Effects of two different accelerated carbonation processes on MSWI bottom ash

Abstract

Abstract This study investigated two different reaction modes with wet and submerged particles for accelerated carbonation of municipal solid waste incinerator (MSWI) bottom ash generated in the Republic of Korea. Additionally, the effects of the two reaction modes were examined in terms of the mineralogical change and leaching behavior of heavy metals during accelerated carbonation. The reaction modes were controlled with water-to-solid ratios of 0.3 and 10 L/kg for the wet and submerged particles, respectively. The CO 2 concentration was kept constant at 30%. The reaction temperature was held at 25 °C. The new, resulting compounds formed by the carbonation reaction in the wet condition precipitated as a thin coating around the bottom ash particles in what is called the carbonated-layer effect. The submerged condition resulted in the formation of only a negligible carbonated-layer. Moreover, the wet condition, due to the carbonated-layer effect, more effectively stabilized the leaching behavior of heavy metals than that of the submerged condition. However, unlike the submerged condition, this carbonated-layer effect did not result in the maximum value of CO 2 reacted with the bottom ash because it prevented the internal diffusion of CO 2 into the particles. The experimental data were fitted with theoretical functions derived from [1 − (1 − X t ) 1/3 ] n = k t. Here, k is the rate constant (h −1 ) of the carbonation reaction and X t is the carbonated fraction vs. time t .