March 2008

Sugar dust likely culprit in refinery blast

Table sugar is sometimes an ingredient in homemade firecrackers.

Amateur rocket builders like to use a mix of sugar and potassium nitrite as fuel. 

Imperial Sugar Company experienced an explosion and fire at its sugar refinery in Port Wentworth, Ga., near Savannah the evening of 7 February. The plant burned for a week, eight workers died, and 20 or so more are scarred for life.

Tiny sugar particles burn up almost instantly because of their high ratio of surface area to volume. A spark could supply enough energy to set off a small explosion and any place containing sugar dust and lots of oxygen, like a sugar silo, could quickly become a dangerous environment reported Slate. 

According to the National Fire Protection Association, a room with at least 5% of its surface area covered with anything more than 1/32nd of an inch of organic dust presents an explosion hazard. 

At high temperatures sugar itself can be set ablaze. Extreme heat forces sucrose to decompose and form a volatile chemical called hydroxymethylfurfural, which easily ignites and sets the rest of the sugar on fire.

The especially combustible sugar dust at a refinery comes from the last stage of processing, after the crystals have passed through a heated dryer to remove the last bits of moisture. As the refined sugar drops onto a conveyer belt and moved into a silo, dust can float into the air. 

The factory might also grind sugar to make confectionary powder or just to make sure the grains are all the same size, which also creates more sweet dust. An electrical spark from a motor, a pump, from ball bearings rubbing together, or even from a light switch on a wall can set off an explosion. 

In addition, once a fire gets going in a silo, temperatures can keep rising as long as there is a large fuel source-the sugar, which at this point has no water and is completely flammable-and no easy exit for the heat.

The Georgia fire reached 4,000°F at one point.