A dust vortex compression blocking function explosion-proof fan system for air route transportation

Abstract

The application relates to the technical field of gas path dust conveying explosion-proof equipment, and discloses a dust vortex compression block forming function air path transportation explosion-proof fan system which comprises an explosion-proof fan body, a vortex compression block forming mechanism and an explosion-proof control unit; the system utilizes the centrifugal force of the fan to guide dust-containing airflow into a tapered vortex passage, and through spiral pressurization and closing compression, the dust is pressed into dense blocks, and the dust is actively separated from the air path; in cooperation with a two-point concentration sensor, a staged linkage inert gas inerting system, a multiple passive protection of a flame-proof baffle, a fire-retardant flame-proof net and a pressure relief valve, a three-stage explosion-proof system of 'active dust reduction-precise inerting-passive explosion isolation' is constructed; the application eliminates the dust explosion hidden danger from the source, the dust is formed into blocks without secondary dust raising, the explosion-proof safety and dust treatment efficiency are remarkably improved, and the application is suitable for various combustible dust air path transportation scenes.

Description

Technical Field

[0001] This invention belongs to the technical field of explosion-proof equipment for gas-borne dust conveying, specifically an explosion-proof fan system for gas-borne transportation with the function of dust vortex compression into blocks. Background Technology

[0002] In pneumatic conveying systems for powder materials, explosion-proof fans are the core power equipment, but there are two major safety hazards during their operation: First, combustible dust is easily deposited on the impeller and inner wall of the casing of the fan. After long-term accumulation, a thick dust layer is formed, which can cause a dust explosion when it encounters friction sparks or static electricity; Second, the dust concentration in the conveying airflow fluctuates greatly. When the concentration is in the explosive limit range, even a very small ignition energy can trigger an explosion.

[0003] In existing technologies, conventional explosion-proof fans only achieve passive protection through explosion-proof housings and inlet / outlet flame arresters, which cannot actively eliminate dust accumulation and excessive concentration problems, resulting in low inherent safety. Some supporting dust removal equipment solutions have obvious defects: bag filter cartridges are prone to clogging, requiring frequent shutdowns for replacement, making them unsuitable for continuous production scenarios, and the dust removal process is prone to generating secondary dust; ordinary cyclone dust collectors can only achieve gas-solid separation, and the collected dust is still loose powder, which is easily re-entrained by the airflow. The dust removal efficiency decreases with increasing concentration, and it is not linked with the explosion-proof system, so the improvement of explosion-proof performance is limited.

[0004] In addition, existing inert gas explosion-proof systems are mostly single-point concentration detection and on / off control, which cannot dynamically adjust the amount of inert gas according to the concentration distribution in different areas of the fan. This results in problems such as response lag, nitrogen waste, and local concentration exceeding the standard. Furthermore, there is a lack of special explosion-proof design for the dust collection process, and the collected loose dust itself is a major safety hazard.

[0005] To date, no fan system in the industry has deeply integrated eddy current compression technology with multiple explosion-proof systems, and it is impossible to achieve the full-chain explosion-proof of "active dust reduction and solidification - precise inerting protection - passive explosion-proof pressure relief" at the same time. There is a clear technological gap and market demand. Summary of the Invention

[0006] The purpose of this invention is to provide an explosion-proof fan system for air transport with a dust vortex compression and block formation function, in order to solve the problems mentioned in the background art of existing explosion-proof fans, such as passive protection, large dust accumulation hazards, low dust treatment efficiency, and poor explosion-proof specificity. By actively solidifying dust through vortex compression and block formation, combined with graded linkage explosion-proof control and multiple passive explosion-proof structures, it achieves all-dimensional explosion-proof safety and efficient dust treatment.

[0007] To achieve the above objectives, the present invention provides the following technical solution: an explosion-proof fan system for air transport with dust vortex compression and agglomeration function, comprising an explosion-proof fan body, a vortex compression and agglomeration mechanism, and an explosion-proof control unit;

[0008] The explosion-proof fan body includes an explosion-proof fan casing, a drive motor, a centrifugal impeller, an air inlet, and an air outlet, providing power for air delivery;

[0009] The eddy current compression and agglomeration mechanism includes an eddy current compression chamber, a gradually narrowing eddy current channel, a guide air inlet, an explosion-proof guide plate, an agglomeration discharge channel, and an explosion-proof agglomeration mechanism, which are used to achieve centrifugal separation, agglomeration and compression into agglomerates, and sealed discharge of dust.

[0010] The explosion-proof control unit includes a first dust concentration sensor, a second dust concentration sensor, an inert gas storage tank, a solenoid valve, a gas supply nozzle, and a controller, used to realize concentration monitoring, graded inerting, and linked material discharge.

[0011] Furthermore, the outlet is equipped with a flame-arresting and explosion-proof mesh to prevent the flame from spreading to the outlet pipe; the inner wall of the vortex compression chamber and the surface of the tapering vortex channel are equipped with a wear-resistant lining to extend the service life of the equipment; the inlet is equipped with a flow guide vane to optimize the airflow field and improve centrifugal separation efficiency; and the top of the explosion-proof fan casing is equipped with a pressure sensor and a pressure relief valve to realize overpressure monitoring and emergency pressure relief.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] (1) Active dust reduction and solidification to eliminate the hidden danger of dust explosion from the source. This invention utilizes the centrifugal force of the impeller of the fan itself to introduce the high-concentration dust-laden airflow into the vortex compression block mechanism through the flow guide structure. The centrifugal separation and compression of dust can be achieved without additional power, actively solidifying and separating the dust from the air path, greatly reducing the dust concentration in the main air path, reducing dust deposition on the impeller and the inner wall of the casing, eliminating the material basis for dust explosion from the source, and significantly improving the intrinsic safety, which is different from the traditional passive explosion protection technical approach.

[0014] (2) The dust is compacted into blocks, completely eliminating the risk of secondary dust generation. Through the spiral pressurization and compression structure of the gradually narrowing vortex channel, the loose dust can be squeezed into a dense block. The dust block has high density and strength and will not be blown away by the airflow again. There is no secondary dust generation during the transportation, transfer and subsequent processing. This not only avoids dust backflow and reduces dust removal efficiency, but also eliminates the explosion hazard in the dust collection and transfer process. At the same time, it greatly reduces the volume of waste and reduces the treatment cost.

[0015] (3) Dual-point hierarchical joint control to achieve precise and efficient active inerting. The dust concentration detection is set at two points: the air inlet and the vortex cavity. The linear adjustment strategy of three-level concentration threshold can dynamically adjust the amount of inert gas replenishment according to different areas and different concentration levels. It can operate in energy-saving mode at low concentration, accurately inerting at medium concentration, and quickly protecting at high concentration. It not only ensures explosion-proof safety, but also greatly reduces the consumption of inert gas, improving the economic efficiency of operation by more than 40%. At the same time, it links the rotation speed of the discharge mechanism to maintain the stability of the vortex cavity concentration, realizing explosion-proof control under all working conditions.

[0016] (4) Multiple passive explosion-proof measures to build a full-dimensional explosion-proof system. In addition to active dust reduction and inerting protection, it integrates a triple passive explosion-proof structure of explosion-proof guide plate, flame-arresting explosion-proof net and pilot-operated pressure relief valve: explosion-proof guide plate realizes one-way explosion-proof between eddy cavity and main cavity, blocking flame spread; flame-arresting explosion-proof net blocks flame propagation in inlet and outlet pipelines; pressure relief valve realizes rapid overpressure relief; the three work together to form a full-dimensional passive protection system of "cavity isolation-pipeline blocking-pressure relief", so that even if an accidental explosion occurs, the impact can be controlled to the minimum range and the accident can be avoided from escalating.

[0017] (5) Integrated design, strong adaptability and low operation and maintenance cost. The vortex compression block mechanism is integrated into the side wall of the fan casing. The overall structure is compact and does not require additional installation space. It can directly replace the traditional explosion-proof fan and connect to the existing air conveying system. The modification and adaptation cost is low. The system has no filter elements or other vulnerable parts. The core components use wear-resistant ceramic lining, which has a long service life and long operation and maintenance cycle. Daily maintenance only requires periodic inspection of lining wear and material level in the collection hopper. The workload and cost of operation and maintenance are greatly reduced. Moreover, there is no need to stop the machine for dust removal, which can ensure the continuity of production. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0019] In the attached diagram:

[0020] Figure 1 This is a block diagram of the system air path structure of the present invention;

[0021] Figure 2 This is a block diagram illustrating the explosion-proof control principle of the present invention;

[0022] In the diagram: 1. Explosion-proof fan housing; 2. Drive motor; 3. Centrifugal impeller; 4. Air inlet; 5. Air outlet; 6. Vortex compression chamber; 7. Gradually contracting vortex channel; 8. Guide air inlet; 9. Explosion-proof guide plate; 10. Block discharge channel; 11. Explosion-proof block discharge mechanism; 12. First dust concentration sensor; 13. Second dust concentration sensor; 14. Inert gas storage tank; 15. Solenoid valve; 16. Air supply nozzle; 17. Controller; 18. Flame-arresting explosion-proof mesh; 19. Wear-resistant lining; 20. Rectifying guide vane; 21. Pressure sensor; 22. Pressure relief valve; 23. Return spring; 24. Limit stop; 25. Dust guide ridge; 26. Sealing stuffing box; 27. Layered jet pipe. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] This embodiment provides an explosion-proof fan system for pneumatic transportation of dust with vortex compression and agglomeration function. It has a rated air volume of 18000 m³ / h and a total pressure of 3200 Pa, suitable for pneumatic transportation of combustible dust such as calcium carbide dust. The overall explosion-proof rating is ExdⅡCT4, conforming to the requirements of GB3836.1-2010 and GB3836.15-2017 standards. The specific structure and working principle are as follows:

[0025] I. Main Structure of Explosion-proof Fan

[0026] The explosion-proof fan body provides the power for air delivery to the system. The whole body adopts an explosion-proof design, which can withstand the impact of internal explosions without being damaged or transmitting the explosion.

[0027] Explosion-proof fan housing 1: The housing is made of Q235-B cast steel in a single-piece volute structure with a wall thickness of 10mm. It has passed a 1.5MPa water pressure test without leakage and can withstand an explosive impact pressure of 1.0MPa. The volute base circle diameter of the housing is 450mm, the outlet width is 500mm, and the flow channel surface is smoothly polished to reduce airflow resistance and dust adhesion. Sealed end caps are provided on both sides of the housing. The mating surface between the end cap and the housing is an explosion-proof surface with a surface roughness Ra≤6.3μm and a mating surface width of 25mm. A nitrile rubber explosion-proof sealing gasket with a thickness of 5mm is embedded in the middle to ensure explosion-proof performance. An integrated mounting base is provided at the bottom of the housing and is fixed to the on-site foundation by anchor bolts.

[0028] Drive motor 2: A YB3 series explosion-proof three-phase asynchronous motor with a power of 75kW, 4 poles, rated speed of 1480r / min, insulation class F, protection class IP65, and explosion-proof mark ExdⅡCT4 is used. The motor is bolted to the motor mount on the left end cover of the explosion-proof fan housing. The output shaft extends through the end cover into the housing. A labyrinth seal + skeleton oil seal combination explosion-proof sealing structure is provided between the shaft and the end cover, combined with the explosion-proof bearing housing, to ensure the explosion-proof performance of the shaft end. The motor junction box uses an explosion-proof gland for cable entry, ensuring reliable cable sealing.

[0029] Centrifugal impeller 3: Made of 6061-T6 antistatic aluminum alloy, integrally milled, with backward-curved blades, a total of 12 blades, impeller diameter 420mm, outlet width 180mm, blade outlet installation angle 45°; impeller surface is hard anodized, surface resistivity ≤10 Ω. 9 The impeller has anti-static properties, preventing static sparks from dust friction; the impeller is dynamically balanced to G2.5 level, with a vibration intensity of ≤2.8mm / s, ensuring smooth operation; the impeller is fixed to the output shaft end of the drive motor by a flat key and a locking nut, with an anti-loosening washer to prevent loosening during operation.

[0030] Air Inlet 4: A hyperbolic collector structure, integrally mounted on the right axial center of the explosion-proof fan casing. It has an inlet diameter of 500mm and an outlet diameter of 420mm, with a 2mm radial clearance to the centrifugal impeller inlet to ensure efficient air intake. A PN16 raised-face flange is located at the right end of the air inlet for connection to the air intake pipe. Six rectifier guide vanes (20 in total) made of aluminum alloy are fixed inside the air inlet, evenly arranged circumferentially, with an installation angle of 15° to the airflow direction. A central guide cone with a 30° cone angle and a length of 150mm is connected to the inner end of each guide vane, with its tip pointing towards the air intake direction. Both the guide vanes and the central guide cone are coated with an 80μm thick antistatic epoxy coating. This coating eliminates airflow swirl and turbulence, ensuring a uniform and stable airflow into the impeller center, improving the impeller's air delivery efficiency and centrifugal separation effect, while reducing static electricity generated by dust collisions.

[0031] Outlet 5: A square interface, integrally installed at the top tangential position of the explosion-proof fan casing, with a cross-sectional size of 500mm × 400mm. A PN16 connecting flange is installed at the top for connection to the gas outlet pipe. Inside the outlet, near the lower end, is a flame-arresting and explosion-proof mesh 18, composed of three layers of 304 stainless steel corrugated flame-arresting cores, each layer 10mm thick, with a corrugation height of 0.4mm. The corrugation directions of adjacent layers are perpendicular, with a total thickness of 35mm. Stainless steel perforated grilles are fixed on both sides of the flame-arresting cores, with a grille aperture of 3mm and an opening rate of 60%. The outer periphery of the flame-arresting and explosion-proof mesh is pressed into the installation groove on the inner wall of the outlet by an explosion-proof sealing ring. The groove is filled with graphite sealing rope to ensure sealing and explosion-proof performance. Its function is to prevent the spread of flames generated by an explosion inside the casing to the outlet pipe, while also blocking large dust particles from impacting the pipe at high speed, providing buffer protection.

[0032] Pressure monitoring and pressure relief components: A pressure sensor 21 and a pressure relief valve 22 are respectively installed on the top end cover of the explosion-proof fan housing; the pressure sensor 21 is an explosion-proof diffused silicon pressure transmitter, model CYB-20S, explosion-proof mark ExdⅡCT4, measuring range 0-0.2MPa, accuracy class 0.2, output signal 4-20mA, response time ≤100ms; the sensor is installed on the top of the housing through an M20×1.5 external thread, and the sensing end extends 100mm into the inner cavity of the housing to avoid airflow dead zones and monitor the air pressure changes inside the housing in real time; The pressure relief valve 22 is a pilot-operated explosion-proof pressure relief valve with a nominal diameter of DN80, a set opening pressure of 0.08MPa, and a reseating pressure of 0.06MPa. The valve body is made of cast steel, and the sealing surface is made of hard alloy. The outlet end of the pressure relief valve is connected to a silencer pressure relief pipe, which is made of galvanized steel pipe with a diameter of DN80 and a length of 5m. The end extends to an outdoor safe area, and the pipe opening is set downward to prevent rainwater from entering. A sound-absorbing plate is installed inside the silencer pipe to reduce noise during pressure relief. When the pressure inside the casing exceeds the set value, the pressure relief valve automatically opens to quickly relieve pressure and prevent the casing from being damaged due to overpressure.

[0033] II. Eddy Current Compression Block Structure

[0034] The vortex compression and block-forming mechanism is integrated and installed on the lower side wall of the explosion-proof fan casing. It is the core structure for achieving dust separation and solidification. No additional power is required; the dust can be compressed into blocks by relying on the centrifugal force of the fan itself.

[0035] Eddy current compression chamber 6: This is a vertical cylindrical sealed chamber made of the same Q235-B cast steel as the casing, with a wall thickness of 10mm, an inner diameter of 650mm, and a height of 900mm. The top side wall of the chamber is welded to the lower side wall of the explosion-proof fan casing as one piece using continuous full welding with a weld height of 8mm. After welding, a kerosene penetration test is performed, and there is no leakage, ensuring the overall explosion-proof continuity. The bottom of the chamber is a 60° conical bottom, which facilitates the concentrated sliding of dust blocks. The central outlet of the conical bottom is connected to form a block discharge channel. The side wall of the chamber is equipped with a 400mm×300mm explosion-proof maintenance door, which is fastened with bolts. An explosion-proof sealing gasket is installed on the joint surface for periodic inspection of the internal eddy current channel and lining wear.

[0036] Air inlet 8: It is a strip-shaped opening, 450mm long and 90mm wide, and is located on the common side wall of the explosion-proof fan casing and the vortex compression chamber. The upper edge of the opening is flush with the highest point of the outer edge of the centrifugal impeller, and the lower edge is 50mm lower than the lowest point of the impeller, so that the high-concentration dust-laden airflow thrown out by the impeller can enter the vortex chamber through the opening to the maximum extent. The edge of the opening is rounded with R3mm to reduce airflow resistance and dust erosion wear.

[0037] Explosion-proof deflector 9: Located on the side of the air inlet facing the inner cavity of the casing, it is made of 6mm thick Q235 steel plate and has an overall arc structure. The radius of the arc is the same as the outer edge radius of the impeller, which is 215mm. The plate is 440mm long and 100mm wide. The size is slightly larger than the air inlet to ensure that it can completely cover the opening when closed.

[0038] The upper end of the deflector is hinged to the bearing seat on the upper edge of the air inlet via a 304 stainless steel explosion-proof hinge shaft. The hinge shaft has a diameter of 12mm and a clearance of 0.1mm, which meets the requirements of the explosion-proof joint surface. Two return spring mounting seats are provided on the back of the deflector (facing the housing side), which are connected to two return springs 23 respectively. The return springs are 304 stainless steel compression springs, and the other end of the springs is connected to the spring seat on the inner wall of the housing. A limit block 24 is welded to the lower edge of the air inlet. It is a steel block with a height of 20mm, which is used to limit the maximum opening angle of the explosion-proof deflector. During normal operation, under the combined action of the spring force of the return spring and the airflow impact force, the deflector maintains an opening angle of 30°, and the lower end abuts against the limit block.

[0039] The explosion-proof baffle has dual functions of guiding and explosion protection: During normal operation, the arc-shaped guide surface matches the tangential rotation of the impeller, which can smoothly guide the dust-laden airflow thrown out by the impeller into the vortex compression chamber, with airflow resistance loss ≤5% and improved dust separation efficiency; When an accidental combustion and explosion occurs in the vortex chamber, the pressure inside the chamber rises instantly, and the high-pressure airflow impacts the back of the baffle, overcoming the spring force to push the baffle to close quickly around the hinge shaft, with a closing response time ≤10ms, completely blocking the air inlet and achieving one-way explosion protection, effectively preventing the spread of flames and shock waves to the main chamber of the fan; After the explosion, the pressure inside the chamber drops, and the baffle automatically opens under the action of the reset spring, returning to normal operation without manual reset.

[0040] The tapered vortex channel 7 is fixedly installed at the center of the vortex compression chamber. It has a spiral conical tapered structure and is made of 2mm thick 304 stainless steel plate rolled and welded. The diameter of the upper air inlet of the vortex channel is 500mm, the diameter of the lower air outlet is 140mm, the total height is 700mm, the number of spiral turns is 4, and the spiral helix angle gradually decreases from 25° to 12° from top to bottom. This makes the rotation radius continuously decrease and the tangential speed gradually increase as the airflow moves downward.

[0041] The inner wall of the gradually narrowing vortex channel is stamped with eight dust-guiding protrusions 25 along the spiral path. The cross-section is semi-circular with a radius of 5mm. The distance between adjacent dust-guiding protrusions gradually decreases from 60mm to 20mm from top to bottom. The function of the dust-guiding protrusions is to quickly guide the dust particles thrown towards the inner wall to move downstream, reducing the adhesion and accumulation of dust on the wall surface. At the same time, it enhances the probability of collision between particles, promotes dust agglomeration, and improves the agglomeration efficiency.

[0042] The lower outlet of the gradually narrowing vortex channel is equipped with an annular compression constriction with a constriction cone angle of 18°, a constriction length of 50mm, and an outlet diameter of 120mm. When the airflow carrying dust agglomerates passes through the constriction, the channel cross-section suddenly contracts, and the airflow pressure increases instantaneously. This can forcefully compress the loose dust agglomerates into dense blocks, improving the density and strength of the dust blocks and preventing them from breaking during the fall.

[0043] The gradually narrowing vortex channel is fixed to the inner wall of the vortex compression chamber by three radial support rods. The support rods are made of 304 stainless steel round steel with a diameter of 16mm. One end is welded to the outer wall of the vortex channel, and the other end is fixed to the mounting base on the inner wall of the chamber by bolts. During installation, ensure that the air inlet end of the vortex channel is directly opposite the outlet of the guide air inlet so that the airflow enters the vortex channel smoothly along the tangential direction without deflection or energy loss.

[0044] Wear-resistant lining 19: The inner walls of the vortex compression chamber, the inner walls of the guide air inlet, and the inner walls of the converging vortex channel are all covered with a wear-resistant lining. The lining is a 95% alumina ceramic lining, with a single piece size of 50mm×50mm, a thickness of 4mm, a Mohs hardness of 9, and a wear resistance more than 20 times that of ordinary steel. The linings are spliced ​​together using a tongue and groove structure with a groove depth of 1mm and a splicing gap of ≤0.1mm to prevent dust from entering the back of the lining and causing it to fall off. The back of the lining is bonded with high-temperature resistant inorganic ceramic adhesive with a bonding strength of ≥5MPa and a long-term operating temperature of ≤200℃.

[0045] The lining surface of the inner wall of the vortex compression chamber is also equipped with arc-shaped dust guide grooves arranged along the vortex direction. The grooves are 2mm deep and spaced 50mm apart, guiding dust downwards along the airflow direction and reducing dust accumulation in the chamber. The wear-resistant lining can significantly improve the equipment's resistance to erosion and wear, with a service life of ≥40,000 hours, extending the maintenance cycle and reducing operation and maintenance costs.

[0046] Block discharge channel 10: It is a circular channel with a diameter of 140mm and a length of 200mm. The upper end is integrally welded to the center outlet of the conical bottom of the eddy current compression chamber, and the lower end is equipped with a PN16 connecting flange, which is connected to the feed port flange of the explosion-proof block discharge mechanism. The inner wall of the channel is also lined with a wear-resistant ceramic lining to reduce the scouring and wear of dust blocks.

[0047] Explosion-proof block discharge mechanism 11: It adopts an explosion-proof horizontal spiral discharge valve with an overall explosion-proof rating of ExdⅡBT4. It is used to continuously and sealably discharge dust blocks while achieving air sealing and maintaining the stability of the flow field in the vortex cavity.

[0048] The mechanism consists of three parts: an explosion-proof geared motor, a screw conveyor, and a conveyor housing. The explosion-proof geared motor has a power of 1.1kW, a reduction ratio of 1:30, and an output speed that is steplessly adjustable from 0 to 50 r / min. The speed is controlled by a controller via a frequency converter. The conveyor housing is made of carbon steel with a wall thickness of 6mm, an inner diameter of 150mm, and a length of 600mm. It has an inlet flange at the top and an outlet flange at the bottom. The screw conveyor is made of 304 stainless steel with a screw blade diameter of 148mm, a gap of ≤1mm between the screw and the inner wall of the housing, a pitch of 100mm, a blade thickness of 5mm, and a polished surface to reduce dust adhesion.

[0049] A sealing stuffing box 26 is provided between the two ends of the screw conveyor and the end cover of the conveyor housing. The stuffing box is filled with flexible graphite packing. By pressing it with a pressure cap, a dynamic seal is achieved at the shaft end. This ensures that the conveyor rotates normally, prevents external air from entering the cavity, avoids leakage of dust-containing gas in the cavity, maintains the pressure stability of the vortex cavity, and ensures the gas sealing effect and explosion-proof performance.

[0050] The lower end of the discharge port of the conveying shell is connected to a sealed collection hopper with a volume of 0.05m³ via a flange. A discharge gate valve is installed at the bottom of the collection hopper. A rotary explosion-proof material level switch is installed on the side wall of the collection hopper and is electrically connected to the controller. When the material level reaches the upper limit, a signal is output to the controller to trigger an alarm and prompt the staff to unload the material in time.

[0051] III. Explosion-proof control unit structure and control logic

[0052] The explosion-proof control unit is used to realize system status monitoring, active explosion-proof linkage and operating parameter adjustment. All electrical components meet the explosion-proof standards. The overall control logic is clear, with hierarchical response, and takes into account both safety and economy.

[0053] 1. Sensor assembly

[0054] The first dust concentration sensor 12: adopts a laser scattering type explosion-proof dust concentration sensor, model GCG1000, explosion-proof mark ExibⅡBT4, measurement range 0-1000g / m³, resolution 0.1g / m³, response time ≤1s; it is installed on the side wall of the air inlet through M27×2 thread, with the detection window facing the airflow direction at a 45° angle to avoid dust directly impacting the window and causing pollution; the sensor has a built-in compressed air purging device, which can automatically purge the optical window at regular intervals to reduce dust adhesion and ensure measurement accuracy.

[0055] The second dust concentration sensor 13 is the same model as the first dust concentration sensor. It is installed on the upper side wall of the vortex compression chamber, 150mm away from the top of the chamber. The detection window faces downward and is directly opposite the air intake area of ​​the gradually narrowing vortex channel. It monitors the dust concentration in the vortex chamber in real time. It is also equipped with an automatic purging device.

[0056] Pressure sensor 21: As mentioned above, it monitors the pressure inside the housing cavity in real time.

[0057] Material level sensor: monitors the material level status in the sealed hopper.

[0058] 2. Inert gas source and actuator

[0059] Inert gas storage tank 14: It adopts a high-pressure nitrogen storage tank with a design pressure of 2.5MPa, a rated working pressure of 1.6MPa, and a volume of 2.5m³. The tank body is made of Q345R and meets the requirements of GB150 standard. The storage tank is equipped with safety valves, pressure gauges, level gauges and other safety accessories, and is located in an explosion-proof safety area next to the fan. The outlet pipeline of the storage tank is equipped with a high-pressure pressure reducing valve to stabilize the outlet pressure at 0.3MPa, providing a stable inert gas source for the system.

[0060] Solenoid valve 15: Explosion-proof electric regulating valve, model ZDLP-16C, explosion-proof mark ExdⅡCT4, nominal diameter DN25, regulating accuracy ±1%, regulating range 0-100%, input signal 4-20mA, response time ≤2s; valve body material cast steel, sealing surface hard alloy, leakage class IV; the solenoid valve is installed on the pipeline downstream of the pressure reducing valve, and its opening is controlled by the controller to regulate the nitrogen supply.

[0061] Layered jet pipe 27 and supplementary air nozzle 16: The explosion-proof fan casing is equipped with two layers of annular jet pipes, made of 304 stainless steel with a diameter of DN20. They are fixed to the upper and lower parts of the casing cavity by brackets, respectively. Three supplementary air nozzles are evenly arranged on the upper annular jet pipe, with the nozzles facing the leading edge of the centrifugal impeller blades and the spray direction being the same as the impeller rotation direction. They are used to dilute the high concentration of dust in the impeller area. Two supplementary air nozzles are evenly arranged on the lower annular jet pipe, with the nozzles facing the guide air inlet area at the bottom of the casing. They are used to dilute the dust concentration before entering the vortex cavity.

[0062] The supplementary air nozzle 16 is a fan-shaped atomizing nozzle with a spray diffusion angle of 60° and a nozzle diameter of 2mm. It is made of 304 stainless steel and can evenly diffuse nitrogen into the entire inner cavity of the casing to form a uniform inert atmosphere, avoid local dust concentration exceeding the standard, and improve the inertization effect. The layered air jet pipe is led out through the explosion-proof wall-penetrating joint on the side wall of the casing and connected to the outlet end of the solenoid valve through a seamless stainless steel pipeline. All pipelines are welded connections, ensuring good airtightness.

[0063] The controller 17 uses a Siemens S7-1200 series PLC as its core control unit and is installed in a wall-mounted explosion-proof control cabinet. The cabinet has an explosion-proof rating of ExdⅡBT4 and a protection rating of IP65. The cabinet is equipped with a switching power supply, analog input / output modules, relay output modules, a 7-inch explosion-proof touchscreen, and an explosion-proof audible and visual alarm. All incoming and outgoing cables are sealed with explosion-proof glands, and a dedicated grounding terminal is installed inside the cabinet for reliable grounding. The controller incorporates a concentration grading threshold module, an inerting linkage module, a discharge speed control module, a pressure monitoring and depressurization module, and a fault alarm module. The specific functions and logic are as follows:

[0064] Concentration grading threshold module: Sets three concentration thresholds: low, medium, and high. For the inlet side (first dust concentration sensor), the low threshold is 20% of the lower explosive limit (100g / m³), the medium threshold is 40% of the lower explosive limit (200g / m³), and the high threshold is 60% of the lower explosive limit (300g / m³). For the vortex cavity side (second dust concentration sensor), the corresponding thresholds are 150g / m³, 250g / m³, and 350g / m³. All thresholds can be modified and adjusted via the touch screen according to the actual type of dust being transported, adapting to the explosion-proof requirements of different combustible dusts.

[0065] Inerting linkage module: Based on the detection value of the first dust concentration sensor, the opening degree of the solenoid valve is controlled in stages to achieve precise inerting.

[0066] ① When the detected value is <100g / m³ (below the low threshold), it is determined to be a low-concentration safe operating condition. The solenoid valve remains fully closed and no nitrogen is added. The system only relies on the eddy current compression block mechanism to reduce the dust concentration, save nitrogen consumption, and reduce operating costs.

[0067] ② When the detected value is between 100g / m³ and 200g / m³ (intermediate threshold range), it is determined to be a medium concentration warning condition. The solenoid valve opens linearly according to the concentration. For every 10g / m³ increase in concentration, the valve opening increases by 10%, and nitrogen is added in real time to control the oxygen concentration in the casing below 12%, eliminating the combustion-supporting conditions among the three elements of explosion, while avoiding excessive waste of nitrogen.

[0068] ③ When the detected value is ≥200g / m³ (above the advanced threshold), it is determined to be a high-concentration hazardous condition. The solenoid valve is fully opened to inject nitrogen at the maximum flow rate to quickly dilute the dust concentration and at the same time reduce the oxygen concentration to below 8%. At the same time, the controller triggers the explosion-proof audible and visual alarm, which issues an audible and visual alarm signal to prompt on-site personnel to check the cause of the abnormal dust concentration in the intake air and take timely action.

[0069] Discharge speed control module: Based on the detection value of the second dust concentration sensor, the speed of the explosion-proof block-discharging mechanism's reduction motor is continuously adjusted via a frequency converter to adjust the discharge speed in real time and maintain a stable dust concentration in the vortex cavity.

[0070] ① When the concentration in the eddy cavity is <150g / m³, the discharge mechanism maintains a low speed of 10r / min to ensure that a small amount of dust is continuously discharged.

[0071] ② When the concentration is between 150g / m³ and 250g / m³, the rotation speed increases linearly with the concentration. For every 20g / m³ increase in concentration, the rotation speed increases by 5r / min to accelerate the discharge speed and prevent dust from accumulating in the vortex chamber.

[0072] ③ When the concentration is ≥250g / m³, the discharge mechanism will increase to the maximum speed of 50r / min for full-speed discharge, and at the same time trigger an early warning signal to prevent the dust concentration in the vortex cavity from continuing to rise to the explosion limit.

[0073] Pressure monitoring and relief module: Based on the pressure sensor readings, it provides tiered responses to pressure anomalies.

[0074] ①The system operates normally when the pressure is <0.05MPa.

[0075] ② When the pressure reaches the 0.05MPa warning value, the controller automatically increases the opening of the solenoid valve to increase the nitrogen supply and triggers a pressure warning signal to prompt the staff to check for abnormalities.

[0076] ③ When the pressure reaches the 0.08MPa activation value, the controller controls the pilot-operated pressure relief valve to open, quickly relieve pressure, and control the pressure inside the casing within a safe range to prevent damage to the casing due to overpressure; at the same time, the pressure relief triggers an emergency alarm and can interlock the upstream conveying system to slow down or stop.

[0077] ④ When the pressure drops below 0.06MPa, the pressure relief valve will automatically close and return to normal operation.

[0078] Fault alarm module: Real-time monitoring of the working status of each sensor and actuator. When abnormal situations such as sensor disconnection, solenoid valve failure, motor overload, or material level exceeding the limit occur, a fault alarm signal is immediately issued and the fault location and cause are displayed on the touch screen, which facilitates maintenance personnel to quickly troubleshoot and handle the situation.

[0079] IV. Overall System Working Process

[0080] 1. Start-up phase: Connect the power supply to the explosion-proof control cabinet, the controller completes self-test, confirms that the status of each sensor and actuator is normal, and the pressure of the inert gas storage tank meets the requirements; then start the drive motor, the centrifugal impeller gradually increases to the rated speed, and at the same time the explosion-proof block mechanism starts running at the basic speed, and the system enters the standby state.

[0081] 2. Normal conveying and dust agglomeration process: The dust-laden airflow enters through the inlet, and after being rectified by the rectifier guide vanes and the central guide cone, the swirling and turbulent flow is eliminated, and the airflow enters the central inlet of the centrifugal impeller evenly and smoothly. The high-speed rotation of the impeller does work on the airflow, giving the airflow centrifugal force and kinetic energy, and causing it to flow towards the outer edge of the impeller. Since the density of dust particles is much greater than that of gas, under the action of centrifugal force, the dust particles are thrown towards the inner wall of the casing at the outer edge of the impeller, forming a high-concentration dust-laden airflow layer.

[0082] Most of the airflow flows upward along the volute channel, is discharged through the outlet, and enters the subsequent air delivery pipeline; a small portion of the high-concentration dust-laden airflow, under the action of centrifugal force and inertia, passes through the guide inlet on the lower side wall of the casing, is guided by the arc-shaped guide surface of the explosion-proof guide plate, and smoothly enters the upper inlet of the gradually narrowing vortex channel tangentially, resulting in low airflow resistance and low energy loss.

[0083] After the dust-laden airflow enters the gradually narrowing vortex channel, it rotates downwards at high speed along the spiral channel. As the channel diameter gradually decreases and the spiral angle gradually decreases, the tangential velocity of the airflow continuously increases, reaching a maximum of 40 m / s. Under the action of strong centrifugal force, the dust particles in the airflow are continuously thrown towards the inner wall of the vortex channel and spiral downwards along the dust-guiding ridges on the inner wall. During the movement, the dust particles collide and rub against each other continuously, and gradually agglomerate under the action of van der Waals forces and electrostatic forces, forming small dust agglomerates.

[0084] As the airflow continues to flow downwards, the cross-section of the channel further shrinks, the airflow pressure gradually increases, the agglomerates are gradually squeezed, and the gaps between particles continuously decrease. When the airflow reaches the annular compression opening at the lower end, the cross-section of the channel suddenly contracts, and the pressure instantly rises to 0.12 MPa (gauge pressure). The loose dust agglomerates are forcefully squeezed to form dense block dust. The density of the dust block can reach 0.9-1.3 g / cm³, and the volume is only 1 / 5-1 / 8 of the original loose dust, with a significant volume reduction effect.

[0085] The compressed dust blocks are discharged from the converging outlet and fall into the block discharge channel at the bottom of the vortex chamber. They then enter the spiral conveyor housing of the explosion-proof block collection mechanism. The spiral conveyor rod rotates continuously, smoothly conveying the dust blocks forward. Finally, the dust blocks are discharged from the discharge port into the sealed collection hopper, completing the entire process of dust separation, solidification, and discharge. The purified airflow flows back upward from the center of the gradually narrowing vortex channel, returns to the main chamber of the blower through the upper gap of the guide air inlet, and is discharged from the outlet along with the main airflow, forming a complete air circulation.

[0086] 3. Explosion-proof linkage process: Throughout the entire operation, the explosion-proof control unit collects data from various sensors in real time and dynamically adjusts operating parameters to achieve active explosion-proof protection; when the dust concentration in the intake air increases, the solenoid valve is opened in stages to introduce nitrogen for inerting; when the dust concentration in the vortex cavity increases, the speed of the discharge mechanism is increased to accelerate discharge; when the pressure inside the casing increases abnormally, a staged warning is issued and emergency pressure is released; when an accidental combustion and explosion occurs in the vortex cavity, the explosion-proof guide plate closes quickly to block the flame, and in conjunction with the flame arrestor and explosion-proof mesh and pressure relief valve, the impact of the explosion is controlled to a minimum, preventing the accident from spreading and escalating.

[0087] V. Verification of Implementation Results

[0088] The system in this embodiment has a separation efficiency of ≥95% for dust particles larger than 10μm, a total dust removal rate of ≥85%, and a dust accumulation rate of more than 90% compared to traditional explosion-proof fans, which significantly reduces the risk of dust explosion from the source. There is no secondary dust generation after the dust clumps together, and the transportation and treatment process is safe and environmentally friendly, with a dust volume reduction rate of ≥80%.

[0089] In terms of explosion-proof performance, the overall explosion-proof safety performance is improved by more than 3 times compared with traditional single explosion-proof fans through triple protection of active dust reduction, precise inerting and multiple explosion-proof layers; at the same time, the graded control strategy can reduce nitrogen consumption by more than 40%, significantly improving the economic efficiency of operation.

[0090] The system has no easily damaged parts such as filter cartridges, the core wear-resistant liner has a service life of ≥40,000 hours, the maintenance cycle is extended to more than 2 years, the maintenance cost is reduced by 60%, and there is no need to stop the machine for dust cleaning, which can ensure the continuity of production and the overall economic benefits are significant.

[0091] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An explosion-proof fan system for pneumatic transportation of dust using a dust vortex compression and agglomeration function, characterized in that, Includes the explosion-proof fan body, the vortex compression block forming mechanism, and the explosion-proof control unit; The explosion-proof fan body includes an explosion-proof fan housing (1), a drive motor (2) fixed to one side of the explosion-proof fan housing (1), and a centrifugal impeller (3) disposed inside the explosion-proof fan housing (1) and connected to the output shaft of the drive motor (2). An air inlet (4) is provided at the axial end of the explosion-proof fan housing (1), and an air outlet (5) is provided at the tangential end of the explosion-proof fan housing (1). The eddy current compression block forming mechanism includes an eddy current compression chamber (6) disposed on the side wall of the explosion-proof fan housing (1), a gradually narrowing eddy current channel (7) disposed inside the eddy current compression chamber (6), and a guide air inlet (8) connecting the inner cavity of the explosion-proof fan housing (1) and the eddy current compression chamber (6). An explosion-proof guide plate (9) is hinged at the guide air inlet (8). A block forming discharge channel (10) is disposed at the bottom center of the eddy current compression chamber (6). An explosion-proof block forming mechanism (11) is sealed and connected to the lower end of the block forming discharge channel (10). The explosion-proof control unit includes a first dust concentration sensor (12) disposed on the side wall of the air inlet (4), a second dust concentration sensor (13) disposed on the side wall of the eddy current compression chamber (6), an inert gas storage tank (14), a solenoid valve (15) disposed on the outlet pipeline of the inert gas storage tank (14), a gas supply nozzle (16) disposed on the inner wall of the explosion-proof fan housing (1), and a controller (17). The first dust concentration sensor (12), the second dust concentration sensor (13), the solenoid valve (15), and the explosion-proof block mechanism (11) are all electrically connected to the controller (17). The gas supply nozzle (16) is connected to the outlet end of the solenoid valve (15) through a pipeline.

2. The explosion-proof fan system for pneumatic transportation with dust vortex compression and agglomeration function according to claim 1, characterized in that, The inside of the air outlet (5) is fixed with a flame-arresting and explosion-proof mesh (18). The flame-arresting and explosion-proof mesh (18) is composed of at least three layers of corrugated stainless steel flame-arresting cores stacked together. The corrugation directions of adjacent flame-arresting cores are perpendicular to each other. The outer periphery of the flame-arresting and explosion-proof mesh (18) is fixed in the mounting groove on the inner wall of the air outlet (5) by an explosion-proof sealing ring.

3. The explosion-proof fan system for pneumatic transportation with dust vortex compression and agglomeration function according to claim 2, characterized in that, The inner wall of the vortex compression chamber (6) and the surface of the gradually narrowing vortex channel (7) are both covered with a wear-resistant lining (19). The wear-resistant lining (19) is a spliced ​​alumina ceramic lining. The linings are spliced ​​together by a tongue and groove structure. The back of the lining is bonded to the substrate surface with high-temperature resistant inorganic adhesive. The surface of the lining is provided with arc-shaped dust guide grooves arranged along the vortex direction.

4. The explosion-proof fan system for pneumatic transportation with dust vortex compression and agglomeration function according to claim 3, characterized in that, The upper end of the explosion-proof guide plate (9) is hinged to the upper edge of the air inlet (8) via an explosion-proof hinge shaft. A reset spring (23) is provided on the back of the explosion-proof guide plate (9), and the other end of the reset spring (23) is connected to the inner wall of the explosion-proof fan housing (1). A limit stop (24) is provided on the lower edge of the air inlet (8), and the limit stop (24) is used to limit the maximum opening angle of the explosion-proof guide plate (9).

5. The explosion-proof fan system for pneumatic transportation with dust vortex compression and agglomeration function according to claim 4, characterized in that, The inner wall of the gradually narrowing vortex channel (7) is provided with several dust-guiding protrusions (25) along the spiral path. The cross-section of the dust-guiding protrusions (25) is semi-circular, and the distance between adjacent dust-guiding protrusions (25) gradually decreases along the airflow direction. The inner wall of the outlet end of the gradually narrowing vortex channel (7) is provided with an annular compression opening, and the cone angle of the annular compression opening is 15°-20°.

6. The explosion-proof fan system for pneumatic transportation with dust vortex compression and agglomeration function according to claim 5, characterized in that, The air inlet (4) is fixed with a flow guide vane (20). The flow guide vane (20) is evenly arranged around the circumference of the air inlet (4). The installation angle of the flow guide vane (20) is 15° with the direction of the airflow. The inner end of the flow guide vane (20) is connected to a central flow guide cone. The tip of the central flow guide cone faces the direction of airflow. The surface of the flow guide vane (20) is coated with an antistatic coating.

7. The explosion-proof fan system for pneumatic transportation with dust vortex compression and agglomeration function according to claim 1, characterized in that, A pressure sensor (21) and a pressure relief valve (22) are respectively installed on the top of the explosion-proof fan housing (1). The detection end of the pressure sensor (21) extends into the central area of ​​the inner cavity of the explosion-proof fan housing (1). The pressure relief valve (22) is a pilot-operated explosion-proof pressure relief valve. The outlet end of the pressure relief valve (22) is connected to a silencer and pressure relief pipe. Both the pressure sensor (21) and the pressure relief valve (22) are electrically connected to the controller (17). The controller (17) is equipped with a pressure threshold module. When the detection value of the pressure sensor (21) reaches the warning threshold, the controller (17) outputs a warning signal and simultaneously opens the solenoid valve (15).

8. The explosion-proof fan system for pneumatic transportation with dust vortex compression and agglomeration function according to claim 7, characterized in that, The explosion-proof block mechanism (11) includes an explosion-proof geared motor, a spiral conveying rod and a conveying housing. A sealing stuffing box (26) is provided between the two ends of the spiral conveying rod and the conveying housing. The sealing stuffing box (26) is filled with graphite packing. A sealing hopper is connected to the lower end of the discharge port of the conveying housing. A material level sensor is provided on the sealing hopper.

9. The explosion-proof fan system for pneumatic transportation with dust vortex compression and agglomeration function according to claim 8, characterized in that, The air supply nozzle (16) is fixed to the inner wall of the explosion-proof fan housing (1) via a layered jet pipe (27). The layered jet pipe (27) is provided with two layers of nozzles along the axial direction of the housing. The upper nozzle group faces the leading edge of the centrifugal impeller (3) blades, and the lower nozzle group faces the lower flow channel of the housing. Each nozzle group includes at least two air supply nozzles (16) evenly arranged in the circumferential direction. The air supply nozzle (16) is a fan-shaped atomizing nozzle with a spray diffusion angle of 60°.

10. The explosion-proof fan system for pneumatic transportation with dust vortex compression and agglomeration function according to claim 9, characterized in that, The controller (17) has a built-in concentration grading threshold module, an inertia linkage module and a discharge speed regulation module. The concentration grading threshold module is set with three concentration thresholds: low, medium and high. The inertia linkage module is configured to: keep the solenoid valve (15) closed when the concentration is in the low threshold range; open the solenoid valve (15) linearly proportionally when the concentration is in the medium threshold range; and fully open the solenoid valve (15) and trigger an audible and visual alarm when the concentration is in the high threshold range. The discharge speed regulation module is configured to steplessly adjust the conveying speed of the explosion-proof block mechanism (11) according to the detection value of the second dust concentration sensor (13) to maintain the dust concentration in the eddy current compression chamber (6) stable.

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