Search Documents

By Walter E. Kramer

The advantages derived from the use of pellet burdens in blast furnaces are so great, that hematite ores are being converted into pellets in greater quantities each year. The conversion of these ores into pellets appears on the surface to be relatively simple. In reality, this is not so. Serious difficulties are encountered in drying these pellets that do not exist in the drying of taconite concentrate pellets. The ores that present problems are goethite and earthy hematites. Green pellets prepared from these ores have very law shock temperatures, 200-600° F. The shock temperature of a green pellet according to our definition is the highest initial temperature to which a green pellet may be exposed without suffering decrepitation. Decrepitation may involve spalling, fracturing or total disintegration. The poor shock properties of these green pellets result from the inability of the vaporized water to escape freely and easily as it is formed with¬out affecting the integrity of the pellet. As a consequence, the pellets must be carefully dried prior to induration. This careful treatment is costly. The slow drying process restricts productivity and requires larger furnaces than desired. The use of an additive to elevate the shock temperature of the green pellets would increase productivity. Bentonite is used in some pellet plants to improve balling but it raises the shock temperature only slightly. Nalco became interested in the shock temperature problem because of its activity in the development of organic pelletizing aids for taconite concentrates. The findings reported here are an outgrowth of our experimental work on the development of shock temperature additives.

Jan 1, 1967

By J. E. Miller

The development of a new means of measuring the relative abrasivity of a slurry came about by necessity in 1967 during a full scale loop test of a 560 H.P. reciprocating pump handling magnetite slurry. In order to evaluate the life of expendable fluid end parts, the question of the amount of attrition in a re-circulated slurry had to be considered. An expected reduction in abrasivity as a result of this attrition would certainly give erroneous data on a parts life test. There- fore, some means of measuring such change in abrasivity became imperative. Several test methods were investigated1 but it was felt that these did not fully represent the wear due to back and forth rubbing action associated with a reciprocating pump. A "rubbing block" device used some years ago to determine the quality of hard facing materials was recalled, along with its shortcomings, in that an attempt was made to suspend a small percentage of abrasive particles in a colloidal viscous "mud". Erratic results were attributed to the fact that it was difficult to maintain a consistent slurry concentration under the metal wear block and the reciprocating speed was not great enough to maintain good agitation.

Jan 1, 1973

Valuers of mineral properties should be aware that accountants are a major user of their opinions of value. Reliance by accountants can range from obtaining comfort that book values in balance sheets are not overstated to establishing values by which to assess the fairness of a takeover offer. Accountants using mineral property valuations clearly can't be expected to have the same level of expertise as the valuer and ""second guess"" the valuation. But they do have an obligation, under the ASC guidelines and their own professional standards, to'check the logic and reasonableness of the valuation before being able to rely on it. This means reviewing the valuation report for general sensibility, discussing the methodologies and assumptions with the valuer and being satisfied as to his competence and independence. This paper outlines how accountants use mineral property valuations, the level of scrutiny applied to such valuations and the problems commonly encountered in practice by accountants seeking to rely on them. The paper also explains how values of-mineral properties are established in company balance sheets and why these often differ, quite validly, from fair market values.

Jan 1, 1994

By H. C. Fiedler

The development of cube-on-edge secondary re crystallization texture in Si-Fe strip depends upon the ability of inclusions, such as manganese sulfide, to restrain nomal grain gvowth. The ability of inclusions to perform this function is shown to depend upon their size and distribution. The desired uniform dispersion of many small inclusions is obtained by controlling the cooling rate from above the solution tempmature of the inclusions or, alternatively, by drastic 'quenching from above the solution temperature followed by heat treating at a lower temperature. The development of the cube-on-edge secondary recrystallization texture in Si-Fe strip depends upon both establishing the proper primary recrystallization texture and having inclusions to restrain normal grain growth. It has been suggested that the first requirement is met with a texture which, though weak, is near (110)[001]. A mechanism for secondary recrystallization originally proposed by ielsen' is consistent with the presence of this primary texture. It is visualized that a secondary grain appears where two adjacent grains happen to be sufficiently similar in orientation to be capable of behaving as a single large grain. This pair of grains will grow at the expense of its smaller neighbors as a consequence of its having lower grain boundary free energy. Other explanations of the origin of the secondary recrystallization texture have been offered,' and it can be concluded that the mechanism is not fully understood. Nevertheless, it is apparent that operationally the necessary primary recrystallization texture is obtained simply by interposing an anneal during the cold reduction to final gage. The role of inclusions in the development of the secondary recrystallization texture has been demonstrated by May and Turnbull4 in a comparison of a high-purity heat and a heat containing manganese sulfide. They showed that the driving force for secondary recrystallization is inversely proportional to the diameter of the matrix grains and that the function of the inclusions is to maintain a small matrix grain size. Other inclusions, such as various sul- fides,')' silicon nitride,8 and vanadium nitride,' titanium carbide,'' and vanadium carbide," have been shown to be effective in promoting secondary recrystallization to the cube-on-edge texture. There is also evidence that silica inclusions in Si-Fe strip made by powder-metallurgy techniques perform this function.' This report is concerned with the second of the two requirements for secondary recrystallization, namely the importance of the metallurgical control of the size and therefore number of inclusions. While the concepts involved are simple, they are fundamental to the making of this material. EXPERIMENTAL PROCEDURE A heat containing 3.27 pct Si, 0.026 pct S, 0.06 pct Mn, and 0.004 pct C was made in an air induction furnace from electrolytic iron, 98 pct ferro-silicon, electrolytic manganese, and iron sulfide. The heat was divided between graphite and baked-sand molds with a cavity 2-5/8 by 5 in. and with walls 2-3/4 in. thick. Slabs, 1 in. thick and 2-5/8 by 5 in., were cut from the ingots and hot-rolled either in the as-cast condition or after one of the heat treatments described later. After pickling, the 80- to 100-mil-thick hot-rolled band was, unless otherwise noted, heat-treated for 5 min at 900°C before being cold-rolled to 25 mils. After a heat treatment of 1 to 3 min at 860°C, the strip was cold-rolled to 12 mils, the final thickness. The percent cube-on-edge texture was determined by dividing the maximum torque as averaged from four samples by the maximum torque of a 3-1/4 pct Si-Fe single crystal having the (110) plane in the plane of the sample. The torque measurements were made in a field of 1000 oe on 1-in.-diam disks. RESULTS AND DISCUSSION The importance of the thermal history of the ingot is evident in Fig. 1 from the appearance of strips heat-treated in a temperature gradient. The sample

Jan 1, 1964

By C Jones

Ridgeway Deeps is a block cave (BC) located down dip of the operating Ridgeway sublevel cave (SLC) mine. The BC is located approximately 210 m vertically below the lowest SLC level and approximately 1100 m below surface. Due to the mine layout containing a number of common pieces of key infrastructure the activities of both were interlinked.When investigating project construction options for the BC, a number of potential risks were identified including a conflict of priorities between operational and project deliverables and the varying safety and work methods between an owner mining approach in the SLC and a potential contractor workforce in the BC. This led to a review of the construction philosophy and the opportunity to utilise the existing SLC workforce as the basis of all activities in the mine. It was identified that a number of synergies existed with the current SLC operators and mine supervision including common work practices and the opportunity to build on the unique SLC skills of the operators and supervisors which could then be used at other Newcrest caving mines.With the commitment to this philosophy of building on the existing SLC crews and supervision the number of employees reporting through the superintendent underground operations grew from 95 to 245. This increase led to a restructuring of the reporting and work requirements of the superintendent, foremen and shift bosses. In order for the foreman and shift bosses to focus on running the larger crew numbers for the full 12 hour shift the mine superintendent became a pseudo human resources manager taking over all non-mine focused activities including overtime allocation and work and behavioural performance management. In simple terms, ensuring there were competent bums on seats when and where required. As the additional workers were recruited to top up the existing employee numbers, their employment history was used to place them in the most suitable roles. For example, those with building industry experience were placed on the civil construction crews and those with a farming background were used as truck drivers, nippers or on the service crews. To cope with the increased number of new starters a number of key personnel were seconded from the crews into the training group to act as on shift trainers. This initially caused a reduction in mine performance as the main operators were reassigned but it proved a valid move as the time for new operators to reach acceptable levels was significantly reduced with safe operating standards being maintained. This paper discusses how the Ridgeway Deeps Project was delivered on time and under budget whilst at the same time retaining its position globally as an operation to be benchmarked against.

Mar 21, 2011

By J. D. McKay

Flotation columns have been readily accepted for use in most sulfide flotation plants; however, recently columns are being used in many other areas. Recent improvements in design methodologies have overcome many operating problems and led to improvements in metallurgy. In addition, physical improvements in column design have simplified their operation while leading to better control. The Turbo-Air External Bubble Generator has provided a method for bubble size control and variation in air holdup and carrying capacity. These have enabled commercial operations to improve grades and recoveries by optimizing performance.

Jan 1, 1990

By James J. Dowd

The investigation to evaluate the reserves of coking coal is being made by the Bureau of Mines in three parts: (1) To estimate known (measured plus indicated) recoverable reserves of all coking coal, (2) to upgrade marginal coals through effective preparation, and (3) to study the carbonizing properties of coal and coal blends not now widely used for metallurgical coke making. This is the seventh of a series of reports giving the results of studies by counties under part (1) of the investigation. (See appendix.) This report covers Floyd County, KY., which comprises parts of the Paintsville, Prestonsburg, Harold, Hindman, and Pikeville quadrangles. (See fig. 1.) A base map for each bed in each quadrangle was made to the scale of 1 inch equals 1,200 feet. Maps of mines, locations of drill holes, bed and total coal thicknesses, and the outcrop of the bed were plotted on the maps. With all avail-able data plotted, isopach lines were drawn to limit areas of known unmined reserves in beds up to 14 inches thick, 14 to 28 inches thick, 28 to 42 inches thick, and over 42 inches thick. These areas of coal reserves also were divided into "measured" and "indicated" categories. All areas in each thickness range and in each category, mined-out areas, areas excluded from the estimate but which may contain reserves based only on geologic inference, and areas outside of the outcrop were measured by planimeter on the base maps. Estimates of total reserves 14 inches and more thick and maps for individual beds were prepared from these data.

Jan 1, 1951

By P. Cleyle, J. H. Masliyah, R. S. Chow, Z. H. Xu, Z. A. Zhou

Bubble nucleation in water under dynamic conditions was investigated using an autoclave at an air saturation pressure of 7 atm. Agitation during air saturation of water was found to be crucial in enhancing tiny bubble formation. More bubbles nucleated on hydrophobic surfaces at a higher agitation rate, due to cavity formation by the more intense hydrodynamic conditions. Flotation recovery of bitumen from oil sands demonstrated a significant role of bubbles nucleated in water: more than 50-170% increase in bitumen recovery from different oil sands was obtained by using air supersaturated than the regular water.

Jan 1, 2009

By Harry J. Evans

DURING the fury of the conflict it was believed quite generally that World War II was being fought for and would accomplish a permanent peace. Yet, before the guns were actually stilled on all fronts, the American people realized that the devastated world would continue to be dominated by suspicion and uncertainty. The misunderstandings which rapidly developed indicated that it may prove unwise to rely wholly on mutual international agreements and contracts to avoid war. Before the celebrations of V-Day died down serious thought was being given toward measures for preparedness for the next conflict. Along with a realization of the enormous loss of life caused by the destructive forces of war, the American people came to understand the seriousness of the rapid and unwarranted depletion of our natural resources. During the last half of 1945 the question of stock-piling strategic and critical raw materials for a future national emergency became an intensely live subject.

Jan 1, 1946

By G. Chancellor

"INTRODUCTION The paste plant is located at the Barrick Goldstrike mine in Northern Nevada on the Carlin Trend. The Goldstrike property consists of an open pit and an underground mine; along with two processing facilities: a roaster and an autoclave. The underground portion of the mine produces approximately 1,800,000 ore tons per year and approximately 400,000 ounces. The mine is broken up into four distinct zones: Banshee, Meikle, Rodeo and Northpost. The current paste plant services both the Rodeo and Northpost zones. Development of the conceptual designs and permit approval for this plant was an extensive process that took over a decade to complete. A testing program was developed in conjunction with this process and implemented throughout to ensure the following metrics were achieved: ensure no environmental impact, material available onsite would be able to flow through the pipe to all required locations, and that this material could achieve the appropriate final strength. PLANT AND UNDERGROUND CONSTRUCTION This is the first paste plant to be built in Nevada. The paste plant at Goldstrike began construction in January 2012 and was completed in March of 2013. This plant was constructed to service the Rodeo side of the underground mine which previously utilized a cemented rock fill (CFR) plant to meet their backfill needs. However, in March of 2013, the same month the plant was commissioned, the raise that fed this CRF plant was mined out in a planned phase of the adjacent open pit. This made the switch to paste all the more difficult as it was being relied on for as the sole source of backfill production even though the system yet to be fully tested and optimized. The plant was designed to be fed with onsite Roaster tailing which would be thickened and then mixed with cement and fly ash. The plant was designed to pump 177 tons of paste per hour with a utilization of 65%. The original design specifications for the paste were 77% solids with varying binder contents depending on where the paste was being placed"

Jan 1, 2015

By R. Hemp

This paper describes in broad outline the development of a computer programme for determining the effects of changes in various factors in the condenser water circuit on the operation of a cooling plant. The programme is used to obtain design figures which result in minimum total power consumption. This was done for a range of different upcast air quantities, and the implications of low air quantities for heat rejection are discussed.

By R. F. Hadley

Alluvial valley floors constitute a valuable land resource and have been important to ranching operations in semiarid western United States. This resource may be in jeopardy locally if the alluvial deposits are disturbed by surface mining of coal deposits. Erosion problems caused by poor land-use practices can cause trenching of the unconsolidated alluvium with a consequent lowering of the water table and depletion of soil moisture needed to support vegetation. Historical evidence of this sequence of events is abundant in geologic literature and serves as the basis for assessing potential impacts of surface mining. The potential geomorphic impacts of surface mining on alluvial valley floors with regard to fluvial processes are: (1) disruption of the longitudinal profile followed by valley trenching and high sediment yields downstream and (2) replacement of the excavated alluvium with unconsolidated material that does not have similar physical characteristics and may be susceptible to erosion. Mining may disrupt the existing hydrologic framework affecting streamflow, ground-water levels and water quality of both surface water and ground water. Although functional hydrologic and geomorphic processes are similar, each valley represents a complex environment that does not submit to broad generalizations.

Jan 1, 1978

By James Westfield

Uranium activity has introduced a comparatively new hazard to United States mining. In addition to the hazards common to all mines, uranium mines have a complex health problem of radiation damage. Like many new processes, radiation and nuclear energy can be made to serve man in many useful ways when properly understood and handled; but, like fire, gases, and electricity, their potential dangers must be known and respected, and appropriate precautions must be taken or death may result. Since 1950 the Public Health Service has been conducting basic investigations on exposure to radon and its daughter products and the effect of exposure upon the health of miners in uranium mines of the Western States. The Bureau of Mines assisted in several of these investigations, especially in mines on Indian lands. The studies have shown that a serious health hazard exists from radioactive exposure that might cause lung cancer if continued over a number of years. The Public Health Service report, Control of Radon and Daughters in Uranium Mines and Calculations on Biologic Effects,6/ shows that 55 percent of the uranium mines employing 64 percent of the miners had atmospheric concentrations more than five times the working level now accepted as reasonably safe for industrial exposures. Extensive control measures are necessary to reduce these concentrations to the suggested working level of less than 300 micromicrocuries of total radon daughter products per liter of air.

Jan 1, 1958

By W. R. Junge

The investigation, selection, and implementation of remedial activities for large, complex mining and milling sites is dependent on the cost-effective management of tailing and waste materials. Site investigations evaluate the contaminant source areas, assess the potential release rate of contaminants, and determine the acceptable contaminant release rate for the site. Selection of appropriate remedial activities is based on evaluation of constructability, reliability, performance, effectiveness, permanence and cost. Remedial technologies available for tailing and waste material include removal, consolidation, capping and drainage control. Proper implementation and documentation of the selected remedial activities are critical to the overall success or failure of the remedial program. A step-by-step process, established at the initiation of a project, should accurately document all construction activities, monitor environmental conditions at the site, assess the performance of the remedial activities, and, ultimately certify that the remedial activities have met relevant and appropriate standards. Case histories are presented for a uranium mill at Uravan, Colorado and a lead, zinc mine at Gilman, Colorado. These case histories provide examples as to the combination of remedial technologies that have been applied at these specific sites.

Jan 1, 1989

By J. E. Gill

"THE YEAR 1959 appeared to be a good one in which to attempt a summary of progress in the location and study of sulphide deposits in Canada because a temporary surplus of metals caused prices to fall and many geologists who had been working like beavers were suddenly not so hard pressed. So it was •decided to arrange a Symposium. The response to the call for contributions was excellent and the result is the interesting collection of papers that follow.Activity in the search for massive sulphide deposits has never been as intense as in Canada since 1954. That was the year when the airborne electro-magnetometer first became generally available on a contract basis. These instruments work best on massive sulphide bodies, as do most of the ground electrical survey devices, so much of the new information relates to these. It was decided, therefore, to focus attention in the preparation of symposium papers on such masses. This served also to keep the survey within reasonable limits."

Jan 1, 1960

By W. M. Bangert, F. S. Boericke

"INTRODUCTION Determination of the thermodynamic properties of metallurgically important compounds of chromium has been one of the activities of the Pacific Experiment Station of the Bureau of Mines. Earlier reports have dealt with the entropies 4/ 5/ of chromium, chromic oxide, and chromous and chromic chlorides, with the thermodynamic properties of the chlorides of chromium, 6/ and wits the thermodynamic properties of the carbides and oxide of chromium. 7/ Evaluation of the thermodynamic properties of chromite, FeO.Cr2O3, is desirable, as this material in impure form constitutes the only natural source of chromium of any consequence.Two general methods are available for directly determining heats of formation - (1) measurement of heats of combustion and (2) measurement of heats of solution. Neither of these methods is directly applicable at present to ferrous chromite, which accounts for the lack of previous data. Combustion of a stoichiometrical mixture of iron and chromium under conditions prevailing in a calorimetric bomb yields a mixture of iron and chromium oxides rather than chromite. None of the usual calorimetric solution media dissolve chromite at temperatures low enough for solution calorimetry. Sulfuric acid and an oxidizing agent, such as MnO2 or CrO3, are known to dissolve chromite, but the possible calorimetric use of t is medium would require long preliminary investigation. Consequently, recourse must be taken to some indirect method. At the start of the present work, the most promising method appeared to be the determination of equilibria in the selective, reduction of the iron in chromite by hydrogen;"

Jun 1, 1945

By J. J. Jakosky

THE method of electrical mapping of oil structures to be described possesses certain limitations, as well as certain definite advantages. It, in common with other geophysical methods, is not a panacea for the solution of all subsurface geological problems. It operates on differences in electrical conductivity of the geological strata, whereas the other most-used methods operate on (1) differences in magnetic properties, (2) differences in gravimetric properties, or (3) differences in seismic properties. This modification of the resistivity method is therefore able to obtain subsurface information under conditions not favorable to the other methods mentioned. Where the other methods have been employed with ambiguous results it may act as a complementary method.

Jan 1, 1936

Formation of either sodium jarosite or lead jarosite from concentrated chloride solutions containing small concentrations of sulphate has been demonstrated. Sodium jarosite is precipitated at 95-100°C from FeC13-FeCI2-NaCI-PbCI2 solutions to which was added Na2SO4 or Li2SO4 in amounts greater than 0.05 M. In the absence of alkali metal ions capable of forming jarosites, lead jarosite was precipitated from either FeCI3-PbCI2 or FeCI3-FeCI2-LiCI-PbCI2 solutions to which had been added small amounts of sulphate. Many of the factors affecting jarosite precipitation from chloride solution have been elucidated, and the most critical were sulphate concentration and initial pH. Concentrations of HCI in excess of O. I M essentially suppressed the production of jarosite in chloride media. Alkali jarosite, precipitated in the presence of dissolved lead, incorporates a small amount of this metal into the alkali jarosite lattice. Small but significant amounts of copper can also be incorporated into alkali jarosite and the amount is further increased in the presence of lead. Other divalent base metals such as Zn, Cd or Ni are not significantly precipitated. Sulphate control in either FeCI3 or FeCl3-NaCI leaching systems could likely be maintained by jarosite precipitation provided that the acid concentration of the solution was low.

Jan 1, 1981

By W. J. Roberds

A formal and explicit yet cost-effective approach is proposed to ensure that decisions made during mine development are optimum (with respect to their ultimate consequences) as well as defensible. This risk management approach is based on probabilistic risk assessment and established decision analysis techniques, and appropriately considers the relationships among various mine development decisions, tradeoffs among consequences, the uncertainty in predicting consequences, and the benefits of flexibility to respond to changed conditions.

Jan 1, 1992

By C. Barnett

"The mill at Noranda Mines Limited, Geco Division in Manitouwadge, Ontario went into production in 1957 treating 3,500 tons per day of copper, zinc, silver, lead ore. It was not until 1964, however, that the zinc concentrate drying plant was constructed. In 1970, milling capacity was increased from 4,000 to 5,000 tons per day. The zinc content of the ore is quite variable so that the tonnage of zinc concentrate dried varies from 200 to 650 tons per day.The drying plant was designed to dry 25 tons of zinc concentrate, dry basis, per hour from an initial moisture of 8.5% to a final moisture of 2%. Major components were selected so that capacity could be increased to 35 tons per hour with minor modifications.The rotary dryer is a Hardinge type ""XH-12"" with a diameter of 80"" and a length of 50 feet. The all welded construction shell is 1/2 inch thick mild steel plate with 3/4"" thick reinforcing bands under the tires arranged for operation at a slope of 1/2 inch to the foot. The 3/8"" x 12"" radial flights are welded to the shell. There are no flights in the last ten feet of the shell in order to reduce dusting. This unit is driven by a 50 HP motor through a Hamilton type CD250 double reduction helical gear speed reducer. The shell speed is 5.8 RPM.The standard Peabody horizontal air heater has a rated capacity of 10,000,000 B.T.U. 's/Hr. The combustion chamber is lined with high temperature refractory brick and is air cooled. The conical outlet section of the air heater is lined with insulating fire-brick. The burner is a type AT wide range mechanical atomizer fired by a type ""CR"" gas-electric ignitor.The Bunker ""C"" fuel is supplied by a Compower duplex pumping, heating and straining unit, including tank hotwell, Powertronic oil line heating system with a 550/24 volt transformer."

Jan 1, 1972