Porous networks
within coal can determine its value as a fuel; porosity helps define how
well certain types of coal burn and whether methane in the pores can be
extracted efficiently from coal beds as an additional
source of energy. Determining the porosity of complex natural materials
such as coal is difficult, because a sample may contain many networks of
pores that can be often disconnected from each other and from the
surface of samples. Although several techniques
for measuring porosity exist, Melnichenko
et al. used small-angle
neutron scattering to examine the interconnectivity of pores within
coal samples as a function of pore size in a noninvasive and
quantitative manner. They compared the scattering profiles
of a coal sample in a vacuum and the same sample saturated with
contrast-matching gases that fill accessible pores and make them
invisible to the neutron beam. The analysis confirms that the proportion
of isolated and accessible pores varies widely based on
coal type, but also shows that pore accessibility varies with gas
overpressure. These results may eventually help determine the
feasibility of enhanced methane recovery from coal beds by injecting CO
2 gas at high pressure.
Fuel 90, 10.1016/j.fuel.2011.06.026 (2011).Source:
SCIENCE, Volume 334, Issue (6052); Editors' Choice: Highlights of the recent literature