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By Gerasimenko MP

The authors consider the features and advantages of a new promising trend in mineral processing - column flotation. Design aerohydrodynamic and process characteristics of pilot-scale columns are studied. Optimum process parameters for various ores and operations are studied. Flow patterns in cells of various cross-sections are investigated and the relationship between Peclet criterion and specific capacity of cell is determined. On this basis options were developed for optimisation of hydrodynamic characteristics of large capacity cells, including longitudinal sectionalising of the collection zone. It is shown that advantages of high column cells (10 - 13 m) produced in the West can be implemented in a sectionalised machine of smaller height (5 - 6 m). Investigations on the influence of slurry and air bubbles flow patterns indicated that to increase flotation rate of particles of various flotabilities it is expedient to combine co- and counter-current flows of phases in a single column. The proposed designs allow tailings to repeatedly return tailings to the collection zone and alternate co- and counter-current slurry and air flows. For the first time columns with alternating slurry flows (combination of co- and counter-current flows) are developed and commercialised. Unique multi-sectional cells having a number of essential advantages compared to monocells are developed. Design features of the cell allow: implementation of different flotation process flowsheets in a single unit, improved beneficiation process results, reduced specific power requirement, and elimination of sludging of the aerator and cell bottom part. Operational problems restricting introduction of column cells are connected with the aeration unit. The new cells are supplied with pneumohydraulic and stepped airlift spargers, allowing control of bubble size distribution with a service life of not less than three years. Successful operation of the new generation of columns with cell volumes of 15, 25, 40, and 80 cu m and the height of 5 - 6 m in copper, molybdenum, antimony, tungsten and nickel ores and coal slurry processing at different plants in this country illustrated their considerable process and operational advantages and verified the proposed options and relationships. A simulation technique of the flotation process and models for the solution of various problems are developed. A modular model of column flotation is constructed taking into account the kinetic relationship of the process and the hydrodynamic regime in the cell. Based on this, a technique of calculating the column parameters based on laboratory tests is developed (scaling-up), and applied for calculating the design of commercial-scale columns is developed.

Jan 1, 1993

By Drupad B. Desai, Alexander Rosenbaum

In recent years, there has been an increasing use of two-pass tunnel lining system consisting of segmental unbolted expandable precast concrete initial lining and cast-in¬place concrete final lining in the United States. Used so far in soft ground tunneling performed under free air, it often includes a waterproofing or gasproofing membrane placed between the initial and final linings. This paper describes the utilization of this two-pass system for an extension of the Baltimore Metro, constructed in part under compressed air. It offers a description of the extension project, known as Section C; addresses the tunnel lining selection process and the design of the lining elements; examines the effect of the adopted lining system and tunneling technique on the design of the project's major structural components; and describes design modification instructions in order to accommodate constantly changing field conditions.

Jan 1, 1993

By R. G. Horvath

The Statnamic loading test is a new and innovative method for testing deep foundations. The test is relatively inexpensive, quick, easily mobilized, provides for direct measurement of applied load and corresponding displacement, and is capable of very high loading capacities. The long duration of the applied loading, as compared to a dynamic loading test, allows for a straightforward determination of the static behaviour of the foundation tested. A new method of analysis of the Statnamic loading test, the Equilibrium Point Method, is presented. A description is given of the pile-soil model and a demonstration of how the static load-displacement behaviour of deep foundations may be predicted from the Statnamic loading test data. The Equilibrium Point Method of analysis is applied to three types of deep foundations in soils which respond differently to fast loading rates. These case histories, from Canada and the United States, include data from static loading tests for direct comparison, and demonstrate the ability of the Equilibrium Point Method to predict static behaviour of the deep foundations.

Jan 1, 1993

By Gary R. Corbett

The federally owned Cape Breton Development Corporation (CBDC) mines approximately 2.5-3.0 Mt of coal per annum from its Phalen Colliery. As part of an ongoing process to become more commercially viable the Corporation has implemented changes in its support method, namely, the transition from traditional steel set inseam supports to roof bolts as primary support in the single entry longwall retreat drivages. During 1991 and 1992, a monitoring program was implemented by the Cape Breton Coal Research Laboratory (CBCRL) to determine the loading on support systems and ground reaction in the gateroads in front of the retreating longwall faces of the 4 East and 5 East panels at Phalen Mine. The 4 East gateroad had been supported by steel sets alone. The 5 East gateroad had been supported by steel sets as well as roof bolting and strapping of the gateroad roof. Steel sets in both gateroads were instrumented with strain gauges and load cells to record support reaction to the retreating face abutment pressure. Multipoint borehole extensometers and multipoint strain gauged roof bolts were installed in the gateroad roof to monitor strata displacement and bolt loading above the gateroad as the longwalls retreated. This paper describes the details of the instrumentation and monitoring techniques utilized during this program and discusses the results, trends and differences observed in the two differently supported access roadways. Work on future data acquisition instrumentation is also briefly described.

Jan 1, 1993

By Jamsa-Jouneia SL, Lahteenmaki S

Sophisticated control systems require sufficient and reliable information from the process to be controlled. At the Pyhasalmi concentrator two novel measurements, a particle size indicator (PSI) and a mill level monitor (MLM), have led to significant progress in the control of the grinding circuit. The PSI and the MLM measurements have brought additional information from the process. The PSI has been an absolute prerequisite for determining the overall grinding circuit efficiency and the design of the integrated grinding and flotation control system. The MLM measurement has enabled studies on the volumetric filling of a mill to be utilised for maximising the mill throughput. The paper describes the operation principles of the PSI and MLM devices and the additional process information received. The results of a metallurgical pre-control audit are discussed and finally the design of the integrated control system is outlined.

Jan 1, 1993

A computer simulation of the automatic control of continuous mining machines has been prepared, similar to previous simulations of longwall mining systems and coal thickness sensors. The simulation allows for programmed variation of the horizon detection method, the azimuthal guidance system, the type and configuration of the miner, varying hardness in the unmined face material (leading to varying error in the machine heading), and the miner's cutting cycle. It simulates control of the miner in three axes. Use of the simulator makes it possible to anticipate problems arising from the complex character of underground mining, which include unpredictable multi-pass coupling and unpredictable variation in geological conditions.

Jan 1, 1993

Alluvial gold was found in the Terawhiti area, West of Wellington, in the 1850s. This led to the discovery of reef gold. Periods of minor 'gold fever', company flotations, and mining activity occured between 1869 - 1973, 1881 - 1986, and in the late 1880s, with one final company active in 1911 - 1914. 1n the early 1980s, further field work was carried out. No viable mining operations resulted from any of this activity.

Jan 1, 1993

By Zhang Hengzhong

Based on thermodynamics of surfaces and a proposed two-dimensional state equation for surfaces, the relationship between the surface tension (Y) of a solution and the activity (a1) of its component (i) was derived: (1/Y)r2-.¬E (ai/Yl) The derived equation was verified with reported experimental data of water-alcohol systems and water-acetone system, the calculated results showed astonishing coincidence with experimental. Applications of the equation to the five matte systems Cu2S-FeS, Ni3S2-FeS, FeS-PbS, Cu2S-PbS and FeS-Cu22S-PbS also demonstrated that at given matte compositions the calculated surface tensions agreed with experimental fairy well.

Jan 1, 1993

By Nielen van der Merwe

Mr Janisch' s comment' in the August issue on Dick Stacey's remarks about safety factors indeed requires wider debate. The example he quoted to illustrate the successful application of the safety factor concept in coal mining, namely the Salamon formula, is to my knowledge the only recognized application of that concept. Not only that, but that particular formula should be used only for what it was intended, namely to prevent major disasters. It was never intended to indicate long-term pillar stability, and it should not be used for that.

Jan 1, 1993

By Peter Cain

The Phalen Colliery in the Sydney Coalfield is extracting the 2.6 m thick Phalen Seam by the panel and pillar longwall retreat method. Abandoned workings occur in the Harbour Seam 140 m above and overlie the Phalen Colliery. Parts of these workings are flooded, and pose a number of questions relating to the safety of operations in the Phalen Colliery. In order to answer some of these questions, the Cape Breton Development Corporation re-entered an abandoned non-flooded roadway in the Harbour Seam directly above a retreat panel in the Phalen Seam to allow the deployment of instrumentation to monitor interaction effects. Fifteen monitoring sites, each 4.5 m apart, were installed in the 5 East Top Level after it had been re-entered and made safe. Each monitoring station included a vibrating wire strain gauge piezometer and a potentiometric extensometer. The piezometers were attached to rock bolts anchored into the floor and were connected by a flexible standpipe to a constant head apparatus. Variations in hydraulic head due to subsidence were monitored to determine subsidence. The extensometer units were mounted on rock bolts anchored into the floor of the roadway beneath the ribside and monitored ground strains. The instrumentation was capable of remote reading in the event that access to the site was restricted after installation. This paper describes the instrumentation, the installation programme, and some preliminary results.

Jan 1, 1993

By Egan J. R

Changes have recently been applied to the Sullivan Concentrator lead and zinc circuits to treat fine-grained ores which make-up the majority of ore reserves in the mine. Pilot plant testwork conducted in 1990 - 91 indicated that concentrate grades would be substantially improved by reducing the particle size (Pao) of the lead from 38 to 15 ¦m and the zinc from 45 to 24 ¦m. Circuit revisions involved installation of major new equipment including: two 600-kilowatt Vertimills for regrinding, a four metre diametre column flotation cell and a four metre diameter hyperbaric pressure filter for dewatering. Duties of the existing regrind mills were Reassigned.

Jan 1, 1993

By R. V. Ramani

One area of study in the Coal Mine Injury Analysis project was to illustrate and enhance the ability of mine safety management personnel to apply analytical techniques to injury experience data and to justify requests for funds for safety enhancement actions on a cost/benefit and other quantitative basis. Four volumes of this final project report detail (1) the objectives and scope of the mine safety management research, (2) the results of literature review, and case studies, and (3) models developed for mine safety management. The four volumes are titled as Volume III: Mine Safety Management, Volume IV: Analytical Techniques for Mine Safety Management; Volume V: Mine Safety Management Case Studies and Volume IX: Training Cost Model. This volume deals with the development of a microcomputer based training cost model (TCM) which can be used to analyze training cost implications of various types of training. The model has been developed using Aston Tate's dBASE III plus language. The computer program and a test run of the model are presented in this report.

Jan 1, 1993

By Koppe J. C

This paper describes the methodology developed to establish a sequentia mining plan applied to a coal mine, using computers. Firstly, isocontou. maps were generated from the drill holes and outcrop description information, representing the thickness and depth of the rock formation: present in the mine site. The procedure relies on the repeated application of the cross validation techniques, until the standard deviation of thi estimation is reduced to a minimum.From this map the coal reserves of the two coal seams, the overburdet (separated in hard and soft material) and the interburden were calculated After that, the maps were transferred in digital files to AutoCAI software, where different mining plan simulations were performed. 7b ore evaluation in each case was done automatically, including tonnages volumes and stripping relations. The final mine configuration consider the economic aspects of the operation.

Jan 1, 1993

By M. J. Virnig, Peihao Qi, J. Brent Hiskey

The mechanism of gold uptake from iodide solutions by carbon has been investigated. Adsorption isotherms for gold and iodine were established. For activated carbon, approximately 300 mg of gold and 1000 mg of iodine were extracted per gram of carbon at maximum loading. Examination of loaded activated carbon particles by scanning electron microscopy reveals isolated patches of gold deposited on the carbon surface. High-resolution transmission electron microscopy shows that fine gold particles (1-4 nm diameter) are uniformly distributed within the carbon. Iodine was also observed throughout the matrix. The uptake of gold by carbon from iodide solution involves a combined reduction and adsorption process, where the gold iodide species is reduced to the metallic state superficially and adsorbed in the porous structure of carbon. A few experiments for the gold-chloride and gold-bromide systems were carried out for comparison.

Jan 1, 1993

By Ann G. Kim

Fires that occur in abandoned coal mines, waste banks, and in coal outcrops constitute a serious health, safety, and environmental hazard. Toxic fumes, the deterioration of air quality, and subsidence constitute the greatest hazards from these fires. Although tires on abandoned mined land (AML) occur in every coal-producing state, the severity of the problem varies. Methods to extinguish or control AML fires, including excavation, fire barriers, and sealing, are generally expensive and have a relatively low probability of success This U.S. Bureau of Mines report includes information from a variety of sources, i.e., agencies of the Federal Government, State agencies, research reports, conference proceedings, product information, and technical literature. This information has been collated into a comprehensive discussion of AML fire problems. Data on past fire control projects and on the estimated extent of the current problem have been compiled. Factors affecting the occurrence, propagation, and extinguishment of AML fires are discussed. Conventional fire control methods are described, and their probable effectiveness is evaluated. Information on the hazards of AML fires and safety considerations is included. The status of current technology, recent improvements in fire control methods, and areas of current research are discussed.

Jan 1, 1993

By D. M. Larsen

Since start-up in 1985, the Cannon Mine has produced and shipped a 170-g/ton (5 oz/ton) gold flotation concentrate to various smelters for gold and silver recovery. Several processes have been investigated to economically produce done' at the mine site from the refractory concentrate. This paper describes laboratory and pilot scale test work used in the process design and engineering. feasibility study of a 73-t/d (80 stpd) pressure oxidation and carbon-in-leach (CIL) facility. The designed pressure oxidation circuit utilizes a series of verti¬cal autoclave units operating at 170°C (338F) and 1.4 MPa (200 psig). Projected operating costs are discussed.

Jan 1, 1993

By Laurance L. Oden, Jack C. White, Alan D. Hartman

The U.S. Bureau of Mines, under a Memorandum of Agreement with the American Society of Mechanical Engineers (ASME), established design criteria for a facility to field residues from municipal waste combustion. This facility, which is available to potential users on a cost-sharing basis, is also applicable to a variety of inorganic waste materials from smelting or melting operations. The design consists of a mechanical feed handling system, electric arc melting furnace, fume-off gas handling system, and thermal oxidizer for final off gas treatment. Screw conveyors and a bucket elevator deliver up to 2,000 Ib/h of minus I-in material to a three-phase electric arc melting furnace. This unique 800-kVe A furnace has a water-cooled shell and roof to minimize interaction of the melt with the refractory lining. The volume of the hearth below the slag taphole is approximately 1.2 st of steel. The furnace is sealed, allowing atmosphere control within the furnace and fume duct by nitrogen or inert gas injection. A jet-pulsed baghouse removes particulate from the off gas and serves as an acid gas scrubber. The clean off gas is heated to 1,800' F for 1 s in a propane-fired thermal oxidizer before being vented to the atmosphere.

Jan 1, 1993

Mssissippi Valley-type (MVT) and sedimentary-exhalative (SEDEX) zinc-lead deposits represent about half to three-quarters of the world's production and reserves of lead and zinc. The two deposit-types have traditionally been regarded as separate entities in terms of genesis largely because they possess very different morphologies, resulting from the epigenetic nature of MVT deposits and the syngenetic origin of SEDEX deposits. Similarities in regional setting, metal ratios, size and grade, lead and sulphur isotopes, and source(s) of fluids and metals in the two deposit-types, however, suggest that they could be products of similar genetic processes. The physical properties of MVT ore fluids suggest that certain types of SEDEX deposits could have been formed from fluids possessing similar salinities and temperatures. The hypothesis is further strengthened by the facts that: 1. in several cases MVT and SEDEX mineralisation occurs in the same region, and 2. recent advances in establishing the timing of MVT mineralisation has revealed that some MVT deposits are contemporaneous with nearby SEDEX deposits. If MVT and SEDEX zinc-lead deposits do indeed share a common ultimate derivation from fluids that emanated from sedimentary basins, then the presence of one deposit-type in a region could be used to infer the possible presence of undetected deposits of the other type. Furthermore, knowledge of the mineralisation age of one type will constrain the exploration target host rocks of the other type. A genetic relationship between MVT and SEDEX mineralisation may also explain why certain individual deposits, such as several in Ireland and eastern Canada, appear to be 'hybrids' and possess geological attributes of both end-member types.

Jan 1, 1993

By Thomas M. Sweeney

This open-file map is a quick reference containing location, ownership, and general lithology information on 124 active or significant Nevada gold mines. The map includes all counties, significant towns, and major highways in Nevada to aid in mine location. Several geologic trends with which the mines are associated are also depicted. General ore genesis for each deposit, including sedimentary, volcanic, plutonic, and placer-hosted deposits, are also identified. Gold mines are also listed alphabetically, by mine name, on the map. Each entry includes the appropriate county, percent of company ownership, operating company, and the property status as of May 1992. For additional information, contact Thomas M. Sweeney, U.S. Bureau of Mines, Western Field Operations Center, 360 East Third Avenue, Spokane, WA 99202; telephone (509) 353-2700.

Jan 1, 1993

By M D. Goodz, Wright R. F

This paper highlights the importance of accurate observational technical reports compiled by Mining Geologists and Engineers. Before uncovering the original reports in July 1992, all previous investigations discounted returning to old mining areas on the belief that all operations were suspended because they were 'unpayable'. However, the detail of the original reports removed any doubt of the economic value of retrieving remnant ore.The important feature was that the description of 'unpayable' by GMA could be equated to 11.6 - 35 g/t over the history of the mine. On the basis of these reports the Morning Star mine has been re-opened.

Jan 1, 1993