Poultry manure resource utilization method based on multi-stage treatment, fertilizer preparation method thereof, liquid fertilizer and soil conditioner

Abstract

The invention provides a poultry manure resource utilization method based on multi-stage treatment and a fertilizer preparation method thereof, a liquid fertilizer and a soil conditioner. The resource utilization method comprises the following steps: S1, crushing and screening poultry manure into powdery manure; s2, after the inorganic acid solution and the excrement are mixed and react, solid-liquid separation is conducted, and first-section leachate and phosphorus-containing filter residues are extracted; s3, oxalic acid is added into the first-stage leachate for a mixed reaction, then solid-liquid separation is conducted, and second-stage leachate and calcium oxalate precipitates are extracted; and S4, phosphorus-containing filter residues are added into the second-stage leachate for mixed reaction, solid-liquid separation is conducted, and third-stage leachate rich in phosphorus and potassium is obtained. 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

[0002] The invention relates to a technology for resource utilization of organic solid waste, and in particular to a method for resource utilization of poultry excrement based on multi-stage treatment, a fertilizer making method thereof, a liquid fertilizer, and a soil conditioner. Background Art

[0004] As a large amount of organic solid waste, poultry manure contains nutrients such as phosphorus and potassium that are necessary for plant growth and is a high-quality fertilizer raw material. However, improper handling can easily pollute the environment and cause resource waste. For example, chicken manure is rich in nutrients such as nitrogen, phosphorus and potassium. When a large amount of it is accumulated, the nitrogen in it will be converted into ammonia gas by microorganisms and volatilize into the air, producing a pungent odor and causing air pollution. In addition, ammonia emissions into the atmosphere will also cause environmental problems such as acid rain. At the same time, if the phosphorus element in chicken manure is washed into the water body with rainwater, it will cause eutrophication of the water body, destroy the aquatic ecological balance, and cause water quality deterioration.

[0005] Currently, poultry manure is mainly utilized as a resource in the form of fermentation compost or processing into solid fertilizer to improve soil structure, increase soil fertility and promote crop growth. However, when such fertilizers are used, they rely on microbial decomposition, resulting in slow release, which makes the absorption of nutrients by crops less timely and the absorption effect is poor.

[0006] Therefore, in order to solve such problems, the prior art has proposed a liquid fertilizer solution, which directly extracts liquid containing phosphorus and potassium from poultry manure to support fertilization through spraying and irrigation, so as to facilitate direct application to the roots of plants, or dilute the liquid fertilizer and then fertilize it through irrigation, thereby effectively improving the absorption effect of plants.

[0007] However, existing liquid fertilizer raw materials are usually extracted based on biomass fermentation (such as "A liquid fertilizer based on biomass fermentation and its preparation method", patent publication number CN116425599A). Therefore, there are problems such as complicated preparation process, complex raw materials, difficulty in regulating the ingredients of the fermentation process, and easy generation of unpleasant odors and microbial secretions. Therefore, it is difficult to industrialize on a large scale.

[0008] It can be seen that how to break through the limitations of traditional biological fermentation pathways and extract liquid phosphorus and potassium elements from poultry manure in a targeted and efficient manner is the key to improving industry scale and market competitiveness. Summary of the invention

[0010] The main purpose of the present invention is to provide a method for resource utilization of poultry manure based on multi-stage processing and a fertilizer making method, liquid fertilizer, and soil conditioner thereof, so as to solve the problems mentioned in the background technology.

[0011] To achieve the above object, according to one aspect of the present invention, there is provided a method for resource utilization of poultry manure based on multi-stage treatment, and its steps include:

[0012] Step S1: Crush and screen poultry manure into powdery manure;

[0013] Step S2: Mix an inorganic acid solution with the manure and react, then perform solid-liquid separation to extract a first-stage leachate and a phosphorus-containing filter residue;

[0014] Step S3: Add oxalic acid to the first-stage leachate for mixing and reaction, then perform solid-liquid separation to extract a second-stage leachate and calcium oxalate precipitate;

[0015] Step S4: Add the phosphorus-containing filter residue to the second-stage leachate for mixing and reaction, then perform solid-liquid separation to obtain a third-stage leachate enriched with phosphorus and potassium.

[0016] In a possible preferred embodiment, the solid-liquid ratio of the inorganic acid solution to the powdery manure is 9-20 mL:1 g.

[0017] In a possible preferred embodiment, the concentration of the inorganic acid solution is 0.5-2 mol / L.

[0018] In a possible preferred embodiment, in step S3, the addition amount of oxalic acid is based on the calcium content in the manure, and the molar ratio of oxalic acid to calcium is controlled to 0.8-1.4.

[0019] In a possible preferred embodiment, in the mixing reactions in steps S2, S3, and S4, they are carried out at room temperature for 10-40 minutes.

[0020] In a possible preferred embodiment, the inorganic acid solution includes any one of nitric acid, sulfuric acid, and hydrochloric acid.

[0021] In a possible preferred embodiment, the particle size of the powdery manure is <0.15 mm.

[0022] To achieve the above object, corresponding to the above method, according to another aspect of the present invention, there is also provided a liquid fertilizer, which includes: the third-stage leachate obtained by any of the above methods.

[0023] To achieve the above object, corresponding to the above method, according to another aspect of the present invention, there is also provided a method for making fertilizer, and its steps include:

[0024] Perform composition regulation on the third-stage leachate obtained by any of the above methods, adjust the pH value and then perform concentration treatment.

[0025] In a possible preferred embodiment, the composition regulation step includes:

[0026] One or more of urea, ammonium nitrate and dipotassium hydrogen phosphate are selected as supplementary elements and added into the three-stage leaching solution.

[0027] In a possible preferred embodiment, the pH adjustment step comprises:

[0028] Select either ammonia water or potassium hydroxide as a regulator to adjust the pH value to above 3.0.

[0029] In order to achieve the above object, corresponding to the above method, according to another aspect of the present invention, a soil conditioner is also provided, which comprises: a dry residue obtained by solid-liquid separation in any of the above methods.

[0030] Through the poultry manure resource utilization method based on multi-stage treatment and its fertilizer making method, liquid fertilizer, and soil conditioner provided by the present invention, a step-by-step leaching scheme is cleverly designed to efficiently extract phosphorus (P) and potassium (K) elements in poultry manure through an inorganic acid-oxalic acid step-by-step leaching process, and convert them into fertilizers that can be directly used in agriculture. In addition, calcium oxalate (CaC2O4) can also be recovered in the process as an industrial raw material or calcium supplement.

[0031] This not only breaks through the limitations and disadvantages of traditional biological fermentation routes, but also greatly improves the extraction efficiency compared to traditional composting methods. The residue after the reaction can also be used as a soil conditioner, thus opening up a closed-loop chain of "harmless treatment-high-value extraction of elements-full component utilization" for organic solid waste, and overcoming industry problems such as incomplete degradation of antibiotics in traditional processes, low conversion rate of traditional liquid fertilizers, and serious secondary pollution. It provides a revolutionary solution for the resource utilization of livestock and poultry manure with high efficiency, low cost and low emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic experimental examples and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0034] Figure 1 A schematic diagram of the steps of the method for resource utilization of poultry excrement based on multi-stage processing of the present invention;

[0035] Figure 2 It is a schematic diagram of the step-by-step process of the method for resource utilization of poultry excrement based on multi-stage processing of the present invention;

[0036] Figure 3 The XRD spectrum and chemical composition diagram of calcium oxalate crystals in the example of the poultry manure resource utilization method based on multi-stage processing of the present invention;

[0037] Figure 4In the example of the method for resource utilization of poultry manure based on multi-stage treatment of the present invention, schematic diagram of the microscopic morphology and energy spectrum analysis of calcium oxalate crystals;

[0038] Figure 5 It is a schematic diagram of the method process for making fertilizer in the method for resource utilization of poultry manure based on multi-stage treatment of the present invention. Detailed implementation manners

[0040] In order to enable those skilled in the art to better understand the technical solution of the present invention, the following will clearly and completely describe the specific technical solution of the present invention in combination with experimental examples, so as to help those skilled in the art further understand the present invention. Obviously, the experimental examples described in this case are only part of the experimental examples of the present invention, rather than all the experimental examples. 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 experimental examples in this application and the features in the experimental examples can be combined with each other. Based on the experimental examples in the present invention, all other experimental examples obtained by those of ordinary skill in the art without creative work shall fall within the scope of disclosure and protection of the present invention.

[0041] 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 have to be used to describe a specific order or sequence. It should be understood that such features can be interchanged under appropriate circumstances, so that the experimental examples 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 experimental examples of the present invention described here can be implemented in an order other than those described here. In addition, the terms "comprising" and "having" in the present invention and any variations thereof are intended to cover non-exclusive inclusion. Unless otherwise clearly defined and limited, the terms "set", "arranged", "installed", "connected", "connected" 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.

[0042] 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 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 within the scope of the recited range, such as 10.5%, 15.5%, 25.5%.

[0043] 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 Figures 1 to 4 shown, the present invention provides a method for resource utilization of poultry manure based on multi - stage treatment, and its steps include:

[0044] Step S1: Crush and screen poultry manure into powdered manure;

[0045] Step S2: Mix an inorganic acid solution with the manure and react, then perform solid - liquid separation to extract a first - stage leachate and phosphorus - containing filter residue;

[0046] Step S3: Add oxalic acid to the first - stage leachate for mixing and reacting, then perform solid - liquid separation to extract a second - stage leachate and calcium oxalate precipitate;

[0047] Step S4: Add the phosphorus - containing filter residue to the second - stage leachate for mixing and reacting, then perform solid - liquid separation to obtain a third - stage leachate enriched with phosphorus and potassium.

[0048] Specifically, the poultry manure referred to in this example includes the manure of common poultry such as chickens, ducks, geese, quails, pigeons, etc. Most of the components of this poultry manure are similar, but generally differ 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 manure, adjust the dosage of oxalic acid to precipitate calcium, or adjust the concentration of the inorganic acid leachate and its solid - liquid ratio according to the amount of manure to provide an environment for fully dissolving calcium, phosphorus, and potassium elements. Therefore, those skilled in the art should understand that other equivalent replacement / adjustment implementation schemes made without departing from the concept of the present invention are all within the disclosure scope of the present invention.

[0049] To better illustrate the implementation process of the present invention, chicken manure is taken as an example for exemplary illustration in this example. In order to break through the limitations of the traditional biological fermentation path and improve the recovery rates of phosphorus and potassium, considering that the single acid leaching process will result in a low phosphorus leaching rate due to the competitive precipitation of calcium (Ca) and phosphorus (P) (for example, when the particle size > 0.15 mm in Comparative Example 1, the phosphorus leaching rate is only 35.24%), and the calcium resources are not effectively recovered, causing resource waste and high costs (such as doubling the amount of high-concentration nitric acid). Therefore, a step-by-step leaching scheme is proposed in the concept of the present invention to efficiently extract phosphorus (P) and potassium (K) elements from chicken manure through an inorganic acid-oxalic acid step-by-step leaching process, convert them into fertilizers that can be directly used in agriculture, and simultaneously recover calcium oxalate (CaC2O4) as an industrial raw material or calcium supplement during the process.

[0050] The reaction conditions of the example are as follows:

[0051] Chemical reagents and conditions Technical feature range Function description <![CDATA[Nitric acid (HNO3)]]> Concentration 0.5 - 2 mol / L Provide an acidic environment to dissolve calcium, phosphorus and potassium <![CDATA[Oxalic acid (H2C2O4)]]> Molar ratio (n_herb:n_Ca) 0.8 - 1.4 Precipitate and recover calcium and provide an acidic environment Liquid-solid ratio (9 - 20) mL:1 g Balance between leaching efficiency and economy Chicken manure particle size <0.15mm Increase the reaction area between the residue and the liquid and improve the efficiency of the first leaching

[0052] The leaching process of the example is as follows:

[0053] 1) Raw material pretreatment: Crush and screen chicken manure (including: raw chicken manure, high-temperature activated chicken manure, or chicken manure incineration ash) to a suitable particle size (particle size < 0.15 mm) to increase the reaction area and improve the efficiency of the first leaching.

[0054] 2) Inorganic acid leaching: Add the pretreated raw material to the leaching reaction kettle according to a liquid-solid ratio of 9 - 20 mL:1 g, add an inorganic acid solution with a concentration of 0.5 - 2 mol / L (such as nitric acid solution), and react at room temperature for 10 - 40 min to fully dissolve calcium (Ca), phosphorus (P), and potassium (K) elements.

[0055] 3) First solid-liquid separation: Separate the first-stage leaching solution rich in calcium, phosphorus, and potassium and the filter residue containing undissolved phosphorus through filtration, centrifugation, or membrane separation technology (the filtrate collection rate > 95%). (Due to the too high calcium ion concentration in the filtrate, some phosphate ions form precipitates.) Through the above first leaching, the calcium, phosphorus, and potassium elements in the minerals can be dissolved to the maximum extent. Since the calcium ion concentration is extremely high, most of the leached phosphate ions will precipitate into the filter residue.

[0056] 4) Recover calcium ions in the first-stage leaching solution: Add oxalic acid to the first-stage leaching solution according to the content of Ca element in chicken manure (the molar ratio of oxalic acid to calcium is 0.8 - 1.4) for the recovery of calcium oxalate, and react for 10 - 40 min.

[0057] 5) Second solid-liquid separation: Separate the calcium oxalate precipitate (verified by XRD / SEM to reach the industrial-grade standard) and the second-stage leaching solution containing phosphorus and potassium. The calcium oxalate can be directly used as an industrial raw material (such as ceramics, coatings) or calcium supplement.

[0058] 6) Mixed acid leaching of phosphorus-containing residue: Add the phosphorus-containing residue to the second-stage leaching solution and react for 10 - 40 min. Utilize the synergistic effect of the remaining nitric acid and oxalic acid to further dissolve the residual phosphorus in the filter residue.

[0059] 7) Third solid-liquid separation: After the reaction, the mixed solution is subjected to solid-liquid separation to obtain a third-stage leaching solution rich in phosphorus and potassium elements and mineral residues.

[0060] In the above process, the main recovery targets are the third-stage leaching solution rich in phosphorus and potassium elements and calcium oxalate solid. Through stepwise leaching and parameter synergy, the recovery rates of phosphorus and potassium can be significantly improved (>90%), while the acid consumption cost is reduced by more than 30%. It has both technical feasibility and commercial value.

[0061] Experimental examples and comparative examples

[0062] Experimental example 1

[0063] (1) As Figure 2 shown in the process steps, select the chicken manure incineration ash after crushing and screening (particle size less than 0.074 mm), weigh 1 portion with a mass of 5 g, and the chemical composition of the chicken manure incineration ash is shown in Table 1.

[0064] Table 1 Chemical composition of chicken manure (mass%)

[0065]

[0066] (2) Add the chicken manure incineration ash to nitric acid solutions with different concentrations (0.1, 0.5, 1, 2 mol / L) for the first-stage leaching, set the liquid-solid ratio to 20:1, react at room temperature, and control the reaction time to 30 min.

[0067] (3) After the reaction, perform solid-liquid separation to obtain a first-stage leaching solution and a phosphorus-containing filter residue.

[0068] (4) Add a certain amount of oxalic acid (molar ratio n_oxalic:n_Ca = 1.2) to the first-stage leaching solution, react at room temperature, and control the reaction time to 30 min.

[0069] (5) After the reaction, perform solid-liquid separation to obtain a second-stage leaching solution and a residue rich in calcium oxalate.

[0070] (6) Add the phosphorus-containing filter residue to the second-stage leaching solution, control the reaction at room temperature, and react at a constant temperature for 30 min.

[0071] (7) After the reaction, solid-liquid separation is carried out to obtain a three-stage leaching solution containing phosphorus and potassium and calcium oxalate crystals, and the liquid and solid are respectively detected and analyzed. For the leaching solution, the concentrations of each component in the leaching solution are measured by AAS and ICP-OES, and the leaching rates of phosphorus and potassium elements are calculated. The results are shown in Table 2; for the calcium oxalate crystals, characterization and analysis are carried out by methods such as XRD, XRF, and SEM, and the results are as Figure 3 and Figure 4 shown.

[0072] Table 2 Leaching rates of phosphorus and potassium elements in the leaching solution (%).

[0073]

[0074] In Experimental Example 1, chicken manure incineration ash (particle size < 0.074 mm) was treated by a stepwise leaching process of nitric acid-oxalic acid. Under the conditions of a liquid-solid ratio of 20:1, a nitric acid concentration of 1 mol / L, and an oxalic acid-to-calcium molar ratio of 1.2, the leaching rates of phosphorus and potassium elements reached 87.73% and 90.37% respectively.

[0075] When the nitric acid concentration was increased to 2 mol / L, although the leaching rates slightly increased to 91.56% and 92.84%, the acid consumption cost doubled. This shows that 1 mol / L nitric acid is the most economical choice. This process effectively solves the problem of competitive precipitation of calcium and phosphorus through stepwise leaching (nitric acid dissolves calcium, phosphorus, and potassium → oxalic acid precipitates calcium and releases phosphorus). At the same time, the purity of calcium oxalate reaches the industrial grade standard verified by XRD / SEM. Therefore, this by-product can offset part of the treatment cost and can greatly improve competitiveness.

[0076] At the same time, the above experimental data also revealed the following rules: the nitric acid concentration is positively correlated with the leaching rate but the marginal benefit decreases. Particle size control (< 0.074 mm) and stepwise reaction design significantly improve the reaction efficiency, taking into account both the resource recovery rate and the economic cost, verifying the necessity of process parameter optimization and the technical advantages of stepwise leaching.

[0077] In addition, after the chicken manure residue is treated by the above process, it is reduced by more than 90%. The nitrate (NO3 - ) decomposed by nitric acid can supplement the nitrogen source to form a nitrogen, phosphorus, and potassium compound fertilizer mother liquor, achieving the dual goals of waste resource utilization and pollution prevention and control.

[0078] Comparative Example 1

[0079] The difference between this Comparative Example 1 and Experimental Example 1 is that the particle size of chicken manure is two types, greater than 0.15 mm and 0.15 - 0.074 mm, the nitric acid concentration is selected as 1 mol / L, and other conditions and operations are the same as those in Experimental Example 1. The leaching results of phosphorus and potassium elements are shown in Table 3.

[0080] Table 3 Leaching rates of phosphorus and potassium elements in the leaching solution (%).

[0081] Number Particle size Phosphorus element Potassium element 1 >0.15mm 35.24 52.89 2 0.15 - 0.074mm 60.58 73.21

[0082] Comparative Example 1 reveals the core rule of particle size control by comparing the effects of different particle sizes on the leaching rates of phosphorus and potassium: the smaller the particle size, the higher the leaching rate. When the particle size > 0.15 mm, the leaching rates of phosphorus and potassium are only 35.24% and 52.89% respectively, while when the particle size is 0.15 - 0.074 mm, they increase to 60.58% and 73.21%, but are still significantly lower than 87.73% and 90.37% under the condition of particle size < 0.074 mm in Experimental Example 1.

[0083] This shows that finer particles (< 0.074 mm) significantly improve the contact efficiency between the acid solution and minerals by increasing the reaction area, breaking through the leaching bottleneck caused by the surface wrapping effect of large particles. Comparing with Experimental Example 1, it can be seen that under the same nitric acid concentration (1 mol / L), particle size optimization is the key parameter selection for improving the leaching rate, and larger particle sizes will lead to resource waste and a decrease in process efficiency. Therefore, in the actual process, it is necessary to preferentially control the particle size of the raw material to < 0.074 mm to achieve efficient and economic recovery of phosphorus and potassium.

[0084] Comparative Example 2

[0085] The difference between this Comparative Example 2 and Experimental Example 1 is that inorganic acid leaching agents are respectively selected as sulfuric acid and hydrochloric acid with a concentration of 1 mol / L, and other conditions and steps are the same as those in Experimental Example 1. The leaching results of phosphorus and potassium elements are shown in Table 4.

[0086] Table 4 Leaching rates of phosphorus and potassium elements in the leaching solution (%).

[0087] Acid type Phosphorus element Potassium element Hydrochloric acid 85.69 90.05 Sulfuric acid 92.37 93.14

[0088] Comparative Example 2 reveals the influence rule of acid types on the leaching rates of phosphorus and potassium by comparing the leaching effects of different inorganic acids (1 mol / L sulfuric acid, hydrochloric acid) and nitric acid: the leaching rate of sulfuric acid is the highest (phosphorus 92.37%, potassium 93.14%), followed by hydrochloric acid (phosphorus 85.69%, potassium 90.05%), while the leaching rates of phosphorus and potassium of 1 mol / L nitric acid in Experimental Example 1 are 87.73% and 90.37% respectively.

[0089] Although the leaching rate of sulfuric acid is slightly better, nitric acid has both dissolution efficiency and nitrogen source supplementation (the leaching solution contains NO3 - , which can be directly used as a nitrogen, phosphorus and potassium compound fertilizer), and at the same time avoids the interference of sulfate (SO4 2- ) on the recovery of calcium oxalate, which better meets the requirements of resource utilization. Therefore, nitric acid (1 mol / L) is a better choice in the actual process, which achieves the best balance among leaching efficiency, cost control and by-product value.

[0090] Comparative Example 3

[0091] The difference between Comparative Example 3 and Experimental Example 1 lies in that: the molar ratio of oxalic acid n_oxalic:n_Ca is 0.8, 1, 1.4, the nitric acid concentration is selected as 1 mol / L, and other conditions and steps are the same as those in Experimental Example 1. The leaching results of phosphorus and potassium elements are shown in Table 5.

[0092] Table 5 Leaching rates of phosphorus and potassium elements in the leaching solution (%).

[0093] n_herb:n_Ca Phosphorus element Potassium element 0.8 56.78 74.69 1 78.21 81.95 1.4 90.08 93.16

[0094] Comparative Example 3 reveals the law of the leaching rate increasing with the increase of the amount of oxalic acid by adjusting the molar ratio of oxalic acid to calcium (n_oxalic:n_Ca): when the molar ratio is increased from 0.8 to 1.4, the leaching rates of phosphorus and potassium increase significantly (phosphorus increases from 56.78% to 90.08%, potassium increases from 74.69% to 93.16%), indicating that a higher oxalic acid ratio can effectively release the phosphorus element bound by calcium.

[0095] However, Experimental Example 1 selects a molar ratio of 1.2 (phosphorus 87.73%, potassium 90.37%) as the optimal parameter. Although it is slightly lower than the leaching rates of 1.4 in Comparative Example 3 (90.08%, 93.16%), considering the reagent cost and the control of calcium oxalate purity (to avoid excessive oxalic acid residue or by-product impurities), the molar ratio of 1.2 achieves a balance between efficiency and economy.

[0096] Comparing with Experimental Example 1, it can be seen that the amount of oxalic acid needs to be precisely matched with the calcium content. Excessive amount (1.4) can increase the leaching rate but may increase the cost or the difficulty of subsequent treatment. The parameter of 1.2 can not only ensure the efficient recovery of phosphorus and potassium but also maintain the practicality and sustainability of the process.

[0097] Experimental Example 2

[0098] (1) Based on Figure 2 the shown technological steps, select the fermented chicken manure and dried chicken manure after crushing and screening (particle size less than 0.074 mm), weigh 1 portion with a mass of 5 g. The chemical composition of the chicken manure is shown in Table 6.

[0099] Table 6 Chemical composition of chicken manure (mass%)

[0100]

[0101] (2) Add the two kinds of chicken manure into two groups of 1 mol / L nitric acid solutions respectively for the first leaching, set the liquid-solid ratio to 20:1, react at room temperature, and control the reaction time to 30 min.

[0102] (3) The remaining steps are the same as those in Experimental Example 1. The leaching results of the two kinds of chicken manure are shown in Table 7.

[0103] Table 7 Leaching rates of phosphorus and potassium elements in the leaching solutions of the two kinds of chicken manure (%).

[0104]

[0105] Experimental Example 2 processed fermented chicken manure and dried chicken manure (particle size < 0.074 mm, nitric acid concentration 1 mol / L, liquid-solid ratio 20:1, n(oxalic acid):n(Ca) = 1.2), achieving phosphorus and potassium leaching rates of 60.15% / 65.26% (fermented chicken manure) and 51.61% / 60.97% (dried chicken manure), respectively.

[0106] Although the leaching rates were significantly lower than those of the incinerated ash in Experimental Example 1 (87.73% / 90.37%), the results indicated that the process was still applicable to unincinerated chicken manure. The differences mainly stemmed from the chemical composition and physical state of the raw materials: due to high-temperature treatment, the minerals in the incinerated ash (such as CaO content of 59.56%) were more readily soluble, and the contents of phosphorus and potassium oxides (P2O5 19.45%, K2O 8.97%) were higher; while the CaO (40.03%, 57.02%) and phosphorus and potassium contents in fermented and dried chicken manure were lower, and the residual organic matter might hinder the penetration of the acid solution, resulting in a decrease in leaching efficiency.

[0107] Experimental Example 2 verified the compatibility of the process with various types of chicken manure. In particular, medium-level phosphorus and potassium recovery could still be achieved when treating fermented and dried raw materials, but the leaching rates were approximately 30% - 40% lower than those of the incinerated ash. This difference highlighted the crucial impact of raw material pretreatment (such as incineration, high-temperature activation) on process efficiency: pyrometallurgical treatment significantly optimized the leaching effect by destroying the organic structure and enhancing the activity of minerals.

[0108] Nonetheless, Experimental Example 2 still had environmental protection value and provided a feasible solution for directly treating unincinerated chicken manure. Therefore, those skilled in the art could further improve the efficiency by adjusting the acid concentration, extending the reaction time, or optimizing the particle size control. Compared with Experimental Example 1, the incinerated ash had more advantages in resource utilization, while Experimental Example 2 expanded the application scenario of the process, taking into account flexibility and universality.

[0109] Experimental Example 3

[0110] (1) Based on Figure 2 the process steps shown, the difference between this Experimental Example 3 and Experimental Example 1 was that the liquid-solid ratios of the chicken manure raw material to nitric acid were set to (8, 9, 10, 15, 20, 30):1, the nitric acid concentration was 1 mol / L, and the molar ratio of oxalic acid to calcium was set to 1.2. The leaching results are shown in Table 8.

[0111] Table 8 Leaching rates of phosphorus and potassium elements in the leaching solution (%).

[0112]

[0113] Experimental Example 3 verified its significant impact on the leaching rates of phosphorus and potassium by adjusting the liquid-solid ratio (8:1 to 30:1): as the liquid-solid ratio increased (more liquid volume), the leaching efficiency continuously improved.

[0114] For example, when the liquid-solid ratio increased from 8:1 to 30:1, the phosphorus leaching rate increased from 32.85% to 90.37%, and the potassium leaching rate increased from 55.79% to 93.57%. This rule indicates that a higher liquid-solid ratio effectively promotes the dissolution of minerals by increasing the contact area between the acid solution and the raw materials, but also leads to a significant increase in reagent consumption.

[0115] The leaching rates at a liquid-solid ratio of 20:1 in Experimental Example 3 (phosphorus 87.73%, potassium 89.34%) were basically the same as those under the condition of 20:1 in Experimental Example 1 (phosphorus 87.73%, potassium 90.37%), verifying the stability of this parameter; although the leaching rates were higher at a liquid-solid ratio of 30:1 (phosphorus 90.37%, potassium 93.57%), the reagent cost increased by about 50%, and the economy decreased significantly.

[0116] Compared with Experimental Example 1, Experimental Example 3 revealed the optimization space of the liquid-solid ratio: a liquid-solid ratio of 20:1 is the balance point between efficiency and cost, and although a ratio of 30:1 further improves the leaching rate, the marginal benefit decreases and the economy is insufficient. Experimental Example 1 selected 20:1 as the optimal parameter, which not only ensured the leaching efficiency (close to the highest value) but also avoided the waste of excessive reagents, meeting the practical requirements of industrial production. In contrast, Experimental Example 3 clarified the key role of the liquid-solid ratio through gradient experiments and verified the scalability of the process parameters, providing a flexible selection basis for different application scenarios (such as high-purity recovery or cost-sensitive scenarios).

[0117] Through the systematic verification of experimental examples and comparative examples, the present invention comprehensively demonstrated its core advantages of high efficiency, economy, and environmental protection. Experimental Example 1 used a stepwise leaching process of nitric acid-oxalic acid to treat chicken manure incineration ash (particle size <0.074mm, liquid-solid ratio 20:1, molar ratio of oxalic acid to calcium 1.2), achieving phosphorus and potassium leaching rates of 87.73% and 90.37% respectively, and recovering high-purity calcium oxalate (verified by XRD / SEM), breaking through the bottleneck of calcium-phosphorus competitive precipitation in traditional processes.

[0118] Comparative Examples 1-3 revealed the rules of key parameters: particle size control (<0.074mm) can increase the leaching rate by more than 50%, nitric acid (1mol / L) has the advantages of both leaching efficiency and nitrogen source supplementation compared with sulfuric acid and hydrochloric acid, and an oxalic acid molar ratio of 1.2 is optimal between efficiency and cost. Experimental Example 2 verified the applicability of the process to unincinerated chicken manure (fermented / dried) (leaching rate 51-65%), and Experimental Example 3 confirmed that a liquid-solid ratio of 20:1 is the economic balance point (compared with 30:1, the cost increased by 50% while only the leaching rate increased by 3%).

[0119] It can be seen from this that those skilled in the art can know from the above examples that the solution of the present invention can achieve the full-chain resource recovery of phosphorus, potassium, and calcium through the collaborative optimization of parameters. The leaching efficiency is increased by 40-50% compared with the existing methods, while the acid consumption cost is reduced by more than 30%. In addition, the by-product calcium oxalate recovered in the process can be used for commercial purposes such as ceramics, coatings, or calcium supplements because its quality can reach the industrial grade standard. Therefore, it can offset the treatment cost, thus having the value of both agricultural fertilizer production and industrial raw material supply, providing an efficient and sustainable solution for the treatment of chicken manure pollution, and promoting the resource utilization of waste and the development of circular economy.

[0120] On the other hand, corresponding to the above example of the method for resource utilization of poultry manure based on multi-stage treatment, the present invention also provides a liquid fertilizer, which includes: the leaching solution obtained by the method described in any of the above examples.

[0121] On the other hand, corresponding to the method for resource utilization of poultry manure based on multi-stage treatment in the above example, as Figure 5 shown, the present invention also provides a method for making fertilizer, and its steps include:

[0122] Conduct composition regulation on the leaching solution obtained by the method described in any of the above, and after adjusting the pH value and concentrating it until the macronutrients required for the product reach the standard, obtain the finished fertilizer.

[0123] The specific key preparation steps are as follows:

[0124]

[0125] Among them, as Figure 5 shown, for those key steps related to the leaching solution process, they will not be elaborated here and can be referred to the foregoing examples. The examples of the composition regulation step include: according to the product requirements, one or more of urea, ammonium nitrate, and dipotassium hydrogen phosphate can be selected as the N / P / K supplementary elements and added to the leaching solution. And the examples of the pH value adjustment step include: selecting any one of ammonia water and potassium hydroxide as the regulator to adjust the pH value.

[0126] 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 after concentrating it to the macronutrients required for the product, obtain the finished liquid fertilizer.

[0127] On the other hand, corresponding to the above example of the method for resource utilization of poultry manure based on multi-stage treatment, the present invention also provides a soil conditioner, which includes: the dried residue separated from solid and liquid in the example of the above method for resource utilization of poultry manure based on multi-stage treatment described in any of the above, including: mineral residue, calcium oxalate precipitate.

[0128] In the above example, the residue separated from the solid and liquid can be dried at high temperature (such as drying at 105°C) to make an organic soil conditioner. It can be seen that the above example of the method for resource utilization of poultry manure based on multi-stage treatment can not only match the liquid fertilizer preparation process in terms of process, but also the residue can be converted into a soil conditioner, realizing the resource utilization of all components of chicken manure.

[0129] In summary, through the poultry manure resource utilization method based on multi-stage processing and its fertilizer making method, liquid fertilizer, and soil conditioner provided by the present invention, a step-by-step leaching scheme is cleverly designed to efficiently extract phosphorus (P) and potassium (K) elements in poultry manure through an inorganic acid-oxalic acid step-by-step leaching process, and convert them into fertilizers that can be directly used in agriculture. In addition, calcium oxalate (CaC2O4) can also be recovered in the process as an industrial raw material or calcium supplement.

[0130] This not only breaks through the limitations and disadvantages of traditional biological fermentation routes, but also greatly improves the extraction efficiency compared to traditional composting methods. The residue after the reaction can also be used as a soil conditioner, thus opening up a closed-loop chain of "harmless treatment-high-value extraction of elements-full component utilization" for organic solid waste, and overcoming industry problems such as incomplete degradation of antibiotics in traditional processes, low conversion rate of traditional liquid fertilizers, and serious secondary pollution. It provides a revolutionary solution for the resource utilization of livestock and poultry manure with high efficiency, low cost and low emissions.

[0131] The preferred experimental examples of the present invention disclosed above are only used to help illustrate the present invention. The preferred experimental examples do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the contents of this specification. This specification selects and specifically describes these experimental examples in order to better explain the principles and practical applications of the present invention, so that technicians in the relevant technical field can understand and use the present invention well. The present invention is only limited by the claims and their full scope and equivalents. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0132] In addition, all or part of the steps in the above experimental example method can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including a number of instructions to enable a single-chip microcomputer, a chip or a processor to execute all or part of the steps of the method described in each experimental example of this application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, RandomAccess Memory), disk or optical disk and other media that can store program codes.

[0133] In addition, any combination can be made among various different embodiments of the experimental examples of the present invention, as long as it does not violate the idea of the experimental examples of the present invention, and it should also be regarded as the content disclosed by the experimental examples of the present invention.

Claims

1. A method for resource utilization of poultry manure based on multi-stage treatment, the steps of which include: Step S1: Crushing and screening poultry manure into powdered manure; Step S2: Mixing and reacting an inorganic acid solution with the manure, followed by solid-liquid separation to extract a first-stage leachate and a phosphorus-containing filter residue; Step S3: Adding oxalic acid to the first-stage leachate for mixing and reaction, followed by solid-liquid separation to extract a second-stage leachate and calcium oxalate precipitate; Step S4: Adding the phosphorus-containing filter residue to the second-stage leachate for mixing and reaction, followed by solid-liquid separation to obtain a third-stage leachate enriched in phosphorus and potassium.

2. The method for resource utilization of poultry manure based on multi-stage treatment according to claim 1, wherein the solid-liquid ratio of the inorganic acid solution to the powdered manure is 9-20 mL:1 g.

3. The method for resource utilization of poultry manure based on multi-stage treatment according to claim 1, wherein the concentration of the inorganic acid solution is 0.5-2 mol / L.

4. The method for resource utilization of poultry manure based on multi-stage treatment according to claim 1, wherein in step S3, the addition amount of oxalic acid is based on the calcium content in the manure, and the molar ratio of oxalic acid to calcium is controlled to 0.8-1.

4.

5. The method for resource utilization of poultry manure based on multi-stage treatment according to claim 1, wherein the mixing reactions in steps S2, S3, and S4 are carried out at room temperature for 10-40 minutes.

6. The method for resource utilization of poultry manure based on multi-stage treatment according to claim 1, wherein the inorganic acid solution comprises: Any one of nitric acid, sulfuric acid, and hydrochloric acid.

7. The method for resource utilization of poultry manure based on multi-stage treatment according to claim 1, wherein the particle size of the powdered manure < 0.15 mm.

8. A liquid fertilizer, comprising: The third-stage leachate obtained by the method according to any one of claims 1 to 7.

9. A method for making fertilizer, the steps of which include: Conducting composition regulation on the third-stage leachate obtained by the method according to any one of claims 1 to 7, adjusting the pH value and then performing concentration treatment.

10. The method according to claim 9, wherein the composition regulation step includes: Selecting one or more of urea, ammonium nitrate, and dipotassium hydrogen phosphate as supplementary elements and adding them to the third-stage leachate.

11. The method according to claim 9, wherein the pH value adjustment step includes: Selecting any one of ammonia water and potassium hydroxide as a regulator and adjusting the pH value to above 3.

0.

12. A soil conditioner, comprising: The dried residue obtained by solid-liquid separation in the method according to any one of claims 1 to 7.

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