Continuous pre-carbonization system and carbonization process thereof

Abstract

The invention discloses a continuous pre-carbonization system and a carbonization process thereof, and belongs to the technical field of lithium battery negative electrode material production. The device comprises a fluidized bed reactor, wherein a material inlet, a carrier gas inlet and a mixed gas outlet are formed in the fluidized bed reactor; wherein the material inlet is connected with a feeding device; the mixed gas outlet is connected with a gas outlet pipeline, a gas-solid separation device and a heater are sequentially arranged on the gas outlet pipeline, and a pyrolysis gas leading-out branch pipe is arranged on the gas outlet pipeline between the gas-solid separation device and the heater; the carrier gas inlet is communicated with a gas outlet of the heater through a gas inlet pipeline, and a gas supplementing branch pipe is arranged on the gas inlet pipeline. The fluidized bed reactor is used as carbonization equipment, and the raw materials are converted into the fluidized state through the carrier gas, so that sufficient and uniform heat exchange can be performed between the raw materials and the high-temperature gas, and the phenomenon of non-uniform carbonization effect of the raw materials caused by accumulation of the raw materials is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium battery negative electrode material production, and more specifically, relates to a continuous pre-carbonization system and a carbonization process thereof. Background Art

[0002] At present, the common lithium battery graphite negative electrode material in the market is mainly artificial graphite, and its basic process flow is crushing, granulation, graphitization, screening, etc. Since the graphitization cost accounts for the highest proportion in the production of negative electrode materials, accounting for about 50% of the cost of negative electrode materials. In order to increase the filling rate of the graphitization process and save costs, the industry will pre-carbonize the materials before graphitization. Pre-carbonization is an important step in the graphitization process, and pre-carbonization can improve the graphitization degree of the material.

[0003] The traditional negative electrode material pre-carbonization process equipment uses a roller kiln. The specific process is to first load the negative electrode material raw materials to be carbonized into a small square sagger, and then place the small square sagger on the kiln roller. The roller drives the small square sagger to move slowly at a speed of several centimeters per hour. The negative electrode material in the small square sagger completes high-temperature carbonization in the roller kiln, and finally passes through the cooling section and is output. The negative electrode material in the small square sagger is sucked out for packaging. This process method is mature and the product quality is reliable, but the production is discontinuous, the waste heat cannot be used, and a large amount of highly polluting gas and dust are generated during the production process.

[0004] After searching, the patent CN114477136A discloses a system and carbonization process for carbonizing negative electrode materials. This application uses an externally heated rotary kiln to carbonize negative electrode materials for lithium batteries. Compared with the traditional roller kiln carbonization process for negative electrode materials, the negative electrode materials do not need to be loaded and taken out through a heating vessel, but are directly heated in the central cylinder of the externally heated rotary kiln. The loading and unloading process is easy to operate, with a high degree of automation, and the labor intensity and working environment have been greatly improved. At the same time, in this application, the overall system structure is optimized and designed to effectively improve the thermal utilization efficiency of the system.

[0005] Patent CN115367746A discloses a continuous granulation / pre-carbonization method and preparation method of graphite negative electrode materials. In this application, the granulation and pre-carbonization processes are carried out in the same kiln body, and the high-temperature flue gas and the material are subjected to reverse heat exchange. First, the heat is exchanged in the pre-carbonization area for pre-carbonization treatment, and the high-temperature flue gas after heat exchange is then circulated to the granulation area for granulation treatment, which not only realizes continuous production, but also improves the utilization rate of the high-temperature flue gas.

[0006] In the above applications, rotary kilns are used instead of roller kilns for pre-carbonization of negative electrode materials. Although this overcomes the defects of traditional roller kilns such as discontinuous production and low heat utilization efficiency. However, since the movement of materials in the rotary kiln is mainly rotation and rolling, there may be varying degrees of retention and accumulation of materials during the forward process, which can easily lead to uneven carbonization of materials. In addition, since the seal between the inner and outer cylinders needs to adopt a dynamic sealing structure, the structure of the entire device is relatively complex and the cost is relatively high. Therefore, the industry still needs more diverse designs to solve the problems of poor continuity and low heat utilization rate in the pre-carbonization of negative electrode materials. Summary of the invention

[0007] 1. Problems to be solved

[0008] In view of at least some of the problems existing in the above prior art, the present invention proposes a continuous pre-carbonization system and a carbonization process thereof, the purpose of which is to solve the problem of uneven carbonization when using a rotary kiln for carbonization of negative electrode materials in the prior art.

[0009] 2. Technical solution

[0010] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] A continuous precarbonization system of the present invention comprises a fluidized bed reactor, wherein the fluidized bed reactor is provided with a material inlet, a carrier gas inlet and a mixed gas outlet; wherein:

[0012] The material inlet is connected with a feeding device;

[0013] The mixed gas outlet is connected to an outlet pipe, on which a gas-solid separation device and a heater are arranged in sequence, and a pyrolysis gas outlet branch pipe is arranged on the outlet pipe between the gas-solid separation device and the heater;

[0014] The carrier gas inlet is communicated with the gas outlet of the heater through an air inlet pipeline, and a gas supplement branch pipe is arranged on the air inlet pipeline.

[0015] Furthermore, the gas-solid separation device is provided with two groups, wherein the gas-solid separation device located in the front is used to collect qualified products, and the gas-solid separation device located in the back is used to collect unqualified products.

[0016] Furthermore, a heat exchange device is provided between the two groups of gas-solid separation devices.

[0017] Furthermore, a circulating fan is provided between the gas-solid separation device located at the rear and the heater; and the pyrolysis gas outlet branch pipe is located between the circulating fan and the heater.

[0018] Furthermore, the gas-solid separation device includes a high-temperature dust collector, and a cooler, a shut-off valve and an air shut-off device are sequentially arranged on the discharge pipeline of the high-temperature dust collector.

[0019] Furthermore, the high-temperature dust collector is a cyclone separator; and the heat exchange device is a superheater.

[0020] Furthermore, the feeding device includes a feeding screw, the discharge port of which is connected to the material inlet of the fluidized bed reactor; the feeding port is connected to the raw material bin, and a shut-off valve and an air shut-off device are sequentially arranged on the connecting pipeline between the two.

[0021] Furthermore, the inner cavity of the fluidized bed reactor is divided into two upper and lower areas by an air distribution plate; wherein the mixed gas outlet is arranged at the top of the upper area, the material inlet is arranged at the lower middle position of the upper area; and the carrier gas inlet is arranged at the bottom of the lower area.

[0022] The present invention also provides a continuous pre-carbonization process, which comprises the following steps:

[0023] Before feeding, the system needs to be filled with carrier gas through the air inlet pipeline; then, the raw materials enter the fluidized bed reactor through the feeding device;

[0024] The raw materials and high-temperature gas are heated in the fluidized bed reactor to remove volatiles, and enter the gas-solid separation device with the airflow for gas-solid separation. The separated qualified products enter the product collection box; the separated gas enters the heater for heating, and the excess gas is led out through the pyrolysis gas outlet branch pipe; the heated gas returns to the fluidized bed reactor for continued use.

[0025] Furthermore, the carrier gas is an inert gas; the operating temperature and outlet temperature in the fluidized bed reactor are both ≥1200°C.

[0026] 3. Beneficial effects

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) A continuous pre-carbonization system of the present invention uses a fluidized bed reactor as a carbonization device, and converts the raw material into a fluidized state through a carrier gas, so that the raw material can fully and evenly exchange heat with the high-temperature gas, thereby avoiding the phenomenon of uneven carbonization of the raw material due to raw material accumulation. At the same time, the mixed gas flowing out of the fluidized bed reactor re-enters the fluidized bed reactor after collecting the solid product, which improves the thermal utilization rate of the system while reducing the emission of tail gas.

[0029] (2) In a continuous precarbonization system of the present invention, two groups of gas-solid separation devices are provided, one group is used to collect qualified products, and the other group is used to collect unqualified products. Such a design not only ensures the qualified rate of the products, but also improves the cleanliness of the mixed gas returned to the fluidized bed reactor.

[0030] (3) A continuous pre-carbonization system of the present invention can utilize the temperature of the mixed gas and improve the heat utilization efficiency of the system by providing a heat exchange device between two sets of gas-solid separation devices; it can also protect downstream equipment by reducing the temperature of the mixed gas. In addition, by providing a cooler on the discharge pipeline of the high-temperature dust collector, the residual heat of the carbonized material can be further utilized. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the overall structure of a continuous pre-carbonization system of the present invention;

[0032] In the figure: 1, fluidized bed reactor; 11, air distribution plate;

[0033] 21. Air outlet pipe; 22. Air inlet pipe; 23. Pyrolysis gas outlet branch pipe; 24. Air supply branch pipe;

[0034] 3. Feeding device; 31. Feeding screw; 32. Raw material bin;

[0035] 4. Gas-solid separation device; 41. High-temperature dust collector; 42. Cooler; 43. Shut-off valve; 44. Air shut-off device;

[0036] 5. Heater; 6. Heat exchange device; 7. Circulating fan. DETAILED DESCRIPTION

[0037] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with the accompanying drawings.

[0038] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0039] The present invention is further described below in conjunction with specific embodiments.

[0040] like Figure 1As shown, a continuous precarbonization system of the present embodiment includes a fluidized bed reactor 1, a feeding device 3, a gas-solid separation device 4 and a heater 5. The fluidized bed reactor 1 is provided with a material inlet, a carrier gas inlet and a mixed gas outlet. The feeding device 3 is connected to the material inlet, and is used to add raw materials into the fluidized bed reactor 1. The carrier gas inlet is connected to an air inlet pipe 22, which is used to transport fluidized carrier gas into the fluidized bed reactor 1. The mixed gas outlet is connected to an air outlet pipe 21, and the gas-solid separation device 4 and the heater 5 are both arranged on the air outlet pipe 21, and the outlet gas of the heater 5 is connected to the air inlet of the air inlet pipe 22.

[0041] The gas-solid separation device 4 is located in front of the heater 5, and is used to perform gas-solid separation on the mixed gas flowing out of the fluidized bed reactor 1. The heater 5 is used to heat the separated mixed gas to meet the carbonization temperature in the fluidized bed reactor 1, and the heated mixed gas is returned to the fluidized bed reactor 1 for continued use.

[0042] A continuous pre-carbonization system of this embodiment uses a fluidized bed reactor 1 as a carbonization device, and cooperates with a feeding device 3. Compared with a roller kiln, continuous production can be carried out, and there is no need to carry out material loading operations, which greatly improves work efficiency. In addition, after the solid product is collected, the mixed gas flowing out of the fluidized bed reactor 1 re-enters the fluidized bed reactor 1, which improves the thermal utilization rate of the system while reducing the emission of tail gas. Compared with a rotary kiln, the raw material is converted into a fluidized state by a carrier gas, so that the raw material can fully and evenly exchange heat with the high-temperature gas, avoiding the phenomenon of uneven raw material carbonization effect due to raw material accumulation.

[0043] Specifically, in this embodiment, an air distribution plate 11 is provided near the bottom of the fluidized bed reactor 1, and the air distribution plate 11 divides the inner cavity of the fluidized bed reactor 1 into two upper and lower areas, namely, a carbonization reaction zone and a wind chamber. The mixed gas outlet of the fluidized bed reactor 1 is provided at the top of the carbonization reaction zone, the material inlet is provided at the lower middle position of the carbonization reaction zone; and the carrier gas inlet is provided at the bottom of the wind chamber.

[0044] At the same time, a pyrolysis gas outlet branch pipe 23 is provided on the gas outlet pipe 21 between the gas-solid separation device 4 and the heater 5, and the pyrolysis gas outlet branch pipe 23 is equipped with a solenoid valve for leading excess gas out of the system through the pyrolysis gas outlet branch pipe 23. A gas supply branch pipe 24 is provided on the gas inlet pipe 22 for supplying carrier gas into the fluidized bed reactor 1. The carrier gas can be used as fluidizing gas on the one hand and as protective gas during the carbonization process on the other hand. Preferably, the carrier gas is an inert gas, such as nitrogen, argon or helium.

[0045] As a preferred implementation of this embodiment, two groups of gas-solid separation devices 4 are provided, wherein the gas-solid separation device 4 located in the front is used to collect qualified products, and the gas-solid separation device 4 located in the back is used to collect unqualified products. The provision of two groups of gas-solid separation devices 4 not only ensures the qualified rate of the products, but also improves the cleanliness of the mixed gas returned to the fluidized bed reactor 1. It is worth mentioning that the front and the back mentioned above are based on the flow direction of the gas in the gas outlet pipe 21.

[0046] At the same time, a circulating fan 7 is provided between the gas-solid separation device 4 and the heater 5 at the rear, and the pyrolysis gas outlet branch pipe 23 is located between the circulating fan 7 and the heater 5. The circulating fan 7 is used to provide power for the gas circulation in the system and also provide a certain positive pressure for the volatile gas generated during the carbonization process to be sent out.

[0047] In this embodiment, in order to further improve the utilization rate of heat in the system, a heat exchange device 6, such as a superheater, is provided between the two groups of gas-solid separation devices 4. The saturated steam of the boiler is heated by the heat exchange device 6, which can not only effectively utilize the waste heat of the separated gas, but also play a certain protective role on the downstream equipment after the temperature of the gas after heat exchange drops.

[0048] Furthermore, the gas-solid separation device 4 in this embodiment includes a high-temperature dust collector 41, and a cooler 42, a shut-off valve 43 and an air shut-off device 44 are sequentially arranged on the discharge pipeline of the high-temperature dust collector 41. Among them, the high-temperature dust collector 41 is used for gas-solid separation, and a cyclone separator or the like may be required. The cooler 42 can also preheat the boiler feed water to ensure material cooling and heat recovery. The shut-off valve 43 is provided to facilitate the control of the discharge. The air shut-off device 44 has a good air locking function, which can ensure that during the separation process, gas backflow is prevented to affect the separation effect and the normal operation of the equipment.

[0049] In this embodiment, the feeding device 3 includes a feeding screw 31, the discharge port of which is connected to the material inlet on the fluidized bed reactor 1; its feeding port is connected to the raw material bin 32, and a shut-off valve 43 and an air shut-off device 44 can also be set on the connecting pipeline between the two.

[0050] A continuous pre-carbonization system of this embodiment has the following working process:

[0051] Before feeding, the system needs to be filled with carrier gas through the gas supply branch pipe 24; then, the raw materials in the raw material bin 32 are transported to the fluidized bed reactor 1 through the feeding screw 31;

[0052] The raw materials and high-temperature gas are heated in the fluidized bed reactor 1 to remove volatiles, and enter the gas-solid separation device 4 in the front along with the air flow. The products with suitable particle sizes are separated by the high-temperature dust collector 41 and then enter the cooler 42 for cooling, and then enter the product collection device through the air lock 44; the products that do not meet the particle size requirements enter the heat exchange device 6 along with the hot air flow, and the gas and small particle products are cooled and sent to the high-temperature dust collector 41 at the rear. The separated small particle products are cooled by the cooler 42 and then enter the conveying device through the air lock 44 and are sent back to the raw material preparation section;

[0053] The clean gas after separation is pressurized by the circulating fan 7 and then sent to the heater 5. The excess gas is sent to the boiler device through the pyrolysis gas outlet branch pipe 23. The gas heated by the heater 5 is sent back to the fluidized bed reactor 1 for continued use; wherein the working temperature and outlet temperature in the fluidized bed reactor 1 are both ≥1200°C. If necessary, new carrier gas can be added through the gas supply branch pipe 24.

[0054] The present invention and its embodiments are described schematically above, and the description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it and designs a structural method and an embodiment similar to the technical solution without creativity without departing from the purpose of the invention, they shall all fall within the protection scope of the present invention.

Claims

1. A continuous precarbonization system, characterized in that: The invention comprises a fluidized bed reactor (1), wherein the fluidized bed reactor (1) is provided with a material inlet, a carrier gas inlet and a mixed gas outlet; wherein: The material inlet is connected to a feeding device (3); The mixed gas outlet is connected to an outlet pipe (21), on which a gas-solid separation device (4) and a heater (5) are sequentially arranged, and a pyrolysis gas outlet branch pipe (23) is arranged on the outlet pipe (21) between the gas-solid separation device (4) and the heater (5); The carrier gas inlet is connected to the gas outlet of the heater (5) through an air inlet pipeline (22), and an air supply branch pipe (24) is provided on the air inlet pipeline (22).

2. A continuous precarbonization system according to claim 1, characterized in that: The gas-solid separation device (4) is provided in two groups, wherein the gas-solid separation device (4) located in the front is used to collect qualified products, and the gas-solid separation device (4) located in the rear is used to collect unqualified products.

3. A continuous precarbonization system according to claim 2, characterized in that: A heat exchange device (6) is provided between the two groups of gas-solid separation devices (4).

4. A continuous precarbonization system according to claim 3, characterized in that: A circulating fan (7) is provided between the gas-solid separation device (4) located at the rear and the heater (5); the pyrolysis gas outlet branch pipe (23) is located between the circulating fan (7) and the heater (5).

5. A continuous precarbonization system according to claim 3, characterized in that: The gas-solid separation device (4) comprises a high-temperature dust collector (41), and a cooler (42), a shut-off valve (43) and an air shut-off device (44) are sequentially arranged on the discharge pipeline of the high-temperature dust collector (41).

6. A continuous precarbonization system according to claim 5, characterized in that: The high-temperature dust collector (41) is a cyclone separator; the heat exchange device (6) is a superheater.

7. A continuous precarbonization system according to any one of claims 1 to 6, characterized in that: The feeding device (3) comprises a feeding screw (31), the discharge port of which is connected to the material inlet of the fluidized bed reactor (1); the feeding port is connected to a raw material bin (32), and a shut-off valve (43) and an air shut-off device (44) are sequentially arranged on the connecting pipeline between the two.

8. A continuous precarbonization system according to claim 7, characterized in that: The inner cavity of the fluidized bed reactor (1) is divided into two upper and lower areas by an air distribution plate (11); wherein the mixed gas outlet is arranged at the top of the upper area, the material inlet is arranged at a lower middle position of the upper area; and the carrier gas inlet is arranged at the bottom of the lower area.

9. A carbonization process is carried out using a continuous pre-carbonization system according to any one of claims 1 to 8, characterized in that: The following steps are included: Before feeding, the system needs to be filled with carrier gas through the air inlet pipe (22); then, the raw materials enter the fluidized bed reactor (1) through the feeding device (3); The raw materials and high-temperature gas are heated in the fluidized bed reactor (1) to remove volatiles, and then enter the gas-solid separation device (4) with the air flow for gas-solid separation, and the separated qualified products enter the product collection box; the separated gas enters the heater (5) for heating, and the excess gas is led out through the pyrolysis gas outlet branch pipe (23); the heated gas returns to the fluidized bed reactor (1) for continued use.

10. A pre-carbonization process according to claim 9, characterized in that: The carrier gas is an inert gas; the operating temperature in the fluidized bed reactor (1) and the outlet temperature are both ≥ 1200°C.

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