Effects of two different accelerated carbonation processes on MSWI bottom ash

• Published in: Process safety and environmental protection 2017-10, Vol.111, p.560-568
• Main Authors: Um, Namil, Ahn, Ji-Whan
• Format: Article
• Language: English
• Subjects: Accelerated carbonation; Bottom ash; Carbon dioxide; Carbonated-layer effect; Carbonation; Carbonation kinetics; Heavy metals; Incineration; Incinerators; Leaching; MSWI bottom ash; Municipal solid waste; Municipal waste management; Particulates; Solid waste management; Solid wastes; Two different reaction modes; Waste disposal
• ISSN: 0957-5820; 1744-3598
• DOI: 10.1016/j.psep.2017.08.028

[Display omitted] •We investigated two different reaction modes with wet and submerged for carbonation.•The two modes were controlled with L/S ratios of 0.3 and 10dm3/kg, respectively.•Carbonated-layer effect was obtained under the wet condition.•The wet condition resulted in effective stabilization compared to the submerged.•Theoretical model fitted well with the kinetics data pertaining to the carbonation. 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 10L/kg for the wet and submerged particles, respectively. The CO2 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 CO2 reacted with the bottom ash because it prevented the internal diffusion of CO2 into the particles. The experimental data were fitted with theoretical functions derived from [1−(1−Xt)1/3]n=kt. Here, k is the rate constant (h−1) of the carbonation reaction and Xt is the carbonated fraction vs. time t.