Increasing particle-size by air-flow modification – An experimental study

Ambient particulate are characterize by submicron particles that may penetrate deep into the lungs, where they become harmful due to their morphology and composition, or due to their role as carriers of harmful chemicals or biological agents. Particle filtration technologies have in general a lower efficiency at diameter size around 0.1–0.3 μm. This study examines the concept of particle grouping as a means to overcome this size-gap, for improving air purification or filtration systems. The grouping manipulation is induced by a controlled rotating valve which creates a sinusoidal flow in the experimental tube, and by modules with varying diameter, forcing a wavy flow. Fine particles with a known size distribution which are introduced into the manipulated flow, exhibit groups of particles in the outflow, hence increase the effective size of the particles. Former successful studies were performed with high flow velocity and particle load of industrial duct and car engine outflow, while in the current study smaller particle loads representing ambient to indoor levels are in operation. Although the low velocity and particle load are challenging, this study shows a promising shift of the particle size distribution from a peak at 0.2–0.3 μm, towards larger particle diameters. Fine powder of dolomite is used in this study and preliminary results of adhesion experiments related to dolomite are also reported.