JPH07213921A - Continuous catalyst baking apparatus and method using the same - Google Patents

Abstract

PURPOSE:To provide a continuous catalyst baking apparatus capable of preventing the lowering of catalytic activity caused by the high temp. combustion and imperfect combustion of the org. molding aid contained in a honeycomb catalyst molded object. CONSTITUTION:In a continuous catalyst baking apparatus continuously baking a honeycomb catalyst molded object containing an oxidizing active component and an org. molding aid in a pre-baking region of 30-300 deg.C and a final baking region of 100-600 deg.C, a catalytic combustion type hot air generator 13 and a hot air temp. control device 15 are provided as a meas for forming the atmospheric gas 7a to be introduced into the pre-baking region 4. By this constitution, the reduction of the active component caused by high temp. heating and reductive gas is prevented and a highly active catalyst can continuously be baked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous catalyst calcination apparatus and a catalyst calcination method using the same, and more particularly to a calcination apparatus and a calcination method for a catalyst molded body in which a catalyst component having an oxidizing activity contains an organic substance. The present invention relates to a continuous catalyst calcination apparatus suitable for obtaining a highly active catalyst body by suppressing the excessive heat generation of the catalyst body by suppressing the generation of heat of oxidation at the time of temperature rise, and a catalyst calcination method using the same.

[0002]

2. Description of the Related Art A catalyst used in an atmosphere having a large amount of treated gas, such as an oxidation catalyst or a denitration catalyst, is generally formed in a honeycomb shape in order to reduce pressure loss per gas contact area. When the catalyst is molded into a honeycomb shape, a carrier, a catalytically active component, in addition to the catalyst raw material such as an inorganic binder, it is usually necessary to add a binder, a wetting agent, an organic molding aid such as a plasticizer, Such an organic molding aid disappears as the honeycomb molded body is fired.

By the way, the addition of the organic molding aid causes a decrease in the activity of the catalyst having an oxidizing activity. That is, (a) there is a problem that the catalyst molded body is excessively heated by the heat of oxidation of the burning of the organic molding aid during the burning of the catalyst, and the activity thereof is reduced.
In particular, the activity of the large-sized catalyst, which has a poor heat dissipation property, is significantly reduced in the central portion. In addition, (b) when the organic molding aid is incompletely burned during the firing of the catalyst, if the reducing gas such as carbon monoxide or aldehyde generated is heated to a high temperature while remaining in the honeycomb molded body, the reducing property is reduced. There is a problem that the catalytic component is reduced by the gas and the activity is reduced.

In order to avoid such problems, an apparatus for firing a honeycomb formed body in two steps has been developed. That is, heating at a relatively low temperature while ventilating the atmosphere gas into the molded body, and heating by the oxidation heat of the organic molding aid,
A pre-baking region that decomposes and removes the molding aid while suppressing reduction of the active component by a reducing gas, and a main baking region that heats and burns at a predetermined temperature in an oxidizing atmosphere to eliminate the rest of the molding aid. It is a continuous catalyst calcination device having and.

FIG. 2 is an explanatory view of such a conventional catalyst burning apparatus. This device reduces the manufacturing cost,
In order to obtain a product of stable quality, it is a continuous-type device for mass production, and is a mesh belt 1 which is a conveying means of the honeycomb catalyst molded body 3, a drive device 2 of the mesh belt 1, and a catalyst. A preliminary firing region 4, a main firing region 5 and a subsequent slow cooling region 6 which are sequentially formed along the transport direction; burner type hot air generators 17a and 17b;
Fuel gas nozzles 12a and 12 for supplying fuel gas and air to the hot air generators 17a and 17b, respectively.
b, blowers 11a and 11b, and outlets 8 and 9 for supplying the hot air generated by the burner hot air generators 17a and 17b as atmospheric gas 7a and 7b from below the mesh belt 1 to above.
And an atmospheric gas exhaust device 10 provided above the mesh belt 1 with a space therebetween.

The air supplied to the burner type hot air generators 17a and 17b through the blowers 11a and 11b is mixed with the fuel gas supplied through the fuel gas nozzles 12a and 12b and burned to become hot air. The generated hot air is blown upward from the lower side of the mesh belt 1 through the blowing ports 8 and 9 to form a preliminary firing region 4 of a low temperature atmosphere and a main firing region 5 of a high temperature atmosphere suitable for catalyst firing. The honeycomb catalyst molded body 3 is placed on the mesh belt 1 of the continuous catalyst calcination device in which the calcination regions 4 and 5 are formed, and while sequentially moving through the pre-calcination region 4, the main calcination region 5 and the slow cooling region 6, It is calcined to be a catalyst calcined body.

However, in such a conventional device,
In the pre-baking region where the organic molding aid disappears at a low temperature, there is a problem that it is not possible to sufficiently prevent the activity of the catalyst from decreasing. That is, since the above-mentioned conventional continuous catalyst calcination device requires a large amount of atmospheric gas, the gas fuel with few impurities was burned by the burner to obtain the atmospheric gas at the time of preliminary calcination. It is not possible to sufficiently reduce the oxygen concentration in the atmospheric gas supplied to the pre-baking region because excess air is required to maintain the above, whereby the organic molding aid is burned in a high oxygen concentration atmosphere, This has been a cause of the catalyst body being heated more than necessary and its activity being lowered. In addition, it is difficult to manufacture a large amount of atmospheric gas with a low oxygen concentration in reality, and it is possible to purchase it separately and indirectly heat it.However, the atmospheric gas consumption in the continuous catalyst calcination device is enormous and practical. Not at all.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to stably produce a large amount of a low oxygen concentration atmosphere gas required for catalyst calcination in a preliminary calcination region. It is an object of the present invention to provide a continuous catalyst calcination device that can be supplied to prevent a decrease in catalyst activity due to high temperature combustion of an organic molding aid, and a catalyst calcination method using the same.

[0009]

Means for Solving the Problems The present inventor has noticed that the organic molding aid itself contains oxygen and that the catalytically active component has an oxidative accelerating action. As a result of diligent research on the firing conditions of the preliminary firing step when firing the honeycomb formed body containing the active component and the organic forming aid, in order to avoid the influence of the heat of oxidation of the organic forming aid, The oxygen concentration of 5% or less, and at least 0.1 m / s for expelling the reducing decomposition gas remaining in the honeycomb molded body.
It has been discovered that it is necessary to introduce an atmospheric gas at a flow rate of ec or more, and in a continuous catalyst calcination apparatus having a low temperature and low oxygen concentration pre-calcination region and a high temperature and high oxygen concentration main calcination region, A catalytic combustion device that can burn at a theoretical air ratio is used as the atmospheric gas generation device.
By adjusting the temperature of hot air having an oxygen concentration of 5% or less generated in this catalytic combustion device and then introducing it into the pre-calcination zone at a flow rate of 0.1 m / sec or more, it is possible to prevent a decrease in catalytic activity during calcination. Heading, arrived at the present invention. When an oxygen concentration gas of 5% or more is used, even if the temperature is relatively low such as about 100 ° C., high temperature combustion of the organic molding aid due to chain reaction occurs, and the temperature of the center of the molded body rises rapidly. Its activity decreases.

That is, the invention claimed in this application is as follows:
It is as follows. (1) Continuously in a pre-baking region for pre-baking a honeycomb-shaped catalyst molded body containing an oxidatively active component and an organic molding aid in the presence of an atmospheric gas, and a main-baking region having a temperature higher than that of the pre-baking region In a continuous catalyst firing device that fires
A continuous catalyst calcination device comprising a catalytic combustion hot air generator and a temperature controller for the generated hot air as a means for generating the atmospheric gas introduced into the preliminary calcination region.

(2) A continuous catalyst calcining apparatus having a honeycomb-shaped catalyst compact containing an oxidizing active component and an organic compacting aid and having a pre-sintering region of 50 to 300 ° C. and a main sintering region of 100 to 600 ° C. In the continuous catalytic calcination method of calcination using, hot air having an oxygen concentration of 5% or less generated by a catalytic combustion hot air generator as an atmosphere gas in the preliminary calcination region is adjusted to a temperature of 0.1 m / sec or more. A catalyst calcination method using a continuous catalyst calcination device, wherein the catalyst is calcinated at a flow rate.

[0012]

By providing a hot air generator of catalytic combustion type and a temperature control device of hot air as a device for generating the atmospheric gas supplied to the pre-firing zone, the fuel gas is theoretically aired in the hot air generator of the catalytic combustion type. A large amount of hot air having an oxygen concentration of 5% or less can be stably obtained by burning at a ratio. The obtained hot air having a low oxygen concentration is temperature-controlled by a temperature controller, and then is supplied to the pre-baking region to maintain the pre-baking region at a low temperature and low oxygen concentration atmosphere, and the organic molding aid is non-oxidizing. Since it can be incinerated in an atmosphere,
It is possible to suppress the generation of combustion heat and prevent the catalyst body from being excessively heated and its activity being lowered.

In the present invention, the atmospheric gas having an oxygen concentration of 5% or less is preferably supplied to the pre-baking region at a flow rate of 0.1 m / sec or more. As a result, the reducing gas generated by the incomplete combustion of the organic molding aid can be expelled from the catalyst molded body, so that the activity reduction due to the reducing gas is prevented. The oxidizing active component in the present invention is not particularly limited as long as it is an oxide having catalytic activity, and in the case of a denitration catalyst, for example, metal oxides such as vanadium, molybdenum, tungsten and titanium can be mentioned. As the organic molding aid, in order to obtain a honeycomb-shaped catalyst molded body, a catalyst carrier powder is optionally mixed with a catalytically active component, and an organic binder for molding in a honeycomb shape (for example, polyvinyl alcohol,
Carboxymethyl cellulose and the like).

[0014]

EXAMPLES Next, the present invention will be described in more detail by way of examples. FIG. 1 is a schematic diagram of a continuous catalyst calcination apparatus showing one embodiment of the present invention. In the figure, the difference between this apparatus and the conventional apparatus of FIG. 2 is that a catalytic combustion hot air generator 13 having a combustion catalyst 14 as an atmosphere gas generator in the pre-baking zone 4 and a heat exchanger for cooling the generated hot air. This is the point where 15 is provided.

In such a structure, the fuel gas introduced from the fuel gas nozzle 12 into the catalytic hot air generator 13 is mixed with the air introduced through the blower 11 and then flows into the combustion catalyst 14, where it is almost theoretical. Stable combustion at an air ratio produces hot air having an oxygen concentration of 5% or less. The generated hot air flows into the heat exchanger 15, where it is cooled to a predetermined temperature by the cold air supplied to the burner type hot air generator 17 through the blower 16, and then, as the atmospheric gas 7a, from the outlet 8 to the pre-baking region. 4 is supplied. Atmosphere gas 7a
The temperature is controlled by increasing or decreasing the amount of air blown to the burner hot air generator 17 through the blower 16.

On the other hand, the air preheated by the heat exchanger 15 via the blower 16 and introduced into the burner hot air generator 17 is burned by the air introduced by the fuel gas nozzle 19 through the blower 18. It is heated to a predetermined temperature by the combustion heat at the time of being heated, and is supplied from the outlet 9 to the main firing region 5 as the atmospheric gas 7b. The exhaust gas 1 is supplied to the pre-baking area 4 and the main-baking area 5, respectively, and the atmosphere gases 7a and 7b arranged in a predetermined atmosphere are provided above the mesh belt 1 with a space therebetween.
It is collected at 0, purified, and then released to the atmosphere.

In this way, the honeycomb structure is formed on the mesh belt 1 of the continuous catalyst calcination apparatus in which the preliminary calcination region 4 having a low temperature and a low oxygen concentration and the main calcination region 5 having a high temperature and a high oxygen concentration are formed. Catalyst molded body 3 containing a molding aid
Is placed and enters the pre-baking region 4 as the mesh belt 1 which is moved at a predetermined speed by the drive device 2 is moved.
The honeycomb catalyst molded body 3 that has entered the preliminary firing region 4 is heated to the ambient temperature, and the organic molding aid contained therein is burned and disappears in the non-oxidizing atmosphere. Further, the reducing gas generated by the incomplete combustion of the organic molding aid flows out from the honeycomb catalyst fired body 3 along the flow of the atmosphere gas 7a introduced from the outlet 8 at a predetermined flow rate. The honeycomb catalyst molded body 3 thus pre-calcined without being affected by the heat of oxidation of the organic molding aid and the decomposition / reducing gas is then moved to the main calcination region 5, where a predetermined high temperature and high temperature are obtained. It is calcined in an oxygen concentration atmosphere to be a calcined catalyst, and then gradually cooled to room temperature through the slow cooling region 6.

According to the present embodiment, the catalytic combustion hot air generator 13 and the hot air temperature controller 15 are provided as a device for generating the atmospheric gas 7a to the pre-baking region 4, so that, for example, the oxygen concentration is 5%. After producing a large amount of the following hot air and adjusting the temperature, the hot air can be supplied to the pre-baking zone 4 to burn the organic molding aid at a low temperature in a non-oxidizing atmosphere. Can be prevented. Further, by setting the flow rate of the atmosphere gas 7b supplied to the pre-baking region 4 to 0.1 m / sec or more, the reducing gas generated by the incomplete combustion of the organic molding aid is discharged from the catalyst body before the main baking. Since it can be expelled, it is possible to prevent a decrease in activity due to reduction of the catalyst component.

Next, specific examples of the present invention will be described. Example 1 The width of the mesh belt 1 is 1.2 m, the length is 40 m, and the lengths of the preliminary firing region 4 and the main firing region 5 are 10 m, respectively.
1, propane gas was used as the fuel gas, and this was burned in the catalytic combustion device 13 at the stoichiometric air ratio to obtain hot air of 700 to 800 ° C. with an oxygen concentration of 3%. 150-160 by introducing this hot air into the heat exchanger 15.
After cooling to 0 ° C., it was introduced into the preliminary firing region 4 at a flow rate of 0.5 m / sec to prepare the atmosphere in the preliminary firing region. on the other hand,
The air preheated by the heat exchanger 15 through the blower 16 was heated by the burner hot air generator 17 to obtain the atmospheric gas 7b having an oxygen concentration of 15% and a temperature of 550 to 570 ° C. Next, this atmosphere gas was flown at a flow rate of 0.5 m / sec to the main firing region 5.
The atmosphere of the main-baking area was adjusted by introducing the above.

Next, a denitration catalyst molded body containing 2 wt% of an organic binder on the mesh belt 1 of the continuous catalyst calcining apparatus in which the atmospheres of both calcining regions are adjusted and molded into a honeycomb shape of 150 mm square and 600 mm long. 3 was placed and moved in the preliminary calcination region 4 and the main calcination region 5 at a speed of 3 m / h for calcination to obtain a catalyst calcined body. The obtained honeycomb-shaped denitration catalyst was highly active, with no decrease in activity observed in the peripheral portion and the central portion.

FIG. 3 shows a comparison between the temperature of the surface and the central portion of the denitration catalyst during calcination in this example and the prior art. In each figure, the temperature is higher than the ambient temperature due to the heat of oxidation of the organic binder, but the ambient temperature is suppressed to 150 ° C. in the conventional example in which the oxygen concentration in the pre-baking region 4 is high. ,
It can be seen that the temperature of the central portion is as high as 600 ° C or higher. It is considered that this is because the high oxygen concentration causes the organic binder to burn in a chain due to the oxidizing action of the catalyst component to generate high-temperature combustion heat.

FIG. 4 shows a comparison of the denitration activity in the central portion and the peripheral portion of the honeycomb-shaped denitration catalysts obtained in this example and the prior art. In the figure,
It can be seen that the denitration catalysts obtained in this example show almost no difference in activity between the central portion and the peripheral portion and show a high value. On the other hand, it can be seen that the denitration catalyst obtained by the conventional technique has a lower activity than that in the examples, and in particular, the activity in the central portion thereof is low. This is because the heat dissipation is worse in the central part, and it is considered that the degree of activity decrease is large.

[0023]

According to the invention described in claim 1 of the present application, a large amount of low oxygen concentration atmospheric gas is produced by using the catalytic combustion hot air generator as the atmospheric gas generator in the pre-baking region. Since the organic molding aid can be eliminated in a non-oxidizing atmosphere, it is possible to prevent the activity from being lowered due to the catalyst being heated more than necessary.

According to the invention of claim 2 of the present application, by introducing an atmosphere gas having an oxygen concentration of 5% or less into the pre-baking region at a flow rate of 0.1 m / sec or more, in addition to the effect of the invention, the catalyst can be obtained. Since the reducing gas remaining in the molded body can be effectively expelled from the catalyst body, it is possible to prevent a decrease in activity due to the reduction of the catalyst component.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a conventional technique.

FIG. 3 is a diagram showing a comparison of catalyst temperatures during firing in Examples and the prior art.

FIG. 4 is a graph showing the activity of the catalyst obtained in the example and the activity of the catalyst obtained by the conventional technique in comparison.

[Explanation of sign]

DESCRIPTION OF SYMBOLS 1 ... Mesh belt, 2 ... Driving device, 3 ... Honeycomb catalyst molded body, 4 ... Pre-firing area, 5 ... Main firing area, 6 ... Slow cooling area, 7 / 7a * 7b ... Atmosphere gas, 8, 9 ... Blowout port 10 ... Exhaust device, 11 (11a ・ 12b) ・ 16 ・
18 ... Blower, 12 (12a * 12b), 19 ... Fuel gas nozzle, 13 ... Catalytic combustion type hot air generator, 14 ... Combustion catalyst, 15 ... Heat exchanger, 17 ... Burner type hot air generator.

Claims (2)

[Claims] 1. A pre-baking region for pre-baking a honeycomb-shaped catalyst molded body containing an oxidizing active component and an organic molding aid in the presence of an atmospheric gas, and a main-baking region having a temperature higher than that of the pre-baking region. In a continuous catalyst calcination device for continuously calcination, a catalyst combustion hot air generator and a temperature controller for the generated hot air are provided as a means for generating an atmospheric gas introduced into the preliminary calcination zone. apparatus. 2. A continuous catalyst calcining apparatus having a honeycomb-shaped catalyst compact containing an oxidizing active component and an organic compacting auxiliary agent and having a pre-sintering region of 50 to 300 ° C. and a main sintering region of 100 to 600 ° C. In the catalyst calcination method of calcination, the temperature of hot air having an oxygen concentration of 5% or less generated by a hot air generator of a catalytic combustion type as the atmosphere gas of the preliminary calcination region is controlled at a flow rate of 0.1 m / sec or more. A catalyst calcination method using a continuous catalyst calcination device, characterized in that the catalyst is calcinated in the preliminary calcination region.