Regeneration of a spent alkaline solution from a biogas upgrading unit by carbonation of APC residues

This work deals with the regeneration of a KOH solution to use in a chemical absorption process for biogas upgrading. The proposed method consists in the caustic recovery of the spent absorption solution by carbonation of selected industrial residues and allows to store the separated CO2 in a solid phase (calcite). This paper presents the main results of the lab scale experiments carried out to evaluate the effects of selected operating parameters on the carbonation reaction so to identify the conditions that allow to maximize the CO2 uptake of the solid residues and the percentage of KOH that can be regenerated for the absorption process. Furthermore, the effects of the tested treatments on the leaching behavior of the residues are also examined. The results presented in this paper were obtained within the UPGAS-LOWCO2 project (LIFE08 ENV/IT/000429) funded by the European Commission.

► Development of an integrated process for landfill gas upgrading with permanent storage of CO2.
► Demonstration of the feasibility of using APC residues to regenerate the spent absorption solution.
► 90% KOH regeneration in the solution and 30% CO2 uptake in the solid were obtained.
► An improvement of the leaching behavior of the treated residues was observed.
► The layout of the integrated process and the operating conditions of the regeneration step were selected.