Method for preparing amino acid compound fertilizer by basic hydrolysis of excess sludge

Abstract

The invention relates to the technical field of sludge treatment and resource utilization, in particular to a method for preparing an amino acid compound fertilizer by basic hydrolysis of excess sludge. According to the invention, the waste residual sludge is taken as a raw material, a low-cost residual sludge hydrolysis process is developed, and protein in the residual sludge is efficiently converted into amino acid, so that the amino acid compound fertilizer capable of being applied to crops is prepared, reduction, harmlessness and recycling of the residual sludge are realized, and the high-quality amino acid compound fertilizer is produced; the problems that the existing residual sludge treatment cost is high, the environmental risk is large, the amino acid fertilizer production raw materials are expensive, the resource consumption is serious and the like can be solved, and remarkable economic and environmental benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of sludge treatment and resource utilization technology, and in particular to a method for preparing amino acid compound fertilizer from residual sludge obtained through alkaline hydrolysis. Background Technology

[0002] With the acceleration of urbanization, the volume of sewage treated has increased year by year, resulting in a sharp rise in the amount of residual sludge. Residual sludge has a complex composition, containing large amounts of organic matter, heavy metals, pathogens, etc. Improper treatment can cause serious environmental problems such as soil and groundwater pollution. Currently, the main methods for treating residual sludge include landfill, incineration, and composting. Landfilling requires a large area and easily produces leachate that pollutes groundwater; incineration is energy-intensive and produces toxic and harmful gases such as dioxins; traditional composting has a long processing cycle, requires a large area, and produces products with low fertilizer efficiency, making it difficult to meet the demands of modern agriculture for high-quality fertilizers. Meanwhile, the demand for amino acid compound fertilizers in agricultural production is growing. Amino acid compound fertilizers can provide crops with abundant amino acid nutrients, promoting crop growth and improving crop yield and quality. Existing amino acid compound fertilizer preparation methods mostly use grains and soybean meal as raw materials, resulting in high costs and consuming large amounts of grain resources. Therefore, finding a low-cost raw material and method for preparing amino acid compound fertilizers has become an urgent problem to be solved.

[0003] Waste sludge contains a large amount of protein, which can be hydrolyzed to produce amino acids, providing a potential raw material for the preparation of amino acid compound fertilizers. Existing sludge hydrolysis methods mainly include acid hydrolysis and enzymatic hydrolysis. While acid hydrolysis has high efficiency, it corrodes equipment, and the subsequent neutralization process produces a large amount of salt, affecting fertilizer quality. Enzymatic hydrolysis has mild reaction conditions, but enzyme preparations are expensive, and the hydrolysis cycle is long, making large-scale industrial production difficult. Therefore, developing an efficient, low-cost, and environmentally friendly waste sludge hydrolysis process for the preparation of amino acid compound fertilizers has significant practical implications and application value. Summary of the Invention

[0004] Therefore, based on the above background, this invention provides a method for preparing amino acid compound fertilizer from waste sludge through alkaline hydrolysis. This invention uses waste sludge as raw material and develops a low-cost waste sludge hydrolysis process that efficiently converts proteins in waste sludge into amino acids to prepare amino acid compound fertilizer that can be used for crops. This method achieves the reduction, harmlessness, and resource utilization of waste sludge and produces high-quality amino acid compound fertilizer. It not only solves the problems of high waste sludge disposal costs and significant environmental risks, as well as the high cost of raw materials for amino acid fertilizer production and serious resource consumption, but also has significant economic and environmental benefits.

[0005] The technical solution provided by this invention is as follows:

[0006] A method for preparing amino acid compound fertilizer from residual sludge obtained from alkaline hydrolysis includes the following steps:

[0007] S100 Residual Sludge Pretreatment

[0008] The remaining sludge is subjected to heavy metal removal treatment to obtain pretreated sludge;

[0009] S200 alkaline hydrolysis treatment

[0010] S201 involves reacting pretreated sludge with alkaline solution in an inert gas atmosphere, controlling the temperature at 80-120℃ and the reaction pressure at 0.1-0.3MPa, under stirring conditions for hydrolysis.

[0011] After the S202 reaction is complete, adjust the pH of the reaction solution to 6.5-7.5, filter, and collect the filtrate.

[0012] S300 amino acid compound fertilizer preparation

[0013] S301 adds a nutrient supplement to the filtrate, mixes it evenly, and obtains a liquid fertilizer.

[0014] Furthermore, the filtrate from step S301 is concentrated before the nutrient supplement is added; the liquid fertilizer is then granulated.

[0015] Furthermore, in step S100, before removing heavy metals from the remaining sludge, dewatering and crushing processes are performed sequentially, specifically:

[0016] First, dewater the remaining sludge and control its moisture content to 60%-70%; then crush it to a particle size of 1-3mm.

[0017] Furthermore, in step S100, heavy metal removal is performed on the remaining sludge, specifically:

[0018] After mixing the remaining sludge with the chelating agent solution, the chelation reaction was carried out under stirring conditions at a temperature of 25-35℃.

[0019] After the chelation reaction, the sludge is separated by centrifugation and the precipitate is collected, which is the pretreated sludge.

[0020] Furthermore, the chelating agent solution is selected as an aqueous solution of disodium ethylenediaminetetraacetate with a concentration of 0.05-0.1 mol / L, and the mass ratio of the remaining sludge to the chelating agent solution is 1:(3-5).

[0021] Further, the alkaline solution in step S201 is selected from a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution with a mass concentration of 10%-20%;

[0022] The mass ratio of the pretreated sludge to the alkaline solution is 1:(2-4).

[0023] Furthermore, the nutritional supplement in step S301 is composed of urea, potassium dihydrogen phosphate, and potassium sulfate in a mass ratio of 2:1:1.

[0024] Based on the same inventive concept, this invention also provides an amino acid compound fertilizer prepared by the method for preparing amino acid compound fertilizer from residual sludge by alkaline hydrolysis.

[0025] Based on the same inventive concept, the present invention also provides the application of the amino acid compound fertilizer as a foliar fertilizer, or a root fertigation fertilizer, or a soilless nutrient solution in crop cultivation.

[0026] Furthermore, the crop includes at least one of rice, wheat, corn, soybeans, peanuts, cucumbers, and chili peppers.

[0027] The beneficial effects achieved by this invention are as follows:

[0028] ① This invention uses residual sludge as raw material to prepare amino acid compound fertilizer, realizing the reduction, harmlessness and resource utilization of residual sludge, solving the problem of residual sludge treatment, reducing environmental pollution, and reducing the preparation cost of amino acid compound fertilizer, thus avoiding the consumption of food resources.

[0029] ② This invention uses an alkaline hydrolysis process to treat residual sludge. Compared with acid hydrolysis, it does not corrode equipment, has low equipment requirements, and produces high-quality fertilizer. Compared with enzymatic hydrolysis, it does not require expensive enzyme preparations, reducing production costs. Furthermore, the hydrolysis reaction cycle is short and efficient, making it suitable for large-scale industrial production.

[0030] ③ This invention removes heavy metals during the pretreatment stage of residual sludge, effectively reducing the heavy metal content in the final product and ensuring that the prepared amino acid compound fertilizer meets national fertilizer quality standards and is safe and reliable to use.

[0031] ④ In the preparation process of this invention, by adjusting the hydrolysis reaction conditions and optimizing the ratio of nutrient supplements, the prepared amino acid compound fertilizer has a high amino acid content and a balanced nitrogen, phosphorus and potassium nutrition, which can provide comprehensive nutrition for crops, promote crop growth, and improve crop yield and quality.

[0032] ⑤ The entire preparation process of this invention is simple, easy to operate, has mild reaction conditions, low energy consumption, and is easy to automate, resulting in good economic, environmental and social benefits. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The technical solution of the present invention:

[0035] A method for preparing amino acid compound fertilizer from residual sludge obtained through alkaline hydrolysis includes the following steps:

[0036] S100 Residual Sludge Pretreatment

[0037] S101 collects the excess sludge generated by the wastewater treatment plant. It first undergoes dewatering treatment using a plate and frame filter press to control the moisture content of the sludge after dewatering to 60%-70%.

[0038] S102 feeds the dewatered sludge into a crusher for crushing, crushing the sludge particles to a size of 1-3mm, and obtaining pretreated sludge.

[0039] S103 performs heavy metal removal treatment on pretreated sludge:

[0040] The pretreated sludge and chelating agent solution are mixed at a mass ratio of 1:3 to 1:5. The mixture is stirred and reacted for 20 to 30 minutes at a temperature of 25-35℃ and a stirring rate of 150-200 r / min. After the reaction, the mixture is centrifuged at a speed of 3000-4000 r / min for 10-15 minutes. The precipitate is collected, which is the heavy metal-free sludge. The chelating agent solution is a disodium ethylenediaminetetraacetate solution with a concentration of 0.05-0.1 mol / L.

[0041] S200 alkaline hydrolysis treatment

[0042] S201 involves adding heavy metal-removed sludge and an alkaline solution to a reaction vessel at a mass ratio of 1:2 to 1:4 and stirring until homogeneous. The alkaline solution is either sodium hydroxide or potassium hydroxide solution with a concentration of 10% to 20%.

[0043] S202 introduces nitrogen gas into the reactor to purge the air inside, then closes the gas inlet valve, heats the reactor to 80-120℃, controls the reaction pressure at 0.1-0.3MPa, and carries out the hydrolysis reaction for 2-4 hours at a stirring rate of 200-300r / min to obtain the hydrolysate.

[0044] During the S203 hydrolysis reaction, samples were taken every 30 minutes to detect the amino acid content in the hydrolysate. The hydrolysis reaction was stopped when the amino acid content no longer increased significantly.

[0045] After the temperature inside the reactor drops to 40-50℃, open the vent valve to release the pressure, then remove the hydrolysate. Adjust the pH of the hydrolysate to 6.5-7.5 using hydrochloric acid solution to obtain a neutralized solution; the mass concentration of the hydrochloric acid solution is 10%-15%.

[0046] S204 sends the neutralized liquid into a filter for filtration, with a filtration accuracy of 5-10μm, to remove impurities from the neutralized liquid and obtain a clear liquid.

[0047] S300 amino acid compound fertilizer preparation

[0048] One method involves adding a nutrient supplement to the concentrate and mixing it for 30-40 minutes at a temperature of 40-50℃ and a stirring rate of 150-200 r / min to obtain a liquid fertilizer. The nutrient supplement is a mixture of urea, potassium dihydrogen phosphate, and potassium sulfate in a mass ratio of 2:1:1.

[0049] Another method involves first concentrating the clarified S205 solution using a vacuum concentration device. The concentration temperature is controlled at 60-70℃, and the vacuum degree is -0.08 to -0.09 MPa. Concentration continues until the solid content of the clarified solution is 30%-40%, yielding a concentrated solution. Then, a nutrient supplement is added to the concentrated solution, and the mixture is stirred for 30-40 minutes at a temperature of 40-50℃ and a stirring rate of 150-200 r / min to obtain a compound fertilizer mixture. The amount of nutrient supplement added is 10%-20% of the concentrated solution's mass, and the nutrient supplement is a mixture of urea, potassium dihydrogen phosphate, and potassium sulfate in a mass ratio of 2:1:1. Finally, the compound fertilizer mixture is fed into a granulator for granulation. The granulation temperature is 60-70℃, and the particle size is controlled at 2-4 mm to obtain compound fertilizer granules.

[0050] The compound fertilizer granules are then fed into a dryer for drying. Hot air drying is used at a temperature of 80-90℃ for 1-2 hours. The moisture content of the compound fertilizer granules is controlled at 5%-8% to obtain the finished amino acid compound fertilizer product.

[0051] The following are specific application examples of the present invention.

[0052] The residual sludge collected in the following application example is from the same batch from the same wastewater treatment plant.

[0053] Application Example 1: Preparation of Amino Acid Compound Fertilizer

[0054] S100 Residual Sludge Pretreatment

[0055] S101 uses a plate and frame filter press to dewater the remaining sludge, controlling the moisture content of the sludge after dewatering to 65%;

[0056] S102 crushes the dewatered sludge to a particle size of 2mm to obtain pretreated sludge;

[0057] S103 pretreated sludge was mixed with 0.08 mol / L disodium ethylenediaminetetraacetate solution at a mass ratio of 1:4, and stirred at 30℃ and 180 r / min for 25 min. Then, it was centrifuged at 3500 r / min for 12 min, and the precipitate was collected to obtain heavy metal-free sludge.

[0058] S200 basic hydrolysis reaction

[0059] S201 adds heavy metal-removed sludge and 15wt% sodium hydroxide solution to a reactor at a mass ratio of 1:3 and stirs until homogeneous. After purging with nitrogen, the temperature is raised to 100℃, the pressure is controlled at 0.2MPa, and the hydrolysis reaction is carried out at 250r / min for 3 hours with stirring. Samples are taken every 30 minutes during the process. The reaction is stopped when the amino acid content is stable, and the hydrolysate is obtained.

[0060] S202 was cooled to 45℃, the pressure was released, the hydrolysate was removed, and the pH was adjusted to 7.0 with 12wt% hydrochloric acid solution to obtain a neutralized solution.

[0061] The S203 neutralized liquid was filtered through a filter with an accuracy of 8μm to remove impurities and obtain a clear liquid.

[0062] S300. Preparation of Amino Acid Compound Fertilizer

[0063] The clarified liquid was concentrated under vacuum at 65℃ and -0.085MPa to a solid content of 35%, resulting in a concentrated liquid.

[0064] Add 15% of the nutrient supplement (urea: potassium dihydrogen phosphate: potassium sulfate (weight ratio) = 2:1:1) to the concentrate, and stir and mix for 35 minutes at 45℃ and 180r / min to obtain the compound fertilizer mixture.

[0065] The compound fertilizer mixture was granulated at 65℃, and the particle size was controlled to 3mm to obtain compound fertilizer granules.

[0066] The compound fertilizer granules were dried with hot air at 85℃ for 1.5 hours, and the moisture content was controlled at 6% to obtain the finished amino acid compound fertilizer.

[0067] The test results for the finished product showed that the amino acid content was 18.5%, the total nitrogen, phosphorus and potassium content was 25.3%, and the moisture content was 6%.

[0068] Application Example 2: Preparation of Amino Acid Compound Fertilizer

[0069] S100 Residual Sludge Pretreatment

[0070] S101 collects residual sludge from wastewater treatment plants and dewaters it to a moisture content of 60% using plate and frame filter press.

[0071] S102 is crushed to a particle size of 1mm to obtain pretreated sludge;

[0072] S103 mixes pretreated sludge with 0.05 mol / L disodium ethylenediaminetetraacetate solution at a mass ratio of 1:3, stirs at 25°C and 150 r / min for 20 min, centrifuges at 3000 r / min for 10 min, and collects the precipitate to obtain heavy metal-free sludge.

[0073] S200 basic hydrolysis reaction

[0074] S201 Add the heavy metal-removed sludge and 10wt% potassium hydroxide solution to the reactor at a mass ratio of 1:2 and stir until homogeneous;

[0075] After purging air with nitrogen in S202, the temperature is raised to 80℃, the pressure is 0.1MPa, and the mixture is stirred at 200r / min for 2 hours for hydrolysis. After sampling and testing, the amino acid content is stabilized and the reaction is stopped to obtain the hydrolysate.

[0076] S203 was cooled to 40℃, and after depressurization, the hydrolysate was removed. The pH was adjusted to 6.5 with 10% hydrochloric acid to obtain a neutralized solution.

[0077] S204 was filtered using a filter with a precision of 2.5μm to obtain a clear liquid;

[0078] S300 amino acid compound fertilizer preparation

[0079] The clarified liquid was concentrated under vacuum at 60℃ and -0.08MPa to a solid content of 30% to obtain a concentrated liquid.

[0080] Add 10 wt% of its own weight of nutrient supplement (urea: potassium dihydrogen phosphate: potassium sulfate (mass ratio) = 2:1:1) to the concentrate, stir and mix at 40℃ and 150 r / min for 30 min to obtain compound fertilizer mixture;

[0081] The compound fertilizer mixture was granulated at 60℃ to a particle size of 2mm to obtain compound fertilizer granules.

[0082] Dry with hot air at 80℃ for 1 hour, with a moisture content of 5%, to obtain the finished amino acid compound fertilizer.

[0083] Test results: Amino acid content 16.2%, total nitrogen, phosphorus and potassium content 23.1%, moisture content 5%.

[0084] Application Example 3: Preparation of Amino Acid Compound Fertilizer

[0085] S100 Residual Sludge Pretreatment

[0086] S101 dewaters the remaining sludge using plate and frame filter press to a moisture content of 70%;

[0087] S102 crushes the remaining sludge to a particle size of 3mm to obtain pretreated sludge;

[0088] S102 was mixed with the remaining sludge at a mass ratio of 1:5 with a 0.1 mol / L disodium ethylenediaminetetraacetate solution, stirred at 35°C and 200 r / min for 30 min, and centrifuged at 4000 r / min for 15 min. The precipitate was collected to obtain the heavy metal-free sludge.

[0089] S200 basic hydrolysis reaction

[0090] S201 Add the heavy metal-removed sludge and 20wt% sodium hydroxide solution to the reactor at a mass ratio of 1:4 and stir until homogeneous;

[0091] After purging air with nitrogen in S202, the temperature is raised to 120℃, the pressure is 0.3MPa, and the mixture is stirred at 300r / min for 4 hours to hydrolyze the amino acid content. The reaction is stopped after the amino acid content stabilizes, and the hydrolysate is obtained.

[0092] S203 was cooled to 50℃, and after depressurization, the hydrolysate was removed. The pH was adjusted to 7.5 with 15% hydrochloric acid to obtain a neutralized solution.

[0093] S204 filters the neutralized liquid using a 10μm precision filter to obtain a clear liquid;

[0094] S300 amino acid compound fertilizer preparation

[0095] The clarified liquid was concentrated under vacuum at 70℃ and -0.09MPa to a solid content of 40%, yielding a concentrated liquid.

[0096] Add 20% of its own weight of nutrient supplement (urea: potassium dihydrogen phosphate: potassium sulfate (mass ratio) = 2:1:1) to the concentrate, stir and mix at 50℃ and 200r / min for 40min to obtain compound fertilizer mixture;

[0097] The compound fertilizer mixture was granulated at 70℃ to obtain compound fertilizer granules with a particle size of 4mm.

[0098] The compound fertilizer granules were dried with hot air at 90℃ for 2 hours, and the moisture content was 8% to obtain the amino acid compound fertilizer product.

[0099] Test results: Amino acid content 20.3%, total nitrogen, phosphorus and potassium content 27.5%, moisture content 8%.

[0100] The above refers to the testing of finished amino acid compound fertilizer products, in which the amino acid content is determined according to the method for determining amino acid content in "NY 1429-2010 Amino Acid Water-Soluble Fertilizers".

[0101] The determination of total nitrogen, phosphorus and potassium content was carried out in accordance with GB / T 17767.1 / 2 / 3-2021 Determination of organic-inorganic compound fertilizers;

[0102] The heavy metal content of Application Examples 1 to 3 was tested and found to be in compliance with the limits of toxic and harmful substances in fertilizers as specified in GB 38400-2019.

[0103] The electrical conductivity of the solid granular amino acid compound fertilizers used in Examples 1 to 3 was tested. The specific testing procedures are as follows:

[0104] After weighing 5.00g of fertilizer sample, it was dissolved in deionized water and the volume was adjusted to 250mL. The reading was measured using a Hach conductivity meter. The conductivity (25℃) of Application Example 1 to Comparative Example 3 were 2.7mS / cm, 1.9mS / cm and 3.4mS / cm, respectively.

[0105] When applying the amino acid compound fertilizer of this invention, it needs to be diluted with water at least 100 times. Therefore, when applying it, its electrical conductivity is relatively low, the soluble salt content is reasonably controlled, and when applied at the recommended dilution concentration, it has little impact on the osmotic pressure of the soil solution, is less likely to cause root or seedling burn, and has high safety in use.

[0106] (1) Example 1 is used as a fertigation fertilizer for chili pepper cultivation.

[0107] The specific experiments are shown below.

[0108] Take nine 2×4.5 cm planting pots, fill them with field soil to a depth of 1 m,

[0109] Plant 30 seedlings of Sujiao No. 5 pepper in a pot (plant when they have 5-6 true leaves, with a plant spacing of 35cm and a row spacing of 60cm).

[0110] Before planting, apply equal amounts of well-rotted organic fertilizer (3 kg / pot) and phosphate fertilizer (superphosphate, 0.5 kg / pot) as base fertilizer to all planting pots.

[0111] The planting pots containing chili seedlings were randomly divided into three groups: Example 1 group, Control 1 group, and Blank Control Group, with three pots in each group.

[0112] Example 1 group applied the amino acid compound fertilizer of Example 1 group through irrigation.

[0113] Compared with control group 1, the nutritional supplement was composed of urea, potassium dihydrogen phosphate and potassium sulfate in a mass ratio of 2:1:1.

[0114] The blank control group was treated with water.

[0115] Specifically, the timing and dosage for each group of applications:

[0116] First application (early flowering stage): After the first pepper flower blooms.

[0117] Second application (peak fruiting period): during the early stage of pepper fruit enlargement.

[0118] Third application (mid-harvest): during the early stage of fruit enlargement in four-mother peppers.

[0119] The application procedure is as follows: add amino acid compound fertilizer to clean water to prepare an application solution with a urea content of 0.65wt%, and then apply the fertilizer to the group in Example 1. Apply 100L of the application solution to each application basin each time.

[0120] Control group 1 prepared a fertigation solution with a urea content of 0.65 wt% by adding the nutrient supplement to water, and applied the solution in the same way as in Example 1.

[0121] The control group, corresponding to Example 1, was irrigated with 100L of clean water at different application times.

[0122] Other water management and pest and disease control are carried out in accordance with conventional management methods.

[0123] After the peppers mature, they are harvested. The growth performance of each group is statistically analyzed, including the number and weight of peppers in each pot. The average value is then taken to calculate the average yield of peppers per pot.

[0124] Then, 15 chili peppers were randomly selected, and their quality indicators, including vitamin C content (2,6-dichlorophenolindophenol titration method) and soluble sugar content (anthrone-sulfuric acid colorimetric method), were tested. The average value was calculated, and the final results are shown in Table 1.

[0125] Table 1: Growth performance and quality indicators of chili peppers

[0126]

[0127] The amino acid compound fertilizer used in Example 1 was a mixture of sludge hydrolysate and nutrient supplements (nitrogen, phosphorus, and potassium). The amino acids can be directly absorbed by crops, promoting photosynthesis, nutrient transport, and fruit development; therefore, the number of chili peppers was significantly higher than in the control group. Small molecule amino acids enhance the synthesis and metabolism of sugars and vitamin C in crops; therefore, the content of soluble sugars and vitamin C was also significantly higher than in the control group.

[0128] The control group received only nutrient supplements (urea + potassium dihydrogen phosphate + potassium sulfate), lacking active amino acid components. Although the supply of nitrogen, phosphorus, and potassium was sufficient, the crop's nutrient utilization efficiency was low. While both yield and quality were higher than the control group, the improvement was limited.

[0129] (2) Example 1 is used as fertilizer in wheat cultivation.

[0130] The specific experiments are shown below.

[0131] Nine 2×4.5 cm planting pots were filled with field soil to a depth of 45 cm. The nine planting pots were randomly divided into an example group, a control group, and a blank control group. Before wheat sowing, each pot in the example group was given well-rotted organic fertilizer (3 kg / pot) and amino acid compound fertilizer (2.5 kg / pot) as base fertilizer.

[0132] Before wheat sowing, the control group was given 3 kg of well-rotted organic fertilizer and a nutrient supplement (0.3 kg / pot) per pot. The nutrient supplement consisted of urea, potassium dihydrogen phosphate and potassium sulfate in a mass ratio of 2:1:1.

[0133] The blank control group was given 3 kg of well-rotted organic fertilizer per pot before wheat sowing.

[0134] Select Zhengmai 136 seeds, sow 30 sterilized seeds in each pot, and thin out the seedlings after emergence, leaving 10 seedlings with uniform growth.

[0135] Then apply fertigation during the jointing stage;

[0136] In the example group, the amino acid compound fertilizer of Example 1 was applied. Specifically, the amino acid compound fertilizer was added to water to prepare a fertigation solution with a urea content of 0.5 wt%. Then, the Example 1 group was fertigated, with 100 L of fertigation solution applied to each fertigation basin each time.

[0137] The control group was given a nutritional supplement (the nutritional supplement was composed of urea, potassium dihydrogen phosphate and potassium sulfate in a mass ratio of 2:1:1). Specifically, the nutritional supplement was added to water to prepare a fertigation solution with a urea content of 0.65wt%, and 100L of the fertigation solution was applied to each fertigation basin each time.

[0138] The blank control group was treated with 100L of clean water.

[0139] Other water management and pest and disease control are carried out in accordance with conventional management methods.

[0140] After the wheat harvest, the number of effective spikes, the number of grains per spike (average), and the yield of each wheat harvested were counted. The results are shown in Table 2.

[0141] Table 2: Wheat Growth Performance

[0142]

[0143] As shown in Table 2, the effective number of spikes, number of grains per spike, and yield of the example group were significantly higher than those of the control group and the blank control group. This indicates that the amino acid compound fertilizer of the present invention is beneficial to promoting wheat tillering and spike formation, as well as promoting floret differentiation and grain development. This may be related to the fact that amino acids enhance nutrient absorption and photosynthesis, and improve nutrient utilization efficiency to promote growth.

[0144] This invention utilizes an alkaline hydrolysis process to efficiently extract amino acids from sludge, combined with heavy metal removal technology to ensure product safety. The data above indicates that amino acid compound fertilizer can significantly improve crop yield and quality.

[0145] The present invention utilizes the recycling of wastewater from alkaline hydrolysis to prepare amino acid compound fertilizer. Compared with acid hydrolysis and enzymatic hydrolysis, this method not only avoids equipment corrosion and high costs, making it suitable for industrial production, but also achieves synergistic effects of nitrogen, phosphorus, potassium and amino acids through optimized formulation of nutrient supplements.

[0146] The present invention and its embodiments have been described above. This description is not restrictive, and the embodiments shown are only one of the embodiments of the present invention. The actual structure is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing amino acid compound fertilizer from residual sludge through alkaline hydrolysis, characterized in that, It includes the following steps: S100 Residual Sludge Pretreatment The remaining sludge is subjected to heavy metal removal treatment to obtain pretreated sludge; S200 alkaline hydrolysis treatment S201 involves reacting pretreated sludge with alkaline solution in an inert gas atmosphere, controlling the temperature at 80-120℃ and the reaction pressure at 0.1-0.3MPa, under stirring conditions for hydrolysis. After the S202 reaction is complete, adjust the pH of the reaction solution to 6.5-7.5, filter, and collect the filtrate. S300 amino acid compound fertilizer preparation S301 adds a nutrient supplement to the filtrate, mixes it evenly, and obtains a liquid fertilizer.

2. The method for preparing amino acid compound fertilizer from residual sludge by alkaline hydrolysis according to claim 1, characterized in that, Before adding the nutrient supplement, the filtrate from step S301 is concentrated; the liquid fertilizer is then granulated.

3. The method for preparing amino acid compound fertilizer from residual sludge by alkaline hydrolysis according to claim 1, characterized in that, In step S100, before removing heavy metals from the remaining sludge, dewatering and crushing processes are performed sequentially. Specifically: First, dewater the remaining sludge and control its moisture content to 60%-70%; then crush it to a particle size of 1-3mm.

4. The method for preparing amino acid compound fertilizer from residual sludge by alkaline hydrolysis according to claim 1, characterized in that, Step S100 involves removing heavy metals from the remaining sludge, specifically: After mixing the remaining sludge with the chelating agent solution, the chelation reaction was carried out under stirring conditions at a temperature of 25-35℃. After the chelation reaction, the sludge is separated by centrifugation and the precipitate is collected, which is the pretreated sludge.

5. The method for preparing amino acid compound fertilizer from residual sludge by alkaline hydrolysis according to claim 4, characterized in that, The chelating agent solution is selected as an aqueous solution of disodium ethylenediaminetetraacetate with a concentration of 0.05-0.1 mol / L, and the mass ratio of the residual sludge to the chelating agent solution is 1:(3-5).

6. The method for preparing amino acid compound fertilizer from residual sludge by alkaline hydrolysis according to claim 1, characterized in that, The alkaline solution in step S201 is selected from a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution with a mass concentration of 10%-20%. The mass ratio of the pretreated sludge to the alkaline solution is 1:(2-4).

7. The method for preparing amino acid compound fertilizer from residual sludge by alkaline hydrolysis according to claim 1, characterized in that, The nutritional supplement in step S301 is composed of urea, potassium dihydrogen phosphate and potassium sulfate in a mass ratio of 2:1:

1.

8. The amino acid compound fertilizer prepared by the method for preparing amino acid compound fertilizer from residual sludge by alkaline hydrolysis according to any one of claims 1 to 7.

9. The application of the amino acid compound fertilizer according to claim 8 as a foliar fertilizer, or a root fertigation fertilizer, or a soilless nutrient solution in crop cultivation.

10. The application according to claim 9, characterized in that, The crops include at least one of rice, wheat, corn, soybeans, peanuts, cucumbers, and peppers.

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