Analysis on the factors that lead to the fire explosion of high-explosive metal powders


Flake powder that has fine particles and coated without protective lubricant coating will be especially sensitive to ignition. As powders will release heat automatically as well as the fine powder has poor heat dispersion, which will lead to high temperature, thus the active gases that derive from the powder processing or combustion reaction and those intercept in metal powders may catch fire and light the dust. Therefore, chemical treatment and oxide film can change the explosibility of powders.

metal powders explosion

Thermite reaction will influence the explosibility of metal compounds

Thermite reaction refers to reduce the metal oxides by using the exothermicity of the powders of another more active metal. This kind of reaction needs no oxygen that provided from the outside environment as the oxygen is supplied by the metal oxides. However, powders will be ignited in the thermite reaction and those dusts that do not participate in the reaction will scatter into the surrounding air, thus the dust cloud can be formed. The uneven mixing of dust and air may reduce the harmfulness of serious explosion, but the conditions may become serious and hard due to the accumulated dust in the air or the equipment, for example, pulverizer, hammer mill and other processing equipments will create appropriate conditions for forming the active dust cloud as they can generate strong disturbance and blend, with which the dust and air will form fairly uniform mixture.

Metal powders will generate great activity under the existence of moisture

Potassium, rubidium and palladium will burn fast and fiercely once contacting with water (which has same effect with the oxidizing agent). Some metals will generate flammable gases or vapor (such as hydrogen) under the existence of moisture, which may cause explosion when the dust cloud exists. For example, magnesium powders, aluminum powders, zinc powders and other kinds of metal powders all can react with water and may release heat automatically that will lead to partial combustion. In addition, some metal powders, such as aluminum powders, will generate drastic action after having oxygen-free oxidation/reduction reaction with halohydrocarbon or other chemical substances. Metal powder will have pyrophorisity and spontaneous activity under the existence of air, which will also lead to explosion.