Cryolite-containing solid waste recovery alkaline leaching liquid treatment system for electrolytic aluminum factory

Abstract

The utility model discloses a cryolite-containing solid waste recovery alkaline leaching liquid treatment system for an electrolytic aluminum factory. The cryolite-containing solid waste recovery alkaline leaching liquid treatment system comprises a carbonization reaction kettle, a first filter, a concentrator, a high-temperature hydrolyzer, a cooler, an alkaline extraction tank, a crystallizer, a high-temperature stirring tank, a centrifugal machine and a drying machine. The method has the advantages that the alkaline leaching solution is firstly subjected to carbon dioxide carbonization reaction and is filtered and separated, and then the separated filtrate is concentrated, so that crude lithium carbonate can be separated; the concentrated solution is subjected to high-temperature hydrolysis through a high-temperature hydrolyzer, so that trace sodium cyanide can be hydrolyzed to realize detoxification, an acid process for detoxification is not needed, the generation of highly toxic hydrogen cyanide gas is avoided, and the safety is improved; alkaline extraction is adopted, lithium in the sodium carbonate solution is separated out in the form of lithium salt, then the sodium carbonate solution is subjected to evaporative crystallization, separation and drying, and a heavy sodium carbonate product is obtained.

Description

Technical field:

[0001] The utility model relates to the technical field of cryolite-containing solid waste recovery in aluminum electrolysis plants, in particular to an alkaline leaching solution treatment system for recovering cryolite-containing solid waste in aluminum electrolysis plants. Background technology:

[0002] The cryolite-containing solid waste produced by electrolytic aluminum plants mainly includes five categories: overhaul slag, cathode carbon blocks, anode carbon blocks, shell blocks, and electrolytes. Among them, the overhaul slag is refractory bricks in addition to the main components Na3AlF6 and Na4Fe(CN)6. The cathode carbon blocks and anode carbon blocks are carbon powder in addition to the main components Na3AlF6, Na2LiAlF6 and Na3Fe(CN)6. The main components of shell blocks are Na3AlF6 and metallic aluminum, and the main components of electrolytes are Na3AlF6 and Na2LiAlF6. At present, an alkaline calcium leaching process has been developed. The above-mentioned cryolite-containing solid waste is pre-treated through crushing, screening, flotation and other processes to remove the elemental aluminum and carbon powder therein to obtain lithium-containing waste cryolite powder; then the lithium-containing waste cryolite powder is mixed with an alkaline calcium (carbide slag, calcium hydroxide) solution for leaching. The reaction equation is as follows:

[0003] 2Na3AlF6+7Ca(OH)2=6NaOH+6CaF2↓+CaAl2(OH)8↓

[0004] 2Li3AlF6+7Ca(OH)2=6LiOH+6CaF2↓+CaAl2(OH)8↓

[0005] 2LiF+Ca(OH)2=LiOH+CaF2↓

[0006] Na3Fe(CN)6+3NaOH=6NaCN+Fe(OH)3↓

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

[0008] After solid-liquid separation, CaF 2、 In view of the alkaline leaching residue mainly composed of CaAl2(OH)8 and Fe(OH)3, and the alkaline leaching solution mainly composed of NaOH, LiOH, NaAlO2 and NaCN, a system for recovering alkaline leaching solution from cryolite-containing solid waste in electrolytic aluminum plants is proposed to achieve the separation and treatment of sodium and lithium. Utility model content:

[0009] The utility model aims to provide an alkaline leaching solution processing system for recovering cryolite-containing solid waste in an electrolytic aluminum plant.

[0010] The utility model is implemented by the following technical solutions: an alkaline leaching solution processing system for recovering cryolite-containing solid waste from an electrolytic aluminum plant, which includes a carbonization reactor, a first filter, a concentrator, a high-temperature hydrolyzer, a cooler, an alkaline extraction tank, a crystallizer, a high-temperature stirring tank, a centrifuge, and a first dryer. The alkaline leaching solution feeding pipe is connected to the inlet of the carbonization reactor, the outlet of the carbonization reactor is connected to the inlet of the first filter, the filtrate outlet of the first filter is connected to the inlet of the concentrator, the solid phase outlet of the first filter is connected to the discharge pipe of aluminum-fluorine-containing crude lithium carbonate; the concentrated liquid outlet of the concentrator is connected to the inlet of the high-temperature hydrolyzer, and the concentrator is connected to the inlet of the high-temperature hydrolyzer. The solid phase outlet of the high-temperature hydrolyzer is connected to the crude lithium carbonate discharge pipe; the outlet of the high-temperature hydrolyzer is connected to the inlet of the cooler, the outlet of the cooler is connected to the inlet of the alkaline extraction tank, the first outlet of the alkaline extraction tank is connected to the lithium salt discharge pipe, and the second outlet of the alkaline extraction tank is connected to the inlet of the crystallizer; the slurry outlet of the crystallizer is connected to the inlet of the high-temperature stirring tank, the outlet of the high-temperature stirring tank is connected to the inlet of the centrifuge, the solid phase outlet of the centrifuge is connected to the inlet of the first dryer, and the liquid phase outlet of the centrifuge is connected to the saturated sodium carbonate discharge pipe; the outlet of the first dryer is connected to the heavy sodium carbonate discharge pipe.

[0011] Furthermore, it also includes a second filter disposed between the cooler and the alkaline extraction tank, the outlet of the cooler is communicated with the inlet of the second filter, and the outlet of the second filter is communicated with the inlet of the alkaline extraction tank.

[0012] Furthermore, the mother liquor outlet of the crystallizer is connected to the inlet of the tee pipe, the first outlet of the tee pipe is connected to the inlet of the crystallizer, and the second outlet of the tee pipe is connected to the mother liquor discharge pipe.

[0013] Furthermore, the aluminum-fluorine-containing crude lithium carbonate discharge pipe, the crude lithium carbonate discharge pipe and the lithium salt discharge pipe are all connected to the inlet of the crude sodium carbonate refining unit.

[0014] Furthermore, the crude sodium carbonate refining unit includes a dissolving tank, the aluminum-fluorine-containing crude lithium carbonate discharge pipe, the crude lithium carbonate discharge pipe and the lithium salt discharge pipe are all connected to the inlet of the dissolving tank, and an acid addition port and an alkali addition port are provided on the top of the dissolving tank. The outlet of the dissolving tank is connected to the inlet of the first washing filter, and the filtrate outlet of the first washing filter is connected to the inlet of the first resin exchange column; the outlet of the first resin exchange column and the pure sodium carbonate feeding pipe are both connected to the inlet of the lithium carbonate precipitation tank, the outlet of the lithium carbonate precipitation tank is connected to the inlet of the second washing filter, the slag discharge port of the second washing filter is connected to the inlet of the pulping tank, the outlet of the pulping tank is connected to the inlet of the centrifuge, the solid phase outlet of the centrifuge is connected to the inlet of the second dryer, and the outlet of the second dryer is connected to a lithium carbonate product discharge pipe.

[0015] Furthermore, the washing water outlet of the first washing filter is connected to the inlet of the dissolving tank.

[0016] Furthermore, the filtrate outlet of the second washing filter is connected to the inlet of the carbon dioxide exhaust tank, and the side of the carbon dioxide exhaust tank is connected to the acid liquid feeding pipe; the outlet of the carbon dioxide exhaust tank is connected to the inlet of the MVR evaporation crystallizer, and the crystallization phase outlet of the MVR evaporation crystallizer is connected to the sodium salt product discharge pipe.

[0017] Furthermore, the mother liquor outlet of the MVR evaporation crystallizer is connected to the inlet of the dissolution tank.

[0018] Furthermore, it also includes a sodium carbonate solution preparation tank, a filter and a second resin exchange column connected in sequence, and the outlet of the second resin exchange column is connected to the inlet end of the pure sodium carbonate feeding pipe.

[0019] Furthermore, the wash water outlet of the second washing filter and the wash water outlet of the centrifuge are both connected to the inlet of the sodium carbonate solution preparation tank.

[0020] The advantages of this utility model are as follows: the alkaline leachate is first subjected to a carbonization reaction with carbon dioxide and filtered and separated, and the separated filtrate is then concentrated to separate crude lithium carbonate, which is then further processed in a crude lithium carbonate refining unit to obtain a lithium carbonate product, and the sodium salt product is recovered; the concentrated solution is subjected to high-temperature hydrolysis in a high-temperature hydrolyzer to hydrolyze trace amounts of sodium cyanide to achieve detoxification without the need for an acid detoxification process, thus avoiding the generation of highly toxic hydrogen cyanide gas and improving safety; alkaline extraction is then used to separate the lithium in the sodium carbonate solution in the form of lithium salt, and the sodium carbonate solution is then evaporated, crystallized, separated, and dried to obtain a heavy sodium carbonate product. The carbonization process uses carbon dioxide as an auxiliary material, which is a low-carbon process; through this system, the sodium in the alkaline leachate can be recovered as heavy soda ash, which is more valuable than recovering it as sodium chloride or sodium sulfate, and safer than recovering it as sodium nitrate. Description of the drawings:

[0021] Figure 1 Schematic diagram of the overall structure of this embodiment.

[0022] Carbonization reactor 1, first filter 2, concentrator 3, high-temperature hydrolyzer 4, cooler 5, alkaline extraction tank 6, crystallizer 7, high-temperature stirring tank 8, centrifuge 9, first dryer 10, alkaline leaching liquid feeding pipe 11, aluminum-fluorine-containing crude lithium carbonate discharge pipe 12, crude lithium carbonate discharge pipe 13, lithium salt discharge pipe 14, saturated sodium carbonate discharge pipe 15, heavy sodium carbonate discharge pipe 16, second filter 17, T-tube 18, dissolution tank 19, acid addition port 20, Alkali port 21, first washing filter 22, first resin exchange column 23, pure sodium carbonate feeding pipe 24, lithium carbonate precipitation tank 25, second washing filter 26, pulping tank 27, centrifuge 28, second dryer 29, lithium carbonate product discharge pipe 30, carbon dioxide discharge tank 31, acid solution feeding pipe 32, MVR evaporation crystallizer 33, sodium salt product discharge pipe 34, sodium carbonate solution preparation tank 35, third filter 36, second resin exchange column 37. Specific implementation method:

[0023] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like indicate positions or locations based on those shown in the accompanying drawings. These terms are intended solely to facilitate the description of this utility model and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third" are used solely for descriptive purposes and should not be construed as indicating or implying relative importance.

[0024] like Figure 1As shown, a system for processing alkaline leaching liquid for recovering cryolite-containing solid waste from an electrolytic aluminum plant comprises a carbonization reactor 1, a first filter 2, a concentrator 3, a high-temperature hydrolyzer 4, a cooler 5, an alkaline extraction tank 6, a crystallizer 7, a high-temperature stirring tank 8, a centrifuge 9, and a first dryer 10. The alkaline leaching liquid feeding pipe 11 is connected to the inlet of the carbonization reactor 1, the outlet of the carbonization reactor 1 is connected to the inlet of the first filter 2, the filtrate outlet of the first filter 2 is connected to the inlet of the concentrator 3, and the solid phase outlet of the first filter 2 is connected to the aluminum-fluorine-containing solid waste. The crude lithium carbonate discharge pipe 12 is connected; the concentrated liquid outlet of the concentrator 3 is connected to the inlet of the high-temperature hydrolyzer 4, and the solid phase outlet of the concentrator 3 is connected to the crude lithium carbonate discharge pipe 13; the outlet of the high-temperature hydrolyzer 4 is connected to the inlet of the cooler 5, and the outlet of the cooler 5 is connected to the inlet of the alkaline extraction tank 6. It also includes a second filter 17 disposed between the cooler 5 and the alkaline extraction tank 6, the outlet of the cooler 5 is connected to the inlet of the second filter 17, and the outlet of the second filter 17 is connected to the inlet of the alkaline extraction tank 6. The first outlet of the alkaline extraction tank 6 is connected to the lithium salt discharge pipe 14, and the second outlet of the alkaline extraction tank 6 is connected to the inlet of the crystallizer 7; the mother liquor outlet of the crystallizer 7 is connected to the inlet of the tee, the first outlet of the tee 18 is connected to the inlet of the crystallizer 7, and the second outlet of the tee 18 is a mother liquor discharge port. The slurry outlet of the crystallizer 7 is connected to the inlet of the high-temperature stirring tank 8, the outlet of the high-temperature stirring tank 8 is connected to the inlet of the centrifuge 9, the solid phase outlet of the centrifuge 9 is connected to the inlet of the first dryer 10, and the liquid phase outlet of the centrifuge 9 is connected to the saturated sodium carbonate discharge pipe 15; the outlet of the first dryer 10 is connected to the heavy sodium carbonate discharge pipe 16.

[0025] The aluminum-fluorine-containing crude lithium carbonate discharge pipe 12, the crude lithium carbonate discharge pipe 13 and the lithium salt discharge pipe 14 are all connected to the inlet of the dissolving tank 19 of the crude sodium carbonate refining unit. An acid addition port 20 and an alkali addition port 21 are provided at the top of the dissolving tank 19. The outlet of the dissolving tank 19 is connected to the inlet of the first washing filter 22, and the filtrate outlet of the first washing filter 22 is connected to the inlet of the first resin exchange column 23; the outlet of the first resin exchange column 23 and the pure sodium carbonate feeding pipe 24 are both connected to the inlet of the lithium carbonate precipitation tank 25, the outlet of the lithium carbonate precipitation tank 25 is connected to the inlet of the second washing filter 26, the slag discharge port of the second washing filter 26 is connected to the inlet of the pulping tank 27, the outlet of the pulping tank 27 is connected to the inlet of the centrifuge 28, the solid phase outlet of the centrifuge 28 is connected to the inlet of the second dryer 29, and the outlet of the second dryer 29 is connected to the lithium carbonate product discharge pipe 30.

[0026] The washing water outlet of the first washing filter 22 is communicated with the inlet of the dissolving tank 19 .

[0027] The filtrate outlet of the second washing filter 26 is connected to the inlet of the carbon dioxide exhaust tank 31, and the side of the carbon dioxide exhaust tank 31 is connected to the acid liquid feeding pipe 32; the outlet of the carbon dioxide exhaust tank 31 is connected to the inlet of the MVR evaporation crystallizer 33, and the crystal phase outlet of the MVR evaporation crystallizer 33 is connected to the sodium salt product discharge pipe 34.

[0028] The mother liquor outlet of the MVR evaporation crystallizer 33 is communicated with the inlet of the dissolution tank 19 .

[0029] It also includes a sodium carbonate solution preparation tank 35, a third filter 36, and a second resin exchange column 37 connected in sequence. The outlet of the second resin exchange column 37 is connected to the inlet of the pure sodium carbonate feed pipe 24. The wash water outlet of the second washing filter 26 and the wash water outlet of the centrifuge 28 are both connected to the inlet of the sodium carbonate solution preparation tank 35.

[0030] Processing process:

[0031] S1: The alkaline leaching solution obtained by leaching a mixture of alkaline calcium and lithium-containing waste cryolite powder is fed into the carbonization reactor 1 through the alkaline leaching solution feeding pipe 11, and reacts with the introduced carbon dioxide to obtain a mixed solution of lithium carbonate and sodium carbonate, and a mixed slurry of lithium carbonate solids; the reaction equation is as follows:

[0032] CO2+2NaOH=Na2CO3+H2O

[0033] CO2+2LiOH=Li2CO3↓+H2O

[0034] 2NaAlO2+CO2+3H2O=2Al(OH)3↓+Na2CO3

[0035] S2: The mixed slurry obtained in S1 is sent to the first filter 2 for solid-liquid separation. The crude lithium carbonate containing aluminum fluoride is separated and discharged to the crude sodium carbonate refining unit through the crude lithium carbonate containing aluminum fluoride discharge pipe 12. The separated sodium carbonate solution is sent to the concentrator 3;

[0036] S3: The concentrator 3 in this embodiment is an MVR evaporation concentrator. The sodium carbonate solution is evaporated and concentrated in the concentrator 3. As the sodium carbonate solution is continuously evaporated and concentrated, lithium carbonate slightly soluble in the sodium carbonate solution precipitates due to supersaturation and is then discharged through the crude lithium carbonate discharge pipe 13 to the crude sodium carbonate refining unit.

[0037] S4: The sodium carbonate solution discharged from the concentrator 3 is sent to the high-temperature hydrolyzer 4, where the trace amount of sodium cyanide in the sodium carbonate solution is converted into sodium formate at high temperature. The solution is then sent to the cooler 5 for cooling. The reaction equation is as follows:

[0038] NaCN+2H2O=HCOONa+NH3↑

[0039] S5: The cooled sodium carbonate solution discharged from the cooler 5 is first passed through a second filter 17 for impurity removal, and then sent to an alkaline extraction tank 6 for lithium separation using an alkaline extractant (HBL121 or 3938H) to obtain a sodium carbonate solution and a lithium salt solution. The lithium salt solution is discharged through a lithium salt discharge pipe 14 to a crude sodium carbonate refining unit;

[0040] S6: The sodium carbonate discharged from the alkaline extraction tank 6 is first sent to the crystallizer 7 for evaporation and crystallization to obtain a sodium carbonate mother liquor and a high-solid content sodium carbonate monohydrate slurry. The liquid phase sodium carbonate mother liquor discharged from the crystallizer 7 contains potassium ions. When the potassium content is low (less than 100 g / L), it is sent back to the inlet of the crystallizer 7 for recrystallization. When the potassium content is high (greater than 100 g / L), it is discharged from the system through the mother liquor discharge port; the high-solid content sodium carbonate monohydrate slurry discharged from the crystallizer 7 is sent to the high-temperature stirring tank 8 for heating and dehydration to obtain a mixed slurry of sodium carbonate solids and a saturated sodium carbonate solution;

[0041] S7: Finally, the mixed slurry discharged from the high-temperature stirring tank 8 is sent to the centrifuge 9 for solid-liquid separation. The separated saturated sodium carbonate solution is discharged to the rear system through the saturated sodium carbonate discharge pipe 15. The separated solid sodium carbonate is sent to the first dryer 10 for drying to obtain a heavy sodium carbonate product, which is discharged from the system through the heavy sodium carbonate discharge pipe 16.

[0042] S8: The materials discharged from the aluminum-fluorine-containing crude lithium carbonate discharge pipe 12, the crude lithium carbonate discharge pipe 13, and the lithium salt discharge pipe 14 are mixed in the dissolution tank 19, and then the crude lithium carbonate is refined; the specific process is as follows:

[0043] S8-1: Add hydrochloric acid from the acid adding port 20 to the dissolving tank 19 to dissolve and obtain a crude lithium chloride solution, the pH of which is controlled at 1-3, wherein part of the aluminum and fluorine are precipitated as Na3AlF6;

[0044] S8-2: Sodium hydroxide solution is added to the dissolving tank 1 through the alkali adding port 21 to adjust the pH to 5-8. The remaining aluminum exists in the form of flocculent Al(OH)3 and has an adsorption effect on fluoride ions;

[0045] S8-3: The slurry in the dissolution tank 19 is sent to the first washing filter 22 for washing and filtering to separate the solid aluminum fluoride slag (which can be sent back to the alkaline leaching process for recycling), the impure lithium salt filtrate and the washing water. The washing water separated by the first washing filter 22 can be sent back to the dissolution tank 19 for recycling. The separated impure lithium salt filtrate is sent to the first resin exchange column 23 to remove the soluble divalent and trivalent metals in the lithium solution to obtain a low-sodium pure lithium solution.

[0046] S8-4: The low-sodium pure lithium solution discharged from the first resin exchange column 23 and the pure sodium carbonate fed from the pure sodium carbonate feed pipe 24 are fed together into the lithium carbonate precipitation tank 25 for mixing to produce lithium carbonate slurry. The lithium carbonate slurry is then fed into the second washing filter 26 for washing and filtration. After slurrying in the slurrying tank 27, the slurry is then centrifuged and dehydrated in the centrifuge 28 and the second dryer 29, and dried to produce a lithium carbonate product, which is then discharged from the system through the lithium carbonate product discharge pipe 30. The pure sodium carbonate fed from the pure sodium carbonate feed pipe 24 is made from industrial-quality sodium carbonate. Specifically, it is fed into the sodium carbonate solution preparation tank 35 and then filtered and impurities removed in the third filter 36 and the second resin exchange column 37 to obtain pure sodium carbonate. The wash water discharged from the second washing filter 26 and the wash water discharged from the centrifuge 28 are returned to the sodium carbonate solution preparation tank 35 for recycling.

[0047] S8-5: The filtrate discharged from the second washing filter 26 is mainly a sodium salt solution, which is first sent to the carbon dioxide discharge tank 31 and hydrochloric acid, sulfuric acid or nitric acid is added through the acid feed pipe 32 to react with the excess sodium carbonate in the solution to discharge carbon dioxide. The solution discharged from the carbon dioxide discharge tank 31 is sent to the MVR evaporation crystallizer 33 for evaporation and crystallization to obtain the corresponding sodium chloride, sodium sulfate or sodium nitrate salt and is discharged from the system through the sodium salt product discharge pipe 34; the mother liquor discharged from the MVR evaporation crystallizer 33 contains a high concentration of lithium and is sent back to the dissolution tank 19 for recycling treatment.

[0048] 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 above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cryolite-containing solid waste recovery and alkali leaching liquid treatment system for an electrolytic aluminum plant, characterized in that: It includes a carbonization reactor, a first filter, a concentrator, a high-temperature hydrolyzer, a cooler, an alkaline extraction tank, a crystallizer, a high-temperature stirring tank, a centrifuge, and a first dryer. The alkaline leaching liquid feeding pipe is connected to the inlet of the carbonization reactor, the outlet of the carbonization reactor is connected to the inlet of the first filter, the filtrate outlet of the first filter is connected to the inlet of the concentrator, the solid phase outlet of the first filter is connected to the discharge pipe of the aluminum-fluorine-containing crude lithium carbonate; the concentrated liquid outlet of the concentrator is connected to the inlet of the high-temperature hydrolyzer, and the solid phase outlet of the concentrator is connected to the discharge pipe of the crude lithium carbonate; The outlet of the high-temperature hydrolyzer is connected to the inlet of the cooler, the outlet of the cooler is connected to the inlet of the alkaline extraction tank, the first outlet of the alkaline extraction tank is connected to the lithium salt discharge pipe, and the second outlet of the alkaline extraction tank is connected to the inlet of the crystallizer; the slurry outlet of the crystallizer is connected to the inlet of the high-temperature stirring tank, the outlet of the high-temperature stirring tank is connected to the inlet of the centrifuge, the solid phase outlet of the centrifuge is connected to the inlet of the first dryer, and the liquid phase outlet of the centrifuge is connected to the saturated sodium carbonate discharge pipe; the outlet of the first dryer is connected to the heavy sodium carbonate discharge pipe.

2. The system for recovering alkaline leaching solution from cryolite-containing solid waste from an electrolytic aluminum plant according to claim 1, characterized in that: It also includes a second filter arranged between the cooler and the alkaline extraction tank, the outlet of the cooler is communicated with the inlet of the second filter, and the outlet of the second filter is communicated with the inlet of the alkaline extraction tank.

3. The system for recovering alkaline leaching solution from cryolite-containing solid waste from an electrolytic aluminum plant according to claim 1, characterized in that: The mother liquor outlet of the crystallizer is connected to the inlet of the tee pipe, the first outlet of the tee pipe is connected to the inlet of the crystallizer, and the second outlet of the tee pipe is connected to the mother liquor discharge pipe.

4. The system for recovering alkaline leaching solution from cryolite-containing solid waste from an electrolytic aluminum plant according to claim 1, characterized in that: The aluminum-fluorine-containing crude lithium carbonate discharge pipe, the crude lithium carbonate discharge pipe and the lithium salt discharge pipe are all connected to the inlet of the crude sodium carbonate refining unit.

5. The system for recovering alkaline leaching solution from cryolite-containing solid waste from an electrolytic aluminum plant according to claim 4, characterized in that: The crude sodium carbonate refining unit includes a dissolving tank, the aluminum-fluorine-containing crude lithium carbonate discharge pipe, the crude lithium carbonate discharge pipe and the lithium salt discharge pipe are all connected to the inlet of the dissolving tank, and an acid addition port and an alkali addition port are provided on the top of the dissolving tank. The outlet of the dissolving tank is connected to the inlet of the first washing filter, and the filtrate outlet of the first washing filter is connected to the inlet of the first resin exchange column; the outlet of the first resin exchange column and the pure sodium carbonate feeding pipe are both connected to the inlet of the lithium carbonate precipitation tank, the outlet of the lithium carbonate precipitation tank is connected to the inlet of the second washing filter, the slag discharge port of the second washing filter is connected to the inlet of the pulping tank, the outlet of the pulping tank is connected to the inlet of the centrifuge, the solid phase outlet of the centrifuge is connected to the inlet of the second dryer, and the outlet of the second dryer is connected to the lithium carbonate product discharge pipe.

6. The system for recovering alkaline leaching solution from cryolite-containing solid waste from an electrolytic aluminum plant according to claim 5, characterized in that: The washing water outlet of the first washing filter is communicated with the inlet of the dissolving tank.

7. The system for recovering alkaline leaching solution from cryolite-containing solid waste from an electrolytic aluminum plant according to claim 5, characterized in that: The filtrate outlet of the second washing filter is connected to the inlet of the carbon dioxide exhaust tank, and the side of the carbon dioxide exhaust tank is connected to the acid liquid feeding pipe; the outlet of the carbon dioxide exhaust tank is connected to the inlet of the MVR evaporation crystallizer, and the crystallization phase outlet of the MVR evaporation crystallizer is connected to the sodium salt product discharge pipe.

8. The system for recovering alkaline leaching solution from cryolite-containing solid waste from an electrolytic aluminum plant according to claim 7, characterized in that: The mother liquor outlet of the MVR evaporation crystallizer is communicated with the inlet of the dissolving tank.

9. The system for recovering alkaline leaching solution from cryolite-containing solid waste from an electrolytic aluminum plant according to claim 5, characterized in that: The invention also includes a sodium carbonate solution preparation tank, a filter and a second resin exchange column which are connected in sequence. The outlet of the second resin exchange column is communicated with the inlet end of the pure sodium carbonate feeding pipe.

10. The system for recovering alkaline leaching solution from cryolite-containing solid waste in an electrolytic aluminum plant according to claim 9, characterized in that: The washing water outlet of the second washing filter and the washing water outlet of the centrifugal separator are both communicated with the inlet of the sodium carbonate solution preparation tank.

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