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Show conversion. The predicted losses are lower than observed under conditions favoring high conversion, an effect which the authors suggested might result from incomplete mixing of char with the remaining oxygen and a decrease in combustion rate due to the presence of ash on the surfaces of partially-burned particles. More than 50 years after the work by Hottel and Stewart, the prediction of carbon loss at high conversion is an active area of research, motivated by the need for greater fuel flexibility, improvement of efficiency, and minimization of solid waste from power production. A session was devoted to carbon burnout at the Eighth International Conference on Coal Science (Pajares and Tascon, 1995). Papers presented at the Conference included studies of char reactivity (Commissaris et aI., 1995; Rybak and Matuszkiewicz, 1995; Thomas et al., 1995; Zhang Xiaoke et aI., 1995), the distribution of char reactivity (Hurt et aI., 1995), thermal deactivation of individual macerals and lithotypes (Beeley et aI., 1995a; Parra et aI., 1995; Varey et aI., 1995), the relationship between inertinite content and reactivity (Menendez et aI., 1995), a detailed mechanistic model for char oxidation (Reade et al., 1995), changes in reactivity of char with pyrolysis conditions (Cai et aI., 1995), fragmentation during combustion (Dacombe et al., 1995), char structure (Bailey, 1995; Lester et aI., 1995), correlations among maceral distribution, mineral matter concentration, and particle density (Beeley et aI., 1995b), effects of coal cleaning (Harris et aI., 1995), and the mixedness of furnace gas (Walsh, 1995). The works cited are examples of those which addressed the issue of fixed carbon conversion in boiler furnaces; many others considered burnout in other types of equipment, or other aspects of coal combustion expected to influence carbon loss, such as ignition and devolatilization behavior. EXPERIMENTAL A series of tests intended to assess effects of weathered coal on plant performance was conducted by the Pennsylvania Electric Company (PENELEC) at its Seward Electric Generating Station (PENELEC, 1992). The tests were performed in boiler no. 12, a twodrum Stirling boiler having a capacity of 136,000 kg steamlhour, designed by the Babcock & Wilcox Company (B&W), normally firing pulverized medium volatile bituminous coal through 6 wall-mounted burners. Although the boiler was built in 1948, it continues to 3 |