Wed February 20, 2013
Coal Without Emissions? A Breakthrough in Chemical Combustion Technology
Researchers at Ohio State University have developed a way to extract energy from coal without burning it, eliminating the greenhouse gases which are usually emitted from the process.
Typical coal-fired power plants burn coal to heat water to make steam, which turns the turbines that produce electricity. In chemical looping, the coal isn't burned with fire, but instead chemically combusted in a sealed chamber so that it doesn't pollute the air. A second combustion unit in the lab does the same thing with coal-derived syngas, and both produce 25 thermal kilowatts of energy.
"In the simplest sense, combustion is a chemical reaction that consumes oxygen and produces heat," [professor Liang-Shih] Fan says. "Unfortunately, it also produces carbon dioxide, which is difficult to capture and bad for the environment. So we found a way to release the heat without burning."
Usually when people talk about clean coal technology, they're referring to Carbon Capture and Sequestration (CCS). This process uses some of the energy generated by burning the coal to separate the carbon dioxide that's emitted, and then injects it deep underground. This new process uses chemical combustion to separate the carbon dioxide, without using any additional energy. Then, presumably, the carbon dioxide would have to be either injected underground or used in enhanced oil recovery. The researchers are calling this process Coal-Direct Chemical Looping, or CDCL.
The process does still release coal ash, so it's probably not the "cleanest energy source there is," as Fox News proclaimed in its headline. But if this technology is actually viable and affordable, it could have a real effect on the coal industry. The real test will be to see if CDCL can operate on a large scale--and if it's cheap enough to convince coal-fired power plants to install it to keep burning coal instead of switching to natural gas.
The next step for the project is a larger-scale test at the Department of Energy's U.S. National Carbon Capture Center in Alabama.