Research On Preparation Of Nickel Ferrite Oxygen Carrier And Its Chemical Looping Combustion Performance

Emissions of greenhouse gases is considered to be the main cause of global warming, and CO2is one of the main greenhouse gas. Therefore, it is generally accepted that a reduction in emissions of greenhouse gases is necessary as soon as possible. Compared with conventional combustion, the dominating advantage of CLC is that it can achieve high concentration CO2only by condensing the exhaust gas without any extra energy penalty. In addition, CLC can minimize formation of NOx at the same time.For CLC, The key issue in the system performance is the oxygen-carrier material. NiO as oxygen carrier has a high reactivity for reduction and oxidation reactions and sufficient oxygen transport capacity, however, the formation of carbon on the surface was correlated to low conversion of the fuel. Fe2O3is considered an attractive option for CLC applications because it is low cost and environmental compatibility. At the same time, it has some disadvantages, such as its weak redox characteristics, low methane conversion and oxygen transport capacity. These constrain the applications of oxygen carrier in CLC. Therefore, NiFe2O4, was first proposed as oxygen carrier. In this paper, the reaction of NiFe2O4with gas fuel (CO and H2) and lignite was studied using TGA.The reaction of NiFe2O4with CO and H2at750℃,850℃and950℃was found that the temperature of850℃is more favourable for the reaction. The investigation of gas fuel with oxygen carrier (NiFe2O4、NiO、Fe2O3) was performed in TGA at850℃. It was found that the activity of NiFe2O4was in between NiO and Fe2O3, and the surface of NiO existed serious carbon deposition, while NiFe2O4, Fe2O3mild carbon deposition phenomenon existed. It has been observed that NiFe2O4showed an excellent chemical stability and high activity in multicycle tests in thermobalance.The pyrolysis reaction of lignite was conducted under the atmosphere of N2and CO2, and found that it was thoroughly under N2. The investigation of lignite with oxygen carrier (NiFe2O4、NiO、Fe2O3) was performed in TGA at850℃. It was found that the activity of NiFe2O4was in between NiO and Fe2O3. The reaction of NiO with lignite was complete in70minutes, while the conversion of NiFe2O4and lignite was only50.42%. From the EDX analysis of the residues of NiO, carbon deposition was found. The coal ash can provent the oxidation of NiFe2O4, so for the application of CLC to coal, separation of ash generated will be important to the success.