System for preparing battery-grade lithium carbonate from black powder

Abstract

The utility model belongs to the technical field of lithium carbonate preparation, and particularly relates to a system for preparing battery grade lithium carbonate from black powder, which comprises a reduction roasting device, a carbonic acid hydrogenation device, a first filter press, a defluorination device, a second filter press and a thermal decomposition device, the front end of the rotary kiln is connected with a black powder bin, the rear end of the rotary kiln is connected with a tail gas treatment device and a spiral discharging machine, the tail gas treatment device is connected with a copper oxide powder filling pipe, and the spiral discharging machine, a carbonic acid hydrogenation device, a first filter press, a defluorination device, a second filter press and a thermal decomposition device are sequentially connected. The reduction roasting device is improved, the tail gas absorption device is additionally arranged, carbon monoxide in tail gas can be converted into non-toxic carbon dioxide, the non-toxic carbon dioxide is used for carbonic acid hydrogenation reaction, zero emission of the tail gas is achieved, and copper oxide powder can be repeatedly utilized through the copper oxide powder filling pipe.

Description

Technical Field

[0001] The utility model belongs to the technical field of lithium carbonate preparation, and specifically relates to a system for preparing battery-grade lithium carbonate from black powder. Background Art

[0002] Battery black powder is an important component of waste lithium batteries, mainly including positive electrode materials, negative electrode materials, a small amount of lithium battery electrolyte, etc. The nickel, cobalt and manganese in the positive electrode materials are all in high valence state. The recovery of valuable metal lithium in black powder is of great significance to achieve energy conservation, emission reduction and sustainable development.

[0003] The existing technology recovers the lithium in black powder mainly in the form of crude lithium carbonate, battery-grade lithium carbonate, and lithium hydroxide. The mainstream processes are divided into two types: wet method and pyrolysis method. The wet method usually involves directly leaching the black powder with an inorganic acid and a reducing agent, then removing impurities from the leachate and finally preparing lithium carbonate or lithium hydroxide. The pyrolysis method usually involves reducing and roasting the black powder and a reducing agent to convert the lithium in the black powder into lithium carbonate, which is then purified to eventually prepare battery-grade lithium carbonate. The purification process is mostly bicarbonation.

[0004] However, the defects of the prior art are that the main improvement of the black powder lithium extraction system is to solve the problems of low carbon dioxide utilization and lithium carbonate crystal deposition in the bicarbonation process, which is mainly achieved by connecting multi-stage carbonization kettles, improving the stirring device, the carbon dioxide intake method, and improving other structures of the carbonization kettle. However, for the production equipment for recovering lithium by the above-mentioned pyrometallurgical process, the treatment of the reduction roasting tail gas, especially the carbon monoxide that may be produced, and the problem of easy agglomeration of materials at the beginning and end of the reduction roasting are generally not considered. At the same time, there are generally disadvantages of low overall safety of the equipment and inconvenient monitoring of the reaction process.

[0005] The information disclosed in this background technology section is only intended to increase the understanding of the overall background of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to a person skilled in the art. Utility Model Content

[0006] The utility model provides a system for preparing battery-grade lithium carbonate from black powder, aiming to solve the technical problems pointed out in the above background technology.

[0007] In order to achieve the above object, the technical solution of the utility model is:

[0008] A system for preparing battery-grade lithium carbonate from black powder, comprising a reduction roasting device, a bicarbonation device, a first filter press, a defluorination device, a second filter press and a thermal decomposition device.

[0009] The reduction roasting device comprises a rotary kiln, an exhaust gas treatment device, a black powder silo and a spiral discharging machine. The front end of the rotary kiln is connected to the black powder silo, and the rear end of the rotary kiln is connected to the exhaust gas treatment device and the spiral discharging machine.

[0010] The tail gas treatment device is connected to the copper oxide powder filling pipe, and the spiral discharging machine, the bicarbonation device, the first filter press, the defluorination device, the second filter press and the thermal decomposition device are connected in sequence.

[0011] Preferably, the bicarbonation device includes a carbonization kettle, a pure water storage tank and a carbon dioxide storage tank, the spiral discharging machine is connected to the carbonization kettle, and the carbonization kettle is respectively connected to the pure water storage tank, the carbon dioxide storage tank and the first filter press.

[0012] Preferably, the defluorination device comprises a first slag storage tank, a defluorination liquid storage tank and a defluorination agent storage tank, the first slag storage tank is connected to the first filter press, and the defluorination liquid storage tank is respectively connected to the carbonization kettle, the first filter press, the defluorination agent storage tank and the second filter press.

[0013] Preferably, the thermal decomposition device includes a second slag storage tank, a pre-evaporation liquid storage tank, an MVR evaporator, a mother liquor storage tank, a centrifuge and a dryer, the second slag storage tank is connected to the second filter press, the pre-evaporation liquid storage tank is respectively connected to the second filter press and the MVR evaporator, the MVR evaporator is connected to the centrifuge, and the centrifuge is respectively connected to the mother liquor storage tank and the dryer.

[0014] Preferably, the utility model further comprises a second carbon dioxide storage tank, and the second carbon dioxide storage tank is connected to the front end of the rotary kiln.

[0015] Preferably, the tail gas treatment device further comprises a pressure gauge and a safety valve arranged at the rear end of the rotary kiln.

[0016] Preferably, the utility model further comprises a heating chamber and an air intake pipe, and the copper oxide powder filling pipe, the heating chamber and the air intake pipe are connected in sequence.

[0017] Preferably, the copper oxide powder filling tube is provided with a filter screen.

[0018] Due to the adoption of the above technical solution, the beneficial effects of the utility model are:

[0019] 1. The utility model provides a system for preparing battery-grade lithium carbonate from black powder, which can reduce the high-valent metal oxides in the black powder and convert the lithium therein into lithium carbonate. The lithium carbonate is extracted and purified through a subsequent bicarbonation device, and then through a defluorination, thermal decomposition and other devices to produce battery-grade lithium carbonate.

[0020] 2. The utility model improves the reduction roasting device and adds a tail gas absorption device, so that the carbon monoxide in the tail gas can be converted into non-toxic carbon dioxide, and the carbon dioxide is used for the bicarbonation reaction, thereby achieving zero emission of tail gas. The copper oxide powder filling tube is set to achieve repeated utilization of the copper oxide powder.

[0021] 3. The utility model can avoid material agglomeration caused by insufficient reducing atmosphere by controlling the timing of introducing carbon dioxide into the rotary kiln in the reduction roasting device. At the same time, carbon dioxide is reacted with graphite in black powder under high temperature conditions to generate carbon monoxide, which is then used as a reducing agent to undergo redox reaction with the positive electrode material in the black powder. Lithium is converted into lithium carbonate in the reaction process.

[0022] 4. The utility model is provided with a defluorination device to remove fluorine in the feed liquid, which is beneficial to improving the purity of the subsequent lithium carbonate. By improving the carbonization kettle and the defluorination liquid storage tank and adding a sampling port, it is convenient to sample and detect the pH value, chemical composition, etc. of the slurry, so as to facilitate the determination of whether to terminate the reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of equipment connection of the utility model.

[0024] The main component symbols in the figure are explained as follows:

[0025] 1. Reduction roasting device; 11. Rotary kiln; 12. Tail gas treatment device; 13. Black powder silo; 14. Screw discharging machine; 2. Bicarbonation device; 21. Carbonization kettle; 22. Pure water storage tank; 23. Carbon dioxide storage tank one; 24. Circulation pipe; 3. First filter press; 4. Defluorination device; 41. First slag storage tank; 42. Defluorination liquid storage tank; 43. Defluorination agent storage tank; 5. Second filter press; 6. Thermal decomposition device; 61. Second slag storage tank; 62. Pre-evaporation liquid storage tank; 63. MVR evaporator; 64. Mother liquor storage tank; 65. Centrifuge; 66. Dryer; 7. Copper oxide powder filling tube; 8. Carbon dioxide storage tank two; 100. Heating chamber; 200. Air intake pipe. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0027] Example

[0028] like Figure 1As shown, a system for preparing battery-grade lithium carbonate from black powder comprises a reduction roasting device 1, a bicarbonation device 2, a first filter press 3, a defluorination device 4, a second filter press 5 and a thermal decomposition device 6, wherein the reduction roasting device 1 comprises a rotary kiln 11, a tail gas treatment device 12, a black powder silo 13 and a spiral discharger 14, the front end of the rotary kiln 11 is connected with the black powder silo 13, the rear end of the rotary kiln 11 is connected with the tail gas treatment device 12 and the spiral discharger 14, the tail gas treatment device 12 is connected with a copper oxide powder filling pipe 7, the spiral discharger 14, the bicarbonation device 2, the first filter press 3, the defluorination device 4, the second filter press 5 and the thermal decomposition device 6 are connected in sequence; the utility model improves the reduction roasting device and adds a tail gas absorption device 12, so that carbon monoxide in the tail gas can be converted into non-toxic carbon dioxide, and the carbon dioxide is used for the bicarbonation reaction, thereby achieving zero emission of the tail gas, and the copper oxide powder filling pipe 7 is arranged to achieve repeated utilization of the copper oxide powder.

[0029] In this embodiment, the bicarbonation device 2 includes a carbonization kettle 21, a pure water storage tank 22 and a carbon dioxide storage tank 23, the spiral discharger 14 is connected to the carbonization kettle 21, and the carbonization kettle 21 is respectively connected to the pure water storage tank 22, the carbon dioxide storage tank 23 and the first filter press 3; during the bicarbonation reaction, the pH of the slurry can be monitored by sampling. When the pH is basically stable for 0.5h, it can be determined that the carbonization reaction is completed, and its components can also be detected to determine whether to terminate the bicarbonation reaction.

[0030] Specifically, the carbonization kettle 21 is a long columnar structure with two stages connected in series. The two stages of the carbonization kettle 21 are connected by a slurry conveying pipe. The slurry conveying pipe is provided with a conveying pump and a control valve (not shown in the figure). The carbonization kettle 21 is provided with a circulation port, which is connected to the carbonization kettle 21 through a circulation pipe 24 to form a loop; the air inlet pipe connected between the two stages of the carbonization kettle 21 is provided with a vacuum pump and a control valve (not shown in the figure). The setting of the two-stage carbonization kettle can improve the utilization rate of carbon dioxide. The circulation pipe 24 cooperates with the vacuum pump to enhance the bicarbonation reaction, and at the same time, it can also avoid the large-scale crystallization of lithium carbonate, which causes the deposition of lithium carbonate solids in the carbonization kettle 21.

[0031] In this embodiment, the defluorination device 4 includes a first slag storage tank 41, a defluorination liquid storage tank 42 and a defluorination agent storage tank 43. The first slag storage tank 41 is connected to the first filter press 3, and the defluorination liquid storage tank 42 is respectively connected to the carbonization kettle 21, the first filter press 3, the defluorination agent storage tank 43 and the second filter press 5; the defluorination agent can use lime milk or zirconium hydroxide slurry, which is passed into the defluorination liquid storage tank 42 for defluorination reaction; during operation, the pH of the slurry after defluorination can be monitored by sampling. When the pH is basically stable for 0.5h, it can be determined that the defluorination reaction is completed, and its components can also be detected to determine whether to terminate the defluorination reaction.

[0032] In this embodiment, the thermal decomposition device 6 includes a second slag storage tank 61, a pre-evaporation liquid storage tank 62, an MVR evaporator 63, a mother liquor storage tank 64, a centrifuge 65 and a dryer 66. The second slag storage tank 61 is connected to the second filter press 5, the pre-evaporation liquid storage tank 62 is respectively connected to the second filter press 5 and the MVR evaporator 63, the MVR evaporator 63 is connected to the centrifuge 65, and the centrifuge 65 is respectively connected to the mother liquor storage tank 64 and the dryer 66.

[0033] In this embodiment, the utility model also includes a carbon dioxide storage tank 28, which is connected to the front end of the rotary kiln 11; the rotary kiln 11 adopts an electric heating method. In order to prevent the reduction roasting material from easily agglomerating due to insufficient atmosphere in the rotary kiln 11, the carbon dioxide storage tank 28 is arranged at the front end of the rotary kiln 11. When the rotary kiln is running, carbon dioxide can enter the rotary kiln 11 to form a reducing atmosphere. When the reduction roasting is completed, the control valve for the carbon dioxide intake is kept open to maintain the reduction atmosphere in the rotary kiln 11. When the discharge is near the end, the control valve for the carbon dioxide intake is closed to prevent the roasting material from agglomerating in the rotary kiln 11, which in turn leads to insufficient reduction of the black powder. In order to improve the safety of the equipment, a pressure gauge and a safety valve are arranged on the carbon dioxide storage tank 28, which can detect the gas pressure in real time and timely discover and eliminate safety hazards.

[0034] In this embodiment, the exhaust gas treatment device 12 also includes a pressure gauge and a safety valve arranged at the rear end of the rotary kiln 11; in addition, the utility model also includes a heating chamber 100 and an air intake pipe 200, and the copper oxide powder filling pipe 7, the heating chamber 100 and the air intake pipe 200 are connected in sequence; after the reduction roasting is completed, the control valve of the copper oxide powder filling pipe 7 is opened, and the carbon monoxide and the copper oxide powder undergo a redox reaction to be converted into copper element and carbon dioxide. When the reduction roasting is performed again, air or oxygen can be introduced to heat the gas in the heating chamber 100, and the copper element that has been reduced will undergo a redox reaction with the element again, and the copper element will be oxidized again into copper oxide powder to continue to be used for the treatment of carbon monoxide exhaust gas.

[0035] In addition, the copper oxide powder filling tube 7 is provided with a filter (not shown in the figure); the filter is used to separate solid powder and gas, and the filter is connected to the air inlet pipe of the carbonization kettle 21 through a pipeline; during reduction roasting, there may be an excess of reducing agent, and the graphite in the black powder is not completely converted into carbon dioxide, but is entrained with some carbon monoxide, and the carbon monoxide is not fully utilized. Carbon monoxide is a highly toxic gas and is very harmful to the environment and human body. In order to improve the safety of the operation, the utility model converts the inadequately reduced carbon monoxide into non-toxic carbon dioxide gas, and the converted gas and the gas in the carbon dioxide storage tank 23 can be introduced into the carbonization kettle 21 for bicarbonate reaction, thereby improving the utilization rate of carbon dioxide and the safety of the equipment.

[0036] In this embodiment, a refrigeration plate (not shown in the figure) is arranged on the air inlet pipe of the carbonizing kettle 21. Since the solubility of lithium carbonate in water decreases with increasing temperature, in order to improve the bicarbonation effect, the material in the carbonizing kettle 21 can be cooled by the setting of the refrigeration plate, and the temperature in the carbonizing kettle 21 is kept below 35°C to ensure that the lithium ion concentration in the system is increased to about 8g / L after the bicarbonation is completed, and at the same time, a large amount of lithium carbonate crystallization can be avoided, which causes the deposition of crystals in the carbonizing kettle 21; in addition, the air inlet pipe of the carbonizing kettle 21 extends to the lower part of the carbonizing kettle 21 and is distributed around it, and the air inlet pipe is provided with evenly distributed small holes so that the carbon dioxide gas can be fully in contact with the solution to improve the utilization rate of the carbon dioxide.

[0037] The carbonization kettle 21, the defluorination liquid storage tank 42 and the defluorination agent storage tank 43 in the text are all provided with a stirring structure (not shown in the figure), and the stirring structure includes a motor, a hollow stirring shaft and a stirring blade connected in sequence. The middle and lower parts of the hollow stirring shaft and the stirring blades are provided with evenly distributed small holes to increase the contact area between carbon dioxide and the solution and improve the utilization rate of carbon dioxide; the carbonization kettle 21 is also provided with a pressure gauge and a safety valve to improve the safety of the equipment.

[0038] The utility model provides a system for preparing battery-grade lithium carbonate from black powder, which can reduce the high-valent metal oxides in the black powder and convert the lithium therein into lithium carbonate. The lithium carbonate is extracted and purified through a subsequent hydrogenation device, and then the battery-grade lithium carbonate is produced through defluorination, thermal decomposition and other devices.

[0039] The above description is a detailed description of the preferred feasible embodiment of the utility model, but the embodiment is not used to limit the scope of the patent application of the utility model. All equivalent changes or modified changes completed under the technical spirit suggested by the utility model should fall within the patent scope covered by the utility model.

Claims

1. A system for preparing battery-grade lithium carbonate from black powder, characterized in that: The invention comprises a reduction roasting device (1), a bicarbonation device (2), a first filter press (3), a defluorination device (4), a second filter press (5) and a thermal decomposition device (6), The reduction roasting device (1) comprises a rotary kiln (11), an exhaust gas treatment device (12), a black powder silo (13) and a screw discharger (14); the front end of the rotary kiln (11) is connected to the black powder silo (13), and the rear end of the rotary kiln (11) is connected to the exhaust gas treatment device (12) and the screw discharger (14). The tail gas treatment device (12) is connected to the copper oxide powder filling pipe (7), and the screw discharger (14), the bicarbonation device (2), the first filter press (3), the defluorination device (4), the second filter press (5) and the thermal decomposition device (6) are connected in sequence.

2. A system for preparing battery-grade lithium carbonate from black powder as claimed in claim 1, characterized in that: The bicarbonation device (2) comprises a carbonization kettle (21), a pure water storage tank (22) and a carbon dioxide storage tank (23); the screw discharger (14) is connected to the carbonization kettle (21); and the carbonization kettle (21) is respectively connected to the pure water storage tank (22), the carbon dioxide storage tank (23) and the first filter press (3).

3. A system for preparing battery-grade lithium carbonate from black powder as claimed in claim 2, characterized in that: The defluorination device (4) comprises a first slag storage tank (41), a defluorination liquid storage tank (42) and a defluorination agent storage tank (43); the first slag storage tank (41) is connected to the first filter press (3); the defluorination liquid storage tank (42) is respectively connected to the carbonization kettle (21), the first filter press (3), the defluorination agent storage tank (43) and the second filter press (5).

4. A system for preparing battery-grade lithium carbonate from black powder as claimed in claim 1, characterized in that: The thermal decomposition device (6) comprises a second slag storage tank (61), a pre-evaporation liquid storage tank (62), an MVR evaporator (63), a mother liquid storage tank (64), a centrifuge (65) and a dryer (66); the second slag storage tank (61) is connected to the second filter press (5); the pre-evaporation liquid storage tank (62) is respectively connected to the second filter press (5) and the MVR evaporator (63); the MVR evaporator (63) is connected to the centrifuge (65); and the centrifuge (65) is respectively connected to the mother liquid storage tank (64) and the dryer (66).

5. A system for preparing battery-grade lithium carbonate from black powder as claimed in claim 1, characterized in that: It also includes a second carbon dioxide storage tank (8), which is connected to the front end of the rotary kiln (11).

6. A system for preparing battery-grade lithium carbonate from black powder as claimed in claim 1, characterized in that: The tail gas treatment device (12) further comprises a pressure gauge and a safety valve arranged at the rear end of the rotary kiln (11).

7. A system for preparing battery-grade lithium carbonate from black powder as claimed in claim 1, characterized in that: It also comprises a heating chamber (100) and an air intake pipe (200), wherein the copper oxide powder filling pipe (7), the heating chamber (100) and the air intake pipe (200) are connected in sequence.

8. A system for preparing battery-grade lithium carbonate from black powder as claimed in claim 1, characterized in that: The copper oxide powder filling tube (7) is provided with a filter screen.

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