April 2014 Labnotes

A Faster Way to Reduce Carbon Footprints

 CCSI

Traditionally, moving energy technologies from discovery to commercialization takes two to three decades.  With a 2010 White House charge to deploy widespread, cost-effective carbon capture and storage (CCS) within 10 years, there is an urgent need to accelerate the development of carbon capture technologies.  NETL’s Carbon Capture Simulation Initiative (CCSI) research team is addressing that need with the help of recent advances in simulation technology and a broad-reaching partnership with several other DOE National Labs, universities, and industry. 

Pulverized coal power plants currently generate approximately 40 percent of the nation’s electricity. Between 2010 and 2030, they are also expected to emit 95 percent of the carbon dioxide (CO2) that comes from all United States coal-based power plants.  The CCSI team is working with the energy industry to deploy models and software packages that will help the plants gear up to capture most of that CO2.

 Simulation snapshot of particle flow past cylindrical objects (white-cylinders; red-solids; blue-gas).

Simulation snapshot of particle flow past cylindrical objects (white-cylinders; red-solids; blue-gas).

The CCSI partnership brought together five national labs, five universities, and a multitude of industry advisors and partners to develop and test a suite of computational tools that will speed up the deployment of post-combustion carbon capture in pulverized coal plants.  This requires new approaches to rapidly transition laboratory concepts to at-scale processes which can be integrated with new and existing power plants.  CCSI uses a science-based approach in the development of its simulation tools that help to design and optimize new capture technologies, as well as mitigate the uncertainties associated with technology scale-up, sharply reducing development cost and time.

The first CCSI Toolset release came in October of 2012 and introduced software tools to demonstrate basic capabilities.  Last year, a second major release introduced 12 new products and made improvements to the original tools.  The Toolset has gotten the attention of industries that develop carbon capture technology, and to date, five companies have licensed it.  Licensees can test and evaluate the tools at no cost for 18 months, with the potential for an extension if they continue to actively test and provide feedback on the results.

 David Miller addresses the CCSI Industry Advisory Board.

David Miller addresses the CCSI Industry Advisory Board.

Elements of the Toolset help identify and model promising carbon capture concepts, optimize process designs, develop advanced control systems, and evaluate the effects of uncertainty in the underlying data used in computer models.  For industry, it’s the equivalent of having “a box of tools in the garage,” says David Miller, Technical Coordinator for the CCSI Team.  “While certain tools are always used together, others tools can be pulled out to address specific types of problems without needing to deploy other tools. This a la carte approach enables industry to quickly utilize those specific tools which are most relevant to their work flow.”

Traditional technology development approaches will typically adopt a new concept only after building, testing, reworking, and rebuilding successively larger real-world versions.  Computational tools such as those CCSI is now distributing to its industrial partners helps to avoid rework and allows smarter, more focused pilot and demonstration projects.  Within a $600 million carbon capture plant, this can mean reaching design capacity 6 months earlier with a cost savings of $30 million.

The CCSI team is working closely with the companies who have licensed the Toolset to help them get the most out of the tools; feedback from the companies allows the CCSI Team to further improve the tools.  These industry partnerships also provide real-world cases for the researchers to learn from.  Says Miller, “They are helping us to ensure the tools and capabilities we’re providing are going to make a significant and lasting difference.”

Contact: David Miller, 412-386-6555


Metallic Membranes: A Road to Hydrogen Fuel

Hydrogen gas (H2) is a valuable commodity for the food and petrochemical industries.  It is used to hydrogenate oils, for example, and to crack heavy hydrocarbons into lighter ones that can be used as fuels or as chemical precursors.  When very pure, it is used in fuel cells to generate power.  Hydrogen is a very abundant element (it’s the H in H2O), but is rarely found on its own in nature, so it must be manufactured by separating it from other commodities.  Most often, it is generated by steam reforming of oil, but it is also produced when coal is gasified to generate hot syngas.

Syngas contains methane, carbon monoxide, carbon dioxide, and hydrogen, with small amounts of other components like sulfur (S), arsenic (As), and selenium (Se) compounds.  To use syngas as a source of hydrogen, separation membranes are being developed that allow the hydrogen to pass through while other gases are kept out.

Simple schematic of a hydrogen separation palladium (Pd) membrane.

Simple schematic of a hydrogen separation palladium (Pd) membrane.

More than a decade ago, NETL developed the capability to handle hydrogen gas at temperatures and pressures such as those found in syngas cleanup systems, and when interest in coal gasification led to a need for separation membrane development, that capability was adapted to include testing membrane materials.  Eventually a test protocol was standardized and implemented, and research labs began sending membrane materials to NETL for performance evaluation, assistance that NETL still provides.  According to researcher Bret Howard, “NETL provides unbiased evaluations of other organizations’ membranes...to independently verify the claimed performance.”

This testing capability eventually expanded into an in-house NETL membrane development research program.  Expertise in alloy development, engineering, materials testing, and corrosion combined to form the NETL-RUA Fuels research team, which includes Federal and URS Corporation researchers at NETL, industry partner Gasification Technologies, Inc. (GTI), the National Carbon Capture Center, and researchers from Carnegie Mellon University. “We are trying to engineer materials that can separate H2 from a mixture of other gases,” says Dirk Link, Technical Coordinator for the NETL-RUA Fuels team. “Some of these are detrimental to the function of the membrane.” 

Metallic membranes are a promising approach to hydrogen separation at high temperatures; palladium metal (Pd) is particularly efficient at helping the hydrogen gas dissociate into hydrogen atoms, which then travel through the membrane’s crystal structure and recombine on the other side as a pure hydrogen gas stream.  Unfortunately, minor syngas components such as hydrogen sulfide (H2S), arsine (AsH3), and hydrogen selenide (H2Se) corrode the metallic membrane and hamper both dissociation of hydrogen gas and transport of hydrogen atoms through the membranes.  Disruption of these processes can cause the system to fail.

Alloy films used by NETL for testing hydrogen dissociation activity and contaminant exposure reactivity.  Continuous gradient compositions of binary (Pd and Cu) and ternary (Pd, Cu, and Au (gold)) mixtures make it possible to test many alloy compositions simultaneously.

 

Alloy films used by NETL for testing hydrogen dissociation activity and contaminant exposure reactivity.  Continuous gradient compositions of binary (Pd and Cu) and ternary (Pd, Cu, and Au (gold)) mixtures make it possible to test many alloy compositions simultaneously. (image courtesy of Jim Miller, Carnegie Mellon University).

Copper (Cu) is a useful addition to Pd in hydrogen membranes; not only does it increase the membrane’s corrosion resistance, but as a cheaper metal, it lowers the cost of the membranes significantly.  The Fuels team is studying membranes made of various combinations of Cu and Pd as well as minor additions of other elements to improve performance – how well hydrogen is transported through the metal – and to increase corrosion resistance.  Minor amounts of magnesium and aluminum have also been added, to improve membrane performance by stabilizing the alloy’s crystal structure and reduce membrane cost.

Results of the research to date show that the extent of corrosion depends very much on the temperatures at which the alloys are tested, the composition of the test membrane, and which corrosive contaminants are present in the gas.  However, in general, they have found that larger amounts of Cu are good; and corrosion increases dramatically at temperatures above 650 °C.

The results thus far are promising, but there is still plenty of work to be done.  NETL’s history of membrane testing, and the partnerships incorporated into the research team, will help move membrane technology further toward the goal of clean hydrogen fuel from syngas.

Contact: Dirk Link, 412-386-5765

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