Furnace Tapping 2022: Session I
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, CaEng Associates; Hugo Joubert, Tenova Pyromet; Phillip Mackey, P.J. Mackey Technology, Inc.

Monday 8:30 AM
February 28, 2022
Room: 213D
Location: Anaheim Convention Center

Session Chair: Joalet Steenkamp, Mintek / University of the Witwatersrand

8:30 AM Introductory Comments

8:40 AM  Keynote
Controlled Tapping – The Research Project: Merete Tangstad1; 1Norwegian University of Science and Technology
    Tapping is an experience based sub-process that is developed over time at the various plants. To expand the knowledge into the scientific world, CFD modelling, industrial campaigns and lab scale experiments has mbeen conducted. A variety of models have been developed describing the tapping rate. We also need to know the mechanisms affecting the tapping of industrial furnaces. Both industrial campaigns and investigations on mechanisms and material at the lab has been conducted. The industrial campaigns as an example been to excavate both Mn-ferroalloy and Si furnaces. In lab scale, the formation of TiC banks in the SiMn furnaces, the formation of slag and the formation of SiO gas in Si furnaces and the pressure build up in charges by fines, have been investigated.

9:25 AM  
MIRS Robotic Tapping and Plugging of Non-ferrous Smelting Furnaces: Rodrigo Madariaga1; Luis Arevalo1; Tom Gabardi1; Phillip Mackey2; 1MIRS Robotics; 2P.J. Mackey Technology, Inc.
    The tapping and plugging operations of a metal, matte or slag taphole of a non-ferrous smelting furnace has a number of common aspects from one facility to another. In simple terms, the taphole initially requires the safe opening, allowing the molten phase to flow through the taphole, and then the taphole needs to be safely closed. Until now, tapping and plugging in non-ferrous smelting operations is largely performed by an operator. Safe operations around the taphole requires proper process control of the smelting furnaces, the correct taphole design for the required duty, and high quality, robust tapping and plugging equipment. This paper describes the successful adaptation of existing MIRS robotic technology to automating the slag tapping and plugging operations at a full commercial scale on a large copper flash furnace. The development of this robotic tapping machine is described and the operating features and performance are discussed. The extension of this design to other non-ferrous tapping applications such as those for copper matte, blister copper, and other non-ferrous operations such as metal and slag in ferronickel smelting are also discussed.

9:45 AM  Invited
CFD Study on Continuous Tapping of Silicon: Jan Erik Olsen1; Michal Ksiazek1; Merete Tangstad2; 1SINTEF; 2NTNU
     Silicon is mostly produced in rotating submerged arc furnaces with continuous tapping of metal. The burden is often dense due to condensates. Thus furnace gas does not escape easily to the top of the burden and some gas escapes through the tap-hole. This can cause an hazardous flame jet out of the tap-hole which poses an HES threat to operators. A mathematical CFD model has been developed to study the flow of gas and metal in the furnace through the tap-hole. A modelling challenge is to account for the continued tapping and the rotating furnace. These aspects differ from earlier CFD studies applied to furnace tapping. Results indicate the difference in tapping behaviour as the burden permeability varies and as the position of the tap-hole varies due to the rotation.

10:05 AM Break

10:25 AM  
Reduced-order Models of Furnace Tapping Systems – A Case Study from a Submerged Arc Furnace Producing Silicomanganese: Quinn Reynolds1; Joalet Steenkamp1; Jakobus Sutherland2; 1MINTEK; 2Transalloys
    In the present paper a reduced order model framework for material flow through a furnace tapping system incorporating the furnace interior, tap-hole, transfer launder, and tapping ladles is presented. The framework is based on governing equations based on fundamental pressure and mass balances, and uses simplified descriptions of each component in the tapping system to obtain an overall model. The utility of the resulting model is assessed by comparison to real-world tapping data obtained from an operating silicomanganese submerged arc furnace. Strengths and weaknesses in the model are subsequently identified and discussed in the context of the potential for such models to act as operator guidance and digital twinning tools. In particular, the effect of parameters which are able to change randomly from tap to tap is assessed in terms of their impact on the confidence associated with the model’s predictions.

10:45 AM  
The Interaction of Slag and Carbon on the Electrical Properties: Gerrit Surup1; Kseniia Koseniuk1; Merete Tangstad1; 1NTNU
    Renewable reducing agents are intended to replace significant amounts of fossil-fuel based reductants in submerged arc furnaces in the upcoming decades. In this study, the interaction of a manganese slag to a charcoal, a semi-coke and a metallurgical coke was investigated. In a first series, the viscosity and wettability of the slag were measured. The electrical resistivity of carbon material was measured by 4-point measurement. It was shown that the contact resistant between the carbon materials significantly decreased by void and pore filling. The results were validated by measuring the bulk resistivity of carbon-slag blended bed. While the slag is nonconductive below melting temperature, electrical current is highly conducted in the molten phase. The higher electrical resistivity of charcoal compared to the fossil fuel-based reductants improve the local heat generation in the carbon bed, concomitant reducing the viscosity of the slag, which may be beneficial for tapping of the furnace.

11:10 AM  
Electrical Resistivity of Transformed Carbon Materials in the Silicon Furnace: Haley Hoover1; Merete Tangstad1; Gudrun Sævarsdóttir2; 1NTNU; 2Reykjavik University
    Optimal current paths through the silicon furnace depend on electrical properties of the charge materials. It is essential for good tapping conditions that sufficient current is supplied to the arc and lower part of the furnace. As such, the electrical resistivity of the charge mix as it is transformed in the furnace is investigated. Various carbon materials (coal, charcoal, and char) are partially transformed at high temperatures to silicon carbide (SiC) through reactions with silicon monoxide (SiO) gas. The temperature gradient in the crucible creates layers of varying degrees of conversion. These layers are separated and characterized based on SiC, carbon, and Si content. The electrical resistivity of each layer is then measured from 25-1600°C. When the majority of the material is transformed to SiC, it will raise the resistivity compared to the carbon material, until silicon forms, when it will decrease again. The original structure appears to be more important to the resistivity than the transformation to SiC.

11:35 AM Concluding Comments