Originally Posted by senix

regen is short in this forum for regeneration of the DPF (dust Particate Filter)
You asked for it so here it is:
Diesel Particulate Filters (DPF)
Overview

Diesel particulate filters applicable to the equipment used in your Metal or Nonmetal mine are designed to filter diesel soot from the hot exhaust. They also replace the muffler. The filter media used in the majority of the commercially available DPFs is made from a porous ceramic material made from either Cordierite or Silicon Carbide. The Silicon Carbide material is more robust, filters slightly more efficiently, but is more expensive.
The filters work by blocking passage of the diesel soot so that much less than 10% of the soot in the engine’s exhaust is released into the mine air. Obviously, soot builds up in the filter and something has to be done to remove it. The process of removing the combustible portion of the collected soot is called "regeneration" which is the burning off of the soot by raising the temperature of the filter element so that combustion of the soot occurs. When the soot combusts, the soot which is almost pure carbon is converted to gaseous carbon dioxide (CO2) and carbon monoxide (CO), which pass through the filter. Diesel soot or DPM is not entirely comprised of combustible carbon but also contains noncombustible ash resulting primarily from the additives used in crankcase lubrication oils, fuel or intake air additives, and from the fuel itself. The removal of the ash from the DPF is called "cleaning" and, although necessary to do, is done much less frequently than regeneration. See the discussion of ash in this document.
DPF regeneration can occur "passively," or naturally when the engine exhaust is hot enough during equipment operation. Some DPFs use a washcoat of specially-formulated catalysts, fuel-borne catalysts (a fuel additive), or both to reduce the exhaust temperature needed for regeneration.
When natural passive regeneration is not possible, the DPF stores the soot during machine operation, and a regeneration must be "actively" performed on a regular schedule, for example once every shift. Active regeneration uses electric heating elements and a controlled air flow to regenerate the filter when the equipment is not in use. The commercially available systems for active regeneration either incorporate the electric heating element into the DPF and regeneration takes place on-board the equipment while the equipment is off duty and parked at a designated location, or require the exchange of the loaded DPF for a regenerated DPF. In the exchange scheme, the loaded DPF is taken to a regeneration station located in a designated area (perhaps with other such regeneration stations) that is ventilated and free of combustibles either underground or on the surface. Another system uses compressed air, flowing in the reverse direction from the normal exhaust flow, to blow out the collected soot and ash into a collection bag.
The exhaust temperature dictates whether passive or active DPFs are applicable for a specific piece of equipment. Active systems are universally applicable because they only collect the soot and can be mounted where convenient, but passive systems impose strict requirements on exhaust temperatures and must be mounted as close to the engine exhaust manifold as possible.