Syngas is a valuable chemical intermediate
for producing commodity
chemicals, such as olefins, methanol, liquid fuels, etc. The chemical
looping route for syngas production presents an attractive alternative
to state-of-the-art technology, such as partial oxidation, autothermal
reforming, and steam methane reforming. Out of the several chemical
looping configurations, the co-current moving-bed reactor with iron
titanium composite metal oxide particles has demonstrated a high-purity
syngas production. In this study, an alternative reactor configuration
(indirect chemical looping system) is proposed to the co-current moving-bed
reactor system (direct chemical looping system) to enhance the syngas
yield. The indirect chemical looping system consists of a fuel reactor
and a syngas generation reactor, both operated in countercurrent mode,
with respect to the gas–solid flow, as opposed to just one
co-current fuel reactor in the direct chemical looping system. This
unique gas–solid contact pattern in the indirect chemical looping
system aids in greater utilization of CO2 and H2O and improves the thermodynamic performance for syngas production.
Thermodynamic simulations in Aspen Plus software are performed for
system analysis and comparison under isothermal and autothermal conditions.
Isothermal analysis at several different temperatures and pressures,
with and without co-injection of CO2/H2O, is
conducted to explain the behavior of the proposed system. Autothermal
operation of the system under different pressures is also evaluated
to determine the maximum syngas yield within the constraints of a
practical system for syngas production to further produce liquid fuels
via Fischer–Tropsch synthesis. The results from these simulations
are compared against the direct chemical looping system to highlight
the difference in thermodynamic constraints between the two processes.
The oxidation behavior of reduced Fe2O3–MgAl2O4 with CO2 and H2O is experimentally
tested at different pressures and temperatures to gain an understanding
for the syngas generation reactor in the indirect chemical looping
system.
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