The impression given by coal-fired power plant is highly polluted and bad for the environment. Recently, Ohio State University at USA has reached a milestone in clean-coal technology. The technology is able to capture 99% of the carbon dioxide (CO2) generated by the research-scale coal combustion system. Now it is ready for large-scale operation.
Coal combustion is a chemical reaction that consumes oxygen and produces heat. The byproduct of the reaction is CO2. For every MWh of electricity generated, 2,000 lbs of CO2 is produced. CO2 is difficult to capture and bad for the environment. Ohio State University found a way to release the heat without burning. They carefully control the chemical reaction so that the coal never burns. Since the coal was never burned so the CO2 is entirely contained inside the reactor.
In the new process, the coal is been ground into a powder and metal beads made of iron oxide composites are used. The coal particles have size about 0.1 mm and the iron beads are 1.5 - 2 mm
The coal and iron oxide are heated to high temperatures, where the materials react with each other. Carbon from the coal binds with the oxygen from the iron oxide and creates CO2, which rises into a chamber where it is captured. Hot iron and coal ash are left behind. Because the iron beads are so much bigger than the coal ash, they are easily separated out of the ash, and delivered to a chamber where the heat energy would normally be harnessed for electricity. The coal ash is removed from the system.
The CO2 is separated and can be recycled or sequestered for storage. The iron beads are exposed to air inside the reactor, so that they become re-oxidized to be used again. The beads can be re-used almost indefinitely, or recycled.
Since the process captures nearly all the carbon dioxide, it exceeds the goals that USA's Department of Environment has set for developing clean energy.