Nested counter-flow preheating reactor for enhanced thermal uniformity in DME autothermal reforming

Dimethyl ether (DME) autothermal reforming represents a promising route for hydrogen production. However, the significant kinetic mismatch between exothermic oxidation reactions and slow endothermic steam-reforming reactions readily induces severe local hot-spots and inlet temperature runaway within fixed-bed reformers. Such sharp axial temperature excursions exert adverse effects on hydrogen production performance. In this work, a concentric nested counter-flow preheating reactor is proposed to tackle this thermal bottleneck. A multi-physics CFD model coupled with well-validated Langmuir-Hinshelwood-Hougen-Watson (LHHW) reaction kinetics is established and calibrated against published experimental datasets, delivering temperature prediction errors below 5%. Numerical simulations are carried out over an inlet-temperature range of 583.15–673.15 K. The nested configuration redistributes excess heat released from oxidation reactions in the radial direction and suppresses axial hot-spot buildup via counter-flow feed heat recuperation. At an inlet temperature of 673.15 K, the bed temperature overshoot drops from 43.6 K of the conventional single-channel reactor to merely 8 K. Higher inlet temperatures promote both DME conversion and hydrogen concentration. The homogenized thermal field mitigates radial species gradients. The proposed reactor achieves steady near-thermally-neutral reforming, providing an effective heat-mass coupling regulation strategy for high-performance compact DME hydrogen-production devices.