Enrichment of Methane Concentration via Separation of Gases using Vortex Tubes

The objective of this work was to determine if a vortex tube can be used as a gas separation device. A vortex tube is a simple mechanical device that has no moving parts. It separates a compressed inlet fluid into two streams, one hot and the other cold. There are a variety of theories to explain this separation. It has been hypothesized that a mixture of compressed gases flown into the vortex tube may separate into individual gas streams by virtue of differential centrifugal forces acting on them. During previous studies by others, conflicting results have been obtained using this hypothesis. Further study of the gas separation process in a vortex tube was carried out. An attempt has been made to separate methane and nitrogen gases using vortex tubes. This particular separation or the resulting enrichment of Methane concentration has applications in the mining industry. Methane is emitted in an underground coal mine. It leaks from the coal seams and is extremely hazardous for workers because of its high explosivity in air. A conventional but costly means of circumventing this problem is methane drainage before mining. Yet another effective method is to blow large amount of air through the mine to locally dilute methane concentration. The mixture of methane and air is directly passed into the atmosphere. There are advantages to separating methane from air at the ventilation exhaust of the mine. First, methane being a greenhouse gas has strict EPA emission standards, and second, methane can be directly used for generating power. In this experimental work, a laboratory size setup was used to investigate the feasibility of using a fixed geometry vortex tube for separating methane and nitrogen from a mixture. It was found that there was partial gas separation leading to a higher concentration of methane at one exit in comparison to the inlet and a lower concentration at the other exit.