Numerical analysis of a helical spiral microevaporator-microreformer system for enhanced methanol conversion and hydrogen production

The study aims to simplify microreactor system design by eliminating the need for a separate evaporator unit while enhancing microreactor performance. This study comprehensively elucidates the transition of fed liquid methanol and water mixture species conversion within this coupled system. The behavior and performance of this coupled system are investigated across variations in reaction parameters, including steam to methanol ratio (S/C ratio=1–3), applied heat flux (q = 100–900 W/m²), and variations in CuO/ZnO/Al₂O₃ catalyst thicknesses (37.5 µm-75 µm) coated onto the wall. The study demonstrates that methanol steam reforming, an endothermic reaction, leads to substantial temperature drops as vapor moves from the microevaporator to the microreformer, balancing the heat supplied and absorbed in the mixture. The temperature range of 225–250 ℃ was found to be critical for complete methanol conversion, with higher heat flux and S/C ratios enhancing conversion rates. Thin catalyst layers in the helical design allow for rapid methanol conversion, while thicker layers result in higher hydrogen (H₂) production rates. Pareto front analysis identifies design D4 (∆t = 37.5 µm) as optimal, requiring a minimum heat flux of 300 W/m² and an S/C ratio of 1 to achieve an H₂ flow rate per unit catalyst weight (r_H2) of 0.034 and 99.4 % methanol conversion performance.