(6b) CO2 Capture with Modified Lime-Based Pellet Sorbents

Yinghai Wu, Vasilije Manovic, Ian He and Edward J. Anthony

CanmetENERGY, Natural Resources Canada

1 Haanel Dr. Ottawa, ON K1A1M1

Abstract

Calcium looping technology is being developed as a promising method for capturing CO₂ from both flue and fuel gases, which typically contain relatively low concentration CO₂ of <14%.   Calcium looping utilizes the reversible carbonation and calcination reactions of CaO (CaO + CO₂  CaCO₃) to produce a highly concentrated CO₂ stream (>90%) suitable for sequestration. Here, modified lime-based pellets were studied as potential regenerable high-temperature CO₂ sorbents using calcium aluminate cement binders to enhance pellet strength. A mechanical pelletizer was used for granulation of the powdered materials, specifically quick lime and hydrated lime, produced from Graymont limestone with the addition of spray water. The CO₂ carrying capacity of both the pellet sorbents and the parent limestone was tested in a thermogravimetric analyzer (TGA) over repeated calcination/carbonation cycles. In addition, the attrition resistance of these pellets was examined using a bubbling fluidized bed (50 mm ID). The particle size distribution (PSD) of both the calcined pellets was determined before and after alternating calcination/carbonation cycles. It was found that the CO₂ carrying capacity of pelletized sorbent was more stable over multiple cycles. Moreover, the results of attrition tests showed that high-temperature fluidization did not result in significantly pronounced attrition for the pellet sorbents.