Micron-scale tensiometry for studying density-matched and highly viscous fluids — with application to bitumen-in-water emulsions

Moran, Kevin; Yeung, Anthony; Czarnecki, Jan; Masliyah, Jacob H.

doi:10.1016/s0927-7757(00)00507-0

Cited by 27 publications

(33 citation statements)

References 16 publications

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“…An example of such a plot is shown in Figure 2. With the values for R d and σ bw known independently (the former from image analysis, and the latter from microcantilever studies (Moran et al, 2000)), it is now possible to use the remaining quantity, µ b , as a fitting parameter: the value of which optimizes agreement between theory and experiment (here, by a least squares criterion) will be the measured viscosity.…”

Section: Experiments Micropipette Apparatus and Drop Shape Recover Y Ementioning

confidence: 99%

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Determining Bitumen Viscosity Through Drop Shape Recovery

Moran

Yeung

2004

Can J Chem Eng

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H igh grade synthetic crude oil is produced from the bitumen found in northern Alberta's oil sands deposits. Before raw bitumen could be upgraded into a feed product for the refineries, it must first be 'extracted' from the sand ore (that is, bitumen must be separated from the sand grains, clays particles and connate water). At present, the most viable method of extracting bitumen is by a flotation process in which mined oil sands, after being slurried with warm or hot water, is fed into a flotation vessel. Once in the vessel, the unwanted solids will settle and be eliminated through the underflow stream, while bitumen -which enters the vessel as small aerated droplets -is collected at the top as a froth. The success of this flotation process depends critically on the tendency of the bitumen droplets to coalesce in aqueous environments. (Coalescence gives rise to bigger droplets, and in turn enhances significantly their rising velocities according to Stokes law; in addition, the quality of a froth is determined by the propensity of the oil drops to coalesce into an oil-continuous dispersion (Shaw et al., 1996).) As the flotation process is one which is continuous in time, an understanding of its fundamental mechanisms must involve studying the dynamics of bitumen-bitumen coalescence. The rate of coalescence between two bitumen droplets in water, it is clear, is driven by the bitumen-water interfacial tension σ bw and limited by the viscosity of oil phase µ b . (The aqueous phase is much less viscous than bitumen and can therefore be treated as inviscid.) Measurements of these two fundamental properties, unfortunately, have not been straightforward: The determination of σ bw is hindered by a vanishingly small density difference between the two immiscible phases (see Moran et al. (2000) for further discussion). This difficulty, however, is recently overcome by the use of a microcantilever technique which operates at the low Bond number limit (Moran et al., 1999;Moran et al., 2000). What remains -and which is the focus of this study -is to determine the bulk viscosity of bitumen. Although a seemingly simple task which has long been carried out, the measurement of µ b is in fact still plagued by problems which arise from effects of dissipative heating -especially at low temperatures when the viscosity of bitumen can be as large as ~10 6 times that of water. (In the following, low temperature will imply temperatures between 20 and 30°C.) With the ever-increasing need in the oil sands industry to operate at minimal energy consumption (for economic as well as environmental reasons), there is a renewed incentive to accurately determine the viscosity of bitumen at temperatures down to around 20°C. Here, using a drop shape recovery technique which avoids dissipative heating altogether, we show that previous measurements of µ b at low tempera- * Author to whom correspondence may be addressed. E-mail addre s s : tony.yeung@ualberta.caIn determining the viscosity of bitumen using conventional methods, the measurements must be...

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Section: Experiments Micropipette Apparatus and Drop Shape Recover Y Ementioning

confidence: 99%

“…The reader is referred to Moran et al (1999Moran et al ( , 2000 for a detailed exposition of this method. In the following, we will give only a very qualitative description of the procedure.…”

Section: Interfacial Tension Measurementsmentioning

confidence: 99%

Determining Bitumen Viscosity Through Drop Shape Recovery

Moran

Yeung

2004

Can J Chem Eng

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“…As a result, all tensiometric techniques that rely on density differentials (e.g., pendant drop, spinning drop, drop volume) become ineffective. In addition, it has been noted that the nearly-matched densities between water and bitumen precluded the use of force-based tensiometers such as the Wilhelmy plate and Du Nouy ring (Pandit et al, 1995;Moran et al, 2000). The maximum bubble pressure method appears to be the only conventional technique that remains unaffected by vanishing density differences (Pandit et al, 1995).…”

Section: Measuring the Bitumewwater Ift Cob+)mentioning

confidence: 99%

“…In this work, an in situ maximum bubble pressure method is developed to estimate ow and will be detailed in the following section. With regard to the interfacial tension obw, because of the high viscosity of bitumen and the small density differential between bitumen and water, no conventional method of tensiometry is suitable for quantifying obw at room temperature (Moran et at., 2000). Recently, a micron-scale tensiometer has been developed to circumvent the difficulties of vanishing density differentials and high viscosities (Moran et al, 1999(Moran et al, , 2000.…”

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confidence: 99%

Factors affecting the aeration of small bitumen droplets

2000

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n the processing of Athabasca oil sands, bitumen' is recovered from the slurried ore via water-based flotation methods, as first developed I by Clark and Pasternack (1932). As the densities of bitumen and water are virtually identical at processing temperatures (Liu, 1989; Pandit et al., 1995;Basu et al., 1996, Shaw et al., 1996, it is essential that a density difference between the two phases be created through aeration of the liberated bitumen drops. In the subsequent flotation step, the aerated bitumen/water/sand slurry is transferred to a quiescent flotation vessel to allow the coarse sand particles to settle and the aerated bitumen droplets to rise to the top, forming a bitumen-rich froth layer which is then collected for further processing. To lower production costs, continual efforts are also made to conduct bitumen extraction a t progressively lower temperatures (Mankowski et al., 1998).Although the importance of air in oil sands extraction process is undeniable, the fundamentals of bitumen aeration has received very little attention. In this area, Drelich and coworkers (1 994, 1995, 1996) have conducted studies on the spreading of diluted bitumen films on millimetresized air bubbles. These studies suggest that the aeration of diluted bitumen occurs spontaneously via encapsulation and is controlled by the bitumen-water interfacial tension. Our present focus, by contrast, will be on the aeration of small bitumen drops that are approximately 10 to 40 pm i.d.; the bitumen in this study is not diluted by any solvent. Such small droplets are an important consideration as they represent the difficult-to-recover portion of the total hydrocarbon in an oil sand slurry. Shaw et al. (1996) noted that, as the characteristic size of the bitumen droplets falls to about 10 to 40 pm, colloidal forces, such as those resulting from electrostatic interactions, may become increasingly important in determining the aeration of the droplets. In this study, the spreading of small (-25 pm) bitumen droplets onto air surfaces is examined-both from a surface energetic perspective as well as from direct observations. Such experiments are conducted using novel micromanipulation techniques which will be described in the next section.Based on principles of surface thermodynamics, the spreading of a fluid onto a substrate can be predicted by the so-called spreading coefficient 5: a positive 5 implies spontaneous spreading of the liquid while a negative value suggests 'beading' on the surface (Adamson, 1976). For the spreading of bitumen on air bubbles, the appropriate expression for 5 is:where ow and ob are, respectively, the surface tensions of water and bitumen, and obw is the bitumen-water interfacial tension (IFT). In order to predict the spreading phenomenon (by estimating the sign of 3, it is Small bitumen droplets, roughly 10 to 40 pm in diameter, constitute a significant fraction of the total hydrocarbon in an oil sands flotation process. In this study, the aeration of such droplets is examinedboth from a surface energetic pe...

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“…Ahmed et al [6] determined the interfacial tension of the Egyptian Geisum heavy oil (18 API) against 2.5% NP(EO) 11 solution to be  0.4 mN m -1 at 30 C. Moran et al [26] used a microtensiometric method to determine the interfacial tension of a Canadian bitumen (Syncrude Canada) as a function of pH. In neutral water, an interfacial tension of 15 -20 mN m -1 was measured which is lower than values for pure oil systems, a consequence of indigenous surface-active material in heavy oils [25].…”

Section: Bitumen/water Interfacial Tension Studiesmentioning

confidence: 99%

Thermal destabilisation of bitumen-in-water emulsions – A spinning drop tensiometry study

Taylor

2011

Fuel

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Micron-scale tensiometry for studying density-matched and highly viscous fluids — with application to bitumen-in-water emulsions

Cited by 27 publications

References 16 publications

Determining Bitumen Viscosity Through Drop Shape Recovery

Determining Bitumen Viscosity Through Drop Shape Recovery

Factors affecting the aeration of small bitumen droplets

Thermal destabilisation of bitumen-in-water emulsions – A spinning drop tensiometry study

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