Method for producing potassium fulvic acid and fulvic acid by straw sugar production

Abstract

The present invention provides a method for producing potassium fulvate and fulvic acid from straw sugar, comprising the following steps: (1) steaming straw in a potassium hydroxide aqueous solution, followed by solid-liquid separation to obtain straw residue and extrudate, wherein the steaming temperature is 130° C. to 180° C. and the pressure is 0.5 to 1.2 MPa; and (2) concentrating the extrudate to obtain liquid potassium fulvate. The preparation method of the present invention simplifies the industrial production process, facilitates large-scale production, and eliminates waste and pollutant discharge during the process.

Description

Technical Field

[0001] The present invention relates to the field of biochemical engineering, and in particular to a method for producing straw sugar and co-producing potassium fulvic acid and fulvic acid. Background Art

[0002] my country is a major agricultural country with abundant straw resources. The main components of straw are lignocellulose, protein, pectin, and mineral elements. Lignocellulose is primarily composed of three polymers: cellulose, hemicellulose, and lignin (collectively, the "three elements"). Cellulose can be hydrolyzed into fermentable small sugars.

[0003] Among the five uses of straw, fertilizer and feed utilization, while significant, are relatively modest in value. Fuel utilization offers a low added value and falls short of the "carbon peak and carbon neutrality" goals. And base material utilization has limited applications. Straw utilization as a raw material primarily focuses on the production of hexoses and pentoses from cellulose and hemicellulose, and the production of fulvic acid from lignin. Straw sugars can be used to produce healthy foods, bio-based materials, and bioenergy, while fulvic acid, when used in organic fertilizer production and returned to the field, improves soil quality, enhances fertilizer efficiency, promotes crop growth, enhances stress tolerance, and improves crop quality. It particularly contributes to soil fertility, improves fertilizer utilization, and shortens crop growth cycles. This not only aligns with the national green and low-carbon development strategy, but also demonstrates the high-value utilization of agricultural waste.

[0004] Currently, many domestic companies, universities, and institutions are researching efficient separation of the intertwined "three elements" in straw, but the overall cost is high, not reaching industrial standards, and hindering large-scale industrialization. Therefore, simplifying the process of high-value straw utilization is key to expanding its use as a raw material. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art and provide a method for producing potassium fulvic acid and fulvic acid by co-producing sugar from straw. The preparation method of the present invention simplifies the industrial production process, facilitates large-scale production, and eliminates waste and pollutants during the process.

[0006] In a first aspect, the present invention provides a method for producing straw sugar and co-producing potassium fulvic acid and fulvic acid, comprising the following steps:

[0007] (1) The straw is steamed in a potassium hydroxide aqueous solution, and then subjected to solid-liquid separation to obtain straw residue and extrudate, wherein the steaming temperature is 130° C. to 180° C., for example, 130° C., 135° C., 140° C., 145° C., 150° C., 155° C., 157° C., 160° C., 163° C., 165° C., 170° C., 175° C., and 180° C.; and the pressure is 0.5 to 1.2 MPa, for example, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa, 1.1 MPa, and 1.2 MPa.

[0008] (2) The extrudate is concentrated to obtain liquid potassium fulvate.

[0009] In some embodiments, the method further comprises the following step (3):

[0010] The liquid potassium fulvic acid is spray-dried to obtain solid potassium fulvic acid.

[0011] In some embodiments, the method further comprises the following step (4):

[0012] (4) The straw residue described in step (1) is subjected to a multi-stage countercurrent washing treatment, and then enzymatically hydrolyzed and filtered to obtain a sugar solution and a sugar residue.

[0013] In some embodiments, the method further comprises the following steps (5) and / or (6):

[0014] (5) cracking and activating the sugar residue to obtain solid fulvic acid;

[0015] (6) Refining the sugar solution to obtain liquid mixed sugar.

[0016] In some embodiments, in step (1), the weight ratio of straw to water is 1:(2-5), for example, 1:2, 1:2.3, 1:2.8, 1:3, 1:3.2, 1:3.7, 1:4, 1:4.4, 1:4.8, or 1:5.

[0017] In some embodiments, the weight ratio of straw to water is 1:(2.5-4).

[0018] In some embodiments, the amount of potassium hydroxide is 3% to 8% relative to the dry weight of the straw, for example, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or 8%.

[0019] In some embodiments, the amount of potassium hydroxide used is 6-8% relative to the dry weight of the straw.

[0020] In some embodiments, in step (1), the cooking temperature is 150°C to 165°C, for example, 150°C, 152°C, 154°C, 156°C, 158°C, 160°C, 162°C, or 165°C.

[0021] In some embodiments, the cooking temperature is 155°C to 165°C.

[0022] In some embodiments, the pressure of the steaming treatment is 0.6-0.8 MPa, for example, 0.6 MPa, 0.65 MPa, 0.7 MPa, 0.75 MPa, or 0.8 MPa.

[0023] In some embodiments, the cooking time is 0.5 to 4 hours, for example, 0.5 hours, 1 hour, 1.2 hours, 1.5 hours, 1.7 hours, 2 hours, 2.3 hours, 2.5 hours, 2.7 hours, 3 hours, 3.5 hours, or 4 hours.

[0024] In some embodiments, the cooking time is 1 to 3 hours.

[0025] In some embodiments, in step (1), the temperature of the steaming treatment is 150-165° C.; and the time of the steaming treatment is 1-3 hours.

[0026] In some embodiments, the straw is pretreated before the cooking process, and the pretreatment includes removing dust and impurities from the straw.

[0027] In some embodiments, the cooking product after the cooking process is subjected to solid-liquid separation by a squeezer to obtain the straw residue and the extrudate.

[0028] In some embodiments, the concentration process uses an MVR concentration device.

[0029] In some embodiments, the filtration is performed using a mechanical filtration device.

[0030] In some embodiments, the filtration is performed using a plate and frame filter.

[0031] In some embodiments, the enzymatic hydrolysis uses a complex enzyme.

[0032] In some embodiments, the multienzyme comprises cellulase, xylanase, and cellobiase.

[0033] In some embodiments, the added amount of cellulase is 0-40 FPA / g dry matter, the added amount of xylanase is 0-3000 U / g dry matter, and the added amount of cellobiase is 2-100 U / g dry matter.

[0034] In some embodiments, in step (5), the cracking activation uses an activator, and the activator includes one or more combinations of ammonium sulfite, potassium sulfite, potassium hydroxide, ammonium persulfate, potassium persulfate, and ammonia water.

[0035] In some embodiments, the added amount of the activator is 5% to 15% of the dry weight of the sugar residue, for example, 5%, 7%, 9%, 11%, 13%, or 15%.

[0036] The innovation of the present invention lies in that: by steaming the straw under specific conditions, potassium fulvic acid with a high content can be produced in one step, and at the same time, the subsequent enzymatic hydrolysis effect is good and the enzymatic hydrolysis rate is high.

[0037] The present invention has the following beneficial effects: a simple process flow, easy scalability, and no waste or pollutants are discharged during the process. The products produced by the method of the present invention are highly valuable. The liquid mixed sugar can be used to produce biodegradable materials such as lactic acid and polylactic acid. Liquid potassium fulvate, solid potassium fulvate, and the byproduct fulvic acid are high-value products that promote plant growth and development and improve soil quality. Furthermore, the present invention achieves comprehensive, high-value utilization of straw, with low overall production costs and high product economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a flow chart of straw sugar production with co-production of potassium fulvic acid and fulvic acid. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the following embodiments and accompanying drawings. The specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention in any way. In addition, descriptions of known structures and techniques are omitted in the following description to avoid unnecessary confusion regarding the concepts of the present disclosure. Such structures and techniques are also described in many publications.

[0040] The embodiment of the present invention is based on Figure 1 Prepared according to the process shown:

[0041] In step S1, after removing impurities and dust, the straw is placed in a digester, where water and potassium hydroxide are added for digestion. After the reaction, the pressure is released and the material is sprayed out. The material passes through a squeezer for solid-liquid separation to obtain straw residue and extrudate. The extrudate passes through an MVR concentrator and a spray dryer to obtain fulvic acid or potassium fulvic acid.

[0042] S2, the straw residue is processed through a multi-stage countercurrent device

[0043] The multi-stage countercurrent device includes a washing device, a solid-liquid separator and an extrusion device. The straw residue is sent to the washing device for washing to obtain straw residue and washing liquid. In the washing device, the mass ratio of straw residue to water is 1:2;

[0044] The washing liquid is returned to the cooking process; and the straw residue is sent to the enzymatic hydrolysis system for enzymatic hydrolysis.

[0045] S3, the straw residue is enzymatically hydrolyzed by an enzymatic hydrolysis system to obtain an enzymatic hydrolysis sugar solution and an enzymatic hydrolysis sugar residue, and the enzymatic hydrolysis sugar residue is used to prepare fulvic acid.

[0046] The enzymatic hydrolysis system comprises an enzymatic hydrolysis tank and a mechanical filtering device.

[0047] The straw residue is fed into an enzymolysis tank; a composite enzyme is also added to the enzymolysis tank; the slurry solid content in the enzymolysis tank is 15-25%, the composite enzyme in the enzymolysis tank includes cellulase, xylanase and cellobiase, etc., the cellulase addition amount is 0-40FPA / g dry matter, the xylanase addition amount is 0-3000U / g dry matter, and the cellobiase addition amount is 2-100U / g dry matter, the temperature is 50°C (±2°C), the stirring speed is 0.5-2rpm, the enzymolysis time is 48-72h, and the solid-liquid separation form is a mechanical filtration device. The enzymolysis sugar residue is used to produce fulvic acid, and an activator (15% (w / w) of ammonium sulfite, 1% (w / w) of ammonium persulfate) and 100kg of water are added to the enzymolysis sugar residue, and cracking activation is carried out in a cracking activation kettle, the cracking activation temperature is 150°C, the reaction time is 2h, and then dried to obtain fulvic acid. The enzymatically hydrolyzed sugar solution is sent to a refining system for refining.

[0048] S5, the enzymatically hydrolyzed sugar solution obtained in S4 is refined through a refining system to obtain a finished liquid mixed sugar

[0049] The refining system includes a decolorization system, a reverse osmosis concentration system, and a thermal concentration system. The enzymatically hydrolyzed sugar solution is decolorized by adding activated carbon and filtered to obtain a decolorized sugar solution. The decolorized sugar solution is then concentrated through a reverse osmosis membrane. The reverse osmosis permeate is then returned to the enzymatic hydrolysis system for reuse. The reverse osmosis concentrate, a concentrated sugar solution, is then concentrated through a thermal concentrator (multi-effect evaporator). The concentrated evaporated solution is then returned to the enzymatic hydrolysis tank. The concentrated product is the finished liquid mixed sugar.

[0050] The method for concentrated sampling and testing of the extrudate in the embodiment of the present invention is as follows:

[0051] 1. Determination of fulvic acid content (reference standard: NY / T3162-2017)

[0052] (1) O-phenanthroline indicator: Weigh 1.490g of o-phenanthroline and dissolve it in 100mL of aqueous solution containing 0.700g of ferrous sulfate, and shake well. It should be stored in a sealed brown bottle. (2) 1 / 2 sulfuric acid solution (0.204mol / L): Measure 5.6mL of sulfuric acid and slowly add sulfuric acid to 700mL of water along the wall of the beaker while stirring continuously. After cooling to room temperature, dilute to 1000mL. (3) Sulfuric acid (analytical grade): content 95-98%. (4) Potassium dichromate sulfuric acid solution (0.4mol / L): Weigh 40g of potassium dichromate (analytical grade) and dissolve it in 600mL-800mL of water, dilute to 1000mL, and transfer this solution to a 3L large beaker. Take another 1000mL of sulfuric acid and slowly pour it into the potassium dichromate aqueous solution while stirring continuously. To avoid a sudden rise in temperature, pause for a moment after adding approximately 100 mL of sulfuric acid and place the beaker in a container of cold water to cool. When the temperature of the solution drops to a level that is not too hot to touch, add another portion of sulfuric acid until all the solution has been added. (5) Potassium dichromate standard solution (0.2000 mol / L): Accurately weigh 9.808 g of potassium dichromate standard reagent that has been dried at 130°C for 2 to 3 hours, dissolve it in a small amount of water, then transfer it to a 1000 mL volumetric flask and add water to the volume. (6) Ferrous sulfate standard titration solution: Weigh 56.0 g of ferrous sulfate and dissolve it in 600 mL to 800 mL of pure water. Add 20 mL of sulfuric acid and stir evenly. After standing for a while, filter it with filter paper into a 1 L volumetric flask, wash the filter paper with water, and add water to 1 L. The exact concentration should be calibrated each time it is used. Standardization of ferrous sulfate standard titrant: Pipette 10.0mL of potassium dichromate standard solution into a 250mL Erlenmeyer flask, add 3mL of sulfuric acid and 3-5 drops of o-phenanthroline indicator, and titrate with ferrous sulfate solution. Calculate the concentration c of ferrous sulfate standard titrant based on the consumed volume. Calculate according to the formula.

[0053]

[0054] Where: C-----concentration of ferrous sulfate standard titrant, mol / L;

[0055] C1----concentration of potassium dichromate standard solution, mol / L;

[0056] V1----The volume of potassium dichromate standard solution absorbed, mL;

[0057] V2----The volume of ferrous sulfate standard solution consumed during titration, mL.

[0058] 2. Determination of dry matter content: Loss on drying method (reference standard: NY / T302):

[0059] Place the aluminum box at an angle and put the lid into an electric blast constant temperature drying oven at 100-105℃ and bake for 30 minutes. Take out and cover it, move it into a desiccator to balance for 20 minutes, take it out and weigh it. Bake it for another 30 minutes and weigh it under the same conditions as above until the difference between the two masses does not exceed 1mg, which is constant weight. Weigh about 5g of the sample to the nearest 0.001g, spread it flat on an aluminum box with a known constant weight, cover it, and move it into an electric blast constant weight drying oven that has been preheated to 105℃ (the aluminum box should be close to the horizontal position of the thermometer mercury ball and not close to the inner wall of the box), open the lid and place it at an angle, then close the door. Dry it at 105±2℃ for 8h. Cover the box and take it out, move it into a desiccator to balance for 30 minutes, take it out and weigh it. The moisture content is expressed as a percentage by mass (%) and is calculated as follows:

[0060]

[0061] Where: m1----mass of air-dried sample and aluminum box, g;

[0062] m2----mass of dried sample and aluminum box, g;

[0063] m0----mass of aluminum box, g.

[0064] Dry matter content equals 100% minus moisture (air-dried basis).

[0065] 3. Determination of potassium oxide content: (reference standard: GB / T8574-2010)

[0066] Reagents and materials: Tetraphenylboric acid solution: 15 g / L; Disodium ethylenediaminetetraacetic acid solution: 40 g / L; Sodium hydroxide solution: 400 g / L; Bromine aqueous solution: approximately 5% (mass fraction); Sodium tetraphenylborate washing solution: 1.5 g / L; Phenolphthalein: 5 g / L ethanol solution, dissolve 0.5 g phenolphthalein in 100 mL 95% (mass fraction) ethanol; Activated carbon: should not adsorb or release potassium ions.

[0067] Prepare the experimental sample according to GB / T8571: weigh 2-5 g (accurate to 0.0002 g) of a sample containing approximately 400 mg of potassium oxide into a 250 mL conical flask, add approximately 150 mL of water, heat and boil for 30 min, cool, quantitatively transfer to a 250 mL volumetric flask, dilute to the mark with water, mix, dry filter, and discard the first 50 mL of filtrate.

[0068] Pipette 25mL of the above filtrate into a 200mL beaker, add 5mL of bromine solution, and boil the solution until all the bromine water is completely removed (no bromine water color). If it contains other colors, evaporate the solution to less than 100mL. After the solution cools, add 0.5g of activated carbon and stir thoroughly to adsorb it. Then filter and wash 3-5 times with about 5mL of water each time. Collect all the filtrate and add 20mL of EDTA solution (add 40mL if it contains more cations). The following steps are the same as above. Add 2-3 drops of phenolphthalein solution and sodium hydroxide solution until red appears. Filter 1mL and slowly boil in a well-ventilated cabinet for 15 minutes. Then let it cool or cool it to room temperature with running water. If the red color disappears, adjust the color to red with sodium hydroxide solution.

[0069] Under constant stirring, add sodium tetraphenylborate solution dropwise to the sample solution (above) at a rate of 0.5 mL per 1 mg of potassium oxide, with an excess of approximately 7 mL. Continue stirring for 1 minute. Let stand for at least 15 minutes. Filter the precipitate by decantation into a No. 4 glass crucible filter pre-weighed at 120°C. Wash the precipitate 5 to 7 times with sodium tetraphenylborate washing solution, using approximately 5 mL each time. Finally, wash it twice with water, using 5 mL each time. Place the crucible containing the precipitate in a drying oven at 120±5°C and dry for 1.5 hours. Then cool it in a desiccator and weigh it.

[0070] Potassium content W, expressed as potassium oxide (K2O) mass fraction (%), is calculated according to the formula:

[0071]

[0072] Where:

[0073] m2----the mass of potassium tetraphenylborate precipitate, g;

[0074] m1----The mass of potassium tetraphenylborate precipitate obtained in the blank test, g;

[0075] 0.1314 --- The coefficient for converting the mass of potassium tetraphenylborate to the mass of potassium oxide;

[0076] m0----the mass of the sample, g;

[0077] 4. Enzymatic sugar concentration: (Fehling's method)

[0078] Main reagents and solutions: (1) Fehling's solution A: weigh 30.4 g copper sulfate and add 0.1 g methylene blue, dissolve in distilled water to make 2000 mL; (2) Fehling's solution B: dissolve 150 g sodium hydroxide, 100 g potassium sodium tartrate, and 8 g potassium ferrohydride in distilled water to make 2000 mL; (3) Glucose standard solution (0.1%): accurately weigh 2.000 g anhydrous glucose, dissolve in water, add 10 mL concentrated hydrochloric acid, and dilute to 2000 mL with distilled water; (4) Sulfuric acid: analytical grade (98%).

[0079] Accurately weigh 1.0g of the sample (accurate to 0.0001g) in a 250mL volumetric flask, dilute with water to the mark, take 1.0g of the above dilution (accurate to 0.0001g) in a conical flask with 5mL of solution A and solution B, add an appropriate amount of 0.1% glucose standard solution, shake well and heat on an electric stove, control the liquid in the bottle to boil within 2 minutes, and keep it boiling slightly, then drip at a rate of 4-5s / drop until the blue color disappears. After heating, the 0.1% glucose standard solution consumed in the titration should not exceed 1mL, and the titration process should not exceed 1min, otherwise the titration should be repeated. Record the volume V1 of the sample solution consumed in the titration. The mixed sugar concentration w is calculated according to the formula:

[0080]

[0081] Where: V0——the volume of glucose standard titration solution consumed in the blank test, in milliliters (mL);

[0082] V1——The volume of glucose standard titration solution consumed by the sample, in milliliters (mL);

[0083] C——the concentration of glucose standard titration solution, in (%);

[0084] M1——The mass of the first sample, in grams (g);

[0085] M2——The mass of the second sample, in grams (g).

[0086] 5. Determination of humic acid content (reference standard: NY / T1971-2010)

[0087] 5.1 Reagents:

[0088] (1) O-phenanthroline indicator: Weigh 1.490 g of o-phenanthroline and dissolve it in 100 mL of aqueous solution containing 0.700 g of ferrous sulfate. Shake well. Store in a sealed brown bottle. (2) Sulfuric acid solution: c[1 / 2(H2SO4)] = 2 mol / L.

[0089] (3) Sodium hydroxide solution: c(NaOH) = 0.1 mol / L. (4) Potassium dichromate solution (1 mol / L): Weigh 49.031 g of potassium dichromate and dissolve it in 500 mL of water (heat to dissolve if necessary). Cool the solution and transfer it to a 1 L volumetric flask. Shake well.

[0090] (5) Potassium dichromate standard solution (0.2000 mol / L): Accurately weigh 9.807 g of potassium dichromate standard reagent dried at 120°C to constant weight, dissolve it in a small amount of water, dilute to 1 L, and shake well. (6) Ferrous sulfate standard titration solution: Weigh 56 g of ferrous sulfate and dissolve it in 600-800 mL of pure water, add 20 mL of sulfuric acid, dilute to 1 L, and store in a brown bottle. Ferrous sulfate solution is easily oxidized in air, so the accurate concentration should be calibrated before use.

[0091] Standardization of ferrous sulfate standard titrant: Pipette 20.0mL of potassium dichromate standard solution into a 250mL Erlenmeyer flask, add 3mL of sulfuric acid and 3-5 drops of o-phenanthroline indicator, and titrate with ferrous sulfate solution. Calculate the concentration c of ferrous sulfate standard titrant based on the consumed volume. Calculate according to the formula.

[0092]

[0093] Where: C-----concentration of ferrous sulfate standard titrant, mol / L;

[0094] C1----concentration of potassium dichromate standard solution, mol / L;

[0095] V1----The volume of potassium dichromate standard solution absorbed, mL;

[0096] V2----The volume of ferrous sulfate standard solution consumed during titration, mL.

[0097] 5.2 Sample preparation:

[0098] After multiple fractionation and shrinkage, take about 100 g of the solid sample, crush it and grind it until it passes through a 0.5 mm pore size sieve. If the sample is moist, it can pass through a 1.00 mm pore size sieve. Mix it evenly and place it in a clean, dry container.

[0099] 5.2.1 Solid samples

[0100] Weigh approximately 0.5g of the sample (accurate to 0.0001g) into a 50ml beaker. Add approximately 10ml of water. Stir with a glass rod and let it stand for a moment. Transfer the solution to a 100ml volumetric flask. Add approximately 10ml of water to the beaker again and repeat this step three times. Add 1ml of sodium hydroxide solution to the residue, stir until dissolved, transfer to a volumetric flask, dilute to volume with water, and mix thoroughly.

[0101] 5.2.2 Liquid samples

[0102] Weigh 2-3 g (accurate to 0.0001 g) of the sample into a 100 mL volumetric flask, add 1 mL of sodium hydroxide solution and a small amount of water, dissolve thoroughly, make up to volume, and mix thoroughly.

[0103] 5.2.3 Precipitation of humic acid in sample solution

[0104] Accurately transfer 5.0 mL of the sample solution to a centrifuge tube, add 5 mL of sulfuric acid solution, and mix thoroughly. Centrifuge the tube at 3000-4000 rpm for 10 minutes, then discard the supernatant.

[0105] 5.2.4 Oxidation of humic acid

[0106] Add 5.0 mL of potassium dichromate solution to the centrifuge tube, then slowly add 5 mL of sulfuric acid. Gently shake the tube to mix the contents. Place the tube in a tube rack, cover with a funnel, and heat in a boiling water bath for 30 minutes. Remove the tube, cool, and transfer the contents to a 250 mL Erlenmeyer flask. The volume should be between 60 and 80 mL.

[0107] 5.2.5 Titration

[0108] Add 3 to 5 drops of o-phenanthroline indicator to the conical flask and titrate the remaining potassium dichromate with a standard ferrous sulfate solution. The solution changes color from orange to blue-green until it becomes brown-red, which indicates the endpoint. If the volume consumed in the titration is less than 1 / 3 of the volume consumed in the titration blank, the sample weight should be reduced and the titration should be repeated. Perform a blank test at the same time. Except for not adding the sample, the other steps are the same as the sample solution determination. Only when the absolute difference in the titration of the two blank tests is ≤0.06mL can the average value be substituted into the formula.

[0109] 5.2.6 Result calculation

[0110] The humic acid content W is expressed as mass fraction (%) and is calculated according to the formula:

[0111]

[0112] In the formula: C-------the concentration of ferrous sulfate standard solution, the unit is mol / L;

[0113] V0-----The volume of ferrous sulfate standard solution consumed in the blank test, in mL;

[0114] V-------The volume of ferrous sulfate standard solution consumed in sample determination, in mL;

[0115] 0.003 - the mass of carbon in grams equivalent to 1.00 mL of standard ferrous sulfate solution [c(FeSO4) = 1.000 mol / L];

[0116] 1.724-----The coefficient for converting organic carbon to organic matter;

[0117] 1.43-----The product of the oxidation correction factor of 1.3 and the humic acid precipitation coefficient of 1:1;

[0118] M------The mass of the sample weighed, in g;

[0119] D-------Dilution multiple of the sample solution during measurement (100 / 5).

[0120] 6. Organic matter content detection (potassium dichromate volumetric method) (reference standard: NY / Y525-2021):

[0121] 6.1 Reagents:

[0122] (1) Silicon dioxide: powder; (2) Sulfuric acid (ρ = 1.84 g / mL); (3) Potassium dichromate standard solution c (1 / 6K2Cr2O7) = 0.1 mol / L: Weigh 4.9031 g of potassium dichromate (reference reagent) that has been dried at 130°C to constant weight (3 h-4 h), dissolve it in a small amount of water, then transfer it to a 1 L volumetric flask, dilute to the mark with water, shake well and set aside; (4) Potassium dichromate solution c (1 / 6K2Cr2O7) = 0.8 mol / L: Weigh 39.23 g of potassium dichromate (analytical grade) and dissolve it in 600-8 00mL water (heat to dissolve if necessary), cool and transfer to a 1L volumetric flask, dilute to the mark with water, shake well and set aside; (5) o-phenanthroline indicator: weigh 0.695g of ferrous sulfate (analytical grade) and 1.485g of o-phenanthroline (analytical grade) and dissolve in 100mL of water, shake well and set aside; (6) Ferrous sulfate standard solution: C(FeSO4) = 0.2mol / L, weigh 55.6g of (FeSO4·7H2O) analytical grade, dissolve in 900mL of water, add 20mL of concentrated sulfuric acid to dissolve, dilute to 1L, shake well and set aside (filter if necessary).

[0123] 6.2 Calibration method:

[0124] Pipette 20mL of potassium dichromate standard solution into a 150mL Erlenmeyer flask. Add 3mL-5mL of concentrated sulfuric acid and 2-3 drops of o-phenanthroline indicator. Titrate with ferrous sulfate standard solution. Calculate the exact concentration based on the amount of ferrous sulfate standard solution consumed during titration.

[0125]

[0126] Where: C1: concentration of potassium dichromate standard solution, unit is mole per liter (mol / L);

[0127] V1: The volume of potassium dichromate standard solution absorbed, in milliliters (mL);

[0128] V2: The volume of ferrous sulfate standard solution consumed during titration, in milliliters (mL).

[0129] 6.3 Determination steps:

[0130] Weigh 0.2g~0.5g (accurate to 0.0001g, containing organic carbon ≤15mg) of air-dried sample passed through a Φ1mm sieve, place it in a 500mL conical flask, accurately add 50mL of potassium dichromate solution (0.8mol / L), then add 50mL of sulfuric acid, add a small curved-neck funnel, place it in boiling water, and start timing after the water boils, keeping it for 30 minutes. Take it out and cool to room temperature, rinse the small funnel with a small amount of water, and collect the washing liquid in the conical flask. Transfer the reactants in the conical flask to a 250mL volumetric flask without damage, cool to room temperature, make up to volume and shake well, draw 50mL of the solution into the 250mL conical flask, add water to about 100mL, add 2~3 drops of o-phenanthroline indicator, and titrate with ferrous sulfate standard solution near the end point. When the solution turns from green to dark green, add more dropwise until a brick red color is generated. At the same time, weigh 0.2 g (accurate to 0.0001 g) of silicon dioxide to replace the sample, and perform a blank test according to the same analytical steps and using the same reagents.

[0131] 6.4 Calculation of results:

[0132] The organic matter content is expressed as the mass fraction X (%) of the fertilizer and is calculated according to the following formula:

[0133]

[0134] Where: C: concentration of ferrous sulfate standard solution, unit is mole per liter (mol / L);

[0135] V0: The volume of ferrous sulfate standard solution consumed during the blank test, in mL;

[0136] V: The volume of ferrous sulfate standard solution consumed during sample determination, in mL;

[0137] 0.003: The mass of carbon equivalent to 1.00 mL of 1.00 mol / L ferrous ammonium sulfate standard titration solution, in grams (g);

[0138] 1.724: Coefficient for converting organic carbon to organic matter;

[0139] M: The value of the air-dried sample mass, in grams (g);

[0140] D: aliquot ratio; fixed volume / aliquot volume, 250 / 50.

[0141] Example 1

[0142] according to Figure 1 In the process shown, 150 kg of straw was added to a digester, along with 450 kg of water and 3% (w / w) potassium hydroxide. The digester was steamed at 155°C and 0.7 MPa. After one hour of reaction, the pressure was released and the material was sprayed out. The material was then passed through a squeezer for solid-liquid separation, yielding straw residue and extrudate. The digestion parameters are shown in Table 1. Testing revealed that the straw residue had a dry matter concentration of 26.55% (w / w), cellulose of 40.31%, hemicellulose of 19.51%, and lignin of 22.10%, as shown in Table 2.

[0143] The above-mentioned extrudate was concentrated by MVR and sampled for testing: the dry matter concentration was 42.25%, the fulvic acid concentration was 20.72%, the fulvic acid content was 49.04% on a dry basis, and the potassium oxide content was 6.15% (tested and analyzed according to the potassium fulvic acid industry standard HG / T5334-2018), as shown in Table 2.

[0144] The straw residue obtained above was subjected to multi-stage countercurrent washing and then put into an enzymatic hydrolysis tank, into which 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added, respectively. After maintaining at 50°C (±2°C) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 3.23%, and the calculated enzymatic hydrolysis rate was 56.29%; the sugar concentration at 48 hours was 3.5%, and the calculated enzymatic hydrolysis rate was 60.99%; the sugar concentration at 72 hours was 3.95%, and the calculated enzymatic hydrolysis rate was 68.83%; the sugar concentration at 96 hours was 3.73%, and the calculated enzymatic hydrolysis rate was 65.01%, as shown in Table 3.

[0145] The enzymatic hydrolysis product was separated into solid and liquid using a plate and frame filter, yielding enzymatic sugar residue and sugar solution. Testing revealed a sugar concentration of 52.22% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization, and the finished liquid mixed sugar was obtained through a concentration system.

[0146] Sugar residue is used to make fulvic acid. 50 kg of sugar residue was placed in a reactor, and 15% (w / w) ammonium sulfite, 1% (w / w) ammonium persulfate, and 100 kg of water were added. The reaction was carried out at 150°C for 2 hours. Afterwards, samples were taken for analysis: the dry matter concentration was 22.80%, fulvic acid was 6.85%, and the calculated fulvic acid content was 30.04% on a dry basis; humic acid was 9.34%, and the calculated humic acid content was 40.96% on a dry basis; and the organic matter concentration was 17.13%, and the calculated organic matter content was 75.13% on a dry basis, as shown in Table 4.

[0147] Example 2

[0148] 150 kg of straw was placed in a digester, along with 450 kg of water and 3% (w / w) potassium hydroxide. After reacting at 150°C and 0.6 MPa for one hour, the pressure was released and the material was sprayed out. The material was separated into solid and liquid by a squeezer, yielding straw residue and extrudate. Testing revealed that the straw residue had a dry matter concentration of 27.97% (w / w), cellulose of 44.12%, hemicellulose of 17.04%, and lignin of 24.24%.

[0149] After the extrudate was processed, samples were taken for testing: the dry matter concentration was 40.69%, the fulvic acid concentration was 17.98%, the fulvic acid content calculated on a dry basis was 44.19%, and the potassium oxide content was 6.01%.

[0150] The straw residue obtained above was subjected to multi-stage countercurrent washing treatment and then put into an enzymatic hydrolysis tank, into which 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 4.14%, and the enzymatic hydrolysis rate was calculated to be 55.39%; the sugar concentration at 48 hours was 4.39%, and the enzymatic hydrolysis rate was calculated to be 58.73%; the sugar concentration at 72 hours was 4.27%, and the enzymatic hydrolysis rate was calculated to be 57.13%; the sugar concentration at 96 hours was 3.98%, and the enzymatic hydrolysis rate was calculated to be 53.25%.

[0151] The enzymatic hydrolysis product was subjected to solid-liquid separation using a plate-and-frame filter, yielding an enzymatically hydrolyzed sugar residue and a sugar solution. Testing revealed a sugar concentration of 50.36% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization, and the solution was then passed through a concentration system to yield the finished liquid mixed sugar. The sugar residue was treated as in Example 1, and after completion of the reaction, samples were collected for analysis: dry matter concentration was 30.16%, fulvic acid content was 8.54%, and the calculated fulvic acid content was 28.33% on a dry basis; humic acid content was 11.96%, and the calculated humic acid content was 39.67% on a dry basis; and organic matter concentration was 20.88%, and the calculated organic matter content was 69.24%.

[0152] Example 3

[0153] 150 kg of straw was placed in a digester, along with 450 kg of water and 3% (w / w) potassium hydroxide. After reacting at 160°C and 0.8 MPa for one hour, the pressure was released and the material was sprayed out. A squeezer was used to separate the solid and liquid, yielding straw residue and extrudate. Testing revealed the residue to have a dry matter concentration of 22.71% (w / w), 47.06% cellulose, 15.90% hemicellulose, and 23.66% lignin.

[0154] The extrudate was treated in the manner of Example 1 and then sampled for testing: the dry matter concentration was 41.91%, the fulvic acid concentration was 18.77%, the fulvic acid content calculated on a dry basis was 44.79%, and the potassium oxide content was 5.97%.

[0155] The straw residue obtained above was subjected to multi-stage countercurrent washing and then put into an enzymatic hydrolysis tank, and 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added thereto, respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 4.28%, and the calculated enzymatic hydrolysis rate was 56.65%; the sugar concentration at 48 hours was 4.32%, and the calculated enzymatic hydrolysis rate was 57.18%; the sugar concentration at 72 hours was 4.41%, and the calculated enzymatic hydrolysis rate was 58.37%; the sugar concentration at 96 hours was 4.26%, and the calculated enzymatic hydrolysis rate was 56.39%.

[0156] The enzymatic hydrolysis product was subjected to solid-liquid separation using a plate-and-frame filter to obtain enzymatic hydrolysis sugar residue and sugar solution. Testing revealed a sugar concentration of 52.87% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization, and the solution was then passed through a concentration system to obtain the finished liquid mixed sugar. The sugar residue was treated as in Example 1, and after completion of the reaction, samples were taken for analysis: dry matter concentration was 29.56%, fulvic acid content was 8.24%, and the calculated fulvic acid content was 27.89% on a dry basis; humic acid content was 11.36%, and the calculated humic acid content was 38.44% on a dry basis; and organic matter concentration was 19.87%, and the calculated organic matter content was 67.21%.

[0157] Example 4

[0158] 150 kg of straw was placed in a digester, along with 450 kg of water and 3% (w / w) potassium hydroxide. After reacting at 165°C and 0.9 MPa for one hour, the pressure was released and the material was sprayed out. A squeezer was used to separate the solid and liquid, yielding straw residue and extrudate. Testing revealed the residue to have a dry matter concentration of 39.71% (w / w), 44.16% cellulose, 21.15% hemicellulose, and 19.18% lignin.

[0159] The extrudate was treated in the manner of Example 1 and then sampled for testing: dry matter concentration was 40.74%, fulvic acid concentration was 18.81%, fulvic acid content on a dry basis was 46.18%, and potassium oxide content was 6.20%.

[0160] The straw residue obtained above was subjected to multi-stage countercurrent washing and then put into an enzymatic hydrolysis tank, and 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added thereto, respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 3.92%, and the calculated enzymatic hydrolysis rate was 53.41%; the sugar concentration at 48 hours was 5.13%, and the calculated enzymatic hydrolysis rate was 69.90%; the sugar concentration at 72 hours was 5.13%, and the calculated enzymatic hydrolysis rate was 69.90%; the sugar concentration at 96 hours was 5.3%, and the calculated enzymatic hydrolysis rate was 72.21%.

[0161] The enzymatic hydrolysis product was subjected to solid-liquid separation using a plate-and-frame filter to obtain enzymatic hydrolysis sugar residue and sugar solution. Testing revealed a sugar concentration of 53.39% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization, and the solution was then passed through a concentration system to obtain a finished liquid mixed sugar. The sugar residue was treated as in Example 1. After the reaction, samples were collected for analysis, revealing a dry matter concentration of 25.18%, 7.53% fulvic acid, or 29.92% fulvic acid content on a dry basis; 10.29% humic acid, or 40.88% humic acid content on a dry basis; and 17.87% organic matter, or 70.98% organic matter content on a dry basis.

[0162] Example 5

[0163] 150 kg of straw was placed in a digester, along with 450 kg of water and 3% (w / w) potassium hydroxide. After reacting for one hour at 140°C and 0.4 MPa, the pressure was released and the material was sprayed out. A squeezer was used to separate the solid and liquid, yielding straw residue and extrudate. Testing revealed the residue to have a dry matter concentration of 20.98% (w / w), 38.15% cellulose, 19.87% hemicellulose, and 17.51% lignin.

[0164] The extrudate was treated in the manner of Example 1 and then sampled for testing: the dry matter concentration was 36.11%, the fulvic acid concentration was 14.52%, the fulvic acid content on a dry basis was 40.21%, and the potassium oxide content was 5.13%.

[0165] The straw residue obtained above was subjected to multi-stage countercurrent washing treatment and then put into an enzymatic hydrolysis tank, into which 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 2.80%, and the enzymatic hydrolysis rate was calculated to be 40.22%; the sugar concentration at 48 hours was 3.13%, and the enzymatic hydrolysis rate was calculated to be 44.96%; the sugar concentration at 72 hours was 3.55%, and the enzymatic hydrolysis rate was calculated to be 50.99%; the sugar concentration at 96 hours was 3.40%, and the enzymatic hydrolysis rate was calculated to be 48.84%.

[0166] The enzymatic hydrolysis product was subjected to solid-liquid separation using a plate-and-frame filter to obtain enzymatic hydrolysis sugar residue and sugar solution. Testing revealed a sugar concentration of 48.21% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization. The solution then passed through a concentration system to obtain a finished liquid mixed sugar. The sugar residue was treated as in Example 1. After the reaction, samples were collected for analysis and showed a dry matter concentration of 30.09%, 5.81% fulvic acid, or 19.32% on a dry basis; 8.46% humic acid, or 28.11% on a dry basis; and 15.25% organic matter, or 50.69% on a dry basis.

[0167] Example 6

[0168] 150 kg of straw was placed in a digester, along with 450 kg of water and 3% (w / w) potassium hydroxide. After reacting for one hour at 120°C and 0.2 MPa, the pressure was released and the material was sprayed out. A squeezer was used to separate the solid and liquid, yielding straw residue and extrudate. Testing revealed the residue to have a dry matter concentration of 25.57% (w / w), 43.96% cellulose, 18.33% hemicellulose, and 19.86% lignin.

[0169] The extrudate was treated in the manner of Example 1 and then sampled for testing: the dry matter concentration was 22.47%, the fulvic acid concentration was 5.65%, the fulvic acid content calculated on a dry basis was 25.14%, and the potassium oxide content was 4.74%.

[0170] The straw residue obtained above was subjected to multi-stage countercurrent washing treatment and then put into an enzymatic hydrolysis tank, into which 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 2.05%, and the enzymatic hydrolysis rate was calculated to be 27.60%; the sugar concentration at 48 hours was 2.75%, and the enzymatic hydrolysis rate was calculated to be 37.02%; the sugar concentration at 72 hours was 3.09%, and the enzymatic hydrolysis rate was calculated to be 41.60%; the sugar concentration at 96 hours was 2.88%, and the enzymatic hydrolysis rate was calculated to be 38.77%.

[0171] The enzymatic hydrolysis product was subjected to solid-liquid separation using a plate-and-frame filter to obtain enzymatic hydrolysis sugar residue and sugar solution. Testing revealed a sugar concentration of 50.69% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization. The solution then passed through a concentration system to obtain a finished liquid mixed sugar. The sugar residue was treated as in Example 1. After the reaction, sampling and analysis revealed a dry matter concentration of 25.60%, 3.21% fulvic acid (calculated on a dry basis, 12.54%), 5.32% humic acid (calculated on a dry basis, 20.79%), and 9.90% organic matter (calculated on a dry basis, 38.66%).

[0172] Example 7

[0173] 150 kg of straw was placed in a digester, along with 450 kg of water and 3% (w / w) potassium hydroxide. After reacting at 180°C and 1.2 MPa for one hour, the pressure was released and the material was sprayed out. A squeezer was used to separate the solid and liquid, yielding straw residue and extrudate. Testing revealed the residue to have a dry matter concentration of 28.55% (w / w), 39.78% cellulose, 11.32% hemicellulose, and 27.21% lignin.

[0174] The extrudate was treated in the manner of Example 1 and then sampled for testing: dry matter concentration was 40.88%, fulvic acid concentration was 12.43%, fulvic acid content on a dry basis was 30.41%, and potassium oxide content was 6.03%.

[0175] The straw residue obtained above was subjected to multi-stage countercurrent washing treatment and then put into an enzymatic hydrolysis tank, into which 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 3.71%, and the enzymatic hydrolysis rate was calculated to be 50.45%; the sugar concentration at 48 hours was 3.87%, and the enzymatic hydrolysis rate was calculated to be 52.63%; the sugar concentration at 72 hours was 4.16%, and the enzymatic hydrolysis rate was calculated to be 56.57%; the sugar concentration at 96 hours was 4.04%, and the enzymatic hydrolysis rate was calculated to be 54.94%.

[0176] The enzymatic hydrolysis product was subjected to solid-liquid separation using a plate-and-frame filter to obtain enzymatic hydrolysis sugar residue and sugar solution. Testing revealed a sugar concentration of 54.06% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization. The solution then passed through a concentration system to obtain a finished liquid mixed sugar. The sugar residue was treated as in Example 1. After the reaction, sampling and analysis revealed a dry matter concentration of 32.12%, 8.38% fulvic acid, or 26.10% fulvic acid content on a dry basis; 11.01% humic acid, or 34.28% humic acid content on a dry basis; and 20.90% organic matter, or 65.07% organic matter content on a dry basis.

[0177] Example 8

[0178] The difference from Example 1 is that the amount of potassium hydroxide used in the cooking treatment is 4.5% relative to the dry weight of the straw.

[0179] After the reaction, the straw residue was detected to have the following contents: dry matter concentration of 33.49% (w / w), cellulose of 39.14%, hemicellulose of 19.17%, and lignin of 23.71%.

[0180] The extrudate was treated in the manner of Example 1 and then sampled for testing: dry matter concentration was 48.72%, fulvic acid concentration was 25.96%, fulvic acid content on a dry basis was 53.28%, and potassium oxide content was 6.40%.

[0181] The straw residue obtained above was subjected to multi-stage countercurrent washing treatment and then put into an enzymatic hydrolysis tank, into which 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 4.19%, and the enzymatic hydrolysis rate was calculated to be 57.09%; the sugar concentration at 48 hours was 5.17%, and the enzymatic hydrolysis rate was calculated to be 70.44%; the sugar concentration at 72 hours was 5.38%, and the enzymatic hydrolysis rate was calculated to be 73.30%; the sugar concentration at 96 hours was 5.25%, and the enzymatic hydrolysis rate was calculated to be 71.53%.

[0182] The enzymatic hydrolysis product was subjected to solid-liquid separation using a plate-and-frame filter to obtain enzymatic hydrolysis sugar residue and sugar solution. Testing revealed a sugar concentration of 55.11% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization. The solution then passed through a concentration system to obtain a finished liquid mixed sugar. The sugar residue was treated as in Example 1. After the reaction, samples were collected and analyzed, revealing a dry matter concentration of 23.03%, 7.71% fulvic acid (calculated on a dry basis, 33.47%), 9.81% humic acid (calculated on a dry basis, 42.60%), and 17.95% organic matter (calculated on a dry basis, 77.93%).

[0183] Example 9

[0184] The difference from Example 1 is that the amount of potassium hydroxide used in the cooking treatment is 6% relative to the dry weight of the straw.

[0185] After the reaction, the straw residue was detected to have the following contents: dry matter concentration of 37.61% (w / w), cellulose of 37.91%, hemicellulose of 15.67%, and lignin of 24.80%.

[0186] The extrudate was treated in the manner of Example 1 and then sampled for testing: the dry matter concentration was 45.14%, the fulvic acid concentration was 27.06%, the fulvic acid content on a dry basis was 59.95%, and the potassium oxide content was 8.76%.

[0187] The straw residue obtained above was subjected to multi-stage countercurrent washing treatment and then put into an enzymatic hydrolysis tank, into which 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 5.23%, and the enzymatic hydrolysis rate was calculated to be 69.97%; the sugar concentration at 48 hours was 6.30%, and the enzymatic hydrolysis rate was calculated to be 84.28%; the sugar concentration at 72 hours was 6.55%, and the enzymatic hydrolysis rate was calculated to be 87.63%; the sugar concentration at 96 hours was 6.14%, and the enzymatic hydrolysis rate was calculated to be 82.14%.

[0188] The enzymatic hydrolysis product was subjected to solid-liquid separation using a plate-and-frame filter to obtain enzymatic hydrolysis sugar residue and sugar solution. Testing revealed a sugar concentration of 58.68% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization. The solution then passed through a concentration system to obtain a finished liquid mixed sugar. The sugar residue was treated as in Example 1. After the reaction, sampling and analysis revealed a dry matter concentration of 26.64%, 9.46% fulvic acid, or 35.51% fulvic acid content on a dry basis; 11.91% humic acid, or 44.69% humic acid content on a dry basis; and 21.4% organic matter, or 80.32% organic matter content on a dry basis.

[0189] Example 10

[0190] The difference from Example 1 is that the weight ratio of the steamed straw to water is 1:4, that is, 600 kg of water is added into the steamer.

[0191] After the reaction, the straw residue was detected to have the following contents: dry matter concentration of 36.77% (w / w), cellulose of 38.16%, hemicellulose of 10.18%, and lignin of 24.28%.

[0192] The extrudate was treated in the manner of Example 1 and then sampled for testing: dry matter concentration was 50.67%, fulvic acid concentration was 29.87%, fulvic acid content on a dry basis was 58.95%, and potassium oxide content was 8.33%.

[0193] The straw residue obtained above was subjected to multi-stage countercurrent washing and then put into an enzymatic hydrolysis tank, and 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added thereto, respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 5.88%, and the calculated enzymatic hydrolysis rate was 68.84%; the sugar concentration at 48 hours was 6.41%, and the calculated enzymatic hydrolysis rate was 75.05%; the sugar concentration at 72 hours was 7.27%, and the calculated enzymatic hydrolysis rate was 85.14%; the sugar concentration at 96 hours was 6.90%, and the calculated enzymatic hydrolysis rate was 80.78%.

[0194] The enzymatic hydrolysis product was subjected to solid-liquid separation using a plate-and-frame filter to obtain enzymatic hydrolysis sugar residue and sugar solution. Testing revealed a sugar concentration of 61.32% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization. The solution then passed through a concentration system to obtain a finished liquid mixed sugar. The sugar residue was treated as in Example 1. After the reaction, sampling and analysis revealed a dry matter concentration of 27.15%, 9.26% fulvic acid, or 34.09% fulvic acid content on a dry basis; 10.95% humic acid, or 40.32% humic acid content on a dry basis; and 17.95% organic matter, or 66.11% organic matter content on a dry basis.

[0195] Example 11

[0196] The difference from Example 1 is that the cooking time is 1.5 hours.

[0197] After the reaction, the straw residue was detected to have the following contents: dry matter concentration of 34.26% (w / w), cellulose of 36.38%, hemicellulose of 11.51%, and lignin of 25.25%.

[0198] The extrudate was treated in the manner of Example 1 and then sampled for testing: dry matter concentration was 53.13%, fulvic acid concentration was 32.66%, fulvic acid content on a dry basis was 61.47%, and potassium oxide content was 10.64%.

[0199] The straw residue obtained above was subjected to multi-stage countercurrent washing treatment and then put into an enzymatic hydrolysis tank, into which 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 5.50%, and the enzymatic hydrolysis rate was calculated to be 72.80%; the sugar concentration at 48 hours was 6.45%, and the enzymatic hydrolysis rate was calculated to be 85.37%; the sugar concentration at 72 hours was 7.23%, and the enzymatic hydrolysis rate was calculated to be 95.70%; the sugar concentration at 96 hours was 7.09%, and the enzymatic hydrolysis rate was calculated to be 93.84%.

[0200] The enzymatic hydrolysis product was subjected to solid-liquid separation using a plate-and-frame filter to obtain enzymatic hydrolysis sugar residue and sugar solution. Testing revealed a sugar concentration of 60.10% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization. The solution then passed through a concentration system to obtain a finished liquid mixed sugar. The sugar residue was treated as in Example 1. After the reaction, samples were collected for analysis and showed a dry matter concentration of 34.94%, 13.02% fulvic acid, or 37.27% fulvic acid content on a dry basis; 16.29% humic acid, or 46.61% humic acid content on a dry basis; and 29.69% organic matter, or 84.97% organic matter content on a dry basis.

[0201] Example 12

[0202] The difference from Example 1 is that the cooking time is 2.5 hours.

[0203] After the reaction, the straw residue was detected to have the following contents: dry matter concentration of 32.56% (w / w), cellulose of 35.95%, hemicellulose of 13.88%, and lignin of 22.52%.

[0204] The extrudate was treated in the manner of Example 1 and then sampled for testing: dry matter concentration was 53.61%, fulvic acid concentration was 32.87%, fulvic acid content on a dry basis was 61.31%, and potassium oxide content was 10.08%.

[0205] The straw residue obtained above was subjected to multi-stage countercurrent washing treatment and then put into an enzymatic hydrolysis tank, into which 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 5.44%, and the enzymatic hydrolysis rate was calculated to be 71.23%; the sugar concentration at 48 hours was 6.18%, and the enzymatic hydrolysis rate was calculated to be 80.92%; the sugar concentration at 72 hours was 7.00%, and the enzymatic hydrolysis rate was calculated to be 91.65%; the sugar concentration at 96 hours was 6.87%, and the enzymatic hydrolysis rate was calculated to be 89.95%.

[0206] The enzymatic hydrolysis product was subjected to solid-liquid separation using a plate-and-frame filter to obtain enzymatic hydrolysis sugar residue and sugar solution. Testing revealed a sugar concentration of 60.88% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization. The solution then passed through a concentration system to obtain a finished liquid mixed sugar. The sugar residue was treated as in Example 1. After the reaction, samples were collected and analyzed, revealing a dry matter concentration of 30.80%, 9.60% fulvic acid, or 31.18% fulvic acid content on a dry basis; 12.58% humic acid, or 40.84% ​​humic acid content on a dry basis; and 23.64% organic matter, or 76.76% organic matter content on a dry basis.

[0207] Example 13

[0208] The difference from Example 10 is that the weight ratio of the steamed straw to water is 1:5, that is, 750 kg of water is added into the steamer.

[0209] After the reaction, the straw residue was detected to have the following contents: dry matter concentration of 31.11% (w / w), cellulose of 34.07%, hemicellulose of 11.95%, and lignin of 23.38%.

[0210] The extrudate was treated in the manner of Example 1 and then sampled for testing: the dry matter concentration was 51.12%, the fulvic acid concentration was 29.94%, the fulvic acid content on a dry basis was 58.57%, and the potassium oxide content was 9.65%.

[0211] The straw residue obtained above was subjected to multi-stage countercurrent washing and then put into an enzymatic hydrolysis tank, into which 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 5.75%, and the enzymatic hydrolysis rate was calculated to be 82.59%; the sugar concentration at 48 hours was 6.66%, and the enzymatic hydrolysis rate was calculated to be 95.66%; the sugar concentration at 72 hours was 6.32%, and the enzymatic hydrolysis rate was calculated to be 90.78%; the sugar concentration at 96 hours was 5.98%, and the enzymatic hydrolysis rate was calculated to be 85.89%.

[0212] The enzymatic hydrolysis product was separated into solid and liquid using a plate-and-frame filter, yielding a sugar residue and a sugar solution. Testing revealed a sugar concentration of 57.97% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization, and the resulting liquid mixed sugar was then concentrated through a concentration system. The residue was then used to make fulvic acid. 50 kg of the residue was placed in a reactor, and 6% (w / w) ammonia water, 3% (w / w) potassium hydroxide, 0.2% (w / w) ammonium persulfate, and 150 kg of water were added. The reaction was carried out at 150°C for 2 hours. After completion, samples were collected and analyzed, revealing a dry matter concentration of 28.49%, fulvic acid of 8.53%, or 29.95% on a dry basis; humic acid of 10.86%, or 38.11% on a dry basis; and organic matter of 19.41%, or 68.12% on a dry basis.

[0213] Example 14

[0214] The difference from Example 11 is that the amount of potassium hydroxide used is 8% (relative to the dry weight of the straw).

[0215] After the reaction, the straw residue was detected to have the following contents: dry matter concentration of 29.90% (w / w), cellulose of 32.33%, hemicellulose of 12.56%, and lignin of 24.49%.

[0216] The extrudate was treated in the manner of Example 1 and then sampled for testing: dry matter concentration was 54.24%, fulvic acid concentration was 33.20%, fulvic acid content on a dry basis was 61.21%, and potassium oxide content was 12.50%.

[0217] The straw residue obtained above was subjected to multi-stage countercurrent washing and then put into an enzymatic hydrolysis tank, and 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added thereto, respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 5.15%, and the calculated enzymatic hydrolysis rate was 72.39%; the sugar concentration at 48 hours was 5.75%, and the calculated enzymatic hydrolysis rate was 80.82%; the sugar concentration at 72 hours was 6.48%, and the calculated enzymatic hydrolysis rate was 91.08%; the sugar concentration at 96 hours was 6.13%, and the calculated enzymatic hydrolysis rate was 86.16%.

[0218] The enzymatic hydrolysis product was separated into solid and liquid using a plate-and-frame filter, yielding a sugar residue and a sugar solution. Testing revealed a sugar concentration of 59.68% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization, and the resulting liquid mixed sugar was then concentrated through a concentrator. The residue was then used to make fulvic acid. 50 kg of the residue was placed in a reactor, and 3% (w / w) ammonia water, 1.5% (w / w) potassium hydroxide, 0.1% (w / w) ammonium persulfate, and 150 kg of water were added. The reaction was carried out at 150°C for 2 hours. After completion, samples were collected and analyzed, revealing a dry matter concentration of 21.45%, fulvic acid of 6.46%, or 30.13% on a dry basis; humic acid of 8.00%, or 37.28% on a dry basis; and organic matter of 14.46%, or 67.39% on a dry basis.

[0219] Comparative Example 1

[0220] Refer to Example 10, but different from Example 10 is that during the cooking process, potassium hydroxide is replaced by ammonium sulfite.

[0221] After the reaction, the straw residue was detected to have the following contents: dry matter concentration of 23.36% (w / w), cellulose of 30.10%, hemicellulose of 16.67%, and lignin of 21.61%.

[0222] The extrudate was treated in the manner of Example 1 and then sampled for testing: the dry matter concentration was 43.19%, the fulvic acid concentration was 10.66%, and the fulvic acid content calculated on a dry basis was 24.68%.

[0223] The straw residue obtained above was subjected to multi-stage countercurrent washing and then put into an enzymolysis tank, and 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added thereto, respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 2.88%, and the enzymolysis rate was calculated to be 42.37%; the sugar concentration at 48 hours was 2.93%, and the enzymolysis rate was calculated to be 43.10%; the sugar concentration at 72 hours was 3.17%, and the enzymolysis rate was calculated to be 46.63%; the sugar concentration at 96 hours was 2.84%, and the enzymolysis rate was calculated to be 41.78%.

[0224] The enzymatic hydrolysis product was separated into solid and liquid using a plate and frame filter, yielding enzymatic sugar residue and sugar solution. Testing revealed a sugar concentration of 45.28% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization, and the finished liquid mixed sugar was obtained through a concentration system.

[0225] The sugar residue was treated in the manner of Example 1 to produce fulvic acid. After the reaction, samples were taken for detection and analysis: the dry matter concentration was 10.27%, the fulvic acid content was 1.29%, and the fulvic acid content was 12.55% on a dry basis; the humic acid content was 2.12%, and the humic acid content was 20.67% on a dry basis; the organic matter concentration was 3.81%, and the organic matter content was 37.14% on a dry basis.

[0226] Comparative Example 2

[0227] After removing impurities and dust, the straw is chopped into 0-10 cm chopped straw; the chopped straw is evenly mixed with water in a mass ratio of 1:1, and the mixture is kept at 50°C for 90 minutes to obtain water-extracted straw; the water-extracted straw is sent to a twin-screw extrusion and kneading machine to obtain an extruded and kneaded material and a first extruded water; the first extruded water is filtered through a plate and frame filter press and then reused in the water extraction step; the extruded and kneaded material is sent to a hydrothermal decomposition tank for hydrothermal decomposition, an alkaline decomposition liquid is added to the hydrothermal decomposition tank, the mass ratio of the extruded and kneaded material to the alkaline decomposition liquid is 1:1, the mass ratio of potassium hydroxide to water in the alkaline decomposition liquid is 1:10, and the mixture is kept at 50°C for 120 minutes to obtain a pretreated product.

[0228] The straw residue obtained above was subjected to multi-stage countercurrent washing and then put into an enzymatic hydrolysis tank, and 30 FPA / g dry matter of cellulase, 1000 U / g dry matter of xylanase and 50 U / g dry matter of cellobiase were added thereto, respectively. After maintaining at 50° C. (±2° C.) for 24 hours, 48 ​​hours, 72 hours and 96 hours, samples were taken to detect the sugar concentration: the sugar concentration at 24 hours was 5.67%, and the calculated enzymatic hydrolysis rate was 75.94%; the sugar concentration at 48 hours was 6.53%, and the calculated enzymatic hydrolysis rate was 87.46%; the sugar concentration at 72 hours was 6.88%, and the calculated enzymatic hydrolysis rate was 92.15%; the sugar concentration at 96 hours was 6.47%, and the calculated enzymatic hydrolysis rate was 86.65%.

[0229] The enzymatic hydrolysis product was separated into solid and liquid using a plate-and-frame filter, yielding enzymatic sugar residue and sugar solution. Testing revealed a sugar concentration of 55.57% in the sugar solution. 3% (relative to the dry weight of the sugar solution) of powdered charcoal was added for decolorization, and the finished liquid mixed sugar was obtained through a concentration system. The residue was then used to make fulvic acid. 50 kg of the residue was placed in a reactor, and 3% (w / w) ammonia water, 1.5% (w / w) potassium hydroxide, 0.1% (w / w) ammonium persulfate, and 150 kg of water were added. The reaction was carried out at 150°C for 2 hours. After completion, samples were collected and analyzed, revealing a dry matter concentration of 19.60%, fulvic acid of 6.38%, or 32.55% calculated on a dry basis; humic acid of 6.50%, or 33.16% calculated on a dry basis; and organic matter of 13.61%, or 69.44% calculated on a dry basis.

[0230] Table 1

[0231]

[0232] Table 2

[0233]

[0234]

[0235] Table 3

[0236]

[0237]

[0238] Table 4

[0239]

[0240]

[0241] The inventors have discovered through experiments that when the cooking conditions are selected as follows: 155°C to 165°C, a reaction time of 1.5 hours, a potassium hydroxide dosage of 6-8% relative to the dry weight of the straw, and a straw-to-water weight ratio of 1:2.5-4, the potassium fulvic acid content produced in the first step is high, and the subsequent enzymatic hydrolysis is effective and has a high enzymatic hydrolysis rate. In Comparative Example 1, replacing the potassium hydroxide in the cooking conditions with ammonium sulfite not only resulted in no potassium fulvic acid production during cooking, but also showed poor enzymatic hydrolysis, resulting in a low sugar yield. The sugar residue also showed a significant difference when used as fulvic acid fertilizer. In Comparative Example 2, the straw pretreatment process is more detailed, using potassium hydroxide solution to decompose the three elements in the straw and extract most of the lignin, resulting in the production of trace amounts of potassium fulvic acid. This also has significant advantages in the enzymatic hydrolysis process, unlike the cooking reaction principle. The method provided by the present invention has a simple process flow, is easily scalable, and eliminates waste and pollutants during the process.

[0242] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the technical concept of the present invention, various simple modifications may be made to the technical solution of the present invention, including combining the various technical features in any other appropriate manner. These simple modifications and combinations should also be considered as disclosed herein and fall within the scope of protection of the present invention.

Claims

1. A method for producing sugar from straw and co-producing potassium fulvic acid and fulvic acid, comprising the following steps: (1) The straw is steamed in a potassium hydroxide aqueous solution, and then subjected to solid-liquid separation to obtain straw residue and extrudate, wherein: The cooking temperature is 155° C. and the pressure is 0.7 MPa. The amount of potassium hydroxide used is 3% of the dry weight of the straw. The cooking time is 1.5 hours. (2) concentrating the extrudate to obtain liquid potassium fulvate; (3) spray drying the liquid potassium fulvate to obtain solid potassium fulvate; (4) subjecting the straw residue described in step (1) to a multi-stage countercurrent washing treatment, followed by enzymatic hydrolysis and filtration to obtain a sugar solution and a sugar residue; (5) cracking and activating the sugar residue to obtain solid fulvic acid; (6) refining the sugar solution to obtain a liquid mixed sugar; The enzymatic hydrolysis uses a composite enzyme, which includes cellulase, xylanase and cellobiase. The added amount of cellulase is 0-40 FPA / g dry matter, the added amount of xylanase is 0-3000 U / g dry matter, and the added amount of cellobiase is 2-100 U / g dry matter.

2. The method according to claim 1, characterized in that In step (1), the weight ratio of straw to water is 1:(2-5).

3. The method according to claim 1, characterized in that In step (1), the weight ratio of straw to water is 1:(2.5-4).

4. The method according to claim 1, wherein Before the cooking process, the straw is pretreated, and the pretreatment includes removing dust and impurities from the straw; and / or The cooking product after the cooking treatment is subjected to solid-liquid separation by a squeezer to obtain the straw residue and the extrudate.

5. The method according to claim 1, wherein In step (5), the cracking activation adopts an activator, and the activator includes one or more combinations of ammonium sulfite, potassium sulfite, potassium hydroxide, ammonium persulfate, potassium persulfate, and ammonia water.

6. The method according to claim 5, characterized in that The added amount of the activator is 5% to 15% of the dry basis mass of the sugar residue.

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