Kinetics of Decomposition of Colorado Oil Shale. II. Carbonate Minerals

摘要

The kinetics of decomposition of nahcolite, dawsonite, dolomite, and calcite in oil shale have been investigated using heating rates expected during typical combustion retorting. Furthermore, the rates of decomposition of calcite and dolomite in shale have been studied over a range of heating conditions from 2 to 20 exp 0 C/min and CO sub 2 partial pressures of 0 to 1.0 atm. These results lead to the conclusion that, under typical combustion retorting conditions, most of the calcite reacts with SiO sub 2 , rather than decomposing to CaO. Activation energies and preexponential factors characterizing the rate constants for the above reactions are also given; these ''engineering'' rate data are expressed in a form amenable for use in mathematical models of the retorting process. Also presented are x-ray data on the final product mineral phases in fully burned oil shale. These are found to be mainly members of the akermanite-gehlenite series and diopside. These products are formed from reactions in the solid state of the carbonates and/or their oxides with other minerals in the shale. A summary of enthalpy data for these reactions is given. Finally, the practical implications and limitations of these results for computational and experimental studies of large-scale shale combustion retorting processes are discussed. Included in this discussion are recent results showing the effects of steam on the mineral reactions in shale. (ERA citation 04:005254)