The Study On The Anticorrosion Property Of GFRP And Titanium Against Sulfuric Acid For Application In FGD Chimney

It is well known that rapid economic development can’t sustain at the sacrifice of environmental pollution. Billions tons of coal was burned in China every year and let out most of gaseous pollutants into the air. Flue-gas Desulfurization(FGD) equipment which is installed in coal-fired power plants can release the emissions of many kinds of gaseous pollutants. Limestone-gypsum gas desulfurization is most widely applied in chimneys in China which causes serious corrosion. Ti-steel composite plate and glass fiber reinforced plastics(GFRP) are most common materials used in chimney for corrosion protection. Therefore, it is important to study their anticorrosion property in actual conditions.Based on practical projects and documentary records, the reasons and features of corrosion happening in FGD chimney are examined in this paper. Thereafter, sulfuric acid is taken as the main cause of the high corrosive property of smoke condensate. The influence of the concentration and temperature of sulfuric acid on the materials’ anticorrosion property are then investigated thoroughly in this research. The change of appearance, weight loss and mechanical property are examined to investigate the materials’ anticorrosion property under different concentrations(1%、5%、10%、15%) and at different temperatures(50℃、60℃、70℃、80℃). To explore the anticorrosion behavior of the two materials in practice, the samples are also tested in artificial smoke condensate. Furthermore, as mechanical joint is critical but weak place in chimney, and its production and anticorrosion property are different from the structure of base material, the corrosion resistance of the joints is investigated carefully as a key part of chimney structure.The results show that both GFRP and titanium are quite stable in sulfuric acid of low concentration(1%). However, their strengths weaken as the concentration of sulfuric acid increases. And the corrosion problem titanium encounters is much more serious than GFRP in sulfuric acid of high concentration. The influence of temperature on the anticorrosion property is significant for both materials. Titanium samples dissolved entirely in 10% sulfuric acid at 70℃ after 60 days and 80℃ after 45 days. In the smoke condensate of 50℃, GFRP and titanium samples performed very well. According to the tests, the retained strength ratio of all samples can be up to 97%. GFRP joints show the same anticorrosion property as the base material. On the other hand, welded joints are more easily corroded than titanium itself. The welded joints were broken after 60 days in 10% sulfuric acid at 50℃. Due to the high temperature encountered during welding process for titanium. In summary, both GFRP and titanium show good anticorrosion performance under normal working conditions in the application of inner chimney, practical choice shall be made according to the on-site engineering conditions. However, as far as the local condensation of smoke condensate and the durability of structural joint are taken into account, GFRP shows better anticorrosion performance.