Theoretical prediction of acid dew point and safe operating temperature of heat exchangers for coal-fired power plants

Research on acid dew point and condensation process of flue gas is necessary for making full use of waste heat in coal-fired boilers and reducing low temperature corrosion of heat exchangers. The iterative calculation of acid condensation is studied with consideration of both the gas-liquid equilibrium effect and multi-component diffusion effect. Furthermore, based on the thermodynamic data of water vapor and sulfuric acid vapor, the iterative calculation model of the acid dew point is proposed. The iteration result shows great consistency with the experimental data, and with the maximum and minimum deviation being around 2.68 °C and 2.07 °C, respectively. The single-factor and orthogonal calculations are analyzed to obtain the effects of temperature, acid vapor content and water vapor content on the acid condensation. In addition, the safe operating temperature of heat exchanger is suggested based on the analysis of corrosion mechanism and acid condensation calculation results. The lowest temperature of heat exchanger is recommended above 80 °C in the practical application of waste heat utilization in coal-fired boilers.