(470e) ATR-Based Compact Reactor System for the Distributed Hydrogen Production

ATR-based compact reactor system for the distributed hydrogen
production

Vincenzo Palma¹, Antonio Ricca^1*, Biagio Addeo¹,
Maurizio Rea², Gaetano Paolillo², Paolo Ciambelli¹

^1*Dep. of Industrial Engineering,
University of Salerno, via Giovanni Paolo II 132,
84084 Fisciano, ITALY, aricca@unisa.it

²R&D - SOL s.p.a, Via Borgazzi 27, 20900 Monza (MB), ITALY

INTRODUCTION

The well-known problems linked to the depletion of fossil fuels and to
the growing energy demand address the industrial research toward the
development of effective innovative routes for alternative energy resources. If
in one hand hydrogen is pointed as the best clean energy vector (to employ in
fuel cell systems), in the other hand its production through hydrocarbon
reforming still appears as the most viable solution in a transition period
towards a hydrogen based economy.  One of
the main limitation connected to the hydrogen employment diffusion is linked to economic issues related to the H₂
transport and storage. In this aim, distributed hydrogen production appeared an
optimal solution, both for the stationary and mobile installations. From this
point of view, hydrocarbons catalytic Auto-Thermal Reforming (ATR) appears the
best candidate process¹: it combines the partial oxidation and the
steam reforming processes, since hydrocarbons react with both oxygen and steam
to obtain a self-sustained and very fast process. Anyway the high carbon
monoxide content of the produced stream require a further catalytic stage, the
Water-Gas Shift (WGS) in which CO reacts with steam to produce further
hydrogen. Anyway, the very different operating temperature of ATR and WGS
stages resulted in the necessity of a heat exchange system, with a consequent
increasing in plant size and operating costs.

Aim of this work was to design and test a thermally integrated fuel
processor based on natural gas ATR, aimed to the hydrogen production
intensification and to the external duty minimization. 

EXPERIMENTAL

A compact fuel processor based on Auto-Thermal Reforming process for
natural gas conversion was designed and configured to produce
up to 10 Nm³/h of hydrogen. Water and air were
delivered to the system, together with the hydrocarbon. The system was
provided to 2 catalytic stage: in the ATR module, the hydrocarbons conversion
to syngas was obtained, in the WGS  module the CO present in the syngas
was converted increasing hydrogen content. In the ATR module a 0.5 L commercial
(Johnson Matthey) honeycomb catalyst noble metals based was loaded, while in
the WGS 2 L of commercial (JM) pellets catalysts were
employed. Due to the very different temperature in the two stages, a
compact and optimized heat exchange module were designed and
placed between the two reaction volumes. In this way, sensible heat of
effluent gas from ATR volume was exploited to pre-heat reactants before feeding
to it; moreover, effluent gas were cooled to a temperature consistent to the
WGS stage. Such configuration allowed to feed all reactants
at room temperature, without external heat exchangers; moreover, the thermal
integration was able to reduce system start-up transient times. Preliminary
studies were carried out in order to evaluate the
reactants rate and the feed ratios effect on system performances.

RESULTS AND DISCUSSION

Preliminary
tests confirmed that the designed system was characterized by very short
start-up times, being able to produce up to 5 Nm³/h of hydrogen
(27%vol) in less than 3 minutes. The transitory phases were strictly
related to the overall gas rate, since higher stream rate resulted in
faster system response. Despite thermodynamic predictions, due to the thermal
integration the system seemed not to be greatly affected
by steam content, since too high steam-to-carbon ratio resulted in a decreasing
in system temperature. In Fig. 1, the system performances are
summarized in a selected operating condition. As reported, the ATR
module well approached the thermodynamic equilibrium, reaching a total methane
conversion. On the other hand, WGS module was able to convert only the 51% of
CO, mainly due to the thermodynamic limitations, so
also affecting the thermal efficiency that anyway reached very promising
values.

Fig.
1 System performances (H₂O:O₂:CH₄ =
0.65:0.65:1)

CONCLUSION

An ATR-based fuel processor thermally integrated was
designed and realized. Preliminary tests evidenced the quick start-up
and response of the system, that showed very good
performances by producing up to 7.4 Nm³/h of H₂. WGS
module seemed to suffer for thermodynamic limitation, suggesting to feed more
steam to the system, as well as to modify catalytic formulation. As a future
enhancement, a heat recovery module may be placed
downstream the WGS module for a further heat recovery.