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Show 4. RESULTS AND DISCUSSION Figures 4 and 5 and Table 2 present the most significant results of the standardized flame/nonflame, coal/non-coal ignition/burnout time tests for neat pulverized coals and their slurries. Figure 4 shows the combustion tests that addressed the question of what physicochemical fuel property (volatile matter and/or reactivity) determines and controls ignition. As far as can be determined, the results shown in Figure 4 corroborate the results of dTGA burning profiles [5-8]. Hence, the plane flame combustion/ignition test has been calibrated with the dTGA noncombustion/ignition test. For high-rank bitumious coal, it appears that the solid fuel's volatile matter content is the primary factor in controlling ease of ignition and that reactivity plays a subordinate role. A 15% reduction (38.9% to 32%) in the volatile matter content of the coal results in the development of an ignition delay time when there was none for the higher volatile (>35%) bituminous coal. Further reduction in coal volatility makes the ignition delay time substantial, i.e., up a factor of 7. Said another way, every percentage point loss in volatile matter results in an approximately 8-10 millisecond increase in the ignition delay time, all other coal parameters equal. The change (factor of 2) in bituminous coal reactivity cannot account for this loss. Thus, as was reported earlier in a complementary study [1], coal volatile matter provides a useful measure of coal ignitability. As Figure 4 shows, for low-rank coals, ignition performance is dominated by the reactivity criterion: at constant volatile matter content (-30%), ignition time is decreased about 5-fold for a 4-fold increase in reactivity (see Table 1A). For chars from the same coal with differing degrees of devolatilization, the data in Figure 4 seem to indicate that a combination of volatile matter and reactivity control the ease of ignition, because the slope of the curve for the three chars gasified from the same coal is intermediate between that for bituminous coal (volatile matter-controlled) and lignite coal (reactivity-controlled). Finally, for chars from different coals, reactivity seems to be the predominant factor in controlling ease of ignition. Because volatile matter could 22-15 |