NiO/NiAl2O4 載氧體應用於化學迴圈之研究

Abstract

For combustion with CO2 capture, chemical looping combustion (CLC) with inherent separation of CO2 is a promising technology. CLC is the new technology developed in recent years, which is used the metal oxide as an oxygen carrier, which can help to enhance the capturing of carbon dioxide effectively. This study was discussed the performance of nickel-based oxygen carrier in chemical looping. The experiment was synthesized NiAl2O4 spinel as a support through the urea combustion method, evaluating the effect of urea/nitrate (U/N) ratio and calcination temperature. In addition, the effects of supports and metal loadings for supported oxygen carriers, on the performance of chemical looping combustion were compared. In addition, several transition metal based oxides (Cu and Fe) with the spinel structure have been prepared, characterized and compared. Characterization of samples was analyzed by using the techniques of Brunauer–Emmett–Teller (BET) surface area, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and temperature-programmed reduction (TPR). The capacity of oxygen carrier was tested using a TGA apparatus simulating the oxidation and reduction periods in CLC. In this work, the behavior of an impregnated supported oxygen carrier (MO/NiAl2O4) was studied in a TGA using methane as fuel gas and fuel and the air reactor temperatures at 850 °C. The stability of oxygen carriers were exposed to a total of five and twenty oxidation/reduction cycles. Experimental results of chemical looping combustion indicated that the highest oxygen transfer capacity is achieved when the NiO/NiAl2O4 oxygen carrier is supported on NiAl2O4 support with U/N ratio of 1 and calcination temperature of 900 °C. Moreover, NiAl2O4 as inert supports can avoid the reaction between NiO and Al during chemical looping combustion processes. The 7Ni-UN1-9 was showed high stability after repeating re-oxidation reaction in twenty cycles. In summary, a NiAl2O4 carrier support with low crystallinity, large specific surface area and low microporosity is likely to have a higher oxygen transfer capacity. This study is of interest for application of NiO/NiAl2O4 materials in CLC processes.