Ceramic filter for trapping diesel particles

Abstract

Abstract Exhaust gas discharged from diesel engine vehicles, plant facilities, etc. has become a major concern as a cause of air pollution, health disturbances, and offensive odors. Gas emissions, especially those from diesel engine vehicles, are drawing close attention for their PM (particulate matter: suspended PM defined in Japan as particles with a grain diameter of 10 μm or less). The PM in gas emissions can be easily seen as black fumes. PM is now established to be carcinogenic and may act in ways similar to environmental hormones (Kajiwara, 2001). This redoubles the need to reduce the discharge of gas emissions and nitrogen oxide. There are various ways to reduce the harmful substances discharged from diesel engine vehicles. One is the common rail fuel injection system. Through recent technical innovations, gas emissions from diesel engine vehicles can now be purified to some extent. Better purification has recently enabled the design of high-performance diesel engine vehicles. Thanks to this improvement, in combination with the excellent fuel efficiency and durability of diesel engines, diesel engine vehicles now make up about 50% of the total sales of passenger cars in Europe. With the demand for diesel engine vehicles increasing, further purification of gas emissions is extremely important. Automakers will have to make diesel engine vehicles more environment friendly while maintaining their high performance. Fig. 30.1 shows the regulatory trends for the control of gas emissions from diesel engine vehicles around the world. This control value for the discharge of PM from diesel engines is equal to or stricter than that from gasoline engines, and still it continues to grow stricter. The elimination of air pollution by the diesel particulate filter is a very effective means to achieve the control value. The following sections describe the basic properties and characteristics of a ceramic filter for trapping diesel particles with a porous silicon carbide obtained by a recrystallization method. Details are given on several basic study items applied in the testing of the filter medium for practical use: the trapping efficiency, pressure loss, strength, and heat resistance, etc.