Comprehensive study on parabolic trough solar receiver-reactors via a novel efficient optical-thermal-chemical model of catalyst packed bed characteristics

Abstract

The catalyst packed bed structure plays an important role in the promising solar-driven catalyst packed bed based thermochemical hydrogen production systems. However, corresponding accurate yet efficient numerical methods for characterizing and optimizing the catalyst packed bed structure as well as the whole complex solar-driven thermochemical process is still urgently needed. In this paper, a novel three-dimensional comprehensive model is proposed for the hydrogen production of methanol steam reforming reaction (MSRR) in parabolic trough solar receiver-reactors (PTSRR). A relatively realistic porosity distribution obtained by the discrete element method was combined with the optical-thermal-chemical coupling model. The proposed model was validated, proved to improve the accuracy of numerical predictions in a more efficient way. Moreover, it was effectively applied to tune the overall energy flow of the complex optical-thermal-chemical process of PTSRR-MSRRs for better performance, by optimizing the catalyst packed bed structure in aspects of catalyst sizes and packing methods. The results revealed that single packed beds of larger catalyst particles show better performance within the selected catalyst size range. The radial layered packing method of larger particle-to-particle diameter ratios can bring higher energy conversion efficiency and lower flow resistance, as compared to the single packing method and fully mixed packing method. This study could provide an efficient numerical modelling method and significant guidance for other similar solar-driven thermochemical applications of catalyst packed beds.