Theoretical studies on the collection efficiency in spray tower

The spray towers are widely used for the purpose of dust and mist collection, gas absorption and humidification. The scrubbing processes in the spray towers are among the oldest and simplest known to man. A liquid is employed to achieve or assist in the removal of dispersoids from gases. Water is generally employed as the scrubbing agent, and atomized by spray nozzles. A dust-laden gas flows upwards slowly and sprays descend gravitationally. When the gas impinges on a spray sphere, it will be deflected around the spray, where as the dust particles, by virtue of their greater inertia, will tend to be collected on the surface of the spray. The basic principles of impingement can be presented in terms of so-called ”target efficiency”. Target efficiency represents the fraction of particles in the gas volume swept by the spray which will impinge on the spray. Thus, for flow around a spray sphere, as shown in Fig. l, all particles that are inertially carried in the gas between streamlines A and B will be collected on the body and the target efficiency will be (b/D)^2. It can be shown that the target efficiency η will be a function of the dimensionless group K. (eq(2)). While the relationships given by the investigators are somewhat conflicting, the recent values reported by Langmuir and Blodgett are believed to be reliable. (Fig.2). Appling the conception of target efficiency, authors derive the new calculating formula for the collection efficiency by scrubbing in the spray tower. Calculations are performed for some illustrations, and the results reveal that the most effective spray will be 0.5 mm in diameter at air stream.