Utilização de membrana dinâmica com vistas à recuperação do metano dissolvido em efluente de reatores UASB via membranas desgaseificadoras

Abstract

The research consisted on investigating the main obstacles of the recovery of dissolved methane through desgassing membranes. Membrane fouling due to solids contained in the effluent of UASB reactors was the first aspect investigated. For this, post-treatment systems based on dynamic membranes arranged in series, made of polyester support medium with 100, 50 and 5 micrometer meshes, were developed aiming at the investigation of: (i ) the cake layer formation time; (ii) the performance of configurations with disc filter and stone filter before the dynamic membrane reactors in terms of clarification of the effluent and losses of dissolved methane; (iii) the total membrane resistance in each unit. The second point that we looked for enlightening is the possibility of energy recovery of the dissolved methane after mixing the recovered gas with the biogas, so the fourth objective of this work was: (iv) to define the relations between gas and liquid flows which the energy utilization of the mixture between the gas recovered by degassing membrane and the biogas generated by the UASB would be possible. The system presented excellent performance in the removal of turbidity (below 8 UNT) and solids (below 2 mg.L-1 of SST) in the three configurations studied, highlighting the possibility of exclusion of the 5- micrometer mesh of the process. The theoretical simulations carried out in this research indicated that for a dissolved methane concentration of UASB effluent of 25 mg.L-1, the relationships between gas and liquid flows of 0.03 to 0.05 generate a gas mixture with a higher methane content to 50%, requirement for thermal and electrical energy cogeneration engines.