A suspension crystallization washing apparatus and method

Abstract

The application provides a suspension crystallization washing device and method, which comprises a raw material slurry pipeline, a washing tank, a product tank, a residual liquid pipeline and a product pipeline, wherein the washing tank is at least four, and the operation process comprises the following steps: a, unloading; b, feeding; c, final-stage washing; d, intermediate washing; and e, primary-stage washing; during the operation, at least one washing tank is in the step a or b, one washing tank is in the step c, one washing tank is in the step e, and the rest of the washing tanks are in the step d. Compared with the existing mechanical washing tower, the suspension crystallization washing device does not involve a dynamic sealing device; compared with the existing centrifuge washing device, the purification effect is good, and the manufacturing cost and difficulty of the device are significantly reduced.

Description

A suspension crystallization washing device and method Technical Field

[0001] This invention relates to the field of melt crystallization, and more particularly to a suspension crystallization washing device and method. Background Technology

[0002] Melt crystallization is an important separation, purification, and concentration method in the chemical, pharmaceutical, and food industries, characterized by high selectivity, low energy consumption, low-temperature operation, no solvent required, and no wastewater generation. Based on the crystal growth method, melt crystallization is divided into layer-by-layer crystallization and suspension crystallization. Compared with layer-by-layer crystallization, suspension crystallization has advantages such as high single-stage separation efficiency, large production capacity per unit volume, low energy consumption, and ease of continuous operation. Suspension crystallization typically involves two steps: crystallization and solid-liquid separation. Because crystallization itself has very high separation efficiency, the small amount of mother liquor remaining in the crystals during solid-liquid separation can significantly affect the final product. To improve product quality, a washing step is often added during solid-liquid separation to reduce mother liquor residue. The washing liquid is usually the product from melt crystallization or other high-purity products.

[0003] In industrial production, solid-liquid separation typically employs centrifuges, gravity scrubbing towers, or mechanical scrubbing towers. Compared to scrubbing towers, centrifuges are currently the most common solid-liquid separation equipment. As a dynamic device with three-dimensional motion, they operate at high speeds and can separate solid particles from liquids in suspensions, as well as two immiscible liquids of different densities in emulsions. However, this method generally has limited washing effectiveness, consumes a large amount of scrubbing liquid, and has a relatively low overall separation efficiency. Gravity scrubbing towers have more limitations, only suitable for systems with larger crystal diameters. Mechanical scrubbing towers represent a more ideal separation process, but their manufacturing is challenging, involving numerous dynamic seals and requiring high mechanical strength and manufacturing precision. Therefore, the size of the equipment is currently limited, and the technology is monopolized by a few foreign manufacturers.

[0004] The patent with publication number CN105561658A discloses a separation and purification device and method for molten crystallization suspension, which can operate well between 5% and 55% of the solid content of the system. However, there is no good connection between the washing units, and the process flow is long, which may lead to high operating costs. Summary of the Invention

[0005] In view of this, the present invention provides a suspension crystallization washing device and method with high separation and purification efficiency.

[0006] The technical solution of this invention is implemented as follows:

[0007] On one hand, the present invention provides a suspension crystallization washing device, characterized in that it includes a raw material slurry pipeline, a washing tank, a finished product tank, a residual liquid pipeline, and a finished product pipeline, wherein there are multiple washing tanks;

[0008] The raw material slurry pipeline is used to transport materials to the washing tank;

[0009] The washing tank is used to wash materials and achieve solid-liquid separation.

[0010] The finished product tank is used to collect the solid phase after washing;

[0011] The residual liquid pipeline is used to collect the liquid phase after washing;

[0012] The finished product pipeline is used to transport the solid phase to the finished product tank;

[0013] The raw material slurry pipeline is connected to multiple washing tanks; the multiple washing tanks are connected in series, each washing tank has a feed inlet and a washing outlet at the top, and a product outlet and a filtrate outlet at the bottom; the finished product tank is connected to the washing outlet and the product outlet respectively; the residual liquid pipeline is connected to the filtrate outlet and the multiple washing tanks respectively; and the finished product pipeline is connected to the product outlet and the finished product tank respectively.

[0014] More preferably, the washing tank further includes a tank body, a heating jacket, a filter plate, and several partitions;

[0015] The tank has a hollow structure and is equipped with a feed inlet, a washing inlet, a product outlet, and a filtrate outlet on the outside.

[0016] The heating jacket is located on the outside of the tank and is used to heat the material inside the tank.

[0017] The filter plate is installed inside the tank and is arranged horizontally along the tank body, dividing the tank body into an upper cavity and a lower cavity. The upper cavity is provided with a feed inlet, a washing inlet and a product outlet, and the lower cavity is provided with a filtrate outlet, which is used to filter materials to achieve solid-liquid separation.

[0018] The baffles are all located in the upper cavity of the tank and abut against the filter plate. The baffles are arranged at intervals along the vertical direction of the tank to divide the upper cavity of the tank into multiple non-interconnected flow channels, which reduces the short circuit and radial flow of the washing liquid.

[0019] More preferably, it also includes an interstage booster pump and a finished product pump. The interstage booster pump is located between adjacent washing tanks and is connected to the washing port and the filtrate port to provide pressurization to the washing tanks. The finished product pump is located inside the finished product tank and is connected to the washing port to transport the liquid finished product to the washing port.

[0020] More preferably, it also includes a first valve, a second valve, a third valve, a fourth valve, and a fifth valve;

[0021] The first valve is connected to the raw material slurry pipeline and the feed inlet;

[0022] The second valve is connected to the finished product pump and the washing port;

[0023] The third valve is connected to the finished product tank and the product outlet;

[0024] The fourth valve is connected to the residual liquid pipeline and the filter port;

[0025] The fifth valve is connected to the interstage booster pump and the washing port.

[0026] More preferably, it also includes a heat transfer medium pipeline, which is connected to the heating jacket and the finished product tank respectively, for transferring heat to the heating jacket and the finished product tank.

[0027] More preferably, the number of washing tanks is at least four.

[0028] On the other hand, the present invention also provides a method for washing suspended crystals, comprising the following steps:

[0029] Step a, unloading: A heat transfer medium is introduced into the heating jacket of the first washing tank to melt all the material inside the first washing tank. The third valve is then opened to put all the material into the finished product tank.

[0030] Step b, feeding: Open the first valve and the fourth valve to fill the first washing tank with material; when the first washing tank is in step b, the second washing tank, the third washing tank, and the fourth washing tank are in steps e, d, and c respectively;

[0031] Step c, final stage washing: Open the fifth valve and use the filtrate from the fourth washing tank as the washing liquid for washing; then open the fourth valve again and discharge the filtrate from the first washing tank as residual liquid; while the first washing tank enters step c, the second, third, and fourth washing tanks enter steps a, e, and d respectively.

[0032] Step d, intermediate washing: Keep the fifth valve open and use the filtrate from the fourth washing tank as the washing liquid; turn on the interstage booster pump to use the filtrate from the first washing tank as the washing liquid for the second washing tank. While the first washing tank enters step d, the second, third, and fourth washing tanks enter steps c, a, and e respectively.

[0033] Step e, primary washing: Open the second valve and wash the material with fresh washing liquid. Keep the interstage booster pump running and use the filtrate from the first washing tank as washing liquid for the second washing tank. While the first washing tank is entering step e, the second, third, and fourth washing tanks are entering steps d, c, and a, respectively.

[0034] After the first washing tank completes step e, it proceeds to step a. At the same time, the second, third, and fourth washing tanks enter steps e, d, and c respectively, starting a new washing cycle.

[0035] More preferably, when the material system is difficult to wash or the product quality requirements are high, the number of washing tanks can be increased, and multiple adjacent washing tanks can perform step d simultaneously.

[0036] More preferably, the suspension crystals are suspension crystals of p-xylene and its isomers, with the mass content of the suspension crystal solids being 5%-55%.

[0037] More preferably, the method for washing p-xylene suspension crystals by suspension crystallization specifically includes the following steps:

[0038] Step a, unloading: A heat transfer medium is introduced into the heating jacket of the first washing tank to melt all the paraxylene crystals inside the first washing tank. The third valve is then opened to put all the paraxylene into the finished product tank.

[0039] Step b, Feeding: Open the first valve and the fourth valve to fill the first washing tank with paraxylene crystals; when the first washing tank is in step b, the second washing tank, the third washing tank, and the fourth washing tank are in steps d, a, and c, respectively;

[0040] Step c, final stage washing: Open the fifth valve and use the filtrate from the fourth washing tank as the washing liquid; then open the fourth valve again and discharge the filtrate from the first washing tank as residual liquid; while the first washing tank enters step c, the second, third, and fourth washing tanks enter steps a, d, and b respectively;

[0041] Step d, intermediate washing: Keep the fifth valve open and use the filtrate from the fourth washing tank as the washing liquid; turn on the interstage booster pump to use the filtrate from the first washing tank as the washing liquid for the second washing tank. While the first washing tank enters step d, the second, third, and fourth washing tanks enter steps c, a, and e respectively.

[0042] Step e, primary washing: Open the second valve and wash the paraxylene crystals with fresh washing solution. Keep the interstage booster pump running and use the filtrate from the first washing tank as washing solution for the second washing tank. While the first washing tank is entering step e, the second, third, and fourth washing tanks are entering steps d, c, and a, respectively.

[0043] After the first washing tank completes step e, it proceeds to step a. At the same time, the second, third, and fourth washing tanks enter steps e, d, and c respectively, starting a new washing cycle.

[0044] More preferably, the temperature of the finished product tank is 5-20°C above the melting point of the material, and the weight of fresh washing liquid accounts for 5-40% of the product.

[0045] The suspension crystallization washing equipment and method of the present invention have the following advantages over the prior art: (1) Existing mechanical washing tower equipment is difficult to manufacture and has many dynamic seals. The suspension crystallization washing equipment of the present invention has multiple washing tanks connected in series and does not involve dynamic seals. The equipment manufacturing cost and difficulty are greatly reduced, and it has good industrial application prospects.

[0046] (2) The suspension crystal washing method of the present invention controls multiple washing tanks to work in a cycle by controlling valves. The finished product pipeline then transports the washed product from the washing tank back to the washing tank for washing again. The residual liquid pipeline discharges the separated suspension crystal residual liquid from the device. The washing liquid consumption is small, which effectively improves the product purification effect. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 is a schematic diagram of the washing tank device of the present invention.

[0049] In Figure 1, 201 is the feed inlet; 202 is the washing inlet; 203 is the product outlet; 204 is the filtrate outlet; 21 is the tank body; 22 is the heating jacket; 23 is the filter plate; and 24 is the partition plate.

[0050] Figure 2 is a flow chart of the suspension crystallization washing equipment of the present invention with 4 washing tanks.

[0051] In Figure 2, 1 is the raw material slurry pipeline; 2 is the washing tank; 3 is the finished product tank; 31 is the finished product pump; 4 is the residual liquid pipeline; 5 is the finished product pipeline; 6 is the interstage booster pump; 7 is the first valve; 8 is the second valve; 9 is the third valve; 10 is the fourth valve; 11 is the fifth valve; and 12 is the heat transfer medium pipeline. Detailed Implementation

[0052] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0053] Example 1

[0054] A suspension crystallization washing device includes a raw material slurry pipeline 1, four washing tanks 2, a finished product tank 3, a residual liquid pipeline 4, and a finished product pipeline 5;

[0055] The raw material slurry pipeline 1 is connected to four washing tanks 2. The four washing tanks 2 are connected in series. Each washing tank 2 has a feed inlet 201 and a washing outlet 202 at the top and a product outlet 203 and a filtrate outlet 204 at the bottom. The finished product tank 3 is connected to the washing outlet 202 and the product outlet 203 respectively. The residual liquid pipeline 4 is connected to the filtrate outlet 204 and the four washing tanks 2 respectively. The finished product pipeline 5 is connected to the product outlet 203 and the finished product tank 3 respectively.

[0056] It also includes an interstage booster pump 6 and a finished product pump 31. The interstage booster pump 6 is located between adjacent washing tanks 2 and is connected to the washing port 202 and the filtrate port 204 to provide pressurization for the washing tank 2. The finished product pump 31 is located inside the finished product tank 3 and is connected to the washing port 202 to transport the solid phase to the washing port 202.

[0057] It also includes the first valve 7, the second valve 8, the third valve 9, the fourth valve 10, and the fifth valve 11;

[0058] The first valve 7 is connected to the raw material slurry pipeline 1 and the feed inlet 201;

[0059] The second valve 8 is connected to the finished product pump 31 and the washing port 202;

[0060] The third valve 9 is connected to the finished product tank 3 and the product outlet 203;

[0061] The fourth valve 10 is connected to the residual liquid pipeline 4 and the filter port 204;

[0062] The fifth valve 11 is connected to the interstage booster pump 6 and the washing port 202.

[0063] It also includes a heat transfer medium pipeline 12, which is connected to the heating jacket 22 and the finished product tank 3 respectively, for transferring heat to the heating jacket 22 and the finished product tank 3.

[0064] The raw material slurry pipeline contains a paraxylene crystal suspension. The solid content of the feed suspension is 5% by mass. The melting point of paraxylene is 12℃. The temperature of the finished product tank is 32℃. The amount of washing liquid used is 5% of the product output.

[0065] The specific operating steps include the following:

[0066] Step a, unloading: A heat transfer medium is introduced into the heating jacket 22 of the first washing tank 2 to melt all the paraxylene crystals inside the first washing tank 2. Then, the third valve 9 is opened to put all the paraxylene into the finished product tank 3.

[0067] Step b, feeding: Open the first valve 7 and the fourth valve 10 to fill the first washing tank 2 with paraxylene crystals; when the first washing tank 2 is in step b, the second washing tank 2, the third washing tank 2, and the fourth washing tank 2 are in steps d, a, and c, respectively;

[0068] Step c, final stage washing: Open the fifth valve 11 and use the filtrate from the fourth washing tank 2 as the washing liquid; then open the fourth valve 10 and use the filtrate from the first washing tank 2 as the residual liquid discharge device; while the first washing tank 2 enters step c, the second washing tank 2, the third washing tank 2, and the fourth washing tank 2 enter steps a, d, and b respectively.

[0069] Step d, intermediate washing: Keep the fifth valve open and use the filtrate from the fourth washing tank as the washing liquid; turn on the interstage booster pump to use the filtrate from the first washing tank as the washing liquid for the second washing tank. While the first washing tank enters step d, the second, third, and fourth washing tanks enter steps c, a, and e respectively.

[0070] Step e, primary washing: Open the second valve and wash the paraxylene crystals with fresh washing solution. Keep the interstage booster pump running and use the filtrate from the first washing tank as washing solution for the second washing tank. While the first washing tank is entering step e, the second, third, and fourth washing tanks are entering steps d, c, and a, respectively.

[0071] After the first washing tank 2 completes step e, it proceeds to step a. At the same time, the second washing tank 2, the third washing tank 2, and the fourth washing tank 2 enter steps e, d, and c respectively, starting a new round of washing cycle.

[0072] Example 2

[0073] A suspension crystallization washing device and method are disclosed, wherein the raw material slurry pipeline contains a paraxylene crystal suspension, the solid mass content of the feed suspension is 55%, and the difference from Example 1 is that the temperature of the finished product tank is 17°C, and the amount of washing liquid used is 40% of the product yield.

[0074] Example 3

[0075] A suspension crystallization washing device and method are disclosed, wherein the raw material slurry pipeline contains a paraxylene crystal suspension, the solid mass content of the feed suspension is 40%, and the difference from Example 1 is that the temperature of the finished product tank is 22°C, and the weight of the washing liquid used is 25% of the product yield.

[0076] Example 4

[0077] A suspension crystallization washing device and method, which differs from Example 1 in that the raw material slurry pipeline contains a dibenzyl ether crystal suspension.

[0078] Comparative Example 1

[0079] A suspension crystallization washing device and method differs from Example 1 in that a mechanical washing tower is used for solid-liquid separation, requiring a solid mass content ratio of 40% and a washing liquid weight of 30% of the product yield.

[0080] Comparative Example 2

[0081] A suspension crystallization washing device and method differs from Example 1 in that a conventional piston pusher centrifuge is used for solid-liquid separation, requiring a solid mass content ratio of 40% and a washing liquid weight of 25% of the product yield.

[0082] Comparative Example 3

[0083] A suspension crystallization washing device and method differs from Example 3 in that it has only one washing tank.

[0084] Table 1 Washing Results

[0085]

[0086]

[0087] It is evident that the suspension crystallization washing equipment and method of the present invention have a significantly better purification effect than centrifugal separation and are basically equivalent to mechanical washing towers, but the equipment manufacturing cost and difficulty are significantly reduced.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for washing suspension crystals, characterized in that, A suspension crystallization washing device is used, which includes a raw material slurry pipeline (1), a washing tank (2), a finished product tank (3), a residual liquid pipeline (4), and a finished product pipeline (5). There are multiple washing tanks (2). The raw material slurry pipeline (1) is connected to multiple washing tanks (2). The multiple washing tanks (2) are connected in series. Each washing tank (2) has a feed inlet (201) and a washing outlet (202) at the top, and a product outlet (203) and a filter outlet (204) at the bottom. The finished product tank (3) is connected to the washing outlet (202) and the product outlet (203) respectively. The residual liquid pipeline (4) is connected to the filter outlet (204) and the multiple washing tanks (2) respectively. The finished product pipeline (5) is connected to the product outlet (203) and the finished product tank (3) respectively; the method includes the following steps: Step a, unloading: heat transfer medium is introduced into the heating jacket (22) of the first washing tank (2) to melt all the material inside the first washing tank (2), and the third valve (9) is opened to put all the material into the finished product tank (3); Step b, feeding: the first valve (7) and the fourth valve (10) are opened to fill the first washing tank (2) with material; when the first washing tank (2) is in step b, the second washing tank (2), the third washing tank (2), and the fourth washing tank (2) are in steps e, d, and c respectively; Step c, final washing: the first washing tank (2) is opened to fill the first washing tank (2) with material. Five valves (11) are used to wash the first washing tank (2) with the filtrate from the fourth washing tank (2); then the fourth valve (10) is opened to discharge the filtrate from the first washing tank (2) as residual liquid; while the first washing tank (2) enters step c, the second washing tank (2), the third washing tank (2), and the fourth washing tank (2) enter steps a, e, and d respectively; Step d, intermediate washing: the fifth valve (11) is kept open, and the filtrate from the fourth washing tank (2) is used as washing liquid; the interstage booster pump (6) is turned on to use the filtrate from the first washing tank (2) as washing liquid for the second washing tank (2), while the first washing tank (2) enters step d, the second washing tank (2), the third washing tank (2), the fourth ... the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth washing tank (2), the fourth Washing tank (2) and fourth washing tank (2) enter steps c, a, and e respectively; Step e, primary washing: open the second valve (8), wash the material with fresh washing liquid, keep the interstage booster pump (6) open, and use the filtrate of the first washing tank (2) as washing liquid for the second washing tank (2); while the first washing tank (2) enters step e, the second washing tank (2), the third washing tank (2), and the fourth washing tank (2) enter steps d, c, and a respectively; after the first washing tank (2) completes step e, it executes step a, and at the same time, the second washing tank (2), the third washing tank (2), and the fourth washing tank (2) enter steps e, d, and c respectively, and start a new round of washing cycle.

2. The suspension crystallization washing method as described in claim 1, characterized in that, The washing tank (2) also includes a tank body (21), a heating jacket (22), a filter plate (23), and several partitions (24); the tank body (21) is a hollow structure, with an inlet (201), a washing port (202), a product outlet (203), and a filtrate outlet (204) on the outside; the heating jacket (22) is located on the outside of the tank body (21); the filter plate (23) is located inside the tank body (21), and the filter plate (23) is horizontally aligned with the tank body (21). The tank (21) is divided into an upper cavity and a lower cavity. The upper cavity is provided with a feed inlet (201), a washing inlet (202) and a product outlet (203), and the lower cavity is provided with a filtrate outlet (204). The partitions (24) are all located in the upper cavity of the tank (21) and abut against the filter plate (23). The partitions (24) are arranged in sequence at intervals along the vertical direction of the tank (21) to divide the upper cavity of the tank (21) into multiple non-interconnected flow channels.

3. The suspension crystallization washing method as described in claim 1, characterized in that, It also includes an interstage booster pump (6) and a finished product pump (31). The interstage booster pump (6) is located between adjacent washing tanks (2) and is connected to the washing port (202) and the filtrate port (204). The finished product pump (31) is located inside the finished product tank (3) and is connected to the washing port (202).

4. The suspension crystallization washing method as described in claim 1, characterized in that, It also includes a first valve (7), a second valve (8), a third valve (9), a fourth valve (10), and a fifth valve (11); the first valve (7) is connected to the raw material slurry pipeline (1) and the feed inlet (201); the second valve (8) is connected to the finished product pump (31) and the washing port (202); the third valve (9) is connected to the finished product tank (3) and the product outlet (203); the fourth valve (10) is connected to the residual liquid pipeline (4) and the filter port (204); and the fifth valve (11) is connected to the interstage booster pump (6) and the washing port (202).

5. The suspension crystallization washing method as described in claim 1, characterized in that, It also includes a heat transfer medium pipeline (12), which is connected to the heating jacket (22) and the finished product tank (3), respectively.

6. The suspension crystallization washing method as described in claim 1, characterized in that, The washing tank (2) consists of at least four tanks.

7. The suspension crystallization washing method as described in claim 1, characterized in that, The material is a suspension crystal of p-xylene and its isomers, with the mass content of the suspension crystal solids ranging from 5% to 55%.

8. The suspension crystallization washing method as described in claim 1, characterized in that, The temperature of the finished product tank (3) is 5-20°C above the melting point of the material, and the weight of fresh washing liquid accounts for 5-40% of the product.

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