Oxygen separation in a vortex tube with applied magnetic field

Abstract

The large scale and efficiency of air separation units remain key barriers towards modular, distributed liquid oxygen systems. Identifying new physical separation mechanisms, or novel combinations of established methods, could enable the development of smaller, more modular air separation systems. This paper investigates the combination of centrifugal separation with paramagnetism of liquid oxygen in a vortex tube. The magnetic field is applied via externally mounted 1.5-T bar magnets along the length of the periphery of the vortex tube. Calibrated air mixtures with 21.1-21.4% oxygen and the remainder nitrogen are tested. Inlet vortex tube fluid conditions are held between 89 and 90 K and 305-320 kPa and expanded to 162-286 kPa. Gas chromatography analysis on the calibrated air samples shows the magnetic field gradient on the vortex tube produces up to a 42.09% purity as opposed to 27.95% purity in identical trials without a gradient. Purity and yield are shown to be inversely related in the periphery and directly related in the core. The results indicate a potential to increase oxygen purity and yield in a more compact form factor.