Macroscopic analysis of chemical looping combustion with ilmenite versus conventional oxides as oxygen carriers

Abstract

Over 40% of global energy-related CO2 emissions are due to the combustion of fossil fuels for electric energy generation. Albeit CO2 capture and storage have been identified as promissory actions to mitigate its emissions, the problem separating N2 and CO2 remains. A very effective solution for the former problem is to obtain the combustion CO2 as a pure molecule, which is possible using the Chemical Looping Combustion (CLC) technology, which uses a solid oxygen carrier to transport the oxygen from an oxidating media (regeneration reactor) to a reducing media (combustion reactor). One of the key issues to apply CLC is to find or develop some material, suitable from the kinetic and thermodynamic points of view, for the reduction-oxidation cycles taking place inside combustion and regenerator reactors. The evaluation of “oxygen carrier” candidates for CLC is based on reactivity (rates and conversions), resistance to carbon accumulation, and “regenerability”, which means the ability of the material for cyclic reduction and oxidation. Another challenging issue to use CLC processes is the loss of oxygen carrier; this problem involves the use of supported metals on materials, such as zirconia, Al2O3, etc. Preparation of this kind of supported carriers requires time, money, and equipment. Meanwhile, the natural mineral ore named ilmenite, which consists of a mixture of iron and titanium oxides, and do not need to be supported, has been seen as promising to increase CLC efficiency as oxygen carrier. In this work, the performance of ilmenite is compared with some other oxygen carriers used in CLC.

Integration of Chemical Looping Combustion to a Gasified Stream with Low Hydrogen Content

“…Fe 2 O 3 supported on MgAl 2 O 4 , for instance, has demonstrated significant reactivity in fluidized bed reactors [15]. While NiO-based carriers have shown promising results at pilot scale, their toxicity and environmental impact raise concerns [6].…”