Study On The Influence Of Typical Inert Powder-calcium Carbonate On Ignition Characteristics Of Wood Dust Layer

Dust explosion accidents have happened at times.Thermal decomposition of deposited dust under certain conditions is one of the common causes for dust explosions.Inerting technology plays an important role in industrial dust explosion protection.In the production process with wood as the main raw material,there is generally a large amount of deposited wood dust.As a result,there is not only a fire hazard,but also a greater risk of dust explosions.Currently,the study on the inerting explosion-proof technology of sedimentary wood dust is relatively lacking,and the influence law of solid inertant has not been systematically revealed.Based on this,this paper studies the effect of typical inert powders on the ignition characteristics of wood dust layers with the help of the dust layer ignition temperature test device and the self-designed and developed experimental platform for the research on the ignition characteristics of sedimentary dust.The main research contents are as follows.（1）The effect of calcium carbonate（Ca CO₃）on the minimum ignition temperature（MIT）of wood dust layer was studied by means of a dust layer ignition temperature test device.The results show that without adding Ca CO₃,the MIT of the dust layer of polished painted wood powder and hand polished wood powder is 324℃and 332℃,respectively.After adding Ca CO₃,the MIT of the wood dust layer increases due to the heat absorption of Ca CO₃ to accelerate heat consumption,reduce oxygen concentration,and reduce wood dust concentration.When the mass fraction of Ca CO₃ is40%,the MIT of the wood dust layer increases sharply,and a sudden change of ignition temperature occurs.When the mass fraction of Ca CO₃is 80%,the maximum temperature of the hot surface is set to 400°C,and the dust layer does not catch fire.（2）Independently designed and established an experimental platform for the research on ignition characteristics of deposited dust.The platform includes a dust layer burning spread test system,an airflow velocity and temperature adjustment system,an ignition control system,an airflow velocity and temperature monitoring system,and a camera system.Control the initial airflow velocity and temperature by setting the hot air blower.The morphological changes and temperature changes of the dust layer combustion were observed by setting up the camera equipment.Under the coupling effect of multiple factors such as airflow and ambient temperature,the burning spread characteristics of the wood dust layer were revealed.The visualization of the research process is also realized.（3）The burning spread characteristics of wood dust layer under different initial airflow velocity and temperature conditions were studied through the experimental platform for the research on ignition characteristics of sedimentary dust.The results show that the dust layer burns and spreads at a uniform speed under different conditions.As the initial airflow in the pipeline increases,the oxygen supply rate increases,and the initial temperature increase,the oxidative combustion and decomposition reaction speed of wood dust accelerates.Then,the burning velocity of the dust layer and the temperature at the front of the burning spread increase accordingly.（4）The effect of Ca CO₃ on the burning spread characteristics of wood dust layer was studied through the experimental platform for the study of ignition characteristics of sedimentary dust.The results express that with the increase of Ca CO₃ content,the burning spread velocity of the dust layer increases.When the mass fraction of Ca CO₃ is 50%,the burning spread velocity of the dust layer reaches its peak value,and when it reaches 70%and above,the dust layer cannot catch fire and spread.With the increase of the mass fraction of Ca CO₃,the temperature of the ignition front of the dust layer decreased,and the decreasing range increased with the increase of Ca CO₃ mass fraction.Therefore,the inerting effect of Ca CO₃ on the wood dust layer has a multiplicity.According to the Gauss Amp model of the burning rate of wood dust layer and the mass fraction of Ca CO₃,it is found that the burning rate of dust layer reaches its peak when the mass fraction of Ca CO₃ is between 40%and 50%.