Search Documents

By R. Hogg

Based on a simplified model for the motion of particulate materials in horizontal, rotating cylinders, approximate expressions have been derived relating the power consumption of a tumbling mill to its dimensions and speed of rotation and to the amount and nature of the charge. The basic assumptions underlying the model are that there is no slip between the charge and the mill shell, that the free surface of the charge remains essentially planar during rotation and that there is no transfer of momentum from the material flowing down the free surface back to the mill shell. The relationships formulated from this model have been shown to be in excellent agreement with experimental results taken from the literature. While the requirements of the model are most closer met at low speeds of rotation, the results appear to be valid even for speeds up to 70-80 percent of the critical speed. Poorer agreement between theory and experiment is found when the charge consists of relatively large particles (balls) and when the filling of the mill exceeds 50 percent of the available volume. Qualitative explanations of these deviations have been offered.

Jan 1, 1971

By E. R. Palowitch

On February 5, 1973, Eastern Associated Coal Corp began shortwall mining in their Federal No. 1 Mine, thus marking the first attempt in the United States at modern shortwall mining, i.e., using a continuous miner to extract coal open-ended from pillars 100 to 200 feet wide, under the protection of a self¬-advancing roof support system (1)1/. Since then, four additional shortwall faces have been operated. While the number of face-years of shortwall experience in the United States is limited, this experience has been anything but uniform. Differences in operator motivation, coalbed parameters, geologic conditions, panel dimensions, and face equipment all have contributed to a wealth of knowledge which can provide guidance for the design of future shortwalls. The purpose of this paper is to review the history of shortwall mining in the United States and to assess its value to the U.S. coal industry in terms of the health and safety of the miner, the percentage of coal recovered, coal production, worker productivity, and relative cost performance.

Jan 1, 1976

By Stanisław Lasocki

We present an algorithm to integrate the uncertainties of mean activity rate and magnitude cumulative distribution function in the interval estimation of the primary seismic hazard parameters: the exceedance probability and the mean return period. The algorithm is applicable for both the parametric and nonparametric modeling of magnitude distribution. When the Gutenberg-Richter relation-based parametric model of magnitude distribution is used, the interval estimation of its parameters is based on the asymptotic normality of the maximum likelihood estimators. When the nonparametric kernel estimation of magnitude distribution is used, we apply the iterated bias-corrected and accelerated method for the interval estimation, based on the smoothed bootstrap and second-order bootstrap samples. Previous studies indicated that the uncertainty of mean activity rate significantly affects the interval estimates of hazard functions only when the activity rate is low and the inference period is not long (Orlecka-Sikora & Lasocki 2017). With increasing mean activity rate, the uncertainty of magnitude distribution dominates over the uncertainty of mean activity rate in the aggregated uncertainty of the hazard functions. The provided algorithm is generic and can be applied to capture the uncertainty of any multiparameter function from the uncertainties of its parameters. Here we present a further development of the algorithm developed by Orlecka-Sikora & Lasocki (2017) by presenting its implementation in the Traffic Light System approach. As an example of use, we present the confidence intervals estimation of hazard parameters for the datasets related to induced seismicity accompanying underground exploitation of copper ore in the Legnica-Głogów Copper District (LGCD) in Poland. The algorithm is under implementation to the EPISODES platform (https://tcs.ah-epos.eu/) - an IT platform that provides access to integrated research infrastructures of the Thematic Core Service of Anthropogenic Hazards (TCS AH) of EPOS (European Plate Observing System). The algorithm is also a component of the pilot developed within the EPOS SP project (No 871121), which aims to strengthen the interaction with the private sector and the added value for society. The pilot demonstrates the potential of the IS-EPOS platform software applications for the technology-related probabilistic assessment of time-dependent seismic hazard. The pilot supports a Traffic Light System approach. The current seismic hazard is compared to threshold values based on the exceedance probability for a given magnitude.

Apr 26, 2022

By L. Yuan, J. H. Rowland III

"In 1995 and 2003, the Mine Safety Health Administration (MSHA) conducted surveys to determine the number of atmospheric monitoring systems (AMS) being used in underground coal mines in the United States. The survey reports showed data for the different AMS manufacturers, the different types of equipment monitored, and the different type of gas sensors and their locations. Since the last survey in 2003, MSHA has changed the regulation requirements for early fire detection along the belt haulage entries. As of December 31, 2009, point-type heat sensors were prohibited for use for an early fire detection system; instead carbon monoxide (CO) sensors are now required. This report will examine the number of AMS currently used in underground mines in the United States to see if there is a change in their use. The locations and parameters monitored by AMS are also discussed. INTRODUCTION The last survey conducted by the Mine Safety and Health Administration (MSHA) on atmospheric monitoring systems (AMS) used in underground coal mines in the United States (US) was in 2003 [1]. The survey report states that since 1995 there had been a steady increase in the use of AMS in underground coal mines as the technology of CO sensors was improved by manufacturers. AMS had become more reliable and some CO sensors could be purchased with the capability to discriminate between the CO produced from a fire versus CO produced from diesel equipment. This increase in reliability had reduced the number of false alarms and the response time. The faster response time to a developing fire allowed for the miners to take the necessary action to put out the fire or exit the mine. It should also be noted that at the time of last MSHA survey, some mines still used point-type heat sensors to detect the presence of a fire on conveyor belts. This detection method works by measuring the temperature of the air around the sensor. As a fire starts to develop, smoke and hot gases are produced from the combustion process, and the air is heated up. Once the air and gases reach a designated temperature detected by the point-type heat sensor, a fire alarm signal is generated. Studies have shown that the response times for detecting the presence of a fire using CO sensors are much shorter than using point-type heat sensors [2]. Finally, since the last MSHA survey, regulations have changed on the type of automatic fire detection systems permitted to be used in conveyor belt entries. As of December 31, 2009, point-type heat sensors are not permitted to be used for fire detection in underground coal mines in the US; instead CO sensors are required as a replacement (30 CFR 75.1103-4). This study will examine how the changing of the above regulations has impacted the use of CO sensors in underground coal mines in the US compared to their use based on the last MSHA survey. Importantly, in the previous MSHA survey, the data was recorded for producing and non-producing coal mines. In this study, only the data from the producing coal mines was recorded. Data was collected from a total of 235 coal mines for this study with the help of the MSHA district offices."

Jan 1, 2017

By Kevin B. Doyle

Virtually all industries use sulphur in some form. About half of the world's production is used in the production of fertilizers. Sulphur is produced in one form or another in over sixty countries in the world. The major producing countries, in order of importance, are: U.S.A., Canada, U.S.S.R., Poland, Japan, France, Mexico, and Spain. Canada is the largest exporter of sulphur presently supplying about 30% of the world elemental sulphur export trade. It has held this position since 1968. World sulphur resources are virtually unlimited. Future world competition will come from Iraq and other Middle East countries as well as Central and South America.

Jan 1, 1978

By B. A. Rose

Coal is being thermally dried in ever increasing tonnages today. Because of fire and explosion hazards, it is important that drying equipment be designed for maximum safety in operation. It is well then that we review dryer design and operation to bring out those features and operating practices which will provide maximum safety to equipment and personnel. This paper presents the author's views regarding the fundamental requirements for safety and explains the Heyl and Patterson approach to the meeting of those requirements in the design and operation of their dryer.

Jan 1, 1962

By Donald G. Rogich

The concept of initiating a large action-oriented contract, directed toward inherently safe mining systems, was conceived by the U. S. Bureau of Mines in January 1970. At that time we were in the process of establishing research contracts and grants, about 100 of which were let in FY 71 to deal individually with fairly specific technological areas. These projects in the aggregate covered a wide spectrum of health and safety problems. What appeared to be necessary was the creation of a project or program that would provide a focal point for the demonstration of many of the results of this research and also in the action sense culminate with working hardware and systems that could be tested and demonstrated over a fairly long teen. The concept of working demonstrable systems, rather than just a conceptual study, was, felt to be necessary for two significant reasons. In the development of any new system, the translation from concept to working hardware is usually a costly and time consuming process which acts as a deterrent to implementation. Secondly, many decisions in the mining community to change equipment or systems ,are based on first hand observation of the new system, in operational practice, an attitude which is certainly understandable in view of the high capital costs of equipment. The decision was made to procure a single R&D contract which would be aimed at developing underground coal mining systems which

Jan 1, 1972

By B. Kraus

Many of us who have interacted with senior executives from leading oil and gas companies over the last few years on the subject of HSE performance have observed a marked shift in their engagement on this aspect of their business performance. There seems to be a shared impression that HSE performance will have markedly increased impact on their businesses going forward. On the back of this very real concern, many are taking material actions to secure a step change in their safety and environmental performance: hiring respected mainstream operational personnel to lead their HSE function; investing in capacity/skills development for HSE professionals to increase their effectiveness in addressing the needs of the business; taking a hard look at the efficacy of established management and audit programs (too much paper, not enough results?); investing in information management systems so they can have access to real time reliable performance indicators; and, critically, initiatives to reduce accident statistics (especially focused on fatalities and contractors? activities) and deliver meaningful reductions in their environmental footprints. Underpinning all of these actions is a clear sense that substantial, very well-intentioned activity and investment in HSE aspects of the business has not been hitting the mark and yielding too little return in terms of performance improvement. The very serious recent events on the US Gulf Coast and at a refinery in the US Pacific Northwest have added fuel to this fire. The need for approaches which will secure a step-change in performance on the front line in the global oil and gas industry has never been greater.

Jan 1, 2011

By J. B. Yianatos

This paper addresses the impact on performance of column height (H), and column height to diameter (H/D) ratio by modelling the effect of HID on mixing and consequently on recovery and grade. Mineral recovery increases with increasing H/D ratio for a constant column volume and feed flowrate, while the concentrate grade decreases to a minor extent. Columns 10-15m in height with H/D-10 are well suited for feed rates 150-600 L/min. Maximum H/D is determined by the gas carrying capacity, an important consideration for pilot units where H/D?200.

Jan 1, 1987

By P K. Kaiser, D A. Malovichko

Highly stressed excavations in hard brittle rock may fail by self-initiated, triggered or dynamically loaded strainbursts (Moss and Kaiser 2021). The low-frequency part of seismic radiation associated with strainbursts is described by a crush-type seismic source mechanism with a significant negative (implosive) isotropic component and a ‘pancake-shape’ CLVD deviatoric component. The seismic source is co-located with the excavation damage site. For such strainbursts, the ejection velocity is primarily related to the depth of strainbursting, the rock mass bulking characteristics, the duration of the bulking process, and the effectiveness of the support system. For dynamically loaded strainbursts, the displacement and energy demand may be augmented by the impact of the stress wave from a distant seismic event. This article describes the failure process and factors contributing to rock deformation and energy demands for support design. Case examples are used to demonstrate the dependence of rock displacements, rock ejection and energy demand on the factors described above. A seismic source model is proposed to assess the depth of strainbursting and the duration of the related bulking process by using seismic monitoring data. The implications for support design are briefly discussed.

Apr 26, 2022

By J. P. H. Steele, T. Vincent, C. Debrunner, M. Whitehorn

For a variety of reasons, the need for automation of underground mining equipment is growing dramatically, e.g., improved safety and health, availability of labor, deeper mines, and desire for more focused excavation. While there has been tremendous progress made in this direction, much needs to be done to reach the holy grail of an autonomous mining machine. This paper reviews a number of technological developments and presents research and development needs for future development. A report on our current project for the Western Mining Resource Center at CSM is included.

Jan 1, 2000

The implementation of NAFTA in January of 1994 was expected to have small but beneficial effects for the Mexican economy, mostly through increased investment flows. Mexico's mining industry was especially likely to benefit, as mineral investment funds would be diverted to the now safer Mexico and away from similarly endowed but more risky Latin American mineral economies. The results of the past two years have shown that it is governments and macroeconomic factors that influence investment flows, rather than the fine-tuning of trade flows through so called "free-trade" agreements.

Jan 1, 1996

By T. Kontos

Rogers Group, Inc., is the nation's largest privately held aggregates producer (primarily producing crushed limestone and secondarily sand & gravel) and a major regional asphalt paving construction contractor. The company also has interests in building supplies and coal. Facilities are concentrated in five states in the central U.S. (Ohio, Indiana, Kentucky, Tennessee, and Alabama), with an additional location in Southwestern Virginia. At the request of its then CEO and with support from the company's ownership, Rogers embarked on a strategic planning program in late 1986 by retaining an outside management consulting firm. The ultimate goal of this program was to develop a self-sustaining strategic planning process to inject a strategic dimension into every manager's business thinking and to improve company performance. Since then, Rogers has internalized the outside consultants' strategic planning framework --initially, using it wholesale, and later, greatly streamlining and tailoring both the planning process and product to meet the specific needs of the company. Implementation of strategies developed from strategic planning has resulted in significant improvements throughout the organization. The latest product of the strategic planning effort is a company-wide (or, "corporate") strategic plan that carries the theme of "Market Leadership through Excellence". This paper provides a case study of successful corporate strategic planning by examining the evolution of strategic planning at Rogers and by summarizing the key elements of a sound planning process and product.

Jan 1, 1994

By R. M. Rowe, T. E. Irwin

A flowsheet was developed for upgrading Climax tin concentrate to about 45 percent Sn. Bench-scale test work conducted at AMAX Extractive Research and Development, Inc., was used to design a multiple-stage tin- processing flowsheet which included screening, high-intensity magnetic separation, and high- tension (electric- static) separation. Formal engineering and plant installation was accomplished in-house by Climax mill personnel. The successful start-up operation of the facility was the joint effort of the AMAX R&D and Climax-mill staffs.

Jan 1, 1986

By A. Mull, J. Weyer, J. Brune

"The “Reiche Zeche” mine in Freiberg, Germany, a 600-year-old lead-zinc-silver mine with extensive open mine workings, experiences severe ventilation losses due to leakage. Much air leaks into abandoned workings, decreasing the airflow available to active working areas. Usually, this leakage occurs in remote areas that lack transportation infrastructure like roadways or rail, making it difficult to haul construction materials to the sites to erect passive ventilation controls such as stoppings, regulators and seals. Transportation distances make it impractical to hand carry traditional construction materials, such as bricks and concrete. Alternative materials, such as brattice, foaming polymers, concrete canvas, and some innovative ventilation control designs have been investigated for this purpose. The suitability of the materials investigated depends on many factors including the pressure it can withstand, the ease of transportation, and workability. Impacts of mine water must be considered, as the Reiche Zeche is below drainage and experiences significant inflow of water. Researchers must consider the effects water inundation as well as how the stopping construction material reacts to being exposed to acidic mine water. INTRODUCTION Problem Statement Mining in the area around Freiberg, Germany began in the 12th century. The mine is used for research, mining engineering education, tourism and air conditioning for a local hospital. The first records of mining in the Reiche Zeche are from around 1384. Due to the strength and competency of the host rock, many of the oldest workings still stand and remain open today, although they may not be accessible. Reiche Zeche also connects to several other, closed mines in the area that are largely unmapped. This allows air to leak into neighboring mines, reducing the air available to ventilate to the working areas of Reiche Zeche. In order to improve ventilation efficiency, it is necessary to control the ventilation and reduce leakage by constructing seals, stoppings and regulators. A challenge with building traditional seals and stoppings in the Reiche Zeche is that the old workings lack transportation pathways or rails. Also, the lack of compressed air, water or electricity makes it difficult to operate power tools and drills. This means that construction materials must be hand carried – some over distances of several kilometers. Figure 1 shows a typical drift in the Reiche Zeche. Researchers investigated using lighter, more easily transportable materials including concrete canvas, expanding polyurethane and polyurea foams, and brattice. The applicability and utility of these materials depends on a variety of factors including the ventilation air pressure, chemical resistance to acidic and mineral-laden mine waters, ease of transport, and ease of construction. Stoppings and seals must be substantially constructed so that they remain tight and do not require maintenance. It is also important to consider the toxicity of the construction materials in case of a mine fire."

Jan 1, 2016

By J. Kretschmann, T. Rudolph, L. Michael, P. Goerke-Mallet

The mining value chain plays an important role in our societal development. Even in a circular economy, mining and raw materials are in great demand, and so are skilled engineers. In Germany, many students decide to pursue STEM studies in the tertiary degree. Nevertheless, the OECD reports low completion rates in obtaining the degree of studies [1]. Generally, the dropout rates in STEM education are high [2]. Many students have difficulties with basic subjects such as science and mathematics, in which they lack knowledge they should have acquired in school [2]. With the German STE(A)M project PepperMINT (https://peppermint.thga.de/), the Technische Hochschule Georg Agricola (THGA) offers a digital and open educational platform, as a dynamic, massive open, online course (MOOC) for students and prospective engineers. The project is funded by the RAG-Stiftung (RAG-Foundation; No. 20-0004). Using adaptable MOOC classes and applied examples from the wide-ranging cycle of mining activities, we motivate students to engage in STEM studies. Our adaptive and application-oriented content demonstrates the diversity of jobs and career paths in the mining industry. The integrations of applied examples and research activities of the Technische Hochschule Georg Agricola can increase the curiosity and motivation of learners. In mathematics, mine-surveiying technologies and geomonitoring methods (see figure 1) can be used to teach trigonometry. Additionally the concept of the free open online classes enables students in high school to get insights into the field of engineering before they decide the subject of their studies. For freshmen who already decided to pursue a STEM degree, the PepperMINT courses can help to identify and close knowledge gaps and to align different levels of knowledge within a heterogeneous student body. Empowering students in STEM education and integrating examples from mining research can help us train the mining engineers of the future.

Mar 2, 2022

By B. G. Stone

"INTRODUCTION “Sampling is the process of taking a small portion of an article such that the consistency of the portion shall be representative of the whole” (Baxter and Parks, 1939) “An orebody is a mixture of minerals in proportions that vary in different parts of the mass. As a consequence the proportion of contained metals also varies from place to place. Therefore, a single sample taken in any particular place would not contain the same proportion of metals as does the orebody as a whole except by a highly improbable coincidence. The probable error, which would be very large if only one sample were taken, decreases with the number of samples, but it never disappears completely unless the samples are so numerous and so large that their aggregate is equal to the orebody itself, in which case the orebody would be completely used up in the process of sampling. Since carrying sampling to such an extreme would defeat its own purpose, some probable error is always present in actual cases and the practical objective is to reduce this probable error to allowable limits. This means balancing the number of samples against the desired accuracy; if there are not enough samples the result is unreliable; if there are too many, the time and expense of taking them is excessive.” (McKinstry, et al., 1948). In an actual orebody, the accuracy of sampling depends not alone on the number of samples but also on proper distribution of them throughout the orebody, for it would obviously be incorrect to take all of the samples either in a rich part or a lean part. Therefore it is important to select the places in such a way that all parts of the orebody will be represented. “For those who cultivate land which is alike arid, heavy , and barren, and in which they sow seeds, do not make so great a harvest as those who cultivate a fertile and mellow soil and sow their grain in that. And since by far the greater number of miners are unskilled rather than skilled in the art, it follows that mining is a profitable occupation to very few men, and a source of loss to many more.” (Georgius Agricola page 5 Book 1 as translated by H.C. Hoover and Lou Henry Hoover, 1950)“It is evident that mining is very profitable to those who give it care and attention”"

Jan 1, 2015

By J. F. Snyder

Minor elements determined by atomic absorption spectroscopy include: zinc, cadmium, copper, cobalt, nickel, chromium, manganese, and iron. Of these elements, only three; zinc, cadmium, and copper are found to have been introduced with the ore-forming fluids. Iron, manganese, chromium, and nickel were increased in dolo-stone lithologies when compared to limestone lithologies. The uniform distribution of cobalt suggests this element was neither increased nor decreased during ore emplacement nor during dolomitization of the rocks. Zinc increases adjacent to ore result from leakages into open spaces rather than as pervasive aureoles surrounding ore bodies.

Jan 1, 1977

By Harry Deitzer

Within the industrial marketplace barium sulfate has an established role as a filler or extender pigment for use in a wide array of applications. The focus of this paper is to outline a number of these applications and in each one characterizes those features of barium sulfate which provide value. Following this is a discussion of the process techniques which have been used to develop value from a selected class of barite ores found in southern Missouri. It is appropriate to define some terms which may help in clarifying some concepts as presented. Use of the term barium sulfate refers broadly to the chemical compound BaSO4 Barite will generally refer to the naturally occurring barium sulfate ores and their properties. Barytes, whether bleached or not, will refer to barite ore made suitable for industrial applications.

Jan 1, 1993

By Y. C. Kim

The strongly skewed grade distributions and the need to estimate the local recoverable reserves in a selective mining environment are the two problems that Ordinary Kriging (OK) cannot easily handle. With the recent introduction of the nonparametric, distribution-free technique of Indicator Kriging (IK), the above problems can be solved. This paper describes the results of performance evaluation of IK in an open-pit gold-silver deposit. For performance evaluation, the predictions of local recoverable reserves using IK were compared with the actual reserves based on blast hole information. The IK estimator, although a bit optimistic, performed very well in predicting the total recoverable ounces of gold from each panel on a test bench. The OK estimator was also used to try to predict local recoverable reserves, by treating each panel as either waste or ore, depending on the panel's average grade. Under this criterion. OK was found to be very biased and pessimistic.

Jan 1, 1986