PURPOSE: To prevent deterioration of catalyzer and enable highly stable removal of NOx for a long period of time, by adsorbing and removing sulfur trioxide, sulfur and dust before dry type ammonia contact reduction of combustion exhaust gas containing nitrogen oxides and sulfur oxides.
CONSTITUTION: Since deterioration of catalyzer for denitration is mainly caused by SO3 contained usually about 5 to 7 vol.% of total SOx volume, it is removed, before denitration treatment, through granular adsorbent layer at room temperature to 300°C. For instance, the combustion exhaust gas from a boiler 1 is passed through a granular adsorbent filled layer 2a such as γ-alumina, and SO3 is removed. Then, after a certain period of time, when the adsorption of SO3 roughly reaches the saturated state, valves before and after the adsorbent filled tower 2a are opened and closed to change the process line to tower 2b. On the other hand, the regenerative gas is passed into the tower 2a from a blower 5 and heat exchanger 6, and adsorbed SO3 is removed, and the exhaust gas is taken out from the top of the tower. The exhaust gas rid of SO3 is catalytically reduced by NH3 coming from a tank 3 in a denitration reaction tower 4.
ITOU SAKAE
MIFUJI YUTAKA
HIRANO TATSUO
SAWADA YOUSUKE
