CONVERSION INTO HEAT OF MICROWAVE POWER USED IN THE MANUFACTURING PROCESS OF GLASS FOAM

Abstract

The manufacture of glass foams from container glass waste, silicon carbide as a foaming agent (1.75-1.9 wt.%) and an addition of 1:6 aqueous solution of KNO₃ (0-1.75 wt.%) was performed at sintering temperatures between 913-952 ºC. Using the effect of the microwave power conversion into heat, the predominantly direct and partially indirect microwave heating reached high heating rates (25.2-28.8 ºC/min) and the specific energy consumption had very low values (0.70-0.83 kWh/kg), generally, below the values of industrial manufacturing processes. The characteristics of the glass foam products were excellent, the optimal sample obtained with 1.9% SiC and 1% KNO₃ having an apparent density of 0.28 g/cm³, porosity of 87.3%, compressive strength of 5.1 MPa and pore size between 0.25-0.45 mm. The material is a very good thermal insulator for civil engineering.