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.

Microwave technology has for decades been a tool for astronomers in their work to map and understand the complexities of the universe in terms of composition and extent but it is also used at laboratory scale by spectroscopists to examine the properties of atomic and molecular compounds. This paper discusses the use of microwave technology for the investigation of liquid slag structures. Preliminary results indicate that alteration of slag composition could be correlated to the measured microwave refractive index. Investigations have been performed on Al2 O3 -CaO-SiO2.

Within the metallurgical industry as well as the underground mine industry, there is a need for on-line level detection in the different production processes and their material feeding systems. Microwave technology is a versatile, non-invasive measurement technique, which has a number of advantages compared with penetrating probes, laser and radar technology, and echo sound technique. In its extension, it could also be used for qualitative and quantitative analysis of waste gases due to the presence of specific molecules. This contribution describes the introduction of microwave technology in different metallurgical as well as underground mine production processes with the emphasis on EAF's.

In many metallurgical operations, effective analysis of the processes can be very difficult with available technology. This is especially true if the analysis is to be performed on-line and in a harsh environment characterized by high temperatures, dust and liquid metal. Protection of the equipment requires both rugged encapsulation as well as elaborate sampling systems and exposure of the equipment to the hazardous environment must be minimised. Often this result in an increased level of service and maintenance requirements and, in the worst case, the maintenance cost might be so high that the equipment is not installed. Microwave technology is a versatile and powerful tool with many different applications in the scientific community. It is insensitive to dust and fume and, for several years, the technology has been tested at MEFOS and evaluated for different metallurgical processes. It has been applied to slag thickness measurement and slag composition in an induction furnace, 3D imaging of the burden surface in a charging model on pilot scale as well as raceway depth measurements in a Blast Furnace. The idea of using microwave technology for gas analysis in metallurgical processes has also been explored. However, despite its many advantages, microwave technology is still not employed extensively in the steel and metal industries. Copyright © 2007 ISIJ.

Microwave technology has for decades been a tool for astronomers in their work to map and understand the complexities of the universe due to composition and extent. The technology is also frequently used on laboratory scale to examine properties of atomic and molecular compounds. Combining the knowledge gained in those these fields of research and transferring it to the environment of the Steel and metal industry, a project to investigate microwave spectroscopy for on-line process control has been launched. Due to the fact that the dynamic in most metallurgical processes as well as combustion processes is very fast and the response time for conventional extractive gas analysers is long, off-gas analysis for on-line process control is not expedient with this technology. On the other hand, by exploiting microwave technology, its short response time and high sensitivity for gas analysis, disadvantages such as long response time could be eliminated, and thus improve the process efficiency. With this approach a process control on-line in “real time” is possible. On- line gas analysis entails an improved process control, which for metallurgical and combustion processes implies energy savings, reduced emissions of green house gases and improved productivity. In this novel work we will present a series of trials in which a high tempered gas flow is spectroscopically analysed in a frequency band ranging from 110 to 120 GHz. The objective is to stimulate compounds sensitive to radiation in this frequency band to make a transition from one energy level to another and in doing so giving up energy that can be detected by the measuring system. Of interest for the steel and metal industry are molecular compounds such as CO, CO₂ (isotope), O₂, NO, NO₂, H₂O, OH and SO₂.

By using a Tunable Diode Laser spectrometer the oxygen concentration and the temperature in the off-gases of an electric arc furnace, EAF, have simultaneously been monitored during operation. The spectrometer operates at a group of absorptoin lines lines in the near infrared wavelength region to measure the oxygen concentration and the temperature. The O₂ absotion line parameters used were determined in a controlled pilot experiment using a heated measurement path. The temperature is measured using the relative intensity of the absoption lines and thereafter concentration is calculated from the temperature compensated absorption. The measurements were performed in-situ with a specially designed high temperature sensor mounted on the furnace wall. Optical fibers were used to carry the probing light between the TDL spectrometer and the measurement point. This novel work shows the potential of using TDL spectrometer to measure O₂ and temperature in-situ in a steel making process.

Increased demands on quality control, reduced production-time, energy savings and reduction of green-house-gas emission in various metallurgical processes have created an interest for new methods to monitor and control the processes. By using Tunable Diode Laser spectrometers the gas temperature as well as the concentration of 0 2, CO and C02 have been monitored. Laboratory experiments were carried out in a specially designed high-temperature furnace at MEFOS to determine a set of absorption lines suitable for simultaneous 02ffemperature and CO/COz measurements. Field trials were carried out in an Electric Arc Furnace and a reheating furnace. 

The aim of the project is to use radio-wave interferometry to determine the BOF slag and metal heights in both a quiescent and a blowing BOS convertor. The hydrodynamics of the slag/metal emulsion and 1, 2 and possibly 3D representations of slag and metal movements during the blowing phase will be made. Process factors such as vessel shape, lance movements, bath agitation, flux/ore additions and fume generation will be considered.

Within the global steel-and metal industry there is a growing need for new sensor systems to measure and control the industrial process. New technologies for new sensors are continuously being developed for an ever growing market. The growth in the steel making industry is based on ore and Blast Furnaces therefore play an increasingly important role for the production of hot liquid iron and steel. We present a new interferometer micro wave system to makethree dimensional topographic maps of the blast furnace burden surface. The Blast Furnace process is one of the oldest industrial processes. The furnace is tall and round. Layers of Coke ands iron ore are successively laid, and air, pre-heated to 1200 °C, as fuel to the process. The coke and iron layers become semi-liquid and then liquid in the cohesive zone. The carbon from the coke reacts with the oxygen in the ore (which is Fe2O3or Fe3O4) and form CO and CO2which goes off as off-gas. The iron, now mixed with some amount of carbon, is tapped in liquid form from the bottom. This is then taken to a converter, where oxygen is added to remove the carbon to form the final product of liquid steel.

There are many known technologies that can be used to monitor surfaces, but the most of them requires a transparent environment to be functional. In the Blast Furnace where the environment is full of dust and fume at high temperatures those technologies are not applicable.

With a functional technology in such an environment the burden surface could be analysed and monitored, which in its extension would lead to a way to control the charging operation in the BF and thus a better use of raw material and also a better gas utilization.

In this paper we will discuss the use of microwave technology as one technology with the potential to create a topographical image of the burden surface in the Blast Furnace during operation.

Tunable diode laser absorption spectroscopy (TDLAS) is a recent development in process instrumentation. A commercial TDLAS instrument has been tested both in an industrial steel reheating furnace and in a pilot furnace at MEFOS for continuous oxygen analysis of the furnace combustion gases. Automatic control of the air-to-fuel ratio (AFR) was proven using a time-averaged oxygen concentration signal with a TDC2000 furnace controller at MEFOS. The oxygen concentrations measured by the TDLAS instrument compared well with local measurements of the oxygen concentration using a conventional zirconia probe in both furnaces. The diode laser has the advantages of high reliability for average gas concentration measurements in the path of the beam, when compared to point gas analysis with conventional zirconia instrumentation. Reliable gas analysis offers the benefits of improved process control, which for steel reheating furnaces include energy savings, reduced emissions and improved productivity.

Increased demands on energy savings and quality control in metallurgical processes have created incentives for new methods to monitor and control the process. In this paper we will present a field trial that shows the potential of tunable diode-laser spectroscopy (TDLS) for simultaneous contact free measuring and monitoring of the oxygen concentration as well as the gas temperature in a reheating furnaceduring production. The field trials were carried out at an oil-fueled reheating furnace during 7 weeks of production. The tunable diode-laserspectrometer was measuring in situ across the preheating zone and the soaking zone in the furnace. During the campaign the oxygenconcentration and the gas temperature in the furnace environment were simultaneously monitored and instantaneous variations in these parameters could easily be recorded and subsequently correlated to actual changes in the process. Furthermore, the much shorter response-time of the TDLS technique compared with conventional measurement methods such as thermocouples and extractive gas analyzers was also demonstrated during the trials. The results show the potential for the TDLS technique to be used for energy savings as well as product quality improvements by controlling the burners in the reheating furnace. The results show that it would be possible to control and optimize the oxygenconcentration with TDLS in the control loop of the reheating furnace. © 2002 Elsevier Science B.V. All rights reserved.