Comparison of composite metal oxides as oxygen carrier for methane chemical looping reforming

The amount of greenhouse gases has increased considerably in recent years. Additionally, the energy required by humanity for daily activities is also on the rise. The planet is facing one of its worst crises, characterized by the overexploitation of fossil fuels due to population growth. It is estimated that by 2050, the global population will exceed 9 billion inhabitants. Chemical looping combustion (CLC), offers a potential solution. This process involves usually two interconnected reactors, usually with a fluidized bed, where combustion takes place in an alternate way. In this process, the oxygen required for combustion is provided by a solid oxygen carrier, the capacity of this depends on the nature of the material and is crucial to define the most effective one by a comparative study. Moreover, methane emissions are a significant concern, as methane is a potent greenhouse gas with a 25 times greater impact on the atmosphere compared to carbon dioxide as greenhouse gases. To address this, methane reforming in chemical cycles, such as Steam Reforming Chemical Looping Combustion (SR-CLC) or chemical looping reforming (CLR), is proposed. Using a Gibbs reactor and oxygen carrier data reported in the literature, the analysis of NiWO4, FeMoO4, Fe2MnO4 and FeZnO4, their operation, energy yield when exposed to a methane stream and the comparison between different forms of reforming schemes, as well as the estimation of the carrier needed for the process, are presented. Results indicate that after calculations, the g-carrier/g-fuel ratio for NiWO4 is almost 100 % higher than the other carriers studied in this work. Water vapor reforming generates 30.0930 kW and a stream of pure hydrogen that can be separated while carbon dioxide reforming is a general endothermic process that requires 12.22 kW of energy for this process scheme. Once the ideal carrier has been analyzed, the proposed future work should focus on the optimal design of a reaction system that will allow it to operate efficiently under the conditions encountered. In addition, it will be necessary to find the replacement rate for the carrier that will allow us to operate our system continuously.