Particle Removal Efficiency of Gravitational Wet Scrubber Considering Diffusion,Interception,and Impaction

Abstract

A method of predicting the particle removal efficiency of gravitational wet scrubbers and the particle size distribution properties, that considers diffusion, interception, and impaction, is presented to study the particle removal mechanisms of gravitational wet scrubbers. This method assumes a lognormal size distribution of aerosol particles as well as three additive collection efficiencies. Thus, the overall collection efficiency is described as the sum of all three. It is represented as a U-shaped curve with a minimum in the region of around 1.0 μm in particle diameter. This allows aerosols in the diffusion- and in the impaction-dominant regions to be removed at a higher rate compared with aerosol in the intermediate region. As aerosols pass through the gravitational wet scrubber, the geometric standard deviations of the size distribution of polydispersed aerosols decrease. The geometric mean diameter of aerosol in the diffusion-dominant region increases, whereas it decreases in the impaction-dominant region. The present study also shows that in optimum operation conditions such as low droplet falling velocity, small droplet size, and high liquid-to-gas flow ratio, the gravitational wet scrubber has sufficient ability to remove particles whose diameters are much smaller than 1.0 μm.