| Description |
The chemical-looping technology is quickly becoming an attractive alternative for the combustion of fossil fuels in energy production. With the rapid growth in the anthropogenic production of carbon dioxide (CO2) due, in large part, to the combustion of fossil fuels, it is becoming increasingly important to identify technologies that are capable of producing energy, at the same rate as traditional fossil-fuels units, while serving in a secondary capacity of managing emissions. Among the materials suggested for use in chemical-looping, copper-oxide has emerged as a front runner. Materials such as copper oxide allow the direct combustion of solid fuels, without an intermediary gasification step, by spontaneously decomposing from cupric oxide (CuO) to cuprous oxide (Cu2O), liberating free oxygen in the process. The rate at which these particles decompose can be as much as 50 times faster than the rates of gasification. This work provides the academic community with results geared toward the production and implementation of copper-based oxygen carriers by: 1. Developing novel oxygen carrier materials and, 2.Developing models describing both the oxidation and decomposition of copper oxide-based materials. It has been determined that the decomposition of copper-oxide is well described by a global reaction rate for a wide range of copper oxide-based oxygen carrier materials. This global reaction rate suggests that the activation energy of decomposition that best predicts reaction rates of the different CuO-based materials is 62 kJ/mol and that the rate law has a zero order dependence on the concentration of the solid carrier. The modeled oxidation kinetics of Cu2O to CuO for two different oxygen carrier materials is presented. Unlike the simple case of decomposition of CuO, the oxidation of Cu2O is highly dependent on the solid concentration. During oxidation, the volume change of the solid is about a 5% increase. This causes a pore-blocking effect which is observed at low temperatures (below 700°C). However, at higher temperatures (above 800°C), this effect is not apparent. These two regimes are best described by two different kinetic models: pore-blocking kinetics is used for the lower temperature regime while nucleation/growth kinetics, given by Avrami-Erofeev, is used to model the higher temperature regimes. |
