Performance and kinetics of CO_2 sequestration by direct gas-solid carbonation of APC residues

摘要

Direct gas-solid carbonation of alkaline residues from Air Pollution Control (APC) systems was investigated with the aim of evaluating its contribution as a CO_2 storage option as well as its effect on the properties of the residues, namely the leaching behaviour, which may affect the strategies for their disposal or reuse. APC residues from a medical solid waste incinerator located in the vicinity of Rome were selected for performing carbonation experiments with pure CO_2 at reaction temperatures in the 200-500°C range. The extent of calcium conversion to the carbonate form was found to be negligible below 300°C, whereas conversions of around 60% was measured at 400°C and higher temperatures. A kinetics study was also done, by performing direct gas/solid carbonation experiments in a CO_2/Ar atmosphere, with a 10% CO_2 volumetric content at temperatures in the 300-500°C range. Kinetic constant of the carbonation process were found to range between 1.1 10~(-3) cm~4 mol~(-1) s~(-1) at 300°C and 1.16 10~(-2) cm~4 mol~(-1) s~(-1) at 500°C, with an estimated activation energy of 44.1 kJ/mol.