European Bio-Energy Projects

AER-GAS
Objectives
Development of a new, efficient and low
cost single step process (Absorption
Enhanced Reforming, AER) for clean
biomass conversion into a hydrogen rich
gas (H2 conc. > 80 vol. %) with low tar
content.
Development and selection of efficient
catalytic CO2 absorbent bed materials with
improved mechanical and chemical
stability for the AER process.
Design of an AER biomass plant with
investment costs less than 800 €/kW and
energetic efficiency for H2 production
higher than 75%.
New approach for biomass
gasification to hydrogen
Challenges
The main characteristic of the proposed process
for efficient and low cost conversion of biomass
is the CO2 removal in the reaction zone of the
gasifier. Due to the shifting of the reaction
equilibrium the hydrogen concentration increases
significantly. Therefore, the single step generation
of a product gas with high hydrogen content for
fuel cell applications is achievable. As the CO2
absorption is a highly exothermic reaction, the
realised heat is integrated directly into the
endothermic gasification/reforming process.
The spent absorbent has to be regenerated in a
subsequent process step (Figure 1).
The main advantages of the AER process are
summarised as follows: a) product gas with
a hydrogen content higher than 80 vol. %,
b) complete CO2 removal from the product gas,
c) in situ heat supply for the endothermic
biomass conversion process (thermally selfsustaining
conversion process), d) easy CO
cleaning for fuel cell applications of the product
gas, and e) simple conversion technology.
For the realisation of the proposed technology,
a fluidised bed reactor will be employed
containing a CO2 absorbent, e. g. dolomite. The
development of a catalytic absorbent material
with high tar cracking efficiency is also a key
aspect of the AER process. Therefore, the
ongoing project work is focused on the
investigation of different natural and synthetic
absorbent materials with regard to their CO2
absorption capacity, chemical and mechanical
stability under real process conditions with
repeated absorption – regeneration steps. The
process parameters defined in a fixed bed and
70
in a fluidised bed reactor will be applied to a
circulating fluidised bed system (Fast Internally
Circulating Fluidised Bed, FICFB reactor), that
allows a continuous production of hydrogen
parallel to absorbent regeneration.
Project structure
The project is co-ordinated by the Centre for
Solar Energy and Hydrogen Research, Stuttgart,
Germany (ZSW). There are four work packages
(WP) which address the technical and economic
objectives.
WP 1 concentrates on the development and
improvement of a catalytic absorbent material
which is a core component of the AER process.
Natural materials (dolomite marble litter, raw
dolomite, olivine) and synthetic materials
(chemically modified absorbents, e.g. by addition
of silica, alumina or zirconia) are investigated as
CO2 absorbents mainly by thermal gravimetric
analysis (Figure 2).
The catalytic activity of the investigated bed
materials is characterised by dependence on
their physical (morphology and surface area)
and chemical (bulk and surface) properties. The
performance of the bed material is determined
applying a fixed bed AER reactor. Pre-selected
materials are provided to the partners of the WP
2 and WP 3.
In WP 2, the AER process is investigated in
fluidised bed (FB) reactors. The main goals are
the determination of the mechanical stability of
the bed materials as well as the definition of
optimal operation conditions for fluidised bed
operation (temperature, residence time, etc.)
to provide a product gas with a high hydrogen and
a low tar content.