Mineral reactions in the processing of Australian Tertiary oil shales

Abstract Mineralogical, mineral characterization and thermogravimetric studies were made of raw and processed shale samples from the most prospective sections of the Rundle, Stuart, Condor, Duaringa, Nagoorin South, Nagoorin, Yaamba and Lowmead oil shale deposits. The effects of processing on minerals were determined in sufficient detail to establish the relevance of the various minerals and their reactions in oil shale processing. Minerals identified as the most significant in processing were smectite, kaolinite, siderite-type minerals and pyrite. Smectite and siderite-type minerals are characteristic of the oil shales of eastern Queensland. Smectites were found to be comparable in the various deposits and to be members of the montmorillonite/nontronite series with unusually low thermal stability. Four types of siderite (siderite, manganoan siderite, magnesian siderite and high magnesian siderite) were found, with progressively increasing decomposition temperatures in the retort. The most important mineral reactions occurring in the preheater, retort and combustor have been identified. Endothermic dehydroxylation and decomposition reactions of smectite, kaolinite, siderite minerals and pyrite influence heat requirements and gaseous products from retorting and combustion. The results indicate the possibility of transferring some of these reactions from the retort to the combustor by control of partial pressures of vapour phases in the retort. A sound basis has been established for future studies of the effects of specific minerals on oil coking reactivity and oil yields in retorting.