Production of aggregates from incinerator fly ash with carbonation treatment.
Date Issued
2009
Date
2009
Author(s)
Lin, Li-Hsiang
Abstract
Fly ash generated from MSW incinerator, containing high contents of alkali chlorides and trace amounts of heavy metals and toxic organic chlorides, is classified as a hazardous waste. The aim of this study is to develop a technique to produce synthetic aggregates, which can be used as a construction material, from fly ash by removing the alkali and toxic organic chlorides and stabilizing the heavy metals. This study focus on the effect of carbonation treatment on the compressive strength and the resistance to weathering of a cylinder made of washed fly ash. Fly ash, collected from the air pollution control unit of a MSW incinerator, was washed with deionized water (at liquid/solid weight ratio L/S=1~10) or with H3PO4(1~10wt%), NaOH solution(0.5~3N), and Na2CO3 (0.01~1M) solutions at L/S=10, with and without simultaneous liquid-phase carbonation. The dry washed samples were pelletized with a pressure of 5000psi and subjected to high temperature calcination(800~1000℃) and carbonation (500~850℃). arbonation at 700℃ gave the highest compressive strength for cylinders of water-washed fly ash(L/S=1); the compressive strength decreased when the calcination or carbonation time was longer than 1h. After liquid-phase and high temperature carbonation, cylinders of water-washed fly ash(L/S=1) absorbed a significant amount of water but did not disintegrate after one month at room temperature; cylinder of NaOH-washed fly ash did not absorb water appreciably or disintegrate, but those of Na2CO3-washed fly ash disintegrated. The cylinders of fly ash washed with 5 and 10wt% H3PO4 had high compressive strengthes, 70-300kgf/cm2, and did not disintegrate after one month at room temperature. The compressve stregnthes of cylinders of washed fly ash could reach or exceed the level of sandstone(14 kgf/cm2), if fly ash was washed with water at L/S<5, or with H3PO4 at concentrations ≧1wt%, or with NaOH at concentrations ≧1N accompanied by liquid-phase carbonation. Leaching tests for the cylinders showed that the amounts of heavy metals leached were far less than the regulatory limits in Taiwan.
Subjects
incinerator
carbonation
waste recycling
SDGs
Type
thesis
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