| 초록 |
Recently, much more regulations on the air quality to reduce pollutants produced by automobiles are forced. Among the many pollutants included in the exhausts from the diesel engine, particulate matter smaller than 10 mm (PM10) is more often responsible for the severe situation. Ceramic filters made of cordierite or silicon carbides, which have excellent thermal shock properties, are usually used in a honeycomb type (wall flow type). However, the breakdown of the thin wall of the honeycomb due to the carbon combustion is a major disadvantage. In this paper, we present a novel ceramic filter structure which prevent the loss of the filtering ability even though the ceramic body has been cracked. The pore of the ceramic filter body is consists of two types: the first is the macro and continuous pores penetrating through the body, and the second is meso-pores that are formed in the ceramic body. The main function of the continuous pores is to offer the fluent flow of the exhaust gas through the body. During passing the pores PMs are collided with the ceramic wall and are caught by the meso-pores. Namely the meso-pores offer the capturing sites of PMs. By heating the ceramic filter at elevated temperature, the captured PMs are burned out. In this type of filter, even though the cracks due to excessive combustion of PMs are formed in the ceramic body, the filtering function still operates because the actual capture happens at the meso-pores. Furthermore, as a ceramic body any type of materials can be used regardless of the thermal expansion and stability. We tried mullite ceramic body made from waste coal fly ash, and LaFeO3 meso-pores were formed on it. |
