Pilot-scale investigation of an innovative process for biogas upgrading with CO2 capture and storage

In this work an innovative carbon dioxide removal method that, differently from the currently employed commercial techniques, allows also to capture and store the separated CO2 is investigated. This process, Alkali absorption with Regeneration (AwR), consists in a first step in which CO2 is separated from the biogas by chemical absorption with an alkali aqueous solution followed by a second step in which the spent absorption solution is regenerated for reuse in the first step and the captured CO2 is stored in a solid and thermodynamically stable form. The latter process is carried out contacting the spent absorption solution, rich in carbonate and bicarbonate ions, with a waste material characterized by a high content of calcium hydroxide and leads to the precipitation of calcium carbonate and to the regeneration of the alkali hydroxide content of the solution. The proposed processes were first investigated by preliminary laboratory and simulation analysis. On the basis of the results of these tests, air pollution control (APC) residues from Waste-to-Energy plants were selected as the material to use for the regeneration step and a pilot-scale regeneration plant was designed, built and installed in a landfill site downstream of the already existing absorption column. In this paper the sizing and design of the regeneration plant and the results of the preliminary AwR pilotplant tests are reported. This study was carried out within the framework of the UPGAS-LOWCO2 (LIFE08/ENV/IT/000429) Life+ project.