A method for recycling carbonaceous materials in carbon-containing waste from aluminum electrolysis

Abstract

The present invention belongs to the technical field of aluminum electrolysis hazardous waste treatment, and specifically relates to a method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis. The high-temperature ball milling device is used to assist in recovering the carbonaceous materials contained in the carbon-containing hazardous waste in aluminum electrolysis. The mixing treatment, high-temperature activation roasting, and high-pressure activation leaching are all carried out in the high-temperature mechanical activation device. By constructing an oxidation-fluorination roasting system and an HF-HCl / H2SO4 / HNO3 mixed acid purification system, on the one hand, the safe dissociation of cyanide / fluorine toxic substances can be achieved, and on the other hand, the effective separation of complex and poorly soluble aluminosilicates can be realized. The fixed carbon content of the recovered carbonaceous materials is ≥99.0%. On the other hand, in view of the physical and chemical properties of the roasting flue gas and the acid leaching waste liquid, the treatment processes such as pH value regulation, seed addition, and cooling crystallization are innovatively coupled to realize the recycling of solid reaction reagents, with a recovery rate of ≥85% and no risk of secondary pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum electrolysis hazardous waste treatment, and specifically to a method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis. Background Art

[0002] During the aluminum electrolysis production process, carbon-containing hazardous wastes such as waste cathode carbon blocks and carbon slag rich in fluorine / cyanide toxic substances are continuously generated, posing a serious pollution risk to the ecological environment. At the same time, carbon-containing waste in aluminum electrolysis usually contains 30%-40% low-sulfur petroleum coke (carbon slag) or 50%-70% high-quality graphite carbon (waste cathode carbon blocks), which has significant recycling value. Therefore, the clean and efficient recovery of carbonaceous materials from carbon-containing waste in aluminum electrolysis has become a hot topic of concern in the industry.

[0003] Patent document CN103726074B discloses a method for recycling aluminum electrolysis waste materials to produce electrolyte for aluminum production and recover carbon. The crushed waste cathode carbon blocks or carbon slag are subjected to magnetic separation to remove iron, and then diesel oil and coal flotation GF oil are added to a microbubble countercurrent flotation column. After the foam is filtered by pressure and dried, carbon powder with a fixed carbon content ≥75% is obtained. However, during the flotation process, the separation of carbonaceous materials from toxic substances is not thorough, and the purity is relatively low, which limits the resource utilization of the recovered carbonaceous materials.

[0004] Patent document CN111196609B discloses a method for recovering carbonaceous materials from waste carbon materials in aluminum electrolysis. The sieved carbon slag or waste cathode carbon blocks are mixed with 18 mol / L sulfuric acid solution and subjected to primary roasting and secondary roasting at 100-300°C and 300-600°C respectively to obtain the recovered carbonaceous materials. However, it is difficult to remove complex aluminum silicates during the sulfation roasting process, and it is easy to react with calcium-containing components to form complex insoluble minerals, resulting in relatively low purity of the recovered carbonaceous materials.

[0005] Patent document CN112108489A discloses a high-temperature vacuum treatment method, treatment device and operation method for aluminum electrolysis waste cathode, carbon slag or silicon carbide bricks. The waste cathode carbon blocks or carbon slag are refined and mixed, and then placed in a high-temperature vacuum treatment device, and vacuum distilled at 30-500 Pa and 600-1100°C for 2-8 h to obtain carbonaceous materials with a content ≥80%. However, the high-temperature vacuum treatment process has high energy consumption, and at the same time, the purity of the recovered carbonaceous materials is relatively low.

[0006] Patent document CN107285354B discloses a method for continuous separation of carbonaceous hazardous waste in the aluminum industry by low-temperature melting infiltration and the resulting products. The waste cathode carbon blocks and carbon slag are crushed and de-ironed, and then subjected to low-temperature electrocalcination and high-temperature electrocalcination at 1000 - 1200 °C and 1300 - 1600 °C respectively to obtain a carbonaceous material with a fixed carbon content ≥ 99%. However, maintaining both the low-temperature electrocalcination and high-temperature electrocalcination processes requires a large amount of energy consumption, and at the same time, the fluorine-containing flue gas will severely corrode the inner lining of the equipment and the conveying pipeline. Summary of the Invention

[0007] To solve the problems existing in the prior art, the main object of the present invention is to propose a method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis, realizing the low-cost (treatment temperature ≤ 250 °C, recycling of reaction reagents), green (no secondary pollution), and high-grade (fixed carbon content ≥ 99%) recovery of carbonaceous materials from carbon-containing waste in aluminum electrolysis, with the characteristics of simple process flow, environmental protection, and high efficiency.

[0008] To solve the above technical problems, according to one aspect of the present invention, the following technical solutions are provided:

[0009] A method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis, comprising the following steps:

[0010] S1. Crushing, classifying, and drying the carbon-containing waste in aluminum electrolysis to obtain pretreated materials;

[0011] S2. Adding the pretreated materials and a solid reaction reagent into a high-temperature ball milling device according to a mass ratio of 1:1 - 6 for mixing treatment;

[0012] S3. After the mixing treatment is completed, continue to carry out high-temperature activation roasting in the high-temperature ball milling device to obtain roasted materials and roasting flue gas. The roasting temperature is 100 - 250 °C, the activation roasting time is 0.5 - 4.0 h, the activation rotation speed is 100 - 300 r / min. After completion, open the exhaust valve to collect the roasting flue gas;

[0013] S4. Close the exhaust valve, add an acidic purification solution to the high-temperature ball milling device for high-pressure activation leaching. The activation rotation speed is 100 - 300 r / min, the leaching temperature is 40 - 220 °C, the leaching time is 0.1 - 1.0 h. After the activation leaching is completed, perform solid-liquid separation to obtain acid leaching waste liquid and residual solid materials. The residual solid materials are then separated by a vibrating screen, washed with water, and then subjected to solid-liquid separation to obtain carbonaceous materials and washing liquid.

[0014] As a preferred embodiment of the method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis according to the present invention, wherein: after the step S4, it further includes:

[0015] S5. Feed the calcination flue gas generated in step S3 into the acid leaching waste liquid generated in step S4, then add seeds, and recover the solid reaction reagent through vacuum concentration, cooling crystallization, centrifugal separation, and low-temperature drying in sequence.

[0016] As a preferred embodiment of the method for recovering carbonaceous materials from aluminum electrolysis carbon-containing waste in the present invention, wherein: in step S1, the aluminum electrolysis carbon-containing waste is a waste cathode carbon block or carbon slag, and the particle size of the pretreated material is ≤ 3 mm.

[0017] As a preferred embodiment of the method for recovering carbonaceous materials from aluminum electrolysis carbon-containing waste in the present invention, wherein: in step S2, the ball milling speed is 150 - 350 r / min, and the mixing time is 0.1 - 1.0 h.

[0018] As a preferred embodiment of the method for recovering carbonaceous materials from aluminum electrolysis carbon-containing waste in the present invention, wherein: in step S2, the solid reaction reagent is ammonium fluoride or ammonium bifluoride.

[0019] As a preferred embodiment of the method for recovering carbonaceous materials from aluminum electrolysis carbon-containing waste in the present invention, wherein: in step S2, the high-temperature ball milling device is lined with polytetrafluoroethylene, has a heating function, and is equipped with an exhaust valve at the top.

[0020] As a preferred embodiment of the method for recovering carbonaceous materials from aluminum electrolysis carbon-containing waste in the present invention, wherein: in step S4, the acidic purification solution is one or more of sulfuric acid, hydrochloric acid, and nitric acid, the concentration of the acidic purification solution is 1 - 10 mol / L, and the liquid-solid ratio of the acidic purification solution to the calcined material is 5 - 20 mL / g.

[0021] As a preferred embodiment of the method for recovering carbonaceous materials from aluminum electrolysis carbon-containing waste in the present invention, wherein: in step S4, the fixed carbon content of the carbonaceous material is ≥ 99.0%, and the washing liquid includes a low-concentration washing liquid and a high-concentration washing liquid. Among them, the pH value of the low-concentration washing liquid is > 2, and it is recycled for washing treatment; the pH value of the high-concentration washing liquid is ≤ 2, and it is combined with the acid leaching waste liquid for treatment.

[0022] As a preferred embodiment of the method for recovering carbonaceous materials from aluminum electrolysis carbon-containing waste in the present invention, wherein: in step S5, before adding seeds, use the calcination flue gas generated in step S3 to adjust the pH values of the acid leaching waste liquid and the high-concentration washing liquid generated in step S4 to 3.5 - 6.5.

[0023] As a preferred embodiment of the method for recovering carbonaceous materials from aluminum electrolysis carbon-containing waste in the present invention, wherein: in step S5, the seeds are ammonium fluoride and / or ammonium bifluoride.

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

[0025] The present invention provides a method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis. A high-temperature ball milling device is used to assist in the recovery of carbonaceous materials contained in carbon-containing hazardous waste in aluminum electrolysis. Mixing treatment, high-temperature activation roasting, and high-pressure activation leaching are all carried out in a high-temperature mechanical activation device. By constructing an oxidation-fluorination roasting system and a mixed acid purification system of HF-HCl / H2SO4 / HNO3, on the one hand, the safe dissociation of cyanide / fluorine toxic substances can be achieved, and on the other hand, the effective separation of complex and poorly soluble aluminosilicates can be realized. The fixed carbon content of the recovered carbonaceous materials is ≥99.0%. On the other hand, in view of the physical and chemical properties of roasting flue gas and acid leaching waste liquid, treatment processes such as pH value regulation, seed addition, and cooling crystallization are innovatively coupled to realize the recycling of solid reaction reagents, with a recovery rate of ≥85% and no risk of secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0027] Figure 1 It is a schematic flow chart of the method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis of the present invention.

[0028] The realization of the object, functional features, and advantages of the present invention will be further described in conjunction with the embodiments with reference to the drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The following will clearly and completely describe the technical solutions in the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0030] Due to the adoption of a high-temperature ball milling device to assist in the recovery of carbonaceous materials from carbon-containing hazardous waste in aluminum electrolysis: Firstly, the mixing treatment, high-temperature activation roasting, and high-pressure activation leaching are all carried out in a high-temperature mechanical activation device. Compared with the traditional mechanical activation → high-temperature roasting → wet leaching step-by-step treatment, it has the characteristics of simple process flow, high treatment efficiency, low equipment cost, and small floor area. Secondly, through high-temperature mechanical activation, not only can the reaction activity of carbon-containing hazardous waste in aluminum electrolysis be improved, but also the dynamic reaction process with solid / liquid reagents in the high-temperature roasting and wet leaching links can be realized, which can enhance the contact effect of the reaction system and significantly improve the reaction efficiency. Thirdly, by utilizing the heating function and sealing performance of the high-temperature ball milling device, a high-pressure reaction environment can be formed in the wet leaching link, further promoting the separation effect of carbonaceous materials and non-carbon impurities in carbon-containing hazardous waste in aluminum electrolysis. Finally, by constructing an oxidation-fluorination roasting system and an HF-HCl / H2SO4 / HNO3 mixed acid purification system, on the one hand, the safe dissociation of cyanide / fluoride toxic substances can be achieved, the leaching rate of fluorides ≥ 99.0%, and the dissociation rate of cyanides ≥ 99.2%. On the other hand, the effective separation of complex and poorly soluble aluminosilicates can be realized, and the fixed carbon content of the recovered carbonaceous materials ≥ 99.0%. On the other hand, aiming at the physicochemical properties of roasting flue gas and acid leaching waste liquid, innovative treatment processes such as pH value regulation, seed addition, and cooling crystallization are coupled to realize the recycling of solid reaction reagents, with a recovery rate ≥ 85% and no risk of secondary pollution.

[0031] According to one aspect of the present invention, the present invention provides the following technical solution:

[0032] As Figure 1 shown, a method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis includes the following steps:

[0033] S1. Crush, classify, and dry the carbon-containing waste in aluminum electrolysis to obtain pretreated materials;

[0034] S2. Add the pretreated materials and solid reaction reagents to a high-temperature ball milling device according to a mass ratio of 1:1 to 6 for mixing treatment; specifically, the mass ratio of the pretreated materials to the solid reaction reagents can be, for example but not limited to, any one or the range between any two of 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6;

[0035] After the mixing process is completed, continue with high-temperature activation roasting in a high-temperature ball milling device to obtain roasted materials and roasting flue gas. The roasting temperature is 100 - 250 °C, the activation roasting time is 0.5 - 4.0 h, the activation rotation speed is 100 - 300 r / min. After completion, open the exhaust valve to collect the roasting flue gas. Specifically, the roasting temperature can be, for example but not limited to, any one of or the range between 100 °C, 110 °C, 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, 250 °C; the activation roasting time can be, for example but not limited to, any one of or the range between 0.5 h, 1.0 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h, 3.5 h, 4.0 h; the activation rotation speed can be, for example but not limited to, any one of or the range between 100 r / min, 120 r / min, 150 r / min, 170 r / min, 200 r / min, 230 r / min, 250 r / min, 280 r / min, 300 r / min;

[0036] S4. Close the exhaust valve, add the acidic purification solution to the high-temperature ball milling device for high-pressure activation leaching. The activation rotation speed is 100 - 300 r / min, the leaching temperature is 40 - 220 °C, and the leaching time is 0.1 - 1.0 h. After the activation leaching is completed, perform solid-liquid separation to obtain acid leaching waste liquid and residual solid materials. The residual solid materials are then separated by a vibrating sieve, washed with water, and then subjected to solid-liquid separation again to obtain carbonaceous materials and washing liquid. Specifically, the activation rotation speed can be, for example but not limited to, any one of or the range between 100 r / min, 120 r / min, 150 r / min, 170 r / min, 200 r / min, 230 r / min, 250 r / min, 280 r / min, 300 r / min; the leaching temperature can be, for example but not limited to, any one of or the range between 40 °C, 50 °C, 100 °C, 150 °C, 200 °C, 220 °C; the leaching time can be, for example but not limited to, any one of or the range between 0.1 h, 0.2 h, 0.3 h, 0.4 h, 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h;

[0037] Preferably, after step S4, it further includes:

[0038] S5. Pass the roasting flue gas generated in step S3 into the acid leaching waste liquid generated in step S4 or the mixed liquid of the high-concentration washing liquid generated in step S4 and the acid leaching waste liquid generated in step S4, then add crystal seeds, and sequentially perform vacuum concentration, cooling crystallization, centrifugal separation, and low-temperature drying to recover solid reaction reagents.

[0039] Preferably, in the step S1, the carbon-containing waste in aluminum electrolysis is waste cathode carbon blocks or carbon slag, and the particle size of the pretreated material is ≤3 mm. Specifically, the particle size of the pretreated material can be, for example but not limited to, any one of ≤3 mm, ≤2 mm, ≤1 mm, ≤0.5 mm, ≤0.15 mm, ≤0.074 mm.

[0040] Preferably, in the step S2, the ball milling speed is 150 - 350 r / min and the mixing time is 0.1 - 1.0 h. The solid-state reaction reagent is ammonium fluoride or ammonium bifluoride. The high-temperature ball milling device is lined with polytetrafluoroethylene, has a heating function, and is equipped with an exhaust valve at the top. Specifically, the ball milling speed can be, for example but not limited to, any one of 150 r / min, 200 r / min, 250 r / min, 300 r / min, 350 r / min or any range between any two of them; the mixing time can be, for example but not limited to, any one of 0.1 h, 0.2 h, 0.3 h, 0.4 h, 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h or any range between any two of them;

[0041] Preferably, in the step S4, the acidic purification solution is one or several of sulfuric acid, hydrochloric acid, and nitric acid, the concentration of the acidic purification solution is 1 - 10 mol / L, and the liquid-solid ratio of the acidic purification solution to the calcined material is 5 - 20 mL / g. Specifically, the concentration of the acidic purification solution can be, for example but not limited to, any one of 1 mol / L, 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 or any range between any two of them; the liquid-solid ratio of the acidic purification solution to the calcined material can be, for example but not limited to, any one of 5 mL / g, 6 mL / g, 7 mL / g, 8 mL / g, 9 mL / g, 10 mL / g, 11 mL / g, 12 mL / g, 13 mL / g, 14 mL / g, 15 mL / g, 16 mL / g, 17 mL / g, 18 mL / g, 19 mL / g, 20 mL / g or any range between any two of them.

[0042] Preferably, in the step S4, the fixed carbon content of the carbonaceous material is ≥99.0%, and the residual solid material needs to be washed 3 - 4 times. The concentration of the washing liquid in the first wash is very high, and the concentration of the washing liquid decreases successively with the number of washing times. Therefore, the washing liquid includes a high-concentration washing liquid and a low-concentration washing liquid; among them, the pH value of the low-concentration washing liquid > 2, and it is recycled for washing treatment, and the pH value of the high-concentration washing liquid ≤ 2, which is combined with the acid leaching waste liquid for treatment.

[0043] Preferably, in step S5, before adding seeds, the pH value of the acid leaching waste liquid or the mixture of the acid leaching waste liquid and the high-concentration washing liquid generated in step S4 is adjusted to 3.5-6.5 by using the calcination flue gas generated in step S3. The seeds are ammonium fluoride and / or ammonium bifluoride. Specifically, the pH value can be, for example but not limited to, any one of 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5 or the range between any two of them.

[0044] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0045] Example 1

[0046] A method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis includes the following steps:

[0047] S1. Crushing, grading, and drying the waste cathode carbon block of aluminum electrolysis to obtain a pretreated material with a particle size ≤ 0.074 mm;

[0048] S2. Adding the pretreated material and ammonium fluoride into a high-temperature ball milling device according to a mass ratio of 1:2 for mixing treatment; the ball milling speed is 300 r / min and the mixing time is 0.5 h;

[0049] S3. After the mixing treatment is completed, continue to carry out high-temperature activation calcination in the high-temperature ball milling device to obtain calcined materials and calcination flue gas. The calcination temperature is 250 °C, the activation calcination time is 1.0 h, the activation speed is 250 r / min. After completion, open the exhaust valve to collect the calcination flue gas;

[0050] S4. Close the exhaust valve, add sulfuric acid solution into the high-temperature ball milling device for high-pressure activation leaching. The activation speed is 200 r / min, the leaching temperature is 220 °C, the leaching time is 1.0 h, the concentration of the sulfuric acid solution is 4 mol / L, and the liquid-solid ratio of the sulfuric acid solution and the calcined material is 20 mL / g; after the activation leaching is completed, carry out solid-liquid separation to obtain acid leaching waste liquid and residual solid materials. The residual solid materials are then separated by a vibrating sieve and washed with water, and then solid-liquid separation is carried out to obtain carbonaceous materials and washing liquid. The low-concentration washing liquid is recycled for washing treatment. The fixed carbon content of the carbonaceous materials is 99.85%, the leaching rate of fluorides is 99.50%, and the decomposition rate of cyanides is 99.90%.

[0051] S5. Use the calcination flue gas generated in step S3 to adjust the pH value of the mixture of the acid leaching waste liquid and the high-concentration washing liquid generated in step S4 to 5.0, then add ammonium fluoride seeds, and sequentially recover ammonium fluoride through vacuum concentration, cooling crystallization, centrifugal separation, and low-temperature drying. The recovery rate is 91.45%.

[0052] Example 2

[0053] A method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis, comprising the following steps:

[0054] S1. Crushing, classifying, and drying the waste cathode carbon blocks of aluminum electrolysis to obtain a pretreated material with a particle size ≤ 0.15 mm;

[0055] S2. Adding the pretreated material and ammonium fluoride into a high-temperature ball milling device according to a mass ratio of 1:2.5 for mixing treatment; the ball milling speed is 350 r / min, and the mixing time is 0.25 h;

[0056] S3. After the mixing treatment is completed, continue to carry out high-temperature activation roasting in the high-temperature ball milling device to obtain roasted material and roasted flue gas. The roasting temperature is 200 °C, the activation roasting time is 2.0 h, the activation speed is 300 r / min. After completion, open the exhaust valve to collect the roasted flue gas;

[0057] S4. Close the exhaust valve, add hydrochloric acid solution into the high-temperature ball milling device for high-pressure activation leaching. The activation speed is 250 r / min, the leaching temperature is 200 °C, the leaching time is 0.5 h, the concentration of the hydrochloric acid solution is 8 mol / L, and the liquid-solid ratio of the hydrochloric acid solution and the roasted material is 20 mL / g; after the activation leaching is completed, carry out solid-liquid separation to obtain acid leaching waste liquid and residual solid material. The residual solid material is then separated by a vibrating sieve, washed with water, and then subjected to solid-liquid separation to obtain carbonaceous material and washing liquid. The low-concentration washing liquid is recycled for washing treatment. The fixed carbon content of the carbonaceous material is 99.37%, the leaching rate of fluoride is 99.28%, and the decomposition rate of cyanide is 99.69%.

[0058] S5. Use the roasted flue gas generated in step S3 to adjust the pH value of the mixed solution of the acid leaching waste liquid and the high-concentration washing liquid generated in step S4 to 5.5, then add ammonium fluoride seeds, and sequentially recover ammonium fluoride through vacuum concentration, cooling crystallization, centrifugal separation, and low-temperature drying. The recovery rate is 90.85%.

[0059] Example 3

[0060] A method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis, comprising the following steps:

[0061] S1. Crushing, classifying, and drying the waste cathode carbon blocks of aluminum electrolysis to obtain a pretreated material with a particle size ≤ 1.0 mm;

[0062] S2. Adding the pretreated material and ammonium fluoride into a high-temperature ball milling device according to a mass ratio of 1:1.5 for mixing treatment; the ball milling speed is 300 r / min, and the mixing time is 0.5 h;

[0063] After the mixing process is completed, continue with high-temperature activation roasting in a high-temperature ball milling device to obtain roasted materials and roasting flue gas. The roasting temperature is 200 °C, the activation roasting time is 1.0 h, the activation rotation speed is 200 r / min. After completion, open the exhaust valve to collect the roasting flue gas;

[0064] Close the exhaust valve, add sulfuric acid solution to the high-temperature ball milling device for high-pressure activation leaching. The activation rotation speed is 200 r / min, the leaching temperature is 140 °C, the leaching time is 1.0 h, the concentration of the sulfuric acid solution is 6 mol / L, and the liquid-solid ratio of the sulfuric acid solution to the roasted materials is 20 mL / g. After the activation leaching is completed, perform solid-liquid separation to obtain acid leaching waste liquid and residual solid materials. The residual solid materials are then separated into balls by a vibrating sieve, washed with water, and then subjected to solid-liquid separation again to obtain carbonaceous materials and washing liquid. The low-concentration washing liquid is recycled for the washing process. The fixed carbon content of the carbonaceous materials is 99.10%, the leaching rate of fluoride is 99.16%, and the decomposition rate of cyanide is 99.47%.

[0065] Use the roasting flue gas generated in step S3 to adjust the pH value of the mixed solution of the acid leaching waste liquid and the high-concentration washing liquid generated in step S4 to 4.5, then add ammonium fluoride seeds, and sequentially perform vacuum concentration, cooling crystallization, centrifugal separation, and low-temperature drying to recover ammonium fluoride, with a recovery rate of 85.40%.

[0066] Example 4

[0067] A method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis, comprising the following steps:

[0068] Crush, classify, and dry the aluminum electrolysis carbon slag to obtain pre-treated materials with a particle size ≤ 0.074 mm;

[0069] Add the pre-treated materials and ammonium fluoride to a high-temperature ball milling device according to a mass ratio of 1:5 for mixing treatment; the ball milling rotation speed is 300 r / min, and the mixing time is 1.0 h;

[0070] After the mixing process is completed, continue with high-temperature activation roasting in a high-temperature ball milling device to obtain roasted materials and roasting flue gas. The roasting temperature is 250 °C, the activation roasting time is 2.0 h, the activation rotation speed is 250 r / min. After completion, open the exhaust valve to collect the roasting flue gas;

[0071] S4. Close the exhaust valve, add sulfuric acid solution to the high-temperature ball milling device for high-pressure activation leaching. The activation rotation speed is 200 r / min, the leaching temperature is 200 °C, the leaching time is 1.0 h, the concentration of the sulfuric acid solution is 6 mol / L, and the liquid-solid ratio of the sulfuric acid solution to the roasted material is 20 mL / g. After the activation leaching is completed, solid-liquid separation is carried out to obtain acid leaching waste liquid and residual solid material. The residual solid material is then separated into balls by a vibrating sieve, washed with water, and then solid-liquid separated again to obtain carbonaceous material and washing liquid. The low-concentration washing liquid is recycled for washing treatment. The fixed carbon content of the carbonaceous material is 99.68%, the leaching rate of fluoride is 99.37%, and the decomposition rate of cyanide is 99.82%.

[0072] S5. Use the roasted flue gas generated in step S3 to adjust the pH value of the mixed liquid of the acid leaching waste liquid and the high-concentration washing liquid generated in step S4 to 4.5, then add ammonium fluoride seeds, and sequentially carry out vacuum concentration, cooling crystallization, centrifugal separation, and low-temperature drying to recover ammonium fluoride, and the recovery rate is 91.18%.

[0073] Example 5

[0074] A method for recovering carbonaceous material from carbon-containing waste in aluminum electrolysis includes the following steps:

[0075] S1. Crush, classify, and dry the aluminum electrolysis carbon slag to obtain a pretreated material with a particle size ≤ 0.15 mm;

[0076] S2. Add the pretreated material and ammonium fluoride to the high-temperature ball milling device according to a mass ratio of 1:6 for mixing treatment; the ball milling rotation speed is 300 r / min, and the mixing time is 1.0 h;

[0077] S3. After the mixing treatment is completed, continue to carry out high-temperature activation roasting in the high-temperature ball milling device to obtain roasted material and roasted flue gas. The roasting temperature is 250 °C, the activation roasting time is 1.5 h, the activation rotation speed is 200 r / min. After completion, open the exhaust valve to collect the roasted flue gas;

[0078] S4. Close the exhaust valve, add hydrochloric acid solution to the high-temperature ball milling device for high-pressure activation leaching. The activation rotation speed is 200 r / min, the leaching temperature is 220 °C, the leaching time is 0.5 h, the concentration of the hydrochloric acid solution is 8 mol / L, and the liquid-solid ratio of the hydrochloric acid solution to the roasted material is 15 mL / g. After the activation leaching is completed, solid-liquid separation is carried out to obtain acid leaching waste liquid and residual solid material. The residual solid material is then separated into balls by a vibrating sieve, washed with water, and then solid-liquid separated again to obtain carbonaceous material and washing liquid. The low-concentration washing liquid is recycled for washing treatment. The fixed carbon content of the carbonaceous material is 99.46%, the leaching rate of fluoride is 99.21%, and the decomposition rate of cyanide is 99.72%.

[0079] S5. Adjust the pH value of the mixed solution of the acid leaching waste liquid and the high-concentration washing liquid generated in step S4 to 5.5 by using the calcination flue gas generated in step S3, then add ammonium fluoride seeds, and sequentially recover ammonium fluoride through vacuum concentration, cooling crystallization, centrifugal separation, and low-temperature drying, with a recovery rate of 90.70%.

[0080] Example 6

[0081] A method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis, comprising the following steps:

[0082] S1. Crush, classify, and dry the aluminum electrolysis carbon slag to obtain a pretreated material with a particle size ≤ 1.0 mm;

[0083] S2. Add the pretreated material and ammonium fluoride to a high-temperature ball milling device according to a mass ratio of 1:6 for mixing treatment; the ball milling speed is 300 r / min, and the mixing time is 0.5 h;

[0084] S3. After the mixing treatment is completed, continue to carry out high-temperature activation calcination in the high-temperature ball milling device to obtain calcined materials and calcination flue gas. The calcination temperature is 200 °C, the activation calcination time is 1.0 h, the activation speed is 250 r / min, and after completion, open the exhaust valve to collect the calcination flue gas;

[0085] S4. Close the exhaust valve, add hydrochloric acid solution to the high-temperature ball milling device for high-pressure activation leaching. The activation speed is 200 r / min, the leaching temperature is 160 °C, the leaching time is 1.0 h, the concentration of the hydrochloric acid solution is 6 mol / L, and the liquid-solid ratio of the hydrochloric acid solution to the calcined material is 15 mL / g; after the activation leaching is completed, carry out solid-liquid separation to obtain acid leaching waste liquid and residual solid materials. The residual solid materials are then separated by a vibrating sieve machine, washed with water, and then subjected to solid-liquid separation to obtain carbonaceous materials and washing liquid. The low-concentration washing liquid is recycled for washing treatment. The fixed carbon content of the carbonaceous materials is 99.15%, the leaching rate of fluoride is 99.10%, and the decomposition rate of cyanide is 99.55%.

[0086] S5. Adjust the pH value of the mixed solution of the acid leaching waste liquid and the high-concentration washing liquid generated in step S4 to 5 by using the calcination flue gas generated in step S3, then add ammonium fluoride seeds, and sequentially recover ammonium fluoride through vacuum concentration, cooling crystallization, centrifugal separation, and low-temperature drying, with a recovery rate of 88.65%.

[0087] The present invention uses a high-temperature ball milling device to assist in the recovery of carbonaceous materials contained in carbon-containing hazardous waste from aluminum electrolysis. The mixing treatment, high-temperature activation roasting, and high-pressure activation leaching are all carried out in a high-temperature mechanical activation device. By constructing an oxidation-fluorination roasting system and a mixed acid purification system of HF-HCl / H2SO4 / HNO3, on the one hand, the safe dissociation of cyanide / fluorine toxic substances can be achieved, and on the other hand, the effective separation of complex and poorly soluble aluminosilicates can be realized. The fixed carbon content of the recovered carbonaceous materials is ≥99.0%. On the other hand, in view of the physical and chemical properties of the roasting flue gas and the acid leaching waste liquid, treatment processes such as pH value regulation, seed addition, and cooling crystallization are innovatively coupled to realize the recycling of solid reaction reagents with a recovery rate of ≥85% and no risk of secondary pollution.

[0088] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made using the content of the specification of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A method for recovering carbonaceous materials from carbon-containing waste in aluminum electrolysis, characterized in that, It includes the following steps: S1. Crush, classify, and dry the carbon-containing waste from aluminum electrolysis rich in fluorine / cyanide toxic substances to obtain pretreated materials; S2. Add the pretreated materials and solid reaction reagents in a mass ratio of 1:4 - 6 to a high-temperature ball milling device for mixing treatment; the solid reaction reagent is ammonium fluoride or ammonium bifluoride; S3. After the mixing treatment is completed, continue to carry out high-temperature activation roasting in the high-temperature ball milling device to obtain roasted materials and roasted flue gas. The roasting temperature is 100 - 250 °C, the activation roasting time is 0.5 - 4.0 h, the activation rotation speed is 100 - 300 r / min. After completion, open the exhaust valve to collect the roasted flue gas; S4. Close the exhaust valve, add an acidic purification solution to the high-temperature ball milling device for high-pressure activation leaching. The concentration of the acidic purification solution is 1 - 10 mol / L, the liquid-solid ratio of the acidic purification solution and the roasted materials is 5 - 20 mL / g, the activation rotation speed is 100 - 300 r / min, the leaching temperature is 40 - 220 °C, and the leaching time is 0.1 - 1.0 h. After the activation leaching is completed, carry out solid-liquid separation to obtain acid leaching waste liquid and residual solid materials. The residual solid materials are then separated by a vibrating sieve, washed with water, and then subjected to solid-liquid separation again to obtain carbonaceous materials and washing liquid; By constructing an oxidation-fluorination roasting system and an HF-HCl / H2SO4 / HNO3 mixed acid purification system, the safe dissociation of cyanide / fluoride toxic substances is realized, the leaching rate of fluoride is ≥99.0%, and the dissociation rate of cyanide is ≥99.2%.

2. The recycling method according to claim 1, characterized in that, After the step S4, it further includes: S5. Pass the roasted flue gas generated in step S3 into the acid leaching waste liquid generated in step S4, then add seeds, and successively carry out vacuum concentration, cooling crystallization, centrifugal separation, and low-temperature drying to recover the solid reaction reagent.

3. The recovery method according to claim 1 or 2, characterized in that, In the step S1, the carbon-containing waste from aluminum electrolysis rich in fluorine / cyanide toxic substances is waste cathode carbon blocks or carbon slag, and the particle size of the pretreated materials is ≤3 mm.

4. The recycling method according to claim 1 or 2, characterized in that In the step S2, the ball milling rotation speed is 150 - 350 r / min, and the mixing time is 0.1 - 1.0 h.

5. The recycling method according to claim 1 or 2, characterized in that, In the step S2, the high-temperature ball milling device is lined with polytetrafluoroethylene, has a heating function, and is equipped with an exhaust valve at the top.

6. The recovery method according to claim 2, characterized in that, In the step S4, the fixed carbon content of the carbonaceous materials is ≥99.0%. The washing liquid includes low-concentration washing liquid and high-concentration washing liquid. Among them, the pH value of the low-concentration washing liquid is >2, and it is recycled for washing treatment. The pH value of the high-concentration washing liquid is ≤2, and it is combined with the acid leaching waste liquid for treatment.

7. The recovery method according to claim 6, wherein In the step S5, before adding seeds, use the roasted flue gas generated in step S3 to adjust the pH value of the acid leaching waste liquid and the high-concentration washing liquid generated in step S4 to 3.5 - 6.

5.

8. The recovery method according to claim 2, wherein In the step S5, the seeds are ammonium fluoride and / or ammonium bifluoride.

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