Page 480 - Dust Explosions in the Process Industries

Sizing of Dust Explosion Vents 447

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$. EVA Figure 6.15 Results from vented dust explosions in
n I a 0.32 m3cyclone using two different Dolvmer dusts
0 500 1000 and two d/fferent me&ods of dust daubs genera-
tion, 0.03-0.04 mzopen vents with ducts (Data from
NOMINAL DUST CONC. [g/m31 Hayahsi and Matsuda, 1988; from Eckhoff, 7 990).

6.2.5
REALISTIC EXPERIMENTS IN BAG FILTERS

6.2.5.1
Vented Explosions in a 6.7 m3Industrial Bag Filter Unit in the United Kingdom

Lunn and Cairns (1985) reported on a series of dust explosion experiments in a 6.7 m3
industrial bag filter unit. The experiments were conducted during normal operation of
the filter, which was of the pulsed-air, self-cleaning type. Four different dusts were used,
and their Kstvalues were determined according to IS0 (1985) (see Chapter 7). The igni-
tion source was located in the hopper below the filter bag section. In the experiments of
main interest here, the vent was in the roof of the filter housing. Hence, to get to the vent,
the flame had to propagate all the way up from the hopper and through the congested
filter bag section. The results from the experiments are summarized in Figure 6.16,
together with the corresponding VDI 3673 (1979 edition) predictions.
Figure 6.16 first shows that the Predin the actual filter explosions were mostly con-
siderably lower than the corresponding VDI 3673 predictions and close to the theoreti-
cal minimum value 0.1 bar(g) at which the vent cover ruptured. Second, there is no
sensible correlation between the VDI 3673 ranking of expected pressures according to
the Ks, values and the ranking actually found.
Lunn and Cairns (1985) also reported on a series of dust explosion experiments in a
generously vented 8.6 m3 empty horizontal cylindrical vessel of LID = 6. The same
dusts were used as in the filter experiments, but the dust clouds were generated “artifi-
cially” by injection from pressurized reservoirs as in the standard VDI 3673 method. In
spite of the similarity between the dust dispersion method used and the VDI 3673 dis-
persion method, there was no correlationbetween Predand ICst.