BDP acid washing, alkali washing and water washing system and washing process

Abstract

The invention provides a BDP acid washing, alkali washing and water washing system. An outlet of a static mixer is connected with an inlet of a filter; an outlet of the filter is connected with an inlet of the centrifugal extractor, and an upper light-phase stream outlet of the centrifugal extractor is connected with an inlet of the coalescence separator. The method comprises the following steps: carrying out liquid-liquid contact on a BDP crude product, circulating diluted hydrochloric acid and a mixed solvent in a static mixer to remove impurities in the BDP crude product; the mixed water-oil mixed stream enters a filter for filtering and deslagging, and then enters a centrifugal extractor for primary extraction separation, so that primary separation of an organic phase and acid liquor is realized; a light-phase stream obtained after primary extraction separation enters a coalescence separator, and thorough separation of an organic phase and a trace amount of acid liquor is achieved; by adopting the scheme, alkali washing and water washing processes are carried out again. The method can be used for most phosphate ester products to meet the requirements of low chromaticity and high purity of the products.

Description

Technical Field

[0001] The invention relates to a purification process and a purification device for BDP, and in particular to a related process and a device for BDP using acid washing, alkali washing and water washing. Background Art

[0002] The main properties of flame retardant BDP are: first, it contains a high phosphorus content and contains more benzene rings in the molecule, which has good flame retardant properties; second, it has a large molecular weight, low volatility, symmetrical structure, good compatibility with materials, is not easy to precipitate, and has long-lasting flame retardant properties; third, it has a high thermal decomposition temperature and good thermal stability, which can better meet the material processing temperature requirements. Flame retardant BDP is mainly used to flame retard PC, PC / ABS plastic alloy, PPO, PPO / HIPS plastic alloy and epoxy resin and other materials.

[0003] BDP is a colorless or light yellow liquid, insoluble in water, and soluble in organic solvents such as dichlorotoluene, toluene, methanol, methylcyclohexane and methyl ethyl ketone. The crude product of BDP production contains a large amount of impurities such as unreacted raw materials and by-products. Generally, the crude product needs to be washed with acid, alkali, water, etc. After washing, the organic phase and the aqueous phase are separated to improve the purity and quality of the product. The existing traditional washing process is to first add organic solvent to dissolve and disperse, then perform acid washing to remove the catalyst, the BDP crude product is evenly mixed with the mixed solvent and transferred to the acid washing kettle, stirred and washed for a certain period of time, and then allowed to stand and separate, and the organic phase is transferred to the alkali washing kettle, and the washing temperature is controlled at above 50-70°C; then perform alkali washing to remove phenol and acidic organic impurities, add alkali solution quantitatively to the alkali washing kettle, transfer the acid washing organic material, stir and wash and let stand and separate, the organic phase is transferred to the water washing process, and the washing temperature is controlled at 50-70°C; finally, perform water washing to remove alkali and salt, add process water quantitatively to the water washing kettle, transfer the alkali washing organic material, stir and wash and let stand and separate, and finally remove the organic solvent from the organic phase by distillation to obtain the BDP product. The entire washing process adopts a kettle intermittent process, which is cumbersome and time-consuming, and the organic phase and the aqueous phase are not completely separated. Not only is the work efficiency low, but the equipment investment is large, the equipment structure is complex, and it is inconvenient to use. Summary of the invention

[0004] In response to the above technical problems, the present invention provides a BDP acid washing, alkali washing and water washing system, in which the outlet of the static mixer is connected to the inlet of the filter; the outlet of the filter is connected to the inlet of the centrifugal extractor, and the upper light phase stream outlet of the centrifugal extractor is connected to the inlet of the coalescing separator.

[0005] The static mixer is lined with polytetrafluoroethylene and filled with interlaced corrugated plates, wherein the material of the corrugated plates is selected from acid and alkali corrosion resistant materials such as titanium and zirconium. The filter is selected from a plate and frame filter, a filter bag filter, a precision filter, and a core filter device, and a slag discharge port is arranged at the bottom of the filter.

[0006] The lower heavy phase stream outlet of the centrifugal extractor is connected to the inlet of the circulation pump, and the outlet of the circulation pump is connected to the inlet of the static mixer; a mixed material inlet is arranged in the middle of the centrifugal extractor; and a light phase overflow port is arranged at the top of the centrifugal extractor.

[0007] The coalescing separator is provided with coalescing internals, preferably any one of polyester fiber, glass fiber, and polypropylene; and cavities are formed at the upper and lower ends of the coalescing separator. The coalescing separator is provided with a top oil phase outlet and a bottom water phase outlet.

[0008] In the technical solution of the present invention, it should be understood that the above-mentioned device is a whole, and this whole structure is used in the water washing process. At the same time, the above-mentioned whole structure can also be used in the alkali washing structure or in the water washing structure.

[0009] That is, the processes of pickling, alkali washing and water washing adopt the same structure. After the pickling, the washed material is passed into the static mixer again for alkalinity. After the alkali washing, the washed material is passed into the static mixer again for water washing.

[0010] In some embodiments, the acid washing, alkali washing, and water washing processes use the same structure, and the structures of the acid washing, alkali washing, and water washing are assembled in series, and then the acid washing, alkali washing, and water washing processes are performed in series. The oil phase outlet at the top of the coalescing separator in the acid washing structure is connected to the static mixer in the alkali washing structure to achieve series connection; the oil phase outlet at the top of the coalescing separator in the alkali washing structure is connected to the static mixer in the water washing structure to achieve series connection.

[0011] The system also includes an alkali washing system, which is connected in series with the acid washing system. The alkali washing system and the acid washing system have the same structure, and the top oil phase outlet in the acid washing system is connected to the static mixer of the alkali washing system.

[0012] The system also includes a water washing system, which is connected in series with the alkali washing system. The water washing system has the same structure as the alkali washing system and the acid washing system, and the top oil phase outlet in the alkali washing system is connected to the static mixer of the water washing system.

[0013] In view of the above technical solution, the present invention also provides an acid washing, alkali washing and water washing process including BDP, using the above device, including the following steps: (1) The crude BDP, circulating dilute hydrochloric acid and mixed solvent are in liquid-liquid contact in a static mixer, and the impurities in the crude BDP are dissolved in the dilute hydrochloric acid or react with the dilute hydrochloric acid and transferred to the aqueous phase, thereby removing the impurities in the crude BDP; (2) The mixed water-oil stream enters the filter to filter out the residue and then enters the centrifugal extractor for primary extraction and separation to achieve preliminary separation of the organic phase and the acid solution; (3) The light phase stream after the primary extraction and separation enters the coalescing separator to achieve complete separation of the organic phase and trace acid solution; Repeat steps (1), (2), and (3) to perform alkaline washing; Repeat steps (1), (2), and (3) to wash with water to purify BDP.

[0014] It can be understood by the technicians of the present invention that the pickling process adopts the above-mentioned device to implement the pickling process, the material after pickling adopts the above-mentioned device again to implement the alkali washing process, and the material after alkali washing is further washed with water again to implement the water washing process. That is, the devices used for pickling, alkali washing and water washing are the same as a whole, and only new solvents do not need to be added in the alkali washing and water washing processes.

[0015] The concentration of the circulating dilute hydrochloric acid in step (1) is 1-15% by mass. When the concentration is insufficient, fresh dilute hydrochloric acid is added. The mixed solvent is selected from one or a mixture of toluene, methylcyclohexane, and methyl ethyl ketone. The mass ratio of the mixed solvent at the inlet of the static mixer to the crude BDP is (1-1.5:1).

[0016] In the centrifugal extraction process in step (2), the extraction is carried out at a rotation speed of 500-15000 rpm and dilute hydrochloric acid conditions, wherein the mass concentration of the dilute hydrochloric acid is 1-20%; and in step (3), the filtration accuracy of the filter is 0.5-5 microns. The operating pressure of the static mixer is 0.1MPaG~0.5MPaG, and the operating temperature is 50~80℃; the pressure of the lower cavity of the coalescing separator is 0.1MPaG~0.5MPaG, and the operating temperature is 50~80℃, the pressure of the upper cavity is 0.05~0.2MPa, the temperature is 50~80℃, and the upper and lower pressure difference is 0.1-0.2MPa; the residence time of the oil phase in the coalescing separator is 20~60min, preferably 20~40min.

[0017] The repeating of steps (1), (2) and (3) for alkali washing means that the acid-washed purified BDP is alkali washed again using the process described above, and in step (1) of the alkali washing process, 1-20% by mass of circulating dilute liquid alkali is added for mixing to achieve alkali washing purification of BDP, and fresh liquid alkali is added when the concentration is insufficient.

[0018] The repeated steps (1), (2) and (3) for water washing means that the BDP purified by alkali washing is washed again by the process described above. In the step (1) of the water washing process, circulating pure water is added for mixing to achieve water washing and purification of BDP. When the water volume is insufficient, fresh pure water is added. The crude BDP in step (1) (a colorless or light yellow liquid containing a large amount of impurities such as unreacted raw materials and by-products, which needs to be subjected to multiple washing processes such as acid washing, alkali washing, and water washing, and then the organic phase and the aqueous phase are separated after washing to improve the purity and quality of the product in turn) is insoluble in water and is compatible with organic solvents such as toluene, methylcyclohexane and methyl ethyl ketone. In the present invention, the crude BDP and the organic solvent are fully mixed in a static mixer (better mixing effect and shorter time than the traditional kettle stirring mixing), in order to increase its dispersion without changing the properties of the original product so that it can fully carry out subsequent reactions.

[0019] In step (2), the main shaft speed of the high-speed dispersion system is 500-15000 rpm; the mass concentration of the hydrochloric acid is 1-20%. The two are fully mixed and reacted by high-speed stirring in the high-speed dispersion system, and the metal catalyst (such as magnesium chloride) in the crude product is fully removed by acid washing. At the same time, impurities such as benzoquinone can be removed by chemical reaction. This process has better mixing effect and shorter time than the traditional kettle stirring and mixing process.

[0020] In step (3), the coalescing filter element is made of acid-resistant, alkali-resistant and organic solvent-resistant materials such as polyester fiber, glass fiber, and polypropylene, with an operating temperature of 0 to 100°C and a filtration accuracy of 0.1 to 5 microns. Under the temperature and pressure difference between the upper and lower cavities, the organic phase and the acid solution are quickly separated by the coalescing filter. The separation time is shorter than that of the traditional static phase separation, and it is more thorough.

[0021] The acid-washed purified BDP is again subjected to alkali washing in the process of steps (1), (2) and (3). In the alkali washing process, in step (1), 5-20% by mass of liquid alkali is added for dispersion, thereby finally achieving alkali washing purification of BDP.

[0022] During the alkaline washing process, no mixed solvent needs to be added, but the washing process still starts with mixing in a static mixer.

[0023] In some embodiments, the organic phase from the outlet of the pickling system enters the static mixer through the inlet, and the dilute alkaline solution (i.e., the water phase inlet) enters the static mixer through the inlet. The two are fully mixed and reacted through the static mixer. Impurities such as phenols and a small amount of residual acid in the crude product are removed through chemical reactions through alkaline washing. This process has better effect and shorter time than traditional kettle stirring and mixing.

[0024] Then the material enters the filter through the inlet, and the solid insoluble matter produced in the alkaline washing process is removed to prevent the subsequent process from clogging the centrifugal extractor and coalescing separator. The discharge port is the slag discharge port, and the waste residue enriched in the filter can be blown out and discharged through the nitrogen backflush system.

[0025] The filtrate enters the coalescing separator, and under the action of the temperature and pressure difference between the upper and lower cavities, the organic phase and the alkali solution are quickly separated through the coalescing separator. Compared with the traditional static phase separation time, it is shorter and more thorough.

[0026] In some embodiments, the alkali washing system is at least a primary alkali washing system. When it is a secondary or higher alkali washing system, the organic phase enters the secondary alkali washing system from the outlet, and then undergoes a complete washing process again through a static mixer, a filter, a centrifugal extractor, and a coalescing separator.

[0027] In some embodiments, the organic phase exiting the alkali washing system (or the multi-stage alkali washing system after multi-stage alkali washing) enters the static mixer through the inlet, and pure water enters the static mixer through the inlet (i.e., the water phase inlet). The two are fully mixed and reacted through the static mixer, and the residual alkali, salts and other impurities after the secondary alkali washing are removed by water washing. This process has better effect and shorter time than traditional kettle stirring and mixing.

[0028] No solvent needs to be added during the water washing process, but mixing is still performed through a static mixer.

[0029] Then the material enters the filter through the inlet to remove the solid insoluble matter that may exist in the water washing process to prevent the subsequent process from clogging the coalescing separator. The discharge port is the slag discharge port, and the waste slag accumulated in the filter can be blown out and discharged through the nitrogen backflush system.

[0030] The filtrate enters the coalescing separator, through which the organic phase and the aqueous phase are quickly separated. Compared with the traditional standing phase separation, the time is shorter and more thorough.

[0031] In some embodiments, the water washing system is at least a primary water washing system. When it is a secondary or higher water washing system, the organic phase enters the secondary water washing system from the outlet, and then undergoes a complete washing process again through a static mixer, a filter, a centrifugal extractor, and a coalescing separator.

[0032] The technical solution of the present invention has the following beneficial effects: The present invention improves and optimizes the integration of the existing washing process of BDP industrial production, and can remove impurities in a directional manner through the optimized combination of multiple processes. On the basis of the series connection of the operating steps of the present invention, the single operating step in the processing flow of the present invention can be optimized according to actual conditions, but the overall series connection sequence cannot be changed. Through the perfect treatment of multiple processes, the chromaticity of BDP can be reduced to the greatest extent, and the phenolic and ester impurities in BDP can be effectively removed, and continuous operation can be realized, which greatly shortens the time of the washing process, improves efficiency, saves equipment investment, and reduces production costs. In addition, the present invention can also be used for most phosphate products to meet the needs of low chromaticity and high purity of its products. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a pickling process flow chart of the present invention.

[0034] Figure 2 It is a process flow chart of alkali washing or water washing of the present invention.

[0035] M1 is a static mixer, F1 is a filter, M2 is a centrifugal extractor, D1 is a coalescing separator, and P1 is a pump; (1) is a mixed solvent, (2) circulating dilute hydrochloric acid, (3) is crude BDP, (4) is a water-oil mixed stream, (5) is a water-oil mixed stream after filtration, (6) is a filter residue, (7) is a light phase stream, (8) is a heavy phase stream, (9) is an external heavy phase stream, (10) is fresh dilute hydrochloric acid, (11) is a light phase stream, and (12) is an external heavy phase stream. When it is an alkali washing or water washing process, (1) does not contain a mixed solvent. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the appended claims of the application.

[0037] Comparative Example 1 500 g of crude BDP was dissolved and dispersed in 1000 g of a mixed solvent of toluene and methylcyclohexane, and then transferred to a high-speed dispersion system for acid washing. 150 g of 10% dilute hydrochloric acid was added from the water phase inlet, and the mixture was stirred at 60°C for 1 hour, and allowed to stand for stratification. The upper organic phase was transferred to a primary alkali washing kettle; 150 g of 10% liquid alkali was added to the primary alkali washing kettle, and the mixture was stirred at 60°C for 1 hour, and allowed to stand for stratification. The upper organic phase was transferred to a secondary alkali washing kettle; 150 g of 5% liquid alkali was added to the secondary alkali washing kettle, and the mixture was stirred at 60°C for 1 hour, and allowed to stand for stratification. The upper organic phase was transferred to a primary water washing kettle; 150 g of pure water was added to the primary water washing kettle, and the mixture was stirred at 60°C for 1 hour, and allowed to stand for stratification. The upper organic phase was transferred to a secondary water washing kettle; 150 g of pure water was added to the secondary water washing kettle, and the mixture was stirred at 60°C for 1 hour, and allowed to stand for stratification. The upper organic phase was transferred to a desolventizing system, and the organic solvent was removed by distillation to obtain a BDP product.

[0038] Example 1 A BDP acid washing, alkali washing and water washing system, wherein the outlet of a static mixer M1 is connected to the inlet of a filter F1; the outlet of the filter F1 is connected to the inlet of a centrifugal extractor M2, and the upper light phase stream outlet of the centrifugal extractor M2 is connected to the inlet of a coalescing separator D1.

[0039] The static mixer M1 is lined with polytetrafluoroethylene and filled with interlaced corrugated plates, and the material of the corrugated plates is selected from acid and alkali corrosion resistant zirconium material.

[0040] The filter F1 is selected from a plate-and-frame filter, a filter bag filter, a precision filter, and a core filter, and a slag discharge port is provided at the bottom of the filter F1. In this embodiment, a precision filter is used as an example to carry out the process.

[0041] The lower heavy phase stream outlet of the centrifugal extractor M2 is connected to the inlet of the circulating pump P1, and the outlet of the circulating pump P1 is connected to the inlet of the static mixer M1; a mixed material inlet is arranged in the middle of the centrifugal extractor M2; and a light phase overflow port is arranged at the top of the centrifugal extractor M2.

[0042] The coalescing separator D1 is provided with coalescing internals, preferably any one of polyester fiber, glass fiber, and polypropylene; and cavities are formed at the upper and lower ends of the coalescing separator D1. The coalescing separator is provided with a top oil phase outlet and a bottom water phase outlet.

[0043] The system also includes an alkali washing system, which is connected in series with the acid washing system. The alkali washing system and the acid washing system have the same structure, and the top oil phase outlet in the acid washing system is connected to the static mixer of the alkali washing system.

[0044] The system also includes a water washing system, which is connected in series with the alkali washing system. The water washing system has the same structure as the alkali washing system and the acid washing system, and the top oil phase outlet in the alkali washing system is connected to the static mixer of the water washing system.

[0045] The above process is used to carry out the following BDP acid washing, alkali washing and water washing steps: Pickling: (1) BDP crude product at 60°C (feed flow rate: 50 g / min), dilute hydrochloric acid with a mass fraction of 10% (feed flow rate: 15 g / min), and a mixed solvent of toluene and methylcyclohexane at 60°C (feed flow rate: 100 g / min) are respectively introduced into a static mixer for liquid-liquid contact; the operating pressure of the static mixer is 0.3 MPaG and the operating temperature is 70°C; (2) After uniform mixing, the water-oil mixed stream enters the filter to filter out the residue and then enters the centrifugal extractor for primary extraction and separation to achieve preliminary separation of the organic phase and the acid solution. At the same time, 10% dilute hydrochloric acid at 60°C (feed flow rate: 15 g / min) is added. The filtration accuracy of the filter is 0.5~5 microns; the speed during the centrifugal extraction process is 5000 rpm; (3) The light phase stream after the primary extraction separation enters the coalescing separator, and a polyester fiber coalescing internal is arranged inside the coalescing separator. The pressure of the lower cavity of the coalescing separator is 0.2 MPaG, and the operating temperature is 70-80°C. The pressure of the upper cavity is 0.05 MPa, and the temperature is 70-80°C. The residence time of the middle oil phase in the coalescing separator is 40 minutes, so that the organic phase and the trace acid liquid are completely separated. The acid liquid is discharged through the outlet, and the organic phase enters the alkali washing device through the outlet.

[0046] Example 2 Pickling: The pickling steps are the same as in Example 1.

[0047] Alkaline washing: (1) The organic phase after acid washing (feed flow rate: 50 g / min) and the dilute alkali solution with a mass fraction of 10% (feed flow rate: 15 g / min) are respectively fed into a static mixer for liquid-liquid contact; the operating pressure of the static mixer is 0.3 MPaG and the operating temperature is 70°C; (2) After being evenly mixed, the water-oil mixed stream enters the filter to filter out the residue and then enters the centrifugal extractor for primary extraction and separation to achieve preliminary separation of the organic phase and the acid solution. The filtration accuracy of the filter is 0.5-5 microns; the rotation speed during the centrifugal extraction process is 5000 rpm; (3) The light phase stream after the primary extraction separation enters the coalescing separator, and a polyester fiber coalescing internal is arranged inside the coalescing separator. The pressure of the lower cavity of the coalescing separator is 0.2 MPaG, and the operating temperature is 70-80°C. The pressure of the upper cavity is 0.05 MPa, and the temperature is 70-80°C. The residence time of the middle oil phase in the coalescing separator is 40 minutes, so that the organic phase and the trace acid solution are completely separated. The alkali solution is discharged through the outlet, and the organic phase enters the water washing device through the outlet.

[0048] Example 3 Pickling: The pickling steps are the same as in Example 1.

[0049] Alkali washing: The alkali washing step is the same as in Example 2.

[0050] First level water washing: (1) The organic phase after alkali washing (feed flow rate: 50 g / min) and circulating pure water (feed flow rate: 15 g / min) are respectively fed into a static mixer for liquid-liquid contact; the operating pressure of the static mixer is 0.3 MPaG and the operating temperature is 70°C; (2) After being evenly mixed, the water-oil mixed stream enters the filter to filter out the residue and then enters the centrifugal extractor for primary extraction and separation to achieve preliminary separation of the organic phase and the acid solution. The filtration accuracy of the filter is 0.5-5 microns; the rotation speed during the centrifugal extraction process is 5000 rpm; (3) The light phase stream after the primary extraction separation enters the coalescing separator, and a polyester fiber coalescing internal is arranged inside the coalescing separator. The pressure of the lower cavity of the coalescing separator is 0.2 MPaG, and the operating temperature is 70-80°C. The pressure of the upper cavity is 0.05 MPa, and the temperature is 70-80°C. The residence time of the middle oil phase in the coalescing separator is 40 minutes, so that the organic phase and the trace acid solution are completely separated. The water phase is discharged through the outlet, and the organic phase enters the secondary water washing device through the outlet.

[0051] Secondary washing: (1) The organic phase after primary water washing (feed flow rate: 50 g / min) and circulating pure water (feed flow rate: 15 g / min) are respectively fed into a static mixer for liquid-liquid contact; the operating pressure of the static mixer is 0.3 MPaG and the operating temperature is 70°C; (2) After being evenly mixed, the water-oil mixed stream enters the filter to filter out the residue and then enters the centrifugal extractor for primary extraction and separation to achieve preliminary separation of the organic phase and the acid solution. The filtration accuracy of the filter is 0.5-5 microns; the rotation speed during the centrifugal extraction process is 5000 rpm; (3) The light phase stream after the primary extraction separation enters the coalescing separator, and a polyester fiber coalescing internal is arranged inside the coalescing separator. The pressure of the lower cavity of the coalescing separator is 0.2 MPaG, and the operating temperature is 70-80°C. The pressure of the upper cavity is 0.05 MPa, and the temperature is 70-80°C. The residence time of the middle oil phase in the coalescing separator is 40 minutes, so that the organic phase and the trace acid solution are completely separated. The aqueous phase is discharged through the outlet, and the organic phase enters the desolventizing system through the outlet, and the organic solvent is removed by distillation to obtain the BDP product.

[0052] The analysis results of the crude BDP used in Examples 1, 2, 3 and Comparative Example 1 are shown in Table 1: Table 1

[0053] The above, the analysis results after pickling of Examples 1, 2, 3 and Comparative Example 1 are shown in Table 2: Table 2

[0054] The above, the analysis results after alkali washing of Examples 2, 3 and Comparative Example 1 are shown in Table 3: Table 3

[0055] The above analysis results after washing of Example 3 and Comparative Example 1 are shown in Table 4:

[0056] Undetectable is less than 0.01 ppm.

[0057] It can be seen that the present invention has a significant improvement in the removal of catalysts, phenol and other organic impurities compared with the existing washing process for BDP industrial production, and has a better effect on improving product quality.

Claims

1. A BDP acid washing, alkali washing and water washing system, characterized in that: The outlet of the static mixer (M1) is connected to the inlet of the filter (F1); the outlet of the filter (F1) is connected to the inlet of the centrifugal extractor (M2); and the upper light phase stream outlet of the centrifugal extractor (M2) is connected to the inlet of the coalescing separator (D1).

2. The BDP acid washing, alkali washing and water washing system according to claim 1, characterized in that: The static mixer (M1) is lined with polytetrafluoroethylene and filled with interlaced corrugated plates, wherein the material of the corrugated plates is selected from titanium and zirconium acid and alkali corrosion resistant materials.

3. The BDP acid washing, alkali washing and water washing system according to claim 1, characterized in that: The filter (F1) is selected from a plate and frame filter, a filter bag filter, a precision filter, and a core filter device, and a slag discharge port is provided at the bottom of the filter F1.

4. The BDP acid washing, alkali washing and water washing system according to claim 1, characterized in that: The heavy phase stream outlet at the bottom of the centrifugal extractor (M2) is connected to the inlet of the circulation pump (P1), and the outlet of the circulation pump (P1) is connected to the inlet of the static mixer (M1); a mixed material inlet is arranged in the middle of the centrifugal extractor (M2); and a light phase overflow port is arranged at the top of the centrifugal extractor (M2).

5. The BDP acid washing, alkali washing and water washing system according to claim 1, characterized in that: The coalescing separator (D1) is provided with coalescing internals, preferably any one of polyester fiber, glass fiber, and polypropylene; and cavities are formed at the upper and lower ends of the coalescing separator (D1). The coalescing separator is provided with a top oil phase outlet and a bottom water phase outlet.

6. A process for acid washing, alkali washing and water washing of BDP, using the device according to any one of claims 1 to 5, characterized in that: The steps include: (1) The crude BDP, circulating dilute hydrochloric acid and mixed solvent are in liquid-liquid contact in a static mixer to remove impurities in the crude BDP; (2) The mixed water-oil stream enters the filter to filter out the residue and then enters the centrifugal extractor for primary extraction and separation to achieve preliminary separation of the organic phase and the acid solution; (3) The light phase stream after the primary extraction and separation enters the coalescing separator to achieve complete separation of the organic phase and trace acid solution; Repeat steps (1), (2), and (3) to perform alkaline washing; Repeat steps (1), (2), and (3) to wash with water to purify BDP.

7. The acid washing, alkali washing and water washing process including BDP according to claim 6, characterized in that: The concentration of the circulating dilute hydrochloric acid in step (1) is 1-15% by mass; the mixed solvent is selected from toluene, methylcyclohexane, methyl ethyl ketone or a mixture of two thereof.

8. The acid washing, alkali washing and water washing process including BDP according to claim 6, characterized in that: In the centrifugal extraction process in step (2), the extraction is carried out at a rotation speed of 500-15000 rpm and dilute hydrochloric acid conditions, wherein the mass concentration of the dilute hydrochloric acid is 1-20%; and the filtration accuracy of the filter in step (2) is 0.5-5 microns.

9. The acid washing, alkali washing and water washing process including BDP according to claim 6, characterized in that: The operating pressure of the static mixer is 0.1MPaG~0.5MPaG, and the operating temperature is 50~80℃; the pressure of the lower cavity of the coalescing separator is 0.1MPaG~0.5MPaG, and the operating temperature is 50~80℃, the pressure of the upper cavity is 0.05~0.2MPa, the temperature is 50~80℃, and the upper and lower pressure difference is 0.1-0.2MPa; the residence time of the oil phase in the coalescing separator is 20~60min, preferably 20~40min.

10. The acid washing, alkali washing and water washing process including BDP according to claim 6, characterized in that: The BDP purified by acid washing is again subjected to alkali washing by the process described in any one of claims 6 to 8, wherein step (1) in the alkali washing process is to add 1-20% by mass of circulating dilute alkali for mixing to achieve alkali washing purification of BDP; the BDP purified by alkali washing is again subjected to water washing by the process described in any one of claims 6 to 8, wherein step (1) in the water washing process is to add circulating pure water for mixing to achieve water washing purification of BDP, and fresh pure water is added when the water volume is insufficient.

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