Cyclone cones

The vortex of a cyclone will precess (or wobble) about the center axis of the cyclone. This motion can bring the vortex into close proximity to the wall of the cone of the cyclone and pluck off and reentrain the collected solids flowing down along the wall of the cone. The vortex may also cause erosion of the cone if it touches the cone wall. Sometimes an inverted cone or a similar device is added to the bottom of the cyclone in the vicinity of the cone and dipleg to stabilize and fix the vortex. If it is placed correctly, the vortex will attach to the cone and the vortex movement will be stabilized, thus minimizing the efficiency loss due to plucking the solids off the wall and erosion of the cyclone cone. 

A much more scientific proof of the crowding theory has recently emerged from some mathematical modelling work by Bloor et This is a hydro-dynamic model of the flow both in the cyclone body and in the boundary layer (the cyclone design is that of Kelsall ), but it makes no predictions of conditions at underflow because it breaks down at the vertex. The model assumes inviscid flow in the main body and viscous flow in the boundary layer. It allows plots of particle trajectories, assuming their homogeneous distribution on entry to the cyclone cone. 

Blockages, usually caused by overloading of the sohds outlet orifice, is one of the most common causes of failure in cyclone operation. The cyclone cone rapidly fills up with dust, the pressure drop increases and efficiency falls dramatically. Blockages arise due to mechanical defects in the cyclone body (bumps on the cyclone cone, protruding welds or gasket) or changes in chemical or physical properties of the solids (e.g. condensation of water vapour from the gas onto the surface of particles). 

There are two primary types of cyclones the reverse-flow cyclone and the uniflow cyclone. The reverse-flow (Fig. 1) is by far the most common. It is called a reverse-flow cyclone because the gas-solids mixture enters the cyclone tangentially at its periphery, spirals around the barrel, and then the gas reverses flow and exits through a gas outlet tube (also called the vortex finder or the vortex tube) at the top of the cyclone. The solids spiral down around the barrel of the cyclone at an angle of approximately 15 degrees and enter the cyclone cone attached to the bottom of the barrel. The solids exit the reverse-flow cyclone at the bottom of the cyclone cone. 

Bryant et al. (1983) also reported that in tests with sticky particles that adhered to the wall of the eyelone, particles adhered to the cyclone cone at a distanee greater than 1.6Z)i, below the gas outlet tube but above this length the cyclone was clean. This result indicates that it would be better to have short cyclones when operating with sticky cyclones. 

Separate single stainless-steel modules allow individual optimisations for the specific conveying tasks. A successful conveying may, for example just depend on the detail design of the suction module which could have a radial or tangential inlet (Figure 17.11). Tangential inlet is applied for extremely fine powders such as toner or soot and keeps the filter surface load low. The collection of the material in the lower half of the conveyor is improved if in addition a further cyclone cone is inserted. 

Fig. 15.1.8. Cyclone cone geometry and its construction pattern The pattern angle 6 is given by ...

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