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Jan 1, 1947

Jan 1, 1948

Jan 1, 1948

By Daniel R. Shawe

Ore deposits of the western U.S. are divisible broadly into two genetic groups, a smaller one that fits the plate tectonic model of subduction and a larger one that appears unrelated to subduction. Some of the middle Paleozoic and lower-middle Mesozoic ore deposits in the western U.S. are associated with eugeosynclinal rocks and lie a few hundred kilometers west of reconstructed continent margins. These deposits probably formed as a result of subduction beneath oceanic or thin continental crust that was analogous to subduction predicated for the Kuroko massive sulfide deposits of Japan. Some middle Mesozoic porphyry copper deposits may have formed east of the continental margin when subduction-generated magmas were emplaced high in continental crust in a manner analogous to subduction-generated magmas that formed the Andean porphyry copper deposits. Most Cretaceous-Cenozoic ore deposits lie in a broad region extending many hundreds of kilometers east of the continent margin and characterized by conjugate tectonic zones, high terrestial heat flow, and low seismic velocity in the upper mantle. The deposits likely were formed in relation to magmas generated along the conjugate tectonic zones during differential northwestward drift and internal wrenching of the continental plate.

Jan 1, 1978

By M. H. Brady, J. G. Roscoe

Continental No. 1 This mine in Lisbon Valley has an orebody about 1200 ft long and varying from 250 to 70 ft wide. Average width is about 100 ft and stope heights average about 9 ft. It was developed by a 350-ft, 11º inclined shaft for trackless haulage, although a hoist and track are installed for auxiliary hoisting. Mining has been done from horizontal open stopes with random pillar support, using a HD5 tractor for mucking and a 4-wheel drive Gettman shuttle car for tramming. Slushers have been used to some extent in thin ore zones. Back support for stopes and haulage ways has been accomplished by rock bolts and landing mat. The most interesting feature of this mine has been pillar extraction. Mining was done under contract during the first year of operations with little regard for an orderly plan of stope layout or regularity of openings. Most of this work was done in the largest area of the orebody; consequently, pillar recovery has been accomplished under conditions which are far from ideal. However, a workable system has been developed which is competitive, both in cost and production rate, with open stoping.

Jan 7, 1958

By Donald W. Gentry

The recently established SME-AIME Education Board has completed its first full year of operation, and its six constituent committees-Accreditation, Career Guidance, Continuing Education, Educational Statistics, and Scholarship-have been extremely active in identifying and initiating programs to serve the educational needs of the Society of Mining Engineers and its members. The Continuing Education Committee-primarily concerned with the needs and problems associated with providing a continuing education program for SME members-is responsible for: (1) determining the need for short course offerings; (2) developing needed courses, along with new means and opportunities of presentation; and (3) scheduling and evaluating course presentation. In response to this charge, the committee has sponsored two short courses at the SME-AIME Fall Meeting in St. Louis and three short courses at the AIME Annual Meeting in Denver. Its major effort, however, has been directed toward the 1978 SME-AIME Fall Meeting to be held in Orlando, Fla., where 18 days of short-course instruction have been scheduled. A portion of these courses will be presented prior to the meeting, with the remainder to be presented in Nassau, Bahamas, immediately following the meeting.

Jan 7, 1978

By A. L. Johnson, S. C. Lyons

A FEW years ago a leading American builder of centrifuges said, "No one uses a centrifuge if the job can be done any other way." This statement was essentially true at that time, not because the basic functional and economic principles involved did not frequently favor centrifugal methods, but rather because so many of the highly specialized features of the mechanical and functional peculiarities of continuous centrifuges had not been fully developed. The idea of using centrifuges in mineral dressing is definitely not new. There are literally hundreds of patents on centrifugal machines and processes for the mining industry. Many of them cover principles that are basic to the functioning of most centrifuges in operation today. In spite of this, until 1935, there were practically no successful applications of continuous centrifuges in the United States in the mineral industry, nor for that matter were there more than a mere handful of such machines in operation in North America in any industry. This was true despite the obvious desirability of machines that could furnish the advantages of high centrifugal settling forces in a continuous operation. The reasons for this are simple, even if not obvious: I. Finely divided solids, when thrown out of fluid suspension under high centrifugal forces, frequently exhibit physical properties (particularly rheological or flow properties) that are markedly different from those they possess when settled out by gravity alone, and machines that are not designed in careful detail to cope with these peculiarities seldom function satisfactorily. 2. Most continuous centrifuges embody a solids-conveying element in the form of a very special screw conveyor. The rotation of this member under conditions of operation calls for drive designs that were not satisfactorily provided until the introduction of the Bird gear unit about 1934. These matters will be touched on later. Continuous centrifuges are now operating successfully in the mineral industry. Some units have singly handled more than 500,000 tons of solids during the past ten years. Generally their operation has been characterized by large unit capacities, complete elimination of labor, minimum supervision, moderate maintenance and power costs. TYPICAL CENTRIFUGE APPLICATIONS Most materials classified by centrifuges are of subsieve particle size. Practically speaking, this means finer than l00-mesh. A unit of measure other than screens is needed in order to consider these products properly. Such a unit is the micron, which is equal to one one-millionth of a meter; roughly 1/25,000 of an inch. The opening in a standard 200-mesh screen is about 75 microns while a 325-mesh opening is roughly 43 microns.

Jan 1, 1947

By T. B. Counselman

Continuous countercurrent decantation calculations have always been a headache to the cyanide man (and the chemical engineer) because of the simultaneous equations involved. These are tedious to solve, and there is considerable opportunity for mathematical error. This paper presents a shortcut method for making these calculations, which has been in successful use for twenty years by the author, and which is particularly valuable in selecting the best of several possible flowsheets, or evaluating the effect of various assumptions.

Jan 2, 1950

By T. B. Counselman, T. B.

Continuous countercurrent decantation calculations have always been a headache to the cyanide man (and the chemical engineer) because of the simultaneous equations involved. These are tedious to solve, and there is considerable opportunity for mathematical error. This paper presents a shortcut method for making these calculations, which has been in successful use for twenty years by the author, and which is particularly valuable in selecting the best of several possible flowsheets, or evaluating the effect of various assumptions.

Jan 1, 1950

By Clement K. Chase

ION exchange recovery of uranium has been proved successful in many operating plants in various parts of the world. First used in column plants processing clear liquors, ion exchange has more recently been applied in basket resin-in-pulp systems. A logical further development is the application of truly continuous processing techniques to the ion exchange recovery of metals, since previous systems have been semicontinuous at best. Column ion exchange is a valuable technique and has been used extensively in South Africa and elsewhere. However, it requires clear liquors. To produce these clear liquors, considerable investment in filter plant and clarification equipment is necessary. In the cases where it is very difficult or impossible to produce clarified liquors, column ion exchange is not so useful. Moreover, some liquors suffer from post-precipitation after clarification, which can become a serious problem.

Jan 9, 1957

By R. W. Kobler, D. A. Dahlstrom

Since the development of the pelletizing process in the fifties for relatively high purity pellets from low grade taconites, there have been several distinctive changes in filter construction for the dewatering step preceding balling. In the original large pilot plant run by Reserve Mining Co. in Babbitt, MN, the disk type filter employing agitation (Agidisc filter) was selected as the most economical. Size was limited to 2.1 m (6 ft, 9 in.) in diameter. The second generation occurred in the sixties with a jump to 2.70 m (8 ft, 10 in.) in diameter to reduce capital costs per annual ton of pellet. In the early seventies, the third generation was the steam drying disk filter which became necessary to achieve balling moistures with specific surface areas of 2200 cm2/g to as high as 3800 cm2/g caused by finer grinding to obtain higher purities. Finally, the fourth generation has recently been developed to reduce maintenance costs and further improve hydraulics to ensure minimum moisture contents.

Jan 1, 1980

By Reinhard H. Wöhlbier, George E. Aiken

8.4-1. Introduction. Surface excavating is done on a continuous basis with a variety of machines: 1) trenchers and ditchers, 2) conveyor loaders, and 3) bucket-chain and bucket-wheel excavators (BWE). Surface mining is largely concerned with only the last two machines, although some of the conveyor-loader types are often used by contractors for large-scale earth moving, and the engineer should be aware of these applications. This chapter is restricted to discussing only the bucket-chain and bucket-wheel excavators, with special emphasis on the latter. Continuous digging with these machines is done with evenly spaced buckets on either an endless chain or on the periphery of a rotating wheel. The bucket-chain digger excavates and takes the material away from the face with the same machinery. In the case of the bucket-wheel machine, these two functions are separate. Material is excavated by the buckets and then flows in a continuous stream via a transfer to the conveyor system, which in turn transports it to the discharge point. The wheels are adjustable in rpm and mount 6 to 12 buckets of equal size. These are classed as celled, cell-less or semicelled. The digging ladders for both types can move simultaneously in the horizontal and vertical planes. Ladder control is similar to the operation of a bucket-line dredge. Some ladder-chain and all wheel excavators have the machinery deck and superstructure mounted on a 360° swing circle. Other chain diggers have a fixed machinery deck. Deep and/or high cutting models are available in either the chain or wheel excavator. Machines can be either rail or crawler mounted, but the trend is to crawlers. Many of the early ladder-chain, rail-mounted excavators have been converted to crawlers. These may be either of the single or bogie type, depending on the conditions. Large machines usually use the superior three-point crawler suspension.

Jan 1, 1968

By B. R. Eichbaum, J. E. Murphy, J. A. Eisele

The US Bureau of Mines demonstrated ferric chloride leaching of galena concentrate on a continuous bench scale basis. Leaching was performed at 95°C (200°F) and with a contact time of 15 minutes. The ferric chloride leaching solution was continuously fed to a leaching tank at a constant rate for periods up to 45 hours. In each test, a constant redox potential was maintained in the slurry exiting the leaching tank by controlling the concentrate feed rate. In the 45 hour test, lead extraction exceeded 99.5%, and the lead chloride produced was 99.97% pure.

Jan 1, 1986

By R. C. Emmett, D. A. Dahlstrom

Application of continuous filtration to precipitate dewatering requires not only careful equipment selection, choice of appropriate media, but also close control of precipitation technique itself.

Jan 1, 1961

By Eugene C. Robertson

INTRODUCTION A direct proportionality between the observed displacement of a fault and its thickness of breccia and gouge has been proposed recently (Robertson, in press). To validate this finding, an explanation of the mechanics of continuous breccia formation is needed and is offered in this paper. A summary of evidence for the finding will show why an explanation is needed. The correlation between fault displacement [d] and accompanying breccia- plus-gouge thickness [t] seems to be linear and reasonably well established over 6 orders of magnitude, with a range in [d] from 1 mm to 1 km, on a trend of [d/t]= 100, shown in Figure 1. Most of the points are for faults observed underground in mines. The [d] – [t] relation is limited to normal and reverse faults, that have a flat to steep dip and a displacement less than 5 km. It is not applied to large strike-slip and low-angle overthrust faults, whose displacements and breccia thicknesses are widely variable and uncertain. Undisplaced jointed rock is not included in the thickness measurement. A complete description of sources and analysis of the data is given in Robertson (in press). One would intuitively expect that continued movement on a fault would grind up the previously formed breccia and gouge and not produce any more, but the evidence (Fig. 1) indicates otherwise. A physical model to explain continuous formation of gouge and breccia from the wall rocks can be obtained from laboratory experiments on friction.

Jan 1, 1982

By W. D. Mayercheck

Beginning in 1974, the Bureau of Mines, US Department of Interior, sponsored research and development efforts related to further development and use of continuous face haulage in underground coal mines (Cowan, 1975). The Department of Energy continued this effort as of Oct. 1977. This paper represents an update of an article previously published in Mining Engineering magazine (Mayercheck, 1979). Development progress is summarized for a variety of prototype systems for components now being built, surface tested, or tried underground.

Jan 1, 1984

By Stephen Krickovic

THERE is today no proven continuous mining machine that can be used under all the varying conditions found in most bituminous coal mines. During the last five years, however, both the machines and methods of using them have been improved. Coal operators can now exercise a fair degree of selectivity, except those who must struggle with thick and hard partings and operate in seams less than 40 in. thick. It must be realized, then, that more than one type of continuous miner may be used advantageously in the same coal mine. Although this appears to violate the standardization generally sought after, the gain can more than offset added maintenance and, to a lesser degree, operating problems.

Jan 12, 1957

By F. Rosenblum, P. Spira, F. Kitzinger

The possibility of increasing the efficiency of mineral processing plants by means of computer control has prompted metallurgists to examine their flowsheets more critically in order to develop practical control strategies. Control schemes in use to date generally rely on the automation of traditional and previously manually regulated control loops, e.g., the addition of reagents to maintain a constant assay or a constant pH. This approach is predicated on the availability of well established primary sensors such as pH electrodes or on-stream analyzers. Noranda Research Center, in cooperation with Noranda Group concentrators, has developed a froth level monitor and a pulp density meter adaptable to this type of control. Although some of the basic principles on which they are based have been known for some time, their incorporation into the design of reliable, direct-reading instruments which can be interfaced with a computer is believed to be novel.

Jan 4, 1979

By F. Rosenblum, P. Spira, F. Kitzinger

The possibility of increasing the efficiency of mineral processing plants by means of computer control has prompted metallurgists to examine their flowsheets more critically in order to develop practical control strategies. Control schemes in use to date generally rely on the automation of traditional and previously manually regulated control loops, e.g., the addition of reagents to maintain a constant assay or a constant pH. This approach is predicated on the availability of well established primary sensors such as pH electrodes or on-stream analyzers. Noranda Research Center, in cooperation with Noranda Group concentrators, has developed a froth level monitor and a pulp density meter adaptable to this type of control. Although some of the basic principles on which they are based have been known for some time, their incorporation into the design of reliable, direct-reading instruments which can be interfaced with a computer is believed to be novel.

Jan 1, 1980

By R. W. Rausch

BELT-CONVEYOR 'history in this country dates back to the end of the eighteenth century. Up to 1896 they were crude in design and application. The second era, dating from 1896 to about 1920, saw special study given to belt construction and idler design. The latter part of this era saw the beginning of the present-day antifriction idler. The third era followed World War I, when industry began to expand rapidly. Mines and quarries, steel mills, and power-generating plants became larger and greater quantities of ore, stone, and coal were being handled. It became vital that belts handle larger capacities, that they be longer, and that they be dependable for 24 hours per day. In this third era a radical change in belt conveyor design and application occurred. The design has became more scientific. Studies have been made to find out what factors influenced the power required for a belt conveyor and it was found that the sag of the belt between idlers and the flattening of the load between idlers had considerable effect on power requirements. So definite initial tension was put into the belt at the loading end and idler spacing was reduced at the foot end to limit this sag. Belt manufacturers made tougher and stronger belts.

Jan 1, 1947