Full-scale accelerated carbonation of waste incinerator bottom ash under continuous-feed conditions

Bottom ash (BA) is the dominant residue derived from the incineration of municipal solid waste or refuse-derived fuel (RDF). Costs for the disposal of the material chiefly depend on the leachability of salts and trace metals which may be cut by ageing the BA for several months to promote carbonation via uptake of carbon dioxide (CO₂). Enhanced exposure to CO₂ sources has been referred to as accelerated carbonation. Here we report on the successful implementation of the accelerated carbonation of BA in a continuously fed full-scale rotating drum reactor. The reactor was operated with the fine fraction (< 20 mm) of BA from an RDF incinerator and the exhaust of a combined heat and power unit was used as the reactant gas. The system was tested in 15 experiments and the process efficiency was addressed by maximizing the reactor loading and minimizing the BA residence time. Results confirmed that the reactor loading depended on the rotation-normalized mass flow rate of BA where the slope and intercept of the characteristic varied with the design of the reactor discharge and the use of mixing tools. According to leaching test results, BA residence times as low as 60 min were sufficient to render the carbonated BA a non-hazardous waste and convert it to a material suited for geotechnical applications. This outperforms previous laboratory findings and opens new perspectives for implementing the accelerated carbonation at incinerator sites.