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317228 Evaluation of Spray Dried Oxygen Carriers Based On Manganese Ore and Ca(OH)2 for Chemical-Looping With Oxygen Uncoupling
Evaluation of spray dried oxygen carriers based on manganese ore and Ca(OH)2 for chemical-looping with oxygen uncoupling
Sebastian Sundqvist†,*, Tobias Mattisson‡, Henrik Leion†, Anders Lyngfelt‡.
† Department of Chemical and Biological Engineering, Division of Environmental Inorganic
Chemistry, Chalmers University of Technology, S-412 96 Goteborg, Sweden
‡ Department of Energy and Environment, Division of Energy Technology, Chalmers University of
Technology, S-412 96 Goteborg, Sweden
*Corresponding author
The suitability of an oxygen carrier in chemical-looping combustion (CLC) or chemical-looping with oxygen uncoupling (CLOU) is determined by its lifetime and reactivity. Both are factors relates to the cost of the oxygen carrier in relation to the amount of carbon dioxide captured. There are likely losses of oxygen carrier from attrition in continuous operation and in the case with solid fuels there are additional losses expected together with the ash extraction. Hence there is a need to produce inexpensive oxygen carriers which requires the use of cheap raw materials, such as ores or industrial waste materials.
One type of oxygen carrier that has been shown to have reasonable reactivity is the perovskite structured calcium manganite, or CaMnO3. The oxygen carrier has oxygen uncoupling properties, that is, it releases oxygen in the gas phase, the amount which is governed by the partial pressure of oxygen in the surroundings. In this project, the aim was to produce a CaMnO3 particle from cheap raw materials such as manganese ore and commercial Ca(OH)2 and test these with respect to parameters important for CLC and CLOU.
Several oxygen carriers of CaMnO3 have been produced utilizing different manganese ores as starting material. The manganese ores were mixed with commercial Ca(OH)2 and each material was calcined at both 1200°C and 1275°C for 4h. Particles were then produced using spray-drying and sieved to obtain particles in the size range of 125-180 µm. The evaluation was conducted in a fluidized batch reactor, where the particles were alternatingly exposed to reducing and oxidizing conditions using methane CH4 and syngas (50/50 H2/CO) at 950°C. For the experiment 15 g of oxygen carrier was used with a flow of 450 ml/min of reducing gas. The oxygen carriers were also evaluated at different temperatures (850°C-1050°C) under inert conditions to measure the oxygen release (CLOU properties) and conversion of CH4.
Most of the oxygen carriers have full conversion of syngas but the results for CH4 conversion varies greatly between the different materials, with the average conversion ranging between 40-75% under the reducing period. However the release of oxygen during inert conditions is almost the same for all materials. The oxygen release also increases with temperature, and for some oxygen carriers the oxygen release rate doubles with a temperature increase of just 50°C.