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EGR doesn't depend on ultra-low-sulphur fuel
Page 26
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IN SETTING OUT the relative merits of SCR and EGR, Oliver Dixon is wrong to assert that EGR -demands low-sulphur fuel" (CM 14 July).
For the past three years North American EGR engines complying with EPA 2004 emissions legislation have managed perfectly well on fuel with up to 500ppm sulphur.
The US requirement for 15ppm sulphur fuel to be available from 2006 is based on the need for diesel particulate filters (DPFs) which will have to augment EGR in meeting the very severe PM (particulate matter) limits set for EPA 2007.
Self-regenerating DPFs like Johnson Matthey's CRT and Englehard's DPX rely on a platinum catalyst which cannot tolerate more than about 50ppm sulphur (the present maximum in the UK).
It seems likely that. in view of the forecast 12 cents per gallon price penalty for 15ppm fuel in the US, some truck manufacturers will opt for DPFs with electrically heated or fuel-burner rather than catalyticregeneration.
They will eat into fuel consumption but that might well not matter, in cost if not in greenhouse gas terms, because users can carry on using cheaper highsulphur fuel.
But the crunch will come in 2010 when American diesel engine makers are expected to adopt lean-NOx traps (LNTs) which are even more sensitive to sulphur that catalytic DPFs.
Alan Bunting Harpenden Herts