Page 643 - Dust Explosions in the Process Industries

6 7 0 Dust Explosions in the Process Industries

for foam layer destruction were determined. Britan et al. (1994b) analyzed the features
of the transmitted shock wave and the waves reflected from the aidfoam boundary and
the walls of the experimental channel.

9.3
STATUS AND OUTSTANDING PROBLEMS IN PREVENTING
AND MITIGATING DUST EXPLOSIONS IN INDUSTRY

9.3.1
THE ROLE OF FUNDAMENTAL KNOWLEDGE IN ASSESSING
HAZARDS IN PRACTICE

The various aspects of applied dust explosion research and development may be sys-
tematized as shown in Table 1.9 in Chapter 1.A number of fundamentalresearch topics
are listed in Table 9.1. The two are intimately related because fundamental knowledge
is essential for proper understanding of practical aspects. Experience has shown that the
development of good practical solutions may be hampered by not accounting for rele-
vant fundamental knowledge. In recent years, the appreciation of the benefits that can
be harvested from cross fertilizationbetween fundamentalresearch and applied research
and development has been increasing.
Deng and He (1994) pointed out the need for using thermodynamics,chemical reac-
tion kinetics, and fluid dynamics for the proper description of ignition and flame prop-
agation phenomena in dust clouds and layers. These topics constitute central elements
of classic chemical reaction engineering, and Deng and He proposed a corresponding
concept, dust explosion reaction engineering (DERE) for the dust explosion domain.
Siwek (1994) presented a concentrated overview of current methods for dust explo-
sion prevention and mitigation in the process industries, based mainly on pragmatic
experimental research and development performed within the SwidGerman domain.
Siwek’s paper reflects the important fact that industry needs practical solutions for
today. It cannot wait for more ideal solutions that may become available in some distant
future. However, industrial pragmatism must not, on the other hand, block the constant
striving for better solutions based on improved basic understanding of the phenomena
involved. It seems as if the mutual understanding and respect between the two parties,
the industry and the researchers, is growing.
The point is illustrated by Eckhoff (1995), who reviewed the state of the art on pre-
venting and mitigating dust explosions in ferroalloy crushing and grinding plants. Silicon
crushing and grinding was considered specifically by Eckhoff (1996b). In general, both
electric spark ignition sensitivity and explosion violence (&) of metal dusts increase
markedly with decreasingparticle size, right down to the 1pm. In the past, this was seldom
taken into account. Often particle size was just pragmatically specified in terms of “less
than 74 pm” or “less than 63 pm,” but this is by no means satisfactory. More systematic
research is needed, in particular on alloys, where the most hazardous components may
sometimes accumulate in the fine tail of the particle size distribution.The specific roles
of the chemistry and particle size of the various components in ferroalloy dusts at large