Production process of anti-condensation and anti-caking taurine crystal

Abstract

The application discloses a production process of anti-condensation and anti-caking taurine crystals, which comprises the following steps: (1) a homogeneous feed liquid with taurine concentration of 10-15 wt% and temperature of 35-50 DEG C is introduced into a flash evaporator to perform flash cooling to form a low supersaturation solution with temperature of 25-35 DEG C; (2) the low supersaturation solution is introduced into the top of a plug flow crystallizer, and the crystals spontaneously nucleate and grow in the descending process of the plug flow crystallizer, and slurry with complete supersaturation release is obtained at the bottom outlet; (3) the slurry is introduced into a thickener, and after the solid content is increased to 30-40%, filtration is performed, and the obtained solid is dried to obtain the taurine crystals. The taurine crystals obtained by the production process have the advantages of less defects, smooth crystal surface, narrow particle size distribution, small aspect ratio, good fluidity, and greatly improved anti-condensation and anti-caking performances.

Description

Technical Field

[0001] This invention belongs to the field of taurine preparation, specifically relating to a production process for taurine crystals that prevent condensation and agglomeration. Background Technology

[0002] Taurine, chemically known as 2-aminoethanesulfonic acid, is a naturally occurring β-sulfonated amino acid and a sulfur-containing amino acid essential for the activities of humans and mammals. Although it does not directly participate in the synthesis of proteins and enzymes in the body, it has extremely important physiological functions. It not only participates in maintaining normal homeostasis of the internal environment, but also plays an important regulatory role in the normal physiological functions of the central nervous system, cardiovascular system, digestive system, urinary system, immune system, endocrine system, and reproductive system.

[0003] Taurine has a wide range of applications due to its unique physiological and pharmacological functions: when added to food, it can enhance physical fitness, prevent diseases, eliminate fatigue, and improve work efficiency; in the pharmaceutical field, it can help treat diseases such as fatty liver, myocarditis, heart failure, and arteriosclerosis; when added to animal feed, it can promote animal growth, development, and reproduction. Taurine has a promising market prospect.

[0004] Currently, the main industrial production methods for taurine are the ethanolamine method and the ethylene oxide method, with crystallization being a crucial step in separation, purification, and product refinement. Taurine is a colorless or white needle-like crystal or crystalline powder, odorless, and readily soluble in water. Commercially available taurine products suffer from problems such as small and unevenly distributed crystal particle size, low bulk density, poor flowability, and a tendency to agglomerate. Furthermore, production enterprises face drawbacks due to the simplistic crystallization methods and cumbersome processes, including low production efficiency, high raw material costs, high energy consumption in public works, and low equipment utilization. Poor taurine crystal quality and low production efficiency are significant factors affecting product prices, enterprise profitability, and market application.

[0005] Patent CN101857558A discloses a segmented cooling crystallization method for purifying 2-aminoethanesulfonic acid from industrially pure 2-aminoethanesulfonic acid, avoiding the problem of 2-aminoethanesulfonic acid agglomeration. However, this method requires high-pressure reaction conditions, and also necessitates the addition of alkanols to promote activated carbon decolorization and impurity removal, as well as maintaining the cooling crystallization time of the filtrate to obtain taurine crystals. This not only leaves alkanol impurities in the taurine crystals, but also results in cylindrical needle-shaped crystals, which differ from columnar crystals. Furthermore, these cylindrical needle-shaped taurine crystals require aluminum-plastic film packaging to effectively prevent taurine from absorbing moisture and agglomerating.

[0006] Patent CN109574886A describes a method for preparing taurine crystals with improved bulk density, fluidity, and non-agglomeration. However, this method requires adding a certain amount of antisolvent to the system at a certain dropping rate, which introduces a large amount of organic impurities. These impurities accumulate during industrial production, making it difficult to completely separate them from the mother liquor. Furthermore, separation also increases costs significantly.

[0007] Patent CN112479944A describes a method for recrystallizing taurine and the same. By controlling the temperature in stages and holding the temperature, a columnar crystal form is finally achieved. The axial length of the crystal is 600μm to 950μm, the radial length is 250μm to 450μm, and the aspect ratio is 2:1 to 3:1. The particles are relatively small. At the same time, microscopic images show that the columnar crystal form is different from the standard columnar crystal form. The particle surface is irregular, which will affect the agglomeration performance of the product.

[0008] Patent CN115141126A describes a method for efficiently preparing columnar taurine through a cyclic process. This involves preparing an aqueous taurine solution and treating it with an alkaline resin to remove alkali metal salts and derivatives of hydroxyethyl sulfonate. Substituting the solution with substandard effluent and performing crystallization, the process yields columnar taurine crystals. However, this process involves intermittent crystallization, resulting in low production efficiency. Particle collisions cause surface breakage or wear, exposing internal regions containing mother liquor or impurities. These regions are more prone to trapping mother liquor or impurities, reducing product purity or yield. This process primarily involves secondary nucleation crystallization, resulting in a wide particle size distribution (PSD), rough and irregular particle surfaces, and an increased tendency to agglomerate. Numerous crystal defects increase pore water (capillary) concentration, leading to higher drying weight loss and a greater tendency for product condensation.

[0009] In summary, the existing intermittent crystallization method has the following main drawbacks: the obtained taurine crystals have a wide particle size distribution, rough crystal surface, large aspect ratio, and many crystal defects; the drying time is long and the drying weight loss is high; and temperature fluctuations during product storage can easily cause condensation and clumping. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a production process for taurine crystals that prevent condensation and agglomeration. The taurine crystals obtained by this production process have fewer defects, smooth crystal surfaces, narrow particle size distribution, small aspect ratio, and good flowability, and the anti-condensation and anti-agglomeration properties are greatly improved.

[0011] The technical solution of the present invention is as follows:

[0012] A production process for taurine crystals that prevent condensation and agglomeration includes the following steps:

[0013] (1) A homogeneous liquid with a taurine concentration of 10~15wt% and a temperature of 35~50℃ is fed into a flash evaporator for flash evaporation and cooling to form a low supersaturation solution at 25~35℃.

[0014] (2) The above low supersaturation solution enters the top of the plug flow crystallizer. During the descent of the plug flow crystallizer, the crystals spontaneously nucleate and grow, and the slurry with complete supersaturation release is obtained at the bottom outlet.

[0015] (3) The above slurry enters the thickener and is filtered after the solid content is increased to 30-40%. The solid is obtained by filtration and then dried to obtain the taurine crystals.

[0016] This invention reduces the supersaturation during crystallization and employs a flash cooling-flat flow crystallization process, making the nucleation and growth rates of the crystallization process adjustable and controllable. This effectively avoids the impact of secondary nucleation on the crystallization process, resulting in taurine crystals with fewer defects, smooth crystal surfaces, narrow particle size distribution, small aspect ratio, and good fluidity. The anti-condensation and anti-caking properties are also significantly improved.

[0017] Preferably, in step (1), the homogeneous feed solution is obtained by mixing taurine mother liquor with crude taurine solution using a static mixer; the mixing is carried out in a Venturi mixer. Further, the concentration of the taurine mother liquor is 8-12 wt%, and the temperature is 30-40°C; the concentration of the crude taurine solution is 28-32 wt%, and the temperature is 90-96°C; further, the mass ratio of taurine mother liquor to crude taurine solution is 4-6:1.

[0018] Preferably, in step (1), the condensate distilled from the flash evaporator is used to dissolve the crude taurine.

[0019] Preferably, in step (2), the height of the push flow section in the push flow crystallizer is 10~15m, the diameter of the push flow section is 0.2~0.4m, the vacuum degree is controlled at 0.080-0.090MPa, and the residence time of the low supersaturation solution in the push flow crystallizer is 3~7min.

[0020] Preferably, the slurry temperature in the thickener is 25~30℃.

[0021] Preferably, in step (3), the overflow clear liquid obtained from the thickener is used as taurine mother liquor to prepare homogeneous liquid.

[0022] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0023] (1) This invention achieves controllable and stable nucleation and growth processes by using a continuous crystallization method of "flash cooling-flat flow crystallization" combined with low supersaturation feeding and narrow cooling range. It fundamentally suppresses secondary nucleation and explosive nucleation, and solves the problems of numerous crystal defects and wide particle size distribution caused by large fluctuations in supersaturation in intermittent crystallization and conventional continuous crystallization.

[0024] (2) The present invention adds a Venturi mixer to avoid excessive local concentration from causing explosive nucleation and crystallization, thereby reducing crystal defects.

[0025] (3) The crystals obtained by the present invention have a narrow particle size distribution, a small aspect ratio, a smooth crystal surface, and few crystal defects, resulting in fast crystal drying speed, low product moisture content, no condensation after 30 days of storage at 5~30℃, long anti-caking period, and good fluidity and dispersibility after long-term storage. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the present invention;

[0027] Figure 2 This is a schematic diagram of the flash cooling plug flow crystallizer of the present invention;

[0028] Figure 3 Here is a diagram showing the crystal morphology of the product obtained in Example 1;

[0029] Figure 4 This is a cross-sectional view of the crystallization of the product obtained in Example 1;

[0030] Figure 5 The image shows the crystal DSC curve of the product obtained in Example 1.

[0031] Figure 6 Here is a diagram showing the crystal morphology of the product obtained in Example 2;

[0032] Figure 7 This is a cross-sectional view of the crystallization of the product obtained in Example 2;

[0033] Figure 8 The image shows the crystal DSC curve of the product obtained in Example 2;

[0034] Figure 9 Here is a diagram showing the crystal morphology of the product obtained in Example 3;

[0035] Figure 10 This is a cross-sectional view of the crystallization of the product obtained in Example 3;

[0036] Figure 11 The image shows the crystal DSC curve of the product obtained in Example 3;

[0037] Figure 12Here is a diagram showing the crystal morphology of the product obtained in Comparative Example 1;

[0038] Figure 13 This is a cross-sectional view of the crystallization of the product obtained in Comparative Example 1;

[0039] Figure 14 The crystal DSC curve of the product obtained in Comparative Example 1;

[0040] Figure 15 Here is a diagram showing the crystal morphology of the product obtained in Comparative Example 2;

[0041] Figure 16 This is a cross-sectional view of the crystallization of the product obtained in Comparative Example 2;

[0042] Figure 17 The image shows the crystal DSC curve of the product obtained in Comparative Example 3. Detailed Implementation

[0043] Figure 1 This is a process flow diagram of the present invention, such as... Figure 1 As shown, the production process is as follows:

[0044] (1) The taurine mother liquor is mixed with the crude taurine solution through a static mixer to form a homogeneous liquid with a concentration of 10-15% and a temperature of 35-50℃. The liquid enters the flash evaporator to complete the flash evaporation and cooling to 25-35℃ to form a low supersaturation solution. During the descent process in the plug flow crystallizer, the crystal spontaneous nucleation and growth are completed. The vacuum degree is controlled at 0.080-0.090MPa. The length of the plug flow crystallizer at the bottom of the flash evaporator is 10-15m.

[0045] (2) The slurry with complete release of supersaturation enters the thickener, and after the solid content is increased to 30-40%, it is filtered. The mother liquor is used to crystallize crude taurine, and the condensate is used to dissolve crude taurine.

[0046] (3) Filter out the crystals and dry them. The overflow of the thickener is recycled into the mother liquor buffer tank.

[0047] Figure 2 This is a schematic diagram of the flash cooling and plug flow crystallizer of the present invention. The flash cooling and plug flow crystallizer includes a flash evaporator and a plug flow crystallizer. The flash evaporator consists of an upper cylindrical body and a lower cone with a gradually decreasing diameter. The plug flow crystallizer has a slender cylindrical structure, and its upper part is connected to the cylindrical body of the flash evaporator. The flash evaporator is equipped with a wire mesh to remove air bubbles or foam.

[0048] The specific parameters of the flash cooling plug flow crystallizer used in this embodiment of the invention are as follows:

[0049]

[0050] In one specific implementation, the liquid level difference between the push flow crystallizer and the thickener is ≥10m, and the push flow crystallizer is insulated.

[0051] Unless otherwise specified, the concentrations mentioned in the following examples are all mass percentage concentrations.

[0052] The method for preparing crude taurine used in this invention is existing technology. For details, please refer to the preparation process of crude taurine in the example of CN112898187A.

[0053] Example 1

[0054] A crude taurine aqueous solution with a concentration of 29.2% (1000 kg / h) and a temperature of 94.3℃ is uniformly mixed with a refined mother liquor with a concentration of 9.6% (6000 kg / h) and a temperature of 34.5℃ to form a feed solution with a concentration of 12.4% and a temperature of 43.0℃. This feed solution enters a flash evaporator. A top-sprayed diluted mother liquor (8% concentration, 25℃) at a rate of 800 kg / h is used. The solution is then flash-cooled to 27-28℃ under a vacuum of 0.085-0.090 MPa. The flash liquid concentration is... The concentration of the flash slurry is 12±0.5%. The slurry crystallizes in a plug flow crystallizer to form a slurry, with a residence time of 5 minutes. It then enters a thickener, where the temperature is controlled at 27-28℃. The slurry (40% solids content) is pumped to a centrifuge for filtration to obtain wet taurine, which is then dried at a rate of 251 kg / h to obtain taurine crystals. The upper layer of mother liquor from the thickener overflows back to the mother liquor tank, which is maintained at 34.5℃ by heating. The flash condensate is used to prepare a 29.2% taurine solution.

[0055] See the crystal morphology diagram of the product. Figure 3 Crystallization section diagram is shown below. Figure 4 The DSC curve of the crystal is shown in Figure 5. The results show that the weight loss during drying is 0.041%, and the angle of repose is 27.9°. The crystal surface is smooth with few defects, the DSC curve is smooth, and there are few endothermic peaks. The crystal does not condense or clump when stored at 5~30℃ for 30 days.

[0056] Example 2

[0057] A crude taurine aqueous solution with a concentration of 30.7% (1200 kg / h, 95.7℃) and a refined mother liquor with a concentration of 10.3% (6000 kg / h, 35.6℃) is uniformly mixed to form a feed solution with a concentration of 13.7% (45.6℃). This solution is then fed into a flash evaporator. A top dilute mother liquor (9% concentration, 30℃) is sprayed at a rate of 850 kg / h. The solution is flash-cooled to 30-31℃ under a vacuum of 0.08-0.085 MPa, resulting in a flash liquid concentration of 11±0.5%. The flash liquid crystallizes in a plug flow crystallizer to form a slurry, which remains in the crystallizer for 5 minutes. The slurry then enters a thickener, where the temperature is controlled at 30-31℃. The slurry is pumped to a centrifuge for filtration to obtain wet taurine, which is then dried. Taurine crystals are obtained at a rate of 323 kg / h. The upper mother liquor overflows back into the mother liquor tank, which is maintained at 35.6℃ by heating. Flash condensate is used to prepare a 30.7% taurine solution.

[0058] See the crystal morphology diagram of the product. Figure 6 Crystallization section diagram is shown below. Figure 7 The DSC curve of the crystal is shown in Figure 8. The results show that the weight loss during drying is 0.041%, and the angle of repose is 27.9°. The crystal surface is smooth with few defects, the DSC curve is smooth, and there are few endothermic peaks. The crystal does not condense or clump when stored at 5~30℃ for 30 days.

[0059] Example 3

[0060] A crude taurine aqueous solution with a concentration of 30.4% (1500 kg / h, 95.2℃) and a refined mother liquor with a concentration of 10.5% (6000 kg / h, 36.4℃) are uniformly mixed to form a 14.5% concentration and 48.2℃ solution, which is then fed into a flash evaporator. A top dilute mother liquor (8% concentration, 25℃) is sprayed at a rate of 900 kg / h. The solution is flash-cooled to 31-32℃ under a vacuum of 0.08-0.085 MPa, resulting in a flash liquid concentration of 11±0.5%. The flash liquid crystallizes in a plug flow crystallizer to form a slurry, which remains in the crystallizer for 5 minutes. The slurry then enters a thickener, where the temperature is controlled at 30-31℃. The slurry is pumped to a centrifuge for filtration to obtain wet taurine, which is then dried at a rate of 402 kg / h to obtain taurine crystals. The upper mother liquor overflows back into the mother liquor tank, which is maintained at 36.4℃ by heating. Flash condensate is used to prepare a 30.4% taurine solution.

[0061] See the crystal morphology diagram of the product. Figure 9 Crystallization section diagram is shown below. Figure 10 The DSC curve of the crystal is shown in Figure 11. The results show that the weight loss during drying is 0.046% and the angle of repose is 28.9°. The crystal surface is smooth with few defects, the DSC curve is smooth, and there are few endothermic peaks. The crystal does not condense or clump when stored at 5~30℃ for 30 days.

[0062] The results of Examples 1-3 show that the plug flow crystallization has fewer crystal defects (no endothermic peak in DSC, and the drying weight loss is reduced to about 0.04%), strong anti-condensation and anti-caking ability, small angle of repose of the product, and no condensation or agglomeration when placed in an environment of 25°C for more than 30 days.

[0063] Comparative Example 1

[0064] The batch crystallization device uses a crystallization kettle with a 29wt% taurine aqueous solution. The solution is dissolved at 90-95℃, and then cooled to 75-78℃ with circulating water to precipitate crystals. The temperature is maintained for 4 hours. Low-temperature water is used to cool the solution to 20-25℃ at a rate of 10℃ / 30min, and the temperature is maintained for 30min. Crude taurine is obtained by filtration.

[0065] See the crystal morphology diagram of the product. Figure 12 Crystallization section diagram is shown below. Figure 13 See the crystal DSC curve. Figure 14 The results showed that compared with the flash cooling-flat flow crystallization process, the intermittent crystallization process has a wide PSD, coarse particles, and many defects. The product is not easy to dry, and condensation occurs after 1-2 days when placed in a 25℃ environment, and clumping occurs after about 7 days.

[0066] Comparative Example 2

[0067] Taurine continuous crystallization employs a two-stage cooling method, using OSLO crystallizers with external mother liquor circulation, and circulating mother liquor of 22wt% (flow rate 2000 m³ / h). 3 / h) First mix with the incoming material concentration of 30wt% and 20m 3 A 90-95℃ taurine aqueous solution is mixed and fed into the first-stage OSLO, then cooled under vacuum at 60℃, and continuously discharged from the bottom side to the second-stage OSLO at a discharge flow rate of 18m³ / h. 3 The liquid enters the secondary OSLO at 25°C and is cooled under vacuum. The slurry is then filtered to obtain crude taurine. The entire crystallization process takes 4-6 hours.

[0068] See the crystal morphology diagram of the product. Figure 15 Crystallization section diagram is shown below. Figure 16 See the crystal DSC curve. Figure 17 The results showed that compared with the flash cooling-flat flow crystallization process, the continuous crystallization crystals have a wide PSD, coarse particles, and many defects. The product is not easy to dry, and condensation occurs after 1-2 days when placed in a 25℃ environment, and clumping occurs after about 7 days.

[0069] The results of Comparative Examples 1 and 2 show that, compared with the flash cooling-push flow crystallization process, the intermittent crystallization and continuous crystallization processes are more prone to secondary induced nucleation, resulting in more endothermic peaks in the crystal DSC curve, wider PSD, coarser particles, more defects, and products that are difficult to dry, with a high tendency to agglomerate and a high risk of condensation.

Claims

1. A production process for taurine crystals that prevent condensation and agglomeration, characterized in that, Includes the following steps: (1) A homogeneous liquid with a taurine concentration of 10~15wt% and a temperature of 35~50℃ is fed into a flash evaporator for flash evaporation and cooling to form a low supersaturation solution at 25~35℃. (2) The low supersaturation solution is fed into the top of the plug flow crystallizer. During the descent of the plug flow crystallizer, the crystals spontaneously nucleate and grow, and the slurry with complete supersaturation release is obtained at the bottom outlet. (3) The slurry is fed into a thickener and filtered after the solid content is increased to 30-40%. The solid obtained by filtration is dried to obtain the taurine crystals.

2. The production process of taurine crystals according to claim 1, characterized in that, In step (1), the homogeneous feed solution is obtained by mixing taurine mother liquor with crude taurine solution through a static mixer; The mixing is carried out in a Venturi mixer.

3. The production process of taurine crystals according to claim 2, characterized in that, The concentration of the taurine mother liquor is 8~12wt%, and the temperature is 30~40℃; The concentration of the crude taurine solution is 28-32 wt%, and the temperature is 90-96℃.

4. The production process of taurine crystals according to claim 2 or 3, characterized in that, The mass ratio of the taurine mother liquor to the crude taurine solution is 4~6:

1.

5. The production process of taurine crystals according to claim 2, characterized in that, In step (1), the condensate distilled from the flash evaporator is used to prepare a crude taurine solution.

6. The production process of taurine crystals according to claim 1, characterized in that, In step (1), the concentration of the low supersaturation solution obtained by flash evaporation is 10~13wt%.

7. The production process of taurine crystals according to claim 1, characterized in that, In step (2), the height of the push flow section in the push flow crystallizer is 10~15m and the diameter of the push flow section is 0.2~0.4m.

8. The production process of taurine crystals according to claim 1, characterized in that, In step (2), the residence time of the low supersaturation solution in the plug flow crystallizer is 3 to 7 minutes, and the vacuum degree is controlled at 0.080 to 0.090 MPa.

9. The production process of taurine crystals according to claim 1, characterized in that, In step (3), the temperature of the slurry in the thickener is 25~30℃.

10. The production process of taurine crystals according to claim 2, characterized in that, In step (3), the overflow clear liquid obtained from the thickener is used as taurine mother liquor to prepare homogeneous feed solution.

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