| 摘要 |
<p>The invention has its object to prevent the deposition of acidic ammonium sulfate on a low-temperature heat transfer tube and obtain a high heat recovery rate by almost completely decomposing surplus ammonia downstream of an NOx reduction apparatus in an exhaust gas boiler provided therein with the NOx reduction apparatus even when sulphur oxides are contained in an exhaust gas. To this end, a high pressure evaporator is divided into sections (3a, 3b), between which a residual ammonia decomposition apparatus (14) is provided. Surplus ammonia which has not been consumed in the NOx reduction apparatus (13) is decomposed into nitrogen gas and water vapor by the residual ammonia decomposition apparatus (14). Between the high pressure evaporator sections (3a, 3b) is formed a temperature area where a rate of ammonia decomposition is high. According to the invention, heat recovery is effected even from a low temperature area of the exhaust gas, so that a plant efficiency is enhanced. Also, an adequate amount of ammonia can be assuredly supplied with ammonia inflow nozzles (15) upstream of the NOx reduction apparatus (13), thereby ensuring a high NOx reduction rate.</p> |
