Preliminary mineralogical investigation of Leicestershire low-rank coal

A preliminary mineralogical/geochemical investigation of low-rank coals from Leicestershire, England, has been carried out with a view to their future beneficiation. Analytical scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) have been used to identify and assess the distribution of mineral phases likely to give corrosion-producing or slag-forming materials during combustion, and those minerals which would be potentially valuable by-products of beneficiation processes. Differences in the mineral petrography of borehole samples from the Vale of Belvoir Prospect and coal from Bagworth Colliery are compared. Samples from both areas contain substantial amounts of epigenetic minerals: calcite, dolomite, kaolinite and fluor-apatite are important phases in the Bagworth sample, whilst gypsum, illite, quartz, kaolinite, barytocelestine, pyrite, chalcopyrite, anatase, galena and sphalerite occur in the Vale of Belvoir samples. Whereas the presence of halides in the Bagworth coal would seem to be a possible source of boiler-corrosion problems, the major undesirable characteristic of the Vale of Belvoir coal is the presence of significant amounts of metal sulphides. However, extraction of sulphides from this coal prior to combustion could provide a valuable source of metals as a by-product. Certain trace element concentrations in the Vale of Belvoir samples have also been determined by instrumental neutron activation analysis (INAA) and higher levels of lanthanide elements are present in the whole coal relative to mineral veins (mainly gypsum). Trace-element signatures may provide a useful distinction between syngenetic and epigenetic mineral formation.