Method for preparing and purifying lithium carbonate by dissolving waste lithium battery with mixed acid

Abstract

The application discloses a method for preparing and purifying lithium carbonate by dissolving waste lithium batteries in mixed acid, comprising the following steps: decomposing and treating the positive electrode of the waste lithium battery to obtain crude lithium phosphate; adding the crude lithium phosphate into mixed acid to react and filter; adding a certain amount of calcium chloride to react for a period of time, then adding liquid alkali to react and filter to obtain a third mixed solution; mixing and oscillating the washed extractant with the third mixed solution, then performing liquid separation to obtain a raffinate; adding the heated pure alkali solution into the raffinate to react, filtering and separating the filter residue, and washing and drying to obtain lithium carbonate. In the application, the crude lithium phosphate is added into mixed acid to react, then a certain amount of calcium chloride and liquid alkali are added to react to obtain a third mixed solution, calcium ions in the third mixed solution are removed by extraction, then the pure alkali solution is added to react, the filter residue is separated by filtering, and lithium carbonate is obtained, so that the crude lithium phosphate is treated to finally obtain purified lithium carbonate, which can be continuously recycled and used as the positive electrode of a battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery recycling, in particular to a method for preparing lithium carbonate and purification by dissolving waste lithium batteries with mixed acid. BACKGROUND

[0002] Waste lithium ion batteries contain rich resources such as nickel, cobalt and lithium, among which the content of lithium oxide is 5-10%, and the content of cobalt and nickel is about 20%. China is a country seriously short of cobalt, and cobalt resources almost completely rely on imports. Lithium resources mainly come from South American brine and Western Australian lithium spodumene. In addition, waste batteries contain a large amount of toxic and harmful substances such as electrolyte, and if not properly treated, they will cause serious pollution to the environment. Therefore, the treatment and recycling of waste lithium ion batteries have economic and environmental benefits.

[0003] The recycling technology of waste lithium ion batteries usually first separates copper and aluminum metals, metal shells, plastics and ternary powders, and then reduces and leaches the ternary powders to obtain nickel, cobalt and manganese sulfates, and then recovers nickel, cobalt and manganese through extraction and back extraction, while lithium remains in the raffinate. The recycling enterprises mainly recover nickel, cobalt and copper metals.

[0004] In addition, lithium can also be recovered by precipitating lithium phosphate with trisodium phosphate. The crude lithium phosphate contains a large amount of sodium phosphate, sodium sulfate and organic impurities, and can only be recovered as a crude lithium compound. The recovered crude lithium phosphate cannot be directly used as a lithium source for further use. SUMMARY

[0005] Therefore, the present application provides a method for preparing lithium carbonate and purification by dissolving waste lithium batteries with mixed acid, which effectively solves the problem that most of the existing lithium ion battery recycling technology can only recover crude lithium compounds, and the recovered crude lithium phosphate cannot be directly used as a lithium source for further use.

[0006] To solve the above technical problems, the present application specifically provides the following technical scheme: a method for preparing lithium carbonate and purification by dissolving waste lithium batteries with mixed acid, comprising:

[0007] decomposing and treating the positive electrode of the waste lithium battery to obtain crude lithium phosphate;

[0008] taking a certain amount of crude lithium phosphate, adding mixed acid obtained by mixing hydrochloric acid and sulfuric acid, adjusting the pH value of the reaction solution to 1-3 to obtain a first mixed solution;

[0009] stirring the first mixed solution to promote the reaction of the first mixed solution until all the solid materials are dissolved, filtering to obtain a second mixed solution composed of lithium dihydrogen phosphate, lithium chloride and lithium sulfate;

[0010] Part of the second mixed solution is taken into a container, a certain amount of calcium chloride is added into the container to react for a period of time, liquid alkali is added to adjust the pH value to 10-12, and the third mixed solution is obtained after filtration;

[0011] The extractant is washed with acid solution and aqueous solution in sequence, the washed extractant is mixed with the third mixed solution and shaken, and the raffinate is obtained after separation by liquid-liquid extraction;

[0012] The pure alkali solution and the raffinate are heated respectively, the heated pure alkali solution is added into the raffinate to react, and the filter residue is separated after filtration, and the lithium carbonate is obtained after washing and drying.

[0013] Further,

[0014] The method for obtaining the third mixed solution by taking part of the second mixed solution into a container, adding a certain amount of calcium chloride into the container to react for a period of time, adding liquid alkali to adjust the pH value to 10-12, and filtering after reaction, comprises the following steps:

[0015] The second mixed solution is placed into a container, and the container is placed in a water bath to heat and keep at 50°C for stirring;

[0016] According to the content of phosphate in the second mixed solution, the amount of calcium chloride to be added is calculated, and a certain amount of calcium chloride is added according to the calculation result and stirred;

[0017] After stirring, liquid alkali is added to make the pH value of the solution 10-12, and the stirring is continued;

[0018] After the stirring is completed, filtration is performed to separate the calcium phosphate filter residue to obtain the third mixed solution composed of lithium chloride and lithium sulfate.

[0019] Further,

[0020] The method for filtering comprises the following steps:

[0021] The solution to be filtered is sequentially subjected to first filtration and second filtration to filter out filter residues with gradually decreasing sizes in the first filter layer and the second filter layer respectively;

[0022] A negative pressure is formed in the first filter layer and the second filter layer to suck water to clean the filter residues;

[0023] The filter residues are taken out after washing.

[0024] Further,

[0025] The method for filtering is implemented in a filter container;

[0026] The filter container comprises a filter cartridge cabin, an output cartridge arranged at the bottom of the filter cartridge cabin, and a liquid outlet nozzle threadedly installed at the bottom of the output cartridge;

[0027] The filter cartridge cabin bottom is connected with the output cylinder, and the inner diameter of the output cylinder is smaller than that of the filter cartridge cabin.

[0028] Further,

[0029] The liquid outlet nozzle comprises two shapes, one is a conical structure with a bottom opening larger than a top opening, and the other is a combination structure of an inverted conical body and a cylindrical body with a bottom opening smaller than a top opening.

[0030] Further,

[0031] The inner wall of the output cylinder is provided with a thread groove, the output cylinder is provided with a threaded column, the outer wall of the threaded column is provided with a threaded protrusion, the threaded protrusion is fitted and installed in the thread groove, and the width of the threaded protrusion is smaller than the width of the thread groove.

[0032] There is a gap between the threaded protrusion and the thread groove, and the solution in the filter cartridge cabin can enter the bottom of the output cylinder through the gap.

[0033] Further,

[0034] A ladder-shaped groove is formed in the threaded column, and the inner diameter of the bottom of the ladder-shaped groove is smaller than the inner diameter of the top of the ladder-shaped groove.

[0035] A lifting valve block is movably arranged in the ladder-shaped groove, at least part of the outer wall of the lifting valve block is fitted with the inner side wall of the bottom of the ladder-shaped groove, a lifting rod is connected to the lifting valve block, a conical rod is connected to the lifting rod, an outer thread is arranged on the outer periphery of the top opening of the filter cartridge cabin, a filter top cover is screwed onto the outer thread, a threaded ring seat is arranged on the inner bottom of the filter top cover, an inner filter cabin is arranged in the threaded ring seat, a base is screwed onto the bottom of the inner filter cabin, a conical groove is formed in the base, the conical rod penetrates through the conical groove, and the outer wall of the conical rod is fitted with the inner wall of the conical groove, a connecting rod is arranged at the top end of the conical rod, and the connecting rod penetrates through the filter top cover.

[0036] Further,

[0037] The inner diameter of the upper part of the conical groove is smaller than the inner diameter of the lower part of the conical groove.

[0038] Further,

[0039] A liquid inlet is formed in the filter top cover, a sealing cover is screwed onto the liquid inlet, the liquid inlet is opposite to the inner filter cabin, and two suction ports are formed in the filter top cover and are opposite to the inside of the filter cartridge cabin and the inside of the inner filter cabin, respectively.

[0040] A suction pump is connected to the outside of the suction port.

[0041] Further,

[0042] The filter cartridge cabin is externally provided with a cleaning round cabin, water is stored in the cleaning round cabin, a supporting protrusion is arranged on the outer wall of the filter cartridge cabin, a supporting groove is arranged on the inner wall of the opening part of the cleaning round cabin, and the supporting protrusion is supported and installed on the supporting groove.

[0043] The outlet nozzle bottom is lower than the liquid level in the cleaning round cabin.

[0044] Compared with the prior art, the present application has the following beneficial effects:

[0045] In the present application, the waste lithium battery positive electrode is decomposed and treated to obtain crude lithium phosphate, mixed acid is added for reaction to obtain a second mixed solution containing lithium dihydrogen phosphate, a certain amount of calcium chloride and liquid alkali are then added for reaction to obtain a third mixed solution, calcium ions in the third mixed solution are removed by extraction, and then a sodium carbonate solution is added for reaction, and then the filter residue is separated by filtration, washed and dried to obtain lithium carbonate. The above method for preparing and purifying lithium carbonate can treat crude lithium phosphate to obtain purified lithium carbonate, which can be continuously recycled as a battery positive electrode.

[0046] The present application also provides a filter container, which is suitable for various chemical reaction processes, can filter, wash the filter residue after filtration, and wash the container itself after filtration, and realizes efficient filtration and simple treatment process of the filter residue after filtration. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only exemplary, and for those skilled in the art, other drawings can be obtained from the provided drawings without creative labor.

[0048] Figure 1 The flow chart of the method for preparing and purifying lithium carbonate by dissolving waste lithium batteries with mixed acid provided in the present application embodiment;

[0049] Figure 2 The structural schematic diagram of the filter container in the present application embodiment;

[0050] Figure 3 The structural schematic diagram of the filter container in the present application embodiment in the filtration process;

[0051] Figure 4 The internal structural schematic diagram of the solution in the filter container in the present application embodiment in the reaction process;

[0052] Figure 5Fig. 1 is a schematic diagram of the internal structure of the filter container in the filtering process according to an embodiment of the present application;

[0053] Figure 6 Fig. 2 is a schematic diagram of the internal structure of the filter container in the washing process according to an embodiment of the present application;

[0054] Figure 7 Fig. 3 is a schematic diagram of the top view of the output cylinder and the threaded column according to an embodiment of the present application.

[0055] The reference signs in the figures represent the following:

[0056] 1 - filter container;

[0057] 11 - filter cylinder cabin; 12 - output cylinder; 13 - liquid outlet nozzle; 14 - threaded groove; 15 - threaded column; 16 - threaded protrusion; 17 - gap; 18 - ladder-shaped groove; 19 - lifting valve block; 110 - lifting rod; 111 - conical rod; 112 - filter top cover; 113 - threaded ring seat; 114 - inner filter cabin; 115 - base; 116 - conical groove; 117 - connecting rod; 118 - liquid inlet; 119 - sealing cover; 120 - suction port; 121 - air suction pump; 122 - cleaning round cabin; 123 - supporting protrusion; 124 - supporting groove; 125 - sealing column. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0059] As shown in Figure 1 the present application provides a method for preparing and purifying lithium carbonate by dissolving waste lithium batteries with mixed acid, which comprises the following steps:

[0060] The positive electrode of the waste lithium battery is decomposed to obtain crude lithium phosphate;

[0061] A certain amount of crude lithium phosphate is taken, mixed acid obtained by mixing hydrochloric acid and sulfuric acid is added, and the pH value of the reaction solution is adjusted to 1-3 to obtain a first mixed solution;

[0062] The first mixed solution is stirred to promote the reaction of the first mixed solution until all the solid materials are dissolved, and then filtered to obtain a second mixed solution composed of lithium dihydrogen phosphate, lithium chloride and lithium sulfate;

[0063] Part of the second mixed solution is taken into a container, a certain amount of calcium chloride is added to react in the container for a period of time, and liquid alkali is added to adjust the pH value to 10-12. After reaction, a third mixed solution is obtained by filtration;

[0064] The extractant is washed with acid solution and aqueous solution in sequence, the washed extractant is mixed with the third mixed solution, and after oscillation, liquid separation is carried out to obtain the raffinate;

[0065] The pure alkali solution and the raffinate are heated respectively, the heated pure alkali solution is added into the raffinate to react, and after reaction, the filter residue is separated by filtration and washed and dried to obtain lithium carbonate.

[0066] In the application, the positive electrode of the waste lithium battery is decomposed to obtain crude lithium phosphate, mixed acid is added for reaction to obtain a second mixed solution containing lithium dihydrogen phosphate, a certain amount of calcium chloride and liquid alkali are added for reaction to obtain a third mixed solution, calcium ions in the third mixed solution are extracted, then pure alkali solution is added for reaction, then the filter residue is separated by filtration, and washed and dried to obtain lithium carbonate.

[0067] In the application, there are multiple reactions, the first reaction is the reaction of crude lithium phosphate and mixed acid, the second reaction is the reaction of lithium dihydrogen phosphate, calcium chloride and liquid alkali, and the last reaction is the reaction of raffinate and pure alkali solution, wherein the raffinate is extracted, and the extraction process is also an important process in the application, which aims to screen out calcium ions in the solution.

[0068] In the application, the first step is to decompose the positive electrode of the waste lithium battery to obtain crude lithium phosphate, the second step is to take a certain amount of crude lithium phosphate, add mixed acid obtained by mixing hydrochloric acid and sulfuric acid, adjust the pH value of the reaction solution to 1-3 to obtain a first mixed solution, the third step is to stir the first mixed solution to promote the reaction of the first mixed solution until the solid material is completely dissolved, filter to obtain a second mixed solution composed of lithium dihydrogen phosphate, lithium chloride and lithium sulfate.

[0069] In the third step, the first mixed solution is stirred to accelerate the reaction of the mixed acid and the first mixed solution, the stirring time of the first mixed solution is 1.5 hours, and after the solid material in the first mixed solution is completely dissolved and the stirring is completed, the filtration is carried out to obtain the second mixed solution and the filter residue.

[0070] The reaction of crude lithium phosphate and mixed acid includes: Li3PO4+2HCl→LiH2PO4+2LiCl, Li3PO4+H2SO4→LiH2PO4+Li2SO4, and the mixed reaction of crude lithium phosphate and mixed acid obtains lithium dihydrogen phosphate, lithium chloride and lithium sulfate.

[0071] The fourth step is to take part of the second mixed solution into a container, add a certain amount of calcium chloride to react in the container for a period of time, add liquid alkali to adjust the pH value to 10-12, and after reaction, filter to obtain a third mixed solution.

[0072] Wherein, take part of the second mixed solution into the container, add a certain amount of calcium chloride in the container to react for a period of time, add liquid alkali to adjust the pH value to 10-12, and filter after reaction to obtain the third mixed solution, including:

[0073] Put the second mixed solution into the container (about 450 ml of the second mixed solution is taken in actual application), and place the container in a water bath to heat and keep 50℃ for stirring;

[0074] According to the content of phosphate in the second mixed solution, calculate the amount of calcium chloride to be added, and add a certain amount of calcium chloride according to the calculation result, and stir;

[0075] After stirring (1.5 hours), add liquid alkali to make the pH value of the solution 10-12, and continue to stir (1 hour);

[0076] After the stirring is completed, filter to separate the calcium phosphate filter residue to obtain the third mixed solution composed of lithium chloride and lithium sulfate.

[0077] The role of stirring in the above process is also to accelerate the reaction of the second mixed solution with liquid alkali and sodium chloride, and the reaction mode of the second mixed solution with calcium chloride and liquid alkali is:

[0078] 2LiH2PO4+3CaCl+4NaOH→Ca3(PO4)+2LiCl+4NaCl+4H2O, wherein, lithium dihydrogen phosphate in the second mixed solution reacts with calcium chloride and liquid alkali to obtain calcium phosphate, lithium chloride, sodium chloride and water, plus lithium chloride and lithium sulfate contained in the second mixed solution, after separating out the calcium phosphate, the third mixed solution mainly contains lithium chloride, sodium chloride, lithium sulfate and part of unreacted calcium ions.

[0079] The fifth step is to wash the extractant with acid solution and aqueous solution in turn, mix the washed extractant with the third mixed solution and shake, and then separate to obtain the raffinate.

[0080] Wherein, the extractant is mixed with the third mixed solution to remove the calcium ions in the third mixed solution to obtain the purified solution composed of lithium chloride and lithium sulfate (which also contains sodium chloride).

[0081] The sixth step is to heat the pure alkali solution and the raffinate respectively, add the heated pure alkali solution into the raffinate to react, separate out the filter residue after reaction, and wash and dry to obtain lithium carbonate.

[0082] Wherein, the reaction mode of the raffinate and the pure alkali solution is:

[0083] Na2CO3+2LiCl→Li2CO3+2NaCl;

[0084] Na2CO3+Li2SO4→Li2CO3+Na2SO4, the raffinate is reacted with soda solution to obtain lithium carbonate precipitate, and the lithium carbonate is obtained after washing and drying.

[0085] In the present application, the third step, the fourth step and the sixth step can be filtered by the filtering container 1.

[0086] The filtering method comprises:

[0087] The to-be-filtered solution is sequentially subjected to first filtering and second filtering, so as to filter out filter residues with gradually smaller sizes in the first filtering layer and the second filtering layer respectively.

[0088] A negative pressure is formed in the first filtering layer and the second filtering layer, and the water body is sucked to clean the filter residues.

[0089] The filter residues are taken out after flushing.

[0090] That is, the size of the filtering gap of the first filtering is greater than the size of the filtering gap of the second filtering, the filter residues are gradually filtered, the filtering rate is improved, and excessive accumulation of filter residues in the first filtering layer can be avoided.

[0091] The filtering container 1 is also designed as follows:

[0092] As shown in Figure 2 The filtering container 1 comprises a filtering cylinder cabin 11, an output cylinder 12 arranged at the bottom of the filtering cylinder cabin 11, and a liquid outlet nozzle 13 threadedly installed at the bottom of the output cylinder 12, the bottom of the filtering cylinder cabin 11 is connected with the output cylinder 12, and the inner diameter of the output cylinder 12 is smaller than the inner diameter of the filtering cylinder cabin 11.

[0093] In the present application, the liquid outlet nozzle 13 has two embodiments, and the liquid outlet nozzle 13 comprises two shapes, the first embodiment is a conical structure with a larger bottom opening than a top opening, and the second embodiment is a combination structure of an inverted conical body and a cylindrical body with a smaller bottom opening than a top opening.

[0094] The liquid outlet nozzle 13 of the first embodiment can be used for washing the inside of the filtering cylinder cabin 11, and the liquid outlet nozzle 13 of the second embodiment can be used for the filtering process, and the specific embodiments will be described in detail in the subsequent part.

[0095] In the present application, two layers of filtering are designed, which are upper filtering (first filtering) and lower filtering (second filtering), and the filtering in the present application is performed from top to bottom, wherein the main design of the lower filtering is as follows, such as Figure 3 and Figure 7As shown, the inner wall of the output cylinder 12 is provided with a thread groove 14, the output cylinder 12 is provided with a threaded column 15, the outer wall of the threaded column 15 is provided with a threaded protrusion 16, the threaded protrusion 16 is fitted in the thread groove 14, the width of the threaded protrusion 16 is smaller than the width of the thread groove 14, and there is a gap 17 between the threaded protrusion 16 and the thread groove 14, and the solution inside the filter cylinder cabin 11 can enter the bottom of the output cylinder 12 through the gap 17.

[0096] In the above embodiment, from the cross section of the threaded column 15, the width of the threaded protrusion 16 on the threaded column 15 is smaller than the width of the thread groove 14, that is, the threaded protrusion 16 does not completely fit the thread groove 14, and the threaded protrusion 16 only occupies part of the thread groove 14, and the inner wall of the thread groove 14 can also support the threaded protrusion 16, and the gap 17 between the threaded protrusion 16 and the thread groove 14 is the area for the solution to pass through, and reasonable setting of the size of the gap can realize secondary filtration of the solution.

[0097] In order to realize the upper layer filtration (first filtration) and realize washing, the application also designs as follows, Figure 4 As shown, the threaded column 15 is provided with a ladder-shaped groove 18, the inner diameter of the bottom of the ladder-shaped groove 18 is smaller than the inner diameter of the top of the ladder-shaped groove 18, and the design of the ladder-shaped groove 18 makes the threaded column 15 hollow.

[0098] In order to adjust the overall communication state of the threaded column 15, the application also designs as follows, Figure 4 As shown, the ladder-shaped groove 18 is movably provided with a lifting valve block 19, at least part of the outer wall of the lifting valve block 19 fits the inner side wall of the bottom of the ladder-shaped groove 18, the lifting valve block 19 is connected with a lifting rod 110, the lifting rod 110 is connected with a tapered rod 111, the outer periphery of the top opening of the filter cylinder cabin 11 is provided with an external thread, and a filter top cover 112 is threadedly installed thereon, the inner bottom of the filter top cover 112 is provided with a threaded ring seat 113, the threaded ring seat 113 is provided with an inner filter cabin 114, and the bottom of the inner filter cabin 114 is threadedly installed with a base 115, the base 115 is provided with a tapered groove 116, the tapered rod 111 penetrates the tapered groove 116, and the outer wall of the tapered rod 111 fits the inner wall of the tapered groove 116, the top end of the tapered rod 111 is provided with a connecting rod 117, the connecting rod 117 penetrates the filter top cover 112, and the inner diameter of the upper part of the tapered groove 116 is smaller than the inner diameter of the lower part of the tapered groove 116.

[0099] In the above embodiment, the tapered groove 116 and the tapered rod 111 form the upper layer filtration, and the design of the lifting valve block 19 and the ladder-shaped groove 18 makes the overall communication state of the threaded column 15 adjustable.

[0100] In the filtering process, the lifting valve block 19 is completely fitted with the inner wall of the ladder-shaped groove 18, the tapered rod 111 is not completely fitted with the tapered groove 116, and there is a gap between the tapered rod 111 and the tapered groove 116, so that the solution can flow out of the inner filter cabin 114 and flow into the filter cylinder cabin 11.

[0101] In the washing process, the connecting rod 117 is moved upwards to drive the tapered rod 111 to move upwards, thereby driving the lifting valve block 19 to move upwards, and gradually forming a gap between the lifting valve block and the ladder-shaped groove 18, at which time the washing action can be performed.

[0102] In order to ensure the washing process and inject the solution into the inner filter cabin 114, the following design is made: the filter top cover 112 is provided with a liquid inlet 118, the liquid inlet 118 is threadedly installed with a sealing cover 119, the liquid inlet 118 is opposite to the inner filter cabin 114, and the filter top cover 112 is also provided with two suction ports 120, which are respectively opposite to the inside of the filter cylinder cabin 11 and the inner filter cabin 114, and the suction ports 120 are connected with a gas suction pump 121.

[0103] Before filtering in the present application, the inner filter cabin 114 can be used as a reaction place between the above-mentioned solutions, for example, the connecting rod 117 is moved upwards to drive the tapered rod 111 to completely fit with the tapered groove 116, part of the second mixed solution is injected into the inner filter cabin 114 from the liquid inlet 118, a certain amount of calcium chloride is added to react in the inner filter cabin 114 for a period of time, and liquid alkali is added to adjust the pH value to 10-12, after the reaction, the connecting rod 117 is moved downwards to realize filtering, the third mixed solution enters the filter cylinder cabin 11 through the gap, and then is subjected to secondary filtering through the gap 17, and is finally discharged from the liquid outlet nozzle 13.

[0104] In order to cooperate with the washing process, the following design is also made, as shown in the figure, a cleaning circular cabin 122 is arranged outside the filter cylinder cabin 11, water is stored in the cleaning circular cabin 122, a supporting protrusion 123 is arranged on the outer wall of the filter cylinder cabin 11, a supporting groove 124 is formed in the inner wall of the opening part of the cleaning circular cabin 122, the supporting protrusion 123 is supported and installed on the supporting groove 124, and the bottom of the liquid outlet nozzle 13 is lower than the liquid level in the cleaning circular cabin 122. Figure 2 When washing is needed, the connecting rod 117 is moved upwards, so that there is a gap between the tapered rod 111 and the tapered groove 116, and there is also a gap between the lifting valve block 19 and the ladder-shaped groove 18, at this time, the sealing cover 119 seals the liquid inlet 118, the gas suction pump 121 sucks the gas, so that the inside of the filter cylinder cabin 11 and the inner filter cabin 114 are in a negative pressure state, the water in the cleaning circular cabin 122 is driven into the filter cylinder cabin 11 and the inner filter cabin 114 through the liquid outlet nozzle 13, and repeated suction is performed to wash the inner wall of the filter cylinder cabin 11 and the inner filter cabin 114, and also to wash the filter residue in the filter cylinder cabin 11.

[0105] ​

[0106] In the sixth step "separately heat the soda solution and the raffinate, add the heated soda solution into the raffinate to react, and then separate the filter residue after the reaction, and wash and dry to obtain lithium carbonate.", the filter container 1 is taken as an example, and the specific implementation process is as follows:

[0107] As shown in Figure 3 , first, the outlet nozzle 13 (using the second embodiment) is installed on the output cylinder 12, and the inner filter cabin 114 is used as the reaction place of the soda solution and the raffinate;

[0108] As shown in Figure 4 , the connecting rod 117 is moved upwards to drive the conical rod 111 to completely engage with the conical groove 116, the soda solution and the raffinate are heated separately, the heated raffinate is injected into the inner filter cabin 114 from the liquid inlet 118, and then the heated soda solution is injected into the inner filter cabin 114 from the liquid inlet 118, and the reaction occurs, after the reaction is completed, the connecting rod 117 is moved downwards, as shown in Figure 5 , the lifting valve block 19 completely engages with the inner wall of the ladder-shaped groove 18, and there is a gap between the conical rod 111 and the conical groove 116, so that the solution can flow out of the inner filter cabin 114 through the gap and flow into the filter cylinder cabin 11, the gap 17 between the threaded protrusion 16 and the threaded slot 14 is the area for the solution to pass through, and the solution realizes secondary filtration by passing through the gap, and then is discharged through the output cylinder 12 and the outlet nozzle 13;

[0109] The remaining filter residue in the inner filter cabin 114, as shown in Figure 6 , another outlet nozzle 13 (using the first embodiment) is then installed on the output cylinder 12, and the support protrusion 123 is supported and installed on the support slot 124, and the outlet nozzle 13 extends into the water in the cleaning circular cabin 122;

[0110] The connecting rod 117 is moved upwards, so that there is a gap between the conical rod 111 and the conical groove 116, and there is also a gap between the lifting valve block 19 and the ladder-shaped groove 18, at this time, the sealing cover 119 seals the liquid inlet 118, the air pump 121 pumps air, so that the inside of the filter cylinder cabin 11 and the inner filter cabin 114 is in a negative pressure state, and the water in the cleaning circular cabin 122 is driven into the filter cylinder cabin 11 and the inner filter cabin 114 through the outlet nozzle 13, and repeated suction is performed to wash the inner walls of the filter cylinder cabin 11 and the inner filter cabin 114, and also to wash the filter residue in the inner filter cabin 114;

[0111] After the washing is completed, the filter top cover 112 is unscrewed, and then the base 115 and the inner filter cabin 114 are removed in sequence, and the washed lithium carbonate filter residue on the base 115 is taken out.

[0112] In order to avoid the solution from entering into the upper part of the ladder-shaped groove 18 during the solution filtering process, a sealing column 125 can be sleeved on the lifting rod 110, and the sealing column 125 can just seal the opening part of the ladder-shaped groove 18 during the filtering process. During the washing process, the sealing column 125 follows the upward movement and no longer seals the ladder-shaped groove 18.

[0113] The above embodiments are only exemplary embodiments of the present application, and are not used to limit the present application, and the protection scope of the present application is defined by the claims. Those skilled in the art can make various modifications or equivalent replacements to the present application within the spirit and protection scope of the present application, and such modifications or equivalent replacements are also regarded as falling within the protection scope of the present application.

Claims

1. A method for preparing and purifying lithium carbonate by dissolving waste lithium batteries with mixed acids, characterized in that, include: Crude lithium phosphate is obtained by decomposing and processing the positive electrode of waste lithium batteries. Take a certain amount of crude lithium phosphate, add it to a mixed acid obtained by mixing hydrochloric acid and sulfuric acid, adjust the pH of the reaction solution to 1-3, and obtain the first mixture. Stir the first mixture to promote the reaction until all the solid material is dissolved, filter, and obtain a second mixture composed of lithium dihydrogen phosphate, lithium chloride and lithium sulfate. Take a portion of the second mixture into a container, add a measured amount of calcium chloride and react in the container for a period of time, add liquid alkali to adjust the pH value to 10-12, and filter after the reaction to obtain the third mixture; The extractant was washed sequentially with acid solution and aqueous solution. The washed extractant was then mixed with the third mixture and shaken. After shaking, the mixture was separated to obtain the raffinate. The soda ash solution and raffinate were heated separately. The heated soda ash solution was added to the raffinate to react. After the reaction, the residue was separated by filtration, washed and dried to obtain lithium carbonate. The filtration method is implemented in the filtration container; The filter container includes a filter chamber, an output cylinder disposed at the bottom of the filter chamber, and an outlet nozzle threaded onto the bottom of the output cylinder; The bottom of the filter chamber is connected to the output cylinder, and the inner diameter of the output cylinder is smaller than the inner diameter of the filter chamber. The liquid outlet includes two shapes: one is a conical structure with a bottom opening larger than the top opening, and the other is a combination of an inverted cone and a cylinder with a bottom opening smaller than the top opening. The inner wall of the output cylinder is provided with a threaded groove, the output cylinder is provided with a threaded post, the outer wall of the threaded post is provided with a threaded protrusion, the threaded protrusion is fitted into the threaded groove, and the width of the threaded protrusion is smaller than the width of the threaded groove. There is a gap between the threaded protrusion and the threaded groove, allowing the solution inside the filter chamber to enter the bottom of the output cylinder through the gap.

2. The method for preparing and purifying lithium carbonate by dissolving waste lithium batteries with mixed acid according to claim 1, characterized in that, A portion of the second mixture is taken into a container, a measured amount of calcium chloride is added, and the mixture reacts in the container for a period of time. Liquid alkali is added to adjust the pH value to 10-12. After the reaction, the mixture is filtered to obtain the third mixture, which includes: Place the second mixture into a container and heat it in a water bath at 50°C while stirring. Calculate the amount of calcium chloride to be added based on the phosphate content in the second mixture, and add the required amount of calcium chloride according to the calculation results, then stir. After stirring, add liquid alkali to bring the pH of the solution to 10-12, and continue stirring. After stirring, the mixture is filtered to separate the calcium phosphate residue, resulting in a third mixture composed of lithium chloride and lithium sulfate.

3. The method for preparing and purifying lithium carbonate by dissolving waste lithium batteries with mixed acid according to claim 2, characterized in that, The filtering method includes: The solution to be filtered is subjected to a first filtration and a second filtration in sequence, so as to filter out filter residues with progressively smaller sizes in the first filtration layer and the second filtration layer respectively. Negative pressure is created in the first and second filter layers to draw water and clean the filter residue. After rinsing, remove the filter residue.

4. The method for preparing and purifying lithium carbonate by dissolving waste lithium batteries with mixed acid according to claim 1, characterized in that, The threaded column has a trapezoidal groove inside, and the inner diameter of the bottom of the trapezoidal groove is smaller than the inner diameter of the top of the trapezoidal groove; A lifting valve block is movably disposed within the trapezoidal groove. At least part of the outer wall of the lifting valve block fits into the inner wall of the bottom of the trapezoidal groove. A lifting rod is connected to the lifting valve block, and a tapered rod is connected to the lifting rod. An external thread is provided on the outer periphery of the top opening of the filter chamber, and a filter top cover is threaded onto the threaded portion. A threaded ring seat is provided at the bottom of the filter top cover, and an inner filter chamber is threaded onto the inner thread of the threaded ring seat. A base is threaded onto the bottom of the inner filter chamber, and a tapered groove is formed on the base. A tapered rod passes through the tapered groove, and the outer wall of the tapered rod fits into the inner wall of the tapered groove. A connecting rod is provided at the top of the tapered rod, and the connecting rod passes through the filter top cover.

5. The method for preparing and purifying lithium carbonate by dissolving waste lithium batteries with mixed acid according to claim 4, characterized in that, The inner diameter of the upper part of the conical groove is smaller than the inner diameter of the lower part of the conical groove.

6. The method for preparing and purifying lithium carbonate by dissolving waste lithium batteries with mixed acid according to claim 5, characterized in that, The filter top cover is provided with a liquid inlet, and a sealing cap is threaded onto the liquid inlet. The liquid inlet faces the inside of the inner filter chamber. The filter top cover is also provided with two extraction ports, which face the inside of the filter cartridge chamber and the inside of the inner filter chamber, respectively. An air pump is connected to the external of the extraction port.

7. The method for preparing and purifying lithium carbonate by dissolving waste lithium batteries with mixed acid according to claim 6, characterized in that, A cleaning chamber is provided outside the filter cartridge chamber, and water is stored inside the cleaning chamber. A support protrusion is provided on the outer wall of the filter cartridge chamber, and a support groove is provided on the inner wall of the opening of the cleaning chamber. The support protrusion is supported and installed on the support groove. The bottom of the liquid outlet is lower than the liquid level inside the cleaning chamber.

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