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Thermal in Situ and System-Integrated Regeneration Strategy for Adsorptive On-Board Desulfurization Units
journal contribution
posted on 2017-10-19, 00:00 authored by Raphael Neubauer, Norbert Kienzl, Brigitte Bitschnau, Hartmuth Schroettner, Christoph HochenauerThis work deals with the introduction
and investigation of a novel
system-integrated thermal regeneration strategy based on hot off-gas
for on-board desulfurization units. A highly thermally stable Ag–Al2O3 material was used as the adsorbent because it
has the advantage of being active in the oxidized form so that it
requires no activation after regeneration in an oxidative atmosphere.
Dibenzothiophene (DBT) was used as the representative polycyclic aromatic
sulfur heterocycle (PASH) in Jet A-1 fuel with a total sulfur concentration
of 900 ppmw. This PASH has a stronger adsorption energy and is significantly
more stable than benzothiophene or thiophene. This is why oxidative
thermal regeneration strategies had formerly been failing to fully
regenerate any type of adsorbent after the adsorption of DBT. This
work reports excellent regeneration results upon the use of the hot
off-gas from a solid-oxide-fuel-cell- (SOFC-) driven auxiliary power
unit (APU) as the regeneration medium. The highly thermally stable
Ag–Al2O3 showed a high breakthrough adsorption
capacity of 2.2 mg-S/g-adsorbent in the first desulfurization cycle
that was fully recovered by regeneration with hot APU off-gas. This
is the first time that 100% regeneration has been reported for thermal
regeneration after the adsorption of DBT. Additional investigations
were performed to gain deeper insight into the overall desorption
mechanism. The H2O content has an especially significant
influence on the overall desorption mechanism of DBT. With a H2O content of 12.4 mol %, full regeneration was also obtained
by reducing the final regeneration temperature from 525 to 450 °C.
The results reported herein show that this novel regeneration strategy
requires no additional regeneration medium, no additional tanks, and
no additional bulky equipment and is thus fully integrated into the
concept of an SOFC-operated APU.