The Reverse Water-Gas Shift Reaction as an Intermediate Step for Synthetic Jet Fuel Production: A Reactor Sizing Study at Two Different Scales

This paper presents a reactor model for the reverse water-gas shift reaction (rWGS)
implemented in the framework of captured CO2 conversion. Kinetics are included in the
model and validated with experimental data from the literature. The model is used to size
a reactor at two scales: a small pilot (inlet H2 of 1.5 Nm³/h) and a mature plant (inlet H2
of 1,500 Nm³/h). The designs at both scales differ by the heating configuration; it is
assumed that the small-scale unit is isothermal while the industrial-scale unit is adiabatic.
For the small-scale unit, it is shown that the equilibrium conversion (65.6 %) can easily
be reached within 30 cm at 1 bar. However, this reactor is not optimal for a 20-bar
operation as the maximum conversion (65.2 %) is reached in the first centimetres before
decreasing to 62.1 %, as methanation occurs, leading to an outlet CH4 selectivity of 17.3
%. In the large-scale adiabatic unit, both operating pressures lead to a sudden temperature
drop due to the endothermic reaction followed by a temperature increase, but this latter is
more important at high pressure due to methanation accentuation. This difference in the
temperature profile results in a CO2 conversion of 64.8 % at 20 bar against 51.1 % at 1
bar. In summary, the equilibrium conversion in an isothermal unit is slightly higher at 1
bar, even in a reactor adequately sized for each pressure. In an adiabatic unit, the
equilibrium conversion is reached within the same length for both pressures and is
significantly higher at 20 bar, at the extent of an accentuated methanation.