CFD analysis of the effects of the flow distribution and heat losses on the steam reforming of methanol in catalytic (Pd/ZnO) microreactors

•Several flow distributing headers considered for 3D CFD simulations.•Large values of the flow diffuser expansion angle lead to flow maldistribution.•The effect is more important for geometries with low surface-to-volume ratio.•Heat losses are critical for microreactor operation mainly at low space velocity.•Losses can easily reach values above 80–90% of the energy input.

A three-dimensional computational fluid dynamics (CFD) simulation study of the effects of the flow distribution and the heat losses on the performance of microchannels and microslits reactors for the steam reforming of methanol (SRM) over Pd/ZnO is presented. Several flow distributing headers covering a wide range of the flow diffuser expansion angle (α) have been considered. Large values of α lead to flow maldistribution characterized by jet flow resulting in negative effects on the SRM conversion and hydrogen yield, especially for the microslits at high reaction temperatures and space velocities. Simulations have also evidenced that heat losses constitute a critical issue for microreactors operation, particularly at low space velocities. Heat losses may reach very high values, above 80–90% of the energy supplied to the microreactor, with the consequence that it may be necessary to provide up to 9 times the heat of the SRM reaction to achieve high methanol conversions.

Graphical abstractCFD simulations allowed to design the flow distributing header and studying heat losses from a microchannel reactor for the steam reforming of methanol.Figure optionsDownload full-size imageDownload as PowerPoint slide