Evaluation of a new treatment technology for improving oil sands tailings management

Fernando Da Silva, Michael Graham, J. Don Scott, G. Ward Wilson

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Laboratory and Field Testing

ABSTRACT: of a new treatment technology for improving oil sands tailings management Fernando Da Silva Chevron Canada Limited, Calgary, Alberta, Canada Michael Graham Shell Canada Limited, Calgary, Alberta, Canada J. Don Scott & G. Ward Wilson Department of Civil & Environmental Engineering, University of Alberta, Edmonton, Alberta, Canada ABSTRACT The accumulation of large volumes of mature fine tailings (MFT) has been a major concern for the oil sands industry for decades. Currently there are several tailings initiatives directed at MFT fines capture and shear strength with the aim to comply with the Alberta Energy Regulator (AER) Directive 074. However, there are still significant challenges involved in the conversion of MFT into trafficable deposits to facilitate reclamation within a reasonable timeframe. Tailings dewatering technologies have advanced considerably through the use of improved flocculants and altered tailings chemistry in an attempt to achieve non-segregating tailings. The effect of coagulation and flocculation on the behaviour of MFT comprised predominantly of non-clay mineral fines and, to a lesser degree, of clay minerals is evaluated in this study. The mechanism by which coagulation and flocculation occur is interpreted on the basis of a new tailings technology that integrates the initial slurry density with chemical treatment. The chemical treatment utilizes an inorganic metal salt as a coagulant and an anionic polymer with a low charge density and very high molecular weight as a flocculant. Supporting data include geotechnical laboratory test results in the form of inherent and mechanical properties of the treated MFT. These test results are compared to other data available in the literature. RÉSUMÉ L'accumulation de grandes quantités de résidus fins (MFT) a été une preoccupation majeure pour l'industrie des sables bitumineux depuis des décennies. Actuellement, il existe plusieurs initiatives visant à la capture des residus fins de MFT et l'augmentation de sa force de cisaillement pour assurer la conformité de la directive 074 de l'Alberta Energy Regulator (AER). Cependant, il y a encore des défis importants liés à la conversion de MFT dans les dépôts praticables dans des délais raisonnables qui facilitent la réhabilitation de terrains. Les technologies de déshydratation ont considérablement progressé grâce à l'utilisation d'agents de flocculation améliorées et en modifiant la chimie des résidus pour atteindre des résidus non en ségrégation. L'effet de la coagulation et de floculation sur le comportement des MFT compose majoritairement de non-argile fines minérales et, à un moindre degré, des minéraux argileux est évaluée dans la présente étude. Le mécanisme par lequel la coagulation et la floculation se produit est interprété sur la base d'une nouvelle technologie qui intègre la densité de la suspension initiale à un traitement chimique. Le traitement chimique utilise un sel métallique inorganique en tant que coagulant et un polymère anionique ayant une densité de charge faible et de très haut poids moléculaire comme floculant. Données à l'appui comprennent les résultats des tests de laboratoire géotechnique sous la forme de propriétés inhérentes et mécaniques de la MFT traité. Ces résultats d'essai sont comparés à d'autres données disponibles dans la littérature. 1 INTRODUCTION The purpose of this study is to evaluate a new treatment technology that converts oil sands mature fine tailings (MFT) into consolidated trafficable deposits to advance land reclamation, as per the Alberta Energy Regulator (AER) Directive 074 (D74). It is a well-known fact that compliance with AER-D74 is still a problem to be solved in the majority of oil sands operations. The accumulation of large volumes of MFT has been a major concern for the oil sands industry for decades. Currently, there are several tailings initiatives directed at fines capture and dewatering to achieve compliance with AER-D74. The emphasis in the existing technologies for MFT treatment has been almost entirely on the tailings solid phase (fines capture), while the properties of the tailings liquid phase and soil-water-chemistry interactions have received less attention. The majority of oil sands operators thicken tailings by the addition of synthetic polymers, with the expectation that the flocculants will provide the beneficial effect of fine tailings particle agglomeration. Unfortunately, significant amounts of trapped water still remain in the flocculated tailings at the discharge point, resulting in a low rate of shear strength gain and therefore long consolidation timeframes. To reiterate, very little attention has been directed to the interactions between tailings mineralogy, tailings pore water chemistry, the acid-base nature of the tailings liquid phase and the development of treatment technologies that will maximize fines capture and provide efficient water release before, during and after tailings deposition. Therefore, it is our view that the current

RÉSUMÉ: ation of a new treatment technology for improving oil sands tailings management Fernando Da Silva Chevron Canada Limited, Calgary, Alberta, Canada Michael Graham Shell Canada Limited, Calgary, Alberta, Canada J. Don Scott & G. Ward Wilson Department of Civil & Environmental Engineering, University of Alberta, Edmonton, Alberta, Canada ABSTRACT The accumulation of large volumes of mature fine tailings (MFT) has been a major concern for the oil sands industry for decades. Currently there are several tailings initiatives directed at MFT fines capture and shear strength with the aim to comply with the Alberta Energy Regulator

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Fernando Da Silva; Michael Graham ; J. Don Scott; G. Ward Wilson (2014) Evaluation of a new treatment technology for improving oil sands tailings management in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper448,author = Fernando Da Silva; Michael Graham ; J. Don Scott; G. Ward Wilson,title = Evaluation of a new treatment technology for improving oil sands tailings management ,year = 2014}