Page 310 - Dust Explosions in the Process Industries

Propagation of Flames in Dust Clouds 279

These measurements showed that the preheating zone was about 2 mm thick and on the
same order as for gases of similarburning velocities and that the total thickness of a lam-
inar lycopodiudair flame is on the order of a few mm.
More recently Proust and Veyssiere (1988) studied the propagation of genuinely lam-
inar dust flames in clouds of maize starch of 6% moisture content in air. They used the
comparativelylarge apparatus illustrated in Figure 4.14. Dust clouds were generated in

dust-air separator

electropneumatic gate vaive

steel section ( 1m x 0.2 m x 0.2 rn I

glass section ( 2 m x 0.2 rnx 0.2 m 1

I / I
t-diaphragm @

porous membrane

isothermic bath compressed
\ air
V
the elutriator and its electmpneurnatic air flow meter SUPP[Y
removal system

Figure 4.14 Large vertical duct for studying flame propagation in dust clouds (From Proust and
Veyssiere, 1988).