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By S. P. Mehrotra, P. C. Kapur

A phase-species classification is suggested for the mathematical models of flotation kinetics. Important models are discussed and the structure of their rate constants and parameters is analyzed. Split or enhancement factors are formulated for different kinetic models. The steady state dynamics of the flotation circuits can always be described in terms of these factors. For simulation of circuits, feed is characterized in a formal manner starting from a multivariate distribution of particles in flotation rate, size and mineral content. Synthesis of optimum circuits which simultaneously searches for the best process variables and structural parameters from a generalized master network is described. Trends in the areas of search algorithms, role of middlings and feed identification etc. are indicated.

Jan 1, 1989

By Felicia F. Peng

In operation of column flotation of fine coal, the smaller bubbles are required to effectively recovery of fine hydrophobic particles. However, smaller size bubbles alone does not ensure an efficient flotation for fine particles. The sufficient available bubble surface area per unit column are essential for effective column flotation. The experiments are conducted in a lab-scale column using two different bubble size distributions and three different particle size distributions for flotation of Pittsburgh No.8 seam coal. The interaction between particle size, aeration rate, feed rate and wash water addition are examined in this investigation to establish the optimal operation conditions for flotation of fine coal. Despite of wide range of operation conditions used in this study, it is found that the experimental data fall in a single characteristic recovery-ash curve for a given bubble size distribution and particle size distribution. The major parameters affect the flotation performance points along -the characteristic recovery-ash curves are aeration rate/frother dosage, feed rate and wash water rate-.

Jan 1, 1994

By Agne Rustan

INTRODUCTION This work is a continuation of the preparatory study by Rustan and Stöckel 1979 (3) and (4) of the possibilities to introduce automatic mine ventilation in Swedish mines and construction works. The preparatory study has been financed by the Swedish Board of Technical Development. In the study it was recommended that an automatic step by step control of the fans near the working place due to diesel exhaust emission would be the best solution. A more advanced alternative would be to regulate the fresh air continuously in proportion to the contamination. The latter alternative has been studied by Boliden Mineral Co in the Udden mine. In this study it was found that the air supply could be regulated continuously but it was very important where the sensors feeling the contamination were placed. An intense study of the environment underground is now being planned by our division together with specialists from the National Board of Health and Safety, The Swedish Work Environment Fund, LKAB and the local Governmental Inspection of the Workers Safety. Different gases, radon, dust, airspeed, moisture temperature and pressure is planned to be measured continuously and correlation between the parameters is going to be established to decide the best measurement parameters for regulating the system. The best situation of sensors is also going to be studied. Despite this work hasn't been done yet this paper covers some of the problems which could be encounted with continuous regulation. In this report the environment has been studied during the test with step by step regulation of fans by radio. Diesel vehicles are the largest polluters under ground in Swedish mines and we have therefore suggested that the large diesel vehicles should regulate the fans. The goal of this study has therefore been to find how active diesel vehicles should be able to start and stop gallery fans at both intake and return air. In this paper different methods for activating fans are discussed. Then the best methods are chosen and tested in the mine. In this study we have found that changes of temperature is a cheap and effective method to start and stop cross cut fans in sublevel caving and radio signals seem to be an attractive system for start and stop of gallery fans. This work has been done in close collaboration between LKAB in Kiruna and the University of Luleå - Division of Electronics and Division of Mining and Rock Excavation. A reference group for the project has been established with ventilation experts from the mines, representatives for the local mine worker's unions and authorities from the local Governmental Inspection of the Workers Safety. VENTILATION SYSTEM STUDIED In the project the ventilation system at LKAB in Kiruna has been studied. The mining method used is sublevel caving with 9-13 m slice height. The air is heated winter time over ground by hot water heat exchanger. The main fans are pushing air down to a main distribution level along the 4000 m long and about 100 m wide orebody. From the distribution level, air is taken through shafts down to the sublevels, where it is pushed through the levels by local gallery fans on both intake and return side, see fig 1. The air ( ~ 8 m3/s) is moving freely through the gallery head. The cross cuts are ventilated with smaller fans, diameter 500 mm, and flexible duct, see fig 2. The aim of this study has been to study how to start and stop gallery- and cross fans and examine the environment when the fans are stopped . In Sweden there are no regulations telling that a minimum of air amount must be supplied. Instead the hygienic limits must be fullfilled.

Jan 1, 1981

By Kim A. Lapakko, William W. III White

The ASTM standard method D 5744-96 was developed to provide a well-defined kinetic test protocol, conducted under controlled reaction conditions, with the intent of generating reproducible results. A preliminary indication of the repeatability of a simplified alternative method (MN DNR method) was assessed and results from the MN DNR method were compared to those from the ASTM method. To provide an indication of repeatability, six samples from three different rock types were subjected to dissolution testing for periods of 20 to 68 weeks. Drainage pH values at the end of the tests were within 0.5 units in all cases and within 0.05 units in four cases. The percent difference from the mean for overall sulfate rates from paired cells ranged from 0.04 to 1756, with a median of 6.3%. Nine samples from four rock types were subjected to both MN DNR and ASTM tests for periods of 20 to 132 weeks. The difference in final drainage pH values forsix of the samples was less than 0.1 unit, and these values were less than pH 3.65 or greater than pH 8.0. The final drainage pH difference for the last three samples ranged from 0.15 to 0.4, and these values were ill the pH range of 6.2 to 7.2. The sulfate release rates for the periods of record for the MN DNR method were 70 to 150% of those for the ASTM method, with a median value of 110%. Sulfate and calcium release from the two methods was not substantially different. The MN DNR method typically produced higher magnesium release.

Jan 1, 2000

By Christopher J. Hall

This paper describes the results from computer runs simulating 24 different mine ventilation configurations with the main fan situated first at the top of the upcast shaft and then at the top of the downcast shaft. Real air was used, with evaporation, condensation and heat exchange. The results showed that power requirements for the forcing fan were up to 20% less than for the exhausting fan for equal mass flow rates.

Jan 1, 1989

By R. Codell, D. L. Hughson

The authors benchmarked the integrated finite-volume code MULTIFLO against the analytical solution of Philip et al. (1989) for cylindrical underground openings. They found that the numerical simulation of dripping threshold flux was consistently higher than the analytical solution for rectangular and unstructured grids. The magnitude of this error was proportional to the alpha parameter characterizing capillarity. This error may bias estimates of seepage into drifts for repository performance towards nonconservatism.

Jan 1, 2002

By Michael J. Virnig, Murdoch W. MacKenzie, Michael R. Davis

The objective of this paper is to present preliminary capital and operating cost estimates (±25%) comparing conventional carbon-in-solution (CIS) with resin-in­solution (RIS) using AuRIX® 100 for the recovery of gold and silver from typical heap leach solutions. Preliminary testwork was carried out with AuRIX® 100 using real and synthetic leach solutions to determine the technical viability of the resin for gold/silver recovery and to provide process design parameters for the preliminary RIS circuit. The scope of the resin testwork was sufficient to support the level of accuracy applied in the capital and operating cost estimates. No parallel testwork was carried out with activated carbon. Industry standard design data and operating data from existing CIS operations were used as a basis for the comparison. Both the capital and operating cost comparisons indicate a substantial savings for a RIS circuit using AuRIX® 100 (- 14 to 18% in terms of capital and 25 to 35% in terms of operating costs) over a conventional CIS circuit depending upon solution flows and grade.

Jan 1, 1999

By Thomas J. Feeley

The US Department of Energy (DOE) is supporting the engineering development of three advanced physical coal cleaning technologies: selective agglomeration, advanced flotation and advanced cycloning. Each is capable of significantly reducing the pyritic-sulfur content of US coals. The objective is to provide the coal and electric-utility industries with a cost-effective option for addressing the SO, emission reductions required by the 1990 Clean Air Act Amendments (CAA). A secondary objective is to evaluate the potential of advanced coal cleaning for removing trace elements that are precursors to the formation of hazardous air pollutants (HAS). The proposed National Energy Strategy (NEE) and the 1990 CAA lay a foundation for a more efficient and environmentally sustainable energy future (1991). The need to use energy resources in an environmentally sound manner presents critical challenges and opportunities for coal preparation during the next decade, particularly regarding the control of SOS and HAY emissions. The principal challenge is the development of cost-effective coal preparation approaches for sulfur and HAY precursor removal.

Jan 1, 1993

By Ronald B. Gabitzsch, Norbert P. Hanke

During 1982, record advances have been achieved in the excavation of vertical shafts with a V-Mole (a vertical shaft boring machine). The V-Mole, supplied by Wirth GmbH in Erkelenz, West Germany, has been used in West German coal mines since the early seventies, mainly for the construction of internal shafts. In 1981, it was brought into the United States for the construction of a series of ventilation shafts with depths varying between 512 m (1680 ft.) and 622 m (2040 ft.) excavated to 7.0 m (23 ft.) diameter. These shafts were needed for the development of coal mines for Jim Walter Resources, Inc. in Brookwood, Alabama. After a description of the mechanized shaft excavation system with the V-Mole, the conditions and parameters, such as ground, shaft dimensions, and linings are discussed. These factors are important considerations for a technically and economically feasible utilization of the V-Mole. In addition, the advantages and disadvantages of using the V-Mole technology in comparison to other shaft construction methods are evaluated.

Jan 1, 1983

By Richard H. Adams

INTRODUCTION With the discovery and depletion over the years of near surface ore bodies, exploration targets are tending to be at greater depth or overlain by various types of overburden which in some cases extends to considerable depth or is heavily water bearing. Access to these types of deposits for exploration and development often requires vertical shafts. This paper discusses the concept of small shaft engineering and construction, primarily for underground exploration but also for use as a low tonnage production facility or for mine ventilation. The option of a small shaft may be attractive in a number of cases, some of which are: The underground exploration of a deposit at depth where minimal expenditure is desirable until the potential of the deposit has been determined. The exploration shaft in many cases later serves as a ventilation way and second means of egress. Production of ore in a small tonnage/high-grade operation where decline access is impractical. For ventilation where other types of openings are impractical or would delay start-up of mine operations.

Jan 1, 1987

By Betty L. Gibbs

A clear and accurate knowledge of the status of ventilation in an underground mine is essential to continuing safe operation. In a small mine with a few working faces, the problem is simple and can easily be solved by choosing the appropriate fan. In larger, more complex mines the problem of supplying the working faces with fresh air is a problem beyond the scope of 'finger in the wind' analysis. In today's climate of stiffer government regulation and mining company concern for the safety of workers, computer programs which analyze ventilation networks are helping mining companies meet the standards. The development of computer programs for ventilation network analysis is summarized. Early programs were developed at universities or government agencies and required large expensive computers. As computers have become smaller and less expensive, the development or revision of programs for micro computers has become more available. Prices have lowered to the point of affordability even for medium and small companies. A list of ventilation network analysis programs is provided along with a summary of capabilities, costs, and hardware requirements for each program.

Jan 1, 1987

In his keynote address at the 18th International Minerals Processing Conference (IMPC), R.P. King, director of the University of Utah Comminution Center, said "it will be the application of very fundamental physical principles that is likely to bring major advances in comminution technology (IMPC, pp. 39-45)." It is evident from the literature published in 1993 that many of these fundamental studies, particularly as they relate to single-particle fracture mechanics and mineral liberation, are starting to bear fruit. The beginnings of fundamental mathematical models for design, scale-up and control of comminution systems are now taking shape. Modeling/fundamentals Population balance models (PBM) have been used to describe grinding systems for 20 to 30 years. However, Williams and Meloy (IMPC, pp. 73-79) pointed out some of the inherent problems with this modeling approach and that there is no unique solution for the unconstrained PBM for grinding. Many of the current constraints used to back-fit selection and breakage functions were also shown to have problems. The need for a more fundamental means of determining these parameters was indicated.

Jan 1, 1994

By Harrie van Dijk

Feeding laterite nickel slurry into high pressure acid­leach (HPAL) autoclaves in an aggressive environment with slurries heated up to 200°C requires a special pump design. For decades the GEHO piston diaphragm pumps have been used for autoclave feeding at gold ore pressure oxidation plants with slurries up to l 77°C. Lessons learned from these installations have been instrumental in designing second generation feed pumps for processing laterite nickel with operating temperatures of 200°C and a flow rate of 400 m3/h. The Australian nickel industry is using momentarily 8 GEHO positive displacement piston diaphragm pumps. For this application six GEHO ZPM 900 "dropleg" pumps have been supplied to the Murrin Murrin project and two to Bulong.

Jan 1, 2000

By Stephen J. Navin, Francis P. D. Navin

Long-distance movement of various materials by conveyor is becoming common; therefore, it is no surprise that conveyors are frequently found in very long tunnels. In such long tunnels, there is a continual controversy between the tunnel operator's requirement for a maximum of clear space for the conveyor and vehicles and the investor's wish to make the minimum capital investment for excavation. This analysis shows that the question becomes more pressing as the tunnel becomes longer. The result given in this paper is a straightforward method by which an economic and operational optimal tunnel width may be selected for any specified tunnel length. Detailed computational formulas are developed relating costs of construction, vehicle operation, vehicle accidents, and conveyor downtime to both tunnel width and length.

Jan 1, 1985

By James A. Brierley, Rong Yu Wan

Bacterial pretreatment was evaluated as a process for enhancing gold recovery from a refractory ore from Newmont Cold's Cold Quarry deposit. This ore is refractory due to sulfide locking of the gold and preg-robbing carbon. The microbe Thiobacillus ferrooxidans effectively oxidized the sulfide component of the ore, but the preg-robbing carbon continued to be active. Thiourea was examined as an alternative to cyanide for extraction of the gold from the biooxidized ore. The thiourea, coupled with CIL, was effective for gold extraction resulting in up to 89% gold recovery for the sulfidic-carbonaceous refractory ore. The thiourea gold complex appears not to be bound by the preg- robbing carbon of the ore when in the presence of recovery carbon (CIL)

Jan 1, 1990

By W. Kennedy Gauger, Tim Oolman, Debra L. Bisson

Radian Corporation (Radian) has developed a process for treating Cr(V1)-contaminated soils that involves: 1) soil washing using an alkaline extractant, 2) biological reduction of Cr(V1) to Cr(II1) in the soil wash effluent, and 3) separation of Cr(II1) from the biologically treated effluent. Biological treatment has been demonstrated for immobilized cells in fluidized bed bioreactors and suspended cells in slurry bioreactors for Cr(V1) levels ranging from 30 to 600 mg/L which have been reduced to non-detectable levels (< 0.05 mg/L; method detection limit [MDL]) during hydraulic residence times as short as 12 hours. The resulting Cr(II1)-containing effluent stream was chemically treated to precipitate chromium hydroxide for removal by physical separation.

Jan 1, 1995

By Daniel J. Kennedy, George W. Klinowski

A significant portion of each mine is ventilated with the help of auxiliary fans delivering fresh air to the faces of its developing headings via flexible or rigid ducts. Quality and volumes of air delivered to the blind working faces are essential for creation of safe and acceptable conditions for employed crews. Well designed and properly maintained delivery systems are necessary in each mine. The Cape Breton Coal Research Laboratory, part of the Canada Centre for Mineral and Energy Technology located in Sydney, Nova Scotia, Canada, developed a tracer gas based technique which provides fast and accurate evaluation of any auxiliary ventilation system performance. In addition, important information about the system&apos;s behaviour is gathered which can be used for designing a similar system in comparable conditions.

Jan 1, 1989

By G. Knight

It is shown that the dust exposure of all underground workers varies greatly from day to day even though each man did the same job in the same working place each day. The variability follows a logarithmic normal distribution with a geometric standard deviation of about 1.6 for the three dust assessments; total respirable dust, respirable combustible dust and respirable quartz dust in both mines studied. The variability was homogeneous for all men and most jobs. The differences between men doing the same job was found not to be significant and it is suggested that the dust sampling program should determine the average for each job and use this as the best estimate of the exposure for each man.

Jan 1, 1980

At periodic intervals-typically at the end of each month, quarter, and year- the accounting department in each division of a company distributes a set of reports to the division&apos;s managers. These reports describe the financial performance of the division and its major departments over the time period. They identify the revenues generated from the division&apos;s products and the costs incurred in their production. The results from individual departments are combined to determine divisional results, and the results from individual divisions are in turn consolidated to determine the results for the overall corporation. Cost reports for each of these activities show actual amounts, budgeted amounts, and the differences between the two. This reporting is carried out for the individual period and for the year to date.

Jan 1, 1999

By S. S. Vasan, K. A. Natarajan, J. M. Modak

The biological removal of calcium from a bauxite ore in the presence of the soil bacterium Paenibacillus polymyxa is demonstrated. A column bioreactor that can be either operated in a fluidized-bed (FB) mode for coarser particles or in a total-recycle-slurry (TRS) mode for finer particles was designed, fabricated and tested for this purpose. For the efficient removal of calcium from the ore to the required levels, leach solution should not be allowed to accumulate in the reactor. Therefore, the solution needs to be drained out periodically. Cascade leaching was found to be more effi¬cient. A direct correlation between pH changes in the leach solution and calcium solubility could be made. More than 85% of the calcium could be removed through cascade leaching.

Jan 1, 2000