Small Scale Simulation of Pipeline or Stirred Tank Conditioning of Oil Sands: Temperature and Mechanical Energy

Abstract

The oil sands industry is moving away from tumbler conditioning at 80 °C to pipeline conditioning, often at significantly lower temperatures. This lower temperature conditioning can be less efficient, requiring longer conditioning times. Control of conditioning time in a pipeline is difficult and inadequate conditioning can result in either lower recoveries or higher froth densities, depending upon the operating conditions. A bench scale test was developed at CANMET to simulate the mechanical conditioning environment found in a stirred tank or in a pipeline. A small scale extraction test has been used at CANMET to investigate the relationship between the efficiency of oil sands conditioning and various process variables. A shift from relatively high temperature tumbler conditioning to pipeline or hydrotransport conditioning requires a slightly different approach to batch extraction testing. The CANMET test protocol has been compared to pipeline and stirred tank conditioning at a pilot scale and has been used to investigate the effect of several process variables in oil sands extraction. This technology brief discusses the preliminary findings and a potential link to operating experience.Introduction. Conditioning is conventionally considered to be the separation of bitumen from the mineral matrix, combined with air attachment. At low temperatures, bitumen separation may be complete, but inadequate air attachment can result in poor bitumen recovery. Oxidation or degradation of the bitumen can negatively impact the bitumen separation, but not necessarily reduce the efficiency of air attachment. This can result in poor bitumen froth quality, while maintaining high recovery. In cases where there is a combination of low temperatures and a degraded or oxidized bitumen component in the oil sand, recovery as well as froth quality can be drastically affected(1).Ordinarily, extraction experiments are carried out in a small scale unit where various stirring, aeration, and water additions are done in an attempt to mimic the commercial extraction process. The froth quality and bitumen recovery determined from these experiments allows for investigation of trends as a function of ore type, water chemistry, temperature, and other process variables. Previous studies have investigated the various factors that impact extraction performance, but limitations in the batch (or small scale) extraction protocol often limits the discussion to impacts on recovery only(2–6). Furthermore, it is often not possible to separate the effects of the bitumen liberation and air attachment, the two key points in conditioning of oil sands.Recent CANMET work has overcome some of these experimental difficulties and focused on the relationship between temperature, mechanical energy, and process chemicals in the conditioning step and the resulting impact on both recovery and froth quality(7). It was shown that to a certain extent, increasing mechanical energy can substitute for higher extraction temperatures and/or chemical process aids. By far the most important factor is process temperature, largely because of a change in the bitumen- air attachment mechanism as the temperature is reduced.