Explosion hazard study of lead dust/air mixture

Introduction. Lead dust/air mixture has an ignition temperature of 710 °C and an estimated maximum explosion pressure of 400 kPa. At the same time, the lead dust/air mixture does not explode in a 20-litre chamber with
an ignition source having energy of 2.5 kJ. These circumstances make it difficult to answer the question about the explosiveness of lead dust under normal handling conditions. In this paper, arguments in favour of explosion safety of this dust at a temperature of 25 °C are obtained.

Lead dust and method of its study. Lead concentrate dust (d50 = 8.5 microns, d90 = 36.6 microns) with lead content of at least 99 % (wt.) was studied in a 20-liter Sivek explosion chamber with an ignition source of increased energy (10 kJ).

Results. The explosion hazard of lead dust was manifested in the range of dust concentrations from the lower limit (500 g/m3) to the upper limit (1,500 g/m3). In the whole specified range, the occurrence of lead dust explosion from experiment to experiment was random. The maximum explosion pressure was 150 kPa, the explosion index Kst was 2 bar ∙ m/s. The explosion pressure dependence on time P(t) had two inflection points, in the first of which the minimum dP/dt was reached, and in the second point the maximum dP/dt was reached.

Discussion and conclusions. The results of the study of lead dust have features characteristic of a dispersed material that is explosion-proof under normal handling conditions: Kst < 45 bar ∙ m/s (Proust, Accorsi, Dupont, 2007); the random nature of the explosion in a wide range of dust concentrations and the two-stage explosion (Poletaev, Sazonov, Koptev, 2024). Thus, it is most likely that the investigated lead dust is explosion-proof. The cases of its explosion are due to the “overdrive” effect — airborne dust preheating in experiments using an energy-intensive ignition source.

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