abrasion and peeling due to collision with coal ash are unlikely to occur, and the denitration catalyst has excellent abrasion resistance and peeling resistance, and the reduction in the denitration rate is suppressed, resulting in a long-life denitration catalyst. Therefore, it is possible to provide a denitration catalyst that can improve abrasion resistance and peeling resistance.

[0054] A denitration catalyst according to a third aspect is the denitration catalyst according to the first or second aspect, and contains a sulfate. Preferably, the denitration catalyst is calcined after being impregnated with an aqueous solution of a water-soluble binder containing a sulfate.

[0055] According to this configuration, since there are few cracks present in the direction perpendicular to the gas flow direction, abrasion and peeling due to collision with coal ash are unlikely to occur, and the denitration catalyst has excellent abrasion resistance and peeling resistance, and the reduction in the denitration rate is suppressed, resulting in a long-life denitration catalyst. Therefore, it is possible to provide a denitration catalyst that can improve abrasion resistance and peeling resistance.

[0056] The denitration catalyst according to the fourth aspect is a denitration catalyst according to any one of the first to third aspects, in which the average crack area ratio, which is the ratio of the area of ​​the openings of all cracks in one randomly selected region on the surface of the molded body to a specified area of ​​the region, is 1% or more and 6% or less.

[0057] According to this configuration, since there are few cracks present in the direction perpendicular to the gas flow direction, abrasion and peeling due to collision with coal ash are unlikely to occur, and the denitration catalyst has excellent abrasion resistance and peeling resistance, and the reduction in the denitration rate is suppressed, resulting in a long-life denitration catalyst. Therefore, it is possible to provide a denitration catalyst that can improve abrasion resistance and peeling resistance.

[0058] A method for removing nitrogen oxides from combustion exhaust gas according to a fifth aspect includes a step of treating a combustion exhaust gas containing nitrogen oxides in the presence of a denitration catalyst made of a molded body containing a catalyst component and having cracks on the surface of the molded body, and the cracks on the surface of the molded body have a width of 10 μm or more and an angle of −90° to −45° or 45° to 90° with respect to the gas flow direction of 4 cracks / mm. ２ The following is the result.

[0059] According to this configuration, since there are few cracks in the denitration catalyst in the direction perpendicular to the gas flow direction, the denitration catalyst has excellent abrasion resistance and peeling resistance, and a decrease in the denitration rate is suppressed, and nitrogen oxides can be removed from combustion exhaust gas using a long-life denitration catalyst. Therefore, a method for removing nitrogen oxides from combustion exhaust gas that can improve abrasion resistance and peeling resistance can be provided.

[0060] A method for removing nitrogen oxides from combustion exhaust gas according to a sixth aspect is the method for removing nitrogen oxides from combustion exhaust gas according to the fifth aspect, wherein the surface of the molded body has a ratio of the number of cracks having a width of 10 μm or more and forming an angle with the gas flow direction of −90° or more and −45° or more, or 45° or more and 90° or less, to the total number of cracks having a width of 10 μm or more, of 20% or less.

[0061] According to this configuration, since there are few cracks in the denitration catalyst in the direction perpendicular to the gas flow direction, the denitration catalyst has excellent abrasion resistance and peeling resistance, and a decrease in the denitration rate is suppressed, and nitrogen oxides can be removed from combustion exhaust gas using a long-life denitration catalyst. Therefore, a method for removing nitrogen oxides from combustion exhaust gas that can improve abrasion resistance and peeling resistance can be provided.

[0062] Although the embodiments of the present disclosure have been described above, the embodiments are not limited to the contents of these embodiments. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiments.

[0063] 1 Flue duct 10 Denitrification device C Crack D1, D2 Dust GDR Gas flow direction

Claims

1. A molded body containing a catalyst component, the molded body having cracks on the surface, the cracks having a width of 10 μm or more, and the number of cracks forming an angle with the gas flow direction of -90° to -45° or 45° to 90° is 4 / mm. ２ The following is a denitrification catalyst.

2. The denitration catalyst according to claim 1, wherein the molded body has cracks on the surface, and the ratio of the number of cracks having a width of 10 μm or more and forming an angle of -90° to -45° or 45° to 90° with respect to the total number of cracks having a width of 10 μm or more is 20% or less.

3. The denitration catalyst according to claim 1 or 2, which contains a sulfate.

4. A denitration catalyst according to claim 1 or claim 2, wherein the average crack area ratio, which is the ratio of the area of ​​the openings of all cracks in a randomly selected region on the surface of the molded body to the specified area of ​​the region, is 1% or more and 6% or less.

5. A method for treating a combustion exhaust gas containing nitrogen oxides in the presence of a denitration catalyst having a molded body containing a catalytic component and having cracks on the surface of the molded body, wherein the surface of the molded body has cracks with a width of 10 μm or more and an angle of -90° to -45° or 45° to 90° with respect to the gas flow direction, with the number of cracks being 4 per mm. ２ A method for removing nitrogen oxides from combustion exhaust gas, comprising:

6. A method for removing nitrogen oxides from combustion exhaust gas as set forth in claim 5, wherein the ratio of the number of cracks on the surface of the molded body that are 10 μm or more in width and that form an angle of between -90° and -45° or between 45° and 90° with the gas flow direction to the total number of cracks that are 10 μm or more in width is 20% or less.

Images