Direct flue gas CO2 mineralization using activated serpentine: Exploring the reaction kinetics by experiments and population balance modeling

Abstract

Avoiding CO2 emissions to the atmosphere by its safe and permanent storage is required for all options within the CCS framework. Only mineral carbonation allows for a sequestration process, where the carbon is rapidly converted to its chemically most stable form, a carbonate. So far, most researchers looking into mineral carbonation focused on routes that involve an aqueous medium, where carbonation takes place under an atmosphere of pure CO2, either in a single or multi-step process. We have started to investigate a novel approach to aqueous mineral carbonation where the costly capture step is avoided by the direct mineralization of flue gas CO2 at the point source. For the present study, we have built a set-up to perform mineralization experiments under a variety of conditions in both batch or flow-through mode. The residence times of the reactor solution and gas phase involved can be freely adjusted: the design allows for flowing both the feed solution and the flue gas continuously through an autoclave that contains a sample of activated serpentine. The use of online ion chromatography and in-situ Raman spectroscopy allows monitoring magnesium concentration as well as the solids and dissolved phases throughout an experimental run. A population balance equation model has been developed and its solution was coupled with the continuous flow-through reactor model. The experimental data serves as input to the model in order to regress reaction rates under a variety of operating conditions. A precise knowledge of the dissolution and precipitation kinetics is required for the optimal design and scale-up of the mineralization process. Moreover, the ultimate particle size distribution is of key importance for mineralization product processing and product applications. © 2011 Published by Elsevier Ltd.