Investigation of an innovative process for biogas up-grading – pilot plant preliminary results

Biogas up-grading treatments aimed at producing biomethane to fuel vehicles or to inject into the gas grid, are applications that are gaining increasing interest throughout Europe. Several different commercial methods are available for separating carbon dioxide from biogas. In this work an innovative carbon dioxide removal method that, differently fromthe currently employed commercial techniques, allows also to capture and store the separated CO2is investigated.This process, named Alkali absorption with Regeneration (AwR),consists in a first step in which CO2is separated from the biogas by chemical absorption wit h an alkali aqueous solution followed by a second step in which the spent absorption solution is regeneratedfor reuse in the first step of the upgrading process and the captured CO2is stored in a solid and thermodynamically stable form. The latter process is carried outcontacting the spent absorption solution, rich in carbonate and bicarbonate ions, with a waste material characterized by a high content of calcium hydroxide andleads to the precipitation of calcium carbonate and to the regeneration of the alkali hydroxide content of the solution.The proposed processes werefirst 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 waste material to use for the regeneration step and a pilot-scale regeneration plant to place downstream of an existing absorption column installed at a landfill site was designed and built.In this paper the layout of the plants, their operating conditions and the results obtained bypreliminary pilot-plant tests are reported.This study was conducted in the framework of theUPGAS-LOWCO2 (LIFE08/ENV/IT/000429) Life+ project.