EXHAUST GAS PURIFICATION SYSTEM AND EXHAUST GAS PURIFICATION METHOD

摘要

This exhaust gas purification system is provided with an oxidation catalyst, a filter, and a selective catalytic reduction catalyst with piping therebetween in the given order in the direction of flow of exhaust gas in the exhaust pathway of a diesel engine, and the exhaust gas purification system is provided with a means for supplying ammonia between the filter and the selective catalytic reduction catalyst. The filter is a honeycomb structure having a honeycomb unit wherein a plurality of through-holes are provided in parallel in the lengthwise direction separated by partitions, and one end of the through holes is closed. The selective catalytic reduction catalyst is a honeycomb structure having a honeycomb unit wherein a plurality of through-holes are provided in parallel in the lengthwise direction separated by partitions. The ratio of the area of the cross section perpendicular to the lengthwise direction of the selective catalytic reduction catalyst to the area of the cross section perpendicular to the lengthwise direction of the filter is 0.55-0.90 inclusive, and the area of the cross section perpendicular to the lengthwise direction of the filter is 300-1000 cm2 inclusive.