Mecanismo de degradação da Goma Guar submetida a escoamento turbulento
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Data
2019-04-16
Autores
Motta, Marcus Vinícius Lisboa
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Universidade Federal do Espírito Santo
Resumo
Internal turbulent flows are commonly found in industrial applications in fluid transport. This flow regime is associated with additional energy losses in relation to the laminar flow due to the existence of complex dissipative structures in the flow and to the greater friction suffered by the flow with the internal walls of the pipe. In order to maintain this flow regime, the main flow must supply energy from the pumping unit. Reducing the demand for energy to promote internal turbulent flows can be done by the injection of drag reducing additives, usually polymeric in nature. In the studied condition the polymers undergo mechanical degradation and lose the ability to promote drag reduction over time. Studies indicate that the drag reduction may be related to the flexibility of the polymer and the size of the macromolecules of the additive used, which can interact with the vortices and reduce energy dissipation. In this study, the aqueous solution of the guar gum polysaccharide 400 ppm was subjected to a turbulent flow regime with the objective of monitoring, in an experimental plant, molecular degradation, drag reduction and energy demand. For this purpose, solution samples were removed during two hours of flow and the polysaccharide was isolated for characterization of the degradation. FTIR and NMR spectroscopy suggest that the mechanical degradation occurs with the hydrolysis of the a (1 ? 6) bond of the main chain with (D) -galactose due to the appearance of the carbonyl functional group. Thermal analysis revealed a decrease in the thermal stability of the polysaccharide by the decrease of the polymer chain. Finally, the understanding of this mechanism aims at the use of more efficient polymers in the reduction of drag and the decrease of the demand of energy in pumping processes that use these drag reducing macromolecules. Fourier transform infrared spectroscopy (FTIR), solid state nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and viscosity in diluted solution were analyzed. It was characterized, that the drag reduction efficiency promoted by guar gum is compromised by the polysaccharide undergoes chemical degradation, promoted by mechanical stress. As evidence, the viscosimetric analysis of guar gum showed the reduction of molecular weight in the period. FTIR and NMR spectroscopy suggest that the mechanical degradation occurs with the hydrolysis of the a (1 ? 6) bond of the main chain with (D) -galactose due to the appearance of the carbonyl functional group. Thermal analysis revealed a decrease in the thermal stability of the polysaccharide by the decrease of the polymer chain. Finally, the understanding of this mechanism aims at the use of more efficient polymers in the reduction of drag and the decrease of the demand of energy in pumping processes that use these drag reducing macromolecules.
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Polímeros - Biodegradação , Goma guar - indústria , Redução de arraste , Degradação