FIELD TEST OF WATERWALL CORROSION IN A CFB WASTE BOILER

摘要

A field-test was done in a Circulating Fluidized Bed (CFB) boiler burning refuse derived fuel (RDF). The corrosion of alloys ranging from carbon steel (CS) to a nickel based superalloy was tested in panels in the waterwall for 738h. The metal temperatures were kept at about 300°C and 338°C, controlled by separate oil cooling systems. The flue gas composition in the boundary layer at the test panels was on average 27 ppm HC1, 2.6 ppm SO_2, 5% O_2, 13% CO_2 and 2% CO. The corrosion rates were consistently estimated from the weight loss per length unit, and by a profilometry method developed for the test. TP310 (UNS S31008) had the lowest corrosion rates at both temperatures (176 and 284 μm/lOOOh). The highest corrosion rate at 300cC was 264 μm/lOOOh for Alloy 625 (UNS N06625). This was due to the pitting corrosion of Alloy 625 that occurred at both temperatures. At 338°C the highest rates were 823um/1000h for the CS and 400 um/lOOOh for TP304L (UNS S30403). Analyzed outer deposits mainly consisted of KC1, NaCl and CaSO_4. A layer with mainly potassium oxide was found within the Fe_2O_3 on CS. For Alloy 28 (UNS N08028) and Alloy 625 a layer of KC1 was found in connection to Cr-Ni-Fe oxide.