A conveyor belt combustion test box integrated exhaust system and a working method thereof

Abstract

The application discloses a conveying belt combustion test box integrated air draft system and method, relates to the technical field of conveying belt combustion test, and comprises a combustion test box which is placed in a smoke collecting box; an exhaust port of the combustion test box is connected with a variable frequency air draught fan through a first hierarchical flow guide air duct, a low disturbance smoke collecting hood is arranged in the smoke collecting box, the low disturbance smoke collecting hood is connected with the variable frequency air draught fan through a second hierarchical flow guide air duct; an air outlet of the variable frequency air draught fan is connected with a waste gas purification unit, and the waste gas purification unit comprises a primary filter unit and an activated carbon adsorption unit which are arranged in sequence along the air flow direction; the application realizes real-time exhaust of smoke gas in the whole test process without interfering with the combustion flame and under the premise that the wind speed of the test position is less than or equal to 0.2 m / s, the air draft flow does not disturb the test flame, and the accurate and compliant detection data of the conveying belt combustion test are ensured.

Description

Technical Field

[0001] This invention relates to the field of conveyor belt combustion testing technology, specifically to an integrated ventilation system for a conveyor belt combustion test chamber and its working method. Background Technology

[0002] Conveyor belts are critical continuous material handling equipment in industries such as coal mining, ports, and power generation. To evaluate their response to fire, laboratory-scale combustion characteristic tests are widely used both domestically and internationally. Conveyor belts are composed of polymer materials, which produce large amounts of smoke and toxic gases when burned. The smoke and toxic gases generated during the combustion of polymer materials can affect the health of operators, and smoke in the test area should be promptly removed. Therefore, ensuring the accuracy and compliance of combustion test data while preventing the diffusion of toxic fumes into the laboratory during operation has long been a technical challenge for this type of testing equipment.

[0003] Existing conveyor belt combustion testing equipment is typically equipped with a ventilation and exhaust system. Taking a common laboratory-scale vertical combustion test chamber as an example, the top of the chamber has a ventilation and exhaust system that expels exhaust gases outdoors upon completion of the test, but the system remains shut down during the test. The ventilation and exhaust system usually has an exhaust fan installed after the exhaust duct, with the airflow rate controlled by adjusting a control valve. Its exhaust hood is positioned directly above the test chamber to extract the flue gas diffusing from outside the furnace during the test.

[0004] The existing devices have the following prominent problems in actual use: (1) Because the combustion test requires the air velocity in the test area to be maintained within a specific range to ensure the stability of the flame shape, for example, some combustion tests require the air velocity near the combustion point to not exceed 0.2 m / s. However, when the conventional exhaust system is turned on, it will form a concentrated strong suction airflow at the combustion point, causing the local air velocity to exceed 0.2 m / s, which will then wash away the test flame, change the combustion shape, and distort the test data. In order to avoid this interference, the existing test chambers generally adopt a compromise solution of stopping the exhaust during the test and only starting the exhaust after the test. This makes it impossible to collect a large amount of toxic smoke generated during the entire combustion stage from the source, and it continues to spread to the laboratory, corridor and other areas, posing a risk of inhaling toxic and harmful smoke to the operators and surrounding personnel. (2) The exhaust fans of the existing devices are mostly fixed speed or only roughly adjusted by manual valves, lacking the ability to monitor and dynamically adjust the local air velocity at the combustion point in real time. They cannot control the local airflow disturbance caused by the exhaust within the standard allowable range during the combustion process, so they can only choose to stop the machine to avoid it. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides an integrated exhaust system for a conveyor belt combustion test chamber and its working method, which can achieve real-time exhaust of flue gas throughout the test without interfering with the combustion flame and under the premise that the wind speed at the test position is ≤0.2m / s.

[0006] The technical solution of the present invention is as follows: In a first aspect of the present invention, an integrated exhaust system for a conveyor belt combustion test chamber is provided, comprising a combustion test chamber placed inside a smoke collection box; the exhaust port of the combustion test chamber is connected to a variable frequency exhaust fan through a first graded air duct; a low-disturbance smoke collection hood is provided inside the smoke collection box; and the low-disturbance smoke collection hood is connected to the variable frequency exhaust fan through a second graded air duct. The low-disturbance smoke hood is a gradually expanding smoke collection chamber structure that is narrow at the top and wide at the bottom. The hood opening covers the combustion test area of ​​the combustion test chamber. The hood opening is equipped with at least two layers of honeycomb rectifier mesh to disperse the exhaust airflow into a uniform negative pressure airflow. One end of the graded air duct is connected to the low-disturbance smoke hood, and the other end is connected to the air inlet of the variable frequency exhaust fan. The cross-section of the duct smoothly transitions along the airflow direction, and an arc-shaped guide plate is provided at the turning point of the duct. The outlet of the variable frequency exhaust fan is connected to the exhaust gas purification unit, which includes a primary filtration unit and an activated carbon adsorption unit arranged sequentially along the airflow direction.

[0007] In some embodiments of the present invention, a wind speed closed-loop control module is also included. The wind speed closed-loop control module includes a wind speed sensor, a PLC controller, an air volume regulating device, and the variable frequency exhaust fan arranged near the combustion point and the smoke hood. The wind speed sensor collects wind speed data of the combustion area in real time and transmits it to the PLC controller. The PLC controller automatically adjusts the operating frequency of the variable frequency exhaust fan and the opening degree of the air volume regulating device in the graded air duct according to the comparison result between the received wind speed data and the preset threshold, so as to maintain the air flow velocity near the combustion point below the standard limit.

[0008] In some embodiments of the present invention, the wind speed closed-loop control module operates continuously throughout the entire process of the conveyor belt combustion test, and the air velocity near the combustion point never exceeds 0.2 m / s.

[0009] In some embodiments of the present invention, the wind speed sensor is in three sets, with at least one set arranged at a distance of 50 mm from the combustion point, and the rest arranged near the smoke hood.

[0010] In some embodiments of the present invention, the inner wall of the low-disturbance smoke hood is an arc-shaped curved surface, and three layers of regular hexagonal honeycomb rectifier mesh are arranged in layers from top to bottom inside the hood opening. The rectifier mesh is detachably fixed to the hood body by buckles, and an inspection opening is provided on the side wall of the smoke hood.

[0011] In some embodiments of the present invention, the cross-section of the graded airflow duct smoothly tapers from the smoke hood connection end to the fan installation end; an electric airflow regulating valve is installed inside the graded airflow duct, the blades of the electric airflow regulating valve are arc-shaped guide blades and are driven by a micro servo motor; a sealing groove is provided at the splicing flange of the graded airflow duct, and a high-temperature resistant sealing gasket is installed in the sealing groove.

[0012] In some embodiments of the present invention, the connection points between the low-disturbance smoke hood, the graded air duct, and the variable frequency exhaust fan are all equipped with flexible sealing interfaces; the flexible sealing interface includes a high-temperature resistant silicone rubber bellows, a stainless steel wire support skeleton is wound inside the bellows, and flanges are provided at both ends of the bellows. A high-temperature resistant sealing gasket is provided between the flange and the mating flange to form a double seal.

[0013] In some embodiments of the present invention, the primary filtration unit uses pleated fiberglass filter cotton to intercept smoke particles and carbon ash impurities; the activated carbon adsorption unit is filled with columnar high-iodine-value activated carbon to adsorb volatile organic compounds and toxic and irritating gases in the flue gas; both the primary filtration unit and the activated carbon adsorption unit are drawer-type detachable structures.

[0014] In a second aspect of the present invention, a method for operating an integrated ventilation system for a conveyor belt combustion test chamber is provided, comprising the following steps: S1. Before the test ignition, the air duct and fan were run under no-load to confirm that there was no leakage and the wind speed monitoring was normal. S2. After the sample is ignited on the conveyor belt, it automatically enters the low air volume stable exhaust mode. The variable frequency exhaust fan runs at the initial air volume. The flue gas is diverted by the honeycomb rectifier mesh and then drawn into the graded guide air duct by the smoke collection hood. S3. Throughout the entire combustion test, the wind speed in the combustion zone is continuously and stably controlled at 0.1~0.2m / s, with gentle airflow and no flame disturbance; S4. After the combustion test is completed, switch to high air volume exhaust mode. The variable frequency exhaust fan runs at full load to remove the residual smoke from the combustion test chamber and pipeline. S5. The exhaust gas is sequentially filtered and purified by activated carbon adsorption before being discharged into the outdoor exhaust outlet in compliance with standards.

[0015] In some embodiments of the present invention, the PLC controller compares the real-time flow rate with a preset threshold: when the detected flow rate is higher than 0.2 m / s, it automatically lowers the operating frequency of the variable frequency exhaust fan and simultaneously reduces the opening of the air volume regulating device; when the detected flow rate is lower than 0.1 m / s, it automatically increases the fan frequency and increases the opening of the air volume regulating device, so that the flow rate at the combustion point remains stable within the range of 0.1~0.2 m / s.

[0016] One or more technical solutions of the present invention have the following beneficial effects: (1) The present invention integrates the combustion test chamber into the smoke collection box and is equipped with a dual-stage guide air duct connecting the exhaust port of the test chamber and the smoke collection hood. The same variable frequency fan enters the low-volume exhaust mode at the moment of combustion ignition. The main flue gas is actively extracted from the top of the chamber and the escaped diffused flue gas is collected by the bottom of the smoke collection hood. The flue gas collection efficiency is increased to more than 95%, which solves the problem of large-scale flue gas diffusion caused by the start of exhaust after the existing test. It substantially reduces the risk of toxic gas inhalation for operators and surrounding personnel.

[0017] (2) This invention solves the problem that the axial negative pressure induced downwards through the exhaust opening of traditional simple smoke hoods leads to excessive flow velocity at the combustion point, thus affecting the test results. By adopting a low-disturbance structure design with a gradually expanding arc-shaped smoke collection chamber and a three-layer honeycomb rectifier mesh, the originally concentrated strong suction negative pressure inside the hood is decomposed into a gentle micro-negative pressure that is evenly distributed across the surface, thereby cutting off the path of negative pressure induction and transmission to the combustion point. Combined with the staged guide air duct diameter reduction and the low-resistance design of the arc guide plate, although the suction action continues, the combustion point no longer senses the suction force generated by the airflow, ensuring that the flame shape is not disturbed by the suction airflow throughout the test, and significantly improving the reproducibility of combustion data.

[0018] (3) The wind speed closed-loop control module of the present invention dynamically adjusts the exhaust air volume and stably controls the wind speed in the combustion zone to ≤0.2m / s. The exhaust airflow will not scour or interfere with the test flame, and the combustion mode will not be affected. This improves the accuracy of the conveyor belt combustion test data and fully meets the requirements of the testing standards. The air duct adopts a variable diameter gradual transition and arc guide structure, with low wind resistance and no turbulence. It is equipped with a flexible sealing interface for double sealing to prevent pipeline smoke leakage. The whole machine is equipped with a sound insulation and vibration reduction structure, with low operating noise, which improves the laboratory working environment. The two-stage integrated exhaust gas purification unit can filter smoke and dust and adsorb toxic odor gases. After the exhaust gas is treated, it meets the standards for external discharge, realizing the harmless treatment of laboratory exhaust gas.

[0019] (4) Unlike the crude control of existing fixed-speed fans or manual valve adjustment, this invention deploys a core wind speed sensor 50mm away from the combustion point to provide real-time feedback of local flow velocity through high-frequency sampling. The PLC controller executes a hysteresis threshold algorithm of 0.1~0.2m / s to synchronously link the frequency of the variable frequency fan and the opening of the branch electric regulating valve. This dual-parameter dynamic adjustment mechanism has a fast response speed and no overshoot, and can continuously and strictly suppress the air flow velocity at the combustion point within the standard limit of 0.2m / s. Attached Figure Description

[0020] Figure 1 This is a front view of the integrated ventilation system of the conveyor belt combustion test chamber of the present invention; Figure 2 This is a top view of the integrated ventilation system of the conveyor belt combustion test chamber of the present invention; Figure 3 This is a side view of the integrated ventilation system of the conveyor belt combustion test chamber of the present invention.

[0021] In the diagram: 1. Low-disturbance smoke hood; 2. Variable diameter structure; 3. High-temperature resistant silicone gasket; 4. Variable frequency exhaust fan; 5. Primary filter unit; 6. Activated carbon adsorption unit; 7. Exhaust gas outlet; 8. Electric air volume regulating valve; 9. Combustion test chamber; 10. Fan outlet; 11. First-stage guide air duct; 12. Arc guide structure; 13. Wind speed sensor; 14. Sliding door; 15. Control box; 16. Second-stage guide air duct; 17. Smoke collection box; 18. Honeycomb rectifier mesh. Detailed Implementation

[0022] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is intended to include the plural form as well. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] Example 1 In a typical embodiment of the present invention, an integrated exhaust system for a conveyor belt combustion test chamber is proposed, such as... Figures 1 to 3As shown, the system mainly includes a combustion test chamber 9, a smoke collection box 17, a graded airflow duct, a variable frequency exhaust fan 4, and a waste gas purification unit. Specifically, the combustion test chamber 9 is placed inside a smoke collection box 17 to collect any smoke that may overflow during the test. The exhaust port of the combustion test chamber 9 is connected to a variable frequency exhaust fan 4 through a first graded airflow duct 11 to actively extract the smoke generated inside the combustion test chamber 9. Simultaneously, a low-disturbance smoke hood 1 is also installed inside the smoke collection box 17. This low-disturbance smoke hood 1 is connected to the same variable frequency exhaust fan 4 through a second graded airflow duct 16, thereby achieving effective collection of diffused smoke within the smoke collection box 17.

[0025] The low-disturbance smoke hood 1 is designed with a gradually expanding smoke collection chamber structure that is narrower at the top and wider at the bottom. This structure helps guide the airflow smoothly and reduces local eddies. Its opening covers the combustion test area of ​​the combustion test chamber 9 to ensure effective capture of rising smoke. Inside the opening, at least two layers of honeycomb rectifier mesh 18 are provided. The honeycomb rectifier mesh 18 can disperse and redistribute the concentrated airflow generated by the exhaust fan, thereby forming a large-area, uniform, and stable negative pressure airflow field below the low-disturbance smoke hood 1, effectively avoiding disturbance to the combustion flame below due to uneven suction.

[0026] One end of the graded flow guide duct is connected to the low-disturbance smoke hood 1, and the other end is connected to the air inlet of the variable frequency exhaust fan 4. The graded flow guide duct is equipped with a variable diameter structure 2, so that the cross-sectional shape of the entire duct smoothly transitions along the airflow direction, aiming to minimize airflow resistance and pressure loss. At the turning points of the duct, arc-shaped flow guide structures 12 are provided. The arc-shaped flow guide structure 12 can be an arc-shaped guide plate to guide the airflow to turn smoothly, further preventing smoke from accumulating at corners and forming turbulence.

[0027] The outlet 10 of the variable frequency exhaust fan 4 is connected to the exhaust gas purification unit. This purification unit consists of a primary filtration unit 5 and an activated carbon adsorption unit 6 arranged sequentially along the airflow direction, forming a two-stage purification process. The primary filtration unit 5 is mainly responsible for physical interception, removing larger particulate matter such as soot and soot carried in the flue gas. The subsequent activated carbon adsorption unit 6 utilizes the large specific surface area and strong adsorption properties of activated carbon to chemically adsorb various volatile organic compounds and toxic or irritating gaseous components in the flue gas, ensuring that the final emitted gas meets environmental protection requirements.

[0028] In this embodiment, the system also includes a wind speed closed-loop control module, comprising wind speed sensors 13 arranged at key monitoring points, a PLC controller serving as the control center, an airflow adjustment device for fine adjustment, and the variable frequency exhaust fan 4. The PLC controller is housed within a control box 15. Specifically, the wind speed sensors 13 are positioned in real-time in key areas near the combustion point and the low-disturbance smoke hood 1, continuously collecting actual wind speed data at these locations and transmitting it to the control box 15 immediately. The control box 15 has a preset wind speed threshold that meets the test standards. It compares the received real-time wind speed data with the preset threshold. Based on the deviation signal generated by the comparison result, the control box 15 generates corresponding control commands to automatically and precisely adjust the operating frequency of the variable frequency exhaust fan 4 (thus changing the fan speed and total exhaust volume), and simultaneously adjust the opening of the airflow adjustment device (such as an electric airflow adjustment valve 8) installed in the graded airflow duct. Through this dual adjustment mode, the airflow velocity near the combustion point is dynamically and precisely maintained within a stable and ideal range below the standard limit.

[0029] Furthermore, the wind speed closed-loop control module ensures continuous and stable operation throughout the entire conveyor belt combustion test, enabling uninterrupted monitoring and adjustment. Through the precise control of this module, the air velocity near the combustion point is consistently and strictly limited to an extremely low level of no more than 0.2 m / s throughout the entire test, thus providing a near-static air environment for the combustion test.

[0030] To obtain comprehensive and reliable wind speed data, the wind speed sensors 13 are arranged in three locations. Two of the wind speed sensors 13 are precisely arranged inside the two combustion test chambers 9 at a distance of 50 mm from the combustion point to obtain core data that most directly reflects the degree of influence of airflow on the flame. The remaining wind speed sensor 13 is arranged near the entrance of the low-disturbance smoke hood 1 to monitor the uniformity of the smoke collection airflow field and the overall suction effect.

[0031] In this embodiment, the inner wall of the low-disturbance smoke hood 1 is an arc-shaped curved surface, integrally bent from 304 stainless steel, which can buffer the rising smoke and further optimize the airflow path. Inside the hood opening, three layers of rectifier mesh with a regular hexagonal honeycomb structure, namely the honeycomb rectifier mesh 18, are arranged from top to bottom. These multi-layered honeycomb rectifier meshes 18 disperse the concentrated airflow, dispersing the single strong draft airflow into a uniform and gentle negative pressure airflow, preventing localized strong drafts from disturbing the surrounding airflow, and reducing air disturbance in the combustion zone from the source. The honeycomb rectifier mesh 18 is detachably fixed to the hood using a convenient snap-fit ​​method, facilitating daily cleaning and maintenance. Furthermore, a maintenance opening is specially provided on the side wall of the low-disturbance smoke hood 1, providing convenience for internal inspection and component replacement.

[0032] In this embodiment, the graded airflow duct is constructed entirely of thickened galvanized steel sheet welded together. The first graded airflow duct 11 and the second graded airflow duct 16, from one end connected to the low-disturbance smoke hood 1 to the other end connected to the fan, exhibit a smoothly tapering cross-section along the airflow direction. This tapering tube design facilitates airflow acceleration and maintains flow stability. An electric airflow regulating valve 8 is installed inside the duct. The valve's blades feature an aerodynamically designed arc-shaped guide vane and are driven by a micro servo motor, enabling rapid and precise adjustment of the opening and closing degree. Furthermore, dedicated sealing grooves are machined at each flange joint of the graded airflow duct, and high-temperature resistant silicone gaskets 3, capable of withstanding the high-temperature environment within the system, are installed within the grooves to ensure airtightness at the pipe connections.

[0033] Considering the potential for slight vibrations or installation errors between components, flexible sealing interfaces are provided at all connection points between the low-disturbance smoke hood 1, the first-stage guide duct 11, the second-stage guide duct 16, and the variable frequency exhaust fan 4. These flexible sealing interfaces are primarily composed of high-temperature resistant silicone rubber bellows, with a stainless steel wire support frame wound inside to maintain shape and pressure resistance. Flanges are located at both ends. During installation, the flanges align with the flanges of the mating components, and a high-temperature resistant silicone gasket 3 is added between them, thus forming a double-sealing structure combining the bellows' own sealing and the flange gasket sealing, preventing smoke leakage from the pipe joints.

[0034] In this embodiment, the primary filter unit 5 in the exhaust gas purification unit specifically uses pleated fiberglass filter cotton. Its numerous pleats provide a large filtration area, effectively intercepting solid impurities such as smoke particles and carbon ash in the flue gas. The activated carbon adsorption unit 6 is filled with columnar high-iodine-value activated carbon. This type of activated carbon has strong adsorption capacity and is particularly suitable for adsorbing complex volatile organic compounds and toxic and irritating gases in flue gas. For easy maintenance and replacement, both the primary filter unit 5 and the activated carbon adsorption unit 6 are designed with a drawer-type detachable structure, making operation simple.

[0035] It should be noted that the combustion test chamber 9 has a smoke exhaust opening at the top. Although the low-disturbance smoke hood 1 is mounted on the outside of the test chamber, the combustion test chamber 9 is not completely sealed. Therefore, when the variable frequency exhaust fan 4 is running, an axial negative pressure center is formed in the smoke collection box 17. This negative pressure is conducted into the combustion test chamber 9 through the smoke exhaust opening, forming a local induced airflow at the combustion point. By adopting a gradually expanding arc-shaped smoke collection chamber that is narrow at the top and wide at the bottom for the low-disturbance smoke hood 1, the average wind speed at the hood opening is naturally reduced by gradually increasing the cross-section of the chamber. At the same time, three layers of regular hexagonal honeycomb rectifier mesh 18 are arranged in layers on the inner side of the hood opening. By utilizing the forced diversion effect of the honeycomb channels, the originally concentrated axial suction negative pressure in the smoke collection chamber is dispersed into a gentle micro-negative pressure that is evenly distributed over a surface area. The honeycomb mesh eliminates localized turbulent dead zones and strong suction centers within the enclosure, while also blocking the downward induction of negative pressure into the combustion test chamber 9. This ensures that even if the exhaust is continuously turned on throughout the combustion test, the air velocity near the combustion point can still be suppressed within the standard limit.

[0036] In one specific embodiment of this invention, the variable frequency exhaust fan 4 is a low-power variable frequency centrifugal fan. The outer layer of the fan casing is wrapped with polyurethane sound insulation cotton to reduce the overall operating noise. The fan impeller uses forward-inclined arc-shaped noise-reducing blades, and the bottom of the fan is equipped with shock-absorbing rubber supports to block vibration from being transmitted to the air duct and combustion test chamber 9. The fan has a built-in variable frequency drive module, which can receive signals from the control box 15 to steplessly adjust the fan speed, achieving a continuously adjustable air volume of 500~1200m³ / h.

[0037] In one specific embodiment of this example, a sliding door 14 is provided on the smoke collection box 17, which can selectively isolate the combustion test area from the rest of the space.

[0038] In one specific embodiment of this example, the first staged airflow duct 11 and the second staged airflow duct 16 can be connected to a fan respectively, so that the smoke exhaust process in the combustion test chamber 9 and the smoke collection box 17 does not affect each other.

[0039] The principle of the integrated ventilation system for the conveyor belt combustion test chamber provided in this embodiment is as follows: During the conveyor belt combustion test, the sample is ignited inside the combustion test chamber. Because the combustion test chamber is not a completely sealed structure, approximately 85%–90% of the main flue gas, due to thermal buoyancy, directly enters the first-stage guiding air duct through the exhaust port at the top of the chamber; however, due to thermal convection and the influence of open-door observation, a small amount of diffused flue gas and toxic gases still escapes into the external environment. This invention integrates the entire combustion test chamber into a smoke collection box, where the escaping flue gas is captured in real-time by a low-disturbance smoke collection hood at the end of the second-stage guiding air duct. Both flue gas streams ultimately converge into the same variable frequency exhaust fan, achieving comprehensive flue gas collection throughout the entire test process and cutting off the path of toxic flue gas diffusion into the laboratory corridor at its source.

[0040] When a traditional ventilation system is started, the fan creates a strong axial suction center within the ductwork. This negative pressure is transmitted downwards through the exhaust opening of the test chamber, generating uncontrollable induced airflow at the combustion point, causing the flame to be pulled off course or even extinguished. To address this problem, this invention employs a gradually expanding arc-shaped cavity, narrower at the top and wider at the bottom, inside the smoke hood. As the cavity cross-section increases downwards, the average dynamic pressure at the hood opening naturally decreases. Simultaneously, three layers of regular hexagonal honeycomb rectifier mesh are arranged at the hood opening. Utilizing the forced damping effect of the duct walls, the originally concentrated strong axial negative pressure within the smoke collection cavity is dispersed into a uniformly distributed, gentle micro-negative pressure field. The honeycomb mesh eliminates localized turbulent dead zones and strong suction centers within the hood. While the ventilation continues, the combustion point does not experience the pulling force of the ventilation, thus avoiding the problem of flame morphology being disturbed by airflow.

[0041] After the rectifier network softens the basic flow field, the system further achieves precise speed control through a closed-loop wind speed control module. Among the three wind speed sensors, the core sensor located approximately 50mm from the combustion point uses high-frequency sampling to feed local flow velocity data back to the PLC controller in real time. The system has a built-in comparison threshold of 0.1~0.2 m / s: when combustion intensifies, causing a sudden increase in thermal buoyancy and the local flow velocity approaches the 0.2 m / s upper limit, the PLC does not simply reduce the frequency; instead, it simultaneously issues commands to lower the operating frequency of the variable frequency exhaust fan and reduce the opening of the arc-shaped flow regulating valves in the first / second stage air ducts. This dual-parameter adjustment of "total airflow + branch resistance" avoids the response lag caused by relying solely on frequency reduction. Conversely, when combustion enters the residual flame stage and thermal buoyancy weakens, causing the flow velocity to drop below 0.1 m / s, the system automatically increases the frequency and opens the valves to compensate for the slight negative pressure. The entire process strictly controls the flow velocity in the combustion zone within the standard allowable range.

[0042] During combustion, the extracted mixed flue gas first enters the primary filtration unit, where pleated fiberglass cotton intercepts carbon black and particulate matter. It then enters the activated carbon adsorption unit, where high-iodine-value columnar carbon adsorbs volatile organic compounds and irritating toxic gases. After the test, the system exits the closed-loop fine-tuning mode and switches to high-volume exhaust mode with a single button press. The fan operates at full load, using a short period of high airflow to thoroughly clean the residual smoke adhering to the surface of the smoke collection box and rectifier mesh. The purified gas that meets the standards is then discharged through the outdoor outlet. The entire process requires no manual intervention in starting and stopping the fan, ensuring occupational health and safety while guaranteeing the authenticity and reproducibility of each set of combustion test data.

[0043] Example 2 In a typical embodiment of the present invention, a method for operating an integrated ventilation system for a conveyor belt combustion test chamber is provided, the method comprising the following steps: S1. Before the formal ignition test of the conveyor belt sample, the system is first started for a no-load test run of the air duct and fan. During this stage, the entire exhaust duct system is checked and confirmed to have no gas leaks, and the monitoring functions of each wind speed sensor are verified to be normal, in preparation for the formal test.

[0044] S2. Once the conveyor belt sample is ignited and the combustion test officially begins, the system automatically switches to a low-volume, stable exhaust mode. At this time, the variable frequency exhaust fan operates at a pre-set low initial airflow. As the combustion gas rises, it first passes through the honeycomb rectifier mesh inside the smoke hood for uniform distribution and rectification, and then is smoothly drawn into the connected graded guide duct by the smoke hood.

[0045] S3. Throughout the entire combustion test, the wind speed closed-loop control module operates continuously. Through real-time monitoring and feedback adjustment, it stably and precisely controls the wind speed at key points in the combustion zone within the ideal range of 0.1~0.2 m / s. This results in a gentle airflow, avoiding any unnecessary disturbance to the combustion flame due to airflow fluctuations, thus ensuring the stability and repeatability of the test conditions.

[0046] S4. When the combustion test ends as planned and the sample stops burning, the system operating mode is switched. The variable frequency exhaust fan switches to high airflow exhaust mode to quickly remove residual smoke and potentially harmful gases remaining in the test chamber, fume hood, and ductwork, preparing a clean and safe environment for subsequent operations or the next test. In this mode, the variable frequency exhaust fan operates continuously at full load power, quickly and thoroughly removing all residual smoke from the combustion test chamber and its connected piping system, ensuring a clean internal environment after the test and preparing for the next test. S5. Flue Gas Treatment Process: The flue gas being extracted first passes through a primary filtration interception device to remove larger particles of smoke and dust and impurities. Subsequently, the flue gas enters an activated carbon adsorption purification unit, where the high-efficiency adsorption performance of activated carbon is used to deeply remove harmful gas components and odor substances from the flue gas. After the above two-stage purification treatment, the clean gas that finally meets the emission standards is safely and environmentally compliantly discharged through an outdoor exhaust outlet.

[0047] In this embodiment, the PLC controller uses a built-in control algorithm to dynamically compare and judge the continuously monitored real-time airflow velocity with a preset velocity threshold range: when the detected real-time velocity is higher than the preset upper limit of 0.2 m / s, the system will automatically reduce the operating frequency of the variable frequency exhaust fan to reduce its suction power and simultaneously reduce the opening of the air volume regulating device to reduce the air intake; conversely, when the detected real-time velocity is lower than the preset lower limit of 0.1 m / s, the system will automatically increase the operating frequency of the variable frequency exhaust fan to enhance its suction power and simultaneously increase the opening of the air volume regulating device to increase the air intake. Through the above closed-loop feedback regulation mechanism, the system can intelligently and accurately control the airflow velocity at the combustion point continuously and stably within the optimal working range of 0.1~0.2 m / s, thereby ensuring the constancy of combustion test conditions and the reliability of test results.

[0048] In this embodiment, a touch screen is installed on the outside of the control box, which can manually switch between low air volume test mode and high air volume exhaust mode, and has functions such as real-time wind speed display, fault alarm, and running time recording.

[0049] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. An integrated ventilation system for a conveyor belt combustion test chamber, characterized in that, The system includes a combustion test chamber, which is placed inside a smoke collection box; the exhaust port of the combustion test chamber is connected to a variable frequency exhaust fan through a first-stage guide air duct; a low-disturbance smoke collection hood is installed inside the smoke collection box, and the low-disturbance smoke collection hood is connected to the variable frequency exhaust fan through a second-stage guide air duct. The low-disturbance smoke hood is a gradually expanding smoke collection chamber structure that is narrow at the top and wide at the bottom. The hood opening covers the combustion test area of ​​the combustion test chamber. The hood opening is equipped with at least two layers of honeycomb rectifier mesh to disperse the exhaust airflow into a uniform negative pressure airflow. One end of the graded air duct is connected to the low-disturbance smoke hood, and the other end is connected to the air inlet of the variable frequency exhaust fan. The cross-section of the duct smoothly transitions along the airflow direction, and an arc-shaped guide plate is provided at the turning point of the duct. The outlet of the variable frequency exhaust fan is connected to the exhaust gas purification unit, which includes a primary filtration unit and an activated carbon adsorption unit arranged sequentially along the airflow direction.

2. The integrated ventilation system for the conveyor belt combustion test chamber as described in claim 1, characterized in that, It also includes a wind speed closed-loop control module, which includes a wind speed sensor, a PLC controller, an air volume regulating device, and the variable frequency exhaust fan arranged near the combustion point and the smoke hood. The wind speed sensor collects wind speed data in the combustion area in real time and transmits it to the PLC controller. The PLC controller automatically adjusts the operating frequency of the variable frequency exhaust fan and the opening of the air volume regulating device in the graded air duct according to the comparison result between the received wind speed data and the preset threshold, so as to maintain the air velocity near the combustion point below the standard limit.

3. The integrated ventilation system for the conveyor belt combustion test chamber as described in claim 2, characterized in that, The wind speed closed-loop control module runs continuously throughout the entire process of the conveyor belt combustion test, and the air velocity near the combustion point never exceeds 0.2 m / s.

4. The integrated ventilation system for the conveyor belt combustion test chamber as described in claim 2, characterized in that, The wind speed sensor consists of three sets, with at least one set positioned 50 mm from the combustion point and the rest positioned near the smoke hood.

5. The integrated ventilation system for the conveyor belt combustion test chamber as described in claim 1, characterized in that, The inner wall of the low-disturbance smoke hood is an arc-shaped curved surface. The inside of the hood opening is arranged in three layers of regular hexagonal honeycomb rectifier mesh from top to bottom. The rectifier mesh is detachably fixed to the inside of the hood by buckles. The side wall of the smoke hood is provided with an inspection opening.

6. The integrated ventilation system for the conveyor belt combustion test chamber as described in claim 1, characterized in that, The graded airflow duct has a smooth tapering section from the smoke hood connection end to the fan installation end; the graded airflow duct is equipped with an electric airflow regulating valve, the blades of which are arc-shaped guide vanes and driven by a micro servo motor; the splicing flange of the graded airflow duct is provided with a sealing groove, and a high-temperature resistant sealing gasket is installed in the sealing groove.

7. The integrated ventilation system for the conveyor belt combustion test chamber as described in claim 1, characterized in that, The connection points between the low-disturbance smoke hood, the graded air duct, and the variable frequency exhaust fan are all equipped with flexible sealing interfaces. The flexible sealing interface includes a high-temperature resistant silicone rubber bellows, with a stainless steel wire support frame wound inside the bellows. Both ends of the bellows are provided with flange pressing edges, and a high-temperature resistant sealing gasket is provided between the flange pressing edges and the mating flange to form a double seal.

8. The integrated ventilation system for the conveyor belt combustion test chamber as described in claim 1, characterized in that, The primary filtration unit uses pleated fiberglass filter cotton to intercept smoke particles and carbon ash impurities; the activated carbon adsorption unit is filled with columnar high-iodine-value activated carbon to adsorb volatile organic compounds and toxic and irritating gases in the flue gas; both the primary filtration unit and the activated carbon adsorption unit are drawer-type detachable structures.

9. A method for operating the integrated exhaust system of the conveyor belt combustion test chamber as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Before the test ignition, the air duct and fan were run under no-load to confirm that there was no leakage and the wind speed monitoring was normal. S2. After the sample is ignited on the conveyor belt, it automatically enters the low air volume stable exhaust mode. The variable frequency exhaust fan runs at the initial air volume. The flue gas is diverted by the honeycomb rectifier mesh and then drawn into the graded guide air duct by the smoke collection hood. S3. Throughout the entire combustion test, the wind speed in the combustion zone is continuously and stably controlled at 0.1~0.2m / s, with gentle airflow and no flame disturbance; S4. After the combustion test is completed, switch to high air volume exhaust mode. The variable frequency exhaust fan runs at full load to remove the residual smoke from the combustion test chamber and pipeline. S5. The exhaust gas is sequentially filtered and purified by activated carbon adsorption before being discharged into the outdoor exhaust outlet in compliance with standards.

10. The working method of the integrated exhaust system of the conveyor belt combustion test chamber as described in claim 9, characterized in that, The PLC controller compares the real-time flow rate with a preset threshold: when the detected flow rate is higher than 0.2 m / s, it automatically lowers the operating frequency of the variable frequency exhaust fan and simultaneously reduces the opening of the air volume regulating device; when the detected flow rate is lower than 0.1 m / s, it automatically increases the fan frequency and increases the opening of the air volume regulating device, so that the flow rate at the combustion point remains stable within the range of 0.1~0.2 m / s.

Images