Bottom Blown Converter Research Articles

Simulation of Fluid Flow in the Top–Bottom Combined Blowing Converter

The flow in the top–bottom combined blowing converter has an important impact on processes such as slagging, dephosphorization, decarburization, the heating of molten steel, and the homogenization of steel composition and temperature. A 1/6 reduced scale model based on a 210 t converter was used for the mathematical simulation. The validity of the model was verified by comparing the variation in cavity sizes caused by changes in the lance height and flow rate of the physical model with the numerical results. It was found that, in the bottom blowing converter, the area with higher velocity was distributed in the inverted conical plume. In top blowing, the area with higher velocity was distributed on the surface of a molten bath. The area of higher molten bath velocity in the combined blowing converter further increased. Compared with the top blowing converter, the increased percentage of the area-averaged velocity in the combined blowing converter first increased and then decreased as the distance from the bottom increased. When the top blowing flow rate changed, the combined blowing made the velocity change at the top of a molten bath smaller. The decrease in lance height significantly reduced the ratio of “inactive zone”, while the effect of the change in the flow rate was slight.

Numerical investigation on influences of injection angle of bottom blowing bubbles on multiphase flow characteristics and wall erosion of converter

In this work, a novel bottom blowing approach based on inclined injection bubbles to enhance the multiphase flow mixing is proposed. An Eulerian-Eulerian model, validated via published experimental data, is established to numerically reproduce the stirring process of a bottom blowing converter. The effects of injection angle on the multiphase flow characteristics and wall erosion are then systematically investigated. Firstly, the influence of bottom blowing flow rate (10 m/s, 14 m/s, 20 m/s) on the mixing efficiency is discussed. Then, the effects of injection angle (0°, 5°, 10°, 15°, 20°) on the flow characteristics, mixing efficiency and wall erosion are studied in detail based on the bottom blowing flow rate of 14 m/s. The results show that increasing the bottom blowing flow rate is beneficial to shorten the mixing time. With the increase of the injection angle, the mixing time first decreases and then increases. As a result, the optimal angle for the most efficient mixing is determined as 5° when the flow rate is 14 m/s. When the injection angle is 5°, the air velocity on the axis and the negative tangent line is maximum. But the velocity is minimal on the positive tangent line. The injected air forms bubble plume that promotes the circulation of water. The most serious erosion area of the converter wall is located at the junction of molten steel surface and converter wall, followed by vicinity of the tuyere. However, with the increase of the injection angle, the average wall shear stress fluctuates only slightly. The obtained results are helpful to better understand the mechanism of bubble flow field in gas-liquid two-phase and also to improve the smelting efficiency in iron and steel metallurgy.

Physical Modeling of Slag Foaming in Combined Top and Bottom Blowing Converter

Physical Modeling of Slag Foaming in Combined Top and Bottom Blowing Converter

Research on the Gas–Solid Jet Flow and Erosion Wear Characteristics in Bottom Injecting Lance Used for Oxygen–Lime Powder Bottom Blowing Converter

Research on the Gas–Solid Jet Flow and Erosion Wear Characteristics in Bottom Injecting Lance Used for Oxygen–Lime Powder Bottom Blowing Converter

Toward the Bath Flow Interaction of a 250 t Combined Top and Bottom Blowing Converter Based on a Mathematical Modeling

Herein, the fluid mechanical aspects involving flow interactions between flows formed by the top impinging jet and bottom blowing bubbles in a combined blowing converter bath are focused on. The effects of different operation conditions on the flow field and the kinetic energy of the bath are investigated to examine different roles of the blowing operations with the help of numerical model. It is found that the stirring intensity in the region near the bath wall is decreased even though the flow is more active in the vicinity of the impact cavity when the top lance declines. For the combined blowing converter, the bottom blowing plumes normally dominate the bath flow. However, the bath stirring intensity is increased slightly when the bottom blowing flowrate is higher than a critical value (0.08 Nm3 min−1 t−1). In addition, the results of energy dissipation demonstrate that higher flowrate of bottom blowing causes more intensive interaction between flows formed by the top and the bottom blowing, which, in turn, causes more energy dissipation.

Physical Simulation and Industrial Testing of Bottom-Blown O2-CaO Converter for Steelmaking Process

Bottom-blowing O2-CaO steelmaking technology has numerous advantages such as low iron and steel consumptions, low dust emissions, and molten steel cleanliness. Responsive to a weak stirring and high iron oxide slag in a 120-ton conventional “combined blowing” converter in a factory, a cold model of bottom-blowing O2-CaO was designed. Bottom-blowing and top-blowing parameters on the mixing effect of bottom-blowing O2-CaO converter were studied. Two symmetrical points on 0.4R trunnion connection of the bottom-blowing converter were sought as the optimum hole location. The total flow rate of bottom–blowing and top-blowing was 8.2 and 75 Nm3/h, respectively. The optimum top-blowing position was 400 mm and the optimum solid–gas ratio was found to be 9.0. The optimum scheme under laboratory conditions was converted and applied to a 120-ton bottom-blown O2-CaO converter; subsequently, hundred industrial tests were performed. The stirring strength of the molten bath was enhanced remarkably and the metallurgical effect was improved remarkably. Carbon and oxygen product of the end-point molten steel was reduced by 5.87 × 10−4 while the iron oxide content in the final slag was reduced by 1.99 pct. This laid a foundation for industrial applications of the bottom-blown O2-CaO converter steelmaking technology.

Physical simulation of converter steelmaking with powder injection

A water model of top and bottom blown converter with top lance powder injection and bottom tuyere powder injection was established to investigate the powder injection. The results show that the powder penetration ratio under the condition of top lance injection is greater than that under the condition of bottom tuyere powder injection. In both cases, the powder penetration ratio increases with the increase of solid/gas ratio and powder particle size. Powder uniform dispersion time with top lance powder injection is longer than that with bottom tuyere powder injection. Top lance powder injection, lance height of 258 mm, bottom blowing rate of 1·96 Nm3 h−1 and powder particle size of 0·212–0·380 mm are suggested as the optimum powder injection operation under the experimental condition. The corresponding optimum operation for prototype is top lance powder injection with lance height of 1550 mm, powder size of 1–5 mm and bottom blowing rate of 450 Nm3 h−1.

Performance Assessment of Partially Pre-fused Synthetic Flux in Basic Oxygen Steel Making

Lump lime as the most common flux and iron ore as a coolant are used in basic oxygen steel making. However, high melting point, poor dissolution property, fines generation tendency and hygroscopic nature of lump lime often create problems in operation. As the combination of both iron oxide (Fe2O3) and CaO shows eutectic at 1 230 °C, a combined mass of iron oxide and lime melts at lower temperature and dissolves faster in a molten bath. A partially pre-fused synthetic flux (PSF) was prepared through an innovative way in combination of iron oxide fines viz. Linz Donawitz converter sludge and blast furnace flue dust and lime fines by micro-pelletization of the mix followed by coke breeze free sintering. The developed PSF shows good cold handling strength, low melting point (1 180 °C), good thermal shock resistance, etc. As a low melting synthetic flux, its performance was assessed through dissolution/melting study in hot metal bath and refining of hot metal in a simulated bottom blown converter using (i) PSF, (ii) only lump lime and (iii) lump lime with iron ore when keeping other conditions identical. Very fast dissolution (27–80 s for 1–3 g lumps), enhanced removal of C and P (11–12 min), controlled slag foaming, and reduced oxygen consumption was obtained for using PSF.

BASIC OXYGEN CONVERTER PROCESS WITH PULSATING TOP AND BOTTOM BLOWING

The article considers the peculiarities of the steel refining processes in top and bottom blown converter. Converter operation technology perfection and thermal balance improvement problems are discussed. The authors proposed two out-look versions of control actions: pre-assigned amplitude-frequency characteristics of pulsating gas jets in steelmaking with gas blowing and waste gases post combustion just above metal surface for effective chemical reaction heat transfer. Special blast designs are proposed for implementation of these assignments.

Numerical and Physical Simulations of a Combined Top-Bottom-Side Blown Converter

In this study, a side tuyere was introduced to investigate how it is possible to lower the mixing time and to avoid problems of a reduced stirring when using the application of slag splashing process in the combined top and bottom blown converter. Both physical and mathematical models were applied to study the flow in the bath. Specifically, the effects of a side-blowing gas jet on the bath stirring intensity was studied. The results indicate that the mixing time for a side blown converter is decreased profoundly compared to a conventional combined top and bottom blown converter. Overall, the mathematical model showed similar trends and a good agreement with that of the physical modeling data. Furthermore, the shear stress at the wall in the top-bottom-side (TBS) converter was considered, since the furnace lining is important when side blowing is used in the converter. It was found that the side wall shear stress is increased by introducing side blowing, especially in the region near the side blowing plume. Three side tuyeres with different locations in the same level did not show any obvious effects on the mixing of the bath, but showed apparent differences in the shear stress and the oscillation of the bath. Overall, the results showed that the mathematical model can be used to design the configuration of the metallurgical vessels when it is necessary to consider the oscillation and the shear stress of the bath.

Production and Application of High Capacity Bottom Blowing Purging Plugs for Converter

The article main discusses the development, production and application of directional multi -microtubule purging plugs which used in large or medium sized bottom blowing converter. This type of purging plug makes the gas flow in the metal pipes with very small resisting force and good air tightness. It is produced by using cold isostatic pressing, and has high strength and good corrosion resistance. Mainly employed high purity fused magnesia, flake graphite as raw material, and used phenolic resin as binder, and added titanium carbide, boron carbide as antioxidants and additives, which improved anti-oxidation, corrosion resistance and washing resistance, and the life of purging plug is highly improved accordingly.

Hydraulic Model Experimental Study on Coherent Jet Flow Field

Based on Anshan Iron and Steel Company 180t top-bottom converter prototype, the operating parameters and the structural parameters for best stirring effect of bottom-blowing converter and top-bottom converter was given by the hydraulic model test in this article. Coherent jet oxygen lance converter smelting effect was simulated under the condition of keeping the best top blowing gas flow rate. The experiment result shows that coherent jet oxygen lance may achieve the result of top-bottom converter stirring effect. If coherent jet oxygen lance could be applied in the converter, bottom blowing system of converter could be canceled. In that case, not only the converter equipment can be simplified, but also the converter lining life can be improved, bring steel-making technology transformation.

Development of Top and Bottom Blown Converter with Wide Range of Bottom Gas Flow Rate

Development of Top and Bottom Blown Converter with Wide Range of Bottom Gas Flow Rate

底吹き転炉の冶金反応特性に及ぼす酸素供給速度と羽口圧力の影響

底吹き転炉の冶金反応特性に及ぼす酸素供給速度と羽口圧力の影響

予備処理溶銑を用いた酸素上底吹き転炉の吹錬条件と冶金反応特性

予備処理溶銑を用いた酸素上底吹き転炉の吹錬条件と冶金反応特性

上底吹き転炉を用いた転炉滓系フラックスによる溶銑脱りん

上底吹き転炉を用いた転炉滓系フラックスによる溶銑脱りん

Converter steel production with the use of fluoritized limestone and a combination blow

Bottom-blowing converter steelmaking makes it possible to intensify mass transfer and the refining of the metal. However, such a practice also entails an increase in the consumption of expensive and scarce fluorspar, which is used to thin the slag. The Cherepovets combine made heats of steels 2sp and 3sp in 350-ton converters in which the slag was thinned with fluoritized limestone instead of a mixture of fluorspar and bauxite (the fluoritized limestone is a by-product of fluorspar production and contains 92.5% CaF2). In the trial heats, the consumption of inert gas through the bottom was 12-13 m3/min (0.030-0.045 m3/min.ton). The bath was blown from below for 1-3 min after the end of the top oxygen blow. We used pig iron containing 0.45... 1.18% Si; 0.17...0.24% Mn; 0.009...0.038% S; 0.037...0.057% P, while the slag-forming materials were partially burnt lime and dolomite. The fluoritized limestone was added in batches. It was established that with a consumption of fluoritized limestone of 1.11 tons per heat (versus 0.69 tons of the fluorspar-bauxite mixture), the steel has nearly the same contents of sulfur and phosphorus. With satisfactory slag formation, the slag at the sampling point was sufficiently fluid and was easily removed. No metallization of the lance or deterioration in the performance of the converter lining were observed.

排ガス分析情報による底吹き転炉の脱炭反応速度の推定とその吹錬終点制御,ガス回収技術への適用

排ガス分析情報による底吹き転炉の脱炭反応速度の推定とその吹錬終点制御,ガス回収技術への適用

Effect of pulverized lime injection on reduction of chromium oxide and desulfurization of stainless steel melt in bottom blown converter.

Hot and cold model experiments were made to find out the effect of pulverized lime injection on the reaction rate during the reduction period of refining of stainless steel melt.The reduction rate of chromium oxide and the desulfurization rate were measured by the use of a 5t test converter and an 85t top- and bottom-blown converter. The capacity coefficient for reduction of chromium oxide, which proceeds on the permanent reaction site, is proportional to e0.84, where e is the input rate of stirring energy into steel melt. Desulfurization proceeds on both of the permanent and transitory reaction sites. The capacity coefficient for desulfurization in the permanent reaction site is proportional to e0.82, while that in the transitory one is proportional to e-1/3 H (m/Wm)1.5, where H is the depth of bath and (m/Wm) is the injection rate of pulverized lime per unit weight of steel melt.In the cold model experiment with iron powder injection, gas holdup in mercury was measured by means of the electroresistivity probe technique. The upward flow velocity of the mixture of gas, liquid and solid is proportional to the cubic root of e.The effects of the operation factors such as m, H and gas flow rate, q, on the desulfurization rate were analyzed under the consideration of the two reaction sites. The ratio of desulfurization rate in the transitory site to that in the overall one increases with increases in m/Wm and H, and with a decrease in q. Moreover, the relation between q and H was calculated in the lime injection practice whose desulfurization rate was equal to that without lime injection on the basis of the experimental results.

Development of bottom-blowing nozzle for combined blowing converter.

A bottom-blowing nozzle of a converter, being featured by a wide range of flow rate controllability and a low wearing rate, has been studied with the view of developing a top- and bottom-blowing converter which is capable of producing a wide variety of steel.(1)When an inert gas is injected into the steel bath through the bottom-blowing nozzle, a so-called mushroom (solidified iron) having extremely small pores is formed atop the nozzle by the cooling effect of gas.(2) When a stable mushroom is formed atop the nozzle, the flow rate controllability and the wear rate of the nozzle are improved.(3) In order to form a stable mushroom atop the nozzle, it is most effective to use a nozzle consisting of multiple small-diameter pipes.(4) There is a proper range for the diameter of individual pipes. On the basis of the heat transfer model it has been established that, for the specified diameter, there is the minimum value both for the distance between neighboring pipes and for the gas flow rate to form a stable mushroom atop the nozzle.(5) This bottom-blowing nozzle allows to control the bottom gas flow rate over a wide range and ultimately makes it possible to control the iron content in slag (T.Fe) widely. In a low carbon region, the iron content can be reduced by bottom gas injection with the full flow rate. In a high carbon region, the nozzle can be used at a low gas flow rate to increase the iron content and ensure proper dephosphorization of the same level as in a top-blowing converter. Thus, this process is applicable for the production of all grades of plain carbon steel.