JPH10286469A - Plate-like catalyst structural body and catalytic reaction device using the catalyst structural body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst structural body for efficiently decomposing and removing CO and NOx without any problem even in an exhaust gas of a system coexistent with SOx by using the catalyst structural body having relatively small ventillation resistance while utilizing the effect of accelerating mass transfer by the turbulence of the gas. SOLUTION: The catalyst structural body is formed by laminating plural sheets of plate-like catalyst elements which are constituted by carrying a catalyst component having catalytic activity on the surface and alternately repeating a projected line part composed of a belt-like projection and a flat part at a certain interval, in the state that the projected line parts are contacted each other by pressing, contains (1) at least one kind of an oxide selected from TiO2 , SiO2 , Al2 O3 and SiO2 -Al2 O3 , (2) at least one kind of an oxide selected from V, W and Mo respectively and as the case may be, (3) at least one kind selected from Pt, Ir, Rh and Pd and has >=120 m/hr to <500 m/hr a film coefficient of mass transfer of a reaction material among overall reaction rates of the catalyst and has >0 deg. to <50 deg. crossing angles of the projected line parts of the catalyst elements adjacent to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst structure for purifying exhaust gas, and more particularly to a nitrogen oxide (NOx) and a carbon monoxide (C) when a sulfur oxide (SOx) is present in the exhaust gas.
The present invention relates to a catalyst structure using a plate-like catalyst for efficiently removing organic compounds such as O) and / or dioxin (DXN), and a catalyst reaction device in which the catalyst structure is disposed in an exhaust gas channel.

[0002]

2. Description of the Related Art NOx in flue gas emitted from power plants, various factories, automobiles, etc. is a cause of photochemical smog and acid rain. As an effective method of removing NOx, ammonia (NH ₃ ) is reduced. The flue gas denitration method by selective catalytic reduction as an agent has been widely used mainly in thermal power plants.

As a catalyst, a titanium oxide (TiO ₂ ) catalyst containing vanadium (V), molybdenum (Mo) or tungsten (W) as an active component is used. In particular, vanadium is contained as one of the active components. Catalysts have become the mainstream of the current denitration catalysts because they have high activity, are less deteriorated by impurities contained in exhaust gas, and can be used at lower temperatures (Japanese Patent Laid-Open No. 50-12).
868, etc.).

[0004] Exhaust gas generated from thermal power plants and the like contains not only nitrogen oxides (NOx) but also other harmful gas components, which are subject to emission regulations. Effective removal of these gaseous components is also needed.

For example, the harmful gas components include carbon monoxide (CO) in gas turbine exhaust gas and dioxin (D) discharged from incineration facilities such as municipal waste and industrial waste.
XN) and the like.

In removing such harmful gases, a catalyst for removing carbon monoxide (CO) in exhaust gas by adding a noble metal such as platinum, iridium, rhodium or palladium to the above-mentioned denitration catalyst together with nitrogen oxides. (JP-A-5-329334).

[0007] On the other hand, highly toxic dioxins discharged from incineration facilities for municipal garbage and industrial waste have become a major social problem, and effective reduction techniques are desired. Dioxin is an organic chlorine compound, polychlorinated dibenzo-p-chloride.
dioxins: PCDDs) are extremely stable substances,
There are many isomers and homologues. Polychlorinated dibenzofurans (PCDFs) are compounds having similar properties, and are collectively referred to as dioxins together with dioxins. As a measure to reduce the emission of dioxins, Europe has been strictly controlling the emission from municipal waste incineration facilities since the late 1980s, and Japan has recently been regulated as an Air Pollution Control Law. I have.

[0008] Regarding the removal of dioxins in such exhaust gas, attention has been paid to a method in which oxidative decomposition by a catalyst does not produce a residue. For example, JP-A-2-35914.
Japanese Patent Application Publication No. JP-A-2005-115122 discloses an exhaust gas treatment method in which exhaust gas discharged from a waste incinerator is cooled and then dust is removed by a dust collector. In the exhaust gas treatment method, an aromatic chlorine compound is decomposed by a catalyst by setting the exhaust gas after dust removal to 150 ° C. or higher. The catalyst is disclosed as at least one selected from titanium oxide, vanadium oxide, tungsten oxide, platinum, and palladium.
They say they use seeds. Further, JP-A-3-841
No. 5 discloses a method for removing dioxins in exhaust gas using a catalyst, wherein the temperature is 250 ° C. or more and the SV (space velocity = processing gas amount / catalyst amount) is 50,000 1 / h.
And AV (area velocity = processed gas amount / catalyst geometric surface area) of less than 250 m / h.
It is also described that a honeycomb catalyst is preferable as the catalyst.

In general, a catalyst used for removing harmful substances in exhaust gas as described above is usually used after being formed into a honeycomb shape or a plate shape, and various production methods therefor have been invented. Among them, a metal plate obtained by subjecting a metal sheet to metal lath processing and then applying a sprayed mesh or ceramic fiber woven or non-woven fabric to a substrate, applying the above-mentioned catalyst component to the substrate, and press-bonding the same to the plate-shaped catalyst shown in FIG. After processing into a shape having a waveform as shown in the cross-sectional view of the catalyst element, a catalyst structure (see Japanese Patent Application Laid-Open No.
-79188, Japanese Patent Application No. 63-324676, etc.) have smaller ventilation loss and are less likely to be blocked by dust or coal combustion ash, as compared to a honeycomb-shaped catalyst structure formed by extrusion-molding a paste of a catalyst component. It is currently widely used as a denitration catalyst for boiler exhaust gas for thermal power generation.

[0010]

The harmful substances present in the above-mentioned exhaust gas are generally very low in concentration. For example, the concentration of carbon monoxide (CO) in the exhaust gas of a gas turbine is on the order of several ppm, and it is required for the catalyst to remove 50% or more of the concentration. In addition, dioxins are present in the exhaust gas discharged from municipal waste incineration equipment and industrial waste incineration equipment in the order of nanograms (10 ^-9 g) per 1 m ³ N. Therefore, emission control of dioxins is required. The values are also specified in the order of ng / m ³ N. As can be seen from the above-mentioned emission control law and the like, a catalyst for purifying exhaust gas is desired to be capable of efficiently decomposing and removing such a toxic substance having a low concentration.

Here, the gas passage in the catalyst structure used in the above-mentioned prior art is parallel to the gas flow direction, and usually has a Re (Reynolds number) of 200.
Since it is used in a region of 0 or less, the flow pattern of the gas in the catalyst layer is laminar, and has a characteristic that the ventilation resistance is extremely small. However, on the other hand, the reactants (harmful substances) generated by the decomposition reaction of the harmful substances on the catalyst surface are:
Even in the vicinity of the catalyst surface, there is a problem that the catalyst reaction rate is reduced because the concentration is low. That is, the reaction causes a concentration gradient between the catalyst surface and the gas phase (bulk) at a certain distance from the catalyst surface, but the diffusion from the bulk is rate-limiting because the reaction gas component is diluted, and the reaction rate is increased. Become smaller.

In general, the reaction rate of a catalyst is expressed by the following equation. 1 / K = 1 / Kr + 1 / Kf K: Overall reaction rate coefficient (m / h) Kr: Reaction rate constant per unit surface area (m / h) Kf: Film reaction rate coefficient of reactant (m / h)

The reaction rate (overall reaction rate constant K) of the catalyst as a whole is such that the specification (composition) of the catalyst is constant, that is, the coefficient K
When r is constant, the reaction material is promoted to move (diffusion) to the surface of the catalyst, and thus becomes higher. Therefore, how to promote the diffusion of the reaction material to the surface of the catalyst is important for effectively performing the catalytic reaction. is important. However, the above prior art does not take such considerations.

That is, the above-mentioned prior arts do not take into account the influence of the reaction of a dilute substance to be treated (reactive gas) on the catalyst, and the above-mentioned facilities as the above-described conventional exhaust gas treatment apparatuses are not used. There has been a problem that the amount of the catalyst to be used increases when the technical catalytic method is applied.

Further, the exhaust gas from an oil-fired boiler, a coal-fired boiler, or a municipal waste incineration facility contains not only nitrogen oxides (NOx) and carbon monoxide (CO) but also sulfur oxides (SOx). However, this sulfur oxide (mostly SO ₂ ) is partially oxidized by a catalyst, and is subjected to the reaction shown by the following formula, particularly in a low temperature range, so that ammonium sulfate (NH ₄ ) ₂ S
O ₄ and ammonium acid sulfate NH ₄ HSO ₄ are generated, which not only deteriorates the performance of the catalyst, but also adversely affects devices in the exhaust gas flow path downstream of the place where the catalyst device is disposed. 2NH ₃ + SO ₃ + H ₂ O → (NH ₄ ) ₂ SO ₄ NH ₃ + SO ₃ + H ₂ O → NH ₄ HSO ₄

Here, the inventors have found that this undesirable SO ₂ oxidation reaction has a relatively low reaction rate under normal reaction conditions and is proportional to the geometric surface area of the catalyst. ing.

On the other hand, carbon monoxide (C
O) and a noble metal-added catalyst such as platinum are excellent for oxidatively decomposing dioxin (DXN). In this case, the oxidation reaction of SO ₂ is also promoted.
In the above-mentioned prior art in which the overall reaction rate constant K per unit surface area of the catalyst is small (in other words, the surface area is large), there is a problem that it is difficult to achieve both of these facts.

An object of the present invention is to eliminate the above-mentioned problems of the prior art and to use a catalyst structure having a relatively small ventilation resistance while utilizing the effect of promoting mass transfer by gas turbulence. By providing a catalyst structure that efficiently decomposes and removes carbon monoxide (CO) and the like and nitrogen oxides (NOx) without any problem even in (SOx) coexisting exhaust gas, it is possible to provide a catalyst reaction device using the catalyst structure. is there.

[0019]

The above objects can be achieved by the following means (1) to (5). (1) A catalyst component having catalytic activity is carried on the surface, and ridges and flat portions formed of strip-like projections having an intersection angle with respect to the exhaust gas flow of more than 0 and less than 50 degrees are alternately repeated at intervals. A plate-shaped first catalyst element,
A catalyst component having catalytic activity is supported on the surface, and the ridge portion and the flat portion, which are formed of band-shaped protrusions having an intersection angle with respect to the exhaust gas flow of more than 0 and less than 130 degrees, are alternately repeated at intervals. A catalyst structure in which a plurality of plate-shaped second catalyst elements are alternately laminated with their ridges in contact with each other, wherein titania and silica are used as first components of a catalyst component having catalytic activity. , Alumina and silica
It contains at least one oxide selected from alumina and at least one oxide selected from vanadium, tungsten and molybdenum as the second component. Membrane mass transfer coefficient of 120 m / h or more, 500
a plate-like catalyst structure having a m / h of less than m / h.

(2) In addition to the first component and the second component, the third component further includes, as a third component, at least one selected from platinum, iridium, rhodium, palladium, and oxides thereof. A plate-like catalyst structure having the same structure as the plate-like catalyst structure of 1).

(3) The plate-like catalyst structure described in (1) or (2) above, wherein the superficial velocity of the gas to be treated is 2 m / s or more,
A catalytic reactor used by being arranged in an exhaust gas flow path having a range of less than 10 m / s.

(4) The plate-shaped catalyst structure according to the above (1) or (2) is used as a gas-fired boiler, an oil-fired boiler, a coal-fired boiler, a gas turbine, a diesel engine, a municipal refuse incinerator, and a sintering machine. Or a catalytic reaction device placed in the flow path of exhaust gas discharged from a chemical plant.

(5) Nitrogen in the exhaust gas is provided by providing an injection portion for a reducing agent of nitrogen oxide on the upstream side of the exhaust gas channel in which the catalyst structure according to the above (1) or (2) is disposed. A catalytic reactor for simultaneously removing oxides, carbon monoxide and / or dioxins.

The second catalyst element of the present invention may have any crossing angle as long as the crossing angle between the ridge and the exhaust gas flow is less than 130 degrees, but the first catalyst element is turned over. By using such a material, the production cost of the catalyst element can be significantly reduced.

[0025]

The operation of the present invention will be described with reference to the drawings. FIG.
Is obtained by shaping a titanium-molybdenum-vanadium-based denitration catalyst and a titanium-molybdenum-vanadium-platinum-based catalyst into a plate shape, cutting them into a fixed test size (20 × 100 mm), and measuring each catalyst at a temperature of 380 ° C. 1 shows the SO ₂ oxidation rate of the sample. From FIG. 3, it can be seen that the SO ₂ oxidation rate is inversely proportional to the AV (area rate) in all the catalysts, that is, increases as the geometric surface area of the catalyst increases, and the increasing tendency is remarkable in the platinum added system. It is clear that

Next, FIG. 4 shows the C-C value of the titanium-molybdenum-vanadium-platinum catalyst at a constant temperature (350 ° C.).
It shows the O oxidation rate. FIG. 4 shows that the oxidation rate of CO also increases in inverse proportion to AV.

That is, the results shown in FIGS. 3 and 4 show that when the titanium-molybdenum-vanadium-platinum catalyst is used as a denitration catalyst, the geometric surface area of the catalyst is required to suppress the undesired SO ₂ oxidation rate. Should be reduced as much as possible. On the other hand, carbon monoxide (C
This is a different result that it is better to use a catalyst having a large surface area to oxidatively decompose O).

However, the present inventors have found that in the catalyst containing the first component and the two components or the catalyst structure containing the first to third components according to claims 1 and 2 of the present invention, the overall reaction rate of the catalyst is determined. Among them, a catalyst structure having a film mass transfer coefficient Kf of a reactant of 120 m / h or more and less than 500 m / h was manufactured and tested. It was confirmed that with the same SO ₂ oxidation performance as that of the type catalyst, the same or higher denitration performance and oxidation performance of CO and dioxins could be achieved.

This is because the use of the catalyst structure of the present invention facilitates the diffusion (mass transfer) of a very dilute gas to be treated to the catalyst surface and increases the overall reaction rate per unit surface area. , those derived from the oxidation reactions such as denitrification reactions and CO catalyst becomes easy to occur, SO ₂ oxidation reaction Conversely, no high reaction rate originally added the the structure of such a plate-shaped catalyst It is considered that the improvement in the denitration performance and the oxidation performance such as CO enabled the required geometric surface area of the catalyst to be reduced.

On the other hand, similarly to carbon monoxide (CO), dioxins in exhaust gas generated by incineration of municipal garbage and industrial waste also increase the overall reaction rate constant K of the catalyst structure to increase the overall catalyst. It was noted that the reaction rate was improved. In particular, as described above, since the concentration of dioxins in the exhaust gas is extremely low, the effect of the present invention for promoting diffusion is great.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail. Example 1 Metatitanate slurry (TiO ₂ content: 30 wt%, S
O ₄ content: 8 wt%) 67 kg to 2.7k ammonium molybdate _{((NH 4) 6 · Mo} 7 O 24 · 4H 2 O)
g, ammonium metavanadate (NH ₄ VO ₃ ):
28 kg was added and kneaded while evaporating water using a heating kneader to obtain a paste having a water content of about 36%. This was extruded into a 3φ column, granulated, dried by a fluidized bed drier, and then fired in the air at 250 ° C. for 2 hours. The obtained granules were pulverized with a hammer mill to a particle diameter of an average particle diameter of 5 μm to obtain a catalyst composition comprising the first component and the second component of the present invention. The composition at this time is V / Mo / Ti = 4/5/91 (atomic ratio).

On the other hand, chloroplatinic acid (H ₂ [PtC ₁₆ ] .6
To a solution prepared by dissolving 0.665 g of H ₂ O in 1 liter of water, 500 g of fine silica powder was added and evaporated to dryness on a sand bath to carry platinum. After drying this at 180 ° C for 2 hours,
Fired at 500 ° C for 2 hours in air, 0.05wt% Pt-
The silica was adjusted to obtain a composition comprising a catalyst component comprising the third component of the present invention.

To 20 kg of the powder comprising the first and second components and 408 g of the third component obtained by the above method, Al ₂ O ₃ was added.
3 kg of SiO ₂ -based inorganic fiber and 10 kg of water were kneaded for 1 hour using a kneader to make a clay. The catalyst paste is applied to the surface of a SUS304 metal lath substrate having a width of 500 mm and a thickness of 0.2 mm, which has been subjected to aluminum spraying and roughened by using a roller, between the laths and on the surface using a roller to have a thickness of approximately 0.9 mm and a length of approximately 0.9 mm. A 500 mm-thick plate catalyst was obtained. A flat portion 3 as shown in FIG.
A plurality of ridges 2 provided at predetermined intervals in parallel with each other
Was formed, and calcined in air at 500 ° C. for 2 hours.

The obtained catalyst element 1 and a catalyst element 1 ′ having a ridge 2 ′ and a flat portion 3 ′ obtained by turning over the catalyst element 1 shown in FIG. The ridge lines 2 and 2 ′ were brought into contact with each other and alternately laminated one by one to obtain a catalyst structure having a configuration of 150 square × 500 mm and having the configuration shown in FIG.
Of the exhaust gas 6 by 30 degrees (angle θ = 3
0 °), and the ridge 2 ′ of the catalyst element 1 ′ is set at 150 ° (angle θ ′ = 15) with respect to the flow direction of the exhaust gas 6.
0 °).

Example 2 The catalyst element 1 and the catalyst element 1 ′ prepared in the same manner as in Example 1 were alternately stacked one by one so that the ridges of the ridges 2 and 2 ′ abut each other. Square x 500
A catalyst structure having a length of mm and having the structure shown in FIG. 1C was obtained. At this time, the ridge 2 of the catalyst element 1 is provided so as to be 45 degrees (angle θ = 45 °) with the flow direction of the exhaust gas 6, and the ridge 2 ′ of the catalyst element 1 ′ is aligned with the flow direction of the exhaust gas 6. 1
It is provided so as to be 35 degrees (angle θ ′ = 135 °).

Example 3 Al ₂ O 3 was added to 20 kg of a powder of a catalyst (only the first and second components of the present invention) prepared in the same manner as in Example 1 except that platinum as the third component of the present invention was not supported. The mixture was kneaded with 3 kg of O ₃ · SiO ₂ -based inorganic fiber, 10 kg of water and a kneader for 1 hour to form a clay. This catalyst paste is 500 mm wide,
A SUS304 metal lath substrate having a thickness of 0.2 mm is sprayed with aluminum and roughened by applying a roller to the gap between the lattices and the surface using a roller to have a thickness of about 0.9 mm and a length of 5 mm.
A 00 mm plate catalyst was obtained. The catalyst was press-formed to form a waveform as shown in FIG. 1 (a), air-dried, and then baked in air at 500 ° C. for 2 hours.

The obtained catalyst element 1 and the catalyst element 1 ′ provided with a ridge 2 ′ and a flat portion 3 ′ shown in FIG. The ridge lines 2 and 2 ′ were brought into contact with each other and alternately laminated one by one to obtain a catalyst structure having a configuration of 150 square × 500 mm and having the configuration shown in FIG.
Of the exhaust gas 6 by 30 degrees (angle θ = 3
0 °), and the ridge 2 ′ of the catalyst element 1 ′ is set at 150 ° (angle θ ′ = 15) with respect to the flow direction of the exhaust gas 6.
0 °).

[0038] Example 4 Titanium oxide powder (TiO ₂ content: 90 wt%, SO ₄ content: 3 wt%) 22 kg of ammonium molybdate _{((NH 4) 6 · Mo} 7 O 24 · 4H 2 O) 2. 8 kg, 2.6 kg of ammonium metavanadate (NH ₄ VO ₃ )
In addition, the mixture was kneaded using a heating kneader to obtain a paste having a water content of about 36%. The composition at this time is V / Mo / Ti = 7/5
/ 88 (atomic ratio) and is a catalyst comprising the first component and the second component of the present invention. To the catalyst paste obtained by the above method, 10 kg of Al ₂ O ₃ .SiO ₂ inorganic fibers was added and kneaded for about 1 hour. This catalyst paste is 500m wide
m, a SUS304 metal lath substrate with a thickness of 0.2 mm, which is subjected to aluminum spraying and roughened by a roller. A catalyst was obtained.

The catalyst was press-formed to form a waveform as shown in FIG. 1 (a), air-dried, and then fired in air at 500 ° C. for 2 hours. The obtained catalyst element 1 and a catalyst element 1 ′ having a ridge 2 ′ and a flat portion 3 ′ shown in FIG. The ridge lines of '′ were brought into contact with each other and alternately laminated one by one to obtain a catalyst structure having a configuration of 150 squares × 500 mm and having the configuration shown in FIG. 2 is 30 degrees with the flow direction of the exhaust gas 6 (angle θ = 30
°), and the ridge 2 ′ of the catalyst element 1 ′ is set at 150 ° (angle θ ′ = 15) with respect to the flow direction of the exhaust gas 6.
0 °).

Example 5 The ridge line of the ridge 2 was 45 degrees with the flow direction of the exhaust gas 6 (θ = 4
5 °), the ridge line of the ridge 2 ′ is aligned with the flow direction of the exhaust gas 6
A catalyst element 1 and a catalyst element 1 'were prepared in the same manner as in Example 4, except that the catalyst element was formed so as to be 5 degrees (θ' = 135 °). The obtained catalyst element 1 and a catalyst element 1 ′ having a flat portion 3 ′ and a ridge portion 2 ′ shown in FIG. 2 'ridges are brought into contact with each other and alternately 1
Fig. 1 (c) with a length of 150 squares x 500mm laminated one by one
A catalyst structure having the structure shown in the following was obtained. At this time, the ridge 2 of the catalyst element 1 is provided so as to be 45 degrees (angle θ = 45 °) with the flow direction of the exhaust gas 6, and the ridge 2 ′ of the catalyst element 1 ′ is aligned with the flow direction of the exhaust gas 6. 135 degrees (angle θ '
= 135 °).

Example 6 As the third component of the present invention, 0.0 was used in place of Pt of Example 1.
A catalyst structure was obtained in the same manner as in Example 1, except that 5 wt% Ir was added.

Example 7 As the third component of the present invention, 0.0 was used in place of Pt in Example 1.
A catalyst structure was obtained in the same manner as in Example 1 except that 5 wt% Rh was added.

Example 8 As the third component of the present invention, 0.0 was used instead of Pt of Example 1.
A catalyst structure was obtained in the same manner as in Example 1, except that 5 wt% Pd was added.

EXAMPLE 9 3.6 kg of ammonium metatungstate 2.6 kg of ammonium metavanadate was added to 22 kg of titanium oxide powder (TiO ₂ content: 90 wt%, SO ₄ content: 3 wt%).
g was kneaded using a kneader to obtain a paste having a water content of about 36%. The composition at this time was V / W / Ti = 7/5/88 (atomic ratio), and a catalyst structure was obtained in the same manner as in Example 4 except for the above.

Example 10 A catalyst structure was obtained in the same manner as in Example 1 except that 17 kg of silicon oxide powder was used instead of the titanium oxide powder.

Comparative Example 1 A catalyst element 11 as shown in FIG. 7 was formed from only the first component and the second component of the present invention prepared in the same manner as in Example 1, and the ridge line of the projection 12 was in the gas flow direction. 9 (a) (a diagram viewed from the upstream side of the exhaust gas flow) having a size of 150 mm × 500 mm was obtained.

COMPARATIVE EXAMPLE 2 A catalyst element 1 prepared in the same manner as in Example 1 was obtained, and the catalyst element 1 and the ridge 2 ′ and the flat part 3 shown in FIG. And a catalyst element 1 'having a ridge of 2, and a ridge line 2 and 2' are brought into contact with each other and alternately stacked one by one to form a square of 150 × 5.
A 00 mm long catalyst structure having the configuration shown in FIG. 1C was obtained. At this time, the ridge 2 of the catalyst element 1
Is provided so as to be at 50 degrees (angle θ = 50 °) with respect to the flow direction of the exhaust gas 6 at 130 degrees (angle θ ′ = 130 °) with the flow direction of the exhaust gas 6. Provided.

COMPARATIVE EXAMPLE 3 A catalyst prepared in the same manner as in Example 1 was press-formed to form a waveform having ridges 12 and flat portions 13 as shown in FIG. By calcining, a catalyst element 11 was obtained. The obtained catalyst elements 11 are laminated one by one so that the ridge lines of the ridges 12 are all parallel to the flow direction of the exhaust gas 6, and are 150 mm square × 500 mm
A catalyst structure as seen from the upstream side of the exhaust gas flow as shown in FIG. 9A was obtained.

COMPARATIVE EXAMPLE 4 A catalyst prepared in the same manner as in Example 1 was press-formed to form a waveform having ridges 12 and flat portions 13 as shown in FIG. By calcining, a catalyst element 11 was obtained. The obtained catalyst elements 11 are alternately stacked one by one on the one in which the ridge lines of the ridges 12 are arranged so as to be orthogonal to the flow direction of the exhaust gas 6 and in the other, and are arranged one by one. A catalyst structure having the configuration shown in FIG.

Comparative Example 5 The catalyst prepared in the same manner as in Example 1 was formed into a corrugated plate having no flat portions and ridges 22 by press molding as shown in FIG. The resultant was calcined at 550 ° C. for 2 hours in the air to obtain a catalyst element 21. The obtained catalyst element 21 and the catalyst element 21 ′ shown in FIG. 8B obtained by turning the catalyst element 21 upside down are alternately brought into contact by bringing the ridge lines of the ridges 22, 22 ′ into contact with each other. The catalyst structures were laminated one by one to obtain a catalyst structure having a configuration of 150 square × 500 mm and having the configuration shown in FIG. 9C. At this time, the protrusions 22 of the catalyst element 21 are provided so as to be at 30 degrees (angle θ = 30 °) with the flow direction of the exhaust gas 6, and the catalyst element 21 ′
Is provided so as to be 160 degrees (angle θ ′ = 160 °) with the flow direction of the exhaust gas 6.

Comparative Example 6 A catalyst element 1 and a catalyst element 1 ′ prepared in the same manner as in Example 4 were obtained, and the ridges of the ridges 2, 2 ′ were brought into contact with each other and alternately laminated one by one. 150 x 500
A catalyst structure having a length shown in FIG. 1C and having a length of mm was obtained.
At this time, the ridge 2 of the catalyst element 1 is provided so as to be at an angle of 50 degrees (angle θ = 50 °) with the flow direction of the exhaust gas 6,
The projecting ridge 2 ′ of the catalyst element 1 ′ is provided so as to have an angle of 130 degrees (angle θ ′ = 130 °) with the flow direction of the exhaust gas 6.

Table 1 summarizes the specifications of the catalysts shown in Examples and Comparative Examples. The catalysts of Examples 1 to 5 and the catalyst structures of Comparative Examples 1 to 6 were each charged into a reactor, and the LPG combustion exhaust gas was charged. , CO oxidation performance and SO
_{(2) The} oxidation performance was measured and the ventilation resistance of the catalyst structure was examined.

[0053]

[Table 1]

[0054]

[Table 2]

The results obtained are shown in Table 3 together with the membrane mass transfer coefficients of the tested catalysts. As is clear from Table 3, the catalyst structures of Examples 1 and 2 of the present invention have lower ventilation resistance than the catalyst structures of Comparative Examples 2, 4 and 5 prepared with the same catalyst specifications, and have substantially the same denitration. It can be seen that performance and CO oxidation performance can be obtained. This includes a film mass transfer coefficient of 12
Although it is a necessary condition to be higher than 0 m / h, if the intersection angle between the ridge 2 of the adjacent catalyst element 1 and the gas flow 6 is too large, the pressure loss as the catalyst structure becomes too high, and Because of the above problem, it is necessary that the intersection angle θ is less than 50 ° and the intersection angle θ ′ is less than 130 ° as shown in Table 3. In other words, the denitration reaction and CO removal reaction improve with an increase in the membrane mass transfer coefficient, but their values are limited, whereas the pressure loss of the catalyst structure increases to a value that makes practical use difficult. It is.

[0056]

[Table 3]

On the other hand, the SO ₂ oxidation performance was lower in the catalyst structures of Examples 1 and 2 and Comparative Examples 2 and 4 than in the catalyst structure of Comparative Example 3, and the noble metal such as platinum shown in Comparative Example 1 was added. This was equivalent to a conventional catalyst structure having a parallel flow type gas flow path not provided.

In other words, when the catalyst structures shown in Examples 1 and 2 are compared with the same catalyst volume, they have lower ventilation resistance than the conventional catalysts to which a noble metal such as platinum is added (Comparative Examples 2 and 4). With the increase, the catalyst has the same denitration performance and CO oxidation performance, and has the same SO ₂ oxidation performance as the conventional catalyst (Comparative Example 1) to which noble metals such as platinum are not added.

On the other hand, FIG. 5 shows the flow rate characteristics of the catalytic denitration performance of Examples 1, 3 and 4 and Comparative Examples 1 and 3. The catalytic structure having a parallel flow gas flow path of Comparative Examples 1 and 3 is shown. In comparison, it can be seen that the catalytic performance of the catalyst units of Examples 1, 3 and 4 increases sharply as the gas flow rate increases. The performance of the catalyst structures of Examples 1, 3 and 4 was reduced to almost the same level as Comparative Examples 1 and 3 when the gas superficial velocity was around 2 m / s. This corresponds to each catalyst element 1 of the catalyst structure of Example 1, 3 or 4.
Θ = 30 degrees (θ ′ = 1) with respect to the flow direction of the exhaust gas 6
The ridges of the ridges 2 and 2 'existing at an angle of 50 °) act as turbulence promoters when the superficial flow velocity is high, but conversely form flow stagnation in the low flow velocity area and cause mass transfer. It is considered to be because

Accordingly, the plate-like catalyst structure according to the present invention
The flow rate is preferably in the range of an exhaust gas flow of at least m / s and less than 10 m / s, where an increase in pressure loss does not pose a practical problem.

Next, with respect to Examples 1 to 5 and Comparative Examples 1, 3 and 5, the performance of removing dioxins by various catalysts was compared using actual exhaust gas from a municipal waste incinerator. Table 4 shows the test conditions, and Table 5 shows the dioxin removal performance of each catalyst.

[0062]

[Table 4]

[0063]

[Table 5]

As shown in Table 5, when comparing the removal performance of dioxins (PCDD _S + PCDF _S ) per the same catalyst volume, Examples 1 to 5 showed the same dioxin removal as Comparative Examples 1, 3 and 5. It can be seen that performance is obtained.
That is, as in the case of carbon monoxide (CO) shown in Table 3, the removal rates of the dioxins in the catalysts shown in Examples 1 to 5 are equivalent to the results of Comparative Examples 1, 3 and 5, and It was confirmed that dioxins can be efficiently removed with a smaller surface area by increasing the membrane mass transfer coefficient.

FIG. 6 shows the catalytic activities of the catalysts of Example 3 and Comparative Example 1 when the concentration of dioxins at the catalyst inlet was changed. From FIG. 6, it can be seen that the catalyst of Example 3 has less decrease in the dioxin removal performance in the low concentration region as compared with Comparative Example 1. That is, the third embodiment
The catalyst shown in (1) is easy to diffuse (migrate) the reactants, so that dioxins can be efficiently removed up to a low concentration. Normally, dioxins contained in the exhaust gas discharged from municipal waste incinerators are extremely low in concentration, and the catalyst is required to further reduce this low concentration of dioxins, so that such diffusion is easy. A suitable catalyst shape has a large effect.

[0066]

According to the present invention, it is possible to provide a compact exhaust gas treatment apparatus capable of efficiently realizing denitration and decomposition and removal of CO and dioxins by gas turbulence while suppressing the ventilation resistance in the catalyst structure. Can be.

[Brief description of the drawings]

1 (a) and 1 (b) are structural diagrams of a catalyst element of the present invention, and FIG. 1 (c) is a diagram showing a method of laminating a catalytic element of the present invention.

FIG. 2 is a diagram showing a structural example of a projecting portion of the catalyst element of the present invention.

FIG. 3 is a diagram showing the relationship between the AV value and the SO ₂ oxidation rate of the catalyst of the present invention.

FIG. 4 is a diagram showing the relationship between the AV value and the CO oxidation rate of the platinum-added catalyst of the present invention.

FIG. 5 is a diagram showing flow velocity characteristics of catalysts shown in examples of the present invention and comparative examples.

FIG. 6 is a graph showing the relationship between the concentration of dioxins at the catalyst inlet of the present invention and the activity (performance) of the catalysts of Examples and Comparative Examples.

FIG. 7 is a structural view of a catalyst element according to the related art.

FIG. 8 is a structural view of a catalyst element according to the related art.

FIG. 9 is a view showing a catalyst structure in which the catalyst elements of FIG. 7 or 8 are stacked.

[Explanation of symbols]

1, 11, 21, 1 ', 11', 21 'Catalyst element 2, 2' Ridge 3, 3 'Flat part 5 Frame 6 Exhaust gas

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B01J 23/652 B01J 23/64 102A 103A (72) Inventor Takashi Michimoto 6-9 Takara-cho, Kure-shi, Hiroshima Pref. 72) Inventor Kazunori Ito 6-9 Takara-cho, Kure-shi, Hiroshima Babcock-Hitachi Kure Factory

Claims (6)

[Claims] 1. A ridge and a flat portion, each of which has a catalyst component having catalytic activity on the surface and has a crossing angle with respect to the exhaust gas flow of more than 0 and less than 50 degrees, are alternately spaced apart from each other. A plate-like first catalyst element composed of repetitions, and a ridge formed of a strip-like projection carrying a catalytic component having catalytic activity on the surface and having an intersection angle with respect to the exhaust gas flow of more than 0 and less than 130 degrees. A catalyst structure comprising a plurality of plate-like second catalyst elements, which are alternately repeated at intervals, and a plurality of the plate-like second catalyst elements, which are alternately stacked in a state where the ridges are in contact with each other, At least one oxide selected from titania, silica, alumina and silica-alumina as a first component of a catalytic component having catalytic activity and vanadium, tungsten and molybdenum as a second component A plate containing at least one selected oxide and having a membrane mass transfer coefficient of a reactant of 120 m / h or more and less than 500 m / h among the coefficients relating to the overall reaction rate of the catalyst. Catalyst structure. 2. A catalyst component having catalytic activity, in addition to the first component and the second component, at least one selected from the group consisting of platinum, iridium, rhodium, palladium and oxides thereof as a third component. The plate-shaped catalyst structure according to claim 1, comprising: 3. Nitrogen oxides and carbon monoxide (C) in exhaust gas
The plate-shaped catalyst structure according to claim 1, which is used for removing O) and / or dioxin (DXN). 4. A catalyst, wherein the plate-like catalyst structure according to claim 1 is disposed in an exhaust gas flow path in which the superficial velocity of the gas to be treated is in the range of 2 m / s or more and less than 10 m / s. Reactor. 5. The catalyst structure according to claim 1, wherein the catalyst structure is provided in a flow path of an exhaust gas discharged from a gas-fired boiler, an oil-fired boiler, a coal-fired boiler, a gas turbine, a diesel engine, a municipal garbage incinerator, a sintering machine, or a chemical plant. A catalytic reactor characterized by disposing. 6. The catalytic reactor according to claim 5, wherein an injection portion for a reducing agent of nitrogen oxide is provided in an exhaust gas flow path on the upstream side of the exhaust gas flow path in which the catalyst structure is disposed. .