Abstract
Particle size distributions of high-solids acrylic-enamel paint overspray aerosols were determined isokinetically in a downdraft spray painting booth in which a 7-stage cascade impactor was used. Three different industrial paint atomizers were used in this study, and the paint aerosols were characterized before and after a paint booth scrubber. The mass median aerodynamic diameter (MMAD) of a metallic basecoat and an acrylic clearcoat paint aerosol from air-atomized spray guns ranged from 4-12 µm and was dependent on atomization pressure. The clearcoat paint aerosols also were generated from rotary atomizers and had MMADs, which ranged from 20-35 µm depending on rotational speed. When the paint booth was operated under controlled conditions simulating those in a plant, the collection efficiency of paint overspray aerosols by a paint scrubber was found to be size dependent and decreased sharply for particles smaller than 2 µm to as low as 64% for clearcoat paint particles of 0.6 µm. Based on the performance characteristics of this scrubber, improvement in the overall particulate removal efficiency can be achieved by optimizing the spray painting operations so as to produce the least amount of fine overspray paint aerosols less than 2 µm. Maintaining a higher static pressure drop across the paint booth scrubber also will improve scrubber performance. A correlation relating the penetration of the high-solids paint aerosols to an inertial parameter was obtained which can be used to predict the scrubbing efficiency over a range of practical operating conditions.