Chemical Engineering June 2019 - 37

tive, the particle size of table salt is
around 100 microns.
Primary and secondary explosions
One of the main dangers of a dust explosion
occurs when combustible dusts
ignite and cause a chain reaction with
other
dusts. Dust explosions
create
their own self-sustaining domino effect,
which continues as long as fuel exists. A
secondary explosion occurs when dust
accumulated on floors or other surfaces
is lifted into the air and ignited by the primary
explosion. The primary explosion
liberates dust from surrounding surfaces
(including beams and ledges), causing
them to be suspended in air and dispersed.
The secondary explosion propagates
from the resulting dust cloud.
Secondary explosions occurring when
the structural integrity of the facility may
already be compromised can result in
catastrophic results.
Primary and secondary explosions
often occur together, allowing for transitions
from fire to multiple explosions
and vice versa. In many cases, a priCall
the
Solids Mixing
Ribbon & Cone Blenders
Fluidizing Mixers
Sigma Blade Mixers
(also for high-viscosity mixing)
Size Reduction
Wet & Dry Size Reduction
Steel & Ceramic Lined Mills
Jars & Jar Rolling Mills
Vacuum Drying
Dryers & Complete Systems
TABLE 2. PARTICLE SIZES OF SOME COMMON COMBUSTIBLE AND NON-COMBUSTIBLE
MATERIALS (IN MICRONS)
Talcum powder, red blood cells, fine silt, cocoa 5 to 10
Pollen, milled flour, coarse salt 44 to 74
Table salt 105 to 149
Cornstarch from Port Wentworth facility storage silo 10
Powdered sugar product from the Port Wentworth facility 23
Ganulated sugar product from the Port Wentworth facility 286
mary explosion occurs inside a process
vessel, such as a sieve, dryer, mixer,
conveying system or silo (Figure 3). It is
within these confined environments that
the five elements of the dust explosion
pentagon are met. The resulting impact
of the first explosion usually ignites the
second. Unburned fuel from the primary
explosion is ejected by the blast outside
the enclosure, causing dust to become
airborne, where it is susceptible to ignition
and is capable of triggering a secondary
explosion.
A secondary explosion can be more
destructive than the primary due to the
increased concentration of dispersed
for all your solids processing
Experts
Applications:
APIs ∙ Ag-Chemicals
Biologics ∙ Catalysts
Ceramics ∙ Chemicals
Food Ingredients
Herbicides ∙ Minerals
Nutraceuticals ∙ Pesticides
Pharmaceuticals ∙ Pigments
Polymers ∙ Powdered Metals
Proteins ∙ Resins ∙ Vitamins
Shield your
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CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
JUNE 2019
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37
Q ual
191
ity &
Since
1
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Chemical Engineering June 2019

Table of Contents for the Digital Edition of Chemical Engineering June 2019
