Laboratory corrosion tests for simulating fireside wastage of superheater materials in waste incinerators

Laboratory corrosion tests were performed to clarify the effects of relative amounts of fused salts in tube deposits on corrosion rates of superheater materials in WTE plants. All test exposures were at 550 degrees C and of 100 h duration. The nine synthetic ashes used as corrodents consisted of mixtures of chlorides, sulfates and oxides. The test materials were alloy steel T22, stainless steels TP347H, TP310HCbN, and alloys HR11N and 625. The gas atmosphere consisted of 500 to 3000 ppm HCl-30 ppm SO2-10% O-2-10% CO2- 20% H2O-bal.N-2. Generally, the relative amount of fused salts in non-fused ash constituents at 550 degrees C increased with increasing the chlorine content of the ashes. The corrosion rate of T22 steel did not depend directly on ash chlorine content, but for ashes of 7.7 wt.% CI, the corrosion rate depended on the calculated amount of fused salt at 500 degrees C. The corrosion rates of TP347H steel and alloy 625 were maximum for ashes of 6-8 wt.% Cl. For ashes of 7.7 wt.% Cl, the corrosion rates of T22 steel, stainless steels, and alloys increased with ashes having higher amounts of fused salts. Increased HCl content of the gas caused higher corrosion of the stainless steels and high-nickel alloys, but there was no clear corrosion-exacerbating effect with T22 steel.