| OCR Text |
Show (and to a lesser extent operating variables) is an important influence in determining whether a particular power plant/coal combination will experience slagging and/or fouling problems. The figures included within this paper are the first publication of which we are aware that relates the likelihood of a unit having slagging and/or fouling problems to both coal properties and boiler design. Thus, it is our hope that these figures will be useful to the industry in selecting appropriate boiler/coal combinations. One fact that has become clear in our study of these data is the fact that the slagging frequency for many boiler/coal combinations can be accurately categorized using almost any of the recognized parameters. Also, a few combinations seem to be impossible to properly categorize using any of the parameters. Therefore, the comparison of the various parameters hinges on one parameter being better than another parameter for categorizing the boiler/coal combinations for which different parameters place the unit in different categories. Table 1 summarizes numerically the results for the four "best" slagging predictors. Table 2 is a summary of the percent of units properly categorized by the parameters discussed in this paper, and of the units missed by one or by two categories. Of the slagging parameters discussed in this paper, the ash softening temperature range and the silica percentage produced somewhat higher "correct" percentages than the other parameters. The ash fusion temperature range produced the smallest percentage of correct responses. The B&W slagging factor had the smallest percentage of major errors, defined as to missing the correct categories by two categories. To minimize the possibility of under predicting the slagging frequency, it might be advisable to apply several slagging parameters and use the "worst" predicted case as the expected slagging frequency. For example, one might use slagging factor, base/acid ratio, silica percentage, and ash softening temperatures. Table 3 shows the results of applying this practice. Thirty-three units are predicted to have frequent slagging. Of these, only 45 percent actually have frequent slagging, but 84 percent have frequent or occasional slagging. Eight of the units predicted to have occasional slagging actual experience occasional slagging, and twelve o 1-12 |
