Prejudgment method for qualification of materials in artificial graphite pre-carbonization process

Abstract

The invention discloses a method for pre-judging whether materials in an artificial graphite pre-carbonization process are qualified or not. The method comprises the following steps: 1) putting qualified materials obtained by a machine grinding process into a silicon carbide crucible; 2) putting the crucible filled with the material into a corresponding train number for pre-carbonization process treatment, and counting the temperature condition of the kiln car marked with the serial number in the tunnel kiln in the carbonization process; (3) carrying out area integration on the temperature data recorded in the step (2) at 1000 DEG C or above for calculation; (4) detecting the pre-carbonized material; and 5) carrying out multiple batches of experiments. According to the method, the pre-carbonization condition can be effectively and rapidly known through the integral change of the temperature curve area, the process parameters can be rapidly adjusted, in the continuous large-scale production process, the pre-carbonization result can be predicted in advance by using the temperature integral area judgment method, the qualified stability of petroleum coke material products is ensured, the product percent of pass is improved, and the production cost is reduced. And the time consumed in the production material detection process is shortened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of artificial graphite negative electrode material preparation, in particular to a pre-judgment method for whether the material of the artificial graphite pre-carbonization process is qualified, which provides data support and decision basis for the optimization of the artificial negative electrode graphite material pre-carbonization process by applying the temperature curve in the pre-carbonization process and the material performance change rule. BACKGROUND

[0002] The artificial graphite negative electrode is one of the four main materials of lithium ion batteries, and pre-carbonization is one of the key steps in the processing of artificial graphite negative electrodes, which has a greater impact on the performance and processing cost of the product. In terms of process, pre-carbonization can improve the graphitization degree of the product and the filling rate of the crucible in the graphitization process, which helps to optimize the microstructure of the material, improve its electrical conductivity and reduce the power consumption of graphitization. In terms of material performance, pre-carbonization can improve the thermal stability and purity of the material, and by pre-carbonization, the volatile matter in the raw material can be removed to improve the carbon purity and create favorable conditions for subsequent high-temperature graphitization treatment. In addition, pre-carbonization can also reduce the oxygen functional groups in the material, further improving the thermal stability and chemical stability of the material, and helping to reduce the specific surface area of the material in the subsequent graphitization process. However, the traditional pre-carbonization process of artificial graphite material mainly relies on empirical tests and adjustments, which has the following problems: 1. High test cost: Since the pre-carbonization process of graphite material involves complex physical and chemical changes, in order to find suitable process parameters, a large number of tests need to be carried out, which has a high test cost.

[0003] 2. Difficult process optimization: The traditional method is difficult to accurately analyze the interaction between various parameters in the pre-carbonization process, resulting in a lack of systematization and accuracy in process optimization, which is difficult to meet the needs of high-quality graphite material production.

[0004] 3. Inaccurate process control: In actual production, it is difficult to accurately grasp the temperature, material reaction state and other key information in the pre-carbonization process in real time, which can easily lead to unstable product quality and post-control. SUMMARY

[0005] The purpose of the present application is to provide a method for judging whether the tap density, true density and other data of the material meet the requirements according to the area integral of the temperature change curve. This method can further optimize the pre-carbonization process, ensure the qualification of the material, and reduce the cost. In order to achieve the above purpose, the present application is realized by the following technical scheme.

[0006] According to one aspect of the present application, one purpose of the present application is to provide a pre-judgment method for whether the material of the artificial graphite pre-carbonization process is qualified, comprising the following steps: Step 1, the qualified material completed by the ball mill process is put into a silicon carbide crucible; Step 2, the crucible with the material is put into the corresponding vehicle for pre-carbonization process, and the temperature of the marked sequence kiln car during the carbonization process in the tunnel kiln is counted; Step 3, the temperature data recorded in step 2 is imported into Origin software for area integration above 1000℃ for calculation; Step 4, the pre-carbonized material is vibrated, the true density and volatile content are detected; Step 5, multiple batch experiments are carried out.

[0007] Preferably, the data of vibration, true density and volatile content detected in step 4 are statistically correlated with the area integral of the temperature above 1000℃ of the corresponding vehicle, a linear mathematical model is established, and the vibration, volatile and true density data of the material are calculated by inputting the temperature area integral into the model, the correlation mathematical model is y=2.51x10 -10 x 3 -1.12x10 -6 x 2 +0.0015x+0.123, wherein X is the temperature integral area and y is the vibration detection data.

[0008] Preferably, the above mathematical calculation model can be adjusted according to different materials, and the vibration density during pre-carbonization of the material can be predicted by inputting the integral area, and it is determined whether to extend the heating time or increase the temperature according to the requirements.

[0009] Preferably, the silicon carbide crucible in step 1 is 800-1200mm long and 500-600mm in diameter, and the crucible filling amount is about 60-90kg.

[0010] Preferably, the pre-carbonization treatment device in step 2 is a tunnel kiln with a total length of 120-160m, a width of 2.5-3.5m and a height of 3.5-4.5m, and 25-45 temperature points are arranged in the kiln, and 40-60 rail cars are arranged in the furnace.

[0011] Preferably, the pre-carbonization temperature statistics in step 2 are as follows: the speed of the kiln car entering the kiln and the time required for the kiln car to pass through each temperature section in the tunnel kiln are counted, the temperature curve of the kiln car passing through each temperature zone is recorded, and in order to ensure that the material in the middle of the kiln car can also be fully carbonized, the temperature in the high temperature section is above 1000℃.

[0012] Preferably, in step 3, the counted temperature in the interval is imported into Origin to obtain the integral area above 1000℃.

[0013] Preferably, the pre-carbonized material in step 4 is cooled by a quenching fan, part of the material in the crucible is taken for detection, the material is detected by using a tap density instrument, the true density is detected by using a gas displacement method true density instrument, the detected results are associated with the integral area above 1000 DEG C, the tap density standard that meets the requirements is determined according to the calculation formula, the integral area of the required temperature is inferred, and the integral area that needs to be increased is increased by increasing the feed speed or increasing the temperature of the furnace.

[0014] Advantages The present application can effectively and quickly understand the pre-carbonization condition by the integral area of the temperature curve, and quickly adjust the process parameters. In the process of continuous large-scale production, the method of using the integral area of the temperature to judge the tap density and the true density of the material can predict the pre-carbonization result in advance, ensure the stability of the qualified petroleum coke material product, improve the product qualification rate, and reduce the time consumed in the production material detection process.

[0015] The present application is simple and convenient to operate in the implementation process, and is very helpful to improve product quality.

[0016] The present application has the effect of stabilizing product performance, and the size of temperature change can be effectively judged according to the slope of the front end temperature point in the integral area graph, and the running phenomenon caused by too large temperature gradient when the kiln car passes can be reduced by adjusting.

[0017] The present application can infer the temperature change in the tunnel kiln according to the curve slope of the front end temperature and the rear end temperature in the high temperature section of the temperature curve, judge whether the temperature moves forward or backward, timely adjust the temperature in the kiln, increase the safety of production, and improve the stability of product quality. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0019] Figure 1 The integral area graph calculation method of example 2 Zhoushan coke tunnel kiln 60 minutes per car 1-6 car. DETAILED DESCRIPTION

[0020] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Prior to describing the present disclosure, it should be understood that the term used in the specification and the appended claims should not be construed as a limitation on the general and dictionary meanings and should be interpreted as having a meaning that is consistent with the technical ideas of the present disclosure on the basis of a principle that the inventors can properly define the concept of the terms to best explain the present disclosure. Therefore, the description herein is merely a preferred example and does not limit the scope of the present disclosure, and it should be understood that other equivalents and modifications can be made thereto without departing from the spirit and scope of the present disclosure.

[0021] In the present specification, the terms "comprise", "include", "have", "contain", or other similar terms are open-ended transitional phrases, which are intended to encompass non-exclusive inclusion. For example, a composition or article containing a plurality of elements is not limited to only the elements listed in the present specification, but can also include other elements not explicitly listed but generally inherent to the composition or article. In addition, unless explicitly stated otherwise, the term "or" refers to inclusive "or", not exclusive "or". For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and A and B are both true (or exist). In addition, in the present specification, the terms "comprise", "include", "have", "contain" should be interpreted as having been specifically disclosed and encompassing "consist of" and "consist essentially of" closed or semi-closed conjunctions.

[0022] In the present specification, all features or conditions defined in the form of a numerical range or a percentage range are for convenience and brevity only. Accordingly, the description of the numerical range or the percentage range should be considered to have encompassed and specifically disclosed all possible sub-ranges and individual numbers within the range, particularly integer numbers. For example, the range description "1 to 8" should be considered to have specifically disclosed all sub-ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., particularly sub-ranges defined by all integer numbers, and to have specifically disclosed individual numbers such as 1, 2, 3, 4, 5, 6, 7, 8, etc. within the range. The foregoing interpretation method applies to all contents of the present disclosure throughout the specification, regardless of the extent of the range, unless otherwise indicated.

[0023] If a number or other numerical values or parameters are expressed in a range, a preferred range, or a series of upper and lower limits, it should be understood that all ranges formed by any pair of the upper limit or the preferred value of the range and the lower limit or the preferred value of the range have been specifically disclosed herein, regardless of whether the ranges are separately disclosed. In addition, if a range of values is referred to herein, unless otherwise stated, the range should include its endpoints and all integers and fractions within the range.

[0024] In this document, numerical values ​​are to be understood as having a precision with significant digits, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover a range from 39.50 to 40.49.

[0025] The following embodiments are merely examples illustrating implementations of the present invention and do not constitute any limitation on the present invention. Those skilled in the art will understand that modifications made without departing from the spirit and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following embodiments are commercially available products.

[0026] Example A method for pre-judging the quality of materials in the pre-carbonization process of artificial graphite negative electrodes includes the following steps: Step 1: Put the qualified petroleum coke from the machine into the silicon carbide crucible, about 65 kg per crucible.

[0027] Step 2: Load the crucibles into railcars 1-6, with two layers of crucibles in each car, for a total of 32 crucibles. The railcars then enter the kiln according to the set process.

[0028] Step 3: Record the inlet temperature and control the inlet speed according to process requirements. The tunnel kiln is 130m long, and the time is relatively short. The high-temperature section temperature must be above 1000℃, and six temperature zones are set. Adjust the length and temperature of the high-temperature section according to the inlet time, utilizing the volatilization of raw materials to reduce gas consumption, but the highest temperature in the high-temperature section must be ≥1000℃. Record the temperature curve to determine if the pre-carbonization process is normal.

[0029] The specific feeding process is shown in Table 1 below.

[0030] Table 1

[0031] Step 4: Import the temperature detected by the furnace probe into Origin and calculate the integral area above 1000℃.

[0032] Step 5: After cooling, the petroleum coke material is tested using a tap density meter and its true density is tested using a gas displacement true density meter.

[0033] The test data is shown in Table 2 below.

[0034] Table 2

[0035] Example 1: The raw material was Zhoushan coke, the feed rate was 40 minutes / min, the high-temperature section temperature was set to ≥1000℃, and the pre-carbonization time was 1840 minutes. Example 2: raw material is Zhoushan coke, charging time is 60 minutes / min, set high temperature section temperature ≥ 1000℃, pre-carbonization time is 2760 min.

[0036] Example 3: raw material is Zhoushan coke, charging time is 70 minutes / min, set high temperature section temperature ≥ 1000℃, pre-carbonization time is 3220 min.

[0037] Example 4: raw material is Zhoushan coke, charging time is 90 minutes / min, high temperature section temperature ≥ 1000℃, pre-carbonization time is 4140 min.

[0038] Example 5: raw material is Zhoushan coke, charging time is 60 minutes / min, high temperature section temperature ≥ 1000℃, pre-carbonization time is 2760 min.

[0039] Example 6: raw material is Zhoushan coke, charging time is 40 minutes / min, high temperature section temperature ≥ 1000℃, pre-carbonization time is 4140 min.

[0040] Comparative examples 1, 2, 3, 4, 5, 6 and the above examples are different in that the raw material is replaced by Fushan needle coke. See Table 3 below.

[0041] Table 3

[0042] From the above results, it can be seen that the greater the integral area, the higher the tamping, when the charging time is 40 min / car, the set temperature of the high temperature section is ≥ 1000 degrees, due to the fast feeding speed, the material itself volatilizes and burns, causing the actual temperature in the kiln to reach 1320℃, the average value of the integral area is 2230, the average tamping is 1.08, when the feeding speed is 60 min / car, the average value of the integral area of each car above 1000℃ is 2620, the average tamping reaches 1.12, and the true density is about 2.0551, in the case of 70 min / car, due to the reduction of volatilization, the actual highest temperature is 1250 degrees, the tamping of the material is the average tamping 1.10, the average integral area is 2400, in the case of 90 min / car, the amount of volatile matter is reduced, when the high temperature section temperature is reduced to 1150℃, the average integral area is about 1500, the average tamping is about 1.05, and the average true density is 2.047. Similarly, the same process is carried out on Fushan coke, and the data is shown in Table 1. In summary, the integral area process can be changed according to the pre-carbon requirement, and is suitable for various petroleum coke materials, needle coke, and the change of tamping and true density of the material after pre-carbonization can be inferred by changing the integral area.

[0043] The cubic polynomial expression in Example 1 is: Y = 6e -11 X 3 -3e -07 X 2+0.0005X+0.7805, (y represents tap density, X represents temperature integral area), for example, in Example 1, when the temperature integral = 2000, the calculated tap density at this time is Y = 1.0605, and the measured value is 1.07, which basically matches. Comparative Example Y = 2e -11 X 3 -9e -8 X 2 +0.002X+0.8574, when the temperature integral is 1300, the calculated tap density is 1.03. The temperature in the kiln can be adjusted by adjusting the amount of natural gas combustion.

[0044] The above merely describes the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for pre-judging whether the material of a synthetic graphite pre-carbonization process is qualified, comprising the following steps: Step 1. Put the qualified material completed by the machine grinding process into a silicon carbide crucible; Step 2. Put the crucible with the material into the corresponding train for pre-carbonization process treatment, and at the same time, count the temperature of the marked serial number kiln car during the carbonization process in the tunnel kiln; Step 3. Import the temperature data recorded in step 2 into Origin software for area integration above 1000℃ for calculation; Step 4. Detect the tap density, true density, and volatile content of the pre-carbonized material; Step 5. Perform multiple batch experiments.

2. The pre-judgment method of claim 1, wherein The data of the tap density, true density, volatile matter in step 4 are statistically associated with the area integral of the corresponding train No. above 1000 DEG C temperature, a linear mathematical model is established, the tap density, volatile matter, true density and other data of the material are calculated by inputting the temperature area integral into the model, the correlation mathematical model is y=2.51x10 -10 x 3 -1.12x10 -6 x 2 +0.0015x+0.123, wherein X is the temperature integral area and y is the tap density detection data.

3. The pre-judgment method of claim 1, wherein Adjust the above mathematical calculation model according to different materials, and by inputting the integral area, the tap density during the pre-carbonization process of the material can be predicted, and according to the requirements, it is determined whether to extend the heating time or increase the temperature.

4. The pre-judgment method of claim 1, wherein The silicon carbide crucible in step 1 is 800-1200mm long and 500-600mm in diameter, and the crucible loading capacity is 60-90kg.

5. The pre-judgment method of claim 1, wherein The pre-carbonization treatment device in step 2 is a tunnel kiln with a total length of 120-160m, a width of 2.5-3.5m, and a height of 3.5-4.5m. There are 25-45 temperature points in the kiln, and 40-60 track cars are arranged in the furnace.

6. The pre-judgment method of claim 1, wherein The pre-carbonization temperature statistics in step 2 are as follows: count the speed of the kiln car entering the kiln, the time required for the kiln car to pass through each temperature section in the tunnel kiln, and record the temperature curve of the kiln car passing through each temperature zone. To ensure that the material in the middle of the kiln car can also be fully carbonized, the temperature in the high temperature section is above 1000℃.

7. The pre-judgment method of claim 1, wherein In step 3, the temperature in the interval is imported into Origin to calculate the integral area above 1000℃.

8. The pre-judgment method of claim 1, wherein In step 4, the pre-carbonized material is cooled by a quenching fan, and part of the material in the crucible is detected. The material is detected using a tap density instrument, and the true density is detected using a gas displacement method true density instrument. According to the detection results and the integral area above 1000℃, the required temperature integral area is determined according to the calculation formula, and the tap density standard that meets the requirements is determined. It is inferred that the integral area needs to be increased to delay the feeding speed, or the temperature of the furnace needs to be increased.

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