TGA and kinetic modelling of Co, Mn and Cu oxides for chemical looping gasification (CLG)

Abstract

Oxygen carriers for biomass gasification are capable of absorbing oxygen from air and desorbing it in the gasifier. Based on thermodynamic equilibrium, copper, manganese, and cobalt oxides have the highest oxygen release capacities among the different oxygen carriers. These oxygen carriers were deposited on alumina via incipient wetness impregnation. The weight loss of the CuO-Cu 2 O carrier, as measured in a thermogravimetric analyzer, was 10 % while it was 7 % for the Co 3 O 4 -CoO couple and only 3 % for the Mn 2 O 3 -Mn 3 O 4 couple. The optimum operating temperature for the CuO oxygen carrier was 100 8C higher compared to the other two at 950 8C. A modified nuclei growth model (MNG) characterizes the weight loss/gain during the reduction-oxidation cycles. The reduction rate is 3 times higher at 875 8C compared to 825 8C while the oxidation rate decreases more than 10 times. The CuO carrier surface area decreased by 70 %, while it was 30 % and 60 % in the Co 3 O 4 and Mn 2 O 3 carriers, respectively. Cobalt has a lower tendency to sinter at high temperature compared to either copper or manganese and has a higher oxygen transport capacity and oxidation-reduction rates. Therefore, despite its higher cost and toxicity, it might be considered as a potential oxygen carrier especially for solid fuel gasification.

Techno‐Economic Comparison of a 7‐MWth Biomass Chemical Looping Gasification Unit with Conventional Systems

“…On the other hand, X Red and t oc are related to each other according to the reaction rate expression [15]:…”

“…Aghabararnejad et al [15] compared the oxygen release capacity as well as oxidation, reduction rates of copper, cobalt and manganese oxides. They concluded that cobalt with 7 % of oxygen transport capacity has superior properties and can serve as an excellent oxygen carrier especially for solid fuel conversion.…”

Transient modeling of biomass steam gasification with Co3O4

“…Cobalt has a moderate oxygen carrying capacity (7% of its weight) but the oxidation-reduction rates are 3 times greater and the thermal stability is superior compared to manganese and copper. Furthermore, experiments in a bubbling fluidized bed (7.8 cm ID, 2 m height) in the presence of biomass have shown that, sulfur has little effect on the cobalt oxide performance [3].…”

“…The oxygen is provided from cobalt oxide by reduction of Co 3 outlet. The experimental data were used to validate a kinetic based approach model.…”

Experimental and Theoretical Study of the Interactions between Fe2O3/Al2O3 and CO

“…It should possess excellent properties, including enough reactivity, high oxygen transfer capacity, low production cost, environmental friendliness, and a low tendency of fragmentation and attrition [8][9][10]. The main materials used as OCs are transition metal oxides, such as Mn3O4, Fe2O3, NiO, CuO, and CoO [11][12][13][14][15][16]. Among these metal oxides, Fe-based OC has been recognized as one of the most promising candidates, because it possesses the advantages of being low cost, having a good thermal stability, and being environmentally friendly [17][18][19][20].…”