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By M. Carvalho, R. Bicallho, M. Queiroz, R. Gomide, V. Silva, R. Toubes

Since it is becoming increasingly important, from an environmental viewpoint, to minimize blast vibrations induced in urban dwellings and improve rock fragmentation in order to reduce costs with loading, transportation crushing and grinding, a cooperative research project was established between Companhia Vale do Rio Doce - CVRD and the Blasting Research Group in the Department of Mining Engineering at Escola de Minas - UFOP to investigate which elements interfere on ground vibration, air blast, flyrock and rock fragmentation related to rock blasting activities at Conceição Mine, located in Itabira city, state of Minas Gerais, Brazil. This research also involved development of a new explosives formulation in order to minimize the total blasting cost. This paper presents the general scheme of the research running from May 1995 to May 1997 and a summary of the results obtained in the field tests that were carried out in this mine.

Jan 1, 1998

By K. H. McDaniel, K. G. Wallace

This paper describes the development of a Windows-based interactive mine ventilation simulation software program at the Waste Isolation Pilot Plant (WIPP). To enhance the operation of the underground ventilation system, Westinghouse Electric Corp. developed a program called WIPPVENT. While WIPPVENT includes most of the functions of the commercially available simulation program VNETPC from Mine Ven- tilation Services Inc. and uses the same subroutine to calculate airflow distributions, the user interface was completely rewritten as a Windows application with screen grap-hics. WIPPVENT is designed to interact with WIPP ventilation-monitoring systems through the sitewide central monitoring system. Data (e.g., air quantity and differential pressure) can be continuously collected from the underground ventilation remote-monitoring and control system and from the mine's weather stations (psychrometric data). Furthermore, WIPPVENT incorporates regulator characteristic curves specific to the site. The program utilizes this data to create and continuously update a real-time ventilation model. This paper discusses the design, the key features and the interactive capabilities of WIPPVENT.

Jan 1, 1998

The Boliden Aitik concentrator in Sweden processes 2,000 tph of low grade copper ore. The plant consists of five grinding lines feeding four bulk flotation banks with a scavenger concentrate regrind mill, and a column cleaner circuit with a regrind mill. The authors installed a model-based expert, optimizing control system to maximize copper recovery in the bulk flotation circuit while maintaining an appropriate copper grade in the cleaner feed. The optimizing control system uses on-line assays and calculates and implements set points for cell pulp levels, air rates and reagent addition rates. It combines the power of a dynamic population balance model which estimates mineral liberation in each stream, an optimizer which computes appropriate set points and a rule-based module which implements the strategy. The benefits have been evaluated over three months. The model-based expert, optimizing control system generates a measurable increase in copper recovery, around 0.5 per cent and an optimized bulk concentrate grade. The need to maintain the optimizing control system and other practical aspects are discussed.

Jan 1, 1998

By S. Liu

A general account of nitrogen-generating systems, including the surface fixed, surface-mobile and underground-mobile types is presented. These systems have recently been adopted in coal mines in China to prevent and extinguish fires. The paper stresses nitrogen -injection technology and relevant systems of monitoring and stopping air leakage.

Jan 1, 1998

By K J. Kidd

There is general understanding of hoisting systems throughout the mining industry. However, the relative importance of the various parameters influencing hoist selection and utilization is not completely understood. In order to determine if these parameters can be identified and prioritized, data covering 613 hoist installations were compiled. The 613 installations represent hoisting systems in 30 countries on six continents. This study compares data to historical trends, correlates design parameters in an attempt to identify underlying selection criteria, and comments on the apparent trends in recent developments in hoist design.

Jan 1, 1998

By Paul Clifford

The Florida Institute of Phosphate Research (FIPR) is an independent, state of Florida research agency. It was created in 1978 to conduct research to enhance the competitiveness of the Florida phosphate industry. The institute also conducts research to prevent, minimize or rectify environmental impacts caused by the industry. And it helps educate the public concerning phosphate-related technology and issues. FIPR is funded by a severance tax on the industry and is governed by a five-member board of directors appointed by the governor. FIPR's research is playing a role in enhancing the competitiveness of the Florida phosphate industry. Its technology research program seeks to improve surface mining and pipeline transportation while reducing the energy cost for pumping phosphate matrix. It is developing new and improved methods of beneficiation and fertilizer production. This includes new process flowsheets and on-line analyzers and process control methods. FIPR is also developing uses for the phosphogypsum byproduct of phosphoric acid production and evaluating the risks associated with its uses.

Jan 1, 1998

By B. H. Kim

The use of a 25.4 mm diameter water-only hydrocyclone for separating fine-size (-150 µm), high-density (>4.5 g/cc) particles from similar-size, lower-density (2.65 glee) particles was investigated. It was found that a single-stage separation recovered nearly 90% of the heavy minerals (7.0 g/cc), while achieving a volume reduction of about 70%. The use of dense medium in a single stage improved volume reductions to 90% at similar heavy mineral recoveries. In addition, computer simulations of a three-stage circuit were performed, which showed that recoveries approaching 97% with volume reductions of 95% were possible.

Jan 1, 1998

By A. Vien

A major thrust in Industrial automation over the past few years has been the exploration and incorporation of higher level (supervisory and optimizing) control strategies aimed at more fully exploiting the existing control system infrastructure. There is little doubt that this is worthwhile pursuit, however, one must not lose sight of the maintenance and development requirements of the basic control system. Statistics on loop performance indicate that this too is an area of considerable potential. In this paper the authors look at some of the less elegant, but arguably equally important issues in mineral processing plant control. The focus is on controller structures, loop tuning, sampling, filtering, and some of the other principal components of the regulatory control foundations. In many cases significant improvements In control performance can be achieved by getting back to the basics.

Jan 1, 1998

By R. R. Klimpel

The efficiencies of plant scale comminution processes are often evaluated by various indices that are calculated and/or measured somewhat independent of the performance of any associated downstream froth flotation processes. In order to compare some specific comminution factors such as energy utilization, media consumption, equipment utilization time, etc. comparisons of comminution efficiency independent of flotation behavior are appropriate. However, as more and more detailed plant level information is gathered on the joint and highly interactive nature of comminution and froth flotation, it is becoming increasingly obvious that knowing and using simple efficiency indices are not enough. What is needed are more performance related measures of the efficiencies of the combined size reduction -froth flotation system for effective plant level economic optimization to occur. The purpose of this paper is to present some examples of important interactions that influence the joint efficiencies of size reduction and froth flotation processes.

Jan 1, 1998

By R. A. Haney

The Mine Safety and Health Administration has developed a model to estimate diesel particulate (dp) exposures in underground mines. The estimate uses either in-mine measured dp concentrations or engine manufacturers' standardized emission data and through a series of calculations estimates full shift dp concentrations by applying standard engineering principles of ventilation, control technology and work cycle. This model, in the form of a computer spreadsheet, provides the mining industry with a method to estimate diesel particulate levels and determine the impact of various diesel particulate controls on occupational exposure to dp in underground mines. A detailed description of the estimator and several examples demonstrating the results are provided.

Jan 1, 1998

The 71st Annual Meeting of the Minnesota Section of SME and the 59th Annual University of Minnesota Mining Symposium were held jointly April 14-16, 1998, in Duluth, MN. Registration was estimated at 450 people, about the same as last year's attendance. A short course on mine productivity and a trade show that included about 75 exhibitors were also held in conjunction with the SME meeting. This year's theme was "Iron ore and integrated steel - where are we going?" Although generally optimistic in the near term, the general feeling among the attendees is that the industry faces serious competitive challenges. The iron mining industry in Minnesota experienced a tremendous rebound from the devastating downturn of the 1980s. Today, however, all seven of Minnesota's taconite plants are operating at full capacity. And these high production levels are expected to continue during the next several years. Longer-term, however, Minnesota's producers face an increasingly competitive worldwide market, including stiff competition from Canadian operations. Because of the increasing competition, industry representatives in Minnesota believe that it is critical to strengthen their operations. To accomplish this, companies are looking to: ? Further reduce production costs. ? Bring new technologies into their operations. ? Develop value-added facilities such as direct-reduced iron. ? Expand their markets. The industry is also seeking more collaboration between industry and government. The National Steel Pellet Co. and Minntac are looking at using ported kilns, which would reduce energy consumption significantly. Cleveland Cliffs, EVTAC, Northshore Mining and Minnesota Iron and Steel are all looking at building value-added plants. One such project that received attention among the attendees was Minnesota Iron and Steel's proposed $1.2 billion combined mine, taconite plant, direct reduced iron facility and steel production facility. If the operation is built, it would produce about 3.4 Mt/a (3.39 million ltpy) of direct-reduced iron pellets. Financing is pending. An announcement is expected in the fall of 1998. The pellets, containing 70% iron, would be processed into steel in electric arc furnaces. The steel produced would then be processed into hot-rolled coil, which is used by the appliance and automobile industries. The keynote addresses and technical sessions focused on these issues as well as on environmental issues.

Jan 1, 1998

By Kevin DeSomber, Scott Bird

Larger grinding mills continue to utilize large gear-driven drives or electrical wraparound drives. The panel will include presenters from operations with large mechanical and electrical drives. JIM HANDLEY: Before we get to the third and final session, I want to introduce my co-conspirator for this session, John Mansanti. John is manager of milling with Newrnont Gold Company, Carlin, Nevada, and was very active in securing participation in this innovative symposium. I'm Jim Handley and I'm with Cyprus-Amax Minerals at the Sierrita copper and molybdenum mine. Our third presentation is titled "Geared Up or Wrapped Up?" I hear this topic discussed, but never at great length. I think that's because the opinions are fairly strong and diverse, and people generally aren't reinforced properly in their arguments. The first person to enlighten us on this topic is Scott Bird. He has more than 20 years with Kennecott, is a graduate in metallurgical engineering from the University of Utah, and is currently operations superintendent and deals with this phenomenon every day.

Jan 1, 1998

By J. H. Kempton

The scrutiny given to model predictions of pit-lake water quality has focused attention on the uncertainty associated with long-term predictions. Although comparison of probabilistic predictive modeling of water quality in existing pit lakes indicates that short-term predictions can bracket most parameters, uncertainties in wall-rock reactions and the stability of groundwater composition and climate remain unquantified. This overview of the uncertainties associated with longer-term predictions is presented as support for those considering policy decisions that must be made in the absence of reliable estimates of future conditions.

Jan 1, 1998

By C. I. Richman

The E h potential during of a iron reducing bacteria such as Aquaspirillum Magnetotacticum (A.M.) can be predicted by a growth model. It also reflects the adsorption of Fe+2 Cu+2 and Mn +2 ions, that can be incorporated into magnetic material called magnetosomes. The Ferric ion concentration during controlled growth of Thiobacillus Ferrooxidans (T.F.) is a function of the bacteria population curve, while A. M. ferrous ion concentration is a function of the integral of the population curve. Charting of the redox potential of T.F. during batch oxidation of refractory ores such as pyrite and pyrrhotite can be helpful to establishing onset and rate the bulk bio-oxidation rate. The onset of biooxidation is marked by an increase in Fe +3 ions that can be correlated with increased growth due to adsorbed electrons.

Jan 1, 1998

By D. D. Runnells, D. C. Keith, G. A. Doyle, J. Tilk

Until the suspension of conventional operations in 1996, the White Pine Mine was the second-largest active underground copper mine in the United States, underlying an area of approximately 30 km2 (13 sq. miles) in the Upper Peninsula of Michigan. The mine operator intends to initiate in-stope solution copper mining by circulating a solution (lixiviant) of mine water, sulfuric acid and ferric iron through rubblized ore. As planned, the solution would be retired in the mined-out stopes following completion of the solution-mining activities. Investigations into the fate of the retired solution indicated that the solution, through time, would change from an acidic, metal-rich solution to a near-neutral, reducing solution containing much lower concentrations of metals. Investigations included reaction-path modeling (EQ3/6) and laboratory and in-mine tests. The combination of neutralization and reduction will result in precipitation of most metals, primarily as metallic sulfates, chlorides and sulfides.

Jan 1, 1998

By C. Sun

Due to unfavorable geological condition, excessive deformation of mine drifts occurred in a large underground copper and nickel mine. In searching for a solution, a comprehensive underground monitoring program was implemented and the opening convergence and the surrounding rock deformation were monitored. A large number of field data were collected and thoroughly analyzed. The convergence and deformation as function of time and depth were determined and a rock stability index was proposed. Based on the deformation-time and deformation-depth relations, critical deformation times and locations were identified and defined as characteristic values to be used for mine opening and support designs. The characteristic values are critical in the application of two-step supporting system, and the determination of support parameters. The application of the method developed in this study has demonstrated that this practical approach in support design and installation is effective. With the two-step supporting system, a long-term drift stability can be achieved in the mine.

Jan 1, 1998

By H. R. Manouchehri

The responses of calcite, feldspar, and quartz minerals In a laboratory free fall electrostatic separator, before and after tribocharging with stainless steel, PVC, and copper plates, have been investigated. The effect of H3BO3 and BaCl2 chemicals pre-treatment on the electrical properties of the minerals is examined. The changes in the electrical properties are discussed with the determined charge, dielectric constant, and electrical conductivity of the mineral samples. Electrical properties of the minerals and their responses to the electrical field during separation, after tribocharging and chemical pre-treatment, are explored for the need to characterize the electrical behaviour of the minerals.

Jan 1, 1998

By M. Bleeck

Calcium carbonate (CaCO3) is one of the most ubiquitous and versatile minerals found in the earth's crust. Its availability, attractive physical properties and relatively low processing cost make CaCO3 the most widely used filler material today. It is mined in three different forms - chalk, limestone and marble. Each physical form of CaCO3 has different qualities due to differences in postdepositional geology. But the chemical composition remains the same, with CaCO3 an inert component of the finished product. In the past, the paper industry largely left CaCO3 by the wayside, as it cannot withstand the acid-based papermaking process. But conversion to an alkaline system by many US mills changed this picture. Carbonate suppliers have put time and effort into research and development, demolishing barriers and creating new possibilities for what is a simple, natural product. By controlling particle size, size distribution and particle charge, the industry uses ground calcium carbonate (GCC) as a performance enhancer and as an extender for more expensive ingredients. It is estimated that the United States uses 3.6 to 4.1 Mt/a (4 to 4.5 million stpy) of CaCO3. Consolidations and mergers are taking place in the industry. Of the 12 major GCC producers in operation nine years ago, seven are left. Mineral Technology (US) is the dominant precipitated calcium carbonate (PCC) producer with more than 50 satellite plants worldwide. Other producers include Georgia Marble (French); Franklin Industries (US); OMYA (Swiss); J.M. Huber (US); ECC (English); and Filler Products (US). Global Stone PenRoc (Canada) is the only newcomer. In addition to this group, there are three small producers left in North America, each with a capacity of less than 100 kt/ a (.110,000 stpy). The trade organization operating as the Pulverized Limestone Division of the National Stone Association renamed itself the Pulverized Mineral Division, to increase its membership pool. The US paper industry is a predominant GCC con¬sumer, using approximately 800 kt/a (882,000 stpy) at an approximate cost of $130/t ($1.43/st). European paper mills pioneered alkaline papermaking. In the early 1960s, they began using GCC as filler and soon thereafter added GCC to their coating formulations. A decade later, the North American paper industry followed suit. The conversion from acid to alkaline paper production benefits the economic and performance aspects of the industry. Less pulp is needed, paper machine maintenance and effluent treatment costs are reduced, and sheet strength, opacity and brightness are increased. Perhaps most important to the reader, the sheet is desensitized to ultraviolet light, extending the paper's archival ability. CaCO3 can provide the papermaker with additional control of his paper. For example, PCC has long supplied the tobacco industry with a means to slow down the burning rate of cigarettes. Due to enhanced performance with regard to bulk and opacity, filler PCC use has risen to 1,500 kt/a (1,650 stpy) in the United States, at an approximate price of $130/t ($143/st). The majority is produced onsite at the paper mill, using "satellite plants." This concept reduces freight cost because only quicklime (CaO) is shipped to the mill, not CaCO3 slurry. The future of CaCO3 is encouraging. The amount of natural ground CaCO3 used is expected to double by the year 2005 to approximately 8 Mt (8.8 million st) worldwide. Acid papermaking practices will feel an increasing pressure to convert to an alkaline process as larger volumes of GCC containing paper enter the recycling market. CaCO3 reserves are plentiful. They will supply the ever growing demand for increasingly sophisticated paper. The plastics industry is supplied with almost 900 kt/ a (990,000 stpy) GCC at an annual growth rate of 4% to 5%. The price of a functional, inorganic filler, surface modified for the plastics industry, has an average selling price of $220/t ($243/st). GCC represents the most common filler, creating a product with higher gloss, better dielectric properties, impact resistance, weatherability and shrinkage control. CaCO3-filled plastics surround us - auto hubcaps and dashboards, shower enclosures, floor tiles, wire coatings, microwave dishes and Tupperware. The caulking and sealant industry is an enormous GCC user, with annual consumption requiring 1.13 Mt (1.2 million st) at about $44/t ($48.50/ st). Caulking and sealant may be highly filled with GCC yet undergo no adverse flow effects, with a narrow particle-size-distribution filler decreasing the binder demand. The CaCO3 industry, as well as the carpet industry, are more or less tied to the growth rates of the construction industry. It is estimated that the carpet industry uses some 680 kt/a (750,000 stpy) of GCC at about $25/t ($27.50/st). The paint industry uses approximately 300 kt/a (331,000 stpy) at a 1 % to 1.5% annual growth rate. Here, too, GCC is the dominant filler. It is used to enhance flow characteristics and color uniformity. It also extends costly titanium dioxide, creates sheen and controls roughness, hardness and tack. More CaCO3 should be used in the future as industry shifts from solvent-free or water-based formulations that can accommodate higher GCC volumes. CaCO3 is not imported or exported in any great quantity. Most areas have reserves of their own and the selling price is relatively low. Even so, quality varies from deposit to deposit. As our needs become morespecific, it remains a challenge to provide varying industries with a fitting product.

Jan 1, 1998

Ferric (Fe3+) ions are omnipresent in flotation circuits. Depending on pH and the nature of the ore body, Fe3+ ions may play a role in the adsorption of thiol collectors on sulfide minerals. To investigate this possibility, a two-compartment galvanic coupling cell was designed. This cell was used to monitor changes in contact angle of a sulfide mineral in one compartment, while varying concentrations of the Fe3+ ions in the other. The results showed that Fe3+ ions promote xanthate adsorption as indicated by the increase in contact angle. Implications of this finding in sulfide mineral flotation in general will be discussed.

Jan 1, 1998

By Walter E. Cook

BOB FALCONER: Without further ado I'm going to introduce our first speaker, Walt Cook. Walt is president of Strata Resources and is here with his business partner Joe Nenni. Joe would you stand up here. You'll be on the tag-team with Walt. Walt and Joe are in a consulting business associated with coal as well as metal and nonmetal industries. Their presentation will be on gainsharing. WALTER COOK: How many of you have gainsharing plans in place currently at your location? [show of hands] A considerable number-more than about half the room. Of those plans, how many of them do you consider as meeting your needs and being successful? [show of hands, far fewer, general audience laughter] You have all at least heard the word "gainsharing." Some of you undoubtedly aren't quite sure what gainsharing is, while others obviously have gainsharing plans in place and are looking for ways to improve them. In the short time I have now I'll be able to give you a precursory look at gainsharing and some brief ideas on where to look to improve your current plans. Over the years, I've found that it is often best to explain gainsharing by comparing it to other forms of employee compensation

Jan 1, 1998