(76a) Sorbent-Enhanced Water Gas Shift Reaction Studies

An Integrated Gasification Combined Cycle (IGCC) is a power plant configuration that turns coal into synthesis gas. Impurities are removed from the coal gas before combustion, resulting in lower emissions and improved efficiency compared to conventional pulverized coal plants. Sorbents capable of capturing CO2 at the moderate temperature and high pressure of the IGCC process are necessary for an environmentally-friendly operation of the IGCC plant. In IGCC, the water gas shift (WGS) reaction, CO + H2O °ú H2 + CO2, is typically used to upgrade the hydrogen content of the syngas stream but also produces CO2 as a product. CO2 capture/removal may take place either downstream to the WGS unit or within it. The latter offers the advantage of not only less unit operations within the plant, but also shifts the equilibrium of the WGS reaction itself as CO2 is removed from the gas phase, enhancing the conversion of CO.

NETL researchers have developed novel CO2 capture sorbents for the moderate temperature application of the WGS reaction. The sorbents were evaluated for their ability to enhance the WGS reaction at temperatures of 300 ¨C 600 °C, both in the presence and absence of catalyst. Testing at 500 ¨C 600 °C in the absence of catalyst resulted in CO conversions of nearly 100% prior to sorbent saturation, surpassing the thermodynamic equilibrium CO conversion of the gas-phase WGS reaction under identical conditions. The sorbents were also tested during the WGS reaction at 400°C and 150 psig in the presence of a Pt/Ce2O3 catalyst.