JPS63267446A - Baking of catalyst for denitration - Google Patents

Abstract

PURPOSE:To improve denitration rate or mechanical characteristics by providing desulfurization catalytic units arranged on a reticulate belt with a fresh hot blast so that a hot blast passage direction may be reversed and the sulfuric acid radical content of the catalyst may be 4-7wt.%. CONSTITUTION:Plate-like catalytic units 3 for denitration are arranged on an endless reticulate belt 4 which are tensely installed on two rolls in such a manner that the flow direction of a hot blast may be vertical. Then hot blast 1 (1a, 1b-1n) is permitted to pass upward from under the reticulate belt 4 which advances as shown by an arrow mark 5. At that time, the hot blast is controlled so that the sulfuric acid radical content of the catalytic units 3 may be 4-7wt.%. Consequently, the temperature of the catalytic units 3 increases and is baked by keeping the temperature at the same level. As the belt 4 moves, the catalytic units proceed to a position where a hot blast 1' is supplied, thus permitting them to undergo further baking. When the baking is completed, the catalytic units are lowered from the reticulate belt 4.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for firing a denitrification catalyst, and particularly to a method for firing a denitrification catalyst suitable for obtaining a denitrification catalyst having uniform performance. .

[Conventional technology]

BACKGROUND ART Catalysts based on metal oxides such as titanium, vanadium, and molybdenum are conventionally known as catalysts used for exhaust gas denitration to reduce nitrogen oxides contained in exhaust gas with ammonia. Since the strength of the metal oxides mentioned above is low if they are formed as is, a method is used to form a plate-shaped catalyst by using a plate-shaped porous support as a core material and applying a catalyst substance to the front and back surfaces of the core material (U.S. Pat. 4,567.630
issue).

An example of its manufacturing method is to heat and knead the raw material slurry of the catalyst material, extrude it into granules, dry it, pre-calcine it, finely grind it, add water and filler, and knead it into a paste state. It is applied and pressed onto metal, processed into a plate-like shape with a Z-shaped protrusion in cross section, then cut and air-dried. After the main firing, the obtained plate-shaped catalyst elements are impregnated with other catalyst components as necessary, and then stacked in a frame to form a catalyst unit. This catalyst unit is finally fired and made into a product.

As the firing furnace used for the above-mentioned firing, a so-called hot air circulation furnace has conventionally been used in which hot air is circulated from one direction through catalyst units arranged on a trolley.

However, in such furnaces, the performance of the products obtained after firing is not constant, and in particular the quality of the catalyst at the inlet and outlet of the hot blast furnace deteriorates, making it impossible to use it as a product. There were problems in that the volume decreased, energy loss increased, and firing time took longer.

[Problem that the invention seeks to solve]

An object of the present invention is to uniformly fire a catalyst unit formed by stacking plate-shaped catalysts regardless of the location of the hot blast furnace, and to produce a uniform catalyst with excellent denitrification rate and mechanical properties. An object of the present invention is to provide a method for firing a denitrification catalyst.

[Means for solving problems]

The present invention includes a step of arranging a denitrification catalyst unit on a mesh belt that moves continuously in a furnace, and a step of disposing a denitrification catalyst unit on a mesh belt that moves continuously in a furnace, and a process in which fresh hot air is It consists of a step of feeding hot air and a step of removing the catalyst unit from the mesh belt, and the step of passing the hot air is performed when the content of sulfate groups in the catalyst is
The method is characterized in that the speed of the hot air is controlled so that the amount of hot air is 7% by weight.

The present inventors investigated the reason why calcination is not performed uniformly in a conventional calcination furnace using hot air circulation, and as a result, it was found that the sulfate radicals remaining in the catalyst have a large effect on the quality of the catalyst. In other words, oxides of metals such as titanium, vanadium, and molybdenum, which are catalyst raw materials, are added as sulfates or sulfuric acid solutions, so sulfate groups are present in the catalyst composition and ultimately remain in the catalyst. It was found that the denitrification rate and mechanical properties of the catalyst were affected by the content of sulfate radicals. Figure 5 shows the relationship between the amount of SO4 in the catalyst (wt%), the amount of wear of the catalyst, and the denitrification rate.
As the S04 content increases, the wear amount of the catalyst decreases, and on the other hand, the denitrification rate shows the maximum value when the SO4 content is in the range of about 4 to 6 M%. It has been found that by adjusting the content within the range of 4 to 7% by weight, preferably 5 to 6% by weight, a catalyst of high quality and uniform performance can be obtained.

In the present invention, the direction of hot air passing is reversed at the front and rear parts of the continuously moving mesh belt, for example, from below to above at the front part of the mesh belt, and conversely from above at the rear part of the mesh belt. Sends fresh hot air downward. The catalyst disposed on the belt is first heated to a specified temperature and heat-treated by blowing hot air from the bottom to the top through the catalyst layer from a hot air supply means provided below. Next, as the belt moves, the catalyst moves upward to a position where a hot air supply means is provided, and as the next step, it is heat-treated by hot air blowing from above to below. In this way, as the belt continues to move, the catalyst is heat-treated almost uniformly while passing through the section where hot air supply means are provided above and below.

If hot air is passed through the catalyst unit only from one direction, the performance of the catalyst will be different between the inlet side and the outlet side of the hot air (for example, the inlet side of the hot air will have high activity, low strength,
One outlet side has low activity and high strength), making it impossible to obtain a catalyst with uniform performance. According to the research of the present inventors, this is due to the influence of the distribution of sulfate groups in the catalyst, and as the catalyst temperature on the upstream side of the hot air increases, the sulfate groups on the upstream side begin to be extracted first. , the hot air gradually flows downstream, and the sulfuric acid radicals flowing out from the catalyst surface on the upstream side adhere to the downstream side. Therefore, the residual sulfuric acid radicals on the upstream side of the hot air are low, and the residual sulfuric acid radicals on the downstream side are high, resulting in poor catalyst performance. It becomes uniform.

The above hot air must be fresh. When used hot air is recirculated, the sulfuric acid released from the catalyst will adhere to the catalyst again, and it will take a long time to reduce the sulfuric acid content in the catalyst to a specified value, and the sulfuric acid content in the catalyst at the hot air inlet will increase. increases, resulting in non-uniform catalyst quality. The preferred conditions for the hot air oven to burn the catalyst and bring the content of sulfate groups in the catalyst within a predetermined range are a hot air temperature of 350 to 600.
℃, more preferably 450 to 550℃, hot air speed 0
．． 1 to 0.9 m/sec, more preferably 0°3
~0.5 m/sec, catalyst residence time in the furnace 1 to 4 hours,
More preferably, the time is 2 to 3 hours, and these conditions are appropriately combined to increase the content of sulfate groups in the catalyst to 4 to 7% by weight.
, preferably within the range of 5 to 6% by weight.

If the hot air temperature is too low or the hot air speed is too low, the firing time will take a long time, and if the temperature is too high or the hot air speed is too high, cracks may occur in the catalyst.

Next, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a perspective view of a plate-shaped catalyst firing furnace showing one embodiment of the present invention. As shown in FIG. 3, the plate-shaped catalyst unit 3 arranged on the mesh belt 4 in FIG. 1 is a unit made by laminating corrugated plates or flat plates with spacers and storing them in a case. .

As shown in FIG. 1, denitrification plate catalyst units 3 are arranged on an endless mesh belt 4 stretched between two rolls so that the flow direction of the hot air is vertical. Hot air 1 (la, lb
. During the firing, as the reticulated belt 4 moves, it moves to a position where the hot air 1' (1a l, lb', IC') is fed from above to below the catalyst unit 3, and the temperature is further maintained. Firing is carried out by
After the firing is completed, it is unloaded from the mesh belt 4.

The loading method and arrangement of the plate-shaped catalyst unit 3 may be such that hot air can pass through the catalyst layer. For example, in this embodiment, hot air is sent from the bottom to the top in the front stage of the mesh belt 4, and from the top to the bottom in the rear stage, but conversely, the hot air is sent from the top to the bottom in the front stage, and the hot air is delivered from the bottom to the top in the rear stage. The same goes for feeding, and a uniform firing effect can be obtained.

Further, in FIG. 1, the accompanying equipment such as walls and ceilings are omitted from illustration, but in order to keep the heat in the actual machine, the parts through which hot air flows are sealed, and a flue for exhaust is provided.

FIG. 2 is a plan view showing another embodiment of the invention. Hot air 1a, lb, and IC are supplied from the side, and hot air 1 is supplied from the middle.
Since a1, lb', and IC+ are supplied from other sides, it is possible to obtain a catalyst with uniform performance in the longitudinal and middle directions of the plate-shaped catalyst as in Example 1.

Although the embodiments of the present invention have been explained using a plate-shaped catalyst unit as an example, the present invention can also be applied to firing a honeycomb catalyst or the like.

According to the above embodiment, by switching the flow direction of the hot air midway, the catalyst is fired uniformly in the gas flow path direction, and the amount of residual sulfuric acid radicals in the catalyst is averaged, resulting in a catalyst with uniform performance. can be obtained.

〔Example〕

A mixture of titanium oxide, molybdenum oxide, vanadium oxide, and alumina silicate fibers is attached to both sides of an expanded metal plate, and the plate-shaped catalyst obtained by forming it into a Z-shaped cross section is stacked and housed in a frame, Catalyst unit as shown in Figure 3 (approximately 465 x 465 x 5601 m)
It was created. This catalyst unit was supplied onto a mesh belt 4 as shown in FIG. 1, and the catalyst was fired. The firing conditions are: hot air at a temperature of 1.1°, approximately 500°C, and a wind speed of approximately 0.4 m/5e when passing through the catalyst unit 3.
When treated with a residence time of 2.5 hours in the furnace of C1 catalyst unit 3, the content of sulfate groups in the catalyst was approximately 5.5% by weight.
A denitrification catalyst unit with very little variation in quality was obtained. Furthermore, when exhaust gas denitration was performed using the obtained catalyst, the denitration rate was 61% or more, and the amount of catalyst wear was as small as 0.16 g or less per test piece (100 x 100 m5).

[Comparative example]

For comparison, the same catalyst as in the example was fired under the same conditions as in the example except that hot air was supplied from only one direction of the catalyst unit as shown in FIG.

As a result, the sulfuric acid radical content of the catalyst in the unit showed a distribution of about 3 to 8% from the hot air inlet side to the outlet side, resulting in large variations in quality. Furthermore, when exhaust gas was denitrated using the obtained catalyst, the denitrification rate was 55-63%, the amount of wear was 0.12-0.25 g/T,
P, and variations in performance were observed.

Further, in the above comparative test, when hot air was circulated, about 10 hours of calcination was required to obtain the same sulfate content and catalytic performance as above.

〔Effect of the invention〕

According to the present invention, it is possible to sinter a catalyst with uniform physical properties in terms of catalyst performance, that is, wear strength and activity, and therefore the yield of the catalyst during sintering of the catalyst is also improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the catalyst firing furnace of the present invention, FIG. 2 is a plan view showing another embodiment of the present invention, and FIG. 3 is a perspective view of a plate-shaped catalyst unit for denitrification. 4 is a perspective view of a heat treatment furnace that supplies hot air from only one direction, FIG. 5 is a sectional view taken along the V-V direction line in FIG. 4, and FIG.
FIG. 3 is a diagram showing the relationship between the SO4 content of the catalyst, the denitrification rate, and the amount of wear. 1.1°...hot air, la, lb, IC11al, 1b
", I C1...Hot air, 3...Catalyst unit, 4.
... Reticulated belt, 5... Traveling direction, 6... Rotating roll, 7... Plate catalyst. Agent Patent Attorney Takenaga Kawakita Figure 1 False 2 Figure 31″′J

Claims (11)

[Claims] (1) A step of arranging a denitrification catalyst unit on a mesh belt that moves continuously in the furnace, and supplying fresh hot air so that the direction of hot air passing through the catalyst unit is reversed at least at the front and rear parts of the mesh belt. and a step of removing the catalyst unit from the reticulated belt.
A method for firing a denitrification catalyst, comprising controlling the speed of the hot air so that the amount of the hot air reaches % by weight. (2) A method for firing a denitrification catalyst according to claim 1, wherein the hot air is fed so that the hot air passes in the opposite direction at the front and rear parts of the reticulated belt. (3) In claim 1, the temperature of the hot air is 3.
A method for firing a denitrification catalyst within the range of 50 to 600°C. (4) In claim 3, the temperature of the hot air is 4
A method for firing a denitrification catalyst within the range of 50 to 550°C. (5) The method for firing a denitrification catalyst according to claim 1, wherein the residence time of the catalyst unit passing through the furnace is within the range of 1 to 4 hours. (6) The method for firing a denitrification catalyst according to claim 5, wherein the residence time of the catalyst unit passing through the furnace is within the range of 2 to 3 hours. (7) In claim 1, the wind speed of hot air is 0.
．． A method for firing a denitrification catalyst within the range of 1 to 0.9 m/sec. (8) In claim 7, the wind speed of hot air is 0.
．． A method for firing a denitrification catalyst within the range of 3 to 0.5 m/sec. (9) A method for firing a denitrification catalyst according to claim 1, wherein the content of sulfate groups in the catalyst is within the range of 5 to 6% by weight. (10) A method for firing a denitrification catalyst according to claim 1, wherein the catalyst component is an oxide of at least one metal selected from titanium, molybdenum, vanadium, tungsten, and manganese. (11) In claim 1, the catalyst unit includes stacking a large number of plate-shaped catalysts formed by coating catalysts on the front and back surfaces of a porous plate-shaped support having protrusions via the protrusions, A method for firing a denitrification catalyst in which the catalyst is housed in a frame.