Electrochemical particulate trap for diesel engine exhaust.
Exhaust from diesel engines are known to be one of the major causes of air pollution, especially in big cities. The soot content is one of the main factors in smog formation, and it is known to be carcinogenic. The Electrochemical Reactor (ECR) project aimed to develop a device for removing soot particles from diesel engine exhaust based on an electrochemical combustion process. The interest in electrochemical gas purification is primarily based on the present demand for adding emission controls to the large fleet of diesel driven vehicles in Europe, and to achieve conformity with future emission standards in the EU for new vehicles. The project methodology proposed was based on an electrochemical principle, whereby the exhaust gas from diesel engines would be filtered through an electrochemical reactor (ECR). The reactor would be composed of an oxygen ion conducting electrolyte, covered by an electron conducting, catalytic active electrode material. The materials and optimal microstructure were defined by an ongoing development project at Dinex Filter Technology A/S, and the quantitative efficiency and effect on gaseous pollution were investigated. The aim of the development project was to construction a working demo-filter to be tested on a small engine in a test bench. The proposed LIFE project involved the continuation of the development project to the establishment of a pilot scale production of filter elements, and functional tests of the trap system on a fleet of city busses. The project also included the evaluation of pilot scale production methods for electrochemical reactor elements, control and operation systems for the trap, design and integration in exhaust system, endurance test in the laboratory and functional test in city busses.
The aim of the project was to construct a prototype particulate trap system, including a control system, for the removal and continuos burn off of soot particles from the exhausts of diesel engines. The system was also expected to remove gaseous pollution components such as unburned hydrocarbons, carbon monoxide and possibly nitrogen oxides. The prototype trap system was to be tested on city busses. The main deliverables of the project were an Electrochemical Reactor (ECR) for the removal of particulate matter (PM) and gaseous pollutants from diesel engine exhausts against the following targeted measurable criteria: PM retention of over 90% CO conversion of better than 80% CH conversion of better than 80% NOx reduction of more than 50% Fuel penalty of less than 1%
The ECR operates as a continuously regenerating filter without significant use of precious metals at temperatures present in the diesel engine exhaust flow. The ECR has also demonstrated great potential for reducing Nitrogen Oxides (NOx) under lean conditions, without the use of any reducing agents or additives. The system is practically maintenance free, has only a low fuel penalty and is not sensitive to sulphur in diesel fuel. With little or no use of precious metals, the system will, if produced on a large scale, be a price competitive installation with no negative external impacts on the environment. The project has ended up with a set of durable prototypes running in a smaller fleet of buses, a passenger car and in an industrial diesel engine. The concept has proven its capacity to remove hazardous compounds and was considered to be ready for larger pilot production in 2001.