| 摘要 |
PURPOSE:To control the temp. of the denitration catalytic apparatus to a proper temp. range by recirculating the outlet gas of said catalyst apparatus to the inlet thereof to prevent temp. rise of a catalyst layer due to reaction heat when a NOX concn. is high. CONSTITUTION:A gas 7 to be treated is passed through a preheater 1 and, after NH3 3 is added to said gas, NOX in the gas is subjected to contact reduction in a catalyst tower 2. The treated gas is cooled in a cooler 4 to lower only the temp. raised in the catalyst tower 2 and, after cooling, a part thereof is exhausted from a blower and the remainder is returned to the inlet side of the preheater 1 through a recirculation line 6. When an exhaust gas recirculating amount is defficient, an inert gas 12 is introduced from a three-way control valve 11. The temp. control of a catalyst layer is carried out by adjusting the opening degree of the three-way control valve 11 so as to adjust the temp. detected by a thermometer 2A to a definite temp. range. As described above, by recirculating an appropriate amount of the exhaust gas corresponding to the temp. of the catalyst layer in the catalyst tower, the temp. rise of the catalyst layer is suppressed and catalytic capacity can be kept high. |
