Condensation Characteristic of Sulfuric Acid Vapor on Low-Temperature Surface of Tube Heat Exchanger

Abstract

In the low-low temperature flue gas system, a part of the H2SO4 vapor is adsorbed by the ash particles, and the other part will condense on the surface of the heat exchanger, resulting in low-temperature corrosion. In this paper, a numerical model for the condensation of H2SO4 vapor on low-temperature surface is constructed. This model combines the thermodynamic phase equilibrium theory, the multicomponent transport theory and the heat transfer theory. The effects of flue gas properties, the size and arrangement of heat exchanger are studied. The results show that, the condensation rate is mainly related to the concentration gradient of H2SO4 vapor near the surface. As the flue gas or surface temperature increases, condensation rate decreases. When the flue gas velocity increases, the mass transfer resistance is reduced, thereby the condensation rate is increased. As the content of H2SO4 in the flue gas increases, the concentration gradient of H2SO4 vapor near the surface increases, and the condensation rate of increases linearly. But the content of water vapor has little effect on the H2SO4 condensation rate. For the tube heat exchanger, when the working conditions keep the same, the smaller the outer diameter of the tube, the greater the condensation rate of the H2SO4 vapor. Compared with the inline arrangement, when the tubes are staggered, the disturbance of flue gas is stronger, and the condensation rate is larger.KeywordsCondensation characteristicLow-low temperature flue gas systemCorrosionTube heat exchanger