Camera based Identification and Control of the Waelz Process

Abstract

The Waelz process is the most common technique for the pyro-metallurgical treatment of zinc-bearing residues using a rotary kiln. However, this process will only result in a good zinc recovery, if the temperature of the material (slag) within the kiln is controlled at specific optimal setpoints depending on the material mixture. Until now, slag temperature measurement is carried out by pyrometers which give only pointwise information that can be disturbed by cold slag lumps. Additionally, the temperature control is performed only manually by operators, who have to adapt the amount of process air frequently to keep the process stable at the desired setpoints. In this paper an infrared-camera based measurement of the slag temperature using image processing techniques is presented. Based on that temperature measurement a process model is conducted. Its parameters are estimated by a model-output-error based process identification. The process model is used for the tuning of parameters of an automatic closed loop control. Finally, results from an industrial application of the new camera based slag temperature control are given.Matthes, J., Waibel, P., Keller, H. and Gröll, L. Camera based Identification and Control of the Waelz Process.

Advanced Methods for Kiln-Shell Monitoring to Optimize the Waelz Process for Zinc Recycling

“…In addition, camera-based parameters are used. A particular infrared camera system [5], which provides information about the current slag temperature [6], is available to control the air supply at the end of the kiln [7]. This supply significantly influences the temperature of the kiln gas.…”