A novel visualization cell was designed to study the
kinetics of
bitumen liberation from oil sands. This novel visualization cell allows
for direct observation of bitumen recession from sand grains in real
time under various experimental conditions, thereby providing a better
understanding of bitumen liberation and the critical role of process
conditions in bitumen extraction from oil sands ores. Although direct
recession of bitumen from sand grains is found to be the primary mechanism
of bitumen liberation, the presence of entrained air in oil sands
ores greatly enhances bitumen liberation via bitumen spreading over
air bubbles. Imaging analysis of the recorded real-time bitumen liberation
process allowed for quantitative analysis of bitumen liberation kinetics.
A rapid bitumen recession and, consequently, high bitumen recovery
were observed for a good processing ore, in contrast to a slower bitumen
liberation and lower bitumen recovery for a high-fines ore, which
was considered to be a poor processing ore. The weathering (aging)
of good processing ore was found to significantly reduce bitumen liberation
kinetics, leading to a lower bitumen recovery, even though the bitumen
content and solids composition of the ore remained the same. These
findings confirmed the critical role of bitumen liberation in bitumen
extraction. Increasing the process water temperature was found to
increase significantly bitumen liberation kinetics and led to a higher
degree of bitumen liberation. While high pH facilitated bitumen liberation,
the presence of excessive salts (16 000 ppm sodium) was found
to be detrimental to bitumen liberation, in particular at high pH.
The bitumen liberation study using this novel visualization cell was
extremely valuable for identifying and understanding critical operating
parameters that control bitumen liberation and, hence, ore processability,
providing a scientific basis for designing breakthrough technology
to improve processability of oil sands ores and reducing the environmental
impact of oil sands development.
The effect of pH on the non-Newtonian viscosity ( ) of aqueous Carbopol 940 solutions is presented with high resolution (pH increments about 0.4) between pH ϭ ϭ ϭ ϭ ϭ 2.8 and 12.7. Aqueous NaOH was used to adjust pH of 1.48 wt % Carbopol solutions. A Contraves viscometer was used to measure steady-flow shear stress at known shearϪ Ϫ1 . Yield stresses and shear-thinning (␥ ␥ ␥ ␥ ␥) were observed. Data were fitted with a Herschel-Bulkley model, whose parameters (including yield stress) were expressed as functions of pH. Comparisons were made of (␥ ␥ ␥ ␥ ␥) to the dynamic viscometric properties Ј Ј Ј Ј Ј( ) and *( ) for comparable ranges of ␥ ␥ ␥ ␥ ␥ и и и и и and frequency ( ): A fairly close match was found between and * but ӷ Ј ӷ Ј ӷ Ј ӷ Ј ӷ Ј. pH dependence included previously unreported extrema of h(pH) in the range of pH ϭ ϭ ϭ ϭ ϭ 6.2 to 6.6. Because of sensitive control of rheological properties with pH, Carbopol solutions can be used to mimic a great range of shear-thinning and yield-stress behavior that should make them useful for model studies directed toward process and equipment design and evaluation.
The mass transfer efficiencies of dualflow trays with open hole areas of 20, 28 and 37% were experimentally investigated under total reflux conditions in a 300‐mm diameter distillation column using methanol‐water and methanol‐isopropanol systems. The results indicate that the efficiency of a dualflow tray is a strong function of the open hole area, the vapor/liquid load, and liquid properties such as surface tension and density. A fundamental model was developed to predict tray efficiency. The prediction was found to agree with the measured data to within 15.3%.
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