真空下钢液脱氮工艺研究

在４０ｋｇ真空感应炉上进行了真空下钢液脱氮工艺的实验研究。实验考察了真空下碳氧反应工艺、表面活性元素控制和脱氮渣系等因素对钢液脱氮动力学的影响。研究结果表明：（１）真空下强烈的碳氧反应能有效地脱除钢中的氮;（２）当钢中硫含量较低时,脱氮速率很快,随着硫含量的逐步增加,脱氮速率相应降低;（３）５０％ＳｉＯ２－４０％Ｂ２Ｏ３－１０％ＴｉＯ２渣系有明显的脱氮效果。     

430铁素体不锈钢脱氮工艺

430铁素体不锈钢中的氮能恶化晶间腐蚀、低温冲击韧性、缺口敏感性以及焊接等性能。在热力学分析的基础上,研究了430铁素体不锈钢冶炼过程中初始碳质量分数、温度、氩氧比以及冶炼时间等工艺参数与对终点氮质量分数的影响。研究表明,在一定范围内,初始碳质量分数越高,氩氧比越大,脱氮效果越好;吹氩20min左右时脱氮效果最好,脱氮率可达到60%左右,继续延长冶炼时间会有回氮现象发生。     

Behaviors of Denitrogenation in RH-MFB

 According to the analysis related to kinetic mechanism of vacuum denitrogenation and combining with the actual production of RH-MFB (a combination of Ruhstahl-Hausen vacuum degassing process with a multifunctional oxygen lance) at Liansteel, the limit step and model equation of vacuum denitrogenation are determined. Meanwhile, the influencing factors of nitrogen removal from liquid steel in vacuum of RH-MFB are analyzed. The results show that the limit step of vacuum denitrogenation in RH-MFB is the mass transfer of nitrogen in liquid boundary layer and the reaction follows first order kinetics. Keeping the necessary circulation time under the working pressure (67 Pa) is helpful to nitrogen removal from steel. The oxygen content in molten steel has little influence on the removal of nitrogen after deep deoxidation, while the sulphur content in liquid steel is always relatively low and has little effect on denitrogenation. The sharp decrease of carbon content in steel drives the process of denitrogenation reaction so as to exhibit a faster denitrogenation rate. The interfacial chemical reaction and argon blowing play a major role in the nitrogen removal when the carbon content in liquid steel is stable.     

CO2顶吹比例对转炉终点控制的影响

结合CO₂的高温反应特性,针对性地制定了CO₂冶炼工艺,并对转炉顶吹CO₂比例对终点磷、氮和碳氧浓度积的影响进行了工业试验研究。结果表明:随着转炉冶炼前中期CO₂顶吹比例由4.84%逐渐提高到9.68%,转炉终点磷的质量分数先下降后基本不变,氮的质量分数逐渐下降,碳氧浓度积与渣中TFe变化趋势基本相同,均为先降低后增加,对于不同指标最佳顶吹CO₂比例不同。试验转炉终点磷、氮的质量分数、碳氧浓度积与渣中TFe均下降,下降比例最高分别为20.4%、34.3%、12.92%和8.89%。      

Dynamic model for on‐line observation of the current process state during RH degassing

Based on the principles of thermodynamics and reaction kinetics, a dynamic model for the vacuum circulation (RH) process was developed. It comprises decarburisation, oxygen removal, dehydrogenation, denitrogenation and the course of steel temperature. The process model was validated by comparison of simulation results with measured process data from the RH/1 plant of Voest Alpine Stahl Linz (VASL). At this plant, it is used for on‐line observation of the contents of carbon, oxygen, hydrogen and nitrogen as well as the steel temperature. Based on cyclically measured values of vessel pressure, lift gas flow rate as well as waste gas flow rate and composition, the current heat status is calculated reliably. The accuracy of the carbon balance with measured waste gas values was improved remarkably by a model‐based correction calculation. The on‐line process observation system provides the operator with valuable information on the progress of vacuum treatment.     

VD真空精炼脱氢和脱氮过程的三维数值模拟

基于质量、动量守恒计算了真空脱气装置内流场,并结合反应热力学和动力学理论建立了真空精炼过程中脱氢、脱氮与流场耦合的三维数学模型,研究了不同工艺参数对VD脱氢和脱氮过程的影响。结果表明:钢包内流场对脱气过程中氢和氮浓度空间分布具有明显影响;脱氢和脱氮速率随底吹气量的增加而增大,终点氢和氮浓度随底吹气量的增加而减小;在实际生产中,应在避免发生卷渣的前提下合理选择吹气量;不同底吹方式对脱氢和脱氮过程影响明显,其中偏心底吹效果优于中心底吹,双底吹效果最好。     

烧结机风箱中烟气排放规律及分析

 为了研究烧结机各个风箱中烟气的变化规律,选择某400 m2烧结机为研究对象,通过使用不同的烟气分析仪器对烧结机48个风箱中的烟气进行检测,得出了大型烧结机不同风箱中烟气温度、负压、流速、烟气成分(包括氧气、二氧化硫、一氧化碳、氮氧化物)等的变化规律;将烧结过程的料层分为6个状态,结合料层状态和风箱烟气参数分析了不同风箱对应的料层状态,解析了各个风箱烟气参数变化与料层状态的关联性和各个参数之间的相关性。可以得出,烟气的负压与流速的变化正相关;烟气温度与二氧化硫质量浓度变化趋势一致;氧气体积分数与一氧化碳、氮氧化物质量浓度变化呈现负相关趋势;一氧化碳和氮氧化物质量浓度变化一致;不同风箱烟气参数变化与风箱对应的烧结料层状态密切相关。     

Oxidation of molten impurities in converters by means of combustion flames: Thermodynamic principles. 2. Interaction of flame with metal and slag in converter bath

Thermodynamic analysis is applied to the physicochemical processes in the converter bath when intensifying bath heating by means of gas–oxygen burners. In the converter’s working space, when the combustion flames interact with the liquid bath, the oxygen and natural gas supplied through the burners and the oxygen supplied through the tuyere interact in a bubbling slag–metal emulsion. As a result, iron and the impurities are oxidized. The use of such burners changes the gas composition: not only O₂, CO, and CO₂ are present, but also H₂ and H₂O, which changes the oxidative capacity of the gas phase. The presence of solid carbon (for example, pulverized coal) in the burner flame may be used to control and intensify the combustion process. Combustion is most effective in the oxidation of carbon to CO when the oxygen excess is less than 1.0. The oxidation conditions of carbon in the melt change with variation in its activity as a function of its concentration and the temperature. The equilibrium in the M–O–C system may be described by the oxygen partial pressure \({P_{{O_2}}}\), which may be regarded as a universal characteristic. In addition, the equilibrium may be assessed on the basis of the associated ratios \({P_{CO}}/{P_{C{O_2}}}\) and \({P_{{H_2}}}/{P_{{H_2}O}}\) It is found that iron may be oxidized by oxygen and, to some extent, by carbon dioxide. At 1600–2000 K, there is practically no oxidation of iron by steam. The carbon dissolved in the steel is oxidized relatively effectively by oxygen and carbon dioxide until its concentration is less than 0.1% C. Steam oxidizes carbon very poorly and is not much more effective with manganese and silicon. With increase in temperature, the rate at which carbon dissolved in steel is oxidized by oxygen increases, while the oxidation rate of manganese and silicon falls. Above 1800 K, superoxidized slag with a high FeO content actively oxidizes silicon (to <2% Si), manganese (to <1% Mn), and carbon (to <1.5% C).     

Kinetics of the reaction of SiO(g) with carbon saturated iron

The reaction of SiO(g) with carbon saturated iron plays an important role in silicon transfer in the iron blast furnace. In the tuyere zone SiO(g) is generated from the reaction of coke with its ash, and the SiO(g) reacts with carbon saturated iron droplets as they pass through the furnace. This reaction may also play a role as a gaseous intermediate reaction for the reduction of SiO₂ from slags by carbon dissolved in iron. The rate and controlling mechanism for the SiO reaction with carbon dissolved in liquid iron was determined in the temperature range 1823 to 1923 K. A constant pressure of SiO(g) was generated by the reaction of CO with SiO₂; the reaction of carbon with SiO₂ gave higher but decreasing pressures of SiO with time. The SiO(g) generated was then reacted with carbon saturated iron under conditions for which the gas phase mass transfer conditions are clearly defined. By a systematic variation of the appropriate variables it was demonstrated that the rate was controlled by gas phase transfer of SiO to the gas-metal interface. The rate changed with gas diffusional distance but was not a strong function of temperature or of melt composition. The rate calculated for gas phase mass transfer was in good agreement with the experimental results. An erratum to this article is available at .     

Kinetic Model of Decarburization and Denitrogenation in Vacuum Oxygen Decarburization Process for Ferritic Stainless Steel

The characteristics and classification of decarburization and denitrogenation in the vacuum vessel for stainless steel production are analyzed. Based on the analysis of movements of the liquid steel and bubbles, the kinetics of decarburization and denitrogenation in the vacuum oxygen decarburization (VOD) process has been studied. A kinetic model of decarburization and denitrogenation has been developed to simulate the VOD process, considering each reaction zone as oxygen blowing crater, bottom blowing plume, steel/slag interface, and plume eye. As a result, it is possible to quantify the contribution of each reaction zone in decarburization and denitrogenation rate at a different stage in the VOD process. Specific trials at a vacuum induction furnace were performed to refine stainless steel in vacuum carbon deoxidation (VCD) and VOD style, respectively. The trial results are in good agreement with the model calculation. Combining the trials and the model calculation and the influence of temperature control, critical carbon content selection on the terminal total [C] + [N] content can be discussed further to provide a reasonable proposal for high-quality ferritic stainless steel production. This article is based on a presentation given at the International Symposium on Liquid Metal Processing and Casting (LMPC 2007), which occurred in September 2007 in Nancy, France.     

应用炉气分析的转炉动态模型初步研究

运用物料平衡及反应平衡原理,利用炉气连续分析的数据,建立了转炉冶炼过程的动态模型.本模型的计算结果表明:(1)通过烟气流量、成分及原料中初始碳含量可动态地确定熔池中的碳含量;(2)以动态确定的碳含量为基础,经过热力学平衡分析,可确定熔池内温度及氧含量的动态变化.     

Dissolution kinetics of particulate graphite injected into iron/carbon melts

An experimental investigation was undertaken to study the kinetics of graphite dissolution in gasstirred iron/carbon melts. Laboratory apparatus was developed to allow the injection of closely sized graphite into the bottom of a 1 kg scale reactor with nitrogen as a carrier gas. The effects of gas flow, particle loading, particle size, bath sulfur, and temperature on the rate of dissolution were assessed. It was found under the experimental conditions used that the graphite dissolution rate kept pace with the injection rate up to approximately 85 pct of carbon saturation, except when sulfur is present in the bath, in which case the dissolution rate is retarded. Modeling the rate of graphite particle dissolution supports the experimental results in that particle dissolution occurs quickly and under mass transport limitations. Computer generated gas-stirred flow field diagrams for the experimental reactor indicate that conditions exist for particle entrainment in the bath, and hence complete contact with the melt at all times during dissolution. formerly Experimental Scientist, CSIRO, Division of Mineral Engineering     

Dissolution kinetics of particulate graphite injected into iron/carbon melts

An experimental investigation was undertaken to study the kinetics of graphite dissolution in gasstirred iron/carbon melts. Laboratory apparatus was developed to allow the injection of closely sized graphite into the bottom of a 1 kg scale reactor with nitrogen as a carrier gas. The effects of gas flow, particle loading, particle size, bath sulfur, and temperature on the rate of dissolution were assessed. It was found under the experimental conditions used that the graphite dissolution rate kept pace with the injection rate up to approximately 85 pct of carbon saturation, except when sulfur is present in the bath, in which case the dissolution rate is retarded. Modeling the rate of graphite particle dissolution supports the experimental results in that particle dissolution occurs quickly and under mass transport limitations. Computer generated gas-stirred flow field diagrams for the experimental reactor indicate that conditions exist for particle entrainment in the bath, and hence complete contact with the melt at all times during dissolution. formerly Experimental Scientist, CSIRO, Division of Mineral Engineering     

电弧炉炼钢中碳氧二次燃烧的影响因素和应用

电弧炉炼钢时，废气与熔池和渣子接触，CO气体的温度接近钢水温度，整个过程基本由反应动力学条件控制，凭借吹氧可以在熔池上方进行二次燃烧。1台60t电弧炉2000多炉的二次燃烧的应用结果表明，当吹入氧气操作得当，二次燃烧对水冷炉壁、炉顶、电极寿命、3角区耐火材料寿命、金属烧损率均无影响，氧耗增加7．93m^3/t，电耗降低38kWh/t，冶炼周期可稳定缩短4min。     

Nitrogenation and decarburization of stainless steel

The rate of nitrogenation of iron alloys by nitrogen bubbling was determined. The rate of nitrogen pickup in iron with high oxygen activities was controlled by a chemical reaction at the gas bubble-metal interface. For an 18-8 type stainless steel and for iron containing between 50 and 400 ppm oxygen, the rate is controlled by a chemical reaction and liquid-phase mass transfer in series. The rate equation for this case was developed. The rates calculated from existing rate data and the fluid dynamic properties of the system were in good agreement with the experimental results. When argon-oxygen mixtures are bubbled through shallow (7.5 cm) stainless-steel melts, the rate of oxidation of chromium is considerably faster than that of carbon. It is suggested that oxygen primarily oxidizes chromium and iron and as the oxides are carried through the bath by argon bubbles they oxidize the carbon.     

Oxygen Solubility in Fe–Co Melts Containing Carbon

In thermodynamic analysis of solutions of oxygen in Fe–Co melts containing carbon, the equilibrium constants of reactions between carbon and oxygen are determined, as well as the activity coefficients at infinite dilution and the interaction parameters in melts of different composition at 1873 K. The dependence of oxygen solubility in such melts on the cobalt and carbon content is calculated. In iron–cobalt melts, carbon has high oxygen affinity. The deoxidizing ability of carbon increase significantly with increase in cobalt content in the melt. In pure cobalt, it is more than an order of magnitude greater than in pure iron. Deoxidation by carbon produces gaseous oxides: carbon monoxide (CO) and dioxide (CO₂). The reaction of carbon and oxygen dissolved in the melt and hence the deoxidizing ability of carbon depend on the total gas pressure above the melt. Decrease in gas pressure significantly improves the reducing properties of carbon. The minimum oxygen concentration for alloys of the same composition is reduced by practically an order of magnitude with tenfold decrease in the total gas pressure. The gas composition above Fe–Co melts and the equilibrium carbon and oxygen concentrations in the melt are calculated with total gas pressures of 1.0, 0.1, and 0.01 atm. The optimal oxygen concentration (1–10 ppm) in Fe–Co melts is reached at carbon concentrations between 0.01 and 1% depending on the total gas pressure (0.01–1 atm). The solubility of oxygen in iron–cobalt melts containing carbon passes through a minimum, which is shifted to lower carbon content with increase in the melt’s cobalt content. Further additions of carbon increase the oxygen concentrations in the melt. With increase in cobalt content, this increase will be sharper.     

A numerical study of high-velocity oxygen fuel thermal spraying process. Part I: Gas phase dynamics

A mathematical model is formulated to simulate the effect of operational parameters on the gas dynamics that occur during high-velocity oxygen fuel (HVOF) thermal spraying. Computational fluid dynamic techniques are implemented to solve the Favre-averaged mass, momentum, and energy conservation equations. The renormalization group (RNG) κ-ɛ turbulence model is used to account for the effect of turbulence, and high-order interpolation schemes are employed to resolve compressibility effects in the supersonic jets. The calculated results show that the most sensitive parameters affecting the process are propylene flow rate, total flow rate of oxygen and propylene (oxyfuel flow rate), total inlet gas flow rate, and barrel length. The results show that increasing the total inlet gas flow rate has limited effect on the gas velocity and temperature inside the nozzle for the parameter range investigated in the present study. However, increasing the total inlet gas flow rate increases the total thermal inertia and momentum inertia; moreover, under these conditions the flame gas is retained at a high velocity and temperature for a longer distance. Increasing the oxyfuel flow rate significantly increases flame velocity and temperature, particularly after exiting the nozzle. The effect of propylene flow rate is significant and complex. In order to minimize the extent of the oxidation of the sprayed powder particles and to achieve a high flame temperature and velocity, the overall injected stream should be adjusted to be propylene-rich. The nitrogen flow rate significantly affects the gas flow inside the gun. On the basis of the calculated results, it is evident that, in order to obtain maximum gas velocity and temperature, the nitrogen flow rate should be kept to a minimum, provided that particles can be delivered to the gun in a smooth manner. By minimizing the entrainment of the surrounding air, a nozzle with a longer barrel length achieves a relatively high gas velocity and temperature for a longer distance than does a nozzle with a shorter barrel length. The calculated results are in good agreement with available experimental results.     

吸附塔工艺参数对活性炭烧结烟气脱硫的影响

活性炭可高效脱除烧结烟气中的SO₂,但同时受到吸附塔工艺参数的制约。为了揭示工艺参数对脱硫率的影响规律,采用控制变量法,通过模拟烧结烟气进行活性炭脱硫研究。结果表明,空速、烟气湿度、含氧量和活性炭床温度对脱硫影响较大,活性炭粒度对脱硫率影响较小;降低空速、活性炭床温度及活性炭粒度,均有利于SO₂物理吸附进而促进脱硫率提高;烟气湿度和含氧量的增加,有利于SO₂的化学吸附进而提高脱硫率,但湿度大于12%时,水蒸气会在活性炭上聚集形成水膜而导致脱硫率下降。     

不锈钢渣熔融还原中铬在铁浴和熔渣间的分配行为研究

通过正交试验考察不锈钢渣铁浴熔融还原中反应温度、炉渣碱度、渣中Al2O3含量及铁水初始铬含量对铬在铁浴和碱性炉渣间分配行为的影响。试验在石墨坩埚内进行,还原剂为碳饱和铁水中的碳。试验结果表明,对影响渣中铬还原因素的显著性顺序依次为:炉渣碱度>渣中Al2O3含量>铁水初始铬含量>反应温度。此外采用模式识别方法对试验样本进行聚类分析和优化,以获得对渣中氧化铬还原的最佳参数。     

Oxidation kinetics of molten copper sulfide

The oxidation kinetics of molten Cu₂S baths, during top lancing with oxygen/nitrogen (argon) mixtures, have been investigated as a function of oxygen partial pressure (0.2 to 0.78), bath temperature (1200 °C to 1300 °C), gas flow rate (1 to 4 L/min), and bath mixing. Surface-tension-driven flows (the Marangoni effect) were observed both visually and photographically. Thus, the oxidation of molten Cu₂S was found to progress in two distinct stages, the kinetics of which are limited by the mass transfer of oxygen in the gas phase to the melt surface. During the primary stage, the melt is partially desulfurized while oxygen dissolves in the liquid sulfide. Upon saturation of the melt with oxygen, the secondary stage commences in which surface and bath reactions proceed to generate copper and SO₂ electrochemically. A mathematical model of the reaction kinetics has been formulated and tested against the measurements. The results of this study shed light on the process kinetics of the copper blow in a Peirce-Smith converter or Mitsubishi reactor.