Time scale analysis & characteristic times in microscale-based chemical and biochemical processes: Part I – Concepts and origins

Time-Scale Analysis and Characteristic Times are suggested as a novel and useful tool in the analysis of the performance of microscale-based reactors, unit operations, and plant flow-sheet diagrams embodying microscale-based chemical processes. Transport phenomena, reaction kinetics, and phase contacting in microstructured architecture can be easily represented by unique time constants, τis. These Characteristic Times are estimated from first principles and are controlled by a user to support a meaningful chemical process analysis and provide insight or suggestions for successful design choices. While the origin of Characteristic Times in microscale-based processes is rooted in fundamentals of molecular transport and reaction kinetics, the evolution of Characteristic Time definitions could be easily found in detailed mathematical models of microscale-based reaction processes and operations. The user-defined scaling parameters contribute to the flexibility of Time Scale Analysis implementation. This work uses a microscale-based solid catalyzed reaction process to demonstrate the concept of Time Scale Analysis and systematically define Characteristic Times and their origin. Lastly, varying forms of Time Scale Analysis have been implemented to evaluate specific phenomena or aspects of processes but have yet to encompass the full unit operation or process within the analysis. Part I and Part II of this work develop a comprehensive Time Scale Analysis for unit operations and a (bio)chemical process flowsheet (Part II only).