Scholarly record

CHARACTERIZATION IN TERM OF THE SELF-IGNITION BEHAVIOR FOR COMBUSTIBLE DUSTS DERIVED FROM TECHNOLOGICAL PROCESSES

Irina Nalboc, Maria Prodan, Andrei Szollosi Mota, Sonia Suvar

Abstract

Combustible dusts are presented in industry as a finished products or process intermediates created voluntarily by milling or involuntarily by abraison of larger sized solid. Spontaneous combustion is a phenomenon that occurs by self-heating, increase in temperature due to exothermic internal reactions, followed by thermal runaway (self heating which rapidly accelerates to high temperatures) and finally, autoignition. The oxidation of combustible powders occurs when they react with air oxygen, producing carbon dioxide, carbon monoxide, water and other gases, the composition of which is influenced by the temperature of the oxidation process. Thermal runaway can occur when the amount of heat produced is greater than the rate at which the heat is lost. Materials that produce a lot of heat may combust in relatively small volumes, while materials that produce very little heat may only become dangerous when well insulated or stored in large volumes. Combustible dusts can self-ignite depending on their chemical makeup, the characteristics of their constituent components, the particle size and mass geometry, and last but not least, the ambient temperature. Self-ignition is a complicated process that occurs in three subsequent or concurrent stages of development, namely self-heating, humidity evaporation, and self-ignition. In the present paper experimental tests were performed in order to describe / present the self-ignition behavior of combustible dusts by volume by means of drying tests under constant temperature conditions, parameter needed to take the appropriate measures to ensure work and installation safety.

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