(133g) Particle Model Development and Validation for the Conversion of Boehmite to ?/?-Alumina Driven By Concentrating Light

Solar energy conversion to chemicals and fuels receives progressively more attention. Many of the possible conversion routes incorporate particles or could be transformed into particle-phase reactions. When the particles are diluted into a fluid stream, usually a carrier inert gas or a reacting gas mixture, belong to the large family of aerosol processes. An aerosol process is the central theme of this presentation; particularly, one where solid particles are directly irradiated with concentrated light.

Aerosol phase reactors with a directly irradiated reaction zone can employ direct solar power with potentially higher solar to chemical energy efficiencies than the indirect solar reactors. Many studies investigate particle reactors such as fluidization and moving, but only a few of them focus on aerosol reactors. On the other hand, aerosol phase processes are very similar to solid fuel combustion and gasification, and free-board reactions. Therefore, in this study, we investigated the particle phase reactions of aluminum hydroxides (boehmite or gibbsite) converted to γ- and a-alumina. Two aluminum oxides favored for their unique properties in industrial catalysis and refractory ceramics, respectively.

The aluminum hydroxides as dry particles or water-based solutions have been exposed to various dosages of concentrating light, i.e., variable irradiance levels and exposure duration. The experiments have been conducted at our high flux solar simulator facility, which utilizes six Xe-arc lamps of 6KWe each, able to achieve heat fluxes of more than 5,000 kW/m2. The calcined and irradiated particles have been characterized with the combined use of scanning electronic microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffractometry (XRD), and attenuated total reflectance (ATR). The experimental observations were employed to develop a mathematical model and the results to fit the model parameters. After the successful verification and validation of the model, it was applied to predict the transient evolution of the particles exposed to concentrating light. Overall, the numerical model can predict the particle phase reactions accurately. However, the numerical predictions are very sensitive to the irradiance levels. In other words, the predictions of the particle model can vary significantly depending on the assumed irradiance of the concentrating light, which implies that further work is essential in order to estimate the overall solar-to-chemical energy conversion efficiency.