A fast and simple method to monitor carbonation of MSWI bottom ash under static and dynamic conditions

Abstract

Accelerated carbonation may be employed to improve the leaching behaviour and the geotechnical properties of MSWI bottom ash (BA). Here we report on a novel method to monitor and evaluate the progress of carbonation in both static and dynamic reactor systems. The method is based on following the pressure drop in the gas phase induced by the CO₂-uptake of BA and was benchmarked against carbonate contents as measured by thermogravimetry. Laboratory results demonstrated the serviceability and reproducibility of the method. Complementary logging of relative humidity and temperature showed constant moisture conditions and self-heating induced by the exothermal carbonation reaction, respectively. Under dynamic conditions BA carbonation was higher than in the static reactor. Consistently, the self-heating was more pronounced. After a reaction time of 120 min the pressure records indicated a CO₂-uptake of 1.5 g CO₂/100 g BA (static tests) and of 2.6 g CO₂/100 g BA (dynamic tests). The proposed method is suited to study carbonation processes at minimum analytical expense and integrates over the small-scale heterogeneity of BA.

Keywords: Accelerated carbonation; Alkaline waste; Bottom ash; Carbon dioxide.