Method for preparing soil conditioner from fly ash and application of soil conditioner

Abstract

The invention discloses a method for preparing a soil conditioner from fly ash and application, and belongs to the field of soil improvement and solid waste recycling, the method comprises the steps of fly ash grading screening, microwave-mechanical synergistic activation, acid-base modification, formula compounding, secondary biological activation and forming post-treatment, and the soil conditioner is prepared through multi-element activation and compounding. The activity and pore structure of the fly ash are improved. According to the method, the raw material utilization rate is high, the energy consumption is reduced by over 30%, the cost is low, and the prepared conditioner can remarkably reduce the pH and the total salt content of the saline-alkali soil, increase the porosity, organic matter and nutrients of the soil and improve the microbial environment; and the special formula can be used for promoting the growth of crops and increasing the yield by 15-20%, so that the special fertilizer is easy to industrially popularize and has both environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of soil improvement technology, and in particular to a method for preparing soil conditioners using fly ash, belonging to the fields of soil improvement and solid waste resource utilization technology. Background Technology

[0002] Soil compaction, salinization, and decreased fertility have significantly impacted agricultural production and the ecological environment, severely restricting crop growth and sustainable agricultural development. Soil conditioners, as a key means of improving soil properties, have attracted considerable attention, making the development of effective soil conditioners crucial. Fly ash is a major solid waste emitted by coal-fired power plants, generated in enormous quantities with limited resource utilization efficiency in the past. Large-scale accumulation not only occupies land resources but may also cause environmental pollution. However, it is rich in trace elements such as silicon, calcium, magnesium, iron, and aluminum, which are essential for plants, possessing natural potential for the preparation of soil conditioners.

[0003] However, existing technologies for preparing soil conditioners using fly ash have significant shortcomings: natural fly ash particles are small, prone to agglomeration, have a small specific surface area, and low porosity, resulting in insufficient activity and poor improvement effects when applied directly; beneficial elements are not sufficiently activated, failing to provide plants with adequately absorbable active ingredients; the preparation process is energy-intensive and costly, making large-scale industrial application difficult; and the improvement effect on overall soil performance is limited, especially in improving the soil microbial environment and long-term water and fertilizer retention. Therefore, developing a method for preparing soil conditioners that can effectively improve fly ash performance, is simple in process, low in cost, and environmentally friendly has become an urgent problem to be solved. Summary of the Invention

[0004] This invention aims to provide a method for preparing soil conditioners using fly ash, addressing the problems of low fly ash activity, poor soil improvement effect, complex processes, and high costs in existing technologies. By modifying and activating fly ash to enhance its pore structure, specific surface area, and activity, and combining this with the synergistic effect of additives, a conditioner that significantly improves the physical, chemical, and biological properties of soil is prepared. Simultaneously, this method achieves the resource utilization of fly ash, reduces production costs, and combines environmental and economic benefits.

[0005] To solve the above problems, the technical solution of the present invention is: a method for preparing a soil conditioner using fly ash, characterized by comprising the following steps:

[0006] Fly ash grading and screening: Fly ash discharged from power plants is collected and graded using a three-layer vibrating screen with screen apertures of 0.3mm, 0.15mm, and 0.075mm. The fly ash is divided into four grades: coarse particles >0.3mm, medium particles 0.15-0.3mm, fine particles 0.075-0.15mm, and micro powder <0.075mm. The coarse particles, such as sand, can be used as building materials. The medium, fine, and micro powder particles are collected separately for later use.

[0007] Activation and modification treatment: Fine fly ash particles are fed into a microwave-assisted ball mill and treated for 10-60 minutes under microwave power of 300-500W, ball-to-material ratio of 8-10:1, and rotation speed of 20-300r / min. Through the synergistic effect of microwave thermal effect and mechanical force, the agglomeration structure of fly ash particles is broken, and its specific surface area and active sites are increased.

[0008] Acid-base modification treatment: The fine fly ash powder after microwave-mechanical synergistic activation treatment and the micro powder separated by grading and screening are thoroughly mixed and fed into a reaction vessel, and mixed with the modifier at a mass ratio of 1:10-1:100. The mixture is stirred evenly and reacted at room temperature or 60-80℃ for 0.5-2 hours. The modifier is one or more of acid, alkali, salt or surfactant.

[0009] Formula compounding: Mix the activated and modified fine and micro-powdered fly ash with medium-powdered fly ash in a ratio of 1:1 to 10:1, and then add 10%-20% of desulfurized gypsum, 5%-10% of humic acid or biomass carbon, and appropriate amounts of nitrogen fertilizer, phosphate fertilizer, potassium fertilizer, bentonite, zeolite and other auxiliary materials.

[0010] Secondary biological activation: Introduce a compound microbial agent into the above-treated fly ash, add an appropriate amount of water to make the material moisture content reach 30%-50%, and let it stand and cultivate at 15-30℃ for 3-10 days. The nutrients in the fly ash are further activated by the metabolic action of microorganisms. The compound microbial agent includes Bacillus mucilaginosus, phosphate-solubilizing bacteria and actinomycetes in a ratio of 2:2:1.

[0011] Molding and post-processing: Add an appropriate amount of binder to the mixed raw materials that have undergone the above treatment, and form particles with a particle size of 2-5mm by a disc granulator or extrusion granulator. Dry the particles at 60-80℃ until the moisture content is less than 20%. After screening to remove unqualified particles, the qualified products are quantitatively packaged by an automatic packaging machine to obtain the finished soil conditioner. In the granulation step, the binder is starch paste.

[0012] Preferably, the acid in the modifier is one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, with a mass fraction of 10%-20%; the alkali is one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide, with a concentration of 0.1-3 mol / L; the salt is one or two of ammonium chloride and calcium chloride, with a mass fraction of 5%-10%; and the surfactant is sodium lignosulfonate or potassium lignosulfonate, with a mass fraction of 0.01%-0.05%.

[0013] Preferably, in the fly ash modification treatment step, the reaction temperature is 60-80℃ and the reaction time is 0.5-2 hours.

[0014] Preferably, in the raw material mixing step, the nitrogen fertilizer is one or two of urea and ammonium sulfate, the phosphate fertilizer is one, two or three of potassium dihydrogen phosphate, superphosphate, and ammonium phosphate, the potassium fertilizer is one or two of potassium chloride and potassium sulfate, and the ammonium phosphate includes monoammonium phosphate and diammonium phosphate.

[0015] Preferably, in the drying and packaging step, the moisture content of the dried granules is 10%-20%.

[0016] The advantages of this invention compared to existing technologies are as follows: High raw material utilization rate: Through grading, screening, and targeted treatment, efficient utilization of different particle sizes of fly ash is achieved, improving raw material utilization and reducing waste generation; Significant activation effect: A multi-faceted activation method combining microwave-mechanical synergistic activation, composite acid-base modification, and secondary biological activation is adopted, allowing the active components in fly ash to be fully released, increasing its specific surface area by 2-3 times and its ion exchange capacity far exceeding that of traditional processes; The graded, activated, modified, and compounded fly ash has a richer porous structure that can reduce soil bulk density, increase porosity, and improve aeration and permeability. Combined with humic acid, biochar, and other auxiliary materials, it can improve soil cation exchange capacity, organic matter content, and water and fertilizer retention capacity, effectively alleviating soil compaction and salinization problems, especially significantly reducing the pH value and total salt content of saline-alkali soils; Strong targeted improvement effect: Formulas can be formulated and compounded according to the characteristics of soils with different salinity levels. Meanwhile, the micronutrients in fly ash, along with added nitrogen, phosphorus, and potassium fertilizers, provide comprehensive nutrition for crops. Microbial agents promote nutrient conversion and release, effectively increasing the content of available nitrogen, available phosphorus, and readily available potassium in the soil. This process reduces energy consumption and production costs; compared to traditional high-temperature calcination activation, energy consumption is reduced by more than 30%. The use of graded utilization and optimized formulas reduces the consumption of raw materials and fully utilizes beneficial components for soil and crop growth. The process is low-cost, simple, and requires only basic equipment and operating procedures, facilitating large-scale resource utilization of fly ash, reducing waste accumulation pollution, and promoting industrial application. Attached Figure Description

[0017] Figure 1This is a process flow diagram of the present invention. Detailed Implementation

[0018] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. Identical components are indicated by the same reference numerals.

[0019] It should be noted that the terms “front,” “back,” “left,” “right,” “up,” and “down” used in the following description refer to the directions shown in the attached diagram, while the terms “inside” and “outside” refer to the directions toward or away from the geometric center of a specific component, respectively.

[0020] To make the content of this invention easier to understand, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings.

[0021] like Figure 1 As shown, a method for preparing soil conditioner using fly ash includes the following steps: fly ash grading and screening, activation and modification treatment, acid-base modification treatment, formula compounding, secondary biological activation and molding, and post-treatment.

[0022] The grading and screening of fly ash begins with the collection and grading of raw materials. Fly ash emitted from power plants is collected and graded using a three-layer vibrating screen with screen apertures of 0.3mm, 0.15mm, and 0.075mm. This grading process separates the fly ash into four grades: coarse particles (>0.3mm), medium particles (0.15-0.3mm), fine particles (0.075-0.15mm), and micro-powder (<0.075mm). The coarse particles, mostly sand and other impurities, can be used as building materials. The medium, fine, and micro-powder particles are collected separately for subsequent processing. This grading process removes impurities and lays the foundation for targeted processing of different particle sizes.

[0023] Activation and modification treatment: Fine fly ash particles obtained by sieving are activated through microwave-mechanical synergistic activation. The particles are fed into a microwave-assisted ball mill, with the microwave power set to 300-500W, the ball-to-material ratio controlled at 8-10:1, and the ball mill speed adjusted to 20-300r / min. Under these conditions, the fine fly ash particles are treated for 10-60 minutes. With the synergistic effect of microwave thermal effect and mechanical force, the agglomeration structure of fly ash particles can be effectively broken, thereby increasing its specific surface area and active sites, solving the problem of insufficient activity of natural fly ash.

[0024] Acid-base modification treatment: The fine fly ash powder after microwave-mechanical synergistic activation treatment and the micro powder separated by grading and sieving are thoroughly mixed, and then the mixture is fed into a reaction vessel. The modifier is added at a mass ratio of 1:10 to 1:100 of the mixture and stirred evenly. The mixture is then reacted at 60-80℃ for 0.5-2 hours. The modifier can be one or more of the following: acid, alkali, salt or surfactant. If an acid is selected, one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid can be chosen, with a mass fraction of 10%-20%. If an alkali is selected, one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide can be chosen, with a concentration of 0.1-3 mol / L. If a salt is selected, one or two of ammonium chloride and calcium chloride can be chosen, with a mass fraction of 5%-10%. If a surfactant is selected, sodium lignosulfonate or potassium lignosulfonate can be used, with a mass fraction of 0.01%-0.05%. Through this step, the activity of beneficial elements in fly ash can be further enhanced, providing plants with absorbable active ingredients.

[0025] Formula compounding: Activated and modified fine-particle and micro-powdered fly ash are mixed with previously collected medium-particle fly ash at a ratio of 1:1 to 10:1. Then, 10%-20% of desulfurized gypsum and 5%-10% humic acid or biomass carbon (by mass) are added to the mixture. Simultaneously, appropriate amounts of nitrogen fertilizer, phosphate fertilizer, potassium fertilizer, and other auxiliary materials such as bentonite and zeolite are added. Nitrogen fertilizer can be one or two of urea and ammonium sulfate; phosphate fertilizer can be one, two, or three of potassium dihydrogen phosphate, superphosphate, and ammonium phosphate (including monoammonium phosphate and diammonium phosphate); and potassium fertilizer can be one or two of potassium chloride and potassium sulfate. This step, through proper compounding, can enhance the soil conditioner's effect on improving overall soil performance.

[0026] Secondary biological activation: A compound microbial agent, comprising Bacillus mucilaginosus, phosphate-solubilizing bacteria, and actinomycetes, is introduced into the fly ash treated with the above-mentioned formula in a ratio of 2:2:1. Then, an appropriate amount of water is added to bring the material's moisture content to 30%-50%. The mixture is then statically incubated at 15-30℃ for 3-10 days. The metabolic activity of the microorganisms further activates the nutrients in the fly ash and helps improve the soil's microbial environment.

[0027] Molding and Post-processing: An appropriate amount of binder, such as starch paste, is added to the mixed raw materials that have undergone secondary bio-activation treatment. The mixed raw materials are then granulated into particles with a diameter of 2-5 mm using a disc granulator or extrusion granulator. The particles are then dried at 60-80℃ to control the moisture content of the dried particles to 10%-20%. After drying, unqualified particles are sieved to remove them, and qualified products are quantitatively packaged using an automatic packaging machine to obtain the finished soil conditioner. This molding and post-processing step is simple, helps reduce costs, and facilitates large-scale industrial application.

[0028] Experimental verification

[0029] Soil conditioner application: Apply the soil conditioner evenly to the saline-alkali land and plow it. The dosage is 3000 kg / mu, and the plowing depth is 20-30 cm.

[0030] Soil sample collection: Before the start of the experiment and after the rice harvest each year, soil samples from the 0-30cm soil layer of each plot were collected. Five sampling points were randomly selected from each plot, and the "five-point sampling method" was used. After the collected soil samples were mixed evenly, about 1kg was taken back to the laboratory to determine the physicochemical properties of the soil, such as pH value, total salt content, organic matter content, and heavy metal content.

[0031] Rice sample collection: Five quadrats were randomly selected from each plot during the rice maturity period. Each quadrat had an area of ​​1 square meter. Rice was harvested and the plant height was measured by the method of measuring the height from the ground to the top of the rice panicle. The effective panicle number was the number of rice panicles with more than 5 full grains per square meter. The number of grains per panicle was the total number of grains on each panicle. The thousand-grain weight was measured by weighing 1,000 full grains randomly selected and repeating the process three times to obtain the average value. The actual yield was measured by threshing and drying the rice in the quadrat and then weighing it. The yield was converted into yield per mu and other agronomic traits and yield indicators.

[0032] Experimental results

[0033] A comparative experiment was conducted between treatment 1 in the above examples and treatment 2 of saline-alkali land under the same environmental conditions without the addition of conditioning agents. The results are as follows:

[0034] Soil changes

[0035] Soil pH value: Before the experiment, the soil pH value of each treatment group was around 9.7-9.9. After three years of experimentation, the soil pH value of treatment 1, which applied the conditioner of the example, showed a decreasing trend year by year, dropping below 8.6 after the first year's harvest and below 8.0 in the second year. In contrast, the soil pH value of treatment 2, which did not apply the conditioner, remained basically unchanged, fluctuating between 9.7 and 9.8. This indicates that the soil conditioner of the present invention can effectively reduce the pH value of saline-alkali soil.

[0036] Total salt content: At the beginning of the experiment, the total salt content of the soil in each treatment group was relatively high, all above 0.6%. After three years of experimentation, the total salt content of the soil in treatment 1, which was treated with the conditioner of the example, decreased from 0.6% to 0.09%, a reduction of 85%. In contrast, the total salt content of the soil in treatment 2, which was not treated with the conditioner, did not change significantly and remained above 0.6%. This indicates that the soil conditioner of the present invention has a significant effect on reducing soil salinity.

[0037] Rice growth indicators

[0038] Plant height: In the experiment, the rice plant height of treatment 1 was significantly higher than that of treatment 2. At the maturity of the first year, the average plant height of treatment 1 was 95 cm, while that of treatment 2 was 88 cm. In the second year, treatment 1 increased to 102 cm, while treatment 2 only increased to 90 cm. This shows that the soil conditioner improved the aeration and permeability of the soil by adjusting the soil pH and reducing the salt content, creating a good environment for the growth of rice roots, enabling the roots to absorb water and nutrients more effectively, thereby significantly promoting the growth of the above-ground parts of the plant.

[0039] Other indicators and yield: Soil bulk density decreased by 0.12-0.15 g / cm³ in treatment 1. 3 The porosity increased by 8%-10%; available nitrogen in the soil increased by 25-30 mg / kg, available phosphorus increased by 8-10 mg / kg, available potassium increased by 15-20 mg / kg, organic matter increased by 0.5%-0.6%, and the number of effective panicles, number of grains per panicle, and thousand-grain weight of rice all increased significantly, with yield increasing by 15%-20%, all of which were significantly better than the control group of treatment 2.

[0040] The soil conditioner prepared by this invention has a significant effect on improving saline-alkali land. It can effectively improve the physical and chemical properties of saline-alkali soil in Ningxia, reduce soil pH and total salt content, increase soil organic matter and nutrient content, improve soil structure, and create a good soil environment for rice growth.

[0041] This soil conditioner has a significant promoting effect on the growth and yield of rice in saline-alkali land. By improving the physical and chemical properties of the soil, it promotes the growth of rice roots and the absorption of nutrients, thereby increasing rice plant height, effective panicle number, number of grains per panicle, thousand-grain weight, number of tillers, and leaf area index, enhancing photosynthesis, and ultimately increasing rice yield.

[0042] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. 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, such designs should fall within the protection scope of the present invention.

Claims

1. A method for preparing a soil conditioner using fly ash, characterized in that: Includes the following steps: Fly ash grading and screening: Fly ash discharged from power plants is collected and graded using a three-layer vibrating screen with screen apertures of 0.3mm, 0.15mm, and 0.075mm. The fly ash is divided into four grades: coarse particles >0.3mm, medium particles 0.15-0.3mm, fine particles 0.075-0.15mm, and micro powder <0.075mm. The coarse particles, such as sand, can be used as building materials. The medium, fine, and micro powder particles are collected separately for later use. Activation and modification treatment: Fine fly ash particles are fed into a microwave-assisted ball mill and treated for 10-60 minutes under microwave power of 300-500W, ball-to-material ratio of 8-10:1, and rotation speed of 20-300r / min. Through the synergistic effect of microwave thermal effect and mechanical force, the agglomeration structure of fly ash particles is broken, and its specific surface area and active sites are increased. Acid-base modification treatment: The fine fly ash powder after microwave-mechanical synergistic activation treatment and the micro powder separated by grading and screening are thoroughly mixed and fed into a reaction vessel, and mixed with the modifier at a mass ratio of 1:10-1:

100. The mixture is stirred evenly and reacted at room temperature or 60-80℃ for 0.5-2 hours. The modifier is one or more of acid, alkali, salt or surfactant. Formula compounding: Mix the activated and modified fine and micro-powdered fly ash with medium-powdered fly ash in a ratio of 1:1 to 10:1, and then add 10%-20% of desulfurized gypsum, 5%-10% of humic acid or biomass carbon, and appropriate amounts of nitrogen fertilizer, phosphate fertilizer, potassium fertilizer, bentonite, zeolite and other auxiliary materials. Secondary biological activation: Introduce a compound microbial agent into the above-treated fly ash, add an appropriate amount of water to make the material moisture content reach 30%-50%, and let it stand and cultivate at 15-30℃ for 3-10 days. The nutrients in the fly ash are further activated by the metabolic action of microorganisms. The compound microbial agent includes Bacillus mucilaginosus, phosphate-solubilizing bacteria and actinomycetes in a ratio of 2:2:

1. Molding and post-processing: Add an appropriate amount of binder to the mixed raw materials that have undergone the above treatment, and form particles with a particle size of 2-5mm by a disc granulator or extrusion granulator. Dry the particles at 60-80℃ until the moisture content is less than 20%. After screening to remove unqualified particles, the qualified products are quantitatively packaged by an automatic packaging machine to obtain the finished soil conditioner. In the granulation step, the binder is starch paste.

2. The method for preparing a soil conditioner using fly ash according to claim 1, characterized in that: The modifier contains one or more of the following acids: hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, with a mass fraction of 10%-20%; one or more of the following bases: sodium hydroxide, potassium hydroxide, and calcium hydroxide, with a concentration of 0.1-3 mol / L; one or two of the following salts: ammonium chloride and calcium chloride, with a mass fraction of 5%-10%; and one or more of the following surfactants: sodium lignosulfonate or potassium lignosulfonate, with a mass fraction of 0.01%-0.05%.

3. The method for preparing a soil conditioner using fly ash according to claim 1, characterized in that: In the fly ash modification process, the reaction temperature is 60-80℃ and the reaction time is 0.5-2 hours.

4. The method for preparing a soil conditioner using fly ash according to claim 1, characterized in that: In the raw material mixing step, the nitrogen fertilizer is one or two of urea and ammonium sulfate, the phosphate fertilizer is one, two or three of potassium dihydrogen phosphate, superphosphate, and ammonium phosphate, the potassium fertilizer is one or two of potassium chloride and potassium sulfate, and the ammonium phosphate includes monoammonium phosphate and diammonium phosphate.

5. The method for preparing a soil conditioner using fly ash according to claim 1, characterized in that: In the drying and packaging steps, the moisture content of the dried granules is 10%-20%.

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