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Proceedings of Symposium on Energy Engineering in the 21<sup>st</sup> Century (SEE2000) Volume I-IV

ISSN:
1-56700-132-7 (Print)

NEW CONCEPTS AND TEST PROCEDURES IN THE ASSESSMENT OF HAZARDS DUE TO SPONTANEOUS HEATING OF TRANSPORTED COMBUSTIBLE SOLIDS

J.C. Jones
Department of Engineering University of Aberdeen

Abstract

The author has pursued a major appraisal of test procedures for propensity to spontaneous heating, such as that issued by IMCO, which are used to determine whether a particular material such as a coal is safe to be shipped. An extensive body of published work has resulted. The current tests involve the heating at 140°C of a sample of the subject material and monitoring of the central temperature. The Frank-Kamenetskii (F-K) model of thermal ignition is invoked, on the basis of which critical behaviour at an ambient temperature of 140°C in the sample size used in the test is equivalent to criticality at 50°C in a 3m cube shipping hold. There is the flaw that this calculated equivalence of critical ambient temperatures for the small and large assemblies involves assumption of a particular value of the activation energy of the reaction, and because in the F-K model the activation energy appears in an exponential, small uncertainties in it are 'blown up'. The current test procedures are frequently applied in total ignorance of the activation energy of the material under examination. Accordingly the author has developed a means of estimating the activation energy of any particular subject material by a simple extension of the current test. For the longer term, a move away from 'critical ignition temperature' towards 'heat-release rate at criticality' is recommended as a quantity upon which to focus when assessing hazards.