THE RELATIVE EROSIVITY OF LIMESTONE, DOLOMITE AND COAL SAMPLES FROM AN OPERATING BOILER

The erosivity of limestone, dolomite and coal samples retrieved from a n operating boiler was determined in an elevated-temperature laborator y erosion tester. Test conditions attempted to simulate the erosion co nditions found at the tubes in the bare tube-refractory interface area of CFBC boilers. Elevated-temperature erosion tests were conducted on AISI 1018 steel. Test results were compared to erosion test data for bed ash, limestone and dolomite samples retrieved from other plants an d tested under similar conditions. Data comparison indicated that all five samples tested in this work had relatively low erosivity and the erosivity of limestones (or dolomites) retrieved from different source s varied widely. The value difference between the highest erosive dolo mite and the lowest erosive one may reach 100-fold. Some high erosive dolomites may even show higher erosivity than the high erosive bed ash es. Therefore, some limestones (or dolomites) can contribute to the er osivity of the ash in FBCs. Among the three coal samples tested, the H awthorn coal (Indiana coal) caused the highest wastage, whereas the Ro chelle coal (Western coal) caused the lowest erosion wastage, with 5-f old difference between the highest and lowest values. Higher wastage w as associated with lower moisture content, higher ash content and the higher concentration of hard erosive species in the coal ash, such as SiO2, Al2O3, and Fe2O3. The influence of limestone and coal mineralogy was discussed with regards to erosion potential in the boiler. (C) 19 98 Elsevier Science S.A.