A plausible mechanism for initiation of dust explosion by electrostatic spark discharges in industrial practice

摘要

A study of ignition of dust clouds by electrostatic spark discharges triggered by the explosive dust cloud itself has been performed. This trigger mechanism probably operates when dust explosions are initiated accidentally by electrostatic sparks in real industrial situations. In conventional methods for determining the minimum ignition energy (MIE) of dust clouds in the laboratory, the delay between dust cloud generation and spark discharge can be chosen at liberty to create the most favourable conditions for ignition. However, this degree of freedom does not exist in an accidental industrial situation. The present investigation nevertheless indicates that for some dusts MIE values produced by the inherent dust cloud trigger method are only modestly higher than values for the same dusts obtained by standard laboratory methods. For other dusts, however, the discrepancies were considerable, and a possible main reason for this is suggested. As opposed to the spark triggering methods used in current standard MIE testing of dusts, the inherent dust triggering method also works for spark energies < 1 mJ. It is suggested, therefore, that a new standard MIE test for dust clouds for the MIE range < 1 mJ may be developed based on this method of spark triggering. In addition to resembling an electrostatic spark ignition mechanism likely to operate in practice, this triggering method also simplifies the test apparatus. If required, an additional series inductance can easily be incorporated in the discharge circuit. However, before apparatus and test method can be specified it is necessary to resolve some remaining puzzles.