Catalyst unit for purifying exhaust gas and plate-shaped catalyst element for use in the catalyst unit for purifying exhaust gas

Abstract

To provide a catalyst unit for cleaning exhaust gas having high rigidity even in a thine plate thickness, low in SO2 oxidation activity, and high in denitration activity, and a platy catalyst element.SOLUTION: A catalyst unit for cleaning exhaust gas comprises a plurality of platy catalyst elements 101 composed of one flat plate part 3 and one waved plate part 2 superimposed by touching apexes of peaks of a waved plate part of one platy catalyst element to a flat plate part of an adjacent platy catalyst element so as to secure a gas flow path by the waved plate part, where projections from a principal plane of the flat plate part and the waved plate part each form tetragons, one side of the waved plate part is connected to one side of the flat plate part, and the total of a peak number and a valley number of the waved plate part is four or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a catalyst unit and a plate-shaped catalyst element for purifying exhaust gas. More specifically, the present invention relates to a catalyst unit and a plate-shaped catalyst element for purifying exhaust gas that have high rigidity even with a thin plate thickness, low SO2 oxidation activity, and high denitrification activity. [Background technology]

[0002] In the exhaust gas purification process, nitrogen oxides in the exhaust gas from furnaces such as boilers in thermal power plants and various factories are decomposed in the presence of a denitration catalyst. Various denitration catalyst structures have been proposed to decompose the nitrogen oxides in the exhaust gas with high efficiency.

[0003] For example, Patent Document 1 discloses a catalyst structure for exhaust gas purification in which a large number of catalyst elements, each having a catalyst component supported on the surface of a substrate, are stacked via a mesh material having a large number of holes penetrating from the front to the back, wherein the catalyst elements are flat catalyst elements and the mesh material is a mesh material obtained by bending a rectangular or square flat mesh material in opposite directions at predetermined intervals in a direction parallel to a pair of sides to form alternate flat portions and stepped portions, or a mesh material obtained by curving the flat mesh material in a corrugated shape at predetermined intervals in a direction parallel to a pair of sides to form alternate peaks and valleys.

[0004] Patent Document 2 discloses a plate-shaped catalyst assembly structure in which a plate-shaped catalyst is configured by repeating at intervals a protrusion portion having a band-shaped protrusion and a flat portion, and a new band-shaped protrusion is provided from the protrusion portion to the flat portion in a direction approximately perpendicular to the band-shaped protrusion, and which is characterized in that a large number of such plate-shaped catalysts are stacked and stored within a unit frame, using the protrusion portions as spacers.

[0005] Patent Document 3 discloses a catalyst structure in which multiple plate-shaped catalyst elements, each of which has a catalyst component supported on its surface and has alternately arranged parallel protrusions and flat portions and is arranged so that the protrusions block the gas flow, are stacked on top of each other, and the protrusions are adjacent to each other alternately on the front and back of the plate-shaped catalyst element, each of which has two or more equal numbers of band-shaped protrusions and the protrusions are arranged so that 0<θ≦90° (where θ is the inclination angle of the protrusions with respect to the gas flow direction), and the plate-shaped catalyst elements are stacked in order with the front and back of the elements alternately flipped over. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2001-79422 A [Patent Document 2] JP 2000-296333 A [Patent Document 3] JP 2000-117120 A Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a catalyst unit and a plate-shaped catalyst element for exhaust gas purification which have high rigidity even with a thin plate thickness, low SO2 oxidation activity, and high denitration activity. [Means for solving the problem]

[0008] As a result of investigations aimed at solving the above problems, the present invention has been completed, including the following aspects.

[0009] [1] A catalyst unit for purifying exhaust gas, comprising a plurality of plate-shaped catalyst elements each consisting of one flat portion and one corrugated portion, stacked together so that the peaks of the corrugated portion of one plate-shaped catalyst element abut against the flat portion of an adjacent plate-shaped catalyst element and a gas flow path is secured by the corrugated portion, wherein the flat portion and the corrugated portion each form a quadrangle when projected from the normal direction of the main surface, one side of the flat portion is connected to one side of the corrugated portion, and the total number of peaks and valleys of the corrugated portions is 4 or more.

[0010] [2] The catalyst unit for purifying exhaust gas according to [1], wherein one side of the corrugated plate portion connected to one side of the flat plate portion is a side passing through a ridge line or a valley line of the corrugated plate portion.

[0011] [3] A catalyst unit for purifying exhaust gas according to [1], wherein one side of the corrugated plate portion connected to one side of the flat plate portion is a side passing through the center between the ridge line and the valley of the corrugated plate portion.

[0012] [4] A plate-shaped catalytic element consisting of one flat plate portion and one corrugated plate portion, The flat plate portion and the corrugated plate portion each form a rectangle when projected from the normal direction of the main surface. One side of the flat plate portion is connected to one side of the corrugated plate portion, and The total number of peaks and valleys in the corrugated sheet is 4 or more. A plate-shaped catalyst element for use in a catalyst unit for purifying exhaust gas, in which the peaks of the corrugated plate portion of one plate-shaped catalyst element are abutted against the flat plate portion of another adjacent plate-shaped catalyst element, and the two elements are overlapped so that a gas flow path is secured by the corrugated plate portion. Effect of the Invention

[0013] The catalytic unit for exhaust gas purification of the present invention has high rigidity even with a thin plate thickness, low SO2 oxidation activity, and high denitration activity. The catalytic unit for exhaust gas purification of the present invention has higher denitration performance with the same amount of catalyst than conventional products, so it is possible to significantly reduce the amount of catalyst used to ensure the same denitration performance as conventional products. The catalytic unit for exhaust gas purification of the present invention is particularly suitable for treating gas containing a relatively large amount of dust discharged from coal-fired boilers. The plate-shaped catalytic element of the present invention can be manufactured cheaply and easily by pressing or the like. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing one embodiment of a plate-shaped catalytic element used in the present invention. [Diagram 2] FIG. 2 is a diagram showing the size of the plate-shaped catalytic element shown in FIG. 1. [Diagram 3] FIG. 2 is a diagram showing a state in which the plate-shaped catalytic elements shown in FIG. 1 are overlapped. [Figure 4] FIG. 2 is a diagram showing a catalyst unit for purifying exhaust gas, which is composed of the plate-shaped catalyst element shown in FIG. [Diagram 5] FIG. 11 is a diagram showing another embodiment of the plate-shaped catalytic element used in the present invention, stacked together. [Figure 6] FIG. 1 is a diagram showing one embodiment of a plate-shaped catalytic element used in the prior art. [Figure 7] FIG. 7 is a diagram showing a catalyst unit for purifying exhaust gas, which is composed of the plate-shaped catalyst element shown in FIG. 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the accompanying drawings. It should be noted that the scope of the present invention is not limited to the following embodiments.

[0016] The exhaust gas purifying catalyst unit of the present invention comprises a plurality of plate-shaped catalyst elements. Each plate-shaped catalytic element is composed of one flat plate portion and one corrugated plate portion. The flat plate portion and the corrugated plate portion each form a rectangle when projected from the normal direction of the main surface. The rectangle projected by the flat plate portion and the rectangle projected by the corrugated plate portion preferably have substantially the same shape and substantially the same area. The plate thickness t of the flat plate portion and the corrugated plate portion is preferably 0.2 to 1 mm, more preferably 0.3 to 0.7 mm. The thinner the plate thickness, the lower the manufacturing cost and the lower the SO2 oxidation activity.

[0017] The corrugated plate portion is a part that is wavy. Examples of the waveform include a shape corresponding to a fundamental wave such as a sine wave, a rectangular wave, a sawtooth wave, a trapezoidal wave, a triangular wave, and a water surface wave, or a shape corresponding to a wave (synthetic wave) formed by combining fundamental waves. In the present invention, a shape corresponding to a sine wave or a wave obtained by combining a triangular wave and a sine wave having the same wavelength and the same phase is preferable. The total number of peaks and the number of valleys of the corrugated plate portion is 4 or more, preferably 6 or more. It is preferable that each peak has the same height. The height of the peak, that is, the value (h) corresponding to twice the amplitude, is preferably 2 mm to 20 mm. The distance between the peaks of the peaks, that is, the value (d) corresponding to the wavelength, is preferably 3 mm to 40 mm. The angle (β) of the maximum inclination part of the peak side is preferably 35 degrees to 70 degrees, more preferably 40 degrees to 65 degrees. The angle (α) of the peak is preferably 40 degrees to 110 degrees, more preferably 50 degrees to 100 degrees. When the angle α or β is within the above range, the contact efficiency between the plate-shaped catalyst element and the gas is high.

[0018] The plate-shaped catalytic element has one side of a flat plate portion connected to one side of a corrugated plate portion. In the plate-shaped catalytic element 101 shown in FIG. 1 or 3, one side of the corrugated plate portion 2 connected to one side of the flat plate portion 3 passes through the center between the ridge line and the valley line of the corrugated plate portion 2. In the plate-shaped catalyst element 102 shown in FIG. 5, one side of the corrugated plate portion 2 connected to one side of the flat plate portion 3 passes through a ridge line or a valley line of the corrugated plate portion 2.

[0019] As shown in FIG. 3, the plate-shaped catalyst elements are stacked so that the peaks of the corrugated plate parts of one plate-shaped catalyst element come into contact with the flat plate parts of another adjacent plate-shaped catalyst element, and are stored in an outer frame as shown in FIG. 4. The corrugated plate parts act as spacers to ensure a gas flow path between the plate-shaped catalyst elements. Since there are many parts where the corrugated plate parts and the flat plate parts come into contact with each other, even if the plate thickness of the plate-shaped catalyst element is thin, the rigidity of the catalyst unit for exhaust gas purification is maintained high and it can withstand vibration during transportation. In addition, even if a load is applied to pack the plate-shaped catalyst elements by the outer frame 10, the plate-shaped catalyst elements will not deform or break. In addition, the plate-shaped catalyst elements will not be damaged by soot blowing, which is performed to remove accumulated ash, soot, dust, etc.

[0020] A plate-shaped catalyst element can be obtained, for example, by supporting a catalyst component on a plate-shaped substrate such as metal lath or inorganic fiber woven or nonwoven fabric by impregnation or coating, and then subjecting the substrate to press working or the like.

[0021] The catalyst component is not particularly limited as long as it has a denitration catalytic effect. For example, there can be mentioned a catalyst containing an oxide of titanium, an oxide of molybdenum and / or tungsten, and an oxide of vanadium (titanium-based catalyst); a catalyst containing mainly an aluminosilicate such as zeolite carrying metals such as Cu and Fe (zeolite-based catalyst); and a catalyst containing a mixture of a titanium-based catalyst and a zeolite-based catalyst. Among these, titanium-based catalysts are preferred.

[0022] Examples of titanium-based catalysts include Ti-VW catalysts, Ti-V-Mo catalysts, and Ti-VW-Mo catalysts. The ratio of V element to Ti element is preferably 10% by weight or less, more preferably 8% by weight or less, as a weight percentage of V2O5 / TiO2. When an oxide of molybdenum and an oxide of tungsten are used in combination, the ratio of Mo element and / or W element to Ti element is preferably 20% by weight or less, as a weight percentage of (MoO3+WO3) / TiO2.

[0023] In the preparation of titanium-based catalysts, titanium oxide powder or titanium oxide precursors can be used as the raw material for the titanium oxide. Examples of titanium oxide precursors include titanium oxide slurry, titanium oxide sol, titanium sulfate, titanium tetrachloride, titanates, titanium alkoxides, etc. In the present invention, the raw material for the titanium oxide is preferably one that forms anatase-type titanium oxide. As the raw material of vanadium oxide, vanadium compounds such as vanadium pentoxide, ammonium metavanadate, and vanadyl sulfate can be used. As the raw material of the oxide of tungsten, ammonium paratungstate, ammonium metatungstate, tungsten trioxide, tungsten chloride, etc. can be used. As the raw material of the oxide of molybdenum, ammonium molybdate, molybdenum trioxide, etc. can be used.

[0024] The catalyst component used in the present invention may contain, as a promoter or additive, an oxide of P, an oxide of S, an oxide of Al (e.g., alumina), an oxide of Si (e.g., glass fiber), an oxide of Zr (e.g., zirconia), gypsum (e.g., gypsum dihydrate, etc.), zeolite, etc. These can be used in the form of powder, sol, slurry, fiber, etc., when preparing the catalyst.

[0025] Example 1 Titanium dioxide 10 kg, ammonium molybdate ((NH4)6·Mo7O 241 kg of ammonium metavanadate (4H2O), 0.3 kg of ammonium metavanadate, and 0.5 kg of oxalic acid were mixed and kneaded in a kneader for 1 hour while adding water. Then, 2 kg of silica-alumina inorganic fibers were added and kneaded for another 30 minutes to obtain a catalyst paste. The obtained catalyst paste was applied to the laths and surface of a 500 mm wide stainless steel strip metal lath prepared in advance using a pair of rolling rollers to obtain a strip catalyst. After forming a corrugated part and a flat part on the strip catalyst using a forming roller, it was cut to the specified dimensions with a cutting machine to produce a plate-shaped catalyst element 101 with a plate thickness of 0.3 mm, an angle α of 60 degrees, a height h of 6 mm, and one side of the flat part connected at the side passing through the center between the ridge line and the valley line of the corrugated part as shown in Figure 1. As shown in Figure 3, multiple plate-shaped catalyst elements were stacked alternately while changing the direction by 180 degrees, and loaded into an outer frame of 150 mm wide and 150 mm high as shown in Figure 4. This was air-dried for 24 hours, and then calcined at 500°C for 2 hours while air was flowing to obtain a catalyst unit for purifying exhaust gas. In order to support the flat plate portion of the plate-shaped catalyst element located at the outermost position when stacked together, a rib 5 was provided on the inner surface of the outer frame body facing the flat plate portion. Even with a plate thickness of 0.3 mm, the corrugated plate portion did not deform, and sufficient gaps between the flat plate portions were secured.

[0026] The exhaust gas purification catalyst unit was set in the denitrification reaction device, and NO x The denitrification rate was measured by passing a simulated combustion exhaust gas containing 350 ppm, 4% O2, 12% H2O, and 350 ppm NH3 through the filter at 6 m / s. Then, at a temperature of 380°C, x The SO2 oxidation rate was measured by passing a simulated combustion exhaust gas containing 2000 ppm, 4% O2, and 12% H2O at 6 m / s. Table 1 shows the relative values ​​of the denitration rate and the SO2 oxidation rate in Example 1 when the denitration rate and the SO2 oxidation rate in Comparative Example 1 are used as the standard.

[0027] Example 2 By bending and cutting the belt-shaped catalyst obtained in Example 1, a plate-shaped catalyst element was produced, in which the plate thickness was 0.3 mm, the angle α was 60 degrees, and the height h was 6 mm, and one side of the flat plate part was connected at the side passing through the ridge line or valley of the corrugated plate part. As shown in FIG. 5, a plurality of plate-shaped catalyst elements 102 were stacked while being turned over every other sheet, and loaded into an outer frame body having a width of 150 mm and a height of 150 mm. This was air-dried for 24 hours, and then baked at 500°C for 2 hours while flowing air, to obtain a catalyst unit for purifying exhaust gas. Even with a plate thickness of 0.3 mm, the corrugated plate part did not deform and sufficient gaps between the flat plate parts were secured. The relative values ​​of the denitration rate and the SO2 oxidation rate in Example 2 when the denitration rate and the SO2 oxidation rate in Comparative Example 1 are used as the standard are shown in Table 1.

[0028] Comparative Example 1 By bending and cutting the belt-shaped catalyst obtained in Example 1, a plate-shaped catalyst element having a plate thickness of 0.3 mm, an angle α of 60 degrees, a height h of 6 mm, and four flat plate parts and three ridge parts as shown in Figure 6 was produced. As shown in Figure 7, when a plurality of plate-shaped catalyst elements 111 were stacked while being alternately rotated 180 degrees and loaded into an outer frame having a width of 150 mm and a height of 150 mm, the ridge parts were deformed and the gap between the flat plate parts could not be sufficiently secured. This was air-dried for 24 hours, and then calcined at 500°C for 2 hours while flowing air, to obtain a catalyst unit for purifying exhaust gas.

[0029] Comparative Example 2 A plate-shaped catalyst element 111 having a plate thickness of 1 mm, an angle α of 60 degrees, a height h of 6 mm, four flat plate parts and three ridge parts as shown in FIG. 6 was produced in the same manner as in Comparative Example 1 except that the plate thickness was changed to 1 mm. As shown in FIG. 7, a plurality of plate-shaped catalyst elements 111 were stacked while being alternately rotated 180 degrees, and loaded into an outer frame having a width of 150 mm and a height of 150 mm. This was air-dried for 24 hours, and then baked at 500°C for 2 hours while flowing air, to obtain a catalyst unit for purifying exhaust gas. The plate thickness of 1 mm prevented the ridge parts from deforming. Table 1 shows the relative values ​​of the denitration rate and SO2 oxidation rate in Comparative Example 2 when the denitration rate and SO2 oxidation rate in Comparative Example 1 are used as the reference.

[0030] [Table 1] [Explanation of symbols]

[0031] 101, 102: Plate-shaped catalytic element of the present invention 111: Prior art plate-shaped catalytic element 2: Corrugated sheet section 3: Flat plate part 4: Convex stripe 5: Rib 8: Exhaust gas 10: Outer frame

Claims

1. A plurality of plate-shaped catalytic elements each consisting of one flat plate portion and one corrugated plate portion are arranged in a single unit. The apex of the corrugated plate portion of one plate-shaped catalyst element is in contact with the flat plate portion of another adjacent plate-shaped catalyst element, and the corrugated plate portions are overlapped so as to ensure a gas flow path; The flat plate portion and the corrugated plate portion each form a rectangle when projected from the normal direction of the main surface. The rectangle projected by the flat plate portion has approximately the same shape and area as the rectangle projected by the corrugated plate portion, One side of the corrugated plate portion is connected to one side of the flat plate portion, the one side of the corrugated plate portion being parallel to the ridgeline of the mountain of the corrugated plate portion, and The total number of peaks and valleys in the corrugated plate portion is 4 or more, The plate-shaped catalytic element is a catalytic component supported on a metal lath, an inorganic fiber woven fabric, or an inorganic fiber nonwoven fabric. Catalyst unit for purifying exhaust gas.

2. 2. The exhaust gas purifying catalyst unit according to claim 1, wherein one side of the corrugated plate portion connected to one side of the flat plate portion passes through a ridge line or a valley line of the corrugated plate portion.

3. 2. The exhaust gas purifying catalyst unit according to claim 1, wherein one side of the corrugated plate portion connected to one side of the flat plate portion is a side passing through the center between a ridge line and a valley line of the corrugated plate portion.

4. 4. The exhaust gas purifying catalyst unit according to claim 1, wherein the plate thickness of the flat plate portion and the corrugated plate portion is 0.2 to 1 mm.

5. The catalyst unit for purifying exhaust gas according to any one of claims 1 to 4, wherein the angle of the apex of the mountain is 40 degrees to 110 degrees, or the angle of the maximum inclination of the mountainside of the mountain is 35 degrees to 70 degrees.

6. A plate-shaped catalytic element consisting of one flat plate portion and one corrugated plate portion, The flat plate portion and the corrugated plate portion each form a rectangle when projected from the normal direction of the main surface. The rectangle projected by the flat plate portion has approximately the same shape and area as the rectangle projected by the corrugated plate portion, One side of the corrugated plate portion is connected to one side of the flat plate portion, the one side of the corrugated plate portion being parallel to the ridgeline of the mountain of the corrugated plate portion, and The total number of peaks and valleys in the corrugated plate portion is 4 or more, The plate-shaped catalytic element is a catalytic component supported on a metal lath, an inorganic fiber woven fabric, or an inorganic fiber nonwoven fabric, A plate-shaped catalyst element for use in a catalyst unit for purifying exhaust gas, in which the peaks of the corrugated plate portion of one plate-shaped catalyst element are abutted against the flat plate portion of another adjacent plate-shaped catalyst element, and the two elements are overlapped so that a gas flow path is secured by the corrugated plate portion.

7. A plate-shaped catalyst element for use in a catalyst unit for purifying exhaust gas as described in claim 6, wherein the thickness of the flat plate portion and the corrugated plate portion is 0.2 to 1 mm.

8. A plate-shaped catalytic element for use in a catalytic unit for exhaust gas purification described in claim 6 or 7, wherein the angle of the apex of the mountain is 40 degrees to 110 degrees, or the angle of the maximum slope of the mountainside is 35 degrees to 70 degrees.

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