Process tomography for mixing, stirring and flow processes


© Fraunhofer IKTS
Evaluation of mixing processes using process tomography to increase the efficiency of biogas reactors and sewage treatment plants.
© Fraunhofer IKTS
Determination of bubble size distributions in bubble column reactors for optimization of chemical or biological reaction processes.

Electrical process tomography (ERT) is an established technique for three-dimensional visualization and quantification of a wide variety of mixing, stirring and flow processes in fluid volumes. It is based on the spatially resolved measurement of electrical conductivity differences, which are caused, for example, by different liquid phase components, such as water and oils, the introduction of fibers or salts or also by gas bubbles. Similar to other tomographic methods, 3D sectional images are reconstructed from the measurement data, which map the distribution of electrical conductivity in the reactor, vessel or tube under investigation. With the ERT system used at Fraunhofer IKTS, up to ten such tomograms can be recorded per second, which means that process sequences can also be investigated regarding time resolution. In this way, quantitative statements can be made on the spatio-temporal distribution of phases and concentration differences and thus on mixing qualities, flow ratios and other process parameters. Problematic dead zones as well as floating and sedimentation layers can be detected with this method, as can macroscopic foreign bodies and gas bubbles. In contrast to optical methods, ERT is also suitable for the investigation of opaque media and allows the characterization of highly concentrated, multidisperse non-Newtonian multiphase systems.


Application examples


  • Biological and chemical batch and flow reactors (e.g. bubble columns)
  • Fermenters in biogas plants
  • Wastewater treatment and sewage treatment plants
  • Tanks and reservoirs for liquids
  • Aquaculture and hydroponics systems


Services offered


  • Process engineering and energetic evaluation of mixing, stirring and dissolution processes as well as flows on pilot-plant and pilot scale
  • Tomography-assisted design, optimization and scaling of mixing processes, reactors and mixing systems
  • Determination of fluid dynamic parameters and size distributions of gas bubbles and macroscopic bodies in bubble column reactors and other reactor types
  • Qualitative and quantitative characterization of flow processes and modeling by numerical methods               


Project examples


  • FlexPump: Smart pump systems for mixing of biogas reactors
  • BioStore: Bubble columns for biological methanation
  • SensOMix: Automated stirring systems in biogas plants for load-flexible and demand-oriented biogas production