Location and distribution of inorganic material in a low ash yield, subbituminous coal

Previous studies of mineral matter in low ash yield, low rank coals have suggested that much of the inorganic material is present as organically bound elements rather than as discrete minerals. This study investigates the location and occurrence of this inorganic material to the angstrom level using non-invasive small angle scattering techniques.Microstructural analysis conducted on matrix and vitrain samples, collected from the subbituminous coals of the Huntly coalfield, found that the inorganic material is located in the 12.5 Å < r < 125 Å size range. This was consistent for all samples, irrespective of seam or location. As there was greater influence on X-ray scattering curves seen in the vitrain samples than the matrix samples, it is suggested that the inorganic material is located within the structured vitrinite tissues, likely originating from the original plant material rather than being precipitated post deposition. The fitting of microstructural models to the scattering curves suggests that the inorganic material exists as inorganic shells or coatings.

► We investigate the occurrence of inorganic material in a low ash yield, low rank coal. ► Microstructural analysis was conducted using small angle scattering techniques. ► The inorganic material exists as coatings in the 12.5 Å < r < 125 Å size range. ► The inorganic material is predominately located within the structured vitrinite tissues.