Review of flue gas acid dew-point and related low temperature corrosion

Abstract Acid dew-point (ADP) is the temperature at which the acid vapor, normally means sulfuric acid (H2SO4), in flue gas begins to condense. Acid condensation can result in low-temperature corrosion (LTC), which can threaten the safety of boilers. An exhaust temperature higher than ADP can relieve LTC, however, result in a low thermal efficiency. Therefore, ADP is regarded as a key parameter to guide safety and efficiency of boilers. Previous investigations on ADP are abundant, but a comprehensive review is absent. This work tried to fill this gap. First, the existing methods for ADP determination, including empirical models, semi-empirical models, and measurement methods, were explained. The empirical models were specially classified according to the transformation path of SO3/H2SO4 in flue gas. Then, these methods were compared and evaluated, and the difficulty in identifying the beginning of the acid condensation was considered to result in the different results among varied methods. A new method which can reveal the acid condensing process was recommended for evaluating and discussing the issue of ADP. Moreover, this paper also involved the topic on preventing LTC below ADP focused by the currently popular deep waste heat recovery field. Finally, future research directions were suggested.