Search Documents

By Mark E. White, John H. McCowan, Michael C. Costello

Minproc Engineers has carried out the design construction and commissioning of thirty two process plants in the period 1978-87. Twenty eight are gold silver recovery plants, and of these twenty two were gold alone and six were gold and silver. In most plants carbon was used for gold adsorption. Desorption has been carried out using the USBM Homestake method, the Anglo American Research Laboratories method, and the Micron Methanol method. Electrowinning has utilised steel wool, stainless steel wool, and aluminium cathodes. Electrorefining using polished stainless steel cathodes is practised. This paper summarises the experience gained in these operations

Jan 1, 1987

By G. Vijaya Kumar, B. Srinivasa Rao, G. V. Krishna Rao

The paper outlines the ventilation practices prevailing in coal mines of Singareni Collieries Company (South India). The high annual average surface temperature and relatively steep geothermic gradient results in virgin strata temperatures in the region of 38- 42°C creating environmental problems in the working places. Expensive methods of air cooling can not be employed as the mines are small, and production and productivity do not justify the costs of artificial cooling of mine air. Controlled recirculation of mine air -- the unconventional technique being tried with success in some coal mines in U.K. has been analysed for improving the environmental conditions. The analysis shows that the method is safe, cost effective and can be applied with very little extra equipment.

Jan 1, 1991

By Alan A. Campoli, Michael D. Zuber, Frank E. McCall, Gerald L. Finfinger

Injecting water under pressure to wet the coalbed in advance of mining reduces mining-generated respirable dust. Owing to economic and geological barriers, water infusion for longwall dust control in the United States is currently limited to the Pocahontas No. 3 Coalbed in Virginia. Water is pumped into the coalbed through underground boreholes drilled horizontally from the headgate toward the tailgate side of retreat longwall panels. This paper theorizes that the barriers to widespread utilization of water infusion for longwall dust control could be overcome by long-duration, low-pressure water infusion through vertical gob gas boreholes. Currently, 43% of the 72 longwall mines in the United States employ vertical gob gas boreholes. Computer coalbed reservoir simulation suggests that one vertical surface borehole could infuse the same longwall panel area as four horizontal boreholes in the current water infusion system for longwall dust control in the Pocahontas No. 3 Coalbed.

Jan 1, 1995

By D. D. Lei, H. Sevim, S. M. Gwamaka

Three transportation and handling alternatives for delivering dry coal combustion residues from power plants to underground coal mines were evaluated both technically and economically. The objective was to transport, handle and inject the residues into the old workings of the mine at minimum cost. This was accomplished in the following two steps: simulation models were developed and utilized in identifying technically feasible designs for each alternative and the technically feasible designs were economically evaluated to obtain the cost per ton of material transported. An analysis was conducted for varyous distances and tonnages to reveal favorable operating ranges for each alternative.

Jan 1, 1998

By M. Li, J. D. Miller

Recently water insoluble alcoholic solutions of alkyl hydroxamic acid collectors have been shown to be particularly effective in the flotation of coarse feed material sampled from phosphate operations in Florida, North Carolina and Utah (Miller et al., 2000). The experimental results indicate that high separation efficiencies can be achieved in single stage flotation with these new collectors. In some cases the concentrate grade reached 34% P2O5 with 93% recovery from single stage bench scale flotation experiments. Critical aspects of the composition and structure of these new collectors are discussed with respect to their effectiveness in phosphate flotation. The wetting characteristics at fluorapatite, francolite, dolomite and quartz surfaces are being investigated with the new collector. Finally, other surface chemistry considerations in the development of these new collectors for phosphate flotation are discussed.

Jan 1, 2002

By David J. Hammel

This chapter will summarize some of the important applications in the geotechnical (pit slope, spoil pile and tailings stability, and hydrology), the environmental (including reclamation), and equipment selection and analysis areas. Virtually all aspects discussed are applicable both for planning of new mines and for evaluating existing operations. Probably the most influential item which has affected the areas discussed in this chapter and possibly most areas discussed in this book is and will continue to be, in the next decade, the myriad federal and state environmental, safety, and reclamation regulations affecting new mine development and continued operation of existing properties. Computer applications have been and will continue to be instrumental in assisting in planning to meet the challenges of the requirements dictated by these regulations.

Jan 1, 1979

By A. D. Davis, C. J. Webb, F. W. Beaver

The proposed National Underground Science Laboratory will be housed in the former Homestake Gold Mine at Lead, South Dakota. Uses will include underground neutrino experiments that must be shielded by several thousand feet of rock, as well as ground-water research in fracture-flow environments, and investigation of the microbiology of extreme environments. The Homestake Mine has about 300 miles of underground workings. Seepage of ground water into the mine openings is approximately 500 gallons per minute. Average annual precipitation in the northern Black Hills is approximately 28 inches per year. The majority of this becomes surface-water runoff or evapotranspiration, with little ground-water recharge because of the low permeability of the Precambrian rocks in the area. Dewatering of the workings over the 125 years of operation of the mine has influenced the subsurface hydrology of the 8,000-footdeep mine.

Jan 1, 2003

By K. Gorazda

The population growth, urban and industry development cause the increased pollution with different substances, which contain phosphorus. It contributes to the increased demand for its compounds, increasing the use of its natural resources, which is considered to be the most accessible source. The forecasts regarding the world natural reserves of phosphorus deposits are saying that more than 50% of resources used currently will be exhausted within next 60-70 years (Steen, 1998). European Union formulated its goals regarding the waste management in 1990. Its main rules include prevention of waste generation, recycling, reuse of waste as the raw materials in technological processes, separate collection and optimization of final removal. The phosphorus recovery from waste is realized currently in many ways: directly from the waste water stream in sewage-treatment plant, from the sewage sludge, from animal waste, industrial waste and other emissions from industry (Przewrocki et al., 2004). According to the rules of cleaner production the waste should be treated as the source of resources for the production of products with full value (Kowalski, 1998).

Jan 1, 2005

By D. Veigel, J. D. McKay

Model enhanced Expert control has been implemented at the Newmont Lone Tree mill grinding plant as well as rule based Expert control for flotation and thickening circuits. The project has been successful in producing benefits but more importantly has contributed to an ongoing effort for continuous process improvement. This paper discusses how the control at Lone Tree has evolved and the part that Expert control has played in the overall improvements made. Specific examples of how the advanced control has integrated with instrumentation and stabilizing control are given and illustrations of how it has been effective in defining limitations and bottlenecks in the process or process control areas are provided.

Jan 1, 2002

By Alex Harrison, Steve Kasper

Various countries around the world have testing and manufacturing standards in place for steel cord belting. These standards are very comprehensive in what they allow the end user to specify, however, their practical significance in terms of belt life is more difficult to quantify. Such testing standards will be briefly reviewed in this paper in relation to the implication for end user expectancy. Since there is no US standard of manufacture, the end user is left with writing their own specifications. In addition, such standards do not address the effect on belt life of manufacturing faults, such as cord plane buckles, or lateral cord movement. Some new technology used to test steel cord belting will be described as an aid to both manufacturer and end user. Specific end user related issues addressed on this paper are: Tracking and belt quality Cord plane irregularities and performance Cord size and belt life Cord fatigue and testing

Jan 1, 1993

By Kenneth N. Han, Xinghui Meng, A. J. Monhemius, G. W. Warren, E. Peters

The leaching of gold in ammoniacal solutions containing various oxidants in an autoclave has been investigated. Also studied are thermodynamic and kinetic aspects of the ammonia leaching of gold and silver. The variables studied included stirring speed, temperature, concentration of ammonia, ammonium, and various anions. Arrhenius activation energy values were found to be between 47.1 kJ/mol and 86.2 kJ/mol depending upon the kinds of oxidants used. An electrochemical reaction controlling mechanism has been proposed for the dissolution reaction. The leaching behavior of gold and silver from various ores in ammoniacal solutions containing various oxidants has also been investigated. The samples tested included sulfidic as well as carbonaceous refractory ores. The recoveries of gold and silver from these refractory ores were better than 96% within 2-3 hours of leaching time.

Jan 1, 1993

By David J. Brown, Richard C. Fountain, Marc V. Hurst

The Central Florida Phosphate District, one of the most productive phosphate districts in the world, has been mined principally within Polk and Hillsborough Counties, Florida. Recent development is extending the district southward into Hardee, Manatee, and DeSoto Counties. This area is known as the Southern Extension. The combined area of these two phosphate-bearing areas encompasses about 2,000 square miles. Structurally, the district and its Southern Extension lie at the southern end of the Ocala Arch and are flanked by the Hillsborough High to the northwest. South of this area is the South Florida Embayment. The Osceola Low lies to the east. The phosphorite within the Central Florida Phosphate District generally dips very gently (<0.1°) to the south. The boundaries of the central Florida Phosphate District are generally defined by thinning of the phosphorite due the adjacent structurally high areas to the north, west, and east, and by increased clay, CaO, and MgO content reflecting lithologic differences to the east and south. The Bone Valley Member of the Peace River Formation and reworked sediments of more recent age were the primary ore-bearing horizon in the Polk-Hillsborough County area. As those reserves are depleted, the less desirable phosphorites of the Peace River Formation are being exploited in the Southern Extension.

Jan 1, 1993

By Steven W. Hunt, Steven B. Fradkin, Roger J. Maurer

During the 1980s and 1990s, twenty deep shafts were constructed in Milwaukee to depths from 85 to 91 m (280 to 300 feet) through soil and weak rock thicknesses ranging from 37 to 69 m (122 to 227 ft). Adjacent compressible soils, settlement sensitive structures and high groundwater levels required that shafts be constructed without dewatering. Contractors attempted several methods of ground support and groundwater cutoff. Significant problems developed during construction of 11 of the 20shafts. One shaft collapsed; groundwater blow-ins occurred at five of the shafts; and seepage caused unfrozen windows at three of the freezewalls. Ultimately, combinations of grouting and ground freezing were utilized to complete all of the shafts into bedrock. This paper discusses the main design and construction challenges experienced and the lessons learned.

Jan 1, 2003

Land management planning is an important issue in all jurisdictions, especially as it relates to mineral development. These planning documents are prepared at different intervals and reflect the realities at the time that they were prepared. The Seven Questions to Sustainability developed during the North American Process of the Mining, Minerals and Sustainable Development (MMSD) project are proposed for the evaluation of Land Use Plans as they relate to Mineral Development. This paper provides the background to the Seven Questions to Sustainability and how it can be applied to the evaluation of land use plans with specific reference to Resource Management Plans developed by the U. S. Department of the Interior?s Bureau of Land Management in Nevada. While this paper is focused on Nevada, the approach is broadly applicable and may be used in other planning regimes.

Jan 1, 2007

By W. A. Crosby

The ability of open pit mines to steepen overall final wall angles allows significant cost reductions as a result of reduced waste movement requirements. Final wall angles are principally controlled by three factors: geological conditions; hydrological conditions; and wall control blasting practices. The first of these factors is not controllable by the mine operator, the second can be influenced to some degree, but the last one certainly can be controlled, hence the current interest in final wall blasting practice at many mining companies. This paper discusses common blasting techniques employed to steepen final pit walls and outlines the attractiveness of moving from small hole high cost systems to the use of full size production drills as a means of reducing wall control blast costs. Attempts to make this change have been limited at many mines by the physical size of the drills and their inability to reverse drill. In the past, pres pi it, pre-shear or trim holes have had to be drilled vertically, at considerable distance from the upper bench toe, with the result that inter-berm face stability is reduced and final wall angles have to be made somewhat more shallow than desirable. The paper concludes with a description of how these problems can be overcome by utilizing the new Bucyrus 39R which has the capability of drilling at a ?15 degree angle underneath the machine. It is concluded that the resulting wall control blast designs will offer large mines improved final wall angles with resulting significant overall cost reductions.

Jan 1, 1998

By L. Alan Weakly

The Powder River Basin is the largest strippable reserve of compliant coal in the United States. It is the mother lode, for this Basin is currently supplying 25 percent of the coal produced in the US annually. This paper updates what has happened in the Basin since 1993 in terms of increased production, higher productivity, changes in mine ownership, safety statistics, new equipment, latest coal technologies, and electrical deregulation ramifications.

Jan 1, 1998

By Randall C. Divito, Craig R. Eckdahl, Bruce D. Wagener, Joseph Klejwa

The existing Central City Tunnel was built primarily in the 1930s with a small portion as old as the 1880s. It conveys stormwater in downtown Minneapolis. It is a 4,400-ft long tunnel located 80 feet underground. The Central City Tunnel has experienced surcharging and surface overflows during heavy rainfall events. This paper presents the details of tunnel and shaft design for the new Central City Parallel Tunnel to mitigate the overflows. The design considered hydraulics and geotechnical engineering for the structural geologic conditions including the weak Saint Peter Sandstone and overlying strong Platteville Limestone. Ground conditions resulted in tunnel designs including large flat-back box tunnels and unique cathedral-shaped tunnel sections.

Jun 13, 2023

By Russell E. Martin

Excavating and lining twin interstate highway tunnels each 11.3 m (37 ft) high by 14.6 m (48 ft) wide by 183 m (600 ft) long. A discussion of the geology of the site and problems occurring at the portals and the solutions to the problems. The methods used in placing the concrete lining are also discussed.

Jan 1, 1987

By William F. Riggs

The characteristics of frothers can often be determined by the proper selection of various chemical groups. There are three basic groups utilized in the application of frothers. These are alcohols, polyglycol ethers, and polyglycols. Some of the chemical groups are separated in subgroups. Each chemical group provides particular characteristics which affect load support, bubble diameter, water retention, air dispersion, and kinetics of froth formation. These chemical groups may be preblended in various percentages to optimize frother characteristics for a particular ore deposit.

Jan 1, 1986

By R. F. Shurtz

This paper uses a simple model to illustrate the fact, widely known to information theorists, that the covariogram represents only half the information in the data used to construct it. It suggests and illustrates methods of putting the other half to use in describing mineral deposits. It also identifies applications in which the phase information is not needed.

Jan 1, 1986