Method for preparing nitrogen-rich liquid fertilizer and soil conditioner from agricultural biomass waste

Abstract

The invention provides a method for preparing a nitrogen-rich liquid fertilizer and a soil conditioner from agricultural biomass wastes, and belongs to the technical field of humic acid synthesis. According to the agricultural biomass waste treatment method, nano-bubble nitrogen sources are coupled with agricultural biomass waste for a hydrothermal reaction, and the nitrogen sources in the method serve as additives to provide nitrogen elements to improve the quality of humic acid and serve as catalysts to improve the yield; by adopting a nano bubble solution system, the contact area of a nitrogen source, agricultural biomass waste and water is increased, and the yield and quality of a product are improved. According to the method disclosed by the invention, the quality and yield of humic acid and hydrothermal carbon are improved, the content of nutrient elements such as nitrogen element in the product is increased, the problems of low nitrogen fertilizer utilization rate, single returning nutrient of fulvic acid, humic acid or hydrothermal carbon and the like are solved, and a new thought is provided for resource utilization of agricultural biomass wastes such as straws and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of humic acid synthesis, and in particular relates to a method for preparing nitrogen-rich liquid fertilizer and soil conditioner from agricultural biomass waste. Background Art

[0002] my country has a huge amount of agricultural biomass resources. It is of great significance to convert agricultural biomass waste such as straw into humus-like hydrothermal biochar through hydrothermal humification technology. It is a new way to efficiently return agricultural biomass waste to the field. It can not only increase the content of soil organic matter, improve soil structure, and improve the soil's ability to retain water and fertilizer, but also reduce the use of chemical fertilizers and pesticides. Patent CN202110756585.X discloses a method for strengthening the hydrothermal humification of lignocellulosic waste by acid hydrothermal pretreatment, wherein the reaction system is adjusted to an acidic environment for a first hydrothermal reaction to obtain a hydrothermal product, and alkali is continued to be added to adjust to an alkaline environment for a second hydrothermal reaction. Although the yield of humic acid is improved, the discontinuous reaction system in the intermediate operation consumes a lot of energy, the operation is complicated, and the quality of humic acid is not significantly improved. Patent CN202310720611.2 discloses a method for hydrothermal conversion of biomass into humic acid by multi-stage pressure regulation. Humic acid is separated from aqueous and solid products by high-pressure-low-pressure multi-stage regulation, which effectively improves the yield of humic acid, but its quality improvement is not significant. At the same time, the invention has high requirements for equipment. The pressure of high-pressure hydrothermal reaction is 10-30Mpa, which increases the cost of hydrothermal reaction. Patent CN202310556443.8 discloses a method and application of promoting biomass humification by iron ion catalysis. Iron ion catalysis increases the yield of artificial humic acid, but the catalytic effect is limited.

[0003] How to efficiently utilize agricultural biomass waste and convert it into humic acid, while increasing the humic acid yield, can also improve the quality of humic acid, which has important positive significance for humic acid synthesis. Summary of the invention

[0004] In view of the defects in the prior art, the object of the present invention is to provide a method for hydrothermal reaction of nanobubble nitrogen source coupled with agricultural biomass waste, which can simultaneously improve the yield and quality of humic acid.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a method for treating agricultural biomass waste, which utilizes nanobubble nitrogen source to couple agricultural biomass waste to perform hydrothermal reaction, comprising the following steps:

[0007] preparing a nitrogen source nanobubble solution;

[0008] After mixing the nitrogen source nanobubble solution with agricultural biomass waste, a hydrothermal reaction is carried out to obtain a hydrothermal reaction product; the mass ratio of the nitrogen source substance in the nitrogen source nanobubble solution to the agricultural biomass waste is (0.3-3): (1-6);

[0009] Performing solid-liquid separation on the hydrothermal reaction product to obtain a solid phase and a liquid phase of the hydrothermal reaction product;

[0010] The liquid phase is subjected to nanobubble treatment to obtain a nanobubble liquid phase.

[0011] Preferably, the mass ratio of the nitrogen source substance to the agricultural biomass waste in the nitrogen source nanobubble solution is 1:(1-4).

[0012] Preferably, the temperature of the hydrothermal reaction is 180°C to 240°C; the time of the hydrothermal reaction is 1 to 4 hours; when the hydrothermal reaction is carried out under acidic conditions, the pH of the hydrothermal reaction is 5 to 7; when the hydrothermal reaction is carried out under alkaline conditions, the pH of the hydrothermal reaction is 8 to 14.

[0013] Preferably, the nanobubble particle size in the nitrogen source nanobubble solution is 70 to 180 nm; the concentration of nanobubbles in the nitrogen source nanobubble solution is 6.8×10 6 ~3.8×10 8 Pieces / mL.

[0014] Preferably, the method for preparing the nitrogen source nanobubble solution comprises:

[0015] The nitrogen source solution is subjected to nanobubble treatment to obtain a nitrogen source nanobubble solution;

[0016] Alternatively, water or alkaline solution is subjected to nanobubble treatment, and then a nitrogen source is added to the nanobubble solution to obtain a nitrogen source nanobubble solution.

[0017] Preferably, the gas flow rate for nanobubble treatment is 0.1 to 0.3 L / min, the liquid flow rate is 1.5 to 3 L / min, the pressure is 0.3 to 0.7 MPa, and the time is 10 to 15 min.

[0018] Preferably, the nitrogen source includes any one or more of urea, ammonium sulfate, ammonium chloride and diammonium phosphate; the agricultural biomass waste includes any one or more of forestry waste, rice husks, straw, livestock and poultry manure and biogas slurry and residue.

[0019] The invention provides a nitrogen-rich liquid fertilizer, which is a nanobubble liquid phase obtained by the treatment method described in the technical scheme.

[0020] Preferably, the particle size of the nanobubbles in the nitrogen-rich liquid fertilizer is 100-180 nm; the concentration of the nanobubbles in the nitrogen-rich liquid fertilizer is 4.8×10 5 ~3.8×10 7 Pieces / mL.

[0021] The present invention provides a soil conditioner, comprising a solid phase obtained by the treatment method described in the above technical solution.

[0022] Beneficial effects of the present invention:

[0023] The present invention provides a method for treating agricultural biomass waste, which utilizes nanobubble nitrogen source to couple agricultural biomass waste for hydrothermal reaction, comprising the following steps: preparing a nitrogen source nanobubble solution; mixing the nitrogen source nanobubble solution with agricultural biomass waste, and then performing a hydrothermal reaction to obtain a hydrothermal reaction product; the mass ratio of the nitrogen source substance in the nitrogen source nanobubble solution to the agricultural biomass waste is (0.3-3):(1-6); performing solid-liquid separation on the hydrothermal reaction product to obtain a solid phase and a liquid phase of the hydrothermal reaction product; and performing nanobubble treatment on the liquid phase to obtain a nanobubble liquid phase. The present invention utilizes nanobubble nitrogen source to couple agricultural biomass waste for hydrothermal reaction, mainly utilizing nanobubble technology to add a nitrogen source substance in the hydrothermal reaction, wherein the nitrogen source nanobubble solution refers to a nanobubble solution containing a nitrogen source. In the treatment method, the nitrogen source is used as an additive to provide nitrogen elements to improve the quality of humic acid, and also as a catalyst to increase the yield. The treatment method adopts a nanobubble solution system containing a nitrogen source to increase the contact area between the nitrogen source, agricultural biomass waste and water; the nanobubble solution is combined with a hydrothermal humification reaction to increase the mass transfer efficiency of the reaction system and improve the yield and quality of the product; wherein, unstable nanobubbles are explosively broken and rapidly dissolved during the hydrothermal process, and strong oxidizing substances such as hydroxyl radicals released during the expansion and crushing process promote the formation of humic acid precursor substances and the formation of porous hydrothermal carbon, thereby increasing the specific surface area of ​​the hydrothermal carbon; oxygen in the nanobubbles can play an oxidizing role in the hydrothermal process, replacing the catalyst in the previous hydrothermal process, and has low investment cost, no pollution and convenient treatment during use.

[0024] The treatment method of the present invention prepares nitrogen-rich liquid fertilizer containing fulvic acid and / or humic acid and humic acid-rich porous hydrothermal charcoal by coupling nitrogen source nanobubble solution with agricultural biomass waste for hydrothermal reaction, thereby improving the quality and yield of humic acid and hydrothermal charcoal, increasing the content of nutrient elements such as nitrogen in the product, and solving the problems of low nitrogen fertilizer utilization rate, and relatively single nutrients returned to the field by fulvic acid, humic acid or hydrothermal charcoal. The results of the embodiments show that the treatment method of the present invention can significantly increase the content of fulvic acid or humic acid in the solid and liquid phases of the hydrothermal reaction product, increase the total nitrogen content in the hydrothermal reaction product, increase the yield of the hydrothermal reaction product, and also improve the quality of the hydrothermal reaction product. In summary, the treatment method provided by the present invention significantly improves the yield and quality of humic acid prepared by hydrothermal reaction of agricultural biomass waste, and provides a new idea for the high-value utilization of agricultural biomass waste such as straw. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0026] Figure 1 The present invention is a process flow chart of the method for treating agricultural biomass waste. DETAILED DESCRIPTION

[0027] The present invention provides a method for treating agricultural biomass waste, which utilizes nanobubble nitrogen source to couple agricultural biomass waste to perform hydrothermal reaction, comprising the following steps:

[0028] preparing a nitrogen source nanobubble solution;

[0029] After mixing the nitrogen source nanobubble solution with agricultural biomass waste, a hydrothermal reaction is carried out to obtain a hydrothermal reaction product; the mass ratio of the nitrogen source substance in the nitrogen source nanobubble solution to the agricultural biomass waste is (0.3-3): (1-6);

[0030] Performing solid-liquid separation on the hydrothermal reaction product to obtain a solid phase and a liquid phase of the hydrothermal reaction product;

[0031] The liquid phase is subjected to nanobubble treatment to obtain a nanobubble liquid phase.

[0032] The present invention utilizes nanobubble nitrogen source to couple agricultural biomass waste for hydrothermal reaction, mainly utilizing nanobubble technology to add nitrogen source material in the hydrothermal reaction, wherein the nitrogen source nanobubble solution refers to a nanobubble solution containing a nitrogen source. The present invention utilizes nanobubble nitrogen source to couple agricultural biomass waste for hydrothermal reaction, that is, the nanobubble solution containing the nitrogen source is mixed with the agricultural biomass waste and then subjected to hydrothermal reaction. The present invention obtains a solid phase and a liquid phase of the hydrothermal reaction product through the hydrothermal reaction; the solid phase of the hydrothermal reaction product obtained can be directly used as a soil conditioner, or as a component of a soil conditioner; the nanobubble liquid phase obtained by nanobubble treatment of the liquid phase of the hydrothermal reaction product can be used as a nitrogen-rich liquid fertilizer, or as a component of a nitrogen-rich liquid fertilizer.

[0033] In the present invention, the hydrothermal reaction can be carried out under acidic conditions or under alkaline conditions. When the hydrothermal reaction is carried out under acidic conditions, the pH of the hydrothermal reaction can be 5-7, or 6; when the hydrothermal reaction is carried out under alkaline conditions, the pH of the hydrothermal reaction can be 8-14, or 10-14, or 13. In the present invention, if the hydrothermal reaction is carried out under acidic conditions, it is preferred to directly mix the nitrogen source nanobubble solution with agricultural biomass waste before the hydrothermal reaction; if the hydrothermal reaction is carried out under alkaline conditions, it is preferred to mix the nitrogen source nanobubble solution containing alkali solution with agricultural biomass waste before the hydrothermal reaction. In the present invention, the hydrothermal reaction can also be referred to as a hydrothermal humification reaction.

[0034] In the present invention, the mass ratio of the nitrogen source substance to the agricultural biomass waste in the nitrogen source nanobubble solution can be (0.3-3): (1-6), or (0.9-3): (1-6), or 1: (1-4), or 1:3, 1:4, 1:6 or 1:2. When the nitrogen source nanobubble solution and the agricultural biomass waste are mixed in the present invention, it is preferred to mix the prepared nitrogen source nanobubble solution and the agricultural biomass waste based on the volume of the solution before the nitrogen source nanobubble solution is prepared. In the present invention, the volume of the solution before the nitrogen source nanobubble solution is prepared is referred to as the volume before the nanobubble solution. When the present invention is mixed, the mass of the solid and the volume before the nanobubble solution can be 1g: (6-10) mL; as an embodiment, the mass of the solid and the volume before the nanobubble solution can be 1g: (7-9) mL, or 1g: (8-9) mL. In the present invention, the mass of the solid is the sum of the masses of the agricultural biomass waste and the nitrogen source.

[0035] The present invention does not specifically limit the source of the nitrogen source, and any conventional nitrogen fertilizer in the art may be used. In the present invention, the nitrogen source may be a nitrogen-containing organic substance such as urea or a nitrogen-containing inorganic substance containing ammonium ions, nitrate ions, and nitrite ions. Different nitrogen sources, such as strong acid and weak base salts-ammonium sulfate, have weak acidity, which can change the initial pH of the hydrothermal reaction and promote the formation of hydrothermal charcoal; nitrogen has a strong electronegativity and can form a carbon-nitrogen bond, participate in the formation of amino groups in humic acid molecules, and increase the content of nitrogen in humic acid. As an embodiment, the nitrogen source may include any one or more of urea, ammonium sulfate, ammonium chloride, and diammonium phosphate. In the present invention, the nanobubble particle size in the nitrogen source nanobubble solution may be 70 to 180 nm. As an embodiment, the nanobubble particle size may be 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm or 170 nm. The concentration of nanobubbles in the nitrogen source nanobubble solution may be 6.8×10 6 ~3.8×10 8 / mL, or 2.3×10 7 ~4.8×10 7 The present invention has no special limitation on the preparation method of the nitrogen source nano bubble solution, and any conventional preparation method in the art can be used. As an embodiment, the nitrogen source nano bubble solution of the present invention can be prepared by a pressurized gas dissolution method.

[0036] As an embodiment, the preparation method of the nitrogen source nano bubble solution may include: subjecting the nitrogen source solution to nanobubble treatment to obtain the nitrogen source nano bubble solution. The present invention does not specifically limit the preparation method of the nitrogen source solution, and any conventional preparation method in the art may be used. As an embodiment, the nitrogen source solution is obtained by fully dissolving the nitrogen source substance in deionized water. The volume of deionized water used in this embodiment is the volume before the nano bubble solution described above. The gas flow rate for the nanobubble treatment of the present invention may be 0.1 to 0.3 L / min; in an embodiment of the present invention, the gas flow rate may be 0.2 L / min. In the present invention, the gas may be air or oxygen. As an embodiment, the flow rate of the liquid for the nanobubble treatment of the present invention may be 1.5 to 3 L / min, or 2 L / min. As an embodiment, the pressure for the nanobubble treatment of the present invention may be 0.3 to 0.7 Mpa, or 0.4 to 0.6 Mpa; in an embodiment of the present invention, the pressure for the nanobubble treatment may be 0.3 Mpa, 0.4 Mpa, 0.5 Mpa, 0.6 Mpa or 0.7 Mpa. As an embodiment, the nanobubble treatment time of the present invention can be 10 to 15 minutes; in the embodiment of the present invention, the nanobubble treatment time can be 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes or 15 minutes. As an embodiment, the temperature of the nanobubble treatment of the present invention can be 20 to 30 degrees Celsius, or 22 to 28 degrees Celsius, or 25 degrees Celsius. During the nanobubble treatment of the present invention, when the solution changes from milky white to clear, a nitrogen source nanobubble solution is obtained.

[0037] As another embodiment, the preparation method of the nitrogen source nanobubble solution may include: subjecting water or alkali solution to nanobubble treatment, and then adding a nitrogen source to the nanobubble solution to obtain a nitrogen source nanobubble solution. The volume of water or alkali solution used in this embodiment is the volume before the nanobubble solution described above. As an embodiment, the water may include deionized water; the alkali solution may include 0.5-2 mol / L potassium hydroxide or sodium hydroxide, or 0.5 mol / L potassium hydroxide. The method for nanobubble treatment of the present invention is the same as above, and will not be repeated here. In the process of nanobubble treatment of water or alkali solution of the present invention, after the solution changes from milky white to clear, a nanobubble solution is obtained. As an embodiment, after obtaining the nanobubble solution, the present invention adds a nitrogen source to the nanobubble solution to obtain a nitrogen source nanobubble solution. As an embodiment, the nanobubble treatment of the present invention is carried out in a nanobubble generator.

[0038] As an embodiment, when the hydrothermal reaction of the present invention needs to be carried out under alkaline conditions, the alkali solution can be directly subjected to nanobubble treatment to obtain a nanobubble solution, and then a nitrogen source is added. As another embodiment, when the hydrothermal reaction of the present invention does not need to be carried out under alkaline conditions, the nitrogen source solution is directly subjected to nanobubble treatment to obtain a nitrogen source nanobubble solution; or water is subjected to nanobubble treatment to obtain a nanobubble solution and then a nitrogen source is added to obtain a nitrogen source nanobubble solution. The present invention provides an alkaline environment for the hydrothermal reaction by adding alkali solution when preparing the nanobubble solution; the hydrothermal product obtained by the hydrothermal reaction under an alkaline environment is alkaline. The present invention does not add alkali solution when preparing the nanobubble solution, and when the obtained nanobubble solution is subjected to a hydrothermal reaction, the obtained hydrothermal reaction product is acidic.

[0039] After obtaining the nitrogen source nanobubble solution, the present invention mixes the nitrogen source nanobubble solution with agricultural biomass waste. As an embodiment, the agricultural biomass waste may include any one or more of forestry waste, rice husks, straw, livestock and poultry manure, and biogas slurry and biogas residue; the forestry waste may include wood processing residues and / or logging residues; the wood processing residues may include sawdust and / or scraps; the logging residues may include tree roots and / or rattan. The present invention does not specifically limit the source of the agricultural biomass waste, and any conventional source in the field may be used. As an embodiment, in the present invention, the agricultural biomass waste may be dried agricultural biomass waste. The present invention does not specifically limit the drying method, and any conventional drying method in the field may be used. As an embodiment, the drying method of the present invention may include drying. As an embodiment, the drying of the present invention may be dried to a moisture content of the agricultural biomass waste of ≤5%. As an embodiment, the drying temperature of the agricultural biomass waste can be 60°C; the drying time of the agricultural biomass waste can be 12 to 24 hours, or 16 to 18 hours, and the drying is carried out until the mass remains unchanged after repeated weighing; the drying can be carried out in an oven. After obtaining the agricultural biomass waste, that is, after obtaining the dried agricultural biomass waste, the present invention preferably crushes the agricultural biomass waste. The present invention does not specifically limit the crushing method, and any conventional crushing method in the art can be used. As an embodiment, after obtaining the crushed agricultural biomass waste, the present invention preferably sieves the crushed material; the aperture of the sieve is preferably 30 to 60 meshes, and more preferably 40 meshes. The present invention preferably takes the undersize to obtain the crushed agricultural biomass waste.

[0040] After obtaining the crushed agricultural biomass waste, the present invention preferably mixes the crushed agricultural biomass waste with a nitrogen source nanobubble solution. The present invention does not specifically limit the mixing method, and any conventional mixing method in the art can be used. As an embodiment, the present invention mixes the nitrogen source nanobubble solution with the agricultural biomass waste in a hydrothermal reactor. After the mixing is completed, the present invention performs a hydrothermal reaction. As an embodiment, the temperature of the hydrothermal reaction can be 180°C to 240°C, or 190°C, 200°C, 210°C, 220°C or 230°C. As an embodiment, the time of the hydrothermal reaction can be 1 to 4h, or 2h, 2.5h, 3h or 3.5h. As an embodiment, when no alkali solution is added, the pH of the hydrothermal reaction can be 5 to 7, or 6. As an embodiment, when alkali solution is added, the pH of the hydrothermal reaction can be 8 to 14, or 10 to 14, or 12 or 13. After the hydrothermal reaction is completed, the present invention preferably obtains a hydrothermal reaction product. In the present invention, the nanobubble solution system containing a nitrogen source is used in the treatment method to increase the contact area between the nitrogen source, agricultural biomass waste and water; the nanobubble solution is combined with the hydrothermal humification reaction to increase the mass transfer efficiency of the reaction system and improve the yield and quality of the product; wherein, the unstable nanobubbles are explosively broken and rapidly dissolved during the hydrothermal process, and the strong oxidizing substances such as hydroxyl radicals released during the expansion and fragmentation process promote the formation of humic acid precursor substances and the formation of porous hydrothermal carbon, thereby increasing the specific surface area of ​​the hydrothermal carbon; the oxygen in the nanobubbles can play an oxidizing role in the hydrothermal process, replacing the catalyst in the previous hydrothermal process.

[0041] After obtaining the hydrothermal reaction product, the present invention performs solid-liquid separation on the hydrothermal reaction product to obtain a solid phase and a liquid phase; the solid phase is also referred to as hydrothermal charcoal. As an embodiment, if the pH of the hydrothermal reaction product is acidic, most of the humic acid in the reaction product exists in the hydrothermal charcoal, and the obtained hydrothermal charcoal can be referred to as humic acid-rich nitrogen-rich hydrothermal charcoal, or nitrogen-rich porous hydrothermal charcoal, or humic acid-rich porous hydrothermal charcoal, and the obtained liquid phase can be referred to as nitrogen-rich humic acid liquid phase, or a humic acid-containing liquid phase. As an embodiment, due to the addition of alkali solution under the initial reaction conditions, when the pH of the hydrothermal reaction product is alkaline, most of the humic acid in the reaction product exists in the liquid phase, and the obtained liquid phase can also be referred to as nitrogen-rich humic acid liquid phase, or a humic acid-containing liquid phase, and the obtained solid phase is referred to as porous nitrogen-rich hydrothermal charcoal, or nitrogen-rich porous hydrothermal charcoal. In the present invention, the solid phase can be used as a soil conditioner, or as a component of a soil conditioner.

[0042] As an embodiment, after obtaining the liquid phase of the hydrothermal reaction product, the present invention preferably performs nanobubble treatment on the liquid phase to obtain a nanobubble liquid phase. In the present invention, the nanobubble liquid phase can be used as a nitrogen-rich liquid fertilizer; the nitrogen-rich liquid fertilizer contains nano-fulvic acid and / or nano-humic acid, or it can be referred to as the nitrogen-rich nano liquid fertilizer containing fulvic acid and / or humic acid. In the present invention, as an embodiment, if the pH of the hydrothermal reaction product is acidic, a nitrogen-rich liquid fertilizer containing nano-fulvic acid is obtained, or it can be referred to as fulvic acid nitrogen-rich nano liquid fertilizer. In the present invention, as an embodiment, if the pH of the hydrothermal reaction product is alkaline, a nitrogen-rich liquid fertilizer containing nano-humic acid is obtained, or it can be referred to as humic acid nitrogen-rich nano liquid fertilizer. As an embodiment, the nanoparticle size in the nitrogen-rich liquid fertilizer can be 100-180nm, or 100-140nm. As an embodiment, the concentration of nanobubbles in the nitrogen-rich liquid fertilizer can be 4.8×10 5 ~3.8×10 7 / mL, or 2.3×10 7 / mL. The conditions of the nanobubble treatment described in the present invention are the same as above and will not be elaborated here. As an embodiment, after the nanobubble treatment is completed, the present invention preferably allows the obtained nanobubble solution to stand; the standing time can be 5h. The present invention further improves the quality of the liquid phase containing humic acid or fulvic acid through nanobubble technology. The strongly oxidizing hydroxyl radicals in the nanobubbles promote the degradation of organic pollutants, such as components in the liquid phase of the hydrothermal reaction product that are unfavorable to crops, such as phenols and furans, among which the percentage of furans can be reduced by about 7% to 10%. At the same time, nanobubbles contain oxygen, carbon dioxide, etc., which can improve the oxygen supply to the root system of crops and provide a carbon source for crops, which is further conducive to promoting crop growth.

[0043] The treatment method described in the above technical solution of the present invention can significantly improve the yield and quality of the hydrothermal reaction products of agricultural biomass waste, improve the quality and yield of the obtained humic acid and hydrothermal charcoal, increase the content of nutrients such as nitrogen in the products, and solve the problems of low nitrogen fertilizer utilization rate, relatively single nutrients returned to the field by fulvic acid, humic acid or hydrothermal charcoal, etc., and provide a new idea for the comprehensive utilization of fertilizers such as nitrogen fertilizer and agricultural biomass waste such as straw. The method provided by the present invention improves the quality of the two-phase products of the hydrothermal reaction products according to the properties of different hydrothermal products, improves the utilization value of the liquid phase and solid phase of the hydrothermal reaction products, and the raw material utilization rate is close to 100%, providing a diversified reference for the processing and utilization of the products.

[0044] The present invention also provides a soil conditioner prepared by the treatment method described in the above technical solution, and the soil conditioner includes the hydrothermal charcoal prepared by the treatment method described in the above technical solution. In the present invention, when the pH of the hydrothermal reaction product is acidic, the content of humic acid in the hydrothermal charcoal is about 52.3%, and the nitrogen content is about 6.80%. In the present invention, when the pH of the hydrothermal reaction product is alkaline, the content of humic acid in the hydrothermal charcoal is about 27.30%, and the nitrogen content is about 6.30%; when the pH of the hydrothermal reaction product is alkaline, the humic acid content in the liquid phase is about 42.78g / L. In the embodiment of the present invention, the soil conditioner is referred to as a high-quality soil conditioner.

[0045] The present invention also provides a nitrogen-rich liquid fertilizer, including the nanobubble liquid phase prepared by the treatment method described in the above technical solution. In the present invention, the nitrogen-rich liquid fertilizer is a nitrogen-rich liquid fertilizer containing nano-fulvic acid and / or nano-humic acid; in the present invention, it can also be referred to as the nitrogen-rich liquid fertilizer containing fulvic acid and / or humic acid. As an embodiment, the particle size of the nanobubbles in the nitrogen-rich liquid fertilizer can be 100 to 180 nm, or 100 to 140 nm. As an embodiment, the concentration of nanobubbles in the nitrogen-rich liquid fertilizer can be 4.8×10 5 ~3.8×10 7 / mL, or 2.3×10 7 / mL. In the present invention, when the pH of the hydrothermal reaction product is acidic, the content of humic acid in the nitrogen-rich liquid fertilizer can be 11-16g / L, or 12.75g / L, the content of fulvic acid can be 110-135g / L, or 120.56g / L, and the total nitrogen content can be 6600-7100mg / L, or 6940mg / L; when the pH of the hydrothermal reaction product is alkaline, the content of humic acid in the nitrogen-rich liquid fertilizer can be 42-50g / L, or 42.78g / L; the total nitrogen content can be 6900-7300mg / L, or 7100mg / L. In the present invention, the nitrogen-rich liquid fertilizer is obtained by further subjecting the obtained liquid phase to nanobubble treatment after obtaining the liquid phase of the hydrothermal reaction product. The nitrogen-rich liquid fertilizer significantly reduces the phenols and furans in the liquid phase that are harmful to crops through nanobubble treatment, wherein the content of furans can be reduced by about 7% to 10%; at the same time, the nanobubbles in the nitrogen-rich liquid fertilizer contain oxygen, carbon dioxide, etc., which improve the oxygen supply to the root system of crops and provide a carbon source for crops. The liquid fertilizer of the present invention can better promote crop growth as a crop fertilizer. In an embodiment of the present invention, the liquid phase of the hydrothermal reaction product is treated with nanobubbles, so that the furans in the liquid fertilizer are reduced by 7.76% and 7.16% respectively, thereby achieving the effect of improving the quality of the liquid fertilizer.

[0046] In order to further illustrate the present invention, the technical solution provided by the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0047] The hydrothermal reaction in the present invention is a hydrothermal humification reaction.

[0048] Test Case

[0049] Add different nitrogen sources to straw to verify the effects of different nitrogen sources on the hydrothermal reaction products

[0050] Mix 40-mesh corn stalk powder, nitrogen source material, and 72 mL of deionized water in a hydrothermal reactor, set the hydrothermal reaction time to 1 hour, the reaction temperature to 180°C, start the hydrothermal reaction, and take out the hydrothermal mixture after the reaction to separate the solid and liquid to obtain a humic acid-rich liquid phase and humic acid-rich hydrothermal charcoal. Since the pH of the mixture after the reaction is acidic, the humic acid in the mixture is mainly present in the hydrothermal charcoal, which can be used as a high-quality soil conditioner. The humic acid-rich liquid phase can be used as a humic acid-containing nitrogen-rich liquid fertilizer.

[0051] Different nitrogen sources were used as different test groups, and a blank control group without nitrogen source addition was set up. The design of the different nitrogen source test groups and the blank control group is shown in Table 1. After the hydrothermal reaction was completed, the hydrothermal charcoal yield and the humic acid yield in the hydrothermal charcoal were calculated, and the results are shown in Table 1. The C / N in Table 1 is the mass ratio of the total carbon and nitrogen in the straw and nitrogen source additives. Since carbon is one of the main elements constituting hydrothermal charcoal and humic acid, in order to exclude the possibility of yield changes caused by different carbon and nitrogen contents in different nitrogen source additives (that is, it is impossible to determine whether the yield changes are caused by the different qualities of the added carbon or nitrogen or the different properties of the nitrogen source additives themselves), the carbon and nitrogen of different nitrogen source additives are set to remain consistent.

[0052] Table 1 Related parameters of different test groups in the test case and the solid phase product yield of each test group

[0053]

[0054] The carbon-nitrogen ratio of the straw and the above-mentioned nitrogen source is shown in Table 2. The carbon-nitrogen ratio of the straw and nitrogen source mixture is further calculated from the carbon and nitrogen contents of the straw and the carbon and nitrogen contents of the nitrogen source in Table 2, which is the C / N in Table 1.

[0055] Table 2 Mass percentage of carbon and nitrogen in straw and nitrogen source materials

[0056] substance C(％) N(％) <![CDATA[CO(NH2)2]]> 20％ 46.67％ <![CDATA[NH4Cl]]> 0 26.17％ <![CDATA[(NH4)2SO4]]> 0 21.21％ <![CDATA[NH4H2PO4]]> 0 12.17％ Straw 42.42％ 1.68％

[0057] As shown in Table 1, adding different nitrogen sources can improve the yield of hydrothermal carbon of the solid phase product of the hydrothermal reaction to a certain extent, and at the same time improve the yield of humic acid. Among them, compared with other nitrogen sources, ammonium sulfate has the best effect in improving the yield of hydrothermal carbon and humic acid in the hydrothermal reaction. Therefore, the following examples take ammonium sulfate as an example to conduct specific tests on the method of nanobubble nitrogen source coupling agricultural biomass waste for hydrothermal reaction.

[0058] The process flow chart of the method for treating agricultural biomass waste in the following embodiments is as follows: Figure 1 As shown, with the following description:

[0059] Example 1

[0060] A method for treating agricultural biomass waste, namely a method for coupling a nanobubble nitrogen source with agricultural biomass waste to perform hydrothermal reaction, the steps are as follows:

[0061] Raw materials: 2g ammonium sulfate, 6g corn stalk powder and 72mL deionized water. The volume of deionized water is the volume before the nanobubble solution; the mass ratio of ammonium sulfate to corn stalk powder is 1:3; the mass of the solid and the volume before the nanobubble solution is 1g:9mL.

[0062] Step 1: First, 2 g of ammonium sulfate was dissolved in 72 mL of deionized water to obtain an ammonium sulfate solution, and the ammonium sulfate solution was introduced into the nanobubble generator. The operating parameters of the nanogenerator were as follows: temperature was 25 °C, air flow rate was 0.2 L / min, ammonium sulfate solution flow rate was 2 L / min, operating pressure was 0.6 MPa, and operating time was 15 min. After the solution changed from milky white to clear, the particle size of the nanobubbles was measured to be between 100 and 180 nm, and the concentration of the nanobubbles was 6.8 × 10 6 ~4.8×10 7 / mL, and the ammonium sulfate nanobubble solution was obtained.

[0063] Step 2: 6g of 40-mesh corn stalk powder and the ammonium sulfate nanobubble solution obtained in step 1 are mixed evenly in a hydrothermal reactor, the hydrothermal reaction time is set to 1h, the reaction temperature is set to 180°C, and the hydrothermal reaction is started. After the reaction is completed, the hydrothermal mixture is taken out for solid-liquid separation to obtain a nitrogen-rich fulvic acid liquid phase (or a liquid phase containing fulvic acid) and humic acid-rich nitrogen-rich hydrothermal charcoal (also referred to as humic acid-rich porous hydrothermal charcoal, or nitrogen-rich humic acid-rich porous hydrothermal charcoal). Since the pH of the mixture after the reaction is acidic, the humic acid in the mixture is mainly present in the hydrothermal charcoal, which can be used as a high-quality soil conditioner. Among them, the percentage of furan substances in the nitrogen-rich fulvic acid liquid phase is 16.79%.

[0064] Step 3: Introduce the nitrogen-rich fulvic acid liquid phase into the nanobubble generator. The operating conditions of the nanogenerator are: temperature of 25°C, air gas flow rate of 0.2L / min, solution flow rate of 2L / min, operating pressure of 0.5Mpa, and operating time of 10min. After standing for 5 hours, a nitrogen-rich liquid fertilizer containing nano fulvic acid (or fulvic acid nitrogen-rich nano liquid fertilizer) is obtained, which is referred to as nitrogen-rich liquid fertilizer or liquid fertilizer. The particle size of the nanobubbles in the liquid fertilizer is 100-180nm, and the concentration of the nanobubbles is 4.8×10 5 ~3.8×10 7 The percentage of furan substances in liquid fertilizer is 9.63%.

[0065] Example 2

[0066] A method for treating agricultural biomass waste, namely a method for coupling a nanobubble nitrogen source with agricultural biomass waste to perform hydrothermal reaction, the steps are as follows:

[0067] Raw materials: 2g ammonium sulfate, 6g corn stalk powder and 72mL 0.5mol / L KOH solution. The volume of KOH solution is the volume before nanobubble solution; the mass ratio of ammonium sulfate to corn stalk powder is 1:3; the mass of solid and the volume before nanobubble solution is 1g:9mL.

[0068] Step 1: First, 72 mL of 0.5 mol / L KOH solution was introduced into the nanobubble generator. The operating conditions of the nanogenerator were: temperature 25 °C, air flow rate 0.2 L / min, potassium hydroxide solution flow rate 2 L / min, operating pressure 0.6 Mpa, and operating time 15 min. After the solution changed from milky white to clear, the particle size of the nanobubbles was measured to be between 100 and 140 nm, and the concentration of the nanobubbles was 2.3 × 10 7 ~3.8×10 8 / mL, add 2g of ammonium sulfate and stir to dissolve to obtain ammonium sulfate nanobubble solution.

[0069] Step 2: Mix 6g of 40-mesh corn stalk powder and the ammonium sulfate nanobubble solution obtained in step 1 in a hydrothermal reactor, set the hydrothermal reaction time to 1h and the reaction temperature to 180°C, take out the hydrothermal mixture after the reaction is completed, filter and separate the solid and liquid, and obtain a nitrogen-rich humic acid liquid phase (or a liquid phase containing humic acid) and porous nitrogen-rich hydrothermal charcoal (also referred to as nitrogen-rich porous hydrothermal charcoal). Due to the addition of KOH under the initial reaction conditions, the pH of the mixture after the reaction is alkaline, and most of the humic acid exists in the liquid phase. The obtained hydrothermal charcoal can be used as a high-quality soil conditioner. Among them, the percentage of furan substances in the nitrogen-rich humic acid liquid phase is 15.79%.

[0070] Step 3: Introduce the nitrogen-rich humic acid liquid phase into the nanobubble generator. The operating conditions of the nanogenerator are: temperature 25°C, air gas flow rate 0.2L / min, solution flow rate 2L / min, operating pressure 0.5Mpa, and operating time 10min. After standing for 5 hours, a nitrogen-rich liquid fertilizer containing nano humic acid (or humic acid nitrogen-rich nano liquid fertilizer) is obtained, which is referred to as nitrogen-rich liquid fertilizer or liquid fertilizer. The nanoparticle size in the liquid fertilizer is 100-180nm, and the concentration of nanobubbles is 4.8×10 5 ~3.8×10 7 The percentage of furan substances in liquid fertilizer is 8.03%.

[0071] Comparative Example 1

[0072] A method for hydrothermal reaction of agricultural biomass waste, comprising the following steps:

[0073] Step 1: Take 54 mL of deionized water and introduce it into the nanobubble generator. The operating parameters of the nanogenerator are as follows: temperature 25°C, air flow rate 0.2 L / min, deionized water flow rate 2 L / min, operating pressure 0.6 Mpa, and operating time 15 min. After the solution changes from milky white to clear, the particle size of the nanobubbles is between 100 and 180 nm, and the concentration is between 5.8 × 10 6 ~2.8×10 7 / mL, and the nanobubble solution was obtained.

[0074] Step 2: Mix 6 g of 40-mesh corn stalk powder and the nanobubble solution obtained in step 1 in a hydrothermal reactor, set the hydrothermal reaction time to 1 hour and the reaction temperature to 180°C, start the hydrothermal reaction, and after the reaction is completed, take out the hydrothermal mixture for solid-liquid separation to obtain a fulvic acid-rich liquid phase and humic acid-rich hydrothermal charcoal. Since the pH of the mixture after the reaction is acidic, the humic acid in the mixture is mainly present in the hydrothermal charcoal, which can be used as a high-quality soil conditioner.

[0075] Step 3: Introduce the fulvic acid-rich liquid phase into the nanobubble generator. The operating conditions of the nanogenerator are: temperature 25°C, gas flow rate 0.2L / min, solution flow rate 2L / min, operating pressure 0.5Mpa, and operating time 10min. After standing for 5 hours, liquid fertilizer containing nano fulvic acid is obtained, which is referred to as liquid fertilizer. The particle size of the nanobubbles in the liquid fertilizer is 100-180nm, and the concentration of the nanobubbles is 4.8×10 5 ~3.8×10 7 Pieces / mL.

[0076] Comparative Example 2

[0077] A method for hydrothermal reaction of agricultural biomass waste, comprising the following steps:

[0078] Step 1: First, 54 mL of 0.5 mol / L KOH solution was introduced into the nanobubble generator. The operating conditions of the nanogenerator were: temperature 25 °C, air flow rate 0.2 L / min, KOH solution flow rate 2 L / min, operating pressure 0.6 Mpa, and operating time 15 min. After the solution changed from milky white to clear, the particle size of the nanobubbles was measured to be between 100 and 180 nm, and the concentration was 7.8 × 10 6 ~3.8×10 7 / mL, and the nanobubble solution was obtained.

[0079] Step 2: Mix 6 g of 40-mesh corn stalk powder and the nanobubble solution obtained in step 1 evenly in a hydrothermal reactor, set the hydrothermal reaction time to 1 hour and the reaction temperature to 180°C, and after the reaction is completed, take out the hydrothermal mixture for solid-liquid separation by suction filtration to obtain a humic acid-rich liquid phase and humic acid-rich hydrothermal charcoal. Since KOH was added under the initial reaction conditions, the pH of the mixture after the reaction is alkaline, and most of the humic acid exists in the liquid phase. The obtained hydrothermal charcoal can be used as a high-quality soil conditioner.

[0080] Step 3: Introduce the humic acid-rich liquid phase into the nanobubble generator. The operating conditions of the nanogenerator are: temperature 25°C, air gas flow rate 0.2L / min, solution flow rate 2L / min, operating pressure 0.3Mpa, and operating time 10min. After standing for 5 hours, liquid fertilizer containing nano humic acid is obtained, which is referred to as liquid fertilizer.

[0081] Comparative Example 3

[0082] A method for hydrothermal reaction of agricultural biomass waste, comprising the following steps:

[0083] Mix 6g of 40-mesh corn stalk powder and 54mL of deionized water in a hydrothermal reactor, set the hydrothermal reaction time to 1h and the reaction temperature to 180℃, start the hydrothermal reaction, and take out the hydrothermal mixture after the reaction to separate the solid and liquid to obtain a humic acid-rich liquid phase and humic acid-rich hydrothermal charcoal. Since the pH of the mixture after the reaction is acidic, the humic acid in the mixture is mainly present in the hydrothermal charcoal, which can be used as a high-quality soil conditioner. The humic acid-rich liquid phase can be used as a liquid fertilizer containing humic acid, referred to as liquid fertilizer.

[0084] Comparative Example 4

[0085] A method for hydrothermal reaction of agricultural biomass waste, comprising the following steps:

[0086] Mix 6g of 40-mesh corn stalk powder, 2g of ammonium sulfate, and 72mL of deionized water in a hydrothermal reactor, set the hydrothermal reaction time to 1h and the reaction temperature to 180°C, start the hydrothermal reaction, and take out the hydrothermal mixture after the reaction to separate the solid and liquid to obtain a humic acid-rich liquid phase and humic acid-rich hydrothermal charcoal. Since the pH of the mixture after the reaction is acidic, the humic acid in the mixture mainly exists in the hydrothermal charcoal, which can be used as a high-quality soil conditioner. The humic acid-rich liquid phase can be used as a humic acid-containing nitrogen-rich liquid fertilizer, referred to as liquid fertilizer.

[0087] Comparative Example 5

[0088] A method for hydrothermal reaction of agricultural biomass waste, comprising the following steps:

[0089] Mix 6g of 40-mesh corn stalk powder, 2g of ammonium sulfate, and 72mL of 0.5mol / LKOH solution in a hydrothermal reactor. Set the hydrothermal reaction time to 1h and the reaction temperature to 180℃ to start the hydrothermal reaction. After the reaction is completed, take out the hydrothermal mixture for solid-liquid separation to obtain nitrogen-rich fulvic acid liquid phase and nitrogen-rich humic acid hydrothermal charcoal. Since KOH was added under the initial reaction conditions, the pH of the mixture after the reaction is alkaline, and most of the humic acid exists in the liquid phase. The obtained hydrothermal charcoal can be used as a high-quality soil conditioner. The nitrogen-rich fulvic acid liquid phase can be used as a nitrogen-rich fulvic acid liquid phase fertilizer.

[0090] Application Example 1

[0091] The fulvic acid content, humic acid content and total nitrogen content of the liquid fertilizers of Examples 1 to 2 and Comparative Examples 1 to 5, as well as the hydrothermal charcoal yield, humic acid content and nitrogen content of the high-quality soil conditioner were measured. The results are shown in Table 3. Three parallel tests were conducted for each group of the above tests, and the average value of the results of each group of tests was taken.

[0092] Reference for determination of fulvic acid content: National Standard HG / T 5937-2021 "Rapid determination method for humic acid and fulvic acid content", reference for determination of humic acid content: International Humic Association "alkali dissolution and acid precipitation method" to extract humic acid, and then calculate the yield and determine the nitrogen content, reference for determination of total nitrogen content: National Standard HJ 636-2012 "Determination of total nitrogen in water quality - alkaline potassium persulfate digestion ultraviolet spectrophotometry".

[0093] Table 3 Test results of fulvic acid, humic acid and nitrogen content of liquid fertilizer and high-quality soil conditioner in Examples 1 to 2 and Comparative Examples 1 to 5

[0094]

[0095]

[0096] Note: - indicates that the content of fulvic acid is relatively small and negligible compared with other test groups.

[0097] As can be seen from Table 3, by comparing Example 1 with Comparative Example 3, the method of using nanobubble nitrogen source to couple agricultural biomass waste for hydrothermal reaction can significantly increase the content of fulvic acid, humic acid and total nitrogen in the liquid phase of the hydrothermal reaction product (i.e., liquid fertilizer) compared with the conventional method, that is, no nitrogen source is added and no nanobubble treatment is performed; and the yield of hydrothermal charcoal, humic acid content and nitrogen content in the solid phase of the hydrothermal reaction product are increased.

[0098] By comparing Example 1, Comparative Example 1 and Comparative Example 4, and Example 2, Comparative Example 2 and Comparative Example 5, it can be concluded that the method provided by the present invention uses nanobubbles and a nitrogen source to couple the hydrothermal reaction to achieve a synergistic technical effect in increasing the fulvic acid content, the humic acid content and the nitrogen content.

[0099] The embodiment of the present invention takes straw as an example to illustrate the method for treating agricultural biomass waste. Other agricultural biomass wastes include forestry wastes, rice husks, biogas slurry and livestock and poultry manure, which contain a large amount of lignocellulose, and their main components are similar to those of straw. They can all be subjected to hydrothermal reactions. Adding nitrogen sources and using nanobubble technology can achieve similar effects.

[0100] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for treating agricultural biomass waste, characterized in that: The hydrothermal reaction of agricultural biomass waste coupled with nanobubble nitrogen source includes the following steps: preparing a nitrogen source nanobubble solution; After mixing the nitrogen source nanobubble solution with agricultural biomass waste, a hydrothermal reaction is carried out to obtain a hydrothermal reaction product; the mass ratio of the nitrogen source substance in the nitrogen source nanobubble solution to the agricultural biomass waste is (0.3-3): (1-6); Performing solid-liquid separation on the hydrothermal reaction product to obtain a solid phase and a liquid phase of the hydrothermal reaction product; The liquid phase is subjected to nanobubble treatment to obtain a nanobubble liquid phase.

2. The processing method according to claim 1, characterized in that: The mass ratio of the nitrogen source material to the agricultural biomass waste in the nitrogen source nanobubble solution is 1:(1-4).

3. The processing method according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 180° C. to 240° C.; the time of the hydrothermal reaction is 1 to 4 hours; when the hydrothermal reaction is carried out under acidic conditions, the pH of the hydrothermal reaction is 5 to 7; when the hydrothermal reaction is carried out under alkaline conditions, the pH of the hydrothermal reaction is 8 to 14.

4. The processing method according to claim 1, characterized in that: The nanobubble particle size in the nitrogen source nanobubble solution is 70 to 180 nm; the concentration of nanobubbles in the nitrogen source nanobubble solution is 6.8×10 6 ~3.8×10 8 Pieces / mL.

5. The processing method according to claim 1, characterized in that: The preparation method of the nitrogen source nano bubble solution comprises: The nitrogen source solution is subjected to nanobubble treatment to obtain a nitrogen source nanobubble solution; Alternatively, water or alkaline solution is subjected to nanobubble treatment, and then a nitrogen source is added to the nanobubble solution to obtain a nitrogen source nanobubble solution.

6. The processing method according to claim 5, characterized in that: The gas flow rate for the nanobubble treatment is 0.1 to 0.3 L / min, the liquid flow rate is 1.5 to 3 L / min, the pressure is 0.3 to 0.7 MPa, and the time is 10 to 15 min.

7. The processing method according to claim 1, characterized in that: The nitrogen source material includes any one or more of urea, ammonium sulfate, ammonium chloride and diammonium phosphate; the agricultural biomass waste includes any one or more of forestry waste, rice husks, straw, livestock and poultry manure and biogas slurry and biogas residue.

8. A nitrogen-rich liquid fertilizer, characterized in that: The invention comprises a nanobubble liquid phase obtained by the treatment method according to any one of claims 1 to 7.

9. The nitrogen-rich liquid fertilizer according to claim 8, characterized in that: The particle size of the nanobubbles in the nitrogen-rich liquid fertilizer is 100-180 nm; the concentration of the nanobubbles in the nitrogen-rich liquid fertilizer is 4.8×10 5 ~3.8×10 7 Pieces / mL.

10. A soil conditioner, characterized in that: The solid phase comprises the solid phase obtained by the treatment method according to any one of claims 1 to 7.

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