Citation:

Lee, J., T. C. Keener, AND Y. J. YANG. Potential Flue Gas Impurities in Carbon Dioxide Streams Separated from Coal-fired Power Plants. JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION. Air & Waste Management Association, Pittsburgh, PA, 59(6):725-732, (2009).

Impact/Purpose:

An analysis

Description:

For geological sequestration of CO₂ separated from pulverized coal combustion flue gas, it is necessary to adequately evaluate the potential impacts of flue gas impurities on groundwater aquifers in the case of the CO₂ leakage from its storage sites. This study semi-quantitatively analyzed the potential impacts through the evaluation of upstream CO₂ separation technologies. Specifically, levels of acid gases and mercury vapor in the separated CO₂ stream in monoethanolamine (MEA) absorption were estimated based on published performance parameters of existing systems. Among the flue gas constituents considered, SO₂ is known to have the most adverse impact on the MEA absorption. When a wet flue gas desulfurization (FGD) system achieves 95% SO₂ removal, approximately 2,400 ppmw SO₂ could be included in the separated CO₂ stream. The estimated concentration level was reduced to as low as 135 ppmw for the SO₂ of <10 ppmv in the flue gas entering the MEA unit. In addition, heat-stable salts formation could further reduce the SO₂ concentration below 40 ppmw in the separated CO₂ stream. In this study, it is realized that the formation rates of heat-stable salts in MEA solution are not readily available in the literature and critical to estimating the levels and compositions of flue gas impurities in sequestered CO₂ streams, a knowledge gap requiring further studies. In addition to SO₂, Hg and other impurities in separated CO₂ stream could vary depending on pollutant removal at the power plants and impose potential impacts on the groundwater. Such a variation and related process control in the upstream management of carbon separation and sequestration have implications for groundwater protection at carbon sequestration sites, and warrants necessary considerations in overall sequestration planning, engineering, and management.

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