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By H. C. Voges

An account is given of the tests being conducted by Iscor on the following processes for the beneficiation of coal fines: froth flotation, gravity separation, heavy-medium separation, and pneumatic and column flotation. The coals used in the tests came from the Durnacol, Tshikondeni, Grootegeluk, and Hlobane collieries. The problems involved in the dewatering of fine products are stressed. From a theoretical study of the efficiencies that should be possible for a hypothetical South African coal, it is concluded that future fines-beneficiation plants in South Africa may use standard heavy-medium cyclones for coal down to 1 mm in size, fines heavy-medium separation for the 1 mm to 450 µm fraction, and column or pneumatic flotation for the minus 450 µm fines.

Jan 1, 1991

By J. W. Leonard, D. A. Newman

Discussion by N. Standish and P.N. Standish Leonard and Newman (1989) describe concepts and plans of their forthcoming project designed to increase the bulk density of broken coal at various stages of its production and handling. This is an excellent idea and something that will certainly be useful to the coal mining industry worldwide. The authors seek to achieve bulk density increase by "reducing oreliminating, through chemical additives and engineering design, particle voidage and enhance particle consolidation trickling between the point of breakage (at the face) and loading (in the shuttle car) to increase coal bulk density and productivity." In the paper, they present some supporting results of bulk density versus moisture, with or without oil addition, from the steel industry research. Unfortunately, the paper contains many misconceptions and half-truths that detract from an otherwise excellent objective of the project of increasing bulk density by reducing particle voidage-"the bottom line evaluator." Correct. Theory Definitions Coal bulk density is the ratio of the mass of a collection of discrete particles to the volume that it occupies (ASA, 1980). There can be no possible argument about this definition. Mass and volume are readily measured both in laboratory and large scale installations. So, to obtain the bulk density, one simply divides the measured mass by the measured volume. It is here that we come unstuck as everybody who has ever had to reconcile book values with the measured stock tonnages knows. Where does the problem originate? Almost invariably in a too casual a reading of the above definition and the words "a collection of discrete particles." The word collection means "a number of objects collected or gathered together, viewed as a whole" (The Oxford English Dictionary, 1989). If one knows the bulk density of a pile of coal viewed as a whole,

Jan 1, 1991

By Fred R. Biggs

This report was prepared by the U.S. Bureau of Mines to present a brief history of the listing of Iron Mountain Mine as a Superfund site on the National Priorities List (NPL) and subsequent remedial actions. The mine area is located on 4,400 acres near Redding, CA, and includes underground workings, an open-pit area, waste rock dumps, and tailings piles. This property involves multiple sources of acid mine drainage (AMD) that are high in copper, zinc, and cadmium. The selected remedial actions, based on the Record of Decision of 1986, would partially cap the Richmond mineralized zone to reduce infiltration of clean water, divert clean surface waters away from contaminated areas, fill surface subsidence areas, and enlarge the Spring Creek debris dam to provide increased surge capacity. Site remediation efforts at Iron Mountain are well into the remedial design-remedial action phase. Costs to date for remedial action are $7.5 million. Details of activities and designs of remedial elements are presented and future activities discussed.

Jan 1, 1991

Mine scheduling is a process which represents what happens in a mine over time. An optimised plan involves selecting the best workable plan which meets a stated objective. This paper discusses some of the theory and philosophy behind mine scheduling and explains how scheduling is a step in the total iterative mine planning process. Several schedules may be necessary before arriving at a mine plan which can be considered optimal. A description of broadbrush and detailed scheduling is given and the features of computer assisted scheduling are also described. The use of mathematical modelling techniques in conjunction with scheduling to optimise the mine plan is explained. The need to incorporate these techniques to optimise the whole mining system rather than only a part, is emphasised.

Jan 1, 1991

By P. L. Webster, S. D. Thompson

Sevim and Wang (1988a) have presented a model for designing haulage systems in underground coal mines. The authors contend that their model uses a heuristic algorithm to optimize various haulage system parameters. In reality, it would be nearly impossible to optimize a haulage system, because mining plans are uncertain and often change with respect to time. Therefore, haulage system design poses both a stochastic and a dynamic design problem, and its optimization appears to be well beyond the scope of heuristic algorithms. In regard to the authors' design model and its practical significance, a number of additional issues warrant further discussion and clarification. These issues include: l) their model's alleged advantage over simulation models, 2) the correctness of their belt network design, 3) the correctness of their bunker design, 4) the necessity of their proposed bunker clearance policies, 5) the correctness of their shaft-bottom bin design, and 6) the

Jan 1, 1991

By C B. McCampbell, R W. Jr Bickes

Sandia National Laboratories has developed a semiconductor bridge (SCB) igniter for the ignition of a variety of explosive materials. When subjected to a low-energy current pulse, the bridge bursts into a plasma causing rapid ignition of the explosive material pressed against the bridge. Despite the low energies required for ignition, SCB components have proven to be explosively safe, meeting both no-fire and electrostatic discharge (ESD) safety requirements.

Jan 1, 1991

By Victor C. Bryan

One of the most sought after answers in any consideration of blasting activities relative to mines and quarries is how to safely and efficiently use explosives. While that discussion might be relatively straightfonvard in a “site specific” situation. it becomes more complex when viewed from a broad geographic perspective. Such is the case in considering the operations of one United States producer of crushed stone with surface and underground mines spread over a thirteen state area. Differing geologic environments set conditions that dictate to the blaster as now specifically to get optimum results from the blast hole. This treatise is a discussion of the various methods, materials, and principles used in conducting such blasting operations.

Jan 1, 1991

By Victor F. Hollister

This section describes two exploration models currently used in the search for porphyry exploration deposits: the hood and the vertical cylinder. Each has alternate names within industry and in the literature. The hood is also known as the Climax or Henderson and the vertical cylinder has also been called the Mt. Pleasant model. The paper by Hollister (1978, abstract herewith) refers to the vertical cylinder as the zoned model in reference to the horizontal sulfide and silicate zonation evident in and peripheral to the vertical cylinder of molybdenite mineralization. The distinct ore body geometry in each model type necessitates differing drilling and exploration strategies. Drilling for a hood shape is clearly different from drilling for a vertical cylinder type target. The paper by Wallace et al. (1968, abstract herewith) on multiple intrusion and mineralization at Climax, CO, well describes the hood model. That description is supplemented by the paper by Wallace et al. (1978, abstract with Chap. 37) on the geology of the Urad and Henderson deposits. The paper by Hollister (1978, abstract herewith) describes the vertical cylinder model.

Jan 1, 1991

By L. Betteridge, A. Marks

"An OK 300 cu. ft. Skim - Air cell was installed at the HBM&S concentrator in Flin Flon in 1987. Since that time, 3 additional OK Skim - Air cells have been installed in HBM&S concentrators. The cell treats a coarse 70% solids slurry with a residence time of 2.5 minutes. The product from the cell (a unit cell type application) is a final grade copper concentrate with high precious metal values. Since its installation, the cell has improved gold recovery by 10 - 15%. Process variables such as circulating load, pH, froth depth, feed size, and reagent additions all have an effect on the operation of the cell. Maintenance on the cell has been minimal. Initial operating problems involving level control have been significantly reduced and operations are now relatively trouble free. Although very successful at Flin Flon, site specific operating circumstances will determine the suitability of this cell. INTRODUCTIONHudson Bay Mining and Smelting operates four concentrators in Northern Manitoba. Three treat copper-zinc ores, the fourth mills a copper-nickel ore. The Flin Flan concentrator operates two circuits in parallel which treat copper and zinc ores from the Trout Lake and Callinan mines. Both circuits in the Flin Flan mill have Skim-Air cells integrated into the grinding circuits.The Trout Lake cell was installed first and had a payback period of a few months. Required modifications to the cell were made to enhance its performance. These included changing the discharge valve size, tuning the level controller, and installing an insert into the rubber valve sleeve to increase its wear life. The payback period on the Callinan cell was significantly reduced because these modifications were completed prior to its installation.The cells produce a final grade copper concentrate and since their installation gold and silver recoveries to the final copper concentrate have increased significantly. Operating parameters such as coarseness of cell feed dictate the metal recoveries and froth depth determines the selectivity of the cell and therefore the grade of the concentrate.The Skim-Air cell can be suitable in applications where a final product is generated. However, when a bulk concentrate, which requires further separation, is produced, the coarseness of the product may not make it amenable to conventional flotation.The Flin Flan mills Skim-Air cells have worked exceptionally well with little maintenance required."

Jan 1, 1991

By C. A. F. Pinto

In the present work compared flotation kinetics of apatite with four different collectors was established. Sodium oleate and rice bra~ oil were used to represent conventional collectors. The new collectors included a sulfosuccinate and a sulfosuccinamate. It was observed that the collection ability of each reagent was very dependent upon the mineral size ranges. The results-were analyzed in terms of size-by-size recovery curves. Flotation rates were also very dependent on size ranges of the mineral particles. One of the new collectors displayed higher flotation rates for coarser particles than the other reagents tested. Synergetic effects were also apparent when a conventional collector was mixed to a new collector.

Jan 1, 1991

By Ernest L. Ohle

Since the first recorded discovery of lead in southeast Missouri near Fredericktown about 1720, knowledge of the deposits has advanced in spurts as a result of outlying discoveries: 1864 Bonne Terre 1890 Flat River, Desloge, Leadwood 1948 Indian Creek 1955 Viburnum The original discoveries at Bonne Terre consisted of residual galena in clay, similar to that in the previous finds at Fredericktown. Occurrences in solid dolomite were not noted until mining of the clay pits exposed the walls of the weathered depressions. The St. Joseph Lead Co. had been established to conduct the operations and it was J. Wyman Jones, first president of St. Joe, who at that time brought about the first of the technological advances that were to occur in the district. He proposed use of the newly invented diamond drill to explore the bedrock showings, after observing the machines in the Vermont Marble Belt.

Jan 1, 1991

By Zhou Lu-Jian

The Port of Shekou is situated at Shenzhen Bay on the east bank of Lingding Ocean. Its coastline is about 6 km long and the water depth near the shore is Favourable. Across the bay is the ' New Territories " of Hong Kong. The port is at a distance of 22-23 seamilesaway from center of Hong Kong and 80 seamiles to Huangpu Harbour of Guangzhou, its highway links with Shen-Guang Highay. Since 19 79 China Merchants Group of the Transportation Department, began to set up Shekou Industrial Zone, the port has been developing and flouri­shing in business. With 15 large or small berths in all, the present portline is 2600 m, and the annual cargo throughout is over 3,000,000 tons and the annual passenger traffic is about 2,000,000 persons. Equalling a medium-scale seaport, it has been officially approved as an oceangoing transit port by the ministry of Transportation. The construction of Shekou port is chara-terized by the self-collected funds and the short construction period. In view of this, the optional plan of the port structure must serve the requirements of simplicity in struture, economy in mate­rial and speed in construction. That accounts for the most application of the sheet piling type to the port in Shekou. Once the project was approved, the cons­truction started. Only within an average period of 7-8 months, a deep water pier was completed and put into operation, which covered series of processes from exploration, designing, tender for con­struction to completion.

Jan 1, 1991

By Jan Visman, James W. Parkinson

GENERAL INTRODUCTION Sample collection, preparation and analysis are all steps in a single process designed to provide information about a much larger amount of material than the sample itself. For example, information about the ash content of a unit train load of coal may be derived from a single, relatively small sample of perhaps a few hundred pounds (liters) extracted from the entire shipment. These three steps can be thought of as links in a chain, allowing the simple analogy that the strength of the chain, or, in other words, the value of the information is only as strong as the weakest link. Sample collection, discussed in Part 1 of this chapter, is critical because analytical procedures can do no more than reveal the characteristics of the sample presented to the laboratory. If that sample does not properly represent the population to be characterized, neither will the analysis of that sample. Sample preparation is also a critical part of the chain. Any change in the nature of a sample between the time it is collected and the time it is analyzed will appear to reflect the nature of the population. For example, sample preparation procedures that allow air to partially dry the coal sample before reaching the laboratory will cause the sample analysis to indicate a lower moisture content than the sample originally had. Other changes can be more subtle. Second only to moisture loss, oxidation reactions generally cause the greatest problems. Oxidation of a coal sample can alter surface properties, changing flotation response. In extreme cases, combustion parameters, such as caking or agglomerating properties or mineral composition, such as pyrite content, can change. Water samples can also be altered by oxidation. For example, ferrous iron can oxidize to ferric iron, possibly changing water quality parameters such as pH. Sample analysis, the subject of Part 2 of this chapter, is the final link in the chain. Obviously, no laboratory procedure can correct for problems created by improper sample collection and preparation. At the same time, poor analytical techniques will create incorrect information about the total amount of coal from which the sample was extracted (the population) in the same manner as improper sample collection and preparation. The key to gaining correct information about the population is to view these three steps as parts of a single process. Following proper techniques through only one or two steps of the process will not produce accurate information.

Jan 1, 1991

By T. Gouri Charan, G. V. Rao

A spherical agglomeration process for the separation of scheelite fines of less than 30 µm in very low concentration of 0.04% WO3 in a binary mixture with quartz fines of less than 30 pm has been described. A concentrate containing 14% WO, with more than 90% recoveries could be achieved by means of anionic sodium sulfo succinate collector at pH 3.5 and also with commonly used anionic sodium oleate at pH 10.5 as per the conceptual flowsheet suggested. Such a process is envisaged as commercial potential for the recovery of fine-grained scheelite present in the tailings of gold plants as found in India.

Jan 1, 1991

By Ware AR, Doyle BJ, Hoogvliet H

The Ladolam deposit lies within the altered volcanic rocks of the caldera floor, part of which now forms Luise Harbour. It was discovered in 1982 in the course of a reconnaissance drainage sediment sampling programme. This was designed to follow up indications of surface hydrothermal activity noted by Government geologists during an earlier survey of the Tabar-Feni island chain. Diamond drilling began in September 1983 and by the end of 1989 a payable and proved mineable reserve containing 19 million ounces of gold had been established. Rock types and structures are masked at the surface by intense alteration and weathering. An extensive drilling programme has enabled the identification of these features and the relationships between them necessary for an understanding of the factors controlling gold mineralisation. It has also led to the recognition of two distinct phases of alteration. The first phase of porphyry-style potassic alteration was followed by violent caldera formation, producing extensive brecciation and veining. The second alteration phase partly over- printed the first phase and was an epithermal one, evidenced by argillic, advanced argillic and phyllic assemblages. During this event, a large volume of fluids circulated under the favourable structural conditions; these fluids included a sulphur- rich, neutral chloride brine believed to have transported the gold. Boiling and mixing of circulating fluids in the open breccias is thought to have resulted in deposition of the gold. There is evidence that this process is continuing at the present day.

Jan 1, 1991

By B. J. Pieters

The paper describes the difficulties experienced with inferior coking coals as Iscor began using larger blast furnaces for the production of liquid iron. Research conducted at Iscor from 1977 to 1979 showed that benefits could be gained from the use of partially briqueted charges, and it was decided to install briqueting plants at the Vanderbijlpark and Newcastle Works. Details are given of the later plant, which was supplied by a consortium consisting of Voest Alpine, Didier Engineering, and Sumitomo Metal Industries. Sumitomo also supplied information on the optimization of coke quality along the lines of their Sumicoal System. The results have been a marked improvement in coke quality, much better blast-furnace operation, and increased productivity.

Jan 1, 1991

By Jinrong Zhang

Fresh cyanide solution was treated by near UV light with the assistance of photocatalysts. Cyanide was oxidized mainly to cyanate. Photochemical behavior of the anatase and rutile forms of TiO2 was compared. It is found that anatase has a much higher activity than that of rutile. Bubbling of oxygen in the reactor showed no appreciable increase in cyanide oxidation, implying that the reaction is surface controlling. A very interesting finding in this study is that a natural mineral, ilmenite, can replace chemical titanium dioxide as the photocatalyst. Ilmenite without any treatment did not catalyze the oxidation of cyanide. But, after being roasted at high temperature with oxygen, the oxidation was enhanced dramatically. The mechanisms of photooxidation of cyanide and the roasting of ilmenite are proposed.

Jan 1, 1991

By Thomas C. Anderson

Tiedback walls are now recognized and accepted as a good solution for a variety of structural problems: ? Retaining Walls and Bridge Abutments in cut situations ? Landslide stabilization ? Repair/support of existing walls Acceptable techniques have been developed for anchoring in cohesive and granular soils and in any kind of rock. Methods have been developed for adequately protecting tieback tendons against corrosion and for testing every tieback to verify its long-term load-carrying capacity. However, the major problem that the industry faces today is how do we get constructable and economical tiedback walls contracted for and built with minimal claims. This paper will explore the issue of "constructability" through a look at specific problems from actual projects. From a research report from the Construction Industry Institute, Austin, Texas (1986), constructability is defined "as the optimum use of construction knowledge and experience in planning, design, procurement and field/operations to achieve overall project objectives." Maximum benefits occur when people with construction knowledge and experience become involved at the very beginning of the project." The design and installation of tiebacks has been developed primarily by specialty contractors; each contractor has evolved its own methods of performing the work, and consequently, many of the techniques are patented and proprietary. The real question is, how do we make effective use of this knowledge and experience during the design phase of the project?

Jan 1, 1991

By Joseph Matoney, B. K. Parekh

INTRODUCTION The term "dewatering" refers to removal of water from coal. Water associated with coal can be categorized as "free or surface" and "inherent or chemically bound" moisture.' The free moisture is found on the surface of coal, in capillaries and small spaces between two or more particles. The inherent or chemically bound water is found in the interior of the coal and as part of coal structure. A significant amount of free moisture can be removed by mechanical dewatering techniques. However, inherent moisture can only be removed by applying energy intensive techniques, e.g., direct or indirect heating. Moisture in the coal offsets some of the benefits of coal cleaning. Extra water in clean coal adds to extra cost in transportation, heat lost during vaporization, and plugging of chutes. From a utility perspective, a 1 % increase in moisture can offset a 4.5% decrease in ash.2 Mechanical dewatering can be classified into two major process categories according to the principles involved, namely, 1. Sedimentation-liquid is constrained and particles move freely. 2. Filtration-particles are constrained by a medium and the liquid flows through. Each of the process categories is composed of various separation techniques shown in Fig. Equipment currently being used by the mechanical dewatering of coal of varying size ranges and final moisture content is illustrated in Fig. 8-2. This figure indicates that sizes larger than 13/, in. (37.5 mm) present no particular dewatering problem. Shaker screens of the very crudest types and designs are capable of producing these sizes at low surface moistures. High-speed vibrators are used for the intermediate sizes and can be used for smaller sizes down to 0.02 in. (0.5 mm) if high moistures (15% surface moisture or greater) can be tolerated in the product. Usually, however, the vibrator is not used below 3/, to 3/, in. (9.5 to 6.3 mm) because of the moisture associated with these fine sizes. At this level, centrifugal force is usually employed to aid dewatering. Centrifuges of various types and designs are used practically

Jan 1, 1991

By Kousik Sinha

The advantage of using a clean coal as a feedstock in a direct liquefaction plant is improved performance of the plant by several factors e.g., increased throughput of coal; reduced wear and tear of valves, pipes, and pumps; increased liquid yields, etc. This paper examines the technical feasibility for cleaning Illinois #6 coal as a feedstock to a direct coal liquefaction plant via selective agglomeration using a coal-derived heavy distillate, Wilsonville V-1074 as agglomerant. Effects of addition of Kerosene or coal-derived Naphtha as conditioner, coal particle size, slurry pH, oil to coal ratio, and operating temperature on ash reduction and clean coal weight recovery have been studied. Results show that about 70% of the ash can be removed from this coal and the clean coal weight recovery over 85% can be achieved by using this technique with suitable selection of coal particle size, slurry pH, mixing intensity and oil to coal ratio.

Jan 1, 1991