Preparation method and application of gasified slag-based carbon-silicon composite material

Abstract

The invention discloses a preparation method and application of a gasified slag-based carbon-silicon composite material, the method comprises the following steps: gasified slag alkali reaction: alkali and gasified slag are reacted, and ash in the gasified slag is fully activated by using pore channels in the gasified slag; carrying out acid reaction on the gasified slag: washing the gasified slag reacted with the alkali with water to remove redundant alkali and alkali soluble substances, then adding an acid solution for reaction to remove acid soluble substances, and precipitating silicon dioxide in pores of carbon of the gasified slag to obtain a carbon / silicon dioxide intermediate; reduction of the carbon / silicon dioxide intermediate: reducing silicon dioxide contained in the obtained carbon / silicon dioxide intermediate to prepare a carbon / silicon composite material; according to the invention, the gasified slag is utilized to the greatest extent, and the carbon obtained after the gasified slag is subjected to high-temperature treatment has good conductivity; silicon dioxide is reduced in porous carbon, and the mixing uniformity of carbon and silicon is good.

Description

Technical Field

[0001] This invention belongs to the field of disposal, utilization and resource utilization technology of coal chemical solid waste, and relates to the disposal and utilization technology of gasification slag, and particularly to a method for preparing gasification slag-based carbon silicon composite material and its application. Background Technology

[0002] Coal gasification is a crucial operational unit in modern coal chemical industry, providing the syngas and hydrogen required for coal chemical processes. Coal gasification slag, also known as gasification residue, is a solid waste generated during the gasification process of coal or coke in a gasifier, where it reacts with gasifying agents such as oxygen and steam under high-temperature conditions to produce syngas. Gasification slag can be further divided into coarse gasification slag and fine gasification slag. Coarse gasification slag consists of relatively large, blocky particles formed after molten slag flows down the gasifier wall to the bottom and solidifies upon cooling. Fine gasification slag consists of small particles carried by the gas flow to a dust removal device, where they are collected after washing and settling.

[0003] The main components of gasification slag are residual carbon and silicon-containing ash. Developing carbon-silicon materials based on gasification slag is an important way to efficiently and effectively utilize gasification slag. Current methods for preparing carbon-silicon composite materials include hydrothermal synthesis, mechanical synthesis, chemical vapor deposition, and biomass synthesis. Hydrothermal synthesis involves a hydrothermal reaction of organosilicon compounds with a solvent to prepare silicon-containing microspheres, which are then further carbonized and reduced to obtain the carbon-silicon composite material. Mechanical synthesis involves ball milling carbon-containing raw materials with silicon, followed by pyrolysis after pitch coating. Chemical vapor deposition involves introducing silane into porous carbon, followed by high-temperature pyrolysis and deposition of nano-silicon to obtain the carbon-silicon composite material.

[0004] To address the aforementioned issues, there is an urgent need to develop a gasification slag-based carbon-silicon composite material that can fully utilize the residual carbon and silicon elements in gasification slag, thereby achieving the resource utilization and high-value utilization of gasification slag.

[0005] Currently, there are insufficient methods for the disposal and utilization of gasification slag, with stockpiling and landfilling being the main approaches, leading to environmental damage and pollution problems. This technology provides a new method for utilizing gasification slag and disposing of it properly.

[0006] Currently, the high cost and limited availability of raw materials for silicon-carbon composite materials restrict the development of related applications. This invention develops a special process that cleverly combines the porous characteristics of gasification slag residue and the silicon element in the gasification slag ash, thus expanding the technical raw material sources for traditional silicon-carbon composite materials.

[0007] This aspect mainly solves the special process problems of gasification slag treatment, preparation of intermediates for carbon / silicon composite materials, and process problems of reducing intermediates to prepare carbon / silicon composite materials. Summary of the Invention

[0008] This invention provides a method for preparing a carbon / silicon composite material based on gasification slag and its application. This method processes gasification slag, cleverly utilizing the residual carbon component and silicon element in the ash to prepare a carbon / silicon composite material. Therefore, this method provides a solution for the resource utilization and high-value-added processing of coal gasification slag. Simultaneously, by innovating a special treatment process for gasification slag, it also expands the raw material sources for traditional carbon / silicon composite materials, which can promote the development of related applications.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a gasification slag-based carbon-silicon composite material includes the following steps: Step S1, Alkali reaction of gasification slag: A certain proportion of alkali is reacted with gasification slag at a certain temperature, and the ash in the gasification slag is fully activated by utilizing the pores in the gasification slag. Step S2, acid reaction of gasification slag: For the gasification slag that has reacted with alkali at a certain temperature, wash away excess alkali and alkali solubles with water, then add acid to react and remove acid solubles, while allowing silica to precipitate in the carbon channels of the gasification slag. After washing with water and drying, a carbon / silica intermediate is obtained. Step S3, Reduction of carbon / silica intermediate: The carbon / silica intermediate is reduced to obtain carbon / silica composite material. Step S4: Purification of the carbon / silicon composite material: After reduction of the carbon / silicon dioxide intermediate, the carbon / silicon composite material is further purified by washing with dilute acid. The mass ratio of acid to (carbon / silicon composite material) is 0.5-30:1, preferably 1-15:1, and the concentration of dilute acid is 1-30wt%, preferably 5-20wt%. The reaction is stirred at 5-95℃ for 0.1-24hr, preferably 0.2-12hr. Excess metals and impurities are washed away by filtration, and the mixture is dried to obtain the carbon / silicon composite material.

[0010] As a preferred embodiment, in step S1, the mass ratio of alkali to gasification slag is 0.5-10:1, preferably 1-5:1.

[0011] As a preferred embodiment, in step S1, the alkali is any one or a mixture of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, and potassium bicarbonate.

[0012] As a preferred embodiment, in step S1, the reaction temperature between the gasification slag and the alkali is 300-1000℃, preferably 320-680℃.

[0013] As a preferred embodiment, in step S1, the alkaline reaction time is 0.1-6 hours, preferably 0.2-3 hours.

[0014] If the reaction time is too short or the temperature is too low, the ash in the gasification slag will not be fully activated; if the reaction time is too long or the temperature is too high, the residual carbon in the gasification slag will react with the alkali, resulting in excessive loss and reducing the utilization rate of the gasification slag. At the same time, the loss of alkali will also affect the activation of the ash in the gasification slag, resulting in an increase in impurities in the carbon / silica intermediates and carbon / silicon composite materials.

[0015] As a preferred embodiment, in step S2, the acid / gasification slag mass ratio is 0.5-30:1, preferably 1-15:1.

[0016] As a preferred embodiment, in step S2, the reaction temperature is 5-95℃ and the acid reaction time is 0.1-6hr, preferably 0.2-3hr.

[0017] As a preferred embodiment, in step S2, the acid solution is a dilute acid, specifically, an inorganic acid such as sulfuric acid, nitric acid, or hydrochloric acid, or an organic acid such as formic acid, acetic acid, oxalic acid, or citric acid. The concentration of the dilute acid is 1-30 wt%, preferably 5-20 wt%. A low acid / gasification slag mass ratio will affect impurity removal and silica deposition in the residual carbon channels of the gasification slag; therefore, sufficient acid and suitable reaction conditions must be ensured.

[0018] As a preferred embodiment, in step S3, the obtained carbon / silica intermediate is reduced by methods such as aluminothermic, magnesian, carbothermic, molten salt, or hydrogen reduction.

[0019] As a preferred embodiment, in step S4, the dilute acid is an inorganic acid such as sulfuric acid, nitric acid, or hydrochloric acid, or an organic acid such as formic acid, acetic acid, oxalic acid, or citric acid.

[0020] A carbon / silicon composite material obtained by the above preparation method is used to prepare a battery anode.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention provides a new approach for the disposal and utilization of gasification slag with high added value; 2. This invention makes maximum use of the gasification slag itself as raw material, including residual carbon and ash; 3. This invention provides a novel method for preparing carbon / silicon materials. The carbon obtained after high-temperature treatment of gasification slag exhibits good electrical conductivity; silicon dioxide is reduced in porous carbon, resulting in good carbon-silicon mixing uniformity. Attached Figure Description

[0022] Figure 1 This is a flowchart of a method for preparing a gasification slag-based carbon-silicon composite material according to the present invention. Detailed Implementation

[0023] The present invention will be further described below with reference to embodiments.

[0024] Figure 1 This is a flowchart illustrating a method for preparing a gasification slag-based carbon-silicon composite material proposed in this invention. According to the flowchart, gasification slag and alkali are added to the alkaline reaction unit, and an activation reaction is carried out under controlled conditions. In the acid reaction unit, dilute acid is added to remove impurities and precipitate carbon dioxide in the pores of the gasification slag. In the carbon / silicon dioxide intermediate reduction unit, a reducing agent is added to reduce silicon dioxide under certain conditions to obtain the carbon / silicon composite material, which can be used in fields such as battery anodes.

[0025] The yield of residual carbon from gasification slag after alkali treatment is defined as: Y = m2 / m1 × %. Wherein, m1 is the mass of a unit mass of dried gasification slag reduced by ignition at 815℃ according to GB / T 34231-2017 "Determination of Loss on Ignition of Coal Combustion Residues", and m2 is the mass of the same mass of dried gasification slag reduced by ignition at 815℃ after alkali treatment and washing and drying.

[0026] Example 1: The gasification slag produced by a coal chemical enterprise has a loss on ignition of 48.3% and a BET specific surface area of ​​283m. 2 / g. The ash composition of the gasified slag after burn-off was determined by XRF, as shown in Table 1.

[0027] Table 1. Chemical composition (%) of gasification slag ash determined by XRF.

[0028]

[0029] Sodium hydroxide was mixed with gasification slag at a weight ratio of alkali to gasification slag of 3:1. Nitrogen gas was introduced into a tubular furnace, and the mixture was heated to 650°C for 1 hour to activate the reaction. After cooling, excess alkali and alkali-soluble substances were washed away with water, and the mixture was dried. Testing showed that the alkali recovery rate from the residual carbon in the gasification slag was 70%.

[0030] Add 10wt% hydrochloric acid at a mass ratio of 15:1, stir and react at 60℃ for 1 hour, filter, wash, and dry to obtain a carbon / silica intermediate. XRF analysis was performed, and the composition is shown in Table 2.

[0031] Table 2. Chemical composition (%) of carbon / silica intermediates prepared under XRF detection at 650℃ for 1hr.

[0032]

[0033] Take 5g of carbon / silicon dioxide intermediate, add 0.3g of metallic aluminum, and heat to 700℃ in a tube furnace under argon gas, performing aluminothermic reduction for 3 hours. Add 10% hydrochloric acid at a mass ratio of 15:1, and stir the reaction at 60℃ for 3 hours. Filter to wash away excess metallic aluminum and impurities, and dry to obtain the carbon / silicon composite material. XRF analysis was performed, and the composition is shown in Table 3.

[0034] Table 3. Chemical composition (%) of carbon / silicon composite materials prepared under XRF detection at 650℃ for 1hr.

[0035]

[0036] Example 2: The gasification slag from Example 1 was taken and mixed with potassium hydroxide and sodium hydroxide (in a 1:1 ratio) at an alkali / gasification slag ratio of 5:1. Nitrogen gas was introduced into a tubular furnace and the mixture was heated to 360°C for 3 hours to activate the reaction. After cooling, excess alkali and alkali-soluble substances were washed away with water, and the mixture was dried. The yield of residual carbon from the gasification slag after alkali treatment was found to be 85%. 20 wt% sulfuric acid was added at a mass ratio of 3:1, and the mixture was stirred at 90°C for 0.5 hours. Other operations were the same as in Example 1 to prepare the carbon / silica intermediate and the carbon / silicon composite material.

[0037] Example 3: The gasification slag from Example 1 was taken and mixed with potassium hydroxide and sodium hydroxide (1:1 ratio) at an alkali / gasification slag ratio of 6:1. Nitrogen gas was introduced into a tubular furnace and the mixture was heated to 750°C for 1.5 hours to activate the reaction. After cooling, excess alkali and alkali-soluble substances were washed away with water and dried. The yield of residual carbon from the gasification slag after alkali treatment was found to be 25%. 5 wt% nitric acid was added at a mass ratio of 25:1, and the mixture was stirred at 15°C for 12 hours. Other operations were the same as in Example 1 to prepare the carbon / silica intermediate and the carbon / silicon composite material.

[0038] Example 4: The gasification slag from Example 1 was taken and mixed with sodium hydroxide, sodium bicarbonate, sodium carbonate, potassium hydroxide, potassium bicarbonate, and potassium carbonate (in a ratio of 1:1:1:1:1:1) at an alkali / gasification slag ratio of 3:1. Nitrogen gas was introduced into a tube furnace and the mixture was heated to 850°C for 5 hours to activate the reaction. After cooling, excess alkali and alkali-soluble substances were washed away with water and dried. The yield of residual carbon from the gasification slag after alkali treatment was found to be 10%. 10 wt% acetic acid was added at a mass ratio of 10:1, and the mixture was stirred at 40°C for 6 hours. Other operations were the same as in Example 1 to prepare the carbon / silica intermediate and the carbon / silicon composite material. The composition of the carbon / silica intermediate and the carbon / silicon composite material was determined by XRF, as shown in Tables 4 and 5.

[0039] Table 4. Chemical composition (%) of carbon / silica intermediates prepared under XRF detection at 850℃ for 5 hours.

[0040]

[0041] Table 5. Chemical composition (%) of carbon / silicon composite materials prepared under XRF detection at 850℃ for 5 hours.

[0042]

[0043] Example 5: Take 1 g of the carbon / silica intermediate prepared in Example 1, and sample it according to the ratio of intermediate:aluminum powder:anhydrous aluminum chloride 1:0.8:8. Mix it evenly in a polytetrafluoroethylene liner and load it into a stainless steel reactor. Place the sealed autoclave in an oven and heat it to 200°C for molten salt reduction for 10 h. Take out the product after natural cooling, and react it with 10% sulfuric acid at 60°C for 6 h at a mass ratio of 30:1 to remove unreacted aluminum powder, anhydrous aluminum chloride and by-products. After washing and drying, the gasification slag-based carbon-silicon composite material is obtained.

[0044] Example 6: Take 1 g of the carbon / silica intermediate prepared in Example 1, pass hydrogen gas into a tube furnace and heat to 1200°C, reduce with hydrogen gas for 2 h, and cool to obtain gasified slag-based carbon-silica composite material.

[0045] Example 7: Take 1 g of the carbon / silica intermediate prepared in Example 1, pass argon gas into a high-temperature muffle furnace and heat to 2000℃, carbotherm reduction for 5 h, and obtain gasified slag-based carbon-silica composite material after cooling.

[0046] Example 8: Take 1 g of the carbon / silica intermediate prepared in Example 1, and mix it with magnesium chloride at a ratio of 1:0.8:6. Introduce argon gas in a tube furnace and heat to 700°C for magnesium thermal reduction for 5 h. Remove the product after natural cooling, and react it with 30% sulfuric acid at 90°C for 3 h at a mass ratio of 10:1 to remove byproducts such as magnesium oxide and magnesium silicide. After washing and drying, obtain the gasified slag-based carbon-silica composite material.

[0047] Comparative Example 1: Based on 202510086415.3 The gasification slag from Example 1 was ball-milled, physically floated, and then ground using a sand mill. It was then acid-washed to remove impurities, using 15% hydrochloric acid at a slag:hydrochloric acid mass ratio of 1:10. After filtration with 10wt% alkali (slag:sodium hydroxide mass ratio of 1:10), the filtrate was treated with a template agent, cetyltrimethylammonium bromide, and subjected to a hydrothermal reaction at 90-130°C to prepare silica molecular sieves. The template agent was then removed by calcination at 500-650°C. Subsequently, the silica molecular sieves were reduced with hydrogen at 1200°C to obtain a nano-silicon framework. This nano-silicon framework was then composited with organic carbon polyvinyl alcohol (PCE) at a mass ratio of 1:10, and calcined in nitrogen at 700°C to obtain a C / Si composite material.

[0048] As can be seen from Examples 1-8 and Comparative Example 1 above, compared with Patent 202510086415.3, this invention proposes a novel method for preparing gasification slag carbon / silicon composite materials. Its advantages lie in fully utilizing the carbon and silicon resources in the gasification slag. The carbon in the gasification slag after high-temperature treatment exhibits good electrical conductivity. The invention innovatively employs a carbon / silica intermediate route to prepare gasification slag-based carbon / silicon composite materials, and the direct reduction of carbon and silicon by silica in the porous carbon of the gasification slag results in good uniformity of the mixture. As can be seen from Examples 1-4, as the reaction time between the alkali and the gasification slag becomes too long or the temperature too high, the yield of residual carbon from the gasification slag after alkali treatment decreases significantly, while the impurities in the carbon / silica intermediate and the carbon / silicon composite material increase significantly.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a gasification slag-based carbon-silicon composite material, characterized in that, Includes the following steps: S1. Alkali reaction of gasification slag: Alkali reacts with gasification slag, and the ash in the gasification slag is fully activated by utilizing the pores in the gasification slag. S2. Acid reaction of gasification slag: For the gasification slag after reaction with alkali, wash away excess alkali and alkali solubles with water, then add acid to react and remove acid solubles, while causing silica to precipitate in the carbon channels of the gasification slag. After washing with water and drying, a carbon / silica intermediate is obtained. S3, Reduction of carbon / silica intermediate: The carbon / silica intermediate is reduced to reduce the silica contained therein to prepare a carbon / silica composite material.

2. The method for preparing gasification slag-based carbon-silicon composite material according to claim 1, characterized in that, In step S1, the mass ratio of alkali to gasification slag is 0.5-10:1; The alkali is any one or a mixture of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, and potassium bicarbonate.

3. The method for preparing gasification slag-based carbon-silicon composite material according to claim 1, characterized in that, In step S1, the reaction temperature between the gasification slag and the alkali is 300-1000℃. In step S1, the alkaline reaction time is 0.1-6 hours.

4. The method for preparing gasification slag-based carbon-silicon composite material according to claim 1, characterized in that, In step S2, the acid / gasification slag mass ratio is 0.5-30:

1. The acid solution is a dilute acid with a concentration of 1-30 wt%.

5. The method for preparing gasification slag-based carbon-silicon composite material according to claim 1, characterized in that, In step S2, the reaction temperature is 5-95℃ and the acid reaction time is 0.1-24hr.

6. The method for preparing gasification slag-based carbon-silicon composite material according to claim 1, characterized in that, In step S3, the obtained carbon / silica intermediate is reduced by aluminothermic, magnesian, carbothermic, molten salt, or hydrogen reduction methods.

7. The method for preparing gasification slag-based carbon-silicon composite material according to claim 4, characterized in that, It also includes the following steps: S4. Purification of carbon / silicon composite material: After the carbon / silicon dioxide intermediate in step S3 is reduced, it is washed with dilute acid to remove impurities and further purify the carbon / silicon composite material. The mass ratio of acid to carbon / silicon composite material is 0.5-30:1, and the acid concentration is 1-30wt%. The reaction is stirred at 5-95℃ for 0.1-24 hours. Excess metals and impurities are filtered and washed, and then dried to obtain the carbon / silicon composite material.

8. The method for preparing gasification slag-based carbon-silicon composite material according to claim 7, characterized in that, The dilute acid is any one of sulfuric acid, nitric acid, hydrochloric acid, formic acid, acetic acid, oxalic acid, and citric acid.

9. The method for preparing gasification slag-based carbon-silicon composite material according to claim 7, characterized in that, In step S1, the alkali / gasification slag mass ratio is 1-5:1, the reaction temperature of the gasification slag and alkali is 320-680℃, and the alkali reaction time is 0.2-3hr. In step S2, the acid / gasification slag mass ratio is 1-15:1, the acid reaction time is 0.2-3 hours, and the dilute acid concentration is 5-20 wt%. In step S4, the mass ratio of acid to carbon / silicon composite material is 1-15:1, and the concentration of dilute acid is 5-20wt%.

10. The carbon / silicon composite material obtained by any one of the preparation methods according to claims 1-9 is used to prepare a battery anode.

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