Method for producing fermentation sugar from straw raw material

Abstract

The application relates to the chemical industry field and discloses a preparation method of straw raw material for producing fermentation sugar, which comprises the following steps: pretreating straw raw material, then sequentially performing pre-enzymolysis, enzymolysis, solid-liquid separation, membrane separation, first desalination, decoloration and second desalination to obtain liquid material containing fermentation sugar; wherein the pretreatment method comprises the following steps: S1, performing winnowing on the straw raw material to obtain material after winnowing; S2, performing crushing on the material after winnowing to obtain material after crushing; and S3, performing acid gas explosion on the material after crushing. The method for producing fermentation sugar can improve the yield of cellulose and hemicellulose, efficiently removes impurities in straw enzymolysis liquid, improves the concentration of fermentation sugar in the enzymolysis liquid, and improves the yield and purity of sugar syrup in the fermentation sugar liquid material.

Description

Technical Field

[0001] This invention relates to the field of chemical engineering, and specifically to a method for preparing fermentable sugars from straw raw materials. Background Technology

[0002] Fuel ethanol is a green and renewable energy source. It is mainly produced from grains (corn, wheat, etc.), tubers (sweet potatoes, cassava, and potatoes, etc.), sugars (waste molasses), or cellulose (crop straw, waste wood, and waste pulp, etc.) through fermentation and distillation to obtain 95% (v / v) ethanol. After dehydration, fuel ethanol is obtained, and denaturing agents are added to obtain denatured fuel ethanol.

[0003] Straw is a solid material with low bulk density and large volume. During transportation, the raw material is prone to fluctuations, exhibiting a pulsating state, and is easily scattered, resulting in a poor workshop environment. Furthermore, the moisture content of straw is unstable, varying from 10% to 45% throughout the year, which also affects bulk density. The proportions of straw leaves, stems, and pith also vary depending on the type of bale (round / square) or batch, leading to different bulk densities. This instability in material bulk density directly impacts the stability and load capacity of key pretreatment equipment.

[0004] The core equipment in the pretreatment section is the feeder for the gas explosion unit. Straw under atmospheric pressure is pressurized in this equipment before entering the gas explosion cooking reactor for cooking and gas explosion. Therefore, a stable, uniform, and continuous straw supply from this feeder is crucial for the stable operation of subsequent equipment. However, in practice, due to the low bulk density of straw and significant volume fluctuations, the material is fed in a pulsating manner, making uniform and stable feeding impossible. This leads to large fluctuations in the feeder's operation, making it prone to clogging and even shutdown. The clogging of the feeder also affects the process stability of the cooking reactor, and the discharge port of the gas explosion unit is prone to coking and clogging, subsequently impacting the efficiency of subsequent enzymatic hydrolysis and fermentation units, as well as the overall operating rate of the plant.

[0005] Straw-based biomass raw materials are mainly composed of cellulose, hemicellulose, and lignin. After enzymatic hydrolysis, straw raw materials produce fermentable sugars (mainly hexoses and pentoses), but also generate various complex fermentation inhibitors, primarily organic acids (such as formic acid, acetic acid, and lactic acid), aldehydes (represented by 5-hydroxymethylfurfural), and phenolic compounds as byproducts. Furthermore, since the enzymatic hydrolysate originates from dilute acid gas explosions, the straw hydrolysate contains not only sugars but also a large amount of inorganic ions (potassium ions, sodium ions, calcium ions, magnesium ions, chloride ions, and sulfate ions), with sulfate ions being particularly abundant.

[0006] Compared to traditional corn starch saccharification materials, straw enzymatic hydrolysate has a more complex composition, making impurity removal crucial for obtaining high-purity sugar. Traditional methods for removing impurities from corn starch saccharification mainly include: liquefying and saccharifying the corn starch emulsion; filtering the resulting saccharified liquid to remove precipitated proteins, fats, and other insoluble impurities, resulting in a clear saccharified liquid; using powdered activated carbon to remove colored substances from the saccharified liquid, followed by filtering the activated carbon using a candle filter; then subjecting the saccharified liquid to ion exchange to remove anions, cations, and organic impurities; and finally concentrating the colorless, transparent, dilute syrup after ion exchange. While these methods can remove pigments, proteins, insoluble impurities, and some inorganic ions from corn starch saccharification materials, the resulting fermented syrup from straw enzymatic hydrolysate still contains relatively high levels of inorganic ions (especially sulfate ions), organic acids (such as formic acid, acetic acid, and lactic acid), and furfural, failing to meet the requirements for high-quality fermented syrup. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems of low bulk density and large volume fluctuations in straw materials in existing technologies. The material conveying is pulsating and unstable, leading to large fluctuations in feeder operation, easy blockage, and coking and blockage at the discharge port of the gas explosion equipment. These problems result in low operating rates, high enzyme dosage, high impurity content in the fermented syrup, and low yield and purity of the fermented syrup. This invention provides a method for preparing fermented sugar from straw materials. This method ensures the stability of straw moisture, uniformity of particle size, and cleanliness, thereby ensuring the stability of material bulk density. This, in turn, ensures stable, uniform, and continuous feeding of the feeder, maintaining long-term stable operation of the equipment, achieving efficient utilization of subsequent equipment, reducing enzyme dosage, increasing operating rates, and efficiently removing impurities from the straw enzymatic hydrolysate, thus improving the purity and yield of the fermented sugar.

[0008] To achieve the above objectives, the present invention provides a method for preparing fermentable sugars, the method comprising: pre-treating straw raw materials, and then sequentially performing pre-enzymatic hydrolysis, enzymatic hydrolysis, solid-liquid separation, membrane separation, first desalting, decolorization and second desalting to obtain a liquid containing fermentable sugars;

[0009] The preprocessing method includes:

[0010] S1. The straw raw material is subjected to air separation to obtain the air-separated material;

[0011] S2. The air-separated material is crushed to obtain the crushed material;

[0012] S3. The crushed material is subjected to intermittent acidic gas explosion.

[0013] Through the above technical solution, the present invention achieves at least the following beneficial technical effects:

[0014] (1) The method of the present invention ensures that the straw particle size is uniform and clean, and the bulk density is stable. It avoids the pulse fluctuation of the feeder material, feeder wear and blockage failure, ensures the stability, uniformity and continuity of the feed, and maintains the long-term stable operation of the equipment, which significantly improves the equipment operating rate. In the preferred case, the operating rate reaches more than 90%.

[0015] (2) The method provided by the present invention makes full use of heat, separating wet dregs and evaporated syrup into a biomass boiler, which provides steam for the whole plant. The whole plant does not need to provide steam separately, which reduces energy consumption and saves costs. In the preferred case, energy saving and consumption reduction is 20-30%.

[0016] (3) The method of the present invention can efficiently remove impurities in straw enzymatic hydrolysate and improve the yield and purity of fermented sugar. In the preferred embodiment, the yield of fermented sugar is more than 90% and the purity of fermented sugar is more than 90%, which can meet the raw material requirements of downstream biochemical products.

[0017] (4) The method of the present invention can increase the concentration of fermentable sugars (including pentoses and hexoses) in the straw enzymatic hydrolysate. In a preferred embodiment, the concentration of fermentable sugars in the enzymatic hydrolysate reaches more than 15%. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of a preferred embodiment of the present invention for preparing fermentable sugar.

[0019] Figure 2 This is a flowchart of the production process for extracting fermentable sugars from corn stalk emulsion in Comparative Example 2.

[0020] Explanation of reference numerals in the attached figures

[0021] T1 Air separation unit, T2 Crushing unit, T3 Acid leaching unit

[0022] T4 Acid Recovery Unit, T5 Gas Explosion Unit, T6 Pre-enzymatic Hydrolysis Unit

[0023] T7 Enzymatic hydrolysis unit; T8 Plate and frame separation unit; T9 Membrane separation unit.

[0024] T10 Size Exclusion Chromatography Unit; T11 Decolorization Unit; T12 Ion Exchange Unit

[0025] T13 Evaporation Unit, T14 Biomass Unit Detailed Implementation

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] This invention provides a method for preparing fermentable sugars, the method comprising: pre-treating straw raw materials, and then sequentially performing pre-enzymatic hydrolysis, enzymatic hydrolysis, solid-liquid separation, membrane separation, first desalting, decolorization and second desalting to obtain a liquid containing fermentable sugars;

[0028] The preprocessing method includes:

[0029] S1. The straw raw material is subjected to air separation to obtain the air-separated material;

[0030] S2. The air-separated material is crushed to obtain the crushed material;

[0031] S3. The crushed material is subjected to acidic gas explosion.

[0032] In this invention, the straw raw material is air-separated to remove impurities such as stones, iron blocks, and sand, ensuring the cleanliness of the material, reducing wear and tear on equipment and pipelines, preventing material blockage in the equipment, and ensuring stable operation of the device.

[0033] In this invention, air separation can be performed using equipment conventional in the art. For example, according to some embodiments of the invention, in S1, the air separation is performed using an air separator.

[0034] To further improve the yield of cellulose raw materials, the air separation conditions preferably include: the screen aperture of the air separator is 5-8 mm; the air separation speed of the air separator is 5-20 m / s, preferably 10-15 m / s.

[0035] According to some embodiments of the present invention, the straw yield in the wind-separated material is ≥98wt%.

[0036] According to some embodiments of the present invention, in S2, the pulverization conditions are such that the content of material with a particle size of 3-5 cm is greater than or equal to 85 wt%; the content of material with a particle size of greater than or equal to 10 cm is less than or equal to 10 wt%; and the content of material with a particle size of less than 2 cm is less than or equal to 5 wt%.

[0037] To make the particle size of the crushed straw material more uniform, thereby improving the subsequent air explosion effect, preferably, the crushing conditions are such that the content of the crushed material with a particle size of 3-5cm is 87-93wt%; the content of the material with a particle size of 10cm or more is 5-8wt%; and the content of the material with a particle size of less than 2cm is 2-5wt%.

[0038] The present invention does not have any particular restrictions on the type of straw raw material, and conventional cellulose-containing raw materials can be selected. Preferably, the straw raw material is corn straw and / or wheat straw.

[0039] According to some embodiments of the present invention, the method of acid gas explosion includes: mixing the pulverized material and acid solution for cooking in the presence of medium-pressure steam.

[0040] Preferably, the weight ratio of the dry weight of the pulverized material to the weight of the acid solution is 1:(1-3), more preferably 1:(2-2.5).

[0041] Preferably, the acid content in the acid solution is 0.5-5 wt%, more preferably 1-3 wt%; the temperature of the acid solution is 40-50°C.

[0042] Preferably, the cooking conditions include: the pressure of the medium-pressure steam is 0.6-1 MPaG, preferably 0.6-0.8 MPaG; the temperature of the medium-pressure steam is 160-200℃, preferably 160-180℃; and the cooking time is 10-60 min, preferably 15-30 min.

[0043] According to some embodiments of the present invention, the solid content of the material obtained after the acidic gas explosion is 30-50 wt%, preferably 32-36 wt%; the cellulose yield is ≥90%, and the hemicellulose yield is ≥70%.

[0044] According to the present invention, cellulose yield (%) = 100% × (mass of dry matter in the material after gas explosion / hour × mass percentage of cellulose) / (mass of dry matter in the crushed straw / hour × mass percentage of cellulose); hemicellulose yield (%) = 100% × (mass of dry matter in the material after gas explosion / hour × mass percentage of hemicellulose) / (mass of dry matter in the crushed straw / hour × mass percentage of hemicellulose).

[0045] In this invention, the material after acidic gas explosion enters an enzymatic hydrolysis tank for pre-enzymatic hydrolysis, followed by enzymatic hydrolysis.

[0046] Preferably, the method further includes diluting the material obtained after acidic gas explosion treatment with water before pre-enzymatic hydrolysis to obtain the material to be enzymatically hydrolyzed, wherein the amount of water used is such that the solid content in the material to be enzymatically hydrolyzed is 15-25 wt%.

[0047] According to some embodiments of the present invention, the pre-enzymatic hydrolysis conditions include: a temperature of 50-55°C, a time of 6-15 hours, and continuous enzymatic hydrolysis.

[0048] Preferably, the enzyme used in the pre-enzymatic hydrolysis is cellulase.

[0049] Preferably, the cellulase is a complex enzyme preparation composed of endoglucanase, exoglucanase and β-glucosidase.

[0050] Preferably, when performing the pre-enzymatic hydrolysis, the amount of cellulase used is 100-300 kg, more preferably 180-250 kg, based on the production of 1 ton of fuel ethanol.

[0051] According to some embodiments of the present invention, the viscosity of the enzymatic hydrolysate obtained after pre-enzymatic hydrolysis is 100-300 CP.

[0052] According to some embodiments of the present invention, the conditions for enzymatic hydrolysis include: a temperature of 50-55°C, a time of 55-80 hours, and intermittent enzymatic hydrolysis.

[0053] Preferably, when performing the enzymatic hydrolysis, the amount of the enzyme preparation used is 50-100 kg per ton of straw raw material, more preferably 60-80 kg.

[0054] In this invention, the enzymatically hydrolyzed material undergoes solid-liquid separation, and the separated wet residue is sent to a biomass boiler as a heat source; the separated clear liquid enters a membrane device for ion exclusion chromatography, followed by decolorization with activated carbon and adsorption by ion exchange chromatography to obtain a fermentable dilute syrup; the dilute syrup is evaporated to a concentration of 70% or higher for easy transportation, and different concentrations of syrup can also be obtained by evaporation according to the requirements of subsequent products.

[0055] According to some embodiments of the present invention, the solid-liquid separation method includes: performing plate and frame separation on the straw enzymatic hydrolysate to obtain a clear liquid and a filter cake.

[0056] Preferably, the solid-liquid separation conditions are such that the solid content in the clarified liquid after solid-liquid separation is 5-7 wt%, and the solid content in the filter cake is 40-50 wt%.

[0057] Preferably, the conditions for solid-liquid separation include: a pressure of 0.3-0.4 MPa, more preferably 0.35-0.38 MPa; and a temperature of 35-80°C, more preferably 40-50°C.

[0058] According to some embodiments of the present invention, the conditions for membrane separation include: a membrane pore size of 0.1-10 μm, a temperature of 40-50°C, and a pressure of 0.3-0.4 MPa.

[0059] According to some embodiments of the present invention, the first desalting method includes: separating the clear liquid after membrane separation by passing it through an ion size exclusion chromatography column.

[0060] Preferably, the ion exclusion chromatography column is a sulfonated polystyrene-type cation exchange resin.

[0061] Preferably, the conditions for the first desalination include: a temperature of 40-50℃, a pressure of 0.2-0.3MPa, and an injection flow rate of 0.5-2.5BV / h.

[0062] According to some embodiments of the present invention, the salt content in the clarified liquid after the first desalination treatment is ≤0.04wt%.

[0063] According to some embodiments of the present invention, the decolorization method includes: subjecting the clarified liquid after the first desalination treatment to activated carbon adsorption and plate and frame filtration.

[0064] Preferably, the activated carbon has a particle size of 20-60 mesh.

[0065] Preferably, the mass ratio of the clarified liquid after the first desalination treatment to the activated carbon is (10-30):1.

[0066] Preferably, the conditions for activated carbon adsorption include: an injection flow rate of 1-3 BV / h and an inlet temperature of 70-80℃.

[0067] Preferably, the conditions for the plate and frame filter include: pressure ≤ 0.35 MPa and temperature 70-80℃.

[0068] According to some embodiments of the present invention, the second desalination method includes: sequentially adsorbing the decolorized clear liquid with a cation exchange resin and an anion exchange resin.

[0069] Preferably, the cation exchange resin is a strongly acidic cation exchange resin.

[0070] Preferably, the conditions for adsorption by the cation exchange resin include: inlet temperature ≤ 40℃, outlet pH 3-5, and injection flow rate 1-3 BV / h.

[0071] According to some embodiments of the present invention, the anion exchange resin is a weakly basic anion exchange resin.

[0072] Preferably, the conditions for adsorption by the anion exchange resin include: inlet temperature ≤ 40℃, outlet pH 6-7, and injection flow rate 1-3 BV / h.

[0073] According to some embodiments of the present invention, the method further includes concentrating the material after the second desalination, wherein the concentration is performed by quadruple-effect evaporation.

[0074] Preferably, the conditions for the four-effect evaporation include: the temperature of the first effect evaporation is 95-100℃ and the pressure is 90-100kPa; the temperature of the second effect evaporation is 60-70℃ and the pressure is 20-30kPa; the temperature of the third effect evaporation is 50-60℃ and the pressure is 15-30kPa; and the temperature of the fourth effect evaporation is 50-55℃ and the pressure is 10-25kPa.

[0075] Preferably, the volume of the clear liquid after the first-effect evaporation is 10%-20% of the volume of the clear liquid before concentration.

[0076] Preferably, the volume of the clear liquid after the second evaporation is 20%-40% of the volume of the clear liquid before concentration.

[0077] Preferably, the volume of the clarified liquid after the third-effect evaporation is 40%-60% of the volume of the clarified liquid before concentration.

[0078] Preferably, the volume of the clarified liquid after the third-effect evaporation is 60%-80% of the volume of the clarified liquid before concentration.

[0079] According to a particularly preferred embodiment of the present invention, a method for preparing fermentable sugar is provided, the method comprising:

[0080] S1. The corn stalks are air-separated. The screen of the air separator has a mesh size of 6-8mm and the air separation speed is 12-14m / s. Heavy impurities such as stones, iron blocks, and sand are removed. The corn stalk yield of the material after air separation is ≥98wt%.

[0081] S2. The corn stalks after wind separation are crushed. The crushed material contains 91-93 wt% of material with a particle size of 3-5 cm, 5-6 wt% of material with a particle size of 10 cm or more, and 2-3 wt% of material with a particle size of less than 2 cm.

[0082] S3. After mixing the crushed material with dilute sulfuric acid solution, the mixture is fed into the cooking reactor of the gas explosion equipment. The mixture is cooked in the presence of medium-pressure steam at a pressure of 0.7-0.8 MPa and a temperature of 165-180℃ for 15-30 minutes.

[0083] The weight ratio of the dry weight of the pulverized material to the dilute sulfuric acid solution (the acid content in the dilute sulfuric acid solution is 0.5-5 wt%) is 1:(1-1.5), and the temperature of the dilute sulfuric acid solution is 40-45℃.

[0084] The solid content of the material obtained after acidic gas explosion is 35-38 wt%, the yield of cellulose is ≥90%, and the yield of hemicellulose is ≥80%.

[0085] S4. Add water to dilute the product after the acidic gas explosion to obtain the material to be enzymatically hydrolyzed. The amount of water used is such that the solid content in the material to be enzymatically hydrolyzed is 15-25 wt%. The material to be enzymatically hydrolyzed is subjected to a continuous enzymatic hydrolysis process. Cellulase (200-250 kg of cellulase is used for 1 ton of ethanol product) is added to the product after the acidic gas explosion, and enzymatic hydrolysis is carried out at 50-55℃ for 6-8 hours to obtain a liquefied liquid.

[0086] S5. The pre-enzymatically hydrolyzed liquefied liquid is subjected to an intermittent enzymatic hydrolysis process. Cellulase is added to the above liquefied liquid (70-80 kg of cellulase is used for 1 ton of ethanol product), and the enzymatic hydrolysis is carried out at 50-55℃ for 60-80 h to obtain the enzymatic hydrolysate.

[0087] S6. The enzymatic hydrolysate of straw after enzymatic hydrolysis is separated by plate and frame separation to obtain clear liquid and filter cake;

[0088] The pressure for plate-frame separation is 0.36-0.38 MPa, and the temperature is 45-50℃.

[0089] The solid content in the clarified liquid is 6-7 wt%, and the solid content in the filter cake is 45-50 wt%.

[0090] S7. Perform membrane separation on the above-mentioned clear liquid to remove solids from the clear liquid;

[0091] The conditions for membrane separation include: membrane pore size of 1-10 μm, temperature of 45-50℃, and pressure of 0.35-0.4 MPa.

[0092] S8. The supernatant after membrane separation is subjected to a first desalting treatment using an ion size exclusion chromatography column. The salt content in the supernatant after the first desalting treatment is less than 0.04 wt%.

[0093] The conditions for the first desalination include: a temperature of 40-50℃, a pressure of 0.2-0.3MPa, and an injection flow rate of 0.5-1.5BV / h.

[0094] S9. The clear liquid after the first desalination treatment is decolorized by activated carbon adsorption, and the waste carbon is filtered by a plate and frame filter press.

[0095] The activated carbon has a particle size of 30-60 mesh, and the mass ratio of the clear liquid after the first desalination treatment to the activated carbon is (25-29):1.

[0096] The conditions for activated carbon adsorption include: an injection flow rate of 1.5-2.5 BV / h and an inlet temperature of 70-80℃.

[0097] The conditions for plate and frame filtration include: pressure ≤ 0.35MPa and temperature 75-80℃;

[0098] S10. Adsorb the decolorized clear liquid with cation exchange resin and anion exchange resin respectively.

[0099] The cation exchange resin is a strongly acidic cation exchange resin. The conditions for cation exchange resin adsorption include: inlet temperature ≤ 40℃, outlet pH 3-5, and injection flow rate 1.5-2.5 BV / h.

[0100] The anion exchange resin is a weakly basic anion exchange resin. The conditions for anion exchange resin adsorption include: inlet temperature ≤ 40℃, outlet pH 6-7, and injection flow rate 2-2.5 BV / h.

[0101] S11. The clear liquid after the second desalination treatment is subjected to four-effect evaporation to obtain a liquid containing fermentable sugars;

[0102] The conditions for the four-effect evaporation are as follows: the temperature for the first effect evaporation is 95-100℃ and the pressure is 90-100kPa; the temperature for the second effect evaporation is 60-70℃ and the pressure is 20-30kPa; the temperature for the third effect evaporation is 50-60℃ and the pressure is 15-30kPa; and the temperature for the fourth effect evaporation is 50-55℃ and the pressure is 10-25kPa.

[0103] The present invention will be described in detail below through embodiments.

[0104] In the following examples, the activated carbon was purchased from McLean Company, and the product model was "Electroplating Decolorization Special" with a particle size of 50±10 mesh.

[0105] The enzyme preparations used in both the pre-enzymatic hydrolysis and enzymatic hydrolysis were cellulases. The cellulases were complex enzyme preparations composed of endoglucanase, exoglucanase, and β-glucosidase. The cellulases were purchased from Novozymes, and the product model was Novozymes SD.

[0106] The continuous enzymatic hydrolysis method includes continuously injecting the solution to be hydrolyzed and the enzyme preparation into the enzymatic hydrolysis reactor to achieve a continuous reaction process.

[0107] The intermittent enzymatic hydrolysis method includes: filling the fermenter with the detoxified enzymatic hydrolysate all at once, cooling the enzymatic hydrolysate to 30-33℃, adding the enzyme preparation, mixing evenly, and then carrying out enzymatic hydrolysis.

[0108] The type of cation exchange resin is a strong acid cation exchange resin, purchased from Lanxiao Company, product model LSH-Q.

[0109] The anion exchange resin is a weakly basic anion exchange resin, purchased from Lanxiao Company, product model LSH-R.

[0110] The size exclusion column was sulfonated S-DVB cation exchange resin (sulfonated polystyrene cation exchange resin), purchased from Hamilton, product model PRP-X300.

[0111] The method for determining the solid content in syrup solutions and wet residues includes: separating the syrup solution and wet residues into solid and liquid components, drying the obtained solids, and then weighing them.

[0112] Unless otherwise specified, the materials are commercially available.

[0113] Example 1

[0114] according to Figure 1 The process flow diagram shown illustrates a 50,000-ton / year fermented sugar plant that produces fermented syrup from straw raw materials. The specific methods are as follows:

[0115] S1. At normal temperature and pressure, 13 tons of corn stalks (containing 15% moisture and 10% impurities) were air-separated in the T1 air separation unit (air separator). The screen of the air separator had a mesh size of 6mm and the air separation speed was 12m / s. Heavy impurities such as stones, iron blocks, and sand were removed. The corn stalk recovery rate of the material after air separation was 98%.

[0116] S2. The corn stalks after air separation are crushed in the T2 crushing unit (crusher). The crushed material has the following contents: 92wt% of material with a particle size of 3-5cm, 5wt% of material with a particle size of 10cm or more, and 3wt% of material with a particle size of less than 2cm.

[0117] S3. After mixing the crushed material and dilute sulfuric acid solution in the T3 acid leaching unit, the mixture is introduced into the T5 gas explosion unit (the steaming reactor of the gas explosion equipment) through a regulating valve. The mixture is steamed in the presence of medium-pressure steam at a pressure of 0.7 MPa and a temperature of 165°C for 30 minutes.

[0118] The weight ratio of the dry weight of the pulverized material to the dilute sulfuric acid solution (the acid content in the dilute sulfuric acid solution is 0.5 wt%) is 1:1.5, and the temperature of the dilute sulfuric acid solution is 45℃.

[0119] The solid content of the material obtained after acidic gas explosion is 35 wt%, the yield of cellulose is 90%, and the yield of hemicellulose is 80%.

[0120] S4. Add water to dilute the product after the acidic gas explosion to obtain the material to be enzymatically hydrolyzed. The amount of water used is such that the solid content in the material to be enzymatically hydrolyzed is 15 wt%. The material to be enzymatically hydrolyzed is subjected to a continuous enzymatic hydrolysis process in the T6 pre-enzymatic hydrolysis unit. Cellulase (200 kg of cellulase is used for 1 ton of ethanol product) is added to the product after the acidic gas explosion, and enzymatic hydrolysis is carried out at 50°C for 6 hours to obtain a liquefied liquid.

[0121] S5. The pre-enzymatically hydrolyzed liquefied liquid is subjected to intermittent enzymatic hydrolysis in the T7 enzymatic hydrolysis unit. Cellulase (70 kg of cellulase is used for 1 ton of ethanol product) is added to the above liquefied liquid and enzymatically hydrolyzed at 50°C for 60 h to obtain the enzymatic hydrolysate.

[0122] S6. The enzymatic hydrolysate of straw after enzymatic hydrolysis is subjected to the first solid-liquid separation in the T8 plate and frame separation unit to obtain clear liquid and filter cake.

[0123] The pressure of the first solid-liquid separation is 0.36 MPa, and the temperature is 45℃.

[0124] The solid content in the clarified liquid was 6 wt%, and the solid content in the filter cake was 45 wt%.

[0125] S7. The above-mentioned clear liquid is subjected to a second solid-liquid separation in the T9 membrane separation unit to remove solids from the clear liquid;

[0126] The conditions for the second solid-liquid separation include: a membrane pore size of 1 μm, a temperature of 45 °C, and a pressure of 0.35 MPa.

[0127] S8. The clear liquid after membrane separation is introduced into the T10 size exclusion chromatography unit (ion size exclusion chromatography column) for the first desalting treatment. The salt content in the clear liquid after the first desalting treatment is less than 0.04 wt%.

[0128] The conditions for the first desalination included: a temperature of 40℃, a pressure of 0.2MPa, and an injection flow rate of 0.5BV / h.

[0129] S9. The clear liquid after the first desalination treatment is decolorized by activated carbon adsorption in the T11 decolorization unit, and the waste carbon is filtered by a plate and frame filter press.

[0130] The activated carbon has a particle size of 30 mesh, and the mass ratio of the clear liquid after the first desalination treatment to the activated carbon is 29:1.

[0131] The conditions for activated carbon adsorption include: an injection flow rate of 1.5 BV / h and an inlet temperature of 70℃.

[0132] The conditions for plate and frame filtration include: pressure of 0.35 MPa and temperature of 75℃.

[0133] S10. The decolorized liquid is subjected to a second desalination treatment in the T12 ion exchange unit. Specifically, the decolorized liquid is adsorbed by cation exchange resin and anion exchange resin respectively.

[0134] The conditions for cation resin adsorption include: inlet temperature of 40℃, outlet pH of 3, and injection flow rate of 1.5 BV / h.

[0135] The conditions for anion exchange resin adsorption include: inlet temperature of 40℃, outlet pH of 7, and injection flow rate of 2 BV / h.

[0136] S11. The clear liquid after the second desalination treatment is subjected to four-effect evaporation in the T13 evaporation unit to obtain a liquid containing fermentable sugars with a concentration of 70% (this concentration is convenient for transportation and can also be adjusted according to subsequent processes).

[0137] The conditions for the four-effect evaporation are as follows: the temperature of the first effect evaporation is 95℃ and the pressure is 90kPa; the temperature of the second effect evaporation is 60℃ and the pressure is 20kPa; the temperature of the third effect evaporation is 50℃ and the pressure is 15kPa; and the temperature of the fourth effect evaporation is 50℃ and the pressure is 10kPa.

[0138] Example 2

[0139] according to Figure 1 The process flow diagram shown illustrates a 50,000-ton / year fermented sugar plant that produces fermented syrup from straw raw materials. The specific methods are as follows:

[0140] S1. At normal temperature and pressure, 13 tons of corn stalks (containing 15% moisture and 10% impurities) were air-separated in the T1 air separation unit (air separator). The screen of the air separator had a mesh size of 6mm and the air separation speed was 10m / s. Heavy impurities such as stones, iron blocks, and sand were removed. The corn stalk recovery rate of the material after air separation was 98%.

[0141] S2. The corn stalks after air separation are crushed in the T2 crushing unit (crusher). The crushed material has the following contents: 90wt% of material with a particle size of 3-5cm, 8wt% of material with a particle size of 10cm or more, and 2wt% of material with a particle size of less than 2cm.

[0142] S3. After mixing the crushed material and dilute sulfuric acid solution in the T3 acid leaching unit, the mixture is introduced into the T5 gas explosion unit (the steaming reactor of the gas explosion equipment) through a regulating valve. The mixture is steamed in the presence of medium-pressure steam at a pressure of 0.8 MPa and a temperature of 180°C for 20 minutes.

[0143] The weight ratio of the dry weight of the pulverized material to the dilute sulfuric acid solution (the acid content in the dilute sulfuric acid solution is 0.5 wt%) is 1:2.5, and the temperature of the dilute sulfuric acid solution is 45℃.

[0144] The solid content of the material obtained after acidic gas explosion was 43 wt%, the yield of cellulose was 90%, and the yield of hemicellulose was 70%.

[0145] S4. Add water to dilute the product after the acidic gas explosion to obtain the material to be enzymatically hydrolyzed. The amount of water used is such that the solid content in the material to be enzymatically hydrolyzed is 25 wt%. The material to be enzymatically hydrolyzed is subjected to a continuous enzymatic hydrolysis process in the T6 pre-enzymatic hydrolysis unit. Cellulase (250 kg of enzyme preparation is used for 1 ton of ethanol product) is added to the product after the acidic gas explosion, and enzymatic hydrolysis is carried out at 50°C for 12 h to obtain a liquefied liquid.

[0146] S5. The pre-enzymatically hydrolyzed liquefied liquid is subjected to intermittent enzymatic hydrolysis in the T7 enzymatic hydrolysis unit. Cellulase (80 kg of enzyme is added for 1 ton of ethanol product) is added to the above liquefied liquid and enzymatically hydrolyzed at 50°C for 60 h to obtain the enzymatic hydrolysate.

[0147] S6. The enzymatic hydrolysate of straw after enzymatic hydrolysis is subjected to the first solid-liquid separation in the T8 plate and frame separation unit to obtain clear liquid and filter cake.

[0148] The pressure for the first solid-liquid separation is 0.38 MPa, and the temperature is 50 °C.

[0149] The solid content in the clarified liquid was 5 wt%, and the solid content in the filter cake was 45 wt%.

[0150] S7. The above-mentioned clear liquid is subjected to a second solid-liquid separation in the T9 membrane separation unit to remove solids from the clear liquid;

[0151] The conditions for the second solid-liquid separation include: a membrane pore size of 10 μm, a temperature of 45 °C, and a pressure of 0.35 MPa.

[0152] S8. The clear liquid after membrane separation is introduced into the T10 size exclusion chromatography unit (ion size exclusion chromatography column) for the first desalting treatment. The salt content in the clear liquid after the first desalting treatment is less than 0.04 wt%.

[0153] The conditions for the first desalination included: a temperature of 45℃, a pressure of 0.25MPa, and an injection flow rate of 2BV / h.

[0154] S9. The clear liquid after the first desalination treatment is decolorized by activated carbon adsorption in the T11 decolorization unit, and the waste carbon is filtered by a plate and frame filter press.

[0155] The activated carbon has a particle size of 30 mesh, and the mass ratio of the clear liquid after the first desalination treatment to the activated carbon is 20:1.

[0156] The conditions for activated carbon adsorption include: an injection flow rate of 3 BV / h and an inlet temperature of 75℃.

[0157] The conditions for plate and frame filtration include: pressure of 0.35 MPa and temperature of 75℃.

[0158] S10. The decolorized liquid is subjected to a second desalination treatment in the T12 ion exchange unit. Specifically, the decolorized liquid is adsorbed by cation exchange resin and anion exchange resin respectively.

[0159] The conditions for cation resin adsorption include: inlet temperature of 40℃, outlet pH of 4, and injection flow rate of 3 BV / h.

[0160] The conditions for anion exchange resin adsorption include: inlet temperature of 40℃, outlet pH of 7, and injection flow rate of 3 BV / h.

[0161] S11. The clear liquid after the second desalination treatment is evaporated in the T13 evaporation unit in four-effect evaporation to obtain a liquid containing fermentable sugar (the concentration of fermentable sugar is 70%).

[0162] The conditions for the four-effect evaporation are as follows: the temperature of the first effect evaporation is 95℃ and the pressure is 90kPa; the temperature of the second effect evaporation is 65℃ and the pressure is 25kPa; the temperature of the third effect evaporation is 55℃ and the pressure is 20kPa; and the temperature of the fourth effect evaporation is 50℃ and the pressure is 20kPa.

[0163] Example 3

[0164] according to Figure 1 The process flow diagram shown illustrates a 50,000-ton / year fermented sugar plant that produces fermented syrup from straw raw materials. The specific methods are as follows:

[0165] S1. At normal temperature and pressure, 13 tons of corn stalks (containing 15% moisture and 10% impurities) were air-separated in the T1 air separation unit (air separator). The screen of the air separator had a mesh size of 8mm and the air separation speed was 15m / s. Heavy impurities such as stones, iron blocks, and sand were removed. The corn stalk recovery rate of the material after air separation was 98%.

[0166] S2. The corn stalks after air separation are crushed in the T2 crushing unit (crusher). The crushed material has the following contents: 92wt% of material with a particle size of 3-5cm, 5wt% of material with a particle size of 10cm or more, and 3wt% of material with a particle size of less than 2cm.

[0167] S3. After mixing the crushed material and dilute sulfuric acid solution in the T3 acid leaching unit, the mixture is introduced into the T5 gas explosion unit (the cooking reactor of the gas explosion equipment) through a regulating valve. The mixture is then cooked in the presence of medium-pressure steam at a pressure of 0.6 MPa and a temperature of 160°C for 15 minutes.

[0168] The weight ratio of the dry weight of the pulverized material to the dilute sulfuric acid solution (the acid content in the dilute sulfuric acid solution is 0.5 wt%) is 1:2, and the temperature of the dilute sulfuric acid solution is 45℃.

[0169] The solid content of the material obtained after acidic gas explosion is 38 wt%, the yield of cellulose is 90%, and the yield of hemicellulose is 75%.

[0170] S4. Add water to dilute the product after acidic gas explosion to obtain the material to be enzymatically hydrolyzed. The amount of water used is such that the solid content in the material to be enzymatically hydrolyzed is 20wt%. The material to be enzymatically hydrolyzed is subjected to continuous enzymatic hydrolysis in the T6 pre-enzymatic hydrolysis unit. Cellulase (180kg of enzyme preparation is used for 1 ton of straw ethanol product) is added to the product after acidic gas explosion, and enzymatic hydrolysis is carried out at 50℃ for 9 hours to obtain liquefied liquid.

[0171] S5. The pre-enzymatically hydrolyzed liquefied liquid is subjected to intermittent enzymatic hydrolysis in the T7 enzymatic hydrolysis unit. Cellulase is added to the above liquefied liquid (60 kg of cellulase is used for 1 ton of ethanol product), and the enzymatic hydrolysis is carried out at 50°C for 56 h to obtain the enzymatic hydrolysate.

[0172] S6. The enzymatic hydrolysate of straw after enzymatic hydrolysis is subjected to the first solid-liquid separation in the T8 plate and frame separation unit to obtain clear liquid and filter cake.

[0173] The pressure for the first solid-liquid separation is 0.3 MPa, and the temperature is 40℃.

[0174] The solid content in the clarified liquid was 7 wt%, and the solid content in the filter cake was 50 wt%.

[0175] S7. The above-mentioned clear liquid is subjected to a second solid-liquid separation in the T9 membrane separation unit to remove solids from the clear liquid;

[0176] The conditions for membrane separation include: a membrane pore size of 0.1 μm, a temperature of 50 °C, and a pressure of 0.4 MPa.

[0177] S8. The clear liquid after membrane separation is introduced into the T10 size exclusion chromatography unit (ion size exclusion chromatography column) for the first desalting treatment. The salt content in the clear liquid after the first desalting treatment is less than 0.02 wt%.

[0178] The conditions for the first desalination included: a temperature of 50℃, a pressure of 0.3MPa, and an injection flow rate of 2.5BV / h.

[0179] S9. The clear liquid after the first desalination treatment is decolorized by activated carbon adsorption in the T11 decolorization unit, and the waste carbon is filtered by a plate and frame filter press.

[0180] The activated carbon has a particle size of 60 mesh, and the mass ratio of the clear liquid after the first desalination treatment to the activated carbon is 10:1.

[0181] The conditions for activated carbon adsorption include: an injection flow rate of 1 BV / h and an inlet temperature of 80℃.

[0182] The conditions for plate and frame filtration include: pressure of 0.3 MPa and temperature of 80℃.

[0183] S10. The decolorized liquid is subjected to a second desalination treatment in the T12 ion exchange unit. Specifically, the decolorized liquid is adsorbed by cation exchange resin and anion exchange resin respectively.

[0184] The conditions for cation resin adsorption include: inlet temperature of 38℃, outlet pH of 5, and injection flow rate of 1 BV / h.

[0185] The conditions for anion exchange resin adsorption include: inlet temperature of 38℃, outlet pH of 7, and injection flow rate of 1 BV / h.

[0186] S11. The clear liquid after the second desalination treatment is evaporated in the T13 evaporation unit in four-effect evaporation to obtain a liquid containing fermentable sugar (the concentration of fermentable sugar is 70%).

[0187] The conditions for the four-effect evaporation are as follows: the temperature of the first effect evaporation is 100℃ and the pressure is 100kPa; the temperature of the second effect evaporation is 70℃ and the pressure is 30kPa; the temperature of the third effect evaporation is 60℃ and the pressure is 30kPa; and the temperature of the fourth effect evaporation is 55℃ and the pressure is 25kPa.

[0188] Example 4

[0189] The method of Example 1 is followed, except that the ion size exclusion column in the T10 size exclusion chromatography unit is replaced with BlueDragon Technology Seplite cationic resin to obtain a liquid containing fermentable sugars.

[0190] Example 5

[0191] The method of Example 1 is different in that, during the activated carbon adsorption decolorization treatment in the T11 decolorization unit, the injection flow rate is 5 BV / h, and a liquid containing fermentable sugars is obtained.

[0192] Example 6

[0193] The method of Example 1 is followed, except that the cation exchange resin in the T12 ion exchange unit is replaced with Seplite cation exchange resin from Lanxiao Technology to obtain a liquid containing fermentable sugars.

[0194] Example 7

[0195] The method of Example 1 is followed, except that the anion exchange resin in the T12 ion exchange unit is replaced with Seplite cation exchange resin from Lanxiao Technology to obtain a liquid containing fermentable sugars.

[0196] Example 8

[0197] The method of Example 1 differs in that the degree of pulverization is different in S2. Specifically, the pulverization conditions are such that the content of material with a particle size of 3-5 cm is 60 wt%, the content of material with a particle size of 10 cm or more is 20 wt%, and the content of material with a particle size of less than 2 cm is 20 wt%, resulting in a liquid containing fermentable sugars.

[0198] Example 9

[0199] The method is the same as in Example 1, except that in S3, the pressure of the acidic gas explosion is 1.2 MPaG, and a liquid containing fermentable sugars is obtained.

[0200] Comparative Example 1

[0201] The method described in Example 3 differs in that a neutral gas explosion is used instead of an acidic gas explosion. The specific method for a neutral gas explosion includes: the crushed straw material is introduced into the cooking reactor of the gas explosion equipment through a regulating valve; in the presence of medium-pressure steam at a pressure of 1.6 MPa and a temperature of 250°C, the crushed material and water are mixed and cooked for 30 minutes; the weight ratio of the crushed material to water is 1:1.

[0202] Comparative Example 2

[0203] according to Figure 2 The production process shown uses corn stalk emulsified material as raw material to extract fermentable sugars.

[0204] Test Example 1

[0205] The yields of cellulose and hemicellulose from the straw raw materials after steam explosion, as well as the operating rate of the equipment and steam consumption, were measured in each example and comparative example. The results are shown in Table 1.

[0206] 1) Cellulose yield (%) = 100% × (mass of dry matter in the material after air explosion / hour × mass percentage of cellulose) / (mass of dry matter in the crushed straw / hour × mass percentage of cellulose);

[0207] 2) Hemicellulose yield (%) = 100% × (mass of dry matter in the material after air explosion / hour × mass percentage of hemicellulose) / (mass of dry matter in the crushed straw / hour × mass percentage of hemicellulose);

[0208] 3) Operating rate (%) = Operating time (hours) ÷ 8000 (designed operating time 8000 or 7200) × 100%;

[0209] 4) Steam consumption (kg / h) = Steam consumption of each piece of equipment / time.

[0210] Table 1

[0211]

[0212] Test Example 2

[0213] The sugar concentration, syrup yield and purity, inorganic ion concentration (total amount of potassium, sodium, calcium, magnesium, chloride and sulfate ions), and sulfate ion concentration in the enzymatic hydrolysate, were tested in the examples and comparative examples, respectively. The results are shown in Table 2.

[0214] The content of inorganic ions (calculated as the total amount of potassium ions, sodium ions, calcium ions, magnesium ions, chloride ions and sulfate ions) is expressed by conductivity. If the conductivity is less than 50, the removal of inorganic ions is considered to be qualified. The content of inorganic ions is measured by a conductivity meter.

[0215] The concentration of sulfate ions was measured using a sulfate analyzer.

[0216] Table 2

[0217]

[0218] Comparing Examples 1-3 with Examples 4-9, it can be seen that the preferred embodiments of the present invention can ensure the stability of straw moisture, the uniformity of particle size, and the cleanliness of straw, thereby ensuring the stability of material bulk density, and thus ensuring the stable, uniform, and continuous feeding of the feeder, maintaining the long-term stable operation of the equipment, realizing the efficient utilization of subsequent equipment, improving the operating rate, and at the same time efficiently removing impurities in the straw enzymatic hydrolysate, improving the concentration of fermentable sugar in the enzymatic hydrolysate and the purity and yield of syrup in the fermentable sugar solution.

[0219] Compared with the examples, Comparative Example 1 uses neutral gas explosion, which results in a high reaction temperature, poor gas explosion effect, low cellulose and hemicellulose yield, high energy consumption, and reduced concentration of fermentable sugar in the enzymatic hydrolysate, as well as reduced yield and purity of syrup in the fermentable sugar solution. In Comparative Example 2, corn stalk emulsion is used as raw material to extract fermentable sugar. However, due to the presence of complex impurities in the corn stalk emulsion, the process using corn raw materials results in a lower concentration of fermentable sugar in the enzymatic hydrolysate, and the yield and purity of fermentable sugar cannot reach the requirement of over 90%.

[0220] In summary, the method of the present invention for producing fermentable sugar can improve the yield of cellulose and hemicellulose, while efficiently removing impurities from the straw enzymatic hydrolysate, increasing the concentration of fermentable sugar in the hydrolysate, as well as the yield and purity of syrup in the fermentable sugar solution.

[0221] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing fermentable sugar, characterized in that, The method includes: pre-treating the straw raw material, and then sequentially performing pre-enzymatic hydrolysis, enzymatic hydrolysis, solid-liquid separation, membrane separation, first desalination, decolorization and second desalination to obtain a liquid containing fermentable sugars; The preprocessing method includes: S1. The straw raw material is subjected to air separation to obtain the air-separated material; S2. The air-separated material is crushed to obtain the crushed material; S3. The crushed material is subjected to acidic gas explosion.

2. The method according to claim 1, wherein, In S1, the air separation is performed using an air separator; Preferably, the conditions for air separation include: the screen aperture of the air separator is 5-8 mm; the air separation speed of the air separator is 5-20 m / s, preferably 10-15 m / s; And / or, the straw yield in the air-separated material is ≥98wt%.

3. The method according to claim 1 or 2, wherein, In S2, the pulverization conditions are such that the content of material with a particle size of 3-5 cm in the pulverized material is greater than or equal to 85 wt%, preferably 87-93 wt%; the content of material with a particle size of 10 cm or greater is less than or equal to 10 wt%, preferably 5-8 wt%; and the content of material with a particle size of less than 2 cm is less than or equal to 5 wt%, preferably 2-5 wt%. Preferably, the straw raw material is corn straw and / or wheat straw.

4. The method according to any one of claims 1-3, wherein, In S3, the method of acid gas explosion includes: mixing the pulverized material and acid solution for cooking in the presence of medium-pressure steam; Preferably, the weight ratio of the dry weight of the pulverized material to the weight of the acid solution is 1:(1-3), more preferably 1:(2-2.5); Preferably, the acid content in the acid solution is 0.5-5 wt%, more preferably 1-3 wt%; the temperature of the acid solution is 40-50°C. Preferably, the cooking conditions include: the pressure of the medium-pressure steam is 0.6-1 MPaG, preferably 0.6-0.8 MPaG; the temperature of the medium-pressure steam is 160-200℃, preferably 160-180℃; and the cooking time is 10-60 min, preferably 15-30 min. And / or, the solid content of the material obtained after the acidic gas explosion is 30-50 wt%, preferably 32-36 wt%; the cellulose yield is ≥90%, and the hemicellulose yield is ≥70%; Preferably, the method further includes diluting the material obtained after acidic gas explosion treatment with water before pre-enzymatic hydrolysis to obtain the material to be enzymatically hydrolyzed, wherein the amount of water used is such that the solid content in the material to be enzymatically hydrolyzed is 15-25 wt%. And / or, the pre-enzymatic hydrolysis conditions include: a temperature of 50-55°C, a time of 6-15 hours, and continuous enzymatic hydrolysis; Preferably, the enzymes used in the pre-hydrolysis and hydrolysis are each cellulase independently; Preferably, the cellulase is a complex enzyme preparation composed of endoglucanase, exoglucanase and β-glucosidase; Preferably, when performing the pre-enzymatic hydrolysis, the amount of cellulase used is 100-300 kg, more preferably 180-250 kg, based on the production of 1 ton of fuel ethanol. And / or, the viscosity of the enzymatic hydrolysate obtained after pre-enzymatic hydrolysis is 100-300 CP; And / or, the conditions for the enzymatic hydrolysis include: a temperature of 50-55°C, a time of 55-80 h, and intermittent enzymatic hydrolysis; Preferably, when performing the enzymatic hydrolysis, the amount of enzyme preparation used is 50-100 kg per ton of straw raw material, more preferably 60-80 kg.

5. The method according to any one of claims 1-4, wherein, The solid-liquid separation method includes: performing plate and frame separation on the straw enzymatic hydrolysate to obtain a clear liquid and a filter cake; Preferably, the solid-liquid separation conditions are such that the solid content in the clear liquid after solid-liquid separation is 5-7 wt%, and the solid content in the filter cake is 40-50 wt%. Preferably, the conditions for solid-liquid separation include: a pressure of 0.3-0.4 MPa, more preferably 0.35-0.38 MPa; and a temperature of 35-80°C, more preferably 40-50°C. And / or, the conditions for membrane separation include: a membrane pore size of 0.1-10 μm, a temperature of 40-50 °C, and a pressure of 0.3-0.4 MPa.

6. The method according to any one of claims 1-5, wherein, The first desalting method includes: separating the clear liquid after membrane separation by passing it through an ion size exclusion chromatography column; Preferably, the ion size exclusion chromatography column is a sulfonated polystyrene-type cation exchange resin; Preferably, the conditions for the first desalination include: a temperature of 40-50℃, a pressure of 0.2-0.3MPa, and an injection flow rate of 0.5-2.5BV / h; And / or, the salt content in the clarified liquid after the first desalination treatment is ≤0.04wt%.

7. The method according to any one of claims 1-6, wherein, The decolorization method includes: passing the clear liquid after the first desalination treatment through activated carbon adsorption and plate and frame filtration; Preferably, the activated carbon has a particle size of 20-60 mesh; Preferably, the mass ratio of the clarified liquid after the first desalination treatment to the activated carbon is (10-30):1; Preferably, the conditions for activated carbon adsorption include: an injection flow rate of 1-3 BV / h and an inlet temperature of 70-80℃; Preferably, the conditions for the plate and frame filter include: pressure ≤ 0.35 MPa and temperature 70-80℃.

8. The method according to any one of claims 1-7, wherein, The second desalination method includes: sequentially adsorbing the decolorized clear liquid with cationic resin and anionic resin; Preferably, the cation exchange resin is a strongly acidic cation exchange resin; Preferably, the conditions for adsorption by the cation exchange resin include: inlet temperature ≤ 40℃, outlet pH 3-5, and injection flow rate 1-3 BV / h.

9. The method according to claim 8, wherein, The anion exchange resin is a weakly basic anion exchange resin; Preferably, the conditions for adsorption by the anion exchange resin include: inlet temperature ≤ 40℃, outlet pH 6-7, and injection flow rate 1-3 BV / h.

10. The method according to any one of claims 1-9, wherein, The method also includes concentrating the material after the second desalination, wherein the concentration is performed by quadruple-effect evaporation; Preferably, the conditions for the four-effect evaporation include: the temperature of the first effect evaporation is 95-100℃ and the pressure is 90-100kPa; the temperature of the second effect evaporation is 60-70℃ and the pressure is 20-30kPa; the temperature of the third effect evaporation is 50-60℃ and the pressure is 15-30kPa; and the temperature of the fourth effect evaporation is 50-55℃ and the pressure is 10-25kPa. Preferably, the volume of the clear liquid after the first-effect evaporation is 10%-20% of the volume of the clear liquid before concentration; Preferably, the volume of the clarified liquid after the second evaporation is 20%-40% of the volume of the clarified liquid before concentration; Preferably, the volume of the clarified liquid after the third-effect evaporation is 40%-60% of the volume of the clarified liquid before concentration; Preferably, the volume of the clarified liquid after the third-effect evaporation is 60%-80% of the volume of the clarified liquid before concentration.

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