| dc.description.abstract | This research investigated that the feasibility of carbon dioxide capture by municipal solid waste incinerator (MSWI) bottom ash and electric arc furnace (EAF) reductive slag using the accelerated carbonation system combined with semi-dry rotary kiln. The experiments were conducted by controlling liquid-solid ratio (ranged from 0.2 to 0.4), 10% carbon dioxide concentration and 15 ppm sulfur dioxide concentration.
The experimental results showed that MSWI bottom ash and EAF reductive slag were alkaline solid residues containing high calcium content. In the case of liquid-to-solid ratio 0.2, the carbon dioxide captured by bottom ash and reductive slag were 42.5 g/kg and 69.1 g/kg, respectively. When the liquid-solid ratio was increased to 0.3, the carbon dioxide captured by bottom ash and reductive slag were significantly increased to 78.3 g/kg and 82.7 g/kg, respectively. Consequently, controlling the appropriate liquid-solid ratio could exhibit a good CO2 capture performance. However, in the case of liquid-solid ratio 0.4, the carbon dioxide captured by bottom ash and reductive slag were slightly decreased to 41.1 g/kg and 63.2 g/kg, respectively. This is because the higher moisture content of ash could tend to block the pores of alkaline residues, hence, it will be resulted in a decrease in carbon dioxide diffusion. On the other hand, due to the reductive slag had a higher specific surface area than that of bottom ash, it can provide the higher porosity and perform a good potential for carbon dioxide diffusion. Therefore, reductive slag exhibited a good carbon dioxide capture efficiency than that of bottom ash.
With sulfur dioxide (SO2) addition, a competitive reaction between calcium ion and sulfur ion could occur during accelerated carbonation process. It implied that carbon dioxide capture efficiency could decreased with an increase in SO2 concentration. In the case of liquid-to-solid ratio 0.3, the carbon dioxide was captured by bottom ash and reductive slag were decreased from 78.3g/kg to 54.7 g/kg, and from 82.7 g/kg to 77.1 g/kg with SO2 concentration increased from 0 ppm to 15 ppm, respectively.
Based on the analysis results of heavy metals stabilization in carbonated residues, all the tested heavy metals from carbonated bottom ash and reductive slag were in compliance with current Taiwan EPA regulation thresholds. In case of bottom ash after accelerated carbonation reaction, the Cr concentration was significantly decreased from 0.33 mg/L to the analytical detection limit. Meanwhile, in case of reductive slag, the Cr6+ concentration was also significantly decreased from 0.06±0.02 mg/L to the analytical detection limit after accelerated carbonation reaction. It could conclude that the accelerated carbonation has a good potential for enhancing the Cr and Cr6+ stabilization in bottom ash and reductive slag.In summary, this research has been successfully developed and proven the performances of accelerated carbonation reaction system combined with semi-dry rotary kiln. The multiple purposes of resources reduction, harmless of alkaline solid residues, and carbon dioxide sequestration by accelerated carbonation have been conducted in this research. | en_US |