Effect of Composition on the First Melting Temperature of Fireside Deposits in Recovery Boilers, 1998 Engineering Conference Proceedings

The first melting temperature (FMT) of fireside deposits, the temperature at which the deposit begins to melt, is of vital importance to the control of superheater corrosion in krafi recovery boilers. Chemical analysis and FMT data for more than 150 deposits and precipitator dusts from various recovery boilers were examined. The results show that of the minor components in the deposit, potassium has the greatest impact in lowering the FMT. Carbonate may also lower the FMT, but the effect is much smaller than potassium. Sulphide has an even smaller effect. Since deposits usually contain some chloride, an increase in chloride content would have little effect on the FMT. The difference in the effect of individual components on the FMT can be explained using phase equilibrium principles. A temperature contour map has been constructed which can be used to determine the FMT of a typical deposit as a function of potassium and carbonate contents.