Method for synergistically preparing carbon-based soil conditioner from coal gangue and straw

Abstract

The invention discloses a method for synergistically preparing a carbon-based soil conditioner from coal gangue and straw, and relates to a method for preparing the carbon-based soil conditioner. The invention aims to solve the technical problem that a large amount of coal gangue and agricultural straws are accumulated as wastes in the prior art to cause harm to the environment. The preparation method comprises the following steps: firstly, carrying out ultramicro activation pretreatment on coal gangue through mechanical grinding; then, adopting a double-atmosphere segmented pyrolysis process: generating a plant ash silicon fertilizer rich in KCl and K2CO3 in an air atmosphere; preparing a biochar material with a hierarchical porous structure under the protection of nitrogen; accurate compounding of the activated silicon fertilizer and the porous biochar is achieved through solid-phase mixing, finally, the activated silicon fertilizer and the porous biochar cooperate with the vinegar residue organic material to form the organic-inorganic composite carbon-based soil conditioner, the soil conditioner has the weakly acidic pH regulation and control function, the mineral nutrition slow release characteristic and the multi-scale pore structure characteristic, formation of saline-alkali soil aggregates is effectively promoted, the soil structure is improved, and the soil quality is improved. The volume weight of soil is reduced, and the effectiveness of phosphorus and the bioavailability of silicon are remarkably improved.

Description

Technical Field

[0001] The present invention relates to a method for preparing a carbon-based soil conditioner. Background Art

[0002] Gangue, a solid waste derived from the coal industry, is traditionally disposed of by stockpiling. However, this occupies land and can cause spontaneous combustion, dust, and leachate contamination of soil and groundwater. Gangue is rich in silicate minerals (SiO2 content 40%-60%) and trace nutrients. In recent years, it has been explored as a new silicon fertilizer for soil improvement and plant nutrition enhancement. Gangue is primarily composed of silicon-containing minerals such as quartz and kaolinite, with the silicon present in crystalline form. High-temperature activation can convert the silicon in gangue into partially soluble components, increasing its effectiveness as a silicon fertilizer.

[0003] Agricultural straw is an agricultural waste product primarily composed of cellulose, hemicellulose, lignin, and small amounts of inorganic components such as KCl, K2CO3, K2SO4, CaCO3, and CaPO4. Producing biochar from agricultural straw as a soil conditioner is an emerging method for utilizing agricultural straw. Biochar can increase soil porosity, reduce soil bulk density, improve aggregate structure, provide a suitable breeding ground for microorganisms, and increase the availability of essential organic and inorganic nutrients in the soil. Summary of the Invention

[0004] The present invention aims to solve the technical problem that coal gangue and agricultural straw are accumulated in large quantities as wastes, which harms the environment, and provides a method for preparing a carbon-based soil conditioner by synergistically using coal gangue and straw.

[0005] The method for preparing a carbon-based soil conditioner by synergistically using coal gangue and straw of the present invention is carried out according to the following steps: 1. Prepare raw materials: grind the gangue mechanically and activate it to obtain gangue powder with a mesh size of 100-200 mesh; Dehydrate and grind the agricultural straw to obtain straw powder with a mesh size of 60-200 mesh; 2. The gangue powder and straw powder prepared in step 1 are uniformly mixed, and then microwave pyrolysis is carried out in an air atmosphere at a pyrolysis temperature of 350°C to 750°C for 0.5h to 2h, and the mixture is naturally cooled to room temperature to obtain silicon-potassium fertilizer; the mass ratio of the gangue powder to the straw powder is 1:(0.25-10); The gangue powder and straw powder prepared in step 1 are uniformly mixed, and then microwave pyrolysis is performed under a nitrogen atmosphere at a pyrolysis temperature of 350° C. to 750° C. for 0.5 h to 2 h, and the mixture is naturally cooled to room temperature to obtain biochar rich in silicon fertilizer; the mass ratio of the gangue powder to the straw powder is 1:(0.25-10); 3. Mix the silicon-potassium fertilizer prepared in step 2 with biochar, then add vinegar dregs or wine dregs to adjust the pH to 5.5-7, and the mass ratio of silicon-potassium fertilizer to biochar is 1:(5-20) to obtain a soil conditioner.

[0006] The microwave pyrolysis in step 2 is a volumetric heating method from the inside out. Microwave pyrolysis can quickly make the sample reach the specified temperature and make the temperature of the pyrolysis sample uniform.

[0007] The soil conditioner prepared by the present invention can be used in the fields of fertilizing poor-quality soils such as salinized and desertified soils and subsided soils in mining areas, increasing crop yields, and preventing and controlling pests and diseases.

[0008] The present invention innovatively proposes a staged pyrolysis-synergistic activation preparation process. First, the gangue is pretreated by mechanical grinding and ultrafine activation. The purpose of activation is to destroy the crystal structure of the gangue and promote the effective release of Si in the gangue. Then, a dual-atmosphere staged pyrolysis process is adopted: the silicon component of the gangue is activated in an air atmosphere, and alkaline substances such as K2CO3 and CaCO3 in the straw ash are used as auxiliary agents or activators to catalyze the conversion of the gangue crystal SiO2 into plant-available silicon, and simultaneously generate plant ash silicon fertilizer rich in KCl and K2CO3; under nitrogen protection, a biomass with a multi-level pore structure (microporous-mesoporous) is prepared. biochar materials; and then through solid-phase mixing, the precise compounding of activated silicon fertilizer and porous biochar is achieved, and finally the organic materials of vinegar dregs are coordinated to form an organic-inorganic composite carbon-based soil improver. The addition of vinegar dregs or wine dregs is to provide the organic nutrients required by plants. The prepared improver has a certain improvement effect on the soil aggregate structure and air permeability and water retention properties. The final prepared soil improver has the function of weakly acidic pH regulation, the slow-release characteristics of mineral nutrients and the characteristics of multi-scale pore structure, which can effectively promote the formation of saline-alkali soil aggregates, improve soil structure, reduce soil bulk density, and significantly improve the effectiveness of phosphorus and the bioavailability of silicon.

[0009] The soil conditioner prepared by the present invention can increase soil organic matter and inorganic nutrients while improving soil aggregate structure and air permeability and water retention. The soil conditioner prepared by the present invention can be used to fertilize poor-quality soils such as salinized and desertified soils and subsided soils in mining areas, increase crop yields, and control pests and diseases.

[0010] The present invention has the advantages of simple preparation process and ease of large-scale industrial production, as well as the comprehensive advantages of low raw material cost, environmental protection and efficient utilization of solid waste resources.

[0011] The present invention utilizes coal gangue and agricultural straw to prepare the improver, thereby improving the silicon dissolution rate, increasing the dissolved phosphorus and available phosphorus content in the soil, and increasing the utilization of available phosphorus nutrients in saline-alkali soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a data graph showing the effects of three soil amendments on the electrical conductivity (EC) of saline-alkali soil in Experiment 1; Figure 2 This is a data graph showing the effects of three soil amendments on the content of water-stable aggregates in saline-alkali soil in Experiment 1; Figure 3 The effects of three soil amendments on K in saline-alkali soil in experiment 1 + / Na + Ratio data graph; Figure 4 This is a data chart showing the effects of three soil amendments on corn seed germination rate in Experiment 1. DETAILED DESCRIPTION

[0013] Specific embodiment 1: This embodiment is a method for preparing a carbon-based soil conditioner by synergistically using coal gangue and straw, which is specifically carried out in the following steps: 1. Prepare raw materials: grind the gangue mechanically and activate it to obtain gangue powder with a mesh size of 100-200 mesh; Dehydrate and grind the agricultural straw to obtain straw powder with a mesh size of 60-200 mesh; 2. The gangue powder and straw powder prepared in step 1 are uniformly mixed, and then microwave pyrolysis is carried out in an air atmosphere at a pyrolysis temperature of 350°C to 750°C for 0.5h to 2h, and the mixture is naturally cooled to room temperature to obtain silicon-potassium fertilizer; the mass ratio of the gangue powder to the straw powder is 1:(0.25-10); The gangue powder and straw powder prepared in step 1 are uniformly mixed, and then microwave pyrolysis is performed under a nitrogen atmosphere at a pyrolysis temperature of 350° C. to 750° C. for 0.5 h to 2 h, and the mixture is naturally cooled to room temperature to obtain biochar rich in silicon fertilizer; the mass ratio of the gangue powder to the straw powder is 1:(0.25-10); 3. Mix the silicon-potassium fertilizer prepared in step 2 with biochar, then add vinegar dregs or wine dregs to adjust the pH to 5.5-7, and the mass ratio of silicon-potassium fertilizer to biochar is 1:(5-20) to obtain a soil conditioner.

[0014] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that in step 2, microwave pyrolysis is performed in an air atmosphere, the pyrolysis temperature is 550° C., and the pyrolysis time is 0.5 h. Other aspects are the same as specific embodiment 1.

[0015] Specific embodiment 3: This embodiment differs from specific embodiment 2 in that, in step 2, microwave pyrolysis is performed in an air atmosphere at a temperature of 550°C for 0.5 hours, followed by natural cooling to room temperature to produce silicon-potassium fertilizer; and the mass ratio of the coal gangue powder to the straw powder is 1:4. Other aspects are the same as specific embodiment 2.

[0016] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that in step 2, microwave pyrolysis is performed under a nitrogen atmosphere, the pyrolysis temperature is 550° C., and the pyrolysis time is 0.5 h. Other aspects are the same as specific embodiments 1 to 3.

[0017] Specific embodiment 5: This embodiment differs from specific embodiment 4 in that, in step 2, microwave pyrolysis is performed under a nitrogen atmosphere at a temperature of 550°C for 0.5 h, followed by natural cooling to room temperature to produce biochar rich in silicon fertilizer; and the mass ratio of the coal gangue powder to the straw powder is 1:4. Other aspects are the same as specific embodiment 4.

[0018] Specific embodiment 6: This embodiment differs from specific embodiment 5 in that the mass ratio of silicon-potassium fertilizer to biochar in step 3 is 1:8. Other aspects are the same as specific embodiment 5.

[0019] The present invention is verified by the following test: Experiment 1: This experiment is a method for preparing a carbon-based soil conditioner by synergistically using coal gangue and straw. The specific steps are as follows: 1. Prepare raw materials: select coal gangue from a coal mine in Changzhi, which contains 58.96% SiO2 by mass; grind the gangue into ultrafine powder in a steam mill to obtain a mesh size of 100-200 mesh; Rice straw was selected, with a SiO2 content of 48.43%, a CaO content of 13.37%, a K2O content of 9.17%, and a P content (calculated as P2O5) of 2%. The agricultural straw was dehydrated and ground to obtain straw powder with a mesh size of 60-200 mesh. 2. The gangue powder and straw powder prepared in step 1 are uniformly mixed, and then microwave pyrolysis is performed under air atmosphere. Three pyrolysis temperatures are selected for comparative tests, namely 350°C, 550°C and 750°C. The pyrolysis time is 0.5h, and the mixture is naturally cooled to room temperature to obtain silicon-potassium fertilizer; the mass ratio of the gangue powder to the straw powder is 1:4; The gangue powder and straw powder prepared in step 1 are uniformly mixed, and then microwave pyrolysis is performed under a nitrogen atmosphere. Three pyrolysis temperatures are selected for comparative tests, namely 350°C, 550°C, and 750°C. The pyrolysis time is 0.5 h, and the mixture is naturally cooled to room temperature to obtain biochar rich in silicon fertilizer. The mass ratio of the gangue powder to the straw powder is 1:4; The pyrolysis temperatures in the above two pyrolysis processes are the same; 3. Mix the silicon-potassium fertilizer prepared in step 2 with biochar, and then add vinegar dregs or wine dregs to adjust the pH to 6.5. The mass ratio of silicon-potassium fertilizer to biochar is 1:8 to obtain three soil conditioners, which are respectively recorded as 350C1R4, 550C1R4 and 750C1R4, corresponding to the pyrolysis temperatures of 350℃, 550℃ and 750℃ in step 2, respectively.

[0020] The three soil conditioners prepared in Experiment 1 were applied to saline-alkali soil in Taiyuan (pH 7.57, conductivity 2513 μS / cm) at a 1% addition rate. The control group (CK) received no soil conditioners. The addition of the soil conditioners significantly increased the available silicon content in the saline-alkali soil, with the addition of 550C1R4 and 750C1R4 reaching 257% and 266% of that in the CK, respectively.

[0021] Figure 1 Figure 3 shows the effects of three soil amendments on the electrical conductivity (EC) of saline-alkali soil. It can be seen that the addition of 550C1R4 and 750C1R4 soil amendments has a significant effect on reducing soil salt content compared with the control group (CK).

[0022] Figure 2 The figure shows the effects of three soil amendments on the content of water-stable aggregates in saline-alkali soil. It can be seen that the addition of three soil amendments has a significant effect on increasing the content of soil aggregates > 0.25 mm compared with the control group (CK).

[0023] Figure 3 Effects of three soil amendments on K in saline-alkali soil + / Na + It can be seen that the addition of three soil amendments has a greater impact on soil K than the control group (CK). + / Na + There is a significant improvement effect than the previous one.

[0024] Figure 4 The figure shows the effects of three soil amendments on the germination rate of corn seeds. It can be seen that the addition of three soil amendments has a significant improvement effect on the germination rate of corn seeds compared with the control group (CK).

Claims

1. A method for preparing a carbon-based soil conditioner by synergistically using coal gangue and straw, characterized in that The method for preparing a carbon-based soil conditioner by synergistically using coal gangue and straw is carried out in the following steps:

1. Prepare raw materials: grind the gangue mechanically and activate it to obtain gangue powder with a mesh size of 100-200 mesh; Dehydrate and grind the agricultural straw to obtain straw powder with a mesh size of 60-200 mesh; 2. The gangue powder and straw powder prepared in step 1 are uniformly mixed, and then microwave pyrolysis is carried out in an air atmosphere at a pyrolysis temperature of 350°C to 750°C for 0.5h to 2h, and the mixture is naturally cooled to room temperature to obtain silicon-potassium fertilizer; the mass ratio of the gangue powder to the straw powder is 1:(0.25-10); The gangue powder and straw powder prepared in step 1 are uniformly mixed, and then microwave pyrolysis is performed under a nitrogen atmosphere at a pyrolysis temperature of 350° C. to 750° C. for 0.5 h to 2 h, and the mixture is naturally cooled to room temperature to obtain biochar rich in silicon fertilizer; the mass ratio of the gangue powder to the straw powder is 1:(0.25-10); 3. Mix the silicon-potassium fertilizer prepared in step 2 with biochar rich in silicon fertilizer, then add vinegar grains or wine grains to adjust the pH to 5.5-7, and the mass ratio of silicon-potassium fertilizer to biochar rich in silicon fertilizer is 1:(5-20) to obtain a soil conditioner.

2. The method for preparing a carbon-based soil conditioner by synergistically using coal gangue and straw according to claim 1, characterized in that In step 2, microwave pyrolysis is performed under air atmosphere, the pyrolysis temperature is 550° C., and the pyrolysis time is 0.5 h.

3. The method for preparing a carbon-based soil conditioner by synergistically using coal gangue and straw according to claim 1, characterized in that In step 2, microwave pyrolysis is carried out in an air atmosphere at a pyrolysis temperature of 550° C. for 0.5 h, and the temperature is naturally lowered to room temperature to obtain silicon-potassium fertilizer; the mass ratio of the coal gangue powder to the straw powder is 1:

4.

4. The method for preparing a carbon-based soil conditioner by synergistically using coal gangue and straw according to claim 1, characterized in that In step 2, microwave pyrolysis was performed under a nitrogen atmosphere, the pyrolysis temperature was 550° C., and the pyrolysis time was 0.5 h.

5. The method for preparing a carbon-based soil conditioner by synergistically using coal gangue and straw according to claim 1, characterized in that In step 2, microwave pyrolysis is carried out under a nitrogen atmosphere at a pyrolysis temperature of 550° C. for 0.5 h, and the temperature is naturally cooled to room temperature to obtain biochar rich in silicon fertilizer; the mass ratio of the coal gangue powder to the straw powder is 1:

4.

6. The method for preparing a carbon-based soil conditioner by synergistically using coal gangue and straw according to claim 1, characterized in that The mass ratio of silicon-potassium fertilizer to biochar described in step three is 1:8.

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