METHOD AND APPARATUS FOR OPERATING A METHANE-FUELLED ENGINE AND TREATING EXHAUST GAS WITH A METHANE OXIDATION CATALYST

摘要

A method and apparatus is provided for operating a methane-fuelled engine in a lean burn operating mode or a stoichiometric operating mode. When a methane oxidation catalyst is employed to treat the exhaust gas from an engine running in a lean burn operating mode, the catalyst can be inhibited by SOx reducing the catalyst's methane conversion efficiency. When an engine is running in a stoichiometric operating mode, desulphation of the catalyst can occur, thereby restoring the catalyst's methane conversion efficiency. The disclosed method relates to fuelling the engine with a lean fuel mixture when operating the engine at one of a predetermined first set of points on an engine map, and fuelling the engine with a rich fuel mixture when operating the engine at one of a predetermined second set of points on said engine map. The exhaust gas from the engine flows through a methane oxidation catalyst, which is preferred embodiments is adapted to promote the reduction of NOx when the engine is running in the stoichiometric operating mode. The apparatus comprises means for detecting and controlling lambda, and an electronic controller programmed to operate the engine in one of a lean burn mode and a fuel-rich mode at respective predetermined points on an engine map.