A method for co-resource utilization of carbon-containing hazardous waste from aluminum electrolysis

Abstract

This invention belongs to the field of aluminum electrolysis hazardous waste treatment technology, specifically a method for the co-resource utilization of carbon-containing hazardous waste from aluminum electrolysis. It couples multiple treatment processes—mechanical activation, mixing, activation decyanation, and high-temperature-high-pressure activation leaching—within a high-temperature ball mill, achieving the co-resource utilization of waste cathode carbon blocks and slag. This invention has the technical advantages of simple process, high added value of recycled products, low risk of secondary pollution, and low equipment investment and site occupation. It also possesses the ability to co-resource non-carbon hazardous waste aluminum ash slag from aluminum electrolysis, with a cyanide dissociation rate ≥99.5%, a fixed carbon content of the mixed carbon material ≥99.0%, and a fluorine recovery rate ≥97.5%.

Description

Technical Field

[0001] This invention relates to the field of hazardous waste treatment technology in aluminum electrolysis, specifically a method for the co-resource utilization of carbon-containing hazardous waste from aluminum electrolysis. Background Technology

[0002] The aluminum electrolysis production process generates hazardous carbon-containing waste such as waste cathode carbon blocks and carbon slag, which contain high concentrations of soluble fluorides / cyanides. Currently, due to the lack of efficient treatment methods that simultaneously address the clean disposal of toxic substances and the comprehensive recovery of valuable elements, the vast majority of aluminum electrolysis carbon-containing hazardous waste is stockpiled. Its significant leaching toxicity poses a serious pollution risk to the ecological environment, while also leaving a large amount of high-quality carbon resources idle. Therefore, scholars both domestically and internationally have conducted extensive research on the safe disposal and resource utilization of waste cathode carbon blocks or carbon slag, but research on the synergistic disposal of the two is relatively limited, currently focusing mainly on the following aspects:

[0003] Patent document CN114751746A discloses a method for treating carbon-containing solid waste from the aluminum electrolysis industry. The method involves mixing crushed waste cathode carbon blocks and carbon slag from aluminum electrolysis, then adding the mixture to a high-temperature fluidized bed furnace at 550–750°C for oxygen-enriched combustion for 1.5 hours to obtain an electrolyte with a carbon content ≤0.5%. However, this high-temperature combustion process generates significant energy consumption and carbon emissions. Furthermore, the high-quality graphite and low-sulfur calcined petroleum coke contained in the waste cathode carbon blocks and slag are used as low-value fuels, resulting in limited economic benefits. Additionally, the complex and insoluble impurities contained in the waste cathode carbon blocks also enter the recycled products, severely impacting the recycling of the regenerated electrolyte.

[0004] Patent document CN113426807B discloses a method for the combined treatment and comprehensive utilization of hazardous waste residue from aluminum electrolysis. This method uses an aluminum-containing acidic solution generated from pressurized water leaching and sulfuric acid leaching of aluminum ash to leach carbon slag. Subsequently, the leaching waste liquid is neutralized by a fluorine-containing alkaline solution generated from pressurized alkaline leaching of waste cathode carbon blocks. This achieves the synergistic utilization of acidic and alkaline waste liquids from the disposal of three hazardous wastes: overhaul slag, carbon slag, and aluminum ash. However, this method involves three treatment processes—overhaul slag, carbon slag, and aluminum ash—as well as the synergistic utilization of intermediate products, resulting in an extremely complex process flow, low processing efficiency, and significant challenges in large-scale production.

[0005] Patent document CN107626712A discloses a comprehensive treatment method and resource utilization of hazardous solid waste from aluminum electrolysis. The method involves refining, pulping, and flotation of waste cathode carbon blocks and slag to recover carbon powder and electrolyte powder. This electrolyte powder is then used in a smelting reduction furnace with waste refractory materials, a mixture of waste alumina solid waste, and pure alumina to prepare silicon-aluminum alloy and electrolyte. However, this method involves separate processing steps for raw materials such as the waste alumina solid waste mixture, waste cathode carbon blocks, slag, and waste refractory materials. The process is complex, the co-processing is difficult, and the recovered carbon powder has low purity, resulting in limited economic benefits.

[0006] Patent document CN113278808B discloses a method for the integrated recovery of various solid wastes from the aluminum smelting process. The method involves sequentially crushing, mixing, screening, and magnetically separating aluminum ash and waste cathode carbon blocks to remove elemental aluminum and high-iron materials. Afterward, water leaching and hot acid leaching are performed. The resulting hot acid leaching slurry is mixed with decarburized carbon slag recovered from carbon slag flotation and leached. The resulting mixed leaching residue is returned to the carbon slag flotation process for deep impurity removal. The mixed leaching solution is neutralized, precipitated, and calcined at high temperature to obtain a mixed product of aluminum fluoride and alumina. However, this method involves two processing steps: wet leaching of aluminum ash / waste cathode carbon blocks and carbon slag flotation. The process is complex, material matching is difficult, and processing efficiency is low. Summary of the Invention

[0007] To address the problems existing in the prior art, the main objective of this invention is to propose a collaborative resource recovery method for carbon-containing hazardous waste from aluminum electrolysis. This method constructs a centralized disposal process for various carbon-containing hazardous wastes from aluminum electrolysis, enabling the collaborative recovery of carbon materials and fluorine-containing components contained in aluminum electrolysis waste cathode carbon blocks and carbon slag. It features high added value of recovered products, simple process flow, and green environmental protection.

[0008] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution:

[0009] A method for the co-resource utilization of carbon-containing hazardous waste from aluminum electrolysis includes the following steps:

[0010] S1. The waste cathode carbon blocks and carbon slag are refined and dried respectively to obtain waste cathode carbon block powder and carbon slag powder.

[0011] S2. Waste cathode carbon block powder and carbon slag powder are added to a high-temperature ball mill at a mass ratio of 1:0.5~3.0 for high-temperature activation and mixing pretreatment to obtain mixed powder material A; the pretreatment speed is 100~400 r / min, the pretreatment time is 0.1~1.0h, and the pretreatment temperature is 100~250℃.

[0012] S3. Add aluminum nitride-containing powder to a high-temperature ball mill at 10-30% of the mass of mixed powder material A to obtain mixed powder material B. Then add hydrogen peroxide solution with a concentration of 1-10 mL / L, controlling the liquid-solid ratio of hydrogen peroxide solution to mixed powder material B to be 2-20 mL / g, and perform activation and decyanation treatment to obtain decyanated material and ammonia. After the decyanation is completed, collect and store the ammonia.

[0013] S4. Add the reaction agent to the high-temperature ball milling device for high-temperature-high-pressure activation leaching. Control the volume ratio of the decyanated material to the reaction agent to be 1:0.5~3.0, the concentration of the reaction agent to be 2~12 mol / L, the rotation speed to be 100~300 r / min, the leaching time to be 0.5~5.0 h, and the leaching temperature to be 120~240℃. After leaching, perform solid-liquid separation and ball material separation in sequence to obtain residue and initial waste liquid. After the residue is treated by countercurrent water washing, perform solid-liquid separation to obtain mixed carbon material and water washing waste liquid.

[0014] As a preferred embodiment of the co-resource utilization method for carbon-containing hazardous waste from aluminum electrolysis according to the present invention, in step S1, the particle size of both the waste cathode carbon block powder and the carbon slag powder is <0.074 mm.

[0015] As a preferred embodiment of the co-resource utilization method for carbon-containing hazardous waste from aluminum electrolysis according to the present invention, in step S2, the high-temperature ball mill is equipped with an exhaust valve, and the inner lining material of the high-temperature ball mill is polytetrafluoroethylene.

[0016] As a preferred embodiment of the co-resource utilization method for carbon-containing hazardous waste from aluminum electrolysis according to the present invention, in step S3, the aluminum nitride-containing powder material is aluminum nitride or aluminum ash slag with a particle size <0.074 mm.

[0017] As a preferred embodiment of the co-resource utilization method for carbon-containing hazardous waste from aluminum electrolysis according to the present invention, in step S3, the decyanation rotation speed is 150~350 r / min, the decyanation time is 0.1~2.0 h, and the decyanation temperature is 100~250℃.

[0018] As a preferred embodiment of the co-resource utilization method for carbon-containing hazardous waste from aluminum electrolysis according to the present invention, in step S4, the reaction agent is one or more of sulfuric acid, hydrofluoric acid, hydrochloric acid, and nitric acid.

[0019] As a preferred embodiment of the co-resource utilization method for carbon-containing hazardous waste from aluminum electrolysis according to the present invention, in step S4, the washing waste liquid includes strongly acidic washing waste liquid and weakly acidic washing waste liquid, wherein the pH value of the strongly acidic washing waste liquid is ≤2, the strongly acidic washing waste liquid is mixed with the initial waste liquid to obtain a high-concentration waste liquid, the pH value of the weakly acidic leaching waste liquid is >2, and the weakly acidic washing waste liquid is recycled for countercurrent washing treatment.

[0020] As a preferred embodiment of the co-resource utilization method for carbon-containing hazardous waste from aluminum electrolysis according to the present invention, wherein: after step S4, the method further includes:

[0021] S5. The pH value of the initial waste liquid or high-concentration waste liquid is adjusted to 4-6 using the ammonia gas stored in step S3, and then concentrated, crystallized, separated and dried in sequence to obtain ammonium fluoride and supernatant.

[0022] As a preferred embodiment of the co-resource utilization method for carbon-containing hazardous waste from aluminum electrolysis according to the present invention, in step S5, the pH value of the supernatant is adjusted to 6~10, the temperature is controlled at 40~90℃ to crystallize cryolite, and cryolite and residual solution are obtained after solid-liquid separation.

[0023] As a preferred embodiment of the co-resource utilization method for carbon-containing hazardous waste from aluminum electrolysis according to the present invention, in step S5, the residual solution is mixed with weakly acidic water washing waste liquid and then recycled for countercurrent water washing treatment.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention proposes a method for the co-resource utilization of carbon-containing hazardous waste from aluminum electrolysis. It couples multiple processing steps—mechanical activation, mixing, activation decyanation, and high-temperature-high-pressure activation leaching—within a high-temperature ball mill, achieving the co-resource utilization of waste cathode carbon blocks and carbon slag. This invention offers technical advantages such as simple process, high added value of recycled products, low risk of secondary pollution, and minimal equipment investment and site occupation. It also possesses the ability to co-resource non-carbon hazardous waste from aluminum electrolysis—aluminum ash slag—with a cyanide dissociation rate ≥99.5%, a fixed carbon content of the mixed carbon material ≥99.0%, and a fluorine recovery rate ≥97.5%. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1This is a schematic diagram of the process for the co-resource utilization of carbon-containing hazardous waste from aluminum electrolysis according to the present invention.

[0028] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0029] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.

[0030] This invention proposes a method for the co-resource utilization of carbon-containing hazardous waste from aluminum electrolysis. It couples multiple processing steps—mechanical activation, mixing, activation decyanation, and high-temperature-high-pressure activation leaching—within a high-temperature ball mill, achieving the co-resource utilization of waste cathode carbon blocks and carbon slag.

[0031] (1) High-temperature mechanical activation and mixing process: The reaction activity of powder materials is enhanced by mechanical activation-thermal activation, and the uniformity of mixing of aluminum electrolysis waste cathode carbon blocks and carbon slag is ensured.

[0032] (2) Activation of the decyanation process: Mechanical activation can improve the kinetic conditions of the decyanation reaction. At the same time, the generation of ammonia will create a high-pressure environment in the high-temperature ball mill, which together promotes the oxidative decomposition of highly toxic cyanide in waste cathode carbon blocks and aluminum ash. The dissociation rate of cyanide is ≥99.5%.

[0033] (3) High-temperature-high-pressure activation leaching process: Utilizing the resource interaction properties of various aluminum electrolysis hazardous wastes to form Al 3+ -H + The -HF composite enhanced leaching system, while constructing a high-temperature and high-pressure reaction environment, also has a mechanical activation and enhancement effect, which can significantly increase the removal rate of non-carbon components and recover the fixed carbon content of mixed carbon materials ≥99.0%.

[0034] (4) Waste liquid treatment: Ammonium fluoride products are prepared by adjusting the pH value of acidic waste liquid with ammonia gas. This avoids the environmental pollution risk of waste gas and waste liquid while realizing the high-value recovery of valuable components. The fluorine recovery rate is ≥97.5%.

[0035] According to one aspect of the present invention, the present invention provides the following technical solution:

[0036] like Figure 1 As shown, a method for the co-resource utilization of carbon-containing hazardous waste from aluminum electrolysis includes the following steps:

[0037] S1. The waste cathode carbon blocks and carbon slag are refined and dried respectively to obtain waste cathode carbon block powder and carbon slag powder.

[0038] S2. Waste cathode carbon block powder and carbon slag powder are added to a high-temperature ball mill at a mass ratio of 1:0.5~3.0 for high-temperature activation and mixing pretreatment to obtain mixed powder material A; the pretreatment speed is 100~400 r / min, the pretreatment time is 0.1~1.0 h, and the pretreatment temperature is 100~250℃; specifically, the mass ratio of waste cathode carbon block powder to carbon slag powder can be, for example, but not limited to, any one or any two of 1:0.5, 1:1.0, 1:1.5, 1:2.0, 1:2.5, 1:3.0, and the pretreatment speed can be, for example, but not limited to, 100 r / min, 150 r / min, 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min. The pretreatment time can be any one or a range between any two of the following: r / min; for example, but not limited to, 0.1h, 0.2h, 0.3h, 0.4h, 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1.0h; and the pretreatment temperature can be any one or a range between any two of the following: 100℃, 125℃, 150℃, 175℃, 200℃, 225℃, 250℃.

[0039] S3. Add aluminum nitride-containing powder to a high-temperature ball mill at 10-30% of the mass of mixed powder material A to obtain mixed powder material B. Then add hydrogen peroxide solution with a concentration of 1-10 mL / L, controlling the liquid-solid ratio of hydrogen peroxide solution to mixed powder material B to be 2-20 mL / g, and perform activation and decyanation treatment to obtain decyanated material and ammonia gas. After decyanation is completed, collect and store the ammonia gas. Specifically, the amount of aluminum nitride-containing powder added can be, for example, but not limited to, any one or any two of 10%, 15%, 20%, 25%, and 30% of the mass of mixed powder material A. The concentration of the hydrogen peroxide solution can be, for example, but not limited to, any one or any two of 1 mL / L, 2 mL / L, 3 mL / L, 4 mL / L, 5 mL / L, 6 mL / L, 7 mL / L, 8 mL / L, 9 mL / L, 10 mL / L; the liquid-solid ratio of the hydrogen peroxide solution to the mixed powder material B can be, for example, but not limited to, any one or any two of 2 mL / g, 4 mL / g, 6 mL / g, 8 mL / g, 10 mL / g, 12 mL / g, 14 mL / g, 16 mL / g, 18 mL / g, 20 mL / g;

[0040] S4. Add the reaction agent to the high-temperature ball milling device for high-temperature-high-pressure activation leaching. Control the volume ratio of the decyanated material to the reaction agent to be 1:0.5~3.0, the concentration of the reaction agent to be 2~12 mol / L, the rotation speed to be 100~300 r / min, the leaching time to be 0.5~5.0 h, and the leaching temperature to be 120~240℃. After leaching, perform solid-liquid separation and ball material separation in sequence to obtain residue and initial waste liquid. After the residue is treated by countercurrent water washing, perform solid-liquid separation to obtain mixed carbon material and water washing waste liquid. Specifically, the volume ratio of the decyanation material to the reaction agent can be, for example, but not limited to, any one or any two of 1:0.5, 1:1.0, 1:1.5, 1:2.0, 1:2.5, 1:3.0; the concentration of the reaction agent can be, for example, but not limited to, any one or any two of 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L; and the rotation speed can be, for example, but not limited to, 100 r / min, 120 r / min, 140 r / min, 160 r / min, 180 r / min, 200 r / min, 220 r / min, 240 r / min, 260 r / min, 280 r / min. The leaching speed can be any one of r / min, 300 r / min, or a range between any two; the leaching time can be, for example, but not limited to, any one of 0.5 h, 1.0 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h, 3.5 h, 4.0 h, 4.5 h, 5.0 h, or a range between any two; the leaching temperature can be, for example, but not limited to, any one of 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, or a range between any two.

[0041] Preferably, in step S1, the particle size of both the waste cathode carbon block powder and the carbon slag powder is <0.074mm.

[0042] Preferably, in step S2, the high-temperature ball milling device is equipped with an exhaust valve, and the inner lining material of the high-temperature ball milling device is polytetrafluoroethylene.

[0043] Preferably, in step S3, the aluminum nitride-containing powder material is aluminum nitride or aluminum ash slag with a particle size <0.074 mm. Before the activation and decyanation treatment, the exhaust valve of the high-temperature ball mill is closed; before collecting ammonia, the exhaust valve of the high-temperature ball mill is opened.

[0044] Preferably, in step S3, the decyanation rotation speed is 150~350 r / min, the decyanation time is 0.1~2.0 h, and the decyanation temperature is 100~250℃. Specifically, the decyanation rotation speed can be, for example, but not limited to, any one or any two of 150 r / min, 200 r / min, 250 r / min, 300 r / min, 350 r / min; the decyanation time can be, for example, but not limited to, any one or any two of 0.1 h, 0.25 h, 0.5 h, 0.75 h, 1.0 h, 1.25 h, 1.5 h, 1.75 h, 2.0 h; and the decyanation temperature can be, for example, but not limited to, any one or any two of 100℃, 125℃, 150℃, 175℃, 200℃, 225℃, 250℃.

[0045] Preferably, in step S4, the reaction agent is one or more of sulfuric acid, hydrofluoric acid, hydrochloric acid, and nitric acid. The residue needs to be washed 3-4 times. The pH value of the wastewater from the first wash is very low, and the pH value of the wastewater increases sequentially with each wash. Therefore, the wastewater includes strongly acidic wastewater and weakly acidic wastewater. The pH value of the strongly acidic wastewater is ≤2. The strongly acidic wastewater is mixed with the initial wastewater to obtain a high-concentration wastewater. The pH value of the weakly acidic wastewater is >2. The weakly acidic wastewater is recycled for countercurrent washing treatment.

[0046] Preferably, after step S4, the method further includes:

[0047] S5. Using the ammonia gas stored in step S3, adjust the pH of the initial waste liquid or high-concentration waste liquid to 4-6, and then perform concentration, crystallization, separation, and drying processes sequentially to obtain ammonium fluoride and supernatant. Adjust the pH of the supernatant to 6-10, and control the temperature at 40-90℃ to crystallize cryolite. After solid-liquid separation, obtain cryolite and residual solution. The residual solution is mixed with weakly acidic water washing waste liquid and recycled for countercurrent water washing treatment.

[0048] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0049] Example 1

[0050] A method for the co-resource utilization of carbon-containing hazardous waste from aluminum electrolysis includes the following steps:

[0051] S1. The waste cathode carbon blocks and carbon slag are refined and dried respectively to obtain waste cathode carbon block powder and carbon slag powder with a particle size <0.074 mm.

[0052] S2. Waste cathode carbon block powder and carbon slag powder are added to a high-temperature ball mill in a 1:1 mass ratio for high-temperature activation and mixing pretreatment to obtain mixed powder material A; the pretreatment speed is 300 r / min, the pretreatment time is 0.5h, and the pretreatment temperature is 240℃.

[0053] S3. Add aluminum nitride powder to the high-temperature ball mill at 10% of the mass of mixed powder material A to obtain mixed powder material B. Then add hydrogen peroxide solution with a concentration of 6 mL / L, controlling the liquid-solid ratio of hydrogen peroxide solution to mixed powder material B to be 15 mL / g. Close the exhaust valve and perform activation and decyanation treatment to obtain decyanated material and ammonia. The decyanation speed is 250 r / min, the decyanation time is 1.0 h, and the decyanation temperature is 240℃. After the decyanation is completed, open the exhaust valve, collect the ammonia and store it. The dissociation rate of cyanide is 99.88%.

[0054] S4. Sulfuric acid is added to a high-temperature ball mill for high-temperature-high-pressure activation leaching. The volume ratio of the decyanated material to sulfuric acid is controlled at 1:1, the sulfuric acid concentration is 6 mol / L, the rotation speed is 250 r / min, the leaching time is 1.0 h, and the leaching temperature is 220℃. After leaching, solid-liquid separation and ball material separation are performed sequentially to obtain residue and initial waste liquid. The residue is subjected to countercurrent water washing and then solid-liquid separation to obtain mixed carbon material and water washing waste liquid. The strongly acidic water washing waste liquid is mixed with the initial waste liquid to obtain a high-concentration waste liquid. The residual solution is mixed with the weakly acidic water washing waste liquid and recycled for countercurrent water washing treatment. The weakly acidic water washing waste liquid is recycled for countercurrent water washing treatment. The fixed carbon content of the mixed carbon material is 99.38%.

[0055] S5. The pH of the high-concentration waste liquid is adjusted to 5 using the ammonia gas stored in step S3. The liquid is then concentrated, crystallized, separated, and dried sequentially to obtain ammonium fluoride and a supernatant. The pH of the supernatant is adjusted to 9, and cryolite crystallization is performed at 80℃. After solid-liquid separation, cryolite and a residual solution are obtained. The residual solution is mixed with weakly acidic water washing waste liquid and recycled for countercurrent water washing treatment. The fluorine recovery rate is 98.75%.

[0056] Example 2

[0057] A method for the co-resource utilization of carbon-containing hazardous waste from aluminum electrolysis includes the following steps:

[0058] S1. The waste cathode carbon blocks and carbon slag are refined and dried respectively to obtain waste cathode carbon block powder and carbon slag powder with a particle size <0.074 mm.

[0059] S2. Waste cathode carbon block powder and carbon slag powder are added to a high-temperature ball mill at a mass ratio of 1:2 for high-temperature activation and mixing pretreatment to obtain mixed powder material A; the pretreatment speed is 200 r / min, the pretreatment time is 1.0 h, and the pretreatment temperature is 200℃.

[0060] S3. Add aluminum nitride powder to a high-temperature ball mill at 15% of the mass of mixed powder material A to obtain mixed powder material B. Then add hydrogen peroxide solution with a concentration of 4 mL / L, controlling the liquid-solid ratio of hydrogen peroxide solution to mixed powder material B to be 15 mL / g. Close the exhaust valve and perform activation and decyanation treatment to obtain decyanated material and ammonia. The decyanation speed is 250 r / min, the decyanation time is 1.0 h, and the decyanation temperature is 240℃. After the decyanation is completed, open the exhaust valve, collect the ammonia and store it. The dissociation rate of cyanide is 99.80%.

[0061] S4. Hydrochloric acid is added to a high-temperature ball mill for high-temperature-high-pressure activation leaching. The volume ratio of the decyanated material to hydrochloric acid is controlled at 1:1.5, the hydrochloric acid concentration is 8 mol / L, the rotation speed is 250 r / min, the leaching time is 1.5 h, and the leaching temperature is 200℃. After leaching, solid-liquid separation and ball material separation are performed sequentially to obtain residue and initial waste liquid. The residue is subjected to countercurrent water washing and then solid-liquid separation to obtain mixed carbon material and water washing waste liquid. The strongly acidic water washing waste liquid is mixed with the initial waste liquid to obtain a high-concentration waste liquid. The residual solution is mixed with the weakly acidic water washing waste liquid and recycled for countercurrent water washing treatment. The weakly acidic water washing waste liquid is recycled for countercurrent water washing treatment. The fixed carbon content of the mixed carbon material is 99.20%.

[0062] S5. The pH of the high-concentration waste liquid is adjusted to 4.75 using the ammonia gas stored in step S3. The liquid is then concentrated, crystallized, separated, and dried sequentially to obtain ammonium fluoride and a supernatant. The pH of the supernatant is adjusted to 8.75, and cryolite crystallization is performed at 70℃. After solid-liquid separation, cryolite and a residual solution are obtained. The residual solution is mixed with weakly acidic washing waste liquid and recycled for countercurrent washing treatment. The fluorine recovery rate is 98.28%.

[0063] Example 3

[0064] A method for the co-resource utilization of carbon-containing hazardous waste from aluminum electrolysis includes the following steps:

[0065] S1. The waste cathode carbon blocks and carbon slag are refined and dried respectively to obtain waste cathode carbon block powder and carbon slag powder with a particle size <0.074 mm.

[0066] S2. Waste cathode carbon block powder and carbon slag powder are added to a high-temperature ball mill in a 1:1 mass ratio for high-temperature activation and mixing pretreatment to obtain mixed powder material A; the pretreatment speed is 300 r / min, the pretreatment time is 0.5h, and the pretreatment temperature is 240℃.

[0067] S3. Add aluminum ash slag powder to the high-temperature ball mill at 20% of the mass of mixed powder material A to obtain mixed powder material B. Then add hydrogen peroxide solution with a concentration of 6 mL / L, controlling the liquid-solid ratio of hydrogen peroxide solution to mixed powder material B to be 20 mL / g. Close the exhaust valve and perform activation and decyanation treatment to obtain decyanated material and ammonia. The decyanation speed is 250 r / min, the decyanation time is 1.0 h, and the decyanation temperature is 240℃. After the decyanation is completed, open the exhaust valve, collect the ammonia and store it. The dissociation rate of cyanide is 99.62%.

[0068] S4. Hydrochloric acid is added to a high-temperature ball mill for high-temperature-high-pressure activation leaching. The volume ratio of the decyanated material to hydrochloric acid is controlled at 1:1.5, the hydrochloric acid concentration is 8 mol / L, the rotation speed is 300 r / min, the leaching time is 2.0 h, and the leaching temperature is 220℃. After leaching, solid-liquid separation and ball material separation are performed sequentially to obtain residue and initial waste liquid. The residue is subjected to countercurrent water washing and then solid-liquid separation to obtain mixed carbon material and water washing waste liquid. The strongly acidic water washing waste liquid is mixed with the initial waste liquid to obtain a high-concentration waste liquid. The residual solution is mixed with the weakly acidic water washing waste liquid and recycled for countercurrent water washing treatment. The weakly acidic water washing waste liquid is recycled for countercurrent water washing treatment. The fixed carbon content of the mixed carbon material is 99.14%.

[0069] S5. The pH of the high-concentration waste liquid is adjusted to 5.25 using the ammonia gas stored in step S3. The liquid is then concentrated, crystallized, separated, and dried sequentially to obtain ammonium fluoride and a supernatant. The pH of the supernatant is adjusted to 9.25, and cryolite crystallization is performed at 70℃. After solid-liquid separation, cryolite and a residual solution are obtained. The residual solution is mixed with weakly acidic washing waste liquid and recycled for countercurrent washing treatment. The fluorine recovery rate is 97.73%.

[0070] Example 4

[0071] A method for the co-resource utilization of carbon-containing hazardous waste from aluminum electrolysis includes the following steps:

[0072] S1. The waste cathode carbon blocks and carbon slag are refined and dried respectively to obtain waste cathode carbon block powder and carbon slag powder with a particle size <0.074 mm.

[0073] S2. Waste cathode carbon block powder and carbon slag powder are added to a high-temperature ball mill at a mass ratio of 1:0.5 for high-temperature activation and mixing pretreatment to obtain mixed powder material A; the pretreatment speed is 250 r / min, the pretreatment time is 0.5h, and the pretreatment temperature is 240℃.

[0074] S3. Add aluminum ash slag powder to a high-temperature ball mill at 25% of the mass of mixed powder material A to obtain mixed powder material B. Then add hydrogen peroxide solution with a concentration of 4 mL / L, controlling the liquid-solid ratio of hydrogen peroxide solution to mixed powder material B to be 20 mL / g. Close the exhaust valve and perform activation and decyanation treatment to obtain decyanated material and ammonia. The decyanation speed is 200 r / min, the decyanation time is 0.5 h, and the decyanation temperature is 240℃. After the decyanation is completed, open the exhaust valve, collect the ammonia and store it. The dissociation rate of cyanide is 99.54%.

[0075] S4. Sulfuric acid is added to a high-temperature ball mill for high-temperature-high-pressure activation leaching. The volume ratio of the decyanated material to sulfuric acid is controlled at 1:2, the sulfuric acid concentration is 6 mol / L, the rotation speed is 200 r / min, the leaching time is 0.5 h, and the leaching temperature is 220℃. After leaching, solid-liquid separation and ball material separation are performed sequentially to obtain residue and initial waste liquid. The residue is subjected to countercurrent water washing and then solid-liquid separation to obtain mixed carbon material and water washing waste liquid. The strongly acidic water washing waste liquid is mixed with the initial waste liquid to obtain a high-concentration waste liquid. The residual solution is mixed with the weakly acidic water washing waste liquid and recycled for countercurrent water washing treatment. The weakly acidic water washing waste liquid is recycled for countercurrent water washing treatment. The fixed carbon content of the mixed carbon material is 99.03%.

[0076] S5. The pH of the high-concentration waste liquid is adjusted to 5.5 using the ammonia gas stored in step S3. The liquid is then concentrated, crystallized, separated, and dried sequentially to obtain ammonium fluoride and a supernatant. The pH of the supernatant is adjusted to 9.5, and cryolite crystallization is performed at 60℃. After solid-liquid separation, cryolite and a residual solution are obtained. The residual solution is mixed with weakly acidic washing waste liquid and recycled for countercurrent washing treatment. The fluorine recovery rate is 97.55%.

[0077] This invention has the advantages of simple process, high added value of recycled products, low risk of secondary pollution, and low equipment investment and site occupation. It also has the ability to synergistically utilize non-carbon hazardous waste from aluminum electrolysis and aluminum ash slag. The dissociation rate of cyanide is ≥99.5%, the fixed carbon content of mixed carbon materials is ≥99.0%, and the fluorine recovery rate is ≥97.5%.

[0078] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for co-processing of carbon-containing hazardous waste in aluminum electrolysis, characterized by, The method comprises the following steps: S1. separately refining and drying the waste cathode carbon block and the carbon residue to obtain waste cathode carbon block powder material and carbon residue powder material; S2. adding the waste cathode carbon block powder material and the carbon residue powder material into a high-temperature ball mill device according to a mass ratio of 1:0.5-3.0 for high-temperature activation and uniform mixing pretreatment to obtain mixed powder material A; the pretreatment speed is 100-400 r / min, the pretreatment time is 0.1-1.0 h, and the pretreatment temperature is 100-250 DEG C; S3. adding aluminum nitride-containing powder material according to 10-30% of the mass of the mixed powder material A into the high-temperature ball mill device to obtain mixed powder material B, then adding hydrogen peroxide solution with a concentration of 1-10 mL / L, controlling the liquid-solid ratio of the hydrogen peroxide solution and the mixed powder material B to be 2-20 mL / g, and performing activation and de-cyanation treatment to obtain de-cyanation material and ammonia gas, and the dissociation rate of cyanide is greater than or equal to 99.5%; after the de-cyanation is completed, the ammonia gas is collected and stored; S4. adding a reaction reagent into the high-temperature ball mill device for high-temperature-high-pressure activation leaching, controlling the volume ratio of the de-cyanation material and the reaction reagent to be 1:0.5-3.0, the reaction reagent being one or more of sulfuric acid, hydrofluoric acid, hydrochloric acid and nitric acid, the concentration of the reaction reagent being 2-12 mol / L, the speed being 100-300 r / min, the leaching time being 0.5-5.0 h, and the leaching temperature being 120-240 DEG C; after the leaching is completed, solid-liquid separation and ball-material separation are sequentially performed to obtain residue and initial waste liquid; the residue is subjected to countercurrent water washing treatment and then solid-liquid separation to obtain mixed carbon material and water washing waste liquid; the fixed carbon content of the mixed carbon material is greater than or equal to 99.0%.

2. The method of claim 1, wherein, In the step S1, the particle size of the waste cathode carbon block powder material and the carbon residue powder material is less than 0.074 mm.

3. The method of claim 1, wherein, In the step S2, the high-temperature ball mill device is provided with an exhaust valve, and the inner lining material of the high-temperature ball mill device is polytetrafluoroethylene.

4. The method of claim 1, wherein, In the step S3, the aluminum nitride-containing powder material is aluminum nitride or aluminum ash residue, and the particle size is less than 0.074 mm.

5. The method of claim 1, wherein, In the step S3, the de-cyanation speed is 150-350 r / min, the de-cyanation time is 0.1-2.0 h, and the de-cyanation temperature is 100-250 DEG C.

6. The method of claim 1, wherein, In the step S4, the water washing waste liquid includes strong acid water washing waste liquid and weak acid water washing waste liquid, wherein the pH value of the strong acid water washing waste liquid is less than or equal to 2, the strong acid water washing waste liquid is mixed with the initial waste liquid to obtain high-concentration waste liquid, the pH value of the weak acid water washing waste liquid is greater than 2, and the weak acid water washing waste liquid is recycled for countercurrent water washing treatment.

7. The method of claim 6, wherein, The method further comprises the following step after the step S4: S5. adjusting the pH value of the initial waste liquid or the high-concentration waste liquid to 4-6 by using the ammonia gas stored in the step S3, and sequentially performing concentration, crystallization, separation and drying treatment to obtain ammonium fluoride and supernatant; the recovery rate of fluorine is greater than or equal to 97.5%.

8. The method of claim 7, wherein, In the step S5, the pH value of the supernatant is adjusted to 6-10, and the temperature is controlled to be 40-90 DEG C for cryolite crystallization, and cryolite and residual solution are obtained after solid-liquid separation.

9. The method of claim 8, wherein, In the step S5, the residual solution is mixed with the weak acid water washing waste liquid and recycled for countercurrent water washing treatment.

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