Coal gangue treatment method

Abstract

The invention provides a coal gangue treatment method which comprises the following steps: 1) under the condition that the oxygen content is less than or equal to 0.5%, performing pyrolytic reaction on coal gangue to be treated and limestone by using a monatomic catalyst to obtain combustible gas and a first intermediate; 2) performing alkali treatment on the first intermediate to obtain a soluble aluminum salt solution and silicon slag; 3) adding carbon dioxide into the soluble aluminum salt solution to obtain an aluminum hydroxide precipitate, and 4) calcining the aluminum hydroxide precipitate to obtain aluminum oxide.The coal gangue treatment method provided by the invention can improve the decomposition efficiency and resource utilization rate of coal gangue.

Description

Technical Field

[0001] This invention belongs to the field of coal gangue processing technology, and particularly relates to a method for processing coal gangue. Background Technology

[0002] Coal gangue, a large amount of solid waste generated during coal mining and processing, has long been considered an environmental burden. However, with resource scarcity and increased environmental awareness, the comprehensive utilization of coal gangue has gradually become a research and application hotspot. Coal gangue is mainly composed of minerals such as silicon, aluminum, and iron, and has potential utilization value. Its utilization methods include the preparation of building materials, soil conditioners, chemical raw materials, and fuels. Among these, coal gangue combustion, as a direct utilization of its calorific value, has attracted much attention.

[0003] Despite the potential for cleaner and more efficient coal gangue combustion, several challenges remain in practical applications. First, the low volatile matter and high ash content of coal gangue result in low combustion efficiency, making complete combustion difficult. Second, existing combustion technologies are not fully adapted to the characteristics of coal gangue, leading to low resource utilization. Therefore, improving the decomposition efficiency and resource utilization of coal gangue has become a crucial direction for current technological research and development. Summary of the Invention

[0004] The main objective of this invention is to provide a method for processing coal gangue, which can improve the decomposition efficiency and resource utilization rate of coal gangue.

[0005] This invention provides a method for processing coal gangue, comprising the following steps:

[0006] 1) Under conditions of oxygen content ≤0.5%, a single-atom catalyst is used to carry out pyrolysis of coal gangue and limestone to be treated, to obtain combustible gas and a first intermediate;

[0007] 2) The first intermediate is subjected to a second alkali treatment to obtain a soluble aluminum salt solution and silicon slag;

[0008] 3) Carbon dioxide is added to the soluble aluminum salt solution to obtain aluminum hydroxide precipitate;

[0009] 4) The aluminum hydroxide precipitate is calcined to obtain aluminum oxide.

[0010] In the coal gangue treatment method described above, the temperature of the pyrolysis reaction is 600-900℃, preferably 700-800℃;

[0011] And / or, the pressure of the pyrolysis reaction is 0.1-1.0 MPa, preferably 0.1-0.4 MPa;

[0012] And / or, the pyrolysis reaction takes 30-60 minutes.

[0013] In the coal gangue treatment method described above, the mass ratio of the single-atom catalyst to the coal gangue to be treated is (1-10):1000, preferably (2-4):1000;

[0014] And / or, the single-atom catalyst comprises a carbon support and transition metal atoms supported on the carbon support, the transition metal atoms comprising at least one of Ni, Fe, and Co.

[0015] In the coal gangue treatment method described above, the mass ratio of the coal gangue to be treated to the limestone is 1:(0.5-1), preferably 1:(0.6-0.8).

[0016] In the coal gangue treatment method described above, the temperature of the alkali treatment is 60-90℃, preferably 70-80℃;

[0017] And / or, the alkali treatment time is 2-4 hours.

[0018] The coal gangue treatment method described above includes the following steps: adding sodium carbonate solution to the first intermediate and reacting to obtain the soluble aluminum salt solution and silica slag.

[0019] In the coal gangue treatment method described above, the mass concentration of the sodium carbonate solution is 15-25%.

[0020] And / or, the mass ratio of the sodium carbonate solution to the first intermediate is (3-5):1, preferably (3-4):1.

[0021] In the coal gangue treatment method described above, carbon dioxide is added to the soluble aluminum salt solution to adjust the pH of the system to 8.5-9.5, thereby obtaining the aluminum hydroxide precipitate.

[0022] In the coal gangue processing method described above, the calcination temperature is 950-1050℃ and the time is 1-2 hours.

[0023] The coal gangue treatment method described above further includes: crushing the coal gangue to be treated so that the proportion of particles with a diameter <20mm in the coal gangue to be treated is ≥95%.

[0024] The coal gangue processing method provided by this invention improves the decomposition efficiency and resource utilization rate of coal gangue by using a single-atom catalyst to carry out the pyrolysis reaction of the coal gangue to be treated, and then combining it with other processing methods. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] This invention provides a method for processing coal gangue, comprising the following steps:

[0027] 1) Under conditions of oxygen content ≤0.5%, a single-atom catalyst is used to carry out pyrolysis of coal gangue and limestone to be treated, to obtain combustible gas and a first intermediate;

[0028] 2) The first intermediate is subjected to alkali treatment to obtain a soluble aluminum salt solution and silicon slag;

[0029] 3) Adding carbon dioxide to a soluble aluminum salt solution yields aluminum hydroxide precipitate;

[0030] 4) The aluminum hydroxide precipitate is calcined to obtain aluminum oxide.

[0031] The coal gangue processing method provided by the present invention improves the decomposition efficiency and resource utilization rate of coal gangue by using a single-atom catalyst to carry out the pyrolysis reaction of the coal gangue to be treated.

[0032] For example, the oxygen content in step 1) can be a range of 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any two of these.

[0033] It is understandable that coal gangue is a solid waste generated during coal mining and washing. Its main components vary depending on the geological conditions of the coal mine and the type of coal. It mainly includes silicate minerals, aluminosilicate minerals, iron compounds, organic matter, and other impurities. Among these, silicate minerals are the most abundant component of coal gangue, usually existing in the form of quartz (SiO2) and feldspar. Aluminosilicate minerals include kaolinite (Al2Si2O5(OH)4), montmorillonite, etc., which are common clay minerals found in coal gangue. Iron compounds, such as pyrite (FeS2) and hematite (Fe2O3), give coal gangue a certain iron content. Carbonate minerals, such as calcite (CaCO3) and dolomite (CaMg(CO3)2), may also be present in some coal gangue. Organic matter includes small amounts of unburned organic carbon or coal that may remain in the coal gangue. Other impurities include small amounts of sulfides, phosphates, and other trace elements.

[0034] In step 1), it can be understood that a single-atom catalyst consists of metal dispersed on a support in the form of individual atoms, each atom being an active site, greatly increasing the effective contact area. Secondly, the strong interaction between the metal and the support can alter the reaction pathway and reduce the energy required for the reaction. That is, a single-atom catalyst can significantly reduce the pyrolysis activation energy, lower the pyrolysis temperature, and enhance the reactivity of the first intermediate, thereby improving subsequent leaching efficiency.

[0035] Using a single-atom catalyst in pyrolysis reactions under conditions of oxygen content ≤0.5% helps to maximize the decomposition of organic components in coal gangue, generating combustible gases such as CH4, H2, and CO. This not only improves pyrolysis efficiency but also reduces the amount of residual solid waste. The use of single-atom catalysts improves reaction selectivity and efficiency, resulting in milder reaction conditions and lower energy consumption. The first intermediate may include calcium silicate, alumina, iron compounds, and other impurities.

[0036] Specifically, the coal gangue to be processed can be fed into a closed rotary pyrolysis furnace containing a single-atom catalyst and limestone, where a pyrolysis reaction can be carried out. The generated combustible gas can be recovered through a condensation separation system, and the first intermediate can be stabilized for its high reactivity through a quenching device (water cooling or inert gas cooling).

[0037] By converting silicon dioxide in coal gangue into calcium silicate through pyrolysis, the aluminum and silicon components in the coal gangue can be effectively separated and extracted, thereby improving the utilization rate of resources.

[0038] In step 2), the first intermediate is subjected to alkali treatment, which generates soluble sodium aluminate and insoluble silicon slag. This process not only facilitates the extraction of silicon but also simplifies subsequent processing steps, making the entire process more efficient.

[0039] Specifically, the first intermediate can be added to a corrosion-resistant stirred reactor, along with an alkaline solution, and the reaction can be carried out under normal pressure to convert the alumina in the first intermediate into aluminate.

[0040] Specifically, a two-stage filtration system is used to separate the silicate precipitate, i.e., silica slag, to obtain a soluble aluminum salt solution. The silica slag also contains iron compounds and other impurities.

[0041] This invention does not limit the type of filtration system, as long as it ensures the separation of silica slag and soluble aluminum salt solution. Preferably, plate and frame filter press and ceramic membrane filtration can be used.

[0042] In step 3), carbon dioxide is added to the soluble aluminum salt solution to generate aluminum hydroxide precipitate. This process is not only simple and efficient, but also utilizes carbon dioxide, which helps reduce the carbon footprint of the process.

[0043] Specifically, a soluble aluminum salt solution can be added to a carbon separation tower and carbon dioxide gas can be introduced to adjust the pH and generate aluminum hydroxide precipitate.

[0044] In step 4), the aluminum hydroxide precipitate is calcined to obtain alumina. Calcination is a mature process that can effectively convert aluminum hydroxide into high-purity alumina, suitable for various industrial applications.

[0045] Specifically, aluminum hydroxide precipitate can be calcined and refined in a rotary kiln, and the particle size of alumina can be controlled and spherized by an air jet mill or spray granulation equipment.

[0046] Therefore, the coal gangue processing method provided by this invention achieves efficient separation and extraction of silicon and aluminum elements from coal gangue, maximizing its resource potential while reducing waste generation and environmental impact. This comprehensive processing method not only improves the decomposition efficiency of coal gangue but also significantly enhances resource utilization, resulting in good economic and environmental benefits. It is particularly suitable for processing low-calorific-value coal gangue.

[0047] In some embodiments of the present invention, the temperature of the pyrolysis reaction is 600-900°C, for example, it can be a range of 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C or any two of them, preferably 700-800°C.

[0048] Within the aforementioned temperature range, the organic components and some minerals in coal gangue can be effectively decomposed, releasing combustible gases and valuable byproducts such as tar. This temperature range helps to achieve efficient pyrolysis reactions while avoiding energy waste and equipment damage caused by excessively high temperatures.

[0049] In some embodiments, the pressure of the pyrolysis reaction is 0.1-1.0 MPa, for example, it can be a range of 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1.0 MPa or any two of these, preferably 0.1-0.4 MPa.

[0050] Under the aforementioned pyrolysis pressure, the reaction rate can be increased, which helps to improve pyrolysis efficiency. The relatively lower pressure requirements reduce equipment design and operating costs while improving safety.

[0051] In some embodiments, the pyrolysis reaction time is 30-60 min, for example, it can be a range of 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min or any combination thereof.

[0052] The aforementioned pyrolysis reaction time ensures the complete decomposition of organic components in the coal gangue, maximizing the production of gas and tar. Furthermore, this time range is suitable for continuous industrial production, facilitating stable process control and increased production capacity.

[0053] In some embodiments of the present invention, the mass ratio of the single-atom catalyst to the coal gangue to be treated is (1-10):1000, for example, it can be a range of 1:1000, 2:1000, 3:1000, 4:1000, 5:1000, 6:1000, 7:1000, 8:1000, 9:1000, 10:1000 or any two of these, preferably (2-4):1000.

[0054] Single-atom catalysts, due to their high dispersibility, can provide more active sites, thereby significantly improving catalytic efficiency. This high catalytic efficiency helps accelerate the pyrolysis of coal gangue. Furthermore, the mass ratio of single-atom catalyst to coal gangue being treated is as described above, meaning only a small amount of catalyst is needed to significantly improve reaction efficiency, which not only reduces the cost of catalyst use but also minimizes potential environmental impact.

[0055] In some embodiments, the single-atom catalyst includes a carbon support and transition metal atoms supported on the carbon support, wherein the transition metal atoms include at least one of Ni, Fe, and Co.

[0056] Transition metals such as Ni, Fe, and Co possess excellent catalytic properties and can participate in a variety of chemical reactions, including hydrogenation, dehydrogenation, and cracking. This makes single-atom catalysts versatile in processing coal gangue, adaptable to different reaction requirements. Carbon supports not only provide good dispersibility and stability but also excellent thermal conductivity and chemical stability, helping to maintain the catalyst's activity and structural integrity under high-temperature conditions.

[0057] By improving reaction selectivity and efficiency, single-atom catalysts can reduce the formation of unnecessary byproducts, thereby reducing environmental pollution. Furthermore, by selecting different transition metals and adjusting their loading methods on carbon supports, highly efficient catalysts for specific reactions can be designed. This tunability broadens the application range of catalysts.

[0058] The preparation method of the single-atom catalyst in this invention may include the following steps:

[0059] 1) Pretreatment of carbon support: Activated carbon, carbon nanotubes, or graphene are selected as the support. The carbon is refluxed with nitric acid (4-6 mol / L) for 4-8 hours at 70-90℃ to remove impurities and introduce surface functional groups. After washing and drying, activated carbon support (specific surface area ≥1000 m²) is obtained. 2 / g).

[0060] 2) Mix the transition metal salt solution, such as FeCl3 solution, Co(NO3)2 solution or NiCl2 solution with the activated carbon support, and use ultrasonic-assisted impregnation (30-50kHz, 1-3h) to ensure that the transition metal salt is uniformly adsorbed on the activated carbon support to obtain the intermediate; the loading of the transition metal can be 0.5-3wt%.

[0061] 3) Staged heat treatment under argon protection: First, heat the intermediate to 250-350℃ at 2-5℃ / min and hold for 0.5-2h to remove residual solvent. Then, heat to 700-900℃ at 3-8℃ / min and hold for 1-3h to allow metal atoms to combine with carbon defect sites and obtain pyrolysis products.

[0062] 4) Mix the pyrolysis product with urea (C:N=1:1.5-1:2.5) and treat it in an NH3 atmosphere at 650-750℃ for 0.5-2h to form an MNC (M includes at least one of Fe, Co, and Ni) active structure, thus obtaining a single-atom catalyst.

[0063] In some embodiments of the present invention, the mass ratio of the coal gangue to limestone to be treated is 1:(0.5-1), for example, it can be a range of 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1 or any two of them, preferably 1:(0.6-0.8).

[0064] The optimal mass ratio of coal gangue to limestone ensures that limestone fully participates in the reaction, providing sufficient calcium oxide to promote the conversion of silica. Furthermore, by optimizing the amount of limestone used, excessive use is avoided, reducing material costs and minimizing unnecessary solid waste generation.

[0065] In some embodiments of the present invention, the temperature of the alkali treatment is 60-90°C, for example, it can be a range of 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C or any combination thereof, preferably 70-80°C.

[0066] Within the aforementioned temperature range, alkali treatment can effectively generate soluble aluminum salt solutions and silica slag, which helps to improve the resource utilization rate of the final coal gangue.

[0067] In some embodiments, the alkali treatment time is 2-4 hours, for example, it can be a range of 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours or any two of these.

[0068] Within the aforementioned time frame, sufficient contact and reaction between the alkali and the material surface can be ensured, enhancing the material's reactivity and more effectively generating a soluble aluminum salt solution.

[0069] In some embodiments of the present invention, the alkali treatment includes: adding a sodium carbonate solution to a first intermediate and reacting to obtain a soluble aluminum salt solution and silicon slag.

[0070] Sodium carbonate provides an alkaline environment, which enhances the solubility of aluminum, thereby improving the extraction efficiency of aluminum salts.

[0071] In some embodiments of the present invention, the mass concentration of the sodium carbonate solution is 15-25%, for example, it can be a range of 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or any two of these.

[0072] When the sodium carbonate solution concentration is within the above-mentioned range, it provides a sufficiently alkaline environment to promote aluminum dissolution and improve the extraction efficiency of aluminum salts. Furthermore, the appropriate concentration facilitates solution preparation and processing, reducing operational complexity and safety risks.

[0073] In some embodiments, the mass ratio of sodium carbonate solution to the first intermediate is (3-5):1, for example, it can be a range of 3:1, 3.2:1, 3.5:1, 3.7:1, 4:1, 4.5:1, 5:1 or any two of them, preferably (3-4):1.

[0074] Maintaining the mass ratio of sodium carbonate solution to the first intermediate within the aforementioned range ensures sufficient contact and reaction between the reactants, improving reaction efficiency and product yield. Furthermore, optimizing the mass ratio reduces the excessive use of sodium carbonate, lowering chemical costs and minimizing the burden of wastewater treatment.

[0075] In some embodiments of the present invention, carbon dioxide is added to a soluble aluminum salt solution to adjust the pH of the system to 8.5-9.5, for example, it can be a range of 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5 or any two of them, to obtain aluminum hydroxide precipitate.

[0076] A pH range of 8.5-9.5 is optimal for aluminum hydroxide precipitation. Within this range, aluminum ions can be effectively converted into aluminum hydroxide precipitate, ensuring high precipitation efficiency and yield. Within this pH range, many impurity ions (such as iron and calcium) are less likely to form precipitates, thus improving the purity of aluminum hydroxide. Precise pH control allows adjustment of the particle size and morphology of the aluminum hydroxide precipitate, which is crucial for subsequent processing and applications. Using carbon dioxide as a pH adjuster is not only economical and readily available but also reduces environmental impact. Carbon dioxide forms carbonic acid in water, gradually releasing hydrogen ions and gently adjusting the pH.

[0077] In some embodiments of the present invention, the calcination temperature is 950-1050℃, for example, it can be a range of 950℃, 960℃, 970℃, 980℃, 990℃, 1000℃, 1010℃, 1020℃, 1030℃, 1040℃, 1050℃ or any two of these, and the time is 1-2h, for example, it can be a range of 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2h or any two of these.

[0078] The calcination temperature within the aforementioned range is sufficient to promote the conversion of aluminum hydroxide to alumina, while avoiding excessive grain growth or increased energy consumption due to excessively high temperatures. This temperature range facilitates the formation of the desired alumina phase (such as α-Al₂O₃), improving material properties. Furthermore, under these temperature and time conditions, the grain size of alumina can be effectively controlled, resulting in products with excellent physical and chemical properties. Additionally, under appropriate calcination conditions, volatile impurities in the material can be effectively removed, further improving product purity.

[0079] In some embodiments of the present invention, the method further includes: crushing the coal gangue to be processed so that the proportion of particles with a diameter <20mm in the coal gangue to be processed is ≥95%, for example, it can be a range of 95%, 96%, 97%, 98%, 99%, 100% or any two of them.

[0080] For example, the particle size can be a range of 1 mm, 2 mm, 5 mm, 8 mm, 10 mm, 12 mm, 15 mm, 17 mm, 18 mm, 19 mm or any two of these.

[0081] Before processing coal gangue, it is first crushed, i.e., pretreatment. This significantly increases the specific surface area of ​​the gangue, thereby increasing the contact area with chemical reagents (such as alkaline solutions), promoting the reaction, and improving the reaction rate and efficiency. Simultaneously, smaller and more uniform particle sizes help achieve a more uniform reaction in subsequent chemical processing, ensuring consistency and controllability of the treatment effect. Furthermore, crushing allows for more effective utilization of valuable components in the coal gangue, reducing waste of unreacted materials and improving resource utilization.

[0082] This invention does not limit the type of crusher used for crushing, and may include jaw crushers, cone crushers, drum crushers, impact crushers, roller crushers, hammer crushers, etc., as long as the crushed coal gangue can achieve a particle size of <20mm with a particle size of ≥95%.

[0083] Preferably, a jaw crusher combined with a drum crusher can be used. Specifically, a jaw crusher can be used for coarse crushing to achieve a particle size of 50-100mm, followed by secondary crushing with a drum crusher to <20mm, and finally a vibrating screen can be used to achieve a particle size of <20mm with a proportion of ≥95%.

[0084] In summary, the coal gangue processing method provided by this invention enables comprehensive resource utilization and energy recovery. Through single-atom catalyst pyrolysis technology, the carbon components in the coal gangue are directionally cracked under low oxygen content conditions to generate high-value-added combustible gases. Carbon, aluminum, silicon, and other elements in the coal gangue are respectively converted into combustible gases, alumina, and silicon-based materials, achieving complete resource utilization with a efficiency exceeding 95%. Furthermore, this processing method is not limited to high-calorific-value coal gangue but is also suitable for processing low-calorific-value coal gangue.

[0085] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0086] Example 1

[0087] The coal gangue processing method of this embodiment includes the following steps:

[0088] 1) Take 1000 kg of low-calorific-value coal gangue from a coal mine in northern Shaanxi (the main components are SiO2, Al2O3, Fe2O3, etc., with a calorific value of about 4MJ / kg), crush and screen it with a jaw crusher and a drum crusher until the proportion of particles with a diameter of less than 20mm is 95%.

[0089] 2) The self-made single-atom catalyst (the single-atom catalyst uses nitrogen-doped activated carbon as a support and loads two transition metals, Fe and Co, with a loading of 2wt%) is mixed with the above-mentioned coal gangue and limestone. The mass ratio of the single-atom catalyst to the coal gangue is 2:1000 and the mass ratio of the coal gangue to the limestone is 1:0.7. The mixture is pyrolyzed for 45 minutes under the conditions of 0.5% oxygen content, 700℃ and 0.1MPa to recover combustible gases (H2, CO) and obtain the first intermediate.

[0090] 3) The first intermediate was added to a 20wt% Na2CO3 solution (the mass ratio of Na2CO3 solution to the first intermediate was 3.5:1), and the mixture was stirred at 75℃ and normal pressure for 3 hours to obtain a soluble sodium aluminate solution and an insoluble silica slag.

[0091] 4) Pass CO2 (1L / min) into the NaAlO2 solution and control the final pH to 9.0 to generate Al(OH)3 precipitate. After centrifugation and dehydration, the Al(OH)3 precipitate is calcined in a rotary kiln at 1000℃ for 1.5h and finally pulverized by air jet to obtain alumina powder.

[0092] Example 2

[0093] The treatment method of coal gangue in this embodiment is basically the same as that in Example 1, except that the temperature of the pyrolysis reaction is 600℃, the pressure is 1.0MPa, and the time is 30min.

[0094] Example 3

[0095] The treatment method of coal gangue in this embodiment is basically the same as that in Example 1, except that the temperature of the pyrolysis reaction is 800℃, the pressure is 0.4MPa, and the time is 60min.

[0096] Example 4

[0097] The processing method of coal gangue in this embodiment is basically the same as that in Example 1, except that the temperature of the pyrolysis reaction is 900℃.

[0098] Example 5

[0099] The method for processing coal gangue in this embodiment is basically the same as that in Example 1, except that the mass ratio of the single-atom catalyst to the coal gangue is 1:1000.

[0100] Example 6

[0101] The method for processing coal gangue in this embodiment is basically the same as that in Example 1, except that the mass ratio of the single-atom catalyst to the coal gangue is 4:1000.

[0102] Example 7

[0103] The method for processing coal gangue in this embodiment is basically the same as that in Example 1, except that the mass ratio of the single-atom catalyst to the coal gangue is 10:1000.

[0104] Example 8

[0105] The treatment method of this embodiment is basically the same as that of Example 1 for coal gangue, except that the temperature of the alkali treatment is 60°C and the time is 2 hours.

[0106] Example 9

[0107] The treatment method of this embodiment is basically the same as that of Example 1 for coal gangue, except that the temperature of the alkali treatment is 90℃ and the time is 4h.

[0108] Example 10

[0109] The treatment method of this embodiment is basically the same as that of Example 1 for coal gangue, except that the temperature of the alkali treatment is 70°C.

[0110] Example 11

[0111] The treatment method of this embodiment is basically the same as that of Example 1 for coal gangue, except that the temperature of the alkali treatment is 80°C.

[0112] Example 12

[0113] The method for processing coal gangue in this embodiment is basically the same as that in Embodiment 1, except that the mass ratio of the coal gangue to be processed to limestone is 1:0.5.

[0114] Example 13

[0115] The method for processing coal gangue in this embodiment is basically the same as that in Embodiment 1, except that the mass ratio of the coal gangue to be processed to limestone is 1:1.

[0116] Example 14

[0117] The method for processing coal gangue in this embodiment is basically the same as that in Embodiment 1, except that the mass ratio of the coal gangue to be processed to limestone is 1:0.6.

[0118] Example 15

[0119] The method for processing coal gangue in this embodiment is basically the same as that in Embodiment 1, except that the mass ratio of the coal gangue to be processed to limestone is 1:0.8.

[0120] Example 16

[0121] The method for processing coal gangue in this embodiment is basically the same as that in Embodiment 1, except that the mass concentration of sodium carbonate solution is 25% and the mass ratio of sodium carbonate solution to the first intermediate is 3:1.

[0122] Example 17

[0123] The method for processing coal gangue in this embodiment is basically the same as that in Embodiment 1, except that the mass concentration of the sodium carbonate solution is 15% and the mass ratio of the sodium carbonate solution to the first intermediate is 4:1.

[0124] Example 18

[0125] The method for processing coal gangue in this embodiment is basically the same as that in Embodiment 1, except that the mass ratio of sodium carbonate solution to the first intermediate is 5:1.

[0126] Comparative Example 1

[0127] The treatment method of this comparative example is basically the same as that of coal gangue in Example 1, except that the catalyst used in the pyrolysis reaction is ferric oxide.

[0128] Comparative Example 2

[0129] The treatment method of this comparative example is basically the same as that of coal gangue in Example 1. The difference is that the pyrolysis reaction does not use a catalyst, but is carried out for 45 minutes under the conditions of 0.5% oxygen content, 1200℃ and 0.1MPa.

[0130] Experimental example:

[0131] 1. Aluminum leaching rate: Aluminum leaching rate = mass of aluminum in leachate / mass of total aluminum in coal gangue × 100%.

[0132] The mass of aluminum in the leachate: The aluminum content in the soluble aluminosilicate solution was determined by ICP-OES (inductively coupled plasma optical emission spectrometry) or chemical titration.

[0133] The total aluminum content in coal gangue was determined by XRF (X-ray fluorescence spectroscopy) or ICP-OES after acid digestion, and then converted into the mass of aluminum element.

[0134] 2. Purity of silicon slag: Purity of silicon slag = mass of SiO2 in silicon slag / total mass of silicon slag × 100%.

[0135] Mass of SiO2 in silicon slag: The SiO2 content in silicon slag is determined by XRF or chemical analysis methods (such as gravimetric method).

[0136] Total mass of silicon slag: The dried mass of silicon slag obtained after pulverization and separation and filtration.

[0137] 3. Alumina purity: Alumina purity = mass of Al2O3 / total mass of alumina powder × 100%.

[0138] The quality of Al2O3: The content of Al2O3 in calcined alumina powder was determined by quantitative analysis of XRD (X-ray diffraction) or chemical titration.

[0139] Total mass of alumina powder: the dried mass of the product after calcination.

[0140] Table 1. Aluminum leaching rate, silica slag purity, and alumina purity of Examples 1-18 and Comparative Examples 1-2

[0141]

[0142] As shown in Table 1, compared with the comparative example, the coal gangue treatment method provided by the present invention can improve the decomposition efficiency and resource utilization rate of coal gangue by using a single-atom catalyst to carry out the pyrolysis reaction of the coal gangue to be treated, and then combining it with other treatment methods.

[0143] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to what has been described above. Various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for processing coal gangue, characterized in that, Includes the following steps: 1) Under conditions of oxygen content ≤0.5%, a single-atom catalyst is used to carry out pyrolysis of coal gangue and limestone to be treated, to obtain combustible gas and a first intermediate; 2) The first intermediate is subjected to alkali treatment to obtain a soluble aluminum salt solution and silicon slag; 3) Carbon dioxide is added to the soluble aluminum salt solution to obtain aluminum hydroxide precipitate; 4) The aluminum hydroxide precipitate is calcined to obtain aluminum oxide.

2. The method for processing coal gangue according to claim 1, characterized in that, The temperature of the pyrolysis reaction is 600-900℃, preferably 700-800℃; And / or, the pressure of the pyrolysis reaction is 0.1-1.0 MPa, preferably 0.1-0.4 MPa; And / or, the pyrolysis reaction takes 30-60 minutes.

3. The method for processing coal gangue according to claim 1, characterized in that, The mass ratio of the single-atom catalyst to the coal gangue to be treated is (1-10):1000, preferably (2-4):1000; And / or, the single-atom catalyst comprises a carbon support and transition metal atoms supported on the carbon support, the transition metal atoms comprising at least one of Ni, Fe, and Co.

4. The method for processing coal gangue according to claim 1, characterized in that, The mass ratio of the coal gangue to be processed to the limestone is 1:(0.5-1), preferably 1:(0.6-0.8).

5. The method for processing coal gangue according to claim 1, characterized in that, The temperature of the alkali treatment is 60-90℃, preferably 70-80℃; And / or, the alkali treatment time is 2-4 hours.

6. The method for processing coal gangue according to claim 5, characterized in that, The alkaline treatment includes: adding sodium carbonate solution to the first intermediate, and reacting to obtain the soluble aluminum salt solution and silicon slag.

7. The method for processing coal gangue according to claim 6, characterized in that, The sodium carbonate solution has a mass concentration of 15-25%; And / or, the mass ratio of the sodium carbonate solution to the first intermediate is (3-5):1, preferably (3-4):

1.

8. The method for processing coal gangue according to claim 1, characterized in that, Carbon dioxide is added to the soluble aluminum salt solution to adjust the pH of the system to 8.5-9.5, thereby obtaining the aluminum hydroxide precipitate.

9. The method for processing coal gangue according to claim 1, characterized in that, The calcination treatment is carried out at a temperature of 950-1050℃ for 1-2 hours.

10. The method for processing coal gangue according to any one of claims 1-9, characterized in that, Also includes: The coal gangue to be processed is crushed so that the proportion of particles with a diameter of <20mm in the coal gangue to be processed is ≥95%.

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