|TITLE||A Carbon Dioxide Decomposition Technology Using Oxygen Deficient Iron Oxides.
(Joint Program to Promote Technological Development with the Private Sectors)
RITE|FUKUOKA@NO.2 LABORATORY in KYUSHU ELECTRIC POWER CO., INC.
For the purpose of reducing the amount of carbon dioxide discharged from power plants, we developed a carbon dioxide decomposition technology which used activated iron oxides. Activated iron oxides are formed by deoxidizing iron oxides over hydrogen. They have a spinel structure and are strong reducing agents. When carbon dioxide gas is ventilated and allowed to react with them, oxygen atoms in molecules of carbon dioxide become incorporated into the oxygen deficient parts of the iron oxides. The carbon atoms in the carbon dioxide molecules are fixed to the surface of the iron oxides. The fixed carbon atoms are highly reactive and converted into methane by hydrogen. These reactions proceed in the range of 300 to 400. We carried out studies on the iron oxides concerning properties, configuration and temperature to elucidate their optimum working conditions. The gas containing 20% carbon dioxide (nitrogen balanced) by volume was completely decomposed by the iron oxides at 350 in a laboratory test. The concentration of the gas was equal to that of the exhaust gas of LNG power plants. Next, we developed a technology to utilize the carbon atoms that fixed on the iron oxides. We also optimized methanation using the iron oxides as well as carbon dioxide decomposition. The fixed carbon atoms were converted almost completely into methane by hydrogenation at 350. A system to effectively utilize carbon was also investigated. It was concluded that repeatedly alternating between carbon dioxide decomposition reaction and the methanation reaction while circulating a gas mixture of unreacted hydrogen and produced methane could generate methane at high concentrations of 80% and greater from the carbon dioxide of the exhaust gas.