Review of oil sands tailings technology options

Unidirectional consolidation of clay soils and flocculated suspensions

“…A feedback system at the base could be used to monitor the effective stress of the consolidated soil exiting the system [25]. An advantage of the proposed design is that the tailings mixture can be piped directly into the system (figure 4) avoiding the detrimental segregation that occurs on the beach area of large tailings ponds [21,26]. The smaller design may also allow the consolidation system to be placed near to the extraction plant; in this case heat from the tailings slurry can be maintained within the system, with the recovered hot water reused, rather than dissipating as the slurry is piped to remote tailings ponds.…”

“…Equation (21) shows that the effective stress on the soil matrix increases with z from its initial value σ 0 at z = 0. As an example, for a clay slurry with initial effective stress σ 0 = 0.1 kPa, consolidation coefficient Because of the very slow sedimentation and self-weight consolidation rate of colloidal particles, the estimated reclamation time is several centuries [7,8], and the pond steadily increases in volume during the lifetime of the mine.…”

“…These colloidal particles then take many decades to sediment to a water content low enough for land reclamation. One method that has been used to enhance the rate of consolidation is to install vertical wick drains in the top of the pond [21]. While this method works well, it is expensive and labour-intensive, the drains tend to deform over time [19], and the method does not eliminate the need for the tailings pond itself.…”

“…A tailings suspension is a multicomponent mixture of colloidal particles (clay+silt), a coarse fraction (silt+sand) and a suspending fluid (water+dissolved ions+residual oil) [4]. A major challenge of tailings treatment methods is the safe and economical removal of the fine clays from the suspension [5]. Currently the most widely used method is long-term sedimentation and self-weight consolidation [6].…”

Impact of fugitive bitumen on polymer‐based flocculation of mature fine tailings

“…Several patents and publications describing techniques to enhance tailings consolidation are available in the open literature. The proposed approaches can be summarised as: (i) composite/consolidate tailings (CT) process, (ii) CO 2 enhanced CT process, (iii) flocculation‐assisted centrifugation, (iv) freeze thaw dewatering and (v) flocculation‐assisted thin lift/drying . The use of polymer flocculants has been considered in detail.…”