Abstract
Chemical Looping Combustion (CLC) technology has emerged as a promising alternative capable of restricting the effects of global warming due to anthropogenic gas emissions, especially CO2, through its inherent capture. This study aims to synthesize and evaluate Cu-based oxygen carriers supported on natural materials such as diatomite and kaolin, through the incipient wet impregnation method for CLC process applications. Oxygen carriers were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), and scanning electron microscopy with surface energy dispersive x-ray spectroscopy (SEM-EDS). The mechanical strength of the two oxygen carrier particles was determined after the sintering procedure resulting in high crushing force. Reactivity of oxygen carriers was evaluated in a thermobalance with CH4 and H2 gases. Different reaction pathways were attempted when undergoing the redox cycles: total direct reduction of CuO to Cu0 for Cu-K and partial reduction of CuO to Cu2O and CuO to Cu-D. However, the highest reactivity and reaction rate was achieved in Cu-D due to the pore structure of diatomite, the chemical composition and the resulting interaction between CuO and the support. H2 gas reactivity tests showed a higher conversion rate and greater stability between cycles for both oxygen carriers. Thus, the reducible CuO content present in Cu-Diatomite during the reactivity test with H2 as the fuel gas was ideal for achieving high solids conversion, tendency for greater stability and a higher reaction rate.
Highlights
Sustainability is one of the most important and necessary challenges for societies today
The conversions obtained by Cu-K and copper oxide supported on diatomite (Cu-D) were calculated from the possible redox reactions involved, according to their oxidation degree and in terms of sample weight variation, as shown in Figures 4a and b
It is reported that the reduction reactions occurred in two steps in both samples; the first when there is only N2(g) atmosphere, which involves reactions of the Chemical Looping with Oxygen Uncoupling (CLOU) process, causing the transformation of CuO → Cu2O, and the second when there is the supply of H2(g) or CH4(g) as combustible gases
Summary
Sustainability is one of the most important and necessary challenges for societies today. Carbon dioxide (CO2) is a long-lived anthropogenic gas in the atmosphere and there is an intensification of the effects of global warming due to its progressive emission from fossil fuel combustion processes (Takht & Saeed, 2014; Fernandes et al, 2019; Oliveira et al, 2020; Gomes et al, 2021). The Paris Agreement was established in order to limit these effects, requiring the decarbonization of the world’s energy systems, limiting the average global temperature increase to 2 °C for the century. In order to achieve this goal, Chemical Looping Combustion (CLC) has emerged as a promising technology for CO2 capture in power plants and industrial applications with low energy penalty compared to other competing CO2 capture and storage (CCS) technologies (Adánez-Rubio et al, 2018; Adánez et al, 2018; McGlashan et al, 2012; Wang, Yan et al, 2018)
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