Innovative Contact Free Sensors for Metallurgical Process Control

Sammanfattning: The steel- and metal industry has an extensive production processing comprising many different process steps of solid, gaseous and liquid nature. Thus it is obvious that a number of different measurement technologies must be used to collect and evaluate key physical parameters which are necessary to control the production processes. In this respect, the software to monitor the processes have, during the past decade, undergone extensive improvement whilst the sensors reading off the instantaneous process status have not and are still afflicted with severe drawbacks. This situation, in combination with increased demands on energy savings and rules regarding reduction of green house gas emission (the Kyoto protocol), has created incentives for the development and implementation of new technologies to monitor and control production processes in the steel and metal industry. The objectives in this thesis are to develop and evaluate sensor technology that can be used for in-situ on line analysis of metallurgical processes. The work is divided into: - To test and evaluate microwave technology for on line slag analysis. - To design, develop and evaluate microwave sensors for off gas analysis. - To evaluate laser sensors for simultaneous analysis of the process environment in metallurgical processes with emphasis on measuring the oxygen concentration and temperature in a steel reheating furnace During the work on slag a broad band antenna was used for the microwave investigations on solid and liquid slag. The results show that it is possible to evaluate a refractive index for both solid and liquid slag. The results also show that there is a weak correlation between the refractive index for liquid slag and slag basicity. Trials on off gases from a pilot process as well as a full scale metallurgical production processes have been performed with microwave technology. The instrument used for the microwave trials has been developed from individual components. The results show that it is possible to use the technology for process analysis however the data collected regarding individual spectral lines still remain to be correlated to known molecular frequencies. Laser technology for gas analysis is a known technology in many different industrial applications. However, using the technology in steel and metal production processes requires that the technology must be adapted to the environment specific to those processes. Trials on a pilot process has been performed to find a suitable set of O2 absorption line parameters to be used during the forthcoming trials of full scale production processes. The outcome of these trials clearly show that the TDLAS technology can be used successfully on reheating furnaces but have a limited application potential on the LD converter process as well as the EAF. The benefit of the presented work will on production scale contribute to a lowered emission of green house gases, lowered energy consumption and an improved production yield. Key words: microwave spectroscopy, laser, TDLAS, high temperature, gas, slag