Acoustic agglomeration is a potential pretreatment technology for efficient reduction of particulate matter emission in flue gas. However

high energy consumption restricts its commercial application. To improve acoustic agglomeration efficiency

droplet spray was added to aerosol. The influences of operating parameters on agglomeration efficiency were studied to explore compounding effect of acoustic field and droplet spray. The results showed that acoustic agglomeration efficiency was increased by 25% to 40% with addition of droplet spray. Whether the droplet spray existed or not

similar influence of sound frequency on agglomeration was observed with optimum frequency at 1400 Hz. The agglomeration efficiency rose with the increase of sound power

liquid-gas ratio or aerosol residence time

which reached to maximum when liquid-gas ratio was over 0.10 or aerosol residence time exceeded 4.2 s. Two main mechanisms were proposed for the improvement of agglomeration efficiency with presence of droplet spray. One was that droplet spray created liquid bridge forces between particles

which were much stronger than van der Waals forces

and increased collision efficiency greatly. The other was that liquid droplets acted as particle seeds for agglomeration

which had significantly different entrainment factors compared to surrounding small particles. Consequently

relative movement among aerosol particles was enhanced so agglomeration efficiency was promoted. The results suggest that energy consumption of acoustic agglomeration process can be reduced dramatically with addition of droplet spray.