Role of solid wettability in two processes : bubble generation from porous media and froth treatment in processing oil sands

Chen, Fu, 1960-; Chen, Fu, 1960-

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Role of solid wettability in two processes : bubble generation from porous media and froth treatment in processing oil sands

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Chen, Fu, 1960-

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Solid wettability plays an important role in many industrial processes. Two examples of processes dependent on solid wettability are: Bubble generation from porous media (project one) and the bitumen froth treatment process in the recovery of oil from oil sands (project two). Project one. Bubble size has a profound effect on flotation efficiency controlling particle collection and froth stability. Models of bubble generation at a rigid sparger usually include a wettability effect (i.e., contact angle). The role of sparger wettability on bubble formation was examined using three rigid spargers exhibiting water contact angles of 0, 64 and >90°. The wettability was varied by heating the sparger, and the contact angle was determined by the Washburn and modified Washburn methods. By measuring permeability, it was determined that heating had no effect on sparger pore structure. The results showed no detectable wettability effect on bubble formation over the practical operating range of column flotation. The lack of wettability effect may be attributed to the highly irregular morphology of the sparger surface. The bubble size, it was shown, can be predicted by using the concept of sparger equivalent pore diameter and active pore number, which are estimated by a back-calculation routine. Project two. Production of oil from oil sand deposits in northern Alberta involves open pit mining, mixing the ore with water, extraction of bitumen from the slurry by a flotation-related process (Hot Water Extraction Process), removal of water and solids from the froth formed (froth treatment process), and upgrading the heavy bitumen to liquid hydrocarbons. The froth treatment process to remove fine solids and water from the bitumen froth depends on the wettability of the solids. Fine solids were extracted from samples of bitumen froth using heptane. A mixture of heptane and toluene (diluent) was used to study fine solid wettability. The contact angle (sessile drop method) and partition of the fine solids among the aqueous, diluent and interphase regions were determined. The effect of diluent composition, sample drying, and surface washing was examined. The partition of the particles correlated well with their wettability, and the results helped interpret observations from plant practice.

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