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By A. R. Biggart, A. Walters, G. J. E. Kramer

The Owner Procurement Process or OPP is a proven, viable alternative contract delivery method that is potentially applicable to many tunnel projects. Using the OPP, the owner specifies and procures major tunnel construction items such as tunnel boring machines and tunnel linings and provides them to a tunnel excavation contractor in order to manage risk and accelerate project schedule. However, due to industry perceptions regarding potential owner risk, it is seldom considered or is rejected out of hand. In fact, past performance demonstrates that the process significantly minimizes owner, contractor and over-all project risk and mitigates the impact of any claims and differing site conditions. The paper outlines how the process should be structured to achieve schedule, cost, quality and risk management benefits. Potential and perceived disadvantages are discussed and how the process can be structured to mitigate or avoid them. The planned implementation of this process on the tunnels for the Silicon Valley Rapid Transit Project in San Jose, California is discussed.

Jan 1, 2005

By Lawrence E. Mannion

In southwest Wyoming lies buried the world's largest source of natural sodium carbonate, or soda ash. Perhaps a hundred billion tons of trona (sodium sesquicarbonate) are contained in ancient lake beds in the Green River basin'). There the Green River Formation encloses more than 40 extensive beds of trona. At least 25 of these exceed 3 feet (1 meter) in thickness and most of them are more than 300 square miles in extent. Five have been exposed in mines and lie between 800 and 1500 feet below the surface. Others lie at depths of from 400 to 3500 feet. Three companies have underground mines that supply trona to adjacent soda ash plants. These are the FMC Corporation, Allied Chemical Corporation, and Stauffer Chemical Company. A fourth, Texasgulf Corporation, has a mine under development. In 1974, annual soda ash capacity in the Green River area was approximately 4,300,000 tons, which requires the mining of about 7,500,000 tons of trona.

Jan 1, 1975

By Keith Jones, Martin Knights, Timothy Watson

In 1996 a KBR (Brown and Root) led international JV was appointed to design and supervise an underground and surface package. The design of 6 km of tunnels, plus enlargements, deep shafts in glacial and sandstone deposits for the conversion of the existing LEP underground laboratory at CERN, Geneva adjacent to the Jura Mountains/Lake Geneva had to be undertaken in an operational environment and in conjunction with other underground constructions associated with the US$3bn refurbishment.

Jan 1, 2003

By N. S. Tanious

The accuracy of vibrating wire stress meters has been questioned by various users in the mining industry. During an in situ coal pillar study, a laboratory evaluation program was developed to determine whether stress meters could produce reliable measurements in coal. More than $0 stress meters were tested for accuracy, repeatability, effects of setting pressure, and the concept of using a single curve for interpreting the stress-meter data. The testing medium was lucite, a material with a modulus of elasticity very similar to coal. The evaluation demonstrated that the stress meters did provide repeatable measurements, but that accuracy was lacking when the recommended interpretation technique was used. Therefore, a new technique was developed that required all stress meters to be calibrated in the laboratory before use in the field. This new technique reduced the average error to typically less than 10% and, in the worst case, to below 15%.

Jan 1, 1988

By K. Oraee

Excessive emissions of methane from the coal seams can have a serious adverse effect on both safety and productivity of longwall coal faces. Mechanization of coal faces has increased production possibilities to the extent that normal ventilation systems may not be able to ventilate coal face areas in order to lower methane content in the air to within legal limits. Production increases may therefore be prohibited for this reason, especially in gassy seams. Methane drainage from the coal seam by means of long holes and before production starts can act as a useful remedial action. In this paper a two dimensional mathematical model has been produced. The model that is based on finite elements, simulates a methane drainage system where the resultant risk is linked to the coefficient of diffusion, coal permeability, holes pattern and the duration for which the seam is subject to drainage. It is concluded that methane drainage of this type can assist in achieving production increases in many coals seems, especially where high gas content is a virtue of the seam.

Jan 1, 2010

By Dean H. Herrick

The production of crushed stone in the United States has exceeded 1.0 Gtpy since 1987. Eighty percent of the crushed stone produced is used in the aggregate industry, accounting for over half of the quantity of natural aggregate consumed in the United States. Approximately 718 of the crushed stone produced in 1989 was limestone and dolomite followed by granite, traprock, sandstone and quartzite, miscellaneous stone, marble, shell, calcareous marl, volcanic cinder and scoria, and slate in order of descending volume (Table 1). Of the remaining 20% crushed stone produced in the United States and not used as aggregate, 12% is used in the manufacture of cement which is an important construction material. Only 8% of crushed stone is used in specialty products not associated with the construction industry. Therefore, this chapter will concentrate on crushed stone as used in aggregates, with occasional reference to other uses or to chapters which discuss specific nonconstruction uses of crushed stone. Construction aggregates are hard, essentially inert materials suitable for being formed into a stable mass by the addition of cementing or binding materials that produce a concrete by compaction, or by natural weight to produce a road or foundation fill. Aggregates are usually from 80 to 100% of the material volume of the construction masses in which they are used. Conditions necessary for a rock deposit to be developed for construction crushed stone include: Quality-should pass rigid specifications for strength and durability; Quantity-adequate volume of rock is needed to have a production life of at least 10 years, preferably 20 or more years; Market-must have adequate market to support a new crushed stone operation; Transportation-transportation cost must be competitive for the intended market; Environmental-the impacts of mining, processing and transportation of crushed stone on the environment at or surrounding the mine site must be within acceptable limits; Permitability-mining, processing and transportation of crushed stone must usually be permitted by governing agency. The following discussion will touch upon all facets of crushed stone operations from the mineral deposit and its geology to technology, uses, economic factors and end with governmental regulations of mining crushed stone. The sections are not designed to answer all questions, but rather to be an introduction to the crushed stone industry. Where more information is required, The Aggregate Handbook by Barksdale (1991) is recommended as the best general source.

Jan 1, 1994

By A. M. Stone

INTRODUCTION In ore beneficiation one of the simplest methods of mineral concentration is hand picking to remove either the ore or the waste material from a moving table or conveyor belt. Ore Sorting Equipment may be defined as equipment for mechanized picking. This type of equipment has been used successfully over the past thirty years or so to beneficiate ores of various types in particle mesh sizes between 1mm and 200mm.. at throughputs of up to 150 tonnes per hour. In general for ore sorting to be a consideration the ore and the waste material must be well liberated in the feed to the sorter (that is into practically discrete particles of ore and waste). The larger the liberation size the more likely sorting is to be cost effective. Correct selection of ore sorting equipment is most important and often special machine features are developed for an individual application. Sorter performance can be best determined by extensive testwork of representative ore at design tonnage on prototype or preferably on production model sorting machines. ADVANTAGES OF SORTING ORE The four main advantages of sorting ore are: Reduced milling cost. Reduced processing cost. Higher overall recovery. Reduced transportation costs. Reduced Milling Cost With sorters installed the milling plant following the sorter is generally smaller and hence less costly to install and operate as it only has to handle the sorter product. However this benefit is somewhat offset by the increased cost of the screening and washing plant prior to the sorter and the cost of the sorting plant itself. Reduced Processing Cost As there is less material of higher grade presented to the concentrating plant following the sorter, this plant will generally be smaller and less costly to construct and operate than a plant treating the total quantity of material. Higher Overall Recovery The economic recovery is often misunderstood by plant operators when evaluating the advantages of sorters

Jan 1, 1986

By A. Ballester, F. Gonzalez, M. L. Blázquez

Pyrometallurgical process are usually used to recover valuable metals from metal sulphide concentrates. However, their use is diminishing as the cost of energy rises and pollution controls become strictes. An alternative method of treatment sulphides could be bacterial leaching due its simplicity and negligible contamination (1-2). This process is presently used commercially to re cover metals such as Cu and U from low grade ore concentrates. In spite of numerous researchs during recent years (3-5) there exists very little kinetic data concerning the speed of bioleaching process. The kinetic analysis of bacterial activity is related with the metabolism and growth of microox ganisms . This fundamental information permits ma- king the best utilization of bacterial oxidation and to suggest techniques which might increase the production of the products desired. However, bio- kinetic models are especially complicated due to the existence of many metabolic routes and parallel reactions which are important for the life of the bacteria. Microbiological oxidation of a mineral substrate is influenced by its own inicial concentration: This influence can be determined by means of a kinetic study. In a medium with sufficient concentration of nutrients (nitrogen, phosphorous and potassium) and an adequate supply of 0, and CO2, as the only & L source of carbon for the biochemical synthesis, the substrate concentration would remain the only limitation in the rate of leaching. In this case the Michaelis-Menten model could be applied (6). The model is based on an association of the enzyme (El with the substrate (S) with consequent decomposition of the latter into enzyme and products [ ] The rate of dissolution is defined by the equation : [ ] Were V is the rate of metal extraction (mg 1-1 1 h-1 ) ; S is the pulp density Mn is the maximum rate for metal extraction (mg 1-1 h-1) and K is the constant of Michaelis (concentration of substrate that yields Vm/2). This method is applicable only when the rate of bacterial growth is similar to the rate of metal extraction. It would therefore be sufficient to control the concentration of metal in the medium over the period of time. In the present work a systematic study of the kinetics of ZnS and CuFeS bioleaching in sphalerite and complex ore concengrates was carried out. The rate of dissolution of the Zn and Cu as function of the pulp density and temperature was determined. However, most oxidations of sulphide dissolution take place with a very slow kinetic; but, this can be accelerated considerably by the addition to the solution of suitable catalytic ions, as was Suggested many years ago by Bjorling (7). Such ions can exercise an important influence on the rate of the oxidation-reduction reactions, both homogenous and heterogenous, which take place during the leaching of sulphides; they also affect the nature of the reaction products. The action of catalytic ions has been fully developed in aqueous systems, but in the absence of bacteria (8 - 11) although the actual machanisms is not totally known. The mechanisms proposed as hypotheses in the literature (8) indicate that, in the case of ZnS, the catalyst ion act through an electrochemical mechanism according to the reactions: [ ]

Jan 1, 1989

By Brij M. Moudgil, Shoulian Zhu, J. L. Pinault

A new technique, prompt neutron activation probe (PNAP), for analyzing phosphate rock slurry in-situ was evaluated both in the laboratory and at the plant. The technique yielded a high precision in the analysis of Ca, Si and H using 252Cf source. Low accuracy of the direct measurement of P using 241Am/Be in the laboratory tests was attributed to the interference of rare earth elements present in the samples, particularly Gadolinium. No significant effect of variables such as solids loading, particle size distribution, and flotation reagents was observed on the probe performance. The probe can detect the compositional changes of the feed, tailings and the concentrate streams in the plant.

Jan 1, 1993

By V. O. Tenorio, K. W. B. Requist

As the mining industry begins efforts to examine the feasibility of extraterrestrial resource utilization, the extraction and processing of icy regolith containing water and other volatile materials will be the initial focus for future expansion of capabilities. Pure water is essential for human consumption, and a source of oxygen and hydrogen. The latter, along with the volatile materials, lend themselves to the creation of fuels that may be used for further space exploration at distances not currently feasible. For any extraterrestrial scoping project, the transport of materials to geoscientists remains virtually impossible. Therefore, analysis must be done in-situ, possibly millions of miles away from the nearest human. To address the need for geologic resource estimation in the absence of geoscientists, an infrared framework has been developed for the analysis of water ice content in simulants of permanently shaded lunar regolith. This framework relies on a convolutional neural network model for the rapid analysis of percent water ice content in samples, at which point standard geostatistical methods may be employed.

Feb 1, 2023

By Siegfried Zell

INTRODUCTION Denmark is a small country with a population of about 5.5 million in the north of Europe. A substantial part of Denmark consists of islands, and the Danes have been familiar with ferry links between their islands for ages. However, their wish for fixed links has resulted in the con¬struction of bridges between most of Denmark's islands in this century. (Fig. 1) A fixed link across the Store Belt or Great Belt, Denmark's most important waterway bet¬ween the island of Fyn and main island of Sjaelland, on which the capital of Copenhagen is situated, has remained to be constructed hitherto. In 1987, the Danish government decided that the Great Belt should be crossed by a fixed link, incorporating a two-track railway line and four-lane motorway. The Storebaelt Forbindelsen AS, a joint stock company in the sole ownership of the Dan¬ish state, has been established for the purpose of planning, constructing and operating the Great Belt Link. The company will refinance the construction project by charging toll to the motorway users and fees to the state railway. Here it should be mentioned that Denmark and Sweden are about to jointly realize the fixed rail and road link across the Øresund or The Sound between Denmark and Sweden on the basis of the realization model of the Great Belt link. At present, the project is at the com¬petitive tendering or contract awarding stage. In the near future, also the third fixed link of comparable extent, that is the crossing of the Fehmarn Belt between Denmark and Germany, will go into the decisive projecting stage prob¬ably in conformity with the aforementioned pattern. Going back to the Great Belt, it should be noted that this fixed link involves three exten¬sive sections and has been under construction since December 1988.

Jan 1, 1995

By Mark R. Stanton

Geochemical and mineralogical analyses of 46 samples from six drill cores in the Mayday mine pile near Silverton, Colorado, demonstrate wide variability in trace metal contents with spatial location. This variability results from the original geochemical composition of mined rocks, mixing of ore and non- ore rocks during emplacement of the pile, and weathering since rocks were placed in the pile. Weathering reactions are controlled by factors such as pile thickness (depth), water availability, microbial activity, and mineral dissolution and formation kinetics. These factors result in variable redistributions of trace metals from primary (ore) to secondary (weathering products) minerals within each core.

Jan 1, 2000

By PETER ROBINSON, KEVIN BARBER, OLIVER WHATNALL

The investigation and uptake of filtered tailings continues to grow around the world, but cost and scalability are deterrents for mining companies. Filtration technology that is currently in use is unable to meet the needs of many operations and projects that would otherwise adopt filtered tailings. For tailings to reach the desired moisture content for dry stacking, the majority of processes require pressure filtration, with significant upfront and ongoing maintenance costs. Given the comparative lower costs associated with low-pressure Viper vacuum belt filtration, this technology has the potential to alleviate dependency on high-pressure applications and make efficient dewatering and handling of tailings a more economic and sustainable solution.

By Igor V. Nazarov

INTRODUCTION Tens of deposits in' coal basins of Western and Eastern Siberia are being open-mined with the technology of overburden rehandling into the mined out space of pits by excavators - draglines. This technology is preferred due to the high productive Russian equipment, comparatively low cost, and relatively small Influence exerted on the environment. The basic tendency of the last decades is the aspiration for enlarging the sphere of the' technology application for development of gentle and steeply dipping seams with the use of blast destruction of overburden and with combined winning of loose alluviums and rock partings. Complex technological schemes with multiple rehandling are widely used. In addition to it, stripping workings, intermediate storage of mineral resources, placing of transport dumps, and engineering construction can be realized with the use of draglines. More than ten of dragline faces are simultaneously exploited in some pits, and the rehandling coefficient ranks from 0.1 to 8. Here, conditions of winning and placing (position of a face and existing dump) are varying in space and time; this leads to the necessity of reconsidering the order for conduction of works (schemes) within the current designing. By now, in order to this, it is required to realize complex engineering calculations by graph-analytical methods and definite experience. The need is available for automatization of this process by creation of the corresponding software. The software is to: • Orient on the active pits and use information on the existing geology, equipment, and situation in mine. • Calculate the existing schemes more operative and on a higher qualitative level to model their development in a pit space with parameter optimization. • Predict situations demanding to change the existing technology for mining operations and recommend optimal technological schemes. METHODOLOGICAL FOUNDATIONS FOR MODELING The problem is not new, it has more than fifty year-old history of creating mathematical models algorithms, and programs in Russia, Ukraine, USA, Canada. Australia and other countries with the developed mining branch. Conventionally, all population of programs can be divided into three groups depending on goal and interval of prediction: • Long-term programs used in designing and intended for substantiation of the nine capacity, selection of mining system, establishment of limits for applying the technology of overburden rehandling. Mid-term programs used in current planning for calculation of technological schemes and certificates of face in active mines.INTRODUCTION Tens of deposits in' coal basins of Western and Eastern Siberia are being open-mined with the technology of overburden rehandling into the mined out space of pits by excavators - draglines. This technology is preferred due to the high productive Russian equipment, comparatively low cost, and relatively small Influence exerted on the environment. The basic tendency of the last decades is the aspiration for enlarging the sphere of the' technology application for development of gentle and steeply dipping seams with the use of blast destruction of overburden and with combined winning of loose alluviums and rock partings. Complex technological schemes with multiple rehandling are widely used. In addition to it, stripping workings, intermediate storage of mineral resources, placing of transport dumps, and engineering construction can be realized with the use of draglines. More than ten of dragline faces are simultaneously exploited in some pits, and the rehandling coefficient ranks from 0.1 to 8. Here, conditions of winning and placing (position of a face and existing dump) are varying in space and time; this leads to the necessity of reconsidering the order for conduction of works (schemes) within the current designing. By now, in order to this, it is required to realize complex engineering calculations by graph-analytical methods and definite experience. The need is available for automatization of this process by creation of the corresponding software. The software is to: • Orient on the active pits and use information on the existing geology, equipment, and situation in mine. • Calculate the existing schemes more operative and on a higher qualitative level to model their development in a pit space with parameter optimization. • Predict situations demanding to change the existing technology for mining operations and recommend optimal technological schemes. METHODOLOGICAL FOUNDATIONS FOR MODELING The problem is not new, it has more than fifty year-old history of creating mathematical models algorithms, and programs in Russia, Ukraine, USA, Canada. Australia and other countries with the developed mining branch. Conventionally, all population of programs can be divided into three groups depending on goal and interval of prediction: • Long-term programs used in designing and intended for substantiation of the nine capacity, selection of mining system, establishment of limits for applying the technology of overburden rehandling. • Mid-term programs used in current planning for calculation of technological schemes and certificates of face in active mines.

Jan 1, 2002

By David Martin Menne

In a small tank, slurry is passed through the high shear impeller zone with small time intervals, and a large proportion is regularly exposed to air at the surface, and at relatively high shear rates. This accounts for significant differences in the performance of large and small tanks. It is preferable to derive data where possible directly from an operating plant rather than applying data generated in small tanks where allowances must be estimated for the above differences [and where slurry aging and often substantial cooling compared to hot freshly milled ore further distorts results]. Various measurements have shown that many gold slurries can suffer extreme variability, as streamers of bypassing material or boules of hold-up periodically condstitute the instantaneous discharge from a tank - the relatively high Yield stress of slurries [around 1 to 10 Pa] causes very incomplete homogenization of slurry in any tank, the worse the larger the tank and the more viscous the slurry. To provide a background for this subject, this monograph presents leach and adsorption models based on the fundamental physics and chemistry of these processes, and includes quantitative discussions of factors which can lead to deviations on scale-up. The Throughflow model which avoids the need for such alowances is then presented, as well as a Computer Programme applying this model, and which allows direct calculation of the effects of:

Jan 1, 1995

By Gerald H. Luttrell, Roe-Hoan Yoon

Flotation columns are becoming increasingly popular due to their ability to improve selectivity and to reduce operating costs. Unfortunately, these advantages are not often realized because of poor operating practices and difficulties associated with design and maintenance. This article provides guidelines for the operation and design of columns. The discussion will focus on designing proper wash water systems for improved selectivity, maximizing throughput by increasing the bubble surface area rate, and minimizing operating and maintenance costs. It is suggested that the design of the air sparging system is the most critical element in column flotation.

Jan 1, 1993

By Robert H. Merrill

INTRODUCTION In most cases, the design of an underground mine is based upon the premise that the ground either will cave or will be stable. This chapter concerns the design of a mine in ground that will cave readily or with some as¬sistance, such as by long-hole drilling and blasting. Some of the more widely used caving systems of mining are panel caving, block caving, sublevel caving, and large pillar recovery. Some of the less widely used systems are glory-hole, top slicing, and induction caving. Al¬though the common practice of pillar robbing is not usually considered to be a caving system, this subject will be treated as a part of this chapter. BASICS OF CAVING Caving systems are most successful in ground that will cave in sizes that will flow through openings and grizzlies, and will easily load in cars or on belts for haul¬age. The ground most likely to cave well is highly frac¬tured and contains breaks, flaws, or other discontinui¬ties that form planes of weakness. Also, caving action can be greatly enhanced if the host rock itself is low in compressive, shear, and tensile strength. Ideally, a cav¬ing system of mining is best employed when the criteria for caving is a feature of the ore body and the develop¬ment drifts, haulageways, and drawpoints can be mined in a highly competent rock beneath the mineralized zone. However, the development is often in the same, or similar, fractured rock and the openings require sub¬stantial artificial support to assure stability. Several clues can be assembled to identify potential caving ground; however, for borderline cases, no sure method has been devised to date. The diamond-drill cores taken for exploration can provide an excellent clue provided drilling is performed carefully by experienced drillers. For example, if the ground is cored in such a manner that the breaks in the core are caused more by failure of the rock than by whipping core barrels, plugged drill bits, or other drilling causes, and the intact core lengths are consistently long [say, 0.6 to 3 m (2 to 10 ft) of unbroken core], there is little reason to believe the ground will cave without considerable as¬sistance. This is especially true for rocks with compres¬sive strengths above 34.5 MPa (5000 psi) and tensile strengths above 2.1 MPa (300 psi). On the other hand, if core recovery is low (below 80%) and the recovered ore is broken in small pieces and the breaks are along obvious weaknesses in the rock, the chances are excel¬lent that the ground will cave. This is true even when the rock between the defects has high compressive and tensile strength. Another clue has already been mentioned, that is, the measurement of the physical properties of the rock and the natural planes of weakness or defects in the rock. The planes of weakness in the rock can often be detected from outcrops, cores, or other exposures of the rock under consideration. Some rock types are known to be strong and will sustain large, unsupported open¬ings and would be difficult to cave intentionally. Yet the same rock type can also contain unbonded or weak planes of weakness or fractures, and in these locations the rock would undoubtedly cave with little assistance. Therefore, although the inherent strength of the rock is a factor in caving, the natural defects in the rock are more often the deciding factor. DESIGN CONCEPTS For the most part, the design of openings for caving ground is a problem of the interaction of openings over a relatively large area of the mine. To illustrate, Fig. 1 is a simplified section of a series of openings along the grizzly level or draw level of a block caving or panel caving development, and above this opening is a simpli¬fied section of a room-and-pillar arrangement on the undercut level. At this stage of the development, the stresses around the openings on the grizzly level are only moderately influenced by the openings on the undercut level and vice versa. Therefore, the stresses around the openings are approximated by the stresses around single or multiple openings in rock, the values of which are de¬scribed in the literature (Obert, Duvall, and Merrill, 1960; Obert and Duvall, 1967). Once the pillars on the undercut level are blasted (Fig. 2), the situation changes abruptly. The undercut opening (prior to caving) now can be approximated as an ovaloidal opening above the grizzly drifts and this opening tends to shield the vertical stress field. As the caved stage is drawn the stope approximates a much larger rectangular or square opening filled with rock, and if the rock is not sustaining a major portion of the stress field, this opening can be considered (for en¬gineering purposes) to be empty and the stresses that interact between the larger and the smaller openings take on a totally new perspective (see Fig. 3). Next, let the material cave to the surface, and let the caving ma¬terial sustain some stress, but much less than if the ma¬terial were intact. This condition is similar to a soft inclusion in a rigid body and has been treated in the literature (for example, Donnell, 1941). At this point in time, the grizzly drifts are subjected to the stress con-

Jan 1, 1982

By Mark Godfrey, Wickus Slabbert, Debra Miller, Dave Dew

Sao Bento Mlnerai;;ao Mine (SBM), located 100 kms northwest of Belo Horlzante, Brazil, was commissioned In 1987t1l to produce 185 kg per month of gold from 240 tpd of refractory sulphide flotation concentrate. The concentrate Is processed by a Sherrill Gordon design pressure oxidation circuit followed by conventional CIL gold recovery process (Flgur .. J). The original plant design foresaw expansion to 480 tpd, and In this regard the acidic effluent neutralisation, CIL and carbon circuits were designed for future expansion to treat the higher tonnage. The pressure oxidation section was sized for 240 tpd with the Intention to double the Installed plant equipment to provide 480 tpd capacity when required. This decision was based In part on the novelty of pressure oxidation to treat refractory sulphide concentrates in 1984 when the process design was finalised. General Mining, Metals & Minerals (Pty) Ltd (GENMIN), has been actively Involved for the past 30 years in the development of bacterial process for the oxidation of refractory gold concentrates; the results of this development program have provided the registered process BIOx®. The successful Implementation of BIOx® technology for treatment of refractory gold concentrates at GENMIN's Fairview Mine In October 1986t2l, as well as the substantial experience accumulated in laboratory and pilot testing of some 40 other sulphide concentrates, Justified reconsideration of the oxidation process best suited to provide the Incremental sulphide oxidation capacity planned for SBM.

Jan 1, 1992

By Stanley Bunk

The fluidized bed was invented by Fritz Winkler of Germany in 1921. The first application in the U.S. was in the development of the fluidized bed catalytic cracking of petroleum in 1942. Today, fluid bed cracking reactors are an integral part of every oil refinery. When fluid bed technology was first considered for applications outside the petroleum industry it was recognized to have uniform temperature, close control of the gaseous atmosphere and excellent mixing between solids and gases. Roasting of sulfide ores and concentrates was an obvious match. The first application was a single stage roaster for gold refining in 1947. There have been over four hundred commercial fluid bed roasters built and operated successfully in the four decades since the fluid bed was invented. There are three general categories of roasting applications. The largest number of roasters fall into the dead roasting category which includes gold ore roasters. The other categories are sulfating roasters and partial roasters (Reference 1).

Jan 1, 1990

By R. A. Pyper, J. L. Hendrix

Laboratory leaching experiments were conducted to ascertain the effectiveness of acidic solutions of thiourea, CS(NH2)2, for dissolving gold from finely disseminated gold ores. The ore tested was from the Chipmunk ore body of the Northumberland mining district in Nye County, Nevada, USA. Extractions of up to 90% were attained from the ore. Extraction was shown to be dependent on thiourea concentration, ferric sulfate oxidant concentration, acid concentration, and leaching time. Optimum conditions were an ambient temperature leach near pH 1.0 utilizing 100 to 200 kg/ton thiourea and 50 kg/ton ferric sulfate for 8 to 24 hours.

Jan 1, 1981