Study On The Effect Of Simulated Incineration Flue Gas On MSWI Fly Ash Using Accelerated Carbonation

Municipal solid waste incinerator (MSWI) flue gas contains 10¹5% CO₂, which can be used in accelerated carbonation technology for stabilization treatment of MSWI fly ash and decrease of greenhouse gases emission. Therefore, the purpose of the study is to investigate the effect of properties of fly ash and gas on the sequestration capacity of CO₂ and stabilization of fly ash through the dynamic experiment of different components simulated gas reacted with fly ash. The main conclusions are as follow:The basic properties of fly ash show that the content of Ca in fly ash is as high as 25.84%. The BET surface area of fly ash is 3.0013m²/g, and total pore volume is 0.011122 m3/g. The residual fraction of Cd, Pb and Zn in fly ash is low, that is easy to leach. And the residual fraction of Cr and Fe is high. Under different leaching methods, the heavy metal elements such as Pb, Zn and Cd leach from fly ash, especially Pb.The results of dynamic experiment and thermal gravimetric analysis showed that fly ash has the sequestration capacity of CO₂ in three simulated gas. Fly ash can react with 100% CO₂ (gas 1 #) quickly, and the sequestration capacity of CO₂ can reach 87 gCO₂/kg fly ash. The CO₂ absorbed in fly ash from gas 1 # can be released completely under high temperature. When the CO₂ content is down to 12% (gas 2 #), the sequestration capacity of CO₂ decreases to 41 gCO₂/kg fly, and only 53.2% CO₂ absorbed in fly ash from gas 2 # can be released under high temperature. When the CO₂ content remaine 12% and the presence of SO₂ (gas 3#), the sequestration capacity of CO₂ further decreases to 17.3 gCO₂/kg fly ash, and only 35.9% CO₂ absorbed in fly ash can be released.After carbonation the BET surface area and total pore volume of fly ash decrease. The total pore volume of fly ash reacted with gas 3 # reduce at the largest level. SO₂ hinder the absorption of CO₂ is due to pores plugging. Comparing to raw ash, the pH of leachate and the leaching concentration of heavy metals decrease after carbonation in general. The leaching concentration of Pb in fly ash reacted with gas 3 # is lower than that in fly ash reacted with gas 2 #. The results of pH dependence leaching test of carbonated fly ash is similar with raw ash. The stabilization of carbonated fly ash is due to the improvement of acidic buffering capacity. After carbonation, the residual fraction and carbonate fraction of most of heavy metals increase, and the exchangeable fraction significantly decrease.