Temperature analysis of reheater in coal-fired thermal power plant radiant boiler

Coal-fired power plants continue to play a central role in Japan’s electricity supply, accounting for approximately 28% of total generation in 2023. Within these plants, boilers are critical components that generate high-temperature, high-pressure steam through complex heat exchange processes involving radiation and convection. Superheaters (SH) and reheaters (RH), located in regions exposed to the highest combustion gas temperatures, are particularly susceptible to tube damage, making accurate predictions of local temperature and heat flux distributions essential for safe and efficient operation. In this study, a computational fluid dynamics model, which utilized the radiation (DO model) and turbulence models (k-ε RNG model), was developed to analyze the temperature of the superheaters (SH(I), SH(II)) as well as the reheater (RH). The model incorporated three-dimensional steam flow and examined two cases: a model with ash deposition on the tube surfaces and a model without ash deposition. Results indicated that the ash model had only minor influence on overall combustion gas flow when calibrated against the actual plant data. Radiation heat transfer contributed most significantly in SH (I), closest to the burner, while its relative importance decreased downstream. The low-velocity regions of the gas flow were identified at the lower region of SH (II) and at the upstream bends of RH, whereas downstream bends of RH were exposed to high-velocity gas regions. Therefore, tube surface temperatures in RH at downstream bends occurred hot spots. Furthermore, circumferential temperature variations were more pronounced in the model without ash deposition. These findings provide insight into localized thermal behavior in reheaters, supporting improved design of tube performance and enhanced reliability of coal-fired boiler operation.