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

Area of Science:

• Chemical Engineering
• Materials Science
• Environmental Science

Background:

• Calcium looping is a key technology for carbon capture and storage (CCS).
• Sorbent performance, particularly limestone's carbonation efficiency, is crucial for process viability.
• Sulfur dioxide (SO2) impurities in flue gas can impact sorbent reactivity and process efficiency.

Purpose of the Study:

• To investigate the effect of varying SO2 concentrations on limestone carbonation conversion during cyclic carbon capture.
• To model the carbonation reaction kinetics under different SO2 levels and cycle numbers.
• To predict long-term carbonation performance using the best-fit kinetic model.

Main Methods:

• Experimental carbonation tests using limestone in dual-interconnected fluidized bed reactors.
• Testing under three SO2 conditions: no sulfur (NS), 75 ppm (SP), and 1500 ppm (SR).
• Kinetic modeling using Shrinking Core Model (SCM), Random Pore Model (RPM), and Fractal-like Random Pore Model (RPM-F).

Main Results:

• Higher SO2 concentrations and increased carbonation cycles significantly decrease carbonation conversion.
• Carbonation conversion dropped from 28.6% (cycle 1) to 8.8% (cycle 10) in NS conditions.
• RPM-F model showed the best fit to experimental data, with maximum absolute errors of 1.7% (NS), 1.3% (SP), and 0.9% (SR) in the first cycle.

Conclusions:

• Sulfur dioxide negatively impacts limestone's carbonation efficiency in calcium looping.
• The Fractal-like Random Pore Model (RPM-F) accurately describes the carbonation kinetics.
• Predicted 100-cycle conversions are substantially reduced, especially under high SO2 conditions (0.19% in SR).