System for separating lithium, aluminum, potassium and sodium from electrolytic aluminum shell fabric alkaline leaching solution

Abstract

The utility model discloses a system for separating lithium, aluminum, potassium and sodium from electrolytic aluminum shell fabric alkaline leaching liquid. The system comprises a cooler, an extraction tank, a first reaction kettle, a first filtering machine, an evaporation crystallizer, a drying machine, a freezing crystallizer, a first centrifugal machine, a second reaction kettle and a second centrifugal machine. The system has the advantages that separation of aluminum, lithium, sodium and potassium in the alkaline leaching liquid is achieved, all effective components can be recycled, and the overall recycling benefit is increased.

Description

Technical Field:

[0001] The utility model relates to the technical field of treating alkaline calcium leaching solution of solid waste in electrolytic aluminum plants, and specifically relates to a system for separating lithium, aluminum, potassium and sodium from the alkaline leaching solution of electrolytic aluminum shell surface material. Background Technique:

[0002] The scrapped shell surface blocks generated by electrolytic aluminum plants are the electrolyte hard shells on the surface of molten aluminum. They also contain metallic aluminum, metallic lithium and Na3AlF6. At present, lithium carbonate manufacturers mainly recycle the metallic lithium among them as one of the raw materials for lithium carbonate required in the new energy industry. The main recycling method is to grind the shell surface blocks into powders through jaw crusher - cone mill - Raymond mill, and then react the powders with hydrochloric acid or sulfuric acid. The fluorine is converted into cryolite, aluminum trifluoride and other substances, and the sodium is converted into sodium chloride or sodium sulfate to achieve the purpose of decomposing Na3AlF6. At the same time, the lithium in the shell surface blocks is also converted into lithium chloride or lithium sulfate; the acid slag after decomposition is filtered and washed to obtain aluminum fluoride slag, and an acidic decomposition solution containing a large amount of aluminum and fluorine is obtained; then the acidic decomposition solution is added with sodium carbonate, calcium carbonate or calcium hydroxide for purification and impurity removal. After the impurity removal slurry is filtered and washed, aluminum fluoride calcium purification slag and sodium chloride lithium solution or sodium sulfate lithium solution are obtained. Then the purified sodium chloride lithium or sodium sulfate lithium solution is evaporated and concentrated to increase the lithium content, and then sodium carbonate solution is added to precipitate lithium carbonate.

[0003] The above method mainly recovers lithium and by-produces sodium chloride or sodium sulfate, while the aluminum fluoride slag is treated as solid waste, and aluminum and fluorine are not recovered, resulting in waste of resources; moreover, a large amount of aluminum precipitates and adsorbs lithium during purification and impurity removal, resulting in low recovery rate of metallic lithium.

[0004] Currently, an alkaline leaching process has been developed, that is, after the above solid waste is crushed to a certain particle size, alkaline calcium is used for alkaline leaching at 70 - 80 °C. For example, the reaction equation for leaching with calcium hydroxide is as follows:

[0005] 2Na3AlF6 + 7Ca(OH)2 = 6NaOH + 6CaF2↓ + CaAl2(OH)8↓

[0006] 2Na2LiAlF6 + 7Ca(OH)2 = 4NaOH + 2LiOH + 6CaF2↓ + CaAl2(OH)8↓

[0007] Na3AlF6 + 2Ca(OH)2 = 2NaF + NaAlO2 + 2CaF2↓ + 2H2O

[0008] Na3AlF6 + Ca(OH)2 = NaAlF4 + 2NaOH + CaF2↓ + 2H2O

[0009] 2KF + Ca(OH)2 = 2KOH + CaF2↓

[0010] Li+ +F - = LiF↓

[0011] After solid-liquid separation, a leaching solution mainly composed of NaOH, LiOH, NaAlO2, and KOH, and a leaching residue mainly composed of CaAl2(OH) 8、 CaF2 and LiF are obtained. In order to recover lithium, potassium, and sodium in the leaching solution, a system for separating lithium, aluminum, potassium, and sodium from the alkaline leaching solution of electrolytic aluminum shell fabric has been developed. Summary of the utility model:

[0012] The purpose of the present utility model is to provide a system for separating lithium, aluminum, potassium, and sodium from the alkaline leaching solution of electrolytic aluminum shell fabric.

[0013] The present utility model is implemented by the following technical solutions: A system for separating lithium, aluminum, potassium, and sodium from the alkaline leaching solution of electrolytic aluminum shell fabric, which includes a cooler, an extraction tank, a first reaction kettle, a first filter, an evaporation crystallizer, a dryer, a freezing crystallizer, a first centrifuge, a second reaction kettle, and a second centrifuge. The leaching solution feed pipe is connected to the inlet of the cooler, the outlet of the cooler is connected to the inlet of the extraction tank, the first outlet of the extraction tank is connected to a lithium salt discharge pipe, the second outlet of the extraction tank is connected to the inlet of the first reaction kettle, the outlet of the first reaction kettle is connected to the inlet of the first filter, the solid phase outlet of the first filter is connected to an aluminum hydroxide discharge pipe, the filtrate outlet of the first filter is connected to the inlet of the evaporation crystallizer, the slurry outlet of the evaporation crystallizer is connected to the inlet of the dryer, and the outlet of the dryer is connected to a heavy soda ash discharge pipe; the mother liquor outlet of the evaporation crystallizer is connected to the inlet of a three-way pipe, the first outlet of the three-way pipe is connected to the inlet of the evaporation crystallizer, the second outlet of the three-way pipe is connected to the inlet of the freezing crystallizer, the outlet of the freezing crystallizer is connected to the inlet of the first centrifuge, the liquid phase outlet of the first centrifuge is connected to the inlet of the second reaction kettle, the outlet of the second reaction kettle is connected to the inlet of the second centrifuge, and the solid phase outlet of the second centrifuge is connected to a potassium bicarbonate discharge pipe.

[0014] Further, the solid phase outlet of the first centrifuge is connected to the inlet of a dissolution tank, and the outlet of the dissolution tank is connected to the inlet of the evaporation crystallizer.

[0015] Further, the liquid phase outlet of the second centrifuge is connected to the inlet of a concentrator, and the outlet of the concentrator is connected to the inlet of the freezing crystallizer.

[0016] Advantages of the present utility model: After the alkali leaching solution is cooled by a cooler, an alkaline extractant is added in an extraction tank to separate lithium from sodium and potassium. The separated lithium salt has a low sodium property, meeting the conditions for one-step production of industrial-grade and battery-grade lithium carbonate, and reducing the cost of producing battery-grade lithium carbonate. After the sodium and potassium solution after extraction reacts with carbon dioxide, aluminum hydroxide is separated. Compared with the aluminum in the acid process which forms part of the waste residue, the resources and value are reflected. Then, the different crystallization temperatures of sodium carbonate and potassium carbonate are utilized to separate sodium and potassium. The sodium salt is recovered as sodium carbonate, whose value is 10 times higher than that of sodium chloride or sodium sulfate, and potassium is finally recovered as potassium bicarbonate. This system realizes the separation of aluminum, lithium, sodium, and potassium in the alkali leaching solution, enables the recycling of each effective component, and improves the overall recycling benefit. Brief Description of the Drawings:

[0017] Figure 1 It is a schematic diagram of the overall structure of this embodiment.

[0018] Cooler 1, extraction tank 2, first reaction kettle 3, first filter 4, evaporation crystallizer 5, dryer 6, freezing crystallizer 7, first centrifuge 8, second reaction kettle 9, second centrifuge 10, leaching solution feed pipe 11, lithium salt discharge pipe 12, aluminum hydroxide discharge pipe 13, heavy soda ash discharge pipe 14, three-way pipe 15, potassium bicarbonate discharge pipe 16, dissolution tank 17, concentrator 18. Detailed Embodiment:

[0019] In the description of the present utility model, it should be noted that when terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the present utility model. In addition, when terms such as "first", "second", "third" appear, they are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0020] Such as Figure 1As shown in the figure, a system for separating lithium, aluminum, potassium, and sodium from the alkali leaching solution of electrolytic aluminum shell fabric includes a cooler 1, an extraction tank 2, a first reaction kettle 3, a first filter 4, an evaporation crystallizer 5, a dryer 6, a freezing crystallizer 7, a first centrifuge 8, a second reaction kettle 9, and a second centrifuge 10. The leaching solution feed pipe 11 is connected to the inlet of the cooler 1, the outlet of the cooler 1 is connected to the inlet of the extraction tank 2, a lithium salt discharge pipe 12 is connected to the first outlet of the extraction tank 2, the second outlet of the extraction tank 2 is connected to the inlet of the first reaction kettle 3, the outlet of the first reaction kettle 3 is connected to the inlet of the first filter 4, a discharge pipe 13 for aluminum hydroxide is connected to the solid phase outlet of the first filter 4, the filtrate outlet of the first filter 4 is connected to the inlet of the evaporation crystallizer 5, the slurry outlet of the evaporation crystallizer 5 is connected to the inlet of the dryer 6, and a discharge pipe 14 for heavy soda ash is connected to the outlet of the dryer 6; the mother liquor outlet of the evaporation crystallizer 5 is connected to the inlet of a three-way pipe 15, the first outlet of the three-way pipe 15 is connected to the inlet of the evaporation crystallizer 5, the second outlet of the three-way pipe 15 is connected to the inlet of the freezing crystallizer 7, the outlet of the freezing crystallizer 7 is connected to the inlet of the first centrifuge 8, the liquid phase outlet of the first centrifuge 8 is connected to the inlet of the second reaction kettle 9, the solid phase outlet of the first centrifuge 8 is connected to the inlet of a dissolution tank 17, and the outlet of the dissolution tank 17 is connected to the inlet of the evaporation crystallizer 5. The outlet of the second reaction kettle 9 is connected to the inlet of the second centrifuge 10, and a discharge pipe 16 for potassium bicarbonate is connected to the solid phase outlet of the second centrifuge 10. The liquid phase outlet of the second centrifuge 10 is connected to the inlet of a concentrator 18, and the outlet of the concentrator 18 is connected to the inlet of the freezing crystallizer 7.

[0021] Separation process:

[0022] S1: The leaching solution sent by the leaching solution feed pipe 11 is first sent to the cooler 1 to be cooled to 40 °C, and then sent to the extraction tank 2, where an alkaline extractant (HBL121 or 3938H) is added to extract lithium. The extracted lithium salt solution is discharged through the lithium salt discharge pipe 12 to the subsequent lithium salt recovery system, and the remaining first solution is sent to the first reaction kettle 3 and carbon dioxide is introduced to obtain a mixed slurry containing sodium carbonate, potassium carbonate, and aluminum hydroxide. The reaction equations are as follows:

[0023] CO2 + 2NaOH = Na2CO3 + H2O

[0024] 2NaAlO2 + CO2 + 3H2O = 2Al(OH)3↓ + Na2CO3

[0025] 2KOH + CO2 = K2CO3 + H2O

[0026] S2: Feed the mixed slurry obtained in S1 into the first filter 4 for filtration. The filtered aluminum hydroxide is discharged through the aluminum hydroxide discharge pipe 13, and the filtered filtrate is fed into the evaporation crystallizer 5. The sodium carbonate precipitated by evaporation is sent to the dryer 6 for drying and dehydration to obtain heavy soda ash. When the potassium content of the mother liquor discharged from the evaporation crystallizer 5 is lower than 100 g / L, it is sent back to the evaporation crystallizer for cyclic crystallization. When the potassium content of the mother liquor discharged from the evaporation crystallizer 5 is higher than 100 g / L, it is sent to the freezing crystallizer 7 for freezing crystallization. During the cooling crystallization, potassium carbonate does not crystallize, and sodium carbonate crystallizes into sodium carbonate decahydrate, realizing the separation of sodium and potassium. At the same time, one molecular weight of sodium carbonate (106) will carry away 180 parts by weight of water, increasing the concentration of potassium carbonate.

[0027] S3: Feed the slurry in the freezing crystallizer 7 into the first centrifuge 8 for solid-liquid separation to separate sodium carbonate decahydrate. The separated filtrate is sent to the second reaction kettle 9, and at the same time, carbon dioxide is introduced to convert potassium carbonate into potassium bicarbonate. The reaction equation is as follows:

[0028] K2CO3 + CO2 + H2O = 2KHCO3↓

[0029] S4: Feed the solution discharged from the second reaction kettle 9 into the second centrifuge 10 for solid-liquid separation. The obtained potassium bicarbonate product is discharged through the potassium bicarbonate discharge pipe 16, and the separated liquid is sent to the concentrator 18 to concentrate and increase the solution concentration, and then sent back to the freezing crystallizer 7 for cyclic treatment.

[0030] S5: Feed the sodium carbonate decahydrate discharged from the first centrifuge 8 into the dissolution tank 17 to melt and then send it back to the evaporation crystallizer 5 for evaporation crystallization, finally recovering the sodium carbonate decahydrate as heavy soda ash to increase the profit.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for separating lithium, aluminum, potassium, and sodium from the alkaline leaching solution of electrolytic aluminum shell fabric, characterized in that, Cooler, extraction tank, first reactor, first filter, evaporation crystallizer, dryer, freeze crystallizer, first centrifuge, second reactor and second centrifuge. The leaching solution feed pipe is connected to the inlet of the cooler, the outlet of the cooler is connected to the inlet of the extraction tank, the first outlet of the extraction tank is connected to a lithium salt discharge pipe, the second outlet of the extraction tank is connected to the inlet of the first reactor, the outlet of the first reactor is connected to the inlet of the first filter, the solid phase outlet of the first filter is connected to an aluminum hydroxide discharge pipe, the filtrate outlet of the first filter is connected to the inlet of the evaporation crystallizer, the slurry outlet of the evaporation crystallizer is connected to the inlet of the dryer, and the outlet of the dryer is connected to a heavy soda ash discharge pipe; the mother liquor outlet of the evaporation crystallizer is connected to the inlet of a three-way pipe, the first outlet of the three-way pipe is connected to the inlet of the evaporation crystallizer, the second outlet of the three-way pipe is connected to the inlet of the freeze crystallizer, the outlet of the freeze crystallizer is connected to the inlet of the first centrifuge, the liquid phase outlet of the first centrifuge is connected to the inlet of the second reactor, the outlet of the second reactor is connected to the inlet of the second centrifuge, and the solid phase outlet of the second centrifuge is connected to a potassium bicarbonate discharge pipe.

2. The system for separating lithium, aluminum, potassium and sodium from the alkali leaching solution of electrolytic aluminum shell fabric according to claim 1, wherein, The solid phase outlet of the first centrifuge is connected to the inlet of a dissolution tank, and the outlet of the dissolution tank is connected to the inlet of the evaporation crystallizer.

3. A system for separating lithium, aluminum, potassium, and sodium from the alkaline leaching solution of electrolytic aluminum shell fabric, according to claim 1 or 2, characterized in that, The liquid phase outlet of the second centrifuge is connected to the inlet of a concentrator, and the outlet of the concentrator is connected to the inlet of the freeze crystallizer.

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