A review of the effects of minerals in processing of Australian oil shales

Abstract

In recent years considerable effort has been devoted to the characterization and processing of the major oil shale deposits in Queensland, with emphasis on nine deposits: Rundle, Stuart, Condor, Nagoorin, Nagoorin South, Duaringa, Lowmead, Yaamba and Julia Creek. Variations in mineralogy are important in the selection of optimum process conditions. This paper reviews the main effects of the minerals on processing and indicates how these influence the choice of process conditions. Mineralogical analyses are presented for each of the deposits, with emphasis on the significant minerals, including the clay minerals smectite and kaolinite, the carbonate minerals calcite and siderite, pyrite and buddingtonite. Of these minerals, smectite, siderite-type minerals and buddingtonite are rarely found in oil shales outside Australia and required chemical and thermal characterization. The minerals are decomposed endothermically in the retort and/or combustor. The carbonate minerals are important in limiting SO 2 emissions, and the clay minerals act as catalysts in oil coking reactions. In addition, minerals are sources of trace elements which are of environmental concern or are of by-product potential. Significant mineral reactions are listed in relation to processing using an above-ground process with combusted solids recycled as a heat carrier to the retort. The importance of the minerals in processing is illustrated by example for the appropriate deposit or deposits. Examples are given of the ways in which process conditions can be modified to control mineral reactions for improved processing. Areas for future work on mineral reactions and effects are indicated.