Crystallization centrifugation process of bisphenol A

Abstract

The invention relates to the technical field of organic matter purification, and particularly discloses a bisphenol A crystallization centrifugal process. The crystallization and centrifugation process of bisphenol A adopts first-stage two-step suspension crystallization, first-stage vacuum filtration, second-stage two-step suspension crystallization and second-stage centrifugation, impurities in a product can be effectively separated by using a vacuum filter in the first stage, the productivity of a device can be improved by using a centrifugal machine in the second stage, the crystallization and centrifugation process is obviously superior to the existing crystallization and centrifugation process, the purity of obtained BPA reaches 99.9 wt% or above, and the purity of the BPA reaches 99.9 wt% or above. The content of 2, 4-bisphenol A isomers is remarkably reduced, and the 2, 4-bisphenol A resin has smaller melting color and luster and solution color and luster indexes, meets the production requirements of colorless and transparent polycarbonate resin, and has a wide market prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of organic matter purification, and more specifically, it relates to a crystallization and centrifugation process for bisphenol A. Background Art

[0002] Bisphenol A (BPA), as an important industrial chemical raw material, is widely used in the production of polycarbonate and epoxy resin. Currently, bisphenol A is usually continuously condensed from 2 moles of phenol and 1 mole of acetone in the liquid phase under the action of an acidic catalyst. In the mixed solution generated by the reaction, in addition to bisphenol A, it also contains impurities such as phenol, 2,4-BPA, tri-phenol, and acidic substances. In the traditional separation and purification process of bisphenol A, if the distillation method is used to remove bisphenol A, due to the need for a relatively high temperature, bisphenol A and impurities will undergo thermal decomposition in the presence of acidic substances, resulting in deterioration of product quality and coloring, and it is difficult to meet the requirements for producing high-quality bisphenol A products.

[0003] Currently, there are various technical solutions for the crystallization and centrifugation process of bisphenol A. For example: the process route of using a one-stage two-step suspension crystallization + a one-stage vacuum filter + a two-stage two-step suspension crystallization + a two-stage vacuum filter + a three-stage centrifuge. This process has a large number of equipment, complex operations, and high costs; the process of using a one-stage two-step stirring crystallization + a one-stage centrifuge + a two-stage two-step stirring crystallization + a two-stage centrifuge, although it simplifies the process to a certain extent, still has deficiencies in terms of impurity separation effect and product purity improvement; the process of using a one-stage one-step suspension crystallization + a one-stage vacuum filter + a three-stage falling film crystallization. This process has limitations in terms of crystallization method and equipment combination, and it is impossible to simultaneously achieve efficient impurity separation and high production capacity.

[0004] CN119350132A also discloses a crystallization method and a production method for bisphenol A, including the following steps: the liquid containing bisphenol A enters the first falling film crystallizer through a first feed tank for first-stage falling film crystallization, then enters the first falling film crystallizer through a second feed tank for second-stage falling film crystallization, and then enters the second falling film crystallizer through a third feed tank for third-stage falling film crystallization; wherein, the number of the first falling film crystallizers is two or more, and two or more first falling film crystallizers are connected in parallel; the number of the second falling film crystallizers is one or more. When the number of the second falling film crystallizers is multiple, multiple second falling film crystallizers are connected in parallel; this crystallization method still has the defects of complex process flow, a large number of equipment, and incomplete impurity separation. Therefore, the present invention proposes a crystallization and centrifugation process for bisphenol A. Summary of the Invention

[0005] The purpose of the present invention is to provide a crystallization and centrifugation process for bisphenol A, aiming to solve the problems in the prior art such as complex process flow, a large number of equipment, incomplete impurity separation, and low product quality.

[0006] The present invention provides a crystallization and centrifugation process for bisphenol A, adopting the following technical solution:

[0007] A crystallization and centrifugation process for bisphenol A includes the following steps:

[0008] S1. Primary two-step suspension crystallization

[0009] The mother liquor is cooled in the primary one-step crystallizer. After the formed slurry is pumped out, a part of it is circulated and the other part is sent to the primary two-step crystallizer; the slurry is cooled in the primary two-step crystallizer and then sent to the primary vacuum filter.

[0010] S2. Primary vacuum filtration

[0011] The slurry is rinsed after vacuum filtration, and the filter cake enters the dissolution tank; mother liquor is added to the dissolution tank to form a mixed solution, and the mixed solution is sent to the secondary one-step crystallizer.

[0012] S3. Secondary two-step suspension crystallization

[0013] The mixed solution is cooled in the secondary one-step crystallizer. After the formed slurry is pumped out, a part of it is circulated and the other part is sent to the secondary two-step crystallizer; the slurry is cooled in the secondary two-step crystallizer and then sent to the secondary centrifuge.

[0014] S4. Secondary centrifugation

[0015] The slurry is centrifuged by a sedimentation centrifuge to obtain bisphenol A, and the centrifugate is collected.

[0016] Furthermore, before the mother liquor in step S1 enters the primary one-step crystallizer, it is first heat-exchanged with the dehydration tower feed through a dehydration tower preheater, and then cooled to 80 - 85 °C by a crystallizer feed cooler.

[0017] Furthermore, the cooling temperature of the mother liquor in step S1 in the primary one-step crystallizer is 58 - 66 °C, and the cooling time is 0.5 - 2 h; the crystallization amount of the slurry obtained from the primary one-step crystallizer is 16 - 19 wt%.

[0018] Furthermore, the cooling temperature of the mother liquor in step S1 in the primary two-step crystallizer is 50 - 55 °C, and the cooling time is 0.5 - 2 h; the crystallization amount of the slurry obtained from the primary two-step crystallizer is 22 - 25 wt%.

[0019] Furthermore, the slurry obtained after the primary two-step suspension crystallization in step S1 consists of 1 mole of BPA and 1 mole of phenol.

[0020] Furthermore, the vacuum degree of the vacuum filtration in step S2 is (-0.08) - (-0.09) MPa.

[0021] Further, in the step S2, the liquid used for rinsing the crystal cake is the mother liquor or the centrifugate obtained by secondary centrifugation.

[0022] Further, the content of BPA in the mixed liquid obtained in the step S2 is 25-30 wt%.

[0023] Further, the cooling temperature of the mixed liquid in the secondary one-step crystallizer in the step S3 is 58-66°C, and the cooling time is 0.5-2 h; the crystallization amount of the slurry obtained through the secondary one-step crystallizer is 16-19 wt%.

[0024] Further, the cooling temperature of the mother liquor in the secondary two-step crystallizer in the step S3 is 50-55°C, and the cooling time is 0.5-2 h; the crystallization amount of the slurry obtained through the secondary two-step crystallizer is 22-25 wt%.

[0025] Further, the rotation speed of the centrifuge in the step S4 is 3000-4000 r / min, and the centrifugation time is 5-10 min.

[0026] In summary, the present invention has the following beneficial effects:

[0027] 1. The mother liquor of the present invention not only contains bisphenol A and phenol, but also 2,4-bisphenol A isomers, other heavy component impurities and acidic substances; in the first-stage crystallization, by controlling the cooling crystallization temperature and time, most of the bisphenol A can be precipitated in the form of adduct crystals, and at the same time, impurities can be prevented from being excessively wrapped in the crystals; in the second-stage crystallization, by controlling the cooling crystallization temperature and time, the crystallization process becomes more orderly, effectively reducing the entrainment of impurities and further improving the purity of bisphenol A crystals.

[0028] 2. The present invention adopts first-stage two-step suspension crystallization + first-stage vacuum filter + second-stage two-step suspension crystallization + second-stage centrifuge, shortening the process flow of the existing technology. The second-stage centrifuge is used to replace the second-stage vacuum filter + third-stage centrifuge, reducing the number of equipment. The first-stage use of the vacuum filter can effectively separate impurities in the product, and the second-stage use of the centrifuge can improve the production capacity of the device. The purity of the obtained BPA reaches 99.95 wt%, significantly reducing the content of 2,4-bisphenol A isomers; and it has smaller melting color and solution color indexes, meeting the production requirements of colorless and transparent polycarbonate resin. Specific Embodiments

[0029] The following further describes the present invention in detail with reference to embodiments.

[0030] Examples 1-5 provide a crystallization and centrifugation process for bisphenol A.

[0031] Example 1

[0032] A crystallization and centrifugation process for bisphenol A, comprising the following steps:

[0033] S0. Pretreat the mother liquor

[0034] The mother liquor is heat-exchanged with the dehydration tower feed through the dehydration tower preheater, and then cooled to 80 °C through the crystallizer feed cooler, and then the mother liquor is sent to the primary one-step crystallizer;

[0035] S1. Primary two-step suspension crystallization

[0036] The mother liquor is cooled to 60 °C in the primary one-step crystallizer, and the cooling time is 2 h to form a slurry containing 17 wt% crystals; the slurry is pumped out by the primary one-step crystallizer fine crystal pump, 1 / 3 of the slurry quality is recycled, and the rest is sent to the primary two-step crystallizer; the slurry is cooled to 50 °C in the primary two-step crystallizer, and the cooling time is 2 h to form a slurry containing 23 wt% crystals, and the formed slurry is composed of 1 mole of BPA and 1 mole of phenol, and then the slurry is sent to the primary vacuum filter through a pump;

[0037] S2. Primary vacuum filtration

[0038] The slurry separates the crystals from the mother liquor through vacuum filtration. The inside of the entire rotary drum filter is evacuated to -0.08 MPa by a liquid ring vacuum pump. After the crystal cake on the filter cloth is washed, it is discharged by nitrogen back blowing, and the removed filter cake falls into the dissolution tank; mother liquor is added to the dissolution tank to adjust the concentration of BPA to 25 wt%, and the mixed liquid is sent to the secondary one-step crystallizer;

[0039] S3. Secondary two-step suspension crystallization

[0040] The mixed liquid is cooled to 60 °C in the secondary one-step crystallizer, and the cooling time is 1 h to form a slurry containing 17 wt% crystals; the slurry is pumped out by the secondary one-step crystallizer fine crystal pump, 1 / 3 of the slurry quality is recycled, and the rest is sent to the secondary two-step crystallizer; the slurry is cooled to 50 °C in the secondary two-step crystallizer, and the cooling time is 1 h to form a slurry containing 23 wt% crystals, and then the slurry is sent to the secondary centrifuge through a pump;

[0041] S4. Secondary centrifugation

[0042] The slurry is centrifuged by a sedimentation centrifuge, the rotation speed of the centrifuge is 3500 r / min, and the centrifugation time is 8 min to obtain bisphenol A product and collect the centrifugate.

[0043] Example 2

[0044] A crystallization and centrifugation process for bisphenol A, comprising the following steps:

[0045] S0. Pretreat the mother liquor

[0046] The mother liquor exchanges heat with the dehydrator feed through the dehydrator preheater, and after being cooled to 82°C by the crystallizer feed cooler, the mother liquor is sent to the first-stage single-step crystallizer;

[0047] S1. First-stage two-step suspension crystallization

[0048] The mother liquor is cooled to 66°C in the first-stage single-step crystallizer, with a cooling time of 1.5 h, to form a slurry containing 19 wt% crystals; the slurry is pumped out by the fine crystal pump of the first-stage single-step crystallizer, 1 / 3 of the slurry mass is recycled, and the remaining is sent to the first-stage two-step crystallizer; the slurry is cooled to 55°C in the first-stage two-step crystallizer, with a cooling time of 1.5 h, to form a slurry containing 25 wt% crystals, and the formed slurry is composed of 1 mole of BPA and 1 mole of phenol, and then the slurry is sent to the first-stage vacuum filter by a pump;

[0049] S2. First-stage vacuum filtration

[0050] The slurry separates the crystals from the mother liquor through vacuum filtration. The inside of the entire rotary drum filter is evacuated to -0.08 MPa by a liquid ring vacuum pump. After the crystal cake on the filter cloth is rinsed, it is discharged by nitrogen back blowing, and the removed filter cake falls into the dissolution tank; mother liquor is added to the dissolution tank to adjust the concentration of BPA to 27 wt%, and the mixed liquid is sent to the second-stage single-step crystallizer;

[0051] S3. Second-stage two-step suspension crystallization

[0052] The mixed liquid is cooled to 63°C in the second-stage single-step crystallizer, with a cooling time of 1.5 h, to form a slurry containing 19 wt% crystals; the slurry is pumped out by the fine crystal pump of the second-stage single-step crystallizer, 1 / 3 of the slurry mass is recycled, and the remaining is sent to the second-stage two-step crystallizer; the slurry is cooled to 54°C in the second-stage two-step crystallizer, with a cooling time of 1.5 h, to form a slurry containing 25 wt% crystals, and then the slurry is sent to the second-stage centrifuge by a pump;

[0053] S4. Second-stage centrifugation

[0054] The slurry is centrifuged using a sedimentation centrifuge, with the centrifuge rotating speed of 3000 r / min and the centrifugation time of 5 min, to obtain bisphenol A product and collect the centrifugate.

[0055] Example 3

[0056] A crystallization and centrifugation process for bisphenol A includes the following steps:

[0057] S0. Pretreat the mother liquor

[0058] The mother liquor exchanges heat with the dehydrator feed through the dehydrator preheater, and after being cooled to 83°C by the crystallizer feed cooler, the mother liquor is sent to the first-stage single-step crystallizer;

[0059] S1, First-stage two-step suspension crystallization

[0060] The mother liquor is cooled to 62 °C in the first-stage one-step crystallizer for 1 h to form a slurry containing 18 wt% crystals; the slurry is pumped out by the fines pump of the first-stage one-step crystallizer, 1 / 3 of the slurry quality is recycled, and the remaining is sent to the first-stage two-step crystallizer; the slurry is cooled to 52 °C in the first-stage two-step crystallizer for 1 h to form a slurry containing 24 wt% crystals, and the formed slurry is composed of 1 mole of BPA and 1 mole of phenol, and then the slurry is sent to the first-stage vacuum filter by a pump;

[0061] S2, First-stage vacuum filtration

[0062] The slurry separates the crystals from the mother liquor by vacuum filtration. The inside of the entire rotary drum filter is evacuated to -0.09 MPa by a liquid ring vacuum pump. After the crystal cake on the filter cloth is washed, it is discharged by nitrogen back blowing, and the removed filter cake falls into the dissolution tank; mother liquor is added to the dissolution tank to adjust the concentration of BPA to 26 wt%, and the mixed liquid is sent to the second-stage one-step crystallizer;

[0063] S3, Second-stage two-step suspension crystallization

[0064] The mixed liquid is cooled to 61 °C in the second-stage one-step crystallizer for 2 h to form a slurry containing 18 wt% crystals; the slurry is pumped out by the fines pump of the second-stage one-step crystallizer, 1 / 3 of the slurry quality is recycled, and the remaining is sent to the second-stage two-step crystallizer; the slurry is cooled to 53 °C in the second-stage two-step crystallizer for 2 h to form a slurry containing 24 wt% crystals, and then the slurry is sent to the second-stage centrifuge by a pump;

[0065] S4, Second-stage centrifugation

[0066] The slurry is centrifuged using a sedimentation centrifuge at a rotational speed of 3200 r / min for 7 min to obtain bisphenol A product and collect the centrifugate.

[0067] Example 4

[0068] A crystallization and centrifugation process for bisphenol A, comprising the following steps:

[0069] S0, Pretreatment of mother liquor

[0070] The mother liquor is heat-exchanged with the dehydration tower feed through the dehydration tower preheater, and then cooled to 84 °C through the crystallizer feed cooler, and then the mother liquor is sent to the first-stage one-step crystallizer;

[0071] S1, First-stage two-step suspension crystallization

[0072] The mother liquor is cooled to 61 °C in the first-stage one-step crystallizer for 1.5 h to form a slurry containing 18 wt% crystals; the slurry is pumped out by the fines pump of the first-stage one-step crystallizer, 1 / 3 of the slurry mass is recycled, and the rest is sent to the first-stage two-step crystallizer; the slurry is cooled to 51 °C in the first-stage two-step crystallizer for 1 h to form a slurry containing 24 wt% crystals, and the formed slurry is composed of 1 mole of BPA and 1 mole of phenol, and then the slurry is sent to the first-stage vacuum filter by a pump;

[0073] S2. First-stage vacuum filtration

[0074] The slurry separates the crystals from the mother liquor by vacuum filtration. The inside of the entire rotary drum filter is evacuated to -0.08 MPa by a liquid ring vacuum pump. After the crystal cake on the filter cloth is rinsed, it is discharged by nitrogen back blowing, and the removed filter cake falls into the dissolution tank; mother liquor is added to the dissolution tank to adjust the concentration of BPA to 28 wt%, and the mixed liquid is sent to the second-stage one-step crystallizer;

[0075] S3. Second-stage two-step suspension crystallization

[0076] The mixed liquid is cooled to 59 °C in the second-stage one-step crystallizer for 1.5 h to form a slurry containing 18 wt% crystals; the slurry is pumped out by the fines pump of the second-stage one-step crystallizer, 1 / 3 of the slurry mass is recycled, and the rest is sent to the second-stage two-step crystallizer; the slurry is cooled to 52 °C in the second-stage two-step crystallizer for 1 h to form a slurry containing 24 wt% crystals, and then the slurry is sent to the second-stage centrifuge by a pump;

[0077] S4. Second-stage centrifugation

[0078] The slurry is centrifuged using a sedimentation centrifuge at a rotational speed of 3800 r / min for 9 min to obtain bisphenol A product and collect the centrifugate.

[0079] Example 5

[0080] A crystallization and centrifugation process for bisphenol A, comprising the following steps:

[0081] S0. Pretreatment of mother liquor

[0082] The mother liquor exchanges heat with the dehydration tower feed in the dehydration tower preheater, and then is cooled to 85 °C by the crystallizer feed cooler, and then the mother liquor is sent to the first-stage one-step crystallizer;

[0083] S1. First-stage two-step suspension crystallization

[0084] The mother liquor is cooled to 58 °C in the first-stage one-step crystallizer for 0.5 h to form a slurry containing 16 wt% crystals; the slurry is pumped out by the fines pump of the first-stage one-step crystallizer, 1 / 3 of the slurry mass is recycled, and the remaining is sent to the first-stage two-step crystallizer; the slurry is cooled to 55 °C in the first-stage two-step crystallizer for 0.5 h to form a slurry containing 22 wt% crystals, and the formed slurry is composed of 1 mole of BPA and 1 mole of phenol, and then the slurry is sent to the first-stage vacuum filter by a pump;

[0085] S2. First-stage vacuum filtration

[0086] The slurry separates the crystals from the mother liquor by vacuum filtration. The inside of the entire rotary drum filter is evacuated to -0.08 MPa by a liquid ring vacuum pump. After the crystal cake on the filter cloth is rinsed, it is discharged by nitrogen back blowing, and the removed filter cake falls into the dissolution tank; mother liquor is added to the dissolution tank to adjust the concentration of BPA to 30 wt%, and the mixed liquid is sent to the second-stage one-step crystallizer;

[0087] S3. Second-stage two-step suspension crystallization

[0088] The mixed liquid is cooled to 58 °C in the second-stage one-step crystallizer for 0.5 h to form a slurry containing 16 wt% crystals; the slurry is pumped out by the fines pump of the second-stage one-step crystallizer, 1 / 3 of the slurry mass is recycled, and the remaining is sent to the second-stage two-step crystallizer; the slurry is cooled to 50 °C in the second-stage two-step crystallizer for 0.5 h to form a slurry containing 22 wt% crystals, and then the slurry is sent to the second-stage centrifuge by a pump;

[0089] S4. Second-stage centrifugation

[0090] The slurry is centrifuged using a sedimentation centrifuge at a rotational speed of 4000 r / min for 10 min to obtain bisphenol A product and collect the centrifugate.

[0091] To verify the performance of the bisphenol A provided by the present invention, the applicant set Comparative Examples 1-5, wherein:

[0092] Comparative Example 1

[0093] A crystallization and centrifugation process for bisphenol A includes the following steps:

[0094] S0. Pretreatment of mother liquor

[0095] The mother liquor is heat-exchanged with the dehydration tower feed through the dehydration tower preheater, and then cooled to 80 °C through the crystallizer feed cooler, and then the mother liquor is sent to the first-stage one-step crystallizer;

[0096] S1. First-stage two-step suspension crystallization

[0097] The mother liquor is cooled to 60 °C in the first-stage one-step crystallizer for 2 h to form a slurry containing 17 wt% crystals; the slurry is pumped out by the fine crystal pump of the first-stage one-step crystallizer, 1 / 3 of the slurry quality is recycled, and the rest is sent to the first-stage two-step crystallizer; the slurry is cooled to 50 °C in the first-stage two-step crystallizer for 2 h to form a slurry containing 23 wt% crystals, and the formed slurry consists of 1 mole of BPA and 1 mole of phenol, and then the slurry is sent to the first-stage vacuum filter by a pump;

[0098] S2. First-stage vacuum filtration

[0099] The slurry separates the crystals from the mother liquor by vacuum filtration. The inside of the entire rotary drum filter is evacuated to -0.08 MPa by a liquid ring vacuum pump. After the crystal cake on the filter cloth is rinsed, it is discharged by nitrogen back blowing to obtain bisphenol A product.

[0100] Comparative Example 2

[0101] A crystallization and centrifugation process for bisphenol A includes the following steps:

[0102] S0. Pretreatment of mother liquor

[0103] The mother liquor is heat-exchanged with the dehydration tower feed through the dehydration tower preheater, and then cooled to 80 °C through the crystallizer feed cooler, and then the mother liquor is sent to the first-stage one-step crystallizer;

[0104] S1. First-stage two-step suspension crystallization

[0105] The mother liquor is cooled to 60 °C in the first-stage one-step crystallizer for 2 h to form a slurry containing 17 wt% crystals; the slurry is pumped out by the fine crystal pump of the first-stage one-step crystallizer, 1 / 3 of the slurry quality is recycled, and the rest is sent to the first-stage two-step crystallizer; the slurry is cooled to 50 °C in the first-stage two-step crystallizer for 2 h to form a slurry containing 23 wt% crystals, and the formed slurry consists of 1 mole of BPA and 1 mole of phenol, and then the slurry is sent to the first-stage centrifuge by a pump;

[0106] S2. First-stage centrifugation

[0107] The slurry is centrifuged by a sedimentation centrifuge. The rotational speed of the centrifuge is 3500 r / min, and the centrifugation time is 8 min to obtain bisphenol A product and collect the centrifugate.

[0108] Comparative Example 3

[0109] A crystallization and centrifugation process for bisphenol A includes the following steps:

[0110] S0. Pretreatment of mother liquor

[0111] The mother liquor exchanges heat with the dehydration tower feed through the dehydration tower preheater, and after being cooled to 80°C through the crystallizer feed cooler, the mother liquor is sent to the first-stage one-step crystallizer;

[0112] S1. First-stage two-step suspension crystallization

[0113] The mother liquor is cooled to 60°C in the first-stage one-step crystallizer, with a cooling time of 2 h, to form a slurry containing 17 wt% crystals; the slurry is pumped out by the first-stage one-step crystallizer fines pump, 1 / 3 of the slurry mass is recycled, and the remaining is sent to the first-stage two-step crystallizer; the slurry is cooled to 50°C in the first-stage two-step crystallizer, with a cooling time of 2 h, to form a slurry containing 23 wt% crystals, and the formed slurry is composed of 1 mole of BPA and 1 mole of phenol, and then the slurry is sent to the first-stage vacuum filter by a pump;

[0114] S2. First-stage vacuum filtration

[0115] The slurry separates the crystals from the mother liquor through vacuum filtration. The entire inside of the rotary drum filter is evacuated to -0.08 MPa by a liquid ring vacuum pump. After the crystal cake on the filter cloth is rinsed, it is discharged by nitrogen back blowing, and the removed cake falls into the dissolution tank; mother liquor is added to the dissolution tank to adjust the concentration of BPA to 25 wt%, and the mixed liquid is sent to the second-stage one-step crystallizer;

[0116] S3. Second-stage two-step suspension crystallization

[0117] The mixed liquid is cooled to 60°C in the second-stage one-step crystallizer, with a cooling time of 1 h, to form a slurry containing 17 wt% crystals; the slurry is pumped out by the second-stage one-step crystallizer fines pump, 1 / 3 of the slurry mass is recycled, and the remaining is sent to the second-stage two-step crystallizer; the slurry is cooled to 50°C in the second-stage two-step crystallizer, with a cooling time of 1 h, to form a slurry containing 23 wt% crystals, and then the slurry is sent to the second-stage vacuum filtration by a pump;

[0118] S4. Second-stage vacuum filtration

[0119] The slurry separates the crystals from the mother liquor through vacuum filtration. The entire inside of the rotary drum filter is evacuated to -0.08 MPa by a liquid ring vacuum pump. After the crystal cake on the filter cloth is rinsed, it is discharged by nitrogen back blowing to obtain bisphenol A product.

[0120] Comparative Example 4

[0121] A crystallization and centrifugation process for bisphenol A includes the following steps:

[0122] S0. Pretreat the mother liquor

[0123] The mother liquor exchanges heat with the dehydration tower feed through the dehydration tower preheater, and after being cooled to 80°C through the crystallizer feed cooler, the mother liquor is sent to the first-stage one-step crystallizer;

[0124] S1, First-stage two-step suspension crystallization

[0125] The mother liquor is cooled to 60 °C in the first-stage one-step crystallizer for 2 hours to form a slurry containing 17 wt% crystals; the slurry is pumped out by the fines pump of the first-stage one-step crystallizer, 1 / 3 of the slurry quality is recycled, and the remaining is sent to the first-stage two-step crystallizer; the slurry is cooled to 50 °C in the first-stage two-step crystallizer for 2 hours to form a slurry containing 23 wt% crystals, and the formed slurry is composed of 1 mole of BPA and 1 mole of phenol, and then the slurry is sent to the first-stage centrifuge by a pump;

[0126] S2, First-stage centrifugation

[0127] The slurry is centrifuged using a sedimentation centrifuge at a rotational speed of 3500 r / min for 8 minutes, and the centrifuged material is transferred to the dissolution tank; mother liquor is added to the dissolution tank to adjust the BPA concentration to 25 wt%, and the mixed solution is sent to the second-stage one-step crystallizer;

[0128] S3, Second-stage two-step suspension crystallization

[0129] The mixed solution is cooled to 60 °C in the second-stage one-step crystallizer for 1 hour to form a slurry containing 17 wt% crystals; the slurry is pumped out by the fines pump of the second-stage one-step crystallizer, 1 / 3 of the slurry quality is recycled, and the remaining is sent to the second-stage two-step crystallizer; the slurry is cooled to 50 °C in the second-stage two-step crystallizer for 1 hour to form a slurry containing 23 wt% crystals, and then the slurry is sent to the second-stage centrifuge by a pump;

[0130] S4, Second-stage centrifugation

[0131] The slurry is centrifuged using a sedimentation centrifuge at a rotational speed of 3500 r / min for 8 minutes to obtain bisphenol A product, and the centrifugate is collected.

[0132] Comparative Example 5

[0133] A crystallization and centrifugation process for bisphenol A, comprising the following steps:

[0134] S0, Pretreatment of mother liquor

[0135] The mother liquor is heat-exchanged with the dehydration tower feed through the dehydration tower preheater, and then cooled to 80 °C through the crystallizer feed cooler, and then the mother liquor is sent to the first-stage one-step crystallizer;

[0136] S1, First-stage two-step suspension crystallization

[0137] The mother liquor is cooled to 60 °C in the first-stage one-step crystallizer for 2 hours to form a slurry containing 17 wt% crystals; the slurry is pumped out by the fine crystal pump of the first-stage one-step crystallizer, 1 / 3 of the slurry quality is recycled, and the rest is sent to the first-stage two-step crystallizer; the slurry is cooled to 50 °C in the first-stage two-step crystallizer for 2 hours to form a slurry containing 23 wt% crystals, and the formed slurry is composed of 1 mole of BPA and 1 mole of phenol, and then the slurry is sent to the first-stage centrifuge by a pump;

[0138] S2. First-stage centrifugation

[0139] The slurry is centrifuged using a sedimentation centrifuge. The rotation speed of the centrifuge is 3500 r / min, and the centrifugation time is 8 minutes. The centrifuged material is transferred to the dissolution tank; mother liquor is added to the dissolution tank to adjust the concentration of BPA to 25 wt%, and the mixed solution is sent to the second-stage one-step crystallizer;

[0140] S3. Second-stage two-step suspension crystallization

[0141] The mixed solution is cooled to 60 °C in the second-stage one-step crystallizer for 1 hour to form a slurry containing 17 wt% crystals; the slurry is pumped out by the fine crystal pump of the second-stage one-step crystallizer, 1 / 3 of the slurry quality is recycled, and the rest is sent to the second-stage two-step crystallizer; the slurry is cooled to 50 °C in the second-stage two-step crystallizer for 1 hour to form a slurry containing 23 wt% crystals, and then the slurry is sent to the second-stage vacuum filter by a pump;

[0142] S4. Second-stage vacuum filtration

[0143] The slurry separates the crystals from the mother liquor through vacuum filtration. The inside of the entire rotary drum filter is evacuated to -0.08 MPa by a liquid ring vacuum pump. After the crystal cake on the filter cloth is rinsed, it is discharged by nitrogen back blowing to obtain bisphenol A product.

[0144] The purity, melting color and solution color of the bisphenol A obtained in Examples 1-5 and Comparative Examples 1-5 are detected respectively, and the following result parameters are obtained. See Table 1 for details:

[0145] Table 1:

[0146] Purity / wt% Melt Color / APHA Solution Color / APHA Example 1 99.95 9 5 Example 2 99.96 8 6 Example 3 99.99 7 6 Example 4 99.98 8 6 Example 5 99.97 8 5 Comparative Example 1 92.23 86 79 Comparative Example 2 89.45 102 94 Comparative Example 3 97.56 61 52 Comparative Example 4 95.98 69 58 Comparative Example 5 99.07 34 27

[0147] It can be seen from the data shown in Table 1 above that the crystallization and centrifugation process of the present invention adopts first-stage two-step suspension crystallization + first-stage vacuum filtration + second-stage two-step suspension crystallization + second-stage centrifugation, which is significantly superior to the existing crystallization and centrifugation process. The purity of the obtained BPA reaches more than 99.9 wt%, and it has smaller melting color and solution color indexes, meeting the production requirements of colorless and transparent polycarbonate resin.

[0148] This specific embodiment is only an interpretation of the present invention and is not a limitation thereof. After reading this specification, those skilled in the art may make modifications to this embodiment that do not contribute creatively as needed, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A crystallization centrifugation process for bisphenol A, characterized in that, It includes the following steps: S1. First-stage two-step suspension crystallization: The mother liquor is cooled in the first-stage one-step crystallizer. After the formed slurry is pumped out, a part of it is circulated and the other part is sent to the first-stage two-step crystallizer; the slurry is cooled in the first-stage two-step crystallizer and then sent to the first-stage vacuum filter. S2. First-stage vacuum filtration The slurry is filtered under vacuum and then rinsed. The filter cake enters the dissolution tank; mother liquor is added to the dissolution tank to form a mixed solution, and the mixed solution is sent to the second-stage one-step crystallizer. S3. Second-stage two-step suspension crystallization The mixed solution is cooled in the second-stage one-step crystallizer. After the formed slurry is pumped out, a part of it is circulated and the other part is sent to the second-stage two-step crystallizer. The slurry is cooled in the second-stage two-step crystallizer and then sent to the second-stage centrifuge. S4. Second-stage centrifugation The slurry is centrifuged using a sedimentation centrifuge to obtain bisphenol A, and the centrifugate is collected.

2. The centrifugation process for bisphenol A crystallization according to claim 1, characterized in that, Before the mother liquor in step S1 enters the first-stage one-step crystallizer, it is first heat-exchanged with the dehydration tower feed through a dehydration tower preheater and then cooled to 80 - 85 °C through a crystallizer feed cooler.

3. A crystallization centrifugation process for bisphenol A according to claim 1, characterized in that, The cooling temperature of the mother liquor in step S1 in the first-stage one-step crystallizer is 58 - 66 °C, and the cooling time is 0.5 - 2 h; the crystal content of the slurry obtained from the first-stage one-step crystallizer is 16 - 19 wt%.

4. A crystallization centrifugation process for bisphenol A according to claim 1, characterized in that, The cooling temperature of the mother liquor in step S1 in the first-stage two-step crystallizer is 50 - 55 °C, and the cooling time is 0.5 - 2 h; the crystal content of the slurry obtained from the first-stage two-step crystallizer is 22 - 25 wt%.

5. A crystallization centrifugation process for bisphenol A according to claim 1, characterized in that, The vacuum degree of the vacuum filtration in step S2 is (-0.08) - (-0.09) MPa.

6. The crystallization centrifugation process of bisphenol A according to claim 1, characterized in that, In step S2, the liquid used to rinse the crystal filter cake is mother liquor or the centrifugate obtained from the second-stage centrifugation.

7. A crystallization centrifugation process for bisphenol A according to claim 1, characterized in that, The content of BPA in the mixed solution obtained in step S2 is 25 - 30 wt%.

8. A crystallization centrifugation process for bisphenol A according to claim 1, characterized in that, The cooling temperature of the mixed solution in step S3 in the second-stage one-step crystallizer is 58 - 66 °C, and the cooling time is 0.5 - 2 h. The crystal content of the slurry obtained from the second-stage one-step crystallizer is 16 - 19 wt%.

9. A crystallization centrifugation process for bisphenol A according to claim 1, characterized in that, The cooling temperature of the mother liquor in step S3 in the second-stage two-step crystallizer is 50 - 55 °C, and the cooling time is 0.5 - 2 h. The crystal content of the slurry obtained from the second-stage two-step crystallizer is 22 - 25 wt%.

10. A crystallization centrifugation process for bisphenol A according to claim 1, characterized in that, In step S4, the rotation speed of the centrifuge is 3000 - 4000 r / min, and the centrifugation time is 5 - 10 min.