Cats could replace traps
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• Catalytic convertors could replace particulate traps in the search to clean up diesel exhaust emissions. Michael Davies of the Harwell Atomic Energy Establishment told an Institute of Mechanical Engineers seminar that a platinum or palladium catalyst will burn off particulates harmlessly at normal diesel exhaust temperatures.
A filter trap simply collects the particulates, which must then be burned off at temperatures over 900'C using an external heat source.
A maintenance-free catalyst is being developed at Harwell with funding from Ford and Perkins. The silencer-size box acts as an oxidation catalyst while trapping and burning off the unwanted particulates.
Several van manufacturers, including Ford, Vauxhall and VW offer oxidation catalysts as optional equipment to treat carbon monoxide (CO) and hydrocarbon (HC) emissions An exhaust treatment is not yet available for nitrous oxides (N0x).
Catalytic and chemical exhaust treatments for NOx were discussed at the seminar, but some catalysts increase the amount of HC present in the gases and increase fuel consumption by up to 8%. Chemical alternatives include injecting gases or liquids into the exhaust.