REMOVING METHOD FOR NITROGEN OXIDE IN EXHAUST GAS

摘要

PROBLEM TO BE SOLVED: To efficiently remove NOx in exhaust gas even if a varying region of exhaust gas temp. is large by bisecting a catalyst layer, disposing the catalyst layer having a high denitrating performance at a moderate high temp. region on an upstream side and disposing the catalyst layer having high denox performance at a moderate low temp. region on a downstream side and injecting a reducing agent at the upstream of the catalyst layer. SOLUTION: The catalyst layer is bisected at the time of removing a nitrogen oxide in the exhaust gas by subjecting it to catalytic reduction under the presence of the reducing agent. Then the catalyst layer 3 having the high denitrating performance at the moderate high temp. region of about 350-600 deg.C such as TiO2 -WO2 based catalyst is disposed on the upstream side of the waste gas stream. Then the catalyst layer 4 having high denitrating performance at the moderate low temp. region of about 200-450 deg.C such as TiO2 -V2 O5 -WO3 based catalyst is disposed on its downstream side. Then a reducing agent injection port 2 is provided on the upstream side of the catalyst layer. In this way, the NOx removing efficiency at the moderate low temp. region is improved and an unreacted reducing agent at high temp. region is reduced.