Magnesium Oxide-Based Absorbents for CO₂ Capture at Medium Temperature

MgO-based absorbent has been recognized as a promising CO₂ absorbent at intermediate temperature, though the carbonation performance of pure MgO is poor. Researchers have been devoted to optimize the CO₂ absorption ability via introducing alkali metal carbonates or nitrates. In this paper, the absorption performance of MgO-based absorbents promoted by alkali metal carbonates or modified by alkali metal nitrates has been summarized, and the affecting mechanism has been concluded. Alkali metal nitrates are essential for high absorption ability, and alkali metal carbonates facilitate high-temperature carbonation. Effects of fuel gas conditions and absorbent pelletization are also mentioned for practical applications. H₂O can accelerate the carbonation rate effectively, but the influencing mechanism of H₂O and the CO₂ absorption stability in presence of H₂O was not clearly reported. Further investigations on pelletized MgO-based absorbents modified by alkali metal salts considering regeneration conditions of high CO₂ concentration are proposed based on the recent research findings.