The measurement of the separation of fine solid particles in multiwir packings

In this paper, a new type of packing for the separation of solid particles from gases is presented. The so called Multiwir (multiple vortex) [1, 2] pa ckings (see Figure 1) consist of multiple adjacent layers of strips spaced uniformly. As the layers are placed oblique to each other, the incoming gas stream passes the packings in the form of a large number of smaller stream s which cross each other spatially and thus induce rotational motion in eac h other. Under centrifugal forces and due to turbulent and electrostatic ef fects, the particles settle on the surfaces of the strips where they are co llected. In this paper, some of the experimental results are described obtained in t he investigation of Multiwir-packings, consisting of metal or plastic strip s, with different limestone aerosols and feed particle size distributions w ith particles smaller than approximately 3 mu m and 10 mu m The following r esults have been obtained: - the Multiwir separator should be used for the removal of fine particles. Particles smaller than 10 mu m in size can only be collected if special pre cautions are used, - the efficiency of the separator is dominated by the gas velocity, the,geo metry of the packing, the material of the strips and the size distribution of the feed material, - the smaller the feed particles are, the smaller the distance between adja cent strips should be, - the reduction of the distance between adjacent strips is limited however by an increase of the pressure drop across the packing, - adhesion between particles and strip surface strongly influences the perf ormance of the packing. The surface of the strips should therefore be wette d, for example with a thin oil film, - the collection of small particles can be further improved if the feed par ticles are charged electrostatically in front of the packing, - the total grade efficiency of the packings investigated lies between T-0= 0.6 and 0.9. Extremely good results have been obtained with perforated plas tic strips. Simplified mathematical models have been used to describe the phenomenon of particle deposition in Multiwir packings due to inertia effects and turbul ent diffusion.