Core-in-Shell CaO/CuO-Based Composite for CO2 Capture

摘要

This paper describes the preparation of composite materials containing both CaO as a reversible CO2 sorbent and CuO, serving as an oxygen carrier, which allows the spent Ca sorbent to be regenerated in a fuel gas stream after it has been used for CO2 capture. Calcium aluminate cement is used as a support to enhance pellet strength. The pellets were prepared in a mechanical pelletizer for granulation of powdered materials with addition of spray water. Three types of pellets were prepared: (i) core-in-shell with 50% CuO and 50% CaO (75% CuO and 25% CaO in the core), (ii) core-in-shell with 50% CuO, 40% CaO, and 10% cement (75% CuO and 25% CaO in the core), and (iii) homogeneous pellets with 50% CuO, 40% CaO, and 10% cement addition as a binder. CO2/O2 carrying activity of the pellets was then tested in a thermogravimetric analyzer (TGA). The attrition resistance of the obtained material was examined during attrition tests in a bubbling fluidized bed (i.d. 50 mm). The oxygen carrying capacity of pellets indicates that 25% CaO in the core is sufficient to support the CuO and prevent decay of its activity as an oxygen carrier during reduction/oxidation cycles. To demonstrate that the pellets produced actually have a core-in-shell pattern, larger cross-sectioned particles were analyzed using the scanning electron microscope/energy dispersive X-ray method (SEM/EDX). The SEM/ EDX analyses clearly showed different morphology and elemental composition of the core and shell, with ahigher content of CuO in the core. The results of attrition tests showed that after fluidization for 2 h, particle size distribution changed negligibly and high temperature did not cause significantly more pronounced attrition. These tests clearly showed that the procedure employed is suitable for large-scale preparation of core-in-shell CaO/CuO-based pellets which have numerous benefits.