Municipal solid waste incineration (MSWI) bottom ash includes a large proportion of Ca- containing minerals (20%-30% CaO by mass), which is a potential source for sequestration of CO_2. Despite the abundance of calcium in bottom ash, not all of them can be carbonated directly. Therefroe it is important to make clear the chemical proportion of various Ca- containing minerals in bottom ash. ANC (acid neutralization capacity) experiment of the bottom ash was an effective approach for stepwise dissolution of Ca- containing minerals with the aid of analyzing ANC residuals and associated Ca~(2+) concentrations in equilibrium solutions. Consequentially, nearly 45% of calcium in bottom ash was proved to be easily soluble, decalcified, and furthermore theoretically carbonated. To identify the real sequestration capacity of CO_2, lab-scale accelerated carbonation was performed using freshly quenched bottom ash (from Seibu Incineration Plant, Fukuoka, Japan). Finally it was proved that 1.85 mol Ca~(2+)/kg bottom ash can be carbonated, and accordingly the sequestration capacity of bottom ash was determined to be 1.32 mol CO_2/ kg bottom ash by subtracting original carbonate in specimens.
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