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What the filters do for you


ACCORDING to Tim Rogers, Clean Diesel Technologies offers four levels of retrofitting providing varying degrees of particulate reduction (and an improvement in fuel efficiency of up to 15 per cent):

The use of a platinum fuel-borne catalyst (FBC) on its own - this reduces particulates by 15 per cent to 25 per cent;

The use of a platinum FBC plus a diesel oxidation catalyst - this reduces particulates by more than 40 per cent;

The use of a platinum FBC plus a wire mesh filter - this reduces particulates by more than 65 per cent;

The use of a platinum FBC plus a DPF - this reduces particulates by more than 95 per cent.

'The use of FBCs enables the emissions control devices to work , ' explains Mr Rogers.

It does this by overcoming one of the problems inherent in any filter system: how to stop it becoming blocked.

'The soot particles that are captured on the DPF must be oxidised - the filter must be regenerated, ' he explains.

'This can be done in a number of ways.

First, by removing the DPF from the machine and manually heating it to a high enough temperature to burn off the soot. An alternative is to increase the back pressure to raise temperatures (this is how it's done on 2.5 million Peugeot cars and vans). The third option is to add a catalyst.

By using the FBC, the temperature at which the DPF can be regenerated is reduced from 600 deg C to 300 deg C, which overcomes the need for the other solutions as these temperatures can be at tained even if the engine is not constantly running at full power.

The application of the FBC is achieved by fitting an active catalyst delivery system and an on-board diagnostic unit to measure delivery.

Mr Rogers says: 'It could be added manually, but it's better to be sure it's added at the right time in the right quantities. One of the systems we've put in place has enough catalyst stored to run for one-and-a-half years.'

In addition to the catalyst delivery system, the machinery also needs to be fitted with a filter. Mr Rogers says: 'As a rule of thumb, if there's any noise attenuation muff ler then there's room for a DPF or wire mesh filter, although they add weight - there's no getting around it.'

A lthough the drop in particulates is comprom ised , Mr Rogers points out that for those concerned about the longevity of DPFs in the rigorous working environment of most plant, a wire mesh filter can still provide significant reductions.