Integrated purification device for crystallization and solid-liquid separation

Abstract

The present invention relates to an integrated purification device and a purification method using the purification device, the integrated purification device comprising: a crystallizer including an upper crystallizer region in which a compound solution is provided to form crystals and a lower crystallizer region which is positioned under the upper crystallizer region and stores and discharges slurry including crystals formed in the upper crystallizer region; and a solid-liquid separator including a cylindrical main body having a slurry inlet provided on one side to receive the slurry from the crystallizer and an outlet provided on the other side to discharge pulverized crystals obtained by separation from the slurry and then compressing and washing, wherein the cylindrical main body is divided into a first region, a second region, and a third region, in sequence from one side of the cylindrical main body.

Description

Integrated purification device for crystallization and solid-liquid separation

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0115767, filed August 28, 2024, Korean Patent Application No. 10-2024-0115785, filed August 28, 2024, Korean Patent Application No. 10-2024-0115803, filed August 28, 2024, and Korean Patent Application No. 10-2025-0115557, filed August 20, 2025, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to an integrated purification device combining a crystallizer and a solid-liquid separator.

[0005] Compounds used as raw materials for various resins can be manufactured by obtaining a compound-containing solution through a synthetic reaction and then going through a subsequent process of purifying the compound from the solution.

[0006] For example, acrylic acid can be produced by subjecting propane, propylene, etc. to a gas phase oxidation reaction in the presence of an appropriate catalyst within a reactor to obtain a gaseous stream containing acrylic acid, which is then contacted with water in an absorption tower to obtain an aqueous acrylic acid solution. The aqueous acrylic acid solution can then undergo crystallization and solid-liquid separation to purify the acrylic acid.

[0007] The above crystallization is a process of precipitating a compound as a solid by utilizing the difference in solubility of a substance according to temperature in a liquid mixture, and a solution in which the compound is dissolved in a solvent is converted into a slurry-type suspension in which the compound as a solid crystal floats in the remaining liquid (mother liquor).

[0008] The above solid-liquid separation is a process for separating the compound crystals formed in the above crystallization process from the residual liquid phase, and can be performed using devices such as a washing column, a centrifuge, or a filter. In particular, the washing column is not only effective in separating the compound crystals from the mother liquor, but can also remove the residual liquid phase and impurities contained in the separated compound crystals through washing, and thus can be used in processes requiring high purity or ultra-high purity.

[0009] The present invention is intended to solve the problem mentioned in the background technology of the above invention, and to provide a purification device capable of solving pipe blockage that occurs during slurry transport in the crystallization and solid-liquid separation process of a compound, and a method for producing a compound at a high yield using the same.

[0010] According to one aspect of the present invention for solving the above problem, there is provided a crystallizer comprising: a crystallizer upper region for forming crystals by supplying a compound solution; and a crystallizer lower region provided below the crystallizer upper region for storing and discharging a slurry containing crystals formed in the crystallizer upper region; And a solid-liquid separator including a cylindrical body having a slurry inlet provided on one side for receiving the slurry from the crystallizer and an outlet provided on the other side for discharging washed crystals obtained by separating from the slurry and then squeezing and washing, wherein the cylindrical body is divided into a first region, a second region, and a third region in order from one side of the cylindrical body, the first region including an internal screw for moving the slurry supplied to the slurry inlet toward the second region, the second region including a filter for separating the crystals from the slurry and a scraping knife for crushing the washed crystals to form crushed crystals, and the third region including an outlet for discharging the crushed crystals out of the cylindrical body.

[0011] In addition, according to another aspect of the present invention, a method for purifying and recovering crystals from a solution that has completed a reaction in a reactor using the purification device is provided, comprising: (S1) supplying a compound solution that has completed a reaction in the reactor to an upper region of a crystallizer and crystallizing the solution to form a slurry containing crystals, supplying the slurry to a first region of a solid-liquid separator through a lower region of the crystallizer, (S2) moving the slurry supplied to the first region of the solid-liquid separator to a second region by an internal screw, separating the crystals and the mother liquor from the slurry through a filter provided in the second region, and discharging the mother liquor out of the solid-liquid separator, (S3) compressing the crystals separated by the filter in the second region of the solid-liquid separator to form a crystal bed, washing the crystal bed with a concentrate to form washed crystals, and crushing the washed crystals with a scraping knife to form crushed crystals, (S4) discharging the crushed crystals out of the solid-liquid separator through an outlet in a third region of the solid-liquid separator, and discharging the crushed crystals out of the solid-liquid separator. A purification method is provided, comprising: supplying and melting a concentrate to a heat supply device to form the concentrate; (S5) supplying at least a portion of the concentrate to the third zone; the pressure of the third zone is formed to be more than 1 bar to 2 bar; and the concentrate is supplied toward the second zone by an overpressure formed by the pressure of the third zone to wash the crystal bed.

[0012] The purification device according to the present invention supplies a slurry containing crystals formed in the crystallizer (20) to the solid-liquid separator (30), separates the crystals and the mother liquor in the solid-liquid separator (30), and washes the crystals to obtain purified crystals from which impurities such as the mother liquor have been removed.

[0013] The above solid-liquid separator (30) is supplied with a slurry containing crystals supplied from the crystallizer, and has regions for separating and washing the crystals from the mother liquor and discharging the washed crystals, each of which is sequentially divided, so that the slurry can pass through these regions sequentially to obtain a final product in a simple manner.

[0014] In addition, the solid-liquid separator (30) is equipped with an internal screw, a filter, and a scraping knife, so that the slurry can be separated into the crystals and the mother liquor, and the crystals can be collected and discharged.

[0015] In addition, the high-purity separator (30) can obtain a final product with higher purity by washing the crystal to remove impurities such as mother liquor.

[0016] In addition, the purification device according to the present invention configures the lower region of the crystallizer in a cone shape and combines it with a solid-liquid separator, so that when purifying a compound solution obtained through a synthetic reaction in a reactor, crystallization and solid-liquid separation of the compound can be performed within one device.

[0017] Therefore, when the crystallizer and the solid-liquid separator are combined to form an integrated device, there is no need to provide separate pipes and pumps for transporting slurry between them, so problems such as compound loss and pipe clogging that occurred during the slurry transport process in the prior art can be solved.

[0018] In addition, by uniformly distributing the slurry using oxygen to prevent slurry from accumulating at the joint of the crystallizer and the solid-liquid separator and inducing smooth discharge, clogging of the joint can be prevented.

[0019] Moreover, by maintaining the third zone of the solid-liquid separator at a pressure of more than 1 bar to 2 bar, the crystal purity can be improved by the washing effect without loss of washing liquid and without the need for an increase in the device size.

[0020] Furthermore, it is possible to reduce installation space and installation costs as well as simplify the process through a single integrated device.

[0021] Figure 1 illustrates a purification device according to one embodiment of the present invention and a process for purifying crystals from a compound solution using the same.

[0022] Figure 2 illustrates a solid-liquid separator included in a purification device according to one embodiment of the present invention.

[0023] FIG. 3 is a cross-sectional view of the width of a solid-liquid separator according to one embodiment of the present invention, illustrating a filter and a mother liquor discharge pipe.

[0024] The terms or words used in the description and claims of the present invention should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0025] The term "stream" herein may refer to the flow of fluid within a process, and may also refer to the fluid itself flowing within a moving line (pipe). Specifically, the "stream" may refer to both the fluid itself flowing within the pipe connecting each device and the flow of the fluid. Furthermore, the fluid may refer to one or more of gas, liquid, and solid.

[0026] Additionally, terms such as “include,” “contain,” “have,” or “have” are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described herein, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0027] In addition, when it is said that a component is 'connected', 'supported' or 'in contact' with another component, this includes not only cases where the components are directly connected, supported or in contact, but also cases where the components are indirectly connected, supported or in contact through a third component.

[0028] One embodiment of the present invention relates to a purification device capable of performing crystallization and solid-liquid separation of a compound within one device.

[0029] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

[0030] Figure 1 illustrates a purification device according to one embodiment of the present invention and a purification process using the same to perform crystallization and solid-liquid separation of a compound solution.

[0031] Fig. 2 illustrates in detail a solid-liquid separator included in a purification device according to one embodiment of the present invention, and Fig. 3 illustrates in detail a form in which a filter and a mother liquor discharge port are provided in the solid-liquid separator. The arrows in Fig. 3 indicate the direction in which the mother liquor passes through the filter and is discharged through the mother liquor discharge pipe (33).

[0032] According to the drawings, the purification device of the present invention comprises a crystallizer including a crystallizer upper region for supplying a compound solution to form crystals, and a crystallizer lower region provided below the crystallizer upper region for storing and discharging a slurry including crystals formed in the crystallizer upper region; and a solid-liquid separator including a cylindrical body including a slurry inlet provided on one side for supplying the slurry from the crystallizer, and an outlet provided on the other side for discharging washed crystals obtained by separating from the slurry and then washing them, wherein the cylindrical body is divided into a first region, a second region, and a third region in order from one side of the cylindrical body, the first region including an internal screw for moving the slurry supplied to the slurry inlet toward the second region, the second region including a filter for separating the crystals from the slurry and a scraping knife for crushing the washed crystals to form crushed crystals, and the third region including an outlet for discharging the crushed crystals out of the cylindrical body.

[0033] Referring to FIG. 1, the purification device of the present invention may include the crystallizer (20) and the solid-liquid separator (30), and may further include a feed tank (10) for supplying a compound solution to the crystallizer (20) as needed. The crystallizer (20) may be divided into a crystallizer upper region (20a) equipped with a stirrer to form crystals from the compound solution supplied from the feed tank (10), and a crystallizer lower region (20b) for supplying a slurry including crystals formed in the crystallizer (20) to the solid-liquid separator (30).

[0034] The crystallizer (20) is specifically provided with the crystallizer lower region (20b) below the crystallizer upper region (20a), so that the slurry formed in the crystallizer upper region (20a) can be moved to the crystallizer lower region (20b). At this time, the crystallizer upper region (20a) where the feed is supplied and crystallization takes place includes the stirrer, and can be formed in a cylinder shape having a cross-section of the same width so that the stirrer can stir. In addition, the crystallizer lower region (20b) can be formed in a cylinder shape like the crystallizer upper region, or can be formed in a cone shape whose width becomes narrower toward the bottom so that the slurry can be well collected. At this time, the lower region of the crystallizer (20b) may be the lower part of the region where the stirrer rotates, or, if the lower region of the crystallizer (20b) is cone-shaped, it may mean the lower part of the region where the stirrer rotates and the lower part from where the width of the barrel shape begins to narrow.

[0035] In one embodiment, the upper region (20a) of the crystallizer can crystallize a specific component into a solid by utilizing the difference in solubility of the components contained in the compound solution according to temperature. Specifically, the compound solution transferred from the feed tank (10) is supplied to the upper region (20a) of the crystallizer, and crystallization is performed while the compound solution is made fluid by a stirrer, thereby obtaining a slurry containing crystals of the compound contained in the compound solution.

[0036] The compound solution supplied to the upper region (20a) of the crystallizer refers to a solution containing a compound produced by a synthesis reaction in any reactor. For example, the compound solution may be a feed supplied to the crystallizer, and specifically, may be an acrylic acid aqueous solution obtained through an absorption process in which propane, propylene, etc. are subjected to a gas phase oxidation reaction in the presence of an appropriate catalyst in a reactor to obtain a gas phase stream containing acrylic acid, and then the gas phase stream is brought into contact with water in an absorption tower. In addition, a solution containing a compound used as a raw material for various resins may be applied as the compound solution in the present invention.

[0037] Additionally, when the compound solution is an acrylic acid aqueous solution, the crystal may be an acrylic crystal formed by crystallizing the acrylic acid aqueous solution.

[0038] In addition, the slurry obtained from the upper region (20a) of the crystallizer refers to a suspension in which the compound contained in the compound solution is precipitated as solid crystals and floats in the liquid mother liquor.

[0039] The stirrer installed inside the upper region (20a) of the crystallizer may have a shape including a plurality of blades, and can induce crystal formation and crystal growth while stirring the compound solution during crystallization.

[0040] In one embodiment of the present invention, the stirrer provided in the upper region (20a) of the crystallizer may be configured with a shape including a plurality of blades, and the stirring speed of the stirrer may affect crystal growth and thus determine the size of the formed crystals. In consideration of this, the stirrer may be operated at a speed of 5 to 100 rpm or 10 to 80 rpm. If the speed of the stirrer is less than 5 rpm, the circulation of the resulting crystal slurry may be limited, and if it exceeds 100 rpm, the compound crystals contained in the slurry may be broken.

[0041] In addition, the blades of the agitator have an incline, and while the agitator rotates, the slurry obtained in the upper region (20a) of the crystallizer can move to the lower region (20b) of the crystallizer by gravity. More specifically, the blades of the agitator can be rotated by being inclined at an angle of 30° to 50°, for example, 45°, and during the rotation process, the fluid receives a force in the direction of gravity, and the crystals formed in the fluid can descend downward by gravity as their density increases. The incline angle of the blades of the agitator can be an angle based on the direction of gravity with respect to the ground, and can also be an angle based on a horizontal cross section of the upper region (20a) of the crystallizer.

[0042] Meanwhile, the upper region (20a) of the crystallizer may be configured to maintain a constant liquid level. For example, the liquid may be filled without any empty space from the upper region (20a) of the crystallizer to the third region (30c) of the solid-liquid separator (30). Specifically, the compound solution supplied from the feed tank (10) of the front end to the upper region (20a) of the crystallizer using a pump is continuously supplied in an amount equal to the sum of the amount of the mother liquor discharged through the filter in the solid-liquid separator (30) of the rear end and the amount of the final product (P) discharged through the product discharge pipe, thereby maintaining the liquid level of the crystallizer (20) constant. In other words, the amount of the compound solution injected into the crystallizer (20) and the amount of the mother liquor and final product (P) discharged from the solid-liquid separator (30) (here, the amount of the final product means the amount obtained by subtracting the amount of the concentrate supplied to the third region (30c) from the amount of the washed crystals discharged from the outlet (Out)) are maintained constant, so that the liquid level of the crystallizer (20) can be maintained, and through this, the crystallizer and the solid-liquid separator can be continuously operated in a steady state.

[0043] In addition, the crystallization temperature may vary depending on the concentration of the compound solution supplied to the upper region (20a) of the crystallizer. For example, the higher the concentration of the compound in the supplied compound solution, the higher the crystallization temperature will be, and the lower the concentration of the compound contained in the compound solution, the lower the crystallization temperature will be. This crystallization temperature can be controlled to be maintained at a constant level by installing an external jacket in the upper region (20a) of the crystallizer and circulating a medium such as hot water or cooling water.

[0044] It is preferable that the crystallization in the upper region (20a) of the crystallizer be performed so that the obtained slurry satisfies a crystal content within a predetermined range. Specifically, the slurry obtained from the crystallization may contain 5 to 40 wt% or 10 to 30 wt% of solidified crystals based on its weight. If the crystal content in the slurry is less than 5 wt%, the yield of the final obtained crystals is reduced, and if it exceeds 40 wt%, the crystal content in the slurry is increased, making it difficult to mix the slurry by a stirrer in the upper region (20a) of the crystallizer and to transfer the slurry to the solid-liquid separator (30) via the lower region (20b) of the crystallizer.

[0045] In addition, the compound crystals included in the slurry may have a size of 200 to 800 μm or 300 to 700 μm, and when the size is satisfied, it is advantageous for transport in the solid-liquid separator (30).

[0046] The lower region (20b) of the crystallizer is a region where slurry containing crystals obtained from the upper region (20a) of the crystallizer is collected and discharged, and may be configured in the shape of a barrel with a constant width or a cone shape with a cross-sectional diameter that decreases as it goes down. In addition, the lower region of the crystallizer (20b) may have an open bottom, and the lower end of such an open shape may be inserted into and integrated with the slurry inlet of the solid-liquid separator. A joint O-ring may be provided between the lower end of the crystallizer lower region (20b) and the slurry inlet of the solid-liquid separator to ensure a strong connection and prevent leakage. For example, an O-ring made of chemically resistant silicone rubber may be installed to prevent leakage and be connected by fixing the inserted state.

[0047] Through this, the crystallizer (20) and the solid-liquid separator (30) can be integrated without a separate pipe connecting them, thereby solving problems such as compound loss and pipe clogging that occurred during the slurry transport process in the prior art. In addition, when the crystallizer and the solid-liquid separator are combined and integrated, there is no need to have not only the pipe connecting them but also the slurry pump required for slurry transport, thereby reducing the installation area and installation cost and realizing process simplification.

[0048] In addition, when the lower region (20b) of the crystallizer is cone-shaped, the diameter of the lowermost cross-section may be configured to have a cross-sectional diameter that is reduced by 0.05 to 0.4 times or 0.1 to 0.3 times compared to the diameter of the uppermost cross-section of the upper region (20a) of the crystallizer. When the diameter of the lowermost cross-section of the lower region (20b) of the crystallizer is less than 0.05 times the diameter of the uppermost cross-section of the upper region (20a) of the crystallizer, a clogging phenomenon may occur when the slurry moves from the lower region (20b) of the crystallizer to the solid-liquid separator (30), and when it exceeds 0.4 times, the area where the slurry is introduced into the solid-liquid separator (30), i.e., the slurry inlet area, may increase, thereby reducing the efficiency of squeezing crystals in the slurry by the internal screw.

[0049] In the integrated purification device of the present invention, the solid-liquid separator (30) may be coupled horizontally or vertically to the lower region (20b) of the crystallizer. As an example, FIG. 1 illustrates an embodiment in which the solid-liquid separator (30) is coupled while being arranged horizontally, and in this case, the long side of the solid-liquid separator (30) may be perpendicular to the crystallizer (20).

[0050] Referring again to the drawings, in the purification device according to the present invention, the solid-liquid separator (30) includes a cylindrical body, a slurry inlet provided on one side of the cylindrical body for receiving the slurry from the crystallizer, and an outlet provided on the other side of the cylindrical body for discharging crushed crystals obtained by separating from the slurry and then pressing and washing. The cylindrical body may be divided into a first region, a second region, and a third region in that order from one side of the cylindrical body, the first region including an internal screw for moving the slurry supplied to the slurry inlet toward the second region, the second region including a filter for separating the crystals from the slurry and a scraping knife for crushing the washed crystals to form crushed crystals, and the third region may include an outlet for discharging the crushed crystals out of the cylindrical body.

[0051] In addition, according to one embodiment, in the purification device of the present invention, the solid-liquid separator (30) may be coupled horizontally or vertically to the lower region (20b) of the crystallizer. As an example, FIG. 1 illustrates an embodiment in which the solid-liquid separator (30) is coupled horizontally to the lower region (20a) of the crystallizer. In this case, the long sides of the crystallizer (20) and the solid-liquid separator (30) may be vertical. When the crystallizer (20) and the solid-liquid separator (30) are coupled vertically, the slurry (or the crystal) supplied to the solid-liquid separator (30) may be moved from the first region to the third region by an internal screw provided inside the solid-liquid separator (30).

[0052] Specifically, the first region (30a) of the solid-liquid separator receives the slurry introduced through the slurry inlet (In), and the slurry can be moved toward the second region (30b) by the rotation of the internal screw. In addition, the first region (30a) can optionally include an oxygen inlet (34) to facilitate the introduction and movement of the slurry, and oxygen can be introduced through the oxygen inlet (34) connected to an external oxygen supply line.

[0053] The internal screw (S) may be configured to have spiral blades centered on a central axis and rotate by receiving power from a motor (M) to move the slurry toward the second region (30b). The internal screw (S) may be configured to rotate by having the spiral blades pivotally rotate centered on a central axis.

[0054] The internal screw may have a length from one end of the solid-liquid separator (30) to the boundary between the first and second regions, or from one end of the solid-liquid separator (30) to the region where the filter is provided. This may be a length that allows the internal screw to effectively move the slurry to the region where the filter is provided and to transmit sufficient power to the slurry and crystals (or the crystal bed and washed crystals).

[0055] The internal screw may rotate at 5 to 100 rpm or 10 to 80 rpm, taking into account the pressure of the concentrate recycled to the third region (30c), to move the slurry and compress the crystals. When the rotation speed of the internal screw is less than 5 rpm, the force for pushing the crystals inside the solid-liquid separator (30) is insufficient, and thus the crystal bed may not be sufficiently compressed. On the other hand, when the rotation speed of the internal screw exceeds 100 rpm, excessive force may be applied to the crystals, which may cause coagulation during crystal compression, and an impermeable material layer may be formed on the crystal bed, making normal operation difficult. The impermeable material layer means that the concentrate is excessively compressed to the extent that it cannot wash the crystal bed while passing between the crystal beds and the mother liquor between the crystal beds cannot escape. Therefore, when the impermeable material layer is formed, the crystal bed may not be sufficiently washed, and the purity of the washed crystals may be lowered.

[0056] Additionally, the first region (30a) may further include the oxygen inlet (34).

[0057] The oxygen inlet (34) has an opening through which oxygen can escape and is provided to surround the inner wall of the cylindrical body, and is connected to an external oxygen supply line to supply oxygen to the first region (30a). The oxygen inlet (34) is provided to prevent slurry from accumulating at the connection portion between the crystallizer (20) and the solid-liquid separator (30) by supplying oxygen to the first region (30a) while the slurry is introduced and moved in the first region (30a) of the solid-liquid separator.

[0058] Specifically, the oxygen inlet (34) is connected to an external oxygen supply line, and a certain amount of oxygen can be supplied through a pump installed in the oxygen supply line. The oxygen supplied to the oxygen inlet (34) forms bubbles in the slurry, and moves toward the crystallizer (20) due to the pressure difference between the crystallizer (20) at atmospheric pressure and the second and third regions, which are the right regions of the solid-liquid separator (30) where overpressure is formed as described below, thereby preventing slurry accumulation at the connection portion between the crystallizer (20) and the solid-liquid separator (30), thereby inducing uniform distribution and smooth discharge of the slurry.

[0059] It is preferable that the oxygen for this operation be supplied before the slurry forms a crystal bed in the solid-liquid separator (30). Therefore, it is advantageous that the oxygen inlet (34) be installed at a position close to the slurry inlet (In) in the first region (30a) of the solid-liquid separator, for example, at a middle position based on the entire length of the first region (30a), specifically, at a position of about 20% to 60% or 30% to 55% of the first region (30a) from one side of the solid-liquid separator. In addition, the oxygen inlet (34) must be installed so as not to impede the movement of the slurry within the solid-liquid separator (30), and may be formed, for example, on the inner wall surface of the cylindrical body as shown in FIG. 2.

[0060] The range of the first region (30a) may be a range capable of accommodating the internal screw having a length capable of transmitting power capable of moving the slurry, the crystal bed, and the washed crystals. The first region (30a) of the solid-liquid separator may occupy an area corresponding to 10 to 60% or 20 to 50% of the total length of the solid-liquid separator.

[0061] Meanwhile, specifically, the solid-liquid separator (30) may include the second region. The second region (30b) of the solid-liquid separator may be located between the first region (30a) and the third region (30c) as a middle region of the solid-liquid separator. The filter (31) may be provided at the front end of the second region (30b) closer to the first region (30a), and the scraping knife (32) may be provided at the end closer to the third region (30c).

[0062] Specifically, referring to FIG. 3, the filter (31) surrounds the inner wall surface of the cylindrical body and is provided along the inner wall surface of the cylindrical body, and can separate the slurry into the crystals and the mother liquor, respectively. In addition, the mother liquor separated through the filter (31) is discharged out of the solid-liquid separator (30), and the crystals can be moved toward the third region (30c) by the internal screw. In this manner, the crystals and the mother liquor are separated from the slurry, and the mother liquor that has exited the filter (31) can be discharged out of the solid-liquid separator (30) through the mother liquor discharge pipe (33) connected to the filter (31). At this time, a pump for controlling the discharge amount of the mother liquor can be installed in the mother liquor discharge pipe (33).

[0063] The above filter may be provided in the direction of the second region (30b) with the boundary between the first region (30a) and the second region (30b) as the starting point.

[0064] The above crystals can be separated from the mother liquor through the filter (31) and compressed to form the crystal bed. In the second region (30b) after the region equipped with the filter, most of the mother liquor is discharged to the filter, so that the amount of the crystals becomes relatively large, and the crystals can be compressed by the pushing force of the internal screw to form the crystal bed. The crystal bed fills the internal space of the second region (30b), and can move toward the third region (30c) by the pushing force of the internal screw. At this time, since the crystal bed is compressed to an extent that the impermeable material layer is not formed as described above, it may contain impurities including a trace amount of mother liquor remaining between the crystals forming the crystal bed, and it is necessary to wash the crystal bed to remove such impurities.

[0065] To this end, the crystal bed compressed in the second region (30b) can be washed by a concentrate supplied from the third region (30c) to form the washed crystal. The concentrate is formed by melting the pulverized crystals finally discharged from the solid-liquid separator (30), and can be discharged through an outlet (out) equipped with a product discharge valve to obtain the final product (P), but at least a portion of the concentrate can be recycled to the third region (30c) to be used to wash the crystal bed. The concentrate can be supplied to the third region (30c) to form an overpressure in the third region (30c) and flow in the opposite direction to the movement of the crystal bed, that is, from the third region (30c) toward the second region (30b), thereby washing away impurities including the residual mother liquor remaining in the crystal bed. The above overpressure means a pressure higher than atmospheric pressure, and the overpressure can be formed by the amount of the crystal bed moved from the second region (30b) to the third region (30c) by the internal screw and the flow rate of the solution recycled to the third region (30c) by controlling the valve of the final product discharge line. In other words, if the pressure formed by the flow rate of the concentrate supplied to the third region (30c) is higher than the pressure formed in the second region (30b), overpressure is formed in the third region (30c), and the crystal bed can be washed while the concentrate moves toward the second region (30b) by the pressure difference caused by the overpressure. The washed crystal formed by being washed by the concentrate can have a high purity because impurities are significantly reduced.

[0066] When the above concentrate is supplied in the direction of the second region (30b) by overpressure, a reverse flow opposite to the direction of progression of the crystal bed may be formed. At this time, a wash front (W / F), which is a boundary between the concentrate and the impurities including the residual mother liquor, may be created in the second region (30b). The impurities may include the mother liquor that was not discharged through the filter, and the reverse flow may be formed by the pressure at which the wash liquor is supplied, so that it may be discharged through the filter.

[0067] The position of the washing front may be formed between the filter and the scraping knife within the second region (30b), and the position may be adjusted by the overpressure. For example, when the overpressure is strong, the washing front may be formed close to the filter, and when the overpressure is weak, the washing front may be formed close to the scraping knife. The position of the washing front is preferably formed close to the center between the filter and the scraping knife. When the washing front is formed too close to the filter, the concentrate may be discharged to the outside through the filter, resulting in loss, and when it is formed too close to the scraping knife, the crystal bed may not be sufficiently washed, resulting in a decrease in the purity of the concentrate (or final product (P)). In the crystals accumulated in the space between the washing front and the scraping knife (32), residual mother liquor may be removed, thereby increasing the crystal purity.

[0068] The crystal bed washed with the above-described concentrate can form the above-described washed crystals. That is, the crystals present in the direction of the third region (30c) from the washing front may be washed crystals from which the impurities have been removed. The above-described concentrate may be included between the crystals forming the above-described washed crystals, but the above-described concentrate does not affect the purity as it is formed by melting the washed crystals after they are crushed. That is, by washing the above-described crystal bed with the above-described concentrate, the impurities can be removed without affecting the purity of the above-described washed crystals.

[0069] Afterwards, the washed crystals can be crushed by mechanical action caused by rotation of the scraping knife (32) and then moved to the third region (30c).

[0070] The scraping knife (32) may be positioned from the boundary between the second region (30b) and the third region (30c) to the second region (30b). The scraping knife (32) may have a plurality of blades formed from the center of the cylindrical body toward the wall surface of the cylindrical body. Specifically, the scraping knife may be a fan-shaped or rotating disk-shaped knife having blades provided inside the cylindrical body. The scraping knife (32) may rotate in place to crush the washed crystals by the blades, thereby forming crushed crystals.

[0071] The inside of the solid-liquid separator (30) is such that the slurry moves toward the third region (or the second region) by the rotation of the internal screw, the crystal bed also moves toward the third region by the pushing force of the slurry, and the washed crystals and crushed crystals can also move toward the third region (30c) by the pushing force of the crystal bed.

[0072] The second region (30b) may occupy an area corresponding to 20 to 70% or 30 to 60% of the total length of the solid-liquid separator. The starting point of the second region (30b) may be the point where the first region (30a) ends.

[0073] Meanwhile, the solid-liquid separator (30) may include the third region (30c). The third region may be provided on the other side of the cylindrical body and may include an outlet (Out) for discharging the crushed crystals out of the cylindrical body. The outlet may be connected to the heat supply device to melt the crushed crystals.

[0074] The above-mentioned crushed crystals can be transported from the third region (30c) to the heat supply device (H) through the outlet (Out). The heat supply device (H) may be a heat exchanger, and when the above-mentioned crushed crystals are supplied, the concentrated crystals are melted by heat to form a concentrate, which can be recovered as a purified final product (P).

[0075] As previously described, at least a portion of the concentrate may be recycled to the third region (30c), and the recycled concentrate may be moved toward the second region (30b) and used as a washing liquid to remove impurities remaining in the crystal bed. Since the concentrate is a melt of the pulverized crystals, the purity of the concentrate and the pulverized crystals may be the same.

[0076] The flow rate of the concentrate recycled to the third region (30c) of the solid-liquid separator can be controlled to an extent that the content of the washed crystals (or crushed crystals) is maintained at an appropriate level.

[0077] Meanwhile, the crushed crystals can be moved in the form of a slurry containing the crushed crystals in the concentrate to maintain flowability in the third region (30c), and the flow rate of the concentrate can be controlled so that the content of the crushed crystals contained in the concentrate is maintained at an appropriate level.

[0078] The flow rate of the concentrate may affect the pressure formed in the third region (30c). The third region (30c) of the solid-liquid separator may form an overpressure of more than 1 bar to 2 bar or more than 1 bar to 1.5 bar in order to maintain a uniform reverse flow of the recirculated concentrate and thereby enhance the washing effect. When the overpressure is less than 1 bar, it is difficult for the reverse flow of the concentrate to occur, and the washing front portion is formed close to the scraping night, making it difficult to expect an improvement in purity through the washing effect. On the other hand, when the overpressure exceeds 2 bar, the reverse flow is excessively formed, causing the washing front portion to be formed close to the filter, and the concentrate may move toward the filter, resulting in a loss of the concentrate. In addition, when the overpressure exceeds 2 bar, the amount of the recirculated concentrate increases, thereby reducing the amount of the final product (P), and the size of the purification device may increase to obtain a desired production volume, which may be economically disadvantageous.

[0079] The third region (30c) of the solid-liquid separator may occupy an area corresponding to 3 to 20%, or 5 to 15%, of the entire length of the solid-liquid separator. The starting point of the third region (30b) may be the point where the second region (30a) ends.

[0080] Additionally, the interior of the solid-liquid separator (30) may be maintained with insulation to promote smooth movement of the slurry and crystal separation efficiency. For example, the exterior of the solid-liquid separator (30) may be manufactured in the form of a jacket to form a vacuum state, thereby minimizing heat loss and maintaining insulation.

[0081] The purification device of the present invention as described above can supply crystals formed in the crystallizer (20) to the solid-liquid separator (30), separate the crystals and mother liquor in the solid-liquid separator (30), and wash the crystals to obtain purified crystals from which impurities such as the mother liquor have been removed.

[0082] The above solid-liquid separator (30) is supplied with a slurry containing crystals supplied from the crystallizer, and has regions for separating and washing the crystals from the mother liquor and discharging the washed crystals, each of which is sequentially divided, so that the slurry can pass through these regions sequentially to obtain a final product in a simple manner.

[0083] In addition, the solid-liquid separator (30) is equipped with an internal screw, a filter, and a scraping knife, so that the slurry can be separated into the crystals and the mother liquor, and the crystals can be collected and discharged.

[0084] In addition, the high-purity separator (30) can obtain a final product with higher purity by washing the crystal to remove impurities such as mother liquor.

[0085] In addition, the purification device of the present invention as described above can form an integrated device by configuring the lower region (20b) of the crystallizer in a cone shape and combining it with the solid-liquid separator (30), and can perform crystallization and solid-liquid separation within one device.

[0086] When the above crystallizer (20) and solid-liquid separator (30) are combined, there is no need to provide separate pipes and pumps for transporting slurry between them, so problems such as compound loss and pipe clogging that occurred during the slurry transport process in the prior art can be solved.

[0087] Additionally, it is possible to reduce installation space and installation costs as well as simplify the process through a single integrated device.

[0088] In addition, according to one embodiment, the present invention further provides a method for purifying a compound solution, which is a solution supplied after completing a reaction in a reactor using the purification device.

[0089] The purification method comprises: (S1) supplying a compound solution that has completed a reaction in a reactor to an upper region of a crystallizer and crystallizing the solution to form a slurry containing crystals, supplying the slurry to a first region of a solid-liquid separator having first to third regions in sequence through a lower region of the crystallizer, (S2) moving the slurry supplied to the first region of the solid-liquid separator to the second region by rotating an internal screw, separating the crystals and the mother liquor from the slurry through a filter provided in the second region, and discharging the mother liquor out of the solid-liquid separator, (S3) compressing the crystals separated by the filter in the second region of the solid-liquid separator to form a crystal bed, washing the crystal bed with a concentrate to form washed crystals, and crushing the washed crystals with a scraping knife to form crushed crystals, (S4) discharging the crushed crystals out of the solid-liquid separator through an outlet in the third region of the solid-liquid separator, and supplying the crushed crystals to a heat supply device to melt them. A purification method comprising forming a concentrate, (S5) supplying at least a portion of the concentrate to the third zone, wherein the pressure of the third zone is formed to be greater than 1 bar to 2 bar, and the concentrate is supplied toward the second zone by an overpressure formed by the pressure of the third zone to wash the crystal bed.

[0090] In addition, the purification method according to the present invention can prevent accumulation of slurry at the connection portion between the solid-liquid separator (30) and the crystallizer (20) by introducing oxygen into the first region (30a) of the solid-liquid separator and moving it toward the crystallizer.

[0091] In the purification method according to one embodiment of the present invention, the description of the crystallizer (20), the solid-liquid separator (30) and the combination thereof is the same as the purification device according to the present invention described above within the overlapping range.

[0092] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present invention, and the scope of the present invention is not limited to these examples alone.

[0093] Example 1:

[0094] As illustrated in Fig. 1, compound purification was performed using a purification device in which a crystallizer (20) and a solid-liquid separator (30) are integrated.

[0095] Specifically, an acrylic acid solution containing acrylic acid (98 wt%), acetic acid (1 wt%), and water (1 wt%) was supplied as a compound solution feed to the upper region (20a) of the crystallizer and crystallized to obtain a slurry containing compound crystals, and then the slurry was introduced into the first region (30a) of the solid-liquid separator through the cone-shaped lower region (20b) of the crystallizer.

[0096] The slurry introduced into the first region (30a) of the solid-liquid separator was moved by the internal screw (S), and the mother liquor was discharged through the filter (31) included in the second region (30b) to separate the crystals. At this time, the internal screw was rotated at 40 rpm.

[0097] In the second region (30b) of the solid-liquid separator, the crystals separated by the filter (31) were pressed by the internal screw to form a crystal bed. The crystal bed was washed with the concentrate transferred from the third region (30c) to form washed crystals, and the washed crystals were crushed by a scraping knife (32) in the form of a rotating disk to form crushed crystals, which were then moved to the third region (33c). While maintaining the pressure of the third region (33c) at 1.1 to 1.2 bar, the crushed crystals were melted while passing through the heat supply device (H) via the outlet (Out) to form a concentrate. A portion of the concentrate was supplied to the third region (30c), and the remainder was obtained as a purified final product (P).

[0098] Examples 2 to 3 and Comparative Example 1:

[0099] The same process as Example 1 was performed except that the pressure in the third region in the solid-liquid separator was changed as shown in Table 1.

[0100] Pressure (bar) of the third zone in the solid-liquid separator Composition of the final product Acrylic acid (wt%) Acetic acid (wt%) Water (wt%) Example 11.1-1.29 9.48 0.33 0.19 Example 212-1.39 9.5 0.27 0.23 Example 31.3-1.49 9.6 30.21 0.16 Comparative example 1198.5 30.76 0.71

[0101] As can be seen in Table 1 above, Examples 1 to 3, in which the third zone in the solid-liquid separator combined with the crystallizer maintained a pressure exceeding 1 bar, induced a reverse flow of the washing liquid due to overpressure, thereby improving crystal purity, whereas in Comparative Example 1, since the pressure in the third zone was 1 bar, the reverse flow of the washing liquid did not occur, resulting in a decrease in the crystal purity of the acrylic acid included in the final product. On the other hand, when the pressure in the third zone in the solid-liquid separator exceeds 2 bar, although the crystal purity in the final product can be improved, there is a loss of the concentrate moving from the third zone (30c) toward the second zone (30b), and since the amount of the concentrate recycled increases, there is a limitation that the size of the purification device must be expanded to obtain a desired production volume, which is not preferable.

[0102] [Explanation of symbols]

[0103] 10: Feed tank

[0104] 20: Crystallizer, 20a: Upper crystallizer area, 20b: Lower crystallizer area

[0105] 30: solid-liquid separator, 30a: first zone, 30b: second zone, 30c: third zone

[0106] 31: Filter, 32: Scraping knife, 33: Mother liquor discharge pipe

[0107] 34: Oxygen inlet, S: Internal screw

[0108] In: slurry inlet, Out: outlet,

[0109] H: Heat supply device

Claims

1. A crystallizer comprising a crystallizer upper region for forming crystals by supplying a compound solution, and a crystallizer lower region provided below the crystallizer upper region for storing and discharging a slurry containing crystals formed in the crystallizer upper region; and A solid-liquid separator comprising a cylindrical body including a slurry inlet provided on one side to receive the slurry from the crystallizer and an outlet provided on the other side to discharge crushed crystals obtained by separating from the slurry, pressing, and washing, An integrated purification device in which the cylindrical body is divided into a first region, a second region, and a third region in order from one side of the cylindrical body, the first region including an internal screw that moves the slurry supplied to the slurry inlet toward the second region, the second region including a filter that separates the crystals from the slurry and a scraping knife that crushes the washed crystals to form crushed crystals, and the third region includes an outlet that discharges the crushed crystals out of the cylindrical body.

2. In paragraph 1, Further comprising a heat supply device connected to the above outlet, The above crushed crystals are melted in the heat supply device to form a concentrate, An integrated purification device wherein at least a portion of the concentrate is supplied to the third region to wash the crystal bed formed in the second region by compressing the crystals to form the washed crystals.

3. In paragraph 2, The pressure of the third region is formed to be more than 1 bar to 2 bar, An integrated purification device comprising the above concentrate being supplied toward the second region by overpressure formed by the pressure of the third region to wash the crystal bed.

4. In paragraph 1, The lower region of the crystallizer is a cone shape that narrows as it goes down. An integrated purification device having a lower region of the crystallizer having the above cone shape and having a form combined with the slurry inlet of the solid-liquid separator.

5. In paragraph 4, An integrated purification device in which the diameter of the lowest cross-section of the lower region of the crystallizer is 0.05 to 0.4 times the diameter of the uppermost cross-section of the upper region of the crystallizer.

6. In paragraph 1, An integrated purification device wherein the slurry formed in the upper region of the crystallizer comprises 5 to 40 wt% of the crystals based on the weight of the slurry.

7. In paragraph 1, The first region further includes an oxygen inlet, The above oxygen inlet is an integrated purification device that supplies oxygen to the first region to prevent accumulation of the slurry.

8. In paragraph 1, The filter is provided in the second region from the boundary between the first region and the second region, An integrated purification device having a shape that surrounds the inner wall of the cylindrical body in a circular shape and separates the slurry into the crystals and the mother liquor.

9. In paragraph 1, The above internal screw is an integrated purification device that rotates by a motor provided at one end of the cylindrical body.

10. In paragraph 1, The above internal screw is an integrated purification device that rotates at a speed of 5 to 100 rpm. 11.(S1) The compound solution that has completed the reaction in the reactor is supplied to the upper region of the crystallizer and crystallized to form a slurry containing crystals, and the slurry is supplied to the first region of the solid-liquid separator sequentially provided with the first region to the third region through the lower region of the crystallizer. (S2) The slurry supplied to the first region of the solid-liquid separator is moved to the second region by rotating the internal screw, and the crystals and mother liquor are separated from the slurry through a filter provided in the second region, and the mother liquor is discharged out of the solid-liquid separator. (S3) In the second region of the solid-liquid separator, the crystals separated by the filter are pressed to form a crystal bed, the crystal bed is washed with a concentrate to form washed crystals, and the washed crystals are crushed by a scraping knife to form crushed crystals. (S4) In the third region of the solid-liquid separator, the crushed crystals are discharged out of the solid-liquid separator through an outlet, and the crushed crystals are supplied to a heat supply device to melt them and form the concentrate. (S5) comprising supplying at least a portion of the above concentrate to the third region; The pressure of the third region is formed to be more than 1 bar to 2 bar, A purification method comprising supplying the concentrate toward the second region by overpressure formed by the pressure of the third region to wash the crystal bed.

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