Search Documents

By Steve Kral

Americans are taking a more critical view of various environmental laws because the effects of those laws are becoming more pervasive and intrusive, according to William Perry Pendley. And Secretary of the Interior Bruce Babbitt is seemingly so unpopular in the West, he no longer campaigns there for Clinton Administration policies. Pendley is president and chief legal officer of the Mountain States Legal Foundation, a public service, non-profit law association that takes on property rights cases for people who cannot afford representation. He was one of the luncheon speakers at the 101st Northwest Mining Association meeting, held in Spokane, WA in early December.

Jan 1, 1996

By W. I. van Drunick

The Anglogold Ashanti (AGA) Navachab single stage SAG mill has provided an excellent setting for incremental optimization. Over the past decades, several interventions have resulted in marked improvements in specific performance; including steel ball scat removal, re-design of the mill lifters, replacement the pebble crusher and cyclone cluster, as well as the use of a vibrating screen in place of a discharge trommel. Recent initiatives now include an operating fine DMS circuit, studies on pre-crushing of the ROM feed and also fine-screening as an alternative to hydrocyclone classification. The current optimized state of the Navachab mill allows it to operate at approximately 20% higher efficiency when compared to mills of similar shell dimensions in gold mining, treating similar ore. This paper describes the systematic improvement of the SAG circuit to its current state.

Jan 1, 2012

By Lucas Gonçalves Generoso, Larissa Rodrigues de Carvalho Rocha, Mauro Vivaldino Fernandes, Gustavo Serrano dos Santos, Gustavo Alexandre da Costa Manso

O Alto-Forno 3 da Usiminas iniciou sua atual campanha em 1999. Projetada para durar 15 anos de operação, previa-se uma produção de 41 Mt de gusa. A partir de 2008, iniciaram as avarias mais significativas no sistema de refrigeração, possibilitando a entrada de água e os consequentes distúrbios operacionais. Buscando estender a atual campanha até 2021, a Usiminas realizou, dentre outras atividades de preservação, duas trocas de staves, em 2015 e 2018. Neste trabalho, são apresentados o planejamento e os principais procedimentos relacionados à parada operacional do alto-forno para a segunda troca de staves, com foco nas atividades operacionais que permitiram a redução do nível da carga até 25,1 metros em relação ao stock line. Destacam-se os cuidados e o êxito no abaixamento de carga até o nível das ventaneiras e a metodologia de troca de staves adotada. Por fim, a previsão de extensão da campanha em 7 anos, possibilitará atingir uma produção acumulada de 53,5 Mt, superando em 12,5 Mt o valor projetado.

Oct 1, 2019

By John D. Thornley

Alaskan villages typically store a one-year supply of fuel to reduce significant delivery costs. Alaska Village Electric Cooperative (AVEC), an electric utility cooperative providing power to 51 Alaska villages, has made a concerted effort to upgrade and improve their undersized and aging facilities. The Village of Stebbins, located south of Nome on Norton Sound is receiving upgrades to its AVEC bulk fuel facilities. Stebbins offered unique challenges from a foundations perspective due to the nature of the soil. The geotechnical investigation found the soil below roughly a third of the footprint of the bulk fuel facility to be thawed with seasonal freezing and the remainder was found to be warm permafrost with ground temperatures of between 30°F and 32°F. This is a unique and challenging arctic engineering design issue because foundations are designed differently for frozen ground conditions. Driven piles were selected because of site constraints, such as the design flood elevation and the change from thawed to frozen ground conditions. The pile design specified that the pile embedment depths would be selected based on the results of pile driving analyzer (PDA) testing during construction in the thawed ground and maintained within the frozen ground portion of the footprint. Difficulties during pile driving in the frozen ground resulted in several piles becoming severely damaged, requiring subsequent removal. This resulted in a reevaluation of the means and methods for pile installation. Additional fieldwork was performed to further characterize the subsurface soils and their frozen nature. Options for installation of piles in difficult areas were evaluated including ground thawing, predrilling, and reducing embedment depths. Presented within this paper are the findings from the initial and subsequent field explorations, discussion of the design methodology, and the decisions that led to successful installation of piles at this challenging remote village.

By John D. Thornley

Alaskan villages typically store a one-year supply of fuel to reduce significant delivery costs. Alaska Village Electric Cooperative (AVEC), an electric utility cooperative providing power to 51 Alaska villages, has made a concerted effort to upgrade and improve their undersized and aging facilities. The Village of Stebbins, located south of Nome on Norton Sound is receiving upgrades to its AVEC bulk fuel facilities. Stebbins offered unique challenges from a foundations perspective due to the nature of the soil. The geotechnical investigation found the soil below roughly a third of the footprint of the bulk fuel facility to be thawed with seasonal freezing and the remainder was found to be warm permafrost with ground temperatures of between 30°F and 32°F. This is a unique and challenging arctic engineering design issue because foundations are designed differently for frozen ground conditions. Driven piles were selected because of site constraints, such as the design flood elevation and the change from thawed to frozen ground conditions. The pile design specified that the pile embedment depths would be selected based on the results of pile driving analyzer (PDA) testing during construction in the thawed ground and maintained within the frozen ground portion of the footprint. Difficulties during pile driving in the frozen ground resulted in several piles becoming severely damaged, requiring subsequent removal. This resulted in a reevaluation of the means and methods for pile installation. Additional fieldwork was performed to further characterize the subsurface soils and their frozen nature. Options for installation of piles in difficult areas were evaluated including ground thawing, predrilling, and reducing embedment depths. Presented within this paper are the findings from the initial and subsequent field explorations, discussion of the design methodology, and the decisions that led to successful installation of piles at this challenging remote village.

Jan 1, 2017

By Lindsay D. Norman

Eleven major pyrometallurgical processes and operations suggested for recovering manganese from domestic resources are described. These include seven pyrometallurgical processes that usually yield a ferroalloy or a product from which ferromanganese can be produced in one operation. The remaining four involve pyrometallurgical operations whose products require either an additional two-stage process to produce ferromanganese or chemical processing to recover a high-quality manganese oxide product.

Jan 1, 1962

By Stoyan Groudev

Two experimental plots consisting of a slightly acidic soil heavily contaminated with radionuclides (mainly uranium and radium) and non-ferrous metals (mainly copper, zinc, and cadmium) were treated in situ under real field conditions using the activity of some representatives of the indigenous soil microflora. This activity was enhanced by suitable changes in the levels of some essential environmental factors such as pH and water, oxygen and nutrient contents of the soil. The treatment was connected with solubilization and removal of the contaminants from the top soil layer (horizon A) due to the joint action of the soil microorganisms (mainly acidophilic chemolithotrophic bacteria) and leach solutions (diluted sulphuric acid) used to irrigate the soil. In one of the plots, the dissolved contaminants were removed from the soil profile through the drainage soil effluents and were subjected to cleaning by a constructed wetland located near this plot. In the other plot, the dissolved contaminants were transferred to the deeply located soil subhorizon B2 where they were precipitated as the relevant insoluble forms (uranium as uraninite, and the non-ferrous metals as the relevant sulphides) as a result of the activity of the sulphate-reducing bacteria inhabiting this soil subhorizon. This activity was enhanced by injecting water solutions of acetate, lactate, ammonium, and phosphate ions to this soil subhorizon.

Sep 1, 2012

By Kaushik Dey

Bord and pillar is the most predominant method of wining of coal in Indian underground coal mines. Development heading in coal mines often encounters roof stability problem and results in roof overbreak. Research on this reveals that the blast-induced ground vibration may have significant contribution in roof overbreak, especially, when solid blasting is carried out in the bord and pillar method. Solid blasting, in general, is associated with higher charge confinement due to lack of free face and generates higher ground vibration, which in turn results in excess overbreak.

Jan 1, 2008

By Rob Thomas

It is generally agreed that standing support should be installed in roadways that will for various reasons, be holed through with a longwall. Considering the magnitude of the associated abutment loading in conjunction with the need to ensure that the material used is cuttable, some form of cementitious support is often used.

By Henry J. Schwellenbach

The New York Trap Rock Corporation has four plants located along the Hudson River, all within 70 miles of New York City. The company produces crushed stone for use as construction aggregate, with a total annual production amounting to 6 million tons. The crushed stone is moved to markets in metropolitan New York, New Jersey and Long island areas by water transportation. There are daily deliveries of approximately 35 scowloads to the market area. Its customers are contractors with ready-mixed concrete and asphalt plants located on the water, where the aggregate is unloaded for its ultimate use. For a number of years capital equipment was replaced only when the current operating machinery was no longer serviceable, or when' a need was apparent for a different type of equipment. There was no particular regard for efficiency or for operating and maintenance costs. Such lack of system often resulted in the emergency purchase of equipment which was later found to be unsuitable for the job. A few years ago it became apparent that a systematic procedure was necessary. After evaluation of several systems, an individualized plan was evolved from the basic pattern developed by the Machinery and Allied Products Institute. The system adopted by New York Trap Rock has proved wholly satisfactory.

Jan 1, 1959

By Daniel Augusto Godinho de Carvalho

Since the beginning of BOF process, slag formation has been subjected to extensive development. During the initial stages of the blow, fast slag formation is primordial for the process performance. This is mainly to allow oxidizing reactions, and also to protect the refractory. A modeling of BOF process for the purpose of process optimization requires precise knowledge concerning the dissolution of CaO and MgO based materials. Using this knowledge, the optimal process conditions can be ensured by a controlling of the slag formation during the converter steelmaking process. Taking into account an application of large amount of different raw materials, as well as location-specific process conditions, the characterization of the dissolution behavior of different additives is an important key to improve the technological process. Thereby, in the frames of this project, an appropriate model for slag formation is established and compared to operational results for a 330t BOF, operating at ThyssenKrupp CSA, Santa Cruz, Brazil.

Aug 16, 2017

By Santo Ranieri

We will briefly review the nickel market in 2003 and look forward to the supply demand balance for the next few years focusing in on the key factors influencing future price dynamics. On the supply side we will examine slated brownfield and greenfield expansions including the Norilsk factor and the small to mid-range 'supply creep'. We will also review the cost side of the industry and what to expect going forward. On the demand side, we will discuss the stainless steel and non-stainless demand, the China factor and the stainless steel scrap supply cycle. We will conclude by pinpinting where the market is on the current price cycle, and where we believe the mid-term direction is headed.

Jan 1, 2004

By T N. Little

This review paper presents an integrated and practical insight to blasting geology and its importance. This approach involves developing blasting objective up front and implementing geology specific blast designs. The author refers to this approach as ‘starting at both ends’. There are many human-imposed controls on blasting operations, such as: safety, security, legislative, company standards, heritage, and environmental constraints. Thus it is possible for some operators to lose sight of the controls imposed by nature. This paper demonstrates how site geology controls or influences many aspects of the rock breaking processes and how a focus on this aspect has potential to add considerable value to mining operations. It is obvious that mining companies concentrate their efforts on economic/ore geology (good rock geology). However it is the author’s experience that they also concentrate on engineering geology (bad rock geology) only when forced to do so by the ground conditions, but seem to run out of puff before they apply blasting geology (big rock geology). This paper contains five main sections. In the first section, the impact of geological controls on blasthole drilling is briefly discussed in terms of drill selection, penetration rates, bit wear, blasthole stability, blasthole deviation, and health precautions. In the second section the geological controls on aspects of geometric design are reviewed. These include: hazardous minerals, valuable minerals, selection of the blasting techniques, geological structures, blasting direction, and blasting geometry. Section three overlaps with the geometric design section and deals with aspects related to explosives. Topics addressed include selecting the explosive type based on geology, distribution of explosive charge in space and time, explosive performance, and the rock response to explosive loading. In the fourth section, examples are given of the operational complexity needed to implement a blast to cater for difficult bench geologies, environment constraints, past mining (voids) and need for a high degree of quality control. Section five demonstrates geological controls on blast results. Blasting results include the muck pile characteristics, downstream handling and processing, damage to the remaining rock, and blasting emissions.

Nov 8, 2011

By Leandro Moosher

A crescente geração e disposição de resíduos sólidos tornou-se preocupante, para tanto busca-se um fim adequado aos mesmos. Este trabalho objetivou avaliar a viabilidade técnica, ambiental e financeira do uso das areias fenólica e verde usadas de fundição como co-produto em substituição parcial ao agregado miúdo areia natural de rio na fabricação de blocos de concreto para pavimentação. Produziu-se 3 traços com 25% e 50% de substituição da areia natural por uma composição de areia de fundição com os mesmos equipamentos e parâmetros comerciais e obteve-se resultados satisfatórios, como a resistência à compressão através do traço rico em consumo de cimento e com 25% de substituição da areia natural pelo co-produto atingindo 37,2 MPa, cerca de 6% acima do mínimo requerido pela NBR 9780. Já na avaliação ambiental esses blocos foram classificados como Resíduo Classe II-A Não Inerte e a análise de viabilidade financeira mostrou custo 1% menor que o bloco convencional.

Aug 8, 2018

By J. A. Herbst

Ball mill grinding circuits can be subject to upsets that arise from variable characteristics of the feed ore. These upsets are transients in critical circuit variables such as ball mill mass holdup, circulating load, sump level, cyclone efficiency and product particle size. They may occur frequently so that the operation is continuously fluctuating or they may be of such magnitude that some of the equipment is overloaded, resulting in shutdown, or an undesirable product particle size. The feed ore characteristics that influence ball mill circuit behavior in this manner include the grindability of the ore, the eventual transport characteristics of the ore in the mills and the feed ore size distribution. Control strategies for grinding circuits using conventional proportional-integral (PI) control have limitations to their effectiveness in controlling against feed ore disturbances. The first of these are the interactive nature of two or more control loops on a single circuit. Under some circumstances they begin to fight each other, increasing control error and settling time. PI control loop gain constants can be tuned to give best response for some set of conditions but once these change, as they would with a change in the feed ore, they are no longer the "best" ones (Shinsky, 1967). Due to these limitations, alternatives to conventional PI control strategies have been investigated for grinding as well as other mineral processing operations. These alternatives, all computer-based, include self tuning regulators, decoupling control and optimal control (Herbst and Bascur, 1983).

Jan 1, 1984

By I. Haskett

ABSTRACT The Redwater pool, in north-central Alberta, was discovered in October, 1948, and at the end of 1950 was about 85 per cent developed. Production is from a Devonian coral limestone reef and is found at an average depth of 3,150 feet. The pool has an estimated .productive area of 37,000 acres, and a maximum oil zone thickness of slightly over 200 feet. Wide variations exist in both type and values of porosity, with the average value determined for the reservoir being 6.16 per cent. The total stock tank oil in place is about 1.24 billion barrels. The crude has a saturation pressure of 485 psig, com-pared to the original value of 1,050 psig for the reservoir, and the principal recovery mechanism so far has been the natural water drive. Cumulative production to January 1st, 1951, has been about 15.5 million barrels. These withdrawals resulted in a reservoir pressure decline of slightly over 100 psi. Predictions of future behaviour indicate that the water drive will not be of sufficient magnitude to maintain the reservoir above saturation pressure past 1953, and that, with natural depletion, the pool will be produced largely by a solution gas drive. Pressure maintenance by water injection has been considered and the possibility of raising the pressure to the original value of 1,050 psig is also discussed. INTRODUCTION WITH the discovery of the Lewduc pool, early in 1947, the Devonian limestone became the major geological formation contributing to Western Canada's rapidly growing petroleum reserves. Redwater, discovered in October, 1948, is now the largest known Devonian pool in Canada, with a recoverable reserve estimated at approximately 500 million barrels. Until recent years, the knowledge of the nature and characteristics of this type of limestone reservoir has been comparatively limited.

Jan 1, 1951

By W. C. Smith

Even with conservative mine planning, rib instability can progress from a nuisance to a major safety hazard. This Bureau of Mines paper examines the mechanisms of progressive rib failure in high mine openings and discusses techniques to control rib slabbing. A field test site in a longwall mine was instrumented to investigate rib behavior during mining. While data analysis showed minor pillar dilation. sporadic zones of progressive rib instability were detected that culminated in eventual rib failure. The failure occurred despite conservative pillar dimensions and shallow depth. Models were used to demonstrate the mechanisms of rib failure and then evaluate the influence of support and other mine-related parameters on rib behavior.

Jan 1, 1991

By L Munholand, G. Soucy, P. Quintal

This work presents early results from the first study to optimize the hydrodynamics of a Plasma Lift Reactor (PLR). The PLR is designed to break down organic contaminants in aqueous solutions. New experimental results are presented for air/water tests and for plasma degradation of organic contaminants in Bayer liquor. In addition, a multiphase Computational Fluid Dynamics (CFD) model has been developed which predicts the hydrodynamic behavior in the PLR. These results of this work suggest the PLR is effective at reducing contaminants in the Bayer liquor and that the CFD model adequately describes the hydrodynamic flow.

Jan 1, 2005

By O. C. Blade

This report on the properties of motor fuels sold through service stations in the United States was made in accordance with a cooperative agreement between the American Petroleum Institute, and the Bureau of Mines of the United States Department of the Interior. This paper is a continuation of a series made in cooperation with the Coordinating Fuel Research (CFR) Committee of the Coordinating Research Council (CRC), Inc. The first of this series of reports presented data on motor gasolines sold during the winter of 1935-36, and succeeding reports described motor gasolines sold during the summers and winters to and including the summer of 1941. No reports were made on motor gasolines sold during the winter of 1941-42 and during the summer of 1942. However, starting with the winter of 1942-43, the semiannual reports were resumed

Jan 1, 1948

By G V. R Goodman, G J. Chekan, J M. Listak

The extraction and transport of coal from underground coal mines can result in significant liberation of coal and/or silica dust into the mine atmosphere. Mine operators have long used ventilating air as a primary means of diluting generated dust, removing dust from the working faces and preventing dust from reaching the minersÆ working environment. As production levels have increased, mine operators continue to be challenged in maintaining dust concentrations below compliance levels. The need for maximising the effectiveness of available ventilating air in conjunction with other effective controls, such as water sprays and dust collectors, continues to be critical to the long-term health of mine workers. The National Institute for Occupational Safety and Health (NIOSH) has conducted full-scale laboratory and mine-site research to evaluate improved application of dust controls for both longwall and continuous mining methods. A summary of recent research results and recommended practices will be provided.

Jan 1, 2005