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By E. S. Peterson, M. K. Harrup, K. A. Dolbeare, J. E. Wey

Efficient methods for the removal of copper from heap-leach solutions without mobile organic phases are a current mining industry need. To satisfy this need, a selective, high-capacity, durable solid material is required. The Idaho National Engineering and Environmental Laboratory (INEEL) developed a set of materials based on current solvent-extraction chelates that provide selective copper concentration in the presence of high concentrations of iron. In contrast to conventional solvent extractions, the author's strategy anchors the chelators to a nonpolymeric solid substrate through the use of a custom-designed linker molecule. The fundamental synthetic routes to these materials have already been established, and attachment to the solid surfaces have been achieved in an efficient manner. The author's continuing research is focused on the optimization of the synthetic pathways to these solid materials and the evaluation of their copper-capturing capabilities.

Jan 1, 2003

By S. L. Patil, D. E. Walsh

A novel form of calibration of on-line analyzers was implemented. Rather than simple equations, a neural network was used to model the relationship between the scintillation counts (Am and Cs) of an analyzer, and the measured ash for improved on-line analysis of run-of-mine (r.o.m.) coal. Also, a new approach was followed to better evaluate neural network performance. Samples were first divided into various statistically different groups using a Kohonen network. Data was then selected for the training, calibration and prediction subsets, using criteria developed in this paper for sparse data, with representation from each group. A backpropagation based neural network architecture was used in conjunction with quick stop training. Due to noise in the data, the predictions were very good on average, but not individually.

Jan 1, 2003

By G W. Wilson, P Ritchie, N A. Currey

The design and rehabilitation of potentially acid forming (PAF) waste rock dumps is site specific, being a function, among other factors, of the rock types, the dumping and storage method employed, and the climatic setting. The æstore and releaseÆ cover system developed to manage acid rock drainage (ARD) from mineralised waste rock dumps at Kidston Gold MinesÆ open pit operations in the semi-arid climate of North Queensland, Australia, has been monitored for seven years. The paper describes the philosophy behind the design of the PAF dump and æstore and releaseÆ cover system and the adaptation of the cover system over time to suit KidstonÆs conditions. The results of monitoring over the seven years since the first cover was constructed are presented, and the approach being taken at Kidston to ensure that the risk of impacts from any residual ARD is accommodated and to facilitate lease surrender are described. The Kidston story is a valuable case study of a successful approach to remediating an identified source of ARD in a semi-arid climate, which has actively engaged all Stakeholders.

Jan 1, 2003

This paper characterizes the copper cycle, that is, the flows of copper entering and leaving the African economy over a one-year period (1994). The major flows over the entire life-cycle of copper are examined; these include production (mining, milling and refining), fabrication of semi-products and manufacturing of finished products, use, and the waste management system. The results reveal that substantial amounts of copper (of order705 Gg/yr) are mined in Africa; of that amount, about 70 per cent is exported following processing, 18 per cent is utilized by African fabricators, and 12 per cent is discarded. The flows of copper products from African fabricators and product imports from other continents exceed product discards by large amounts. This difference, about 0.25 kg Cu/capita/yr on average, is added to in-use stock, largely as wire, plumbing tube, and in electronics. Some 65 per cent of the copper in discard flows is contained in electrical and electronic products, where it is relatively easy to collect and process for reuse. About a third of the copper discard flows known is recycled. The actual percentage is almost certainly higher because of informal (and unrecorded) recycling. Much of the remaining discarded copper is diluted into the municipal waste stream, where recovery and recycling are probably not economically justified. Keywords: material flow analysis, resource management, material budgets, copper, stocks and flows, systems analysis, Africa, developing country

Jan 1, 2003

By M. C. Bétournay

Strainbursts are common in overstressed brittle rock around deep mine openings. Such failures are characterized by a biaxial state of stress in the plane of the opening boundary. A zone of compressive stresses imposes initial failures near or at the surface of the opening that results in spalling of thin slabs of rock roughly parallel to the free face. While the failure of rock under biaxial loading conditions is increasingly common in deep underground mines, only a few representative laboratory studies have been reported in the literature, without emphasis on rockbursting aspects, and none in the last decade. This paper presents the results of a testing program on a granite rock type. Biaxial testing, conducted on 100 mm cubic samples, was carried out to examine the influence of lateral confinement and loading rate on the rock’s ultimate strength. The paper reports the test results in terms of normalized biaxial failure envelope s1/sc-s2/sc. A discussion of the failure mechanisms observed is presented. Les coups de toits de déformations sont choses communes dans le rock cassant surcontraint en place autour des ouvertures minières profondes. De telles ruptures sont caractérisées par un état de contraintes biaxiales dans le plan de la périphérie de l’ouverture. Une zone de contraintes compressives impose des ruptures initiales à ou près de la surface de l’ouverture, qui produit des relâchements de minces plaques de roc plus ou moins parallel à la surface. Bien que les ruptures de roc sous des conditions biaxiales sont de plus en plus communes dans les mines à grandes profondeurs, il n’y a eu que quelques études représentatives en laboratoire de publiées, sans emphase sur des aspects de coups de terrains, et aucunes publiées depuis la dernière décennie. L’article présente les résultats d’une campagne d’essais appliquée à un type de granit. La campagne d’essais biaxiaux, sur des échantillons cubiques de 100 mm, avait pour objectif d’examiner l’influence du confinement latéral et le taux de chargement sur la résistance ultime du roc. Cet article fait part des résultats en terme de l’enveloppe de rupture biaxiale normalisée s1/sc-s2/sc. Une discussion sur les mécanismes de ruptures observés est présentée. Dehnungsbrüche findet man häufig in übergespannten spröden Felsen um die Öffnung von tiefen Minen. Solche Brüche sind von einer zweiachsigen Spannung in der Ebene der Grenze der Öffnung charakterisiert. Eine Zone von Druckspannungen verursacht initiale Brüche, entweder an der Öberflache der Öffnung oder in der Nähe. Davon scheiden sich dünne Felsplatten mehr oder weniger parallele mit der freien Wand. Obwohl Felsbrüche unter zweiachsiger Beanspruchung immer mehr häufig in tiefen Minen beobachtet sind, hat man über nur einige repräsentative Laborversuche in der Literatur berichtet. Diese Studien diskutieren das Thema ohne Betonung auf Felsbrüchen, und keine sind in den letzten zehn Jahren erschienen. Die vorliegene Arbeit gibt die Ergebnisse eines Testprogramms auf einem Typ von Granitfels. Durch zweiachsige Prüfungen von kubischen Proben mit Seitenlangen von 100 mm sollte man den Einfluss von seitlicher Ermittlung und der Beanspruchungsrate auf die Bruchfestigkeit des Felsen studieren. Man findet auch die Prüfergebnisse in bezug auf das normalisierte, zweiachsige Bruchkriterium s1/sc-s2/sc. Die beobachteten Bruchmechanismen sind auch diskutiert.

Jan 1, 2003

Remnants of Plio-Pleistocene hot spring systems in Northland, New Zealand contain sulfide minerals, principally pyrite, marcasite and cinnabar. The climate is warm temperate to subtropical, with up to 3 m of rainfall per annum, and rocks are deeply weathered. Decomposition of the iron sulfides in natural outcrops and human excavations results in acid rock drainage with pH typically between 2 and 5, and locally down to pH 1. Deeply weathered basement greywacke is clay-rich and has negligible neutralisation capacity. Some overlying volcanic flows have resisted weathering, and pH is kept near neutral by relict secondary calcite in small areas. Natural rainforest soils commonly have pH between 4 and 5 over mineralised and unmineralised greywacke. Mineralised zones are enriched in arsenic, which occurs in solid solution (up to 1 wt per cent) in sulfides and phosphate minerals. Mercury also occurs in solid solution in some of these minerals, as well as in cinnabar. Base metals are present in low (background) concentrations only. Decomposition of the iron sulfides and phosphates releases the solid solution arsenic and mercury into the acid rock drainage solutions. Arsenic is readily adsorbed on to iron oxyhydroxides formed in acid rock drainage situations, and can be effectively removed from the biosphere. However, this arsenic is released back into the environment if the pH rises, as adsorbed oxyanions become less strongly bound and are displaced by hydroxyl ions. Behaviour of dissolved mercury is similar to that of arsenic but less well understood in these settings. Both arsenic and mercury are readily leached into pH 6 solutions from solid material collected from acid rock drainage sites. These observations suggest that neutralisation of acid rock drainage sites is undesirable in this setting, as arsenic and mercury will become more mobile in the environment. The naturally low pH of 4 to 5 of the forest floor, or even lower pH of natural acid rock drainage, is a preferable management option.

Jan 1, 2003

Mining of the silver-lead-zinc orebodies at the George Fisher Mine officially started in 2000. A review of mining performance to date shows that many of the extracted primary stopes have experienced some degree of hangingwall dilution. The degree of hangingwall failure in the stopes became progressively more extensive throughout mining of the orebodies in 2001 and 2002, culminating in the unplanned catastrophic failure of the 744D stope in which the ore between 13C (2683RL) and 12L (2714RL) sublevels caved into the previously mined cavity between 13L (2654RL) and 13C sublevels. This was followed several months later by another unplanned caving event in a nearby stope, 740D. As a direct result of these unplanned failures it was decided to mine the stopes with a smaller span than had been previously planned and in a primary-secondary pyramidal stoping sequence. To limit the exposure of the stope hangingwall, a hangingwall drive is no longer developed and therefore geologists no longer have access to the detailed geological information that this provided. Geologists at George Fisher Mine have had to be adaptable and flexible in response to these proposed changes and rely more on data from drilling than mapping for their geological interpretation. The result is that the drilling cycle has become much more critical in the planning process.

Jan 1, 2003

By J. Broadhurst

"A number of metal supplying industries have in recent years seen the compilation of life cycle inventories (LCIs) and life cycle assessments (LCAs). The activity has largely been driven by the interest of ultimate metal users, such as the automotive industry, in the interest of designing more sustainable products. Often, the compilation of such inventories has been little more than an auditing exercise. However, the process of conducting an LCA can have more value, guiding designers and operators to points within the technology train where significant emissions and impacts originate. The LCA product can thus be used to inform on-site environmental management, and, where process data is used to construct dynamic operational models, to support strategic decision making in the realm of project planning and technology selection. LCA thus serves as a valuable tool to support the industry’s drive to support the sustainable development of the societies in which it operates.This paper reviews and compares the priorities of environmental and closure planning in the design phase, with environmental management and auditing during operation, and with green procurement of minerals and metals products. It shows how life cycle assessments of various complexities can be used to reconcile these various objectives, ensuring that the latter, critical to business success, can be addressed from the outset in a new project. The paper then reviews a case study of the use of LCA in the base & precious metals industry, where the complexity of the operation disallowed the simpler auditing process so that a detailed process understanding had to be built up in order to compile a meaningful life cycle inventory."

Jan 1, 2003

By Ian M. Ritchie

Cementation or metal displacement reactions such as Cu2+ + Fe Cu + Fe2+ are among the oldest known hydrometallurgical reactions. They are still used in the recovery of some metals and in the purification of process liquors and waste water streams. However, they are often more complex than the stoichiometric reaction would suggest because they involve the simultaneous deposition of one metal onto a second which is dissolving. For example, sometimes a cementation will not take place, even though it is thermodynamically favoured. On other occasions, a cementation reaction will start but come to a halt as the depositing metal blankets the reacting surface. On yet other occasions, side reactions, catalyzed by the deposit, can be important. In this paper, the electrochemical basis of cementation reactions is described. The conditions for each of the complications encountered in these reactions are described and illustrated by examples drawn from a number of hydrometallurgical processes. The cementation reaction between activated carbon and gold thiosulfate is also briefly described, this reaction being unusual in that no dissolution of the carbon occurs.

Jan 1, 2003

"Boston’s Central Artery passes beneath nine active railroad tracks carrying commuter and Amtrak trains into South Station, the City's busiest rail terminal. These railroad operations had to remain in service throughout the construction of the “Big Dig”. The solution was to jack the tunnel under the tracks, rather than build the tunnel by more conventional means.Jacking of utility pipes is fairly common, but jacking boxes as big as a highway had never been done in North America, until the Big Dig came along.Soil freezing was decided upon as a means of stabilizing the soil under the tracks. This allows the tunnels to be jacked into place without soil caving when the soil is excavated at the leading face of the advancing tunnel boxes. Hundreds of pipes were driven into the ground between the tracks. Inside the steel pipes were smaller plastic pipes. A freezing plant near the railroad tracks pumped refrigerated brine into the inner plastic pipes. The brine ran out the bottom of the inner pipe, flowed up to the top inside the outer pipe, and was re-circulated to the freezing plant and back again into the ground. Over several weeks the circulating brine drew the heat out of the soil little by little, and froze the ground outward from the pipes. Soil FreezingThe plan required the construction of jacking pits in which the tunnel boxes could be constructed, and from which they could be jacked forward to their final locations, as described in the accompanying article. Once the jacking pit was built and the tunnel box constructed inside the pit, crews made an opening in the headwall of the pit to allow passage of the tunnel sections, excavated about three feet of the frozen soil, pushed the tunnel box ahead, and repeated the procedure again and again."

Jan 1, 2003

By Supachai Surapunt

The distribution behavior of V A minor elements (As, Sb and Bi) in the smelting stage of the Mitsubishi process were evaluated thermodynamically based on thermodynamic data and operating data. The fractional distributions between the gas, slag and matte phases considered as the degree of vapor saturation of 1.0 are as follows: 53.8, 27.2 and 19% for As, 23.6, 56.6 and 19.8% for Sb, and 91.3, 1.1 and 7.6% for Bi, respectively. Arsenic is mostly distributed to the gas and slag phases. It is effectively eliminated by volatilizing and slagging. Antimony is mainly in the slag phase, which is suitably removed by slagging. Bismuth is easily vaporized to gas phase. The degree of vapor saturation has a large effeet on the distribution behaviors of the three elements between the three phases. The amount of a minor element in the charge has an effect on the distribution of As but no effect on the distributions of Sb and Bi. Increasing matte grade and temperature results in the change of distributions for As and Sb, significantly. The change in the distribution ratio between slag and matte phases also considerably affects the distributions of As and Sb. The distribution behavior of Bi is not significantly changed by the change in matte grade, temperature and distribution ratio.

Jan 1, 2003

By M. Brennan, A. Majumder

"The mineral processing research community has devoted enormous efforts to the modelling of mineral separators over the last 50 years. While many efforts have been made to use only fundamental physics as a basis for the models, fluid flow patterns in separators are not simple while the motion of particle swarms through fluids is extremely complex.Sluices are the simplest forms of the flowing film concentrators and have been used in the mineral industry since at least the 15th century (Agricola, 1556). Flowing film concentrators, in general, still have widespread applications in the mineral industry and their designs vary according to the specific need.Particle separation in a sluice appears deceptively simple, but the separation mechanism has proven complex and difficult to quantify. Separation in the sluice takes place in a flowing film a few millimetres thick. The particles are suspended by turbulent eddies and motion relative to the fluid takes place in socalled hindered settling mode. The difficulty arises because the presence of the particles influences the flow pattern and when the particles are fully transported by the flow, the flowing slurry may not have the same viscosity as water and does not have the same density. For this reason a universal theory which can explain the behaviour of a suspension in a sluice or any other gravity equipment has still not been developed. Few attempts have been made to analyse the mechanisms involved in the concentrating processes of pinched sluices and Reichert cones.Fluid flow behaviour and slurry transportation characteristics in open channels have, however, been active research topics in the disciplines of fluid mechanics, chemical engineering and civil engineering for many years. As a result, an extensive literature is available, which has led to the development of the model described in this paper.In an effort to test the extent to which fundamental fluid mechanics can provide a prediction of particle separation, a study on a simple parallel-sided sluice has been carried out using glass beads at various particle concentrations and flow rates, and the actual particle separation taking place compared to predictions from modelling.The modelling strategy was divided into two parts; the first was to predict the horizontal slurry flow velocity profile and the second to predict the solid particle concentration over the depth of the flow at different flow conditions. The predictions were then validated with measured data sets. This can easily be done if the slurry flow is split at different fractional flow depths so that the mass flow of solids over different flow heights is measured accurately over a fixed period. Mass flow splits can then be calculated by integrating the product of the predicted slurry velocity profile and the predicted solids concentration profiles from the base of the sluice bed to the slurry free surface."

Jan 1, 2003

By M Titley, E Maidens

Many gold deposits were mineralised by fluids and processes that also altered the host rocks. This alteration may often be a useful visual aid that distinguishes barren, low-grade from high-grade regions in a rock mass. Alteration intensity is commonly used in gold deposits as a visual tool, along with face sampling or grade control support, to define oreblocks and guide excavation in underground and open pit mining. However, alteration is not often used at the resource estimation stage. Mineralised lodes are usually defined by geologists using a ægeo-grade envelopeÆ, where a number of constraints are considered, including an (arbitrary) cut-off grade; the ænaturalÆ grade break between high- and low-grades; and geological features including structural, lithological or alteration continuity. The geo-grade envelope is usually thought to satisfy the requirements of stationarity for grade estimation, and is considered a single domain. This paper examines a modelling technique combining gold grade and alteration, applied to the Wallaby deposit in Western Australia, to imbue a greater level of detail to the grade estimation in a region tested by relatively sparse drilling. This was achieved by utilising the correlation of gold grade and alteration, along with the spatial characteristics of the alteration, when estimating grades within a number of lodes. The alteration-driven estimation was utilised in conjunction with an unfolding approach, and the use of probability estimates, to overcome geometric data constraints. This technique allows greater control and most likely provides a more reliable estimate of the mineable resources than a global grade cut-off when visual control is to be a major vector in grade control.

Jan 1, 2003

By F. M. C. C. Vieira

Four mining alternatives for exploiting an ultra-deep orebody were assessed through a multidisciplinary evaluation process which involved: the generation of a 3D geological model; the design and scheduling of life-of-mine layouts; the analysis of anticipated ventilation and cooling conditions; the study of rock-related risks of mining in ultra-deep stress environments; the logistic implications of transporting men, rock and materials; and, lastly, the economic implications of each option. Once results from the integrated mine design assessment were available, mine planners were faced with an important problem to solve: how to identify the optimal mine design alternative when numerous assessment measures and multiple decision criteria needed to be considered simultaneously? To address this ‘multiple-attribute decision problem’ and arrive at the ‘optimal layout for ultra-depth’, a generic decision methodology that uses principles of ‘utility’ was applied. The methodology assumes that ‘single-value risk estimators’ do not account for the inherent variability of real conditions. Therefore, risk estimators were represented by statistical distributions of their incremental changes, where applicable. The stochastic variables, once defined, are used as inputs in the ‘utility’-based layout decision scheme. This ‘utility’-based decision methodology offers a framework for mine design decisions to be made objectively, when complex trade-offs between multiple risk domains need to be considered simultaneously. Upon applying it, one of the layouts emerged as the preferred alternative. Keywords: Utility; mine design; multiple-attribute decision; layout selection

Jan 1, 2003

By S. K. Gilman, V. E. Hugo

A common problem encountered in the mineral sands industry is that the mineralogical measurements used in defining the resource are not readily converted to metallurgical recoveries, which are used to predict the quantity of the final products. The problem stems from the different objectives of the exploration and metallurgical assessment programmes, and is often compounded by the use of different laboratory techniques and mineral definitions. Common mistakes include the misapplication of routine analysis, incorrect interpretation of mineral recovery, the confusion of mineral recovery with product yield and inconsistent definition of the same mineral. Experience has shown that unless these potential mistakes are identified, the measurement techniques used during exploration and metallurgical assessment are not compatible, often resulting in large errors in the prediction of mineral production. There are no easy solutions to the problem, as there is no universal assay technique which can cost effectively characterize all the mineral sands resources. The recommended course of action will therefore require several iterations to optimize the assay technique to suit the resource. Fundamental to the success of the measurement technique is the understanding of the mineralogy, its behaviour during mineral processing and the quality requirements for the final products.

Jan 1, 2003

By Chu Yong Cheng

Synergists can be used in solvent extraction to improve the selectivity of extractants for metals. Research work carried out by the SX group at the AJ Parker Cooperative Research Centre for Hydrometallurgy / CSIRO Minerals has shown that the pH isotherm of nickel with Versatic 10 was significantly lowered by the addition of the synergist Acorga CLX50. The paper discusses how this synergistic shift can be used to alleviate a gypsum formation problem at Bulong nickel laterite operation in Western Australia. Metal pH isotherms were obtained with Versatic 10 and synergist CLX50 using synthetic leach solutions. In terms of pH50, the extraction order of the metals with 0.5 M Versatic 10 alone was Cu > Zn > Ni > Co > Mn > Ca > Mg, whilst the extraction order with Versatic 10 and 20% by volume CLX50 was Cu > Ni Zn > Co > Mn > Ca > Mg with the pH50 (Mn-Co) significantlyincreased. This is significant because the isotherms of valuable metals Ni, Cu, Co and Zn shift more towards low pH than those of the waste metals Mn, Mg and Ca, resulting in a possible good separation of Ni, Cu, Co and Zn from Mn, Mg and Ca. The use of intermediate precipitation, solids/liquid separation and re-leach in the three Western Australian nickel plants make these processes complicated and costly in capital and operation. The research work carried by the SX groupat the AJ Parker Centre has led to the development of direct SX (DSX) processes to recover nickel and cobalt from leach solutions using synergistic organic systems. Semi-continuous tests with a BHP Billiton pilot plant leach solution showed that Ni and Co together with Zn and Cu were separated from the major impurities, Mn, Mg, Ca, and Cl, in the first SX circuit. The co-extracted impurities were easily scrubbed. After stripping, Ni and Co together with Zn and Cu were concentrated, resulting in a much smaller second SX circuit in the down stream processes.

Jan 1, 2003

By J Mar·n, R Anderson, S Strohma, R Harvey

Xstrata is the operator of both Minera Alumbrera Ltd (50 per cent Xstrata, 50 per cent Wheaton River) and Ernest Henry Mining Pty Ltd, (99.99 per cent Xstrata), both copper-gold deposits, using conventional SAG/ball milling at current capacities of 36 Mt/yr and 10.3 Mt/yr respectively. Alumbrera is located in Catamarca Province, in the north west of Argentina. Ernest Henry is located in Cloncurry, north west Queensland, Australia. Both operations started in late 1997, with commercial production achieved in early 1998. Different designs and equipment are in use for both operations, however the evolution of SAG milling performance, although logically related to their specific features, reflect similar trends of consistent increases in throughput. This paper will discuss the main changes to the SAG mill liners in both operations and the results achieved to date. A summary of the operating strategies will be included.

Jan 1, 2003

By W. Kuckshinrichs

Metallic raw material flows are characterized by a complex global network of producers and consumers, as well as by a multitude of ecological, economic and social impacts across national boundaries and on different scales. This leads to the need to develop methodologies, which allow identifying obstacles that prevent metallic raw material flows to contribute to sustainable development. From a scientific point of view CRC 525 (Martens 2003) has developed an holistic indicator set consisting of approximately 80 different indicators. This set is taking into account the multi-dimensional character of sustainable development. Moreover the indicators reflect different system boundaries according to different actor levels and decision contexts. The full indicator set is important in scientific considerations and suitable for scientific awareness creation. However, to fulfil the function of a decision support approach for political and economic decision-makers some modifications are of central concern. At first a reduction of the full indicator set by selection of core indicators enables decision-makers to deal with complex issues of contrary economic and societal protection targets. Secondly, as thresholds of indicators justify societal call for action, they are discussed against its political or scientific origin. The proposed methodology is exemplified by indicator-based studies of the material flow of aluminium.

Jan 1, 2003

By P. M. Solozhenkin

"Galvanochemical process (GChP)) cleaning of sewages is realized in the field of shortcirquited galvanic elements from the mixture current the materials place in purification’s solution and form multitude galvanopairs without external electric field in presence oxygen of the air. The galvanochemical process is electrochemical process utilizing galvanic pairs: coke - iron, iron - copper and others and process does not require chemical reagents.The effect of basic parameters of the cleaning effectiveness have been studied depending on oxidizing of galvanopairs. Adjusting nature, type of galvanic pairs and forming three component system possible to enlarge emf circuits to 2.378 V.The role of ?2, as basic agent, for generation of hydrogen peroxide and hydroxyl ions.It was stated, that removing of metal ions from solutions occur mainly on account of sorption and hydrolytic sedimentation of iron oxihydrates.Determined separate stages of the process: coagulation, sorptions of admixtures on freshly formed ferric oxides and oxidizing destruction of organic components of effluents in presence of ?2 ? ?2?2. Shown efficiency of the method for removing of Cu, Cr, Ni, Zn, As ions, as well as fluoride, phosphate and cyanide anions and oil products, surface-active and flotation reagents. Cleaned water can be recycled for some processes non-critical toward residual concentration of admixtures, as total salt contents is lowered on 60-75 % and reaching limits of concentration for toxic components.The concept of high power unit creation was developed, and galvanochemical pulsator is presented. The pulsator is not expensive, and exploitation expences are low, as well as servise is simple with high effectiveness, and capacity. The galvanoflotation process is developing, combining galvanochemistry and flotation of hydrofobic admixtures (oil, surface-active agents).The galvanochemical flotators are presented."

Jan 1, 2003

By A. González

Arsenic is one of the main contaminants present in Chilean copper concentrates and its abatement represents a challenge for the process metallurgy, particularly under the strong environmental requirements in the global community. The possibility to form ferric arsenate directly from a gas phase by means of a heterogeneous reaction between an arsenic gas bearing and iron oxide was studied at laboratory scale. A thermodynamical analysis for the system Fe-As-O-S has been initially made, in order to obtain the stability conditions for the ferric arsenate or other FexAs2O2 type compounds. Experiments were made using an hematite sample suspended in a thermogravimetric device. AS4O6 gas generated from solid AS203 that was passed through the iron oxide sample and its instantaneous weight change was recorded directly. A kinetic study for the AS4O6 volatilization was made to control the gas composition. A chemical control between 300 and 600°C with an apparent activation energy of around 14 Kcal/mol As2O3 was determined. The samples after the reactions were chemically and XRD analysed. Arsenates detected corresponds to complex compounds. Results shows a dependence on temperature and oxygen content in the gas phase. The kinetics for iron arsenates formation is slow, reaching an arsenic capture of 6% after 80 minutes of reaction when an oxygen content of 50% is fed continuously at 800°C and 3,56% As in the gas. Experiences made at the same temperature but under higher oxygen content in a closed reactor, allowed arsenic capture close to 60%. For higher temperatures the capture is considerably lower.

Jan 1, 2003