Reuse of bottom ash and fly ash from mechanical-bed and fluidized-bed municipal incinerators in manufacturing lightweight aggregates

Abstract

This study involved the reuse of residues, including fly ash (FA) and bottom ash (BA), from municipal solid waste (MSW) incineration and reservoir sediment (RS) to make lightweight aggregates (LWAs) and to evaluate the effects of the incinerator type, material mixing ratio, and preparation conditions on the properties of the resulting aggregates. The MSW incineration ashes were mixed in three different ratios (65% BA + 15% FA, 70% BA + 10% FA, and 75% BA + 5% FA) with reservoir sediment and were sintered at temperatures of 950–1050 °C. The ash samples were obtained from an incineration plant equipped with fluidized-bed (FB) and mechanical-bed (MB) furnaces. The ash from the FB incinerator could be turned into LWAs at a relatively low temperature (1000 °C). Compressive strength measurements indicated that these aggregates were stronger than those manufactured using the ash from the MB incinerator. The BA and FA from the FB incinerator showed good chemical stabilities due to the operating conditions of the incinerator, suggesting that they are suitable for fabricating LWAs. Thus, the thermal synthesis of LWAs from mixtures of incineration residue and RS is a highly effective method for the recycling/disposal of MSW incinerator ash.