Rocket Nozzles Could Pull Carbon from Air

An aerospace firm is working to turn rocket nozzle technology into a novel method for cleaning up the carbon-laced air emitted by coal-burning power plants.

"It is radically different," said Arun Majumdar, director of the Department of Energy's Advanced Research Projects Agency, known as ARPA-E, which is funding the research.

The idea is to use aerodynamic force, rather than chemicals, to separate out carbon dioxide from a power plant's air before it is released into the atmosphere, a technique that should be considerably cheaper than currently available systems.

"Today's carbon capture technology adds 80 percent to the cost per kilowatt hour of electricity delivered," ATK vice president Robert Bakos told Discovery News. "With our approach, we could knock that down to 30 percent."

Currently, coal burning accounts for 36 percent of the total carbon dioxide emissions in the United States, according to the U.S. Energy Information Administration. Carbon dioxide is among the so-called greenhouse gases that trap heat in the atmosphere.

Yet mining the country's coal reserves -- the biggest in the world -- is a tempting solution to the problem of relying on foreign oil to satisfy domestic demands for energy.

"In the future, we will be living in a carbon-constrained world. And in that case, any emissions should be looked at seriously," Majumdar said. "The role of carbon capture is actually critical."

ATK, which builds the space shuttles' booster rockets, cites not only rocket technology, but also high-speed aerodynamics as the driver for its carbon-capture system, which is being developed in partnership with ACENT Laboratories of New York.

"When you accelerate air to very high speed, you have to expand the air very quickly. It cools the air and in some cases if you have water (vapor) in the air, it will make it condense into water or even snow. The same idea applies if you have carbon dioxide," Bakos said.

Carbon dioxide is a gas under normal conditions, but when frozen forms into what is known as dry ice. The particles can then be pulled from the air by various means, and stored, treated or used in other applications.

ATK proposes to pressurize a power plant's exhaust gas, then put it through a rocket nozzle so that it expands and cools, allowing dry ice to form.

"It's relatively simple, but as they say, the devil is in the details," Bakos said.

The company plans to demonstrate the technology in a laboratory within 14 months, then move on to a pilot program at a power plant.

"We have to see if it will work," added Majumdar. "If we could scale it up, that'd be really interesting."