EVALUATION OF NEW CORROSION-RESISTANT SUPERHEATER TUBING IN HIGH-EFFICIENCY WASTE-TO-ENERGY PLANTS

Field corrosion tests were conducted on eight single tube materials an d two welded overlay materials in three typical Japanese waste inciner ation plants in an effort to develop new corrosion-resistant superheat er tubes capable of functioning efficiently under temperature and pres sure conditions of 500 degrees C and 100 kgf/cm(2)-g in high-efficienc y waste-to-energy (WTE) plants. Austenitic alloys containing higher co ncentrations of chromium, nickel, and molybdenum [Cr + Ni + Mo] showed excellent corrosion-resistant properties, and the new alloys JHN24 an d HR30M showed good corrosion resistance. Different corrosion rates fo und in each of the three plants were explained by differences in opera ting conditions, such as gas temperature, concentration of molten salt s resulting from chlorine (Cl) content of deposits, heavy metal (zinc oxide [ZnO] + lead oxide [PbO]) content, etc. It was conformed that th e corrosion rate of materials positioned in the first tube row facing the oncoming flow of gas was somewhat higher than rates of materials i n the second row because of the higher Cl content in the deposits. A p ilot plant capable of processing 50 tons of waste per day under respec tive 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.