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Computer modeling of high-pressure leaching process of nickel laterite by design of experiments and neural networks

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International Journal of Minerals,Metallurgy and Materials 2012年第7期19卷 584-594页

作者： Milovan Milivojevic Srecko Stopic bernd friedrich Boban Stojanovic Dragoljub Drndarevic Technical and Business College IME Process Metallurgy and Metal Recycling RWTH Aachen University Department of Mathematics and Informatics Faculty of Science University of Kragujevac

Due to the complex chemical composition of nickel ores, the requests for the decrease of production costs, and the increase of nickel extraction in the existing depletion of high-grade sulfide ores around the world, computer modeling of nickel ore leaching process be- came a need and a challenge. In this paper, the design of experiments （DOE） theory was used to determine the optimal experimental design plan matrix based on the D optimality criterion. In the high-pressure sulfuric acid leaching （HPSAL） process for nickel laterite in ＂Rudjinci＂ ore in Serbia, the temperature, the sulfuric acid to ore ratio, the stirring speed, and the leaching time as the predictor variables, and the degree of nickel extraction as the response have been considered. To model the process, the multiple linear regression （MLR） and response surface method （RSM）, together with the two-level and four-factor full factorial central composite design （CCD） plan, were used. The proposed re- gression models have not been proven adequate. Therefore, the artificial neural network （ANN） approach with the same experimental plan was used in order to reduce operational costs, give a better modeling accuracy, and provide a more successful process optimization. The model is based on the multi-layer neural networks with the back-propagation （BP） learning algorithm and the bipolar sigmoid activation function.

关键词： nickel laterite leaching computer simulation design of experiments (DOE) response surface method (RSM) neural networks

Production of High Purity Metals: A Review on Zone Refining Process

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Journal of Crystallization Process and Technology 2018年第1期8卷 33-55页

作者： Xiaoxin Zhang Semiramis friedrich bernd friedrich IME Process Metallurgy and Metal Recycling RWTH Aachen University Aachen Germany

Purification is a primary application of zone melting, in which the improvement of efficiency, production yield and minimum achievable impurity level are always the research focus due to the increasing demand for high purity metals. This paper has systematically outlined the whole development of related research on zone refining of metals including basic theories, variants of zone refining, parametric optimization, numerical models, and high purity analytical methods. The collection of this information could be of good value to improve the refining efficiency and the production of high purity metals by zone refining.

关键词： Zone Refining Zone Melting High Purity Distribution Coefficient Aluminium Germanium Ultra-Pure Metal

Reducing Greenhouse Gas Emission from the Neodymium Oxide Electrolysis. Part II: Basics of a Process Control Avoiding PFC Emission

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International Journal of Nonferrous Metallurgy 2017年第3期6卷 27-46页

作者： Hanno Vogel bernd friedrich RWTH Aachen University IME Institute of Process Metallurgy and Metal Recycling Intzestra&#223 e 3 Aachen Germany

The neodymium electrolysis produces unnecessary high emission of CF4 and C2F6. These perfluorocarbons (PFCs) are potent greenhouse gases and are not filtered or destroyed in the off-gas. A process control in analogy to the aluminum electrolysis can reduce the PFC emission to a great extend and keep the process in a green process window. Therefore, a theoretical analysis is done of the cell voltage of the industrial neodymium electrolysis in dependence on the neodymium oxide concentration in the electrolyte. The analysis shows the different contributions to the cell voltage focusing on the impact of the anodic overvoltage on the cell voltage, by which the electrolysis process can be controlled. The model of the cell voltage is evaluated by laboratory neodymium electrolysis with a similar setup as the industrial cell. The relation of the oxide concentration, the anodic current density and the cell voltage with the cell resistance are measured. The continuous off-gas measurements show the gas concentration and PFC emissions. The effect of Nd2O3 feeding on the galvanostatic electrolysis is analyzed as well. Based on the results a process control strategy is proposed similar to the aluminum electrolysis strategy. The green process window is in a narrow oxide concentration range, making a continuous and precise oxide feeding essential.

关键词： Rare Earth Neodymium Electrolysis Greenhouse Gas Emission Process Control

Effect of Process Parameter Variation on Purity during Rotary Fractional Crystallization of Aluminum

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Open Journal of Metal 2017年第2期7卷 25-38页

作者： Semiramis friedrich Danilo Coladetti Curtolo bernd friedrich IME Process Metallurgy and Metal Recycling RWTH Aachen University Aachen Germany

High pure and ultrapure Aluminum is increasingly used in highly corrosion resistant applications or to replace copper in conductive parts such as high voltage cable and transformers due to their higher electrical conductivity properties. Ultrapure Aluminum is also used in semiconductors industry. Hence, the market demands innovative refining technologies, which consume less energy, take less time and lead to higher resource efficiencies. The most common methodology to produce ultrapure Aluminum is zone refining, based on the principle of fractional crystallization. Zone refining is however a very time-consuming process. In order to achieve a purity of 6N, several passes along the crucible with each full day treatment must be carried out. Also this method cannot be conducted continuously. This paper presents first time a new and eco-efficient method, which offers high potential to meet the mentioned multi-dimensional demands. Firstly, distribution coefficients of main impurities in Aluminum—a deciding factor to forecast and assess the removal behavior of impurities-were studied theoretically as a function of temperature using thermo-chemical calculation in FactSageTM. Secondly, the innovative method using a rotating and gas cooled crystallizer (“cooled finger”) was developed to validate the principle. The influencing process parameters such as temperature gradient, cooling gas flow rate, etc. were experimentally investigated and the theoretical results could be verified.

关键词： Fractional Crystallization Aluminum High Purity Distribution Coefficient Temperature Gradient Cooled Finger FactSage Burton-Prim-Slichter Model

High Purity Germanium, a Review on Principle Theories and Technical Production Methodologies

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Journal of Crystallization Process and Technology 2017年第4期7卷 65-84页

作者： Danilo C. Curtolo Semiramis friedrich bernd friedrich IME Institute of Process Metallurgy and Metal Recycling RWTH Aachen University Aachen Germany

Since the early 1950’s the use of Germanium has been continuously growing as new applications are being developed. Its first commercial usage as the main material, from which the semiconductors were made, was later replaced by Silicon. The applications were then shifted to a key component in fiber optics, infrared night vision devices and space solar cells, as well as a polymerization catalyst for polyethylene terephthalate (PET). With the advance development in new technologies, the attentions have been brought back to Germanium due to its excellent semiconductor properties. New applications on the field of high efficiency solar cells, SiGe based chips, LED technologies, etc., are being developed and show a great potential. According to DERA (Deutsche Rohstoffagentur/German Mineral Resources Agency), the demand for Ge will grow considerably by 2030, pushed mostly by the increase in the fiber optics market and advanced materials sector [1]. Therefore, this paper focuses on an overview of the production chain of Germanium, especially from its concentrate up to the single crystal growth of its valuable ultra-pure metallic form to be used in high technological applications.

关键词： Germanium Fractional Crystallization Crystallization Refining High Purity Zone Melting Czochralski

A Review on Prerequisites of a Set-Up for Particle Detection by Ultrasonic Waves in Aluminium Melts

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Open Journal of Metal 2016年第1期6卷 13-24页

作者： Mertol Gökelma Damien Latacz bernd friedrich IME Process Metallurgy and Metal Recycling RWTH Aachen University Aachen Germany

In many applications in aluminium industry, the number of inclusion-critical products increases and the quality of those products depend on the inclusion concentration and size. In order to improve the quality of aluminium products and the effectiveness of the processes, a reliable and cheaper on-line detection method is needed. Ultrasonic detection has been used in steel industry, but relatively rare in aluminium industry, although it would theoretically allow for an online non-intrusive detection of the cleanliness of the melt. In this work, the current information on ultrasonic inclusion detection was gathered and recommendations were provided on the Prerequisites for a set-up for ultrasonic detection of non-metallic inclusions in aluminium as a contribution on previous works. It has been concluded that ultrasonic waves seem promising, and should be experimented more on an industrial level to have a clear view on the potentials of the method.

关键词： Non-Metallic Particles Ultrasonic Waves Aluminium Online Detection

A Review on Alternative Gold Recovery Re-agents to Cyanide

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Journal of Materials Science and Chemical Engineering 2016年第8期4卷 8-17页

作者： Mertol Gökelma Alexander Birich Srecko Stopic bernd friedrich IME Process Metallurgy and Metal Recycling RWTH Aachen University Aachen Germany

The importance of gold recovery from low grade ores and flotation tailings is continuously increasing due to raising gold demand and thereby high gold prices. However, due to raising social awareness of the ecological impacts of cyanidic gold extraction and environ-mental specifications, the development and the implementation of alternative hydrometallurgical extraction processes have been a focus for many research institutions in last decades. Present work gives a comparison between compatible extraction reagents, with focus on less harmful processes. The target of this review is to point out the best cyanide-free processes of following methods and reagents: Bioleaching, Chlorination, Aqua Regia, Bromine, Thiocyanate, Thiosulfate and Thiourea leaching. For this propose, the gold leaching reagents are described and discussed in terms of their environmental and economical points of view. As result of this comparison, thiourea stands out as the most promising alternative gold leaching reagent to cyanide.

关键词： Hydrometallurgy Leaching Cyanide Alternative Reagents Recovery

Influence of Oxygen Addition on Structure and Properties of Titanium Produced by Electroslag Remelting

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Materials Sciences and Applications 2016年第3期7卷 139-149页

作者： Olga Snizhko Anatoliy Ryabtsev Alexandr Troyanskyy Vladimir Pashinskii bernd friedrich Johannes Morscheiser Marek Bartosinski Department of Electrometallurgy Donetsk National Technical University Donetsk Ukraine IME Process Metallurgy and Metal Recycling RWTH Aachen University Aachen Germany

The current work is devoted to the investigation of oxygen impact on the structure and properties of titanium. For this purpose, oxygen was introduced into titanium during chamber electro-slag remelting by three different methods: alloying by oxygen-rich residues from the Kroll process to final values between 0.053 wt.-% and 0.40 wt.-%, by reaction with the gas phase to 0.27 wt.-% and by introduction of TiO2 nanoparticles to 0.73 wt.-%. The influence of oxygen on microstructure of titanium during crystallization, heat treatment and deformation is determined as well as the effect of oxygen on the hardness and the mechanical properties of the material in different structural states. Furthermore, control methods of the structure formation process by thermal effects are proposed. Results show that the chamber electroslag remelting allows obtaining a homogeneous structure of the ingot in the investigated range of oxygen content in titanium. The hardness does not vary by more than 10 percent in longitudinal or radial direction in any of the remelted ingots.

关键词： Titanium Oxygen Electroslag Remelting Alloying Heat-Treatment Shear Transformation Recrystallization Deformation Work-Hardening Structure Refinement

Nanoscale Particles Enhanced Gold Plating

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Nanoscale Particles Enhanced Gold Plating