New method and experiment of methane enrichment under low concentration and weak vortex field

The massive emission of low concentration methane from the ventilation roadway results in the waste of re- sources and environmental pollution. For this serious situation,the vortex tower for methane enrichment with low con- centration was designed and the segregation and non-segregation experiments were carried out as well as the compari- son with numerical simulation results. The results reveal that the stable concentration of methane under segregation state in the vortex tower gradually increases from bottom to top (0. 50% -0. 70% ),which demonstrates that the meth- ane enrichment effect is significant in the weak vortex field under segregation state. However,the increase of the meth- ane concentration under non-segregation state in the upper part of the vortex tower is not obvious (0. 50% -0. 55% ). In both cases,the methane concentration at the bottom of the vortex firstly grows and then gradually reduces to stable state (less than 0. 50% ). The stability time of methane concentration in the upper (middle) part of the vortex tower under segregation state is longer than that under the non-segregation state while the stability time at the bottom of the vortex shows similar discipline. The stability time of the methane concentration is significantly affected by the speed of the blade in the weak vortex field while insensitive to the impact of the final gas concentration. Finally,the improved Richardson Numbers were used to discuss the strength and weak control of vortex field in terms of the speed of the mixing methane and the thickness of methane layer. The reasons for the methane enrichment in the prominent segrega- tion state with low concentration whereas that on the weak condition in non-segregation state under the weak vortex field were revealed.