Method and arrangement for purifying exhaust gas in an internal combustion engine

摘要

The invention relates to a method for purifying exhaust gas in an internal combustion engine provided with an LNT and a particulate matter filter arranged in an exhaust gas conduit of the engine. The method includes de-sulfurization of the LNT and regeneration of the particulate matter filter. The invention includes the following steps: initiating a heating phase wherein the engine is set to generate heat sufficient for the de-sulfurization and the regeneration; initiating a de-sulfurization phase during a first time period (t1), in which the engine is set to generate a rich exhaust gas in the exhaust gas conduit; keeping the first time period below a first maximum value so as to avoid release of emissions of H2S from the engine; initiating a regeneration phase during a second time period, in which the engine is set to generate a lean exhaust gas in the exhaust gas conduit; keeping the second time period below a second maximum value so as to avoid thermal damage to the particulate matter filter; and repeating the de-sulfurization phase and the regeneration phase in a periodical manner.