Journal of Environmental Sciences 2011, 23(8) 1233–1239 Factors affecting the direct mineralization of CO 2 with olivine Soonchul Kwon 1 , Maohong Fan 1,2, ∗ , Herbert F. M. DaCosta 3 , Armistead G. Russell 1 1. School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA. E-mail: soon76.kwon@sansumg.com 2. Department of Chemical and petroleum Engineering, University of Wyoming, Laramie, WY 82071, USA 3. Caterpillar Inc., P.O. Box 1875, Peoria, Illinois 61656, USA Received 10 May 2011; revised 05 July 2011; accepted 16 July 2011 Abstract Olivine, one of the most abundant minerals existing in nature, is explored as a CO 2 carbonation agent for direct carbonation of CO 2 in flue gas. Olivine based CO 2 capture is thermodynamically favorable and can form a stable carbonate for long-term storage. Experimental results have shown that water vapor plays an important role in improving CO 2 carbonation rate and capacities. Other operation conditions including reaction temperature, initial CO 2 concentration, residence time corresponding to the flow rate of CO 2 gas stream, and water vapor concentration also considerably affect the performance of the technology. Key words: carbon dioxide; mineralization; flue gas; carbonation DOI: 10.1016/S1001-0742(10)60555-4 Citation: Kwon S, Fan M H, DaCosta H M D, Russell A G, Armistead G R, 2011. Factors affecting the direct mineralization of CO 2 with olivine. Journal of Environmental Sciences, 23(8): 1233–1239 Introduction The rapid growth in the demands of industrial energy has led to the accumulation of carbon dioxide, the primary factor responsible for global climate change. The Interna- tional Panel on Climate Change (IPCC) report stated that CO 2 concentration in the Earth’s atmosphere has increased from 280 ppm prior to industrial era to 380 ppm in 2005, and it is expected to rise to 590 ppm by 2100 (IPCC, 2005). Since about 40% of the total CO 2 emissions in the U.S. is released from fossil fuels based power stations, many studies have focused on the promotion of highly efficient technologies of CO 2 capture or storage from the flue gas stream of coal-fired power plants (Carapellucci and Milazzo, 2003). Among the various CO 2 separation processes, adsorp- tion is considered to be one of the promising technologies (Meisen and Shuai, 1997; Khatri et al., 2005, 2006; Plaza et al., 2007). Unlike liquid sorbents, solid adsorbents are relatively easy to handle, and could mitigate corrosion problems and be less energy-intensive (Niswander et al., 1993; Veawab et al., 1999). Therefore, many researchers are interested in the development and the application of cost-effective solid sorbents. As an alternative CO 2 capture technology, mineralizing CO 2 has also attracted many people’s attentions. Olivine ((Mg,Fe) 2 SiO 4 ) is a feedstock candidate for feasible CO 2 mineralization due to its high abundance in nature, low * Corresponding author. E-mail: mfan@uwyo.edu supplying cost ($4–5/ton), and environmentally-friendly characteristics (Herzog, 2002; Lackner et al., 1995; Maroto-Valer et al., 2005). In addition, the solid byprod- ucts resulting from the olivine based CO 2 mineralization can be used as soil amendments (Maroto-Valer et al., 2005). The reaction of olivine with CO 2 can be written as: 1/2(Mg,Fe) 2 SiO 4 + CO 2 ←→ (Mg,Fe)CO 3 +1/2SiO 2 (1) Reaction (1) is exothermic and its Gibbs free energy change is negative under standard conditions. However, Reaction (1) is slow, which has made the direct carbonation method less atrravitve (Herzog, 2002; Maroto-Valer et al., 2005; Seifritz, 1990). To accelerate the carbonation rate, many pretreatment processes such as magnetic separation, heat and acid treatments have been studied (Herzog, 2002; Maroto-Valer et al., 2005). However, these pretreatments are long processes and energy intensive, resulting in the increase in energy penalty to electricity outputs of power plants by more than 20% (Herzog, 2002; Maroto-Valer et al., 2005). Thus, alterative simple and direct approaches to significant increases in the reaction rate of Reaction (1) need to be sought before the mineral carbonation process can be applied in power plants. In this study, water in flue gas was used to accelerate the direct mineralization of CO 2 with olivine. Flue gas streams from coal-fired power generation facilities generally con- tain 8–10 vol.% water vapor. Flue gas can still contain up to 5 vol.% water at ambient condition even after it is pretreated by power plants (Bearat et al., 2006; Weissbart and Rimstidt, 2000; Dean, 1992). In the presence of water