The operation types and operation window for high-purity hydrogen production for the sorption enhanced steam methane reforming in a fixed-bed reactor

The operation types and operation window for high-purity H2 production for the sorption enhanced steam methane reforming (SE-SMR) with Ni/Al2O3 catalyst and CaO sorbent in a fixed-bed reactor are investigated by an experimentally verified 2D numerical method. Four chemical reactions including steam reforming, water gas shift, global steam reforming, and CO2 sorption are considered. The operation window is defined as the H2 and CO molar fractions at outlet satisfying both yH2,out >= 90% and yCO,out <= yCO,allow (= 1%, 2% or 3%) in dry base. Under the conditions of yH2,out and yCO,allow, there are six operation types, of which 2 types are within the operation window and 4 types are not within the operation window as the temperature, weight hourly space velocity (WHSV) and steam to methane (S/C) molar ratio vary. For a common case of S/C = 3, the operation windows for yCO,allow = 3% at WHSV = 8.5 h-1 and 42.5 h-1 are located at 570-670 degrees C and 640-690 degrees C respectively, based on the parameters in this work. The operation window of temperature is wider with decreasing WHSV, and it becomes wider remarkably as the S/C ratio increases. The lowest temperature inside the operation window is 550 degrees C. The effects of the temperature, WHSV and S/C ratio on the operating types, yH2,out and yCO,out are also presented and discussed in details. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.