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By Donald A. Dahlstrom

INTRODUCTION Solid-liquid separation is an important and many times a critical step (or steps) in a mineral or coal processing plant. Some examples of typical critical separations are as follows: 1. Operating a seven to eight stage CCD thickening circuit to re¬cover almost all of the caustic and alumina trihydrate values in an alumina plant. This must be accomplished with highly scaling slurries, starting temperatures of over 100°C and operate on a closed circuit system. 2. Making a filter step operate to produce a proper moisture for the balling step so that the pellet furnace can produce a proper product. Bentonite addition must be minimized and a good quality filtrate must be maintained to prevent abrasion of the internal parts of the filter. 3. Operating a closed water system in a coal washing plant so that reclaimed water containing less than one percent suspended solids is produced for reuse to maintain beneficiation ef¬ficiency. Refuse solids must also be thickened so that they can be effectively dewatered to meet state disposal requirements. 4. Recovering phosphoric acid values from a slurry containing gypsum and other gangue solids at an elevated temperature. This must be done while minimizing wash water and maximizing P2O5 re¬covery while simultaneously minimizing scale problems. While solid-liquid separations are important to overall performance in the processing plant flowsheet, it is also a significant factor in plant costs. Capital and operating costs for all the solid-liquid separation steps (includ¬ing water reclamation for reuse) in such plants are probably between 10 and 20%. Energy consumption can also be important in these separations. For example, in the copper concentrator, it is the third largest category in energy consumption, after comminution and flotation. Obviously, solid-liquid separation steps in a plant demand proper atten¬tion in design in order to achieve both optimum performance and cost. Simultaneously, knowledge of funda¬mentals are important to improve results in existing plants.

Jan 1, 1986

By William E. Cutcliffe, John A. Ames, John D. MacFadyen

Webster's dictionary nearly equates portland cement with its current primary definition of cement. Although such equation may be a triumph of common usage, the confusion between the terms cement and concrete unfortunately is very widespread. Full definition of cement properly would extend to many substances, but for purposes of this chapter cement is restricted to varieties of portland cement including portland-pozzolan cement. Among the usually recited historical notes concerning cement is that it was developed by the Romans. Their use of cement in the great structures of Rome, and even in the far comers of their Empire, such as Hadrian's Wall in the north of England, testifies to the antiquity of a major cement industry. From English sources we know of John Smeaton's carefully proportioned hydraulic cement mixed in 1756 and of Joseph Aspdin's patented cement to which, in 1824, he gave the name portland cement. (He claimed that his cement mortar looked like the famous dimension limestone quarried from the Isle of Portland on England's south coast.) The year 1971 marked the centennial of portland cement manufacture in the United States. A fair historical account of the many real contributors to the cement industry since 1756 unfortunately would be too extensive for this chapter. Development of rotary kiln practice and burning at higher temperatures clearly was the major move into today's technology. Cement manufacture is the processing of selected and prepared mineral raw materials to produce the synthetic, mineral mixture (clinker) that can be ground to a powder having the specified chemical composition and physical properties of cement. Cement making incorporates a number of distinct steps, but it is characterized by the key pyroprocessing (or burning) step, which brings about the necessary changes in the raw materials. This pyroprocessing is a chemical process. Conversion of large volumes of mineral raw materials into specification-controlled cement at relatively low cost is the objective. Statistics on the cement industry are of uneven quality. The US Bureau of Mines (USBM) is the principal collector of available data. These statistics can be only as good as the quality of information supplied by the reporting companies. The data perhaps most often questioned relates to productive capacity of the industry. The questions submitted by USBM are valid, nevertheless, and the information gained from them, as good as is available, is what is generally used. The Portland Cement Association also is a source of much quality information. In analyzing cement industry production rates, it is well to keep in mind that measurement of raw materials requires the reader to recognize that approximately 1.6 t of dry raw materials are required to make 1 t of clinker. This number can vary depending on the amount of kiln dust wasted. Also that to produce 1 t of portland cement required .94 to .96 t of clinker, the remainder being gypsum or anhydrite. A ton of masonry cement or pozzolanic cement re- quires considerably less clinker.

Jan 1, 1994

By J. Simmons, P. Ziemkiewicz

Acid-Base Accounting (ABA) is an analytical procedure that provides values to help assess the acid-producing and acid-neutralizing potential of overburden rocks prior to coal mining and other large-scale excavations. This procedure was developed by West Virginia University scientists during the 1960s. After the passage of laws requiring an assessment of surface mining on water quality, ABA became a preferred method to predict post-mining water quality,and permitting decisions for surface mines are largely based on thevalues determined by ABA. In order to predict the post-mining water quality, the amount of acid-producing rock is compared to the amount of acid-neutralizing rock, and a prediction of the water quality at the site (whether acid or alkaline) is obtained. We gathered geologic and geographic data for 56 mined sites in West Virginia, which allowed us to estimate total overburden amounts, and values for maximum potential acidity (MPA), neutralization potential (NP), net neutralization potential (NNP), and NP/MPA ratios for each site based on ABA. These values were correlated to post-mining water quality from springs or seeps on the mined property. Overburden mass was determined by three methods, with the method used by Pennsylvania researchers showing the most accurate results to actual overburden mass. A poor relationship existed between MPA and post-mining water quality, NP was intermediate, and NNP and the NP/MPA ratio showed the best prediction accuracy. In this study, NNP and the NP/MPA ratio gave identical water quality prediction results. Therefore using NP/MPA ratios, values were separated into categories: <1 should produce acid drainage, between 1 and 2 can produce either acid or alkaline water conditions, and >2 should produce alkaline water. On our 56 surface mined sites, NP/MPA ratios varied from 0.1 to 31, and six sites (11%) did not fit the expected pattern using this category approach. Two of eight sites with ratios <1 did not produce acid drainage as predicted (the drainage was neutral), and four of 40 sites with a ratio >2 produced acid drainage when they should not have. These latter four sites were either mined very slowly, had non-representative ABA data, received water from an adjacent underground mine, or had a surface mining practice that degraded the water. In general, an NP/MPA ratio of <1 produced acid or neutral drainage sites, between 1 and 2 produced mostly alkaline drainage sites, while NP/MPA ratios of >2 produced alkaline drainage with a few exceptions. ABA is a good tool to assess overburden quality before surface mining and to predict post-mining drainage quality after mining. The interpretation from ABA values was correct in 50 out of 52 cases (96%), excluding the four anomalous sites, which had acid water for reasons other than overburden quality.

Jan 1, 2003

By Stuart R. Cotterill, Jack D. Nelmark

Introduction Opencast surface mining requires blasthole drilling to achieve mine planning. No single method of mining is right for all conditions. Occasionally, mine planners introduce a project with little regard to drilling and blasting. These costs are usually a significant percentage of total mine overhead. One drilling and blasting method that can be used to reduce overall mine expense is inclined or angle hole drilling. But inclined-hole drilling will not cut costs unless a set of required circumstances is met. Several conditions of mine design indicate the use of angle drilling. Geotechnical problems must first be analyzed. Primary considerations are safety, fragmentation, production, and maintenance. Secondary considerations are, in some instances, reduction in amount of explosives, which lowers blasting costs; reduction of practical fragmentation beyond blasting pattern limits; and reductions in overall costs due to reduced volume of excavation. Future trends in blasthole drilling may include incorporation of drill equipment designed to allow rapid change from vertical to inclined drilling. This will allow the operator to adapt to changing hole requirements with minimal production loss. Another improvement may be the ability to chamber holes at any elevation throughout the hole depth. This will allow more charge to be placed at strategic locations to improve fragmentation. Merits of Drilling Inclined Holes Drilling is performed to create voids for explosives. It is done either to recover minerals or to excavate a volume of earth. The manner of mining or excavation can greatly affect the economics of the overall project. Many innovations and methods have been tried, but the most practical and economical is still drilling holes and using explosives to fragment the material. To break up the material, the practice has been to place charges within the mass. This is done by drilling holes of a specific diameter and depth into the material. The holes are of such magnitude as to develop sufficient energy to break or loosen this material, providing for easier removal. In general, more open or exposed faces must exist to aid material breakage when blasting. Inclined drilling can be advantageous in open-cut mining with highwall depths of at least 24 m (80 ft). A minimum of two faces are open in open-cut mining and the material can be thrown outward to cover pre-mined volume. This cuts cost by eliminating the need to remove or relocate a large portion of material. Sometimes the material is of such a mass that more energy per unit is required to loosen it than can easily be done by blasting vertically. Inclined holes allow a more uniform loading of drilled holes. The unit of energy is raised, so little or no secondary blasting is required. This usually comes about only if the main plan calls for drilling holes deeper than 24 m (80 ft). For shallow holes, spacing and burden can be made closer to allow sufficient energy to blast the toe. If the open face is in only one

Jan 9, 1984

By Robert R. Brandom

The Boss-Bixby deposit is one of several iron deposits that occur in the Precambrian igneous rocks of southeastern Missouri. It differs, however, from all of those deposits by its significant contents of copper, cobalt, and titanium, and its close relationship with a basic igneous intrusion. Ore microscopic study of selected drill core samples has shown that the hypogene ore minerals are magnetite, hematite, chalcopyrite, bornite, covellite, ilmenite, rutile, sphalerite, cobaltian pyrite, carrollite, scheelite, and wolframite. Subsequent partial oxidation has formed martite, pseudobrookite, and anatase. Textural evidence indicates that two stages of iron and iron-titanium oxide formation were followed by the deposition of the copper-iron sulfide minerals and carrollite.

Jan 1, 1985

By Gretchen K. Hoffman, George S. Austin

Soil amendments or soil conditioners generally carry the con- notation of being useful for problem soils or soils needing special treatments to produce maximum yields. Many different materials have been utilized, both inorganic and organic. Only the most commonly used and those that appear to have potential to become commonly used will be discussed. Soil productivity depends on many factors. Soil amendments mainly modify physical characteristics and microbial action, and/or change the pH of a soil, rather than directly supplying plant nutrients. They give soil the needed physical properties to allow plant growth, fight erosion, or save water. Some soil amendments provide nutrients in addition to altering the physical, biological, or chemical characteristics of soil. The term "soil amendment," as it is used by Soil Science Society of America, allows soil amendments to be materials other than those used primarily as fertilizers (Anon.,1987). Soil amendments as fertilizers of any type will not be considered here because this aspect is more relevant to the previous chapter entitled "Agricultural Materials: Fertilizers" in this volume. Several inorganic soil amendments have been used since the early 20th century to alter the character of soil: limestone, lime, and similar calcium-rich carbonates and oxides for acid soils, and calcium sulfate (gypsum) and native or uncombined sulfur for alkaline soils. The use of these amendments (limestone, lime, gypsum, and sulfur) or their equivalents has been studied and documented in many basic soils tests (McCaslin and Boyle, 1980). Perlite and vermiculite are considered in separate chapters and only a brief statement of their use as soil conditioners will be made in this chapter. Peat is the principal natural organic soil amendment, but manure, both as a fertilizer and soil conditioner, is used in every part of the world. In less-developed countries, manure is the primary soil fertilizerlconditioner. An organic-rich material designated as "humate" has been marketed as a soil amendment for many years and will be addressed in this paper. Other materials are discussed by the Soil Science Society of America in its Special Publication 7, "Soil Conditioners" (Stewart, 1975). They include bitumen emulsion, polyacrylamide, polyvinyl acetate, polyvinyl alcohol, bentonite, nonionic surfactants, and natural mulches. Zeolites can be added to the list of miscellaneous soil amendments (McCaslin and Boyle, 1980), as can calcium chloride (Pressler and Pelham, 1985), sulfuric acid, ferric and ferrous sulfate, aluminum sulfate, ammonium polysulfide, calcium polysulfide, and ammonium bisulfite (Stromberg and Tisdale, 1979). Sludge will not be considered as a soil amendment because it has properties more consistent with fertilizers. All these "other materials" account for a very small amount of the volume and value of soil amendments used and will be only briefly discussed.

Jan 1, 1994

By Michael T. Ballard

The key to productive computer usage is system software integration with full compatibility among individual components. The majority of software developers in our industry are still in the process of perfecting individual components. As a result, exchange and validation of data between disciplines becomes an arduous process. We at Morrison Knudsen Engineers, Inc. (MKE) have integrated an entire system, allowing exploration, geology, modeling, mine planning, and operation modules to work as a single, complete system with direct exchange and validation of data. The importance of integration to both developers and users of today&apos;s mining soft- ware is becoming increasingly apparent as we, an industry, move toward growth and enhancement of the technology of ore reserve acquisition, evaluation, and management. It is also important to understand the present state of integration and where it is leading US. Not long ago, another industry passed through the same stages we are now setting up for the mining industry. The stereo industry began with a few individual components, the record player, tape recorder, and radio. People were able to play records, listen to the radio and record conversations and music only through microphones on their tape recorders. Soon, one enterprising individual discovered he could tape sound directly from the radio or record player by capturing audio output from the speaker wires. Interfaces and patch cords were developed, providing a means to transfer audio information between components with not only little loss of sound quality, but also the elimination of back- ground noise. The industry took another step forward with the introduction of "integrated" stereo, where the components were packaged in one cabinet with shared resources. This reduced overall cost which paved the way for better quality. Today&apos;s stereos are now so well integrated that many of the components share data and resources from the same manufacturer, designed to work together for almost perfect data transfer between any of the components. The result is better sound, convenience, and reduced cost. This is the ultimate goal for integration. Any system development passes through these same steps on the road to total interaction. Initially, the components are designed, tested, and marketed individually, often by separate companies. As the users become familiar with the components, the need arises for an automatic interface between the components. This is necessary to cut down on error during data transfer and to eliminate the redundant work required to enter results from one component into the next component in the system. As a result, interfaces must then be developed to aid in this data transfer. After data transfer is accomplished, the next step is resource sharing. Resource sharing is careful design and engineering by either cooperative, individual manufacturers or one firm taking on the task to produce a single package product. Design and resource sharing leads to lower overall cost, while still providing component capability with options to grow as the user grows. The mining software industry has been working to develop some very high quality component software and has indeed accomplished this task in every aspect of the mining industry. However, realizing the importance of integration, some companies with limited individual resources have started working together to interface their individual components. Other firms have undertaken the project of developing complete, integrated systems.

Jan 1, 1987

By Deepak Malhotra, Linda Battich

INTRODUCTION Mineral processing plants generally operate efficiently within the technical, economic and management constraints applied to them. They have no choice, because the dynamic and competitive nature of the mineral business dictates that survival and/or prosperity of the company depends on being a low cost producer. Progressive mineral companies realize that market downturns will occur, and they must continuously strive for lower unit production costs rather than be satisfied with the status quo. Mineral companies generally tend to reduce costs during market downturns. This short-term solution is achieved by high grading of ores, and cut-backs In waste stripping, exploration, and capital expenditures.(1) However, to remain a low-cost producer in the long term, companies must enhance revenue and reduce cost simultaneously. This Involves continuous evaluation of technologies and reagents, periodic audits to locate revenue losses; and gathering and analyzing statistical plant data to clearly understand the Impact of process variables on efficiency. Mineral companies are caught in a Catch-22. They need resources to accomplish the objectives outlined above. Most mill stuffs have been cut to the minimum level necessary to maintain production. Resources such as time, manpower and money are scarce, and mill metallurglsts struggle to use these resources productively. Is your flotation plant optimized? History Indicates that successful operations constantly tune the flotation circuits to Improve metallurgy or reduce cost. This Is the essence of evolutionary change In mineral processing operations. A plant auditing approach can play a key role in assisting the process engineers to achieve the overall objective of enhancing metallurgy and reducing cost with limited resources through evolutionary improvements. FLOTATION SYSTEM The flotation process is the most widely wed concentration process In the world today. The number of variables that can affect the flotation results Is very large, maybe over 100. These variables can be divided Into three main groups: (2) (1) ore and mineral properties; (2) reagent treatment; and (3) flotation machine characteristics. Some of these variables can be controlled while others have to be accepted. Recently, Investigators (3,4) have attempted to describe the flotation process as an engineering system which includes chemistry, equipment and operating variables. Though some of the variables are Independent, most are co-dependent. thus making it difficult to develop simple cause and effect relationships. For example, it is easy to understand the effect of reagent change on recovery and grade In the rougher circuit, but very difficult to quantify Its impact on filtration downstream. Plant audits on a periodic basis are necessary to develop an understanding of the Interactive nature of the system. Auditing provides comparisons of plant operating performance before and after variable changes. OVERVIEW OF PLANT AUDITING An audit Is a formal, thorough and periodic examination of a system. There are various types of audits (i.e., geological, environmental, metallurgical. economic, etc.), and each serves a different purpose. (5) The discussion here is related to plant and/or metallurgical audits. Neale and Flintoff note that two key factors governing changes In an operation are: (1) the opportunity must be recognized; and (2) the justification for change must exist. (6) Both factors emphasize the critical role of successful plant auditing. Without plant audits. many opportunities for improvement must go unrecognized. On the other hand, when a situation ripe for improvement Is recognized. the hard data from a plant audit can reveal the expected impact of an operating change.

Jan 1, 1993

Introduction One hundred years ago, a recent college graduate created the US aluminum industry. He found an economic way to crack the primeval bond that makes the metal so special. Aluminum doesn&apos;t "rust" - oxidize progressively. Rather, when exposed to air, it instantly forms a gem-hard but microscopic oxide coating. This seals off oxygen from the metal underneath. Scratch it and the seal reforms instantly. That tight chemical bond is the reason the metal is not found in nature; it exists only as a compound. The bond had to be broken to free the shiny metal. But once it is free, that self-sealing protection, alongside a remarkable strength-to-weight ratio, offers a marvelous material. Until 100 years ago, finding a way to do that economically was a challenge that defied science. Then it was solved, in a remarkable coincidence, on both sides of the Atlantic. And the way was paved for a material that would become the second most widely used metal in the world. Until that time, aluminum was a rare and precious metal. But then two young scientists independently invented the process that took aluminum outside the laboratory and into applications ranging from pots and pans to spacecraft. Discovery of aluminum Other major metals - copper, iron, lead, gold, and silver - had been used for thousands of years. But aluminum was entirely unknown until 1782, when French chemist Antoine Lavoisier suspected its presence. It was not actually discovered until Sir Humphry Davy, in England, detected it in clay in 1807. It was first isolated as a free metal only in 1825, by Denmark&apos;s Hans Christian Oersted. For years, laboratory methods yielded aluminum only in tiny amounts costing about $1200/kg ($545 per lb) - $13,333/kg ($6000 per lb) in today&apos;s dollars. Methods developed by French scientist Henri Sainte-Claire Deville in 1854 cut the cost to about $200/kg ($90 per lb). King Frederick VII of Denmark had a helmet of aluminum and gold. And Emperor Napoleon III of France reportedly served his most exalted guests at a state dinner with aluminum plates. He left the lower ranks to dine from pure gold. Deville and others continued to reduce production costs. But the price of aluminum still rivaled silver - $31/kg ($14 per lb) versus about $35/kg ($16 per lb) for silver. Then in 1884, a 2.8-kg (6.25-1b), 230-mm-tall (9-in.-tall) aluminum pyramid was cast as the tip of the Washington Monument. It was probably the first architectural use of aluminum. And it is still there after more than a century. The attractive properties of aluminum were obvious: it is lightweight but strong, conducts heat and electricity, reflects light and other electromagnetic radiation, and resists corrosion. But its commercial promise was blocked by its cost. In 1885, the price of aluminum was $17.70/kg ($8 per lb). It stayed there for the next couple of years until the Hall-Heroult process brought it down sharply. Hall-Heroult process lowers aluminum costs The characteristic that kept aluminum hidden so long continued to thwart chemists. Aluminum clings to oxygen so tightly that it is never found as a free metal in nature, and it is hard to break that bond chemically. The best chemical methods of the 1880s required sodium, and sodium itself was expensive. At Oberlin College in Ohio, chemistry professor Frank Fanning Jewett advised his students that anyone who could make aluminum inexpensive would do humanity a favor and get rich as well.

Jan 3, 1987

By Niels Jonassen

INTRODUCTION The occurrence of the radioactive element radium, [2gg~a], often in trace amounts, in the crust of the earth gives rise to a flux of the daughter product radon, [&apos;ii~n], across the earth-air interface. This so-called exhalation process has been studied by many investigators [KO 45, Kra 64, Pe 66, Wi 741] over several decades. In the earlier investigations the exhalation process was studied in a purely geophysical context, but over the last 20 years it has been realized, that under certain conditions the exhalation may be intense enough to also have radiological implications. This is for example the case where relatively radium-rich wastes or by-products, like uranium mill tailings and phospho-gypsum, are stored in larger quantities. In order to be able to predict the radiological impact on the environnent it is necessary to know the rate of exhalation of radon from the surface of the exhaling material. Usually the determination of these exhalation rates has been done by measurements in situ directly upon the accumulated material [~le 74, Ha 791. Although such field measurements have the obvious merit of dealing directly with the full scale problem, the results are often lacking in generality, making predictions for other situations difficult or even impossible. The present paper describes some results of an investigation where it is attempted from laboratory measurements on samples of limited size to obtain material parameters, which are suited for extrapolating and predicting the radiational behaviour of larger accumulations of the material. THEORY Let us consider a sample of a radon exhaling material enclosed in a container with a dead space volume, Vd, and initially containing radon free air. If the total exhalation rate (number of atoms per unit time) is c, the radon concentration (number of atoms per unit volume) N will initially grow with the time t according to the equation [ ] where [R] is the decay constant of radon. As the concentration (or activity) in the container grows, the net exhalation rate will slow down because of back diffusion, and, furthermore, radon atoms may be removed from the container, not only by radioactive decay, but also by diffusion leakage [JO 81 ]. If, however,only the initial. part of the activity growth curve is considered, the total exhalation rate, c, is given by [c = r•Vd(2) where r is the initial activity growth rate in the container. Let the container be cylindrical with an inner cross-section S and filled to a height L with a radon exhaling material with the specific mass p, the porosity E, the radon pore production rate f and the diffusion length i. When the container is left open,i.e. the radon exhalation takes place into a virtually radon free room, the radon area exhalation rate, E, can be written [Jo 80] E = Ef?t tanh L.R (3) assuming the exhalation only takes place in one direction, towards the surface of the material. It appears that for values of L > 2•ithe area exhalation rate becomes E a = Efi (4) independently of the sample dimensions and the total exhalation rate c is then c = E •S (5) For L ;~ 0.5•i, tanh P _ k and equation (3) may be written E ~ EfL (6) then c = EfL•S = p•m= Em •m (7) where m is the mass of the sample and Em = P (8) is the mass exhalation rate. It thus appears that the radon exhalation rate from a given amount of material may often be conveniently expressed by c = E •Sfor L z 2•I (5) a orc = Em •mfor L0.5•i (7) where S is the total exhaling area and m the total exhaling mass, E and E the area and mass exhalation rates respectively defined by equations (4) and (8).]

Jan 1, 1981

By Joseph L. Walker

INTRODUCTION In looking over the diversity of the papers that are being presented during this meeting on The Industrial Practice of Fine Coal Processing one cannot help but be impressed with the progress the industry has made in beneficiating fine raw coals, and in the number of innovations that are under study to increase recovery and to improve the quality of the finest size particles produced at a preparation plant. Those who are not in our industry, who look at the technical program, might be confused, when they see that the papers include such topics as cleaning to zero and heavy media cyclone cleaning 28M x 100M; application and performance of fine coal jigs, tables, hydrocyclones, spirals, and flotation; filtration, dewatering and thermal drying; and ancilliary aspects such as fines handling, instrumentation and process control plus screening and liberation. This is an observation and not a criticism of the diversity of papers being presented. The program fits within the parameters of fine coal preparation as the term "coal preparation" is defined, but perhaps not as the term "fine coal" is defined. Admittedly these definitions are sometimes loose. However, each should be made more definitive if a meaningful fine coal preparation overview is to be possible. COAL PREPARATION DEFINED In the opinion of the writer, the term "coal preparation" should be defined as including all work activities that are performed on all components of a run-of-mine coal from the time it leaves a surface reserve or an underground portal, until all components are either ready for shipment or are stowed on, or in the earth in an environmentally acceptable manner. This definition excludes the work that is performed to improve coal quality or handleability inside the mine or pit. This work is commonly called "face" or "pit" preparation. FINE COAL DEFINED The term "fine coal" means different things to different people. In the past, anthracite finer than No. 3 Buckwheat (3/16 in.) was considered fines which often were discarded from the breaker as an unsalable by product; and bituminous coals finer that about 1/4 in. (slack) were either discarded or sold at cost to prevent an accumulation of "no bills" which referred to a product having no immediate sale. Although a standard definition of "fine coal" is yet to be accepted by the industry, a designation of coals by particle-size range has evolved through the wide use of three-circuit flowsheets, wherein the optimum size range by washer type determines the size fractions: a coarse-coal circuit for the plus 3/8 in., a -11- coal circuit for the 3/8 in. x 28 Mesh, and a fine-coal circuit for the remaining 28 Mesh x 0. Logically, the term "fine coal" should refer to some resultant size fraction or some top size by zero. This definition should include a 28 Mesh x 0 feed to a flotation cell but should exclude a 28 x 100 Mesh size fraction fed to a heavy media cyclone. Failure to include the resultant sizes in the definition precludes accounting of the full range of particle sizes present in the feed to the plant. Since the 28 Mesh x 0 fraction is treated in the final circuit of the three discreet washing circuits, now almost always used in U.S. commercial applications, and since it contains all of its resultant sizes, in the writer&apos;s opinion, it should be designated "fine coal". FINE COAL CLEANING Cleaning coal fines, which in the past was at best marginally profitable, is now an essential part of coal preparation strategy for a number of reasons : 1. Raw coals now cost more to produce and

Jan 1, 1988

By William R. Henkle

High-calcium limestone has been intermittently produced from the Monarch quarry since the late 1800s. Initial production was used in sugar processing and for a smelter located near Salida, Colorado. During the 1920s, Colorado Fuel and Iron Company (CF&I) began to exploit the deposit as a source of flux stone for its blast furnace steel operations at Pueblo. The deposit was operated for many years as a captive quarry by CF&I. In 1984, CF&I closed the quarrying operations at Monarch; flux stone was no longer required since the blast furnaces were taken off line in 198 1. In 1994, Colorado Lime Company, a subsidiary of United States Lime and Minerals, Inc. acquired the property. Limestone was mined from the Castle Butte Member of the Leadville Limestone (Lower Missippian). Some high- magnesium dolomite was also mined during WWII from the Redcliff Dolomite Member which directly underlies the Castle Butte. Past production was from both an upper and lower quarry at elevations ranging from 10,000 to 11,000 feet (3,048 m-3,353 m) mean sea level (m.s.1.). The reserves at Monarch quarry are in a dip slope deposit, occupying the northwest slope of Monarch Hill. The structural geology of the deposit is complex on both a region- al and mine scale. The reserves are located on the eastern limb of the Syncline Hill syncline. The beds on this limb of the structure strike to the northeast and dip to the northwest from 30 to 45 degrees. A major reverse fault separates the reserves into an upper and lower deposit. Numerous smaller normal and reverse faults cut the deposit, requiring a flexible mine plan. At the Monarch quarry, the Castle Butte Member con- sists of two stratigraphic units. The Upper unit (Mlu) is a thick-bedded, fine-grained crystalline dolomitic limestone from 0 to 300 feet (0-90 m) thick. The unit generally has an Si02 content of less than 4 percent. A bedded chert horizon and a karst horizon at the base of the unit locally raise the Si02 content as high as 20 percent. The underlying Quarry Stone unit (Mlq) is a light-gray, massive, bedded, calcilutite/micrite limestone from 90 to 130 feet (27-40 m) thick. The Quarry Stone unit is remarkably uniform chemically throughout it&apos;s entire thickness. Average analysis is CaC03 - 95 percent, MgC03 - 3.5 percent, and Si02 - 0.5 percent. The Footwall dolomite unit (Mld) of the Redcliff Member of the Leadville Limestone is a dark gray to black, blocky, medium-to-thick-bedded, calcilutite/micrite dolomite from 150 to 180 feet thick (46-55 m). The upper 100 feet (30 m) of the unit is a low-silica facies with an average Si02 content of less than 0.5 percent. MgC03 content is con- sistent at 39.8 percent throughout the upper 50 feet (15 m) of the unit but varies from 15 percent to 39.8 percent in the lower portion (50 to 100 feet [15-30 m]) of the low-silica facies. The lowest portion of the unit, 100 feet (30 m) to base of unit is high in silica and is not considered chemical grade. Current in-place, surface-minable reserves at the quarry are estimated to be 14 million short tons (st) (13 million metric tons [mt]) of limestone and 50 million st (45 million mt) of dolomite. A 1.4 million st (1.3 million mt) stockpile of finely crushed limestone is also present on the property. Colorado Lime is presently processing approximately 2,000 st (1,800 mt) per month from the crushed limestone stockpile. This material is pulverized and sold to underground coal mines for use as rock dust, some of this product is also used for environmental purposes. Limestone mining is scheduled to resume in spring of 2000.

Jan 1, 2001

By W. K. Fletcher

As part of an ongoing programme on behaviour of heavy minerals In streams, the dispersion of Au as free gold (Day and Fletcher, 1987), Sn in cassiterite (Fletcher et al, 1987) and W in scheelite (Saxby and Fletcher, 1987) have been investigated downstream of mineralization. The studies of Au and W were undertaken, in British Columbia and the Yukon Territory, respectively, in streams that are strongly influenced by spring snowmelt floods. Sn was investigated under tropical rainforest conditions in Peninnsular Malaysia.

Jan 1, 1988

By Agne Rustan

INTRODUCTION This work is a continuation of the preparatory study by Rustan and Stöckel 1979 (3) and (4) of the possibilities to introduce automatic mine ventilation in Swedish mines and construction works. The preparatory study has been financed by the Swedish Board of Technical Development. In the study it was recommended that an automatic step by step control of the fans near the working place due to diesel exhaust emission would be the best solution. A more advanced alternative would be to regulate the fresh air continuously in proportion to the contamination. The latter alternative has been studied by Boliden Mineral Co in the Udden mine. In this study it was found that the air supply could be regulated continuously but it was very important where the sensors feeling the contamination were placed. An intense study of the environment underground is now being planned by our division together with specialists from the National Board of Health and Safety, The Swedish Work Environment Fund, LKAB and the local Governmental Inspection of the Workers Safety. Different gases, radon, dust, airspeed, moisture temperature and pressure is planned to be measured continuously and correlation between the parameters is going to be established to decide the best measurement parameters for regulating the system. The best situation of sensors is also going to be studied. Despite this work hasn&apos;t been done yet this paper covers some of the problems which could be encounted with continuous regulation. In this report the environment has been studied during the test with step by step regulation of fans by radio. Diesel vehicles are the largest polluters under ground in Swedish mines and we have therefore suggested that the large diesel vehicles should regulate the fans. The goal of this study has therefore been to find how active diesel vehicles should be able to start and stop gallery fans at both intake and return air. In this paper different methods for activating fans are discussed. Then the best methods are chosen and tested in the mine. In this study we have found that changes of temperature is a cheap and effective method to start and stop cross cut fans in sublevel caving and radio signals seem to be an attractive system for start and stop of gallery fans. This work has been done in close collaboration between LKAB in Kiruna and the University of Luleå - Division of Electronics and Division of Mining and Rock Excavation. A reference group for the project has been established with ventilation experts from the mines, representatives for the local mine worker&apos;s unions and authorities from the local Governmental Inspection of the Workers Safety. VENTILATION SYSTEM STUDIED In the project the ventilation system at LKAB in Kiruna has been studied. The mining method used is sublevel caving with 9-13 m slice height. The air is heated winter time over ground by hot water heat exchanger. The main fans are pushing air down to a main distribution level along the 4000 m long and about 100 m wide orebody. From the distribution level, air is taken through shafts down to the sublevels, where it is pushed through the levels by local gallery fans on both intake and return side, see fig 1. The air ( ~ 8 m3/s) is moving freely through the gallery head. The cross cuts are ventilated with smaller fans, diameter 500 mm, and flexible duct, see fig 2. The aim of this study has been to study how to start and stop gallery- and cross fans and examine the environment when the fans are stopped . In Sweden there are no regulations telling that a minimum of air amount must be supplied. Instead the hygienic limits must be fullfilled.

Jan 1, 1981

By F. Rosenblum, P. Cancilla

The manual moisture determination methods employed today by mineral processing plants falls short in providing timely information required for automatic control. The costs associated with transporting and handling concentrates still represent a major portion of the overall treatment price. When considering the cash flow of a mining operation, that is governed by both the smelter contract, with moisture penalties and the quantity and quality of the concentrates shipped, an efficient method of on-line moisture content would be a welcome tool. A novel on-line determination system for ore concentrate moisture content would replace the normally tedious classic manual procedure. Since the introduction of microelectronic¬based control systems, operators have strived to reduce the treatment costs to the minimum therefore a representative and timely determination of on-line moisture content becomes vital for control set points and timely feedback. Reliable sensors have long been on the "wish list" of mineral processors since the problem has always been that you can only control what you can measure. Today, the task of moisture determination is still done in the classical technique of loss in weight utilizing uncontrolled procedures. These same methods were introduced in the earliest base metal concentrators. Generally, it is acceptable to have ore concentrate moisture content vary within a range of 7 to 9%. Many times, delays in manually achieving reliable feedback on the moisture content results in the moisture varying from 5 to 12% before corrective actions can be made. This paper first reviews the traditional and widely available methods for determining moisture content in granular materials by applying physical principals and properties to measure moisture content. All methods are in some form affected when employed on mineral ore concentrates. This paper describes a unique and promising on-line moisture sensor in two mineral processing applications, which not only automates the tedious tasks but also results in reliable moisture feedback that can be used in the optimization of the de-watering process equipment such as pressure or vacuum filters and fuel-fired driers. Finally, two measurement applications will be presented to indicate the usefulness and to summarize the measurement requirements for the proposed method of employing drag force and mechanical properties of the material itself to determine the moisture content.

Jan 1, 2002

By Harold B. Goldman

On the basis of tonnage, the sand and gravel industry is the second largest nonfuel mineral industry in the United States. In 1990, the production of sand and gravel was 927 Mt valued at $3.4 billion. California, which leads the nation with more than 126 Mt, together with Texas, Washington, Michigan, and Ohio, account for 36% of the total production in the nation (Table 1). In commercial usage, sand applies to rock or mineral fragments ranging in size from particles retained on a No. 200 Sieve (0.074 mm openings) to those passing a No. 4 Sieve (4.76 mm openings). Gravel consists of rock or mineral fragments larger than 4.76 mm, ranging up to 88.9 mm maximum size. The construction industry consumes 97% of the sand and gravel produced; the remainder is sand used for specialized products such as glass (see chapter on Industrial Sand and Sandstone and Glass Raw Materials). Utilization The building industry uses sand and gravel chiefly as aggregate in portland cement concrete, mortar, and plaster; the paving industry uses sand and gravel in both asphaltic mixtures and portland cement concrete. Aggregate is commonly designated as the inert fragmental material that is bound into a conglomerate mass by a cementing material such as portland cement, asphalt, or gypsum plaster. Sand and gravel is also used as construction fill, road base and subbase, and decorative material. Portland Cement Concrete Aggregates: Portland cement concrete consists of sand and gravel surrounded and held together by hardened portland cement paste. Concrete mixes commonly contain 15 to 20% water, 7 to 14% cement, and66 to 78% aggregate. Sand and gravel used as concrete aggregate have to meet many requirements (Goldman and Reining, 1983). Premature deterioration of concrete has been traced in many instances to the use of unsuitable aggregates. Asphaltic Aggregate: Asphaltic mixtures used predominantly for paving consist of combinations of sand, gravel, and mineral filler (material finer than 0.076 mm), uniformly coated and mixed with asphalt produced in the refining of petroleum. Sand and gravel used as asphaltic aggregate must meet the same general physical requirements as materials used for portland cement aggregate. GEOLOGY General Requirements of Aggregates Construction aggregate has many requirements that are difficult to meet if only unprocessed material from natural deposits is used. Suitable material is composed of clean, uncoated, properly shaped particles that are sound and durable. Soundness and durability are terms used to denote the ability of aggregates to retain a uniform physical and chemical state over a long period of time so as not to disintegrate when exposed to weathering and other destructive processes. Individual particles must be tough and firm, possessing the strength to resist physical stresses and chemical and physical changes, that may cause swelling, cracking, softening, and leaching. The aggregate should not be contaminated by excessive clayey material, silt, mica, organic matter, chemical salts, and surface coatings. Physical Properties: The quality of aggregate depends upon its physical and chemical properties. These, in turn, may be inherent mineralogical and textural features of the rock or may be the effects of later changes such as tectonics, mechanical or chemical weathering, or incrustations. The physical properties most significant for concrete use are: 1) abundance and nature of fractures and pores, 2) particle shape and surface texture, and 3) volume changes which may occur because of freezing and thawing or wetting and drying. An aggregate is considered to be physically sound if it is adequately strong and capable of resisting the agencies of weathering without disruption or decomposition. Minerals or rock particles that are physically weak, extremely water absorptive, and easily cleavable are susceptible to breakdown. The use of such materials in concrete reduces strength or leads to early deterioration by promoting weak bond between cement and aggregate, or by inducing cracking, spalling, or popouts. Severely weathered, soft, micaceous, or porous materials may cause localized stresses to develop in concrete by swelling and shrinking during wetting and drying or freezing and thawing cycles. Physical Suitability of the Various Rock Types. Sedimentary rocks have a wide range in physical and chemical qualities. Sand- stones and limestones, if hard and dense, are ordinarily satisfactory, but many sandstones are friable and excessively porous and commonly are clay-bearing. Shales generally make poor aggregate material, being soft, weak, and absorptive. Most igneous rocks are satisfactory, being normally hard, tough, and dense. Tuffs and certain flow rocks may be extremely porous and have high water absorption and low strength. Metamorphic rocks differ in character. Most quartzites are massive, tough, and dense. Fine-grained marbles are usually durable, but coarse-grained marbles have low abrasion resistance. Gneisses are ordinarily very tough and durable. Some schists contain micaceous minerals that are undesirable because they are soft, laminated, and absorptive. Micaceous minerals are susceptible to splitting along cleavage planes and thereby impair particle strength and durability. Some schists and slates in particular are thinly laminated and tend to assume flat slabby shapes that lack strength-and do not pack well. Any or all of these rock types may be rendered undesirable because of harmful exterior coatings. Weathering processes, particularly the action of ground waters, deposit these coatings. The most common coatings are calcium carbonate, clay, silt, opal, chalcedony, iron oxide, manganese oxide, and gypsum. Particles with these coatings are undesirable as aggregates because the bond between particle and coating may be weak, and decreasing the strength of the aggregate-cement bond.

Jan 1, 1994

By John R. Turney

MARY KORPI: Harry Hinds will be filling in for John Turney today. Harry is an exception to the industry these days, in more ways than one. He has worked for the same mining company for 33 years. That is something very few of us can claim. He is currently metallurgical superintendent for Homestake Mining Company in Lead, South Dakota. Harry is also the envy of many of us as he will be retiring this year and working on lowering that handicap! Harry will be discussing the "Role of Consultants."

Jan 1, 1998

By H. J. Zhang, W. Wui

With the adoption of market-oriented economic policies, Chinese non-ferrous metals industry has gained remarkable progress. The continuously increasing domestic demand for non-ferrous metals, however, calls for more import of raw materials in short supply, such as copper concentrate and bauxite. As an alternative for balancing the shortage and assurance of more stable mineral supply, direct investment in oversea mining project has come to the agenda. This paper discusses the computer-assisted method used for evaluation and comparison of potential mining projects.

Jan 1, 1996

By M. B. Mirza, W. A. Sadik, B. T. Stanley

This paper presents the ventilation design for an underground testing facility in a salt medium. The under-ground workings consist of two 3.6 m-diam (12 ft-diam) watertight shafts and about 1830 m (6000 ft) of drifting. These facilities are designed to provide access for an in situ testing of a salt horizon in which a variety of hazardous and nonhazardous materials could be temporarily stored or permanently deposited. The ventilation system includes a design basis for gassy mine conditions and provides for the option of bulk air cooling and heating.

Jan 1, 1987

By Kal V. S. Sastry

Mathematical and expert system models are being used extensively for mineral process engineering; nevertheless, standardized methodologies for their computer implementation do not exist. In meeting this need, this paper introduces the concept of a process software model, or more specifically an object-oriented software model, and presents a detailed methodology for its development involving software model specification and development. These software models provide a formal basis for the subsequent design and construction of software objects corresponding to the real world process objects.

Jan 1, 1995