Geochemical Characteristics of Oil Sand Tailings and Bitumen Upgrading By-Products, Alberta, Canada

摘要

Few studies have characterized the metal leaching and acid rock drainage (ML/ARD) potential of tailings from oil sand production, and associated by-products from bitumen upgrading. In order to address this gap, Suncor Energy Inc. undertook sampling to characterize their various tailings and by-products using ML/ARD characterization methodologies typically applied to coal and metal mine wastes. Tailings types characterized were mature fine tailings (MFT), dried mature fine tailings (DMFT), and froth treatment tailings (FTT). Bitumen upgrading by-products characterized were coke and coke ash. Methods used included conventional acid-base accounting, net acid generation testing, X-ray diffraction, and humidity-cell testing.The characteristics of MFT, DMFT, and FTT reflected the mineralogy of the McMurray Formation, which includes pyrite, siderite, ankerite, and various clay minerals. In contrast, the characteristics of coke are carried over from the bitumen though pyrite is not destroyed because cokers operate under reducing conditions. Coke ash is mostly composed of amorphous aluminosilicate melts, and contains readily leachable concentrations of nickel and vanadium. The application of standard ML/ARD characterization methods to oil sands is complicated by the presence of residual bitumen, which makes tailings hydrophobic and rich in organic carbon.