Enhanced Hydrogen Production Integrated with CO2 Separation in a Single-Stage Reactor

Abstract

High purity hydrogen is commercially produced from syngas by the Water Gas Shift Reaction (WGSR) in high and low temperature shift reactors using iron oxide and copper catalysts respectively. However, the WGSR is thermodynamically limited at high temperatures towards hydrogen production necessitating excess steam addition and catalytic operation. In the calcium looping process, the equilibrium limited WGSR is driven forward by the incessant removal of CO 2 by-product through the carbonation of calcium oxide. At high pressures, this process obviates the need for a catalyst and excess steam requirement, thereby removing the costs related to the procurement and deactivation of the catalyst and steam generation. Thermodynamic analysis for the combined WGS and carbonation reaction was conducted. The combined WGS and carbonation reaction was investigated at varying pressures, temperatures and S/C ratios using a bench scale reactor system. It was found that the purity of hydrogen increases with the increase in pressure and at a pressure of 300 psig, almost 100% hydrogen is produced. It was also found that at high pressures, high purity hydrogen can be produced using stoichiometric quantities of steam. On comparing the catalytic and non catalytic modes of operation in the presence of calcium oxide, it was found that there was no difference in the purity of hydrogen produced at elevated pressures. Multicyclic reaction and regeneration experiments were also conducted and it was found that the purity of hydrogen remains almost constant after a few cycles. 1

New Design of a Separator Unit with Metal Hydride and an Analysis of Its Potential Application in the Process of Hydrogen Separation from a Binary Mixture of Gases

“…The steam/CO ratio in a reaction chamber should be as much as 3:1. The conversion of gas is carried out on the basis of a water-gas shift reaction, while the equilibrium constant is defined by the following equation: [6].…”

“…The water-gas shift reaction is thermodynamically limited and is accompanied by adding excess steam to the process; this improves the ratio of hydrogen and carbon monoxide content at the outlet. Higher hydrogen recovery rates are achieved by extending the conversion with a second-degree process that uses copper-based catalysers and by lower temperatures in the reaction chamber [6].…”