Patent ID: 7571599
Filing Date: 2009-08-11
Classification: B01D,F01N,Y02T

Abstract:
1. An exhaust gas purification apparatus of an engine comprising: a nitrogen oxide reduction catalyst arranged in an engine exhaust gas passage to reduce and purify nitrogen oxide in exhaust gas using a liquid reducing agent; a nozzle having an injection hole that opens into the exhaust gas passage, and positioned on an exhaust gas upstream side of said nitrogen oxide reduction catalyst; an operating state detecting device that detects an engine operating state; a reducing agent injection-supply device that injection-supplies the liquid reducing agent into the exhaust gas passage from said nozzle injection hole during operation of the engine according to an injection flow rate of the liquid reducing agent based on the engine operating state detected by said operating state detecting device; and a pressure-reducing device switchable to either let compressed air from an air reservoir tank directly pass to supply high pressure air into said nozzle for a predetermined period during operation of the engine when the injection flow rate of said liquid reducing agent from said reducing agent injection-supply device becomes zero, or to reduce the pressure of the compressed air from the air reservoir tank to a predetermined pressure as it passes through said pressure-reducing device, wherein said reducing agent injection supply device uses the compressed air that has been reduced in pressure to the predetermined pressure.