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By Richard Klimpel

A common problem in mineral processing and chemical engineering is the need to estimate flow rates and/or weight ratios involved with engineering operations for which it is inherently difficult to directly measure stream weights. Simple examples of this situation include stream separators (a classifier operating on a particle flow) and stream mixers (the mixing of new feed and circulating load in a ball mill circuit). Often in these types of operations, it is possible to sample the streams involved to get approximate component analyses (e.g. size distributions of solid streams, chemical composition of chemical streams). In this paper various formulae are developed which can be used to estimate stream flow rates or weight ratios given information on the stream components. The type and level of experimental error present in the stream component analyses does have an important bearing on the numerical values (and reliability) of the weight ratios calculated by the various formulae. A simple but theoretically sound method is shown for selecting appropriate estimation formulae for any given engineering operation. The derived formulae are applied to sets of experimental classification data for illustration purposes.

Jan 1, 1979

By M. B. Mooiman

It has recently been discovered that the pH at which gold can be extracted from cyanide solution with primary, secondary, and tertiary amines can be increased 2 to 5 pH units by the addition of modifiers. Under these circumstances gold can be extracted at pH values from 9 to 11, commensurate with the pH range found in cyanide leach liquors. The selectivity of the amines and amine/modifier combinations for AU (CN)[-2] over other metal -cyanide complexes is presented and discussed. In addition, potential applications for the solvent extraction of gold from cyanide solutions are discussed.

Jan 1, 1983

By S. L. Manske

The Mesquite gold deposit is a recent discovery of Gold Fields Mining Corporation lying 65 kilo- meters northeast of El Centro in Imperial County, California (Figure 1). The deposit is located on the southwestern flank of the Chocolate Mountains and is a bulk-minable, low grade "disseminated" orebody. Although the host rocks of the deposit are part of a regional high-grade metamorphic terrane, abundant brittle fractures, brecciation, and open-space vein fillings indicate that Mesquite mineralization is epithermal. Faulting which postdates the hydrothermal activity has complicated the original geometry of the orebody. Alluvium effectively hides most surface expression of the mineralization, but open-pit mining is now revealing the details of Mesquite geology.

Jan 1, 1987

By Charles B. Escapule

The first successful heap leach of silver ores in the State of Arizona has been under continuous operation since early 1976 at the State of Maine Mine, two miles southwest of Tombstone, Arizona. The silver produced from leaching old mine dumps at this property vas the first in the Tombstone mining district to achieve a 999+ purity. While cyanide leaching of silver and gold ores is a time-proven accepted practice, a relatively new method of treatment called "heap" leaching was employed. Heap leaching is a comparatively inexpensive fast way to recover precious metals from low grade material.

Jan 1, 1981

By John S. Burton

Mineral policy in Canada has been in a state of transition and change over the past several years. 1976 has witnessed some settling of troubled waters and the pattern of the currents of change is becoming more clear. The provinces play a key role in this process and have provided much of the thrust for new initiatives. On the other hand, the federal government in Canada in recent years has taken a much more active interest in mineral affairs than previously and has asserted its powers on a number of key policy questions. Some of the initiatives from the two levels of government in Canada have come into conflict with each other and, thus, contributed materially to a state of affairs that includes change, uncertainty and conflict.

Jan 1, 1976

By W. W. Wen

The objective of this investigation was to study the electrokinetic behavior of oxidized coals to indicate the feasibility of separating oxidized coals from ash materials and pyrite by an mine flotation process. The effects of soluble inorganic electrolyte products from coal oxidation were also examined. The electrokinetic behavior of coals of different rank and degree of oxidation were studied by an electrophoreses technique. Generally, increasing the oxidation increases the negative value of the zeta-potential and decreases the isoelectric point (IEP). Flotation results indicate that the flotation recovery increases with decreasing pH values, and that with ferrous sulfate at pH 6.5 the flotation recovery is optimum while the pyrite was depressed. Comparing the flotation results with the electrokinetic results verified that in the presence of ferrous sulfate, the maximum hydrophobicity of oxidized coal with dodecylamine and frother is near its IEP which is around pH 6.5 to 7.0.

Jan 1, 1976

By A. J. Neale

Much has been published lately about the application of advanced control strategies in the automatic control of autogenous and semi-autogenous grinding circuits. The application of adaptive control algorithms, self-tuning controllers, state estimation, and expert systems has been well documented. While these approaches can be very effective; experience has shown that quite often simply "fixing the fundamentals" can have a significant positive impact on overall grinding circuit performance. This paper will highlight the results of process optimization and process control work by the authors at a variety of autogenous and semi-autogenous installations. A review of one approach for quantifying the mill load/bearing pressure/power relationship is provided. Accurate monitoring of key mill process variables is a necessary prerequisite for both effective process analysis and process control. This paper discusses some of the concerns related to defining steady state operating conditions and the issues related to signal conditioning. The paper concludes with a discussion of an effective application of algorithmic constraint control which incorporates many of these considerations.

Jan 1, 1994

By James A. Commins

Accurate engineering predictions of energy needs for pollution control equipment used in surface mining operations is critically important to sound management selection of control alternatives. This paper will describe a procedure for evaluating two control alternatives with different energy needs. Three steps are involved: an analysis of the pertinent regulations, a determination of the size distribution of the particles being emitted, a calculation of the energy needs and costs of the candidate control systems as a function of these regulations and emission characteristics. The principal air pollutant to be controlled in surface mining operations is particulates, or dust, some of which is already on the material introduced into the primary crusher and other dust which is generated by the various steps in the subsequent processes. The requirement for control stems both from regulations concerning workers at the operating site, and the community surrounding the operations. In order to speak quantitatively about the need for control we will use regulations that pertain in Pennsylvania although it must be borne in mind that such regulations vary according to juristiction.

Jan 1, 1975

By A. Heriba

Cyanide is highly toxic to humans and other organisms. Concentrations of RCN as low as 0.05 ppm can be lethal to fish (Scott and Ingle', 1981). In wet climates and in colder climates where natural degradation is slow, it is becoming mandatory to destroy cyanides in effluents before they can be discharged. The disposal of spent gold ore as tailings from cyanide heap leach processing facilities is a matter of concern to the public, the mining industry, and regulatory agencies. South Dakota mining laws and regulations require that spent ore be neutralized to a suitable level with respect to cyanide before disposal (Durkin, 1990). To safeguard the environment and protect ground-water and surface-water supplies adequately, a reliable test is needed to determine the amount of cyanide in the solid spent ore.

Jan 1, 1993

By D. Kang

The adsorption behavior of silver in ammoniacal solutions on to activated carbon has been studied. The parameters affecting the adsorption of silver on to activated carbon included temperature, agitation speed, concentration of cations and anions as well as that of ammonia. It was found that the adsorption of silver from ammoniacal solutions was dependent upon the initial silver concentration in the solution and other factors. The recovery of silver from ammoniacal solutions was found to be not so effective as the case with gold reported earlier. The adsorption rate was relatively slow overall, despite a rather fast initial adsorption. The apparent activation energy for the adsorption was measured to be 30.2 kJ/mol. It was believed that the kinetics of the silver adsorption on activated carbon was limited by a mixed control mechanism.

Jan 1, 1998

By Dean E. Albon

In the late 1940's and early 50's in southern Illinois, the usual open pit blasting in the coal field consisted of one or two rows of churn drilled vertical holes being shot with instant electric blasting caps. The entire shot detonated at one rime. In southern Indiana and Ohio most mines were drilling horizontal holes and they too were primed with instant EB caps. During the ten years from 1355 through 1965 many changes occurred in drilling and blasting methods. The churn drill in southern Illinois and the horizontal drill in Indiana and Ohio were replaced by the rotary vertical drill. The ammonia dynamites and liquid oxygen explosives were replaced by ANFO. The elctric blasting cap in the hole was replaced by a detonating cord down line and detonating cord trunk lines made the connections between holes and rows of holes. Host open pit mining was in areas far enough from town that the noise and vibration from blasting was, if not ignored, at least tolerated. During the 1960's open pit mining expanded to account for nearly 50% of the coal produced. Mines came closer to town and towns expanded along the highways with suburban homes and mobile homes. The mines began receiving complaints about the noise and vibrations from blasting operations.

Jan 1, 1976

By Y. Luo

Surface subsidence monitoring is the most effective means for investigating the nature of, and developing the techniques for predicting, the surface movement and deformation process. However, because of imperfection in survey equipment and field practices, the surface movement data collected from field survey are not error-free. Also due to lack of proper numerical techniques for computing surface deformation from the measured surface movement data, a relatively large portion of the subsidence data collected could not provide more information other than surface movement. In this paper, the sources and magnitude of errors in the measured surface movements and calculated surface deformation are discussed. Techniques for improving the accuracy of the calculated deformation indices (i.e., slope, strain, and curvature) are developed. The proposed techniques include: (1) proper selection of monument spacing for subsidence monitoring; (2) a data smoothing technique for data pre-processing; and (3) a number of numerical methods and/or procedures for calculating surface deformation indices from the measured surface movement data.

Jan 1, 1992

By Sammie D. Guy

This paper discusses the subject of "Improving Contracting Methods" from the owners point of view, particularly the public. An overview is given of the work of the U.S. National Committee on Tunneling Technology and some apparent results of the implementation of these recommendations or lack thereof. Selected recommendations that are not being implemented are discussed as to the the desirability and the possible impact of their implementation. Impediments to acceptance of the recommendations are identified and solutions proposed. The difference in the flexibility, attitudes and approaches of owners, public, quasi-public and private, toward improving contracting methods are discussed. Particular emphasis is given to the fact that the onus to improve is on the owner because they usually develop the contractual language or at least have the final decision on its content and are or should be an equal party to the contract during its administration.

Jan 1, 1983

By Arthur M. Ribe

In my experience, nothing helps me better to get off to a good start in preparing a paper or a talk than a copious consultation with a comprehensive dictionary. I also feel defining the perimeters of a particular subject is helpful to the listener and reader. Sometimes thus precisely defining even the most common of words is helpful. Our general topic this morning as all of you know is "Transportation of Industrial Minerals." The definition of transportation given by the dictionary which I think is appropriate here is: "Systems and modes of conveyance of persons or goods from place to place." Our preceding panelists have outlined for you the state of the art inso¬far as systems and modes of conveyance from place to place are concerned today via rail, water and motor. My assignment is somewhat different as indicated by my topic, "The Traffic Manager in an Industrial Minerals Operation."

Jan 1, 1969

By Joseph R. Wojcik

Introduction Placer deposits account for one-half to two-thirds of the total gold produced worldwide. As many as 311 t (10 million oz) have been produced from some major districts. Several others are credited with 155 t (5 million oz). All the major districts and many lesser ones have similar characteristics. Consideration of these characteristics offers insight into the origin of gold in the deposit. Knowing the gold deposit's geologic history leads to useful conclusions in exploring for placer deposits and for deposits in consolidated areas. Placer Deposit Characteristics Table 1 lists 17 placer gold districts around the world and their characteristics. These include type and age of, mineralized source rocks, associated intrusive rocks, and age of intermediate sedimentary cycles. Although quartzite or sandstone occurs in the bedrock sequence in four of the 17 districts, slates, phyllites, or schists are present in all of the districts. Additionally, in all but three, the slates are pre-Mesozoic. And, in six of the remaining 14, the slates are Precambrian. Rocks intrusive into the slates are all of intermediate to acidic composition and are emplaced as stocks, dikes, or sills, rather than being batholithic in proportions. Intermediate interceptors have not been recognized in only three of the 17 districts. Data from China and Mongolia are inconclusive as to this characteristic. Black Shale Gold Higher than average gold values are found in modern sedimentary rocks in coarse granulites, conglomerates, sandstones, and gray-wackes. Not so predictably, higher than average gold values also occur in black shales and carbonaceous argillities. Li and Shokena (1974) found that, in the Proterozoic sedimentary and equivalent metamorphic rocks of the Enisei Ridge, carbonaceous and graphitic phyllites and schists were particularly enriched in gold. Korotayeva and Polikarpochkin (1969) reported gold content in organic rocks to be enriched up to 15 times more than the organic free shales and siltstones of the Nerchinsk Zavod region of eastern Transbaikal. Black shales can be gold interceptors as are rocks of the granulite facies. Gold occurs in shales in particulate, free form, in pyrite, adsorbed on clays, and precipitated on carbon. In copper-bearing shales of Poland's Fore-Sudetic monocline, Kucha (1973) reported gold present in organic compounds as well as in silver bearing minerals. Anoshin (1969) found a strong correlation between gold and the pelitic fraction of sediments in certain rocks of the Atlantic Ocean basin. Heavy metal absorption on clays results in agglomeration to the extent that the particles settle with the heavy mineral fraction in enriched strata. Piper and Graef (1974) think that gold in sediments on the flank of the East Pacific rise is of lithogenic origin. Crockett (1973), however, proposed a volcanogenic exhalative origin. A strong correlation between gold and volcanic activity exists in rocks of the Canadian Shield where tuffaceous sediments and porphyries are more frequently enriched in gold than rocks with no volcanic components. Volcanic rocks of intermediate to acidic composition are considered here to be the primary source of gold in black shales. Gold is concentrated in shales as detrital free grains with diameters less than 50 µm (270 mesh), as precipitates, and in pyrite or other sulfide minerals. This is the first step in the history of gold placer deposits. Grain Size Modification Gold, as free grains with diameters less than 50 µm (270 mesh), is too light to be concentrated hydraulically into placer deposits. Some process has increased the average size of the gold grains. Mobilization during regional metamorphism converts most of the gold into particulate grains or entrains it in microfractures in the sulfide minerals. With moderate folding, small, white, vitreous quartz veins develop. As deformation continues, larger, more conspicuous quartz veins are formed. The larger veins are folded and faulted and contain native gold as minute specks and flakes not visi-

Jan 11, 1984

By H. V. S. Tingley, D. Helfant Ghose

"Ten years ago," said a mining industry personnel manager, "we used to wine and dine new mining engineering graduates. Now I can pick and choose among men with 10 years of experience." Comments like that are common throughout the industry today. During the 1970s, the US and Canada did indeed suffer from a severe shortage of mining engineers, especially experienced ones. Moreover, it seemed likely this North American shortage would worsen. Increased production of minerals and coal was pushing demand for mining engineers upwards, and there appeared to be substantial new employment prospects for them in the nascent synfuels industry. The oil majors entering the mining industry were pushing for an increased professionalization of mining management, heralding a trend towards higher intensity in the use of mining engineers. In response to the shortage, mining schools expanded their programs dramatically. By 1982, American schools were churning out more than 600 new mining engineers per year, compared to barely 200 in 1970 (Table 1). The timing of the explosion in the number of mining engineers could not have been worse. The downturn in the economy and the resulting slump in the mining industry coincided almost exactly with peak output of mining engineers. The market for mining engineers shifted from shortage to surplus with startling rapidity. The new crop of engineers, no longer courted by the mining companies, struggled to find any mining jobs. At the same time, experienced mining engineers found themselves thrown into the job market, some for the first time in decades. The current oversupply of mining engineers is assumed to be a temporary phenomenon. As the economy recovers, the demand for mining engineers is expected to pick up at least enough to absorb today's surplus. Not so, according to a recent study by Fenvessy and Schwab, a general management consulting and executive recruiting firm. In 1979, Fenvessy and Schwab was commissioned by a group of major mining companies to conduct a worldwide study of supply and demand for mining engineers to the year 2000*. The study began at the height of the North American shortage. One major objective of the study was "to identify means by which business and educational institutions may cope with and alleviate a future shortage of mining engineering talent." The findings, however, ran directly counter to expectations. The current oversupply will not disappear with economic recovery, the study concluded. In fact, the US and Canada are facing a massive oversupply that will probably last until the end of the century, unless enrollments in schools are reduced. Study Method Fenvessy and Schwab's conclusions are based on supply and demand models for mining engineers that it developed in the course of the study. Specifically, predictions for the supply of mining engineers are based on a survey of the 54 mining schools that account for about 90% of the world's annual output of mining engineering graduates. This survey asked for data on historical and projected number of graduates, obstacles to further expansion, changing trends in the use of mining engineers, and graduate career patterns. Fenvessy and Schwab developed three mining engineering supply scenarios from the survey data. The high case, considered unlikely for most of the industrialized world, is based on a continuation of the 1970's soaring growth rates. The middle case was established from the mining schools' own estimates of future growth in the number of graduating mining engineers. Finally, a "low growth" case for the US and Canada assumed that the number of graduating engineers will remain at current levels. Mining engineering demand was forecast using a complex model based on the demand for 50 major minerals. Formulas were

Jan 9, 1983

By A. T. Yu

Two major events highlight recent developments in US ore and coal ports: completion of the last series of modern taconite pellet transshipment facilities on the Great Lakes; and modernization and construction of coal ports, particularly on the East and Gulf Coasts. The New Taconite Transportation System To reduce raw material transportation costs, a fleet of new generation high-capacity 304-m (1,000-ft) self-unloading vessels were built to carry iron ore pellets from the Minnesota-Michigan iron ranges to the steel plants on the lower Great Lakes. Existing port facilities had to be modernized, revised, or completely rebuilt to accommodate these large vessels. Some of these were Burlington Northern's Allouez, WI, loading dock; Duluth, Missabe & Iron Range Railway Co.'s Two Harbors, MN, facility; Republic Steel's Lorain, OH, facility; and Chessie's Toledo, OH, dock. Allouez and Two Harbors receive taconite pellets from unit trains and load them onto large vessels either after dumping or via a large stockpile and reclaim system. The Lorain facility receives iron ore pellets from self-unloading vessels' discharge boom conveyor and reloads the pellets into rail cars or small vessels destined to inland steel mills. The Toledo facility receives Armco pellets from vessels, stockpiles them through the winter, and reloads into unit trains destined for Armco's mills along Chessie's rail tracks. Burlington Northern's $75-million Allouez pellet dock, completed in June 1977, was built to receive pellets produced by Hibbing Taconite Co. and National Pellet Plant in Minnesota, stockpile them through the winter when the lakes are frozen, and load them into 304-m (1,000-ft) vessels in the shipping season. As much as 10 Mt (11 million st) of pellets may be stockpiled within the loop track. A 6-km (4-mile) long conveyor system connects the stockpile area and the dock. Thirty-six new concrete silos were built on the dock to house 2 kt (2,000 st) each of pellets before shiploading. The $35.5-million expansion of the Two Harbors transshipment facilities began shiploading in July 1978 after ground breaking in Aug. 1974. Particularly noteworthy is the first application of the Orboom system-a breakthrough in technology for the modernization of the century-old pocket docks on the Great Lakes to accommodate the new generation of super vessels. The pocket-type loading dock has been a standard on the lakes for nearly a hundred years. Bottom-dump rail cars fill the ore pockets on top of a finger pier. Gravity chutes matching standardized ore ship hatch spacings are lowered to fill the holds of a 20.3-kt (20,000-dwt) ship. The construction is simple and the loading swift. In spite of advances in technology elsewhere, most of these docks continue to serve the iron ore and coal trade in the same manner they did in the 19th century. Although performance of the pocket docks on small vessels remains outstanding, the new 304-m (1,000-ft) vessels are beyond the reach of the old docks. After extensive development, the Orboom system (Patent No. 4,065,002) for pocket docks was successfully developed. The heart of the Orboom system is the retractable shuttle loading arm which loads the wide beam vessels. The Orboom shuttles are fed by existing pockets of the dock that, in turn, are charged by a tripper conveyor along the length of the dock. The Two Harbors shiploading system is supported by a 0.9 Mt (1 million st) storage-reclaim network. Unit trains are bottom dumped. Taconite pellets are stacked and reclaimed by bucket wheel reclaiming systems. Lower Lakes New Ore Ports At the lower Great Lakes receiv-

Jan 10, 1982

Disposal of solid and liquid wastes from mining and milling operations has become a focus of attention in recent years. Consequently, the geotechnical engineer is more frequently associated with design of disposal facilities. Jack Wulff, a representative of one consulting firm with experience in this field, talks with ME about the geotechnical engineer's contribution. Mr. Wulff, mine and mill waste disposal today is receiving more attention-and many more dollars-than in the past. Regulatory agencies have promulgated demanding requirements concerning mill waste (especially uranium mill waste) and specialist consultants are frequently being called in to design disposal systems. What can the experienced geotechnical engineer add to the development of waste disposal facilities? It's true that geotechnical engineers have recently become more visible in the minerals sector, but we've been around mining for a long time-as foundation engineers for mills and mine support buildings, and for geotechnical aspects of open pits, pipelines, railroads, roads, and so forth. We've also designed water supply dams, which could be considered recursors of tailings dams and other forms of disposal systems. Let me show by example what geotechnical engineering can contribute to waste disposal facility design. I recently was asked to look at several small wastewater impoundments which had failed. The design of the earth embankments appeared, at first glance, to be rather conservative. They were only about 3.4 m high, the slopes were 3 to 1 (horizontal to vertical), with about 24 m of bottom contact with the earth foundation. But there had been three episodes of dike failure in a few months, all upon initial filling. The problem was the nature of some material in the foundation that was also used as structural fill-a dispersive clay that readily deflocculated and eroded on contact with water, especially with seeping or flowing water. The design did not include the defensive measures required to use such materials confidently in water retention structures. Apparently, the designer did not recognize the potential problem posed by the unusual soil characteristics. That's the sort of engineering information fundamental to geotechnical engineering, but not necessarily a part of the civil, structural, or mining engineer's professional training or experience. This difference in expertise is not simply a matter of factual knowledge-it also affects the design process. The structural engineer can design a structure to fit the client's functional needs and can specify the materials (grade of steel, PVC, concrete, etc.) to meet the demands of the design. The geotechnical engineer's design process is somewhat different, since we work with natural materials, not man-made materials produced according to specification. We first have to establish what kinds of materials are available (usually directly from the chosen site, since importation of materials becomes expensive). Then we determine the engineering properties and characteristics and, finally, design the structure to fulfill the client's requirements within parameters dictated by available materials. In brief, the geotechnical engineer works with naturally-evolved, not man-made, materials and uses design techniques developed to accommodate that fact. Because no two sites are exactly alike in configuration, structural (geologic) characteristics, or available materials, there will be unique design and judgmental questions to be resolved on virtually every project. You said that water retention dams could be considered the precursors of tailings dams-you probably had a specific technical relationship in mind. There's a very strong carryover of methodology from earth dam design, where the technology developed and where it has become very refined. In designing a tailings impoundment or similar facility, essentially the same procedures of field sampling are involved (with a geotechnical engineer or an engineering geologist directing the program since representative

Jan 7, 1980

By Victor F. Hollister

Introduction Trends of successful discovery technology and psychology emerge from a thoughtful study of various companies' exploration programs. These subjective patterns can be generalized into groups of factors for discussion. Here, for convenience, factors that influence exploration success are separated into management and geologic concerns. Most successful discoveries have a demonstrably favorable management combined with a technically competent geologic input. Both are required. But the management input is decisive. Management factors include the correct definition of management's role; cost of exploration; time needed for exploration; commodity selection; and the fostering of autonomy, creativity, and confidence in the geology department. Geologic factors include imaginative technical competence (field as well as academic), correct development and use of empirical exploration or prospecting models, and dedication. Success comes to those entities that are properly managed and have technological competence. A management team that directs a company's business has been compared to a dynasty. The dynasty lays out policy and follows up with appropriate action. In that management's power is pervasive, the term is appropriate. Management's role is, however, more important. Many examples can be cited where the geologic input was impeccable. But management somehow snatched defeat from the jaws of victory, and the exploration success was turned to a third party's profit. Management Factors Management's role can be broadly generalized to four parts. These are to identify the commodities it seeks, define its part in the exploration process, develop a functioning exploration department, and have the desire to succeed. It must have confidence in its geologists and delegate to them the authority and responsibility they need to operate successfully. Head office management cannot do the thinking for a field staff thousands of kilometers away. There is no substitute for confidence and delegation of authority. Successes came to those who had the freedom to act. Motivation is a management requisite. Management's role is to prevent destructive, internecine political battles within the corporate structure. Most large US mining corporations have well known histories of political strife that have damaged their exploration efforts. Management's role must, above all, include the desire to succeed. There are cases where management has been confronted with a commercial exploration success, but their reaction is to request additional study or exploration. Perhaps the problem of bringing a commercial find into production is beyond their capabilities. But a bona fide discovery sent back for additional work commonly is lost due to that management. The cost of exploration is a factor that management must accept. A variety of studies made during the past 40 years shows the cost per discovery to be $25 million, $38 million, $200 million, or even $290 million. These figures are derived by dividing the total exploration expenditure by the number of discoveries. However, successful management dynasties have a much lower cost per discovery during their management regime. Asarco, from 1948 through 1963, had one of the lowest cost discovery rates in the world. Duval Corp., from 1948 through 1968, had comparably low discovery costs. Placer Development, from 1955, was equally successful. Western Mining in Australia has had one of the longest lived dynasties associated with exploration success. Time is vital in exploration success. Most successful exploration case histories stress sufficient time in project exploration so that the target is well tested. A large target cannot always be adequately evaluated by a few holes (strat or concept testing). Serendipity helps in exploring large targets, but it best operates in a lengthy program. Numerous case histories include pleasant surprises. But these came mostly after the 10th hole. Commodity markets are important factors governing exploration success. Management's decision to explore for a specific commodity can doom its effort if that product suffers from severe oversupply. Unquestionably, progressive copper price increases from 1948 through 1968 helped convert marginal porphyry copper discoveries

Jan 8, 1985

By Carl D. Wood

Traditionally, when one considers the optimization of a flotation circuit, the scope of work focuses on a review of unit process equipment. This usually includes topics such as grinding ball typed, grind size, classifier efficiency, mill liner design, chemical reagent addition rates, alternative chemical reagents, on-line process analysis, and automated control strategy. However, since very few companies can afford the capital expenditure needed to completely automate the processes, the flotation operator remains as a critical link in optimization of the circuit. Therefore, upgrading of operator skills and knowledge through training must be considered as equally as important as unit process review. This paper will review some concepts and approaches to innovative operator training. INTRODUCTION Consider for a moment the fantastic changes that have occurred in process automation at many flotation plants during the last several years. Flowmeters, density gages, and on-stream analyzers now routinely measure process conditions and effect control strategy. These functions had until recently been entrusted to human flotation operators. Now with a little stretching of the imagination it is possible to envision a plant where very little human intervention would be required. However, when one begins to calculate the capital cost required to fully install automatic equipment, it quickly becomes apparent that many parts of flotation plants will continue to require skilled, knowledgeable operators to ensure successful operation. Additionally as these automatic systems are put into place, the operator's duties become increasingly complex. Therefore no flotation plant can be considered optimized without upgrading each operator's skill and knowledge to match the technology utilized. BACKGROUND At Henderson, one of the hardest steps towards the optimization of operators was to realize that present level of operator skill and knowledge was not sufficient. Since Henderson had a track record of producing the highest quality molybdenum concentrate in the world, it was difficult to accept the idea that change was needed, or even possible. This realization came about as Henderson began a program to modernize the cleaner plant circuit. Henderson utilizes a complex cleaner flotation circuit involving multiple stages of flotation, with a counter- current routing of flotation tailings. Since start-up in 1976 Henderson had relied upon next-day laboratory analysis techniques, that provided an after the fact measurement of process. Hour to hour process control was implemented by the operator, the basis for the operators' control decisions was primarily the individual operator's experience and "feel'. Bench marking of current flotation technology indicated that on-stream analysis was a proven state-of-the-art method for improving process control. An Outokumpu Courier 30 analyzer was purchased and installed to provide real-time analysis of critical cleaner plant flows. The analyzer quickly began to provide valuable assay information, allowing the metallurgists to develop specific target values for important flotation variables. However due to the complexity of the circuit, the analyzer information showed that a problem was usually caused when several targeted parameters went out of range simultaneously. This made it difficult for the operator to determine just where to implement the proper corrective action. It became apparent that to take full advantage of the new analyzer information each operator would have to become proficient at understanding the material balance of the entire circuit. TRAINING PLAN CONCEPTS With the goal of giving each operator a working knowledge of a circuit material balance the following concepts were applied to develop a training plan: - Most operators were high school graduates, but had fairly weak mathematical skills, and had very little experience at metallurgical calculations. - The training would have to address a wide range of topics from basic fundamentals to complex material balance. The basic sequence decided upon, was to present a fundamental topic to the entire group, break into small groups to work a “hands on'”case study example of that topic, and design the case study results so that they could be combined to highlight a major portion of the material balance concept.

Jan 1, 1993