Issues on soot removal from exhaust gases by means of radial flow ceramic traps

Radial flow ceramic foam traps (uncatalytic and catalytic) for soot removal from the exhausts of combustion systems were prepared. Their performances were tested by treating the exhaust of a gas-oil burner. Two different trap volumes (0.5 and 1.5 l) were employed to evaluate the effect of gas velocity on the trap filtering performances. It was found that at high gas velocity through the trap critical conditions leading to soot blow off may be reached in dependence of gas velocity and temperature, soot load on the trap and burner operating conditions (quantity and quality of particulate matter). At lower velocity critical conditions are unlikely to be achieved but the behaviour is still strongly dependent of the burner operating conditions. The catalytic trap showed good performances being able to remove soot from the burner exhaust gases with an efficiency of 70% and allowing the simultaneous filtration and combustion of the captured soot as well of part of the soot accumulated when the trap operating conditions were not favourable for soot combustion.