Page 369 - Dust Explosions in the Process Industries

338 Dust Explosions in the Process Industries

- 0 250 500 750 1000
DUST CONCENTRATION Ig/m31

0.95m3

/*yo\
--m
/
I
V=4.2 m/s

L/ MAIZE STARCH, 4% MOISTURE, ~74pm

0 250 500 750 1000
DUST CONCENTRATION Ig/m31

Figure 4.46 The effect of turbulence on maximum explosion pressure in a 0.95 m3spherical closed
bomb (From Kauffman et al., 1984a).
steep rise of both P,,, and (dPldt),,, with increasing dispersion pressure and suggested
that this was probably due to a combined effect of improved dust dispersion and increased
initial turbulence. A similardistinct influence on P,, of the intensity of the air blast used
to disperse the dust was also found by Amyotte and Pegg (1989). This could be inter-
preted in terms of improved dust dispersion or deagglomeration,rather than turbulence,
being responsiblefor more effectivecombustion and thus higher P,,,. Therefore,the pri-
mary effect on P,,, of increasing v‘ in Kauffman et al.’s (1984a) experiments could be
improved dust dispersion.
The rms turbulenceintensitiesin Amyotte and Pegg’s (1989) investigationwere deter-
mined by a laser-doppler velocimeter, whereas Kauffman et al. (1984a) used a hot-wire
anemometer.Therefore the two sets of v’ values may not be directly comparable.Amyotte
and Pegg’s values were generally lower than those of Kauffman et al.