Apparatus for reducing nitrogen oxide contained in exhaust gas

Abstract

An apparatus for reducing NO x contained in exhaust gas as an exemplary embodiment of the present invention may include: a DOC device primarily oxidizing an exhaust materials containing THC and CO in the exhaust gas by using a first DOC; a CPF device mounted downstream of the DOC device to receive the exhaust gas primarily oxidized by the DOC device, further oxidizing the exhaust materials containing the THC and the CO by heat generated during the primary oxidation and an oxidizing agent coated therein, and oxidizing NO in the exhaust gas into NO 2 by using the generated heat and the oxidizing agent coated therein; a nozzle mounted downstream of the CPF device, and dosing a reductant to the exhaust gas; and a SCR device mounted downstream of the nozzle, and reducing NO x in the exhaust gas into N 2 by using the NO 2 generated in the CPF device and the reductant.

1 . An apparatus for reducing nitrogen oxide contained in exhaust gas, comprising:
 a diesel oxidation catalyst (DOC) device primarily oxidizing an exhaust materials containing total hydrocarbon (THC) and carbon monoxide (CO) in the exhaust gas by using a first diesel oxidation catalyst (DOC);   a catalyzed particulate filter (CPF) device mounted downstream of the DOC device so as to receive the exhaust gas that is primarily oxidized by the DOC device, further oxidizing the exhaust materials containing the THC and the CO by heat generated during the primary oxidation and an oxidizing agent coated therein, and oxidizing nitrogen monoxide (NO) in the exhaust gas into nitrogen dioxide (NO 2 ) by using the generated heat and the oxidizing agent coated therein;   a nozzle mounted downstream of the CPF device, and dosing a reductant to the exhaust gas; and   a selective catalytic reduction (SCR) device mounted downstream of the nozzle, and reducing nitrogen oxide (NO x ) in the exhaust gas into nitrogen gas (N 2 ) by using the NO 2  generated in the CPF device and the reductant.   
   
   
       2 . The apparatus of  claim 1 , wherein the DOC device, the CPF device, the nozzle and the SCR device are mounted on an exhaust pipe. 
   
   
       3 . The apparatus of  claim 3 , wherein the DOC device and the CPF device are positioned upstream of the exhaust pipe and the nozzle and the SCR device are mounted downstream of the exhaust pipe. 
   
   
       4 . The apparatus of  claim 1 , further comprising a turbo charger mounted upstream of the DOC device, wherein the turbo charger is disposed apart from the DOC device by a predetermined distance such that the first oxidation reaction occurs at a good pace in the DOC device. 
   
   
       5 . The apparatus of  claim 4 , wherein the predetermined distance is between about 100 mm and about 150 mm. 
   
   
       6 . The apparatus of  claim 5 , wherein the turbo charger, the DOC device, the CPF device, the nozzle and the SCR device are mounted on an exhaust pipe. 
   
   
       7 . The apparatus of  claim 6 , wherein the turbo charger, the DOC device, the CPF device are positioned upstream of the exhaust pipe and the nozzle and the SCR device are mounted downstream of the exhaust pipe. 
   
   
       8 . The apparatus of  claim 1 , wherein a noble metal comprising platinum (Pt) and palladium (Pd) is used for the first DOC in the DOC device, and wherein a ratio of the platinum to the palladium is 1:1-12:1. 
   
   
       9 . The apparatus of  claim 8 , wherein the diameter of the first DOC is between about 100 mm and about 144 mm, and the length thereof is between about 100 mm and about 120 mm. 
   
   
       10 . The apparatus of  claim 9 , wherein a loading amount of the noble metal in the first DOC is about 80-150 g/ft 3 . 
   
   
       11 . The apparatus of  claim 1 , wherein the oxidizing agent is coated at a catalyzed particulate filter (CPF) of the CPF device. 
   
   
       12 . The apparatus of  claim 11 , wherein a noble metal comprising Pt and Pd is used for the oxidizing agent, and wherein a ratio of the Pt to the Pd is 2:1-6:1. 
   
   
       13 . The apparatus of  claim 12 , wherein a loading amount of the noble metal in the oxidizing agent is 30-80 g/ft 3 . 
   
   
       14 . The apparatus of  claim 13 , wherein 60-80% of the oxidizing agent is coated at a front portion in the CPF. 
   
   
       15 . The apparatus of  claim 1 , wherein the reductant is ammonia. 
   
   
       16 . The apparatus of  claim 15 , wherein the reductant is dosed in form of urea. 
   
   
       17 . The apparatus of  claim 1 , wherein the selective catalytic reduction (SCR) device includes a Fe-zeolite catalyst.