Carbonation performance of lime for cyclic CO 2 capture following limestone calcination in steam/CO 2 atmosphere Masoud Kavosh, Kumar Patchigolla, Edward J. Anthony, John E. Oakey ⇑ Institute for Energy and Resource Technology, Cranfield University, UK highlights  Testing of cyclic CO 2 capture under simulated industrial conditions.  Sorbent size, bed inventory and repeatability investigated to select the optimum operating conditions.  Steam enhancement on the capacity of sorbent higher with higher steam levels in the calciner.  Steam shown to have a larger effect on carbonation when present in the calciner rather than the carbonator. article info Article history: Received 19 April 2013 Received in revised form 14 April 2014 Accepted 14 May 2014 Keywords: Cyclic CO 2 capture Steam/CO 2 atmosphere Capture characteristics Sorbent enhancement Under industrial conditions abstract Steam can be used to lower calcination temperatures or to provide the process heat for calcination in a Ca-looping cycle because it can be removed from the CO 2 stream by simple condensation. Here, the per- formance of limestone for CO 2 removal from flue gases, calcined in the presence of steam, has been inves- tigated. Three steam concentrations (28%, 48% and 78%) were used to investigate the effect of high- temperature steam in the calciner. For comparison, the effects of steam were compared to similar levels of N 2 as the primary diluent. Subsequent to calcination at elevated steam levels, the performance of the calcined sorbent was tested during carbonation with two levels of steam (6% and 20%) typical for flue gases from fossil fuel power plants. This allowed the effects of steam in carbonation to be investigated as well. As this study focused on CO 2 capture from flue gases produced by existing power plants (using Ca-looping as a post-combustion process), the corresponding industrial conditions were simulated for the carbonation atmosphere. Steam addition in the calciner was found to be more effective in improving cap- ture than steam addition in the carbonator, with CO 2 capture capacity being increased with increasing steam levels in the calciner. Ó 2014 Published by Elsevier Ltd. 1. Introduction CO 2 capture is the key step for carbon capture and storage (CCS) as it represents around 75% of the overall CCS cost [1,2]. Amongst the different CCS technologies investigated, using limestone in a Ca-looping cycle appears to be a promising option offering signifi- cant potential benefits [3–6], given the high sorption capacity of CaO [7–9] and the fact that natural limestone is both cheap and abundant [5,10]. The possibility of using the calciner purge as a cement feedstock is another potential advantage of limestone use since this material might also be used to partially decarbonize the cement industry [11]. In addition, this technology can be combined with other power generation processes, such as an Inte- grated Gasification Combined Cycle (IGCC), as well as serving as a post-combustion technology for conventional coal combustion schemes [3]. Hydrocarbon fuel conversion via combustion or gasification always results in steam production. Fuels must be burned in a limestone calciner to maintain the required temperature for calci- nation and the flue gases to be decarbonized will also contain steam. Furthermore, in the case of a pre-combustion system (e.g. for IGCC), the reformer will also contain steam. The percentage of steam in these different process components depends both on the fuel type and the process (e.g. air or oxy-fuel combustion). The use of Ca-based sorbents has received increasing attention, not only for CO 2 reduction from flue gases, but also directly for pro- cesses such as reforming and gasification. Limestone and dolomite can be used for enhancement of hydrogen production for steam reforming [12–15], steam gasification and the water gas shift http://dx.doi.org/10.1016/j.apenergy.2014.05.020 0306-2619/Ó 2014 Published by Elsevier Ltd. ⇑ Corresponding author. Tel.: +44 (0)1234 750111; fax: +44 (0)1234 754036. E-mail addresses: m.kavosh@cranfield.ac.uk (M. Kavosh), k.patchigolla@ cranfield.ac.uk (K. Patchigolla), b.j.anthony@cranfield.ac.uk (E.J. Anthony), J.E.Oakey@cranfield.ac.uk (J.E. Oakey). Applied Energy 131 (2014) 499–507 Contents lists available at ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy