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By I. Dymov

"The extractive metallurgy of precious metal ores involves gravity concentration, flotation and cyanide leaching. Pre-oxidation, such as roasting, autoclaving, bacterial oxidation and other techniques, is required for processing refractory ores. Selection of the process is mainly driven by the grade, reserve and mineralogy of the target elements. The concentrations of precious metals in the crust are extremely low and highly variable, resulting in ore variability in many gold, silver and PGE deposits. More importantly, precious metals in an ore may occur in two or three forms (i.e. microscopic, submicroscopic and surface-bound), making ore processing of precious metals extremely challenging. The objective of geometallurgy and process mineralogy is to reduce and minimize the technical risk in project evaluation, process selection, mine planning and production forecasting through geometallurgical modelling, representative sampling and subsequent systematic mineralogical characterization and metallurgical testwork. Geometallurgy is a technique to document variability within an orebody and quantify and evaluate the impact of many factors including geology and mineralogy on grinding, flotation, leaching and metal recovery processes, while mineralogy is one of the major predictive and trouble-shooting tools for many new mineral projects and operating mines. This paper presents an overview of fundamentals, methodologies and techniques applied in geometallurgy and process mineralogy and highlights the importance of both disciplines in process selection and plant optimization with applicable case studies. INTRODUCTION Precious metals, including gold, silver and platinum group elements (PGE) occur in various geological settings and ore types. The concentrations of these metals in the crust are extremely low and highly variable, resulting in ore variability in many gold, silver and PGE deposits. More importantly, precious metals in an ore may occur in two or three forms (i.e. microscopic, submicroscopic and surface-bound), making ore processing of precious metals extremely challenging. Process selection is most important in any precious metals project and is mainly driven by the grade, reserve and mineralogy of the target elements. Free-milling ores, such as Kupol in Russia, Hemlo in Canada, Grasburg in Indonesia, UG-2 in South Africa, Lac des Iles in Canada, and Noril’sk in Russia, can be processed using flotation or cyanidation with or without gravity. B2Gold Corp, a Canadian gold company, just started a number of new and under construction free-milling gold operations such as Fekola mill in Mali, Mastbati mine in Philippins and Otjikoto mine in Nambia. However, refractory ores (particularly gold ores), such as the Carlin and Goldstrike mines in the USA, Giant in Canada, Pueblo Viejo in Dominican Republic, Porgera and Lihire in PNG, Kittilla in Finland, Fairview in South Africa and Shuiyindong in China, must be processed using pre-oxidation prior to cyanide leaching. In some mildly refractory gold ores, such as Kumtor mine in Kyrgyzstan and KCGM in Australia, ultrafine grinding is required to liberate fine-grained gold particles. For some gold ores containing both free-milling and refractory components (such as Cripple Creek mine in Colorado, USA), two or more recovery processes may be required. The variability of grade, metal deportment, ore hardness and other parameters is one of the risks that encountered in development and operation of many precious metals projects. To minimize and reduce the technical risk caused by ore variability, geometallurgy and process mineralogy have been used by mining companies in the last two decades to measure and quantify the spatial variability of the deposits that are being developed. This paper presents an overview of fundamentals, methodologies and techniques applied in geometallurgy and process mineralogy, it highlights the importance of both disciplines in process selection and plant optimizat"

Jan 1, 2018

By S. J. Neethling

"Liberation is a key driver in all mineral separation processes as it limits the maximum possible grade for a given recovery. In flotation, this is further complicated by the fact that it is surface exposure of the floatable minerals that determines the ultimate performance. Liberation, grade and surface exposure are commonly quantified using Scanning Electron Microscopy coupled to Energy Dispersive X-ray spectroscopy (SEM/EDX) analysis of polished sections. The intrinsically 2D nature of this technique can result in significant sampling errors and stereological effects that can affect the quantification of the ore’s textural characteristics. X-ray micro-Tomography (XMT) is an imaging method that can non-invasively and non-destructively delineate ore fragments in 3D, thus providing an alternative method that eliminates the need for stereological corrections and readily provides surface exposure. A methodology and automated algorithm were designed for extracting this information from images of closely packed particles, thus allowing samples containing a large number of particles to be assessed.The main drawback of XMT is that, unlike SEM/EDX, it cannot directly measure the mineralogy of the sample, instead producing a 3D X-ray attenuation map. We therefore also present an algorithm for calibrating the thresholding of the XMT images based on SEM/EDX images of sections through the same sample, thus allowing the liberation analysis to be carried out on a 3D mineral map in which the uncertainty in the mineral assignment is small and statistically quantified.The methodology was tested on low grade porphyry copper ore as this is both an industrially relevant and traditionally difficult system to quantify using XMT due to the similarity in the X-ray attenuation of the sulphide species, especially the pyrite and chalcopyrite. As each 3D volume imaged contain 100-1000s of grains, large data sets can be readily produced. By dividing these particles into classes based on both their surface exposure and grade, the extent to which there is preferential breakage of the particles can be assessed—an important consideration if sufficient surface liberation for good flotation performance is to be achieved at coarser particle sizes. It is also shown that erroneous conclusions can be drawn when basing the analysis on 2D sections through the particles."

Jan 1, 2018

By A. Oleynik

The paper presents the modeling and simulation experience in field of research into the mineral row material separation. Features of the subject domain generate a need of different approaches using for modeling and simulation. The general scheme of separation modeling process and some examples of developed simulators are presented. Due to different features and standards of knowledge, different formal models should be used to describe and analyze separation processes in the frame of general scheme. The main types of simulators are modeling tools based on statistical, analytical or expert (logical) methods. Advantages and disadvantages of each method above are mentioned in the paper. Based on the studies in the field considered, an aggregated mathematical model of a separation process has been generated. The aggregated model is presented by two combined equations. The actual apparatus model is formed by substitution of the particular functional expressions of the forces acting in the apparatus into the aggregated model. The developed simulation tools are based on integration of limited experimental data and on ex-pert knowledge available on separation processes. Simulation does not allow producing an optimal, in terms of mathematics, solution. But it gives an opportunity to produce and compare quite adequate solution variants in real time. The results obtained are the theoretical and methodological base for integrated information technologies to support studies in the field of mineral processing.

Jan 1, 2014

By V. K. Kuppusamy, M. Holuszko

"Lamps and lighting products are the most commonly used electrical products around the globe. With the improvement in lamp technologies, lighting products have grown complex and hence require an improved recycling process. The LED lamps consist of various valuable metals such as iron, copper, aluminum, chromium, silver, and gold, as well as non-metals such as glass, plastics, and fibers. In addition, there are also traces of hazardous substances such as lead, arsenic, and mercury. A major step in the recovery process is size reduction, and researchers have suggested that up to 40% of the total valuable material is lost during the shredding and grinding processes. SELFRAG is a high voltage selective fragmentation comminution technology that uses high voltage pulses in a water medium to efficiently separate the metals at a coarser size without generating many fine particles. It has been proposed that during the fragmentation process of electronic waste (e-waste), the metals can be separated without fine grinding. This research considers the applicability of high voltage pulse fragmentation for LED lamps. Eight different types of LED lamps were processed through the SELFRAG unit at varying pulses to study metal liberation. The product obtained was characterized for metal liberation, metal grades, and liberation analysis. The specific energy consumption for this size reduction process was also monitored. INTRODUCTION Lamps and bulbs are the most commonly used electrical products in homes, offices, industrial operations, and streets. According to Energy Star research (2006), an average US household has more than 40 sockets for light bulbs and consumes approximately 2100kWh every year for lighting. The development in lamp technology has pushed the boundary for newer products. The LED lamps have been taking over the market from the incandescent bulbs and compact fluorescent lamps (CFL). According to the US Department of Energy (2012) and myLEDlight.com (2007), LED lamps have several benefits over other lamps. LEDs produce light hemi-spherically, which increases their efficiency in directional light emission. It has higher breakage resistance from vibration or transportation. LED lamps use up to 90% less power than incandescent bulbs thus making them highly energy efficient; They have a longer lifespan, lasting 10 times longer than a CFL and 133 times longer than the traditional incandescent bulb. Because of all the benefits, Smallwood (2014) suggested that the market of LED lamps will grow to $12.2 billion by 2018."

Jan 1, 2018

Anglo American Platinum practices fine grinding in its processing plants to enhance the liberation of valuable minerals. If the fine particles of valuable minerals generated during fine grinding are not recovered during the flotation process, this could significantly contribute to the overall losses. This study examines the flotability of fine moncheite (PGE mineral) particles in a controlled environment (moncheite size distribution, concentration and liberation). A barren Norite ore ground to 40% and 80% passing 53µm was spiked, with four different size fractions of moncheite (-5, -10+5, -25+10 and -53+25µm) in order to evaluate the effect of particle size on flotation. The investigation also included the effect of energy input and collector dosage on the flotation of two moncheite size fractions, namely -5µm and -10+5µm. The results showed that the moncheite particle size has a significant impact on flotation. Coarse particles (-53+25µm) showed the highest Pt flotation kinetics and overall recoveries. The -5µm size fraction of moncheite could also be recovered by flotation, however, at a lower rate compared to the other size classes investigated. The increased collector dosage of 300g/t at the finer Norite grind of 80% passing 53µm enhanced the flotation rate of the -5µm size fraction of moncheite when compared to the lower collector dosage of 150g/t. The higher energy input during laboratory flotation, at an impeller speed of 1000rpm also increased the flotation rate of the -5µm size range, however, at a lower concentrate grade, when compared to the lower impeller speed of 700rpm. More favourable Pt flotation kinetics data was obtained for the -53 +25µm size fraction of moncheite at the fine Norite grind when compared to the coarse Norite grind. Keywords: flotation, moncheite, particle size, energy input and SIBX

Sep 1, 2012

Three high-grade limestone ores (CaO content over than 53 %) with different geological origin have been characterized for the synthesis of aragonite precipitated calcium carbonate. Limestone ores examined in this study showed different crystal particle size that cause difference in disintegration degree and surface area of the synthesized slaked limes. The limestone ore with smaller crystal particle size showed higher disintegration degree and also yielded slaked lime with smaller surface area, which is good for the synthesis of aragonite precipitated calcium carbonate. The synthesis of aragonite PCC using the limestone with a small crystal particle size was yielded needle-shaped aragonite with the aspect ratio of about 14. Keywords: limestone, lime, slaked lime, precipitated calcium carbonate, aragonite, accelerated carbonation

Sep 1, 2012

By T. C. Alex

Mechanical activation of gibbsite [?-Al(OH)3] is the theme of this paper. Industrially prepared gibbsite used in the study has a mono modal size distribution with a median size, d50=110 µm. Mechanical activation of this gibbsite has been carried out in a planetary mill at ambient conditions. Mechanical activated gibbsite samples are characterised in terms of particulate characteristics, structural characteristics and reactivity. As a result, of milling, mono modal size distribution of the unmilled gibbsite changes to a broad multimodal distribution. Size reduction has been sharp in the initial stages of milling; median size reduces to ~7 µm during 15 min of milling. Thereafter no decrease in median size is observed; rather it is found to increase gradually with further increase in milling time, indicating particle aggregation. Morphological studies of milled gibbsite have shown that the platelets forming the agglomerate are separated first; the separated platelets then undergo breakage. Aggregation of particles sets in the later stages of milling as a result of increased surface area and surface energy. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies have clearly revealed the changes in gibbsite structure during milling. Analyses of XRD data show that the crystallite size of gibbsite decreases as the milling time progresses whereas its microstrain is found to increase. Accumulation of energy in the structure is the result in both cases. TEM micrographs with signs of defects leading to disordering of gibbsite structure complement the XRD results. Reactivity of milled gibbsite, decrease in its deydroxylation temperature and increase in alkali dissolution, is found to increase with mechanical activation. Increased reactivity of milled gibbsite is found to have a strong correlation with the BET specific surface area. Keywords: mechanical activation, gibbsite, alkali dissolution, thermal dehydroxylation, reactivity

Sep 1, 2012

By T. Lang

Clay sorbents from the North Bohemian Brown Coal Basin represent important but still some-what neglected accessory raw material. Submitted paper is concerned with relation between mineral structure, sorptive efficiency and reclamation exploitation of these rocks. Characters and localities of main clay sorbents from the North Bohemian Brown Coal Basin are shortly evaluated in an introduction. In next part, methodology of mineralogy survey for these accessory raw materials is stated, it is based on diffract analyse with D 5000 Siemens X-ray diffracto-meter. At the conclusion results are stated of mineralogy analyses from several clay sorbents. The determination of the zeolite and montmorillonite localities was accentuated. The paper presents also possibilities of practical clay sorbents utilization, especially by reclamation works.

Jan 1, 2014

By G. C. He

Effects of irregularity, rough surface and aggregation of fine particles on ultrasonic attenuation are significant. The effects should be considered while predicting particle size by ultrasonic attenuation technology. The scanning electron microscope micrographs analysis also shows that particles surface is rough and irregularity. Any slurries has its fractal structure and its special fractal scale and dimension, so, effects of irregularity, rough surface and aggregation of fine particles can be de-scribed by fractal model. The discrepancies between predictions of ultrasonic attenuation based on the assumption of smooth spherical particles and data obtained from slurries of irregular particles indicated that there were different fractal structures. The ultrasonic attenuation model was modified by fractal dimensions. The result of experimental data and analogue calculation indicated that pre-dictions of the fractal modification of ultrasonic attenuation model show good agreement with experimental data. On the other hand, from the values of fractal obtained by inversely calculation, the degree of effects of irregularity, rough surface and aggregation of particles can be estimated. The positive value of fractal dimension indicates that the aggregation has the dominant effect on ultra-sonic attenuation, otherwise, the irregularity and rough surface has the dominant effect.

Jan 1, 2014

By Liang Dianyin

In this paper, the molybdenite flotation tailing of cleaner-scavenger bank which has a mass of very fine particles has been taken as raw ore to be processed by flotation with/without ultrasonic. The effect of ultrasonic frequency, intensity, processing time and uploading location on molybdenite flotation efficiency is investigated by four-factor three-level orthogonal experiment, and the effect significances of these ultrasonic variables to molybdenite flotation efficiency have also been evaluated. Single-factor analysis of variance is conducted to investigate whether the effect of ultrasonic on molybdenum ore flotation efficiency is significant or not. The samples extracted from different ore species in different time have been mixed to analyze the particle size. The results show that the particle size of +38µm in concentrate obviously increases while the particle size of -25µmobviouslydecreaseswith ultrasonic, which means that ultrasonic is good for flotation due to sludge removing effect. Keywords: ultrasonic, flotation efficiency, sulfide ore, tailing, grade, sludge removing

Sep 1, 2012

By P. Condori

In spite of the importance of the slurry transport and discharge in autogenous and semiautogen-ous (AG/SAG) mills, it is evident that a more comprehensive and useful model is still required. Semi-empirical models used up to now have many limitations and cannot be used beyond the ranges in which they were developed. The breakage of particles as they are transported along a mill com-plicates the experimental analysis and the modelling of the transport process within the mill. The interaction of the grate discharge and the pulp lifters, with the added issue of backflow from the pulp chamber into the mill, makes the discharge modelling process difficult. In order to overcome these difficulties, a mechanistic approach has been applied. The general transport and discharge model was subdivided into four independent models: Flow through the charge, flow through the grate, flow in the pulp lifter, and flow-back. This paper gives an overall description of the modelling approach and discusses in particular the modelling of transport of fluids through the charge. In order to evaluate and calibrate the model, experimental work was carried out. To evaluate the gradient pressure under different conditions of charge packing and flow rate, a specialised experimental rig with a highly sensitive pressure gauge was used. Preliminary results identify the differences of the charge and grate on the restriction of flow. The existence of a dynamic voidage in our particular system was more evident and as a result, a semi-empirical correlation for the voidage was developed. In general, results show that the me-chanistic model derived from Ergun?s equation for flow through a packed bed can be satisfactorily adapted.

Jan 1, 2014

By H. Deng

Oxidized zinc ores are the main source of zinc metal except sulfides. To have a better understanding about the performance of smithsonite and the main gangue, quartz, in flotation, the aggregation behaviors of smithsonite and quartz in water were confirmed by different techniques (sedimentation tests and optical microscopy). The experimental results show that smithsonite and quartz particles aggregate in the pH range 7.5-11. The results of zeta potential suggest that the aggregation does not correlate with the DLVO theory, when the iso-electric point of smithsonite and quartz is 8.0 and 2 respectively. When the solution pH is less than 8.0, smithsonite has an opposite charge to the quartz particles. Electrostatic adsorption makes effort on these two kinds of particles according to DLVO theory. Whereas, solution chemistry calculation shows the pH range 8-11 corresponds to hydroxide formation, suggesting that this is the species responsible for aggregation. And their concentrations are much higher in sodium hydroxide system than that in sodium carbonate system. Aggregation of smithsonite and quartz due to the flocculation action of zinc hydroxide is proposed.

Sep 1, 2012

By S. M. Mustakim

Red mud is the major waste material produced during digestion of bauxite ores with caustic soda in alumina production following the Bayer?s process. Its disposal remains a worldwide issue in terms of environmental concerns. A lot of research and developmental activities are going on throughout the world to find effective utilization of red mud, which involves various product developments. At present, building materials, industries are fast growing industrial sector where the need of various raw materials is enormous. The use of red mud in building material production is one of the options for conservation of natural resources and reduction of environmental pollution. A cost-effective and energy efficient mineral cementation process has been developed at CSIR-IMMT, Bhubaneswar for use of red mud in manufacture of building brick, block and aggregate. The red mud is an alkaline material, which contains both leachable and non-leachable soda along with different mineral constituents of alumina, iron and silica. The effort has been made to use the mineral constituents of red mud to develop cold setting building brick by mineral cementation process using a binder specially prepared from Portland Slag Cement, Lime, Gypsum and Alkali metal sulfates. The red mud has been used from 40 to 70% by weight along with fly ash and binder in development of cold setting building brick conforming to the specification of IS:12894:2002.

Sep 1, 2012

By L. Rintala

The design of a hydrometallurgical process starts with the analysis of the raw materials to be treated, for example mineralogy, chemistry, deposit size are analysed. Based on this information suitable unit processes for pre-treatment, leaching, solution purification and product recovery are selected. Typically, process design for the new ore deposit relies on laboratory tests such as pre-treatment and leaching experiments. The experimental work is the most time consuming and expensive part of the process design. Reducing the number of experiments would shorten the time of designing a new flowsheet or development of new process technology. A large amount of information is available about the hydrometallurgical experiments and the amount is increasing continuously. For example, word search using ?hydrometallurgy? from Scopus database results in over 4 000 publications with the word in title, abstract or keywords. This number consists of 2 500 articles, 900 conference papers, and 90 reviews since 1972. The number of hydrometallurgical publications per year has increased from 13 in 1972 to 150-200 in the last few years. The objective of this study was to analyze how detailed data of experiments about the gold extraction is published and how that data could be exploited more effectively when designing hydrometallurgical processing for new ore. The leading idea is that similar ores should have the similar response in leaching. If the published information was used more efficiently, the amount of experiments would be reduced. More than 200 cases of experimental data of gold leaching have been analyzed for this study. There are over 30 factors that could be used in comparison when selecting process alternatives, but challenging fact is that not all these factors are documented in all publications. Results show that the usefulness of the published data in the development of hydrometallurgical flow sheet for gold using decision-support tools is not that straightforward. The quality of the published information about gold extraction varied between the publications and the descriptions of the raw materials, experimental arrangements and results were often missing details. Methods to normalize the data for description of the cases and a system to describe different features unambiguously are needed. Keywords: refractory gold, host mineral, leaching, data analysis, case-based reasoning

Sep 1, 2012

By K. Saberyan

In this study, solvent extraction of zirconium by using triphenylphosphine oxide as extractant has been investigated. The results showed that extraction of zirconium by triphenylphosphine oxides in nitric acid and hydrochloric acid media were negligible. Extraction of zirconium in acetic acid media with concentration of 0.01~0.2 M has been studied and the results showed that the maximum percent of zirconium extraction was 40% in acid acetic with concentration of 0.01 M. By addition complexing agents such as potassium thiocyanate with the concentration of 0.01~0.2 M zirconium extraction increased up to 86% in 0.2 M potassium thiocyanate. By addition of sodium salicylate with concentration of 0.01 M and in pH=2.5, the maximum extraction of 96% was achieved. The striping of zirconium from organic phase can be carried out by 0.5 M solution of sulfuric acid.

Jan 1, 2014

Vanadium-titanium magnetite from Panzhihua was crushed with open and closed circuit process by high pressure grinding roller (HPGR). The particle size characteristics of the crushed product were analyzed and the micro-cracks generated by HPGR during the crushing process were studied. The results showed that, in crushed products, the reduction ratio increases and the size distribution becomes more uniform with increasing of the pressure on roller?s surfaces. The fine fraction content of crushing products from -3.2 mm classification closed-circuit by HPGR increases obviously compared with that by Jaw Crusher and particle size distribution is more uniform. Large amount of intra-crystalline cracks and cleavage cracks are generated in vanadium-titanium magnetite crushed by HPGR, which makes the specific surface area larger and Bond grinding work index (objective particle size is 0.074 mm) decreased by 14.05% than that by Jaw Crusher. And the liberation degree of monomer of the product crushed by HPGR increased compared with that by Jaw Crusher with the similar fineness of grinding. Keywords: iron ore, high pressure grinding roller, micro-crack

Sep 1, 2012

By B. S. Moroney

Elemental distribution varies widely in the ores, minerals and beneficiated products depending on the constituents. Accurate analysis of each element present in various beneficiated products is utmost required to assess the grade in view of zero waste technology. Hence, the suitable methods and instrumental technique is of prime importance as the distribution of various elements differs in the beneficiated products. Conventional classical technique of analysis is absolute and due to this, it has not become obsolete. Besides, it is much needed for making standards for various relative techniques. Instrumental techniques comprising of X-ray fluorescence, Induced Coupled Plasma Analyzer, Carbon-Sulphur Analyzer, Atomic Absorption Spectrometer etc. are important for quick and accurate analysis. However, the selection of these instruments depend on the nature of material to be analyzed. This paper highlights the importance and use of various methods/techniques and instruments involved in the analysis of various ores, minerals and beneficiated products. Keywords: wet classical, x-ray fluorescence, induced coupled plasma analyzer, atomic absorption spectrometer

Sep 1, 2012

By D. B. Mazzinghy, L. C. de R. Machado, H. Delboni, M. G. Bergerman

"The use of vertical stirred mills in the mining industry has increased remarkably over the past few decades, as a result of growing requirement for finer ore grinding. This equipment delivers higher energy efficiency in fine grinding operations when compared to conventional tubular mills. Methods for designing vertical stirred mills involve operational experience, pilot plants and bench tests. An important issue is that these tests require, at a laboratory scale, at least 10–20 kg of material, depending on its density, which is not available in many cases, particularly in the early stages of greenfield projects. For the regrind of flotation concentrates, several bench scale flotation cycles are required to generate such a sample. This paper describes the development of a laboratory jar mill test using a 6”x8” jar – smaller than that commonly used – based on the overall specific energy method, which requires significantly less mass compared with existing tests. The proposed test has proven to be more practical than tests normally used, requiring about a quarter of the mass, and also shows good adherence to industrial results for the studied iron ore processing plant. INTRODUCTION A significant demand for finer grinding has been noticed over the past few decades in several mining projects to achieve the mineral liberation required for the concentration of valuable minerals. However, the finer the product size, the greater the grinding energy consumption, resulting in an overall increase in operating costs, which may reach or even exceed 50% of the mineral processing cost (VIEIRA, PERES, 2013; DANIEL, LEWIS-GREY, 2011). Comminution technology can have a major impact on subsequent ore concentration stages (DANIEL, LEWIS-GREY, 2011; MARSDEN, 2009; NAPIER-MUNN, 2012; PEASE et al., 2010), which further strengthens the importance of proper technology and equipment selection. Adequate grinding circuit selection and design is thus a key aspect associated with mining projects."

Jan 1, 2018

By C. R. Mambote

Vanadium is an important metal that is used mainly in ferrous and non-ferrous alloys due to the high tensile strength, hardness, fatigue resistance and corrosion resistance. Vanadium consumption in the steel industry represents about 85% of the vanadium-bearing products produced worldwide. The primary sources of the metal are patronite, roscoelite, and mottramite. Vanadium has also been produced as a by-product of the uranium production program which uses carnotite ores as a source of uranium. Vanadiferous magnetite iron ores are used for producing vanadium as well. In addition, it is known that vanadium can be recovered from the ashes of crude oil and petroleum coke. The process for treating boiler residues, fly ash and petroleum coke is similar to the process used to treat spent catalysts and ores. However, some of these materials may contain high carbon that must be removed at specific stage of the operation. Several processes are available for obtaining vanadium from fly ash, such as roasting vanadium bearing materials in the presence of sodium salt. The salt roasted calcine is subsequently leached with an alkaline or acidic solution. To obtain a cal-cine from which the vanadium can subsequently be recovered, the carbon in the source materials has to be eliminated prior to the roasting process. Other processes use the conventional hydrometallurgical route, in which fly ash is leached with sulphuric acid to obtain an impure vanadium pentoxide. The impure vanadium pentoxide is then treated with a sodium carbonate solution under atmospheric conditions to subsequently precipitate vanadium as ammonium metavanadate. Actually, the salt roasting process is the only process used commercially. In the present study, the progress in the technology of vanadium extraction from secondary materials is reviewed. The perspectives and the challenges for new process development are discussed.

Jan 1, 2014

By Peter Ay, Florian Logsch, Satyanarayana Narra

"The traditional lignin separation process from the precipitated suspension creates severe filtration problems by plugging of the filter medium due to the small particle size (20 to 60 µm) of the suspended lignins. The plugging causes further problems in the successive processing of the filter cake. A new lignin separation process has been developed at the Brandenburg University of Technology (BTU) Cottbus as a part of the Research and Development and Demonstration (R & D & D) project "LignoBioFuel". The new developed process separates lignin in the form of granules with diameters ranging from 100 µm to 300 µm. The restrainment of the granule’s size in their successive treatments is expected to result in higher filtration efficiencies and reduction in plugging of filter mediums. To evaluate the filtration efficiency, the filtration resistance of the produced granules as well as the conventional suspensions has been investigated. The results show that there is a 60 to 80 % filtration efficiency increase and around 60 % reduction in plugging of filter mediums with the lignin granules in comparison to the conventional suspensions. Furthermore the successive processing of lignin granules was easier due to their porous structures removing the impurities such as adherent acids and salts. The purity of the separated lignin was measured with their sulphur (reduced from 7 % to 2.7 %) and ash (reduced from 46 % to 0.5 %) contents. The newly developed process has displayed better results in comparison to that of the conventional process. The new process displays high potentials in optimizing and improving the present state of the art treatments and is promising several ecological, economical and environmental improvements."

Jan 1, 2014