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By Michael J. Rinker, R. V. Nicholson

Waste rock and tailings from a proposed nickel-copper mine were evaluated extensively for potential on-land and under water disposal. Standard humidity cell and column tests were conducted over a two year period and underwater tests were conducted for more than one year. Nickel concentrations or release rates from the waste were consistent with nickel to sulphur ratios in the solids. This relationship provided a tool to assess the risk of metal leaching in wastes using nickel and sulphide assays. Nickel release and mobilization was found to occur for both oxidizing leach tests and under water tests even when pH values exceeded 7.0. Geochemical model calculations showed that iron oxyhydroxide solids can scavenge nickel from leachate and that the nickel inventory can be released from solids at relatively lower, but neutral pH values.

Jan 1, 2000

By F. F. Aplan

Rather than reiterate what is well known about the flotation of the non-sulfide minerals, emphasis has been placed on those separations which are not so effective. These difficult separations are largely connected with problems of selectivity in the flotation of the base metal oxides, the other slightly soluble minerals, the insoluble oxides and the naturally floatable minerals. The paper discusses possible methods of improving selectivity between similar species and of improving selectivity against the gangue minerals.

Jan 1, 1994

By B. S. Treiber, R. A. Lohnes, S. M. Levorson

As part of a research program to develop a coal-handleability index that would predict the ease with which a coal would flow through a handling system, an apparatus was developed to directly measure the unconfined Yield strength and bulk density of consolidated-coal samples. The new test apparatus provides a fast and simple method for determining the strength and compressibility parameters that are associated with the handling characteristics of crushed coal. Comparative tests were conducted using a low-stress triaxial-test apparatus. To check the accuracy of the new method, four coals with a variety of moisture contents and gradations were tested using the new method. These tests indicate that the new test device yields valid results. Further, the speed and ease of operation of the new device makes it suitable for quality control and quality assurance in plants.

Jan 1, 1996

By K. Ohga

Japan has produced 14-16 million tons of coal per year in the past several years. About half of the production comes from eight coal mines in the Ishikari coal field, Hokkaido. Most of the gassy coal mines are in this field and the average mining depth of these coal mines has already attained about 700 m from the surface. Therefore, most of the coal mines have suffered from occurrences of coal and gas outbursts. To prevent outbursts and to reduce ventilation air, gas drainage has been carried out at all of these coal mines and these have had successful results. However, the methods of gas drainage differ from mine to mine. In this report, an outline of the main methods of gas drainage are described.

Jan 1, 1987

By H. L. Ehrlich

Modes of microbial attack of metal carbonates, metal silicates, metal oxides and metal sulfides are summarized. The current status of microbial redox mechanisms, whereby metals in metal oxides and sulfides are mobilized, is discussed. Opposing theories of a single mode of attack involving interaction with a microbially produced reductant or oxidant in the bulk phase and of dual modes of attack involving a reaction requiring physical contact between microbe and mineral surface on the one hand and microbial production of a reductant or oxidant in the bulk phase that reacts with the mineral on the other hand are considered. No one mode when finally completely unraveled should be expected to fit all cases. Some biochemical, electronmicroscopic and spectrophotometric approaches for elucidation of missing details of different modes are suggested. Key words: Bioleaching, Biobeneficiation, Metal mobilization

Jan 1, 2003

By P. C. Thakur

In gassy coal mines, some methane drainage is essential for mine safety, but the ratio of total methane drained to total methane produced by the mine can vary from 10 to 70 percent. The volume of methane not captured is diluted by ventilation air and vented to the atmosphere. Since captured methane can be processed and sold, it makes sense to maximize methane drainage from coal mines. This paper describes ventilation and methane drainage schemes to achieve these goals.

Jan 1, 2003

By D. C. Seidel, W. K. Tolley

Supercritical water alters the structure of common sulfide minerals by partially removing sulfur from the mineral structure. This discovery has been applied to the treatment of pyritic gold ores to improve precious metal recovery without generating or utilizing environmentally sensitive products such as S02, chlorine, or cyanide. Pretreating pyrite concentrates in supercritical water under mildly oxidizing conditions provided by certain metal oxides or oxygen improved gold leaching using thiourea. The pretreatment differs from chlorination or roast pretreatments in that elemental sulfur rather than sulfuric acid is the major product. A pyritic ore containing 58 g/mt Au was pretreated with oxygenated supercritical water at 24 MPa and 400°C, then leached with 20 g/L thiourea. With pretreatment, gold recovery was 90%; by contrast, gold recovery was below 10% without pretreatment.

Jan 1, 1990

By Hajime Miki, Michael J. Nicol

Relatively simple techniques have been developed which enable the electrochemistry of sulfide minerals to be studied with particles varying in size from above 100 pm to less than 1 pm. Both oxidative and reductive processes have been studied wing the minerals pyrite, arsenopyrite and chalcopyrite. It has been shown that it is possible to completely oxidise or reduce the minerals during a single voltammetic sweep. The resulting voltammogram produces peaks which are characteristic of each mineral and can be used to qualitatively identify the minerals. In the case of chalcopyrite, it has been demonstrated that the charge involved in the anodic oxidation can be quantitatively related to the amount of copper dissolved. Quantitative information can be obtained using peak fitting techniques. Interesting differences in the behaviour of the minerals in sulfuric and hydrochloric acids have been observed, particularly in the case of pyrite for which a second major peak is obtained which has been attributed to the oxidation of elemental sulfur in the presence of chloride ions. The technique offers the possibility of providing mineralogical information of individual particles based on an electrochemical voltammetic finger print.

Jan 1, 2005

By James J. Scott

Introduction Friction Rock Stabilizers, trade name Split Sets, are presently under research and development by Ingersoll-Rand Company and Dr. James J. Scott, inventor. Conceived in 1953, the system is a patented process undergoing extensive field and laboratory testing. The author has published papers on the Split Set System earlier (References 4, 5, 6) The Split Set System holds promise to be a revolutionary development in the field of ground control. The system produces an interior reinforcement to a rock mass which: 1. Is simple in its concept. 2. Adjusts to the degree of restraint needed to match rock properties. 3. Provides a yieldable support and, later, a more rigid support as it is needed. 4. Pre-loads the rock in compression to increase stability. 5. Is a full-contact, fully tensioned device to resist rock loads. 6. Minimizes the stress concentration effects inherent in many interior support devices. 7. Improves safety for the miner. 8. Is cheaper than a grouted system. 9. Offers the rock mechanics engineer an opportunity to design in a fashion not before possible.

Jan 1, 1977

By Gary Buchan

During several months in 1996 and 1997, Cyprus Twentymile Coal Co. (TCC) set world production records at its Twentymile Mine in northwestern Colorado. These records were due to the company's implementation of a state-of-the-art longwall mining and conveyance system along with a -highly dedicated work force. This article is a case study of the design of long panels at the mine from conception to implementation. Obstacles that needed to be overcome included subsidence engineering, environmental regulations, conveyance, ventilation, equipment design and continuous miner (CM) development timing.

Jan 1, 1998

By Steven A. Atkin, William D. Schrand

Closure plans for open pit mines require the prediction of final pit lake water chemistry. The geochemical models used for water quality predictions make assumptions about the physical and chemical behavior of the water in the lake; however, few pit lakes have been well documented to provide empirical data for model design. The pit lake at the Sleeper Mine has been characterized with regular water chemical analyses and regular, continuous, multi-parameter profiles through the water column. The lake has undergone repeated periods of chemical and thermal stratification, punctuated by rapid turnover events resulting in vertical homogenization within the water column.

Jan 1, 2000

By M. J. Laurila

Utilizing data compiled from a drilling program and bulk samples taken from a coal reserve, flowsheet performance for a coal preparation plant can be calculated using a desktop computer. Sets of equations defining material balances involving coal preparation plant unit operations are employed to depict plant performance. Techniques are discussed for interpolating washability data and extrapolating size distributions and other critical data to expand on oftentimes limited sets of quality data to a useable data base from which projections can be made. Simulation of flowsheets can be done for a number of different conditions and configurations while still remaining in a limited working memory capacity of 32,000 bytes. Presented within this paper are several pertinent examples.

Jan 1, 1982

By P. Coleman, J. C. Kerkering, S. Iverson

A fatal accident may result when a dozer is driven over a hidden void in a coal surge pile and the dozer falls into the void, burying and suffocating the dozer operator. This type of accident was analyzed by researchers from the Spokane Research Laboratory of the National Institute for Occupational Safely and Health using inexpensive fault-tree programs that had been developed, for use on a personal computer. Fault-tree analysis is a systematic safety-analysis tool that proceeds deductively from the occurrence of an accident event to the identification of the root causes of that event. The analysis identified basic and intermediate events that led to the burial of the dozer and graphically depicted the interrelationship between the basic events as well as the intermediate events leading up to the accident. A sensitivity analysis on assigned probabilities showed which events had the greatest influence on dozer burial in a coal surge pile. Operational guidelines and engineering controls are suggested to decrease the probability of a burial event.

Jan 1, 2002

By P. J. Brown, R. W. Nice

The Thalanga Copper-Lead-Zinc Concentrator in Northern Queensland was commissioned in early 1990. The design of a flotation process for the sequential production of separate copper, lead, and zinc concentrates has always been a most formidable mineral processing challenge. In 1988-1989 during the process design phase, sized fractions of various samples were subjected to quantitative and qualitative mineral analyses. These analytical techniques are collectively known as modal analysis. Modal analysis aided in the selection of key process treatment parameters for the initial laboratory testwork on the Thalanga ore. The work also guided the flowsheet development and quantified the mineralogically imposed limitations on the separation process. This paper describes in general terms how these modal techniques were used to guide the program of laboratory flotation testwork which constituted the flowsheet design phase of this project. During these design studies, the primary grind and regrind requirements were deduced and the basic flowsheet configuration selected. Recent operating plant performance data are to illustrate the value of modal methods in addressing complex metallurgical separation problems.

Jan 1, 1995

By J. M. Mutmansky

Introduction Since the Hardy Cross numerical algorithm was applied to the solution of mine ventilation networks, numerous developments have taken place in ventilation network analysis procedures. The Newton-Raphson method, the linear theory method and the second-order approximation method are three of the additional approaches that have been applied. The efficiency of a ventilation network analysis procedure depends not only on the method of solving the system of equations derived from ventilation networks but also on the method of deriving the equations through selection of the meshes. This paper investigates the impacts of three mesh selection methods on the efficiencies of four ventilation network procedures. The minimum-resistance spanning tree method is the most popular procedure for selecting meshes. The shortest-path method was suggested by Epp and Fowler (1970) for improvement of the Newton-Raphson method. The minimum-resistance-path method is suggested here as the third method of selecting meshes. The effects of these three methods on the Hardy Cross method, the Newton-Raphson method, the linear theory method and the second-order approximation method are analyzed in this paper. These network analysis methods have been summarized in the paper by Kim and Mutmansky (1991). Mesh selection methods A procedure for mine ventilation network solution based on mesh equations typically consists of two steps: • the mesh selection step and • the network solution step. The mesh selection step establishes a set of independent equations to solve the network. The resulting equations are nonlinear. One method of solving nonlinear equations is to linearize the equations and iteratively solve these linear equations. The four analysis methods previously discussed in this paper use this approach. The linear equations required for solution can be written in matrix form as: P•dQ = dF (1) where P is the pseudo-resistance matrix, Q is the quantity matrix, and F is the Jacobian matrix (Kim and Mutmansky, 1991). The efficiency of the solution method depends on the characteristics of the P matrix, which in turn depend on the method of selecting meshes. To understand the impacts of the mesh selection methods on the efficiency of the ventilation network analysis procedures, the characteristics of the P matrix must be understood first. The diagonal elements of the P matrix, m in number, are the sums of the pseudo-resistances of the branches contained in the m meshes necessary for solution. The off-diagonal elements are the sums of the pseudo-resistances of the branches shared by two meshes. For example, P12 (first row, second column element of the P matrix) is the sum of the pseudo-resistances of the branches common to mesh 1 and mesh 2. When solving the system of equations expressed in Eq. (1), three of the iterative procedures (the Newton-Raphson, the linear theory and the second-order approximation methods) use the direct factorization method (Burden and Faires, 1985) on the P matrix. When the direct factorization method is used, the computational efficiency is enhanced by larger diagonal elements and a sparser P matrix. Generally, the sparsity of the P matrix is more important than the size of the diagonal elements. There is no known mathematical method of predicting the efficiency of these procedures, but heuristic methods can be used to study the efficiency. The Hardy Cross algorithm applies the Gauss-Seidel method of splitting the P matrix and applies the Newton-Raphson procedure. The efficiency of the Hardy Cross method depends on the spectral radius of the matrix[[D-L]-1U], where D is the diagonal, L is the lower triangle and U is the upper triangle of the P matrix for the Newton-Raphson method (Ortega, 1972). The smaller the value of the spectral radius, the faster the convergence. As with the other three methods, larger diagonal elements and a sparser matrix aid in faster convergence. With the Hardy Cross method, however, the size of the diagonal elements is more important than the sparsity of the matrix. Remembering that each of the diagonal elements of the P matrix is the sum of the pseudo-resistances of the branches in a mesh and that each off-diagonal element is the sum of the pseudo-resistances of the branches shared by two different meshes, the following strategies can be used: • Avoid having branches with larger resistance values shared by multiple meshes. This increases the size of the diagonal elements and reduces the chance of off-diagonal elements being large.

Jan 1, 1993

By K. A. Natarajan, J. M. Modak

A review of published literature on the biosorption of metals using nonliving biomass is presented. Factors such as pH, temperature, initial metal concentration, biomass loading, the presence of co-ions and the pretreatment of biomass influence the metal uptake by biomass. Although few generalizations are possible, unified theories regarding the mechanism of uptake are not available. Therefore, the above aspects of metal biosorption have to be defined individually for each biomass and metal-ion pair.

Jan 1, 1996

By J. Felipe Costa, Andrew H. White, Marcot T. M. B. Vilhena

Ordinary kriiing (OK) is an interpolation algorithm mostly used in earth sciences applications where it provides satisfactory results. Robust kriging (RK) is an alternative algorithm which at- tempts to minimise the problems caused by the existence of outlier values within a given data set. Robust kriging essentially consists of an editing step prior to running the traditional OK method. This study compares the interpolation results obtained by OK and RK. Two data sets were used. The first data set consists of 140 samples mimicking a drilling survey named cluster.dat. An additional feature of this sample data is that its parent population, the reference data set, is available, thus permitting direct quantitative assessment of the effectiveness of a given estimation technique. The second data set consists of a grid sampled at 1x1 m. The estimates obtained by OK and RK using cluster.dat were compared to the reference data set. RK provided better results in terms of quality of the estimates than OK

Jan 1, 1996

By Robert Dimock

The successful management of large dispersed mineral operations is dependent upon accurate and timely decision making. The plant locations providing the data to support the decision making process are generally separated by distances which elongate the time required to accumulate the data at a central focus. The need exists to examine operational data in context with total mining operations, and in relation to target projections and historical trends. The use of microcomputers for local information tasks is an established capability. Grouping microcomputers into local-area networks is rapidly becoming established. Interconnecting multiple local-area networks to provide a free flowing stream of information between all operational locations of a mining enterprise is possible with use of some emerging technologies. The benefit of the potential interconnections and rapid transfer of information can readily be seen from a production reporting perspective. Numerous other advantages exist' by providing routing to enable a workgroup to be established between separated work functions.

Jan 1, 1989

By L. W. Stanger, Erich U. Petersen, William J. Tafuri, Donald M. Hausen, Douglas N. Halbe

Gold mineralization at the Mercur Mine was controlled primarily by structure and secondarily by lithology in Mississippian-age sedimentary rocks. Gold was localized where Sevier-age high angle northeast-striking faults are intersected by younger northwest-striking fault zones. The Lulu Graben is a northeast- striking fault zone composed of a south-dipping master fault coupled with subsidiary or antithetic faults. The Twist Fault zone, a sinuous, low-displacement , north-striking zone of fracturing, bisects the graben. Large- tonnage disseminated ore bodies formed east of the Twist Fault zone within silty, thin-bedded, bioclastic carbonates. West of the Twist Fault zone, gold was restricted to rock near peripheral faults surrounding a subvertical collapsed pipe developed within the graben. An overlying thick carbonaceous shale capped the ore zone. Presence of abundant limited- displacement faulting and of hydrothermal jasperoid is associated with cartonate-hosted disseminated gold. Conversely, increased fault displacement and widespread brecciation are associated with reduced dissemination of gold into normally receptive carbonates.

Jan 1, 1990

By A. Mehmet, W. A. M. te Riele

A pilot-plant investigation in a NIMCIX contactor has shown that activated carbon can extract more than 93% of the gold in return-dam solutions. The average gold concentration in the barren solution was less than 0.003 mg/L from a feed averaging 0.048 mg/L. The carbon was eluted by the Zadra procedure. The operating conditions of the elution-electrowinning circuit are reported, and the elution of the gold and other metals is discussed. The reactivation of the carbon by use of the Rintoul kiln is described, together with the results of reactivation. The consumption of reagents in the process cycle is presented in sufficient detail to allow the economic viability of this technique to he evaluated for the recovery of gold from low-grade solutions.

Jan 1, 1990