A n essential step in the extraction of bitumen from oil sands is the mixing of ore, water, and air prior to bitumen recovery in the p r i m a ry separation vessel (PSV). The purpose of this conditioning step is first to liberate bitumen from the oil sands matrix and then to allow coalescence of bitumen drops and air bubbles so that large, aerated drops can be recovered easily (Shaw et al., 1996). Process variables determining the efficiency of conditioning include ore properties (grade and fine solids content), temperature, mixing time, shear rate, and water chemistry.The conventional method of preparing an oil sands slurry has been to mix oil sands with hot water at pH ≈ 8.5 in a rotating vessel (tumbler). With the recent implementation of hydrotransport technology, in which an oil sands slurry is pipelined directly from the mine site to the PSV, it is expected that the conditioning occurring in the pipeline is sufficient to ensure good bitumen recovery in the PSV. For either method, a knowledge of how the slurry evolves in time for given operating conditions would be invaluable in predicting the physical state of the bitumen and solid phases at the end of the process.Bitumen recovery and froth quality in the PSV depend in large part on the size and density of the bitumen drops. During conditioning, the size distribution of drops at any time is a function of their initial sizes and their subsequent growth due to coalescence with other drops and air bubbles entrained in the slurry. Drop density increases if solid particles are present in or attached to the bitumen and decrease when air bubbles become attached or engulfed. If the kinetics of the particulate phases in the slurry are understood, the process can be controlled to produce a slurry that is conditioned for optimized separation in the PSV.The objective of modelling the kinetics of aggregation and fragmentation processes in a flowing oil sands slurry is to describe the distribution of bitumen in the drops and bitumen-sand aggregates in the system. This information can then serve as input to a model for predicting bitumen recovery and product quality in the PSV.One common method of modelling a particulate system is to solve population balance equations (PBE). In this approach, the motions of individual particles or clusters are ignored; instead, their average behaviour is described by rate equations for mass transfer between classes of aggregates, where each class is defined by a unique composition and structure. The result is a system of coupled integro-differential equations that are analytically intractable except for a small number of simple expressions for the rate constants (kernels) describing particle aggregation and fragmentation.
* Author to whom correspondence may be addressed. E-mail address: friesen @nrcan.gc.ca.Conditioning of an oil sand slurry is a critical step in the extraction of bitumen from oil sand ore. To model the conditioning process, a constant-number Monte Carlo algorithm is used to simulate the mean-field kinetics of coalescing ...