Method for synergistic recycling of coal gangue and aluminum electrolysis anode carbon residue

Abstract

The present application relates to solid waste recycling technical field, specifically a kind of method for recycling and utilizing coal gangue and aluminum electrolysis anode carbon residue, and the recycling and utilizing method includes the following steps: S1, aluminum electrolysis anode carbon residue is crushed, grinds to particle size is 80-200 mesh;S2, after crushing, aluminum electrolysis anode carbon residue is mixed with modified coal gangue, and the raw material of stirring and mixing uniformly;S3, the raw material of mixing uniformly in step S2 is sent into cyclone burner, and molten electrolyte is obtained by burning;S4, after burning, molten electrolyte is extracted from the discharge port at the bottom of burner using vacuum ladle with heat preservation effect, and molten electrolyte is filtered to obtain pure molten electrolyte.The present application creatively utilizes the common characteristics of coal gangue and aluminum electrolysis anode carbon residue, and carries out synergistic combustion, which provides a new idea for the recycling and utilization of solid waste.

Description

Technical Field

[0001] This invention relates to the field of solid waste recycling technology, specifically a method for the co-recycling of coal gangue and aluminum electrolytic anode carbon slag. Background Technology

[0002] Coal gangue is a major solid waste generated during coal mining and washing, with a comprehensive utilization rate of less than 75%. Large-scale coal gangue accumulation not only occupies land resources but also causes soil, water, and air pollution due to weathering and leaching. Coal gangue contains a certain amount of carbonaceous material (usually 8-15%) and is rich in alumina (25-35%) and silicon dioxide (40-55%), possessing some potential for resource utilization. However, its main disposal methods currently remain stockpiling or low-calorific-value combustion, with the resulting waste residue being piled up, resulting in extremely low resource utilization.

[0003] Anode carbon slag from aluminum electrolysis is a hazardous solid waste generated during the aluminum electrolysis production process. It is retrieved from the electrolyte in the aluminum electrolysis cell and its main components include 50%–60% electrolyte and 40%–50% carbon particles. The electrolyte is mainly composed of cryolite, sodium fluoride, and aluminum fluoride, and is an indispensable raw material in aluminum electrolysis production. Currently, the main methods for treating anode carbon slag are flotation and vacuum roasting. Flotation can separate the electrolyte and carbon products, but the separated carbon powder still contains a certain amount of electrolyte and remains a hazardous solid waste. Furthermore, the electrolyte also contains a certain amount of carbon, and directly recycling it into the aluminum electrolysis cell would adversely affect the electrolysis process. Vacuum roasting utilizes a high-temperature vacuum environment to distill the electrolyte components from the carbon slag, achieving separation of the electrolyte and carbonaceous components. However, this method requires additional energy for heating, resulting in high energy consumption.

[0004] In summary, coal gangue can be used as fuel, but the solid waste residue after combustion cannot be effectively utilized as a resource. Wet processing of charcoal slag yields poor separation results and insufficient product purity, while pyrometallurgical methods are too energy-intensive. Therefore, we propose using the carbonaceous components of coal gangue and charcoal slag to generate high temperatures through combustion. This heat melts the solid electrolyte in the charcoal slag, forming a liquid electrolyte. The solid waste residues such as alumina and silica in the coal gangue dissolve into the electrolyte. The resulting liquid electrolyte containing dissolved alumina and silica can then be directly electrolyzed in an electrolytic cell to produce aluminum-silicon alloys. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the co-recycling and utilization of coal gangue and aluminum electrolysis anode carbon slag, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for the co-recycling of coal gangue and aluminum electrolysis anode carbon residue, comprising the following steps: S1. Crush and grind the aluminum electrolytic anode carbon slag to a particle size of 80-200 mesh; S2. Mix the crushed aluminum electrolytic anode carbon slag with modified coal gangue, put it into a mixing device and stir for 15-30 minutes to obtain a uniformly mixed raw material; S3. The uniformly mixed raw materials from step S2 are fed into a cyclone burner and co-combusted in an air atmosphere to obtain a molten electrolyte. S4. After combustion, the molten electrolyte is extracted from the discharge port at the bottom of the burner using a vacuum lifter with heat preservation effect, and a high-temperature resistant metal ceramic filter is installed at the inlet of the lifter pipe to filter the molten electrolyte and obtain pure molten electrolyte. The method for preparing the modified coal gangue includes the following steps: S101. Crush and grind the coal gangue to a particle size of 500-800 mesh; S102. The coal gangue treated in step S101 is placed in hydrochloric acid for 3-6 minutes, then filtered. The filtered product is washed with sufficient deionized water and then dried. S103. Continue ball milling the coal gangue treated in step S102 with ammonium bicarbonate for 2-4 hours to obtain a mixture; S104. The mixture obtained in step S103 is heated under an inert gas, and the heated product is further ground to 80-200 mesh to obtain modified coal gangue.

[0007] Furthermore, in step S2, the mass ratio between the modified coal gangue and the crushed aluminum electrolytic anode carbon slag is 1:(5-10).

[0008] Furthermore, in step S3, the air velocity in the burner is 1.2-1.8 m / s, the combustion temperature is 1000-1100℃, and the combustion time is 1.5-3 h.

[0009] Furthermore, the concentration of hydrochloric acid in step S102 is 0.5-1 mol / L.

[0010] Furthermore, in step S102, the drying temperature is 40-60℃ and the drying time is 5-8 hours.

[0011] Furthermore, in step S103, the mass ratio between the coal gangue processed in step S102 and ammonium bicarbonate is (3-5):1.

[0012] Furthermore, the heating process in step S104 is as follows: first, the temperature is increased to 250-300℃ at a rate of 2℃ and held for 1-2 hours; then, the temperature is increased to 450-550℃ at a rate of 5℃ and held for 0.5-1 hours.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, coal gangue and aluminum electrolysis anode carbon slag are jointly burned. Under high temperature conditions, the electrolyte remaining after the carbon slag is oxidized will become liquid. At the same time, the aluminum oxide and silicon oxide remaining in the coal gangue will dissolve in the cryolite-based electrolyte. The final electrolyte contains a high concentration of aluminum oxide and silicon oxide, which can be directly poured into the aluminum electrolysis cell to replenish the aluminum oxide and silicon oxide in the electrolyte of the aluminum electrolysis cell. This allows for the electrolytic generation of aluminum-silicon alloy without the need to add additional aluminum oxide and silicon oxide, thus realizing the comprehensive resource utilization of aluminum electrolysis anode carbon slag and coal gangue. 2. Furthermore, this invention utilizes the addition of coal gangue, which contains components such as alumina and silicon dioxide. Coal gangue can absorb hydrogen fluoride gas produced during combustion, reducing the amount of hydrogen fluoride gas produced when aluminum electrolysis anode carbon slag is burned alone. In addition, this invention further improves the coal gangue by first acid washing to increase its surface activation, allowing more active components to be exposed. Then, through combined heating with ammonium bicarbonate, the ammonium bicarbonate decomposes to produce gas, facilitating expansion between the coal gangue layers and further enhancing the exposure of active components, thereby increasing the absorption capacity for hydrogen fluoride. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is a process flow diagram for preparing modified coal gangue in this invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Please see Figures 1 to 2 The present invention provides: Example 1 A method for the co-recycling of coal gangue and aluminum electrolysis anode carbon residue, comprising the following steps: S1. Crush and grind the aluminum electrolysis anode carbon slag to a particle size of 120 mesh; S2. The crushed aluminum electrolytic anode carbon slag and modified coal gangue are mixed at a mass ratio of 8:1 and stirred in a mixing device for 20 minutes to obtain a uniformly mixed raw material. S3. The uniformly mixed raw materials from step S2 are fed into a cyclone burner and co-combusted in an air atmosphere to obtain a molten electrolyte. The air velocity in the burner is 1.6 m / s, the combustion temperature is 1050℃, and the combustion time is 2 h. S4. After combustion, the molten electrolyte is extracted from the discharge port at the bottom of the burner using a vacuum lifter with heat preservation effect, and a high-temperature resistant metal ceramic filter is installed at the inlet of the lifter pipe to filter the molten electrolyte and obtain pure molten electrolyte. The preparation method of modified coal gangue includes the following steps: S101. Crush and grind the coal gangue to a particle size of 600 mesh; S102. The coal gangue treated in step S101 is placed in hydrochloric acid with a concentration of 0.8 mol / L for 5 min. The hydrochloric acid completely submerges the coal gangue. After filtration, the filtered product is washed with sufficient deionized water and then dried. S103. Continue ball milling the coal gangue treated in step S102 and ammonium bicarbonate for 3 hours. The mass ratio of the coal gangue treated in step S102 to ammonium bicarbonate is 4:1, and a mixture is obtained. S104. The mixture obtained in step S103 is heated under an inert gas. The heating process is as follows: first, the temperature is increased to 280°C at a rate of 2°C and held for 1.5 hours; then, the temperature is increased to 500°C at a rate of 5°C and held for 0.8 hours. The heated product is then ground to 120 mesh to obtain modified coal gangue.

[0017] Example 2 A method for the co-recycling of coal gangue and aluminum electrolysis anode carbon residue, comprising the following steps: S1. Crush and grind the aluminum electrolysis anode carbon slag to a particle size of 80 mesh; S2. The crushed aluminum electrolytic anode carbon slag and modified coal gangue are mixed at a mass ratio of 5:1 and stirred in a mixing device for 15 minutes to obtain a uniformly mixed raw material. S3. The uniformly mixed raw materials from step S2 are fed into a cyclone burner and co-combusted in an air atmosphere to obtain a molten electrolyte. The air velocity in the burner is 1.2 m / s, the combustion temperature is 1000℃, and the combustion time is 1.5 h. S4. After combustion, the molten electrolyte is extracted from the discharge port at the bottom of the burner using a vacuum lifter with heat preservation effect, and a high-temperature resistant metal ceramic filter is installed at the inlet of the lifter pipe to filter the molten electrolyte and obtain pure molten electrolyte. The preparation method of modified coal gangue includes the following steps: S101. Crush and grind the coal gangue to a particle size of 500 mesh; S102. The coal gangue treated in step S101 is placed in hydrochloric acid with a concentration of 0.5 mol / L for 3 min. The hydrochloric acid completely submerges the coal gangue. Then, it is filtered. The filtered product is washed with sufficient deionized water and then dried. S103. Continue ball milling the coal gangue treated in step S102 and ammonium bicarbonate for 2 hours. The mass ratio of the coal gangue treated in step S102 to ammonium bicarbonate is 3:1, and a mixture is obtained. S104. The mixture obtained in step S103 is heated under an inert gas. The heating process is as follows: first, the temperature is increased to 250°C at a rate of 2°C and held for 1 hour; then, the temperature is increased to 450°C at a rate of 5°C and held for 0.5 hours. The heated product is then ground to 80 mesh to obtain modified coal gangue.

[0018] Example 3 A method for the co-recycling of coal gangue and aluminum electrolysis anode carbon residue, comprising the following steps: S1. Crush and grind the aluminum electrolysis anode carbon slag to a particle size of 200 mesh; S2. The crushed aluminum electrolytic anode carbon slag and modified coal gangue are mixed at a mass ratio of 10:1 and stirred in a mixing device for 30 minutes to obtain a uniformly mixed raw material. S3. The uniformly mixed raw materials from step S2 are fed into a cyclone burner and co-combusted in an air atmosphere to obtain a molten electrolyte. The air velocity in the burner is 1.8 m / s, the combustion temperature is 1100℃, and the combustion time is 3 h. S4. After combustion, the molten electrolyte is extracted from the discharge port at the bottom of the burner using a vacuum lifter with heat preservation effect, and a high-temperature resistant metal ceramic filter is installed at the inlet of the lifter pipe to filter the molten electrolyte and obtain pure molten electrolyte. The preparation method of modified coal gangue includes the following steps: S101. Crush and grind the coal gangue to a particle size of 800 mesh; S102. The coal gangue treated in step S101 is placed in hydrochloric acid with a concentration of 1 mol / L for 6 min, then filtered, and the filtered product is washed with sufficient deionized water and dried. S103. Continue ball milling the coal gangue treated in step S102 and ammonium bicarbonate for 4 hours. The mass ratio of the coal gangue treated in step S102 to ammonium bicarbonate is 5:1, and a mixture is obtained. S104. The mixture obtained in step S103 is heated under an inert gas. The heating process is as follows: first, the temperature is increased to 300°C at a rate of 2°C and held for 2 hours; then, the temperature is increased to 550°C at a rate of 5°C and held for 1 hour. The heated product is then ground to 200 mesh to obtain modified coal gangue.

[0019] In step S3 of this invention, during combustion, the carbonaceous components in the mixed raw materials (including carbonaceous materials in coal gangue and carbonaceous materials in anode carbon slag) are fully combusted, releasing a large amount of heat, which melts the electrolyte in the anode carbon slag to form a liquid electrolyte phase. At the same time, the high-temperature environment promotes the full dissolution of alumina and silicon dioxide in the coal gangue in the liquid electrolyte, forming a molten electrolyte system containing alumina and silicon dioxide. In addition, under the high-temperature environment, some hydrogen fluoride gas will be released from the electrolyte, and the alumina and silicon dioxide in the coal gangue will adsorb the hydrogen fluoride gas, significantly reducing the emission of fluorides. The excess heat can be used for steam in the production plant area, and oxygen can also be used to assist combustion in step S3.

[0020] In step S4 of this invention, the molten electrolyte is filtered to remove a small amount of undissolved solid residue (mainly undissolved impurities in coal gangue and a small amount of incompletely burned carbon particles) to obtain pure molten electrolyte. The filtered solid residue can be returned to the cyclone burner for further combustion treatment to improve resource utilization.

[0021] The coal gangue used in this invention has the following composition: 28.82% alumina, 48.27% silicon dioxide, and 11.34% fixed carbon. The composition of the aluminum electrolysis anode carbon slag is as follows: Na3AlF6: 40.86%, AlF3: 4.27%, CaF2: 3.29%, LiF: 2.41%, Al2O3: 2.56%, MgF2: 0.50%, KF: 1.63%, impurities: 2.01%, C: 42.47%. Three groups of pure molten electrolytes were prepared through Examples 1-3. The composition of these three groups of molten electrolytes was analyzed, as shown below: Example 1: Alumina content 8.21%, silicon oxide content 8.64%, and the remaining components are Na3AlF6: 64.48%, AlF3: 6.83%, CaF2: 4.61%, LiF: 2.97%, MgF2: 0.83%, KF: 2.51%, and iron oxide: 0.92%.

[0022] Example 2: Alumina content 11.61%, silicon oxide content 12.75%, and the remaining components are Na3AlF6: 57.31%, AlF3: 6.12%, CaF2: 4.69%, LiF: 3.46%, MgF2: 0.74%, KF: 2.46%, and iron oxide: 0.86%.

[0023] Example 3: Alumina content 6.72%, silicon oxide content 6.61%, and the remaining components are Na3AlF6: 67.30%, AlF3: 7.49%, CaF2: 4.49%, LiF: 2.81%, MgF2: 0.99%, KF: 2.53%, and iron oxide: 1.06%.

[0024] As can be seen from the data in Examples 1-3, the molten electrolyte obtained by the present invention contains alumina and silicon dioxide from coal gangue.

[0025] To further investigate the concentration of hydrogen fluoride gas generated during the combined calcination process, the following comparative example was set up: Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the modified coal gangue in step S2 is replaced with the same amount of unmodified coal gangue, and the selected coal gangue particle size is exactly the same as that in Example 1.

[0026] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that step S2 was completely eliminated, and the crushed and ground aluminum electrolytic anode carbon slag was directly burned in the burner.

[0027] The concentration of hydrogen fluoride produced during the combustion process of Examples 1-3 and Comparative Examples 1-2 was measured, and the results are shown in Table 1 below: Table 1: Hydrogen fluoride concentration during combustion in Examples 1-3 and Comparative Examples 1-2 As can be seen from the data in Comparative Example 2 and Example 1 in Table 1 above, the present invention can greatly reduce the generation of hydrogen fluoride by combining the combustion of coal gangue and aluminum electrolysis anode carbon slag. The data comparison between Comparative Example 1 and Example 1 shows that after the coal gangue is improved in the present invention, the exposure of alumina in the coal gangue is further improved, and the absorption effect of hydrogen fluoride is further improved.

[0028] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for synergistic recycling of coal gangue and aluminum electrolysis anode carbon residue, characterized in that, The recycling method includes the following steps: S1. Crush and grind the aluminum electrolytic anode carbon slag to a particle size of 80-200 mesh; S2. Mix the crushed aluminum electrolytic anode carbon slag with modified coal gangue, and stir in a mixing device for 15-30 minutes to obtain a uniformly mixed raw material. S3. The uniformly mixed raw materials from step S2 are fed into a cyclone burner and co-combusted in an air atmosphere to obtain a molten electrolyte. S4. After combustion, the molten electrolyte is extracted from the discharge port at the bottom of the burner using a vacuum lifter with heat preservation effect, and a high-temperature resistant metal ceramic filter is installed at the inlet of the lifter pipe to filter the molten electrolyte and obtain pure molten electrolyte. The method for preparing the modified coal gangue includes the following steps: S101. Crush and grind the coal gangue to a particle size of 500-800 mesh; S102. The coal gangue treated in step S101 is placed in hydrochloric acid for 3-6 minutes, then filtered. The filtered product is washed with sufficient deionized water and then dried. S103. Continue ball milling the coal gangue treated in step S102 with ammonium bicarbonate for 2-4 hours to obtain a mixture; S104. The mixture obtained in step S103 is heated under an inert gas, and the heated product is further ground to 80-200 mesh to obtain modified coal gangue. In step S103, the mass ratio between the coal gangue processed in step S102 and ammonium bicarbonate is (3-5):

1. The heating process in step S104 is as follows: first, the temperature is increased to 250-300℃ at a rate of 2℃ and held for 1-2 hours; then, the temperature is increased to 450-550℃ at a rate of 5℃ and held for 0.5-1 hours.

2. The method for synergistic recycling of coal gangue and aluminum electrolysis anode carbon residue according to claim 1, characterized in that, In step S2, the mass ratio between the modified coal gangue and the crushed aluminum electrolytic anode carbon slag is 1:(5-10).

3. The method for synergistic recycling of coal gangue and aluminum electrolysis anode carbon residue according to claim 1, characterized in that, In step S3, the air velocity in the burner is 1.2-1.8 m / s, the combustion temperature is 1000-1100℃, and the combustion time is 1.5-3 h.

4. The method for co-recycling and utilizing coal gangue and aluminum electrolysis anode carbon slag according to claim 1, characterized in that, The concentration of hydrochloric acid in step S102 is 0.5-1 mol / L.

5. The method for co-recycling and utilizing coal gangue and aluminum electrolysis anode carbon slag according to claim 1, characterized in that, In step S102, the drying temperature is 40-60℃ and the drying time is 5-8 hours.

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