Tanks used in refining equipment

Abstract

The present invention provides a method for stably obtaining a product. The present invention relates to a tank used in a refining device, characterized in that: the tank is a crystallization tank for generating a slurry that contains crystals of a compound, and / or an aging tank in which the crystals of the compound in the tank can be retained in a suspended state; and the tank comprises a nozzle for causing a compound-containing solution or a compound-crystal-containing slurry to hit an inner wall surface of the tank and supplying the compound-containing solution or compound-crystal-containing slurry into the tank, and a heating mechanism for heating the portion of the inner wall surface that is hit by the compound-containing solution or compound-crystal-containing slurry.

Description

[Technical Field]

[0001] The present invention relates to a vessel used in a purification apparatus, and more particularly to a vessel used in a purification apparatus, a purification apparatus, a method for producing a compound, and a method for purifying a compound. [Background technology]

[0002] Purification apparatuses are widely used industrially to purify compounds used as raw materials for resins, etc. In many fields of the chemical industry, there is a demand for obtaining high-quality compounds with reduced impurities, and various investigations have been conducted into better purification apparatuses for this purpose.

[0003] In industry, many crude compounds before purification are purified by a continuous purification process. For example, a method for producing acrylic acid has been disclosed in which an acrylic acid-containing gas obtained by catalytic gas-phase oxidation of a raw material gas is collected and purified by crystallization, and a Michael adduct of acrylic acid contained in the remaining mother liquor is decomposed and returned to the collection step (see, for example, Patent Document 1).

[0004] In the purification step, a tank for producing a slurry containing crystals of the compound (crystallization tank) and a tank for growing crystals of the compound (aging tank) are used to obtain a compound with higher purity in a higher yield. Conventional purification methods using a crystallization tank and an aging tank are disclosed in Patent Documents 2 to 4. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-182437 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-28214 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-140471 [Patent Document 4] Japanese Patent Application Laid-Open No. 2002-204937 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, there is a need for a better purification apparatus for producing compounds, and a method for stably obtaining products (compounds). The present invention has been made in view of the above-mentioned current situation, and aims to provide a method for stably obtaining products. [Means for solving the problem]

[0007] The present inventors have investigated methods for stably obtaining products and focused on tanks used in purification apparatuses. They have found that when a solution or slurry is supplied to a crystallization tank that produces a slurry containing compound crystals or an aging tank that can maintain the compound crystals in a suspended state within the tank, if the solution or slurry is supplied along the inner wall surface of the tank to prevent splashing, fine crystals formed from the mother liquor in the solution or slurry adhere to the inner wall surface, form nuclei, and grow to form coarse crystals. After extensive research, the present inventors have found that a tank equipped with a nozzle for supplying the solution or slurry into the tank by hitting the inner wall surface of the tank, as well as a heating mechanism for heating the portion of the inner wall surface onto which the solution or slurry is applied, can sufficiently prevent splashing when the solution or slurry is supplied into the tank, thereby preventing fine crystals from adhering to the inner wall surface of the tank and forming nuclei to grow, thereby enabling stable production of a product. This finding led to the present invention.

[0008] That is, the present invention relates to a tank used in a purification apparatus, which is a crystallization tank that produces a slurry containing compound crystals and / or an aging tank that can maintain compound crystals in a suspended state within the tank, and which is characterized by comprising a nozzle for supplying a compound-containing solution or a slurry containing compound crystals into the tank by applying it to the inner wall surface of the tank, and a heating mechanism for heating the portion of the inner wall surface against which the compound-containing solution or the slurry containing compound crystals is applied. [Effects of the Invention]

[0009] By using the refining apparatus of the present invention, a product can be obtained stably. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view of an example of a tank of the present invention as seen from the side. [Figure 2] FIG. 2 is a perspective view showing a nozzle and a heating mechanism in the tank shown in FIG. [Figure 3] FIG. 3 is a schematic cross-sectional view of an example of a tank of the present invention as viewed from the side. [Figure 4] 4(a) to 4(c) are schematic diagrams showing examples of nozzles used in the tank of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below. In addition, a combination of two or more of the individual preferred features of the present invention described below is also a preferred embodiment of the present invention.

[0012] In the following, first, the tank of the present invention (crystallization tank and / or aging tank used in the purification apparatus) will be explained, followed by the purification apparatus of the present invention, the method for producing the compound of the present invention, and the method for purifying the compound of the present invention.

[0013] (Tank used in refining equipment) The vessel may be a crystallization vessel that produces a slurry containing crystals of the compound and / or an aging vessel that can maintain the crystals of the compound in a suspended state within the vessel. The tank is equipped with a nozzle for supplying a compound-containing solution or a slurry containing compound crystals (also referred to simply as a solution or a slurry in this specification) into the tank by applying it to the inner wall surface of the tank, and a heating mechanism for heating the portion of the inner wall surface onto which the compound-containing solution or the slurry containing compound crystals is applied.

[0014] The nozzle is used to supply a compound-containing solution or a slurry containing compound crystals into the tank by hitting it against the inner wall surface of the tank, and typically extends from the outside to the inside of the tank, with its tip on the inside of the tank (the supply port for the solution or slurry into the tank) facing toward and close to the inner wall surface of the tank. The nozzle may be, for example, one that penetrates the top plate of the tank. Here, the nozzle may be one that penetrates the top plate of the tank vertically, has a curved portion inside the tank, and has a tip that is positioned toward the inner wall surface, or one that penetrates the top plate of the tank obliquely. Among these, the nozzle that penetrates the top plate of the tank vertically, has a curved portion inside the tank, and has a tip that is positioned toward the inner wall surface is preferred.

[0015] For example, the nozzle is preferably provided so that its tip faces downward, and from the viewpoint of stably obtaining a product, it is more preferably provided so that it faces downward at an angle of 5° or more from the horizontal, even more preferably at an angle of 10° or more, and even more preferably at an angle of 15° or more. Furthermore, from the viewpoint of more suitably applying the solution or slurry to the inner wall surface and directing it along the surface, the tip of the nozzle faces downward at an angle of more preferably 70° or less from the horizontal, even more preferably at an angle of 60° or less, and particularly preferably at an angle of 50° or less. The downward angle of the nozzle tip with respect to the horizontal is the angle α formed by the horizontal and the nozzle tip, as shown by the dashed line in FIG. 4(a).

[0016] The distance (shortest distance) between the tip of the nozzle and the inner wall surface is preferably 0.1 to 5 times the inner diameter of the nozzle, more preferably 0.2 to 2 times, even more preferably 0.3 to 1 times, particularly preferably 0.4 to 0.9 times, and most preferably 0.6 to 0.7 times.

[0017] The inner diameter of the nozzle is preferably 2 to 300 mm, and more preferably 10 to 200 mm. The material of the nozzle is not particularly limited, but it is preferably made of a metal or an alloy. The shape of the nozzle tip is not particularly limited and may be flat or pointed, but the angle that the nozzle tip surface (the surface formed by the nozzle hole and its periphery) forms with the inner wall surface is preferably 15° or less, more preferably 10° or less, and even more preferably 5° or less, and is particularly preferably parallel to the inner wall surface. The angle that the nozzle tip surface forms with the inner wall surface is the angle represented by β in Figure 4(b) or the angle represented by γ in Figure 4(c).

[0018] In addition, in Fig. 1 described later, only one nozzle is used to deliver the solution or slurry 11 to the tank 1, and only one supply port for the solution or slurry is provided in the tank 1. However, as shown in Fig. 3, the tank may be provided with multiple nozzles. In this case, it is sufficient that any one of the nozzles satisfies the above-described configuration of the present invention, but it is preferable that all of the nozzles satisfy the configuration of the present invention. Furthermore, one or more heating mechanisms may be provided for the multiple nozzles, or one or more heating mechanisms may be provided for each of the multiple nozzles.

[0019] The heating mechanism is for heating the portion of the inner wall surface that is to be contacted with a compound-containing solution or a slurry containing compound crystals. The heating mechanism is not particularly limited, and examples thereof include a heat transfer medium, steam tracing, electric tracing, a known heater for adjusting the environmental temperature of the tank, etc. The heating mechanism may be the portion of the inner wall surface to which the compound-containing solution or the slurry containing compound crystals is applied. In particular, in the tank of the present invention, the heating mechanism is preferably a jacket-type heating mechanism. When the heating mechanism is of a jacket type, the material thereof is not particularly limited, and may be made of metal (for example, SUS, carbon steel) or resin.

[0020] The jacket-type heating mechanism preferably has a vertical length and a horizontal length on the wall surface of the vessel that are each at least once the inner diameter of the nozzle. The vertical length is more preferably at least two times the inner diameter of the nozzle, even more preferably at least three times, and particularly preferably at least five times. The upper limit of the vertical length relative to the inner diameter of the nozzle is not particularly limited, but is, for example, 20 times. The horizontal length is more preferably at least two times the inner diameter of the nozzle, even more preferably at least three times, still more preferably at least four times, and particularly preferably at least five times. The upper limit of the lateral length relative to the inner diameter of the nozzle is not particularly limited, but is, for example, 100 times. The jacket-type heating mechanism may be rectangular or may have other shapes (for example, circular, polygonal, etc.), but is preferably rectangular.

[0021] The tip of the nozzle is preferably positioned such that the extension line of the center of its hole is at least 1 / 6 from the bottom of the vertical length of the heating mechanism, more preferably at least 1 / 5 from the bottom, and even more preferably at least 2 / 5 from the bottom. The tip of the nozzle is preferably located such that the extension line of the center is located at a position not exceeding 9 / 10 from the bottom of the vertical length of the heating mechanism, more preferably not exceeding 4 / 5 from the bottom. Furthermore, it is preferable that the tip of the nozzle is located such that the extension line of the center is at least 1 / 10 of the horizontal length of the heating mechanism from both the left and right (closer to the center), and it is more preferable that it is located at least 1 / 5 of the horizontal length of the heating mechanism from both the left and right.

[0022] The jacket may be divided and may be operated so that each jacket has a different temperature (different heat medium). It is also possible to install a heat insulating material, traces, etc. on the outside of the jacket. The inside of the jacket may be provided with a structure for promoting heat transfer, such as a baffle, although this is not particularly limited.

[0023] The average thickness of the jacket (the width of the space through which the heat transfer medium flows) is preferably, for example, 5 to 200 mm. The heat flux through the jacket wall of the tank is 100 W / m 2 More than 200W / m is preferable. 2 More than 500W / m is more preferable. 2 The above is more preferable. The upper limit of the heat flux through the wall surface of the tank in the jacket is not particularly limited, but is usually 4000 W / m 2 The following is the result.

[0024] The heat medium is not particularly limited and may include water, antifreeze, methanol water (methanol aqueous solution), gas, steam, etc. The heat medium may be appropriately selected taking into consideration the freezing point of the compound to be purified, etc.

[0025] The crystallization tank can be equipped with a cooling mechanism and is not particularly limited as long as it can cool a solution of a compound to precipitate crystals and produce a slurry containing the crystals and a mother liquor. Broadly speaking, crystallization tanks can be broadly classified into a system in which a cooling jacket is attached to the tank itself and the inside of the tank (excluding the part where the solution or slurry is applied) is directly cooled to produce crystals, and a system in which the cooling mechanism is separate from the tank and connected by piping to cool and circulate the cooling mechanism to produce crystals. Although the method in which the cooling jacket is attached to the tank itself has the advantage of requiring fewer pieces of equipment, the tank itself must be made larger in order to increase the heat transfer area.When high production capacity is required, the tank size becomes excessively large, which has disadvantages in terms of initial investment and site area.

[0026] Therefore, when the size of the tank itself is limited or when purifying a compound that requires high production capacity, a system in which the contents of the tank are cooled outside the tank is preferred. In this way, if the tank and the cooling mechanism are connected by piping, and a portion of the compound solution (or slurry containing crystals) in the tank is sent to the cooling mechanism to produce crystals in the cooling mechanism, and the slurry containing the produced crystals is returned to the tank, the heat transfer area can be easily increased by increasing the number of cooling mechanisms, and the crystallization tank can be easily scaled up.

[0027] In this case, the cooling mechanism is not particularly limited as long as it can cool the compound solution and precipitate crystals. However, it is preferable to use a shell-and-tube heat exchanger, a spiral heat exchanger, or the like, which can ensure a large heat transfer area, or a cooling disk crystallizer or a scraping-type cooling crystallizer, which performs crystallization while scraping the cooling surface. The cooling disk crystallizer may be any device that cools a solution of a compound to precipitate crystals and scrapes off the precipitated crystals. For example, it may be a device that is composed of a tube and a number of cooling plates that separate the tube, where crystals are formed on the wall surfaces of the cooling plates, and where stirring blades with wipers are rotated inside the tube to scrape off the crystals.

[0028] The scraping-type cooling crystallizer may be any device that cools a solution of a compound to precipitate crystals and scrapes off the precipitated crystals, but it may also be a device that is composed of a double-structured tube, in which a refrigerant flows through the outer tube and a solution of the compound (or a slurry containing the crystals) in a tank flows through the inner tube to form crystals on the wall of the inner tube, and a shaft with a scraping blade rotates inside the inner tube to scrape off the crystals.

[0029] The crystallization temperature in the crystallization tank may be adjusted appropriately depending on the type of compound being purified, but is generally in the range of -1 to -15°C relative to the melting point of the pure substance, preferably -1.5 to -13.5°C, more preferably -3.5 to -12.5°C, and even more preferably -5 to -11.5°C. Furthermore, when the compound being purified is (meth)acrylic acid, the temperature is preferably 0 to 12°C. More preferably, it is 1 to 10°C, and even more preferably 2 to 8.5°C. A high temperature in the crystallization tank produces highly pure crystals, but, for example, when the crystallization tank uses a scraper-type cooling crystallizer, problems such as the need for a large amount of power to scrape the crystals in the crystallization tank may occur. Furthermore, if the temperature difference between the refrigerant and the inside of the crystallization tank is too high, problems such as blocking of the scraper may occur when the crystallization tank uses a scraper-type cooling crystallizer, making it difficult to continue operation. Therefore, when the temperature of the crystallization tank is high, it is necessary to reduce the temperature difference between the refrigerant and the inside of the crystallization tank and reduce the amount of crystals produced per heat transfer area. Although the purity of the crystals produced decreases when the temperature of the crystallization tank is low, if the crystallization tank uses a scraping-type cooling crystallizer, less power is required to scrape the crystals in the crystallization tank, and scraper blocking is less likely to occur even if the temperature difference between the refrigerant and the inside of the crystallization tank is increased. As a result, it is possible to increase the temperature difference between the refrigerant and the inside of the crystallization tank and increase the amount of crystals produced per heat transfer area. However, if the crystallization temperature is too low, the particle size of the produced crystals will be small and the crystals will tend to be difficult to settle.

[0030] The aging tank is not particularly limited as long as it can maintain crystals of the compound in a suspended state within the tank. By maintaining the crystals for a certain period of time, fine crystals melt due to Ostwald ripening, and larger crystals grow further, narrowing the crystal size distribution and further improving the purification efficiency in the washing column. Furthermore, even in a crystallization tank, the same effect as that of an aging tank can be expected by maintaining the crystals for a certain period of time.

[0031] The aging tank is usually provided with a withdrawal port near the bottom for withdrawing the slurry containing the compound crystals from the aging tank. The aging tank may be provided with a baffle therein. Examples of materials for the baffle plate include metals such as stainless steel, and resins. A plurality of the baffles may be provided in the aging tank.

[0032] The aging tank may further include a drain port near the top plate for draining the supernatant mother liquor from the aging tank. The drained mother liquor can be recycled, thereby improving the yield of the compound. For example, the drained mother liquor can be returned to the tank related to the previous step (previous stage). The nozzle or pipe constituting the drain port is not particularly limited in terms of material, and may be made of, for example, a metal or alloy. The maturation tank may be provided with only one or more outlets for withdrawing the mother liquor.

[0033] The aging tank may be provided with a mechanism (such as a partition plate or a weir) for preventing crystals of the compound from entering the mother liquor outlet, thereby further preventing crystals from entering the mother liquor outlet.

[0034] The size of the crystallization tank or aging tank is not particularly limited, but it is preferable that the inner diameter is 100 to 50,000 mm, and the height is 1,000 to 100,000 mm, for example.

[0035] The residence time of the compound in the aging tank may be adjusted appropriately depending on the type of compound to be purified, but from the viewpoint of adjusting the particle size distribution of the slurry sent to the washing column and reducing the reflux ratio in the washing column (flow rate of washing liquid / flow rate of purified compound), the residence time is preferably 0.5 to 6 hours. When the compound is (meth)acrylic acid, the residence time is more preferably 1 to 5 hours, and even more preferably 1.2 to 4.5 hours. The residence time is calculated as the volume of the suspension in the aging tank divided by the flow rate at which the slurry is supplied from the aging tank to the washing column in the next step (later stage). The size of the crystallization tank is determined by the required heat transfer area, etc. The residence time of the compound in the crystallization tank depends on the operating conditions.

[0036] Instrumentation devices such as thermometers, pressure gauges, level gauges (radar type, etc.), and level switches (float type, etc.) may be provided in or around the crystallization tank or aging tank, and in such cases, these may be covered with a cover. Furthermore, sight glasses (sight windows) may be provided on the side plates, etc. of the aging tank, manholes, handholes (holes for reaching inside during maintenance), etc. may be provided on the top plate, side plate, etc. of the aging tank, and ruptures, etc. may be provided on the top plate, etc. of the aging tank. There is no limit to the number of these devices that may be provided.

[0037] The tank of the present invention is not limited to a particular state of use, but may have the above-described configuration and may be configured such that, when the tank of the present invention is in use, the solution or slurry can be applied to and aligned with the heated portion on the inner wall surface of the tank.

[0038] FIG. 1 is a schematic cross-sectional view of an example of a tank of the present invention as seen from the side. A solution or slurry 11 is supplied into a tank 1 (FIG. 1 shows an aging tank equipped with an agitator 3) through a nozzle 12. Here, the nozzle 12 penetrates the top plate of the tank 1 vertically, has a curved tip, and is arranged so that the supply port faces a heated portion (a portion heated by a heating mechanism 13) on the inner wall surface of the tank and is close to the heated portion. By aligning the solution or slurry 11 along the inner wall surface of the tank in this way, splashing that occurs when the solution or slurry 11 is dropped directly onto the liquid surface can be prevented, and by hitting the solution or slurry 11 against the heated portion on the inner wall surface of the tank, it is possible to sufficiently prevent crystal nuclei from forming on the inner wall surface and scaling to grow into coarse crystals.

[0039] FIG. 2 is a perspective view showing a nozzle and a heating mechanism in the tank shown in FIG. 2, the heating mechanism is of a jacket type, and can heat a vertical and horizontal range larger than the inner diameter of the nozzle 12. This can sufficiently prevent crystal nuclei from forming on the inner wall surface.

[0040] FIG. 3 is a schematic cross-sectional view of an example of a tank of the present invention as viewed from the side. The tank shown in FIG. 3 is provided with a nozzle 12a in addition to the nozzle 12 shown in FIG. 1. A solution or slurry 11a is supplied into the tank 1 through the nozzle 12a. Here, like the nozzle 12, the nozzle 12a also penetrates the top plate of the tank 1 vertically, has a curved tip, and its supply port faces a heated portion on the inner wall surface of the tank and is disposed close to the heated portion. By aligning the solution or slurry 11a along the inner wall surface of the tank in this way, splashing that occurs when the solution or slurry 11a is dropped directly onto the liquid surface can be prevented. Furthermore, by hitting the heated portion on the inner wall surface of the tank with the solution or slurry 11a, it is possible to sufficiently prevent crystal nuclei from forming on the inner wall surface and scaling to grow into coarse crystals. When a nozzle for supplying a slurry and a nozzle for supplying a solution are provided in the tank, the height of the tips of these nozzles may be the same, or the nozzles may be arranged so that the height of the tip of the nozzle for supplying the slurry is lower than the height of the tip of the nozzle for supplying the solution. When the nozzles are arranged so that the height of the tip of the nozzle for supplying the slurry is lower than the height of the tip of the nozzle for supplying the solution, the height of the tip of the nozzle for supplying the slurry is preferably 10 to 500 mm lower, more preferably 50 to 400 mm lower, and even more preferably 80 to 300 mm lower than the height of the tip of the nozzle for supplying the solution. This not only prevents the slurry from scattering, the adhesion of crystals to the inner wall surface, and the growth of crystals using these as nuclei, but also allows the scale attached to the inner wall surface to be washed away while it is still minor, even if the slurry is scattered and scale adheres to the inner wall surface. The height of the nozzle tip refers to the height of the center of the hole on the nozzle tip surface. The height difference is the difference in height in the vertical direction. For example, a preferred embodiment is one in which the slurry is supplied into the tank 1 through a nozzle 12 shown in FIG. 3, and the solution is supplied into the tank 1 through a nozzle 12a. The direction in which the solution is discharged from the nozzle for supplying the solution is preferably the same as the direction in which the slurry is discharged from the nozzle for supplying the slurry. The direction in which the solution or slurry is discharged from the nozzle refers to the direction of an extension of the center of the hole at the tip of the nozzle. From a similar viewpoint, the height of the position where an extension line of the center of the hole at the tip of the nozzle for supplying the slurry intersects with the heating mechanism may be the same as the height of the position where an extension line of the center of the hole at the tip of the nozzle for supplying the solution intersects with the heating mechanism, or the height of the position where an extension line of the center of the hole at the tip of the nozzle for supplying the slurry intersects with the heating mechanism may be lower than the height of the position where an extension line of the center of the hole at the tip of the nozzle for supplying the solution intersects with the heating mechanism. When the height of the position where an extension line of the center of the hole at the tip of the nozzle for supplying the slurry intersects with the heating mechanism is lower than the height of the position where an extension line of the center of the hole at the tip of the nozzle for supplying the solution intersects with the heating mechanism, the difference in height is preferably 10 to 500 mm, more preferably 50 to 400 mm, and even more preferably 80 to 300 mm. This allows scaling formed on the inner wall surface to be constantly washed away with the solution while the purification apparatus is in operation. Furthermore, one or more heating mechanisms may be provided for a plurality of nozzles such as nozzle 12 and nozzle 12a, or one or more heating mechanisms may be provided for each of a plurality of nozzles.

[0041] Furthermore, the nozzle for supplying the slurry and the nozzle for supplying the solution are preferably located close to each other in terms of horizontal distance when viewed from above. The horizontal distance is preferably 5 to 2500 mm, more preferably 10 to 1500 mm, and even more preferably 15 to 900 mm. Note that the horizontal distance refers to the distance (horizontal component distance) viewed from above, based on the center of each nozzle. This not only prevents the slurry from scattering, the adhesion of crystals to the inner wall surface, and the growth of crystals using these as nuclei, but also allows the scale attached to the inner wall surface to be washed away while it is still minor, even if the slurry is scattered and scale adheres to the inner wall surface.

[0042] (Purification device of the present invention) The present invention also relates to a purification apparatus comprising a vessel of the present invention. When the purification apparatus of the present invention includes the crystallization tank, it can have one or more crystallization tanks. When the purification apparatus of the present invention has multiple crystallization tanks (crystallization tanks 1 to N), it is preferable that these multiple crystallization tanks are connected in series. In this case, the purification apparatus of the present invention usually has a line for sending a slurry containing compound crystals from one crystallization tank to another crystallization tank, optionally via a solid-liquid separation device. In addition, in this case, the purification apparatus of the present invention has a line for supplying a solution to be purified containing the compound to at least one crystallization tank. Furthermore, when the purification apparatus of the present invention further includes an aging tank, it is preferable that at least the Nth crystallization tank has a line for supplying a slurry containing compound crystals to the aging tank. When the purification apparatus of the present invention has a plurality of tanks as described above, any one of the tanks may be the tank of the present invention, but it is preferable that all of the tanks are the tanks of the present invention.

[0043] The purification apparatus of the present invention is preferably capable of carrying out a continuous purification process, and may further include, for example, a washing column (preferably a washing column for forcibly transporting crystals) downstream of the tank of the present invention. When the purification apparatus of the present invention further includes the washing column, it is preferable that the purification apparatus of the present invention has a line for supplying a slurry containing crystals of a compound from a tank included in the purification apparatus of the present invention (for example, from the last tank when the purification apparatus of the present invention includes multiple tanks connected in series) to the washing column. The purification apparatus of the present invention preferably further comprises a line for discharging the product from the washing column. The purification apparatus of the present invention may further include a line for returning the mother liquor from a downstream tank or apparatus to a upstream tank or apparatus. The purification apparatus of the present invention may further include a mechanism for controlling the amount of the slurry sent and the amount of the mother liquor returned. Examples of such a control mechanism include valves attached to various lines. The refining apparatus of the present invention may also include other devices that are generally used in refining apparatuses.

[0044] (Method for producing the compound of the present invention) The present invention is a method for producing a compound, comprising the steps of supplying a compound-containing solution or a slurry containing compound crystals into a tank by applying the solution to the inner wall surface of the tank, and heating the portion of the inner wall surface onto which the compound-containing solution or the slurry containing compound crystals is applied, wherein the tank is a crystallization tank that produces a slurry containing compound crystals and / or an aging tank that can maintain compound crystals in a suspended state within the tank.

[0045] In the compound production method of the present invention, the step of supplying into the tank and the step of heating are basically performed in this order on the target of purification. Below, the step of supplying into the tank and the step of heating will be described in order, and then the other steps will be described. In a continuous purification step, each step is usually performed simultaneously when viewed as the entire purification apparatus. In this specification, "compound" refers to a compound obtained by the production method of the present invention, and does not refer to raw materials, by-products, or solvents in the production method of the present invention. "Compound" can be rephrased as "target compound" or "target product." In this specification, "impurities" refer to components other than "compound," such as raw materials, by-products, and solvents.

[0046] <Step of supplying a compound-containing solution or a slurry containing compound crystals into the tank by applying it to the inner wall surface of the tank> In the step of supplying the solution or slurry into the tank, the solution or slurry is supplied into the tank by hitting it against the inner wall surface of the tank. The part where the slurry is hit has been heated in the heating step, as described below. The slurry is a suspension of compound crystals and mother liquor; in other words, the liquid part of the slurry containing the compound crystals supplied to the tank is the mother liquor. The slurry containing the crystals can be obtained by generating crystals in a compound-containing solution (for example, a crude (meth)acrylic acid aqueous solution or a crude (meth)acrylic acid solution), and the compound-containing solution may be prepared by the manufacturer or procured from another source. The compound-containing solution referred to here also includes crude compounds.

[0047] In the step of supplying the solution or the slurry containing the compound crystals into the aging tank, it is preferable to supply the solution or the slurry into the aging tank from near the top plate of the aging tank. For example, it is preferable to supply the solution or the slurry into the tank through a nozzle provided on the top plate of the aging tank.

[0048] In the step of supplying the solution or slurry into the tank, the solution or slurry can be supplied into the tank by hitting the inner wall surface of the tank using, for example, the nozzle described above.

[0049] In the step of supplying the solution or slurry into the tank, the supply rate of the solution or slurry is not particularly limited. In an industrial-scale aging tank, the supply rate is, for example, 0.2×10 per nozzle. 3 ~4.0×10 5 kg / h.

[0050] In the step of supplying the solution or slurry into the tank, the supply temperature can be appropriately set depending on the melting point of the compound, and can be adjusted, for example, within the range of 0 to 80°C. For example, when the compound is (meth)acrylic acid, the supply temperature of the solution or slurry is preferably 5 to 13°C, more preferably 6 to 12°C. The supply temperature of the solution or slurry is the temperature of the mother liquor in the solution or slurry containing crystals immediately before being supplied to the vessel (for example, the solution or slurry in the nozzle that supplies the solution or slurry to the aging vessel).

[0051] The solution supplied to the tank contains the compound. Examples of the solution include the compound, an aqueous solution of the compound, etc. The solution usually contains impurities other than the compound and water. In the method for producing a compound of the present invention, the solution supplied to the tank preferably has a purity (mass proportion) of the compound of 99 mass % or less. The mass proportion of the compound in the solution is preferably 80 mass % or more.

[0052] From the viewpoint of obtaining a product more stably, the mass proportion of the crystals in the slurry containing the crystals supplied to the tank is preferably 25 mass% or more, more preferably 30 mass% or more, and even more preferably 35 mass% or more. From the viewpoint of improving the fluidity of the slurry and further reducing the risk of pipe clogging, the mass proportion of the crystals is preferably 55% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. The crystal-containing slurry to be supplied to the aging tank may be concentrated using, for example, a solid-liquid separator. In this specification, when simply referring to "slurry containing crystals to be supplied into a tank," the slurry containing crystals to be supplied into the aging tank refers to a slurry containing crystals immediately before being supplied to the aging tank, for example, a slurry containing crystals in a pipe or nozzle for supplying the slurry containing crystals into the aging tank.

[0053] The crystal-containing slurry supplied to the tank preferably contains the compound in its mother liquor. Examples of the mother liquor include the compound and an aqueous solution of the compound. The mother liquor usually contains impurities other than the compound and water. In the method for producing a compound of the present invention, the purity (mass proportion) of the compound in the mother liquid of the slurry containing the crystals supplied to the tank is preferably 99 mass % or less. The mass proportion of the compound in the mother liquor is preferably 80 mass % or more.

[0054] In the production method of the present invention, the compound is preferably an easily polymerizable compound having a reactive double bond. In particular, in the production method of the present invention, the compound is more preferably an unsaturated carboxylic acid, further preferably (meth)acrylic acid, and particularly preferably acrylic acid. In this specification, (meth)acrylic acid refers to acrylic acid and / or methacrylic acid.

[0055] The inside of the tank may be operated under increased pressure, normal pressure, or reduced pressure. The step of supplying the solution into the tank may be intermittent, but is preferably carried out essentially continuously while the tank is in use.

[0056] <Step of heating the portion of the inner wall surface to which the compound-containing solution or the slurry containing compound crystals is applied> In the heating step, the portion of the inner wall surface to which the solution or slurry is applied is heated. The heating step can be suitably carried out using, for example, the above-mentioned heating mechanism (preferably, a jacket-type heating mechanism).

[0057] The heating temperature can be set appropriately from the viewpoint of preventing crystals from adhering to the inner wall surface, and can be adjusted appropriately generally within a range of +3 to +100°C relative to the temperature of the compound-containing solution or the slurry containing compound crystals, preferably within a range of +7 to +80°C, and more preferably within a range of +12 to +60°C. For example, when the compound is (meth)acrylic acid, the heating temperature is preferably 17 to 100°C, more preferably 20 to 80°C, and even more preferably 25 to 60°C. The heating temperature may be measured by measuring the outer wall surface of the portion where the slurry is applied with a thermometer, or by measuring the temperature of the heat medium when the heating mechanism is of a jacket type. The heating step may be intermittent, but is preferably carried out essentially continuously while the vessel is in use. The heating mechanism is usually placed above the liquid surface in the tank.

[0058] <Step of feeding into the washing column> The production method of the present invention may further include a step of withdrawing a slurry containing crystals of a compound from a tank (for example, from the last tank when the purification apparatus of the present invention includes multiple tanks connected in series) and supplying the slurry containing crystals of the compound to a washing column.

[0059] In the step of supplying the compound to the washing column, the slurry containing the compound crystals is first extracted from the tank, preferably from near the bottom of the tank. The slurry containing the extracted compound crystals is then fed to a washing column. In the step of supplying the slurry to the washing column, the slurry containing the compound crystals is preferably supplied to the washing column from the top plate of the washing column or near the top plate thereof. For example, the slurry containing the compound crystals is preferably supplied to the washing column through a nozzle provided on the top plate of the washing column. The step of supplying the solution to the washing column can be suitably carried out using a pump such as a centrifugal pump, a diaphragm pump, or a rotary pump.

[0060] The mass proportion of the crystals in the slurry containing the crystals supplied to the washing column is preferably 1 mass% or more, more preferably 3 mass% or more, even more preferably 5 mass% or more, and particularly preferably 10 mass% or more. The mass proportion of the crystals is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 20% by mass or less. In this specification, when the term "crystal-containing slurry to be supplied to a washing column" is simply used, the crystal-containing slurry to be supplied to the washing column refers to the crystal-containing slurry immediately before being supplied to the washing column, for example, the crystal-containing slurry in a pipe or nozzle that supplies the crystal-containing slurry to the washing column.

[0061] The crystal-containing slurry supplied to the washing column preferably contains the compound in its mother liquor, similar to the crystal-containing slurry supplied to the aging tank. Examples of the mother liquor include the compound and an aqueous solution of the compound. The mother liquor usually contains impurities other than the compound and water. The preferred ranges of the purity of the compound, the mass proportion of water, and the mass proportions of impurities other than the compound and water in the mother liquor are the same as the preferred ranges of the purity of the compound, the mass proportion of water, and the mass proportions of impurities other than the compound and water in the mother liquor in the pouring step described below.

[0062] In the step of supplying the crystal-containing slurry to the washing column, the supply rate is not particularly limited. In an industrial-scale washing column, the supply rate is, for example, 0.2 × 10 3 ~4.0×10 5 kg / h.

[0063] In the step of supplying the crystal-containing slurry to the washing column, the supply temperature can be appropriately set depending on the melting point of the compound, and can be adjusted, for example, within the range of 0 to 80°C. For example, when the compound is (meth)acrylic acid, the supply temperature of the slurry containing the crystals is preferably 5 to 13°C, and more preferably 6 to 12°C. The supply temperature of the crystal-containing slurry is the temperature of the mother liquor in the crystal-containing slurry immediately before it is supplied to the washing column (for example, the crystal-containing slurry in the pipe or nozzle that supplies the crystal-containing slurry to the washing column).

[0064] <Stirring process in the aging tank> The production method of the present invention may include a step of stirring a slurry containing crystals of a compound in an aging tank. In the stirring step, the crystal-containing slurry is usually stirred using a stirrer provided in the aging tank. In the stirring step, the rotation speed of the stirrer is preferably within the range of 5 to 500 rpm, and more preferably within the range of 10 to 300 rpm. The stirring may be intermittent, but it is preferable that the stirring is basically carried out continuously while the aging tank is in use.

[0065] <Process of removing the mother liquor from the maturation tank> The production method of the present invention may include a step of removing the supernatant mother liquor from the aging tank. The extracted mother liquor can be recycled and reused. For example, by supplying the extracted mother liquor to a crystallization tank in a previous stage and reusing it, the quality of the compound can be further improved. The step of extracting the mother liquor may be carried out using a pump or the like.

[0066] <Step of obtaining slurry containing crystals> The production method of the present invention preferably further comprises the step of obtaining a slurry containing crystals of the compound from the compound-containing solution. The compound-containing solution is preferably a crude (meth)acrylic acid aqueous solution or a crude (meth)acrylic acid solution. The crude (meth)acrylic acid aqueous solution refers to a solution in which (meth)acrylic acid is dissolved in water and contains impurities such as by-products produced during the production of (meth)acrylic acid. The crude (meth)acrylic acid solution refers to a solution consisting of (meth)acrylic acid and containing impurities such as by-products produced during the production of (meth)acrylic acid. These can be obtained, for example, by collecting in an absorption tower and optionally distilling the gas of a compound that is a reaction product obtained by the gas-phase oxidation reaction of propylene and isobutylene. However, they are not limited to those synthesized by themselves and may be procured from other sources. The crude (meth)acrylic acid aqueous solution or crude (meth)acrylic acid solution can be cooled, for example, using the crystallization tank described above, to obtain a slurry containing (meth)acrylic acid crystals. Examples of the impurities include acids such as propionic acid, acetic acid, maleic acid, benzoic acid, and acrylic acid dimer, aldehydes such as acrolein, furfural, formaldehyde, and glyoxal, acetone, and protoanemonin. In addition, solvents such as toluene and methyl isobutyl ketone may be contained. The production method of the present invention makes it possible to sufficiently remove impurities contained in the compound-containing solution.

[0067] <Step of Obtaining a Compound-Containing Solution> In the production method of the present invention, it is preferable that the production method further comprises a step of obtaining a compound-containing solution from a raw material.

[0068] The step of obtaining the compound-containing solution is not particularly limited as long as a compound-containing solution can be obtained. When the compound is (meth)acrylic acid, the step can be suitably carried out, for example, by a synthesis step of acrylic acid or a collection step of acrylic acid described in JP-A-2007-182437 (Patent Document 1). In the method for producing a compound of the present invention, the (meth)acrylic acid is preferably prepared from at least one raw material selected from the group consisting of propane, propylene, acrolein, isobutene, methacrolein, acetic acid, lactic acid, isopropanol, 1,3-propanediol, glycerol, and 3-hydroxypropionic acid. The (meth)acrylic acid and / or the raw material may be derived from a renewable raw material to produce a bio-based (meth)acrylic acid.

[0069] In the process of obtaining the compound-containing solution, impurities such as by-products are generally produced. For example, when the compound is (meth)acrylic acid, impurities that are produced include water, acids such as propionic acid, acetic acid, maleic acid, benzoic acid, and acrylic acid dimer, aldehydes such as acrolein, furfural, formaldehyde, and glyoxal, acetone, methyl isobutyl ketone, toluene, and protoanemonin. However, by purification using an aging tank according to the production method of the present invention, the impurities can be separated with excellent efficiency, and the product can be obtained efficiently.

[0070] (Method for purifying compounds) The present invention also relates to a method for purifying a compound, the method comprising the steps of supplying a compound-containing solution or a slurry containing compound crystals into a tank by applying the solution to the inner wall surface of the tank, and heating the portion of the inner wall surface onto which the compound-containing solution or the slurry containing compound crystals is applied, wherein the tank is a crystallization tank that produces a slurry containing compound crystals and / or an aging tank that can maintain the compound crystals in a suspended state within the tank.

[0071] The purification method of the present invention allows stable purification of compounds. A preferred embodiment of the purification method of the present invention is the same as the preferred embodiment of the production method of the present invention described above. [Example]

[0072] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples, and can be practiced with appropriate modifications within the scope of the above and below-described aims, and all such modifications are included in the technical scope of the present invention. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass".

[0073] Example 1 (How to obtain acrylic acid aqueous solution) According to the method described in WO 2010 / 032665, propylene was subjected to catalytic gas phase oxidation to obtain an acrylic acid-containing gas, and the obtained acrylic acid-containing gas was treated in an absorption tower to obtain an aqueous acrylic acid solution.

[0074] (How to obtain the supply slurry) An aqueous solution of acrylic acid was supplied to a crystallization tank. A refrigerant was supplied to a jacket attached to the peripheral wall of the crystallization tank to indirectly cool the crystals. Crystals adhering to the inner surface of the crystallization tank were scraped off with a scraper attached inside the crystallization tank, thereby preparing a slurry containing crystals (supply slurry).

[0075] (Purification equipment / purification conditions) The purification apparatus used included the crystallization tank as the upstream stage and an aging tank. The aging tank was equipped with the following equipment. Nozzles (solution supply nozzle and slurry supply nozzle) for supplying a solution or a slurry containing crystals into the tank by hitting it against the inner wall of the tank (one of each: both penetrate the top plate of the aging tank vertically, have a curved section inside the aging tank, and are positioned so that their tips face the inner wall of the tank. The tips face downward at 45° from the horizontal. Inner diameter: 80 mm, distance from the inner wall: 50 mm. The shape of the nozzle tip is such that the tip surface (the surface formed by the nozzle hole and its periphery) is parallel to the inner wall of the tank. Slurry supply temperature: 8°C, solution supply temperature: 10°C) A heating mechanism for heating the portion of the inner wall surface where the solution or slurry containing crystals is applied (heating temperature: 32°C, heating fluid: water, vertical length: 500 mm, horizontal length: 2600 mm, shape: rectangular, the extensions of the centers of the holes in the tip of the slurry supply nozzle and the tip of the solution supply nozzle are located 200 mm from the bottom of the heating mechanism, and both are located 1300 mm from the left and right of the heating mechanism. When viewed from above, the direction in which the slurry is discharged from the tip of the slurry supply nozzle is different from the direction in which the solution is discharged from the tip of the solution supply nozzle. Jacket width (width of the space through which the heat medium flows): 25 mm)

[0076] The aging tank was operated, and the compound crystals were maintained in a suspended state within the tank, allowing the crystals to grow. By heating the portion of the inner wall surface where the crystal-containing slurry was applied, and by making the slurry adhere to the inner wall surface, it was possible to sufficiently suppress the scattering of the slurry and the crystals adhering to the inner wall surface, forming nuclei and growing into coarse crystals, and a stable product was obtained.

[0077] <Example 2> The aging tank was operated in the same manner as in Example 1, with the exception that the direction of solution discharge from the tip of the solution supply nozzle in the aging tank was the same as the direction of slurry discharge from the tip of the slurry supply nozzle, and the extension of the center of the hole at the tip of the solution supply nozzle was positioned 300 mm from the bottom of the heating mechanism. The aging tank was maintained in a suspended state within the tank, and crystals were grown. In addition to the effects of Example 1, scaling formed on the inner wall surface could be constantly washed away with solution from above while the purification apparatus was in operation, suppressing the occurrence of scaling and enabling stable production of the product.

[0078] <Comparative Example 1> Except for not using a heating mechanism, the aging tank was operated in the same manner as in Example 1. As a result, crystal nuclei were formed on the inner wall surface of the tank, causing scaling. [Explanation of symbols]

[0079] 1: Tank 3: Mixer 11, 11a: Solution or slurry 12, 12a: Nozzle 13:Heating mechanism

Claims

1. A tank used in a purification device, the tank is a crystallization tank for producing a slurry containing compound crystals and / or an aging tank capable of holding the compound crystals in a suspended state within the tank, and is equipped with a nozzle for supplying the compound-containing solution or the compound crystal-containing slurry from the outside of the tank into the tank by applying the compound-containing solution or the compound crystal-containing slurry to the inner wall surface of the tank, and a heating mechanism for heating the portion of the inner wall surface onto which the compound-containing solution or the compound crystal-containing slurry is applied; The compound is an unsaturated carboxylic acid.

2. The tank according to claim 1 , wherein the heating mechanism is a jacket-type heating mechanism.

3. The tank according to claim 2, wherein the jacket-type heating mechanism has a vertical length and a horizontal length on the wall surface of the tank that are each equal to or greater than the inner diameter of the nozzle.

4. A purification device comprising the tank according to any one of claims 1 to 3.

5. A method for producing a compound, comprising: The production method includes a step of supplying a compound-containing solution or a slurry containing compound crystals from outside the tank into the tank by applying the solution to the inner wall surface of the tank; heating a portion of the inner wall surface to which the compound-containing solution or the slurry containing crystals of the compound is applied; the tank is a crystallization tank for producing a slurry containing crystals of the compound and / or an aging tank capable of maintaining crystals of the compound in a suspended state within the tank; The compound is an unsaturated carboxylic acid, The method for producing a compound, wherein the temperature at which the part to which the compound-containing solution or the slurry containing the compound crystals is applied is heated in the heating step is +3 to +100°C higher than the temperature of the compound-containing solution or the temperature of the slurry containing the compound crystals.

6. The method for producing a compound according to claim 5, wherein the compound is (meth)acrylic acid.

7. 7. The method for producing a compound according to claim 6, wherein the (meth)acrylic acid is produced using at least one raw material selected from the group consisting of propane, propylene, acrolein, isobutene, methacrolein, acetic acid, lactic acid, isopropanol, 1,3-propanediol, glycerol, and 3-hydroxypropionic acid.

8. 1. A method for purifying a compound, comprising: The purification method includes a step of supplying a compound-containing solution or a slurry containing crystals of the compound from outside the tank into the tank by applying the solution to an inner wall surface of the tank; heating a portion of the inner wall surface to which the compound-containing solution or the slurry containing crystals of the compound is applied; the tank is a crystallization tank for producing a slurry containing crystals of the compound and / or an aging tank capable of maintaining crystals of the compound in a suspended state within the tank; The compound is an unsaturated carboxylic acid, A method for purifying a compound, wherein the temperature at which the part to which the compound-containing solution or the slurry containing compound crystals is applied in the heating step is heated is +3 to +100°C higher than the temperature of the compound-containing solution or the temperature of the slurry containing compound crystals.

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