Search Documents

By Ben L. Seegmiller

How to obtain optimum slope angles for future open pit mines using the rock mechanics approach is the subject of this paper. In the past ten years significant developments in open pit rock mechanics have come about. This has been due to the mining industry's need for the steepest, yet safe, pit slope angles attainable. Requirements for economically achieving slope stability and the actual payoff that may be achieved through stability studies have been previously discussed', by stability engineers. While the emphasis has generally been placed on the concept of "stable slopes" in the past, it is suggested that emphasis now be placed on "optimum slopes" or "optimum slope angles". A definition of an optimum slope angle is one which (1) is as steep as possible and practical from orebody and mining constraint standpoints and yet, (2) maintains the accepted standard of safety defined by a safety factor against failure and/or a probability of failure. In other words, the emphasis is placed on achieving practical stability results as defined by safety and economic considerations, as opposed to simply achieving stability. The essential purposes of this paper are to (1) outline the need for optimum slope angles, (2) discuss the procedures for using the rock mechanics approach in slope angle design for a future open pit and (3) specify the end results that may be achieved by using such an approach. While the basic concepts and recommendations outlined in this paper may be equally applicable to soil as well as rock slopes, the emphasis and procedures have been directed at rock slope angle design.

Jan 1, 1976

By Juan L. Sepulveda

An MPSI KW-20 Tower mill has been tested at the Butte Molybdenum plant of Anaconda Minerals Company, as a substitute for the conventional 1.5x3.0 m (5x10 ft) tumbling ball mill currently used for regrind purposes. The Tower mill was operated in both open and closed continuous circuits. These results were complemented with a series of batch grinding tests to determine some of the operational features of this mill. The relative grinding efficiency of the Tower mill with respect to the tumbling ball mill was determined and the applicability of this new mill to a plant/heavy duty environment was assessed. Experimental results obtained on the regrind of moly concentrates indicate that approximately 40% energy savings can be realized by using the Tower mill instead of the ball mill.

Jan 1, 1984

By B. E. Davis

A problem that has continued to plague the Florida phosphate industry is the loss of coarse phosphate in the flotation circuit. Attempts to remedy this problem such as floating the coarse material (plus 425 µ m) in a separate circuit have resulted in limited success, but recovery is still not optimum. The Bureau of Mines is investigating ways to improve the recovery of coarse phosphate through improvements in the conditioning step. Studies to optimize conditioning parameters such as agitation energy, conditioning time, conditioner solids, and residual clay content have resulted in improved P2O5 recovery. Optimizing these and other conditioning parameters resulted in a rougher concentrate grading 30 pct P2O5 with a P2O5 recovery of 97 pct.

Jan 1, 1993

By Todd Loudin

A majority of the chemical process industry uses lime in either a powder or liquid form. Engineering and maintenance personnel often face a long and potentially expensive trial-and-error period in order to find the best process equipment to handle lime. Limestone is mined from a quarry in the form of calcium carbonate (CaCO3). Then, it is crushed and fed into a kiln at approximately 1,093° C (2,000° F), where the carbon dioxide is burned off (calcining) to make calcium oxide (CaO).

Jan 1, 2010

By A. Frank Alsobrook

DOUG HALBE: Thanks, Terry. And in spite of your introductory comments, I'm going to attempt to continue our hallowed tradition of saying nice things about the speakers. This is really a serious comment now. We, as mineral processing and mill people, don't often talk to people outside our general operating area. One thing that we've tried to do in this operators' symposium is get speakers from various types of plant operations to help illustrate all the things we have in common. Our next speaker is from the industrial minerals area. I think there's a lot to be learned from industrial minerals operations. Some of the people in the last session learned some things about fine grinding in industrial mineral operations. I was a little surprised to see people there grind to 2 microns. Our next speaker is Frank Alsobrook. Frank is another nonmetallurgical engineer. He has a degree in geology, a master's of science from the University of Wisconsin. He's had his own very successful consulting company for a number of years. This is your 11th anniversary, Frank? Very good. He's also the immediate past chair of the industrial minerals division. I think the folks at the speakers' table should be ashamed. You have been so rowdy that Frank chose to sit in the audience. [laughter] We'd like you to come up now, Frank, and tell us some things that you've seen that might be useful to us. INTRODUCTION FRANK ALSOBROOK: The three topics addressed briefly are (1) teamwork and operations modeling, (2) the pitfalls of capital conservatism, and (3) the potential for by-product recovery. Ideas for improvements in these areas are not unique to industrial minerals but apply to metal mining and processing operations, as well. Several additional topics are suggested at the end of the paper.

Jan 1, 1998

By Magnus Ericsson

The unexpectedly quick recovery in world crude steel production in the second half of 2009 was due almost entirely to increased production in China that began in late 2008. Previous peaks in monthly production in China were matched by April 2009. The rest of the world had still not reached pre-crisis production rates by May 2010. Chinese production drives growth, but there has been some growth in most other larger crude steel producing countries as well, compared to production in 2009. If the production rate of the first four months of 2010 continues, the total output of crude steel in 2010 will be somewhere around 1,410 Mt (1.5 billion st), the same as in the record year of 2007.

Jan 1, 2010

By Ralph C. Kirby

The U.S. produces about 34 percent of the world's aluminum yet must import 90 percent of the raw materials needed. There are abundant resources of aluminum-bearing minerals such as clay, anorthosite, alunite, shale, and dawsonite, but none of the numerous processes proposed for recovering alumina from them has yet proved economically competitive with the Bayer process using imported bauxite. To help develop an economically viable process for utilizing these resources, the Bureau of Mines is testing on a common basis several proudsing processing techniques. New improvements and approaches developed by industry and the Government are being evaluated on a mall scale to obtain enough information on which to form a judgment regarding the best processes for commercial adoption. A continuous miniplant having a feed rate of about 70 pounds per hour is being operated now to investigate the nitric acid process for recovering alumina from clay. Parts of this plant will be used subsequently for work on other processes for recovering alumina from clay, anorthosite, alunite, and dawsonite. Initial results of the operation and plans for the overall project will be discussed.

Jan 1, 1974

By M. Xing, S. Usman, K. Awuah-Offei

"While mines generally focus on achieving operational efficiency, creating shared value for all stakeholders is also a management goal. This includes taking a holistic view of their supply chains and increasing local participation. This paper examines the role of supply chain management in mine management; in particular the effect of a strong local supply chain on regional economic impacts. Using input-output analysis, the impact of a local supply chain on a mining sector’s regional economic impact is examined by increasing local sourcing (increasing local purchase percentage -- LPP) for 10 key commodities. An approach, based on multipliers and excess local capacity is used to identify key commodities. The impacts examined are sales, employment, labor income, and value added. The work is illustrated with stone mining and quarrying in Missouri. Ten percent increases in LPP of the key commodities, in this example, result in $4.1 million additional impact on the Missouri economy. This work can provide insight on how to better create shared value for all stakeholders. INTRODUCTION Little research has been published on improving mine supply chain management (SCM) to enhance regional economic impacts. Although some extensive academic research has explored the importance of an industries’ supply chain, not much is known about how a locally-based supply chain increases shared value in the resource sector. Across industries, traditional SCM is getting more and more complex. This is true of the mining sector as well. However, this increased sophistication is not directed towards increasing shared value for all stakeholders, particularly, the local communities. Further research is required to develop new SCM strategies that enhance local participation. One major point of difference between this work and traditional supply chain management is the inclusion of stakeholders’ shared value as a goal in SCM. Creating shared value has become a business goal in recent years (Porter and Kramer, 2011). The authors use input-output analysis (Leeuw, 2012) to evaluate the regional economic impacts of supply chain decisions, which is not part of traditional SCM. Although input-output analysis has been applied to SCM for decades, most of the research uses input-output analysis as a tool to advance an industries’ own operational efficiency (Accenture, 2014)."

Jan 1, 2015

By S. Komar Kawatra, J. J. Carlson

"It is widely known that steel made from iron ore pellets high in phosphorus is brittle. Removal of phosphorus from iron ores such as hematite has proven to be difficult. The majority of research on phosphorus removal from hematite ores has been focused on flotation. The purpose of this study was to assess phosphorus distribution under current operations at an existing hematite concentrator and determine how efficient the plant is at removing phosphorus. Objectives included: (1) Perform a phosphorus balance at an operating plant to assess phosphorus distribution under current operations; (2) Determine phosphorus removal efficiency of each separating unit and (3) Perform a quantitative liberation analysis to determine max phosphorus removal by physical means. Liberation was quantitatively determined using wet high intensity magnetic separation (WHIMS) to separate iron ore from liberated apatite (and other nonmagnetic compounds).It was observed that 61.2% of the total phosphorus entering Plant F was rejected during current operations. The desliming process was the most efficient step at removing phosphorus (45.1% P removed), whereas the flotation step was much less effective (16.1% P removed). Liberation analyses indicated that the deslime thickener may have been more efficient at removing phosphorus than the flotation circuit due to the greater abundance of liberated phosphorus in the deslime thickener feed. The scavenger returns stream was identified as having a high concentration of phosphorus and a possible point of phosphorus removal. However, liberation analyses indicated that only 32.4% of the total phosphorus in the stream was liberated. Grinding the scavenger returns to 80% passing 5.2 µm increased the amount of liberated phosphorus in the stream to 70.4%."

Jan 1, 2014

By R. H. King

Recently, the North American mining industry experienced a severe recession, forcing managers to take dramatic steps to cut costs and compete in the difficult international market. Some of these steps were closing mines, reducing work forces, renegotiating wage agreements, and purchasing the most productive equipment. Managers are now looking beyond these traditional avenues and are focusing more on advanced technology. In the present environment, it is essential that mine operators obtain the maximum use of capital expended on equipment. However, mine workers do not obtain maximum efficiency or productivity from equipment because the adverse and hazardous mine environment impedes human performance. Also, the efficient use of large, complex machines calls for levels of precision that many times are beyond the capability of even highly trained miners. A possible solution to this problem is a machine that mines without operators - autonomous mining machines. However, numerous problems confront researchers who are attempting to develop such equipment. Some mining tasks are not always composed of a series of cyclic motions readily performed by factory floor robots. In addition, mining takes place in the geological environment where conditions are highly variable and unpredictable. As a result, these machines must be able to sense and adapt to variations in operating tasks and environment. Considerable autonomous vehicle research has been completed, especially for defense. However, autonomous vehicle (AV) technology has not advanced to practical application yet (King, 1988) and mining research is necessary in areas: representing mining specific knowledge; •analyzing and reasoning about sensor data in the mining environment; and •discovering completely new mining methods or new approaches to existing methods that become apparent when we remove the constraints imposed by the necessity of human operators. A specific machine, the LHD, can be used to show the problems for researchers who are attempting to develop autonomous machines for mining. This author chose the LHD because it can borrow concepts developed for autonomous navigation by military programs. But considerable mining research is also required. Furthermore, studies done at the Henderson mine, in Colorado, show autonomous LHD 's promise cost and safety benefits (King, 1988). At Henderson, LHDs load ore from draw points, tram to an ore pass, dump and return, or switch to another draw point. An autonomous LHD must sense vehicle position along the route, relate sensor data to stored-map information, to determine location, follow drift center lines, plan paths between dump position and initiate appropriate control commands, sense vehicle operating status and vehicle health, key on features or targets for special tasks like high speed turns, perform end of travel tasks (loading and dumping), and detect and avoid obstacles. These goals are similar to those for shuttle cars, trucks, and front-end loaders. Therefore, much of the technology is transferable. Each Henderson LHD extracts six to 40 dippers from each of a series of draw points. The LHD transports the ore to an ore pass within 55 m (180 ft) of the draw point, making the longest round trip 110 m (360 ft). The LHDs have very fast hydraulic dumping and loading systems that reduce the round trip cycle to less than one minute. Even though the LHD is capable of 500 trips per shift, the average production is 300 dippers. Man trip and lunch reduce available operating time to 6.5 hours per shift. Mucking difficulties (setting large boulders aside), operator breaks for activities like talking shop, and cleaning and smoothing roads further reduce operating time. Supervised autonomy can reduce the number of operating units by increasing operating time per shift since computer controlled machines can operate during lunch and between shifts and reduce operator errors. If dippers per shift increase from 300 to 350 (long-range goals are 500 dippers per shift), constant production requires only 10 operating LHDs and two spares. Manpower requirements drop from 24 to four by controlling five machines from one workstation. A review of technology available from the Autonomous Land Vehicle, the Advanced Ground Vehicle Technology, the Ground Surveillance Robot, and other programs, show the following differences between others work and mining industry needs: •If we focus initially on mobile haulage vehicles, we can navigate from a map. We do not need to explore. •We can modify the environment to reduce the navigation requirements. •We have a harsher environment than any of the research programs have encountered. •Our equipment must operate faster and more precisely than present AVs. •Our equipment must operate reliably over long periods of time. •We must have better onboard machine health monitoring and diagnostics. •The AV programs do not address geosensing. •The major AV programs are not cost-effective. For example, we cannot afford the computer power for robust image processing, yet. To computer control an LHD, we must replace the guidance and monitoring skills of experienced operators with sensors, computing hardware, interfaces, and several software mod¬ules. Experienced operators avoid collisions and load efficiently in piles that may contain oversize muck. Collision avoidance without an operator requires sensing all obstacles in the draw

Jan 1, 1991

By N. Teasdale

The Bousquet #2 deposit, located within the Blake River Group in the Abitibi Greenstone belt, midway between the towns of Val d'Or and Rouyn-Noranda, exhibits all of the distinguishing characteristics of volcanogenic massive sulfide (VMS) deposits. As such, the deposit can be compared with other gold-rich VMS deposits such as the world-class Home deposit in Rouyn-Noranda, Quebec, Canada and the Mount Morgan deposit near Rockhampton, Queensland, Australia.

Jan 1, 1995

By P. R. Taylor

Three refractory gold concentrates have been tested to evaluate the effect of roasting with hydrated lime followed by cyanidation. The results indicate that it may be possible to roast in such a manner as to contain nearly all of the sulfur, arsenic and antimony in the roaster calcine. Cyanidation results indicate that the gold recoveries are greater than 80% for all three concentrates.

Jan 1, 1993

By I. Duckworth

P.T. Freeport Indonesia operates a mining complex located in the highlands of Papua, Indonesia. This district consists of both underground and surface operations. The East Ertsberg Skarn System (EESS) is one of the major orebodies in this district. Subsurface caving of the EESS has been carried out in a systematic series of mining lifts dating back almost 30 years. Present production is from the third lift (Deep Ore Zone), which is scheduled to peak at 80,000 mtpd during 2009, with this rate sustained through 2015. The orebody is proven below the existing caving level, with the next vertical block called the Deep Mill Level Zone (DMLZ). This paper presents an overview of the DMLZ Mine based on recent feasibility level study. The mine is being designed for a peak production rate of 29.2 million mtpy, with 1,803 total ore draw points spread over a panel caving footprint of about 1.3km by 375m. The present reserves for this mine total 501 million tonnes. Located 1,400-1,800m below the original surface, the DMLZ will be one of the deepest caving operations in the world. Production is scheduled to commence in 2015. Discussion is provided on most design aspects including; caving methodology and layouts, geotechnical predictions and risks, ore handling systems, ventilation design and associated infrastructure, high-lift pumping system, cost estimation and expenditure scheduling.

Jan 1, 2010

By P. Jonsén

Understanding mill charge motion is important. In the charge, the centre of gravity is shifted from the rotational centre of the mill system, and its motion is induced by rotation of the mill, while at the same time the charge creates a torque into the mill system. Breakage of ore particles and wear of liners/ball media are closely linked to the motion. To study these phenomena in a physically correct manner, numerical models for different parts of the mill system are needed. Validations of such models are scarce, because of the difficulty to measure in a tumbling mill. Experimental measurements in a lab mill were done for diverse load cases: varying feed materials, mill fillings, mill speeds and pulp liquids. The mill is set up to directly measure the charge-induced torque. The accuracy is good with relative uncertainty smaller than ±2% for relevant load cases. A full three dimensional numerical model of the whole mill is used to predict induced torque. Agreement between predicted and measured torque at steady-state is good. In addition, the model can accurately predict the mill start-up behavior for torque and mill power. This proves that the model is physically correct, and can be used for full-scale mills.

Feb 27, 2013

By R. Sellaro

It has long been understood that extended occupational exposures to respirable mine dusts can lead to chronic lung disease. In underground coal mines, CWP and silicosis are major concerns. While there have been many studies aimed at understanding total dust concentrations and silica content associated with different mining conditions (e.g., locations/occupations within a mine, cutting methods, geologic strata), little research has been completed to more comprehensively characterize respirable dust (i.e., by particle composition, size distributions, shapes). This preliminary study sought to characterize dust from an underground coal mine in Central Appalachia using scanning electron microscopy with energy dispersive x-ray (SEM-EDX). Respirable dust samples were collected from various locations in the study mine, and individual dust particles were identified and classified by mineral type. A continuous personal dust monitor was also used to estimate total respirable dust concentrations during sampling. Here we report initial results of this work, and discuss advantages and challenges of particle-level characterization of mine dusts in terms of occupational health research.

Feb 23, 2014

By Dipl. -Ing. Mertens

Gentlemen: I am pleased and regard it as a priviledge to give you a report on rapid roadheading with heading machines in the coal mining industry of Western Germany. Importance of Heading Operations in the West German Coal Mining Industry Every year about 770 km of headings are driven In the seams of the West German coal mines, most of them gate roads, the rest rise headings, to open new faces. In thick seams the heading operations are carried out entirely in the coal, in thin seams the country rock has to be ripped. The total length of 770 km corresponds to a rock volume of roughly 9.5 million m3; this figure underlines the importance of the heading operations in the coal mining industry of our country.

Jan 1, 1970

By Anna Eleria, Joseph Welna, Jim Herber, Nathan Campeau

Constructed by stonemasons over 120 years ago, a portion of the Trout Brook Storm Sewer Interceptor (TBI) owned and operated by the Capitol Region Watershed District in Saint Paul, Minnesota, needed rehabilitation. A routine inspection of the 10-foot limestone block tunnel revealed degraded and missing mortar between the blocks, allowing significant infiltration and soil migration through the tunnel joints. Conditions, including damaged and missing blocks, were considerably worse in a 250-foot-long segment beneath a busy mainline railroad corridor. Barr’s solution included tuck-pointing to repair the mortar joints, shotcrete overlay, and construction of a hybrid cast-in-place/shotcrete “tunnel within a tunnel” to support the mainline railroad loads.

Jun 13, 2021

By Michael A. Werner

"A Yieldable Structure for Use in Areas of High Rock Stress & Deformation." Rock stress of up to 9000 psi have been recorded in the mines of the Coeur d'Alene Mining district. Associated with these large stresses are rock fractures and deformation. In order to maintain openings required for mining, large wood preparation structures are constructed to provide access to the work areas for men and materials. These wood raise preparation structures are costly to construct and maintain. Therefore a steel-foam concrete structure was designed and proposed for testing which would be less costly to construct, require no maintainence and maintain its structural integrity while allowing up to 53 inches of wall rock deformation.

Jan 1, 1984

By G. Barbery

A review is given of the present applications of random sets and integral geometry in fragmentation and liberation models of ores and minerals. Although attempts have ben made in the past to apply such mathematical techniques to the comminution of solids, it is shown that it would not result in major progress. In liberation modelling, it is demonstrated that the approach can lead to fruitful results. Following a recent paper by Davy (1984), a model of liberation prediction is developped, which can be calibrated far ore texture and breakage using image analyzers. The model is demonstrated for the case of a Poisson polyhedra ore texture and monodisperse fragment size. The model enables to predict the complete composite particle distribution, and is thus valuable for integration of ore breakage models with minerals separation models.

Jan 1, 1985

By S. S. Peng

A well designed mining plan is one which minimizes the cost and the mining induced problems and maximizes the recovery of the coal reserve. In order to minimize the negative effects on surface structures caused by ground subsidence process due to underground mining activities, two kinds of practices are commonly employed by the mine operators. One is the support techniques which leaves an area of coal un-mined or partially mined beneath the structure to be supported. The other is the protection techniques which protect the structure when it is subsiding with ground taking advantage of the ground subsidence process (Luo et al., 1992). In designing the supporting techniques, the only currently available method in the U.S. is the one stated in the Pennsylvania Underground Coal Mining Rules (1985). However; The size of the support area designed by this method will be excessively large resulting in wasteful use of coal reserve when the overburden depth is more than 350 ft. A more scientific method is proposed in this paper for de-signing the support area. This method is based on a large amount of subsidence data collected throughout a number of major U.S. coal fields and the authors' experience with monitoring and protecting surface structures undermined by longwall panels. It considers the critical deformation in-dices that a structure can tolerate, and depth and height of underground extraction. The support area designed by this new method will not only assure the safety of the structure to be supported but also maximize the extraction of the coal reserve.

Jan 1, 1993