Method and apparatus for operating a methane-fuelled engine and treating exhaust gas with a methane oxidation catalyst

Abstract

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.

Description

Technical field [0001] The invention relates to a method and equipment for operating an engine using methane as fuel and treating exhaust gas with a methane oxidation catalyst. The present invention can be applied to vehicle engines or other engines operating with variable load cycles to reduce emissions of carbon monoxide, methane and other unburned hydrocarbons. Background technique [0002] Natural gas is mainly composed of methane. Natural gas is burned as a fuel in internal combustion engines because in many markets around the world, natural gas costs less than diesel or gasoline from an energy point of view. In addition, natural gas burns cleaner than diesel or gasoline, which can help improve air quality, thereby providing another motivation to replace diesel or gasoline-burning vehicle engines with natural gas-burning vehicle engines. However, in the exhaust gas discharged from the combustion chamber of an internal combustion engine, unburned fuel remains, and this is als...

AI Technical Summary

Problems solved by technology

The problem with this approach is that it increases the complexity of controlling the engine, as it involves calculating the timing of desulfurization of the methane oxidation catalyst, as well as the timing of the two control strategies to run the engine in lean or rich mode, because The timing corresponding to operating in rich mode depends on the calculated timing that can occur at any point on the engine map

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