Regenerated graphite surface oxidation treatment method and fluidization reaction device

Abstract

The invention belongs to the technical field of environmental protection, and discloses a method and a device for surface oxidation treatment of regenerated graphite, which are used for recycling waste lithium battery electrode powder resources. The device comprises a first-stage reactor and a second-stage reactor which are connected in series, the first-stage reactor and the second-stage reactor are connected through a first-stage exhaust pipe and a second-stage discharge pipe, the outer side of the outer wall of the first-stage reactor is wrapped with a heating body, heat is generated through an external energy source to heat the first-stage reactor and internal materials, and an airflow distributor is located on the lower middle portion of the cross section of the first-stage reactor. Materials can be supported, and gas can pass through from bottom to top. The two-stage reactor is used for performing stage treatment on materials, and working gas can be respectively introduced into the two-stage reactor, so that the independent control on the reaction intensity of different areas is realized. By utilizing the device, the regenerated graphite powder can be subjected to surface oxidation treatment to realize material modification, so that the product is more suitable for lithium battery negative electrode production. According to the method, the materials are treated in a fluidization manner, so that the production efficiency is improved, the treatment time is shortened, and the product performance is improved.

Description

Technical Field

[0001] The invention belongs to the field of environmental protection technology and relates to a solid waste resource technology of recycled graphite, in particular to a processing method and equipment for recycling and reusing waste lithium battery electrode powder resources. Background Art

[0002] With the rapid development of the lithium battery field, the number of lithium batteries produced has exploded. As the service life of lithium batteries is consumed, more and more waste lithium batteries need to be processed. Among the related wastes generated by waste lithium batteries, the negative electrode graphite material is difficult to restore to the level of artificial graphite, the raw material of lithium batteries, after being regenerated by existing technologies, and cannot be used for the production of new batteries of the same quality. The main reasons include the peeling of the graphite particle surface caused by charging and discharging during the use of the battery, or the surface of the graphite particles is broken during the regeneration process, which leads to an increase in the specific surface area of ​​the graphite powder, resulting in the problem of low efficiency of batteries made with recycled graphite. Surface oxidation technology can improve the surface morphology of graphite particles and solve the above problems. Existing surface oxidation technical means do not have equipment and treatment methods for recycled graphite powder, and cannot be used for large-scale industrial production.

[0003] In view of the above problems, it is urgent to develop a new treatment method and equipment to solve the problem of surface oxidation treatment of recycled graphite, improve product performance, reduce energy consumption and regeneration costs, and achieve higher value resource utilization of waste materials. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to overcome the shortcomings of the prior art, provide a surface oxidation treatment method for regenerated graphite and a fluidized reaction device, improve the quality of recycled resources, and meet the performance requirements of raw materials for battery production.

[0005] A regenerated graphite surface oxidation treatment fluidized reaction device, used for the regeneration treatment of lithium battery negative electrode graphite powder, characterized in that: it comprises a primary reactor (1) and a secondary reactor (10) connected in series, connected through a primary exhaust pipe (9) and a secondary discharge pipe (15), the outer side of the outer wall of the primary reactor (1) is wrapped with a heating element (2), and heat is generated by an external energy source to heat the primary reactor and the internal materials, and an air flow distributor (3) is located in the middle and lower part of the cross section of the primary reactor (1), which can support the materials and allow the gas to pass from bottom to top, and the primary reactor (1) The reactor comprises five interfaces, a first-level feed port (4) is located on the side wall, a first-level fluidizing air inlet (5) is located in the middle of the bottom plate, a first-level exhaust port (6) is located at the top, a first-level working air inlet (7) is located on the side wall near the upper surface of the air flow distributor, a first-level reflux feed port (8) is located at the top, and a second-level reactor (10) comprises four interfaces, a second-level air inlet (11) is located on the side wall, a second-level exhaust port (12) is located at the top, a second-level working air inlet (13) is located on the side wall near the bottom, and a second-level discharge port (14) is located at the bottom, and the reactor has a cone or square cone shape.

[0006] The first-stage reactor (1) described above can be a hollow cylinder with a variable inner diameter, with a small diameter at the bottom and a large diameter at the top. The fluidizing air inlet (5) at the bottom is arranged concentrically with the reactor. The shell of the first-stage reactor (1) is made of quartz, corundum or other high-temperature and oxidation-resistant materials. The first-stage feed inlet (4) adopts pneumatic conveying to transport materials. The first-stage exhaust port (6) is arranged at the center of the top cover, and the first-stage working air inlet (7) is arranged in the tangential direction of the outer wall of the reactor.

[0007] The secondary reactor (10) described above is a hollow cylinder with a variable inner diameter, a small diameter at the bottom and a large diameter at the top. The secondary air inlet (11) is located in the tangential direction of the outer wall of the secondary reactor, and the secondary working gas inlet (13) is located in the tangential direction of the outer wall of the secondary reactor. The rotation direction of the working gas inlet is the same as the direction of flow of the gas-solid mixture in the reactor.

[0008] The heating element (2) described above adopts resistance heating, and the distance between the heating element and the reactor shell is 2-50mm. Insulating material is arranged outside the heating element, and the heating element and the first-stage reactor are enclosed in a thermal insulation space.

[0009] The air flow distributor (3) mentioned above is in the form of a perforated plate, with an umbrella-shaped air lifting cap disposed on the hole, and the hole diameter is 1-5 mm.

[0010] The working gas mentioned above is oxygen-enriched air with an oxygen content of 21%-50%.

[0011] The ratio of the gas flow cross-sectional areas of the primary reactor (1) and the secondary reactor (10) described above is between 1:1.5 and 1:5.

[0012] A method for surface oxidation treatment of regenerated graphite, wherein the material treated by the method is graphite powder of the negative electrode of waste lithium batteries or graphite powder waste generated in battery production, characterized in that the method uses the surface oxidation treatment fluidized reaction device described above, and the steps are as follows:

[0013] S1. The material to be processed is delivered into the primary reactor (1) by pneumatic conveying.

[0014] S2. Start the heating element (2) to heat the primary reactor. Through the heat conduction effect, the material in the primary reactor is heated to a constant temperature of 200-500 degrees Celsius. After the temperature is constant, set the heating element to automatic control and change the heating power as the temperature changes to keep the temperature constant.

[0015] S3. Fluidizing gas is introduced from the primary fluidizing air inlet (5). The introduced gas is nitrogen. The gas flow rate is controlled to gradually increase so that the powder enters a fluidized state. The gas flow rate is controlled at 0.1-2 meters per second.

[0016] S4. Introduce working gas into the primary working gas inlet (7), wherein the molar ratio of the total amount of the primary working gas to the material to be processed is 1:5-1:20.

[0017] S5. Under the action of the fluidizing gas, part of the material flows into the secondary reactor (10) along with the gas flow. The working gas is introduced into the secondary working gas inlet (13), and the total amount of the secondary working gas is 1-5 times the total amount of the primary working gas.

[0018] S6. According to the type and characteristics of the material, the duration and flow rate of ventilation are controlled. After all the working gases have reacted, the heating element is stopped and the reacted materials are discharged.

[0019] The advantages and positive effects achieved by the present invention are:

[0020] 1. This device regenerates the negative electrode graphite powder of lithium batteries based on the principle of surface oxidation, reduces the specific surface area of ​​the material, improves the performance of this recycled material in battery manufacturing, and improves the initial efficiency of the battery. Through experimental verification, the specific surface area of ​​the material decreased by more than 30%, the initial efficiency increased by more than 3%, and the use value of the recycled graphite was improved.

[0021] 2. This device uses fluidization technology to carry out surface oxidation treatment on the material, which greatly improves the heat conduction and material transfer in the treatment process, makes the reaction more uniform, improves the uniformity of the product, reduces the reaction time, and improves the production efficiency.

[0022] 3. This device is designed with suitable structural forms and process parameters according to the special particle characteristics of recycled graphite materials, controls the internal flow process, solves the problem that traditional surface oxidation equipment is not suitable for materials in this particle size range, and provides a more energy-saving and efficient surface oxidation device and technical route. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of a fluidized reaction device for surface oxidation treatment of regenerated graphite in the present invention.

[0024] The figures are as follows:

[0025] A primary reactor (1), a heating element (2), an air flow distributor (3), a primary feed port (4), a primary fluidizing air inlet (5), a primary exhaust port (6), a primary working air inlet (7), a primary reflux feed port (8), a primary exhaust pipe (9), a secondary reactor (10), a secondary air inlet (11), a secondary exhaust port (12), a secondary working air inlet (13), a secondary discharge port (14), and a secondary discharge pipe (15). DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the embodiments. The following embodiments are descriptive rather than restrictive, and the protection scope of the present invention cannot be limited by the following embodiments.

[0027] The various commonly used technical means involved in the specific embodiments are all conventional technologies in the field. For the parts not specially annotated in this document, ordinary technicians in this field can implement them by referring to various commonly used reference books, scientific and technological literature or related instructions, manuals, etc. before the filing date of this invention.

[0028] A surface oxidation treatment fluidized reaction device is used for the regeneration of graphite powder, a negative electrode active material in waste lithium battery electrodes, comprising a primary reactor (1) and a secondary reactor (10) connected in series, which are connected via a primary exhaust pipe (9) and a secondary discharge pipe (15). The gas used for fluidization passes through the primary reactor and the secondary reactor in sequence, and is finally discharged from the secondary exhaust port of the secondary reactor. The solid material to be treated is added to the primary reactor, and moves with the fluidization gas. The particles with smaller particle size flow out from the primary exhaust port and enter the secondary reactor. The air inlet of the secondary reactor is set at a tangential position. The gas-solid mixture enters the secondary reactor to form a spiral motion. Under the action of inertia, the gas and solid are separated, and the gas is discharged through the secondary exhaust port. The solid powder flows back to the primary reactor by gravity and is finally discharged by a separate discharge device. This discharge device can be an external device for negative pressure suction, or other conventional technical means that can realize the discharge function.

[0029] The primary reactor (1) is a hollow cylinder with a variable inner diameter, with a small diameter at the bottom and a large diameter at the top. The bottom is conical, which can achieve the effect of rectification and facilitate the fluidizing air to flow in a more uniform flow field after entering. The design of small at the bottom and large at the top makes the flow rate gradually decrease when the airflow moves upward, thereby achieving the effect of grading the processed materials. The shell of the primary reactor is made of quartz, corundum or other high-temperature and oxidation-resistant materials to resist oxidation and wear at working temperature. The primary feed port (4) is set above the middle of the side wall of the primary reactor, and the material is transported by pneumatic conveying, so that uniform feeding can be achieved, and the fluidized and expanded fluid will not be damaged during continuous feeding and discharging. The primary fluidizing air inlet (5) is used to introduce fluidizing gas, which passes through the airflow distributor from bottom to top, so that the airflow acts on the material powder above the distributor to form a suspended fluidized state. The primary exhaust port (6) is arranged at the top of the primary reactor, from which the fluidizing gas can be discharged, and the powder of the processed material is also partially or completely discharged with the airflow, and enters the secondary air inlet through the primary exhaust pipe (9). According to the different particle size distributions, the fluidizing gas volume can be adjusted to control the particle size distribution of the material flowing out of the primary exhaust port. The primary exhaust port is arranged at the center position of the top, which further improves the effect of separating particles of different particle sizes. The primary working gas inlet (7) is arranged in the tangential direction of the outer wall of the reactor, near the bottom of the distributor, and is used to pass the oxidant gas into the reactor. After the tangential airflow enters, a rotation motion can be formed, so that particles of different particle sizes in the material are separated, and smaller particles are more likely to flow out from the middle exhaust port.

[0030] The outer side of the primary reactor (1) is wrapped with a heating element (2), which generates heat through an external energy source to heat the primary reactor and the internal materials. The heating element can be heated by resistance heating or induction heating. Different materials for the shell of the primary reactor are selected according to different heating methods. The distance between the heating element and the reactor shell is 2-50 mm. Insulating material is arranged outside the heating element, and the heating element and the primary reactor are wrapped in the same sealed area.

[0031] The gas flow distributor (3) is located in the lower middle part of the cross section of the first reactor (1), and can support the material and allow the gas to pass from bottom to top. It can be a perforated plate with an umbrella-shaped gas lifting cap on the hole, and the hole diameter is 1-5mm. The gas flow distributor is made of quartz, corundum or other high temperature and oxidation resistant materials.

[0032] The secondary reactor (10) is a hollow cylinder with a variable inner diameter, a small diameter at the bottom, a large diameter at the top, and a conical bottom, so that the separated materials can be returned to the primary reactor by gravity flow. The design of a small bottom and a large top makes the flow rate gradually decrease when the airflow moves from bottom to top, so as to achieve the effect of gas-solid separation of the processed materials. The shell of the secondary reactor is made of quartz, corundum or other high temperature and oxidation resistant materials. The secondary air inlet (11) is arranged in the tangential direction of the outer wall of the secondary reactor, and is used to send the gas and materials discharged from the primary reactor into the secondary reactor. The flow in the tangential direction causes the gas-solid mixture entering the reactor to generate a rotating airflow, so as to achieve the effect of gas-solid separation. The secondary exhaust port (12) is located at the center of the top of the secondary reactor, and is used to discharge all gases out of the reactor. Under the action of the rotating airflow, the powder concentration at the center is the lowest, so as to achieve the best gas-solid separation effect. The secondary working gas inlet (13) is located in the tangential direction of the side wall of the secondary reactor, near the bottom of the secondary reactor, and is used to pass the oxidant gas into the reactor. The rotation direction of the working gas inlet is the same as the rotation direction of the gas-solid mixture, and is mixed with the fluidizing gas by diffusion, thereby improving the uniformity of the mixing and improving the utilization rate of the reaction gas. The secondary discharge port (14) is located at the bottom of the secondary reactor and is conical in shape. It is used to discharge the material in the secondary reactor and transport it into the primary reflux feed port (8) through the secondary discharge pipe (15).

[0033] Because of their different working purposes, the primary reactor and the secondary reactor need to use a suitable diameter ratio to achieve the classification effect of the processed materials. The primary reactor uses a smaller diameter and a faster flow rate to separate a part of the particles with smaller particle size from the processed material and transport them to the secondary reactor. The controlled air flow velocity determines the segmentation particle size, which needs to be calculated and set according to the concentration of the reaction gas in the two reactors. The secondary reactor selects a larger diameter and a slower flow rate to achieve the final purpose of gas-solid separation. The ratio of the gas flow cross-sectional area is usually selected between 1:1.5-1:5.

[0034] The working gas concentrations controlled by the primary reactor and the secondary reactor are different according to the different intensities of their respective surface oxidation treatments. The particles in the primary reactor are larger, requiring a weaker intensity of surface oxidation treatment, and the working gas concentration is controlled to be lower. The particles in the secondary reactor are smaller, requiring a stronger intensity of surface oxidation treatment, and the working gas concentration is controlled to be higher. A feedforward control method is adopted to calculate the required working gas flow rate based on the material processing delivery volume, determine the surface oxidation temperature and reaction time based on the physical properties of the material, such as particle size distribution, specific surface area, pore analysis results, etc., adjust the reactor concentration setting range, and control the working gas flow rate. The working gas concentration in the secondary reactor is usually controlled to be higher than that in the primary reactor, and the concentration ratio is usually 1-5 times.

[0035] The working gas introduced into the primary reactor and the secondary reactor is oxygen-enriched air with an oxygen content of 21%-50%, which is supplied by an external gas source. The oxygen concentration needs to be adjusted according to the characteristics of the material and maintained in coordination with the heating temperature and processing time to achieve the best processing effect.

[0036] The process of surface oxidation treatment of graphite powder, a negative electrode active material of waste lithium batteries or graphite powder waste generated in battery production is carried out according to the following steps.

[0037] S1. Ensure that the gas path of the device is unobstructed, and the tail gas emission is connected to the tail gas treatment system. The treated material is sent into the primary reactor (1) by pneumatic conveying, and the material is added according to the rated volume of the reactor. After completion, stop adding the material.

[0038] S2. Start the heating element (2) to heat the primary reactor, and heat the material in the primary reactor to a constant temperature of 200-500 degrees Celsius through heat conduction effect. Set the heating element to automatic control, and change the heating power as the temperature changes to keep the temperature constant.

[0039] S3, introducing fluidizing gas from the primary fluidizing air inlet (5), the introduced gas is nitrogen, and the gas flow rate is controlled to make the powder enter the fluidized state, and the gas flow rate is controlled at 0.1-2 meters per second. The fluidized state of the material in the reactor is determined by detecting the pressure difference between the inlet and outlet of the primary reactor. The gas flow rate is controlled according to the physical property test data of the material. The higher the particle size distribution Dv50, the greater the gas speed control.

[0040] S4. Introduce working gas into the primary working gas inlet (7), wherein the molar ratio of the total amount of the primary working gas to the material to be processed is 1:5-1:20.

[0041] S5. Under the action of the fluidizing gas, part of the material flows into the secondary reactor (10) along with the gas flow. The working gas is introduced into the secondary working gas inlet (13), and the total amount of the secondary working gas is 1-5 times the total amount of the primary working gas.

[0042] S6. According to the type and characteristics of the material, the duration and flow rate of ventilation are controlled. After all the working gases have reacted, the heating element is stopped and the reacted materials are discharged.

[0043] The above method was used to treat two samples, and the specific fluidizing gas velocity (specific fluidizing gas velocity - the minimum gas velocity that can fluidize a sample is the start-up fluidizing gas velocity, and the ratio of the gas velocity during operation to the start-up fluidizing gas velocity is the specific fluidizing gas velocity), reaction temperature and the first and second level working gas volume ratio were changed respectively. The comparative experimental results are as follows:

[0044]

[0045] It can be seen from the experimental results that the samples treated by this method can effectively reduce the specific surface area of ​​the product, improve the initial efficiency of battery production, and better achieve the purpose of improving product value.

[0046] The continuous surface oxidation treatment of the material can be carried out according to the following steps.

[0047] S1. Start the device according to the steps described above, keep the device in a constant temperature state, keep the material in a fluidized state, and keep the material between the primary reactor and the secondary reactor in a stable circulation state.

[0048] S2. Continuously pneumatically conveying the material to be processed into the primary reactor (1). The conveying amount is calculated based on the processing capacity of the reaction device to ensure that the ratio of the total amount of material accommodated in the reaction device to the amount of material to be processed added per minute is greater than 10.

[0049] S3. Stably introduce the reaction gas into the primary reactor and the secondary reactor. The gas flow rate is adjusted according to the amount of the material to be processed. The introduction flow rate of the primary and secondary reaction gases is controlled according to the set molar ratio.

[0050] S4. A discharge port is set on the side wall of the primary reactor. The discharge port is located above the air flow distributor. The gas-solid mixture of the material is sucked out by an external negative pressure device. The sucked-out amount is related to the amount of the processed material added, so as to keep the amount of material contained in the reaction device unchanged.

[0051] S5. The device stopping method is the same as the intermittent working stopping method.

[0052] Although the embodiments of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments.

Claims

1. A fluidized reaction device for surface oxidation treatment of regenerated graphite, used for regeneration of negative electrode graphite powder of lithium battery, characterized in that: The invention comprises a primary reactor (1) and a secondary reactor (10) connected in series, which are connected via a primary exhaust pipe (9) and a secondary discharge pipe (15). The outer side of the outer wall of the primary reactor (1) is wrapped with a heating element (2), which generates heat through an external energy source to heat the primary reactor and the internal materials. The airflow distributor (3) is located in the middle and lower part of the cross section of the primary reactor (1), and can support the materials and allow the gas to pass from bottom to top. The primary reactor (1) comprises five interfaces, a primary feed port (4) is located on the side wall, a primary fluidizing air inlet (5) is located in the middle of the bottom plate, a primary exhaust port (6) is located at the top, a primary working air inlet (7) is located on the side wall near the upper surface of the airflow distributor, and a primary reflux feed port (8) is located at the top. The secondary reactor (10) comprises four interfaces, a secondary air inlet (11) is located on the side wall, a secondary exhaust port (12) is located at the top, a secondary working air inlet (13) is located on the side wall near the bottom, and a secondary discharge port (14) is located at the bottom. The shape of the secondary reactor is a cone or a square cone.

2. The fluidized reaction device for surface oxidation treatment of regenerated graphite according to claim 1, characterized in that: The first-stage reactor (1) is a hollow cylinder with a variable inner diameter, with a small diameter at the bottom and a large diameter at the top. The fluidizing air inlet (5) at the bottom is arranged concentrically with the reactor. The shell of the first-stage reactor (1) is made of quartz, corundum or other high-temperature and oxidation-resistant materials. The first-stage feed inlet (4) adopts pneumatic conveying to convey materials. The first-stage exhaust port (6) is arranged at the center of the top cover, and the first-stage working air inlet (7) is arranged in the tangential direction of the outer wall of the reactor.

3. The fluidized reaction device for surface oxidation treatment of regenerated graphite according to claim 1, characterized in that: The secondary reactor (10) is a hollow cylinder with a variable inner diameter, with a small diameter at the bottom and a large diameter at the top. The secondary air inlet (11) is located in the tangential direction of the outer wall of the secondary reactor, and the secondary working gas inlet (13) is located in the tangential direction of the outer wall of the secondary reactor. The rotation direction of the working gas inlet is the same as the flow direction of the gas-solid mixture in the reactor.

4. The fluidized reaction device for surface oxidation treatment of regenerated graphite according to claim 1, characterized in that: The heating element (2) is heated by resistance, the distance between the heating element and the reactor shell is 2-50 mm, and a heat preservation material is arranged outside the heating element, so that the heating element and the first-stage reactor are enclosed in a heat preservation space.

5. The fluidized reaction device for surface oxidation treatment of regenerated graphite according to claim 1, characterized in that: The air flow distributor (3) is of a perforated plate type, and an umbrella-shaped air lifting cap is arranged on the hole, with a hole diameter of 1-5 mm.

6. The fluidized reaction device for surface oxidation treatment of regenerated graphite according to claim 1, characterized in that: The working gas is oxygen-enriched air with an oxygen content of 21%-50%.

7. The fluidized reaction device for surface oxidation treatment of regenerated graphite according to claim 1, characterized in that: The ratio of the gas flow cross-sectional areas of the primary reactor (1) and the secondary reactor (10) is between 1:1.5 and 1:

5.

8. A method for surface oxidation treatment of regenerated graphite, wherein the material treated by this method is graphite powder of the negative electrode of waste lithium batteries or graphite powder waste generated in battery production, characterized in that: The method uses the surface oxidation treatment fluidized reaction device according to any one of claims 1 to 7, and the steps are as follows: S1. The material to be processed is delivered into the primary reactor (1) by pneumatic conveying. S2. Start the heating element (2) to heat the primary reactor. Through the heat conduction effect, the material in the primary reactor is heated to a constant temperature of 200-500 degrees Celsius. After the temperature is constant, set the heating element to automatic control and change the heating power as the temperature changes to keep the temperature constant. S3. Fluidizing gas is introduced from the primary fluidizing air inlet (5), wherein the introduced gas is nitrogen, and the gas flow rate is controlled to gradually increase so that the powder enters a fluidized state. The gas flow rate is controlled at 0.1-2 m / s. S4. A working gas is introduced into the primary working gas inlet (7), wherein the molar ratio of the total amount of the primary working gas to the material to be processed is 1:5-1:

20. S5. Under the action of the fluidizing gas, part of the material flows into the secondary reactor (10) along with the gas flow. The working gas is introduced into the secondary working gas inlet (13), and the total amount of the secondary working gas is 1-5 times the total amount of the primary working gas. S6. According to the type and characteristics of the material, control the duration and flow rate of ventilation, stop heating the heating element after all the working gases have reacted, and discharge the reacted materials.

Images