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.     

Desulfurization kinetics of molten copper by gas bubbling

Molten copper with 0.74 wt pct sulfur content was desulfurized at 1523 K by bubbling Ar-O₂ gas through a submerged nozzle. The reaction rate was significantly influenced not only by the oxygen partial pressure but also by the gas flow rate. Little evolution of SO₂ gas was observed in the initial 10 seconds of the oxidation; however, this was followed by a period of high evolution rate of SO₂ gas. The partial pressure of SO₂ gas decreased with further progress of the desulfurization. The effect of the immersion depth of the submerged nozzle was negligible. The overall reaction is decomposed to two elementary reactions: the desulfurization and the dissolution rate of oxygen. The assumptions were made that these reactions are at equilibrium and that the reaction rates are controlled by mass transfer rates within and around the gas bubble. The time variations of sulfur and oxygen contents in the melt and the SO₂ partial pressure in the off-gas under various bubbling conditions were well explained by the mathematical model combined with the reported thermodynamic data of these reactions. Based on the present model, it was anticipated that the oxidation rate around a single gas bubble was mainly determined by the rate of gas-phase mass transfer, but all oxygen gas blown into the melt was virtually consumed to the desulfurization and dissolution reactions before it escaped from the melt surface.     

转炉氧枪枪位对炼钢熔池流速的影响

转炉炼钢利用供氧枪位的改变实现前期化渣、中期脱碳升温以及后期强化搅拌的目的.本文基于100t炼钢转炉,研究了四孔超音速氧枪喷吹时枪位变化对熔池流动状况的影响.研究发现：低枪位有利于增加射流冲击深度,加速熔池表层钢液;高枪位有利于增大射流冲击面积,促进钢液速度在径向方向上均匀分布,增加熔池底部钢液速度.随着枪位从1.2m提高至1.8m,冲开渣层的直径从2.119m增加为2.645m,射流的冲击深度显著降低.     

Effect of oxygen on the surface tension of liquid copper

The influence of oxygen on the surface tension of liquid copper has been determined by the sessile drop technique. The surface tension of pure liquid copper at 1108 °C is found to be equal to 1.320 ± 0.015 N/m. The effect of oxygen is investigated for partial pressures of oxygen ranging from 10?13 to 5 X 10?6 atm. The surface activity of oxygen is deduced to equal 3200 ± 600 N/m and the saturation adsorption to equal 5.72 X 10"6 mole/m², which corresponds to a saturation area of 29 ±5Ų per adsorbed oxygen atom. The adsorption of oxygen on liquid copper is consistent with the formation at the metal surface of a two-dimensional compound of stoichiometry Cu³O. It is also concluded that equivalent attractive forces operate between neighboring adsorbed atoms.     

The kinetics of selenium removal from molten copper by powder injection

Chemical thermodynamic calculations show that selenium removal from copper melts using sodium carbonate (soda ash) is only effective under reducing conditions. Reducing conditions can be generated by carbon, but even more effectively by calcium carbide which has not been used previously for such a purpose. To clarify the kinetics of these multiphase, multicomponent reactions, various mixtures were either placed on top of or injected into 70 kg heats of molten copper. The following reagents were found to be effective in removing selenium: soda ash-graphite mixtures, calcium carbide, and calcium carbide-soda ash mixtures, in increasing order of effectiveness. Experiments were also performed with synthetic blister copper containing oxygen, selenium, tellurium, bismuth, nickel, silver, and lead. As expected from the thermodynamic analysis, only the first three of these elements were removed. A mathematical model was developed to describe the diffusion-controlled reaction kinetics of selenium and oxygen removal at calcium carbide particle interfaces. Very good agreement between the model and experiments was achieved for the reaction paths of selenium and oxygen when 35 pct of the particles were in contact with the melt. The utilization of powder varied over a wide range (0 to 10 pct), depending on the selenium and oxygen contents. The industrial implications of this work are discussed in terms of multielement removal, refractory erosion, temperature loss, and reagent utilization.     

On the thermodynamics of oxygen in molten copper,Cu-Sn,and Cu-Ag alloys

Measurements of oxygen activity in molten copper, Cu-Sn, and Cu-Ag alloys at 1135°C have been made utilizing the solid-state electrolyte technique. The activity coefficient of oxygen in molten copper at low oxygen levels (<0.1 pet) was found to be 0.12. The interaction parameters of silver and tin on oxygen were found to be ε _O ^Ag = 4.52 and ε _O ^Sn =-10.5. Comparison of experimental data with solution models revealed that the behavior of oxygen in Cu-O-Ag alloys is in accordance with predictions of Alcock and Richardson’s quasichemical model when a coordination number between 1 and 4 is assumed, depending on the silver and oxygen content. Furthermore, agreement with Belton’s quasichemical model based on the assumption of Ag-O dipoles serves to strengthen the evidence for the existence of Ag-O species in solution. The behavior of oxygen in the Cu-O-Sn system also shows better agreement with the quasichemical model than with the random model, with low coordination numbers favored in dilute tin solutions, increasing to larger values in Cu-60 Sn solutions.     

Arsenic and lead volatilization from molten copper at high oxygen levels

Thermodynamic calculations for the volatilization of arsenic and lead from molten copper at high oxygen level were performed using available thermodynamic data. An experimental setup was built in order to validate the predictions. Three experimental tests confirmed both the moderate volatility for Pb species (Pb+PbO) and the extremely low vapor pressure of As-O species, even at high oxygen and arsenic levels in molten copper.     

Influence of deposit morphology on the kinetics of copper cementation on pure iron

The kinetics of copper cementation on pure iron substrates were studied using a rotating disc geometry. The effect of rotational speed of the iron disc, copper ion concentration, hydrogen ion concentration, and temperature on the kinetic response was investigated. The range of each parameter studied was selected with some consideration for commercial operations for copper recovery using iron as the precipitant metal. The optimum values of each parameter for maximum cementation rate were determined. At low temperatures (10–30°C), an experimental activation energy of 22.89 kcal mol^?1 was calculated indicating that the system is strongly controlled by a surface reaction mechanism or pore diffusion process. At high temperatures (30–60°C), an experimental activation energy of 7.94 kcal mol^?1 was obtained which shows that the system may be controlled by both diffusion and surface reaction mechanisms. The deposits obtained were pure copper and not a copper-iron alloy. The total iron consumption, presented as can factor, was around 1.0.The structural characteristics of the resultant deposits were studied with the help of a scanning electron microscope. The structure and morphology of the deposits were analyzed in conjunction with their respective specific rate constants. A change in the surface roughness of the rotating disc and hence in the effective deposition surface area as a result of modification to the deposit morphology obtained for different experimental conditions was found to be the major reason for variations in the reaction rate. For the experimental conditions employed in this study, most of the deposits seen were bulbous or botryoidal crystal masses of different degrees of texture and size.     

钢包耐火材料对钢中氧含量及钢水温降的影响

利用氧势指数分析了钢包耐火材料组成、配比以及加热温度对耐火材料分解和向钢中传氧的影响,并利用热传导理论计算了钢包包衬耐火材料的绝热性能对钢水温降的影响.结果表明:随着耐火材料材质由碱性向中性和酸性的顺序变化及温度的升高,耐火材料的氧势指数增大,由耐火材料向钢中的传氧能力增加;通过使用绝热性能良好的耐火材料,可以显著降低...     

Interaction of copper sulfides with copper oxides in the molten state

Reactions of Cu₂S with Cu₂O, CuS with Cu₂O and CuS with CuO in the molten state were examined in the presence of one atmosphere of argon at 1200°C. A rate law of the form,r _SO2 =kN_SN_O was applicable for each reaction system studied. Comparison of the rate constants for the systems, under conditions of similar initial mole fraction of sulfur to mole fraction of oxygen ratios, showed that Cu₂O was much more reactive than CuO in its reaction with copper sulfides. These results are incorporated in a mechanism in which Cu₂O reacts with the sulfide in the rate determining step. Experiments carried out in the presence of oxygen indicated the importance of a CuO-Cu₂O equilibrium in the overall reaction mechanism.     

Effect of oxygen flow rate and temperature on supersonic jet characteristics and fluid flow in an EAF molten bath

A new operation method for the oxygen lance of an electric arc furnace (EAF) was proposed, meeting the simultaneous demand for low oxygen flow rate and high stirring power in a particular smelting stage. When the oxygen flow rate needs to be reduced, the stirring power of the jet can be improved by increasing oxygen temperature properly. Free supersonic jet characteristics at different flow rates and stagnation temperatures were studied by numerical simulation and validated by a jet measurement experiment. The results showed that the designed Mach number can be maintained by coupling adjustment of flow rate and stagnation temperature. Meanwhile, a three-phase, full-scaled numerical model for a commercial 75t EAF with three oxygen lances on the side-wall was established to study the fluid flow in the molten bath. The velocity distribution, cavity profile and total kinetic energy of the EAF bath induced by the impingement of supersonic jets onto the liquid bath were discussed and compared. It was found that the fluid flow characteristics of the EAF molten bath can be improved even if the oxygen flow rate was reduced as long as the oxygen temperature could be increased reasonably.     

The kinetics of nitrogen absorption and desorption from a plasma arc by molten iron

A plasma torch and refractory-lined furnace with a 10 kg capacity were used to study the kinetics of nitrogen absorption and desorption in molten iron. In this study, melts containing both oxygen and sulfur were used. In accord with earlier studies, a limiting rate constant of 0.020 cm/s-pct was observed at high oxygen and/or sulfur contents. At lower oxygen and/or sulfur contents, the measured desorption rates are smaller than most of the reported values and appear to be limited by mixed melt, mass transfer chemical control. Absorption of nitrogen from the plasma arc is limited by mass transfer in the melt. The dominant form of convection in the vicinity of jet impingement is surface tension driven flow. The reaction N(g)=N(pct) appears to be responsible for the enhanced nitrogen content of the melt. The nitrogen content of a melt in equilibrium with the atomic nitrogen content of an Ar-5 pct N₂ plasma jet was determined to be 0.30 wt pct or thirty times the equilibrium value. T. B. KING, formerly Professor of Metallurgy at the Massachusetts Institute of Technology, Cambridge, MA, is deceased. This paper is based on a presentation made in the T.B. King Memorial Symposium on “Physical Chemistry in Metals Processing” presented at the Annual Meeting of The Metallurgical Society, Denver, CO, February, 1987, under the auspices of the Physical Chemistry Committee and the PTD/ISS.     

Oxidation of molten copper matte

An amount of 80 mg of molten copper matte of a pseudo-ternary Cu₂S-FeS-Fe system contained in a slender alumina sample tube was oxidized at 1503 and 1533 K in a mixed O₂-Ar gas stream and the oxidation path was followed, comparing the overall rate of oxidation with the gaseous diffusion in the sample tube. The following successive reactions were found to be controlled by gas diffusion. Initially, Fe was oxidized to form FeO. After the melt composition reached a pseudo-ternary Cu₂S-FeS-FeO system, FeS was oxidized to form FeO. As the amount of FeO increased, Fe₃O₄ was also formed and subsequently Cu was produced by the oxidation of Cu₂S. In the latter stage, the Cu was oxidized, and the final product under the condition of gas diffusion control was composed of Cu₂O, Fe₃O₄, and CuFeO₂. On the other hand, the rate of formation of Fe₂O₃, CuO, and CuFe₂O₄ was much slower and they were not formed during the oxidation duration where the overall rate of oxidation was controlled by gas diffusion.     

Arsenic activities in molten copper and copper sulfide melts

In recent years, the concentration of the group Va elements such as arsenic, antimony, and bismuth has been increasing in copper concentrates. The elimination and recovery of these elements during the copper smelting process have presented serious problems. While the distribution of minor elements has been studied extensively, very little knowledge exists on the activities of these minor elements in copper mattes. Consequently, in this study the activities of arsenic were measured to determine activity coefficients of arsenic in the dilute solution region of molten copper, in Cu₂S saturated copper, and in copper mattes equilibrated with copper at 1423 K by a mass spectrometric Knudsen effusion technique. Formerly with the Department of Metallurgy and Materials Science, University of Toronto, Toronto, ON, Canada     

惰气熔融-红外吸收法测定高纯铜中痕量氧

为降低氧的空白,在不添加助熔剂的条件下建立了惰性气体熔融-红外吸收法准确测定高纯铜中痕量氧的分析方法。实验表明:称取0.8 g左右的样品,在标准石墨坩埚中进行测定,控制吹扫时间为35 s,排气时间为25 s,排气周期为2 次,排气功率为4 500 W,分析功率为4 000 W,测得空白标准偏差为0.027 μg/g,氧的定量限可降至0.27 μg/g。准确称取10~30 μg高纯氧化铁于锡囊中,用于仪器的校正,获得校正系数为1.034,解决了没有合适标准物质的难题。采用实验方法对高纯铜实际样品进行测定,测得铜中氧的质量分数为2.43 μg/g,相对标准偏差(RSD)不大于7.7%。在测量不确定度评定中考虑了校正样品测量重复性、氧化铁试剂纯度、样品测量重复性和空白等影响因素,计算得到铜中氧质量分数的不确定度为 0.33 μg/g (k=2)。在高纯铜中加入高纯氧化铁进行加标回收试验,回收率在100%~105%之间。     

Settling of copper drops in molten slags

The settling of suspended metal and sulfide droplets in liquid metallurgical, slags can be affected by electric fields. The migration of droplets due to electrocapillary motion phenomena may be used to enhance the recovery of suspended matte/metal droplets and thereby to increase the recovery of pay metals. An experimental technique was developed for the purpose of measuring the effect of electric fields on the settling rate of metallic drops in liquid slags. Copper drops suspended in CaO−SiO₂−Al₂O₃−Cu₂O slags were found to migrate toward the cathode. Electric fields can increase the settling rate of 5-mm-diameter copper drops 3 times or decrease the settling until levitation by reversal of the electric field. The enhanced settling due to electric fields decreases with increasing Cu₂O contents in the slag.     

Simulation of the kinetics of the autoclave dissolution of copper and nickel sulfides in the presence of oxygen

Kinetic regularities of the oxidative autoclave dissolution of iron, copper, and nickel sulfides when leaching the ore of the Shanuch deposit are investigated in controllable experimental conditions. It is shown that the dissolution rate of sulfides is limited by the oxygen absorption.