Evaluation of new corrosion-resistant superheater tubing in high-efficiency waste-to-energy plants

Field corrosion tests were conducted on eight single tube materials and two welded overlay materials in three typical Japanese waste incineration plants in an effort to develop new corrosion-resistant superheater tubes capable of functioning efficiently under temperature and pressure conditions of 500 degrees C and 100 kgf/cm(2)-g in high-efficiency waste-to-energy (WTE) plants. Austenitic alloys containing higher concentrations of chromium, nickel, and molybdenum [Cr + Ni + Mo] showed excellent corrosion-resistant properties, and the new alloys JHN24 and HR30M showed good corrosion resistance. Different corrosion rates found in each of the three plants were explained by differences in operating conditions, such as gas temperature, concentration of molten salts resulting from chlorine (Cl) content of deposits, heavy metal (zinc oxide [ZnO] + lead oxide [PbO]) content, etc. It was conformed that the corrosion rate of materials positioned in the first tube row facing the oncoming flow of gas was somewhat higher than rates of materials in the second row because of the higher Cl content in the deposits. A pilot plant capable of processing 50 tons of waste per day under respective temperature and pressure conditions of 500 degrees C, 100 kgf/cm(2)-g was constructed, and 11 conventional and new tubings were tested over a 2-year period.