Energy Consumption for CO₂ Capture by means of the Calcium Looping Process: A Comparative Analysis using Limestone, Dolomite, and Steel Slag

Abstract

The calcium looping (CaL) process, based upon the dry carbonation/calcination of CaO/CaCO3, is at the center of a potentially low‐cost, second‐generation technology for CO2 capture. This manuscript analyzes the energy penalty that arises from the integration of the CaL process into a coal‐fired power plant using cheap and abundantly available CaO precursors such as natural limestone, dolomite, and steel slag. Experimental results on their multicycle capture capacity behavior obtained from thermogravimetric analysis (TGA) at realistic CaL conditions for CO2 capture are used to this end. This work shows that the specific energy consumption for CO2 avoided (SPECCA) is reduced by using either dolomite or steel slag, whose carbonation kinetics in the diffusive phase are accelerated as compared to limestone. Thus, the use of dolomite as CaO precursor would yield a low SPECCA value of approximately 2 MJ kg−1 CO2 for a residence time of the solids in the carbonator of approximately 10 minutes, which is clearly below the SPECCA value usually reported for conventional amine‐based CO2 capture systems.

The Oxy-CaL process: A novel CO 2 capture system by integrating partial oxy-combustion with the Calcium-Looping process

“…Figure 10b shows however that under prolonged solids residence times of τ =10 min (corresponding to a reduced solids recirculation flow FR/F0=4 and fixing Ws=400 tons as solids inventory) the capture efficiency of the oxy-CaL systems is hindered since carbonation in the solid-state diffusion controlled stage is not significant for carbonation under relatively high CO 2 vol% as was seen from the TGA tests (section 3.b). As discussed above and according to recent works [13,47], energy consumption in the CaL process is highly dependent on the carbonation rate in the solid-state diffusion controlled phase (SDP), which determines the role of the solids residence time τ in the carbonator. Figure 11 shows how SPECCA evolves as τ is increased for the CaL and hybrid oxy-CaL processes.…”

Effect of milling mechanism on the CO2 capture performance of limestone in the Calcium Looping process

“…Thus, the enhancement of CO 2 capture in the SDP, as would be the case for example when using dolomite instead of limestone, would help decreasing the energy consumption for CO 2 avoided (SPECCA) while the capture efficiency is kept high [39].…”

Scaling-up the Calcium-Looping Process for CO₂ Capture and Energy Storage

“…As shown in Fig. 2, the evolution of CaO conversion with the number of cycles is, however, highly dependent on the carbonation-calcination conditions (temperature, reactor pressure and atmosphere) (Benitez-Guerrero et al, 2017a) and the type of CaO precursor used (Ortiz et al, 2016b). Conditions that would optimize the integration of the CaL process in CSP plants would involve calcination at lower temperatures, whereas carbonation would be carried out at higher temperatures under pure CO 2 .…”

“…The efficiency of integration greatly conditions the energy consumption per kilogram of CO 2 avoided (SPECCA), whose value for the already mature technology based on amines is around 4 MJ/kg CO 2 (CAESAR project, 2011). The CaL process has the potential to reduce further this value to around 2-3 MJ/kg CO 2 (Astolfi et al, 2019;Ortiz et al, 2016b;Romano, 2013). Energy penalty values in the range of 3-9 % are reported in the literature (Perejón et al, 2016b).…”