Exhaust gas treatment system and exhaust gas purification method

Abstract

The present invention is directed to solve problems in conventional HC-SCR systems and provide cost-effective exhaust gas treatment systems with high NOx removal rates especially at low temperatures. A hydrocarbon selective catalytic reduction (HC-SCR) system in which H 2 is added to a diesel oxidation catalyst (DOC) along with hydrocarbon. In other words, it can be said as an exchange gas purification method including removing NOx from an exhaust gas by adding H 2 to a diesel oxidation catalyst (DOC) along with hydrocarbon in a hydrocarbon selective catalytic reduction (HC-SCR) system.

1 . An exhaust gas treatment system wherein H 2  is added to a diesel oxidation catalyst along with hydrocarbon in a hydrocarbon selective catalytic reduction (HC-SCR) system. 
     
     
         2 . An exhaust gas treatment system wherein
 in a hydrocarbon selective catalytic reduction (HC-SCR) system comprising, in order of inflow of an exhaust gas, an upstream diesel oxidation catalyst removing NOx from the exhaust gas using hydrocarbon, a diesel particulate filter, and a downstream diesel oxidation catalyst removing an excess of the hydrocarbon by oxidation, H 2  is added to the upstream diesel oxidation catalyst along with hydrocarbon.   
     
     
         3 . An exhaust gas purification method comprising:
 removing NOx from an exhaust gas by adding H 2  to a diesel oxidation catalyst along with hydrocarbon in a hydrocarbon selective catalytic reduction (HC-SCR) system.   
     
     
         4 . An exhaust gas treatment system comprising, in order of inflow of an exhaust gas, a diesel oxidation catalyst removing NOx from the exhaust gas using hydrocarbon, a diesel particulate filter, and a urea SCR catalyst removing NOx, H 2  is added to the diesel oxidation catalyst along with hydrocarbon. 
     
     
         5 . The exhaust gas treatment system according to  claim 4 , further comprising, downstream of the urea SCR catalyst, a catalyst removing excess ammonia that is a degradation product of the urea.