Diesel Oxidation Catalyst System For PM Control 2004-28-0069

PM (Particulate Matter) emission from Diesel vehicles has been a major concern to countries worldwide due to the negative impact on human health and the environment. With the increasing stringency of emissions regulations, new effective diesel emission control systems are needed for in-use and new diesels vehicles.

In order to improve SPM levels in the urban areas of Japan, most local governments are considering new legislation. This legislation will require old in-use diesel vehicles to be retrofitted with a PM reduction device, such as a DOC (Diesel Oxidation Catalyst), DPF (Diesel Particulate Filter) or CRT™ (Continuously Regenerating Technology). The CRT™ (Continuously Regenerating Technology) system is an effective device for reduction of PM from in-use diesels. The CRT™ consists of a DOC and a particulate filter which is conventionally a wall-through filter. In the present, more than 30,000 vehicles worldwide are operating with this device. However, due to the lower NOx/PM ratio from Japanese in-use diesels, only a limited number of vehicles can be equipped with this conventional system. Improvement is necessary for the vehicle with low NOx/PM ratio.

A new PM emission control device which consists of a DOC and an unique Catalysed Soot Filter (CSF) capable of dealing with the lower NOx/PM ratio has been developed for retrofit application. In this paper, the impact of DOC to reduce unregulated emissions and PM is first studied under simulated practical driving conditions. The concept of this new DOC + CSF enables the system operation using CRT™ principle under the low NOx/PM ratio condition.