(300a) Experimental and Simulation Study of Ethanol Steam Reforming Reaction for Hydrogen Production in Large Scale Catalytic Membrane Reactor

Experimental and
simulation study of ethanol steam reforming reaction for hydrogen production in
large scale catalytic membrane reactor

Rui Ma, Bernardo Castro-Dominguez, Ivan P. Mardilovich, Anthony G. Dixon,
Yi Hua Ma

Center for Inorganic
Membrane Studies, Department of Chemical Engineering, Worcester Polytechnic
Institute, 100 Institute Road, Worcester, MA 01609, USA.

           
Production of hydrogen from ethanol
steam reforming (ESR) has attracted more interest due to the massive
application of hydrogen and carbon neutral property of bio-ethanol.  In hydrogen production, the process
intensification concept has been applied to ESR by conducting the reaction in a
catalytic membrane reactor (CMR) in order to generate and separate pure hydrogen
in the same unit simultaneously. Since the product is being removed during the
reaction, the conversion is improved.

         
In the present study, ESR was carried out in a large scale CMR with a
150 cm² membrane surface area. The process was investigated both
experimentally and with Computational Fluid Dynamics (CFD) simulation. A defect-free
membrane was prepared as Pd/Au/Pd/Au
and placed in the center of a double screen annular cage while a nickel-based
commercial catalyst (HiFUEL R110) was loaded between the
double screens surrounding the membrane as shown in Figure 1, thus the catalyst
particles were not in direct contact with the membrane surface. The reaction
was performed under different operating conditions: liquid hourly space
velocity (LHSV), operating pressure and temperature as well as steam to ethanol
(S/E) ratio. Under 300 hours of operation, 100% conversion of ethanol was achieved
under all conditions; H₂ with 99.9% purity was produced with the
rate of 0.38 g/h at LHSV= 3.77 h^-1, P=5 bar, T= 500 ¡C and S/E= 5.
It was shown that the process is enhanced by high pressure, high S/E ratio and
high temperature. The effect of each condition is discussed in detail in this
work.   

          
Simulation models were developed in 1-D and 2-D utilizing Polymath and
COMSOL Multiphysics respectively. The kinetics used in the model were
validated against experimental outcomes from previous publications using the
1-D model. In the 2-D model, the hydrogen permeation process was simulated as a
flux term on both shell side (retentate) and tube side (permeate) applying
SievertsÕ law:

in which PH2shell and PH2tube represent
H₂ partial pressure at the retentate side and permeate side
respectively.

For the 2-D
simulation, the equation of motion and the species continuity equations were
solved simultaneously using a finite element method. The effect of the catalytic
bed was considered by implementing the Darcy-Forchheimer
law to describe the extra resistance to the flow, in which Ergun equation was
used to describe the pressure drop in the porous medium.  The simulation results were compared
with experimental data and showed an accuracy of 84% for 1-D simulation and 91%
for 2-D simulation.

           
Applying the simulation model, the benefits of process intensification were
observed by comparing the H₂ production rate from ESR in a traditional
packed bed reactor (PBR) and in the CMR. While operating the reaction at higher
temperatures and higher pressures, an improvement of up to 122% of H₂
generation in CMR was shown.

Figure 1. Representation of ESR carried out in a CMR.