Kinetic analysis of a Cu-based oxygen carrier: Relevance of temperature and oxygen partial pressure on reduction and oxidation reactions rates in Chemical Looping with Oxygen Uncoupling (CLOU)

Abstract

The kinetic of reduction of CuO to Cu 2 O with N 2 +O 2 mixtures and the oxidation of Cu 2 O to CuO with O 2 of a Cu-based oxygen carrier for the CLOU process has been determined in a TGA. For kinetic determination, the O 2 concentrations were varied between 0 and 9 vol.% for reduction, and between 21 and 1.5 vol.% for oxidation reactions; temperature was varied between 1148 and 1273 K for the reduction and between 1123 and 1273 K for the oxidation. The oxygen carrier showed high reactivity 2 both in oxidation and reduction reactions. The nucleation and nuclei growth model with chemical reaction control properly described the evolution of solids conversion with time. The Langmuir-Hinshelwood model was able to describe the effect of oxygen concentration on reduction and oxidation rates. The reaction order was 0.5 for reduction and 1.2 for the oxidation. The kinetic constant activation energies were 270 kJ mol -1 for the reduction and 32 kJ mol -1 for the oxidation. The kinetic model was used to calculate the solids inventory needed in the fuel reactor for complete combustion of three different rank coals. It was possible to use a low oxygen carrier inventory in the fuel reactor (160 kg/MW th ) to supply the oxygen required to full lignite combustion.However, to reach high CO 2 capture efficiencies (³95%), oxygen carrier inventories in fuel reactor higher than 600 kg/MW th were needed with the lignite.

Characterization of a sol–gel derived CuO/CuAl2O4 oxygen carrier for chemical looping combustion (CLC) of gaseous fuels: Relevance of gas–solid and oxygen uncoupling reactions

“…6.A. Thus, re-oxidation of CuAlO 2 formed during reduction was not allowed, which was also observed by others in previous works [17,44] [31]. Considering the incomplete decomposition and oxidation of the CuAl 2 O 4 , the effective oxygen transport capacity was R OC,CLOU =2.2 wt.%, which means that only the first 40 seconds in Fig.…”

“…The results suggested that the solids inventory in the fuel reactor could be higher than 600 kg/MW th to reach CO 2 capture higher than 95% for the lignite combustion [31]. Thus, an excess of oxygen would be expected in gas stream from fuel reactor, if both high CO 2 capture and complete fuel combustion was desired.…”

Chemical-Looping Combustion and Gasification of Coals and Oxygen Carrier Development: A Brief Review

“…CLOU is considered a promising technology to burn solid fuels with CO2 capture [14]. Oxygen release from oxygen carriers, coal pyrolysis, and char/syngas combustion all take place in the fuel reactor (Reactions 3, 6-8) [46]. Three of the major metal oxide systems identified for CLOU are CuO/Cu2O, Mn2O3/Mn3O4, and Co3O4/CoO [14].…”

“…The impregnated carrier may have a slightly higher degree of dispersion of the active phase than the physically mixed carrier. Adábez-Rubio et al studied the kinetics of Cu-based oxygen carriers (Cu60MgAl) for CLOU using TGA [46]. The reduction of CuO to Cu2O was done under a mixture of N2 + O2 and the oxidation of Cu2O to CuO was done under O2.…”

“…CLC processes typically use two interconnected fluidized beds in both batch and continuous operation. TGA is also used to conduct comparison studies and provide helpful kinetic information [46].…”