Rajinder Pal

Rheology of oil-in-water emulsions with added solids

Abstract This paper presents experimental results on the rheology of oil-in-water emulsions with added solids. The oil used was a refined mineral oil (Bayol-35). The oil concentration, solids-free basis, was varied up to 70% by volume. The added solids were irregular shaped silica sand and spherical glass beads. The size of the solids was varied from 9 to 44 μm. The solids volume fraction was varied up to 0.2 of the total mixture. When the oil concentration was 40% or below, the solids-free emulsions behaved as Newtonian fluids; above 40%, these emulsions exhibited shear thinning behaviour. The addition of solids to the emulsions increased their viscosity and enhanced their non-Newtonian behavior. The type of added solids played an important role. Solids of irregular shape (silica sand) gave a much higher viscosity than the spherical solids (glass beads) at the same solids volume fraction. For given oil and solids concentrations, the smaller solids gave a higher viscosity than the larger solids. This effect was observed for both silica sand and glass beads. The data analysis indicated that the studied emulsion can be treated as a continuous phase towards the solids when the ratio of the solid particle size to the oil droplet size is greater than 3.

Rheology of clay-in-oil suspensions with added water droplets

Abstract The effect of added water droplets on the rheology of clay-in-oil suspensions was investigated. Three different kaolinite-type clays were studied. The range of the clay volumetric concentration, water-free basis, was 0–31.2% and the water volume fraction was 0–0.6. The rheological behaviour of binary systems, i.e. clay/oil suspensions and water/oil emulsions, was observed to be Newtonian at low values of dispersed-phase concentrations. At high values of dispersed-phase concentrations, binary systems exhibited shear-thinning behaviour. Similar behaviour was also observed in the case of ternary clay/oil/water systems. The viscosity of the ternary clay/oil/water mixture can be predicted from the viscosity of the respective binary mixtures, clay-in-oil suspensions and water-in-oil emulsions.

On the flow characteristics of highly concentrated oil-in-water emulsions

Abstract The laminar flow characteristics of oil-in-water emulsions with oil concentrations greater than 59% by volume have been investigated experimentally. Up to an oil concentration of 65% by volume, the emulsions exhibited power-law non-newtonian behaviour. At a higher oil concentration, of 72.21% by volume, a dramatic change in the flow behaviour of the emulsion was observed. The flow curve, i.e. shear stress vs. shear rate plot on a log-log scale, clearly exhibited the presence of a yield-stress. The rheological data on the emulsions were used to correlate the laminar pipeline transport data on the same emulsions. For power-law emulsions, values of the drop in pipeline pressure could be accurately predicted from simple rheological measurements. For a yield-stress emulsion, the experimental pipeline data deviated from the predicted values especially at low values of shear stress.

Viscosity correlations for emulsion—solids mixtures as bimodal systems

Abstract Viscosity data of oil-in-water emulsions with added solids were analyzed using the concept for a bimodal mixture. Three different oils and four types of solids were used. The size ratio of the added solids to that of the oil droplets was greater than 3. The oil-in-water emulsions behaved as a continuous phase to the added solids. The viscosity of an emulsion—solids mixture, η ows , is given as η ows (β o , ϕ s ) = η ow (β o )η sw (ϕ s )/η w where η ow (β o ), η sw (ϕ s ) and η w are the viscosities of the oil-in-water emulsion, solids-in-water suspension, and water, respectively. ϕ s is the volume fraction of the solids in the emulsion—solids mixture and β o is the oil volume fraction, solids-free basis.

EVALUATION OF THE MOONEY VISCOSITY/CONCENTRATION EQUATION FOR LIQUID-LIQUID EMULSIONS

Abstract Mooneys viscosity equation, originally proposed for concentrated solids in liquid suspensions, has been tested for stable liquid in liquid emulsions. Nine different emulsion systems have been considered. In none of the cases considered, Mooneys equation is found to adequately describe the viscosity/concentration behavior. However, the modified form of the Mooneys equation 𝛈r = exp[K 1𝛗/(1—K 2𝛗)]& is found to fit the data quite well. The K1 varies from 2.2 to 5.0 depending on the emulsion system; the K2 varies from 0.6 to 2.1.