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 CO2 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 CO2 emissions and the CO2 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 CO2. In order to investigate the performance of ionic liquids for capturing CO2 from flue gas of the cement kiln tail, an experiment system was established and an ionic liquid, [APMIm][NTf2] (1-aminopropyl-3-imidazolium bis(trifluoromethylsulfonyl)imine), was tested using pure CO2 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 CO2, the absorption capacity is 0.296 mol(CO2).mol(IL)(-1) at 30 degrees C and 0.067 molCO(2).mol(IL)(-1) at 70 degrees 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 CO2, a sharp decrease of the absorption capacity and rate was observed obviously. The absorption capacity at 30 degrees C dropped even to 0.038 mol(CO2).mol(IL)(-1), 12.8% of that for pure CO2. Additionally, a natural desorption of CO2 from the ionic liquid was observed and affected the experimental results of the absorption capacity and the absorption-desorption rate to some extent.