A preliminary investigation of sludge rheology was carried out on two tailings pond sludge samples; a low bitumen content (1%) and a high bitumen content (3–4%) sample. Steady state shear stress versus shear rate measurements and dynamic measurements were performed. Quanlitativ8 measurements of structure buildup and breakdown as a function of time were obtained. Strain sweep analysis on sludge samples was determined and Ihe linear Viscoelastic region was defined (the region where the sludge structure has not been broken). Viscoelastic properties of the sludge in the linear yiscoelastic region were characterized. Preliminary investigation of high bitumen content sludge indicated that varying amounts of bitumen are present within the sample. Therefore, it is possible to misinterpret bitumen peaks in shear stress versus shear rate plots as significant stress overshoot or yield points. A general overview or the rheological properties of sludge will be presented.
Investigation of the rheological properties or a low bitumen (1%) and high bitumen (3–4%) oil sand tailing sludge has been carried out as part or CANMET'S contribution to the Sludge Consortium research program. Previous work at CANMET and at Syncrude [1] has demonstrated Ihe need to characterize the rheology of sludge at low shear rales and the need 10 define the elastic properties of sludge structure by means ot dynamic testing at frequencies where the sludge structure is not broken. A Bohtin VOR rheometer was commissioned at CANMET in January 1990 for this purpose. Results obtained in the preliminary investigation of oil sand tailing sludge and some of the problems encountered when performing rheological studies are presented.
Representative samples allow bitumen [2] and high bitumen [3] oil sand tailings were obtained. In order to obtain reproducible data on the high bitumen sludge it was necessary to remove manually as much bitumen as possible from representative splits before doing rheological determinations.
Rheological measurements were conducted on a BOHLIN VOR rheometer using a concentric cylinder sensor system (Model C25) which has a viscosity range of 1x104 to 1x10−5 Pa.s [4] The gap spacing is 2,5 mm and the radius of the bob is 25 mm with radius of the rolating cup being 27.5 mm. The C25 has a large sensing area and is the most sensitive of the standard concentric cylinder types available. A sample volume of 13 ml is required to cover the stationary bob which is 37.5 mm in height. Torsion bars of 1, 11, 90 g cm were used depending on What shear rate regine was studied. The system was operated at 10.0 ± 0.5 °C for low bitumen sludge and 20.0 ± 0.5 °C for high bitumen sludge to reflect actual pond sludge temperatures. A Neslab RTE110 circulating bath was used to maintain stable temperatures.
The sludge samples were genlly mixed in their representative split containers prior to measuring Qut a 13 ml sample for use in the viscometer.
