FIELD CORROSION EXPERIENCE WITH STAINLESSMATERIALS IN FLUE GAS DESULPHURISATION

摘要

The field tests with stainless materials in the inlet of flue gas to scrubber after long timernexposition presented in the paper can be used to establish a materials election guide for slurry absorbedrnenvironment. Molybdenum additions of more than 3 % to alloys containing chromium and nickel wererngenerally found necessary. Whether the alloy is iron base with low chromium content or withoutrnchromium and/or nickel base, corrosion resistance properties are greatly influenced by the addition ofrnchromium. It is desirable that the passive film should form quickly, and repassivate at any breaks. Thernbetter acid chloride pitting and crevice corrosion resistance of stainless materials can be attributed inrnlarge part to molybdenum. The aggressive constituents of the raw gas are SO2, SO3, HCl and HF withrnSO2 being the most concentrated. The slurry is not very corrosive, but due to closure of water circuit andrnto the composition of some coal grades, the chloride content can be very high and sometime fluor-ionsrnare also present. Moreover, corrosion by solid sulphate salts produced by chemical reaction betweenrnSO2/H2SO3 and lime or limestone can destroy the passive conditions of stainless material on various partsrnof the scrubber.