Method and apparatus for treating diesel exhaust gas to remove fine particulate matter

A method for regenerating a first ceramic filter and a second ceramic filer both loaded with particulates from exhaust gases of a diesel engine, said filters being in joint communication with the exhaust from a diesel engine and each being provided at the intake end thereof with first and second switchable heaters, respectively, operable when turned on to uniformly heat a stream of exhaust gas passing therethrough to a temperature sufficient to sustain combustion of particulate on said filters, comprising the steps of:

• (a) turning on said first heater for a selected period of time, such that a portion of the particulates held by said first ceramic filter is burned off during passage of heated exhaust gases therethrough and the flow rate of exhaust gases through said fist ceramic filter becomes substantially greater than the flow rate of exhaust gases through said second ceramic filter;
• (b) turning off said first heater and turning on said second heater for a selected period of time, such that the initially lower flow of heated exhaust gas through said second filer regenerates it essentially completely and the flow rate of exhaust gases through said second filter becomes greater than through the partially regenerated first filter;
• (c) turning off said second heater and turning on said first heater for a selected period of time, such that the initially lower flow of heated exhaust gas through the partially regenerated first filter regenerates it essentially completely;
• and
• (d) turning off said first heater and turning on said second heater for a selected period of time to ensure complete regeneration of said second filter,
• wherein the exhaust from the diesel engine is passed through a catalytic purifier before passing through said first and second heaters.