| 摘要 |
A previous-stage oxidation catalyst device, a Diesel Particulate Filter (DPF) device, a turbine of a turbocharger, a previous-stage NOx selective reduction catalyst device, and a subsequent-stage NOx selective reduction catalyst device in an exhaust system of an internal combustion engine in this order from an exhaust port side. An ammonia-based solution feeder is on an inlet side or outlet side of the DPF device. The previous-stage NOx selective reduction catalyst device is a rare earth composite oxide catalyst, and the subsequent-stage NOx selective reduction catalyst device is a zeolite catalyst. The NOx removal rate is improved in wide ranges from low to high temperatures and to high flow rates, and the temperature of the DPF device is kept high to increase the time and frequency of continuous regeneration, thereby reducing the frequency of forced regeneration and an amount of discharge of CO2 during the forced regeneration. |
| 主权项 |
1. An exhaust gas purification system for removing nitrogen oxides in an exhaust gas of an internal combustion engine, comprising:
an ammonia-based solution feeder, a previous-stage NOx selective reduction catalyst device, and a subsequent-stage NOx selective reduction catalyst device disposed in an exhaust system of the internal combustion engine in this order from an exhaust port side, a NOx selective reduction catalyst of the previous-stage NOx selective reduction catalyst device made of a catalyst containing a rare earth composite oxide, and a NOx selective reduction catalyst of the subsequent-stage NOx selective reduction catalyst device made of a zeolite catalyst; and a controller for the ammonia-based solution feeder, which controller is configured to— find, from an equivalence ratio of a chemical equation, an amount which enables reduction of an amount of NOx discharged from the internal combustion engine, calculate a first ammonia-based solution amount larger than the amount enabling the reduction, calculate a second ammonia-based solution amount from a difference between a NOx target discharge amount from the internal combustion engine, and an amount of NOx measured downstream of the subsequent-stage NOx selective reduction catalyst device, when an amount of NOx measured downstream of the previous-stage NOx selective reduction catalyst device is larger than the NOx target discharge amount of the internal combustion engine, set an amount of an ammonia-based solution to be fed to the exhaust system based on the sum of the first ammonia-based solution amount and the second ammonia-based solution amount, and feed the set amount of the ammonia-based solution from the ammonia-based solution feeder. |
