A method for preparing nano-graphene powder

Abstract

The application relates to the technical field of graphene processing, and particularly discloses a preparation method of nano-graphene powder, which comprises the following steps: weighing graphite raw materials; opening a discharge valve of a feeding cabin, and feeding the graphite raw materials into a pressure stabilizing cabin; sucking the graphite raw materials from the pressure stabilizing cabin into a high-pressure cabin of a first airflow mill, and performing first-stage airflow grinding to obtain first-stage grinding materials; conveying the first-stage grinding materials with a thickness not greater than 10 microns to a high-pressure cabin of a second airflow mill; processing the first-stage grinding materials in the high-pressure cabin of the second airflow mill to obtain second-stage grinding materials; conveying the second-stage grinding materials with a thickness not greater than 100 nanometers to a flow energy depolymerization cabin; and processing the second-stage grinding materials in the flow energy depolymerization cabin to screen and obtain nano-graphene powder; the high-purity graphite raw materials are processed through a three-stage gradient processing architecture, a negative feedback adjustment scheme is introduced in each processing link, the quality of products in different stages is controlled, a progressive processing technology is constructed, and the product yield is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of graphene processing technology, specifically a method for preparing nano-graphene powder. Background Technology

[0002] Nano-graphene powder possesses high specific surface area, excellent electrical / thermal conductivity, good mechanical properties, and chemical stability, and its functions cover multiple fields, including at least thermal conductivity and heat dissipation, catalysis, adsorption and environmental protection, biomedicine, and reinforced composite materials. Its preparation process is crucial. There are many existing methods for preparing nano-graphene powder, including physical exfoliation, chemical vapor deposition, and redox methods. Among these methods, physical exfoliation is relatively easy to operate, extremely environmentally friendly, and produces products with intact structures. However, its drawback is also obvious: the yield is generally low. Therefore, how to improve the yield of physical exfoliation is the technical problem that this invention aims to solve. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing nano-graphene powder to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for preparing nano-graphene powder, the method comprising:

[0006] Step S1: Weigh the graphite raw material; the purity of the graphite raw material is not less than 99%, and the precision is 100 mesh;

[0007] Step S2: Start the suction pump to suck the graphite raw material into the feeding chamber;

[0008] Step S3: Open the discharge valve of the feeding chamber and feed the graphite raw material into the pressure stabilizing chamber;

[0009] Step S4: The graphite raw material is drawn from the pressure stabilizing chamber into the high-pressure chamber of the primary air jet mill for primary air milling to obtain primary abrasive.

[0010] Step S5: The first classifier classifies the primary abrasive, and the primary abrasive with a thickness greater than 10 micrometers is transported to the high-pressure chamber of the primary air jet mill, while the primary abrasive with a thickness of no more than 10 micrometers is transported to the high-pressure chamber of the secondary air jet mill.

[0011] Step S6: The primary abrasive is processed by the high-pressure chamber of the secondary airflow mill to obtain the secondary abrasive;

[0012] Step S7: The second classifier classifies the secondary abrasives, and the secondary abrasives with a thickness greater than 100 nanometers are transported to the high-pressure chamber of the secondary airflow mill, while the secondary abrasives with a thickness of no more than 100 nanometers are transported to the fluid energy deagglomeration chamber.

[0013] Step S8: The secondary abrasive is processed by the flow energy depolymerization chamber and screened to obtain nano-graphene powder; the thickness of the nano-graphene powder is no more than 2 nanometers.

[0014] As a further aspect of the present invention: the air pressure of the primary air mill high-pressure chamber is 0.39-0.59MPa, the nozzle diameter is 2.2-3.0mm, the gas flow rate is 1.5-3.0m³ / min, the processing time is 3-6min / batch, and the mass of the graphite raw material entering the primary air mill high-pressure chamber is no more than 100kg per batch.

[0015] As a further aspect of the present invention: the air pressure of the secondary air mill high-pressure chamber is 0.69-0.88MPa, the nozzle diameter is 0.8-1.4mm, the gas flow rate is 1.5-2.5m³ / min, and the processing time is 6-12min / batch.

[0016] As a further aspect of the present invention: the air pressure of the flow energy depolymerization chamber is 0.98–1.37 MPa, the nozzle flow rate is 4–6 times the speed of sound, the single cycle time is 3–6 s, and the number of cycles is 600–1200.

[0017] As a further embodiment of the present invention: the first classifier has a classifying disc diameter of 250–350 mm, a rotation speed of 1000–1300 rpm, an air intake volume of 2.0–2.5 m³ / min, and an inlet-outlet pressure difference of 150–350 Pa; the second classifier has a classifying disc diameter of 120–220 mm, a rotation speed of 3000–4500 rpm, an air intake volume of 1.6–2.0 m³ / min, and an inlet-outlet pressure difference of 300–800 Pa.

[0018] As a further aspect of the present invention: the equipment used to detect the thickness of the primary abrasive, the secondary abrasive, and the nano-graphene powder in the preparation method is an online particle size analyzer; the output result is a thickness distribution curve, which is used to represent the distribution of the proportion of particles of different thicknesses.

[0019] As a further aspect of the present invention, the preparation method further includes:

[0020] An online particle size analyzer-based detection step is added between step S4 and step S5:

[0021] Based on the thickness distribution curve of the primary abrasive detected by an online particle size analyzer, D50 and D90 are determined from the thickness distribution curve;

[0022] When D50 and D90 reach the preset threshold, proceed to step S5;

[0023] When D50 and D90 do not reach the preset threshold, increase the air pressure in the high-pressure chamber of the first-stage air mill.

[0024] An online particle size analyzer-based detection step is added between step S6 and step S7:

[0025] Based on the thickness distribution curve of the secondary abrasive detected by an online particle size analyzer, D50 and D90 are determined from the thickness distribution curve;

[0026] When D50 and D90 reach the preset threshold, proceed to step S7;

[0027] When D50 and D90 do not reach the preset threshold, increase the air pressure in the high-pressure chamber of the secondary air mill.

[0028] As a further aspect of the present invention: step S5 in the preparation method further includes:

[0029] The initial discharge amount is detected by the online particle size analyzer built into the first classifier; the process of determining the initial discharge amount is as follows: the input material amount is acquired in real time, and when the input material amount reaches the batch amount of the preset ratio, the material amount entering the high-pressure chamber of the secondary air jet mill is acquired as the output material amount, and the ratio of the output material amount to the input material amount is calculated.

[0030] The batch quantity is determined based on the calculated ratio, and a control command is generated to direct the unloading valve based on the batch quantity.

[0031] The working time of the first-stage gas mill high-pressure chamber, the second-stage gas mill high-pressure chamber, and the flow energy depolymerization chamber are adjusted synchronously.

[0032] As a further aspect of the present invention, the preparation method further includes:

[0033] Measure the physical parameters of graphite raw materials;

[0034] The operating parameters of the discharge valve, the high-pressure chamber of the first-stage airflow mill, the high-pressure chamber of the second-stage airflow mill, and the flow energy depolymerization chamber are set in a gradient manner as initial operating parameters; the initial operating parameters are an array, where each element corresponds to a parameter type, and the element value is the parameter quantity of the parameter type;

[0035] Collect physical parameters, initial working parameters, and corresponding preparation rates, and create a record table;

[0036] Add a step between step S1 and step S2:

[0037] Measure the physical parameters of the graphite raw material, match the initial working parameters that maximize the preparation rate in the record table, and send them to the corresponding equipment.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] This invention processes high-purity graphite raw materials through a three-level gradient processing architecture. A negative feedback adjustment scheme is introduced in each processing step to control the product quality at different stages, thus constructing a progressive processing technology that greatly improves the product yield.

[0040] Furthermore, in the existing two-stage processing, the product yield is highly dependent on the experience of the workers. The workers adjust the equipment parameters based on the actual results, which in turn affects the product yield. In the technical solution of this invention, a detection and recursive control scheme based on an online particle size analyzer is introduced. On the one hand, this reduces the dependence on workers, and on the other hand, it also reduces the amount of rework in the processing process and shortens the processing time. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention.

[0042] Figure 1 The process layout diagram for the graded processing is shown.

[0043] In the diagram: 1-Feeding chamber, 2-Feeding negative pressure chamber, 3-Mixing dryer, 4-Pressure stabilizing chamber, 5-First-stage air jet mill high-pressure chamber, 6-First-stage air jet mill negative pressure chamber, 7-First-stage classifier, 8-Second-stage air jet mill high-pressure chamber, 9-Second-stage air jet mill negative pressure chamber, 10-Second-stage classifier, 11-Fluid energy depolymerization pretreatment chamber, 12-Fluid energy depolymerization chamber, 13-Finished product negative pressure chamber, 14-Finished product automatic packaging machine. Detailed Implementation

[0044] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0045] Material:

[0046] Unless otherwise specified, all methods used in this invention are conventional methods known to those skilled in the art, and all reagents and materials used are commercially available products.

[0047] equipment:

[0048] Unless otherwise specified, all equipment used in this invention is conventional equipment known to those skilled in the art. Comparative Examples 2 and 3, as well as Examples 1-4 provided in this invention, all employ conventional equipment. Figure 1 The equipment layout shown is as follows: Figure 1 It is only used to represent the layout architecture of the entire production process.

[0049] Example 1:

[0050] In this embodiment of the invention, a method for preparing nano-graphene powder is provided, the method comprising:

[0051] Step S1: Weigh 500 kg of graphite raw material; the purity of the graphite raw material is not less than 99%, and the precision is 100 mesh; the graphite raw material is in powder form;

[0052] Step S2: Start the suction pump to suck the graphite raw material into the feeding chamber; the negative pressure of the suction pump is -0.06Mpa;

[0053] Step S3: Open the discharge valve of the feeding chamber and put the graphite raw material into the pressure stabilizing chamber. The pressure stabilizing chamber is maintained at 0.05MPa. The discharge valve is a controllable valve with a single discharge capacity of 100kg.

[0054] Step S4: The graphite raw material is drawn from the pressure stabilizing chamber into the high-pressure chamber of the primary air jet mill for primary air milling to obtain primary abrasive. The high-pressure chamber of the primary air jet mill is equipped with a negative pressure device. After the pressure stabilizing chamber stabilizes, the graphite raw material is drawn from the pressure stabilizing chamber into the high-pressure chamber of the primary air jet mill by the negative pressure device. The negative pressure of the negative pressure device is -0.05MPa. The air pressure of the high-pressure chamber of the primary air jet mill is 0.5MPa, its nozzle diameter is 2.5mm, the gas flow rate is 2.5m³ / min, the processing time is 5min, and the mass of the graphite raw material entering the high-pressure chamber of the primary air jet mill is 100kg.

[0055] Step S5: The first classifier classifies the primary abrasive, and the primary abrasive with a thickness greater than 10 micrometers is transported to the high-pressure chamber of the primary air-flow mill, while the primary abrasive with a thickness of no more than 10 micrometers is transported to the high-pressure chamber of the secondary air-flow mill; the first classifier has a classification disc diameter of 300 mm, a rotation speed of 1000 rpm, an air intake volume of 2.2 m³ / min, and an inlet-outlet pressure difference of 200 Pa.

[0056] Step S6: The primary abrasive is processed by the high-pressure chamber of the secondary air mill to obtain the secondary abrasive; the air pressure of the high-pressure chamber of the secondary air mill is 0.8MPa, the nozzle diameter is 1.1mm, the gas flow rate is 2m³ / min, and the processing time is 10min.

[0057] Step S7: The second classifier classifies the secondary abrasive, and the secondary abrasive with a thickness greater than 100 nanometers is transported to the high-pressure chamber of the secondary airflow mill, while the secondary abrasive with a thickness of no more than 100 nanometers is transported to the fluid energy deagglomeration chamber; the second classifier has a classification disc diameter of 150 mm, a rotation speed of 4000 rpm, an air intake volume of 1.6 m³ / min, and an inlet and outlet pressure difference of 600 Pa;

[0058] Step S8: The secondary abrasive is processed by the flow energy depolymerization chamber and screened to obtain nano-graphene powder; the thickness of the nano-graphene powder is no more than 2 nanometers; the air pressure of the flow energy depolymerization chamber is 1.2 MPa, the nozzle flow rate is 6 times the speed of sound, the single cycle time is 5 seconds, and the number of cycles is 900.

[0059] The first classifier, the second classifier, and the flow energy depolymerization chamber are equipped with an online particle size analyzer to obtain the thickness of the output, which represents the thickness of the primary abrasive, the secondary abrasive, and the nano-graphene powder, respectively.

[0060] Example 2:

[0061] The difference from Example 1 is that a detection step based on an online particle size analyzer is added between step S4 and step S5:

[0062] Based on the thickness distribution curve of the primary abrasive detected by an online particle size analyzer, D50 and D90 are determined from the thickness distribution curve; D50 is the median diameter, indicating that 50% of the particle size is smaller than this value; D90 is the coarse thickness, indicating that 90% of the particle size is smaller than this value; when both D50 and D90 reach the preset threshold, step S5 is performed; the threshold for D50 is 8 micrometers, and the threshold for D90 is 20 micrometers.

[0063] When D50 and D90 do not reach the preset thresholds, the air pressure in the high-pressure chamber of the first-stage air mill is increased. Specifically, the adjustment method is to calculate the difference between the threshold and D50, input the difference into a preset conversion formula, and determine the amount of pressure increase. The formula is: In the formula, This represents the increase in air pressure, expressed in MPa. The difference is expressed in micrometers. The value is 0.05; of course, the k value can also be modified by the staff. In addition, the high-pressure chamber of the first-level air mill has a preset threshold, which is not more than 1 MPa and not less than 0.35 MPa.

[0064] Of course, a calculation process based on the difference between the threshold and D90 can also be introduced. In this case, the formula is: In the formula, For the increase in air pressure, This is the difference between the threshold and D50. The difference between the threshold and D90. It is 0.04. It is 0.01.

[0065] An online particle size analyzer-based detection step is added between step S6 and step S7:

[0066] Based on the thickness distribution curve of the secondary abrasive detected by an online particle size analyzer, D50 and D90 are determined from the thickness distribution curve;

[0067] When D50 and D90 reach the preset threshold, proceed to step S7;

[0068] When D50 and D90 do not reach the preset threshold, increase the air pressure in the high-pressure chamber of the secondary air mill.

[0069] Its workflow is similar to that of the high-pressure chamber of the first-stage gas mill, the difference being that the threshold of D50 is 80 nanometers and the threshold of D90 is 20 nanometers.

[0070] When D50 and D90 do not reach the preset thresholds, the air pressure in the high-pressure chamber of the secondary air mill is increased. Specifically, the adjustment method is to calculate the difference between the threshold and D50, input the difference into a preset conversion formula, and determine the amount of pressure increase. The formula is: In the formula, This represents the increase in air pressure, expressed in MPa. The difference is expressed in nanometers. The value is 0.005; of course, the k value can also be modified by the staff. In addition, the high-pressure chamber of the first-level air mill has a preset threshold, which is not more than 1 MPa and not less than 0.35 MPa.

[0071] Of course, a calculation process based on the difference between the threshold and D90 can also be introduced. In this case, the formula is: In the formula, For the increase in air pressure, This is the difference between the threshold and D50. The difference between the threshold and D90. It is 0.004. It is 0.001.

[0072] Example 3:

[0073] Unlike Example 2, step S5 in the preparation method further includes:

[0074] The initial discharge volume is detected by the online particle size analyzer built into the first classifier;

[0075] The process for determining the initial material quantity is as follows: The input material quantity is acquired in real time. When the input material quantity reaches a preset batch quantity, the material quantity entering the high-pressure chamber of the secondary air jet mill is acquired as the output material quantity, and the ratio of the output material quantity to the input material quantity is calculated. The preset ratio can be 50%. When the graphite raw material is 100 kg, while the primary air jet mill high-pressure chamber processes 100 kg of graphite raw material, the primary abrasive is fed into the first classifier for classification. When the material quantity entering the first classifier reaches 50% of the batch quantity, i.e., 50 kg, the material quantity entering the high-pressure chamber of the secondary air jet mill is acquired as the output material quantity, and the ratio of the output material quantity to the input material quantity is calculated. This represents the initial working rate of the primary air jet mill high-pressure chamber. In the above preparation method, there is a negative feedback cyclic processing process (substandard raw materials are returned to the original equipment for processing). Given sufficient time, the final product is qualified. Based on this, the initial working rate is equivalent to the conversion situation during the initial processing, essentially reflecting the quality of the raw materials.

[0076] The batch quantity is determined based on the calculated ratio, and a control command is generated to direct the unloading valve based on the batch quantity.

[0077] The current batch size is 100kg per batch. The control command pointing to the unloading valve is used to control the batch size. The larger the ratio, the better the raw material quality. The relationship is as follows: In the formula, For the change in mass, For the calculated ratio, The preset ratio is 0.8. The preset correction factor is [value] kg. The value can be 100kg; when When the ratio is 0.82, it indicates that the ratio has increased, which means that the raw material quality is better. At this time, the weight can be increased by 100 * 0.02, which is 2 kg. The batch quantity becomes 102 kg.

[0078] Synchronously adjust the working time of the first-stage air mill high-pressure chamber, the second-stage air mill high-pressure chamber, and the fluid energy depolymerization chamber;

[0079] When batch quantities change, the operating times of the primary air mill high-pressure chamber, the secondary air mill high-pressure chamber, and the fluid energy depolymerization chamber should be adjusted synchronously. The specific adjustment scheme is as follows: In the formula, To increase the amount of time, As a correction factor, the high-pressure chamber of the first-stage air mill corresponds to... The time is 6 minutes, corresponding to the high-pressure chamber of the secondary air mill. The duration is 12 minutes, corresponding to the flow energy depolymerization chamber. It is the product of the current loop count and the duration of the current single loop.

[0080] In the above content, the working time of the first-stage gas mill high-pressure chamber, the second-stage gas mill high-pressure chamber, and the fluid energy depolymerization chamber are set with peak values ​​of 8 min, 15 min, and 120 min, respectively; the batch quantity is also set with a peak value of 120 kg.

[0081] Example 4:

[0082] Unlike Example 3, the preparation method further includes:

[0083] Measure the physical parameters of graphite raw materials; physical parameters include humidity, powder density, electrostatic potential and thickness distribution;

[0084] The operating parameters of the unloading valve, the high-pressure chamber of the first-stage airflow mill, the high-pressure chamber of the second-stage airflow mill, and the flow energy depolymerization chamber are set in a gradient as initial operating parameters. These initial operating parameters are an array, where each element corresponds to a parameter type, and the element value is the parameter quantity of that parameter type. For the unloading valve, the gradient is set to the raw material input amount (1 kg), the pressure gradient of the high-pressure chamber of the first-stage airflow mill is 0.02 MPa, the gas flow rate gradient is 0.1 m³ / min, and the processing time gradient is 30 s; the pressure gradient of the high-pressure chamber of the second-stage airflow mill is 0.02 MPa, the gas flow rate gradient is 0.1 m³ / min, and the processing time gradient is 30 s; the pressure gradient of the flow energy depolymerization chamber is 0.02 MPa, the nozzle velocity gradient is 0.1 times the speed of sound, the single cycle time gradient is 0.1 s, and the number of cycles is 5.

[0085] Collect physical parameters, initial working parameters, and corresponding preparation rates, and create a record table;

[0086] Add a step between step S1 and step S2:

[0087] Measure the physical parameters of the graphite raw material, match the initial working parameters that maximize the preparation rate in the record table, and send them to the corresponding equipment;

[0088] The measurement process is as follows: humidity is measured using a capacitive humidity sensor, thickness distribution (PSD) is measured using an online laser particle size analyzer, powder density is measured using a tap density meter, and electrostatic potential is measured using an electrostatic potential sensor.

[0089] Comparative Example 1:

[0090] In this embodiment of the invention, a method for preparing nano-graphene powder is provided, the method comprising:

[0091] Step S1: Weigh 500 kg of graphite raw material; the purity of the graphite raw material is not less than 99%, and the precision is 100 mesh; the graphite raw material is powder.

[0092] Step S2: Start the suction pump to suck the graphite raw material into the feeding chamber; the negative pressure of the suction pump is -0.06Mpa;

[0093] Step S3: Open the discharge valve of the feeding chamber and put the graphite raw material into the pressure stabilizing chamber. The pressure stabilizing chamber is maintained at 0.05MPa. The discharge valve is a controllable valve with a single discharge capacity of 100kg.

[0094] Step S4: The graphite raw material is drawn from the pressure stabilizing chamber into the high-pressure chamber of the air jet mill for processing to obtain abrasive. The high-pressure chamber of the air jet mill is equipped with a negative pressure device. After the pressure in the pressure stabilizing chamber stabilizes, the graphite raw material is drawn from the pressure stabilizing chamber into the high-pressure chamber of the air jet mill via the negative pressure device. The negative pressure of the negative pressure device is -0.05 MPa. The air pressure in the high-pressure chamber of the air jet mill is 0.7 MPa, the nozzle diameter is 1.4 mm, the gas flow rate is 1.6 m³ / min, and the processing time is 15 min.

[0095] Step S5: The abrasive is processed by the flow energy depolymerization chamber and screened to obtain nano-graphene powder; the thickness of the nano-graphene powder is no more than 2 nanometers; the air pressure of the flow energy depolymerization chamber is 1.0 MPa, the nozzle flow rate is 5 times the speed of sound, the single cycle time is 5 seconds, and the number of cycles is 600.

[0096] Comparative Example 2:

[0097] In this embodiment of the invention, a method for preparing nano-graphene powder is provided, the method comprising:

[0098] Step S1: Weigh 500 kg of graphite raw material; the purity of the graphite raw material is not less than 99%, and the precision is 100 mesh; the graphite raw material is in powder form;

[0099] Step S2: Start the suction pump to suck the graphite raw material into the feeding chamber; the negative pressure of the suction pump is -0.06Mpa;

[0100] Step S3: Open the discharge valve of the feeding chamber and put the graphite raw material into the pressure stabilizing chamber. The pressure stabilizing chamber is maintained at 0.05MPa. The discharge valve is a controllable valve with a single discharge capacity of 100kg.

[0101] Step S4: The graphite raw material is drawn from the pressure stabilizing chamber into the high-pressure chamber of the primary air jet mill for primary air milling to obtain primary abrasive. The high-pressure chamber of the primary air jet mill is equipped with a negative pressure device. After the pressure stabilizing chamber stabilizes, the graphite raw material is drawn from the pressure stabilizing chamber into the high-pressure chamber of the primary air jet mill by the negative pressure device. The negative pressure of the negative pressure device is -0.05MPa. The air pressure of the high-pressure chamber of the primary air jet mill is 0.4MPa, the nozzle diameter is 3mm, the gas flow rate is 2m³ / min, the processing time is 4min, and the mass of the graphite raw material entering the high-pressure chamber of the primary air jet mill is 100kg.

[0102] Step S5: The first classifier classifies the primary abrasive, and the primary abrasive with a thickness greater than 10 micrometers is transported to the high-pressure chamber of the primary air-flow mill, while the primary abrasive with a thickness of no more than 10 micrometers is transported to the high-pressure chamber of the secondary air-flow mill; the first classifier has a classification disc diameter of 300 mm, a rotation speed of 1000 rpm, an air intake volume of 2.2 m³ / min, and an inlet-outlet pressure difference of 200 Pa.

[0103] Step S6: The primary abrasive is processed by the high-pressure chamber of the secondary air mill to obtain the secondary abrasive; the air pressure of the high-pressure chamber of the secondary air mill is 0.7MPa, the nozzle diameter is 1.4mm, the gas flow rate is 1.6m³ / min, and the processing time is 8min.

[0104] Step S7: The second classifier classifies the secondary abrasive, and the secondary abrasive with a thickness greater than 100 nanometers is transported to the high-pressure chamber of the secondary airflow mill, while the secondary abrasive with a thickness of no more than 100 nanometers is transported to the fluid energy deagglomeration chamber; the second classifier has a classification disc diameter of 150 mm, a rotation speed of 4000 rpm, an air intake volume of 1.6 m³ / min, and an inlet and outlet pressure difference of 600 Pa;

[0105] Step S8: The secondary abrasive is processed by the flow energy depolymerization chamber and screened to obtain nano-graphene powder; the thickness of the nano-graphene powder is no more than 2 nanometers; the air pressure of the flow energy depolymerization chamber is 1.0 MPa, the nozzle flow rate is 5 times the speed of sound, the single cycle time is 5 seconds, and the number of cycles is 600.

[0106] The first classifier, the second classifier, and the flow energy depolymerization chamber are equipped with an online particle size analyzer to obtain the thickness of the output, which represents the thickness of the primary abrasive, the secondary abrasive, and the nano-graphene powder, respectively.

[0107] Comparative Example 3:

[0108] Unlike Comparative Example 2:

[0109] In step S4: the air pressure in the high-pressure chamber of the first-stage air mill is 0.55MPa, the nozzle diameter is 2.2mm, the gas flow rate is 3m³ / min, the processing time is 6min, and the mass of the graphite raw material entering the high-pressure chamber of the first-stage air mill is 100kg.

[0110] In step S6: the air pressure in the high-pressure chamber of the secondary air mill is 0.85 MPa, the nozzle diameter is 0.8 mm, the gas flow rate is 2.5 m³ / min, and the processing time is 12 min;

[0111] In step S8: the abrasive is processed by the flow energy depolymerization chamber and screened to obtain nano-graphene powder; the thickness of the nano-graphene powder is no more than 2 nanometers; the air pressure of the flow energy depolymerization chamber is 1.35 MPa, the nozzle flow rate is 6 times the speed of sound, the single cycle time is 6 seconds, and the number of cycles is 1000 times.

[0112] Tests of Examples 1-4 and Comparative Examples 1-3:

[0113] Regarding the descriptions of Examples 1-4 and Comparative Examples 1-3: Comparative Example 1 is an ungraded processing procedure, which is also the most conventional physical peeling method. Comparative Examples 2, 3 and Example 1 are graded processing procedures, but the specific equipment parameters are different. Example 2 introduces a pressure regulation process, Example 3 introduces a batch quantity regulation process, and Example 4 introduces an initial parameter matching process.

[0114] Test method:

[0115] Examples 1-4 and Comparative Examples 1-3 all included a feeding chamber. Five batches of graphite raw materials from different production batches were obtained. Each batch consisted of 3500 kg of graphite raw material. Each batch of graphite raw material was divided into seven groups of 500 kg each, and placed into the feeding chambers of Examples 1-4 and Comparative Examples 1-3 respectively. The preparation methods provided in Examples 1-4 and Comparative Examples 1-3 were performed. The total processing time for each 500 kg of graphite raw material was measured, and the mass of the produced nano-graphene powder was measured. There were a total of five batches of graphite raw materials. Each preparation method in Examples 1-4 and Comparative Examples 1-3 could obtain the total processing time and mass. Each preparation method could obtain five pairs of total processing time and mass. The average of the total processing time and the average of the mass were calculated as the final total processing time and mass.

[0116] The total processing time can be measured simply by timing, and the mass can be measured simply by weighing. However, the timing of these two parameters is important. The total processing time is calculated from the time the raw material is added until there is no raw material in the feeding chamber. The time period is the total processing time. When there is no raw material in the feeding chamber, the mass of the nano-graphene powder produced at this time is taken as the mass.

[0117] Test results:

[0118] Table 1

[0119]

[0120] Results Explanation:

[0121] Comparative Example 1 is a conventional scheme that does not employ a graded processing method in the initial processing stage. In other words, it is only a two-stage processing scheme, with one stage being initial processing and the other being finishing processing. It has the fastest processing time, but the product yield is very low. Comparative Example 2 introduces a graded processing process in the initial processing stage, but its parameters are relatively mild. Therefore, the processing time is similar, but the product yield is greatly improved. Comparative Example 3 uses high-intensity parameters, which results in a long processing time, but the product yield is improved compared to Comparative Example 2.

[0122] Based on the above Comparative Examples 1-3, the embodiments will be described. First, there is Example 1, which has equipment processing parameters between Comparative Example 3 and Comparative Example 2. Its processing time is between Comparative Example 3 and Comparative Example 1, and its product yield is also between Comparative Example 3 and Comparative Example 2. However, its processing time is about 12 hours, and considering the cost, its product yield is high enough, and the time is easier to coordinate, which is more in line with the existing shift system. Among Example 1, Comparative Example 3 and Comparative Example 2, Example 1 is considered to be the optimal one.

[0123] Then, based on Example 1, Example 2 introduces a pressure regulation process, which is based on a negative feedback regulation architecture of intelligent devices. During operation, the pressure is adjusted according to the actual output, and the total processing time is slightly shortened because the processing parameters are automatically adjusted to reduce rework. In addition, the product yield is also increased. Example 3 introduces a batch quantity regulation process based on Example 2, which can better control how 500kg of graphite raw material is processed in batches (originally 100kg per batch). The time is not fixed and may increase or decrease. During the test, it is similar to Example 2, slightly increased, but the product yield is improved. Example 4 matches better initial processing parameters based on Example 3, that is, there is a pre-matching process. The pre-matching process significantly reduces blind compensation and rework, the total processing time is reduced, and the product yield is also the highest, reducing losses.

[0124] In summary, without considering equipment costs, Example 4 is the optimal solution. In fact, the costs of different preparation methods mainly consist of two aspects: one is the equipment operating cost, which is mainly due to the processing time; the other is the equipment cost. Given the widespread availability of existing intelligent equipment, the cost of adding intelligent modules is not high, and relative to the yield, this cost is almost negligible. Of course, based on actual costs, Examples 2 and 3 are both feasible solutions. Introducing more intelligent equipment increases the possibility of damage, which is ignored in the technical solution of this invention. The specific choice should be made by the staff based on the circumstances.

[0125] It is worth mentioning that, for the above Examples 1-4 and Comparative Examples 1-3, because they use physical methods, there is almost no loss. As long as there is enough time, all raw materials will be processed into nano-graphene powder. Since substandard products will be returned to the previous processing step during the grading process, the final product rate is not 100% in a limited time (when all 500kg are put into the processing equipment). However, if there is enough time, the product rate can almost reach 100%.

[0126] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing nano-graphene powder, characterized in that, The method includes: Step S1: Weigh the graphite raw material; the purity of the graphite raw material is not less than 99%, and the precision is 100 mesh; Step S2: Start the suction pump to suck the graphite raw material into the feeding chamber; Step S3: Open the discharge valve of the feeding chamber and feed the graphite raw material into the pressure stabilizing chamber; Step S4: The graphite raw material is drawn from the pressure stabilizing chamber into the high-pressure chamber of the primary air jet mill for primary air milling to obtain primary abrasive. Step S5: The first classifier classifies the primary abrasive, and the primary abrasive with a thickness greater than 10 micrometers is transported to the high-pressure chamber of the primary air jet mill, while the primary abrasive with a thickness of no more than 10 micrometers is transported to the high-pressure chamber of the secondary air jet mill. Step S6: The primary abrasive is processed by the high-pressure chamber of the secondary airflow mill to obtain the secondary abrasive; Step S7: The second classifier classifies the secondary abrasives, and the secondary abrasives with a thickness greater than 100 nanometers are transported to the high-pressure chamber of the secondary airflow mill, while the secondary abrasives with a thickness of no more than 100 nanometers are transported to the fluid energy deagglomeration chamber. Step S8: The secondary abrasive is processed by the flow energy depolymerization chamber and screened to obtain nano-graphene powder; the thickness of the nano-graphene powder is no more than 2 nanometers; The preparation method further includes: An online particle size analyzer-based detection step is added between step S4 and step S5: Based on the thickness distribution curve of the primary abrasive detected by an online particle size analyzer, D50 and D90 are determined from the thickness distribution curve; When D50 and D90 reach the preset threshold, proceed to step S5; When D50 and D90 do not reach the preset threshold, increase the air pressure in the high-pressure chamber of the first-stage gas mill. An online particle size analyzer-based detection step is added between step S6 and step S7: Based on the thickness distribution curve of the secondary abrasive detected by an online particle size analyzer, D50 and D90 are determined from the thickness distribution curve; When D50 and D90 reach the preset threshold, proceed to step S7; When D50 and D90 do not reach the preset threshold, increase the air pressure in the high-pressure chamber of the secondary air mill. Step S5 in the preparation method further includes: The initial discharge amount is detected by an online particle size analyzer built into the first classifier; the process of determining the initial discharge amount is as follows: the input material amount is acquired in real time, and when the input material amount reaches the batch amount of the preset ratio, the material amount entering the high-pressure chamber of the secondary air jet mill is acquired as the output material amount, and the ratio of the output material amount to the input material amount is calculated. The batch quantity is determined based on the calculated ratio, and a control command is generated to direct the unloading valve based on the batch quantity. The working time of the high-pressure chamber of the first-stage gas flow mill, the high-pressure chamber of the second-stage gas flow mill, and the flow energy depolymerization chamber are adjusted synchronously.

2. The method for preparing nano-graphene powder according to claim 1, characterized in that, The high-pressure chamber of the primary airflow mill has a gas pressure of 0.39-0.59 MPa, a nozzle diameter of 2.2-3.0 mm, a gas flow rate of 1.5-3.0 m³ / min, a processing time of 3-6 min / batch, and the mass of graphite raw material entering the high-pressure chamber of the primary airflow mill is no more than 100 kg per batch.

3. The method for preparing nano-graphene powder according to claim 2, characterized in that, The high-pressure chamber of the secondary airflow mill has a gas pressure of 0.69-0.88 MPa, a nozzle diameter of 0.8-1.4 mm, a gas flow rate of 1.5-2.5 m³ / min, and a processing time of 6-12 min / batch.

4. The method for preparing nano-graphene powder according to claim 1, characterized in that, The pressure of the flow energy depolymerization chamber is 0.98–1.37 MPa, the nozzle flow rate is 4–6 times the speed of sound, the single cycle time is 3–6 s, and the number of cycles is 600–1200.

5. The method for preparing nano-graphene powder according to claim 1, characterized in that, The first classifier has a classifying disc diameter of 250–350 mm, a rotation speed of 1000–1300 rpm, an air intake volume of 2.0–2.5 m³ / min, and an inlet-outlet pressure difference of 150–350 Pa; the second classifier has a classifying disc diameter of 120–220 mm, a rotation speed of 3000–4500 rpm, an air intake volume of 1.6–2.0 m³ / min, and an inlet-outlet pressure difference of 300–800 Pa.

6. The method for preparing nano-graphene powder according to claim 5, characterized in that, In the preparation method, the equipment used to detect the thickness of the primary abrasive, the secondary abrasive, and the nano-graphene powder is an online particle size analyzer; the output result is a thickness distribution curve, which is used to represent the distribution of the proportion of particles of different thicknesses.

7. The method for preparing nano-graphene powder according to claim 1, characterized in that, The preparation method further includes: Measure the physical parameters of graphite raw materials; The operating parameters of the discharge valve, the high-pressure chamber of the first-stage airflow mill, the high-pressure chamber of the second-stage airflow mill, and the flow energy depolymerization chamber are set in a gradient manner as initial operating parameters; the initial operating parameters are an array, where each element corresponds to a parameter type, and the element value is the parameter quantity of the parameter type; Collect physical parameters, initial working parameters, and corresponding preparation rates, and create a record table; Add a step between step S1 and step S2: Measure the physical parameters of the graphite raw material, match the initial working parameters that maximize the preparation rate in the record table, and send them to the corresponding equipment.

Images