Low temperature active regeneration of soot using hydrogen in a multi-channel catalyzed DPF

Diesel particulate filter (DPF) systems are being used to reduce the particulate matter emissions of diesel vehicles. The DPF should be regenerated after certain driving hours or distance to eliminate soot in the filter. The most widely used method is active regeneration with oxygen at 550∼650°C. Fuel penalty occurs when the exhaust gas temperature is increased. The low temperature oxidation technique is needed to reduce fuel consumption. In this study, we found that hydrogen could be used to decrease the PM oxidation temperature significantly on a catalyzed DPF (CDPF). The oxidation characteristics of PM with hydrogen supplied to CDPF were studied using a partial flow system. The partial flow system was used to control temperature and a flow rate independently. The CDPF was coated with Pt/Al₂ O ₃ 25g/ft ³, and a multi-channel CDPF (MC CDPF) with a square cross section of 1.65cm width and length of 10cm was used. Firstly, a hydrogen oxidation was tested for DPFs with and without a catalyst. The oxygen concentration was fixed at 10%, and hydrogen concentration was changed from 2% to 8%. For the DPF without a catalyst, there was no significant hydrogen oxidation below 300°C. However for the CDPF, the hydrogen oxidation started actively over 120°C. Secondly, soot regeneration experiments were performed to investigate hydrogen exothermic reaction effects on soot oxidation in a CDPF. Prior to perform oxidation experiments, PM was collected about 8g/L at the CDPF with a engine speed of 1500rpm and BMEP of 8bar. Also, partial flow temperature of 200°C was used to minimize the NO₂ passive regeneration effect. The test was carried out with a wide range of temperatures and hydrogen concentrations. Soot oxidation in the CDPF started when H₂ concentration was 3% and the temperature was as low as 180°C. Regeneration became faster when H₂ concentration was higher.