Capturing CO2 in flue gas from fossil fuel-fired power plants using dry regenerable alkali metal-based sorbent

CO2 capture and storage (CCS) has received significant attention recently and is recognized as an important option for reducing CO2 emissions from fossil fuel combustion. A particularly promising option involves the use of dry alkali metal-based sorbents to capture CO2 from flue gas. Here, alkali metal carbonates are used to capture CO2 in the presence of H2O to form either sodium or potassium bicarbonate at temperatures below 100 degrees C. A moderate temperature swing of 120-200 degrees C then causes the bicarbonate to decompose and release a mixture of CO2/H2O that can be converted into a "sequestration-ready" CO2 stream by condensing the steam. This process can be readily used for retrofitting existing facilities and easily integrated with new power generation facilities. It is ideally suited for coal-fired power plants incorporating wet flue gas desulfurization, due to the associated cooling and saturation of the flue gas. It is expected to be both cost effective and energy efficient. This paper provides the first comprehensive review of the major research progress on this technology. To date such research has focused on two main areas: sorbent development and process development. In the case of sorbent development, pure sodium carbonate and potassium carbonate were tested directly. More recent research has concentrated on using supported sorbents which provide the necessary attrition resistance for use with fluidized-bed or transport reactors. Research on sorbent development has included an examination of the physical properties, carbonation and regeneration reaction behavior, reaction kinetic behavior, and multi-cycle behavior of these alkali metal-based sorbents. By contrast, process development activities have focused on solving the many unique challenges associated with post-combustion CO2 capture using alkali metal-based sorbents. The research on process development included exploration of the effects of operation conditions such as reaction temperature, gas composition, operation pressure, and gas impurities on CO2 capture behavior, continuous operation of the CO2 capture process, and economic evaluation of this process. Finally, this paper discusses the research challenges and opportunities that exist with this technology. (C) 2013 Elsevier Ltd. All rights reserved.