How does an autothermal reformer work and what are the design considerations?

Autothermal reforming (ATR) combines partial oxidation (exothermic) with steam reforming (endothermic) to achieve thermal balance. Oxygen reacts with hydrocarbon at top producing CO2, H2O, and heat; this heat drives subsequent steam reforming reactions. Design considerations: oxygen-to-carbon ratio (thermal balance), steam-to-carbon ratio (carbon formation prevention, hydrogen yield), operating temperature (typically 900-1100C), catalyst selection (partial oxidation zone: no catalyst; reforming zone: nickel-based), and refractory lining for high temperature. Used in syngas/hydrogen production and GTL.