Top Lance Research Articles

転炉型溶銑脱燐時の上吹き酸素による酸化鉄生成挙動の基礎検討

The effects of hot metal temperature, oxygen gas flow rate from a top lance and argon gas flow rate from an injection lance on iron oxide formation and dephosphorization rates in hot metal were investigated with 3 kg- and 200 kg-scale furnaces. The results were summarized as follows.1) Iron oxide formation rate increased with lower hot metal temperature, higher oxygen gas flow rate and lower argon gas flow rate.2) A kinetic model was developed to estimate the iron oxide formation on hot metal, and a mathematical model for hot metal dephosphorization has been made based on the aforementioned model of iron oxide formation and the coupled reaction model.3) Dephosphorization and the formation rate of iron oxide in 200 kg-scale tests agreed well with those were obtained by the mathematical model.4) Oxygen activity at slag/metal interface obtained by the mathematical model agreed with the equilibrium oxygen activity with FeO in slag.5) In the early stage of dephosphorization, the gas flow rate of the bottom blowing need to be lower in order to enhance the iron oxide formation. In the late stage of dephosphorization, that needs to be higher in order to enhance the mass transfer of phosphorus in hot metal.6) Industrial hot metal dephosphorization tests were carried out with a 350 t-scale top and bottom converter. The conditions of top blowing oxygen and bottom blowing nitrogen have been improved by adopting the mathematical model in order to increase the iron oxide content in slag. It has been possible to increase dephosphorization efficiency without fluor spar at lower hot metal temperature (below 1300°C) by improving the blowing conditions.

Frequency of Bubble Formation from a Multi-Hole Nozzle Attached to a Top Lance

Water model experiments have been carried out to understand the bubble formation from a multi-hole nozzle attached to an immersion top lance in the pretreatment process for sulfur. The number of holes is varied from one to four. Although desulfurization agents such as CaO particles are injected into the reactor together with carrier gas in the real process, only gas is injected, in this study, into a water bath through the holes in the horizontal direction. Three types of bubble formation patterns are observed depending on the gas flow rate: synchronized, partlysynchronized, and non-synchronized bubble formation patterns. The frequency of bubble formation at each nozzle is measured with a highspeed camera. An empirical equation is proposed for the frequency of bubble formation as a function of the number of holes, inner diameter of hole, and the physical properties of fluids. [doi:10.2320/matertrans.M2009091]

Application of computational fluid dynamics to steelmaking processes

Today, the numerical simulation of fluid dynamic phenomena (CFD) in steelmaking applications is state of the art. The latest simulation results for the BOF and AOD as well as the thin strip casting process are described. The basic influence of the process parameters, e.g. blowing and stirring rate, vessel dimension, location of top lance, number and arrangement of porous plugs, on the converter melt flow and mixing time is simulated. In the case of thin strip casting, the free melt flow on the moving belt is influenced by an induced electromagnetic field. The respective MHD (magneto-hydrodynamic) is presented.

Study on the optimization of the combined blown converter process in Chongqing Iron and Steel Company

The effects of lance height and bottom blown flowrate on the mixed time, the splashing amount, the penetrating depth, and the level fluctuation of an 85 t combined blown converter have been studied using a water model. The results show that the maximal stirring energy is provided to the bath at the top lance height of about 50-100 mm. When the top lance height is in the range of 90-110 mm, the splashing amount caused by the top jet can reach the maximal value. The appropriate operational parameters of Chongqing Iron and Steel Company (CISC) converter have been established that the top lance height is 1600-1760 mm and the bottom blowing flowrate is 240-480 Nm 3/h in the primary phase of a heat, 1100-1300 mm and 160-200 Nm 3/h in the second phase, and 1040-1120 mm and 200-350 Nm 3/h in the end phase. Also, the trial shows that the metallurgical result of the studied blow pattern is better than that of the former pattern. At the starting 3-4 min of a heat, the strong splashing is eliminated.

Bubble Formation from a Two-Hole Nozzle Attached to a Top Lance

Submerged powder injection is widely used for steel refining processes. Powder is usually injected downwards through a single-hole nozzle or horizontally through a two-hole nozzle attached to a top lance into the molten metal bath with carrier gas. In this study we investigate fundamentally horizontal injection through a two-hole nozzle to enhance the refining efficiency of the processes. As a first step, experimental investigation is carried out on the bubble formation from the two-hole nozzle in the case that only gas is injected into the bath. Two types of bubble formation patterns are observed depending on the gas flow rate: synchronized and non-synchronized bubble formations. A synchronization ratio is newly introduced in this study to describe the degree of synchronization. The frequency of bubble formation at each nozzle is measured with a high-speed video camera and compared with existing empirical equations for a single-hole nozzle because no empirical equation is available for the frequency of bubble formation for a two-hole nozzle.

Study on Mass Transfer Characteristics in an AOD Converter Bath under Conditions of Combined Side and Top Blowing

The mass transfer characteristics in a steel bath during the AOD refining process with the conditions of combined side and top blowing were investigated. The experiments were conducted on a water model unit of 1/4 linear scale for a 120‐t combined side and top blowing AOD converter. Sodium chloride powder of analytical purity was employed as the flux for blowing, and the mass transfer coefficient of solute (NaCI) in the bath was determined under the conditions of the AOD process. The effects of the gas flow rates of side and top blowing processes, the position arrangement and number of side tuyeres, the powdered flux particle (bubble) size and others on the characteristics were examined. The results indicated that, under the conditions of the present work, the mass transfer coefficient of solute in the bath liquid is in the range of (7.31×10−5‐3.84×10−4) m/s. The coefficient increases non‐linearly with increasing angle between each tuyere, for the simple side blowing process at a given side tuyere number and gas side blowing rate. The gas flow rate of the main tuyere has a governing influence on the characteristics, and the gas jet from the top lance decreases the mass transfer rate, the relevant coefficient being smaller than that for a simple side blowing. Also, in the range of particle (bubble) size used in the present work and with all other factors being constant, raising particle (bubble) size increases the coefficient. Excessively fine powder particle (bubble) sizes are not advantageous to strengthening the mass transfer. With the oxygen top blowing rate practiced in the industrial technology, the side tuyere arrangements of 7 and 6 tuyeres with an angular separation of 22.5° and 27° between each tuyere, as well as 5 tuyeres with an angle of 22.5° between each tuyere can provide a larger mass transfer rate in the bath. Considering the relative velocity of the particles to the liquid, the energy dissipation caused by the fluctuation in the velocity of the liquid in turbulent flow and regarding the mass transfer as that between a rigid bubble and molten steel, the related dimensionless relationships for the coefficient were obtained.

The Analysis of the Blowing Process with the Top Lance of the Argon Oxygen Decarburization (AOD) in Baosteel

The applications of the single-hole top lance, the 110-three-holes top lance and the 150-three-holes top lance in the speed of the decarburization are compared. The amount of the Chromium oxidized, and the temperature-increasing speed of the bath is analyzed. The result shows, if the lance gap is set suitably, the 110-three-holes top lance will be the most beneficial to the stainless steel-making in the AOD when the high-carbon pre-metal from the EAF is charged.

Preliminary Investigation of Mathematical Modeling of Stainless Steelmaking in an AOD Converter: Mathematical Model of the Process

Mathematical modeling of stainless steelmaking in an AOD (argon‐oxygen decarburisation) converter with side and top combined blowing has been preliminarily investigated. The actual situations of the side and top combined blowing AOD process were analysed. A mathematical model for the whole refining process of stainless steel has been proposed and developed. The model is based on the assumption that one part of the oxygen blown through a top lance reacts with CO escaping from the bath, another part of the oxygen oxidizes the elements in the molten steel droplets splashed by the oxygen jet, and the remaining oxygen penetrates and dissolves into the molten steel through the pit stroked by the jet. All the oxygen entering into the bath oxidizes C, Cr, Si, and Mn dissolved in the steel and also the Fe of the steel melt, but the FeO generated is also an oxidant of C, Cr, Si, and Mn in the steel. During the process, all possible oxidation‐reduction reactions occur simultaneously and reach their equilibria, respectively their combined equilibrium, in competition at the liquid/bubble and liquid/slag interfaces. In the simple side blowing after the top blowing operation is finished, the possible reactions take place simultaneously and reach a combined equilibrium in competition at the liquid/bubble interfaces. The overall decarburization rate in the refining process is the sum of the contributions of both the top and side blowing processes. It is also assumed that at high carbon concentrations, the oxidation rates of elements are mainly dependent upon the supplied oxygen rate, and at low carbon contents, the rate of decarburisation is primarily related to the mass transfer of carbon from the molten steel bulk to the interface. It is further assumed that the non‐reacting oxygen blown into the bath does not accumulate in the steel and will escape from the bath and react with CO in the atmosphere above the bath. The study presents calculations of the refining rate and the mass and heat balances of the system for the whole process. Additionally, the influences of the operating factors, including addition of slag materials, scrap, and alloy agents, the non‐isothermal conditions, the changes in the amounts of metal and slag during the whole refining process, and others have all been considered.

Swirl Motion Caused by Top Lance Gas Injection in Bottomless Cylindrical Vessel

Swirl Motion Caused by Top Lance Gas Injection in Bottomless Cylindrical Vessel

A Physical Model Study of Swirl Phenomena in a Top Blown Bath

The present study is focused on swirl motion in a top blown water model, where a deep water swirl motion is observed. During the experiments, the top lance, with cylindrical nozzles, was placed above the water surface and thereby produced an external force on the bath. The effect on how different parameters, such as nozzle diameter and the distance between the bath surface and nozzle exit, i.e. the lance height, affect the swirl motion were studied. More specifically, the amplitude and period of the swirl as well as the starting and damping time of the swirl were determined. The amplitude was found to increase with an increased nozzle diameter and gas flow, while the period had a constant value of about 0.5 s for all nozzle diameters, gas flows and lance heights. The starting time for the swirl motion was found to decrease with an increased gas flow, while the damping time was found to be independent of gas flow rate, nozzle diameter, lance height and ratio of depth to diameter.

Reduction Behaviors of Hot Metal Dephosphorization Slag in a Slag Regenerator

The reduction behavior of dephosphorization slag on the iron bath in the reduction furnace of the slag regeneration process was researched by test converter experiments. Dephosphorization slag and coke as the reduction agent and the heat source were added to the hot metal in the converter and oxygen was blown through the top lance. During the blowing, the reduction of (P 2 O 5 ), (FeO) and (MnO) in the slag proceeded simultaneously. The amount of phosphorus and manganese oxide in the slag decreased and the amount of phosphorus and manganese in the metal increased in turn during the reduction. The unknown amount of these elements which occupied about 20 % of total input also existed. The unknown parts of phosphorus and manganese in material balance are seemed to be caused mainly by the vaporization of phosphorus and manganese from the droplets generated by the reduction at the slag/coke interface.

Numerical Simulation of Secondary Combustion in Converter Using Lattice Boltzmann Method

In this study, numerical simulation on fluid flow and secondary combustion reaction in a converter has been conducted, where CO formed from the high-temperature molten steel is reacted with oxygen. With top blowing lance, the oxygen jet impinges on liquid metal to produce a cavity under gravity. To consider two phases, molten steel and mixture of O2, CO, CO2, the Lattice Boltzmann method is used. As for the combustion reaction, the flameter model and finite reaction model are used to discuss the mass and heat transport in the conveter. Results show that the time-averaged cavity shape corresponds to the empirical model derived from the experiments and theoretical consideration. Then, the fluctuated liquid surface with the oxygen jet impingement is well simulated. By increasing the oxygen injection velocity, the surface of molten steel is largely wrinkled. The convection and reaction of CO are affected, with smaller secondary combustion ratio.

Fluid Flow in a Combined Top and Bottom Blown Reactor

Physical modeling was done to study the flow field in a cylindrical bath agitated by bottom purging, top lance blowing and a combination of both injection types. A particle image velocimetry (PIV) ...

Physical Modeling and Optimization of Bottom Tuyere Configuration and Blowing Parameters in a Top and Bottom Combined Blowing Converter

AbstractOptimizing experiments for the bottom tuyere configuration and blowing parameters of the 120 tonne top and bottom combined blowing converter at Shaoguan Iron & Steel Co. were carried out in a reduced‐scale water model. Results showed that the former configuration with 6 bottom tuyeres in the converter was not suitable with bath stirring because of the two tuyeres arranged in 0.33D pitch circle which caused the cavity deformation and stirring energy loss. Ideal bath stirring in the converter was obtained by using a new arrangement with 4 bottom tuyeres, two being in 0.57D pitch circle and the other two in 0.42D pitch circle. The optimal blowing parameters of the converter with the new bottom tuyere configuration were 1.26 Nm3/h of bottom gas flow rate, 160 mm of top lance height, and 30.52 Nm3/h of top gas flow rate.

Preliminary Investigation of Fluid Mixing Characteristics during Side and Top Combined Blowing AOD Refining Process of Stainless Steel

The fluid mixing characteristics in the bath during the side and top combined blowing AOD (argon‐oxygen decarburization) refining process of stainless steel were preliminarily investigated on a water model unit of a 120 t AOD converter. The geometric similarity ratio between the model and its prototype (including the side tuyeres and the top lances) was 1:4. On the basis of the theoretical calculations for the parameters of the gas streams in the side tuyeres and the top lances, the gas blowing rates used for the model were more reasonably determined. The influence of the tuyere number and position arrangement, and the gas flow rates for side and top blowing on the characteristics was examined. The results demonstrated that the liquid in the bath underwent vigorous circulatory motion during gas blowing, without obvious dead zone in the bath, resulting in a high mixing effectiveness. The gas flow rate of the main tuyere had a governing role on the characteristics, a suitable increase in the gas flow rate of the subtuyere could improve mixing efficiency, and the gas jet from the top lance made the mixing time prolong. Corresponding to the oxygen top blowing rate specified by the technology, a roughly equivalent and good mixing effectiveness could be reached by using six side tuyeres with an angle of 27 degrees between each tuyere, and five side tuyeres with an angular separation of 22.5 or 27 degrees between each tuyere. The relationships of the mixing time with the gas blowing rates of main‐tuyeres and sub‐tuyeres and top lance, the angle between each tuyere, and the tuyere number were evaluated.

Slag splashing at the Fos steelplant: new converters scheduling and results

Slag splashing is a way of maintaining converters lining, started at the Fos steel plant in December 2003. Systematic slag splashing on converters lining, by nitrogen injection with the top lance, after tapping, protects refractory. The aim of the project is to disconnect the two converters, from the refractory point of view, and to reach a refractory lining lifetime of 5,000 heats.

Mathematical Simulation of Different Argon Blowing Style in Ladle Furnace

In the present paper, applied the experiential correlation, the gas holdup and distribution of two phase zone which formed by argon blown were determined. The flow variables of molten steel and turbulence parameters in the Ladle Furnace were estimated utilizing the results of frontal calculation and through numerically solution momentum Navier-Stokes equation in conjunction with k-εturbulence model. Several different spray styles including blowing through single hole, double holes, top lance were simulated and compared in this project.

Kinetics of Oxygen Refining Process for Ferromanganese Alloys

The present analysis of the experimental data by Yamamoto et al. permitted to determine the rate controlling mechanisms for the decarburization and evaporative manganese loss concurrently taking place during the oxygen refining process of ferromanganese melt.When oxygen is supplied by a top lance blowing mode, the decarburization reaction takes place by three different mechanisms in sequence. The chemical reaction at the melt-gas interface controls the rate of decarburization during the first period, the rate of oxygen supply through the boundary layer in gas during the second period, and the mass transfer rate of carbon in melt during the third period when the carbon content is less than 2 mass%.Manganese is lost primarily by evaporative reaction, but its dynamics are affected by the prevailing excess oxygen after accounting for CO formation. The excess oxygen and manganese vapor establish counter-current flux and form MnO mist at some distance away from the metal-gas interface. This creates two diffusion boundary layers, one for the flux of manganese vapor adjacent to the melt-gas interface and the other for the flux of excess oxygen in the gas phase. When the vapor pressure of manganese at the metal-gas interface is low, the rate of manganese vapor loss is controlled by the flux of excess oxygen. Otherwise, it is determined by the flux of manganese vapor.

Aspects of the High-Temperature Reduction of Manganese Ores by Coal

The existing technology for producing ferroalloys based on manganese is quite energy-intensive and entails relatively large losses of the main element. The use of ore-coal briquets makes it possible to speed up the reduction of manganese oxides and improve on the performance characteristics of traditional ferroalloy production methods [1]. Ore-coal briquets or pellets are particularly effective if used in a new type of process unit ‐ the oxygen reactor developed by the Moscow State Institute of Steel and Alloys [2]. The technology involves the introduction of a charge containing ore-based materials, fluxes, and a carbon fuel, injecting oxygen or air into the fuel column through lances located in the lower part of the reactor, and injecting gas with an oxygen content in the range 5‐95% through top (auxiliary) lances located above the stockline. The ore-based materials are charged in agglomerated or pulverized form. Coke and/or coal is used as the carbon-bearing fuel. The main feature of the process is complete use of the calorific value of the coal and coke inside the reactor as a result of combustion of carbon monoxide above the column of carbon-bearing solid material. In addition, the use of green ore-coal pellets causes the reduction zone to be localized mainly on the surface of the coke column ‐ in the space where most of the heat used in the process is concentrated. The technology reduces the total consumption of carbon-bearing fuel, allows much of the coke to be replaced by coal in the green ore-coal pellets or briquets, and speeds up the smelting of pig iron and ferroalloys. The consumption of carbon fuel is as follows: for smelting pig iron ‐ 500 kg/ton (coke ‐ 200 kg/ton, coal in the briquets ‐ 300 kg/ton), instead of 600 kg of coke per ton of pig iron in blast furnaces; in the production of ferroalloys based on manganese, chromium, or silicon ‐ roughly 700 kg/ton (coke ‐ 300 kg/ton, coal in the briquets ‐ 400 kg/ton), instead of 2000 kg/ton in blast furnaces. Unlike blast furnaces, the reactor has no shaft, stoves, or complex charging equipment. This article reports the results of our determination of the optimum conditions for the rapid and complete reduction of manganese ores by coal under smelting conditions in the oxygen reactor in order to obtain carbon-bearing ferromanganese and silicomanganese. We studied the reduction of different manganese ores: oxide and carbonate Polynochnyi ores (Russia); Zhairemsk ore (Kazakhstan); Groote Eyland (Australia); Comilog (Gabon); Wessels High Grade (South Africa). The reducing agent used was gas coal of grade G containing 10‐15% ash and 15‐20% volatile matter (Table 1). The amount of reducing agent (carbon) needed was determined on the basis of the criterion of achieving complete reduction of the oxides of iron and manganese (Fe 3 O 4 and Mn 3 O 4 ). A prepared mixture with a mass of 2‐3 g was placed in an alundum crucible, covered with a tungsten cover, and lowered into a graphite-heater-equipped furnace that had been preheated to the test temperature (1600°C). The mixture was kept in the furnace for 3‐7 min. We measured the amount of mass lost by the specimen as a function of time under isothermal conditions. The degree of reduction of the charge was calculated as follows: α = {[(16/28)⌉M]/(M 0 Fe + M 0 Mn )}·100, %,

RH真空槽の上吹きランスから吹きつけた粉体の取鍋内溶鋼での挙動

RH真空槽の上吹きランスから吹きつけた粉体の取鍋内溶鋼での挙動