Exhaust gas purification system of an internal combustion engine and method for purifying the exhaust gases thereof

Abstract

An exhaust gas purification system for purifying the exhaust gas of an internal combustion engine, especially an internal combustion engine featuring auto-ignition and/or direct fuel injection, is provided. The system includes at least one oxidation catalytic converter disposed in an exhaust gas duct of the internal combustion engine, at least one device for selective catalytic reduction of the exhaust gases which is installed downstream of the oxidation catalytic converter, and a feed device for feeding reducing agent into the exhaust gas stream upstream of, or in, the device for selective catalytic reduction. A switch-over device is provided for selectively feeding reducing agent into the exhaust gas stream upstream of, or inside, the at least one oxidation catalytic converter. A corresponding method for purifying the exhaust gas of an internal combustion engine is also provided.

Description

FIELD OF THE INVENTION [0001] The present invention relates to an exhaust gas purification system of an internal combustion engine having a device for selective catalytic reduction, and relates particularly to a method for purifying exhaust gases of an internal combustion engine, in which an exhaust gas stream is passed through a device for selective catalytic reduction. BACKGROUND INFORMATION [0002] To lower the nitrogen oxide content of oxygen-rich exhaust gas, such as that emitted by diesel internal combustion engines and by internal combustion engines featuring direct gasoline injection, it is known to introduce a reducing agent into an exhaust tract. A suitable reducing agent is, for example, NH3, which may be introduced as a gas into the exhaust gas stream. In such so-called selective catalytic reduction (SCR), the ammonia is selectively reacted with the nitrogen oxides present in the exhaust gas to form molecular nitrogen and water. [0003] The insufficient activity of the kno...

AI Technical Summary

Benefits of technology

[0005] An exhaust gas purification system in accordance with the present invention includes at least one oxidation catalytic converter disposed in an exhaust gas duct of an internal combustion engine, and at least one device for selective catalytic reduction of the exhaust gases, which device is installed downstream of the oxidation catalytic converter. The exhaust gas purification system further includes a feed device for feeding reducing agent into the exhaust gas stream and admixing it therewith upstream of the device, or in the device, for selective catalytic reduction (SCR catalytic converter). According to the invention, the exhaust gas purification system has a switch-over device and/or a further feed device for selectively feeding reducing agent into the exhaust gas stream upstream of, or inside,

Problems solved by technology

The insufficient activity of the known SCR system at exhaus

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