Method and system for producing taurine

Abstract

The invention provides a method and a system for producing taurine. The method comprises the following steps: providing a first solution containing sulfuric acid alkali metal salt, isethionic acid alkali metal salt and optional taurine alkali metal salt; mixing the first solution with ammonia to obtain a solid-liquid mixed second solution, and removing at least part of impurities in the second solution; carrying out ammonolysis reaction on the second solution subjected to impurity removal in the previous step to obtain a third solution containing taurine alkali metal salt; performing flash evaporation and evaporation treatment on the third solution to obtain a fourth solution; and acidizing the fourth solution, cooling and crystallizing after acidification, and filtering to obtain taurine and a taurine mother solution. The method can effectively remove impurities in the taurine production process, improves the quality, yield and production efficiency of the taurine product, reduces the cost, and is suitable for industrial popularization and application.

Description

Technical Field

[0001] The present invention relates to the field of chemical industry. In particular, the present invention relates to a method and system for producing taurine. Background Art

[0002] Taurine is an important food additive, widely used in functional beverages, food, feed, infant formula and other products. The global consumption is about 70,000 tons per year, and more than 90% of the world's taurine is produced in China. Taurine is mainly prepared by chemical methods in industry. The chemical preparation process of taurine is mainly divided into ethylene oxide method and ethanolamine method. Due to the low production efficiency of ethanolamine method, it is gradually being eliminated.

[0003] The process of preparing taurine by ethylene oxide method is mainly divided into the following steps:

[0004] (1) Preparation of alkali metal isethionate

[0005] Ethylene oxide and alkali metal sulfite solution undergo a synthesis reaction under the action of an alkaline catalyst to obtain a solution whose main component is alkali metal hydroxyethyl sulfonate, commonly known as hydroxylation solution.

[0006] (2) Preparation of taurine alkali metal salt

[0007] The hydroxylated liquid and excess ammonia undergo an ammonolysis reaction under high temperature and high pressure in an alkaline environment to obtain a solution whose main component is taurine alkali metal salt. The excess ammonia is converted into gaseous ammonia or ammonia water or a mixture of gaseous ammonia and ammonia water by flash evaporation and then reused.

[0008] (3) Preparation of taurine

[0009] The solution containing the taurine alkali metal salt is acidified to obtain a solution whose main component is taurine.

[0010] (4) Purification of taurine

[0011] The taurine solution is cooled and crystallized, and after solid-liquid separation, a crude taurine product and a taurine mother liquor are obtained. The taurine mother liquor is heated, desalted, cooled, crystallized, and taurine is separated to obtain a final mother liquor.

[0012] A large amount of impurities are easily generated in the process of preparing alkali metal salt of isethionic acid intermediate and taurine by ethylene oxide method. If the impurities are not effectively separated during the reaction, the production efficiency and product quality of taurine will be seriously affected. Therefore, how to effectively remove the impurities in the process of preparing alkali metal salt of isethionic acid intermediate and the impurities generated in the process of preparing taurine from alkali metal salt of isethionic acid has become a problem to be solved urgently. Summary of the invention

[0013] The present invention aims to solve at least one of the technical problems existing in the prior art to a certain extent. To this end, the present invention provides a method and system for producing taurine from a high-quality alkali metal isethionate intermediate, thereby effectively removing impurities in the preparation process of alkali metal isethionate, thereby overall controlling impurities in the preparation process of taurine, improving the quality, yield and production efficiency of taurine products, reducing costs, and being suitable for industrial promotion and application.

[0014] It should be noted that the present invention is completed based on the following findings of the inventors:

[0015] In the step (1) of the process for preparing taurine by the ethylene oxide method described in the background art, the byproducts of preparing alkali metal isethionate mainly include ethylene glycol and polyethylene glycol, as well as unknown colored impurities. In the process of preparing alkali metal isethionate, in order to fully react the high-value ethylene oxide, a slightly excessive amount of alkali metal acid sulfite is often added in the first step of the synthesis reaction in the industry. The excessive alkali metal acid sulfite can be oxidized into alkali metal sulfate during the reaction. Ethylene glycol, unknown colored impurities and alkali metal sulfate can seriously affect the quality of alkali metal isethionate.

[0016] In industrial production, since step (1) and step (2) are continuous, during the process of preparing taurine alkali metal salt in step (2), the impurities in step (1) will continue to react with the newly added raw materials in step (2), so the newly generated by-products in step (2) mainly include ethanolamine, polyethanolamine and unreacted hydroxyethyl sulfonic acid alkali metal salt. The presence of these impurities will also seriously affect the yield of taurine alkali metal salt.

[0017] On the other hand, since step (2) is a high-temperature and high-pressure reaction, the reaction is generally carried out in a high-pressure synthesis tower. The sodium sulfate impurity produced in step (1) will aggregate into blocks in the high-pressure synthesis tower, affecting the heat transfer of the synthesis tower materials, reducing the ammonolysis yield, and shortening the service life of the synthesis tower.

[0018] In step (3), the taurine alkali metal salt can be acidified by sulfuric acid acidification, electrolytic acidification, ion exchange resin acidification, etc. If sulfuric acid is used for acidification, a large amount of alkali metal sulfate by-product will be produced. If other methods are used for acidification, a small amount of alkali metal sulfate by-product will also be produced.

[0019] In industrial production, since reaction steps (1) to (3) are all continuous reactions, impurities such as ethylene glycol, polyethylene glycol, unknown colored impurities, ethanolamine, polyethanolamine, alkali metal sulfate, etc. are all accumulated in the mother liquor. After the taurine mother liquor is heated and crystallized to separate and remove most of the alkali metal sulfate, and cooled and crystallized to separate most of the taurine, the last mother liquor still contains residual taurine or taurine alkali metal salt, hydroxyethyl sulfonic acid alkali metal salt, alkali metal sulfate, ethylene glycol, ethanolamine, colored impurities, etc.

[0020] "Shandong Chemical Industry Trade" Issue 8, August 2013, page 120, "Process Design of Taurine Ammonolysis Step" (author: Liu Fuming) describes in detail the process of taurine reaction, as well as other organic impurities such as ethylene glycol and polyethylene glycol present in the reaction. It also analyzes the effect of sodium hydroxyethyl sulfonate, sodium ditaurate, etc. in the taurine mother liquor on improving the overall taurine yield when used in the ammonolysis step.

[0021] Sodium isethionate, sodium ditaurate, etc. in the taurine mother liquor can be used in the aminolysis to improve the overall taurine yield. The higher the amount of mother liquor used in the reaction system, the higher the product yield. However, the amount of mother liquor used in the actual production process cannot be increased indefinitely. As the number of times the mother liquor is reused increases, a large amount of by-products accumulate in the reaction system, reaching a certain threshold, which will seriously affect the quality of the taurine product. In order to improve the quality of isethionate alkali metal salts, the prior art CN114436904A discloses a method for preparing isethionate alkali metal salts by ethylene oxide method, comprising the following steps: (1) hydrogenating and / or passivating the interface solvent; (2) reacting sodium bisulfite solution with ethylene oxide through the treated interface solvent to obtain sodium isethionate; (3) using nitrogen to blow off excess ethylene oxide after the reaction, and centrifuging the interface solvent and the reaction solution and then recycling. This method avoids the miscibility of ethylene oxide and sodium bisulfite solution, reduces the generation of impurities such as ethylene glycol, and greatly improves the product quality of sodium hydroxyethyl sulfonate. However, in this process, on the one hand, a new interface solvent is introduced, which is easy to generate new impurities in the system. On the other hand, in order to improve the yield of alkali metal salt of hydroxyethyl sulfonate, this method uses excessive ethylene oxide. Since ethylene oxide is toxic, it is easy to cause safety problems during the nitrogen purging process.

[0022] The prior art US10131621B uses an organic solvent extraction method to remove impurities such as ethylene glycol and ethanolamine generated during the taurine reaction. This method not only wastes solvents but also cannot be applied to industrial production. The prior art CN111039832B uses an anion resin to remove impurities such as ethylene glycol and ethanolamine generated during the taurine reaction. During the industrial production process, due to the large amount of materials, a large amount of investment is required to establish an ion exchange resin column. Therefore, this method greatly increases the production cost of alkali metal isethionate and taurine.

[0023] In view of this, the inventors of the present invention have designed a method and system for producing taurine from a high-quality alkali metal salt of isethionate intermediate. Specifically, before the ammonolysis reaction, ammonia (preferably, the sulfate is derived from the final mother liquor obtained and recovered from the reaction of ethylene oxide with an alkali metal salt of sulfite) is introduced into a solution containing an alkali metal salt of sulfate and an alkali metal salt of isethionate, and the solution is supersaturated to allow the salt to crystallize. During the precipitation and sedimentation process, the salt can encapsulate some impurities such as ethylene glycol, polyethylene glycol, and colored impurities. The impurities are then removed by filtering or standing to obtain a high-quality solution of the alkali metal salt of isethionate, which is conducive to the occurrence of the ammonolysis reaction. Moreover, the ammonia removed by the ammonolysis reaction, flash treatment, and evaporation treatment can be recycled for impurity removal of the solution containing the alkali metal salt of sulfate and the alkali metal salt of isethionate, thereby achieving a balance of ammonia as a whole, reducing the input amount of ammonia, reducing production costs, and improving production efficiency.

[0024] Furthermore, by introducing ammonia into the final taurine mother liquor, the solution is supersaturated to cause salt crystals to precipitate, and the main impurities in the final taurine mother liquor are alkali metal sulfates, which can carry away polyethylene glycol, polyethanolamine, colored impurities, etc. during the precipitation and sedimentation process. The final mother liquor after impurity removal can be reused in taurine production to improve material utilization.

[0025] In addition, in the process of taurine cyclic production, the two ammonia impurity removals before and after are coordinated with each other, which can not only improve the quality of alkali metal isethionate, but also improve the quality of the mother liquor used. After the cyclic production is realized, the new ammonia entering the whole system comes from the mother liquor after ammonia impurity removal, and the excess ammonia in the ammonolysis process is used in the ammonia impurity removal before ammonialysis, so the ammonia balance of the whole system can be achieved.

[0026] To this end, in one aspect of the present invention, a method for producing taurine is provided. According to an embodiment of the present invention, the method comprises: (1) providing a first solution containing an alkali metal sulfate salt, an alkali metal isethionate salt and an optional alkali metal taurine salt; (2) mixing the first solution with ammonia to obtain a second solution of a solid-liquid mixture, and removing at least part of the impurities in the second solution; (3) subjecting the second solution after the impurity removal step to an ammonolysis reaction to obtain a third solution containing an alkali metal taurine salt; (4) subjecting the third solution to a flash and evaporation treatment to obtain a fourth solution; (5) subjecting the fourth solution to an acidification treatment, cooling and crystallizing after the acidification is completed, and filtering to obtain taurine and a taurine mother liquor.

[0027] In the method according to the embodiment of the present invention, before the ammonolysis reaction is carried out, ammonia is introduced into the solution containing the alkali metal sulfate and the alkali metal isethionate, and the solution is supersaturated to allow the salt to crystallize out. The upper layer liquid is filtered or collected after standing to remove impurities such as the alkali metal sulfate, which is conducive to the occurrence of the ammonolysis reaction, improves the production efficiency, and is suitable for industrial promotion and application.

[0028] According to an embodiment of the present invention, the above method for producing taurine may also have the following additional technical features:

[0029] According to an embodiment of the present invention, the ammonia content in the second solution is 0.21-0.28 g / mL.

[0030] According to an embodiment of the present invention, the system temperature during the mixing process in step (2) is 40-60°C.

[0031] According to an embodiment of the present invention, in step (2), removing at least part of the impurities in the second solution includes: performing solid-liquid separation on at least part of the second solution and collecting the filtrate; and / or allowing at least part of the second solution to stand, forming a precipitate at the bottom of the solution, and collecting the upper liquid.

[0032] According to an embodiment of the present invention, in step (3), the third solution is heated to remove excess ammonia, and the excess ammonia is collected for performing the operation of step (2) with the first solution.

[0033] According to an embodiment of the present invention, in step (4), the ammonia removed by the flash treatment and evaporation is collected and used to perform the operation of step (2) with the first solution.

[0034] According to an embodiment of the present invention, the method further comprises: (6) subjecting the taurine mother liquor to at least one temperature-raising desalination treatment and at least one temperature-lowering crystallization treatment to obtain a final taurine mother liquor; (7) mixing the final taurine mother liquor with ammonia to obtain a fifth solid-liquid mixed solution, and removing at least part of impurities in the fifth solution; (8) returning the fifth solution after impurity removal in the previous step to step (2) to perform the mixing operation.

[0035] According to an embodiment of the present invention, in step (7), removing at least part of the impurities in the fifth solution includes: performing solid-liquid separation on at least part of the fifth solution and collecting the filtrate; and / or allowing at least part of the fifth solution to stand, forming a precipitate at the bottom of the solution, and collecting the upper liquid.

[0036] According to an embodiment of the present invention, the ammonia content in the second solution is higher than the ammonia content in the fifth solution.

[0037] According to an embodiment of the present invention, the temperature fluctuation range of the system during the mixing process of step (2) is greater than the temperature fluctuation range of the system during the mixing process of step (7).

[0038] According to an embodiment of the present invention, the ammonia content in the fifth solution is 0.16-0.25 g / mL.

[0039] According to an embodiment of the present invention, the system temperature during the mixing process in step (7) is 45-55°C.

[0040] According to an embodiment of the present invention, the taurine concentration in the final taurine mother liquor is 0.15-0.25 g / mL, and the alkali metal sulfate content is 0.02-0.10 g / mL.

[0041] According to an embodiment of the present invention, the temperature of the final taurine mother liquor is 45-55°C.

[0042] In another aspect of the present invention, a system for producing taurine is provided. According to an embodiment of the present invention, the system comprises: a first mixing device, the first mixing device is used to mix a first solution containing an alkali metal sulfate salt, an alkali metal isethionate salt and an optional alkali metal taurine salt with ammonia to obtain a second solution mixed with solid and liquid; a first impurity removal device, the first impurity removal device is connected to the first mixing device, and is used to remove at least part of the impurities in the second solution; an ammonolysis reaction device, the ammonolysis reaction device is connected to the first impurity removal device, and is used to perform an ammonolysis reaction on the second solution after impurity removal to obtain a third solution containing an alkali metal taurine salt; a flash evaporation device, the flash evaporation device is connected to the first impurity removal device, and is used to perform an ammonolysis reaction on the second solution after impurity removal to obtain a third solution containing an alkali metal taurine salt; and a flash evaporation device. The ammonolysis reaction device is connected to the third solution for flash evaporation; the evaporation device is connected to the flash evaporation device, and is used to evaporate the product obtained by the flash evaporation to obtain the fourth solution; the acidification device is connected to the evaporation device, and is used to acidify the fourth solution; the first crystallization device is connected to the acidification device, and is used to cool and crystallize the acidification product; the first filtering device is connected to the first crystallization device, and is used to filter the liquid after cooling and crystallization to obtain taurine and taurine mother liquor. Therefore, the system according to the embodiment of the present invention can effectively remove impurities in the taurine production process, improve the quality, yield and production efficiency of taurine products, reduce costs, and is suitable for industrial promotion and application.

[0043] According to an embodiment of the present invention, the ammonolysis reaction device is connected to the first mixing device, and is used to use excess ammonia collected from the ammonolysis reaction to perform the mixing operation with the first solution.

[0044] According to an embodiment of the present invention, the flash device and the evaporation device are respectively connected to the first mixing device, and are used to use the ammonia recovered from the flash treatment and the evaporation treatment for the mixing operation with the first solution.

[0045] According to an embodiment of the present invention, the system further includes: a second crystallization device, which is connected to the first filtering device and is used to subject the taurine mother liquor to at least one temperature increase desalination treatment and at least one temperature decrease crystallization treatment to obtain a final taurine mother liquor; a second mixing device, which is used to mix the final taurine mother liquor with ammonia to obtain a fifth solution of a solid-liquid mixture; a second impurity removal device, which is respectively connected to the second mixing device and the first mixing device, and is used to remove at least part of the impurities in the fifth solution, and mix the fifth solution after impurity removal with the first mixed solution.

[0046] According to an embodiment of the present invention, the first impurity removal device includes a second filtering device.

[0047] According to an embodiment of the present invention, the second impurity removal device includes a third filtering device.

[0048] According to an embodiment of the present invention, the second mixing device comprises: a reaction unit, a containing chamber is formed in the reaction unit, a first port and a second port are arranged on the top of the containing chamber, the first port is used to introduce the last mother liquor of taurine into the containing chamber; a liquid ammonia coil is arranged outside the containing chamber, the liquid ammonia coil is connected to the second port, and the liquid ammonia can be introduced into the liquid ammonia coil and enter the containing chamber through the second port. When the liquid ammonia passes through the coil, the pressure is reduced, and most of it is vaporized. After absorbing the heat of the last mother liquor in the containing chamber, it is further vaporized completely, and at the same time, the temperature of the last mother liquor is absorbed to cool the last mother liquor.

[0049] According to an embodiment of the present invention, the second port is provided with a jet mixer for mixing the feed liquid in the containing chamber with liquid ammonia and spraying the mixture into the containing chamber.

[0050] According to an embodiment of the present invention, a circulation pump is provided in the reaction unit for pumping the liquid in the containing chamber into the jet mixer.

[0051] According to an embodiment of the present invention, centrifugal pumps are independently arranged between the first mixing device and the first impurity removing device and between the second mixing device and the second impurity removing device.

[0052] According to an embodiment of the present invention, a temperature detection component and an ammonia content detection component are independently provided in the first mixing device and the second mixing device; a first valve is provided between the second mixing device and the second impurity removal device, and a second valve is provided between the first mixing device and the first impurity removal device.

[0053] According to an embodiment of the present invention, the system further includes: a control component, which is respectively connected to the ammonia content detection component, the first valve, the second valve, the first impurity removal device and the second impurity removal device, and is used to control the opening and closing of the first valve and the second valve and the opening and closing of the first impurity removal device and the second impurity removal device based on the ammonia content in the slurry of the first mixing device and the second mixing device.

[0054] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0056] Figure 1 and Figure 2 A schematic flow chart of a method for producing taurine according to an embodiment of the present invention is shown respectively;

[0057] Figure 3 and Figure 4 Schematic diagrams of the system structure for producing taurine according to an embodiment of the present invention are respectively shown. DETAILED DESCRIPTION

[0058] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0059] The present invention provides a method and system for producing taurine from a high-quality alkali metal isethionate intermediate, which will be described in detail below.

[0060] Method for producing taurine from high-quality isethionate alkali metal salt intermediate

[0061] In one aspect of the present invention, the present invention provides a method for producing taurine from a high-quality alkali metal isethionate intermediate. Figure 1 and Figure 2 The method includes: S100 providing a first solution; S200 mixing the first solution with ammonia and filtering; S300 ammonolysis reaction; S400 flash evaporation and evaporation treatment; S500 acidification treatment, cooling crystallization and filtration. Each step will be described in detail below.

[0062] S100 provides the first solution

[0063] In this step, a first solution containing an alkali metal salt of sulfate and an alkali metal salt of isethionate and optionally an alkali metal salt of taurine is provided.

[0064] In this document, the term "optional" may or may not describe a feature. For example, the first solution may contain an alkali metal sulfate and an alkali metal isethionate, or may contain an alkali metal sulfate, an alkali metal isethionate, and an alkali metal taurine. The present invention does not strictly limit the source of the first solution, as long as it contains two or three of the above components. For example, the first solution may be obtained by reacting ethylene oxide with an alkali metal sulfite solution. The "first solution" is also called a "hydroxylated solution".

[0065] S200 first solution mixed with ammonia and impurity removal

[0066] In this step, the first solution is mixed with ammonia to obtain a second solution of a solid-liquid mixture, and at least part of the impurities in the second solution are removed. Before the ammonolysis reaction, the first solution is mixed with ammonia, the solution gradually reaches a saturated state, and alkali metal sulfate is precipitated. Impurities such as alkali metal sulfate can be removed by filtering or collecting the upper liquid after standing, thereby improving the purity and yield of the final product. In addition, the inventors have found that if liquid ammonia is directly added to the first solution for the ammonolysis reaction, there will be certain safety issues due to the high pressure. Therefore, if the ammonia in the first solution comes from ammonia water or ammonia gas or a mixture of ammonia water and ammonia gas recovered by the system, it will be safer.

[0067] In this article, the term "ammonia" mainly refers to liquid ammonia or ammonia gas, which can be flexibly selected according to actual conditions; the "second solution" is also called "adjusting solution".

[0068] According to an embodiment of the present invention, in step S200, removing at least part of the impurities in the second solution includes: performing solid-liquid separation on at least part of the second solution and collecting the filtrate; and / or allowing at least part of the second solution to stand, forming a precipitate at the bottom of the solution, and collecting the upper liquid.

[0069] In some embodiments, the entire second solution may be filtered; or part of the second solution may be left to stand, and the precipitated impurities may settle to the bottom of the solution. Collecting the upper solution may also achieve the purpose of separating the impurities, and the upper solution may be used for the aminolysis reaction.

[0070] According to an embodiment of the present invention, the ammonia content in the second solution is 0.21-0.28 g / mL; the system temperature during the mixing process of step (2) is 40-60°C. The solubility of alkali metal sulfate is closely related to the material temperature and the concentration of ammonia. Generally, below 45°C, the solubility of alkali metal sulfate increases with increasing temperature, and above 45°C, the solubility of alkali metal sulfate decreases with increasing temperature. On the other hand, the solubility of alkali metal sulfate decreases with increasing ammonia concentration, but with increasing temperature, the solubility of ammonia decreases again, so it is necessary to find a balance between temperature and ammonia concentration. Furthermore, the inventor creatively obtained better conditions after a large number of experiments. When ammonia is introduced into the first solution at 40-60°C in the reaction system until the ammonia content in the mixed solution is 0.21-0.28 g / mL, impurities such as alkali metal sulfate are precipitated in large quantities, and the impurities such as alkali metal sulfate are collected by filtration, so as to achieve a better purpose of impurity removal. In addition, it can avoid that too high ammonia content puts higher requirements on the ammonia solution equipment.

[0071] S300 Ammonolysis Reaction

[0072] In this step, the filtered second solution is subjected to an ammonolysis reaction to obtain a third solution containing an alkali metal salt of taurine. The impurity content of the alkali metal salt of sulfate in the second solution after impurity removal is low, which helps to better cause the ammonolysis reaction, while preventing a large amount of impurities from agglomerating into a mass in the ammonolysis treatment device, promoting heat transfer of materials, and extending the service life of the device.

[0073] According to an embodiment of the present invention, in step S300, after the ammonolysis reaction, the third solution is heated to remove excess ammonia. At this time, the ammonia separated from the solution can be collected and used for impurity removal of the first solution in step S200, thereby reducing the ammonia introduced into the first solution for impurity removal and reducing production costs.

[0074] S400 Flash and Evaporation Process

[0075] In this step, the third solution is flashed and evaporated to obtain a fourth solution, thereby achieving the purpose of concentration and ammonia removal. The ammonia removed by the flashing and evaporation can be used for impurity removal of the first solution in step S200, thereby reducing the ammonia introduced into the first solution for impurity removal and reducing production costs.

[0076] S500 acidification, cooling crystallization and filtration

[0077] In this step, the fourth solution is subjected to acidification treatment, and after the acidification is completed, the solution is cooled to crystallize, and filtered to obtain taurine and taurine mother liquor.

[0078] According to an embodiment of the present invention, the method for producing taurine further includes: S600 heating desalination treatment and cooling crystallization treatment; S700 mixing and filtering the last taurine mother liquor and ammonia; S800 performing the mixing operation of step S200 on the filtered fifth solution.

[0079] S600 heating desalination treatment and cooling crystallization treatment

[0080] In this step, the taurine mother liquor is subjected to at least one temperature-raising desalination treatment and at least one temperature-lowering crystallization treatment to obtain a final taurine mother liquor.

[0081] S700 taurine final mother liquor and ammonia mixed and filtered

[0082] In this step, the final taurine mother liquor is mixed with ammonia to obtain a fifth solution of solid-liquid mixture, and at least part of the impurities in the fifth solution are removed. The main impurities in the final taurine mother liquor are alkali metal sulfates. By introducing ammonia into the final taurine mother liquor, the solution is supersaturated to allow the salt to crystallize out. The alkali metal sulfate can carry away impurities such as polyethylene glycol and polyethanolamine during the sedimentation process, thereby removing the impurities.

[0083] According to an embodiment of the present invention, in step S700, removing at least part of the impurities in the fifth solution includes: performing solid-liquid separation on at least part of the fifth solution and collecting the filtrate; and / or allowing at least part of the fifth solution to stand, forming a precipitate at the bottom of the solution, and collecting the upper liquid.

[0084] In some embodiments, the entire fifth solution may be filtered; or part of the fifth solution may be left to stand, and the precipitated impurities may settle to the bottom of the solution, and collecting the upper solution may also achieve the purpose of separating the impurities. The upper solution is returned to step S200 for mixing operation, and can be used for aminolysis reaction.

[0085] According to an embodiment of the present invention, the ammonia content in the second solution is higher than the ammonia content in the fifth solution, and the temperature fluctuation range of the system during the mixing process of step S200 is greater than the temperature fluctuation range of the system during the mixing process of step S700. Therefore, not only the ammonia demand in the subsequent ammonolysis process is met, but also impurities can be removed to the maximum extent. In addition, after the circular production is realized, almost all the new ammonia in the entire production system comes from the fifth solution after filtration, and it is necessary to achieve the balance of ammonia in the entire system through the ammonia introduced into the fifth solution. Since in step S700, liquid ammonia is generally introduced, a large amount of heat will be released during the mixing process of liquid ammonia and water, so it is necessary to control the temperature during the mixing process to improve the overall impurity removal effect.

[0086] It should be noted that "system temperature fluctuation range" means that the system temperature takes values ​​between the maximum and minimum values, and "large system temperature fluctuation range" means that the difference between the maximum and minimum values ​​is large. For example, "system temperature is 40-60°C" indicates that the system temperature fluctuation range is from 40°C to 60°C, and the difference between the maximum and minimum values ​​is 20°C; "system temperature is 45°C to 55°C" indicates that the system temperature fluctuation range is from 45°C to 55°C, and the difference between the maximum and minimum values ​​is 10°C. Therefore, it is believed that the fluctuation range of "system temperature is 40-60°C" is greater than that of "system temperature is 45°C to 55°C".

[0087] According to an embodiment of the present invention, the ammonia content in the fifth solution is 0.16-0.25 g / mL; and the system temperature during the mixing process of step S700 is 45-55°C.

[0088] The solubility of alkali metal sulfate is closely related to the material temperature and the concentration of ammonia. Generally, below 45°C, the solubility of alkali metal sulfate increases with the increase of temperature, and above 45°C, the solubility of alkali metal sulfate decreases with the increase of temperature. On the other hand, the solubility of alkali metal sulfate decreases with the increase of ammonia concentration, but with the increase of temperature, the solubility of ammonia decreases again, so it is necessary to find a balance between temperature and ammonia concentration. Furthermore, the inventor creatively obtained the best conditions after a large number of experiments. When ammonia is introduced into the last mother liquor of taurine at 45 to 55°C in the reaction system until the ammonia content in the mixed solution is 0.16 to 0.25 g / mL, alkali metal sulfate precipitates in large quantities, and alkali metal sulfate and impurities such as polyethylene glycol and polyethanolamine carried by filtration are collected, so as to achieve the purpose of better impurity removal. In addition, the newly introduced ammonia of the entire production system almost all comes from the fifth solution after filtration, and the fifth solution contains the above-mentioned content of ammonia, which can achieve the balance of ammonia in the entire system. In step S700, liquid ammonia is generally introduced, and a large amount of heat is released during the mixing process of liquid ammonia and water. Therefore, controlling the temperature of the system in the above step S700 can improve the overall impurity removal effect.

[0089] According to an embodiment of the present invention, the taurine concentration in the final taurine mother liquor is 0.15-0.25 g / mL, the alkali metal sulfate content is 0.02-0.10 g / mL, and the temperature of the final taurine mother liquor is 45-55°C.

[0090] According to an embodiment of the present invention, the ammonia used in step S700 is liquid ammonia. Since the temperature of liquid ammonia is relatively low, it is passed into the taurine final mother liquor reaction device through the coil and vaporizes to absorb heat, so it can exchange heat with the high-temperature material in the device, thereby reducing the use of cooling water and reducing costs.

[0091] S800 returns the filtered fifth solution to step S200 for mixing operation

[0092] In this step, the filtered fifth solution is returned to step S200 for a mixing operation.

[0093] System for producing taurine from high quality alkali metal isethionate intermediates

[0094] In another aspect of the present invention, a system for producing taurine from a high-quality alkali metal isethionate intermediate is provided. Figure 3 and Figure 4 The system includes: a first mixing device 100, a first impurity removal device 200, an ammonolysis reaction device 300, a flash device 400, an evaporation device 500, an acidification device 600, a first crystallization device 700, and a first filtering device 800. Each device will be described in detail below.

[0095] According to an embodiment of the present invention, the first mixing device 100 is used to mix a first solution containing an alkali metal sulfate salt, an alkali metal isethionate salt, and an optional alkali metal taurine salt with ammonia to obtain a second solution of a solid-liquid mixture. Before the ammonolysis reaction, the first solution and ammonia are mixed, and when the mixed solution reaches a supersaturated state, salt crystals are precipitated. Specifically, the last mother liquor after impurity removal first enters the mother liquor impurity removal storage tank A, and is injected into the first mixing device 100 when needed.

[0096] According to an embodiment of the present invention, the first impurity removal device 200 is connected to the first mixing device 100 and is used to remove at least part of the impurities in the second solution.

[0097] According to an embodiment of the present invention, the ammonolysis reaction device 300 is connected to the first impurity removal device 200, and is used to perform an ammonolysis reaction on the filtered second solution to obtain a third solution containing taurine alkali metal salt.

[0098] According to an embodiment of the present invention, the ammonolysis reaction device 300 is connected to the first mixing device 100, and is used to mix the excess ammonia collected by the ammonolysis reaction with the first solution.

[0099] According to an embodiment of the present invention, the flash evaporation device 400 is connected to the ammonolysis reaction device 300 and is used to flash the third solution.

[0100] According to an embodiment of the present invention, the evaporation device 500 is connected to the flash evaporation device 400 and is used to evaporate the product obtained by the flash evaporation treatment.

[0101] According to an embodiment of the present invention, the flash device 400 and the evaporation device 500 are respectively connected to the first mixing device 100, and are used to mix the ammonia recovered from the flash treatment and the evaporation treatment with the first solution.

[0102] According to an embodiment of the present invention, the acidification device 600 is connected to the evaporation device 500 and is used to perform acidification treatment on the fourth solution.

[0103] According to an embodiment of the present invention, the first crystallization device 700 is connected to the acidification device 600 and is used to cool and crystallize the acidification product.

[0104] According to an embodiment of the present invention, the first filtering device 800 is connected to the first crystallization device 700, and is used to filter the liquid after the cooling and crystallization to obtain taurine and taurine mother liquor.

[0105] According to an embodiment of the present invention, the system further comprises: a second crystallization device 10 , a second mixing device 20 and a second impurity removal device 30 .

[0106] According to an embodiment of the present invention, the second crystallization device 10 is connected to the first filtering device 800, and is used to subject the taurine mother liquor to at least one temperature increase desalination treatment and at least one temperature decrease crystallization treatment to obtain a final taurine mother liquor.

[0107] According to an embodiment of the present invention, the second mixing device 20 is used to mix the final taurine mother liquor with ammonia to obtain a fifth solid-liquid mixed solution. By introducing ammonia into the final taurine mother liquor, the solution is supersaturated to allow salt crystals to precipitate.

[0108] According to an embodiment of the present invention, the second impurity removal device 30 is connected to the second mixing device 20 and the first mixing device 100, respectively, and is used to remove at least part of the impurities in the fifth solution, and the fifth solution after impurity removal is mixed with the first mixed solution. The main impurities in the final mother liquor of taurine are alkali metal sulfates, and the crystallized salts can be removed by filtering. The alkali metal sulfates can take away impurities such as polyethylene glycol and polyethanolamine during the sedimentation process, and the impurities are removed by filtering.

[0109] According to an embodiment of the present invention, the first impurity removal device 200 includes a second filter device, and the second impurity removal device 30 includes a third filter device. Impurities are removed by filtering, which is convenient for operation. The first filter device, the second filter device and the third filter device of the present invention can be the same device, or can be partially the same or completely different devices, which can be flexibly selected according to actual conditions.

[0110] According to an embodiment of the present invention, the second mixing device 20 includes: a reaction unit, in which a containing chamber is formed, a first port 21 and a second port 22 are arranged on the top of the containing chamber, and the first port 21 is used to introduce the final taurine mother liquor into the containing chamber; a liquid ammonia coil 23 is arranged outside the containing chamber, and the liquid ammonia coil 23 is connected to the second port 22, and liquid ammonia can be introduced into the liquid ammonia coil 23 and enter the containing chamber through the second port 22.

[0111] When liquid ammonia (pressure is 0.1-1Mpa) enters the liquid ammonia coil in the mother liquor impurity removal device, the pressure is reduced and most of it is vaporized. After absorbing the heat of the last mother liquor in the containing chamber, it is further vaporized completely. At the same time, it absorbs the temperature of the last mother liquor to cool the last mother liquor. After the gas ammonia after cooling the material is mixed with the material, the temperature of the material rises due to the heat release of the reaction between water and ammonia. The high-temperature material entering the tank exchanges heat with the liquid ammonia in the liquid ammonia coil to cool it down. If the material temperature exceeds 55°C, cooling water needs to be introduced into the cooling water coil in the second mixing device to cool it down, and the temperature is controlled at 45-55°C.

[0112] According to an embodiment of the present invention, the second port 22 is provided with a jet mixer for mixing the liquid material in the containing chamber with liquid ammonia and spraying the mixture into the containing chamber, thereby helping to circulate the material to participate in the reaction and improve the impurity removal efficiency.

[0113] According to an embodiment of the present invention, a circulation pump is provided in the reaction unit for pumping the liquid in the containing chamber into the jet mixer.

[0114] According to an embodiment of the present invention, centrifugal pumps are independently provided between the second mixing device 20 and the second impurity removal device 30 and between the first mixing device 100 and the first impurity removal device 200, respectively, so as to facilitate solid-liquid separation.

[0115] According to the embodiment of the present invention, the first mixing device 100 and the second mixing device 20 are each independently provided with a temperature detection component and an ammonia content detection component. This helps to detect the temperature and ammonia content, and when the system reaches a specific temperature and ammonia content, the solid and liquid are separated to achieve the purpose of impurity removal.

[0116] According to an embodiment of the present invention, a first valve is provided between the second mixing device 20 and the second impurity removal device 30. Thus, when ammonia is passed through the last taurine mother liquor in the second mixing device for reaction, the first valve is closed, and when a predetermined ammonia concentration is reached, the first valve is controlled to open, and the material enters the second impurity removal device for filtration to remove impurities.

[0117] According to an embodiment of the present invention, a second valve is provided between the first mixing device 100 and the first impurity removal device 200. Thus, when the first solution reacts with ammonia in the first mixing device, the second valve is closed, and when a predetermined ammonia concentration is reached, the second valve is controlled to open, and the material enters the first impurity removal device for filtration to remove impurities.

[0118] According to an embodiment of the present invention, the system further includes: a control component, which is respectively connected to the ammonia content detection component, the first valve, the second valve, the first impurity removal device and the second impurity removal device, and is used to control the opening and closing of the first valve and the second valve and the opening and closing of the first impurity removal device and the second impurity removal device based on the ammonia content in the slurry of the first mixing device and the second mixing device.

[0119] The system for producing taurine according to an embodiment of the present invention is used to implement the method for producing taurine described above. The features and advantages described for the method for producing taurine are also applicable to the system for producing taurine, and will not be described in detail here.

[0120] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0121] Example 1: Preparation of taurine by ethylene oxide method

[0122] Step 1: Prepare the Hydroxylation Solution

[0123] In a 5L reactor, 532mL of sodium bisulfite solution (0.43g / mL) and 8g of sodium hydroxide were added, and after stirring evenly, 88g of ethylene oxide was introduced, and the mixture was reacted at 70°C for 2 hours. After the reaction was completed, the mixture was cooled to obtain a hydroxylated liquid containing sodium hydroxyethyl sulfonate.

[0124] Step 2: Prepare the adjustment solution

[0125] 2 g of sodium hydroxide was added to the hydroxylation solution, and 976 g of aqueous ammonia (32% wt) was introduced to obtain about 1486 mL of an adjustment solution. During the whole process, the system temperature was maintained at 40-60° C., and the ammonia content in the adjustment solution was about 0.21 g / mL.

[0126] Step 3: Divide the adjusted solution into two equal parts, filter and remove impurities in one part, and do not filter and remove impurities in the other part

[0127] Stir the adjusted solution evenly and divide it into two equal portions, each about 743 mL, numbered A and B respectively.

[0128] A was filtered to obtain about 725 mL of filtered adjustment solution A1, and samples were taken to detect the transmittance (430 nm), sodium sulfate content, and ethylene glycol content of the A1 solution.

[0129] Sampling was performed to detect the transmittance (430 nm), sodium sulfate content, and ethylene glycol content of solution B.

[0130] Step 4: Prepare taurine with two different adjustment solutions

[0131] Add the remaining A1 solution to a 2L reactor, react at 250°C for 2 hours, cool after the reaction, transfer the solution to a glass, heat it in an open air, remove excess ammonia, until there is no ammonia smell, acidify the sodium taurine solution obtained by the reaction system with sulfuric acid until the pH is 7-8, remove excess water by rotary evaporation, cool and crystallize in an ice-water bath, filter out taurine, and obtain taurine mother liquor. Heat the taurine mother liquor to 110°C, evaporate to remove excess water until sodium sulfate precipitates, filter to remove sodium sulfate while hot, and cool the obtained mother liquor to crystallize, filter to obtain taurine, repeat the steps of heating to remove sodium sulfate and cooling to crystallize to obtain taurine twice, separate the crude taurine, combine and collect the taurine obtained by multiple separations, weigh after drying, and calculate the yield.

[0132] Add the remaining B solution to a 2L reactor, react at 250°C for 2 hours, cool after the reaction, transfer the solution to a glass, heat in an open air, remove excess ammonia, until there is no ammonia smell, acidify the sodium taurine solution obtained by the reaction system with sulfuric acid until the pH is 7-8, remove excess water by rotary evaporation, cool and crystallize in an ice-water bath, filter out taurine, and obtain taurine mother liquor. Heat the taurine mother liquor to 110°C, evaporate to remove excess water until sodium sulfate precipitates, filter to remove sodium sulfate while hot, and cool the obtained mother liquor to crystallize, filter to obtain taurine, repeat the steps of heating to remove sodium sulfate and cooling to crystallize to obtain taurine twice, separate the crude taurine, combine and collect the taurine obtained by multiple separations, weigh after drying, and calculate the yield.

[0133] The analysis results of the adjustment solutions A1 and B and the yield of taurine (calculated as ethylene oxide) after the aminolysis reaction of the adjustment solutions A1 and B are shown in the following table:

[0134] Table 1 Analysis results of adjustment solutions A1 and B and corresponding taurine yields obtained

[0135]

[0136] Judging from the reaction results, removing impurities from the adjustment liquid can significantly reduce the content of ethylene glycol and sodium sulfate in the adjustment liquid, and can remove some colored impurities, thereby increasing the yield of sodium taurine obtained by aminolysis.

[0137] Example 2: Circular preparation of taurine - impurity removal of adjustment solution

[0138] (1) The feed amount was halved, and steps 1 and 2 in Example 1 were repeated. The adjusted solution obtained in step 2 was filtered to obtain about 725 mL of the adjusted solution after impurities were removed.

[0139] (2) The adjusted solution after impurity removal is subjected to ammonolysis and ammonia removal reaction after ammonolysis according to the steps in step 4 of Example 1, and the sodium taurine solution finally obtained from the reaction system is acidified with sulfuric acid until the pH is 7-8, and after removing excess water by rotary evaporation, it is cooled and crystallized in an ice-water bath, and taurine is filtered out to obtain a taurine mother liquor. The taurine mother liquor is heated to 110° C., and excess water is evaporated to remove excess water until sodium sulfate is precipitated, and sodium sulfate is removed by hot filtration. The obtained mother liquor is then cooled and crystallized, and taurine is filtered out to obtain taurine. The steps of heating and removing sodium sulfate and cooling and crystallizing to obtain taurine are repeated twice, and the taurine obtained by multiple separations is combined and collected, dried and weighed, and the yield is calculated. The final mother liquor is decolorized with activated carbon and the content of sodium sulfate and ethylene glycol therein is detected.

[0140] (3) The last mother liquor after decolorization is recycled to (1) and used together with the fresh hydroxylation liquid to prepare the adjustment liquid after the mother liquor is applied. The impurities are first removed and the transmittance is tested. Then, the ammonolysis reaction is carried out. The sodium taurine solution obtained by the reaction system is acidified with sulfuric acid until the pH is 7-8. After the excess water is removed by rotary evaporation, the solution is cooled in an ice-water bath for crystallization, and taurine is filtered out to obtain a taurine mother liquor. The taurine mother liquor is heated to 110°C and the excess water is evaporated until sodium sulfate is precipitated. The sodium sulfate is removed by hot filtration. The mother liquor obtained is then cooled and crystallized, and taurine is filtered out. The steps of heating to remove sodium sulfate and cooling and crystallizing taurine are repeated twice to obtain the last mother liquor of taurine. The last mother liquor is decolorized by activated carbon and the contents of sodium sulfate, taurine and ethylene glycol therein are tested.

[0141] Table 2: The mass of the adjusted solution and the taurine yield data (calculated based on the molar amount of ethylene oxide) before applying the mother liquor in step (2)

[0142]

[0143] Table 3 The mass of the adjusted solution obtained by recycling the last mother liquor and the last mother liquor itself and the total yield of taurine (calculated as the molar amount of ethylene oxide)

[0144]

[0145]

[0146] Judging from the reaction results, if the adjusted liquid is only filtered to remove impurities, the yield will gradually decrease as the number of times the mother liquid is used increases.

[0147] Example 3: Circular preparation of taurine - impurity removal of adjustment solution and final mother liquor

[0148] (1) The feed amount was halved, and steps 1 and 2 in Example 1 were repeated. The adjusted solution obtained in step 2 was filtered to obtain about 725 mL of the adjusted solution after impurities were removed.

[0149] (2) The adjusted solution after impurity removal is subjected to ammonolysis and ammonia removal reaction after ammonolysis according to the steps in step 4 of Example 1, and the sodium taurine solution finally obtained from the reaction system is acidified with sulfuric acid until the pH is 7-8, and after removing excess water by rotary evaporation, it is cooled in an ice-water bath for crystallization, and taurine is filtered out to obtain a taurine mother liquor. The taurine mother liquor is heated to 110° C., and excess water is evaporated to remove until sodium sulfate is precipitated, and sodium sulfate is removed by hot filtration. The obtained mother liquor is then cooled and crystallized, and taurine is filtered out to obtain taurine. The steps of heating and removing sodium sulfate and cooling and crystallizing to obtain taurine are repeated twice, and the taurine obtained by multiple separations is combined and collected, and weighed after drying, and the yield is calculated to obtain a final taurine mother liquor, and the final mother liquor is decolorized with activated carbon. Liquid ammonia was added to the final mother liquor after decolorization to make the ammonia content in the final mother liquor 0.16 g / mL, and impurities were removed by filtration to obtain the final mother liquor after impurity removal. The contents of sodium sulfate, taurine and ethylene glycol in the final mother liquor after impurity removal were detected.

[0150] (3) The final mother liquor after impurity removal is recycled to (1) and used together with the fresh hydroxylation liquid to prepare the adjustment liquid after applying the mother liquor. After impurity removal, the transmittance is tested and then the aminolysis reaction is carried out. The sodium taurine solution obtained by the reaction system is acidified with sulfuric acid until the pH is 7-8. After removing excess water by rotary evaporation, the solution is cooled in an ice-water bath for crystallization and taurine is filtered out to obtain a taurine mother liquor. The taurine mother liquor is heated to 110° C., and excess water is evaporated off until sodium sulfate is precipitated. The sodium sulfate is removed by hot filtration, and the obtained mother liquor is cooled and crystallized, and taurine is obtained by filtration. The steps of heating to remove sodium sulfate and cooling and crystallizing taurine are repeated twice to obtain a final taurine mother liquor. The final mother liquor is decolorized by activated carbon, and liquid ammonia is added to the decolorized final mother liquor. The whole process is maintained at 45-55° C. When the ammonia content in the final mother liquor reaches 0.16 g / mL, impurities are removed by filtration to obtain a final mother liquor after impurities are removed, and the contents of sodium sulfate, taurine, and ethylene glycol in the final mother liquor after impurities are removed are detected.

[0151] Table 4: The mass of the adjusted solution and the taurine yield data (calculated based on the molar amount of ethylene oxide) before applying the mother solution in step (2)

[0152]

[0153] Table 5 The mass of the last mother liquor obtained by recycling the last mother liquor and the total yield of taurine (calculated as the molar amount of ethylene oxide)

[0154]

[0155] From the experimental results, on the one hand, the total yield of taurine can be effectively improved by passing ammonia through the mother liquor and removing impurities from the adjustment liquid, and the taurine yield can be kept at a relatively stable state as the number of cycles increases. On the other hand, the last mother liquor is applied to the adjustment liquid, and after passing ammonia, the impurities are removed again, which can effectively remove colored impurities.

[0156] Example 4: Circular preparation of taurine - final mother liquor impurity removal

[0157] (1) The feed amount is halved and steps 1 and 2 in Example 1 are repeated to obtain an adjusted solution.

[0158] (2) The adjusted solution was subjected to ammonolysis and ammonia removal reaction after ammonolysis according to the steps in step 4 of Example 1, and deionized water was added to the glass bottle until the total amount of the solution was 600 mL. The contents of ethylene glycol and sodium sulfate were detected.

[0159] The sodium taurine solution finally obtained from the reaction system is acidified with sulfuric acid until the pH is 7-8, and after the excess water is removed by rotary evaporation, the solution is cooled and crystallized in an ice-water bath, and taurine is filtered out to obtain a taurine mother liquor. The taurine mother liquor is heated to 110°C, and the excess water is removed by evaporation until sodium sulfate is precipitated, and the sodium sulfate is removed by hot filtration. The obtained mother liquor is then cooled and crystallized, and taurine is filtered out to obtain taurine. The steps of heating and removing sodium sulfate and cooling and crystallizing to obtain taurine are repeated twice, and the taurine obtained by multiple separations is combined and collected, and weighed after drying, and the yield is calculated to obtain the final taurine mother liquor, and the final mother liquor is decolorized by activated carbon. Liquid ammonia is added to the final mother liquor after decolorization, so that the ammonia content in the final mother liquor is 0.16g / mL, and impurities are removed by filtration to obtain the final mother liquor after impurities are removed, and the content of sodium sulfate, taurine, and ethylene glycol in the final mother liquor after impurities are detected.

[0160] (3) The final mother liquor after impurity removal is recycled to (1) and used together with the fresh hydroxylation liquid to prepare the adjustment liquid after applying the mother liquor. After impurity removal, the transmittance is tested and then the aminolysis reaction is carried out. The sodium taurine solution obtained by the reaction system is acidified with sulfuric acid until the pH is 7-8. After removing excess water by rotary evaporation, the solution is cooled in an ice-water bath for crystallization and taurine is filtered out to obtain a taurine mother liquor. The taurine mother liquor is heated to 110° C., and excess water is evaporated off until sodium sulfate is precipitated. The sodium sulfate is removed by hot filtration, and the obtained mother liquor is cooled and crystallized, and taurine is obtained by filtration. The steps of heating to remove sodium sulfate and cooling and crystallizing taurine are repeated twice to obtain a final taurine mother liquor. The final mother liquor is decolorized by activated carbon, and liquid ammonia is added to the decolorized final mother liquor. The whole process is maintained at 45-55° C. When the ammonia content in the final mother liquor reaches 0.16 g / mL, impurities are removed by filtration to obtain a final mother liquor after impurities are removed, and the contents of sodium sulfate, taurine, and ethylene glycol in the final mother liquor after impurities are removed are detected.

[0161] Table 6 The mass of the adjusted solution and the taurine yield data (calculated based on the molar amount of ethylene oxide) before applying the mother solution in step (2)

[0162]

[0163] Table 7 The mass of the adjusted solution obtained by recycling the last mother liquor and the last mother liquor itself and the total yield of taurine (calculated as the molar amount of ethylene oxide)

[0164]

[0165]

[0166] From the experimental results, if the adjustment liquid is not purified and only the final mother liquor is purified, the first-time yield of taurine is low. After the mother liquor is recycled, the total yield of taurine increases slowly at first, but then decreases slowly as the number of times increases.

[0167] Example 5: Effect of the content of ammonia in the adjustment liquid and the content of ammonia in the last mother liquor on the impurity composition in the continuous taurine removal system

[0168] Step 1: Prepare the Hydroxylation Solution

[0169] In a 5L reactor, 532mL of sodium bisulfite solution (0.43g / mL) and 8g of sodium hydroxide were added, and after stirring evenly, 88g of ethylene oxide was introduced, and the mixture was reacted at 70°C for 2 hours. After the reaction was completed, the mixture was cooled to obtain a hydroxylated liquid containing sodium hydroxyethyl sulfonate.

[0170] Step 2: Prepare the adjustment solution and remove impurities

[0171] Add 2 g of sodium hydroxide to the hydroxylation liquid, pass a mixture of ammonia water and ammonia gas, adjust the ammonia content in the hydroxylation liquid to obtain an adjusted liquid. During the whole process, maintain the system temperature at 40-60°C. Filter the adjusted liquid to remove insoluble impurities, and detect the contents of sodium sulfate and ethylene glycol in the adjusted liquid.

[0172] Step 3: Aminolysis

[0173] The adjusted solution after impurities removal is reacted at 250°C for 2 hours. After the reaction is completed, the excess ammonia in the system is recovered by distillation to obtain a sodium taurine solution. The recovered ammonia is a mixture of ammonia water and ammonia gas, which is reused in step 2.

[0174] Step 4: Neutralization

[0175] The sodium taurine solution is diluted with water until the content of sodium taurine in the solution is 30-40%, and sulfuric acid is added to neutralize until the pH is 7-8 to obtain a suspension containing taurine.

[0176] Step 5: Crystallization

[0177] The suspension containing taurine is cooled in an ice-water bath for crystallization, and the taurine is filtered out to obtain a taurine mother liquor.

[0178] Step 6: Removal of impurities from mother liquor

[0179] The taurine mother liquor is heated to 110°C, and the excess water is evaporated until sodium sulfate is precipitated. The sodium sulfate is removed by hot filtration, and the obtained mother liquor is cooled and crystallized, and taurine is obtained by filtration. The steps of heating and removing sodium sulfate and cooling and crystallizing to obtain taurine are repeated twice. The taurine obtained by multiple separations is combined and collected, and weighed after drying. The yield is calculated to obtain the final taurine mother liquor. The final mother liquor is decolorized by activated carbon, and liquid ammonia is added to the decolorized final mother liquor to adjust the ammonia concentration in the final mother liquor. The whole process is maintained at 45-55°C, and impurities are removed by filtration to obtain the final mother liquor after impurities are removed. The contents of sodium sulfate and ethylene glycol in the final mother liquor after impurities are detected. The yield of taurine (in terms of ethylene oxide) is calculated.

[0180] Step 7: Recycle the stock solution

[0181] The obtained mother liquor after impurity removal is returned to step 2 for aminolysis. In the circulation step, the concentration of ammonia during the impurity removal and mother liquor impurity removal is kept the same as the previous time.

[0182] Table 8 Step 6 First Reaction Results

[0183]

[0184] Table 9 Reaction results after recycling mother liquor

[0185]

[0186] From the results, it can be seen that when the concentration of ammonia in the adjustment solution is 0.21-0.28 g / mL and the concentration of ammonia in the mother liquor is 0.16-0.25 g / mL, the single yield of taurine or the yield after recovering the mother liquor can be maintained at a high level. On the other hand, although the yield of taurine can reach 88% when the concentration of ammonia in the adjustment solution reaches 30 g / 100 mL or more, the high concentration of ammonia increases the recovery cost on the one hand and requires higher requirements for equipment on the other hand. Therefore, the concentration of ammonia should not be too high.

[0187] Example 6: Effect of system temperature during the process of adjusting liquid impurity removal and final mother liquid impurity removal on the impurity composition in the continuous taurine removal preparation system

[0188] Step 1: Prepare the Hydroxylation Solution

[0189] In a 5L reactor, 532mL of sodium bisulfite solution (0.43g / mL) and 8g of sodium hydroxide were added, and after stirring evenly, 88g of ethylene oxide was introduced, and the mixture was reacted at 70°C for 2 hours. After the reaction was completed, the mixture was cooled to obtain a hydroxylated liquid containing sodium hydroxyethyl sulfonate.

[0190] Step 2: Prepare the adjustment solution and remove impurities

[0191] 2 g of sodium hydroxide was added to the hydroxylation liquid, and aqueous ammonia (32% wt) was introduced to adjust the ammonia content in the hydroxylation liquid to 0.21 g / mL to obtain an adjusted liquid. During the whole process, the temperature of the system was maintained within a certain range. The adjusted liquid was filtered to remove insoluble impurities, and the contents of sodium sulfate and ethylene glycol in the adjusted liquid were detected.

[0192] Step 3: Aminolysis

[0193] The adjusted solution after impurities removal is reacted at 250° C. for 2 hours. After the reaction is completed, the excess ammonia in the system is recovered by distillation to obtain a sodium taurine solution. The recovered ammonia is reused in step 2.

[0194] Step 4: Neutralization

[0195] The sodium taurine solution is diluted with water until the content of sodium taurine in the solution is 30-40%, and sulfuric acid is added to neutralize until the pH is 7-8 to obtain a suspension containing taurine.

[0196] Step 5: Crystallization

[0197] The suspension containing taurine is cooled in an ice-water bath for crystallization, and the taurine is filtered out to obtain a taurine mother liquor.

[0198] Step 6: Removal of impurities from mother liquor

[0199] The taurine mother liquor is heated to 110°C, and excess water is evaporated until sodium sulfate is precipitated. The sodium sulfate is removed by hot filtration, and the obtained mother liquor is cooled and crystallized, and taurine is obtained by filtration. The steps of heating to remove sodium sulfate and cooling and crystallizing to obtain taurine are repeated twice to obtain a final taurine mother liquor. The final mother liquor is decolorized by activated carbon, and liquid ammonia is added to the decolorized final mother liquor to adjust the ammonia concentration in the final mother liquor to 0.16 g / mL. The temperature is kept within a certain range during the whole process, and impurities are removed by filtration to obtain a final mother liquor after impurities removal.

[0200] Step 7: Recycle the stock solution

[0201] The obtained mother liquor after impurity removal is returned to step 2 for aminolysis. After the reaction is complete, the total yield of taurine (in terms of ethylene oxide) is calculated.

[0202] Table 10 Taurine yield under different impurity removal temperature conditions

[0203]

[0204] The solubility of alkali metal sulfate is closely related to the material temperature and the concentration of ammonia. Generally, below 45°C, the solubility of alkali metal sulfate increases with increasing temperature, and above 45°C, the solubility of alkali metal sulfate decreases with increasing temperature. On the other hand, the solubility of alkali metal sulfate decreases with increasing ammonia concentration, but as the temperature increases, the solubility of ammonia in the solution decreases. Therefore, if the temperature of the adjustment and impurity removal of the mother liquor is not well controlled, a higher yield cannot be obtained. When the temperature of the system during the adjustment liquid impurity removal process is 40-60°C and the temperature of the system during the last mother liquor impurity removal process is 45-55°C, the single yield of taurine or the yield after recovering the mother liquor can be maintained at a high level.

[0205] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0206] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for producing taurine, characterized in that: include: (1) providing a first solution containing an alkali metal sulfate salt and an alkali metal isethionate salt and optionally an alkali metal taurine salt; (2) mixing the first solution with ammonia to obtain a second solid-liquid mixed solution, and removing at least part of impurities in the second solution; (3) subjecting the second solution after impurities removal in the previous step to an ammonolysis reaction to obtain a third solution containing an alkali metal salt of taurine; (4) flashing and evaporating the third solution to obtain a fourth solution; (5) Acidifying the fourth solution, cooling and crystallizing the solution, and filtering the solution to obtain taurine and taurine mother liquor.

2. The method according to claim 1, characterized in that The ammonia content in the second solution is 0.21 to 0.28 g / mL; Optionally, the system temperature during the mixing process of step (2) is 40 to 60° C.; Optionally, in step (2), removing at least part of the impurities in the second solution comprises: performing solid-liquid separation on at least a portion of the second solution and collecting the filtrate; and / or allowing at least a portion of the second solution to stand to form a precipitate at the bottom of the solution, and collecting the upper layer of the solution; Optionally, in step (3), the third solution is heated to remove excess ammonia, and the excess ammonia is collected for use in the operation of step (2) with the first solution; Optionally, in step (4), the ammonia removed by the flash treatment and evaporation is collected and used to perform the operation of step (2) with the first solution.

3. The method according to claim 1 or 2, characterized in that: Further including: (6) subjecting the taurine mother liquor to at least one temperature-raising desalting treatment and at least one temperature-lowering crystallization treatment to obtain a final taurine mother liquor; (7) mixing the final taurine mother liquor with ammonia to obtain a fifth solid-liquid mixed solution, and removing at least part of the impurities in the fifth solution; (8) returning the fifth solution after impurity removal in the previous step to step (2) to perform the mixing operation; Optionally, in step (7), removing at least part of the impurities in the fifth solution comprises: performing solid-liquid separation on at least a portion of the fifth solution and collecting the filtrate; and / or At least a portion of the fifth solution is allowed to stand to form a precipitate at the bottom of the solution, and the upper layer of the solution is collected.

4. The method according to claim 3, characterized in that The ammonia content in the second solution is higher than the ammonia content in the fifth solution.

5. The method according to claim 3, characterized in that: The ammonia content in the fifth solution is 0.16-0.25 g / mL; The system temperature during the mixing process of step (7) is 45-55°C.

6. The method according to claim 3, characterized in that The taurine concentration in the final taurine mother liquor is 0.15-0.25 g / mL, and the alkali metal sulfate content is 0.02-0.10 g / mL; The temperature of the final taurine mother liquor is 45-55°C.

7. A system for producing taurine, characterized in that: include: a first mixing device, the first mixing device being used to mix a first solution containing an alkali metal sulfate salt, an alkali metal isethionate salt, and optionally an alkali metal taurine salt with ammonia to obtain a second solution mixed with solid and liquid; a first impurity removal device, the first impurity removal device being connected to the first mixing device and being used for removing at least part of impurities in the second solution; an ammonolysis reaction device, the ammonolysis reaction device being connected to the first impurity removal device and being used for performing an ammonolysis reaction on the second solution after impurity removal to obtain a third solution containing taurine alkali metal salt; A flash evaporation device, the flash evaporation device is connected to the ammonolysis reaction device and is used to flash the third solution; an evaporation device, the evaporation device being connected to the flash evaporation device and used for evaporating the product obtained by the flash evaporation treatment to obtain a fourth solution; an acidification device, the acidification device being connected to the evaporation device and being used for acidifying the fourth solution; A first crystallization device, which is connected to the acidification device and is used to cool and crystallize the acidification product; The first filtering device is connected to the first crystallization device and is used for filtering the liquid after the cooling and crystallization to obtain taurine and taurine mother liquor.

8. The system according to claim 7, characterized in that The ammonolysis reaction device is connected to the first mixing device and is used to use the excess ammonia collected by the ammonolysis reaction to perform the mixing operation with the first solution; The flash device and the evaporation device are respectively connected to the first mixing device, and are used to use the ammonia recovered from the flash treatment and the evaporation treatment to mix with the first solution; Optionally, the system further comprises: a second crystallization device, the second crystallization device is connected to the first filtering device, and is used to subject the taurine mother liquor to at least one temperature-raising desalting treatment and at least one temperature-lowering crystallization treatment to obtain a final taurine mother liquor; a second mixing device, the second mixing device being used to mix the final taurine mother liquor with ammonia to obtain a fifth solid-liquid mixed solution; The second impurity removal device is connected to the second mixing device and the first mixing device respectively, and is used to remove at least part of impurities in the fifth solution and mix the impurity-removed fifth solution with the first mixed solution.

9. The system according to claim 8, characterized in that The second mixing device comprises: A reaction unit, wherein a containing chamber is formed in the reaction unit, and a first port and a second port are provided on the top of the containing chamber, wherein the first port is used to introduce the final taurine mother liquor into the containing chamber; A liquid ammonia coil is arranged outside the accommodation chamber, the liquid ammonia coil is connected to the second port, and the liquid ammonia can flow into the liquid ammonia coil and enter the accommodation chamber through the second port; Optionally, the second port is provided with a jet mixer for mixing the feed liquid in the containing chamber with liquid ammonia and spraying the mixture into the containing chamber; Optionally, a circulation pump is provided in the reaction unit for pumping the liquid in the containing chamber into the jet mixer; Optionally, centrifugal pumps are independently arranged between the first mixing device and the first impurity removal device, and between the second mixing device and the second impurity removal device.

10. The system according to claim 8, characterized in that The first mixing device and the second mixing device are each independently provided with a temperature detection component and an ammonia content detection component; A first valve is provided between the second mixing device and the second impurity removal device, and a second valve is provided between the first mixing device and the first impurity removal device; The system further comprises: A control component is respectively connected to the ammonia content detection component, the first valve, the second valve, the first impurity removal device and the second impurity removal device, and is used to control the opening and closing of the first valve and the second valve and the opening and closing of the first impurity removal device and the second impurity removal device based on the ammonia content in the slurry of the first mixing device and the second mixing device.

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