Hydrogen generation in spatially coupled cross-flow microreactors

Thermal management of microreactors is very important for process intensification to achieve higher efficiency and for maximum heat utilization. In this work, a cross-flow spatial coupling between endothermic ammonia decomposition reaction and exothermic propane combustion in a microreactor is explored. Unlike the conventional co-current or counter-current reactors, the combustion channels in the cross-flow microreactor are aligned in transverse direction, perpendicular to the ammonia flow direction. The cross-flow coupling mode is parametrically analyzed to delineate the operating region and efficiency of the microreactor. The effect of inlet flow rates of propane and ammonia, reactor wall thermal conductivity on the performance of cross-flow microreactor are studied in detailed, and design guidelines are depicted through operating diagrams, which are quantitatively valid for the reactor dimensions and flow rates simulated in this work. The performance of the cross-flow coupling is compared with co-current coupling in terms of energy efficiency and the range of feasible operating conditions. The results show that energy efficiency of co-current coupled microreactor is higher than that of cross-flow coupled microreactor, whereas cross-flow coupled microreactors show advantages when operating at lower ammonia flow rates (i.e., lower hydrogen throughput).

• A spatially coupled cross-flow microreactor is explored for H2 generation for fuel cells. • Design guidelines are provided through operating diagrams for both microreactors. • Cross-flow microreactors showed more stability for lower H2 throughput. • Co-current microreactors showed higher operating efficiency at higher H2 throughput. • Higher wall thermal conductivity materials are recommended for better stability.