Method for preparing composite soil conditioner and artificial soil by cooperatively treating livestock and poultry manure through coal gasification slag

Abstract

The invention relates to a method for preparing a composite soil conditioner and artificial soil, in particular to a method for preparing a composite soil conditioner and artificial soil by co-processing livestock and poultry manure through coal gasification slag. The invention aims to solve the technical problems of low utilization rate of coal gasification slag and low utilization rate of effective components in livestock manure at present. According to the method, firstly, efficient adsorption and stabilization of dissolved organic matter in liquid dung are achieved by optimizing components of the coal gasification slag, then the coal gasification slag loaded with the dissolved organic matter serves as a core matrix to be scientifically matched with the dung, and the high-performance artificial soil is prepared. According to the technology disclosed by the invention, the synergistic conversion of the two wastes is realized, and the product shows excellent physical and chemical properties and a remarkable plant growth promoting effect. The method is simple and convenient to operate, has industrial amplification potential, provides a systematic solution with environmental friendliness and economic feasibility for ecological restoration of mining areas and improvement of degraded cultivated land, and has important engineering application value and ecological significance.

Description

Technical Field

[0001] The invention relates to a method for preparing a composite soil conditioner and artificial soil. Background Art

[0002] Coal gasification slag is a solid waste generated during the coal chemical gasification process. Its main components are aluminosilicates, residual carbon, and trace metal elements. my country emits over 50 million tons of coal gasification slag annually, but its comprehensive utilization rate is less than 30%. The large-scale accumulation of coal gasification slag not only occupies land but also poses risks of heavy metal leaching and dust pollution. Meanwhile, the rapid development of the livestock and poultry farming industry has led to a surge in manure emissions. By 2023, the national output of livestock and poultry manure was approximately 4 billion tons. Traditional treatment methods (such as composting and anaerobic digestion) are plagued by low efficiency, nitrogen and phosphorus loss, and secondary pollution. The synergistic utilization of coal gasification slag and livestock and poultry manure, achieving "waste-to-waste treatment," has become an important research direction in the field of solid waste resource utilization. Currently, coal gasification slag is mostly used as building materials or roadbed materials, but its high porosity and mineral activity have yet to fully explore their potential in soil improvement. Directly returning livestock and poultry manure to farmland can easily lead to salinization and the spread of pathogens, necessitating stabilization treatment to improve safety. Therefore, it is necessary to develop a resource utilization technology based on the coordinated treatment of coal gasification slag and manure, which has both environmental and economic benefits.

[0003] In recent years, solid waste-based soil conditioners have become a research hotspot due to their low cost and environmental friendliness. For example, steel slag and fly ash are used to adjust soil pH and supplement trace elements, but they pose the risk of heavy metal activation. Biochar-based conditioners can immobilize pollutants, but raw materials are limited and production is energy-intensive. Coal gasification slag, due to its unique mineral composition (such as CaO and SiO2) and porous structure, shows potential for adsorbing ammonia nitrogen and passivating heavy metals, but the mechanism of its synergistic interaction with organic waste remains unclear. Artificial soil technology, on the other hand, simulates the natural soil-forming process by combining organic solid waste (such as sludge and straw) with inorganic materials. However, existing processes often rely on high-temperature sintering or chemical binders, which are costly and damage organic matter. A few studies have attempted to prepare artificial soil using manure, but these methods suffer from low strength and nutrient imbalance. Therefore, a green and low-carbon approach is urgently needed to simultaneously prepare conditioners and synthesize soil through the physicochemical-biological synergy of coal gasification slag and manure, filling the technological gap in this field.

[0004] The high moisture content (70%-90%) and complex composition (antibiotics, heavy metals, pathogens) of livestock and poultry manure are major obstacles to its resource utilization. Traditional solid-liquid separation often requires anaerobic treatment, but this results in low biogas yields and difficult digestion of the biogas liquid. Solid manure composting processes are long and result in significant carbon and nitrogen losses. Existing technologies, such as aerobic fermentation and pyrolysis carbonization, can reduce waste but struggle to simultaneously recover nutrients. Summary of the Invention

[0005] The present invention aims to solve the current technical problems of low utilization rate of coal gasification slag and low utilization rate of effective components in livestock and poultry manure, and provides a method for preparing composite soil improver and artificial soil by co-processing livestock and poultry manure with coal gasification slag.

[0006] The method of preparing a composite soil conditioner and artificial soil by co-processing livestock and poultry manure with coal gasification slag of the present invention is carried out according to the following steps:

[0007] 1. Allowing the coarse coal gasification slag and the fine coal gasification slag to stand and air dry until the moisture content is 5% to 30%, and then mixing the coarse coal gasification slag and the fine coal gasification slag in a mass ratio of (4-2):(2-1) to obtain compound coal gasification slag;

[0008] Separate the livestock and poultry manure into solid and liquid to obtain manure and fecal water;

[0009] 2. The composite coal gasification slag in step 1 and the sewage in step 1 are placed in an oscillating mixer and mixed at a temperature of 15° C. to 30° C. to obtain an improver slurry; a pH regulator is added to the improver slurry to a pH of 6 to 9, and then the solid portion is filtered and retained, and dried to obtain a coal gasification slag-based improver;

[0010] The mass ratio of the manure water to the composite coal gasification slag is (10-20):(3-6) to control the C / N ratio in the improver slurry to (20-30):1;

[0011] 3. Mixing the feces obtained in step 1 with the composite coal gasification slag, wherein the mass fraction of the composite coal gasification slag is 0-10%, stirring in a compost fermentation reaction device for 30-60 minutes, and the fermentation temperature is 25-80°C. During fermentation, water is added to ensure that the moisture content of the material is 40-60%, and oxygen is introduced once a week for 20-24 hours and stirred for 30-60 minutes to ensure that the material is fermented in a sufficient amount of oxygen; when the pile temperature reaches 50-55°C, stirring the pile and turning it to cool it down, and fermenting for 30-45 days to obtain feces fermentation;

[0012] Fourth, the coal gasification slag-based amendment prepared in step 2 is mixed with the feces fermentation product prepared in step 3, with the coal gasification slag-based amendment accounting for 60% to 80% by mass in the mixed system. The mixture is allowed to stand at room temperature for aging and fermentation for 20 to 30 days to obtain artificial soil.

[0013] The coarse coal gasification slag in step 1 has a relatively large particle size ranging from 1.2 mm to 4.75 mm, is blocky or granular, has a relatively rough surface, and may have some irregular shapes and textures.

[0014] The coal gasification fine slag in step 1 has a particle size of less than 1.2 mm, is usually in the form of powder or fine particles, has a relatively fine texture, and may appear closer to dust.

[0015] In step 4, the present invention adds fecal fermentation products to a coal gasification slag-based amendment and ferments them to produce artificial soil. First, this process enhances the humification process through the synergistic effect of minerals and organic matter. The aluminosilicates and metal oxides in the coal gasification slag adsorb small organic molecules in the feces, promoting polymerization and forming a stable humus structure. Second, the alkalinity of the coal gasification slag neutralizes fecal acidification products, maintaining the pH stability of the fermentation system. Its porous structure provides microbial habitats, significantly improving cellulose degradation efficiency. Third, the process achieves a gradient passivation of heavy metals: the coal gasification slag first fixes free heavy metals in the feces through surface complexation, and the humus-mineral complex formed during subsequent fermentation further reduces the bioavailability of heavy metals. This phased treatment strategy provides a new approach for regulating the physical and chemical properties of solid waste-based artificial soils.

[0016] The present invention innovatively develops a "solid (gasification slag)-liquid (manure) synergistic" resource utilization process: first, by optimizing the composition of gasification slag, efficient adsorption and stabilization of dissolved organic matter in manure is achieved. Then, the gasification slag loaded with dissolved organic matter is used as the core matrix and scientifically proportioned with manure to prepare high-performance artificial soil.

[0017] The technology of this invention not only achieves the synergistic transformation of two wastes, but the resulting product also exhibits excellent physical and chemical properties and significant plant growth-promoting effects. This method is simple to operate and has the potential for industrial scalability. It provides an environmentally friendly and economically viable system solution for ecological restoration in mining areas and improvement of degraded farmland, with important engineering application value and ecological significance.

[0018] The coal gasification slag has an adsorption effect on the soluble organic carbon and plant nutrients in the livestock and poultry manure, and the prepared improver realizes the adsorption and utilization of the effective components in the livestock and poultry manure to the greatest extent.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The method for obtaining coal gasification slag in the present invention is simple, the raw materials are abundant, and the time and economic costs are low;

[0021] 2. The present invention adopts an integrated collaborative treatment process to achieve the simultaneous resource treatment of different types of coal gasification slag and livestock and poultry manure, and prepares coal gasification slag-based soil conditioner and artificial soil products respectively. This process significantly improves the treatment efficiency of coal gasification slag, and its single batch processing capacity can reach 5 to 10 tons;

[0022] 3. The present invention can achieve "waste treatment with waste", reduce the cost of treating livestock manure, and reduce the cost of landfilling and disposing of coal gasification slag;

[0023] 4. The carbon content of coal gasification slag is high, which is conducive to absorbing sunlight. The addition of coal gasification slag is conducive to increasing the temperature during the composting process;

[0024] 5. The coal gasification slag has a porous structure and a large specific surface area, which can effectively absorb ammonia nitrogen, phosphorus, heavy metals and organic pollutants in livestock manure, reducing the cost of manure treatment;

[0025] 6. The present invention can kill pathogens and degrade antibiotics through aerobic fermentation, thereby improving safety;

[0026] 7. The particle characteristics of coal gasification slag enhance the soil's ability to resist erosion and reduce soil and water loss;

[0027] 8. Organic-inorganic (organic is manure, inorganic is coal gasification slag) composite matrix can slowly release nutrients and reduce the frequency of fertilization;

[0028] 9. Iron and aluminum oxides in coal gasification slag can fix heavy metals and reduce their bioavailability;

[0029] 10. The artificial soil prepared by the present invention can replace natural soil and be used for mine restoration, saline-alkali land improvement or urban greening, thereby alleviating the problem of soil resource shortage. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the SEM image of the coal gasification crude slag in step 1 of experiment 1;

[0031] Figure 2 This is the SEM image of the coal gasification fine slag in step 1 of experiment 1;

[0032] Figure 3 This is the XPS test chart;

[0033] Figure 4 This is a photo of the second experiment after 20 days of cultivation of the coal gasification slag-based amendment as the ecological substrate;

[0034] Figure 5 This is the SEM image of the coal gasification slag-based artificial soil prepared in step 3 of experiment 1;

[0035] Figure 6 This is a photo of Experiment 2 after 20 days of cultivation of medium coal gasification slag-based artificial soil as the ecological matrix;

[0036] Figure 7 This is a process flow chart of specific implementation method one. DETAILED DESCRIPTION

[0037] Specific embodiment 1: This embodiment is a method for preparing composite soil conditioner and artificial soil by co-processing livestock and poultry manure with coal gasification slag. Figure 7 As shown, the specific steps are as follows:

[0038] 1. Allowing the coarse coal gasification slag and the fine coal gasification slag to stand and air dry until the moisture content is 5% to 30%, and then mixing the coarse coal gasification slag and the fine coal gasification slag in a mass ratio of (4-2):(2-1) to obtain compound coal gasification slag;

[0039] Separate the livestock and poultry manure into solid and liquid to obtain manure and fecal water;

[0040] 2. Mixing the composite coal gasification slag in step 1 with the sewage in step 1 at a temperature of 15° C. to 30° C. to obtain an improver slurry; adding a pH regulator to the improver slurry until the pH is 6 to 9, then filtering and retaining the solid portion, and drying to obtain a coal gasification slag-based improver;

[0041] The mass ratio of the manure water to the composite coal gasification slag is (10-20):(3-6) to control the C / N ratio in the improver slurry to (20-30):1;

[0042] 3. Mixing the feces obtained in step 1 with the composite coal gasification slag, wherein the mass fraction of the composite coal gasification slag is 0-10%, stirring in a compost fermentation reaction device for 30-60 minutes, and the fermentation temperature is 25-80°C. During fermentation, water is added to ensure that the moisture content of the material is 40-60%, and oxygen is introduced once a week for 20-24 hours and stirred for 30-60 minutes to ensure that the material is fermented in a sufficient amount of oxygen; when the pile temperature reaches 50-55°C, stirring the pile and turning it to cool it down, and fermenting for 30-45 days to obtain feces fermentation;

[0043] Fourth, the coal gasification slag-based amendment prepared in step 2 is mixed with the feces fermentation product prepared in step 3, with the coal gasification slag-based amendment accounting for 60% to 80% by mass in the mixed system. The mixture is allowed to stand at room temperature for aging and fermentation for 20 to 30 days to obtain artificial soil.

[0044] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the particle size of the coal gasification coarse slag in step 1 is between 1.2 mm and 4.75 mm, and is in the form of blocks or particles. Other aspects are the same as specific embodiment 1.

[0045] Specific embodiment 3: This embodiment differs from specific embodiments 1 or 2 in that the particle size of the coal gasification slag in step 1 is less than 1.2 mm and is in powder or fine granular form. Other aspects are the same as specific embodiments 1 or 2.

[0046] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that in step 1, livestock manure is separated into solid and liquid by a screw extrusion separator to obtain manure and fecal liquid. Other aspects are the same as specific embodiments 1 to 3.

[0047] Specific embodiment 5: This embodiment differs from specific embodiment 4 in that in step 2, the composite coal gasification slag in step 1 is mixed with the sewage in step 1 for 12 hours to 24 hours. Other steps are the same as those in specific embodiment 4.

[0048] Specific embodiment 6: This embodiment differs from specific embodiment 5 in that the drying temperature in step 2 is 80° C. The rest is the same as specific embodiment 5.

[0049] The present invention is verified by the following test:

[0050] Experiment 1: This experiment is a method for preparing composite soil conditioner and artificial soil by co-processing livestock and poultry manure with coal gasification slag. The specific steps are as follows:

[0051] 1. Allowing the coarse coal gasification slag and the fine coal gasification slag to stand and air dry until the moisture content is 20%, and then mixing the coarse coal gasification slag and the fine coal gasification slag in a mass ratio of 2:1 to obtain compound coal gasification slag;

[0052] The cow dung is separated into solid and liquid by a screw extrusion separator to obtain dung and dung water;

[0053] The coal gasification coarse slag described in step 1 has a particle size of 1.2 mm to 4.75 mm and is in a granular form;

[0054] The coal gasification slag in step 1 has a particle size of less than 1.2 mm and is in the form of powder or fine particles;

[0055] 2. Stirring and mixing the composite coal gasification slag in step 1 and the sewage in step 1 for 24 hours at a temperature of 25° C. to obtain an improver slurry; adding a pH regulator to the improver slurry until the pH is 7.7, then filtering and retaining the solid portion, and drying at 80° C. to obtain a coal gasification slag-based improver;

[0056] The mass ratio of the manure water to the composite coal gasification slag is 3:1 to control the C / N ratio in the improver slurry to 25:1;

[0057] 3. Mixing the feces obtained in step 1 with the composite coal gasification slag, wherein the mass fraction of the composite coal gasification slag is 10%, stirring in a compost fermentation reaction device for 40 minutes, and the fermentation temperature is 60°C. During fermentation, water is added to ensure that the moisture content of the material is 50%, and oxygen is introduced once a week for 24 hours and stirred for 50 minutes to ensure that the material is fermented in an environment with sufficient oxygen; when the pile temperature reaches 55°C, the pile is stirred and turned to cool down, and the fermentation period is 45 days to obtain fecal fermentation product;

[0058] Fourth, the coal gasification slag-based amendment prepared in step 2 was mixed with the feces fermentation product prepared in step 3, with the coal gasification slag-based amendment accounting for 70% by mass in the mixed system. The mixture was allowed to stand at room temperature for aging and fermentation for 30 days to obtain artificial soil.

[0059] Figure 1 This is the SEM image of the coal gasification slag in step 1 of experiment 1. Figure 2 This is the SEM image of the coal gasification fine slag in step 1 of experiment 1.

[0060] Figure 3These are XPS test images. The two images in the first row are from the composite coal gasification slag prepared in step 1 of Experiment 1, and the two images in the second row are from the coal gasification slag-based modifier prepared in step 2 of Experiment 1. It can be seen that after adsorption in step 2, the COC and C-OH in the C1s of the composite coal gasification slag are converted to C=C. For the C-OH structure, this may be because CGS (coal gasification slag) is inherently acidic. Under the action of its surface acidic active sites, a dehydration reaction similar to acid catalysis may occur. The oxygen atom in the C-OH is first protonated, making the -OH a free radical. Subsequently, the H atom on the adjacent C atom is removed under the influence of the CGS surface groups, forming a C=C double bond. For the COC structure, acid-catalyzed elimination reactions may also occur under the influence of the CGS surfactant. Under the action of certain metal ions or functional groups on the CGS surface, the oxygen atom in the COC bond may be polarized, causing the bond on the adjacent C atom to break, and the hydrogen atom or other groups to leave, thereby achieving the transformation to C=C. The OC in O1s transforms into C=O before and after adsorption. The possible reasons are: when humic substances approach the CGS surface, the active sites on the CGS surface interact with the OC structure in the humic substances, changing the electron cloud distribution around the OC bond, causing the electron cloud on the O atom connected to the C to shift toward the active center on the CGS surface, resulting in the weakening of the OC bond. At the same time, the O atom on the adjacent C atom migrates or leaves under the catalytic action of the CGS surface, forming an active intermediate. This intermediate further rearranges, forming a double bond between the O atom and the C atom, thus completing the transformation from OC to C=O. This structural transformation may be affected by the synergistic effects of multiple factors, including temperature, surface charge, and chemical composition, during the complex interfacial reaction process of humic substance adsorption on CGS, ultimately leading to the reconstruction of the chemical bonds of the humic substances, forming C=C and C=O structures. This transformation may further affect the adsorption stability and chemical activity of humic substances on the CGS surface.

[0061] The coal gasification slag-based modifier prepared in step 2 of experiment 1 was subjected to multiple tests, and the results were as follows: EC value (electrical conductivity): 500 μS / cm; mass content of organic matter: 49.6%; total mass content of N, P and K: 6.6%; planting germination index: 70%.

[0062] Figure 5The SEM image of the artificial soil prepared in step 4 of Experiment 1 shows that the surface pores of the CGS-based artificial soil particles increase to a certain extent during the incubation process, and the specific surface area increases. This is because some unreacted organic matter may still exist in the fermented cow dung product. After mixing with CGS, due to changes in environmental conditions, fermentation or other chemical reactions may continue, producing gases such as carbon dioxide and ammonia. These gases build up pressure within the particles. When the gases escape, they create new pores within the particles, thereby increasing the porosity. Simultaneously, the acid-base neutralization reaction between CGS and the fermented cow dung product may produce some soluble salts. These salts will crystallize and precipitate as water evaporates during subsequent drying processes. The crystallization process will occupy a certain amount of space, and when the crystals dissolve or are removed, pores will remain. In addition, some metal ions may undergo precipitation reactions to form precipitates. The presence of these precipitates will also affect the structure of the particles, increasing the porosity and improving the water and fertilizer retention of the artificial soil.

[0063] The artificial soil prepared in step 4 of Experiment 1 was subjected to multiple tests, and the results were as follows: EC value (electrical conductivity): 1350 μS / cm; organic matter content by mass: 48.7%; total content by mass of N, P, and K: 7.8%; and germination index: 83%.

[0064] Experiment 2: The coal gasification slag-based amendment prepared in step 2 of Experiment 1 and the artificial soil prepared in step 4 were respectively subjected to potted plant experiments. The experimental conditions were the same: a 0.2L plastic flower pot was used for planting, and 0.3kg of the coal gasification slag-based amendment or artificial soil was placed as the ecological matrix. Then 15 ryegrass seeds were placed, and 30% of the weight of the ecological matrix was added with water. The greenhouse potted plant culture experiment was carried out. After sowing, water was added to each pot every two days to maintain 70% of the soil's water holding capacity. The plants were cultured for 20 days under the conditions of air humidity of 70% and temperature of 28°C. Planting effect after 20 days: The height corresponding to the coal gasification slag-based amendment as the ecological matrix was 36.7cm (such as Figure 4 ); the height of artificial soil as ecological matrix is 23.8 cm (such as Figure 6 ).

Claims

1. A method for preparing composite soil conditioner and artificial soil by co-processing livestock and poultry manure with coal gasification slag, characterized in that The method for preparing composite soil conditioner and artificial soil by co-processing livestock and poultry manure with coal gasification slag is carried out in the following steps:

1. Allowing the coarse coal gasification slag and the fine coal gasification slag to stand and air dry until the moisture content is 5% to 30%, and then mixing the coarse coal gasification slag and the fine coal gasification slag in a mass ratio of (4-2):(2-1) to obtain compound coal gasification slag; Separate the livestock and poultry manure into solid and liquid to obtain manure and fecal water; 2. Mixing the composite coal gasification slag in step 1 with the sewage in step 1 at a temperature of 15° C. to 30° C. to obtain an improver slurry; adding a pH regulator to the improver slurry until the pH is 6 to 9, then filtering and retaining the solid portion, and drying to obtain a coal gasification slag-based improver; The mass ratio of the manure water to the composite coal gasification slag is (10-20):(3-6) to control the C / N ratio in the improver slurry to (20-30):1; 3. Mixing the feces obtained in step 1 with the composite coal gasification slag, wherein the mass fraction of the composite coal gasification slag is 0-10%, stirring in a compost fermentation reaction device for 30-60 minutes, and the fermentation temperature is 25-80°C. During fermentation, water is added to ensure that the moisture content of the material is 40-60%, and oxygen is introduced once a week for 20-24 hours and stirred for 30-60 minutes to ensure that the material is fermented in a sufficient amount of oxygen; when the pile temperature reaches 50-55°C, stirring the pile and turning it to cool it down, and fermenting for 30-45 days to obtain feces fermentation; Fourth, the coal gasification slag-based amendment prepared in step 2 is mixed with the feces fermentation product prepared in step 3, with the coal gasification slag-based amendment accounting for 60% to 80% by mass in the mixed system. The mixture is allowed to stand at room temperature for aging and fermentation for 20 to 30 days to obtain artificial soil.

2. A method for preparing composite soil conditioner and artificial soil by co-processing livestock and poultry manure with coal gasification slag, characterized in that The particle size of the coal gasification coarse slag in step 1 is between 1.2 mm and 4.75 mm, and is in the form of blocks or particles.

3. A method for preparing composite soil conditioner and artificial soil by co-processing livestock and poultry manure with coal gasification slag, characterized in that The coal gasification fine slag described in step 1 has a particle size of less than 1.2 mm and is in the form of powder or fine particles.

4. A method for preparing composite soil conditioner and artificial soil by co-processing livestock and poultry manure with coal gasification slag, characterized in that In step 1, the livestock manure is separated into solid and liquid by a screw extrusion separator to obtain manure and manure water.

5. A method for preparing composite soil conditioner and artificial soil by co-processing livestock and poultry manure with coal gasification slag, characterized in that In step 2, the composite coal gasification slag in step 1 is mixed with the sewage in step 1 for 12 hours to 24 hours.

6. A method for preparing composite soil conditioner and artificial soil by co-processing livestock and poultry manure with coal gasification slag, characterized in that The drying temperature in step 2 is 80°C.

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