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The CO 2 capture performance of sorbents derived from three distinct limestones, including a metamorphosed limestone, is studied under conditions relevant for calcium looping CO 2 capture from power plant flue gas. The combined and individual influence of flue gas H 2 O and SO 2 content, the influence of textural changes caused by sequential calcination/carbonation cycles, and the impact of CaSO 4 accumulation on the sorbents’ capture performance were examined using bubbling fluidized bed reactor systems. The metamorphosed limestone-derived sorbents exhibit atypical capture behavior: flue gas H 2 O negatively influences CO 2 capture performance, while limited sulfation can positively influence CO 2 capture, with space time significantly impacting CO 2 and SO 2 co-capture performance. The morphological characteristics influencing sorbents’ capture behavior were examined using imaging and material characterization tools, and a detailed discussion is presented. This insight into the morphology responsible for metamorphosed limestone-derived sorbent’s anomalous capture behavior can guide future sorbent selection and design efforts.

This paper presents an experimental investigation at a 20 kW th calcium looping (CaL) facility with a twofold focus. The first objective is on assessing the multicyclic behavior of limestone under continuous dual fluidized bed (DFB) operation. Different carbonation conditions were employed to derive a mathematical expression that is valid to compare the results from DFB and thermogravimetric analysis (TGA) with adequate accuracy. A preliminary screening of three morphologically distinct limestones was conducted by TGA including exposure to SO 2 and H 2 O during carbonation. The second objective is to analyze the influence of multiple process variables (i.e., temperature, CO 2 loading, and H 2 O concentration) on the performance of the 20 kW th CaL facility's bubbling fluidized bed carbonator. Within the investigated range of operating conditions, the chosen carbonator design allowed for CO 2 capture efficiencies as high as 0.99 mol/mol, yielding an apparent carbonation rate (k S φ) of 0.09 s −1 . Paving the way to a more flexible usage of CaL systems, the proposed carbonator design could be integrated into the existing load-following power plants, in preference to a conventional circulating fluidized bed carbonator that is heavily penalized when forced to operate under low capacity factors.

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