Influence of flow arrangement in catalytic plate reactors for methane steam reforming

A theoretical study of the influence of flow arrangement on the thermal behaviour of a catalytic plate reactor (CPR) for steam reforming of methane using methane catalytic combustion as heat source based on a two-dimensional model is presented. CPR performance and thermal behaviour is strongly affected by overall and local balance between heat generated on the exothermic side and heat consumed on the endothermic one, which in turn is influenced by flow arrangement. Simulations for co-current and counter-current flow were carried out for similar inlet conditions and catalyst loadings. It was found that the reactor is better balanced thermally for co-current operation. For counter-current arrangement, higher conversions and better utilization of the overall heat generated in the exothermic process are achieved at the expense of pronounced temperature extremes. Thus, reforming conversion for counter-current operation is 62.8% compared with 52% for co-current operation, whilst maximum transverse temperature difference for co-current operation is only 16.5K compared with 310K for counter-current operation. This increases the chances of the reactor running away and of homogeneous combustion being initiated. Utilization of a non-uniform catalyst distribution can overcome the heat imbalance by inducing favourable reactant depletion along the reactor during counter-current flow.