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Technical Paper

An Experimental Investigation on Low Temperature CDPF Regeneration Utilizing Hydrogen

Soot particles accumulated in a DPF should be removed after a certain service time due to high pressure drop. The most common method is oxygen active regeneration which sometimes DPF cracking or melting. In this study, the authors aim to investigate the low temperature regeneration with hydrogen, which could prolong the DPF lifespan and facilitate CDPF regeneration efficiency. The DPF used in this research was coated with Pt/Al₂O₃ 25 g/ft₃ and all experiments were performed on engine test bench. Results showed that DPF regeneration can be realized at about 150°C or even lower. During regeneration, the inside temperature at front part (about 20 mm) of DPF was about 40°C higher than the other parts during regeneration. The maximum inside temperatures during regeneration depend only on the hydrogen concentration and soot oxidation can be calculated simply from the Arrhenius equation using the experimental temperatures.
Technical Paper

Hydrogen Effect on the DeNOX Efficiency Enhancement of Fresh and Aged Ag/Al2O3 HC-SCR in a Diesel Engine Exhaust

HC-SCR is more convenient when compared to urea-SCR, since for HC-SCR, diesel fuel can be used as the reductant which is already available onboard the vehicle. However, the DeNOX efficiency for HC-SCR is lower than that of urea-SCR in both low and high temperature windows. In an attempt to improve the DeNOX efficiency of HC-SCR, the effect of hydrogen were evaluated for the fresh and aged catalyst over 2 wt.% Ag/Al₂O₃ using a Euro-4 diesel engine. In this engine bench test, diesel fuel as the reductant was injected directly into the exhaust gas stream and the hydrogen was supplied from a hydrogen bomb. The engine was operated at 2,500 rpm and BMEP 4 bar. The engine-out NOX was around 180 ppm-200 ppm. H₂/NOX and HC₁/NOX ratios were 5, 10, 20, and 3, 6, 9, respectively. The HC-SCR inlet exhaust gas temperatures were around 215°C, 245°C, and 275°C. The catalyst volumes used in this test were 2.5L and 5L for both fresh and aged catalysts.
Technical Paper

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/Al₂O₃ 25g/ft₃, and a multi-channel CDPF (MC CDPF) with a square cross section of 1.65 cm width and length of 10 cm was used.