System for recovering fluorine and lithium from alkaline calcium leaching residues of shell block produced by electrolytic aluminum factory

Abstract

The utility model discloses a system for recovering fluorine and lithium from shell block alkaline calcium leaching residues in an electrolytic aluminum factory. The system comprises an acid leaching reaction tank, a first filter, a purification tank, a second filter, a lithium carbonate precipitation tank, a third filter, a pulping tank, a separator and a dryer. The method has the advantages that CaAl2 (OH) 8 in the alkaline leaching residues reacts with hydrochloric acid to be thoroughly dissolved into aluminum hydroxide and calcium fluoride, and lithium fluoride in the alkaline leaching residues can also be decomposed into lithium chloride and calcium fluoride; aluminum hydroxide and calcium fluoride can be filtered out by the first filter, calcium carbonate obtained by adding sodium carbonate into the filtered solution is separated out by the second filter, solid lithium carbonate slurry can be obtained by adding sodium carbonate into filtrate filtered out by the second filter, and then the solid lithium carbonate slurry is filtered and separated by the third filter; performing pulping, separation and drying on the separated wet lithium carbonate to obtain lithium carbonate solid, adding acid into the separated liquid to discharge carbon dioxide to obtain a sodium salt solution, and performing evaporative crystallization on the sodium salt solution through an MVR evaporator to obtain a sodium salt product.

Description

Technical field:

[0001] The utility model relates to the technical field of shell surface block alkaline calcium leaching slag treatment, in particular to a system for recovering fluorine and lithium from shell surface block alkaline calcium leaching slag produced in an electrolytic aluminum plant. Background technology:

[0002] Scrapped aluminum shells produced by aluminum smelters are the electrolyte crust on the surface of molten aluminum, containing aluminum, lithium, and Na₃AlF₆. Currently, lithium carbonate manufacturers primarily recover the lithium metal as a raw material for lithium carbonate used in the new energy industry. The primary recovery method involves grinding the shells into a powder using a jaw crusher, cone mill, and Raymond mill. This powder is then reacted with hydrochloric acid or sulfuric acid to convert fluorine into metacryolith, aluminum trifluoride, and other substances, and sodium into sodium chloride or sodium sulfate, thereby decomposing the Na₃AlF₆. Simultaneously, the lithium in the shells is converted into lithium chloride or lithium sulfate. The resulting acid residue is filtered and washed to produce an aluminum-fluoride residue, which in turn produces an acidic decomposition solution containing significant amounts of aluminum and fluorine. This acidic decomposition solution is then purified and cleaned with sodium carbonate, calcium carbonate, or calcium hydroxide. The cleaned slurry is filtered and washed to produce an aluminum-fluoride-calcium purified residue and a sodium chloride or sodium sulfate solution. The purified sodium chloride or sodium sulfate solution is then evaporated and concentrated to increase the lithium content, and then sodium carbonate solution is added to precipitate the lithium carbonate.

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

[0004] At present, an alkaline leaching process has been developed, which is to crush the above solid waste to a certain particle size and then use alkaline calcium to 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] Li + +F - =LiF↓

[0010] After solid-liquid separation, the leaching solution mainly composed of NaOH, LiOH and NaAlO2, and the leaching solution mainly composed of CaAl2(OH) 8、 In order to recover fluorine and lithium from the leaching residue mainly composed of CaF2 and LiF, a system for recovering fluorine and lithium from the alkaline calcium leaching residue of the shell surface blocks of the electrolytic aluminum plant has been developed. Utility model content:

[0011] The utility model aims to provide a system for recovering fluorine and lithium from alkaline calcium leaching slag of shell surface blocks produced in an electrolytic aluminum plant.

[0012] The utility model is implemented by the following technical scheme: a system for recovering lithium fluoride from alkaline calcium leaching slag of shell surface blocks produced in an electrolytic aluminum plant, which includes an acid leaching reaction tank, a first filter, a purification tank, a second filter, a lithium carbonate precipitation tank, a third filter, a pulping tank, a separator, and a dryer. A leaching slag feeding pipe is connected to the inlet of the acid leaching reaction tank, and the top of the acid leaching reaction tank is connected to a first hydrochloric acid pipe; the outlet of the acid leaching reaction tank is connected to the inlet of the first filter, the solid phase outlet of the first filter is connected to a calcium fluoride discharge pipe, and the liquid phase outlet of the first filter is connected to the The inlet of the purification tank is connected; the outlet of the purification tank is connected to the inlet of the second filter, the solid phase outlet of the second filter is connected to a calcium carbonate discharge pipe, the liquid phase outlet of the second filter is 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 third filter, the solid phase outlet of the third filter is connected to the inlet of the pulping tank, the outlet of the pulping tank is connected to the inlet of the separator, the solid phase outlet of the separator is connected to the inlet of the dryer, and the outlet of the dryer is connected to a lithium carbonate discharge pipe.

[0013] Furthermore, the liquid phase outlet of the third filter is connected to the inlet of the carbon dioxide exhaust tank, and the upper part of the carbon dioxide exhaust tank is connected to a second hydrochloric acid pipe; the outlet of the carbon dioxide exhaust tank is connected to the inlet of the MVR evaporator, and the solid phase outlet of the MVR evaporator is connected to a sodium salt discharge pipe.

[0014] Furthermore, the liquid phase outlet of the MVR evaporator is connected to the inlet of the lithium carbonate precipitation tank.

[0015] Furthermore, the first filter is a first integrated filter-washer, and the washing water outlet of the first integrated filter-washer is connected to the inlet of the acid leaching reaction tank.

[0016] Furthermore, the second filter is a second integrated filter-washer, and the washing water outlet of the second integrated filter-washer is connected to the inlet of the acid leaching reaction tank.

[0017] Furthermore, the third filter is a third integrated filter-washer, and the washing water outlet of the third integrated filter-washer is connected to the inlet of the lithium carbonate precipitation tank.

[0018] The advantages of this utility model are as follows: CaAl2(OH)8 and LiF in the alkali leaching residue react with hydrochloric acid to produce solid aluminum hydroxide and calcium fluoride, and liquid calcium chloride and lithium chloride. The first filter removes the aluminum hydroxide and calcium fluoride, and sodium carbonate is added to the filtered solution to obtain calcium carbonate, which is then separated by the second filter. Soda ash is added to the filtrate from the second filter to obtain a slurry of solid lithium carbonate. This is then filtered and separated by a third filter. The separated wet lithium carbonate is pulped, separated, and dried to obtain solid lithium carbonate. The separated liquid is then acidified to discharge carbon dioxide, obtaining a sodium salt solution. This is then evaporated and crystallized in an MVR evaporator to obtain a sodium salt product. This system can separate aluminum, fluorine, and lithium from the alkali leaching residue, improving the recovery rate of the active ingredients and removing calcium carbonate residue. The resulting lithium carbonate is of high purity. Furthermore, when separating calcium fluoride and aluminum hydroxide, lithium exists in the solution as a lithium salt, thereby preventing lithium from being discharged with the aluminum-fluoride residue and improving the lithium recovery rate. Description of the drawings:

[0019] Figure 1 Schematic diagram of the overall structure of this embodiment.

[0020] Acid leaching reaction tank 1, first filter 2, purification tank 3, second filter 4, lithium carbonate precipitation tank 5, third filter 6, pulping tank 7, separator 8, dryer 9, leached residue feeding pipe 10, calcium fluoride discharge pipe 11, calcium carbonate discharge pipe 12, lithium carbonate discharge pipe 13, carbon dioxide discharge tank 14, MVR evaporator 15, sodium salt discharge pipe 16, first hydrochloric acid pipe 17, second hydrochloric acid pipe 18. Specific implementation method:

[0021] 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.

[0022] like Figure 1As shown, a system for recovering lithium fluoride from alkaline calcium leaching residue of shell blocks produced in an electrolytic aluminum plant comprises an acid leaching reaction tank 1, a first filter 2, a purification tank 3, a second filter 4, a lithium carbonate precipitation tank 5, a third filter 6, a pulping tank 7, a separator 8, and a dryer 9.

[0023] The leached residue feeding pipe 10 is connected to the inlet of the acid leaching reaction tank 1, and the top of the acid leaching reaction tank is connected to the first hydrochloric acid pipe 17; the outlet of the acid leaching reaction tank 1 is connected to the inlet of the first filter 2, the solid phase outlet of the first filter 2 is connected to the calcium fluoride discharge pipe 11, and the liquid phase outlet of the first filter 2 is connected to the inlet of the purification tank 3;

[0024] The outlet of the purification tank 3 is connected to the inlet of the second filter 4, the solid phase outlet of the second filter 4 is connected to the calcium carbonate discharge pipe 12, the liquid phase outlet of the second filter 4 is connected to the inlet of the lithium carbonate precipitation tank 5, the outlet of the lithium carbonate precipitation tank 5 is connected to the inlet of the third filter 6, the solid phase outlet of the third filter 6 is connected to the inlet of the pulping tank 7, the outlet of the pulping tank 7 is connected to the inlet of the separator 8, the solid phase outlet of the separator 8 is connected to the inlet of the dryer 9, and the outlet of the dryer 9 is connected to the lithium carbonate discharge pipe 13.

[0025] The liquid phase outlet of the third filter 6 is connected to the inlet of the carbon dioxide exhaust tank 14, and the upper part of the carbon dioxide exhaust tank is connected to the second hydrochloric acid pipe 18; the outlet of the carbon dioxide exhaust tank 14 is connected to the inlet of the MVR evaporator 15, and the solid phase outlet of the MVR evaporator 15 is connected to the sodium salt discharge pipe 16.

[0026] The liquid phase outlet of the MVR evaporator 15 is communicated with the inlet of the lithium carbonate precipitation tank 5 .

[0027] Processing process:

[0028] S1: After the shell noodle block powder is leached with alkaline calcium, the leached residue is sent to the acid leaching reaction tank 10 through the leached residue feeding pipe 10, and hydrochloric acid is added for leaching. The solid-liquid ratio is 1:1-4, the leaching temperature is 30-100°C, the leaching time is 30-300 minutes, and the leaching pH is 0.5-5. The reaction equation is as follows:

[0029] CaAl2(OH)8+2HCl=2Al(OH)3↓+CaCl2+2H2O

[0030] Ca(OH)2+2HCl=CaCl2+2H2O

[0031] 2LiF+CaCl2=2LiCl+CaF2↓

[0032] S2: The liquid after the reaction in the acid leaching reaction tank 10 is sent to the first filter 2 for filtration and separation. The calcium fluoride containing aluminum hydroxide is separated and discharged to the subsequent equipment through the calcium fluoride discharge pipe 11. The separated liquid phase is mainly a mixed solution of calcium chloride and lithium chloride, which is sent to the purification tank 3. At the same time, sodium carbonate is added to the purification tank 3 to remove calcium ions in the solution and the pH is adjusted to 6;

[0033] S3: The liquid obtained in S2 is passed through a second filter 4 for solid-liquid separation to separate calcium carbonate slag and purified lithium salt solution;

[0034] S4: feeding the purified lithium salt solution discharged from the second filter 4 into the lithium carbonate precipitation tank 5, and adding 10-30% soda ash solution to the lithium carbonate precipitation tank, the reaction temperature is 80-100°C, the reaction time is 30-300 minutes, and the soda ash is in excess of 10-30%, to obtain lithium carbonate slurry;

[0035] S5: The lithium carbonate slurry discharged from the lithium carbonate precipitation tank 5 is sent to the third filter 6 for solid-liquid separation. The separated lithium carbonate solid is sent to the pulping tank 7 for pulping with pure water to clean the lithium carbonate, wash off the surface solution, and improve its purity. The obtained lithium carbonate slurry is separated into solid and liquid by the separator 8, and the separated liquid is sent back to the lithium carbonate precipitation tank 5 for circulation. The separated solid is sent to the dryer for drying. The dried lithium carbonate product is discharged from the system through the lithium carbonate discharge pipe 13;

[0036] The crystallization mother liquor discharged from the third filter 6 is a lithium-containing sodium carbonate solution, which is sent to the carbon dioxide exhaust tank 14 and hydrochloric acid is added to react to obtain a lithium-containing sodium chloride solution; the solution discharged from the carbon dioxide exhaust tank 14 is then sent to the MVR evaporator 15 to evaporate and crystallize the sodium carbonate, and then discharged from the system through the sodium salt discharge pipe 16. The high-concentration lithium liquid discharged from the MVR evaporator 15 is sent to the lithium carbonate precipitation tank 5 for circulation treatment.

[0037] In this embodiment, the first filter 2 is a first integrated filter-washer, whose wash water outlet is connected to the inlet of the acid leaching reaction tank 1. The second filter 4 is a second integrated filter-washer, whose wash water outlet is connected to the inlet of the acid leaching reaction tank 1. The wash water discharged from the first and second integrated filter-washers is returned to the acid leaching reaction tank 1 for recycling.

[0038] The third filter 6 is a third integrated filter-washer. The washing water outlet of the third integrated filter-washer is connected to the inlet of the lithium carbonate precipitation tank 5. The washing water discharged from the third filter-washer is sent to the lithium carbonate precipitation tank 5 for circulation treatment.

[0039] 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 system for recovering fluorine and lithium from alkaline calcium leaching residue of shell blocks in an electrolytic aluminum plant, characterized in that: It includes an acid leaching reaction tank, a first filter, a purification tank, a second filter, a lithium carbonate precipitation tank, a third filter, a pulping tank, a separator, and a dryer. The leached residue feeding pipe is connected to the inlet of the acid leaching reaction tank, and the top of the acid leaching reaction tank is connected to a first hydrochloric acid pipe; the outlet of the acid leaching reaction tank is connected to the inlet of the first filter, the solid phase outlet of the first filter is connected to a calcium fluoride discharge pipe, and the liquid phase outlet of the first filter is connected to the inlet of the purification tank; the outlet of the purification tank is connected to the inlet of the second filter, the solid phase outlet of the second filter is connected to a calcium carbonate discharge pipe, the liquid phase outlet of the second filter is 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 third filter, the solid phase outlet of the third filter is connected to the inlet of the pulping tank, the outlet of the pulping tank is connected to the inlet of the separator, the solid phase outlet of the separator is connected to the inlet of the dryer, and the outlet of the dryer is connected to a lithium carbonate discharge pipe.

2. The system for recovering fluorine and lithium from alkaline calcium leaching residue of shell surface blocks in an electrolytic aluminum plant according to claim 1, characterized in that: The liquid phase outlet of the third filter is connected to the inlet of the carbon dioxide exhaust tank, and the upper part of the carbon dioxide exhaust tank is connected to a second hydrochloric acid pipe; the outlet of the carbon dioxide exhaust tank is connected to the inlet of the MVR evaporator, and the solid phase outlet of the MVR evaporator is connected to a sodium salt discharge pipe.

3. The system for recovering fluorine and lithium from alkaline calcium leaching residue of shell surface blocks in an electrolytic aluminum plant according to claim 1, characterized in that: The liquid phase outlet of the MVR evaporator is communicated with the inlet of the lithium carbonate precipitation tank.

4. The system for recovering fluorine and lithium from alkaline calcium leaching residue of shell blocks in an electrolytic aluminum plant according to claim 1, characterized in that: The first filter is a first integrated filter-washer, and a washing water outlet of the first integrated filter-washer is connected to the inlet of the acid leaching reaction tank.

5. The system for recovering fluorine and lithium from alkaline calcium leaching residue of shell blocks in an electrolytic aluminum plant according to claim 1, characterized in that: The second filter is a second integrated filter-washer, and the washing water outlet of the second integrated filter-washer is connected to the inlet of the acid leaching reaction tank.

6. The system for recovering fluorine and lithium from alkaline calcium leaching residue of shell surface blocks in an electrolytic aluminum plant according to claim 1, characterized in that: The third filter is a third integrated filter-washer, and the washing water outlet of the third integrated filter-washer is connected to the inlet of the lithium carbonate precipitation tank.

Images