Electromagnetic Measurement of Molten Metal Level in Pyrometallurgical Furnaces

Accurate control of molten metal levels during pyrometallurgical smelting operations is critical to improve process decision-making and maximizing production efficiency, such as when to commence tapping and the duration of the tapping operation. In addition, molten metal level control is important for long-term structural integrity of the furnace. Current methods to measure molten metal levels have limited accuracy and are intermittent, as they require manual measurement from above the furnace. In this paper, a continuous measurement system was designed to improve the molten metal level measurement in pyrometallurgical furnaces. This paper describes the tests of an electromagnetic sensing system consisting of eddy current drive and pickup coils that could be embedded in the wall of a furnace. As part of the development, portions of the system were simulated using COMSOL, and a prototype of the key hardware components was built and tested in the laboratory to validate the simulation results. Differential coil hookup provided a low-noise and high-resolution response. The system obtained a molten metal level detection resolution of 5 mm at liftoff distances approximately 300 mm from the simulated metal bath. Projection to latent structures (or partial least square) and regression analyses were applied to signal response to predict metal height, and a good agreement between predicted and measured laboratory metal heights was obtained. Initial results of the prototype system demonstrate its potential to accurately and continuously measure molten metal level, thereby improving safety and control of furnace operations.