Fundamental study on utilization of tin and zinc-bearing iron concentrate by selective chlorination

The feasibility and technologies of comprehensive recovery of tin, zinc, arsenic and iron from the complex iron ores by selective chlorination roasting were studied by thermodynamic analysis and roasting experiments. Investigation shows that the product pellets with the compression strength of 2 625 N/P, the tumble index of 97. 26%, the abrasion index of 1. 35%, tin, arsenic and zinc residue of 0. 043%, 0. 046% and 0.058% respectively can be achieved if bailing a concentrate containing 0.39 % tin, 0.40% arsenic and 0.28% with addition of 8% coke breeze and 0. 5% CaCl2 and roasting the pellets at 1 060 - 1 080℃ for 40 min. The volatilization of tin, arsenic and zinc is 91.75 %, 93.42 % and 81.12 % respectively. The performances of the product pellets are able to meet the requirements of blast furnace ironmaking.     

Synchronous Volatilization of Sn,Zn, and As,and Preparation of Direct Reduction Iron (DRI) from a Complex Iron Concentrate via CO Reduction

Sn-, Zn-, and As-bearing iron ores are typical complex ores and are abundantly reserved in China. This kind of ore is difficult to use effectively due to the complicated relationships between iron and the other valuable metal minerals. Excessive Sn, Zn, and As contents would adversely affect ferrous metallurgy operation as well as the quality of the products. In this study, thermodynamic calculations revealed that it was feasible to synchronously volatilize Sn, Zn, and As via CO reduction. Experimental results showed that preoxidation was necessary for the subsequent reductive volatilization of Zn from the pellets, and the proper preoxidation temperature was 700–725°C under air atmosphere. Synchronous volatilization of Sn, Zn, and As was realized by roasting under weak reductive atmosphere after the pellets were preoxidized. The volatilization ratios of 75.88% Sn, 78.88% Zn, and 84.43% As were obtained, respectively, under the conditions by reduction at 1000°C for 100 min with mixed gas of 50% CO + 50% CO₂ (in vol.). A metallic pellet (direct reduction iron) with total iron grade of 87.36%, Fe metallization ratio of 89.27%, and residual Sn, Zn, and As contents of 0.071%, 0.009%, and 0.047%, respectively, was prepared. Sn and As were mainly volatilized during weak reductive atmosphere roasting, and those volatilized in the metallization reduction process were negligible. Most of Zn (78.88%) was volatilized during weak reductive atmosphere roasting, while the metallization reduction process only contributed to 16.10% of total Zn volatilization.     

Kinetics of isothermal reduction of stainless steelmaking dust pellets

The stainless steelmaking dust pellets were reduced in isothermal temperature condition simulating the direct recycling practice in the stainless steel production and the kinetics of the reduction process was investigated.The pellets were formed after mixing the dust with carbon as the reducing agent and dolomite as the binder and smelting flux. An electric furnace was used to heat the pellets and an electrical microbalance was used to check the mass of the pellets in the reduction process. The reduction rate was calculated according to the data of pellet mass change in consideration of the evaporation of moisture, zinc and lead at high temperature. The results of the experi-ments show that the reduction process is in two consecutive stages. The reduction kinetic models were set up for each stage and the kinetic parameters such as activation energy and frequency factor were determined. The apparent activation energy of the first stage is 21.69 kJ/mol, and this stage is controlled by chemical reaction. The apparentactivation energy of the second stage is 17.35 kJ/mol, and this stage is controlled by the diffusion of carbon monox-ide through the resultants of reaction.     

REDUCTION BEHAVIOR OF IRON ORE PELLETS CONTAINING CARBON UNDER NON-ISOTHERMAL CONDITION

The reduction behavior of iron ore pellets containing carbon under non-isothermal condition in the temperature range from 573 to 1373K has been investigated in a laboratory scale setup. The test results show that carbon content has no obvious effect on reduction degree of composite pellets (C/O mole ratio=1.0) by CO in the temperature range from 575 to 1373K under linear temperature-rising program; reduction degree of iron ore pellets containing carbon is larger in 90%CO-10%CO2 mixture than that of in 100%CO atmosphere or in 80%CO-20%CO2 mixture; the s type temperature-rising program has a better effect than that of linear one to increase the reduction degree; and reduction degree of slower linear temperature-rising program is greater than that of faster one, but the final reduction degrees, i.e., those at the highest temperature are about same for various CO partial pressures or temperature-rising programs. The kinetic analysis also shows that the reduction of iron ore-carbon composite pellets by CO or CO-CO2 mixture under non-isothermal condition should be controlled 6y surface reaction, and the apparent reduction activation energy changes with the reduction progress under various test conditions.     

高砷铅阳极泥水蒸气焙烧脱砷实验研究

针对目前工业上难处理的高砷铜阳极泥 ,作者提出在水蒸气气氛中焙烧脱砷的新工艺。实验主要对反应气氛、焙烧温度、焙烧时间等影响因素进行了系统考查。结果表明 ,在水蒸气气氛下焙烧高砷铅阳极泥 ,脱砷率≥ 87% ,焙砂含砷 <3% ,脱砷效果明显好于空气气氛。同时 ,通过XRD分析 ,对焙烧脱砷过程中的物相变化及反应机理进行了探讨。     

PREPARATION OF IRON CARBIDE FROM MAGNETITE PELLETS BY CO-H2 MIXTURES REDUCTION

1. Introduction Iron carbide has some advantages over products of direct reduction iron and has been put into production in industrial scale[1,21, however, the present process only uses natural gas and hematite as material to prepare iron carbide, which has a great limit to the source of kind of reactant gas and iron ore. In recent years, people have done some investigations on preparation of iron carbide using other kind of reactant gas. For example, Hayashi et al[~1 made some investigation …     

Simultaneous extraction of gold and zinc from refractory carbonaceous gold ore by chlorination roasting process

A novel process based on chlorination roasting was proposed to simultaneously recover gold and zinc from refractory carbonaceous gold ore by using NaCl as chlorination agent. The effects of roasting temperature, roasting time and NaCl content on the volatilization rates of gold and zinc were investigated. The reaction mechanism and the phase transition process were also analyzed by means of SEM, EDS and XRD. The results demonstrated that under the optimal conditions of NaCl content of 10%, roasting temperature of 800 °C, roasting time of 4 h and gas flow rate of 1 L/min, the rates of gold and zinc were 92% and 92.56%, respectively. During low-temperature chlorination roasting stage, a certain content of sulfur was beneficial to the chlorination reactions of gold and zinc; and during high-temperature chlorination roasting stage, the crystal structure of vanadium-bearing mica was destroyed, and the vanadium-containing oxides were beneficial to the chlorinating volatilization of gold and zinc. Eventually, the chlorinated volatiles of gold and zinc could be recovered by alkaline solution.     

Hochtemperaturschäden bei hitzebeständigem Stahlguß

High temperature failures of heat resistant cast steel Heat resistant cast steel can fail by high temperature, the atmosphere, deposits and mechanical stresses. High temperature corrosion by gas atmospheres can be oxidation, nitriding, carburization, metal dusting, sulphur and chlorine attack. Corrosion by deposits as oil ash or chromates and liquid metals as copper base alloys, lead, tin and zinc leads to a rapid reduction in wall thickness. Besides there are mechanical stresses which lead to failures by stress rupture cracks or thermoshock. The additional effect by material aging should be considered as well.     

某新型清洗剂在弹药弹筒表面漆膜清洗上的应用

目的用某新型清洗剂代替酒精、汽油应用于弹药弹筒表面漆膜清洗。方法选取先进、可靠、安全环保的某新型清清洗剂,应用于弹药弹筒表面漆膜中间过程中漆膜上的油污、汗渍、红丹、记号笔、药粉等污物的清洗。通过对弹药弹筒表面漆膜的特点、漆膜上各类污渍的组成以及对漆膜中间清洗工艺过程进行分析,同时针对上述特点,拟定清洗剂选用原则,结合清洗剂的组成、特点、除污机理,通过对清洗剂进行应用试验,从清洗剂安全性能、清洗后漆膜附着力性能、清洗后漆膜耐盐雾性能、清洗剂的清洗效果、清洗剂的挥发速度、清洗剂气味等几个方面进行试验。结果某新型清洗剂具备清洗效果好、挥发速度快、清洗效率高等优点,清洗后对弹药弹筒表面漆膜无影响,满足弹劳逸结合漆膜清洗质量要求。结论某新型清洗剂可以代替酒精和汽油在弹药弹筒表面漆膜清洗上进行应用,具有环保、无毒等特点,在弹药弹筒表面漆膜清洗应用领域具有推广意义。     

电收尘器在锌浸出渣挥发窑烟气收尘中的应用

针对锌浸出渣挥发窑烟气的特点,及在传统收尘流程中存在的问题,结合实际生产经验,对云南冶炼厂锌系统环境治理改造工程中,电收尘器在锌浸出渣挥发窑烟气收尘中的应用情况进行了探讨。     

Isothermal reduction kinetics of zinc calcine under carbon monoxide

The reduction kinetics of zinc calcine under a CO atmosphere was evaluated by isothermal reductive roasting in a temperature range of 600−800 °C. The extent of reaction of zinc calcine was measured using thermogravimetry (TG), and the decomposition mechanism of zinc ferrite in zinc calcine was analyzed based on variations in the soluble zinc and ferrous contents. The results indicate that the reaction was controlled by the nucleation of the products, with an apparent activation energy of 65.28 kJ/mol. The partial pressure of CO affected the reaction rate more strongly than the CO intensity (defined as P_CO/(P_CO+P_CO2)). The generation rate of zinc oxide was higher than that of ferrous oxide; therefore, the nucleation of ferrous oxide is the rate-determining step of the reaction.     

煤油渗碳碳势控制技术研究

通过对煤油加空气渗碳碳势控制技术的研究，探讨了煤油加空气渗碳过程中各工艺参数对碳势的影响。结果表明，炉内气氛碳势与氧势和ＣＯ２值有良好的对应关系，在生产中应用两年多来的结果证明这是一种操作简单，稳定可靠怕可控气氛。     

Probleme der Inhibitoren in der Galvanotechnik

Problems of inhibition in electroplating Inhibition in electroplating is understood to be a hindrance or perturbation of the electrocrystallization; these phenomena may, however, have a positive effect, too, and are often a necessary condition for obtaining coatings with particular properties. The inhibitors used are mostly connected with the incorporation of foreign matter in the coating. Inhibition is of particular importance with respect to the throwing and the levelling power, the type of deposit (e.g. glossy coatings) and various chemical and physical coating properties. The various metals are characterised by various sensitivities with respect to the inhibitor effect: nickel and other transition metals are highly sensitive, copper has medium sensitivity and zinc, cadmium and lead are little sensitive. Gloss formation is controlled in the case of nickel coatings by an inhibited crystallization which, in turn, is controlled by amorphous adsorption layers; it is characteristic in this context that the texture of the base material disappears already at low coating thicknesses, while it can be observed in the case of mat coatings even at considerable coating thicknesses.     

Developing and studying the properties of Pb–TiO2 alloy coated lead composite anodes for zinc electrowinning

Abstract

A new anodic material for zinc electrowinning from sulphate electrolytes has been developed. This is a lead–titanium alloy coated lead composite electrode containing titanium nanoparticles. The titanium is present in the lead matrix as n-type TiO₂. It has been established that the optimal content of the Ti in the composite coatings is about 0·5 wt-%. The behaviour of the lead–titanium anodes during the zinc electrowinning has been studied by means of galvanostatic polarisation investigations. The depolarising of the anodic reaction at lead–titanium composite electrodes is attributed to the increased anode area during continued polarisation. The processes occurring on the lead–titanium anodes during zinc electrowinning have been studied by cyclic voltammetry. The surface morphology of the composite lead–titanium electrodes was investigated by scanning electron microscopy.     

Long-term atmospheric corrosion of zinc

A great deal of information is available on the short- and mid-term atmospheric corrosion of zinc: corrosion rate data as a function of atmosphere type, corrosion mechanisms, effect of environmental variables, effect of surface orientation, damage functions, etc. However, very little information has been published on the atmospheric corrosion of zinc over long time periods (10-20 years), despite its great usefulness. On the other hand, many studies have analyzed the nature of corrosion products formed on zinc in a wide range of atmospheric environments, using different experimental techniques, but few have focused on the morphology of corrosion product layers. This paper reports the characteristics—mainly composition and morphology—of corrosion products formed on zinc panels after long-term exposure (13-16 years) in various types of atmospheres in Spain: rural, urban, industrial, mild marine and severe marine.     

Process of electroless deposition of zinc and lead on aluminum in electrolyte melt by contact exchange method

The mechanism of electroless deposition of lead and zinc and their codeposition on an aluminum substrate in a chloride electrolyte melt at temperatures below the melting point of aluminum has been studied. It is shown that lead forms a dense thick (up to 60 μm) porousless layer on aluminum during the contact exchange, whereas zinc coatings are not more than 30 μm thick and have a number of pores a few nm to 1 μm in diameter penetrating to the aluminum substrate. When lead and zinc are deposited simultaneously, the whole aluminum surface is covered with a two-phase coating lead precipitates as round spots with zinc between them; areas with deposited lead are free of zinc and vice versa.     

Low-temperature sintering process for UO2 pellets in partially-oxidative atmosphere

Low-temperature sintering（LTS） experiments of UO2 pellets and their results were reported. Moreover, a routine process of LTS for UO2 pellets was primarily established. Being sintered at 1 400 ℃ for 3 h in a partially-oxidative atmosphere, the relative density of the pellet can be up to around 94%. Pellets with such a high density are of benefit for following-up reduction-sintering processes. Orthogonal test indicates that the importance of factors affecting the density decreases in the sequence of partial-oxidative sintering temperature and time, reduction-sintering time and temperature, and sintering atmosphere. It is found that it is helpful to introducing a small amount of water vapor into the sintering atmosphere during the latter stage. It is believed that it is the key factor to raise the O/U ratio of original powder in order to improve the properties of the low-temperature sintered pellets.     

Corrosion mechanism of hot-dip galvanised reinforcement bar in cracked concrete

In this paper, probable corrosion mechanisms of hot-dip galvanised reinforcement bar in cracked concrete based on long-term durability tests and other studies are determined. The fist mechanism consists of a local dissolution of eta (η) and zeta (ζ) phase. In the second mechanism due to non-uniform zinc coating local dissolution of eta (η) and zeta (ζ) phase together with longitudinal and perpendicular cracking in zinc layer may lead to separation of zinc layer. In the third mechanism due to non-uniform zinc coating full dissolution of eta (η) and partial dissolution of zeta (ζ) phase together with longitudinal and perpendicular cracking in ferrite may lead to separation of zinc layer and ferrite. Corrosion rate with used cement type was decreasing. That is not dependent on concrete quality. However, concrete type has an effect on corrosion rate and moisture conditions.     

图像识别技术研究有色金属大气腐蚀早期行为

提出了基于图像识别技术研究有色金属大气腐蚀早期行为的方法，用扫描仪获取试样的大气腐蚀形貌图像，采用连续小波变换对图像进行分解并提取能量值作为特征信息，研究了图像特征值和试样腐蚀失重数据之间的相关性，运用该方法分析了北京郊区纯锌的大气腐蚀试样，结果表明，该方法可以对纯锌的大气腐蚀早期行为进行判断和预测。     

Corrosion testing of phosphatized steel samples

A method for corrosion testing of phosphatized steel samples has been described. The specimens, treated with different phosphatizing, solutions and covered by a chemically inert paint film, have been exposed in a sulphur-dioxide-polluted atmosphere with 90% relative humidity at 22.0°C. The corrosion rate has been measured as an increase in weight. The corrosion resistance shows a good correlation with the crystal coverage of the zinc phosphate layers. Filiform corrosion can be inhibited by zinc phosphate as well as iron phosphate coatings. However, underfilm corrosion is more frequent on the iron phosphatized samples.