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TitleApplication of wet oxidation for the treatment of oil sands mature fine tailings
Publication TypeThesis
Year of Publication2014
AuthorsKhan, M. F.
Pagination100 pages
Date Published11/2014
PublisherUniversity of Alberta Department of Civil and Environmental Engineering
Place PublishedEdmonton, AB
Publication Languageeng
Keywordstailings, tailings treatment, UofA

The extraction of bitumen from oil sands in Alberta, Canada, leads to the creation of tailings that are contained in lake-sized ponds under zero discharge policy. Stratification of tailings over time leads to the formation of mature fine tailings (MFT), an oil based emulsion containing residual bitumen and trapping water in between soil particles. Polymer flocculation treatments are effective in dewatering the tailings, however, the consolidated material still contains the residual bitumen which is not environmentally safe. This study investigates the breaking of MFT emulsion from tailing ponds and recovering the trapped water using an advanced oxidation process called Wet Oxidation. Three batch scale experiments were carried out, wet air oxidation (WAO), wet air peroxide oxidation (WAPO) and WAO (extended). The reactor was heated to 200⁰C and pressurized at 500 psi (±50 psi). Three process times 5, 15 and 30 min were explored. A fast disintegration of emulsion was observed with rapid release of trapped water and consolidation of solid particles under WAPO. Residual bitumen was collected as froth from the surface by flotation after every cycle of WAO and was calculated in average to be 5% (wt.) per dry weight of MFT during WAOextended. Less froth was recovered after WAPO. The released water showed a high transmissivity, increased concentration of dissolved organic carbon (DOC) while inorganic carbon declined with subsequent cycles and was completely removed during WAOextended. 80% higher DOC was recorded in recovered water after WAPO compared to WAO. More than 70 – 80% of DOC were low molecular weight carboxylic acids (acetic and formic acids) while the remaining were dissolved natural organic matter (NOMs). Increase in DOC was due to the oxidation of residual bitumen by hydroxyl radicals during oxidation. Mineral composition in the consolidated solids were dominated by quartz, kaolinite and muscovite with a total of 60% clay particles overall. Scavenging effect of hydroxyl radicals towards residual bitumen on particle surfaces were observed under scanning electron microscope with increased surface area of clay particles after oxidation.

Locational Keywords

Alberta oil sands

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