JP5121664B2 - Gas phase exothermic reaction method - Google Patents

Description

  The present invention relates to a gas phase exothermic reaction method using a fluidized bed reactor having a plurality of heat removal tubes.

Fluidized bed technology has been applied to various manufacturing technologies since it was developed in the late 19th century. Main industrial applications of fluidized beds include coal gasification furnaces, FCC plants, acrylonitrile production plants by propylene ammoxidation, polyethylene gas phase polymerization plants, maleic anhydride production plants, and the like. Since the fluidized bed reactor can easily remove or add heat of reaction, the inside of the bed can be maintained at a uniform temperature, the high concentration gas in the explosion range can be treated, and the productivity is high. Future applications and improvements are expected.
Usually, a dispersion pipe and / or a dispersion plate for supplying a reaction raw material are installed at the lower part of the fluidized bed reactor. When performing a gas phase exothermic reaction, a heat removal pipe is provided inside the reactor, and heat of reaction is removed by circulating water or steam to control the reaction temperature. A cyclone is installed at the upper part of the reactor to capture the catalyst in the reaction gas and return the catalyst to the lower part through the dipreg.

  In Patent Document 1, when a solid catalyst containing molybdenum is placed in a reactor through which a cooling pipe utilizing sensible heat is passed, the reactant is introduced into the reactor and an exothermic reaction is performed at 200 to 500 ° C. Describes a gas phase oxidation method in which the flow direction of the cooling medium passing through the cooling pipe is reversed every predetermined time. Patent Document 2 describes a gas phase oxidation method in which the difference between the temperature in the reactor and the average surface temperature of the cooling pipe is 55 ° C. or less in the same reaction. According to both of the above documents, when the reaction is carried out at a high temperature when the solid catalyst contains molybdenum, the volatilization of molybdenum occurs, and the volatilized molybdenum adheres to the cooling pipe having a low temperature, from the solid catalyst to the cooling medium. It is described that there is a tendency for the heat transfer efficiency to deteriorate. And it describes that adhesion of the volatilized molybdenum to the piping can be prevented by reversing the flow direction of the cooling medium every predetermined time. Furthermore, it is described that molybdenum can be peeled off more reliably by providing a plurality of cooling pipes and operating while switching the cooling pipes to be used.

JP 2005-154327 A JP 2005-154332 A

  Here, the reaction temperature in the gas phase exothermic reaction is one of important control factors when operating the fluidized bed reactor, and is controlled by a heat removal pipe provided inside the reactor. Stabilization of the reaction temperature is an essential matter from the viewpoint of maintaining the yield of the target product at a high level and from the viewpoint of safe operation. In addition, maintaining the capacity of the heat removal pipe at a high level for a long period of time and enabling the fluidized bed reactor to continue operating for a long period of time leads to an increase in the yield of the target product. However, there is still room for improvement in the method of using the heat removal tube of the fluidized bed reactor that satisfies both process stability and economy.

For example, when the present inventor operated a fluidized bed reactor continuously for a long period of time according to the method described in Example 1 of Patent Document 1 and carried out a gas phase exothermic reaction, the heat removal tube was passed as the reaction time passed It was not possible to prevent the problem that the heat removal ability declined due to the contamination on the surface. After the heat removal capability declines, in order to secure the heat removal amount necessary to continue the exothermic reaction, it is necessary to increase the number of heat removal tubes to be used. All the heat removal tubes were to be operated. However, the reduction of the heat removal amount continued thereafter, and the necessary heat removal amount could not be secured, and it was necessary to stop the continuous operation and remove the dirt.
In addition, when a gas phase exothermic reaction was performed according to the method described in Patent Document 2, even when the temperature calculated by the equation (1) of the document is 55 ° C. or less, the heat removal ability decreased over time. Admitted. Furthermore, the dirt adhering to the heat removal tube increased with the lapse of the reaction time, and eventually the necessary amount of heat removal could not be secured, resulting in the same result as in Patent Document 1.

  In view of the above circumstances, the problem to be solved by the present invention is that when a gas phase exothermic reaction is performed using a fluidized bed reactor having an internal heat removal tube, the heat removal tube maintains its heat transfer capability over a long period of time, To provide a gas phase exothermic reaction method capable of stably controlling the temperature of a reactor for a long period of time.

As a result of intensive studies on a method related to maintaining the heat removal capability of the heat removal tube of the fluidized bed reactor, the present inventors have found that the above-mentioned problems can be solved by the following means, and have completed the present invention.
That is, the present invention is a gas phase exothermic reaction method as described below.
[1]
A method of supplying a reaction raw material to a fluidized bed reactor having a fluidized bed catalyst containing molybdenum and a plurality of heat removal tubes therein to cause a gas phase exothermic reaction,
A method comprising repeating each heat removal tube of the plurality of heat removal tubes for 18 days or less and 24 hours or more of nonuse.
[2]
The method according to [1] above, wherein the reaction raw material contains an alkane and / or alkene having 2 to 4 carbon atoms.
[3]
The method according to [2] above, wherein the alkane is propane and / or isobutane.
[4]
The method according to [2] or [3] above, wherein the alkene is propylene and / or isobutylene.
[5]
The method according to any one of [1] to [4], wherein the gas phase exothermic reaction is an ammoxidation reaction.
[6]
The fluidized bed catalyst has a particle content of 3.0 wt. % Or less of the method according to any one of [1] to [5] above.

  According to the present invention, when a gas phase exothermic reaction is performed using a fluidized bed reactor having an internal heat removal tube, the heat removal tube can maintain its heat transfer capacity over a long period of time, and the reactor can be stably used for a long time. It is possible to provide a gas phase exothermic reaction method excellent in process stability and economy capable of performing temperature control.

  Hereinafter, the best mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  The gas phase exothermic reaction method of the present embodiment is a method in which a reaction raw material is supplied to a fluidized bed reactor having a fluidized bed catalyst containing molybdenum and a plurality of heat removal tubes to cause a gas phase exothermic reaction. Each of the heat removal tubes of the plurality of heat removal tubes includes repeated use for 18 days or less and non-use for 24 hours or more.

  FIG. 1 conceptually shows an example of a fluidized bed reaction apparatus having a plurality of heat removal tubes of the present embodiment. The fluidized bed reactor 1 may be the same as a known one. For example, the fluidized bed reactor 1 has a dispersion plate of air (oxygen) as a reaction raw material and a dispersion pipe 5 of a reaction raw material other than air (oxygen) in the lower part thereof. In the upper part, a cyclone 7 for collecting the catalyst mixed in the reaction gas flowing out from the fluidized bed reactor is provided. In this case, the reaction raw materials and reaction products generally flow from bottom to top.

  Air (oxygen) A is supplied to a fluidized bed reactor 1 filled with a required amount of a fluidized bed catalyst in a dispersion plate 3 through an introduction pipe 2 connected from the lower side of the fluidized bed reactor 1. . The reaction raw material B other than air (oxygen) passes through the introduction pipe 4 connected from the lower side of the fluidized bed reactor 1, and the fluidized bed reactor 1 in which the required amount of the fluidized bed catalyst is filled in the dispersion pipe 5. To be supplied. In the case of a gas phase exothermic reaction that does not use air (oxygen), the introduction tube 2 and the dispersion plate 3 can be omitted.

  The fluidized bed catalyst flows due to the introduction of the reaction raw material gas. The interface of the fluidized catalyst layer 9 is not necessarily determined as exactly as the liquid level, but is only measured approximately and averagely because there are protrusions due to large and small bubbles.

  The heat generated by the gas phase exothermic reaction is removed by cooling with a plurality of heat removal tubes 6 provided in the fluidized bed reactor 1, and the reaction temperature is controlled. Although reaction temperature is measured with a thermometer, if it is a normal thing used for a chemical plant, a format will not be specifically limited. It is preferable to install a plurality of thermometers at locations where the temperature distribution of the catalyst layer can be grasped.

  The reaction gas flows into the cyclone 7, and the catalyst is returned to the lower part of the reactor. The reaction gas C from which the catalyst has been substantially removed is extracted through the outflow pipe 8.

  The gas phase exothermic reaction is not particularly limited, and examples thereof include an oxidation reaction, an ammoxidation reaction, an alkylation reaction, and the like performed at a reaction temperature of 200 ° C to 500 ° C.

  The reaction raw material is not particularly limited as long as it is a raw material for the gas phase exothermic reaction. For example, hydrocarbons such as alkanes, alkenes, alcohols, aromatic hydrocarbons, and, if necessary, ammonia in addition to the hydrocarbons. And / or air (oxygen) is used. Specifically, in the case of an oxidation reaction, the hydrocarbon and an oxidizing agent such as oxygen or air are used. In the case of an ammoxidation reaction, the hydrocarbon, an oxidizing agent such as oxygen or air, and ammonia are used. In the case of the alkylation reaction, two or more kinds of substances selected from the hydrocarbons are used.

  Examples of alkane include those having 1 to 4 carbon atoms (methane, ethane, propane, n-butane, isobutane, etc.), and examples of alkenes include those having 2 to 4 carbon atoms (ethylene, propylene, n-butylene, isobutylene, t -Butylene and the like), examples of the alcohol include methanol, ethanol, and tertiary butyl alcohol, and examples of the aromatic hydrocarbon include benzene, phenol, o-xylene, and naphthalene. When the gas phase exothermic reaction is an ammoxidation reaction, methane, propane and / or isobutane is used as the alkane, and propylene and / or isobutylene is used as the alkene from the viewpoint of the value of the generated nitrile compound as a chemical intermediate material. preferable.

  In addition, the fluidized bed catalyst for the gas phase exothermic reaction filled in the fluidized bed reactor is not particularly limited as long as it is a solid catalyst and contains molybdenum. For example, at least molybdenum supported on silica or the like. The metal oxide catalyst containing this is mentioned. Taking the ammoxidation of propane or propylene as an example, it is a composite oxide of Mo-V- (Sb and / or Ti), Mo-V-Fe, or Mo-Bi-Fe, and is 90% by mass or more The catalyst particles having a particle diameter of 10 to 197 μm and a crushing strength of 10 MPa or more are preferably used as the fluidized bed catalyst.

  The heat removal pipe 6 performs heat removal in the fluidized bed reactor 1, and a plurality of series are arranged in parallel inside the reactor 1. As the refrigerant to be circulated through the heat removal pipe 6, water, water vapor, and molten salt are preferable, and one kind of single use may be used, or two or more kinds may be combined.

  Although FIG. 1 shows an example of two series of heat removal tubes composed of a straight tube portion and a U-shaped bend portion, the heat removal tube is not limited to this form. The heat removal pipe 6 penetrating through the reactor wall is bent downward in the reactor at the bend portion, and further bent through the straight pipe portion and further inverted at the bend portion. This is called one pass. The heat removal tube 6 in FIG. 1 is an example of two passes and three passes. The heat removal tube 6 passes through the reactor wall again at the other end. This is called one series, and a plurality of series of heat removal tubes 6 are installed.

  The tube diameter of the heat removal tube is 20 mm to 200 mm on the basis of the outer diameter, and the length of the straight tube portion of the heat removal tube is not particularly limited as long as it is within the reactor length, but is 0.05 to 0 of the reactor length. It is preferable that the length is 8 times, and there is a flowing catalyst, and the reaction temperature can be controlled. The number of passes of the heat removal tube 6 is preferably 1 to 10 passes. If the refrigerant used is the same and the installation position of the heat removal tube in the reactor height direction is the same, the thermal capacity of the heat removal tube is defined by the size of the outer surface area. On the basis of the external surface area of the heat removal tube having the smallest external surface area, the external surface area of the other heat removal tubes is preferably 1 to 10 times, and more preferably 1 to 5 times. In addition, the heat removal tube having a small outer surface area is convenient for fine adjustment of the reaction temperature compared to the heat removal tube having a large outer surface area.

  The material of the heat removal pipe 6 can employ, for example, a steel pipe defined in JIS G-3458 and an elbow pipe defined in JIS B-2311, and is not particularly limited as long as the use conditions of temperature and pressure are satisfied. .

When water is circulated as a refrigerant in the heat removal pipe 6, the circulated water is heated due to an exothermic reaction in the fluidized bed reaction vessel 1, and at least a part thereof is evaporated. This heat removal tube is classified as a type of heat removal tube that uses the latent heat of vaporization of the refrigerant. The amount of water vapor generated by this evaporation is preferably such that the evaporation rate Rv calculated by the following formula (1) is 5 to 30%. Moreover, it is preferable that the supply temperature of water is the temperature range of (reaction temperature-100) -100 degreeC.
Rv = (water vapor mass) / (mass of water supplied to the heat removal tube 6) × 100 (1)

  When water vapor or molten salt is circulated through the heat removal pipe 6 as a refrigerant, the water vapor or molten salt that is circulated is heated due to an exothermic reaction in the fluidized bed reaction vessel 1 and the temperature rises. This heat removal tube is classified as a type of heat removal tube that utilizes the sensible heat of the refrigerant. The supply temperature of steam or molten salt to the heat removal tube 6 is preferably in the temperature range of (reaction temperature−100) ° C. or less.

Hereinafter, an example of the gas phase exothermic reaction method according to the present embodiment will be described.
In order to set the temperature of the gas phase exothermic reaction to an optimum temperature value for the reaction, the reaction temperature is adjusted by the number of the heat removal tubes used. For example, when the optimum temperature is 400 ° C. and the actual temperature is 420 ° C., an appropriate heat removal pipe that is not used is selected to reduce the temperature by 20 ° C., and its use is started to adjust the temperature. . When changing the reaction amount, the optimum temperature is maintained by using or not using an appropriate heat removal tube.

  When the inventors conducted a gas phase exothermic reaction without depending on the method of the present embodiment, in order to keep the reaction temperature constant, the total outer surface area value of the heat removal tube used over time was increased. I found out that it was necessary. That is, 70% of the total outer surface area was used at the beginning of the reaction, and 30% was not used. However, as the reaction time elapsed, the usage percentage had to be increased from 70%. Therefore, as a result of intensive studies by the present inventors on the cause of the increase in the total outer surface area of the heat removal tube, it has been found that dirt adheres to the outer surface of the heat removal tube used and the heat transfer capability is reduced. Further, when the deposit was observed with a scanning electron microscope, it was found that a small amount of catalyst particles having a relatively large particle diameter was incorporated, but a large number of catalyst particles of 24 μm or less were incorporated. Furthermore, it was also found by analysis of the composition component that the catalyst particles were incorporated mainly from molybdenum oxide.

  The present inventors considered the contamination generation mechanism on the outer surface of the heat removal tube as follows. Molybdenum contained in the catalyst is sublimated from the catalyst as molybdenum oxide in an atmosphere of high temperature and moisture. The outer surface of the heat removal tube used is cooled, and the molybdenum oxide in the vapor state adheres and solidifies. Contamination due to small particle size catalyst particles collides with the outer surface of the heat removal tube, and some adhere to them, but small size small particle size catalysts are relatively easy to adhere and occupy the majority. If the use of the heat removal pipe is continued, the process of sublimation and adhesion of the molybdenum oxide and the adhesion of the catalyst particles proceeds, the thickness of the dirt increases, and the capacity of the heat removal pipe decreases.

  Therefore, it is essential to secure a necessary amount of heat removal for a plurality of heat removal tubes, but it should not be continued to use only a certain heat removal tube, focusing only on the amount of heat removal. In the gas phase exothermic reaction method of the present embodiment, after each heat removal tube has been used for a certain period of 18 days or less, it is repeatedly not used for a certain period of 24 hours or more, and is used throughout a plurality of heat removal tubes. Rotate things and unused ones. If the heat removal tube is used continuously, dirt is likely to adhere because the surface is low in temperature, but if it is not used, the surface temperature of the heat removal tube rises to near the reaction temperature and the dirt peels off. It becomes easy.

  By the rotation of the heat removal tube described above, the cooling capacity of the heat removal tube can be maintained and the fluidized bed reactor can be stably operated for a long period of time. The reason why the cooling capacity is restored is probably that the temperature of the surface of the heat removal tube rises when the use is stopped. In the case of an ammoxidation reaction of alkane and / or alkene using a molybdenum-containing catalyst, it is considered that the heat transfer coefficient of the cooling coil is recovered by resublimation or scattering of molybdenum oxide adhering to the surface. In addition, when the molybdenum oxide is sublimated or scattered, it is considered that the fine particle catalyst adhering to the surface is also scattered.

  In addition, in order to obtain the necessary heat removal amount while repeatedly using and not using each heat removal tube, the heat removal tubes are "rotated" at regular intervals, but "rotation" is not necessarily in a certain order. There is no. As long as the period of continuous use does not become too long and a sufficient period of non-use is ensured, the plurality of heat removal tubes may be turned on and off at random. When performing a gas phase exothermic reaction, it may be desirable to use a heat removal tube at a specific location in order to remove locally generated heat. A heat removal tube may be used. Whether the order of on / off is constant or random, as long as a specific heat removal tube is set to repeat use and non-use without being continuously used, it is within the scope of this embodiment. is there.

  In order to make full use of the capacity of the heat removal pipe, it is important to set the use period and non-use period of the heat removal pipe. In the gas phase exothermic reaction of the present embodiment, the use period of each of the heat removal pipes existing in plurality is set to 18 consecutive days or less, and the nonuse period is set to 24 hours or more. According to the study by the present inventor, the period of use should be 18 days or less, and the period of non-use should be 24 hours or more in order to maintain the cooling capacity of the heat removal tube and continue the gas phase exothermic reaction. It was necessary to satisfy both. When each heat removal tube was continuously used for more than 18 days, the heat removal capability was not recovered even if a non-use period was set thereafter. Moreover, even if the period of use was 18 consecutive days or less, the recovery of the heat removal capability was incomplete unless the period of non-use was 24 hours or longer. Therefore, during repeated use and non-use, deposits that were not removed accumulated, and the heat removal capability was reduced to the extent that the required heat removal amount could not be obtained. Preferably, the usage period is 12 days or less and the non-use period is 2 days or more, more preferably the use period is 8 days or less and the non-use period is 3 days or more. By setting the use period as described above, it is possible to prevent the contamination of the heat removal tube from becoming a fatal unrecoverable state. The non-use period is a period required for the dirty heat removal tube to recover.

  In order to rotate the heat removal tube, it is necessary that at least one heat removal tube is not used and has been waiting for a predetermined period. At the time of carrying out the gas phase exothermic reaction, the heat removal tube in use is at least one heat removal tube with a use of 0.40A to 0.85A, where A is the total outer surface area of all heat removal tubes. It is possible to stand by for a specified period or longer when not in use. The reason why the lower limit is provided is that the number of heat removal tubes that can be installed in the reactor is physically limited and that the investment equipment cost is reduced.

It has also been found that the degree of contamination on the surface of the heat removal tube varies depending on the reaction type. That is, when the fluidized bed catalyst for the gas phase exothermic reaction contains molybdenum, the amount of sublimation from the catalyst, which is one of the sources of contamination, differs depending on the type of reaction, resulting in a difference in the degree of contamination. . The sublimation of molybdenum oxide is affected by temperature and moisture. For example, in the case of acrylonitrile production reaction by ammoxidation of propylene or propane, the reaction temperature of both methods is almost the same, but the proportion of complete oxidation reaction in which propane has more hydrogen atoms and produces CO ₂ Because of its high water production. For this reason, the sublimation of molybdenum oxide is promoted and the contamination of the heat removal tube is increased.

  With respect to catalyst particles of 24 μm or less that are incorporated in a large amount of dirt in the heat removal tube, the content in the fluidized bed catalyst is 3.0 wt. % Or less, preferably 2.0 wt. % Or less is preferable. The particle size of the fluidized bed catalyst can be measured by using SK Laser Micron Sizer Pro-7000S (manufactured by Seishin Enterprise Co., Ltd.) with a dispersion time of 90 seconds. By prescribing a catalyst particle concentration of 24 μm or less in the fluidized bed catalyst, it contributes favorably to cooling capacity recovery by heat removal tube rotation.

  As described above, the presumed mechanism of operation of the present embodiment has been described mainly using a method of ammoxidizing propylene or propane using a catalyst containing molybdenum. However, each heat removal tube is repeatedly used and not used. Of course, it is not limited to this reaction that the gas phase exothermic reaction method operating as described above is effective. As described above, providing a period for increasing the surface temperature of the heat removal pipe without continuously using each heat removal pipe for a certain period of time makes it easier for the deposits during heat removal to peel off, reducing the capacity of the heat removal pipe. Since it is presumed that it contributes to the continuous reaction by preventing it, it can be said that the gas phase exothermic reaction method of the present embodiment is suitable if it is a reaction system applicable to this mechanism. That is, when a substance that vaporizes and / or sublimates is present in the reaction system at the temperature at which the reaction proceeds, the substance vaporized and / or sublimated during the reaction tends to adhere to the surface of the low-temperature heat removal tube and is removed by adhesion. Since the heat capacity is considered to decrease, it is assumed that setting the period during which the surface temperature of the heat removal tube is raised leads to the recovery of the heat removal tube capacity. Accordingly, it can be said that the present invention is particularly effective in a reaction system in which a substance that vaporizes and / or sublimates at the reaction temperature exists.

This embodiment will be described in more detail with reference to examples and comparative examples. However, this embodiment is not limited to the following examples. The fluidized bed reactor used in the examples is the same as that shown in FIG. 1. The fluidized bed reactor has a gas dispersion tube and a dispersion plate at the lower part of the fluidized bed reactor, A heat removal tube was installed for removal. In addition, the upper part of the fluidized bed reactor had a cyclone for collecting the catalyst mixed in the reaction gas flowing out from the reactor.
The instrument and attached equipment were normally used and were within the normal error range.

  The particle size of the fluidized bed catalyst was measured using SK Laser Micron Sizer Pro-7000S (manufactured by Seishin Enterprise Co., Ltd.) with a dispersion time of 90 seconds.

The yield and unreacted rate of the reaction product were calculated from the analytical data obtained by sampling the reaction gas and measured by gas chromatography according to the following equation.
(Yield (%) of reaction product) = (carbon weight (g) in product) / (carbon mass (g) in organic compound as reaction raw material supplied) × 100
(Unreacted rate (%)) = (Carbon mass (g) in organic compound as unreacted reaction raw material) / (Carbon mass (g) in organic compound as supplied reaction raw material) × 100

[Example 1]
Propylene, ammonia and air as reaction raw materials were supplied to a fluidized bed reactor 1 similar to that shown in FIG. 1, and an ammoxidation reaction of propylene was performed as follows. The heat removal tubes were provided with those shown in Table 1 of 32 series. Series No. The heat removal pipes 1 to 28 are of the type that removes heat by using the latent heat of vaporization of the refrigerant, and the number of passes is different in the series. However, 30 kg / cm ² G saturated water is used as the material and refrigerant. Use, the evaporation rate Rv in each heat removal pipe of the saturated water is 10 to 15%, the outer diameter is 114 mm, and the installation position of the reactor height method is 0.7 m to 9 m above the air dispersion plate. .6 m was the same. Series No. The heat removal tubes 29 to 33 are of a type that removes heat using the sensible heat of superheated steam. The number of passes, the material used, and 30 kg / cm ² G saturated steam as the refrigerant are used, and the outer diameter is 114 mm. It was the same that the installation position of the reactor height method was 0.7 m to 9.6 m above the air dispersion plate.

  The fluidized bed reactor 1 was a vertical cylindrical type having an inner diameter of 8 m and a length of 20 m, and had an air dispersion plate 3 at a position 2 m from the bottom and a raw material dispersion tube 5 thereon. In order to measure the temperature of the catalyst layer, 20 thermometers were attached between 1.5 to 4.5 m above the air dispersion plate.

The catalyst has a content of 1.4 wt.% With a particle size of 10-100 μm, an average particle size of 55 μm, and a particle size of 24 μm or less. % Molybdenum-bismuth-iron-based supported catalyst and packed so as to have a stationary layer height of 2.7 m. Air was 56000Nm ³ / h supplied from the air distribution plate, a 6200Nm ³ / h and ammonia propylene from raw gas dispersion tube was 6600Nm ³ / h feed. The pressure in the reactor was 0.70 kg / cm ² G.
The target value of the reaction temperature was set to 440 ° C., and the temperature control was performed by adjusting the use series of the heat removal tube 6. The average reaction temperature (hereinafter simply referred to as reaction temperature) of 20 thermometers between 1.5 and 4.5 m above the air dispersion plate was 440 ° C. Table 2 shows the usage state of the heat removal tube. The total outer surface area of the latent heat type heat removal tubes used was 568 m ² , which was 71% of the total outer surface area A of all latent heat type heat removal tubes (0.71A). The total surface area of the used sensible heat type heat removal tubes was 57 m ² , which was 60% of the total outer surface area B of all sensible heat type heat removal tubes (0.60 B). The steam flow rates leading to the sensible heat type heat removal tubes were 5800 to 6100 kg / h, the inlet steam temperature was 235 ° C., and the outlet steam temperature was 398 to 405 ° C.

使用系列の欄で●は、使用を表し、空欄は、不使用を表す。

In the column of use series, ● represents use, and a blank column represents non-use.

When the reaction results were analyzed immediately after the start of the reactor operation, the yield of acrylonitrile was 81.5%, and the unreacted rate of propylene was 1.1%.
The operation was continued with the heat removal tubes shown in Table 2 in use. During 4 days, the reaction temperature continued to rise slowly and reached 441 ° C. From the fifth day, rotation of the heat removal tube was started with the use period of the heat removal tube being 12 days or less and the non-use period being 3 days or more. The reaction temperature varied between 438 and 442 ° C during the two year operation. The yield of acrylonitrile varied from 80.9 to 81.7%, and the unreacted ratio of propylene varied from 0.80 to 1.3%. Also, during this period, the use of latent heat type heat removal tubes varied from 0.70A to 0.74A. The use of sensible heat type heat removal tubes varied between 0.60B and 0.80B.
Two years later, when the reactor was stopped and the heat removal tube was observed, a scale with a thickness of about 1 to 3 mm was attached to the surface of about 30% of the heat removal tube.

[Example 2]
The reaction raw material was supplied to the fluidized bed reactor under the same conditions as in Example 1 except that propylene was replaced with propane, and the propane ammoxidation reaction was performed as follows.
The catalyst has a content of 1.3 wt.% With a particle size of 10-100 μm, an average particle size of 55 μm, and a particle size of 24 μm or less. % Molybdenum-vanadium-based supported catalyst and packed so as to have a stationary layer height of 2.2 m. Air was 64500Nm ³ / h supplied from the air distribution plate, a 4300Nm ³ / h and ammonia propane from feed gas dispersion tube was 4300Nm ³ / h feed. The pressure in the reactor was 0.75 kg / cm ² G.
The target value of the reaction temperature was set to 440 ° C., and the temperature control was performed by adjusting the use series of the heat removal tube 6. The reaction temperature was 441 ° C. Table 3 shows the usage state of the heat removal tube. The total surface area of the latent heat type heat removal tubes used was 490 m ² , which was 61% of the total external surface area value A of all latent heat type heat removal tubes (0.61A). The total surface area of the used sensible heat type heat removal tubes was 57 m ² , which was 60% of the total outer surface area B of all sensible heat type heat removal tubes (0.60 B). The steam flow rates leading to the sensible heat type heat removal tubes were 5800 to 6100 kg / h, the inlet steam temperature was 235 ° C., and the outlet steam temperature was 398 to 405 ° C.

使用系列の欄で●は、使用を表し、空欄は、不使用を表す。

In the column of use series, ● represents use, and a blank column represents non-use.

When the reaction results were analyzed immediately after the start of the reactor operation, the yield of acrylonitrile was 52.1%, and the unreacted rate of propane was 10.8%.
The operation was continued with the heat removal tubes shown in Table 3 in use. During the 4 days, the reaction temperature continued to rise slowly to 442 ° C. From the fifth day, rotation of the heat removal tube was started with the use period of the heat removal tube being 6 days or less and the non-use period being 3 days or more. The reaction temperature varied between 438 and 442 ° C during the two year operation. The yield of acrylonitrile varied from 51.7 to 52.5%, and the unreacted rate of propane varied from 9.9 to 11.3%. During this period, the use of latent heat type heat removal tubes varied from 0.60 A to 0.70 A. The use of sensible heat type heat removal tubes varied between 0.60B and 0.80B.
Two years later, when the reactor was stopped and the heat removal tube was observed, a scale with a thickness of about 1 to 5 mm was attached to the surface of about 30% of the heat removal tube.

[Example 3]
The content of catalyst particles with a particle size of 24 μm or less is 3.2 wt. %, Propylene ammoxidation was carried out in the same manner as in Example 1. Table 2 shows the usage state of the heat removal tube.
When the reaction results were analyzed immediately after the start of the reactor operation, the yield of acrylonitrile was 81.6%, and the unreacted rate of propylene was 1.1%.
The rotation of the heat removal tube was started with the use period of the heat removal tube being 12 days or less and the non-use period being 3 days or more. The reaction temperature fluctuated between 438 and 443 ° C. during the two year operation. The yield of acrylonitrile varied from 80.7 to 81.8%, and the unreacted rate of propylene varied from 0.78 to 1.3%. During this period, the use of latent heat type heat removal tubes varied from 0.70A to 0.78A. The use of sensible heat type heat removal tubes varied between 0.60B and 0.80B.
Two years later, when the reactor was stopped and the heat removal tube was observed, a scale with a thickness of about 2 to 5 mm adhered to the surface of about 30% of the heat removal tube.

[Comparative Example 1]
In the same manner as in Example 1, an ammoxidation reaction of propylene was performed. Table 2 shows the usage state of the heat removal tube. The total outer surface area of the latent heat type heat removal tubes used was 568 m ² , which was 71% of the total outer surface area A of all latent heat type heat removal tubes (0.71A). The total surface area of the used sensible heat type heat removal tubes was 57 m ² , which was 60% of the total outer surface area B of all sensible heat type heat removal tubes (0.60 B). The steam flow rates leading to the sensible heat type heat removal tubes were 5800 to 6100 kg / h, the inlet steam temperature was 235 ° C., and the outlet steam temperature was 398 to 405 ° C.
When the reaction results were analyzed immediately after the start of the reactor operation, the yield of acrylonitrile was 81.5%, and the unreacted rate of propylene was 1.1%.
As the reaction temperature increased with the progress of operation, a heat removal pipe was added to maintain the reaction temperature, and if the temperature dropped too much, adjustments were made not to use the other series of heat removal pipes. Carried out.
Table 4 summarizes the adjustment status of the heat removal tubes. Although the reaction temperature was 440 ° C., it gradually increased with the progress of operation. 28 started to be used. On the 20th, no. 7 started to be used. Since the temperature was lower than 440 ° C., no. 12 and no. 25 was unused. The same applies thereafter.
The series of heat removal tubes used over time increased, and after six months, all heat removal tubes were in use.

Although the operation was continued, the reaction temperature rose to 450 ° C., and it was judged that control was difficult, and the reactor was stopped.
During the operation period of 185 days, the reaction temperature changed from 438 to 450 ° C., and the reaction temperature was higher in the later operation period. The acrylonitrile yield was 78.9-81.7%, and the acrylonitrile yield was worse in the later stage of operation. The unreacted rate of propylene was 0.31 to 1.3%.
On the 190th day, the reactor was stopped and the heat removal tube was observed. As a result, a scale of about 7 to 11 mm in thickness adhered to the surface of most of the heat removal tubes.

[Comparative Example 2]
In the same manner as in Example 1, an ammoxidation reaction of propylene was performed. Table 2 shows the usage state of the heat removal tube. When the reaction results were analyzed immediately after the start of the reactor operation, the yield of acrylonitrile was 81.5%, and the unreacted rate of propylene was 1.1%.
The rotation of the heat removal tube was started with the use period of the heat removal tube being 19 days or less and the non-use period being 3 days or more. As the operation progressed, the reaction temperature showed an increasing trend, so a heat removal tube was added to maintain the reaction temperature. The number of unused heat removal tube lines gradually decreased, and rotation with a use period of 19 days or less and a non-use period of 3 days or more was not possible. The period of use has increased from 19 days, the period of non-use has decreased from 3 days, and finally it has become impossible to take time for non-use.
During the operation period of 8 months, the reaction temperature changed from 438 to 451 ° C., and the reaction temperature was higher in the later operation period. The acrylonitrile yield was 78.8-81.6%, and the acrylonitrile yield was worse in the later stage of operation. The unreacted rate of propylene was 0.30 to 1.2%.
When the reactor was stopped at 8 months and the heat removal tube was observed, a scale having a thickness of about 7 to 11 mm was attached to the surface of most of the heat removal tubes.

[Comparative Example 3]
Propane ammoxidation was carried out in the same manner as in Example 2. Table 3 shows the usage state of the heat removal tube.
When the reaction results were analyzed immediately after the start of the reactor operation, the yield of acrylonitrile was 52.1%, and the unreacted rate of propane was 10.8%.
The rotation of the heat removal tube was started with the use period of the heat removal tube being 19 days or less and the non-use period being 3 days or more. As the operation progressed, the reaction temperature showed an increasing trend, so a heat removal tube was added to maintain the reaction temperature. The number of unused heat removal tube lines gradually decreased, and rotation with a use period of 19 days or less and a non-use period of 3 days or more was not possible. The period of use has increased from 19 days, the period of non-use has decreased from 3 days, and finally it has become impossible to take time for non-use.
During the operation period of 5 months, the reaction temperature changed from 438 to 450 ° C., and the reaction temperature was higher in the latter half of the operation. The acrylonitrile yield was 47.8 to 52.3%, and the acrylonitrile yield was worse in the later stage of operation. The unreacted ratio of propane was 7.9 to 11.3%.
When the reactor was stopped at 5 months and the heat removal tube was observed, a scale having a thickness of about 7 to 11 mm was attached to the surface of most of the heat removal tubes.

[Comparative Example 4]
The content of catalyst particles with a particle size of 24 μm or less is 3.2 wt. The propane ammoxidation reaction was carried out in the same manner as in Example 2 except that the content was%. Table 3 shows the usage state of the heat removal tube.
When the reaction results were analyzed immediately after the start of the reactor operation, the yield of acrylonitrile was 52.3%, and the unreacted rate of propane was 10.7%.
The rotation of the heat removal tube was started with the use period of the heat removal tube being 19 days or less and the non-use period being 3 days or more. As the operation progressed, the reaction temperature showed an increasing trend, so a heat removal tube was added to maintain the reaction temperature. Gradually, the number of unused heat removal tube lines decreased, and rotation with a use period of 19 days or less and a non-use period of 3 days or more was no longer possible. The period of use has increased from 19 days, the period of non-use has decreased from 3 days, and finally it has become impossible to take time for non-use.
During the operation period of 4 months, the reaction temperature changed from 438 to 450 ° C., and the reaction temperature was higher in the later operation period. The acrylonitrile yield was 47.6-52.5%, and the acrylonitrile yield was worse in the later stage of operation. The unreacted rate of propane remained at 7.7 to 11.0%.
When the reactor was stopped at 4 months and the heat removal tube was observed, a scale having a thickness of about 8 to 11 mm adhered to the surface of most of the heat removal tubes.

  The method of the present invention can be effectively used when a gas phase exothermic reaction is carried out using a fluidized bed reactor.

It is the schematic which shows an example of the fluidized bed reaction apparatus which has a some heat removal tube.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fluidized bed reactor 2 Air (oxygen) introduction pipe 3 Air (oxygen) dispersion plate 4 Raw material introduction pipe 5 Raw material dispersion pipe 6 Cooling coil apparatus 7 Multistage cyclone 8 Outflow pipe 9 Fluidized catalyst bed A Air (oxygen)
B Raw material C Reaction product gas

Claims (6)

A method of supplying a reaction raw material to a fluidized bed reactor having a fluidized bed catalyst containing molybdenum and a plurality of heat removal tubes therein to cause a gas phase exothermic reaction,
A method comprising repeating each heat removal tube of the plurality of heat removal tubes for 18 days or less and 24 hours or more of nonuse.   The method according to claim 1, wherein the reaction raw material contains an alkane and / or alkene having 2 to 4 carbon atoms.   The method according to claim 2, wherein the alkane is propane and / or isobutane.   The method according to claim 2 or 3, wherein the alkene is propylene and / or isobutylene.   The method according to claim 1, wherein the gas phase exothermic reaction is an ammoxidation reaction.   The fluidized bed catalyst has a particle content of 3.0 wt. The method of any one of Claims 1-5 which is% or less.

Images