PURPOSE: To prevent corrosion of a heat exchanger and improve the dust collection efficiency of an electrical dust precipitator by providing an SO2 conversion reactor and the heat exchanger to the flow-rate-controllable bypass provided to the main pipeline to the electrical dust precipitator for dust-laden waste combustion gases.
CONSTITUTION: NH3 from an NH3 injecting device 2 is added to the waste gas from a combustion apparatus 1, and NOx is denitrated in a denitrating device 3 for reduction. Part of the waste gas after the denitration is introduced via a damper 9 into a conversion reactor 8, where SO2 is converted to SO3, after which the gas is returned via a secondary air preheater 10 to the front flow of an electrical dust precipitator 5. The gas flows of the main pipeline and bypass pipeline are controlled with the damper 9 so that the SO3 supplied to the dust precipitator 5 attains a proper amount. On the other hand, air is preheated in a primary air preheater 11, after which it is conducted through a pipeline 12 into the preheater 10. In this way, the gas temperatures of the air preheaters 10, 11 are maintained higher than dew point of acid, whereby condensation, etc. of acids are avoided and corrosion is prevented.
MORITA TAKETO
MORI YOSHIMICHI
