Bisphenol A production method and crystallization refining system

Abstract

The invention relates to the technical field of bisphenol A preparation, in particular to a bisphenol A production method and a crystallization refining system. The invention provides a reverse heating crystallization bisphenol A production method, which comprises the following steps: carrying out shock cooling on a dehydrated and flashed bisphenol A reaction liquid to form a first reaction liquid containing primary large crystals, so as to reduce the crystal viscosity, reduce the adhesion and wall hanging of the crystals on positions such as the wall surface of a crystallizer and improve the scaling problem, and then carrying out subsection small gradient heating and heat preservation on the first reaction liquid to obtain the primary large crystals. According to the invention, the small-size crystal is dissolved and the secondary growth of the large crystal is promoted, so that bisphenol A with larger particle size and narrower particle size distribution can be obtained, the scaling problem is improved, the reaction efficiency is improved, and the equipment operation and maintenance cost is reduced.

Description

Technical Field

[0001] This application relates to the field of bisphenol A preparation technology, and in particular to a method for producing bisphenol A and a crystallization and refining system. Background Technology

[0002] Bisphenol A (BPA) is an important organic chemical raw material and a major raw material for the production of polycarbonate and epoxy resin. The traditional preparation method of BPA uses continuous cooling crystallization, which precipitates crystals by gradually lowering the temperature. However, this method has the following problems: 1) The crystal particle size distribution is wide, and small-sized crystals are prone to clogging the equipment, making separation difficult; 2) The inner wall of the crystallizer is frequently scaled, requiring monthly shutdown for cleaning.

[0003] To address the above issues, industrial production mainly improves the situation by optimizing cooling curves, washing parameters, and equipment insulation and heat tracing, but these methods have failed to solve the problems of scaling and crystal particle size control. Summary of the Invention

[0004] Therefore, the main objective of this application is to provide a method for producing bisphenol A by reverse temperature crystallization, in order to control the crystal particle size distribution and improve the scaling problem. Simultaneously, this application provides a crystallization and refining system that can meet the requirements of the above production method.

[0005] In a first aspect, this application provides a method for producing bisphenol A, comprising the following steps:

[0006] The bisphenol A reaction solution after dehydration and flash evaporation is cooled from the flash evaporation temperature to the first crystallization temperature and kept at that temperature for the first time to form the first reaction solution; the first crystallization temperature is 48℃-60℃.

[0007] The first reaction solution is heated to the second crystallization temperature and then kept at that temperature for a second time to form the second reaction solution;

[0008] The second reaction solution is heated to the third crystallization temperature and held at that temperature for a third time to form a third reaction solution containing the target crystals; the third reaction solution is then subjected to solid-liquid separation to prepare the bisphenol A.

[0009] The second crystallization temperature is 4°C-6°C higher than the first crystallization temperature; the third crystallization temperature is 4°C-6°C higher than the second crystallization temperature.

[0010] In some embodiments, the first crystallization temperature is 50°C-55°C.

[0011] In some embodiments, the duration of the first heat preservation, the duration of the second heat preservation, and the duration of the third heat preservation are each independently 1h-3h.

[0012] In some embodiments, the flash temperature is 120°C-130°C.

[0013] In some embodiments, the bisphenol A production method is carried out using a crystallization and refining system, which includes a dehydration unit, a flash evaporation unit, and a crystallization unit connected in sequence; the crystallization unit includes a first crystallizer, a second crystallizer, and a third crystallizer connected in sequence, with the first crystallizer connected to the flash evaporation unit;

[0014] The bottom inner wall of the first crystallizer is equipped with a distributor; the second and third crystallizers are equipped with an external circulation heating device on the outside and a spiral coil heating device inside.

[0015] The bisphenol A reaction solution is passed into the dehydration unit and the flash evaporation unit for dehydration and flash evaporation; the bisphenol A reaction solution after dehydration and flash evaporation is transported to the first crystallizer, and a liquid low-boiling-point substance is introduced into the distributor of the first crystallizer to cool the bisphenol A reaction solution after dehydration and flash evaporation to the first crystallization temperature and perform the first heat preservation to form the first reaction solution;

[0016] The first reaction solution is transported to the second crystallizer, and heated to the second crystallization temperature by an external circulation heating device and a spiral coil heating device, and then subjected to a second heat preservation to form the second reaction solution;

[0017] The second reaction solution is transported to the third crystallizer and heated to the third crystallization temperature by an external circulation heating device and a spiral coil heating device, and then subjected to a third heat preservation to form a third reaction solution containing the target crystals.

[0018] Optionally, the liquid low-boiling-point substance includes alkanes with a boiling point of 28°C-50°C.

[0019] In some embodiments, the amount of the liquid low-boiling-point substance injected is 5%-15% of the volume of the bisphenol A reaction liquid;

[0020] And / or, the liquid low-boiling-point substance includes at least one of liquid pentane, liquid isopentane, and liquid cyclopentane.

[0021] In some embodiments, the conditions for heating by the external circulation heating device and the spiral coil heating device include: heating a portion of the corresponding reaction solution to 70°C-85°C via the external circulation heating device and then returning it to the corresponding crystallizer, while simultaneously introducing hot water at 60°C-75°C into the spiral coil heating device for internal heating.

[0022] In some embodiments, the corresponding reaction solution is 10v / v%-30v / v of the corresponding reaction solution.

[0023] In some embodiments, the heat distribution ratio between the external circulation heating device and the spiral coil heating device is (1.2-1.8):1.

[0024] In some embodiments, the dehydration unit is provided with multiple sections of packing from top to bottom, with feed coming from the upper middle part, a condensation device at the top of the tower, and a reboiling device at the bottom of the tower.

[0025] In some embodiments, the flash unit is equipped with a condensation device and a reboiling device, and has an internal cavity with a shape that is wider at the top and narrower at the bottom.

[0026] In some embodiments, the crystallization purification system further includes a centrifuge for solid-liquid separation of the third reaction liquid to prepare the bisphenol A.

[0027] A second aspect of this application provides a crystallization refining system, comprising a dehydration unit, a flash evaporation unit, and a crystallization unit connected in sequence; the crystallization unit includes a first crystallizer, a second crystallizer, and a third crystallizer connected in sequence, the first crystallizer being connected to the flash evaporation unit;

[0028] The first crystallizer has a distributor on the bottom inner wall and a condenser on the top inner wall; the second and third crystallizers are equipped with an external circulation heating device on the outside and a spiral coil heating device on the inside.

[0029] The dehydration unit and flash evaporation unit are used to dehydrate and flash evaporate the bisphenol A reaction solution;

[0030] The first crystallizer, the second crystallizer, and the third crystallizer are used sequentially to cool, heat, and heat the bisphenol A reaction solution after dehydration and flash evaporation, respectively, to form a reaction solution containing the target crystals.

[0031] The distributor is used to inject liquid low-boiling-point substances to cool the bisphenol A reaction solution after dehydration and flash evaporation.

[0032] The external circulation heating device is used to introduce a portion of the corresponding reaction liquid for external circulation heating, and the spiral coil heating device is used to introduce hot water for internal heating, thereby achieving the first heating and the second heating.

[0033] Studies have found that the traditional method for preparing bisphenol A uses continuous cooling crystallization, which precipitates crystals by gradually lowering the temperature. However, this method has the following problems: 1) the crystal particle size distribution is wide, and small-sized crystals easily clog the equipment, making separation difficult; 2) frequent scaling occurs on the inner wall of the crystallizer, requiring monthly shutdowns for cleaning. Industrial production mainly improves these methods by optimizing cooling curves, washing parameters, and equipment insulation and heat tracing, but these methods have not solved the scaling and crystal particle size control problems.

[0034] Based on this, this application provides a method for producing bisphenol A by reverse heating crystallization. The bisphenol A reaction solution after dehydration and flash evaporation is rapidly cooled to form a first reaction solution containing primary large crystals. This reduces the viscosity of the crystals and decreases the adhesion of crystals to the crystallizer wall and other locations, thus improving the scaling problem. Then, the first reaction solution is heated in stages with small gradients and kept at the temperature to dissolve the small-sized crystals and promote the secondary growth of large crystals. This can obtain bisphenol A with larger particle size and narrower particle size distribution, improve the scaling problem, increase reaction efficiency, and reduce equipment operation and maintenance costs. Attached Figure Description

[0035] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0036] Figure 1 This is a schematic diagram of a crystallization purification system according to an embodiment of this application;

[0037] Figure 2 The particle size and particle size distribution of bisphenol A in Example 1 and Comparative Example 1 of this application are shown.

[0038] The components include: 1. Dehydration tower; 2. Dehydration tower reflux tank; 3. Flash evaporation unit; 4. First crystallizer; 5. Second crystallizer; 6. Third crystallizer; 7. Horizontal screw centrifuge; 8. Bisphenol A reaction liquid feed pipe; 9. Light component discharge pipe; 10. Dehydration tower bottom discharge pipe; 11. Flash evaporation phenol discharge pipe; 12. Flash tank discharge pipe; 13. Liquid low-boiling-point substance feed pipe; 14. Vaporized liquid low-boiling-point substance discharge pipe; 15. First crystallizer discharge pipe; 16. Discharge pipe; 17. Second crystallizer discharge pipe; 18. Discharge pipe; 19. Third crystallizer discharge pipe; 20. Centrifuge filtrate discharge pipe; 21. Centrifuge washing liquid discharge pipe; 22. Centrifuge solid phase discharge pipe. Detailed Implementation

[0039] The following detailed description of the bisphenol A production method and crystallization purification system of this application, with reference to specific embodiments, provides further details. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0041] In this application, the terms “center,” “upper,” “lower,” “left,” “right,” “vertical,” “horizontal,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0042] In this article, "one or more" refers to any one, two or more of the listed items.

[0043] In this application, terms such as "first aspect," "second aspect," "third aspect," and "fourth aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, terms such as "first," "second," "third," and "fourth" serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0044] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0045] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0046] Unless otherwise specified, the percentage content mentioned in this application refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures.

[0047] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0048] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows for temperature fluctuations within the precision range controlled by the instrument.

[0049] In this application, the annual operating load is calculated as follows: the single crystal melting cycle is 15 days, and the production load during the crystal melting period is 30%, taking the bisphenol A crystal yield of Comparative Example 1 as 100%; the annual operating load = number of crystal meltings × 15 × 30% / 365 + (365 - number of crystal meltings × 15) × bisphenol A crystal yield / 365. Taking Comparative Example 1 as an example, its annual operating load = 12 × 15 × 30% / 365 + (365 - 12 × 15) × 100% / 365 = 65.48%; taking Example 1 as an example, its annual operating load = 2 × 15 × 30% / 365 + (365 - 2 × 15) × 100% / 365 = 94.25%; taking Comparative Example 1 as an example, its annual operating load = 2 × 15 × 30% / 365 + (365 - 2 × 15) × 85% / 365 = 80.5%.

[0050] In this application, the overall impurity removal rate is determined by the following method: the impurities in the crystallizer feed and discharge are tested by high performance liquid chromatography, and the removal rate is calculated, i.e., removal rate = (impurity content in crystallizer feed - impurity content in crystallizer discharge) / impurity content in crystallizer feed × 100%; the dry basis purity of the product is determined by the following method: by high performance liquid chromatography; the particle size and particle size distribution of bisphenol A are determined by the BT-2900 dynamic image particle size and shape analysis system (dry method).

[0051] like Figure 1 As shown, this is an exemplary illustration of the crystallization and refining system of this application and not a limitation thereof. In some embodiments, the crystallization and refining system of this application includes a dehydration unit (dehydration tower) 1, a flash evaporation unit (flash tank) 3, a crystallization unit, and a centrifugation device (horizontal screw centrifuge) 7 connected in sequence; the crystallization unit includes a first crystallizer 4, a second crystallizer 5, and a third crystallizer 6 connected in sequence.

[0052] The dehydration tower 1 includes a top condenser and a bottom reboiler. Its interior is packed with multiple sections of packing from top to bottom, with feed entering from the upper middle section. The dehydration tower 1 is equipped with a bisphenol A reaction liquid feed pipe 8 (for introducing the bisphenol A reaction liquid) and a dehydration tower bottom discharge pipe 10 (for conveying the dehydrated bisphenol A reaction liquid to the flash evaporation unit 3). A dehydration tower reflux tank 2 is connected to the upper part of the dehydration tower 1. The dehydration tower reflux tank 2 is equipped with a light component discharge pipe for discharging water and some light components such as phenol.

[0053] Flash tank 3 includes a flash tank condenser and a reboiling device. It has an internal cavity and a shape that is wider at the top and narrower at the bottom. Flash tank 3 is equipped with a flash phenol discharge pipe 11 (used to transport flash phenol to centrifuge device 7 as washing liquid to wash bisphenol A) and a flash tank discharge pipe 12 (used to transport the flashed reaction liquid to the first crystallizer 4).

[0054] Crystallization unit: connected to flash tank, the bottom inner wall of the first crystallizer 4 is provided with a distributor and the middle is provided with a stirring paddle; the bottom of the first crystallizer 4 is provided with a liquid low boiling point substance feed pipe 13 (connected to the distributor, used to transport liquid low boiling point substances) and a first crystallizer discharge pipe 15 (used to discharge the first reaction liquid containing primary large crystals to the second crystallizer 5); the upper part of the first crystallizer 4 is provided with a vaporized liquid low boiling point substance discharge pipe 14, used to discharge the vaporized liquid low boiling point substance;

[0055] The second crystallizer 5 and the third crystallizer 6 are equipped with an external circulation heating device and an internal spiral coil heating device, with a stirring paddle in the middle. The second crystallizer 5 has a discharge pipe 16 at the top (for discharging low-boiling-point substances in the system) and a second crystallizer discharge pipe 17 at the bottom (for transporting the second reaction liquid containing secondary crystals to the third crystallizer 6). The third crystallizer 6 has a discharge pipe 18 at the top (for discharging low-boiling-point substances in the system) and a second crystallizer discharge pipe 19 at the bottom (for transporting the third reaction liquid containing target crystals to the centrifuge device 7). The first crystallizer 4, the second crystallizer 5, and the third crystallizer 6 are all equipped with a guide tube to enhance the mixing of the corresponding reaction liquids. The guide tube can be fixed by the internal suspension rod of the corresponding crystallizer. The top of the first crystallizer 4, the second crystallizer 5, and the third crystallizer 6 are all equipped with a condenser to realize the condensation and recovery of volatile or vaporizable components.

[0056] The centrifuge device 7 is equipped with a centrifuge filtrate discharge pipe 20 (for discharging the liquid phase), a centrifuge washing liquid discharge pipe 21 (for discharging the washing liquid), and a centrifuge solid phase discharge pipe 22 (for conveying bisphenol A to the subsequent purification unit).

[0057] In some embodiments of this application, a method for producing bisphenol A is provided, comprising the following steps:

[0058] The bisphenol A reaction solution after dehydration and flash evaporation is cooled from the flash evaporation temperature to the first crystallization temperature and kept at that temperature for the first time to form the first reaction solution; the first crystallization temperature is 48℃-60℃.

[0059] The first reaction solution is heated to the second crystallization temperature and then kept at that temperature for a second time to form the second reaction solution;

[0060] The second reaction solution is heated to the third crystallization temperature and held at that temperature for a third time to form a third reaction solution containing the target crystals; the third reaction solution is then subjected to solid-liquid separation to prepare the bisphenol A.

[0061] The second crystallization temperature is 4°C-6°C higher than the first crystallization temperature; the third crystallization temperature is 4°C-6°C higher than the second crystallization temperature.

[0062] This application rapidly cools the dehydrated and flash-evaporated bisphenol A reaction solution to form a first reaction solution containing primary large crystals. This reduces crystal viscosity, decreases crystal adhesion to the crystallizer wall and other locations, and improves scaling. Then, the first reaction solution is heated in stages with small gradients and kept at the temperature to dissolve small-sized crystals and promote the secondary growth of large crystals. This results in bisphenol A with larger particle size and narrower particle size distribution, improves scaling, increases reaction efficiency, and reduces equipment operation and maintenance costs.

[0063] In some embodiments, the primary large crystal D90 particle size is 800μm-1000μm; the secondary crystal D90 particle size is 500μm-800μm; and the target crystal D90 particle size is 300μm-400μm.

[0064] Understandably, cooling from the flash temperature to the first crystallization temperature can be achieved by transferring the reaction solution to a reactor at the target temperature, supplemented by cooling operations (such as introducing a liquid low-boiling-point substance), or by cooling operations within the same reactor. Typically, cooling from the flash temperature to the first crystallization temperature is achieved within 2-10 seconds. Shorter cooling times facilitate rapid cooling, forming the first reaction solution containing large primary crystals.

[0065] Heating the first reaction solution to the second crystallization temperature, or the second reaction solution to the third crystallization temperature, can be achieved by transferring the reaction solution to a reactor at the target temperature and supplementing it with heating operations (such as external circulation heating and internal heating), or by heating operations within the same reactor. Typically, the above heating process is completed within 2s-10s.

[0066] By transferring the reaction solution to the reactor at the target temperature and then heating or cooling it, it is beneficial to rapidly heat up and cool down, effectively control the heating and cooling rates, increase production capacity, and avoid reactor damage caused by continuous heating and cooling operations, thus reducing maintenance costs.

[0067] In some embodiments, the second crystallization temperature can be 4°C, 4.5°C, 5°C, 5.5°C, or 6°C higher than the first crystallization temperature; the third crystallization temperature can be 4°C, 4.5°C, 5°C, 5.5°C, or 6°C higher than the second crystallization temperature. Controlling the second and third crystallization temperatures within the above ranges can promote the dissolution of small-sized crystals and induce the secondary growth of large crystals, which is beneficial for obtaining bisphenol A with larger particle size and narrower particle size distribution.

[0068] In some embodiments, the first crystallization temperature can be selected as 50℃-55℃. This first crystallization temperature is beneficial for obtaining large primary crystals and reducing crystal adhesion to the crystallizer walls and other locations, thus improving scaling issues. Specifically, the first crystallization temperature can be 48℃, 49℃, 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, etc.

[0069] In some embodiments, the duration of the first, second, and third heat treatments is independently 1-3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc. Heat treatment times exceeding these durations are beneficial for promoting crystallization or crystal growth, resulting in the desired reaction products.

[0070] In some embodiments, the flash temperature is 120°C-130°C, for example 120°C, 122°C, 124°C, 125°C, 126°C, 128°C, or 130°C.

[0071] In some embodiments, the bisphenol A production method employs a crystallization and refining system, which includes a dehydration unit 1, a flash evaporation unit 3, and a crystallization unit connected in sequence; the crystallization unit includes a first crystallizer 4, a second crystallizer 5, and a third crystallizer 6 connected in sequence.

[0072] The first crystallizer 4 has a distributor on the bottom inner wall and a condenser on the top inner wall; the second crystallizer 5 and the third crystallizer 6 have an external circulation heating device on the outside and a spiral coil heating device inside.

[0073] The bisphenol A reaction solution is passed into the dehydration unit 1 and the flash evaporation unit 3 for dehydration and flash evaporation; the bisphenol A reaction solution after dehydration and flash evaporation is transported to the first crystallizer 4, and a liquid low-boiling-point substance is introduced into the distributor of the first crystallizer 4 to cool the bisphenol A reaction solution after dehydration and flash evaporation to the first crystallization temperature and perform the first heat preservation to form the first reaction solution.

[0074] The first reaction solution is transported to the second crystallizer 5 and heated to the second crystallization temperature by an external circulation heating device and a spiral coil heating device, and then subjected to a second heat preservation to form the second reaction solution.

[0075] The second reaction solution is transported to the third crystallizer 6, and heated to the third crystallization temperature by an external circulation heating device and a spiral coil heating device, and then subjected to a third heat preservation to form a third reaction solution containing the target crystal.

[0076] Understandably, after the reaction liquid is dehydrated and flashed by the dehydration unit 1 and flash evaporation unit 3, it is transported to the first crystallizer 4. A liquid low-boiling-point substance is then introduced through the bottom distributor of the first crystallizer 4. The liquid low-boiling-point substance is dispersed into droplets by the atomizing nozzle of the bottom distributor, evaporates and absorbs heat to become a gas phase (for example, at 0.1MPa-0.3MPa), and is discharged from the top of the first crystallizer. After being condensed by the condenser, it is recycled. Therefore, the reaction liquid in the first crystallizer 1 can be rapidly cooled to form a first reaction liquid containing primary large crystals. This can reduce the viscosity of the crystals, reduce the adhesion of crystals to the crystallizer wall and other locations, and improve the scaling problem. The first reaction solution containing primary large crystals is transported to the second crystallizer 5. A portion of the corresponding reaction solution is heated by an external circulation heating device and then returned to the crystallizer. Simultaneously, a spiral coil heating device is installed inside the crystallizer, and hot water is introduced to achieve internal temperature gradient, forming a second reaction solution containing secondary crystals. The second reaction solution containing secondary crystals is then transported to the third crystallizer 6. A portion of the corresponding reaction solution is heated by an external circulation heating device and then returned to the crystallizer. Simultaneously, a spiral coil heating device is installed inside the crystallizer, and hot water is introduced to achieve internal temperature gradient, forming a third reaction solution containing the target crystals. By using segmented small-gradient heating and heat preservation in the second and third crystallizers 2 and 3, small-sized crystals dissolve and promote the secondary growth of large crystals, resulting in bisphenol A with larger particle size and narrower particle size distribution. This also improves scaling issues, increases reaction efficiency, and reduces equipment operating and maintenance costs. Specifically, the crystal melting cycle was reduced from 12 times / year to 2 times / year, significantly increasing the operating load of the unit (by about 30%), while improving operational stability and reducing losses during the crystal melting and balancing stages.

[0077] In addition, compared with the traditional continuous gradient cooling process, this application does not add new equipment and chemical reagents, and can guarantee product quality; all the stream materials in this application are materials in the original bisphenol A device system, with no new substances, such as waste gas, waste liquid, etc., and have no impact on the operation of the original system. The whole process realizes efficient utilization of resources.

[0078] Understandably, by introducing a liquid low-boiling-point substance into the bottom of the crystallizer, rapid crystallization can be achieved as the liquid low-boiling-point substance vaporizes. Furthermore, the vaporized liquid low-boiling-point substance can be discharged from the top of the crystallizer and recycled after condensation. Therefore, it has the characteristics of high efficiency, environmental protection, and economy.

[0079] In some embodiments, the liquid low-boiling-point substance includes alkanes with a boiling point of 28°C-50°C. Specifically, the boiling point can be 28°C, 30°C, 40°C, 50°C, etc. It is understood that the above boiling points refer to the boiling points under normal pressure. Alkanes with the above boiling points are liquid at room temperature, but can rapidly vaporize above their boiling points, absorbing heat and thus having a cooling effect.

[0080] In some embodiments, the amount of the liquid low-boiling-point substance injected is 5%-15% of the volume of the bisphenol A reaction liquid, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc. Controlling the amount of the liquid low-boiling-point substance injected within the above range can balance the stability of cooling and the crystallization efficiency.

[0081] In some embodiments, the liquid low-boiling-point substance includes liquid pentane. Liquid pentane is an inert liquid low-boiling-point substance, and the raw material is readily available, which can avoid side reactions and reduce costs.

[0082] In some embodiments, the heating conditions using the external circulation heating device and the spiral coil heating device include: heating a portion of the corresponding reaction solution to 70℃-85℃ (e.g., 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, 82℃, 84℃, 85℃, etc.) via the external circulation heating device and then returning it to the corresponding crystallizer; simultaneously, introducing hot water at 60℃-75℃ (e.g., 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 75℃, etc.) into the spiral coil heating device for internal heating. Understandably, the simultaneous heat transfer via the external circulation heating device and the spiral coil heating device can significantly reduce crystal adhesion to the walls and agitator, thus effectively extending the melting cycle, increasing the operating load of the device, improving operational stability, and reducing losses.

[0083] In some embodiments, the corresponding reaction solution is 10v / v%-30v / v% of the corresponding reaction solution, such as 10v / v%, 15v / v%, 20v / v%, 25v / v%, 30v / v%, etc. Heating the reaction solution with the above volume percentages through an external circulation heating device helps to control the heating rate.

[0084] In some embodiments, the heat distribution ratio between the external circulation heating device and the spiral coil heating device is (1.2-1.8):1, for example, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, etc. Controlling the heat distribution ratio between the external circulation heating device and the spiral coil heating device within the above range is beneficial for controlling the heating rate and reducing crystal adhesion to the wall surface and the stirring paddle.

[0085] In some embodiments, the dehydration unit 1 has multiple sections of packing material arranged from top to bottom, feeds from the upper middle part, has a condensation device at the top of the tower, and has a reboiling device at the bottom of the tower.

[0086] Understandably, dehydration unit 1 removes water and some light components such as phenol generated during the synthesis of bisphenol A. Furthermore, the upper packing of dehydration unit 1 is equipped with a bisphenol A reaction liquid feed pipe 8, with the reaction liquid fed from the top to remove light components and completely remove moisture from the feed, controlling the crystal state of the crystallization unit. The distillation column conditions include a temperature of 160℃-190℃ and a pressure of 50KPa-70KPa; the phenol content in the top product is 20wt%-25wt% to ensure the bottom of the column is completely free of water.

[0087] In some embodiments, the flash evaporation unit 3 is equipped with a condensation device and a reboiling device, and has an internal cavity with a shape that is wider at the top and narrower at the bottom. Furthermore, the feed position of the flash evaporation unit 3 is above the liquid level. Understandably, the function of the flash evaporation unit is to flash-evaporate excess phenol, control the concentration of bisphenol A in the reaction solution, and facilitate the control of the temperature parameters of the crystallization unit; the flash-evaporated phenol can be recovered and reused as raw material in the reaction unit; the aforementioned shape facilitates maintaining a shorter holding time while keeping a certain liquid level. The flash evaporation temperature is 120℃-130℃, and the pressure is 8KPa-12KPa; the bottom discharge of the flash evaporation unit yields a phenol mixed solution with a bisphenol A concentration of 25wt%-35wt% (preferably 28wt%-32wt%), which serves as the bisphenol A reaction solution for crystallization.

[0088] In some embodiments, the crystallization and refining system further includes a centrifuge device 7; optionally, the centrifuge device 7 is equipped with a screen, an internal spiral rotor, and washing nozzles. The reaction liquid of the third crystallizer 6 is conveyed to the centrifuge device 7, where the liquid portion of the reaction liquid is removed by centrifugal force, the solid is propelled forward by the internal spiral rotor, and phenol sprayed through the washing nozzles washes impurities on the crystal surface. The washing phenol comes from the phenol removed by the flash evaporation unit. The liquid in the reaction liquid and the washing phenol are conveyed to the front-end reaction unit through the discharge port at the bottom of the centrifuge device, and the solid crystal is conveyed to the downstream refining unit through the internal spiral rotor to produce qualified bisphenol A.

[0089] In some embodiments, the first crystallizer 4, the second crystallizer 5, and the third crystallizer 6 are equipped with a stirring paddle and a flow guide. Understandably, the stirring paddle and flow guide enable mixing of the reaction solution.

[0090] Some embodiments of this application provide a crystallization refining system, including a dehydration unit 1, a flash evaporation unit 3, and a crystallization unit connected in sequence; the crystallization unit includes a first crystallizer 4, a second crystallizer 5, and a third crystallizer 6 connected in sequence;

[0091] The first crystallizer 4 has a distributor on its bottom inner wall; the second crystallizer 5 and the third crystallizer 6 have an external circulation heating device on their exterior and a spiral coil heating device on their interior.

[0092] The dehydration unit 1 and flash evaporation unit 3 are used to dehydrate and flash evaporate the bisphenol A reaction solution;

[0093] The first crystallizer 4, the second crystallizer 5, and the third crystallizer 6 are used sequentially to cool, heat up, and heat up the bisphenol A reaction solution after dehydration and flash evaporation, respectively, to form a reaction solution containing the target crystals.

[0094] The distributor is used to inject liquid low-boiling-point substances to cool the bisphenol A reaction solution after dehydration and flash evaporation.

[0095] The external circulation heating device is used to introduce a portion of the corresponding reaction liquid for external circulation heating, and the spiral coil heating device is used to introduce hot water for internal heating, thereby achieving the first heating and the second heating.

[0096] A liquid low-boiling-point substance is introduced through the bottom distributor of the first crystallizer. This substance is dispersed into droplets by the atomizing nozzles of the bottom distributor, evaporates and absorbs heat to become a gas phase, achieving rapid cooling of the reaction liquid in the first crystallizer. This forms a first reaction liquid containing large primary crystals, reducing crystal viscosity and minimizing crystal adhesion to the crystallizer walls, thus improving scaling. Furthermore, by returning a portion of the corresponding reaction liquid to the crystallizer after heating via an external circulation heating device, and simultaneously installing a spiral coil heating device within the crystallizer to introduce hot water for internal heating, segmented small-gradient heating and heat preservation are achieved in the second and third crystallizers. This dissolves small-sized crystals and promotes secondary growth of large crystals, resulting in bisphenol A with larger particle size and narrower particle size distribution. Therefore, crystal particle size distribution can be controlled, scaling problems can be improved, reaction efficiency is increased, and equipment operating and maintenance costs are reduced.

[0097] For experimental parameters not specified in the following specific embodiments, please refer to the guidelines given in this application document first, or refer to experimental manuals or other experimental methods known in the art, or refer to the experimental conditions recommended by the manufacturer.

[0098] Unless otherwise specified, all raw materials and reagents used in this application can be purchased commercially. The following is an example.

[0099] Example 1

[0100] The main sources of raw materials and equipment are as follows:

[0101] Bisphenol A reaction solution: The reaction solution obtained after the reaction unit of the bisphenol A process in Wanhua's bisphenol A production unit has completed the reaction.

[0102] Dehydration tower: from Beijing Zehua Chemical Engineering Co., Ltd., with an inner diameter of 3.8m and a height of 29m. It has two sections of packing: a rectification section and a stripping section. The packing types are Mellap-ak 2Y and I-Ring #50.

[0103] Flash evaporator: from Jiangsu Yongda Pressure Vessel Manufacturing Co., Ltd., with an upper and lower inner diameter of 4400mm and 2400mm respectively, and an overall volume of 2.44m³. 3 Design pressure 0.35 / FV (MPaG), design temperature 4.8 / 225℃.

[0104] Crystallizers (main bodies of the first, second, and third crystallizers): from Shanghai Sensong, with an inner diameter of 6600mm, a height of 17300mm, and an overall volume of 667m³. 3 The design pressure is 0.35 / FV (MPaG), and the design temperature is 150℃.

[0105] The internal stirring paddle of the crystallizer is from Laining Stirrer, with a displacement coefficient of 0.60 and a power coefficient of 0.46.

[0106] Spiral coil heating device: from Jiangsu Zhong Sheng heat exchanger manufacturer, designed temperature 150℃.

[0107] Centrifuge: from Andritz.

[0108] like Figure 1 As shown, the bisphenol A reaction solution originates from the reaction unit. The material contains 28%–30% bisphenol A, 64%–67% phenol, and a small amount of water and byproducts generated during the reaction. It enters the upper packing of the dehydration tower 1 through the bisphenol A reaction solution feed pipe 8 to remove water and some light components such as phenol produced during the bisphenol A synthesis process. The dehydration tower 1 operates at 175℃ and 60 kPa. Part of the material from the reaction is returned to the top of the tower via the top dehydration tower reflux tank 2 for reflux, ensuring the separation effect of the dehydration tower 1. The light components of the reaction solution are collected through the light component discharge pipe 9. The phenol content in the collected material ranges from 20% to 25%, ensuring that the dehydrated bisphenol A reaction solution discharged through the dehydration tower bottom discharge pipe 10 is completely water-free.

[0109] The dehydrated bisphenol A reaction solution is conveyed to the flash tank 3 via the discharge pipe 10 of the dehydration tower. The flash tank 3 has a hollow interior and a shape that is wider at the top and narrower at the bottom. This is used to maintain a certain liquid level and, while ensuring that the bottom pump of the flash tank 3 does not run dry, to maintain the material at a relatively short temperature and avoid the decomposition of the bisphenol A reaction solution. The feed line of flash tank 3 is located above the liquid surface. The flash tank temperature is 125℃ and the pressure is 10KPa. Excess phenol is flash-evaporated. The flash-evaporated phenol is conveyed to the horizontal screw centrifuge 7 via flash phenol discharge pipe 11 as washing liquid to wash bisphenol A and then recovered as raw material for the reaction unit for continued use. The reaction liquid after flash evaporation (a phenol mixed solution with bisphenol A concentration of 39wt%) is collected from the flash tank discharge pipe 12 and conveyed by a pump to the lower part of the first crystallizer 4 (temperature set at 50℃). Mixing is achieved in the crystallizer by the internal guide tube and stirring paddle. Liquid low-boiling-point substances are introduced from the liquid low-boiling-point substance feed pipe 13 at the bottom of the first crystallizer 4. Liquid n-pentane is used as the cooling medium for the material. The amount of n-pentane injected is 12% of the volume of the reaction liquid. The reaction liquid is rapidly cooled from 125°C to 50°C through the heat absorption of pentane vaporization, achieving rapid crystallization. The liquid n-pentane is dispersed into droplets through the atomizing nozzle of the bottom distributor. It evaporates and absorbs heat under a pressure of 0.2MPa. The vaporized liquid low-boiling-point substance discharge pipe 14 at the top discharges the flash pentane in the gas phase. After being condensed by the condenser, it is recycled. The solid content of the reaction liquid after flash evaporation is 33%. After being kept at 50°C for 2 hours, it is mixed and sheared to form the first reaction liquid containing primary large crystals with a D90 particle size of 800μm-1000μm.

[0110] The first reaction liquid containing primary large crystals is transported by gravity through the discharge pipe 15 of the first crystallizer to the lower part of the second crystallizer 5, where it is mixed by the internal guide tube and stirring paddle. During the crystallizer heating stage, 15% of the volume of the reaction liquid is extracted from the crystallizer, heated to 70°C through an external circulation heating device (external heat exchanger), and then returned to the crystallizer to achieve heating. At the same time, a spiral coil is installed in the crystallizer, and 70°C hot water is introduced to achieve internal heating. The heat distribution ratio between the external circulation and the internal coil is 1.5:1, maintaining a vertical temperature gradient of ≤1°C / m. The material temperature rises from 50°C to 55°C, the solid content of the reaction liquid is 30%, and the holding time is 1 hour, forming a second reaction liquid containing secondary crystals with a D90 particle size of 500-800μm.

[0111] The second reaction liquid containing secondary crystals is transported by gravity through the discharge pipe 17 of the second crystallizer to the lower part of the third crystallizer 6, where it is mixed by the internal guide tube and stirring paddle. During the crystallizer heating stage, 20% of the reaction liquid is extracted from the crystallizer, heated to 75°C through an external heat exchanger, and then returned to the crystallizer to achieve heating. At the same time, a spiral coil is installed in the crystallizer, and 75°C hot water is introduced to achieve internal heating. The heat distribution ratio between the external circulation and the internal coil is 1.5:1, maintaining a vertical temperature gradient of ≤1°C / m. The material temperature is raised from 55°C to 60°C, the solid content of the mixture is 28%, and the holding time is 1.5h, forming a third reaction liquid containing target crystals with a D90 particle size of 400-500μm.

[0112] The third reaction liquid containing the target crystal is conveyed by gravity flow to the horizontal screw centrifuge 7 through the discharge pipe 19 of the third crystallizer. The centrifuge includes a screen, an inner screw rotor, washing nozzles, and heat tracing. First, the liquid in the material is removed by centrifugal force in the centrifugation zone. The material is then pushed to the washing zone by the inner screw. The surface of the crystal is washed by the flash phenol separated by the flash tank 3, which washes away the residual liquid on the surface of the crystal and removes surface impurities. Finally, the solid crystal is conveyed to the downstream refining unit through the inner screw to produce qualified bisphenol A.

[0113] After the production process was put into operation, the operating parameters and product quality were monitored. The melting cycle of the first crystallizer was reduced from 12 times / year in Comparative Example 1 to 2 times / year (a single melting cycle is 15 days, and the production load during the melting period is 30%). The second and third crystallizers controlled the crystal form by using a small gradient heating method. Heat was simultaneously delivered through an external circulation heating device and a spiral coil heating device, which effectively improved the adhesion of crystals to the wall and the stirring paddle. Compared with Comparative Example 1, the overall operating load of the device was reduced by about 30%. At the same time, the morphology of bisphenol A was more stable and uniform (the crystal particle size and particle size distribution of Example 1 are shown in the figure). Figure 2 The overall impurity removal rate is >99%, and the dry basis purity of the product is >99.5%, which improves the overall operational stability and product purity.

[0114] Example 2

[0115] Except for the first crystallization temperature, the second crystallization temperature, and the third crystallization temperature, which are 60℃, 66℃, and 70℃ respectively, the rest is the same as in Example 1. The melting cycle of the first crystallizer was reduced from 12 times / year in Comparative Example 1 to 2 times / year (a single melting cycle is 15 days, and the production load during melting is 30%). The second and third crystallizers control the crystal form through a small gradient heating method, and heat is simultaneously delivered through an external circulation heating device and a spiral coil heating device, which effectively improves the adhesion of crystals to the wall and the stirring paddle. The overall impurity removal rate is >99%, and the dry basis purity of the product is >99.5%. Due to the higher third crystallization temperature, the amount of crystal precipitation is about 85% of that in Example 1, and the overall operating load of the device is reduced by about 15% compared to Comparative Example 1.

[0116] Comparative Example 1

[0117] Compared to Example 1, the difference lies in the use of a traditional continuous gradient cooling method for crystallization. Crystals precipitate by gradually decreasing the temperature. The temperatures of the two-stage crystallizers (the main body of the crystallizer is the same as in Example 1) are 60℃ (held for 1.5h) and 55℃ (held for 1h), respectively. The solid content in the material exiting the secondary crystallizer is 28%, and the tested crystal particle size is 150μm~450μm, with a relatively wide overall distribution (for the crystal particle size and particle size distribution of Comparative Example 1, see...). Figure 2 The centrifugal unit has a 96% impurity removal rate and a product purity of 99.91%. However, the inner walls of the two-stage crystallizer and the agitator are frequently scaled, requiring monthly shutdown for cleaning (i.e., the crystal melting cycle is 12 times / year, each crystal melting cycle is 15 days, and the production load during crystal melting is 30%).

[0118] As can be seen from the above, the normal distribution curve of bisphenol A crystals in Example 1 is narrower, and the crystal particle size is larger, which is more conducive to the removal of impurities in the centrifugation process, improves the overall impurity removal rate, and the product quality is better than that of Comparative Example 1 (traditional continuous gradient cooling). The two-stage crystallization process is carried out 12 times / year, which is 30% lower than the annual operating load in Example 1. At the same time, the production method of Example 1 does not add new equipment or chemical reagents, and all the stream materials are materials from the original bisphenol A unit system. There are no new substances, such as waste gas and waste liquid, which have no impact on the operation of the original system. The whole process realizes efficient utilization of resources and is superior to the traditional process in terms of stability and product quality, which greatly improves the production efficiency of the unit and enhances the competitiveness of the product in the industry.

[0119] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0120] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for producing bisphenol A, characterized in that, Includes the following steps: The bisphenol A reaction solution after dehydration and flash evaporation is cooled from the flash evaporation temperature to the first crystallization temperature and kept at that temperature for the first time to form the first reaction solution; the first crystallization temperature is 48℃-60℃. The first reaction solution is heated to the second crystallization temperature and then kept at that temperature for a second time to form the second reaction solution; The second reaction solution is heated to the third crystallization temperature and held at that temperature for a third time to form a third reaction solution containing the target crystals; the third reaction solution is then subjected to solid-liquid separation to prepare the bisphenol A. The second crystallization temperature is 4°C-6°C higher than the first crystallization temperature; the third crystallization temperature is 4°C-6°C higher than the second crystallization temperature.

2. The method for producing bisphenol A as described in claim 1, characterized in that, The first crystallization temperature is 50℃-55℃.

3. The method for producing bisphenol A as described in claim 1, characterized in that, The duration of the first heat preservation, the duration of the second heat preservation, and the duration of the third heat preservation are each independently 1 hour to 3 hours. And / or, the flash temperature is 120℃-130℃.

4. The method for producing bisphenol A according to any one of claims 1-3, characterized in that, The bisphenol A production method employs a crystallization and refining system, which includes a dehydration unit, a flash evaporation unit, and a crystallization unit connected in sequence; the crystallization unit includes a first crystallizer, a second crystallizer, and a third crystallizer connected in sequence, with the first crystallizer connected to the flash evaporation unit; The bottom inner wall of the first crystallizer is equipped with a distributor; the second and third crystallizers are equipped with an external circulation heating device on the outside and a spiral coil heating device inside. The bisphenol A reaction solution is passed into the dehydration unit and the flash evaporation unit for dehydration and flash evaporation; the bisphenol A reaction solution after dehydration and flash evaporation is transported to the first crystallizer, and a liquid low-boiling-point substance is introduced into the distributor of the first crystallizer to cool the bisphenol A reaction solution after dehydration and flash evaporation to the first crystallization temperature and perform the first heat preservation to form the first reaction solution; The first reaction solution is transported to the second crystallizer, and heated to the second crystallization temperature by an external circulation heating device and a spiral coil heating device, and then subjected to a second heat preservation to form the second reaction solution; The second reaction solution is transported to the third crystallizer and heated to the third crystallization temperature by an external circulation heating device and a spiral coil heating device, and then subjected to a third heat preservation to form a third reaction solution containing the target crystals. Optionally, the liquid low-boiling-point substance includes alkanes with a boiling point of 28°C-50°C.

5. The method for producing bisphenol A as described in claim 4, characterized in that, The amount of the liquid low-boiling-point substance injected is 5%-15% of the volume of the bisphenol A reaction liquid; And / or, the liquid low-boiling-point substance includes at least one of liquid pentane, liquid isopentane, and liquid cyclopentane.

6. The method for producing bisphenol A as described in claim 4, characterized in that, The conditions for heating using the external circulation heating device and the spiral coil heating device include: heating a portion of the corresponding reaction solution to 70℃-85℃ using the external circulation heating device and then returning it to the corresponding crystallizer, while simultaneously introducing 60℃-75℃ hot water into the spiral coil heating device for internal heating.

7. The method for producing bisphenol A as described in claim 6, characterized in that, The corresponding reaction solution is 10v / v%-30v / v% of the corresponding reaction solution. And / or, the heat distribution ratio of the external circulation heating device and the heat distribution ratio of the spiral coil heating device is (1.2-1.8):

1.

8. The method for producing bisphenol A as described in claim 4, characterized in that, The dehydration unit has multiple packing sections arranged from top to bottom, with feeding from the upper middle part. There is a condensation device at the top of the tower and a reboiler at the bottom of the tower. And / or, the flash unit is equipped with a condensation device and a reboiling device, and has an internal cavity with a shape that is wider at the top and narrower at the bottom.

9. The production method as described in claim 4, characterized in that, The crystallization and refining system also includes a centrifuge device for solid-liquid separation of the third reaction liquid to prepare bisphenol A.

10. A crystallization refining system, characterized in that, It includes a dehydration unit, a flash evaporation unit, and a crystallization unit connected in sequence; the crystallization unit includes a first crystallizer, a second crystallizer, and a third crystallizer connected in sequence, and the first crystallizer is connected to the flash evaporation unit; The first crystallizer has a distributor on the bottom inner wall and a condenser on the top inner wall; the second and third crystallizers are equipped with an external circulation heating device on the outside and a spiral coil heating device on the inside. The dehydration unit and flash evaporation unit are used to dehydrate and flash evaporate the bisphenol A reaction solution; The first crystallizer, the second crystallizer, and the third crystallizer are used sequentially to cool, heat, and heat the bisphenol A reaction solution after dehydration and flash evaporation, respectively, to form a reaction solution containing the target crystals. The distributor is used to inject liquid low-boiling-point substances to cool the bisphenol A reaction solution after dehydration and flash evaporation. The external circulation heating device is used to introduce a portion of the corresponding reaction liquid for external circulation heating, and the spiral coil heating device is used to introduce hot water for internal heating, thereby achieving the first heating and the second heating.

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