Structural and Thermodynamic Studies of Ilmenite Oxygen Carriers for Chemical Looping

Abstract

To overcome the carbon dioxide effects on the environment, chemical looping processes are considered a novel way of burning carbonaceous fuel in which CO2 can be inherently separated. Chemical looping combustion (CLC) is a promising technology to separate CO2 from power plants that contains two reactor beds, a fuel reactor, and an air reactor. Solid oxygen carriers move cyclically between these interconnected reactors for the transfer of oxygen from the air to fuel without any contact between them. Ilmenite (FeTiO3), is an attractive and low-cost promising oxygen carrier material for CLC. This project aims to study the structural and thermodynamic properties of ilmenite through several characterizations to investigate the feasibility of using ilmenite as an oxygen carrier in chemical-looping combustion. Ilmenite show low reactivity towards fuel in CLC. Cerium due to its catalytic properties was used as an additive in ilmenite to enhance its reactivity and oxygen transport capacity. Preparation of material was done by the Solid-state reaction method. The thermogravimetric analysis (TGA) technique was used to investigate the redox cycle behavior, OTC, fractional oxidation, and fractional reduction of mass of ilmenite at a temperature of 900℃. Oxygen transfer capacity (OTC) of ilmenite increased from 0.53% to 1.41% with a gradual increase in the amount of ceria. The structural properties are studied with the help of XRD and obtained a cubic fluorite structure for both Cerium oxide and iron titanium oxide. The identification peak of ilmenite was observed at 413cm-1, 403cm-1, and 395cm-1 wavelengths, and cerium oxide shows the peaks at second order bands are observed through Raman Spectra of the synthesized material. The vibratory characteristics are studied through FTIR spectroscopy. The peak at 657cm-1 may show the stretching vibrations of Fe-O and Ti-O. The characteristic band of Ce-O vibrations considers being a shoulder peak at 810cm-1 wavenumber. Some stretching bands of C-O and O-H are also observed. SEM analysis confirms the formation of the pores on the ilmenite surface due to cerium oxide diffusion and iron ions migration from bulk to the particle surface. Similarly, confirmation of elemental composition was done by EDX