Carbonate Mineral Reactions During Combustion Retorting of Oil Shale: ABSTRACT

Oil shale generally contains approximately 50% mineral carbonates by weight. During combustion retorting some or all of these carbonates decompose and/or react with other mineral species in the shale. Because the heat requirement for these reactions is large, they have a strong influence on the retorting process.

Data on the kinetics of decomposition of the major carbonates in oil shale have been obtained with heating rates and gas environments (N₂, CO₂ and H₂O) expected during typical combustion retorting.

Activation energies and preexponential factors characterizing the rate constants for these reactions have been expressed in a form amenable for use in mathematical models of the retorting process. X-ray data on the final-product mineral phases in fully burned oil shale indicate them to be mainly members of the akermanite-gehlenite series, merwinite, and diopside. These products are formed by reactions between carbonates in the solid state and/or their oxides and other minerals in the shale.

These results have implications for the processing and environmental aspects of oil shale retorting.