Crystallization method and production method of bisphenol A

Abstract

The invention relates to the technical field of organic matter purification, in particular to a crystallization method and a production method of bisphenol A. The crystallization method comprises the following steps that liquid containing bisphenol A enters the first falling film crystallizer through the first-stage feeding tank to be subjected to first-stage falling film crystallization, then enters the first falling film crystallizer through the second-stage feeding tank to be subjected to second-stage falling film crystallization, and then enters the second falling film crystallizer through the third-stage feeding tank to be subjected to third-stage falling film crystallization; wherein the number of the first falling film crystallizers is more than two, and the more than two first falling film crystallizers are connected in parallel; the number of the second falling film crystallizers is one or more, and when the number of the second falling film crystallizers is more than one, the second falling film crystallizers are connected in parallel. According to the bisphenol A crystallization method disclosed by the invention, the falling film crystallizers connected in parallel are arranged, so that the falling film crystallization effect can be improved, the falling film crystallization stage number is reduced, and the total period time of falling film crystallization separation is shortened.

Description

Technical Field

[0001] The invention relates to the technical field of organic matter purification, and in particular to a crystallization method and a production method of bisphenol A. Background Art

[0002] In the prior art, the bisphenol A content obtained by the method for producing bisphenol A is relatively low, and it is necessary to perform a four-stage falling film crystallization separation and purification operation to achieve the required bisphenol A quality requirements. During the four-stage falling film crystallization separation operation, there are many falling film crystallization separation stages, the total production time of each batch is long, and the product yield obtained after the four-stage falling film crystallization separation is low. The annual output of the device is more than 90kt, which results in high energy consumption and high cost per ton of product, affecting the economic benefits of the device. Summary of the invention

[0003] The invention provides a crystallization method and a production method of bisphenol A, which are used to solve the problems of the existing crystallization method for producing bisphenol A, such as multiple falling film crystallization separation stages, long total production time of each batch, low product output, large product energy consumption, high cost, etc.

[0004] According to a first aspect of the present invention, the present invention provides a method for crystallizing bisphenol A, comprising the following steps: The liquid containing bisphenol A enters the first falling film crystallizer through the first-level feed tank for first-level falling film crystallization, then enters the first falling film crystallizer through the second-level feed tank for second-level falling film crystallization, and then enters the second falling film crystallizer through the third-level feed tank for third-level falling film crystallization; wherein the number of the first falling film crystallizers is more than two, and more than two of the first falling film crystallizers are connected in parallel; the number of the second falling film crystallizers is one or more, and when the number of the second falling film crystallizers is more than one, multiple second falling film crystallizers are connected in parallel.

[0005] Further, the number of the first falling film crystallizers is three, and the number of the second falling film crystallizers is one; or, the number of the first falling film crystallizers is two, and the number of the second falling film crystallizers is two.

[0006] Furthermore, the liquid containing bisphenol A entering the primary feed tank includes bisphenol A obtained through suspension crystallization, solid-liquid separation, and vacuum dephenolization and bisphenol A obtained through static crystallization separation.

[0007] Further, the residual liquid 1R after the primary falling film crystallization separation is sent to a static crystallizer to recover bisphenol A, and heat transfer oil is introduced into the box body of the static crystallizer for cooling. Bisphenol A is crystallized on the cooling surface of the box body inside the static crystallizer, and the residual liquid containing the remaining bisphenol A and other impurities is left in the static crystallizer. After the residual liquid amount reaches a set value, the cooling crystallization process is stopped, and the residual liquid left in the static crystallizer is emptied and incorporated into the suspended crystallization feed for recovery treatment; Heat transfer oil is introduced into the box body of the static crystallizer for heating, the bisphenol A crystallized on the outer surface of the box body in the static crystallizer is heated and melted, and the molten bisphenol A is fed into the primary feed tank.

[0008] Furthermore, in the first-stage falling film crystallization process, the starting temperature of cooling is 140-143° C., the cooling rate is -0.28~-0.32° C. / min, and the temperature at the end of crystallization is 125-128° C.

[0009] Furthermore, in the secondary falling film crystallization process, the starting temperature of cooling is 142-145°C, the cooling rate is -0.32~-0.35°C / min, and the temperature at the end of crystallization is 128-132°C.

[0010] Furthermore, the residual liquid 2R after the secondary falling film crystallization separation is discharged into the primary feed tank; and the residual liquid 3R after the tertiary falling film crystallization separation is discharged into the secondary feed tank.

[0011] Furthermore, the time of the first falling film crystallization is 130-150 min; the time of the second falling film crystallization is 120-140 min.

[0012] According to the second aspect of the present invention, the present invention also provides a method for producing bisphenol A, which specifically comprises the following steps: Phenol and acetone react in the SEC200 unit to synthesize bisphenol A, which is then vacuum dehydrated and sent to the SEC700 unit to recover phenol and acetone, and the process wastewater is discharged; The mixed solution containing phenol and bisphenol A solution after vacuum dehydration from the SEC200 unit is sent to the SEC230 unit for suspension crystallization and filtration; the filter cake obtained by filtration is heated and melted and then sent to the SEC300 unit for vacuum dephenolization, and the dephenolized solution is then sent to the SEC400 unit for falling film crystallization, separation and purification; the falling film crystallization adopts the above-mentioned crystallization method.

[0013] Preferably, the phenol is sent to the SEC300 unit for vacuum dephenolization, and the dephenolized solution comprises the following components in weight percentage: 0.4-1.2% phenol, 97-99% bisphenol A, and 0.8-2.5% total impurities, wherein the total impurities include 2.4-BPA; preferably, the weight percentage of 2.4-BPA in the total impurities is 15-35%.

[0014] Furthermore, in the falling film crystallization, the liquid bisphenol A separated by the secondary falling film crystallization is stripped by a stripping tower and then sent to an epoxy resin device for downstream epoxy resin production; the liquid bisphenol A separated by the tertiary falling film crystallization is stripped by a polycarbonate-grade stripping tower to prepare polycarbonate-grade bisphenol A solid particles.

[0015] Preferably, the output of epoxy resin and polycarbonate-grade bisphenol A is adjusted by switching the number of crystallizers in the first falling film crystallizer and the second falling film crystallizer.

[0016] Furthermore, most of the mother liquor after filtration in the SEC230 unit is returned to the SEC200 unit, and a part is sent to the SEC280 unit for isomerization, dephenolization, and suspension crystallization recovery operations; the mother liquor after suspension crystallization separation in the SEC280 unit is sent to the SEC800 unit for catalytic decomposition of heavy components, and the phenol recovered after the catalytic decomposition is subjected to a synthetic reaction recovery with para-isopropenylphenol, and the remaining heavy components or substances (polyphenols) are discharged from the device.

[0017] Furthermore, the filter cake from the suspension crystallization separation in the SEC280 unit is heated and melted and then returned to the suspension crystallization feed in the SEC230 unit.

[0018] The bisphenol A crystallization method provided by the present invention can improve the effect of falling film crystallization, reduce the number of falling film crystallization stages, and shorten the total cycle time of falling film crystallization separation by arranging falling film crystallizers in parallel.

[0019] The present invention provides a method for producing bisphenol A, which improves the device capacity by shortening the falling film crystallization separation stages and the entire falling film crystallization cycle time, thereby reducing the energy consumption of the bisphenol A device and the product manufacturing cost; and transports the liquid bisphenol A to a downstream epoxy resin device through a pipeline for production, thereby reducing the bisphenol A granulation, packaging and transportation costs and improving the device capacity.

[0020] Compared with the prior art, the bisphenol A production method of the present invention has the following advantages: (1) the output of the bisphenol A device is increased, from 90,000 tons per year to 150,000 tons; (2) the energy consumption of the bisphenol A device is reduced, and the energy cost per ton of product is reduced by more than RMB 400; (3) the solid particle product meets the polycarbonate grade quality standard; (4) upstream and downstream integrated production, the annual production capacity of the epoxy resin device is increased by 25,000 tons (from 100,000 tons per year at that time to 125,000 tons); (5) the number of crystallizers in the first falling film crystallizer and the second falling film crystallizer can be switched at any time to adjust the output of epoxy grade and polycarbonate grade bisphenol A to meet production needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1A process flow chart of a bisphenol A crystallization method provided in an embodiment of the present invention.

[0023] Figure 2 This is one of the schematic diagrams of falling film crystallization in a crystallization method of bisphenol A provided in an embodiment of the present invention.

[0024] Figure 3 The second schematic diagram of falling film crystallization in a crystallization method of bisphenol A provided in an embodiment of the present invention.

[0025] Figure 4 A process flow chart of a method for producing bisphenol A provided in an embodiment of the present invention.

[0026] Figure 5 A schematic diagram of falling film crystallization feed in a bisphenol A crystallization method provided in an embodiment of the present invention.

[0027] Figure 6 The third schematic diagram of falling film crystallization in a crystallization method of bisphenol A provided in an embodiment of the present invention.

[0028] Figure 7 A process flow chart of a method for producing bisphenol A provided in Comparative Example 1 of the present invention.

[0029] Figure 8 for Figure 7 Schematic diagram of the structure of the SEC400 falling film crystallization unit.

[0030] Fig. 9 This is a schematic diagram of falling film crystallization in a bisphenol A crystallization method provided in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In a first typical embodiment of the present invention, the present invention provides a method for crystallizing bisphenol A. According to some specific embodiments of the present invention, the crystallization method comprises the following steps: like Figure 1As shown, the liquid containing bisphenol A enters the first falling film crystallizer through the first-level feed tank (V412) for first-level falling film crystallization, then enters the first falling film crystallizer through the second-level feed tank (V432) for second-level falling film crystallization, and then enters the second falling film crystallizer through the third-level feed tank (V422) for third-level falling film crystallization; wherein the number of the first falling film crystallizers is more than two, and more than two of the first falling film crystallizers are connected in parallel; the number of the second falling film crystallizers is one or more, and when the number of the second falling film crystallizers is more than one, the plurality of the second falling film crystallizers are connected in parallel.

[0033] In the above scheme, a bisphenol A crystallization method of the present invention can improve the effect of falling film crystallization, reduce the number of falling film crystallization stages, and shorten the total cycle time of falling film crystallization separation by setting a falling film crystallizer in parallel.

[0034] In order to further shorten the total cycle time of falling film crystallization separation, according to some specific embodiments of the present invention, Figure 2 As shown, the number of the first falling film crystallizers (CS410, CS420, CS430) is three, and the number of the second falling film crystallizer (CS440) is one.

[0035] In the above scheme, three first falling film crystallizers are used to increase the output of liquid bisphenol A after the first and second falling film crystallization separation.

[0036] When it is necessary to increase the yield of polycarbonate grade (PC grade) bisphenol A, according to some specific embodiments of the present invention, such as Figure 3 As shown, the number of the first falling film crystallizers (CS410, CS420) is two, and the number of the second falling film crystallizers (CS430, CS440) is two. The two second falling film crystallizers are produced together to increase the output of PC-grade bisphenol A after three-stage falling film crystallization separation. After the liquid PC-grade bisphenol A is stripped, a stream of material can be separated and sent to the liquid epoxy-grade bisphenol A for mixing, which can improve the quality of epoxy-grade bisphenol A and be used to improve the quality of epoxy resin products to meet customers' specific requirements for products.

[0037] According to some specific embodiments of the present invention, the liquid containing bisphenol A entering the primary feed tank includes bisphenol A obtained by suspension crystallization and solid-liquid separation, phenol-bisphenol A adduct crystals obtained by heating and melting, vacuum dephenolization, and bisphenol A obtained by static crystallization separation.

[0038] According to some specific embodiments of the present invention, the residual liquid 1R after the first-stage falling film crystallization separation is sent to a static crystallizer to recover bisphenol A, and heat transfer oil is introduced into the box body of the static crystallizer for cooling. Bisphenol A is crystallized on the cooling surface of the box body inside the static crystallizer, and the residual liquid containing the remaining bisphenol A and other impurities is left in the static crystallizer. After the residual liquid amount reaches a set value, the cooling crystallization process is stopped, and the residual liquid left in the static crystallizer is emptied and incorporated into the suspended crystallization feed for recovery treatment; Heat transfer oil is introduced into the box body of the static crystallizer for heating, the bisphenol A crystallized on the outer surface of the box body in the static crystallizer is heated and melted, and the molten bisphenol A is fed into the primary feed tank.

[0039] According to some specific embodiments of the present invention, in order to improve the efficiency of the first-stage falling film crystallization, during the first-stage falling film crystallization process, the starting temperature of cooling is 140-143°C, the cooling rate is -0.28~-0.32°C / min, and the temperature at the end of crystallization is 125-128°C.

[0040] According to some specific embodiments of the present invention, in order to improve the efficiency of secondary falling film crystallization, during the secondary falling film crystallization process, the starting temperature of cooling is 142-145°C, the cooling rate is -0.32~-0.35°C / min, and the temperature at the end of crystallization is 128-132°C.

[0041] According to some specific embodiments of the present invention, Figure 1 As shown, the residual liquid 2R after the secondary falling film crystallization separation is discharged into the primary feed tank, so that the residual liquid is recycled and the yield is improved; the residual liquid 3R after the tertiary falling film crystallization separation is discharged into the secondary feed tank, so that the residual liquid is recycled and the yield is improved.

[0042] According to some specific embodiments of the present invention, the time for the primary falling film crystallization is 130-150 min; the time for the secondary falling film crystallization is 120-140 min.

[0043] Optionally, the time for the primary falling film crystallization may be 130 min, 131 min, 132 min, 133 min, 134 min, 135 min, 136 min, 137 min, 138 min, 139 min or 140 min, 141 min, 142 min, 143 min, 144 min, 145 min, 146 min, 147 min, 148 min, 149 min or 150 min, etc.; the time for the secondary falling film crystallization may be 120 min, 121 min, 122 min, 123 min, 124 min, 125 min, 126 min, 127 min, 128 min, 129 min, 130 min, 131 min, 132 min, 133 min, 134 min, 135 min, 136 min, 137 min, 138 min, 139 min or 140 min, etc.

[0044] In a second typical embodiment of the present invention, the present invention also provides a method for producing bisphenol A, referring to Figure 4 As shown, the specific steps include: Phenol and acetone react in the SEC200 unit to synthesize bisphenol A, which is then vacuum dehydrated and sent to the SEC700 unit to recover phenol and acetone, and the process wastewater is discharged; The mixed solution containing phenol and bisphenol A solution after vacuum dehydration from the SEC200 unit is sent to the SEC230 unit for suspension crystallization and filtration; the filter cake obtained by filtration is heated and melted and then sent to the SEC300 unit for vacuum dephenolization, and the dephenolized solution is then sent to the SEC400 unit for falling film crystallization, separation and purification; the falling film crystallization adopts the above-mentioned crystallization method.

[0045] In the above scheme, the mixed solution containing phenol and bisphenol A solution after vacuum dehydration from the SEC200 unit is sent to the SEC230 unit for suspension crystallization and filtration, which can achieve the effect of increasing the falling film crystallization feed concentration, and then the falling film crystallization separation stage can be shortened, and the entire falling film crystallization cycle time can be shortened to increase the device production capacity and reduce the energy consumption of the bisphenol A device and the product manufacturing cost.

[0046] Preferably, the phenol is sent to the SEC300 unit for vacuum dephenolization, and the dephenolized solution comprises the following components in weight percentage: 0.4-1.2% phenol, 97-99% bisphenol A, and 0.8-2.5% total impurities, wherein the total impurities include 2.4-BPA; preferably, the weight percentage of 2.4-BPA in the total impurities is 15-35%.

[0047] According to some specific embodiments of the present invention, the liquid bisphenol A separated by the secondary falling film crystallization is sent to the epoxy resin device for downstream epoxy resin production after epoxy stripping; the liquid bisphenol A separated by the tertiary falling film crystallization is prepared into solid granular polycarbonate-grade bisphenol A after polycarbonate-grade stripping.

[0048] In the above scheme, the liquid bisphenol A separated by the secondary falling film crystallization is sent to the epoxy resin device for downstream epoxy resin production after epoxy stripping, which reduces the bisphenol A granulation, packaging and transportation costs, improves the device capacity, and cancels the bisphenol A solid feeding process in the epoxy resin production, shortening the batch production time of the epoxy resin. The liquid bisphenol A separated by the tertiary falling film crystallization is made into solid granular polycarbonate-grade bisphenol A for external market sales after polycarbonate-grade stripping (bisphenol A has higher purity and lower phenol content), realizing the graded manufacturing of different products. The production method of the present invention outputs two products, liquid bisphenol A and solid granular bisphenol A, which improves the total output of the device, meets the production needs of different users, reduces the energy consumption of the device, and reduces the packaging and manual transportation costs of solid granular products.

[0049] According to some specific embodiments of the present invention, most of the mother liquor after filtration in the SEC230 unit is returned to the SEC200 unit, and a part is sent to the SEC280 unit for isomerization, dephenolization, and suspension crystallization recovery operations; the mother liquor after suspension crystallization separation in the SEC280 unit is sent to the SEC800 unit for catalytic decomposition of heavy components, and the phenol and para-isopropenylphenol obtained after the catalytic decomposition are subjected to a synthetic reaction recovery, and the remaining heavy components or substances (polyphenols) are discharged from the device.

[0050] According to some specific embodiments of the present invention, the filter cake from the suspension crystallization separation in the SEC280 unit is heated and melted and then returned to the suspension crystallization feed in the SEC230 unit.

[0051] Example 1

[0052] This embodiment provides a method for crystallizing bisphenol A, referring to Figure 4 As shown, the following steps are included: After the raw materials react in the reactor, the average concentration of each component of the solution is: acetone 1.25%, water 1.28%, phenol 64.4%, bisphenol A 22.5%, and other total impurities 10.57%. It is sent to the dehydration tower for dehydration operation. The dehydration operation is carried out under the operating conditions of 15KpaA top pressure of the dehydration tower and 128°C bottom temperature. The material removed from the top of the tower contains acetone, water and phenol, which is sent to the SEC700 unit to recover phenol and acetone, and the process wastewater is discharged. The material component concentration obtained at the bottom of the dehydration tower is: 0% acetone, 0.07% water, 64.7% phenol, 24% bisphenol A, and 11.23% total impurities. The bisphenol A residual liquid obtained from the static crystallizer and the molten filter cake obtained by isomerization recovery are sent to the suspension crystallizer of the SEC230 unit for cooling crystallization. The solution temperature of the material in the suspension crystallizer is controlled at 50-53°C before entering the vacuum filter for separation, so that the adduct crystals formed by bisphenol A and phenol are precipitated in the solution to form a suspension, which is sent to the vacuum filter for solid-liquid separation operation. After the mother liquor is separated, the bisphenol A content in the mother liquor is about 10%, and the filter cake is the adduct crystals of phenol and bisphenol A.

[0053] The filter cake obtained by vacuum filtration is heated to 120-140℃ and melted into liquid. The flow rate is 51-52t / h. The average concentration of each component in the material is: acetone 0%, water <0.1%, phenol 53.70%, bisphenol A 45.64%, impurities 0.55%. It is sent to the SEC300 unit for three-stage vacuum dephenolization operation under the conditions of pressure 0.5-20KpaA and temperature 148-170℃. The solution after dephenolization: phenol 1.06%, bisphenol A 97.69%, total impurities 1.25%, among which 2.4-BPA is the most impurity. The impurities contained in the first falling film crystallization process were 0.43% and 0.82% respectively, and the other impurities contained 0.82% (the concentration of the material components is shown in Table 1 below). The impurities were then sent to the SEC400 unit for multi-stage falling film crystallization, separation and purification operations. The starting temperature, cooling rate and residual liquid volume of the heat transfer oil cooling during the graded falling film crystallization process were controlled to achieve the purification of the falling film crystallization products at each level. The starting temperature of the heat transfer oil cooling during the first falling film crystallization process was 140-143°C, the cooling rate was -0.28~-0.32°C / min, the heat transfer oil temperature corresponding to the end of crystallization was 125-128°C, and the second falling film crystallization process was 140-143°C. The starting temperature of the thermal oil cooling for film crystallization is 142-145°C, the cooling rate is -0.32~-0.35°C / min, and the thermal oil temperature corresponding to the end of crystallization is 128-132°C. The purity of the bisphenol A melt obtained by the secondary falling film crystallization separation reaches more than 99.85% after stripping in the epoxy stripping tower, and is sent to the epoxy resin device for downstream epoxy resin product production. The solution concentration of the tertiary falling film crystallization separation operation is: phenol 0.06%, bisphenol A 99.76%, and total impurities 0.23% (including 2.4-BPA 0.05%, other impurities 0.18%) (material component concentrations are shown in Table 2 below). After further removing impurities, the bisphenol A melt obtained is stripped in a polycarbonate-grade stripping tower and sent to the SEC500 unit for granulation and the SEC600 unit for packaging. Finally, solid granular bisphenol A products are obtained. The average daily output (liquid bisphenol A + solid product) is 472 tons. The average indicators of each batch of granulated products (tested according to the national standard method) are: melt color: No. 11, solution color: No. 4, purity: 99.92%, phenol: 8ppm, 2.4-bisphenol A: 246ppm, water: 253ppm.

[0054] The first-stage residual liquid 1R from the falling film crystallization of the SEC400 unit is subjected to the static crystallization operation of the SEC400 unit to recover bisphenol A. Heat transfer oil is introduced into the box inside the static crystallizer to cool it down to 110-115°C. Bisphenol A is crystallized on the cooling surface of the box inside the static crystallizer, and the residual liquid (including remaining bisphenol A and other impurities) remains in the static crystallizer. When the residual liquid volume reaches the set value, the cooling crystallization process is stopped, and the residual liquid remaining in the static crystallizer is emptied at a flow rate of 6t / h and transported to the suspended crystallization feed of the SEC230 unit by a pump.

[0055] Heat transfer oil is introduced into the box of the static crystallizer for heating. The heat transfer oil is heated to 170°C to melt the bisphenol A crystals crystallized on the surface of the box inside the static crystallizer and discharge them into the bisphenol A recovery tank. The molten bisphenol A is sent to the SEC400 unit primary falling film crystallization feed tank V412 for recovery.

[0056] Most of the mother liquor after vacuum filtration from the SEC230 unit is returned to the reaction unit, of which 10-14t / h of the mother liquor is sent to the SEC280 unit for isomerization, dephenolization, suspension crystallization, and solid-liquid separation and recovery operations. The filter cake obtained after separation is heated and melted (flow rate is 1.5-2t / h) and returned to the SEC230 unit suspension crystallization feed. The mother liquor with a flow rate of 3.5-5t / h discharged after solid-liquid separation is sent to the SEC800 unit dephenolization tower after dephenolization. The dephenolized solution is catalytically decomposed under alkaline conditions of 206-212°C. The phenol recovered by the catalytic decomposition is reacted with p-isopropenylphenol for recovery, and the remaining heavy components or substances (polyphenols) are discharged from the device.

[0057] After suspension crystallization, solid-liquid separation and dephenolization in SEC230 unit, the purity of bisphenol A in the bisphenol A solution entering SEC400 unit is increased. The feed concentration of falling film crystallization in SEC400 unit is shown in Table 1 below. The average concentration of bisphenol A is 97.69wt%, which is 8.657wt% higher than the bisphenol A content (89.029wt%) after dehydration and dephenolization in the original technology. The falling film crystallization separation stage can be shortened to produce bisphenol A.

[0058] Table 1

[0059] Among them, the total impurities in Table 1 include 2.4-BPA.

[0060] Falling film crystallization no longer performs a four-stage separation operation, but becomes a two-stage and three-stage falling film crystallization separation operation. The process diagram of falling film crystallization is shown in Figure 1 As shown. In the above process, the liquid bisphenol A with a purity of more than 99.85% after the secondary falling film crystallization separation is sent to the epoxy resin device for downstream epoxy resin production after epoxy stripping, and the liquid bisphenol A after the tertiary falling film crystallization separation is made into solid particles of polycarbonate-grade bisphenol A with a purity of 99.92% after polycarbonate-grade stripping for external market sales, realizing graded manufacturing of different products. By reducing the number of falling film crystallization separation stages, the separation process time is shortened, the device output is increased, energy consumption is reduced, and the overall economic benefits of the device are improved.

[0061] Falling film crystallizers CS410 and CS420 are used for one-stage and two-stage falling film crystallization separation operation, falling film crystallizer CS430 is changed to one-stage and two-stage falling film crystallization separation operation, and falling film crystallizer CS440 is changed to three-stage falling film crystallization separation operation, such as Figure 2 shown.

[0062] Due to the high concentration of bisphenol A and reduced impurities in the primary falling film crystallization feed, the combined batch time of the primary and secondary falling film crystallizations becomes shorter. Normally, the cycle time for the primary falling film crystallization separation is about 140 minutes, and the cycle time for the secondary falling film crystallization separation is about 130 minutes.

[0063] When the production of polycarbonate grade (PC grade) bisphenol A needs to be increased, the falling film crystallizer CS430 is not used for the first and second stage falling film crystallization separation operations, but is changed to the third stage falling film crystallization separation operation.

[0064] The concentration of bisphenol A in the three-stage falling film crystallization feed tank V422 is increased to more than 99.5wt%. For example, it is shown in Table 2 below: Table 2

[0065] Among them, the total impurities in Table 2 include 2.4-BPA.

[0066] Example 2

[0067] On the basis of Example 1, the falling film crystallization process was further refined. The phenol-bisphenol A adduct crystals obtained from the suspension crystallization and solid-liquid separation were heated and melted, and vacuum dephenolized by the SEC300 unit, and then fed together with the bisphenol A product obtained by static crystallization separation into the falling film crystallization primary feed tank V412. The feed rate was 27.185 t / h, of which 22.8 t / h came from the SEC300 dephenolization unit, and the other part (4.385 t / h) came from the bisphenol A product obtained after static crystallization separation (such as Figure 5 ).

[0068] The temperature of the two materials after mixing is 175℃, and the concentration of each component is: phenol 0.7%, bisphenol A 98.46%, total impurities 0.84% ​​(including 2.4-BPA), combined Figure 6As shown, the 175°C molten bisphenol A is pumped to the bottom trough of the falling film crystallizer CS410 or CS420, and the molten bisphenol A in the trough is sent to the S-type distributor above the top tube array of the falling film crystallizer by the discharge pump. The molten bisphenol A circulates inside the tube array of the crystallizer, and heat transfer oil is introduced into the outside of the tube array to form film cooling. The cooled heat transfer oil starts to cool from 143°C at a rate of -0.28°C / min, and bisphenol A crystals begin to form inside the tube array of the falling film crystallizer CS410 or CS420. Crystallization, the thickness of the crystal layer gradually increases, the liquid in the bottom trough of the crystallizer gradually decreases, and the liquid level continues to decrease. When the residual liquid reaches the set value, the residual liquid is discharged, and then the heat transfer oil outside the crystallizer tube is heated and heated at a rate of 0.7℃ / min. After it reaches 175℃, the temperature is maintained. The bisphenol A crystals crystallized on the inner wall of the crystallizer tube are heated and melted, and fall into the bottom trough of CS410 or CS420. The molten bisphenol A product (FF1P) in the trough is discharged into the first-level falling film crystallization product tank V432.

[0069] The first-stage falling film crystallization product FF1P obtained above is mixed with the residual liquid obtained from the third-stage falling film crystallization separation in tank V432, and sent to the falling film crystallizer CS410 or CS420 for secondary falling film crystallization separation operation. A total of 70 tons of material is fed, and the heat transfer oil crystallization cooling, bisphenol A residual liquid discharge, and bisphenol A crystals are heated and melted according to the same method as above to obtain the secondary falling film crystallization product FF2P, which is discharged into the secondary falling film crystallization product tank V422.

[0070] The first and second stage falling film crystallization separation operation of falling film crystallizer CS430 is the same as that of CS410 or CS420. The 175°C molten bisphenol A (from V412) with the same composition as the first stage falling film crystallizer feed CS410 or CS420 is pumped into the bottom trough of falling film crystallizer CS430, 42 tons of material is fed, and the discharge pump of the bottom trough of CS430 is started. The molten bisphenol A in the trough is sent to the S-type distributor above the top tube of falling film crystallizer CS430 through the discharge pump. The molten bisphenol A circulates inside the crystallizer tubes, and heat transfer oil is introduced into the outside of the tubes for falling film cooling. The starting temperature of the heat transfer oil cooling is 143°C, and the cooling rate is -0.28°C / min. When the residual liquid reaches the set value, the residual liquid is discharged, and the heat transfer oil is heated at a rate of 0.7°C / min. After the temperature is raised to 175°C, the temperature is maintained. The bisphenol A crystals crystallized on the inner wall of the crystallizer tubes are heated and melted to obtain a first-level falling film crystallization product FF1P, which is discharged into the first-level falling film crystallization product tank V432. The bisphenol A melt (FF1P) from the first-level falling film crystallization product tank is sent to CS430 for a second-level falling film crystallization separation operation to obtain a second-level falling film crystallization product FF2P. The cycle time of the first and second-level falling film crystallizations is approximately 140min and 130min.

[0071] The residual liquid volume of the first falling film crystallization from the falling film crystallizers CS410, CS420 and CS430 is 6.26 t / h, and the residual liquid of the second falling film crystallization is discharged into the first falling film crystallization feed. Figure 4 shown.

[0072] The secondary falling film crystallization product FF2P from falling film crystallizers CS410, CS420 and CS430 is stored in storage tank V422 and pumped to the epoxy stripping tower at a flow rate of 10.8t / h for dephenolization. After the molten bisphenol A is stripped by 5KpaA vacuum absolute pressure and 180℃ superheated steam, it is pumped to the epoxy resin unit for downstream product production. The daily supply of liquid bisphenol A directly to the epoxy resin unit is 259.7 tons. The purity of bisphenol A is above 99.85%.

[0073] The falling film crystallizer CS440 was used for three-stage falling film crystallization separation operation, with a total feed of 42 tons (the feed came from V422), the starting temperature of the crystallizer heat transfer oil cooling was 146°C, the cooling rate was -0.3°C / min, and after the residual liquid in the bottom trough of the falling film crystallizer CS440 reached the set value, the cooling crystallization was stopped, the residual liquid was discharged, and the heat transfer oil was heated at a heating rate of 1.0°C / min. After the heat transfer oil was heated to 175°C, the temperature was maintained until the bisphenol A crystals in the internal tubes of the crystallizer were completely melted, and the three-stage falling film crystallization product FF3P was obtained (stored in the PC-level product tank V491). The three-stage falling film crystallization cycle time of the falling film crystallizer CS440 is 100min.

[0074] The three-stage falling film crystallization product from CS440 is sent to the PC-grade stripping tower for dephenolization. After dephenolization by 5KpaA vacuum absolute pressure and 180℃ superheated steam stripping, the molten bisphenol A is pumped to the granulation tower for granulation and packaging. The polycarbonate grade product is obtained, with a molten color of No. 10, a solution color of No. 4, a phenol content of less than 10ppm, 2.4-bisphenol A of 256ppm, and a moisture content of less than 300ppm. The purity of the product after removing moisture and other impurities is 99.92-99.94wt%, and the daily output of solid granular bisphenol A is 243 tons.

[0075] The total flow rate of the above liquid and solid particle products is 20.925t / h, and the daily output is 502.7 tons.

[0076] Example 3

[0077] The difference in Example 1 is that the process flow of falling film crystallization is different. The specific process flow chart is as follows: Figure 3 shown.

[0078] The phenol-bisphenol A adduct crystals obtained from suspension crystallization and solid-liquid separation are heated, melted, vacuum-dephenolized, and then fed into the primary feed tank of falling film crystallization. The concentrations of each component are: phenol 0.42%, bisphenol A 97.61%, total impurities 1.97% (including 2.4-BPA 0.38% and other impurities 1.59%), and the feed flow rate is 18.621t / h. The molten bisphenol A is pumped to the bottom trough of the falling film crystallizer CS410 or CS420, totaling 73 tons. The discharge pump of the bottom trough of CS410 or CS420 is started, and the molten bisphenol A in the trough is fed into the S-type distributor above the top tube of the falling film crystallizer through the discharge pump. The molten bisphenol A circulates inside the tube of the crystallizer, and heat transfer oil is introduced into the outside of the tube to form film cooling. The cooled heat transfer oil starts to cool from 143°C to -0. The temperature is lowered at a rate of 3°C / min. Bisphenol A crystals begin to crystallize inside the tubes of the falling film crystallizer CS410 or CS420. The thickness of the crystal layer gradually increases, the liquid in the bottom trough of the crystallizer gradually decreases, and the liquid level continues to decrease. When the residual liquid reaches the set value, the residual liquid is discharged, and then the heat transfer oil outside the crystallizer tube is heated and heated. After the heat transfer oil is heated to 175°C, the temperature is maintained. The bisphenol A crystals crystallized on the inner wall of the crystallizer tube are heated and melted, and fall into the bottom trough of CS410 or CS420. The molten bisphenol A product (FF1P) in the trough is discharged into the primary falling film crystallization product tank.

[0079] The first-stage falling film crystallization product FF1P obtained above is fed into the falling film crystallizer CS410 or CS420 for second-stage falling film crystallization separation operation, with a total feed of 70 tons, and the heat transfer oil crystallization cooling (heat transfer oil cooling starting temperature 145°C, cooling rate -0.32°C / min), bisphenol A residual liquid discharge, bisphenol A crystal heating and melting are carried out in the same manner as above to obtain the second-stage falling film crystallization product FF2P, which is discharged into the second-stage falling film crystallization product tank. The cycle time of the first and second-stage falling film crystallization is about 140min and 130min respectively.

[0080] The residual liquid discharged from the first-stage falling film crystallization separation is 2.08t / h, which is discharged into the static crystallizer for bisphenol A recovery.

[0081] The above-mentioned secondary falling film crystallization product is sent to the epoxy grade bisphenol A stripping and then sent to the epoxy resin device, with a flow rate of 10.416t / h, bisphenol A purity of 99.85-99.86%, solution color of 17-19, 2.4-bisphenol A less than 450ppm. The daily output is 250 tons.

[0082] Falling film crystallizer CS440 is used for three-stage falling film crystallization separation operation. The molten bisphenol A is pumped into the bottom trough of the falling film crystallizer CS440, 42 tons of material is fed, and the discharge pump of the bottom trough of CS440 is started. The molten bisphenol A in the trough is sent to the S-type distributor above the top tube of the falling film crystallizer CS440 through the discharge pump. The molten bisphenol A circulates inside the tube of the crystallizer, and heat transfer oil is introduced into the outside of the tube for falling film cooling. The starting temperature of the heat transfer oil cooling is 145°C, and the cooling rate is -0.32°C / min. When the residual liquid reaches the set value, the residual liquid is discharged, and the heat transfer oil is heated at a heating rate of 1°C / min. After the temperature is raised to 175°C, the temperature is maintained. The bisphenol A crystals crystallized on the inner wall of the crystallizer tube are heated and melted to obtain the three-stage falling film crystallization product FF3P, which is discharged into the three-stage falling film crystallization product tank. The three-stage falling film crystallization cycle time of the falling film crystallizer CS440 is 100min.

[0083] Falling film crystallizer CS430 can be used for three-stage falling film crystallization separation operation to increase the three-stage falling film crystallization yield. The three-stage falling film crystallization product liquid is stripped to reduce the phenol content, and a part of the material can be separated and added to the epoxy grade product to improve the quality of the epoxy grade product.

[0084] The flow rate of the polycarbonate grade product fed into the granulation tower for granulation is 6.125 t / h, the purity is 99.94%, the molten color is No. 11, the solution color is No. 4, phenol is 8-10 ppm, 2.4-bisphenol A is 250 ppm, and the daily output is 147 tons.

[0085] The total output of the above two solid and liquid products is 250+147=397 tons.

[0086] Comparative Example 1

[0087] This comparative example provides a crystallization method for producing bisphenol A, the process flow is as follows: Figure 7 As shown, the specific steps include: Phenol and acetone are used to synthesize bisphenol A in the SEC200 reaction unit. The solution after the reaction is vacuum dehydrated by SEC200 to remove unreacted acetone, generated water and a part of phenol, and then sent to the SEC700 unit to recover phenol and acetone, and process wastewater is discharged. The bottom materials after dehydration from the SEC200 unit are phenol and bisphenol A solution (including other impurities), which are sent to the SEC300 unit for three-stage vacuum dephenolization operation. The concentration of each component in the solution after dephenolization is: 0.60% phenol, 89.03% bisphenol A, and 10.37% total impurities. It is then sent to the SEC400 unit for multi-stage melt crystallization (falling film crystallization) operation. After the multi-stage falling film crystallization separation and impurities removal, the bisphenol A melt obtained is sent to the SEC500 granulation unit and the SEC600 packaging unit for granulation and packaging operations, and finally a solid granular bisphenol A product is obtained. The first-stage residual liquid obtained from the falling film crystallization separation of SEC400 is subjected to the static crystallization operation of SEC400 to recover bisphenol A (static crystallization product). The residual liquid is sent to the SEC800 unit for dephenolization and then subjected to catalytic decomposition and recovery operation to discharge polyphenols.

[0088] After three-stage dephenolization by the SEC300 unit, the concentrations of the components in the bisphenol A solution obtained from FV330 are shown in Table 3 below.

[0089] Table 3

[0090] In the sampling analysis, the impurity content of the bisphenol A solution in the first falling film crystallization feed tank was 10.373wt% on average, and the purity of bisphenol A was 89.029wt%. Due to the high impurity content in this component and the relatively low bisphenol A content, it is necessary to perform a four-stage falling film crystallization separation and purification operation to achieve the required bisphenol A quality requirements. The process flow chart of the four-stage falling film crystallization separation operation is shown in Figure 8 The bisphenol A solution from the SEC300 three-stage vacuum dephenolization is fed into the first-stage falling film crystallization feed tank V412, mixed with the residual liquid 2R from the second-stage falling film crystallization, and then fed into the Figure 8The first-stage falling film crystallizers CS410 and CS420 shown perform a first-stage falling film crystallization separation operation. Through the cooling of the heat transfer oil on the outer surface of the falling film crystallizer tube, bisphenol A crystals are precipitated on the inner surface of the falling film crystallizer tube. As the cooling temperature of the heat transfer oil continues to decrease, the thickness of the bisphenol A crystal layer on the inner wall of the falling film crystallizer tube continues to increase, and the bisphenol A remaining in the residual liquid continues to decrease. After reaching the set value of the residual liquid, the crystallization cooling operation is stopped, and the first-stage falling film crystallization residual liquid 1R (bisphenol A and its impurities that have not been crystallized) is discharged from the crystallizer, and the heat transfer oil cooling is switched to heating operation. The heat transfer oil is set to a certain heating rate to heat the bisphenol A crystals in the inner tube of the falling film crystallizer. The bisphenol A crystals are heated and melted to become the first-stage falling film crystallization product 1P, which is sent to the second-stage falling film crystallization feed tank V432. The third-stage falling film crystallization residual liquid 3R after the third-stage falling film crystallization separation operation is also discharged into V432.

[0091] The operation of the second to fourth falling film crystallization separation is similar to that of the first falling film crystallization separation. The feed of the fourth falling film crystallizer comes from the product 3P after the third falling film crystallization separation. The falling film crystallizer CS420 performs the first and second falling film crystallization separation operations, and the falling film crystallizers CS430 and CS440 perform the third and fourth falling film crystallization separation operations. The falling film crystallizers of each level and the falling film crystallization cycle time are as follows Fig. 9 shown.

[0092] Through the multi-stage falling film crystallization operation, the bisphenol A content in each level of solution continued to increase. Sampling and analysis showed that the average values ​​of the feed concentrations of the first, second and third stage falling film crystallization were 90.814wt%, 96.68wt% and 98.98wt% respectively (the bisphenol A concentration in the third stage falling film crystallization feed tank V422 of Example 1 was 99.5wt%), and the product concentration obtained after the fourth stage falling film crystallization separation was 99.896wt%. The purity of the product after the fourth stage falling film crystallization separation was not less than 99.85wt%, which met the quality index requirements of the polycarbonate grade, as shown in Table 4 below: Table 4

[0093] The above four-stage falling film crystallization separation method has the following disadvantages: (1) There are many falling film stages, and four-stage falling film crystallization separation operations are required. The total batch time of the falling film crystallization separation operation from the first stage to the last stage is long (185 minutes for the first stage, 130 minutes for the second stage, 120 minutes for the third stage, and 90 minutes for the fourth stage), and the output of each stage gradually decreases. The original design of the first-stage falling film crystallization feed rate of the device was 15.28 t / h. After four-stage falling film crystallization separation operations, the product output was 11.82 t / h (purity was 99.9 wt%), and the yield was 11.82 / 15.28 = 77.356%. The yield was low, the energy consumption per ton of product was high, the steam consumption per ton of product was 4.3 t / t, and the product manufacturing cost was high.

[0094] (2) Before the technical transformation of the device, the first-stage feed composition of bisphenol A in the falling film crystallization unit was: phenol 1.05%, bisphenol A 92.8%, and other impurities 11.12%. Although it was higher than the designed purity (the designed feed composition was: phenol 0.86%, bisphenol A 86.02%, and other impurities 13.14%), the product purity after four-stage falling film crystallization separation was low and contained many impurities. The phenol content in the bisphenol A product was higher than 50ppm, and the 2.4-bisphenol A content was higher than 300ppm. It did not meet the polycarbonate grade index and was an epoxy premium product.

[0095] (3) Before the technical transformation, falling film crystallization was divided into four stages. After the four-stage falling film crystallization, the molten bisphenol A was granulated and packaged to make products. No liquid bisphenol A was produced. The device only produced solid granulated products. The output of the device was low. The annual output of the device was 85,000 tons. Calculated based on an annual production time of 8,000 hours, the average daily output was 255 tons.

[0096] (4) The liquid bisphenol A obtained after the four-stage falling film crystallization separation is granulated and packaged to form a solid particle bisphenol A product, and the solid particle product made after granulation and packaging is then used in the company's downstream epoxy resin production, which increases the packaging and transportation costs of bisphenol A and increases the solid feeding time, thereby increasing the production costs of the upstream and downstream equipment products.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for crystallizing bisphenol A, characterized in that: The steps include: The liquid containing bisphenol A enters the first falling film crystallizer through the first-level feed tank for first-level falling film crystallization, then enters the first falling film crystallizer through the second-level feed tank for second-level falling film crystallization, and then enters the second falling film crystallizer through the third-level feed tank for third-level falling film crystallization; wherein the number of the first falling film crystallizers is more than two, and more than two of the first falling film crystallizers are connected in parallel; the number of the second falling film crystallizers is one or more, and when the number of the second falling film crystallizers is more than one, multiple second falling film crystallizers are connected in parallel.

2. The crystallization method according to claim 1, characterized in that The number of the first falling film crystallizers is three, and the number of the second falling film crystallizers is one; or, the number of the first falling film crystallizers is two, and the number of the second falling film crystallizers is two.

3. The crystallization method according to claim 1, characterized in that The liquid containing bisphenol A entering the primary feed tank includes bisphenol A sequentially subjected to suspension crystallization, solid-liquid separation, and vacuum dephenolization and bisphenol A separated by static crystallization; Preferably, the residual liquid 1R after the first-stage falling film crystallization separation is sent to a static crystallizer to recover bisphenol A, and heat transfer oil is introduced into the box body of the static crystallizer for cooling, and bisphenol A is crystallized on the cooling surface of the box body inside the static crystallizer, and the residual liquid containing the remaining bisphenol A and other impurities is left in the static crystallizer. After the amount of the residual liquid reaches a set value, the cooling crystallization process is stopped, and the residual liquid left in the static crystallizer is emptied and incorporated into the suspended crystallization feed for recovery treatment; Heat transfer oil is introduced into the box body of the static crystallizer for heating, bisphenol A crystallized on the outer surface of the box body in the static crystallizer is heated and melted, and the molten bisphenol A is fed into the primary feed tank.

4. The crystallization method according to claim 1, characterized in that In the first-stage falling film crystallization process, the starting temperature of cooling is 140-143°C, the cooling rate is -0.28-0.32°C / min, and the temperature at the end of crystallization is 125-128°C; And / or, in the secondary falling film crystallization process, the starting temperature of cooling is 142-145°C, the cooling rate is -0.32~-0.35°C / min, and the temperature at the end of crystallization is 128-132°C.

5. The crystallization method according to claim 1, characterized in that The residual liquid 2R after the secondary falling film crystallization separation is discharged into the primary feed tank; the residual liquid 3R after the tertiary falling film crystallization separation is discharged into the secondary feed tank.

6. The crystallization method according to claim 1, characterized in that The time for the first falling film crystallization is 130-150 min; the time for the second falling film crystallization is 120-140 min.

7. A method for producing bisphenol A, characterized in that: The specific steps include: Phenol and acetone react in the SEC200 unit to synthesize bisphenol A, which is then vacuum dehydrated and sent to the SEC700 unit to recover phenol and acetone, and the process wastewater is discharged; The mixed solution containing phenol and bisphenol A solution after vacuum dehydration in the SEC200 unit is sent to the SEC230 unit for suspension crystallization and filtration; the filter cake obtained by filtration is heated and melted and then sent to the SEC300 unit for vacuum dephenolization, and the dephenolized solution is then sent to the SEC400 unit for falling film crystallization, separation and purification; the falling film crystallization adopts the crystallization method described in any one of claims 1 to 6; preferably, the solution is sent to the SEC300 unit for vacuum dephenolization, and the dephenolized solution includes the following components in weight percentage: 0.4-1.2% of phenol, 97-99% of bisphenol A, and 0.8-2.5% of total impurities, wherein the total impurities include 2.4-BPA; preferably, in the total impurities, the weight percentage of 2.4-BPA is 15-35%.

8. The production method according to claim 7, characterized in that: In the falling film crystallization, the liquid bisphenol A separated by the secondary falling film crystallization is stripped by a stripping tower and then sent to an epoxy resin device for downstream epoxy resin production; the liquid bisphenol A separated by the tertiary falling film crystallization is stripped by a polycarbonate grade to prepare polycarbonate grade bisphenol A solid particles; Preferably, the output of epoxy resin and polycarbonate-grade bisphenol A is adjusted by switching the number of crystallizers in the first falling film crystallizer and the second falling film crystallizer.

9. The production method according to claim 7, characterized in that: A portion of the mother liquor after filtration in the SEC230 unit is returned to the SEC200 unit, and a portion is sent to the SEC280 unit for isomerization, dephenolization, and suspension crystallization recovery operations; the mother liquor after suspension crystallization separation in the SEC280 unit is sent to the SEC800 unit for catalytic decomposition of heavy components, and the phenol obtained after the catalytic decomposition and p-isopropenylphenol are subjected to a synthetic reaction recovery, and the undecomposed heavy components or substances are discharged from the polyphenol.

10. The production method according to claim 9, characterized in that: The filter cake from the SEC280 unit after isomerization, dephenolization and suspension crystallization separation is heated and melted and then returned to the SEC230 unit for suspension crystallization and vacuum filtration operations.

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