Study On The Mechanism Of Auto Ignition Of Aluminum Dust From Polishing Process

Because of the lack of study on the mechanism of auto ignition of aluminum dust from polishing process at home and abroad,and the status quo of the accident due to auto ignition of aluminum happen frequently.This paper treat the Kunshan dust explosion accident as the background,the aluminum dust from polishing process as the subject.Study systematically on the experiment and theory of auto ignition of aluminum dust from polishing process.At first,the effect of water and Fe2O3 on the sensitivity of ignition of aluminum dust from polishing process was studied with the MIT device and MIE-III device.Found that water has a inhibitory effect on the sensitivity of ignition of aluminum dust from polishing process overall,when the ratio of water at 5?15%,MIT decrease with the increase of water content,when it over 15%,MIT increase with the increase of water content.MIT decrease with the increase of the Fe2O3 content,MIE increases with the increase of water content,when the ratio of Fe2O3 at 0-10%,MIE decrease with the increase of water content,when it over 10%,MIE decrease with the increase of the content of Fe2O3.Then an experimental system for the study of auto ignition of aluminum dust from polishing process was built,aluminum dust piled in a cubic metal basket whose bottom immersed in a sink filled with water,put the basket with sink in the thermostat,using thermocouples to monitor the temperature of aluminum dust.Eventually in the ambient temperature of 70? after 22 hours and 55 minutes,the aluminum dust fired.The process of which can be divided into 3 periods,induction,ignition delay and combustion.Then the influence of ambient temperature,the size of aluminum dust and ph on the auto ignition of aluminum dust.The results show that auto ignition need to meet 3 necessary condition,they are continuously being damp,a necessary size and an ambient temperature which reach the critical value.Induction period and the ignition delay time decrease with the increase of ambient temperature,critical ambient temperature decrease with the increase of the size of aluminum dust.induction period shorten lightly when the ph is 3,and shorten obviously when the ph is 11,ignition delay time have no obviously change in both situations.Kinetic parameters of the reaction aluminum and water was solved in a method called crossing point of temperature,then get the activation energy of the reaction is 22.22kJ/mol.Then the safe size in different shape of aluminum dust piled was studied using Frank-kamenetskii theory,the relations of safe size and critical ambient temperature was obtained.The formula can be used to guide the prevention of auto ignition of aluminum dust.