A Digital Sensor Technology to Help Increase Resource Efficiency

The Institute for Advanced Mining Technologies (AMT) at RWTH Aachen University, headed by Professor Elisabeth Clausen and Professor Karl Nienhaus, and the Department of Mineral Processing (AMR), led by Professor Hermann Wotruba, jointly developed an on-line measuring system through their efforts in the OMMA research project. Their measuring system can be used to characterize the material flow of gypsum and anhydrite in processing plants of the gypsum industry and is already being implemented in industrial practice. The system can be integrated into the preparation process for on-line analysis of a material flow and enables factories to determine the gypsum content in real-time at one-second intervals. This allows for a faster response to fluctuations in material quality, which increases raw material efficiency and cost-effectiveness. For their findings, the two RWTH institutions have now received the 2020 German “Rohstoffeffizienzpreis,” or Raw Materials Efficiency Award, from the Federal Ministry for Economic Affairs and Energy. The prize is awarded for outstanding material-efficient products, processes, services, or application-oriented scientific work.

As a result of the coal phase-out, the quantity of high-quality gypsum produced during flue gas desulphurization, which has been meeting around 50 percent of the demand in Germany, will fall sharply within the next few years. Unlike gypsum from primary deposits, whose composition naturally varies, “synthetic gypsum” is characterized by its high purity. Therefore, it is often used as an admixture to achieve the necessary high-quality standards in the construction materials sector. However, to meet future demand for gypsum, especially in the construction materials industry, natural gypsum must be increasingly mined from primary deposits. At the same time, existing gypsum plants must rev up their production output. The quantities produced must, however, also meet the high-quality standards.

In natural deposits, gypsum usually occurs together with the mineral anhydrite in various mixing ratios. For high-quality applications, the two minerals must be separated from each other. To do this, one must know how much gypsum a raw material contains – a number that tends to fluctuate. Currently, in operational practice, this requires costly sampling and laboratory testing. Due to such time-delayed laboratory analyses, the analog methods used up to now do not allow for reliable quality management in real-time. The technique developed in the “OMMA” project will now help gypsum plant operators quickly determine the gypsum and anhydrite content in raw materials and allow them to still produce high-quality gypsum in the future.