Prospects of Al₂O₃ and MgAl₂O₄-Supported CuO Oxygen Carriers in Chemical-Looping Combustion (CLC) and Chemical-Looping with Oxygen Uncoupling (CLOU)

Abstract

The chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) processes are attractive solutions for efficient combustion with direct separation of carbon dioxide. In this work, the feasibility of CuO supported on Al 2 O 3 and MgAl 2 O 4 for CLC and CLOU processes are investigated. The oxygen carriers were produced by freeze-granulation and calcined at 950 and 1050°C. The chemical-looping characteristics were evaluated in a laboratoryscale fluidized bed at 900 and 925°C under alternating reducing and oxidizing conditions. Tendencies towards agglomeration, defluidization and loss of active phase were analyzed by changing the experimental process variables, such as reaction time, temperature and reducing and inert environments. Complete conversion of methane was obtained for all oxygen carriers investigated in this work. Three out of four oxygen carriers also featured the rapid release of oxygen in an inert environment (CLOU). In case of Al 2 O 3 as support, a CLC and a CLOU oxygen carrier were obtained depending on the calcination temperature. In addition, analyses of the CuO-Al 2 O 3 phase equilibria system under oxidizing and reducing conditions has been carried out. At the investigated temperatures, it is inferred for the case of Al 2 O 3 as support that part of the active phase (either CuO or CuAl 2 O 4) is bound as CuAlO 2 during incomplete reduction with slow kinetics for re-oxidation. However, when complete reduction is attained, the original active phase composition is rejuvenated upon oxidation. As a result, the use of CuAl 2 O 4 is suggested for CLC processes from the point of agglomeration and attrition-free functioning of the oxygen carrier. In case of MgAl 2 O 4 as support, the oxygen carrier exhibited a stable oxygen releasing behavior due to the existence of relatively intact CuO. Together with the absence of agglomeration and major morphological changes, the use of MgAl 2 O 4-supported CuO is suggested as a suitable oxygen carrier for CLOU processes.

Thermal-Chemical Characteristics of Al–Cu Alloy Nanoparticles

“…01-1153) produced by the chemical reactions between copper oxide and -, -alumina were also found, which is consistent with some early results [37][38][39].The main reaction paths in the temperature range of 600 ~ 1100 o C can therefore be proposed as…”

Preparation and Characterization of Lanthanum-Promoted Copper-based Oxygen Carriers for Chemical Looping Combustion Process

“…There were clear evidences of the formation of an integrated crystal phase between CuO and Al 2 O 3 , i.e., CuAl 2 O 4 spinel. This agreed with all previous studies regarding the use of copper as an ingredient of oxygen carriers (Adanez et al, 2006;Arjmand et al, 2011Arjmand et al, , 2012. The formation of CuAl 2 O 4 spinel was found for all tested oxygen carriers in this study although to different degrees.…”

Combined oxides as oxygen-carrier material for chemical-looping with oxygen uncoupling

“…CuO is commonly proposed and has been shown to release O 2 rapidly via reaction (6) at temperatures in the range of 850-950°C, see for example Leion et al [4], Gayán et al [5], Eyring et al [6] and Arjmand et al [7]. Further, Mn 2 O 3 could release O 2 via reaction (7), but reoxidation is restricted to low temperatures where the rate of reaction appears to be too slow to be practically applicable [3].…”