3 November 2004

Sweden’s STT Emtec announced introduction of a new active diesel particulate filter system for retrofitting of heavy-duty diesel engines. The filter regeneration is based on catalytic combustion of diesel fuel injected into the exhaust gases.

The filter system is controlled by an electronic control module designed by STT Emtec. When the filter needs to be regenerated, diesel fuel is injected into the exhaust gas and oxidized over an oxidation catalyst. The resulting increased exhaust gas temperature allows to burn the soot collected in the filter.

The new filter system has been tested in cooperation with Connex Sverige, a provider of public transportation services throughout Sweden. The field trial has shown good results, said STT Emtec.

Growing diesel retrofit market has stimulated the development of active filter systems by a number of manufacturers. Most of the newly developed systems utilize fuel energy for regeneration, either through flameless catalytic oxidation or through burner combustion. Active filters—while more complex and expensive—can be installed on vehicles regardless of their duty cycle, as opposed to passive filters which rely on the “natural” exhaust heat for regeneration and, thus, can be installed only on hot running engines.

For several years, STT Emtec has been supplying its DNOx retrofit exhaust gas recirculation system that reduces NOx emissions. The DNOx system has been used, primarily in urban bus applications, in Europe, Asia, as well as in the diesel retrofit program in the Houston area in Texas.

Source: STT Emtec