(148c) Extraction of Bitumen from Athabasca Oil Sand by Combining the Benefits of Mechanical Solid Liquid Separation and Drying

The conventional processing of Canadian oil sand (Athabasca oil sand) comes along with many difficulties concerning sustainability and energy efficiency. The conventional water based processing leads to byproducts as the Mature Fine Tailings (MFTs). The recycling of these byproducts is not a focus of the oil sands industry, but leads to immense ecological problems. This gave the motivation for the development of an alternative process to avoid the formation of stable colloidal suspensions. The benefit of the developed processing is the large reduction of the water demand. To gain the bitumen from the mined oil sand and leave a clean and dry solid the  process combines mechanical solid liquid separation and drying [1].

The Athabasca oil sand is mixed with two organic solvents to deliberate and solve the organic contents of the oil sand; the proof of concept is appropriated in previous works [2] [3] [4]. An aromatic solvent is needed to dissolve the asphaltenes within the bitumen and allow a high bitumen recovery rate. The viscosity of bitumen is affected by the asphaltene content. The solution of flocculated asphaltene particles increases the yield and minimizes the quantity of high viscous particles within the filter cake, which would lead to filtration problems and higher resistance respectively.

After extraction and solution of the bitumen the organic suspension is processed with an integrated steam pressure filtration (SPF) step, which includes a washing stage.

This processing consists of three main process phases:

• The cake formation, where the filtration properties determine the throughput. Focus lies on the filtration resistance and the prevention of a covering layer on top of the filter cake. This layer is negatively affecting the throughput, the bitumen recovery and the following process phases.
• The filter cake washing, which replaces the bitumen loaded pore liquid by a pure and volatile pore liquid, determines the yield of bitumen. The amount of washing liquid used is determined by the amount of pore liquid within the cake and the specified washing ratio to be reached within the filter cake with the different organic solvents.
• The steam pressure displacement [5], during which the pore liquid is mechanically displaced. Further bitumen can be recovered and finally with the steam breakthrough steam drying, stripping of the volatile solvents, occurs. The previous washing with a paraffinic solvent is advantageous, as this solvent has a lower boiling point and higher vapor pressure. These properties provide better displacement and hence mechanical or thermal drying of the cake in the further treatment. The final product is a solvent-free filter cake with minimal aqueous moisture.

In the conventional process the average recovery rates of bitumen are set around 80 % of the initial bitumen content. To compete with this the alternative processing has to reach comparable results, which have been reached and even exceeded at lab scale.

The cost-effectiveness of the process depends on the total energy consumption, it has to compete with the conventional processing, the Clarke-process, and with a non-aqueous extraction process using filtration and drying. In this context the price development of energy, oil and gas respectively, influences the process evaluation.

1.         Schmidt, E., F. Schmidt, and U.A. Peuker. The non-aqueous filtration and washing of oil sand - developing a process for sustainable processing of Canadian oil sands. in WFC 2012. 2012. Graz, Austria.

2.         Avid, B., et al., Characterization of asphaltenes from Brazilian vacuum residue using heptane-toluene mixtures. Energy and Fuels, 2004. 18(6): p. 1792-1797.

3.         George, S., Measurement and Modeling of Asphaltene-Rich Phase Composition. 2009, University of Calgary.

4.         Saadatmand, M., H.W. Yarranton, and K. Moran, Rag Layers in Oil Sand Froths. Industrial & Engineering Chemistry Research, 2008. 47(22): p. 8828-8839.

5.         Peuker, U.A. and W. Stahl, Scale-up of steam pressure filtration. Chemical Engineering and Processing: Process Intensification, 1999. 38(4–6): p. 611-619