A sorbent that enhances the water-gas shift reaction

Scientists at the National Energy Technology Laboratory (NETL; Morgantown, W. Va.; www.netl.doe.gov) have demonstrated a process for enhancing the efficiency of the water-gas shift (WGS) reaction. The process revolves around a magnesium hydroxide sorbent material that can remove CO2 from coal gasification products at elevated temperatures. The industrially significant WGS reaction, often used to increase H2 gas concentration following gasification, is equilibrium-limited, and the carbon dioxide removal helps drive the reaction in the forward direction. In a conventional WGS process using pressure-swing absorption technology, CO2 removal occurs at below 50°C, which necessitates cooling and reheating steps that reduce the overall efficiency of the process. The NETL process (see flowsheet) uses a patented Mg(OH)2 sorbent material to remove CO2 at a temperature between 200 and 300°C, which is ideal for gas entering a WGS reactor. The ability to remove CO2 at higher temperatures retains most of the thermal energy of the steam and improves overall efficiency. The sorbent material can be regenerated at temperatures of 400°C, significantly lower than other sorbents reported in the scientific literature, says the NETL research team,…