JP2003010700A - Method for baking inorganic compound and method for manufacturing oxidizing catalyst using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of controlling the generation of heat at the time of baking of an inorganic compound to certainly prevent the generation of trouble such as the abnormal generation of heat and baking the inorganic compound under a uniform condition. SOLUTION: A fixed bed type baking furnace is filled with the inorganic compound to form a filled bed and the inorganic compound is baked while gas is allowed to flow through the filled bed. In this case, the temperature in the filled bed is measured at one or more points and the highest temperature among the measured temperatures is controlled on the basis of an inlet temperature of the gas to be allowed to flow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for burning an inorganic compound and a method for producing an oxidation catalyst using the same, and more specifically, it can reliably prevent troubles such as abnormal heat generation and can be fired under uniform conditions. The present invention relates to a method for calcining possible inorganic compounds and a method for producing an oxidation catalyst using the same.

[0002]

2. Description of the Related Art Organic molding aids are often added to the molding of inorganic compounds. Further, a method has been proposed in which an organic substance or an inorganic substance is added for molding and then firing for the purpose of controlling the pore structure of the inorganic compound. For example, as a method for producing a catalyst for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein, JP-A-55-73347 discloses that 1 to 1 of an organic substance such as cellulose or polyvinyl alcohol is used.
A method in which 10 wt% is added and molded and then fired to obtain a catalyst, and in JP-A-60-239439, an organic nitrogen-containing compound such as pyridine is added and molded, and then fired to obtain a catalyst. A method has been proposed.

As an example of a method for producing a catalyst for vapor-phase catalytic oxidation of methacrolein to produce methacrylic acid, in which an organic compound is not added, JP-A-10-244160 discloses an average particle diameter of 0.1 to 100 μm. Japanese Patent Laid-Open No. 5-279291 discloses a method in which powder of a carbonate compound such as ammonium carbonate is added and molded, followed by firing to form a catalyst by adding ammonium nitrate to a catalyst slurry and drying. A method has been proposed in which a solid material is molded and then fired to obtain a catalyst.

[0004]

However, when an organic compound is used as an additive, local reduction or sintering occurs due to combustion of the organic compound during the subsequent firing, which causes the performance of the inorganic compound to be impaired. Furthermore, in the case of a system containing ammonium radicals and nitrate radicals derived from raw materials, ammonium nitrate and organic compounds coexist, so there is concern about the danger of an ammonium nitrate explosion during firing on an industrial scale. Further, even when ammonium nitrate is added instead of the organic compound, heat is generated due to thermal decomposition of ammonium nitrate, which may cause a danger of ammonium nitrate explosion.

These are mainly related to the type of additive and its physical properties, and no particular consideration is given to the firing method and the heat generation control method.

On the other hand, as a method of controlling the heat generation during firing, an aeration firing method in which firing is performed while gas is flowing can be considered. This method removes heat generation as sensible heat of the distribution gas, and it is necessary to bring the distribution gas and the inorganic molded product into contact with each other sufficiently efficiently.

However, even in the aeration firing method, once the amount of ventilation or the temperature is erroneously controlled and a high temperature part is formed, the heat generation rate of the part is improved, and the temperature rise is locally accelerated to heat spot. Was formed, and this was the starting point, and the heat generation part expanded, making it impossible to control heat generation, resulting in runaway and abnormal heat generation.

As a countermeasure for this, Japanese Patent Laid-Open No. 2-83042
In the publication, a method of firing by controlling the oxygen concentration of the atmosphere is proposed. However, in this method, only the inlet temperature and the outlet temperature of the circulating gas are measured and not the temperature inside the heat generating gas is measured. In addition, since nitrogen gas is required, it is costly and not preferable.

Further, in Japanese Unexamined Patent Publication No. 10-263420, heat generation is controlled by measuring the concentration of CO or CO _{2 at} the outlet of a circulating gas generated as a result of a combustion reaction and controlling the temperature or ventilation conditions. A method has been proposed. However, since this method is also a method of indirectly detecting heat generation, rather than measuring the internal temperature of heat generation,
It is not sufficient from the viewpoint of preventing heat spot formation. Further, in the drawings of the examples described in the publication, there is a space portion in which the inorganic molded article does not exist, and the gas flowing in this portion does not contribute to heat removal, which is inefficient.

Further, Japanese Patent Laid-Open No. 10-263419 proposes to periodically change the inlet temperature of the circulating gas. However, this method is not sufficient from the viewpoint of preventing formation of heat spots because it does not measure the internal temperature of heat generation. In addition, in the manufacturing on an industrial scale, the heat capacity of the device is large, and it is very difficult to control the temperature of the circulating gas with high accuracy periodically. Further, the heat generation rate of these inorganic molded products may differ due to slight differences in the manufacturing method and conditions,
The preset temperature cycle alone is not sufficient, and it is necessary to detect the actual heat generation behavior and perform control.

In view of the above-mentioned circumstances of the prior art, the present inventors have found that when the inorganic compound is exothermic during firing,
By controlling the heat generation during firing of the inorganic compound, it is possible to reliably prevent troubles such as abnormal heat generation, and as a result of extensive studies aimed at providing a method for firing under uniform conditions, the inorganic compound Is packed in a fixed bed type firing furnace, and is baked while circulating gas in the packed bed, and by controlling the maximum temperature in the packed bed by the inlet temperature of the circulating gas,
The inventors have found that the above goals can be achieved and completed the present invention.

[0012]

That is, the characteristic constitution of the method for calcination of an inorganic compound according to the present invention is that a fixed layer type calcination furnace is filled with the inorganic compound to form a packed layer, and gas is charged in the packed layer. During firing while flowing, the temperature in the packed bed is measured at one or more points, and the maximum temperature therein is controlled by the inlet temperature of the gas to be passed.

According to this structure, when the inorganic compound is heated during the baking, the heat generated during the baking of the inorganic compound can be controlled so that troubles such as abnormal heat generation can be reliably prevented, and a uniform condition can be obtained. It can be baked in. Therefore, it is possible to obtain a firing method that is excellent in productivity and has a high production yield.

It is preferable that the temperature control is performed by setting one of the two or more heating means for raising the temperature and the other in the immediate vicinity of the packed bed.

According to this structure, it is possible to set the portion having the highest possibility of becoming the starting point of abnormal heat generation to the set temperature,
By changing the inlet temperature of the circulating gas, abnormal heat generation can be reliably prevented and controlled.

A raw material for an oxidation catalyst may be used as the inorganic compound. Oxidation catalyst can be produced with good productivity by reliably preventing troubles during firing.

A characteristic constitution of the method for producing an oxidation catalyst according to the present invention is that the firing method according to any one of claims 1 to 3 is used.

According to this structure, even when heat is generated when the oxidation catalyst is produced by firing the inorganic compound, the heat generation during firing of the inorganic compound is controlled to ensure that trouble such as abnormal heat generation does not occur. Therefore, it is possible to provide a method for producing an oxidation catalyst which can be prevented from occurring and can be calcined under uniform conditions.

The oxidation catalyst is preferably any one of acrolein, acrylic acid, methacrolein and methacrylic acid production catalysts.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. In the present invention, when the inorganic compound is fired, the inorganic molded product before firing is charged into a fixed-bed type firing furnace, and the firing is performed while a gas is passed through the filled layer.

There is no particular restriction on the molding method or shape of the inorganic molded product to be filled, and various molded products such as ring-shaped, pellet-shaped, spherical or honeycomb-shaped molded by a method such as tablet molding or extrusion molding can be used. . The firing furnace to be used is also not particularly limited, and a normal fixed bed type firing furnace can be used. Even if the shape is cylindrical, it has a polygonal tube shape or other indeterminate cross-sectional shape. Alternatively, various firing furnaces can be used.

The filling height of the inorganic molded article (corresponding to the flow path length of the gas flowing through the packed bed in the present invention) is not particularly limited, and the heat generation rate, temperature, and amount of flowing gas of the inorganic molded article are not particularly limited. It is decided from the viewpoint of safety and economic efficiency by considering the pressure loss, etc., but if the filling height is too small, the equipment will be large and not economical, and if it is too large, the pressure loss will increase. Therefore, 0.1 to 2 m is preferable, and
2-1 m is more preferable.

In the present invention, the kind of the circulating gas is not particularly limited, and usually air is used, but an inert gas such as nitrogen or argon can be used, and air and nitrogen or argon are mixed and used. You can also

The flow direction of the gas is also not particularly limited, and it may be vertical, horizontal, or oblique. However, in order to remove the heat generation in the packed bed, the inside of the packed bed is removed. Need to pass through.

The gas flow rate is also not particularly limited, and it is determined from the viewpoint of safety and economical efficiency in consideration of the filling height, the heat generation rate of the inorganic molding, the temperature and the pressure loss.
It is preferably 0.1 to 2 Nm / s. Further, in order to make the heat removal of the packed bed more efficient, the circulating gas is preferably circulated at a uniform speed in the packed bed as much as possible, and thus the shape of the inorganic molded product is made more uniform, and It is preferable to uniformly fill at the time of filling.

In the packed bed, the temperature rises from the inlet direction to the outlet direction of the circulating gas due to the heat generated during firing, and a temperature distribution is generated. This temperature distribution changes over time,
When the exothermic substance disappears, the temperature difference in the packed bed disappears. The higher the filling height and the smaller the amount of flowing gas, the greater the temperature difference in the packed bed, and the higher the possibility of forming a heat spot and becoming uncontrollable.

In the present invention, the temperature in the packed bed is measured at one or more points, and the temperature distribution in the packed bed which changes with time is grasped in real time. The part that has the highest possibility of forming a heat spot and becoming the starting point of abnormal heat generation is the part with the highest temperature in the packed bed, so that the maximum temperature in this packed bed is the set temperature, It is controlled by changing the inlet temperature. That is, when the maximum temperature in the packed bed is higher than the set temperature, lower the inlet temperature,
On the other hand, if the temperature is lower than the set temperature, adjust by increasing the inlet temperature.

The maximum temperature in the packed bed varies depending on the composition of the inorganic molded product and the type and amount of the heat-generating substance. The heat generation rate of the inorganic molded product is measured in advance to determine the heat generation rate, the filling height and the gas flow. The mass balance and heat balance can be examined and set from the amount. The set temperature is set to a temperature at which the maximum temperature in the packed bed shows a deviation higher than the set temperature and when the operation of lowering the inlet temperature of the circulating gas is taken, the temperature can be sufficiently controlled even if the delay in response is taken into consideration. It is necessary. For example,
In calcination of the catalyst molded product for producing methacrylic acid by vapor-phase catalytic oxidation of methacrolein containing 10% or more of ammonium nitrate, the maximum temperature in the packed bed is set to 18
The temperature is preferably 0 to 260 ° C, more preferably 210 to 250 ° C.

The setting of the maximum temperature in the packed bed may be changed in multiple steps because the heat generation rate decreases as the firing proceeds.

The larger the temperature difference in the packed bed, the more likely it is to become a starting point for the formation of a heat spot and runaway, and the difference in the baking temperature may cause a difference in the performance of the product after baking. It is preferable to set the maximum temperature in the packed bed so that the temperature difference in the bed is 50 ° C. or less, and further, set the maximum temperature in the packed bed so that the temperature difference in the packed bed is 30 ° C. or less. It is more preferable to set.

There is no particular limitation on the method of controlling the inlet gas temperature, and it is possible to control by one or a combination of heating means, cooling means, the amount of gas newly supplied into the system, etc. It is preferable to adopt a good method.

The firing of the inorganic substance is often performed at a high temperature, and the temperature is raised by using a heating means such as a heater.
There is often a large difference between the capacity of the heating means necessary for raising the temperature and the capacity of the heating means necessary for controlling the inlet gas temperature during firing, and the maximum temperature in the packed bed is responsive and accurate. In order to control, it is preferable to use two or more heating means, one of which is used for raising the temperature and the other is installed in the vicinity of the packed bed and used for temperature control.

There are no particular restrictions on the method of heating means and cooling means, and an electric heater, a multi-tube heat exchanger, or the like can be used, but it is preferable to use a method with good responsiveness.

The calcination method of the present invention can be preferably used for calcination of oxidation catalysts among inorganic compounds, and more preferably, for acrolein, acrylic acid, methacrolein and methacrylic acid production catalysts. You can

[0035]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 Ammonium nitrate and ion-exchanged water were added and kneaded, and the mixture was extruded into a cylindrical shape having a diameter of 5 mm and a length of 6 mm, followed by drying to methacrolein, which was subjected to vapor phase catalytic oxidation. A molded article of the catalyst for producing methacrylic acid was fired in the firing apparatus shown in FIG. 1 to produce the catalyst. This firing apparatus includes a firing furnace 1, an apparatus capable of recirculating a gas flowing through the firing furnace with a blower 4, an electric heater 2 serving as a heating unit for increasing a temperature,
An electric heater 3 which is a heating means for controlling the gas temperature,
A gas supply line 6 for introducing a new gas and a gas discharge line 7 for discharging a part of the circulating gas are provided. Although not shown, a control device is connected to the electric heaters 2 and 3.

First, a cylinder made of stainless steel having an inner diameter of 150 mm was filled with the catalyst molding so as to have a height of 60 cm to form a packed layer. The ammonium nitrate content in the molded product is 21%. A protective tube with an inner diameter of 4 mm was installed in the center of the packed bed, and the entrance of the packed bed was 0 mm (catalyst bed entrance), 100 mm, 200 mm, 300 mm, 400 m.
A multipoint thermocouple 5 was installed so that the temperatures of m, 500 mm, and 600 mm (catalyst layer outlet portion) could be measured. The flow rate of the circulating gas was 300 m ³ / h, the flow rate of the newly introduced air was 2.4 m ³ / h, and the gas temperature at the inlet of the catalyst layer was raised from room temperature to 220 ° C. at a rate of 50 ° C./h while circulating the gas. After that, the gas temperature at the inlet of the packed bed was further increased to 230 ° C. at a rate of 5 ° C./h. After that, the temperature was controlled by changing the gas temperature at the inlet of the packed bed so that the maximum temperature in the packed bed was 230 ° C. The change over time in the temperature in the packed bed during this time is shown in FIG.

With the lapse of time, heat was gradually generated, and the position of maximum temperature moved to the outlet side. During this time, the temperature difference in the packed bed remained below 15 ° C. The inlet temperature of the circulating gas is 2
By gradually decreasing from 29 ℃ to 216 ℃,
The maximum temperature in the packed bed was controlled to be 230 ° C.
After the lapse of 13 hours, the amount of ammonium nitrate in the system decreased and the temperature difference in the packed bed decreased, so the maximum temperature in the packed bed was changed to 250 ° C. and firing was continued. After 18.5 hours, the temperature difference in the packed bed fell below 2 ° C, so it was judged that almost all of the ammonium nitrate in the system could be removed, and thereafter, in a nitrogen stream, at 50 ° C / h. Heating up to 435 ° C at 4
After holding at 35 ° C. for 3 hours for firing, further in an air stream,
It was calcined at 390 ° C. for 3 hours to obtain a catalyst.

(Comparative Example 1) In the same manner as in Example 1, 230
After the gas temperature at the inlet of the packed bed is raised to ℃, the gas temperature at the inlet of the packed bed is adjusted to 23 ° C. without controlling the gas temperature at the inlet of the packed bed so that the maximum temperature in the packed bed becomes 230 ° C.
Firing was performed while maintaining the temperature at 0 ° C. After about 10 hours, the maximum temperature in the packed bed exceeded 250 ° C,
Although the operation of lowering the output of the electric heater and lowering the temperature was carried out, it was not in time. After that, the temperature rapidly increased and exceeded 300 ° C., so the calcination was interrupted and the catalyst could not be obtained.

[0040]

According to the method of the present invention, it is possible to control the heat generation of an inorganic compound during firing so that the inorganic compound can be fired under uniform conditions without causing abnormal heat generation. The oxidation catalyst can be produced under uniform conditions without causing abnormal heat generation.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a firing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a change with time in the temperature in the packed bed in the example of the present invention.

[Explanation of symbols]

1 firing furnace 2,3 heating means

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuaki Hiraishi             Sumitomo Chemical 5-1, Soukai-cho, Niihama-shi, Ehime             Industry Co., Ltd. (72) Inventor Koichi Nagai             Sumitomo Chemical 5-1, Soukai-cho, Niihama-shi, Ehime             Industry Co., Ltd. F-term (reference) 4G069 AA08 CB10 CB17 DA05 FA01                       FB30

Claims (5)

[Claims] 1. An inorganic compound is charged into a fixed-bed type firing furnace to form a packed bed, and the temperature in the packed bed is measured at one or more points when firing is carried out while flowing gas through the packed bed. And a method for firing an inorganic compound, the temperature of which is controlled by the inlet temperature of the gas through which the maximum temperature of the gas flows. 2. The temperature control is performed by one of two or more heating means.
2. The method for calcination of an inorganic compound according to claim 1, wherein the heating is performed for increasing the temperature, and the other is installed in the vicinity of the filling layer. 3. The method for calcination of an inorganic compound according to claim 1, wherein a raw material for an oxidation catalyst is used as the inorganic compound. 4. A method for producing an oxidation catalyst using the calcination method according to claim 1. 5. The method for producing an oxidation catalyst according to claim 4, wherein the oxidation catalyst is any one of acrolein, acrylic acid, methacrolein, and a catalyst for producing methacrylic acid.