Moisture adsorption and desorption characteristics of some South African coals
QP Campbell, MD Barnardo, JR Bunt
The high final total moisture content of fine coal after mining and
processing is one of the major reasons that this resource is not
extensively used in subsequent power generation, combustion, or
other conversion processes. Some coal products, like export coal, may
be subjected to a variety of environmental conditions during
transport and storage, such as temperature and humidity. To
understand the mechanisms by which moisture is attracted and held
on and within fine coal particles, further information is needed
regarding the processes occurring at the coal surface. In order to
determine the correlation between physical coal properties and its
moisture adsorption and desorption characteristics, a series of
sorption experiments were conducted on various coal samples under
climatically controlled conditions. Equilibrium moisture data was
collected while changing the temperature and humidity. This data
was correlated to coal properties such as particle size, porosity,
maceral composition, and mineral content. All the coals that were
studied were medium-rank bituminous coals. It was found that the
best predictors for moisture adsorption and desorption were the
mineral and inertinite contents.
Keywords: moisture, adsorption, desorption, fine coal, surface properties.