Concept of Limited Corrosion Dew Point for Coal-Fired Boiler and Experimental Research

Abstract

Inadequacy was discussed of using acid dew point temperature (ADT) as safe low limitation of exhaust gas temperature on the background of waste heat deep utilization of flue gases. Concept of limited corrosion dew point (LCT) was presented based on corrosion property of ordinary carbon steel and binary phase equilibrium of H2SO4-H2O system,. Calculation formula of LCT was solved by establishing fugacity equation of H2O with a fixed concentration and constant pressure. The results show that LCT lies during 68-84°C when volume percentage of H2O vapor varies from 6-12% which is in line with that of exhaust gas of boiler. The maximum relative error of the calculated data is 1.43% in contrast to reported data. Ordinary carbon steel in contact with flue gas with its surface temperature above LCT will not occur obvious corrosion and wet soot deposition through observation of experiment on site. It is available for exhaust gas temperature to decline below ADT but above LCT in process of deep utilization of waste heat of flue gas.