Alkali leaching recovery system for solid waste produced by electrolytic aluminum factory

Abstract

The utility model discloses an alkaline leaching recovery system for solid waste produced by an electrolytic aluminum factory. The alkaline leaching recovery system comprises a leaching tank, a first filter, a first carbon dioxide reaction kettle, a second filter, a first concentrator, a high-temperature hydrolysis tank, a cooler, an extraction tank, a first slurrying tank, a calcium leaching tank, a third filter and a calcium chloride purification tank. The method has the advantages that (1) alkaline calcium and waste cryolite are mixed for alkaline leaching, cyanide in the solution is removed through high-temperature hydrolysis, no hydrogen cyanide or hydrogen fluoride gas is generated, and the safety is improved; (2) cheap alkaline calcium such as carbide slag, calcium hydroxide or calcium oxide is used as an auxiliary material for alkaline leaching recovery of the solid waste produced by the electrolytic aluminum factory, so that the use of acid is reduced, and the recovery cost is greatly reduced; and (3) by utilizing the system, effective components such as sodium, aluminum, lithium and fluorine in the waste cryolite can be recycled, and the separated calcium fluoride component is high in content and can be sold as fluorite powder, so that the solid waste stacking stock is greatly reduced, and the economic benefit is improved.

Description

Technical Field:

[0001] The utility model relates to the technical field of solid waste treatment in electrolytic aluminum plants, and particularly relates to a solid waste alkali leaching recovery system produced by electrolytic aluminum plants. Background Art:

[0002] The cryolite-containing solid wastes produced by electrolytic aluminum plants mainly include five categories: overhaul slag, cathode carbon block, anode carbon block, crust block, and electrolyte. Among them, the overhaul slag, in addition to the main components Na3AlF6 and Na4Fe(CN)6, is refractory bricks. The cathode carbon block and anode carbon block, in addition to the main components Na3AlF6, Na2LiAlF6, and Na4Fe(CN)6, are carbon powder. The main components of the crust block are Na3AlF6 and metallic aluminum. The main components of the electrolyte are Na3AlF6 and Na2LiAlF6.

[0003] Currently, for the solid wastes produced by electrolytic aluminum plants, the main treatment process is acid leaching with sulfuric acid or hydrochloric acid to extract lithium salts. Sodium ions are replaced with low-valent sodium chloride or sodium sulfate, while carbon and fluorine cannot be recovered and are treated as secondary solid wastes. Moreover, the cathode carbon block, anode carbon block, and overhaul slag contain fluorine and cyanide, and highly toxic hydrogen cyanide gas and strongly corrosive hydrogen fluoride gas will be generated during acid leaching, posing extremely high safety risks. Summary of the Utility Model:

[0004] The purpose of the utility model is to provide a solid waste alkali leaching recovery system produced by electrolytic aluminum plants.

[0005] The present utility model is implemented by the following technical solutions: A solid waste alkali leaching recovery system for an electrolytic aluminum plant, characterized in that it includes a leaching tank, a first filter, a first carbon dioxide reactor, a second filter, a first concentrator, a high-temperature hydrolysis tank, a cooler, an extraction tank, a first pulping tank, a calcium leaching tank, a third filter, and a calcium chloride purification tank. The inlet of the leaching tank is connected to an alkaline calcium feed pipe and a waste cryolite powder feed pipe. The outlet of the leaching tank is connected to the inlet of the first filter. The liquid phase outlet of the first filter is connected to the inlet of the first carbon dioxide reactor. The outlet of the first carbon dioxide reactor is connected to the inlet of the second filter. The outlet of the second filter is connected to the inlet of the first concentrator. The liquid phase outlet of the first concentrator is connected to the inlet of the high-temperature hydrolysis tank. The outlet of the high-temperature hydrolysis tank 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 the inlet of the sodium carbonate storage tank. The solid phase outlet of the second filter, the solid phase outlet of the first concentrator, and the second outlet of the extraction tank are all connected to the inlet of the lithium salt solution storage tank. The solid phase outlet of the first filter is connected to the inlet of the first pulping tank. The outlet of the first pulping tank is connected to the inlet of the calcium leaching tank. The top of the calcium leaching tank is connected to a hydrochloric acid feed pipe. The outlet of the calcium leaching tank is connected to the inlet of the third filter. The solid phase outlet of the third filter is connected to a calcium fluoride discharge pipe. The liquid phase outlet of the third filter is connected to the inlet of the calcium chloride purification tank. The drain outlet of the calcium chloride purification tank is connected to the inlet of the calcium chloride solution storage tank.

[0006] Further, the outlet of the sodium carbonate storage tank is connected to the inlet of the second concentrator. The solid phase outlet of the second concentrator is connected to the inlet of the heating and stirring tank. The outlet of the heating and stirring tank is connected to the inlet of the first centrifuge. The solid phase outlet of the first centrifuge is connected to the inlet of the dryer. The outlet of the dryer is connected to a heavy sodium carbonate discharge pipe.

[0007] Further, the liquid phase outlet of the second concentrator is connected to the inlet of the first three-way pipe. One outlet of the first three-way pipe is connected to the inlet of the second concentrator. The other outlet of the first three-way pipe is connected to the inlet of the high-potassium crystallization mother liquor storage tank.

[0008] Further, the liquid phase outlet of the first centrifuge is connected to the inlet of the second three-way pipe. One outlet of the second three-way pipe is connected to the inlet of the second concentrator. The other outlet of the second three-way pipe is connected to the inlet of the high-potassium crystallization mother liquor storage tank.

[0009] Further, the outlet of the calcium fluoride discharge pipe is communicated with the inlet of the second pulping tank, the outlet of the second pulping tank is communicated with the inlet of the alkali leaching stirring tank, the top of the alkali leaching stirring tank is communicated with a sodium hydroxide feeding pipe, the outlet of the alkali leaching stirring tank is communicated with the inlet of the fourth filter, and the solid phase outlet of the fourth filter is communicated with a high-grade calcium fluoride discharge pipe.

[0010] Further, the liquid phase outlet of the fourth filter is communicated with the inlet of the second carbon dioxide reactor, the outlet of the second carbon dioxide reactor is communicated with the inlet of the fifth filter, and the solid phase outlet of the fifth filter is communicated with an aluminum hydroxide discharge pipe.

[0011] Further, the liquid phase outlet of the fifth filter is communicated with the inlet of the sodium carbonate storage tank.

[0012] Further, the first filter is a first filter and washing integrated machine, and the washing water outlet of the first filter and washing integrated machine is communicated with the inlet of the leaching tank.

[0013] Further, the fifth filter is a fifth filter and washing integrated machine, and the washing water outlet of the fifth filter and washing integrated machine is communicated with the inlet of the second pulping tank.

[0014] Advantages of the present utility model: (1) Alkaline leaching is carried out by mixing alkaline calcium with waste cryolite, and hydrogen cyanide and hydrogen fluoride gases are not generated by high-temperature hydrolysis to remove cyanide in the solution, improving safety; (2) Inexpensive alkaline calcium such as carbide slag, calcium hydroxide or calcium oxide is used as an auxiliary material for alkali leaching recovery of solid waste produced in an electrolytic aluminum plant, reducing the use of acid and greatly reducing the recovery cost; (3) Using this system, effective components such as sodium, aluminum, lithium, and fluorine in waste cryolite can be recovered and utilized, and the separated calcium fluoride component has a high content and can be sold as fluorite powder, greatly reducing the solid waste stockpile and improving economic benefits. Description of the drawings:

[0015] Figure 1 It is a schematic diagram of the overall structure of this embodiment.

[0016] Leaching tank 1, first filter 2, first carbon dioxide reactor 3, second filter 4, first concentrator 5, high-temperature hydrolysis tank 6, cooler 7, extraction tank 8, first pulping tank 9, calcium leaching tank 10, third filter 11, calcium chloride purification tank 12, alkaline calcium feed pipe 13, waste cryolite powder feed pipe 14, lithium salt solution storage tank 15, hydrochloric acid feed pipe 16, calcium fluoride discharge pipe 17, sodium carbonate storage tank 18, calcium chloride solution storage tank 19, second concentrator 20, heating and stirring tank 21, first centrifuge 22, dryer 23, heavy sodium carbonate discharge pipe 24, high-potassium crystallization mother liquor storage tank 25, first three-way pipe 26, second three-way pipe 27, second pulping tank 28, alkali leaching stirring tank 29, sodium hydroxide feed pipe 30, fourth filter 31, high-grade calcium fluoride discharge pipe 32, second carbon dioxide reactor 33, fifth filter 34, aluminum hydroxide discharge pipe 35. Detailed implementation mode:

[0017] In the description of the present invention, 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 invention 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, so it cannot be understood as a limitation to the present invention. 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.

[0018] Such as Figure 1As shown in the figure, a solid waste alkali leaching recovery system for an electrolytic aluminum plant includes a leaching tank 1, a first filter 2, a first carbon dioxide reactor 3, a second filter 4, a first concentrator 5, a high-temperature hydrolysis tank 6, a cooler 7, an extraction tank 8, a first pulping tank 9, a calcium leaching tank 10, a third filter 11, and a calcium chloride purification tank 12. The inlet of the leaching tank 1 is connected to an alkaline calcium feed pipe 13 and a waste cryolite powder feed pipe 14. The outlet of the leaching tank 1 is connected to the inlet of the first filter 2. The liquid phase outlet of the first filter 2 is connected to the inlet of the first carbon dioxide reactor 3. The outlet of the first carbon dioxide reactor 3 is connected to the inlet of the second filter 4. The outlet of the second filter 4 is connected to the inlet of the first concentrator 5. The liquid phase outlet of the first concentrator 5 is connected to the inlet of the high-temperature hydrolysis tank 6. The outlet of the high-temperature hydrolysis tank 6 is connected to the inlet of the cooler 7. The outlet of the cooler 7 is connected to the inlet of the extraction tank 8. The first outlet of the extraction tank 8 is connected to the inlet of a sodium carbonate storage tank 18. The solid phase outlets of the second filter 4, the first concentrator 5, and the second outlet of the extraction tank 8 are all connected to the inlet of a lithium salt solution storage tank 15. The solid phase outlet of the first filter 2 is connected to the inlet of the first pulping tank 9. The outlet of the first pulping tank 9 is connected to the inlet of the calcium leaching tank 10. The top of the calcium leaching tank 10 is connected to a hydrochloric acid feed pipe 16. The outlet of the calcium leaching tank 10 is connected to the inlet of the third filter 11. The solid phase outlet of the third filter 11 is connected to a calcium fluoride discharge pipe 17. The liquid phase outlet of the third filter 1 is connected to the inlet of the calcium chloride purification tank 12. The drain outlet of the calcium chloride purification tank 12 is connected to the inlet of a calcium chloride solution storage tank 19.

[0019] The outlet of the sodium carbonate storage tank 18 is connected to the inlet of a second concentrator 20. The solid phase outlet of the second concentrator 20 is connected to the inlet of a heating and stirring tank 21. The outlet of the heating and stirring tank 21 is connected to the inlet of a first centrifuge 22. The solid phase outlet of the first centrifuge 22 is connected to the inlet of a dryer 23. The outlet of the dryer 23 is connected to a heavy sodium carbonate discharge pipe 24.

[0020] The liquid phase outlet of the second concentrator 20 is connected to the inlet of a first three-way pipe 26. One outlet of the first three-way pipe 26 is connected to the inlet of the second concentrator 20. The other outlet of the first three-way pipe 26 is connected to the inlet of a high-potassium crystallization mother liquor storage tank 25.

[0021] The liquid phase outlet of the first centrifuge 22 is connected to the inlet of a second three-way pipe 27. One outlet of the second three-way pipe 27 is connected to the inlet of the second concentrator 20. The other outlet of the second three-way pipe 27 is connected to the inlet of a high-potassium crystallization mother liquor storage tank 25.

[0022] The outlet of the calcium fluoride discharge pipe 17 is connected to the inlet of the second slurry tank 28, the outlet of the second slurry tank 28 is connected to the inlet of the alkali leaching stirring tank 29, the top of the alkali leaching stirring tank 29 is connected to the sodium hydroxide feeding pipe 30, the outlet of the alkali leaching stirring tank 29 is connected to the inlet of the fourth filter 31, and the solid phase outlet of the fourth filter 31 is connected to the high-grade calcium fluoride discharge pipe 32.

[0023] The liquid phase outlet of the fourth filter 31 is connected to the inlet of the second carbon dioxide reactor 33 , the outlet of the second carbon dioxide reactor 33 is connected to the inlet of the fifth filter 34 , and the solid phase outlet of the fifth filter 34 is connected to the aluminum hydroxide discharge pipe 35 .

[0024] The liquid phase outlet of the fifth filter 34 is communicated with the inlet of the sodium carbonate storage tank 18 .

[0025] The first filter 2 is a first integrated filter-washer machine, and the washing water outlet of the first integrated filter-washer machine is connected to the inlet of the leaching tank 1 .

[0026] The fifth filter 34 is a fifth integrated filter-washer, and the washing water outlet of the fifth integrated filter-washer is connected to the inlet of the second slurry tank 28 .

[0027] Before alkaline calcium leaching of solid waste from an aluminum electrolytic plant, the cryolite-containing solid waste blocks from the electrolytic plant are mixed and crushed to remove elemental aluminum and elemental iron. The waste is then finely ground into a powder with a mesh size of less than 200. The powder is then subjected to flotation to remove carbon powder, obtaining the waste cryolite powder raw material. This system is then used for recycling. The specific recycling process is as follows:

[0028] S1: Alkaline calcium leaching

[0029] Alkaline calcium (carbide slag, calcium hydroxide or calcium oxide) and waste cryolite powder are fed into the leaching tank 1 through the alkaline calcium feeding pipe 13 and the waste cryolite powder feeding pipe 14, respectively. In this embodiment, the alkaline calcium fed is calcium hydroxide, and the following leaching reaction occurs:

[0030] 2Na3AlF6+7Ca(OH)2=6NaOH+6CaF2↓+CaAl2(OH)8↓

[0031] 2Li3AlF6+7Ca(OH)2=6LiOH+6CaF2↓+CaAl2(OH)8↓

[0032] 2LiF+Ca(OH)2=LiOH+CaF2↓

[0033] Na4Fe(CN)6+3NaOH=6NaCN+Fe(OH)3↓

[0034] Na3AlF6 + 2Ca(OH)2 = 2NaF↓ + NaAlO2 + 2CaF2↓ + 2H2O

[0035] 2KF + Ca(OH)2 = 2KOH + CaF2↓

[0036] The mixed slurry after the reaction in the leaching tank 1 is sent to the first filter 2 for solid-liquid separation to obtain an alkaline leaching residue mainly composed of NaF, CaF 2、 CaAl2(OH)8 and Fe(OH)3, as well as an alkaline leaching solution mainly composed of NaOH, LiOH, NaAlO2 and NaCN;

[0037] The first filter 2 is a filter and washer integrated machine, and the discharged washing water is sent back to the leaching tank 1 for recycling treatment.

[0038] S2: Treatment of alkaline leaching solution

[0039] First, the alkaline leaching solution is sent to the first carbon dioxide reaction kettle 3 and carbon dioxide is introduced. The carbon dioxide reacts with the alkaline leaching solution as follows:

[0040] CO2 + 2NaOH = Na2CO3 + H2O

[0041] CO2 + 2LiOH = Li2CO3↓ + H2O

[0042] 2NaAlO2 + CO2 + 3H2O = 2Al(OH)3↓ + Na2CO3

[0043] 2KOH + CO2 = K2CO3 + H2O

[0044] Then, the mixed slurry discharged from the first carbon dioxide reaction kettle 3 is sent to the second filter 4. The crude lithium carbonate solution containing aluminum hydroxide is separated and sent to the lithium salt solution storage tank 15; the filtrate separated by the second filter 4 is sent to the first concentrator 5 for evaporation and crystallization to supersaturate and precipitate the slightly soluble lithium carbonate in the first sodium carbonate solution and then sent to the lithium salt solution storage tank 15. After that, the mother liquor discharged from the first concentrator 5 is sent to the high-temperature hydrolysis tank 6;

[0045] The solution is heated by the high-temperature hydrolysis tank 6 to convert sodium cyanide in the solution into sodium formate. The reaction equation is as follows:

[0046] NaCN + 2H2O = HCOONa + NH3↑

[0047] Next, the solution discharged from the high-temperature hydrolysis tank 6 is sent to the cooler 7 for cooling and then sent to the extraction tank 8. An alkaline extractant is added for lithium extraction. The extracted lithium salt solution is sent to the lithium salt solution storage tank 15, and the remaining solution is sent to the sodium carbonate storage tank 18 for temporary storage;

[0048] Afterwards, the solution temporarily stored in the sodium carbonate storage tank 18 is sent to the second concentrator 20 for evaporation crystallization. Utilizing the difference in the crystallization temperatures of sodium carbonate and potassium carbonate, monohydrate sodium carbonate is crystallized out and sent to the heating and stirring tank 21 for heating and stirring to remove the crystal water, obtaining a product containing solid sodium carbonate and saturated sodium carbonate solution. It is then centrifugally separated by the first centrifuge 22. The separated sodium carbonate is dried by the dryer 23 to obtain a heavy sodium carbonate product, which is then discharged through the heavy sodium carbonate discharge pipe 24;

[0049] When the potassium content of the sodium carbonate saturated mother liquor separated by the second concentrator 20 and the first centrifuge 22 is lower than 100 g / L, it is sent back to the sodium carbonate storage tank 18 and then re-enters the second concentrator 20 for cyclic crystallization treatment; when the potassium content of the sodium carbonate saturated mother liquor separated by the second concentrator 20 and the first centrifuge 22 is higher than 100 g / L, it is sent to the high-potassium crystallization mother liquor storage tank 25, and then the recovery treatment of potassium carbonate is carried out.

[0050] S3: Treatment of alkali leaching residue

[0051] First, the alkali leaching residue filtered out by the first filter 2 is sent to the first pulping tank 9 to be mixed with calcium chloride solution for pulping, and then sent to the calcium leaching tank 10, and hydrochloric acid is added through the hydrochloric acid feed pipe 16, and the following reactions occur:

[0052] CaAl2(OH)8 + 2HCl = 2Al(OH)3↓ + CaCl2 + 2H2O

[0053] CaCl2 + 2NaF = 2NaCl + CaF2↓

[0054] Fe(OH)3 + 3HCl = FeCl3 + 3H2O

[0055] Al(OH)3 + 3HCl = AlCl3 + 3H2O

[0056] Next, the low-grade calcium fluoride slurry discharged from the first pulping tank 9 is sent to the calcium leaching tank 10 and hydrochloric acid is added. Then, it is subjected to solid-liquid separation by the third filter 11. The separated calcium chloride solution dissolved with ferric chloride and a small amount of aluminum chloride is sent to the calcium chloride purification tank 12, and calcium hydroxide is added to the calcium chloride purification tank 12 to precipitate the iron and aluminum slag in the calcium chloride solution. The obtained purified calcium chloride solution is stored in the calcium chloride solution storage tank 19;

[0057] The solid phase separated by the third filter 11 is sent to the second pulping tank 28 to be made into a medium-grade calcium fluoride slurry with water, and then sent to the alkali leaching stirring tank 29, and sodium hydroxide solution is added through the sodium hydroxide feed pipe 30 to convert aluminum hydroxide into sodium aluminate and ferric chloride into ferric hydroxide. The reaction equations are as follows:

[0058] Al(OH)3 + NaOH = NaAlO2 + 2H2O

[0059] After that, the slurry in the alkali leaching stirring tank 29 is sent to the fourth filter 31 to separate high-grade calcium fluoride containing a small amount of Fe(OH)3;

[0060] The solution separated by the fourth filter 31 is sent to the second carbon dioxide reaction kettle 33 and carbon dioxide is introduced to convert NaAlO2 into aluminum hydroxide. The reaction equation is as follows:

[0061] 2NaAlO2 + CO2 + 3H2O = Na2CO3 + 2Al(OH)3↓

[0062] 2NaOH + CO2 = Na2CO3 + H2O

[0063] The slurry discharged from the second carbon dioxide reaction kettle 33 is sent to the fifth filter 34 for solid-liquid separation to obtain aluminum hydroxide products and sodium carbonate mother liquor. The separated sodium carbonate mother liquor is sent to the sodium carbonate storage tank 18 and then enters the post-system for the recovery of sodium carbonate.

[0064] The fourth filter 31 selects a filter and washing integrated machine, and the discharged washing water is sent to the second pulping tank 28 for pulping.

[0065] 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 them; 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 described 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. An electrolytic aluminum plant solid waste alkali leaching recovery system, characterized in that, It includes a leaching tank, a first filter, a first carbon dioxide reactor, a second filter, a first concentrator, a high-temperature hydrolysis tank, a cooler, an extraction tank, a first pulping tank, a calcium leaching tank, a third filter, and a calcium chloride purification tank. The inlet of the leaching tank is connected to an alkaline calcium feed pipe and a waste cryolite powder feed pipe. The outlet of the leaching tank is connected to the inlet of the first filter. The liquid phase outlet of the first filter is connected to the inlet of the first carbon dioxide reactor. The outlet of the first carbon dioxide reactor is connected to the inlet of the second filter. The outlet of the second filter is connected to the inlet of the first concentrator. The liquid phase outlet of the first concentrator is connected to the inlet of the high-temperature hydrolysis tank. The outlet of the high-temperature hydrolysis tank 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 the inlet of the sodium carbonate storage tank. The solid phase outlet of the second filter, the solid phase outlet of the first concentrator, and the second outlet of the extraction tank are all connected to the inlet of the lithium salt solution storage tank. The solid phase outlet of the first filter is connected to the inlet of the first pulping tank. The outlet of the first pulping tank is connected to the inlet of the calcium leaching tank. The top of the calcium leaching tank is connected to a hydrochloric acid feed pipe. The outlet of the calcium leaching tank is connected to the inlet of the third filter. The solid phase outlet of the third filter is connected to a calcium fluoride discharge pipe. The liquid phase outlet of the third filter is connected to the inlet of the calcium chloride purification tank. The drain outlet of the calcium chloride purification tank is connected to the inlet of the calcium chloride solution storage tank.

2. The waste solid alkali leaching and recycling system for an electrolytic aluminum plant according to claim 1, wherein The outlet of the sodium carbonate storage tank is connected to the inlet of the second concentrator. The solid phase outlet of the second concentrator is connected to the inlet of the heating and stirring tank. The outlet of the heating and stirring tank is connected to the inlet of the first centrifuge. The solid phase outlet of the first centrifuge is connected to the inlet of the dryer. The outlet of the dryer is connected to a heavy sodium carbonate discharge pipe.

3. The waste solid alkali leaching and recovery system for an electrolytic aluminum plant according to claim 2, wherein The liquid phase outlet of the second concentrator is connected to the inlet of the first three-way pipe. One outlet of the first three-way pipe is connected to the inlet of the second concentrator. The other outlet of the first three-way pipe is connected to the inlet of the high-potassium crystallization mother liquor storage tank.

4. The waste solid alkali leaching and recovery system for an electrolytic aluminum plant according to claim 2, wherein The liquid phase outlet of the first centrifuge is connected to the inlet of the second three-way pipe. One outlet of the second three-way pipe is connected to the inlet of the second concentrator. The other outlet of the second three-way pipe is connected to the inlet of the high-potassium crystallization mother liquor storage tank.

5. An electrolytic aluminum plant solid waste alkali leaching recovery system according to claim 1, characterized in that, The outlet of the calcium fluoride discharge pipe is connected to the inlet of the second pulping tank. The outlet of the second pulping tank is connected to the inlet of the alkali leaching and stirring tank. The top of the alkali leaching and stirring tank is connected to a sodium hydroxide feed pipe. The outlet of the alkali leaching and stirring tank is connected to the inlet of the fourth filter. The solid phase outlet of the fourth filter is connected to a high-grade calcium fluoride discharge pipe.

6. The waste solid alkali leaching and recycling system for an electrolytic aluminum plant according to claim 5, wherein The liquid phase outlet of the fourth filter is connected to the inlet of the second carbon dioxide reactor. The outlet of the second carbon dioxide reactor is connected to the inlet of the fifth filter. The solid phase outlet of the fifth filter is connected to an aluminum hydroxide discharge pipe.

7. An electrolytic aluminum plant solid waste alkali leaching recovery system according to claim 6, characterized in that, The liquid phase outlet of the fifth filter is connected to the inlet of the sodium carbonate storage tank.

8. The waste solid alkali leaching and recovery system for an electrolytic aluminum plant according to claim 1, wherein The first filter is a first integrated filter and washer, and the wash water outlet of the first integrated filter and washer is communicated with the inlet of the leaching tank.

9. The waste solid alkali leaching and recovery system for an electrolytic aluminum plant according to claim 6, characterized in that, The fifth filter is a fifth integrated filter and washer, and the wash water outlet of the fifth integrated filter and washer is communicated with the inlet of the second pulping tank.

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