Page 12 - Dust Explosions in the Process Industries

Contents ix

2.9.1 General outline 182
2.9.2 Explosion initiation and development, Scenario 1 184
2.9.3 Explosion initiation and development, Scenario 2 186
2.9.4 Additional remarks 187
2.10 Fires and explosions in coal dust plants 187
2.10.1 Methane explosion in 17,000m3coal silo at Elkford,
British Columbia, Canada, in 1982 187
2.10.2 Methane/coal dust explosion in a coal storage silo
at a cement works in San Bernardino County, California 188
2.10.3 Gas and dust explosion in a pulverized coal
productiodcombustion plant in a cement factory
in Lagerdorf, Federal Republic of Germany, in October 1980 B 89
2.10.4 Further explosion and fire incidents involving coal 189
2.11 Dust explosion in a silicon powder grinding plant at Bremanger,
Norway, in 1972 190
2.12 Two devastating aluminum dust explosions 192
2.12.1 Mixing section of premix plant of slurry explosive factory
at Gullaug, Norway, in 1973 192
2.12.2 Atomized aluminum powder production plant at Anglesey,
United Kingdom, in 1983 P95

3 Generation of Explosible Dust Clouds by Reentrainment
and Redispersion of Deposited Dust in Air 199
3.1 Background 199
3.2 Structure of the problem 200
3.3 Attraction forces between particles in powder or dust deposits 202
3.3.1 Van der Waals forces 202
3.3.2 Electrostatic forces 203
3.3.3 Interparticle forces due to liquids 204
3.4 Relationship between interparticle attraction forces and strength
of bulk powder 206
3.4.1 Theories 206
3.4.2 Measurement of the mechanical strength of cohesive bulk
powders and dusts 208
3.5 Dynamics of particles suspended in a gas 213
3.5.1 Terminal settling velocity of a particle in the gravitational field 213
3.5.2 Drag on a particle in general 215
3.5.3 Movement of a particle in an arbitrary flow 218
3.5.4 Speed of sound in a dust cloud 219
3.5.5 Propagation of large-amplitudepressure waves in dust clouds 221
3.6 Dislodgement of dust particles from a dust or powder deposit
by interaction with an airflow 221
3.6.1 Airflow parallel to a monolayer of particles on a plane,
smooth surface 221
3.6.2 Airflow parallel to the surface of a powder or dust deposit 224
3.6.3 Entrainment of particles by an upward airflow through
a particle bed 230