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By S. A. Moffatt, S. K. Kawatra, T. C. Eisele

This paper describes the decomposition of bulk samples to fine particles using alkali metal vapors. Basalt, pyrite, alumina, pyrex and quartz glass samples were exposed to sodium vapors at elevated temperatures for different time periods up to 30 hours. Examination of the particles showed that fragmentation occurred preferentially along grain boundaries. Emphasis of this paper is on the theory of the degradation mechanism and the size distribution of the particles produced.

Jan 1, 1992

By Henry T. Miller

INTRODUCTION The basic purpose of this paper is to suggest procedures and practices to insure that no employee working in a uranium milling operation receives exposure to radioactive, toxic, or other materials or agents that might produce a permanent, deleterious effect upon his physical health and well-being. This program is also designed to insure that each employee can carry out his assigned duties without risk to his health or to that of his fellow workers. The assumptions underlying this program are by necessity, conservative, with emphasis being placed upon prevention rather than correction or reaction to an undesirable situation. The limits specified-either as Threshold Limit Values (TLVs), Maximum Permissible Concentrations (MPCs), or Radiation Protection Guides (RPGs)--represent both standards of best practice and those of law and regulation. The total program is envisioned as a balanced combination of occupational hygiene and radiation monitoring. This includes surveying, air sampling, personnel dosimetry, bioassay, medical surveillance, epidemiology, and training--all backed by a thoroughly tested and evaluated set of emergency procedures. The program, as presented, is keyed to the results of monitoring, surveying, air sampling, medical surveillance, and epidemiology--it being obvious that no problem can result when no hazard can be identified. The lack of an identified hazard, however, does not negate the need for such a program and prudence suggests the need for routine surveillance programs in the best-designed facility. [The Model Mill] The model mill used in this paper is that presented by the U. S. Environmental Protection Agency in its study of the uranium fuel cycle1. The model mill processes 600,000 metric tons of ore per year into 1,140 metric tons of U308 as yellowcake per year using an acid leach process. Other characteristics of the mill such as location, tailings dam design, number of light water reactors supported, and geographical location are not pertinent to this paper. The usual remote western location of these facilities produce some difficulties in delivering the required occupational medical services and is not within the scope of this paper. The operating lifetime of most mills is commonly estimated as from 12 to 15 years in actual practice; however, the U. S. Environmental Protection Agency estimated a 20-year lifetime for its model. The principal steps in the acid leach process include :2 (a) Ore is blended and crushed to pass through a 2.5 cm (one inch) screen. The crushed ore is then wet ground in a rod or ball mill and is transferred as a slurry to leaching tanks. (b) The ore is contacted with sulfuric acid solution and an oxidizing reagent to leach uranium from the ore. The product liquor is pumped to the solvent-extraction circuit while the washed residues (tailings) are sent to the tailings pond or pile. (c) Solvent extraction is used to purify and concentrate the uranium. (d) The uranium is precipitated with ammonia and transferred as a slurry. (e) Thickening and centrifuging are used to separate the uranium concentrate from residual liquids. (f) The concentrate is calcined and pulverized. (g) The concentrate or yellowcake is packaged in 208 liter drums for shipment. This process is illustrated in Figure 1.3

Jan 1, 1981

By B. A. Hancock

New permit discharge standards instituted at Hecla Limited?s Lucky Friday Mine required installation of water treatment plants to manage water quality at two outfalls to the South Fork of the Coeur d?Alene River. The 002 Outfall Water Treatment Plant (WTP) is a clarification-filtration plant for treating the combined mill and underground discharge water flows. Process optimization efforts were a significant challenge until the negative impact the exploration diamond drilling products had on the clarification process was identified and resolved. The products were being wasted directly to the mine water discharge system which was pumped to the surface WTP. Anionic soluble oil and polyacrylamide based products were causing TSS particle hydrophobicity and dispersion that greatly affected coagulation and flocculation response, resulting in excessive chemical usage and treatment control issues. This paper details how problems associated with the drill products negatively impacted the 002 WTP and how system changes, alternative product usage and treatment at the source resulted in more consistent plant performance.

Jan 1, 2011

By G. Piegols, J. A. Lombardi

Substantial volumes of cyanide are consumed in precious metals mining due to the purposeful destruction of base metal cyanide complexes and free cyanide to meet surface discharge regulations. This destruction of cyanide resource runs counter to the prevailing social ethic of resource conservation wherein cyanide recovery-and-reuse is considered a more socially responsible cyanide use pattern than systematic cyanide destruction. HW Process Technologies, Inc. (HWPT) has developed membrane based methods for the recovery of cyanide from barren solution as a means to reduce cyanide waste. The HWPT Engineered Membrane Separation (EMS™) system uses state-of-the-art spiral wound membrane elements that are engineered specifically for the treatment of high pH cyanide process solutions. The membranes fully reject WAD CN, SAD CN and most minor metals, and partially reject SCN, Free CN and precious metal cyanide from a high clarity barren solution feed to a small volume EMS™ “concentrate” stream. The EMS™ “concentrate” stream is returned to the process. The large percentage of the EMS™ process feed exits the system as cyanide lean EMS™ “permeate.” The EMS™ permeate, after residual cyanide destruction, polishing, and pH adjustment, is, thereafter, typically suitable for discharge. Separately, the HWPT EMS™-PLS method of cyanide recycling is an internal plant cyanide recovery step that removes base metal cyanides from a pregnant leach solution to a small volume EMSTM concentrate stream. The concentrate stream is then typically processed further for the recovery of metals and recovery-recycling of cyanide. The method makes it economically practical to recover gold from Merrill-Crowe or car-bon plant “fouling” solutions, e.g., those with greater than 400 ppm Cu, as might result from the use of the EMS™ method wherein EMS™ concentrate is constantly thrown back into the mine leach solution pool as part of the free cyanide recycle process, or as might result from the single-pass leach treatment of high copper content ores or concentrates. The EMS™ cyanide recovery method for barren solution treatment is shown to be “economic” for the treatment of clear solutions at the approximately 200 ppm total cyanide level (CNT), and for slurries at the approximately 400 ppm total cyanide level, where economic is defined as a 2 year EMS™ plant payback. The EMS™ plant payback calculation includes the beneficial monetary impacts of gold and free cyanide recycling and the avoided operating cost of cyanide destruction.• The cyanide recovery plant payback period is reduced further when the avoided capital costs for cyanide destruction (EMS™ permeate “clear solution CN destruction polish” only required) and/or metals precipitation are considered.

Jan 1, 2004

Maximizing margins in competitive markets demands superior productivity. Unfortunately, management systems developed early this century for other industries often drive counterproductive behaviors choking mining productivity. Many executives and managers waste valuable time and effort relying on simply training and communicating to improve managerial practices and attitudes. In covering practical human behaviour, the paper explains why this fails -and explains how to use systems to successfully drive improved managerial practices and attitudes. It highlights use of modern performance Measurement, Analysis and Reporting systems to drive behaviors and improve margins -without capital investment -and make executive and managerial work easier and more effective.

Jan 1, 1999

By David R. Klug, Chris Gause, Troy L. Page

The Inter-Island Tunnel is one of two undersea tunnels which are part of the Boston Harbor Clean-Up Program. The tunnel is 7.7 km (25,160 ft) long, bored to a 4.3 m (14 ft) diameter in the Cambridge Argillite Formation and was finished to a 3.5 m (11.5 ft) diameter final concrete lining. The owner is the Massachusetts Water Resources Authority (MWRA) who is a regional authority responsible for overall design and construction. The tunnel's primary purpose is the transport of untreated effluent from Nut Island facility in Quincy, MA to the new treatment plant at Deer Island. Two sludge lines are installed for the transport of sludge from Deer Island to Nut Island. During construction the contractor encountered fault zones, fractured strata, and soft ground tunnel sections which liberated more ground water than was originally anticipated by the project designer. Ground water was controlled during mining and the placing of the final lining. The final lining of cast-in-place concrete had to be backfill grouted to cut off water inflows and provide contact for equal tunnel loading which is critical in long-term design. This paper deals with an engineered backfill grouting system which was the first of its type to be used in North America. It discusses the geological conditions encountered, the design criteria used in the evaluation process, and an indepth review of the various system components. It demonstrates how contractors can use knowledgeable and professional industry suppliers to solve difficult construction problems.

Jan 1, 1999

By A. Haile, A. Poole

During 2001-2002, the Granny Smith Mine of Western Australia undertook the development of a planned circular failure. Excavation took place in an interim pit wall that intersected the transported sediments, lake clays, and palaeo channel sands that overlay the deposit. The purpose of the study was to refine feasibility level slope parameters used for the initial design of the Wallaby pit, with the intent of increasing the overall slope when excavating the ultimate pit limits. During excavation, the geological and hydrogeological characteristics were studied in detail and data was collected using area-specific instrumentation and monitoring. Failure occurred in mid February 2002, at which time a detailed survey of the excavated slope using laser technology was conducted to provide geometric information suitable for back analysis of the material shear strength. The slope failure and associated information was analysed by geotechnical consultants. The revised shear strength and hydrogeological parameters were then applied to design the final pit walls. The slope redesign provided a cost saving of approximately seven hundred thousand US dollars. Design, slope formation, back analysis, the geology of the clay units, the hydrological environment, planned infrastructure, management and safety issues, and the on-going slope performance of the final slope are discussed.

Jan 1, 2004

By Daniel T. Hegyan

The employment of continuous rotary vacuum disc filters to filter refuse from the fine coal washing circuits has been increasing as it has become more important to close the water circuits and eliminate sludge holding ponds. This paper will discuss our past experience filtering refuse, effects of solids concentration in the filter feed, use of polymer flocculation aids, effect of flocculation devices, and effects of particle size and ash content on the filtration rate. Detailed tests were performed on existing installations utilizing coal refuse filters to determine optimum flocculant dosage, solids concentration, and disc rotation speed to form a dischargeable cake. Information was also obtained showing effect of flocculant addition on the moisture of the filter cake. Our test work has shown that the continuous filtration dry cake rates for fine coal refuse correlates very well with the data developed and presented by Silverblatt and Dahlstrom1 except that the curves have moved up the scale by use of polymer flocculant additions. These polymers were not available at that writing. Finally, our tests also confirmed the general premise stated by S. K. Mishra2 that controlled additions of polymer flocculants will reduce filter refuse cake moistures somewhat.

Jan 1, 1974

By Y. H. Cheng, H. EI-shall, S. Gupta, N. A. Abdel-Khalek

A 14.6 cm (5.75 in.) diameter by 1.83 m (6 ft) tall laboratory-size column is used in flotation of Florida phosphates of different feed sizes. In this paper, the effects of different parameters on the flotation efficiency of coarse particles (belt feed, -1.4 + 0.5 mm, i.e., 14 x 35 mesh) under negative bias are discussed. Parameters included collector dosage, frother type and dosage, and conditioning water, which contained a residual concentration of collector. Flotation tests were performed using statistical designs. The results strongly suggest that flotation performance is dependent on the used combination of reagents. Interactions between frothers and the collector and, consequently, the flotation efficiency were found to be dependent on frother type and presence or absence of conditioning water. Under the negative bias, an excellent recovery of more than 98% of phosphate was achieved in concentrates of high grade (above 31% P205) from such feed of coarse particles.

Jan 1, 1999

By R. W. Smith, M. C. Fuerstenau, G. X. Xang

Nonliving dried water hyacinth (Eichhornia crassipes (Mart.) Solms) roots were investigated for the biosorption of cadmium, lead and other heavy metal ions from aqueous solutions. Dried water hyacinth roots, when suspended in solution, strongly and rapidly sorb several different metal ions. Factorssuch as reaction time, pH, the initial concentration of metal ions, the presence of other metal ions and biomass concentration were investigated. The adsorption was shown to follow the generalized Langmuir adsorption equation. The relative affinity of the roots for lead is greater than that for cadmium. The batch sorption kinetics of the uptake of cadmium and lead can be described by an apparent first-order reversible reaction model. The roots could be regenerated after the metal ions were stripped. Successful desorption of Cd and Pb from the biomass by acidic CaCl2 solutions revealed that the metal uptake phenomenon is reversible, implying physical sorption of Cd and Pb.

Jan 1, 2000

By Richard Switalski, Mark R. Kritzer, Boro J. Lukajic, Robert Pintabona

Ground freezing was chosen as an initial support method during construction of two deep shafts at the Mill Creek project. The Mill Creek, Phase 2 tunnel (MCT-2) is utilized to convey and store combined storm and sanitary sewage collected from the member communities in the greater Cleveland area. The main objective of groundfreezing was to provide a strong support structure to resist soil and groundwater pressures. This was achieved by creating a watertight, frozen-ground barrier around the shaft perimeter. The paper will provide an overview of ground freezing techniques applied during the construction of two shafts, each 250-feet deep.

Jan 1, 2003

By Michael J. Sapko, Robert A. Cortese

A flame powered trigger device has been developed to explosively activate suppression barriers to quench gas and coal dust explosions. The important feature of the device is a silicon solar panel, which collects 0.3 p to 1.1 D wavelength radiation from the developing explosion, and generates electrical energy to initiate a detonator, which in turn causes the rapid explosive release of an extinguishing agent into the advancing flame front. Solar panels that are rated to produce 20 w of electrical power when exposed to the sun light are producing about 200 w when exposed to full-scale dust explosion propagating in the U.S. Bureau of Mines' Lake Lynn Experimental Mine. The solar panel is electrically isolated from the detonator by a pressure sensitive switch until the arrival of the precursor pressure pulse, which always precedes a deflagration. This combination of pressure arming and flame powered photo generator prevents false barrier activation and requires no external power supply.

Jan 1, 1991

By D. M. Thayer

In the last decade public awareness of the need for pollution abatement has increased greatly. The concern that had been previously shared by local and state conservation groups has spread to create a national concern for preservation of our non-polluted environmental assets and regeneration of those that have been wasted. Because other current matters such as inflation, civil rights,' tax reform and the Vietnam situation have been the object of most national concern, an extremely strong national pressure base has not been brought to bear on the pollution control crisis. Yes, the word is crisis, for in many areas pollution is of critical concern. One has only to look at Lake Erie, the skies about our major urban areas and many of our major rivers and streams to see this crisis These are not situations that can be corrected overnight. We are faced with two basic problems that should be attacked simultaneously: (1) Cleaning up the present sources of pollution and (2) preventing the generation of new pollution sources. What approach should be taken? As in any engineering problem, the limits must be well defined before a final solution is attempted. Pollution must be defined on a national basis. This means that basic Federal legislation and control is necessary. This should reduce any competitive advantage that can presently be gained by movement of operations from one state or geographical area to another on the basis of differences in local legislation .and enforcement. By giving real numbers as guidelines, selective enforcement can be avoided. As a starting point, for a definition of pollution let us use the following - "Any change in the environment occurring from other than natural causes." This definition may not be satisfactory to all but surely we must be somewhat dramatic in our statements to counteract the present prevailing philosophy. Our statement of this philosophy - "At what level of pollution can we afford to operate?" On the basis of our general definition we would like to state what we feel should be the philosophical statement - "How little can we change our physical environment as a result of operations?"

Jan 1, 1970

By W. J. C. Meynink

In drier regions of the world, total containment of cyanide liquors for rainfalls less than a specific design value is often required by government regulation. For example, in Queensland total containment is required for rainfalls up to 'the 1% annual exceedence probability. In equatorial regions, where rainfall greatly exceeds evaporation, a total containment requirement is unrealistic and this is recognized by regulatory authorities. Regulatory constraints typically require that cyanide concentrations at an agreed downstream compliance point not exceed a specific value more than a specified fraction of the time. While the excessive rainfall prevents total containment, it does provide substantial dilution. This paper outlines a methodology for assessing the distribution of cyanide concentrations at a downstream compliance point in an equatorial region with limited hydrometeorological data. Consider the hypothetical mine environs depicted in Figure 1. The mine is located near the catchment divide and draws its water supply via a gravity line. Tailings from the process plant are piped to a tailings dam on a sub-catchment below the plant site. The objective is to determine the distributions of cyanide species concentrations at a compliance point just upstream of a major settlement to ensure they do not exceed regulatory limits.

Jan 1, 1991

By W. DR. Fritz

Technical progress depends on strategic objectives and a concept showing how to benefit from the effects of novel techniques in an innovation process and how to implement them creatively in harmony with manpower capabilities. With the invention of prime movers, it was initially power engineering which dominated the development of industrial history before it was replaced by production techniques resulting from the more widespread use of machines. With the advances in the field of data processing and with the introduction of novel communication techniques, it is information technology- which today is having an ever increasing impact on technological progress. The main objectives of information technology in this context are a positive influence on the ?time? factor as well as the provision of tools to handle the complexity governing many operational processes through a concentration of information for the decision-making process. The German hardcoal industry became aware of the chances inherent in these new technological possibilities for the optimization of operational sequences and of decision-making and planning processes as a potential for success at an early stage and it has worked out a purposeful concept for their implementation.

Jan 1, 1992

By David C. McLean, Peter Penner, Martin de G. Salter

The Rogers Pass Project for C.P. Rail includes a 14.7 km tunnel and an 8.5m diameter concrete lined ventilation shaft to a depth of about 335m. The shaft collar is in bouldered water bearing glacial till to a depth of about 95m. Initial excavation in the overburden was with the aid of dewatering wells. When ground support problems arose the excavation was completed by a two stage freeze programme. Freeze holes were drilled from the shaft bottom. This most unusual method was successful in overcoming the difficulties safely and efficiently. The remainder of the shaft was sunk and lined conventionally. Finally, a central dividing wall was poured by jump forming from the bottom up. The wall was completed to a high standard at up to about 20 vertical metres per day.

Jan 1, 1989

By R. W. Lai

Cyclic voltammetry (CV), flotation response, evolved-gas analysis (EGA), and X-ray photoelectron spectroscopy (XPS) were employed to evaluate the major differences in the surface property and surface reactivity of coal pyrite and mineral pyrite.

Jan 1, 1989

By S. C. Gambrell

The practice of roof bolting in world-wide mining activities is very well known, having been used extensively for over 50 years. The theory of roof bolting, however, is extremely complicated, and only recently have investigators attempted to explain the theory. Discussions of the mechanics involved usually originate with actual experience gained in the use of roof bolts. The use of roof bolting in mines has grown dramatically during the period after World War II. Other scientific techniques have emerged in mining research in the same period. Included in these techniques is the study of rock mechanics, which has now developed into an impressive research effort. Various means of analysis have been utilized in rock mechanics, most of which reduce rock to an isotropic, homogeneous medium that could be easily analyzed. Because of the inherent nature of rock, direct research methods frequently are not certain to provide satisfactory results, whereas indirect methods must idealize a given set of conditions in order to be useful. One of the indirect research methods is the photoelastic technique, the theory of which is widely known and needs no elaboration. This technique has been used extensively to examine the state of stress around underground openings of various shapes in certain types of strata, and under various configurations (1,2,3,4,5). Much of the theory used now in the design of underground openings is based on photoelastic evaluation. Unless rigorously applied, how- ever, the photoelastic technique is at best a qualitative means of evaluation. It is useful, however, for unusual examples which can be more or less easily analyzed to obtain the overall state of stress which could not be determined by other means. Little work has been done in the photoelastic analysis of rock bolting, mainly because direct research techniques have proven useful.

Jan 1, 1970

By W. L. Wilson

This article could be entitled "The Rediscovery of the Windfall Mine," since it was originally discovered early in this century. The "Rediscovery" was made by personnel of Idaho Mining Corp. during the course of an investigation of the Windfall mine beginning in 1967. There had been historic production from the Windfall mine sporadically from 1908 until 1951 and there was present during much of this time a mill that vat leached crushed ore. Mining was underground to a depth of 91 m (300 ft). Prior to Idaho's activities, the mine had been inactive since the early 1950s. Idaho Mining Corp. was an "exploration company," privately owned and based in Reno, NV. The writer was at that time manager of exploration for Idaho Mining. The company held interests in the Cortez Gold mine, then being readied for production, and had conducted exploration for various mineral commodities in Nevada for several years. Idaho's attention was first directed to the Windfall mine in the Eureka District, Eureka County, Nevada (see Fig. 1, Nevada map) by a search of published geologic literature of the state of Nevada. An attempt was made to acquire a library consisting of all of the published geo-data for the state of Nevada as well as to obtain as much of the unpublished material as could be acquired. A study of these data, and in particular Tom Nolan's Professional Paper 406 (1962), indicated that the Windfall mine was anomalous for the Eureka District in that it contained deposits of disseminated gold. This source and other sources indicated that the Windfall had produced from underground operations approximately 59 kt (65,000 tons) grading 12.6 g/t (0.368 oz per ton) gold ore that was processed in a vat leaching operation and that the gold was "invisible" to the naked eye and could not be panned. It was ascertained that there were no active operations near the mine and a geologic reconnaissance was made and a few samples were taken to attempt to determine if the mineralization was indeed disseminated. The initial group of samples around the mine area averaged 1.25 ppm [11.5 g/t gold (0.036 oz per ton)] and the mineralization did appear to disseminate into the wallrock. The next step involved researching the ownership of property in the immediate area of the mine, and [ ] a property map was constructed that showed six or seven different ownerships of patented and unpatented claims, as well as some open ground, in the target area. Negotiations were commenced with the claim owners, ultimately resulting in the acquisition of all of the desired property, although some of

Jan 1, 1990

By D. Farnell

Large semi-autogenous (SAG) or autogenous grinding mills have become the work-horse of the modern high volume concentrator. They typify the economy of scale - fewer, larger machines doing more work, more economically. With fewer machines, equipment reliability becomes of paramount importance. Realizing this, companies installing new or modernizing existing facilities have placed extraordinary emphasis on purchasing a reliable mill. This, in turn, has had a significant impact on mill design. Kennecott And Codelco - Two Different Approaches Last year, two of the world's largest copper producers, Codelco and Kennecott, undertook the modernization of their main grinding facilities at Chuquicamata and the Utah Copper Division (UCD) respectively. Both selected semi-autogenous milling and both, recognized the importance of the reliability of the primary mills. Each, however, decided on a different approach to optimizing reliability. Codelco placed the emphasis on technical innovation in design and opted for a gearless driven mill. Kennecott chose the more conservative approach of active participation and exceptional quality assurance in mill design and manufacture.

Jan 1, 1987