Failure of carbon steel tubes in a fluidized bed combustor

Plain carbon steels are used in power plants for transfer of heat from the flue gases/fluidized bed to water. In the present study, the failure of a few super heater tubes at localized regions in an atmospheric fluidized bed combustor was studied. The main reason of the failure was attributed to high oxidation at these localized regions and spalling off of the oxides due to high operating temperature and high velocity of the alumina and silica particles in the fluidized bed. Obvious design changes and/or bandaging with a stainless steel sleeve at the affected regions coming in direct path of the fuel nozzle were recommended in this case.