本研究以兩種粒徑(0.5-4.75mm、0.5-25.4mm)之焚化底渣於200℃、不同的二氧化碳、水氣含率及反應時間等操作參數下進行加速碳酸化,探討加速碳酸化對焚化底渣特性之影響,以評析焚化底渣加速碳酸化之可行性、最適操作參數及反應行為。由研究結果可以發現,焚化底渣之主要化學組成為Ca、Si、Al等氧化物,其中以鈣的成分居多。而焚化底渣加速碳酸化於最適操作條件(200℃、15%CO2及60%H2O)下進行加速碳酸化,兩種粒徑之焚化底渣其pH值分別從12.29及10.87下降至10.88及9.87。由XRD晶相繞射及FTIR光譜發現,焚化底渣表層有Calcite晶相及碳酸根吸收峰存在。另外,水溶性氯離子之溶出隨CO2含量增加有大量減少的趨勢,因此可得知加速碳酸化確實可減少焚化底渣其水溶性氯離子之溶出,由毒性溶出特性試驗及管柱溶出試驗得知加速碳酸化後焚化底渣之重金屬Cu、Pb及Zn均有明顯下降的趨勢,進一步利用MINTEQA2軟體模擬其重金屬之溶出行為,由模擬結果顯示,Ca之溶出量於高pH值(pH>10)時有明顯之減少,而Ca之溶出在pH為4-8時,其溶出行為為gypsum,當pH為8-12時其Ca之溶出是以calcite之溶出行為。Al、Ca及SO4溶出為gibbsite (Al(OH)3(s))、gypsum (CaSO4 .2H2O) 及 ettringite (Ca6Al2(SO4)3(OH)12 •26H2O(s))。綜合以上研究結果顯示,焚化底渣進行加速碳酸化於其表層所形成之碳酸鈣,具有降低焚化底渣高鹼性及提昇其重金屬穩定性之功效,不僅可提昇焚化底渣資源化利用之價值,亦可兼具二氧化碳減量之效果。
In this study, the effects of accelerated carbonation on the chemical properties, mineral morphologies and microstructures of Bottom ash under various accelerated carbonation parameters are evaluated. Under optimum accelerated carbonation parameters, the results indicate that particle size 0.5 to 4.75mm and 0.5 to 25.4mm of Bottom ashs individually lowered their pH values from 12.29 and 10.87 to 10.88 and 9.87. The XRD patterns of accelerated carbonation Bottom ashs show that there were calcite on the surface of Bottom ash and the spectra of FTIR of accelerated carbonation Bottom ashs indicate that there were CO32- function groups presenting on surface of carbonated accelerated carbonation Bottom ashs. Other Water-soluble chloride ion dissolved a large decline with CO2 content increased. Therefore that accelerated carbonation can actually reduce Bottom ash leaching of water-soluble chloride ion. The results in accordance with TCLP and Column Leaching Test indicate that the leaching concentration of Cu, Pb, Zn in accelerated carbonation Bottom ash was obviously decreased. Further uses the MINTEQA2 software simulation of the dissolution behavior of heavy metal. By the simulation results show the dissolution of Ca had a large decrease at high pH (pH> 10), The Ca of the dissolution at pH 4-8, its dissolution behavior to gypsum. When the pH at 4-8, its dissolution behavior to calcite. Al, Ca and SO4 dissolves behavior to gibbsite (Al(OH)3(s))、gypsum (CaSO4 .2H2O) and ettringite (Ca6Al2(SO4)3(OH)12 •26H2O(s)). Based on the above results, accelerated carbonation of Bottom ash not only reduces high alkalinity of Bottom ash and leachability of heavy metals in Bottom ash, but also promotes the utilization of Bottom ash and reaches the reduction of carbon dioxide.
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