Hydrogen damage in a power boiler: Correlations between damage distribution and thermal-hydraulic properties

Abstract

This study investigates the correlation between the damage distribution in the evaporator tube and thermal-hydraulic properties of a boiler with hydrogen damage caused by a decrease in the pH of the boiler water. The hydrogen damage in the vertical upward flow tube of the boiler was located in the transition region from the slightly subcooled boiling region to the saturated boiling region. Thermal-hydraulic analysis suggested that this region may have an environment with a gentler flow and a higher concentration of chemical species on the heat transfer surface than that in a fully saturated boiling region. Based on these findings, in the vertical upward flow tube downstream (upper part) from the damaged part of the boiler furnace, material diffusion on the surface becomes more active owing to the acceleration and stirring effect caused by bubbling in the main stream. Therefore, the concentration on the heat transfer surface is moderated. In addition, in the upper part, the effect of decreasing the heat flux due to the distance from the burner is compounded, and the risk of hydrogen damage is further reduced.