Guarding Against Fires and Explosions Caused by Self-Heating

• Published in: Chemical Engineering Vol. 124; no. 6; p. 65
• Main Author: Zhao, Guibing
• Format: Magazine Article Trade Publication Article
• Language: English
• Published: New York Access Intelligence, LLC 01-06-2017; Access Intelligence LLC
• Subjects: Accessibility; Analysis; Chemical engineering; Chemical reactions; Driers; Dust; Electric motors; Environmental aspects; Exothermic reactions; Explosions; Exposure; Extrapolation; Fire protection; Fires; Fixtures; Gases; Geometry; Heat transfer; Heating; Hot surfaces; Ignition; Illumination; Lighting; Mills; Oil recovery; Operating temperature; Oxygen; Pipes; Powders (Particulate matter); Prevention; Reaction kinetics; Research methodology; Safety and security measures; Screening; Smoldering; Storage; Temperature; Thermal properties; United States
• ISSN: 0009-2460; 1945-368X

Bulk storage of heated powders and powder accumulations on hot surfaces or in heated environments can potentially lead to self-heating and spontaneous ignition. Examples of locations within processing companies where self-heating of powder accumulations may be expected include uninsulated steam pipes, inappropriately rated or selected electric motors and lighting fixtures, mechanical mills and inside surfaces of various dryers. Self-heating is a complicated phenomenon consisting of both an exothermic chemical reaction and a heat-transfer process, which can cause material smoldering and even lead to fires and dust-cloud explosions. The parameters that affect the actual self-heating for a given material, include bulk size and shape, temperature, time and oxygen/air accessibility. This article introduces the "layer powder" screening and the advanced "basket" tests that may be used to deduce the reaction kinetics and therefore to extrapolate the laboratory-scale test data to the plant-scale so that the data can be used to establish safe operating limits for operating temperature, critical bulk size, and residence/exposure time.