Optimization And Pilot Scale Study On Solidification Technology For MSWI Fly Ash With Geopolymer

With the advantages of remarkable volume-reduction, weight-reduction and energy-recovery, in recent years, disposal of municipal solid waste by incineration is becoming applicated and promoted rapidly. However, there are large amount of high toxic equivalent matter, soluble heavy metals and salts in municipal solid waste incinerator （MSWI） fly ash. If treated improperly it would lead to secondary pollution. Therefore, MSWI fly ash is considered as hazardous waste, and need special treatment.Geopolymer is a new kind of inorganic polymer. The molecularity consists of Si, O, Al and mainly connected by electrovalent bond and covalent bond, it is able to solidify heavy metal ion effectively because of its cage shape like zeolite.A lot of research works has been done on effective solidification of heavy metals in MSWI fly ash with geopolymer. The characterization of MSWI fly ash involving mineral, chemical compositions and leaching toxicity, were observed under X-ray diffraction analyses, energy-dispersive X-ray spectroscopy, Toxicity Characteristic Leaching Procedure tests. The influence factor of solidification efficiency and the stability on forms were studied.The results show: （1） In same curing conditions, the solidification effect of MSWI fly ash with geopolymer can be improved by adding additive （2% zeolite or 2% cement）. The expansion of forms can be relieved with adding 2% cement. （2） The optimized combination was achieved: n（Na₂O）/n（SiO₂）=0.30, n（SiO₂）/n（Al₂O₃）=4.9, mixing with mixer for cement paste, single adding water way, curing humidity 60% and temperature 20℃, etc. （3） The use of solidified matrices was promising potential when the amount of MSWI fly ash was 60% by adding retarder. （4） Solidification body has better anti-acid and anti-fire.The solidification mechanism and efficiency of solidification of MSWI fly ash with geopolymer were analysed, then the geopolymerization feasibility was confirmed.