含锌冶金尘泥在微波场中的升温特性

为了弄清含锌冶金尘泥脱锌的反应机理,在微波场中研究了含锌冶金尘泥的升温特性.研究表明,含锌冶金尘泥对微波有很强的吸收能力,其升温速率与微波加热比功率成正比,与质量成反比;增大单位物料质量接受微波的辐射面积可以提高物料的升温速度.     

微波辅助浸出铁矾渣中锌的试验研究

对比研究了直接硫酸浸出、微波酸浸、先碱浸再酸浸和先碱浸再微波酸浸工艺从铁矾渣中浸出锌。结果表明:浸出过程中引入微波可以提高锌浸出率;微波酸浸之前先进行碱浸有利于锌的浸出;微波功率对微波酸浸和先碱浸再微波酸浸有明显影响,不同微波功率条件下,先碱浸再微波酸浸的效果优于直接微波酸浸效果;碱浸后再微波酸浸,浸出时间、反应温度、硫酸初始浓度、液固体积质量比都对锌的浸出有较大影响。研究结果对类似铁矾渣的综合利用有一定参考价值。     

从高冰镍浸出渣中浸出铜

高冰镍浸出系统产出的高冰镍浸出渣中铜含量较高,研究了采用微波辅助加热、Fe_2(SO_4)_3氧化浸出工艺从渣中浸出铜,考察了微波功率、硫酸质量浓度、Fe_2(SO_4)_3用量、浸出时间、液固体积质量比对铜浸出率的影响。利用JMP软件分析试验结果,确定了Fe_2(SO_4)_3用量、硫酸质量浓度是影响铜浸出的显著因素,适宜的浸出条件为微波功率700 W,Fe_2(SO_4)_3质量浓度100g/L,硫酸质量浓度184g/L,液固体积质量比8∶1,浸出时间120min。在适宜条件下,铜浸出率为89.82%。     

美国用微波烧结法制出粉末冶金件

日常生活中人们一般都知道在微波炉中不能使用金属器皿进行加热 ,因为金属会反射微波辐射从而影响到烹饪效果。但美国科学家一项新的研究发现表明 ,金属处于粉末状态时对微波辐射会有很强的啄性 ,利用这一特性可为汽车等行业加工出高性能的金属部件。美国宾夕法尼亚州立大学材料研究实验室的科学家在最新一期英国《自然》杂志上介绍说 ,他们在研究中采用 2 45ｋＨｚ的微波场来对铁、镍、钴、钼、铜、铝和锡等金属的粉末进行加热试验 ,并利用微波加热烧结法成功地用金属粉末制成小型齿轮及其它环状、管状的机械零件。与利用普通高温加热烧结…     

脉冲微波助磨工艺参数对钛铁矿升温性能的影响研究

为了提高钛铁矿回收效率,对钛铁矿在脉冲微波条件下的升温行为进行了研究,采用自制的脉冲微波设备,对钛铁矿进行脉冲微波预处理。研究了不同辐照时间、脉冲微波功率、矿样质量和不同矿样粒度对钛铁矿升温性能的影响。采用X射线衍射仪对矿样组成进行分析,利用激光粒度仪对样品粒度进行检测。研究结果表明:物料在微波场中的升温行为,既决定于矿物本身的性质,又与微波加热设备的功率密切相关。当矿样粒度为25 mm、质量为40 g、辐照时间为30 s、微波平均功率为3 kW时,样品的升温性能最好。该研究对脉冲微波在助磨领域的应用具有重要意义。     

低品位氧化锌矿石铁还原度对硫酸浸出锌的影响

研究了低品位氧化锌矿石的微波还原焙烧—硫酸浸出锌,考察了微波功率、活性炭粉加入量和微波加热时间对矿石中铁还原度及铁还原度对锌、铁浸出率的影响。结果表明:低品位氧化锌矿中铁的还原度随微波功率、活性炭粉加入量和加热时间的增大而增大,锌浸出率随铁还原度的增大而升高;铁还原度控制在60%以下,用质量浓度为80g/L的硫酸溶液浸出,锌浸出率为85.36%,铁浸出率为33.75%。     

用微波辅助碱性氧化工艺从废手机元器件中浸出锡铅锌

研究了用微波辅助碱性氧化浸出工艺从废手机线路板元器件中回收锡、铅和锌等两性金属,并与传统碱性浸出工艺进行对比。结果表明:采用微波加热,可显著提高两性金属的浸出率;在氢氧化钠质量浓度263g/L、硝酸钠质量浓度76g/L、微波功率500 W、液固体积质量比60/1、温度90℃条件下浸出90min,金属锡、铅、锌浸出率分别为83.19%、69.69%、88.21%,浸出效果较好。     

微波加热配碳还原分解铁酸锌的工艺及机理研究

研究了利用微波配碳还原焙烧分解铁酸锌的工艺及机理。利用碳气化控制、化学控制及扩散控制模型研究了样品中铁酸锌分解的动力学行为,并考察了微波功率、反应温度、配碳比和粒度对铁酸锌分解率的影响。结果表明,样品的微波加热碳热还原试验的控制步骤为碳气化控制,活化能为39.21kJ/mol,在微波加热温度850℃、C/ZnFe2O4质量比为1∶4、粒径74～89μm、微波功率1.8kW、加热时间60min的条件下,铁酸锌的分解率达到90%。     

用硫酸-二氧化硫体系从锌浸出渣中还原浸出有价金属

研究了用硫酸-二氧化硫体系从锌浸出渣中还原浸出锌、铁、铜、铟等有价金属,考察了初始硫酸质量浓度、反应温度、液固体积质量比、搅拌速度、SO_2分压对锌、铁、铜、铟浸出率的影响。结果表明:用SO_2对锌浸出渣还原浸出,可有效缓解溶液中高浓度三价铁离子对铁酸锌分解的抑制作用,大幅提高有价金属浸出率;浸出渣主要物相为PbSO_4和ZnS,铁酸锌完全分解。     

红土矿的微波浸出研究

本文研究了红土矿的微波加热浸出,采用X射线衍射分析和原子吸收分光光度法研究了红土矿物相和组成,主要物质为二氧化硅、蛇纹石和针铁矿,镍主要存在于蛇纹石及针铁矿中.研究了微波辐射加热条件下,红土矿的浸出过程.考察了微波辐射功率、H2SO4浓度、液固比、加热时间、铜离子浓度等因素对氧化镍矿浸出的影响,结果表明,镍、铁浸出率和反应体系的温度随着微波辐射功率的提高而增加;在微波功率为955W,H2SO4浓度为0.90mol/L,液固比为6∶1,反应时间40 min的条件下,镍的浸出率为99%,实验证明矿浆中少量的铜离子,即可起到较强的催化作用.以收缩未反应核模型为基础,建立了红土矿的微波浸出的动力学模型.对实验数据进行多相反应动力学处理,用1-2α/3-(1-α)2/3～t作图得到近似直线.     

Modeling of microwave heating of particulate metals

Recent studies have shown that metal powder compacts can be heated to high temperatures using microwaves. While microwave heating of ceramics is well understood and modeled, there is still uncertainty about the exact mechanism and mode of microwave heating of particulate metals. The current study describes an approach for modeling the microwave heating of metal powder compacts using an electromagnetic-thermal model. The model predicts the variation in temperature with time during sintering. The effect of powder size, emissivity, and susceptor heating on the heating rate has also been assessed. These predictions have been validated by the experimental observations of the thermal profiles of Sn-, Cu-, and W-alloy compacts, using a 2.45 GHz multimode microwave furnace.     

铁精矿氧化球团微波加热直接还原新方法

传统加热直接还原具有热效率低、球团"冷中心"和废热废气量大等问题,造成还原时间长、能耗高和污染大。试验利用微波的选择加热、快速加热、体积加热和清洁干净等优点,以及铁矿球团和无烟煤强的吸波特性,开发了铁矿球团煤基微波竖炉直接还原这一新工艺。研究表明,铁矿球团外配煤粉在1 050℃的微波加热条件下还原焙烧65min,可以获得95.25%的金属化率,同时具有1718.88N/个的抗压强度。与常规加热相比,微波加热还原焙烧的时间可以缩短27.78%,抗压强度增加近1倍,而且还原过程产生的废热废气量很少。     

微波加热技术在铝酸钙炉渣浸出过程中的应用

在微波辐射加热条件下考察了微波辐射功率、浸出用液的Na2Oc质量浓度、液固比等对高炉铝酸钙渣的浸出过程的影响,并与传统加热浸出进行了比较。结果表明,氧化铝浸出率和反应体系的温度随着微波辐射功率的提高而增加。在温度未达到溶液沸点之前,反应体系为非恒温反应过程。微波辐射浸出与传统加热浸出相比较,微波辐射加热下炉渣中氧化铝浸出速率较传统加热方式浸出快得多,微波浸出可降低浸出用液的Na2Oc质量浓度,缩短浸出时间。     

红土镍矿低温还原+微波冶炼镍铁新技术

红土镍矿的低温还原热力学和低温还原动力学研究表明,在1 350℃左右半熔融状态下可以得到镍铁合金颗粒。利用微波内加热和选择性加热的特点,能够明显改善加热效率和渗碳效果,促进弥散在炉渣中的镍铁粉聚集长大成镍铁颗粒。在此基础上研发出红土镍矿低温还原+微波冶炼镍铁新技术,并建成了世界上第一条新技术示范生产线。与RK-EF工艺相比,新技术取消了后续的电炉熔炼工艺,使冶炼温度降低了250℃左右,电耗降低45%以上。新技术实现了高效率、低能耗、环保及低成本生产镍铁合金。     

Interfacial tension between low pressure argon plasma and molten copper and iron

The interfacial tension between the molten metal and the surrounding plasma environment affects the circulation of molten metal in the weld pool, heat transfer, and the eventual structure and properties of the weld metal. Since the effect of plasma on the interfacial tension of molten metals is not known, interfacial tension values between low pressure argon plasma and pure copper and iron were measured. The variables studied were temperature and the intensity of plasma emission.     

Absorption of gaseous oxygen by liquid cobalt,copper, iron and nickel

An experimental investigation of the rates of oxygen solution in molten cobalt, copper, iron and nickel was carried out using pure oxygen and a constant-volume Sieverts’ method. It was found that the volume of gaseous oxygen which initially reacted with the inductively stirred metals was strongly dependent on the physical nature of the oxide film which formed during the first stage of reaction. The initial temperature of the molten iron, cobalt, and nickel was 1600°C, and for copper was 1250°C. For initial oxygen pressures above the melt of about one atmosphere both molten iron and copper, which formed liquid surface oxides, initially absorbed nearly 20 cm³ (STP) O₂/cm² of melt surface area, while molten cobalt and nickel, which formed solid oxides, absorbed about 6 cm³ (STP) O₂/cm² under the same experimental conditions. For approximately 30 s after the initial reaction between these liquid metals and gaseous oxygen, the oxygen absorption rate was proportional to the square root of the oxygen pressure above the melt, and proportional to the melt surface area, but independent of melt volume. The rate-limiting step for oxygen absorption by liquid iron, cobalt and copper can be described by dissociative adsorption of oxygen molecules at the gas/oxide interface. After 30 s of reaction, the rate of oxygen absorption became less dependent on the oxygen pressure above the melt. This indicated that the rate-controlling step was changing from a surface reaction to growth of the oxide layer by cationic diffusion in the bulk oxide. The oxidation rate of liquid nickel appears to be too complex to be described by models for dissociative adsorption of oxygen molecules at the gas/oxide interface and parabolic growth of the oxide layer. The formation of a thin layer of nickel oxide which allows oxygen to migrate through cracks or grain boundaries may be responsible for the relatively high oxygen absorption rate compared to that of liquid cobalt. R. H. RADZILOWSKI, formerly a Graduate Studient at The University of Michigan     

Absorption of gaseous oxygen by liquid cobalt, copper, iron and nickel

An experimental investigation of the rates of oxygen solution in molten cobalt, copper, iron and nickel was carried out using pure oxygen and a constant-volume Sieverts' method. It was found that the volume of gaseous oxygen which initially reacted with the inductively stirred metals was strongly dependent on the physical nature of the oxide film which formed during the first stage of reaction. The initial temperature of the molten iron, cobalt, and nickel was 1600‡C, and for copper was 1250‡C. For initial oxygen pres-sures above the melt of about one atmosphere both molten iron and copper, which formed liquid surface oxides, initially absorbed nearly 20 cm³ (STP) O₂/cm² of melt surface area, while molten cobalt and nickel, which formed solid oxides, absorbed about 6 cm³ (STP) 0₂/cm² under the same experimental conditions. For approximately 30 s after the initial reaction between these liquid metals and gaseous oxygen, the oxygen absorption rate was proportional to the square root of the oxygen pressure above the melt, and pro-portional to the melt surface area, but independent of melt volume. The rate-limiting step for oxygen absorption by liquid iron, cobalt and copper can be described by dissocia-tive adsorption of oxygen molecules at the gasJoxide interface. After 30 s of reaction, the rate of oxygen absorption became less dependent on the oxygen pressure above the melt. This indicated that the rate-controlling step was changing from a surface reaction to growth of the oxide layer by cationic diffusion in the bulk oxide. The oxidation rate of liquid nickel appears to be too complex to be described by models for dissociative ad-sorption of oxygen molecules at the gasJoxide interface and parabolic growth of the oxide layer. The formation of a thin layer of nickel oxide which allows oxygen to migrate through cracks or grain boundaries may be responsible for the relatively high oxygen ab-sorption rate compared to that of liquid cobalt. Formerly a Graduate Student at The University of Michigan     

Effect of conventional and microwave sintering on the properties of yttria alumina garnet-dispersed austenitic stainless steel

The current study examines the effect of heating mode, temperature, and varying yttria alumina garnet (YAG) addition (5 and 10 wt pct) on the densification and properties of austenitic (316L) stainless steel. The straight 316L stainless steel and 316L-YAG composites were heated in a radiatively heated (conventional) and 2.45 GHz microwave sintering furnace. The compacts were consolidated through solid state as well as supersolidus sintering at 1200 °C and 1400 °C, respectively. Both 316L and 316L-YAG compacts couple with microwaves and heat to the sintering temperature rapidly (∼45 °C/min). The overall processing time was reduced by about 90 pct through microwave sintering. As compared to conventional sintering, compacts sintered in microwaves exhibit higher densification and finer microstructure but no corresponding improvement in mechanical properties and wear resistance. This has been correlated to elongated, irregular pore structure in microwave-sintered compacts.     

Influence of microwave heating on the microstructures of iron ore pellets with coal during reduction

Iron ore oxidised pellets as the burden of blast furnace present many advantages, such as uniform size, high iron grade and high physical strength. A comparison of the iron ore oxidised pellets with coal (out-proportioning) by conventional heating and microwave heating was carried out in this paper. Microstructure transformations during reduction process were investigated by optical microscopy and scanning electron microscope with energy dispersive spectrometry analysis. Micro-hardness of metallic iron phase formed in the reduction was tested with digital micro-hardness tester. The influences of microwave heating on reduction degree, morphology, iron phase and gangues were investigated, respectively. The results show that reduction time can be greatly shortened by microwave heating even at lower temperatures. The fine cracks generated, as the pellets were heated by microwave, were irradiated due to the selectivity of microwave heating. Densification of the metallic iron phase and the separation of the iron and gangues were both found to be enhanced by microwave heating.