Solutions of xanthan gum/guar gum mixtures: shear rheology,porous media flow,and solids transport in annular flow |
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Authors: | J L Amundarain L J Castro M R Rojas S Siquier N Ramírez A J Müller A E Sáez |
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Institution: | (1) Grupo de Polímeros USB, Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Caracas, 1080A, Venezuela;(2) Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ 85721, USA;(3) Departamento de Termodinámica y Fenómenos de Transferencia, Universidad Simón Bolívar, Caracas, 1080A, Venezuela |
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Abstract: | Mixtures of xanthan and guar gum in aqueous solution were studied in two flow situations: simple shear and porous media. In
addition, solids transport in vertical annular flow of sand suspensions was explored. The zero shear rate viscosity of the
solutions displayed a pronounced synergy: the viscosity of the mixture is higher than that of the polymer solutions in a wide
range of relative concentrations of the two polymers, in agreement with previous literature. However, at relatively high shear
rates, the viscosity approaches the value of the more viscous xanthan gum solutions at mass fractions of xanthan gum between
0.1 and 0.15, and the degree of synergy substantially decreases. Stress relaxation experiments in simple shear indicate that
the polymer mixtures exhibit a well-defined yield stress after relaxation that is absent in solutions of pure polymers. In
porous media flow experiments, a synergistic behavior mimicking the shear flow results was obtained for the polymer mixtures
at low shear rates. However, at a critical shear rate, the apparent viscosity in porous media flows exceeds the shear viscosity
due to the elongational nature of flow in the pores. The solids transport capacity in annular flows is well-represented by
trends in shear viscosity and stress relaxation behavior. However, the lack of viscosity synergy at high shear rates limits
the applicability of the mixtures as a way to improve solids suspension capacity in annular flows. |
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Keywords: | Suspension Annular flow Porous media Guar gum Xanthan gum |
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