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By J. C. Irvine

Meramec Mining Company, a joint venture by Bethlehem Steel Corporation and St. Joe Minerals Corporation, is engaged in the mining, concentrating, and pelletizing of iron ore from the Pea Ridge Mine located near Sullivan, Missouri, about 70 miles southwest of St. Louis. The orebody was delineated in the mid-1950's by St. Joe during an exploration program to discover new lead orebodies. An airborne magnetometer survey which was run by the U. S. Geological Survey, the Missouri Geological Survey, and several min¬ing companies was published in 1950 and showed an anomaly in the Pea Ridge area. Test holes drilled in 1953 and 1954 revealed the presence of a large orebody of probable commercial significance; additional drilling in 1956 and 1957 provided confirmation of this. Meramec Mining Company was incorporated in 1957 and shaft sinking began in the latter part of that year. The Pea Ridge orebody lies under about 1300 feet of sediments. It is tabular, about 2600 feet long and up to 600 feet thick, and lies in an approximate east-west delineation. The orebody dips about 800S and is of unknown depth. The ore is primarily high grade magnetite with smaller zones of specular hematite, The Pre-cambrian wall rock is rhyolite porphyry. The mine is serviced through two concrete-lined shafts, 19 feet 1 inch in diameter and 2500 feet deep. No. 1 shaft, equipped with an "A" type head-

Jan 1, 1972

By John M. Smith

Kaolin is an important industrial mineral because of its unique properties and low cost. Strictly defined, kaolin is the name given to a group of hydrous aluminum silicates of which kaolinite is the most common mineral (1). Through common usage the mineral, kaolinite, is called "kaolin" or "china clay". In 1972 over 4, 000, 000 tons of kaolin will be beneficiated and shipped by domestic producers. By far the largest user of kaolin is the paper industry which utilizes approximately 65 to 70 per cent of the total production. Kaolin is used in paper as a filler in the interstices of the sheet and as a coating to impart smoothness, gloss, brightness, and printability to the paper. The rubber industry is also a large user of kaolin where it is used as a filler because it adds strength, abrasion resistance, and rigidity to both natural and synthetic rubber goods. Kaolin is used as an extender in paints because it is chemically inert, has a high covering power, gives desirable flow properties, and is low in cost. In ceramics, kaolin is used in whitewares, tile, insulators, refractories, and in some face brick where a white color is desired. Kaolin is also used extensively in plastics as a filler in thermosetting and thermoplastic mixes to give smoother surfaces, a more attractive finish, good dimensional stability, and resistance to chemical attack. Many other process industries use kaolin as a filler, suspending medium, or for color improvement.

Jan 1, 1972

By W. S. Hannan

History Leaching of sulfide ore was first attempted by the Phelps Dodge Corporation about 1900 at Bisbee, Arizona, when Dr. James Douglas conducted experiments in an attempt to apply the leaching techniques then in use at Rio Tinto, Spain. Although this initital attempt was unsuccessful, research work was continued which culminated in successful leaching operations at Tyrone, New Mexico, in 1917 and at Bisbee beginning in 1920. Leaching has continued intermittently since that date, with material from the Lavender Pit being leached today. The Lavender Pit Leach Dump Stripping for the Lavender Pit was started in 1951, with mining operations on stream in 1954 and continuing to the present. All material removed from the pit has been classified as waste, leach material, milling ore, or direct smelting ore, depending upon grade and degree of oxidation. Lavender Pit leach material has been stockpiled in a single dump, called No. 7 Dump. This dump covers an area of approximately 135 acres and average about 300 feet in height. The dump has been deposited over a period of 20 years by truck haulage and contains several layers, each of which has a permeable boulder layer at the bottom and a compacted layer at the top. Leaching of Lavender Pit material was started in 1956 and has proceeded simultaneously with dump construction. Former leach pond areas and haulage surfaces have been ripped with D-9 tractors before deposition of succeeding layers of ore.

Jan 1, 1972

By Ernest Y. Baafi

The technique of linear kriging as a grade estimation method of mining blocks is reasonably established in the mining industry. Because of the nonbias condition imposed in kriging which requires that the kriging weights (?i) add up to one, negative weights are sometimes used in kriging. The use of negative weights is not justifiable from the practical standpoint. Also, negative block grades can be obtained in some extreme situations which makes no practical sense. To guarantee non-negative weights an additional constraint is required in the kriging system of equations. Unfortunately, the nonnegative weight constraint results in a set of non- linear system of equations. In this paper, a derivation of the resulting set of nonlinear equations is presented and a numerical algorithm is developed for the solution of the equations. Because the algorithm developed does not remove negative weights arbitrarily, optimal nonnegative weights are always guaranteed. Results obtained using the developed algorithm were compared with those using the standard linear kriging, in terms of computer time and the estimation results. Both the computer time and the kriging variance were found to be higher with nonnegative constraint, as expected. However, some systematic pattern was observed in the kriged values (i.e., over or under estimation) with or without the nonnegative constraint. The study also demonstrated when one should generally expect negative kriging weights in practice, and what practical impact the negative weights can have on the kriging estimates.

Jan 1, 1984

By John E. Newby

Washington?s King County is constructing a new regional wastewater treatment facility, called Brightwater, in response to growth in the greater Seattle region. Planning conducted in the late 1950s identified the need for two regional treatment facilities. Constructed in the 1960s, these plants have served the region well. However, an eventual need for a third facility was also recognized. The Brightwater project implements the final phases of the long-term plan. The project includes a new treatment plant and an extensive conveyance system. When completed in 2010, the Brightwater facilities will treat sanitary sewer flows from growing populations living in northern King County and southern Snohomish County. The new system will fulfill commitments to provide wastewater services to local jurisdictions and sewer service providers in the King County Service Area. It will also provide more flexibility in the operation of the King County regional wastewater system. The Brightwater wastewater treatment plant will provide secondary treatment capacity using membrane bioractor technology in 2010 for 36 million gallons per day (mgd), with anticipated expansion in 2040 to 54 mgd, using membrane bioreactor technology. These capacities are for average wet-weather flows. The plant will also accommodate peak hourly flows of 130 mgd by 2010 and 170 mgd by 2040. The Brightwater Conveyance System consists of more than 8.1 km (13 miles) of tunneled influent and effluent conveyance lines, five tunnel portals/shafts, microtunneled influent and outfall connec-

Jan 1, 2007

By W. W. Harvey

The work to be described was part of an exploratory research program directed toward identifying potentially useful but little known reactions in extractive metallurgy. In particular, the major copper sulfide minerals, as a group, have long been considered insoluble in nonoxidizing acids (e.g. Forward and Barren, 1J60; Parsons and Ingraham, 1970; Peters et al. 1972). This generalization was considered to include nonoxidizing conditions in warm aqueous MC1 solutions (Ingraham et al. 1972) and, indeed, was consistent with our own chemical and mineralogical experience. On the other hand, under hydrothermal conditions, copper and sulfide species are carried in solution and deposited as sulfides in mineralized veins. The question that poses itself is: what are the mildest conditions of temperature and fluid composition under which commercially important copper sulfide minerals can be solubilized in the absence of an oxidizing agent? A reference to H2S formation during oxygen-sulfuric acid pressure leaching (Warren, 1958) of chalcopyrite, when the oxygen partial pressure was allowed to fall, provided a clue. In the present study, experimentation with chalcopyrite concentrate in dilute hydrochloric acid, under re flux conditions (in Pyrex flasks) and with an inert purge gas, revealed substantial amounts of H2S production and iron solubilization, cite negligible copper solubilization, after 2 ½ -4 days. Under comparable conditions the extent of reaction with dilute sulfuric, acetic and phosphoric acids was markedly less.

Jan 1, 1976

By Paul Hosford, B. Thrall

There has been a surge of exploration activity and interest in mineral properties located in cold Northern climates, with gold and copper properties as the two most attractive targets. There are already a number of mining operations located in the Arctic, for example, Red Dog, Polaris, and Lupin, all located in the Canadian Arctic. The logistics of sustaining operations, the engineering design and construction methods for such inhospitable regions are now relatively well understood. However, at least three of the proposed new mines in the Yukon Territory, Canada are designed to be heap leach operations. Rescan Engineering has recently completed Feasibility studies for two heap leach operations in the Yukon, one of which, the Brewery Creek Mine, is now in operation. The purpose of this paper is to explore some of the engineering and operating concepts that have been developed to make heap leaching an appropriate process method for gold recovery in a cold climate. Many of the readers will be familiar with the general and specific details of heap leaching, and it is not the intention of the authors to deal with any of the established "do's" and "don'ts" that have been addressed in numerous previous papers, but only with those pertaining to cold weather operations. This paper also examines these design concepts in specific relation to the results of the first winter's operation at Brewery Creek Mine, the first "far" North heap leach operation.

Jan 1, 1997

By Z. T. Bieniawski

Results of in situ investigations are discussed providing comparisons of rock mass deformability measurements by three methods: 'petite sismique' technique, the Goodman borehole jack and flat jacks. The tests were performed in exploratory tunnels constructed for site characterization purposes of an underground hydro-electric scheme. Due to the large number of data (41 petite sismique measurements, 45 Goodman jack tests and 19 flat jack measurements), it was possible to evaluate thoroughly the testing techniques employed. The purpose of this paper is to indicate the problems encountered in the interpretation of the results and to offer suggestions for selecting in situ tests. INTRODUCTION In situ tests are expensive and time consuming but they are an important aid in tunneling applications since they can provide deformability data of rock masses in contrast to rock material characteristics obtainable from small laboratory specimens. Some in situ tests are relatively easy to perform but their reliability may be in question unless a comparison of the data obtained by several different test methods is possible. Although many in situ techniques are available for determination of rock mass deformability (1), those more convenient to use are the Goodman jack, flat jacks and 'petite sismique. These methods are considered convenient because the Goodman jack is a borehole device; flat jacks can provide not only deformability data but also information about the stress field around excavations; while 'petite sismique' is based on seismic refraction surveys. Accordingly, these three methods have been selected for comparison.

Jan 1, 1979

By Byron Belew, Juris R. Harlamovs, D. B. Dreisinger, John L. Watson, G. A. Kordosky, Thomas O. O’Keefe

Unwanted impurities, present in raw materials, are often coextracted along with desired constituents during leaching. Due to its abundance and ease of extraction, the presence of ferric iron in leach solutions, solvent extraction circuits, and subsequently in electrowinning circuits, has always been a problem. In the case of zinc hydrometallurgical processing, iron is frequently an impurity in leach solutions. Purification of such solutions by solvent extraction, using di (2-ethylhexyl) phosphoric acid (D2EHPA) in a kerosene diluent, results in ferric ions being readily extracted along with zinc into the organic phase. Ferric iron has proven difficult to strip from the organic phase, but it is known that ferrous iron may be easily stripped from D2EHPA, and hence a process to effect reduction of iron present in the organic would have great potential. This research investigated a process to directly reduce ferric to ferrous iron in the organic phase, and to strip the ferrous iron using a dilute acid solution. The process utilized metallic zinc as the reductant and a low concentration sulfuric acid stripping solution. The results of the laboratory tests illustrated that iron could be readily removed from the organic phase by simultaneous direct reduction and acid stripping. The reductive stripping process was subsequently utilized in industry at the laboratory and pilot plant levels. The results of the industrial tests were encouraging and demonstrated the potential of this novel concept.

Jan 1, 1993

By Maria S. Adusumilli, A. Bhaskara Rao

ABSTRACT The presence of gold in lateritic crusts over mafic and ultramafic volcanogenic complexes in / and greenstohe belts, has called the attention in several parts of Brazil and also in Australia. Recent studies reveal the variety of structures and mineralogy of such crusts, and their importance in correlation with host(bed) rock types, as exploration guides, specially for greenstone belt metallogeny. The expected nature of growth of plates and/or nuggets in such crusts is under detailed study, and is considered as possibly due to dissolution and reprecipitation phenomenae of disseminated-fine-low grade ore in the host rock, in this investigation, laterite geochemistry, though incipiently discussed todate, is of fundamental importance and significance. Lateritic gold can be classified texturally as: dusty and diffused, fine, thin platy, taDular, and nuggets. Such gold is pure, and is often restricted to nodular (pisoliths, ooliths, concretions) forms or the matrix, that constitute the crusts or lateritised gravel beds which have an essentially goetnitic nature. Further this gold is recovered directly by mining the crusts or the adjoining placers with the metal derived from them. The thickness and extension of laterite crust zones is extremely variable depending oh the paleoclimatic conditions, and is conditioned to the favourable lithology and its structural expression. However, the "growth" of gold in these laterites will be conductive , without doubt, to several small scale mining activities, specially in the developing countries and regions limited to latitudes 309N and 309S.

Jan 1, 1987

By Z. T. Bieniawski, E. H. Skinner, R. A. Cummings, F. S. Kendorski

INTRODUCTION Caving Mine Drift Support Design The support of production drifts remains a high-cost item facing the developer or operator of an underground caving mine. Support costs are incurred well in advance of ore production, and there is a strong need to minimize these pre-production commitments of capital. Due to the extensive rock loads that normally develop during the caving process, the support used in caving mines is typically quite heavy and therefore costly. The process of designing this support increasingly makes use of basic tunneling principles, but is hindered by the still-incomplete state of knowledge of rock behavior in caving mines, and high variability of geological conditions in caving orebodies. Caving mines differ from tunnels in that the deformations and rock loads induced are transient and dynamic in occurrence, and are normally large in magnitude, often well in excess of rock mass strength. As opposed to tunnels, caving mine layouts are more intricate, and the methods and effects of construction ordinarily are not as closely monitored. Safety factors in mining tend to be lower and rock masses tend to he weaker. These aspects prevent strict application of tunnel design technology to caving mine drift support, with the result that mine drift supports are commonly designed chiefly on the basis of experience at other mines. Mining procedures at caving mines are evolved in response to site-specific requirements, to the extent that there are really as many caving methods as there are caving mines.

Jan 1, 1983

By Frank F. Aplan

Introduction Heavy media separation (HMS), also called dense media or float¬sink separation, is one of the newer forms of gravity concentration. Though the concept can be traced to the last century, the process has enjoyed its major growth since 1940. Heavy liquid separation is a mutation. The heavy media process is used extensively to clean coal and for the concentration of a wide variety of ores such as those of iron, lead-zinc, chrome, manganese, tin, tungsten, fluorspar, magnesite, sylvite, garnet, diamonds, gravel, etc. It may be used where ever a significant density difference occurs between two minerals, and commercial separations are typically made in the range of 1.3 to 3.8 sp gr. The particle size treated ranges downward from 6-8 in. top size. Particles greater than about 1/16-in. (10 mesh) may be treated in a "static" bath, though for reasons of separation efficiency, + 1/2 -in- feed is usually preferred. For particles less than this size, separation in a heavy media cyclone is generally used. The flowsheet of a typical heavy media process, in this case one using a ferrous medium, is shown in Fig. I. In essence, the process consists of: (1) preparation of the feed usually by wet screening to remove undesired fines, (2) heavy medium separation, and (3) removal and recovery of the medium from the separated products. Many muta¬tions of the basic scheme are possible and numerous options are possi¬ble. HMS offers the following potential advantages:12 1) Ability to make sharp separations. 2) Ability to change the specific gravity of separation quickly to meet changing conditions. 3) Ability to remove products continuously. 4) Ability to treat a broad size range of products. 5) Ease of start-up and shutdown without loss of separating efficiency. 6) Relatively low medium cost and low media losses. 7) Low operating and maintenance costs. 8) High capacity with the use of relatively little floor space. 9) Relatively low capital investment per ton of capacity. The process may be used to produce a finished concentrate, two finished concentrates, or a concentrate and a middling of differing quality, or a preconcentrate by rejection of unwanted gangue. It is an ideal method for the reprocessing of coarse waste dumps. The greatest use for the process lies in coal cleaning and in the preconcentration of ores. The relatively inexpensive heavy media process may be used advantageously to reject large quantities of coarsely crushed gangue. When used in this way, the process will allow: (1) the use of lower cost but less selective mining methods with the "overbreak" material being removed at the front end of the concentrator or preparation plant; (2) a substantial reduction in the quantity of ore that must be finely ground for subsequent mineral liberation and separa¬tion. Since comminution is often the single most expensive step in beneficiation, it is desirable to eliminate as many essentially barren pieces of rock as possible before the grinding step, (3) a decrease in overall plant capital cost per ton of concentrate since the size of the plant from the dense medium step onward will be smaller. Several general references are available,12-18 though much of the technical data on the process is widely scattered in the general litera¬ture. Heavy Liquid Separation Organic Liquids Given sufficient settling time, it is possible to make a perfect separa¬tion between two particles of differing density by placing them in a liquid whose density is intermediate between the two. This means of achieving a perfect separation has proven to be elusive because of problems in feed preparation, particle settling rates, operational considerations, and economic constraints. There are a wide variety of heavy liquids that could be used, most of them halogenated hydrocarbons, and a few typical examples are given in Table 4. These liquids are most commonly used in ore dressing for the laboratory fractionation of ore particles on the basis of specific gravity. Laboratory Separations. Using liquids typified by those given in Table 4, separations are made to develop either the standard washability curves used to estimate the response of a given sample to gravity concentration or to prepare a partition curve to evaluate the effective¬ness of a given gravity separation process or piece of equipment. A typical washability curve is given in Fig. 2.19 Such curves are generated for raw coal, e.g., by treating either the whole or various size fractions of the sample in a series of heavy liquids and analyzing the various specific gravity fractions so produced. The procedure is relatively simple for coal samples because of the ready availability of a wide variety of relatively low cost heavy liquids in the density range 1.2¬-2.0. For ores the problem is much more complicated, because only a few high density liquids, all of rather high cost, are available. Parti¬tion curves are generated in the same manner by treating the separated products in the same liquids. Greater details on the procedures to be used in heavy liquid separa¬tions are to be found in the literature (for coal, Refs. 13, 14 and 19 and for ore, Refs. 20 and 21). For testing coal, calcium and zinc chloride solutions have been used extensively in the past, though today halogenated hydrocarbons (available under the trade name Certigrav) are the preferred media. The liquids shown in Table 4 may

Jan 1, 1985

By G. C. Kachel

During the past two years, there has been an increasing acceptance of process automation among ferrous, non-ferrous and non-metallic rock processing operations in an attempt to keep total unit costs in line in a market situation where labor and material costs are rising almost daily. Previous technical papers (1) (2) (3) (4) (5) have described, in considerable detail, instrumentation and automatic control devices that have been successfully applied in a wide variety of crushing and grinding facilities. While many of the basic control philosophies that evolved almost ten years ago remain essentially unchanged, new components and devices have been developed during the past two years that permit these philosophies to be better implemented in operating plants. Some of these devices and their application will be discussed with particular emphasis placed in describing the basic control philosophy employed as well as some of the hardware or components comprising typical crushing and grinding circuit control systems. Before any instrumentation or automatic control system can be successfully devised for a specific facility, there must be a clear understanding and agreement by supplier and user as to the control system objective. In the case of a crusher feed rate control system, the objective is generally to maximize thru-put of a given finished product size. While this is often the case in a grinding circuit automatic control system, the reasons may be entirely different. Taconite processors whose end product is to be pelletized, generally attempt to control their grind within narrow limits to optimize balling action. Other milling operations are more concerned with obtaining metallurgical liberation and can, in many cases, tolerate wider swings in finished grind.

Jan 1, 1969

By Cengiz Karagüzel, Ömer Canıeren

The mobility of gold and silver metals from refractory ores is very low due to free metal ions in their bodies that bind the transportable and free metal molecules or they are encapsulated in minerals such as sulfides, arsenosulfides, carbonaceous, and clayey materials which make it difficult to extract them. As known from the literature, the enrichment of oxide refractory gold, silver ores, Ag, and Au-rich flotation concentrated from sulfur refractory ores can be leached in the chloride-hypochlorite solutions. In this work, the leaching approach was studied to extract silver ions from refractory ores in the presence of hypochlorite media under high pressure. The mineralogical and scanning electron microscopy analysis of the sample indicated that the silver was encapsulated in barite and quartz minerals in fine sizes. In order to obtain the optimum leaching conditions for the silver ore, the effects of several parameters, namely, temperature, leaching time, NaCl and NaOCl concentration, solid ratio, and particle size on the leaching recovery were investigated in detail. The leaching experiments showed that the highest silver recovery of 62.35% was obtained under the following conditions: temperature of 150 °C, oxygen pressure of 1800 kPa, leaching time of 2 h, concentrations of 2 mol/dm3 and 0.4 mol/dm3 for NaCl and NaOCl, respectively, the solid ratio of 30%, and particle size (d80) 15 μm. The results obtained from this study indicated that the enrichment of refractory silver ores to extract the silver encapsulated in barite and quartz minerals could be possible in the chlorite-hypochlorite under high pressure, a relatively shorter leaching time compared to conventional cyanide leaching.

Jan 28, 2021

By R. E. Hamilton

Automation is a word whose meaning has been broadened by popular usage to include any labor saving device. We with restrict our usage to the replacement of human judgement by instrumental measurement and mathematical analysis in the control of industrial processes. Mineral concentration is an area which has resisted automation because of the great difficulty in developing measuring instruments which can exist in the rugged environment and can measure useful properties with acceptable accuracy. This is not the only factor limiting progress, but until recently it has been of over-whelming importance. The development of on-stream X-ray analysers, magnetic flowmeters and nuclear density meters for mineral slurries has eliminated this obvious barrier and is enabling us to locate and attack the less obvious problems which still limit our ability to automate concentrators. If we examine the history of automation in industries which are highly automated we find that it has usually gone through three distinct phases. The first phase has been regulation. This is the simplest form of control and involves manipulating some variable whose value is of no importance in order to maintain the value of some other variable which is important at a constant specified value in spite of disturbances which may occur in other variables which affect it. A simple example is the use of a control valve to maintain a constant flow of fluid in a line in spite of changes in pressure in the vessels at the ends of the line. The position of the valve stem is of no consequence, as long as it is within its operating range. Unfortunately we soon run out of variables which can be

Jan 1, 1971

By Thomas A. Thorson

Bentonite is a common name applied to a variety of clays that develope swelling properties when associated with water. Useful bentonite deposits occur in many Western and Southern states. Their origins may consist of the alteration of volcanic sediments or the decomposition of shallow lake deposits. The specific type of bentonite that will be discussed in this review will be only the Western or high swelling sodium type bentonite that is mined primarily in Wyoming. Wyoming bentonite first entered the market in the late 1880's when it was used as an oil absorbing cosmetic. In the 1920's it was discovered that superior binding properties were present which created new opportunities in pharmaceutical, animal feed, and steel foundries. The swelling properties that were exhibited by the high swelling Wyoming bentonites soon led to its use in oil exploration when the rotary drilling process developed a need for multipurpose fluids. Bentonites in general and Wyoming bentonite in particular have fascinated chemists and process development specialists since the 1920's. There exists a long list of industrial uses that has led to hundreds of patents and extensive literature reviews. The binding and swelling properties are developed as a result of large surface areas and high cation exchange properties. Water, being a di polar molecule, attaches to the ionic vacancies and forms a network of tightly held water particles which in turn produces an impermeable seal or a binding characteristic in unconsolidated powder. Newer uses for Wyoming bentonite that once again utilized the binding and swelling properties include the pelletizing of iron ore and a vast array of civil engineering applications including slurry trenching, lagoon sealing, and garbage landfill sealing.

Jan 1, 1983

By William E. Horst

Ore grindability data based on various techniques to measure comminution characteristics are used to evaluate the crushing and grinding efficiency in mineral processing operations. The importance of achieving improved comminution efficiency, in terms of energy consumption, has been emphasized by recent increases in the cost of electricity. From a theoretical standpoint, the objective of a grinding operation might be expressed as maximizing the production rate at a given grind size while minimizing the energy consumption per ton of material ground. To achieve this objective in an industrial operation presents a challenge especially in view of changes in the raw material which are normally encountered. Various procedures1-5 used to determine energy-size parameters and grindability measurements have been reported. The proposed relationships between particle size and energy consumed have much in common between many of the techniques for measuring grindability. Probably the most widely used parameter to measure ore grindability in recent years is the Bond work index6, Wi, which is defined as the kw-hr per ton required to break from infinite size to a product size of 80 percent passing 100 microns. If the breakage characteristics of a material remain constant over all size ranges, then the calculated work index would be expected to remain-constant since it expresses the resistance of material to breakage. However for most naturally occurring raw materials differences exist in the breakage characteristics depending on particle size, which can result in variations in the work index depending on grind size. Consequently work index values are generally obtained for some specified grind size which typifies the comminution operation being designed or evaluated.

Jan 1, 1975

By R. H. Smith

The total energy demand in the United States increased about 4 per cent annually during the 1960's 1 and is expected to increase at the same rate during this decade. Z Fuel oil growth in the 1960's was only Z per cent per year until 1968, but it increased to 8 per cent in 1969 and 11 per cent in 1970. Fuel oil demand is expected to grow at a 6 per cent rate through the 1970's. Part of this rapid increase in demand has been caused by restrictions placed on the sulfur content of fuels. High sulfur coal can no longer be burned in many parts of the country and has been replaced by low sulfur fuel oil. An insufficient supply of natural gas has also contributed to fuel oil demand. Air pollution regulations have not only caused an increase in fuel oil consumption, but they have also caused a reduction of sulfur content in residual fuel oils. Current regulations call for 1 per cent maximum sulfur content fuels over much of the country. Sulfur contents of fuels are limited to 0. 3 per cent in certain areas on the east and west coasts. Sulfur in residual fuel oils from high sulfur imported crude oil is reduced to 1 per cent currently. However, sulfur reduction to 0. 3 per cent is difficult and expensive.4 As a result, refiners may be hard pressed to supply the market for low sulfur fuel oil. The oil shale deposits in Colorado and Wyoming potentially are a huge source of low sulfur fuel oil. It will be shown that the low sulfur content and more importantly the sulfur

Jan 1, 1972

By John A. Herbst

In recent years, diminishing supplies of high grade ores and increasing consumption of mineral and metal products have demanded high efficiencies in extraction processes. The rising cost of energy has influenced plant operating policies. Rather than merely processing as much ore as possible, other process factors are being considered in process analysis, with energy consumed per ton of product produced taking on increased importance. Alternate processes and more efficient plant design may satisfy part of the demand placed on the mineral processing industries. However it is expected that the improvement of existing operatives will be responsible for most of the gains in efficiency in the short term. Even slight improvements in process efficiency lead to significant cost saving. Grinding, for example, is an inherently energy-intensive process. Grinding circuit capital and operating costs are high and it is essential that circuits run as efficiently as possible. In flotation plants, low-grade ores demand optimum recovery of valuables to maintain overall metallurgical efficiency. The use of modern data, treatment methods and systems analysis provide the means to achieve many goals, previously beyond reach. The design of more efficient plants and the evaluation and. improvement of existing plant operations constitute the general area of process analysis. Process analysis can be used to identify the capacity available in a process unit in some cases. In other cases, the goal may be to investigate alternative equipment configurations for an existing plant for possible improvement in efficiency. This goal is virtually impossible to achieve using plant data alone. A simulator of the process units involved can provide an excellent basis for performing the required process analysis.

Jan 1, 1979

By Pieter Berendsen

Lamproite occurs in two locations in southeastern Kansas that are in close proximity to each other. In both locations, the lamproite is restricted to north- east-elongated, ellipsoidal depressions measuring about 3 mi by 1.5 mi. At the surface and in the shallow subsurface, lamproite occurs as sills that were intruded into Middle and Upper Pennsylvanian rocks consisting of shale, limestone, and minor sandstone. Isotopic age determinations by Zartman and others (1967) indicate that the lamproite was intruded during the Late Cretaceous (88-91 my). Drillholes for hydrocarbon exploration down to a depth of about 1,400 ft (top of the Mississippian) and numerous shallow drillholes (mostly 200-300 ft) by the Kansas Geological Survey in the northern portion of Silver City dome helped to understand the structural complexity and extent of the near-surface sills. Numerous radial faults showing small apparent vertical offsets limit the lateral continuation of individual sills. Concentric faults are believed to mark the edge of the depression. Wagner (1954) mapped the geology of Silver City dome in considerable detail and recognized a northward dipping, 120-ft-thick, lamproite sill exposed at the surface along the northeastern edge of the dome. The upper 40-50 ft of the sill weathers olive-brown and has a soft, clayey consistency in which only the phlogopite mica is recognizable. The weathered material has been mined by Micro-Lite LLC since 1982 from the exposed sill in an open-pit that measures about half a mile extending in an east- west direction. The bulk of the material, about 98%, is used as an additive in mineral supplements for cattle feed.

Jan 1, 1999