(559i) Invited Talk: Numerical and Experimental Investigation of Aerosol Particles Reactions Driven By Concentrating Solar Power

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; specifically, one where solid or liquid particles are directly irradiated with concentrated solar power.

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 the oxygen evolution step of the sulfur-ammonia water-splitting cycle where ammonium and potassium-based sulfate particles decompose and convert to pyrosulfates with the gradual release of ammonia and sulfur oxide gases.

Particles of different compositions were synthesized via evaporation, crystallization, and drying of precursor aqueous solutions of potassium sulfate, potassium pyrosulfate, and ammonium sulfate. The onset temperatures, reaction energies, and exact mechanisms were extracted using bench-scale experiments with a combination of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transformation infrared spectroscopy (FTIR), and mass spectroscopy (MS). 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 evolution of the particles exposed to concentrating light. Finally, more experiments were conducted into our high flux solar simulator to compare the numerical with experimental results. 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.