Combined Effects of Overheating and Soot-Blower Erosion on Reheater Tubing in a Gas-Fired Large Capacity Boiler

In a large capacity tangentially fired boiler, the final reheater tubing sustained abnormal oxidation and localized excessive metal wastage in a short time of the unit operation. The root causes of the problem are identified by test data analysis. The test data indicated that the reheater tubing metal temperatures in the affected areas exceeded the recommended limit of the metal oxidation temperature due to higher than expected local gas temperatures and velocities. A soot-blower facing the overheated portion of the reheater leading tubes accelerated the process of metal wastage by periodically removing the oxide layer. The configuration of the boiler internals upstream of the reheater section is found to be the main cause of the localized overheating. Side-to-side gas flow/temperature stratification due to tangential firing contributed to a lesser degree to the problem. The results and conclusions presented in this paper should be a beneficial guide to the designer of large capacity boilers.