A conveyor return belt cleaning device

Abstract

A conveyor return belt cleaning device, comprising a rack, a flexible breaking structure and a material collecting and recycling assembly arranged along the running direction of the return belt on the rack; the flexible breaking structure comprises a microwave softening assembly and a pneumatic stripping assembly; the microwave softening assembly comprises at least one magnetron and a microwave resonant cavity transverse to the width direction of the return belt, the lower wall and the peripheral side wall of the microwave resonant cavity are metal shielding layers, the upper wall of the microwave resonant cavity is composed of a microwave transmission material, and a gap is maintained between the upper wall and the surface of the return belt; the magnetron is fixedly connected to the outside of the metal shielding layer of the microwave resonant cavity through a waveguide, and the microwave emission port of the magnetron leads to the inside of the microwave resonant cavity, thereby improving the overall cleaning efficiency of sticky coal.

Description

Technical Field

[0001] This invention relates to a conveyor return belt cleaning device, belonging to the field of belt cleaning technology. Background Technology

[0002] Belt conveyors are widely used in material conveying systems in the coal and mining industries. During operation, their return belts often accumulate damp pulverized coal or muddy materials. If this coal is not removed promptly, it can fall along the path, causing environmental pollution, and its accumulation can damage equipment components and even pose safety hazards. Therefore, effective cleaning of the return belt is crucial for ensuring the clean, safe, and efficient operation of the system.

[0003] Currently, common cleaning technologies mainly include mechanical scraper cleaning and water washing. Mechanical scrapers rely on close contact and scraping against the conveyor belt surface to remove sticky coal, but long-term use inevitably leads to belt wear, and when the sticky coal is damp and caking, the scrapers are easily clogged, causing a rapid decline in cleaning effectiveness and requiring frequent adjustments or replacements. High-pressure water washing can remove some sticky coal, but it generates a large amount of coal slurry wastewater, which can cause secondary pollution if not properly treated, and there is also a risk of freezing in cold regions.

[0004] Chinese patent CN121894390A discloses an automatic cleaning coal conveyor belt, which adopts a three-stage progressive cleaning structure of ash sweeping, washing, and water scraping, and is equipped with a water recycling system. Wastewater is collected through a water tank, filtered in a water tank, and then reused for washing, aiming to achieve water resource recycling and improve cleaning effect. However, this solution is essentially a wet cleaning method, which must rely on water as the cleaning medium, resulting in problems such as water consumption, wastewater treatment, and freezing in cold environments. At the same time, its cleaning effect mainly relies on the mechanical friction of the brushes and the scouring of the water flow, which has limited cleaning power for firmly adhered and internally hardened sticky materials (such as wet coal slime), and it is difficult to achieve deep drying of the conveyor belt. Summary of the Invention

[0005] In order to solve the above-mentioned problems existing in the prior art, a conveyor return belt cleaning device is provided. This invention provides a conveyor return belt cleaning device that improves the overall cleaning efficiency of sticky coal.

[0006] The technical solution of the present invention is as follows: A conveyor return belt cleaning device includes a frame, a softening and crushing structure and a material collection and recovery assembly arranged on the frame along the running direction of the return belt; the softening and crushing structure includes a microwave softening assembly and a pneumatic stripping assembly; the microwave softening assembly includes at least one magnetron and a microwave resonant cavity spanning the width direction of the return belt, the lower wall and surrounding side walls of the microwave resonant cavity are metal shielding layers, the upper wall of the microwave resonant cavity is made of microwave transmitting material, and a gap is maintained between the upper wall and the surface of the return belt; the magnetron is fixedly connected to the outside of the metal shielding layer of the microwave resonant cavity through a waveguide, and the microwave emission port of the magnetron leads to the interior of the microwave resonant cavity.

[0007] The pneumatic stripping assembly includes a pulsed pneumatic cavity located sequentially at the top of the microwave resonant cavity. The pulsed pneumatic cavity is made of microwave-transmitting material, and the top of the pulsed pneumatic cavity is a jet plate with several Venturi holes through the surface of the jet plate. The pulsed pneumatic cavity is connected to a compressed air source through an air path, and a pulsed solenoid valve is provided on the air path to provide pulsed airflow to the pulsed pneumatic distribution cavity.

[0008] The Venturi holes on the jet plate are arranged at an acute angle to the vertical direction for air outlet. A collection groove is provided on the surface of the jet plate, and the bottom of the collection groove is connected to the inlet of at least one material collection component. The material collection component is located on the side of the jet plate and the pulse pneumatic chamber. The material collection component includes a Venturi tube, the inlet of which is connected to the pulse pneumatic chamber for diverting part of the pulse airflow, and the throat section of which has a suction port connected to the bottom of the collection groove. The outlet of the diffuser section of the Venturi tube is connected to the material collection and recovery component via a conveying pipe.

[0009] The jet plate is divided into an airflow injection zone and a vibration transmission zone along the running direction of the return belt. The airflow injection zone is the area of ​​the Venturi holes. An acoustic resonant cavity is provided inside the jet plate corresponding to the vibration transmission zone. The acoustic resonant cavity is connected to the pulse pneumatic cavity through at least one sound inlet hole. Multiple acoustic vibration protrusions are provided on the surface of the jet plate corresponding to the vibration transmission zone. The acoustic vibration protrusions are provided with sound wave channels connected to the acoustic resonant cavity. An inclined acoustic reflection surface is provided on the side of the acoustic vibration protrusion. The reflection surface is used to reflect and converge the sound waves transmitted through the sound wave channels to the surface of the return belt. The top of the acoustic vibration protrusion is a closed vibration transmission end face.

[0010] The material collection and recovery assembly includes a main recovery box, a return air pipeline, and an ejector. The main recovery box is divided into a settling chamber and a negative pressure collection chamber by a perforated partition. The diffuser outlet of the venturi tube is connected to the settling chamber of the main recovery box. One end of the return air pipeline is connected to the negative pressure collection chamber of the main recovery box, and the other end extends downstream of the vibration transmission zone of the jet plate, and is provided with an airflow outlet facing the surface of the return belt. The ejector is located on the return air pipeline, and the compressed air source of the pulse pneumatic chamber provides driving airflow to the inlet of the ejector through a branch. A gas outlet is provided on the top of the main recovery box.

[0011] The acoustic vibration protrusion is a solid structure made of a material with high stiffness and low sound loss.

[0012] The outlet plane of the venturi hole in the airflow injection zone maintains a first working distance from the lower surface of the return belt, and the surface of the jet plate maintains a second working distance from the lower surface of the return belt, wherein the second working distance is smaller than the first working distance.

[0013] The softening and crushing structure is mounted on the frame via an electric push rod, and the distance between its working surface and the return belt surface can be adjusted by the electric push rod.

[0014] The system also includes an air path switching module, which comprises a valve body located on the air path between the compressed air source and the air inlet of the pulse pneumatic chamber. A pressure-stabilizing airflow channel and a pulse airflow channel are connected in parallel through the valve body. The pulse solenoid valve is connected in series on the pulse airflow channel. A normally open solenoid valve and a pressure-stabilizing chamber are connected in series along the airflow direction on the pressure-stabilizing airflow channel. A porous medium plate is fixedly installed in the pressure-stabilizing chamber. A manifold is provided in the valve body, and the downstream ends of the pulse airflow channel and the pressure-stabilizing airflow channel converge into the manifold. An output interface communicating with the manifold is provided on the valve body, and the output interface is connected to the air inlet of the pulse pneumatic chamber through a pipeline.

[0015] The present invention has the following beneficial effects: This invention improves the overall removal efficiency of coal with complex physical states by constructing a multi-level combination of microwave pretreatment, pulsed pneumatics, and acoustic vibration, and adopting matching removal strategies for different adhesion states of coal from internal structure to surface interface.

[0016] This invention uses high-pressure pulsed airflow controlled by a pulsed solenoid valve as the main stripping method, which realizes non-contact removal of sticky coal after microwave softening, reducing wear on the conveyor belt body; at the same time, its transient impact characteristics can more effectively separate the brittle sticky coal lumps from the return belt surface compared with stable airflow.

[0017] This invention utilizes an acoustic protrusion with an integrated acoustic resonant cavity to combine sound wave focusing with high-frequency micro-vibration, specifically targeting stubborn interface residue layers that are difficult to remove with pulsed airflow, thus achieving deep cleaning of the belt surface. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a partial half-sectional view of the pulse pneumatic cavity and jet plate of the present invention; Figure 3 This is a schematic diagram of the gas path switching module of the present invention.

[0019] The reference numerals in the figure are as follows: 1. Frame; 2. Return belt; 5. Electric push rod; 6. Microwave resonant cavity; 7. Magnetron; 8. Pulse pneumatic cavity; 9. Jet plate; 10. Collection groove; 11. Venturi tube; 12. Suction port; 13. Acoustic resonant cavity; 14. Sound inlet; 15. Acoustic vibration protrusion; 16. Main recovery box; 17. Return air pipeline; 18. Settling chamber; 19. Negative pressure collection chamber; 20. Valve body; 21. Pulse solenoid valve; 22. Normally open solenoid valve; 23. Pressure stabilizing chamber; 24. Porous dielectric plate; 25. Manifold; 26. Output interface. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] Please see Figures 1 to 3 The invention provides a technical solution: Example 1: The conveyor return belt cleaning device of this embodiment includes a frame 1, a softening and crushing structure and a material collection and recycling component arranged on the frame 1 along the running direction of the return belt 2.

[0022] The primary component in softening the fracture structure is the microwave softening assembly, which includes at least one magnetron 7 and a microwave resonant cavity 6 spanning the width of the return belt 2. The lower wall and surrounding side walls of the microwave resonant cavity 6 are made of metal plates (such as aluminum or stainless steel) to form an electromagnetic shielding layer, which confines microwave energy to ensure operational safety and concentrates the energy inside the cavity.

[0023] The upper wall of the resonant cavity 6 is made of a microwave-transmitting material (such as special ceramics or high-temperature resistant polymers), which allows microwave energy to penetrate efficiently while also providing some heat insulation and sealing. A gap is maintained between the upper wall and the lower surface of the running return belt 2, which is sufficient to allow microwave energy to be concentrated on the adhering material on the surface of the return belt 2.

[0024] The magnetron 7 serves as a microwave source and is fixedly connected to the outside of the metal shielding layer of the microwave resonant cavity 6 via a waveguide. The microwave emission port of the magnetron 7 is precisely aligned with the waveguide and leads to the interior of the microwave resonant cavity 6, thereby feeding the generated microwaves into the microwave resonant cavity 6.

[0025] Microwaves were chosen as a pretreatment method primarily because of their unique heating mechanism. Microwaves can penetrate materials and are selectively absorbed by residual water molecules and some organic matter in sticky coal, causing high-speed molecular friction and generating heat. This method allows the coal slime, especially the internally wet or hardened parts, to heat up as a whole in a short time. The rapid vaporization of internal moisture generates steam pressure, while the uneven thermal expansion of different components generates thermal stress. These two effects work synergistically to create a large number of microcracks inside the sticky coal, significantly reducing its overall structural strength and making the sticky coal loose and brittle.

[0026] The pneumatic stripping assembly includes a pulse pneumatic cavity 8 at the top of the microwave resonant cavity 6 or a pulse pneumatic cavity 8 disposed behind the microwave resonant cavity 6 along the running direction of the return belt 2. The pulse pneumatic cavity 8 is made of microwave-transmitting material, and the top of the pulse pneumatic cavity 8 is a jet plate 9. Several venturi holes are provided through the surface of the jet plate 9. The pulse pneumatic cavity 8 is connected to a compressed air source through an air passage, and a pulse solenoid valve 21 is provided on the air passage to provide pulse airflow to the pulse pneumatic cavity 8.

[0027] Specifically, if the pulsed pneumatic cavity 8 is adopted as an embodiment that is tightly attached to and fixed on the upper wall of the microwave transmission of the microwave resonant cavity 6, its own cavity is preferably made of a material with extremely low microwave interference, so as to ensure that the microwave energy does not produce significant attenuation or reflection when it penetrates.

[0028] The jet plate 9 mounted on top of the pulse pneumatic chamber 8 is usually made of metal or high-strength composite material and has an array of Venturi holes. When the airflow passes through the contraction section of the Venturi holes, it is accelerated and reaches the highest speed and lowest pressure at the throat. Subsequently, the speed decreases and the pressure partially recovers in the expansion section. This can transform the input ordinary airflow into a more concentrated, higher speed air jet with a local low-pressure effect.

[0029] The pulse pneumatic chamber 8 is connected to an external compressed air source through an air passage, and a high-frequency pulse solenoid valve 21 is connected in series in this air passage. By quickly controlling the on and off of the pulse solenoid valve 21, continuous and stable compressed air can be converted into intermittent high-pressure pulse airflow and supplied to the pulse pneumatic chamber 8.

[0030] Pulsed airflow is a non-contact operation method that fundamentally avoids the wear caused by mechanical scraping on the conveyor belt surface. Furthermore, compared to continuous and stable ordinary air blowing, the core advantage of pulsed airflow lies in its instantaneous high-power characteristics. The pulse valve releases stored energy instantaneously at high flow rates. This transient impact load generates peeling stress on the material that is far greater than that of a stable airflow with the same average volume, especially for agglomerated materials with a certain degree of cohesion, where its breaking efficiency is even higher.

[0031] Microwave treatment causes numerous micro-cracks to form inside the sticky coal due to moisture vaporization and thermal stress, resulting in a loose overall structure and a significant decrease in cohesion. The high-pressure pulsed airflow that follows not only allows the high-speed airflow to penetrate into the micro-cracks on the coal slime caused by microwaves, but also causes the airflow to expand and pressurize within the cracks, generating peeling stress, which in turn tears the sticky coal from these weak internal surfaces.

[0032] Furthermore, several Venturi holes are provided through the surface of the jet plate 9, and the direction of the air outlet is at an acute angle to the return belt 2. This tilt angle allows the pulsed airflow to sweep and collect towards the collection groove 10 opened on the surface of the jet plate 9 while stripping away the sticky coal with impact force.

[0033] The collecting groove 10 is typically an elongated recess extending along the width of the return belt 2, with a slope at the bottom to guide the material flow to at least one centralized outlet, which is in sealed communication with the inlet of a material collecting assembly.

[0034] The material collection assembly is located on the side of the pulse pneumatic chamber 8, and it is a venturi tube 11. The inlet of the constriction section of the venturi tube 11 is connected to the pulse pneumatic chamber 8, thereby diverting a portion of the high-pressure pulse airflow as its working power source.

[0035] When the diverted pulsed airflow enters the throat at high speed through the contraction section of the Venturi tube 11, the flow velocity reaches its peak, causing the static pressure in the throat region to be significantly lower than atmospheric pressure, forming a localized strong negative pressure zone. The suction port 12, opened on the wall of this throat section, is directly connected to the bottom of the collecting groove 10 via a pipe. Because the pressure at the suction port 12 is much higher than that in the negative pressure zone of the throat, under the action of the pressure difference, the coal slurry collected in the collecting groove 10 is drawn into the throat of the Venturi tube 11.

[0036] Subsequently, the inhaled material immediately mixes with the high-speed mainstream airflow and enters the diffuser section. In the diffuser section, the airflow velocity decreases, and some of the kinetic energy is converted into pressure energy, giving this gas-solid mixture sufficient conveying power. Finally, it is reliably blown through the conveying pipe connected to the outlet of the diffuser section to the collection and recovery assembly, which is far away from the clean working area.

[0037] The physicochemical state of the adhesion interface between the sticky coal and the rubber substrate of the return conveyor belt 2 often differs from that of the sticky coal itself. The interface may have less moisture, or contain an oily medium, or even form a tight adsorption structure dominated by intermolecular forces. The microwave energy is mainly absorbed by the moisture inside the coal slime, resulting in a relatively indirect and limited heating and weakening effect on the interface.

[0038] Therefore, when the pulsed airflow faces this tightly fitted interface layer, it is difficult to effectively wedge in and scoop it up as a whole, leaving behind a stubborn bottom layer.

[0039] The jet plate 9 is divided into an upstream airflow injection zone and a downstream vibration transmission zone along the belt running direction. The upstream zone is the Venturi aperture array, while in the downstream vibration transmission zone, an acoustic resonant cavity 13 is machined inside the jet plate 9 substrate. This cavity is connected to the pulsed pneumatic cavity 8 above through one or more sound inlets 14. In this way, the periodic pressure fluctuations generated when the pulsed airflow is working can be transmitted into this cavity, exciting the air inside to produce acoustic resonance at a specific frequency, thereby converting the fluctuation energy of the airflow into strong sound waves of a specific frequency.

[0040] On the upper surface of this area, multiple acoustic vibration protrusions 15 are arranged in an array. Each acoustic vibration protrusion 15 has a tiny acoustic wave channel inside that is connected to the resonant cavity 13 below. Its top is a closed vibration transmission end face, and its side is machined into an inclined parabolic acoustic reflection surface.

[0041] The sound waves transmitted through the sound wave channel are reflected and converged when they propagate inside the sound vibration protrusion 15 to the inclined reflective surface, thus directing the sound wave energy onto the belt surface above.

[0042] Simultaneously, the strong sound wave drives the acoustic vibration protrusion 15 to generate micro-vibration, which is transmitted through its closed top. The outlet plane of the Venturi hole on the airflow injection zone maintains a first working distance with the lower surface of the return belt 2, and the surface of the jet plate 9 maintains a second working distance with the lower surface of the return belt 2. The second working distance is smaller than the first working distance. The first working distance ensures that the pulse airflow can obtain enough space to fully develop after being ejected, thereby effectively impacting the sticky coal and smoothly blowing the stripped coal slime to the downstream collection groove 10, avoiding the coal slime from rebounding or stagnating in the narrow space.

[0043] The purpose of the second working spacing is to shorten the transmission path of vibration and sound wave energy.

[0044] High-frequency vibrations and sound waves attenuate significantly when propagating in the air. A small working gap can reduce energy loss and ensure that the high-frequency micro-amplitude vibration energy generated by the acoustic vibration protrusion 15 itself, as well as the sound wave energy converged by its side reflection surface, can pass through the air gap with higher efficiency and act on the surface of the return belt 2.

[0045] Specifically, the vibration of the acoustic vibration protrusion 15 establishes a local high-frequency shear force field near the lower surface of the return belt 2 through this second working gap. On the one hand, the vibration is transmitted through the air medium in the air gap, applying shear stress to the residual interface thin layer; on the other hand, under the working pressure of the device, the tip of the acoustic vibration protrusion 15 may make intermittent elastic contact with the return belt 2, thereby transmitting the vibration shear force more directly to the interface between the residue and the return belt 2.

[0046] Microwaves, pulses, and sound waves form an increasingly efficient and complementary operational chain. Microwaves disintegrate the overall structural strength of the sticky coal from the inside, creating the conditions for stripping. Pulsed airflow uses macroscopic kinetic energy to efficiently remove the disintegrated material body, completing most of the cleaning work. Sound waves use their cavitation effect and high-frequency vibration shearing to specifically destroy and remove the interface bonding layer that the former two cannot reach.

[0047] As a preferred embodiment, at least one cavity wall of the acoustic resonant cavity 13 is formed by a flexible resonant diaphragm; and the opening of the sound inlet 14 is disposed directly opposite to or adjacent to the flexible resonant diaphragm. When a high-pressure pulsed airflow is generated in the pulsed pneumatic cavity 8, the airflow impacts the flexible resonant diaphragm through the sound inlet 14, causing it to bulge into the acoustic resonant cavity 13, resulting in an instantaneous decrease in the effective volume of the cavity and an increase in the resonant frequency; when the pulsed airflow is intermittent or the pressure decreases, the flexible resonant diaphragm rebounds or resets under its own elasticity or the pressure difference between the inside and outside of the cavity, resulting in an increase in the effective volume of the acoustic resonant cavity 13 and a decrease in the resonant frequency; When facing thick layers of caking coal, the system activates high-intensity, high-duty-cycle pulses. At this time, the flexible resonant diaphragm is continuously subjected to strong pressure, which stabilizes the acoustic resonant cavity 13 at a higher resonant frequency. This high-frequency sound wave, after being reflected and converged by the acoustic protrusion 15, has a shorter wavelength and stronger directivity.

[0048] When faced with thin layers, loose coal residue, or interface residue, the intensity or duty cycle of the pulsed airflow decreases, the force on the flexible resonant diaphragm decreases, the degree of reset increases, and the resonant frequency of the acoustic resonant cavity 13 decreases accordingly. This low-frequency sound wave has a longer wavelength and a wider diffusion angle, which can better cover a larger area and peel off the loose thin layer as a whole.

[0049] The aggregate recovery assembly includes a main recovery box 16, a return air pipeline 17, and an ejector. The main recovery box 16 is divided into a settling chamber 18 and a negative pressure collection chamber 19 by a perforated partition. The diffuser outlet of the venturi tube 11 is connected to the settling chamber 18 of the main recovery box 16. One end of the return air pipeline 17 is connected to the negative pressure collection chamber 19 of the main recovery box 16, and the other end extends to the downstream of the vibration transmission zone of the jet plate 9, and is provided with an airflow outlet facing the surface of the return belt 2. The ejector is installed on the return air pipeline 17, and the compressed air source of the pulse pneumatic chamber 8 provides driving airflow to the ejector inlet through a branch. A gas outlet is provided on the top of the main recovery box 16.

[0050] The driving airflow from the compressed air source of the pulse pneumatic chamber 8 enters the ejector set on the return air line 17, and a stable negative pressure is generated at the suction end of the ejector (i.e. the suction port of the return air line 17 extending downstream of the vibration transmission area). This negative pressure will draw the fine interface residues that have been treated by sound waves and detached from the surface of the belt in a dispersed state into the return air line 17 along with the air. Meanwhile, the Venturi tube 11, which draws in the mixture of coal slime and air that has been stripped by the pulsed airflow, transports it to the settling chamber 18 of the main recovery box 16. In the settling chamber 18, coarse coal slime particles settle rapidly due to gravity and deceleration. The gas, initially purified in the settling chamber 18, flows into the adjacent negative pressure collection chamber 19 through the perforated partition. At this point, the airflow carrying fine residue gains kinetic energy in the ejector and is also blown into the negative pressure collection chamber 19, mixing with the gas from the settling chamber 18. The velocity of the mixed airflow is further reduced in the larger space of the negative pressure collection chamber 19, allowing the fine particles to settle again. Finally, the relatively clean gas, having completed gas-solid separation, is orderly discharged from the system through the gas outlet at the top of the main recovery box 16 under the drive of a slight positive pressure within the system.

[0051] The acoustic vibration protrusion 15 is a solid structure made of a material with high stiffness and low sound loss.

[0052] The softening crushing structure is mounted on the frame 1 via an electric push rod 5, and the distance between its working surface and the surface of the return belt 2 can be adjusted by the electric push rod 5.

[0053] To ensure the cleaning device can flexibly respond to the operational needs of different adhesion states and cleaning stages, this embodiment also includes an integrated air path switching module. This module includes a valve body 20, located on the pipeline between the compressed air source and the air inlet of the pulse pneumatic chamber 8. A pressure-stabilizing airflow channel and a pulse airflow channel are connected in parallel within the valve body 20. The downstream ends of both channels converge into the same confluence chamber 25, and then flow to the pulse pneumatic chamber 8 via an output interface 26. A pulse solenoid valve 21 is connected in series in the pulse airflow channel to generate a high-frequency pulse airflow; a normally open solenoid valve 22 and a pressure-stabilizing chamber 23 with a built-in porous media plate 24 are connected in series in the pressure-stabilizing airflow channel to provide a stable, uniform, and continuous airflow.

[0054] By controlling the opening and closing of two solenoid valves, this module allows the device to switch between pulse impact and continuous air curtain operating modes. When dealing with sticky coal that is still relatively hardened after microwave softening, the pulse mode is activated, using transient high-pressure airflow for crushing and stripping; while during the intervals between pulse operations, or when processing loosened sticky coal, the device switches to continuous air curtain mode. The continuous air curtain maintains the blowing of the conveyor belt surface, preventing the stripped material from re-adhering before falling, and uses its uniform airflow to guide the material to the collection groove 10. The built-in porous media plate 24 effectively balances the airflow in the pressure stabilizing chamber 23, eliminates eddies, and ensures that the ejected continuous air curtain is stable and uniform.

[0055] Example 2: The improvement of this embodiment is that a micro cavitation cavity is machined on the closed end face of at least one acoustic vibration protrusion 15. This micro cavitation cavity is connected in parallel with the main acoustic wave channel inside the acoustic vibration protrusion 15 through a capillary channel, thereby connecting to the acoustic resonant cavity 13.

[0056] Parabolic reflectors concentrate sound wave energy delivery, while micro cavitation cavities, when liquid is present inside the coal slime, can resonate with sound waves of a specific frequency due to their specific geometric dimensions, thereby highly localizing and amplifying the sound energy and providing conditions for generating cavitation effects.

[0057] The specific geometric dimensions are not arbitrary values, but rather precise acoustic structural parameters required for the micro cavitation cavity to resonate with the introduced sound waves. Firstly, during the design phase, the geometric dimensions of the micro cavitation cavity (e.g., the diameter-to-depth ratio of a cylindrical cavity) are not arbitrarily chosen, but optimized through theoretical calculations and experimental verification, targeting the typical acoustic parameters of the most common liquid state in the target coal slime (usually considered a water-based medium). The velocity of sound in water varies relatively little within a certain temperature and common impurity range, providing a basis for determining a central design frequency. Secondly, a well-designed cavitation cavity itself possesses a certain resonant bandwidth, rather than a single resonant peak. By optimizing the cavity shape (e.g., using a specific streamlined or composite shape), it can produce a strong sound field enhancement effect over a relatively wide frequency range, thus providing some tolerance to small changes in the medium's sound velocity. Furthermore, from a system adaptability perspective, it can endow the sound wave generating device (i.e., the excitation source of the acoustic resonant cavity) with a certain frequency adjustment capability. For example, by changing the frequency of the pulsed airflow or using a frequency-adjustable acoustic generator, the frequency of the acoustic wave output by the system can be adjusted within a small range to actively match the optimal resonance point corresponding to the coal slime liquid medium under different working conditions, thereby ensuring that the cavitation effect can be effectively excited under different coal slime conditions.

[0058] Specifically, upon system startup, the microwave softening component operates first. This differs from the rapid vaporization of internal moisture by high-temperature microwaves in Example 1, which generates steam pressure. While microwaves can penetrate materials, due to the high dielectric loss of water, its energy is preferentially absorbed by the extremely thin water film that may exist at the interface between the sticky coal and the conveyor belt. This water film is rapidly heated to a high temperature (e.g., 60-90°C), resulting in a decrease in viscosity, a reduction in surface tension, and an increase in internal vapor pressure.

[0059] The physical principle of cavitation is that when strong sound waves act on a liquid, the periodic pressure changes cause the liquid to be torn apart and generate tiny bubbles at negative pressure. Then, at positive pressure, the bubbles are rapidly compressed and imploded, releasing micro-jet streams with extremely strong impact force.

[0060] In this scheme, the physical properties of residual moisture at the interior and interface of the sticky coal after microwave preheating have changed, resulting in reduced viscosity and increased fluidity, making it easier to generate cavitation bubbles under the action of a sound field. If only the sound waves radiated by the parabolic reflector are relied upon, the energy is not concentrated enough at the open interface, making it difficult to reliably excite a cavitation effect of sufficient intensity to destroy the stubborn interface layer.

[0061] When a pulsed airflow flows at high speed through the opening of a micro cavitation cavity, its intense pressure pulsations interact with the acoustic pressure field within the cavity. Specifically, the negative pressure phase of the pulsed airflow assists the sound waves in pulling the liquid to generate more bubble nuclei, while its positive pressure phase enhances the compression of the bubbles by the sound waves, thereby synergistically modulating and amplifying the intensity of cavitation bubble collapse.

[0062] At the same time, after the pulsed airflow combines with the microscopic destruction interface of the cavitation effect, it immediately blows away the loosened residue and prevents it from re-attaching, thus achieving a seamless connection between destruction and removal.

[0063] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A conveyor return belt cleaning device, characterized in that: The assembly includes a frame (1), a softening crushing structure and a material collection and recovery assembly arranged on the frame (1) along the running direction of the return belt (2); the softening crushing structure includes a microwave softening assembly, a pneumatic stripping assembly and an acoustic assembly, the pneumatic stripping assembly includes a pulse pneumatic cavity (8) arranged on the top of the microwave resonant cavity (6), the top of the pulse pneumatic cavity (8) is a jet plate (9), and the surface of the jet plate (9) is provided with a number of venturi holes to transport pulse airflow, the acoustic assembly includes an acoustic resonant cavity (13) arranged inside the jet plate (9), the acoustic resonant cavity (13) is connected to the pulse pneumatic cavity (8), and a micro cavitation cavity is provided at the end of the pulse pneumatic cavity (8), the micro cavitation cavity is connected to the acoustic resonant cavity (13) through a capillary channel.

2. The conveyor return belt cleaning device as described in claim 1, characterized in that: The jet plate (9) is divided into an airflow injection zone and a vibration transmission zone along the running direction of the return belt (2). The airflow injection zone is the area of ​​the Venturi holes. An acoustic resonant cavity (13) is set in the vibration transmission zone of the jet plate (9). The acoustic resonant cavity (13) is connected to the pulse pneumatic cavity (8) through at least one sound inlet hole (14). A plurality of acoustic vibration protrusions (15) are provided on the surface of the jet plate (9) located in the vibration transmission zone. The acoustic vibration protrusion (15) has a sound wave channel connected to the acoustic resonant cavity (13) inside. An inclined acoustic reflection surface is provided on the side of the acoustic vibration protrusion (15). The reflection surface is used to reflect and converge the sound waves transmitted through the sound wave channel to the surface of the return belt (2). The top of the acoustic vibration protrusion (15) is a closed vibration transmission end face. A micro cavitation cavity is set on the closed vibration transmission end face at the top of the acoustic vibration protrusion (15).

3. The conveyor return belt cleaning device as described in claim 2, characterized in that: The softening and breaking structure includes a microwave softening component and a pneumatic stripping component; the microwave softening component includes at least one magnetron (7) and a microwave resonant cavity (6) spanning the width direction of the return belt (2). The lower wall and the surrounding side walls of the microwave resonant cavity (6) are metal shielding layers, and the upper wall of the microwave resonant cavity (6) is made of microwave transmitting material; the magnetron (7) is fixedly connected to the outside of the metal shielding layer of the microwave resonant cavity (6) through a waveguide, and the microwave emission port of the magnetron (7) leads to the interior of the microwave resonant cavity (6).

4. The conveyor return belt cleaning device as described in claim 3, characterized in that: The pulse pneumatic cavity (8) is made of microwave-transmitting material, and the pulse pneumatic cavity (8) is connected to a compressed air source through an air path, and a pulse solenoid valve (21) is provided on the air path to provide pulse airflow to the pulse pneumatic distribution cavity.

5. The conveyor return belt cleaning device as described in claim 3, characterized in that: The surface of the jet plate (9) is provided with a collection groove (10), the bottom of which is connected to the inlet of at least one material collection component; the material collection component is disposed on the side of the jet plate (9) and the pulse pneumatic chamber (8), the material collection component includes a venturi tube (11), the inlet of the constriction section of the venturi tube (11) is connected to the pulse pneumatic chamber (8) for diverting part of the pulse airflow, the throat section of the venturi tube (11) is provided with a suction port (12), the suction port (12) is connected to the bottom of the collection groove (10); the outlet of the diffuser section of the venturi tube (11) is connected to the material collection and recovery component through a conveying pipe.

6. The conveyor return belt cleaning device as described in claim 5, characterized in that: The aggregate recovery assembly includes a main recovery box (16), a return air pipeline (17), and an ejector. The main recovery box (16) is divided into a settling chamber (18) and a negative pressure collection chamber (19) by a perforated partition. The outlet of the diffuser section of the venturi tube (11) is connected to the settling chamber (18) of the main recovery box (16). One end of the return air pipeline (17) is connected to the negative pressure collection chamber (19) of the main recovery box (16), and the other end extends to the downstream of the vibration transmission zone of the jet plate (9), and is provided with an airflow outlet facing the surface of the return belt (2). The ejector is set on the return air pipeline (17), and the compressed air source of the pulse pneumatic chamber (8) provides driving airflow to the inlet of the ejector through a branch. A gas outlet is opened on the top of the main recovery box (16).

7. The conveyor return belt cleaning device as described in claim 2, characterized in that: The acoustic vibration protrusion (15) is a solid structure made of a high-rigidity, low-sound-loss material. The outlet plane of the Venturi hole on the airflow jet zone maintains a first working distance from the lower surface of the return belt (2), and the surface of the jet plate (9) maintains a second working distance from the lower surface of the return belt (2), the second working distance being smaller than the first working distance.

8. The conveyor return belt cleaning device as described in claim 1, characterized in that: The softening crushing structure is mounted on the frame (1) by an electric push rod (5), and the distance between its working surface and the surface of the return belt (2) can be adjusted by the electric push rod (5).

9. A conveyor return belt cleaning device as described in claim 6, characterized in that: It also includes an air path switching module, which includes a valve body (20) located on the air path between the compressed air source and the air inlet of the pulse pneumatic chamber (8). A pressure-stabilizing airflow channel and a pulse airflow channel are connected in parallel through the valve body (20). The pulse solenoid valve (21) is installed in series on the pulse airflow channel. A normally open solenoid valve (22) and a pressure-stabilizing chamber (23) are installed in series along the airflow direction on the pressure-stabilizing airflow channel. A porous medium plate (24) is fixedly installed in the pressure-stabilizing chamber (23). A manifold (25) is provided in the valve body (20). The downstream ends of the pulse airflow channel and the pressure-stabilizing airflow channel converge into the manifold (25). An output interface (26) connected to the manifold (25) is provided on the valve body (20). The output interface (26) is connected to the air inlet of the pulse pneumatic chamber (8) through a pipeline.

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