TABLE OF CONTENTS Wherever combustible dusts are handled, there is a chance of dust explosion. A large range of materials can give rise to dust explosions. More people (36) were killed in a dust explosion of a wheat silo (Westwego, Louisiana, 1977) than were killed in the Phillips Petrochemical plant explosion at Pasadena (24) in 1989 (see Chapter 13).
Because the combustible component of the fuel-air mixture (i.e., the dust) does not occupy significant volume, it is possible for a given volume of dust-air mixture to contain more fuel and oxygen than a similar volume of gas-air mixture. Thus a dust explosion in a closed vessel can generate higher pressures than a vapor explosion. Typically, dust explosions in closed vessels can generate peak pressures of up to 10 times (and more in some cases) the initial pressure in the vessel.
Typical scenarios for serious dust explosions are as follows:
A combustible solid is being ground in a machine. Dust from previous operations has accumulated on all horizontal surfaces in the building, on ledges, girders, etc. Overheating or a spark between striking metal surfaces causes a small local explosion in the grinding machine. That local explosion shakes loose the accumulated dust in the building. Incandescent dust particles from the first explosion ignite the secondary cloud, and a very large secondary explosion occurs.
A small dust explosion inside a machine ruptures the casing of the machine and propels the settled powder in the machine into the surrounding...
