An Examination of the Relationship Between Ash Chemistry and Ash Fusion Temperatures in Various Coal Size and Gravity Fractions Using Polynomial Regression Analysis

Abstract

Fireside fouling and slagging properties of western subbituminous coals were studied. An examination of the relationship between the ash chemistry and ash fusion temperature indicates variation in softening temperature of individual species within the coal and may be important for those ashes whose bulk basicity is in the vicinity of 20 and 60 percent and whose ash softening temperature is approximately 1533/sup 0/K. Variations in melting temperatures of independent specie in ash whose composite softening temperature is greater than 1533/sup 0/K contribute little to the fouling problem. By including the determination of ash fusion temperature and ash chemistry in washability studies of coals with several different size distributions, fuel preparation can be evaluated as a means of modifying coals to meet air pollution prevention standards and to avoid fireside fouling and slagging problems. The regression analysis has indicated that a simple relationship exists between the ash softening temperature and the basic constituents, using the silica to alumina ratio as a parameter. The relationships appear to apply to all coals within a given rank. A generalization such as this, however, requires confirmation with many more analyses. A statistical examination of the data fit by the regression analysis indicates the standard errormore » is approximately 55/sup 0/K for data generated in a single laboratory, as well as for data generated in several laboratories. This points to a confidence limit of only 68.7 percent on a deviation in softening temperature twice the limits set by the ASTM procedure.« less