Investment grows in supersonic shockwave compression technology- by dj slater

American Electric Power (AEP) has committed US$2 million to support the commercial development of advanced compression technology for carbon dioxide (CO2) as part of an ongoing initiative that includes the U.S. Department of Energy’s National Energy Technology Lab (NETL), Ramgen Power Systems LLC and Dresser-Rand. The initiative is developing a supersonic shockwave compression system that will reduce the cost and energy consumption associated with compressing CO2 for storage in porous rock formations deep underground.

Ramgen used the Rampressor test rig to showcase the capabilities of a shockwave compression system.

Sequestering CO2 in underground formations requires compressing the gas to more than 103 bar. Existing compression technology represents a substantial part of the capital and operating costs of developing CO2 capture and storage systems. Ramgen’s advanced compression system will use supersonic shockwaves to compress CO2 for capture and storage, according to the company. If successful, the shockwave compression technology is projected to reduce the capital cost of CO2 compression equipment by as much as 50% and reduce operating costs of a carbon capture and sequestration (CCS) system by at least 15%. “If we are successful, this system will be a game changer,” said Peter Baldwin, Ramgen’s president. “The industry has been good with incremental change, and this has the potential to be a game changer.”

Compressor designs for CO2 capture and storage demand a pressure ratio of 100:1 and require stainlesssteel construction in the presence of water vapor, according to Ramgen. The most significant cost, however, comes from the aerodynamic design practice that limits the design pressure ratio per stage on heavier gases.

Ramgen’s proposed system would be able to reach the 100:1 pressure ratio in two stages of compression instead of eight, which is typical for most compressors, according to Ramgen. The compressor system, which could run at about 8 MW, could achieve about 39 kg/sec. at a 10:1 pressure ratio, Baldwin said. The technology behind this system comes from the Rampressor, the company’s core design, which features a rotating disk that operates at the high peripheral speeds necessary to achieve supersonic effect in a stationary environment, said Ramgen.

The rim of the disk has three raised sections and cavities that mimic the effect of the center-body and channels of a conventional ramjet inlet. Air enters through a common inlet and is then ingested into the annular space between the supersonically spinning disk and the outer edge of the casing, according to the company. When the air flow enters this space, the raised sections of the rim create a “ramming” effect, generating shock waves and air compression. The disk chambers are angled, so the compressed air is rotated into a collector and then into the compressed air system. The compression process is also oil free, requiring no oil for lubrication or sealing, according to Ramgen.

A cross-section of the Rampressor test rig.

The idea behind using shockwaves in compressors originated with Shawn Lawlor, Ramgen’s founder and chief technology officer. Lawlor knew that the U.S. Air Force had spent considerable money and research in supersonic flight capabilities to improve the effectiveness of shock compression, Baldwin said. He then wondered if that technology could be applied to stationary equipment. The idea became a reality about 10 years in the making. In recent years, other entities have taken notice of Ramgen’s work, AEP being the latest.

Before AEP, the U.S. Dept. of Energy provided a four-year, US$11 million grant for Ramgen to develop the compressor system. On Aug. 10, 2009, the Dept. of Energy awarded Ramgen a US$20 million grant from the American Recovery and Reinvestment Act in order to accelerate the development of a commercial-scale unit. The commercial product, the HP-12, is the high-pressure stage of a matched set that would be suitable for 200 to 250 MW coal-fired power plants, according to Ramgen. Ramgen said that its proposed supersonic shockwave compression system offers four distinct advantages when compared with existing compressor technologies.

The system can achieve high compression efficiency and is capable of producing very high, single-stage compression ratios. The system’s simplicity and size make it less expensive to manufacture, and it is capable of significant waste heat recovery, according to Ramgen. “I think that I speak for the entire company in saying that it is very rewarding, both personally and professionally, to be involved in such an important initiative,” Baldwin said. “At some point in our careers, we all say ‘We want to make a difference.’ The folks at Ramgen are making a difference.”

AEP’s involvement is another set of good news for Ramgen, Baldwin said, especially considering its work in advancing CCS technologies. AEP began capturing and sequestering CO2 Oct. 1, 2009, from 20 MW of the flue gas at its Mountaineer Plant in New Haven, West Virginia, U.S.A., using chilled ammonia technology developed by Alstom. The company said that the Mountaineer CCS project is the first integrated CO2 capture and sequestration project at an operating coal-fueled power plant.

On Dec. 4, 2009, AEP received US$334 million in funding from the U.S. Department of Energy Clean Coal Power Initiative Round 3 to pay part of the costs to scale up the chilled ammonia process to capture at least 90% of the CO2 from 235 MW of the plant’s 1300 MW of capacity. The captured CO2, about 1.5 million tonnes per year, will be treated and compressed, then injected into suitable geologic formations for permanent storage approximately 2.4 km below the surface.

“Advancing technologies to capture and permanently store carbon dioxide from coal-fueled power plants is critical if we are going to reduce global concentrations of greenhouse gases,” said Nick Akins, AEP executive vice president, Generation. “Now that we have completed construction and are operating the CCS validation system at our plant in West Virginia, our focus is on working to better understand and optimize that process to help ensure that the economics of CCS make sense for our customers and for use on the world’s vast fleet of coal-fueled power plants.”

In addition to providing financial support, AEP will consult on the development and demonstration of the CO2 compressor that will be tested at Dresser-Rand’s test facility in Olean, New York, U.S.A., in the second quarter of 2011. AEP has also committed to working with Ramgen and Dresser-Rand on potential future tests of the shockwave compression technology at AEP sites.


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