Rate of Bitumen Film Transfer from a Quartz Surface to an Air Bubble as Observed by Optical Microscopy
The rate of bitumen transfer from a bitumen-coated quartz plate to a gas bubble surface in aqueous alkaline solutions was recorded photographically. During bitumen spreading, a bulk layer followed the formation of thin bitumen films (precursor films). The bulk layer spread at the bubble surface with a velocity of about one order of magnitude less than the velocity of the precursor film. The energy of activation for spreading of the bulk layer varied from about 66 to 123 kJ/mol depending on the stage of bitumen spreading but remained constant at about 105 kJ/mol for the precursor film. Results are discussed with respect to fundamental issues associated with flo t a t i o n r e c o v e ry of heavy oils.
Effect of polyelectrolyte charge density and molecular weight on the flotation of oil in water emulsions
Abstract The effect of polyelectrolyte charge density and molecular weight on the flotation of oil emulsified in aqueous electrolyte was investigated. Flotation performance improved with increasing polyelectrolyte charge density, while polyelectrolyte intrinsic viscosity (molecular weight) had no effect on flotation over the range 6–12 dl g −1 . Turbidity removal improved as floc size increased, indicating that polyelectrolyte enhanced flotation by increasing the floc size. The trends in the flotation and flocculation behaviour of the emulsion with changing polyelectrolyte intrinsic viscosity (molecular weight) were consistent with electrostatic patch flocculation. Raising the charge density of the oil increased the amount of polyelectrolyte required for optimal flotation and led to improved performance, while raising the background KNO 3 concentration from 10 −3 to 10 −1 M decreased flotation performance. The effect of electrolyte concentration was greatest at low oil charge density (pH 5) and low polyelectrolyte charge density. It is proposed that the reduction in flotation performance with rising electrolyte concentration was due to increased electrostatic shielding leading to smaller floc sizes, as electrostatic attraction between charged patches on the oil was thought to be the flocculation mechanism. The flotation process was more robust towards changes in polyelectrolyte dose when polyelectrolytes of lower charge density were used.
Measurement of pump-induced transient lensing in a cryogenically-cooled high average power Ti:sapphire amplifier.
The transient thermal lensing in a liquid-nitrogren cooled kilohertz multipass amplifier is quantitatively measured with spatially-resolved Fourier transform spectral interferometry. A pump-probe arrangement allows the observation of a polarization-dependent non-thermal component following the fluorescence timescale: additional cooling would not suppress this residual lensing. We also observe a time-dependent thermal component that has a timescale sufficiently fast to indicate that there is cooling between shots even at a repetition rate of 1 kHz. The value of pump-induced lensing would be underestimated when performing time-averaged measurements of pump-induced phase shifts.