CAPTURE OF CO 2 WITH CaO IN A PILOT FLUIDIZED BED CARBONATOR EXPERIMENTAL RESULTS AND REACTOR MODEL. Carlos Salvador 1 , Dennis Y. Lu 1 , Edward J. Anthony 1 , J. Carlos Abanades 2 1 CANMET Energy Technology Centre-Ottawa, Natural Resources Canada; 1 Haanel Drive, Ottawa, ON, K1A 1M1 Canada 2 Instituto Nacional del Carbón (CSIC), Francisco Pintado Fe, 26, 33011 Oviedo, Spain ABSTRACT Calcium oxide particles can absorb CO 2 at high temperatures (>600ºC) to form CaCO 3 , which can be regenerated back to CaO and pure CO 2 in a calciner. We are investigating this chemical loop to develop more energy-efficient post-combustion systems. In this work we present the results of pilot-scale tests of one of the key units for the process: the high-temperature fluidized bed absorber. Fluidized beds of calcined limestone are shown to be very effective absorbers of CO 2 from a typical flue gas at atmospheric pressure, as long as there is a sufficient fraction (>5%) of CaO in the bed material reacting in the fast-carbonation regime. The experimental results with different limestones, and after several cycles of carbonation-calcination, are very encouraging. They are interpreted with a well-established fluid bed reactor model (the Kunii-Levenspiel model) that allows an extrapolation of the results to conditions beyond those tested in the pilot rig. These include a special case for in-situ CO 2 capture in fluidized bed combustion at low temperatures that can be of interest for highly reactive fuels like biomass; this is discussed to some extent in this work. INTRODUCTION For post-combustion CO 2 capture systems, the leading option to separate CO 2 involves amine-based absorption systems. However, this technology introduces severe efficiency penalties and added costs [1]. Furthermore, lower efficiency penalties will also have positive implications for the public acceptability of any CO 2 capture technology. High-temperature separation processes are intrinsically associated with low efficiency penalties. We have been developing in the last few years [2-6] post-combustion systems that make use of the carbonation-calcination reaction of CaO/CaCO 3 . The background for this separation process dates back to 1867, but for CO 2 capture systems, the basic process was first outlined by Silaban and Harrison [7] and Shimizu et al . [8]. Figure 1 outlines the main flows in the capture-regeneration chemical loop, which conceptually does not differ from other sorption-desorption systems, except that it uses one of the cheapest possible regenerable sorbents, natural limestone [9]. As can be seen in this Figure, one of the key steps in the process is the separation of CO 2 at high temperatures (>600ºC) using particles of CaO as sorbent: CaO (s) + CO 2 (g) → CaCO 3 (s) T between 650ºC and 850ºC, depending on pressure (1) CaCO 3 can be reacted in a different reactor to deliver CO 2 for storage: CaCO 3 (s) → CaO (s) + CO 2 (g) T > 850ºC, depending on CO 2 partial pressure (2) Specific process configurations vary depending on conditions in the main units (temperature, pressure, reaction atmosphere, fuel type) and on the method adopted to regenerate the sorbent by calcination, producing a concentrated CO 2 stream suitable for storage. For the purpose of the present work, Figure 1 is focused on fuel and sorbent flows related to the carbonation of CaO in a fluidized bed carbonator-combustor and the regeneration (calcination) of CaCO 3 in an O 2 -fluidized bed calciner-combustor.