Evaporation from synthetic incinerator ashes melted by plasma arc

Synthetic incinerator ashes of 40 mass %SiO₂-40CaO-20Al₂O₃ (named Glass) and 36 mass %SiO₂-36CaO-18Al₂O₃-10Fe₂O ₃ (named Fe-Glass) were melted by argon plasma arc, with iron rods used for arc ignition. A direct current transferred type plasma generator was used with an output power of 6 kW. During arc melting, the iron rod was melted and located in the centre of the molten ash. The temperature at the boundary between the iron and ash melts was 2200 K and that at the edge of the ash 1870 K. X-Ray diffraction showed that the deposit vaporised from Glass was composed of Fe, FeSi and amorphous SiO₂. The evaporation rates from Glass and Fe-Glass were 3.8 × 10^-4 g/s and 1.4 × 10^-4 g/s, respectively. It has been concluded that the rate of evaporation from the molten ash is affected by the vaporisation reaction which determines the oxygen partial pressure in the whole system.