Instrumented flow-following sensor particles have been developed for investigation of hydrodynamic and biochemical processes in chemical reactors and bioreactors, where standard measurement techniques are not applicable. The sensor particles allow autonomous long-term measurement of spatially distributed process parameters in the chemically and mechanically harsh environments of e.g. agitated industrial vessels. Each sensor particle comprises of an on-board measurement electronics that logs the signals of the embedded sensors. A buoyancy control unit enables automated taring to achieve neutral buoyancy of the sensor particles. Moreover, controlled floating of the sensor particles is possible to expose them for recovery from the liquid surface. Macro-flow tracking of the sensor particles is validated with circulation time reference measurements by means of salt tracer experiments in a stirred model reactor and CFD simulations. Moreover, process characterization with sensor particles is demonstrated in three further applications, namely a biogas pilot digester, an air-water column and a biological wastewater treatment basin. Acquired data were used to fit mixing model parameters, namely effective circulation time, circulation number, degree of suspension and Péclet number.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).