Page 205 - Dust Explosions in the Process Industries

178 Dust Explosions in the Process Industries

Figure 2.19 View of damaged loft of silo plant in Stavanger, Norway, after smoldering gas explo-
sion in November 7 985 (Courtesy of 0yvind Ellingsen, Stavanger Aftenblad, Norway).

2.7
SMOLDERING GAS EXPLOSIONS IN A LARGE
STORAGE FACILITY FOR GRAIN AND FEEDSTUFFS
IN TOMYLOVO, KNIBYSHEV REGION, USSR

This extensive series of explosions were of the same nature as the smoldering gas explo-
sion discussed in Section 2.6. The report of the event was provided by Borisov and
Gelfand (personal communication from A. Borisov and B. Gelfand, USSR Academy of
Science, Moscow, 1989).
The large storage facility for grain and feedstuffs consisted of four sections of 60 silo
cells each, that is, 240 silo cells altogether. As indicated in Figures 2.20 and 2.21, each
cell had a 3 m x 3 m square cross section and 30 m height. The first explosion occurred
in December 1987 in a silo cell containing moist sunflower seed, which was not sup-
posed to be stored in such silos due to the risk of self-heating. However, this had nev-
ertheless been done, and the resulting self-heating developed into extensive smoldering
decomposition, during which methane and carbon monoxide were produced and mixed
with the air in the empty top part of the silo, above the powder bed surface. It is rea-
sonable to believe that the primary explosion was in this mixture of explosive gas and
air and that the ignition source was the smoldering combustion when it penetrated to
the powder bed top surface, as illustrated in Figure 1.9 in Chapter 1. However, dust
deposits on the internal silo walls and roof may well have become entrained by the ini-
tial blast and involved in the explosion. This was only the first of a large series of 20-30
subsequent explosions that took place in the same facility, in one silo cell after the other,
during 1988 and 1989.