Abstract
In order to develop new corrosion resistant superheater tubes capable of functioning efficiency under temperature and pressure conditions of 500°C and 100ata used in high efficient waste-to-energy (WTE) plants, field corrosion tests were conducted on eight single tube materials and two welded overlay materials at metal temperatures of 450°C and 550°C for 700 and 3000 hours, respectively, in three typical Japanese waste incineration plants.
The test results indicate that austenitic alloys containing higher concentrations of [Cr + Ni + Mo] show excellent corrosion resistant properties and new alloys of JHN24 and HR30M have good corrosion resistance.
The different corrosion rate found for each of the three plants could be explained by differences in the severity of corrosion factors, such as, gas temperature, concentration of molten salts due to Cl content of deposits, and heavy metal [ZnO + PbO] content etc. It was also confirmed that the corrosion rate of materials positioned in the first tube row facing the oncoming flow of gas show somewhat higher rate than those in the second row due to higher Cl content in the deposits.
Applying the above informations, a pilot plant capable of processing 50 tons of waste per day, under respective temperature and pressure conditions of 500°C, 100 ata is now under construction, and eleven conventional and new tubings will be tested over a two year period.
