Title: Dry regenerable sorbents for the separation and capture of CO₂ from large point sources

Authors: Daniel J. Fauth, James S. Hoffman, Henry W. Pennline

Addresses: US Department of Energy, National Energy Technology Laboratory, P.O. Box 10940, Pittsburgh, PA 15236, USA. ' US Department of Energy, National Energy Technology Laboratory, P.O. Box 10940, Pittsburgh, PA 15236, USA. ' US Department of Energy, National Energy Technology Laboratory, P.O. Box 10940, Pittsburgh, PA 15236, USA

Abstract: The combustion of fossil fuels generates large quantities of carbon dioxide (CO₂), a greenhouse gas most likely to influence global warming and climate change. Large stationary sources that include coal-based electric generating stations are plausible targets for the removal of CO₂. Chemical absorption of CO₂ is viewed as one option that could be applicable for its separation from both fuel gas and flue gas streams. Processes based on solid regenerable sorbents that efficiently absorb CO₂ and release it in concentrated form have the potential to be cost-effective relative to solvent-based practices. This communication summarises a preliminary investigation exploring the reaction of CO₂ with a number of calcium-based sorbents using a thermogravimetric (TG) analyser. Upon reaction at high temperature with pure CO₂, these materials are converted into metal carbonates. Thermal regeneration of the sorbents was accomplished upon heating spent materials to higher temperature in a nitrogen stream. TG studies show the absorption reaction for Ca-based materials was initially rapid and then entered into a slower kinetic regime. Multi-cycle testing conducted within the TG analyser indicated sorbents could be regenerated and reused. Theoretical conversions ranging from 50–75% were observed for the calcium/zirconia sorbents in comparison to 15–20% for the calcium/lanthanum-doped alumina sorbent. Improved conversion was attributed to the pore size differential between mesoporous zirconia and microporous lanthanum-alumina. TG studies performed at 500°C with lithium zirconate show that the rate of CO₂ absorption was continuous with time on stream. Under nitrogen, rapid regeneration of the lithium carbonate product occurred at temperatures greater than 700°C.

Keywords: calcium oxide; carbon capture; carbon sequestration; lithium zirconate; solid regenerable sorbents.

DOI: 10.1504/IJETM.2004.004632

International Journal of Environmental Technology and Management, 2004 Vol.4 No.1/2, pp.68 - 81

Published online: 26 May 2004 *

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