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By Zuomei Jin

A laboratory study was conducted on the separation of Zn, Pb, Cu and Ag from a finely dissem-inated interlocked silver-rich multimetal sulphidc ore. These are often difficult to separate from each other by flotation. The thermodynamic calculations of Zn-S-O, Cu-S-O systems at different tem¬peratures were presented on predominance diagrams. Based on these diagrams the optimum temperature and gas composition were selected for roasting. The results of separating Zn, Cu from calcine by neutral leaching and acid leaching were found to be satisfactory. The distribution of silver in the roasting and leaching processes were tested. A flow sheet was proposed.

Jan 1, 1993

By Renato G. Bautista

"The development of processing methods for the preparation .of three electronic materials with rare-earth components is discussed. The resulting processing innovations are the results of a search for an economically competitive pilot scale or industrial production flowsheet without compromising the required properties of the final products. The three cases highlighted in this presentation are: 1) The preparation of high energy (Pr-Nd-Ce)FeB magnets for MRI application from a mixed-rare-earth oxide with a narrow range of composition directly prepared from the solvent extraction circuit of bastnaesite ore. 2) The kg production of the giant magnetocaloric effect Gds(SixGe1-x)4 magnetic refrigerant materials from commercial grade gadolinium metal (95 to 98 at. % pure) instead of high purity gadolinium metal (99.8 at. %); and 3). An industrial chemical synthesis flowsheet for the production of the superconductor precursor of YBa2Cu3O7.INTRODUCTIONIn the laboratory discovery stage, the synthesis of a new material is carried out using very high purity components, usually the highest purity available. As the new material is studied and characterized, the effectiveness of its desirable properties becomes better defined and understood. The evaluation of the effectiveness of the .property over the range of a given parameter and other interactions are further studied. Once it's potential application becomes clear, a practical and economical processing method need to be developed. The successful material processing flow sheet does not necessarily have to be a scale up of the laboratory procedure. At this stage, substitution of starting components and with lower purity materials is considered as the economics of the processing becomes a major issue. In addition, other approach to it's synthesis"

Jan 1, 2000

By Florian Kongoli

The so-called "fayalite" slag, despite problems associated with it, is the most widely used slag in copper smelting processes. Thirty years ago, in order to overcomes some drawbacks of this slag a new "calcium ferrite" slag was proposed especially for continuous copper converting. Since both slags have strong and weak points depending on the field of their application about 8 years ago another new "ferrous calcium silicate" slag was proposed that is expected to solve the drawbacks of each slag. This new slag is defined as mainly consisting of FeOx, CaO and SiO2 as its main components but it can practically have several combinations of these constituents. In order to determine the best area of this slag for possible industrial application the quantification of phase relations is an important subject. In this paper the work carried out by the authors in quantifying through an original physical model the phase relations, liquidus surface, liquidus regions, behavior of solid phases and the effect of minor components is reviewed. Several special compositions of this slag have been identified and discussed for possible applications in the industrial practice.

Jan 1, 2006

By M. Nienoord, O. S. L. Bruinsma, J. A. F. M. Schade Van Westrum, W. H. Sillekens, B. Mehmetaj

Recycling of aluminium is an effective way of enhancing the efficient use of energy and limiting the burden on the environment. Where cascade recycling is an established way of using reclaimed aluminium, closing the recycling chain is currently hampered by the unavailability of suitable techniques for refining contaminated scrap on an industrial scale. To overcome this problem, purification based on fractional crystallisation appears to be a promising option. This implies that the material is to be processed in the semi-solid state; that is, at a temperature where a solid and a liquid phase co-exist. In the current paper, it is shown that zone melting can serve as an indi.cative test for assessing the refining potential of fractional crystallisation processes, since they are both based on the same thermodynamic principle. Next, the results of zone-melting experiments are presented for some representative aluminium model alloys. The BPS-model (developed by Burton, Prim and Stichter) is used to interpret these results, from which it is concluded that the model needs extension to obtain a predictive tool for fractional crystallisation processes.

Jan 1, 2000

By A. V. Tarasov

The natural resources of lead and zinc are primarily constituted by polymetallic and lead-zinc ores. Beneficiation of these types of ores to produce standard nonmetallic concentrates inevitably results in an increase in the loss of base and precious metals with tailings. An improvement in the grades of lead and zinc concentrates can be achieved by re-cleaner flotation, but it results in production of intermediate products (middlings) to which substantial amounts of lead, zinc, copper and precious metals report. Without an appropriate technology for treating such intermediate products, the recoveries of valuable constituents from lead-zinc ores would remain unsatisfactory. A process has been developed in the Gintsvetmet Institute for processing of polymetallic intermediate products produced at the ore beneficiation plants. This process is based on electrothermic smelting to produce lead bullion containing precious metals, commercial-grade copper-lead matte and high-zinc slags (up to 15-20% Zn) from which zinc can be extracted by slag-fuming or Waelz process. Tests have indicated that the recovery of lead from intermediate products into lead bullion and matte is about 83-85% and 13-14% respectively (the total recovery is 97-98%), while copper recovery into the matte and zinc recovery into the slag is 90-92% and 95-96% respectively. Precious metals (about 96-97%) report into the lead bullion.

Jan 1, 2006

By Keiji Okumura, Hong Lan, Masamichi Sano

"Magnesium has been well known as one of the excellent agent of desulfurization, deoxidation, etc. in iron- and steelmaking because of its high reactivity. Since its production is energy nitensive, the price is very high. Thus magnesium has not widely been used as an agent in metal refining ·processes. In the present work, reduction of magnesia by carbon and aluminum is examined. Because the reaction is very sensitive to temperature, non-isothermal technique is applied to investigate the reaction kinetics. The effects of heating rate .and reaction interface area on the reaction kinetics .are studied. .A kinetic model is proposed based on the experimental results.IntroductionFor the metal refining processes, the production of high purity metal has been one of the most important research subject. In order to produce the high purity metal, the amount of the refining agent and the consumed energy is increasing. Therefore, if the future earth environment is taken into consideration, the further efficient and energy saving processes are required. Generally, Cao slag has mainly been used for desulfurization of molten iron as a desulfurization agent. However, environmental problems, such as recycling of disposal slags, are still unsolved. On the other hand, the deoxidation of molten steel is mainly performed by addition of aluminum. Therefore, the alumina inclusions· remain in. molten steel and the great efforts have been made to the removal of the inclusions. The affinity of magnesium with sulfur and oxygen is strong, and magnesium is well known as a powerful desulfurization and deoxidation agent. However, magnesium has been seldom used for the steel' refining process. The following reasons are considered. Generally, magnesium is expensive. And at iron- and steelmaking temperatures, the refining efficiency becomes low due to its abruptly .evaporation."

Jan 1, 2000

By D. Georgiou

Direct sulphuric acid leaching of nickeliferous limonites is the process of choice to recover nickel and cobalt from equatorially located lateritic ores. These ores are rich-in-iron (-45 wt%) existing in the form of goethite enriched with nickel. The merit of this process is due to its high nickel selectivity because of simultaneous iron separation and acid regeneration. Under acid leaching conditions (-250 to 270°C) iron follows an acid dissolution-hydrolytic precipitation path yielding a very low concentration level depending on temperature and acidity of the final leach liquor. The primary precipitation product of iron is hematite which also forms as a scale on reactor internals along with co-existing aluminum. In this paper, an overview of the behaviour of iron solid products under process conditions is made. The evolution of goethite to hematite transformation, as well as the role of iron in reactor scale production, are studied using SEM/EDX characterization techniques.

Jan 1, 1995

By Alex Mezei

Experimental rheology data are needed to produce design criteria for mass and energy transfer processes. Large throughput plants operate under continuous flow mode. The capital cost is determined by the accuracy of the rheology data used for design. The operating cost is dictated by the energy required to sustain the flowing conditions of various process slurries. Typically, rheology investigations are carried out during the final stages of metallurgical testwork, which is too late to set the design criteria for the pilot plant. This leads to increased testwork cost, and sometimes lowers confidence in the quality of the data produced. In addition, the engineering and feasibility studies are often delayed because of the lack of pertinent rheology data. One of the objectives of this paper is to emphasize the importance of timely planning and execution of the rheology study, which is shown to be a critical component of the overall testwork program. Various applications are discussed, including elaboration of process and equipment design criteria. In this paper, the emphasis is placed on gold and nickel laterite hydrometallurgy applications.

Jan 1, 2003

By Min Chen, Nan Wang, Zhen Tian, Yingying Shen

"The enrichment behavior of phosphorus in CaO-SiO2-FeOx-P2O5 slag was studied by making an investigation on the distribution of phosphorous content in slag and 2CaO·SiO2 phase. The research results showed that the existing 2CaO·SiO2 solid particles in slag were the sites for the phosphorous enrichment. The enrichment process of phosphorus in CaO-SiO2-FeOx-P2O5 slag can be recognized as: mass transfer of phosphorus from bulk slag toward the surface of 2CaO·SiO2 particle, superficial dissolution reaction of phosphorus to 2CaO·SiO2 and diffusion of phosphorus through the product layer of 2CaO·SiO2-3CaO·P2O5 solid solution to the inner of 2CaO·SiO2 particle. Compared to the 2CaO·SiO2 particles with larger size (500µm to 1000µm), the completion time of enrichment was shorter for the particles with smaller size (less than 50µm).IntroductionDuring ironmaking and steelmaking, significant amounts of slag are produced. Contrast to the high utilization of ironmaking slag, the treatment of steelmaking slag is more difficult and challengeable, and therefore, an alternative approach is to recycle the steelmaking slag inside the ironmaking and steelmaking process itself. The main limitation to the reuse of steelmaking slag inside the process is that the refining process may be aggravated caused by the phosphorous accumulation if it is used in the blast furnace burden [1]. At the same time, the phosphorous content of steelmaking slag (approximately 1%~5% P2O5) is too low for it to be used as raw material for fertilizer [2, 3]. Moreover, owing to the diminishing supply of global iron ores with low phosphorous content, the control of phosphorus in iron and steelmaking processes has become an increasing problem, and as a result, more amounts of high phosphorus containing steelmaking slag are produced. Therefore, a valuable approach is quite appreciated in which the steelmaking slag is recycled within the ironmaking and steelmaking process and at the same time, the high phosphorus-containing phases in the steelmaking slag, suitable for use as fertilizer can be separated and recycled effectively [4]."

Jan 1, 2011

By B. Q. Li, S. P. Song

"Numerical models are developed to represent complex electromagnetic, free surface deformation and fluid flow phenomena in floating zone refining processes with radio frequency inductive heating. The computational methodology is based on the coupled finite/boundary element method for the electromagnetic field distribution and the Galerkin finite element method for magnetically driven fluid flow and free surface profiles of the molten zone. With the models, the complex transport and free surface phenomena in a floating zone system can be studied as a function of various operating conditions including applied current, frequency, inductor position and shape, surface tension, floating zone diameter and height. Results show that the equilibrium shape is sensitive to the height of the molten zone and that the free surface shapes can have a significant effect on the melt flow in the molten zone. Our extensive simulations also suggest that to ensure accurate results, the same mesh should be used, whenever possible, for both the electromagnetic forces and fluid flow calculations.1. IntroductionThe floating zone processes have been widely used in the materials industry to grow ultra-pure rare earth metal or semiconductor single crystals for sensor or electronic applications that have a tough demand on purity. Developed based on the principle of magnetic melting/levitation, the processes possess a main advantage that the molten zone is supported in air by the electromagnetic forces generated by the coil (see Figure 1), and therefore is free from contamination from a container. Consequently, the final products made from the floating zone processes have higher inherent purity than those by other techniques [1-4].Complex physical phenomena occur in the floating zone processing of materials. These include free surface deformation, magnetically-driven melt flow, which may be turbulent or mildly turbulent [5] depending on the applied conditions, and solidification. Thermal stresses also develop in the single crystals, which are affected by the flow and temperature field and which can have direct implications to qualities of single crystals [6]. An understanding of the fundamentals governing these physical phenomena can be of critical value in elucidating the physics that controls the properties of the metal or semiconductor crystals being produced, thereby providing a rational basis for process improvement and quality control."

Jan 1, 1997

By Samson Adeosun, Sanmbo Balogun, David Esezobor

"In a typical year, approximately 1.7 million tons of residues and wastes are expected from Ajaokuta integrated steel plant, Nigeria. They will be generated mainly from sinter plant, blast furnace (BF), and basic oxygen furnace (BOF) operations and during rolling and finishing. The residues and wastes include slag, dust, sludge and slurries from gas cleaning, waste water, mill scales and other associated scraps. In this paper concepts for the utilization of residues and wastes in Ajaokuta Steel Plant where no reclamation routines have been provided for in the first and second phases of its project implementation is designed. The paper analyses the sources of the iron oxide wastes and evaluates the quantities expected from the main production facilities of the plant which include the two 312 m2 capacity sintering machines, the two 2000 m3 blast furnaces and two 130-T BOF (of the 2nd phase expansion of the Steel Plant). A reclamation routine designed for Ajaokuta residues and wastes is presented.IntroductionIn the steel industry, approximately 550kg of residues per ton of crude steel arise from the production processes and from pollution control facilities [1- 4]. These residues consist of slag, dusts and sludge, mill scale, spent pickle liquor, and other iron bearing materials. The main by – products generated in the steel industry are listed in Table I.Although major progress has been made in the recycling and use of some of these residues, particularly flue dust, blast furnace and steel making slag, yet a significant quantity are land filled or stockpiled. These unsightly stockpiles occupy valuable real estate and may become a source of environmental pollution if not otherwise disposed. In any case, the dumping option has become quite costly. For instance, one ton of iron ore costs between 28 and 34 US dollar, whereas as much as $20 per ton of steel produced is required to meet environmental compliance obligation in the USA [5, 6]."

Jan 1, 2008

By Yong .. Jun Wu

Laminated ceramics have received widely scientific and commercial attention because their properties, such as mechanical properties and electrical properties, can be tailored by adjusting the structure, thickness and composition of the different layers. For example, ferroelectric Bi4Ti3O12 (BIT) which has a positive temperature coefficient of dielectric constant (,E) can be used to modify the negative tE of typical microwave dielectric ceramic BaNd2Ti4O12(BNT), However, BaNd2Ti4O12/Bi4TiO12/Bi4Ti3O12/BaNd2Ti4O12 (BNT/BIT/BNT) laminated ceramics could not be prepared by the general method because the optimal sintering temperature of BaNd2Ti4O12 ceramic (around 1350°C) was much higher than that of Bi4Ti3O12 ceramic (around 1100°C). In this research, a new method of spark plasma sintering (SPS) combined with post-sintering was successfully proposed to prepare BNT/BIT/BNT laminated ceramics. It was divided into three steps. In first step, the BaNd2Ti4O12 ceramics were prepared by conventional sintering method. In second step, the calcined and pre-pressed Bi4Ti3O12 powders were sandwiched between BaNd2Ti4O12 ceramic pellets and spark plasma sintered at 900°C for 10min to synthesize BNT/BIT/BNT composite ceramics. In the last step, a post-sintering was employed to reoxidize the partially reduced BNT/BIT/BNT composite ceramics. The results of scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) showed that BNT layer and BIT layer were well bonded and no significant interfacial infiltration between them was observed. The sandwiched BNT/BIT/BNT ceramic with 10.7% BIT in volume has a dielectric constant of 92.85, a low dielectric loss of 01068 and a small temperature coefficient of dielectric constant of 35 ppm/°C at MHz.

Jan 1, 2003

By Rodney L. Williamson

Vacuum arc remelting (V AR) is an industrial metallurgical process widely used throughout the specialty metals industry to cast large alloy ingots. Part of the V AR control problem consists of adjusting arc current to control electrode melt rate which also depends on the electrode temperature distribution. Because the temperature distribution responds very slowly (1-4 hours depending on size and material) to changes in melt power, the melt rate response is history dependent and highly nonlinear. The situation is complicated further because measurement of the electrode temperature distribution is not practical. To solve the problem of accurate, responsive melt rate control. a low order electrode melting model has been developed and incorporated into a V AR process controller. Data from laboratory and industrial tests show that the goal of responsive, accurate melt rate control has been achieved, even when melting under highly dynamic process conditions. Keywords: Vacuum Arc Remelting. Model-Based Control

Jan 1, 2003

By S. Motoiu

Data acquisition is widely used for controlling flash smelting furnaces. A Romanian smelter from which a large amount of data can be collected uses such a technique. A computer program was developed for interpretation of the data. Inputs to the program are the process data files. Abnormal data are identified using standard statistical techniques; they can be edited if necessary. The following methods can be used for the analysis: linear correlation (single or multiple), polynomial correlation or comparison of two average values. Time variation graphs and histograms can be displayed. The random balance method was used for determination of significant parameters influencing the process performance. Not all process parameters are recorded, and some of them are not even measured. The software can compute some of these parameters such as: air flow rate required and the oxygen content of the gas: exiting the reaction tower. The software was used for the interpretation of a large amount of process data. The analysis showed that the process did not operate properly at some times.

Jan 1, 1999

By M. J. Bagshaw, J. D. Hunt, R. M. Jordan

"Continuous casting processes, and the roll casting process in particular, offer considerable potential to the Aluminium industry, both meatallurgically and economically.The three major limiting process problems that occur during roll casting are Centre Line Segregation', 'Sticking' where metal adheres to the rolls during casting, and 'Heat Line' formation. 'Heat Lines' are localised semi-continuous longitudinal defects, usually a few cms in width, where the cast metal leaves the roll bite partially molten. These defects occur at relatively low casting speeds when the mean slab exit temperature remains several hundred degrees below the solidus temperature. The objective of the work described here is to develop a better understanding of the roll casting process in general, and in particular, to understand the phenomenon of 'Heat Line' formation.A steady state two dimensional finite difference model has been developed to describe the roll casting process, incorporating a variable heat transfer coefficient through the roll bite. In the model the difference equations are formulated using a control volume method and latent heat is incorporated according to the Scheil equation. A Gauss-Seidel type technique is used to obtain the solution. Because the rate of heat evolution is non-linear the temperature in each box is determined by using a Newton-Raphson method. The solution for a box can be multi valued and therefore lead to instability particularly near the vicinity of the front. A stability 'criterion is presented which shows that to obtain a stable solution it is better to have long narrow boxes rather than boxes with small dimensions in both directions.The model explains why heat lines form in terms of the variable slab/roll heat transfer coefficient.Experimental measurements of slab exit temperatures are also presented. These were obtained on a Hunter twin roll caster for the binary AI-Cu system, at two compositions over as wide a range· of casting speeds as possible. The experimental results are compared with the predicted ones."

Jan 1, 1986

By Jeaneth S. Benedetto

The physical and chemical processes developed for recovery of uranium and phosphor from phosphoro-uraniferous ore bodies consists of three basic steps: concentration of the phosphate bearing uranium by flotation, chemical dissolution of the concentrate by wet phosphoric acid and extraction of uranium by solvent. In this process two products are obtained: 1) uranium and 2) phosphoric acid. The purpose of this work was to develop technological know-how of phosphoric acid purification though an extraction of P2O5 by solvents. It was investigated by two lines of research. In the first one the uranium was extracted before the phosphoric acid purification. In the second, the phosphoric acid was extracted before uranium recovery. The comparison of the two processes is shown in this paper. Experimental work was developed on a laboratory scale to select and optimize the process variables. After the laboratory study, the research of extraction and stripping was continued on a pilot scale in pulsed perforated-plate columns in order to investigate the main operational and process conditions. The first phosphoric acid extraction experiments showed good results using a raffinate sample obtained from the uranium extraction process. It was possible to obtain a high purity phosphoric acid.

Jan 1, 2003

By D. Silva-Galvan, R. D. Morales, S. Gonzáelez-López, A. Romero-Serrano, G. Plascencia-Barrera, F. Chavez-Alcala

This work is focussed on lead decopperising by two techniques: conventional top addition of sulfur and injection of sulfur powder. It is found that the first method proceeds under equilibrium conditions and the second one depends on kinetic considerations. Experiments were carried out using 15 kg lead baths at two temperatures, 340°C and 380°C. The carrying gas used for the injection trials was nitrogen at flow rates of 6.3 and 18.6 L min- 1• The results show that 'decopperising process is more efficient at temperatures close to the melting point of lead for the sulfur top addition process, whereas high temperatures produce better copper removal for the injection of sulfur powder. Besides, the sulfur injection with the higher nitrogen flow rate (18.6 L min-1) produced higher decopperising rates. Thermodynamic and kinetic models are used to simulate this lead refining process.

Jan 1, 2000

By Michael S. Moats, Alexander Derrick

"The Winand Diagram was developed and has been used for decades to illustrate the interaction between polarization, mass transport and inhibition on the resulting structure of a metal electrodeposit. Recently, Adcock et al. criticized the Winand Diagram and developed their own structural diagram based on nucleation and plating overpotentials. Their work was based on zinc electrodeposition using a galvanostatic staircase method. This work explores the nucleation and plating overpotentials for copper electrodeposition using conditions typical for primary electrowinning and the galvanostatic staircase experimental technique. Additionally, the effects of organic additives and plating substrate on these overpotentials are reported.IntroductionThe control of electrodeposited structures is critically important to modem electrometallurgy operations to insure proper quality and efficient energy use. Electrodeposition of base metals for primary recovery (e.g. electrowinning or electrorefining), while similar to plating for decorative or device manufacturing, differs in the need to produce deposits that cover large areas and grow to significant thickness. Thus, controlling nucleation and particularly growth of electrodeposits is critically important for base metal electrometallurgical operations.The control of nucleation and growth on an industrial scale is most influenced by five parameters - current density, temperature, metal concentration, electrolyte agitation and additives. The effects of these parameters on electrodeposition are interrelated. To describe their effects on the type ofelectrodeposits generated and provide practitioners with a useful tool, Winand developed what is known as the Winand Diagram [1-2]. An adapted version of the Winand Diagram is shown in Figure 1.Winand characterized electrodeposits using Fischer's classification [3] and plotted the various deposit types versus inhibition on a vertical axis and the ratio of current density to bulk metal concentration on the horizontal axis. Inhibition intensity is a complex parameter and is still not well understood even though Fischer introduced the term in 1960 [4]. Often, inhibition intensity is simplified to equal the concentration of organic additive at the deposit surface and is related to the inverse of the exchange current density of the metal being deposited. The ratio of current density to bulk metal concentration is used to represent the ratio of crystallization overvoltage to mass transport of the depositing ion. As such i/iL could also be along the horizontal axis, where iL is the limiting current density of the electrodeposition reaction."

Jan 1, 2012

By Alexander I. Raitchenko

"An electroconductive viscous liquid may flow in laminar or turbulent regime under Lorentz-force generated by the intercrossed electric current and magnetic field. When there is a starting flat layer between hard and free boundaries with surface tension the spatial Lorentz-force can create a specific stationary regime of flow: the plane free surface will transform into the wavy one, and the movement in the depth will be not laminar and not turbulent, but this regime will be characterized by organized forms with indications of ""rolling of long cylindrical drops"". Wave-length is determined by the viscosity, the density, the surface tension, the average thickness of layer, and Lorentz-force. ·The limit of wavy regime is determined by most long of wave which is directly proportional to the critical value of specific flow and inversely proportional to the kinetic viscosity. The proper critical value of Reynolds number is determined by the dimensionless combination containing surface tension, density, viscosity, and Lorentz-force. The mentioned dimensio.nless combination in our case is some criterion substituting the known Kapitsa number for case of the thin viscous liquid layers under gravity. Spreading of admixture by mechanism of wavy regime is more rapid than by common diffusion or by laminar flow. The suggested conception can be a contribution into the theoretical basis for elaboration of some specific liquid metals technologies."

Jan 1, 1999

By Dean G. Heitt

"The Rain and SMZ mines from 1987 to 1994 produced a total of22.0 t of gold from a pre-mine reserve of 14.24 Mt of ore grading 2.13 g/t Au.Gold at Rain is hosted within the basal portion of the Mississippian Webb Formation. ·Mineralization is closely tied to the Rain Fault which is interpreted to be the main feeder for the deposit. Multiple collapse and hydrothermal breccia events provided permeability for the mineralizing fluids in the otherwise unreactive siltstones. Major alteration events include: decalcification and dolomitization of the Devils Gate Limestone; and silicification, baritization, argillization and oxidation of the Webb Fm. Six ore types based on XRD and visual rock chip Jogging have been identified: siliceous ore containing >40% quartz and <30% barite; siliceous-baritic ore containing mostly silica but >30% barite; baritic ore containing >40% barite; argillaceous ore containing >40% total clays (including alunite); calcareous ore containing mostly calcite and dolomite; and carbonaceous ore which has significant pyrite and organic carbon. Metallurgical testing of the oxide leach grade ores found that recoveries, on -1.3 cm crushed material, were greater than 70%. Results also found that Rain ore has strong grind dependency due to silica encapsulation.The Rain leach pad was commissioned in 1988, and to date 9.3·Mt at an average grade of0.65 g/t Au have been placed. Life to date recovery, through December 1995, is approximately 51 %, for a total of3.87 t of gold produced. Two major factors have contributed to the low leach recoveries at Rain when compared with the metallurgical testing: 1) More argillaceous ore than expected was placed on the pad especially late in the mine life and 2) approximately 50% of the tons placed were run-of-mine with no agglomeration."

Jan 1, 1997