Propagation Law Of Aluminum-alloy Polishing Dust Explosion In Pipes

With the development of industrial powder technology,dust explosion accidents have occurred from time to time.After the Kunshan 8.2 dust explosion accident,the government supervision department attaches great importance to the prevention and control of dust explosion accidents.The accident investigation showed that after the initial explosion inside the precipitator,the explosive combustion materials spread along the dust removal pipe and then sprayed into the workshop from the suction branch pipe,causing huge loss of life and property.Therefore,reproducing the development process of dust explosion in the vessel-piping system can provide experimental basis and theoretical guidance for dust explosion protection in process industry enterprises.In this paper,a 15-liter explosive vessel and five branched pipelines are used to build a dust removal pipe network system.The aluminum-alloy polishing dust is used as the experimental medium.Three dust mass concentrations of 300 g/m3,400 g/m3,and 500 g/m3 are selected.Pressure acquisition system and high-speed camera technology to study the propagation law of dust explosion in the vessel-piping system.The specific conclusions are as follows:(1)The dust mass concentration has a significant influence on the pressure development in the explosion chamber.In the selected concentration range,the overpressure in the explosion chamber gradually increases with the increase in concentration,and the maximum overpressure is 12 KPa,but when the explosive chamber is connected to the pipeline with branch structure,the overpressure in the explosion chamber is always lower than the connection Straight pipeline means that when the pipeline contains branch structures,it has a better pressure relief effect on the explosive vessel.At the same time,the pressure change curve shows a slow rise first and then a slow decline trend at 300 g/m3.When the concentration is 400 g/m3 and 500 g/m3,it shows a slow rise first,then a rapid rise and then a stepwise decline.The development process lasts 80～100 ms.(2)The dust mass concentration also affects the flame propagation in the pipeline.When the concentration is 300 g/m3,the flame contour is a discrete luminous structure,and the flame brightness is relatively dim;when the concentration is 400 g/m3 and 500 g/m3,the flame contour has a clear and regular structure,and the spatially continuous bright yellow flame fills the entire pipeline.The flame propagation in the main pipeline is continuously accelerating,and the flame propagation speed gradually increases with the increase of concentration,and the maximum flame propagation speed is 426.7 m/s.(3)When the aluminum-alloy polishing dust explosion propagation in a pipe containing a branch structure,the installation of the overpressure in the explosion chamber under the three dust mass concentrations from large to small branch pipes is 150° on both sides,150° on one side,90° on one side、30° on one side,30° on both sides,and the maximum flame propagation speed is 30° on one side,90° on one side,30° on both sides,150° on one side,and 150° on both sides in descending order.The installation angle of branch pipes and the installation of single and double sides affect the development process of dust explosion:with the increase of the installation angle of branch pipes,the suppression of flame propagation becomes more obvious,and the flame propagation speed shows a gradual decay trend,but the pressure development in the explosion chamber shows a gradual increase trend on the contrary;When the double-sided branch pipes are installed in the forward direction,the relatively same angle of the single-sided branch pipe has a weakening effect on the pressure development and flame propagation,while the reverse flow direction will increase the pressure and weaken the flame propagation.(4)When the aluminum-alloy polishing dust explosion propagation in the two-section branch structure pipeline,the overpressure in the explosion chamber under the three dust mass concentrations are 150° on both sides,150° on one side,90° on one side,30° on one side,and 30° on both sides in order from large to small.The flame propagation behavior is mainly divided into three stages:the flame growth stage,the accelerated propagation stage of different paths in the branch structure,and the flame attenuation stage.The installation angle of the two-section branch structure and the installation of single and double sides have more complicated effects on flame propagation:when the installation angle is 30°,the flame can propagate in two single and double side branch pipes at the same time;when the installation angle is 90°,there is continuous flame propagation in the first section of the branch pipe,and the second section of the branch pipe only has a weak flame at the front end of the branch when the concentration is 400 g/m3and 500 g/m3;when the installation angle is 150°,only the first section of the branch pipe has weak flame propagation,the second section of the branch pipe junction has a bright luminous area,but the flame does not propagate into the branch pipe.Therefore,when the installation angle of the branch structure is 30°,it is more conducive to the propagation of flame in the branch pipe.