Estudo da fluidodinâmica da dessalinização das águas salobras via osmose reversa: modelagem e simulação.

Abstract

In the last decades, the concern with water scarcity, caused by the increase of the global population and by the drastic climate change of the planet, has been even more accentuated. Based on this problem, numerous studies have been intensified for the development of techniques and / or technologies with the main objective of increasing the amount of drinking water in the world, one of these techniques being desalination by the membrane separation process via reverse osmosis. With the help and evolution of computing, it became feasible to perform numerical simulations with complex models capable of understanding the real behavior of the phenomena present in this process, so it will be possible to optimize it and make it more efficient. Within this context, this work aims to present a study of computational modeling focusing on the optimization of the membrane separation process via reverse osmosis through the analysis of the permeation module geometry and the effects of the turbulence promoters. The computational modeling was performed by ANSYS FLUENT software through finite volume method, with the use of UDFs (User Defined Function). The mathematical modeling was based on mass conservation, movement and species transport equations, also, the Spiegler and Kedem model was used in order to characterize the effects of the membrane on the permeation flow. The results in the simulations obtained by the proposed model provided a detailed analysis of the hydrodynamic behavior of the flow and the formation of the concentration polarization limit layer by under the effects of turbulence promoters, in which, when comparing with results reported in the literature, it was observed discrepancies below 7%. When analyzing the effect of the turbulence promoters, it was found a beneficial effect in the reduction of solute along the membrane surface and that there was variation in the performance of the process when there were geometric changes in the spacers; so, it was possible to quantify their efficiencies through the use of parameters, such as SPMP (Spacer Performance Ratio), SPMPmod, pressure loss per unit length and amount of permeate flow. Based on these parameters and studied geometries, it was observed that the circular spacers had better process performances, presenting the best balance between pressure loss and production capacity of the final product, which is drinking water. For the three-dimensional geometries used, there were changes in the formation of the concentration polarization layer when the channels geometry was modified and that the transversal filaments to the flow are more effective in combating the polarized layer than the longitudinal filaments.