Development of a Continuous Ultrasonic Sensor for Monitoring Liquid Levels in the Presence of Interfacial Layers

Liquid level measurement is of central importance in many industries for process monitoring and control. It is indispensable, particularly in the chemical industry, the oil and gas industry, food and beverage production, the pharmaceutical industry, water treatment, and other sectors. However, during the storage or separation of media with different compositions, the formation of interface or boundary layers has a negative impact on the process. In wastewater treatment plants, gas stations, or car washes, for example, separators for light liquids, organic fats and oils, starch separators, sludge traps, and sedimentation tanks, as well as sampling wells and devices, are used, all of which require sensors to detect these layers. In the pump control system of washing plants, for example, a signal must be triggered and different control measures initiated whenever the limit values for each layer are exceeded, depending on the state of the liquid, the liquid level, and the thickness of the three layers (sludge at the bottom, water above the sludge, and oil/light liquids at the surface). For this reason, it is very important not only to determine the total fill level but also to accurately measure the fill levels of the interface layers. Only in this way can a strict separation of the various liquids be ensured. Interface measurement thus helps prevent contamination, ensure high product quality, and reduce environmental impact. Precise level and interface measurements also prevent overfilling or underfilling of tanks in industrial plants, which optimizes material and resource usage and reduces operating costs. The risk of plant damage and the release of potentially toxic substances into the environment is reduced, thereby preventing environmental and health hazards. Particularly in process engineering, where natural raw materials are increasingly being used (e.g., for biopolymer production), the storage and processing of these heterogeneous materials—and the associated sensory detection of them, e.g., via interface sensors—will play an increasingly important role.

The goal of this project is to develop a new method for level and interface measurement based on guided acoustic waves (GAW). This innovative ultrasonic method is intended to combine a physical measurement principle with a sensor to enable precise and continuous level and interface measurement. Compared to existing commercial products, the sensor is designed to function even in highly corrosive media. The method is intended to enable better return of media to the process, as well as improved separation and recycling of liquids and chemicals compared to existing measurement methods. This results in more efficient, environmentally friendly, and resource-conserving process control overall, which enables the optimization of industrial processes, particularly when integrated into digitized control and regulation processes.

Funding agency:  Bundesministerium für Forschung, Technologie und Raumfahrt