MELTING OF FLY ASHES AND PRODUCT PROPERTIES

Combustion of municipal waste yields fly ashes. The ashes contain haza rdous metals in a soluble form. Recycling or disposal of such residues requires separation of the hazardous metals or vitrification of ashes . The glass product must be chemically durable enough to prevent signi ficant leaching of the hazardous metals. The vitrification process req uires knowledge of the viscosity and the crystallization properties of the melt and of the electrical resistivity if the melt is directly he ated. These properties were investigated in dependence of the temperat ure and the chemical melt composition and the results are presented gr aphically so that melt properties can be predicted for certain melt co mposition ranges. The chemical durability was measured using various t est methods (Soxhlet, ISO 719, ''Swiss Test''). The chemical durabilit y was also tested as a function of temperature, pH value, glass surfac e area to solution volume ratio and the content of organics (citric ac id, humic acid) in the solution. First results are presented.