,
Self-ignition of dust at reduced volume fractions of ambient oxygen
Journal of Loss Prevention in the Process Industries, 16 (2): 141--147 (марта 2003)
DOI: http://dx.doi.org/10.1016/S0950-4230(02)00095-5
Аннотация
Experiments were performed to investigate the self-ignition behaviour
of accumulations of four different technical dusts at oxygen volume
fractions ranging from 1.3 to 21%. For this purpose a laboratory
oven used for hot storage testing was modified to allow flushing
with the pre-mixed oxygen/nitrogen mixture of the desired composition.
It was found that for all sample volumes investigated the self-ignition
temperatures were higher the lower was the oxygen volume fraction.
In addition, the type of reaction changed obviously, since the apparent
activation energy significantly decreased at oxygen volume fractions
below 6%. However, it was still possible to observe exothermic effects
at oxygen volume fractions as low as 1.3%. A numerical model was
established to simulate the process of self-ignition including the
coupled heat and mass transfer within the dust accumulation using
a finite element solver. The model consists of six balance equations
for the heat transfer and the transport of five chemical species.
It shows that the model reflects self-ignition in dust accumulations
with satisfying accuracy, as long as the input data generated by
preceding experiments are reliable.
