A recrystallization recovery device and method for a vitamin c mother liquor component

Abstract

The application discloses a kind of recrystallization recovery device and method of vitamin C mother liquor component, recrystallization recovery device includes concentration mechanism, recovery mechanism and collection mechanism, concentration mechanism is communicated with recovery mechanism and collection mechanism, concentration mechanism is used to evaporate and concentrate mother liquor, recovery mechanism is used to recover the hydrochloric acid generated by evaporation, collection mechanism is used to separate vitamin C crude product from solution, concentration mechanism is separated vitamin C in mother liquor using the method of continuous recrystallization, by gradually evaporating and concentrating mother liquor, so that vitamin C forms crystallization in mother liquor, recovery mechanism is used to recover the hydrochloric acid generated in the process of concentration, so that it is recycled, resource is saved, collection mechanism is used to collect the vitamin C crude product crystallized in mother liquor, to facilitate the processing of subsequent process.

Description

Technical Field

[0001] This invention relates to the field of vitamin production technology, specifically to a recrystallization and recovery device and method for vitamin C mother liquor components. Background Technology

[0002] Currently, the main method for producing vitamin C in China is the alkaline conversion method, which has a long process flow and low production efficiency, but the technology is relatively mature. In recent years, some manufacturers have successfully developed a new process for producing vitamin C using hydrochloric acid conversion. This method has a shorter process flow, higher production efficiency, and lower unit production cost, offering several advantages. However, during implementation, because it uses single-effect and double-effect falling film evaporation crystallization processes to separate vitamin C from the mother liquor, the heating medium (steam or hot water) in the heater has a high temperature, causing localized overheating of the heater tube walls. Since vitamin C is a heat-sensitive medium, it frequently decomposes, cokes, and carbonizes, clogging the heater channels. Because the heater is made of graphite, this further leads to the rupture and damage of the graphite heat exchange tubes, preventing the concentration process from proceeding normally. Therefore, this manufacturer has essentially stopped using the hydrochloric acid conversion method for producing vitamin C.

[0003] Current crystallization processes for vitamin C conversion mother liquor generally involve direct freeze crystallization or evaporation concentration followed by freeze crystallization. The direct freeze crystallization method involves cooling the reaction solution or mother liquor in a cooling tank or through a heat exchanger using low-temperature water or chilled brine. The solubility of vitamin C continuously decreases until saturated crystals precipitate. According to solubility tables, the solubility of vitamin C decreases by approximately 7 g / L for every 1°C decrease in temperature. This method requires a refrigeration unit to continuously generate low-temperature water for heat exchange, resulting in high energy consumption and low production efficiency.

[0004] Evaporation and concentration can employ single-effect or multi-effect processes, falling film evaporation, or forced circulation evaporation, among others. Regardless of the method, a high-temperature heat source (typically hot water, low-pressure steam, or other heat sources) is required to heat the material to its boiling point for operation. Due to the highly heat-sensitive nature of vitamin C, it is extremely prone to decomposition, coking, or even carbonization during heating, leading to equipment and pipeline blockages, highly unstable and difficult-to-control operation, and low product yield. Summary of the Invention

[0005] The purpose of this invention is to provide a recrystallization and recovery device and method for vitamin C mother liquor components, so as to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: the recrystallization recovery device includes a concentration mechanism, a recovery mechanism and a collection mechanism. The concentration mechanism is connected to the recovery mechanism and the collection mechanism. The concentration mechanism is used to evaporate and concentrate the mother liquor. The recovery mechanism is used to recover the hydrochloric acid produced by evaporation. The collection mechanism is used to separate crude vitamin C from the solution.

[0007] The concentration unit uses a continuous recrystallization method to separate vitamin C from the mother liquor. By gradually evaporating and concentrating the mother liquor, vitamin C crystals form in the mother liquor. The recovery unit is used to recover the hydrochloric acid generated during the concentration process, allowing it to be recycled and saving resources. The collection unit is used to collect the crude vitamin C crystals in the mother liquor for subsequent processing.

[0008] Furthermore, the concentration mechanism includes a heater and a continuous recrystallizer. The outlet of the heater is connected to the continuous recrystallizer, which is connected to the recovery mechanism and the collection mechanism. The continuous recrystallizer is divided into multiple crystallization chambers of different volumes, which are connected by arc-shaped holes. The number of crystallization chambers is n, where n≥3.

[0009] If the temperature of the raw material solution is too low, it can be appropriately heated by a heater. The heat source is hot water generated during the initial concentration process, with a temperature not exceeding ℃. The continuous recrystallizer adopts a horizontal or vertical structure; this invention is an example of a horizontal structure. The continuous recrystallizer is divided into multiple crystallization chambers of unequal volume, which are connected by specially designed arc-shaped holes. The flow rate of the solution through the arc-shaped holes is controlled between 0.1 and 1.2 m / s to ensure the stability of the crystallization process. By gradually increasing the vacuum degree of each crystallization chamber, the solution temperature is continuously reduced, while evaporation continues. The removed solvent includes a mixture of hydrochloric acid and water, which is condensed and recovered by a subsequent recovery mechanism for recycling. Simultaneously, the difference in vacuum degree between each crystallization chamber is used as a driving force to propel the solution from the first chamber to the nth chamber. The process does not require external power (such as a pump). The principle of temperature gradient is used to gradually increase the concentration of vitamin C and other substances in the mother liquor, while ensuring that the solution temperature is always controlled at a relatively stable state for vitamin C, until vitamin C crystals continuously precipitate, forming a supersaturated concentrate.

[0010] Furthermore, a gas distribution mixer is provided at the bottom of the crystallization chamber to prevent crystal deposition. The gas distribution mixer includes a horizontal distributor and a spiral distributor.

[0011] To ensure the supersaturated vitamin C solution remains suspended and the crystals are kept at a suitable size, a gas distribution mixer is designed at the bottom of the crystallizer chamber. This mixer uses air flotation to control the crystal state and prevent crystal deposition. Furthermore, the number and size of crystals are adjusted by controlling the number and size of the distribution holes on the gas distribution mixer, based on the degree of crystallization in different chambers. There are two types of gas distribution mixers: horizontal and spiral. In a horizontal distributor, gas moves upwards after exiting the small holes in the gas flow channel, with bubbles carrying crystal particles vertically. In a spiral distributor, the airflow moves tangentially along the small holes in the gas flow channel, causing the particles to rotate in the solution, resulting in more spherical and uniformly sized particles. The combination of these two types of gas distribution mixers also significantly reduces the existence of dead zones in the mixing process.

[0012] Furthermore, the recycling mechanism includes a partition wall condenser, a vacuum system, and a storage tank. The partition wall condenser is connected to the continuous recrystallizer and is adapted to the crystallization chamber. The vacuum system is connected to the partition wall condenser, and the storage tank is connected to the outlet of the partition wall condenser.

[0013] The hydrochloric acid vapor generated by evaporation in each crystallization chamber is condensed and recovered by a partition condenser. The vacuum system is formed by a steam ejector and a vacuum pump connected to the partition condenser. When the vacuum system is activated, it draws the hydrochloric acid vapor generated by evaporation in each crystallization chamber back to the partition condenser for recovery. The partition condenser corresponds one-to-one with the crystallization chamber, thus maintaining different vacuum states in each crystallization chamber of the continuous recrystallizer. The vacuum level of each level is related to the amount of gas injected by the gas distributor at the bottom of the corresponding chamber and the amount of gas extracted by the vacuum system. As the amount of injected gas increases, the amount of extracted gas decreases, and the vacuum level decreases, and vice versa. The combination of these two factors adjusts the absolute pressure in the crystallization chamber to decrease sequentially, thereby driving the liquid flow in different crystallization chambers through pressure difference and promoting the evaporation of the solution.

[0014] Furthermore, the collection mechanism includes a hydrocyclone separator, a centrifuge, a mother liquor tank, a slurry pump, and a transfer pump. The inlet of the slurry pump is connected to the outlet of the continuous recrystallizer, and the outlet of the slurry pump is connected to the hydrocyclone separator. The two outlets of the hydrocyclone separator are connected to the centrifuge and the mother liquor tank, respectively. The inlet of the transfer pump is connected to the mother liquor tank, and the outlet of the transfer pump is connected to the continuous recrystallizer.

[0015] After the solution has crystallized, it is pumped into a hydrocyclone separator using a salt slurry pump to perform preliminary separation using centrifugal force. The upper layer, containing more fine crystal particles, is returned to the continuous recrystallizer, while the lower layer, a supersaturated solution with a higher concentration, is fed into a centrifuge to separate crude vitamin C. The centrifugal mother liquor, along with the upper clear liquid from the hydrocyclone separator, enters the mother liquor tank and is then returned to the continuous recrystallizer via a transfer pump to continue participating in the crystal formation and grain control process, which helps to improve the quality of the crystallized product.

[0016] like Figure 1-7 As shown, the method includes the following steps:

[0017] 1) Determine the content of the main components of the concentrated mother liquor, and calculate and determine the size and number of crystallization stages of the continuous recrystallizer;

[0018] The vitamin C content in the concentrated mother liquor is detected by a detector. Based on the vitamin C solubility table, the size and number of crystallization stages of the continuous recrystallizer are designed to ensure crystallization efficiency.

[0019] 2) The concentrated mother liquor is fed into the crystallization chamber of the continuous recrystallizer for continuous recrystallization, and the temperature of the fed concentrated mother liquor is controlled within a suitable range by a heater, and crystal deposition is prevented by a gas distribution mixer.

[0020] If the temperature of the raw material solution is too low, it can be appropriately heated by a heater. The heat source is hot water at no more than 60°C generated during the front-end concentration process. During the crystallization process, the gas distribution mixer works and uses air flotation to control the state of the crystals and prevent crystal deposition. At the same time, according to the degree of crystallization of the crystals in different chambers, the number and size of the crystals are adjusted by controlling the number and size of the distribution holes on the gas distributor.

[0021] 3) The hydrochloric acid vapor generated by evaporation in the continuous recrystallizer is condensed by the indirect condenser absorber to recover the hydrochloric acid;

[0022] During crystallization, evaporation continues, and the solvent removed includes a mixture of hydrochloric acid and water. The hydrochloric acid is then condensed and recovered through a partition wall condenser for recycling.

[0023] 4) The supersaturated crystallization slurry generated by the continuous recrystallizer is sent to the hydrocyclone separator for separation by a salt slurry pump. The upper clear liquid after centrifugation overflows into the mother liquor tank, and the lower high-concentration slurry enters the centrifuge.

[0024] After the solution has crystallized, it is pumped into a hydrocyclone separator using a salt slurry pump to perform preliminary separation using centrifugal force. The upper layer, containing more fine crystal particles, is returned to the continuous recrystallizer, while the lower layer, a supersaturated solution with a higher concentration, is fed into a centrifuge to separate crude vitamin C.

[0025] 5) The centrifuge separates the larger-sized crude vitamin C particles into the next process. The centrifugal mother liquor and the clear liquid from the hydrocyclone separator first enter the mother liquor tank, and then return to the continuous recrystallizer through the transfer pump to continue to participate in the crystal forming and crystal control process.

[0026] After the centrifugal mother liquor and the clear liquid from the upper layer of the hydrocyclone enter the mother liquor tank together, they are returned to the continuous recrystallizer by a transfer pump to continue participating in the crystal forming and grain control process, which is beneficial to improving the quality of the crystallized product.

[0027] Furthermore, in step 2), the absolute pressure during continuous recrystallization is controlled between 0.01 and 10 kPa, the recrystallization temperature range is between -5 and 45°C, and the temperature difference between each two connected crystallization chambers is 3 to 10°C.

[0028] According to the solubility table of vitamin C aqueous solution, the solubility of vitamin C decreases by approximately 7 g / L for every 1°C decrease in temperature. Therefore, the temperature difference between each two connected crystallization chambers needs to be set at 3–10°C to ensure that the solubility of vitamin C continuously decreases until saturated crystals precipitate. However, vitamin C is a heat-sensitive medium and is prone to decomposition when overheated. Therefore, the recrystallization temperature range needs to be controlled between -5 and 45°C to prevent thermal decomposition of vitamin C. The pressure should also be controlled at a low pressure between 0.01 and 10 kPa, as low pressure promotes solvent evaporation and solution concentration.

[0029] The recrystallization and recovery method for vitamin C mother liquor components is also applicable to the recovery of mother liquor components in vitamin C production using general acid conversion and alkali conversion methods.

[0030] The recrystallization recovery method for vitamin C mother liquor components of this application has wide applicability and can be used for the recovery of vitamin C mother liquor with different components.

[0031] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The process of the present invention, compared with the traditional crystallization process, avoids the coking rate of the product because it does not require heating, evaporation and concentration, thus improving production efficiency and stability; by adopting the method of returning the clear liquid at the top of the hydrocyclone separator and the mother liquor from the centrifuge to the crystallizer for mixing, and by using the bottom air flotation method in the crystallizer chamber to increase the number of crystals formed and the size of the crystals, the product quality and yield are improved. Attached Figure Description

[0032] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0033] Figure 1 This is a schematic diagram of the process flow for the recrystallization and recovery of vitamin C mother liquor components;

[0034] Figure 2 This is a schematic diagram of the concentration mechanism;

[0035] Figure 3 This is a schematic diagram of the recycling facility;

[0036] Figure 4 This is a diagram of the collection mechanism;

[0037] Figure 5 This is a schematic diagram of a continuous recrystallizer.

[0038] Figure 6 This is a schematic diagram of a gas distribution mixer.

[0039] Figure 7 This is a schematic diagram of an arc-shaped hole;

[0040] In the diagram: 1-Concentration mechanism, 11-Heater, 12-Continuous recrystallizer, 121-Circular arc orifice, 122-Gas distribution mixer, 1221-Horizontal distributor, 1222-Spiral distributor, 2-Recovery mechanism, 21-Indirect condenser absorber, 22-Vacuum system, 23-Storage tank, 3-Collection mechanism, 31-Swirl separator, 32-Centrifuge, 33-Mother liquor tank, 34-Salt slurry pump, 35-Transfer pump. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The present invention provides the following technical solution:

[0043] like Figure 1 As shown, the recrystallization recovery device includes a concentration unit 1, a recovery unit 2, and a collection unit 3. The concentration unit 1 is connected to the recovery unit 2 and the collection unit 3. The concentration unit 1 is used to evaporate and concentrate the mother liquor. The recovery unit 2 is used to recover the hydrochloric acid produced by evaporation. The collection unit 3 is used to separate crude vitamin C from the solution.

[0044] Concentration unit 1 uses a continuous recrystallization method to separate vitamin C from the mother liquor. By gradually evaporating and concentrating the mother liquor, vitamin C crystals form in the mother liquor. Recovery unit 2 is used to recover the hydrochloric acid generated during the concentration process, so that it can be recycled and resources are saved. Collection unit 3 is used to collect the crude vitamin C crystals in the mother liquor for subsequent processing.

[0045] like Figure 1 , Figure 2 , Figure 7 As shown, the concentration mechanism 1 includes a heater 11 and a continuous recrystallizer 12. The outlet of the heater 11 is connected to the continuous recrystallizer 12. The continuous recrystallizer 12 is connected to the recovery mechanism 2 and the collection mechanism 3. The continuous recrystallizer 12 is divided into multiple crystallization chambers of different volumes. The crystallization chambers are connected to each other through arc holes 121. The number of crystallization chambers is n, where n≥3.

[0046] If the temperature of the raw material solution is too low, it can be appropriately heated by heater 11. The heat source is hot water at no more than 60°C generated during the front-end concentration process. The continuous recrystallizer 12 adopts a horizontal or vertical structure. In this invention, it is a horizontal structure. The continuous recrystallizer 12 is divided into multiple crystallization chambers with different volumes. The crystallization chambers are connected by specially designed arc holes 121. The flow rate of the solution through the arc holes 121 is controlled between 0.1 and 1.2 m / s to ensure the stability of the crystallization process. The solution temperature is continuously reduced by gradually increasing the vacuum degree of each crystallization chamber. At the same time, evaporation is continuously generated. The solvent removed includes a mixture of hydrochloric acid and water. The hydrochloric acid is condensed and recovered by the subsequent recovery mechanism 2 for recycling. Simultaneously, the difference in vacuum level between each crystallization chamber is used as a driving force to propel the solution from the first-stage chamber to the nth stage. The process does not require external power (such as a pump). The concentration of vitamin C and other substances in the mother liquor is gradually increased by utilizing the principle of temperature gradient, while ensuring that the solution temperature is always controlled at a state where vitamin C properties are relatively stable, until vitamin C crystals continuously precipitate out, forming a supersaturated concentrate.

[0047] like Figure 1 , Figure 2 , Figure 5 , Figure 6 As shown, a gas distribution mixer 122 is provided at the bottom of the crystallization chamber. The gas distribution mixer 122 is used to prevent crystal deposition. The gas distribution mixer 122 includes a horizontal distributor 1221 and a spiral distributor 1222.

[0048] To ensure the supersaturated vitamin C solution remains suspended and the crystal particles are maintained at a suitable size, a gas distribution mixer 122 is designed at the bottom of the crystallizer chamber. This mixer uses air flotation to control the crystal state and prevent crystal deposition. Furthermore, the number and size of crystals are adjusted by controlling the number and size of the distribution holes on the gas distribution mixer 122 according to the degree of crystallization in different chambers. The gas distribution mixer 122 comes in two types: horizontal and spiral. In the horizontal distributor 1221, gas moves upwards after exiting the small holes in the airflow pipe, with bubbles carrying crystal particles vertically. In the spiral distributor 1222, the airflow moves tangentially along the small holes in the airflow pipe, causing the particles to rotate in the solution, making the particles closer to spherical and more uniform in size. The combination of these two types of gas distribution mixers also significantly reduces the existence of dead zones in the mixing process.

[0049] like Figure 1 , Figure 3 As shown, the recovery mechanism 2 includes a partition wall condenser 21, a vacuum system 22, and a storage tank 23. The partition wall condenser 21 is connected to the continuous recrystallizer 12 and is adapted to the crystallization chamber. The vacuum system 22 is connected to the partition wall condenser 21, and the storage tank 23 is connected to the outlet of the partition wall condenser 21.

[0050] The hydrochloric acid vapor generated by evaporation in each crystallization chamber is condensed and recovered by the partition condenser 21. The vacuum system 22 is formed by a steam ejector and a vacuum pump connected to the partition condenser. When the vacuum system 22 is activated, it draws the hydrochloric acid vapor generated by evaporation in each crystallization chamber to the partition condenser 21 for recovery. The partition condenser 21 corresponds one-to-one with the crystallization chamber, thereby maintaining each crystallization chamber in the continuous recrystallizer 12 under different vacuum conditions. The vacuum level of each level is related to the amount of gas injected by the gas distributor at the bottom of the corresponding chamber and the amount of gas extracted by the vacuum system 22. As the amount of injected gas increases, the amount of extracted gas decreases, and the vacuum level decreases, and vice versa. The two work together to adjust the absolute pressure in the crystallization chamber to decrease sequentially, thereby driving the liquid flow in different crystallization chambers through pressure difference and promoting the evaporation of the solution.

[0051] like Figure 1 , Figure 4 As shown, the collection mechanism 3 includes a hydrocyclone separator 31, a centrifuge 32, a mother liquor tank 33, a brine pump 34, and a transfer pump 35. The inlet of the brine pump 34 is connected to the outlet of the continuous recrystallizer 12, and the outlet of the brine pump 34 is connected to the hydrocyclone separator 31. The two outlets of the hydrocyclone separator 31 are connected to the centrifuge 32 and the mother liquor tank 33, respectively. The inlet of the transfer pump 35 is connected to the mother liquor tank 33, and the outlet of the transfer pump 35 is connected to the continuous recrystallizer 12.

[0052] After the solution has crystallized, it is pumped into the hydrocyclone 31 by the salt slurry pump 34 and initially separated by centrifugal force. The upper layer of clear liquid containing more small crystal particles is returned to the continuous recrystallizer 12, while the lower layer of supersaturated solution with higher concentration enters the centrifuge 32 to separate crude vitamin C. The centrifugal mother liquor and the upper clear liquid of the hydrocyclone 31 enter the mother liquor tank 33 together, and then return to the continuous recrystallizer 12 by the transfer pump 35 to continue to participate in the crystal forming and grain control process, which is beneficial to improving the quality of the crystallized product.

[0053] like Figure 1-7 As shown, the method includes the following steps:

[0054] 1) Determine the content of the main components of the concentrated mother liquor, and calculate and determine the size and number of crystallization stages of the continuous recrystallizer 12;

[0055] The content of the main components in the concentrated mother liquor was determined, and the size and crystallization stage of the continuous recrystallizer 12 were calculated and determined; the concentrated mother liquor to be treated was 12m 3 The feed rate was 12 m / h, with a feed temperature of 25°C, containing 25% (wt) vitamin C, 10% (wt) gulonic acid or other salts, and 35% (wt) hydrochloric acid. Based on the vitamin C solubility table, a continuous recrystallizer was designed with 12 sections divided into 4 continuous crystallization chambers. In the last chamber, the vitamin C content in the crystallization suspension was 26.4%, with a solubility of only 14.5%, resulting in a large amount of vitamin C crystals precipitating out.

[0056] 2) The concentrated mother liquor is fed into the crystallization chamber of the continuous recrystallizer 12 for continuous recrystallization, and the temperature of the fed concentrated mother liquor is controlled within a suitable range by the heater 11, and crystal deposition is prevented by the gas distribution mixer 122.

[0057] If the temperature of the raw material solution is too low, it can be appropriately heated by heater 11. The heat source is hot water of no more than 60°C generated during the front-end concentration process. During the crystallization process, gas distribution mixer 122 works and uses air flotation to control the state of the crystals and prevent crystal deposition. At the same time, according to the degree of crystallization of the crystals in different chambers, the number and size of the crystals are adjusted by controlling the number and size of the distribution holes on the gas distributor.

[0058] The concentrated mother liquor is directly fed into the first stage chamber K1 of the continuous recrystallizer 12. Its absolute pressure is adjusted to 2.3 kPa and the working temperature is 20°C. After the solution is cooled by negative pressure, it evaporates and vitamin C crystals begin to form. The gas distribution mixer at the bottom of the fourth stage chamber is turned on and the gas flow is adjusted to a suitable state.

[0059] Adjust the absolute pressure of the second-stage crystallizer chamber K2 to 1.7 kPa. Driven by the pressure difference, the solution flows from the arc hole 121 on the partition of the first-stage chamber K1 to the second-stage chamber K2. The temperature is further reduced, and the working temperature is 15℃. The solution continues to evaporate, and the amount of crystallization increases.

[0060] The absolute pressure of the third-stage crystallizer chamber K3 is adjusted to 1.3 kPa. Driven by the pressure difference, the solution flows from the arc hole 121 on the partition of the second-stage chamber K2 to the third-stage chamber K3. The temperature continues to decrease, and the working temperature is 10℃. The solution continues to evaporate, and the amount of crystallization continues to increase.

[0061] Adjust the absolute pressure of the fourth-stage crystallizer chamber k4 to 0.9 kPa. Driven by the pressure difference, the solution flows from the arc hole 121 on the partition of the third-stage chamber K3 to the fourth-stage chamber K4. The temperature further decreases, and the operating temperature is 5℃. The solution continues to evaporate, and the crystallization reaches its maximum.

[0062] 3) The hydrochloric acid vapor generated by evaporation in the continuous recrystallizer 12 is condensed by the indirect condenser 21 to recover the hydrochloric acid;

[0063] The hydrochloric acid vapor generated by evaporation in each chamber is condensed by the partition condenser 21 to recover the hydrochloric acid. The vacuum system is formed by the steam ejectors ED1, ED2, and ED3 connected to the partition condenser and the vacuum pump.

[0064] 4) The supersaturated crystallization slurry generated by the continuous recrystallizer 12 is sent to the hydrocyclone separator 31 for separation by the salt slurry pump 34. The upper clear liquid after centrifugation overflows to the mother liquor tank 33, and the lower high-concentration slurry enters the centrifuge 32.

[0065] After the solution has crystallized, it is pumped into the hydrocyclone 31 by the salt slurry pump 34 and initially separated by centrifugal force. The upper layer of clear liquid containing more tiny crystal particles is returned to the continuous recrystallizer 12, while the lower layer of supersaturated solution with higher concentration enters the centrifuge 32 to separate crude vitamin C.

[0066] 5) The centrifuge 32 separates the crude vitamin C with larger particle size and enters the next process. The mother liquor from the centrifugation and the clear liquid from the upper layer of the hydrocyclone 31 are returned to the continuous recrystallizer 12 to continue to participate in the crystal forming and grain control process.

[0067] Centrifuge 32 separates crude vitamin C with larger particle size and sends it to the next process. The mother liquor from the centrifugation and the clear liquid from the upper layer of the hydrocyclone first enter the mother liquor tank 33, and then return to the continuous recrystallizer 12 via the transfer pump 35 to continue participating in the crystal forming and crystal control process. Guronic acid and other salts do not precipitate crystals because they have not yet reached saturation.

[0068] In step 2), the absolute pressure during continuous recrystallization is controlled between 0.01 and 10 kPa, the recrystallization temperature range is between -5 and 45°C, and the temperature difference between each two connected crystallization chambers is 3 to 10°C.

[0069] According to the solubility table of vitamin C aqueous solution, the solubility of vitamin C decreases by approximately 7 g / L for every 1°C decrease in temperature. Therefore, the temperature difference between each two connected crystallization chambers needs to be set at 3–10°C to ensure that the solubility of vitamin C continuously decreases until saturated crystals precipitate. However, vitamin C is a heat-sensitive medium and is prone to decomposition when overheated. Therefore, the recrystallization temperature range needs to be controlled between -5 and 45°C to prevent thermal decomposition of vitamin C. The pressure should also be controlled at a low pressure between 0.01 and 10 kPa, as low pressure promotes solvent evaporation and solution concentration.

[0070] The recrystallization and recovery method for vitamin C mother liquor components is also applicable to the recovery of mother liquor components in vitamin C production using general acid conversion and alkali conversion methods.

[0071] The recrystallization recovery method for vitamin C mother liquor components of this application has wide applicability and can be used for the recovery of vitamin C mother liquor with different components.

[0072] The working principle of this invention is as follows: The concentration of vitamin C and other main substances in the solution is measured, and the number of stages of the continuous crystallizer, the vacuum degree of each stage, and the operating temperature are calculated and determined. If the temperature of the raw material solution is too low, it can be appropriately heated by heater 11. The solution temperature is continuously reduced by gradually increasing the vacuum degree of each stage chamber, while evaporation continues. The solvent removed includes a mixture of hydrochloric acid and water. The hydrochloric acid is condensed and recovered by the subsequent indirect condenser 21 for recycling. Simultaneously, the difference in vacuum level between each crystallization chamber is used as a driving force to propel the solution from the first-stage chamber to the nth stage. The process does not require external power (such as a pump). The concentration of vitamin C and other substances in the mother liquor is gradually increased by utilizing the principle of temperature gradient, while ensuring that the solution temperature is always controlled at a relatively stable state for vitamin C, until vitamin C crystals continuously precipitate out, forming a supersaturated concentrate. In order to keep the supersaturated vitamin C solution in a suspended state and maintain the crystal particles at a suitable size, a gas distribution mixer 122 is designed at the bottom of the crystallizer chamber. The state of the crystals is controlled by air flotation to prevent crystal deposition. At the same time, according to the degree of crystallization in different chambers, the number and size of the crystals are adjusted by controlling the number and size of the distribution holes on the gas distributor. Gas distribution mixers are divided into horizontal and spiral types. In the horizontal distributor 1221, the gas moves upward after leaving the small holes in the gas flow pipe, and the bubbles carry the crystal particles in vertical motion. In the spiral distributor 1222, the gas flow moves tangentially along the small holes in the gas flow pipe, causing the particles to rotate in the solution, making the particles closer to spherical and more uniform in size. Moreover, the combination of the two types of gas distribution mixers can significantly reduce the existence of dead zones in the stirring. After the solution has crystallized, it is pumped into the hydrocyclone separator 31 by the salt slurry pump 34. The initial separation is carried out by centrifugal force. The clear liquid in the upper layer, which contains more small crystal particles, is returned to the continuous recrystallizer 12. The lower layer, which is a supersaturated solution with a higher concentration, enters the centrifuge 32 to separate crude vitamin C. The mother liquor from the centrifuge and the clear liquid in the upper layer of the hydrocyclone separator enter the mother liquor tank together, and then return to the continuous recrystallizer 12 by the transfer pump 35 to continue to participate in the crystal forming and grain control process, which is beneficial to improving the quality of the crystallized product.

[0073] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0074] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A recrystallization and recovery device for vitamin C mother liquor components, characterized in that: The recrystallization recovery device includes a concentration mechanism (1), a recovery mechanism (2) and a collection mechanism (3). The concentration mechanism (1) is connected to the recovery mechanism (2) and the collection mechanism (3). The concentration mechanism (1) is used to evaporate and concentrate the mother liquor. The recovery mechanism (2) is used to recover the hydrochloric acid produced by evaporation. The collection mechanism (3) is used to separate crude vitamin C from the solution. The concentration mechanism (1) includes a heater (11) and a continuous recrystallizer (12). The outlet of the heater (11) is connected to the continuous recrystallizer (12). The continuous recrystallizer (12) is connected to the recovery mechanism (2) and the collection mechanism (3). The continuous recrystallizer (12) is divided into multiple crystallization chambers with different volumes. The crystallization chambers are connected to each other through arc holes (121). The number of crystallization chambers is n, where n≥3. The bottom of the crystallization chamber is provided with a gas distribution mixer (122), which is used to prevent crystal deposition. The gas distribution mixer (122) includes a horizontal distributor (1221) and a spiral distributor (1222). The recycling mechanism (2) includes a partition wall condenser (21), a vacuum system (22), and a storage tank (23). The partition wall condenser (21) is connected to the continuous recrystallizer (12) and is adapted to the crystallization chamber. The vacuum system (22) is connected to the partition wall condenser (21), and the storage tank (23) is connected to the outlet of the partition wall condenser (21).

2. The recrystallization and recovery device for vitamin C mother liquor components according to claim 1, characterized in that: The collection mechanism (3) includes a hydrocyclone separator (31), a centrifuge (32), a mother liquor tank (33), a slurry pump (34), and a transfer pump (35). The inlet of the slurry pump (34) is connected to the outlet of the continuous recrystallizer (12), and the outlet of the slurry pump (34) is connected to the hydrocyclone separator (31). The two outlets of the hydrocyclone separator (31) are connected to the centrifuge (32) and the mother liquor tank (33), respectively. The inlet of the transfer pump (35) is connected to the mother liquor tank (33), and the outlet of the transfer pump (35) is connected to the continuous recrystallizer (12).

3. A method for recrystallizing and recovering components from vitamin C mother liquor, based on the recrystallization and recovery apparatus for vitamin C mother liquor components as described in claim 2, characterized in that: The method includes the following steps: 1) Determine the content of the main components of the concentrated mother liquor and calculate and determine the size and crystallization level of the continuous recrystallizer (12); 2) The concentrated mother liquor is fed into the crystallization chamber of the continuous recrystallizer (12) for continuous recrystallization, and the temperature of the fed concentrated mother liquor is controlled within a suitable range by the heater (11), and crystal deposition is prevented by the gas distribution mixer (122). 3) The hydrochloric acid vapor generated by evaporation in the continuous recrystallizer (12) is condensed by the indirect condenser (21) to recover the hydrochloric acid; 4) The supersaturated crystallization slurry generated by the continuous recrystallizer (12) is sent to the hydrocyclone separator (31) for separation by the salt slurry pump (34). The upper clear liquid after centrifugation overflows to the mother liquor tank (33), and the lower high-concentration slurry enters the centrifuge (32). 5) The centrifuge (32) separates the large-particle-size crude vitamin C into the next process. The mother liquor from the centrifuge and the clear liquid from the upper layer of the hydrocyclone (31) are returned to the continuous recrystallizer (12) to continue to participate in the crystal forming and grain control process.

4. The method for recrystallization and recovery of vitamin C mother liquor components according to claim 3, characterized in that: In step 2), the absolute pressure during continuous recrystallization is controlled between 0.01 and 10 kPa, the recrystallization temperature range is between -5 and 45°C, and the temperature difference between each two connected crystallization chambers is 3 to 10°C.

5. The method for recrystallization and recovery of vitamin C mother liquor components according to claim 4, characterized in that: The recrystallization and recovery method for vitamin C mother liquor components is also applicable to the recovery of mother liquor components from vitamin C production via acid conversion and alkali conversion methods.

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