(315i) High Temperature Carbon Dioxide Capture and Hydrogen Production Using Engineered Eggshells

Economic analyses of carbon management schemes indicate that CO2 capture costs dominate over the costs of its transportation and sequestration. High temperature CO2 separation processes employing metal oxide fines (1-50 microns) are energy efficient but face engineering challenges for commercial deployment due to particle separation issues. Chicken eggshell, a bioceramic composite rich in calcium, offers a unique combination of particle strength, reactivity and cost. The United States generates 190,000 tons of annual eggshell waste that results in expensive disposal costs. This study demonstrates that chemically treated refuse eggshells attain a CO2 capture capacity as high as 65 weight percent at 700 oC over multiple cycles of alternating reaction and regeneration. A unique dilute acetic acid treatment procedure, which enhances its reactivity, is optimized to physically detach the organic membrane from the eggshell composite. These membranes, rich in collagen, have market value and find use in several biomaterial applications including skin grafting. Furthermore, this technique also enhances its reactivity by creating 2-5 microns long filamentous structure on its surface. In addition, the study reveals that intermediate hydration of calcined eggshell sustains its multicyclic reactivity by generating higher porosity structure which enable better gas accessibility throughout the eggshell depth. Eggshells overcome the engineering challenges confronting the deployment of fines based CCR process. Naturally occurring eggshells thus obviate the necessity to formulate expensive agglomerates from high reactivity calcium fines thereby making the process economical.