JP4914584B2 - Method and apparatus for preventing polymerization of liquid substance stored in storage container - Google Patents

Description

The present invention relates to stabilization of a monomer having an unsaturated bond, particularly an amide compound such as acrylamide or methacrylamide, and more particularly to a method and an apparatus for preventing polymerization of a liquid substance stored in a storage container.

Conventionally, an amide compound such as acrylamide is, for example, a sulfuric acid hydrolysis method including a step of obtaining an acrylamide sulfate by heating a nitrile compound such as acrylonitrile together with sulfuric acid and water, a nitrile compound as a catalyst (for example, metallic copper, copper oxide, Or hydrated in the presence of a copper salt) to produce the corresponding amide compound, or a method of producing acrylamide by hydrating the nitrile compound with a nitrile hydratase derived from a microorganism . The amide compound is useful as a raw material for a polymer having many uses, such as a flocculant, a thickener, a petroleum recovery agent, a paper strength enhancer in the paper industry, or a thickener for papermaking. .
Since this amide compound is a substance that is extremely easily polymerized, when this liquid is stored in a storage tank (storage container), it is polymerized locally around the bottom of the storage tank, or the fluidity is lost. For example, when it is necessary to extract the bottom liquid from the storage tank by open inspection, it may be difficult to extract the bottom liquid.
Furthermore, the polymerization may proceed to only a part of the stored liquid, which may lead to a decrease in product quality.

For this reason, various compounds have been proposed as polymerization inhibitors for acrylamide.
For example, Patent Document 1 discloses a method for suppressing polymerization by allowing a compound belonging to the group consisting of thiourea, rhodanamone, nitrobenzol, O-tolidine, phenothiazine, and nitroso R salt to coexist with acrylamide. . Patent Document 2 discloses a method for stabilizing an acrylamide aqueous solution in which a water-soluble monocarboxylate having 2 or more carbon atoms is added.
Patent Document 3 discloses a method of coating a wall surface of a gas phase part inside an apparatus used for an acrylamide manufacturing process with a synthetic resin material, and Patent Document 4 discloses a method of making a liquid contact part made of resin. , Respectively.
Further, Patent Document 5 discloses a method of performing a dilution purge (discharge) in the process because it is impossible to eliminate the liquid pool in the tank by design contrivance.

Japanese Examined Patent Publication No. 39-10109 Japanese Patent No. 2548051 Japanese Patent Publication No.49-16845 JP 2003-221374 A JP 2003-221373 A

However, the bottom of the tank storing the acrylamide product is extremely susceptible to polymerization even in the presence of a stabilizer, and polymerization is particularly likely to occur in the bottom extraction pipe (extraction path). For this reason, for example, when it is necessary to extract the bottom liquid from the tank by open inspection, it is still difficult to extract acrylamide.
Moreover, since it becomes difficult to dispose of a polymer solution having no fluidity, an environmental load has also occurred.

The present invention has been made in view of such circumstances, and at the time of storage of a compound having an unsaturated bond, for example, as in the prior art, solidification of the compound without affecting the product quality and environment by an additive or dilution purge. It is an object of the present invention to provide a method and an apparatus for preventing polymerization of a liquid substance stored in a storage container that can prevent the above-described problem.

The method for preventing polymerization of a liquid substance stored in a storage container according to the first invention in accordance with the above object comprises a liquid substance containing amide compound, acrylic acid, or methacrylic acid composed of acrylamide, methacrylamide, or crotonamide. A method for preventing polymerization of a liquid substance stored in a storage container having a circulation path that is taken out from the lower part of the storage container having a circular cross section and returned to the upper part of the storage container,
An inflow pipe directed in a tangential direction with respect to the inner peripheral surface of the storage container is provided at a lower portion of the storage container, and the liquid material branched from the circulation path is connected to the storage container via the inflow pipe. It flows along the inner peripheral surface to prevent the liquid material from solidifying.

An apparatus for preventing polymerization of a liquid substance stored in a storage container according to the second aspect of the present invention, which stores an amide compound comprising acrylamide, methacrylamide, or crotonamide, acrylic acid, or a liquid containing methacrylic acid. A storage container having a circular storage cross-section, and an apparatus for preventing polymerization of the liquid stored in the storage container including a circulation pipe for taking out the liquid from the lower part of the storage container and returning it to the upper part of the storage container by a pump,
An inflow pipe directed in the tangential direction of the inner peripheral surface of the storage container is provided at a lower portion of the storage container, and the liquid material is branched from the circulation pipe on the outlet side of the pump and stored from the inflow pipe. By-pass piping that flows along the inner peripheral surface of the container is provided to prevent the liquid material from solidifying.

The method for preventing polymerization of the liquid material stored in the storage container according to the first invention and the polymerization prevention device for the liquid material stored in the storage container according to the second invention can form a swirling flow in the lower part of the storage container, It is possible to prevent the liquid material from staying at the bottom of the storage container and to prevent the liquid material from solidifying.
As a result, when storing liquid materials, the product is stored in a stable state without affecting product quality and the environment, and causing no product loss, for example, by conventional additives or dilution purge. it can.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is an explanatory view of a polymerization preventive device for a liquid substance stored in a storage container according to the first embodiment of the present invention, FIG. 2 is an explanatory view of a first modification of the polymerization preventive device, FIGS. 3A and 3B are explanatory views of second and third modifications of the polymerization preventing apparatus, respectively, and FIG. 4 is a liquid substance stored in a storage container according to the second embodiment of the present invention. It is explanatory drawing of the superposition | polymerization prevention apparatus.

As shown in FIG. 1, a liquid polymerization preventing apparatus (hereinafter also simply referred to as a polymerization preventing apparatus) 10 stored in a storage container according to a first embodiment of the present invention is a liquid containing an unsaturated compound. Storage tank (an example of a storage container) 11 and a circulation path for taking out the liquid material stored in the storage tank 11 from the lower part of the storage tank 11 and returning it to the upper part of the storage tank 11. This will be described in detail below.

The unsaturated compound in the liquid substance stored in the storage tank 11 is a compound having an unsaturated bond in the molecule, and examples of the compound include amide compounds, carboxylic acids, or carboxylic acid esters. Can do.
Here, examples of the amide compound include those having 1 to 20 carbon atoms, preferably 3 to 20 carbon atoms, and examples thereof include acrylamide, methacrylamide, or unsaturated aliphatic amides of crotonamide. it can. Examples of carboxylic acids include acrylic acid or methacrylic acid.

This amide compound can be produced industrially by hydrating the corresponding nitrile compound using, for example, a sulfuric acid hydration method, an acetone cyanohydrin method, a copper catalyst method, or an enzymatic method. However, it is particularly preferable to use a copper catalyst method or an enzyme method. The copper catalyst method is a method for producing an amide compound by directly hydrating a nitrile compound in the presence of a copper catalyst of, for example, metallic copper, reduced copper, or Raney copper. For example, JP-B-52-33092 The method disclosed in the publication can be used. The enzyme method is a method for producing a corresponding amide compound by hydrating a nitrile by the action of a microorganism-derived enzyme having the ability to hydrate the nitrile to produce the corresponding amide. The method disclosed in the 11-89575 publication or the international publication 01/53253 pamphlet can be used.

The storage tank 11 has a cylindrical outer shape, and is within 1/3 or less, preferably 1/4 or less of its height from the bottom of the storage tank 11, for example, the bottom surface of the storage tank 11. An outlet 13 of the circulation pipe 12 is provided, and an inlet 14 of the circulation pipe 12 is provided at the upper end of the storage tank 11. A circulation path for the liquid material is formed by the circulation pipe 12.
In the middle of the circulation pipe 12, a circulation pump (an example of a pump) 15 for the purpose of circulating and mixing the liquid substance stored in the storage tank 11 using the circulation pipe 12, and the circulation Two flow rate adjusting valves 16 and 17 for controlling the flow rate of the liquid material flowing through the pipe 12 are installed. Further, a strainer 18 is provided in the circulation pipe 12 upstream of the circulation pump 15 to remove foreign matters mixed in the liquid material.

In addition, in the downstream side of the circulation pump 15 and between the two flow rate adjusting valves 16 and 17, the liquid material flowing through the circulation pipe 12 is supplied to, for example, a lorry (transport vehicle). A supply pipe 19 for use in loading or supplying to a user (a consumer) is provided.
By controlling the opening degree of the circulation pump 15 and the flow rate adjusting valves 16 and 17 using a control unit (not shown), the supply amount of the liquid material to the circulation pipe 12 and the supply pipe 19 is controlled. Can be adjusted.

The bottom of the storage tank 11 is connected to a liquid material outlet 21 of a pipe 20 for extracting the liquid substance stored in the storage tank 11, and from the upstream side of the extraction pipe 20, that is, from the storage tank 11 side. The extraction valve 22, the on-off valve 23, and the extraction pump 24 are sequentially arranged. A liquid material extraction path is formed by the extraction pipe 20.
Further, the liquid material taken out from the storage tank 11 is returned from the side of the storage tank 11 into the storage tank 11 at the lower side wall of the storage tank 11 and below the outlet 13 of the circulation pipe 12. Inflow pipes 26 (which are also used as take-out pipes for taking out liquid substances in the storage tank 11) 25 are provided. The inflow pipe 25 is provided with an on-off valve 27, and a supply port 28 of the inflow pipe 25 is connected to the extraction pipe 20 between the extraction valve 22 and the on-off valve 23.
The inflow pipe 25 may not be provided in the storage tank 11.

The circulation pipe 12 between the circulation pump 15 and the supply pipe 19 is provided with a bypass pipe 29 branched from the circulation pipe 12 and connected to the inflow pipe 25. A branch path is formed by the bypass pipe 29. Here, a liquid feed pump can be provided in the bypass pipe 29.
When the storage pipe 11 is not provided with the inflow pipe 25, the bypass pipe 29 is directly connected to the extraction pipe 20.
As a result, the liquid material flowing through the circulation pipe 12 is caused to flow from the bypass pipe 29 into the storage tank 11 through a part of the inflow pipe 25 and the extraction pipe 20, and is placed in the lower part of the storage tank 11. An auxiliary circulation flow can be formed.
The above-described opening / closing of the extraction valve 22, the on-off valve 23, and the on-off valve 27 and the operation and stop of the extraction pump 24 are performed by a control unit that operates the circulation pump 15 and the flow rate adjusting valves 16, 17. Can be controlled.

Here, as shown in FIG. 2, the installation position of the liquid material outlet 21 of the extraction pipe 20 installed at the bottom of the storage tank 11 is the inflow pipe having the same function as the inflow pipe 25 described above. It is preferable to provide at 30 positions away from the inlet 31, that is, at positions facing each other around the axis of the storage tank 11. In this case, the length of the inflow piping 30 connected to the extraction piping 20 between the extraction valve 22 and the on-off valve 23 is also increased.
Thereby, the distance from the liquid material outlet 21 of the extraction pipe 20 provided in the storage tank 11 to the inlet 31 of the inflow pipe 30 can be made longer than that in the case of the polymerization preventing apparatus 10. Accordingly, the liquid material moving from the inlet pipe 30 to the outlet 13 of the circulation pipe 12 after flowing into the storage tank 11 through a part (upstream part) of the extraction pipe 20 is also long. As a result, an auxiliary circulation flow can be formed in a wider area below the storage tank 11.

Further, as shown in FIG. 3A, without connecting the bypass pipe 29 to the extraction pipe 20, it is connected to an inflow pipe 33 that forms a plurality of liquid material inflow paths 32 in the lower part of the storage tank 11. It is also possible to do. The liquid material inflow passage formed in the inflow piping may be one.
The inflow ports 34 of the inflow pipe 33 are preferably installed at substantially equal intervals over the entire bottom surface of the storage tank 11, but in particular, an area where liquid substances are likely to stay, for example, the inner peripheral surface of the storage tank 11 It is preferable to provide a plurality in the vicinity.
Further, as shown in FIG. 3B, the plurality of inflow pipes 35 are connected at substantially the same tangential direction to the inner peripheral surface of the storage tank 11 at the same cross-sectional position at the bottom of the storage tank 11. It is also possible to do. The positions of the plurality of inflow pipes may be different positions in the height direction of the storage tank. The inflow pipe may be one place.
As a result, while the liquid material returning to the storage tank 11 is allowed to flow along the inner peripheral surface of the storage tank 11, the auxiliary circulation is performed in a direction below the storage tank 11 and centering on the axis of the storage tank 11. A flow can be formed.

Next, a method for preventing polymerization of the liquid material stored in the storage container according to the first embodiment of the present invention will be described with reference to the polymerization preventing apparatus 10 described above.
When the extraction of the liquid material from the extraction pipe 20 is stopped, the extraction valve 22 of the extraction pipe 20 is opened and the on-off valve 23 is closed. Moreover, the on-off valve 27 provided in the inflow piping 25 is also opened.
Here, the liquid material flowing in the circulation pipe 12 by operating the circulation pump 15 also flows into the bypass pipe 29 by adjusting the flow rate adjusting valve 16 provided on the upstream side, and this bypass pipe. The liquid material that has flowed to 29 flows into the storage tank 11 through the inflow pipe 25 and into the storage tank 11 through part of the inflow pipe 25 and the extraction pipe 20.
Thereby, an auxiliary circulation flow is formed at the bottom of the storage tank 11, and solidification of the liquid material can be prevented.

Next, a liquid polymerization preventing apparatus (hereinafter also simply referred to as a polymerization preventing apparatus) 36 stored in the storage container according to the second embodiment of the present invention will be described, which is the same as the above-described polymerization preventing apparatus 10. The same reference numerals are given to the members, and detailed description is omitted.
As shown in FIG. 4, the polymerization preventing device 36 includes a storage tank 11 that stores a liquid material containing an unsaturated compound, and takes out the liquid material stored in the storage tank 11 from the lower portion of the storage tank 11, thereby circulating a pump. 15 is a device having a circulation path that is returned to the upper part of the storage tank 11 by 15. The storage tank 11 is provided with a circulation pipe 37 that forms a circulation path and is attached with a strainer 18, a circulation pump 15, and a flow rate adjustment valve 17. In addition, a liquid material extraction passage is formed at the bottom of the storage tank 11, and a liquid material outlet 21 of an extraction pipe 20 to which an extraction valve 22, an on-off valve 23 and an extraction pump 24 are attached is connected. Has been.

On the lower side wall of the storage tank 11 and below the outlet 13 of the circulation pipe 37, a liquid material stored in the storage tank 11 can be taken out from the side of the storage tank 11. A liquid material outlet 39 is provided. The downstream end of the extraction pipe 38 (which becomes the liquid material supply port of the extraction pipe 38) is connected to the extraction pipe 20 between the extraction valve 22 and the on-off valve 23. Further, the extraction pipe 38 includes an auxiliary circulation flow forming pump 40 (an example of a second pump) for flowing the liquid in the storage tank 11 to the extraction pipe 38 and a flow path of the extraction pipe 38. An on-off valve 27 that opens and closes is provided. An auxiliary circulation flow forming path is formed by the extraction pipe 38.
Thereby, the liquid substance flowing through the extraction pipe 38 can be caused to flow into the storage tank 11 via a part of the extraction pipe 20, and an auxiliary circulation flow can be formed in the lower part of the storage tank 11.

Next, a method for preventing polymerization of a liquid substance stored in a storage container according to a second embodiment of the present invention will be described with reference to the polymerization preventing device 36 described above.
When the extraction of the liquid material from the extraction pipe 20 is stopped, the extraction valve 22 of the extraction pipe 20 is opened and the on-off valve 23 is closed. Further, the on-off valve 27 provided in the extraction pipe 38 is also opened.
Here, by operating the auxiliary circulation flow forming pump 40, the liquid material that has flowed from the storage tank 11 into the extraction pipe 38 flows into the storage tank 11 through a part of the extraction pipe 20.
Thereby, an auxiliary circulation flow is formed at the bottom in the storage tank 11, and solidification of the liquid material can be prevented.

Using the 50 wt% acrylamide aqueous solution as the liquid material containing the unsaturated compound, using the polymerization prevention apparatus 10 shown in FIG. 1 and extracting the liquid material from the extraction pipe 20, The on-off valve 23 is closed, and a part of the circulating fluid from the bypass pipe 29 branched from the circulation pipe 12 is passed through the inflow pipe 25 from the liquid discharge outlet 21 and the inlet 26 to the storage tank 11. It was made to flow in and circulate. After one year, the on-off valve 23 was opened, and the extraction pump 24 was used to check the extraction. As a result, the liquid substance could be extracted easily. Even if the liquid pump is stopped every two years and the on-off valve 23 is opened and the on-off valve 27 is closed and the liquid material is inspected for extraction, the liquid material is not blocked from the extraction pipe 20 at all. Was able to be extracted. Furthermore, although the strainer 18 was inspected, adhesion of polymer or the like was not observed.
Such regular inspection was carried out 10 times, but no problem was found and no polymer was observed.

(Comparative example)
As a conventional example in which an auxiliary circulation flow is not provided, a circulation operation is normally performed with the extraction on-off valve 22 closed without providing the bypass pipe 29 and the inflow pipe 25 of FIG. After one year, when the opening / closing valve 23 was opened and the extraction pump 24 was inspected for extraction with the same manner as in the example, polymerization of the liquid material occurred at the extraction valve, etc. The liquid material could not be extracted from 20.
Furthermore, when the circulation pump 15 was stopped and the strainer 18 was inspected, adhesion of a large amount of polymer was confirmed.
From the above, by using the polymerization prevention method and apparatus of the present invention, an auxiliary circulation flow is formed in the storage tank bottom portion having a relatively small circulation flow, an auxiliary pipe in which liquid substances are liable to stay, an extraction valve, and the like. Therefore, polymerization can be prevented for a long time.
Further, as in the prior art, the polymerization of the compound can be prevented without affecting the product quality and the environment by the additive or dilution purge.

As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, a case where a part or all of the above-described embodiments and modifications are combined to constitute a method and an apparatus for preventing polymerization of a liquid substance stored in a storage container of the present invention is also included in the scope of the present invention. It is.
In addition, it is preferable to apply the polymerization preventing method and the apparatus for the liquid substance stored in the storage container of the present invention to the manufacturing process of the amide compound.

It is explanatory drawing of the superposition | polymerization prevention apparatus of the liquid substance stored by the storage container which concerns on the 1st Embodiment of this invention. It is explanatory drawing of the 1st modification of the polymerization prevention apparatus. (A), (B) is explanatory drawing of the 2nd, 3rd modification of the superposition | polymerization prevention apparatus, respectively. It is explanatory drawing of the superposition | polymerization prevention apparatus of the liquid substance stored by the storage container which concerns on the 2nd Embodiment of this invention.

10: Device for preventing polymerization of liquid substance stored in storage container, 11: Storage tank (storage container), 12: Pipe for circulation, 13: Outlet, 14: Inlet, 15: Pump for circulation (pump), 16 17: Flow rate adjusting valve, 18: Strainer, 19: Supply pipe, 20: Extraction pipe, 21: Liquid material outlet, 22: Extraction valve, 23: On-off valve, 24: Extraction pump, 25 : Inflow piping, 26: Inlet, 27: On-off valve, 28: Supply port, 29: Bypass piping, 30: Inflow piping, 31: Inlet, 32: Liquid material inflow passage, 33: Inflow piping, 34: Inlet, 35: Pipe for inflow, 36: Polymerization prevention device for liquid material stored in storage container, 37: Pipe for circulation, 38: Pipe for extraction, 39: Liquid material outlet, 40: Auxiliary circulation flow Forming pump (second pump)

Claims (3)

A storage container having a circulation path for taking out an amide compound consisting of acrylamide, methacrylamide, or crotonamide, acrylic acid, or a liquid containing methacrylic acid from the bottom of the storage container having a circular cross section and returning it to the top of the storage container A method for preventing polymerization of a liquid material stored in
An inflow pipe directed in a tangential direction with respect to the inner peripheral surface of the storage container is provided at a lower portion of the storage container, and the liquid material branched from the circulation path is connected to the storage container via the inflow pipe. A method for preventing polymerization of a liquid material stored in a storage container, wherein the liquid material is allowed to flow along an inner peripheral surface to prevent solidification of the liquid material. 2. The method for preventing polymerization of a liquid substance stored in a storage container according to claim 1, wherein the inflow pipe is provided with 2 or 4 in the storage container. Prevention method. A storage container having a circular cross section for storing a liquid substance containing amide compound, acrylamide, or crotonamide, acrylic acid, or methacrylic acid , and the liquid substance is removed from the lower part of the storage container and stored by a pump. An apparatus for preventing polymerization of a liquid substance stored in a storage container having a circulation pipe for returning to the upper part of the container,
An inflow pipe directed in the tangential direction of the inner peripheral surface of the storage container is provided at a lower portion of the storage container, and the liquid material is branched from the circulation pipe on the outlet side of the pump and stored from the inflow pipe. An apparatus for preventing polymerization of a liquid substance stored in a storage container, wherein a bypass pipe that flows along the inner peripheral surface of the container is provided to prevent the liquid substance from solidifying.

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