A Study on the Synthetic Stone from Incinerator Fly Ash
Date Issued
2009
Date
2009
Author(s)
Li, Ying-Song
Abstract
Solid waste treatment is an important environment problem in Taiwan. Incineration can effectively reduce the volume and weight of municipal solid waste (MSW). Twenty-four large incineration plants work in Taiwan. The MSW incineration (MSWI) ashes including bottom and fly ashes are hazardous wastes. For these two ashes, fly ash is most hazardous with heavy metal leaching and dioxin contamination. Thus, it needs further treatment for stabilization and disposal. n this study, the incineration fly ash was stabilized via washing, conditioning and sintering processes. Due to the high content of chlorides in fly ash, it causes high evaporation of metals as the second pollutants during the heat treatment process. The weight loss of fly ash via washing is about 30 ~ 40 wt.%. The results indicate that the washed fly ash (WFA) is already stable under regular toxicity characteristic leaching procedure (TCLP) test without the adjustment the of pH value. However, it does not meet the modified stringent TCLP test with the adjustment of pH value to 4.5. After washing process, the H2SO4, H3PO4 and Na2S were added as stabilization agents to condition the WFA before the sintering process. The dried conditioned sample were then pelletized with a pressure of 5000 psi and sintered at 1150 ℃ for one hour. The resulted sintered cylinders have compressive strengthes over 400 kgf cm-2 and the water absorption of about 3% and meet the more stringent TCLP standard. These pelletized-sintered samples can conform the common bricks standard for the construction purpose of Chinese National Standard (CNS). The sintered sample without pre-pelletization were also conform the soundness of aggregate. The chlorides content of the sample is 0.00189% lower than 0.012% of CNS. It can be used as the raw material of fine concrete. A torch plasma was also used as a heating source for sintering the fly ash in this research. However, the results indicate that it is not suitable for the sintering process because of the disproportionate heat distribution.
Subjects
MSWI fly ash
stabilized agents
recycling
compressive strength
leaching
torch plasma
Type
thesis
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