Recycling method of waste mother liquor after erythritol crystallization

Abstract

The invention belongs to the technical field of erythritol recovery, and particularly relates to a method for recycling waste mother liquor after erythritol crystallization. The method comprises the following steps: filtering the waste mother liquor after erythritol crystallization by using a ceramic membrane, decolorizing, desalting, and carrying out chromatographic separation to obtain an erythritol solution; a hydrogen type chromatographic resin column is used for chromatographic separation. The method comprises the following steps: filtering the waste mother liquor to remove macromolecular substances, decolorizing, desalting, carrying out chromatographic separation to obtain an erythritol solution of which the mass content of erythritol is more than 95% in terms of dry matter, and concentrating and crystallizing or combining the erythritol solution with a stock solution to obtain an erythritol product of which the purity is more than 99.9%. According to the method, the total yield of erythritol exceeds 95%, and the product yield is high. According to the method, sewage discharge is effectively reduced, the erythritol yield is increased, the production cost is reduced, the environmental protection pressure can be relieved, the benefit can be increased, and the method has a huge promotion effect on the development of the erythritol industry.

Description

Technical Field

[0001] The invention belongs to the technical field of erythritol recovery, and particularly relates to a method for recovering waste mother liquor after erythritol crystallization. Background Art

[0002] Erythritol is a four-carbon sugar alcohol that is widely found in nature. Erythritol is a white crystalline powder with a refreshing sweet taste, high temperature resistance, and insensitive to pH changes. Erythritol has the advantages of high temperature stability, non-participation in human metabolism, anti-caries, antioxidant, and moisturizing properties. It has been widely used in beverages, baked goods, candies, desserts, medicine, and cosmetics.

[0003] At present, erythritol is mainly obtained by fermentation. The fermentation broth is filtered through multi-stage membranes and desalted by ion exchange to obtain the stock solution, and then the stock solution is concentrated and crystallized multiple times to obtain qualified erythritol products. The waste mother liquor produced after multiple crystallizations of erythritol has been repeatedly concentrated and crystallized to recover erythritol. Impurities are continuously enriched in the waste mother liquor. Finally, due to the interference of high-concentration impurities, part of the erythritol cannot be recovered again by crystallization, resulting in a decrease in yield. This part of the waste mother liquor contains pigments, 5wt%~10wt% protein, more than 10wt% sugars, and more than 35wt% erythritol. Direct discharge will greatly increase environmental pressure, and erythritol exceeding 5% of the total fermentation production will be lost with the waste mother liquor. If the waste mother liquor is not recycled, the erythritol yield is only between 90%~93%, and the production capacity is low.

[0004] At present, the waste mother liquor after multiple crystallization of erythritol is removed again by membrane filtration, ion exchange desalination, activated carbon decolorization and other means to recover erythritol. However, since most of the impurities in the waste mother liquor are substances that cannot be well removed by the above-mentioned means in the production of the original solution, the waste mother liquor is separated again according to the original solution method, the separation effect is poor and the yield of erythritol is low. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for recycling waste mother liquor after erythritol crystallization. The recycling method of the present invention can separate erythritol from impurities and improve the yield of erythritol.

[0006] The present invention provides a method for recycling waste mother liquor after erythritol crystallization, comprising the following steps: The waste mother liquor after the crystallization of erythritol is filtered through a ceramic membrane to obtain a first filtrate; Decolorizing and desalting the first filtrate to obtain a decolorized and desalted feed solution; The decolorized and desalted feed liquid is subjected to chromatographic separation to obtain an erythritol solution; the chromatographic separation uses a hydrogen-type chromatographic resin column; the erythritol solution has an erythritol mass content of ≥95% based on dry matter.

[0007] Preferably, the chromatographic separation uses 6 hydrogen-type chromatographic resin columns, which are sequentially recorded as 1# column to 6# column, and the height-to-diameter ratio of each hydrogen-type chromatographic resin column is 1.5:1. The chromatographic separation comprises the following steps: Step 1: Connect columns 1# to 5# in series, feed 0.23 BV of decolorized and desalted liquid from column 1# at a rate of 1.7 BV / h, and the material at the outlet of column 5# is recorded as the first material; Step 2: Connect columns 1# to 6# in series to form a closed loop, and run at a rate of 1.56 BV / h for 0.5h; Step 3: Connect columns 2# to 4# in series, add 0.28BV of water from column 2# at a rate of 1.7BV / h, and the material at the outlet of column 4# is recorded as the second material; add 0.22BV of water from column 5# at a rate of 1.6BV / h, and the material at the outlet of column 5# is recorded as the third material; The three steps are repeated in a cycle. Each time the series column number and the inlet and outlet column numbers are extended by one, the columns are repeated between the 1# column and the 6# column. The second material is erythritol solution.

[0008] Preferably, before the ceramic membrane filtration, the process also includes: adjusting the pH value of the waste mother liquor to 3.5-6.5, and heating; the heating temperature is 75-85°C.

[0009] Preferably, the pore size of the ceramic membrane is 20-200 nm.

[0010] Preferably, the decolorization is activated carbon decolorization, and the mass of the activated carbon in the activated carbon decolorization is 0.2% to 5% of the mass of the dry matter in the first filtrate.

[0011] Preferably, the desalination is ion exchange resin desalination, and the ion exchange resin desalination uses cation exchange resin and anion exchange resin, and the cation exchange resin is a strong acid cation exchange resin.

[0012] Preferably, the recycling method further comprises: The erythritol solution is concentrated, crystallized once, centrifuged, dissolved, decolorized, crystallized twice, and dried to obtain the first erythritol; Alternatively, the erythritol solution is mixed with the stock solution and then further processed to obtain the second erythritol; the stock solution is the feed solution obtained after the fermentation liquid is filtered through a ceramic membrane, filtered through a nanofiltration membrane, and subjected to ion exchange desalination treatment in sequence.

[0013] Preferably, the mass concentration of the concentrated material is 45% to 70%.

[0014] Preferably, the primary crystallization and the secondary crystallization are both cooling crystallization, the cooling rate of the cooling crystallization is 1-5°C / h, and the terminal temperature of the cooling crystallization is 20-25°C.

[0015] Preferably, the further treatment includes: concentration, primary crystallization, centrifugation, crystal dissolution, decolorization, secondary crystallization and drying.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The invention provides a method for recycling waste mother liquor after erythritol crystallization, comprising the following steps: filtering the waste mother liquor after erythritol crystallization by using a ceramic membrane to obtain a first filtrate; decolorizing and desalting the first filtrate to obtain a decolorized and desalted feed liquid; performing chromatographic separation on the decolorized and desalted feed liquid to obtain an erythritol solution; the chromatographic separation uses a hydrogen-type chromatographic resin column; and the erythritol solution has an erythritol mass content of ≥95% based on dry matter.

[0017] The invention filters the waste mother liquor to be treated to remove the macromolecular substances in the waste mother liquor, and then performs chromatographic separation after decolorization and desalination, extracts and separates erythritol in the waste mother liquor in one step, and obtains an erythritol solution, the mass content of erythritol in terms of dry matter is more than 95%, and the erythritol solution is concentrated and crystallized, or the erythritol solution is combined with the original solution for treatment, so as to obtain an erythritol product with a purity of more than 99.9%. The invention can make the total yield of erythritol exceed 95%, and the product yield is high. Moreover, the erythritol product obtained by the invention has high purity.

[0018] The present invention can effectively extract erythritol from waste mother liquor at a lower extraction cost through chromatographic separation. The present invention can increase the yield of erythritol, reduce costs, increase profits, and reduce environmental pressure. The promotion of the present invention can greatly promote the development of the erythritol industry. DETAILED DESCRIPTION

[0019] The present invention provides a method for recycling waste mother liquor after erythritol crystallization, comprising the following steps: The waste mother liquor after the crystallization of erythritol is filtered through a ceramic membrane to obtain a first filtrate; Decolorizing and desalting the first filtrate to obtain a decolorized and desalted feed solution; The decolorized and desalted feed liquid is subjected to chromatographic separation to obtain an erythritol solution; the chromatographic separation uses a hydrogen-type chromatographic resin column; the erythritol solution has an erythritol mass content of ≥95% based on dry matter.

[0020] In the present invention, unless otherwise specified, the materials and equipment used are commercially available products in the art.

[0021] The invention uses a ceramic membrane to filter the waste mother liquor after erythritol crystallization to obtain a first filtrate.

[0022] In the present invention, the waste mother liquor after erythritol crystallization is the feed liquid after the original liquid has been crystallized multiple times, and the original liquid is the feed liquid obtained after the fermentation liquid is filtered through a ceramic membrane, filtered through a nanofiltration membrane, and treated with ion exchange desalination in sequence. The number of multiple crystallizations is preferably 3 to 5 times, and specifically can be 4 times.

[0023] In the present invention, the dry matter mass content in the waste mother liquor after erythritol crystallization is about 60%, including 35%-45% erythritol, 10%-15% reducing sugar, 5%-10% protein, 3%-5% ribitol and mannitol, 2% inorganic salt, and also contains pigments and unknown components.

[0024] In the present invention, the ceramic membrane filtration further comprises: adjusting the pH value of the waste mother liquor to 3.5-6.5 and heating. The pH value is preferably 5-5.5; the heating temperature is preferably 75-85°C, specifically 80°C, and the heating serves to denature the protein in the waste mother liquor.

[0025] In the present invention, the membrane inlet pressure of the ceramic membrane filtration is preferably 2-15 bar, specifically 10 bar or 15 bar, and the transmembrane pressure difference is preferably 0-6 bar, specifically 5 bar. The temperature of the waste mother liquor during the filtration is preferably 50-55°C.

[0026] In the present invention, the pore size of the ceramic membrane is preferably 20-200 nm, and specifically can be 50 nm. The function of the ceramic membrane filtration is to remove macromolecular substances, including proteins.

[0027] After obtaining the first filtrate, the present invention decolorizes and desalinates the first filtrate to obtain a decolorized and desalted feed solution.

[0028] In the present invention, the decolorization is preferably activated carbon decolorization, and the mass of the activated carbon in the activated carbon decolorization is preferably 0.2%~5% of the mass of the dry matter in the first filtrate, specifically 2% or 3%; the temperature of the activated carbon decolorization is preferably 55~85°C, specifically 60°C, and the time is preferably 0.5~2h, specifically 1h.

[0029] In the present invention, the decolorization further includes solid-liquid separation, and the solid-liquid separation method is preferably plate and frame filtration to remove activated carbon.

[0030] In the present invention, the desalination is preferably ion exchange resin desalination, and the ion exchange resin desalination preferably uses cation exchange resin and anion exchange resin. The cation exchange resin is preferably a strong acid cation exchange resin, which can be Wandong 001×7 (732) or Zhengguang ZGD001-FD; the anion exchange resin is preferably a strong base or weak base anion exchange resin, the strong base anion exchange resin can be Wandong D201, and the weak base anion exchange resin can be Zhengguang ZGD354-FD.

[0031] In the present invention, the desalination process preferably controls the conductivity of the feed solution to be below 200 μm / cm, specifically below 50 μm / cm, and the chromaticity to be below 100.

[0032] After obtaining the decolorized and desalted feed liquid, the present invention performs chromatographic separation on the decolorized and desalted feed liquid to obtain an erythritol solution; the chromatographic separation uses a hydrogen-type chromatographic resin column; the erythritol solution, calculated on a dry matter basis, has an erythritol mass content of ≥95%.

[0033] In the present invention, the hydrogen-type chromatographic resin column is preferably obtained by acidifying the sodium-type chromatographic separation resin with hydrochloric acid and then filling it.

[0034] In the present invention, the chromatographic separation preferably uses 6 hydrogen-type chromatographic resin columns, which are sequentially recorded as 1# column to 6# column, and the height-to-diameter ratio of each hydrogen-type chromatographic resin column is preferably 1.5:1. The chromatographic separation preferably includes the following steps: Step 1: Connect columns 1# to 5# in series, feed 0.23 BV of decolorized and desalted liquid from column 1# at a rate of 1.7 BV / h, and the material at the outlet of column 5# is recorded as the first material; Step 2: Connect columns 1# to 6# in series to form a closed loop, and run at a rate of 1.56 BV / h for 0.5h; Step 3: Connect columns 2# to 4# in series, add 0.28BV of water from column 2# at a rate of 1.7BV / h, and the material at the outlet of column 4# is recorded as the second material; add 0.22BV of water from column 5# at a rate of 1.6BV / h, and the material at the outlet of column 5# is recorded as the third material; The three steps are repeated in a cycle. Each time the column number and the inlet and outlet column numbers are connected in series, the columns are extended by one, and the columns are repeated between columns 1# and 6#. The second material is erythritol solution. The first material and the third material are waste liquids containing impurities.

[0035] After the decolorized and desalted feed liquid enters the chromatographic column, the different substances migrate at different rates in the chromatographic resin column, thereby separating the pure erythritol. The chromatographic separation conditions of the present invention can separate erythritol from other impurities to obtain an erythritol solution with an erythritol mass content of more than 95% in dry matter. Moreover, the chromatographic separation method of the present invention has a small water consumption ratio, and the water consumption per unit volume of material is only about 2.2.

[0036] In the present invention, the recycling method preferably further comprises: The erythritol solution is concentrated, crystallized once, centrifuged, dissolved, decolorized, crystallized twice, and dried to obtain the first erythritol; Alternatively, the erythritol solution is mixed with the stock solution and further processed to obtain the second erythritol; the stock solution is the feed solution obtained after the fermentation liquid is sequentially filtered through a ceramic membrane, a nanofiltration membrane, and ion exchange desalination.

[0037] In the present invention, the further treatment of mixing the erythritol solution with the stock solution preferably includes: concentration, primary crystallization, centrifugation, crystal dissolution, decolorization, secondary crystallization, and drying.

[0038] In the present invention, the concentration is preferably carried out by using an evaporator, and the evaporator preferably includes a multiple-effect plate evaporator, a multiple-effect rising film evaporator or a multiple-effect falling film evaporator.

[0039] In the present invention, the concentration temperature is preferably 73-80° C., and the pressure is preferably -0.095 MPa.

[0040] In the present invention, the mass concentration of the concentrated material is preferably 45% to 70%, specifically 60%, and the density is preferably 1.185 to 1.19 g / cm 3 .

[0041] In the present invention, the primary crystallization or the secondary crystallization is preferably a cooling crystallization, and the cooling rate of the cooling crystallization is preferably 1-5°C / h, specifically 1-2°C / h or 2-5°C / h; the cooling crystallization process is preferably accompanied by stirring, and the stirring speed is preferably 30rpm or 50rpm; the terminal temperature of the cooling crystallization is preferably 20-25°C.

[0042] In the present invention, the centrifugation preferably adopts a horizontal spiral centrifuge or a flat scraper bottom discharge centrifuge. The crystal dissolution preferably adopts 4°C pure water, and the mass concentration of erythritol in the solution obtained by the crystal dissolution is preferably 55%~60% (W / V), specifically 55% or 58%. The decolorization is preferably activated carbon decolorization, and the mass of activated carbon in the activated carbon decolorization is preferably 0.5%~1% of the dry matter mass, the temperature of the activated carbon decolorization is preferably 70°C, and the processing time is preferably 60min. The drying is preferably 105°C hot air drying, and the drying is preferably carried out using a boiling fluidized bed.

[0043] In the present invention, the purity of the first erythritol and the second erythritol is independently above 99.9%.

[0044] In order to further illustrate the present invention, the method for recycling the waste mother liquor after erythritol crystallization provided by the present invention is described in detail below in conjunction with the examples, but they should not be understood as limiting the scope of protection of the present invention.

[0045] In the embodiment of the present invention, the erythritol waste mother liquor used is the effluent mother liquor after four crystallizations in the erythritol industrial production workshop, containing about 60% dry matter, including about 37% erythritol, 11% reducing sugar, 7% protein, 4% ribitol and mannitol, 2% inorganic salts, and a large amount of pigments and other unknown components.

[0046] Example 1 The pH value of the erythritol waste liquor was adjusted to 5.0 and heated to 75°C to denature the protein therein. After the temperature dropped to 50°C, the filtrate was filtered using a 50nm ceramic membrane at an inlet pressure of 10 bar and a transmembrane pressure difference of 5 bar, and the filtrate was collected.

[0047] To the obtained filtrate, add 3% of the total dry matter weight of the material activated carbon powder, maintain at 60°C for 1 hour for decolorization. After the decolorization is completed, the material is filtered through a plate and frame, and the filtrate is collected.

[0048] The filtrate obtained after decolorization is desalted by using Wandong 001×7 (732) strong acid cation exchange resin and Wandong D201 strong basic anion exchange resin in sequence, and further decolorized at the same time. The conductivity of the material after desalination is controlled to be below 50μm / cm and the chromaticity is below 100 to obtain a decolorized and desalted feed solution.

[0049] The sodium type chromatographic separation resin ZGSPC106Na was converted into hydrogen type chromatographic separation resin with hydrochloric acid and filled into 6 chromatographic columns in the chromatographic separation system. The height-to-diameter ratio of the chromatographic columns was 1.5:1. The columns were connected by pipeline valves, and the material, water and column temperature were maintained at 60±1°C.

[0050] The chromatographic separation process proceeds in a cycle of three steps: Step 1: Connect columns 1# to 5# in series, feed 0.23 BV of decolorized and desalted liquid from column 1# at a rate of 1.7 BV / h, and the material at the outlet of column 5# is recorded as the first material; Step 2: Connect the 6 chromatographic columns from 1# to 6# in series to form a closed loop and run at a rate of 1.56 BV / h for 0.5h; Step 3: Connect columns 2# to 4# in series, add 0.28BV of water from column 2# at a rate of 1.7BV / h, and the material at the outlet of column 4# is recorded as the second material; add 0.22BV of water from column 5# at a rate of 1.6BV / h, and the material at the outlet of column 5# is recorded as the third material; Each time the three steps are cycled, the serial column number and the inlet and outlet column numbers are extended by one, and the cycle is repeated between columns 1# to 6#.

[0051] Different substances migrate at different rates in the chromatographic resin to separate erythritol from other impurities. When the chromatographic column starts running, the three materials are all discharged as water. Repeat the above process, and the concentration of the three materials gradually increases until it stabilizes. The first material and the third material are waste liquids containing impurities, and the second material is an erythritol solution. The erythritol mass content is ≥95% based on dry matter.

[0052] The collected erythritol solution was concentrated using a triple-effect MVR evaporator, with a concentrated discharge temperature of 75°C and a discharge concentration of 60%.

[0053] Using 10m 3 The crystallizer cools and crystallizes the material discharged from the evaporator: stirring frequency is 50 rpm, cooling rate is 2~5℃ / h, and the crystallization discharge temperature is 25℃.

[0054] The crystal slurry after crystallization is centrifuged using a horizontal spiral centrifuge to obtain liquid and wet crystals: The liquid is concentrated and recrystallized, the liquid obtained by recrystallization is mixed into the filtrate obtained by ceramic membrane filtration for reuse, and the wet crystals obtained by recrystallization are mixed into the erythritol solution after chromatographic separation for reuse; The wet crystals were dissolved in pure water to a mass concentration of 60%, and activated carbon powder was added at 1% of the dry matter mass for decolorization. After decolorization, the Ama filter was used for decarbonization. The decolorized material was reused for 10m 3 The crystallizer is cooled and crystallized, and the crystals are separated by a flat scraper bottom discharge centrifuge. The liquid obtained by centrifugation is mixed into the decolorization and desalination liquid before chromatographic separation for reuse. The wet crystals are dried in a fluidized bed, sieved by a swing sieve, iron removed, and packaged to obtain the erythritol product.

[0055] According to the national standard test method for erythritol (GB 26404-2011 Food Safety National Standard Food Additive Erythritol), the test results of various indicators of the erythritol product obtained in Example 1 are as follows in Table 1: Table 1 Test results of various indicators of the erythritol product obtained in Example 1

[0056] It can be seen that the purity of the erythritol product exceeds 99.9%, and the recovery rate is calculated according to: (total mass of recovered erythritol ÷ total mass of erythritol in the initial waste mother liquor) * 100%. The recovery rate of erythritol in the waste mother liquor of this embodiment reaches 91.3%.

[0057] Example 2 The pH value of the waste mother liquor was adjusted to 5.5 and heated to 80°C to denature the protein therein. After the material temperature was reduced to 55°C using a plate heat exchanger, the material was filtered using a 50nm ceramic membrane at an inlet pressure of 15 bar and a transmembrane pressure difference of 5 bar, and the filtrate was collected.

[0058] To the obtained filtrate, add 2% of the total dry matter weight of the material activated carbon powder, maintain at 60°C for 1 hour for decolorization. After the decolorization is completed, the material is filtered through a plate and frame, and the filtrate is collected.

[0059] The filtrate obtained after decolorization is desalted by Zhengguang ZGD001-FD strong acid cation exchange resin and Zhengguang ZGD354-FD weak base anion exchange resin in turn, and further decolorized at the same time. The conductivity of the material after desalination is controlled to be below 50μm / cm and the chromaticity is below 100 to obtain a decolorized and desalted feed liquid.

[0060] The sodium type chromatographic separation resin ZGSPC106Na was converted into hydrogen type chromatographic separation resin with hydrochloric acid and filled into 6 chromatographic columns in the chromatographic separation system. The height-to-diameter ratio of the chromatographic columns was 1.5:1. The columns were connected by pipeline valves, and the material, water and column temperature were maintained at 60±1°C.

[0061] The chromatographic separation process proceeds in a cycle of three steps: Step 1: Connect columns 1# to 5# in series, feed 0.23 BV of decolorized and desalted liquid from column 1# at a rate of 1.7 BV / h, and the material at the outlet of column 5# is recorded as the first material; Step 2: Connect the 6 chromatographic columns from 1# to 6# in series to form a closed loop and run at a rate of 1.56 BV / h for 0.5h; Step 3: Connect columns 2# to 4# in series, add 0.28BV of water from column 2# at a rate of 1.7BV / h, and the material at the outlet of column 4# is recorded as the second material; add 0.22BV of water from column 5# at a rate of 1.6BV / h, and the material at the outlet of column 5# is recorded as the third material; Each time the three steps are cycled, the serial column number and the inlet and outlet column numbers are extended by one, and the cycle is repeated between columns 1# to 6#.

[0062] Different substances migrate at different rates in the chromatographic resin to separate erythritol from other impurities. When the chromatographic column starts running, the three materials are all discharged as water. Repeat the above process, and the concentration of the three materials gradually increases until it stabilizes. The first material and the third material are waste liquids containing impurities, and the second material is an erythritol solution. The erythritol mass content is ≥95% based on dry matter.

[0063] The obtained erythritol solution is mixed into the stock solution production line (original erythritol production line). The stock solution is the material after the fermentation liquid is treated by ceramic membrane, nanofiltration membrane, and ion exchange desalination process. The obtained erythritol solution and the stock solution are concentrated, crystallized once, centrifuged, dissolved, decolorized, crystallized twice, centrifuged, dried, screened, iron removed, and packaged to obtain the erythritol product.

[0064] The test indicators of the obtained erythritol product are shown in Table 2 below: Table 2 Test results of various indicators of the erythritol product obtained in Example 2

[0065] In this embodiment, the extraction yield of the erythritol stock solution production line was increased from 91.5% to 95.2%. Without a significant change in cost, the production capacity was increased by 4%, and the product quality remained stable.

[0066] Comparative Example 1 Refer to the invention patent CN 102603478 A method to treat erythritol mother liquor: 1. Pretreatment: Take the erythritol mother liquor after multiple crystallizations and dilute it to a 20% (W / W) solution with pure water; 2. Ceramic membrane filtration: Filter the above diluted solution using a 50nm ceramic membrane; 3. Nanofiltration membrane filtration: Filter the diluted solution using a 500Da nanofiltration membrane; 4. Activated carbon decolorization: Add 2% of dry matter weight of activated carbon, keep warm at 70℃ for 60min, and filter the activated carbon.

[0067] 5. Ion exchange: Use anion and cation exchange desalination resin to remove salt and part of the pigment in the solution, so that the conductivity of the output is controlled below 500μs / cm.

[0068] 6. Evaporation and concentration: at a temperature of 75°C and a pressure of -0.095 MPa, the above-mentioned liquid was concentrated to a concentration of 60% (W / W); 7. Cooling crystallization: Cool down to 30°C at a rate of 2°C to 5°C per hour. Centrifuge the resulting slurry to collect wet crystals; 8. Drying: Use an oven to dry the wet crystals.

[0069] The indicators of the erythritol product obtained in Comparative Example 1 are shown in Table 3 below: Table 3 Test results of various indicators of the erythritol product obtained in Comparative Example 1

[0070] Since there are many impurities such as ribitol and mannitol in the material, the crystallization rate is low, and the obtained crystals contain a large number of tiny crystals under the influence of impurities and are not easy to recover. The crystal centrifugation process also requires more washing water, resulting in the total yield of erythritol in Comparative Example 1 being only about 44%. In addition, since impurities such as pigments and reducing sugars cannot be completely removed, the obtained product has low light transmittance, yellow color, and a caramel smell.

[0071] Comparative Examples 2 to 7 The pH value of the erythritol waste liquor was adjusted to 5.0 and heated to 75°C to denature the protein therein. After the temperature dropped to 50°C, the filtrate was filtered using a 50nm ceramic membrane at an inlet pressure of 10 bar and a transmembrane pressure difference of 5 bar, and the filtrate was collected.

[0072] To the obtained filtrate, add 3% of the total dry matter weight of the material activated carbon powder, maintain at 60°C for 1 hour for decolorization. After the decolorization is completed, the material is filtered through a plate and frame, and the filtrate is collected.

[0073] The filtrate obtained after decolorization is desalted by using Wandong 001×7 (732) strong acid cation exchange resin and Wandong D201 strong basic anion exchange resin in sequence, and further decolorized at the same time. The conductivity of the material after desalination is controlled to be below 50μm / cm and the chromaticity is below 100 to obtain a decolorized and desalted feed solution.

[0074] The sodium type chromatographic separation resin ZGSPC106Na was converted into hydrogen type chromatographic separation resin with hydrochloric acid and filled into 6 chromatographic columns in the chromatographic separation system. The height-to-diameter ratio of the chromatographic columns was 1.5:1. The columns were connected by pipeline valves, and the material, water and column temperature were maintained at 60±1°C.

[0075] The chromatographic separation process proceeds in a cycle of three steps: Step 1: Connect columns 1# to 5# in series, feed (a) BV of decolorized and desalted liquid from column 1# at a rate of 1.7 BV / h, and the material at the outlet of column 5# is recorded as the first material; Step 2: Connect the 6 chromatographic columns #1 to #6 in series to form a closed loop, and the material runs at a rate of 1.56 BV / h (b) h; Step 3: Connect columns 2# to 4# in series, feed water (c) BV from column 2# at a rate of 1.7 BV / h, and the material at the outlet of column 4# is recorded as the second material; feed water 0.22 BV from column 5# at a rate of 1.6 BV / h, and the material at the outlet of column 5# is recorded as the third material; Each time the three steps are repeated, the serial column number and the inlet and outlet column number are extended by one, and circulated between columns 1# to 6#. The first material and the third material are waste liquid containing impurities, and the second material is erythritol solution.

[0076] The collected erythritol solution was concentrated using a triple-effect MVR evaporator, with a concentrated discharge temperature of 75°C and a discharge concentration of 60%.

[0077] Using 10m 3 The crystallizer cools and crystallizes the material discharged from the evaporator: stirring frequency is 50 rpm, cooling rate is 2~5℃ / h, and the crystallization discharge temperature is 25℃.

[0078] The crystal slurry after crystallization is centrifuged using a horizontal spiral centrifuge to obtain liquid and wet crystals: The liquid is concentrated and recrystallized, the liquid obtained by recrystallization is mixed into the filtrate obtained by ceramic membrane filtration for reuse, and the wet crystals obtained by recrystallization are mixed into the erythritol solution after chromatographic separation for reuse; The wet crystals were dissolved in pure water to a mass concentration of 60%, and activated carbon powder was added at 1% of the dry matter mass for decolorization. After decolorization, the Ama filter was used for decarbonization. The decolorized material was reused for 10m 3 The crystallizer is cooled and crystallized, and the crystals are separated by a flat scraper bottom discharge centrifuge. The liquid obtained by centrifugation is mixed into the decolorization and desalination liquid before chromatographic separation for reuse. The wet crystals are dried in a fluidized bed, sieved by a swing sieve, iron removed, and packaged to obtain the erythritol product.

[0079] The conditions of the chromatographic separation processes a, b and c in Comparative Examples 2 to 7 are shown in Table 4, and the purity and recovery rate of the obtained erythritol products are shown in Table 5.

[0080] Table 4 Specific chromatographic conditions of Comparative Examples 2 to 7

[0081] Table 5 Purity and recovery of erythritol obtained in Comparative Examples 2 to 7

[0082] It can be seen that the feed amount was increased in Comparative Example 2, the volume occupied by the material in the chromatographic column increased, the impurities and erythritol needed to migrate a longer distance in the chromatographic column to be separated, the purity of erythritol obtained in Comparative Example 2 was reduced, and the yield was greatly reduced. Comparative Example 3 reduced the feed amount, and the material and impurities were easier to separate; the purity and yield of the product obtained in Comparative Example 3 were slightly improved, but the water consumption was greatly increased, and the actual water consumption per unit volume of material was 3.4.

[0083] Comparative Example 4 reduces the circulation time of the material in the chromatographic column, but due to insufficient migration of the material in the chromatographic column, the material and impurities are not completely separated, a large amount of impurities are recycled into the material, and the product purity and yield are low. Comparative Example 5 increases the circulation time of the material in the chromatographic column, the production efficiency decreases, and the yield also decreases.

[0084] Comparative Example 6 reduces the amount of water inlet when collecting the erythritol solution, resulting in the failure to fully recycle part of the erythritol and a low yield. Comparative Example 7 increases the amount of water inlet when collecting the erythritol solution, resulting in a decrease in the purity of the erythritol and an increase in water consumption and energy consumption required for subsequent evaporation and concentration.

[0085] Although the above-mentioned embodiments have made a detailed description of the present invention, they are only some embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on the embodiments of the present invention without creative work, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for recycling waste mother liquor after erythritol crystallization, characterized in that: The following steps are involved: The waste mother liquor after the crystallization of erythritol is filtered through a ceramic membrane to obtain a first filtrate; Decolorizing and desalting the first filtrate to obtain a decolorized and desalted feed solution; The decolorized and desalted feed solution is subjected to chromatographic separation to obtain an erythritol solution; The chromatographic separation uses a hydrogen-type chromatographic resin column; The erythritol solution has an erythritol content of ≥95% by mass based on dry matter.

2. The recycling method according to claim 1, characterized in that: The chromatographic separation uses 6 hydrogen-type chromatographic resin columns, which are sequentially recorded as 1# column to 6# column, and the height-to-diameter ratio of each hydrogen-type chromatographic resin column is 1.5:

1. The chromatographic separation comprises the following steps: Step 1: Connect columns 1# to 5# in series, feed 0.23 BV of decolorized and desalted liquid from column 1# at a rate of 1.7 BV / h, and the material at the outlet of column 5# is recorded as the first material; Step 2: Connect columns 1# to 6# in series to form a closed loop, and run at a rate of 1.56 BV / h for 0.5h; Step 3: Connect columns 2# to 4# in series, add 0.28BV of water from column 2# at a rate of 1.7BV / h, and the material at the outlet of column 4# is recorded as the second material; add 0.22BV of water from column 5# at a rate of 1.6BV / h, and the material at the outlet of column 5# is recorded as the third material; The three steps are repeated in a cycle. Each time the series column number and the inlet and outlet column numbers are extended by one, the columns are repeated between the 1# column and the 6# column. The second material is erythritol solution.

3. The recycling method according to claim 1, characterized in that: Before the ceramic membrane filtration, the method also includes: adjusting the pH value of the waste mother liquor to 3.5-6.5 and heating; the heating temperature is 75-85°C.

4. The recycling method according to claim 1 or 3, characterized in that: The pore size of the ceramic membrane is 20-200 nm.

5. The recycling method according to claim 1, characterized in that: The decolorization is performed by activated carbon decolorization, and the mass of the activated carbon in the activated carbon decolorization is 0.2% to 5% of the mass of the dry matter in the first filtrate.

6. The recycling method according to claim 1, characterized in that: The desalination is ion exchange resin desalination, and the ion exchange resin desalination uses cation exchange resin and anion exchange resin, and the cation exchange resin is a strong acid cation exchange resin.

7. The recycling method according to claim 1, characterized in that: The recycling method further comprises: The erythritol solution is concentrated, crystallized once, centrifuged, dissolved, decolorized, crystallized twice, and dried to obtain the first erythritol; Alternatively, the erythritol solution is mixed with the stock solution and then further processed to obtain the second erythritol; the stock solution is the feed solution obtained after the fermentation liquid is filtered through a ceramic membrane, filtered through a nanofiltration membrane, and subjected to ion exchange desalination treatment in sequence.

8. The recycling method according to claim 7, characterized in that: The mass concentration of the concentrated material is 45% to 70%.

9. The recycling method according to claim 7, characterized in that: The primary crystallization and the secondary crystallization are both cooling crystallizations, the cooling rate of the cooling crystallization is 1-5°C / h, and the terminal temperature of the cooling crystallization is 20-25°C.

10. The recycling method according to claim 7, characterized in that: The further treatment includes: concentration, primary crystallization, centrifugation, crystal dissolution, decolorization, secondary crystallization and drying.

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