Extraction of vanadium from athabasca tar sands fly ash
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MANYof the so-called heavy oils throughout the world contain certain metals (e.g. V, Ni, Fe, Ti, Si, A1) and sulfur. The processing of these heavy oils usually involves some form of thermal cracking to produce a "light oil" fraction and a heavier residual oil or a petroleum coke, depending primarily on the characteristics of the heavy oil. The bulk of the metals and some of the sulfur remain associated with the non-volatile components and thus end up in a residual oil fraction or in the petroleum coke by-product. Combustion of either of these fractions will yield a fly ash wherein the heavy metals in particular tend to concentrate. Table I shows the composition of fly ash produced from the burning of residual oil or petroleum coke which has resulted from heavy oil upgrading treatment. The fly ash from the Canadian Petrofina operation resulted from burning coke produced from Venezuelan residual oils. The Amuay and Long Island Lighting Co. fly ash also resulted from burning Venezuelan residual oils and the Great Canadian Oil Sand, Ltd. (GCOS) ash from burning delayed coke produced from the GCOS operation at the Athabasca Tar Sands. The recovery of vanadium from petroleum fly ash is a well established process based on relatively simple leaching operations. In Canada in 1965, Bechtel Corp. built a plant for recovering vanadium pentoxide from petroleum fly ash for Canadiun Petrofina at its facilities in Pointe-aux-Trembles, Quebec. C. O. GOMEZ-BUENO, D. R. SPINK and G. L. REMPEL are with the Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada. Manuscript submitted May 2, 1980. METALLURGICAL TRANSACTIONS B
The technology used in the Canadian Petrofina plant and other operations mentioned above, however, is not suitable for recovering most of the vanadium and other metals present in the GCOS fly ash. In Canada the Athabasca Tar Sands consititute a major source of vanadium. It is estimated6 that there are 2.2 million metric tons of vanadium associated with the recoverable oil in the deposit. At the present time 550 metric tons/year of vanadium are being concentrated as a by-product of the oil recovery process at the Great Canadian Oil Sands plant. As the new Syncrude plant comes into full production, the vanadium potentially available for recovery from the area will amount to about 1660 metric tons/y.6 Furthermore, the current energy situation strongly suggests that oil from the Alberta tar sands deposits will probably be recovered more extensively in the future. Today's commercially proven technology to recover oil from the Athabasca tar sands, as practiced by GCOS, involves two major operations, namely the separation of the bitumen from the sand and upgrading of the bitumen to a "synthetic" oil; in this case, a significant amount (20-30 pct of the bitumen) is converted to a delayed petroleum coke. At GCOS, the bulk of the petroleum coke is burned in boilers to fulfill the energy requirements of the entire operation. GCOS daily fly ash output from their coke boilers was about 82 tons in
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