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Fly ash immobilization with vitrification

Abstract

Raziskali smo možnost imobilizacije letečega pepela iz sežiga komunalnih odpadkov. Leteči pepel smo skupaj s slovenskim odpadnim steklom stalili in ulili v kovinske kokile, da je nastal pretežno amorfen produkt, tj. steklo, ki smo ga toplotno obdelali, da se je tvorila steklokeramika. Leteči pepel je bil sestavljen iz delcev velikosti <1 m, ki se povezujejo v aglomerate velikosti okrog 180 m. Tali se pri temperaturi okoli 1300 °C in se v tekočem stanju dobro meša z odpadnim steklom. Steklo, nastalo pri litju, se pretvori v steklokeramiko pri žarjenju v temperaturnem območju med 700 °C in 950 °C, pri čemer se tlačna trdnost poveča za dvakrat. Vrednosti izluževanja težkih kovin iz vzorčnega letečega pepela prekoračujejo predpisane mejne vrednosti za odlaganje na odlagališčih za nevarne odpadke, medtem ko so vrednosti za nastalo steklo in steklokeramiko pod predpisanimi vrednostmi. Zasteklen leteči pepel lahko odložimo kot stabiliziran in nereaktiven odpadek na odlagališčih nenevarnih odpadkov, mogoče pa bi ga bilo tudi predelati in uporabiti v koristne namene.The possibility of fly ash immobilization was investigated. Municipal solid waste fly ash mixed with waste glass cullet was melted and poured into metal moulds. Mainly amorphous glass product was formed, which was then heat treated to obtain glass- ceramics. Fly ash consisted of particles with size <1m, normally joined to larger agglomerates (r180 m). Its melting temperature was around 1300 °C and it mixed well with the glass cullet in the liquid state. Glass formed during solidification was transformed into the glass-ceramics after heat treatment in the temperature range between 700 °C in 950 °C, that doubled the compressive strength. Leaching of heavy metals from fly ash exceeded the allowed values for dumping dangerous waste in landfill, whereas the values for the produced glass and glass-ceramics were under the allowed values. The produced glass and glass-ceramics can be landfilled as a stabilised and unreactive waste in landfills for nonhazardous wastes. Their properties also offer the possibility for manufacturing useful products

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