Test device and test method for explosion hazard of combustible dust wall surface desorption process

Abstract

The application relates to a testing device and a testing method for the explosion risk of combustible dust wall surface desorption process, and belongs to the technical field of industrial dust explosion protection. The device comprises a device body, a powder spraying system and an ignition device. The bottom end of the device body is connected with the powder spraying system, and the ignition device is installed on the explosion-proof glass of the device body. The device should have the capability of testing the wall surface adsorbed dust load. On the premise, the explosion risk of the ignited wall surface attached dust due to the falling of the dust cloud caused by the accumulation of dust fire load, vibration and other causes is tested. The testing method and the device not only have the testing analysis of the wall surface adsorbed dust capacity, but also can perform the grading evaluation of the explosion risk of the wall surface attached dust after falling, and have the characteristics of operation safety.

Description

Technical Field

[0001] This invention belongs to the field of industrial dust explosion protection technology, and specifically relates to a testing device and method for testing the explosion hazard of combustible dust desorption process on walls. Background Technology

[0002] In the powder processing industry, over 70% of powder materials are flammable, meaning that the vast majority of enterprises handling powder are at risk of dust explosions. To assess the explosion risk of combustible dust, a complete set of dust cloud explosiveness testing standards has been promulgated both domestically and internationally to test and analyze the explosion hazard of combustible dust clouds under actual production conditions. For example, GB / T 16429-1996 and ASTM E1491-2006 test the minimum surface temperature at which a dust cloud is ignited under the influence of a high-heat surface; CEI IEC 61241-2-3-1994 and ASTM E2019-200 test the ignition sensitivity of a dust cloud by an electrical spark; and GB / T 16426-1996 and BS EN14034-2-2006 test the explosion pressure and pressure rise rate of a dust cloud after ignition. All of the above-mentioned test methods and devices for the fire and explosion hazards of combustible dust employ a single-pass airflow to form a combustible dust cloud. In addition, there is another way to form combustible dust clouds in actual industrial production processes. Combustible dust adhering to the wall surface is desorbed due to heat radiation, vibration and other reasons, and then falls off by gravity to form a dust cloud. This wall surface condition where combustible dust is easily attached is widely found in dust collectors, dust storage silos, dust operation workshops and other places in dust explosion-prone enterprises.

[0003] However, there is currently no specific, systematic, standard testing method or supporting equipment for assessing the explosion hazard of combustible dust during wall desorption. Existing standards for combustible dust clouds, such as GB / T 16429-1996, do not address the dust cloud formation conditions associated with wall detachment. The paper "Experimental Study on the Influence of Initial Turbulence on Dust Explosion" demonstrates that the dispersion method significantly affects the turbulence of the dust cloud, thus severely impacting the ignition and explosion hazard of combustible dust. In other words, existing testing devices and methods cannot accurately assess the explosion hazard of combustible dust clouds formed by wall detachment in actual production. Therefore, this paper proposes a testing device and method for assessing the explosion hazard of combustible dust during wall desorption. Summary of the Invention

[0004] The purpose of this invention is to provide a testing device and method for testing the explosion hazard of combustible dust desorption process on a wall. It can test and analyze the influence of factors such as dust particle size, wall material and roughness on the wall's ability to adsorb dust, and on this basis, determine the ignition and explosion characteristics of the adsorbed dust after it falls off and forms a cloud. It has the characteristics of high testing safety.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A testing device for the explosion hazard of combustible dust desorption process on a wall surface includes a device body, a powder spraying system, and an ignition device; the bottom of the device body is connected to the powder spraying system, and an ignition device is installed on the explosion-proof glass of the device body.

[0007] The device body includes a frame, which is composed of angle steel connected in sequence to form a quarter-cylindrical frame. The bottom end of the frame is sealed by installing a quarter-right-angle sector plate. The sector plate has a container mounting through hole near the right angle side. A foldable container is installed at the container mounting through hole on the outside of the frame. The bottom end of the foldable container is connected to the dust nozzle of the powder spraying system. Explosion-proof glass is installed on the arc part of the frame. The test wall is installed on the two sides and the top surface of the frame. The right angle of the angle steel of the combined frame restricts the position to form a quarter-hollow cylindrical space. Explosion-proof glass has explosion vents and through holes for the ignition end of the ignition device to pass through. A micro vibrator is installed on the explosion-proof glass.

[0008] The powder spraying system includes an air compressor, which is connected in sequence to an air tank, an air distribution tank, and a nozzle assembly via pipelines. An electromagnetic pulse valve and a manual pressure reducing valve are installed between the air tank and the air distribution tank. The electromagnetic pulse valve is connected to a pulse controller. A one-way valve is installed between the air distribution tank and the spray pipe assembly.

[0009] The blowpipe assembly includes a blowpipe, a nozzle, and a connector therebetween. One end of the blowpipe is connected to the outlet of a one-way valve, and the other end is connected to the nozzle via the connector. A diffuser is mounted on the nozzle, which is located at the bottom of the collapsible container and connected to an opening at the bottom of the collapsible container.

[0010] The ignition device employs either an electric spark generator or a silicon nitride ignition rod.

[0011] A high-speed camera and an infrared thermal imager are mounted on the outside of the frame, facing the explosion-proof glass.

[0012] A testing device for the explosion hazard of combustible dust desorption process on walls, and a testing method for the dust adsorption capacity of different walls and the ignition of adsorbed dust, including the following steps:

[0013] Step 1: Make two rectangular walls and a quarter-circle fan-shaped wall from the wall of a certain material to be tested. Clean the wall to be tested with a brush and measure the original mass of each wall with an electronic balance. Then install them on the two sides and top of the frame and fix the rectangular and fan-shaped walls to the frame with T-bolts and nuts.

[0014] Step 2: Clean the inside of the device with a brush and then turn on the powder spraying system to add the powder to be tested into the collapsible container;

[0015] Step 3: Turn on the powder spraying system, set the spraying frequency and time through the pulse controller, and after the suspended dust falls and disappears, remove the test wall surface, use an electronic balance to measure the mass of each tested wall surface after adsorbing dust, and calculate the mass of dust adsorbed by each wall surface to evaluate the wall surface's ability to adsorb dust.

[0016] Step 4: Reinstall the test wall in its original position, add a quantitative amount of test powder to the bottom foldable container; turn on the powder spraying system to saturate the wall with dust, then turn off the powder spraying system and wait for the suspended dust to settle and disappear.

[0017] Step 5: When the ignition end of the ignition device passes through the hole on the explosion-proof glass to the predetermined position and the power is turned on, observe whether the dust falling off the wall can be ignited.

[0018] The technical effects of this invention are as follows:

[0019] The device should first be capable of testing the dust adsorption load on a wall surface. Under this premise, it should then test the explosion hazard of dust adhering to the wall surface that, due to factors such as accumulated dust fire load and vibration, detaches and forms a dust cloud, which can then be ignited. This testing method and device not only test and analyze the dust adsorption capacity of walls but also perform a graded evaluation of the explosion hazard after the adsorption of combustible dust from the wall surface, while also being operationally safe. Therefore, it is essential to systematically test and analyze the dust adsorption capacity of different walls and the explosion hazard of dust clouds formed after the desorption of combustible dust from the wall surface, thereby improving existing testing conditions for the ignition and explosion hazards of combustible dust and filling the gaps in current combustible dust ignition testing. Attached Figure Description

[0020] Figure 1 Structural schematic diagram of a testing device for the explosion hazard of combustible dust desorption process on wall surfaces;

[0021] Figure 2 A schematic diagram of the frame of a testing device for the explosion hazard of combustible dust desorption process on a wall surface;

[0022] Figure 3 A schematic diagram of the needle tip electrode of an electric spark generator used in a test device for the explosion hazard of combustible dust desorption process on a wall surface.

[0023] Figure 4 A schematic diagram of a silicon nitride ignition rod for a testing device used to assess the explosion hazard of combustible dust desorption from a wall surface.

[0024] 1-Frame, 2-Fan-shaped plate, 3-Through hole, 4-Foldable container, 5-Explosion-proof glass, 6-Explosion vent, 7-Filter cloth, 8-Miniature vibrator, 9-Air compressor, 10-Gas bag, 11-Gas distribution tank, 12-Puff pipe, 13-Scatterer, 14-One-way valve, 15-Electromagnetic pulse valve, 16-Manual pressure reducing valve, 17-Pulse controller, 18-Ignition device, 19-High-speed camera, 20-Infrared thermal imager. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0026] like Figures 1 to 4 As shown, the test device for the explosion hazard of combustible dust desorption process on the wall includes a device body, a powder spraying system and an ignition device 18; the bottom end of the device body is connected to the powder spraying system, and the ignition device is installed on the explosion-proof glass 5 of the device body.

[0027] The device body includes a frame 1, which is composed of angle steel connected in sequence to form a quarter-cylindrical frame. The bottom end of the frame 1 is sealed by a quarter-right-angle sector plate 2. The sector plate 2 has a container mounting through hole near the right angle side. A foldable container 4 is installed at the container mounting through hole. The foldable container 4 is made of stainless steel and its bottom end is connected to the dust nozzle of the powder spraying system. An explosion-proof glass 5 is installed on the arc part of the frame 1 as an observation window for observing the experimental process. The test wall is installed on the two sides and the top surface of the frame 1, and the right angle of the angle steel of the combined frame 1 forms a quarter-hollow cylindrical space. An explosion vent 6 is opened in the middle of the lower part of the explosion-proof glass 5. The explosion vent 6 is 5cm above the bottom and a filter cloth 7 is attached to the explosion vent 6 to prevent dust from leaking out of the explosion vent 6 during powder spraying. Through holes 3 are opened on both sides of the explosion-proof glass 5 below the explosion vent 6 for the ignition end of the ignition device to pass through. A micro vibrator 8 is installed on the bottom left side of the explosion-proof glass 5. In this embodiment, the radius of the sector plate 2 is 25cm, the height of the frame 1 is 40cm, and the volume is 19.635L, which can be compared with a 20L dust explosion test sphere. The explosion relief vent 6 has a size of 5cm×5cm. The foldable container 4 has a large opening at the top and a small opening at the bottom. It is an axially foldable container. When fully folded, it forms a circle, with the bottom located in the middle of the circle and the top located at the edge of the circle. The diameter of the top opening is 10cm, which is used to connect with the container mounting through hole of the sector plate 2, and the bottom opening is used to connect with the nozzle.

[0028] The powder spraying system includes an air compressor 9, which is connected in sequence to an air tank 10, an air distribution tank 11, and a nozzle assembly via pipelines. An electromagnetic pulse valve 15 and a manual pressure reducing valve 16 are installed between the air tank 10 and the air distribution tank 11. The electromagnetic pulse valve 15 is connected to a pulse controller 17. A one-way valve 14 is installed between the air distribution tank 11 and the spray pipe assembly.

[0029] The blowpipe assembly includes a blowpipe 12 and a nozzle. One end of the blowpipe 12 is connected to the outlet of the one-way valve 14, and the other end is connected to the nozzle. A diffuser 13 is installed on the nozzle. The nozzle is located at the bottom of the foldable container 4 and connected to the opening at the bottom of the foldable container 4.

[0030] The ignition device 18 employs either an electric spark generator or a silicon nitride ignition rod for ignition. In the electric spark generator and ignition device, the high-voltage power supply output voltage of the electric spark generator is 5kV to 30kV. The selectable capacitors for the capacitor bank are 20pF, 60pF, 200pF, 600pF, 2nF, 6nF, 20nF, and 1μF. The output energy (ignition energy) is sequentially set to 1mJ, 3mJ, 10mJ, 30mJ, 100mJ, 300mJ, 1000mJ, and 50J. The output energy is calculated using the formula E = CU² / 2, where E is the output energy, C is the capacitor, and U is the output voltage.

[0031] The temperature of the silicon nitride ignition rod is controlled by the power supply voltage and can be adjusted within the range of 400-1000℃.

[0032] A high-speed camera 19 and an infrared thermal imager 20 are installed on the outside of the frame 1. The high-speed camera 19 and the infrared thermal imager 20 are facing the explosion-proof glass 5 and are used to capture and record the process of dust layer ignition during spark discharge, causing dust adsorbed on the wall surface to fall off, ignite, and explode, as well as the temperature distribution.

[0033] The typical wall or ceiling surface characteristics depend primarily on the decorative materials used. Common materials include lime plaster, latex paint (different construction techniques also affect surface characteristics), gypsum board, wall tiles (including glazed tiles, speckled glazed tiles, and unglazed tiles), plywood, wood panels, fiber ceiling panels, and plastic panels. If the wall surface has no decorative materials, it is generally a bare brick wall, profiled steel sheet, or cement wall. Different wall surface characteristics have varying abilities to adsorb dust, significantly influencing the development and occurrence of combustible dust explosions.

[0034] A testing device for the explosion hazard of combustible dust desorption process on walls, and a testing method for the dust adsorption capacity of different walls and the ignition of adsorbed dust, including the following steps:

[0035] Step 1: Prepare two rectangular walls of 250mm×400mm and a quarter-circle fan-shaped wall of 250mm radius from the wall of a certain material to be tested. Clean the wall to be tested with a brush and measure the original mass of each wall with an electronic balance. Then install them on the two sides and top of frame 1 and fix the rectangular and fan-shaped walls to frame 1 with T-bolts and nuts.

[0036] Step 2: Clean the inside of the device with a brush and then turn on the powder spraying system to add the powder to be tested into the collapsible container;

[0037] Step 3: Turn on the powder spraying system, set the spraying frequency and time using the pulse controller, and after the suspended dust has settled and disappeared, remove the test wall surface. Use an electronic balance to measure the mass of dust adsorbed on each tested wall surface, and calculate the mass of dust adsorbed on each wall surface to evaluate the wall surface's dust adsorption capacity. The spraying time is 30s, 60s, 90s, and 180s. Then repeat this step to measure the maximum dust adsorption capacity of the wall surface.

[0038] Step 4: Reinstall the test wall in its original position, add a quantitative amount of test powder to the bottom foldable container 4; turn on the powder spraying system to saturate the wall with dust, then turn off the powder spraying system and wait for the suspended dust to settle and disappear.

[0039] Step 5: When the ignition end of the ignition device 18 passes through the through hole 3 on the explosion-proof glass 5 and the power is turned on, observe whether the dust falling off the wall can be ignited; at the same time, turn on the high-speed camera 19 and the infrared thermal imager 20 to observe and record the dust inside the device body, and transfer the recorded data to the computer.

[0040] When the ignition device 18 in step 5 uses an electric spark generator, the positive and negative needle electrodes are passed through the through hole 3 reserved on the explosion-proof glass 5, the power is turned on, the electric spark generator of the ignition device is started, and the electric spark generator is controlled to output the highest energy; the micro vibrator 8 is turned on to make the dust on the test wall fall off and form a dust cloud, and observe whether the electric spark can ignite the dust cloud that has fallen off the test wall.

[0041] The observation results include the following two types:

[0042] 1) Dust falling off the wall surface forms a dust cloud, which is ignited by an electric spark;

[0043] 2) Dust that fell off the wall surface formed a dust cloud that was not ignited by an electric spark.

[0044] When the ignition device 18 in step 5 uses a silicon nitride ignition rod, the silicon nitride ignition rod is passed through the through hole 3 reserved on the explosion-proof glass 5, the power is turned on, and the foldable container 4 is adjusted to the contracted state. At this time, the remaining powder to be tested in the container will bury the silicon nitride ignition rod. The power output voltage is adjusted to make the temperature of the silicon nitride ignition rod the highest.

[0045] The observation results include the following four types:

[0046] 1) If the accumulated dust is not ignited and no fire occurs, it indicates that the accumulated dust is not sensitive to ignition under the action of a high-temperature heat source.

[0047] 2) The accumulated dust was ignited by the silicon nitride igniter, resulting in a sustained fire spread, but the flame did not cause the dust adsorbed on the wall to fall off and form a dust cloud.

[0048] 3) Accumulated dust was ignited by a silicon nitride igniter, resulting in a sustained fire spread. The flame caused dust adsorbed on the wall to fall off, forming a dust cloud, but it did not cause a fire or explosion of the dust cloud.

[0049] 4) Accumulated dust is ignited by a silicon nitride igniter, causing a sustained fire spread. The flame causes dust adsorbed on the wall to fall off, forming a dust cloud, which then causes a fire and explosion of the dust cloud.

Claims

1. A testing device for the explosion hazard of combustible dust desorption process on a wall surface, characterized in that, It includes a device body, a powder spraying system, and an ignition device; the bottom of the device body is connected to the powder spraying system, and an ignition device is installed on the explosion-proof glass of the device body. The device body includes a frame, which is composed of angle steel connected in sequence to form a quarter-cylindrical frame. The bottom of the frame is sealed by installing a right-angled sector plate. The sector plate has a container mounting through hole near the right angle side. A foldable container is installed at the container mounting through hole on the outside of the frame. The bottom of the foldable container is connected to the nozzle of the powder spraying system. Explosion-proof glass is installed on the arc part of the frame. The test wall is installed on the two sides and the top surface of the frame. The right angle of the angle steel of the combined frame restricts the position to form a quarter-hollow cylindrical space. Explosion-proof glass has explosion vents and through holes for the ignition device to pass through. A micro vibrator is installed on the explosion-proof glass. The powder spraying system includes an air compressor, which is connected in sequence to an air tank, an air distribution tank, and a spray pipe assembly via pipelines. An electromagnetic pulse valve and a manual pressure reducing valve are installed between the air tank and the air distribution tank. The electromagnetic pulse valve is connected to a pulse controller. A one-way valve is installed between the air distribution tank and the spray pipe assembly. The blowpipe assembly includes a blowpipe, a nozzle, and a connector between them. One end of the blowpipe is connected to the outlet of a one-way valve, and the other end is connected to the nozzle via the connector. A diffuser is installed on the nozzle, which is located at the bottom of the collapsible container and connected to the opening at the bottom of the collapsible container.

2. The testing device for the explosion hazard of combustible dust desorption process on a wall surface according to claim 1, characterized in that: The ignition device employs either an electric spark generator or a silicon nitride ignition rod.

3. The testing device for the explosion hazard of combustible dust desorption process on a wall surface according to claim 1, characterized in that: A high-speed camera and an infrared thermal imager are mounted on the outside of the frame, facing the explosion-proof glass.

4. The testing device for the explosion hazard of combustible dust desorption process on a wall surface according to claim 1, and the testing method for the dust adsorption capacity of different wall surfaces and the ignition of adsorbed dust, are characterized in that... Includes the following steps: Step 1: Make two rectangular walls and a quarter-circle sector wall from the wall of a certain material to be tested. Clean the wall to be tested with a brush and measure the original mass of each wall with an electronic balance. Then install them on the two sides and top of the frame and fix the rectangular and sector walls to the frame with screws and nuts. Step 2: Clean the inside of the device with a brush, then turn on the powder spraying system and add the powder to be tested into the collapsible container; Step 3: Turn on the powder spraying system, set the spraying frequency and time through the pulse controller, and after the suspended dust falls and disappears, remove the test wall surface, use an electronic balance to measure the mass of each tested wall surface after adsorbing dust, and calculate the mass of dust adsorbed by each wall surface to evaluate the wall surface's ability to adsorb dust. Step 4: Reinstall the test wall in its original position, add a quantitative amount of test powder to the bottom foldable container; turn on the powder spraying system to saturate the wall with dust, then turn off the powder spraying system and wait for the suspended dust to settle and disappear. Step 5: When the ignition end of the ignition device passes through the hole in the explosion-proof glass and the power is turned on, observe whether the dust falling off the wall can be ignited.

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