Test of a water–gas-shift reactor on a 3 kWe-scale—design points for high- and low-temperature shift reaction

The amount of carbon monoxide in the reformate from the autothermal reforming of liquid hydrocarbons can be significantly reduced by means of the water–gas-shift reaction. It is possible to directly feed the reformate from the autothermal reforming to the water–gas-shift reactor without deactivation of the catalyst. The results of this paper show a clear advantage of the isothermal operation of a water–gas-shift reactor over the adiabatic mode. Thermodynamic equilibrium was reached at clearly lower temperatures in the case of isothermal operation. A two-stage water–gas-shift reactor with a high-temperature shift part running at a gas hourly space velocity (GHSV) of 42,200 h−1 and an inlet temperature of 400 °C and a low-temperature shift stage operated at a GHSV of 26,000 h−1 and an inlet temperature in the range between 280 and 310 °C is able to reduce the carbon monoxide outlet concentration to less than 1 vol.%. This reactor will be suitable for combination with a reactor for the preferential oxidation of carbon monoxide in a fuel processing system. The injection of water between the two shift stages is meaningful because carbon monoxide conversion is enhanced by higher partial pressures of water. Furthermore, the injection of water can be applied to cool down the outlet temperature of the high-temperature shift stage of approximately 420 °C to the inlet temperature of the low-temperature shift stage of approximately 300 °C. The latter function can be dispensed with in the case of water injection between autothermal reforming and the high-temperature shift stage, which therefore reduces the positive impact of this step.