| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust gas cleaning system and an exhaust gas cleaning method capable of improving emission control performance of nitrogen oxides in an SCR with a temperature range wider than before.SOLUTION: An SCR converter 4 comprises an inside part 6 in a radial direction made of a catalytic agent with high low-temperature activity such as a cupper zeolite catalyst; and an outside part 7 made of a catalytic agent with high high-temperature activity such as an iron zeolite catalyst. A duplex tube 10 is provided immediately before the upstream side of the SCR converter via a passage selector valve 11, in which an inner tube 8 of the duplex tube and an outer tube thereof face the inside part 6 of the SCR converter 4 and the outside part 7 thereof with spaces, respectively. The passage selector valve switches over the passage such that at low temperatures of exhaust gas G and the SCR converter 4, the passage for the exhaust gas G is switched to only the inner tube 8 so as to clean emission gas mainly with the cupper zeolite catalyst disposed at the inside part 6, while at high temperatures, the passage for the exhaust gas G is switched to only the outer tube 9 so as to clean emission gas mainly with the iron zeolite catalyst disposed at the outside part 7. |
