Application of new corrosion-resistance superheater tubings for a 500 C, 100 Kgf/cm{sup 2}{center_dot}g high-efficiency waste-to-energy plant

A two-year demonstration run of a 500 C/100kgf/cm{sup 2}{center_dot}g high-efficiency waste-to-energy pilot plant has been started from February 1998; this plant represents as the final stage of the NEDO project of development of a high-efficiency waste-to-energy plant. Alloy 625 (SB444) and 310 HCbN tubings were selected for the 3rd and 2nd superheater of the pilot plant, respectively, and ten kinds of conventional and new solid-wall tubings, weld overlayed tubings, composite tubings, and cermet spray coated tubings were tested. By means of 6000-hour field corrosion test in three typical domestic plants, material life and corrosion environment for superheater tubings installed in the pilot plant were evaluated. Also, the effect of alloying elements Cr, Ni, Mo, corrosion rate law, etc. were investigated in detail. Furthermore, the design conception and basic performance of the pilot plant regarding pollution control and corrosion prevention were determined, based on the fluid dynamic analysis of combustion gas and field tests. To maintain the durability of waterwall, SiC refractory tile, alloy 625 weld overlay, and a NiCrSiB alloy HVOF coating were developed and applied in the pilot plant. From the interim results after approximately 6400 hour operation, the tendency of superheater corrosion in the pilot plant was foundmore » to agree with predicted results from long-time field corrosion tests, and no waterwall damage was detected. At present, the plant shows excellent operating performance with respect to emission control and durability of materials.« less