TY - CONF

T1 - CFD modelling of slag fuming, with focus on freeze-lining formation

AU - Gomes Rodrigues, Christian

AU - Wu, Menghuai

AU - Chintinne, Mathias

AU - Ishmurzin, Anton

AU - Hackl, Gernot

AU - Voller, Nikolaus

AU - Ludwig, Andreas

AU - Kharicha, Abdellah

PY - 2024/6

Y1 - 2024/6

N2 - Slag fuming (SF) is a critical process for recycling zinc-containing slags, but the corrosive nature ofmolten slag poses challenges to the reactor durability. The freeze-lining (FL) technique offers asolution by forming a protective layer on the reactor wall. It requires intensive cooling using water-cooled jackets, which can stabilise the FL while compromising the energy efficiency of the process.This study presents a computational fluid dynamic (CFD)-based model to optimise the SF processby considering FL formation and its impact on heat transfer and reactor wall temperature. A volume-of-fluid (VOF) model is coupled with a mixture continuum (MC) solidification model to capture theintricate multiphase flow dynamics within the SF furnace. Two FL types are considered: FL solidifyingon the reactor wall in the slag bath region; and FL solidifying on the reactor wall in the freeboardregion. The FL of the first type forms when the slag temperature drops below liquidus temperature.The FL of the second type only forms when a splash-induced slag droplet collides with the freeboardwall and solidifies. A series of splashing events are necessary to coat the freeboard wall.The simulation was run until a global energy balance was reached. This means that the heat lossesfrom the water-cooled jacket, bottom wall, outlet and fuming balance the heat gains from the hot gasinjected through the submerged plasma torches. The increase in FL thickness, due to its low thermalconductivity, reduces the heat losses through the reactor walls. The calculated FL thickness andheat fluxes were in good agreement with industrial data, validating the model’s credibility.The simulation results provided valuable insights into the fuming process, including slag bathtemperature evolution, slag splashing dynamics, FL formation patterns, local heat fluxes through thereactor wall and overall energy balance. These findings can inform process optimisation strategiesto enhance the energy efficiency and sustainability of SF operations.The authors have built a prior version of the model framework and applied it to simulate FL formationin an electric smelting furnace (ESF). The results from both the ESF and the current SF highlight theapplicability of such model framework to a range of industrial processes involving FL formation. Thismodel framework can ultimately contribute to more energy-efficient and sustainable industrialoperations.

AB - Slag fuming (SF) is a critical process for recycling zinc-containing slags, but the corrosive nature ofmolten slag poses challenges to the reactor durability. The freeze-lining (FL) technique offers asolution by forming a protective layer on the reactor wall. It requires intensive cooling using water-cooled jackets, which can stabilise the FL while compromising the energy efficiency of the process.This study presents a computational fluid dynamic (CFD)-based model to optimise the SF processby considering FL formation and its impact on heat transfer and reactor wall temperature. A volume-of-fluid (VOF) model is coupled with a mixture continuum (MC) solidification model to capture theintricate multiphase flow dynamics within the SF furnace. Two FL types are considered: FL solidifyingon the reactor wall in the slag bath region; and FL solidifying on the reactor wall in the freeboardregion. The FL of the first type forms when the slag temperature drops below liquidus temperature.The FL of the second type only forms when a splash-induced slag droplet collides with the freeboardwall and solidifies. A series of splashing events are necessary to coat the freeboard wall.The simulation was run until a global energy balance was reached. This means that the heat lossesfrom the water-cooled jacket, bottom wall, outlet and fuming balance the heat gains from the hot gasinjected through the submerged plasma torches. The increase in FL thickness, due to its low thermalconductivity, reduces the heat losses through the reactor walls. The calculated FL thickness andheat fluxes were in good agreement with industrial data, validating the model’s credibility.The simulation results provided valuable insights into the fuming process, including slag bathtemperature evolution, slag splashing dynamics, FL formation patterns, local heat fluxes through thereactor wall and overall energy balance. These findings can inform process optimisation strategiesto enhance the energy efficiency and sustainability of SF operations.The authors have built a prior version of the model framework and applied it to simulate FL formationin an electric smelting furnace (ESF). The results from both the ESF and the current SF highlight theapplicability of such model framework to a range of industrial processes involving FL formation. Thismodel framework can ultimately contribute to more energy-efficient and sustainable industrialoperations.

KW - CFD

KW - Freeze Lining

KW - VOF

KW - ESF

M3 - Paper

SP - 839

EP - 846

T2 - 12th International Conference on Molten Slags, Fluxes and Salts

Y2 - 17 June 2024 through 19 June 2024

ER -