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By Martin Oatman, Lawrence Lenahan

The West Seattle Tunnel is part of a regional sewer conveyance system located in Seattle Washington. The tunnel was constructed for the Waste Water Treatment Division of the King County Department Of Natural Resources, from June of 1995 through the first quarter of 1997. The Geologic setting for this soft-ground tunnel consists of glacial, interglacial, glacio-lacustrine, and alluvial soils. This paper, prepared jointly by the owner and con-tractor, will describe project-related site geology, engineering considerations, construction, and dispute resolution/avoidance practices.

Jan 1, 1997

By K. W. Harris, K. A. Perry

Underground coal mines beneath Black Mountain in the Harlan County district of the Central Appalachian coalfields have an extensive history of bump events, which yields an elevated probability for significant injury or fatality to underground miners. According to Mark (2009), Harlan County has had the greatest concentration of deep-cover retreat mining in the United States. Combined with the extensive multiple seam mining history, room-and-pillar coal bumps have had a disproportionate impact on coal operations in this region. The Harlan seam, one of the principal, economically recoverable coalbeds exploited beneath Black Mountain, has a significant burst history that extends into modern times. A numerical investigation using the LaModel software of 17 bumps that occurred at the same mine in the Harlan seam was conducted and used to create a calibration methodology which serves as the quantitative basis for current and future numerical efforts in an adjacent mine exploiting the same reserve. In addition to this numerical study, a qualitative assessment of the geologic factors that are believed to contribute to the bump potential was completed. Combined with stability prediction using the numerical basis, these geologic factors will be used for recognition of high bump potential areas with the goal of reducing the potential for future bumps, helping to ensure the highest level of safety and productivity for underground personnel.

Jan 1, 2016

By Vernon N. Cox

From comments and questions concerning the meaning of USNR, and "why is the Navy in the mining business?" I believe it is worth while to establish the background and purpose of our company. We are a stock company formed by the purchase and reorganization of a company known as the U. S. Natural Gas Corporation. In May 1969, a group of investors with Mr. Robert L. Katz as president and chief executive officer, created United States Natural Resources, Inc., to develop and purposively use our Natural Resources in four areas: 1. Mines and Minerals 2. Forest Products 3. oil and Gas 4. Recreational Lands As final proof that we are not a government organization, I simply state. "We pay taxes." The mining division was formed in October 1969, with the completion of the merger of USNR and Vibration Measurement Engineers, Inc., Of Evanston, Illinois. Throughout the industry we were known as "VME," our company supplied consulting service in the field of seismic energy control, mining consulting and. we operated drilling, blasting and, contracting organizations in several areas of the country. Since that time we have developed and acquired producing properties in Quarrying, Coal Mining and Cement Copper Production.

Jan 1, 1971

General. Data for the operating information given in the 15 tables in this chapter was obtained from voluminous questionnaires sent to over 100 operating companies in 1972. There has been a considera¬ble change since then in supply and power costs and many companies have had expansions or revisions since that time, so it must be realized that information is valid for the year 1972. This is true except for the three new properties of Sacaton, Metcalf, and Pinto Valley. These three operations started up since 1972 and all information for them was obtained in 1975. The questionnaires were sent to all major copper properties throughout the world as well as to many smaller units and to some mines that had complex or unusual conditions. Properties for which no information is given did not submit completed questionnaires. Several operations were unable to supply information requested be¬cause of company policy prohibiting it. However, data is presented for 75 different operating properties. The reference number of the left-hand column is the same for all 15 tables of data. If the company had several operating properties as of 1972, then subsequent properties use the same number but a different letter. For example, Anaconda's property at Butte, Mont., is IA, whereas Anaconda's (now Anamax) Twin Buttes property in Arizona is IB. Table I gives general data for the properties including exact loca¬tion, milling rate, pertinent assay values and recoveries, and a brief listing of ore and gangue minerals. It was not possible to obtain any more information from the properties in Chile except that given in Table I. Crushing. Crushing plant operating data is given in Table 2. This table gives data on the crushers, feeders, and screens used at each property. The data obtained on feeders was confusing, but, rather than completely eliminate this information, it was decided to report it as given. The confusion lies only in the description of where the feeder is located. Where a primary feeder is listed it was not possible to determine if this feeder was on primary feed or primary discharge. For secondary feeders it is known that the feeder listed usually is feeding the secondary crushers, but at some properties it is handling the secondary crusher discharge. The same reasoning holds true for tertiary feeders-they handle either tertiary feed or discharge. This table contains a voluminous amount of data. A column giving tons per day per square foot of screen area would have been very informative, but some properties included circulating load in the feed rate and others listed new feed only, so calculations were meaningless. Autogenous Mills. The use of autogenous or semiautogenous mills for any property must be given serious consideration in the future. Table 3 lists data for four properties that are fully autogenous and four more semiautogenous mills that use balls to supplement the chunks of ore. This method of grinding is especially applicable when the ore is of such a nature that crushing problems would be severe, such as when ore is wet or sticky or contains a lot of fines. Paradoxically, it should also be considered when ore is tough and hard and blocky because then the competency of the ore means it can serve well as the grinding media. Where the ore varies greatly in hardness, as at Cyprus Pima and Lornex, semiautogenous grinding has been especially beneficial with capital costs and operating costs both 10-20% lower than could be obtained with conventional crushing and grinding. Rod Mills. For a great many years the standard milling operation used two- or three-stage crushing followed by open circuit rod mills and then ball mills in closed circuit with classifiers of some kind. A surprising number of properties crush to the fine size of about 3/8 in. and then use ball mills only, in closed circuit, with no rod mills. It is difficult to say whether rod mill-ball mill circuits or ball mill only is the best. One can be certain of two things: (1) the argument will go on for a long time and (2) for some mills one method obviously was superior over the other. As ball mills of 14, 15 ft, and larger came into use, more properties like Duval Sierrita (16b ft diam by 19 ft long) and Bougainville (18 x 21 ft) were built with single-stage ball mill grinding. Although there are larger rod mills used, especially in the iron ore industry, the largest rod mills on copper ore are at Twin Buttes (14 x 18.5 ft) and at Gibraltar (13'A x 20 ft). Table 4 lists operating data for rod mills. If a company is listed in Table I

Jan 1, 1985

By Joseph B. Gillenwater

Miss Gertrude Carey lived next to us in Martinsburg, West Virginia for several years. She was a retired school teacher. She was also a cousin to Messers Dan and Joe Baker who owned and operated Standard Lime and Stone Company, a predecessor of Martin Marietta Corporation. She-was well acquainted with the Baker family and their history. Here is one of the legends she told my wife, Jean, and me. The Bakers were originally Tanners. They had a tannery near Frederick, Maryland. There were several boys in the family and when they were grown each man had specified responsibilities. Will Baker was assigned the duty of locating, buying, and transporting tanbark and lime. As he traveled through Maryland, Virginia, Pennsylvania, and West Virginia to locate and buy tanbark, he also talked the farmers out of some pieces of lime, which the farmers had produced in holes dug and filled with layers of limestone and wood. Will Baker took the lime and soaked a piece of hide in the milk of lime. If the lime did not spot the hide, Will Baker would get the farmer to burn some lime for him, and further tests would be made. If these tests were good - the Bakers bought the land. They eventually discovered that the limestone that would make lime that wouldn't spot the hide would also be suitable for producing steel. They began producing lime just outside Harpers Ferry, West Virginia in pots and upright kilns. That stone too small for the kilns was just perfect for railroad ballast. Now you know how "Baltimore Blue Bloods" got together!!

Jan 1, 1979

By W. R. Bruce, R. W. Wittkopp, R. L. Parratt

Introduction The Relief Canyon gold deposit is about 24 km (15 miles) east of Lovelock at the south end of the Humboldt Range in northwestern Nevada. The deposit, is in the Relief-Antelope Springs mining district, which has historically produced silver, antimony, and mercury. There is, however, no mention in the literature of commercial gold production. Fluorite prospects at the gold deposit site have had no reported production. At Relief Canyon, the Late Triassic Grass Valley formation overlies and is in fault contact with the Late Triassic Natchez Pass formation. Epithermal disseminated gold mineralization is found within the various types of fault breccia between these two formations. Geology The Natchez Pass formation of Late Middle to Late Triassic age is composed of more than 300 m (985 ft) of massive gray to dark gray locally carbonaceous dolomitic limestone. Some minor beds of shale and siltstone up to 1 m (3 ft) thick are found in the project area. The limestone is locally silty or sandy. The color of this formation below the oxidation base ranges from gray to black and appears to be a function of carbon content. The Grass Valley formation of Late Triassic age is composed of more than 200 m (655 ft) of interbedded units of thinly parted argillite, hard gray to brown quartzite, siltstone, and shale. Within the oxidation zone, these units are olive gray. A few beds within this formation are slightly calcareous and a number of sections, especially those containing shale, are dolomitic. Below the oxidation zone, the quartzite beds are often slightly carbonaceous and the argillite, siltstone, and shale beds are often highly carbonaceous, giving them a black color. Two types of intrusive rocks have been recognized at the Relief Canyon deposit. Both appear to predate mineralization. Fine to moderately fine grained quartz monzonite dikes, up to 3 m (10 ft) thick, were encountered in several drill holes. In a number of intervals, these dikes have undergone either propylitic or argillic alteration. The age of these types of dikes is not known. It appears, however, that they are either Jurassic or Cretaceous. No gold mineralization has been found in this type of dike. Diabase dikes were also encountered in a number of drill holes. These dikes have almost always been propylitically altered. Although the exact age of the diabase dikes is not known, they are probably equivalent in age to the quartz monzonite dikes. Quaternary alluvium is found forming fans at the base of steep slopes and as recent fill in present day drainages. The alluvium is composed of either Natchez Pass limestone or Grass Valley quartzite and siltstone, depending on which unit served as the bedrock source. A significant portion of the Relief Canyon deposit is covered by Quaternary alluvium. Figure 1 shows a generalized geologic map of the Relief Canyon area. At the deposit's site, the Grass Valley formation appears to have been thrust over the Natchez Pass formation. The age of the thrust is probably correlatable with the Nevadan Orogeny, which gives it a Jurassic-Cretaceous age. The general strike of the thrust, referred to as the Relief Fault, is in a northwest direction. The strike of the bedding of both the Natchez Pass and Grass Valley formations roughly parallel the strike of the Relief Fault. The general dip of both the Natchez Pass and Grass Valley formations is in a southwest direction. The general dip of the Relief Fault, in the area of the Relief Canyon gold deposit, varies and has the appearance of a northeast-southeast striking anticline that plunges in a southwest direction. A small fold perpendicular to the plunge of this anticline forms a dome over the southerly portion of the Relief Canyon deposit. A number of northeast and northwest trending normal faults slightly offset the Relief Fault. Because of their small displacement, they are not shown on the generalized map. Gold Mineralization Gold mineralization occurs along the highly brecciated fault contact between the Natchez Pass and Grass Valley formations. Weak gold mineralization often occurs up to 2 m (6.5 ft) above the thrust in the Grass Valley formation. Most of the ore grade mineralization, however, is present below the Grass

Jan 11, 1984

By Barrie Butt, V. S. Znamensky

The opportunity for an exploration geologist to follow a successful exploration project through the feasibility, financing, construction, development, and exploitation phase is rare. In addition, it is not often that the exploration geologist can be present during the mining of a deposit to explain why certain actions were taken or interpretations made, and to find out how these interpretations turned out in actuality. At the Woodsreef chrysotile asbestos mine in New South Wales, Australia, mining has been- in progress for seven years and the writer of this chapter has been intimately associated with the project during the five years of exploration and seven years of exploitation. The Woodsreef mine has had major production problems, the majority of which have stemmed from the unique characteristics of the ore body and fiber. Because of the latter feature, much research has been undertaken by Woods- reef and other scientific organizations in Australia, England, and Canada regarding the Woodsreef fiber. The answers to some of the problems have negated some accepted concepts of asbestos ore milling and led to the development of new techniques. Some of these new techniques include the adoption of microscopic fiber counts as a routine procedure, the modification of accepted evaluation procedures, the development of new machines for dedusting fibers, and the recognition of a fiber with a unique milling behavior pattern and, possibly, properties. The problems experienced can be broadly divided into those associated with the geology and the physical properties of the fiber. It is possible that the same features may manifest themselves in other deposits around the world, and if they can be recognized during the exploration stages, a feasiblity evaluation may be just a little closer to the actual. The Woodsreef chrysotile asbestos deposit (latitude 30°24' S, longitude 150°44' E) is located 80 km north of Tamworth, NSW, Australia. The mine has been in production for six years and has a present scheduled mining rate of 33.11 Mt/y. An eight rock line mill treats an average of 7000 t/day, after beneficiation, and yields fiber grades in the range of group 4 to group 6 with some floats. The estimated re- serves of 30.56 Mt, with an ore to waste ratio of 1:3.0, are contained in two main zones that are designated the North and South zones. Mining started in the South Zone in 1972 and then, be- cause of the higher ore value, moved to the North Zone in 1975. Presently, there are two distinct open cuts referred to as the South and North pits that will eventually be worked together. The Woodsreef mine is owned by Woodsreef Mines Ltd. and is operated by Chrysotile Corp. of Australia Pty. Ltd., and is one of only two producing asbestos mines in Australia. The second mine is at Baryulgil, (latitude 29°13' S, longitude 152°37' E), and is operated by a subsidiary of Woodsreef Mines Ltd. This operation produces about 500 t/y for a captive market. An exploration program is being conducted in the area surrounding this small producer with a significant degree of success. The concepts developed during the exploitation of the Woodsreef deposit are being incorporated in the evaluation of the Baryulgil area, and if the Baryulgil deposit proves to be eco- nomic it is hoped that this approach will eliminate some of the major crises that have beset the production at Woodsreef during the first four years of operation. The purpose of this chapter is to describe the Woodsreef deposit, and more important, to

Jan 1, 1986

By H. M. Breza

Utilization of Bucket Wheel Excavators and Overland Conveyor Systems to remove overburden provides increased productivity and flexibility to a surface mining operation. The utilization of such a system at the Texasgulf Inc. Aurora, North Carolina Mine has significantly improved the overall productivity of the mining operation. System flexibility is evidenced by adaptation to operation requirements such as mining area moves, movement of excavated overburden to designated sites, selective handling of overburden, spoil placement contouring, and providing an environmentally sound and safe operation. System productivity is evidenced by actual case studies relating to overall production, excavation rates, and cost effectiveness.

Jan 1, 1993

By K. Perry, R. Eades

"Highwall miners continue to be implemented by operations to increase recovery, improve margins, and justify higher stripping ratios as high quality surface reserves become increasingly rare. Many times, operations facilitate projected underground operations by leaving an intact highwall for development purposes. These facts result in larger highwalls that are left standing for increased periods of time prior to reclamation. As a consequence, worker exposure and risk is also elevated, resulting in higher potential for accidents or fatalities relating to surface highwalls. Highwall stability is a complex issue, dependent on both geologic and mining factors. Dynamic numerical modeling offers the capability to assess possible stability issues related to blasting-induced ground vibrations. Research has been conducted to evaluate the effect of highwall stability due to ground vibrations from blasting events. Additionally, the relationship of amplitude and frequency, and their impact on highwall stability is investigated. The results of this modeling indicate that amplitude has little impact on stability. However, frequency has a significant impact on highwall stability. INTRODUCTION The number of mining fatalities has declined since 2010, and 2016 is currently on pace to continue this trend (MSHA 2016). This decline can be directly correlated to the decline in surface mining activity and the overall decline of the coal industry. However, since 2002 the percentage of surface coal mine fatalities associated with highwall activities remains relatively high, constituting approximately 15% of all surface mine fatalities. 2014 was the first year with a highwall failure fatality since 2011. Most recent surface coal mining fatalities are associated with machinery and haulage. Table 1 provides a summary of the total surface coal mining fatalities, and the number of highwall failure fatalities dating back to 2010.Highwall stability is a complex issue, dependent upon geology and geologic discontinuities within the rock mass, along with highwall geometry, standing time, and applied stresses. Another possible concern that has not been previously investigated is the effect of blasting-induced stresses on highwall stability and the stability of web/barrier pillar systems as a result of ground vibrations from blasting events. Many modern surface coal mines employ numerous extraction fronts that rely on blasting for primary rock breakage. This results in highwall and highwall pillar systems experiencing blasting-induced stresses of many different types and magnitudes."

Jan 1, 2017

By Jonathan M. Pachter

The Bailey mining complex is located in Greene County, PA in the valley of Talley Run, a small stream tributary to the Enlow Fork of Wheeling Creek as shown on the location map insert found on Figure 1. The Bailey complex includes two Pittsburgh No. 8 Seam deep mines (Bailey and Bailey #2), a coal preparation plant, and two refuse areas (for disposal of coarse and fine processing waste). Clean coal is shipped from the complex via a 24.15 km (15 mile) rail spur, which connects to the Monongahela Railroad in Waynesburg, PA. In early 1981, Consolidation Coal Company (Consol) began a permitting effort aimed at beginning construction of Bailey, the largest underground coal mining complex to be built to date in the United States. Construction of the Bailey Mine began in December, 1981, less than six (6) months following the first application submittal. Clean coal was produced by the Bailey Preparation Plant in September, 1984. Effective project planning, including early formulation of a project planning team, identification of "red flag" issues, innovative responses to environmental questions and development of environmentally sound project designs, all contributed to the relatively quick permitting at Bailey.

Jan 1, 1985

By Randall C. Divito, Craig R. Eckdahl, Bruce D. Wagener, Joseph Klejwa

The existing Central City Tunnel was built primarily in the 1930s with a small portion as old as the 1880s. It conveys stormwater in downtown Minneapolis. It is a 4,400-ft long tunnel located 80 feet underground. The Central City Tunnel has experienced surcharging and surface overflows during heavy rainfall events. This paper presents the details of tunnel and shaft design for the new Central City Parallel Tunnel to mitigate the overflows. The design considered hydraulics and geotechnical engineering for the structural geologic conditions including the weak Saint Peter Sandstone and overlying strong Platteville Limestone. Ground conditions resulted in tunnel designs including large flat-back box tunnels and unique cathedral-shaped tunnel sections.

Jun 13, 2023

By D. A. Robbins

The application of remote sensing for environmental measurements is already being utilized. Aircraft mounted imaging spectroscopy has been utilized to evaluate areas of historical mining operations as well as active mine sites. To the extent that remote sensing can provide more sensitive, cost effective, and timely monitoring potential, the technology is of interest to the industry. Questions remain about the application and validation of the data and the availability of the technology in the private sector. This presentation will discuss some of the potential uses, benefits, and concerns related to remote sensing and efforts to monitor the technology's development.

Jan 1, 1999

By Kunio Hashimoto

The conventional troughed belt conveyor system is the most widely used form of equipment for transporting bulk materials in the world today. The reason is not only because it is possible to transport a great deal over a long distance when compare to other types of equipment but also due to its greater economic efficiency and low initial and running costs. When dry, powdery materials and liquid materials are being conveyed, there are enclosed transport methods such as flow, case, air-slider and pipe line. In addition to features of the belt conveyor, a system employing a pipe line to transport dry powdery and liquid materials has always been considered an ideal method. This has been brought into reality through the Pipe Conveyor Sys tem.

Jan 1, 1984

By G. J. Schneider

The higher stress zone adjacent to an underground opening causes a velocity anomaly that can be mapped in favorable conditions with an acoustic cross-borehole logging system. Bureau personnel used a specialized system at the Colorado School of Mines test site near Idaho Springs, Colorado, to locate the Edgar Mine tunnel and its associated stress anomaly. Data from the logging system' were processed with a tomographic image reconstruction algorithm to map the opening and the location of the high velocity zone around the opening. The velocity imagery from tomographic analysis compared favorably with predictions from numerical modelling of the location of the stress anomaly.

Jan 1, 1988

By David I. Smith, Kenneth Arnold, Bryan Aweh, Vincent Falkowsk, Brian Lakin, Andy Fer

Nassau County, New York, is undertaking several projects to improve the water quality in the Western Bays of Long Island. A major step forward will be the completion of the Bay Park Conveyance Project, which will divert most treated effluent away from the Western Bays to an existing ocean outfall at the Cedar Creek Water Pollution Control Plant. The ongoing works include 3.6 miles of microtunneling, 7 miles of sliplining, 14 shafts, and a 75 MGD pump station. This paper provides an overview of the design and an update on construction progress through December 2022. The project is a collaborative effort between Nassau County, New York State Department of Environmental Conservation, the design-builder, and various consultants.

Jun 13, 2023

By R. Rodgers

The Pinto Valley Concentrator of BHP Copper Inc. restarted its sulphide mining operations in September 2007 to produce copper and moly concentrates. During the plant production ramp up, the copper/moly circuit quickly reached the copper grade and recovery targets, but the production and quality of the moly concentrate continued to be a challenge. Even though several improvements in the moly circuit were completed, the final moly concentrate did not meet contractual specifications. After reviewing several options to improve grade and reduce contaminants, the installation of three flotation columns was chosen. The column design and construction were done utilizing in-house craftsmen and engineers. Ten days after commissioning, the columns successfully reached a steady operation and began producing moly concentrate to the required specifications, that is, high moly tenors and low copper and iron content. In this paper, the operating parameters, mass balance, design, installation, commissioning and operation of the new flotation columns will be discussed.

Jan 1, 2010

By Arthur R. Still, Paul A. Bailly

5.1-PURPOSE, PROCEDURE, METHODS, MANAGEMENT Exploration can be technologically defined, with regard to the discovery of new mineral deposits, as all the activities and evaluations necessary before an intelligent decision can be made establishing size, initial flowsheet and annual output of new extractive operations. The purpose of mineral exploration is the discovery and acquisition of new mineral deposits amenable to economic extractive operations now or in the future. A prime objective of mineral exploration, however, is to find and acquire a maximum number of such mineral deposits at a minimum cost and within a minimum time. Immediately upon the heels of a successful ''exploration" discovery follow activities called, first, development, then operation. Under U.S. Internal Revenue Code regulations (Secs. 1.615.1 and 1.616.1) in effect at the time of this writing, which state that the "development stage" has been reached when "deposits of ore or other minerals are shown to exist in sufficient quantity and quality to reasonably justify commercial exploitation by the taxpayer," exploration in the technological sense may well continue after a mineral property has entered the "development stage" as defined for tax purposes. In many instances continued exploration, after reaching the tax defined "development stage," has disclosed additional reserves which justify a much larger, more efficient and more profitable operation than that which would constitute the minimum feasible. Even after a mine goes into production, continued ore search generally will increase the reserves, either justifying expansions in plant capacity or prolonging the life of the operation, but this work (actually "exploration") is normally considered, for bookkeeping and tax purposes, a part of mine development. Each exploration entity defines its own objectives in terms of acceptable mini- mum rate of return on investment for any deposit found and retained, and in terms of which commodities, and markets, are to be involved. For these reasons, exploration programs, and aims, will vary over a wide range, although all have the common objective of endeavouring to create new profit centers for the future. 5.1.2-EXPLORATION METHODS Exploration has evolved in the past several decades into a highly sophisticated and expensive endeavor in which large corporate entities, or subsidaries, normally are directed and staffed by highly trained exploration specialists. In some instances consultants, with expertise in a given field, are utilized to the benefit of such corporate groups. The "grasshopper" approach to exploration-searching only for outcropping minerals and/or investigating only mineral prospects offered by the discoverers of such outcrops has given us most of the past and present mines in the US., but this method is rapidly approaching the point of diminishing returns in areas that have been thoroughly prospected for currently marketable commodities. With

Jan 1, 1973

By W. S. Sanner

Experiments were conducted to determine the quantity and purity of ultraclean anthracite that could be prepared in the laboratory, using conventional separating techniques. A low-, a medium-, and a high-volatile anthracite were studied. Specific gravity separation followed by grinding, screening, and refloating at lighter specific gravities yielded small quantities of material purified to 1.0 percent ash, as follows: From low-volatile anthracite, 0.7 percent; from medium-volatile coal, 1.0 percent; and from high-volatile coal, 2.3 percent. The reduction in ash had no appreciable effect on the volatile matter or sulfur content of the coal. The limited quantities of material containing 1.0 percent or less ash obtainable indicate that if ultraclean coal is desired, a practical approach should include the processing units as an integral part of a conventional dense-media washing plant.

Jan 1, 1968

By E. B. Fitch, D. A. Dahlstrom

Liquid-solids separation is common to practically all mineral and coal processing as the bulk of beneficiation plants employ water as the major processing vehicle. The growing usage of hydrometallurgy has increased the importance of liquid-solid separation as acidic and basic solutions result in greater amounts of colloidal solids, with their consequent greater difficulty of separation, the economic need for chemical recovery to minimize this operating cost, and the usual necessity of employing more costly construction materials. The three processing steps covered in this section have significant capital costs. Drying, particularly, has an important operating cost because of the obvious need for energy to evaporate the water or solvent. Several common factors influence all three liquid-solid separation steps. Particle Size and Size Distribution. In general, finer particles have slower settling and filtration rates. The specific surface area is increased, which means a lower solids concentration in the thickener underflow and discharged filter cake as well as a grater moisture content to be evaporated in the drying step. Therefore, overgrinding or excessive attrition should be avoided. Consideration should be given to optimum particle size consistent with entire plant operation performance and recovery. Solids Concentration. Increased feed solids concentration will generally minimize required equipment size and costs in all three liquid-solid separation steps. Most thickeners are designed on the basis of unit area required, expressed as square feet per short ton of dry solids per day (square meters per metric ton per day) which will usually decrease with increased feed solids concentration. Filtration rates also increase as the required flow through the capillaries of the filter cake decreases. Dryer capacity increases and less energy per ton of final product is required to evaporate the associated moisture. Particle Shape and Surface Characteristics. Generally, optimum shape is a spherical particle of zero porosity. As either of these factors degrade away from the desired state, difficulty increases. This is particularly true in drying, where porosity can decrease drying rate significantly if the moisture must first reach the particle surface by diffusion

Jan 1, 1985

By R. W. Reisinger

An historic underground copper mine in Wyoming is discharging neutral but copper-laden water into a pristine creek. The EPA-deferred site qualifies for reclamation by the Wyoming Abandoned Mine Land (AML) program. The cleanup goal is to restore the discharge so that the creek can eventually support a trout fishery. Hydrological and geochemical investigations underground have suggested two sources of mine water: one clean and the other containing copper. Results of bench-and pilot-scale tests support the viability of using low-cost passive treatment techniques to reduce copper concentrations in the near-freezing mine discharge.

Jan 1, 2000