Continuous dissolution of sodium and potassium silicate glass in a tower dissolver

Sodium and potassium silicate glass was continuously dissolved in a tower dissolver operated at atmospheric pressure. In pilot experiments the rate, controlled by the dissolution process occurring at the glass/liquor interface, was dependent on surface area, temperature, type, and chemical composition of the glass, but was independent of concentration and flowrate. Activation energies for the dissolution process lay in the range 22-48 kJ/mol, while typical rates of dissolution were 26 and 21 kg m^?3 h^?1 for 2.0 and 3.2 SiO₂/Na₂O weight ratio sodium silicate glass at 99°C. The corresponding rate for potassium silicate glass of SiO₂/K₂O weight ratio 2.0was 195 kgm^?3h^?1 at 80°C. Loss of potassium silicate due to the formation of insoluble compounds was prevented by operating below 93°C. Tower dissolvers warrant further consideration as an alternative to conventional digestors, having the advantages of continuous operation and uniform product density.