To enable towns and cities to comply with the tightened air quality rules laid down by the EU, it is highly important that the pollutant emissions of public transport buses are reduced. To this end, a large proportion of buses have already been equipped with catalytic converters and particulate filters. The problem here, however, is the fact that buses deployed in urban traffic generally don't reach the exhaust-gas temperatures required for the catalyst to function optimally. Frequent "cold phases" at bus stops, traffic lights and while standing in traffic jams make the catalyst age much faster, which leads to an increased build-up of particulate matter (soot) in the diesel particulate filter and, over time, to damage to the filter.
In the case of vehicles that are fitted with a SCRT® system (diesel particulate filter + SCR catalyst) as standard ex-works spec, the low temperature of the catalyst can cause the SCRT system to age prematurely, which in turn leads to faster soot build-up in the particulate filter.
This in turn increases, among other things, the exhaust backpressure, fuel consumption, the amount of maintenance work required (more frequent cleaning) and the risk of SCR (AdBlue®) system malfunctions. If that happens, things get really problematical:
Due to the resulting necessity to remove the emissions system from the vehicle in order to put it through what is an expensive special cleaning process, the bus has to be taken out of service for at least a week – a situation that is far from desirable for any bus operator.
A remedy to this situation is offered by the "Refreshing" solution developed by HJS. This solution involves reactivating the catalytic platinum coating of the aged, original metal catalyst and replacing the diesel particulate filter with an easier-to-maintain, catalytically platinum-coated, flow-optimised sintered metal filter (CSMF). This system is also wrapped in a highly efficient insulation material to stop it from cooling down too quickly. Another nice side effect of this that helps public transport operators make great savings is the fact that they can then in future clean their particulate filters quite easily themselves. Thanks to HJS's "Refreshing" solution, the mileage that can now be expected of an SCRT system equals that of the original system – meaning buses can stay clean and mobile for much longer.