| abstract |
A system for the prevention of hydrocarbon emissions from engines during start up is provided, in which a cold engine generates an exhaust gas rich in unburned or thermally degraded hydrocarbons. The exhaust gas is passed through a hydrocarbon absorbent bed prior to atmospheric discharge, so that hydrocarbon vapor is absorbed in the bed. When the engine and exhaust gas are hot, and hydrocarbon emission low, most of the exhaust gas is discharged directly to atmosphere and the absorbent bed is regenerated by passing a small stream of hot exhaust gas through the bed. The resulting gaseous mixture of exhaust gas plug desorbed hydrocarbon vapor is recycled to the engine. |