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 Diluent Addition on Bitumen Liberation from a Glass Surface
Liberation of bitumen from sand grains is a key step on processing oil sands using water-based extraction processes. In this study, effects of diluent addition on bitumen liberation from a solid surface were investigated under various conditions, including the washing temperature, pH value of the water, and washing time. It was found that more effective bitumen liberation could be achieved by adding diluents, such as kerosene and fatty acid methyl ester (FAME), in the bitumen. Especially, FAME addition was found more efficient to accelerate bitumen liberation than that of kerosene. Rheological characterization showed that bitumen viscosity was greatly decreased with diluent addition, which was responsible for the improved bitumen liberation. The findings in this study might find their applications in the oil sands processing industry.
Slotted Waveguide Antenna With Two Radiation Nulls
A design of a linear array antenna having two radiation nulls and otherwise omnidirectional radiation pattern is reported. A new configuration of a waveguide broad wall longitudinal slot doublet with positive and negative offsets with respect to the waveguide center line is used to design the array. This type of doublet produces two radiation nulls. Each of the null directions can be shifted at least up to plusmn25deg by proper choice of slot offset. Resonance and radiation characteristics of the proposed doublet are also presented. Finally, one linear array antenna consisting of seven doublets has been fabricated. Measurements show that the 15 dB null widths are 14.2deg and the null depths are at least 24.8 dB. Maximum gain ripple in the omnidirectional region is 1.75 dB.