JP2008162956A - System for obtaining (meth)acrylic acid solution, and method for producing (meth)acrylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system for stably obtaining a (meth)acrylic acid solution of high and constant (meth)acrylic acid concentration coming out of a noncondensable gas separation apparatus regardless of the temperature fluctuation of the gas discharged from a vapor phase catalytic oxidation reactor employed in a (meth)acrylic acid production process that employs a vapor phase catalytic oxidation reaction, and a method for producing (meth)acrylic acid that utilizes the system. <P>SOLUTION: The system for obtaining a (meth)acrylic acid solution from gas that contains (meth)acrylic acid by separating noncondensable gas therefrom is comprised of a reactor for producing gas that contains (meth)acrylic acid by a vapor phase catalytic oxidation reaction and a noncondensable gas separation apparatus for separating noncondensable gas from the gas that contains (meth)acrylic acid produced in the reactor to obtain a (meth)acrylic acid solution, which noncondensable gas separation apparatus is equipped with a heating means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a system for obtaining a (meth) acrylic acid solution by separating a non-condensable gas from a gas containing (meth) acrylic acid, and a method for producing (meth) acrylic acid using the system. It is.

  Acrylic acid and methacrylic acid (hereinafter referred to as “(meth) acrylic acid” together) are used as manufacturing raw materials for industrial products, and are chemical substances produced in large quantities at large-scale plants. . In general, these compounds are produced through a process of separating a non-condensable gas from a crude product to obtain a (meth) acrylic acid solution, and various purification processes in order to obtain a high-purity product. .

  For example, in the production process of acrylic acid, propylene, propane, acrolein and the like are subjected to catalytic gas phase oxidation with a molecular oxygen-containing gas in the presence of an oxidation catalyst. In addition to the target acrylic acid, acetic acid, lower aldehyde, water And low boiling point substances such as furfural and maleic anhydride are generated as by-products. For this reason, the obtained mixed gas is guided to a non-condensable gas separation device, and contacted with a collection solvent or condensed to obtain a solution containing acrylic acid and other by-products, and distilled and released from this solution. The product is obtained by separating and purifying acrylic acid by methods such as extraction and crystallization.

  In the non-condensable gas separation apparatus, gaseous non-condensable gas such as propylene and carbon dioxide is separated at room temperature and normal pressure. Here, since the (meth) acrylic acid-containing gas introduced into the non-condensable gas separator is at a high temperature, the target compound (meth) acrylic acid is discharged along with the non-condensable gas. Therefore, conventionally, when a non-condensable gas is separated from a (meth) acrylic acid-containing gas to obtain a (meth) acrylic acid solution, the collection solvent, the non-condensable gas separation device, etc. are cooled as much as possible. It was.

  For example, the technique described in Patent Document 1 uses a collection tower using a collection solvent as a non-condensable gas separation device, and a relatively small amount of (meth) acrylic acid solution obtained from the collection tower is used. It is taken out, cooled to strength, and recycled to the collection tower. Patent Document 2 describes that the amount of heat removal is increased by a heat removal device provided at the bottom or top of the collection tower. In addition, Patent Documents 3 to 5 describe cooling an acrylic acid-containing gas obtained by a catalytic gas phase oxidation reaction.

  However, these prior arts are not sufficient from the viewpoint of stable operation of the production process of (meth) acrylic acid. That is, in the catalytic gas phase oxidation reaction for synthesizing (meth) acrylic acid, inexpensive air is usually used as the oxygen-containing gas, but the moisture in the air always fluctuates. Therefore, the amount of moisture and (meth) acrylic acid concentration in the gas introduced into the non-condensable gas separation device fluctuate, and the concentration of the (meth) acrylic acid solution discharged from the non-condensable gas separation device also fluctuates. End up. As a result, the subsequent purification steps cannot be stably performed under certain conditions.

  On the other hand, as a technique for controlling the concentration of the (meth) acrylic acid solution, it becomes difficult to ensure operational stability after the next step when the amount of water contained in the (meth) acrylic acid solution varies. There is a technique of Patent Document 6. Such a technique is obtained from the collection tower by changing the amount of moisture in the gas discharged from the top of the collection tower by controlling the temperature and pressure at the top of the collection tower, which is a non-condensable gas separation device ( This is a technique for controlling the concentration of a (meth) acrylic acid solution.

Moreover, if the density | concentration of the (meth) acrylic acid solution obtained from a noncondensable gas separation apparatus is high, the efficiency in the refinement | purification process after that will improve. Therefore, a technique for increasing the concentration has also been developed. Patent Document 7 discloses a technique in which an acrylic acid solution obtained in a collection tower that is a non-condensable gas separation apparatus is subjected to a crystallization process and a distillation process, and the resulting distillate is circulated to the collection tower. A high concentration acrylic acid solution of 80% or more is obtained by this technique. However, although a high concentration acrylic acid solution can be obtained according to this technique, this technique is not intended to stably obtain an acrylic acid solution at a constant concentration.
JP-A-8-176062 (Claim 1, paragraphs [0011], [0017], [0022]) Japanese Patent Laying-Open No. 2003-206256 (paragraphs [0025] and [0029]) JP 2003-176252 A (paragraph [0018]) Japanese Patent Laying-Open No. 2005-179354 (paragraph [0016]) JP 2001-19655 A (paragraph [0008]) JP 2003-238485 A (claim, paragraph [0029]) Japanese Patent Laying-Open No. 2005-15478 (paragraph [0065])

  As described above, in the conventional method for producing (meth) acrylic acid, the efficiency of obtaining a (meth) acrylic acid solution by separating the non-condensable gas from the (meth) acrylic acid-containing gas with a non-condensable gas separation device is improved. In order to increase the temperature, the collection solvent, the non-condensable gas separation device, and the like have been cooled as much as possible. Also, a technique for making the concentration of the (meth) acrylic acid solution obtained from the non-condensable gas separation device constant or increasing the concentration has been known. However, it has been found that the prior art is not sufficient to obtain a (meth) acrylic acid solution at a high concentration and stably at a constant concentration.

  That is, the catalytic gas phase oxidation reaction uses a catalyst, which deteriorates with time. Therefore, it is necessary to raise the reaction temperature so that the amount of (meth) acrylic acid produced does not decrease as the catalyst progresses. As a result, the temperature of the (meth) acrylic acid-containing gas obtained by the catalytic gas phase oxidation reaction varies by 100 ° C. or more. Here, in the prior art, since the concentration of the (meth) acrylic acid solution obtained from the non-condensable gas separator was set to about 50 to 70% by mass, the amount of water vapor discharged from the non-condensable gas separator is The amount of the non-condensable gas separation device that needs to be positively cooled is small, and can be controlled with a margin. However, when aiming at a higher concentration (meth) acrylic acid solution, subtle control is required according to the temperature change of the (meth) acrylic acid-containing gas introduced into the non-condensable gas separation device. The controllable range of the property gas separation device may be exceeded, or operation near the limit of the controllable range may be forced, and the concentration of the (meth) acrylic acid solution may fluctuate due to slight disturbance.

  More specifically, when obtaining a (meth) acrylic acid solution having a conventional concentration, assuming that the minimum heat removal amount in the circulating (meth) acrylic acid solution is 100, the maximum heat removal amount may be about 150. However, in order to obtain a highly concentrated (meth) acrylic acid solution, it is necessary to keep the temperature in the separation device relatively high in order to increase the amount of water evaporated in the separation device of the non-condensable gas. Since a very small amount of heat removal is required when the temperature is low, the heat removal amount of the circulating solution is about 26 to 140. In this case, the heat removal amount difference is about 5.4 times (140/26) compared to the conventional 1.5 times (150/100), and the amount of circulating solution passing through the cooler in the circulation line is controlled. Such a means exceeds the possible control range, and density fluctuations occur. That is, the conventional method cannot stably obtain a high-concentration (meth) acrylic acid solution.

  The heat removal in the non-condensable gas separation apparatus is generally performed by cooling a part of the (meth) acrylic acid solution obtained from the tower bottom and circulating it to the separation apparatus. However, in the past, such a system could be used to keep the concentration of the (meth) acrylic acid solution constant, but when trying to obtain a solution with a high concentration, the temperature of the (meth) acrylic acid-containing gas was as described above. The difference in the amount of heat to be removed increases to about 5.4 times according to the fluctuations of the system, exceeding the control range of the conventional system. As a result, the amount of heat removal becomes too small or too large, and the concentration of the (meth) acrylic acid solution cannot be stabilized.

  Therefore, an object of the present invention is obtained from a non-condensable gas separation device in the production process of (meth) acrylic acid by catalytic gas phase oxidation reaction, regardless of temperature fluctuations of gas discharged from the catalytic gas phase oxidation reactor. The object is to provide a system for stably obtaining a (meth) acrylic acid solution at a high concentration and a constant concentration, and a method for producing (meth) acrylic acid using the system.

  The present inventors diligently studied the conditions for stably and uniformly setting a (meth) acrylic acid solution obtained from a non-condensable gas separator regardless of the temperature of the (meth) acrylic acid-containing gas. . As a result, conventionally, it has been common knowledge that the non-condensable gas separation device is cooled in order to efficiently separate the non-condensable gas. Therefore, the conventional system is provided only with a cooling means such as a separation device. As a result, it has been found that the above-mentioned problems can be solved by adjusting the temperature of the separation device or the like with a heating means, and the present invention has been completed.

That is, a system for separating a non-condensable gas from a gas containing (meth) acrylic acid according to the present invention to obtain a (meth) acrylic acid solution,
A reactor for producing a (meth) acrylic acid-containing gas by a catalytic gas phase oxidation reaction;
A non-condensable gas separation device for separating a non-condensable gas from the produced (meth) acrylic acid-containing gas to obtain a (meth) acrylic acid solution,
The non-condensable gas separator has a heating means.

The system preferably has at least one of the following as the heating means.
(1) Jacket type heat exchanger installed at the bottom of the non-condensable gas separator (2) Coil type heat exchanger installed at the bottom of the non-condensable gas separator (3) From the bottom of the non-condensable gas separator The circulation line which heats the obtained (meth) acrylic acid solution and supplies it to the intermediate part of a non-condensable gas separation apparatus.

  Conventionally, when a non-condensable gas is separated from a (meth) acrylic acid solution to obtain a (meth) acrylic acid solution, the non-condensable gas separation device is only cooled to increase efficiency. In the present invention, by deliberately heating the solution, a (meth) acrylic acid solution can be obtained at a high concentration, and the concentration can be easily made substantially constant.

In addition, the method for producing (meth) acrylic acid according to the present invention includes:
A step of producing a gas containing (meth) acrylic acid by subjecting a raw material gas to a catalytic gas phase oxidation reaction in a catalytic gas phase oxidation reactor; and a separation device for the produced (meth) acrylic acid-containing gas to a non-condensable gas And separating the non-condensable gas from the (meth) acrylic acid-containing gas to obtain a (meth) acrylic acid solution having a high concentration of 75% by mass or more,
Using the inventive system described above;
The heating temperature by the heating means is adjusted according to the temperature of the (meth) acrylic acid-containing gas supplied to the non-condensable gas separation device.

  In the above method, further, the temperature of the (meth) acrylic acid-containing gas supplied to the non-condensable gas separator is controlled according to the temperature of the (meth) acrylic acid-containing gas obtained by the catalytic gas phase oxidation reaction. Is preferred. By controlling the gas temperature in advance before supplying to the non-condensable gas separation device, the temperature control of the non-condensable gas separation device becomes easy and the concentration of the (meth) acrylic acid solution is further stabilized. Because it becomes possible. Moreover, it is preferable to control the temperature of the said gas to 200 to 300 degreeC. Even when a highly concentrated (meth) acrylic acid solution is obtained, the temperature controllability of the non-condensable gas separation device can be maintained, and the concentration fluctuation of the resulting (meth) acrylic acid solution can be more easily suppressed. Because it can.

  Furthermore, in the method of the present invention, the water concentration in the (meth) acrylic acid solution discharged from the non-condensable gas separation device is preferably 1 to 10% by mass. Moisture is mainly produced together with acrylic acid in the acrylic acid-containing gas in the catalytic gas phase oxidation reaction, and reducing the water concentration can relatively increase the acrylic acid concentration in the acrylic acid solution. Because it can.

  According to the present invention, it is possible to stably obtain a (meth) acrylic acid solution at a high concentration and substantially constant regardless of the moisture content of the gas discharged from the catalytic gas phase oxidation reactor and the temperature fluctuation. Therefore, the system and the manufacturing method for obtaining the (meth) acrylic acid solution according to the present invention greatly reduce the burden and labor in the steps after the step of obtaining the (meth) acrylic acid solution by separating the non-condensable gas. Therefore, the production efficiency can be further improved as compared with the prior art. In particular, since it becomes possible to stably obtain a high-concentration acrylic acid solution, after the step of obtaining a (meth) acrylic acid solution by separating a non-condensable gas, the crystallization step is performed without passing through a pretreatment step. Production efficiency is further increased. Therefore, this invention is very useful industrially as what enables the efficient manufacture of (meth) acrylic acid.

A system for obtaining a (meth) acrylic acid solution by separating a non-condensable gas from a gas containing (meth) acrylic acid according to the present invention,
A reactor for producing a (meth) acrylic acid-containing gas by a catalytic gas phase oxidation reaction;
A non-condensable gas separation device for separating a non-condensable gas from the produced (meth) acrylic acid-containing gas to obtain a (meth) acrylic acid solution,
The non-condensable gas separator has a heating means. Hereinafter, the present invention will be specifically described.

  First, the production of acrylic acid will be described as a representative example for the catalytic gas phase oxidation reaction. As for methacrylic acid, for example, methacrolein is used instead of acrolein as a raw material, and those skilled in the art can apply it with reference to the following description.

  As a raw material for the reaction, propylene, propane, acrolein or the like is used. In a catalytic gas phase oxidation reactor filled with an oxidation catalyst together with an inert gas and a molecular oxygen-containing gas such as air pressurized by a blower. Supply and generate a gas containing acrylic acid by catalytic gas phase oxidation reaction. The reactor used for the catalytic gas phase oxidation reaction is not particularly limited as long as it generates acrylic acid in the presence of a catalytic gas phase oxidation catalyst. However, a multi-tubular reactor is used in view of excellent reaction efficiency. What is used is preferable. Specifically, using a reactor such as a multi-tubular reactor, a reaction raw material comprising a raw material component such as propylene, propane and acrolein, an inert gas, and a molecular oxygen-containing gas such as air in the presence of an oxidation catalyst. A predetermined amount of gas is supplied to carry out a catalytic gas phase oxidation reaction. At this time, when propylene is used as a raw material component, acrolein is first produced, and acrylic acid is obtained by further subjecting this to catalytic gas phase oxidation. The reaction step employed in the present invention may be a one-stage method in which these reactions are performed in one reactor or a two-stage method in which each reaction is performed in different reactors. The reaction conditions such as the oxidation catalyst to be used, the raw material components, the gas concentration of molecular oxygen, inert gas, etc., the reaction temperature, etc. may be any of the conditions of the conventionally known acrylic acid production reaction step. it can.

  For example, as the raw material component, propylene, propane, acrolein or a mixture of two or more thereof can be used, and these raw material components are 6 to 20% by volume of the reaction raw material gas supplied to the reactor, Preferably it is 8-15 volume%. Further, the reaction raw material gas contains 1 to 3 times (molar ratio) of molecular oxygen with respect to the raw material components to cause an oxidation reaction, and the rest is an inert gas such as nitrogen, carbon dioxide, and water vapor.

  In addition, for example, in the present invention, in order to produce acrylic acid by catalytic gas phase oxidation reaction of propylene-containing gas, a raw material containing propylene as a catalyst used in the preceding reaction for generating acrolein by catalytic gas phase oxidation of propylene An oxidation catalyst generally used for producing acrolein by catalytic gas phase oxidation of gas can be used. Similarly, there is no particular limitation on the catalyst used in the subsequent reaction for producing acrylic acid by catalytic vapor phase oxidation of the acrolein obtained in the preceding reaction, and the reaction gas containing acrolein is oxidized by catalytic vapor phase oxidation. An oxidation catalyst generally used for production can be used.

  Acrylic acid-containing gas obtained by this catalytic gas phase oxidation reaction includes acrylic acid, molecular oxygen, unreacted raw material components, inert gas, and other by-product water, acetic acid, propionic acid, maleic acid, Impurities such as acetone, acrolein, furfural and formaldehyde are included.

  In the above reaction, in order to maintain the amount of (meth) acrylic acid produced, it is necessary to raise the reaction temperature according to the deterioration of the catalyst over time. The reaction temperature varies depending on the catalyst used. For this reason, the temperature of the (meth) acrylic acid-containing gas discharged from the reactor generally has a width exceeding 200 to 350 ° C. and 100 ° C.

  In the present invention, it is preferable to control the temperature of the (meth) acrylic acid-containing gas supplied to the non-condensable gas separator according to the temperature of the (meth) acrylic acid-containing gas obtained by the catalytic gas phase oxidation reaction. This is because a (meth) acrylic acid solution having a high concentration can be obtained more efficiently and constantly.

  Examples of the gas temperature control means disposed between the reactor for obtaining the (meth) acrylic acid-containing gas and the non-condensable gas separator include the following means (A) to (F).

  (A) A waste heat recovery heat exchanger that controls the temperature of the (meth) acrylic acid-containing gas by changing the supply amount of the (meth) acrylic acid-containing gas that passes through the inside. For example, a bypass line for avoiding passage to the waste heat recovery heat exchanger is provided between the reactor and the non-condensable gas separator, and the temperature of the acrylic acid-containing gas after the merge is changed. This can be done by changing the amount of bypass while checking with a meter.

  (B) A heat exchanger that performs heat exchange by generating steam, and is a waste heat recovery heat exchanger that controls the temperature of the (meth) acrylic acid-containing gas by changing the pressure of the steam. The vapor pressure can be changed, for example, by changing the pressure while checking the temperature of the acrylic acid-containing gas with a thermometer.

  (C) A heat exchanger that exchanges heat by generating steam, and recovers waste heat by controlling the temperature of the (meth) acrylic acid-containing gas by changing the liquid level of the liquid to be evaporated inside. Heat exchanger. The liquid level can be changed, for example, while confirming the temperature of the acrylic acid-containing gas with a thermometer and confirming the liquid level with a liquid level indicator.

  (D) A heat exchanger that exchanges heat by passing a cooling medium, and controls the temperature of the (meth) acrylic acid-containing gas by changing the flow rate of the cooling medium. The flow rate change of the cooling medium can be performed, for example, by providing a bypass line for the cooling medium and changing the bypass amount while checking the temperature of the acrylic acid-containing gas with a thermometer.

  (E) A heat exchanger for exchanging heat by bringing a (meth) acrylic acid solution discharged from a non-condensable gas separation device into direct contact with a (meth) acrylic acid-containing gas, the acrylic being cooled by a cooling medium A direct contact heat exchanger that controls the temperature of the (meth) acrylic acid-containing gas by changing the supply amount and / or temperature of the acid solution. The change in the supply amount of the cooled acrylic acid solution is, for example, provided with a line for directly supplying the acrylic acid solution extracted from the bottom of the non-condensable gas separation apparatus to the contact heat exchanger, and the temperature of the acrylic acid-containing gas. Can be performed by changing the supply amount while confirming with a thermometer. In addition, the temperature of the cooled acrylic acid solution can be changed by, for example, providing a line for supplying the acrylic acid solution extracted from the tower bottom of the non-condensable gas separation apparatus directly to the contact heat exchanger. This can be done by changing the supply amount of the cooling medium while checking the temperature with a thermometer.

  (F) Direct contact for controlling the temperature of the acrylic acid-containing gas by changing the number of heat exchangers to which a cooling medium is supplied, by supplying a cooling medium and performing heat exchange Heat exchanger. Such temperature control is a mode in which a plurality of heat exchangers are provided and the temperature of the acrylic acid-containing gas is changed by appropriately combining a heat exchanger to which a cooling medium is supplied and a heat exchanger to which no cooling medium is supplied.

  The temperature of the (meth) acrylic acid-containing gas supplied to the non-condensable gas separator is preferably controlled to 200 to 300 ° C, more preferably 210 to 290 ° C, and further preferably 230 to 280 ° C. By controlling the temperature to 200 ° C. or higher, the suppression of condensation of components having a boiling point lower than that of acrylic acid can be further improved, and the temperature control of the non-condensable gas separation device for keeping the (meth) acrylic acid solution at a high concentration. Is possible. On the other hand, by setting it to 300 ° C. or less, it is possible to reduce the load required for cooling in the step of separating the non-condensable gas from the (meth) acrylic acid-containing gas to obtain a (meth) acrylic acid solution, It becomes possible to further increase the efficiency of obtaining an acrylic acid solution.

  The (meth) acrylic acid-containing gas obtained by the catalytic gas phase oxidation reaction is then supplied to a non-condensable gas separation device, and a (meth) acrylic acid solution is obtained by separating the non-condensable gas. More specifically, for example, when the non-condensable gas separation device is a collection tower, when the (meth) acrylic acid is collected using a collection solvent to separate the non-condensable gas, the gas is It is supplied from the lower part of the collection tower where a packed bed or the like is installed, and is collected in contact with the collection solvent supplied from the upper part of the collection tower. Here, the non-condensable gas refers to a substance that is a gas at normal temperature and pressure, for example, propylene, propane, carbon dioxide, carbon monoxide, nitrogen, oxygen, and the like.

  When the (meth) acrylic acid-containing gas supplied to the collection tower comes into contact with the collection solvent, (meth) acrylic acid and the like are collected in the collection solvent, while most of the non-condensable gas is collected. It is discharged from the top of the column without being collected by the solvent. At this time, whether moisture contained in the (meth) acrylic acid-containing gas is collected in the collection solvent or released as a gas together with the non-condensable gas mainly depends on the temperature of the collection tower. Moreover, if the temperature of the collection tower itself is sufficiently high, moisture will continue to be released from the collection tower. That is, if the temperature of the collection tower is high, more water is released, so that the concentration of the (meth) acrylic acid solution obtained is high. However, if the temperature of the collection tower is too high, the amount of (meth) acrylic acid released together with the non-condensable gas without being collected by the collection solvent will increase. Therefore, the amount of heat removal in the collection tower, that is, the temperature of the collection solvent and the collection tower itself must be determined in consideration of the balance between the amount of moisture released together with the non-condensable gas and (meth) acrylic acid. is there.

  Although the collection solvent to be used is not specifically limited, For example, the thing which uses water as a main component is mentioned. Moreover, as a solution containing water as a main component, a part or all of the waste water generated in the (meth) acrylic acid production process and the waste liquid generated in the next (meth) acrylic acid purification process, etc. are recovered and recycled. It is economical and preferable to use it. In some cases, washing waste liquid or the like can be mixed and used. Furthermore, in order to enable efficient collection of (meth) acrylic acid, the collection solvent for collecting (meth) acrylic acid, that is, a part or all of the (meth) acrylic acid solution is circulated and collected. You may use as a solvent collection.

  Here, as a method for contacting the (meth) acrylic acid-containing gas and the collection solvent, a known contact method can be used, for example, bubble bell tray, uniflux tray, perforated plate tray, jet tray, valve tray. Cross flow contact using Venturi tray and any combination thereof; turbo grid tray, dual float tray, ripple tray, kittel tray, irregular packing, counter packing using any combination of these, etc. Can be mentioned. Among them, the method of bringing the (meth) acrylic acid-containing gas into contact with the collection solvent by countercurrent contact is advantageous. Particularly, in the collection tower, the absorption efficiency is high on the upstream side in the flow of the collection solvent. It is advantageous to install a packing and / or a tray (tray) with a relatively low polymerization capacity downstream of the packing. The supply temperature and supply amount of the collection solvent can be set as appropriate.

  As a non-condensable gas separation device used when a (meth) acrylic acid-containing gas is condensed to obtain a (meth) acrylic acid solution without using a collection solvent, a conventionally known device can be used. For example, a tray such as a bubble tray, a sieve tray, a valve tray, or a distillation column containing a packing, and the introduced (meth) acrylic acid-containing gas can be uniformly cooled by a cooling medium, and the non-condensable gas can be reduced. If it condenses condensation components, such as (meth) acrylic acid, discharging from a tower top and a (meth) acrylic acid solution is obtained, it will not restrict | limit in particular. As a cooling medium for such a non-condensable gas separation device, the obtained (meth) acrylic acid solution cooled by a heat exchanger can be circulated and used.

  Here, in order to obtain a (meth) acrylic acid solution having a higher concentration, the temperature in the non-condensable gas separation device must be increased, and the amount of water discharged must be increased. One means for this is to set the temperature of the non-condensable gas separation device high. Here, in order to obtain a high-concentration (meth) acrylic acid solution when the temperature of the (meth) acrylic acid-containing gas is low, the heat removal amount in the non-condensable gas separation device must be reduced. However, the conventional system has only means for cooling the non-condensable gas separation device in order to efficiently collect (meth) acrylic acid, and the temperature of the (meth) acrylic acid-containing gas is low In order to obtain a high-concentration (meth) acrylic acid solution similar to the case where the temperature is high, it has been impossible to control the temperature of the non-condensable gas separation device by removing a very small amount of heat.

  Therefore, in the present invention, by providing a heating means in the non-condensable gas separation device, the controllability of heat removal of the non-condensable gas separation device can be maintained even when the temperature of the (meth) acrylic acid-containing gas is low, and high It was possible to stably obtain a (meth) acrylic acid solution having a concentration.

  The non-condensable gas separation device used here can be the same as a conventionally known collection tower except that it has a heating means. For example, in the case of a collection tower, the reaction gas obtained by the reactor is supplied from the lower part, the collection solvent is supplied from the upper part, the reaction gas and the collection solvent are brought into contact with each other in the collection tower, and the non-removal is started from the top of the tower. There is no particular limitation as long as it can discharge the condensable gas and discharge the condensed solution from the bottom of the column.

Examples of the heating means of the non-condensable gas separation device included in the system of the present invention are not particularly limited, and examples thereof include the following means (1) to (3).
(1) A coil-type heat exchanger (FIG. 1) disposed at the bottom of the non-condensable gas separator.
(2) A jacket type heat exchanger (FIG. 2) disposed at the bottom of the non-condensable gas separator.
(3) A circulation line that heats the (meth) acrylic acid solution obtained from the bottom of the non-condensable gas separator and supplies it to the intermediate part of the non-condensable gas separator (FIGS. 3, 4, and 5).

  The heating means of the above (1) and (2) are arranged as shown in FIGS. 1 and 2, for example, and the heating amount of the heat exchanger is adjusted while checking the temperature of the discharge part of the non-condensable gas with a thermometer. It is changed and the periphery of the bottom of the non-condensable gas separator is heated. When the temperature of the (meth) acrylic acid-containing gas supplied to the collection tower is low, the amount of heat removal at the bottom of the non-condensable gas separation device is negligible when trying to obtain a highly concentrated (meth) acrylic acid solution. Since it is difficult to control, the amount of heat removal can be easily controlled by heating with the heating means according to the present invention.

  In addition, the heating means (3) above, for example, as shown in FIG. 3, extracts a part of the (meth) acrylic acid solution obtained from the bottom of the non-condensable gas separator, A circulation line that circulates to the part is provided, and a conventionally known heater is provided in the line, and the amount of heating is changed while checking the temperature of the noncondensable gas discharge part of the noncondensable gas separator with a thermometer. Is.

  Here, in general, in the step of separating the non-condensable gas from the (meth) acrylic acid-containing gas to obtain the (meth) acrylic acid solution, in order to increase the efficiency of obtaining the (meth) acrylic acid solution, it is discharged from the tower bottom. The (meth) acrylic acid solution is partially circulated to the middle part of the non-condensable gas separator while being cooled by a cooling means, and the rest is withdrawn to the next step such as distillation, stripping, extraction, crystallization step, etc. It has been carried out. In the present invention, a heating means is provided instead of or in addition to the conventional cooling means. Thus, even when the purpose is to obtain a high-concentration (meth) acrylic acid solution, more detailed temperature control of the non-condensable gas separation device becomes possible.

  As another aspect of the above (3), it is also preferable to heat a circulation line having a cooler (FIGS. 4 and 5). The temperature control of the circulating (meth) acrylic acid solution by such heating means is, for example, providing a bypass line in the cooling circulation line and integrating both lines into the intermediate part of the non-condensable gas separation device. It can be installed by circulating the solution, providing heating means in the integrated path, and changing the bypass amount while checking the temperature of the discharge part etc. of non-condensable gas with a thermometer (Fig. 4). In addition, for example, a cooling circulation line and a bypass line are provided so that a heating medium can be supplied to the conventional cooling means, and the bypass amount is changed while the temperature of the discharge part of the non-condensable gas is checked with a thermometer, and the circulation is also performed. It can carry out by heating a part of (meth) acrylic acid solution (FIG. 5). As the heating means and the cooling means used in the aspect (3), a conventionally known appropriate cooler and heater can be used, and an appropriate cooling medium and heating medium can be used. For example, water can be used as the cooling medium and the heating medium.

  Thus, in the heating means of (3) above, the embodiment having the heating means in the (meth) acrylic acid circulation supply line enables more detailed temperature control by using both the cooling means and the heating means. Therefore, the above (3) is more preferable in that the heating control can be made more useful.

The method for producing (meth) acrylic acid according to the present invention includes:
A step of producing a gas containing (meth) acrylic acid by subjecting a raw material gas to a catalytic gas phase oxidation reaction in a catalytic gas phase oxidation reactor; And separating the non-condensable gas from the (meth) acrylic acid-containing gas to obtain a (meth) acrylic acid solution having a high concentration of 75% by mass or more,
Using the system of the present invention described above;
The heating temperature by the heating means is adjusted according to the temperature of the (meth) acrylic acid-containing gas supplied to the non-condensable gas separation device.

  The heating temperature in the present invention is controlled so that the controllability of the heat removal amount in the non-condensable gas separation device can be maintained in order to make the concentration of the (meth) acrylic acid solution discharged from the non-condensable gas separation device substantially constant. . Conventionally, it has been common technical knowledge to cool a non-condensable gas separation device as much as possible. However, in actual operation, the temperature difference of the (meth) acrylic acid-containing gas introduced into the non-condensable gas separator exceeds 100 ° C. Under such circumstances, when the purpose is to obtain a high concentration (meth) acrylic acid solution, the catalyst of the catalytic gas phase oxidation reaction is sufficiently active and it is not necessary to increase the reaction temperature. When the temperature of the meth) acrylic acid-containing gas is low, it is difficult to reduce the amount of heat removed from the non-condensable gas separation device by the conventional method, so the concentration of the resulting (meth) acrylic acid solution varies. Resulting in. On the other hand, in the present invention, by heating the non-condensable gas separation device, even if the temperature of the (meth) acrylic acid-containing gas changes, the difference in the heat removal amount of the non-condensable gas separation device is reduced. The temperature control of the non-condensable gas separation device can be easily performed.

  The heating temperature of the collection tower is not particularly limited as long as it is determined by a preliminary experiment or the like. For example, the heating temperature may be determined so that the temperature of the discharge part of the non-condensable gas becomes substantially constant.

  As described above, the (meth) acrylic acid-containing gas discharged from the reactor has conventionally been subjected to only a certain amount of heat removal by a waste heat recovery heat exchanger, so that it contains (meth) acrylic acid after pre-cooling. The gas has a temperature range of 100 ° C. or higher. Therefore, it is preferable to control the temperature of the (meth) acrylic acid-containing gas according to the temperature of the (meth) acrylic acid-containing gas obtained by the catalytic gas phase oxidation reaction before supplying it to the non-condensable gas separation device. . This is because the concentration of the (meth) acrylic acid solution can be further stabilized by controlling the gas temperature in advance before supplying the non-condensable gas separation device.

  In the above production method, “substantially the same” as the (meth) acrylic acid concentration in the (meth) acrylic acid solution extracted from the bottom of the non-condensable gas separation apparatus means conditions such as a subsequent purification step. Any range that does not need to be changed may be used. For example, the fluctuation range between the maximum value and the minimum value of the concentration is within ± 2%. Since it is better for the fluctuation range to be smaller, it is more preferably within ± 1%, and most preferably 0%. By setting the fluctuation range to about 0%, it becomes possible to further suppress fluctuations in conditions in the next purification step. As a result, it is possible to further reduce the burden and labor for setting / changing the operating conditions according to the (meth) acrylic acid concentration in the subsequent steps such as the purification step, and more stably (meth) acrylic acid. Can be manufactured.

  The temperature variation of the (meth) acrylic acid-containing gas supplied to the non-condensable gas separation device is preferably controlled within 40 ° C. This is because a highly concentrated (meth) acrylic acid solution can be produced more stably. More preferably, the temperature fluctuation is controlled within 30 ° C.

  Furthermore, the water concentration of the (meth) acrylic acid solution extracted from the bottom of the non-condensable gas separation device is not particularly limited, but is preferably 1 to 10% by mass. By setting the amount to 10% by mass or less, moisture can be sufficiently separated and the (meth) acrylic acid concentration can be relatively increased, so that the purification of (meth) acrylic acid in the subsequent steps is more efficient. It becomes. On the other hand, since it is virtually impossible to make the moisture concentration less than 1% by mass, the lower limit is preferably 1% by mass.

  In the case of a non-condensable gas discharge unit of a non-condensable gas separator, for example, in the case of a collection tower, the temperature at the top of the tower can be set to a conventionally known temperature range, but is not particularly limited, but in the range of 40 to 80 ° C. Preferably there is. If the temperature is lower than 40 ° C, the equipment cost and the utility cost for cooling are increased, and the condensation of the substance having a lower boiling point than (meth) acrylic acid is increased and it is extracted from the bottom of the non-condensable gas separator ( This is because the concentration of (meth) acrylic acid in the (meth) acrylic acid solution is lowered, and the amount of waste water is also increased. Moreover, since the loss of (meth) acrylic acid from a non-condensable gas discharge part will increase when it exceeds 80 degreeC, it leads to the cost increase of a product (meth) acrylic acid, and is unpreferable.

  The pressure of the non-condensable gas discharge part of the non-condensable gas separation device can also be a conventionally known pressure range, and is not particularly limited, but is preferably in the range of 0 to 30 kPa (gauge pressure). If the pressure is lower than 0 kPa (gauge pressure), a pressure reducing device is required, which requires equipment and utility costs. If the pressure is higher than 30 kPa (gauge pressure), it is necessary to enlarge the blower for supplying the raw material gas to the catalytic gas phase oxidation reactor. This is because it is not economical because it costs equipment and utility costs.

  In addition, the non-condensable gas discharged from the non-condensable gas discharge unit of the non-condensable gas separation device may be all treated as exhaust gas, but a part thereof is recycled gas, for example, using a blower. If it is circulated to the reactor, the supply amount of the inert gas or the like can be advantageously reduced.

  As described above, the (meth) acrylic acid solution in which the concentration fluctuation is suppressed is stably obtained from the bottom of the non-condensable gas separation apparatus by the system of the present invention having the heating means of the collection tower and the method of the present invention. Is possible. For this reason, it is possible to reduce facility costs and utility costs in the purification process such as distillation, diffusion, extraction or crystallization process for separating impurities contained in the (meth) acrylic acid solution and to reduce the amount of waste water. Become.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented within a range that can meet the purpose described above and below. All of which are within the scope of the present invention.

Comparative Example A reaction gas was introduced into a multi-tube catalytic gas phase oxidation reactor filled with a catalyst. By a gas phase oxidation reaction, acrylic acid-containing gas having a composition of 7.1% by volume of acrylic acid, 11.6% by volume of water, 76.5% by volume of nitrogen, 1.5% by volume of oxygen, and 3.3% by volume of other gases is obtained. And a part was extracted.

The extracted gas 348.5 Nm ³ / hr was cooled by a waste heat recovery heat exchanger capable of removing heat by generating a certain steam, and then supplied to the lower part of the acrylic acid collection tower. 45 kg / hr of water as a collection solvent is supplied from the top of the collection tower, acrylic acid is collected at a tower top pressure of 11 kPa (gauge pressure) and a tower top temperature of 68 ° C. Non-condensable gas 379.0 Nm ³ / hr containing 4% by volume of water was extracted. In addition, a part of the acrylic acid aqueous solution (temperature: 95 ° C.) obtained from the bottom of the collection tower is removed by a cooler existing in the circulation line, and a part of the acrylic acid aqueous solution is circulated to the lower part of the collection tower. By adjusting the amount passing through the cooler by providing a bypass line that does not pass through the cooler, the cooling (heat removal) of the collection solvent in the collection tower is controlled, and the concentration of acrylic acid in the aqueous acrylic acid solution is controlled. Attempted control.

When the temperature of the acrylic acid-containing gas supplied to the collection tower is 280 ° C. assuming that the catalyst has deteriorated in actual operation, the amount of heat removed from the collection tower needs to be 8600 kcal / hr. It was. Therefore, a 0.22 m ³ / hr of acrylic acid aqueous solution 1.0 m ³ / hr circulated is passed through a condenser heated dividing so as to be the amount of heat removed. At this time, by setting the ratio of the amount of acrylic acid aqueous solution passing through the cooler to the amount of the acrylic acid aqueous solution bypassed to 1: 3.5 within the operation range controllable by the control valve, the target heat removal amount is achieved. Could be controlled. As a result, condensation of the acrylic acid aqueous solution and separation of the non-condensable gas from the acrylic acid-containing gas could be performed stably, and a high concentration acrylic acid aqueous solution having an acrylic acid concentration of 91% by mass could be obtained.

  On the other hand, when the temperature of the acrylic acid-containing gas supplied to the collection tower is 230 ° C. assuming that the catalyst is not deteriorated in actual operation, the temperature at the top of the collection tower is as above. In order to make the concentration of the acrylic acid solution substantially the same as the temperature, it was necessary to calculate the heat removal amount in the collection tower at 1800 kcal / hr. In order to obtain such a heat removal amount, the amount of the acrylic acid aqueous solution passing through the cooler had to be reduced much more than in the above case. Therefore, although an attempt was made to reduce the amount of passage through the cooler, the target flow rate could not be controlled within the operation range of the control valve, and the target heat removal amount could not be obtained. For this reason, the amount of heat removal fluctuated, and the temperature at the top of the collection tower fluctuated in the range of ± 1 ° C. As a result, the amount of acrylic acid condensed and the amount of water withdrawn from the tower top along with the non-condensable gas varied, and the acrylic acid concentration obtained from the bottom of the collection tower varied from 87 to 94%. This forced the reaction and collection to stop.

Example As in the above comparative example, the reaction and cooling by the waste heat recovery exchanger are performed, and the collection tower is provided with a cooling circulation line and a bypass line, and heat that can be heated to the cooling circulation line. An exchanger was installed.

  When the acrylic acid-containing gas sent to the collection tower has a temperature of 230 ° C., it is heated at 4200 kcal / hr by flowing steam of 0.2 MPaG through the heating heat exchanger, and at 6000 kcal / hr in the cooler. Heat removal was performed. As a result, the ratio of the amount of acrylic acid aqueous solution circulating in the cooler to the amount of acrylic acid aqueous solution bypassed is set to 1: 5.6, which is an operation range controllable by a control valve, so that the target heat removal amount (1800 kcal / hr). As a result, condensation of the acrylic acid aqueous solution and separation of the non-condensable gas from the acrylic acid-containing gas could be performed stably, and an acrylic acid aqueous solution having an acrylic acid concentration of 91% by mass could be obtained stably.

  As a result of the above, according to the present invention, regardless of the temperature of the acrylic acid-containing gas discharged from the reactor, it becomes easy to control the temperature of the collection tower by heating the collection solvent supplied into the collection tower, It was possible to suppress fluctuations in the concentration of the acrylic acid aqueous solution obtained from the bottom of the collection tower. Therefore, according to the present invention, a high-concentration (meth) acrylic acid solution can be stably obtained regardless of the temperature fluctuation of the (meth) acrylic acid-containing gas introduced into the non-condensable gas separation device. ) It has been demonstrated that the system for obtaining the acrylic acid solution can be operated stably.

It is explanatory drawing which shows an example for implementing the system of this invention. It is explanatory drawing which shows an example for implementing the system of this invention. It is explanatory drawing which shows an example for implementing the system of this invention. It is explanatory drawing which shows an example for implementing the system of this invention. It is explanatory drawing which shows an example for implementing the system of this invention.

Claims (6)

A system for separating a non-condensable gas from a gas containing (meth) acrylic acid to obtain a (meth) acrylic acid solution,
A reactor for producing a (meth) acrylic acid-containing gas by a catalytic gas phase oxidation reaction;
A non-condensable gas separation device for separating a non-condensable gas from the produced (meth) acrylic acid-containing gas to obtain a (meth) acrylic acid solution,
A system characterized in that the non-condensable gas separation device has heating means. The system according to claim 1, wherein the heating unit includes at least one of the following.
(1) Jacket type heat exchanger installed at the bottom of the non-condensable gas separator (2) Coil type heat exchanger installed at the bottom of the non-condensable gas separator (3) From the bottom of the non-condensable gas separator A circulation line for heating the obtained (meth) acrylic acid solution and supplying it to the middle part of the non-condensable gas separator A method for producing (meth) acrylic acid,
A step of producing a gas containing (meth) acrylic acid by subjecting a raw material gas to a catalytic gas phase oxidation reaction in a catalytic gas phase oxidation reactor; and a separation device for the produced (meth) acrylic acid-containing gas to a non-condensable gas And separating the non-condensable gas from the (meth) acrylic acid-containing gas to obtain a (meth) acrylic acid solution having a high concentration of 75% by mass or more,
Using the system according to claim 1 or 2;
A method for producing (meth) acrylic acid, characterized in that the heating temperature by the heating means is adjusted according to the temperature of the (meth) acrylic acid-containing gas supplied to the non-condensable gas separation device.   The production method according to claim 3, wherein the temperature of the (meth) acrylic acid-containing gas supplied to the non-condensable gas separation device is controlled according to the temperature of the (meth) acrylic acid-containing gas obtained by the catalytic gas phase oxidation reaction. .   The manufacturing method of Claim 4 which controls the temperature of the said gas at 200 to 300 degreeC.   The manufacturing method in any one of Claims 3-5 which makes the water concentration in the (meth) acrylic acid solution discharged | emitted from a non-condensable gas separation apparatus 1-10 mass%.

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