Tuyere Tip Research Articles

Simulation of gas dynamics of oxygen flow and hydrodynamics of cooling water flow in tuyere tips with tangential optimized nozzles and results of their pilot tests.

The blowing mode largely determines the technical and economic indicators of BOF smelting, which was confirmed during the technological audit of the BOF shop of Azovstal Iron and Steel Works, carried out in 2021. It was found that the blowing mode of the process using an oxygen lance of the basic design was noticeably shifted from the optimal one in the direction of “hard” blowing. In a significant number of melts this led to an increase in the specific consumption of metal sheets, deterioration of lime assimilation by slag, dephosphorization and desulphurization of the metal. Taking into account that adjustment of the blowing mode by changing the working height of blowing and oxygen consumption did not provide a stable positive result, changes were made in the design of the tuyere tip. The design of the head with tangential arrangement of nozzles is proposed to “soften” the blowing of melts. The advantages and dis-advantages of oxygen lances of this type are considered. Numerical modeling of the gas dynamics of the oxygen flow and the hydrodynamics of the flow of cooling water in a tip with a tangential arrangement of nozzles has been per-formed. On the basis of simulation results, two variants of an improved design of the tips of 350-t LD converters with five (variant 1) and four (variant 2) main peripheral tangentially oriented nozzles and a central nozzle of lower throughput were developed to use them mainly in the second and first periods of the campaign according to the lining of the converters, respectively. It is shown that the design parameters of the nozzle blocks provide an oxygen jet outflow regime close to the design one in the main range of oxygen operating flow rates and a “non-separated” outflow regime with a decrease in the off-design ratio down to 0.8. The design parameters of the cooling system provide both an acceptable loss of water pressure in the head (0.9 MPa), the absence of local low-speed vortex zones of water, and a fairly high average coolant flow rate along the most heat-stressed (the lower) surface of the tip (about 4.5 m/s). As a result of industrial testing of a pilot batch of experimental heads with five main peripheral tangentially oriented nozzles, manufactured at the plant’s own repair and mechanical base, an increase in the resistance of copper tips was found to be 1.2 times, the resistance of lances to removal for cleaning from accretion was found to be 6.8 times, reduction in the specific consumption of metal charge by 0.9–5.6 kg/t, an increase in the dephosphorization and desulfurization coefficients of metal in the converter by 0.7–1.5 and 1.3–3.2%, respectively.

Investigation of factors affecting the safety of a blast furnace operation

Blast furnace air tuyeres are one of the most important elements of the blast furnace design, determining the efficiency of its operation. Formation of “dead man” on the hearth bottom, or in other words, ore-coke sinter is considered as an unfavorable factor affecting the safety of large-volume blast furnaces. The main factors influencing the formation of "dead man" are violation of normal gas distribution and "cooling" of the blast furnace. This work is devoted to determination of the effluence procedure of the gas-coal flow using the Glinkov criterion. It is shown that a bubble effluent flow prevails in large-volume blast furnaces, i.e. a stable gas zone does not form in front of the tuyere tip. The bubble effluence mode of the gas-coal flow contributes to the growth of "dead man", which, as a result, can lead to an emergence situation. Prerequisites for burnout of the walls of the tuyeres are created in these conditions, while frequent terminations of the blast furnace operation to replace the tuyeres disorganize the melting technology. The maximal temperature in the tuyere zone has been calculated in this work. It exceeds the theoretical combustion temperature in the blast furnace hearth, what can adversely affect its operation, because the likelihood of an explosion of the blown natural gas will increase. The resulting heat flow on the tuyere tip was calculated in the work, taking into account the "dead man" formation. This flow exceeds the allowable one, what provokes a massive burnout of the tuyeres and the tuyere cooler.

Effects of single lance configuration on coal combustion process in tuyere from viewpoint of coal plume

Pulverized coal utilization in the blast furnace is decided by the particle flow and combustion behaviors in the raceway. Under a specific operating condition, these behaviors are directly related to the lance configuration in the upstream tuyere zone. Focusing on single straight lance, six types of single lance configurations were designed by assembling four parameters in different ways. These four parameters are the lance diameter, lance insertion angle, and the horizontal and vertical distances from the lance tip to the tuyere tip. With different lance configuration schemes applied, the pulverized coal combustion process in the lance–blowpipe–tuyere zone was simulated. The simulation results regarding particle diffusion and combustion behaviors were characterized by three indicators from the viewpoint of a coal plume. They are the plume diffusion angle, diffusion uniformity, and the average plume temperature at the tuyere outlet. To promote coal utilization, the values of these indicators under different configurations were analyzed, yielding two optimal configurations. The first one is to reduce the lance length immersed in the blowpipe–tuyere by 100 mm. The other is to increase the horizontal distance from the lance tip to the tuyere outlet by 50 mm, and the insertion angle to 11° with the lance tip located at the tuyere centerline. The findings can enhance the understanding of the influence mechanism of lance configuration on the coal utilization and provide guidelines for the design of new lance configurations.

Numerical investigation of the effects of size segregation on pulverized coal combustion in a blast furnace

Pulverized coal combustion in a blast furnace raceway can play a critical role in blast furnace iron-making operations. This research study integrated the particle combustion and the raceway formation processes using a refurbished coupling method based on computational fluid dynamics (CFD). The CFD model was validated, and there was good agreement between the simulation results and the two sets of experimental data. The combustion behaviors of pulverized coal particles in an industrial blast furnace were also simulated over a wide size range. The simulation results showed that size segregation occurred along the vertical direction in the raceway. Along the coal plume, the effectiveness of the size segregation process can be significantly reduced by the turbulence generated owing to the existence of the lance, the expansion of the gas jet near the tuyere tip, and the gas recirculation at the front end of the raceway. The burnout rate of particles smaller than 60 μm was also shown to be sensitive to the degree of weakening of the size segregation. The particle distribution in the coke bed indicated that the group of particles with diameters equal to 52.5 μm was associated with the largest proportion of unburnt char. This research extended the applicability of the existing numerical methods and provided a better understanding of the pulverized coal injection (PCI) process from the viewpoint of size segregation, which is beneficial to the further optimization of PCI usage

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 $$ \left( {\frac{{l_{\text{P}} }}{{d_{o} }} = 10.7\left( {N^{\prime }_{Fr} } \right)^{0.46} \left( {\rho_{\text{g}} /\rho_{l} } \right)^{0.35} } \right) $$ 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 = 0.2, 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.

Combustion Behaviors of Fine Coal and Its Impact on Gas Permeability at Lower Part of Blast Furnace under High Pulverized Coal Rate Operation

Practical ways of estimating temperatures of coke flowing into raceway as well as the gas core depth validated by direct measurement were suggested for the purpose of better describing the combustion behaviors of injected coal fine in blast furnace raceway. The numerical simulation model was refurnished with the scheme, and helped clarifying an intriguing effect of coal gasification or decomposition degrees before exiting tuyere tip on attained combustibility of coal at raceway boundary.Another scheme for quantitative expression of pressure losses caused exclusively by coal fine residence in and around raceway was also developed by shutting off coal injection for minutes at practical operation. The obtained results lead to developing the advanced tuyere, CD (converged and diverged) tuyere which enabled reducing the interaction between injectants and hot blast inside tuyere and thus improving overall gas permeability even under conditions of massive coal injection over 250 kg/tHM.

Effect of Bottom Blowing Conditions on Refractory Erosion in the Ironmaking Smelter by Water Modeling

A water model was adopted to physically simulate the bottom gas stirring inside an ironmaking smelter. The water model experiments were conducted to investigate the erosion of the bottom refractory lining near the tuyere tip under different gas bottom blowing conditions. In experiments, the major parameters are the gas flow rate, and the inside diameter and placement of bottom blowing tuyeres. The purpose of this study is to provide a design and operation reference of the gas bottom blowing system for CSC’s Ironmaking Smelter. A transparent acrylic water model, which is 60% of the actual furnace’s size, is used to study the erosion of the bottom refractory lining near the tuyere tips. The experiments suggested that the erosion rate of specimens near the tuyere tips reduced with a decrease in the gas flow rate. In the case of the triangle-corners-center placement of four bottom blowing tuyeres, the lowest erosion rate of boric acid specimens was found at a 15 mm tuyere size. In the case of the square-corners placement of four bottom blowing tuyeres, the lowest erosion rate of boric acid specimens was found at a 10 mm tuyere size. With the same blowing conditions, the erosion rate appears to decrease with a decrease in tuyere numbers. It was shown that the erosion rate of the square-corners placement case was lower than that of the triangle-corners-center at the same bottom blowing condition. The results imply that the conditions for the lowest erosion rate of specimens is a bottom blowing gas flow rate for each tuyere of 80 L/min, a tuyere inner diameter of 15.0 mm and three bottom blowing tuyeres, all of which should be in the range of the experimental parameters described above. [doi:10.2320/matertrans.M2009414]

Variation in coke properties within the blast-furnace shop

In active production at OAO Magnitogorskii Metallurgicheskii Kombinat (MMK), samples of melt materials were taken during shutdown and during planned repairs at furnaces 1 and 8. In particular, coke was taken from the tuyere zone at different distances from the tuyere tip. The mass of the point samples was 2-15 kg, depending on the sampling zone. The material extracted from each zone underwent magnetic separation and screening by size class. The resulting coke sample was averaged out and divided into parts: one for determining the granulometric composition and mechanical strength; and the other for technical analysis and determination of the physicochemical properties of the coke.

Control of CO2 Peak Position by Dual Lance Air Curtain Method.

A phenomenon that a CO 2 peak position or temperature peak position of combustion (CO 2 or temperature peak position) in the raceway of blast furnace approaches a tuyere in step with the increase of pulverized coal rate (PCR) changes a gas flow at the lower part of the furnace into a peripheral flow or lowers the temperature at the raceway end, which may be one of the factors making the furnace operation unstable. Therefore, a pulverized coal combustion method (dual lance air curtain method) which interrupts temporarily a contact of pulverized coal and hot air in the vicinity of lance tip by injecting cold air through an opening between inner and outer tubes of the dual lance was examined by performing a hot model experiment and a single tuyere test of actual furnace. The hot model experiment results have revealed that with the increase of the flowing velocity of cold air sent from the outer tube of dual lance, the temperature around the tuyere tip falls and the temperature ranging from the raceway and to a dead man surface rises. According to the examination results of gas temperature under the raceway conditions of actual furnace with the use of one-dimensional raceway model, an estimated value of the moving distance of CO 2 or temperature peak position of combustion toward the dead man side is 480 mm when the dual lance air curtain method has been taken this time at Kimitsu No. 2 blast furnace. The combustion efficiency of pulverized coal could decrease due to movement of CO 2 or temperature peak position of combustion to the dead man side. And in the actual furnace test conducted this time with a single tuyere, the increase range of unburnt char ratio at the inside of dead man is as small as less than 1 % relative to -1 mm fine and the packing structure of dead man surface has been improved.

The effect of pulverized coal injection and volatile matter content of coal on combustion characteristics around the raceway zone in the blast furnace

A two-dimensional mathematical model is developed to describe transport phenomena in a packed bedof coke in front of a blast furnace tuyere with and without pulverized coal injection (PCI). The model consists of two submodels: one is a pulverized coal (PC) combustion model in the blowpipe and the other is a combustion model in the packed bed of coke where the thermal radiation is considered. In this model, coke particles in the raceway are treated as a continuous phase, and both phases of gas and coke particles are calculated by using the Eulerian approach. This model is applied to practical operating conditions in the blast furnace. As the residence time of PCparticles in the blowpipe is quite short, its burn-off in the blowpipe is very small, and the PC particles mainly burn in the raceway cavity. While the burn-off of PC particle increases with the volatile matter content, some particles reach the inner wall of tuyere when high-volatile coal is used. When PC is injected into tuyere, more oxygen is consumed, and a higher temperature rise appears at the region closer to the tuyere tip in the raceway than those of all coke operation. The temperature profiles in the raceway with PCI and without PCI are different from each other due to the difference of flow regime.

Accretion growth on single-pipe tuyeres: Part I. Model development and preliminary analysis

A mathematical model of the growth of accretions on submerged single pipes has been developed based on the heat transfer in the vicinity of the injection point. The model is able to predict the formation of either pipe or hemispherical accretions based only on the input con-ditions. It is assumed that a hemispherical accretion is formed only when a porous plug is formed within the tuyere tip by the freezing of bath material during regular penetration episodes. Gas flow within the bath is calculated from physical modeling results, and allowances are made for the possibility of a gas/bath reaction. A preliminary analysis of the model predictions for copper converter and steel ladle stirring applications has been carried out. The model predicts that, under normal operating conditions, the accretions formed in copper converters are very small but can become appreciable under low superheat conditions. The time required to reach steady state depends upon the final accretion length but can be as much as 5 minutes. In ladle stirring applications, the model predicts that the accretion formed will be approximately 4.5-cm high with a slightly larger basal radius. This accretion requires approximately 10 minutes to reach steady state. The final shape and size of an accretion are dependent upon the balance of heat flows around it, with steady state occurring when heat inputs to the accretion exactly equal heat outputs.

Simulation of Transport Phenomena around the Raceway Zone in the Blast Furnace with and without Pulverized Coal Injection.

A two-dimensional mathematical model is developed to describe transport phenomena in a packed bed of coke in front of blast furnace tuyere with and without pulverized coal injection (PCI). The model consists of two sub-models, one is pulverized coal (PC) combustion model in the blowpipe where the turbulent fluctuation in the gas phase is considered and the other is combustion model in the packed bed of coke. In this model coke particles in the raceway are treated as a continuous phase and both phases of gas and coke particles are calculated by using the Eulerian approach.This model is applied to practical operating conditions. When PC is injected into tuyere, more oxygen is consumed and higher temperature rise appears at the region closer to tuyere tip in the raceway and lower temperature is represented in the coke bed than those of all coke operation. Residence time of PC particles in the blowpipe is quite short, so its burn-off in the blowpipe is very low and the PC particles mainly burn in the raceway cavity. The burn-off of PC particle increases with the volatile matter content, but some particles reach to inner wall of tuyere when high volatile coal is used.

酸化鉄と酸素の同時吹込みによる溶銑の同時脱珪・脱りんと温度制御

A side-blown submerged injection with a downward entry tuyere angle was conducted in a 5t pilot plant scale : where both of oxygen gas and CaO-based powders containing iron oxides were injected in order to control the temperature during the dephosphorization. Ceramic tuyeres were used for their good wear resistance against iron oxides. The results obtained are as follows : (1) Simultaneous removals of silicon and phosphorous were obtained effectively. And the final phosphorous content less than 0.010 percent was gained even with the initial silicon content of as high as 0.50 percent. (2) When the gaseous oxygen ratio to the total oxygen consumption was varied from 30 to 70 percent, the changes in bath temperature were range from - 120 to + 50°C, respectively. (3) The analysis of the mushroom showed that the dephosphorization reaction was proceeded just near by the tuyere tip.

A Unified Representation of Gas Dispersion in Upwardly Injected Submerged Gas Jets

The overall dispersion of gas injected vertically upward into a liquid has been studied. A generalised model has been proposed to delineate the different forms of gas dispersion in the liquid, between gas entry at the tuyere tip and exit at the bath surface. Four dispersion zones have been identified: primarybubble, free-bubble, plume and spout. The regimes have been characterised by means of a dispersion dimensionless group, N D, based on the injection Froude number and the reduced height of the dispersion, which varies with the axial gas fraction in the different regimes. Thus it has been shown that the primary bubbles only exist for values of N D lower than about 2.0 in both the air-water and helium-water systems. The free bubbles or zone of bubble disintegration in these systems occur in the range of ND between 2.0 and 4.5 while the plume extends from about N D = 4.5 to a higher value depending on the depth of the liquid phase. The transition to spout formation beyond the plume is marked by a sudden increase in gas fraction, at a level somewhat lower than the static height of the bath.

A Unified Representation of Gas Dispersion in Upwardly Injected Submerged Gas Jets

The overall dispersion of gas injected vertically upward into a liquid has been studied. A generalised model has been proposed to delineate the different forms of gas dispersion in the liquid, between gas entry at the tuyere tip and exit at the bath surface. Four dispersion zones have been identified: primarybubble, free-bubble, plume and spout. The regimes have been characterised by means of a dispersion dimensionless group, N D, based on the injection Froude number and the reduced height of the dispersion, which varies with the axial gas fraction in the different regimes. Thus it has been shown that the primary bubbles only exist for values of N D lower than about 2.0 in both the air-water and helium-water systems. The free bubbles or zone of bubble disintegration in these systems occur in the range of ND between 2.0 and 4.5 while the plume extends from about N D = 4.5 to a higher value depending on the depth of the liquid phase. The transition to spout formation beyond the plume is marked by a sudden increase in gas fraction, at a level somewhat lower than the static height of the bath.

Kinetics of the zinc slag-Fuming process: Part i. industrial measurements

A study involving industrial measurements and mathematical modeling has been conducted to eluci-date kinetic phenomena in the zinc slag fuming process. In the first part of this three-part paper, the results of industrial measurements and observations are presented. In Part II a mathematical model of the process is developed, and finally in Part III the implications of a kinetic conception of the process for process improvement are explored. The industrial work consisted primarily of slag sampling through the fuming cycles of five different fuming operations. In addition, tuyere back-pressure mea-surements, tuyere photography using a tuyerescope, and sampling of the fume product were under-taken at one operation. Analysis of the slag samples has shown that, in general, the zinc elimination curve is linear with time and that a portion of the injected coal entrains in the slag. Analysis of tuyere back-pressure fluctuations and movie photographs of the tuyere tip indicate that the coal-air mixture enters the slag in the form of discrete bubbles. From these results it can be deduced that the fuming furnace consists of two reaction zones which are created by the division of coal between the slag and the tuyere gas stream. The coal entrained in the slag reduces ZnO and Fe3O4 in a “reduction zone” which is responsible for fuming. The coal remaining in the tuyere gas stream combusts in an “oxidation zone” although a fraction passes through the bath unconsumed and reports to the solid products. The oxidation zone supplies heat to the endothermic reduction reactions and heat losses.

Injection phenomena in nonferrous processes

Injection phenomena in a Peirce-Smith copper converter and a slag fuming furnace have been investigated during blowing. A tuyerescope attached to the back of a given tuyere has been employed to observe the build-up, and to obtain samples, of accretions while a piezoelectric transducer has been used to measure pressure fluctuations in the tuyere. It has been found that in both processes the accretions grow upward by a freezing mechanism from the bottom of the horizontal tuyere. Probing the shape of an accretion in the fuming furnace, without coal injection, showed that the accretion grew into the bath 30 to 40 mm from the tuyere tip. A study of the shape and frequency of the pressure pulses as well as the duration of intervals of low pressure in the tuyere has revealed that the closely spaced tuyeres may operate independently or may interact. Tuyeres in a full slag fuming furnace act independently of one another, and the air discharges in the classical bubbling regime at 5 to 6 bubbles per second. In the copper converter there is more tuyere interaction as bubbles growing at adjacent tuyeres coalesce to form a horizontal unstable gas envelope. In both processes if the tuyeres are shallowly submerged the gas may channel directly to the surface without forming bubbles. The influence of bath viscosity, the extent of wall erosion at the tuyere line, and tuyere submergence on these injection phenomena have been elucidated qualitatively.

Mathematical Model of Bubble Formation at the Tuyeres of a Copper Converter

Based on earlier observations that gas discharges from the tuyeres of a non-ferrous converter as discrete bubbles, a mathematical model has been developed to describe the dynamics of bubble formation in copper converting. The bubbles have been assumed to be spherical in shape and to grow at the tuyere tip under conditions of constant flow. The model incorporates the effects of heat transfer to the bubble, chemical reaction between the bubble and the bath and co flowing bath circulation. The model has been used to predict the concentrations of O2 and SO2, temperature, volume and rise velocity for the bubble as a function of time, while imposition of a detachment condition has permitted the prediction of the bubble frequency. Thus it has been shown that the oxidation reactions have little effect on the bubble formation while convective heat transfer and bath circulation have a large influence. Bath velocity acts to increase the bubble frequency while heat transfer has the opposite effect. Depending on the value of the heat-transfer coefficient employed, the model predicts the velocity of bath circulation in the vicinity of the tuyere to be between 120 and 260 cm/s. For a given bath velocity, the bubble frequency decreases with increasing air input rate. The implications of these predictions for copper converting are discussed, and it is suggested that present converter operation may be “bubble-volume“ limited. Résumé En se fondant sur les observations anterieures que le gaz qui s' échappe des tuyères d'un convertisseur de métaux non-ferreux est sous forme de bulles séparées, nous avons développé un modèle mathématique pour décrire la dynamique de formation des bulles dans le convertissage du cuivre. Nous avons supposé que les bulles ont une forme sphérique et qu'elles croissent à l'extrémité de la tuyère dans des conditions d' écoulement constant. Le modèle incorpore les effets du transfert de chaleur à la bulle, de la réaction chimique entre la bulle et le bain, et la circulation du bain. Le modèle a été utilisé pour prédire les concentrations de O2 et SO2, la température, le volume et la vitesse de montee des bulles en fonction du temps, alors que l'introduction d'une condition de séparation a permis de prédire la fréquence des bulles. Ainsi nous avons montré que les réactions d'oxydation ont peu d'effet sur la formation des bulles alors que le transfert de chaleur par convection et la circulation du bain ont une grande influence. La vitesse du bain accroît la fréquence des bulles alors que le transfert de chaleur a l'effet opposé. Dépendant de la valeur du coefficient de transfert de chaleur employé le modèle predit que la vitesse de circulation du bain dans le voisinage de la tuyère est comprise entre 120 et 260 cm/s. Pour une vitesse donnée du bain, la fréquence des bulles décroît lorsque l'on augmente le taux d'arrivée d'air. Les implications de ces predictions pour le convertissage du cuivre sont discutées et nous suggérons que l'opération actuelle des convertisseurs pourrait être limitée par le volume des bulles.

Flow regimes in submerged gas injection

The behavior of gas discharging into a liquid has been investigated in the labora-tory and in plant. The laboratory work has involved the injection of different gases from a submerged, horizontal tuyere into water, zinc-chloride solution, and a mercury bath. High speed cinematography and pressure measurements in the tuyere have been carried out to characterize the flow regimes. In the case of the mercury bath, a novel “half-tuyere” has been developed to permit visual observation of the gas. In this way, two regimes of flow, bubbling and steady jetting, have been delineated as a function of the modified Froude number and the ratio of gas to liquid densities. Pressure measurements at the tuyere tip have been correlated to the different stages of bubble growth in the bubbling regime, and can be used to distinguish one flow regime from the other. The measured bubble frequency and volume correspond reasonably well to predictions of a simple model of bubble growth under conditions of constant flow. The forward penetration of the jet centerline from the tuyere tip has been measured and found to depend both onN Fr′ andρg/ρl. In the industrial tests, pressure taps have been installed in the tuyeres of a nickel converter to monitor the pressure wave of the jets under normal, low pressure blowing operations. The measurements show that the converter jets operate in the bubbling mode with a bubble frequency of 10 to 12 s−1, similar to a gas jet in mercury. Tests involving higher pressure injection indicate that the steady jetting, or underexpanded, regime obtains at pressures of about 340 kPa (50 psi). Based on equivalent experiments in the laboratory, it is clear that low pressure blowing has the disadvantage of poor penetration of air into the bath so that the jets rise close to the back wall and locally accelerate refractory wear. Moreover between the formation of successive bubbles, the bath washes against the tuyere mouth and contributes to accretion formation. This necessitates periodic punching of the tuyeres which also contributes to refractory wear at the tuyere line. The use of high pressure injection to achieve steady jetting conditions, as currently practiced in the new bottom blown steelmaking processes, should be considered to solve these prob-lems, and possibly usher in a new generation of nonferrous converters.