Characterization of shale oil solids removed by the high-gradient magnetic separation technique

The high-gradient magnetic separation (HGMS) technique has been previously shown to remove solid particles successfully from several types of shale oil. The nature of the separated solids was investigated in this study, principally by thermomagnetic measurements over the temperature range 4.2–1173 K and in applied fields up to 1600 kA m^?1. Several phase transformations were identified in the magnetization profiles as a function of temperature. These transitions varied depending on the particular sample, although the low-temperature behaviour was qualitatively similar for all the solids. The magnetization increased over the range of external field studied. The magnetometric data reflect the differences in composition of the different solid samples and indicate the general occurrence of a paramagnetic phase mixed with a trace amount of ferromagnetic component. The bulk mineralogy and elemental composition of the solids were similar to those of the oil shales prior to retorting. Relatively large concentrations of iron sulphides were identified.