Sustainable revitalization and hydrodynamic characterization of a lab-scale CSTR for process engineering education

The Continuous Stirred Tank Reactor (CSTR) is widely used in process engineering education to demonstrate mixing dynamics, reaction kinetics, and non-ideal flow behavior. Many educational units, however, face reduced functionality due to mechanical wear and outdated instrumentation. This study reports the sustainable revitalization of a lab- scale CSTR to improve performance and pedagogical utility. Refurbishment involved installing a four-blade pitched turbine impeller, adding baffles sized at one-twelfth of the tank diameter, reconfiguring inlet–outlet piping to minimize dead zones, and integrating a continuous conductivity-based tracer measurement system. Hydrodynamic characterization employed residence time distribution (RTD) experiments with pulse injections of CuSO₄ solution at flow rates between 1.5 and 7.0 L/min. The upgraded CSTR achieved dispersion numbers (ND) from 0.24 to 0.34, with optimal well-mixed conditions observed at 3.5–4.0 L/min. Variance decreased as flow rate increased, indicating improved mixing uniformity, while space time showed the expected inverse dependence on flow rate. RTD curves aligned with turbulent, baffled CSTR behavior reported in recent literature. The refurbishment methodology offers a replicable, cost-effective approach to extending laboratory reactor lifespan while supporting sustainability goals. The enhanced unit enables high-resolution, real-time RTD analysis, strengthening experiential learning in chemical and process engineering.