Page 47 - Dust Explosions in the Process Industries

20 Dust Explosions in the Process Industries

- Minimum lncendlvib‘
ignition

Y --1
io5- I
I
104- I
io3-

10’-
IO’ -
5
100- 2
rn
10‘-
Figure 1 .I5 Comparison of ranges of minimum
ignition energies of dusts and gases in air, with the
10’2-
P equivalent energies of various types of electrostatic

1.2
SIGNIFICANCE OF THE DUST EXPLOSION HAZARD:
STATISTICAL RECORDS

1.2.1
RECORDING DUST EXPLOSIONS, AN ACTIVITY
OF LONG TRADITIONS

Dust explosions have been a recognized threat to humans and property for a long time.
One of the earliest comprehensive reports known is Count Morozzo’s (1795) detailed
analysis of an explosion in the flour warehouse of Mr. Giacomelli in Turin in 1785 (see
full report in Chapter 2). It is interesting to observe that Morozzo also mentions even
earlier incidents of violent combustion of clouds of flour in air.
However, at the time of Morozzo, the coal mining industry was not fully aware of the
importantpart played by coal dust in the serious coal mine explosions, which had become
quite common. Faraday and Lyell (1845) were probably some of the first scientists to
realize the central role of coal dust in these explosions. In their report to Sir James
Graham, they discussed the fatal explosion in the Haswell coal mine near Durham,
United Kingdom, on September 28, 1844. It was concluded that the primary event was
a methane/air (“fire-damp”)explosion initiated by a defective Davy lamp. However,the
central role of the coal dust in developing the devastating main explosion was empha-
sized, based on a systematic analysis that is exemplary even today. In their report Faraday
and Lyell stated:
In considering the extent of the fire for the moment of explosion, it is not to be supposed that fire-
damp is its only fuel;.the coal dust swept by the rush of wind and flame from the floor, roof, and
walls of the works would instantly take fire and burn, if there were oxygen enough in the air present