Extraction process for separating and purifying sodium gluconate

Abstract

The application belongs to the technical field of sodium gluconate preparation, and specifically provides a sodium gluconate separation, purification and extraction process, which comprises the following steps: S1, sodium gluconate solution preparation; S2, mixing the sodium gluconate solution obtained in step S1 and sodium gluconate mother liquor with deionized water, adding activated carbon for treatment, and filtering through a nanofiltration membrane to obtain a mixed solution; S3, evaporating and concentrating the mixed solution obtained in S2, and then cooling to obtain a mixture of sodium gluconate crystals and sodium gluconate mother liquor; S4, washing and separating the mixture obtained in S3 with softened water to recycle the sodium gluconate mother liquor, and collecting the sodium gluconate crystals; and S5, adopting a three-stage centrifugal washing system, using a compounded viscosity reducer for washing in a first-stage centrifugal machine, using 60 DEG C softened water for washing in a second-stage centrifugal machine, and using 5 DEG C deionized water for cold washing in a third-stage centrifugal machine; and recycling the water from the third-stage centrifugal machine for dilution of the solution in S2. Through the above process, the by-products and raw materials generated in the process can be fully recycled.

Description

Technical Field

[0001] This invention relates to the field of sodium gluconate preparation technology, and in particular to the process of separating, purifying and extracting sodium gluconate. Background Technology

[0002] Sodium gluconate, as an important organic acid sodium salt, is widely used in building retarders, food additives, pharmaceutical raw materials, and industrial cleaning agents. Currently, the mainstream production process is mainly based on biological fermentation, which uses corn starch as raw material, and produces sodium gluconate solution through liquefaction, saccharification, and fermentation with Aspergillus niger, followed by decolorization, crystallization, separation, and purification to obtain the finished product.

[0003] The main industrial methods for producing sodium gluconate include fermentation, enzyme catalysis, and chemical oxidation. Among these, fermentation is the most traditional method. It uses glucose-containing substances such as corn and grains as raw materials, and uses Aspergillus niger to ferment and produce glucose oxidase. Under oxygen-supplying conditions, glucose is dehydrogenated and oxidized to gluconolactone, which is then decomposed to obtain gluconic acid. Finally, sodium gluconate is obtained through a neutralization reaction with sodium hydroxide.

[0004] The obtained sodium gluconate requires crystallization, separation, and washing to produce sodium gluconate crystals. Crystallization and post-processing are critical steps affecting product quality and production costs. Current sodium gluconate production technologies generally suffer from high consumption, difficulties in mother liquor treatment, and unstable product quality. Summary of the Invention

[0005] To address the aforementioned shortcomings, this invention provides a sodium gluconate separation, purification, and extraction process that can fully reuse byproducts and raw materials generated during the sodium gluconate extraction process, thereby reducing their consumption.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a sodium gluconate separation, purification, and extraction process, comprising:

[0007] S1: Preparation of sodium gluconate solution: Corn starch is slurried to obtain starch milk, and then the starch milk is liquefied and saccharified to obtain saccharified liquid. The saccharified liquid is adjusted to neutral in a fermenter, and then inoculated with Aspergillus niger and fermented under aerobic conditions to obtain sodium gluconate solution.

[0008] S2: Decolorization and filtration: The sodium gluconate solution and sodium gluconate mother liquor obtained in step S1 are mixed with deionized water at a mass ratio of 2:1, activated carbon is added for treatment, and the mixture is filtered through a nanofiltration membrane to obtain the mixed solution.

[0009] S3: Evaporation and crystallization: The mixture obtained in S2 is transferred to a vacuum cooling crystallizer, evaporated and concentrated to a solid-liquid ratio of 50wt%, cooled to 45℃ and kept at that temperature for 1h to obtain a mixture of sodium gluconate crystals and sodium gluconate mother liquor.

[0010] S4: Primary separation: The sodium gluconate crystals obtained in S3 and the sodium gluconate mother liquor are mixed and fed into a centrifuge. Softened water at 25°C is added for washing and centrifugation. The sodium gluconate crystals are collected and the separated sodium gluconate mother liquor is returned to S2 for remixing and recycling.

[0011] S5: Crystal purification: Employs a three-stage series centrifugal washing system, in which:

[0012] The first-stage centrifuge is washed with a compound anti-viscosity agent at 25℃;

[0013] The secondary centrifuge is washed with 60℃ softened water, and the effluent from the secondary centrifuge is reused to separate the sodium gluconate mother liquor.

[0014] The three-stage centrifuge is washed with 5°C deionized water, and the effluent from the three-stage centrifuge is reused for diluting the S2 solution.

[0015] As a further improvement of the present invention, S2 specifically includes:

[0016] S201: Mix sodium gluconate solution and sodium gluconate mother liquor with deionized water at a ratio of 2:1. The deionized water needs to be preheated to 50-55℃, and the temperature should also be controlled at 50-55℃ during the mixing process. The goal is to achieve a solid content of 8-12wt% in the diluted solution after mixing.

[0017] As a further improvement of the present invention, S2 further includes:

[0018] S202: Add 1-2 wt% activated carbon relative to the total weight of the diluent to the mixture, heat to 70°C and maintain for 40-50 minutes, then filter through a nanofiltration membrane to obtain the mixture.

[0019] As a further improvement of the present invention, the vacuum evaporation temperature of the vacuum cooling crystallizer in S3 is 70-80℃, and the vacuum degree is 0.07-0.09MPa.

[0020] As a further improvement of the present invention, the cooling rate in S3 is 1.5-2℃ / h.

[0021] As a further improvement of the present invention, the speed of the first-stage centrifuge is 4000 rpm, the speed of the second-stage centrifuge is 2500 rpm, and the speed of the third-stage centrifuge is 1500 rpm.

[0022] As a further improvement of the present invention, the compound viscosity reducer is prepared by mixing 0.1% sodium polyacrylate and 0.05% corn steep liquor supernatant with deionized water.

[0023] The beneficial effects of this invention are:

[0024] 1. The separated sodium gluconate mother liquor is returned to the decolorization and filtration process for reuse. The softened water used in the secondary centrifugal washing is used for the separation of sodium gluconate and sodium gluconate mother liquor in subsequent batches. The deionized water used in the tertiary centrifugal washing is used for the slurry preparation process in subsequent batches. Through the above-mentioned recycling of sodium gluconate mother liquor and reuse of washing water, the consumption of raw materials is reduced and the internal circulation of resources is realized.

[0025] 2. A three-stage differential centrifugal gradient washing process is adopted, which, combined with the temperature difference between the second and third stages of washing, removes large particle residues, heat-sensitive impurities, and surface-adhered impurities, thereby improving product purity and light transmittance. At the same time, 0.1% sodium polyacrylate and 0.05% corn steep liquor compounding agent are added during the first stage of centrifugation to fully remove impurities and significantly improve washing efficiency. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] This invention provides a process for the separation, purification, and extraction of sodium gluconate, comprising:

[0028] S1: Preparation of sodium gluconate solution.

[0029] S100: Corn starch slurry preparation. Corn starch and amylase are added to a mixing tank to prepare a starch slurry.

[0030] S101: Liquefaction and saccharification of starch milk. The pH of the starch milk is adjusted to acidic by using an acidic solution in a mixing tank, and then saccharifying enzyme is added to obtain a saccharified solution.

[0031] S102: Fermentation of saccharified liquid. The saccharified liquid is introduced into a fermenter and adjusted to neutral by an alkaline solution. Then, gluconate bacteria (Aspergillus niger) are added and fermented under aerobic conditions to obtain sodium gluconate solution.

[0032] As a further explanation of this embodiment, the preparation of sodium gluconate solution is a conventional technical method.

[0033] S2: Decolorization and filtration of sodium gluconate solution.

[0034] S201: Mix sodium gluconate solution and sodium gluconate mother liquor produced in production with deionized water. The mass ratio between sodium gluconate solution and sodium gluconate mother liquor is 2:1. The deionized water needs to be preheated to 50-55℃, and the temperature is also controlled at 50-55℃ during the mixing process. The target is that the solid content of the diluted solution after mixing is 8-12wt%.

[0035] S202: Add 1-2 wt% activated carbon relative to the total weight of the diluent to the mixture, heat to 70°C, maintain for 40-50 minutes, and then filter through a nanofiltration membrane to obtain the mixture.

[0036] S3: Sodium gluconate evaporated and crystallized.

[0037] The mixture is transferred to a vacuum cooling crystallizer. The vacuum evaporation temperature of the vacuum cooling crystallizer is 70-80 degrees Celsius, and the vacuum degree is 0.07-0.09 MPa. The mixture is concentrated through vacuum evaporation until the solid-liquid ratio is 50 wt%. Then, the temperature is lowered at a rate of 1.5-2℃ / h until it reaches 45℃. After cooling, the mixture is kept at this temperature for 1 hour to produce a mixture of sodium gluconate crystals and sodium gluconate mother liquor.

[0038] S4: Separation of sodium gluconate.

[0039] The mixture of sodium gluconate crystals and sodium gluconate mother liquor obtained in S3 is passed into a centrifuge. Then, softened water at 25°C is sprayed into the centrifuge for washing. Through centrifugation, the sodium gluconate mother liquor is separated from the sodium gluconate crystals and collected in a sodium gluconate mother liquor tank. The separated sodium gluconate mother liquor is returned to S2 for remixing and recycling.

[0040] S5: Purification of sodium gluconate crystals.

[0041] Sodium gluconate crystals were subjected to a three-stage series centrifugal washing process, with each stage using a differential speed gradient wash:

[0042] First-stage centrifuge: At a high speed of 4000 rpm, a compound anti-viscosity agent made of 0.1% sodium polyacrylate and 0.05% corn steep liquor supernatant and deionized water is used to clean the centrifuge at 25°C to remove large particulate impurities and insoluble residues.

[0043] As a further explanation of this embodiment, sodium polyacrylate can reduce impurity adhesion and thus peel off particles, while corn steep liquor can inhibit crystal disintegration.

[0044] Secondary centrifuge: Cleaned at a medium speed of 2500 rpm with softened water at 60℃ to dissolve heat-sensitive impurities; the effluent from the secondary centrifuge is reused to separate the sodium gluconate mother liquor.

[0045] Three-stage centrifuge: cold washing is performed at a low speed of 1500 rpm using deionized water at 5°C. The temperature difference with the two-stage centrifugal washing causes the impurities coating the crystal surface to shrink and peel off. The deionized water used in the three-stage centrifuge can also be used in S201 to mix sodium gluconate solution with deionized water.

[0046] Sodium gluconate crystals were obtained as wet material after three-stage centrifugal washing.

[0047] Example 1

[0048] S1: Prepared from sodium gluconate solution.

[0049] S100: Corn starch and amylase are added to a mixing tank to prepare starch milk.

[0050] S101: Adjust the pH of starch milk to 5.8 with dilute sulfuric acid, add 0.1 wt% saccharifying enzyme, and saccharify at 60℃ for 24 hours to obtain saccharified solution.

[0051] S102: The saccharified liquid is pumped into the fermenter, and the pH is adjusted to 7.0 with NaOH solution. Aspergillus niger seed culture is inoculated, sterile air is introduced, and fermentation is carried out at 35°C for 48 hours to obtain sodium gluconate solution.

[0052] S2: Decolorization filtration.

[0053] S201: Add deionized water preheated to 52°C to the sodium gluconate solution obtained in S102 and the sodium gluconate mother liquor produced in the production process, and mix. Maintain the mixing temperature between 50-55°C and dilute to a solid content of 10 wt%.

[0054] S202: Add activated carbon at 1.5 wt% relative to the total weight of the diluent, heat to 70°C, and stir for 45 minutes. Filter through a 0.1 μm nanofiltration membrane to obtain a clear decolorized solution.

[0055] S3: Sodium gluconate evaporated and crystallized.

[0056] The decolorizing solution was transferred to a vacuum cooling crystallizer. The evaporation temperature was 75℃, the vacuum degree was set to 0.08MPa, and the solution was concentrated to a solid-liquid ratio of 50 wt%. Then, the temperature was lowered to 45℃ at a rate of 1.8℃ / h, and the solution was kept at this temperature for 1 hour to grow crystals, resulting in a mixture of sodium gluconate crystals and sodium gluconate mother liquor.

[0057] S4: Separation of sodium gluconate.

[0058] The mixture of sodium gluconate crystals and sodium gluconate mother liquor is pumped into a horizontal screw centrifuge for solid-liquid separation. During separation, an appropriate amount of 25°C softened water is sprayed in for washing. The sodium gluconate mother liquor is collected in a sodium gluconate mother liquor tank. The separated wet crystals proceed to the purification step. The sodium gluconate mother liquor is returned to the next batch in step S201.

[0059] S5: Three-stage series centrifugal washing.

[0060] First-stage centrifuge: Wet crystals enter a first-stage horizontal screw centrifuge with a rotation speed of 4000 rpm, and a compound anti-viscosity agent containing 0.1% sodium polyacrylate and 0.05% corn steep liquor supernatant at 25℃ is sprayed in to complete the first-stage washing of the crystals.

[0061] Secondary centrifuge: After primary washing, the crystals enter a secondary horizontal screw centrifuge at 2500 rpm. Softened water at 60℃ is sprayed in for rinsing, completing the secondary washing process.

[0062] Three-stage centrifuge: After two-stage washing, the crystals enter a three-stage horizontal screw centrifuge at 1500 rpm. Cold washing with 5°C deionized water is then performed. The deionized water from the three-stage centrifugation wash is collected and used for adding deionized water before preheating in the S201 step of the next batch.

[0063] After three stages of washing, high-purity sodium gluconate crystal wet material is obtained.

[0064] Results: After drying, the final wet crystals showed a sodium gluconate product with a purity of 99.5%, a transmittance of 98%, a solubility of 59 g / 100 ml in water at 25°C, and a whiteness of 95%. No significant negative impact from impurity accumulation was observed during the recycling of the sodium gluconate mother liquor.

[0065] Comparative Example 1 (Three-stage washing is omitted, only single-stage washing is performed)

[0066] Process change: The three-stage series centrifugal washing in S5 is omitted. The wet crystals separated in S4 are directly washed once with room temperature softened water in a single centrifuge at 2500 rpm. The amount of washing water is equivalent to the total amount of water used in the three stages in Example 1.

[0067] Results: After drying, the purity of the final wet crystals, sodium gluconate, decreased to 95.8%, transmittance to 92%, and whiteness to 90%. Microscopic observation revealed numerous impurities adhering to the crystal surface. Solubility decreased slightly to 58 g / 100 ml. This indicates that single-stage washing is ineffective in removing impurities of different types and adhering patterns.

[0068] Comparative Example 2 (Replacing / Removing the Compound Tack Reducer)

[0069] Process change: During the S5 primary centrifuge washing process, the compound viscosity reducer was replaced with:

[0070] Option A: Use only an equal amount of 0.1% sodium polyacrylate solution at 25℃.

[0071] Option B: Use only an equal volume of 0.05% corn steep liquor supernatant solution at 25℃.

[0072] Option C: Use only an equal amount of deionized water at 25℃.

[0073] result:

[0074] Option A: After drying, the final wet crystals yielded a sodium gluconate product with a purity of 97.5%, a transmittance of 95%, and a whiteness of 95%. Microscopic observation revealed that some large particulate impurities were not completely removed. The purity, transmittance, and whiteness of the final product were all lower than those in Example 1.

[0075] Option B: After drying, the final wet crystals yielded a sodium gluconate product with a purity of 96.2%, a transmittance of 96%, and a whiteness of 94%. No significant negative impact from impurity accumulation was observed during the recycling of the sodium gluconate mother liquor. Microscopic observation revealed incomplete removal of some large particulate impurities, resulting in lower purity, transmittance, and whiteness of the final product compared to Example 1.

[0076] Option C: After drying, the final wet crystals have a sodium gluconate purity of 97.1%, a light transmittance of 94%, and a whiteness of 92%.

[0077] The purity, transmittance, and whiteness of the product in Comparative Example 2 were significantly lower than those in Example 1. This demonstrates that sodium polyacrylate and corn steep liquor supernatant in the compound viscosity reducer have a synergistic effect.

[0078] Comparative Example 3 (Changing the three-stage washing temperature gradient)

[0079] Process Change: In step S5, the temperature is changed:

[0080] Option D: Use 25℃ softened water for the second stage of washing.

[0081] Option E: Replace the three-stage washing process with 40℃ deionized water.

[0082] result:

[0083] Option D: Increased detection of heat-sensitive impurities in the product by high-temperature burning residue indicates an increase in the content of heat-sensitive impurities and a decrease in light transmittance to 94%.

[0084] Option E: Light transmittance is 96%, whiteness is 93%. Lower than Example 1. The surface smoothness of the crystal decreases, and tiny deposits are visible under a microscope.

[0085] Compared with Example 1, Comparative Example 3 showed that when the temperature gradient between the secondary and tertiary washing stages decreased, the transmittance and whiteness of sodium gluconate decreased, and the amount of impurities increased.

[0086] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above-described embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A process for separating, purifying, and extracting sodium gluconate, characterized in that, include: S1: Preparation of sodium gluconate solution: Corn starch is slurried to obtain starch milk, and then the starch milk is liquefied and saccharified to obtain saccharified liquid. The saccharified liquid is adjusted to neutral in a fermenter, and then inoculated with Aspergillus niger and fermented under aerobic conditions to obtain sodium gluconate solution. S2: Decolorization and filtration: The sodium gluconate solution and sodium gluconate mother liquor obtained in step S1 are mixed with deionized water at a mass ratio of 2:1, activated carbon is added for treatment, and the mixture is filtered through a nanofiltration membrane to obtain the mixed solution. S3: Evaporation and crystallization: The mixture obtained in S2 is transferred to a vacuum cooling crystallizer, evaporated and concentrated to a solid-liquid ratio of 50wt%, cooled to 45℃ and kept at that temperature for 1h to obtain a mixture of sodium gluconate crystals and sodium gluconate mother liquor. S4: Primary separation: The sodium gluconate crystals obtained in S3 and the sodium gluconate mother liquor are mixed and fed into a centrifuge. Softened water at 25°C is added for washing and centrifugation. The sodium gluconate crystals are collected and the separated sodium gluconate mother liquor is returned to S2 for remixing and recycling. S5: Crystal purification: Employs a three-stage series centrifugal washing system, in which: The primary centrifuge is washed with a compound anti-viscosity agent at 25°C. The compound anti-viscosity agent is prepared by mixing 0.1% sodium polyacrylate and 0.05% corn steep liquor supernatant with deionized water. The secondary centrifuge is washed with 60℃ softened water, and the effluent from the secondary centrifuge is reused to separate the sodium gluconate mother liquor. The three-stage centrifuge is washed with 5°C deionized water, and the effluent from the three-stage centrifuge is reused for diluting the S2 solution.

2. The sodium gluconate separation, purification, and extraction process according to claim 1, characterized in that, S2 specifically includes: S201: Mix sodium gluconate solution and sodium gluconate mother liquor with deionized water at a ratio of 2:

1. The deionized water needs to be preheated to 50-55℃, and the temperature should also be controlled at 50-55℃ during the mixing process. The goal is to achieve a solid content of 8-12wt% in the diluted solution after mixing.

3. The sodium gluconate separation, purification, and extraction process according to claim 2, characterized in that, S2 further includes: S202: Add 1-2 wt% activated carbon relative to the total weight of the diluent to the mixture, heat to 70°C and maintain for 40-50 minutes, then filter through a nanofiltration membrane to obtain the mixture.

4. The sodium gluconate separation, purification, and extraction process according to claim 1, characterized in that, The vacuum evaporation temperature of the vacuum cooling crystallizer in S3 is 70-80℃, and the vacuum degree is 0.07-0.09MPa.

5. The sodium gluconate separation, purification, and extraction process according to claim 1, characterized in that, The cooling rate in S3 is 1.5-2℃ / h.

6. The sodium gluconate separation, purification, and extraction process according to claim 1, characterized in that, The first-stage centrifuge has a rotation speed of 4000 rpm, the second-stage centrifuge has a rotation speed of 2500 rpm, and the third-stage centrifuge has a rotation speed of 1500 rpm.