EVIDENCE OF THE NATURAL VORTEX LENGTH AND ITS EFFECT ON THE SEPARATION EFFICIENCY OF GAS CYCLONES

It is widely assumed that the vortex in a cyclone has a well defined l ength, which may be shorter than the physical length of the cyclone, O ne speaks of the 'end' to the vortex, and of the 'natural vortex lengt h' or the 'natural turning length'. The space below the vortex is norm ally assumed to be ineffective for separation, and the transport of so lids along the wall is also inferior there, The axial position of the end of the vortex is thus an important design variable, yet little res earch work has been dedicated to its determination, In the course of r esearch aimed at formulating a new relation for the natural vortex len gth, two experimental methods for determining this parameter have been found: (1) the position of the end of the vortex was visible for a pe riod of time after smoke had been introduced in a glass cyclone; and ( 2) the position was found to be visible in the pattern of wall deposit s after experimental runs with gas/solid cyclones, The paper presents results obtained in variations on a standard cyclone geometry with a t ube section connecting the dust collection vessel to the cyclone, In t hese geometries the end of the vortex was in most cases located in the tube section, Comparisons are made between the two above methods of d etermining the length of the vortex, as well as comparisons with publi shed correlations. The effects on the natural vortex length of the inl et gas velocity, the dimensions of the vortex finder and the length of the cyclone, and the solid loading of the cyclone charge gas are show n, A substantial effect of the length of the vortex on the separation efficiency of the cyclone is also demonstrated,