Device system and method for preparing high-purity lithium carbonate through deep carbonization-pyrolysis of micron / nano bubbles

Abstract

The invention provides a device system and method for preparing high-purity lithium carbonate through micron / nano bubble deep carbonization-pyrolysis. The device system comprises a slurrying device, a first-stage deep carbonization device, a second-stage deep carbonization device, a pyrolysis device, a nano bubble generator, a first-stage micro bubble generator and a second-stage micro bubble generator. The slurrying device, the first-stage deep carbonization device, the second-stage deep carbonization device and the pyrolysis device are sequentially connected along the material flow direction; the first-stage deep carbonization device is bidirectionally connected with the first-stage microbubble generator; the secondary deep carbonization device is bidirectionally connected with the nano bubble generator; and the pyrolysis device is bidirectionally connected with the secondary microbubble generator. A micro-bubble generator or a nano-bubble generator is introduced into the first-stage deep carbonization device, the second-stage deep carbonization device and the pyrolysis device, so that the CO2 mass transfer rate is increased, the deep carbonization of lithium carbonate and the pyrolysis process of lithium bicarbonate are enhanced, and a uniform and fine high-purity lithium carbonate product can be efficiently prepared.

Description

Technical Field

[0001] This invention belongs to the field of high-purity lithium carbonate preparation technology, and relates to an apparatus system and method for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. Background Technology

[0002] High-purity lithium carbonate is a key raw material for preparing high-end lithium-ion battery materials, and its quality and price directly determine the battery's performance and cost. The existing main production process uses lithium hydroxide monohydrate or industrial-grade lithium carbonate as raw materials, employing traditional high-temperature CO2 carbonation pyrolysis to produce high-purity lithium carbonate. However, this process suffers from slow carbonation rates, low carbon dioxide utilization, and low pyrolysis efficiency, and the resulting lithium carbonate particles are small, easily agglomerating, clumping, or granulating. Replacing atmospheric pressure carbonation and conventional pyrolysis with pressurized carbonation and pressurized pyrolysis can effectively improve carbon dioxide utilization and pyrolysis efficiency, but this increases equipment and process costs.

[0003] CN115872422A discloses a method for preparing battery-grade lithium carbonate using microbubbles-enhanced carbon dioxide reaction crystallization. The method involves passing CO2 microbubbles into a mixed solution composed of a lithium-rich solution and NH3∙H2O to perform a gas-liquid reaction crystallization to prepare battery-grade lithium carbonate. CN117263215A discloses a method for preparing high-purity lithium carbonate from an acidic lithium-containing solution. This method sequentially involves resin neutralization, deep purification by adding an alkaline solution and resin neutralization, precipitation of lithium carbonate, and resin neutralization to obtain lithium carbonate. The lithium carbonate is then sequentially subjected to enhanced carbonation using carbon dioxide nanobubbles and a packed reactor, further resin purification, internal slurry circulation for defoaming, and enhanced pyrolysis with additives. After multiple carbonization, impurity removal, and pyrolysis processes, high-purity lithium carbonate is obtained.

[0004] The above-mentioned process mainly utilizes CO2 microbubbles to enhance the deep carbonation process of lithium carbonate, without considering the enhanced escape of CO2 during the pyrolysis process or the recycling of CO2 during the deep carbonation-pyrolysis process. This results in the lithium carbonate product having a larger particle size and a lower recovery rate. Summary of the Invention

[0005] The purpose of this invention is to provide an apparatus system and method for preparing high-purity lithium carbonate through deep carbonization-pyrolysis using micron / nano bubble technology. By introducing microbubble generators or nanobubble generators into the primary deep carbonization device, secondary deep carbonization device, and pyrolysis device, the CO2 mass transfer rate is accelerated, the deep carbonization of lithium carbonate and the pyrolysis process of lithium bicarbonate are enhanced, and by controlling relevant parameters, uniform and fine high-purity lithium carbonate products can be efficiently prepared.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides an apparatus system for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubble, the apparatus system comprising a slurry preparation device, a primary deep carbonization device, a secondary deep carbonization device, a pyrolysis device, a nano bubble generator, a primary micro bubble generator, and a secondary micro bubble generator;

[0008] The pulping device, the primary deep carbonization device, the secondary deep carbonization device, and the pyrolysis device are connected sequentially along the material flow direction;

[0009] The primary deep carbonization device is bidirectionally connected to the primary microbubble generator.

[0010] The secondary deep carbonization device is bidirectionally connected to the nanobubble generator;

[0011] The pyrolysis device is bidirectionally connected to the secondary microbubble generator.

[0012] The device system provided by this invention accelerates the CO2 mass transfer rate and enhances the deep carbonation of lithium carbonate and the pyrolysis process of lithium bicarbonate by introducing microbubble generators or nanobubble generators into the primary deep carbonation device, the secondary deep carbonation device, and the pyrolysis device, thereby enabling the efficient preparation of uniform and fine high-purity lithium carbonate products.

[0013] It should be noted that by setting up a two-stage deep carbonization device, the first stage controls the slurry to be neutral to slightly alkaline, and uses microbubbles of 50μm-300μm for carbonization, mainly for efficient CO2 absorption and inert gas separation; the second stage controls the slurry to be weakly acidic, and uses nanobubbles of 50nm-500nm for carbonization, mainly for the full carbonization of lithium carbonate into lithium bicarbonate; thus, it can not only achieve efficient deep carbonization of lithium carbonate, but also help improve the purity and recovery rate of lithium carbonate products.

[0014] Preferably, the pulping device is independently equipped with a crude lithium carbonate inlet and a purified mother liquor inlet.

[0015] Preferably, the N2 outlet of the primary deep carbonization device is connected to the air inlet of the secondary microbubble generator.

[0016] Preferably, the outlet of the CO2 and N2 mixed gas in the secondary deep carbonization device is connected to the inlet of the primary microbubble generator.

[0017] Preferably, the outlet of the CO2 and N2 mixture in the pyrolysis device is independently connected to the inlet of the primary microbubble generator and the inlet of the nanobubble generator, respectively.

[0018] It should be noted that the device system does not require high-purity CO2 gas, external CO2 / N2 separation devices, or reagents. It achieves the recycling of CO2 and water within the entire system, and the overall process generates no wastewater or waste gas. It has the advantages of being green, low-carbon, and highly efficient.

[0019] Preferably, the first microbubble generated in the primary microbubble generator is a mixture of CO2 and N2 microbubbles.

[0020] Preferably, the average particle size of the first microbubble is 50μm to 300μm, for example, it can be 60μm, 80μm, 100μm, 120μm, 140μm, 150μm, 160μm, 180μm, 200μm, 220μm, 240μm, 250μm, 260μm or 280μm, etc.

[0021] Preferably, the volume content of CO2 in the first microbubble is 30% to 40%, for example, it can be 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38% or 39%, etc.

[0022] Preferably, the nanobubbles generated in the nanobubble generator are mixed nanobubbles of CO2 and N2.

[0023] Preferably, the average particle size of the nanobubbles is 50nm~500nm, for example, it can be 60nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm or 450nm, etc.

[0024] Preferably, the volume content of CO2 in the nanobubbles is 50% to 60%, for example, it can be 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58% or 59%, etc.

[0025] Preferably, the second microbubbles generated in the secondary microbubble generator are mixed microbubbles of CO2 and N2.

[0026] Preferably, the average particle size of the second microbubble is 50μm to 200μm, for example, it can be 60μm, 80μm, 100μm, 120μm, 140μm, 150μm, 160μm or 180μm, etc.

[0027] Preferably, the volume content of CO2 in the second microbubble is 0.2% to 2%, for example, it can be 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.6% or 1.8%, etc.

[0028] It should be noted that the gas source generated by the microbubble generator or nanobubble generator contains CO2 and N2. Using micro / nanobubbles containing CO2 and N2 for deep carbonization of lithium carbonate greatly reduces the carbonization time and improves CO2 utilization efficiency and carbonization rate. The microbubbles containing N2 can promote the rapid escape of CO2 generated by the decomposition of lithium bicarbonate through "gas lift". Furthermore, by controlling the N2 microbubble content, the decomposition rate of lithium bicarbonate and the nucleation and growth of lithium carbonate can be controlled, thereby producing uniform and fine lithium carbonate products.

[0029] It should also be noted that CO2 and N2 gases can be separated and recycled by adjusting the size of the bubbles.

[0030] Preferably, the device system further includes a filtration device and a purification device.

[0031] Preferably, the pyrolysis device is connected in sequence to a filtration device and a purification device.

[0032] Preferably, the impurity removal device is connected to the pulping device.

[0033] Preferably, the filtration device is provided with a high-purity lithium carbonate outlet.

[0034] In a second aspect, the present invention provides a method for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles, wherein the method is performed using the apparatus system described in the first aspect, and the method includes:

[0035] (1) Crude lithium carbonate and purified mother liquor are fed into a pulping device for mixing and pulping to obtain lithium carbonate slurry. Then, the lithium carbonate slurry is fed into a first-stage deep carbonization device for first-stage deep carbonization and a second-stage deep carbonization device for second-stage deep carbonization to obtain lithium bicarbonate solution.

[0036] In the first stage of deep carbonization, the first microbubbles generated by the first stage microbubble generator are introduced into the first stage deep carbonization device, and in the second stage of deep carbonization, the nanobubbles generated by the nanobubble generator are introduced into the second stage deep carbonization device.

[0037] (2) The lithium bicarbonate solution described in step (1) is passed into a pyrolysis device for pyrolysis to obtain lithium carbonate crystals;

[0038] During pyrolysis, the second microbubbles generated by the secondary microbubble generator are introduced into the pyrolysis device.

[0039] The method provided by this invention sequentially involves mixing and slurrying, primary deep carbonization, secondary deep carbonization, and pyrolysis. It combines the use of first microbubbles and nanobubbles to enhance the deep carbonization of lithium carbonate, and second microbubbles to enhance the pyrolysis of lithium bicarbonate, thereby obtaining lithium carbonate crystals. The method features mild reaction conditions, simple operation, and high carbonization and pyrolysis efficiency, producing high-purity lithium carbonate products.

[0040] Preferably, the mass ratio of crude lithium carbonate to purified mother liquor in step (1) is 1:(1~100), for example, it can be 1:5, 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80 or 1:90, etc.

[0041] Preferably, the crude lithium carbonate in step (1) contains ≥98% lithium carbonate, for example, 98.1%, 98.2%, 98.3%, 98.4%, 98.5%, 98.6%, 98.7% or 98.8%.

[0042] Preferably, the stirring speed of the mixed slurry in step (1) is 200 rpm to 400 rpm, for example, it can be 220 rpm, 240 rpm, 260 rpm, 280 rpm, 300 rpm, 320 rpm, 340 rpm, 360 rpm or 380 rpm, etc.

[0043] Preferably, the ratio of the inlet flow rate of the primary microbubble generator in step (1) to the mass of crude lithium carbonate is (0.4~0.8):1m 3 / kg, for example, could be 0.45:1m 3 / kg, 0.5:1m 3 / kg, 0.55:1m 3 / kg, 0.6:1m 3 / kg, 0.65:1m 3 / kg or 0.7:1m 3 / kg, etc.

[0044] Preferably, the pH value of the first-stage deep carbonization in step (1) is 7~9, for example, it can be 7.2, 7.5, 7.6, 7.8, 8, 8.2, 8.5, 8.6 or 8.8, etc.

[0045] Preferably, the temperature of the first-stage deep carbonization in step (1) is 10℃~40℃, for example, it can be 12℃, 15℃, 18℃, 20℃, 22℃, 25℃, 28℃, 30℃, 32℃, 35℃ or 38℃, etc.

[0046] Preferably, the stirring speed of the first-stage deep carbonization in step (1) is 300 rpm to 400 rpm, for example, it can be 310 rpm, 320 rpm, 330 rpm, 340 rpm, 350 rpm, 360 rpm, 370 rpm, 380 rpm or 390 rpm.

[0047] Preferably, the time for the first-stage deep carbonization in step (1) is 0.5h to 2h, for example, it can be 0.6h, 0.8h, 1h, 1.2h, 1.5h, 1.6h or 1.8h.

[0048] Preferably, the N2 generated by the first-stage deep carbonization in step (1) is recycled into the second-stage microbubble generator.

[0049] Preferably, the ratio of the inlet flow rate of the nanobubble generator to the mass of crude lithium carbonate in step (1) is (0.1~0.4):1m 3 / kg, for example, could be 0.15:1m 3 / kg, 0.2:1m 3 / kg, 0.25:1m 3 / kg, 0.3:1m 3 / kg or 0.35:1m 3 / kg, etc.

[0050] Preferably, the pH value of the secondary deep carbonization in step (1) is 5.5 to 6.5, for example, it can be 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3 or 6.4, etc.

[0051] It should be noted that by adjusting the pH range of the primary and secondary deep carbonization processes, not only can CO2 and N2 gases be separated and recycled, but the purity and overall recovery rate of lithium carbonate products can also be improved.

[0052] Preferably, the temperature of the secondary deep carbonization in step (1) is 10℃~40℃, for example, it can be 12℃, 15℃, 18℃, 20℃, 22℃, 25℃, 28℃, 30℃, 32℃, 35℃ or 38℃, etc.

[0053] Preferably, the stirring speed of the secondary deep carbonization in step (1) is 300 rpm to 400 rpm, for example, it can be 310 rpm, 320 rpm, 330 rpm, 340 rpm, 350 rpm, 360 rpm, 370 rpm, 380 rpm or 390 rpm.

[0054] Preferably, the time for the secondary deep carbonization in step (1) is 1h to 2h, for example, it can be 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h or 1.8h.

[0055] Preferably, the CO2 and N2 generated by the secondary deep carbonization in step (1) are recycled into the primary microbubble generator.

[0056] Preferably, the ratio of the air inlet flow rate of the secondary microbubble generator in step (2) to the mass of crude lithium carbonate is (0.2~0.5):1m 3 / kg, for example, could be 0.25:1m 3 / kg, 0.3:1m 3 / kg, 0.35:1m 3 / kg, 0.4:1m 3 / kg or 0.45:1m 3 / kg, etc.

[0057] Preferably, the pyrolysis temperature in step (2) is 90℃~105℃, for example, it can be 92℃, 94℃, 95℃, 96℃, 98℃, 100℃, 102℃ or 104℃, etc.

[0058] Preferably, the stirring speed of the pyrolysis in step (2) is 200 rpm to 400 rpm, for example, it can be 220 rpm, 240 rpm, 250 rpm, 260 rpm, 280 rpm, 300 rpm, 320 rpm, 340 rpm, 350 rpm, 360 rpm or 380 rpm, etc.

[0059] Preferably, the pyrolysis time in step (2) is 2h to 4h, for example, it can be 2.2h, 2.5h, 2.6h, 2.8h, 3h, 3.2h, 3.5h, 3.6h or 3.8h.

[0060] Preferably, the CO2 and N2 generated by the pyrolysis in step (2) are recycled into the primary microbubble generator and the secondary microbubble generator.

[0061] Preferably, the method further includes step (3):

[0062] The lithium carbonate crystals described in step (2) are passed into a filtration device for filtration to obtain high-purity lithium carbonate product and mother liquor. The mother liquor is then passed into a purification device for purification, and the purified mother liquor is reused in the pulping device.

[0063] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] (1) The device system provided by the present invention introduces a microbubble generator or nanobubble generator containing a mixed gas source of CO2 and N2 into the first-stage deep carbonization device, the second-stage deep carbonization device and the pyrolysis device to accelerate the CO2 mass transfer rate, enhance the deep carbonization of lithium carbonate and the pyrolysis process of lithium bicarbonate, and thus can efficiently produce uniform and fine high-purity lithium carbonate products.

[0066] (2) The device system provided by the present invention does not require high-purity CO2 gas, external CO2 / N2 separation device and reagents, realizes the recycling of CO2 and water in the whole system, and the overall process generates no wastewater or waste gas, and has the advantages of being green, low-carbon and efficient.

[0067] (3) The method provided by the present invention combines a process of mixing pulp, primary deep carbonization, secondary deep carbonization and pyrolysis, and utilizes the first microbubble and nanobubble to enhance the deep carbonization of lithium carbonate and the second microbubble to enhance the pyrolysis of lithium bicarbonate, to obtain a lithium carbonate product with a content of >99.9%, an average D90 particle size of <85μm and an overall recovery rate of >77%. Attached Figure Description

[0068] Figure 1 A schematic diagram of the apparatus system for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles provided in Example 1;

[0069] Among them, 1-pulping device, 2-first-stage deep carbonization device, 3-second-stage deep carbonization device, 4-pyrolysis device, 5-filtration device, 6-impurity removal device, 7-first-stage microbubble generator, 8-nanobubble generator, and 9-second-stage microbubble generator. Detailed Implementation

[0070] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0071] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0072] Example 1

[0073] This embodiment provides an apparatus system for preparing high-purity lithium carbonate through deep carbonization-pyrolysis of micron / nanobubbles, such as... Figure 1 As shown, the device system includes a pulping device 1, a primary deep carbonization device 2, a secondary deep carbonization device 3, a pyrolysis device 4, a nanobubble generator 8, a primary microbubble generator 7, a secondary microbubble generator 9, a filtration device 5, and a purification device 6.

[0074] The pulping device 1, the primary deep carbonization device 2, the secondary deep carbonization device 3, and the pyrolysis device 4 are connected sequentially along the material flow direction; the primary deep carbonization device 2 is bidirectionally connected to the primary microbubble generator 7; the secondary deep carbonization device 3 is bidirectionally connected to the nanobubble generator 8; the pyrolysis device 4 is bidirectionally connected to the secondary microbubble generator 9; the pyrolysis device 4 is sequentially connected to the filtration device 5 and the impurity removal device 6; the impurity removal device 6 is connected to the pulping device 1.

[0075] The pulping device 1 is independently equipped with a crude lithium carbonate inlet and a purified mother liquor inlet; the N2 outlet of the primary deep carbonization device 2 is connected to the air inlet of the secondary microbubble generator 9; the mixed gas outlet of CO2 and N2 in the secondary deep carbonization device 3 is connected to the air inlet of the primary microbubble generator 7; the mixed gas outlet of CO2 and N2 in the pyrolysis device 4 is independently connected to the air inlet of the primary microbubble generator 7 and the air inlet of the nanobubble generator 8; the filtration device 5 is equipped with a high-purity lithium carbonate outlet.

[0076] The first microbubble generated in the primary microbubble generator 7 is a mixture of CO2 and N2 microbubbles; the average particle size of the first microbubble is 100 μm; and the volume content of CO2 in the first microbubble is 40%.

[0077] The nanobubbles generated in the nanobubble generator 8 are mixed nanobubbles of CO2 and N2; the average particle size of the nanobubbles is 200 nm; and the volume content of CO2 in the nanobubbles is 50%.

[0078] The second microbubble generated in the secondary microbubble generator 9 is a mixture of CO2 and N2 microbubbles; the average particle size of the second microbubble is 50 μm; and the volume content of CO2 in the second microbubble is 1%.

[0079] Example 2

[0080] This embodiment provides an apparatus system for preparing high-purity lithium carbonate through deep carbonization-pyrolysis of micron / nanobubbles. The system includes a first microbubble generated in the primary microbubble generator, which is a mixture of CO2 and N2 microbubbles; the average particle size of the first microbubble is 300 μm; and the volume content of CO2 in the first microbubble is 30%.

[0081] The nanobubbles generated in the nanobubble generator are a mixture of CO2 and N2; the average particle size of the nanobubbles is 50 nm; and the volume content of CO2 in the nanobubbles is 55%.

[0082] The second microbubble generated in the secondary microbubble generator is a mixture of CO2 and N2 microbubbles; the average particle size of the second microbubble is 100 μm; except that the volume content of CO2 in the second microbubble is 2%, all other conditions are the same as in Example 1.

[0083] Example 3

[0084] This embodiment provides an apparatus system for preparing high-purity lithium carbonate through deep carbonization-pyrolysis of micron / nanobubbles. The first microbubble generated in the primary microbubble generator is a mixture of CO2 and N2 microbubbles; the average particle size of the first microbubble is 50 μm; and the volume content of CO2 in the first microbubble is 35%.

[0085] The nanobubbles generated in the nanobubble generator are mixed nanobubbles of CO2 and N2; the average particle size of the nanobubbles is 500 nm; and the volume content of CO2 in the nanobubbles is 60%.

[0086] The second microbubble generated in the secondary microbubble generator is a mixture of CO2 and N2 microbubbles; the average particle size of the second microbubble is 200 μm; except that the volume content of CO2 in the second microbubble is 0.2%, all other conditions are the same as in Example 1.

[0087] Example 4

[0088] This embodiment provides an apparatus system for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. Except that the average particle size of the second microbubble is 900 μm, all other conditions are the same as in Example 1.

[0089] Example 5

[0090] This embodiment provides an apparatus system for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. Except that the first and second microbubbles are both CO2 microbubbles and the nanobubbles are CO2 nanobubbles, all other conditions are the same as in Example 1.

[0091] Comparative Example 1

[0092] This comparative example provides an apparatus system for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. Except for adjusting that the primary deep carbonization device, the secondary deep carbonization device, and the pyrolysis device are all bidirectionally connected to the CO2 microbubble generator, and the average particle size of the CO2 microbubbles is 100 μm, all other conditions are the same as in Example 1.

[0093] Comparative Example 2

[0094] This comparative example provides an apparatus system for preparing high-purity lithium carbonate through deep carbonization-pyrolysis of micron / nanobubbles. Except for adjusting the bidirectional connection between the secondary deep carbonization device and the third microbubble generator, the third microbubbles generated in the third microbubble generator are mixed microbubbles of CO2 and N2; the average particle size of the third microbubbles is 100 μm; and the volume content of CO2 in the third microbubbles is 40%, all other conditions are the same as in Example 1.

[0095] Comparative Example 3

[0096] This comparative example provides an apparatus system for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nanobubbles. Except for adjusting the bidirectional connection between the primary deep carbonization device and the nanobubble generator, the nanobubbles generated in the nanobubble generator are mixed nanobubbles of CO2 and N2; the average particle size of the nanobubbles is 200 nm; and the volume content of CO2 in the nanobubbles is 50%, all other conditions are the same as in Example 1.

[0097] Comparative Example 4

[0098] This comparative example provides an apparatus system for preparing high-purity lithium carbonate through deep carbonization-pyrolysis of micron / nanobubbles. Except for adjusting the bidirectional connection between the pyrolysis device and the nanobubble generator; the nanobubbles generated in the nanobubble generator are mixed nanobubbles of CO2 and N2; the average particle size of the nanobubbles is 100 nm; and the volume content of CO2 in the nanobubbles is 1%, all other conditions are the same as in Example 1.

[0099] Comparative Example 5

[0100] This comparative example provides an apparatus system for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. Except for the absence of a secondary deep carbonization device and a nanobubble generator bidirectionally connected to it, all other conditions are the same as in Example 1.

[0101] Application Example 1

[0102] This application example provides a method for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. The method is carried out using the apparatus system provided in Example 1, and includes the following steps:

[0103] (1) Crude lithium carbonate (lithium carbonate content of 98.8%) and purified mother liquor were fed into a slurry mixing device at a mass ratio of 1:50 and mixed at a stirring speed of 300 rpm to obtain lithium carbonate slurry. The lithium carbonate slurry was then fed into a primary deep carbonization device at a temperature of 30°C, a stirring speed of 400 rpm, and a pH of 8 for 1 hour and into a secondary deep carbonization device at a temperature of 30°C, a stirring speed of 350 rpm, and a pH of 6 for 1.5 hours to obtain lithium bicarbonate solution.

[0104] In the first-stage deep carbonization process, the first microbubbles generated by the first-stage microbubble generator are introduced into the first-stage deep carbonization device. The ratio of the inlet flow rate of the first-stage microbubble generator to the mass of crude lithium carbonate is 0.7:1m. 3 / kg; the N2 generated during the first-stage deep carbonization is recycled into the second-stage microbubble generator; during the second-stage deep carbonization, nanobubbles generated by the nanobubble generator are introduced into the second-stage deep carbonization device, and the ratio of the inlet flow rate of the nanobubble generator to the mass of crude lithium carbonate is 0.2:1m. 3 / kg; the CO2 and N2 produced by the secondary deep carbonization are recycled to the primary microbubble generator;

[0105] (2) The lithium bicarbonate solution described in step (1) is passed into a pyrolysis device and pyrolyzed for 3 hours at a temperature of 98°C and a stirring speed of 300 rpm to obtain lithium carbonate crystals;

[0106] In this process, the second microbubbles generated by the secondary microbubble generator are introduced into the pyrolysis device, and the ratio of the inlet flow rate of the secondary microbubble generator to the mass of crude lithium carbonate is 0.3:1m³. 3 / kg; the CO2 and N2 produced by pyrolysis are recycled into the primary and secondary microbubble generators;

[0107] (3) The lithium carbonate crystals described in step (2) are passed into a filtration device for filtration to obtain lithium carbonate products and mother liquor. The mother liquor is then passed into a purification device for purification, and the purified mother liquor is reused in the pulping device.

[0108] Application Example 2

[0109] This application example provides a method for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. The method is carried out using the apparatus system provided in Example 2, and includes the following steps:

[0110] (1) Crude lithium carbonate (lithium carbonate content of 98%) and purified mother liquor were fed into a slurry mixing device at a mass ratio of 1:100 and mixed at a stirring speed of 200 rpm to obtain lithium carbonate slurry. The lithium carbonate slurry was then fed into a first-stage deep carbonization device at a temperature of 10°C, a stirring speed of 350 rpm, and a pH of 7 for 0.5 h and into a second-stage deep carbonization device at a temperature of 10°C, a stirring speed of 300 rpm, and a pH of 5.5 for 2 h to obtain lithium bicarbonate solution.

[0111] In the first-stage deep carbonization process, the first microbubbles generated by the first-stage microbubble generator are introduced into the first-stage deep carbonization device. The ratio of the inlet flow rate of the first-stage microbubble generator to the mass of crude lithium carbonate is 0.8:1m. 3 / kg; the N2 generated during the first-stage deep carbonization is recycled into the second-stage microbubble generator; during the second-stage deep carbonization, nanobubbles generated by the nanobubble generator are introduced into the second-stage deep carbonization device, and the ratio of the inlet flow rate of the nanobubble generator to the mass of crude lithium carbonate is 0.1:1m. 3 / kg; the CO2 and N2 produced by the secondary deep carbonization are recycled to the primary microbubble generator;

[0112] (2) The lithium bicarbonate solution described in step (1) is passed into a pyrolysis device and pyrolyzed at a temperature of 90°C and a stirring speed of 400 rpm for 4 hours to obtain lithium carbonate crystals;

[0113] In this process, the second microbubbles generated by the secondary microbubble generator are introduced into the pyrolysis device, and the ratio of the inlet flow rate of the secondary microbubble generator to the mass of crude lithium carbonate is 0.5:1m³. 3 / kg; the CO2 and N2 produced by pyrolysis are recycled into the primary and secondary microbubble generators;

[0114] (3) The lithium carbonate crystals described in step (2) are passed into a filtration device for filtration to obtain lithium carbonate products and mother liquor. The mother liquor is then passed into a purification device for purification, and the purified mother liquor is reused in the pulping device.

[0115] Application Example 3

[0116] This application example provides a method for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. The method is carried out using the apparatus system provided in Example 3, and includes the following steps:

[0117] (1) Crude lithium carbonate (lithium carbonate content of 98.5%) and purified mother liquor were fed into a slurry mixing device at a mass ratio of 1:10 and mixed at a stirring speed of 400 rpm to obtain lithium carbonate slurry. The lithium carbonate slurry was then fed into a primary deep carbonization device at a temperature of 40°C, a stirring speed of 300 rpm, and a pH of 9 for 2 hours and into a secondary deep carbonization device at a temperature of 40°C, a stirring speed of 400 rpm, and a pH of 6.5 for 1 hour to obtain lithium bicarbonate solution.

[0118] In the first-stage deep carbonization process, the first microbubbles generated by the first-stage microbubble generator are introduced into the first-stage deep carbonization device. The ratio of the inlet flow rate of the first-stage microbubble generator to the mass of crude lithium carbonate is 0.4:1m. 3 / kg; the N2 generated during the first-stage deep carbonization is recycled into the second-stage microbubble generator; during the second-stage deep carbonization, nanobubbles generated by the nanobubble generator are introduced into the second-stage deep carbonization device, and the ratio of the inlet flow rate of the nanobubble generator to the mass of crude lithium carbonate is 0.4:1m. 3 / kg; the CO2 and N2 produced by the secondary deep carbonization are recycled to the primary microbubble generator;

[0119] (2) The lithium bicarbonate solution described in step (1) is passed into a pyrolysis device and pyrolyzed at a temperature of 105°C and a stirring speed of 200 rpm for 2 hours to obtain lithium carbonate crystals;

[0120] In this process, the second microbubbles generated by the secondary microbubble generator are introduced into the pyrolysis device, and the ratio of the inlet flow rate of the secondary microbubble generator to the mass of crude lithium carbonate is 0.2:1m³. 3 / kg; the CO2 and N2 produced by pyrolysis are recycled into the primary and secondary microbubble generators;

[0121] (3) The lithium carbonate crystals described in step (2) are passed into a filtration device for filtration to obtain lithium carbonate products and mother liquor. The mother liquor is then passed into a purification device for purification, and the purified mother liquor is reused in the pulping device.

[0122] Application Example 4

[0123] This application example provides a method for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. Except that the method is carried out using the apparatus system provided in Example 4, all other conditions are the same as in Application Example 1.

[0124] Application Example 5

[0125] This application example provides a method for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. Except that the method is carried out using the apparatus system provided in Example 5, all other conditions are the same as in Application Example 1.

[0126] Application Example 6

[0127] This application example provides a method for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. Except for the pH value of 6 in the first-stage deep carbonization described in step (1), all other conditions are the same as in application example 1.

[0128] Application Example 7

[0129] This application example provides a method for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. Except for the pH value of 7.5 for the secondary deep carbonization in step (1), all other conditions are the same as in application example 1.

[0130] Application Example 8

[0131] This application example provides a method for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. Except for the pyrolysis temperature of 80°C in step (2), all other conditions are the same as in application example 1.

[0132] Application Example 9

[0133] This application example provides a method for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. Except for the pyrolysis temperature of 110°C in step (2), all other conditions are the same as in application example 1.

[0134] Compare and contrast examples 1-5

[0135] Comparative Application Examples 1-5 provide a method for preparing high-purity lithium carbonate by deep carbonization-pyrolysis of micron / nano bubbles. Except that the method uses the apparatus system provided in Comparative Examples 1-5, all other conditions are the same as in Application Example 1.

[0136] The performance of the lithium carbonate products obtained in the above application examples and comparative application examples was tested, and the overall recovery rate of lithium carbonate was calculated. The results are shown in Table 1.

[0137] The lithium carbonate content was measured according to the test method of the standard "YS / T 546-2021 High Purity Lithium Carbonate" (100% minus the total measured impurities in the above standard). The average D90 particle size of lithium carbonate was analyzed using a particle size analyzer.

[0138] Overall lithium carbonate recovery rate = (lithium carbonate product quality × content) / (crude lithium carbonate quality × content) × 100.

[0139] Table 1

[0140]

[0141] As shown in Table 1:

[0142] The apparatus and method provided by this invention, by introducing microbubble generators or nanobubble generators into the primary deep carbonization device, the secondary deep carbonization device, and the pyrolysis device, and combining this with the control of relevant parameters, can efficiently prepare uniform, fine, high-purity lithium carbonate products. The resulting lithium carbonate product has a content >99.9%, an average D90 particle size <85μm, and an overall recovery rate >77%.

[0143] By combining Application Example 1 and Application Example 4, and comparing Application Example 4, it can be seen that if the average particle size of the microbubbles introduced during pyrolysis is too large, the number of bubbles will decrease due to the larger particle size of N2 microbubbles, resulting in a reduction in the gas-liquid mass transfer area and a decrease in the CO2 mass transfer rate. The reduced mass transfer rate will reduce the number of lithium carbonate crystal nuclei, leading to a larger average D90 particle size of the lithium carbonate product. The reduced mass transfer rate will also reduce the amount of lithium bicarbonate decomposed, resulting in a significant decrease in recovery rate. If nanobubbles are introduced during pyrolysis, the smaller particle size of N2 nanobubbles and the significantly increased number of bubbles will increase the gas-liquid mass transfer area, leading to a significant increase in the CO2 mass transfer rate and the number of lithium carbonate crystal nuclei, resulting in extremely fine lithium carbonate crystals. After agglomeration, the average D90 particle size of the lithium carbonate product will be larger. The fine lithium carbonate crystals will adsorb impurities and trap mother liquor, affecting the growth of lithium carbonate crystals and leading to a significant decrease in recovery rate.

[0144] A comparison of Application Example 1 and Application Examples 6-7 shows that if the first-stage deep carbonization is carried out under weakly acidic conditions, the conversion efficiency of lithium carbonate is low due to the low pH of the first-stage deep carbonization, and some lithium carbonate fails to be converted into lithium bicarbonate, resulting in low purity and yield of lithium carbonate product. If the second-stage deep carbonization is carried out under weakly alkaline conditions, the remaining lithium carbonate after the first-stage carbonization is difficult to completely convert into lithium bicarbonate under the higher alkaline conditions, resulting in low purity and yield of lithium carbonate product.

[0145] A comparison of Application Examples 1 and 8-9 shows that if the pyrolysis temperature is too low, the slow decomposition rate of lithium bicarbonate will reduce the number of lithium carbonate crystal nuclei, making it easier to form large-sized crystals. Excessive crystal growth can easily trap impurities, leading to a decrease in the content of lithium carbonate products, a larger average D90 particle size, and a significant decrease in recovery rate. If the pyrolysis temperature is too high, the rapid decomposition rate of lithium bicarbonate will greatly increase the number of lithium carbonate crystal nuclei, resulting in extremely fine lithium carbonate grains. These fine crystals will adsorb impurities and trap mother liquor, leading to a decrease in the content of lithium carbonate products. Furthermore, the agglomeration of these fine crystals will result in a slightly larger average D90 particle size.

[0146] A comparison of Application Example 1 and Comparative Application Example 1 shows that if pure CO2 microbubbles are introduced into the primary deep carbonization device, the secondary deep carbonization device, and the pyrolysis device, the CO2 gas produced by the decomposition of lithium bicarbonate can only promote CO2 mass transfer separation through the disturbance of micron and nanobubbles. It cannot accelerate CO2 separation through mass transfer between microbubbles and solution, resulting in a significant decrease in the mass transfer rate. The decrease in the mass transfer rate will reduce the number of lithium carbonate crystal nuclei, making it easier to form large-sized crystals. Excessive crystal growth can easily encapsulate impurities, leading to a decrease in the content of lithium carbonate products and a larger average D90 particle size. The decrease in the mass transfer rate will also reduce the amount of lithium bicarbonate decomposed, thus resulting in a significant decrease in the recovery rate.

[0147] A comparison of Application Example 1 and Comparative Application Examples 2-3 reveals that if both the primary and secondary deep carbonization devices employ microbubbles or nanobubbles, the primary deep carbonization device, using nanobubbles, exhibits reduced stability under alkaline conditions compared to microbubbles, leading to a lower mass transfer rate. Similarly, the secondary deep carbonization device, using microbubbles, also suffers from a lower mass transfer rate compared to nanobubbles. This reduced mass transfer rate results in a small amount of lithium carbonate failing to convert to lithium bicarbonate, and the continued growth of lithium carbonate crystals during subsequent pyrolysis. All of these factors contribute to a larger average D90 particle size in the lithium carbonate product and a significant decrease in recovery rate.

[0148] A comparison of Application Example 1 and Comparative Application Example 5 shows that if only a single-stage deep carbonization device is installed, the purity and yield of the lithium carbonate product produced by subsequent pyrolysis will be low because a large amount of lithium carbonate will not be converted into lithium bicarbonate.

[0149] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A device system for preparing high-purity lithium carbonate through deep carbonization-pyrolysis of micron / nanobubbles, characterized in that, The device system includes a pulping device, a primary deep carbonization device, a secondary deep carbonization device, a pyrolysis device, a nanobubble generator, a primary microbubble generator, and a secondary microbubble generator; The pulping device, the primary deep carbonization device, the secondary deep carbonization device, and the pyrolysis device are connected sequentially along the material flow direction; The primary deep carbonization device is bidirectionally connected to the primary microbubble generator. The secondary deep carbonization device is bidirectionally connected to the nanobubble generator; The pyrolysis device is bidirectionally connected to the secondary microbubble generator.

2. The device system according to claim 1, characterized in that, The pulping device is independently equipped with a crude lithium carbonate inlet and a purified mother liquor inlet; And / or, the N2 outlet in the primary deep carbonization device is connected to the air inlet of the secondary microbubble generator; And / or, the outlet of the CO2 and N2 mixture in the secondary deep carbonization device is connected to the inlet of the primary microbubble generator; And / or, the outlet of the CO2 and N2 mixture in the pyrolysis device is independently connected to the inlet of the primary microbubble generator and the inlet of the nanobubble generator, respectively.

3. The device system according to claim 1, characterized in that, The first microbubble generated in the primary microbubble generator is a mixture of CO2 and N2 microbubbles; The average particle size of the first microbubble is 50 μm to 300 μm; The volume content of CO2 in the first microbubble is 30%~40%.

4. The device system according to claim 1, characterized in that, The nanobubbles generated in the nanobubble generator are mixed nanobubbles of CO2 and N2; The average particle size of the nanobubbles is 50nm~500nm; The CO2 volume content in the nanobubbles is 50%~60%.

5. The device system according to claim 1, characterized in that, The second microbubble generated in the secondary microbubble generator is a mixture of CO2 and N2 microbubbles; The average particle size of the second microbubble is 50 μm to 200 μm; The volume content of CO2 in the second microbubble is 0.2%~2%.

6. The device system according to claim 1, characterized in that, The device system also includes a filtration device and a debris removal device; The pyrolysis device is connected in sequence to the filtration device and the impurity removal device; The impurity removal device is connected to the pulping device; The filtration device is equipped with a high-purity lithium carbonate outlet.

7. A method for preparing high-purity lithium carbonate through deep carbonization-pyrolysis of micron / nanobubbles, characterized in that, The method is performed using the apparatus system according to any one of claims 1-6, and the method includes: (1) Crude lithium carbonate and purified mother liquor are fed into a pulping device for mixing and pulping to obtain lithium carbonate slurry. Then, the lithium carbonate slurry is fed into a first-stage deep carbonization device for first-stage deep carbonization and a second-stage deep carbonization device for second-stage deep carbonization to obtain lithium bicarbonate solution. In the first stage of deep carbonization, the first microbubbles generated by the first stage microbubble generator are introduced into the first stage deep carbonization device, and in the second stage of deep carbonization, the nanobubbles generated by the nanobubble generator are introduced into the second stage deep carbonization device. (2) The lithium bicarbonate solution described in step (1) is passed into a pyrolysis device for pyrolysis to obtain lithium carbonate crystals; During pyrolysis, the second microbubbles generated by the secondary microbubble generator are introduced into the pyrolysis device.

8. The method according to claim 7, characterized in that, The mass ratio of crude lithium carbonate to purified mother liquor in step (1) is 1:(1~100); And / or, the lithium carbonate content in the crude lithium carbonate of step (1) is ≥98%; And / or, the stirring speed of the mixed slurry in step (1) is 200 rpm to 400 rpm; And / or, the ratio of the inlet flow rate of the primary microbubble generator in step (1) to the mass of crude lithium carbonate is (0.4~0.8):1m 3 / kg; And / or, the pH value of the primary deep carbonization in step (1) is 7~9; And / or, the temperature of the first-stage deep carbonization in step (1) is 10℃~40℃; And / or, the stirring speed for the first-stage deep carbonization in step (1) is 300 rpm to 400 rpm; And / or, the time for the first-stage deep carbonization in step (1) is 0.5h~2h; And / or, the N2 generated by the primary deep carbonization in step (1) is recycled into the secondary microbubble generator; And / or, the ratio of the inlet flow rate of the nanobubble generator in step (1) to the mass of crude lithium carbonate is (0.1~0.4):1m 3 / kg; And / or, the pH value of the secondary deep carbonization in step (1) is 5.5~6.5; And / or, the temperature of the secondary deep carbonization in step (1) is 10℃~40℃; And / or, the stirring speed for the secondary deep carbonization in step (1) is 300 rpm to 400 rpm; And / or, the time for the secondary deep carbonization in step (1) is 1h~2h; And / or, the CO2 and N2 generated by the secondary deep carbonization in step (1) are recycled into the primary microbubble generator.

9. The method according to claim 7, characterized in that, In step (2), the ratio of the inlet flow rate of the secondary microbubble generator to the mass of crude lithium carbonate is (0.2~0.5):1m 3 / kg; And / or, the pyrolysis temperature in step (2) is 90℃~105℃; And / or, the stirring speed for the pyrolysis in step (2) is 200 rpm to 400 rpm; And / or, the pyrolysis time in step (2) is 2h~4h; And / or, the CO2 and N2 generated by the pyrolysis in step (2) are recycled into the primary microbubble generator and the secondary microbubble generator.

10. The method according to claim 7, characterized in that, The method further includes step (3): The lithium carbonate crystals described in step (2) are passed into a filtration device for filtration to obtain high-purity lithium carbonate product and mother liquor. The mother liquor is then passed into a purification device for purification, and the purified mother liquor is reused in the pulping device.

Images