Fractal channel design in a micro methanol steam reformer

Abstract

The aim of the present article is to study the fractal channel pattern design and the gradient catalyst layer in relation to their effects on the performance of a micro methanol steam reformer. A three-dimensional simulation model is established for the purpose of predicting the effects of bio-channel design on the performance of a micro-reformer. The CO concentration in the production gases, which is necessary to avoid the poisoned catalyst layers of low temperature fuel cells, is also investigated. In addition, the distributions of velocity and gas concentrations are predicted, and the methanol conversion ratios are also evaluated. Due to further decreases of the CO in product gases, a gradient catalyst layer arrangement is proposed to delay the timing of hydrogen generation and thus avoid the presence of hydrogen in the catalyst layer too long. This catalyst arrangement can effectively decrease the possibility of a reverse water gas shift reaction to reduce CO generation. Results showed that the fractal channel design increases the conversion ratio, decrease CO as well as decrease the pressure drop in the channels. Relative to a parallel channel design, the CO and methanol conversion ratio of this fractal channel design pattern with uniform catalyst layer can be decreased and increased by 17% and 8%, respectively, based on a 0.3 cc/min flow rate, respectively. Meanwhile, the pressure drops in the parallel channel design and in the fractal channel design were found to be 254 Pa and 51 Pa, respectively. From an energy consumption point of view, a low pressure drop also implies low input pumping power. Furthermore, compared to the fractal design with a uniform catalyst layer, the gradient catalyst layer was demonstrated to effectively increase the conversion ratio by 8.5% and decrease CO by 11% when the inlet liquid flow rate was fixed at 1.0 cc/min.