| 摘要 |
PURPOSE:To prevent a corrosion of material of a heat exchanger applied in a coal combustion boiler etc. by a method wherein a concentration of dust contained in the discharged gas after its dust removal processing and a concentration of sulphur trioxide gas contained in the discharged gas are sensed and a concentration of the dust at the outlet of the dust collector is controlled in such a way as a ratio between these two concentrations is higher then 4 (weight ratio). CONSTITUTION:A discharged gas discharged from a coal burning boiler 1 is supplied to an air heater 3 after its NOx constituent is removed by a denitrification device 2. Then, the discharged gas at the outlet port of the air heater 3 is supplied to an electric dust collector (EP) 4, a concentration of the dust at an outlet port of EP4 is adjusted by the following method in such a way as it is more than a value appropriate to prevent a corrosion of the material of the heat exchanger in the step, i.e. a weight ratio of dust/SO3 is more than 4, preferably more than 10. That is, a concentration of the dust is sensed by a dust densitometer A arranged at an outlet flue of EP4 and then a signal of concentration is fed to the adjustor meter B via line (a). In the adjustor meter B, a predetermined value of EP loading condition (for example, a voltage) is produced at a power pack C through a line (b) in response to a differential value between the fed signal of concentration and the predetermined dust concentration value. |
