Performance test of sorbents
SDT Q600 thermogravimetric analyzer (TGA) was used to test the performance of the synthetic CaO–Al2O3 sorbents. 11∼12 mg of sample was placed in an alumina cup to test its CO2 capture performance over the multiple carbonation and calcination cycles. High purity N2 and 20 vol.% CO2 (mixed with N2) were used at the calcination and carbonation processes, respectively. The flow rates at both processes were set as 200 ml/min. To test the CO2 capture performances of the CaO–Al2O3 sorbents with different CaO contents, the temperature and reaction time for carbonation–calcination were set to 600–850 °C and 20–10 min, and the heating/cooling rate was set to 20 °C/min, as shown in Fig. 3. For the test of the long-term cyclic stability, CaO–Al2O3 sorbent was heated at high temperature (900 °C) for half hour before the carbonation/calcination experiment, then, the temperature and reaction time of carbonation–calcination were set at 650–850 °C and 30–10 min, and the heating/cooling rates were set to 40 °C/min.