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By Shaning Yu, Yosry A. Attia

The purpose of this work was to investigate the feasibility of using column flotation as a floc separation technique. In this study, the ultrafine coal (minus 25 microns) slurries were cleaned by using the Integration of column flotation with selective flocculation. It was found that using column flotation as a floc separation technique during the "cleaning" stage, achieved much better results than that either using column flotation as a rougher separation technique for coal flocs, or using It directly to recover the ultrafine coal from the slurries without adding selective flocculant. Thus, the ultrafine coal slurries were first separated by selective flocculation process to reject a certain amount of the dispersed ultrafine ash minerals, and to aggregate the ultrafine coal particles as flocs. Thus, the entrainment of ultrafine ash minerals Into the coal floc-froth concentrate during flotation could be considerably reduced. Subsequently, the coal flocs were further "cleaned" by column flotation. The experimental results Indicated that this approach was technically feasible and particularly suitable for a slurry containing a large amount of ultrafine particles. The effect of flotation time, and collector dosage on column flotation of coal flocs were also Investigated and reported In this article.

Jan 1, 1988

In 1993, the United States' economy grew at a rate of about 3%. The Gross Domestic Product rose to $6.4 trillion. With more than 258 million people - 599,000 in mining including petroleum - the United States has more than 100 million dwelling units and more than 190 million licensed motor vehicles. New private housing starts rose 7% to 1.3 million units, new car production fell 3% to 5.5 million units and truck and bus production rose 21 % to 4.9 million units. The rate of inflation was under 3% and the prime rate of interest 6%. The Producer Price Index (1982 = 100) was unchanged from 1992 for fuels and re¬lated products and power at 80 and met¬als and metal products at 119, while chemicals and allied products rose 2% to 128 and non-metallic mineral prod¬ucts rose 2% to 120. The merchandise trade deficit rose 27% to $116 billion.

Jan 1, 1994

By Michael L. Nave

Belt Conveyors are an important method for transportation of bulk materials in the mining industry. The control of the application of the starting torque from the belt drive system to the belt fabric affects the performance, life cost, and reliability of the conveyor. This paper examines applications of each starting method within the coal mining industry.

Jan 1, 1993

By D. C. Panigrahi

The paper presents the application of Object Oriented Programming approach for the development of a network simulation model based on nodal pressure method using linearised flow equations. The convergence and computational efficiency of the algorithm have been investigated. Finally the paper re- ports the validation of this algorithm in actual field conditions.

Jan 1, 1996

By F. Chavan

1. Introduction The new Cleuson-Dixence development project in the Valais region of the Swiss Alps, involves the construction of a new link between the Grande-Dixence dam (still world recordholder with a height of 300 m) and a power house on the banks of the Rhone consisting of approximately 20 km tunnels and shafts, and involving a fall of about 1900 m. This 1200 MW project will replace an existing 900 MW structure built in the 1960s, no longer considered efficient. The new project comprises a head race drift about 15.8 km long, a surge tank, an inclined cascade shaft 4,2 km long, and an underground power station. The work for lots C and D (head race drift from Tortin to Tracouet, surge tank, six adits ans the complete inclined shaft) was awarded to our group (Prader, Locher, SELL, Losinger, Evéquoz, Dénériaz, Imboden and Bouygues). The geological conditions are: Lower part of the shaft (300 m) : sedimentary - sandstone and soft tertiary sandstone. Middle and upper part (2600 m) : metamorphic - upper and lower carboniferous, interrupted by triasic chipping. The horizontal section (7 km) consists of mica

Jan 1, 1995

By I. A. Molodkina, A. V. Kurkov, V. V. Shatalov

New compound classes previously unknown in flotation practice of non-sulphide ore beneficiation have been developed. The presented study results consider amine salts of alkyl sulphate and alkyl benzene sulphonic acid used as primary collectors, N-methyl amides of alkyl phosphoric acids - as auxiliary modifying collectors and pentaerythritole ethers of tall oil - as flotation accelerators. These reagents synthesized from accessible raw material are almost ready for commercial production. Efficiency of the new reagents for various non-sulphide ores has been demonstrated in a series of flotation tests.

Jan 1, 1995

By Yi Luo

Subsidence events occurred over inactive room and pillar (R&P) mines, including abandoned mines or sealed portions of active mines, are classified as unplanned subsidence because of their timing and distribution are unpredictable. When investigating such subsidence cases, many uncertainties exist and disputes often focused on whether the observed structural damages are caused by mine subsidence or other natural or artificial causes. However, solid evidences to identify the causes are often lacking. In order to conduct a thorough and impartial investigation, good knowledge in subsidence theories a

Jan 1, 2009

By E. E. Bauer

Oversize boulders in mines and quarries must be broken for waste disposal or further processing of ore. Early methods involved drilling and "shooting" or using a drop ball of sufficient weight to accomplish the purpose. The first "high-energy" hammers for breaking concrete or boulders were pneumatically operated. Blow energy was limited by valving and air pressure. However, smaller boulders of lower compressive strength could be broken. A hydraulic excavator-backhoe type machine was required for either a drop ball or hammer. Standard practice was to break oversize boulders in the pit before hauling to the grizzly or crusher. Generally, quarry boulders were not valuable enough for further processing. Quarry roads were lined with oversize boulders. As safety requirements were advanced, "drill and blast" for boulders was ruled out.

Jan 1, 1994

By Russell E. Martin

Excavating and lining twin interstate highway tunnels each 11.3 m (37 ft) high by 14.6 m (48 ft) wide by 183 m (600 ft) long. A discussion of the geology of the site and problems occurring at the portals and the solutions to the problems. The methods used in placing the concrete lining are also discussed.

Jan 1, 1987

By B. J. Arnold

With the passing of the 1990 Clean Air Act Amendments, many utilities are opting to switch to lower sulfur coal to meet new SO2 emissions requirements. This lower sulfur coal may be from new suppliers or it may be from current suppliers that modify existing cleaning plants or build new plants to produce this higher quality coal. New, sophisticated coal cleaning simulators are useful tools for optimizing cod cleaning circuit operating parameters to maximize the production of clean coal that meets more stringent specifications for SO2 emissions potential. The examples in this paper were developed using the Coal Cleaning Simulator (CCS), running under ASPEN PLUS™, that was developed under a Department of Energy project cosponsored by the Electric Power Research Institute. With advanced sensitivity analysis and optimization features, CCS allows a quick, efficient, cost-effective review of coal cleaning plant performance to meet current production goals and to plan future changes in plant operating parameters or circuitry configurations.

Jan 1, 1995

By J. C. Franklin

The U.S. Department of the Interior, Bureau of Mines, has developed a data acquisition system to continuously monitor radon, working level, absolute pressure, temperature, relative humidity, and air velocity. Data have been taken in intake and exhaust drifts, working stopes, and sealed-off areas of positive and negative ventilated uranium mines. Radon emanation rates, ranging from 1.7- to 12.2 x 2 10-l4 Ci/cm /sec were determined in four mines. The ratios of short duration, primary fan shutdown time to radon normalization time were 1 to 2 and 1 to 4, respectively, for-negatively and positively ventilated mines. Blasting and slushing caused radon increases of 160 and 67 percent, respectively.

Jan 1, 1980

By C. Abbruzzese, L. Piga, P. Fornari, S. Ubaldini, R. Massidda

The effects of certain variables on the extraction of gold by thioureation have been investigated on a quartzose gold-bearing ore using a statistical multifactorial strategy. The factors taken into consideration were milling time (which corresponds to a given grain size), oxidant concentration, thiourea concentration and liquid/solid ratio. The influence of these four variables was ascertained first by a full factorial design at two levels for each variable (16 runs). This permitted the estimation of first-order effects of the factors affecting the process. Then 9 runs were added whose levels were both in the centre of and outside the axes of the previous plan thus originating a central composite design. This permitted estimation both of second-order effects of the factors involved and of parameters of a second-order polynomial model. The results show that extraction of gold depends only on milling time and oxidant concentration, at least in the experimental range considered. The equation fitting experimental data, as calculated by the least squares method, allows a response surface to be drawn. Due to the low gold grade of the ore (6 ppm) statistical analysis could lead to contradictory results, hence strict observance of Gy's rules for sampling and very accurate and precise chemical analyses were required.

Jan 1, 1995

By W. Swisterski, G. Romaniszyn, S. A. Lukasiewicz

The present paper analyzes the motion of a particle of material in a horizontaly rotating tumbling mill. The sliding of the particle under action of dynamic and friction forces and its free flight fall are analyzed. It was found that mechanism of free-fall occurs at supercritical rotations of the mill.

Jan 1, 1991

By M. J. Hrebar

A study was conducted to evaluate the applicability of large wheel loaders (Caterpillar 994 Class) for use as primary loading equipment in open-pit iron-ore operations. Field visits were made to taconite and gold mines that used large wheel loaders. Information was gathered on loader selection rationale; operation and maintenance experience; and production, availability and costs. Brief time studies were conducted to indicate machine performance and utilization. This paper summarizes the field data that was collected, including an economic comparison of wheel loaders and cable shovels in an iron-ore application.

Jan 1, 1998

By M. J. Hrebar

A study was conducted to evaluate the applicability of large wheel loaders (Caterpillar 994 Class) for use as primary loading equipment in open pit iron-ore operations. Field visits were made to taconite and gold mines that used large wheel loaders. Information was gathered on loader selection rationale; operation and maintenance experience; and production, availability and costs. Brief time studies were conducted to indicate machine performance and utilization. This paper summarizes the field data that was collected including an economic comparison of wheel loaders and cable shovels in an iron-ore application.

Jan 1, 1997

[Costs may be classified according to their source and behavior: Scale of aggregation - Total costs - Unit costs Time period for which the costs are charged - Product costs - Period costs Controllability and relevance for decision-making and control - Controllable costs - Noncontrollable costs - Sunkcosts - Opportunity costs Their basic source - Production costs (also termed manufacturing costs) - Nonproduction costs How the costs change with changes in activity - Fixed costs - Variable costs - Semivariable costs Traceability to individual units of production - Direct costs - Indirect costs Use in planning (budgeting) and subsequent control - Standard costs - Normal costs ]

Jan 1, 1999

By M. Ghiani, R. Ciccu

After a short review of the basic concepts underlying the application of selective flotation and electrostatic separation to the beneficiation of phosphate ores, the paper deals with the results obtained with these two technologies for a number of run-of-mine ores of different origin and distinct mineropetrographic features. Problems are discussed in the light of the minero-petrographic characteristics of the ores.

Jan 1, 1993

By S. Di Muzio

Sulphate Reducing Bacteria (SRB) are hetero-trophic anaerobic micro-organisms that can be used to remove sulphates and heavy metals from Acid Mine Drainage (AMD), heavy metal-bearing streams with high iron and sulphate contents and low pH, generated by sulphur bio-oxidation in abandoned mine districts. After the preliminary chemical precipitation of iron with carbonate stones (I step, chemical precipitation) SRB can be used to reduce sulphates to sulphurs then favouring heavy metal removal as sulphur precipitates (II step, biologically mediated precipitation). In this work the experimental results of heavy metal and sulphate removal from column tests were reported. Sulphate and heavy metal abatement in fixed bed column was performed using chemically pre-treated samples of synthetic AMD. Attenuation of toxic effects of treated samples was also ascertained by toxicological tests of germination and radical growth with Lepidium sativum.

Jan 1, 2006

By S. Kesler

Rössing Uranium Limited has operated since 1976 a large open pit uranium mine and extraction plant at a remote site in the Namib desert, South West Africa/Namibia. The geology (Berning, I., et al. Economy Geology) and the technical aspects concerning mining, grade control and metallurgy have previously been described (Rössing Uranium, Mining Magazin and Whyllie, R.J.M. "Rössing Uranium reaches rated production", World Mining). The improvement of leach 'extraction has been reported in 1984 (Kesler, S.B. et. al. "Uranium extraction at Rössing") and the installation of a central process control system has been described (Kesler, S.B. et al. "The introduction of a central process system at Rössing"). At the beginning of 1983 a decision was made to develop a computer system for metallurgical plant optimisation which included mass and volumetric balances, analytical assays for up to 5 chemical elements and the costs for the major consumables. Within 10 months this computer system was developed and implemented. A large number of test runs were made and computer studies were undertaken. The metallurgical division now has a scientific tool for production; planning for actual comparison with plant results and for strategic investigations and decision making.

Jan 1, 1986

By Timothy F. Markey, Brian C. Strohm

This paper presents a case study which applies risk assessment techniques in evaluating potential environmental problems associated with past waste disposal practices at a 65 acre non-ferrous metals and metal alloys manufacturing facility. Waste management activities at the site involved a number of surface impoundments for gangue material, neutralized acid rinse waters, acid rinse sludges, demolition debris, storm water runoff, stockpiled ores, and a permitted residual waste landfill. As a result of these activities, the She contained 9 identifiable waste management areas impacted by over 35 potentially hazardous chemicals and metals. Extensive environmental data obtained from investigations at the Site revealed heavy metal and volatile organic chemical contamination in various environmental media. These data were utilized to evaluate potential risks to human health and the environment. The human health risk assessment estimated potential health risks to workers, residents, and Site trespassers under current and expected future uses of the Site. Areas of the Site were identified which were considered to present potential health concerns under the various exposure scenarios. Results from the human health risk assessment were utilized to develop cost effective risk based soil remediation goals protective of the public health and environment.

Jan 1, 1992