Search Documents

By Alexander E. McHugh

A study of some variables affecting the recovery of molybdenum from oxidized molybdenum minerals was made. The effects of variations in contact time, temperature, pulp density, particle size, and solvent concentration on the recovery of molybdenum using acid and alkaline solvents were investigated. Chemical analyses, screen analyses and microscopic examinations were made and the presence of important elements determined. A hydrometallurgical method was developed to recover the molybdenum from the oxidized molybdenum ore by simultaneous dissolution of the molybdenum with sulfuric acid, adsorption on activated charcoal and flotation of the charcoal. The molybdenum was extracted from the activated charcoal with sodium hydroxide, precipitated with calcium hydroxide as calcium molybdate and this regenerated sodium hydroxide for additional stripping. A solvent extraction method, using mines, was also studied to recover molybdenum from both alkaline and acid molybdenum solutions. Satisfactory results were obtained.

Jan 1, 1967

By Brenton Cook, Nate Long, Larry Applegate, Aaron K. McCain

"The Northgate Link Extension project is the third phase of the Sound Transit master plan to extend light rail throughout the greater Seattle metropolitan area. When completed, the Northgate Link Extension will extend the existing light rail system north by about 7 km (4.3 miles) from the University of Washington to the Northgate neighborhood. A general overview of the project alignment is provided as Fig. 1. The project was funded by a combination of federal grants and allocations from local taxes. The general contractor on the project was JCM Northlink LLC (JCM), a joint venture between Jay Dee Contractors, Frank Coluccio Construction Company and Michels Corp. SoilFreeze, Inc. was retained as a subcontractor to provide ground freezing design and construction services.The project involved the construction of two parallel 5.5-m, 25-cm (18-ft, 10-in.) (inside) diameter tunnels using earth pressure balance (EPB) tunnel boring machines (TBM) and precast segmental concrete tunnel liners. The two tunnels maintained roughly the same elevation along the alignment and were spaced roughly 12 m (40 ft) apart (centerline to centerline). A total of 23 cross-passages connecting the two tunnels were included at approximate 244-m (800-ft) intervals. Cross passage excavations were elliptical in shape with dimensions of approximately 5.6 m (18.5 ft) in height and 5.3 m (17 ft) in width. The cross-passages were 5.8 to 6.1 m (19 to 20 ft) long as measured between the exterior of the tunnels at springline elevation. Cross passages were intentionally located directly beneath public right-of-ways thus avoiding buildings. Many of the cross passages were located beneath narrow roads in residential neighborhoods with mature vegetation, existing utility structures and piping and limited parking areas. Excavation and support for each cross passage was completed using the sequential excavation method (SEM).The subsurface soil and ground water conditions at the cross-passage locations were described in the Northgate Link Geotechnical Baseline Report (GBR) prepared by Jacobs Associates and the Northgate Link Geotechnical Data Report (GDR) prepared by Shannon and Wilson, Inc. Soils along the project alignment were glacially overridden and characterized as very dense or hard. Subsurface soils consisted of cohesionless sand and gravel (CSG), cohesionless silt and fine sand (CSF), cohesive clay and silt (CCS) and till and till-like deposits (TLD)."

Dec 1, 2018

By Michael G. Zabetakis

Effective accident prevention programs utilize a broad spectrum of activities, including meaningful training programs. In practice, such programs must be directed towards specific, defined needs. These needs are considered here for three categories of employees: new, re-assigned, and experienced.

Jan 1, 1983

By Thomas S. Nye

Mineral exploration in the United States relies heavily on theoretical geologic concepts and indirect methods such as geophysics and geochemical prospecting, as there are few exposed areas of mineralization which have not already been explored at least once. In Mexico ore-grade samples can be cut at the surface on vein, replacement, and disseminated types of deposits in many areas. Here the problem is not in finding a mineralized area but in deciding which mineralized area can be explored and developed at the least risk and cost, and have the greatest profit potential, within the framework of Mexican mineral economics and government policies. Mexico's min¬eral industry is regulated through a system of permits for various phases of mineral exploitation, and by taxes. This regulation and its effects are not unlike those which may be expected in the United States if present legislative and administrative trends continue.

Jan 1, 1972

By Y. M. Jiang

Many underground instabilities, such as excessive shield loading and roof falls, occur at longwall faces causing safety problems and production losses. Such instability problems are directly related to roof conditions which can be categorized using geological information. . However, most geologic information describing anomalies and variations of immediate and main roofs are not available before mining resulting in unexpected problems in a longwall face. It is apparent that the evaluation of these geologic anomalies provides a great benefit for longwall stability. The purpose of this study is to evaluate roof categories associated with geological anomalies employing fuzzy set theory. The evaluation is based on real-time monitoring information, such as shield leg pressure, developing load on shields, intervals of periodic weighting, and the ratio of developing loads during periodic to normal times. This paper introduces the application of fuzzy set theory for characterizing roof conditions and evaluating of roof similarities.

Jan 1, 1995

By E. Maré

Some of the members will probably ask themselves what close relationship exists between hydro-metallurgy and a wet scrubber, but we are sure that as soon as deeper thought is given to the matter it will be realised how vital scrubbing, operations are in metallurgical plants. In ordinary metallurgical installations or pyro-metallurgical processes ore concentrates are first of all shifted from place to place and dust is created. In other cases the ores or concentrates are crushed or dried or roasted, and in each one of these operations dust and fumes, are created. All suspended particles and fumes originating from the abovementioned conditions not only, in many instances, provide health hazards which disrupt production and endanger the personnel in the plant, but also are the source of economic losses through extra maintenance and wear to moving machinery due to abrasion and corrosion. Further losses are incurred by the waste of fine, very often valuable, components. The Party who once said that in several metallurgical plants the bulk of the profits was discharged into the atmosphere by the stack wasn't stretching the truth. There is a place in Africa where a gold producing concern used to lose over 5 oz. of fine gold per day out of a total production of 3000 oz. per month. In another instance, copper concentrate going as high as 80% Cu was discharged into the atmosphere at the rate of 4 tons per day. Realising the value of removing and collecting solids and fumes created in metallurgical plants, a thorough study was made of the available plant and equipment offered on the market. Some units were found very efficient, but very expensive; some others also very efficient but with temperature and maintenance limitations. Some others were also efficient but prohibitive from the point of running costs.

Jan 1, 1963

By George D. Brunton

The past and present argillaceous rock studies for the U.S. National Waste Terminal Storage Program consist of: (1) evaluation of the geological characteristics of several wide- spread argillaceous formations in the United States; (2) laboratory studies of the physical and chemical properties of selected argillaceous rock samples; and (3) two full-scale in situ surface heater experiments that simulate the emplacement of heat-generating radioactive waste in argillaceous rock.

Jan 1, 1981

By J. Miller, B. Slaker, M. M. Sears, G. Rashed

Ground falls represent a significant hazard at underground mines in the stone, sand, and gravel (SSG) sector in the USA. Researchers from the National Institute for Occupational Safety and Health (NIOSH) are currently conducting detailed investigations into the complex loading conditions at underground stone mines operating in challenging conditions. This paper presents the application of numerical modeling to analyze pillar and roof stability at a dipping underground limestone mine. A validated numerical model was used to explore the potential behavior of the pillars and roof as loading conditions change. The validated model was used to compare changes in mining sequence, overburden depth, and the in situ stress field. This will allow mine operators and engineers to have a better idea of the conditions that could be encountered as mining progresses. Results from the numerical modeling indicate that roof displacement more than doubles as the vertical stress increases from 10 MPa (1450 psi) to 19 MPa (2750 psi) when the maximum and minimum horizontal stresses were 41 MPa (5950 psi) and 22 MPa (3190 psi), respectively. Consequently, as the pillar load increases, the safety factor of the pillars is projected to decrease by about 25%. The impact of the practical application of numerical models can result in a reduction of ground-fall accidents and injuries as well as generally safer working conditions.

Feb 2, 2021

By Xinyang Wang

It is believed that sulfur and volatile matter con-tents in coals are the main intrinsic properties to cause the self-heating of coal. Their oxidation at lower temperatures than that of fixed carbon to initiate coal's self-heating should be quantified. This study is aimed to improve the previous mathematical model developed by the authors for studying the coal's propensity for spontaneous combustion. It enhances the model's ability to consider the effects of sulfur, volatile matter and moisture contents in the coal three important factors affecting the coal's self-heating process. Sulfur exists in coal primarily in the form of pyrite which will be oxidized rapidly under suitable conditions. Volatile matters, higher in low rank coals, are more easily to be oxidized. Heat of water condensation provides initial energy for low temperature oxidation. Heat release rates for pyrite oxidation and moisture condensation are built in the model. Finally, the simulation results in terms of time versus temperature on pyrite oxidation and moisture condensation are validated with the adiabatic testing data respectively.

Jan 1, 2013

By III Feeley

Coal is the nation's most abundant fossil energy resource and serves as the primary fuel for the U.S. electric-power industry. However, its continued and expanded use is often challenged by the nature and amount of its associated impurities, such as mineral matter, sulfur, and trace elements. The moderate- to high-sulfur content of many U.S. coals is of particular concern today as potentially more stringent regulations requiring further reductions in sulfur dioxide emissions are being considered. The most prevalent method currently employed to control SO2 emissions from coal-burning facilities is post-combustion flue-gas desulfurization. However, physical coal cleaning (a.k.a. beneficiation, preparation) methods can also be effective in removing sulfur and ash impurities from coal prior to combustion. In a typical physical cleaning operation, raw coal is crushed to about 50-mm (2-inch) topsize, and then screened into coarse, intermediate, and fine size fractions. Crushing liberates some of the ash-forming minerals, including the portion of inorganic sulfur (pyritic) not chemically bound to the coal matrix. The percentage of impurities liberated generally increases as the coal particle size is reduced. Coarse- and intermediate-sized coal particles are typically subjected to specific gravity-based cleaning methods, while fine-sized (less than 0.5-mm) coal particles are beneficiated using froth flotation, a technique based on surface property differences. Greater cleaning potential exists at finer sizes because of increased liberation of impurities, but this potential is not fully realized because of inefficiencies associated with fine particle separation using state-of-the-art coal cleaning technologies.

Jan 1, 1990

By Lee W. Saperstein

In surface mining for coal, common practice for the disposal of preparation plant refuse is to bury it. As with surface refuse piles, these buried wastes can ignite and can also lead to ground and surface water pollution. Steps to ameliorate these problems have been devised over the years. C and K Coal Company, of Clarion, Pa., the largest Pennsylvania surface mining company, has incorporated all of these steps and added of few, of their own in their latest disposal practice. In addition to layering and compacting, C and K practices selective placement and dilution to minimize longterm problems.

Jan 1, 1977

By Om P. Garg

The purpose of this paper is: 1) To summarize the capabilities and some of the limitations of the existing mine planning software. 2) To provide some guidelines for acquiring the software. 3) To identify problems and challenges in terms of how to justify increased use of computers (particularly the 32-bit microprocessor based super micro computers), for various activities related to a mining operation No attempt has been made to review the contents of available software packages in detail. Also the scope of this paper is limited to mine planning related computer applications. Applications related to accounting, inventory control, preventive maintenance, equipment scheduling, etc. have not been covered.

Jan 1, 1983

By N. A. Abdel-Khalek

An experimental study was carried out to compare the results of laboratory column flotation versus conventional flotation for the cleaning of fine coals of different rank and their oxidized samples as well as discrete size fractions. Surface oxidation caused a significant reduction in the flotation yields achieved with both methods. However, the column flotation produced concentrates? of lower ash content. The recovery -size curve achieved with column was similar in shape to that obtained with conventional cell, with superior results in the region of fine fractions. The influence of some column operating parameters was also discussed.

Jan 1, 1990

By S. D. Michaelson

Open pits and quarries are the major sources of all "hard rock" tonnage mined today. Normally, ore is fractured from the pit face by blasting and then truck-hauled to a primary crusher where processing begins; over- burden (or waste) is generally truck-hauled from the pit to dump areas. Truck haulage of blasted ore and overburden accounts for some 25 to 50 percent of total mining costs in a typical open pit and commonly is the largest single cost factor. Obviously then, cost reduction efforts should properly focus on improving existing haulage systems and developing new breakthrough techniques for material transport. Continuous flow systems for large tonnages ordinarily will result in a lower cost than batch systems such as truck or rail haulage. Continuous flow with pipelines for liquids and slurries, or conveyors for medium to coarse dry materials (in the -8 in. range) are the accepted economic answers for bulk materials handling over reasonable distances.

Jan 1, 1968

By F. Arslan

Gold extraction from refractory ores is still a problem. Gold losses in the cyanidation process are mainly due to the presence of sulfides and carbonaceous materials. Oxidation of carbon and sulfide minerals by sodium hypochlorite is a possible method to render the ore amenable to cyanidation, and earlier work by the USBM indicates that electrochemical generation of hypochlorite is promising. Laboratory work was carried out on the oxidation of pyrite and carbon in an electrochemical cell with a sodium chloride electrolyte. The results of preliminary tests are discussed in relation to the mechanism of electrooxidation of refractory gold ores and the estimation of current efficiency.

Jan 1, 1991

By SIMON DIAZ-QUEZADA, HUMBERTO ESTAY

The heap-leaching process is widely used for recovering different metals. In Chile, copper production by heap leaching has been accounting for between 30 and 40 percent of annual copper production over the last 10 years. This level of production has been achieved through and supported by the use of a mathematical relation known as the leaching ratio (LR), which correlates operational parameters with metal extraction in a heap-leaching operation. In spite of the widespread industrial use of this relation, few scientific studies mention it. This disparity between industrial practice and scientific research could lead to operational decisions that lack substantial theoretical support and to scientific studies with limited industrial impact. This study describes the LR and its current uses and limitations.

By J. D. Miller

Fluid flow phenomena and therefore the flotation efficiency of air-sparged hydrocyclone (ASH) flotation are strongly dependent on the operating and design variables such as air flow rate, slurry flow rate, underflow and overflow opening areas, percent solids in the feed, reagent levels, particle size, ASH length, etc. Time-averaged multiphase flow characteristics, as deter-mined by x-ray CT and described in a previous publication, are used to understand and explain the steady-state ASH flotation of quartz. A detailed parametric study of quartz flotation by a nominal 2-inch diameter air-sparged hydrocyclone (ASH-2C) revealed the influence of these variables on the flotation response which is discussed in terms of the multiphase flow characteristics. Thus, a phenomenological description of quartz flotation has been established to assist in the further development and utilization of the ASH technology.

Jan 1, 1995

By B. Petkof

Olivine has been an accepted industrial mineral for the last 50 years. Its initial acceptance was based on the recognition of its refractory properties by European research workers in the middle to late 1920's. Initial U.S. olivine production began in the early 1930's in North Carolina and continues there today. Olivine also is produced in the State of Washington and in other countries.

Jan 1, 1982

By John M. Hird

Texas Gulf Sulphur Company's Lee Creek Mine has opened a major phosphate mining district in the Central Coastal Plains of North Carolina (Fig. 1). The ore deposit as it is now known was roughly outlined in 1961 by a Texas Gulf geologist using wire line exploration methods. Slightly uraniferous phosphate materials were detected by a slim-hole gamma ray probe run in numerous farmers' water wells penetrating the formations. A follow-up-core drilling pro- gram determined the economic ore limits to lie in the south central section of Beaufort County beneath 70 feet to 120 feet of unconsolidated sediments. The 50,000 acre deposit is known to contain over two billion tons of phosphate ore amenable to strip mining methods. A part of the deposit underlies several thousand acres of the Pamlico River estuary. The 90 million dollar capital investment plant built by Texas Gulf during 1965-66 included a strip mining operation using a 72-yard walking dragline, a three million product ton per year flotation concentrator, four fluid bed calciners, a sulphuric acid plant (acid for captive use), a phosphoric acid plant, and three solid fertilizer material plants. Shipment to domestic markets is by rail and truck and to over- seas markets by barge to a transshipment terminal at Morehead City, North Carolina. Early mining investigations were conclusive first that the phosphate ore could economically be recovered only by dry strip mining methods, and second that artesian ground waters in the formation (Castle Hayne limestone) underlying the ore would have to be controlled. This report will relate the application of ground water hydrology in depressurizing the Castle Hayne aquifer to facilitate dry strip mining at depths 130 feet below sea level at the Lee Creek Mine.

Jan 1, 1970

By K. Terhaar

The objective was to determine operating protocols for a lead and silver column flotation cleaner, being considered for installation at Sunshine Mining & Refining Co.'s Kellogg mill in Northern Idaho. In this column, tetrahedrite and galena were floated, and pyrite and other gangue minerals, including siderite and silica, were depressed. The procedure was to develop a dynamic simulation using a linear transfer function approach. The transfer function related cause and effect variables such as the influence of collector and depressant dosages on recovery and grades. Bench-scale flotation tests followed by pilot column testing provided the data used to develop a linear transfer function. The transfer function was derived using a spreadsheet. This model was applied to simulate how the flotation column could be made to respond to disturbances in feed grade. The results were that xanthate, zinc sulfate, and sodium cyanide were found to be suitable controls for grade and recovery. Simulations showed the best sequence of manipulations of these reagents, and these sequences were useful for future operator training. The conclusion was that linear transfer functions were able to simulate lead and silver recovery, develop scenarios for operator training, and provide a foundation for future on-line control.

Jan 1, 1999