The environment inside a slagging gasifier is one of the worst imaginable from a materials standpoint. Another extreme environment occurs inside an ultrasupercritical (USC) pulverized coal power plant.

Inside a slagging gasifier the basic process involves a carbon/water slurry mixing with oxygen in a gasification chamber to form syngas (carbon monoxide and hydrogen) and slag. While that may sound tame enough, extremely high temperatures that cycle from 1325°C to 1600°C and back again place an enormous strain on the system. The materials used must not only withstand these temperatures, but they also must avoid cracking during the expansion and contraction that occurs when they repeatedly heat up and cool down. Add to this a corrosive atmosphere that is oxidizing on start-up and reducing during operation; corrosive slags and gases of variable chemistry; and pressures greater than 400 psi, and you have a real materials challenge-the kind that the Advanced Research Materials Development group at NETL tackles routinely.

	Bret Howard, a research chemist in the Office of Research and Development at the Department of Energy’s National Energy Technology Laboratory, analyzes metal alloys used in hydrogen membrane research with the X-ray diffractometer in ORD’s Chemistry and Surface Science Division.

To meet a challenge such as this, scientists and engineers both onsite and at university and industrial laboratories around the country are engaged in investigations that cut across many scientific and technological disciplines to address materials requirements for all fossil energy systems, including innovative advanced power systems. Their goal is to bridge the gap between basic and applied research, often by pursuing “breakthrough” concepts based on mechanistic understanding from any discipline to develop materials with unique thermal, chemical, and mechanical capabilities. These efforts involve:

1. development of a technology base in the synthesis, processing, life-cycle analysis, and performance characterization of advanced materials;
2. development of new materials that have the potential to improve the performance and/or reduce the cost of existing fossil fuel technologies; and
3. development of materials for new energy systems and capabilities.

The success of these research and development projects is a key element in providing energy options to the Nation. One notable NETL success is the development of a chrome oxide refractory material capable of working in the slagging gasifier conditions described above. In this project, researchers first determined that one of the major failure mechanisms for chrome oxide refractories exposed to the intense heat and corrosive environment was spalling, or the chipping or flaking of refractory material from an exposed face. They used this information to formulate a high-chrome oxide refractory composition that resists spalling, resulting in a refractory with a longer service life in the gasifier.

Inside an ultrasupercritical (USC) pulverized coal power plant, materials are exposed to temperatures up to 760°C and pressures up to 5,000 psi. Operating a USC system can improve power plant efficiency up to 47% and reduce emissions. However, finding boiler and turbine materials that can hold up under extreme conditions requires new high-temperature metal alloys and ceramic coatings, as well as computational modeling research to optimize the processing of these materials. Advanced Research Materials Development program successes in this area include the following:

1. Babcock & Wilcox researchers have identified ferritic steels that resist steam oxidation at high temperatures as well as—or better than—more expensive austenitic steels.
2. Researchers at ALSTOM Power have shown that applying advanced coatings to less expensive alloy compositions provides an alternative to using costly, highly alloyed materials for next-generation boiler designs.
3. Investigators at Riley Power Inc. have developed and met ASME standards for a welding procedure for an advanced steel known as SAVE 12. This high-chrome alloy is a candidate material for construction of advanced coal-fired boilers.
4. University of Cincinnati researchers have found that ceramics based on mixed metal niobates and tantalates are particularly promising as protective coatings against aggressive environments associated with the high temperatures of USC boilers.
5. Researchers at Oak Ridge National Laboratory (ORNL) have developed a neural net program to guide heat treatment procedures for advanced alloys. These improved methods can increase the energy efficiency of the process and reduce waste.

The Advanced Research Materials Development program couples these cooperative, cutting-edge R&D efforts with technology transfer mechanisms to help maintain U.S. materials technology capabilities and competitiveness.