Experimental Investigation on the Performance of [APMIm][NTf2] for Capturing CO2 from Flue Gas of the Cement Kiln Tail

Facing the global warming trend, humanity has been paying more and more attention to the Carbon Capture, Utilization and Storage. Large amounts of CO 2 is emitted with burning fossil fuel as well as by some special industrial processes like the decomposition of calcium carbonate in a cement plant. The cement industry contributes about 7% of the total worldwide CO 2 emissions and the CO 2 concentration of flue gas of the cement kiln tail even exceeds 30%. Ionic liquid is considered to be an effective and potential material to capture CO 2 . In order to investigate the performance of ionic liquids for capturing CO 2 from flue gas of the cement kiln tail, an experiment system was established and an ionic liquid, [APMIm][NTf 2 ] (1-aminopropyl-3-imidazolium bis(trifluoromethylsulfonyl)imine), was tested using pure CO 2 and simulated gas. The results showed that both physical and chemical absorption play roles while physical absorption dominates in the absorption process. Both the absorption capacity and rate decrease with raising the operating temperature. In the experiment with pure CO 2 , the absorption capacity is 0.296 mol CO 2 ⋅ mol IL − 1 at 30°C and 0.067 mol CO 2 ⋅ mol IL − 1 at 70°C. Meanwhile, the ionic liquid can be regenerated for recycling without obvious changes of the absorption capacity. When the ionic liquid is used for flue gas of the cement kiln tail rather than pure CO 2 , a sharp decrease of the absorption capacity and rate was observed obviously. The absorption capacity at 30°C dropped even to 0.038 mol CO 2 ⋅ mol IL − 1 , 12.8% of that for pure CO 2 . Additionally, a natural desorption of CO 2 from the ionic liquid was observed and affected the experimental results of the absorption capacity and the absorption-desorption rate to some extent.