| 摘要 |
PROBLEM TO BE SOLVED: To provide an apparatus for denitrating exhaust gas having good denitration performance even under the conditions in which severe NOx regulation is required during the actuation of a waste heat recovering boiler, and a method for operating the apparatus. SOLUTION: The time for starting the injection of ammonia during the actuation of a denitration apparatus is set up at a point of time when the temperature of a denitration catalyst layer part reaches the boiling point or the vicinity of the boiling point of the condensed water of exhaust gas. Since the reduction of NOx can be attempted even in a low temperature area without lowering the activity of the denitration catalyst, the discharge of NOx can be controlled during the operation of a plant. Although an exhaust gas temperature at the outlet of the catalyst layer increases behind that at the inlet of the catalyst layer, when the injection of ammonia is started at 140 deg.C of an exhaust gas temperature at the inlet, an exhaust gas temperature at the outlet corresponds to 100 deg.C (the boiling point of the condensed water of exhaust gas), and since the temperature of the entire catalyst layer is at the lowest 100 deg.C when the injection of ammonia is started at this point of time, the discharge of ammonia or NOx into the air can be prevented. |
