A harmless treatment method of aluminum electrolysis overhaul slag

Abstract

The application discloses a harmless treatment method of aluminum electrolysis overhaul slag, and comprises the following steps: removing large particle iron through magnetic separation, recovering aluminum particles, high-temperature roasting in a clinker kiln, carbon removal through flotation, obtaining high-purity carbon through carbon acid and alkali purification, obtaining iron minerals through flotation, obtaining solid cryolite Na3AlF6 through drum drying, realizing aluminum and silicon mineral separation through reverse flotation desilication, obtaining aluminum mineral liquid, and obtaining aluminum oxide after roasting the aluminum mineral liquid.The application adopts a method of high-temperature roasting, flotation and acid-alkali treatment cooperation, high-temperature roasting makes fluoride in the overhaul slag into harmless calcium fluoride, and toxic cyanide is cracked in high temperature to generate nitrogen oxide, realizing harmless treatment of cyanide.The application realizes effective separation of carbon material, iron ore powder, aluminum ore powder and solid cryolite and other substances in the overhaul slag through multiple flotation treatments, realizes resource utilization of useful elements, opens up a new way for harmless disposal and resource utilization of the overhaul slag, and has very significant economic benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to a harmless treatment method of aluminum electrolysis overhaul slag, and belongs to the technical field of hazardous waste treatment and utilization of aluminum electrolysis overhaul slag. BACKGROUND

[0002] The overhaul slag is a solid waste periodically discharged from an aluminum electrolysis cell, and is a general term for all waste and old lining materials and carbon-containing electrode materials removed during the overhaul of the electrolysis cell, and is a type of waste that is prohibited from being discarded at will by the state.

[0003] The electrolysis waste overhaul slag has high environmental hazards, mainly in the following three points: ①The fluorides in the overhaul slag have leaching toxicity exceeding the standard (100 mg / L) of the Hazardous Waste Identification Standard Leaching Toxicity Identification, and the pH is relatively high, part of which will exceed the standard (12.5) of the Hazardous Waste Identification Standard Corrosivity Identification, and direct stacking will cause the pH of the surrounding groundwater and soil to rise and cause fluorine pollution; ②The overhaul slag contains aluminum nitride, metallic aluminum, aluminum carbide, etc., which will release a large amount of ammonia gas and produce hydrogen gas, methane, hydrogen sulfide and other flammable and explosive gases when coming into contact with water, polluting the atmospheric environment and posing a safety hazard; ③The overhaul slag contains a large amount of soluble salts (chloride salts and fluoride salts), and the accumulation of dissolved seepage will cause soil salinization and water pollution. Since the electrolysis waste is a hazardous waste that is seriously harmful to the environment, and is difficult to treat, it brings great environmental pressure. At present, the main treatment processes for the overhaul slag are landfill treatment, wet treatment, and acid treatment.

[0004] The main treatment method for the electrolysis cell overhaul slag in China at present is landfill method, which has two major drawbacks: one is that it occupies a large amount of land; the other is that it cannot fundamentally treat the toxic and harmful substances. The landfill method cannot completely solve the harmful substances in the overhaul slag, and there are extremely strict requirements for the storage or landfill of the electrolysis cell overhaul slag. Not only huge costs are invested in the construction of the slag field and the daily operation and management, but also there are long-term potential pollution hazards. The construction cost of wet treatment and acid treatment is high, the operation cost is even higher, and secondary pollution is also easy to occur, and the treated overhaul slag cannot be directly treated as general solid waste.

[0005] With the rapid development of the aluminum electrolysis industry, the pollution problems it brings have increasingly attracted people's attention. The electrolytic aluminum production solid waste overhaul slag has complex composition and contains a large amount of toxic substances. If ordinary treatment methods are used, it will cause serious pollution to the natural environment. Therefore, in the process of treating the solid waste overhaul slag, electrolytic aluminum overhaul slag harmless treatment technology should be used, and targeted treatment methods should be used according to the actual situation, so as to fundamentally reduce the pollution of waste to the environment. SUMMARY

[0006] The technical problems to be solved by the present application are: overcoming the shortcomings of the prior art, providing a harmless treatment method for aluminum electrolysis overhaul slag, obtaining purer carbon material, iron ore powder, aluminum ore powder and solid cryolite, which have no dangerous characteristics, better product added value and wider application range.

[0007] The technical solutions adopted by the present application to solve the technical problems are as follows:

[0008] A harmless treatment method for aluminum electrolysis overhaul slag, the specific steps are as follows:

[0009] ① Magnetic separation of iron: after the hazardous waste aluminum electrolysis overhaul slag is crushed to less than 50mm in size, the particle iron is separated by the iron removal magnetic separator, so as to reduce the pressure of the later iron removal;

[0010] ② Aluminum particle recovery: the overhaul slag after magnetic separation is passed through a grid type double-bin ball mill, one bin is filled with steel balls and the other bin is filled with steel forging, the grid type double-bin ball mill forcibly discharges coarse aluminum particles, the steel balls in the first bin are used to break the material, and the steel forging in the second bin is used to grind the material; after grinding in the ball mill, the aluminum powder contained in the overhaul slag is rolled into balls in the ball mill, and a mill head screen is installed at the discharge section of the ball mill to collect aluminum particles;

[0011] ③ High-temperature roasting: the powder material after grinding in the ball mill is sent into a clinker kiln for high-temperature roasting, the roasting temperature is 1000-1200 degrees, and the roasting time is 2-3 hours;

[0012] ④ Carbon removal by flotation: after cooling, the material after high-temperature roasting is sent into a carbon removal flotation machine for stirring and slurry preparation, the material is mixed with water to prepare a slurry Q with a concentration of 30-40%, and a suitable amount of a flotation agent composed of a foaming agent, an inhibitor I and a carbon capturing agent is added, the slurry is continuously stirred during the flotation process, the carbon treated by the capturing agent in the slurry is easily combined with bubbles due to its strong hydrophobicity and is dragged to the liquid surface, after filtration of the flotation liquid, solid material A and slurry B are obtained;

[0013] ⑤ Carbon acid alkali purification: after drying, the solid material A is sent into a roasting furnace, a suitable amount of solid sodium hydroxide is added for roasting and activation, the roasting temperature is 900-1000 degrees, and the roasting time is 1-2 hours, after cooling of the roasting material, the material is acid leached with hydrochloric acid solution with a concentration of 1.5-2 mol / L at a temperature of 50-60 degrees for 1.5-2 hours, and after filtration, water washing and drying, high-purity carbon is obtained for storage;

[0014] ⑥ Iron removal by flotation: the slurry B is sent into an iron removal flotation machine, the pH value is adjusted to 4±0.5, an inhibitor II and an iron capturing agent are added, and the mixture is fully stirred to capture fine particle iron, after filtration of the flotation liquid, solid material C and slurry D are obtained, and after drying of the solid material C, iron ore is obtained;

[0015] ⑦Extracting cryolite: adjust the pH value of the slurry D, and keep stirring during the adjusting process until the pH value is stabilized at 9±0.5, then filter to obtain filtrate E and solid F, and dry the solid F in a roller dryer at a temperature of 150-200 degrees to obtain solid cryolite Na3AlF6;

[0016] ⑧Removing silicon by reverse flotation: send the filtrate E into a silicon removal flotation machine, add inhibitor III and silicon mineral capturing agent, and fully stir at a temperature of 30-50 degrees to make the silicon minerals concentrate on the surface of the liquid phase bubbles and float up to separate the aluminum and silicon minerals, and obtain aluminum mineral liquid G;

[0017] ⑨Obtain aluminum oxide by roasting the aluminum mineral liquid G.

[0018] In step ④, the foaming agent is commercially available 2# oil foaming agent or ether alcohol, the foaming agent disperses air in the slurry to increase the air bubbles around the carbon blocks and thus increase the mechanical strength of the carbon blocks for floating up; the inhibitor I is water glass, the function of the inhibitor I is to weaken and eliminate the interaction of the carbon capturing agent on the floating material; the carbon capturing agent is C11 or C16 alkane, the function of the carbon capturing agent is to selectively act on the surface of the carbon blocks to make the carbon blocks have better hydrophobicity; the mass ratio of the foaming agent, the inhibitor I and the carbon capturing agent is 1:1:1, and the addition amount of the flotation agent composed of the foaming agent, the inhibitor I and the carbon capturing agent is (0.03-0.05)% of the mass of the slurry Q.

[0019] In step ⑤, the mass ratio of the dried solid material A and solid sodium hydroxide is 5:(1-2); in the acid leaching process, the amount of hydrochloric acid solution is enough to immerse the calcined material.

[0020] In step ⑥, the inhibitor II is starch or lime, and the iron capturing agent is butyl xanthate, the mass ratio of the inhibitor II and the iron capturing agent is 1:1, and the addition amount of the inhibitor II and the iron capturing agent is (0.03-0.05)% of the mass of the slurry B.

[0021] In step ⑧, the inhibitor III is starch, and the silicon mineral capturing agent is a hydrocarbon-based acid or an amine substance, the mass ratio of the inhibitor III and the silicon mineral capturing agent is 1:1, and the addition amount of the inhibitor III and the silicon mineral capturing agent is (0.03-0.05)% of the mass of the filtrate E.

[0022] 1. Among the methods for harmless treatment of overhaul slag, flotation can achieve resource recovery to a large extent, but it is not easy to guarantee the purity of the product; acid-base method achieves a large recovery rate and purity of carbon elements and electrolytes, but it has problems such as severe equipment corrosion and high cost, making it difficult to achieve industrialization. This invention adopts a method of combined flotation and acid-base method to achieve effective separation of carbon materials, iron ore powder, aluminum ore powder and solid cryolite in overhaul slag, and the purity of the product meets industrial requirements, opening up a new way for the harmless disposal and resource utilization of overhaul slag.

[0023] 2. This invention involves crushing the slag from an electrolytic aluminum overhaul and then using a magnetic separator to remove particulate iron, thus reducing the pressure on subsequent iron removal. The slag has a complex chemical composition, especially a high iron content, where the iron exists in agglomerated form. If directly ground and beneficiated, coarse iron particles will be ground into a large number of fine iron particles, directly affecting the subsequent iron content processing. Therefore, pre-selection is necessary in the early stage to reduce the pressure on subsequent iron removal.

[0024] 3. This invention uses a grate-type double-compartment ball mill to process the overhaul slag after magnetic separation. The first compartment contains steel balls, and the second compartment contains steel forgings. The grate-type double-compartment ball mill forces the coarse aluminum particles to be discharged. The steel balls in the first compartment crush the material, while the steel forgings in the second compartment grind the material. After grinding in the ball mill, the aluminum powder contained in the overhaul slag will be rolled into balls in the ball mill. A grinding head screen is installed in the discharge section of the ball mill to collect the aluminum particles. The recovery of aluminum particles can bring certain economic benefits to the enterprise.

[0025] 4. This invention feeds the overhaul slag powder, after grinding in a ball mill, into a clinker kiln for high-temperature roasting. The fluorides in the overhaul slag ultimately form harmless calcium fluoride, while the toxic CN- (cyanide) decomposes at high temperature to generate nitrogen oxides. This achieves the harmless treatment of cyanide in electrolytic aluminum overhaul slag. The chemical reaction formula is as follows:

[0026] 2NaF + CaO = CaF2 + Na2O;

[0027] 2AlF3 + 3CaO = 3CaF2 + Al2O3

[0028] 5. This invention achieves the simultaneous recovery and utilization of carbon and electrolyte components through multiple flotation processes, realizing the resource utilization of useful elements and resulting in significant economic benefits. Detailed Implementation

[0029] The present invention will be further explained and described below with reference to specific embodiments:

[0030] Example: A method for harmlessly treating aluminum electrolysis overhaul slag, the specific steps of which are as follows:

[0031] ① Magnetic separation of iron: after the hazardous waste aluminum electrolysis overhaul slag is crushed into particles smaller than 50mm, the magnetic separation of iron is carried out by an iron removal magnetic separator, so as to reduce the pressure of the later iron removal;

[0032] ② Aluminum particle recovery: the overhaul slag after the magnetic separation is sent to a lattice type double-bin ball mill, a bin is filled with steel balls and the other bin is filled with steel forging, the lattice type double-bin ball mill forcibly discharges coarse aluminum particles, the steel balls in the first bin are used to break the materials, and the steel forging in the second bin is used to grind the materials; after the grinding of the ball mill, the aluminum powder contained in the overhaul slag is rolled into balls in the ball mill, and a mill head screen is installed at the discharge section of the ball mill to collect the aluminum particles;

[0033] ③ High-temperature roasting: the powder material of the overhaul slag after the grinding of the ball mill is sent to a clinker kiln for high-temperature roasting, the roasting temperature is 1000-1200 degrees, and the roasting time is 2-3 hours;

[0034] ④ Flotation carbon removal: after the high-temperature roasted material is cooled, it is sent to a carbon removal flotation machine for stirring and slurry preparation, the material is mixed with water to prepare a 30-40% slurry Q, and an appropriate amount of a flotation agent composed of a foaming agent, an inhibitor I and a carbon capturing agent is added, the slurry is continuously stirred during the flotation process, the carbon treated by the capturing agent in the slurry is easily combined with the bubbles due to its strong hydrophobicity and is dragged to the liquid surface, after the flotation liquid is filtered, solid material A and slurry B are obtained;

[0035] ⑤ Carbon acid alkali purification: the solid material A is dried and sent to a roasting furnace, an appropriate amount of solid sodium hydroxide is added for roasting and activation, the roasting is carried out at a temperature of 900-1000 degrees for 1-2 hours, after the roasting material is cooled, it is acid leached with hydrochloric acid liquid with a concentration of 1.5-2 mol / L at a temperature of 50-60 degrees for 1.5-2 hours, and then filtered, washed with water and dried to obtain high-purity carbon for storage;

[0036] ⑥ Flotation iron removal: the slurry B is sent to an iron removal flotation machine, the pH value is adjusted to 4±0.5, an inhibitor II and an iron capturing agent are added, and the mixture is fully stirred to capture fine particle iron, after the flotation liquid is filtered, solid material C and slurry D are obtained, and the solid material C is dried to obtain iron ore;

[0037] ⑦ Extraction of cryolite: the pH value of the slurry D is adjusted, the stirring is continuously carried out during the adjustment process, and the pH value is stabilized at pH=9±0.5, then the mixture is filtered to obtain filtrate E and solid F, the solid F is dried by a roller dryer at a drying temperature of 150-200 degrees, and a drying agent is obtained to obtain solid cryolite Na3AlF6;

[0038] ⑧ Reverse flotation desilication: the filtrate E is sent to a desilicon flotation machine, an inhibitor III and a silicon mineral capturing agent are added, and the mixture is fully stirred at a temperature of 30-50 degrees to make the silicon minerals enriched on the surface of the liquid phase bubbles to float up, so as to separate the aluminum and silicon minerals, and obtain aluminum mineral liquid G;

[0039] 9. The aluminum mineral liquid G is calcined to obtain alumina.

[0040] In step 4, the foaming agent is a commercially available 2# oil foaming agent, or an ether alcohol, the foaming agent disperses air in the ore slurry, increases the air bubbles around the carbon block, and thus increases the mechanical strength of the carbon block floating; the depressor I is water glass, the function of the depressor I is to weaken and eliminate the interaction of the carbon capturing agent on the floating material; the carbon capturing agent is C11 or C16 alkane, the function of the carbon capturing agent is to selectively act on the surface of the carbon block, so that the carbon block has better hydrophobicity; the mass ratio of the foaming agent, the depressor I and the carbon capturing agent is 1:1:1, and the addition amount of the flotation agent composed of the foaming agent, the depressor I and the carbon capturing agent is (0.03-0.05) ‰ of the mass of the slurry Q.

[0041] In step 5, the mass ratio of the dried solid substance A and solid sodium hydroxide is 5: (1-2); in the acid leaching process, the amount of hydrochloric acid solution is enough to immerse the calcined substance.

[0042] In step 6, the depressor II is starch or lime, and the iron capturing agent is butyl xanthate, the mass ratio of the depressor II and the iron capturing agent is 1:1, and the addition amount of the depressor II and the iron capturing agent is (0.03-0.05) ‰ of the mass of the slurry B.

[0043] In step 7, the depressor III is starch, and the silicon mineral capturing agent is a hydrocarbon-based acid or an amine substance, the mass ratio of the depressor III and the silicon mineral capturing agent is 1:1, and the addition amount of the depressor III and the silicon mineral capturing agent is (0.03-0.05) ‰ of the mass of the filtrate E.

[0044] The present application adopts the method of combined cooperation of flotation and acid-base method, realizes the effective separation of carbon material, iron ore powder, aluminum ore powder and solid ice crystal stone and other substances in the overhaul slag, and the purity of the product meets the industrial requirements, and opens up a new way for harmless disposal and resource utilization of the overhaul slag.

[0045] Obviously, the above embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The above embodiments are only used for explaining the present application, and do not constitute the limitation on the protection scope of the present application. Based on the above embodiments, all other embodiments obtained by those skilled in the art without creative labor, i.e. all modifications, equivalent replacements and improvements made within the spirit and principles of the present application, fall within the protection scope of the present application.

Claims

1. A harmless treatment method of aluminum electrolysis overhaul slag, comprising the following specific steps: ① Magnetic separation of iron: after the hazardous aluminum electrolysis overhaul slag is crushed to a particle size of less than 50 mm, the particulate iron is removed by a magnetic separator to reduce the pressure of later iron removal; ② Aluminum particle recovery: the overhaul slag after magnetic separation is passed through a lattice type double-bin ball mill, one bin is filled with steel balls and the other bin is filled with steel hammers, the lattice type double-bin ball mill forcibly discharges coarse aluminum particles, the steel balls in the first bin crush the materials, and the steel hammers in the second bin grind the materials; after the grinding of the ball mill, the aluminum powder contained in the overhaul slag is rolled into balls in the ball mill, and a mill head screen is installed at the discharge section of the ball mill to collect aluminum particles; ③ High-temperature roasting: the powder material after the grinding of the ball mill is sent into a clinker kiln for high-temperature roasting, the roasting temperature is 1000-1200 degrees, and the roasting time is 2-3 hours; ④ Carbon flotation: after the high-temperature roasted material is cooled, it is sent into a carbon flotation machine for stirring and slurry preparation, the material is mixed with water to prepare a slurry Q with a concentration of 30-40%, an appropriate amount of a flotation agent composed of a foaming agent, an inhibitor I and a carbon capturing agent is added, the slurry is continuously stirred during the flotation process, the carbon treated by the capturing agent in the slurry is easily combined with bubbles due to its strong hydrophobicity and is dragged to the liquid surface, after the flotation liquid is filtered, solid material A and slurry B are obtained; ⑤ Carbon acid alkali purification: the solid material A is dried and sent into a roasting furnace, an appropriate amount of solid sodium hydroxide is added for roasting and activation, the roasting temperature is 900-1000 degrees, the roasting time is 1-2 hours, after the roasting material is cooled, it is acid leached with hydrochloric acid liquid with a concentration of 1.5-2 mol / L at a temperature of 50-60 degrees for 1.5-2 hours, after filtration, water washing and drying, high-purity carbon is obtained and stored for use; ⑥ Iron flotation: the slurry B is sent into an iron flotation machine, the pH value is adjusted to 4±0.5, an inhibitor II and an iron capturing agent are added, the mixture is fully stirred to capture fine iron particles, after the flotation liquid is filtered, solid material C and slurry D are obtained, the solid material C is dried to obtain iron minerals; ⑦ Extraction of cryolite: the pH value of the slurry D is adjusted, the stirring is not stopped during the adjustment process, until the pH value is stabilized at 9±0.5, after filtration, filtrate E and solid F are obtained, the solid F is dried by a roller dryer, the drying temperature is controlled at 150-200 degrees, and the dried solid is cryolite Na3AlF6; ⑧ Reverse flotation desilication: the filtrate E is sent into a desilicon flotation machine, an inhibitor III and a silicon mineral capturing agent are added, the mixture is fully stirred at a temperature of 30-50 degrees to make the silicon minerals enriched on the surface of the liquid bubbles to float, so as to separate the aluminum and silicon minerals, and obtain aluminum mineral liquid G; ⑨ The aluminum mineral liquid G is roasted to obtain alumina.

2. The method for harmless treatment of aluminum electrolysis overhaul slag according to claim 1, characterized in that: In step Ⅳ, the frother is commercially available 2# oil frother, or ether alcohol, the frother disperses air in the ore pulp, increases the air bubbles around the carbon block, and thus increases the mechanical strength of the carbon block floating; the depressor I is water glass, the depressor I weakens and eliminates the interaction of the carbon capturing agent with the float; the carbon capturing agent is C 11 or C 16 alkane, the carbon capturing agent selectively acts on the surface of the carbon block, and thus makes the carbon block have better hydrophobicity; the mass ratio of the frother, the depressor I and the carbon capturing agent is 1:1:1, and the addition amount of the floatation agent composed of the frother, the depressor I and the carbon capturing agent is (0.03-0.05) ‰ of the mass of the pulp Q.

3. The method for harmless treatment of aluminum electrolysis overhaul slag according to claim 1, characterized in that: In step ⑤, the mass ratio of the dried solid material A to the solid sodium hydroxide is 5:(1-2); in the acid leaching process, the amount of hydrochloric acid liquid is enough to immerse the roasting material.

4. The method for harmless treatment of aluminum electrolysis overhaul slag according to claim 1, characterized in that: In step ⑥, the inhibitor II is starch or lime, the iron capturing agent is butyl xanthate, the mass ratio of the inhibitor II to the iron capturing agent is 1:1, and the addition amount of the inhibitor II and the iron capturing agent is (0.03-0.05) ‰ of the mass of the slurry B.

5. The method for harmless treatment of aluminum electrolysis overhaul slag according to claim 1, characterized in that: In step 7, the inhibitor III is starch, the silicate mineral capturing agent is a hydrocarbon acid or amine substance, the mass ratio of the inhibitor III and the silicate mineral capturing agent is 1:1, and the adding amount of the inhibitor III and the silicate mineral capturing agent is (0.03-0.05)‰ of the mass of the filtrate E. In step 7, the inhibitor III is starch, the silicate mineral capturing agent is a hydrocarbon acid or amine substance, the mass ratio of the inhibitor III and the silicate mineral capturing agent is 1:1, and the adding amount of the inhibitor III and the silicate mineral capturing agent is (0.03-0.05)‰ of the mass of the filtrate E. In step 7, the inhibitor III is starch, the silicate mineral capturing agent is a hydrocarbon acid or amine substance, the mass ratio of the inhibitor III and the silicate mineral capturing agent is