Monitoring of furnace tapping: contact-free measurements by means of multispectral imaging

Transfer of liquid metal from smelting furnaces and induction furnaces is a critical process in metallurgical operations. Today, the processes are normally controlled and monitored manually. The most critical parameters in monitoring are temperature, flow rate and velocity, as well as slag/metal composition. Since the material is hot (approx. 1500 °C), it will emit intense radiation in both the visible and infrared spectrum. A trained operator can form a reasonable estimate of the three critical parameters by looking at the width of the beam and the color of the light it emits.

In this project, the main goal has been to provide a better estimate of these parameters using a hyper- and multispectral camera that takes film of the molten metal stream and use these data analysis to calculate the desired parameters. The tests were carried out on two different furnaces at REC Solar in Kristiansand, a melting furnace and an induction furnace. The project has provided information on several important elements in relation to the possibilities for further developing camera-based monitoring of the furnace tapping streams. In relation to spatial resolution and visibility, the measurements have confirmed the hypothesis that the hyperspectral and multispectral cameras are little affected by smoke. This means that the camera could be placed at a distance from the oven and optical zoom used to get the desired resolution in the image. Clearly delineated images are necessary for the estimation of flow rate and velocity. Although the project has not attempted to calculate these parameters from the images, the possibilities look promising.