Industrial-scale carbonation of alkaline residues for the final storage of CO2

Abstract

Limiting climate change requires a substantial reduction in global greenhouse gas emissions. Mineral carbonation of alkaline residues can contribute to this by capturing CO2 and permanently binding it as carbonates. This experimental work investigated the mineral carbonation of various alkaline residues focusing on the industrial-scale implementation of this waste treatment and CO2 sequestration process using rotating drum reactors. The research was guided by the following questions: 1) How can the CO2 sequestration capacity of alkaline material be determined? 2) Which effect has water on the CO2 uptake in terms of capacity and kinetics? 3) How can the optimum amount of water be added to a rotating drum reactor? 4) How can a rotating drum reactor be upscaled and operated to achieve the target conversion of an alkaline material? The evalauted analytical methods to determine CO2 sequestration capacity could not accurately predict the experimentally achievable CO2 uptake. The water content of alkaline materials in fixed-bed experiments showed a considerable effect on the CO2 uptake, while in a rotating drum setup the achieved uptake was less sensitive to the water content. Water was successfully added to the rotating drum carbonation reactor while reducing the water consumption. A rotating drum reactor with a continuous feed has been upscaled to process hundreds of kilograms per hour while maintaining consistent product quality through residence time control. While further work is needed to understand some fundamental mechanisms of mineral carbonation of alkaline residues, this research demonstrated that the process can be performed on an industrial scale.