A method for preparing artificial soil based on coal gangue

Abstract

This invention relates to a method for preparing artificial soil based on coal gangue, specifically including the following steps: (1) screening coal gangue; (2) crushing the screened coal gangue and crushing diatomaceous earth; (3) mixing the crushed coal gangue and diatomaceous earth; (4) heat treatment: heating the mixed coal gangue and diatomaceous earth to remove crystallization water; (5) rapid cooling: spraying water to rapidly cool the dehydrated materials; (6) maturation: piling the rapidly cooled materials for natural maturation to form artificial soil; (7) analyzing and evaluating the artificial soil. Compared with existing coal gangue artificial soil preparation technologies, the method for preparing artificial soil based on coal gangue of this invention is simpler, lower in cost, and produces environmentally friendly soil. The method uses thermal energy to remove crystallization water from coal gangue and diatomaceous earth, and the heating temperature is 450-550℃, which ensures the removal of crystallization water from the treated materials without causing combustion loss of carbon in the coal gangue.

Description

Technical Field

[0001] This invention relates to the fields of soil reconstruction technology and comprehensive resource utilization technology, specifically to a method for preparing artificial soil mainly composed of coal gangue. Background Technology

[0002] Coal gangue is a solid waste generated during coal mining and washing. It is a dark gray rock with a low carbon content and harder than coal, which is associated with coal seams during coal formation. It includes gangue from tunnel excavation, gangue extracted from the roof, floor, and interlayers during mining, and gangue from coal washing. Its main components are SiO2 and Al2O3, and it also contains varying amounts of Fe2O3, CaO, MgO, Na2O, K2O, P2O5, SO3, and trace rare elements (gallium, vanadium, titanium, cobalt). Its emissions are equivalent to about 15-25% of the annual coal production, making it one of the largest sources of industrial and mining solid waste in my country, with a cumulative stockpile of nearly 5 billion tons, covering an area of ​​approximately 120,000 hectares. The large-scale dumping of coal gangue not only encroaches on land and impacts the ecological environment, but the leachate from the gangue also pollutes the surrounding soil and groundwater. Furthermore, coal gangue contains combustible materials that can spontaneously combust under suitable conditions, releasing harmful gases such as sulfur dioxide, nitrogen oxides, carbon oxides, and soot, polluting the atmosphere and affecting the health of residents in mining areas. With the increasing enforcement of national environmental protection laws and rising public demands for environmental quality, addressing the environmental pollution caused by coal gangue has become increasingly crucial. Since the 1960s, many countries have begun to pay attention to the treatment and utilization of coal gangue. The utilization methods can be summarized as follows: (1) Recovering coal and pyrite, and using the residue as building materials; (2) Using it for power generation: mainly using middlings and washed gangue to generate electricity, the calorific value of the mixture is about 2000 kcal per kg, and the slag can be used to produce slag bricks and slag cement; (3) Manufacturing building materials: replacing clay as a raw material for brick making, utilizing the calorific value of coal gangue itself, and saving coal; (4) Replacing clay components to produce ordinary cement and sintering lightweight aggregates; (5) Coal gangue can also be used to produce low-calorific-value gas, manufacture ceramics, make soil conditioners, or be used for paving roads, underground filling, and surface filling for land reclamation.

[0003] The chemical composition of coal gangue is related to the coal formation process and the surrounding geological structure. Generally, the alumina content is around 20% and the iron oxide content is around 8%. Compared with other regions, the alumina content in southern my country is lower and the iron oxide content is higher. In addition, the calcium and magnesium content in coal gangue generally exceeds 5%, and some even reach more than 15%, which is not conducive to the direct refining of gangue bricks. However, it is rich in rare elements, which is more beneficial to plant cultivation.

[0004] In the preparation of soil from coal gangue, most methods involve grinding to meet the requirements for soil particle size and physical properties, followed by the addition of other nutrients or microorganisms, achieving good results. However, the physical properties of the soil or its environmental impact have not been evaluated. Existing technologies for meeting the requirements for soil particle size and physical properties through grinding include the following:

[0005] The patent with patent number CN109438116B, entitled "A Method for Preparing Soil Conditioner by Modifying Coal Gangue and Wood Ash," describes a process where coal gangue is mechanically ground and ultra-micro activated in a steam mill to obtain coal gangue with a particle size of 2μm to 10μm; wood ash is dehydrated and ground to obtain wood ash with a mesh size of 60 to 200 mesh, wherein the mass fraction of potassium in the wood ash is 10% to 15%; the coal gangue and wood ash are uniformly mixed and then calcined at a temperature of 600℃ to 900℃ for 0.5 to 2 hours, and then allowed to cool naturally to room temperature to obtain a silicon-potassium fertilizer; the silicon-potassium fertilizer is then compounded with weathered coal at a mass ratio of 1:(0.1 to 10), and then granulated to obtain the soil conditioner.

[0006] The patent with patent number CN116376562A, entitled "A Method for Preparing a Novel Coal Gangue Soil Conditioner", comprises 50-60 parts modified coal gangue, 10-20 parts vermiculite, 10-15 parts potassium humate, 3-5 parts phosphogypsum powder, 1-2 parts ammonium sulfate, and 1-2 parts potassium phosphate. The preparation process is as follows: (1) First, dry the coal gangue at 120°C, then pulverize it to a particle size between 80-100 mesh. Take two-thirds of the coal gangue and place it in a sealed container. Heating under air-isolated conditions, with the temperature controlled between 400-600℃, reacting for 1-2 hours, then stopping heating and allowing the coal gangue to cool naturally under air-isolated conditions. The cooled coal gangue and the remaining one-third of the unreacted coal gangue are mixed together, and the resulting product is modified coal gangue. (2) Vermiculite, potassium humate, phosphogypsum powder, ammonium sulfate, and potassium phosphate solids are mixed together, and the resulting solids are then fully mixed with the modified coal gangue. The final product is the result of the mixture.

[0007] Existing technologies for preparing artificial soil by directly incorporating a portion of natural soil or by synergistically adding microorganisms include the following:

[0008] The patent with patent number CN104630109B, entitled "Microbial Agent for Reclaiming Coal Gangue Hill Soil and Method for Reclaiming Coal Gangue Soil Using the Agent," describes a method of layering and covering a coal gangue hill with soil, and then applying a microbial agent to each layer. The reclaimed coal gangue soil is arranged from bottom to top as follows: a first gangue layer, a mixed layer of clay loess and fly ash, a second gangue layer, a fly ash layer, a fine-particle gangue layer, and a loess layer. The microbial agent consists of three independently used types: Type I, Type II, and Type III. Type I microbial agent is applied to the mixed clay loess and fly ash layer, Type II to the fly ash layer, and Type III to the loess layer. Crops are planted on the loess layer. Calcium magnesium phosphate fertilizer is used as an active additive, with an addition amount of 8-15 wt% of the total amount of Type III microbial agent.

[0009] The patent with patent number CN112789964A, entitled "A Method for Preparing Artificial Soil for Ecological Restoration," involves reconstructing coal gangue and soil in different compound ratios. The process includes drying the coal gangue and soil, crushing and grinding them, and sieving them. The coal gangue to soil compound ratio is (1:9)-(1:5). A 1766.25cm-3 ring cutter is used for soil reconstruction and filling. The soil bulk density is fixed at 1.3g / cm³. Mixing coal gangue and soil in this ratio significantly improves the latter's water retention capacity.

[0010] Patent CN115443879A, entitled "A Method for Preparing Matrix-Based Coal Gangue and a Seedling Substrate Based on Coal Gangue," describes a process where coal gangue is crushed to obtain coal gangue particles, and different particle sizes are mixed in a specific ratio. Biomass and water are mixed and added to a high-pressure hydrothermal reactor for hydrothermal carbonization. After solid-liquid separation, solid hydrothermal carbon and a hydrothermal solution are obtained. The mixed coal gangue particles, hydrothermal carbon, and soil are thoroughly mixed to prepare matrix-based coal gangue. The obtained coal gangue matrix is ​​then mixed with the hydrothermal carbonization solution and a small amount of chemical fertilizer to obtain a seedling substrate.

[0011] Existing technologies indicate that coal gangue can be used to prepare artificial soil. After modification, the addition of nutrients, or direct mixing with natural soil, the resulting artificial soil is rich in nutrients and has good physical properties. However, none of these methods address the evaluation of the leaching content of pollutants in the coal gangue, nor do they consider the environmental impact during use. On the other hand, to ensure the physical properties of artificial soil, most methods employ grinding processes, which are costly and difficult to promote on a large scale. Drawing on existing technological experience and addressing existing problems, this invention proposes selecting coal gangue whose leachate contains major basic elements at levels lower than the maximum limits for Class III water quality in the GB3838-2002 Surface Water Environmental Quality Standard. The process involves heating to remove free water and most of the crystalline water from the coal gangue, followed by rapid cooling and maturation via water spraying. This utilizes internal heat energy to accelerate feldspar weathering, promote the dissociation of aluminosilicate minerals, and synergistically induce the shrinkage and expansion of clay minerals, thus completing the soil transformation of the coal gangue. Furthermore, leveraging the high specific surface area, abundant mesopores, strong adsorption capacity, and ease of mudification of diatomaceous earth, the physicochemical properties of the coal gangue-based artificial soil are improved. Simultaneously, pollutants in the artificial soil are stabilized, ensuring that the heavy metal content in the leachate is lower than the maximum limits for Class III water quality in the GB3838-2002 Surface Water Environmental Quality Standard, meeting the requirements for soil remediation materials. Summary of the Invention

[0012] The purpose of this invention is to provide a method for preparing artificial soil based on coal gangue to improve the utilization rate of coal gangue resources, solve the practical problem of large-scale stockpiling of coal gangue, and provide artificial soil with excellent physical properties for soil remediation of barren mountains, mine pits, etc.

[0013] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing artificial soil primarily composed of coal gangue is provided, the innovation of which lies in the following steps:

[0014] (1) Screening coal gangue;

[0015] (2) The screened coal gangue is crushed and the diatomite is crushed;

[0016] (3) Mix the crushed coal gangue and diatomaceous earth at a dry basis mass ratio of 7-9:1-3;

[0017] (4) Heat treatment: The mixed coal gangue and diatomaceous earth are heated to remove crystallization water. The heating temperature is 450-550℃ and the heating time is 30-60min.

[0018] (5) Sudden cooling: The material after decrystallization is sprayed with water for sudden cooling, and the material is kept moist.

[0019] (6) Maturation: The materials that have been rapidly cooled are piled up and naturally matured until they form artificial soil;

[0020] (7) The prepared artificial soil was analyzed and evaluated.

[0021] Furthermore, the leachate from the coal gangue screened in step (1) contains less than 1.0 mg / L of copper, less than 1.0 mg / L of zinc, and less than 1.0 mg / L of F. - Content less than 1.0 mg / L, arsenic content less than 0.05 mg / L, mercury content less than 0.0001 mg / L, cadmium content less than 0.005 mg / L, Cr +6 The content of lead is less than 0.05 mg / L, the content of volatile phenols is less than 0.005 mg / L, the content of sulfides is less than 0.2 mg / L, and the pH of the leachate from the screened coal gangue is 6-9.

[0022] Furthermore, the particle size requirements for the crushed coal gangue in step (2) are as follows: the weight ratio of particles with a diameter >20mm is <5%, the weight ratio of particles with a diameter of 10-20mm is ≤20%, the weight ratio of particles with a diameter of 5-10mm is ≤30%, the weight ratio of particles with a diameter of 1-5mm is >30%, and the weight ratio of particles with a diameter <1mm is >15%.

[0023] Furthermore, in step (6), the time range for natural maturation of the material is 15-30 days, and the material is kept moist during the maturation period.

[0024] Furthermore, the analysis and evaluation in step (7) includes determining that the copper content in the leachate of the artificial soil is less than 1.0 mg / L, the zinc content is less than 1.0 mg / L, and the F content is less than 1.0 mg / L. - Content less than 1.0 mg / L, arsenic content less than 0.05 mg / L, mercury content less than 0.0001 mg / L, cadmium content less than 0.005 mg / L, Cr +6 The content of pollutants is less than 0.05 mg / L, lead content is less than 0.05 mg / L, volatile phenol content is less than 0.005 mg / L, sulfide content is less than 0.2 mg / L, and the pH of the leachate in the artificial soil is 6-9.

[0025] Furthermore, the analysis and evaluation in step (7) includes the following particle size range for artificial soil: <1% by weight for particles >10mm, <3% by weight for particles 8-10mm, <5% by weight for particles 5-8mm, <15% by weight for particles 4-5mm, >15% by weight for particles 3-4mm, >15% by weight for particles 2-3mm, >20% by weight for particles 1-2mm, and >30% by weight for particles <1mm.

[0026] Furthermore, the analysis and evaluation in step (7) includes the loose density of the artificial soil being <1.1 kg / dm³. 3 The pH range is 6.5-7, the water retention rate is ≥55%, the loss rate is ≤2.0%, and the porosity is ≥60%.

[0027] Furthermore, the analysis and evaluation in step (7) includes using artificial soil as soil remediation material for barren mountains, abandoned mines, and gullies, and for planting artificial forests and pastures, and then for economic purposes or planting crops.

[0028] Compared with the prior art, the beneficial effects of this invention are as follows:

[0029] (1) Compared with the existing coal gangue-based artificial soil preparation technology, the artificial soil preparation method of the present invention is simple, low-cost, and produces pollution-free soil, which is environmentally friendly.

[0030] (2) The method for preparing artificial soil based on coal gangue of the present invention uses thermal energy to remove the crystal water of coal gangue and diatomite. During heating, the heat treatment temperature is 450-550℃, which ensures that the treated material is dehydrated without causing the combustion loss of carbon in the coal gangue.

[0031] (3) The present invention provides a method for preparing artificial soil based on coal gangue. This method utilizes the characteristics of diatomaceous earth—high specific surface area, abundant mesopores, strong adsorption, and easy mudification—to improve the physicochemical properties of the coal gangue artificial soil. Simultaneously, it stabilizes pollutants in the artificial soil. The resulting soil leachate contains major basic pollutants at levels lower than the maximum limits for Class III water in the GB3838-2002 Surface Water Environmental Quality Standard, and has a loose density of <1.1 kg / dm³. 3 It has a pH range of 6.5-7, a water retention rate of ≥55%, a loss rate of ≤2.0%, and a porosity of ≥60%. It can be used as a soil remediation material for barren mountains, abandoned mines, and valleys, and for planting artificial forests and pastures, followed by economic uses or crop cultivation. It is an environmentally friendly soil. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a flowchart of a method for preparing artificial soil based on coal gangue, according to the present invention. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below through specific embodiments.

[0035] This invention provides a method for preparing artificial soil mainly composed of coal gangue, the specific process of which is as follows: Figure 1 As shown, the specific steps include:

[0036] (1) Screening of coal gangue; the screened coal gangue is coal gangue whose content of the main basic items in its leachate is less than the maximum limit of Class III water in GB3838-2002 Surface Water Environmental Quality Standard. The specific parameters are shown in Table 1 (except for pH, the units of the other parameters in the table are mg / L):

[0037] Table 1

[0038] content pH copper Zinc <![CDATA[F - ]]> arsenic mercury cadmium <![CDATA[Cr +6 ]]> lead volatile phenols sulfides Standard requirements 6-9 1.0 1.0 1.0 0.05 0.0001 0.005 0.05 0.05 0.005 0.2

[0039] Specifically, the leachate from the screened coal gangue contained copper content less than 1.0 mg / L, zinc content less than 1.0 mg / L, and F... - Content less than 1.0 mg / L, arsenic content less than 0.05 mg / L, mercury content less than 0.0001 mg / L, cadmium content less than 0.005 mg / L, Cr +6 The content of lead is less than 0.05 mg / L, the content of volatile phenols is less than 0.005 mg / L, the content of sulfides is less than 0.2 mg / L, and the pH of the leachate from the screened coal gangue is 6-9.

[0040] (2) The screened coal gangue is crushed, and the diatomaceous earth is crushed; the particle size requirements of the crushed coal gangue are shown in Table 2:

[0041] Table 2

[0042] Particle size (mm) ＞20 10-20 5-10 1-5 ＜1 Percentage (wt%) ＜5 ≤20 ≤30 ＞30 ＞15

[0043] Specifically: the weight ratio of particles with a diameter >20mm is <5%, the weight ratio of particles with a diameter of 10-20mm is ≤20%, the weight ratio of particles with a diameter of 5-10mm is ≤30%, the weight ratio of particles with a diameter of 1-5mm is >30%, and the weight ratio of particles with a diameter <1mm is >15%.

[0044] (3) Mix the crushed coal gangue and diatomaceous earth at a dry basis mass ratio of 7-9:1-3;

[0045] (4) Heat treatment: The mixed coal gangue and diatomaceous earth are heated to remove crystallization water. The heating temperature is 450-550℃ and the heating time is 30-60min.

[0046] (5) Sudden cooling: The material after decrystallization is sprayed with water for sudden cooling (the material must be taken out immediately after the heating time is up and sprayed with water for sudden cooling) and the material is kept moist.

[0047] (6) Maturation: The material after rapid cooling is piled up and naturally matured. The natural maturation time range is 15-30 days. During the maturation period, water is sprayed to keep the material moist according to the air humidity until artificial soil is formed.

[0048] (7) The prepared artificial soil was analyzed and evaluated.

[0049] The principle of the artificial soil preparation method based on coal gangue of the present invention is to use heating to remove crystallization water and then spray water for rapid cooling. The internal heat energy is used to accelerate the weathering of feldspar and promote the dissociation of aluminosilicate minerals. At the same time, due to the shrinkage and expansion of clay minerals, the expansion of coal gangue particles can be accelerated. After a certain period of maturation, the transformation of coal gangue into soil is completed, which greatly shortens the weathering time of coal gangue.

[0050] The artificial soil prepared by the method of this invention produces artificial soil with leachate containing major basic components at levels lower than the maximum limits for Class III water quality in GB3838-2002 Surface Water Environmental Quality Standard. Specifically, the leachate contains less than 1.0 mg / L copper, less than 1.0 mg / L zinc, and less than 1.0 mg / L sulfur. - Content less than 1.0 mg / L, arsenic content less than 0.05 mg / L, mercury content less than 0.0001 mg / L, cadmium content less than 0.005 mg / L, Cr +6 The content of pollutants is less than 0.05 mg / L, lead content is less than 0.05 mg / L, volatile phenol content is less than 0.005 mg / L, sulfide content is less than 0.2 mg / L, and the pH of the leachate in the artificial soil is 6-9.

[0051] The particle size range of the artificial soil prepared by this invention is shown in Table 3:

[0052] Table 3

[0053] Particle size (mm) ＞10 8-10 5-8 4-5 3-4 2-3 1-2 ＜1 Percentage (wt%) ＜1 ＜3 ＜5 ＜15 ＞15 ＞15 ＞20 ＞30

[0054] Specifically: the weight ratio of particles with a diameter >10mm is <1%, the weight ratio of particles with a diameter of 8-10mm is <3%, the weight ratio of particles with a diameter of 5-8mm is <5%, the weight ratio of particles with a diameter of 4-5mm is <15%, the weight ratio of particles with a diameter of 3-4mm is >15%, the weight ratio of particles with a diameter of 2-3mm is >15%, the weight ratio of particles with a diameter of 1-2mm is >20%, and the weight ratio of particles with a diameter <1mm is >30%.

[0055] The main material properties of the artificial soil prepared by this invention are shown in Table 4:

[0056] Table 4

[0057] Loose packing density pH Water retention rate Churn rate Thermal insulation Porosity <![CDATA[<1.1kg / dm 3 ]]> 6.5-7 ≥55％ ≤2.0％ Superior to natural soil (comparison results) ≥60％

[0058] The artificial soil based on coal gangue of this invention is environmentally friendly and has excellent performance. It can be used as a soil remediation material for barren mountains, abandoned mines, and valleys, and can also be used for planting artificial forests and pastures. Afterward, it can be used for economic purposes or for planting crops.

[0059] Based on the above technical solutions, the following embodiments further describe the solutions of the present invention.

[0060] Example 1

[0061] (1) Screening of coal gangue; The specific parameters of the coal gangue screened in this embodiment are shown in Table 5 (except for pH, the units of the other parameters in the table are mg / L):

[0062] Table 5

[0063] content pH copper Zinc <![CDATA[F - ]]> arsenic mercury cadmium <![CDATA[Cr +6 ]]> lead volatile phenols sulfides Standard requirements 6.5 0.8 0.5 0.6 0.03 0.00006 0.004 0.04 0.03 0.003 0.1

[0064] (2) The screened coal gangue is crushed, and the diatomaceous earth is crushed; the particle size requirements of the crushed coal gangue in this embodiment are shown in Table 6:

[0065] Table 6

[0066] Particle size (mm) ＞20 10-20 5-10 1-5 ＜1 Percentage (wt%) 3 20 23 36 18

[0067] (3) Mix the crushed coal gangue and diatomaceous earth at a dry weight ratio of 8:2;

[0068] (4) Heat treatment: The mixed coal gangue and diatomaceous earth are heated to remove crystallization water. The heating temperature is 450℃ and the heating time is 60min.

[0069] (5) Sudden cooling: The material after decrystallization is sprayed with water for sudden cooling, and the material is kept moist.

[0070] (6) Maturation: The material after rapid cooling is piled up and naturally matured. The natural maturation time range is 30 days. During the maturation period, water is sprayed every 3 days to keep the material moist until artificial soil is formed.

[0071] (7) The prepared artificial soil was analyzed and evaluated.

[0072] The content of major basic items in the leachate of the artificial soil prepared in this embodiment is less than the maximum limit of Class III water in GB3838-2002 Surface Water Environmental Quality Standard.

[0073] The particle size range of the artificial soil prepared in this embodiment is shown in Table 7:

[0074] Table 7

[0075] Particle size (mm) ＞10 8-10 5-8 4-5 3-4 2-3 1-2 ＜1 Percentage (wt%) 0.8 2.1 2.5 8.6 17 16 21 32

[0076] Specifically: the weight ratio of particles with a diameter >10mm is 0.8%, the weight ratio of particles with a diameter of 8-10mm is 2.1%, the weight ratio of particles with a diameter of 5-8mm is 2.5%, the weight ratio of particles with a diameter of 4-5mm is 8.6%, the weight ratio of particles with a diameter of 3-4mm is 17%, the weight ratio of particles with a diameter of 2-3mm is 16%, the weight ratio of particles with a diameter of 1-2mm is 21%, and the weight ratio of particles with a diameter <1mm is 32%.

[0077] The main physical properties of the artificial soil prepared in this embodiment are shown in Table 8 after testing.

[0078] Table 8

[0079] Loose packing density pH Water retention rate Churn rate Thermal insulation Porosity <![CDATA[1.05kg / dm 3 ]]> 6.5 57％ 1.9％ Superior to natural soil (comparison results) ≥63％

[0080] The artificial soil based on coal gangue in this embodiment is environmentally friendly and has excellent performance. It can be used as a material for the remediation of barren mountain soil, and for the planting of artificial forests and pastures, and can then be used for economic purposes.

[0081] Example 2

[0082] (1) Screening of coal gangue; The specific parameters of the coal gangue screened in this embodiment are shown in Table 9 (except for pH, the units of the other parameters in the table are mg / L):

[0083] Table 9

[0084] content pH copper Zinc <![CDATA[F - ]]> arsenic mercury cadmium <![CDATA[Cr +6 ]]> lead volatile phenols sulfides Standard requirements 6.0 0.9 0.8 0.5 0.04 0.00008 0.004 0.03 0.04 0.004 0.15

[0085] (2) The screened coal gangue is crushed, and the diatomaceous earth is crushed; the particle size requirements of the crushed coal gangue in this embodiment are shown in Table 10:

[0086] Table 10

[0087] Particle size (mm) ＞20 10-20 5-10 1-5 ＜1 Percentage (wt%) 4 18 21 37 20

[0088] (3) Mix the crushed coal gangue and diatomaceous earth at a dry weight ratio of 9:1.

[0089] (4) Heat treatment: The mixed coal gangue and diatomaceous earth are heated to remove crystallization water. The heating temperature is 500℃ and the heating time is 45min.

[0090] (5) Sudden cooling: The material after decrystallization is sprayed with water for sudden cooling, and the material is kept moist.

[0091] (6) Maturation: The material after rapid cooling is piled up and naturally matured. The natural maturation time range is 20 days. During the maturation period, water is sprayed every 3 days to keep the material moist until artificial soil is formed.

[0092] (7) The prepared artificial soil was analyzed and evaluated.

[0093] The content of major basic items in the leachate of the artificial soil prepared in this embodiment is less than the maximum limit of Class III water in GB3838-2002 Surface Water Environmental Quality Standard.

[0094] The particle size range of the artificial soil prepared in this embodiment is shown in Table 11:

[0095] Table 11

[0096] Particle size (mm) ＞10 8-10 5-8 4-5 3-4 2-3 1-2 ＜1 Percentage (wt%) 0.8 2.5 3.5 7.2 16 18 21 31

[0097] Specifically, the weight percentage of particles with a diameter >10mm is 0.8%, the weight percentage of particles with a diameter of 8-10mm is 2.5%, the weight percentage of particles with a diameter of 5-8mm is 3.5%, the weight percentage of particles with a diameter of 4-5mm is 7.2%, the weight percentage of particles with a diameter of 3-4mm is 16%, the weight percentage of particles with a diameter of 2-3mm is 18%, the weight percentage of particles with a diameter of 1-2mm is 21%, and the weight percentage of particles with a diameter <1mm is 31%.

[0098] The main physical properties of the artificial soil prepared in this embodiment are shown in Table 12 after testing.

[0099] Table 12

[0100] Loose packing density pH Water retention rate Churn rate Thermal insulation Porosity <![CDATA[1.08kg / dm 3 ]]> 6.2 55％ 1.7％ Superior to natural soil (comparison results) ≥60％

[0101] The artificial soil based on coal gangue in this embodiment is environmentally friendly and has excellent performance. Its particle size distribution and main characteristic indicators are similar to those of natural soil. It can be used as a soil remediation material for abandoned mines, and can also be used for planting artificial forests and pastures, and subsequently for economic purposes.

[0102] Example 3

[0103] (1) Screening of coal gangue; The specific parameters of the coal gangue screened in this embodiment are shown in Table 13 (except for pH, the units of the other parameters in the table are mg / L):

[0104] Table 13

[0105] content pH copper Zinc <![CDATA[F - ]]> arsenic mercury cadmium <![CDATA[Cr +6 ]]> lead volatile phenols sulfides Standard requirements 7.5 0.5 0.3 0.8 0.04 0.00008 0.003 0.04 0.04 0.003 0.15

[0106] (2) The screened coal gangue is crushed, and the diatomaceous earth is crushed; the particle size requirements of the crushed coal gangue in this embodiment are shown in Table 14:

[0107] Table 14

[0108] Particle size (mm) ＞20 10-20 5-10 1-5 ＜1 Percentage (wt%) 4 15 24 33 24

[0109] (3) Mix the crushed coal gangue and diatomaceous earth at a dry weight ratio of 7:3.

[0110] (4) Heat treatment: The mixed coal gangue and diatomaceous earth are heated to remove crystallization water at a temperature of 550℃ for 30 minutes.

[0111] (5) Sudden cooling: The material after decrystallization is sprayed with water for sudden cooling, and the material is kept moist.

[0112] (6) Maturation: The material after rapid cooling is piled up and naturally matured. The natural maturation time range is 15 days. During the maturation period, water is sprayed every 3 days to keep the material moist until artificial soil is formed.

[0113] (7) The prepared artificial soil was analyzed and evaluated.

[0114] The content of major basic items in the leachate of the artificial soil prepared in this embodiment is less than the maximum limit of Class III water in GB3838-2002 Surface Water Environmental Quality Standard.

[0115] The particle size range of the artificial soil prepared in this embodiment is shown in Table 15:

[0116] Table 15

[0117] Particle size (mm) ＞10 8-10 5-8 4-5 3-4 2-3 1-2 ＜1 Percentage (wt%) 0.2 1.5 2.5 4.3 16 17.5 23 35

[0118] Specifically: the weight ratio of particles with a diameter >10mm is 0.2%, the weight ratio of particles with a diameter of 8-10mm is 1.5%, the weight ratio of particles with a diameter of 5-8mm is 2.5%, the weight ratio of particles with a diameter of 4-5mm is 4.3%, the weight ratio of particles with a diameter of 3-4mm is 16%, the weight ratio of particles with a diameter of 2-3mm is 17.5%, the weight ratio of particles with a diameter of 1-2mm is 23%, and the weight ratio of particles with a diameter <1mm is 35%.

[0119] The main physical properties of the artificial soil prepared in this embodiment are shown in Table 16 after testing.

[0120] Table 16

[0121] Loose packing density pH Water retention rate Churn rate Thermal insulation Porosity 1.02％ 6.8 59％ 1.8％ Superior to natural soil (comparison results) ≥68％

[0122] The artificial soil based on coal gangue in this embodiment is environmentally friendly and has excellent performance. Its particle size distribution and main characteristic indicators are similar to those of natural soil. It can be used as a soil remediation material in gullies, and can also be used for planting artificial forests and pastures, and then for planting crops.

Claims

1. A method for preparing artificial soil mainly composed of coal gangue, characterized in that: Specifically, the following steps are included: (1) Screening coal gangue; (2) The screened coal gangue is crushed, and the diatomaceous earth is crushed; (3) Mix the crushed coal gangue and diatomaceous earth at a dry weight ratio of 7-9:1-3; (4) Heat treatment: The mixed coal gangue and diatomaceous earth are heated to remove crystallization water. The heating temperature is 450-550℃ and the heating time is 30-60min. (5) Sudden cooling: The material after decrystallization is sprayed with water for sudden cooling, and the material is kept moist. (6) Maturation: The materials that have been rapidly cooled are piled up and naturally matured until they form artificial soil; (7) The prepared artificial soil was analyzed and evaluated. The loose density of the artificial soil was <1.1 kg / dm³, the pH range was 6.5-7, the water retention rate was ≥55%, the loss rate was ≤2.0%, and the porosity was ≥60%.

2. The method for preparing artificial soil mainly composed of coal gangue according to claim 1, characterized in that: The leachate from the coal gangue screened in step (1) contains less than 1.0 mg / L of copper, less than 1.0 mg / L of zinc, and less than 1.0 mg / L of F. - Content less than 1.0 mg / L, arsenic content less than 0.05 mg / L, mercury content less than 0.0001 mg / L, cadmium content less than 0.005 mg / L, Cr +6 The content of coal gangue is less than 0.05 mg / L, lead content is less than 0.05 mg / L, volatile phenol content is less than 0.005 mg / L, sulfide content is less than 0.2 mg / L, and the pH of the leachate from the screened coal gangue is 6-9.

3. The method for preparing artificial soil mainly composed of coal gangue according to claim 1, characterized in that: The particle size requirements for the crushed coal gangue in step (2) are as follows: the weight ratio of particles with a diameter >20mm is <5%, the weight ratio of particles with a diameter of 10-20mm is ≤20%, the weight ratio of particles with a diameter of 5-10mm is ≤30%, the weight ratio of particles with a diameter of 1-5mm is >30%, and the weight ratio of particles with a diameter <1mm is >15%.

4. The method for preparing artificial soil mainly composed of coal gangue according to claim 1, characterized in that: In step (6), the time range for natural maturation of the material is 15-30 days, and the material is kept moist during the maturation period.

5. The method for preparing artificial soil mainly composed of coal gangue according to claim 1, characterized in that: The analysis and evaluation in step (7) includes determining the copper content, zinc content, and F content in the leachate of the artificial soil to be less than 1.0 mg / L and less than 1.0 mg / L, respectively. - Content less than 1.0 mg / L, arsenic content less than 0.05 mg / L, mercury content less than 0.0001 mg / L, cadmium content less than 0.005 mg / L, Cr +6 The content of pollutants is less than 0.05 mg / L, lead content is less than 0.05 mg / L, volatile phenol content is less than 0.005 mg / L, sulfide content is less than 0.2 mg / L, and the pH of the leachate in the artificial soil is 6-9.

6. The method for preparing artificial soil mainly composed of coal gangue according to claim 1, characterized in that: The analysis and evaluation in step (7) includes the following particle size range for artificial soil: <1% by weight for particles >10mm, <3% by weight for particles 8-10mm, <5% by weight for particles 5-8mm, <15% by weight for particles 4-5mm, >15% by weight for particles 3-4mm, >15% by weight for particles 2-3mm, >20% by weight for particles 1-2mm, and >30% by weight for particles <1mm.

7. The method for preparing artificial soil mainly composed of coal gangue according to claim 1, characterized in that: The analysis and evaluation in step (7) includes using artificial soil as soil remediation material for barren mountains, abandoned mines, and valleys, and for planting artificial forests and pastures, and then for economic purposes or planting crops.

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