(439a) High Purity Hydrogen Production in a 10 kWth Fixed Bed RESC Prototype System

Abstract

The reformer sponge iron cycle (RESC) provides a
suitable concept to realize high-purity pressurized hydrogen from a broad range
of renewable resources as e.g. biogas or gasified biomass from wood or residues
in decentralized on-site applications [1-3]. The on-site production of
renewable hydrogen allows the realization of an infrastructure for low emission
fuel cell based power production and mobility. The
reformer steam iron process is introduced as the technological option to realize
on-site hydrogen production by combining production, purification and storage
with a low environmental impact [4,5].

A prototype system was developed, constructed and
operated to produce hydrogen from syngas with a purity of 99.999% and enabling
hydrogen output of up to 10 kW_LHV[2].
The design includes a high-temperature reactor with a combined steam reformer
and a chemical looping section for hydrogen purification, comprising of up to
18 kg iron-oxide based oxygen carrier material. A series of experiments was
conducted in with an enhanced process layout and analytic systems to improve
the feasible hydrogen purity and determine the influence of several process
parameters on hydrogen quality. In the chemical looping section, significant influences
of the exothermic oxidation and endothermic reduction reaction are illustrated
with axial and radial temperature profiles. Highly sensitive gas detection
facilitated the detection of carbonaceous impurities in single digit ppm range.
Furthermore, process analyses were performed to further improve the conversion
efficiency according to thermodynamic simulations and earlier experiments in a
smaller prototype system.

The results exhibit a very high hydrogen purity with
total carbonaceous impurities (carbon monoxide, carbon dioxide, methane) below
10 ppm and a hydrogen output of up to 10kW_LHV. The conversion
stability of the applied oxygen carrier material was reviewed in both
single-particle thermogravimetric experiments and a special fixed-bed thermogravimetric
device. Sintering effects and mechanical degradation of the pelletized material
are illustrated and analyzed with SEM, EDX, XRD, light microscopy and BET
methods.

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.

[1] S. Nestl, G. Voitic, R. Zacharias, S. Bock, and V. Hacker,
“Operation of the reformer steam iron process prototype for hydrogen
production,” J. Energy Technol., 02 March 2018.

[2] S. Bock, R.
Zacharias and V. Hacker, “High purity hydrogen from 10 kW_th
RESC-prototype system”, 2018, in preparation.

[3] G. Voitic, S. Nestl, K. Malli, V. Hacker, et al., “High purity pressurised hydrogen production from
syngas by the steam-iron process,” RSC Adv., 2016, 6, 58, 53533–53541.

[4] G. Voitic, V.
Hacker, “Recent advancements in chemical looping water splitting for the
production of hydrogen”, RSC Advances, No.6, 10 October 2016,  S. 98267-98296.

[5] V. Hacker, “A novel
process for stationary hydrogen production: the reformer sponge iron cycle
(RESC)”, J. Power Sources, Vol. 118, Issues 1–2, 25 May 2003, Pages 311-314.