| OCR Text |
Show CHARACTERIZATION OF COALS Five Eastern bituminous coals with decidedly different mineral distributions but similar composite elemental analyses were selected for laboratory analyses and characterization of mineral content using size and gravity fractionation techniques. The composite fuel analyses are summarized in Table 2. The ash chemistry and ash fusion data appear in Table 3. Mineral analysis, as determined by x-ray diffraction from low temperature ash, is summarized in Table 4. Characterization of the distribution of mineral content was achieved by pulverizing a 200-lb sample of coal to 70 percent through 50 mesh and analyzing four equally weighted size fractions gravimetrically separated into four gravity fractions (i.e., +1.30, -1.30/+1.80, -1.80/+2.85 and -2.85) for elemental composition and ash-fusion temperatures. The raw coal and four coarse gravity fractions were low temperature ashed and analyzed for mineral content using x-ray diffraction. The composite analyses indicate the iron concentration is the greatest in the Kentucky No. 11 and Illinois No. 6 coals. As might be expected, these coals have the lowest softening temperature under reducing conditions. Conventional slagging and fouling indices, based on ash composition, indicate the slagging potential is low to medium, and virtually no fouling is expected. Under reducing conditions encountered during very high plan area heat release rates or during flame impingement on furnace walls, the Kentucky No. 11 or Illinois No. 6 would be expected to be the most troublesome . Rather than summarizing the size and gravity fractionation data in tabular form, the elemental composition has been presented in terms of the percent basic constituents and plotted as a function of the ash-softening temperature in Figure 5. The open symbols represent size and gravity fractionated species. The closed symbols represent the composite analyses. The curve generated for all the data indicates the Upper Freeport, Indiana County, Pennsylvania, and the Lower Freeport, Cambria County, Pennsylvania, coals are more heterogeneous than either the Kentucky No. 11 or the Illinois No. 6 coals. Although both the Pennsylvania composite ash fusion temperatures are reasonably high, there is a great degree of variability in melting temperature of the individual species, ranging from as low as 2000°F to as high as 2700°F. 13 |
