Abstract
The year 1967 can be regarded as the founding year of the "Flammable Dust" working committee of the chemical industry with representatives of BASF, BAYER, Hoechst and Ciba-Geigy AG. Even today, many of the regulations and directives in force [...] are still based on the findings and research results of the above-mentioned working committee in the 1970s - 1980s. These include also many postulates and interpretations for the evaluation or calculation of the ignition and explosion behaviour of substances depended on the ambient conditions, which are actively applied nowadays by experts in industrial practice. However W. Bartknecht and G. Pellmont already pointed out in that the extrapolations of these findings are often of limited value. The paper contains research results and thus serves as an example of those unknown explosion parameters that could not be taken into account. In the first part, the authors report on G. Pellmont's investigations of the temperature dependence of the minimum ignition energy of pyridine-3-carboxylic acid (niacin), which increases with increasing temperature, and not - as the extrapolations of T. Glarner, as well as the interpretations in regulations state - decreases. The second part summarise the experimental investigations of Leksin about the influence of turbulence on the burning behaviour of the dust in the quasi-stationary state in comparison to the sedimented dust, where also for certain dusts the above-mentioned parameter prevents the burning and does not, as expected, influence it more strongly. Both examples from the laboratory investigations shows, that there are a lot of other influencing variables that complicate the approximate predeterminations of explosion processes, not only temperature, admission pressure, humidity (for dusts), turbulence, geometry of the explosion chamber, location of the ignition site, but also the size of the explosion and combustion chamber, effectiveness of "operational" ignition sources, homogeneity, chemical and physical substance properties and many others.
