Operation with Combined Oxides of Manganese and Silica as Oxygen Carriers in a 300 Wth Chemical-looping Combustion Unit

Chemical-looping combustion is a carbon capture technology which has received increased attention during the last years. The technology is based on fuel oxidation with oxygen provided by solid oxygen carrier particles. In this study two such oxygen carrier materials have been examined in a continuously circulating chemical-looping reactor system designed for a thermal power of 300 W. The two materials consisted of manganese and silica oxides, with an addition of titania in one of them. The oxygen carrier particles were produced by spray drying, followed by calcination and sintering. Both materials released gas phase oxygen in inert atmosphere at 800-950 °C, with the highest concentration at 1.8% observed at 850 °C. The oxygen carrier consisting of only manganese and silica gave the highest fuel conversion for both syngas and natural gas. Full fuel conversion was achieved at 950 °C for syngas and at 900 °C for natural gas with this oxygen carrier material. The fuel conversion increased with temperature for both materials. The material consisting of only manganese and silica suffered from severe attrition and could only be operated for seven hours with fuel. The addition of titania increased the mechanical stability of the particles considerably, and this material was operated for 24 h with fuel. No large production of fines was observed with this material. Combined oxides of manganese and silica are shown to be promising as oxygen carriers for chemical- looping. The mechanical stability can be increased by adding titanium to the MnSi material. The composition would however need to be further examined to optimize the performance of the oxygen carrier