https://doi.org/10.3390/ma14164379
“WMP, dolomite and a blend of WMP + dolomite sorbents were tested in a fixed bed reactor CaL unit under mild and realistic calcination conditions for evaluation of their cyclic CO2 capture performance. shows the CaO conversion (%) for 20 carbonation/calcination cycles for all the sorbents using mild (a) or realistic (b) calcination conditions. The sorbents’ CaO conversion was obtained based on the chemical composition of the sorbents () and its CaO content because, under the used experimental conditions, MgO was shown to be inert [44].”
“At mild calcination (a), dolomite sorbent with ca. 33% MgO (calcined basis) presents a higher initial CaO conversion on the first cycle, ca. 91%, and for WMP, it is ca. 80%, but after 20 cycles, the dolomite CaO conversion is approximately twice that of the WMP CaO conversion, i.e., 60 and 32%, respectively. The results show that the CaO content in the sorbent sample is not the most relevant factor, and an improved CaO conversion is achieved for dolomite sorbent due to the presence of other chemical elements (e.g., Mg).
A blend of WMP and dolomite (80% of CaO and 20% of MgO in calcined basis) was also prepared and tested for 20 cycles. An increase in CaO conversion was obtained with the increase of MgO content in the blended sorbent, i.e., the CaO conversion increased from 32% in WMP to 50% for the blended sorbent. The sorbents’ stability after 20 cycles (considering the first cycle CaO conversion as reference) was also evaluated, and the deactivation was 59, 41 and 34%, respectively, for WMP, WMP + dolomite blend and dolomite.
In the present study, the same three sorbents were also tested for 20 cycles under the above-mentioned realistic calcination conditions, and the CaO conversion (b) was compared with the one attained under mild calcination conditions (a). It is observed that the sorbents’ CaO conversion is much lower when realistic calcination conditions are used, but the three sorbents present a similar performance along the first 10 cycles. b shows that in the case of realistic calcination conditions, dolomite achieved a CaO conversion of 20% after 20 cycles, which is higher than the corresponding CaO conversion observed for WMP + dolomite (15%) and for WMP (7%). Therefore, under realistic calcination conditions, the CaO conversion is much lower than under mild calcination conditions, but there is a stronger synergetic effect of inert MgO grains of calcined natural dolomite in the blend WMP + dolomite sorbents that leads to an improved stability along the cycles when compared with WMP used separately as sorbent.”
“Figure 5. CaO conversion of WMP, dolomite and WMP + dolomite blended sorbent after 20 cycles of carbonation at 700 °C and calcination under (a) mild: 800 °C and 100% of N2, or (b) realistic: 930 °C and 80% of CO2 calcination conditions.”
