Regeneration of DPF

It is relatively easy to filter and collect the particulate matter in the trap but the soot is to be burned in-situ i.e., ‘regenerate’ the trap  so that pressure drop across the filter is kept always at an acceptable level.

• Soot and other particulate get collected on the filter that although improves the filtration efficiency, but it results in an increased pressure drop across the filter. The pressure loss in the new and clean filter is about 70 mm H₂O for the 0.1 m/s gas velocity in filter channels. Design considerations limit soot loading to about 10 g/l of filter volume before filter should be cleaned or regenerated. As the soot is collected upto the limit of 10g/l, pressure drop increases to 300-350 mm of . An increase of engine backpressure by 350 mm results in 1 % loss in fuel economy at 65-km/h vehicle speed.  
• For engine out PM emissions of about 0.25 to 0.33 g/kW-h and engine power output of about 17 kW/ liter swept volume, 10g/l soot would get collected on DPF in about 2 hours. Hence, the DPF regeneration should take place approximately every 2 hours. The soot in the filter is to be burned in-situ.
• Burning of soot  particles begins at about 540º C. Such high exhaust gas temperatures do not occur during engine operation for sufficiently long periods of .time. The diesel exhaust gas temperatures in the exhaust pipe typically reach to about 300ºC only.
• For regeneration of the DPF, therefore additional measures are to be adopted.