Predictive insights into CO2 capture carbonation conversion rates under different Ca-looping conditions in fluidized bed reactors

Abstract

Carbonation cycles are vital for the efficiency, sustainability, and cost-effectiveness of the calcium looping process, making it a promising technology for carbon capture and storage. The research presented in this paper is based on experimental carbonation tests conducted on dual-interconnected fluidized bed reactors under realistic operational conditions in three different states including absence (NS, No Sulfur), 75 ppm (SP, Sulfur Poor), and 1500 ppm (SR, Sulfur Rich) SO₂ concentration using high purity limestone as sorbent. Experimental results demonstrated that the carbonation conversion at the end of cycles 1, 2, and 10 was 28.6%, 17.5%, and 8.8% in the NS condition and 26%, 14.3%, and 6% in the SP condition, respectively. In contrast, the SR condition resulted in lower values of 22.24%, 7.32%, and 1.06% for the corresponding cycles, respectively. The results showed that higher SO₂ concentration and reaction cycles reduce carbonation conversion. In this framework, Shrinking Core Model (SCM), Random Pore Model (RPM), and Fractal-like Random Pore Model (RPM-F) were applied in the present study, to model the carbonation reaction rate. Kinetic-model results demonstrated that RPM-F aligns more closely with experimental data in the first cycle than SCM and RPM, as indicated by the maximum absolute errors of 1.7%, 1.3%, and 0.9% in NS, SP, and SR conditions, respectively. By considering RPM-F as the best-fitting kinetic model, the carbonation conversion rates were predicted at 100 cycles in different conditions, yielding carbonation conversion degrees of 7.51%, 3.79%, and 0.19% at the end of the 100th cycle under NS, SP, and SR conditions.

Keywords: Calcium looping; Carbonation; Fluidized beds; Fractal-like Random Pore Model; SO2.