Patent ID: 8453435

Claim:
A method for controlling an exhaust gas purification device, the exhaust gas purification device comprising: a plurality of branch exhaust passages connected to an exhaust passage on the engine side of an internal combustion engine or a burning appliance; an exhaust gas shutoff unit switching between allowing and shutting off the flow of the exhaust gas into the respective branch exhaust passages from the exhaust passage on the engine side by opening or closing the exhaust inlets of the respective branch exhaust passages; a nitrogen oxide adsorbing material, disposed inside each of the respective branch exhaust passages, temporarily adsorbing nitrogen oxides in an excess air atmosphere, and detaching the adsorbed nitrogen oxides in a rising temperature atmosphere or a reducing atmosphere; a first combustion device, disposed on the exhaust upstream side of the nitrogen oxide adsorbing material inside each of the respective branch exhaust passages, and comprising an air supply unit and a fuel supply unit and an ignition unit, and supplying and burning a first mixture gas of fuel and air; and a second combustion device, disposed on the exhaust downstream side of the nitrogen oxide adsorbing material inside each of the respective branch exhaust passages, and comprising an air supply unit and a fuel supply unit and an ignition unit, wherein there are normal operation and regeneration operation performed in the respective branch exhaust passages, and wherein the regeneration operation includes main regeneration operation for detaching the nitrogen oxides adsorbed onto the nitrogen oxide adsorbing material, and the main regeneration operation has at least two stages of operation, the method comprising the steps of: allowing the flow of the exhaust gas into the branch exhaust passage subjected to the normal operation by the switching of the exhaust gas shutoff unit during the normal operation; operating the first combustion device and the second combustion device while the exhaust gas is prevented from flowing into the branch exhaust passage subjected to the regeneration operation by the switching of the exhaust gas shutoff unit during the regeneration operation; controlling the excess air ratio λ of the first mixture gas to λ<1.0 during the main regeneration operation; and decreasing the flow rate of the first mixture gas as the stage of the main regeneration operation advances, wherein the regeneration operation includes post-regeneration operation as a post-stage of the main regeneration operation, the method further comprising: controlling the excess air ratio λ of the first mixture gas to λ>1.0 during the post-regeneration operation.