Integrated purification apparatus for crystallization and solid-liquid separation

Abstract

Provided are an integrated purification apparatus and a purification method using the same, the integrated purification apparatus including: a crystallizer including an upper region of the crystallizer and a lower region of the crystallizer, wherein the upper region of the crystallizer is supplied with a compound solution to form crystals, and the lower region of the crystallizer is disposed below the upper region of the crystallizer and stores and discharges slurry containing the crystals formed in the upper region of the crystallizer; and a solid-liquid separator including a cylinder including a slurry inlet disposed at one side and supplied with the slurry from the crystallizer, and an outlet disposed at the other side and discharging ground crystals obtained by separating and then compressing and washing the slurry, wherein the cylinder is divided into a first region, a second region, and a third region in order from one side of the cylinder.

Description

[0001] Cross-references to related applications

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

[0003] This invention relates to an integrated purification device that combines a crystallizer and a solid-liquid separator. Background Technology

[0004] Compounds used as raw materials for various resins can be prepared by obtaining a solution containing the compound through a synthetic reaction, followed by a subsequent process of purifying the compound from the solution.

[0005] For example, acrylic acid undergoes a gas-phase oxidation reaction with propane, propylene, etc., in a reactor in the presence of a suitable catalyst to obtain a gas stream containing acrylic acid. This gas stream is then subjected to an absorption process to contact water in an absorption tower to obtain an aqueous solution of acrylic acid. Subsequently, the aqueous solution of acrylic acid can be crystallized and subjected to solid-liquid separation to purify the acrylic acid.

[0006] Crystallization is a process that utilizes the difference in solubility of materials in a liquid mixture with temperature to precipitate compounds into solids and transforms the solution in which the compound is dissolved in the solvent into a slurry suspension in which the solid crystalline compound floats in the residual liquid (mother liquor).

[0007] Solid-liquid separation is a process used to separate compound crystals formed during crystallization from residual liquids. It can be performed using devices such as washing columns, centrifuges, and filters. In particular, washing columns are effective for separating compound crystals from the mother liquor and can also remove residual liquids and impurities contained in the separated compound crystals through washing, making them suitable for processes requiring high and ultra-high purity. Summary of the Invention

[0008] Technical issues

[0009] The present invention aims to solve the problems mentioned in the background art, and one object of the present invention is to provide a purification apparatus that can solve the problem of pipeline blockage in slurry transportation in compound crystallization and solid-liquid separation processes, and to provide a method for preparing compounds in high yield.

[0010] Technical solution

[0011] In one general aspect, an integrated purification apparatus includes: a crystallizer comprising an upper region and a lower region, wherein the upper region is supplied with a compound solution to form crystals, and the lower region is disposed below the upper region and stores and discharges a slurry containing the crystals formed in the upper region; and a solid-liquid separator comprising a cylinder including a slurry inlet disposed on one side and supplied with slurry from the crystallizer, and an outlet disposed on the other side and discharging washed crystals obtained by separating, compressing, and washing the slurry, wherein the cylinder is sequentially divided from one side into a first region, a second region, and a third region, the first region including an internal screw for moving 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 scraper for grinding the washed crystals to form ground crystals, and the third region including an outlet for discharging the ground crystals to the outside of the cylinder.

[0012] In another general aspect, a purification method, namely a method for purifying and recovering crystals from a solution in which a reaction has been completed in a reactor using the purification apparatus, comprises: (S1) supplying a compound solution after reaction in the reactor to an upper region of a crystallizer and crystallizing the compound to form a slurry containing crystals, supplying the slurry through a lower region of the crystallizer to a first region of a solid-liquid separator; (S2) moving the slurry supplied to the first region of the solid-liquid separator to a second region by means of an internal screw, separating the crystals and mother liquor from the slurry separately by means of a filter disposed in the second region, discharging the mother liquor from the solid-liquid separator; and (S3) compressing the solid-liquid separator. The crystals separated by the filter in the second region of the solid-liquid separator are used to form a crystal bed. The crystal bed is washed with a concentrate to form washed crystals, and the washed crystals are ground with a scraper to form ground crystals. (S4) The ground crystals in the third region of the solid-liquid separator are discharged from the solid-liquid separator through an outlet. The ground crystals are supplied to a heating device to melt the crystals to form the concentrate. (S5) At least a portion of the concentrate is supplied to the third region, wherein the pressure in the third region is set to be greater than 1 bar and not greater than 2 bar, and the concentrate is supplied to the second region through an overpressure formed by the pressure in the third region to wash the crystal bed.

[0013] Beneficial effects

[0014] In the purification apparatus according to the invention, a slurry containing crystals formed in a crystallizer 20 is supplied to a solid-liquid separator 30, in which the crystals and mother liquor are separated, and the crystals are washed so that purified crystals with impurities such as mother liquor removed can be obtained.

[0015] The solid-liquid separator 30 is divided into the following areas in sequence: a region that supplies slurry containing crystals from the crystallizer, a region that separates and washes the crystals from the mother liquor, and a region that discharges the washed crystals, so that the slurry can pass through these regions in sequence and the final product can be obtained by a simple method.

[0016] Furthermore, the solid-liquid separator 30 is equipped with an internal screw, filter, and scraper, enabling the separation of slurry into crystals and mother liquor, as well as the collection and discharge of crystals.

[0017] In addition, in the solid-liquid separator 30, the crystals are washed to remove impurities, such as mother liquor, thereby obtaining a final product with higher purity.

[0018] Furthermore, in the purification apparatus according to the invention, the lower region of the crystallizer is formed in a conical shape and combined with a solid-liquid separator, so that when purifying the compound solution obtained by the synthesis reaction in the reactor, the crystallization and solid-liquid separation of the compound are carried out in one apparatus.

[0019] Therefore, when an integrated device is formed by combining a crystallizer and a solid-liquid separator, separate pipes and pumps for conveying slurry between them are not required, thus solving problems such as compound loss and pipe blockage that occur during slurry conveying in conventional technologies.

[0020] In addition, oxygen is used to distribute the slurry evenly so that it can be discharged smoothly, preventing the slurry from accumulating at the junction of the crystallizer and the solid-liquid separator, thereby preventing blockage at the junction.

[0021] In addition, the third zone of the solid-liquid separator is maintained at a bar greater than 1 bar and no greater than 2 bar, thereby improving crystal purity through the washing effect without losing washing liquid and increasing device size.

[0022] Furthermore, an integrated device can reduce installation area and costs, and also simplify the process. Attached Figure Description

[0023] Figure 1 A purification apparatus according to an exemplary embodiment of the present invention and a process for purifying crystals from a compound solution using the apparatus are shown.

[0024] Figure 2A solid-liquid separator is shown in a purification apparatus according to an exemplary embodiment of the present invention.

[0025] Figure 3 This is a cross-section of the width of a solid-liquid separator according to an exemplary embodiment of the present invention, and shows the filter and the mother liquor discharge pipe. Detailed Implementation

[0026] Based on the principle that inventors can appropriately define the concepts of terms in order to best describe their own inventions, the terms and words used in the specification and claims of this invention should not be limited to having a general or dictionary meaning, but are to be interpreted as having a meaning and concept that satisfies the technical concept of this invention.

[0027] In this application, the term "flow" can refer to a fluid flow in a process, or it can refer to the fluid itself flowing in a moving pipeline (pipeline). Specifically, "flow" can refer to both the fluid itself flowing in the pipes connecting each device and the fluid flow. Additionally, fluid can refer to any one or more of gases, liquids, and solids.

[0028] Furthermore, terms such as “comprising,” “including,” “equipped with,” or “having” are intended to indicate the presence of the stated features, numbers, steps, operations, constituent elements, components, or combinations thereof in this application, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, constituent elements, components, or combinations thereof.

[0029] In addition, when describing a constituent element as being "connected", "supported", or "in contact" with other constituent elements, it includes not only cases where the constituent elements are directly connected, supported, or in contact, but also cases where they are indirectly connected, supported, or in contact through a third constituent element.

[0030] An exemplary embodiment of the present invention relates to a purification apparatus that can perform crystallization and solid-liquid separation of compounds in one device.

[0031] In the following, specific exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0032] Figure 1 A purification apparatus according to an exemplary embodiment of the present invention and a purification process for crystallizing and separating a compound solution using the apparatus are shown.

[0033] Figure 2 A solid-liquid separator included in a purification apparatus according to an exemplary embodiment of the present invention is shown in detail. Figure 3 The arrangement of the filter and mother liquor outlet in the solid-liquid separator is shown in detail. Figure 3In the image, the arrow indicates the direction in which the mother liquor passes through the filter and is discharged through the mother liquor discharge pipe 33.

[0034] According to the accompanying drawings, the purification apparatus of the present invention includes: a crystallizer comprising an upper region and a lower region, the upper region of the crystallizer being supplied with a compound solution to form crystals, the lower region of the crystallizer being disposed below the upper region of the crystallizer and storing and discharging a slurry containing crystals formed in the upper region of the crystallizer; and a solid-liquid separator comprising a cylinder, the cylinder including a slurry inlet disposed on one side and supplied with slurry from the crystallizer, and an outlet disposed on the other side and discharging washed crystals obtained by separating and then washing the slurry, wherein the cylinder is sequentially divided into a first region, a second region, and a third region from one side of the cylinder, 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 scraper for grinding the washed crystals to form ground crystals, and the third region including an outlet for discharging the ground crystals to the outside of the cylinder.

[0035] Reference Figure 1 The purification apparatus of the present invention may include a crystallizer 20 and a solid-liquid separator 30, and, if necessary, further include a feed tank 10 for supplying a compound solution to the crystallizer 20. The crystallizer 20 may be divided into an upper region 20a and a lower region 20b, wherein the upper region 20a is provided with a stirrer for forming crystals from the compound solution supplied by the feed tank 10; the lower region 20b supplies the slurry containing crystals formed in the crystallizer 20 to the solid-liquid separator 30.

[0036] Specifically, in the crystallizer 20, the lower region 20b of the crystallizer is located below the upper region 20a of the crystallizer, allowing the slurry formed in the upper region 20a to move to the lower region 20b. Here, the upper region 20a of the crystallizer, which receives feed and crystallizes, includes an agitator and can be formed into a barrel shape with a uniform cross-section, allowing the agitator to stir. Furthermore, the lower region 20b of the crystallizer can be formed into a barrel shape similar to the upper region of the crystallizer, or it can be formed into a cone shape with a width that narrows downwards to facilitate slurry collection. Here, the lower region 20b of the crystallizer can be the lower part of the area where the agitator rotates, or when the lower region 20b of the crystallizer has a cone shape, it can refer to the lower part of the area where the agitator rotates, and the portion that narrows from the width of the barrel shape to the lower part.

[0037] In one exemplary embodiment, the upper region 20a of the crystallizer can utilize the temperature-dependent solubility differences of the components contained in the compound solution to crystallize specific components into solids. Specifically, in the upper region 20a of the crystallizer, a compound solution supplied from the feed tank 10 is provided, and crystallization occurs while the compound solution is being circulated by a stirrer, thereby obtaining a slurry containing crystals of the compounds contained in the compound solution.

[0038] The compound solution supplied to the upper region 20a of the crystallizer refers to a solution containing compounds produced by a synthesis reaction in any reactor. As an example, the compound solution can be the feed supplied to the crystallizer, specifically an aqueous solution of acrylic acid obtained by an absorption process in which propane, propylene, etc., are subjected to a gas-phase oxidation reaction in the presence of a suitable catalyst in a reactor to obtain an acrylic acid-containing gas stream, which is then contacted with water in an absorption tower. Furthermore, solutions containing compounds used as raw materials for various resins can be used as the compound solution of this invention.

[0039] Furthermore, when the compound solution is an aqueous solution of acrylic acid, the crystals can be acrylic acid crystals formed by crystallizing the aqueous solution of acrylic acid.

[0040] Furthermore, the slurry obtained in the upper region 20a of the crystallizer refers to a suspension in which the compound contained in the compound solution precipitates as solid crystals and floats in the liquid mother liquor.

[0041] The stirrer installed in the upper region 20a of the crystallizer can have a shape including multiple blades and can induce crystal formation and crystal growth while stirring the compound solution during crystallization.

[0042] In one exemplary embodiment of the invention, the stirrer disposed in the upper region 20a of the crystallizer may be configured to include a plurality of blades, and the stirring speed of the stirrer affects crystal growth to determine the size of the formed crystals. Considering this fact, the stirrer may operate at speeds of 5 rpm to 100 rpm or 10 rpm to 80 rpm. When the stirrer speed is less than 5 rpm, the circulation of the resulting crystal slurry may be limited, and when the speed is greater than 100 rpm, the compound crystals contained in the slurry may break.

[0043] Furthermore, the impeller blades of the agitator can have an inclination angle, and during the rotation of the agitator, the slurry obtained in the upper region 20a of the crystallizer can be moved to the lower region 20b of the crystallizer by gravity. More specifically, the impeller blades of the agitator can be configured to rotate at an inclination angle of 30° to 50° (e.g., 45°), and during rotation, the fluid is forced to flow in the direction of gravity, and the crystals generated in the fluid fall due to gravity, increasing in density. The inclination angle of the agitator blades can be based on the angle relative to the direction of gravity relative to the ground, and can also be based on the angle of the horizontal cross-section of the upper region 20a of the crystallizer.

[0044] Simultaneously, the upper region 20a of the crystallizer can be configured to maintain a constant liquid level. For example, the space from the upper region 20a of the crystallizer to the third region 30c of the solid-liquid separator 30 can be filled with liquid without any empty space. Specifically, the compound solution supplied from the feed tank 10 at the front end to the upper region 20a of the crystallizer using a pump is a combined amount of mother liquor discharged through the filter in the solid-liquid separator 30 and the final product (P) discharged through the product discharge pipe, and is continuously supplied to maintain a constant liquid level in the crystallizer 20. That is, the amount of compound solution added to the crystallizer 20, the amount of mother liquor discharged from the solid-liquid separator 30, and the amount of the final product (P) (wherein the amount of the final product is obtained by subtracting the amount of concentrate supplied to the third region 30c from the amount of washed crystals discharged from the outlet) are kept constant to maintain the liquid level in the crystallizer 20, which allows the crystallizer and the solid-liquid separator to operate continuously in a stable state.

[0045] Furthermore, the crystallization temperature can be varied according to 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; the lower the concentration of the compound in the compound solution, the lower the crystallization temperature. By installing an outer jacket in the upper region 20a of the crystallizer and circulating a medium such as warm water or cooling water, the crystallization temperature can be regulated to maintain a constant level.

[0046] Preferably, crystallization takes place in the upper region 20a of the crystallizer, resulting in a slurry with a crystal content within a predetermined range. Specifically, based on the weight of the slurry, the slurry obtained from crystallization may contain 5% to 40% by weight or 10% to 30% by weight of solidified crystals. When the crystal content in the slurry is less than 5% by weight, the yield of the final crystals decreases; when the crystal content is greater than 40% by weight, the increased crystal content in the slurry makes it difficult to mix the slurry in the upper region 20a of the crystallizer by a stirrer and to convey the slurry through the lower region 20b of the crystallizer to the solid-liquid separator 30.

[0047] Furthermore, the compound crystals contained in the slurry can have a size of 200 μm to 800 μm or 300 μm to 700 μm, and when this size is met, it is advantageous for conveying to the solid-liquid separator 30.

[0048] The lower region 20b of the crystallizer is the area for collecting and discharging the slurry containing crystals obtained in the upper region 20a of the crystallizer, and can be formed into a barrel shape with a constant width or a cone shape with a downwardly decreasing cross-sectional diameter. Additionally, the lower region 20b of the crystallizer can have a shape with an open lower end, and this open lower end can be inserted into and integrated into the slurry inlet of the solid-liquid separator. A joint O-ring for reinforcing the connection and preventing leakage can be provided between the lower end of the lower region 20b of the crystallizer and the slurry inlet of the solid-liquid separator; for example, the connection can be achieved by installing an O-ring made of chemically resistant silicone rubber material to prevent leakage and fixing it in the inserted state.

[0049] Therefore, since the crystallizer 20 and the solid-liquid separator 30 can be integrated without separate piping connecting them, problems such as compound loss or pipe blockage caused in conventional slurry conveying processes can be solved. Furthermore, when the crystallizer and solid-liquid separator are integrated, there is no need to install slurry pumps and connecting pipes required for slurry conveying, and the installation area and costs can be reduced, thereby simplifying the process.

[0050] Furthermore, when the lower region 20b of the crystallizer has a conical shape, the diameter of the lowest cross-section can be reduced to 0.05 to 0.4 times or 0.1 to 0.3 times the diameter of the highest cross-section of the upper region 20a of the crystallizer. When the diameter of the lowest cross-section of the lower region 20b of the crystallizer is less than 0.05 times the diameter of the highest cross-section of the upper region 20a of the crystallizer, blockage may occur when the slurry moves from the lower region 20b of the crystallizer to the solid-liquid separator 30; when it is greater than 0.4 times, the area of ​​slurry added to the solid-liquid separator 30, i.e., the slurry inlet area, increases, thereby reducing the compression efficiency of the internal screw on the crystals in the slurry.

[0051] In the integrated purification apparatus of the present invention, the solid-liquid separator 30 can be combined with the lower region 20b of the crystallizer in a horizontal or vertical direction. As an example, Figure 1 An embodiment of a solid-liquid separator 30 arranged and combined in a horizontal direction is shown, in which the long side of the solid-liquid separator 30 may be perpendicular to the crystallizer 20.

[0052] Referring again to the accompanying drawings, in the purification apparatus according to the invention, the solid-liquid separator 30 includes: a cylinder, a slurry inlet disposed on one side of the cylinder and supplied with slurry from a crystallizer, and an outlet disposed on the other side of the cylinder and discharging ground crystals obtained by separation from the slurry followed by compression and washing. The cylinder is divided into a first region, a second region, and a third region from one side; the first region may include an internal screw that moves the slurry supplied to the slurry inlet toward the second region; the second region may include a filter for separating crystals from the slurry and a scraper for grinding and washing the crystals to form ground crystals; and the third region may include an outlet discharging the ground crystals from the cylinder.

[0053] Furthermore, according to an exemplary embodiment, in the purification apparatus of the present invention, the solid-liquid separator 30 can be combined with the lower region 20b of the crystallizer in a horizontal or vertical direction. As an example, Figure 1 An embodiment is shown in which a solid-liquid separator 30 is horizontally coupled to the lower region 20a of a crystallizer. In this case, the long sides of the crystallizer 20 and the solid-liquid separator 30 can be perpendicular. When the crystallizer 20 and the solid-liquid separator 30 are vertically coupled, the slurry (or crystals) supplied to the solid-liquid separator 30 can be moved from the first region to the third region by an internal screw disposed within the solid-liquid separator 30.

[0054] Specifically, the first region 30a of the solid-liquid separator contains 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. Furthermore, the first region 30a may optionally include an oxygen inlet port 34 for efficient introduction and movement of the slurry, and oxygen can be introduced through the oxygen inlet port connected to an external oxygen supply line.

[0055] The internal screw (S) has the shape of a propeller blade set based on a central axis and can be rotated by receiving power from a motor (M), thereby moving the slurry in the direction of the second region 30b. The internal screw (S) can be rotated by the axial rotation of the propeller blade based on the central axis.

[0056] The internal screw may have a length extending 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 located. This length may be such that the internal screw can effectively move the slurry to the region with the filter and can transmit sufficient power to the slurry and crystals (or crystal bed and washed crystals).

[0057] Considering the pressure of the concentrate recirculated to the third zone 30c, the internal screw can move the slurry and compress the crystals while rotating at 5 rpm to 100 rpm or 10 rpm to 80 rpm. When the internal screw rotates at less than 5 rpm, the force pushing the crystals within the solid-liquid separator 30 is insufficient, making it possible for the crystal bed to be adequately compressed. Simultaneously, when the internal screw rotates at more than 100 rpm, excessive force is applied to the crystals, causing agglomeration during crystal compression and the formation of an impermeable material layer within the crystal bed, thus hindering operation. This impermeable material layer means it is overcompressed, preventing the concentrate from washing the crystal bed as it passes through, and preventing the mother liquor between the crystal beds from escaping. Therefore, when an impermeable material layer forms, the crystal bed cannot be adequately washed, and the purity of the washed crystals may be reduced.

[0058] Additionally, the first region 30a may further include an oxygen input port 34.

[0059] The oxygen inlet port 34 has an opening through which oxygen can enter and is configured to surround the inner wall of the cylinder, but is connected to an external oxygen supply line to supply oxygen to the first region 30a. The oxygen inlet port 34 is used to prevent slurry from accumulating at the connection between the crystallizer 20 and the solid-liquid separator 30 by supplying oxygen to the first region 30a while introducing and moving the slurry in the first region 30a of the solid-liquid separator.

[0060] Specifically, the oxygen inlet port 34 is connected to an external oxygen supply line, and a certain amount of oxygen can be supplied by a pump installed in the oxygen supply line. The oxygen supplied to the oxygen inlet port 34 forms bubbles in the slurry, and moves towards the crystallizer 20 due to the pressure difference between the crystallizer 20 at atmospheric pressure and the right side region of the solid-liquid separator 30 (described later as overpressurized), i.e., the second and third regions. This prevents the slurry from accumulating at the connection between the crystallizer 20 and the solid-liquid separator 30, thereby achieving uniform distribution and smooth discharge of the slurry.

[0061] Preferably, the oxygen for this action is supplied before the slurry forms a crystal bed in the solid-liquid separator 30. Therefore, it is advantageous that the oxygen inlet port 34 is installed in the first region 30a of the solid-liquid separator near the slurry inlet (In), for example, at the midpoint of the total length of the first region 30a, specifically at 20% to 60% or 30% to 55% of the length of the first region 30a from one side of the solid-liquid separator. Furthermore, the oxygen inlet port 34 should be installed such that the movement of the slurry within the solid-liquid separator 30 is unimpeded, and for example, as... Figure 2 As shown. It can be formed on the inner surface of a cylinder.

[0062] The first region 30a can be an area that accommodates an internal screw with a length capable of transmitting power for moving the slurry, crystal bed, and washing the crystals. The first region 30a of the solid-liquid separator can occupy an area corresponding to 10% to 60% or 20% to 50% of the total length of the solid-liquid separator.

[0063] Specifically, the solid-liquid separator 30 may include a second region. The second region 30b of the solid-liquid separator is the middle region of the solid-liquid separator and may be located between the first region 30a and the third region 30c. In the second region 30b, a filter 31 may be provided near the front end of the first region 30a, and a scraper 32 may be provided near the rear end of the third region 30c.

[0064] Specifically, refer to Figure 3 The filter 31 is disposed along and surrounds the inner wall surface of the cylinder, and can separate the slurry into crystals and mother liquor. Furthermore, the mother liquor separated by the filter 31 can be discharged from the solid-liquid separator 30, and the crystals can be moved towards the third region 30c by an internal screw. Crystals and mother liquor can be separated from the slurry in this way, and the mother liquor passing through the filter 31 can be discharged from the solid-liquid separator 30 through a mother liquor discharge pipe 33 connected to the filter 31. Here, a pump for adjusting the mother liquor discharge rate can be installed in the mother liquor discharge pipe 33.

[0065] The filter can be set from the boundary between the first region 30a and the second region 30b, along the direction of the second region 30b.

[0066] The crystals are separated from the mother liquor by filter 31 and compressed to form a crystal bed. In the second region 30b, following the region with the filter, most of the mother liquor is discharged through the filter, the amount of crystals increases, and the crystals can be compressed by the force driven by the internal screw to form a crystal bed. The crystal bed fills the internal space of the second region 30b and can be moved towards the third region 30c by the force driven by the internal screw. Here, because the crystal bed is compressed so that an impermeable material layer as described above is not formed, it may contain impurities, including a small amount of mother liquor remaining between the crystals forming the crystal bed. To remove these impurities, the crystal bed needs to be washed.

[0067] To this end, the compressed crystal bed in the second region 30b is washed with a concentrate supplied from the third region 30c to form washed crystals. The concentrate is formed by melting the ground crystals that are ultimately 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). However, at least a portion of the concentrate can be recycled back to the third region 30c and used to wash the crystal bed. The concentrate is supplied to the third region 30c to create overpressure in the third region 30c and can flow in the opposite direction of the crystal bed movement, i.e., from the third region 30c to the second region 30b, washing away impurities including residual mother liquor remaining in the crystal bed. Overpressure refers to pressure above atmospheric pressure, which can be created by the flow rate of the solution recycled to the third region 30c, and said flow rate is regulated by the amount of crystal bed moved from the second region 30b to the third region 30c by an internal screw and by valves on the final product discharge line. In other words, when 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, an overpressure is formed in the third region 30c, and the concentrate can wash the crystal bed while moving towards the second region 30b due to the pressure difference generated by the overpressure. The washed crystals formed by washing with the concentrate can have significantly reduced impurities and high purity.

[0068] When the concentrate is supplied under this overpressure along the direction of the second region 30b, a countercurrent can be formed opposite to the advancing direction of the crystal bed. Here, in the second region 30b, a wash front (W / F) can be generated, serving as the boundary between impurities, including residual mother liquor, and the concentrate. Impurities may include mother liquor that has not been discharged through the filter and can be discharged through the filter by forming a countercurrent through the pressure supplied by the wash liquid.

[0069] The washing front can be formed between the filter and the scraper in the second region 30b, and this position can be adjusted by the overpressure. For example, when the overpressure is strong, the washing front forms closer to the filter; when the overpressure is weak, the washing front forms closer to the scraper. Preferably, the washing front is formed close to the center between the filter and the scraper. When the washing front forms too close to the filter, the concentrate may be discharged to the outside through the filter, resulting in loss; while when the washing front forms too close to the scraper, the crystal bed may not be adequately washed, resulting in a decrease in the purity of the concentrate (or the final product (P)). Residual mother liquor can be removed from the crystals accumulated in the space between the washing front and the scraper 32 to improve crystal purity.

[0070] In a crystal bed washed with a concentrated solution, washed crystals can be formed. That is, the crystals present in the direction from the washing front towards the third region 30c can be washed crystals from which impurities have been removed. The concentrated solution can be contained between the crystals forming the washed crystals, but it is formed by melting the washed crystals after grinding, and does not affect purity. In other words, by washing the crystal bed with a concentrated solution, impurities can be removed without affecting the purity of the washed crystals.

[0071] Subsequently, the cleaned crystals can be ground by the mechanical action of the rotating scraper 32 and then moved to the third region 30c.

[0072] The scraper 32 can be positioned in the second region 30b, starting from the boundary between the second region 30b and the third region 30c. Multiple blades can be formed in the scraper 32 from the center of the cylinder toward the cylinder wall. Specifically, the scraper can be a fan-shaped or rotating disk-shaped blade with blades disposed within the cylinder. As the scraper 32 rotates in place, the washed crystals are ground by the blades to form ground crystals.

[0073] Inside the solid-liquid separator 30, the slurry can be moved toward the third region (or the second region) by the rotation of the internal screw, the crystal bed can also be moved toward the third region by the force of the slurry, and the washing crystals and grinding crystals can also be moved to the third region 30c by the force of the crystal bed.

[0074] Based on the total length of the solid-liquid separator, the second region 30b can occupy a region corresponding to 20% to 70% or 30% to 60% of the length. The starting point of the second region 30b can be the ending point of the first region 30a.

[0075] Simultaneously, the solid-liquid separator 30 may include a third region 30c. This third region is located on the other side of the cylinder and may include an outlet through which the ground crystals are discharged from the cylinder. The outlet may be connected to a heating device to melt the ground crystals.

[0076] The ground crystals can be conveyed from the third zone 30c to the heating unit via the outlet (Out). The heating unit (H) can be a heat exchanger, and when the ground crystals are supplied, the concentrated crystals are heated and melted to form a concentrate, which can be recovered as the purified final product (P).

[0077] As described above, at least a portion of the concentrate can be recycled to the third region 30c, and the recycled concentrate can move towards the second region 30b and be used as a washing solution to remove residual impurities from the crystal bed. Since the concentrate is a melt of the ground crystals, the purity of the concentrate and the ground crystals can be the same.

[0078] The flow rate of the concentrate circulating to the third zone 30c of the solid-liquid separator can be controlled to maintain the content of washed crystals (or ground crystals) at an appropriate level.

[0079] Meanwhile, in order to maintain fluidity in the third region 30c, the ground crystals can move in the form of a slurry containing the ground crystals in the concentrate, and the flow rate of the concentrate can be controlled to maintain the content of the ground crystals contained in the concentrate at an appropriate level.

[0080] The flow rate of the concentrate can affect the pressure formed in the third zone 30c. The third zone 30c of the solid-liquid separator can generate an overpressure greater than 1 bar but not more than 2 bar, or greater than 1 bar but not more than 1.5 bar, to maintain a uniform countercurrent of the recirculated concentrate, thereby increasing the washing effect. When the overpressure is below 1 bar, it is difficult to generate countercurrent of the concentrate, and the washing front forms close to the scraper, making it difficult to predict the improvement in purity through washing. Simultaneously, when the overpressure is greater than 2 bar, excessive countercurrent forms, causing the washing front to form close to the filter, and the concentrate moves towards the filter, resulting in concentrate loss. Furthermore, when the overpressure is greater than 2 bar, the amount of recirculated concentrate increases, the amount of final product (P) decreases, and the size of the purification unit may need to be increased to obtain the desired yield, which may be economically disadvantageous.

[0081] The third region 30c of the solid-liquid separator can occupy 3% to 20% or 5% to 15% of the total length of the solid-liquid separator. The starting point of the third region 30b can be the ending point of the second region 30a.

[0082] In addition, the interior of the solid-liquid separator 30 can be kept insulated to improve the smooth movement of the slurry and the efficiency of crystal separation. For example, the exterior of the solid-liquid separator 30 is manufactured in the form of a jacket to create a vacuum state, thereby minimizing heat loss and maintaining insulation.

[0083] In the purification apparatus of the present invention as described above, the crystals formed in the crystallizer 20 are supplied to the solid-liquid separator 30, where the crystals and mother liquor are separated, and the crystals are washed to obtain purified crystals from which impurities such as the mother liquor have been removed.

[0084] The solid-liquid separator 30 is divided into the following areas in sequence: a region that supplies slurry containing crystals from the crystallizer, a region that separates and washes the crystals from the mother liquor, and a region that discharges the washed crystals, so that the slurry can pass through these regions in sequence and the final product can be obtained by a simple method.

[0085] Furthermore, the solid-liquid separator 30 is equipped with an internal screw, filter, and scraper, enabling the separation of slurry into crystals and mother liquor, as well as the collection and discharge of crystals.

[0086] In addition, in the solid-liquid separator 30, the crystals are washed to remove impurities, such as mother liquor, thereby obtaining a final product with higher purity.

[0087] Furthermore, in the purification apparatus of the present invention as described above, an integrated device can be formed in which the lower region 20b of the crystallizer is configured in a conical shape and combined with the solid-liquid separator 30, and crystallization and solid-liquid separation can be performed in one device.

[0088] When the crystallizer 20 and the solid-liquid separator 30 are combined, separate pipes and pumps are not required for conveying the slurry between them. Therefore, problems such as compound loss and pipe blockage caused during slurry conveying in conventional technologies can be solved.

[0089] Furthermore, an integrated device can reduce installation area and costs, and also simplify the process.

[0090] Furthermore, according to an exemplary embodiment, the present invention provides a method for purifying a compound solution using the purification apparatus, the compound solution being a solution supplied after the reaction has been completed in a reactor.

[0091] The purification method includes: (S1) supplying the compound solution after reaction in the reactor to the upper region of a crystallizer to crystallize the compound into a slurry containing crystals, supplying the slurry through the lower region of the crystallizer to the first region of a solid-liquid separator having a first region to a third region in sequence; (S2) moving the slurry supplied to the first region of the solid-liquid separator to a second region by rotating an internal screw, separating the crystals and mother liquor from the slurry through a filter in the second region, and discharging the mother liquor from the solid-liquid separator; (S3) compressing the slurry in the second region of the solid-liquid separator by the filter... The crystals separated by the filter are used to form a crystal bed. The crystal bed is washed with a concentrate to form washed crystals, and the washed crystals are ground with a scraper to form ground crystals. (S4) The ground crystals in the third region of the solid-liquid separator are discharged from the solid-liquid separator through an outlet. The ground crystals are supplied to a heating device to melt the crystals to form the concentrate. (S5) At least a portion of the concentrate is supplied to the third region, wherein the pressure in the third region is set to be greater than 1 bar and not greater than 2 bar, and the concentrate is supplied to the second region through an overpressure formed by the pressure in the third region to wash the crystal bed.

[0092] Furthermore, in the purification method according to the invention, oxygen is introduced into the first region 30a of the solid-liquid separator and moves toward the crystallizer, thereby preventing the slurry from accumulating at the connection between the solid-liquid separator 30 and the crystallizer 20.

[0093] In a purification apparatus according to an exemplary embodiment of the present invention, the crystallizer 20, the solid-liquid separator 30, and their combination are consistent with the contents described above in the purification apparatus according to the present invention within the overlapping scope.

[0094] The invention will be described in more detail below by way of examples. However, the following examples are provided to illustrate the invention, and it will be apparent to those skilled in the art that various modifications and alterations can be made without departing from the scope and concept of the invention, and the scope of the invention is not limited thereto.

[0095] Example 1: like Figure 1 As shown, a device integrating a crystallizer 20 and a solid-liquid separator 30 is used for compound purification.

[0096] Specifically, an acrylic acid solution containing acrylic acid (98 wt%), acetic acid (1 wt%) and water (1 wt%) is fed into the upper region 20a of the crystallizer and crystallized to obtain a slurry containing compound crystals. The slurry is then introduced into the first region 30a of the solid-liquid separator through the conical lower region 20b of the crystallizer.

[0097] As the slurry introduced into the first zone 30a of the solid-liquid separator moves through the internal screw (S), the mother liquor is discharged through the filter 31 included in the second zone 30b to separate the crystals. At this time, the internal screw rotates at 40 rpm.

[0098] In the second region 30b of the solid-liquid separator, the crystals separated by the filter 31 are compressed by an internal screw to form a crystal bed. The crystal bed is washed with a concentrate from the third region 30c to form washed crystals, which are then ground by a rotating disc-shaped scraper 32 to form ground crystals. The ground crystals are moved to the third region 33c. While the pressure in the third region 33c is maintained at 1.1 bar to 1.2 bar, the ground crystals pass through a heating device (H) via an outlet (Out) and melt to form a concentrate. A portion of the concentrate is supplied to the third region 30c, and the remainder is obtained as the purified final product (P).

[0099] Examples 2 and 3, and Comparative Example 1: In addition to changing the pressure in the third zone of the solid-liquid separator as follows Figure 1 Except as shown, the process is carried out in the same manner as in Example 1.

[0100] [Table 1]

[0101] As shown in Table 1, Examples 1 to 3, in which a pressure greater than 1 bar is maintained in the third region of the solid-liquid separator combined with the crystallizer, have improved crystal purity due to the backflow of the washing liquid obtained by overpressure, while in Comparative Example 1, where the pressure in the third region is 1 bar and no backflow of washing liquid occurs, the crystal purity of acrylic acid contained in the final product decreases.

[0102] Meanwhile, when the pressure in the third region of the solid-liquid separator is greater than 2 bar, the crystal purity of the final product can be increased, but there is a loss of concentrate moving from the third region 30c to the second region 30b, and the amount of recycled concentrate increases. This leads to a limitation: the size of the purification unit needs to be increased to achieve the desired production volume, which is not preferred.

[0103] [List of reference numerals]

[0104] 10: Feed tank

[0105] 20: Crystallizer

[0106] 20a: Upper region of the crystallizer

[0107] 20b: Lower region of the crystallizer

[0108] 30: Solid-liquid separator

[0109] 30a: First Region

[0110] 30b: Second Zone

[0111] 30c: Third Region

[0112] 31: Filter

[0113] 32: Scraper

[0114] 33: Mother liquor discharge pipe

[0115] 34: Oxygen input port

[0116] S: Internal screw

[0117] In: Slurry inlet

[0118] Out: Export

[0119] H: Heating device

Claims

1. An integrated purification device, comprising: A crystallizer comprising an upper region and a lower region, the upper region being supplied with a compound solution to form crystals, and the lower region being disposed below the upper region and storing and discharging a slurry containing the crystals formed in the upper region. and A solid-liquid separator comprising a cylinder having a slurry inlet on one side for supplying slurry from the crystallizer, and an outlet on the other side for discharging ground crystals obtained by separating, compressing, and washing the slurry. The cylinder is divided into a first region, a second region, and a third region from one side. The first region includes an internal screw that moves the slurry supplied to the slurry inlet toward the second region. The second region includes a filter that separates the crystals from the slurry and a scraper that grinds the washed crystals to form ground crystals. The third region includes an outlet that discharges the ground crystals to the outside of the cylinder.

2. The integrated purification apparatus according to claim 1, further comprising a heating device connected to the outlet. The ground crystals are melted in the heating device to form a concentrated liquid, and At least a portion of the concentrate is supplied to the third region and washes the crystal bed formed in the second region by compressing the crystals to form washed crystals.

3. The integrated purification device according to claim 2, in, The pressure in the third region is greater than 1 bar and not greater than 2 bar, and The concentrate is supplied to the second region via overpressure formed by the pressure in the third region to wash the crystal bed.

4. The integrated purification device according to claim 1, in, The lower region of the crystallizer has a tapered shape that narrows downwards, and The lower region of the crystallizer, which has the cone shape, has a shape that connects with the slurry inlet of the solid-liquid separator.

5. The integrated purification device according to claim 4, wherein, 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 highest cross-section of the upper region of the crystallizer.

6. The integrated purification device according to claim 1, wherein, Based on the weight of the slurry, the slurry formed in the upper region of the crystallizer contains 5% to 40% by weight of the crystals.

7. The integrated purification device according to claim 1, in, The first area further includes an oxygen input port. The oxygen input port supplies oxygen to the first area to prevent the slurry from accumulating.

8. The integrated purification device according to claim 1, in, The filter is disposed in the second region starting from the boundary between the first region and the second region, and The filter is arranged in a ring around the inner wall of the cylinder to separate the crystals and the mother liquor.

9. The integrated purification device according to claim 1, wherein, The internal screw is rotated by a motor located at one end of the cylinder.

10. The integrated purification device according to claim 1, wherein, The internal screw rotates at a speed of 5 rpm to 100 rpm.

11. A purification method, comprising: (S1) The compound solution that has completed the reaction in the reactor is supplied to the upper region of the crystallizer, and the compound is crystallized to form a slurry containing crystals. The slurry is then supplied through the lower region of the crystallizer to the first region of a solid-liquid separator that is sequentially provided with a first region to a third region. (S2) The slurry supplied to the first region of the solid-liquid separator is moved to the second region by rotating the internal screw. The crystals and mother liquor are separated from the slurry by a filter disposed in the second region, and the mother liquor is discharged from the solid-liquid separator. (S3) The crystals separated by the filter in the second region of the solid-liquid separator are compressed to form a crystal bed, the crystal bed is washed with a concentrate to form washed crystals, and the washed crystals are ground with a scraper to form ground crystals. (S4) The ground crystals in the third region of the solid-liquid separator are discharged from the solid-liquid separator through the outlet, and the ground crystals are supplied to a heating device to melt the crystals to form the concentrate. (S5) At least a portion of the concentrate is supplied to the third region. The pressure in the third region is greater than 1 bar and not greater than 2 bar, and The concentrate is supplied to the second region via overpressure formed by the pressure in the third region to wash the crystal bed.

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