The chilled ammonia process—one of several new processes being explored for post-combustion capture—chills the flue gas, recovering large quantities of water for recycle, and then utilizes a CO₂ absorber in a similar way to absorbers used in systems that reduce sulfur dioxide emissions.

The remaining low concentration of ammonia in the clean flue gas is captured by cold-water wash and returned to the absorber. The CO₂ is then compressed for enhanced oil recovery or storage. Studies by the Electric Power Research Institute (EPRI) have indicated that ammonia scrubbing results in a 10% reduction in generated power, while the older MEA (amine scrubbing) cuts generated power by 29%.

AEP and SemGreen have agreed that CO₂ captured at the Oklahoma powerplant will be transported to SemGreen through pipeline and technology provided by SemGreen. The CO₂ would then be used or sold by SemGreen for enhanced oil recovery.

Under this MOU, AEP and SemGreen have begun the necessary engineering and design for the system.

This agreement with SemGreen represents an important step toward our goal of taking carbon capture technology to commercial scale. SemGreen and AEP will work together to develop and integrate an efficient system to compress and transport carbon dioxide captured at the plant.

Technology for carbon capture will continue to develop, but perhaps a more significant challenge is what to do with the CO₂ once it is captured. Permanently storing it underground is one solution, but it would be best to find productive uses for the captured gas. Using the CO2 for enhanced oil recovery—where the gas is injected into older oil wells to improve production, then remains underground afterward—is a logical step for coal-fired plants near oil fields.

—Michael G. Morris, AEP Chairman, President and CEO

In its March announcement, AEP said it would pursue the first commercial use of carbon capture technologies on existing coal-fired power plants, with installation of a commercial-scale system planned for one of the 450-megawatt coal-fired units at Northeastern Station in Oologah, Okla., after the completion of a large-scale product validation on an AEP plant in West Virginia. Plans are for the commercial-scale system to be operational at Northeastern early next decade. It is expected to capture about 1.5 million metric tons of CO₂ a year.

The Alstom technology will be installed for product validation on AEP’s 1300 MW Mountaineer Plant in New Haven, W.Va., where it will capture CO₂ from a slipstream of flue gas from the plant. The slipstream will be equivalent to between 20 and 30 megawatts of generation, an increase from the 10 megawatts included in the March announcement. The Alstom chilled ammonia system is expected to capture between 100,000 and 200,000 metric tons of CO₂ per year, which will be injected for geological storage in deep saline aquifers at the site.

Battelle Memorial Institute is serving as the consultant for AEP on geological storage at Mountaineer. In 2002, Battelle, AEP, the US Department of Energy and others sponsored the world’s first site-specific investigation of carbon storage capabilities at the Mountaineer plant. During the investigation, an approximately 9,000-foot exploratory well and seismic studies determined that the site was suitable for deep geological storage of CO₂.

The validation project at Mountaineer will begin in late 2008, or after completion of a small-scale pilot demonstration of the technology by Alstom and the Electric Power Research Institute on a Wisconsin plant.

Once commercial viability of the technology is validated at Mountaineer, AEP plans to install Alstom’s chilled ammonia technology on Northeastern Station in Oklahoma.

American Electric Power is one of the largest electric utilities in the United States, delivering electricity to more than 5 million customers in 11 states. AEP ranks among the nation’s largest generators of electricity, owning more than 38,000 megawatts of generating capacity in the US. AEP also owns the nation’s largest electricity transmission system, a nearly 39,000-mile network that includes more 765 kilovolt extra-high voltage transmission lines than all other US transmission systems combined.

AEP’s transmission system directly or indirectly serves about 10% of the electricity demand in the Eastern Interconnection, the interconnected transmission system that covers 38 eastern and central US. states and eastern Canada, and approximately 11% of the electricity demand in ERCOT, the transmission system that covers much of Texas.

Resources:

• AEP and Climate Change (AEP presentation)