Mineral Particle Interaction Control Of Tar Sand Sludge Stability

Abstract

Abstract The tar sand tailings derived from the hot water process for recovery of bitumen from the Athabasca tar sands contain three separate components. Of these, the tailings sludge which consists of the tine solids fraction constitutes the major tailings disposal problem. The inability of the tar sand tailings sludge to settle in a reasonable time period requires that measures be taken to provide for effective containment of the sludge. In this study, the stability of the sludge is examined from the viewpoint of fundamental interactions of the various solid constituents (mineral particles) in the sludge with proper accountability for the chemistry of the fluid phase. The particular suspension characteristics associated with non-Stokian behaviour can be described through considerations of double-layer theory provided particle-surcharge loading and pore pressures are properly recognized in the analyses. Comparisons between predicted values for equilibrium sludge suspension volumes and actual sludge volumes, given in terms of solids content and obtained from recent surveys of actual sludge ponds, show excellent agreement. Capability for prediction of the amount of water associated with various mineral solids (suspension volumes) in the tailings pond has been developed from the preceding, utilizing a knowledge of the proportions of the mineral solids in the sludge. Introduction The tar sand tailings obtained as throwaway material in the hot water extractive processing of tar sands can be categorized as follows:Screen oversize.Sand tailings.Tailings sludge Of interest here is the tailings sludge, both as a total sludge and also as individual components which comprise the sludge. The inability of the tailings sludge to settle (sediment) within a short reasonable' time period requires that measures be taken to effectively contain the sludge during the settling process. To provide for a proper appreciation of the stability status of the sludge as a suspension, and to allow for input to planning purposes and subsequent disposal of the settled solids (from the sludge), it becomes necessary to develop an understanding of the various interactions and mechanisms which participate in the production of the dynamic status of the sludge. Note that the contained sludge solids will continue to settle while still being replenished with fresh sludge from the extractive process. This study addresses the phenomenon of mineral solids particle interaction as control of the immediate (and continuing) status of the tailings sludge in view of the above-stated problem. * Tailings Sludge Status Table 1 (from Camp, 1976) shows the typical distribution of tailings sludge material. The minerals of interest in the fine fraction of the solids in the sludge are illite, kaolinite, and montmorillonite. Table 2 shows the types and proportions of minerals present in the fraction of the sludge material. The details shown in the Table have been obtained from analysis of a representative sample obtained in the 1976 G.C.O.S. Pond Survey. Note that this distribution is one of those used for computations of actual void ratio and solids content depicted in Figs. 9 and 10.