High-temperature impurity removal and purification method of graphite material

Abstract

The application relates to the technical field of impurity removal and purification, in particular to a high-temperature impurity removal and purification method for graphite materials, which comprises the following steps: when high-temperature purification is carried out on the graphite materials by using a high-temperature purification furnace, the furnace temperature, the output power and the temperature and voltage of each induction coil at each moment in each monitoring period in each high-temperature purification process are obtained; the first evaluation value, the power fluctuation degree, the second evaluation value and the evaluation coefficient of each monitoring period are calculated; the bridging confidence of each monitoring period in each high-temperature purification process is determined; the bridging phenomenon occurring in each monitoring period in the present high-temperature purification process is evaluated, and the bridging phenomenon existing in the high-temperature purification furnace is eliminated, so that the high-temperature purification is carried out on the graphite materials. The application can accurately evaluate the bridging phenomenon occurring in the high-temperature purification furnace, and ensure the stable operation of the high-temperature purification process and the high-quality purification of the graphite materials.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of impurity removal and purification, and particularly relates to a high-temperature impurity removal and purification method for graphite materials. BACKGROUND

[0002] High-purity graphite is an indispensable key basic material in the fields of semiconductors, photovoltaics, aerospace, nuclear industry and the like, and the purity of the high-purity graphite directly determines the performance and reliability of the final product. High-temperature purification is a core process for preparing high-purity graphite, and in the high-temperature purification process of the graphite material, a high-temperature purification furnace is one of the key devices, the graphite material is placed in a high-temperature environment, the temperature in the furnace is accurately controlled, and thus the impurities in the graphite material are removed to improve the purity of the graphite material.

[0003] In the high-temperature purification process by using the high-temperature purification furnace, the non-uniformity of the temperature in the furnace and the bridging phenomenon caused by the local sintering of the graphite powder at high temperature are not fully considered, the bridging phenomenon not only causes the blockage and interruption of continuous production of the discharge, but also hinders the uniform transmission of heat and reaction gas, resulting in that the purification effect of the graphite powder under the bridging area is not thorough, and the stability of the high-temperature purification process is affected; meanwhile, when the bridging phenomenon is serious, the furnace needs to be stopped for maintenance, which reduces the overall purification efficiency and production efficiency. SUMMARY

[0004] In order to solve the above technical problems, a high-temperature impurity removal and purification method for graphite materials is provided to solve the existing problems.

[0005] The technical problem of the application is solved by providing a high-temperature impurity removal and purification method for graphite materials, comprising the following steps:

[0006] In the high-temperature purification of the graphite material by using the high-temperature purification furnace, the temperature in the furnace, the output power and the temperature and voltage of each induction coil at each time in each monitoring period in each high-temperature purification process are obtained;

[0007] The discrete change conditions of the temperature and voltage of different induction coils at the same time in each monitoring period are analyzed, and the first evaluation value of each monitoring period is calculated;

[0008] The power fluctuation degree of each monitoring period is calculated through the fluctuation conditions of the output power in different local ranges in each monitoring period, and the second evaluation value of each monitoring period is calculated in combination with the synchronization conditions of the change trend of the temperature in the furnace and the output power in each monitoring period;

[0009] Based on the first evaluation value and the second evaluation value, an evaluation coefficient of each monitoring period is obtained; based on the change trend and the difference of the evaluation coefficient of each monitoring period in different high-temperature purification processes, a bridging confidence of each monitoring period in each high-temperature purification process is determined; the bridging confidence of the current and previous high-temperature purification processes in each monitoring period is detected abnormally, the bridging phenomenon in each monitoring period in the current high-temperature purification process is evaluated, and the bridging phenomenon in the high-temperature purification furnace is eliminated, so as to purify the graphite material at high temperature.

[0010] Preferably, the first evaluation value of each monitoring period is calculated, comprising:

[0011] The dispersion degrees of the temperature and the voltage of all the induction coils at each time are calculated respectively, and are recorded as a first dispersion degree and a second dispersion degree respectively;

[0012] The sum of the first dispersion degree and the second dispersion degree of all the times in each monitoring period is taken as a temperature difference degree and a voltage difference degree of each monitoring period respectively;

[0013] The first evaluation value is the result of the fusion of the temperature difference degree and the voltage difference degree.

[0014] Preferably, the specific process of the fusion is that the product of the temperature difference degree and the voltage difference degree is taken as the first evaluation value of each monitoring period.

[0015] Preferably, the power fluctuation degree of each monitoring period is calculated, comprising:

[0016] The output power of all the times in each monitoring period is divided into a plurality of local time periods;

[0017] The overall change trend of the output power of different times in the local time period is analyzed, and a deviation is calculated.

[0018] The power fluctuation degree is the mean value of the deviations of all the local time periods in each monitoring period.

[0019] Preferably, the deviation is calculated by linear fitting the output power of all the times in the local time period, and calculating the fitting error as the deviation.

[0020] Preferably, the second evaluation value of each monitoring period is calculated, comprising:

[0021] The correlation degree between the furnace temperature and the output power of all the times in each monitoring period is calculated, and the absolute value of the correlation degree is positively mapped;

[0022] The second evaluation value is the ratio between the power fluctuation degree and the positively mapped result.

[0023] Preferably, the evaluation coefficient is the product of the first evaluation value and the second evaluation value.

[0024] Preferably, the determination of the bridging confidence of each monitoring period in each high-temperature purification process comprises:

[0025] linearly fitting the evaluation coefficients of each monitoring period in each high-temperature purification process and the same monitoring period in the previous multiple high-temperature purification processes, calculating the slope of the fitting straight line;

[0026] calculating the average of the differences between the evaluation coefficients of each monitoring period in each high-temperature purification process and the same monitoring period in the previous multiple high-temperature purification processes as the deviation accumulation of each monitoring period in each high-temperature purification process;

[0027] the bridging confidence is the product of the slope and the deviation accumulation.

[0028] Preferably, the evaluation of the bridging phenomenon of each monitoring period in the current high-temperature purification process comprises: performing anomaly detection on the bridging confidence of each monitoring period in the current high-temperature purification process and the same monitoring period in the previous multiple high-temperature purification processes, if the bridging confidence of each monitoring period in the current high-temperature purification process is an abnormal value, it is determined that the bridging phenomenon occurs, otherwise, the bridging phenomenon does not occur.

[0029] Preferably, the elimination of the bridging phenomenon in the high-temperature purification furnace comprises: starting the vibration device of the high-temperature purification furnace to implement short-time and low-amplitude vibration on the furnace body of the high-temperature purification furnace, so that the graphite powder existing in the furnace with the bridging phenomenon is loosened and falls.

[0030] The present application has at least the following beneficial effects:

[0031] The application calculates the first evaluation value of each monitoring period by analyzing the temperature fluctuation of different induction coils and the voltage fluctuation at the same time, which has the beneficial effect of reflecting the uneven heating of the induction coil in the monitoring period and preliminarily evaluating the possibility of the existence of the bridging phenomenon in the high-temperature purification furnace; the power fluctuation degree of each monitoring period is calculated, which has the beneficial effect of considering the irregular abnormal fluctuation of the output power of the power supply, reflecting the stability of the output power of the power supply, and evaluating the local heating efficiency decline or load change caused by the bridging phenomenon; the second evaluation value of each monitoring period is calculated, which has the beneficial effect of considering the synchronization of the furnace temperature and the output power, reflecting the fluctuation of the output power of the power supply in the monitoring period and the synchronous change trend of the furnace temperature, and further evaluating the possibility of the existence of the bridging phenomenon in the high-temperature purification furnace; the evaluation coefficient of each monitoring period is obtained, which has the beneficial effect of comprehensively evaluating the possibility of the bridging phenomenon in the monitoring period through multiple dimensions, and further reflecting the stability of the purification process; the bridging confidence of each monitoring period in each high-temperature purification process is determined, which has the beneficial effect of comparing the evaluation coefficients of the same monitoring period in different high-temperature purification processes, identifying the abnormal change compared with the historical normal working condition, and more accurately determining the possibility of the bridging phenomenon; the bridging confidence of the current and previous high-temperature purification processes in each monitoring period is detected, the bridging phenomenon in each monitoring period in the current high-temperature purification process is evaluated, and the existence of the bridging phenomenon in the high-temperature purification furnace is eliminated, so as to purify the graphite material at high temperature, which has the beneficial effect of detecting the same monitoring period in the current high-temperature purification process and the historical different high-temperature purification processes, accurately evaluating the existence of the bridging phenomenon in the high-temperature purification furnace in each monitoring period in the current high-temperature purification process, and timely starting the intervention measures to avoid the production interruption, product quality decline and equipment damage caused by the bridging, which can ensure the stable operation of the high-temperature purification process and the high-quality purification of the graphite material, improve the purification efficiency and the purification quality of the graphite. BRIEF DESCRIPTION OF DRAWINGS

[0032] The graphite material high-temperature impurity purification method provided by the application will be further described in detail below in combination with the drawings.

[0033] Figure 1 The step flow chart of the graphite material high-temperature impurity purification method provided by the embodiment of the application is shown in the figure.

[0034] Figure 2 The step flow chart of the bridging confidence acquisition method provided by the embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application further details a high-temperature impurity removal and purification method of graphite material in combination with the accompanying drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0037] Please refer to Figure 1 which shows a step flow chart of a high-temperature impurity removal and purification method of graphite material provided by an embodiment of the present application, which comprises the following steps:

[0038] Step 1, when high-temperature purification is performed on the graphite material by using a high-temperature purification furnace, the furnace temperature, output power and the temperature and voltage of each induction coil at each time in each monitoring period during each high-temperature purification process are obtained.

[0039] As an important carbon-based material, graphite material has a wide application prospect in the fields of energy storage, sensors, catalysts, etc. The purity of graphite material directly affects its performance and application effect. The purification process takes advantage of the high melting point and high boiling point of graphite, and reduces the impurity content in the graphite powder raw material by high-temperature calcination to decompose and volatilize and by passing in oxidizing gas and metal impurities to react.

[0040] The process of graphite material is as follows:

[0041] Mixing and isostatic pressing: the pitch coke and pitch are weighed according to a certain weight ratio, put into a stirring device, stirred for 6-8 hours to obtain a mixture; the mixture is put into a rubber sleeve, the rubber sleeve is vacuumized, when the vacuum degree in the rubber sleeve reaches 0.06 MPa, the rubber sleeve is sealed and then put into an isostatic pressing machine, and the product is isostatically pressed for 60-70 minutes under a pressure of 150-180 MPa;

[0042] Densification and shaping: the isostatically pressed product is taken out and high-temperature calcined for 600-750 hours, wherein the highest temperature of high-temperature calcination is 900-1000℃, the calcined product is immersed for 1-2 hours under a pressure of 4 MPa, and the immersed product is calcined again, and so on, until the product bulk density reaches 1.72 g / cm 3After that, the product after the densification treatment is roughly crushed and put into an air flow mill for grinding, wherein the average particle size of the powder is 35-45 um; the powder is put into a shaping device to remove burrs and is shaped for 8-10 minutes, then the powder with a particle size of ≥100 um and a particle size of less than 5 um is removed through cyclone classification to obtain a particle size uniform powder, wherein the content of the powder with a particle size of <32 um in the particle size uniform powder is 60-70%;

[0043] High-temperature purification: the particle size uniform powder is put into a crucible, sealed and put into a high-temperature purification furnace for temperature rising and purification, the temperature rising rate is controlled at 6℃ / min, when the furnace temperature of the high-temperature purification furnace reaches 2000℃, chlorine is introduced into the high-temperature purification furnace, and the average chlorine introduced into each ton of product is 35-40 kg; when the furnace temperature of the high-temperature purification furnace reaches 2450℃, freon is introduced into the high-temperature purification furnace, and the average freon introduced into each ton of product is 20-25 kg; after the furnace temperature of the high-temperature purification furnace reaches 3000℃, high-temperature treatment is performed for 36-48 hours, then the product after high-temperature treatment is cooled to obtain a purified graphite powder product.

[0044] In this embodiment, the high-temperature purification furnace adopts a medium-frequency vertical graphite purification furnace, and the graphite material is subjected to high-temperature purification. In the purification process, the purification furnace may have a bridging phenomenon, which refers to the formation of an arch bridge structure of graphite powder in the furnace, which hinders the normal falling of the furnace charge. When the bridging phenomenon occurs, not only will it cause the discharge to be blocked and affect the efficiency of the subsequent impurity removal process, but also it will affect the impurity removal effect of the graphite powder at the bridging position. Therefore, in order to ensure the impurity removal and purification efficiency and effect of the graphite material, the bridging problem needs to be treated in time.

[0045] Secondly, the heating process of the medium-frequency vertical graphite purification furnace mainly relies on the inductive coil to realize energy conversion, and its working principle is as follows: the inductive coil is powered by a medium-frequency power supply, and under the action of alternating voltage and current, a strong alternating magnetic field is generated. When graphite, as a conductor, is placed in the magnetic field, eddy current will be generated due to electromagnetic induction effect. During the flow of the eddy current in the graphite, the electric energy is directly converted into heat energy due to the resistance effect, thereby realizing the heating of the graphite.

[0046] Based on the above analysis, through the heating control system of the purification furnace, the furnace temperature and the output power of the heating power supply at each moment in each monitoring period during each high-temperature purification process are collected; secondly, through the tungsten-rhenium thermocouple, the temperature and voltage of each inductive coil at each moment are measured;

[0047] In this embodiment, the time interval of data collection is 1s, and the length of the monitoring period is 20min. As other implementation manners, the implementer can set it according to the actual situation.

[0048] The collected data in each monitoring period is normalized, and in this embodiment, the maximum-minimum normalization method is used for normalization, wherein the maximum-minimum normalization method is a known technology and will not be described here. As other embodiments, the implementer can use other methods of the prior art, for example, Z-score standardization method, etc., and this embodiment does not make special restrictions.

[0049] At this point, the furnace temperature, output power and the temperature and voltage of each induction coil at each moment in each monitoring period during each high-temperature purification process are obtained.

[0050] Step 2, analyze the discrete change of the temperature and voltage of different induction coils at the same moment in each monitoring period, and calculate the first evaluation value of each monitoring period.

[0051] The intermediate frequency vertical graphite purification furnace is heated by the induction coil, and if the induction coil has a non-uniform magnetic field distribution or coil failure phenomenon, it will cause the graphite powder to be heated unevenly, and the powder in the local area may be sintered more densely, which is easy to cause the bridging phenomenon. Therefore, if the induction coil has a non-uniform magnetic field distribution or coil failure, the heating temperature between different induction coils will be different.

[0052] Secondly, since the induction coil works by relying on power supply, the heating load of the coil will be directly reflected on the voltage characteristics of the coil. If the bridging phenomenon does not occur, the heating load of each coil is consistent, and the voltage of each coil is consistent. If the bridging phenomenon occurs, the local graphite powder becomes more dense and accumulates together due to sintering, which will affect the electrical conductivity and magnetic permeability of the graphite powder in the local area; since the principle of induction heating is to generate a magnetic field by the coil and induce eddy current to heat, when the electromagnetic properties of the local area of the coil change, the heating load of the induction coil corresponding to the local area will also change, thereby causing the voltage to change.

[0053] Therefore, by analyzing the change of the temperature and voltage of different induction coils at the same moment, the first evaluation value is calculated to evaluate whether the purification furnace has a hidden bridging risk, which is specifically:

[0054] The discrete degree of the temperature of all induction coils at each moment is calculated, which is denoted as the first dispersion degree;

[0055] In this embodiment, the discrete degree is measured by calculating the coefficient of variation of the temperature of all induction coils at each moment, and as other embodiments, the implementer can use other methods of the prior art, for example, standard deviation, etc., and this embodiment does not make special restrictions.

[0056] The sum of the first dispersion degree of all moments in each monitoring period is taken as the temperature difference degree of each monitoring period.

[0057] Calculate the degree of dispersion of the voltage of all induction coils at each time point, and denote it as the second degree of dispersion;

[0058] In this embodiment, the degree of dispersion is measured by calculating the coefficient of variation of the voltage of all induction coils at each time point. As in other implementations, implementers may use other methods of the prior art, such as standard deviation, etc. This embodiment does not impose any special restrictions on this.

[0059] The sum of the second dispersion of all times within each monitoring cycle is taken as the voltage difference of each monitoring cycle.

[0060] The product of temperature difference and voltage difference is used as the first evaluation value for each monitoring cycle.

[0061] It should be noted that the larger the first dispersion, the greater the temperature difference between different induction coils at the same time. The greater the temperature difference, the greater the temperature difference between the induction coils, reflecting a more significant heating non-uniformity of the induction coils within the monitoring period. The larger the second dispersion, the greater the voltage difference between different induction coils at the same time. The greater the voltage difference, the greater the voltage difference between the induction coils, reflecting a more significant load non-uniformity of the induction coils within the monitoring period. The larger the obtained first evaluation value, the greater the difference between the heating temperature and load voltage of the induction coils within the monitoring period, the more significant the heating non-uniformity, and the greater the possibility of bridging.

[0062] Thus, the first evaluation value for each monitoring cycle is obtained.

[0063] Step 3: Calculate the power fluctuation of each monitoring cycle by observing the power fluctuations in different local areas within each monitoring cycle; and calculate the second evaluation value for each monitoring cycle by combining the synchronization of the furnace temperature and power change trends within each monitoring cycle.

[0064] Furthermore, when bridging occurs, it not only affects the induction coil but also the output power of the heating power supply to the purification furnace. During normal high-temperature purification, the power supply's output power increases steadily with the furnace temperature, and it tends to stabilize during the holding phase. However, if bridging occurs, the heating load and efficiency of the induction coil will be affected. In order to ensure the furnace temperature rises at the set rate, the power supply's output power may experience irregular and abnormal fluctuations, thus disrupting the stability of the output power change and its synchronization with the furnace temperature trend.

[0065] Secondly, since different temperature stages exist during the high-temperature purification process of graphite materials, in order to accurately analyze the changes in power output, the power output at all times within the monitoring period is divided to analyze the changes in power output. Therefore, by analyzing the fluctuations in power output within a local range, the power fluctuation is calculated, specifically:

[0066] The output power at all times within each monitoring cycle is divided into multiple local time periods;

[0067] In this embodiment, the BG (Bernaola-Galvan) segmentation algorithm is used to divide the output power at all times within each monitoring period. The BG segmentation algorithm is a well-known technology and will not be described in detail here. As other implementation methods, implementers may use other methods of existing technology, such as the MK segmentation algorithm, etc. This embodiment does not impose any special restrictions on this.

[0068] The output power at all times within a local time period is linearly fitted, and the fitting error is calculated as the offset.

[0069] In this embodiment, the least squares method is used for linear fitting. The least squares method is a well-known technique and will not be elaborated upon here. Secondly, the fitting error is measured by calculating the mean square error. The calculation of the mean square error is a well-known technique, and the formula for calculating the mean square error is as follows: ,in, Mean square error, Let be the output power at time i. To fit the predicted value at time i on the straight line, The number of all time points.

[0070] Calculate the average offset of all local time periods within each monitoring period as the power fluctuation of each monitoring period;

[0071] It should be noted that the larger the offset, the more drastic the fluctuation of the output power in a local period, the greater the possibility of deviating from the linear trend, and the greater the possibility of abnormal power output during the purification process; the greater the power fluctuation, the larger the fluctuation of the power output within the monitoring period, and the poorer the stability of the power output.

[0072] Furthermore, by analyzing the synchronization of the changes in furnace temperature and output power during the monitoring period, and combining this with the power fluctuation, a second evaluation value is calculated, specifically:

[0073] Calculate the correlation between furnace temperature and output power at all times within each monitoring cycle, and perform a positive mapping on the absolute value of the correlation.

[0074] In the embodiment, the correlation degree is measured by calculating the Pearson correlation coefficient between the furnace temperature and the output power at all times in each monitoring period, wherein the Pearson correlation coefficient is a known technology and will not be described here again. As other embodiments, the implementer can use other methods of prior art, such as Spearman correlation coefficient, and the embodiment does not make special restrictions on this. Secondly, the specific process of positive mapping is: positive mapping is performed by an exponential function. Assuming that the absolute value of the correlation degree is denoted as , the result of is taken as the result of positive mapping, wherein is an exponential function with a natural constant as the base number. Through the process of positive mapping, the result of positive mapping is greater than 0.

[0075] The ratio between the power fluctuation degree and the result of positive mapping is taken as the second evaluation value of each monitoring period.

[0076] It should be noted that the smaller the result of positive mapping, the lower the synchronization of the furnace temperature and the output power, and the greater the possibility that the output power and the temperature demand are disconnected. The greater the second evaluation value, the more intense the fluctuation of the power output and the lower the synchronous change trend of the furnace temperature, and the greater the possibility that the bridging phenomenon exists.

[0077] Thus, the second evaluation value of each monitoring period is obtained.

[0078] Step 4, based on the first evaluation value and the second evaluation value, the evaluation coefficient of each monitoring period is obtained. Based on the change trend and difference of the evaluation coefficient of each monitoring period in different high-temperature purification processes, the bridging confidence of each monitoring period in each high-temperature purification process is determined. The bridging confidence of the current and previous high-temperature purification processes in each monitoring period is detected abnormally, the bridging phenomenon in each monitoring period in the current high-temperature purification process is evaluated, and the bridging phenomenon in the high-temperature purification furnace is eliminated, so as to purify the graphite material at high temperature.

[0079] Further, based on the first evaluation value and the second evaluation value, the evaluation coefficient is determined, specifically:

[0080] The product of the first evaluation value and the second evaluation value is taken as the evaluation coefficient of each monitoring period.

[0081] It should be noted that the greater the evaluation coefficient, the greater the possibility that the bridging phenomenon exists in the monitoring period, and the bridging phenomenon needs to be processed in time, so as to improve the purification efficiency and purification effect.

[0082] Secondly, in the high-temperature purification process of the graphite material, the furnace conditions in different temperature stages are not consistent due to the continuity and stage characteristics of the evolution of the furnace conditions. Therefore, the data change in a single monitoring period is difficult to accurately distinguish whether the change in the furnace is a normal transition phenomenon or an abnormal disturbance. In order to avoid misjudgment, the corresponding monitoring period in the historical multiple high-temperature purification processes is compared to determine whether there is a large difference in the furnace characteristics in the monitoring period in the current high-temperature purification process.

[0083] The slope of the fitting straight line is calculated by linear fitting the evaluation coefficients of each monitoring period in each high-temperature purification process and the same monitoring period in the previous multiple high-temperature purification processes.

[0084] In this embodiment, the least squares method is used for linear fitting, and the least squares method and the calculation of the slope are both known technologies, which will not be described here.

[0085] It should be noted that there are multiple monitoring periods in each high-temperature purification process. Therefore, the evaluation coefficients of the qth monitoring period in each high-temperature purification process and the qth monitoring period in the previous 50 high-temperature purification processes are linearly fitted, and the implementer can set it according to the actual situation.

[0086] The mean value of the difference between the evaluation coefficients of each monitoring period in each high-temperature purification process and the same monitoring period in the previous multiple high-temperature purification processes is calculated as the deviation accumulation of each monitoring period in each high-temperature purification process.

[0087] In this embodiment, the mean value of the difference between the evaluation coefficients of the qth monitoring period in each high-temperature purification process and the qth monitoring period in the previous 50 high-temperature purification processes is calculated as the deviation accumulation of the qth monitoring period in each high-temperature purification process.

[0088] The product of the slope and the deviation accumulation is used as the bridging confidence of each monitoring period in each high-temperature purification process.

[0089] It should be noted that the larger the slope is, the greater the degree of degradation of the furnace temperature and power compared with the historical same period condition, and the greater the possibility of the existence of the bridging risk. The larger the deviation accumulation is, the higher the possibility of the abnormality of the furnace condition in the monitoring period compared with the historical same period condition, and the greater the possibility of the occurrence of the bridging phenomenon. Therefore, the larger the obtained bridging confidence is, the more consistent the furnace characteristics in the monitoring period are with the load abnormality characteristics caused by the bridging, and the higher the possibility of the occurrence of the bridging phenomenon in the monitoring period is. The step flowchart of the method for obtaining the bridging confidence provided in the embodiment is shown in Figure 2

[0090] ​If the bridge confidence of each monitoring period in the high-temperature purification process is an abnormal value, it is determined that the bridge phenomenon occurs, otherwise, the bridge phenomenon does not occur.

[0091] In the embodiment, the 3 algorithm is used for abnormal detection, wherein, the 3 algorithm is a known technology, and details are not described herein, as other embodiments, the implementer can use other methods of prior art, for example, the Bayesian mutation detection algorithm, the LOF abnormal detection algorithm, etc., and the embodiment does not specially limit this.

[0092] If the bridge phenomenon occurs in a monitoring period in the high-temperature purification process, at this time, the vibration instruction is sent to the electromagnetic vibrator through the control system, the vibration device is started to implement short-time and low-amplitude vibration on the furnace body of the purification furnace, the graphite powder in the area where the bridge phenomenon occurs is loosened and falls, so as to ensure the uniform transmission of heat and reaction gas in the subsequent high-temperature purification process; at the same time, the furnace shutdown and maintenance caused by serious bridge phenomenon are avoided, and the purification efficiency of the whole purification process is improved.

[0093] It should be understood that, although Figure 1 each step in the flowchart is displayed in sequence according to the arrow, these steps are not necessarily executed in sequence according to the arrow. Unless otherwise specified herein, the execution of these steps has no strict order limitation, and these steps can be executed in other order. Moreover, Figure 1 at least part of the steps in the flowchart can include multiple sub-steps or multiple stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily sequential, but can be executed in rotation or alternation with other steps or sub-steps or stages of other steps.

[0094] The technical features of the above embodiments can be combined arbitrarily, in order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0095] The above embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but should not be understood as a limitation on the present application. It should be pointed out that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, without departing from the content of the technical scheme of the present application, all belong to the protection scope of the technical scheme of the present application.

Claims

1. A high-temperature purification method for graphite materials, characterized in that, The method includes the following steps: When using a high-temperature purification furnace to purify graphite materials at high temperatures, the furnace temperature, output power, and temperature and voltage of each induction coil at each moment are obtained during each monitoring cycle of the high-temperature purification process. Analyze the discrete changes in temperature and voltage of different induction coils at the same time within each monitoring cycle, and calculate the first evaluation value for each monitoring cycle; The power fluctuation of each monitoring cycle is calculated by observing the fluctuation of output power in different local areas within each monitoring cycle; the second evaluation value of each monitoring cycle is calculated by combining the synchronization of the furnace temperature and output power change trends within each monitoring cycle. Based on the first and second evaluation values, the evaluation coefficients for each monitoring period are obtained. Based on the changing trends and differences of the evaluation coefficients for each monitoring period in different high-temperature purification processes, the bridging confidence of each monitoring period in each high-temperature purification process is determined. Anomaly detection is performed on the bridging confidence of this and previous high-temperature purification processes under each monitoring period to evaluate the bridging phenomenon that occurs in each monitoring period during this high-temperature purification process, eliminate the bridging phenomenon in the high-temperature purification furnace, and thus purify the graphite material at high temperature. The calculation of the first evaluation value for each monitoring cycle includes: calculating the dispersion of temperature and voltage of all induction coils at each time point, denoted as the first dispersion and the second dispersion, respectively; the sum of the first dispersion and the second dispersion at all times within each monitoring cycle is used as the temperature difference and voltage difference for each monitoring cycle, respectively; the first evaluation value is the result of fusing the temperature difference and voltage difference. The bridging confidence level for each monitoring cycle in each high-temperature purification process is determined by: linearly fitting the evaluation coefficients of each monitoring cycle in each high-temperature purification process with the evaluation coefficients of the same monitoring cycle in previous high-temperature purification processes, and calculating the slope of the fitted line; calculating the mean of the differences between the evaluation coefficients of each monitoring cycle in each high-temperature purification process and the evaluation coefficients of the same monitoring cycle in previous high-temperature purification processes, which is taken as the cumulative deviation of each monitoring cycle in each high-temperature purification process; the bridging confidence level is the product of the slope and the cumulative deviation. The assessment of bridging phenomena in each monitoring cycle during this high-temperature purification process includes: anomaly detection of the bridging confidence of each monitoring cycle during this high-temperature purification process compared to the same monitoring cycle in previous high-temperature purification processes. If the bridging confidence of each monitoring cycle during this high-temperature purification process is an outlier, it is determined that bridging has occurred; otherwise, no bridging has occurred.

2. The high-temperature purification method for graphite materials as described in claim 1, characterized in that, The specific process of fusion is as follows: the product of temperature difference and voltage difference is used as the first evaluation value for each monitoring cycle.

3. The high-temperature purification method for graphite materials as described in claim 1, characterized in that, Calculate the power fluctuation for each monitoring period, including: The output power at all times within each monitoring cycle is divided into multiple local time periods; Analyze the overall trend of output power deviation at different times within a local time period, and calculate the deviation; Power fluctuation is the average of the offsets in all local time periods within each monitoring cycle.

4. The high-temperature purification method for graphite materials as described in claim 3, characterized in that, The offset calculation includes: performing a linear fit on the output power at all times within the local time period, and calculating the fitting error as the offset.

5. The high-temperature purification method for graphite materials as described in claim 1, characterized in that, Calculate the second assessment value for each monitoring period, including: Calculate the correlation between furnace temperature and output power at all times within each monitoring cycle, and perform a positive mapping on the absolute value of the correlation. The second evaluation value is the ratio between the power fluctuation and the result of the positive mapping.

6. The high-temperature purification method for graphite materials as described in claim 1, characterized in that, The evaluation coefficient is the product of the first evaluation value and the second evaluation value.

7. The high-temperature purification method for graphite materials as described in claim 1, characterized in that, Eliminating bridging in high-temperature purification furnaces includes: using the furnace's vibration device to apply short-term, low-amplitude vibration to the furnace body, causing the bridging graphite powder inside the furnace to loosen and fall.

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