Coal and Power Systems
NETL Sorbents Being Developed By Industry for Commercialization
Palladium sorbents have been found to capture trace contaminants such as mercury, arsenic, selenium, and phosphorus at elevated temperatures from syngas. Johnson Matthey licensed the technology from NETL in 2007 for application to coal gasification plants, and is currently testing the technology at larger-scales. The technology received the R&D 100 award in October 2008.
The sorbents were featured in a patent "Method for removing heavy metals from gases", US Patent 8,366,807, issued February 5, 2013. Johnson Matthey scientists found that for very low sulfur gas streams, pre-exposing the palladium sorbent to hydrogen sulfide increases the ultimate capacity for mercury. This step is not necessary for most coal-derived fuel gases, as sulfur species are already present in sufficient concentrations.
Many sorbents have been demonstrated for near-ambient temperature removal of mercury from natural gas and syngas, and for removal of mercury from flue gas at temperatures up to 350°F. Few sorbents have been shown to remove mercury from high temperature syngas.
The sorbents are described in US patent 7,033,419, and in recent issues of the journals Industrial & Engineering Chemistry Research, Fuel, Analytical Chemistry and Main Group Chemistry. Gasification is an important strategy for increasing the utilization of abundant domestic coal reserves. High temperature capture of the trace elements mercury, arsenic, and selenium helps preserve the high thermal efficiency of integrated gasification combined cycle (IGCC) plants versus low temperature capture by activated carbons. With EPA's National Mercury Regulation issued in 2012, the need exists for a low-cost mercury removal technique that can be applied to IGCC and coal-burning power plants. The work is also of interest for other applications, as palladium is a widely utilized catalyst for many oxidation and hydrogenation reactions, and a material used for high temperature separation of hydrogen.