FIELD: chemistry.
SUBSTANCE: exhaust-gas cleaning apparatus has: an exhaust pipe; an aqueous urea injecting unit which injects aqueous urea into the exhaust pipe; a catalyst unit having a urea-using SCR catalyst which facilitates reaction between ammonia and nitrogen oxides, and a support which supports the urea-using SCR catalyst in the exhaust pipe and is placed downstream from the point where aqueous urea is injected; a concentration measuring unit lying downstream of the exhaust gas from the catalyst unit for measuring concentration of ammonia in the exhaust gas which has passed through the urea-using SCR catalyst; a control unit which controls injection of aqueous urea using the aqueous urea injecting unit based on ammonia concentration data measured by the concentration measuring unit; a unit for measuring concentration of isocyanic acid; a temperature control unit.
EFFECT: cleaning exhaust gas, wherein ammonia leakage can be suppressed and content of nitrogen oxides in the exhaust gas can be effectively reduced.
8 cl, 7 dwg
