Book review

Abstract

Lean limit concentrations and limestone rock dust inerting requirements were measured in a 20-L chamber for a range of carbonaceous dusts including various ranks of coal, gilsonite, and artificial mixtures consisting of polyethylene and graphite. Although there is some uncertainty in the true yield of volatiles for some of the fossil mineral dusts, especially at flame flux levels, the data show that the combustible volatile content of the carbonaceous dusts is the dominant factor governing their combustion behavior in the dust explosions. The char residues and graphite are essentially inert on the rapid time scale required for flame propagation processes in explosions. The lean flammability limits of the various dusts correspond to invariant combustible volatile concentrations of about 30 to 40 g/m3. Total interting of the dusts occurs when the inert content of the mixture exceeds about 90 to 95 wt pct or, equivalently, when the combustible volatile content is less than 5 to 10 wt pct. The char's role is equivalent to that of the other inert constituents, such as ash and rock dust.In addition to the 20-L explosibility experiments, volatile yields of the various coals were measured using a high power, carbon dioxide laser at flux levels of 110 to 115 W/cm2. These measurements provide new data on the volatilities of 110 μm particles of the various coals, but some uncertainties remain in the absolute volatilities of the various sized coals used for the 20-L tests.A relatively simple volatility model for the various fossil mineral dusts can be used to explain their explosion propagation behavior and their extinction limits. When the uncertainties in volatility were removed by using the artificial mixtures of a completely volatilizable fuel (polyethylene) and the nonvolatilizable graphite, the model was confirmed.