Particle filtration characteristics of typical packing granular filters used in hot gas clean-up

Abstract

Granular filter is a promising method in hot gas clean-up for advanced coal gasification technologies. Numerical simulations were performed in this paper for the particle filtration characteristics of granular filters with two typical packings: body centered cubic (BCC) and face centered cubic (FCC) packings. Fluid flow characteristics were investigated and pressure drop correlations for the two granular packings were obtained. The pressure drop of both packings increases linearly with the increase of velocity, and the pressure drop of the FCC packing is significantly higher than that of BCC. The discrete phase model (DPM) was employed to trace fly ash particle motion during the filtration process, and particle deposition characteristics on the granular surface, including the particle penetration, deposition distribution of different particle sizes, and deposition distribution along filter layers were determined. The deposition fraction of particles on each layer of granules decreases with the increase of row number, and the maximum deposition location is different for BCC and FCC packings. Large particles mainly deposit on the first four layers of granules, while small particles deposit over all layers. The collection efficiency of BCC and FCC packings increases with the increase of velocity, and they decrease first and then increase with particle diameter. Correlations of collection efficiency for the two granular packings are presented and they have good prediction accuracy.