Device and method for testing lowest ignition temperature of wood-bamboo dust cloud

Abstract

The invention provides a device and a method for testing the lowest ignition temperature of wood-bamboo dust cloud, which can form uniform and stable dust cloud, truly simulate the states of flammable dust cloud with different particle sizes, and are convenient to observe and accurate and reliable in test result. The testing device comprises a compressed air inlet pipe, a heat-resistant glass pipeline, a heating furnace, a funnel-shaped dust storage device and an electric control feeding valve, and the heating furnace comprises a transparent quartz tube with a horizontal tube section and a vertical tube section, a horizontal tube section heating unit, a vertical tube section heating unit, a horizontal thermocouple and a vertical thermocouple; and the compressed air inlet pipe, the heat-resistant glass pipeline and the horizontal pipe section are sequentially communicated. The testing method comprises the following steps: installing and debugging the testing device, opening the electric control feeding valve, spraying dust into the quartz tube to form dust cloud, observing the ignition condition in the quartz tube, repeatedly adjusting the heating temperature according to GB / T16429-1996, recording the temperature, and determining the lowest ignition temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of research on the combustion and explosion of combustible dust clouds during the production and processing of forest products industry, and specifically relates to a device and method for testing the lowest ignition temperature of wood and bamboo dust clouds during the production and processing of wood and bamboo products. Background Art

[0002] During the production and processing of wood and bamboo products, a large amount of combustible dust such as wood powder and bamboo powder is often generated. The combustible dust is centrally processed through dust removal facilities. Since the dust transportation pipeline is mostly in a dry state during transportation, it is easy to generate friction and collision during transportation, resulting in temperature rise. After reaching the ignition point under certain temperature conditions, it will instantly burn and release a large amount of energy, forming an explosion wave and explosion flame and causing a sudden increase in pressure, inducing dust explosion accidents and causing serious personal injuries and economic losses. Therefore, dust explosion prevention has become an important research topic for the wood and bamboo processing industry to prevent and contain major accidents.

[0003] Currently, the testing and research on the combustion and explosion parameters of dust clouds by domestic and foreign scientific research institutions and enterprises mostly follow the requirements of relevant industry standards. The lowest ignition temperature of the dust cloud is the main index for evaluating the ignition difficulty of wood and bamboo dust, and is the core parameter for characterizing the combustion and explosion risk of combustible dust, which can help us understand the ignition mechanism of the dust cloud. The testing method and device for the lowest ignition temperature of the dust cloud mainly rely on the "Determination Method for the Lowest Ignition Temperature of Dust Clouds" (GB / T 16429-1996). The testing device described in the standard mainly blows a certain mass of dust from the dust storage into the furnace tube of the heating furnace through compressed air to form a dust cloud, so that the combustible dust is evenly distributed in the furnace tube, and the lowest ignition temperature of the dust cloud is determined by controlling the stepped temperature in the furnace tube and observing whether there is a flame formation in the dust cloud in the furnace tube within the specified time.

[0004] However, there are many types of wood and bamboo, and there are great differences in physical properties such as density and microscopic structure. In addition, the dust is formed under various product processing technologies and different cutting parameter conditions, and there are large differences in the particle size composition and geometric shape of the dust particles. It is difficult for the dust particles to instantaneously form a dust cloud during the falling process. Moreover, since it is transported into the furnace tube by compressed air in a top-down manner, it is easy to form turbulence in the furnace tube, resulting in uneven distribution of the dust during the falling process, poor dust cloud effect, and affecting the accuracy of the determination of the lowest ignition temperature of the dust and the reliability of explosion prevention.

[0005] In addition, in actual production, combustible dust is generally generated by multiple working stations and transported through the conveying pipeline of the dust suction device to the dust collector for collection and treatment. During this process, when the combustible dust is transported in the pipeline, it does not move in a single horizontal or vertical direction, nor is it a dust cloud with a uniform spatial distribution. However, the test conditions require that the concentration and particle size distribution of the dust cloud are basically constant, which not only increases the complexity of raw material screening during the test, but also the measured data cannot reflect the actual situation during the production process, and the research results still cannot prevent the occurrence of dust explosion accidents in actual production.

[0006] Therefore, it is of great significance to develop a combustible dust combustion and explosion performance test device that can meet the actual process conditions and truly simulate and characterize the lowest ignition temperature of the combustible dust cloud under the actual process conditions. Summary of the Invention

[0007] The object of the present invention is to provide a test device for the lowest ignition temperature of wood and bamboo dust clouds, which can prevent dust aggregation, form a uniform and stable dust cloud, can truly simulate the states of combustible dust clouds with different particle sizes under actual process conditions, has strong adaptability, is convenient to observe, can perform real-time characterization of the lowest ignition temperature of the combustible dust cloud, and the test results are more accurate and reliable, providing technical support for revealing the mechanism of combustible dust combustion and explosion and improving the technical level of on-site prevention and control equipment.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A test device for the lowest ignition temperature of wood and bamboo dust clouds includes a compressed air inlet pipe, a heat-resistant glass pipe, a heating furnace, a funnel-shaped dust storage, and an electric control feeding valve. The heating furnace includes a transparent quartz tube having a horizontally connected section and a vertically connected section, a horizontal tube section heating unit and a vertical tube section heating unit for heating the horizontal tube section and the vertical tube section respectively, a horizontal thermocouple and a vertical thermocouple extending into the horizontal tube section and the vertical tube section respectively; the compressed air inlet pipe, the heat-resistant glass pipe, and the horizontal tube section are connected in sequence; the bottom outlet of the funnel-shaped dust storage is communicated with the dust inlet on the pipe wall of the heat-resistant glass pipe through the electric control feeding valve.

[0010] As a further improvement of the above test device for the lowest ignition temperature of wood and bamboo dust clouds, a rectifying plate with openings is provided inside the heat-resistant glass pipe, so that the compressed air after passing through the rectifying plate forms a uniformly distributed conveying air flow; the rectifying plate is located between the air inlet end where the heat-resistant glass pipe is connected to the compressed air inlet pipe and the dust inlet.

[0011] As a further improvement to the above-mentioned minimum ignition temperature testing device for wood and bamboo dust clouds, the rectifying plate comprises multiple pieces, and the multiple rectifying plates are arranged at intervals inside the heat-resistant glass pipe between the air inlet end of the heat-resistant glass pipe and the dust inlet. From the air inlet end of the heat-resistant glass pipe to the dust inlet, the opening rate of each rectifying plate increases.

[0012] As a further improvement to the above-mentioned minimum ignition temperature testing device for wood and bamboo dust clouds, there are three rectifying plates, namely, a large-hole rectifying plate, a medium-hole rectifying plate, and a small-hole rectifying plate with opening rates of 60%, 75%, and 90% respectively.

[0013] As a further improvement to the above-mentioned minimum ignition temperature testing device for wood and bamboo dust clouds, the horizontal pipe section heating unit and the vertical pipe section heating unit include resistance wires wound around the outer walls of the horizontal pipe section and the vertical pipe section.

[0014] As a further improvement to the above-mentioned minimum ignition temperature testing device for wood and bamboo dust clouds, it includes a controller, and the horizontal pipe section heating unit, the vertical pipe section heating unit, the horizontal thermocouple, the vertical thermocouple, and the electric control feeding valve are all connected to the controller.

[0015] As a further improvement to the above-mentioned minimum ignition temperature testing device for wood and bamboo dust clouds, it includes an anemometer extending into the horizontal pipe section for measuring the wind speed in the horizontal pipe section, and a differential pressure gauge for measuring the pressure difference before and after the rectifying plate; the anemometer and the differential pressure gauge are both connected to the controller.

[0016] As a further improvement to the above-mentioned minimum ignition temperature testing device for wood and bamboo dust clouds, it includes a data acquisition card and a USB interface connected to the controller. The data acquisition card is electrically connected to the anemometer, the differential pressure gauge, the horizontal thermocouple, and the vertical thermocouple for collecting wind speed, pressure, and temperature data.

[0017] As a further improvement to the above-mentioned minimum ignition temperature testing device for wood and bamboo dust clouds, the heat-resistant glass pipe is a Z-shaped transparent glass pipe.

[0018] As a further improvement to the above-mentioned minimum ignition temperature testing device for wood and bamboo dust clouds, the heat-resistant glass pipe is connected to the horizontal pipe section through a connecting flange.

[0019] The present invention also provides a method for testing the minimum ignition temperature of wood and bamboo dust clouds. It is easy to operate, can be applied to dusts of different particle sizes, truly reflects the specific application scenarios in the actual production process, and has good repeatability and accurate and reliable test results.

[0020] The method for testing the minimum ignition temperature of wood and bamboo dust clouds uses the above-mentioned minimum ignition temperature testing device for wood and bamboo dust clouds, and includes the following steps:

[0021] S1. Install and debug the testing device: Ensure that all parts are well-connected and can operate normally;

[0022] S2. Stabilize the temperature according to the set testing requirements;

[0023] S3. Weigh a certain mass of dust sample after particle size screening according to the concentration requirement and place it in the funnel-shaped dust storage for later use;

[0024] S4. Adjust the conveying air flow in the heat-resistant glass pipe to the set pressure;

[0025] S5. Open the electrically controlled feeding valve, and the dust in the funnel-shaped dust storage is sprayed into the heat-resistant glass pipe, forming a dust cloud and then entering the quartz tube in the heating furnace;

[0026] S6. Observe the ignition conditions of the horizontal pipe section and the vertical pipe section in the quartz tube respectively according to the determination method in GB / T 16429-1996, repeatedly adjust the heating temperature according to whether it catches fire, record the corresponding temperature data, and finally determine the minimum ignition temperature of the dust cloud.

[0027] As a further improvement to the above-mentioned method for testing the minimum ignition temperature of wood and bamboo dust clouds, collect the temperature, pressure and wind speed in the horizontal pipe section and the vertical pipe section during the experiment, and transmit the data to a USB flash drive or a computer through a USB interface for storage.

[0028] As a further improvement to the above-mentioned method for testing the minimum ignition temperature of wood and bamboo dust clouds, there is a step after step S6:

[0029] S8. Shut down and clean the testing device: The heating units of the horizontal pipe section and the vertical pipe section stop heating. After the quartz tube cools down, the compressed air stops supplying gas, and clean the dust or the residue of combustion dust inside the heat-resistant glass pipe and the quartz tube.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. The pipe heating part of the testing device of the present invention is provided with a horizontal direction and a vertical direction, and the requirements for the particle size of the dust are relatively loose. The dust cloud states formed by the dust in the horizontal and vertical pipes can truly reflect the specific application scenarios in the actual production process. The repetitive operation is simple, and the test data results are more accurate and reliable.

[0032] The quartz tube has at least a horizontal pipe section and a vertical pipe section, and the compressed air enters from the horizontal pipe section and then enters the vertical pipe section from bottom to top. The dust cloud is stable and uniform in the quartz tube, and the dust will not agglomerate. It has good adaptability to different dust particles, improves the accuracy of the test, and avoids explosions.

[0033] Using a transparent quartz tube facilitates direct observation by testers of the true state of the dust cloud under different conditions, eliminating the need for auxiliary devices for indirect observation, simplifying the structure, and improving the accuracy and reliability of test data.

[0034] 2. A flow rectifying plate is provided in the heat-resistant glass pipe of the test device of the present invention, especially flow rectifying orifice plates with different opening ratios are spaced apart, which can effectively prevent the formation of turbulence in the compressed air, making it more convenient for the uniform dispersion of dust. The dust cloud effect in the pipe is better, which is beneficial to improving the test accuracy of the device.

[0035] The heat-resistant glass pipe uses a Z-shaped transparent glass pipe with two horizontal sections and one vertical section. At the same time, flow rectifying large orifice plates, flow rectifying medium orifice plates, and flow rectifying small orifice plates with opening ratios of 60%, 75%, and 90% respectively are arranged in the horizontal section connected to the compressed air inlet pipe for rectification. Visually, the dust cloud diffusion effect in the heat-resistant glass pipe and the quartz tube is the best, and the dust cloud is evenly dispersed.

[0036] 3. The present invention is improved according to the requirements of GB / T 16429-1996, supports remote process control, greatly improves the operability and safety, and can completely provide technical support for revealing the combustion and explosion mechanism of combustible dust and improving the technical level of on-site prevention and control equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solution or embodiment of the present invention, the following is a description of the drawings. Obviously, the drawings in the following description are only certain embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0038] Figure 1 It is an overall schematic diagram of a test device for the minimum ignition temperature of wood and bamboo dust clouds;

[0039] Figure 2 It is Figure 1 an enlarged view of part A in

[0040] Figure 3 a front schematic diagram of the control box in the control unit of a test device for the minimum ignition temperature of wood and bamboo dust clouds;

[0041] Figure 4 a back schematic diagram of the control box in the control unit of a test device for the minimum ignition temperature of wood and bamboo dust clouds.

[0042] Attached drawing annotation: 1. Compressed air inlet pipe; 2. Pressure regulating switch; 3. Funnel-shaped dust storage; 4. Electrically controlled feeding valve; 5. Differential pressure gauge; 6. Heat-resistant glass pipe; 61. Rectifying large orifice plate; 62. Rectifying medium orifice plate; 63. Rectifying small orifice plate; 7. Anemometer; 8. Connecting flange; 9. Heating furnace; 91. Z-shaped quartz tube, 92. Horizontal pipe section heating unit; 93. Horizontal thermocouple; 94. Heating furnace body, 95. Vertical thermocouple; 96. Vertical pipe section heating unit; 10. Purification and filtration device; 11. Control cabinet; 1101. Cabinet body; 1102. Touch display screen; 1103. Main power switch button; 1104. Horizontal pipe section heating unit switch button; 1105. Vertical pipe section heating unit switch button; 1106. Electrically controlled feeding valve switch button; 1107. Differential pressure gauge interface; 1108. Anemometer interface; 1109. USB interface; 1110. Horizontal pipe section heating unit temperature control interface; 1111. Vertical pipe section heating unit temperature control interface; 1112. Horizontal thermocouple temperature display interface; 1113. Vertical thermocouple temperature display interface. Detailed implementation manners

[0043] Through in-depth research on the content in GB / T 16429-1996, the present invention proposes to improve and optimize the structure of the test device in the standard, aiming to truly simulate the state of combustible dust cloud under real process conditions and conduct real-time characterization of the lowest ignition temperature of the combustible dust cloud, providing technical support for revealing the combustion and explosion mechanism of combustible dust and improving the technical level of on-site prevention and control equipment.

[0044] The following further describes the specific implementation manners of the present invention with reference to the attached drawings.

[0045] Embodiment

[0046] See the attached Figure 1 , the present invention provides a test device for the lowest ignition temperature of wood and bamboo dust cloud, which includes a compressed air inlet pipe 1, a pressure regulating switch 2, a funnel-shaped dust storage 3, an electrically controlled feeding valve 4, a differential pressure gauge 5, a heat-resistant glass pipe 6, an anemometer 7, a connecting flange 8, a heating furnace 9, a purification and filtration device 10, a control cabinet 11 and other components.

[0047] See the attached Figure 1 , Figure 2 , preferably, the heat-resistant glass pipe 6 is a Z-shaped transparent glass tube, the longer end is connected to compressed air through the pressure regulating switch 2, and the shorter end is connected to the Z-shaped quartz tube 91 in the heating furnace 9. The heat-resistant glass pipe 6 is internally provided with a rectifying large orifice plate 61, a rectifying medium orifice plate 62, and a rectifying small orifice plate 63 from the air inlet end. A funnel-shaped dust storage 3 is installed outside the side close to the rectifying small orifice plate, and the heat-resistant glass pipe 6 and the funnel-shaped dust storage 3 are connected through an electrically controlled feeding valve 4.

[0048] See the appendix Figure 2 Furthermore, the opening ratios of the large rectifying orifice plate 61, the medium rectifying orifice plate 62, and the small rectifying orifice plate 63 installed in the heat-resistant glass pipe 6 are 60%, 75%, and 90% respectively, and they are arranged in increasing order of the opening ratio along the air inlet direction, aiming to make the compressed air form a uniformly distributed conveying air flow.

[0049] See the appendix Figure 1 Preferably, the heating furnace 9 includes parts such as a Z-shaped quartz tube 91, a horizontal tube section heating unit 92, a horizontal thermocouple 93, a heating furnace body 94, a vertical thermocouple 95, and a vertical tube section heating unit 96. Both the Z-shaped quartz tube 91 and the heating furnace body 94 are made of transparent materials; the outer side of the horizontal end of the Z-shaped quartz tube 91 is connected to the heat-resistant glass pipe 6 through a connecting flange 8, and the vertical end is externally connected to a dust or ash purification and filtration device 10 to collect the dust and / or ash after spraying.

[0050] See the appendix Figure 1 , Figure 3 , Figure 4 See the appendix

[0051] See the appendix Figure 1 , Figure 2 The other features, such as the compressed air inlet pipe 1, the pressure regulating switch 2, the funnel-shaped dust storage 3, the electric control feeding valve 4, the differential pressure gauge 5, the anemometer 7, the connecting flange 8, the purification and filtration device 10, etc., are all existing mature technologies and can be directly selected and matched in the market, or commissioned for processing.

[0052] The present invention further provides a method for testing the minimum ignition temperature of wood and bamboo dust clouds, which is easy to operate, can be applied to dusts of different particle sizes, truly reflects the specific application scenarios in the actual production process, has good repeatability, and accurate and reliable test results. Using the above-mentioned testing device for the minimum ignition temperature of wood and bamboo dust clouds, the specific steps are as follows:

[0053] S1. Install and debug the testing device: Connect the compressed air, connect each unit in the testing device to the control cabinet 11 using a data cable, turn on the main power supply of the control cabinet 11, and debug each part to ensure that all system connections are intact and can operate normally;

[0054] S2. Turn on the main power switch 1103 of the device, start the switch button 1104 of the horizontal pipe section heating unit and the switch button 1105 of the vertical pipe section heating unit, stabilize the temperature according to the set test requirements, and start the data acquisition system to make it in a normal working state;

[0055] S3. Weigh a certain mass of dust sample after particle size screening according to the concentration requirement, and place it in the funnel-shaped dust storage 3 for use;

[0056] S4. Turn on the pressure regulating switch 2 and adjust the conveying air flow in the heat-resistant glass pipe 6 to the set pressure;

[0057] S5. Turn on the electric control feeding valve 4, spray the dust in the funnel-shaped dust storage 3 into the conveying pipeline, and form a dust cloud and then enter the Z-shaped quartz tube 91 in the heating furnace 9.

[0058] S6. Observe the ignition conditions of the horizontal pipe section and the vertical pipe section in the Z-shaped quartz tube 91 respectively according to the determination method in GB / T 16429-1996, repeatedly adjust the heating temperature according to whether it catches fire, record the corresponding temperature data, and finally determine the minimum ignition temperature of the dust cloud.

[0059] S7. Conduct data acquisition: Through the data acquisition card, the temperature, pressure and wind speed changes in the pipeline during the experiment can be monitored, and the data is transmitted to a USB flash drive or a computer through the USB interface 1109 for storage for subsequent further analysis;

[0060] S8. Shut down and clean the testing device: Shut down the heating element and the data acquisition system. After the temperature in the quartz tube 91 drops, turn off the compressed air pressure regulating switch 2 and the main power switch button 1103, and clean the dust or combustion dust residues inside the heat-resistant glass pipe 6 and the Z-shaped quartz tube 91.

Claims

1. A minimum ignition temperature test device for wood and bamboo dust clouds, comprising a compressed air intake pipe, a heat-resistant glass pipe, a heating furnace, a funnel-shaped dust storage device, and an electrically controlled feeding valve, characterized in that: The heating furnace includes a transparent quartz tube with interconnected horizontal and vertical pipe sections, a horizontal pipe section heating unit and a vertical pipe section heating unit for heating the horizontal and vertical pipe sections respectively, and horizontal thermocouples and vertical thermocouples extending into the horizontal and vertical pipe sections respectively; a compressed air inlet pipe, a heat-resistant glass pipe, and a horizontal pipe section are connected in sequence; and a bottom outlet of a funnel-shaped dust storage device is connected to a dust inlet on the pipe wall of the heat-resistant glass pipe through an electrically controlled feeding valve.

2. The minimum ignition temperature test device for wood and bamboo dust clouds according to claim 1, characterized in that: A rectifier plate with holes is arranged inside the heat-resistant glass pipe so that the compressed air after passing through the rectifier plate forms a uniformly distributed conveying airflow; the rectifier plate is located between the air inlet end of the heat-resistant glass pipe connected to the compressed air inlet pipe and the dust inlet.

3. The minimum ignition temperature test device for wood and bamboo dust clouds according to claim 2, characterized in that: The rectifier plates include multiple rectifier plates, which are arranged at intervals inside the heat-resistant glass pipe between the air inlet end of the heat-resistant glass pipe and the dust inlet. The opening rate of each rectifier plate increases from the air inlet end of the heat-resistant glass pipe to the dust inlet.

4. The minimum ignition temperature test device for wood and bamboo dust clouds according to claim 3, characterized in that: There are three rectifier plates, namely, a rectifier large-hole plate, a rectifier medium-hole plate, and a rectifier small-hole plate, with opening rates of 60%, 75% and 90% respectively.

5. The minimum ignition temperature testing device for wood and bamboo dust clouds according to any one of claims 1 to 4, characterized in that: The utility model comprises a controller, a horizontal pipe segment heating unit, a vertical pipe segment heating unit, a horizontal thermocouple, a vertical thermocouple and an electric control feeding valve which are all connected with the controller.

6. The minimum ignition temperature testing device for wood and bamboo dust clouds according to claim 5, characterized in that: It includes an anemometer extending into the horizontal pipe section for measuring the wind speed in the horizontal pipe section, and a differential pressure meter for measuring the pressure difference before and after the rectifier plate; The anemometer and differential pressure gauge are both connected to the controller.

7. The minimum ignition temperature testing device for wood and bamboo dust clouds according to claim 6, characterized in that: It includes a data acquisition card and a USB interface connected to the controller. The data acquisition card is electrically connected to the anemometer, the differential pressure gauge, the horizontal thermocouple and the vertical thermocouple for collecting wind speed, pressure and temperature data.

8. The minimum ignition temperature test method for wood and bamboo dust clouds is characterized by: Using the wood and bamboo dust cloud minimum ignition temperature testing device according to claim 1, the following steps are included: S1. Install and debug the test device: ensure that all parts are well connected and can operate normally; S2. Control the temperature to be stable according to the set test requirements; S3. Weigh a certain mass of dust sample after particle size screening according to the concentration requirements and put it into the funnel-shaped dust storage for standby use; S4, adjusting the conveying air flow in the heat-resistant glass pipe to a set pressure; S5. Open the electronically controlled feeding valve, and the dust in the funnel-shaped dust storage is sprayed into the heat-resistant glass pipe, and then enters the quartz tube in the heating furnace after forming a dust cloud; S6. Observe the ignition conditions of the horizontal and vertical sections of the quartz tube according to the determination method in GB / T 16429-1996, repeatedly adjust the heating temperature according to whether there is ignition, record the corresponding temperature data, and finally determine the minimum ignition temperature of the dust cloud.

9. The method for testing the minimum ignition temperature of wood and bamboo dust clouds according to claim 8, characterized in that: The temperature, pressure and wind speed in the horizontal and vertical pipe sections are collected during the experiment, and the data are transferred to a USB flash drive or computer for storage through the USB interface.

10. The method for testing the minimum ignition temperature of wood and bamboo dust clouds as claimed in claim 8, characterized in that: Step S6 is followed by the steps: S8. Shut down and clean the test device: Stop heating the horizontal pipe section heating unit and the vertical pipe section heating unit. After the quartz tube cools down, stop supplying compressed air and clean the dust or combustion dust residue inside the heat-resistant glass pipe and the quartz tube.

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