Resourceful treatment method for solid waste of electrolytic aluminum factory

Abstract

The invention belongs to the technical field of solid waste treatment, and provides a resourceful treatment method for solid waste of an electrolytic aluminum factory. According to the method, sodium hypochlorite is added in the wet grinding process, so that cyanide in the solid waste of the electrolytic aluminum factory is oxidized into CO2 and N2, environmental pollution and safety risks caused by the solid waste of the electrolytic aluminum factory are thoroughly eliminated, and harmlessness is achieved. The fluorine source is used as the leaching agent, so that the molecular ratio of the cryolite can be adjusted, and the quality of the regenerated cryolite is improved; hydrochloric acid is used as a leaching agent, so that strict requirements on sulfur content of recycled electrolyte in an electrolytic aluminum factory are met. And meanwhile, no waste gas is generated by the resourceful treatment method. According to the resourceful treatment method, energy consumption is low, no acid mist is released in the operation process, the lithium yield is high, the lithium content in the solid waste of the electrolytic aluminum factory can be reduced to 0.025% from 0.4-2%, cryolite and carbon powder are obtained after filter residues obtained after lithium extraction through leaching are rinsed, separated and dried, and comprehensive resourceful utilization is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste treatment, and particularly relates to a resource treatment method for solid waste of an electrolytic aluminum plant. BACKGROUND

[0002] The main component of the electrolyte used in electrolytic aluminum production is cryolite Na3AlF6, containing a small amount of lithium fluoride, calcium fluoride, magnesium fluoride, potassium fluoride, etc. Due to continuous enrichment in the production process, a small amount of graphitized carbon powder is also mixed in. Due to the carrying of raw materials, lithium fluoride, magnesium fluoride and calcium fluoride in the electrolyte are continuously enriched, which seriously affects the electrolytic aluminum production. Measures have to be taken to regenerate the electrolyte. The existing regeneration method is generally high-temperature calcination followed by leaching. The regenerated cryolite has poor quality.

[0003] The main component of the overhaul slag (hazardous waste code 321-023-48) of the electrolytic aluminum plant is basically the same as that of the electrolyte. The difference is that the carbon and impurities carried are very different, and may contain cyanide and soluble fluorine. It has been classified as hazardous waste and has to be landfilled. The subsequent research and development of using pyroprocessing to harmlessly treat the overhaul slag and carbon slag has the problems of high cost and tail gas emission. SUMMARY

[0004] In view of this, the present application provides a resource treatment method for solid waste of an electrolytic aluminum plant. The resource treatment method provided by the present application has good quality regenerated cryolite and low cost without tail gas pollution.

[0005] In order to achieve the above-mentioned application purpose, the present application provides the following technical scheme:

[0006] The present application provides a resource treatment method for solid waste of an electrolytic aluminum plant, comprising the following steps:

[0007] Mixing the solid waste of the electrolytic aluminum plant, sodium hypochlorite and water, wet grinding to obtain a slurry;

[0008] After preheating the slurry, mixing with water vapor, hydrochloric acid and fluorine source, sequentially leaching and solid-liquid separation to obtain a filtrate and a filter residue;

[0009] The filter residue is sequentially rinsed, separated and dried to obtain cryolite and carbon powder;

[0010] Mixing the filtrate and hydrogen peroxide, and performing iron precipitation under the conditions of aeration and acidity to obtain a ferric hydroxide precipitate and an acidic brine;

[0011] The acidic brine is subjected to carbonate precipitation under the conditions of aeration and alkalinity to obtain a carbon fixation material and an alkaline brine;

[0012] The alkaline brine is subjected to calcium-magnesium precipitation under alkaline conditions to obtain calcium-magnesium precipitate and brine;

[0013] The brine is concentrated by evaporation and crystallization to obtain lithium carbonate and sodium chloride.

[0014] The electrolytic aluminum plant solid waste includes overhaul slag or waste electrolyte.

[0015] Preferably, the particle size of the electrolytic aluminum plant solid waste is 80 mesh or more.

[0016] Preferably, the mass ratio of the sodium hypochlorite to the electrolytic aluminum plant solid waste is 0.1-5:1000.

[0017] Preferably, the solid content of the slurry is 10-35%.

[0018] Preferably, the preheating temperature is ≥70°C.

[0019] Preferably, the mass concentration of the hydrochloric acid is 31%.

[0020] The fluorine source is sodium fluoride or hydrofluoric acid, and the mass concentration of the hydrofluoric acid is 5-15%.

[0021] The mass ratio of the electrolytic aluminum plant solid waste, the hydrochloric acid and the fluorine source is 1:0.8:0.2.

[0022] The pressure of the water vapor is 0.8 MPa.

[0023] Preferably, the leaching time is ≥2 h.

[0024] Preferably, in the iron precipitation process, the mass concentration of the hydrogen peroxide is 20-30%, the hydrogen peroxide is added in an amount of 0.1-2% of the volume of the filtrate, the pH value of the acid is 3.0-3.8, and the aeration gas is air.

[0025] Preferably, in the carbonate precipitation process, the pH value of the alkali is 8-11, and the aeration gas is carbon dioxide.

[0026] Preferably, in the calcium-magnesium precipitation process, the pH value of the alkali is 12, and the alkali adjusting agent is liquid alkali.

[0027] The application provides a resource treatment method of solid waste of an electrolytic aluminum plant.

[0028] Beneficial effects:

[0029] In the wet grinding process, sodium hypochlorite is added, so that cyanide in the solid waste of the electrolytic aluminum plant is oxidized into CO2 and N2, thereby completely eliminating the environmental pollution and safety risk of the solid waste of the electrolytic aluminum plant and realizing harmless treatment.

[0030] On the basis of realizing harmless treatment, the application uses a fluorine source as a leaching agent to adjust the molecular ratio of cryolite and improve the quality of regenerated cryolite; and uses hydrochloric acid as a leaching agent to meet the strict requirement of the electrolytic aluminum plant on the sulfur content of the recycled electrolyte. Meanwhile, the leaching can leach valuable metals in the solid waste of the electrolytic aluminum plant, such as iron, aluminum, calcium, magnesium, lithium and other heavy metals. In addition, the resource treatment method does not produce waste gas and does not cause new environmental pollution.

[0031] The resource treatment method provided by the application has low energy consumption, no acid mist release in the operation process, high lithium yield, can reduce the lithium content in the solid waste of the electrolytic aluminum plant from 0.4-2% to 0.025%, and can obtain cryolite and carbon powder from the filter residue after leaching and lithium extraction, thereby realizing comprehensive resource utilization. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A flowchart of the resource treatment method of the solid waste of the electrolytic aluminum plant provided by the application. DETAILED DESCRIPTION

[0033] Figure 1 A flowchart of the resource treatment method of the solid waste of the electrolytic aluminum plant provided by the application, and the resource treatment method will be described in detail below. Figure 1 The resource treatment method provided by the application is described in detail.

[0034] The application provides a resource treatment method of solid waste of an electrolytic aluminum plant, comprising the following steps:

[0035] Mixing electrolytic aluminum plant solid waste, sodium hypochlorite and water, wet grinding to obtain slurry;

[0036] After the slurry is preheated, mixed with water vapor, hydrochloric acid and fluorine source, leaching and solid-liquid separation are sequentially performed to obtain filtrate and filter residue;

[0037] The filter residue is sequentially rinsed, separated and dried to obtain cryolite and carbon powder;

[0038] The filtrate is mixed with hydrogen peroxide, and iron precipitation is carried out under the conditions of aeration and acidity to obtain iron hydroxide precipitate and acidic brine;

[0039] The acidic brine is subjected to carbonate precipitation (carbon precipitation) under the conditions of aeration and alkalinity to obtain carbon fixation material and alkaline brine;

[0040] The alkaline brine is subjected to calcium and magnesium precipitation under alkaline conditions to obtain calcium and magnesium precipitate and brine;

[0041] The brine is concentrated by evaporation and crystallized to obtain lithium carbonate and sodium chloride;

[0042] The electrolytic aluminum plant solid waste includes overhaul slag or waste electrolyte.

[0043] In the present application, the raw materials used in the present application are preferably commercially available products unless otherwise specified.

[0044] In the present application, the electrolytic aluminum plant solid waste, sodium hypochlorite and water are mixed and wet ground to obtain a slurry.

[0045] In the present application, the electrolytic aluminum plant solid waste includes overhaul slag or waste electrolyte. In the present application, the mass content of lithium oxide in the overhaul slag is preferably 1.5% to 4.5%. In the present application, the mass content of lithium oxide in the waste electrolyte is preferably 0.95% to 2%. In the present application, the particle size of the electrolytic aluminum plant solid waste is preferably 80 mesh or more. In the present application, the electrolytic aluminum plant solid waste is preferably crushed and ground before being treated, and the parameters of the crushing and grinding are not specifically limited in the present application, as long as the particle size of the electrolytic aluminum plant solid waste is 80 mesh or more.

[0046] In the present application, the mass ratio of sodium hypochlorite to electrolytic aluminum plant solid waste is preferably 0.1 to 5:1000, and further preferably 1 to 3:1000.

[0047] In the present application, the particle size of the material obtained by wet grinding is preferably 200 mesh or more.

[0048] After wet grinding, the present application preferably further comprises adding water. In the present application, the solid content of the slurry is preferably 10% to 35%, and further preferably 25% to 30%.

[0049] In the present application, the principle of wet grinding pulping is:

[0050] First, sodium hypochlorite reacts with sodium cyanide in solid waste from an aluminum electrolysis plant to produce sodium chlorite and sodium cyanate; then, sodium chlorite and sodium cyanate react in water and air to produce nitrogen and carbon dioxide.

[0051] Step one: 4NaClO + 2NaCN → 2NaClO2 + 2NaOCN;

[0052] Step two: 4NaClO2 + 4NaOCN + 4H2O + O2 → 4NaCl + 4NaOH + 2CO2 + N2.

[0053] After obtaining the slurry, the slurry is preheated, mixed with water vapor, hydrochloric acid, and a fluorine source, and then subjected to leaching and solid-liquid separation in sequence to obtain a filtrate and a filter residue.

[0054] In the present application, the preheating temperature is preferably ≥ 70°C, and further preferably 70-95°C; and the preheating method is preferably heat exchange.

[0055] In the present application, the hydrochloric acid is preferably industrial hydrochloric acid, and the mass concentration of the hydrochloric acid is preferably 31%. In the present application, using hydrochloric acid as the leaching agent facilitates the strict requirements of the electrolyte on the sulfur content in the aluminum electrolysis plant. For example, if sulfuric acid is used as the leaching agent, it is difficult to make the sulfur content of the regenerated cryolite meet the production requirements, thereby increasing the purification cost.

[0056] In the present application, the fluorine source preferably includes sodium fluoride or hydrofluoric acid, and further preferably hydrofluoric acid; and the hydrofluoric acid or sodium fluoride is preferably waste hydrofluoric acid (hazardous waste code 312-034-48) or sodium fluoride in the photovoltaic industry. In the present application, the mass concentration of the hydrofluoric acid is preferably 5-15%, further preferably 8-12%, and more preferably 10%. The present application uses waste hydrofluoric acid (hazardous waste code 312-034-48) or sodium fluoride in the photovoltaic industry as the fluorine source to reduce the cost of the resource treatment method.

[0057] In the present application, the mass ratio of the solid waste from the aluminum electrolysis plant, the hydrochloric acid, and the fluorine source is preferably 1:0.8:0.2.

[0058] In the present application, the pressure of the water vapor is preferably 0.8 MPa.

[0059] In the present application, the mixing of the preheated slurry with water vapor, hydrochloric acid, and a fluorine source preferably includes: mixing the preheated slurry with water vapor to obtain a first mixture; mixing the hydrochloric acid and the fluorine source to obtain a second mixture, and mixing the first mixture and the second mixture. In the present application, the mixing of the preheated slurry with water vapor is preferably carried out in a pipe mixer; and the mixing of the hydrochloric acid and the fluorine source is preferably carried out in a pipe mixer.

[0060] In the present application, the slurry is preferably pumped into the pipe mixer after preheating, the water vapor is preferably pulsed into the pipe mixer by electromagnetic valve using steam pressure. In the present application, the hydrochloric acid is preferably pumped into the pipe mixer, the hydrofluoric acid is preferably pumped into the pipe mixer.

[0061] In the present application, the leaching time is preferably ≥ 2h.

[0062] In the present application, the leaching is preferably carried out in a pipe reactor. In the present application, the pipe reactor is preferably composed of an insulated pipe, the diameter of the insulated pipe is preferably 100-600mm, the length is preferably 50-400m; the inner lining of the insulated pipe is preferably tetrafluoroethylene; a pipe mixer is preferably arranged every 10-20m on the pipe reactor to supplement water vapor to avoid blockage of the material and reduction of temperature. In the present application, the diameter of the pipe mixer is preferably smaller than the diameter of the insulated pipe.

[0063] After leaching, before solid-liquid separation, the present application preferably further comprises: stirring the obtained leaching mixture, the stirring is preferably carried out in a stirring tank.

[0064] In the present application, the solid-liquid separation method is preferably pressure filtration, which is preferably carried out in a filter press.

[0065] In the present application, the following main chemical reactions occur during leaching:

[0066] Al2O3 + 6HCl = 2AlCl3 + 3H2O;

[0067] LiF + HCl = LiCl + HF;

[0068] Na3AlF6 = 3NaF + AlF3;

[0069] AlCl3 + 3HF = AlF3 + 3HCl;

[0070] Fe2O3 + 6HCl = 2FeCl3 + 3H2O.

[0071] After leaving the pipe reactor, the material cools down and the following reactions occur:

[0072] 3NaF + AlF3 = Na3AlF6.

[0073] Part of the insoluble calcium fluoride and magnesium fluoride in the pipe reactor also undergoes reversible reaction to generate part of calcium chloride and magnesium chloride which are easily soluble in water, thereby playing a role in purifying electrolyte.

[0074] CaF2 + HCl = CaCl2 + 2HF.

[0075] MgF2 + HCl = MgCl2 + 2HF.

[0076] After the filter residue is obtained, the filter residue is rinsed, separated and dried in sequence to obtain cryolite and carbon powder.

[0077] After the filtrate is obtained, the filtrate is mixed with hydrogen peroxide, and iron precipitation is carried out under aeration and acidic conditions to obtain iron hydroxide precipitate and acidic brine. In the present application, the mass concentration of the hydrogen peroxide in the process of iron precipitation is preferably 20-30%, the addition amount of the hydrogen peroxide is preferably 0.1-2% of the volume of the filtrate, further preferably 0.5-1%, the pH value of the acid is preferably 3.0-3.8, the adjusting agent of the acid is preferably sodium hydroxide, the sodium hydroxide is preferably used in the form of a sodium hydroxide solution, the mass concentration of the sodium hydroxide solution is preferably 30%, and the aeration gas is preferably air. In the present application, the iron precipitation is preferably carried out in an aeration tank.

[0078] After the iron precipitation, the present application preferably further comprises: carrying out solid-liquid separation on the obtained iron precipitation system.

[0079] In the present application, the iron precipitation can remove iron and heavy metals in the form of hydroxide from the filtrate.

[0080] After the acidic brine is obtained, the acidic brine is subjected to carbonate precipitation under aeration and alkaline conditions to obtain carbon fixation material and alkaline brine.

[0081] In the present application, the pH value of the alkaline in the process of carbonate precipitation is preferably 8-11, further preferably 9-10, and the maintenance of the pH value of the alkaline is preferably controlled by the aeration gas and liquid alkali; the aeration gas is preferably carbon dioxide. In the present application, the carbonate precipitation is preferably carried out in an aeration tank.

[0082] After the carbonate precipitation, the present application preferably further comprises: standing and solid-liquid separating the obtained carbonate precipitation system to obtain filter residue and alkaline brine, countercurrently rinsing the filter residue, pressure filtering and drying the filter residue to obtain carbon fixation material.

[0083] In the present application, the carbonate precipitation can fix calcium, magnesium and aluminum in the form of carbonate or alkaline carbonate, and further remove calcium, magnesium and aluminum.

[0084] After the alkaline brine is obtained, the alkaline brine is subjected to calcium and magnesium precipitation under alkaline conditions to obtain calcium and magnesium precipitate and brine.

[0085] In the present application, the pH value of the alkaline is preferably 12, and the alkaline adjusting agent is preferably liquid alkali. In the present application, the calcium-magnesium precipitation is preferably static.

[0086] After the calcium-magnesium precipitation, the present application preferably further comprises: performing solid-liquid separation on the obtained calcium-magnesium precipitation system.

[0087] In the present application, the calcium-magnesium precipitation is preferably used as a flame retardant.

[0088] In the present application, the calcium-magnesium precipitation can further fix and remove the calcium ions and magnesium ions still existing in the alkaline brine in the form of hydroxide.

[0089] After obtaining the brine, the brine in the present application is concentrated by evaporation and crystallized to obtain lithium carbonate and sodium chloride.

[0090] The present application does not make specific limitations on the mode of the evaporation concentration and crystallization, and any operation known to those skilled in the art can be adopted.

[0091] In the present application, the evaporation concentration preferably further obtains an evaporation mother liquor, and the evaporation mother liquor is preferably recycled.

[0092] In the present application, the crystallization preferably further obtains condensed water, and the condensed water is preferably recycled.

[0093] The method for resourceful treatment of solid waste of an aluminum electrolysis plant provided by the present application will be described in detail below in combination with examples, but they should not be understood as limitations on the protection scope of the present application.

[0094] Example 1

[0095] The overhauled slag containing 2.2% lithium oxide is crushed and ground to 80 mesh or more, and then wet ground with water and sodium hypochlorite (mass ratio of sodium hypochlorite to overhauled slag is 3:1000) to 200 mesh or more, and then stirred with water to form a flowable slurry (solid content of the slurry is 25%); the slurry is preheated to 70°C or more by heat exchange, and then pumped into a pipe mixer and mixed with 0.8 MPa steam which is pulsed into the pipe, so that the temperature of the mixed solution reaches about 100°C; the heated material is connected to another pipe mixer which is fed with 31% industrial hydrochloric acid and 20% hydrofluoric acid by pumps, and the ratio of the industrial hydrochloric acid to the hydrofluoric acid is controlled by valves; generally, the mass ratio of the overhauled slag to the hydrochloric acid to the hydrofluoric acid is 1:0.8:0.2, but if the chemical composition of the overhauled slag changes greatly, the ratio of the overhauled slag to the hydrochloric acid to the hydrofluoric acid can be adjusted; the mixed solution is mixed with the acid in the pipe reactor which is connected by DN300 mm pipes lined with tetrafluoroethylene and has a length of 250 m; the flow rate of the previous stage is adjusted to ensure that the material stays in the pipe reactor for more than 2 hours; to avoid clogging and maintain the temperature, a pipe mixer is added every 15 meters to supplement the steam into the pipe reactor.

[0096] The material treated in the pipe reactor is fed into a 50 m 3 stirring tank, and the material is continuously stirred; the material in the stirring tank is pumped into a filter press to separate the filter residue and the filtrate; the filter residue is further rinsed, separated and dried to obtain cryolite and carbon powder respectively; the filtrate is aerated (with air), and hydrogen peroxide (30% by mass) is added (amount is 0.5% of the volume of the filtrate); the pH of the filtrate is adjusted to 3.8 by using 30% sodium hydroxide solution, so that a small amount of iron ions in the filtrate form iron hydroxide precipitate and are separated to obtain the iron hydroxide precipitate and the iron-removed acidic brine.

[0097] The acidic brine is further purified and treated by pumping it into an aeration tank; the aeration tank is provided with an aeration disc at the bottom which is connected to a CO2 tank by a pipe; the pH of the aeration tank is controlled to 9-10 by using liquid alkali and carbon dioxide; a large amount of precipitate is generated in the aeration tank and is separated by a filter press to obtain the filter residue and the alkaline brine; the filter residue is countercurrently rinsed, filtered and dried to be sold as a carbon fixation material or a flame retardant; to prevent a small amount of calcium and magnesium ions from remaining in the alkaline brine, the pH of the alkaline brine is adjusted to 12 by using liquid alkali, and then the alkaline brine is left to stand to obtain calcium and magnesium precipitate and brine containing sodium chloride and lithium chloride, and the lithium ion content in the brine is 5 g / L; the brine is evaporated and concentrated and crystallized and separated by using a well-known process to obtain lithium carbonate and sodium chloride, and the condensate and the evaporation mother liquor are recycled.

[0098] The lithium oxide in the regenerated cryolite was detected, and the result was that the mass content of lithium oxide in the regenerated cryolite was 0.06%.

[0099] Example 2

[0100] The waste electrolyte containing 0.95% of lithium oxide was crushed and ground to 80 mesh or more, and the waste electrolyte powder was wet ground to 200 mesh or more by adding water and sodium hypochlorite (the mass ratio of sodium hypochlorite to the spent slag was 3:1000), and the water was stirred to form a flowable slurry (the solid content of the slurry was 30%); and the slurry was preheated to 70°C or more by heat exchange, and the preheated slurry was pumped into a pipeline mixer and mixed with 0.8 MPa steam pulsed into the pipeline, so that the temperature of the mixed solution reached about 100°C; the heated material was connected to another pipeline mixer, and the mass concentration of industrial hydrochloric acid and hydrofluoric acid was 31% and 20% respectively, and the proportion of industrial hydrochloric acid and hydrofluoric acid was adjusted and controlled by valves, and according to the solid content of the preheated slurry in the previous stage and the flow rate through the pipeline, the mass ratio of waste electrolyte:hydrochloric acid:hydrofluoric acid was usually controlled at 1:0.8:0.2, and if the chemical composition of the waste electrolyte was greatly changed, the proportion of waste electrolyte, hydrochloric acid and hydrofluoric acid could be adjusted. After the mixed solution was mixed with the acid, a violent reaction occurred in the pipeline reactor, the pipeline reactor was connected by a heat preservation pipeline with a diameter of DN250 mm lined with tetrafluoroethylene, the length was 320 m, and the flow rate of the previous stage was adjusted to ensure that the material stayed in the pipeline reactor for more than 2 hours, and to avoid blockage and maintain the temperature, a pipeline mixer was added every 20 meters to supplement the mixing of water vapor into the pipeline reactor.

[0101] The material treated by the pipeline reactor entered a 50 m 3 stirring tank, and the material was continuously stirred, and the material in the stirring tank was pumped into a filter press for pressure filtration separation to obtain filter residue and filtrate. The filter residue was further rinsed, separated and dried to obtain cryolite and carbon powder respectively; the filtrate was aerated (the gas was air), hydrogen peroxide (the mass concentration of hydrogen peroxide was 30%, and the amount of hydrogen peroxide added was 0.5% of the volume of the filtrate), and the pH was adjusted to 3.8 by using a sodium hydroxide solution with a mass concentration of 30% to make a small amount of iron ions in the brine generate iron hydroxide precipitate and separate to obtain iron hydroxide precipitate and iron-removed acidic brine.

[0102] The acid brine is further purified and sent into an aeration tank by a pump. An aeration disc is arranged at the bottom of the aeration tank and connected to a CO2 storage tank through a pipeline. At the same time, liquid alkali and carbon dioxide are used to maintain the pH value of the aeration tank at 9-10. A large amount of precipitate is generated in the aeration tank and sent into a filter press for pressure filtration and separation to obtain filter residue and alkaline brine. The filter residue is subjected to countercurrent rinsing, pressure filtration and drying and then sold as a carbon fixation material. In order to prevent a small amount of calcium and magnesium ions from remaining in the alkaline brine, the pH value is adjusted to 12 by using liquid alkali. After standing, calcium and magnesium precipitate and brine containing sodium chloride and lithium chloride are obtained. The content of lithium ions in the brine is 2.8 g / L. The brine is subjected to evaporation and concentration and crystallization separation by using a well-known process to obtain lithium carbonate and sodium chloride. The condensate obtained by crystallization separation and the evaporation mother liquor obtained by evaporation and concentration are recycled.

[0103] The content of lithium oxide in the regenerated cryolite is detected. The result is that the mass content of lithium oxide in the regenerated cryolite is 0.06%.

[0104] 1000 g of the obtained carbon fixation material is heated to 1000°C for 2 hours. The weight of the cooled material is 541.5 g. The residual carbon fixation powder is subjected to chemical analysis. The composition of the residual carbon fixation powder is Al2O3 61.0%, Na2O 37.1%, MgO 1.15%, CaO 0.72%, and the balance is water.

[0105] Example 3

[0106] The large repair slag containing 3.5% of lithium oxide is crushed and ground to more than 80 mesh. Water and sodium hypochlorite (the mass ratio of sodium hypochlorite to large repair slag is 5:1000) are used to wet grind the large repair slag powder to more than 200 mesh. Water is supplemented and stirred to prepare a flowable slurry (the solid content of the slurry is 28%). The slurry is preheated to more than 70°C by using a heat exchange method. The preheated slurry is pumped into a pipeline mixer and mixed with 0.8 MPa steam which is pulsed into the pipeline. The temperature of the mixed liquid is about 100°C. The heated material is connected to another pipeline mixer. Industrial hydrochloric acid with a mass concentration of 31% and hydrofluoric acid with a mass concentration of 10% are pumped into the pipeline mixer, respectively. The ratio of industrial hydrochloric acid to hydrofluoric acid is controlled by a valve. Generally, the ratio of large repair slag:hydrochloric acid:hydrofluoric acid is 1:0.8:0.2 according to the solid content of the preheated slurry and the flow rate of the pipeline. If the chemical composition of the large repair slag raw material changes greatly, the ratio of large repair slag, hydrochloric acid and hydrofluoric acid can be adjusted. After the mixed liquid is mixed with the acid, a violent reaction occurs in the pipeline reactor. The pipeline reactor is connected by a heat preservation pipeline lined with tetrafluoroethylene with a diameter of DN200 mm. The length of the pipeline reactor is 400 m. The flow rate of the previous stage is adjusted to ensure that the material stays in the pipeline reactor for more than 2 hours. In order to avoid blockage and maintain the temperature, a pipeline mixer is added every 20 meters to supplement the mixing of steam into the pipeline reactor.

[0107] The material treated by the pipe reactor enters a 50m 3 stirring tank, the material is continuously stirred, and the material in the stirring tank is pumped into a filter press for pressure filtration separation to obtain filter residue and filtrate. The filter residue is further rinsed, separated and dried to obtain cryolite and carbon powder respectively; the filtrate is aerated (the gas is air), hydrogen peroxide (the mass concentration of the hydrogen peroxide is 30%, and the amount of addition is 0.5% of the volume of the filtrate), a sodium hydroxide solution with a mass concentration of 30% is used to adjust the pH to 3.8, a small amount of iron ions existing in the filtrate is converted into iron hydroxide precipitate, and the iron hydroxide precipitate and the iron-removed acidic brine are obtained after separation.

[0108] The acidic brine is further purified and treated, the acidic brine is pumped into an aeration tank, an aeration disc is arranged at the bottom of the aeration tank and connected to a CO2 storage tank through a pipeline, liquid alkali and carbon dioxide are used to maintain the pH value of the aeration tank at 8-10, a large amount of precipitate is generated in the aeration tank, the precipitate is sent into a filter press for pressure filtration separation to obtain filter residue and alkaline brine; the filter residue is countercurrently rinsed, pressure-filtered and dried to be sold as a carbon fixation material or a flame retardant; in order to prevent a small amount of calcium and magnesium ions from remaining in the alkaline brine, the pH is adjusted to 12 by using liquid alkali, and after standing, calcium and magnesium precipitate and brine containing sodium chloride and lithium chloride are obtained, the content of lithium ions in the brine is 12g / L, and the brine is evaporated and concentrated and crystallized and separated to obtain lithium carbonate and sodium chloride by using a well-known process; the condensate obtained by crystallization and separation and the evaporation mother liquor obtained by evaporation and concentration are recycled.

[0109] The lithium oxide in the regenerated cryolite is detected, and the result is that the mass content of lithium oxide in the regenerated cryolite is 0.06%.

[0110] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for resource recovery of solid waste from an aluminum electrolysis plant, characterized by, The method comprises the following steps: mixing electrolytic aluminum plant solid waste, sodium hypochlorite and water, wet grinding to obtain a slurry; mixing the slurry with water vapor, hydrochloric acid and a fluorine source after preheating, sequentially performing leaching and solid-liquid separation to obtain a filtrate and a filter residue; sequentially performing rinsing, separation and drying on the filter residue to obtain cryolite and carbon powder; mixing the filtrate with hydrogen peroxide, and performing iron precipitation under the conditions of aeration and acidity to obtain iron hydroxide precipitate and acidic brine; performing carbonate precipitation under the conditions of aeration and alkalinity on the acidic brine to obtain carbon sequestration material and alkaline brine; performing calcium and magnesium precipitation under the conditions of alkalinity on the alkaline brine to obtain calcium and magnesium precipitate and brine; evaporating and concentrating the brine to obtain lithium carbonate and sodium chloride; the electrolytic aluminum plant solid waste comprises overhaul slag or waste electrolyte.

2. The method of claim 1, wherein, The particle size of the electrolytic aluminum plant solid waste is greater than 80 mesh.

3. The method of claim 1, wherein, The mass ratio of the sodium hypochlorite to the electrolytic aluminum plant solid waste is 0.1-5:1000.

4. The method of claim 1 or 3, wherein, The solid content of the slurry is 10-35%.

5. The method of claim 1, wherein, The preheating temperature is greater than or equal to 70℃.

6. The method of claim 1, wherein, The mass concentration of the hydrochloric acid is 31%. The fluorine source comprises sodium fluoride or hydrofluoric acid, and the mass concentration of the hydrofluoric acid is 5-15%. The mass ratio of the electrolytic aluminum plant solid waste, the hydrochloric acid and the fluorine source is 1:0.8:0.

2. The pressure of the water vapor is 0.8MPa.

7. The method of claim 1 or 6, wherein, The leaching time is greater than or equal to 2h.

8. The method of claim 1, wherein, In the process of iron precipitation, the mass concentration of the hydrogen peroxide is 20-30%, the addition amount of the hydrogen peroxide is 0.1-2% of the volume of the filtrate, the pH value of the acidity is 3.0-3.8, and the gas for aeration is air.

9. The method of claim 1, wherein, In the process of carbonate precipitation, the pH value of the alkalinity is 8-11, and the gas for aeration is carbon dioxide.

10. The method of claim 1, wherein, In the process of calcium and magnesium precipitation, the pH value of the alkalinity is 12, and the alkaline adjusting agent is liquid alkali.

Images