Furnace Tapping 2022: Session IV
Sponsored by: The Southern African Institute of Mining and Metallurgy, TMS Extraction and Processing Division, TMS: Pyrometallurgy Committee, TMS: Process Technology and Modeling Committee, TMS: Materials Characterization Committee, Industrial Advisory Committee
Program Organizers: Joalet Steenkamp, XPS Glencore; Dean Gregurek, RHI Magnesita; Quinn Reynolds, Mintek; Gerardo Alvear Flores, Codelco; Hugo Joubert, Tenova Pyromet; Phillip Mackey, P.J. Mackey Technology, Inc.
Tuesday 2:30 PM
March 1, 2022
Room: 213D
Location: Anaheim Convention Center
Session Chair: Rodrigo Madariaga, Mirs Usa
2:30 PM Introductory Comments
2:35 PM
Health Friendly Plugging Repair Pastes: Antonio De Pretto1; Lars Lindstad1; 1Elkem Carbon AS
A well-functioning taphole is critical for most furnaces and it is important to have a plugging repair paste that contributes to maintain this. Plugging materials mainly containing carbon and oxides have been studied. The best working pastes in this system often contain Coal Tar Pitch high temperature (CTPht) which has been defined as a ’substance of very high concern’ under the European Chemicals Legislation (European Chemicals Agency, 2017)Taphole pastes that are without CTPht or large amounts of polycyclic aromatic hydrocarbons (PAH), have been developed in this work. An important part has been to develop test and measurement techniques to compare properties of new taphole materials with old well working pastes. Three of these techniques have been; plate viscometry, rapid heat up of samples with or without pressure in simulated tapholes keeping temperatures up to 1200°C. From these, properties of the paste and it’s repairing effect on surrounding materials could be measured.
2:55 PM
Tapblock Refractory Wear Monitoring and Hearth Refractory Design Optimization in Metallurgical Furnaces: Cameron Soltys1; Jayant Borana1; Hamid Ghorbani1; Richard MacRosty1; Tom Plikas1; Chad Van der Woude1; 1Hatch
Monitoring the refractory wear in the tapblock is key to achieving extended taphole and furnace hearth life through informing operation and maintenance plans. The utility of a tapblock condition assessment system can be maximized by enhancing thermal monitoring, using an online monitoring system, data processing, and first-principles process modeling to develop a robust model of the tapblock condition. <p> Another key factor impacting furnace campaign life is the refractory design, which requires balancing of competing priorities such as cost, performance, and constructability. Structural assessment of a hearth system can be used to quantify and optimize these features while identifying potential fatal flaws in a design, avoiding short campaign life. This assessment can be used to determine the impact of design changes, providing confidence in refractory design decisions.<p>This paper will present examples of wear monitoring in the taphole region of a flash converting furnace and refractory design optimization for electric arc furnaces.
3:15 PM
The Evaluation of Chemical Wear of Carbon-based Tap-hole Refractories in Ferrochrome Production: Martin Sitefane1; Joalet Steenkamp1; 1Mintek
In ferrochrome (FeCr) production, the tap-hole refractory represents the highest wear area. As a case in point, In June 2017 during an annual maintenance shutdown of two 63 MVA submerged arc furnaces (SAFs), based in South Africa, wear of the primary carbon tap-hole refractory was observed to be so pronounced that little to no tapblock refractory remained. Preliminary desktop FactSage modelling work indicates that both alloy and slag had the potential to chemically wear the refractory material. The current study seeks to build on the modelling work, by performing laboratory-scale experiments aimed at validating the modelling outcome, as well as provide further insights into the chemical wear mechanism. Additional tests are conducted using alternative, industrially available, carbon refractory material to evaluate the same concepts.
3:35 PM
Metal and Slag Extraction from Different Zones of a Submerged Arc Furnace with Non-uniform Porous Bed Using CFD: Varun Loomba1; Jan Olsen2; Kristian Einarsrud1; 1Norwegian University of Science and Technology; 2SINTEF Industry
In this study, CFD is used to simulate an industrial scale submerged arc furnace (SAF) during tapping and production periods to realize the flow of metal and slag. The flow of the fluids through a porous coke bed is included, which creates a significant pressure loss and thus dominates the tapping flow rates. The aim of this study is to realize whether the metal or the slag being tapped is produced close to the tap-hole or in other parts of the furnace also, which informs us about the accumulation of the fluids in the furnace, thus affecting its efficiency. The first study focusses on flow of metal from different parts of the furnace for a non-porous bottom region (where metal is produced) and a porous top region (where slag is produced), and the second study focusses on flow of slag from different regions for uniform porosity in the furnace.
3:55 PM Break
4:15 PM
Investigation of Melting Behavior and Viscosity of Slags from Secondary Ferromanganese Production: David Scheiblehner1; Christoph Sagadin1; Helmut Antrekowitsch1; Stefan Luidold1; Dieter Offenthaler2; 1Montanuniversität; 2Batrec Industrie AG
Viscosity and melting behavior are two of the most important properties of industrial slags as they directly impact the yield of metallurgical processes. Too high fluidity may cause losses during tapping or infiltration of refractory while too viscous liquids can lead to problems regarding the smelting of charged material or metal inclusions. This paper comprises a determination of melting behavior and viscosity of slags in dependence on their composition. Therefore, 19 mixtures of different oxides have been prepared and fused by means of an induction furnace. An analysis of the resulting slags in a hot stage microscope and the computation of the corresponding viscosities allow a statistical evaluation of the most important parameters. Significant variations of viscosity and characteristic temperatures can be measured as functions of the content of manganese oxide and the ratio between calcium oxide and silicon dioxide respectively besides a strong temperature dependency.
4:35 PM
NOW ON-DEMAND ONLY - Tap-hole Refractory Issues and Remedies: Dean Gregurek1; Christine Wenzl1; Jürgen Schmidl1; Alfred Spanring1; 1RHI Magnesita
Post-mortem investigations of used refractories have proven to be a crucial tool for evaluating process conditions and their effect on the lining. Despite these experiences, refractory samples from tapholes are often neglected and do not get too much attention – there is a general opinion: “taphole refractory wear is due to tapping operations and there is no room for optimization”. However, closer investigations of taphole samples provide some valuable insights into wear phenomena and optimization potential (e.g., slag corrosion, non-oxide infiltration, microstructural changes due to high temperature load). Even though the possible changes to the actual tapping operations might be limited, it is worth considering e.g., refractory upgrades. Additional possibilities for optimized taphole refractory performance and general tapping procedures are various additional technologies, e.g., sensor technologies.
4:55 PM
NOW ON-DEMAND ONLY - Slide Gate Technology for Slag Tapping: Goran Vukovic1; 1RHI Magnesita
A well-functioning tap-hole is an essential requirement for stable melting processes as well as for reliable smelter operation over time. Slag should be tapped from the furnace balancing between production rate, capacity of the downstream vessels and safety of the operators. In stationary vessels tapping flow rate and its flow behavior are strongly dependent on conditions in the furnace (pressure, bath level and liquid properties) as well as on tap-hole geometry and its wear level. These conventional tapping procedures indicate uncontrolled and unsteady flow of slag causing numerous challenges. Slag Slide Gate Technology is a solution that enables an accurate regulation of the slag tapping flow rate and quick reaction by tap-hole closing. This implies controlled and steady slag flow, minimized splashing in the tap-hole surroundings, improved safety due to an immediate tap hole closing in case of an emergency and brings higher degree of automation in a metallurgical plant.
5:15 PM
Tap-hole Clay Technologies for Ferroalloy Reduction Furnaces: Tomas Oliveira1; Wagner Moulin-Silva1; Aloísio Ribeiro1; Modestino Brito2; 1RHI Magnesita; 2Yamagata Consultoria
Taphole clay is a very important material to seal tapholes in Fe-alloy reduction furnaces. Different types of this refractory are available for the Fe-alloy industry and to decide which would be the most appropriate material may be a difficult task. This paper shows a comparison between the properties of four different types of taphole clays that were designed for Fe-alloy furnaces, focusing on the application in metal tapholes. The goals are to improve the knowledge regarding these materials and guide Fe-alloy producers when deciding what type of taphole clay should be used. The analyzed mixes differ from each other mainly in terms of the type of aggregate (basic or nonbasic) and type of binder (tar, resin or synthetic oil).
5:35 PM
NOW ON-DEMAND ONLY - Simulation-based Approaches for Optimized Tap Hole Design: Guenter Unterreiter1; Anton Ishmurzin1; Ulrich Marschall1; Alfred Spanring1; 1RHI Magnesita
For efficient operation of an electric arc furnace the tap-hole region is one of the most important parts. It experiences thermal stresses, creep and erosion. To consider these effects in a virtual design process it is necessary to use both sophisticated thermo-mechanical and fluid dynamics models. In this article we demonstrate application of FEM, CFD and optimization methods to obtain tailored refractory linings. We use linear elastic and creep models to perform numerical analyses of a geometrically simplified tap hole area. An experiment-based methodology to obtain Norton-Bailey creep parameters is presented. The significance of considering creep during the design process is demonstrated. On the CFD side we perform a shape optimization of a tap hole channel. We minimize the flow resistance using an optimization method on a parameterized geometry of the tap hole channel. Using several geometric parameters, we minimize the resulting flow resistance.
5:55 PM Concluding Comments