High temperature reactive separation process for combined carbon dioxide and sulfur dioxide capture from flue gas and enhanced hydrogen production with in-situ carbon dioxide capture using high reactivity calcium and biomineral sorbents

The increasing use of fossil fuels to meet the rising energy demands has led to higher CO2 emissions in the atmosphere. CO2 is the most significant greenhouse gas leading to global warming. Hence, recent emphasis on curbing of global warming is leading to the development of new cost effective technologies for CO2 management. Typically, the overall CO2 management scheme consists of three main areas---separation, transportation and sequestration. The cost of CO2 separation is projected to be as high as 75% of the entire cost of the CO2 sequestration. This corresponds to an increase in the cost of electricity production by about 50-200%. Current low temperature and high pressure CO2 separation technologies impose severe energy penalties and hence an increased cost for CO2 capture. However, the flue gases are present at high temperatures and sub atmospheric pressures. This proposed novel reactive separation technology: the carbonation-calcination reactions (CCR) of calcium oxides for CO 2 removal from flue gas operates at high temperatures, thereby eliminating the energy penalties. Calcium oxide reacts with CO2 to form calcium carbonate, which is then regenerated by calcining to give back the oxide and a pure CO2 stream. These gas phase carbonation reactions occur over a wide range of temperatures and pressures, including those present in the flue gas.; The CCR process employing calcium oxide fines (1-50 microns) is energy efficient but faces 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. This study demonstrates that chemically treated refuse eggshells attain a CO2 capture capacity as high as 65 wt% at 700 °C. 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. 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. (Abstract shortened by UMI.)...