OCR Text |
Show ANALYTICAL TECHNIQUES Both empirical and statistical analytical methods have been used in evaluating the slagging and fouling data. The empirical method consisted of plotting the data for the various power plants on grids -- usually with a coal term as one coordinate and a boiler term as the other coordinate. The severity of slagging and/or fouling problems at each power plant are coded on the plots. Then, by examination, regions of the grid are defined for plants having various degrees of problems, e.g., no problems, occasional problems, and frequent problems. The empirically defined relationships are evaluated by observing the percentage of plants properly classified for each set of parameters. Standard statistical methods also have been used to evaluate slagging and fouling relationships, including developing correlation coef-ficients and R , T, and F values. Because of the complex nature of the relationships between coal and boiler properties and the occurrence of deposit problems, the statistical methods have not been as useful for evaluating single-term relationships as have the empirical methods. However, for more complex relationships involving several terms, the statistical approach has been of more value. EVALUATION OF SLAGGING AND FOULING PARAMETERS Although essentially all slagging and fouling parameters are defined in terms of coal properties, it has been recognized that slagging and fouling problems are a result of a combination of coal and boiler properties. That is, "slagging" coals frequently can be fired in furnaces with low combustion intensities without undue slagging problems. Conversely, a less slagging coal can create slagging problems if fired in a furnace with too high of a combustion intensity. Consequently, the same coal may be "slagging in one furnace and "non-slagging" in another furnace. In recognition that both coal properties and boiler designs are important factors in evaluating slagging and fouling problems, the results presented below include both coal and plant parameters. 1-5 |