New generalized strategy for improving sorption-enhanced reaction process

Abstract

The generalized principle of temperature-induced equilibrium shift was applied to improve the sorption-enhanced reaction (SER) process by controlling the subsection-wall temperature. The other auxiliary subsection-controlling parameters include the number of subsections, the subsection-packing ratio of adsorbent and catalyst, and the side-feed/removal position of the reactants/products. In this paper, a four-step one-bed with three-subsections SER process for steam-methane reforming was taken as an example for hydrogen production, where higher temperature (about 450–490°C) was adopted for subsections-I (inlet zone of the adsorptive reactor) and -II (middle zone of the adsorptive reactor) and lower temperature (about 400–450°C) for subsection-III (outlet zone of the adsorptive reactor), lower packing ratio of adsorbent and catalyst for subsections-I and -III and higher ratio for subsection-II. The feasibility and effectiveness of the subsection-controlling strategy for improving the SER process is analyzed by numerical simulation based on the basic data from literature. A product gas with above 85% hydrogen purity and traces of CO 2 (less than 300 ppm ) and CO (less than 30 ppm ) was continuously produced by using a 6 m long adsorptive reactor with three-subsections and can be directly used in fuel cell applications. The results show that subsection-controlling strategy is an easy and efficient way. The remarkable characteristics of this new process are: (1) the concentrations of CO and CO 2 decrease greatly in the product gas due to the principle of temperature-induced equilibrium-shift, (2) the hydrogen productivity (mole of hydrogen/kg of solid per cycle; CO is less than 30 ppm ) is over twice as large as in the normal SER process, (3) the length of unused bed for adsorption is apparently reduced, and (4) the regeneration of adsorbent can be performed by steam at normal atmospheric pressure.