Bitumen Extraction from Oil Sands using CaO (Lime) and Ozone

Abstract

Abstract Bitumen extraction efficiency is increased in oil sands ore-water slurry based extraction process by increasing solubility of naturally occurred asphaltic acids by addition of CaO (lime) and/or by oxidation of bitumen asphaltenes by Ozone (O3) to surfactant species, at as low as 35 oC temperature. Experimental findings suggest that a non-caustic bitumen extraction process (i.e. without using NaOH as extraction process aid) could be used commercially by conditioning the oil sands orewater slurry with CaO and/or Ozone, which would allow high extraction efficiencies at about 35 oC temperature, reduce energy consumption and CO2 emission for the extraction of bitumen and eliminate the accumulation of Na+ ions in the recycled release water. Further tests are on-going to provide sufficient data for the commercial implementation of the use of CaO and/or Ozone at oil sands-ore water slurry based extraction plants. Introduction In northern Alberta, Canada oil sands resource presents one of the vast world hydrocarbon deposits, which extends over 77,000 km2, distributed in three principle regions: Athabasca, Cold Lake and Peace River. The oil sands deposits of the Athabasca Fort McMurray Formation are shallow enough to enable surface mining, in which bitumen content ranges from 0 to 19 %, averaging 12 %; water runs 3 to 6 %, increasing as bitumen content decreases; mineral content, predominantly quartz, silts and clay, runs 84 to 86 % (all by weight). Clays are occluded in the forms of discontinuous beds or bands varying from 1 cm to 15 cm in thickness. The in-place reserves of crude bitumen in these principal oil sands deposits exceed 1.7 trillion barrels. Of this total, only a small fraction (4 billion barrels) is under development permits. Overburden in the Athabasca deposits is in the range of zero to 600 m. Also, it is estimated that 75 billion barrels crude bitumen is placed in 0 to 45 m overburden and 550 billion barrels in 45 m to 600 m overburden. In northern Alberta three commercial plants produce bitumen from surface mineable Athabasca oil sands that amounts to almost 1,000,000 bbl/d. Recent investments made in the development of surface mineable oil sands indicate that bitumen production capacity would reach 2,000,000 bbl/d by 2010. All of the commercial plants which are operating, in construction or planned for future production use oil sands ore-water slurry based extraction processes which are based on the original work of Clark (Clark and Pasternack, 1932; Clark, 1939). These processes use additives such as NaOH or sodium salts of weak acids increasing the pH of the ore-water slurry. Increase in the pH of the ore-water slurry promotes the solubility of asphaltic acids (partly aromatic, containing oxygen functional groups such as phenolic, carboxylic and sulphonic types) present in bitumen which act as surfactants reducing the surface and interfacial tensions and promote the swelling of clay and disintegration of oil sands structure and promote the liberation of bitumen (Moschopedis et al., 1977 and 1980; Speight and Moschopedis, 1977; Baptista and Bowman, 1969; Bowman, 1968). Oil sands plants in northern Alberta operate with no-discharge policy, therefore, the release water recovered from the tailings effluent has to be recycled. Addition of sodium based additives as process aids; however, results in the accumulation of Na+ ions in the recycle water which cause concerns for the long term operability of the extraction plants. Over the few decades alternative non-caustic and low energy extraction processes have been investigated and commercially applied. Significant research and development have been devoted to improvement extraction efficiency, reduce extraction temperature, improve tailings disposal practice and to improve release water chemistry.