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Treating The Exhaust Gas In IC Engine- Catalytic Converter

The Catalytic converter converts the pollutants like HC, CO and No2 into harmless gases. It is placed between exhaust manifold and silencer. It contains the plastic pallets coated with the catalyst.




All exhaust gas must flow through it. The catalyst causes a chemical change without being a part of the chemical reaction. The catalytic converter may have two different catalysts. One catalyst treats the HC and CO. The other treats No2. The catalyst encourages the HC and CO to unit with oxygen to become H2O and Co2. This type of converter is known as oxidizing converter because it oxidizes the HC and CO. The metal platinum and palladium are used as oxidizing catalysts.

The Catalyst for NO2 splits the oxygen from the NO2. The No2 becomes harmless nitrogen and oxygen. This type of converter is known as reducing converter. The metal rhodium is used as  reducing catalyst Vehicles with catalyst and makes it ineffective. For the catalytic converter to the most effective, the air fuel mixture must have stoichiometric  ratio 14 : 7 :1 

To achieve the described air fuel ratio at all operating conditions, a feed back system is used. It determines the correct air fuel ratio of the intake charge by measuring the amount of oxygen remaining in the exhaust. The diesel engine catalytic converter is a pure oxidation catalytic converter. It oxidizes HC and CO into water and CO2. It can not reduce NO2.   

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