PARTICLE BOUNCE IN CASCADE IMPACTORS

Particle bounce in inertial impactors has been studied. A semiempirical model that relates impact velocity at the inception of bounce, particle diameter, and particle density is proposed. Impact velocity on the center line of both round jets and rectangular jets was calculated by solving the equation of particle motion. Experiments were performed to evaluate the retention efficiency of the Sierra radial slit jet impactor using latex particles collected on uncoated stainless steel. The critical value of the product of calculated impact velocity, particle diameter, and square root of specific gravity was found to be between 2.50 X 10-6 and 4.64 X 10-6 m2/s at the inception of bounce. Values larger than this predict particle bounce. Experimental results show that effects of particle bounce are reduced collection efficiencies, increased wall losses, and altered collection distribution among stages. Criteria are established to minimize these effects by adjusting the operating conditions in both round and rectangular jet cascade impactors. © 1979, American Chemical Society. All rights reserved.