JP5374441B2 - Exhaust gas treatment catalyst regeneration method and exhaust gas treatment catalyst using this method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for regenerating a used exhaust-gas treatment catalyst by which the durability of the regenerated exhaust-gas treatment catalyst can surely be kept satisfactorily over a long period of time, and to provide the exhaust-gas treatment catalyst. <P>SOLUTION: The method for regenerating the used exhaust-gas treatment catalyst 11 having the ash-stuck surface includes: a coarsely crushing step S1 of coarsely crushing the exhaust-gas treatment catalyst 11 to produce coarse chips 12 which accounts for 70-95 wt.% of the total weight of the exhaust-gas treatment catalyst 11 and each of which has the size exceeding the threshold size S (the optional value within 0.105-1.0 mm); a separation step S2 of separating the coarsely-crushed material of the exhaust-gas treatment catalyst 11 into the coarse chips 12 each having the size exceeding the threshold size S and fine powder 13 of the size equal to or smaller than the threshold size S; a finely pulverizing step S3 of finely pulverizing the separated coarse chips 12 into fine powder of &le;0.1 mm average particle size; a kneading step S4 of kneading the fine powder with another raw material; a molding step S5 of molding the obtained kneaded material into the exhaust-gas treatment catalyst; a drying step S6 of drying a green molding of the exhaust-gas treatment catalyst; and a firing step S7 of firing the dried green molding at 615-700&deg;C to obtain the regenerated exhaust-gas treatment catalyst 14. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a method for regenerating an exhaust gas treatment catalyst having ash attached to the surface and an exhaust gas treatment catalyst using this method, and in particular, removing nitrogen oxides in exhaust gas from burned coal with titanium oxide as a main component. It is extremely effective when applied to the regeneration of an exhaust gas treatment catalyst.

For example, an exhaust gas treatment line for treating nitrogen oxides (NO _x ) in the exhaust gas is disposed in an exhaust gas exhaust line from an apparatus that burns coal such as a coal-fired boiler. This exhaust gas treatment catalyst is composed of titanium oxide (TiO ₂ ) as a main component, and further, honeycomb oxide (WO ₃ ), vanadium oxide (V ₂ O ₅ ), etc. are kneaded together with a binder to have a large number of pores. A reducing agent such as ammonia (NH ₃ ) is circulated along with the exhaust gas inside the hole, and the reducing agent is placed on the wall surface of the hole together with the nitrogen oxide in the exhaust gas. By contacting, the nitrogen oxide can be decomposed and removed.

  In such an exhaust gas treatment catalyst, when the ash (fly ash) generated by the combustion of coal circulates in the hole together with the exhaust gas, as it is used, calcium (Ca) and the like in the fly ash are used. The component gradually adheres to the inner wall surface of the hole (thickness: several tens of μm), which inhibits the contact reaction between the nitrogen oxide and the reducing agent on the catalyst surface, and the fly ash itself is It partially accumulates inside the hole and gradually makes it difficult for the exhaust gas to flow through the hole. Finally, the hole is completely blocked and clogged, resulting in a decrease in denitration performance. ing.

  For this reason, in the said exhaust gas treatment catalyst used for the predetermined period, as described in the following patent document 1, for example, the threshold size S (in the range of 70 to 95% by weight with respect to the total weight of the exhaust gas treatment catalyst) The exhaust gas treatment catalyst is coarsely pulverized (coarse pulverization step) so as to produce an excessive coarse piece (any value within the range of 0.105 to 1.0 mm), and the coarsely pulverized product of the exhaust gas treatment catalyst is a threshold size. Separating into coarse particles exceeding S and fine powder having a threshold size S or less (separation step), and finely pulverizing the separated coarse particles into fine powder having an average particle size of 0.1 mm or less (fine pulverization step) ) After fine powder is kneaded with other raw materials and molded into an exhaust gas treatment catalyst (kneading process and molding process), the molded prototype is dried and fired (around 500 ° C.) (drying process) And firing step) to regenerate the exhaust gas treatment catalyst It is.

JP 2009-226388 A JP-A-3-016646 Japanese Patent Laid-Open No. 9-276659

  By the way, in the regeneration method described in Patent Document 1, an exhaust gas treatment catalyst that does not cause a problem can be obtained in many cases, but there may be a problem in long-term durability. It was found to occur rarely.

  If there is a difficulty in such durability, the fly ash collides with the exhaust gas treatment catalyst, so that the exhaust gas treatment catalyst is worn and thinned, and there is a possibility that it cannot be used for a long time.

  For this reason, the present invention provides a method for regenerating an exhaust gas treatment catalyst that can reliably maintain durability for a long period of time even when regenerated by pulverizing and then remolding and firing. And it aims at providing the exhaust-gas-treatment catalyst which uses this method.

The method for regenerating an exhaust gas treatment catalyst according to the first invention for solving the above-described problem is a method for regenerating an exhaust gas treatment catalyst having ash adhered to the surface, wherein the total weight of the used exhaust gas treatment catalyst is relative to produce a crude piece of threshold size S more than in the range of 70 to 95 wt%, a coarse crushing step for coarse crushing the used of the exhaust gas treatment catalyst, the crude crushed the exhaust gas treatment catalyst wherein the coarse pieces and the separation step of separating the said threshold size S less fine powder, a milling step of the separated the coarse pieces pulverized to a fine powder, the fine powder pulverized as raw materials A molding step of molding into an exhaust gas treatment catalyst and a firing step of firing the molded exhaust gas treatment catalyst at a temperature of 615 to 700 ° C. are performed.
However, the threshold size S is a certain value between 0.105 mm and 1.0 mm .

  A method for regenerating an exhaust gas treatment catalyst according to a second invention is characterized in that, in the first invention, the exhaust gas treatment catalyst comprises titanium oxide as a main raw material.

  The regeneration method for an exhaust gas treatment catalyst according to a third aspect of the invention is characterized in that, in the second aspect of the invention, the exhaust gas treatment catalyst treats exhaust gas from burned coal.

  According to a fourth aspect of the present invention, there is provided a method for regenerating an exhaust gas treatment catalyst according to the third aspect, wherein the exhaust gas treatment catalyst treats nitrogen oxides in the exhaust gas.

According to a fifth aspect of the present invention, there is provided a method for regenerating an exhaust gas treatment catalyst according to any one of the first to fourth aspects, wherein the fine pulverization step sets the average particle size of the fine powder to 0.1 mm or less. And the step of pulverizing the coarse pieces.

In addition, the exhaust gas treatment catalyst according to the sixth invention for solving the above-mentioned problems is one that has been regenerated by the exhaust gas treatment catalyst regeneration method of any one of the first to fifth inventions. It is characterized by.

  According to the method for regenerating an exhaust gas treatment catalyst according to the present invention, when a used exhaust gas treatment catalyst is once pulverized and then molded and fired again, the temperature (615 to 615) is higher than when a new exhaust gas treatment catalyst is produced. (700 ° C.), the degree of sintering can be more reliably advanced. For this reason, according to the exhaust gas treatment catalyst of the present invention, sufficient strength can be exhibited throughout, and wear thinning due to fly ash collision can be sufficiently suppressed while maintaining sufficient denitration performance. Therefore, it can be ensured that the durability is sufficiently maintained over a long period of time.

It is a schematic block diagram of the exhaust gas treatment catalyst used in the main embodiment of the regeneration method of the exhaust gas treatment catalyst according to the present invention. It is a flowchart showing the procedure of main embodiment of the regeneration method of the exhaust gas treatment catalyst which concerns on this invention. It is the graph which calculated | required the relationship between the calcination temperature and the abrasion rate in Test Example 2 in the Example of the regeneration method of the exhaust gas treatment catalyst according to the present invention.

  An exhaust gas treatment catalyst regeneration method and an exhaust gas treatment catalyst using this method according to the present invention will be described below with reference to the drawings. However, the present invention is not limited to only the embodiments described below.

[Main embodiments]
A main embodiment of an exhaust gas treatment catalyst regeneration method and an exhaust gas treatment catalyst using this method according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, an exhaust gas treatment catalyst 10 according to this embodiment includes titanium oxide (TiO ₂ ) as a main component, and tungsten oxide (WO ₃ ), vanadium oxide (V ₂ O ₅ ), and the like together with a binder. It is kneaded, formed into a honeycomb shape so as to have a large number of holes 10a, and fired.

Such an exhaust gas treatment catalyst 10 is disposed in an exhaust gas exhaust line from an apparatus that burns coal such as a coal-fired boiler, and a reducing agent such as ammonia (NH ₃ ) together with the exhaust gas inside the hole 10a. The nitrogen oxide can be decomposed and removed by bringing the reducing agent into contact with the wall surface of the hole 10a together with the nitrogen oxide (NO _x ) in the exhaust gas.

  In the exhaust gas treatment catalyst 10, when ash (fly ash) generated with coal combustion flows through the hole 10 a together with the exhaust gas, as it is used, calcium (Ca) and the like in the fly ash are used. The component gradually adheres to the inner wall surface of the hole 10a (thickness: several tens of μm) to inhibit the contact reaction between the nitrogen oxide and the reducing agent on the surface of the hole 10a, and the fly ash The self deposits partially inside the hole 10a, making it difficult for the exhaust gas to gradually flow through the hole, and finally clogging the hole completely, resulting in a decrease in denitration performance. Therefore, after use for a predetermined period, it is taken out from the exhaust gas line and transported to the regeneration treatment facility.

  The used exhaust gas treatment catalyst 11 carried into the regeneration treatment facility is put into a coarse pulverizer such as a crusher without being subjected to a washing treatment step with a washing liquid such as water, and is 70 to 70% of the total weight. Roughly pulverized so as to produce a coarse piece 12 exceeding a threshold size S (an arbitrary value within a range of 0.105 mm to 1.0 mm) in a range of 95% by weight (in FIG. 2, coarsely pulverized step S1). .

  The coarsely pulverized coarsely pulverized product of the exhaust gas treatment catalyst 11 is supplied on a sieve having a mesh size of the threshold size S, and the coarse particles 12 exceeding the threshold size S and fine powders 13 having the threshold size S or less are used. Separated (in FIG. 2, separation step S2).

  The fine powder 13 that has passed through the mesh of the sieve is discarded. On the other hand, the coarse piece 12 remaining on the mesh of the sieve is put into a fine pulverizer such as a hammer mill and finely pulverized so as to become a fine powder having an average particle size of 0.1 mm (preferably 70 μm) or less. (In FIG. 2, fine pulverization step S3).

  The fine powder is supplied as a raw material to a kneader such as a kneader together with another compound such as a binder and water and kneaded uniformly (in FIG. 2, kneading step S4). This kneaded material is supplied to an extrusion molding machine and molded into a honeycomb shape (in FIG. 2, molding step S5). The molded prototype is naturally dried and then dried with hot air (100 ° C.) or the like (in FIG. 2, drying step S6), and then baked in a firing furnace (615 to 700 ° C.) (in FIG. 2, The calcination step S7) becomes the regenerated exhaust gas treatment catalyst 14.

  That is, in the regeneration method of the exhaust gas treatment catalyst described in Patent Document 1, the calcination treatment is performed at around 500 ° C., that is, the calcination treatment at the same temperature as when producing a new (new) exhaust gas treatment catalyst. However, in the regeneration method of the exhaust gas treatment catalyst according to the present embodiment, the firing temperature is 615 to 700 ° C., that is, the firing is performed at a higher temperature than when a new (new) exhaust gas treatment catalyst is manufactured. It was made to process. The reason for this will be described below.

  In the conventional method for regenerating an exhaust gas treatment catalyst described in Patent Document 1, as described above, an exhaust gas treatment catalyst that does not cause a problem can be obtained in many cases. In some rare cases, it would be difficult to achieve durability.

As a result of extensive investigations by the present inventors, the details are not clear, but the main raw material titanium oxide (TiO ₂ ) has a wide variety of thermal histories (heating treatment when manufactured as a raw material ( Detailed temperature is unknown), firing treatment when manufactured as a new article (around 500 ° C), exhaust gas atmosphere exposure when treating exhaust gas (tens of thousands of hours at about 300-400 ° C), etc.) depending on the degree of thermal history of titanium oxide (TiO _2), sintering degree of titanium oxide (TiO ₂₎ causes considerably advanced, than were fired at the same temperature as the manufacture of the new (500 ° C. so) is It was inferred that it was difficult to sinter until it had sufficient strength.

  Therefore, the inventors of the present invention perform the exhaust gas treatment catalyst at a higher temperature (615 to 700 ° C.) than when a new exhaust gas treatment catalyst is newly produced when it is once pulverized and then molded and fired again. As a result, the degree of sintering proceeds more reliably.

  Thereby, in the exhaust gas treatment catalyst 10 according to the present embodiment, as can be seen from the examples described later, it becomes possible to express a sufficient strength over the whole, and fly ash while maintaining sufficient denitration performance. It has become possible to sufficiently suppress wear loss due to collision.

  Therefore, according to the present embodiment, it is possible to ensure that the durability is sufficiently maintained over a long period of time even when the powder is once pulverized and then re-molded and fired.

In addition, as described above, when the firing temperature is less than 615 ° C., depending on the thermal history of titanium oxide (TiO ₂ ), there may be cases where sufficient strength cannot be expressed throughout. When the calcination temperature exceeds 700 ° C., the main raw material titanium oxide (TiO ₂ ) is changed in crystal structure from anatase type to rutile type, and the exhaust gas treatment catalyst contracts, thereby deteriorating the denitration performance. Therefore, it is preferable to perform the firing at 615 to 700 ° C.

  In the coarse pulverization step S1, as described above, it is preferable to coarsely pulverize the coarse pieces 12 in a range of 70 to 95% by weight with respect to the total weight of the used exhaust gas treatment catalyst 11. This is because if the coarse pieces 12 produced by coarse pulverization are less than 70% by weight with respect to the total weight of the used exhaust gas treatment catalyst 11, the amount of exhaust gas treatment catalyst that is discarded together with fly ash or the like is too large. Regeneration efficiency is reduced, and the regeneration cost is increased. On the other hand, when the coarse pieces 12 generated by coarse pulverization exceed 95% by weight with respect to the total weight of the used exhaust gas treatment catalyst 11, the regeneration is performed. This is because the amount of fly ash or the like mixed into the exhaust gas treatment catalyst 14 may increase.

[Other Embodiments]
In the above-described embodiment, the case of the exhaust gas treatment catalyst 10 molded into a honeycomb shape has been described. However, the present invention is not limited to this, and as another embodiment, for example, a pellet shape or a pipe shape is molded. Even in the case of an exhaust gas treatment catalyst, it can be applied in the same manner as in the above-described embodiment.

  Further, in the above-described embodiment, the case of the exhaust gas treatment catalyst 10 disposed in the exhaust line of exhaust gas from a device that burns coal such as a coal-fired boiler has been described, but the present invention is not limited thereto. In the case of an exhaust gas treatment catalyst in which ash in the exhaust gas adheres to or accumulates on the surface, it can be applied in the same manner as in the above-described embodiment.

  The exhaust gas treatment catalyst regeneration method according to the present invention and the confirmation test conducted to confirm the effect of the exhaust gas treatment catalyst using this method will be described below. However, the present invention is limited only to the confirmation test described below. It is not something.

[Test Example 1]
<Preparation of specimen>
<< Specimen A1 >>
Honeycomb shape used in an exhaust gas line of a coal fired boiler (length = 150 mm, width = 150 mm, length = 800 mm, wall thickness = 1.15 mm, pitch (length between adjacent wall centers) ) = 7.4 mm, scale (n) = 20 × 20) denitration exhaust gas treatment catalyst A (TiO ₂ = 77.3%, WO ₃ = 9.00%, V ₂ O ₅ = 0.55) %, Others = 13.15%) is roughly pulverized with a crusher to obtain a coarsely pulverized product a.

  Next, the coarsely pulverized product a is sieved with a sieve (mesh size (nominal size specified in Japanese Industrial Standard (JIS)) = 0.5 mm), and the coarse pieces remaining on the sieve are finely pulverized with a hammer mill. (Average particle size = about 20 μm), the obtained fine powder (15 kg), organic binder (0.7 kg), glass fiber (1.5 kg (diameter = 11 μm, length = 3 mm)) and water (appropriate amount) Are kneaded with a kneader and mixed uniformly, and the obtained kneaded product is supplied to an extrusion molding machine to form a honeycomb (length = 69 mm, width = 69 mm, length = 800 mm, mesh pitch = 7.4 mm, mesh opening) = 6.25 mm, scale (n) = 9 x 9) prototype of exhaust gas treatment catalyst was prepared, and this prototype was sufficiently air-dried and then dried with hot air (100 ° C x 5 hours). Regenerated exhaust gas treatment catalyst by firing treatment (500 ° C x 3 hours) The test body A1 of the medium was obtained.

<< Specimen B1 >>
Honeycomb shape (length = 150 mm, width = 150 mm, length = 800 mm, wall thickness = 1.15 mm, pitch (length between adjacent wall centers) used for about 45,000 hours in a coal fired boiler exhaust line ) = 7.4 mm, scale (n) = 20 × 20) exhaust gas treatment catalyst B for denitration (TiO ₂ = 79.0%, WO ₃ = 8.10%, V ₂ O ₅ = 0.40) %, Other = 12.50%) is roughly pulverized with a crusher to obtain a coarsely pulverized product b.

  Next, the coarsely pulverized product b was treated in the same manner as the coarsely pulverized product a of the test body A1, thereby obtaining a regenerated exhaust gas treatment catalyst test body B1.

<< Specimen C1 >>
Honeycomb shape used for about 40,000 hours in a coal-fired boiler exhaust line (length = 150 mm, width = 150 mm, length = 800 mm, wall thickness = 1.15 mm, pitch (length between adjacent wall centers) ) = 7.4 mm, scale (n) = 20 × 20) exhaust gas treatment catalyst C for denitration (TiO ₂ = 81.0%, WO ₃ = 8.00%, V ₂ O ₅ = 0.60) %, Others = 10.40%) is roughly pulverized with a crusher to obtain a coarsely pulverized product c.

  Next, the coarsely pulverized product c was treated in the same manner as the coarsely pulverized product a of the test body A1, thereby obtaining a regenerated exhaust gas treatment catalyst test body C1.

<Test method>
《Denitration rate》
Two reactors (number of eyes (n) = 6 × 7, length = 800 mm) cut from the specimens A1 to C1 were filled in the reactor, and the denitration rate was determined under the conditions shown below.

* Test conditions, exhaust gas composition -NO _x: 150ppm
NH ₃ : 150 ppm
SO ₂ : 800 ppm
O ₂ : 4%
CO ₂ : 12.5%
H ₂ O: 11.5%
N ₂ : Balance, exhaust gas temperature: 380 ° C
・ Exhaust gas amount: 19.63 Nm ³ / hr
・ U _gs : 2.3 Nm / sec
・ AV: 11.63Nm ³ / m ²・ hr

NOx removal rate (%) = {1− (catalyst outlet NO _x concentration / catalyst inlet NO _x concentration)} × 100

《Abrasion rate》
One gas (number (n) = 6 × 6, length = 100 mm) cut from each of the specimens A1 to C1 was filled in a horizontal reactor, and gas containing dredged sand (average particle size = 37 μm) was contained. The wear rate was determined by circulating (concentration = 70 g / m ³ ) in the horizontal direction under the following conditions.

* Test conditions and temperature: 20 ° C
・ Pressure: Atmospheric pressure ・ Flow velocity (per catalyst cross section): 40 m / sec
・ Distribution time: 30 minutes

Wear rate (%) = {(W ₀ −W) / W ₀ } × 100
However, W ₀ is the catalyst weight before the test, and W is the catalyst weight after the test.

<Test results>
The test results of the denitration rate test and the wear rate test are shown in Table 1 below.

As can be seen from Table 1 above, the denitration rate was able to express sufficient performance in all the specimens A1 to C1. On the other hand, the wear rate was able to express sufficient performance (reference value: 15% or less) in the specimen A1, but sufficient performance (reference value: 15% or less) in the specimens B1 and C1. It could not be expressed. Although this reason is not certain as explained above, it is presumed that it is based on the difference in the thermal history as a total of the main raw material titanium oxide (TiO ₂ ).

[Test Example 2]
<Preparation of specimen>
Using the coarsely pulverized products b and c obtained in Test Example 1, the firing conditions were changed (temperatures: 550 ° C., 600 ° C., 650 ° C., 700 ° C., and 750 ° C., firing time: 5 hours). Specimens B2 to B6 and C2 to C6 were produced by treating in the same manner as in Test Example 1 except that.

<Test method>
In the same manner as in Test Example 1, the denitration rate and the wear rate of the specimens B2 to B6 and C2 to C6 were determined.

<Test results>
The test results of the denitration rate test and the wear rate test are shown in Table 2 below, and a graph showing the relationship between the firing temperature and the wear rate is shown in FIG.

As can be seen from Table 2 above, the specimens B6 and C6 have a firing temperature that is too high (750 ° C.), and the main raw material titanium oxide (TiO ₂ ) causes a change in crystal structure from anatase type to rutile type. As a result, the degree of sintering progressed too much and contracted, and it was not in a state where the function as a catalyst could be expressed.

  On the other hand, it was confirmed that the test bodies B2 to B5 and C2 to C5 can express sufficient performance in the denitration rate.

  As can be seen from the description of FIG. 3, it was confirmed that sufficient performance (15% or less) in terms of wear rate could be exhibited when the firing temperature was 615 ° C. or higher.

  The method for regenerating an exhaust gas treatment catalyst according to the present invention and the exhaust gas treatment catalyst using this method can be used extremely beneficially in various industries.

10 Exhaust gas treatment catalyst 10a Hole

Claims (6)

A method for regenerating an exhaust gas treatment catalyst with ash on the surface,
Range of 70 to 95% by weight relative to the total weight of the used of the exhaust gas treatment catalyst to produce a threshold size S than the coarse pieces, and coarse grinding step for coarse crushing the used of the exhaust gas treatment catalyst,
A separation step of separating the crude crushed the exhaust gas treatment catalyst and the coarse pieces and the threshold size S less fine powder,
A pulverizing step of pulverizing the separated coarse pieces into fine powder;
A molding step of molding the finely pulverized fine powder as a raw material into an exhaust gas treatment catalyst;
A method for regenerating an exhaust gas treatment catalyst, comprising: performing a calcining step of calcining the molded prototype of the exhaust gas treatment catalyst at a temperature of 615 to 700 ° C.
However, the threshold size S is a certain value between 0.105 mm and 1.0 mm . In the regeneration method of the exhaust gas treatment catalyst according to claim 1,
The method for regenerating an exhaust gas treatment catalyst, wherein the exhaust gas treatment catalyst is mainly composed of titanium oxide. In the regeneration method of the exhaust gas treatment catalyst according to claim 2,
A method for regenerating an exhaust gas treatment catalyst, wherein the exhaust gas treatment catalyst treats exhaust gas from burned coal. In the regeneration method of the exhaust gas treatment catalyst according to claim 3,
The exhaust gas treatment catalyst treats nitrogen oxides in the exhaust gas. A method for regenerating an exhaust gas treatment catalyst. In the regeneration method of the exhaust gas treatment catalyst according to any one of claims 1 to 4 ,
The method for regenerating an exhaust gas treatment catalyst, wherein the fine pulverization step is a step of finely pulverizing the coarse pieces so that an average particle size of the fine powder is 0.1 mm or less. An exhaust gas treatment catalyst regenerated by the method for regenerating an exhaust gas treatment catalyst according to any one of claims 1 to 5 .

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