Page 206 - Dust Explosions in the Process Industries

Case Histories 179

Figure 2.20 Corner of the silo complex in Tomylovo, USSR, damaged by smolderinggas explosions,
1987-1989 (Courtesy of A. Borisov and B. Celfand, USSR Academy of Science, Moscow).

There are two main reasons for this continued explosion activity in the silo complex.
The most important is the heat transfer from a silo cell in which smoldering combustion
is taking place to the neighboring cells. Such heat transfer is facilitated by the large con-
tact surface area between the cells provided by the square cross section. Furthermore,
the prefabricated construction elements used throughout the entire facility, as shown in
Figures 2.20 and 2.21, may have been comparatively poor heat insulators.
The second main reason for the repeated explosions was that sunflower seed was not
the only material in the facility that was not supposed to be stored there. Some of the
silo cells contained buckwheat and wheat grain of higher moisture contents than the max-
imum permissible limits for storage in such facilities.
During the period of repeated explosions, attempts were made to break the unfortu-
nate chain of events. Cells were opened at the top for inspection. However, this admit-
ted fresh air to the smoldering mass and enhanced the combustion process. Attempts also
were made to quench and cool the powder mass with liquid nitrogen, but this was only
partly successful.