Parameters affecting reaction rate and conversion of TiO2 chlorination in a fluidized bed reactor: Experimental and modeling approach

Pilot scale chlorination of TiO₂ was carried out with CO as reducing agent. The experimental analysis and modeling of chlorination process of TiO₂ in the presence of CO and Cl₂ in a semi-continuous fluidized bed reactor were aimed. Chlorination process was continuously monitored by measuring the amount of produced TiCl₄ with time. The effects of different operating parameters including chlorination temperature, feedstock particle size and size distribution, amount of feedstock and Cl₂ and CO flow rates on the conversion were systematically investigated. A gradual increase in chlorination temperature led to monotonous increase of conversion rate. Conversion decreased with increased particle size of feedstock. An increase in loaded feedstock led to a decrease in reaction conversion. A model was proposed to predict conversion, particle size distribution and mole fraction of components in gas phase as reaction proceeds. A good agreement between conversions predicted by the model and experimental data under various operating conditions was observed.     

Failure Analysis of an Oxidative Chlorination Reactor Clad with AISI 304L Stainless Steel

Failure analysis of the hermetical AISI 304L stainless steel cladding in oxidative chlorination reactor shows that its pitting and stress corrosion arose due to the presence of chlorine ion in the working environment. In order to improve its corrosion resistance, AISI 316L stainless steel should be utilized.     

Effect of microstructure and defects on fatigue behaviour of directed energy deposited Ti–6Al–4V

Abstract

The fatigue behaviour of laser engineered net shaping (LENS) deposited Ti–6Al–4V is studied in the as built condition. The fatigue properties are measured, and the influence of microstructure and physical defects on fatigue performance is analysed through microscopy and fractography. Fine basketweave microstructure is obtained using a substrate with large equiaxed grains. The presence and location of unmelted particles are observed to significantly affect fatigue life. On the other hand, smaller gas porosity is not found to have major effect on the fatigue life. Further, the fatigue properties in a ‘repair’ condition are evaluated through samples consisting of LENS deposited parts joined to a preexisting wrought part. The properties are compared with the as built LENS parts.     

轴向柱塞泵疲劳损伤分析及寿命预测

轴向柱塞泵工作环境恶劣、工况复杂,柱塞在柱塞腔内做往复直线运动,承受着复杂的交变应力,疲劳损伤是其常见的失效形式之一。为了分析柱塞泵的疲劳损伤、预测其剩余寿命,提高其运行的安全可靠性,提出柱塞泵疲劳损伤分析及寿命预测方法。建立柱塞泵的刚-柔-液耦合模型,进行联合仿真并分析;基于Miner疲劳累计损伤理论,运用ANSYS Workbench软件及nCode模块,得到柱塞的疲劳损伤云图和疲劳寿命云图,对柱塞泵疲劳损伤的薄弱部位以及剩余寿命进行分析,最后探究了主轴转速、工作压力对柱塞泵疲劳损伤及剩余寿命的影响。结果显示：在典型工况下,柱塞的疲劳寿命约为7 448.8 h,基本可以满足柱塞疲劳寿命要求。     

Resistance spot welding of PA2 and D16 aluminium alloy sheets

Abstract

Technologies which make it possible to improve the working properties of surface layers of castings, while utilising traditional materials, are increasingly being used in industrial applications. The life of fabrications can be extended as necessary. It is also possible to manufacture fabricates with working properties that are normally unobtainable in the case of traditional construction materials and technology.     

Analysis of failed nuclear plant components

Argonne National Laboratory has conducted analyses of failed components from nuclear power- gener-ating stations since 1974. The considerations involved in working with and analyzing radioactive compo-nents are reviewed here, and the decontamination of these components is discussed. Analyses of four failed components from nuclear plants are then described to illustrate the kinds of failures seen in serv-ice. The failures discussed are (1) intergranular stress- corrosion cracking of core spray injection piping in a boiling water reactor, (2) failure of canopy seal welds in adapter tube assemblies in the control rod drive head of a pressurized water reactor, (3) thermal fatigue of a recirculation pump shaft in a boiling water reactor, and (4) failure of pump seal wear rings by nickel leaching in a boiling water reactor. Work supported by Commonwealth Edison Company under ACK 85026.     

Selection of oil quenchants for heat treating processes

Abstract

Modern quenching oils offer a wide range of capability and performance. The selection of the proper quench oil is critical for proper heat treating operations. Improper selection of quench oil can result in short oil life, or soft parts. This paper will illustrate the selection factors in choosing a quench oil to ensure proper quality parts.     

海绵钛副产品氯化镁高温气相氧化反应器内流场的模拟研究

本文研究基于利用“原位热解—热法还原炼镁”海绵钛清洁生产新工艺,即还原蒸馏产生的气态氯化镁直接氧化热解制备高纯氧化镁及氯气,氧化镁经热法炼镁返回TiCl₄还原环节、氯气返回沸腾氯化环节作为原料,实现海绵钛生产中新的镁、氯循环。,并针对“海绵钛生产中新的镁、氯循环”中的关键步骤—气态氯化镁与氧气的均相热解反应的反应器进行研究。采用数值模拟和物理模拟方法研究了反应器模型内的浓度场和速度场,在氮气与二氧化碳流量比为6：1时,二氧化碳采用环向四口进气方式,气体混合不均匀度为0.02,气体混合程度最佳。     

Co-extraction of valuable metals and kinetics analysis in chlorination process of low-grade nickel-copper sulfide ore

To efficiently co-extract Ni and Cu from low-grade nickel-copper sulfide ore, chlorination roasting with NH₄Cl followed by a water leaching process was investigated. The results show that 98.4% Ni and 98.5% Cu can be synchronously extracted when the ore particle size is 75-80 μm, the roasting time is 2 h, the mass ratio of NH₄Cl to ore is 1.6:1 and the roasting temperature is 550 °C. The evolution behavior of various minerals was elucidated using X-ray diffraction (XRD) coupled with scanning electron microscopy (SEM). The kinetics of the chlorination process based on the differential thermal and thermogravimetric analysis (DTA-TG) data was analyzed by Kissinger method and Flynn-Wall-Ozawa (FWO) method. The chlorination process of low-grade nickel-copper sulfide ore mainly contains two stages: the decomposition of NH₄Cl and the chlorination of ore. The maximum apparent activation energies (E_a) at two stages are determined to be 114.8 and 144.6 kJ/mol, respectively. The condensed product of exhaust gas is determined to be ammonium chloride, which can be recycled as the reactant again, making the process economic and clean.     

Influence of heat treatment on surface morphology,hardness, wear and corrosion resistance of industrial phosphate coatings

Abstract

New phosphate black coatings for the improvement of mechanical properties on metallic objects have been developed to extend life time of machinery. The performance of phosphate black coatings was evaluated by weight gain studies, micro hardness studies, abrasive wear resistance and corrosion resistant measurement by electrochemical methods. The surface morphology of the coatings was assessed by XRD, SEM and XPS. The absorption coefficient of the coatings was evaluated by UV-visible spectrometer. Salt spray analysis was carried out to follow up the corrosion and get an idea about the performance of black coatings in automobile parts. The mechanical properties were very much improved after heat treatment of coatings at 200°C.     

Progress in theory and practice of thermochemical treatment of steels

Abstract

Recent developments in the thermochemical treatment of steels at MADI, Moscow are presented. These technologies combine nitriding with other methods of surface modification, e.g. thermal diffusion and laser alloying, plasma treatment, galvanic and slurry metallisation, and oxidation. By regulating the parameters of each process, it is possible to control the structure of the surface at the micro- and nanoscales, to form coatings and/or surface layers on various carbon and alloyed steels with tailored properties (hardness, wear and corrosion resistance, etc.) for machine parts used in various working conditions.     

Thermodynamical analysis of Al and Si halide gaseous precursors in CVD. Review and approximation for deposition at moderate temperature in FBR-CVD process

In Chemical Vapour Deposition area, thermodynamic of precursors present in the reactor during process is a useful guide to design the experimental conditions of coating and can help to understand deposition mechanism. This paper, firstly, summarises studies from literature focussed on silicon and aluminium deposition obtain by conventional CVD, pack cementation and CVD-FBR process. Then, thermodynamic calculation was performed using Thermocalc-Software, to study the generation of Al- and Si-precursors at moderate temperature during CVD-FBR process in system Ar/H₂/HCl:Al_(s)/Si_(s). Effect of temperature, input gas and powder mixture on equilibrium precursor partial pressures was discussed as well as effect input condition on chlorination of HCM12 substrate. Coating of such ferritic-martensitic steels requires low temperature process to avoid microstructure change (T < 700 °C) that makes CVD-FBR technique particularly attractive. Deposition mechanisms proposed in the literature were then shortly discussed in regards to the additional calculations performed.     

Research study demonstrates computer simulation can predict warpage and assist in its elimination

Programs for predicting warpage in injection molded parts are relatively new. Commercial software for simulating the flow and cooling stages of injection molding have steadily gained acceptance; however, warpage software is not yet as readily accepted. This study focused on gaining an understanding of the predictive capabilities of the warpage software. The following aspects of this study were unique. (1) Quantitative results were found using a statistically designed set of experiments. (2) Comparisons between experimental and simulation results were made with parts produced in a well-instrumented and controlled injection molding machine. (3) The experimental parts were accurately measured on a coordinate measuring machine with a non-contact laser probe. (4) The effect of part geometry on warpage was investigated.     

High-temperature chlorination of gold with transformation of iron phase

Gold in cyanide tailings from Shandong Province is mainly encapsulated by hematite and magnetite at distribution rates of 76.49 % and 10.88 %, respectively.Chlorination–reduction one-step roasting of cyanide tailings was conducted under the following conditions: calcium chloride dosage of 6 %, bituminous coal dosage of30 %, calcium oxide dosage of 10 %(all dosages are vs.the mass of cyanide tailings) at 1000 °C of roasting temperature. X-ray diffraction(XRD), scanning electron microscopy(SEM), and chemical-phase analysis were performed to investigate the effects of iron phase transformation on the high-temperature chlorination of gold.Results indicate that the lattice structure of hematite undergoes expansion, pulverization, and reorganization when hematite is reduced to magnetite, which leads to42.03 % gold exposure, and the high-temperature chlorination rate of gold is 41.17 % at the same time. The structure of wustite formed by the reduction in magnetite is porous and loose, and thus 44.02 % of gold is exposed. The high-temperature chlorination rate of gold is increased by41.98 percentage points. When wustite is reduced to metallic iron, 4.42 % of gold is exposed, and the hightemperature chlorination rate of gold is increased by3.38 percentage points. Accordingly, the high-temperature chlorination of gold mainly occurs in two stages, in which Fe_2O_3 is reduced to Fe_3O_4, and Fe_3O_4 is reduced to Fe_xO finally.     

Wear resistance of ductile irons

This study was undertaken to evaluate the wear resistance of different grades of ductile iron as alterna-tives to high- tensile- strength alloyed and inoculated gray irons and bronzes for machine- tool and high-pressure hydraulic components. Special test methods were employed to simulate typical conditions of reciprocating sliding wear with and without abrasive- contaminated lubricant for machine and press guideways. Quantitative relationships were established among wear rate, microstructure and micro-hardness of structural constituents, and nodule size of ductile iron. The frictional wear resistance of duc-tile iron as a bearing material was tested with hardened steel shafts using standard test techniques under continuous rotating movement with lubricant. Lubricated sliding wear tests on specimens and compo-nents for hydraulic equipment and apparatus were carried out on a special rig with reciprocating motion, simulating the working conditions in a piston/cylinder unit in a pressure range from 5 to 32 MPa. Rig and field tests on machine- tool components and units and on hydraulic parts have confirmed the test data.     

Homogenisation of heat treatment process in high pressure gas quenching

Abstract

High pressure gas quenching has the advantages of pure convective heat transfer, high levels of control, avoidance of cleaning the quenched parts and low environmental impact. However, typical gas quenching facilities exhibit inhomogeneous flow conditions through the quench load and the parts, resulting in scatter in final properties. The upstream flow profile of the load has been identified as a key factor determining local flow conditions and heat transfer. The intensity of the quenching process is determined by the pressure drop that results from the flow resistance of the quench load, although a significant part of the flow passes between the load and the chamber walls and does not contribute to the quenching process. A simulation of the flow inside a commercial high pressure gas quenching chamber was carried out, using a multiscale model to give faster convergence. An experimental analysis of the flow inside a model quenching chamber through velocity measurements and flow visualisation was also performed. Finally, a quenching run with cylindrical parts in a double-chamber vacuum furnace was used to validate the model results. Various upstream velocity profiles were applied to demonstrate their influence on the quenching result. The multiscale simulation approach and the results of the flow process investigation are reported. Guidelines for gas quenching process optimisation are outlined.     

Stability of Y–Ti–O precipitates in friction stir welded nanostructured ferritic alloys

Abstract

Nanostructured ferritic alloys, which have complex microstructures consisting of ultrafine ferritic grains with a dispersion of stable oxide particles and nanoclusters, are promising materials for fuel cladding and structural applications in the next generation nuclear reactor. This study evaluates microstructure of friction stir welded nanostructured ferritic alloys using electron microscopy and atom probe tomography techniques. Atom probe tomography results revealed that nanoclusters are coarsened and inhomogeneously distributed in the stir zone and thermomechanically affected zone. Three hypotheses on coarsening of nanoclusters are presented. The hardness difference in different regions of friction stir weld has been explained.     

Thermodynamic analysis and process optimization of zinc and lead recovery from copper smelting slag with chlorination roasting

An efficient chlorination roasting process for recovering zinc (Zn) and lead (Pb) from copper smelting slag was proposed. Thermodynamic models were established, illustrating that Zn and Pb in copper smelting slag can be efficiently recycled during the chlorination roasting process. By decreasing the partial pressure of the gaseous products, chlorination was promoted. The Box−Behnken design was applied to assessing the interactive effects of the process variables and optimizing the chlorination roasting process. CaCl₂ dosage and roasting temperature and time were used as variables, and metal recovery efficiencies were used as responses. When the roasting temperature was 1172 °C with a CaCl₂ addition amount of 30 wt.% and a roasting time of 100 min, the predicted optimal recovery efficiencies of Zn and Pb were 87.85% and 99.26%, respectively, and the results were validated by experiments under the same conditions. The residual Zn- and Pb-containing phases in the roasting slags were ZnFe₂O₄, Zn₂SiO₄, and PbS.     

银带熔体片多品种冲孔模设计

介绍了熔体片冲孔模结构及主要零件的设计，设计了符合冲压工艺的多品种模具结构，分析了模具关键零件的设计和制造，并考虑了模具的镶拼结构及模具中使用反推杆结构，保证了细小凸模的刚度不受影响，提高了整副模具的使用寿命，同时设计了送进和取出熔体片的工位器具，获得了满意的使用效果。     

Technological developments for aluminum smeltinq as the industry enters the 21st century

The capital-intensive nature of aluminum smelting, with its low productivity per unit reactor and high electrical consumption rates, has motivated the search for alternative smelting processes to replace the aging Hall-Héroult technology. Optional routes include carbothermic reduction of alumina, chlorination followed by electrolysis of aluminum chloride, and electrolytic decomposition of alumina using inert electrodes. Still in need of some fundamental innovation, the alternative techniques are limited by unsatisfactory materials performance and reactor design constraints. There have been, however, significant advances in the process efficiencies and scale of both the Bayer process and the Hall-Héroult cells. As a result, the basic Hall-Héroult technology will continue as the dominant aluminum smelting process for at least the next 50 years.