Metal dusting in low-NO x recirculation burners for fuel oil

Abstract

Ten low sulphur fuel oils LSFO (sulphur content between 5 and 72 mg kg⁻¹) were tested with a low-NO_x burner. Metal dusting attack on flame recirculation tubes made of the Ni-base alloy Alloy 601 was observed for seven of the fuels. The concentrations of O₂, CO, CO₂, C_xH_y and H₂ close to the inner surface of the flame tubes were measured during burner operation. In the region where the tubes were attacked, a high concentration of hydrocarbons was found giving a carbon activity well in excess of 1. The role of sulphur was investigated by electron probe analysis of the amount of sulphur adsorbed on the surface of the recirculation tube after operation. A low value was found and no significant differences were observed between areas that had and had not suffered from attack. It is concluded that no decisive evidence has been found for the inhibiting effect of adsorbed sulphur on the catalytic activity of surface sites.