509 / 2019-01-04 21:39:39

Effect of sorbent types on the performance of K2CO3-based pellets for CO2 capture

K2CO3/Al2O3, extrusion-spheronization, support materials

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Application of the K2CO3-based sorbents in fluidized-bed demands the material to be in the form of particles or pellets with enough mechanical strength and attrition resistance。In this work, K2CO3-based sorbent pellets were prepared via an extrusion-spheronization method. Four types of biomass materials were used as the supports: alumina (Al2O3), Bayer aluminum hydroxide (BAh), Kaolin clay (KC), and calcium aluminate cement (CC). The CO2 capture performances of the pellets were tested were tested under 60 C, 10%CO2 + 10%H2O using a self-designed CO2 absorption system. Further, the microstructure, CO2 capture performance and mechanical properties of K2CO3-based sorbent pellets with different supports and loadings were investigated by means of some relevant characterization tests. The results show that there are significant differences in the CO2 capture performance of K2CO3-based sorbent pellets with different supports. The Bayer aluminum hydroxide supported sorbent pellet (K2CO3/BAh) presents the best CO2 capture performance, ~1.85mmol/g. The calcium aluminate cement supported sorbent pellets (K2CO3/CC) possess the remarkable mechanical properties, while their CO2 capture performance is inferior. Comprehensively considering the CO2 capture performance and mechanical properties, K2CO3/Al2O3 is the most suitable CO2 sorbent. Moreover, the effect of loading amount of K2CO3 on performance of K2CO3/Al2O3 sorbent pellets was further studied. It is found that the microstructure, CO2 capture performance and mechanical properties of K2CO3/Al2O3 sorbent pellets are significantly different with the change of loading amount of K2CO3. CO2 capture capacity of K2CO3/Al2O3 increases first and then decreases with the increase of K2CO3 loading. Sufficient K2CO3 loading can provide substantive active sites for enhanced CO2 chemisorption, whereas excessive loading will cause particle aggregation and pore structure blockage and affect its CO2 capture capacity adversely. The maximum CO2 capture capacity of 2.81 mmol CO2/g is obtained with an K2CO3 loading of 50 wt.%. In general, the K2CO3-based sorbent pellets prepared via extrusion-spheronization method achieve better fluidization characteristics, CO2 capture performance and mechanical properties, which is suitable for large-scale application in post-combustion flue gas treatment.