Thermodynamic and Equilibrium Composition Analysis of Using Iron Oxide as an Oxygen Carrier in Nonflame Combustion Technology

Nonflame combustion technology （NFCT） is a harmonious energy utilization technology. There are not environmental-unfriendly gases such as NOx, CO2 discharged in the whole combustion process. Combustion processes realizes zero emission through this technology. Fe2O3 is involved as oxygen carrier, is examined thermodynamically, and the thermodynamic data of the redox reactions are calculated. Using the criteria of minimizing the Gibbs free energy, the equilibrium composition was investigated. The equilibrium analysis shows that producing complete oxidized resultants must have high molar ratio of Fe2O3/CH4. If quantity of Fe2O3 is not sufficient, more partial oxidized products such as CO, H2, even C will be produced.

Thermodynamic Analysis and Experimental Investigation into Nonflame Combustion Technology(NFCT) with Thermal Cyclic Carrier

The utilization of fossil fuels causes serious negative impacts on the environment and human life. To mitigate greenhouse gases and other pollutants, a novel combustion process-the nonflame combustion technology with a thermal cyclic carrier of molten salt is introduced. In this technology, a whole combustion is divided into two steps, i.e., the section of producing oxide and the section of combustion. In the first step, oxygen is separated from air, and pure N_2 is simultaneously formed which is easily recovered. In the other step, the fuels react with lattice oxygen in the oxides formed in the first step, and at the same time, thermal energy, CO_2 and H_2O vapor are produced. It is noted that the CO_2 is easily separated from water vapor and ultimately captured. Theoretically, there are no environmental-unfriendly gases such as CO_2, NO_x and SO_2 discharged in the whole combustion process. Some metal oxides scattered into molten salts play the roles of oxygen carriers in the combustion system, and they can constantly charge and discharge oxygen element from air to fuels during the combustion process. A nonflame combustion system with Li_2CO_3+K_2CO_3+Na_2SO_4 as the molten salt system, CH_4 as the fuel and CuO as the catalyst was experimentally investigated. The experimental results show that the combustion process proceeded as it was theoretically analyzed, and CO_2 with a high volume fraction of 77.0%_95.0% and N_2 with a high volume fraction of 91.9%_99.3% were obtained. The high concentration of CO_2 is favorable for capturing and storing subsequently. Therefore, the potential of reducing CO_2 emissions of this nonflame combustion technology is huge.