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The most complete mining show ever held in the United States and the largest exposition of its kind to be held anywhere in the world in 1988. That's how the American Mining Congress is billing its "MINExpo International '88," to be held April 24-28 at Chicago's McCormick Place, the largest exposition facility in the country. MINExpo International '88 will combine for the first time two previously separate AMC-sponsored shows - the International Coal Show and the International Mining Show. Starting with the 1988 show, MINExpo International will be held every four years. The next show, in 1992, will be held in Las Vegas. The MINExpo in Chicago will feature more than 500 mining equipment and services exhibits covering 3 hm2 (320,000 sq ft) of exhibit space. Exhibitors will display products ranging from small safety devices to large earth-moving equipment. MINExpo is one of the few trade shows selected by the US Department of Commerce for its Foreign Buyer Program. Commerce is working with US embassies around the world to publicize MINExpo and to form delegations of visitors from many countries. Overseas visitors to the show will be assisted at an on-site International Business Center. It will provide currency exchange, translation, and other services to foreign buyers. Registrants at MINExpo will also be able to attend their choice of 27 morning-only program sessions. At these sessions, international mining experts from industry, government, and academe will analyze technical, strategic, and policy matters and discuss the outlook for the industry. "Toward the 21st Century" is the theme of this year's program. The technical workshops and managerial seminars are designed to assist mining executives, engineers, and geologists as well as mine superintendents, managers, and foremen in handling their responsibilities. Based on previous attendance at AMC international mining shows, the association says that more than 25,000 persons are expected to attend the Chicago show. It is expected that approximately 15% of the attendees will be from foreign countries. The Soviet Union will be among those exhibiting at MINExpo. The Russians have leased more than 2.8 dame (3000 sq ft) of space to display their mining machinery and equipment. It is the first time that the Russians have joined in an exhibition of mining equipment in the US. The two largest manufacturers of mining equipment in the Soviet Union, Setmash and Avtoexport, will put on display in Chicago a variety of Russian-made equipment. It will range from 100 t (110 st) heavy-duty dump trucks and diesel engines to drilling, hoisting, and conveying equipment. In addition to some 400 US exhibitors of mining equipment and services at MINExpo, nearly 100 companies will be present from other major mining nations such as Australia, Canada, Great Britain, Japan, the Netherlands, and West Germany. And, for the first time, a Chinese manufacturer will take part in the AMC show, participating with its US marketing partner.

Jan 3, 1988

By J. D. Miller

The sedimentary western phosphate deposits of Idaho, Montana, Utah, and Wyoming tend to be calcareous and generally carry a significant amount of dolomite along with collophanite. In some cases, such as the Smokey Canyon Mine, Afton, Wyoming, the ore will also contain mudstone, and in this case the aluminosilicate minerals (clay, feldspar, etc.) together with some dolomite are floated from the collophanite in column flotation cells with an amine in order to meet product specifications (31 % P205) (Service et al.). In other cases, such as the SF Phosphates Limited Mine, Vernal, Utah, the ore is treated by traditional fatty acid flotation of the collophanite with mechanical flotation cells (Weber, 1986). Preliminary tests have now been conducted to evaluate air-sparged hydrocyclone (ASH) technology for the flotation of western phosphate ore. For this preliminary study, samples were taken from the hydrosizer overflow stream (18-21 % P205) at the SF Phosphates Limited Plant in Vernal, Utah for scavenger flotation testing with the 2-inch ASH system in laboratories at the University of Utah. Selected design and operating variables are being studied, and the initial results show that satisfactory separations can be achieved by high-capacity ASH flotation at appropriate operating conditions. For example, with single-stage ASH flotation 80% recovery can be obtained with a scavenger concentrate grade of about 26% P2O5. These results are comparable to, or better than, those obtained at SF plant operations with conventional flotation cells and suggest that ASH flotation technology can be used to good advantage in the phosphate industry. Of course, research should be continued to consider other process streams, optimize the separation efficiency, and evaluate larger diameter ASH units.

Jan 1, 1993

By Verya Nasri

This paper will present the design and construction of a deep underground station of the Réseau Express Métropolitain (REM) project; the Édouard Montpetit station. The Édouard-Monpetit station is an interchange station that will connect the deeply sitting REM tracks to the existing metro station of the same name located closer to the surface. Édouard-Montpetit station is expected to be the deepest in North America, surpassing the famous Forest Glen Station. The various challenges and solutions put forth for the successful completion of this underground work are presented to serve as a valuable example for future deep excavation performed in urban area, in the close vicinity of highly sensitive structures.

Jun 13, 2021

By J. Korak

Belt conveyor systems, long the standard transportation technique in soft-rock open-pit applications, are encountering growing interest in the hard-rock open-pit sector as economic factors force companies to seek an alternative to costly truck haulage. A general review of mine conveyor systems is followed by detailed analysis of the mobile and semi-mobile in-pit crushing plant essential to successful use of mine conveyors. A final section presents case studies of three crusher-conveyor systems handling overburden, copper ore and granite.

Jan 1, 1985

By Parris A. Lyew-Ayee

The Government or Jamaica has just completed agreements with four of the five bauxite/alumina companies operating in Jamaica. These companies are Kaiser, Reynolds, Alcoa, and Alcan, and the Agreements came into effect on February 1, 1980. One of the results of these new Agreements is the Acquisition of all company-owned bauxite lands by the Government and the rationalization of bauxite reserves.

Jan 1, 1980

By WILLIAM M. CROSS, ALBERT ROMKES, BERNARDO MORENO BAQUEIRO SANSAO, Jon J. Kellar

In this research study, the interaction of particles with substrates of different roughness magnitude was investigated. Particle surface treatment, relative humidity (RH), and surface roughness levels were controlled in order to achieve separation of different particles by applying removal forces. Three different approaches to reproducibly roughen surfaces were used. Initially, glass disks were laser engraved to create a reproducible, controlled roughness substrate. However, the laser engraving method produced surface features that were much greater in scale than the particles. These scale differences were such that the substrates produced were not of value to this research. The second option investigated to induce reproducible substrate roughness was to scratch the glass disk using sandpapers of known grain size. A third approach to establish reproducible roughness was to use fine stainless-steel wire mesh substrates. In tests with sanded glass disks, the interfacial energy of plasma-cleaned (hydrophilic) glass beads had a high variation at 40% RH, showing non-uniformity of area of contact between particles and substrates. As the RH increased, it was expected that the interfacial energy of hydrophilic particles would increase, but this behavior was not observed. In addition, comparing the interfacial energy results of hydrophilic particles with hydrophobic particles, a region with significant interfacial energy difference was not identified. In the case of the stainless-steel mesh substrate, the mesh asperities and particle dimensions were comparable. Thus, the smaller particles had more area of contact with the substrate than the larger particles. For the plasma-cleaned (hydrophilic) beads, the recovery values had an average of 92.5% recovery when the RH was between 46 and 85%. For the hydrophobic beads, the average recovery was 19.0% when the RH was between 46 and 75%. Thus, the hydrophobic characteristic of the particle influenced its lower interaction with the mesh substrate. The difference in recovery can be exploited to achieve separation of particles based upon adhesive forces.

Nov 30, 2021

By P. Mills

The four top barite-producing countries in the world are China, India, Morocco and the United States. China is currently the largest exporter of barite followed by India. More than 95 percent of the barite mined today is used by the petroleum industry as driller’s mud. The rest is used in the industrial market and the medical field. Most of the barite mined in the United States is in Nevada. This year, mining activity has increased due to an increase in oil exploration/development. This was caused by an increase in the crude oil prices.

Jan 1, 2005

By Joern Katzer

It is vitally important to any tunnel project to have an accurate and reliable survey control network inside the tunnel for layouts, as-built surveys, and to provide guidance to the tunnel boring machine (TBM). However, the concepts and methodology to provide such a survey network are sometimes not well understood. For example, the first anticipated survey task that takes place during the bidding process is often ignored, which is to provide a comprehensive survey network preanalysis for the surface network and tunnel traverse based on survey statistics that will be used to make informed decisions on the survey requirements and methodology. Instead, these steps are often only vaguely based on previous results and prior tunneling experience. But each tunnel is different, and a solution that worked for one tunnel project might be unsuitable for another. The purpose of this paper is to provide tunnel project engineers, managers and surveyors with the general concepts for tunnel survey methodologies and examines several statistical tools for a basic horizontal and vertical tunnel survey preanalysis. These survey statistics tools provide useful estimates of the expected lateral and vertical tunnel traverse accuracies, but are not a replacement for a comprehensive tunnel network preanalysis. The proposed formulas do not take centering errors into account, are using average distances for each traverse leg, and assume that the survey data is free of outliers in the measurements. It is very important that the estimated instrument accuracy is based on true values that are reflective of measurement precisions that are actually achievable inside the tunnel to provide accurate results.

Dec 1, 2022

By S. Gering, R. Ruiz, C. H. Calderon-Arteaga, J. Barrios

"Located in the northeast corner of Zacatecas State, Mexico, the Peñasquito operation is comprised of the Peñasco and Chile Colorado (Brecha Azul) deposits. Openpit mining (prestripping) began in 2010 and full production commenced during 2011. The openpit mines feed both a sulfide concentrator (mill) and a heap leach pad. The project is owned by Goldcorp Inc. Peñasquito is a poly metallic deposit with Au, Ag, Zn and Pb being recovered as payable metals.As a consequence of lower grade ores expected with advancing mine life, Peñasquito is facing a declining metal production profile. To maximize returns and asset value, plant modifications, including the addition of a carbon prefloat circuit and a pyrite leach circuit to improve recovery, are currently being undertaken. This carbon prefloat circuit will enable the recovery of precious and base metals from carbonaceous sediments. This material is currently being stockpiled. With the associated increase in complexity in the process circuit, the requirement of the ore control system to accurately predict ore feed characteristics is critical to maximizing metal recovery at the Peñasquito operation. The addition of the carbon prefloat circuit was also a key driver in allowing the Chile Colorado openpit to be developed.These conditions alongside Goldcorp’s drive to increase profitability and maximize net asset value has created challenges. These challenges are numerous and multifaceted. However, the ability to accurately route materials from the ore control system is critical to site success, and some of these challenges have been overcome by the adoption and implementation of a new ore control (OC) technology. Examples of these technological innovations in the ore control program are discussed in this article and include improvements in geomodeling, material routing and reconciliation. Successful implementation of these elements has led to significant improvements in selectivity, performance and data management, while reducing the variance between planning and execution, thus helping to drive overall improvement across the operation."

Jan 7, 2018

By A. E. Torma

The efficiency of Thiobacillus ferrooxidans in the desulfurization of a high-sulfur content New Mexico coal was demonstrated. The optimum condition of process variables were found to be pH = 2.3, particle size = 38 µm, pulp density 14.1% (W/V) and temperature 33.9°C. Larger scale experiments carried out with these optimum conditions resulted in coal desulfurizations above 97%, while in sterile controls this was only about 10%.- The rate of desulfurization was described with an exponential expression with respect to the effects of coal particle size. The effect of pulp density on coal desulfurization was quantified by a Monod type equation. The apparent activation and deactivation energies, the frequency factor and temperature coefficient were derived from the effects of temperature to be ?aE - 11720 cal mol-1 and A = 30.44 mol dm-3s-lin the range of 20 - 35°C; ?Ed = 43930 cal mol-1 and A = 9.82 x 10-39 mol dm-3s-1 in the range of 35 - 45°C; and Q10 = 1.94 in the range of 20 - 30°C. The thermodynamic values [(?G+, ?H+ and ?S+)] of the activated complex were calculated. The generalized second order regression equation relating the degree of biodesulfurization of coal to the leach parameters was shown to adequately predict coal desulfurization within the range of process variables studied.

Jan 1, 1987

By B. A. Wills

With the increasing need to mine lower grade ores, high energy-related costs in comminution are of major concern. Very fine grinding is needed to liberate the very fine mineral particles in these ores. Not only is this expensive but it leads to greater losses in 'slimes'. In the early 1970's, 50% of the tin mined in Bolivia, 30% of the phosphate mined in Florida and 20% of the world's tungsten were lost in this way (Somasundaran, 1979). Gravity concentration techniques become unacceptably inefficient for particle treatment below 25-50µm, and even flotation fails in the ultra-fine range. Two approaches can be adopted to try to overcome this problem. The first involves increasing the efficiency of existing equipment or developing new slimes treatment processes. Gravity devices such as the Bartles-Mozley concentrator have been developed for this purpose and good recovery has been reported from 100µm down to 5µm. Such machines, however, have relatively low throughputs, so that large areas of plant space are generally required. Flotation is rapidly growing in importance for the treatment of ultra-fine minerals traditionally treated by gravity concentration.

Jan 1, 1986

By William W. Edgerton, Moussa Wone, David H. Corkum, Carlton M. Ray

"The DC Clean Rivers (DCCR) Project is a 25 year, $2.6 Billion court ordered project to reduce combined sewer overflows (CSOs) discharging into the Potomac and Anacostia Rivers and Rock Creek, and also reduce flooding in the northern areas of the District of Columbia. Like all massive infrastructure programs, DCCR faced technical challenges, management challenges, risks of cost and schedule overruns, procurement challenges, and financing challenges. While DC Water is no stranger to large capital improvement projects (CIP), this CSO Program represents a once in a lifetime event for the Owner requiring the assembly of a single purpose team to implement. Some of the DCCR Project team’s most successful accomplishments to date are attributable to its introduction of early contractor involvement (ECI) to thoroughly vet the work from the perspective of the future constructors, development of functional baselines to share risks that are difficult to price and reduce reliance on geotechnical baseline interpretation during tunnel excavation, and attainment of financing through Municipal Century Green Bonds based on using design criteria of a minimum of 100 year life for the structures to establish intergenerational equity and fairness. This paper will discuss these innovations in detail and provide some sets of recommendations for the underground industry on when and how to use different approaches to better manage projects of this magnitude. INTRODUCTION The District of Columbia Water and Sewer Authority (DC Water) is an independent multi-jurisdictional authority that was established in 1996. Its primary mission is to provide water distribution services to more than 640,000 residents in the District of Columbia (District), and sewer treatment and disposal to 1.6 million residents of the District, Montgomery and Prince George’s counties in Maryland and Fairfax and Loudoun counties in Virginia."

Jan 1, 2016

Refractory copper ores (CROs) in central Africa contain copper minerals that are locked up in a micacious solid matrix or associated with carbonate, sulfide and phosphate minerals. Several researchers have reported that the recovery of copper from CRO material by an acid-leaching process is not economically feasible, due to the presence of excess gangue-acid-consuming minerals such as calcites, dolomite, asbolane and iron oxides. Since the proportion of acid-insoluble copper (CuS) is about 28% of total copper and total free sulfur is extremely small, sulfide flotation was considered unfavorable. Consequently, hundreds of millions of tons of CRO material have been stockpiled specifically at the Nchanga Mine of Zambia. In terms of copper distribution in CRO material, a significant portion of total copper exists as carbonates (39%) and oxides (17%), while 28% of the copper is acidinsoluble (CuS). The rest of the copper is in the form of carbonates (16%) and (hydr) oxides (17%). This means that only about 72% of total copper is recoverable through the non-oxidative acid-leaching process. In this study, batch leach tests were performed on CRO solids (d95 = 95%) to establish the gangue acid consumption values at different feed pH values and to evaluate the leaching characteristics of copper, manganese and iron within the CRO material. Subsequently, continuous leach tests were performed on CRO solids (106 um, 80% passing) using optimum leach conditions derived from batch tests. This paper aims to show that sustainable copper recovery can be achieved by selecting leaching conditions whereby gangue acid consumption (GAC) values become significantly small and the final concentration of manganese and iron in the leach solution are appreciably low.

Nov 1, 2011

Refractory copper ores (CROs) in central Africa contain copper minerals that are locked up in a micacious solid matrix or associated with carbonate, sulfide and phosphate minerals. Several researchers have reported that the recovery of copper from CRO material by an acid-leaching process is not economically feasible, due to the presence of excess gangue-acid-consuming minerals such as calcites, dolomite, asbolane and iron oxides. Since the proportion of acid-insoluble copper (CuS) is about 28% of total copper and total free sulfur is extremely small, sulfide flotation was considered unfavorable. Consequently, hundreds of millions of tons of CRO material have been stockpiled specifically at the Nchanga Mine of Zambia. In terms of copper distribution in CRO material, a significant portion of total copper exists as carbonates (39%) and oxides (17%), while 28% of the copper is acid-insoluble (CuS). The rest of the copper is in the form of carbonates (16%) and (hydr) oxides (17%). This means that only about 72% of total copper is recoverable through the non-oxidative acid-leaching process. In this study, batch leach tests were performed on CRO solids (d95 = 95%) to establish the gangue acid consumption values at different feed pH values and to evaluate the leaching characteristics of copper, manganese and iron within the CRO material. Subsequently, continuous leach tests were performed on CRO solids (106 um, 80% passing) using optimum leach conditions derived from batch tests. This paper aims to show that sustainable copper recovery can be achieved by selecting leaching conditions whereby gangue acid consumption (GAC) values become significantly small and the final concentration of manganese and iron in the leach solution are appreciably low.

Jan 1, 2011

By N. L. Dorset, K. L. Heasley

Unfortunately, mining and mining accidents have gone hand-in-hand since man first started to extract ore from the ground. In the first published treatise on mining, De Re Metallica, Georgius Agricola (1556) stated that cold, water, dust, stagnant and foul air, roof falls, falls from ladders and demons all caused injury and death in the mines of his day. Although demons are no longer considered a cause of accidents in modern mining, the other factors remain with us still. The United States government started keeping track of fatalities with the establishment of the federal Bureau of Mines in 1910. Successor agencies, such as the U.S. Mine Safety and Health Administration (MSHA) continue to track fatalities today. Looking at the records, it can be seen that coal mine fatalities dropped from 2821 in 1910 to only 27 in 2004. The reduction in fatalities and injuries didn’t “just happen.” It took concentrated effort from the entire mining industry: miners, supervisors, safety officials, mining inspectors and mining researchers. But first, specific hazards must be identified before they can be corrected. In past, coal mining accidents have been analyzed by: type (roof fall, electrical, etc), mine attribute (location, seam height, etc.), and aspects of the mineworker (work experience, job classification, etc). Much of this research helped to direct the industry’s attention to where additional vigilance and safety training was needed. No doubt this directed effort has led, at least in part, to the decrease in coal mining fatalities. This paper takes a novel look at coal mining fatalities: it examines the risk of fatalities based on how long the mine has been open.

Jan 1, 2006

By Gordon C. ‘Bud’ Presley

The pumice and pumicite review arrived too late for the June issue. Estimated domestic production of pumice and pumicite in 1992 was up compared with 1991, according to US Bureau of Mines statistics. The Bureau estimate of domestic production of 400 kt (440,000 st) for 1991 turned out to be 401 kt (442,000 st) of actual production, the lowest since 1989. In 1992, the estimated the value of pumice and pumicite sold or used in the United States was $11.6 million, up only $200,000 from the 1991 value. There was an increase in the mine, or mill, average price from the five-year low of $11.44/t ($10.37/st) in 1986 to $26.42/t ($23.96/st) in 1992. Estimated tonnage produced in 1992 was 439 kt (484,000 st). Apparent domestic consumption was 642 kt (707,000 st), up 135 kt (149,000 st) from 1991. Imports for consumption were estimated to be 215 kt (237,000 st) last year. Domestic production supplied 68% of the demand in 1992, with net imports supplying the remaining 32%. This compares with domestic production sup¬plying 53% and net imports supplying 47% of the apparent consumption in 1988. Exports were about 900 t/a (1000 stpy) for the period 1984 to 1988. In 1989, exports rose sevenfold to 7 kt (7700 st) and to 20 kt (22,000 st) in 1990. The Bureau of Mines reported that the amount of pumice and pumicite exported in 1992 was 12 kt (13,200 st). It is assumed that these exports were from the Pacific Coast because imports, mainly from Greece, continued to be a market factor on the East Coast and the Gulf Coast States in the United States.

Jan 1, 1993

By M. Adnan Göksel

Pyrite cinder is generated by roasting pyrite for sulfur dioxide production. It contains up to 62% iron, but also may contain other hazardous or toxic materials such as Zn, Pb, As, T1, Cd, Cu, Sn and S. Furthermore, the physical characteristics are not properly suited for conventional sintering. As a result pyrite cinder is considered to be unsuitable for iron and steelmaking or for outside storage because of its potential for causing environmental problems. In recent years industrialized nations have put increasing pressure on the manufacturers to either use such waste products or properly dispose of them. In this study, solutions to both the iron recovery and disposal problem were attempted by pelletizing the pyrite fines with internal carbon. The pellets, after hydrothermal hardening, were reduced and melted in a furnace for hot metal production. Hot metal of usuable quality was produced and the hazardous materials were either collected with the fumes or in the slag.

Jan 1, 1984

By Jian Wang, Xiaoming Sun, Ming Jiang, Fuxin Shen, Chengyu Miao, Wenchao Zhao, Yong Zhang

The increased thickness of the coal seam leads to higher goaf roof collapse height. In contrast, the dynamic pressure from the mining of ultra-thick coal seams generates higher abutment pressures around the mined area and may affect the stability of roadways servicing these panels. To mitigate the deformation and damage issues in the roadways during the extraction of ultra-thick coal seams under a high depth of cover, researchers have proposed combining high prestress constant resistance support and roof-cutting technology (HPCR-RC). The deformation and failure mechanisms of the roadways during the extraction of ultra-thick coal seams under a high depth of cover, along with the mechanisms and field control effects of the combined support system, have been analyzed through theoretical analysis, numerical simulation, and field experiments. The research findings reveal that the high in situ stress, initial excavation disturbance, rotation, and subsidence of the fractured roof of the extra-thick coal seam led to significant deformation and damage in the roadways. High prestress constant resistance support compensates for the initial stress loss, reduces initial stress concentration, and absorbs deformation energy. Moreover, the roof-cutting technology severs the connection between the goaf roof and the roadway roof, disrupts the path of stress transfer, raises the level of roof backfilling in the goaf, and provides support to the roof, effectively alleviating the pressure on the coal pillar ahead and adjacent to the working face. Field experiments have confirmed the effectiveness of HPCR-RC, as indicated by a substantial decrease in surrounding rock deformation and support pressure within the roadways.

Sep 25, 2023

By Richard L. Ash

In many instances, blasting exerts the dominant control over the economics and safety of excavation, where the materials involved are too hard and tough to be fragmented efficiently by other means. However, associated with the fragmentation process other effects very often result that are not desirable and may even be hazardous, such as fly rock, air blast, excessive overbreak, and damaging ground virbrations. It has always been the desire of those concerned with blasting to better control the forces involved so as to improve the breakage of materials, but at the same time reduce, or eliminate if possible, the unwanted side effects. Until the last decade or two, little was known of the phenomena concerned with blasting. However, since that time many investigators have studied blast mechanisms produced from both chemical and nuclear explosions, with the result that general concepts of the principles have been developed. But, in general, it is assumed that the energy from the explosion would be propagated spherically throughout the material, the latter of which for convenience of analyses is considered homogeneous and isotropic, i.e., the properties are the same in all directions, However, rocks are not isotropic as a rule, and evidence clearly indicates blasting forces rarely function uniformly or in spherical form as theorized.

Jan 1, 1965

By Arvid E. Anderson

The paper describes the unique operating features of the Lebanon Concentrator Plant wherein both magnetic concentration and froth flotation are used. Chalcopyrite is selectively floated by the use of dual collectors, Aerofloats and secondary butyl xanthate. Both potassium ethyl xanthate and sodium isopropyl xanthate (dual collectors) are dissolved and emulsified with pine oil for the flotation of the pyrite. Sketches describing the plant operations are presented and plant operating metallurgical results obtained are also given. The optimum production of minerals by the froth flotation process is normally achieved [ ] smooth operating conditions, The process, because of its many variables, becomes an art as well as a science. Therefore, any phase of the operation which will aid the operator in his control of the numerous variables will help produce a smoother operating plant, One of the most important variables which the operator deals with is the addition of reagents, These are usually costly items and should be used discretely with minimum amount of waste, The danger is that ,this emphasis may reduce the reagent amount to a point below that required, or, on the other hand an excessive amount is added, Both conditions usually yield poor results. The drea of the metallurgist is to provide the operator with the tools enabling him to produce a good mineralized froth at all times. Normally the operator has no control concerning the type of reagents which he must use. This has usually been worked out for him in the laboratory and by plant-scale tests. He does have limited authority to control the amounts of the reagents at his disposal. This, I believe, is as it should be. However, the operator should be provided with the best combination of reagents for his particular job. The providing of this combination of reagents for his particular job, The providing of this combination is often difficult, yet it is very important in order to yield good results, With this in mind, the dual collector idea was introduced for the selective flotation of chalcopyrite, and also later for the flotation of pyrite at the Concentrator Plant of the Bethlehem Cornwall Corporation in Lebanon, Pennsylvania, Supplying several types of collectors has given the operator an additional effective tool, even though great variations are encountered in ore tonnage treated and in ore composition, This paper deals with the use of the dual collectors and with the addition of the reagents in the form of a pine oil emulsion, or more accurately, a pine oil suspension. It is hoped that other operators may find the ideas helpful. There does not seem, to me, to be definite scientific fact which would substantiate the necessity for the use of dual collectors. However, in actual operations, the metallurgical results at Lebanon became more uniform with the use of dual collectors, I look upon it as an "insurance policy" which greatly aids the operator during those periods when he is having trouble, One theory has been advanced, i.e. one collector has a greater tendency to float the coarser minerals, whereas the other one may float the finer ones. Consequently, a combination of the two collectors will result in optimum recoveries, There has been some evidence that this is true, but it is not conclusive, on the other hand, the use of a xanthate-pine oil suspension (or emulsion) should speed up the surface reaction of the collector with the sulfide minerals, result¬ing in more uniform flotation, This has definitely happened in our particular case. A more interesting unexplainable observation has also occurred; i.e., the xanthate solution does not appear to lose its strength as rapidly when it is in the form of an emulsion (or suspension), This was first observed when a 50 gallon drum of a 20% ethyl xanthate solution was taken to Wilmington, Delaware, for a laboratory test, using a homogenizer to produce the xanthate-pine oil emulsion. Upon arrival, the drum of xanthate had developed a considerable internal pressure, The relief of this pressure was accompanied by a strong odor, When the emulsion was returned to Lebanon for the plant test orders were issued to release the pressure prior to emptying the emulsion. Nopressure had developed within the drum and there was no unusual odor present, Since this time it has been observed that xanthate pine oil suspensions have greatly decreased the possible decomposition of the xanthate solutions. In fact, suspensions have been exposed for more than a month without apparently effecting their reactions in the flotation plant. On the other hand, we found that the regularly mixed concentrated xanthate solutions, after standing for several days, did not give the same results as the freshly made ones. This effect was greatly reduced by the use of xanthate pine oil suspension (or emulsion)

Jan 1, 1958