Magnetically Assisted Filtration for Solid Waste Separation and Concentration in Microgravity and Hypogravity

Abstract

Development of efficient means for the recovery of valuable resources from solid waste materials is a critical requirement for future advanced life-support systems that will be needed to support long-duration manned missions in space. Of particular importance are technologies that may be used in hypogravity and microgravity environments. Gradient magnetically assisted fluidized-bed (G-MAFB) technology, which uses magnetic forces to compensate for the absence of gravity, is under development to serve as an operating platform for fluidized-bed and related operations in the space environment. In this study, the G-MAFB is used as a renewable filter in which granular ferromagnetic filtration media are magnetically consolidated into a packed bed. The filtration media attains a substantially different structure from that of an ordinary packed bed, when consolidated under the influence of the magnetic field gradient. This directly influences filtration rates. The fully loaded bed is then regenerated by magnetically controlled fluidization, thereby releasing a concentrated slug of solids, which may be further processed by a variety of treatment schemes. Filtration experiments have shown that G-MAFB-based methods can successfully separate suspended inedible plant biomass waste particles from a recirculating liquid stream. A mathematical model that describes the filtration process in the G-MAFB is presented. Correlations for estimation of the accumulation and detachment coefficients, based on hydrodynamic conditions and geometry of the filtration system, have also been developed. Model predictions are compared with experimental results obtained in the G-MAFB while operated under Earth's gravity conditions (1 g). The experimental data are in good agreement with the theoretical predictions.