Method for preparing organic nutrient soil from sludge

Abstract

The invention discloses a method for preparing organic nutrient soil from sludge. The method comprises the following steps: S1, dewatering and drying, S2, innocent treatment, S3, carbon nitrogen ratio adjustment, S4, nutrient soil formula optimization, S5, screening and granulation, and S6, adding 7-18 parts of pentaerythritol, 5-12 parts of castor oil and 15-34 parts of APTES into a stirrer, and stirring and mixing for 30-45 min. Adding 13 to 27 parts of isocyanate monomer and 0.03 to 0.2 part of dibutyltin dilaurate (DBTDL), mechanically stirring for 50 to 65 minutes, and baking for 2.5 to 3.5 hours at the temperature of 75 to 125 DEG C, so as to obtain a coating; s7, the particles prepared in the step S4 and the coating obtained in the step S6 are put into a heater and stirred, and then the organic nutrient soil is prepared. According to the invention, pentaerythritol is used as a chain extender, so that more crosslinking sites are provided, the hydroxyl density of pentaerythritol is high, and pentaerythritol reacts with silica groups to form a more compact Si-O-C network structure.

Description

Technical Field

[0001] The invention relates to the field of sludge treatment, and in particular to a method for preparing organic nutrient soil from sludge. Background Art

[0002] In the field of materials science and environmental engineering, sludge treatment and resource utilization has always been an important research topic. Sludge, as a by-product of sewage treatment, contains a large amount of organic matter, inorganic matter and microorganisms. Its rational disposal is not only related to environmental protection, but also involves the effective recycling and reuse of resources. In recent years, converting sludge into organic nutrient soil has become a treatment method with broad prospects. This can not only reduce the pollution of sludge to the environment, but also provide high-quality soil conditioners or fertilizers for agricultural production.

[0003] However, traditional sludge-based organic nutrient soil preparation technology often faces many challenges, such as poor stability of organic matter in sludge, easy loss of nutrients, and poor physical and chemical properties, which limit its effectiveness in practical applications. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for preparing organic nutrient soil from sludge.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: The present invention provides a method for preparing organic nutrient soil from sewage sludge, comprising the following steps: S1: Dehydration and drying Mechanical dehydration is used to reduce the moisture content of sludge to 60%-75%, and then natural drying or thermal drying is used to further reduce the moisture content to only 30%-45%, which is convenient for subsequent fermentation; S2: Harmless treatment Kill pathogens and insect eggs through high-temperature composting or steam treatment at 60℃-80℃, and add passivators to adsorb or fix heavy metals (lead, cadmium, mercury, etc.). If heavy metals exceed the standard, pre-treat through chemical leaching or bioleaching technology; S3: Adjust the carbon-nitrogen ratio Add high-carbon auxiliary materials to municipal sludge to adjust the ratio to 30:1-35:1 to promote microbial activity. Mix the sludge and high-carbon auxiliary materials and pile them into the fermentation tank. Turn the pile regularly (once every 2 days) and ventilate and supply oxygen. S4: Optimization of nutrient soil formula Sludge is usually acidic, so add wood ash to adjust it to 6.5-7.5. It is necessary to add humic acid, bone meal, seaweed extract, etc. to improve fertility, and mix vermiculite, perlite or coconut bran to enhance air permeability; S5: Screening and granulation The undecomposed impurities are removed by a drum screening machine, and the particles are crushed and granulated to obtain 2-4 mm particles; S6: Add 7-18 parts of pentaerythritol, 5-12 parts of castor oil, and 15-34 parts of APTES into a stirrer, and stir and mix for 30-45 minutes; then add 13-27 parts of isocyanate monomer and 0.03-0.2 parts of dibutyltin dilaurate (DBTDL), stir mechanically for 50-65 minutes, and bake at 75-125°C for 2.5-3.5 hours to obtain a coating; S7: putting the particles prepared in S4 and the coating obtained in S6 into a heater and stirring them to prepare organic nutrient soil.

[0006] As a preferred technical solution of the present invention, the rotation speed of the mechanical dehydration in S1 is 2500-3500 r / min.

[0007] As a preferred technical solution of the present invention, the passivating agent in S2 is any one of phosphate, biochar and zeolite.

[0008] As a preferred technical solution of the present invention, the formula of the chemical elution in the chemical elution in S2 is EDTA (0.1 mol / L) or citric acid (5%) solution, and it needs to be rinsed with clean water to neutral pH after elution. The biological leaching bacteria in the biological leaching technology in S2 is Thiobacillus ferrooxidans, which can transfer heavy metals from the solid phase to the liquid phase, and the treatment cycle is 12-18 days.

[0009] As a preferred technical solution of the present invention, the high-carbon auxiliary material in S3 is any one or more of straw, sawdust, and rice husk.

[0010] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides more cross-linking sites by using pentaerythritol as a chain extender, and at the same time, its hydroxyl density is high, and it reacts with siloxy groups to form a denser Si-OC network structure. Pentaerythritol is used as a chain extender to react with siloxy groups to form a dense Si-OC network structure, which not only significantly improves the mechanical properties, thermal stability and hydrophobicity of the coating layer, but also optimizes the functionality and environmental friendliness of the material through high cross-linking density and biocompatibility. At the same time, APTES is added, and its molecule contains both amino and siloxy groups. The amino group can react with the carboxyl group in the polyester chain, and the siloxy group forms a three-dimensional siloxy network through hydrolysis and condensation, which improves thermal stability and hydrophobicity. The ricinoleic acid in castor oil provides long-chain fatty acids as a flexible segment for toughening; the unsaturated double bond can participate in cross-linking and enhance weather resistance; the isocyanate monomer reacts with the chain extender and the hydroxyl group in the vegetable oil to form a polyurethane main chain; the high reactivity ensures the cross-linking density, and dibutyltin dilaurate can accelerate the reaction of -NCO and -OH to reduce the activation energy. DETAILED DESCRIPTION

[0011] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0012] Embodiment 1 The present invention provides a method for preparing organic nutrient soil from sludge, comprising the following steps: S1: Dehydration and drying Mechanical dehydration is used to reduce the moisture content of sludge to 60%-75%, and then natural drying or thermal drying is used to further reduce the moisture content to only 30%-45%, which is convenient for subsequent fermentation; S2: Harmless treatment Kill pathogens and insect eggs through high-temperature composting or steam treatment at 60℃-80℃, and add passivators to adsorb or fix heavy metals (lead, cadmium, mercury, etc.). If heavy metals exceed the standard, pre-treat through chemical leaching or bioleaching technology; S3: Adjust the carbon-nitrogen ratio Add high-carbon auxiliary materials to municipal sludge to adjust the ratio to 30:1-35:1 to promote microbial activity. Mix the sludge and high-carbon auxiliary materials and pile them into the fermentation tank. Turn the pile regularly (once every 2 days) and ventilate and supply oxygen. S4: Optimization of nutrient soil formula Sludge is usually acidic, so add wood ash to adjust it to 6.5-7.5. It is necessary to add humic acid, bone meal, seaweed extract, etc. to improve fertility, and mix vermiculite, perlite or coconut bran to enhance air permeability; S5: Screening and granulation The undecomposed impurities are removed by a drum screening machine, and the particles are crushed and granulated to obtain 2-4 mm particles; S6: Add 7-18 parts of pentaerythritol, 5-12 parts of castor oil, and 15-34 parts of APTES into a stirrer, and stir and mix for 30-45 minutes; then add 13-27 parts of isocyanate monomer and 0.03-0.2 parts of dibutyltin dilaurate (DBTDL), stir mechanically for 50-65 minutes, and bake at 75-125°C for 2.5-3.5 hours to obtain a coating; S7: putting the particles prepared in S4 and the coating obtained in S6 into a heater and stirring them to prepare organic nutrient soil.

[0013] By using pentaerythritol as a chain extender, more cross-linking sites are provided. At the same time, its hydroxyl density is high, and it reacts with siloxy groups to form a denser Si-OC network structure. Using pentaerythritol as a chain extender, by reacting with siloxy groups to form a dense Si-OC network structure, not only the mechanical properties, thermal stability and hydrophobicity of the coating layer are significantly improved, but also the functionality and environmental friendliness of the material are optimized through high cross-linking density and biocompatibility. At the same time, APTES is added, which contains both amino and siloxy groups in its molecules. The amino group can react with the carboxyl group in the polyester chain, and the siloxy group forms a three-dimensional siloxy network through hydrolysis and condensation, which improves thermal stability and hydrophobicity. The ricinoleic acid in castor oil provides long-chain fatty acids as a flexible segment for toughening; the unsaturated double bonds can participate in cross-linking and enhance weather resistance. The isocyanate monomer reacts with the chain extender and the hydroxyl group in the vegetable oil to form a polyurethane main chain; the high reactivity ensures the cross-linking density, and dibutyltin dilaurate can accelerate the reaction between -NCO and -OH and reduce the activation energy.

[0014] As a preferred technical solution of the present invention, the rotation speed of the mechanical dehydration in S1 is 2500-3500r / min.

[0015] As a preferred technical solution of the present invention, the passivating agent in S2 is any one of phosphate, biochar and zeolite.

[0016] As a preferred technical solution of the present invention, the formula of the chemical elution in the chemical elution in S2 is EDTA (0.1 mol / L) or citric acid (5%) solution, and it needs to be rinsed with clean water to neutral pH after elution. The biological leaching bacteria in the biological leaching technology in S2 is Thiobacillus ferrooxidans, which can transfer heavy metals from the solid phase to the liquid phase, and the treatment cycle is 12-18 days.

[0017] As a preferred technical solution of the present invention, the high-carbon auxiliary material in S3 is any one or more of straw, sawdust, and rice husk.

[0018] The physical and chemical properties of the sludge particles obtained by S1-S5 are as follows: 1. Physical properties

[0019] 2. Chemical properties

[0020] The physical and chemical properties of the organic nutrient soil prepared by S6-S7 are as follows: 1. Physical properties

[0021] 2. Chemical properties

[0022] Compared with the original sludge, the organic nutrient soil obtained after S6-S7 treatment has improved bulk density, air permeability, compressive strength, organic matter content, total nutrients, carbon-nitrogen ratio, and germination index, and reduced heavy metal content.

[0023] The advantages of changing the parameters of organic nutrient soil are as follows: Improved packing density: 1. Improve wind erosion / water erosion resistance and reduce soil and water loss; 2. Improved stability; 3. Reduce pore collapse; Improved breathability: 1. Root respiration is enhanced, oxygen diffusion rate is increased by 2-3 times, and root development is promoted; 2. Microbial activity is optimized, and the proportion of aerobic bacteria is increased to 70%, which accelerates the decomposition of organic matter; 3. It helps to drain water and prevent waterlogging, avoiding waterlogging and root rot; Improved compressive strength: 1. Stronger engineering applicability; 2. Improved resistance to mechanical crushing; 3. Improve long-term stability and reduce erosion under rainfall; Increased organic matter content: 1. Promote the formation of soil aggregate structure, and the cementation of organic matter increases soil aggregates; 2. Improved water and fertilizer retention capacity; Total nutrients (N+P2O5+K2O) increase: 1. Reduce dependence on chemical fertilizers; 2. The coating layer controls the release of nutrients and provides slow-release fertilizer; 3. Increase crop yields; Carbon-nitrogen ratio (C / N) improvement: 1. Efficient decomposition by microorganisms; 2. Reduced nitrogen loss; 3. A more stable nitrogen supply to plants; Germination index (GI) increased; 1. Improved plant safety; 2. Seedlings grow faster; 3. The applicability of ecological restoration is enhanced; Reduced heavy metal content: 1. Food safety is guaranteed; 2. Meet environmental compliance; 3. Reduce environmental pollution and help protect the ecological chain.

[0024] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing organic nutrient soil from sewage sludge, characterized in that: The following steps are involved: S1: Dehydration and drying Mechanical dehydration is used to reduce the moisture content of sludge to 60%-75%, and then natural drying or thermal drying is used to further reduce the moisture content to only 30%-45%, which is convenient for subsequent fermentation; S2: Harmless treatment Kill pathogens and insect eggs through high-temperature composting or steam treatment at 60℃-80℃, and add passivators to adsorb or fix heavy metals (lead, cadmium, mercury, etc.). If heavy metals exceed the standard, pre-treat through chemical leaching or bioleaching technology; S3: Adjust the carbon-nitrogen ratio Add high-carbon auxiliary materials to municipal sludge to adjust the ratio to 30:1-35:1 to promote microbial activity. Mix the sludge and high-carbon auxiliary materials and pile them into the fermentation tank. Turn the pile regularly (once every 2 days) and ventilate and supply oxygen. S4: Optimization of nutrient soil formula Sludge is usually acidic, so add wood ash to adjust it to 6.5-7.

5. It is necessary to add humic acid, bone meal, seaweed extract, etc. to improve fertility, and mix vermiculite, perlite or coconut bran to enhance air permeability; S5: Screening and granulation The undecomposed impurities are removed by a drum screening machine, and the particles are crushed and granulated to obtain 2-4 mm particles; S6: Add 7-18 parts of pentaerythritol, 5-12 parts of castor oil, and 15-34 parts of APTES into a stirrer, and stir and mix for 30-45 minutes; then add 13-27 parts of isocyanate monomer and 0.03-0.2 parts of dibutyltin dilaurate (DBTDL), stir mechanically for 50-65 minutes, and bake at 75-125°C for 2.5-3.5 hours to obtain a coating; S7: putting the particles prepared in S4 and the coating obtained in S6 into a heater and stirring them to prepare organic nutrient soil.

2. The method for preparing organic nutrient soil from sewage sludge according to claim 1, characterized in that: The rotation speed of the mechanical dehydration in S1 is 2500-3500r / min.

3. The method for preparing organic nutrient soil from sewage sludge according to claim 1, characterized in that: The passivating agent in S2 is any one of phosphate, biochar and zeolite.

4. The method for preparing organic nutrient soil from sewage sludge according to claim 1, characterized in that: The formula of the chemical leaching liquid in the chemical leaching in S2 is EDTA (0.1 mol / L) or citric acid (5%) solution. After leaching, it needs to be rinsed with clean water to neutral pH. The biological leaching bacteria in the biological leaching technology in S2 is Thiobacillus ferrooxidans, which can transfer heavy metals from the solid phase to the liquid phase. The treatment cycle is 12-18 days.

5. The method for preparing organic nutrient soil from sewage sludge according to claim 1, characterized in that: The high-carbon auxiliary material in S3 is any one or more of straw, sawdust, and rice husk.

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