Preparation system and preparation method of large-grain battery-grade lithium carbonate

Abstract

The invention provides a preparation system and a preparation method of large-grain battery-grade lithium carbonate, and relates to the technical field of rotary furnaces. The preparation system comprises a discharging device, a roasting device and a cooling device which are sequentially connected, the roasting device comprises a protective cylinder and a coaxial charging barrel in the protective cylinder, air holes are formed in the inner wall of the charging barrel, the ends of the air holes communicate with a partition cover, the top of the partition cover is connected with a lifting base with an air channel, and first springs are connected between the bottom of the lifting base and the ends of the air holes; and a sealed cavity is arranged between the protective cylinder and the charging barrel. The preparation method comprises the following steps: mixing lithium ore with calcium salt, sulfate and coal water slurry to prepare a forming material; putting the formed material into a preparation system for roasting; grinding the roasted material into powder, and then leaching and separating; adding quick lime and sodium carbonate for impurity removal and filtration to obtain a lithium-containing solution; evaporating and concentrating the lithium-containing solution, then adding a sodium carbonate solution for centrifugal separation, stirring, washing and separating, and drying to obtain lithium carbonate. Lithium ore and salt are uniformly mixed, the roasting efficiency is improved, and the roasting effect is good.

Description

Technical Field

[0001] The invention relates to the technical field of rotary furnaces, and in particular to a preparation system and a preparation method for large-grain battery-grade lithium carbonate. Background Art

[0002] Lithium is the lightest metal in nature. It has physical and chemical properties such as strong electrochemical activity, high specific heat capacity, and high electrical conductivity. It is widely used in new energy materials such as lithium-ion batteries. It is known as the "industrial MSG" and is one of the elements with the most application development potential in the 21st century. Especially with the rapid development of the new energy industry, lithium has become one of the strategic metal elements supporting the realization of the dual carbon goals due to its excellent properties as an "energy metal".

[0003] Lithium carbonate can be used in the manufacture of lithium compounds, enamel and glass. It is the raw material for the production of lithium compounds and metallic lithium and can be used as an additive for the electrolytic bath of aluminum smelting. It is widely used in industries such as glass, ceramics, medicine and food. It can also be used in synthetic rubber, dyes, semiconductors, military defense industry, televisions, atomic energy, medicine, catalysts, etc. It can be used to produce acoustic grade single crystals, optical grade single crystals, and can also be used to treat manic psychosis and make sedatives.

[0004] Lithium carbonate of different purities can be divided into industrial-grade lithium carbonate, battery-grade lithium carbonate and high-purity lithium carbonate. Battery-grade lithium carbonate is mainly used to prepare lithium-ion battery positive electrode materials such as lithium cobalt oxide, lithium manganese oxide, ternary materials and lithium iron phosphate. The main raw material of lithium batteries is battery-grade lithium carbonate. With the advancement of new energy technology, progress and breakthroughs have also begun to be made in the field of transportation. Among them, lithium-ion batteries are the core energy of new energy vehicles and have played a decisive role in the development of new energy vehicles. The use of battery-grade lithium carbonate to prepare lithium batteries has better quality and performance, can reduce interference from the outside world, thereby extending its service life and increasing the actual endurance time, which plays a vital role in the development of the new energy vehicle field.

[0005] At present, the main methods for extracting lithium from lithium ore by roasting are acid roasting and salt roasting. Acid roasting is a method in which lithium ore is fully mixed with acid and then roasted at high temperature to extract lithium. The acid is mainly concentrated sulfuric acid. This method is highly corrosive, requires high equipment, and has high energy consumption, serious pollution, poor operational safety, and great pressure on the environment. It is difficult to meet environmental protection requirements, which restricts its industrial application. Salt roasting is a method in which lithium ore is fully mixed with salt and then roasted at high temperature to extract lithium. Salt roasting has better overcome the corrosive, polluting and safety problems of acid roasting, and is gradually replacing the acid method to become the mainstream method for extracting lithium from lithium ore by roasting.

[0006] In the prior art, lithium ore is roasted by salt method and mixed with salt for reaction. However, the mixture of lithium ore and salt is in powder form and is relatively loose. Even if the mixture is tumbled, the contact area, mixing uniformity and contact tightness between the lithium ore and the salt are difficult to ensure, resulting in insufficient reaction and affecting the efficiency and effect of lithium leaching. Summary of the invention

[0007] The purpose of the present invention is to develop a system and method for preparing large-grain battery-grade lithium carbonate in which lithium ore and salt are evenly mixed and roasting efficiency is improved and roasting effect is good.

[0008] The present invention is achieved through the following technical solutions: A system for preparing large-grain battery-grade lithium carbonate, comprising: The material discharge device is arranged vertically, and the material slides down from the top to the bottom; The roasting device is connected with the feeding device, comprising: Kiln head hood and kiln tail hood; The lower end and the upper end of the inclined casing are connected to the kiln head cover and the kiln tail cover respectively; The barrel is coaxially rotatable in the casing, and its two ends are respectively connected with the kiln head cover and the kiln tail cover in a rotary and sealed manner; A wheel belt is coaxially arranged outside the barrel; A supporting wheel is rotatably mounted on the casing and in rolling contact with the wheel band; A driving source is provided on the casing and drives the barrel to rotate; An igniter, extending into the barrel; A cooling device connected to the roasting device; Among them, the kiln tail hood and the kiln head hood are connected with the bottom of the unloading device and the cooling device respectively, the inner wall of the barrel is evenly covered with a plurality of air holes, and a check structure is provided in the air hole. The check structure allows the airflow to enter the barrel only through the air hole from the outside of the barrel, and the end of the air hole in the barrel is connected with a partition cover, and the top of the partition cover is connected with a lifting seat, and the lifting seat is provided with an air passage passing through it, and a first spring is connected between the bottom of the lifting seat and the end of the air hole, and a sealed cavity is provided between the casing and the barrel, and the cavity is connected with an air inlet pipe for conveying oxygen.

[0009] Optionally, a connecting ring is provided on the top edge of the partition cover, the lifting seat is rotatably provided on the connecting ring, the first spring is connected to the connecting ring, a stirring rod is provided on the outer wall of the lifting seat, a screw connected to the air hole is provided in the partition cover, and the screw is threadedly matched with the lifting seat.

[0010] Optionally, a support plate is provided at the end of the air hole on the inner side of the partition cover, and the support plate is covered with a plurality of through holes. The first spring is connected to the support plate, and the screw is vertically arranged on the top of the support plate and is coaxial with the air hole. The screw passes through the center of the lifting seat.

[0011] Optionally, the top of the lifting seat is spherical, the inner end of the airway is located at the end surface where the lifting seat is rotatably connected to the connecting ring, the outer end of the airway is located at the top of the lifting seat and is radially arranged along the spherical top of the lifting seat, and a limiting ball head is provided at the outer end of the screw. The limiting ball head is spherical and has an outer diameter larger than the screw, and a limiting groove whose shape is adapted to the limiting ball head is provided at the top of the lifting seat.

[0012] Optionally, two annular partitions are provided outside the barrel and are arranged perpendicular to the axial direction of the barrel. The outer wall of the partition is connected to the inner wall of the casing. The inner wall of the partition is rotatably sealed to the outer wall of the barrel. The air hole is arranged on the barrel between the two partitions.

[0013] Optionally, a plurality of baffles are provided between the two baffles at the lower part of the barrel, the baffles are perpendicular to the baffles and arranged radially along the barrel, the inner side edges of the baffles are slidingly sealed with the outer wall of the barrel, the aperture of the air hole is smaller than the thickness of the baffle, and a sealed air cavity is formed between two adjacent baffles in the circumferential direction of the barrel, and the air inlet pipe transports oxygen to part of the sealed air cavity.

[0014] Optionally, the space on the side and top of the barrel where no baffle is provided is a negative pressure chamber, and of the two adjacent sealed air chambers, one is a negative pressure chamber and the other is a boosting chamber, a negative pressure manifold and a boosting manifold are provided outside the protective tube, the negative pressure chamber is connected with the negative pressure manifold through a pipeline, the boosting chamber is connected with the boosting manifold through a pipeline, the air intake pipe is connected with the boosting manifold, the boosting manifold and the negative pressure manifold are connected by a pipeline and a vacuum pump is provided on the pipeline, valves are provided on the pipelines on both sides of the vacuum pump, and air pressure sensors cooperating with the vacuum pump and the valves are provided in the negative pressure chamber and the boosting chamber.

[0015] Optionally, the unloading device includes a hopper, a serpentine hot air pipe is provided at the lower part of the hopper, a smoke chamber is connected to the bottom of the hot air pipe, the smoke chamber is connected to the kiln tail hood, the top of the hot air pipe is connected to two first buffer tanks in sequence, the top of the first buffer tank is provided with an air riser connected to the bottom of the hopper, the top of the air riser is provided with a filter to prevent materials from passing through, a plurality of second buffer tanks arranged in sequence from top to bottom are provided between the top and bottom of the hot air pipe, the second buffer tanks are all located at the bend of the hot air pipe, and an L-shaped hot air pipe section is connected between two upper and lower adjacent second buffer tanks. A feeding pipe is provided at the bottom of the hopper, and the feeding pipe is connected to the bending of the hot air pipe on the sides of the two first buffer tanks. The bottoms of the first buffer tank and the second buffer tank are both connected with a discharge pipe, and the discharge pipe is connected to the bending of the hot air pipe below the first buffer tank or the second buffer tank. The discharge pipe at the bottom of the second buffer tank at the bottom is connected to the smoke chamber, and the diameter of the discharge pipe is smaller than the diameter of the hot air pipe. A return air pipe connected to the upper part of the hot air pipe is provided on the top of the kiln head hood, and an induced draft fan is provided in the return air pipe. An exhaust air pipe is provided on the top of the hopper.

[0016] Optionally, the cooling device includes a cooling box which is disposed at the bottom of the kiln head hood and arranged horizontally, a horizontally arranged conveyor belt is provided in the cooling box, the conveying starting end of the conveyor belt is located at the bottom of the kiln head hood, and the cooling box at the top of the conveying end of the conveyor belt is connected to an induced draft hood, and the induced draft hood is provided with an induced draft duct, a plurality of crushing rollers are rotatably provided at the lower part of the conveying end of the conveyor belt, the conveyor belt is perforated, a plurality of cold air pipes are provided on the inner side of the conveyor belt, and a plurality of air inlet holes are covered on the top of the cold air pipe, a scraper is provided on the top of the lower section of the conveyor belt, the bottom of the scraper is in contact with the top surface of the lower section of the conveyor belt, a plurality of vertically arranged second springs are provided on the top of the scraper, a support rod connected to the cooling box is connected to the top of the second spring, the scraper is inclined in the movement direction of the lower section of the conveyor belt, and the scraper is located at the lower side of the conveying starting end of the conveyor belt.

[0017] A method for preparing large-grain battery-grade lithium carbonate comprises the following steps: S1. The lithium ore crushed material is mixed with calcium salt, sulfate and coal-water slurry to form a mixture, and the mixture is stirred evenly and then allowed to stand for a period of time to homogenize the water content of the mixture and make the overall density uniform; S2. The mixture is pressed or extruded to form a block or spherical molding material; S3. The molding material is placed in the feeding device of the preparation system to prepare for roasting, and the roasted material is obtained after roasting; S4. After the calcined material is ground, the powder is mixed with water to form a slurry and fed to a leaching device to obtain a leachate and lithium slag, and the leachate is filtered to remove impurities; S5. Add quicklime and soda ash to the leachate and mix well, precipitate and remove impurities, and filter to obtain a lithium-containing solution; S6. The lithium-containing solution is evaporated and concentrated to increase the lithium ion concentration; S7. Adding a soda ash solution to precipitate lithium, and then centrifuging, stirring and washing to separate lithium carbonate, the lithium carbonate was dried and crushed to obtain battery-grade lithium carbonate; Wherein, the calcium salt in step S1 is calcium bicarbonate, and both step S1 and step S2 are performed in an environment below 0°C; In step S3, after the molding material enters the feeding device, the temperature of the molding material gradually increases, calcium bicarbonate decomposes to obtain calcium carbonate, carbon dioxide and water, and carbon dioxide gas is released from the molding material so that the molding material has pores. During the process of the molding material falling in the feeding device, it contacts with the smoke generated by the combustion of the igniter to achieve preheating; In the step S3, after the molding material enters the barrel, the igniter roasts the molding material. The molding material contains water-coal slurry, and the molding material is ignited and self-ignites. During this process, the air inlet pipe transports oxygen to the cavity outside the barrel, and the oxygen is transported into the barrel through the pores. The oxygen flows upward from the bottom of the molding material in the barrel. During the process of the pores spraying oxygen, the lifting seat rises and falls accordingly to assist in stirring the molding material. In step S3, the molding material falls into a cooling device from the lower end of the barrel after being sintered, and is cooled, crushed, and then output.

[0018] The beneficial effects of the present invention are: The present invention improves the composition of the molding material by adding calcium bicarbonate and water-coal slurry. The addition of water-coal slurry is not only conducive to controlling the particle size in the molding stage, but also enables the molding material to self-ignite during the roasting process, thereby improving the roasting efficiency and the roasting uniformity. The addition of calcium bicarbonate enables the molding material to have a certain porosity, increases the contact area between the molding material and oxygen, improves the combustion efficiency and uniformity, and enables the material to be burned through without underburning. During the roasting process of the molding material, the barrel rotates so that the air holes circulate through the pressurized chamber and the side of the negative pressure chamber, realizing the lifting and lowering of the diaphragm and the lifting seat. The pressurized chamber is filled with oxygen, and the oxygen is sprayed into the bottom of the material in the barrel by the lifting seat. The lifting seat also stirs the material during the lifting process, which not only increases the oxygen content inside the material, but also improves the combustion efficiency and uniformity of the material, and further improves the fluidity of the material, ensuring the oxygen content in the material, which is conducive to roasting; High-temperature flue gas is introduced into the material discharge device to preheat the material, thereby improving the heat utilization rate. The first buffer tank and the second buffer tank are provided so that the moving speed of the material in the material discharge device can be controlled, thereby increasing the contact time between the material and the high-temperature flue gas and improving the preheating effect. An air source is arranged on the inner side of the conveyor belt of the cooling device, so that the cold air can penetrate the materials upward from the inner side of the conveyor belt, so that the materials at the bottom of the conveyor belt can also exchange heat with the cold air for cooling, thereby improving the cooling efficiency and cooling uniformity of the materials. The scrapers arranged can prevent the accumulation of small-size materials on the inner wall of the conveyor belt, thereby realizing the complete recovery of materials and avoiding the wear of the conveyor belt. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 is a schematic diagram of the structure of the preparation system; Figure 2 is a longitudinal cross-sectional view of the barrel; Figure 3 is a transverse cross-sectional view of the barrel; Figure 4 It is a longitudinal section view of the barrel where the air hole is located; Figure 5 for Figure 1 Enlarged view of point A in the middle.

[0021] Figure numerals: 100, feeding device; 101, hopper; 102, first buffer tank; 103, exhaust pipe; 104, feeding pipe; 105, riser; 106, hot air pipe; 107, feeding pipe; 108, second buffer tank; 109, smoke chamber; 200, roasting device; 201, kiln tail cover; 202, casing; 203, kiln head cover; 204, return air pipe; 205, igniter; 206, barrel; 207, belt; 208, support wheel; 209, partition; 210, baffle; 211, booster chamber; 212, negative pressure chamber; 213, booster Pressure coupling box; 214, negative pressure coupling box; 215, air inlet pipe; 216, vacuum pump; 217, air hole; 218, support plate; 219, screw; 220, first spring; 221, partition cover; 222, connecting ring; 223, lifting seat; 224, stirring rod; 225, limit ball head; 226, air duct; 300, cooling device; 301, cooling box; 302, conveyor belt; 303, induced draft hood; 304, induced draft duct; 305, crushing roller; 306, cold air duct; 307, roller; 308, scraper; 309, second spring; 310, support rod. DETAILED DESCRIPTION

[0022] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0023] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation to the present invention.

[0024] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0025] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0026] like Figure 1~Figure 5 As shown, the present invention discloses a preparation system of large-grain battery-grade lithium carbonate, including a feeding device 100, a roasting device 200 and a cooling device 300. The feeding device 100 includes a hopper 101. A hot air pipe 106 is provided at the lower part of the hopper 101. The hot air pipe 106 is arranged in a serpentine shape. The bottom end of the hot air pipe 106 is connected to a smoke chamber 109. Two first buffer tanks 102 that are at the same horizontal height and connected are provided at the top of the hot air pipe 106. One of the first buffer tanks 102 is connected to the top of the hot air pipe 106, and the top of the other first buffer tank 102 is provided with a riser 105 that is connected to the bottom of the hopper 101. The top of the riser 105 is provided with a filter or other material blocking structure to prevent materials from passing through.

[0027] A plurality of second buffer tanks 108 arranged in sequence from top to bottom are provided between the top and bottom of the hot air pipe 106 . The second buffer tanks 108 are all located at the bends of the hot air pipe 106 , and an L-shaped section of the hot air pipe 106 is connected between two adjacent second buffer tanks 108 .

[0028] A feeding pipe 104 is provided at the bottom of the hopper 101, and the feeding pipe 104 is connected to the bending part of the hot air pipe 106 on the sides of the two first buffer tanks 102. The bottoms of the first buffer tank 102 and the second buffer tank 108 are both connected with a discharge pipe 107, and the discharge pipe 107 is connected to the bending part of the hot air pipe 106 below the first buffer tank 102 or the second buffer tank 108. The discharge pipe 107 at the bottom of the second buffer tank 108 at the bottom is connected to the smoke chamber 109, and the diameter of the discharge pipe 107 is smaller than the diameter of the hot air pipe 106.

[0029] The roasting device 200 includes a barrel 206 which is arranged obliquely, and a protective tube 202 which is coaxial with the barrel 206 is provided at the outer end thereof. A kiln tail cover 201 is provided at the higher end of the barrel 206 and the protective tube 202, and the kiln tail cover 201 is communicated with the smoke chamber 109, and the protective tube 202 is connected with the kiln tail cover 201, and the barrel 206 is connected with the kiln tail cover 201 in a rotary sealing connection, and the barrel 206 is communicated with the smoke chamber 109. A kiln head cover 203 is provided at the lower end of the barrel 206 and the protective tube 202, and the protective tube 202 is connected with the kiln head cover 203, and the barrel 206 is connected with the kiln head cover 203 in a rotary sealing connection. An igniter 205 is provided in the kiln head cover 203, and the igniter 205 extends into the combustion section of the barrel 206 for ignition. A return air pipe 204 is provided on the top of the kiln head cover 203, and the return air pipe 204 is connected to the upper part of the hot air pipe 106. An induced draft fan is provided in the return air pipe 204. An exhaust air pipe 103 is provided on the top of the hopper 101, and the exhaust air pipe 103 is connected to the exhaust gas treatment system. The high-temperature hot air transported by the hot air pipe 106 and the return air pipe 204 is finally sent to the exhaust gas treatment system through the exhaust air pipe 103 for treatment.

[0030] The barrel 206 is coaxially connected to a belt 207 on the outside, and supporting wheels 208 are provided on both sides of the bottom of the belt 207 to roll with it. The supporting wheels 208 are rotatably arranged on the casing 202, and a driving source for driving the barrel 206 is also provided on the casing 202. The driving source can be a motor that drives the supporting wheels 208 to rotate, and the belt 207 is driven to rotate by driving the supporting wheels 208 to rotate and finally the barrel 206 is rotated. The driving source can also be an outer ring gear coaxially arranged on the outer wall of the barrel 206, and a driving gear meshing with the outer ring gear is provided on the side of the outer ring gear and driven to rotate by the motor.

[0031] The interior of the barrel 206 can be divided into a preheating section and a combustion section from high to low. Two partitions 209 are provided outside the barrel 206 of the combustion section. The two partitions 209 are at both ends of the combustion section. The partitions 209 are arranged perpendicular to the axial direction of the barrel 206. The partitions 209 are in a circular ring shape. The outer wall of the partition 209 is connected to the inner wall of the casing 202. The inner wall of the partition 209 is rotationally sealed and connected to the outer wall of the barrel 206. The area between the two partitions 209 is sealed.

[0032] A plurality of baffles 210 are provided between the two baffles 209 at the lower part of the barrel 206. The baffles 210 are perpendicular to the baffles 209 and arranged radially along the barrel 206. The inner side of the baffles 210 is slidably sealed with the outer wall of the barrel 206. A sealed air cavity is formed between two adjacent baffles 210 in the circumferential direction of the barrel 206. The space on the side and upper part of the barrel 206 where the baffles 210 are not provided is a negative pressure cavity 212. Of the two adjacent sealed air cavities, one is a negative pressure cavity 212 and the other is a booster cavity 211.

[0033] A negative pressure manifold 214 and a booster manifold 213 are provided outside the casing 202. The negative pressure chamber 212 is connected to the negative pressure manifold 214 through a pipeline, and the booster chamber 211 is connected to the booster manifold 213 through a pipeline. The booster manifold 213 is also connected to an air inlet pipe 215. The booster manifold 213 is connected to the negative pressure manifold 214 through a pipeline, and a vacuum pump 216 is provided on the pipeline. Valves are provided on the pipelines on both sides of the vacuum pump 216. Air pressure sensors that cooperate with the vacuum pump 216 and the valves are provided in the negative pressure chamber 212 and the booster chamber 211. When the air pressure in the negative pressure chamber 212 rises to a certain level, the vacuum pump 216 operates to evacuate the negative pressure manifold 214, and the gas in the negative pressure chamber 212 is pumped into the booster manifold 213.

[0034] The inner wall of the barrel 206 at the combustion section is evenly covered with multiple air holes 217, the aperture of the air holes 217 is smaller than the thickness of the baffle 210, and a check structure (not shown in the figure) is provided in the air holes 217, which allows the airflow to enter the barrel 206 only from the outside of the barrel 206 through the air holes 217. The end of the air hole 217 in the barrel 206 is connected to a partition 221, and a connecting ring 222 is provided on the top edge of the partition 221. The top of the connecting ring 222 is rotatably connected to a lifting seat 223, and the top of the lifting seat 223 is spherical. A plurality of stirring rods 224 are provided on the outer wall of the lifting seat 223, and a plurality of air passages 226 are provided in the lifting seat 223, the inner end of the air passage 226 is located at the end surface where the lifting seat 223 is rotatably connected to the connecting ring 222, and the outer end of the air passage 226 is located at the top of the lifting seat 223 and is arranged along the radial direction of its spherical top.

[0035] A support plate 218 is provided at the end of the air hole 217 on the inner side of the partition 221. The support plate 218 is covered with a plurality of through holes. A vertically arranged screw rod 219 is provided on the top of the support plate 218. The screw rod 219 is coaxial with the air hole 217. The screw rod 219 passes through the center of the lifting seat 223. The lifting seat 223 is threadedly matched with the screw rod 219. A limiting ball head 225 is provided at the outer end of the screw rod 219. The limiting ball head 225 is spherical and has an outer diameter larger than the screw rod 219. A limiting groove whose shape matches the limiting ball head 225 is provided on the top of the lifting seat 223. A first spring 220 is provided between the connecting ring 222 and the support plate 218. The first spring 220 is sleeved on the outside of the screw rod 219 and is located on the inner side of the partition 221. The two ends of the first spring 220 are fixedly connected to the support plate 218 and the connecting ring 222 respectively.

[0036] The cooling device 300 includes a cooling box 301 disposed at the bottom of the kiln head cover 203. The cooling box 301 is arranged horizontally. A horizontally arranged conveyor belt 302 is arranged in the cooling box 301. The conveying start end of the conveyor belt 302 is located at the bottom of the kiln head cover 203. The materials falling out of the lower end of the barrel 206 enter the kiln head cover 203 and then fall onto the conveyor belt 302 in the cooling box 301. The cooling box 301 at the top of the conveying end of the conveyor belt 302 is connected to the induced draft hood 303. The induced draft hood 303 is provided with an induced draft duct 304 connected to the exhaust gas treatment system. A plurality of crushing rollers 305 are rotatably provided at the lower part of the conveying end of the conveyor belt 302. The materials outputted from the conveying end of the conveyor belt 302 fall onto the plurality of rotating crushing rollers 305, and are squeezed and crushed by the plurality of crushing rollers 305 before being outputted. A plurality of rollers 307 are rotatably provided at the bottom of the upper section of the conveyor belt 302. The rollers 307 enhance the bearing capacity of the conveyor belt 302 and reduce the deformation of the conveyor belt 302. The conveyor belt 302 is perforated with a plurality of pores having a relatively small diameter. A plurality of cooling air pipes 306 are arranged on the inner side of the conveyor belt 302 , and a plurality of air inlet holes are arranged on the top of the cooling air pipes 306 .

[0037] A scraper 308 is provided at the top of the lower section of the conveyor belt 302. The bottom of the scraper 308 contacts the top surface of the lower section of the conveyor belt 302. A plurality of vertically arranged second springs 309 are provided at the top of the scraper 308. The top of the second spring 309 is connected to a support rod 310 connected to the cooling box 301. The elastic force of the second spring 309 keeps the scraper 308 in close contact with the top surface of the lower section of the conveyor belt 302. The scraper 308 is inclined in the moving direction of the lower section of the conveyor belt 302, and the scraper 308 is located at the lower side of the conveying start end of the conveyor belt 302. When the conveyor belt 302 is running, some small-size fine-grained materials fall on the top surface of the lower section of the conveyor belt 302 through the pores. The scraper 308 scrapes the materials on the top surface of the lower section of the conveyor belt 302 and guides them out.

[0038] The material enters the hot air pipe 106 from the feeding pipe 104 at the bottom of the hopper 101, and the high-temperature flue gas generated by the combustion of the igniter 205 enters the hot air pipe 106 from the smoke chamber 109. The high-temperature flue gas gradually rises in the hot air pipe 106 and passes through multiple second buffer tanks 108 and two first buffer tanks 102 in turn before entering the hopper 101. The high-temperature gas in the kiln head hood 203 enters the hot air pipe 106 along the return air pipe 204 and finally enters the hopper 101. After passing through the hopper 101, the gas is sent to the waste gas treatment system through the waste gas pipe 103 for treatment. In this process, the high-temperature flue gas preheats the material. The material entering the hot air pipe 106 from the feeding pipe 104 flows into the two first buffer tanks 102 driven by the airflow, and the material gradually falls in the first buffer tank 102 to the bending of the hot air pipe 106 below. The airflow in the hot air pipe 106 brings the material to the second buffer tank 108 at the bending, and the material gradually falls in the second buffer tank 108 and enters the bending of the hot air pipe 106 below through the discharge pipe 107. The above process is repeated, and the material enters the second buffer tank 108 below from the two first buffer tanks 102 in turn, and then passes through multiple second buffer tanks 108 downward in turn, enters the smoke chamber 109 and finally enters the barrel 206. In this process, the material is preheated.

[0039] like Figure 1 As shown, in the material discharge device 100, the direction of the arrow inside the pipe is the flow direction of the high-temperature flue gas, and the direction of the arrow outside the pipe is the movement direction of the material.

[0040] The barrel 206 rotates continuously, and the material in the barrel 206 rolls and gradually moves to the lower end of the barrel 206 . During this process, the igniter 205 roasts the material in the barrel 206 . In the combustion section of the barrel 206, the air inlet pipe 215 transports oxygen to the boost manifold 213, and the oxygen enters the boost chamber 211. At the same time, the vacuum pump 216 operates to increase the air pressure in the boost chamber 211 and place the negative pressure in the negative pressure chamber 212. When the barrel 206 rotates, when the air hole 217 is at the side of the boost chamber 211, the oxygen in the boost chamber 211 passes through the air hole 217 and enters the baffle 221, and the air flow pushes the connecting ring 222 and the lifting seat 223 to rise. During this process, the air flow is sprayed into the barrel 206 from the air channel 226 on the lifting seat 223. During the rising process of the lifting seat 223, the lifting seat 223 and the screw 219 threadedly cooperate to rotate the lifting seat 223, and the lifting seat 223 drives the stirring rod 224 to rotate to stir the material. As the barrel 206 rotates, when the air hole 217 is at the side of the negative pressure chamber 212, since the negative pressure chamber 212 is in a negative pressure state, a small amount of oxygen in the diaphragm 221 is sucked into the air hole 217 and due to the existence of the check structure, the air hole 217 is blocked, and the gas in the barrel 206 cannot enter the negative pressure chamber 212 through the air hole 217. Under the gravity of the lifting seat 223 and the elastic force of the first spring 220, the lifting seat 223 descends until the first spring 220 is compressed. During the descent of the lifting seat 223, the lifting seat 223 and the screw 219 threadedly cooperate to make the lifting seat 223 rotate and drive the stirring rod 224 to rotate, thereby stirring the material. As the barrel 206 rotates, the air hole 217 alternately passes between the negative pressure chamber 212 and the boost chamber 211, and the lifting seat 223 realizes a cyclic lifting movement and sprays oxygen during the rising process. When at the side and top of the barrel 206, the outside is completely the negative pressure chamber 212, the air hole 217 is closed, the diaphragm 221 and the first spring 220 are compressed, and the lifting seat 223 is closest to the inner wall of the barrel 206. Since the aperture of the air hole 217 is smaller than the thickness of the baffle 210, when the air hole 217 slides on the inner side of the baffle 210 between the boosting chamber 211 and the negative pressure chamber 212, the boosting chamber 211 and the negative pressure chamber 212 will not be connected through the air hole 217.

[0041] After the material is roasted in the combustion section of the barrel 206, it falls from the lower end of the barrel 206 into the kiln head cover 203 and falls onto the conveyor belt 302. The conveyor belt 302 slowly transports the roasted material. During this process, the cold air pipe 306 transports cold air to the upper section of the conveyor belt 302. The cold air rises through the pores and passes through the material to cool the material. After the cold air exchanges heat with the material, a part of it is transported by the return air pipe 204 on the kiln head cover 203, and the other part is transported by the induced draft pipe 304, and finally all are sent to the exhaust gas treatment system. In the process of slowly transporting the material on the conveyor belt 302, it is inevitable that a small amount of small-sized material will pass through the pores and fall onto the top surface of the lower section of the conveyor belt 302. The scraper 308 provided can scrape the material on the top surface of the lower section of the conveyor belt 302 for recycling. After the material is cooled, it is conveyed by the conveyor belt 302 and then falls onto the crushing roller 305. A conveying device or a container is arranged below the crushing roller 305. After the material is crushed by the crushing roller 305, the material is output by the conveying device or loaded by the container.

[0042] The present invention also discloses a method for preparing large-grain battery-grade lithium carbonate, comprising the following steps: S1. The lithium ore crushed material is mixed with calcium salt, sulfate and coal-water slurry to form a mixture, and the mixture is stirred evenly and then allowed to stand for a period of time to homogenize the water content of the mixture and make the overall density uniform; S2. The mixture is pressed or extruded to form a block or spherical molding material; S3. The molding material is placed in the hopper 101 of the preparation system to be prepared for roasting, and the roasted material is obtained after roasting; S4. After the calcined material is ground, the powder is mixed with water to form a slurry and fed to a leaching device to obtain a leachate and lithium slag, and the leachate is filtered to remove impurities; S5. Add quicklime and soda ash to the leachate and mix well, precipitate and remove impurities, and filter to obtain a lithium-containing solution; S6. The lithium-containing solution is evaporated and concentrated to increase the lithium ion concentration; S7. Adding a soda ash solution to precipitate lithium, and then centrifuging, stirring and washing to separate lithium carbonate, the lithium carbonate was dried and crushed to obtain battery-grade lithium carbonate; The calcium salt in step S1 is calcium bicarbonate, and both step S1 and step S2 are performed in an environment below 0° C. to make the calcium bicarbonate relatively stable; In step S3, after the molding material enters the hopper 101, the temperature of the molding material gradually increases, calcium bicarbonate decomposes to obtain calcium carbonate, carbon dioxide and water, and carbon dioxide gas is released from the molding material so that the molding material has pores. The molding material is preheated by the high-temperature flue gas during the process of falling in the feeding device 100; In step S3, after the molding material enters the barrel 206, it is gradually preheated in the preheating section of the barrel 206 and then enters the combustion section. In the combustion section, the igniter 205 roasts the molding material. The molding material contains water-coal slurry, and the molding material is ignited and self-ignites. In this process, the booster chamber 211 at the lower part of the barrel 206 of the combustion section transports oxygen into the barrel 206 through the air hole 217. The oxygen flows upward from the bottom of the molding material in the barrel 206 to improve the combustion efficiency of the molding material. The molding material has pores to further improve the uniformity and efficiency of self-ignition. In the process of the air hole 217 spraying oxygen, the lifting seat 223 rises and falls accordingly to assist in stirring the molding material, improve its fluidity, and improve its combustion uniformity and efficiency; In step S3, after the molding material is sintered, it falls from the lower end of the barrel 206 into the cooling device 300 for cooling, crushing and output.

[0043] The above embodiments are only preferred embodiments of the present invention and are not limitations of the technical solutions of the present invention. Any technical solution that can be implemented on the basis of the above embodiments without creative work should be deemed to fall within the scope of protection of the patent of the present invention.

Claims

1. A system for preparing large-grain battery-grade lithium carbonate, characterized in that: include: The material discharge device is arranged vertically, and the material slides down from the top to the bottom; The roasting device is connected with the feeding device, comprising: Kiln head hood and kiln tail hood; The lower end and the upper end of the inclined casing are connected to the kiln head cover and the kiln tail cover respectively; The barrel is coaxially rotatable in the casing, and its two ends are respectively connected with the kiln head cover and the kiln tail cover in a rotary and sealed manner; A wheel belt is coaxially arranged outside the barrel; A supporting wheel is rotatably mounted on the casing and in rolling contact with the wheel band; A driving source is provided on the casing and drives the barrel to rotate; An igniter, extending into the barrel; A cooling device connected to the roasting device; Among them, the kiln tail hood and the kiln head hood are connected with the bottom of the unloading device and the cooling device respectively, the inner wall of the barrel is evenly covered with a plurality of air holes, and a check structure is provided in the air hole. The check structure allows the airflow to enter the barrel only through the air hole from the outside of the barrel, and the end of the air hole in the barrel is connected with a partition cover, and the top of the partition cover is connected with a lifting seat, and the lifting seat is provided with an air passage passing through it, and a first spring is connected between the bottom of the lifting seat and the end of the air hole, and a sealed cavity is provided between the casing and the barrel, and the cavity is connected with an air inlet pipe for conveying oxygen.

2. The system for preparing large-grain battery-grade lithium carbonate according to claim 1, characterized in that: A connecting ring is provided at the top edge of the partition cover, the lifting seat is rotatably provided on the connecting ring, the first spring is connected to the connecting ring, a stirring rod is provided on the outer wall of the lifting seat, a screw connected to the air hole is provided in the partition cover, and the screw is threadedly matched with the lifting seat.

3. The system for preparing large-grain battery-grade lithium carbonate according to claim 2, characterized in that: A support plate is provided at the end of the air hole inside the partition cover, and the support plate is covered with a plurality of through holes. The first spring is connected to the support plate, and the screw rod is vertically arranged on the top of the support plate and is coaxial with the air hole. The screw rod passes through the center of the lifting seat.

4. The system for preparing large-grain battery-grade lithium carbonate according to claim 3, characterized in that: The top of the lifting seat is spherical, the inner end of the airway is located at the end surface where the lifting seat is rotatably connected to the connecting ring, the outer end of the airway is located at the top of the lifting seat and is arranged radially along the spherical top of the lifting seat, the outer end of the screw rod is provided with a limiting ball head, the limiting ball head is spherical and has an outer diameter larger than the screw rod, and the top of the lifting seat is provided with a limiting groove whose shape is adapted to the limiting ball head.

5. The system for preparing large-grain battery-grade lithium carbonate according to claim 1, characterized in that: Two annular partitions are arranged perpendicular to the axial direction of the barrel outside the barrel, the outer wall of the partition is connected to the inner wall of the casing, the inner wall of the partition is rotatably sealed with the outer wall of the barrel, and the air hole is arranged on the barrel between the two partitions.

6. The system for preparing large-grain battery-grade lithium carbonate according to claim 5, characterized in that: A plurality of baffles are arranged between the two baffles at the lower part of the barrel, the baffles are perpendicular to the baffles and arranged radially along the barrel, the inner side edges of the baffles are slidingly sealed with the outer wall of the barrel, the aperture of the air hole is smaller than the thickness of the baffle, a sealed air cavity is formed between two adjacent baffles in the circumferential direction of the barrel, and the air inlet pipe transports oxygen to part of the sealed air cavity.

7. The system for preparing large-grain battery-grade lithium carbonate according to claim 6, characterized in that: The space on the side and upper part of the barrel without baffles is a negative pressure chamber. Among the two adjacent sealed air chambers, one is a negative pressure chamber and the other is a boosting chamber. A negative pressure manifold and a boosting manifold are provided on the outside of the protective tube. The negative pressure chamber is connected with the negative pressure manifold through a pipeline, and the boosting chamber is connected with the boosting manifold through a pipeline. The air intake pipe is connected with the boosting manifold. The boosting manifold and the negative pressure manifold are connected by pipelines and a vacuum pump is provided on the pipelines. Valves are provided on the pipelines on both sides of the vacuum pump. Air pressure sensors cooperating with the vacuum pump and the valves are provided in the negative pressure chamber and the boosting chamber.

8. The system for preparing large-grain battery-grade lithium carbonate according to claim 1, characterized in that: The unloading device includes a hopper, a serpentine hot air pipe is provided at the lower part of the hopper, a smoke chamber is connected to the bottom of the hot air pipe, the smoke chamber is connected to the kiln tail cover, the top of the hot air pipe is connected to two first buffer tanks in sequence, the top of the first buffer tank is provided with an air riser connected to the bottom of the hopper, the top of the air riser is provided with a filter to prevent materials from passing through, a plurality of second buffer tanks arranged in sequence from top to bottom are provided between the top and bottom of the hot air pipe, the second buffer tanks are all located at the bend of the hot air pipe, and an L-shaped hot air pipe section is connected between two upper and lower adjacent second buffer tanks. A feeding pipe is provided at the bottom of the hopper, and the feeding pipe is connected to the bending of the hot air pipe on the sides of the two first buffer tanks. The bottoms of the first buffer tank and the second buffer tank are both connected with a discharge pipe, and the discharge pipe is connected to the bending of the hot air pipe below the first buffer tank or the second buffer tank. The discharge pipe at the bottom of the second buffer tank at the bottom is connected to the smoke chamber, and the diameter of the discharge pipe is smaller than the diameter of the hot air pipe. A return air pipe connected to the upper part of the hot air pipe is provided on the top of the kiln head hood, and an induced draft fan is provided in the return air pipe. An exhaust air pipe is provided on the top of the hopper.

9. The system for preparing large-grain battery-grade lithium carbonate according to claim 1, characterized in that: The cooling device includes a cooling box which is arranged at the bottom of the kiln head cover and is arranged horizontally, a horizontally arranged conveyor belt is arranged in the cooling box, the conveying starting end of the conveyor belt is located at the bottom of the kiln head cover, an induced draft hood is connected to the cooling box at the top of the conveying end of the conveyor belt, an induced draft hood is provided on the induced draft duct, a plurality of crushing rollers are rotatably provided at the lower part of the conveying end of the conveyor belt, the conveyor belt is perforated, a plurality of cold air pipes are provided on the inner side of the conveyor belt, a plurality of air inlet holes are covered on the top of the cold air pipe, a scraper is provided on the top of the lower section of the conveyor belt, the bottom of the scraper is in contact with the top surface of the lower section of the conveyor belt, a plurality of vertically arranged second springs are provided on the top of the scraper, a support rod connected to the cooling box is connected to the top of the second spring, the scraper is inclined in the moving direction of the lower section of the conveyor belt, and the scraper is located at the lower side of the conveying starting end of the conveyor belt.

10. A method for preparing large-grain battery-grade lithium carbonate, characterized in that: The steps include: S1. The lithium ore crushed material is mixed with calcium salt, sulfate and coal-water slurry to form a mixture, and the mixture is stirred evenly and then allowed to stand for a period of time to homogenize the water content of the mixture and make the overall density uniform; S2. The mixture is pressed or extruded to form a block or spherical molding material; S3. The molding material is placed in a feeding device of the preparation system according to any one of claims 1 to 9 in preparation for roasting, and the roasted material is obtained after roasting; S4. After the calcined material is ground, the powder is mixed with water to form a slurry and fed to a leaching device to obtain a leachate and lithium slag, and the leachate is filtered to remove impurities; S5. Add quicklime and soda ash to the leachate and mix well, precipitate and remove impurities, and filter to obtain a lithium-containing solution; S6. The lithium-containing solution is evaporated and concentrated to increase the lithium ion concentration; S7. Adding a soda ash solution to precipitate lithium, and then centrifuging, stirring and washing to separate lithium carbonate, the lithium carbonate was dried and crushed to obtain battery-grade lithium carbonate; Wherein, the calcium salt in step S1 is calcium bicarbonate, and both step S1 and step S2 are performed in an environment below 0°C; In step S3, after the molding material enters the feeding device, the temperature of the molding material gradually increases, calcium bicarbonate decomposes to obtain calcium carbonate, carbon dioxide and water, and carbon dioxide gas is released from the molding material so that the molding material has pores. During the process of the molding material falling in the feeding device, it contacts with the smoke generated by the combustion of the igniter to achieve preheating; In the step S3, after the molding material enters the barrel, the igniter roasts the molding material. The molding material contains water-coal slurry, and the molding material is ignited and self-ignites. During this process, the air inlet pipe transports oxygen to the cavity outside the barrel, and the oxygen is transported into the barrel through the pores. The oxygen flows upward from the bottom of the molding material in the barrel. During the process of the pores spraying oxygen, the lifting seat rises and falls accordingly to assist in stirring the molding material. In step S3, the molding material falls into a cooling device from the lower end of the barrel after being sintered, and is cooled, crushed, and then output.

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