Method for extracting phosphorus and potassium elements from poultry manure, fertilizer preparation method thereof, liquid fertilizer and soil conditioner

Abstract

The invention provides a method for extracting phosphorus and potassium elements from poultry manure, a fertilizer preparation method thereof, a liquid fertilizer and a soil amendment, and the method for extracting the phosphorus and potassium elements comprises the following steps: S1, drying the poultry manure, and crushing the dried poultry manure into powdery manure; s2, oxalic acid is added into nitric acid to prepare a mixed acid solution, the mixed acid solution and the powdery excrement are mixed and react, phosphorus and potassium are dissolved with the nitric acid as a leaching agent, calcium ions are chelated by the oxalic acid to prevent phosphorus precipitation, and phosphorus and potassium are synchronously enriched. And S3, carrying out solid-liquid separation on reactants, and extracting leachate. Therefore, the limitation of a traditional biological fermentation path is broken through, and liquid phosphorus and potassium elements are directionally and efficiently extracted from the poultry manure.

Description

Technical Field

[0001] The present invention relates to the technology for the resource utilization of organic solid waste, and particularly to a method for extracting phosphorus and potassium elements from poultry manure by using a mixed acid, as well as a fertilizer production method, a liquid fertilizer, and a soil conditioner prepared thereby. Background Art

[0002] As a large amount of organic solid waste, poultry manure contains essential nutrients for plant growth, such as phosphorus and potassium, and is a high-quality fertilizer raw material. However, improper treatment is likely to pollute the environment and cause waste of resources. For example, chicken manure is rich in nutrients such as nitrogen, phosphorus, and potassium. When a large amount of chicken manure is piled up, the nitrogen therein will be converted into ammonia and volatilized into the air under the action of microorganisms, generating a pungent smell and causing air pollution. In addition, the ammonia discharged into the atmosphere will also cause environmental problems such as acid rain. At the same time, if the phosphorus element in chicken manure flows into water bodies with rainwater scouring, it will lead to eutrophication of water bodies, damage the aquatic ecological balance, and cause water quality deterioration.

[0003] At present, the existing poultry manure is mainly utilized in the form of fermentation composting or processed into solid fertilizers to improve the soil structure, increase soil fertility, and promote the growth of crops. However, when using such fertilizers, due to relying on microbial decomposition, the release is slow, resulting in poor timeliness of the absorption of nutrient elements by crops and unsatisfactory absorption effects.

[0004] To solve such problems, the prior art has proposed a liquid fertilizer solution, which directly extracts a liquid containing phosphorus and potassium elements from poultry manure to support fertilization by spraying and irrigation, facilitating direct application to the roots of plants, or diluting the liquid fertilizer and then fertilizing by irrigation, thereby effectively improving the absorption effect of plants.

[0005] However, the existing liquid fertilizer raw materials are usually refined based on biomass fermentation methods (such as "A Liquid Fertilizer Based on Biomass Fermentation and Its Preparation Method", patent publication number CN116425599A). Therefore, there are problems such as cumbersome preparation processes, complex raw materials, difficult component control during the fermentation process, and easy generation of unpleasant odors and microbial secretions. Thus, it is difficult to industrialize on a large scale.

[0006] It can be seen that how to break through the limitations of traditional biological fermentation pathways and efficiently extract liquid phosphorus and potassium elements from poultry manure in a targeted manner is the key to enhancing the industrial scale and market competitiveness. Summary of the Invention

[0007] Therefore, the main object of the present invention is to provide a method for extracting phosphorus and potassium elements from poultry manure, as well as a fertilizer production method, a liquid fertilizer, and a soil conditioner prepared thereby, so as to solve the problems mentioned in the background art.

[0008] To achieve the above object, according to one aspect of the present invention, a method for extracting phosphorus and potassium elements from poultry manure is provided, and its steps include:

[0009] Step S1: After drying the poultry manure, it is crushed into powdered manure;

[0010] Step S2: Oxalic acid is added to nitric acid to prepare a mixed acid solution, which is mixed and reacted with the powdered manure. Nitric acid is used as a leaching agent to dissolve phosphorus and potassium, and oxalic acid chelates calcium ions to prevent phosphorus precipitation, enabling the synchronous enrichment of phosphorus and potassium;

[0011] Step S3: The reactants are separated into solid and liquid, and the leaching solution is extracted.

[0012] In a possible preferred embodiment, when the poultry manure is chicken manure, the ratio of nitric acid to oxalic acid in the mixed acid solution is: nitric acid is 0.1 - 1 mol / L by concentration, and oxalic acid is 1.5 - 5 wt% by mass.

[0013] In a possible preferred embodiment, in step S2, the solid - liquid ratio range of the mixed acid solution to the powdered manure is 9 - 50 mL:1 g.

[0014] In a possible preferred embodiment, in step S2, the mixed reaction step includes:

[0015] Step S31: The mixed acid solution and the powdered manure are stirred evenly and react at a constant temperature at room temperature for 0.5 - 2 hours.

[0016] In a possible preferred embodiment, in step S21, the temperature selection range for the constant - temperature reaction at room temperature is 20 - 40°C.

[0017] In a possible preferred embodiment, in step S1, the particle size of the powdered manure ≥ 200 mesh.

[0018] To achieve the above object, corresponding to the above method, according to another aspect of the present invention, a liquid fertilizer is also provided, which includes: the leaching solution obtained by any of the above - mentioned methods.

[0019] To achieve the above object, corresponding to the above method, according to another aspect of the present invention, a method for extracting phosphorus and potassium elements from poultry manure to produce fertilizer is also provided, and the steps include:

[0020] The leaching solution obtained by any of the above - mentioned methods is subjected to composition regulation, and after adjusting the pH value, it is concentrated.

[0021] In a possible preferred embodiment, the composition regulation step includes:

[0022] One or more of urea, ammonium nitrate, and dipotassium hydrogen phosphate are selected as supplementary elements and added to the leaching solution.

[0023] In a possible preferred embodiment, the pH adjustment step includes:

[0024] Select any one of ammonia water and potassium hydroxide as the regulator to adjust the pH value to above 3.0.

[0025] To achieve the above object, corresponding to the above method, according to another aspect of the present invention, a soil conditioner is further provided, which includes: the dried residue separated from solid and liquid in any of the above methods.

[0026] Through the method for extracting phosphorus and potassium elements from poultry manure provided by the present invention, its fertilizer production method, liquid fertilizer, and soil conditioner, a nitric acid-oxalic acid synergistic leaching process is ingeniously proposed to efficiently extract phosphorus and potassium elements from poultry manure under normal temperature and pressure conditions. This not only breaks through the limitations of the traditional biological fermentation path, but also innovatively combines nitric acid as a dual-functional reagent (leaching agent + nitrogen source supplement) with the oxalic acid chelation anti-precipitation mechanism, replacing multi-stage biological fermentation with a one-step reaction, greatly shortening the entire process flow. This not only reduces the equipment requirements, but also effectively solves the drawbacks of the traditional biological fermentation process, and has less overall production pollution, environmental friendliness, and a well-controlled chemical reaction process. Therefore, it has the conditions for large-scale industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0028] Figure 1 It is a schematic diagram of the steps of the method for extracting phosphorus and potassium elements from poultry manure of the present invention;

[0029] Figure 2 It is a process schematic diagram of the method for extracting phosphorus and potassium elements from poultry manure of the present invention.

[0030] Figure 3 It is a process schematic diagram of the method for producing fertilizer by extracting phosphorus and potassium elements from poultry manure of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In order to enable those skilled in the art to better understand the technical solution of the present invention, the following will, in conjunction with embodiments, clearly and completely describe the specific technical solution of the present invention to assist those skilled in the art in further understanding the present invention. Obviously, the embodiments described in this case are only a part of the embodiments of the present invention, rather than all the embodiments. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention and without conflict with each other, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work should fall within the scope of disclosure and protection of the present invention.

[0032] In addition, the terms "first", "second", "S1", "S2", etc. in the description, claims and drawings of the present invention are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that the features used in this way can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those described here. At the same time, the stages recorded in each step are not forced to be implemented in the same step. It should be understood that the implementation order of the content in each step stage can be adjusted and interchanged without violating the inventive concept so that the step embodiments of the present invention described here can be implemented in an order other than those described here.

[0033] In addition, the terms "comprise" and "have" and any variations thereof in the present invention are intended to cover non-exclusive inclusion. Unless otherwise clearly defined and limited, the terms "set", "arrange", "install", "connect", "couple" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this case can be understood according to specific circumstances in combination with the prior art.

[0034] Also in this specification, when a range of a variable is recited, it should be understood that the variable includes all values within the recited range (including the endpoints of the range). For example, it should be understood that the range of "5 - 10" includes not only the values of 5, 6, 7, 8, 9, and 10, but also any sub - ranges such as 6 - 10, 7 - 10, 6 - 9, 7 - 9, etc., and also any values between integers that fall within the scope of the recited range, such as 5.5, 6.5, 7.5, 5.5 - 8.5, and 6.59. In addition, it should be understood that a range such as "10% - 30%" includes not only values such as 10%, 11%, 12%, 13%, etc. and all integers up to 30% (including 30%), but also any sub - ranges such as 10% - 15%, 12% - 18%, 20% - 30%, etc., and also any values between integers that fall within the scope of the recited range, such as 10.5%, 15.5%, 25.5%.

[0035] In order to break through the limitations of traditional biological fermentation pathways and efficiently extract liquid phosphorus and potassium elements from poultry manure in a targeted manner, as Figure 1 shown, the present invention provides a method for extracting phosphorus and potassium elements from poultry manure, and the steps thereof include:

[0036] Step S1: After drying the poultry manure, it is broken into powdered manure.

[0037] Step S2: Adjust the ratio of nitric acid to oxalic acid in the mixed acid solution to adapt to the corresponding type of poultry manure, and then mix and react with the powdered manure. Using nitric acid as the leaching agent to dissolve phosphorus and potassium, and oxalic acid to chelate calcium ions to prevent phosphorus precipitation, so as to enrich phosphorus and potassium synchronously.

[0038] Step S3: Separate the solid and liquid of the reactant, and extract the leaching solution.

[0039] Specifically, the poultry manure mentioned in this example includes the manures of common poultry such as chickens, ducks, geese, quails, pigeons, etc. Most of the components of this kind of poultry manure are similar, but generally different in the contents of phosphorus, potassium, calcium, etc. Therefore, those skilled in the art can, on the premise of understanding the concept of the present invention, adaptively adjust various ratios, numerical values, etc. in the relevant processes in this example of the present invention for different types of poultry manure. For example, according to the calcium content of different poultry manures, adjust the dosage of oxalic acid to precipitate calcium preferentially to prevent the aggregation of phosphorus elements and calcium ions to form calcium phosphate precipitation, so that the phosphorus elements can remain in the leaching solution as much as possible to improve the recovery efficiency. Therefore, those skilled in the art should understand that other equivalent substitution / adjustment implementation schemes made without departing from the concept of the present invention are all within the disclosure scope of the present invention.

[0040] To better illustrate the implementation process of the present invention, chicken manure is taken as an example for exemplary illustration in this example. Specifically, in order to break through the limitations of the traditional biological fermentation path, a synergistic leaching scheme of nitric acid - oxalic acid is proposed in the concept of the present invention, so as to utilize nitric acid (HNO3) to provide an acidic environment to dissolve phosphorus and potassium, and synergistically chelate calcium ions with oxalic acid (H2C2O4) to prevent phosphorus precipitation, thereby realizing the synchronous enrichment of phosphorus and potassium, and achieving the directional and efficient extraction of phosphorus and potassium elements in chicken manure by chemical wet method under normal temperature and pressure.

[0041] The example reaction conditions are as follows:

[0042] Chemical reagents and conditions Technical feature range Function description <![CDATA[Nitric acid (HNO3)]]> Concentration: 0.1 - 1 mol / L Provide an acidic environment to dissolve phosphorus and potassium <![CDATA[Oxalic acid (H2C2O4)]]> Mass concentration: 1.5 - 5% Chelate calcium ions to prevent phosphorus precipitation Liquid-solid ratio (9 - 50) mL: 1 g Balance between leaching efficiency and economy Reaction temperature 20 ~ 40 ℃ Control at low temperature to reduce energy consumption

[0043] The example leaching process is as follows:

[0044] When the poultry manure is chicken manure (including fermented chicken manure or dried chicken manure), in order to increase the reaction specific surface area, the chicken manure can be dried to a moisture content ≤ 15% and then crushed to a particle size ≥ 200 mesh by an air flow pulverizer to obtain chicken manure micropowder.

[0045] For the incoming chicken manure, in this example, a mixed acid solution is preferably prepared by mixing nitric acid at a concentration of 0.1 - 1 mol / L and oxalic acid at a mass fraction of 1.5 - 5 wt%, and the mixed acid solution is added to the leaching reactor and mixed with the chicken manure micropowder at a liquid - solid ratio of (9 - 50) mL:1 g for mixing reaction.

[0046] The steps of the mixed reaction example include: stirring the mixed acid solution and the powdered manure evenly, selecting a reaction temperature of 20 - 40 °C, and carrying out a constant - temperature reaction for 0.5 - 2 h.

[0047] After the reaction is completed, the reaction mixture is separated by a centrifuge at 4000 rpm for 10 min, and finally a phosphorus - potassium leaching solution and organic matter residue can be obtained.

[0048] Experimental examples and comparative examples

[0049] Experimental example 1

[0050] (1) As Figure 2 shown, select the fermented chicken manure that has been dried, crushed, screened (particle size ≥ 200 mesh), and weigh three portions of 1 g of fermented chicken manure micropowder for experiments. Its chemical composition is shown in Table 1.

[0051] Table 1 Chemical composition of fermented chicken manure (wt%)

[0052]

[0053] (2) Mix nitric acid with concentrations of 0.1, 0.5, and 1 mol / L respectively with oxalic acid with a mass concentration of 2.5% to obtain a nitric acid-oxalic acid mixed solution, and add it to beakers No. 1, 2, and 3 according to a liquid-solid ratio of 20 mL:1 g respectively.

[0054] (3) Add the weighed chicken manure micropowder to the 3 beakers respectively, stir evenly, control the temperature at 25 °C, and stir and react for 1 h.

[0055] (4) After the reaction, carry out solid-liquid separation to obtain the residue and the leachate. Use AAS and ICP-OES to measure the concentrations of each component in the leachate, and the results are shown in Table 2.

[0056] Table 2 Concentrations of each element in the leachate (mg / L)

[0057] Nitric acid concentration Total phosphorus Total potassium 0.1 mol / L 1146 2934 0.5 mol / L 2376 3516 1 mol / L 2882 4730

[0058] The experiment shows that the nitric acid-oxalic acid mixed acid system used in this process has double synergistic advantages:

[0059] 1) Oxalate (C2O4 2- ) preferentially combines with calcium ions in the leachate to form calcium oxalate crystals (Ksp = 2.32×10 -9 ), effectively preventing the aggregation of phosphorus and calcium ions to form calcium phosphate precipitate (Ksp = 2.07×10 -33 ), and increasing the retention rate of phosphorus by more than 40%.

[0060] 2) Nitric acid acts as both a leaching agent and a nitrogen source at the same time. The concentration of nitrate nitrogen (NO3 - -N) in the leachate can reach 1500 - 3000 mg / L, realizing the simultaneous enrichment of nitrogen, phosphorus, and potassium, and reducing the cost of exogenous nitrogen addition by more than 30%.

[0061] Optimal mixed acid ratio: Through gradient experiments, when the nitric acid concentration is 1 mol / L and the mass concentration of oxalic acid is 2.5%, the total phosphorus ≥ 2800 mg / L, the total potassium ≥ 4700 mg / L, and the leaching rates of phosphorus and potassium elements both exceed 85%, and the element extraction effect is good.

[0062] Comparative Example 1

[0063] The difference between this comparative example and Experimental Example 1 is that: 0.5 mol / L nitric acid and 2.5% oxalic acid are selected, and the reaction temperature is controlled at 20 °C and 40 °C. The concentrations of each component in the leachate at 20 °C are not much different from those at 25 °C; at 40 °C, the total phosphorus concentration is about 2500 mg / L and the total potassium concentration is about 3956 mg / L.

[0064] This indicates that when the temperature rises to 40 °C, the extraction efficiency increases slightly, but the increase is not significant, which may mean that the effect of temperature on the reaction is limited within a relatively high range.

[0065] Comparative Example 2

[0066] The difference between this comparative example and Experimental Example 1 lies in: selecting a mixture of 0.5 mol / L nitric acid and 2.5% oxalic acid, controlling the reaction time to 2 h, and under the reaction conditions of 2 h, the total phosphorus concentration is about 2640 mg / L and the total potassium concentration is about 4025 mg / L. This shows that extending the reaction time can improve the extraction efficiency, but the balance between production efficiency and cost needs to be considered.

[0067] Comparative Example 1 reveals the non-linear effect of temperature on the extraction efficiency by changing the reaction temperature: at 40 °C, the phosphorus / potassium concentration increases by 5.2% / 12.5% compared to Experimental Example 1, but the energy efficiency ratio decreases significantly (the energy consumption increases by 60%), corroborating that 25 - 40 °C is the economically preferred range; Comparative Example 2 proves that extending the reaction time to 2 h (2 h vs 1 h in Experimental Example 1) can increase the phosphorus / potassium extraction rate by 11.1% / 14.5%, but the unit production capacity decreases by 50%, comprehensively verifying that the parameter range of 0.5 - 2 h in Experimental Example 1 has both efficiency and economy. The two comparative examples contrast the rationality of the process parameters in Experimental Example 1 from the perspective of the balance between energy consumption and output.

[0068] Experimental Example 2

[0069] The method of this Experimental Example 2 is the same as that of Experimental Example 1, specifically including the following steps:

[0070] (1) Weigh 1 portion of dried chicken manure micropowder with a mass of 1 g (particle size ≥ 200 mesh), and its chemical composition is shown in Table 3.

[0071] Table 3 Chemical composition of dried chicken manure (wt%)

[0072]

[0073] (2) Prepare a mixture of nitric acid with a concentration of 0.5 mol / L and oxalic acid with mass concentrations of 1.5%, 2.5%, 3.5%, and 5% respectively to obtain a nitric acid - oxalic acid mixed solution, and add it to a beaker according to a liquid - solid ratio of 20 mL:1 g; control the temperature at 25 °C and stir for 1 h.

[0074] (3) The post - reaction operation is the same as that in Experimental Example 1, and the results are shown in Table 4;

[0075] Table 4 Concentrations of various elements in the leaching solution (mg / L)

[0076] Nitric acid + oxalic acid Total phosphorus Total potassium 0.5+1.5% 1572 2461 0.5+2.5% 2257 3349 0.5+3.5% 2421 3975 0.5+5% 2843 4537

[0077] By comparing with Example 1, it can be found that the calcium content in the dried chicken manure is more than 15% higher than that in the fermented chicken manure. Therefore, for the mixed acid ratio of dried chicken manure, a relatively higher concentration of oxalic acid needs to be selected to ensure that it can effectively prevent the aggregation of phosphorus and calcium ions to form calcium phosphate precipitation, so that the phosphorus element can remain in the leaching solution as much as possible to improve the recovery efficiency.

[0078] At the same time, it can be seen from this set of data that as the concentration of oxalic acid increases, the increasing trend of phosphorus element does not conform to the linear law, which reflects an unforeseen synergistic effect.

[0079] Comparative Example 3

[0080] In Comparative Example 3, fermented chicken manure and dried chicken manure with different particle sizes were selected. After crushing the two kinds of chicken manure, they were respectively passed through a vibrating screen to screen out several different particle sizes of 50, 100, 150, 200, and 250 meshes; the fermented chicken manure was leached with 1mol / L nitric acid + 2.5% oxalic acid, and the dried chicken manure was leached with 0.5mol / L + 5% oxalic acid. The specific steps are the same as those in Experimental Example 1.

[0081] The leaching results of different particle sizes of fermented chicken manure and dried chicken manure are shown in Table 5 and Table 6 respectively.

[0082] Table 5 Concentrations of various elements in the leaching solution of fermented chicken manure (mg / L)

[0083] Particle size (mesh) Total phosphorus Total potassium 50 1001 2175 100 1189 2742 150 1751 3594 200 2882 4730 250 2907 4794

[0084] Table 6 Concentrations of various elements in the leaching solution of dried chicken manure (mg / L)

[0085] Particle size (mesh) Total phosphorus Total potassium 50 987 1638 100 1288 2145 150 1677 3714 200 2843 4537 250 2917 4614

[0086] It can be seen from Table 5 and Table 6 that when the two kinds of chicken manure are below 200 meshes, although phosphorus and potassium elements can also be extracted and recovered, the leaching efficiency is quite different compared with that above 200 meshes. This is because the specific surface area of 200-mesh particles is greatly increased compared with coarser particles (such as 50 meshes), maximizing the contact area between the acid solution and the phosphorus and potassium minerals in the chicken manure, significantly shortening the diffusion path of the acid solution penetrating into the interior of the particles, and ensuring that the mineral phase (such as calcium phosphate) is fully dissolved. In addition, the crushing energy consumption of 200 meshes is reduced by 50% compared with higher mesh numbers (such as 400 meshes) (measured by the crushing work index), and at the same time, the extraction efficiency reaches the peak of marginal benefit (the difference in extraction amounts between 200 meshes and 250 meshes < 5%), realizing the optimal unity of economy and technical effect.

[0087] It can be seen that from the above experimental examples and comparative examples, the nitric acid-oxalic acid synergistic leaching system proposed by the present invention can achieve the directional and efficient extraction of phosphorus and potassium elements in chicken manure at normal temperature and pressure (20-40°C) through chemical wet methods. Abandoning the traditional high-temperature incineration (>500°C) or multi-day fermentation processes, the energy consumption of the equipment required for production is significantly reduced, and the extraction concentrations of phosphorus and potassium can reach 2882 mg / L and 4730 mg / L, respectively, which is 140-260% higher than that of traditional composting.

[0088] It is also worth mentioning that the present invention creatively combines nitric acid as a dual-functional reagent (leaching agent + nitrogen source supplement) with the oxalic acid chelation anti-precipitation mechanism, replacing multi-stage biological fermentation with a one-step reaction, thereby greatly shortening the overall process flow, and the reaction time can be shortened from several days in the traditional method to 0.5-2 hours.

[0089] It can be seen that the solution of the present invention can efficiently recycle phosphorus and potassium elements in chicken manure at low cost. Nitric acid also provides an acidic condition for wet leaching and supplements nitrogen elements, and oxalic acid can promote the absorption of phosphorus by crops. In addition, the entire technical process of this solution is carried out under acidic conditions, with simple process, low equipment requirements, less pollution, and high production efficiency, having environmental friendliness and good economic benefits. Moreover, the obtained leaching solution containing phosphorus and potassium elements can also be widely applied to various industrial productions, or can be made into liquid fertilizers, which can not only meet the nutritional needs of crops but also improve the absorption effect of crops.

[0090] On the other hand, corresponding to the above-mentioned process method of the examples, the present invention also provides a liquid fertilizer, which includes: the leaching solution obtained by the method described in any one of the above examples.

[0091] On the other hand, corresponding to the above-mentioned process method of the examples, as Figure 3 shown, the present invention also provides a method for extracting phosphorus and potassium elements from poultry manure to make fertilizer, and its steps include:

[0092] Adjust the composition of the leaching solution obtained by the method described in any one of the above, and after adjusting the pH value and concentrating until the macronutrients required for the product reach the standard, obtain the finished fertilizer.

[0093] The specific key preparation steps are as follows:

[0094]

[0095] Among them, as Figure 3As shown above, for those key steps related to the leaching solution process, they will not be elaborated here and can be referred to the previous examples. Examples of the component regulation steps include: according to the product requirements, one or more of urea, ammonium nitrate, and dipotassium hydrogen phosphate can be selected as N / P / K supplementary elements and added to the leaching solution. Examples of the pH adjustment steps include: selecting either ammonia water or potassium hydroxide as the regulator to adjust the pH value.

[0096] For example, in this example, it is preferred to add urea (1 - 3 wt%) and dipotassium hydrogen phosphate (0.5 - 2 wt%) to the leaching solution, adjust the pH to 3.0 ± 0.5 with ammonia water, and concentrate it to the major elements required for the product to obtain the finished liquid fertilizer.

[0097] On the other hand, corresponding to the examples of the method for extracting phosphorus and potassium elements from poultry manure above, the present invention also provides a soil conditioner, which includes: the dried residue separated by solid-liquid separation in any of the above examples of the method for extracting phosphorus and potassium elements from poultry manure.

[0098] Among them, in the above example, the residue separated by solid-liquid separation is subjected to high-temperature drying treatment (such as drying at 105 °C) to prepare an organic soil conditioner. Thus, it can be seen that the method for extracting phosphorus and potassium elements from poultry manure in the above example not only can be matched and connected with the liquid fertilizer preparation process in terms of process, but also the residue can be converted into a soil conditioner, realizing the full-component resource utilization of chicken manure and the zero-waste discharge design, meeting the carbon neutrality goal. In addition, the calcium oxalate remaining in the residue has the property of precipitating and fixing heavy metals, so the environmental protection risk can be reduced. Based on this, a full-closed production mode from phosphorus and potassium extraction - liquid fertilizer preparation - residue resource utilization can be constructed, effectively solving the problems of low efficiency and high energy consumption in the prior art.

[0099] In summary, through the method for extracting phosphorus and potassium elements from poultry manure provided by the present invention, its fertilizer production method, liquid fertilizer, and soil conditioner, a nitric acid - oxalic acid synergistic leaching process is ingeniously proposed to efficiently extract phosphorus and potassium elements from poultry manure under normal temperature and pressure conditions. This not only breaks through the limitations of the traditional biological fermentation path, but also innovatively combines nitric acid as a dual-functional reagent (leaching agent + nitrogen source supplement) with the oxalic acid chelation anti-precipitation mechanism, replacing multi-stage biological fermentation with a single-step reaction, greatly shortening the entire process flow. This not only reduces the equipment requirements, but also effectively solves the drawbacks of the traditional biological fermentation process, and has less overall production pollution, environmental friendliness, and a well-controlled chemical reaction process. Therefore, it has the conditions for large-scale industrial application.

[0100] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, according to the content of this specification, many modifications and changes can be made. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0101] In addition, all or part of the steps in the methods of the above embodiments can be completed by instructing relevant hardware through a program. The program is stored in a storage medium, including several instructions for causing a single-chip microcomputer, a chip or a processor to execute all or part of the steps of the methods described in various embodiments of the present application. The aforementioned storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks or optical disks that can store program codes.

[0102] In addition, any combination can be made between various different embodiments of the embodiments of the present invention, as long as it does not violate the idea of the embodiments of the present invention, and it should also be regarded as the content disclosed in the embodiments of the present invention.

Claims

1. A method for extracting phosphorus and potassium elements from poultry manure, the steps of which include: Step S1: After drying the poultry manure, it is broken into powdered manure; Step S2: Oxalic acid is added to nitric acid to prepare a mixed acid solution, which is mixed and reacted with the powdered manure. Nitric acid is used as a leaching agent to dissolve phosphorus and potassium, and oxalic acid chelates calcium ions to prevent phosphorus precipitation, enabling the synchronous enrichment of phosphorus and potassium; Step S3: The reactant is separated into solid and liquid, and the leaching solution is extracted.

2. The method for extracting phosphorus and potassium elements from poultry manure according to claim 1, wherein when the poultry manure is chicken manure, the ratio of nitric acid to oxalic acid in the mixed acid solution is: nitric acid is 0.1 - 1 mol / L by concentration, and oxalic acid is 1.5 - 5 wt% by mass.

3. The method for extracting phosphorus and potassium elements from poultry manure according to any one of claims 1 or 2, wherein in step S2, the solid-liquid ratio range of the mixed acid solution to the powdered manure is 9 - 50 mL:1 g.

4. The method for extracting phosphorus and potassium elements from poultry manure according to any one of claims 1 or 2, wherein in step S2, the mixed reaction step includes: Step S21: The mixed acid solution and the powdered manure are stirred evenly and reacted at a constant temperature at room temperature for 0.5 - 2 hours.

5. The method for extracting phosphorus and potassium elements from poultry manure according to claim 4, wherein the temperature range for the constant temperature reaction at room temperature in step S21 is 20 - 40 °C.

6. The method for extracting phosphorus and potassium elements from poultry manure according to any one of claims 1 or 2, wherein in step S1, the particle size of the powdered manure ≥ 200 mesh.

7. A liquid fertilizer, which comprises: The leaching solution obtained by the method according to any one of claims 1 to 6.

8. A method for extracting phosphorus and potassium elements from poultry manure to produce fertilizer, the steps of which include: The leaching solution obtained by the method according to any one of claims 1 to 6 is subjected to composition regulation, and after adjusting the pH value, it is concentrated.

9. The method for extracting phosphorus and potassium elements from poultry manure to produce fertilizer according to claim 8, wherein the composition regulation step includes: Select one or more of urea, ammonium nitrate, and dipotassium hydrogen phosphate as supplementary elements and add them to the leaching solution.

10. The method for extracting phosphorus and potassium elements from poultry manure to produce fertilizer according to claim 8, wherein the pH value adjustment step includes: Select any one of ammonia water and potassium hydroxide as a regulator to adjust the pH value to above 3.

0.

11. A soil conditioner, comprising: The dry residue separated from solid and liquid in the method according to any one of claims 1 to 6.

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