To provide an exhaust emission control method and an exhaust emission control system capable of efficiently performing both of regeneration for recovery of NOx purification capacity of NOx direct reduction type catalyst and sulfur purge for removing sulfur adsorbed by the NOx direct reduction type catalyst.
In the exhaust emission control system 1 having oxidation catalyst 3 and NOx direct reduction type catalyst 4 arranged in an exhaust gas passage 2 of an internal combustion engine E in an order from an upstream side and provided with a bypass circuit 5 bypassing the oxidation catalyst 3 and a passage change over means 6, exhaust gas is made pass through the oxidation catalyst 3 at a time of sulfur purge of the NOx direct reduction type catalyst 4 and exhaust gas is made pass through the bypass passage at a time of rich operation other than sulfur purge.
Takashi Noguchi
Kazuhiko Saishita
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