Correlations Between Oil Sands Minerals And Processing Characteristics
Authors: Mikula R.J. , Munoz V.A. , Lam W.W. 
Published: March 2010

The geology and subsequent mineral composition of oil sands deposits have important consequences for their processing behaviour. Differences in oil sands processability and extraction yields can be dependent upon many factors including the composition of the mineral components and the organic complexes that are associated with certain minerals. These mineral-organic associations help provide the bridge which leads to carry over of bitumen with the tailings as well as carry over of water and mineral matter with the product. Characterization of the minerals via various laboratory techniques and the relationship of these measurements to processing behaviour is discussed. Portions of this work were presented at the 1988 annual meetings of The Canadian Institute of Mining and Metallurgy and the Chemical Institute of Canada.

Introduction

Bitumen extraction from oil sands is carried out commercially via the Clark hot water process and involves mixing the raw oil sand with steam and a caustic solution. The bitumen separates from the sand and floats to the surface of the suspension. The amount of water and mineral matter that is carried over with the bitumen product and the amount of bitumen which is lost with the tailings are important parameters in determining the process efficiency.

The recovery of bitumen from oil sands is a complex process With many steps involving the handling of water/oil systems which are often in the form of emulsions. The first stages of the process concentrate on separating the bitumen from the water and mineral matter, whereas later on the main problem is to remove residual water from the bitumen product. In order to facilitate this removal a combination of chemical (demulsifiers) and mechanical (centrifuges) means is often used.

Losses in process efficiency can be due to many factors, several of which are related to the mineralogy of the oil sands feed. Previous studies(1–3) have correlated the amount of fine clay with processing problems; the clays were found to stabilize the water-in- oil emulsions formed in the bitumen product. In addition, clay floes can trap bitumen, carrying it into the tailings stream. Understanding the correlations between the mineralogy of the raw oil sands and the ultimate processability will help develop methods to deal with problem feeds as they reach the extraction plant rather than after they reach the refinery or tailings pond.

The amount and size distribution of the clays has been shown to be important in determining the processability of the oil sands, but equally important is the nature of the mineral matter. Chemical characterization via electron microprobe analysis is a useful tool in determining both the quantity and size distribution of the critical mineral components. Preliminary results have shown the importance of the iron compounds; pyrites appear to be relatively innocuous although iron carbonates and hydroxides seem to provide a bridge for organic-mineral interactions which lead to processing problems, i.e. carry over of water, clays and minerals with the bitumen and loss of bitumen to the tailings.

Direct observation of frozen hydrated samples in the electron microscope has been utilized for evaluation of both the size distribution of the dispersed phase and the chemical composition(4–5).

The size distribution of the dispersed phase is important because centrifugal separation of the emulsions will be more difficult with smaller droplets; as will chemical treatments because surface area is higher per unit volume. The nature of the clays and other minerals which are carried over with the bitumen product also directly affects the bitu