| 摘要 |
PURPOSE:To reduce the leakage of NH3, by a method wherein the concn. of NOx in exhaust gas is detected and the injection amount of NH3 is controlled on the basis of the detection value and, when the concn. of NH3 leaked on the downstream side of a denitration area exceeds a set value, the injection amount of NH3 is controlled on the basis of the concn. of NH3 leaked. CONSTITUTION:The exhaust gas exhausted from an engine 1 is mixed with NH3-gas in a mixer 2 and subjected to selective reducing denitration in a cata lyst tower 7. Normally, a first damper 9a is opened and a second damper 14a is closed and a flow rate control valve 6 is controlled by a control apparatus 19 so that the concns. of NOx on the upstream and downstream sides of a denitration area detected by first and second NOx concn. detectors 11, 12 be come predetermined denitration ratios. When it is detected that the detected concn. exceeds a set value by a leak NH3 concn. detector 13, the injection amount of NH3 is controlled on the basis of the concn. of NH3 leaked. further, the cleaning of a catalyst can be performed by blowing compressed gas to the catalyst at every predetermined time to blow off soot. |
