Experimental study of ignition of bulk storage by hot points

Abstract : Fire and explosion risk is generated by chemical or biological oxidation of combustible materials. An experimental study of ignition risk due to hot points in the storage of bulk materials is required to ensure fire safety. Many parameters are involved in this phenomenon: nature of the material, storage volume and temperature, type and size of hot point, etc. The aim of this study is to describe an adapted experimental procedure to determine critical ignition temperatures of powders for different conditions and with several types of hot points. Material selected for this study is a powder of " Lucy coal ". Ignition is carried out in 1000 and 2700 cm3 cubic baskets for two sizes of inert cylinders at a given temperature and for an inert sphere at a given initial temperature. The critical ignition temperature is defined as the hot point temperature in the middle of a 5°C interval of both temperatures: 1) ignition and 2) no ignition. First results demonstrate that the set-up procedure is relevant. Critical temperatures measured for both cylinders and for the sphere are in the same range. Discrepancies between the results obtained under these three test conditions have been explained by different basket sizes and hot points geometry. Data obtained need now to be compared to available theoretical modelling. These results will then allow predicting material behaviour under other storage conditions.