8th International Congress on Science and Technology of Ironmaking - ICSTI 2018

Content ======= 1. Initial situation 2. New requirements lead to innovative analysis methods 3. Applicable applications for LIBS based smart process control 3.1 Applicable applications –LIBS on the feeding side 3.2 Applicable applications –LIBS in the melt shop 3.3 Applicable applications –LIBS in the milling, rolling and processing lines 3.4Applicable applications – LIBS in the laboratory 4. LIBS capabilities 5. Industry proven even in harsh environments 6. Summary 1. Initial situation ================= In iron making, wet-chemical, spectroscopic and radiometric methods are well established for a long time already. Nonetheless, the industry is struggling with certain shortcomings or disadvantages of these methods and is increasingly asking to overcome such limitations. Some analysis methods are contacting, some may require tedious sample preparation, some are using harmful ionizing radiation, some cannot measure all elements equally, some require a long time until results are available. To make steel production smart a method would be desirable that is universally applicable, provides results continuously, very quick and is easy to use. That would be too good to be true, would it? Well, as already seen in many other applications, the use of lasers can open up new possibilities. 2. New requirements lead to innovative analysis methods ==================================================== Ever increasing competition and rising demands on timely fault-free shipments of ever smaller lot sizes have already led to continuous process improvements in steel mills, e.g. by use of laser sensors for real-time measurement of physical properties, like thickness, width, flatness, length etc. With those properties being no longer a major concern, tighter control of other material properties is gaining more attention, namely alloy (chemical) composition of feeder materials. Tackling the challenge of inconsistent raw materials quality in iron making due to global sourcing of input materials, has also increased the need of continuous monitoring of feeding materials. Input streams that need to be analysed permanently are: - the calorific value and acidity, - the ash percentage - the sulphur and volatile contents of coal - the swelling of coal when coking, - the iron content in the iron ore - the basicity of iron ore - the variety of elements introduced by scrap recycling. - … By knowing what material quality is on hand, corrective action can be taken by targeted addition of deficient elements before or while charging, or by rejection of certain other material batches. 3. Applicable applications for LIBS based smart process control ============================================================ Analysis of the elemental composition is required or desirable in multiple steps and locations of steel making and steel rolling. Let’s have a look at some typical iron industry applications requiring elemental analysis to judge how close this technology can come to above mentioned ideal for the metals industry. 1. Continuous monitoring of the raw feeder materials like coal, coke, limestone, iron ore, scrap metals, sinter etc. on conveyors for charging control of sinter plants, blast furnaces and electric arc furnaces 2. Analysis of the slag composition at furnaces and converters, in solidified or even hot liquid state. 3. Analysis of the composition of steel samples, in solidified or even hot liquid state 4. Identification of alloy changes at the cooling bed exit, especially for SBQ mills, for proper allocation of all partial lengths to the initial billet and rolling order 5. Identification of alloy changes at the end of the (cold) finishing line for proper allocation of each individual rod to the proper shipment batch according to the production schedule 6. Analysis and sorting of head, tail and cobble croppings for alloy-true remelting of internal scrap, avoiding contamination of melts with unwanted elements. 7. 100% material identification at the charging side of reheat furnaces to ensure proper loading according to the production scheduling 8. 100% material identification after de-scaling to ensure proper alloy scheduling at the rolling train entrance. 3.1 Applicable applications –LIBS on the feeding side ------------------------------------------------- Production of the desired steel grade according to Industry 4.0 smart and in the shortest amount of time already begins when charging the (blast or EAF) furnace: Is the proper mix of materials fed to the furnace at the right time, in the right amount? LIBS sensors installed at the charging side allow precise identification and quantification of the currently charged materials, e.g. to avoid charging copper or other detrimental elements, to prevent mishaps in the charging sequence, as well as to charge fluxes in the right composition and basicity range. By ensuring charging of all required elements in the optimum mixture, time consuming analysis and correction phases in the smelting process can be reduced, thus improving the utilization significantly. 3.2 Applicable applications –LIBS in the melt shop ---------------------------------------------- In melt shops, two different measuring methods are commonly in use. One system is to analyse iron and another one is to analyse slags. With LIBS, just one system can do it all. In smelting and in ladle metallurgy, LIBS sensors can precisely determine the composition of slag and metal in real-time because they can measure in hot liquid state already. Thus time-delays incurred by conventional analysis methods requiring cooled down solid samples as well as tedious sample preparation are eliminated. E.g. the optimum tapping point can be determined with continuous monitoring of the iron oxide content in the slag almost to the second Providing immediate results LIBS allows the production process to meet the target slag and alloy compositions much quicker. Hence in these process steps, not only utilization, but also yield can be improved by using LIBS analysis. 3.3 Applicable applications –LIBS in the milling, rolling and processing lines ------------------------------------------------------------------------ Further downstream, Positive Material Identification (PMI) by LIBS sensors in rolling mills and processing line, starting at the reheat furnace entry, down to the finishing line exit, helps all mills dealing with frequent alloy changes. For this purpose, FiberLIBS Inline systems with a compact, separate sensor head, mounted at a suitable location of the respective conveyor system, are the ideal solution. Automatically measuring the composition of each work piece as it passes by on the conveyor, and comparing it against the alloy specification given in the production schedule, detects deviations or confusions immediately. By not only eliminating material confusion, but also allowing to cut down on gaps in the rolling sequence (which now seem to be the common practice to keep different alloys separate) mill utilization can be improved, and costly complaints and rejects due to confused alloys can be avoided. In times of increasing flexibility requirements PMI is a significant improvement especially for SBQ producers dealing with highly customized products. 3.4 Applicable applications – LIBS in the laboratory ------------------------------------------------ Last not least, also in metallurgy labs, LIBS systems can help to increase throughput of sample measurements. It can also solve demanding analysis tasks, like penetration of refractories by alloy elements, fast measurement of segregation effects and patterns in metal samples of almost any size, analysis of even smallest inclusions in metal samples, and so forth. LIBS capabilities Compared to other OES (optical emission spectroscopy) methods LIBS can: - Analyse all known elements, regardless of their atomic weight. There is no limitation regarding „light“ elements. - Electrically conductive as well as nonconductive materials can be analysed. - LIBS analysis can be carried out from a distance without any physical contact - The analysis is very fast, with precise results available within milliseconds - The measurements can be carried out at a high repetition rate up into the kHz range, making it ideally suitable for moving parts with velocities up to 3 m/s and more - Due to the very small spot size, the LIBS method provides a very good spatial resolution, which helps especially with the analysis of elemental distribution of heterogeneous materials. - In LIBS spectroscopy, no harmful ionizing radiation is present. - LIBS analysis typically does not require any material preparation, but can be carried out without sampling directly in the regular production material flow 4. How does LIBS work? =================== A high-energy laser pulse of very short duration (typically 1 to 40 mJ, 1 to 100 ns duration) is focused on the surface of the material to be inspected, generating a plasma fume of the material surface. In this process, some material is ablated, generating a „crater“ of 15 nm to 5um depth and 20 to 100 um diameter, depending on the parameters of the laser in use. Upon recombination of the plasma (also called breakdown), the electrons falling back on their original orbits emit photons (normally visible as light flash) with wavelengths characteristic for the specific elements. („spectral finger print“) A high-resolution spectral analysis of the emitted light (in NIR, VIS and UV, depending on the respective elements) with chemometric methods does not only allow to identify which elements are present, but also a fairly precise computation of their relative amounts. 5. Industry proven even in harsh environments ========================================== The long stand-off distance, combined with a very fast autofocus system of the MineralLIBS, allows the installation in a safe distance above conveyors, measuring on the unconditioned regular material stream. Due to the high measuring frequency and the small spot size, even small impurity events in the measurement track of the material flow can be registered. 6. Summary ======= LIBS is a versatile measurement method addressing current needs and challenges of a globalized world regarding analysis of elemental composition in the metals industries. It has a big potential for improvements of yield and utilization in multiple stages of the production processes, thus enabling metal producers and processors to reduce secondary processing (e.g. waiting) times as well as sourcing costs. In addition LIBS helps to increase process stability and product quality.