Biomass powders, in both raw and thermally treated (torrefied) form, are used in 100%
biomass fired or in coal co-fired plants for power generation. They pose significant fire and
explosion risks during storage, handling, processing and combustion, and therefore their
explosibility characteristics need to be assessed for the design of safe systems and operations.
Wood biomass powders are difficult to characterise for explosibility through standard
methods because of their bulky and fibrous nature. This has resulted in the lack of
reliable data on the explosibility of these materials. In this study we present a new
methodology e with example measurements e for the determination of the minimum
explosible concentrations (MECs) of raw and torrefied wood biomass powders, using a
modified Hartmann tube. This equipment can also be used as a fast screening tool for the
determination of other reactivity parameters, such as flame speeds and rates of pressure
rise, through which the most reactive mixture can be identified for more detailed measurements
in the larger ISO 1 m3 vessel. MEC measurements reported in this paper showed
that both raw and torrefied pulverised wood biomass, were explosible at equivalence ratios
as low as 0.2. This was one-third (1/3) the corresponding concentration for Kellingley coal
(measured with the same method). Flame speeds 5e10 times higher than those of coal
were measured for biomass. Flame speed differences will also have a direct effect on
burner performance and flame stability for systems originally designed to burn coal and
now firing biomass without modifications.