A Fog-and-Tube Scrubber for the Removal of Diesel Particulate Matter from Engine Exhaust

Diesel particulate matter (DPM), the solid portion of diesel exhaust, has been linked to a range of deleterious health impacts. While a number of control strategies have been effective at reducing DPM in some environments, exposure risks are still high in others such as underground mines. In prior work, a novel scrubber treatment that used fog to remove DPM from engine exhaust was successfully prototyped in bench-scale laboratory experiments. Here, for the first time, the treatment concept was scaled up and field tested in a stone mine. An exhaust blower was used to pull fog, diesel exhaust, and mine air through a 30.5-meter long tube, enabling coagulation of DPM and fog drops resulting in their subsequent removal. Excluding one of the eleven tests, which appeared to be an outlier, the results showed that this fog-and-tube scrubber removed an average of 63% of particles (11.5-154 nm) as compared to 18% in the control case (without fog), yielding an average improvement of 45%. Computer simulations suggest that the observed particle removal is predominantly due to rapid thermal coagulation between the DPM and fog drops, followed by removal of the DPM-laden drops via inertial impaction with the tube walls.