Oxygen Carriers for Chemical‐Looping with Oxygen Uncoupling (<scp>CLOU</scp>)

Mattisson, Tobias; Whitty, Kevin J.

doi:10.1002/9783527809332.ch7

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“…Manganese oxides have been combined with iron, silicon, calcium, nickel, magnesium, and copper. , The combined oxide system of manganese and iron has been extensively investigated for chemical looping. − Combined oxides of calcium and manganese in the form of perovskites have been examined in chemical-looping reactors of various sizes in the most recent years. − Recent research has also focused on combined oxides of silicon and manganese, as well as combined oxides of iron, manganese, and silicon. These materials have been examined in laboratory batch reactors. , Two combined manganese and iron oxides and five combined manganese, iron, and silicon oxides , have been operated continuously in a 300-W th reactor system. Combined oxides of manganese and silicon with small amounts of magnesium, titanium, calcium, and aluminum were investigated in a laboratory batch reactor …”

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confidence: 99%

Performance of Combined Manganese–Silicon Oxygen Carriers and Effects of Including Titanium

Hanning¹,

Frick²,

Mattisson³

et al. 2016

Energy Fuels

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Combined oxides of manganese and silicon were previously identified as suitable oxygen carriers for chemicallooping combustion. In this study, one pure manganese−silicon oxide and one similar material with titanium included in the formulation were examined as oxygen carriers. Experiments studying the oxygen release and the reactivity with syngas, methane, and wood char were carried out in a bench-scale circulating chemical-looping combustor and in a batch fluidized-bed reactor in the temperature range of 800−1050 °C. Both oxygen carriers released oxygen in inert atmosphere, and the concentration of oxygen released increased with temperature. The conversion of syngas and methane also increased with temperature for both materials and in both experimental setups. The reactivity with devolatilized wood char showed that the rate of oxygen uncoupling increased with temperature. However, it was concluded that the main fuel conversion mechanism was CLC and not CLOU for these materials. The inclusion of titanium in the manganese−silicon combined oxide significantly affected the physical properties of the oxygen-carrier particles. The MnSi particles could be operated for only 7 h in the bench-scale circulating chemical-looping combustor before the circulation was disrupted by the large formation of fines. The MnSiTi particles were operated for 24 h in the circulating unit without any circulation disruption. It was concluded that it is possible to greatly decrease the attrition rate of the particles by including titanium in the formulation. However, the inclusion of titanium lowered the reactivity with fuel. As the thermodynamic properties are very similar for the two oxide systems, the reduced reactivity is most probably an effect of the lower porosity of MnSiTi. This emphasizes the importance of optimizing the physical structure of oxygen-carrier particles. The physical structure of the particles was found to be greatly affected by the inclusion of titanium, giving, for example, a higher resistance to attrition. The physical structure of the particles is important for fuel conversion as well, as it will likely have implications on the internal diffusion in the particles.

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