2008 Volume 57 Issue 11 Pages 466-471
Though the high temperature corrosion observed at heavy oil fired boilers is known as a typical vanadium attack, the presence of metallic sulfides under the oxide layer and carburization phenomenon are observed by the investigation on the corroded tubes. Those phenomena can not be explained by the laboratory corrosion tests with synthetic oil ashes. Additives, such as MgO or Mg(OH)2 injected with fuel into boilers to inhibit high temperature corrosion. Decrease of tube corrosion rate is improved by the additive-ash reactions which forms a high melting, non corrosive products. However, these additives cause a reduction in thermal absorption efficiency at the combustion furnace tubes due to white color of Mg additives and promoted generation of undesired thermal NOx in combustion gas. This paper highlights the differences of high temperature corrosion phenomena of actual boiler tubes and laboratory corrosion tests, behavior of Mg additives injected with fuel and V2O5 in the boilers, and important role of engineering on the corrosion control techniques applied to boiler plants.