Fault diagnosis method and system for lithium iron phosphate rotary kiln seal failure

Abstract

The present application belongs to the technical field of industrial automation control and fault diagnosis, and relates to a lithium iron phosphate rotary kiln sealing failure fault diagnosis method and system. The method comprises: collecting the instantaneous pressure of the sealing cavity, the rotation angle of the cylinder, the surface temperature and the cumulative running time; calculating the rotation modulation leakage index based on the instantaneous pressure and the rotation angle, and extracting the periodic breathing effect characteristics caused by the eccentricity of the cylinder by angle weighting; calculating the thermal creep correction factor based on time and temperature, and quantifying the material aging tendency; and fusing the two to calculate the sealing failure risk index, and accordingly performing graded early warning or shutdown control. The present application can discover early deformation leakage in advance when the sealing pressure has not yet dropped below the threshold, and adaptively corrects the diagnosis standard under the conditions of equipment aging and high temperature, effectively improving the accuracy and timeliness of fault diagnosis.

Description

Technical Field

[0001] This invention belongs to the field of industrial automation control and fault diagnosis technology, specifically relating to a method and system for diagnosing seal failure in lithium iron phosphate rotary kilns. Background Technology

[0002] In the sintering process of lithium iron phosphate materials, the rotary kiln is the core heating equipment, and its operational stability directly determines the crystal structure and electrochemical performance of the product. Because the sintering process is extremely sensitive to oxidation, a slightly positive pressure environment must be maintained inside the kiln by continuously introducing inert gases such as nitrogen to ensure the stability of the material's valence state and phase purity. Therefore, the sealing performance of the kiln head and tail is crucial for preventing external air from entering and internal gas from leaking out.

[0003] For the special operating conditions of rotary kilns, characterized by high temperatures and dynamic rotation, current industrial applications primarily employ a composite sealing structure combining mechanical and gas seals. The working principle involves injecting a protective gas at a specific pressure into the cavity formed by the mechanical seal, creating an air curtain barrier with a pressure higher than that of the kiln interior and the surrounding atmosphere. Existing methods for monitoring seal failure mainly rely on pressure transmitters to monitor the pressure value within the gas seal cavity. When the detected pressure falls below a preset fixed alarm threshold, the system determines a seal leak and triggers an alarm. However, rotary kilns are typically tens of meters long, and their suspended sections are prone to irreversible material creep and flexural deformation under the combined effects of high-temperature thermal stress and their own gravitational torque. This deformation causes the kiln cross-section to gradually degenerate from an ideal circle to an ellipse, generating periodic eccentric fluctuations during rotation. This results in periodic expansion and contraction of the sealing gap with the rotation angle, the so-called "breathing effect." Existing monitoring systems typically process the pressure signal through low-pass filtering, treating this high-frequency pressure fluctuation caused by periodic gap changes as background noise or arithmetic averaging. This means that when the sealing structure suffers physical structural damage, the system cannot issue a timely warning because the average pressure has not yet fallen below the threshold, leading to the malfunction evolving into a serious accident.

[0004] Furthermore, the operation of a rotary kiln involves a multi-field coupling of heat, force, and fluid. As the cumulative operating time of the equipment increases and the sintering temperature profile is adjusted, the thermal expansion and cumulative creep of the kiln material cause dynamic drift in the reference gap of the sealing interface. Existing fixed threshold methods cannot adapt to this dynamic condition, easily resulting in missed alarms during normal thermal expansion or false alarms during severe high-temperature creep. Current technology severs the inherent physical connection between mechanical rotational motion, material thermal aging characteristics, and sealing cavity pressure; a single pressure indicator cannot distinguish between transient pressure drops caused by fluctuations in the gas supply and structural leaks caused by permanent deformation of the kiln. This lack of diagnostic dimensions makes it difficult for on-site maintenance personnel to quickly locate the root cause of the fault, often missing the optimal equipment maintenance window. Summary of the Invention

[0005] The purpose of this invention is to propose a fault diagnosis method and system for the sealing failure of lithium iron phosphate rotary kilns, in order to solve the technical problems that existing fixed threshold monitoring methods cannot identify periodic leaks caused by cylinder eccentricity, and are difficult to adapt to the sealing reference drift caused by equipment aging and high temperature creep, thus leading to false alarms or missed alarms.

[0006] To address the above problems, the technical solution for the fault diagnosis method of lithium iron phosphate rotary kiln seal failure proposed in this invention is as follows:

[0007] A method for diagnosing seal failure in a lithium iron phosphate rotary kiln includes the following steps:

[0008] The instantaneous pressure of the rotary kiln's sealing cavity, the rotation angle of the cylinder, the surface temperature of the cylinder, and the cumulative effective operating time of the rotary kiln are collected, and the collected data are preprocessed.

[0009] The rotation modulation leakage index is calculated based on the instantaneous pressure and rotation angle. The rotation modulation leakage index is used to characterize the intensity of the periodic fluctuation of the pressure in the sealed cavity with the rotation angle within one rotation cycle, so as to identify structural leakage caused by the eccentric deformation of the cylinder.

[0010] Based on the accumulated effective operating time and cylinder surface temperature, a thermal creep correction factor is calculated. This thermal creep correction factor is used to assess the tendency of the cylinder material to undergo permanent deformation under the current temperature and time accumulation.

[0011] The sealing failure risk index is calculated using the rotational modulation leakage index and the thermal creep correction factor. The sealing failure risk index is then compared with preset warning thresholds and shutdown thresholds. Based on the comparison results, corresponding graded warning or shutdown control strategies are executed.

[0012] Furthermore, the instantaneous pressure of the rotary kiln sealing cavity is collected by: collecting the instantaneous pressure of the gas inside the cavity at the air inlet of the sealing cavity at the kiln head and kiln tail of the rotary kiln through a high-frequency pressure transmitter, with the sampling frequency set to more than 10 times the rotation frequency of the rotary kiln.

[0013] Furthermore, the preprocessing of the collected data includes: aligning the collected data with timestamps, using a low-pass filter to filter out high-frequency electromagnetic noise, and retaining pressure signal components that are in the same frequency as and at harmonics of the rotation frequency; setting a minimum working pressure threshold, and performing subsequent calculations only when the instantaneous pressure is greater than the minimum working pressure threshold.

[0014] Furthermore, the rotation modulation leakage index satisfies the expression:

[0015]

[0016] In the formula, The rotation modulation leakage index, The total number of sampling points within one rotation cycle. For the first Instantaneous pressure values ​​at each sampling point It is the arithmetic mean of the pressure values ​​at all sampling points within this rotation cycle. For the first The rotation angle of the cylinder corresponding to each sampling point This is the gravity phase offset angle.

[0017] Furthermore, the gravity phase offset angle It is a constant determined based on the geometric angle between the installation position of the high-frequency pressure transmitter and the maximum gravity sinking point of the cylinder; the sine term in the expression This is used to assign higher weight to pressure fluctuations during the phase of maximum eccentric deformation of the cylinder, in order to amplify the periodic leakage characteristics caused by gravitational deflection.

[0018] Furthermore, the thermal creep correction factor satisfies the following expression:

[0019]

[0020] In the formula, It is a thermal creep correction factor. To accumulate effective running time, This is the current surface temperature of the cylinder. This is a reference standard temperature used to normalize the effect of temperature. and This is an empirical material coefficient determined based on the cylinder material; this expression reflects the physical characteristics of creep damage increasing logarithmically over time and being accelerated nonlinearly by temperature.

[0021] Furthermore, the reference standard temperature Set to ambient temperature or the rated operating temperature of the rotary kiln; material empirical coefficient The material empirical coefficients are used to characterize the rapid development stage of early creep. Used to characterize the accelerating weight of high temperature on steady-state creep.

[0022] Furthermore, the seal failure risk index is defined as follows: It satisfies the expression:

[0023] .

[0024] Furthermore, the step of executing corresponding graded early warning or shutdown control strategies based on the comparison results includes:

[0025] When the seal failure risk index is less than the warning threshold, the rotary kiln is determined to be in normal operating condition, and the current control strategy is maintained.

[0026] When the seal failure risk index is greater than or equal to the warning threshold and less than the shutdown threshold, the rotary kiln is determined to be in an early deformation leakage condition. The opening of the air inlet valve of the sealing gas source is automatically increased to increase the air supply for pressure compensation, and maintenance suggestions for checking the support condition of the rotary kiln support rollers are generated.

[0027] When the risk index of sealing failure is greater than or equal to the shutdown threshold, the rotary kiln is determined to be in a state of severe sealing failure or severe deformation of the cylinder, triggering an audible and visual alarm, and interlocking to control the heating power supply to reduce the output power and execute the safety shutdown procedure.

[0028] The technical solution of the lithium iron phosphate rotary kiln seal failure diagnosis system proposed in this invention is as follows:

[0029] A fault diagnosis system for the seal failure of a lithium iron phosphate rotary kiln includes a processor and a memory. The memory stores computer program instructions. When the computer program instructions are executed by the processor, the fault diagnosis method for the seal failure of a lithium iron phosphate rotary kiln described in any of the above technical solutions is implemented.

[0030] The beneficial effects of this invention are as follows: By constructing a rotation modulation leakage index, this invention correlates the pressure signal of the rotary kiln sealing cavity with the rotation angle of the cylinder, enabling the specific extraction of periodic pressure fluctuation characteristics caused by the breathing effect. Compared with traditional methods that rely solely on the lower limit of absolute pressure for alarm, this invention can identify leakage signs caused by slight eccentric deformation of the cylinder before the average pressure of the sealing cavity falls below the safety threshold, thus improving the detection rate of minor structural leaks.

[0031] This invention introduces a thermal creep correction factor, dynamically adjusting the criteria for determining seal failure based on the cumulative effective operating time and real-time surface temperature of the rotary kiln. This method conforms to the physical laws of material thermal creep and aging, effectively avoiding false alarms caused by changes in sealing gaps under high-temperature conditions and missed alarms caused by drift in reference pressure after long-term operation, ensuring the accuracy of diagnostic results throughout the entire lifecycle of the equipment.

[0032] To address the technical challenge of gravity-induced sinking in the suspended section of a rotary kiln, this invention utilizes an angle-pressure coupling analysis method to effectively distinguish between two different types of faults: fluctuations in gas supply and deformation of the kiln structure. This provides a clear direction for mechanical adjustments during on-site maintenance. Attached Figure Description

[0033] Figure 1 This is a flowchart of the steps in the fault diagnosis method for the lithium iron phosphate rotary kiln seal failure of the present invention;

[0034] Figure 2 This is a characteristic diagram showing the relationship between the rotation angle of the rotary kiln and the pressure in the sealing chamber;

[0035] Figure 3 This is a chart showing the evolution trend of the seal failure risk index throughout its entire life cycle;

[0036] Figure 4 This is a comparison chart of the timeliness of fault diagnosis between the present invention and existing technologies. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0038] Specific embodiments of the fault diagnosis method for lithium iron phosphate rotary kiln seal failure proposed in this invention:

[0039] like Figure 1 As shown, the fault diagnosis method for the seal failure of a lithium iron phosphate rotary kiln includes steps S1 to S4, which are as follows:

[0040] S1. Collect the instantaneous pressure of the rotary kiln sealing cavity, the rotation angle of the cylinder, the surface temperature of the cylinder, and the cumulative effective operating time of the rotary kiln, and preprocess the collected data.

[0041] Specifically, high-frequency pressure transmitters are installed at the air inlets of the sealed cavities at the kiln head and tail of the rotary kiln to collect the instantaneous pressure of the gas inside the cavities in real time. To capture minute pressure fluctuations with rotation angle, the sampling frequency is set to more than 10 times the rotation frequency. An absolute encoder is installed on the drive motor shaft or the cylinder transmission gear of the rotary kiln to obtain the current rotation angle of the cylinder in real time, with the rotation angle ranging from 0° to 360°. An infrared thermometer or patch thermocouple is deployed on the cylinder surface near the sealing position to monitor the surface temperature of the cylinder in real time. The cumulative effective operating time of the equipment since the last major overhaul or seal replacement is read through the PLC control system.

[0042] The collected data is timestamped and a low-pass filter is used to remove high-frequency electromagnetic noise, retaining pressure signal components that are in sync with or have harmonics of the rotation frequency. A minimum working pressure threshold is set, and the system only initiates subsequent calculations when the rotary kiln speed is stable and the instantaneous pressure exceeds the minimum working pressure threshold. In practical applications, the minimum working pressure threshold is set to 2 kPa.

[0043] Thus, high-frequency synchronous acquisition and preprocessing ensured the spatiotemporal consistency and signal-to-noise ratio of the data for subsequent analysis, laying the foundation for the accurate extraction of rotation-related features.

[0044] S2. Calculate the rotation modulation leakage index based on the instantaneous pressure and rotation angle. The rotation modulation leakage index is used to characterize the intensity of the periodic fluctuation of the pressure in the sealed cavity with the rotation angle within one rotation cycle, so as to identify structural leakage caused by the eccentric deformation of the cylinder.

[0045] Specifically, the discretized weighted root mean square algorithm is used to calculate the first... Rotational modulation leakage index within one rotation cycle It satisfies the following expression:

[0046]

[0047] In the formula, The rotation modulation leakage index; This represents the total number of sampling points collected within one rotation cycle. For the first Instantaneous pressure values ​​at each sampling point; It is the arithmetic mean of the pressure values ​​at all sampling points within this rotation cycle, i.e. ; For the first The rotation angle of the cylinder corresponding to each sampling point; This is the gravity phase offset angle.

[0048] Gravity phase offset angle It is a constant determined based on the geometric angle between the installation position of the high-frequency pressure transmitter and the maximum sinking point of the cylinder; the sine term in the expression This is used to assign higher weight to pressure fluctuations during the phase of maximum eccentric deformation of the cylinder, in order to amplify the periodic leakage characteristics caused by gravitational deflection.

[0049] The following is a simple calculation example demonstrating the calculation process of this expression:

[0050] Assuming the number of sampling points within one rotation cycle average pressure kPa, gravity phase offset angle .

[0051] Among them, the rotation angle of the cylinder at sampling point 1 The sine term is Instantaneous pressure value kPa, which is the same as the average pressure, indicates that there is no pressure fluctuation at this location. Therefore, term 1 is: .

[0052] Rotation angle of the cylinder at sampling point 2 The sine term is Instantaneous pressure value The pressure drop is less than the average pressure, indicating a significant leak causing a pressure decrease. Since this angle corresponds to the location of the maximum gravity weight, the leak signal is significantly amplified by the algorithm; therefore, term 2 is: .

[0053] Rotation angle of the cylinder at sampling point 3 The sine term is Instantaneous pressure value kPa, the value returns to the average level, with no pressure fluctuations, at which point item 3 is 0.

[0054] Rotation angle of the cylinder at sampling point 4 The sine term is Instantaneous pressure value kPa, higher than the average pressure, although there is a pressure deviation similar to that at sampling point 2, the algorithm determines that this fluctuation is a non-structural leak characteristic because it occurs in a non-sensitive phase, thus suppressing the fluctuation signal. Item 4 is then: .

[0055] Summing the above four items yields 0.005. Dividing this by the number of sampling points (4) gives 0.00125. Finally, taking the square root yields the rotation modulation leakage index. .

[0056] This shows that if the traditional variance or root mean square algorithm is used, the sine weight term is absent, and sampling points 2 and 4 will be considered as having the same degree of fluctuation and will be superimposed, leading to misjudgment. However, in the algorithm of this embodiment, a sine term is introduced. This enables selective signal processing:

[0057] At specific sensitive angles, such as the position where gravity causes the cylinder to sink the most, i.e. At sensitive locations, abnormal pressure fluctuations are given higher weight, thus enabling the more acute detection of deformation leaks; at non-sensitive locations, such as... Even pressure fluctuations are treated as interference signals and filtered out. This mechanism ensures that the rotational modulation leakage index can highly accurately characterize structural leaks caused by cylinder rotational eccentricity.

[0058] This step, by constructing a rotation modulation leakage index, can extract the pressure fluctuation characteristics that are strongly correlated with the rotation angle, and intuitively reflect the periodic changes in the sealing gap caused by the eccentricity of the cylinder.

[0059] S3. Based on the accumulated effective operating time and cylinder surface temperature, calculate the thermal creep correction factor, which is used to assess the tendency of the cylinder material to undergo permanent deformation under the current temperature and time accumulation.

[0060] Specifically, the thermal creep correction factor satisfies the following expression:

[0061]

[0062] It is a thermal creep correction factor. To accumulate effective running time, This is the current surface temperature of the cylinder. This is a reference standard temperature used to normalize the effect of temperature. and This is an empirical material coefficient determined based on the cylinder material; this expression reflects the physical characteristics of creep damage increasing logarithmically over time and being accelerated nonlinearly by temperature.

[0063] To verify the thermal creep correction factor The dynamic adjustment capability is calculated using the following parameters: empirical coefficients determined based on the material properties of the cylinder. , and reference standard temperature Set as .

[0064] Scenario 1 represents the initial commissioning phase of a rotary kiln. In this scenario, the rotary kiln is in a brand-new state after being put into use, with the cumulative effective operating time... The time is 0 hours; at the same time, the rotary kiln is in a cold state or operating at room temperature, and the surface temperature of the cylinder is 0 hours. Maintain at Substituting into the above formula, we get:

[0065] The results show that, under ideal conditions of new machine and low temperature, the thermal creep correction factor is extremely small, the system has a high tolerance to pressure fluctuations, and only the basic material safety factor is retained.

[0066] Scenario 2 represents the long-term high-temperature operation phase of the rotary kiln. In this scenario, the rotary kiln has been running continuously for a considerable period, accumulating a total effective operating time. The kiln reached 1000 hours of operation, and was under high-load heating, with the surface temperature of the cylinder reaching [temperature value missing]. Rise to Substituting into the above formula, we get:

[0067] This reflects the fundamental damage caused by the accumulation of material fatigue over time;

[0068] This reflects the nonlinear accelerating effect of high-temperature environment on the creep properties of materials;

[0069] final, .

[0070] Comparing the two scenarios above, the thermal creep correction factor The value surged from an initial 0.05 to 0.827, an increase of more than 16 times. This significant change intuitively reflects the gradual weakening of the stability of the rotary kiln material as operating time accumulates and operating temperature rises.

[0071] By introducing a thermal creep correction factor, the system can dynamically adjust diagnostic criteria according to different stages of the rotary kiln's life cycle: under equipment aging or high-temperature conditions, The automatic increase amplifies the risk index of seal failure. This means that for the same magnitude of pressure fluctuation, the alarm sensitivity of aged equipment will be significantly higher than that of new equipment, effectively avoiding the risk of missed alarms caused by rigid fixed thresholds and ensuring the accuracy and timeliness of fault diagnosis.

[0072] S4. Calculate the seal failure risk index using the rotation modulation leakage index and the thermal creep correction factor, compare the seal failure risk index with the preset warning threshold and shutdown threshold, and execute the corresponding graded warning or shutdown control strategy according to the comparison result.

[0073] Specifically, the seal failure risk index is defined as follows: It satisfies the expression:

[0074] This formula uses a multiplicative coupling model. This is a manifestation of risk. It is an amplifier of risk.

[0075] System preset warning threshold and shutdown threshold ,and .

[0076] when If the rotary kiln is determined to be in normal operating condition, the current control strategy shall be maintained.

[0077] when When the rotary kiln is determined to be in an early deformation and leakage condition, the opening of the air inlet valve of the sealing gas source is automatically increased to increase the air supply for pressure compensation, and maintenance suggestions for checking the condition of the rotary kiln support rollers are sent to the central control room.

[0078] when If the rotary kiln is found to be in a state of severe failure of the sealing structure or severe deformation of the cylinder, an audible and visual alarm will be triggered, and the heating power supply will be interlocked to reduce the output power and execute the safety shutdown procedure.

[0079] The following combination Figure 2 , Figure 3 and Figure 4 The technical solution and technical effects of the present invention will be further explained.

[0080] like Figure 2 As shown in the figure, the dashed line represents the rotary kiln in a new or healthy state. At this time, the sealing pressure remains near the baseline of 100 kPa, exhibiting only random, minor fluctuations with no significant correlation to the rotation angle, indicating a uniform sealing gap and stable pressure. The solid line represents the state after the kiln undergoes eccentric deformation. The pressure curve shows significant sinusoidal periodic fluctuations, i.e., the breathing effect, especially when rotating to approximately 180° to 270°, where the pressure drops sharply. This fluctuation characteristic, highly coupled with the rotation angle, is the physical basis for calculating the rotation-modulated leakage index in this invention.

[0081] Figure 3 It shows the evolution trend of various monitoring indicators throughout the entire life cycle of the rotary kiln. Figure 3 The dashed line represents the rotary modulation leakage index. As operating time increases, the cylinder undergoes physical deformation, and the rotary modulation leakage index rises linearly and slowly, reflecting the physical accumulation of leakage. The dashed line represents the thermal creep correction factor, whose curve increases exponentially over time, objectively reflecting the nonlinear acceleration of structural fragility caused by material aging under high-temperature environments. The thick solid line represents the final seal failure risk index, which shows a nonlinear and rapid upward trend in the later stages of operation. This indicates that the system can automatically increase alarm sensitivity according to the degree of equipment aging, giving higher weight to minor risks at the end of the equipment's lifespan, effectively preventing sudden failures of aging equipment.

[0082] Figure 4 The diagram visually compares the alarm timeliness of fault diagnosis between this invention and existing technologies. The traditional average pressure monitoring curve, representing the sealing system, averages out pressure fluctuations due to the breathing effect, resulting in an extremely slow decrease in average pressure and a significant lag. It only drops below the preset threshold and triggers an alarm around 900 hours of operation, at which point the equipment is often already on the verge of severe leakage. In contrast, the sealing failure risk index curve of this invention, benefiting from the extraction of periodic fluctuation characteristics and correction for thermal creep factors, breaks through the warning threshold around 500 hours of operation. Compared to existing technologies, this invention detects potential faults approximately 400 hours earlier, providing ample time for mechanical adjustments and preventative maintenance, significantly reducing the risk of unplanned downtime.

[0083] In this way, by integrating dynamic leakage characteristics with structural vulnerability and implementing graded control, we can not only provide early warning of potential mechanical failures, but also extend equipment operating time through automatic adjustment in the early stages of failure, ultimately ensuring production safety.

[0084] Specific embodiments of the lithium iron phosphate rotary kiln seal failure diagnosis system proposed in this invention:

[0085] A fault diagnosis system for lithium iron phosphate rotary kiln seal failure includes a processor and a memory. The memory stores computer program instructions. When the computer program instructions are executed by the processor, the fault diagnosis method for lithium iron phosphate rotary kiln seal failure in the above embodiments is implemented.

[0086] The lithium iron phosphate rotary kiln seal failure diagnosis system also includes other components well known to those skilled in the art, such as communication buses and communication interfaces. Their settings and functions are known in the art and will not be described in detail here.

[0087] In this invention, the aforementioned memory can be any tangible medium containing or storing a program that can be used or combined with an instruction execution system, apparatus, or device. For example, a computer-readable storage medium can be any suitable magnetic or magneto-optical storage medium, such as Resistive Random Access Memory (RRAM), Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), Enhanced Dynamic Random Access Memory (EDRAM), High-Bandwidth Memory (HBM), Hybrid Memory Cube (HMC), etc., or any other medium that can be used to store desired information and can be accessed by an application, module, or both. Any such computer storage medium can be part of a device or accessible to or connected to a device. Any application or module described in this invention can be implemented by computer-readable / executable instructions stored or otherwise maintained on such a computer-readable medium.

[0088] In the description of this specification, "multiple" means at least two, such as two, three or more, etc., unless otherwise expressly and specifically defined.

[0089] While various embodiments of the invention have been shown and described in this specification, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will occur to those skilled in the art without departing from the spirit and essence of the invention.

Claims

1. A method for diagnosing seal failure in a lithium iron phosphate rotary kiln, characterized in that, Includes the following steps: The instantaneous pressure of the rotary kiln's sealing cavity, the rotation angle of the cylinder, the surface temperature of the cylinder, and the cumulative effective operating time of the rotary kiln are collected, and the collected data are preprocessed. The rotation modulation leakage index is calculated based on the instantaneous pressure and rotation angle. The rotation modulation leakage index is used to characterize the intensity of the periodic fluctuation of the pressure in the sealed cavity with the rotation angle within one rotation cycle, so as to identify structural leakage caused by the eccentric deformation of the cylinder. Based on the accumulated effective operating time and cylinder surface temperature, a thermal creep correction factor is calculated. This thermal creep correction factor is used to assess the tendency of the cylinder material to undergo permanent deformation under the current temperature and time accumulation. The sealing failure risk index is calculated using the rotational modulation leakage index and the thermal creep correction factor. The sealing failure risk index is then compared with preset warning thresholds and shutdown thresholds. Based on the comparison results, corresponding graded warning or shutdown control strategies are executed.

2. The method for diagnosing seal failure in a lithium iron phosphate rotary kiln according to claim 1, characterized in that, The instantaneous pressure of the sealed cavity of the rotary kiln is collected by means of: at the air inlet of the sealed cavity at the kiln head and kiln tail of the rotary kiln, the instantaneous pressure of the gas in the cavity is collected by a high-frequency pressure transmitter, and the sampling frequency is set to more than 10 times the rotation frequency of the rotary kiln.

3. The method for diagnosing seal failure in a lithium iron phosphate rotary kiln according to claim 1, characterized in that, The preprocessing of the collected data includes: aligning the collected data with timestamps, using a low-pass filter to filter out high-frequency electromagnetic noise, and retaining pressure signal components that are in the same frequency as or at the same harmonic frequency as the rotation frequency; setting a minimum working pressure threshold, and performing subsequent calculations only when the instantaneous pressure is greater than the minimum working pressure threshold.

4. The method for diagnosing seal failure in a lithium iron phosphate rotary kiln according to claim 2, characterized in that, The rotation modulation leakage index satisfies the expression: In the formula, The rotation modulation leakage index, The total number of sampling points within one rotation cycle. For the first Instantaneous pressure values ​​at each sampling point It is the arithmetic mean of the pressure values ​​at all sampling points within this rotation cycle. For the first The rotation angle of the cylinder corresponding to each sampling point This is the gravity phase offset angle.

5. The method for diagnosing seal failure in a lithium iron phosphate rotary kiln according to claim 4, characterized in that, The gravity phase offset angle It is a constant determined based on the geometric angle between the installation position of the high-frequency pressure transmitter and the maximum gravity sinking point of the cylinder; the sine term in the expression This is used to assign higher weight to pressure fluctuations during the phase of maximum eccentric deformation of the cylinder, in order to amplify the periodic leakage characteristics caused by gravitational deflection.

6. The method for diagnosing seal failure in a lithium iron phosphate rotary kiln according to claim 4, characterized in that, The thermal creep correction factor satisfies the following expression: In the formula, It is a thermal creep correction factor. To accumulate effective running time, This is the current surface temperature of the cylinder. This is a reference standard temperature used to normalize the effect of temperature. and This is an empirical material coefficient determined based on the cylinder material; this expression reflects the physical characteristics of creep damage increasing logarithmically over time and being accelerated nonlinearly by temperature.

7. The method for diagnosing seal failure in a lithium iron phosphate rotary kiln according to claim 6, characterized in that, The reference standard temperature Set to ambient temperature or the rated operating temperature of the rotary kiln; material empirical coefficient The material empirical coefficients are used to characterize the rapid development stage of early creep. Used to characterize the accelerating weight of high temperature on steady-state creep.

8. The method for diagnosing seal failure in a lithium iron phosphate rotary kiln according to claim 6, characterized in that, The seal failure risk index is defined as follows: It satisfies the expression: 。 9. The method for diagnosing seal failure in a lithium iron phosphate rotary kiln according to claim 1, characterized in that, The step of implementing corresponding graded early warning or shutdown control strategies based on the comparison results includes: When the seal failure risk index is less than the warning threshold, the rotary kiln is determined to be in normal operating condition, and the current control strategy is maintained. When the seal failure risk index is greater than or equal to the warning threshold and less than the shutdown threshold, the rotary kiln is determined to be in an early deformation leakage condition. The opening of the air inlet valve of the sealing gas source is automatically increased to increase the air supply for pressure compensation, and maintenance suggestions for checking the support condition of the rotary kiln support rollers are generated. When the risk index of sealing failure is greater than or equal to the shutdown threshold, the rotary kiln is determined to be in a state of severe sealing failure or severe deformation of the cylinder, triggering an audible and visual alarm, and interlocking to control the heating power supply to reduce the output power and execute the safety shutdown procedure.

10. A fault diagnosis system for the seal failure of a lithium iron phosphate rotary kiln, characterized in that, It includes a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, the fault diagnosis method for the seal failure of the lithium iron phosphate rotary kiln according to any one of claims 1-9 is implemented.

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