Search Documents

By Michael Michaylov, Elana Vlasseva

This paper presents a method for three-phase foam preparation recipe optimization. The pressurized foam is injected into porous media of gob area for prevention and fighting of SPONCOM fires. The method includes laboratory experiments for main foam properties as well as mathematical optimization procedure. Optimization criteria are formulated reflecting foam application purposes. The influence of solid phase on foam heat stability is shown. Results from optimization procedure for four foam agents by varying fly ash consistency of foam are presented. Theoretical basis for original construction of foam generator, specially constructed for of three-phase foam generation, is set u

Jan 1, 1997

By Gerrit V. R. Goodman, Charles D. Taylor

A technique was developed to determine the fraction of air recirculated from the scrubber exhaust toward the face and the fraction of gas captured by the scrubber. To determine these two values, a series of tests was required. In the first test, gas was released at the face area and concentrations measured at the scrubber exhaust. In the second test, gas was released directly into the scrubber with concentrations again measured in the scrubber exhaust. The simultaneous solution of two independent flow expressions gave values of recirculation and scrubber capture. A series of tests was conducted with various combinations of scrubber flow, curtain flow, setback distance, and machine location. Statistical analyses then were conducted to determine those factors which influenced the levels of scrubber recirculation and scrubber capture in a deep cut. INTRODUCTION As cutting depths increase, the trend is toward the use of blowing face ventilation systems. With these ventilation systems, the potential exists for recirculation between the scrubber exhaust and the intake air stream. One concern is that methane gas, having been removed from the face area, is subsequently recirculated back into the intake airflow. Under these conditions, methane-laden air could be substituted for fresh intake air, leading to increased methane concentrations at the face. There is currently no standard for recirculation between the scrubber and intake airflows. The implied understanding of the Mine Safety and Health Administration (MSHA) is, and has always been, that any recirculation of ventilation air is unacceptable. To minimize recirculation potential, MSHA suggests that operators maintain scrubber and curtain flows within 0.47 m3/sec (1000 cfm) of each other. Given that recirculation may occur in some circumstances, the question arises as to how much recirculation constitutes a hazard for the face workers. Unfortunately, there is currently insufficient information to answer this. Emphasis must instead be placed on means to quantify the amount of recirculation between the scrubber and face area. Methods must also be examined to control this phenomenon. This paper presents a technique for quantifying recirculation and scrubber capture levels in a blowing face ventilation system. Several ventilation parameters are investigated to determine their effects on these levels. DEVELOPMENT OF RECIRCULATION EXPRESSIONS One way to measure airflow quantities at a point near the face would be to measure the gas flow rate Qgas, and gas concentration c at that location. The airflow Qair, would be simply the ratio of these two values, Qair, = Qgas/c. Although gas concentration values, c, can be obtained easily with existing gas monitoring equipment, it is more difficult to obtain gas flow readings, Qgas, at specific locations. To obtain these values of Qgas, another method was needed. Previous work in this area was conducted by Kissell and Bielicki (1975). However, the calculations in their model assumed a constant gas concentration in the region around the continuous miner. In a deep cut, it is questionable that gas concentrations would remain constant or uniform around the mining machine. The technique presented here does not rely on this assumption. It instead assumes that the gas concentration in the scrubber exhaust remains constant. A quantity of gas released at the cutting face either flows into the scrubber inlets or bypasses the inlets and flows around the off-curtain side (in this example, the right side) of the continuous miner (Figure 1). The fraction of the face gas that flows

Jan 1, 1993

By Harold E. Goetzman, Blair R. Benner, Shaolin Zhong, Rodney L. Bleifuss

A commercial high pressure roller press (KHD 90125) was installed at the Coleraine Minerals Research Laboratory for testing in October, 1994. Pilot plant evaluation of the high pressure roller press has shown that it can be used as an alternative to the rod mill for the comminution of taconite. A series of pilot plant tests were run to compare roller press products to rod mill products in a simulated taconite flowsheet using magnet separation and closed circuit ball milling. Further investigation of a hybrid grinding system, roller press crushing followed by ball mill grinding, indicate that the combination may represent the most energy efficient system for taconite processing.

Jan 1, 1998

By George A. Lawrence

A new super-large 100 m3 (3500 A3) pneumatic mechanical flotation cell is now available to meet future mineral processing challenges. Several innovative design concepts represent a marked departure from conventional flotation cell designs. The radial discharge from the pump action rotor and the overhung vane type stator is contained in a conical bottom cylindrical tank with no dead comers. Peripheral launders collect froth overflowing the entire circumference of the tank and these launders are of a hexagonal design permitting cells to be nested together in a honeycomb fashion. This new flotation cell is powered by a custom designed hydraulic motor package that provides infinite speed control in individual cells and a soft start under load

Jan 1, 1993

By E. S. Smith, Sunirmal Banerjee

INTRODUCTION Social awareness of the detrimental impact of man-made wastes on our environment has grown considerably during the last two decades. Increased public and institutional concerns have resulted in the implementation of a wide variety of regulatory controls of disposal of wastes. These regulations have often reflected significant conservatism in expecting guaranteed elimination of pollution risks. This sort of expectation assumed a state of knowledge which was not readily available to the major producers of wastes. The mining industry, in particular, has been affected by such regulations in terms of excessive costs and loss of benefit. As a result, investigations are in progress (1) to generate newer methods for satisfactory stabilization of mine and mill wastes and (2) to apply the available technology to achieve the standards set by the regulatory agencies at reasonable costs. This paper presents a conceptual scheme for stabilization of mill wastes by suitable management of operations and accelerated consolidation of tailings slurries. The main discussion in this paper is aimed at the ability of the proposed scheme to address the major considerations in effective disposal. Comparison in both cost and effectiveness are also made between the proposed scheme and various other currently used disposal concepts. MAJOR CONSIDERATIONS IN EFFECTIVE DISPOSAL The primary objective of an effective tailings disposal scheme is to provide containment of the contaminants in such a manner that the undesirable impact of the wastes on the three basic elements of our environment--land, air, and water-would be minimal. Bearing the above objective in mind, one may justifiably list the major considerations in the choice of the disposal scheme in terms of its effects on land, air, and water (Bromwell, 1976) as follows: Effects on Land (1) whether the scheme makes optimal use of land.

Jan 1, 1980

By D. D. Misra

The paper presents a computer simulation package developed for the size¬-reduction circuits of Indian hematitic iron ores. The package is developed by linking independent procedures describing different unit operations like crushing, screening, recycling, etc. Mathematical models are used to quantify the unit operations involved. The models are selected after thorough analytical studies of the samples and data collected from four operating plants. The package developed gives a fairly accurate result with respect to, size and chemical composition of the flow stream and products. The program written in PASCAL can be used to try the flowsheet with various raw ores, as well as different flowsheets with the same raw ore.

Jan 1, 1989

By Gábor Antal, József Bõhm, Barnabás Csõke

From the waste material of the production of aluminium foil aluminium pigment is produced for the paint industry by grinding it in white spirit. During grinding 1-2 % iron impurity gets into the product, weakening its quality, from the wear of the mill armour and the grinding bodies and from the contamination of the raw material. For deironing the product, a stage-operated electrically induced magnetic filter separator was developed and put into operation. The separator was sited in an explosive environment and therefore required a special design and safety system. The paper describes the results of the development work. the device that was developed, the safety system as well as the results of and experiences with the operation of the separator.

Jan 1, 1995

By G. Granger, D. Malhotra

The paper briefly reviews the criteria employed in the selection of chemical reagents for testing and discusses the steps involved in laboratory and plant evaluation of these reagents. An example of successful implementation of reagent change in the plant is illustrated.

Jan 1, 1986

By Matthew E. Eisenmann, Gerald H. Luttrell

Performance data from phosphate plants are often untrustworthy because of difficulties associated with highly variable feeds and unstable equipment operation. In some cases, this problem is further compounded by improper sampling procedures and unreliable laboratory analyses. Questionable data often lead to misleading conclusions that result in lost productivity and profits. Data reliability may be checked using mass balances, but the mathematics associated with this procedure can be overwhelming when multiple data sets or complex circuits are evaluated. To overcome this problem, a simple spreadsheet-based mass balance program has been developed specifically for plant operators. To use this program, operators simply enter a description of their circuit and input the assay values (e.g., % BPL, % Insol, etc.) for each stream. The program then generates the best estimates of the assay values and flags values that may be unreliable. The spreadsheet is specifically designed to be easy to use and requires no knowledge of statistics or programming. This manuscript reviews the mass balance problem and describes how spreadsheet programs can be used to evaluate plant data. An example problem involving the analysis of data around a two-stage phosphate flotation circuit is presented.

Jan 1, 2002

By William J. Francart

In 2003, MSHA initiated a survey of the 11 Coal Mine Safety and Health Districts to develop a database for the implementation of Atmospheric Monitoring Systems (AMS) in underground coal mines. Mine operators continue to realize the benefits of improved fire detection capabilities, as the number of mines using the systems, as well as the percentage of mines, continues to increase. Fire detection data and new technology implemented in underground coal mines is discussed as well as regulatory compliance, diesel exhaust considerations and hydrogen interference in carbon monoxide detection.

Jan 1, 2005

By H. Suharyono, M. Lutsky, R. Hogg

Sediment consolidation in highly flocculated suspensions occurs only if the self-weight of the material exceeds its compressive yield stress. A simple model for sediment densification is presented and applied to the simulation of thickener operations. Measured relationships between sediment self-weight and the extent of consolidation are used to establish underflow densities. Supernatant turbidity data provide the information necessary to predict overflow clarity. It is shown that thickener depth can play a role in determining solids-handling capacity as well as dewatering performance. The application of the model to the design and operation of full-scale thickeners is described.

Jan 1, 1995

By F. Grandjacques

INTRODUCTION Selective Reduction of Nickel in Oxidized Ores Oxidized nickel ores, either garnieritic or lateritic, contain much more iron than nickel. The regular carbon reduction in an electric furnace is operated in such a manner that the greater part of iron oxides is reduced simultaneously with nickel oxide, resulting in a low nickel content ferronickel. In order that the nickel content of residual slag may be suitably low, -excess carbon must be fed so that the carbon content of the ferronickel thus obtained is that of casting iron. The metal also contains other impurities such as silicon, chrome, etc. In order to convert the casting iron into slightly carburized ferronickel with high nickel content, the greater part of the carbon and more than half the iron contained therein must be oxidized by means of oxygen. Energy is thus consumed as carbon, and power to reduce iron oxides, and more energy is consumed as oxygen to re-oxidize the iron contained. This method can be economically adopted for nickel ores with grades ranging around 2. 5 to 370, but it gets excessively costly when nickel grade falls below these values. This is why, for nickel ores with low nickel grades and high iron content, studies were conducted to develop a selective reduction process which, while reducing only a small part of the iron oxide, would provide efficient reduction of nickel oxide. Rich ferronickel is thereby obtained, with nickel content ranging around 30 to 50%. Due to the presence of slag with a high iron oxide content, the metal thus

Jan 1, 1979

By D. M. Larsen, N. D. King

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 dore' 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 vertical autoclave units operating at 170°C (338°F) and 1.4 MPa (200 psig). Projected operating costs are discussed.

Jan 1, 1994

By Mucella Ersoy, Nese Celebi

Management Information System (MIS), is a system using formalised procedures to provide management with appropriate information to make timely and effective decisions. Before developing MIS, first functions of the organisation should be defined and grouped into subsystems. After determining the information required and produced by each system and interaction between subsystems, the related data resources should be structured into a series of databases and files. In this study, the MIS developed for Soma Open Pit Mines, Turkey is described in this respect. First, analyses of the existing system including user requirements and scope of the system are given. Then the designed information system, its subsystems, interaction between subsystems and system structure are presented in detail.

Jan 1, 2002

By Pierre Louis, Jacques Duparque

ACTIRED is a new process for gold and silver elution from activated carbon based on the addition of hydrazine, needing no extra investment and which generates a systematic increase in elutions kinetics. This process either operates at a lower temperature and maximizes financial gain or reduces elution time or operates at a compromise between these two options taking into account the needs of each plant. Industrial use of the process at SNC Lastours, France (Zadra elution column 3,5 bars -125°C) has proved at 95 ° C the following points:

Jan 1, 1995

By Kenneth L. Myers

The net balance of the inflow and outflow of water in a tailings storage facility has major economic implications in any large mining and milling operation. In a net precipitation environment it can control the ultimate size and storage capacity of a facility or dictate the need for an expensive treatment and discharge program. In a net evaporation environment it can control the extent of the water rights acquisitions required for makeup water and dictate the number and size of expensive wells and pumping and delivery systems. The elements considered in a water balance analysis include the anticipated production rate, the water content of the slurry used to deliver the tailings, inflow from precipitation and snowmelt, and losses from evaporation and seepage. The mine can exert significant control over only one of these elements: the production rate. All others are subject to considerable uncertainty from month to month and year to year. The traditional approach is to analyze in a spreadsheet environment by making simplifying assumptions and using monthly mean or "average" values for precipitation inflows and evaporation losses. Often the analysis will be repeated with values subjectively assigned to represent a "wet" year or "dry'' year. The probabilistic approach uses the same basic spreadsheet model in conjunction with a probabilistic simulation add-in program allowing probability distributions to be substituted for any of the deterministic variables. The resulting analysis shows the full range of variation possible for each parameter of interest (i.e., available return water, makeup water required, storage, seepage losses) and estimates the exceedance probabilities for each. The potential uses and advantages of the probabilistic approach are discussed.

Jan 1, 1992

Floc properties such as density, size, size distribution, porosity and shear strength govern the effectiveness of flocculation as a process for solid-liquid separation. Floc characteristics desired for removal of suspended solids by sedimentation or filtration, for example, are known to be different. In this study, an attempt has been made to evaluate floc density using a simplified procedure and determine the effects of various physical and chemical factors on the density of floes obtained. A brief discussion of techniques employed to measure the shear strength of flocs and the effect of various parameters on the floc strength is also presented.

Jan 1, 1988

By M. C. Mound

A recent development using XRD techniques, a unique fixed detector, specifically permitting full mineralogical information simultaneously for the first time, specially designed sample preparation and presentation system and Rietveld codes provide a continuous real- time analysis on the true contained mineral polymorphic composition of powder streams such as ore materials, cement, ground clinker or any other mineral stream conducive to XRD analysis. There are several COSMA systems currently operating in the US, Canada, Italy and Australia, proving service and reliability of this concept. The mineralogical information generated continuously in real time is used for automated efficiency, product quality and reduces costs. Quantitative Phase Analysis information is transmitted to the plant DCS via Modbus over RS422 or ethernet. Some limited information is stored in the on-board computers for optional future use at the operator?s option.

Jan 1, 2010

By Z. Kowalski

Landfilling of waste causes the degradation of natural environment, not only due to land occupation, but also due to pollution of air, water and soil. The flotation waste from zinc-lead industry also poses such problem. There is a need to find the way to utilise substantial amount of these wastes and backfilling seems to be a good solution. Recently, in Poland only sand was used for backfilling. However, it will be more beneficial to substitute the sand with the industrial solid waste, especially flotation waste. The tests were performed in the laboratory to examine the use of flotation waste as a main ingredient for backfilling. The use of flotation waste is possible only when it is combined with other waste with specific bonding properties, especially regarding the prevention of leakage. The outcome of tests shows that flotation waste combined with cement and fly ashes can be used as a backfilling material. This paper presents the preparation of flotation waste for using it for backfilling.

Jan 1, 2006

By Ian Mitchell, Peter Faganl, Paul Haddad, Rob Dunne

During the gold cyanidation process, cyanide can be lost from the leachate by various chemical routes. The products of these cyanide losses include base metal cyanide complexes, thio­cyanate and cyanate. These losses are particularly important when treating pyritic or cupriferous ores since the two most sig­nificant cyanic ides, in order of importance, are sulfides and cop­per bearing minerals (I). Cyanidation of pyritic minerals results in the formation of thiocyanate. The problems caused by cyanide soluble copper minerals are well known to the gold processing industry and have been reviewed by several authors (e.g. 2, 3). An important consider­ation, especially with a number of more recent leaching tech­nologies, is the effect of the CN :Cu mole ratio, R, on the gold leaching kinetics. In order to efficiently leach cupriferous ores, it is important that R is maintained at a level that allows suffi­ciently rapid leaching without excessive use of cyanide. The optimum value for R in a fixed leaching system would appear to lie between 3 and 4. This is based on the early observations that the leaching rate is very slow when R is below 3, with a rapid increase in the leaching rate above 3 (2, 3,4). The leaching rate increases gradually when R is greater than 4 (4). The major Cu(I)-cyanide complex in this range of R values is the [Cu(CN)J]2· species. It has been postulated that leaching occurs due to either uncomplexed cyanide or the fourth ligand in [Cu(CN)4]3·, since the stepwise formation constant for this complex is very small (2, 3). An additional consideration when leaching cupriferous ores is the oxidation of cyanide by Cu(II) minerals, resulting in the formation of cyanate. It has also been reported that both sulfide minerals (5) and activated carbon (6, 7) catalyse the oxidation of cyanide to cyanate. From the above discussion, it is important for the leaching con­ditions to be carefully controlled when treating pyritic and cuprifer­ous ores in order to achieve efficient and economically viable leach­ing. For example, large concentrations of thiocyanate in the leachate would reveal large cyanide losses and thus indicate the need for a pretreatment step to oxidize the sulfides. Alternatively, a low R value would indicate slow leaching kinetics and consequent low gold recoveries, indicating the need for increased cyanide dosage.

Jan 1, 1996