Ecological technology for co-processing fly ash and straw

Abstract

The invention discloses an ecologicalization technology for coal ash-straw co-processing, and belongs to the technical field of solid waste resource utilization and nutrient soil preparation. The method specifically comprises the following steps: S1, selecting fly ash meeting requirements according to related standards; s2, soybean straw, rape straw and corn straw are selected, smashed and then mixed with the selected fly ash in proportion, and a mixed material is obtained; s3, adding a complex microbial inoculant into the mixed material, adjusting the moisture content, and performing staged decaying treatment; and S4, mixing the decomposed straw humus, fly ash and soil in proportion to obtain the nutrient soil. Humus obtained after straw decaying is rich in organic matter, humic acid and nitrogen, phosphorus and potassium available nutrients, and can be rapidly supplied to plants for growth; fly ash contains medium trace elements such as silicon, calcium, magnesium, iron, potassium and phosphorus, can continuously provide slow-release nutrients, and enhances lodging resistance and disease resistance of crops; ammonium salt in the fly ash is converted into nitrogen nutrition, and the activated carbon improves the water-retaining property of the nutrient soil.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and nutrient soil preparation technology, and in particular to an ecological technology for the co-processing of fly ash and straw. Background Technology

[0002] As a major industrial solid waste emitted by coal-fired power plants, the comprehensive utilization rate of fly ash has always been a key issue in the field of environmental governance. Before its pozzolanic activity was recognized and developed, fly ash was mainly disposed of through open-air stockpiling. This not only occupies a large amount of land resources but also easily causes a series of environmental problems such as dust and leachate pollution, posing a significant threat to ecological security.

[0003] With the iterative upgrades in materials science and technology, the resource value of fly ash has been deeply explored, gradually becoming an indispensable auxiliary cementing material in building products such as concrete and mortar. Previously, relying on the explosive demand in the building materials market brought about by the rapid development of my country's real estate industry, fly ash achieved large-scale and efficient disposal, and the market supply and demand relationship was once in a tight balance. In some areas, the price of fly ash increased by more than 200 yuan / ton, forming a good industrial pattern of "turning waste into treasure".

[0004] However, as the real estate industry enters a new phase of stable development, the demand for fly ash in the building materials market has plummeted. Without the support of this core disposal channel, the challenge of comprehensive utilization of fly ash has once again become prominent, becoming an urgent task for environmental governance departments and coal-fired power plants to solve. At the same time, the widespread adoption of flue gas denitrification technology in coal-fired power plants has led to higher ammonium salt content in fly ash, significantly reducing its compatibility with cement-based materials and further limiting the application of fly ash in the building materials sector.

[0005] Against this backdrop, exploring new pathways for the comprehensive utilization of fly ash is urgently needed. Given the massive volume of fly ash emissions, these new pathways must possess a significant market capacity. Currently, unlike the continued downturn in the construction market, the nutrient soil market is experiencing rapid growth—the total national demand is projected to reach approximately 8 million tons by 2025, with a market size exceeding 15-20 billion yuan, and a compound annual growth rate maintained at 12%-15%. It is projected that total demand will surpass 10 million tons by 2030. If the large-scale application of fly ash in the nutrient soil sector can be promoted, the enormous carrying capacity of the nutrient soil market can absorb a considerable amount of fly ash, effectively addressing the current industry dilemma of difficulty in improving the comprehensive utilization rate of fly ash.

[0006] Traditional potting mixes are primarily composed of soil. Soil, as a multi-mineral mixture, possesses good plasticity, water retention, and fertilizer retention due to its clay mineral content and continuous particle size distribution. However, heavy clay soils are prone to compaction, resulting in poor aeration and permeability. In contrast, fly ash, with its main component being spherical glass microspheres, boasts advantages such as uniform particle size, high porosity, and low bulk density. Although it lacks plasticity and has poor water retention, its incorporation into soil can significantly reduce soil bulk density and increase porosity. Especially for heavy clay soils, it can effectively break up the compaction layer, enhancing soil aeration and permeability.

[0007] Meanwhile, fly ash is rich in micronutrients such as silicon, calcium, magnesium, iron, potassium, and phosphorus, which are essential for plant growth, providing a continuous supply of slow-release micronutrients. It's worth noting that due to the flue gas denitrification process, fly ash often has a high ammonium salt content, a characteristic that limits its application in building materials. However, in nutrient soil systems, this can be transformed into a significant advantage, providing considerable nitrogen nutrition for plant growth.

[0008] Similarly, the activated carbon in fly ash is a harmful component in building materials applications—its porous structure and adsorption properties reduce the flowability of concrete mixtures. However, in potting soil, the porous activated carbon can effectively improve the water retention of fly ash, becoming a beneficial component for promoting plant growth. Therefore, inferior fly ash with high ammonium salt and carbon content is actually more suitable for the preparation of potting soil.

[0009] Furthermore, due to its particle and porosity characteristics, fly ash can also be used as a loosening auxiliary material in the composting process. Adding it at a ratio of 10%-15% of the dry weight of straw can improve the aeration of the compost pile and prevent anaerobic decomposition. When mixing nutrient soil, fly ash can replace 60%-90% of the soil substrate. After conversion, the proportion of fly ash in each ton of nutrient soil exceeds 60%, which is far higher than its traditional admixture in cement concrete.

[0010] Straw itself has inherent characteristics such as low density, large volume, and highly concentrated harvest period. Coupled with the current imperfect straw collection, storage and transportation system and the weak economic viability of some resource utilization paths (such as raw material utilization), straw treatment faces the dual challenges of a sharp increase in short-term disposal pressure and low resource utilization efficiency.

[0011] Using straw through biological decomposition as a core nutrient source for potting soil not only has high added value but is also suitable for small-scale, decentralized production models, thus opening up a practical and feasible new resource utilization path to solve the problem of straw disposal.

[0012] In summary, the innovative application of this patented technology can open up a new path that combines economic and ecological benefits for improving the comprehensive utilization rate of fly ash. Summary of the Invention

[0013] Purpose of the invention: The purpose of this invention is to provide an ecological technology for the co-processing of fly ash and straw; it can solve the problems of difficulty in comprehensive utilization of fly ash and the sharp increase in short-term disposal pressure and low resource utilization efficiency of straw.

[0014] Technical Solution: To solve the above-mentioned technical problems, according to one aspect of the present invention, more specifically, an ecological technology for the co-processing of fly ash and straw, specifically including the following steps: S1. Select fly ash that meets the requirements according to relevant standards; S2. Select soybean straw, rapeseed straw and corn straw, crush them and mix them with selected fly ash in proportion to obtain a mixture. S3. Add compound microbial agent to the mixture, adjust the moisture content, and then carry out staged decomposition treatment. S4. Mix the decomposed straw humus, fly ash, and soil in a certain proportion to obtain nutrient soil.

[0015] Furthermore, in step S1, the selected fly ash is fly ash that meets the requirements for heavy metals and radioactivity in GB 15618-2018 "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)", and fly ash with ammonium salt content or loss on ignition that does not meet the quality requirements of GB / T1596-2017 "Fly Ash for Cement and Concrete" is preferred.

[0016] Furthermore, in step S2, during the crushing process, soybean stalks are crushed to 3-5cm, rapeseed stalks are crushed to 1-2cm, and corn stalks are crushed to 2-3cm by first rolling and then crushing.

[0017] Furthermore, in step S2, soybean straw, rapeseed straw, corn straw, and fly ash are mixed in proportions of 25%, 25%, 35%, and 15% by mass, respectively.

[0018] Furthermore, in step S3, the compound microbial agent is a combination of Bacillus subtilis, Cellomonas, and Trichoderma, wherein Bacillus subtilis accounts for 0.2% of the mass of the mixed straw, and Cellomonas and Trichoderma each account for 0.1% of the mass of the mixed straw.

[0019] Furthermore, in step S3, when adding the compound microbial agent to the mixture, the inoculum is diluted with rice bran at a ratio of 1:10, evenly sprinkled into the straw pile, turned and mixed, and the straw moisture content is adjusted to 55%~60% after inoculation.

[0020] Furthermore, in step S3, the corrosion cycle is 15-20 days, specifically including: a heating period, a high-temperature period, and a cooling period; Heating period: Days 1-3, the pile temperature gradually rises to 55-65℃, and the moisture content is maintained at 55%-60%; High temperature period: Days 4-10, maintain a high temperature of 55-65℃, maintain moisture at 55%-60%, control pH to 6.5-7.5, and adjust pH with saturated slaked lime water if it decreases. Cooling period: Days 11-20, the pile temperature drops to ambient temperature and the moisture content drops below 40%.

[0021] Furthermore, in step S4, the decomposed straw humus, fly ash, and soil are mixed in a mass ratio of 3:6:1 to make nutrient soil; if the montmorillonite content in the soil is high or the loss on ignition in the fly ash is high, the ratio of the decomposed straw humus, fly ash, and soil can be adjusted to 3:6.8:0.2 to make nutrient soil.

[0022] Beneficial effects: Breaking the dilemma of fly ash utilization: This technology can effectively utilize the large amount of industrial solid waste fly ash generated by coal-fired power plants, especially the "inferior fly ash" with high ammonium salt content and loss on ignition that does not meet building material standards. This type of fly ash is restricted in the traditional building materials field due to poor compatibility. This technology can transform it into the core substrate of nutrient soil, expand the new path for large-scale disposal of fly ash, avoid dust and leachate pollution caused by open-air storage, and reduce land occupation.

[0023] Alleviating the pressure of straw disposal: Adapting to the disposal needs under the policy of prohibiting the burning of farmland straw, it solves the pain points of low straw density, large volume, difficulty in collection, storage and transportation, and low resource utilization efficiency. Through biological decomposition, straw is transformed into a core nutrient source for nutrient soil, and it is suitable for small-scale and decentralized production models. It does not require a complex collection, storage and transportation system, which greatly reduces the short-term disposal pressure of straw and avoids air pollution caused by burning.

[0024] Improving soil physical structure: The spherical glass microspheres and high porosity of fly ash can significantly reduce soil bulk density and increase porosity, effectively breaking up the compaction layer of heavy clay soil; at the same time, it can improve soil permeability, solve the problems of poor aeration and permeability of traditional soils, and provide a good environment for crop root growth.

[0025] Provides comprehensive and balanced nutrition: The humus after straw decomposition is rich in organic matter, humic acid, and readily available nutrients such as nitrogen, phosphorus, and potassium, which can quickly supply plant growth; fly ash contains trace elements such as silicon, calcium, magnesium, iron, potassium, and phosphorus, which can continuously provide slow-release nutrients and enhance the crop's resistance to lodging and disease; the ammonium salts in fly ash are converted into nitrogen nutrition, and activated carbon improves the water retention of the nutrient soil, realizing "defect resource utilization".

[0026] Reduce the risk of pests and diseases: The high temperature of 55~65℃ during the decomposition process can effectively kill pathogens and insect eggs in straw, reduce the probability of pests and diseases during crop cultivation, and reduce the need for pesticides.

[0027] Extremely low raw material costs: Fly ash and straw are both widely available industrial / agricultural solid wastes with low acquisition costs. They can also replace traditional nutrient soil substrates, significantly reducing reliance on soil resources and lowering raw material procurement costs.

[0028] High cost-effectiveness in production and application: Compared with commercially available nutrient soil, the nutrient soil prepared by this technology has a lower cost; and the production mode is flexible, which can adopt small-scale decentralized production, without the need for large equipment and complex processes, making it suitable for on-site conversion in rural areas, further reducing transportation and processing costs.

[0029] Reduce environmental pollution: Avoid soil and water pollution from fly ash accumulation, eliminate air pollution from straw burning, achieve a "zero waste" approach to solid waste disposal, and reduce ecological and environmental pressure.

[0030] Promoting soil ecological restoration: The synergistic effect of humus and fly ash in nutrient soil can improve soil structure and enhance soil fertility in the long term, especially suitable for the improvement of degraded soil and heavy clay soil, and help ecological restoration and the improvement of arable land quality.

[0031] Highly efficient resource recycling: Constructing a circular chain of "industrial solid waste (fly ash) - agricultural solid waste (straw) - ecological products (nutrient soil)" to achieve efficient cross-sectoral utilization of resources, which aligns with the concept of green development.

[0032] Wide adaptability of raw materials: Fly ash only needs to meet the requirements of agricultural land soil pollution risk control standards for heavy metals and radioactivity, and straw can be selected from common crops such as soybeans, rapeseed, and corn. The raw materials are easy to obtain and have strong regional adaptability.

[0033] The formula can be flexibly adjusted: for scenarios with high montmorillonite content in the soil or high fly ash loss on ignition, the ratio of straw humus, fly ash, and soil can be adjusted to suit the raw material characteristics and crop planting needs of different regions. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the method. Detailed Implementation

[0035] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Example The selected ash is from Xuzhou Huaneng Power Plant. Its loss on ignition is 11%, residue on a 45μm sieve is 55%, and ammonium salt content is 233 mg / kg. Due to its coarse particle size and high carbon content, it is difficult to use directly as an admixture in concrete. However, its coarse particles provide higher porosity to the potting soil, which is beneficial for improving its air permeability. The high loss on ignition indicates a high content of activated carbon, which can improve the water retention of the potting soil.

[0037] Soybean straw, rapeseed straw, and corn straw, after biological decomposition, were selected as the nutrient source for the potting soil. Soybean straw was crushed into 4cm pieces, rapeseed straw into 2cm pieces, and corn straw was crushed into 3cm pieces using a method of first rolling and then breaking. The soybean straw, rapeseed straw, corn straw, and fly ash were mixed in a ratio of 25%, 25%, 35%, and 15% by weight, respectively.

[0038] A compound inoculant combination of Bacillus subtilis, Cellomonas hydrophila, and Trichoderma was selected, with Bacillus subtilis accounting for 0.2% of the mixed straw mass, and Cellomonas hydrophila and Trichoderma hydrophila each accounting for 0.1% of the mixed straw mass. The inoculum was diluted with rice bran at a ratio of 1:10, evenly sprinkled into the straw pile, and turned over to mix thoroughly to avoid localized high concentrations that could lead to inactivation of the inoculum. After inoculation, the moisture content of the straw was adjusted to 55%–60% (it should clump together when squeezed in the hand, crumble easily when dropped, and be moist but not dripping from between the fingers) to provide a humid environment for inoculum colonization.

[0039] After inoculating the straw with the microbial inoculum, pile it into a clump and let it stand for 3 days. Check if the pile temperature reaches 60℃. If the temperature rises slowly and fails to reach 60℃ after 3 days, cover it with plastic film to retain heat and promote rapid microbial growth. During this process, maintain a moisture content of at least 55%. If insufficient, spray with clean water. If covered with plastic film, no additional water is needed.

[0040] The temperature was then maintained at around 60℃ for 6 days to kill pathogens and insect eggs and degrade the coarse fiber of the straw. During this period, the pile was turned over every 2 days to break up the surface crust and replenish oxygen; the moisture content was maintained at 55%~60% (water was added if necessary), and the pH was controlled at 6.5~7.5 (if the pH dropped, saturated quicklime water was used to adjust it).

[0041] After maintaining high temperatures for 6 days, the pile temperature was lowered to ambient temperature through turning, ventilation, and natural cooling, causing the straw to decompose into loose humus. The pile was turned every 5 days. Turning and ventilation reduced the moisture content of the pile, preventing nutrient loss. The decomposed straw is loose and brittle, lacks a distinct original straw shape, is dark brown or black, and emits an earthy smell.

[0042] Nutrient soil is made by mixing well-rotted straw humus, fly ash, and soil in a mass ratio of 3:6.5:0.5. Compared to pure soil, this nutrient soil has a 20%–30% lower bulk density and a 15%–25% higher water permeability, making it suitable for the root growth needs of most crops. The nutrient soil is rich in organic matter, humic acid, and readily available nutrients such as nitrogen, phosphorus, and potassium, which can quickly supply nutrients for plant growth. Furthermore, fly ash provides trace elements such as silicon, calcium, magnesium, and iron, which can enhance the crop's resistance to lodging and disease.

[0043] Both fly ash and straw are industrial / agricultural solid wastes, widely available and inexpensive to obtain, significantly reducing the raw material costs for preparing nutrient soil. Simultaneously, they reduce the land occupation caused by fly ash storage and the pollution from straw burning, achieving a "waste-to-treasure" transformation. Compared to commercially available nutrient soil, the cost of this self-made mixed substrate can be reduced by 40% to 60%, offering both economic and ecological benefits.

[0044] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An ecological technology for co-disposal of fly ash and straw, characterized in that, Specifically comprising the following steps: S1, selecting fly ash meeting the requirements according to relevant standards; S2, selecting soybean straw, rape straw and corn straw, after crushing treatment, mixing with the selected fly ash according to the proportion to obtain a mixture; S3, adding a compound microbial agent to the mixture, adjusting the moisture content and then carrying out stage-wise putrefaction treatment; S4, mixing the humus of the rotten straw, fly ash and soil according to the proportion to obtain nutrient soil.

2. The ecological technology for co-disposal of fly ash and straw according to claim 1, characterized in that: In the step S1, the fly ash selected is the fly ash meeting the requirements of GB 15618-2018 "Soil Environmental Quality Risk Control Standards for Agricultural Soil Pollution (Trial)" for heavy metals and radioactivity, and the fly ash with ammonium salt or loss on ignition not meeting the quality requirements of GB / T 1596-2017 "Fly Ash for Use in Cement and Concrete" is preferred.

3. The ecological technology for co-disposal of fly ash and straw according to claim 1, characterized in that: In the step S2, during the crushing treatment, the soybean straw is crushed to 3-5 cm, the rape straw is crushed to 1-2 cm, and the corn straw is crushed to 2-3 cm by first rolling and then crushing.

4. The ecological technology for co-disposal of fly ash and straw according to claim 1, characterized in that: In the step S2, the soybean straw, rape straw, corn straw and fly ash are mixed according to the proportion of 25%, 25%, 35% and 15% by mass percentage.

5. The ecological technology for co-disposal of fly ash and straw according to claim 1, characterized in that: In the step S3, the compound microbial agent is a combination of Bacillus subtilis, Cellulomonas and Trichoderma, wherein the Bacillus subtilis accounts for 0.2% of the mass of the mixed straw, and the Cellulomonas and Trichoderma each account for 0.1% of the mass of the mixed straw.

6. The eco-friendly technology for co-disposal of fly ash and crop straw according to claim 1, characterized in that: In the step S3, when the compound microbial agent is added to the mixture, the microbial strain is diluted with rice bran at a ratio of 1:10, uniformly spread into the straw pile, and mixed evenly after inoculation, and then the moisture content of the straw is adjusted to 55%-60%.

7. The eco-friendly technology for co-disposal of fly ash and crop straw according to claim 1, characterized in that: In the step S3, the putrefaction period is 15-20 days, specifically including: a warming period, a high temperature period and a cooling period; Warming period: 1-3 days, the pile temperature gradually rises to 55-65℃, and the moisture content is maintained at 55%-60%; High temperature period: 4-10 days, maintaining high temperature of 55-65℃, moisture content of 55%-60%, pH control to 6.5-7.5, and adjusting with saturated lime water when the pH decreases; Cooling period: 11-20 days, the pile temperature drops to the ambient temperature, and the moisture content drops to below 40%.

8. The eco-friendly technology for co-disposal of fly ash and crop straw according to claim 1, characterized in that: In the step S4, the rotten straw humus, fly ash and soil are mixed according to the mass ratio of 3:6:1 to prepare nutrient soil; if the content of montmorillonite in the soil is high or the loss on ignition of the fly ash is high, the rotten straw humus, fly ash and soil can be mixed according to the mass ratio of 3:6.8:0.2 to prepare nutrient soil.

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