Development and demonstration of the control system for fully automated floc bed control
A new process for process water treatment, established by Fraunhofer IGB, is electro-physical precipitation (EpF), in which the process water to be treated is passed through a reactor, in which an electric current flows through sacrificial electrodes. Electrochemical reactions occurring between the electrodes result in dissolving the sacrificial electrodes, releasing their metal ions. Metal hydroxide flocs are produced in the process, which due to their high adsorption capacity bind to finely dispersed and dissolved materials. The hydroxide flocs together with precipitated substances precipitate in a subsequent flocculation reactor with slow upward flow velocity. The precipitated flocs are periodically drained.
The control of the flocculation bed formed during this EpF process has so far mainly been carried out visually / manually. In the SENSOFLOC project, this limitation will be overcome and a sensor-based control and regulation algorithm for fully automated floc blanket control will be developed and demonstrated. This allows for efficient separation of dissolved or finely dispersed materials without addition of any chemicals at low energy demand. With the automated control of the floc blanket, the advantages of the EpF can be industrially implemented.
The task of Fraunhofer IGB is to provide the necessary development work in the area of process control, while the partner BAMO IER modifies and manufactures one of its optical sensors according to the requirements for monitoring the flocculation bed. For this purpose, the optical properties of the dynamic flocculation bed are examined in all its phases in order to find out which parameters directly correlate to the physical properties of the flocculation bed and thus the optical properties. With this knowledge, a requirement and regulation catalog is created, which allows for the development of operating algorithms for the realization of a fully automated industrial process control of the floc blanket. Furthermore, this information is the basis for sensor modification, development and construction by project partner BAMO IER.
The new sensor is then integrated with the control and regulation system of an industrially-relevant electro-physical precipitation plant (EpF) and the successful development is validated in a comprehensive demonstration phase.