Label-Enhanced Surface Plasmon Resonance: A New Concept for Improved Performance in Optical Biosensor Analysis

Peer reviewe

Chemical-Looping Using Combined Iron/Manganese/Silica Oxygen Carriers

Combined oxides of iron, manganese and silica have been used as oxygen carriers for chemical-looping combustion. Three materials with varying composition of iron, manganese and silica have been evaluated in oxygen release experiments and during continuous operation with syngas and natural gas as fuel. The concentration of oxygen released increased as a function of temperature and the highest concentrations of oxygen were measured with the material with the highest fraction of manganese. It was also this material which gave the best conversion of both syngas and natural gas; essentially full conversion of syngas and above 95% conversion of natural gas above 900\ub0C. The other two materials showed similar performance, albeit with higher syngas conversion for the material with the lowest manganese fraction and the lowest conversion of natural gas for the same material. The materials lasted for 10-14 h of operation with fuel addition before circulation disruption occurred, which was likely caused by particle attrition in all three cases. A phase diagram of the iron-manganese-silica system was constructed and the possible relevant phase transitions were identified. This analysis showed that more phase transitions could be expected for the materials with higher manganese content which could explain the superior performance of the material with the highest manganese content. This could possibly also explain the much higher oxygen release of this material. It should however be noted that this material was operated with the highest fuel reactor inventory per thermal power which could also be a contributing factor to the better performance of this material.The study shows that it is possible to achieve very high fuel conversion with combined oxides of iron, manganese and silica as oxygen carrier. The mechanical stability of the particles was rather poor though and would need to be improved. On the other hand the findings relating to material stability is not necessary valid for natural materials containing a number of additional elements. The results are also of interest as an indication of how natural materials with similar composition, i.e. manganese ores, would perform as oxygen carriers

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 \ub0C, with the highest concentration at 1.8% observed at 850 \ub0C. 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 \ub0C for syngas and at 900 \ub0C 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

Chemical-Looping Using Combined Iron/Manganese/Silica Oxygen Carriers

Combined oxides of iron, manganese and silica have been used as oxygen carriers for chemical-looping combustion. Three materials with varying composition of iron, manganese and silica have been evaluated in oxygen release experiments and during continuous operation with syngas and natural gas as fuel. The concentration of oxygen released increased as a function of temperature and the highest concentrations of oxygen were measured with the material with the highest fraction of manganese. It was also this material which gave the best conversion of both syngas and natural gas; essentially full conversion of syngas and above 95% conversion of natural gas above 900\ub0C. The other two materials showed similar performance, albeit with higher syngas conversion for the material with the lowest manganese fraction and the lowest conversion of natural gas for the same material. The materials lasted for 10-14 h of operation with fuel addition before circulation disruption occurred, which was likely caused by particle attrition in all three cases. A phase diagram of the iron-manganese-silica system was constructed and the possible relevant phase transitions were identified. This analysis showed that more phase transitions could be expected for the materials with higher manganese content which could explain the superior performance of the material with the highest manganese content. This could possibly also explain the much higher oxygen release of this material. It should however be noted that this material was operated with the highest fuel reactor inventory per thermal power which could also be a contributing factor to the better performance of this material.The study shows that it is possible to achieve very high fuel conversion with combined oxides of iron, manganese and silica as oxygen carrier. The mechanical stability of the particles was rather poor though and would need to be improved. On the other hand the findings relating to material stability is not necessary valid for natural materials containing a number of additional elements. The results are also of interest as an indication of how natural materials with similar composition, i.e. manganese ores, would perform as oxygen carriers

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

Combined oxides of manganese and silicon have earlier been identified as suitable oxygen carriers for chemical-looping combustion. In this study, one pure manganese-silicon oxide and one similar material with titanium included in the formulation have been examined as oxygen carriers. Experiments studying the oxygen release and the reactivity with syngas, methane and wood char have been carried out in a bench-scale circulating chemical-looping combustor and in a batch fluidized-bed reactor in the temperature range 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 could be 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 only be operated for 7 h in the bench-scale circulating chemical-looping combustor before the circulation was disrupted due to the large fines formation. 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 the 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 the fuel conversion as well, as it will likely have implications on the internal diffusion in the particles

Investigation of a calcium manganite as oxygen carrier during 99 h of operation of chemical-looping combustion in a 10 kWth reactor unit

Chemical-looping with oxygen uncoupling is a technology for combustion with inherent carbon dioxide separation. A solid oxygen carrier circulates between the fuel reactor, where it provides oxygen for fuel oxidation, and the air reactor, where it is reoxidized. In this study a 10 kWth pilot reactor was used to examine a calcium manganite based oxygen carrier in continuous operation with natural gas as fuel during 99 h. The composition of the oxygen carrier can be described by the formula CaMn0.775Ti0.125Mg0.1O3-δ. The main part of the material forms a perovskite crystal structure which has oxygen releasing properties. The fuel conversion was generally above 95% and full conversion was reached for certain operating conditions. The elutriation of fines, defined as particles smaller than 45 μm, decreased over time to eventually be below detection limit. That suggested a loss of fines of less than 0.011 wt%/h, indicating a lifetime of over 9000 h. A high fuel conversion with no thermodynamic limitation, good mechanical strength, low cost and very low toxicity shows that this calcium manganite material qualifies as a very promising oxygen carrier