Improved process control of hot metal production through a non-intrusive, online sensing system for metals in the topgas of the blast furnace (PROCSSYMO)

At the beginning of the project the main emphasis was laid on the definition of the process requirements and on preliminary work in the labs and in the plants. In order to achieve the main objective of this project, online laser measurements of alkalis, zinc and lead in blast furnace top gas using the LIBS technique (Laser Induced Breakdown Spectroscopy), a measuring concept was developed that met all requirements of the partners involved. This included the design of a housing for the measuring equipment, a mechanical measuring probe and a laser measuring probe for laser measurements in different positions inside the top-gas pipes of the blast furnace plants. This was carried out in agreement with all partners and with special respect to the different constructional features of the 3 blast furnace plants involved, the requirements of the laser measuring technique itself as well as to saftey items during the measurements. The structure of the top gas pipes and the location of existing platforms were the main criteria for selecting the measuring sites. With this in mind, ThyssenKrupp Stahl (TKS-CS) chose BF #2 in Schwelgern and Rautaruukki Oyj (RR) BF #2 at Rautaruukki's Raahe steelworks. Aceralia (ACER) had the choice between BF A or B. In accordance with the measuring concept, the blast furnace plants prepared openings at the top gas pipes and verified the periphery which was necessary for the measurements, e.g. connections for electricity, gas and water supply. At the Institute of Ferrous Metallurgy of the RWTH Aachen (IEHK) a literature survey concerning the circulating elements in the blast furnace was carried out. The influence process of sodium, potassium, zinc, and lead on the blast furnaces were described. Laboratory rigs were set up at the research institutes IEHK, Fraunhofer Institut Lasertechnik (ILT) and the Institute of Electronic Structure & Laser of FORTH (IELS/FORTH) in order to prepare and to support the measurements in the blast furnace plants. The verification of the measuring method, the limits of detection of the elements and the measurement of calibration curves were of major importance here. Measurements were performed on reference materials as well as on different blast furnace flue dust samples which were provided by the steel plants. Different process conditions, e.g. gas velocity and pressure, particle density and gas composition and its influence on the detection of the elements of interest were investigated. The examination of the influence of the top gas pressure on the detection lines of the elements was of special interest and led to the use of a laser system with double pulse option by ILT. With the aid of laboratory experiments, the most prominent detection lines of the elements Na, K, Zn and Pb were established. Under the guidance of ILT a data pool containing all relevant technical data of the laser measuring equipment was compiled to specify the measuring equipment housing in agreement with all partners. Further investigations were carried out by ILT to determine the parameters for the design of the laser measuring probe and in particular of the measuring head. Most of the components of the laser measuring apparatus were specified and tested in the laboratory. The measuring concept which had been defined in the previous phase, was realised. TKS-CS set up the housing for the measuring equipment and constructed the mechanical measuring probe. In order to verify the functional suitability of the measuring system before starting the experiments at the blast furnace, a laboratory simulation rig was set up. This rig simulated a section of the blast furnace top gas pipe and allowed the examination of the original components under similar conditions to the blast furnace. First tests were made in order to test the handling of the movable probe when different pressures in the "top-gas pipe" are adjusted. Further on, the gas tightness of valves and stuffing boxes was examined.