廃棄物焼却ボイラの高温腐食に及ぼす応力の影響

抄録

In superheater tubes of high-efficiency waste-to-energy plants, high temperature corrosion may occur when molten salt containing chlorides or sulfates is formed in the ashes deposited on the fireside tube surface. In addition, if residual stress exists in bent or welded parts, high temperature corrosion may be accelerated or crack-like damage may be caused by the presence of the molten salt. In order to investigate the effect of static stress on the high temperature corrosion, crack-like damage tests were conducted in actual refuse ash and synthetic refuse ash at 823 K under static stress applied by the constant load method.
When buried in synthetic refuse ash containing 20 mass% chlorine under a 0.2% proof stress load condition at 823 K, the SUS304 specimen was fractured by intergranular crack-like damage after 3.6×10 ks. For SUS310J1 and alloy 625, the specimens exhibited no cracking up to 1.08×10³ ks. However, the maximum intergranular corrosion depth of SUS310J1 increased as applied stress was increased. Also, as the chlorine concentration in the refuse ash was increased both the maximum intergranular corrosion depth and the maximum corrosion thickness loss tended to increase.