Dust explosion refers to a chemical reaction in which combustible dust mixes with air in a confined space to form a dust cloud. Under the action of an ignition source, the dust air mixture quickly burns and causes a sudden increase in temperature and pressure. Dust explosions are often occurring in production and processing sites accompanied by aluminum powder, zinc powder, aluminum processing and grinding powder, various plastic powders, intermediates of organic synthetic drugs, wheat flour, sugar, sawdust, dyes, bakelite ash, milk powder, tea powder, tobacco powder, coal dust, plant fiber dust, and so on.
From the perspective of the formation of dust explosions, combustible substances, air, and ignition sources are the three basic conditions for the occurrence of explosion events, namely the three elements of explosion.
Is dust explosive? The use of dust explosion screening devices is mainly used for preliminary identification of whether dust samples have explosiveness, and can be used to determine the explosiveness of dust on site.
(1) Judgment basis: VDI2263.1-1990
(2) Is a sustained flame generated under the condition of 4J ignition energy in the explosion screening device. If dust cannot be ignited in Hartmann, a stronger ignition source is needed in a larger container (1m ³ Test in the tank.
(3) Judgment basis: VDI2263.1-1990
(4) At 1 m ³ The pressure generated under the 10kJ ignition energy condition inside the device is 0.5 bar higher than the initial test pressure.
Dust ignition sensitivity
Dust minimum ignition energy test: Determine whether electrical equipment discharge can ignite explosive dust and air mixtures. The minimum ignition energy is used to evaluate the corresponding ignition hazards caused by electrical or electrostatic discharge, and ultimately determine whether electrical equipment is suitable for installation in places where explosive dust exists.
Dust minimum ignition temperature test: Control the surface hot surface temperature of the equipment to prevent ignition of dust and dust layers, and provide a basis for the selection of dust explosion-proof electrical equipment.
The minimum ignition temperature test provides the following information:
The possible ignition sensitivity caused by hot surfaces in the dryer, the ignition sensitivity caused by overheating of bearings and other mechanical components, the ignition sensitivity caused by friction ignition, and the maximum allowable outer surface temperature of electrical equipment.
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