Active Regeneration
Active regeneration refers to the process of oxidising the accumulated diesel particulate matter (DPM) in a filter without relying on the temperature of the exhaust gas alone. An active approach involves either heating up the exhaust gas or, preferably the filter itself, so that it reaches the point at which the DPM oxidises. The energy to raise the temperature to the level required (about 600 C) is most commonly provided either by a fuel burner or from an electrical supply. If the electrical route is taken, the current required is quite considerable and is beyond the capacity of most vehicles’ electrical systems, therefore in the case of mobile machinery the normal procedure is to connect the filter to a mains supply periodically, for instance at the end of each shift. The inconvenience of this approach is obvious, and leads to many problems caused by staff ‘forgetting’ to regenerate the filter. However, in the case of diesel generators, active regeneration using electricity is a practicable solution since the generator’s own power can be used and the heater can be switched on automatically as and when required.
The fuel-burner approach used a burner similar to that found in a central heating boiler. This always encountered scepticism from customers who were concerned about the fire risk, and was never developed to the stage where it became completely reliable.