(259b) High Pressure Hydrogen Generation and Simultaneous Carbon Dioxide Separation with Chemical Looping Hydrogen

High
pressure hydrogen generation with inherent carbon dioxide separation via fixed
bed chemical looping

Decentralised production of hydrogen
from renewable primary energy sources provides the basis for a sustainable
energy system with low emissions. At Graz University of Technology
the reformer steam-iron cycle (RESC) was developed for the decentralized
production of pure pressurized hydrogen [1]. Synthesis gas from renewable
feedstock, e.g. biogas or gasified biomass, is used in a chemical looping
fixed-bed system to release pure, pressurized hydrogen with efficiencies of up
of 75 % [2],[3]. This process additionally enables the inherent
separation of carbon dioxide from carbonaceous feedstock to facilitate carbon
capture and storage applications. Literature
data showed that the pre-pressurized release of
hydrogen with 100 bar could significantly reduce the
energy demand for compression of up to 80% [4].

The present work proves the possibility of
producing pure, pressurized hydrogen while inherently separating a carbon
dioxide stream with fixed-bed chemical looping [5]. The experiments were
conducted in a tubular fixed bed reactor, which is part of a modified test
system for catalyst characterization (Figure 1). The reactor was filled with
oxygen carrier material in powder form with the composition of 95% Fe₂O₃
+ 5% Al₂O₃, synthesized by wet chemical impregnation
method [6]. Simulated syngas mixtures from methane steam reforming at steam to
carbon ratios from 1.4 to 2.0 were used to reduce the oxygen carrier. The gas
quality during all experiments was measured continuously with a Micro Gas
Chromatograph (Inficon Fusion). Partial reduction led to a pure carbon dioxide offgas stream. The subsequent steam oxidation enabled a
direct pre-pressurized hydrogen withdrawal
at 30 bars with a hydrogen purity of 99.3%.

To investigate the maximum possible hydrogen
outlet pressure of the system an additional
experimental series was conducted to investigate the possibility of
high-pressure steam oxidation. Within the experiments, pressurized steam
oxidations with release pressures of up to 95 bar and hydrogen purities up to 99.9% could be achieved. XRD,
SEM, light microscopy and BET measurements were used to characterize the oxygen
carrier before and after the experiments. The results showed no degradation of
the oxygen exchange capacity over 20 high pressure reduction and oxidation
cycles.

Acknowledgement

The
authors gratefully acknowledge financial support by the Austrian Federal
Ministry of Transport, Innovation and Technology (BMVIT), Austrian Federal
Ministry of Education, Science and Research (BMBFW) and the Austrian Research
Promotion Agency (FFG) through the energy research program.

Figure 1: Scheme of the reactor system for pressures up to 100 bar

Figure 2: SEM and Light microscopy  pictures
of the oxygen carrier

[1]   V. Hacker, “A
novel process for stationary hydrogen production : the reformer sponge
iron cycle ( RESC ),” J. Power Sources, vol. 118, pp. 311–314, 2003.

[2]   G. Voitic, S.
Nestl, K. Malli, J. Wagner, B. Bitschnau, F.-A. Mautner, and V. Hacker, “High
purity pressurised hydrogen production from syngas by the steam-iron process,” RSC
Adv., vol. 6, no. 58, 2016.

[3]   S. D. Fraser,
M. Monsberger, and V. Hacker, “A thermodynamic analysis of the reformer sponge
iron cycle,” J. Power Sources, vol. 161, no. 1, pp. 420–431, 2006.

[4]   M. Ozsaban and
A. Midilli, “A parametric study on exergetic sustainability aspects of
high-pressure hydrogen gas compression,” Int. J. Hydrogen Energy, vol.
41, no. 11, pp. 5321–5334, 2016.

[5]   R. Zacharias,
S. Bock, and V. Hacker, “High pressure hydrogen generation with inherent carbon
dioxide separation via fixed bed chemical looping.,” in preperation.

[6]   C. D. Bohn, J.
P. Cleeton, C. R. Müller, S. Y. Chuang, S. A. Scott, J. S. Dennis, C. R. Müller,
S. Y. Chuang, S. A. Scott, and J. S. Dennis, “Stabilizing Iron Oxide Used in
Cycles of Reduction and Oxidation for Hydrogen Production,” Energy &
Fuels, vol. 24, no. 7, pp. 4025–4033, Jul. 2010.