Thermal Plasma Vitrification of MSWI Fly Ash Mixed With Different Biomass Ashes

Thermal plasma melting is an efficient but energy intensive method for vitrifying municipal solid waste incineration (MSWI) fly ash. To reduce the energy cost and vitrification temperature, different biomass ashes were used as additives in this paper. The effects of the rice husks and wood waste combustion ashes on the MSWI fly ash melting behavior have been studied using a laboratory dc argon plasma torch. The melting heat for ash samples with different mass ratios of MSWI fly ash and biomass ash was predicted by an empirical mathematical model based on the major ash components and measured melting temperatures. The deduced melting heat was used to optimize the parameters of the plasma torch. Melting tests showed that the plasma firing time can be reduced to save energy cost, after biomass ash was added all samples were converted into dark blue glassy materials. When the molten slags were cooled with air, the slags from the rice husks ash mixed samples cracked into irregular pieces, while the slags from the wood ash mixed samples tended to form spherical pellets with a porous microstructure. The results indicate that wood combustion ash is a promising additive to MSWI fly ash for producing high quality construction materials through plasma vitrification with reduced melting energy.