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The advantages of gas/flux injection technology in the unit processes for steelmaking are discussed, covering hot metal pretreatment through to secondary refining. The current status of micro-kinetic issues involved in injection technology is reviewed including gas-in-metal, gas-in-slag, flux-in-metal, metal-in-flux and three-phase dispersion systems with reference to macro-kinetics. Key problems are briefly discussed with the aim of furthering the development of injection technology for steelmaking processes., The advantages of gas/flux injection technology in the unit processes for steelmaking are discussed, covering hot metal pretreatment through to secondary refining. The current status of micro-kinetic issues involved in injection technology is reviewed including gas-in-metal, gas-in-slag, flux-in-metal, metal-in-flux and three-phase dispersion systems with reference to macro-kinetics. Key problems are briefly discussed with the aim of furthering the development of injection technology for steelmaking processes.

The transverse distribution of the axial momentum flux is a dominant factor influencing the penetration behaviour of particles into melts during submerged injection. The transverse distributions of the solids discharge velocity and mass flux at the discharge end of vertical and inclined lances were measured. The effects of gas velocity, solids loading, lance length, lance inclination and particle density were investigated. The particle discharge velocities for vertical downward flows were found to increase with increasing gas velocity, increasing lance length and deceasing particle density. The highest particle discharge velocities occurred near to top of the lance as the horizontal orientation was approached. The transverse mass flux for vertical downwards flow peaked at low gas velocities, particularly for higher density particles. As the horizontal orientation of the lance approached the discharge mass flux decreased. The effect was more pronounced at low gas velocities., The transverse distribution of the axial momentum flux is a dominant factor influencing the penetration behaviour of particles into melts during submerged injection. The transverse distributions of the solids discharge velocity and mass flux at the discharge end of vertical and inclined lances were measured. The effects of gas velocity, solids loading, lance length, lance inclination and particle density were investigated. The particle discharge velocities for vertical downward flows were found to increase with increasing gas velocity, increasing lance length and deceasing particle density. The highest particle discharge velocities occurred near to top of the lance as the horizontal orientation was approached. The transverse mass flux for vertical downwards flow peaked at low gas velocities, particularly for higher density particles. As the horizontal orientation of the lance approached the discharge mass flux decreased. The effect was more pronounced at low gas velocities.

Discussion is presented of some of the experimental techniques which are available to study gas-liquid flows, the conditions where they can best provide the necessary information and their limitations. Techniques included involve photographic methods, video methods, electroresistivity probes, hot film, laser Doppler anemometry (LDA), phase Doppler anemometry and particle image velocimetry (PIV). The use of LDA and PIV has been improved and these methods have provided valuable data for validating mathematical models for simulating gas plumes in liquids., Discussion is presented of some of the experimental techniques which are available to study gas-liquid flows, the conditions where they can best provide the necessary information and their limitations. Techniques included involve photographic methods, video methods, electroresistivity probes, hot film, laser Doppler anemometry (LDA), phase Doppler anemometry and particle image velocimetry (PIV). The use of LDA and PIV has been improved and these methods have provided valuable data for validating mathematical models for simulating gas plumes in liquids.

The new lead smelter started operation in May 1992 and treats various types of lead concentrate and secondary materials coming from the zinc plant without special pretreatment. The smelter operates stably at a total feed rate of 57 tonnes/h. The plant has of several sections: storage and handling of raw material, the QSL reactor, decopperising of bullion, slag handling, heat recovery, gas cleaning, the sulphuric acid plant and the coal crushing plant. Discussion is presented of the two types of movable injectors in the reactor. Oxygen injectors are installed in the oxidation zone to oxidise the feed material and coal injectors are installed in the reduction zone to supply powdered coal as reductant to the bath with oxygen., The new lead smelter started operation in May 1992 and treats various types of lead concentrate and secondary materials coming from the zinc plant without special pretreatment. The smelter operates stably at a total feed rate of 57 tonnes/h. The plant has of several sections: storage and handling of raw material, the QSL reactor, decopperising of bullion, slag handling, heat recovery, gas cleaning, the sulphuric acid plant and the coal crushing plant. Discussion is presented of the two types of movable injectors in the reactor. Oxygen injectors are installed in the oxidation zone to oxidise the feed material and coal injectors are installed in the reduction zone to supply powdered coal as reductant to the bath with oxygen.

MEFOS, the Foundation for Metallogenic Research in Sweden, have been involved in work related to injection technology, specifically in the areas of dust handling (micro-powder), oxy-coal injection into blast furnaces, high temperature powder treatment, destruction of chemicals by the injection of liquids into melts, efficient cooling of liquids, controlled introduction of gases into high pressure tuyeres and variable supersonic flows in BOF., MEFOS, the Foundation for Metallogenic Research in Sweden, have been involved in work related to injection technology, specifically in the areas of dust handling (micro-powder), oxy-coal injection into blast furnaces, high temperature powder treatment, destruction of chemicals by the injection of liquids into melts, efficient cooling of liquids, controlled introduction of gases into high pressure tuyeres and variable supersonic flows in BOF.

The nature of accretions formed during gas injection can have a considerable effect on the life of the lance or the refractories in the tuyere region. There are three basic shapes of accretion formed on tuyeres: pipes, hemispheres and hollow-cored hemispheres. To obtain a better understanding of the effects of process design and operating variables on accretion formation, studies have been carried out of data gathered from operating furnaces and from previous and current mathematical and physical modelling. A rough correlation has been developed which links the material properties of the bath and the injection conditions to the type of accretion formed. The approximate size of the accretion can be related to the relative magnitudes of the primary heat flows away from the tuyere region., The nature of accretions formed during gas injection can have a considerable effect on the life of the lance or the refractories in the tuyere region. There are three basic shapes of accretion formed on tuyeres: pipes, hemispheres and hollow-cored hemispheres. To obtain a better understanding of the effects of process design and operating variables on accretion formation, studies have been carried out of data gathered from operating furnaces and from previous and current mathematical and physical modelling. A rough correlation has been developed which links the material properties of the bath and the injection conditions to the type of accretion formed. The approximate size of the accretion can be related to the relative magnitudes of the primary heat flows away from the tuyere region.

Discussion is presented of fundamental aspects of the Mitsubishi process with regard to injection, especially splashing phenomena. Physical models were used to investigate the splashing on a vertical plane caused by top blowing gas injection onto the liquid surface. The splashing rate on the side wall of the cylindrical vessel was correlated with the physical properties of the bath materials, gas velocity, cavity shape, lance/wall distance and ceiling position. Equations obtained were compiled in a computer program and have been successfully applied to the evaluation of the furnace design., Discussion is presented of fundamental aspects of the Mitsubishi process with regard to injection, especially splashing phenomena. Physical models were used to investigate the splashing on a vertical plane caused by top blowing gas injection onto the liquid surface. The splashing rate on the side wall of the cylindrical vessel was correlated with the physical properties of the bath materials, gas velocity, cavity shape, lance/wall distance and ceiling position. Equations obtained were compiled in a computer program and have been successfully applied to the evaluation of the furnace design.

The Sirosmelt process is based on a simple lance through which process air and fuel are delivered beneath the surface of a liquid slag bath where submerged combustion takes place to give efficient heat transfer to the slag. CSIRO developed the process in the early 1970s for tin smelting and processing tin slags. After a small pilot plant had been built the process was established for treatment of copper, nickel, zinc and cobalt slags. In the late 1970s the process was used for copper and lead smelting. The next decade saw the commercialisation of the processes by Ausmelt with a number of plants being built in Australia. In the 1990s the technology is diversifying outside the non-ferrous and precious metals production industry; it has been recognised that top-submerged lancing technology could also be beneficial to the waste processing, recycling and iron and steel industries., The Sirosmelt process is based on a simple lance through which process air and fuel are delivered beneath the surface of a liquid slag bath where submerged combustion takes place to give efficient heat transfer to the slag. CSIRO developed the process in the early 1970s for tin smelting and processing tin slags. After a small pilot plant had been built the process was established for treatment of copper, nickel, zinc and cobalt slags. In the late 1970s the process was used for copper and lead smelting. The next decade saw the commercialisation of the processes by Ausmelt with a number of plants being built in Australia. In the 1990s the technology is diversifying outside the non-ferrous and precious metals production industry; it has been recognised that top-submerged lancing technology could also be beneficial to the waste processing, recycling and iron and steel industries.

Studies were carried out of the prototype tuyere geometry for injection of inert gas through the bottom of a basic oxygen steel furnace to specify the optimal flow for bottom wear and metal penetration. Flow velocity profile development within the tuyere is thought to be significant and the experimental scheme was designed to test this. It is proposed that the design criterion for the conditions of optimal flow of the prototype geometry be based on the nondimensional mass velocity., Studies were carried out of the prototype tuyere geometry for injection of inert gas through the bottom of a basic oxygen steel furnace to specify the optimal flow for bottom wear and metal penetration. Flow velocity profile development within the tuyere is thought to be significant and the experimental scheme was designed to test this. It is proposed that the design criterion for the conditions of optimal flow of the prototype geometry be based on the nondimensional mass velocity.

Discussion is presented of experimental studies of large and multiple bubbles, top submerged gas injection into slags and the numerical simulation of splash formation. It was found that the amount of splash formed is dependent on the shape, size and position of the bubble relative to the position of the free surface. The effect of multiple bubbles in enhancing splash as a result of coalescence may be a significant splash mechanism. During top submerged gas injection, the shearing of high gas flows by a gas jet is also an important mechanism for the formation of splash and the conditions for its formation can be determined by simple energy balances. The volume of fluid method has become a very useful tool in elucidating the fundamentals of splash formation and substantial advances in splash simulation have been carried out., Discussion is presented of experimental studies of large and multiple bubbles, top submerged gas injection into slags and the numerical simulation of splash formation. It was found that the amount of splash formed is dependent on the shape, size and position of the bubble relative to the position of the free surface. The effect of multiple bubbles in enhancing splash as a result of coalescence may be a significant splash mechanism. During top submerged gas injection, the shearing of high gas flows by a gas jet is also an important mechanism for the formation of splash and the conditions for its formation can be determined by simple energy balances. The volume of fluid method has become a very useful tool in elucidating the fundamentals of splash formation and substantial advances in splash simulation have been carried out.

The essential features of WORCRA technology are continuous feed into the process, continuous flow of metal (or matte) and slag out of the process, the marriage of smelting/melting and refining into one vessel and the counter-flow of metal (or matte) and slag for good refining. Using this technology, highly refined metals can be produced by continuous countercurrent flow of metal and slag. Tracer studies in both hot and cold systems have indicated that longitudinal dispersion can be minimised in refining channels by operating with appropriate flowrates, bubble/lance spacing and gas injection rates. Many issues of channel design remain unresolved, particularly the relationship between mass transfer and dispersion, geometry and dispersion and optimum depths of slag and metal phases. Results obtained in studies of countercurrent refining show that it may be possible to combine high productivity smelting with continuous refining technology., The essential features of WORCRA technology are continuous feed into the process, continuous flow of metal (or matte) and slag out of the process, the marriage of smelting/melting and refining into one vessel and the counter-flow of metal (or matte) and slag for good refining. Using this technology, highly refined metals can be produced by continuous countercurrent flow of metal and slag. Tracer studies in both hot and cold systems have indicated that longitudinal dispersion can be minimised in refining channels by operating with appropriate flowrates, bubble/lance spacing and gas injection rates. Many issues of channel design remain unresolved, particularly the relationship between mass transfer and dispersion, geometry and dispersion and optimum depths of slag and metal phases. Results obtained in studies of countercurrent refining show that it may be possible to combine high productivity smelting with continuous refining technology.

Discussion is presented of solid, gaseous and liquid injection technologies used in the primary and secondary aluminium industries. The solid injection technologies involve injection of powder, shred, granules, rods and lumps; furnace fluxing and inline metal treatment are the gaseous injection technologies. Liquid injection of alloys instead of solid injection would be an ideal process, but is not yet possible. Discussion of gaseous and solids injection processes includes injection in crucibles, furnaces, launders and into special purpose metal treatment boxes., Discussion is presented of solid, gaseous and liquid injection technologies used in the primary and secondary aluminium industries. The solid injection technologies involve injection of powder, shred, granules, rods and lumps; furnace fluxing and inline metal treatment are the gaseous injection technologies. Liquid injection of alloys instead of solid injection would be an ideal process, but is not yet possible. Discussion of gaseous and solids injection processes includes injection in crucibles, furnaces, launders and into special purpose metal treatment boxes.

Mount Isa Mines and CSIRO have developed the Copper Isasmelt process, with the first two commercial plants beginning operation in 1992. The results of four heat balances on the Mount Isa plant are presented and show that the furnace is near chemical equilibrium. The impurity distribution was determined for Cu, Au, As, Cd, Bi, Zn, Sb, Tl, Pb and Te. Bubble frequency of the gas cavity below the foot of the lance was found to be consistent with radial gravity wave motion in the slag bath. Gas bubbling and wave motion appeared to be related; the bubble frequency was twice the slop wave frequency., Mount Isa Mines and CSIRO have developed the Copper Isasmelt process, with the first two commercial plants beginning operation in 1992. The results of four heat balances on the Mount Isa plant are presented and show that the furnace is near chemical equilibrium. The impurity distribution was determined for Cu, Au, As, Cd, Bi, Zn, Sb, Tl, Pb and Te. Bubble frequency of the gas cavity below the foot of the lance was found to be consistent with radial gravity wave motion in the slag bath. Gas bubbling and wave motion appeared to be related; the bubble frequency was twice the slop wave frequency.

An understanding of fluid flow is essential in processes such as copper conversion and bath smelting, where gas is injected into liquid metal, for the calculation of process intensity and optimisation of vessel productivity. Cold model studies have been carried out in which gas reacts with the liquid into which it was injected. The rate of liquid mixing was measured as an indication of the mechanical energy transfer. It was found that gas generated chemically within the liquid was significantly less effective at promoting mixing that the equivalent volume of inert gas. The relative ineffectiveness of chemically produced gas is thought to be due to smaller bubble sizes than in the case of inert gas. Small bubbles characteristic of chemically generated gas move with low slip velocities relative to the liquid and lead to different turbulence generation mechanisms., An understanding of fluid flow is essential in processes such as copper conversion and bath smelting, where gas is injected into liquid metal, for the calculation of process intensity and optimisation of vessel productivity. Cold model studies have been carried out in which gas reacts with the liquid into which it was injected. The rate of liquid mixing was measured as an indication of the mechanical energy transfer. It was found that gas generated chemically within the liquid was significantly less effective at promoting mixing that the equivalent volume of inert gas. The relative ineffectiveness of chemically produced gas is thought to be due to smaller bubble sizes than in the case of inert gas. Small bubbles characteristic of chemically generated gas move with low slip velocities relative to the liquid and lead to different turbulence generation mechanisms.

The Savard-Lee concentric tuyere permitted the bottom injection of oxygen by shrouding the gas with hydrocarbon to protect the adjacent refractory. The importance of this invention to the nonferrous industry as well as the steelmaking industry is recognised in this symposium. The papers assembled have been invited from prominent inventors, researchers and practitioners and cover the many fundamental and applied aspects of bath smelting with an emphasis on injection. Papers cover the steel, base metals and light metals industries so that these industries can learn from each other., The Savard-Lee concentric tuyere permitted the bottom injection of oxygen by shrouding the gas with hydrocarbon to protect the adjacent refractory. The importance of this invention to the nonferrous industry as well as the steelmaking industry is recognised in this symposium. The papers assembled have been invited from prominent inventors, researchers and practitioners and cover the many fundamental and applied aspects of bath smelting with an emphasis on injection. Papers cover the steel, base metals and light metals industries so that these industries can learn from each other.

The Hyuga smelter produces ferronickel by a rotary kiln-electric furnace process in Miyazaki, Japan. Several approaches to improve operations have decreased electrical energy consumption. A new process uses oil and technical oxygen injected through lances to heat up the calcined ores instead of electric power. The main problems in development were the short life of the water-cooled lances, the check on security of the safety system and the eruption of combustion gases through the calcine bed. These have been solved and stable operation can be maintained. The addition of 1 l of heavy oil/tonne ore can reduce the electrical energy requirement by 8.6 kWh/tonne ore. The new process has reduced electrical energy consumption by more than 10%., The Hyuga smelter produces ferronickel by a rotary kiln-electric furnace process in Miyazaki, Japan. Several approaches to improve operations have decreased electrical energy consumption. A new process uses oil and technical oxygen injected through lances to heat up the calcined ores instead of electric power. The main problems in development were the short life of the water-cooled lances, the check on security of the safety system and the eruption of combustion gases through the calcine bed. These have been solved and stable operation can be maintained. The addition of 1 l of heavy oil/tonne ore can reduce the electrical energy requirement by 8.6 kWh/tonne ore. The new process has reduced electrical energy consumption by more than 10%.

The present status of the application of Teniente converter technology at the Caletones smelter, Chile and the projected performance of the Nkana smelter, Zambia, are presented. The process comprises copper concentrate smelting in oxyfuel fired reverberatory furnaces, simultaneous matte converting and autogenous smelting of copper concentrate in Teniente converters (two 5 m diameter by 22 m at Caletones and one 4.5 m diameter by 18 m at Nkana), by blowing oxygen enriched air and producing white metal, and conversion to blister copper in conventional converters. The design operational basis, autogenous smelting throughputs, concentrate to matte ratios and benefits from the use of technical oxygen are presented., The present status of the application of Teniente converter technology at the Caletones smelter, Chile and the projected performance of the Nkana smelter, Zambia, are presented. The process comprises copper concentrate smelting in oxyfuel fired reverberatory furnaces, simultaneous matte converting and autogenous smelting of copper concentrate in Teniente converters (two 5 m diameter by 22 m at Caletones and one 4.5 m diameter by 18 m at Nkana), by blowing oxygen enriched air and producing white metal, and conversion to blister copper in conventional converters. The design operational basis, autogenous smelting throughputs, concentrate to matte ratios and benefits from the use of technical oxygen are presented.

Slag foaming creates large surface areas for multi-phase reactions to take place, can protect electrodes and improve energy efficiency by reducing radiation from hot surfaces, but can also be a source of serious disturbances. Slag foaming experiments were carried out using a synthetic FeO-CaO-SiO2 slag at 1 200-1 350 degrees C. The foam height, gas flow rate, bubble frequency and temperature were continuously monitored. Gas injection rate has a strong effect on slag foam behaviour and the addition of P2O5 favours foam formation and stability., Slag foaming creates large surface areas for multi-phase reactions to take place, can protect electrodes and improve energy efficiency by reducing radiation from hot surfaces, but can also be a source of serious disturbances. Slag foaming experiments were carried out using a synthetic FeO-CaO-SiO2 slag at 1 200-1 350 degrees C. The foam height, gas flow rate, bubble frequency and temperature were continuously monitored. Gas injection rate has a strong effect on slag foam behaviour and the addition of P2O5 favours foam formation and stability.