Coal gangue-based solid fuel and preparation method thereof

Abstract

The invention discloses a coal gangue-based solid fuel which comprises pulverized coal, coal gangue particles, a binder, a combustion improver and a sulfur-fixing agent. After the combustion improver prepared by the method disclosed by the invention is added into the solid fuel, the ignition point of the fuel can be obviously reduced, the flammability index of the fuel is improved, and the combustion performance of the solid fuel is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fuels, and particularly to a coal gangue-based solid fuel and a preparation method thereof. Background Art

[0002] Coal gangue is a solid waste generated during the construction and mining of coal mines and awaits large-scale utilization. The existing stockpile is extremely large. The traditional treatment methods are direct burial and incineration, which bring great pressure to energy and the environment. Therefore, finding a reasonable way to treat coal gangue is very beneficial to green development.

[0003] At present, a common treatment method is to make coal gangue into solid fuel. The preparation method of coal gangue solid fuel is as follows: After crushing coal gangue, by adding a certain proportion of pulverized coal, combustion aids, sulfur-fixing agents, binders, etc., and using a forming machine, directly produce a solid-shaped fuel with a stable calorific value. This solid-shaped fuel can be used as fuel for boilers, cooking stoves, and other combustion devices, and has good social, environmental, and economic benefits. However, the combustion aids selected have an unsatisfactory effect on coal gangue-based fuels and need to be further improved. Summary of the Invention

[0004] For this reason, the present invention provides a coal gangue-based solid fuel, including pulverized coal, coal gangue particles, binder, combustion aid, sulfur-fixing agent, and the preparation method of the combustion aid is as follows: (1) Add n-butanol, octylphenol polyoxyethylene ether, and tetrabutyl titanate to absolute ethanol, stir for more than 20 min to obtain a mixed solution; prepare a composite solution of magnesium nitrate and iron nitrate; heat the mixed solution in a water bath to 60 ± 5 °C for insulation, and then add the composite solution of magnesium nitrate and iron nitrate to the mixed solution under stirring. After the addition is completed, continue to stir for more than 30 min, then add sodium hydroxide solution, stir for more than 30 min after the addition, keep it at 60 ± 5 °C for static aging for more than 12 h. After aging, place it in a closed reaction kettle, heat it to 100 °C for hydrothermal insulation for more than 20 h, perform solid-liquid separation, wash the solid phase with deionized water more than 2 times and with ethanol more than 2 times, dry it, and calcine it at 500 - 550 °C to obtain magnesium-iron composite oxide powder; (2) Add calcium nitrate and cerium nitrate to deionized water, stir to fully dissolve to obtain an aqueous solution, then heat the aqueous solution in a water bath to 85 ± 3 °C for insulation, and then add citric acid and the magnesium-iron composite oxide powder to the aqueous solution under stirring. After the addition, keep it at 85 ± 3 °C for stirring for 3 - 4 h to obtain a composite gel; place the composite gel in an environment of 110 ± 5 °C for drying for more than 15 h to dehydrate and embrittle it, then heat it to 250 - 280 °C for insulation for 3 - 4 h, pulverize it to obtain precursor particles, heat the precursor particles to 800 - 820 °C for insulation for more than 15 h, and then cool it to room temperature with the furnace to obtain coated particles; (3) Prepare an aqueous solution of nickel nitrate; add the coated particles to the aqueous solution of nickel nitrate under stirring. After the addition is completed, continue stirring for more than 20 min to obtain a suspension. Then, add potassium permanganate to the suspension under stirring. After the addition is completed, continue stirring for more than 30 min. Then, let it stand in a negative pressure environment for more than 20 h. Separate the solid from the liquid. Dry the solid at 100 - 120 °C for more than 3 h, and then calcine it at 450 - 480 °C for more than 5 h to obtain the post-treatment powder; (4) Add alkyl glycoside and the post-treatment powder to an aqueous solution of ethanol, and stir for more than 30 min under an ultrasonic environment to obtain a dispersion; heat the dispersion in a water bath to 60 ± 3 °C, and continue constant-temperature stirring for more than 40 h after reaching the temperature; then, add sodium hydroxide, ethylene glycol diglycidyl ether, and isopropanol under stirring. After the addition is completed, raise the temperature to 80 ± 3 °C, keep the temperature and stir for more than 3 h, and then naturally cool to room temperature. Separate the solid from the liquid. Wash the solid with deionized water more than 3 times and with ethanol more than 3 times, and then dry it to obtain the combustion promoter.

[0005] Further, the sulfur-fixing agent is calcium oxide powder; the binder is polyvinyl alcohol.

[0006] Further, each raw material is in parts by weight: 90 - 100 parts of pulverized coal, 100 parts of coal gangue particles, 15 - 20 parts of binder, 10 - 12 parts of combustion promoter, and 5 - 8 parts of sulfur-fixing agent.

[0007] Further, in the step (1), the mass ratio of adding n-butanol, octylphenol polyoxyethylene ether, and tetrabutyl titanate to anhydrous ethanol is n-butanol: octylphenol polyoxyethylene ether: tetrabutyl titanate: anhydrous ethanol = 2 - 3: 2 - 3: 6 - 9: 150; in the composite solution of magnesium nitrate and iron nitrate, the concentration of magnesium nitrate is 30 - 40 g / L, the concentration of iron nitrate is 25 - 28 g / L, and the solvent is water; in the sodium hydroxide solution, the mass percentage of sodium hydroxide is 10%, and the solvent is water; the volume ratio of adding the composite solution of magnesium nitrate and iron nitrate and the sodium hydroxide solution to the mixed solution is mixed solution: composite solution of magnesium nitrate and iron nitrate: sodium hydroxide solution = 10: 10: 3 - 4.

[0008] Further, in the step (2), the amount ratio of adding calcium nitrate and cerium nitrate to deionized water is calcium nitrate: cerium nitrate: deionized water = 30 - 36 g: 18 - 22 g: 100 mL; the amount ratio of adding citric acid and the magnesium-iron composite oxide powder to the aqueous solution is citric acid: magnesium-iron composite oxide powder: aqueous solution = 50 - 55 g: 10 - 20 g: 100 mL.

[0009] Further, in the step (3), in the aqueous solution of nickel nitrate, the concentration of nickel nitrate is 30 - 35 g / L, and the amount ratio of the coated particles and potassium permanganate added to the aqueous solution of nickel nitrate is aqueous solution of nickel nitrate:coated particles:potassium permanganate = 100 mL:5 - 6 g:4.2 - 4.6 g.

[0010] Further, in the step (4), the amount ratio of alkyl polyglycoside and the post-treatment powder added to the aqueous ethanol solution is alkyl polyglycoside:post-treatment powder:aqueous ethanol solution = 20 - 25 g:8 - 10 g:200 mL, and the mass percentage of ethanol in the aqueous ethanol solution is 10% - 20%; the mass ratio of sodium hydroxide, ethylene glycol diglycidyl ether and isopropanol added to the mass of the post-treatment powder added to the solution is sodium hydroxide:ethylene glycol diglycidyl ether:isopropanol:post-treatment powder = 0.5 - 0.6 g:3 - 5 g:10 - 12 g:8 - 10 g.

[0011] The beneficial effects of the present invention are as follows: After adding the combustion improver prepared by the method of the present invention to the solid fuel, it can significantly reduce the ignition point of the fuel, improve the flammability index of the fuel, and greatly improve the combustion performance of the solid fuel. The combustion improver of the present invention first synthesizes porous magnesium and iron-doped titanium oxide powder by hydrothermal method. Among them, the doped magnesium oxide has a promoting effect on carbon combustion, can prevent the formation and polymerization of the carbon particle flame retardant layer during combustion, and promote the combustion of the fuel. Iron oxide can accelerate the combustion of semi-coke and reduce the activation energy of the solid fuel combustion reaction. Subsequently, the oxides of calcium and cerium are partially coated. Among them, the oxide of calcium can have a catalytic effect on the homogeneous ignition process of coal, promote the decomposition of small molecules in the solid fuel, and the oxide of calcium can adsorb volatile components during combustion, promote the contact between active oxygen and carbon, increase the contact time, and promote the combustion reaction. Cerium oxide is a rare earth oxide, which can catalyze the coal combustion reaction, accelerate the decarbonization cracking reaction, and can promote the breaking and decomposition of macromolecular branches in the pulverized coal, leaving holes in the pulverized coal, increasing the contact between carbon and oxygen in the pulverized coal, and improving the combustion rate. Secondly, Ni2O3-MnO2 components are formed by nickel nitrate and potassium permanganate. Among them, Ni2O3 decomposes to form NiO and oxygen during combustion, and MnO2 can also decompose to form MnO and oxygen in a high-temperature environment, serving as an oxygen supply source to promote the combustion reaction. Finally, through the treatment with alkyl polyglycoside, etc., the dispersibility of the combustion improver is improved, the contact area between the pulverized coal and oxygen is enhanced, and the combustion efficiency is improved. Specific Embodiments

[0012] The following further illustrates the present invention with reference to embodiments.

[0013] Example 1 A coal gangue-based solid fuel, comprising pulverized coal, coal gangue particles, a binder, a combustion aid, and a sulfur-fixing agent. The amounts of each raw material in parts by weight are as follows: 90 parts of pulverized coal, 100 parts of coal gangue particles, 15 parts of binder, 10 parts of combustion aid, and 5 parts of sulfur-fixing agent. Among them, the sulfur-fixing agent is calcium oxide powder, the binder is polyvinyl alcohol (type 17-88), and the preparation method of the combustion aid is as follows: (1) Add n-butanol, octylphenol polyoxyethylene ether, and tetrabutyl titanate to absolute ethanol. The mass ratio of n-butanol, octylphenol polyoxyethylene ether, tetrabutyl titanate, and absolute ethanol added to absolute ethanol is n-butanol: octylphenol polyoxyethylene ether: tetrabutyl titanate: absolute ethanol = 2:2:6:150. Stir for 20 min to obtain a mixed solution. Prepare a composite solution of magnesium nitrate and iron nitrate. In the composite solution of magnesium nitrate and iron nitrate, the concentration of magnesium nitrate is 30 g / L, the concentration of iron nitrate is 25 g / L, and the solvent is water. Heat the mixed solution in a water bath to 60 °C and keep it warm. Then, add the composite solution of magnesium nitrate and iron nitrate to the mixed solution under stirring. After the addition is completed, continue stirring for 30 min. Then, add a sodium hydroxide solution. In the sodium hydroxide solution, the mass percentage of sodium hydroxide is 10%, and the solvent is water. The volume ratio of the composite solution of magnesium nitrate and iron nitrate and the sodium hydroxide solution added to the mixed solution is mixed solution: composite solution of magnesium nitrate and iron nitrate: sodium hydroxide solution = 10:10:3. After the addition, stir for another 30 min, keep it warm at 60 °C and let it stand for aging for 12 h. After aging, place it in a closed reaction kettle, heat it to 100 °C and keep it warm under hydrothermal conditions for 20 h. Separate the solid and liquid phases. Wash the solid phase twice with deionized water and twice with ethanol, dry it at 80 °C for 1 h, and calcine it at 530 °C to obtain magnesium-iron composite oxide powder. (2) Add calcium nitrate and cerium nitrate to deionized water. The amount ratio of calcium nitrate, cerium nitrate, and deionized water added to deionized water is calcium nitrate: cerium nitrate: deionized water = 30 g: 18 g: 100 mL. Stir to dissolve completely to obtain an aqueous solution. Then, heat the aqueous solution in a water bath to 85 °C and keep it warm. Then, add citric acid and the magnesium-iron composite oxide powder to the aqueous solution under stirring. The amount ratio of citric acid, magnesium-iron composite oxide powder, and aqueous solution added to the aqueous solution is citric acid: magnesium-iron composite oxide powder: aqueous solution = 50 g: 10 g: 100 mL. After the addition, keep it warm and stir at 85 °C for 3 h to obtain a composite gel. Place the composite gel in an environment at 110 °C and dry it for 15 h to dehydrate and embrittle it. Then, heat it to 250 °C and keep it warm for 3 h, and pulverize it to obtain precursor particles. Heat the precursor particles to 800 °C and keep it warm for 15 h, and then cool it to room temperature in the furnace to obtain coated particles. (3) Prepare an aqueous solution of nickel nitrate; in the aqueous solution of nickel nitrate, the concentration of nickel nitrate is 30 g / L, and the solvent is water; add the coated particles to the aqueous solution of nickel nitrate under stirring, and continue to stir for 20 min after the feeding is completed to obtain a suspension. Then, add potassium permanganate to the suspension under stirring. The dosage ratio of the aqueous solution of nickel nitrate, the coated particles, and potassium permanganate is aqueous solution of nickel nitrate:coated particles:potassium permanganate = 100 mL:5 g:4.2 g; continue to stir for 30 min after the feeding is completed, then let it stand for 20 h under a negative pressure (0.01 standard atmosphere) environment, perform solid-liquid separation, dry the solid phase at 100 °C for 3 h, and then calcine it at 450 °C for 5 h to obtain the post-treated powder; (4) Add alkyl glucoside and the post-treated powder to an aqueous solution of ethanol. The dosage ratio of alkyl glucoside, the post-treated powder, and the aqueous solution of ethanol is alkyl glucoside:post-treated powder:aqueous solution of ethanol = 20 g:8 g:200 mL. The mass percentage of ethanol in the aqueous solution of ethanol is 10%; stir for 30 min under an ultrasonic environment to obtain a dispersion; heat the dispersion in a water bath to 60 °C, and continue to stir at a constant temperature for 40 h after reaching the temperature; then add sodium hydroxide, ethylene glycol diglycidyl ether, and isopropyl alcohol under stirring. The mass ratio of sodium hydroxide, ethylene glycol diglycidyl ether, isopropyl alcohol, and the post-treated powder added to the solution is sodium hydroxide:ethylene glycol diglycidyl ether:isopropyl alcohol:post-treated powder = 0.5 g:3 g:10 g:8 g; after the feeding is completed, raise the temperature to 80 °C, keep stirring for 3 h, then cool naturally to room temperature, perform solid-liquid separation, wash the solid phase 3 times with deionized water, wash it 3 times with ethanol, and dry it at 80 °C for 1 h to obtain the combustion aid.

[0014] Weigh each raw material according to the above weight parts. First, dissolve the binder in hot water at 90 °C to prepare a binder solution with a binder mass fraction of 10%, and then add other raw materials and stir and mix them evenly. The mixture is made into a honeycomb coal shape with a mold to form the solid fuel to be tested in this example.

[0015] Example 2 A coal gangue-based solid fuel, comprising pulverized coal, coal gangue particles, a binder, a combustion aid, and a sulfur-fixing agent. The dosage of each raw material is as follows by weight: 90 parts of pulverized coal, 100 parts of coal gangue particles, 15 parts of binder, 11 parts of combustion aid, and 6 parts of sulfur-fixing agent; wherein the sulfur-fixing agent is calcium oxide powder, the binder is polyvinyl alcohol (type 17-88), and the preparation method of the combustion aid is: (1) Add n-butanol, octylphenol polyoxyethylene ether, and tetrabutyl titanate into absolute ethanol. The mass ratio of n-butanol, octylphenol polyoxyethylene ether, tetrabutyl titanate, and absolute ethanol is n-butanol:octylphenol polyoxyethylene ether:tetrabutyl titanate:absolute ethanol = 2:2:7:150. Stir for 20 min to obtain a mixed solution. Prepare a composite solution of magnesium nitrate and iron nitrate. In the composite solution of magnesium nitrate and iron nitrate, the concentration of magnesium nitrate is 35 g / L, the concentration of iron nitrate is 26 g / L, and the solvent is water. Heat the mixed solution in a water bath to 60 °C and keep it warm. Then, add the composite solution of magnesium nitrate and iron nitrate to the mixed solution under stirring. After the addition is completed, continue stirring for 30 min. Then, add a sodium hydroxide solution. In the sodium hydroxide solution, the mass percentage of sodium hydroxide is 10%, and the solvent is water. The volume ratio of the mixed solution, the composite solution of magnesium nitrate and iron nitrate, and the sodium hydroxide solution added to the mixed solution is mixed solution:composite solution of magnesium nitrate and iron nitrate:sodium hydroxide solution = 10:10:3. After the addition, stir for another 30 min, keep it warm at 60 °C and let it stand for aging for 12 h. After aging, place it in a closed reaction kettle, heat it to 100 °C and keep it hydrothermally warm for 20 h. Separate the solid and liquid. Wash the solid phase twice with deionized water and twice with ethanol, dry it at 80 °C for 1 h, and calcine it in an environment of 530 °C to obtain magnesium-iron composite oxide powder; (2) Add calcium nitrate and cerium nitrate into deionized water. The amount ratio of calcium nitrate, cerium nitrate, and deionized water added into deionized water is calcium nitrate:cerium nitrate:deionized water = 32 g:20 g:100 mL. Stir until fully dissolved to obtain an aqueous solution. Then, heat the aqueous solution in a water bath to 85 °C and keep it warm. Then, add citric acid and the magnesium-iron composite oxide powder to the aqueous solution under stirring. The amount ratio of citric acid, the magnesium-iron composite oxide powder, and the aqueous solution added to the aqueous solution is citric acid:magnesium-iron composite oxide powder:aqueous solution = 50 g:15 g:100 mL. After the addition, keep it warm and stir at 85 °C for 3 h to obtain a composite gel. Place the composite gel in an environment of 110 °C and dry it for 15 h to dehydrate and embrittle it. Then, heat it to 260 °C and keep it warm for 3 h, and crush it to obtain precursor particles. Heat the precursor particles to 800 °C and keep it warm for 15 h, and then cool it to room temperature with the furnace to obtain coated particles; (3) Prepare an aqueous solution of nickel nitrate; in the aqueous solution of nickel nitrate, the concentration of nickel nitrate is 30 g / L, and the solvent is water; add the coated particles to the aqueous solution of nickel nitrate under stirring, and continue to stir for 20 min after the addition is completed to obtain a suspension. Then, add potassium permanganate to the suspension under stirring. The dosage ratio of the aqueous solution of nickel nitrate, the coated particles, and potassium permanganate is aqueous solution of nickel nitrate: coated particles: potassium permanganate = 100 mL: 5 g: 4.4 g; continue to stir for 30 min after the addition is completed, and then stand still for 20 h under a negative pressure (0.01 standard atmosphere) environment. Perform solid-liquid separation, dry the solid phase at 100 °C for 3 h, and then calcine it at 460 °C for 5 h to obtain the post-treated powder; (4) Add alkyl polyglycoside and the post-treated powder to an aqueous solution of ethanol. The dosage ratio of alkyl polyglycoside, the post-treated powder, and the aqueous solution of ethanol is alkyl polyglycoside: post-treated powder: aqueous solution of ethanol = 20 g: 9 g: 200 mL. The mass percentage of ethanol in the aqueous solution of ethanol is 10%; stir for 30 min under an ultrasonic environment to obtain a dispersion; heat the dispersion in a water bath to 60 °C, and continue to stir at a constant temperature for 40 h after reaching the temperature; then add sodium hydroxide, ethylene glycol diglycidyl ether, and isopropanol under stirring. The mass ratio of sodium hydroxide, ethylene glycol diglycidyl ether, isopropanol, and the post-treated powder added to the solution is sodium hydroxide: ethylene glycol diglycidyl ether: isopropanol: post-treated powder = 0.5 g: 4 g: 11 g: 9 g; after the addition is completed, raise the temperature to 80 °C, keep warm and stir for 3 h, then cool naturally to room temperature, perform solid-liquid separation, wash the solid phase 3 times with deionized water and 3 times with ethanol, and dry it at 80 °C for 1 h to obtain the combustion promoter.

[0016] Weigh each raw material according to the above weight parts. First, dissolve the binder in hot water at 90 °C to prepare a binder solution with a binder mass fraction of 10%, and then add other raw materials and stir and mix them evenly. The mixture is made into a honeycomb coal shape with a mold to form the solid fuel to be tested in this example.

[0017] Example 3 A coal gangue-based solid fuel includes pulverized coal, coal gangue particles, a binder, a combustion promoter, and a sulfur-fixing agent. The dosage of each raw material is as follows by weight: 100 parts of pulverized coal, 100 parts of coal gangue particles, 15 parts of binder, 11 parts of combustion promoter, and 7 parts of sulfur-fixing agent; wherein the sulfur-fixing agent is calcium oxide powder, the binder is polyvinyl alcohol (type 17-88), and the preparation method of the combustion promoter is: (1) Add n-butanol, octylphenol polyoxyethylene ether, and tetrabutyl titanate into absolute ethanol. The mass ratio of n-butanol, octylphenol polyoxyethylene ether, tetrabutyl titanate, and absolute ethanol is n-butanol: octylphenol polyoxyethylene ether: tetrabutyl titanate: absolute ethanol = 3:3:8:150; stir for 20 min to obtain a mixed solution; prepare a composite solution of magnesium nitrate and iron nitrate; in the composite solution of magnesium nitrate and iron nitrate, the concentration of magnesium nitrate is 35 g / L, the concentration of iron nitrate is 27 g / L, and the solvent is water; heat the mixed solution in a water bath to 60 °C and keep it warm, then add the composite solution of magnesium nitrate and iron nitrate to the mixed solution under stirring. After the addition is completed, continue stirring for 30 min, and then add a sodium hydroxide solution. In the sodium hydroxide solution, the mass percentage of sodium hydroxide is 10%, and the solvent is water; the volume ratio of the mixed solution, the composite solution of magnesium nitrate and iron nitrate, and the sodium hydroxide solution added to the mixed solution is mixed solution: composite solution of magnesium nitrate and iron nitrate: sodium hydroxide solution = 10:10:4; stir for another 30 min after the addition, keep it warm at 60 °C and stand for aging for 12 h. After aging, place it in a sealed reaction kettle, heat it to 100 °C and keep it hydrothermally warm for 20 h, separate the solid and liquid, wash the solid with deionized water 2 times and ethanol 2 times, dry it at 80 °C for 1 h, and calcine it in an environment of 530 °C to obtain magnesium-iron composite oxide powder; (2) Add calcium nitrate and cerium nitrate into deionized water. The amount ratio of calcium nitrate, cerium nitrate, and deionized water added into deionized water is calcium nitrate: cerium nitrate: deionized water = 34 g: 20 g: 100 mL; stir to dissolve completely to obtain an aqueous solution, then heat the aqueous solution in a water bath to 85 °C and keep it warm, and then add citric acid and the magnesium-iron composite oxide powder to the aqueous solution under stirring. The amount ratio of citric acid, the magnesium-iron composite oxide powder, and the aqueous solution added to the aqueous solution is citric acid: magnesium-iron composite oxide powder: aqueous solution = 55 g: 15 g: 100 mL; stir and keep it warm at 85 °C for 3 h after the addition to obtain a composite gel; place the composite gel in an environment of 110 °C and dry it for 15 h to dehydrate and embrittle it, then heat it to 270 °C and keep it warm for 3 h, and crush it to obtain precursor particles. Heat the precursor particles to 810 °C and keep it warm for 15 h, and then cool it to room temperature with the furnace to obtain coated particles; (3) Prepare an aqueous solution of nickel nitrate; in the aqueous solution of nickel nitrate, the concentration of nickel nitrate is 35 g / L and the solvent is water; add the coated particles to the aqueous solution of nickel nitrate under stirring, and continue to stir for 20 min after the addition is completed to obtain a suspension. Then, add potassium permanganate to the suspension under stirring. The amount ratio of the aqueous solution of nickel nitrate, the coated particles, and potassium permanganate added is aqueous solution of nickel nitrate:coated particles:potassium permanganate = 100 mL:6 g:4.4 g; continue to stir for 30 min after the addition is completed, then let it stand for 20 h under a negative pressure (0.01 standard atmosphere) environment, perform solid-liquid separation, dry the solid phase at 100 °C for 3 h, and then calcine it at 470 °C for 5 h to obtain the post-treated powder; (4) Add alkyl polyglycoside and the post-treated powder to an aqueous solution of ethanol. The amount ratio of alkyl polyglycoside, the post-treated powder, and the aqueous solution of ethanol added is alkyl polyglycoside:post-treated powder:aqueous solution of ethanol = 25 g:9 g:200 mL, and the mass percentage of ethanol in the aqueous solution of ethanol is 10%; stir for 30 min under an ultrasonic environment to obtain a dispersion; heat the dispersion in a water bath to 60 °C, and continue to stir at a constant temperature for 40 h after reaching the temperature; then add sodium hydroxide, ethylene glycol diglycidyl ether, and isopropanol under stirring. The mass ratio of sodium hydroxide, ethylene glycol diglycidyl ether, isopropanol, and the post-treated powder added to the mass of the post-treated powder in the added solution is sodium hydroxide:ethylene glycol diglycidyl ether:isopropanol:post-treated powder = 0.6 g:4 g:11 g:9 g; after the addition is completed, raise the temperature to 80 °C, keep stirring for 3 h, then cool naturally to room temperature, perform solid-liquid separation, wash the solid phase 3 times with deionized water, wash it 3 times with ethanol, and dry it at 80 °C for 1 h to obtain the combustion aid.

[0018] Weigh each raw material according to the above weight parts. First, dissolve the binder in hot water at 90 °C to prepare a binder solution with a binder mass fraction of 10%, and then add other raw materials, stir and mix evenly. The mixture is made into a honeycomb coal shape with a mold to form the solid fuel to be tested in this example.

[0019] Example 4 A coal gangue-based solid fuel includes pulverized coal, coal gangue particles, a binder, a combustion aid, and a sulfur-fixing agent. The amounts of each raw material are as follows by weight: 100 parts of pulverized coal, 100 parts of coal gangue particles, 15 parts of binder, 12 parts of combustion aid, and 8 parts of sulfur-fixing agent; wherein the sulfur-fixing agent is calcium oxide powder, the binder is polyvinyl alcohol (type 17-88), and the preparation method of the combustion aid is: (1) Add n-butanol, octylphenol polyoxyethylene ether, and tetrabutyl titanate into absolute ethanol. The mass ratio of n-butanol, octylphenol polyoxyethylene ether, tetrabutyl titanate, and absolute ethanol is n-butanol: octylphenol polyoxyethylene ether: tetrabutyl titanate: absolute ethanol = 3:3:9:150. Stir for 20 min to obtain a mixed solution. Prepare a composite solution of magnesium nitrate and iron nitrate. In the composite solution of magnesium nitrate and iron nitrate, the concentration of magnesium nitrate is 40 g / L, the concentration of iron nitrate is 28 g / L, and the solvent is water. Heat the mixed solution in a water bath to 60 °C and keep it warm. Then, add the composite solution of magnesium nitrate and iron nitrate to the mixed solution under stirring. After the addition is completed, continue stirring for 30 min. Then, add a sodium hydroxide solution. In the sodium hydroxide solution, the mass percentage of sodium hydroxide is 10%, and the solvent is water. The volume ratio of the mixed solution, the composite solution of magnesium nitrate and iron nitrate, and the sodium hydroxide solution added to the mixed solution is mixed solution: composite solution of magnesium nitrate and iron nitrate: sodium hydroxide solution = 10:10:4. After the addition, stir for another 30 min, keep it warm at 60 °C and let it stand for aging for 12 h. After aging, place it in a closed reaction kettle, heat it to 100 °C and keep it hydrothermally warm for 20 h. Perform solid-liquid separation. Wash the solid phase twice with deionized water and twice with ethanol, dry it at 80 °C for 1 h, and calcine it in an environment of 530 °C to obtain magnesium-iron composite oxide powder; (2) Add calcium nitrate and cerium nitrate into deionized water. The amount ratio of calcium nitrate, cerium nitrate, and deionized water added into deionized water is calcium nitrate: cerium nitrate: deionized water = 36 g: 22 g: 100 mL. Stir until fully dissolved to obtain an aqueous solution. Then, heat the aqueous solution in a water bath to 85 °C and keep it warm. Then, add citric acid and the magnesium-iron composite oxide powder to the aqueous solution under stirring. The amount ratio of citric acid, the magnesium-iron composite oxide powder, and the aqueous solution added to the aqueous solution is citric acid: magnesium-iron composite oxide powder: aqueous solution = 55 g: 20 g: 100 mL. After the addition, keep it warm and stir at 85 °C for 3 h to obtain a composite gel. Place the composite gel in an environment of 110 °C and dry it for 15 h to dehydrate and embrittle it. Then, heat it to 280 °C and keep it warm for 3 h, and crush it to obtain precursor particles. Heat the precursor particles to 820 °C and keep it warm for 15 h, and then cool it to room temperature with the furnace to obtain coated particles; (3) Prepare an aqueous solution of nickel nitrate; in the aqueous solution of nickel nitrate, the concentration of nickel nitrate is 35 g / L, and the solvent is water; add the coated particles to the aqueous solution of nickel nitrate under stirring, and continue to stir for 20 min after the feeding is completed to obtain a suspension. Then, add potassium permanganate to the suspension under stirring. The amount ratio of the aqueous solution of nickel nitrate, the coated particles, and potassium permanganate added is aqueous solution of nickel nitrate: coated particles: potassium permanganate = 100 mL: 6 g: 4.6 g; continue to stir for 30 min after the feeding is completed, then stand for 20 h under a negative pressure (0.01 standard atmosphere) environment, perform solid-liquid separation, dry the solid phase at 100 °C for 3 h, and then calcine at 480 °C for 5 h to obtain a post-treatment powder; (4) Add alkyl polyglycoside and the post-treatment powder to an aqueous solution of ethanol. The amount ratio of alkyl polyglycoside, the post-treatment powder, and the aqueous solution of ethanol added is alkyl polyglycoside: post-treatment powder: aqueous solution of ethanol = 25 g: 10 g: 200 mL, and the mass percentage of ethanol in the aqueous solution of ethanol is 10%; stir for 30 min under an ultrasonic environment to obtain a dispersion; heat the dispersion in a water bath to 60 °C, and continue to stir at a constant temperature for 40 h after reaching the temperature; then add sodium hydroxide, ethylene glycol diglycidyl ether, and isopropanol under stirring. The mass ratio of sodium hydroxide, ethylene glycol diglycidyl ether, isopropanol, and the post-treatment powder added to the mass of the post-treatment powder in the added solution is sodium hydroxide: ethylene glycol diglycidyl ether: isopropanol: post-treatment powder = 0.6 g: 5 g: 12 g: 10 g; after the feeding is completed, raise the temperature to 80 °C, keep stirring for 3 h, then cool naturally to room temperature, perform solid-liquid separation, wash the solid phase 3 times with deionized water and 3 times with ethanol, and dry at 80 °C for 1 h to obtain the combustion improver.

[0020] Weigh each raw material according to the above weight parts. First, dissolve the binder in hot water at 90 °C to prepare a binder solution with a binder mass fraction of 10%, then add other raw materials, stir and mix evenly, and use a mold to make the mixture into a honeycomb coal shape to form the solid fuel to be tested in this example.

[0021] Comparative Example 1 A coal gangue-based solid fuel for comparison, including pulverized coal, coal gangue particles, binder, combustion improver, and sulfur-fixing agent. The amounts of each raw material are as follows by weight: 100 parts of pulverized coal, 100 parts of coal gangue particles, 15 parts of binder, 11 parts of combustion improver, and 7 parts of sulfur-fixing agent; wherein the sulfur-fixing agent is calcium oxide powder, the binder is polyvinyl alcohol (17-88 type), and the preparation method of the combustion improver is: (1) Add n-butanol, octylphenol polyoxyethylene ether, and tetrabutyl titanate to absolute ethanol. The mass ratio of n-butanol, octylphenol polyoxyethylene ether, tetrabutyl titanate, and absolute ethanol added is n-butanol:octylphenol polyoxyethylene ether:tetrabutyl titanate:absolute ethanol = 3:3:8:150; stir for 20 min to obtain a mixed solution; prepare a composite solution of magnesium nitrate and iron nitrate; in the composite solution of magnesium nitrate and iron nitrate, the concentration of magnesium nitrate is 35 g / L, the concentration of iron nitrate is 27 g / L, and the solvent is water; heat the mixed solution in a water bath to 60 °C and keep it warm, then add the composite solution of magnesium nitrate and iron nitrate to the mixed solution under stirring. After the feeding is completed, continue stirring for 30 min, and then add a sodium hydroxide solution. In the sodium hydroxide solution, the mass percentage of sodium hydroxide is 10%, and the solvent is water; the volume ratio of the mixed solution, the composite solution of magnesium nitrate and iron nitrate, and the sodium hydroxide solution added to the mixed solution is mixed solution:composite solution of magnesium nitrate and iron nitrate:sodium hydroxide solution = 10:10:4; after feeding, stir for another 30 min, keep it warm and stand for aging at 60 °C for 12 h. After aging, place it in a sealed reaction kettle, heat it to 100 °C for hydrothermal insulation for 20 h, carry out solid-liquid separation, wash the solid phase with deionized water 2 times and ethanol 2 times, dry it at 80 °C for 1 h, and calcine it in an environment of 530 °C to obtain magnesium-iron composite oxide powder; (2) Prepare an aqueous solution of nickel nitrate; in the aqueous solution of nickel nitrate, the concentration of nickel nitrate is 35 g / L, and the solvent is water; add the magnesium-iron composite oxide powder to the aqueous solution of nickel nitrate under stirring. After the feeding is completed, continue stirring for 20 min to obtain a suspension, and then add potassium permanganate to the suspension under stirring. The amounts of the aqueous solution of nickel nitrate, the magnesium-iron composite oxide powder, and potassium permanganate added are aqueous solution of nickel nitrate:magnesium-iron composite oxide powder:potassium permanganate = 100 mL:6 g:4.4 g; after the feeding is completed, continue stirring for 30 min, and then stand for 20 h under a negative pressure (0.01 standard atmosphere) environment. Carry out solid-liquid separation, dry the solid phase at 100 °C for 3 h, and then calcine it at 470 °C for 5 h to obtain a post-treatment powder; (3) Add the alkyl polyglycoside and the post-treatment powder into an aqueous solution of ethanol. The amount ratio of the alkyl polyglycoside and the post-treatment powder added into the aqueous solution of ethanol is alkyl polyglycoside: post-treatment powder: aqueous solution of ethanol = 25 g: 9 g: 200 mL. The mass percentage of ethanol in the aqueous solution of ethanol is 10%. Stir for 30 min under an ultrasonic environment to obtain a dispersion. Heat the dispersion in a water bath to 60 °C, and continue to stir at a constant temperature for 40 h after reaching the temperature. Then, add sodium hydroxide, ethylene glycol diglycidyl ether, and isopropanol under stirring. The mass ratio of sodium hydroxide, ethylene glycol diglycidyl ether, isopropanol, and the post-treatment powder added into the solution is sodium hydroxide: ethylene glycol diglycidyl ether: isopropanol: post-treatment powder = 0.6 g: 4 g: 11 g: 9 g. After the feeding is completed, raise the temperature to 80 °C, keep stirring for 3 h, then cool naturally to room temperature, separate the solid and liquid, wash the solid with deionized water 3 times, wash with ethanol 3 times, and dry at 80 °C for 1 h to obtain the combustion promoter of this comparative example.

[0022] Weigh each raw material according to the above weight parts. First, dissolve the binder in hot water at 90 °C to prepare a binder solution with a binder mass fraction of 10%, and then add other raw materials, stir and mix evenly. The mixture is made into a honeycomb coal shape with a mold to form the solid fuel to be tested in this comparative example.

[0023] Comparative Example 2 A coal gangue-based solid fuel for comparison includes pulverized coal, coal gangue particles, a binder, a combustion promoter, and a sulfur-fixing agent. The amounts of each raw material are as follows by weight: 100 parts of pulverized coal, 100 parts of coal gangue particles, 15 parts of binder, 11 parts of combustion promoter, and 7 parts of sulfur-fixing agent. Among them, the sulfur-fixing agent is calcium oxide powder, the binder is polyvinyl alcohol (type 17-88), and the preparation method of the combustion promoter is as follows: (1) Add n-butanol, octylphenol polyoxyethylene ether, and tetrabutyl titanate into absolute ethanol. The mass ratio of n-butanol, octylphenol polyoxyethylene ether, tetrabutyl titanate, and absolute ethanol is n-butanol: octylphenol polyoxyethylene ether: tetrabutyl titanate: absolute ethanol = 3:3:8:150; stir for 20 min to obtain a mixed solution; prepare a composite solution of magnesium nitrate and iron nitrate; in the composite solution of magnesium nitrate and iron nitrate, the concentration of magnesium nitrate is 35 g / L, the concentration of iron nitrate is 27 g / L, and the solvent is water; heat the mixed solution in a water bath to 60 °C and keep it warm, then add the composite solution of magnesium nitrate and iron nitrate to the mixed solution under stirring. After the feeding is completed, continue to stir for 30 min, and then add a sodium hydroxide solution. In the sodium hydroxide solution, the mass percentage of sodium hydroxide is 10%, and the solvent is water; the volume ratio of the mixed solution, the composite solution of magnesium nitrate and iron nitrate, and the sodium hydroxide solution added to the mixed solution is mixed solution: composite solution of magnesium nitrate and iron nitrate: sodium hydroxide solution = 10:10:4; stir for another 30 min after feeding, keep it warm and age at 60 °C for 12 h. After aging, place it in a sealed autoclave, heat it to 100 °C and keep it hydrothermally warm for 20 h, carry out solid-liquid separation, wash the solid phase with deionized water 2 times and ethanol 2 times, dry it at 80 °C for 1 h, and calcine it in an environment of 530 °C to obtain magnesium-iron composite oxide powder; (2) Add calcium nitrate and cerium nitrate into deionized water. The amount ratio of calcium nitrate, cerium nitrate, and deionized water added into deionized water is calcium nitrate: cerium nitrate: deionized water = 34 g: 20 g: 100 mL; stir to dissolve completely to obtain an aqueous solution, then heat the aqueous solution in a water bath to 85 °C and keep it warm, and then add citric acid and the magnesium-iron composite oxide powder to the aqueous solution under stirring. The amount ratio of citric acid, the magnesium-iron composite oxide powder, and the aqueous solution added to the aqueous solution is citric acid: magnesium-iron composite oxide powder: aqueous solution = 55 g: 15 g: 100 mL; stir and keep it warm at 85 °C for 3 h after feeding to obtain a composite gel; place the composite gel in an environment of 110 °C and dry it for 15 h to dehydrate and embrittle it, then heat it to 270 °C and keep it warm for 3 h, and crush it to obtain precursor particles. Heat the precursor particles to 810 °C and keep it warm for 15 h, and then cool it to room temperature with the furnace to obtain coated particles; (3) Add the alkyl polyglycoside and the coated particles into an aqueous solution of ethanol. The mass ratio of the alkyl polyglycoside, the coated particles, and the aqueous solution of ethanol is alkyl polyglycoside: coated particles: aqueous solution of ethanol = 25 g: 9 g: 200 mL. The mass percentage of ethanol in the aqueous solution of ethanol is 10%. Stir for 30 min under an ultrasonic environment to obtain a dispersion. Heat the dispersion in a water bath to 60 °C, and continue to stir constantly for 40 h after reaching the temperature. Then, add sodium hydroxide, ethylene glycol diglycidyl ether, and isopropyl alcohol under stirring. The mass ratio of sodium hydroxide, ethylene glycol diglycidyl ether, isopropyl alcohol, and the coated particles added into the solution is sodium hydroxide: ethylene glycol diglycidyl ether: isopropyl alcohol: coated particles = 0.6 g: 4 g: 11 g: 9 g. After the addition is completed, raise the temperature to 80 °C, keep stirring for 3 h, then cool naturally to room temperature, perform solid-liquid separation, wash the solid phase 3 times with deionized water and 3 times with ethanol, and dry at 80 °C for 1 h to obtain the combustion improver of this comparative example.

[0024] Weigh each raw material according to the above weight parts. First, dissolve the binder in hot water at 90 °C to prepare a binder solution with a binder mass fraction of 10%, and then add other raw materials, stir and mix evenly. The mixture is made into a honeycomb coal shape with a mold to form the solid fuel to be tested in this comparative example.

[0025] Comparative Example 3 A coal gangue-based solid fuel for comparison includes pulverized coal, coal gangue particles, a binder, a combustion improver, and a sulfur-fixing agent. The amounts of each raw material are as follows by weight: 100 parts of pulverized coal, 100 parts of coal gangue particles, 15 parts of binder, 11 parts of combustion improver, and 7 parts of sulfur-fixing agent. Among them, the sulfur-fixing agent is calcium oxide powder, the binder is polyvinyl alcohol (type 17-88), and the preparation method of the combustion improver is as follows: (1) Add n-butanol, octylphenol polyoxyethylene ether, and tetrabutyl titanate into absolute ethanol. The mass ratio of n-butanol, octylphenol polyoxyethylene ether, tetrabutyl titanate, and absolute ethanol is n-butanol: octylphenol polyoxyethylene ether: tetrabutyl titanate: absolute ethanol = 3:3:8:150; stir for 20 min to obtain a mixed solution; prepare a composite solution of magnesium nitrate and iron nitrate; in the composite solution of magnesium nitrate and iron nitrate, the concentration of magnesium nitrate is 35 g / L, the concentration of iron nitrate is 27 g / L, and the solvent is water; heat the mixed solution in a water bath to 60 °C and keep it warm, then add the composite solution of magnesium nitrate and iron nitrate to the mixed solution under stirring. After the addition is completed, continue to stir for 30 min, and then add a sodium hydroxide solution. In the sodium hydroxide solution, the mass percentage of sodium hydroxide is 10%, and the solvent is water; the volume ratio of the mixed solution, the composite solution of magnesium nitrate and iron nitrate, and the sodium hydroxide solution added to the mixed solution is mixed solution: composite solution of magnesium nitrate and iron nitrate: sodium hydroxide solution = 10:10:4; stir for another 30 min after the addition, keep it warm and statically age at 60 °C for 12 h. After aging, place it in a closed reaction kettle, heat it to 100 °C and keep it hydrothermally warm for 20 h, carry out solid-liquid separation, wash the solid phase with deionized water 2 times and ethanol 2 times, dry it at 80 °C for 1 h, and calcine it at 530 °C to obtain magnesium-iron composite oxide powder; (2) Add calcium nitrate and cerium nitrate into deionized water. The amount ratio of calcium nitrate, cerium nitrate, and deionized water added into deionized water is calcium nitrate: cerium nitrate: deionized water = 34 g: 20 g: 100 mL; stir to fully dissolve to obtain an aqueous solution, then heat the aqueous solution in a water bath to 85 °C and keep it warm, and then add citric acid and the magnesium-iron composite oxide powder to the aqueous solution under stirring. The amount ratio of citric acid, the magnesium-iron composite oxide powder, and the aqueous solution added to the aqueous solution is citric acid: magnesium-iron composite oxide powder: aqueous solution = 55 g: 15 g: 100 mL; stir and keep it warm at 85 °C for 3 h after the addition to obtain a composite gel; place the composite gel in an environment of 110 °C and dry it for 15 h to dehydrate and embrittle it, then heat it to 270 °C and keep it warm for 3 h, and crush it to obtain precursor particles. Heat the precursor particles to 810 °C and keep it warm for 15 h, and then cool it to room temperature with the furnace to obtain coated particles; (3) Prepare an aqueous solution of nickel nitrate; in the aqueous solution of nickel nitrate, the concentration of nickel nitrate is 35 g / L and the solvent is water; add the coated particles to the aqueous solution of nickel nitrate under stirring, and continue stirring for 20 min after the addition is completed to obtain a suspension. Then, add potassium permanganate to the suspension under stirring. The amount ratio of the aqueous solution of nickel nitrate, the coated particles, and potassium permanganate added is aqueous solution of nickel nitrate: coated particles: potassium permanganate = 100 mL: 6 g: 4.4 g; continue stirring for 30 min after the addition is completed, then stand still for 20 h under a negative pressure (0.01 standard atmosphere) environment, perform solid-liquid separation, dry the solid phase at 100 °C for 3 h, and then calcine it at 470 °C for 5 h to obtain a post-treated powder; as the combustion improver of this comparative example.

[0026] Weigh each raw material according to the above weight parts. First, dissolve the binder in hot water at 90 °C to prepare a binder solution with a binder mass fraction of 10%, and then add other raw materials, stir and mix evenly. The mixture is made into a honeycomb shape with a mold to form the solid fuel to be tested in this comparative example.

[0027] Example 5 Test the solid fuel to be tested prepared by the methods described in the above examples and comparative examples using a synchronous thermal analyzer to obtain the ignition point temperature and the combustibility index. The results are shown in Table 1. Among them, the heating rate is set to 10 °C / min, and the mass of the test sample is 10 mg.

[0028] As can be seen from Table 1, after the combustion improver prepared by the method of the present invention is added to the solid fuel, it can significantly reduce the ignition point of the fuel, improve the combustibility index of the fuel, and greatly improve the combustion performance of the solid fuel. The combustion improver of the present invention first synthesizes porous magnesium- and iron-doped titanium oxide powder by a hydrothermal method. Among them, the doped magnesium oxide has a promoting effect on carbon combustion, can prevent the formation and polymerization of the carbon particle flame retardant layer during combustion, and promote the combustion of the fuel. The iron oxide can accelerate the combustion of char and reduce the activation energy of the solid fuel combustion reaction. Subsequently, the oxides of calcium and cerium are partially coated. Among them, the oxide of calcium can produce a catalytic effect on the homogeneous ignition process of coal, promote the decomposition of the small molecule phase in the solid fuel, and the oxide of calcium can adsorb volatile components during combustion, promote the contact between active oxygen and carbon, increase the contact time, and promote the combustion reaction. Cerium oxide is a rare earth oxide, which can catalyze the coal combustion reaction, accelerate the decarbonization cracking reaction, and can promote the breaking and decomposition of the macromolecular branches in the pulverized coal, leaving holes in the pulverized coal, increasing the contact between carbon and oxygen in the pulverized coal, and improving the combustion rate. Secondly, nickel nitrate and potassium permanganate are used to form the Ni2O3-MnO2 component. Among them, Ni2O3 decomposes to form NiO and oxygen during combustion, and MnO2 can also decompose to form MnO and oxygen in a high-temperature environment, serving as an oxygen supply source to promote the combustion reaction. Finally, treatment with alkyl polyglycoside, etc. is carried out to improve the dispersibility of the combustion improver, enhance the contact area between the pulverized coal and oxygen, and improve the combustion efficiency.

[0029] Table 1 The technical solutions provided by the present invention have been introduced in detail above. For those of ordinary skill in the art, according to the idea of the embodiments of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A coal gangue-based solid fuel, characterized in that, It includes pulverized coal, coal gangue particles, binder, combustion aid, and sulfur-fixing agent. The preparation method of the combustion aid is as follows: (1) Add n-butanol, octylphenol polyoxyethylene ether, and tetrabutyl titanate into absolute ethanol, and stir for more than 20 min to obtain a mixed solution; prepare a composite solution of magnesium nitrate and iron nitrate. Heat the mixed solution in a water bath to 60 ± 5 °C for insulation, then add the composite solution of magnesium nitrate and iron nitrate to the mixed solution under stirring. After the addition is completed, continue to stir for more than 30 min, then add sodium hydroxide solution. After the addition, stir for more than 30 min, keep it at 60 ± 5 °C for static aging for more than 12 h. After aging, place it in a closed reaction kettle, heat it to 100 °C for hydrothermal insulation for more than 20 h, carry out solid-liquid separation, wash the solid phase with deionized water for more than 2 times and with ethanol for more than 2 times, dry it, and calcine it at 500 - 550 °C to obtain magnesium-iron composite oxide powder. (2) Add calcium nitrate and cerium nitrate into deionized water, stir to dissolve completely to obtain an aqueous solution, then heat the aqueous solution in a water bath to 85 ± 3 °C for insulation, and then add citric acid and the magnesium-iron composite oxide powder to the aqueous solution under stirring. After the addition, keep it at 85 ± 3 °C for stirring for 3 - 4 h to obtain a composite gel; place the composite gel in an environment of 110 ± 5 °C for drying for more than 15 h to dehydrate and embrittle, then heat it to 250 - 280 °C for insulation for 3 - 4 h, and pulverize it to obtain precursor particles. Heat the precursor particles to 800 - 820 °C for insulation for more than 15 h, and then cool it to room temperature with the furnace to obtain coated particles. (3) Prepare an aqueous solution of nickel nitrate; add the coated particles to the aqueous solution of nickel nitrate under stirring. After the addition is completed, continue to stir for more than 20 min to obtain a suspension, then add potassium permanganate to the suspension under stirring. After the addition is completed, continue to stir for more than 30 min, then let it stand in a negative pressure environment for more than 20 h, carry out solid-liquid separation, dry the solid phase at 100 - 120 °C for more than 3 h, and then calcine it at 450 - 480 °C for more than 5 h to obtain post-treatment powder. (4) Add alkyl polyglycoside and the post-treatment powder to an aqueous solution of ethanol, stir in an ultrasonic environment for more than 30 min to obtain a dispersion; heat the dispersion in a water bath to 60 ± 3 °C, and continue to stir at a constant temperature for more than 40 h after reaching the temperature; then add sodium hydroxide, ethylene glycol diglycidyl ether, and isopropanol under stirring. After the addition is completed, raise the temperature to 80 ± 3 °C, keep it at a constant temperature and stir for more than 3 h, then naturally cool it to room temperature, carry out solid-liquid separation, wash the solid phase with deionized water for more than 3 times and with ethanol for more than 3 times, dry it to obtain the combustion aid.

2. The coal gangue-based solid fuel according to claim 1, characterized in that, The sulfur-fixing agent is calcium oxide powder; the binder is polyvinyl alcohol.

3. A coal gangue-based solid fuel according to claim 1, characterized in that, Each raw material is in parts by weight: 90 - 100 parts of pulverized coal, 100 parts of coal gangue particles, 15 - 20 parts of binder, 10 - 12 parts of combustion aid, and 5 - 8 parts of sulfur-fixing agent.

4. The coal gangue-based solid fuel according to claim 1, wherein In the step (1), the mass ratio of butanol, octylphenol polyoxyethylene ether and tetrabutyl titanate added to absolute ethanol is butanol: octylphenol polyoxyethylene ether: tetrabutyl titanate: absolute ethanol = 2-3: 2-3: 6-9: 150; in the composite solution of magnesium nitrate and iron nitrate, the concentration of magnesium nitrate is 30-40 g / L, the concentration of iron nitrate is 25-28 g / L, and the solvent is water; in the sodium hydroxide solution, the mass percentage of sodium hydroxide is 10%, and the solvent is water; the volume ratio of the composite solution of magnesium nitrate and iron nitrate and the sodium hydroxide solution added to the mixed solution is mixed solution: composite solution of magnesium nitrate and iron nitrate: sodium hydroxide solution = 10: 10: 3-4.

5. A coal gangue-based solid fuel according to claim 1, characterized in that, In the step (2), the amount ratio of calcium nitrate and cerium nitrate added to deionized water is calcium nitrate: cerium nitrate: deionized water = 30-36 g: 18-22 g: 100 mL; the amount ratio of citric acid and the magnesium-iron composite oxide powder added to the aqueous solution is citric acid: magnesium-iron composite oxide powder: aqueous solution = 50-55 g: 10-20 g: 100 mL.

6. The coal gangue-based solid fuel according to claim 1, characterized in that In the step (3), in the aqueous solution of nickel nitrate, the concentration of nickel nitrate is 30-35 g / L, and the amount ratio of the coated particles and potassium permanganate added to the aqueous solution of nickel nitrate is aqueous solution of nickel nitrate: coated particles: potassium permanganate = 100 mL: 5-6 g: 4.2-4.6 g.

7. The coal gangue-based solid fuel according to claim 1, characterized in that, In the step (4), the amount ratio of alkyl polyglycoside and the post-treatment powder added to the aqueous ethanol solution is alkyl polyglycoside: post-treatment powder: aqueous ethanol solution = 20-25 g: 8-10 g: 200 mL, and the mass percentage of ethanol in the aqueous ethanol solution is 10%-20%; the mass ratio of sodium hydroxide, ethylene glycol diglycidyl ether and isopropanol added to the mass of the post-treatment powder added to the solution is sodium hydroxide: ethylene glycol diglycidyl ether: isopropanol: post-treatment powder = 0.5-0.6 g: 3-5 g: 10-12 g: 8-10 g.

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