Exhaust gas treatment apparatus

An exhaust gas treatment apparatus placed in an exhaust system of a combustion gas, for collecting and removing particulate matter contained in an exhaust gas, the treatment apparatus comprising:

• a casing connected to the exhaust system to serve as a main flow path of the exhaust gas;
• a honeycomb filter placed in the inside of the casing in such a manner that it interrupts the main flow path, the honeycomb filter having a plurality of cells partitioned by partition walls to serve as filter flow paths of the exhaust gas and collecting the particulate matter contained in the exhaust gas;
• and
• plasma generation electrodes composed of a first electrode and an earth electrode, the plasma generation electrodes being capable of generating nonthermal plasma between the first electrode and the earth electrode,
• wherein
• the particulate matter contained in the exhaust gas flowing into the casing is collected by the honeycomb filter,
• nitrogen monoxide contained in the exhaust gas is oxidized to nitrogen dioxide by the nonthermal plasma generated between the first electrode and the earth electrode constituting the plasma generation electrodes, and
• combustible materials in the particulate matter collected and deposited on the surface of the partition walls are removed through oxidation by the nitrogen dioxide produced and thereby the honeycomb filter is regenerated,
• wherein the cells of the honeycomb filter are plugged alternatively at a gas inlet end and a gas outlet end of the honeycomb filter, so that the exhaust gas passes through the partition walls, and
• said first electrode and said earth electrode have one of the following arrangements:
• (i) the electrodes are on opposite side faces of the honeycomb filter which has a rectangular cross section, the side faces extending parallel to the cells,
• (ii) the earth electrode is on the outer peripheral surface of the honeycomb filter, and surrounds the honeycomb filter, extending parallel to the cells, and the first electrode is a rod-shaped electrode inserted in a cell of the honeycomb filter and extending from the gas inlet end to the vicinity of the gas outlet end,
• (iii) the earth electrode is on the outer peripheral surface of the honeycomb filter, and surrounds the honeycomb filter, extending parallel to the cells, and the first electrode is formed as a plurality of needles on a net-shaped insulating plate arranged in front of the gas inlet end of the honeycomb filter.