Abstract

Conventional froth flotation, flotation columns, air-sparged hydrocyclones, and combinations of these were used to recover residual bitumen from extraction plant tailings in bench-scale tests. Intensifying the interaction between air bubbles and bitumen droplets in mechanically agitated flotation cells in conjunction with a quiescent separation process produced promising results. A flowsheet that combines the use of mechanically agitated flotation cells with a stationary separator was developed, which can be described as intensifying aeration and stationary separation processes. The results showed that this process is an effective approach to recover bitumen from tailings with low bitumen content.

The flotation kinetics of bitumen were investigated in a batch flotation cell, which provided information on the relationship between retention (or flotation) time, bitumen recovery, and froth quality. Three flotation models (i.e., simple first-order model, Klimpel model, and fast/slow flotation model) were used to fit the kinetic data. The effect of operating parameters (i.e., impeller rotation speed and aeration rate) on bitumen flotation and the dispersion of bubbles and bitumen was also examined in a lab-scale flotation cell. The results generated are helpful in interpreting and optimizing the bitumen recovery process.

Introduction

The hot water flotation process is applied in a large-scale commercial operation for extracting bitumen from Athabasca oil sands. Tailings from bitumen extraction operations at the Suncor oil sands plant contain from 0.2 to 0.4% bitumen by mass. There is therefore considerable economic incentive to develop processes to recover oil from the tailings streams and, at the same time, to reduce the impact of tailings on the environment.

In order to utilize these low-grade bitumen resources, benchscale tests of Suncor plant tailings were conducted at the Western Research Centre using conventional froth flotation, flotation columns, air-sparged hydrocyclones, and combinations of these units. The flotation kinetics of bitumen were investigated using a batch flotation cell, which provided information on the relationship between retention (or flotation) time, bitumen recovery, and froth quality. The effects of operating parameters (i.e., impeller rotation speed and aeration rate) on bitumen flotation and the dispersion of bubbles and bitumen were also examined in a lab-scale flotation cell. The results generated are helpful in interpreting and optimizing the bitumen recovery process.

Flowsheet Development

In the preliminary tests, an attempt was made to use a flotation cell, a flotation column, and an air-sparged hydrocyclone to recover bitumen from Suncor plant tailings containing 0.09% by mass bitumen at 60 ° C. The preliminary tests indicated that it is difficult to achieve acceptable results using column flotation because of poor bitumen aeration. This can be attributed to limited turbulence and/or attrition in the column which resulted in the lack of effective air bubblelbitumen collision and attachment. The results using an air-sparged hydrocyclone indicated that it tends to intensify bitumen aeration in the centrifugal field. However, attrition in the cyclone generated good-quality froth which reported to both the overflow and underflow of the cyclone, resulting in significant amounts of bitumen lost in the cyclone underflow stream.

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