Patent ID: 9051863
Filing Date: 2015-06-09
Classification: B01D,F01N,Y02T

Abstract:
1. A flue gas purifying device that reduces nitrogen oxides contained in flue gas discharged from a burning appliance, the device comprising: a flue-gas flow path that guides flue gas discharged from the burning appliance; a urea-water injecting unit that injects urea water into the flue-gas flow path; a catalytic unit that includes a urea SCR catalyst that promotes a reaction between ammonia produced from injected urea water and the nitrogen oxides, and a support mechanism arranged inside of the flue-gas flow path to support the urea SCR catalyst in the flue-gas flow path, and that is arranged on a downstream side to a position where the urea water is injected in a flow direction of the flue gas; a first ammonia-concentration measuring unit that measures a concentration of ammonia in flue gas at a measurement position in a region where the catalytic unit is arranged; a second ammonia-concentration measuring unit arranged downstream of the first ammonia-concentration measuring unit in a flow direction of the flue gas, to measure a concentration of ammonia in the flue gas; and a control unit that controls injection of urea water by the urea-water injecting unit based on measurement results acquired by the first and second ammonia-concentration measuring units, wherein the control unit is configured to: set a target concentration of the second ammonia-concentration measuring unit, which is not updated; update a target concentration of the first ammonia-concentration measuring unit based on the measurement result acquired by the second ammonia-concentration measuring unit after comparing the measurement result acquired by the second ammonia-concentration measuring unit to the target concentration of the second ammonia-concentration measuring unit; and control the injection of urea water by the urea-water injecting unit so that a measurement result acquired by the first ammonia-concentration measuring unit becomes the target concentration of the first ammonia-concentration measuring unit.