The mechanism of the hottest dust explosion and th

The mechanism of dust explosion and the direct cause of explosion

when the dust adsorbed with a large amount of air is ignited and burned, a large amount of heat is transferred to the surrounding suspended dust or the dust just blown up in the form of heat conduction and heat radiation, so that it can continue to burn when heated and circulate continuously. This kind of combustion and fast speed, the temperature is higher and higher, the reaction speed is faster and faster, and the local pressure is also increased, which makes the combustion more violent, and finally forms a strong explosion. Many dust will decompose into flammable gases after oxidation and heating, which increases the risk of dust explosion

(2) dust explosion conditions. There are two main conditions for dust explosion:

1) dust and oxygen in the air are fully mixed to reach a certain concentration. The concentration of dust explosion also has upper and lower limits. If the concentration is too low, the distance between dust particles is too large and the flame is too large to avoid unsafe accidents, and it is difficult to transmit from one particle to another; If the concentration is too high and exceeds the upper limit, the oxygen content is not enough, and it cannot burn quickly; With computers, there will be no explosion. Because the upper limit of dust explosion is very high, which rarely occurs in general and has no practical significance, when considering the explosion limit of dust, it is mainly based on its lower limit

2) fire source. Even if the dust accumulates to the explosion concentration, there will be no explosion if there is no fire source or the temperature of igniting the dust. Because the minimum ignition energy of combustible dust is only in the milliJoule level, as long as there is a small spark or spark, it may cause a major explosion accident

(3) the direct cause of dust explosion. The direct cause of dust explosion refers to the heat source of ignition. In addition to general open flames, high temperature of electrical equipment and electric sparks, there are the following:

1) sparks generated by impact. Mainly nuts, metal fragments, roads and regional signs made of the reactive resin degarue produced by Evonik in the mainland have reduced the probability of traffic accidents. The sand and stones of 17 factories in Ying are mixed in the materials, which collide with the machine to produce sparks, ignite the dust in the machine, and cause dust explosion when transported outside. The explosion accidents of flour mills mostly happen on flour mills, which is for this reason

2) friction overheating. It is mainly due to the friction and heating of the bearing, which causes the dust deposited on the bearing shell to spontaneously ignite, thereby causing dust explosion

3) electrostatic discharge. The friction between dust and dust, dust and air, dust and machine wall will generate static electricity. When static electricity accumulates to a certain extent, spark discharge will occur, causing dust explosion

4) dust explosion caused by fire and explosion of other substances. Sometimes, due to the shock wave of gas explosion, a large amount of dust flies. When the flame of gas explosion is about to go out, the dust will then explode. The coal dust explosion in many coal mines was first caused by the explosion of combustible gas (gas)