Core-in-Shell, Cellulose-Templated CaO-Based Sorbent Pellets for CO₂ Capture at Elevated Temperatures

Abstract

Calcium looping is a promising postcombustion CO 2 capture technology due to its low cost and widespread applicability. However, CaO-based sorbents are prone to encounter severe sintering and elutriation during practical carbonation/ calcination cycles. To overcome the above issues, core-in-shell CaO-based pellets composed of a highly reactive CaO-based core and a hard cement-based outer shell were prepared. The highly reactive core contains 80 wt % Ca(OH) 2 and 20 wt % cellulose, which was prepared via an extrusion−spheronization method. The cement-based outer shells were prepared via an approach of coating, and different amounts of cellulose (varying from 0 to 40 wt %) were added as a pore-forming template. It is found that the mechanical properties of the fresh, core-in-shell, cellulose-templated CaO-based pellets are gradually improved with the increased addition ratio of cellulose in the outer shell. It is mainly attributed to the adequately dispersed cellulose fibers reinforcing the cement-based outer shell. Although the high-temperature calcination causes the internal structure of the CaO-based pellets to become loose, they still exhibit relatively desirable compression strengths (0.95−1.80 MPa). Moreover, the porous outer shell contributes to promoting the accessibility of CO 2 to the highly reactive core pellet, consequently obtaining superior CO 2 capture performance. After 15 cycles, the core-in-shell, cellulose-templated CaO-based pellets containing 40 wt % of cellulose in the outer shell exhibit the highest CO 2 capture capacity of 0.144 g/g, which is nearly 6.8 times that of the core-in-shell pellets with pure cement shell.

An Innovative Approach to Prepare Calcium Oxide from Calcium Carbide Slag Based on Sequential Mineral Transformation

“…CS is recycled by directly calcining it to prepare activated calcium oxide. However, its high impurity content, high acid insoluble matter content, and high roughness afford low-compressive strength calcium oxide, cause considerable equipment wear, and result in poor product activity. , Our group has made considerable efforts to remove impurities from CS, such as the removal of large particles of carbon, silicon carbide, and silicon aluminum impurities from CS. − However, impurities such as carbon and silicon carbide in CS are wrapped around each other and difficult to separate. , The complex mineral phase structure of CS and its change during the calcination process are not studied, resulting in the poor strength and activity of CS after calcination, which affect its recycling and reuse. Therefore, it is necessary to conduct in-depth research on mineral transformation, which can help recycle CS.…”

Enhanced CO2 Capture Durability and Mechanical Properties Using Cellulose-Templated CaO-Based Pellets with Steam Injection during Calcination

“…Therefore, improving the carbonation conversion and mechanical strength of the sorbent is crucial to CaL. In recent years, researchers have attempted to enhance the reactivity and durability of CaO-based sorbents by chemical pretreatment, − alkali metals doping, − structural modification, − addition of inert supporters, , and palletization with bio-templates. − To the best of our knowledge, CO 2 capture capacity continues to decline as the number of cycles increases for most modified sorbents.…”

Recent developments in polysaccharide and lignin-based (nano)materials for CO2 capture

“…Cellulose, alginate, starch, gum, chitosan, and pectin are diverse kinds of polysaccharides, which can be applied for the capture of CO 2 . [69][70][71] In addition, lignin-based materials can be used for CO 2 capture applications. [72][73][74][75][76] In fact, the mentioned polysaccharides and lignin have a special chemical structure, which enables them to be used in different forms such as aerogels, composites, N-doped materials, MOFs, membranes, hydrogels, etc.…”