Reaction swing approach for hydrogen production from carbonaceous fuels

The paper presents the results of the investigations on a reaction swing approach for the production of high purity hydrogen from syngas exploiting the Boudouard at temperatures ranging from 550 to 700∘C and pressures ranging from 0 to 150 psig. The concept of the process is the sequential use of a catalyst, that enhances the CO disproportionation reaction in conjunction with the water gas shift reaction to completely eliminate the CO in the product stream, and a CO2CO2 removal agent for in situ capture of the produced CO2CO2. The thermodynamic evaluation of the above system shows the potential of achieving greater than 99% hydrogen purity values in the product stream even at atmospheric pressures. The effects of temperature, pressure and steam addition on the hydrogen enrichment are reported. Experiments were also conducted to evaluate the effect of catalyst and CO2CO2 removal material loadings on the product gases. Increasing the pressure improved the purity and the duration of the enrichment cycle. The separation efficiency was maximized at a temperature of 650∘C. A 1:2 ratio of the catalyst to CO2CO2 removal material was found to be sufficient to produce nearly carbon-free hydrogen for over an hour before regeneration. The use of 25% steam was found to increase the hydrogen yield by nearly 50% (due to the contribution of the water gas shift). The results from simultaneous coal gasification and hydrogen enrichment experiments in a single reactor are also presented. It was found that for a Fe2O3Fe2O3: coal ratio of 22:1 for effective gasification and over 99% pure hydrogen stream.