CN113461003A - Harmless and efficient resource recovery method for waste aluminum electrolytic cell lining and waste cathode - Google Patents
Harmless and efficient resource recovery method for waste aluminum electrolytic cell lining and waste cathode Download PDFInfo
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Abstract
The invention belongs to the technical field of chemical industry, and particularly relates to a harmless and efficient resource recovery method for waste electrolytic cell linings and waste cathodes. The method comprises the steps of charging crushed inner filler blocks, waste cathode blocks, furnace core materials, heat preservation materials and carbon-silicon ratio reaction materials of the waste electrolytic cell into a direct current resistance furnace, electrifying the direct current resistance furnace, heating to 2800-3000 ℃, carrying out anaerobic combustion for 35-38h, cooling for 144h, and discharging to obtain silicon carbide blocks and graphitized cathode carbon blocks; and (3) carrying out defluorination and dust removal treatment on fluoride flue gas generated in the anaerobic combustion process of the direct current resistance furnace. The invention adopts the ultrahigh-temperature oxygen-free combustion process and the defluorination recovery process, not only can completely discharge toxic components in the lining of the waste electrolytic cell and carry out innocent treatment, but also can discharge other impurities and harmful substances together.
Description
Technical Field
The invention belongs to the technical field of chemical industry, and particularly relates to a harmless and efficient resource recovery method for waste aluminum electrolytic cell linings and waste cathodes.
Background
The waste aluminum cell lining is inevitable waste in the electrolytic aluminum industry, and the removed waste cell lining material contains about 70% of carbon material and other elements such as fluoride, aluminum oxide, aluminum-iron alloy and the like; fluorine of waste tank liningThe compound is NaF or CaF2And Na3AIF6In a form in which NaF is readily leachable in water-The harmfulness is extremely high; CaF2Belongs to a stable and insoluble compound and is harmless to the environment; na (Na)3AIF6Easily decomposed by heating to generate NaF and AIF3Thus Na3AIF6Has certain harmfulness.
The flotation process is a separation process that utilizes a specific flotation agent to select a substance from a slurry; the polarization microscope structure analysis of the waste cathode and other waste residues of the waste aluminum electrolytic cell lining shows that the immersed electrolytes NaF and Na3AIF6，AI203The carbon material is uniformly distributed in cracks and holes of the cathode and the refractory bricks, has obvious interfaces with carbon, and can be separated from the cathode and the refractory bricks through physical crushing; according to laboratory and semi-industrial test tests, the particle size of the powder is proper to 165-100 um (100-150 meshes), the graphitization degree of the carbon in the lining of the waste electrolytic tank reaches 80%, the difference between the surface hydrophobicity of the carbon and the surface hydrophobicity of the electrolyte is large, the electrolyte is distributed in cracks and holes of the carbon block and has an obvious interface with the carbon, the carbon and the electrolyte can be completely separated through physical crushing, and the method is the basis of the flotation process of the lining of the waste electrolytic tank; zhaixijing et al studied the separation of electrolytes and carbon in waste cathode carbon blocks of aluminum cell lining by collectors such as sodium dodecyl benzene sulfonate, naphthyl hydroximic acid, oleic acid and sulfosalicylic acid, and examined the influence of the four collectors on the flotation of pure cryolite and alumina and the influence of fluorine ions on the flotation.
However, flotation has the disadvantages of complex process and high cost: in order to improve output, enterprises increase corresponding salt alkaline agents to remove fluorine, so that the carbon powder with the output effect has large impurities and low carbon content, and also has agent components, the generated calcium fluoride has large impurities and low calcium fluoride content, and the extracted cryolite has carbon and agent components; although the purpose of harmless treatment of the waste electrolytic aluminum lining is realized, the resources cannot be efficiently recovered.
Therefore, the flotation method can realize harmless treatment, change toxic and dangerous waste into common solid waste and prevent and reduce environmental pollution, but cannot effectively solve the problem of resource recycling.
Disclosure of Invention
The invention aims to provide a method for harmless and efficient resource recovery of waste aluminum cell linings and waste cathodes aiming at the problems in the prior art.
The specific technical scheme of the invention is as follows:
a method for harmless and efficient resource recovery of waste aluminum electrolysis cell linings and waste cathodes comprises the following steps:
charging crushed waste aluminum electrolytic cell inner filler blocks, waste cathode blocks, furnace core materials, heat preservation materials and carbon-silicon ratio reaction materials into a direct current resistance furnace, electrifying the direct current resistance furnace, heating to 2800-3000 ℃ for anaerobic combustion for 35-38h, cooling for 144h, and discharging to obtain silicon carbide blocks and graphitized cathode carbon blocks; and (3) carrying out defluorination and dust removal treatment on fluoride flue gas generated in the anaerobic combustion process of the direct current resistance furnace.
The furnace charging steps are as follows:
1) laying the furnace bottom in an upper-lower layered mode: the lower layer of the furnace bottom is paved with quartz sand and carbon black, the upper layer is paved with carbon-silicon ratio reaction materials, the quartz sand layer is 600mm in thickness, the carbon black layer is 150mm in thickness, and the mass ratio of silicon to carbon in the carbon-silicon ratio reaction materials is 40: 60, adding a solvent to the mixture;
2) enclosing a furnace core: the partition plates are respectively arranged at two sides of the furnace end to form a furnace core in a surrounding manner, and a furnace wall is fixed outside the furnace core;
3) laying a furnace bottom padding layer: laying a 150mm thick coke particle cushion layer at the bottom of the furnace core;
4) placing the aluminum alloy into a lining block and a waste cathode in a waste aluminum electrolytic cell: laying waste cathode block layers in the central part of the furnace core from bottom to top layer by layer, laying waste electrolytic tank lining block layers around the waste cathode blocks in the periphery of the furnace core from bottom to top layer by layer, filling coke particles or anode particles in gaps between the waste cathode block layers and the waste electrolytic tank lining blocks when each waste cathode block layer and the waste electrolytic tank lining block layer are laid; graphite powder with the inner side of 30cm is paved on the furnace end, the thickness of the lining block layer and the waste cathode block layer of the electrolytic cell is 2000mm, and the graphite powder can protect the electrode of the furnace end and prevent high-temperature burning loss;
5) laying an upper padding layer: covering coke particles and a silicon-carbon ratio reaction material on a lining block and a waste cathode block in a waste electrolytic cell to serve as an upper padding layer, wherein the thickness of the upper padding layer is 150 mm; the coke particles play a role in reducing ash content and preventing silicon gas from flowing inwards, and silicon carbon plays a role in preserving heat compared with a reaction material and reduces heat loss; the silicon carbon has a heat preservation effect compared with the reaction material, and the heat loss is reduced;
6) covering with a heat preservation material: the furnace core is characterized in that heat preservation material layers are covered on two sides and the top layer of the furnace core, the thickness of the heat preservation material layers on the two sides of the furnace core is 1500mm, and the thickness of the heat preservation material layer on the top layer of the furnace core is 700 mm.
The fluoride flue gas defluorination recovery treatment method comprises the following specific steps: flue gas such as fluoride is discharged into a defluorination tower through a flue gas pipeline, a calcium hydroxide solution is sprayed in the defluorination tower to carry out adsorption reaction on the flue gas to generate a mixed liquid of calcium fluoride and sodium salt wastewater, solid-liquid separation is carried out on the mixed liquid of the calcium fluoride and the sodium salt wastewater through a filter press to obtain solid calcium fluoride and sodium salt wastewater, and the sodium salt wastewater is evaporated through an over-temperature evaporator to obtain sodium salt.
The invention has the following beneficial effects:
the invention adopts the ultrahigh-temperature oxygen-free combustion process and the defluorination recovery process, not only can completely discharge toxic components in the lining of the waste electrolytic cell and carry out innocent treatment, but also can discharge other impurities and harmful substances together.
The reaction process of each stage of the high-temperature oxygen-free combustion process comprises the following steps: first stage (1273-1700K) CH4、CO、CO2Fluoride and the like are discharged; in the second stage (1700-2400K), carbide (mainly silicon carbide) is generated and then decomposed at a higher temperature, the thermal vibration frequency of carbon atoms is increased, the distance between carbon nets is reduced, and the transition is carried out to graphitization; in the third stage (above 2400K), the carbon atom graphite crystal grows, the graphitization degree is continuously improved, the crystal grows continuously, and the heat absorption is continuously increased; physical and chemical indexes of the high-purity carburant are as follows: the carbon content is more than or equal to 98.5 percent, the S content is less than or equal to 0.05 percent, the ash content is less than or equal to 0.5 percent, and the graphitization index of the waste cathode can completely reach the standard through an ultrahigh-temperature oxygen-free combustion process.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The method for carrying out harmless treatment and resource recovery on the waste electrolytic cell lining comprises the following steps:
charging the direct current resistance furnace: paving quartz sand on the lower layer of the furnace bottom, paving carbon-silicon ratio reaction materials on the upper layer, paving and tamping, wherein the thickness of the quartz sand layer is 600mm, and the mass ratio of carbon to silicon in the carbon-silicon ratio reaction materials is 40: 60, adding a solvent to the mixture; the partition plates are respectively arranged at two sides of the furnace end to form a furnace core in a surrounding manner, and a furnace wall is fixed outside the furnace core; paving a coke particle cushion material layer with the thickness of 150mm at the bottom of the furnace core; laying waste cathode block layers in the central part of the furnace core from bottom to top layer by layer, laying waste electrolytic tank lining block layers around the waste cathode blocks in the periphery of the furnace core from bottom to top layer by layer, filling coke particles and graphite powder in a gap between the waste cathode block layer and the waste electrolytic tank lining block layer when each waste cathode block layer and the waste electrolytic tank lining block layer are laid, wherein the thicknesses of the electrolytic tank lining block layer and the waste cathode block layer are 2000 mm; covering coke particles with the thickness of 150mm and a silicon-carbon ratio reaction material on the waste cathode block and the waste electrolytic cell lining block as an upper padding layer; covering heat preservation material layers on two sides and the top layer of the furnace core, wherein the thickness of the heat preservation material layers on the two sides of the furnace core is 1500mm in total, and the thickness of the heat preservation material layer on the top layer of the furnace core is 700 mm;
ultra-high temperature oxygen-free combustion: electrifying the direct current resistance furnace, heating to 2800-3000 ℃, carrying out anaerobic combustion for 35h, naturally cooling for 144h, then removing the furnace wall, gradually removing heat preservation materials along with the reduction of the temperature of the furnace core, exposing the product, cleaning the heat preservation materials at two sides of the furnace core, and finally taking out the graphitized cathode carbon block and the silicon carbide block;
defluorination recovery of fluoride flue gas: flue gas such as fluoride overflows through high temperature, enters a 100000 air-volume defluorination tower along with a closed flue gas pipeline along with the suction of an induced draft fan, contains calcium hydroxide liquid, is cooled, sprayed and subjected to adsorption reaction to generate mixed liquid of calcium fluoride and sodium salt wastewater, and the mixed liquid is discharged into a circulating pool, when the concentration of sodium ions in the liquid reaches 58 Ag/Ļ, the mixed liquid of the calcium fluoride and the sodium salt wastewater is pumped into a filter press by a sludge corrosion prevention pump to be subjected to solid-liquid separation to obtain solid calcium fluoride and sodium salt wastewater with overproof concentration, the sodium salt wastewater is subjected to water and sodium salt separation by an over-temperature evaporator, water evaporation gas is forcibly cooled through a pipeline to become water liquid reaching the standard and is recycled, and solid sodium salt left after evaporation is recovered.
The obtained graphitized cathode carbon block and silicon carbide block are detected by the embodiment: the SiC content in the silicon carbide block is more than 70%, the fluoride content in each gram of the silicon carbide block is 12 micrograms, the fluoride content in each gram of the graphitized cathode carbon block is 53 micrograms, the ash content in the graphitized cathode carbon block is 0.18%, the Vdaf volatile matter content is 0.12%, the total sulfur content is 0.01%, and the fixed carbon content is 98.64%.
The data show that the waste electrolytic cell lining is changed into silicon carbide after harmless treatment and can be completely sold as a product, and the waste cathode is changed into a high-purity carburant product after ultrahigh-temperature harmless treatment and completely meets the national GB5085.3-2007 requirement.
Claims (6)
1. A method for harmless and efficient resource recovery of waste aluminum electrolysis cell linings and waste cathodes is characterized by comprising the following steps:
loading the crushed waste aluminum electrolytic cell lining blocks, waste cathode blocks, furnace core materials, heat preservation materials and carbon-silicon ratio reaction materials into a direct current resistance furnace, electrifying the direct current resistance furnace, heating to 2800-3000 ℃ for anaerobic combustion, and cooling to obtain silicon carbide blocks and graphitized cathode carbon blocks; and (3) carrying out defluorination recovery treatment on fluoride flue gas generated in the anaerobic combustion process of the direct current resistance furnace.
2. The method for harmless and efficient resource recovery of the waste electrolytic cell lining and the waste cathode as claimed in claim 1, wherein the charging step comprises:
1) laying the furnace bottom in an upper-lower layered mode: paving quartz sand and carbon black on the lower layer of the furnace bottom, paving a carbon-silicon ratio reaction material on the upper layer, and paving and tamping;
2) enclosing a furnace core: the partition plates are respectively arranged at two sides of the furnace end to form a furnace core in a surrounding manner, and a furnace wall is fixed outside the furnace core;
3) laying a furnace bottom padding layer: laying a coke particle padding layer at the bottom of the furnace core;
4) placing the waste electrolytic cell into a lining block and a waste cathode: laying waste cathode block layers in the central part of the furnace core from bottom to top layer by layer, laying waste electrolytic tank lining block layers around the waste cathode blocks in the periphery of the furnace core from bottom to top layer by layer, filling coke particles or anode particles in a gap between the waste cathode block layer and the waste electrolytic tank lining block layer when each waste cathode block layer and the waste aluminum electrolytic tank lining block layer are laid, and laying graphite powder on a furnace end;
5) laying an upper padding layer: covering coke particles and silicon-carbon ratio reaction materials on lining blocks and waste cathode blocks in the waste aluminum electrolytic cell to serve as an upper lining layer;
6) covering with a heat preservation material: two sides and the top layer of the furnace core are covered with heat preservation material layers.
3. The method for harmless and efficient resource recovery of the waste aluminum electrolysis cell lining and the waste cathode as claimed in claim 2, wherein the method comprises the following steps:
in the step 1), the thickness of the quartz sand layer is 600mm, the thickness of the carbon black layer is 150mm, and the mass ratio of carbon to silicon in the reaction material is 40: 60, adding a solvent to the mixture;
the thickness of the furnace bottom padding layer in the step 3) and the thickness of the upper padding layer in the step 5) are 150 mm;
the thickness of the lining block layer and the waste cathode block layer of the waste electrolytic cell in the step 4) is 2000 mm;
the thickness of the heat preservation material layers on the two sides of the furnace core in the step 6) is 1500mm, and the thickness of the heat preservation material layer on the top layer of the furnace core is 700 mm.
4. The method for harmless and efficient resource recovery of the waste aluminum electrolysis cell lining and the waste cathode as claimed in claim 1 or 2, wherein the method comprises the following steps: the anaerobic combustion time is 35-38 h.
5. The method for harmless and efficient resource recovery of the waste aluminum electrolysis cell lining and the waste cathode as claimed in claim 1 or 2, wherein the method comprises the following steps: the cooling time was 144 h.
6. The method for harmless and efficient resource recovery of the waste aluminum electrolysis cell lining and the waste cathode as claimed in claim 1 or 2, wherein the specific steps of the fluoride flue gas defluorination recovery treatment are as follows: flue gas such as fluoride is discharged into a defluorination tower through a flue gas pipeline, a calcium hydroxide solution is sprayed in the defluorination tower to carry out adsorption reaction on the flue gas to generate a mixed liquid of calcium fluoride and sodium salt wastewater, solid-liquid separation is carried out on the mixed liquid of the calcium fluoride and the sodium salt wastewater through a filter press to obtain solid calcium fluoride and sodium salt wastewater, and the sodium salt wastewater is evaporated through an over-temperature evaporator to obtain sodium salt.
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Application publication date: 20211001 |