Full-component treatment method of coal gangue as well as product and application thereof

Abstract

The invention discloses an all-component treatment method of coal gangue as well as a product and application thereof. The all-component treatment method of the coal gangue comprises the following steps: a) pyrolysis: mixing the coal gangue with an alkaline activator, and performing high-temperature pyrolysis treatment in an inert atmosphere to prepare an alkali-melting coal gangue precursor; b) splitting: carrying out polar hydration treatment on the alkali-molten coal gangue precursor, filtering, and taking filtrate as an inorganic molecular sieve precursor and filter residue as an organic carbon material precursor at the same time; c) synthesis: sequentially carrying out aging treatment, hydrothermal treatment and evaporative crystallization treatment on the inorganic substance molecular sieve precursor to prepare a zeolite molecular sieve; and d) activation: mixing the organic matter carbon material precursor with an alkaline activator, and performing high-temperature pyrolysis treatment in an inert atmosphere to obtain the porous activated carbon. The method can be used for respectively performing high-value utilization on inorganic matters and organic matters of the coal gangue.

Description

Technical Field

[0001] The invention relates to the technical field of mine solid waste treatment, in particular to the technical field of coal gangue treatment. Background Art

[0002] Coal is one of the fossil fuels that humans have been using for centuries, and gangue is the solid waste generated during coal mining and washing. Gangue is a dark gray rock with a low carbon content and a harderness than coal seams. It is produced during the coal formation process and usually accounts for 15-20% of the total raw coal output. Gangue piled in the open air not only takes up a lot of space, but the residual coal and sulfides contained in it are prone to continuous release of heat through oxidation reactions during long-term stacking, and then induce spontaneous combustion after the internal temperature continues to rise, and even lead to disasters such as explosions. In addition, the sulfur-containing and nitrogen-containing substances contained in the gangue will also release harmful gases such as SO2 and NO2 during oxidative combustion, which will cause serious pollution to the mining environment.

[0003] Existing methods for treating coal gangue are mainly concentrated in highway roadbed and mine reclamation and backfilling, brick making and concrete production, such as a coal gangue silicate cement clinker and its preparation method with announcement number CN112028508B and a production method of waste gypsum, red mud and coal gangue sintered brick building materials with announcement number CN111848125B; however, although the above methods are diverse, the overall conversion value is still relatively low.

[0004] The chemical composition of coal gangue is mainly inorganic and organic matter, and the main components of inorganic matter are SiO2 and Al2O3 (clay minerals and quartz), as well as some metal oxides such as Fe2O3 (pyrite) and CaO (calcite), while the main element of organic matter is C (content 15-30%), and it also contains a certain amount of H, N, S and O. Due to its special composition of inorganic and organic matter, coal gangue has broad prospects in high-value resource utilization.

[0005] In addition, a pretreatment system for comprehensive utilization of coal gangue with announcement number CN210979879U can effectively increase the specific surface area of ​​the obtained pretreatment product by combining raw material crushing, drying and preheating, combustion and pore making, and making the coal gangue fully contact with solvents or chemical additives to improve the pore making efficiency, thereby solving the problems of low utilization rate, waste of resources and unsatisfactory pretreatment effect of coal gangue in the existing application process; however, it still cannot make high-value utilization of inorganic and organic matter in coal gangue respectively. Summary of the invention

[0006] The purpose of the present invention is to solve the problems in the prior art, to propose a method for processing all components of coal gangue and its products and applications, so as to make high-value use of inorganic and organic matter in coal gangue respectively.

[0007] To achieve the above object, the present invention proposes a method for processing all components of coal gangue, comprising the following steps: a) Pyrolysis: Mixing coal gangue with an alkaline activator and subjecting it to high-temperature pyrolysis treatment in an inert atmosphere to obtain an alkali-melted coal gangue precursor; b) Splitting: firstly subject the alkali-melted coal gangue precursor to polar hydration treatment, and then after filtering, use the filtrate as the inorganic molecular sieve precursor and the filter residue as the organic carbon material precursor; c) Synthesis: The inorganic molecular sieve precursor is subjected to aging treatment, hydrothermal treatment and evaporation crystallization treatment in sequence to obtain a zeolite molecular sieve; d) Activation: The organic carbon material precursor is mixed with an alkaline activator and then subjected to high-temperature pyrolysis treatment in an inert atmosphere to produce porous activated carbon.

[0008] Preferably, in step a), the mass mixing ratio of the alkaline activator to the coal gangue is not higher than 300% and not lower than 10%, the alkaline activator is a combination of at least two of KOH, NaOH, NaHCO3, Na2CO3 and KHCO3, the temperature condition of the high temperature pyrolysis treatment is 400-950°C and the treatment time is 1-3 h; wherein powdered coal gangue with a particle size of 60 to 200 mesh is used as the solid waste raw material; in step a), the coal gangue will gradually lose moisture and simultaneously release some volatile components as the pyrolysis temperature increases under an inert atmosphere, and on the other hand, its organic components and inorganic components will remain in the solid residue; in addition, during the alkali melting period, two or more alkaline activators will couple and cooperate to combine more inorganic components, and since the main components of the inorganic components in the solid residue are SiO2 and Al2O3, if the alkaline activator is a mixture of NaOH and Na2CO3, sodium silicate and sodium aluminate will be generated through the following reactions (1) to (4), and the organic components in the solid residue will further aromatize to form carbon; SiO2+2NaOH=Na2SiO3+H2O (1); SiO2+Na2CO3=Na2SiO3+CO2↑ (2); Al2O3+2NaOH=2NaAlO2+H2O (3); Al2O3+Na2CO3=2NaAlO2+CO2↑ (4).

[0009] Preferably, in step b), the polar hydration treatment is to dissolve the alkali-melted coal gangue precursor in a slightly alkaline solution, the pH of the slightly alkaline solution is 7-8.5, the dissolution temperature is 50-95°C, the dissolution time is 10-60 min, and the dissolution pressure is not less than 0.2 MPa; taking the generation of sodium silicate and sodium aluminate in step a) as an example, since such alkali-melted products usually have good solubility (their solubility will be better in a slightly alkaline environment), and the organic components in the coal gangue form organic carbon after further carbonization that is insoluble in the slightly alkaline solution, the separation of the organic and inorganic components of the coal gangue can be achieved by dissolution filtration.

[0010] Preferably, in step c), the aging treatment is to age the inorganic molecular sieve precursor at a temperature of 15 to 35° C. for 12 to 48 hours; wherein the aging treatment helps the growth of precipitated crystals, increases the particle size of the crystals, and makes the particle size distribution of the crystals more uniform.

[0011] Preferably, in step c), the hydrothermal treatment is to hydrothermally react the inorganic molecular sieve precursor at a temperature of 100 to 150° C. and a pressure of 1 to 20 MPa for 2 to 24 h; after the hydrothermal treatment, the filtrate is in the form of a uniform colored solution; wherein the hydrothermal reaction can control the formation of the crystal structure, crystal morphology and grain purity of the nanoparticles through the self-ionization phenomenon of water molecules under high temperature and high pressure, thereby providing the necessary conditions for the subsequent crystallization of the zeolite molecular sieve.

[0012] Preferably, in step c), the evaporation crystallization treatment is to evaporate the inorganic molecular sieve precursor at a temperature of 80-100°C until it is fully crystallized; wherein the evaporation crystallization process increases the concentration of the solute in the solution by evaporating the solvent until a saturated state is reached; after the solution reaches saturation, the solute begins to crystallize, and the crystals can gradually grow to a sufficiently large size; after the precipitated crystals are dried, the zeolite molecular sieve can be obtained.

[0013] Preferably, in step d), the mass mixing ratio of the alkaline activator to the organic carbon material precursor is not higher than 50% and not lower than 10%, the alkaline activator is a combination of one or more of KOH, NaOH, NaHCO3, Na2CO3 and KHCO3, the temperature condition of the high temperature pyrolysis treatment is 500-900°C and the treatment time is 1-3 h; step d) is to use the alkaline activator and pyrolysis conditions to activate and expand the pore structure of the organic carbon material; after the carbon pore activation treatment is completed, the alkaline activator can also be removed by acid washing and water washing; when KOH is used as an alkaline activator to further activate the solid organic matter obtained by filtration under a nitrogen atmosphere, the following reactions (5) to (7) will occur; these reactions can form a large number of pores in the organic carbon material precursor, so that the porous activated carbon has more micropores and mesopores, providing good conditions for the subsequent carbon electrode of the supercapacitor: 4KOH+C=K2CO3+K2O+4H2 (5); K2O+C=2K+CO (6); K2CO3+2C=2K+3CO (7).

[0014] The product of the full-component treatment method of coal gangue is obtained by the above-mentioned treatment method. The zeolite molecular sieve is based on the inorganic components in the coal gangue, rich in sodium, silicon and oxygen elements, and the total content of organic elements does not exceed 20wt.%, thereby ensuring the high purity and specific properties of the material; the porous activated carbon is based on the organic components in the coal gangue, rich in carbon, nitrogen and oxygen elements, and the total content of inorganic elements does not exceed 20wt.%.

[0015] Preferably, the average pore size of the zeolite molecular sieve is controlled within the range of 0.1 to 35 nm, and the porous activated carbon has a large number of micropores and mesopores after drying, and the average pore size is controlled within the range of 0.1 to 15 nm.

[0016] The application of the products of the full-component treatment method of coal gangue, specifically the application of the zeolite molecular sieve in material adsorption, and the application of the porous activated carbon in electrical energy storage; wherein, the zeolite molecular sieve has a large number of pores, and can be used to adsorb CO2 after being fully dried, and the adsorption temperature is 20-30°C, and the adsorption pressure is 0.1 MPa (when a high concentration of CO2 with a flow rate of 25 ml / min is introduced, and the whole process adsorption time is about 200 s, the dynamic adsorption amount of CO2 by the zeolite molecular sieve can reach more than 2 mmol / g); for porous activated carbon, when a platinum sheet is used as a counter electrode, a saturated calomel is used as a reference electrode, and the current density is 1 A / g, the specific capacitance can reach more than 100 F / g.

[0017] Beneficial effects of the present invention: 1) The present invention separates the organic matter from the inorganic matter of the coal gangue and uses physical or chemical modification to convert the organic matter of the coal gangue into zeolite molecular sieves that can be used in the adsorption field, and converts the inorganic matter of the coal gangue into porous activated carbon that can be used in the field of electrical energy storage, thereby finally realizing the high-order and high-value utilization of all components of the coal gangue solid waste. This can not only effectively reduce the pollution of the coal gangue to the environment and the land occupation problem (turning the coal gangue into waste and bringing better economic benefits), but also provide a new idea for the harmless, reduced and resource development of coal gangue; 2) The zeolite molecular sieve prepared by the present invention mainly adsorbs CO2 by chemical adsorption (different from the traditional physical adsorption, which occurs in the form of bicarbonate ions and mainly interacts with the water adsorbed in the air), and because it contains a large amount of cations and some carbon silicate-like substances, it can form a complex with CO2 during the adsorption process, thereby further improving the adsorption capacity, and has great utilization prospects; 3) The porous activated carbon prepared by the present invention can be applied to the field of electrical energy storage. Its large number of micropores and mesopores can improve the storage performance of the electrode material on the one hand, which is conducive to full contact with the electrolyte. On the other hand, it can provide Faraday pseudocapacitance, thereby enhancing the specific capacity and cycle rate, and then synthesizing supercapacitor materials with pseudocapacitance and double-layer characteristics, which can not only solve the problem of solid waste disposal, but also expand the application of solid waste in energy storage devices, which has a double meaning for the utilization of new energy and environmental protection.

[0018] The features and advantages of the present invention will be described in detail through embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a process flow chart of the full component treatment method of coal gangue; Figure 2 is a SEM image of zeolite molecular sieve; Figure 3 It is the adsorption process curve of zeolite molecular sieve when adsorbing CO2; Figure 4 It is the dynamic adsorption capacity of zeolite molecular sieve when adsorbing CO2 and the simulation diagram of pseudo-first-order kinetics and pseudo-second-order kinetics models; Figure 5 is the SEM image of porous activated carbon; Figure 6 This is the cyclic voltammetry test curve of porous activated carbon when used as a carbon electrode for supercapacitors; Figure 7 This is the constant current charge and discharge curve of porous activated carbon when used as the carbon electrode of a supercapacitor. DETAILED DESCRIPTION

[0020] See also Figure 1 The method for processing all components of coal gangue comprises the following steps: a) Pyrolysis: Coal gangue is used as solid waste, first ground into fine particles by a pulverizer, and then passed through a 100-mesh screen; then, the ground coal gangue powder and an alkaline activator (the alkaline activator is a mixture of NaOH and Na2CO3 mixed in a mass ratio of 1:1) are fully ground and mixed in a mass ratio of 1:1.2; then, heated at 450°C for 2 h in a N2 atmosphere to obtain alkali-melted coal gangue (alkali-melted coal gangue precursor); b) Splitting: firstly subject the alkali-melted coal gangue precursor to polar hydration treatment (dissolve the alkali-melted coal gangue precursor with deionized water at 90°C under vigorous stirring for 30 min, and control the pH to 8, and the dissolution pressure to not less than 0.2MPa), then use the filtrate as the inorganic molecular sieve precursor and the filter residue as the organic carbon material precursor after natural cooling and filtration; c) Synthesis: The inorganic molecular sieve precursor was subjected to aging treatment (aging at 25°C for 24 h), hydrothermal treatment (first transferred to a stainless steel reaction tank lined with polytetrafluoroethylene, and then hydrothermally reacted at 120°C and 1 MPa for 12 h), and evaporation crystallization treatment (evaporated at 80-100°C until fully crystallized) to obtain a zeolite molecular sieve (SEM image as shown in FIG. Figure 2 shown); d) Activation: After drying, the organic carbon material precursor was ground and mixed with an alkaline activator (KOH) at a mass ratio of 1:0.3; then, it was heated at 750°C for 2 h in a N2 atmosphere; then, it was fully washed with a 1 mol / L hydrochloric acid solution and washed with deionized water until neutral, and then dried in an oven to constant weight to obtain porous activated carbon (SEM image as shown in FIG. Figure 5 as shown).

[0021] The zeolite molecular sieve was transferred to the CO2 adsorption test bench and its adsorption effect on ultra-high purity gaseous CO2 (99.999%) was measured at 20°C and 1 atmosphere. The results are shown in Figure 3 and Figure 4 As shown, the dynamic adsorption capacity of zeolite molecular sieve for CO2 can reach 2.33 mmol / g.

[0022] First, porous activated carbon, polytetrafluoroethylene dispersion and acetylene black were mixed in a mass ratio of 7:2:1 to prepare a working electrode. Then, the working electrode, platinum electrode and calomel electrode were combined to form a three-electrode test system. The cyclic voltammetric characteristics and constant current charge-discharge characteristics of the working electrode were tested using an electrochemical workstation with 6 M / L potassium hydroxide solution as the electrolyte. The results are shown in Figure 2. Figure 6 and Figure 7As shown, after the porous activated carbon was made into a carbon electrode for a supercapacitor, the electrode specific capacitance at 1 A / g was measured to be 111 F / g.

[0023] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Any solution that is a simple transformation of the present invention belongs to the protection scope of the present invention.

Claims

1. A method for treating all components of coal gangue, characterized in that: The steps include: a) Pyrolysis: Mixing coal gangue with an alkaline activator and subjecting it to high-temperature pyrolysis treatment in an inert atmosphere to obtain an alkali-melted coal gangue precursor; b) Splitting: firstly subject the alkali-melted coal gangue precursor to polar hydration treatment, and then after filtering, use the filtrate as the inorganic molecular sieve precursor and the filter residue as the organic carbon material precursor; c) Synthesis: The inorganic molecular sieve precursor is subjected to aging treatment, hydrothermal treatment and evaporation crystallization treatment in sequence to obtain a zeolite molecular sieve; d) Activation: The organic carbon material precursor is mixed with an alkaline activator and then subjected to high-temperature pyrolysis treatment in an inert atmosphere to produce porous activated carbon.

2. The method for treating all components of coal gangue according to claim 1, characterized in that: In step a), the mass mixing ratio of the alkaline activator to the coal gangue is not higher than 300% and not lower than 10%, the alkaline activator is a combination of at least two of KOH, NaOH, NaHCO3, Na2CO3 and KHCO3, the temperature condition of the high temperature pyrolysis treatment is 400-950°C and the treatment time is 1-3 h.

3. The method for treating all components of coal gangue according to claim 1, characterized in that: In step b), the polar hydration treatment is to dissolve the alkali-melted coal gangue precursor in a slightly alkaline solution, the pH of the slightly alkaline solution is 7-8.5, the dissolution temperature is 50-95°C, the dissolution time is 10-60 min, and the dissolution pressure is not less than 0.2 MPa.

4. The method for treating all components of coal gangue according to claim 1, characterized in that: In step c), the aging treatment is to age the inorganic molecular sieve precursor at a temperature of 15 to 35° C. for 12 to 48 hours.

5. The method for treating all components of coal gangue according to claim 1, characterized in that: In step c), the hydrothermal treatment is to hydrothermally react the inorganic molecular sieve precursor at a temperature of 100 to 150° C. and a pressure of 1 to 20 MPa for 2 to 24 h.

6. The method for treating all components of coal gangue according to claim 1, characterized in that: In step c), the evaporation crystallization treatment is to evaporate the inorganic molecular sieve precursor at a temperature of 80-100° C. until it is fully crystallized.

7. The method for treating all components of coal gangue according to claim 1, characterized in that: In step d), the mass mixing ratio of the alkaline activator to the organic carbon material precursor is not higher than 50% and not lower than 10%, the alkaline activator is a combination of one or more of KOH, NaOH, NaHCO3, Na2CO3 and KHCO3, the temperature condition of the high temperature pyrolysis treatment is 500-900°C and the treatment time is 1-3 h.

8. A product of all-component treatment of coal gangue, obtained by the treatment method according to any one of claims 1 to 7, characterized in that: The zeolite molecular sieve is based on inorganic components in coal gangue and the total content of organic elements does not exceed 20wt.%, and the porous activated carbon is based on organic components in coal gangue and the total content of inorganic elements does not exceed 20wt.%.

9. The full-component processed product of coal gangue according to claim 8, characterized in that: The average pore size of the zeolite molecular sieve is controlled within a range of 0.1 to 35 nm, and the average pore size of the porous activated carbon is controlled within a range of 0.1 to 15 nm.

10. The use of the full-component processed product of coal gangue as claimed in claim 9, characterized in that: The application of the zeolite molecular sieve in material adsorption, and the application of the porous activated carbon in electrical energy storage.

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