JP5485585B2 - Method for producing (meth) acrylic acid - Google Patents

Description

  The present invention relates to a method for producing (meth) acrylic acid having a crystallization step and a melting step.

  Conventionally, as a method for industrially synthesizing (meth) acrylic acid, a method of catalytic vapor phase oxidation of a (meth) acrylic acid production raw material is known. The (meth) acrylic acid-containing gas produced by catalytic vapor phase oxidation of the raw material for producing (meth) acrylic acid is collected, for example, in a liquid medium, recovered as a crude (meth) acrylic acid solution, and further diffused and extracted. It is purified by methods such as distillation and crystallization.

  Patent Document 1 discloses a method for purifying a crude (meth) acrylic acid solution by crystallization. When purifying a crude (meth) acrylic acid solution by crystallization, cooling is required to crystallize (meth) acrylic acid from the crude (meth) acrylic acid solution, while crystallized (meth) acrylic acid. Heating is required to obtain purified (meth) acrylic acid by melting However, Patent Document 1 does not specifically describe a cooling method or a heating method during crystallization.

  Patent Document 2 discloses that cold water obtained by an absorption refrigerator is used in a crystallization step when a crude (meth) acrylic acid solution is purified by crystallization. However, Patent Document 2 does not describe a technique for reducing energy consumption of a refrigerator used as a heat source device.

JP 2008-74759 A JP 2007-277182 A

  When the crude (meth) acrylic acid solution is cooled with a cooling medium to crystallize (meth) acrylic acid, the temperature of the cooling medium discharged from the crystallizer tends to be high at the initial stage. When such a high-temperature cooling medium is returned to the heat source unit and used as a cooling medium source, an excessive cooling load is applied to the heat source unit, resulting in unstable operation of the heat source unit and increased energy consumption of the heat source unit. To do. Similarly, when the crystallized (meth) acrylic acid is melted by heating with a heating medium, the temperature of the heating medium discharged from the crystallizer tends to be low at the initial stage. When such a low-temperature heating medium is returned to the heat source machine and used as a heating medium source, an excessive heating load is applied to the heat source machine, the operation of the heat source machine becomes unstable, and the energy consumption of the heat source machine increases. To do.

  The present invention has been made in view of the above circumstances, and its purpose is to perform crystallization with a cooling medium from a heat source machine, and when performing melting with a heating medium from a heat source machine, the cooling load and heating of the heat source machine An object of the present invention is to provide a method for producing (meth) acrylic acid capable of reducing the load and reducing the energy consumption of the heat source device.

  The method for producing (meth) acrylic acid according to the present invention that has solved the above-mentioned problem is that a cooling medium is supplied from a heat source device to the first crystallizer, and a (meth) acrylic solution is obtained from a crude (meth) acrylic acid solution. A step of crystallizing the acid; and a step of supplying a heating medium from the heat source unit to the second crystallizer and melting the crystallized (meth) acrylic acid; cold heat discharged from the first crystallizer It is characterized in that part or all of the medium is used as a heating medium source; part or all of the heating medium discharged from the second crystallizer is used as a cooling medium source. According to the method for producing (meth) acrylic acid of the present invention, a part or all of the cooling medium discharged from the first crystallizer is used as a heating medium source for supplying the second crystallizer, and the second crystallization is performed. The cooling and heating loads of the heat source unit are reduced by using a part or all of the heating medium discharged from the vessel as the cooling medium source that supplies the first crystallizer, and the energy consumption of the heat source unit is reduced. Can do.

  As the heat source machine that supplies the cooling medium and the heat source machine that supplies the heating medium, it is preferable to use a refrigerator that supplies the cooling medium and the heating medium. By using a refrigerator as a heat source machine, it is possible to effectively utilize both cold and hot heat from the refrigerator, and reduce the energy consumption of the heat source machine.

  As a standard for mutually using the cooling medium and the heating medium as a heat medium source, the temperature of the cooling medium discharged from the first crystallizer is higher than the temperature of the heating medium discharged from the second crystallizer. When the temperature is high, the cooling medium discharged from the first crystallizer is used as the heating medium source; the temperature of the heating medium discharged from the second crystallizer is the temperature of the cooling medium discharged from the first crystallizer. When the temperature is lower than the temperature, it is preferable to use the heating medium discharged from the second crystallizer as the cooling medium source.

  As a standard for mutually using the cooling medium and the heating medium as a heating medium source, the temperature of the cooling medium discharged from the first crystallizer is the temperature of the cooling medium and the temperature of the heating medium supplied from the heat source machine. When the temperature is higher than the predetermined temperature during the period, the cooling medium discharged from the first crystallizer is used as the heating medium source; the temperature of the heating medium discharged from the second crystallizer is supplied from the heat source unit When the temperature is lower than the predetermined temperature between the temperature of the cooling medium and the temperature of the heating medium, the heating medium discharged from the second crystallizer is also preferably used as the cooling medium source.

  The temperature of the cooling medium supplied from the heat source machine is −40 ° C. or higher and lower than the melting point of the crude (meth) acrylic acid solution, and the temperature of the heating medium supplied from the heat source machine is the melting point of the crystallized (meth) acrylic acid. It is preferably 45 ° C. or lower. If the temperature of the cooling medium and the heating medium supplied from the heat source device are in the above ranges, the energy consumption of the heat source device does not increase more than necessary, and the heat source device and the crystallizer do not have excessive specifications. Moreover, it becomes easy to obtain (meth) acrylic acid with a high yield.

  The method for producing (meth) acrylic acid of the present invention includes a step of supplying a first cooling medium from a heat source device to a first crystallizer and cooling a crude (meth) acrylic acid solution; Supplying a second cooling medium having a temperature lower than that of the cooling medium to the second crystallizer, crystallizing (meth) acrylic acid from the cooled crude (meth) acrylic acid solution; and a third crystal of the heating medium from the heat source unit; Supplying to the crystallizer and melting the crystallized (meth) acrylic acid; using part or all of the first cooling medium discharged from the first crystallizer as a heating medium source; A part or all of the heating medium discharged from the crystallizer may be used for the first cooling medium source and / or the second cooling medium source.

  By using two types of cooling medium having different temperatures as the cooling medium, it becomes easy to increase the purity of the (meth) acrylic acid crystal, and the energy consumption of the heat source apparatus can be further reduced. In addition, a part or all of the first cooling medium discharged from the first crystallizer is used as a heating medium source that supplies the third crystallizer, and a part of the heating medium discharged from the third crystallizer. Alternatively, by using the whole for the first cooling medium source supplied to the first crystallizer or / and the second cooling medium source supplied to the second crystallizer, the cooling load and the heating load of the heat source unit are reduced, The energy consumption of the heat source machine can be reduced.

  As the heat source machine that supplies the first cooling medium, the heat source machine that supplies the second cooling medium, and the heat source machine that supplies the heating medium, a refrigerator that supplies the first cooling medium, the second cooling medium, and the heating medium is used. It is preferable. By using a refrigerator as a heat source machine, it is possible to effectively utilize both cold and hot heat from the refrigerator, and reduce the energy consumption of the heat source machine.

  In the method for producing (meth) acrylic acid, a part or all of the heating medium discharged from the third crystallizer is used as the second cooling medium source; the second cooling medium discharged from the second crystallizer It is preferable to use a part or all of it as the first cooling medium source. With the above-described configuration, when the first cooling medium, the second cooling medium, and the heating medium are mutually used as the heating medium sources, the operation becomes easy.

  As a standard for mutual use of the first cooling medium, the second cooling medium, and the heating medium as a heat medium source, the temperature of the first cooling medium discharged from the first crystallizer is determined from the third crystallizer. When the temperature of the hot medium discharged is higher than the temperature of the discharged hot medium, the first cold medium discharged from the first crystallizer is used as the hot medium source; the temperature of the hot medium discharged from the third crystallizer is When the temperature of the first cooling medium discharged from the first crystallizer and / or the temperature of the second cooling medium discharged from the second crystallizer is lower, the heating medium discharged from the third crystallizer is It is preferable to use the first cold heat medium source and / or the second cold heat medium source.

  As a reference for mutual use of the first cooling medium, the second cooling medium, and the heating medium as the heat medium sources, the temperature of the first cooling medium discharged from the first crystallizer is supplied from the heat source machine. When the temperature is higher than a predetermined temperature between the temperature of the cooling medium and the temperature of the heating medium, the first cooling medium discharged from the first crystallizer is used as the heating medium source; discharged from the third crystallizer. When the temperature of the heated heating medium is lower than the predetermined temperature between the temperature of the first cooling and heating medium supplied from the heat source machine and the temperature of the heating medium, the heating medium discharged from the third crystallizer is It is also preferable to use the first cooling medium source and / or the second cooling medium source.

  The temperature of the first cooling medium supplied from the heat source machine is −15 ° C. or higher and lower than the melting point of the crude (meth) acrylic acid solution, and the temperature of the second cooling medium supplied from the heat source machine is −40 ° C. or higher, − The temperature of the heating medium that is lower than 15 ° C. and supplied from the heat source device is preferably higher than the melting point of crystallized (meth) acrylic acid and 45 ° C. or lower. If the temperatures of the first cooling medium, the second cooling medium, and the heating medium supplied from the heat source device are within the above ranges, the energy consumption of the heat source device does not increase more than necessary, and the heat source device and the crystallizer have excessive specifications. Don't be. Moreover, it becomes easy to obtain (meth) acrylic acid with a high yield.

  According to the method for producing (meth) acrylic acid of the present invention, the cooling load and the heating load of the heat source device can be reduced, and the energy consumption of the heat source device is reduced.

The 1st heat source machine, the 2nd heat source machine, the 1st crystallizer, the 2nd crystallizer, and the channel which connects them are expressed. The temperature change of a cooling medium and a heating medium when the temperature of the cooling medium discharged | emitted from a 1st crystallizer is low and the temperature of the heating medium discharged | emitted from a 2nd crystallizer is high, and those usage methods are represented. The temperature change of a cooling medium and a heating medium when the temperature of the cooling medium discharged | emitted from a 1st crystallizer is high and the temperature of the heating medium discharged | emitted from a 2nd crystallizer is low, and those usage methods are represented. The 1st heat source machine, the 2nd heat source machine, the 1st crystallizer, the 2nd crystallizer, the cooling-heat-medium source tank, the thermal-heat-medium source tank, and the flow path which connects them are represented. The refrigerator, the 1st crystallizer, the 2nd crystallizer, and the flow path which connects them are represented. The refrigerator, the 1st crystallizer, the 2nd crystallizer, the 3rd crystallizer, and the flow path which connects them are represented. An example of the temperature change of the 1st cooling-heat medium, the 2nd cooling-heat medium, and a heating medium and those usage methods is represented. The temperature change of the 1st cooling-heat medium, the 2nd cooling-heat medium, and a heating medium and the other example of those usage methods are represented.

  In the method for producing (meth) acrylic acid of the present invention, a cooling medium is supplied from a heat source device to the first crystallizer, and (meth) acrylic acid is crystallized from a crude (meth) acrylic acid solution (hereinafter, “ Sometimes referred to as a “crystallization step”); a heating medium is supplied from the heat source device to the second crystallizer, and the crystallized (meth) acrylic acid is melted (hereinafter referred to as “melting step”). There is).

  In the crystallization step, the crude (meth) acrylic acid solution is cooled by the cooling medium supplied from the heat source device to the first crystallizer, and (meth) acrylic acid crystals are obtained. The obtained (meth) acrylic acid crystals may be sorted by any solid-liquid separation means, collected by any physical means, or melted by any melting method. Also good. Preferably, the crystallized (meth) acrylic acid is melted by a melting step described later.

  The crude (meth) acrylic acid solution crystallized in the crystallization step is not particularly limited as long as it is a liquid containing (meth) acrylic acid and other impurities. Examples of the impurities include unreacted (meth) acrylic acid production raw material, water, acetic acid, propionic acid, maleic acid, acetone, acrolein, furfural, formaldehyde and the like.

  The crude (meth) acrylic acid solution preferably has a (meth) acrylic acid concentration of 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more. When the (meth) acrylic acid concentration is 80% by mass or more, it is easy to crystallize a crude (meth) acrylic acid solution. The upper limit of the (meth) acrylic acid concentration is not particularly limited.

  In the melting step, the crystallized (meth) acrylic acid is heated and melted by the heating medium supplied from the heat source device to the second crystallizer. The crystallized (meth) acrylic acid used in the melting step was obtained by crystallizing a crude (meth) acrylic acid solution by supplying a cooling medium from the heat source device to the second crystallizer in advance. It may be obtained by any crystallization method. In the present invention, the (meth) acrylic acid crystal obtained by the former method is preferably melted in the melting step.

  When the crystallized (meth) acrylic acid is melted by heating, the crystallized (meth) acrylic acid is partially melted and crystallized for the purpose of increasing the purity of the resulting (meth) acrylic acid melt. There is a case where an operation (perspiration operation) for washing out impurities existing on the surface or the crystal surface is performed, but in the present invention, the operation is also included in the melting step.

  In the method for producing (meth) acrylic acid of the present invention, the crystallization process is performed in the first crystallizer, the melting process is performed in the second crystallizer, and then the heating medium is transferred from the heat source device to the first crystallizer. It is preferable that the melting step is performed by the first crystallizer and the crystallization step is performed by the second crystallizer by supplying the cooling medium from the heat source unit to the second crystallizer. In this case, efficient (meth) acrylic acid can be produced. In addition, the crystallization step and the melting step may be alternately repeated a plurality of times for one lot of the crude (meth) acrylic acid solution to obtain (meth) acrylic acid with higher purity.

  The heat source apparatus used in the production method of the present invention is not particularly limited as long as it cools the cooling medium and / or heats the heating medium. The heat source device may supply either one of the cooling medium and the heating medium, or may supply both the cooling medium and the heating medium. When the heat source machine supplies either one of the cooling medium or the heating medium, the heat source machine includes a cooling medium heat source machine that supplies the cooling medium, and a heating medium heat source machine that supplies the heating medium. Is used. As the heat source machine, for example, a multi-tube heat exchanger in which steam or liquefied gas is used as a heat source is shown.

  The heat source device is preferably one that cools the cooling medium and simultaneously heats the heating medium, and it is preferable to use a refrigerator as such a heat source apparatus. Specifically, it is preferable to use a refrigerator that supplies the cooling medium and the heating medium simultaneously as a heating source that supplies the cooling medium and a heating source that supplies the heating medium. As the refrigerator, an absorption refrigerator (ammonia absorption type, water-lithium bromide type, etc.), a compression refrigerator, an adsorption refrigerator, or the like can be used. By using a refrigerator as a heat source machine, it is possible to effectively utilize both cold and hot heat from the refrigerator, and reduce the energy consumption of the heat source machine.

  When using a refrigerator as a heat source device, the production method of the present invention includes a step of supplying a cooling medium from the refrigerator to the first crystallizer, and crystallizing (meth) acrylic acid from a crude (meth) acrylic acid solution. And a step of supplying a heating medium from the refrigerator to the second crystallizer and melting the crystallized (meth) acrylic acid. In this case, it is possible to efficiently use the cooling medium and the heating medium discharged from the refrigerator.

  The cooling medium and the heating medium are not particularly limited as long as they maintain a liquid state with a heat source unit and a crystallizer in producing (meth) acrylic acid. In the present invention, a part or all of the cooling medium is used as the heating medium source, and a part or all of the heating medium is used as the cooling medium source. Therefore, the cooling medium and the heating medium are preferably the same. For example, an ethylene glycol aqueous solution, a glycerin aqueous solution, and a methanol aqueous solution are shown.

  The temperature of the cooling medium discharged from the heat source machine is not particularly limited as long as it is lower than the melting point of the crude (meth) acrylic acid solution. The melting point of the crude (meth) acrylic acid solution varies depending on the purity of (meth) acrylic acid. For example, in the case of a crude acrylic acid solution having an acrylic acid concentration of 80% by mass to 95% by mass and most other impurities are water, the melting point is generally more than −5 ° C. and 13.5 ° C.

  The temperature of the cooling medium discharged from the heat source machine is preferably −5 ° C. or lower, more preferably −10 ° C. or lower, and −40 ° C. or higher is preferable, and −30 ° C. or higher is more preferable. As described above, the upper limit of the temperature of the cooling medium exhausted from the heat source device may be lower than the melting point of the crude (meth) acrylic acid solution, but the amount of the cooling medium required for crystallization increases excessively, In order to prevent the size of the analyzer and the cooling medium piping from becoming too large, the temperature of the cooling medium discharged from the heat source device is preferably −5 ° C. or lower. On the other hand, when the temperature of the cooling medium discharged from the heat source device is lower than −40 ° C., the cooling load in the heat source device increases, and a high-spec heat source device may be required, or the energy consumption of the heat source device may increase. Therefore, the temperature of the cooling medium discharged from the heat source machine is preferably −40 ° C. or higher.

  Two or more types of cooling medium having different temperatures may be used. In this case, two or more types of cooling medium having different temperatures may be discharged from one heat source apparatus, and a plurality of heat source apparatuses may be provided for each temperature of the cooling medium.

  The temperature of the heating medium discharged from the heat source machine is not particularly limited as long as it exceeds the melting point of crystallized (meth) acrylic acid. The temperature of the heating medium discharged from the heat source machine is preferably 20 ° C. or higher, more preferably 30 ° C. or higher, preferably 45 ° C. or lower, more preferably 40 ° C. or lower. As described above, the lower limit of the temperature of the heating medium discharged from the heat source machine may be above the melting point of the crystallized (meth) acrylic acid, but the amount of the heating medium necessary for melting increases, In order to prevent the size of the analyzer, the heating medium pipe, and the like from becoming too large, the temperature of the heating medium discharged from the heat source device is preferably 20 ° C. or higher. On the other hand, when the temperature of the heating medium discharged from the heat source machine exceeds 45 ° C., the polymerization reaction of (meth) acrylic acid occurs in the crystallizer, and the purity and yield of the obtained (meth) acrylic acid may be lowered. There is. Moreover, the heating load in the heat source device may increase, and a high-spec heat source device may be required, or the energy consumption of the heat source device may increase. Therefore, it is preferable that the temperature of the heating medium discharged from the heat source machine is 45 ° C. or less.

  Two or more kinds of heating media having different temperatures may be used. In this case, two or more types of heat medium having different temperatures may be discharged from one heat source apparatus, and a plurality of heat source apparatuses may be provided for each temperature of the heat medium.

  The temperatures of the cooling medium and the heating medium discharged from the heat source device are preferably maintained within a certain range, and the temperature range is preferably within 3 ° C, and more preferably within 1 ° C. Moreover, it is preferable that the flow rates of the cooling medium and the heating medium discharged from the heat source device are maintained within a certain range. If the temperature and flow rate of the cooling medium and the heating medium discharged from the heat source device are maintained within a certain range, the crystallization operation and the melting operation in the crystallizer are easily performed stably. The flow rate of the cooling and heating medium discharged from the heat source machine is the temperature of the cooling and heating medium discharged from the heat source machine, the amount and temperature of the crude (meth) acrylic acid solution and crystallized (meth) acrylic acid, etc. It is set appropriately according to

  The crystallizer used in the production method of the present invention is not particularly limited as long as the crude (meth) acrylic acid solution is crystallized and the crystallized (meth) acrylic acid is melted. A cooling medium is supplied from the heat source unit to the first crystallizer, and as a result, (meth) acrylic acid is crystallized from the crude (meth) acrylic acid solution. A heating medium is supplied to the second crystallizer from the heat source unit, and as a result, the crystallized (meth) acrylic acid is melted.

  The crystallizer used in the production method of the present invention preferably has a heat transfer surface. In this case, the crystallizer includes a portion to which a cooling medium and a heating medium are supplied (a heating medium existing portion), a crude (meth) acrylic acid solution and / or a (meth) acrylic acid crystal due to a heat transfer surface. It is preferable to be divided into portions ((meth) acrylic acid existing portions). When the crystallizer has a heat transfer surface, in the crystallization process, a cooling medium is supplied to the crystallizer, and a crude (meth) acrylic acid solution is supplied to the crystallizer so that the heat transfer surface is Then, the crude (meth) acrylic acid solution is cooled by the cooling medium, and (meth) acrylic acid is crystallized. In the melting step, a heating medium is supplied to the crystallizer, and the crystallized (meth) acrylic acid is heated and melted by the heating medium through the heat transfer surface.

  As a crystallizer having a heat transfer surface, a device generally used as a heat exchanger can be employed, and it is particularly preferable to employ a device used as a heat exchanger that performs heat exchange between liquids. For example, plate-type heat exchange in which a single plate is arranged, or a plurality of plates are stacked at intervals, and a heat medium existence part and a (meth) acrylic acid existence part are alternately arranged via the plate Multi-tube type (shell and tube type) heat exchanger in which multiple tubes are arranged in a container and perform heat exchange inside and outside the tube; the inner tube is arranged in the outer tube, Double-tube heat exchanger that exchanges heat inside and outside; Coil-type heat exchanger in which a single tube is arranged in a container in a coil shape and exchanges heat inside and outside the tube; A spiral heat exchanger or the like in which two heat transfer plates are wound in a spiral shape and two spiral flow paths are formed can be employed. In addition, the cross-sectional shape of the tube used in the multi-tube heat exchanger, the double tube heat exchanger, the coil heat exchanger, and the spiral heat exchanger is not particularly limited.

  In the crystallization step, the cooling medium supplied to the first crystallizer is heated by heat exchange with the crude (meth) acrylic acid solution and receiving heat from the crude (meth) acrylic acid solution. In this case, at the initial stage of the crystallization process, the temperature of the cooling medium discharged from the first crystallizer tends to be high. In addition, in the case where the melting step is performed in the first crystallizer before the crystallization step, a high temperature residual heat is generated in the first crystallizer due to the influence of the high temperature heating medium used in the melting step. Remains. As a result, at the initial stage of the crystallization process, the temperature of the cooling medium discharged from the first crystallizer tends to increase. When such a high-temperature cooling medium is used as a cooling medium source, an excessive cooling load is applied to the heat source unit, so that the operation of the heat source unit becomes unstable or the energy consumption of the heat source unit increases.

  In the melting step, the heating medium supplied to the second crystallizer is cooled by heat exchange with the crystallized (meth) acrylic acid and dissipating heat to the crystallized (meth) acrylic acid. In this case, at the initial stage of the melting step, the temperature of the heating medium discharged from the second crystallizer tends to be low. In addition, when the crystallization process is performed in the second crystallizer before the melting process, the low-temperature cooling medium used in the crystallization process has a low temperature in the second crystallizer. Residual heat remains. As a result, at the initial stage of the melting step, the temperature of the heating medium discharged from the second crystallizer tends to be low. When such a low-temperature heating medium is used as a heating medium source, an excessive heating load is applied to the heat source machine, and the operation of the heat source machine becomes unstable or the energy consumption of the heat source machine increases.

  In general, the heat source device has a load range in which it can be efficiently cooled or heated according to its specifications. However, when the cooling load or heating load of the heat source device becomes high, the heat source device may have to be operated in an inefficient load range, and energy consumption increases. In addition, when the heat source machine is operated in an inefficient load range, the operation of the heat source machine tends to become unstable.

  Therefore, in the production method of the present invention, a part or all of the cooling medium discharged from the first crystallizer is used as a heating medium source to be supplied to the second crystallizer, and is discharged from the second crystallizer. Part or all of the heating medium is used as a cooling medium source that supplies the first crystallizer. Preferably, the high temperature cooling medium discharged from the first crystallizer is used as a heating medium source for supplying the second crystallizer, and the low temperature heating medium discharged from the second crystallizer is used as the first crystallizer. Used as a heat medium source to supply to As a result, the cooling load and the heating load of the heat source device are reduced, and the energy consumption of the heat source device can be reduced. This will be described with reference to FIGS. In addition, the manufacturing method of this invention is not limited to the following embodiment.

  FIG. 1 shows an example of a first heat source device that supplies a cooling medium, a second heat source device that supplies a heating medium, a first crystallizer, a second crystallizer, and a flow path connecting them. Yes. The first heat source machine 1A has a cooling medium outlet 2A for discharging the cooling medium and a cooling medium source inlet 3A to which the cooling medium source is returned. The second heat source unit 1B has a heating medium outlet 6B for discharging the heating medium and a heating medium source inlet 7B to which the heating medium source is returned. The first crystallizer 11 includes a first heat medium existence section 12 to which a heat medium is supplied, and a first (meth) acrylic acid existence in which a crude (meth) acrylic acid solution and / or (meth) acrylic acid crystals are present. Part 13. The first heat medium existence part 12 has an inlet 14 and an outlet 15, and the first (meth) acrylic acid existence part 13 has an inlet 16 and an outlet 17. Similarly, the second crystallizer 21 has a second heat medium existence part 22 and a second (meth) acrylic acid existence part 23, and the second heat medium existence part 22 has an inlet 24 and an outlet 25. The second (meth) acrylic acid presence part 23 has an inlet 26 and an outlet 27.

  The cooling medium discharged from the cooling medium outlet 2A of the first heat source machine 1A is supplied to the inlet 14 of the first heating medium existence part 12 of the first crystallizer 11 and is heat-exchanged in the first crystallizer 11. The The cooling medium discharged from the outlet 15 of the first heating medium existence unit 12 is returned to the cooling medium source inlet 3A of the first heat source apparatus 1A, or passes through the flow path 42 and the heating medium source of the second heat source apparatus 1B. Returned to entrance 7B. The heating medium discharged from the heating medium outlet 6B of the second heat source machine 1B is supplied to the inlet 24 of the second heating medium existence part 22 of the second crystallizer 21 and is heat-exchanged in the second crystallizer 21. The The heating medium discharged from the outlet 25 of the second heating medium existence unit 22 is returned to the heating medium source inlet 7B of the second heat source apparatus 1B or the cooling medium source of the first heat source apparatus 1A through the flow path 42. Returned to entrance 3A. The flow path 42 is provided with a flow path for a cooling medium and a flow path for a heating medium.

  2 and 3 schematically show changes in temperature of the cooling medium and the heating medium at the heat source unit outlet, the crystallizer inlet, the crystallizer outlet, and the heat source unit inlet. The temperatures of the heat source machine outlet, the crystallizer inlet, the crystallizer outlet, and the heat source machine inlet are as follows: for the cooling medium, the cooling medium outlet 2A of the first heat source unit 1A, the inlet 14 of the first heating medium existence unit, the first It corresponds to the temperature at the outlet 15 of the first heat medium existence part and the cold heat medium source inlet 3A of the first heat source machine 1A. This corresponds to the temperature at the inlet 24 of the second heat medium, the outlet 25 of the second heat medium existing part, and the heat medium source inlet 7B of the second heat source machine 1B.

  In FIG. 2 and FIG. 3, the heating medium is represented by a solid line, and the cooling medium is represented by a one-dot chain line. The temperature at the heat source outlet of the heating medium is T1, the temperature at the outlet of the crystallizer of the heating medium is T2, the temperature at the outlet of the heat source of the cooling medium is T3, and the temperature at the outlet of the crystallizer of the cooling medium is T4. To do. It is assumed that there is no temperature change between the cooling medium and the heating medium from the heat source machine outlet to the crystallizer inlet and from the crystallizer outlet to the heat source machine inlet.

  FIG. 2 shows changes in temperature of the cooling medium and the heating medium when the temperature of the cooling medium discharged from the first crystallizer 11 is low and the temperature of the heating medium discharged from the second crystallizer 21 is high. Shows how to use. The cold heat medium is supplied from the first heat source unit 1A to the first crystallizer 11 at the temperature T3, is heat-exchanged by the first crystallizer 11, and is heated to the temperature T4. The cooling medium heated to the temperature T4 is returned to the first heat source unit 1A and cooled from the temperature T4 to the temperature T3. On the other hand, the heating medium is supplied from the second heat source device 1B to the second crystallizer 21 at the temperature T1, heat-exchanged by the second crystallizer 21, and cooled to the temperature T2. The heating medium cooled to the temperature T2 is returned to the second heat source device 1B and heated from the temperature T2 to the temperature T1. In FIG. 2, the temperature T2 is sufficiently higher than the temperature T4, and the cooling medium discharged from the first heat source unit 1A is returned to the first heat source unit 1A, used again as the cooling medium source, and discharged from the second heat source unit 1B. The heated heat medium is returned to the second heat source machine 1B and used again as a heat medium source.

  FIG. 3 shows the temperature changes of the cooling medium and the heating medium when the temperature of the cooling medium discharged from the first crystallizer 11 is high and the temperature of the heating medium discharged from the second crystallizer 21 is low. Shows how to use. In FIG. 3, the temperature T4 of the cooling medium at the outlet of the crystallizer is higher than the temperature T2 of the heating medium at the outlet of the crystallizer. In this case, the cooling medium at the outlet of the crystallizer is used as the cooling medium source, and the heating medium at the outlet of the crystallizer is used as the cooling medium source rather than cooling from the temperature T4 to the temperature T3 by the first heat source unit 1A. Cooling from the temperature T2 to T3 with the heat source unit 1A reduces the cooling load of the first heat source unit 1A. Similarly, rather than using the heating medium at the outlet of the crystallizer as the heating medium source and heating from the temperature T2 to the temperature T1 with the second heating source machine 1B, the cooling medium at the outlet of the crystallizer is used as the heating medium source. Heating from the temperature T4 to T1 with the heat source device 1B reduces the heating load of the second heat source device 1B. Therefore, in FIG. 3, the cooling medium discharged from the first crystallizer 11 is used as a heating medium source, and the heating medium discharged from the second crystallizer 21 is used as a cooling medium source.

  As a reference for mutual use of the cooling medium and the heating medium as a heating medium source, the temperature T4 of the cooling medium discharged from the first crystallizer 11 is the temperature of the heating medium discharged from the second crystallizer 21. When the temperature is higher than the temperature T2, the cooling medium discharged from the first crystallizer 11 is used as a heating medium source; the temperature T2 of the heating medium discharged from the second crystallizer 21 is the first crystallizer 11. When the temperature is lower than the temperature T4 of the cooling medium discharged from the heat generator, it is preferable to use the heating medium discharged from the second crystallizer 21 as the cooling medium source (mutual utilization standard 1). As a result, the cooling load from the temperature T4 to the temperature T2 in the first heat source device 1A and the heating load from the temperature T2 to the temperature T4 in the second heat source device 1B are reduced, and energy consumption of each heat source device is reduced. Can do.

  As a reference for mutual use of the cooling medium and the heating medium as a heat medium source, the temperature T4 of the cooling medium discharged from the first crystallizer 11 is the temperature T3 of the cooling medium supplied from the first heat source machine 1A. And when the temperature is higher than a predetermined temperature Ta between the temperature T1 of the heating medium supplied from the second heat source device 1B, the cooling medium discharged from the first crystallizer 11 is used as the heating medium source; The temperature T2 of the heating medium discharged from the vessel 21 is lower than a predetermined temperature Ta between the temperature T3 of the cooling medium supplied from the first heat source unit 1A and the temperature T1 of the heating medium supplied from the second heat source unit 1B. In this case, it is also preferable to use the hot medium discharged from the second crystallizer 21 as a cold medium source (mutual utilization standard 2). In this case, the cooling load in the first heat source unit 1A is suppressed when cooling from the temperature Ta to the temperature T3 at the maximum, and the heating load in the second heat source unit 1B is limited to when heating from the temperature Ta to the temperature T1 at the maximum. It can be suppressed. Accordingly, it is possible to prevent an excessive cooling load or heating load from being applied to the heat source device, and to reduce the energy consumption of each heat source device. When the temperature T4 of the cooling medium and the temperature T2 of the heating medium are the temperature Ta, they may be used for either the cooling medium source or the heating medium source.

  The predetermined temperature Ta may be appropriately determined according to the balance of the usage amount of the cooling medium and the heating medium to each heating medium source. The predetermined temperature Ta is preferably an average value (T1 + T3) / 2 of the temperature T3 of the cooling medium and the temperature T1 of the heating medium.

  In the case of the mutual use standard 2, it is possible to use both the cooling medium discharged from the first crystallizer 11 and the heating medium discharged from the second crystallizer 21 as a cooling medium source or a heating medium source. There is sex. In this case, it is preferable to provide a tank (cold heat medium source tank) for storing the cold heat medium source and a tank (heat medium medium tank) for storing the hot medium medium. This will be described with reference to FIG. In addition, you may provide a cooling-heat-medium source tank and a thermal-heat-medium source tank other than the said objective.

  The cold heat medium source tank 51 has an inlet 52 communicating with the outlets 15 and 25 of the respective heat medium existing portions of the first crystallizer 11 and the second crystallizer 21, and an outlet 53 is a cold heat medium source of the first heat source machine 1A. It communicates with the inlet 3A. The heating medium source tank 54 has an inlet 55 communicating with the outlets 15 and 25 of the respective heat medium existing portions of the first crystallizer 11 and the second crystallizer 21, and an outlet 56 is a heating medium source of the second heat source unit 1B. It communicates with the inlet 7B. By providing the cooling medium source tank 51 and the heating medium source tank 54, for example, both the cooling medium discharged from the first crystallizer 11 and the heating medium discharged from the second crystallizer 21 are the cooling medium source. In the case of being used for the above, an excessive cooling medium source is temporarily stored in the cooling medium source tank 51, or a shortage of the heating medium source returned to the second heat source unit 1B is replenished from the heating medium source tank 54. To do. As a result, each heat source machine can be operated stably.

  Although the said description was related to the embodiment using the 1st heat source machine which supplies a cooling medium as a heat source machine, and the 2nd heat source machine which supplies a heating medium, as a heat source machine, a cooling medium and a heating medium May be a refrigerator that supplies the same at the same time. This will be described with reference to FIG.

  FIG. 5 shows an embodiment in which the first heat source machine and the second heat source machine are replaced with one refrigerator in the embodiment of FIG. The refrigerator 1 includes a cooling medium outlet 2 for discharging the cooling medium, a cooling medium source inlet 3 to which the cooling medium source is returned, a heating medium outlet 6 for discharging the heating medium, and a heating medium to which the heating medium source is returned. And a source inlet 7.

  The cooling medium discharged from the cooling medium outlet 2 of the refrigerator 1 is supplied to the first crystallizer 11, and (meth) acrylic acid is crystallized from the crude (meth) acrylic acid solution. As shown in FIGS. 2 and 3, a part or all of the cooling medium discharged from the first crystallizer 11 is returned to the heating medium source inlet 7 of the refrigerator 1 and used as a heating medium source. The The heating medium discharged from the heating medium outlet 6 of the refrigerator 1 is supplied to the second crystallizer 21, and the crystallized (meth) acrylic acid is melted. As shown in FIG. 2 and FIG. 3, a part or all of the heating medium discharged from the second crystallizer 21 is returned to the cooling medium source inlet 3 of the refrigerator 1 and used as a cooling medium source. The

  In the embodiment shown in FIGS. 1, 4, and 5, after the crystallization process is finished in the first crystallizer 11 and the melting process is finished in the second crystallizer 21, the first heat source machine 1 </ b> A or the refrigerator is used. The cooling medium discharged from 1 is supplied to the second crystallizer 21 through the channel 41, and the heating medium discharged from the second heat source device 1 </ b> B or the refrigerator 1 is supplied to the first crystallizer 11 through the channel 41. It is preferable to supply to. In addition, the flow path 41 is provided with a flow path for a cooling medium and a flow path for a heating medium. Thus, efficient (meth) acrylic acid production is possible by alternately performing the crystallization process and the melting process in the first crystallizer 11 and the second crystallizer 12.

  The description so far has been of the case where there is one kind of cooling medium discharged from the heat source machine, but the cooling medium discharged from the heat source machine may be two or more kinds having different temperatures. Below, the embodiment which uses a refrigerator as a heat source machine and is two types in which the cooling-heat medium discharged | emitted from a refrigerator has a mutually different temperature is demonstrated using FIGS. 6-8.

  FIG. 6 shows a refrigerator 61 that discharges the first cooling medium, the second cooling medium that is lower than the first cooling medium, and the heating medium, and combines the three crystallizers 11, 21, and 31. The example which manufactures (meth) acrylic acid is shown.

  The refrigerator 61 includes a first cooling medium outlet 62 for discharging the first cooling medium, a first cooling medium source inlet 63 to which the first cooling medium source is returned, and a second cooling medium outlet for discharging the second cooling medium. 64, a second cooling medium source inlet 65 to which the second cooling medium source is returned, a heating medium outlet 66 for discharging the heating medium, and a heating medium source inlet 67 to which the heating medium source is returned. . In FIG. 6, a third crystallizer 31 is provided in addition to the first crystallizer 11 and the second crystallizer 21 described above. The third crystallizer 31 has a third heat medium existence part 32 and a third (meth) acrylic acid existence part 33, the third heat medium existence part 32 has an inlet 34 and an outlet 35, The 3 (meth) acrylic acid presence portion 33 has an inlet 36 and an outlet 37.

  In this embodiment, the crude (meth) acrylic acid solution is cooled by the first cooling medium, the first half of the crystallization step is performed, and the (meth) acrylic acid is cooled from the crude (meth) acrylic acid solution cooled by the second cooling medium. Crystallize the acid and perform the second half of the crystallization process. By providing the first cooling medium and the second cooling medium in this manner, the purity of the (meth) acrylic acid crystal can be easily increased, and the energy consumption of the refrigerator can be further reduced. In the first half of the crystallization step, the (meth) acrylic acid may be partially crystallized by cooling the crude (meth) acrylic acid solution with the first cooling medium.

  That is, in the method for producing (meth) acrylic acid in this embodiment, the first cooling medium is supplied from the refrigerator 61 to the first crystallizer 11 and the (meth) acrylic acid is cooled from the crude (meth) acrylic acid solution. And a step of supplying the second chilled heat medium having a temperature lower than that of the first chilled heat medium from the refrigerator 61 to the second crystallizer 21 to crystallize (meth) acrylic acid from the cooled crude (meth) acrylic acid solution. And a step of supplying a heating medium from the refrigerator 61 to the third crystallizer 31 and melting the crystallized (meth) acrylic acid.

  The temperature of the first cooling medium discharged from the refrigerator is preferably −15 ° C. or higher, preferably lower than the melting point of crude (meth) acrylic acid, and more preferably 0 ° C. or lower. The temperature of the second cooling medium is preferably −40 ° C. or higher, and is preferably less than −15 ° C. In addition, the preferable range of the temperature of the thermal medium discharged | emitted from a refrigerator is the same as that of the said description.

  In this embodiment, a part or all of the first cooling medium discharged from the first crystallizer 11 is used as a heating medium source supplied to the third crystallizer 31 and is discharged from the third crystallizer 31. A part or all of the heating medium to be used is used as a first cooling medium source to be supplied to the first crystallizer 11 and / or a second cooling medium source to be supplied to the second crystallizer 21. Specifically, when the temperature of the first cooling medium discharged from the first crystallizer 11 is high, the first cooling medium is returned to the heating medium source inlet 67 of the refrigerator 61 through the flow path 42, and the third When the temperature of the heating medium discharged from the crystallizer 31 is low, the heating medium is returned to the first cooling medium source inlet 63 and / or the second cooling medium source inlet 65 of the refrigerator 61 through the flow path 42. The channel 42 is provided with a channel for the first cooling / heating medium, a channel for the second cooling / heating medium, and a channel for the heating / heating medium.

  7 and 8 schematically show temperature changes of the first cooling medium, the second cooling medium, and the heating medium at the refrigerator outlet, the crystallizer inlet, the crystallizer outlet, and the refrigerator inlet. The temperatures at the refrigerator outlet, the crystallizer inlet, the crystallizer outlet, and the refrigerator inlet are the first cooling medium outlet 62, the first cooling medium outlet 62 of the refrigerator, and the inlet 14 of the first heating medium existing portion, respectively. It corresponds to the temperature at the outlet 15 of the first heat medium existence part and the first cold heat medium source inlet 63 of the refrigerator, and for the second cold medium, the second cold medium outlet 64 of the refrigerator and the second heat medium exist, respectively. This corresponds to the temperature at the inlet 24 of the unit, the outlet 25 of the second heat medium existing unit, and the second cold medium source inlet 65 of the refrigerator, and for the hot medium, the hot medium outlet 66 of the refrigerator and the third heat medium, respectively. It corresponds to the temperature at the inlet 34 of the existence part, the outlet 35 of the third heat medium existence part, and the heating medium source inlet 67 of the refrigerator.

  7 and 8, the heating medium is represented by a solid line, the first cooling medium is represented by a one-dot chain line, and the second cooling medium is represented by a two-dot chain line. The temperature at the refrigerator outlet of the heating medium is T11, the temperature at the outlet of the crystallizer of the heating medium is T12, the temperature at the outlet of the refrigerator of the first cooling medium is T13, and the temperature at the outlet of the crystallizer of the first cooling medium is T13. The temperature is T14, the temperature at the refrigerator outlet of the second cooling medium is T15, and the temperature at the crystallizer outlet of the second cooling medium is T16. It is assumed that there is no temperature change of the first cooling medium, the second cooling medium, and the heating medium from the refrigerator outlet to the crystallizer inlet and from the crystallizer outlet to the refrigerator inlet.

  In FIG. 7, the temperature T12 of the heating medium at the outlet of the crystallizer, the temperature T14 of the first cooling medium, and the temperature T16 of the second cooling medium have a relationship of T14> T16> T12. For example, immediately after the first half of the crystallization process is started in the first crystallizer, the amount of heat received from the crude (meth) acrylic acid solution of the first cooling medium is likely to increase, and as a result, from the first crystallizer, The temperature T14 of the discharged first cooling medium is likely to increase. In addition, immediately after the melting step is started in the third crystallizer, the amount of heat released from the heat medium to the (meth) acrylic acid crystal tends to increase. As a result, the heat medium discharged from the third crystallizer The temperature T12 tends to be low. Furthermore, immediately after the start of the melting process, a very low temperature residual heat remains in the third crystallizer due to the influence of the very low temperature cooling medium (second cooling medium) used in the previous process. The temperature of the heating medium discharged from the third crystallizer may be lowered. In such a case, the relationship of T14> T16> T12 can be established immediately after the start of each process.

  In the case of FIG. 7, the first cooling medium at the outlet of the crystallizer is used as the first cooling medium source, and is cooled from the temperature T14 to the temperature T13 by the refrigerator 61, and the second cooling medium at the outlet of the crystallizer is used as the second cooling medium. Rather than cooling from the temperature T16 to the temperature T15 with the refrigerator 61, the heating medium at the outlet of the crystallizer is used as the second cooling heat source, and the crystallizer is cooled from the temperature T12 to T15 with the refrigerator 61. The cooling load of the refrigerator 61 is reduced by using the second cooling medium at the outlet as the first cooling medium source and cooling from the temperature T16 to T13 by the refrigerator 61. Similarly, rather than using the heating medium at the outlet of the crystallizer as a heating medium source and heating from the temperature T12 to the temperature T11 by the refrigerator 61, the first cooling medium at the outlet of the crystallizer is used as the heating medium source, Heating the temperature from T14 to T11 at 61 reduces the heating load of the refrigerator 61. Accordingly, in FIG. 7, the first cooling medium discharged from the first crystallizer 11 is used as a heating medium source that supplies the third crystallizer 31, and the second cooling medium discharged from the second crystallizer 21 is used. Is used as the first cooling medium source that supplies the first crystallizer 11, and the hot medium discharged from the third crystallizer 31 is used as the second cooling medium source that supplies the second crystallizer 21.

  Immediately after the start of each step, the temperature of each heating medium at the outlet of the crystallizer can satisfy the relationship of T14> T16> T12 as shown in FIG. The temperature T14 of the cooling medium and the temperature T16 of the second cooling medium tend to decrease, and the temperature T12 of the heating medium at the crystallizer outlet tends to increase. FIG. 8 shows the relationship between the temperatures of the first cooling medium, the second cooling medium, and the heating medium in such a case.

  In FIG. 8, the temperature T14 of the first cooling medium at the outlet of the crystallizer is higher than the temperature T12 of the heating medium at the outlet of the crystallizer. In this case, the first cooling medium at the outlet of the crystallizer is used as the first cooling medium, and the heating medium at the outlet of the crystallizer is used as the first cooling medium rather than cooling from the temperature T14 to the temperature T13 by the refrigerator 61. The cooling load of the refrigerator 61 is reduced by using the refrigerator 61 and cooling from the temperature T12 to T13. Similarly, rather than using the heating medium at the outlet of the crystallizer as a heating medium source and heating from the temperature T12 to the temperature T11 by the refrigerator 61, the first cooling medium at the outlet of the crystallizer is used as the heating medium source, Heating the temperature from T14 to T11 at 61 reduces the heating load of the refrigerator 61. Therefore, in FIG. 8, the first cooling medium discharged from the first crystallizer 11 is used as a heating medium source for supplying the third crystallizer 31, and the heating medium discharged from the third crystallizer 31 is used in the first crystallizer 31. It is used as a first cooling medium source to be supplied to one crystallizer 11.

  In FIG. 8, the heating medium at the outlet of the crystallizer is used as the first cooling medium source, but the heating medium at the outlet of the crystallizer may be used as the second cooling medium source. In this case, the second cooling medium at the outlet of the crystallizer may be used as the first cooling medium source. In the present invention, when the temperature of the cooling medium returned to the refrigerator is high and the temperature of the heating medium returned to the refrigerator is low, the cooling medium is used as the heating medium source, and the heating medium is used as the cooling medium source. By mutually using the cooling medium and the heating medium, the cooling load and the heating load of the refrigerator can be reduced. Therefore, in the case where two or more types of cooling medium are used as in the embodiment, mutual use between the cooling mediums is not essential.

  As a reference for mutually using the first cooling medium, the second cooling medium, and the heating medium as the heat medium sources, the temperature T14 of the first cooling medium discharged from the first crystallizer 11 is the third crystallization. When the temperature of the heating medium discharged from the vessel 31 is higher than the temperature T12, the first cooling medium discharged from the first crystallizer 11 is used as a heating medium source; the heating medium discharged from the third crystallizer 31 When the temperature T12 is lower than the temperature T14 of the first cooling medium discharged from the first crystallizer 11 and / or the temperature T16 of the second cooling medium discharged from the second crystallizer 21, the third temperature It is preferable to use the heating medium discharged from the crystallizer 31 as the first cooling medium source and / or the second cooling medium source. More preferably, when the temperature T14 of the first cooling medium discharged from the first crystallizer 11 is higher than the temperature T12 of the heating medium discharged from the third crystallizer 31, the first crystallizer 11 The first cooling medium discharged from the second crystallizer 31 is used as a heating medium source; among the heating medium discharged from the third crystallizer 31 and the second cooling medium discharged from the second crystallizer 21, a high-temperature heating medium is used. The first cold heat medium source is used, and the low temperature heat medium is used as the second cold heat medium source. As a result, the cooling load and the heating load in the refrigerator 61 are reduced, and the energy consumption of the refrigerator 61 can be reduced.

  As a reference for mutually using the first cooling medium, the second cooling medium, and the heating medium as the heat medium sources, the temperature T14 of the first cooling medium discharged from the first crystallizer 11 is When the temperature is higher than a predetermined temperature Tb between the temperature T13 of the first cooling medium to be supplied and the temperature T11 of the heating medium, the first cooling medium discharged from the first crystallizer 11 is used as a heating medium source; When the temperature T12 of the heating medium discharged from the three crystallizer 31 is lower than a predetermined temperature Tb between the temperature T13 of the first cooling medium and the temperature T11 of the heating medium supplied from the refrigerator 61, the third It is also preferable to use the heating medium discharged from the crystallizer 31 for the first cooling medium source and / or the second cooling medium source. In this case, the cooling load in the refrigerator 61 is suppressed at the maximum when cooling from the temperature Tb to the temperature T15, and the heating load in the refrigerator 1 is suppressed at the maximum when heating from the temperature Tb to the temperature T11. Therefore, an excessive cooling load or heating load is prevented from being applied to the refrigerator 61, and the energy consumption of the refrigerator 61 can be reduced. In addition, when the temperature T14 of the first cooling medium and the temperature T12 of the heating medium returned to the refrigerator 61 are the temperature Tb, any of the heating medium sources may be used.

  The predetermined temperature Tb may be appropriately determined according to the balance of the usage amount of the first cooling medium and the heating medium to each heating medium source. As the predetermined temperature Tb, it is preferable to adopt an average value (T11 + T13) / 2 of the temperature T13 of the first cooling medium and the temperature T11 of the heating medium.

  Even when two or more types having different temperatures are used as the cooling medium, as described above, a cooling medium medium tank and a heating medium medium tank may be provided. In this case, the cooling medium source tank is provided for each type of cooling medium source.

  In FIG. 6, after the first half of the crystallization process is completed at the first crystallizer 11, the second half of the crystallization process is completed at the second crystallizer 21, and the melting process is completed at the third crystallizer 31. The second cooling medium is supplied to the first crystallizer 11 through the channel 41, the hot medium is supplied to the second crystallizer 21 through the channel 41, and the first cooling medium is supplied to the third crystallizer 21 through the channel 41. It is preferable to supply to the vessel 31. As a result, the first crystallizer 11 performs the latter half of the crystallization process, the second crystallizer 21 performs the melting process, and the third crystallizer 31 performs the first half of the crystallization process. . The channel 41 is provided with a channel for the first cooling / heating medium, a channel for the second cooling / heating medium, and a channel for the heating / heating medium.

  Furthermore, after the second half of the crystallization process is completed in the first crystallizer 11, the melting process is completed in the second crystallizer 21, and the first half of the crystallization process is completed in the third crystallizer 31, The medium is supplied to the first crystallizer 11 through the channel 41, the first cooling medium is supplied to the second crystallizer 21 through the channel 41, and the second cooling medium is supplied to the third crystallizer 31 through the channel 41. It is preferable to supply to. As a result, the first crystallizer 11 performs the melting process, the second crystallizer 21 performs the first half of the crystallization process, and the third crystallizer 31 performs the second half of the crystallization process. .

  Thus, by combining the refrigerator, the first crystallizer, the second crystallizer, and the third crystallizer, the three crystallizers are out of phase with each other, and the first half of the crystallization step and the crystal The latter half of the conversion step and the melting step are sequentially performed. Therefore, (meth) acrylic acid can be efficiently produced, and the energy consumption of the refrigerator can be further reduced.

  In this case, it is preferable that the reference for mutual use of the first cooling medium, the second cooling medium, and the heating medium as mutual heat medium sources is determined as follows in order to facilitate the operation.

  When the first half of the crystallization process is performed by the first crystallizer 11, the previous process is a melting process. Therefore, in the first half of the crystallization process, the flow of each heat medium in the flow path 42 is changed from the previous process. Instead, the first cooling medium discharged from the first crystallizer 11 is directly returned to the heating medium source inlet 67 of the refrigerator 61. In this case, immediately after the start of the first half of the crystallization process, a very high temperature residual heat remains in the first crystallizer 11 due to the influence of the very high temperature heating medium used in the previous process. The temperature T14 of the first cooling medium discharged from the first crystallizer 11 tends to increase. In this case, the upper limit of the temperature T14 is theoretically the temperature T11. However, as the first half of the crystallization process proceeds, the temperature T14 of the first cooling medium discharged from the first crystallizer 11 decreases and can theoretically decrease to the temperature T13. Therefore, when the temperature T14 of the first cooling medium discharged from the first crystallizer 11 is higher than a predetermined temperature Tc between T11 and T13 (for example, (T11 + T13) / 2), the first crystallizer. The first cooling medium discharged from 11 is returned to the heating medium source inlet 67 of the refrigerator 61 and used as a heating medium source, and the temperature T14 of the first cooling medium discharged from the first crystallizer 11 is the predetermined temperature. When the temperature is lower than the temperature Tc (for example, (T11 + T13) / 2), the first cooling medium discharged from the first crystallizer 11 is returned to the first cooling medium source inlet 63 of the refrigerator 61 to be the first. It is used as a cooling medium source. If the temperature T14 of the first cooling medium is the temperature Tc, it may be returned to either.

  Similarly to the above, when the second crystallizer 21 performs the second half of the crystallization process, the previous process is the first half of the crystallization process, so the second cooling medium discharged from the second crystallizer 21 When the temperature T16 is higher than a predetermined temperature Td between T13 and T15 (for example, (T13 + T15) / 2), the second cooling medium discharged from the second crystallizer 21 is used as the first temperature of the refrigerator 61. The temperature T16 of the second cooling medium returned to the cooling medium source inlet 63 and used as the first cooling medium source and discharged from the second crystallizer 21 is higher than the predetermined temperature Td (for example, (T13 + T15) / 2). When the temperature is low, the second cooling medium discharged from the second crystallizer 21 is returned to the second cooling medium source inlet 65 of the refrigerator 61 to be used as the second cooling medium source. When the temperature T16 of the second cooling medium is the temperature Td, it may be returned to either.

  When the melting step is performed in the third crystallizer 31, the previous step is the latter half of the crystallization step. Therefore, at the initial stage of the melting step, the flow of each heat medium in the channel 42 is not changed from the previous step. The heating medium discharged from the third crystallizer 31 is returned to the second refrigerant source inlet 65 of the refrigerator 61 as it is. In this case, immediately after the start of the melting step, a very low temperature residual heat remains in the third crystallizer 31 due to the influence of the very low temperature second cooling medium used in the previous step. The temperature T12 of the heating medium discharged from the three crystallizer 31 tends to be lowered. In this case, the lower limit of the temperature T12 is theoretically the temperature T15. On the other hand, the upper limit of the temperature T12 in the melting step is theoretically the temperature T11. Therefore, when the temperature T12 of the heating medium discharged from the third crystallizer 31 is lower than a predetermined temperature Te between T11 and T15 (for example, (T11 + T15) / 2), the third crystallizer 31 The discharged heating medium is returned to the second cooling medium source inlet 65 of the refrigerator 61 and used as the second cooling medium source, and the temperature T12 of the heating medium discharged from the third crystallizer 31 is the predetermined temperature Te. When it is higher than (for example, (T11 + T15) / 2), the heating medium discharged from the third crystallizer 31 is returned to the heating medium source inlet 67 of the refrigerator 61 to be used as the heating medium source. . When the temperature T12 of the heating medium is the temperature Te, it may be returned to either.

  That is, in the above, a part or all of the first cooling medium discharged from the first crystallizer is used as a heating medium source, and a part or all of the second cooling medium discharged from the second crystallizer is used. A part or all of the heating medium discharged from the third crystallizer is used as the second cooling medium source. If the first cooling medium, the second cooling medium, and the heating medium are determined as described above as a reference for mutual use as the heat medium sources, the switching operation of the flow path 42 is facilitated.

  The method for producing (meth) acrylic acid of the present invention preferably further includes a step of obtaining a crude (meth) acrylic acid solution. The step of obtaining a crude (meth) acrylic acid solution includes a contact gas phase oxidation reaction step of obtaining a (meth) acrylic acid-containing gas from a (meth) acrylic acid production raw material by a contact gas phase oxidation reaction, and the (meth) acrylic acid-containing step It is preferable to have a collection step of collecting gas with a liquid medium. Furthermore, you may provide a refinement | purification process in the back | latter stage of the said collection process for the purpose of raising the (meth) acrylic acid content rate of the (meth) acrylic acid solution obtained at the said collection process.

  In the catalytic gas phase oxidation reaction step, propane, propylene, (meth) acrolein, isobutylene, or the like is used as a raw material for producing (meth) acrylic acid, and this is subjected to catalytic gas phase oxidation with molecular oxygen to produce a (meth) acrylic acid-containing gas. Get. The catalytic gas phase oxidation reaction is preferably performed using a conventionally known oxidation catalyst.

  In the collection step, the (meth) acrylic acid-containing gas obtained in the catalytic gas phase oxidation reaction step is collected with a liquid medium in a collection tower to obtain a (meth) acrylic acid solution. As the liquid medium, water, (meth) acrylic acid-containing water, a high boiling point solvent (such as diphenyl ether or diphenyl), or the like can be used. In the present invention, the (meth) acrylic acid solution obtained in the collecting step may be subjected to a crystallization step as a crude (meth) acrylic acid solution.

  When the (meth) acrylic acid content of the (meth) acrylic acid solution obtained in the collecting step is low, a purification step is provided after the collecting step, and the (meth) acrylic acid solution obtained in the collecting step May be purified by distillation or diffusion to obtain a crude (meth) acrylic acid solution for use in the crystallization step.

[Example]
Purified acrylic acid was produced from the crude acrylic acid solution using the crystallization system shown in FIG. An absorption refrigerator was used as a heat source device for supplying a cooling medium and a heating medium at the same time. From the absorption refrigerator, the first cooling medium at 0 ° C., the second cooling medium at −30 ° C., and the heating medium at 40 ° C. were each discharged at a flow rate of 300 m ³ / hour. As the crystallizer, a crystallizer having a heat transfer surface and divided into a heat medium existing part and an acrylic acid existing part by the heat transfer surface was used.

  The crude acrylic acid solution contained 94.3% by mass of acrylic acid, 2.3% by mass of water, 2.0% by mass of acetic acid, 0.4% by mass of maleic acid, and 1.0% by mass of other impurities. A crystallization step is performed by supplying 20 t of a 30 ° C. crude acrylic acid solution to the acrylic acid existing part of the first crystallizer and supplying a first cooling heat medium of 0 ° C. to the heat medium existing part of the first crystallizer. Went the first half. In the first crystallizer, the melting step was performed before the first half of the crystallization step.

  At the same time as performing the first half of the crystallization process with the first crystallizer, the second half of the crystallization process was performed with the second crystallizer, and the melting process was performed with the third crystallizer. In the acrylic acid existing part of the second crystallizer, there is a cooled crude acrylic acid solution obtained by performing the first half of the crystallization step, and in the heat medium existing part of the second crystallizer, −30 ° C. The second half of the crystallization step was performed by supplying the second cooling medium. The acrylic acid present part of the third crystallizer contains crystallized acrylic acid obtained by performing the latter half of the crystallization step, and the heating medium is supplied to the heat medium existing part of the third crystallizer. The melting step was performed. As a result, 15 t of an acrylic acid melt (purified acrylic acid) was obtained. In the melting step, sweating operation was also performed.

  The first crystallizer was supplied with a 0 ° C. first cooling medium, but immediately after the first half of the crystallization process was started, the first cooling medium discharged from the first crystallizer had a temperature of 20 ° C. or higher. Therefore, the first cooling medium discharged from the first crystallizer was used as a heating medium source. The first cooling medium discharged from the first crystallizer is used as a heating medium source until the average temperature of the first cooling medium and the heating medium discharged from the refrigerator falls below 20 ° C., and discharged from the first crystallizer. After the temperature of the produced first cooling / heating medium fell below 20 ° C., the first cooling / heating medium was used as the first cooling / heating medium source.

  The second crystallizer was supplied with a second cooling medium at −30 ° C. Immediately after the second half of the crystallization process was started, the second cooling medium discharged from the second crystallizer was at −15 ° C. or higher. Since it had temperature, the 2nd cooling medium exhausted from the 2nd crystallizer was used as the 1st cooling medium source. The second cooling medium discharged from the second crystallizer is used as the first cooling medium until the average temperature of the second cooling medium and the first cooling medium discharged from the refrigerator falls below −15 ° C. After the temperature of the second cooling medium discharged from the crystallizer was lower than −15 ° C., the second cooling medium was used as a second cooling medium source.

  Although the heating medium at 40 ° C. was supplied to the third crystallizer, immediately after the start of the melting process, the heating medium discharged from the third crystallizer had a temperature of 5 ° C. or less. The heating medium discharged from the crystallizer was used as the second cooling medium source. The heating medium discharged from the third crystallizer is used as the second cooling medium source until the average temperature of the heating medium and the second cooling medium discharged from the refrigerator exceeds 5 ° C., and discharged from the third crystallizer. After the temperature of the heated heating medium exceeded 5 ° C., the heating medium was used as a heating medium source.

  Each step was performed for 40 minutes. The average power of the refrigerator in each process was as follows. The refrigeration function required to cool the first cooling medium source to 0 ° C. was 1100 kW. The refrigeration function required to cool the second cooling medium source to -30 ° C was 1100 kW. The refrigeration function required to heat the heating medium source to 40 ° C. was −2250 kW. The refrigeration functional force represents “amount of heat taken from an object per unit time”. Accordingly, the cooling side capacity is represented by “+”, and the heating side capacity is represented by “−”.

[Comparative example]
The first refrigeration medium discharged from the first crystallizer is used as the first refrigeration medium source, the second refrigeration medium discharged from the second crystallizer is used as the second refrigeration medium source, and the third crystallization Each crystallizer was subjected to the first half of the crystallization process, the second half of the crystallization process, or the melting process in the same manner as described above except that all of the heating medium discharged from the vessel was used as the heating medium source.

  The average power of the refrigerator in each process was as follows. The refrigeration function required to cool the first cooling medium source to 0 ° C. was 1225 kW. The refrigeration function required to cool the second cooling medium source to -30 ° C was 1225 kW. The refrigerating function required for heating the heating medium source to 40 ° C. was −2500 kW.

  The present invention can be used in a method for producing (meth) acrylic acid having a crystallization step and a melting step.

1,61: Heat source machine (refrigerator)
2, 62, 64: Cooling medium outlet 3, 63, 65: Cooling medium source inlet 6, 66: Heating medium outlet 7, 67: Heating medium source inlet 11: First crystallizer 21: Second crystallizer 31: Third crystallizer 51: Cold heat medium source tank 54: Hot heat medium source tank

Claims (11)

Supplying a cooling medium from the heat source unit to the first crystallizer, and crystallizing (meth) acrylic acid from the crude (meth) acrylic acid solution;
Supplying a heating medium from a heat source device to the second crystallizer and melting the crystallized (meth) acrylic acid;
Using a part or all of the cooling medium discharged from the first crystallizer as a heating medium source;
A method for producing (meth) acrylic acid, wherein a part or all of the heating medium discharged from the second crystallizer is used as a cooling medium source.   The method for producing (meth) acrylic acid according to claim 1, wherein a refrigeration machine that supplies a cooling and heating medium and a heating medium is used as the heating source that supplies the cooling and heating medium and the heating source that supplies the heating and cooling medium. When the temperature of the cooling medium discharged from the first crystallizer is higher than the temperature of the heating medium discharged from the second crystallizer, the cooling medium discharged from the first crystallizer is used as the heating medium source. Used for:
When the temperature of the heating medium discharged from the second crystallizer is lower than the temperature of the cooling medium discharged from the first crystallizer, the heating medium discharged from the second crystallizer is used as the cooling medium source. The manufacturing method of the (meth) acrylic acid of Claim 1 or 2 used for this. When the temperature of the cooling medium discharged from the first crystallizer is higher than a predetermined temperature between the temperature of the cooling medium supplied from the heat source machine and the temperature of the heating medium, the cooling medium was discharged from the first crystallizer. A cooling medium is used as the heating medium source;
When the temperature of the heating medium discharged from the second crystallizer is lower than the predetermined temperature between the temperature of the cooling medium supplied from the heat source machine and the temperature of the heating medium, the temperature is discharged from the second crystallizer. The method for producing (meth) acrylic acid according to claim 1, wherein a hot heat medium is used for the cold heat medium source. Supplying a first cooling medium from the heat source unit to the first crystallizer and cooling the crude (meth) acrylic acid solution;
Supplying a second cooling medium having a temperature lower than that of the first cooling medium from the heat source unit to the second crystallizer, and crystallizing (meth) acrylic acid from the cooled crude (meth) acrylic acid solution;
Supplying a heating medium from a heat source device to the third crystallizer and melting the crystallized (meth) acrylic acid;
Using a part or all of the first cooling medium discharged from the first crystallizer as a heating medium source;
A method for producing (meth) acrylic acid, wherein a part or all of the heating medium discharged from the third crystallizer is used for the first cooling medium source and / or the second cooling medium source.   Claims that use a refrigerator that supplies a first cooling medium, a second cooling medium, and a heating medium as the heat source that supplies the first cooling medium, the heat source that supplies the second cooling medium, and the heat source that supplies the heating medium. Item 6. The method for producing (meth) acrylic acid according to Item 5. When the temperature of the first cooling medium discharged from the first crystallizer is higher than the temperature of the heating medium discharged from the third crystallizer, the first cooling medium discharged from the first crystallizer is Used for the heating medium source;
The temperature of the heating medium discharged from the third crystallizer is higher than the temperature of the first cooling medium discharged from the first crystallizer and / or the temperature of the second cooling medium discharged from the second crystallizer. The method for producing (meth) acrylic acid according to claim 5 or 6, wherein when the temperature is low, the heating medium discharged from the third crystallizer is used for the first cooling medium source and / or the second cooling medium source. When the temperature of the first cooling medium discharged from the first crystallizer is higher than a predetermined temperature between the temperature of the first cooling medium and the temperature of the heating medium supplied from the heat source unit, the first crystallizer Using the first cooling medium discharged from the heating medium source;
When the temperature of the heating medium discharged from the third crystallizer is lower than the predetermined temperature between the temperature of the first cooling medium and the temperature of the heating medium supplied from the heat source machine, the third crystallizer The method for producing (meth) acrylic acid according to claim 5 or 6, wherein the discharged hot medium is used for the first cold medium or / and the second cold medium. Using a part or all of the heating medium discharged from the third crystallizer as the second cooling medium source;
The method for producing (meth) acrylic acid according to claim 5 or 6, wherein a part or all of the second cooling / heating medium discharged from the second crystallizer is used as the first cooling / heating medium source. The temperature of the cooling medium supplied from the heat source machine is −40 ° C. or higher and lower than the melting point of the crude (meth) acrylic acid solution,
The method for producing (meth) acrylic acid according to any one of claims 1 to 4, wherein the temperature of the heating medium supplied from the heat source device is higher than the melting point of the crystallized (meth) acrylic acid and 45 ° C or lower. . The temperature of the first cooling medium supplied from the heat source machine is −15 ° C. or higher and lower than the melting point of the crude (meth) acrylic acid solution,
The temperature of the 2nd cooling medium supplied from a heat source machine is -40 ° C or more and less than -15 ° C,
The method for producing (meth) acrylic acid according to any one of claims 5 to 9, wherein the temperature of the heating medium supplied from the heat source device is higher than the melting point of the crystallized (meth) acrylic acid and 45 ° C or lower. .

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