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By S. Rupprecht

"INTRODUCTION This paper addresses the prevalence of poor public reporting practices of Coal Exploration Results, Coal Resources and Coal Reserves in southern Africa. Currently, the reporting of coal tonnage without supporting coal qualities or “saleable” tonnes and quality is a poor reporting practice that occurs far too often. Not all coal is equal – therefore it is extremely important that investors or potential investors are provided with the full details of both run-of-mine (“ROM”) and Saleable coal tonnage, their associated qualities and other material and relevant information. Competent or Qualified Persons should note that publicly reported information should be sufficient to enable an informed reader to make a reasonable and balanced assessment of the significance of the information provide. “Companies are encouraged to provide information in their Public Reports, which is as comprehensive as possible” (CRIRSCO, 2013): too often this isn’t the case and material matters are either not reported or inadequately disclosed. According to the South African National Standard (SANS) 10320:2014 draft document - “tonnage and coal quality that will be available for sale, either in the raw ROM state (raw Saleable) at a specified moisture content, or after beneficiation of the ROM coal by processing operations to produce materials at specified qualities, size ranges and moisture contents. The assessments must demonstrate that at the time of reporting, the marketing of the products is reasonably justified. The basis of the predicted practical product yield to achieve the Saleable Coal Reserve must be stated. The moisture basis of reporting shall be stated.” As an example to why coal qualities are so important to the public, the requirements of South Africa’s electric public utility (Eskom) power stations are highlighted. The Kendal power station, commissioned in 1988, operates at a Calorific Value (“CV”) range of 19 to 20MJ/kg, an Ash content between 29 and 34% and Volatiles between 20 to 21%. Other power stations, such as Kriel or Hendrina, may require different qualities such as a CV range of 22 to 23MJ/kg, an Ash content between 20 and 28% and Volatiles between 22 to 23%. Thus, in terms of domestic saleable coal, it isn’t just about reporting the coal qualities but also informing the investor as to which power station the coal is intended to be sold as “boilers are designed to burn particular qualities of coal” and “it is not always possible to transfer coal between stations because of different quality requirements at each station” (Chetty, 2010). Sulphur content is also another important quality with the ideal coal content having a quality of less than 1% Sulphur."

Jan 1, 2018

By S. Rupprecht

"This article addresses the prevalence of poor public reporting practices of coal exploration results, coal resources and coal reserves in southern Africa. Currently, the reporting of coal tonnage without supporting coal qualities or saleable tonnes and quality is a poor reporting practice that occurs far too often. Not all coal is equal — therefore it is extremely important that investors or potential investors are provided with the full details of both run-of-mine (ROM) and saleable coal tonnage, their associated qualities and other material and relevant information.Competent or qualified persons should note that publicly reported information should be sufficient to enable an informed reader to make a reasonable and balanced assessment of the significance of the information provided. “Companies are encouraged to provide information in their public reports, which is as comprehensive as possible (CRIRSCO, 2013).” However, too often this isn’t the case, and material matters are either not reported or inadequately disclosed.According to the South African National Standard (SANS) 10320:2014 draft document, “tonnage and coal quality that will be available for sale, either in the raw ROM state (raw saleable) at a specified moisture content, or after beneficiation of the ROM coal by processing operations to produce materials at specified qualities, size ranges and moisture contents. The assessments must demonstrate that at the time of reporting, the marketing of the products is reasonably justified. The basis of the predicted practical product yield to achieve the saleable coal reserve must be stated. The moisture basis of reporting shall be stated.” An example as to why coal qualities are so important to the public, the requirements of South Africa’s electric public utility (Eskom) power stations are detailed in the followint paragraphs. The Kendal power station, commissioned in 1988, operates at a calorific value (CV) range of 19 to 20 MJ/ kg, an ash content between 29 and 34 percent and volatiles between 20 to 21 percent. Other power stations, such as Kriel or Hendrina, may require different qualities, such as a CV range of 22 to 23 MJ/kg, an ash content between 20 and 28 percent and volatiles between 22 to 23 percent. Thus, in terms of domestic saleable coal, it is not just about reporting the coal qualities but also informing the investor as to which power station the coal is intended to be sold as “boilers are designed to burn particular qualities of coal” and “it is not always possible to transfer coal between stations because of different quality requirements at each station (Chetty, 2010).” Sulfur content is another important quality with the ideal coal content having a quality of less than 1 percent sulfur."

Jul 1, 2019

By D. C. Fuller

CoaLiquid, Inc. (CLI) has been in the coal- oil-mixture (COM) business for over five (5) years. The initial pilot processing facility was replaced by a 2000 barrel per day commercial production facility in August of 1979. For over two (2) years CLI has been expanding its efforts and conducting large scale production and combustion demonstrations successfully in many locations across the United States. To facilitate the marketing effort, CLI has recently constructed a special trailer containing all equipment needed for a temporary COM retrofit. CoaLiquid has conducted commercial scale combustion demonstrations in the following types of combustion units: kilns, calciners, industrial boilers, blast furnaces and driers.

Jan 1, 1982

By D. Erik Spiller

A commercialized dry gravity concentrator is operating on an alluvial gold deposit in the Boludo Mining District, State of Sonora, Mexico. The technology base of the process is the Rotary Air Concentrator (a dry circular air jig) that recovers gold from the desert sand resource. An overview of the Mexican operation and the dry concentration technology is presented. Application of the dry technology to pretreat­ment of heap leach feeds and other heavy minerals is a pos­sibility.

Jan 1, 2000

By Sii Smith-Gruner

Blasthole drilling by todays standards is not a mature operation. In most mining appli¬cations, the blasthole drill rig is the least understood piece of machinery. Draglines, mining shovels, and haulage trucks may have more charisma, but the entire mining process starts with the drilling of blastholes to facilitate removal of the overburden and/or the primary material being mined. There are two (2) principal drilling methods them being rotary and percussion. In certain situations, percussion drilling is the most practical method, but for most applications, rotary drilling using the rotary tricone bit is the common and accepted drilling technique. While the drilling rig is on the surface and quite visible to everyone, it is really the object at the end of the drill pipe, the tricone bit, that is doing the work and drilling the hole. The rig supplies power to the bit and air to clean the hole. In addition, it must be capable of providing certain other functions and should be properly outfitted to adequately support the rotary tricone bit.

Jan 1, 1988

By Kenneth G. Knight, Frank L. Lynch

It's 12:30 A.M. The day before had been a long one with problems ranging from proper application of shotcrete during cold weather and the follow-on precautions for curing, meetings with city officials to avert a job shutdown because traffic wasn't being maintained properly and finally a briefing before METRO's General Manager to bring him up to date on projections for meeting the operational date of June 1975. The phone rings and Officer Jones of the Park Police says "Mr. Lynch, this lady in the apartments overlooking the jobsite is complaining of noise and she wants the job shutdown". "Officer Jones, have you called the Project Manager or the Resident Engineer?" "Yes, sir, but there is no answer!" "O.K., Officer, I'll check it out." In calling the job, I can only get the guard, because the inspector is in the tunnel. After some time, the guard calls back and says he doesn't know the way down into the tunnel. I have since had a difficult time believing that one. In the interim I finally reached the Resident Engineer and explained the situation. And finally at 1:30 A.M. the inspector called the Resident to say that the Park Police stopped the job at 1:00 A.M. because we didn't respond promptly. A similar situation had occurred some 2 years previously. With great expectation, noise specifications were developed to correct the earlier situation that had occurred. These newly developed specifications were in force at the time of this most recent shutdown. Common sense would tell you that even though we had developed and implemented, we believe, some of the best and most practical noise specifications in construction practice today, we had not enforced them. What caused the shutdown - a noisy

Jan 1, 1974

By Robert E. Murray

The title of my paper, "A Company's Response to Federal Coal Leasing," brings to mind a picture of a dog chasing its tail. This is what the coal industry, has been doing since the Federal coal leasing moratorium went into effect in 1971. We've gone around in many circles, but we are only very slowly, if at all, getting closer to catching our tails, i.e., efficient, economical, and rational Federal coal leasing. My companies, The North American Coal Corporation and its four Subsidiaries, The Falkirk and Western Plains Mining Companies and The Coteau and Missouri Valley Properties Companies, together hold in excess of 4.5 billion tons of lignite reserves in North Dakota. Some of our North Dakota properties are substantially interspersed with Federal coal, with the government holding title to the minerals in every other section. This checkerboard pattern of Federal ownership has made it difficult to develop and market some of our reserves, and, as a result, it has become imperative that we be familiar with and active in the Federal Coal Leasing Program.

Jan 1, 1982

By H. EI-shall

In this paper, the results of bench scale testing of five different flotation processes to separate dolomite from phosphate are discussed. The effectiveness of each process interms of phosphate recovery and MgO content in the concentrate is used together with the reagent consumption as the basis of comparison. The water quality is found to play a major role in the performance of these processes. Effect of water hardness as well as other parameters are discussed.

Jan 1, 1995

By G. B. Misra

Heat transfer in partially wet mine airways has been the subject of study for quite some time. Of the available models some are quite empirical while some involve highly complicated computation. Models developed by Amano, Mizuta and Hiramatsu and Banerjee and Chernyak as well as that modified by Misra were evaluated for prediction of the rise in temperature and humidity (mixing ratio ) of partially wet mine airways at four different levels in the Mosaboni Mine of Hindustan Copper Ltd. Measurements of barometric pressure, virgin-rock temperature and changes in dry- and wet-bulb temperatures along a certain length of airway were made. The rise in dry-bulb temperature and mixing ratio of air over the sections were calculated using the three models. The study reveals that calculated values of temperature and moisture content agree within possible rage of experimental error with all the three models in case of three levels with low wetness factor, but the agreement was poor for the relatively more wet airway on the 30th level. Errors in the estimation of fw to the tune of 0.025 can lead to fair error up to 0.94 K in the estimated temperature while alternative ways of estimating the heat transfer coefficient [] can introduce errors up to 1.45 K.

Jan 1, 1987

By Elham Najafi, Sina Ghassa, Ata Akcil, Hadi Abdollahi, Sandeep Panda, Zohreh Boroumand

Bioleaching is an environmental friendly process that has gained much interest for the production of metals from metal-bearing wastes or materials. The process decreases carbon footprint by reducing consumption of fossil fuels. Iron is a key factor in acidophilic iron-oxidizing bacteria’s activity, which is used extensively in the bioleaching of sulfide minerals. In the present study, the effect of different iron sources is investigated on sphalerite (ZnS) bioleaching. For this purpose, the effects of FeSO4  .7H2O, Fe2(SO4  )3 and FeS2 (pyrite) were studied on bacterial activity, and zinc (Zn), lead (Pb), cadmium (Cd) and arsenic (As) dissolutions were monitored from a ZnS concentrate. Under optimum conditions, the dissolutions of Zn, Pb, Cd and As were found to be 39.8, 0.1. 0.03 and 10 percent, respectively, in 25 days.

By Elham Najafi, Sina Ghassa, Ata Akcil, Hadi Abdollahi, Sandeep Panda, Zohreh Boroumand

The present study investigates the influence of ferrous iron (as FeSO4) and ferric iron (as Fe2 (SO4)3), and pyrite (FeS2) on the ability of bacterial leaching of a high-grade sulfide Zn–Pb ore. In this regard, shake flask experiments were carried out at 5% (w/v) pulp density of the ore sample (having 40.7% Zn and 12.4% Pb initial metal content) using a consortium of mesophilic iron and sulfur-oxidizing acidophiles. A concentration of 0.04 mol/L of ferric iron in the leaching media was found to be optimum for zinc extraction without affecting growth of the microorganisms. Under this concentration, the dissolution of Zn, Pb, Cd, and As was found to be 57%, 0.2%, 0.03%, and 9.9% in 25 days. Using ferrous iron in the media, 0.16 mol/L of Fe2+ was found to be the optimum concentration for efficient bacterial growth and metal dissolution (54.6% Zn, 0.08% Pb, 0.03% Cd, and 10.2% As) from the sample in 25 days. On the other hand, using pyrite as the source of energy for bacterial growth, an initial 12-day lag period was observed when compared to the effect of ferrous iron in the media. Under the optimum concentration (test with 0.24 mol/L iron in the form of pyrite), the dissolution of Zn, Pb, Cd, and As was found to be 39.8%, 0.1%, 0.03%, and 10% in 25 days. The surface chemistry analysis indicated formation of a sulfur layer over the particle surface that hindered reagent diffusion and affected metal recovery through bioleaching.

By Robert M. Cox

The principal factor that must be determined for the effective design of a coal mine roof bolt support system is the maximum stable tension that can be developed with a given bolt assembly in a particular roof rock. There are four basic types of roof bolt anchorage techniques available: (I) the splitwedge; (2) mechanical expansion units; (3) resin point anchors or grouted expansion units; and (4) the cone shell which is placed in a reamed hole. A study of this problem has been made which includes theoretical analyses, laboratory experiments and field tests. A static free-body analysis of each of the anchorage techniques has provided formulas for predicting the anchorage capacity for a particular rock from the results of standard pull tests. The formulas also provide an insight into the anchorage mechanism of technique and allow for a comparative evaluation of the methods for design purposes. The theoretical analyses also indicate clearly the pertinent variables affecting the anchorage mechanism of each method.

Jan 1, 1977

By Richard C. Corson

The objective of blending materials in a bedding pile is to reduce the variation in successive samples taken from the materials to be blended. In designing a bedding and reclaiming operation, several mechanisms are available to effect the reduction of variability, or increase in homogeneity, of the materials. These mechanisms can act before stacking, in the stacking process, in reclaiming and after reclaiming. In evaluating alternative methods of stacking and reclaiming, the potential user must judge each method on the basis of certain criteria; the capital cost of the equipment, the allowable absolute variability of the reclaimed product and the effectiveness of blending. Several stacking and reclaiming methods have been tested using a computer simulation. Based on the results of this program, factors were developed to describe the effectiveness of blending for chevron stacking of discrete materials and preblended materials, bucket wheel reclaiming and drum reclaiming. From these factors, the total effectiveness of a combined stacking and reclaiming system can be determined.

Jan 1, 1985

By Gordon C. Gutrath

Queenstake Resources Ltd. has been exploring and mining alluvial gold deposits in the Yukon Territory and British Columbia since 1980. The five mines in production produced, in 1987, a total of 13,222 ounces. This paper will briefly review Queenstake's exploration program, property descriptions and mining methods, environmental concerns and a comparison of costs. (Sueenstake has been successful in developing a cash flow base from these operations that provide the capital for the acquisition and exploration of new, and hopefully, larger scale gold producers. NOTE: The historic alluvial mining unit of ounces per cubic yard and English units of measurement have been used throughout this paper. Dollars are Canadian unless otherwise noted.

Jan 1, 1988

By J. R. Hoskins

Method - A direct approach to instrument users, initially by letter and later by telephone or personal contact was made. The resultant data was compiled to give specific use information on the seven instruments. During the course of the study attempts to evaluate the Griswold Gage were abandoned when it became apparent that the gage was not being commercially produced. One company is developing the gage for its own use. The information presented is the result of over 1200 inquiries.

Jan 1, 1973

By Rajendra K. Devala, Sukumar Bandopadhyay

In order to be able to design an adequate mine ventilation system it is necessary to understand how pollutant masses disperse into turbulent ventilation air streams. The mixing of gases and dusts with ventilating air, and dispersion of these pollutants in mine airways, are important flow or transfer problems. For the solution of such problems, the finite difference technique is often used. In this paper, numerical approximation schemes for the solution of the mass transfer problem have been developed using several explicit finite difference schemes. Results from these schemes have been compared with the analytical solution for spatial and time increments using the concept of Root Mean Square error. The comparison of various schemes reveals that the explicit finite difference schemes analyzed here give more accurate results at lower velocities, though the results are dependent on the spatial and time steps considered. At higher velocities the schemes tends to oscillate about the analytical solution. INTRODUCTION In mining, most of the mine air pollutants, such as respirable dust, methane, blasting fumes and diesel exhaust, are produced at the mine face and in haulageways. Injection of any of these pollutants in the mine ventilating air causes disturbances of the equilibrium state of the pollutant concentration of the ventilating air. The mixing of these gases and dusts with the ventilating air are typical examples of mass transfer processes. Pollutants are diluted by the stream of ventilating air flow along airways and discharged into the outside atmosphere of the mine through a return shaft. The dispersions of these pollutants in mine airways are important flow or transfer problems. Knowledge about pollutant sources, emission and transport of these pollutants are essential for ventilation planning and design to ensure good engineering control over air quality, quantity, and environmental conditions. Modeling of mass transfer phenomena in mine ventilation is largely based on extensive studies of turbulent dispersion in wind tunnels and the lower atmosphere of the earth. The general approach in the formulation of models lies in the recognition that these mass transfer phenomena can be conceptualized as a flow problem that can be solved by the general application of Taylor's theory (1954) of turbulent flow and diffusion with modification appropriate static and dynamic parameters. If the face zone is initially contaminated by a pollutant over a long section (e.g. instantaneous exposure of large gas accumulation, rapid methane release etc.), the process of decontaminating the mine workings can be regarded as displacement and diffusion of the tailing edge of the cloud of contaminates in the form of a semi-infinite gas body, for which a one-dimensional mass transfer equation is represented by: [at + u • ax = Ex ex2 + f (x,t)(1.1)] In Eq. (1.1), the term [~~] is the rate of growth of the concentration in the differential element, while a [(5xx )] is the net gain of material due to convective transfer. The two terms balance the total loss of material due to turbulent dispersion that is represented by [Ex . 21] and f(x,t), the source term for the pollutant in the roadway. Several cases of mass transfer that occur in mining can be identified and modelled using the conservative volume element method. The governing equation, along with the associated boundary and initial conditions, source terms and their solutions are detailed elsewhere (Bandopadhyay and Ramani, 1988, Devala, 1989). Only one mass transfer situation is presented (Figure 1) here for the present analysis. Mixed Evolution of Pollutant (multiple pulses) Typical examples of these situations are emission of pollutants from multiple diesel vehicles in the face area, and gas emission from standing pillars as well as from broken coal seam during coal cutting with a continuous miner. The mathematical statement of the problem along with the initial and boundary conditions are given below, Governing Equation: [do+u- =E d2c(1.2) ataxx dx2] Initial conditions:

Jan 1, 1993

By Alan Rhodes

This study is initiated to investigate the efficiency of separation of mineral slimes using electroflotation as compared to that of column and conventional flotation techniques. Important parameters such as collector concentration, pH, current density, aeration rate, etc., have been studied. The results indicate that electroflotation can be used more efficiently in processing rutile slimes (10 µ) under certain operating conditions.

Jan 1, 1982

By Milka Madahana, John Ekoru

For efficient management of operations, mining companies are required to be able to predict potential scenarios for main market factors. Competitive advantage and value creation are established through managing the value chain well. The mining value chain is usually faced with challenges from various shifts in commodity markets as well as ongoing uncertainties. Therefore, there is a need for accurate analysis of data from the markets, for the prediction of commodities, for instance, Precious Group Metals (PGM). The main objective of this research work is to apply machine learning methodologies with the aim to identify patterns and trends in the Precious Group Metals, and thereafter analyze and predict the future trends of these markets. Numerous machine learning models are applied to a dataset consisting of 15 years of daily price for eight precious metals namely Platinum, Palladium, Rhodium, Ruthenium, Osmium, Indium, Silver, and Gold. The results reveal the patterns and trends within the data sets and that different machine learning methods could be suited for the prediction of market prices for each of the PGMs. The application of an amalgamation of various machine learning methods may result in more accurate predictions of the PGM markets. Accurate prediction of market prices for PGMs will possibly result in unlocking untapped sources of value in the mining industry.

Jun 25, 2023

By Harvey P. Knudsen

This paper describes the results of a comparative study of the geostatistical ore reserve estimation method over three conventional methods; the polygon method, the inverse of the distance squared (IDS) method, and ELIP which is similar to IDS. Each method was evaluated on its ability to accurately predict individual block grades for one bench of the Pima Nine, located near Tucson, Arizona. Results at the Pima Mine indicate that the geostatistical method is no better nor worse in predicting block grades and total tonnage than the ELIP or IDS methods in contrast, the polygon method is clearly inferior. All of the methods would have given better results if geology had been included in the block model. At already producing mines ELlP or IDS may be good choices since they involve substantially less cost in computer time. For prospective or new properties, the geostatistical model is more attractive, due to its ability to construct confidence limits on the estimates.

Jan 1, 1976

By R. K. Devala

In this paper, numerical approximation schemes, for solution of the mass transfer problem in mine ventilation have been developed by using three implicit finite difference schemes. Results from these schemes have been compared with the analytical solution for spatial and time increments, using the concept of Root Mean Square error. For implicit finite difference schemes, in general, the modified central difference scheme is better than the two other schemes at lower velocity. Also, at lower air velocities, implicit schemes underpredicted the concentration values. At higher air velocities, the Crank-Nicholson and Laasonen schemes provided better results than the Modified Central Difference scheme.

Jan 1, 1994