A method and device for sealing the rotor shaft of a composite coal mill

Abstract

The application discloses a composite coal mill rotor seal method and device in the technical field of coal mill shaft seals, comprising the following steps: S1, constructing a cooperative sealing system: including a combined sealing unit, a monitoring unit and a control unit arranged on both sides of the coal mill; S2, monitoring the operating conditions: based on the monitoring unit, real-time acquisition of the working condition parameters reflecting the operating state of the coal mill; S3, executing a cooperative control strategy based on the working condition parameters. The application sets up a negative pressure seal and a contact type compensation seal, the negative pressure seal unit generates local negative pressure in the shaft gap by using high-speed jet, actively blocks the outward leakage of internal high-temperature hot air, the contact type compensation seal unit is designed by radial adhesion and axial floating, automatically compensates the gap change caused by wear, thermal expansion or slight swing of the shaft, and ensures stable and reliable sealing under the conditions of long-term operation and shaft disturbance.

Description

Technical Field

[0001] This invention relates to the field of coal mill shaft sealing technology, and in particular to a composite coal mill auger shaft sealing method and apparatus. Background Technology

[0002] The ball mill is a high-efficiency, large-scale pulverizing equipment mainly used in coal-fired power plants. The core structure of the double-inlet, double-outlet ball mill consists of a horizontally placed cylindrical body containing a large number of steel balls as grinding media. It is equipped with two completely symmetrical augers for feeding, discharging, and conveying coal. During operation, the augers pull the incoming coal into the mill cylinder for grinding and breaking down. The outer shaft seal where the auger shaft passes through the hot air box is made of YS350 asbestos packing, while the inner seal is a copper sealing ring. During operation, the composite seal of the asbestos packing and copper sealing ring prevents hot air leakage from the mill's hot air box.

[0003] During operation, raw coal is mixed with hot air at both ends of the coal mill and fed into the cylinder, where it is crushed into pulverized coal by steel balls inside the rotating cylinder. The hot air acts as both a desiccant and a conveying medium, carrying the qualified pulverized coal out from the outlets at both ends and directly supplying it to the boiler for combustion.

[0004] However, in the existing technology, the asbestos packing of the auger shaft seal on the outside of the hot air box is relatively soft and not wear-resistant. It suffers some natural wear during daily operation. Moreover, the temperature of the hot air box is high, and the aging and pulverization of the asbestos packing gradually accelerates with the increase of operating time. After replacing the packing, the hot air leakage phenomenon increases significantly in less than one month. The inner copper sealing ring of the hot air box is too hard. After a period of operation, the packing wears out and cannot be automatically compensated, resulting in increased external leakage. Furthermore, during operation, encountering large debris such as wood blocks, gangue, or rubber can easily cause the auger shaft to oscillate slightly radially. This leads to direct friction between the auger shaft and the asbestos packing and sealing ring, further widening the sealing gap of the auger shaft seal. Since these two sealing materials cannot compensate for the sealing gap on the opposite side of the oscillation direction, hot air leakage at the shaft seal is exacerbated, resulting in fly ash leakage, environmental pollution, and harm to the health of workers. Therefore, we propose a composite auger shaft seal method and device for coal mills. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a composite coal mill auger shaft sealing method and device. By setting up a combined internal and external synergistic sealing and dynamic compensation system, it replaces the traditional packing and metal rings that wear out quickly and have poor compensation, thereby solving the problems of hot air leakage and dust pollution.

[0006] The objective of this invention is achieved as follows: a method and apparatus for sealing the shaft of a composite coal mill auger, comprising the following steps: S1, Construct a collaborative sealing system: including a combined sealing unit, a monitoring unit, and a control unit installed on both the inside and outside of the coal mill; The combined sealing unit includes a negative pressure sealing unit disposed inside the hot air box and a contact compensation sealing unit disposed outside the hot air box. S2, Monitoring operating conditions: Real-time acquisition of operating condition parameters reflecting the operating status of the coal mill based on the monitoring unit; The operating parameters include at least the unit load; S3 executes a collaborative control strategy based on operating condition parameters; The collaborative control strategy includes high-load mode, transition mode, and economic mode; The collaborative control strategy is executed by the control unit commanding the joint sealing unit.

[0007] Optionally, in step S1, the negative pressure sealing unit specifically comprises: The negative pressure sealing unit is sleeved on the outside of the auger shaft to form a gap channel. A jet hole with an incident angle is opened on the inner wall of the gap channel and connected to an air pump device. Air flows into the gap channel through the jet hole, generating a local negative pressure in the gap and preventing the internal airflow from leaking to the outside through the gap. The axis of the jet hole is set at an acute angle to the axis of the auger shaft, ranging from 10° to 20°. The jet holes are multiple in number and arranged in multiple staggered rows. A circumferential phase difference is provided between adjacent rows of jet holes to form a continuous negative pressure sealing environment in the circumferential range.

[0008] Optionally, the supply pipeline of the air pump device is integrated with a set of high-frequency pulse valves, which control each row of jet holes to perform pulse injection of the system pulse strategy, forming a negative pressure traveling wave that moves along the axial direction to eliminate shaft resonance. The specific collaborative pulse strategy is as follows: at least two sets of independently controllable jet holes are required, which are alternately opened and closed according to a time sequence with a fixed phase difference, and a dynamic negative pressure field is periodically and directionally excited and maintained in the gap channel between the negative pressure sealing unit and the winch shaft.

[0009] Optionally, in step S1, the contact-type compensating sealing unit includes at least two sealing groups arranged sequentially along the medium leakage direction; The primary sealing assembly is the main seal, featuring an internal elastic structure and wear-resistant sealing material, providing initial sealing preload. P 1. Used to overcome the internal pressure of the hot air box under normal operation; The second-stage sealing assembly is a safety seal with a built-in elastic structure, providing a safety seal preload.P 2. Used to provide a backup seal after the primary seal fails; The contact-type compensation sealing unit is radially fitted to the winch shaft, and radial movement is not allowed. The contact-type compensation sealing unit and the winch shaft are allowed to float axially, and the floating stroke is less than or equal to the elastic compensation stroke of the elastic structure.

[0010] Optionally, the relationship between the safety seal preload and the initial seal preload is as follows:

[0011] In the formula: This is the safety margin factor, which is usually a constant greater than 1; The maximum sudden pressure difference expected to act on the secondary sealing ring group when the first-stage sealing group fails is taken as the maximum instantaneous positive pressure that may occur in the coal mill hot air box under abnormal operating conditions. With atmospheric pressure The difference, that is ; This refers to the effective sealing area between the second-stage sealing assembly and the journal of the winch shaft. The abnormal operating conditions include deflagration and sudden coal shortage.

[0012] Optionally, the wear-resistant sealing material is arranged in a gradient structure, specifically comprising, from the inside out: The inner matrix layer is connected to the elastic structure; The intermediate transition layer contains wear-resistant particles, which gradually increase the elastic modulus. The surface functional layer, which contacts the auger shaft, contains high-hardness wear-resistant particles, solid lubricant particles, and low-temperature phase change material microcapsules. The high-hardness wear-resistant particles include: silicon carbide and aluminum oxide; The solid lubricant particles include: graphite and molybdenum disulfide.

[0013] Optionally, in step S3, the cooperative control strategy specifically includes: When the monitoring unit detects that the unit load has reached a preset load threshold, the control unit executes the corresponding load mode according to the threshold. When the monitoring unit detects an additional abnormal signal, it forces the control unit to execute a high-load mode; The additional abnormal signals include the instantaneous value of the hot air box pressure and the abnormal rise in bearing temperature.

[0014] Optionally, the preset load threshold includes a first load threshold and a second load threshold; When the unit load is less than or equal to the first load threshold, the economic mode is executed and the negative pressure sealing unit is not activated. When the unit load is greater than the first load threshold and less than the second load threshold, the transition mode is executed, and the air pump device of the negative pressure sealing unit is instructed to operate at a low frequency. When the unit load is greater than or equal to the second load threshold, the high load mode is executed, instructing the air pump device of the negative pressure sealing unit to operate at a high frequency, allowing the elastic structure to increase the preload.

[0015] A composite coal mill auger shaft sealing device is used to implement the composite coal mill auger shaft sealing method described in any of the above claims, comprising a collaborative sealing system, wherein the collaborative sealing system comprises a combined sealing unit, a monitoring unit, and a control unit; The combined sealing unit includes a negative pressure sealing seat and a contact-type compensation sealing unit; The negative pressure sealing unit is used to set up the negative pressure sealing unit. The negative pressure sealing seat is formed in an annular arrangement and has an array of jet holes connected to the air pump device. The jet hole array is arranged in multiple staggered rows, with at least two rows, and a circumferential phase difference is set between adjacent rows of jet holes; The contact-type compensation sealing unit includes a sealing gland, and a multi-stage sealing group is provided between the sealing gland and the winch shaft; The sealing assembly is arranged in at least two layers along the direction of medium leakage, including an elastic structure and a wear-resistant sealing material; The elastic structure includes an electrically controlled spring, a pneumatic actuator, and an electric push rod; The monitoring unit includes at least a load sensor, a pressure sensor, a temperature sensor, and a displacement sensor; The control unit is used to receive electrical signals from the monitoring unit, and to make logical judgments and decisions based on the embedded collaborative control strategy, and then issue control commands to the combined sealing unit. The control commands include adjusting the pressure regulating valve of the air pump device to control the air pressure, flow rate, and start / stop frequency of the jet orifice output; It also includes the output of the command elastic structure, which in turn controls the magnitude of the preload force of the sealing assembly.

[0016] Optionally, the working process of the negative pressure sealing seat is as follows: during operation, filtered air is alternately introduced from each jet orifice according to a time sequence through the high-frequency pulse valve of the air pump device, and a dynamic negative pressure field is formed in the local area around the shaft of the auger shaft based on the hydrodynamic effect, which prevents the leakage of high-temperature gas containing dust inside.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: Traditional seals rely on the filling and wear of the material itself, and the sealing effect decreases linearly with the running time. The present invention improves the reliability and environmental tolerance of the seal by combining non-contact negative pressure sealing and contact floating compensation sealing. In this application, the negative pressure sealing unit set on the inner side uses high-speed jet to generate local negative pressure in the shaft gap, actively blocking the leakage of internal high-pressure hot air to the outside, forming the first active, non-contact sealing barrier. At the same time, the contact compensation sealing unit on the outer side achieves an initial tight seal through radial fitting and axial floating design, and can automatically compensate for the gap changes caused by wear, thermal expansion or slight shaft swing, fundamentally overcoming the defects of traditional seals such as fast wear and poor compensation, ensuring that the sealing performance remains stable and reliable under long-term operation and shaft disturbance conditions, and effectively solving the problem of hot air and dust leakage. Furthermore, the collaborative control strategy of this application intelligently switches between economic mode, transition mode and high load mode according to the unit load, and dynamically adjusts the start-up, shutdown and intensity of the negative pressure seal and the pre-tightening force of the contact seal, so that the sealing system can operate in energy-saving mode under low load and provide full protection under high load, thereby significantly reducing energy consumption. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the composite coal mill auger shaft seal collaborative control strategy provided by the present invention; Figure 2 This is a schematic diagram of the composite coal mill auger shaft sealing method provided by the present invention; Figure 3 A schematic diagram of the composite coal mill auger shaft sealing device provided by the present invention.

[0020] In the diagram: 1. Negative pressure sealing seat; 2. Air pump device; 3. Hot air box shell; 4. External flange; 5. Sealing gland; 6. Elastic structure; 7. Screw shaft; 8. Jet hole; 9. Wear-resistant sealing material. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] like Figures 1 to 3 The method and apparatus for sealing the shaft of a composite coal mill auger shown includes a collaborative sealing system, which mainly comprises a combined sealing unit, a monitoring unit, and a control unit. The combined sealing unit includes a negative pressure sealing seat 1 and a contact-type compensation sealing unit; Furthermore, the system provided in this application mainly consists of three functional modules: a combined sealing unit, a monitoring unit, and a control unit. These three units are linked through mechanical connections, electrical circuits, and a data bus to jointly achieve dynamic sealing of the high-speed rotating auger shaft 7 under harsh working conditions. The combined sealing unit is the physical actuator of this device, acting directly on the auger shaft 7 to form a barrier to prevent media leakage. Specifically, it includes a negative pressure sealing seat 1 and a contact-type compensating sealing unit. The negative pressure sealing seat 1 is usually installed near the inside of the coal mill hot air box (i.e., the high-pressure side), while the contact-type compensating sealing unit is installed on the outside of the hot air box (i.e., the low-pressure side or atmospheric side). The two are arranged in series along the axial direction of the auger shaft 7 to jointly perform the sealing function. First, the negative pressure sealing seat 1 is annular in shape and is usually made of high temperature resistant alloy steel (such as 310S stainless steel) or special ceramics to ensure that it has sufficient structural strength and dimensional stability in high temperature environment. It is fixed to the shell of the coal mill by bolts or flanges, and an annular gap is formed between its inner hole wall and the outer surface of the auger shaft 7. An array of inclined jet holes 8 is precisely machined on the inner wall of the aforementioned gap channel (i.e., the shaft hole wall of the negative pressure sealing seat 1). The jet hole array 8 is arranged in multiple staggered rows, with at least two rows, for example, three rows of jet holes 8, which are distributed equidistantly or unequally along the axial direction of the auger shaft 7. Within the same row, the jet holes 8 are uniformly opened in the circumferential direction. More importantly, adjacent rows of jet holes 8 are provided with a fixed phase difference in the circumferential direction. For example, if the first row has 12 holes, each spaced 30° apart, the holes in the second row can be rotated 15° relative to the first row, thus staggering with the holes in the first row in the circumferential direction. This is intended to form a continuous, uniform, and dead-angle-free dynamic negative pressure distribution area near the entire circumferential surface of the auger shaft 7 when each row of jet holes 8 works simultaneously or alternately, significantly improving the circumferential uniformity and sealing efficiency of the non-contact seal.

[0023] Each jet orifice 8 is connected to the air supply line of the external air pump device 2 through an independent micro-channel or a common annular air collection chamber. It should be noted that the axial direction of the jet hole 8 is at an acute angle to the axial direction of the auger shaft 7, so that the ejected airflow has a tangential component, which is conducive to forming a rotating airflow layer around the shaft and enhancing the entrainment and blocking effect on the leaked gas.

[0024] Secondly, between the sealing gland 5 and the winch shaft 7, at least two stages of sealing groups are arranged sequentially along the direction of medium leakage from the hot air box to the outside. The first stage of sealing group serves as the main seal, bearing the main sealing pressure; the second stage of sealing group serves as a safety seal, acting as an important backup barrier after the main seal fails. Each stage of sealing group consists of two parts: an elastic structure 6 that provides axial clamping force, and a wear-resistant sealing material 9 that provides the radial sealing interface. The elastic structure 6 is the core component for realizing dynamic adjustment of the sealing preload. Its specific form can be selected according to design requirements and site conditions. A preferred embodiment adopts an electronically controlled spring assembly, which includes a set of disc springs or helical springs connected to an adjusting screw driven by a servo motor. By controlling the forward and reverse rotation of the servo motor, the compression of the spring can be precisely adjusted, thereby linearly changing the preload acting on the sealing ring. Another implementation uses a pneumatic actuator, such as a small cylinder, and the air pressure entering the cylinder is adjusted by a control unit, which changes the thrust of the piston rod accordingly, thereby controlling the sealing preload. Another implementation method can use a precise electric actuator, where the extension and retraction of the actuator is directly driven by a motor to apply or release pressure; The aforementioned elastic structure 6 can be installed in the seat of the sealing cover 5, and its output force can be directly or through the pressure ring to the wear-resistant sealing material 9, so that it maintains a controllable contact pressure with the surface of the winch shaft 7. The wear-resistant sealing material 9 has a gradient structure, specifically including the following from the inside out: The inner matrix layer is connected to the elastic structure 6; The intermediate transition layer contains wear-resistant particles, which gradually increase the elastic modulus. The surface functional layer, which is in contact with the auger shaft 7, contains high-hardness wear-resistant particles, solid lubricant particles, and low-temperature phase change material microcapsules. The wear-resistant sealing material 9 is not a single homogeneous material. Its structure has a gradient function. The innermost layer is the matrix layer, which is usually a high-toughness high-temperature alloy or a high-strength engineering plastic, and is fixedly connected to the elastic structure 6. The middle layer is a transition layer, in which hard wear-resistant particles such as tungsten carbide or alumina are dispersed. From the inside to the outside, the concentration of particles and the overall elastic modulus of the material gradually increase to achieve a smooth stress transition. The outermost surface functional layer is the surface functional layer that is in direct contact with the auger shaft 7 (usually with a hardened surface). This layer is made of composite material, and its matrix can be a special copper alloy or a modified engineering plastic. High-hardness wear-resistant particles are dispersed and are made of materials such as tungsten carbide and ceramic microparticles to bear contact stress and resist abrasive wear. Solid lubricant particles are made of materials such as graphite and molybdenum disulfide and are uniformly dispersed in the surface functional layer. They can be transferred to the friction interface during continuous friction to form a stable lubricating film, thereby effectively reducing the coefficient of friction and reducing frictional heat and wear. Microcapsules containing low-temperature phase change materials have an outer shell that protects the internal phase change materials, preferably paraffin-based or alloy-based. When friction causes local hot spots to appear in the contact area and the temperature exceeds the phase change melting point, the microcapsules rapidly absorb a large amount of latent heat and undergo a phase change, achieving instantaneous cooling and temperature stabilization of the friction surface. This prevents the sealing material from burning out, degrading in performance, or sticking to the shaft due to overheating.

[0025] The monitoring unit includes at least a load sensor, a pressure sensor, a temperature sensor, and a displacement sensor; The monitoring unit is responsible for collecting various parameters that reflect the operating status of the coal mill and the working condition of the sealing device in real time. It includes at least the following types of sensors: load sensors, which are used to monitor the output power of the generator set or the feeder speed / current of the coal mill, and indirectly reflect the load level inside the coal mill. A pressure sensor is installed inside the hot air box or near the negative pressure sealing seat 1 to monitor the pressure in the sealing cavity and its transient fluctuations in real time. Temperature sensors, typically thermocouples or PT100 resistance thermometers, are installed at bearing housings, the outer side of sealing gland 5, and near negative pressure sealing seat 1, and are used to monitor temperature changes in critical components. Displacement sensors are used for non-contact monitoring of the axial displacement or radial vibration amplitude of the winch shaft 7 relative to the housing. All sensors transmit electrical signals to the control unit. The control unit is typically implemented using an industrial-grade programmable logic controller (PLC) or an embedded industrial computer. Its internal memory contains a collaborative control strategy program written based on the operating characteristics and sealing principle of the coal mill. The control unit receives electrical signals from various sensors of the monitoring unit in real time through its input module to obtain accurate operating condition parameter values. Based on this real-time data, the control unit executes the embedded collaborative control strategy.

[0026] The control commands include adjusting the pressure regulating valve of the air pump device 2 to control the air pressure, flow rate and start / stop frequency of the jet orifice 8; It also includes the output of the instruction elastic structure 6, which in turn controls the magnitude of the pre-tightening force of the sealing assembly.

[0027] The method for sealing the 7th shaft of a composite coal mill auger provided in this application includes the following steps: S1, Construct a collaborative sealing system: including a combined sealing unit, a monitoring unit, and a control unit installed on both the inside and outside of the coal mill; S2, Monitoring operating conditions: Real-time acquisition of operating condition parameters reflecting the operating status of the coal mill based on the monitoring unit; S3 executes a collaborative control strategy based on operating condition parameters; Specifically, in step S1, the negative pressure sealing unit is as follows: The negative pressure sealing unit is sleeved on the outside of the auger shaft 7 to form a gap channel. A jet hole 8 with an incident angle is opened on the inner wall of the gap channel and connected to the air pump device 2. Air flows into the gap channel from the jet hole 8, generating local negative pressure in the gap and preventing the internal airflow from leaking to the outside through the gap. The axis of the jet hole 8 is set at an acute angle to the axis of the auger shaft 7, ranging from 10° to 20°. Furthermore, the core function of the jet hole 8 is to inject high-pressure airflow into the gap between the auger shaft 7 and the sealing seat, and to entrain the leaking gas in the gap through the ejection effect, thereby creating a local negative pressure zone in the gap and blocking the leakage. The incident angle is a key geometric parameter that determines the ejection efficiency, negative pressure intensity and circumferential coverage uniformity.

[0028] Axial sealing component and circumferential sweeping effect: When the incident angle is greater than 0°, the jet velocity can be decomposed into axial and tangential (circumferential) components. The axial component directly counteracts the leakage airflow from inside the hot air box to the outside, and is the direct driving force for generating a reverse pressure gradient and establishing a sealing negative pressure. The tangential component causes the jet to "sweep" along the shaft surface, which helps to form a uniform rotating airflow layer around the shaft, prevents dust from depositing locally, and can more effectively transport the entrained leakage gas to the exhaust port. To verify the above theoretical analysis and determine the optimal angle range, this application constructed a scaled-down test bench. Under constant intake pressure (0.5 MPa), constant gap (0.5 mm), and standard leakage pressure difference (2 kPa), the system tested the effects of different incident angles on the core sealing performance indicators, namely, the minimum pressure value in the negative pressure zone (absolute pressure, characterizing sealing capability) and circumferential pressure non-uniformity (characterizing sealing uniformity). The experimental results are shown in Table 1 below: Table 1: Experimental data on the effect of the incident angle of jet orifice 8 on sealing performance

[0029] The data in the table above clearly shows that: When the incident angle increases from 5° to 10°, the lowest pressure in the negative pressure zone... P minContinuous reduction (enhanced sealing ability), while circumferential pressure unevenness σ It also significantly improved (uniformity increased), and the overall evaluation value reached its peak.

[0030] Within the range of 10° to 20°, the lowest pressure in the negative pressure zone P min All below 92.5 kPa Circumferential pressure unevenness σ All values ​​were below 5.5%, and the overall evaluation values ​​were all above 0.90, demonstrating excellent and stable comprehensive sealing performance.

[0031] When the angle exceeds 20°, the performance indicators begin to decline synchronously; when it exceeds 30°, the performance deterioration intensifies.

[0032] Therefore, limiting the incident angle of the jet orifice 8 to the range of 10° to 20° is a technical choice based on in-depth analysis of fluid dynamics mechanisms and rigorous experimental verification, ensuring that the negative pressure sealing unit can achieve the best dynamic pressure sealing effect with the highest energy efficiency and the most stable working state.

[0033] Specifically, there are multiple jet holes 8 arranged in multiple staggered rows, with a circumferential phase difference between adjacent rows of jet holes 8 to form a continuous negative pressure sealing environment in the circumferential range; In the supply pipeline of the air pump device 2, a set of high-frequency pulse valves are integrated to control each row of jet holes 8 to perform pulse jetting of the system pulse strategy, forming a negative pressure traveling wave that moves along the axial direction to eliminate shaft resonance. The coordinated pulse strategy specifically requires at least two sets of independently controllable jet holes 8, which alternately open and close according to a time sequence with a fixed phase difference, to periodically and directionally excite and maintain a dynamic negative pressure field in the gap channel between the negative pressure sealing unit and the winch shaft 7.

[0034] Furthermore, from a spatial perspective, the array of jet holes 8 arranged in multiple rows with circumferential phase difference ensures that a continuous airflow is injected into the sealing gap from both axial and circumferential dimensions, thereby eliminating the negative pressure "blind zone" or periodic weak point caused by a single row of holes or holes with the same phase, and forming a continuous and uniform negative pressure sealing ring on the entire circumference of the auger shaft 7. From a time perspective, by implementing alternating pulse control with a fixed phase difference for each jet orifice 8 through a high-frequency pulse valve, a "negative pressure traveling wave" that periodically moves a pressure field in the axial direction is excited in the gap. On the one hand, it can continuously clean and re-stabilize the gap flow field like a "broom", compensate for local pressure fluctuations caused by slight shaft eccentricity or disturbance, and make the seal more robust. More importantly, the frequency and wave number of this directional periodic excitation can be precisely set by the program. When it matches and is out of phase with the potential natural vibration frequency of the shaft system, it can play an active damping role, effectively interfering with and canceling the lateral or torsional resonance of the shaft system that may be caused by fluid excitation (such as rotational stall, Alfvén wave), thereby improving the stability and reliability of the entire rotor system while achieving sealing performance.

[0035] Specifically, in step S1, the contact-type compensation sealing unit includes at least two sealing groups arranged sequentially along the direction of medium leakage; The first-stage sealing assembly is the main seal, with an internal elastic structure 6 and wear-resistant sealing material 9, providing initial sealing preload. P 1. Used to overcome the internal pressure of the hot air box under normal operation; The initial sealing preload P 1. Must meet the following requirements:

[0036] In the formula: This refers to the operating pressure of the hot air box during normal operation. The effective area of ​​a primary seal; The frictional forces that need to be overcome for sealing during startup and operation; The second-stage sealing assembly is a safety seal, with a built-in elastic structure 6 providing a safety seal preload. P 2. Used to provide a backup seal after the primary seal fails; The relationship between the safety seal preload and the initial seal preload is as follows:

[0037] In the formula: This is the safety margin factor, which is usually a constant greater than 1; The maximum sudden pressure difference expected to act on the secondary sealing ring group when the first-stage sealing group fails is taken as the maximum instantaneous positive pressure that may occur in the coal mill hot air box under abnormal operating conditions. With atmospheric pressure The difference, that is ; The effective sealing area between the second-stage sealing assembly and the journal of the auger shaft 7 ( ) Abnormal operating conditions include deflagration and sudden coal shortage.

[0038] To intuitively demonstrate the safety margin coefficient kThe selection within the range of 1.5 to 2.5 is based on the comprehensive optimal solution of its functional realization and engineering benefits. A set of experimental data for dynamic wear test of the 7 seals of the auger shaft of a composite coal mill was designed and simulated.

[0039] Experimental setup: Primary sealing target clamping force The reference is 100 N, and the initial clamping force of the secondary seal is adjusted. Monitoring different k The overall performance of the system is shown under simulated wear cycles (100 hours). It is assumed that the primary seal will experience an average 25% decrease in clamping force during use.

[0040] Table 2: Test results of shaft seal performance under different safety margin factors k.

[0041] As shown in Table 2, when k When the pressure is 1.0, after the primary seal wears by 25%, the secondary seal is unable to compensate (the remaining pressure is negative), resulting in leakage. when k When the value is greater than 1.5, even with 25% wear of the primary seal, the secondary seal still has a positive clamping force of at least 75N. Therefore, 1.5 is the starting effective value to ensure reliability.

[0042] along with k As the value increases, power loss (mainly reflected in additional frictional energy consumption and temperature rise) increases sharply. k As the value increased from 1.5 to 2.5, the power consumption increased by approximately 2.2 times.

[0043] exist k At a power consumption of 2.5, although reliability remains "good," excessive power consumption can lead to bearing overheating, increased energy consumption, and unnecessary excessive wear of the sealing components. k With the version now up to 3.0, the negative effects of this over-design are already becoming apparent.

[0044] Experimental results show that, k Once the value exceeds 1.5, the system has sufficient redundancy, therefore the safety margin factor... k The value ranges from 1.5 to 2.5.

[0045] Specifically, the contact-type compensation sealing unit is radially fitted with the winch shaft 7, and radial movement is not allowed; Axial floating is allowed between the contact-type compensation sealing unit and the winch shaft 7, and the floating stroke is less than or equal to the elastic compensation stroke of the elastic structure 6.

[0046] Furthermore, the radially tight initial fit directly eliminates the main leakage gap, while the axial floating provides a compensation function, allowing the sealing unit to "adaptively" move in response to thermal expansion and contraction, vibration, or slight axial displacement generated by the winch shaft 7 during operation. At the same time, the elastic structure 6 continuously provides uniform clamping force to automatically compensate for wear. This ensures that the sealing fit remains intact under dynamic operating conditions, effectively compensating for wear (preventing gap expansion), and also avoids increased friction, jamming, or structural damage caused by rigid connections, thereby improving the long-term reliability and service life of the seal.

[0047] In step S3, the cooperative control strategy is specifically as follows: When the monitoring unit detects that the unit load has reached a preset load threshold, the control unit executes the corresponding load mode according to the threshold. When the unit load is less than or equal to the first load threshold, the economic mode is executed and the negative pressure sealing unit is not activated. When the unit load is greater than the first load threshold and less than the second load threshold, the transition mode is executed, and the air pump device 2 of the negative pressure sealing unit is instructed to operate at a low frequency. When the unit load is greater than or equal to the second load threshold, the high load mode is executed, and the air pump device 2 of the negative pressure sealing unit is instructed to operate at a high frequency, allowing the elastic structure 6 to increase the preload.

[0048] When the monitoring unit detects an additional abnormal signal, it forces the control unit to execute a high-load mode; Additional abnormal signals include abnormal instantaneous values ​​of hot air box pressure and abnormal increases in bearing temperature.

[0049] Furthermore, the advantage of the collaborative control strategy is that it can intelligently switch the sealing strength according to the actual operating load of the unit, avoid unnecessary energy consumption in the low-load economic mode, and gradually increase the sealing negative pressure and pre-tightening force as the load increases, matching the sealing requirements of different operating conditions, thereby maximizing energy-saving benefits while ensuring sealing reliability. More importantly, the introduced additional abnormal signals serve as the mandatory triggering condition for the high-load mode, giving it the ability to actively protect itself. When the system senses potential leakage risks such as sudden changes in hot air box pressure or fault precursors such as bearing overheating, it can immediately raise the seal to the highest defense level without waiting for leakage to occur, effectively preventing abnormal operating conditions from evolving into leakage accidents. It should be noted that in the collaborative control strategy, the operating frequency of the air pump device (2) is an important control variable, specifically: The low-frequency operation of the air pump device (2) aims to generate a stable but gentle negative pressure field, which needs to initially counteract the slight increase in internal pressure and leakage tendency due to the increase in load, as a supplement to the basic seal, while keeping energy consumption at a low level. The purpose of high-frequency operation is to generate a strong and continuous negative pressure field in the shortest possible time, specifically including: 1. providing a strong suction force sufficient to balance the internal pressure of the hot air box under high load (or abnormal high pressure); 2. forming a more effective dynamic air seal barrier in the sealing gap by strengthening the negative pressure. Therefore, the specific power or speed of the air pump device (2) for low-frequency or high-frequency operation needs to be determined based on the actual performance of the device used.

[0050] For example, based on the Φ160mm diameter of the main shaft journal of a certain auger, four Φ162×260×125 negative pressure sealing seats 1 are designed and manufactured for each unit's two coal mills. The negative pressure sealing seats 1 are welded to the hot air box shell 3. On the inner wall of the negative pressure sealing seat 1, jet holes 8 with an inclination angle of 15º and a diameter of Φ6mm are machined every 12mm. The second row of jet holes 8 is machined with a center distance of 6mm offset from the first row, and the circumferential phase difference is 180°. Compressed air flows out rapidly through the jet hole 8, and by utilizing the principle of fluid jetting, a local negative pressure effect is formed at this point, thereby achieving a dynamic sealing effect. A sealing cover 5 is installed on the outside of the hot air box shell 3 and mounted on the external flange 4 of the hot air box shell 3. Two sets of gapless compensation sealing groups with elastic sealing rings are machined inside the sealing cover 5. The sealing group consists of several electrically controlled springs and wear-resistant sealing material 9.

[0051] Combined use under high load mode during operation: When the monitoring unit detects that the unit load reaches or exceeds the preset second load threshold, in this embodiment, 75% of the rated load is taken. The control unit determines that the coal mill is in a high-load operation state. At this time, the internal pressure and temperature of the hot air box are high, and the driving force for gas leakage is large. Therefore, the high-load mode is executed, specifically manifested as follows: The control unit commands the air pump device 2 to start and operate in a high-frequency, high-pressure mode. The high-frequency pulse valve works according to the coordinated pulse strategy to generate a dynamic negative pressure field with high intensity and wide coverage to prevent leakage. The control unit instructs the electrically controlled spring inside the sealing assembly to increase the output force, thereby raising the pre-tightening force of the sealing assembly to a higher set value, enhancing the fit and pressure resistance of the contact seal, and working in conjunction with the negative pressure seal to create a double sealing guarantee. Single use under the economic model: When the monitoring unit detects that the unit load is lower than or equal to the preset first load threshold, this embodiment uses 30% of the rated load. During the low-load warm-up phase after unit ignition and startup, the sliding pressure shutdown process, or deep peak shaving operation, the control unit determines that the internal pressure of the coal mill is low and the risk of leakage is small. In order to maximize the saving of plant compressed air energy consumption, and considering that appropriately increasing the internal temperature of the coal mill at the beginning of startup helps coal powder drying and stable combustion, the control unit automatically executes the economic mode, which is specifically manifested as follows: Negative pressure sealing seat 1: The control unit issues a command to close the air supply valve of the air pump device 2 or put it into standby mode, stopping the supply of compressed air to the jet hole 8, thus saving compressed air consumption; Contact-type compensating sealing unit: The initial pre-tightening force provided by the first-stage sealing group is sufficient to meet the sealing requirements under low load due to its good basic sealing performance. At the same time, since the supply of cooling gas to the negative pressure sealing seat 1 is stopped, the stability of the internal thermal environment is conducive to maintaining and increasing the inlet temperature of the coal mill, further saving losses. Coordinated use in transition mode: When the unit load is between the first load threshold and the second load threshold, the coal mill is in a medium load operation state, and the control unit executes the transition mode. Negative pressure sealing seat 1: The control unit commands the air pump device 2 to start, and the high-frequency pulse valve opens alternately at a lower frequency, or reduces the total air supply pressure, which not only establishes an effective negative pressure sealing assistance, but also reduces the consumption rate of compressed air. Contact-type compensating seal unit: maintains its initial preload operation as the primary static seal.

[0052] The workflow of this invention does not involve the fixed simultaneous use of two seals. Instead, through intelligent decision-making by the control unit, the negative pressure sealing seat 1 and the contact-type compensating sealing unit are flexibly combined and dynamically matched according to the actual load and other abnormal signals (such as sudden changes in pressure and temperature). When enhanced sealing capability is required, the two work together to strengthen it, while when demand is low, energy saving is prioritized, achieving an adaptive optimal balance between sealing performance and operational economy. Compared with the prior art, the present invention, through the coordinated control strategy of the 7th seal of the auger shaft of the coal mill, firstly eliminates the leakage of hot air at the 7th seal of the auger shaft, and prevents the dust mixed in the leaked hot air from contaminating the on-site equipment and the ground. Secondly, there is no longer any hot air leaking out and blowing towards the auger shaft 7 bearing seat, which allows the bearing temperature to be controlled and protects the lubricating oil film from being damaged. At the same time, there is no longer any hot air mixed with dust blowing into the bearing inside the bearing seat, which effectively reduces the failure rate of the auger shaft 7 bearing and increases the service life of the auger device bearing. More importantly, the improved indoor working temperature in summer is beneficial to the physical and mental health of daily inspection and maintenance personnel.

[0053] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for sealing the shaft of a composite coal mill auger, characterized in that, Includes the following steps: S1, Construct a collaborative sealing system: including a combined sealing unit, a monitoring unit, and a control unit installed on both the inside and outside of the coal mill; The combined sealing unit includes a negative pressure sealing unit disposed inside the hot air box and a contact compensation sealing unit disposed outside the hot air box. S2, Monitoring operating conditions: Real-time acquisition of operating condition parameters reflecting the operating status of the coal mill based on the monitoring unit; The operating parameters include at least the unit load; S3 executes a collaborative control strategy based on operating condition parameters; The collaborative control strategy includes high-load mode, transition mode, and economic mode; The collaborative control strategy is executed by the control unit commanding the joint sealing unit.

2. The composite coal mill auger shaft sealing method according to claim 1, characterized in that: In step S1, the negative pressure sealing unit specifically comprises: The negative pressure sealing unit is sleeved on the outside of the winch shaft (7) to form a gap channel. A jet hole (8) with an incident angle is opened on the inner wall of the gap channel and connected to the air pump device (2). Air flows into the gap channel from the jet hole (8) to generate local negative pressure in the gap, which prevents the internal airflow from leaking to the outside through the gap. The axis of the jet hole (8) is set at an acute angle to the axis of the auger shaft (7), ranging from 10° to 20°. The number of jet holes (8) is multiple, arranged in multiple staggered rows, and a circumferential phase difference is set between adjacent rows of jet holes (8) to form a continuous negative pressure sealing environment in the circumferential range.

3. The method for sealing the shaft of a composite coal mill auger according to claim 2, characterized in that: The supply pipeline of the air pump device (2) is integrated with a set of high-frequency pulse valves, which control each row of jet holes (8) to perform pulse jetting of the system pulse strategy, forming a negative pressure traveling wave that moves along the axial direction to eliminate shaft resonance. The specific collaborative pulse strategy is as follows: at least two sets of independently controllable jet holes (8) are used to alternately open and close according to a time sequence with a fixed phase difference, and a dynamic negative pressure field is periodically excited and maintained in the gap channel between the negative pressure sealing unit and the winch shaft (7).

4. The method for sealing the shaft of a composite coal mill auger according to claim 1, characterized in that: In step S1, the contact-type compensation sealing unit includes at least two sealing groups arranged sequentially along the medium leakage direction; The first-stage sealing assembly is the main seal, with an internal elastic structure (6) and wear-resistant sealing material (9) providing initial sealing preload. P 1; The second-stage sealing assembly is a safety seal with a built-in elastic structure (6) that provides a safety seal preload. P 2. Used to provide a backup seal after the primary seal fails; The contact-type compensation sealing unit is radially fitted with the winch shaft (7) and radial movement is not allowed; The contact-type compensation sealing unit and the winch shaft (7) are allowed to float axially, and the floating stroke is less than or equal to the elastic compensation stroke of the elastic structure (6).

5. The composite coal mill auger shaft sealing method according to claim 4, characterized in that: The relationship between the safety seal preload and the initial seal preload is as follows: In the formula: This refers to the safety margin factor. The maximum sudden pressure difference expected to act on the secondary sealing ring group when the first-stage sealing group fails is taken as the maximum instantaneous positive pressure that may occur in the coal mill hot air box under abnormal operating conditions. With atmospheric pressure The difference, that is ; The effective sealing area between the second-stage sealing group and the journal of the winch shaft (7); The abnormal operating conditions include deflagration and sudden coal shortage.

6. The composite coal mill auger shaft sealing method according to claim 4, characterized in that: The wear-resistant sealing material (9) is arranged in a gradient structure, specifically including, from the inside out: The inner matrix layer is connected to the elastic structure (6); The intermediate transition layer contains wear-resistant particles, which gradually increase the elastic modulus. The surface functional layer is in contact with the auger shaft (7) and contains high-hardness wear-resistant particles, solid lubricant particles and low-temperature phase change material microcapsules. The high-hardness wear-resistant particles include: silicon carbide and aluminum oxide; The solid lubricant particles include: graphite and molybdenum disulfide.

7. The composite coal mill auger shaft sealing method according to claim 1, characterized in that: In step S3, the cooperative control strategy specifically includes: When the monitoring unit detects that the unit load has reached a preset load threshold, the control unit executes the corresponding load mode according to the preset load threshold. When the monitoring unit detects an additional abnormal signal, it forces the control unit to execute a high-load mode; The additional abnormal signals include abnormal instantaneous values ​​of hot air box pressure and abnormal increases in bearing temperature.

8. A method for sealing the shaft of a composite coal mill auger according to claim 7, characterized in that: The preset load threshold includes a first load threshold and a second load threshold; When the unit load is less than or equal to the first load threshold, the economic mode is executed and the negative pressure sealing unit is not activated. When the unit load is greater than the first load threshold and less than the second load threshold, the transition mode is executed, and the air pump device (2) of the negative pressure sealing unit is instructed to operate at a low frequency. When the unit load is greater than or equal to the second load threshold, the high load mode is executed, and the air pump device (2) of the negative pressure sealing unit is instructed to operate at a high frequency, allowing the elastic structure (6) to increase the preload.

9. A composite coal mill auger shaft sealing device, used to implement the composite coal mill auger shaft sealing method described in any one of the above claims, comprising a cooperative sealing system, characterized in that: The collaborative sealing system includes a combined sealing unit, a monitoring unit, and a control unit; The combined sealing unit includes a negative pressure sealing seat (1) and a contact compensation sealing unit; The negative pressure sealing unit is used to set the negative pressure sealing unit. The negative pressure sealing seat (1) is formed in an annular arrangement and has an array of jet holes (8) connected to the air pump device (2). The jet hole (8) array is arranged in multiple staggered rows, with at least two rows, and a circumferential phase difference is provided between adjacent rows of jet holes (8); The contact-type compensation sealing unit includes a sealing cover (5), and a multi-stage sealing group is provided between the sealing cover (5) and the winch shaft (7); The sealing assembly is arranged in at least two layers along the direction of medium leakage, including an elastic structure (6) and a wear-resistant sealing material (9). The elastic structure (6) includes an electrically controlled spring, a pneumatic actuator, and an electric push rod; The monitoring unit includes at least a load sensor, a pressure sensor, a temperature sensor, and a displacement sensor; The control unit is used to receive electrical signals from the monitoring unit, and to make logical judgments and decisions based on the embedded collaborative control strategy, and then issue control commands to the combined sealing unit. The control commands include adjusting the pressure regulating valve of the air pump device (2) to control the air pressure, flow rate and start / stop frequency output by the jet orifice (8); It also includes the output of the instruction elastic structure (6), which in turn controls the magnitude of the pre-tightening force of the sealing assembly.

10. A composite coal mill auger shaft sealing device according to claim 9, characterized in that: The working process of the negative pressure sealing seat (1) is as follows: During operation, the filtered air is introduced alternately from each jet orifice (8) through the high-frequency pulse valve of the air pump device (2) in a time sequence. Based on the hydrodynamic effect, a dynamic negative pressure field is formed in the local area around the shaft of the winch shaft (7), which prevents the leakage of high-temperature gas containing dust inside.

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