Produção de biodiesel em reator de membrana com uso de misturador estático e simulação em CFD

Abstract

The use of membrane reactors for the production of biodiesel has been presented as one of the most promising alternatives for the production of biofuels due to the need to reduce the use of fossil fuels due to damage to the environment. However, little has been studied about the influence of concentration polarization in membranes where there is a reaction occurring. Due to the difficulty of detecting this phenomenon by experimental means, computational fluid dynamics is shown to be a robust tool for the study of mass transfer phenomena in membranes. Thus, in this work the influence of the presence of a static helical mixer on the thickness of the concentration polarization layer in a membrane reactor and by means of CFD simulations was studied. The influence of the following conditions on permeate conversions and masses was experimentally studied: transmembrane pressure of 1.0, 1.5 and 2.0 bar, molar ratio between methanol/sunflower oil of 9/1, 12/1 and 15/1, pore size of the ceramic membrane of 0.05, 0.1 and 0.2 μm, as well as in the presence of a static mixer of the Kenics type. For the simulations, the Navier-Stokes equation was used to solve the mass and continuity balances of the problem, while the Kozeny-Carman equation was used to model the porous medium of the membrane. The results show good agreement of the computational results with the experimental ones, where the thickness of the polarization layer increases with the reaction time, due to the action of mass convection, but the effect of permeability on the thickness of the layer was negligible. The highest conversions were achieved under conditions with molar ratio 15/1, transmembrane pressure of 1.0 bar, in the presence of static mixer, reaching values of 92.49%, 85.25%, respectively, while pore size did not have a significant influence on conversion. The results also showed that the use of a static mixer was efficient in reducing the thickness of the polarization layer of the concentration. Thus, the use of static mixer in membrane reactor showed great improvement in relation to the formation of concentration polarization.