CN-121539956-B - Method and system for diagnosing sealing failure fault of lithium iron phosphate rotary kiln

CN121539956BCN 121539956 BCN121539956 BCN 121539956BCN-121539956-B

Abstract

The invention belongs to the technical field of industrial automation control and fault diagnosis, and relates to a method and a system for diagnosing sealing failure faults of a lithium iron phosphate rotary kiln. The method comprises the steps of collecting instantaneous pressure of a sealing cavity, rotation angle of a cylinder, surface temperature and accumulated running time, calculating rotation modulation leakage index based on the instantaneous pressure and the rotation angle, extracting periodic respiratory effect characteristics caused by eccentricity of the cylinder by utilizing angle weighting, calculating thermal creep correction factors based on time and temperature, quantifying ageing tendency of materials, calculating seal failure risk index by combining the two, and executing grading early warning or shutdown control. The invention can discover early deformation leakage in advance when the sealing pressure has not fallen to the threshold value, adaptively correct the diagnosis standard of equipment aging and high-temperature working conditions, and effectively improve the accuracy and timeliness of fault diagnosis.

Inventors

SUN LIUHUI
SU GENHUA
JIN LIUBIN
GE YANJIE
SUN YANGFAN

Assignees

河南郑矿机器有限公司

Dates

Publication Date: 20260512
Application Date: 20251224

Claims (10)

1. The method for diagnosing the sealing failure fault of the lithium iron phosphate rotary kiln is characterized by comprising the following steps of: Collecting instantaneous pressure of a sealing cavity of the rotary kiln, rotation angle of a cylinder, surface temperature of the cylinder and accumulated effective running time of the rotary kiln, and preprocessing collected data; Calculating a rotation modulation leakage index based on the instantaneous pressure and the rotation angle, wherein the rotation modulation leakage index is used for representing the periodic fluctuation intensity of the pressure of the sealing cavity along with the change of the rotation angle in one rotation period so as to identify structural leakage caused by eccentric deformation of the cylinder; Calculating a thermal creep correction factor based on the accumulated effective run time and the barrel surface temperature, the thermal creep correction factor being used to evaluate the propensity of barrel material to permanently deform under current temperature and time accumulation; and calculating a seal failure risk index by using the rotation modulation leakage index and the thermal creep correction factor, comparing the seal failure risk index with a preset early warning threshold value and a preset shutdown threshold value, and executing a corresponding grading early warning or shutdown control strategy according to a comparison result.
2. The method for diagnosing the sealing failure fault of the lithium iron phosphate rotary kiln is characterized in that the method for collecting the instantaneous pressure of the sealing cavity of the rotary kiln comprises the step of collecting the instantaneous pressure of gas in the cavity at the air inlets of the sealing cavities of the kiln head and the kiln tail of the rotary kiln through a high-frequency pressure transmitter, wherein the sampling frequency is set to be more than 10 times of the rotation frequency of the rotary kiln.
3. The method for diagnosing the sealing failure of the lithium iron phosphate rotary kiln according to claim 1, wherein the preprocessing of the collected data comprises the steps of performing time stamp alignment on the collected data, filtering high-frequency electromagnetic noise by adopting a low-pass filter, retaining pressure signal components which are the same as and frequency-doubled with the rotation frequency, setting a minimum working pressure threshold, and executing subsequent calculation only when the instantaneous pressure is larger than the minimum working pressure threshold.
4. The method for diagnosing a seal failure in a lithium iron phosphate rotary kiln according to claim 2, wherein the rotation modulation leakage index satisfies the expression: In the formula, In order to rotate the modulation leakage index, For the total number of sampling points in one rotation period, Is the first The instantaneous pressure values of the individual sampling points, Is the arithmetic average of the pressure values of all the sampling points in the rotation period, Is the first The rotation angles of the cylinder corresponding to the sampling points, The gravity phase offset angle.
5. The method for diagnosing a seal failure in a lithium iron phosphate rotary kiln according to claim 4, wherein the gravity phase offset angle Is a constant determined according to the geometric included angle between the installation position of the high-frequency pressure transmitter and the maximum gravitational sinking point of the cylinder, and the sine term in the expression For imparting a higher weight to the pressure fluctuations at the phase of maximum eccentric deformation of the cylinder to amplify the periodic leakage characteristics due to gravity deflection.
6. The method for diagnosing a seal failure in a lithium iron phosphate rotary kiln according to claim 4, wherein the thermal creep correction factor satisfies the expression: In the formula, As a thermal creep correction factor, In order to accumulate the effective run time, The current cylinder surface temperature; the temperature sensor is used for normalizing the temperature influence for reference standard temperature; And The expression is used for reflecting the physical characteristics that creep damage is logarithmic in growth along time and is subjected to temperature nonlinear acceleration.
7. The method for diagnosing a seal failure in a lithium iron phosphate rotary kiln according to claim 6, wherein the reference standard temperature Setting the temperature to normal temperature or rated working temperature of the rotary kiln, and setting the material experience coefficient Fast-evolving stage weights for characterizing early creep, the material experience coefficient And the acceleration weight of the high temperature to the steady state creep is used for representing.
8. The method for diagnosing a seal failure in a lithium iron phosphate rotary kiln according to claim 6, wherein the seal failure risk index is defined as Which satisfies the expression: 。
9. The method for diagnosing a sealing failure of a lithium iron phosphate rotary kiln according to claim 1, wherein the step of executing a corresponding hierarchical early warning or shutdown control strategy according to the comparison result comprises the steps of: When the seal failure risk index is smaller than the early warning threshold value, judging that the rotary kiln is in a normal operation condition, and maintaining a current control strategy; When the seal failure risk index is larger than or equal to the early warning threshold value and smaller than the shutdown threshold value, judging that the rotary kiln is in an early deformation leakage working condition, automatically adjusting the opening of an air inlet valve of a seal air source to increase the air supply amount for pressure compensation, and generating maintenance advice for checking the supporting condition of the riding wheel of the rotary kiln; When the sealing failure risk index is greater than or equal to the shutdown threshold value, judging that the rotary kiln is in the working condition of serious failure of the sealing structure or serious deformation of the cylinder, triggering an audible and visual alarm, controlling the heating power supply to reduce the output power by the parallel lock, and executing a safe shutdown program.
10. A lithium iron phosphate rotary kiln seal failure fault diagnosis system comprising a processor and a memory, the memory storing computer program instructions which, when executed by the processor, implement the lithium iron phosphate rotary kiln seal failure fault diagnosis method of any one of claims 1 to 9.

Description

Method and system for diagnosing sealing failure fault of lithium iron phosphate rotary kiln Technical Field The invention belongs to the technical field of industrial automation control and fault diagnosis, and particularly relates to a method and a system for diagnosing sealing failure faults of a lithium iron phosphate rotary kiln. Background In the sintering process of lithium iron phosphate materials, the rotary kiln is core heating equipment, and the running stability of the rotary kiln directly determines the crystal structure and the electrochemical performance of the product. Because the sintering process is extremely sensitive to oxidation, the micro-positive pressure environment is maintained by continuously introducing inert gases such as nitrogen and the like into the kiln so as to ensure the valence stability and the phase purity of the material. Therefore, kiln head and kiln tail sealing performance of the rotary kiln is important for blocking external air from entering and preventing internal air from leaking. Aiming at the special working conditions of high temperature and dynamic rotation of the rotary kiln, the current main stream of the industrial site adopts a composite sealing structure of mechanical sealing and air sealing. The working principle is that protective gas with specific pressure is injected into a cavity formed by mechanical sealing, so that an air curtain barrier with pressure higher than that of kiln and ambient atmosphere is constructed. The existing seal failure monitoring method mainly depends on a pressure transmitter to monitor the pressure value in an air seal cavity, and when the detected pressure is lower than a preset fixed alarm threshold value, the system judges that the seal leaks and triggers an alarm. However, rotary kilns are typically tens of meters in length, and their suspended section cylinders are susceptible to irreversible material creep and deflection under the dual action of high temperature thermal stress and self-gravity moment. This deformation causes the cylinder cross-section to gradually degenerate from an ideal circular shape to an elliptical shape, creating a periodic eccentric runout during rotation, thereby inducing a periodic expansion of the sealing gap with the rotation angle, the so-called breathing effect. Existing monitoring systems typically process the pressure signal by low pass filtering, treat such high frequency pressure fluctuations due to periodic changes in the gap as background noise or be arithmetically averaged. When the physical structure of the sealing structure is damaged, the system cannot give out early warning in time because the average pressure does not drop down to the threshold value, so that the fault evolves into a serious accident. In addition, the operation of the rotary kiln is a process involving thermal, force, flow multi-field coupling. As the accumulated operating time of the equipment increases and the sintering temperature profile adjusts, thermal expansion and accumulated creep of the barrel material can cause dynamic drift of the baseline gap of the sealing interface. The existing fixed threshold method cannot adapt to the dynamic working condition, and is easy to report in a missed manner during normal thermal expansion or in a false manner during severe high-temperature creep. The prior art breaks the inherent physical link between mechanical rotational movement, thermal aging characteristics of the material and pressure in the sealed cavity, and a single pressure indicator cannot distinguish whether the pressure is due to transient depressurization caused by fluctuation of the air supply source or structural leakage caused by permanent deformation of the cylinder. This lack of diagnostic dimensions makes it difficult for field maintenance personnel to quickly locate the root cause of the fault, often missing the optimal equipment maintenance window. Disclosure of Invention The invention aims to provide a method and a system for diagnosing sealing failure faults of a lithium iron phosphate rotary kiln, which are used for solving the technical problems that the conventional fixed threshold monitoring method cannot identify periodic leakage caused by cylinder eccentricity, and sealing standard drift caused by equipment aging and high-temperature creep is difficult to adapt to, so that false alarm or missing alarm is caused. In order to solve the problems, the technical scheme of the lithium iron phosphate rotary kiln sealing failure fault diagnosis method provided by the invention is as follows: the method for diagnosing the sealing failure fault of the lithium iron phosphate rotary kiln comprises the following steps: Collecting instantaneous pressure of a sealing cavity of the rotary kiln, rotation angle of a cylinder, surface temperature of the cylinder and accumulated effective running time of the rotary kiln, and preprocessing collected data; Calculating a rotation modulation leakage index bas