Study on stable hydrogen production by indirectly solar thermal methanol steam reforming

The indirectly heated solar reactor can eliminate the effect of fluctuating solar radiation on the reactor for continuous and stable hydrogen production. In order to investigate the effects of different heat transfer fluids and flow arrangements on reactor performance, this paper first established a three-dimensional numerical model to analyze the heat and mass transfer process in the indirectly heated reactor. Solar thermal oil (STO), which has both good fluidity and thermal storage properties, is more suitable for the indirectly heated methanol steam reforming reactor than molten salt and hot air. The reactor under counter-flow arrangement achieved higher methanol conversion and higher thermal efficiency than under co-flow arrangement. Afterwards, based on the indirectly STO heated reactor with counter-flow arrangement, the effects of STO inlet temperature, weight hourly space velocity (WHSV), molar ratio of steam to methanol (S/C) on methanol conversion, hydrogen production rate, and CO selectivity were further experimentally analyzed. Also, the operating parameters were optimized by Analysis of Variance method. The results indicated that increasing the STO inlet temperature and S/C as well as decreasing the WHSV and catalyst particle size both improved methanol conversion. Compared to other factors, STO inlet temperature had the largest significance on the reactor performance responses. Under optimal condition with STO inlet temperature of 553K, WHSV of 1.78 h⁻¹ and S/C of 1.3, the reactor obtained methanol conversion of 92.15 %, hydrogen production rate of 53.87 ml min⁻¹∙g⁻¹ and CO selectivity of 5.80 %.