Heliumvolume dynamics of Upper Freeport coal powder and .
WEBJan 7, 2009 · Apparently, the dimensions of a typical building block in the coal powder and lumps do not significantly exceed the particle size in the coal powder (< 150 μm). Evolution of the sorption–desorption rates indies that exposure to 7 MPa of helium at room temperature may change the texture and apparent (helium) density (by 1–3%) of dry coal.