阅读说明：本技术 一种c4-c6混合二元酸溶液的冷却结晶装置及提纯方法 (Cooling crystallization device and purification method for C4-C6 mixed binary acid solution ) 是由 陈恩之 赵风轩 唐丽华 谢毅 李志国 于彬 杨建新 于 2020-12-17 设计创作，主要内容包括：一种C4-C6混合二元酸溶液的冷却结晶装置,包括至少三个结晶器以及固液分离器,各所述结晶器的内空设有搅拌器,各所述结晶器设有盘管和/或夹套,位于最上游的结晶器侧壁上部设有进料口,用于与C4-C6混合二元酸源连接,相邻的结晶器之间通过第一溢流管连接,位于最下游的结晶器通过第二溢流管与所述固液分离器相连,该固液分离器的液相出口通过第一管路对下游工序供料,且通过第二管路与位于最上游的结晶器相连,第一管路、第二管路上分别设有阀门。本发明结构简单、操作方便,可以长时间连续进行分离提纯,且结晶收率可达80％以上,有效满足企业的实际需求。(A cooling crystallization device for a C4-C6 mixed dibasic acid solution comprises at least three crystallizers and a solid-liquid separator, wherein a stirrer is arranged in each crystallizer, each crystallizer is provided with a coil and/or a jacket, a feed inlet is formed in the upper part of the side wall of the crystallizer positioned at the most upstream and used for being connected with a C4-C6 mixed dibasic acid source, adjacent crystallizers are connected through a first overflow pipe, the crystallizer positioned at the most downstream is connected with the solid-liquid separator through a second overflow pipe, a liquid phase outlet of the solid-liquid separator supplies materials for a downstream process through the first pipeline and is connected with the crystallizer positioned at the most upstream through the second pipeline, and valves are respectively arranged on the first pipeline and the second pipeline. The invention has simple structure and convenient operation, can continuously separate and purify for a long time, has the crystallization yield of over 80 percent, and effectively meets the actual requirements of enterprises.)

1. a cooling crystallization device for a C4-C6 mixed dibasic acid solution is characterized in that: comprises at least three crystallizers (1) and solid-liquid separators (2),

a stirrer (3) is arranged in the hollow space of each crystallizer (1), each crystallizer (1) is provided with a coil pipe and/or a jacket, adjacent crystallizers (1) are connected through a first overflow pipe (4),

the upper part of the side wall of the crystallizer positioned at the most upstream is provided with a feeding hole (5) for being connected with a C4-C6 mixed binary acid source, the crystallizer positioned at the most downstream is connected with the solid-liquid separator (2) through a second overflow pipe (6), a liquid phase outlet of the solid-liquid separator (2) supplies materials for a downstream process through a first pipeline (7), and is connected with the crystallizer positioned at the most upstream through a second pipeline (8), and valves are respectively arranged on the first pipeline (7) and the second pipeline (8).

2. The cooling crystallization device for C4-C6 mixed dibasic acid solution as claimed in claim 1, wherein: the stirrer (3) is a single-layer or double-layer paddle stirrer, and the rotating speed of the paddle stirrer is 180-200 rpm.

3. The cooling crystallization device for C4-C6 mixed dibasic acid solution as claimed in claim 1, wherein: the heat exchange medium of the coil and/or the jacket is chilled water.

4. The cooling crystallization device for C4-C6 mixed dibasic acid solution as claimed in claim 1, wherein: the number of the crystallizers (1) is five or six or seven.

5. The cooling crystallization device for C4-C6 mixed dibasic acid solution as claimed in claim 1, wherein: the upstream end of the first overflow pipe (4) is positioned at the upper part of the side wall of the upstream crystallizer and is positioned below the feeding hole of the most upstream crystallizer.

6. The cooling crystallization device for C4-C6 mixed dibasic acid solution as claimed in claim 1, wherein: the bottom of each crystallizer (1) is respectively provided with an emptying valve (9) which is connected with an emptying pipeline (10) in parallel.

7. The method for purifying the mixed dibasic acid solution of C4-C6 by using the cooling crystallization device as claimed in any one of claims 1 to 6, which is characterized by comprising the following steps:

1) C4-C6 mixed dibasic acid solution is continuously pumped from the feed inlet of the uppermost crystallizer, and the temperature is controlled to be 43-52 ℃;

2) C4-C6 mixed binary acid solution in the most upstream crystallizer overflows to the most downstream crystallizer step by step, the temperature of the downstream crystallizer is 2-5 ℃ lower than that of the upstream crystallizer, and the stirring time of the C4-C6 mixed binary acid solution in each stage of crystallizer is more than or equal to 1 h;

3) C4-C6 mixed dibasic acid solution in the most downstream crystallizer overflows to a solid-liquid separator at the temperature of 15-30 ℃, the separated solid is C4-C6 mixed dibasic acid wet crystal, and the separated mother liquid partially reflows to the most upstream crystallizer.

8. The method as claimed in claim 7, wherein the concentration of the mixed dibasic acid solution of C4-C6 in the step 1) is 35-85 wt%.

9. The process according to claim 7, wherein 40 wt% of the mother liquor separated in step 3) is refluxed to the most upstream crystallizer.

Technical Field

The invention relates to the field of chemical industry, in particular to a cooling crystallization device and a purification method for a C4-C6 mixed binary acid solution.

Background

With the rapid development of polyester, polyurethane, caprolactam, nylon 66 and other industries, the yield of adipic acid is continuously expanded, and the quality requirement on the adipic acid is gradually improved.

The industrial production of adipic acid adopts an alcohol ketone nitric acid oxidation method to produce refined adipic acid, the method can produce a byproduct of 5-6% of C4-C6 mixed dibasic acid, and the byproduct needs to be extracted out of a system so as not to influence the quality of the refined adipic acid product. The C4-C6 mixed dibasic acid is also called nylon acid, nylon dibasic acid, AGS acid, dicarboxylic acid and DBA. The mixed dibasic acid contains 20-30% of succinic acid C4, 50-60% of glutaric acid C5, 15-20% of adipic acid C6 and 3-5% of other impurities.

Therefore, how to separate and recover the dibasic acids with high efficiency is an urgent problem to be solved by those skilled in the art.

Disclosure of Invention

The invention aims to provide a cooling crystallization device for a C4-C6 mixed binary acid solution, which has the advantages of simple structure, convenient operation, long-time continuous separation and purification, crystallization yield of over 80 percent and capability of effectively meeting the actual requirements of enterprises.

The technical scheme of the invention is as follows: a cooling crystallization device for a C4-C6 mixed dibasic acid solution comprises at least three crystallizers and a solid-liquid separator, wherein a stirrer is arranged in each crystallizer, each crystallizer is provided with a coil pipe and/or a jacket, adjacent crystallizers are connected through a first overflow pipe, a feed inlet is formed in the upper portion of the side wall of the uppermost crystallizer and used for being connected with a C4-C6 mixed dibasic acid source, the lowermost crystallizer is connected with the solid-liquid separator through a second overflow pipe, a liquid phase outlet of the solid-liquid separator supplies materials to a downstream process through a first pipeline and is connected with the uppermost crystallizer through a second pipeline, and valves are respectively arranged on the first pipeline and the second pipeline.

The stirrer is a single-layer or double-layer paddle stirrer, and the rotating speed of the paddle stirrer is 180-200 rpm.

The heat exchange medium of the coil and/or the jacket is chilled water.

The number of the crystallizers is five or six or seven.

The upstream end of the first overflow pipe is positioned at the upper part of the side wall of the upstream crystallizer and is positioned below the feeding hole of the most upstream crystallizer.

And the bottom of each crystallizer is respectively provided with an emptying valve and is connected with an emptying pipeline in parallel.

The method for purifying the mixed dibasic acid solution of C4-C6 by using any one of the cooling crystallization devices comprises the following steps:

1) C4-C6 mixed dibasic acid solution is continuously pumped from the feed inlet of the uppermost crystallizer, and the temperature is controlled to be 43-52 ℃;

2) C4-C6 mixed binary acid solution in the most upstream crystallizer overflows to the most downstream crystallizer step by step, the temperature of the downstream crystallizer is 2-5 ℃ lower than that of the upstream crystallizer, and the stirring time of the C4-C6 mixed binary acid solution in each stage of crystallizer is more than or equal to 1 h;

3) C4-C6 mixed dibasic acid solution in the most downstream crystallizer overflows to a solid-liquid separator at the temperature of 15-30 ℃, the separated solid is C4-C6 mixed dibasic acid wet crystal, and the separated mother liquid partially reflows to the most upstream crystallizer.

The concentration of the mixed dibasic acid solution of C4-C6 in the step 1) is 35-85 wt%.

40 wt% of the mother liquor separated in step 3) was refluxed to the uppermost crystallizer.

Adopt above-mentioned technical scheme to have following beneficial effect:

1. the cooling crystallization device provided by the invention is provided with the multistage crystallizer to gradually cool and crystallize, so that the binary acid in the mixed binary acid solution is crystallized and separated out as much as possible, and the recovery rate of the binary acid in the mixed binary acid solution is effectively improved. The binary acid solution/saturated solution/supersaturated solution in the upstream crystallizer flows to the downstream crystallizer in a step-by-step overflow mode, and the quality of the obtained crystals can be effectively ensured.

2. The liquid phase outlet of the solid-liquid separator of the cooling crystallization device provides mother liquor for the most upstream crystallizer through the second pipeline, so that the fluidity of the mixed binary acid solution is increased, and crystal nuclei are provided to facilitate crystallization of the binary acid solution.

3. The crystallizer of the cooling crystallization device is matched with a single-layer or double-layer paddle type stirrer, and the rotating speed is set to be 180 plus 200rpm, so that the mixed binary acid solution in the crystallizer forms a vortex, the crystal precipitation caused by crystallization can be effectively avoided from settling, the crystal precipitated by crystallization can be also avoided from being crushed, the crystals in overflowed materials are uniform and complete, the solid-liquid separation of the materials of the solid-liquid separation device is facilitated, and the yield of wet crystals obtained by the solid-liquid separation is ensured.

4. According to the method for purifying the mixed dibasic acid material by using the cooling crystallization device, the discharge temperature of the most upstream crystallizer is controlled to be 43-52 ℃ according to different crystallization points corresponding to 35-85 wt% of C4-C6 mixed dibasic acid solution, so that the C4-C6 mixed dibasic acid solution generates seed crystals, the discharge temperature of the most downstream crystallizer is controlled to be 15-30 ℃, so that the C4-C6 mixed dibasic acid solution completes crystal growth in the overflow process, and the subsequent solid-liquid separation efficiency and the yield of the dibasic acid can be effectively ensured.

5. According to the purification method, the temperature difference between adjacent crystallizers is controlled to be 2-5 ℃, so that the dibasic acid in the C4-C6 mixed dibasic acid solution is crystallized and separated out as much as possible, and the crystal quality is good; the stirring time of the mixed dibasic acid solution in each crystallizer is more than or equal to 1h, and if the stirring time (solution retention time) is too low, the crystallization efficiency is poor, so that the yield of the final dibasic acid is reduced.

6. According to the purification method, 40 wt% of the separated mother liquor is refluxed to the uppermost-stream crystallizer and used as a diluent and crystal nuclei, if the amount of the refluxed mother liquor is too low, the fluidity of the material is poor, and finally the yield of the dibasic acid is poor.

The applicant verifies that the mixed binary acid solution is purified by adopting the cooling crystallizer, the crystallization yield can reach more than 80 percent, the scabbing of the crystallizer can be avoided, and the operation period of the crystallizer can reach more than 20 days.

The following further description is made with reference to the accompanying drawings and detailed description.

Drawings

FIG. 1 is a schematic diagram of the three-stage purification according to the present invention;

FIG. 2 is a schematic diagram of the four-stage purification of the present invention.

In the attached drawing, 1 is a crystallizer, 2 is a solid-liquid separator, 3 is a stirrer, 4 is a first overflow pipe, 5 is a feed port, 6 is a second overflow pipe, 7 is a first pipeline, 8 is a second pipeline, 9 is an emptying valve, and 10 is an emptying pipeline.

Detailed Description

Example one

Referring to fig. 1 and 2, a specific embodiment of a cooling crystallization device for a mixed dibasic acid solution of C4-C6 is shown. The cooling crystallization device for the mixed dibasic acid solution of C4-C6 comprises at least three crystallizers 1 and a solid-liquid separator 2, the number of the crystallizers is usually three to seven in consideration of the yield of dibasic acid and the purification efficiency, wherein the purification efficiency is high when the number of the crystallizers is five, six or seven, but the purification time is long, and particularly in the present embodiment, the number of the crystallizers is three. The stirrer 3 is respectively arranged in the inner space of each crystallizer 1, the stirrer adopts a single-layer or double-layer paddle type stirrer, and the rotating speed of the paddle type stirrer is 180-200 rpm. Each crystallizer 1 is provided with a coil and/or a jacket, and the coil or the jacket adopts chilled water as a heat exchange medium. The adjacent crystallizers 1 are connected through a first overflow pipe 4. The upper part of the side wall of the crystallizer (left side) positioned at the most upstream is provided with a feed inlet 5 which is used for connecting with a C4-C6 mixed dibasic acid source, and the height of the feed inlet is higher than that of each first overflow pipe. The crystallizer positioned at the most downstream is connected with the solid-liquid separator 2 through a (right side) second overflow pipe 6, a liquid phase outlet of the solid-liquid separator 2 supplies materials for a downstream process through a first pipeline 7, and is connected with the crystallizer positioned at the most upstream through a second pipeline 8, specifically, the downstream end of the second pipeline can be directly connected with a feeding hole, and can also be directly connected with the hollow space of the crystallizer positioned at the most upstream. The first pipeline 7 and the second pipeline 8 are respectively provided with a valve. The bottom of each crystallizer 1 is respectively provided with an emptying valve 9 which is connected with an emptying pipeline 10 in parallel.

Example two

The cooling crystallization device of the first embodiment is adopted to carry out three-stage purification on the mixed dibasic acid solution of C4-C6, as shown in figure 1:

1) C4-C6 mixed dibasic acid solution (wherein, succinic acid C4 component accounts for 20-30%, glutaric acid C5 component accounts for 50-60%, adipic acid C6 component accounts for 15-20%) is continuously pumped from a feed inlet of the 1# crystallizer, a jacket or a coil pipe is utilized to control the material temperature in the 1# crystallizer to be 43-52 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the 1# crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the detention time of the C4-C6 mixed dibasic acid solution in the 1# crystallizer is 1 h;

2) C4-C6 mixed binary acid solution overflows from the No. 1 crystallizer to the No. 2 crystallizer, the temperature of the material in the No. 2 crystallizer is controlled by a jacket or a coil pipe to be reduced by 2-5 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the No. 2 crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the detention time of the C4-C6 mixed binary acid solution in the No. 2 crystallizer is 1 h;

3) C4-C6 mixed dibasic acid solution overflows from a 2# crystallizer into a 3# crystallizer, the temperature of materials in the 3# crystallizer is controlled by a jacket or a coil pipe to be reduced by 2-5 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the 3# crystallizer overflows when rising to the upstream end of an overflow pipe, the residence time of the C4-C6 mixed dibasic acid solution in the 3# crystallizer is 1h, the discharge temperature is 15-30 ℃, the mixed dibasic acid solution enters a solid-liquid separator to obtain C4-C6 mixed dibasic acid wet crystals, 40 wt% of the obtained mother solution reflows to the 1# crystallizer, and the rest mother solution is sent to a downstream process.

EXAMPLE III

The four-stage purification of the mixed dibasic acid solution C4-C6 is carried out by adopting a device with the same principle as the cooling crystallization device for implementing the first step, as shown in the figure 2:

1) C4-C6 mixed dibasic acid solution (wherein, succinic acid C4 component accounts for 20-30%, glutaric acid C5 component accounts for 50-60%, adipic acid C6 component accounts for 15-20%) is continuously pumped from a feed inlet of the 1# crystallizer, a jacket or a coil pipe is utilized to control the material temperature in the 1# crystallizer to be 43-52 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the 1# crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the detention time of the C4-C6 mixed dibasic acid solution in the 1# crystallizer is 1 h;

2) C4-C6 mixed binary acid solution overflows from the No. 1 crystallizer to the No. 2 crystallizer, the temperature of the material in the No. 2 crystallizer is controlled by a jacket or a coil pipe to be reduced by 2-5 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the No. 2 crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the detention time of the C4-C6 mixed binary acid solution in the No. 2 crystallizer is 1 h;

3) C4-C6 mixed binary acid solution overflows from the 2# crystallizer to the 3# crystallizer, the temperature of the material in the 3# crystallizer is controlled to be reduced by 2-5 ℃ by utilizing a jacket or a coil pipe, the rotating speed of a stirrer is 190rpm, the liquid level of the 3# crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the retention time of the C4-C6 mixed binary acid solution in the 3# crystallizer is 1 h;

4) C4-C6 mixed dibasic acid solution overflows from a 3# crystallizer into a 4# crystallizer, the temperature of materials in the 4# crystallizer is controlled by a jacket or a coil pipe to be reduced by 2-5 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the 4# crystallizer overflows when rising to the upstream end of an overflow pipe, the retention time of the C4-C6 mixed dibasic acid solution in the 4# crystallizer is 1h, the discharge temperature is 15-30 ℃, the mixed dibasic acid solution enters a solid-liquid separator to obtain C4-C6 mixed dibasic acid wet crystals, 40 wt% of the obtained mother solution reflows to the 1# crystallizer, and the rest mother solution is sent to a downstream process.

Example four

And (3) performing five-stage purification on the mixed dibasic acid solution of C4-C6 by adopting a device with the same principle as the cooling crystallization device for implementing the first step:

1) C4-C6 mixed dibasic acid solution (wherein, succinic acid C4 component accounts for 20-30%, glutaric acid C5 component accounts for 50-60%, adipic acid C6 component accounts for 15-20%) is continuously pumped from a feed inlet of the 1# crystallizer, a jacket or a coil pipe is utilized to control the material temperature in the 1# crystallizer to be 43-52 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the 1# crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the detention time of the C4-C6 mixed dibasic acid solution in the 1# crystallizer is 1 h;

2) C4-C6 mixed binary acid solution overflows from the No. 1 crystallizer to the No. 2 crystallizer, the temperature of the material in the No. 2 crystallizer is controlled by a jacket or a coil pipe to be reduced by 2-5 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the No. 2 crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the detention time of the C4-C6 mixed binary acid solution in the No. 2 crystallizer is 1 h;

3) C4-C6 mixed binary acid solution overflows from the 2# crystallizer to the 3# crystallizer, the temperature of the material in the 3# crystallizer is controlled to be reduced by 2-5 ℃ by utilizing a jacket or a coil pipe, the rotating speed of a stirrer is 190rpm, the liquid level of the 3# crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the retention time of the C4-C6 mixed binary acid solution in the 3# crystallizer is 1 h;

4) C4-C6 mixed binary acid solution overflows from the 3# crystallizer to the 4# crystallizer, the temperature of the material in the 4# crystallizer is controlled to be reduced by 2-5 ℃ by utilizing a jacket or a coil pipe, the rotating speed of a stirrer is 190rpm, the liquid level of the 4# crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the retention time of the C4-C6 mixed binary acid solution in the 4# crystallizer is 1 h;

5) C4-C6 mixed dibasic acid solution overflows from a No. 4 crystallizer into a No. 5 crystallizer, the temperature of materials in the No. 5 crystallizer is controlled by a jacket or a coil pipe to be reduced by 2-5 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the No. 4 crystallizer overflows when rising to the upstream end of an overflow pipe, the residence time of the C4-C6 mixed dibasic acid solution in the No. 5 crystallizer is 1h, the discharge temperature is 15-30 ℃, the mixed dibasic acid solution enters a solid-liquid separator to obtain C4-C6 mixed dibasic acid wet crystals, 40 wt% of the obtained mother solution reflows to the No. 1 crystallizer, and the rest mother solution is sent to a downstream process.

EXAMPLE five

And (3) carrying out six-stage purification on the mixed dibasic acid solution of C4-C6 by adopting a device with the same principle as the cooling crystallization device for implementing the first step:

1) C4-C6 mixed dibasic acid solution (wherein, succinic acid C4 component accounts for 20-30%, glutaric acid C5 component accounts for 50-60%, adipic acid C6 component accounts for 15-20%) is continuously pumped from a feed inlet of the 1# crystallizer, a jacket or a coil pipe is utilized to control the material temperature in the 1# crystallizer to be 43-52 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the 1# crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the detention time of the C4-C6 mixed dibasic acid solution in the 1# crystallizer is 1 h;

2) C4-C6 mixed binary acid solution overflows from the No. 1 crystallizer to the No. 2 crystallizer, the temperature of the material in the No. 2 crystallizer is controlled by a jacket or a coil pipe to be reduced by 2-5 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the No. 2 crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the detention time of the C4-C6 mixed binary acid solution in the No. 2 crystallizer is 1 h;

3) C4-C6 mixed binary acid solution overflows from the 2# crystallizer to the 3# crystallizer, the temperature of the material in the 3# crystallizer is controlled to be reduced by 2-5 ℃ by utilizing a jacket or a coil pipe, the rotating speed of a stirrer is 190rpm, the liquid level of the 3# crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the retention time of the C4-C6 mixed binary acid solution in the 3# crystallizer is 1 h;

4) C4-C6 mixed binary acid solution overflows from the 3# crystallizer to the 4# crystallizer, the temperature of the material in the 4# crystallizer is controlled to be reduced by 2-5 ℃ by utilizing a jacket or a coil pipe, the rotating speed of a stirrer is 190rpm, the liquid level of the 4# crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the retention time of the C4-C6 mixed binary acid solution in the 4# crystallizer is 1 h;

5) C4-C6 mixed binary acid solution overflows from a No. 4 crystallizer into a No. 5 crystallizer, the temperature of materials in the No. 5 crystallizer is controlled by a jacket or a coil pipe to be reduced by 2-5 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the No. 5 crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the retention time of the C4-C6 mixed binary acid solution in the No. 5 crystallizer is 1 h;

6) C4-C6 mixed dibasic acid solution overflows from a 5# crystallizer into a 6# crystallizer, the temperature of materials in the 6# crystallizer is controlled by a jacket or a coil pipe to be reduced by 2-5 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the 6# crystallizer overflows when rising to the upstream end of an overflow pipe, the retention time of the C4-C6 mixed dibasic acid solution in the 6# crystallizer is 1h, the discharge temperature is 15-30 ℃, the mixed dibasic acid solution enters a solid-liquid separator to obtain C4-C6 mixed dibasic acid wet crystals, 40 wt% of the obtained mother solution reflows to the 1# crystallizer, and the rest mother solution is sent to a downstream process.

EXAMPLE six

And (3) performing seven-stage purification on the mixed dibasic acid solution of C4-C6 by adopting a device with the same principle as the cooling crystallization device for implementing the first step:

1) C4-C6 mixed dibasic acid solution (wherein, succinic acid C4 component accounts for 20-30%, glutaric acid C5 component accounts for 50-60%, adipic acid C6 component accounts for 15-20%) is continuously pumped from a feed inlet of the 1# crystallizer, a jacket or a coil pipe is utilized to control the material temperature in the 1# crystallizer to be 43-52 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the 1# crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the detention time of the C4-C6 mixed dibasic acid solution in the 1# crystallizer is 1 h;

2) C4-C6 mixed binary acid solution overflows from the No. 1 crystallizer to the No. 2 crystallizer, the temperature of the material in the No. 2 crystallizer is controlled by a jacket or a coil pipe to be reduced by 2-5 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the No. 2 crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the detention time of the C4-C6 mixed binary acid solution in the No. 2 crystallizer is 1 h;

3) C4-C6 mixed binary acid solution overflows from the 2# crystallizer to the 3# crystallizer, the temperature of the material in the 3# crystallizer is controlled to be reduced by 2-5 ℃ by utilizing a jacket or a coil pipe, the rotating speed of a stirrer is 190rpm, the liquid level of the 3# crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the retention time of the C4-C6 mixed binary acid solution in the 3# crystallizer is 1 h;

4) C4-C6 mixed binary acid solution overflows from the 3# crystallizer to the 4# crystallizer, the temperature of the material in the 4# crystallizer is controlled to be reduced by 2-5 ℃ by utilizing a jacket or a coil pipe, the rotating speed of a stirrer is 190rpm, the liquid level of the 4# crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the retention time of the C4-C6 mixed binary acid solution in the 4# crystallizer is 1 h;

5) C4-C6 mixed binary acid solution overflows from a No. 4 crystallizer into a No. 5 crystallizer, the temperature of materials in the No. 5 crystallizer is controlled by a jacket or a coil pipe to be reduced by 2-5 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the No. 5 crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the retention time of the C4-C6 mixed binary acid solution in the No. 5 crystallizer is 1 h;

6) C4-C6 mixed binary acid solution overflows from the 5# crystallizer to the 6# crystallizer, the temperature of the material in the 6# crystallizer is controlled to be reduced by 2-5 ℃ by utilizing a jacket or a coil pipe, the rotating speed of a stirrer is 190rpm, the liquid level of the 6# crystallizer overflows downstream when rising to the upstream end of an overflow pipe, and the retention time of the C4-C6 mixed binary acid solution in the 6# crystallizer is 1 h;

6) C4-C6 mixed dibasic acid solution overflows from a 6# crystallizer into a 7# crystallizer, the temperature of materials in the 7# crystallizer is controlled by a jacket or a coil pipe to be reduced by 2-5 ℃, the rotating speed of a stirrer is 190rpm, the liquid level of the 7# crystallizer overflows when rising to the upstream end of an overflow pipe, the retention time of the C4-C6 mixed dibasic acid solution in the 7# crystallizer is 1h, the discharge temperature is 15-30 ℃, the mixed dibasic acid solution enters a solid-liquid separator to obtain C4-C6 mixed dibasic acid wet crystals, 40 wt% of the obtained mother solution reflows to the 1# crystallizer, and the rest mother solution is sent to a downstream process.

The wet crystals obtained in the second to sixth separation of examples were examined by the applicant and the data are shown in the following table: