Process Intensification through Directly Coupled Autothermal Operation of Chemical Reactors (vol 4, pg 2268, 2020)

Autothermal operation of a chemical reactor involves coupling exothermic and endothermic chemical reactions for the purpose of thermal management without resorting to external energy sinks or sources. Often this is accomplished through regenerative or recuperative heat exchange between spatially or temporally separated exothermic and endothermic reactions. However, it is also possible to directly couple these reactions simultaneously within the same reactor volume, eliminating the heat-transfer bottleneck that characterizes much of chemical manufacture. It is not widely recognized that directly coupled autothermal operation allows dramatic process intensification. This perspective defines autothermal operation and contrasts it with conventional heat transfer for thermal management of chemical processes. The intensification and cost savings that can be achieved are quantified, and the implications to modular chemical process intensification are presented. Guidelines are proposed for designing directly coupled autothermal processes. Diverse examples are presented. Several challenges to expanding the field are critically discussed. Autothermal operation combines energy-absorbing and energy-releasing chemical reactions to control the temperature of a chemical reactor instead of removing or adding heat. Eliminating heat transfer simplifies reactor design and reduces costs. Furthermore, by eliminating the processing bottleneck that heat transfer often represents, the reactor can convert reactants into products at rates much higher than are possible in a conventional reactor of the same physical dimensions. Such “process intensification” is key to advancing industries that produce energy, fuels, consumer goods, and food products. Process intensification also enables modular manufacturing in which a manufacturing plant is constructed from factory-built modules that are shipped to the construction site rather than constructed from the ground up. Instead of capturing the economic advantages of a few very large plants, modular manufacturing captures the benefits of many smaller plants close to resources and markets. Autothermal operation of chemical reactors couples exothermic and endothermic chemical reactions to control reactor temperature without transferring heat to or from the reactor. By eliminating the heat-transfer bottleneck characteristic of many conventional chemical reactors, chemical processes can be dramatically intensified. This perspective defines autothermal processing and quantifies the intensification and cost savings that can be achieved. Guidelines are proposed for designing autothermal processes and several examples are presented. Challenges to expanding the field are critically discussed. © 2020 Elsevier Inc.