The process has been simulated using AspenTech’s process engineering software
HYSYS® version 3.1 [16]. The process flow diagram of the simulation done in HYSYS is
presented in Fig. 2. The process feed consists of liquid water and methane gas at ambient
temperature. Reactions (r1), (r2) and (r3) take place in the reformer, simulated as a plug flow
reactor (PFR) with the kinetic models propose by Xu and Froment [11] producing a gas with
46% (molar) H2. Heat, in the amount of 233.67 kJ/s, is provided to the reformer. A high
temperature water gas shift reactor (HT WGS) is used to raise the concentration of hydrogen
to 52.8%, and a low temperature water gas shift reactor (LT WGS) provides an additional 1%
increase in hydrogen content. Only the exothermic reaction (r2) takes place in these last two
reactors, which are simulated as adiabatic PFRs using the kinetic models proposed by Keiski
et al. [12] and Rase [13], respectively.
Hydrogen purification starts with the condensation and flash separation of liquid water
by cooling down the gases, and is finalized in the PSA unit with adsorption of grand majority
of the remaining contaminant gases, resulting in the production of 20.98 kg/h of a gas stream
with 99.8% H2 at 21 atm. The hydrogen produced from the PSA unit is compressed in three
stages up to 300 atm, which is within typical storage pressure for hydrogen powered vehicles
and related hydrogen fueling stations.