Method for preparing high-purity potassium fulvate from livestock and poultry manure fermented biogas residues

Abstract

The invention relates to a method for preparing high-purity potassium fulvic acid from livestock and poultry manure fermented biogas residues, which comprises the following steps: (1) drying and grinding the livestock and poultry manure fermented biogas residues to obtain dried crushed aggregates; (2) mixing the dried crushed aggregates with deionized water in which 1% of potassium persulfate is dissolved, carrying out a first hydrothermal reaction, and carrying out solid-liquid separation to obtain a hydrothermal solution; (3) adding the dried crushed aggregates into the hydrothermal solution obtained in the step (2) again, and carrying out a second hydrothermal reaction in the step (2) to obtain a hydrothermal product; (4) repeating the step (3) to perform third and fourth hydrothermal cycles; (5) after the fourth hydrothermal reaction is finished, carrying out solid-liquid separation to obtain a liquid-phase product containing high-purity potassium fulvate; and (6) carrying out spray drying on the liquid-phase product to obtain a pure potassium fulvate product. By introducing a novel catalyst potassium persulfate and adopting multiple hydrothermal cycles, the yield and the purity of the potassium fulvate are remarkably improved, and meanwhile, the environmental protection property and the economical efficiency of the process are ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of waste biomass resource utilization, and in particular relates to a method for preparing high-purity potassium humate by fermenting biogas residues from livestock and poultry excrement. Background Art

[0002] With the development of the economy, the livestock and poultry farming industry has gradually changed from free-range farming to large-scale farming, and the number of livestock and poultry on hand has shown a growing trend. While my country's livestock and poultry farming industry is developing rapidly, the environmental problems it brings are also becoming increasingly serious. If livestock and poultry manure is not disposed of in time, it will not only cause soil salinization and spread microorganisms, but also cause air pollution and water pollution, causing serious harm to the ecological environment. Among the existing livestock and poultry manure treatment technologies, anaerobic fermentation is mainly used to produce biogas. However, the amount of biogas residue remaining after anaerobic fermentation is huge (annual production exceeds 130 million tons), and it cannot be well treated. Biogas residue has a high water content and is rich in organic matter. Under normal circumstances, the technology for treating biogas residue is to further carry out intensive composting, but composting occupies a large area, takes a long time, and is prone to produce foul-smelling gases. Therefore, it is crucial to find a technology for high-value utilization of biogas residue.

[0003] Hydrothermal technology is a thermochemical conversion technology that uses water as the reaction medium to convert biomass at a certain temperature and pressure in a closed high-pressure reactor. Hydrothermal technology is not restricted by the moisture content of the raw materials and is particularly suitable for wastes with high moisture content such as biogas residues. It is simple to operate, has low energy consumption, and can greatly reduce operating costs. Using hydrothermal technology to treat biogas residues can not only obtain biochar materials with high purity, good dispersibility, and easy-to-control particle size, but the hydrothermal liquid is also rich in small molecular organic matter such as fulvic acid.

[0004] Among them, fulvic acid is a water-soluble reddish brown or black powdery substance with a molecular weight of 680 to 1750 Daltons. It can stimulate plant root growth and promote cell division. It is a chelating agent in the soil and has chelation, buffering, adsorption and catalytic capabilities; a powerful antioxidant and free radical scavenger; a natural small molecule chelating detoxifier. At present, fulvic acid is mainly extracted from fossil energy sources such as peat, lignite, and weathered coal. The production of fulvic acid by treating biogas residue with hydrothermal technology can indirectly save the utilization of non-renewable resources. In contrast, potassium fulvic acid has higher solubility and better application effect. Potassium fulvic acid can not only be absorbed into the soil faster and is not easy to acidify the soil, but also has superior biological activity. Therefore, the production of potassium fulvic acid by treating biogas residue with hydrothermal technology has more significant advantages than the generation of fulvic acid. Therefore, preparing high-purity potassium humate by treating livestock and poultry manure fermentation residue with hydrothermal technology can not only efficiently utilize the residue resources and solve the environmental pollution problem, but also provide high-quality and efficient fertilizer for agricultural production. It has broad application prospects and important practical significance. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing high-purity potassium humate by fermenting biogas residue from livestock and poultry manure, so as to overcome the problems of low efficiency, high consumption and environmental pollution in traditional methods, and to achieve rapid and high-yield extraction of potassium humate by optimizing reaction conditions and process flow, which is environmentally friendly and economical and efficient.

[0006] The present invention provides a method for preparing high-purity potassium humate by fermenting biogas residue from livestock and poultry manure, comprising:

[0007] (1) drying and grinding the fermented biogas residues from livestock and poultry manure to obtain dry crushed materials;

[0008] (2) mixing the dried crushed material with deionized water containing 1% potassium persulfate, and performing a first hydrothermal reaction at a solid-liquid ratio of (2.050-2.060) g / 40 ml, at a reaction temperature of 180-220° C., for a reaction time of 2-12 h, and obtaining a hydrothermal liquid after solid-liquid separation of the hydrothermal product;

[0009] (3) adding the dried crushed material to the hydrothermal solution obtained in step (2) again, and performing a second hydrothermal reaction in the same manner as in step (2) to obtain a hydrothermal product;

[0010] (4) repeating step (3) for a third and fourth hydrothermal cycle to ensure the gradual accumulation of potassium humate in the reaction system and the improvement of its purity;

[0011] (5) After the fourth hydrothermal reaction is completed, the hydrothermal product is subjected to solid-liquid separation to obtain a liquid product containing high-purity potassium humate and a solid residue;

[0012] (6) spray drying the liquid product to obtain pure potassium humate.

[0013] Furthermore, the drying temperature in step (1) is 105°C.

[0014] Furthermore, in step (2), the solid-liquid ratio is 1:20, the reaction temperature is 200° C., and the reaction time is 4 h.

[0015] Furthermore, in step (2), the pH value in the reaction system is adjusted to 12 by 1% potassium persulfate.

[0016] By means of the above scheme, the method for preparing high-purity potassium humate by fermenting biogas residue from livestock and poultry manure has the following technical effects:

[0017] 1) This method significantly improves the yield and purity of potassium humate by improving the hydrothermal cycle technology, introducing a new catalyst - potassium persulfate, and using multiple hydrothermal cycles, while ensuring the environmental protection and economy of the process.

[0018] 2) By precisely controlling the parameters of the hydrothermal reaction, the production efficiency and product quality of potassium humate are significantly improved, while water consumption is greatly reduced.

[0019] 3) The approach also focuses on the environmental impact of the entire production process, ensuring the cleanliness and sustainability of the process.

[0020] 4) Through this method, not only potassium humate is effectively utilized, but the solid residue can also be converted into valuable products, such as biochar or soil conditioner, thus realizing the resource utilization of all components of waste biomass.

[0021] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic flow chart of a method for preparing high-purity potassium humate by fermenting biogas residues from livestock and poultry manure in an embodiment of the present invention;

[0023] Figure 2 The results of potassium humate yields with different mass ratios of potassium persulfate after the hydrothermal test in the embodiments of the present invention are as follows;

[0024] Figure 3 The results of potassium humate yield at different reaction temperatures after the hydrothermal test of the embodiment of the present invention;

[0025] Figure 4 The potassium humate yield results obtained after different hydrothermal cycle test times in the embodiments of the present invention;

[0026] Figure 5 These are the total organic carbon results of the liquid phase products obtained after different hydrothermal cycle test times in the embodiments of the present invention. DETAILED DESCRIPTION

[0027] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0028] Ginseng Figure 1 As shown, this embodiment provides a method for preparing high-purity potassium humate by fermenting livestock and poultry manure biogas residue, comprising:

[0029] (1) Drying and grinding the fermented biogas residue of livestock and poultry manure to obtain dry crushed material. The specific operating conditions of drying and crushing are not particularly limited. For example, the material can be placed at 105° C. for drying and crushed for subsequent processing.

[0030] (2) The dried crushed material is mixed with deionized water dissolved with 1% (about 0.02 g) potassium persulfate, and the solid-liquid ratio is (2.050-2.060) g / 40 ml (based on the dry basis of the dried crushed material), and the first hydrothermal reaction is carried out at a reaction temperature of 180-220° C. and a reaction time of 2-12 h. After solid-liquid separation of the hydrothermal product, a hydrothermal liquid is obtained.

[0031] (3) Adding the dried crushed material to the hydrothermal solution obtained in step (2) again, and performing a second hydrothermal reaction in the same manner as in step (2) to obtain a hydrothermal product.

[0032] (4) Repeat step (3) for a third and fourth hydrothermal cycle to ensure the gradual accumulation of potassium humate in the reaction system and the improvement of its purity.

[0033] (5) After the fourth hydrothermal reaction, the hydrothermal product is subjected to solid-liquid separation to obtain a liquid phase product containing high-purity potassium humate and a solid residue. After four hydrothermal cycle reactions, the solid phase in the material is significantly reduced, and the yield of potassium humate is significantly increased. After the fifth hydrothermal cycle reaction, the yield of potassium humate is reduced.

[0034] (6) spray drying the liquid product to obtain pure potassium humate.

[0035] Through the above method, the dried livestock and poultry manure fermentation residues are first subjected to a first hydrothermal reaction. After the first hydrothermal reaction, the solid phase in the material is significantly reduced, and the yield of potassium humate is significantly increased. Subsequently, the hydrothermal liquid continues to further process the material through the second, third and fourth hydrothermal reactions (the hydrothermal liquid obtained from each hydrothermal reaction directly participates in the next hydrothermal reaction), thereby obtaining potassium humate in high yield. After the hydrothermal product is subjected to solid-liquid separation, a liquid phase product and a solid residue containing potassium humate can be obtained. The conversion process is convenient, and the by-product solid residue can be used as a clean fuel, adsorbent, carbon-based soil remediation agent and the like. The method has the advantages of short time consumption, high yield, and clean and environmentally friendly production process.

[0036] According to some embodiments of the present invention, the solid-liquid ratio may be 1:20. If the solid-liquid ratio is too low, the hydrothermal efficiency is low, resulting in a waste of water resources, which is not conducive to engineering applications; if the solid-liquid ratio is too high, the hydrolysis may be insufficient and the raw material may be directly carbonized, resulting in limited potassium humate effect.

[0037] According to some embodiments of the present invention, the addition of potassium persulfate has a dual effect. On the one hand, potassium persulfate acts as a catalyst in the hydrothermal reaction, promoting the degradation and conversion of organic matter in livestock and poultry manure sludge by generating sulfate radicals, thereby effectively generating potassium humate. On the other hand, potassium persulfate can adjust the pH value of the reaction system to an alkaline environment suitable for the generation of potassium humate. If the pH of the system is too low, more carbon loss may result, and the efficiency of potassium humate generation will eventually decrease; if the pH of the system is too high, the efficiency of potassium humate generation will also decrease due to insufficient hydrolysis of the biomass raw materials. By adjusting the pH to 12, potassium persulfate ensures the optimal reaction conditions and greatly improves the generation rate of potassium humate.

[0038] According to some embodiments of the present invention, the temperature used in the hydrothermal reaction can be 180-220°C, preferably 200°C; the time for the hydrothermal reaction can be 2-12 hours, preferably 4 hours. If the temperature used in the first hydrothermal reaction is too low, it will lead to insufficient hydrolysis of lignocellulosic waste and excessive solid residues, which will lead to a decrease in the yield of the target product potassium humate. If the temperature used in the first hydrothermal reaction is too high, although it is conducive to the hydrolysis of lignocellulosic waste, the excessively high temperature will cause the soluble low-molecular organic matter obtained by hydrolysis to repolymerize into insoluble matter, increase the yield of solid residues, and thus lead to a decrease in the yield of the target product potassium humate; in addition, the excessively high temperature will also lead to the generation of a large amount of carbon-containing gas, resulting in carbon loss, which will lead to a decrease in the yield of the target product potassium humate.

[0039] In addition, according to some embodiments of the present invention, the previous liquid phase product can be further returned to be mixed with the dry crushed material of the livestock and poultry manure fermentation residue and then subjected to the next hydrothermal reaction, thereby saving a large amount of water resources.

[0040] The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0041] Example 1

[0042] Using livestock and poultry manure fermentation residue as raw material, hydrothermal tests were carried out at different potassium persulfate mass ratios. The results are shown in Table 1 below. When the mass ratio of potassium persulfate is 0.50%, the yield of potassium humate is 20.11%. When it increases to 1%, the yield is significantly increased to 56.78%. Further increased to 2%, the yield slightly decreased to 32.98%. The experimental results show that with the increase of potassium persulfate content, the yield of potassium humate also increases. It can be inferred that at a potassium persulfate mass ratio of 1%, the generation of potassium humate reaches the optimal state. This may be because an appropriate amount of potassium persulfate, as a catalyst, effectively promotes the degradation and conversion of organic matter and generates more potassium humate. However, when the amount of potassium persulfate exceeds the optimal point, it may cause side reactions or the decomposition of potassium persulfate itself, resulting in a decrease in yield.

[0043] Table 1 Effect of potassium persulfate mass ratio on hydrothermal potassium humate yield

[0044]

[0045] Example 2

[0046] Using livestock and poultry manure fermentation residue as raw material, experiments were carried out at different hydrothermal temperatures, and the results are shown in Table 1 below. As shown in Table 2, the solid residue yield obtained by livestock and poultry manure fermentation residue under a hydrothermal environment of 180°C is relatively high, which is 18.94%, because the low temperature leads to insufficient hydrolysis. The solid residue yield obtained by livestock and poultry manure fermentation residue under a hydrothermal environment of 200°C is higher than that at 180°C, which is 30.49%. In addition, the yield of potassium humate obtained by hydrothermal treatment of livestock and poultry manure fermentation residue at a temperature of 220°C is relatively low compared to that at 200°C, which is 23.59%. The possible reason is that the high temperature causes a large amount of carbon-containing gas to be produced, resulting in carbon loss. Therefore, a hydrothermal temperature of 200°C is beneficial to the hydrothermal humic acidification of livestock and poultry manure fermentation residue.

[0047] Table 2 Effect of hydrothermal temperature on hydrothermal potassium humate yield

[0048]

[0049] Example 3

[0050] Depend on Figure 4 It can be seen that the solid residue yield obtained from the first hydrothermal reaction test was the highest, which was 14.94 + 1.97wt% (livestock and poultry manure fermentation residue dry basis, the same below) indicates that the liquefaction effect of the first hydrothermal process is relatively low. The solid residue yield obtained in the second hydrothermal test is 11.26 +0.45wt%, significantly lower than the first hydrothermal reaction test, and the solid residue continued to decrease after multiple cycles. This is because the hydrothermal cycle treatment can significantly hydrolyze the cellulose, hemicellulose, lignin and other originally insoluble macromolecular components in the fermented biogas residue of livestock and poultry manure. Figure 5 The TOC (total organic carbon content) results of multiple hydrothermal cycle reaction tests also show this phenomenon, but in the fifth cycle test, the TOC result remains basically unchanged, because the solution reaches a relatively saturated environment, so the most suitable number of cycles is 4. Therefore, this solution not only ensures the yield of the target product, but also saves a lot of water resources.

[0051] Table 3 Effect of cycle number utilization on the yield of potassium humate produced by hydrothermal fermentation of livestock and poultry manure

[0052] .

[0053] The method for preparing high-purity potassium humate by fermenting biogas residue from livestock and poultry manure has the following technical effects:

[0054] 1) This method significantly improves the yield and purity of potassium humate by improving the hydrothermal cycle technology, introducing a new catalyst - potassium persulfate, and using multiple hydrothermal cycles, while ensuring the environmental protection and economy of the process.

[0055] 2) By precisely controlling the parameters of the hydrothermal reaction, the production efficiency and product quality of potassium humate are significantly improved, while water consumption is greatly reduced.

[0056] 3) The approach also focuses on the environmental impact of the entire production process, ensuring the cleanliness and sustainability of the process.

[0057] 4) Through this method, not only potassium humate is effectively utilized, but the solid residue can also be converted into valuable products, such as biochar or soil conditioner, thus realizing the resource utilization of all components of waste biomass.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity potassium humate from fermented biogas residues from livestock and poultry manure, characterized in that: include: (1) drying and grinding the fermented biogas residues from livestock and poultry manure to obtain dry crushed materials; (2) mixing the dried crushed material with deionized water containing 1% potassium persulfate, and performing a first hydrothermal reaction at a solid-liquid ratio of (2.050-2.060) g / 40 ml, at a reaction temperature of 180-220° C., for a reaction time of 2-12 h, and obtaining a hydrothermal liquid after solid-liquid separation of the hydrothermal product; (3) adding the dried crushed material to the hydrothermal solution obtained in step (2) again, and performing a second hydrothermal reaction as in step (2) to obtain a hydrothermal product; (4) repeating step (3) for a third and fourth hydrothermal cycle to ensure the gradual accumulation of potassium humate in the reaction system and the improvement of its purity; (5) After the fourth hydrothermal reaction is completed, the hydrothermal product is subjected to solid-liquid separation to obtain a liquid product containing high-purity potassium humate and a solid residue; (6) spray drying the liquid product to obtain pure potassium humate.

2. The method for preparing high-purity potassium humate from livestock and poultry manure fermentation residue according to claim 1, characterized in that: The drying temperature in step (1) is 105°C.

3. The method for preparing high-purity potassium humate from livestock and poultry manure fermentation residue according to claim 1, characterized in that: In step (2), the solid-liquid ratio is 1:20, the reaction temperature is 200° C., and the reaction time is 4 h.

4. The method for preparing high-purity potassium humate from livestock and poultry manure fermentation residue according to claim 3, characterized in that: In step (2), the pH value in the reaction system is adjusted to 12 by 1% potassium persulfate.

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