| 摘要 |
PURPOSE:To improve the removal efficiency of nitrogen oxides by providing an ammonia spray nozzle intended for downstream injection between intermediate tiers of a plurality of catalyst layers and an ammonia amount adjusting device. CONSTITUTION:An ammonia splay nozzle 6 intended for downstream injection is provided between a second and third catalyst layer 2 and 3 and a NH3 pipe 28 is connected therewith. A NH3 flow setting signal 16 outputted from a multiplier 15 is sent to a computing device 19 and a differentiator 22, which sends a set NH3 flow value changing signal 23 into a converter 24, from which a NH3 complementary signal 25 is outputted to thereby regulate the opening degree of a NH3 complementary adjusting valve 21. When the flow amount of exhaust gas and NOx concentration in the exhaust gas rise and a load on a denitrification device increases, a NH3 complementary adjusting valve 26 on the downstream side of the NH3 pipe 28 is controlled by a signal 25 to increase the amount of NH3 flowing to the ammonia spray nozzle 6, whereby the lowering of the removal rate of nitrogen oxides can be prevented. |
