Using Calculated Adiabatic Flame Temperatures to Determine Dust Explosion
Inerting Requirements
Process Safety and Environmental Protection (Transactions of the
Institution of Chemical Engineers, Part B), (March 2004)DOI: http://dx.doi.org/10.1205/095758204322972780
Abstract
The use of calculated adiabatic flame temperatures (CAFT), along with
a selected limit flame temperature for combustion propagation, has
been shown to be effective in determining the flammability envelope
for hydrocarbon gases. This paper discusses the use of this methodology
to determine the flammability of gaseous fuel–oxidizer–inertant mixtures.
The paper then proceeds to describe how this methodology can be modified
into a predictive tool to determine the flammability of a solid fuel–inertant
mixture in air. The modification proposed here is based upon previous
work by Hertzberg et al. Their model proposes that in the homogeneous
mechanism for combustion (which is predominant for most carbonaceous
fuels and some metal dusts) not all the volatile matter present in
the system can participate in the combustion process. Only a fraction
(termed the beta fraction) can be devolatilized rapidly enough to
take part in combustion. It is this fraction of fuel that is used
for the adiabatic flame temperature calculations. The model presented
here differs from that of Hertzberg et al. in that it has been modified
to allow for comparisons between inerting levels determined in a
20 litre chamber and a 1 m3chamber. The results indicate that the
1 m3 model can be used to predict the experimental inerting levels
of the 1 m3 chamber, with limitations. Additionally, the 20 litre
CAFT model can be used to predict the experimental inerting levels
in the 1 m3 chamber (again, with limitations). Ultimately, the utility
of this modified model as a predictive tool for inerting level and
minimum inerting concentration determination has been demonstrated.