A method for co-producing inositol and phosphate by hierarchical treatment of corn steep water

Abstract

The present invention provides a method for co-producing inositol and phosphate by hierarchical treatment of corn steep water, belonging to the technical field of wastewater treatment. First, the corn steep water is subjected to sedimentation, ultrafiltration, nanofiltration, treatment with an anion resin column and desorption to obtain a phytate solution; the phytate solution is subjected to first decolorization and first evaporation concentration, and then successively subjected to hydrolysis treatment, flash evaporation, second decolorization and chromatographic separation to obtain an inositol solution and a phosphate solution respectively; the inositol solution is successively subjected to membrane concentration, treatment with cation and anion resin columns, second evaporation concentration, first vacuum crystallization and first atmospheric crystallization to obtain inositol; the phosphate solution is successively subjected to third evaporation concentration, third decolorization, second vacuum crystallization and second atmospheric crystallization to obtain phosphate. The method provided by the present invention can effectively treat a large amount of corn steep water, and at the same time can produce high-purity inositol and by-product phosphate.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly relates to a method for the hierarchical treatment of corn steep water to co-produce inositol and phosphate Background Art

[0002] Corn steep water is the wastewater generated during the production of corn starch by the wet milling method. The traditional treatment method for corn steep water is to evaporate and concentrate it to form corn syrup, with low economic benefits. Corn steep water contains components such as phytic acid, water-soluble protein, lactic acid, amino acids, and inorganic salts. If certain components among them can be extracted, recovered, or converted into high-value-added products, the economic benefits can be improved on the basis of effectively treating corn steep water.

[0003] With the rapid development of the corn processing industry, the volume of corn steep water is gradually increasing. In the existing technologies, there are generally problems such as complex processes and unreasonable material recycling in the effective treatment and high-value utilization processes of corn steep water, resulting in relatively high treatment costs and being unfavorable for the healthy development of the corn processing industry. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for the hierarchical treatment of corn steep water to co-produce inositol and phosphate. The method provided by the present invention can effectively treat a large amount of corn steep water, and at the same time can produce inositol and phosphate with high yields and high purities.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a method for the hierarchical treatment of corn steep water to co-produce inositol and phosphate, comprising the following steps:

[0007] Subject the corn steep water to sedimentation to obtain a sedimentation supernatant and a sedimentation concentrate respectively, and return the sedimentation concentrate to the concentration process of the starch factory for making corn syrup;

[0008] Subject the sedimentation supernatant to ultrafiltration to obtain an ultrafiltration permeate and an ultrafiltration concentrate respectively, and return the ultrafiltration concentrate to the concentration process of the starch factory for making corn syrup;

[0009] Subject the ultrafiltration permeate to nanofiltration to obtain a nanofiltration permeate and a nanofiltration concentrate respectively, and return the nanofiltration permeate to the concentration process of the starch factory for making corn syrup;

[0010] Subject the nanofiltration concentrate to sequential treatment and elution through an anion resin column to obtain a phytate solution;

[0011] Subject the phytate solution to sequential first decolorization and first evaporation concentration to obtain a phytate concentrate;

[0012] The phytate concentrate is subjected to hydrolysis treatment, flash evaporation, secondary decolorization, and chromatographic separation in sequence to obtain an inositol solution and a phosphate solution respectively;

[0013] The inositol solution is subjected to membrane concentration, anion and cation resin column treatment, secondary evaporation concentration, primary vacuum crystallization, and primary atmospheric crystallization in sequence to obtain the inositol;

[0014] The phosphate solution is subjected to tertiary evaporation concentration, tertiary decolorization, secondary vacuum crystallization, and secondary atmospheric crystallization in sequence to obtain the phosphate.

[0015] Preferably, the sedimentation time is 1 - 3 h, and the volume of the sedimented concentrate is 3 - 5% of the volume of the corn steep water;

[0016] The conditions for ultrafiltration include: a pressure of 0.5 - 1.0 MPa, and the pore size of the ultrafiltration membrane is 10 - 50 nm; the volume of the ultrafiltration permeate is 95 - 98% of the volume of the sedimented clear liquid;

[0017] The conditions for nanofiltration include: a pressure of 3.0 - 5.0 MPa, and the molecular weight cut-off of the nanofiltration membrane is 1000 - 2000 Da; the mass of dry matter in the nanofiltration concentrate is 60 - 70% of the mass of dry matter in the ultrafiltration permeate, and the solid content of the nanofiltration concentrate is 30 - 40 wt%;

[0018] The conditions for anion resin column treatment include: the filler in the anion resin column is S-486-J type anion resin, and the phytic acid content in the effluent of the anion resin column is ≤0.1 wt%;

[0019] The eluent used for elution includes potassium chloride solution, potassium sulfate solution, potassium nitrate solution, hydrochloric acid, sodium chloride solution, potassium hydroxide solution, or sodium hydroxide solution; the concentration of the eluent is 5 - 20 wt%.

[0020] Preferably, the primary decolorization includes waste carbon decolorization and resin column decolorization in sequence, the secondary decolorization and the tertiary decolorization are activated carbon decolorization, and the waste activated carbon after the secondary decolorization and the tertiary decolorization is recycled for the waste carbon decolorization.

[0021] Preferably, the conditions for waste carbon decolorization include: the dosage of waste activated carbon is 5 - 10 kg / m 3 , the temperature is 20 - 40 °C, and the time is 20 - 40 min;

[0022] The conditions for resin column decolorization include: the filler in the resin column is HA-90 type resin; the light transmittance of the effluent of the resin column decolorization is ≥60%, and the pH value is 3.4 - 4.5;

[0023] The conditions for the secondary decolorization include: the dosage of activated carbon is 3 - 5 kg / m 3, the temperature is 50 - 70 °C, and the time is 20 - 40 min;

[0024] The conditions for the third decolorization include: the dosage of activated carbon is 3 - 5 kg / m 3 , the temperature is 85 - 100 °C, and the time is 20 - 40 min.

[0025] Preferably, the discharge temperature of the first evaporation and concentration is 85 - 95 °C, and the discharge solid content is 35 - 40 wt%.

[0026] Preferably, the conditions for the hydrolysis treatment include: the temperature is 165 - 180 °C, the pressure is 0.7 - 1.0 MPa, and the time is 8 - 12 h;

[0027] The waste heat generated by the flash evaporation provides heat for the first evaporation and concentration; the discharge temperature of the flash evaporation ≤ 70 °C, the discharge solid content is 33 - 40 wt%, and the organic phosphorus content ≤ 0.1 wt%;

[0028] The conditions for the chromatographic separation include: the packing in the chromatographic column is 310K type resin, the feeding temperature is 55 - 60 °C, the mobile phase is water, and the volume ratio of the mobile phase to the second decolorized solution obtained after the second decolorization is preferably 2.5 - 3:1; the purity of the inositol solution ≥ 92%, the conductivity ≤ 2000 μs / cm, the solid content is 4 - 7 wt%, and the pH value is 3.5 - 4.5; the purity of the potassium dihydrogen phosphate solution ≥ 92%, the solid content is 10 - 13 wt%, and the pH value is 3.5 - 4.5.

[0029] Preferably, the discharge solid content of the membrane concentration is 11 - 13 wt%;

[0030] The membrane concentration also obtains permeate water, and the permeate water is recycled for the chromatographic separation;

[0031] The conditions for the treatment by the cation and anion resin columns include: the packing in the cation resin column is 001×8 type cation resin, and the packing in the anion resin column is ZGA - 408 type anion resin; the conductivity of the discharge after the treatment by the cation and anion resin columns ≤ 50 μs / cm, the pH value is 5 - 8, and the transmittance ≥ 99%;

[0032] The discharge temperature of the second evaporation and concentration ≥ 90 °C, and the discharge solid content ≥ 40 wt%; the second evaporation and concentration also obtains condensed water, and the condensed water is recycled for the chromatographic separation.

[0033] Preferably, the discharge temperature of the third evaporation and concentration ≥ 90 °C, and the discharge solid content ≥ 40 wt%; the third evaporation and concentration also obtains condensed water, and the condensed water is recycled for the chromatographic separation.

[0034] Preferably, the conditions for the first vacuum crystallization and the second vacuum crystallization independently include: the vacuum degree is -0.06 to -0.085 MPa, the time is 6 to 8 h, and the discharging temperature is ≤ 50 °C; the conditions for the first atmospheric crystallization and the second atmospheric crystallization independently include: the time is 3 to 5 h, and the discharging temperature is 15 to 25 °C.

[0035] Preferably, after the first atmospheric crystallization, the following steps are further included: subjecting the obtained first atmospheric crystallization stock solution to first centrifugal separation, collecting the solid wet material for first drying, to obtain the inositol;

[0036] After the second atmospheric crystallization, the following steps are further included: subjecting the obtained second atmospheric crystallization stock solution to second centrifugal separation, collecting the solid wet material for second drying, to obtain the phosphate;

[0037] The first drying and the second drying are carried out in a vibrating fluidized bed.

[0038] Beneficial effects: First, the corn steep water of the present invention is subjected to sedimentation, ultrafiltration, nanofiltration, anion resin column treatment and desorption to obtain a phytate solution; the phytate solution is subjected to first decolorization and first evaporation concentration, and then successively subjected to hydrolysis treatment, flash evaporation, second decolorization and chromatographic separation to respectively obtain an inositol solution and a phosphate solution; the inositol solution is successively subjected to membrane concentration, cation and anion resin column treatment, second evaporation concentration, first vacuum crystallization and first atmospheric crystallization to obtain inositol; the phosphate solution is successively subjected to third evaporation concentration, third decolorization, second vacuum crystallization and second atmospheric crystallization to obtain phosphate. In the present invention, the corn steep water is subjected to sedimentation, ultrafiltration, nanofiltration, and anion resin column treatment. Among them, through sedimentation and ultrafiltration, suspended substances and part of vomitoxin in the material can be removed to obtain a mixed solution of phytic acid and protein. The nanofiltration permeate obtained after nanofiltration is returned to the concentration process of the starch factory to be used for making corn syrup (the corn syrup can be further used for preparing feed raw materials); the nanofiltration concentrate obtained after nanofiltration can adsorb phytic acid through anion resin column treatment, and a phytate solution is obtained through desorption; then the decolorization process is reasonably set, and cation and anion resin column treatment is introduced for the inositol solution. At the same time, a vacuum-coupled atmospheric crystallization process is adopted, which can ensure that qualified products can be obtained for inositol and phosphate through one crystallization, the product purity is high, the quality is stable, and the cost is also greatly reduced. Moreover, by using the method of the present invention, the crystallization efficiency of inositol and phosphate is high, the crystal particles are uniform, and the yield is relatively high.

[0039] Furthermore, in the present invention, decolorization is carried out by using activated carbon and resin in combination, and the purification effect is good; among them, the waste activated carbon after the second decolorization and the waste activated carbon after the third decolorization are recycled for waste carbon decolorization, which can realize the reuse of activated carbon; the waste heat generated by flash evaporation is used to provide heat for the first evaporation concentration, which can realize the full utilization of waste heat, effectively reduce steam consumption, greatly reduce production costs, and have better comprehensive benefits.

[0040] Furthermore, in the present invention, the first drying and the second drying are carried out in a vibrating fluidized bed, which is beneficial to improving the drying efficiency and reducing the labor cost compared with drying in an oven in the traditional process. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a flow chart of the hierarchical treatment of corn steeping water for co-producing inositol and phosphate in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0042] The present invention provides a method for the hierarchical treatment of corn steeping water for co-producing inositol and phosphate, comprising the following steps:

[0043] The corn steeping water is sedimented to obtain sedimented clear liquid and sedimented concentrated liquid respectively, and the sedimented concentrated liquid is returned to the concentration process of the starch factory for making corn syrup;

[0044] The sedimented clear liquid is ultrafiltered to obtain ultrafiltration permeate and ultrafiltration concentrated liquid respectively, and the ultrafiltration concentrated liquid is returned to the concentration process of the starch factory for making corn syrup;

[0045] The ultrafiltration permeate is nanofiltrated to obtain nanofiltration permeate and nanofiltration concentrated liquid respectively, and the nanofiltration permeate is returned to the concentration process of the starch factory for making corn syrup;

[0046] The nanofiltration concentrated liquid is sequentially treated and resolved by an anion resin column to obtain a phytate solution;

[0047] The phytate solution is sequentially subjected to first decolorization and first evaporation concentration to obtain a phytate concentrated solution;

[0048] The phytate concentrated solution is sequentially subjected to hydrolysis treatment, flash evaporation, second decolorization and chromatographic separation to obtain an inositol solution and a phosphate solution respectively;

[0049] The inositol solution is sequentially subjected to membrane concentration, cation and anion resin column treatment, second evaporation concentration, first negative pressure crystallization and first atmospheric pressure crystallization to obtain the inositol;

[0050] The phosphate solution is sequentially subjected to third evaporation concentration, third decolorization, second negative pressure crystallization and second atmospheric pressure crystallization to obtain the phosphate.

[0051] In the present invention, unless otherwise specified, the raw materials used are well-known sources or commercially available products to those skilled in the art.

[0052] In the present invention, corn steep water is sedimentated to obtain sedimentation clear liquid and sedimentation concentrated liquid respectively. The sedimentation concentrated liquid is returned to the concentration process of the starch factory for making corn syrup (the solid content of the sedimentation concentrated liquid is preferably 17.2 - 19.8 wt%, more preferably 18.5 wt%; the corn syrup can be further used for preparing feed raw materials, which will not be elaborated hereinafter). In the present invention, the corn steep water is an aqueous solution obtained by soaking corn with water during starch production in the starch factory. The corn steep water preferably contains 1 - 1.5 wt% of phytic acid, 5 - 6 wt% of water-soluble protein, 2 - 3 wt% of lactic acid, 1 - 1.5 wt% of amino acids, 0.5 - 1 wt% of inorganic salts and 5000 - 7000 ppm of potassium ions; more preferably, it contains 1.3 wt% of phytic acid, 5.5 wt% of water-soluble protein, 2.5 wt% of lactic acid, 1.3 wt% of amino acids, 0.7 wt% of inorganic salts and 5000 ppm of potassium ions. In the present invention, the sedimentation time is preferably 1 - 3 h, more preferably 1.5 - 2.5 h, and further preferably 1.8 - 2 h; the volume of the sedimentation concentrated liquid is preferably 3 - 5% of the volume of the corn steep water, more preferably 3 - 4%. The present invention preferably conducts the sedimentation in a vertical flow sedimentation tank. The present invention preferably conducts the sedimentation under the above conditions, which can remove relatively large particle impurities and part of the ash in the material, and is beneficial to the next-step purification of the sedimentation clear liquid.

[0053] After obtaining the sedimentation clear liquid, the present invention ultrafilters the sedimentation clear liquid to obtain ultrafiltration permeate and ultrafiltration concentrated liquid respectively. The ultrafiltration concentrated liquid is returned to the concentration process of the starch factory for making corn syrup. In the present invention, the conditions of ultrafiltration include: the pressure is preferably 0.5 - 1.0 MPa, more preferably 0.5 - 0.6 MPa; the pore size of the ultrafiltration membrane is preferably 10 - 50 nm, more preferably 30 - 50 nm; the ultrafiltration membrane is preferably a tubular membrane, and the ultrafiltration membrane is preferably a ceramic membrane; the volume of the ultrafiltration permeate is preferably 95 - 98% of the volume of the sedimentation clear liquid, more preferably 95 - 96%. The present invention preferably conducts ultrafiltration under the above conditions, which can intercept suspended impurities, part of the ash and vomitoxin in the material, and is beneficial to the stable operation of the liquid when it enters the nanofiltration membrane, and finally obtain high-purity inositol and phosphate.

[0054] After obtaining the ultrafiltration permeate, the present invention subjects the first permeate to nanofiltration to obtain a nanofiltration permeate and a nanofiltration concentrate respectively. The nanofiltration permeate is returned to the concentration process in the starch factory for making corn steep liquor. In the present invention, the conditions for nanofiltration include: the pressure is preferably 3.0 - 5.0 MPa, more preferably 4.0 MPa; the molecular weight cut-off of the nanofiltration membrane is preferably 1000 - 2000 Da, more preferably 1000 - 1500 Da; the mass of dry matter in the nanofiltration concentrate is preferably 60 - 70% of the mass of dry matter in the ultrafiltration permeate, more preferably 65 - 70%; the solid content of the nanofiltration concentrate is preferably 30 - 40 wt%, more preferably 35 - 37 wt%. The present invention preferably performs nanofiltration under the above conditions, which can separate phytic acid, water-soluble proteins and small molecules of lactic acid, amino acids and metal ions in the feed liquid, facilitating the extraction of phytic acid.

[0055] After obtaining the nanofiltration concentrate, the present invention sequentially subjects the nanofiltration concentrate to anion resin column treatment and elution to obtain a phytate solution. In the present invention, the conditions for the anion resin column treatment include: the filler in the anion resin column is preferably S-486-J type anion resin; the phytate content in the effluent obtained after the anion resin column treatment is preferably ≤0.1 wt%, more preferably ≤0.08 wt%, and further preferably 0.040 - 0.065 wt%. The present invention preferably performs the anion resin column treatment under the above conditions, which can fully adsorb the phytate in the feed liquid. In the present invention, the eluent used for elution preferably includes potassium chloride solution, potassium sulfate solution, potassium nitrate solution, hydrochloric acid, sodium chloride solution, potassium hydroxide solution or sodium hydroxide solution, and more preferably potassium chloride solution; the concentration of the eluent is preferably 5 - 20 wt%, more preferably 10 - 15 wt%, and further preferably 12 - 13 wt%; the volume of the eluent is preferably 1.5 - 2.5 BV, and more preferably 2 BV. The phytate solution in the present invention preferably includes potassium phytate solution or sodium phytate solution, and more preferably potassium phytate solution; the potassium phytate in the potassium phytate solution is preferably pentapotassium phytate or hexapotassium phytate; when the potassium phytate is preferably pentapotassium phytate or hexapotassium phytate, the by-product phosphate obtained by the method of the present invention is potassium dihydrogen phosphate. In the present invention, the solid content of the phytate solution is preferably 10 - 20 wt%, more preferably 15 - 18 wt%, and further preferably 15.5 - 16.2 wt%; the pH value of the phytate solution is preferably 3.5 - 4.5, more preferably 3.8 - 4.2, and further preferably 4.0; the phytate content is preferably 10 - 15 wt%, more preferably 12 - 14 wt%, and further preferably 12.2 - 12.5 wt%; the chloride ion content is preferably <1000 ppm, more preferably <950 ppm, further preferably <920 ppm, and still further preferably <900 ppm; the magnesium ion content is preferably <200 ppm, more preferably <180 ppm, further preferably <172 ppm, and still further preferably <170 ppm; the calcium ion content is preferably <20 ppm, more preferably <19.5 ppm, further preferably <18.5 ppm, and still further preferably <16.5 ppm; the protein content is preferably <0.1 wt%, more preferably <0.09 wt%, further preferably <0.016 wt%, and still further preferably <0.015 wt%.

[0056] After obtaining the phytate solution, the present invention sequentially subjects the phytate solution to first decolorization and first evaporation concentration to obtain a phytate concentrate. In the present invention, the first decolorization preferably includes sequential waste carbon decolorization and resin column decolorization. The conditions for the waste carbon decolorization in the present invention preferably include: the amount of waste activated carbon (specifically from the waste activated carbon after subsequent second decolorization and third decolorization) used is preferably 5 - 10 kg / m 3, more preferably 5 - 7 kg / m 3 , the usage amount and recovery amount of the waste activated carbon are preferably kept balanced; the decolorization temperature is preferably 20 - 40 °C, more preferably 25 - 30 °C; the decolorization time is preferably 20 - 40 min, more preferably 30 min. The present invention preferably performs waste carbon decolorization under the above conditions, which can increase the light transmittance of the phytate solution from 1 - 10% to more than 25%, and at the same time can intercept part of the protein, ash, suspended matter and other impurities, reducing the amount of new activated carbon required for the subsequent second decolorization of the phytate solution in the system.

[0057] After the waste carbon decolorization, the present invention preferably filters the obtained feed liquid and performs resin column decolorization on the obtained waste carbon decolorization solution; the light transmittance of the waste carbon decolorization solution is preferably ≥25, more preferably ≥30%, and further preferably ≥35%; the pH value is preferably 3.5 - 4.5, more preferably 3.7 - 4.0. The conditions for the resin column decolorization in the present invention include: the filler in the resin column is preferably HA - 90 type resin; the volume of the waste carbon decolorization solution (i.e., the exchange amount) is preferably 45 - 55 BV, more preferably 50 BV; the light transmittance of the discharged material from the resin column decolorization is preferably ≥60%, more preferably ≥70%, and further preferably 70 - 75%; the pH value is preferably 3.4 - 4.5, more preferably 3.4 - 3.6. The present invention preferably performs resin column decolorization under the above conditions, which can further decolorize the material and at the same time remove the pigments that cannot be removed by the activated carbon, which is beneficial to reducing the amount of activated carbon used in the subsequent second decolorization and third decolorization.

[0058] After the resin column decolorization is completed, the present invention preferably regenerates the resin column and repeats its use. The regeneration method preferably includes: successively performing sodium hydroxide solution rinsing, first pure water rinsing, hydrochloric acid rinsing and second pure water rinsing. The concentration of the sodium hydroxide solution is preferably 4 wt%, the dosage is preferably 2 - 4 BV, the dosage of the first pure water is preferably 4 BV, the concentration of the hydrochloric acid is preferably 2 - 3 wt%, the dosage is preferably 2 BV, and the dosage of the second pure water is preferably 4 BV. The flow rate during the rinsing with each reagent is preferably 0.5 - 1 BV / h.

[0059] After the resin column is decolorized, the present invention preferably performs first evaporation concentration on the obtained resin column decolorized liquid to obtain a phytate concentrate (denoted as the first evaporation concentrate). In the present invention, the discharging temperature of the first evaporation concentration is preferably 85-95°C, more preferably 90-92°C; the discharging solid content is preferably 35-40 wt%, more preferably 36-38 wt%. The heat used for the first evaporation concentration in the present invention is preferably provided by the waste heat generated in the subsequent flash evaporation process. The present invention preferably performs the first evaporation concentration under the above conditions, which can utilize the recovered waste heat as the heat source for the first evaporation concentration, increase the solid content of the incoming liquid (i.e., the resin column decolorized liquid) from 20-30 wt% to 35-40 wt%, and increase the discharging temperature from 20-40°C to 85-95°C, which is beneficial to reducing the steam energy consumption during the hydrolysis of phytate. At the same time, as the volume of the phytate solution decreases, the number of hydrolysis kettles used in the subsequent hydrolysis treatment process also decreases.

[0060] After obtaining the first evaporation concentrate, the present invention sequentially performs hydrolysis treatment, flash evaporation, second decolorization, and chromatographic separation on the first evaporation concentrate to obtain an inositol solution and a phosphate solution respectively. In the present invention, the conditions for the hydrolysis treatment include: the temperature is preferably 165-180°C, more preferably 170-175°C; the pressure is preferably 0.7-1.0 MPa, more preferably 0.75-0.85 MPa; the time is preferably 8-12 h, more preferably 10-12 h. The present invention preferably performs the hydrolysis treatment under the above conditions, which can make the hydrolysis of the phytate solution sufficient and complete, and is beneficial to the production of inositol and phosphate.

[0061] After the hydrolysis treatment, the present invention preferably performs flash evaporation on the obtained hydrolysis liquid; the organic phosphorus content in the hydrolysis liquid is preferably ≤0.1 wt%, more preferably ≤0.07 wt%. In the present invention, the discharging temperature of the flash evaporation is preferably ≤70°C, more preferably 60-68°C; the discharging solid content is preferably 33-40 wt%, more preferably 35-38 wt%; the organic phosphorus content is preferably ≤0.1 wt%. The waste heat generated by the flash evaporation in the present invention is preferably recycled for the first evaporation concentration, that is, to provide heat for the first evaporation concentration. The present invention preferably increases the discharging solid content of the hydrolysis liquid to 33-40 wt% and reduces the temperature to below 70°C after flash evaporation, and at the same time recycles the waste heat for the first evaporation concentration, which is beneficial to the full utilization of waste heat; the discharging temperature is reduced to below 70°C, which can not only meet the decolorization temperature required for the second decolorization but also meet the requirement of the resin for the feeding temperature during chromatographic separation, reducing the second decolorization heating process and the material preheating process before chromatographic separation feeding.

[0062] After the flash evaporation, the present invention preferably performs second decolorization on the obtained flash evaporation liquid. In the present invention, the second decolorization is preferably activated carbon decolorization, and the conditions for the second decolorization include: the dosage of activated carbon is preferably 3-5 kg / m 3 ³, more preferably 3-4 kg / m3 ; The decolorization temperature is preferably 50 - 70°C, more preferably 65 - 68°C; the decolorization time is preferably 20 - 40 min, more preferably 30 min. The waste activated carbon after the second decolorization in the present invention is preferably recycled for the decolorization of waste carbon. The present invention preferably conducts the second decolorization under the above conditions, which can increase the light transmittance of the flash evaporation liquid to ≥80%, facilitating the normal operation of chromatography and the purification of subsequent inositol solution and phosphate solution.

[0063] After the second decolorization, the present invention preferably filters the obtained feed liquid, and conducts chromatography separation on the obtained second decolorized solution to obtain an inositol solution and a phosphate solution respectively. In the present invention, the light transmittance of the second decolorized solution is preferably ≥80%, more preferably 85 - 93%. In the present invention, the conditions for the chromatography separation include: the filler in the chromatography column is preferably 310K type resin, more preferably DuPont Dow 310K type resin; the feeding temperature is preferably 55 - 60°C, more preferably 58 - 60°C; the mobile phase is preferably water, and the volume ratio of the mobile phase to the second decolorized solution is preferably 2.5 - 3:1, specifically it can be 2.6:1, 2.8:1 or 3.0:1. The present invention preferably uses the permeate water generated from the subsequent membrane concentration process and the condensed water generated from the second evaporation concentration and the third evaporation concentration as the mobile phase. In the present invention, the purity of the inositol solution is preferably ≥92%, the conductivity is preferably ≤2000 μs / cm, the solid content is preferably 4 - 7 wt%, and the pH value is preferably 3.5 - 4.9; the purity of the potassium dihydrogen phosphate solution is preferably ≥92%, the conductivity is preferably >20000 μs / cm, the solid content is preferably 10 - 13 wt%, and the pH value is preferably 3.5 - 4.5. The present invention preferably conducts chromatography separation under the above conditions, which can separate inositol and phosphate in the second decolorized solution, facilitating the further purification of the subsequent inositol solution and phosphate solution.

[0064] After obtaining the inositol solution and the phosphate solution, the present invention preferably processes the two respectively, and finally obtains inositol and phosphate respectively. The following is a separate description.

[0065] After obtaining the inositol solution, the present invention sequentially conducts membrane concentration, anion and cation resin column treatment, second evaporation concentration, first vacuum crystallization and first atmospheric crystallization on the inositol solution to obtain the inositol. In the present invention, during the process of membrane concentration, the membrane operating pressure is preferably 0.8 - 0.9 MPa, more preferably 0.85 MPa; the solid content of the discharged material from the membrane concentration is preferably 11 - 13 wt%. The membrane concentration in the present invention is preferably reverse osmosis membrane concentration; the membrane concentration also obtains permeate water, and the permeate water is preferably recycled as the mobile phase for the chromatography separation. The present invention preferably conducts membrane concentration under the above conditions, which can replace the evaporator for primary concentration, facilitating the stability of the material characteristics during low-concentration concentration, and simultaneously reducing steam consumption.

[0066] After the membrane concentration, the present invention preferably subjects the obtained membrane concentrate to treatment with cation and anion resin columns. The treatment with cation and anion resin columns in the present invention preferably includes sequentially performing treatment with a cation resin column and treatment with an anion resin column; the conditions for the treatment with cation and anion resin columns include: the packing in the cation resin column is preferably 001×8 type cation resin, and the packing in the anion resin column is preferably ZGA-408 type anion resin; the exchange capacity is preferably 8-12 BV, more preferably 10 BV; the conductivity of the discharged material from the treatment with cation and anion resin columns is preferably ≤50 μs / cm, more preferably ≤30 μs / cm, and further preferably ≤25 μs / cm; the pH value is preferably 5-8, more preferably 6-7; the light transmittance is preferably ≥99%. The present invention preferably performs the treatment with cation and anion resin columns under the above conditions, which can further improve the purity of inositol and is beneficial to the crystallization of inositol.

[0067] After the treatment with cation and anion resin columns, the present invention preferably regenerates the cation resin column and the anion resin column respectively and then reuses them. The regeneration method of the cation resin column preferably includes: sequentially rinsing with hydrochloric acid (concentration 3-4 wt%) with a volume of 2-4 BV and pure water with a volume of 4-6 BV; the regeneration method of the anion resin column preferably includes: sequentially rinsing with sodium hydroxide solution (concentration 3-4 wt%) with a volume of 2-4 BV and pure water with a volume of 4-8 BV. In the present invention, the waste acid and waste alkali generated during the treatment with cation and anion resin columns are preferably subjected to nanofiltration treatment through a nanofiltration membrane to achieve the recovery of acid and alkali; the cut-off molecular weight of the nanofiltration membrane is preferably 100-300 Da. In the present invention, the recovered acid and alkali are preferably reused for the regeneration of the cation resin column and the anion resin column, which is beneficial to reducing sewage discharge; the nanofiltration treatment preferably also obtains permeate water, and the permeate water is preferably reused for rinsing the cation resin column and the anion resin column.

[0068] After the treatment with the anion resin column, the present invention performs a second evaporation concentration on the effluent from the obtained anion resin column. In the present invention, the discharge temperature of the second evaporation concentration is preferably ≥90 °C, more preferably 90-92 °C; the solid content of the discharged material is preferably ≥40 wt%, more preferably 40-42%. In the present invention, the second evaporation concentration preferably also obtains condensate water, and the present invention preferably uses the condensate water as the mobile phase and reuses it for the chromatographic separation. The present invention preferably performs the second evaporation concentration under the above conditions, which can further increase the concentration of the inositol solution and is beneficial to the subsequent first negative pressure crystallization of the inositol solution.

[0069] After the second evaporation and concentration, the present invention preferably subjects the obtained second evaporation concentrate to first negative-pressure crystallization and first atmospheric-pressure crystallization in sequence. In the present invention, the conditions for the first negative-pressure crystallization include: the vacuum degree is preferably -0.06 to -0.085 MPa, more preferably -0.065 to -0.075 MPa; the time is preferably 6 to 8 h, more preferably 7 to 8 h; the discharging temperature is preferably ≤50 °C. The present invention preferably conducts the first negative-pressure crystallization in a negative-pressure crystallization tank. Specifically, the second evaporation concentrate is conveyed to the negative-pressure crystallization tank, the vacuum valve is opened, and continuous concentration and cooling are carried out under the condition of a vacuum degree of -0.06 to -0.085 MPa. When it is found that crystallization starts in the negative-pressure crystallization tank (it can be determined that crystallization starts when there are reflective flash points in the material seen through the sight glass, and at this time the material temperature is 70 to 80 °C, preferably 73 to 75 °C), the vacuum valve is closed, and crystal growth is carried out for 1 to 2 h (preferably 1 to 1.5 h). After the crystal growth ends, the vacuum valve is opened, and cooling is continued under the condition of a vacuum degree of -0.06 to -0.085 MPa. When the material temperature drops to 50 °C, the vacuum valve is closed, the vacuum is released, and the discharging valve is opened (the time from feeding to discharging is 6 to 8 h) to discharge the material. In the present invention, the conditions for the first atmospheric-pressure crystallization include: the time is preferably 3 to 5 h, more preferably 4 h; the discharging temperature is preferably 20 to 25 °C. The present invention preferably conducts the first atmospheric-pressure crystallization in an atmospheric-pressure crystallization tank. Specifically, the material after the first negative-pressure crystallization is conveyed into the atmospheric-pressure crystallization tank, and then the chilled water valve of the atmospheric-pressure crystallization tank (the temperature is 6 to 8 °C, preferably 6.5 to 7 °C) is opened, and continuous cooling is carried out (the cooling time is preferably 2 to 3.5 h, more preferably 2 to 3 h). When the temperature drops to 2 to 25 °C, the discharging valve is opened (the time from feeding to discharging is 3 to 5 h) to discharge the material. The present invention preferably conducts the first negative-pressure crystallization and the first atmospheric-pressure crystallization under the above conditions, which can enable the inositol solution to continue to concentrate under a negative-pressure state. As the concentration increases and the temperature decreases, a large amount of inositol crystals precipitate. The negative-pressure coupling with atmospheric-pressure crystallization is beneficial to providing more suitable crystallization conditions for the inositol solution, enabling the supersaturation to transition slowly, avoiding the generation of false crystals and fine crystals, making the product crystal grains uniform, and enabling inositol to be obtained with a high yield after subsequent first centrifugation.

[0070] After the first atmospheric crystallization, the present invention preferably subjects the obtained first atmospheric crystallization slurry to first centrifugal separation, collects the solid wet material for first drying, and obtains the inositol. In the present invention, the centrifuge used for the first centrifugation is preferably a pull-bag centrifuge. The present invention preferably transports the first atmospheric crystallization slurry to a pull-bag centrifuge, adds pure water at a temperature of 30-50 °C (preferably 30-40 °C) for rinsing for 30-50 s (preferably 30-40 s), and then performs centrifugal separation (the liquid discharge time is preferably 10-20 min) to obtain a solid wet material. The water content in the solid wet material is preferably ≤3 wt%, and the purity is preferably ≥99%. In the present invention, the first drying is preferably carried out in a vibrating fluidized bed. The conditions for the first drying preferably include: the hot air supply temperature is preferably 100-130 °C, more preferably 110-120 °C; the cold air (relative humidity is preferably ≤30%) supply temperature is preferably 20-30 °C, more preferably 23-25 °C. The present invention preferably performs the first drying under the above conditions, which can reduce the water content of the inositol wet material after centrifugation to below 0.2 wt%, is beneficial to the storage and transportation of the product, and meets the product quality requirements. The water content in the inositol of the present invention is preferably ≤0.2 wt%, more preferably ≤0.08 wt%; the purity is preferably ≥99.3%, more preferably ≥99.8%; the pH value is preferably 5.78-5.80; the percentage of the product with a particle size of 30-150 mesh in the total mass of the product is preferably ≥95%.

[0071] After obtaining the phosphate solution, the present invention sequentially performs third evaporation concentration, third decolorization, second vacuum crystallization and second atmospheric crystallization on the phosphate solution to obtain the phosphate.

[0072] The present invention performs third evaporation concentration on the phosphate solution. In the present invention, the discharge temperature of the third evaporation concentration is preferably ≥90 °C, more preferably 92-95 °C; the solid content is preferably ≥40 wt%, more preferably 40-42 wt%. In the present invention, the third evaporation concentration preferably also obtains condensed water. The present invention preferably uses the condensed water as the mobile phase for reuse in the chromatographic separation. The present invention preferably performs the third evaporation concentration under the above conditions, which can further concentrate the phosphate solution, reduce the volume of the third decolorization slurry, is beneficial to the smooth progress of the third decolorization, and can provide a suitable crystallization concentration for the second vacuum crystallization.

[0073] After the third evaporation concentration, the present invention preferably subjects the obtained third concentrated solution to third decolorization. In the present invention, the third decolorization is preferably activated carbon decolorization. The conditions for the third decolorization include: the amount of activated carbon used is preferably 3-#kg / m 3 , more preferably 3-#kg / m 3; The decolorization temperature is preferably 85 - 95°C, more preferably 90 - 92°C; the decolorization time is preferably 20 - 40 min, more preferably 30 min. The waste activated carbon after the third decolorization in the present invention is preferably recycled for the decolorization of waste carbon. The present invention preferably conducts the third decolorization under the above conditions, which can further remove some proteins, ash and other impurities, increase the light transmittance of the discharged material to >90% (preferably >96%), further improve the purity of the phosphate solution, and is conducive to the subsequent second negative pressure crystallization of the phosphate solution proceeding smoothly.

[0074] After the third decolorization, the present invention preferably subjects the obtained third decolorized liquid to second negative pressure crystallization and second atmospheric pressure crystallization in sequence. In the present invention, the optional conditions for the second negative pressure crystallization and the second atmospheric pressure crystallization are preferably the same as those for the first negative pressure crystallization and the first atmospheric pressure crystallization, and will not be elaborated here.

[0075] After the second atmospheric pressure crystallization, the present invention preferably subjects the obtained second atmospheric pressure crystallization feed liquid to second centrifugal separation, collects the solid wet material for second drying to obtain the phosphate. In the present invention, the centrifuge used for the second centrifugation is preferably a continuous centrifuge, more preferably a horizontal screw thickening and filtering centrifuge; the optional conditions for the second centrifugation and the second drying are preferably the same as those for the first centrifugation and the first drying, and will not be elaborated here. The water content in the phosphate in the present invention is preferably ≤0.3 wt%, more preferably ≤0.26 wt%; the purity is preferably ≥98.5%, more preferably ≥99.0%; the pH value is preferably 4 - 5; the percentage of the product with a particle size of 20 - 200 mesh in the total mass of the product is preferably ≥78%.

[0076] In addition, the production process route of the method in the present invention is short and the degree of automation is high. The main equipment includes an ultrafiltration system, a nanofiltration system, a hydrolysis kettle, a waste heat recovery system (a flash tank, a waste heat evaporator and a vacuum system, wherein the material liquid in the hydrolysis kettle is discharged to the flash tank for flashing, the waste heat generated during the flashing process is recovered to the waste heat evaporator for the first evaporation and concentration, and the flashed material liquid enters a chromatographic device for chromatographic separation after the second decolorization), a chromatographic column, a negative pressure vertical crystallization tank, an atmospheric pressure horizontal crystallization tank, a continuous centrifuge and a vibrating fluidized bed. By adopting advanced technologies such as a simulated moving bed (chromatographic device), a waste heat recovery system, and vacuum-coupled atmospheric pressure crystallization, it can ensure that qualified products can be obtained from inositol and potassium dihydrogen phosphate through one crystallization, and the cost is also greatly reduced.

[0077] Figure 1This is the flow chart of the hierarchical treatment of corn steep water in the present invention for co-producing inositol and phosphates. Hereinafter, in combination with the embodiments of the present invention, the technical solutions in the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0078] In the following embodiments, the corn steep water used is the aqueous solution obtained by soaking corn with water during starch production in a starch factory. After detection, it contains 1.3 wt% phytic acid, 5.5 wt% water-soluble protein, 2.5 wt% lactic acid, 1.3 wt% amino acids, 0.7 wt% inorganic salts, and 5000 ppm potassium ions.

[0079] Example 1

[0080] (1) The corn steep water is subjected to vertical flow sedimentation for 2 h to obtain sedimentation supernatant and sedimentation concentrate respectively. The volume of the sedimentation concentrate is 3% of the total volume of the corn steep water. The sedimentation concentrate (with a solid content of 19.80 wt%) is returned to the concentration process in the starch factory for making corn syrup (the corn syrup is used for preparing feed raw materials).

[0081] (2) The sedimentation supernatant is ultrafiltered to obtain ultrafiltration permeate and ultrafiltration concentrate respectively. The conditions for ultrafiltration include: using a tubular membrane (specifically a ceramic membrane) with a pore size of 50 nm and a pressure of 0.5 MPa. The volume of the ultrafiltration permeate is 95% of the volume of the sedimentation supernatant (i.e., the permeation rate is 95%). The ultrafiltration concentrate is returned to the concentration process in the starch factory for making corn syrup (the corn syrup is used for preparing feed raw materials).

[0082] (3) The ultrafiltration permeate is nanofiltrated to obtain nanofiltration permeate and nanofiltration concentrate respectively. The conditions for nanofiltration include: the cut-off molecular weight of the nanofiltration membrane is 1000 Da and the pressure is 4.0 MPa. The mass of dry matter in the nanofiltration concentrate is 70% of the mass of dry matter in the ultrafiltration permeate (i.e., the dry matter yield in the nanofiltration concentrate is 70%, or the retention rate is 70%). The solid content of the nanofiltration concentrate is 35 wt%. The nanofiltration permeate is returned to the concentration process in the starch factory for making corn syrup (the corn syrup is used for preparing feed raw materials).

[0083] (4) Treat the nanofiltration concentrate with an anion resin column (the used anion resin is S-486-J type anion resin, purchased from Xi'an LX Technology New Materials Co., Ltd.) to adsorb phytic acid, and then perform desorption with a desorbent to obtain a potassium phytate solution; wherein, the volume of the nanofiltration concentrate (i.e., the exchange amount) is 10 BV, and the phytic acid content in the effluent obtained after the treatment of the anion resin column is 0.08 wt%; the desorbent is a potassium chloride solution with a concentration of 12 wt%, and the volume of the desorbent (i.e., the exchange amount) is 2 BV; the solid content of the potassium phytate (including pentapotassium phytate and hexapotassium phytate) solution is 15 wt%, the pH value is 4.0, the phytic acid content is 12 wt%, the chloride ion content < 900 ppm, the magnesium ion content < 180 ppm, the calcium ion content < 19.5 ppm, and the protein content < 0.015 wt%;

[0084] (5) Add waste activated carbon (from the activated carbon after activated carbon decolorization) to the potassium phytate solution at a solid-liquid ratio of 5 kg / m 3 and stir at a temperature of 25 °C for 0.5 h for waste carbon decolorization, and then filter with a diaphragm plate and frame filter press to obtain a waste carbon decolorized solution. The light transmittance of the waste carbon decolorized solution is 25%, and the pH value is 3.9;

[0085] (6) Decolorize the waste carbon decolorized solution with a resin column to obtain a resin column decolorized solution; the conditions for the resin column decolorization include: using HA-90 type resin (purchased from Xi'an Hairun New Materials Co., Ltd.), the volume of the waste carbon decolorized solution (i.e., the exchange amount) is 50 BV, the light transmittance of the resin column decolorized solution is 72.1%, and the pH value is 3.52; after the resin column decolorization, the resin column is regenerated and reused. The regeneration method includes: successively performing sodium hydroxide solution rinsing, first pure water rinsing, hydrochloric acid rinsing and second pure water rinsing, wherein the concentration of the sodium hydroxide solution is 4 wt% and the dosage is 4 BV; the dosage of the first pure water is 4 BV; the concentration of hydrochloric acid is 3 wt% and the dosage is 2 BV; the dosage of the second pure water is 4 BV; the flow rate during the rinsing with each reagent is 1 BV / h;

[0086] (7) Transport the resin column decolorized solution to a waste heat evaporator for the first evaporation and concentration (the heat used comes from the waste heat generated by multi-stage flash evaporation) to obtain a first evaporation concentrate; the discharge temperature of the first evaporation and concentration is 92 °C, and the solid content of the first concentrate is 36 wt%;

[0087] (8) Transport the first evaporation concentrate to a hydrolysis kettle for hydrolysis treatment to obtain a hydrolyzate; the conditions for the hydrolysis treatment include: a temperature of 165 °C, a pressure of 0.72 MPa, and a time of 12 h. The organic phosphorus content in the hydrolyzate is 0.071 wt%;

[0088] (9) Transfer the hydrolyzate to a flash tank for multi-stage flashing to cool the hydrolyzate and recover waste heat, obtaining a flash liquid; the discharge temperature of the multi-stage flashing is 68 °C, and the solid content is 35 wt%; the waste heat generated by the multi-stage flashing is recycled for the first evaporation and concentration;

[0089] (10) Add activated carbon to the flash liquid at a solid-liquid ratio of 3 kg / m 3 Stir at a temperature of 67.5 °C for 0.5 h for activated carbon decolorization, and then filter with a diaphragm plate and frame filter press to obtain an activated carbon decolorized solution. The light transmittance of the activated carbon decolorized solution is 85.5%; the waste activated carbon after activated carbon decolorization is recycled for waste carbon decolorization;

[0090] (11) Use water (from the permeate obtained after reverse osmosis membrane concentration and the condensate generated by evaporation and concentration in the evaporator) as the mobile phase and pass it into a chromatographic column together with the activated carbon decolorized solution for chromatographic separation to obtain an inositol solution and a potassium dihydrogen phosphate solution respectively; the conditions for the chromatographic separation include: the resin filler used in the chromatographic column is DuPont Dow 310K resin (purchased from Shandong Zhaoguang Chromatographic Separation Technology Co., Ltd.), the volume ratio of water to the activated carbon decolorized solution is 2.6:1, and the temperature of the activated carbon decolorized solution and water is 58 °C; the purity of the inositol solution is 92.2%, the conductivity is 1980 μs / cm, the solid content is 6.2 wt%, and the pH value is 4.50; the purity of the potassium dihydrogen phosphate solution is 93.89%, the conductivity > 20000 μs / cm, the solid content is 12.34 wt%, and the pH value is 3.72;

[0091] (111) Concentrate the inositol solution by reverse osmosis membrane with a membrane operating pressure of 0.85 MPa to obtain a membrane concentrate and a permeate respectively. The permeate is recycled for the chromatographic separation, and the solid content in the membrane concentrate is 12.22 wt%;

[0092] The membrane concentrate is treated with cation and anion resin columns to obtain the effluent from the anion resin column. The treatment with cation and anion resin columns includes sequential treatment with a cation resin column and an anion resin column. The treatment with the cation resin column uses a 001×8 type cation resin (purchased from Xi'an LX Technology New Materials Co., Ltd.), and the treatment with the anion resin column uses a ZGA-408 type anion resin (purchased from Tianjin ZhengGuang Synthetic Resin Co., Ltd.), with an exchange capacity of 10 BV. The conductivity of the effluent from the anion resin column is 25 μs / cm, the pH value is 6.5, and the light transmittance is 99.2%. After the treatment with the cation resin column and the anion resin column, the cation resin column and the anion resin column are regenerated and reused. The regeneration method of the cation resin column includes sequential rinsing with hydrochloric acid (concentration: 3 wt%) with a volume of 4 BV and pure water with a volume of 4 BV. The regeneration method of the anion resin column includes sequential rinsing with a sodium hydroxide solution (concentration: 4 wt%) with a volume of 4 BV and pure water with a volume of 5 BV.

[0093] The effluent from the anion resin column is transported to a multi-effect evaporator for secondary evaporation and concentration to obtain a secondary evaporation concentrate. The discharging temperature of the secondary evaporation and concentration is 92 °C, and the solid content in the secondary evaporation concentrate is 40.1 wt%.

[0094] Transfer the second evaporation concentrate to a negative pressure crystallization tank (specifically, a negative pressure vertical crystallization tank), open the vacuum valve, continuously concentrate and cool down under the condition of a vacuum degree of -0.065 MPa. When crystal formation is found in the negative pressure crystallization tank (it can be determined that crystal formation occurs when there are reflective flash points in the material seen through the sight glass, and the material temperature is 75 °C at this time), close the vacuum valve and conduct crystal cultivation for 1 h. After the crystal cultivation is completed, open the vacuum valve and continue to cool down under the condition of a vacuum degree of -0.07 MPa. When the material temperature drops to 50 °C, close the vacuum valve, release the vacuum, open the discharge valve (the time from feeding to discharging is 8 h), and discharge the material in the negative pressure crystallization tank into an atmospheric pressure crystallization tank (specifically, an atmospheric pressure horizontal crystallization tank). Then open the valve of the chilled water (temperature is 7 °C) in the atmospheric pressure crystallization tank and continuously cool down for 3.2 h. When the temperature drops to 25 °C, open the discharge valve (the time from feeding to discharging is 5 h), and discharge the material in the atmospheric pressure crystallization tank into a centrifuge (specifically, a bag-pulling centrifuge), add pure water at a temperature of 40 °C and rinse for 30 s, and then conduct centrifugal separation for 10 min to obtain a solid wet material. The water content in the solid wet material is 2.4 wt%, the purity is 99%, and the single crystallization (that is, through one negative pressure crystallization and one atmospheric pressure crystallization) yield is 65%; transfer the solid wet material to a vibrating fluidized bed for drying through a screw conveyor to obtain an inositol product; wherein the hot air supply temperature for the drying is 120 °C, the cold air (relative humidity ≤ 30%) supply temperature is 25 °C, the water content in the inositol product is 0.08 wt%, the inositol content is 99.5 wt%, the pH value is 5.8, and the percentage of the product with a particle size of 30 - 150 mesh in the total mass of the product is 95%.

[0095] (112) Transfer the potassium dihydrogen phosphate solution to a multi-effect evaporator for the third evaporation concentration to obtain a third evaporation concentrate; the discharge temperature of the third evaporation concentration is 90 °C, and the solid content in the third evaporation concentrate is 40.2 wt%.

[0096] Add activated carbon to the third evaporation concentrate according to a solid-liquid ratio of 3 kg / m 3 Stir and conduct activated carbon decolorization for 0.5 h at a temperature of 90 °C, and then filter with a diaphragm plate and frame filter press to obtain a decolorized potassium dihydrogen phosphate solution. The light transmittance of the decolorized potassium dihydrogen phosphate solution is 96%; the waste activated carbon after the activated carbon decolorization is recycled for waste carbon decolorization;

[0097] Transfer the decolorized potassium dihydrogen phosphate solution to a negative-pressure crystallization tank (specifically, a vertical negative-pressure crystallization tank), open the vacuum valve, and continuously concentrate and cool it under the condition of a vacuum degree of -0.065 MPa. When crystal nucleation is found in the negative-pressure crystallization tank (it can be determined that crystal nucleation occurs when there are reflective bright spots in the material through the sight glass, and the material temperature is 72 °C at this time), close the vacuum valve and carry out crystal cultivation for 1 h. After the crystal cultivation is completed, open the vacuum valve and continue to cool it under the condition of a vacuum degree of -0.07 MPa. When the material temperature drops to 50 °C, close the vacuum valve, release the vacuum, open the discharge valve (the time from feeding to discharging is 8 h), and discharge the material in the negative-pressure crystallization tank into an atmospheric-pressure crystallization tank (specifically, a horizontal atmospheric-pressure crystallization tank). Then open the valve of the chilled water (temperature is 7 °C) of the atmospheric-pressure crystallization tank and continuously cool it. When the temperature drops to 25 °C, open the discharge valve (the time from feeding to discharging is 5 h), and discharge the material in the atmospheric-pressure crystallization tank into a centrifuge (specifically, a horizontal screw thickening and filtering centrifuge), add pure water at a temperature of 40 °C and rinse for 30 s, and then carry out continuous centrifugal separation to obtain a solid wet material. The moisture content in the solid wet material is 2.3 wt%, and the purity is 99%; convey the solid wet material to a vibrating fluidized bed through a screw conveyor for drying to obtain a potassium dihydrogen phosphate product; wherein the hot air supply temperature for the drying is 130 °C, the cold air (relative humidity ≤ 30%) supply temperature is 25 °C, the moisture content in the potassium dihydrogen phosphate product is 0.12 wt%, the potassium dihydrogen phosphate content is 98.5 wt%, the pH value is 4, the water-insoluble matter content is 0.1 wt%, the chloride content is 0.02 wt%, and the percentage of products with a particle size of 20 - 200 mesh in the total mass of the products is 80%.

[0098] Examples 2 - 3

[0099] Operate according to the method of Example 1. The main process parameters and test index data are listed in Tables 1 - 12. The process parameters not specially described are the same as those in Example 1. The results show that the method provided by the present invention can effectively treat a large amount of corn steep water, and at the same time can produce high-purity inositol and by-product phosphate. Among them, for the production of inositol, the inositol yield by single crystallization (that is, through one negative-pressure crystallization and one atmospheric-pressure crystallization) using the method of the present invention is 65%, and the percentage of products with a particle size of 30 - 150 mesh in the total mass of the products is 95%. The product yield is relatively high and the particle size uniformity is good; while the traditional process usually concentrates the inositol solution obtained after chromatographic separation, and then places it in a vertical crystallization tank to cool and crystallize through cooling water. After solid-liquid separation, the obtained inositol crude product is redissolved, then activated carbon is added for decolorization and filtration, and then placed in a vertical crystallization tank to cool and crystallize through cooling water. After solid-liquid separation, the inositol product is obtained. When using this traditional process, the inositol product yield is usually only 50%, and the percentage of products with a particle size of 30 - 150 mesh in the total mass of the products is only 70%. The product yield is relatively low and the particle size is uneven.

[0100] Table 1 Process (sedimentation) parameters and detection indexes in Examples 1 - 3

[0101]

[0102] Table 2 Process (ultrafiltration and nanofiltration) parameters and detection indexes in Examples 1 - 3

[0103]

[0104] Table 3 Process (anion resin column treatment and desorption) parameters and detection indexes in Examples 1 - 3

[0105]

[0106] Table 4 Process (spent carbon decolorization, resin column decolorization and first evaporation concentration) parameters and detection indexes in Examples 1 - 3

[0107]

[0108] Table 5 Process (hydrolysis treatment, flash evaporation and second decolorization) parameters and detection indexes in Examples 1 - 3

[0109]

[0110] Table 6 Process (chromatographic separation) parameters and detection indexes in Examples 1 - 3

[0111]

[0112] Table 7 Process (membrane concentration, cation and anion resin column treatment and second evaporation concentration) parameters and detection indexes in Examples 1 - 3

[0113]

[0114] Table 8 Process (first vacuum crystallization and first atmospheric crystallization) parameters and detection indexes in Examples 1 - 3

[0115]

[0116] Table 9 Process (inositol solid - liquid separation and drying) parameters and detection indexes in Examples 1 - 3

[0117]

[0118] Table 10 Process (third evaporation concentration and third decolorization) parameters and detection indexes in Examples 1 - 3

[0119]

[0120] Table 11 Process (second negative pressure crystallization and second atmospheric pressure crystallization) parameters and detection indexes in Examples 1 to 3

[0121]

[0122] Table 12 Process (solid-liquid separation and drying of potassium dihydrogen phosphate) parameters and detection indexes in Examples 1 to 3

[0123]

[0124] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for co-producing inositol and phosphate by hierarchical treatment of corn steep water, comprising the following steps: Sediment the corn steep water to obtain a sediment supernatant and a sediment concentrate respectively. The sediment concentrate is returned to the concentration process of the starch factory for making corn steep liquor. Ultrafilter the sediment supernatant to obtain an ultrafiltration permeate and an ultrafiltration concentrate respectively. The ultrafiltration concentrate is returned to the concentration process of the starch factory for making corn steep liquor. The conditions of the ultrafiltration include: the pressure is 0.5 - 1.0 MPa, and the pore size of the ultrafiltration membrane is 10 - 50 nm. The volume of the ultrafiltration permeate is 95 - 98% of the volume of the sediment supernatant. Nanofiltrate the ultrafiltration permeate to obtain a nanofiltration permeate and a nanofiltration concentrate respectively. The nanofiltration permeate is returned to the concentration process of the starch factory for making corn steep liquor. The conditions of the nanofiltration include: the pressure is 3.0 - 5.0 MPa, and the molecular weight cut-off of the nanofiltration membrane is 1000 - 2000 Da. The mass of dry matter in the nanofiltration concentrate is 60 - 70% of the mass of dry matter in the ultrafiltration permeate, and the solid content of the nanofiltration concentrate is 30 - 40 wt%. Subject the nanofiltration concentrate to anion resin column treatment and elution in sequence to obtain a phytate solution. Subject the phytate solution to first decolorization and first evaporation concentration in sequence to obtain a phytate concentrate. Subject the phytate concentrate to hydrolysis treatment, flash evaporation, second decolorization and chromatographic separation in sequence to obtain an inositol solution and a phosphate solution respectively. Subject the inositol solution to membrane concentration, cation and anion resin column treatment, second evaporation concentration, first vacuum crystallization and first atmospheric crystallization in sequence to obtain the inositol. The conditions of the cation and anion resin column treatment include: the filler in the cation resin column is 001×8 type cation resin, and the filler in the anion resin column is ZGA - 408 type anion resin. The conductivity of the effluent from the cation and anion resin column treatment is ≤50 μs / cm, the pH value is 5 - 8, and the light transmittance is ≥99%. The outlet temperature of the second evaporation concentration is 90 - 92 °C, and the outlet solid content is 40 - 42 wt%. Subject the phosphate solution to third evaporation concentration, third decolorization, second vacuum crystallization and second atmospheric crystallization in sequence to obtain the phosphate. Carry out the first vacuum crystallization in a vacuum crystallization tank. Transport the second evaporation concentrate to the vacuum crystallization tank, open the vacuum valve, continuously concentrate and cool down under the condition of a vacuum degree of -0.06 - -0.085 MPa. When it is found that crystallization starts in the vacuum crystallization tank and the material temperature is 70 - 80 °C at this time, close the vacuum valve, crystalize for 1 - 2 h. After the crystallization is over, open the vacuum valve and continue to cool down under the condition of a vacuum degree of -0.06 - -0.085 MPa. When the material temperature drops to 50 °C, close the vacuum valve, release the vacuum, open the discharge valve to discharge the material. The time from feeding to discharging is 6 - 8 h. Carry out the first atmospheric crystallization in an atmospheric crystallization tank. Transport the material after the first vacuum crystallization to the atmospheric crystallization tank, continuously cool down for 2 - 3.5 h. When the temperature drops to 20 - 25 °C, open the discharge valve to discharge the material. The time from feeding to discharging is 3 - 5 h. The conditions of the second negative-pressure crystallization and the second atmospheric-pressure crystallization are the same as those of the first negative-pressure crystallization and the first atmospheric-pressure crystallization.

2. The method according to claim 1, characterized in that, The sedimentation time is 1 - 3 h, and the volume of the sedimented concentrated liquid is 3 - 5% of the volume of the corn steep water. The conditions for the treatment by the anion resin column include: the filler in the anion resin column is S-486-J type anion resin, and the phytic acid content in the effluent of the anion resin column is ≤0.1 wt%. The eluent used for elution includes potassium chloride solution, potassium sulfate solution, potassium nitrate solution, hydrochloric acid, sodium chloride solution, potassium hydroxide solution or sodium hydroxide solution; the concentration of the eluent is 5 - 20 wt%.

3. The method according to claim 1 or 2, characterized in that, The first decolorization includes waste carbon decolorization and resin column decolorization in sequence. The second decolorization and the third decolorization are activated carbon decolorization, and the waste activated carbon after the second decolorization and the third decolorization is recycled for the waste carbon decolorization.

4. The method according to claim 3, characterized in that, The conditions for decolorizing the waste carbon include: the dosage of waste activated carbon is 5-10 kg / m 3 , the temperature is 20-40 °C, and the time is 20-40 min; The conditions for the resin column decolorization include: the filler in the resin column is HA-90 type resin; the light transmittance of the discharged material from the resin column decolorization is ≥60%, and the pH value is 3.4 - 4.

5. The conditions for the second decolorization include: the dosage of activated carbon is 3-5 kg / m 3 , the temperature is 50-70 °C, and the time is 20-40 min; The conditions for the third decolorization include: the dosage of activated carbon is 3-5 kg / m 3 , the temperature is 85-100 °C, and the time is 20-40 min.

5. The method according to claim 1, wherein The discharging temperature of the first evaporation and concentration is 85 - 95 °C, and the discharging solid content is 35 - 40 wt%.

6. The method according to claim 1, wherein The conditions for the hydrolysis treatment include: the temperature is 165 - 180 °C, the pressure is 0.7 - 1.0 MPa, and the time is 8 - 12 h. The waste heat generated by the flash evaporation provides heat for the first evaporation and concentration; the discharging temperature of the flash evaporation is ≤70 °C, the discharging solid content is 33 - 40 wt%, and the organic phosphorus content is ≤0.1 wt%. The conditions for the chromatographic separation include: the filler in the chromatographic column is 310K type resin, the feeding temperature is 55 - 60 °C, the mobile phase is water, and the volume ratio of the mobile phase to the second decolorized solution obtained after the second decolorization is 2.5 - 3:1; the purity of the inositol solution is ≥92%, the conductivity is ≤2000 μs / cm, the solid content is 4 - 7 wt%, and the pH value is 3.5 - 4.5; the phosphate solution is potassium dihydrogen phosphate solution, the purity of the potassium dihydrogen phosphate solution is ≥92%, the solid content is 10 - 13 wt%, and the pH value is 3.5 - 4.

5.

7. The method according to claim 1 or 6, characterized in that, The discharging solid content of the membrane concentration is 11 - 13 wt%. The membrane concentration also obtains permeated water, and the permeated water is recycled for the chromatographic separation. The second evaporation and concentration also obtains condensed water, and the condensed water is recycled for the chromatographic separation.

8. The method according to claim 1 or 6, characterized in that, The discharging temperature of the third evaporation and concentration is ≥90 °C, and the discharging solid content is ≥40 wt%; the third evaporation and concentration also obtains condensed water, and the condensed water is recycled for the chromatographic separation.

9. The method according to claim 1, wherein After the first atmospheric-pressure crystallization, it further includes: subjecting the obtained first atmospheric-pressure crystallization feed liquid to first centrifugal separation, collecting the solid wet material for first drying to obtain the inositol. After the second atmospheric-pressure crystallization, it further includes: subjecting the obtained second atmospheric-pressure crystallization feed liquid to second centrifugal separation, collecting the solid wet material for second drying to obtain the phosphate. The first drying and the second drying are carried out in a vibrating fluidized bed.

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