AbstractA Swiss institute for environmental technology developed an “emergency regeneration system” for “passive” diesel particle filters systems such as Continuous Regeneration Trap (CRT). For emergency regeneration at low temperature, glycol is injected upstream of the CRT. The system can be employed as a low-cost retrofit for conventional CRT. Another application is the ignition of additive-loaded soot. The institute is looking for industry partners to further develop it and bring it on the market.
DetailsA Swiss institute for environmental and engineering technology developed an “emergency regeneration system” to regenerate “passive” diesel particle filters (e.g. continuously regenerating diesel particle filter) at low temperature.
Particle filters actually retain even the finest particles of soot emitted by diesel engines. These particles accumulate in the filter. In “passive” filter systems, such as Continuous Regeneration Trap (CRT), the soot is burned off by NO2 which is provided from NO and excess O2 through an oxidation catalyst. However, this does not work at temperatures below 220 degrees Celsius. Particularly in the case of commercial vehicles, there are situations where the operating conditions are such that the exhaust gas temperatures achieved are simply too low to regenerate the filters.
For these cases the Swiss institute developed an additional injection system called Glycocat for the injection of fuel into the exhaust gases (Picture 1). However, glycol is used instead of diesel. Glycol has the advantage that it can be combusted even at low temperatures with the help of an oxidation catalyst. Glycol is much easier to inject compared to diesel and decomposes without residue into gaseous products even at temperatures around 170 degrees Celsius. As the regeneration of the filter takes place under “normal” operating conditions using NO2, a small tank of glycol is sufficient to ensure “emergency regeneration” at abnormal operating conditions.
Glycocat can also be combined with filter systems that rely on the use of diesel-additives. The additive-loaded soot is in OEM systems (like Peugeot) ignited by way of conveying unburnt fuel through the filter unit where it is exothermically oxidized in the catalyst. Alternatively, glycol injection can be used. In this case, fiddling with engine management is not necessary in order to regenerate the filter, which makes Glycocat an ideal system for retrofits.
The system can be used for retrofitting Continuous Regeneration Trap (CRT) equipped engines that occasionally run into regeneration problems due to low exhaust gas temperatures. This problem is aggravated by the fact that the platinum content of catalysts in modern continuously regenerating particle filter (CRPF) systems is minimized in order to avoid excess NO2 production. This leads to insufficient NO2-based regeneration at low temperatures.
• In contrast to diesel, glycol completely decomposes into gaseous products at temperatures of around 170 degrees Celsius. This does away with the need for an atomizing nozzle or pre-evaporator which, in the case of diesel injection, is also prone to clogging through the formation of coking residues.
• The system is entirely autonomous, encompassing a temperature sensor, a backpressure sensor and a small glycol tank plus a simple pump and injector nozzle. It is therefore cheap and simple to install.