Oil yields from combustion retorting of mixtures of Australian low rank oil shale and lignites

Abstract

Rundle oil shale containing 12.9 wt.% of organic carbon was retorted using a combustion-type retort. It was possible to quantify the reduction in oil yield (compared with Fischer assay) due to the combustion of oil vapour during retorting. The oil yield was only 7.2 wt.%, compared with a Fischer assay oil yield of 8.7 wt.%, when retorting was carried out with excess air but no additional source of carbon. Oil yields could be improved by mixing lignite, available from within the Rundle deposit, with oil shale before retorting. Oil yields, based on charge, from mixtures containing more than 10% lignite decreased with increasing lignite content, but were virtually identical with Fischer assay oil yields from the mixtures. The maximum oil yield was about 8.5 wt.% for 6 wt.% lignite in the mixtures. The resulting oils were slightly heavier and more aromatic than the oils obtained by Fischer assay, but showed no significant difference in oxygen content.