CCS AND POWER SYSTEMS
ADVANCED ENERGY SYSTEMS - GASIFICATION SYSTEMS
WARM GAS CLEANUP
Performer: NETL Office of Research and Development
Project No: FWP-2012.03.03 Task 5
- Work to characterize and estimate the cost of a trace Hg removal system using Pd sorbents in syngas cleanup configurations for integrated gasification combined cycle (IGCC) plants has been completed. The system utilizes the Research Triangle Institute (RTI) International warm gas cleanup technology for sulfur removal from raw syngas and bulk trace contaminant removal. Warm gas clean-up enjoys a theoretical thermal efficiency advantage over cold gas clean-up of approximately three percent. The RTI technology removes sulfur and heavy metals from gasification syngas at high temperatures, eliminating the need for cooling and expensive heat recovery systems, increasing thermal efficiency and reducing capital and operating costs compared to conventional contaminant removal technology. The preliminary results are very promising for use of the sorbent as a polishing step to ensure close to 100 percent removal of the trace contaminants.
- Development of a cheaper alloy sorbent for trace contaminant removal, and several inexpensive base metal oxide and sulfide sorbent candidates have been identified in collaborations with Carnegie Mellon University (CMU). NETL-CMU efforts will provide insight into the mechanism of sorbent removal of trace contaminants leading to improved sorbent formulations.
- The team has conducted lab-scale tests to demonstrate online detection of syngas contaminants Hg, P, As, and Se.
- A study has been completed on the sorption of mercury, arsenic, and selenium from warm syngas on materials coated with palladium and low cost mixtures of palladium with other metals. Palladium was found to be an outstanding material for cleanup of the gases in a commercial syngas environment, while low cost mixtures of elements were determined to selectively remove limited amounts of some, but not all, targeted gases.
- There have been six pilot-scale tests conducted to date of the palladium sorbent with Southern Company and Johnson Matthey at the NCCC. Using a ten pound bed of palladium on alumina beads in a slipstream of real syngas, each test has shown near 100% removal of mercury, arsenic, and selenium at 500F and elevated pressures over extended periods of time (typically several weeks). The fifth test was the most challenging long-term exposure of palladium to slipstreams, the sorbent was exposed to syngas for 1,011 hours (over 42 days) at 500°F, a pressure of 180 psig, and a space velocity of 1,704 hr-1. The NETL sorbent removed nearly 100 percent of the mercury present within the syngas, with no breakthrough observed. The last test in March 2014 demonstrated use of a thermally regenerated sorbent.
- Palladium-based sorbents are currently among the most promising candidates for high-temperature capture of mercury, arsenic, selenium, phosphorus, and the other trace elements from syngas. Studies were made of a solid electrolyte technique applicable for determining the thermodynamic activity of hydrogen on a palladium surface under syngas conditions (gas composition and temperature). This technique, called solid electrolyte potentiometry (SEP) will be used to study the interactions of fuel gas constituents such as hydrogen sulfide, carbonyl sulfide, arsine, hydrogen selenide, mercury, phosphine, water, carbon monoxide, and hydrogen with palladium.