Pseudodistributed Feed Configurations for Catalytic Plate Microchannel Reactors

Catalytic plate microchannel reactors (CPRs) are one of the most successful implementations of the process intensification philosophy, and have been recognized as an important contributor in the path toward monetizing distributed natural gas resources through localized, small-scale processing. While their reduced geometric dimensions lead to well-documented energy efficiency gains and lower capital costs, they also give rise to specific control and operation challenges, particularly in terms of preventing temperature excursions and the formation of hotspots that can compromise the integrity of the reactor. In conventional reactors, such issues are typically addressed through external cooling and by judiciously distributing the feed streams along the reactor to modulate the release of reaction heat. Owing to the difficulty of implementing distributed sensors and actuators at a small scale, this solution is not readily applicable to the design and operation of microchannel reactors. As a consequence, in this paper, we propose a novel approach to modulation of heat generation in microchannel reactors, via a segmented catalyst macromorphology consisting of alternating catalytically active and inactive (blank) reactor sections. We also introduce a novel optimization-based strategy for determining the number, length, and axial location of the active sections based on closely tracking a desirable, optimized temperature profile. Using the detailed model of an autothermal methane-steam reforming reactor, we demonstrate the efficacy of the optimized segmented macromorphology in ensuring a uniform axial temperature profile. Further, we demonstrate through simulations that, at the optimum, the temperature and conversion profiles resulting from the proposed segmented macromorphology are similar to those obtained in a microchannel reactor with multiple axially distributed reactant feed points.