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By L. S. Harris

The application of briquetting in various chemical, mineral, mining and metallurgical processes has been rapidly increasing in the past two decades. This is, in part, due to the development of new, more economical and higher performance briquetting equipment. Some of these developments, which have reduced the operating and maintenance costs,, include anti-friction bearings, hydraulically applied pressure enclosed and sealed gearing and bearings, tapered predensification feed screws, water cooling and materials of construction capable of operating at temperatures up to 18000F, and control systems capable of maintaining optimum briquette quality control. The briquets can be formed into almost any desired size and shape, To date, with present rotary briquetting presses in the 25 to 500 ton force range, briquets from 1/4" to 6" length are presently being used, some of which are illustrated in Figure No. 1. In force fed rotary briquet machines, these shapes are produced by feeding the material in between a pair of counter rotating rolls, as illustrated in Figure No. 2. The rolls have forming dies indented into their circumferential surface, as illustrated in Figure No. 3.

Jan 1, 1973

By Art Hamid, Manfred Wong, Carlos Jaramillo, Greg Raines, John Caulfield

"The Central Bayside System Improvement Project (CBSIP) is a critical element of the Sewer System Im-provement Program (SSIP), a 20-year, $6.9-billion investment by the San Francisco Public Utilities Commis-sion (SFPUC) to upgrade San Francisco’s 100+ years old seismically vulnerable combined sewer system. The CBSIP’s centerpiece, a proposed 10,000-foot-long (3,048-meter-long) Channel Tunnel, will provide reliable and redundant gravity conveyance and storage of combined wastewater flows from the northern and central parts of San Francisco to the Southeast Water Pollution Control Plant (SEP) while ensuring compliance with regulatory requirements for combined sewer discharges to the Bay. A tunnel with a diameter of 23 to 30 feet (7 to 9 meter) is being planned using pressurized-face tunnel boring machine technology. Project challenges include tunneling through Franciscan Bedrock, mixed ground conditions in close proximity to the Bay, connector tunnels and shafts, construction in congested urban environment, and challenging real estate issues for shaft access. BACKGROUND AND NEED FOR TUNNEL The City of San Francisco is one of the most beautiful cities in the world. About 850,000 people live in the city and many more come to work, for tourism, and for attending conferences. The SFPUC is a department of the City and County of San Francisco that provides energy, drinking water and wastewater services to San Francisco, wholesale water to three Bay Area counties, and green hydro-electrical and solar power to San Francisco municipal departments. The SFPUC wastewater system includes tunnels, large storage/transport boxes, 1000 miles of collection sewers, 28 pump stations, and three wastewater treatment plants. San Francisco’s combined sewer system collects both wastewater and stormwater in the same sewers, which is then pumped, treated to stringent state standards and discharged into the San Francisco Bay and Pacific Ocean. After decades of service, much of the sewer system is nearing end of its working life. During the 1989 Loma Prieta earthquake, damage to SFPUC water and wastewater infrastructure was extensive. The 11,200-foot-long (3,400-meter-long), 66-inch-diameter (1,676-mm-diameter) Channel Force Main, built in 1976, and a critical component of the SF wastewater system was also damaged. This force main carries 70 percent of the bayside dry weather sewage flow from the northern and central part of the city to the SEP. The force main is at the end of its life and was not constructed to the current seismic code; in addition it has no redundancy. Figure 1 shows the project background and the force main that will be provided redundancy by the new gravity tunnel."

Jan 1, 2016

By T. Reed Scollon

Major interrelated factors to be considered in assessing the impact of air pollution control regulations on coal are: (I) the fuel and fuel-related limitations of such regulations; (2) the rate of adoption and areal scope of the regulations; and (3) the availability of fuels and fuel-burning equipment to meet the requirements. A growing number of regulations contain provisions limiting the emissions of sulfur oxides or the sulfur content of fuels or both. With few exceptions, these limitations have not yet become fully effective in those areas which have already adopted regulations, and pertinent details of future regulations or legislation for most other areas are unknown at this time. Sufficient information is not avail- able to determine the availability of low-sulfur fuels at various demand and price levels, and large-scale commercial feasibility of sulfur-oxides removal processes and equipment is believed to be some years away. Accordingly, with the many uncertainties and unknowns, it is possible at best to make only a rough assessment of the impact of such regulations or legislation on coal.

Jan 1, 1969

By W. S. Urbanski, A. L. Devernoe, M. S. Walker

Theory and practice are described for a new processing method capable of precise mineral separations based primarily on differences in particle specific gravities at specific gravity split points from 1.5 to 21.0 and beyond. Separations are analogous to those achieved using rotating heavy media, except that the effective specific gravity of the fluid is created magnetically using a relatively dilute, low-viscosity, water-based magnetic fluid. Results reported here for a large, laboratory flow-through separator include: 1) 99% grade with 97% recovery in single pass separation of a suite of heavy minerals from quartz at I0 kg/h, 14 tph/rm2 of duct cross section, 2) 90% grade and recovery in single-pass separation of mixtures of sand-size, non-magnetic rutile (4.23 specific gravity) and zircon (4.72 specific gravity) at throughputs of 35 kg/h, 47 tph/rm2 of duct cross section, 3) partition curves having Ep90-10 transition widths 5% or less of mineral specific gravities, and 4) essential confirmation of the theory.

Jan 1, 1991

By Thomas Pollard

It is truly remarkable how the image of longwall as a method of mining has changed. Between 1920 and 19609 viewed on a world wide basis, longwall was regarded as a' system for difficult and deep conditions and associated with intensive labour extraction. Today the world looks on longwall in the hope that it can produce the next really big break through in productivity, Three correlated machinery developments have made this possible, but it is not only the machinery developments, interesting though these be in themselves, but together with developments in control systems of these machines that longwall now looks so much more attractive, The machinery concerned is, of courses:- 1. The Anderton Shearer Loader - A miner that takes a narrow strip off the, face at rates acceptable to modern mining engineers. 2. An Armoured Flexible, Conveyor which can be kept in close contact with the face and still convey coal as it is snaked over to the faces 3. Powered support systems which can be mechanised and controlled with reliability at any distance from the individual support itself.

Jan 1, 1964

By Thorvald Wetlesen

Computer controlled drilling is now proven technology. It was first introduced by the development of the Furuholmen system for a prototype three boom tunneling jumbo in Norway in 1978. Now, 13 rigs with this concept are in operation in Europe, 3. in mining in England and. 10 in tunneling elsewhere in Europe. The system is also adapted to roadheader guidance. Practical experience has shown that the computer control system makes it possible to drive tunnels with a more accurate contour thus reducing the total amount of rock excavated, and where a full concrete lining is required a reduction in concrete volume is achieved. The total tunneling economy is improved. In the future we expect to see a wider range of instrumentation on jumbos, from the simple direction instruments to computer guidance systems for monitoring only, as well as fully automatic drilling to a programmed drilling pattern. More compact and reliable electronics will be available. Systems with low power consumption will fit easily into flameproof applications. Cabling complexity will be reduced by connection of sensors to serial signal lines.

Jan 1, 1989

By J. M. Stewart

The incidence of heat stroke in the South African gold mining industry is today small (less than 1 in 10 6 shifts worked). Acclimatization and selection procedures have been developed and applied throughout the industry, underground working conditions have, and are being improved, and personnel are to-day made more aware of heat stress and its consequences than ever before. Although these actions have, over the years, brought about a steady reduction in the incidence of heat stroke (see Figure 1) the small incidence of heat stroke which persists indicates that heat stress is still a problem. This realization provides the stimulus for the work presented in this paper, which has as its primary objective the development of reliable heat stress limits for men working in South African gold mines. [ ] In keeping with recent trends3I4 the approach followed in this paper is based on the physical principles of heat transfer. Detailed studies of heat transfer from humans have been undertaken,5-l1 and certain of the results form an important aspect of this Paper -

Jan 1, 1980

By L. A. Taylor

The production of oxygen on the Moon utilizing indigenous materials is paramount to a successful lunar colonization. And several processes have been put forth to accomplish this. The LLOX generation schemes which have received the most study to date are those involving?: 1) the reduction of ilmenite (FeTi03) by H2, C, CO, CH4, CO-CI2, & Cl2 plasma, 2) magma electrolysis, both unadulterated and fluoride-fluxed, and 3) several others, including carbo-chlorination, HF acid leaching, fluorine extraction, magma oxidation, and vapor pyrolysis. The H2 reductions of ilmenite and magma electrolysis processes have received the most study to date. They are both feasible schemes with various pros and cons, including their feedstock requirements. However, all processes should be addressed at least at the onset of our considerations. There is an obvious need for considerably more experimentation and study. Some of these requisite studies are in progress, and this paper reviews several of the most studied and feasible processes for winning oxygen from lunar materials.

Jan 1, 1991

By E. R. Hendrickson

About 1/3 of the world's supply of phosphate rock is produced in a relatively small area of the Florida peninsula east of Tampa. Until this past year, a circle with a radius of about 25 miles and centered on Bartow would encompass the major producing areas. During the past year producing areas have opened in North Florida which promise to vie with the Polk-Hillsborough County area in terms of proven reserves. In addition, new phosphate production is planned for counties to the south and west of the present fields. From the existing production areas, however, more than 19 million long tons of phosphate were mined in 1965. As mining engineers most of you probably are familiar with the methods of mining and beneficiating the pebble phosphate rock. You thus recognize that, although some water quality problems may arise from these processes, there is no potential air pollution problem. To make an economically useful product, however, further processing must take place. It is from this additional processing that potentially damaging materials may be discharged to the atmosphere.

Jan 1, 1966

By Hasan Sevim

A computerized heuristic model for an efficient and economic design of belt haulage networks in underground coal mines is discussed. The model is versatile, easy to use, and is valid for all mining methods singly or in combination. It may be used to design new networks or to analyze existing networks. The input data required are 1. maximum production rates from a section, 2. probabilities of production rates, 3. equipment costs, and 4. data necessary for network coding to represent different cases. The objective function is the "expected minimum cost per ton of coal hauled" while meeting production requirements. The output includes belt width, motor horsepower, bin size etc. and also values of operating parameters for each belt such as belt speed, effective tension, power consumption etc. A detailed account of the cost involved is also provided for each unit as well as for the entire network. Description of the model and an example of the design of a belt network in a mine with two longwall and four development sections are presented.

Jan 1, 1986

By Janusz S. Laskowski

Studies carried out over the last 10 years reveal that precipitating particles which may appear in alkaline solutions of long-chain amines and in acidic solutions of fatty acids exhibit clear isoelectric points around pH 10.6-1 1 for dodecylamine and around pH 2.5-3 for fatty acids. These colloidal species can accumulate at solid/liquid and liquid/gas interfaces and affect flotation. While the precipitate in solutions of fatty acids apparently can chemically interact with the mineral surfaces and is flotation-active if sufficiently long conditioning time is available, the cationic flotation of quartz in alkaline solutions is depressed by the colloidal precipitate. The experimental data available in literature on the adsorption, electrokinetic, contact angle and surface forces measurements in the solutions of the weak electrolyte collectors are analyzed and the role played by the precipitate is discussed. It is shown that these concepts allow for an explanation of the selective flotation of sylvite from halite with long-chain amines in potash ore flotation.

Jan 1, 1999

By R. E. Johnson, J. E. Dutrizac, B. R. Palmer

Silver sulphide (acanthite) and lead sulphide (galena) dissolve relatively rapidly in FeCl3 media with the formation of elemental sulphur and soluble silver and lead chlorides. Parabolic kinetics are observed, and the leaching rates are controlled by the outward diffusion of the AgCl and PbCl2 reaction products through the constantly thickening elemental sulphur layer formed on the sulphide. Hence, both leaching rates are strongly dependent on those variables which affect the solubility of AgCl or PbCl2 at the reaction interface. The rates therefore increase with increasing temperature and total chloride ion concentration, but decrease in the presence of elevated concentrations of AgCl or PbCl2. By contrast, neither sulphide is significantly attacked by ferric sulphate media, even at high Eh values. Although the reasons for the refractory behaviour of Ag2S in sulphate media remain unknown, the low rate of PbS attack is attributable to the passivating layer of PbSO4 and elemental sulphur formed on the surface of the galena.

Jan 1, 1993

By Donald M. Keagy

How many times have you said or heard someone say, 'What are you doing right now?" And how many times have you heard the reply, "Breathing air!" Probably never, or at most only a few times in a facetious vein. Breathing air is absolutely necessary to sustain human life, and yet most of us take it completely for granted. Beginning ten to fifteen years ago there was growing concern on the part of the general public that pollution of the air is a threat to man's health and welfare. Concurrently much thought and effort was devoted to the task of defining and resolving the problem of air pollution. In the course of this effort it has become quite clear that our National policy in this regard should be founded upon three basic axioms: (1) Action should not be postponed until emergency conditions make it compulsory; (2) The air cannot be purified after it is polluted, and (3) Air pollution control cannot be accomplished without close cooperation among all levels of government, industry, and the public.

Jan 1, 1967

By Hetland Donald L.

Regional Tertiary formations and basins of local sedimentation which contain uranium deposits west of the Rocky Mountains are mainly of Oligocene, Miocene, and Pliocene age (fig. 1). The host rocks have been derived mainly from intrusive and extrusive igneous rock. The major host formations which cover broad geographic areas include the Esmeralda, Truckee, Humboldt, Thousand Creeks, Payette, Panaca, Cedarville, Coso, and San Joaquin Formations. Local areas of Tertiary sedimentation containing uranium deposits occur near Yuma, Safford and Artillery Peak, Arizona; Dillon and Canyon Ferry, Montana; Spokane Indian Reservation and Pend Orielle River, Washington; Topaz Mountain, Utah; Stanley Basin, Idaho; and Sonora Pass, California. Uranium deposits in these sediments have been classified into five categories based on environment (fig. 2). They are: (1) Deposits in lake sediments consisting mainly of water-laid tuffs; (2) Deposits in lake sediments intruded by volcanic plugs; (3) Deposits in lake sediments interbedded with arkoses near batholiths; (4) Deposits in coarse volcanic sediments in local sedimentary basins; (5) Deposits in arkosic conglomerates in local sedimentary basins.

Jan 1, 1969

By D. V. Professor Keller

The production of premium coal-based fuels (<3% ash) and ultra clean coals (<1% ash) using the process of selective agglomeration requires proper selection of raw coal, rough preparation procedures, milling equipment, product coal size distribution, water purity, agglomerants, agglomeration equipment and operational procedures. Each of the variables can contribute a small fraction to the impurity load in the product coal or limit the ability of the process to separate mineral matter-free coal. Each of the variables and their importance will be examined from data produced at the bench by batch and continuous agglomeratons as well as the results from pilot plant and tonnage production units. The results are discussed which have indicated that some standard commercial coals can be produced with ash contents as low as 0.2 % ash (batch/bench) and several tonnage lots of 0.6% ash in as 200 lb/hr pilot plant. In most cases iron pyrite released from the coal matrix and with proper pH control is rejected from the product coal agglomerates.

Jan 1, 1995

By C. Flores, L. G. Twidwell, T. S. Jordan

It is well known that manguniferous silver ores containing manganese intimate) associated with silver are not amenable to conventional extraction methods. The segregation process has been applied primarily to the recovery of copper from oxidized and oxide-sulfide ores. A new alternative process, consisting of segregation roasting followed by flotation to recover the silver from refractory manganiferous silver ores, was studied using a 23-factorial experimental design. Laboratory investigations were conducted on a manganiferous silver ore analyzing 0.02% copper, 0.09% lead, 0.33% zinc, 12.55% manganese and 187 g/t silver. The investigation was designed to study the effects of the addition of salts, coke and copper (11) oxide on silver recovery. The results indicated that 79.3% of the silver can be recovered in the absence of copper oxide and 88.4% of the silver can be recovered with a copper oxide content of 1.5% at 750°C, 2% salt (NaCI). 1 % coke and 30 min of roasting. It was concluded that the addition of copper oxide improves silver recovery.

Jan 1, 1996

By N. L. Wesis

General History The first jaw crusher in the US was patented about 1830, but the Blake crusher that has maintained a substantial advantage over other types was invented in 1858 by Eli Whitney Blake. For going on 150 years the jaw crusher has been an invaluable machine; even today, when gyratory crushers have assumed most of the burden of crushing large tonnages of large rock and ore, the jaw crusher has a firm place in the mining industry. It is interesting that soon after the invention of the Philetius Gates gyratory crusher in 1881, a contest between the first No. 2 Gates and Blake jaw crushers of equal gape showed the gyratory to be 3.2 times as fast. This foretold a day not far in the future when the jaw crusher would not be adequate on the largest jobs. In his Textbook of Ore Dressing (1909) R. H. Richards recom¬mended that the word breaker be used for all machines breaking to relatively large sizes (say to 5 in. or greater), and crusher be used for finer work. Even in the 1968 US Bureau of Mines dictionary of mining terms the work breaker is defined by Richards in this context. However, in modern US usage it is nearly limited to coal breaking. Over the years the jaw crusher has been developed in a variety of forms but it appears today in these three general forms: (I) Blake type, (2) Dodge type, and (3) single toggle (or overhead eccentric) type. All of these crushers have a fixed jaw and a moving jaw, between which the coarse rock fragments are intermittently caught and crushed. The three types are differentiated by the manner in which the movable jaw is moved in relation to the fixed. Types The Blake-type crusher is shown in cross section in Fig. 1. The simplicity and strength that have made it first among jaw crushers are evident. The movable jaw is suspended from a cross-shaft at its upper end, this shaft being carried in bearings on the sides of the frame. The actuating mechanism consists of an eccentric shaft, also supported in frame-mounted bearings, which imparts through a pit¬ man and a pair of toggles a reciprocating motion to the bottom of the swing jaw, the return movement being effected by several spring¬loaded rods. The whole is built into a box frame with the crushing chamber at one end. As in all jaw crushers, the eccentric shaft is equipped with a heavy flywheel that maintains an even speed through¬out each stroke. The Dodge-type crusher illustrated in Fig. 2 is simple, mechani¬cally. Its movable jaw, being pivoted below the discharge opening, has minimum movement at crusher discharge and maximum at crusher feed. Because the choke point coincides with the point of least motion, these crushers are of relatively low capacity, and the rapid action in the feed area gives the machine the advantages of large reduction ratio and closely sized product. Thus, it fits well into low-capacity operations like sample reduction. Besides low capacity, its principal disadvantages are tendency to pack and make fines. The single-toggle or overhead-eccentric type of jaw crusher (see Fig. 3) has gained in usage, starting as a modification of the Dodge idea in that the greatest movement of the movable jaw occurs at the top, and being gradually improved and strengthened to its position today where it covers just as wide a field of application as the Blake type from the standpoint of feed opening. The motion of the movable jaw is the result of the circular motion of the eccentric shaft at the top of the swing jaw combined with the rocking action imparted to the bottom by the inclined toggle plate. Because of light weight and mechanical simplicity, it is economical in small mills and portable plants where the rock is not as tough and abrasive as to punish the machine with excessive impact from shocks, or excessive wear result¬ing from the pronounced vertical component of motion.

Jan 1, 1985

By John R. Twining, Michael D. Lawton, Ross A. Jeffree

The Finniss River system in tropical northern Australia has received &apos;acid-drainage&apos; contaminants from the Rum Jungle uranium/copper mine site over the past 4 decades. Following mine-site remediation that began in 1981-82 the annual contaminant loads of sulfate, Cu, Zn and Mn have declined by factors of 3, 7, 5 and 4, respectively over 1990-93, compared to the 1969-74 pre-remediation loads. Comparison of the frequency distributions of contaminant water concentrations over these pre- and post-remedial periods have shown varying degrees of reduction in the highest levels following mine-site remediation, that are consistent with reductions in their annual-cycle loads. Among the three selected major metal contaminants the reductions in maximum water concentrations are most pronounced for Cu. The demonstrated reductions in the highest water concentrations of all four contaminants are also associated with previously reported ecological improvement in the Finniss River system, compared to the benchmark of environmental detriment established in 1973fl4, prior to the beginning of remediation at the mine site.

Jan 1, 2000

By Leonhard Schmid

INTRODUCTION In the region of Zurich several of the Swiss Interstate Highways meet and have to be linked to form a continuous network. The subalpine glacial topography with hills, ridges and lakes requires the construction of many tunnels (Figure 1). The Milchbuck Tunnel forms part of the inner arterial highway system of the city of Zurich. It passes underneath the ridge separating the Limmat and Glatt valleys. In its final configuration the tunnel will consist of two parallel three-lane tunnels (Figure 2). For the time being only one tunnel is constructed. This tunnel will be operated with two outbound (climbing) lanes and a single inbound (descending) lane (Figure 3). The owner, the Canton of Zurich, awarded the contract for the construction to a joint venture with the following three contractors: Locher & Cie AG (leader), Prader AG, A. Brunner&apos;s Erben, all located in Zurich. The actual freezing was performed by subcontractor Philipp Holzmann AG, Mannheim, West Germany. Electrowatt Engineering Services Ltd, Zurich, was design engineer and performed the construction supervision.

Jan 1, 1981

Acid mine drainage (AMD) forms when sulfide minerals are exposed to oxidizing conditions in coal and metal mining, highway construction, and other large-scale excavations. Iron sulfides common in coal regions are predominately pyrite and marcasite (FeS2), but other metals may be complexed with sulfides forming chalcopyrite (CuFeS2), covellite (CuS), galena (PbS), and sphalerite (ZnS). Pyrite commonly occurs with these other metal sulfides thereby causing AMD where Cu, Pb, and Zn are mined. Upon exposure to water and oxygen, sulfide minerals oxidize to form acidic, sulfate-rich drainage. Metal concentrations in AMD depend on the type and quantity of sulfide minerals present. The drainage quality emanating from underground mines or backfills of surface mines is dependent on the acid-producing (sulfide) and alkaline (carbonate) minerals contained in the disturbed rock. In general, sulfide-rich and carbonate-poor materials produce acidic drainage. In contrast, alkaline-rich materials, even with significant sulfide concentrations, often produce alkaline conditions in water. Approximately 20,000 km of streams and rivers in the United States are degraded by AMD. About 90% of the AMD reaching streams originates in abandoned surface and deep mines. Since no company or individual claims responsibility for reclaiming abandoned mine lands (AML), no treatment of the AMD occurs and continual contamination of surface and groundwater resources results. The oxidation of iron disulfides and the generation of acidity occur through several reactions (Stumm and Morgan, 1970). The chemical equations can be found in Caruccio and Geidel (2000). If any of the processes represented by the equations were slowed or altogether stopped, the generation of AMD would also slow or cease. The equations show that 1000 Mg of rock containing 1% sulfur, all as pyrite, would yield upon complete reaction 31.25 Mg of acidity. Therefore, 31.25 Mg of 100% CaCO3 would be required to neutralize the acidity. The alkaline content of overburden determines whether there is enough neutralization potential (NP) to counteract the acid produced from pyrite oxidation. Of the many types of alkaline compounds present in rocks, only carbonates and clays occur in sufficient quantity to effectively neutalize AMD. A balance between the acid-producing potential and neutralizing capacity of an overburden sample will indicate the ultimate acidity or alkalinity that might be expected in the material upon complete weathering. Accurate prediction and control of AMD before surface mining require an understanding of three important factors: 1) overburden geochemistry, 2) method and precision of overburden handling and placement in the backfill during reclamation, and 3) the postmining hydrology of the site.

Jan 1, 2002