To provide an exhaust emission control system that can produce a reductive gas in good yield constantly regardless of a variation of fuel properties according to a fuel used in a fuel reformer.
The exhaust emission control system includes a second catalyst converter for purifying NOx within exhaust gas under a reductive atmosphere, the fuel reformer for supplying the fuel and air to a reforming catalyst to produce the reductive gas and supplying the produced reductive gas to the upstream of the second catalyst converter, and a reformer controlling means for controlling an air supply amount and a fuel supply amount for the reforming catalyst. The reformer controlling means increases or reduces a total amount of the air supply amount and the fuel supply amount based on an estimation value of a cetane number of the fuel to be supplied to the reforming catalyst so that a reforming catalyst temperature is within an optimum temperature range and an O/C ratio (rate of the air supply amount to the fuel supply amount) is within an optimum O/C ratio range.
MIKAMI HITOSHI
MOTOHASHI TAKESHI
Hayashi Ichiyoshi
Hiroaki Hoshino