Cerium Diffusion Coating Patent Awarded to NETL Researchers

	The cerium oxide/activator slurry is being painted onto the surface of a solid oxide fuel cell interconnect plate. The slurry has also been applied by dipping and spray coating with equally good results.

NETL researchers Dr. Paul D. Jablonski and Dr. David E. Alman have been awarded a patent for a method of applying a cerium diffusion coating to a metallic alloy.

The NETL-developed technology provides a simple method for improving the oxidation resistance of chromia-forming alloys used in fossil energy applications. 

The treatment has been found to enhance the oxidation resistance of numerous commercial alloys by incorporating cerium or other rare earth elements into the surface.

The technique involves slurry coating the surface of the alloy with a mixture of cerium oxide and a halide activator, followed by a thermal treatment which pre-oxidizes the surface.

The simple technique can be applied to flat or curved structures, including the interior surfaces of tubes, and has been applied to numerous alloys of interest for fossil energy applications, including: ferritic steels for interconnects for solid oxide fuel cells, certain types of steel and nickel base alloys for advanced boiler and turbine applications.

In most cases the surface treatment improves oxidation resistance by a factor of 2 to 3, and in a few alloys it can lead to an order of magnitude improvement in performance.

Researchers Capture Methane Hydrate Formation on Porous Media With X-Ray CT

	The middle yellow body is the surface of hydrate concentrated area. On the right, the square with red area shows the concentration of hydrate on that side; red means higher saturation of hydrate.

Dr. Yongkoo Seol and his gas hydrate laboratory team at NETL have formed methane hydrate in a sandy porous media, and successfully captured real-time X-ray computed tomography (CT) images.

The CT images clearly show patterns of hydrate distribution during the hydrate formation and dissociation within the porous media under high pressure and low temperature.

The experiment was designed to study behavior of methane hydrate under various conditions potentially encountered during methane production and natural hydrate formation.

Dr. Seol’s team is developing a computer program to convert the CT images into model grids for numerical simulation studies.  His team is closely working with the CT scanner project and CO₂ sequestration project team.

The team collaboration made the difficult work efficient and seamless.

NETL Researchers Improve Cell Design for Studying Direct Coal Fired Fuel Cells

	A close view of the new cell design from the first sample before testing.

NETL researchers are studying liquid tin anode solid oxide fuel cells as a coal-based fuel cell system that can run directly on pulverized coal. They changed the cell design, and have produced voltages higher than those obtained with the old design.

Direct consumption of coal would eliminate the need for gasification, potentially increasing efficiency and reducing total system costs.  The project focuses on measuring the kinetic parameters of the liquid tin anode to better understand and optimize the cell’s performance.

Data from initial electrochemical measurements were observed to be below the theoretical limit expected.  To confirm that no solid-to-gas energy losses were the cause for this result, the cell design was changed by replacing a flat button cell with a continuous electrolyte (in crucible form), to which a cathode was painted.

Tests of the new cell design have produced open circuit voltages higher than those obtained with the old cell design, with values equivalent to theoretical values.

The new cell design, which also incorporates extra sensors for temperature and oxygen concentration measurement, allows for more precise and reproducible measurements of the desired kinetic parameters. 

NETL Tests Look into the Fate of Small Channels in Cements

NETL researchers are conducting flow-through tests to investigate the behavior of flow channels in well-bore cements in the presence of pressurized CO₂.

During CO₂ injection in geological sequestration, CO₂ will interact chemically with wellbore cement, which is typically present in deep wells. Fractures or channels in the cement may allow the CO₂ to flow into other formations or to the surface.

Depending on the conditions, flow paths in cement may either be enlarged through dissolution of material or be sealed with new minerals which are deposited as CO₂ and brine flow through the flow paths.

Tests indicate that the closing of a flow path is possible for small channels and low flow velocity of carbonated water.  These results indicate that certain geometries and sizes of physical pathways in wellbore cement may not increase the risk of CO₂ release.

In an experimental setup at NETL, brine simulating deep aquifer fluid is mixed with CO₂ and forced at high pressure through channels of varying sizes in cement cores.  The pressure difference across the core is recorded continuously to judge whether the channel is getting larger or shrinking.  Once the test is completed, the cores are evaluated using CT scanning, X-ray crystallography, and electron microscopy.