A computational fluid dynamic modeling study of slag fuming in top submerged lance smelting furnace

Slag fuming is a process of extracting zinc from molten slag in the form of metal vapor by injecting or adding a reducing source such as pulverized or lump coal, natural gas, etc. Top Submerged Lance (TSL) technology has been successfully applied to extract zinc by a fuming process from residues from the zinc industry, ISF and QSL slag and Lead blast furnace slag. A Computational Fluid Dynamic model has been developed for zinc slag fuming process from ISF slag to investigate details of fluid flow and heat transfer in the furnace. The models integrate complex combustion phenomena and chemical reactions with the heat, mass and momentum interfacial interaction between the phases present in the system. The model is based on 3-D Eulerian multiphase flow approach and it predicted the velocity and temperature field of the molten slag bath and side wall heat fluxes. The model also predicted the mass fractions of slag and gaseous components inside the furnace. The model confirmed that rate of zinc fuming increases with temperature and is broadly consistent with experimental data

CFD modeling of swirl and nonswirl gas injections into liquid baths using top submerged lances

Fluid flow phenomena in a cylindrical bath stirred by a top submerged lance (TSL) gas injection was investigated by using the computational fluid dynamic (CFD) modeling technique for an isothermal air–water system. The multiphase flow simulation, based on the Euler–Euler approach, elucidated the effect of swirl and nonswirl flow inside the bath. The effects of the lance submergence level and the air flow rate also were investigated. The simulation results for the velocity fields and the generation of turbulence in the bath were validated against existing experimental data from the previous water model experimental study by Morsi et al.[1] The model was extended to measure the degree of the splash generation for different liquid densities at certain heights above the free surface. The simulation results showed that the two-thirds lance submergence level provided better mixing and high liquid velocities for the generation of turbulence inside the water bath. However, it is also responsible for generating more splashes in the bath compared with the one-third lance submergence level. An approach generally used by heating, ventilation, and air conditioning (HVAC) system simulations was applied to predict the convective mixing phenomena. The simulation results for the air–water system showed that mean convective mixing for swirl flow is more than twice than that of nonswirl in close proximity to the lance. A semiempirical equation was proposed from the results of the present simulation to measure the vertical penetration distance of the air jet injected through the annulus of the lance in the cylindrical vessel of the model. More work still needs to be done to predict the detail process kinetics in a real furnace by considering nonisothermal high-temperature systems with chemical reactions

Computational fluid dynamics (CFD) investigation of submerged combustion behavior in a tuyere blown slag-fuming furnace

A thin-slice computational fluid dynamics (CFD) model of a conventional tuyere blown slag-fuming furnace has been developed in Eulerian multiphase flow approach by employing a three-dimensional (3-D) hybrid unstructured orthographic grid system. The model considers a thin slice of the conventional tuyere blown slag-fuming furnace to investigate details of fluid flow, submerged coal combustion dynamics, coal use behavior, jet penetration behavior, bath interaction conditions, and generation of turbulence in the bath. The model was developed by coupling the CFD with the kinetics equations developed by Richards et al. for a zinc-fuming furnace. The model integrates submerged coal combustion at the tuyere tip and chemical reactions with the heat, mass, and momentum interfacial interaction between the phases present in the system. A commercial CFD package AVL Fire 2009.2 (AVL, Graz, Austria) coupled with several user-defined subroutines in FORTRAN programming language were used to develop the model. The model predicted the velocity, temperature field of the molten slag bath, generated turbulence and vortex, and coal use behavior from the slag bath. The tuyere jet penetration length (l P) was compared with the equation provided by Hoefele and Brimacombe from isothermal experimental work {Mathematical expression} and found 2.26 times higher, which can be attributed to coal combustion and gas expansion at a high temperature. The jet expansion angle measured for the slag system studied is 85 deg for the specific inlet conditions during the simulation time studied. The highest coal penetration distance was found to be l/L = 0;0.2, where l is the distance from the tuyere tip along the center line and L is the total length (2.44 m) of the modeled furnace. The model also predicted that 10 pct of the injected coal bypasses the tuyere gas stream uncombusted and carried to the free surface by the tuyere gas stream, which contributes to zinc oxide reduction near the free surface

CFD modeling of combustion behavior in slag fuming furnaces

A computational fluid dynamic (CFD) model of a conventional tuyere blown slag fuming furnace has been developed in Eulerian multiphase flow approach. The model was developed by coupling CFD with kinetics equations developed by Richards et al. for zinc fuming furnaces. The model integrates submerged coal combustion and chemical reactions with the heat, mass and momentum interfacial interaction between the phases in the system. The model predicts the velocity, temperature field of the molten slag bath, generated turbulence, vortex and coal utilization behavior from the slag bath. The highest coal penetration distance was found to be at l/L = 0.2, where l is the distance from the tuyere tip and L is the total length (2.44m) of the modeled furnace. The model also predicts that 10% of the injected coal bypasses the tuyere gas stream un-combusted and carried to the free surface, which contributes to ZnO reduction near the free surface

Applications of CFD modelling in smelting industries: some recent developments

Recent advancement in the high performance computing facilities has enabled Computational Fluid Dynamic (CFD) modelling technique as a powerful tool for the researchers working in the metallurgical field. CFD can predict flows ranging from simple single phase flows to complex multiphase flows in high temperature combusting environment associated with metallurgical process and smelting industries. Successful and efficient development of a CFD model can predict the fluid flow behaviour, combustion behaviour, generation of turbulence and splashing and other fluid dynamic parameters inside the furnace. Present authors have developed a CFD model for zinc slag fuming process for top submerged lance smelting furnace. The model integrates complex combustion phenomena and chemical reactions with the heat, mass and momentum interfacial interaction between the phases present in the system. The model is based on 3-D Eulerian multiphase flow approach and commercial CFD package AVL FIRE 2009.2 (AVL, Graz, Austria) coupled with a number of user defined subroutines (UDF) in FORTRAN programming language were used to develop the model

Combustion modelling of top submerged lance furnace by using CFD tool

Top Submerged Lance Technology (TSL) have been successively applied to recovery of a range of metals like tin, lead, copper, zinc, silver, nickel, aluminium, gold etc. around the world. Floyd has described the details of Top Submerged Lance technology and its development since the 1970s. An investigation of fluid flow into a TSL system to reveal the detail process kinetics in a cold flow water model has been carried out by the present authors by using 3-D Computational Fluid Dynamic modelling technique. As a continuation of that research, a Computational Fluid Dynamic (CFD) model of the high temperature combustion phenomena in a TSL furnace was developed by incorporating the detail chemical reactions involving combustion. In the first stage, a single-phase 3-D combustion model for CH4 combustion was developed and temperature profile and mass fractions of fuel and air were investigated inside the combustion chamber at the lance tip. Then the model was extended to Multiphase flow simulation of zinc fuming process of a pilot plant with heat, mass, momentum and turbulence interfacial interaction between the phases. The chemical reactions between the slag components and gaseous species were also taken into account