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By S. G. Malghan

W.H. Moyer In reference to the section “Excess pyrite, ” the author discusses difficulties in separating chalcopyrite from pyrite. A technique does exist, and has been used commercially, for the flotation, separation, and recovery, if desired, of both chalcopyrite and pyrite. The method was described in Mining Engineering, March 1966, “An Improved Flotation Method for Cornwall Sulfides. ” While it was not used on a porphyry copper ore, it was used on a chalcopyrite - pyrite-containing ore and might well have application. Both sulfides, chalcopyrite and pyrite, were floated simultaneously using xanthate as a collector and MIBC frother to produce a cleaned sulfide product. This concentrate was then thickened and conditioned at high solids with aeration and lime to a pH above 12.0 for a period of 1.5 to 2 hr. A supplemental suppressant, such as cyanide, could be used if necessary to sharpen the subsequent separation; however, it was not required at Cornwall. The conditioned sulfides were floated with two stages of cleaning to produce a highgrade chalcopyrite froth product and a pyrite sink product barren in copper. The separation at Cornwall gave a 28.6q. Cu grade chalcopyrite product and a pyrite analyzing 0.0670 Cu. A desliming step on the raw ore initially used at Cornwall for a period of time was later discontinued. Advantages to be found in using a strong sulfide collector, such as a xanthate, is the rapid flotation it induces and, generally, an ability to float at a coarser grind. A following regrind circuit could be used to give maximum liberation and produce a clean sulfide concentration. The “differential” separation is concerned primarily with grade and with assuring a barren pyrite for maximum recovery.

Jan 11, 1986

By Xinyang Wang

It is believed that sulfur and volatile matter contents in coals are the main intrinsic properties to cause the self-heating of coal. Their oxidation at lower temperatures than that of fixed carbon to initiate coal's self-heating should be quantified. This study is aimed to improve the previous mathematical model developed by the authors for studying the coal's propensity for spontaneous combustion. It enhances the model's ability to consider the effects of sulfur, volatile matter and moisture contents in the coal - three important factors affecting the coal's self-heating process. Sulfur exists in coal primarily in the form of pyrite which will be oxidized rapidly under suitable conditions. Volatile matters, higher in low rank coals, are more easily to be oxidized. Heat of water condensation provides initial energy for low temperature oxidation. Heat release rates for pyrite oxidation and moisture condensation are built in the model. Finally, the simulation results in terms of time versus temperature on pyrite oxidation and moisture condensation are validated with the adiabatic testing data respectively.

Jan 1, 2013

Bortech’s BoreClad corrosion protection system will be displayed at MINExpo. BoreClad is an innovative system for inside diameter cladding of nozzles, tubes and other circumferential devices. Pressure vessels, mud pumps and other mining equipment must be protected from corrosive caustic chemicals. Usually manufactured from mild steel, they can be clad with a protective material, such as stainless steel, to provide corrosion resistance. However, most welding processes leave voids where corrosion can damage the base metal. BoreClad provides void-free welds by combining gas metal arc welding with automated feed and rotation of chuckable parts. Workpieces of up to 915-mm- (36-in.-) long with a 460-mm- (18-in.-)swing can be clad with stainless steel, Iconel or other exotic metals. In addition to eliminating the voids associated with hand welds, BoreCladcan lay more than 2.2 kg/h (5 lbs/hour) of metal. That is a significant reduction in weld time. Web sitewww.bortech.com.

Jan 1, 2004

Thallium is an uncommon heavy metal that may be found in concentrations that exceed regulatory limits in mining influenced water associated with processing cadmium, copper, gold, lead, and zinc ores. This study evaluated cost-effective modifications to lime precipitation treatment to reduce thallium concentrations to below the EPA drinking water MCL of 2 ppb. The oxidative precipitation of Tl+ to Tlß+ by potassium permanganate was explored for thallium removal at low concentrations (1 ppm initial thallium). Laboratory batch tests were performed to evaluate the removal of thallium from synthetic solutions. Three ratios of potassium permanganate to oxidizable metals in solution were used (one-half, one and two times stoichiometry). Thallium was removed to less than 1 ppb for all stoichiometric ratios evaluated within 10 minutes of reaction. The efficacy of oxidative precipitation for thallium removal is presented.

Jan 1, 2011

By Yngve Jordal, Sverker Hartwig

The IVAR Project is Norway's largest sewer project presently under construction. One part of it is an 8.1 km (26 575 ft) long, 3.5 m (11 ft 6 in.) diam tunnel, bored in one year. The tunneling project has been running smoothly; however, not everything has been easy. A few of its features are highlighted in this paper: The use of 9 0 (12 cu yd) muck cars on a double track back-up in such a comparatively narrow tunnel. Employing only four men in the tunnel, including the loco driver. A quartzite dyke - 96% quartz with 350 MPa (50 000 psi) and more compressive strength - turned out to be 640 m (2 100 ft) thick instead of the predicted 90 m (300 ft). Passing under a gaseous swamp with only same 5 m (16 ft 5 in.) of rock cover on top.

Jan 1, 1991

By D. Brady

When deciding to deploy rescue teams underground the decision makers need to be able to determine that there won?t be an explosion whilst the rescue teams are underground. Previously general body concentrations in areas likely to be travelled were compared to explosive limits on a one off basis with no formal process looking at trends or other areas. A new approach is being adopted that takes into account the rate of change of gas concentrations with triggers set to enable a withdrawal of personnel prior to a possible explosion and influences such a barometric pressure changes. This paper explains the rationale behind the changes made and the advantages and implications of adopting such an approach.

Jan 1, 2012

By D. D. Xu

A novel system for the depression of pyrite and the ash-forming minerals has been developed. A metal ion, including but not restricted to Fe+2, is added to form a hydroxide coating on the pyrite or ash-forming mineral. A polymeric depressant is then added to attach to this re-surfaced mineral. Nearly 200 flotation tests with a 11 different coals indicate the effectiveness of this system. Many of the important process variables such as the coal source, frother-collector system, grind size and procedure, pH, metal ion, and depressant type and concentration have been studied.

Jan 1, 1994

By Marvin V. Damm, Lloyd C. Venburg, Dan Sokol

Analytical and computer models are used to evaluate information obtained from existing data and investigation programs so mine water control systems can be designed and developed. These models allow the geohydrologist to predict the amount of groundwater inflow and the impact of dewatering and stream diversion on the hydrologic regime, and to determine the schedule and equipment needed for mine dewatering. This article describes uses of the model and the essential components necessary to construct an effective and practical one. Hydrologic models are constructed to determine the extent that mining activities will affect the ground water and surface water hydrologic regime. These models range from basic analytical, mathematical models to the more sophisticated finite difference and finite element groundwater models. Many factors determine the degree of sophistication, including the mining stage, the complexity of the hydrologic regime, the mining process, and regulatory requirements. Model Uses The geohydrologist and engineer construct models so the entire ground and surface water handling and supply system can be integrated and optimized. These models can provide the following data: • Information for water balance studies-the entire hydrologic regime for the area, including precipitation, transpiration, evaporation, infiltration, runoff, and the effect of geologic features. • Data on seepage rates during mining. • Information to design the depressurization and dewatering system, including water well spacing, location of sumping systems, need for grout curtains, and possible horizontal drain and underdrain locations. • Data needed to schedule dewatering and mining operations. • Prediction of initial and long-term impacts of mining and dewatering, including local and areal drawdowns, effects on existing wells, and modifications to the surface-subsurface hydrologic regime. Potentiometric surface maps and hydrographs can be prepared from these data. • Prediction of the effect of discharge from the water control system on the surface hydrology and data input to design systems for water discharge, storage, recharge, or reinjection. The results of a computer study that illustrates the effect of dewatering and reinjection into an aquifer to confine the cone of depression are shown on the accompanying figure. • Information to forecast potentiometric surface recovery after mining ceases. The accompanying figure shows the pumping and reinjection rates in a program that is adequate to dewater a mine and permit the recovery of potentiometric levels to approximate premining levels after mining ceases. • Documentation and design information for monitoring systems to be installed during all mining phases. • Water quality predictions and geochemical changes, including the possibility of brackish or saline water intrusion because of extensive dewatering or depressurization operations. • Documentation and data for acquiring permits from regulatory agencies. Model Input Program For any model to be effective, detailed hydrologic and geologic data must be gathered from a review of existing information and from an investigative program. These data should cover entire model limits. Data updating, revising, and refining should occur as new information is received from the investigation and monitoring programs, and from the mining operation as it progresses through the pre-mining, mining, post-mining, and reclamation

Jan 8, 1982

By G. J. Joy

Although rates of pneumoconiosis in coal miners have declined substantially in the United States since the passage of the Federal Coal Mine Health and Safety Act of 1969, new cases continue to occur, including cases of rapidly progressive disease. In contrast, Australia?s underground coal mining industry has reported few new cases of pneumoconiosis for over twenty years. Mortality from Coal Workers? Pneumoconiosis in official health statistics and the prevalence of pneumoconiosis among miners screened in x-ray surveillance programs are also lower in Australia. To understand this disparity, the National Institute for Occupational Safety and Health was requested by both industry and labor stakeholders to examine this issue, with the ultimate aim of reducing the rate of pneumoconiosis among United States coal miners. A number of factors, including coal dust exposure, silica exposure, and coal rank were examined as potential contributors to the above observed differences. Comparison of coal rank data from each country did not show any significant differences. Air sample data from the coal mining industries in both countries show that coal dust levels in Australian mines are somewhat higher than those reported in similar U.S. mines; however, quartz exposure for Australian miners is lower than for many U.S. miners. Assuming that quartz is contributing to the greater number of cases of advanced pneumoconiosis in the U.S., more effective dust control measures, as well an independent exposure standard for respirable quartz in coal mining, need to be implemented to prevent this potentially disabling condition.

Jan 1, 2011

By J. H. Zietsman

Ilmenite smelting furnaces must be operated with a freeze lining of frozen slag to protect sidewall refractories from chemical attack by liquid slag. The process has two main control objectives: Firstly the slag TiO2 content must be controlled according to specification, and secondly a safe freeze lining thickness must be maintained. This text only concerns itself with the second objective. Freeze lining thickness cannot be measured directly due to conditions inside the furnace. It is therefore inferred from signals of thermocouples installed into the furnace sidewall. These signals are used as the 'controlled variables' in the freeze lining thickness control loop. The dynamic characteristics of these signals are the focus of this text. During this study a model of the process was constructed to study interactions between the slag bath and the freeze lining. This model was used to conduct simulation-type experiments to study the influence of various parameters (temperature, slag composition, ilmenite feed rate, reductant feed rate, power input, etc.) on the slag bath, freeze lining, metal bath, furnace wall and other parts of the process. In the case of the furnace wall, the modelling results were first plotted in the form of time-dependent isotherms. The dynamic thermal behavior of the furnace wall became evident from these results. To illustrate the dynamics of sidewall thermocouple signals, the results were also plotted as time lags between events occurring in the slag bath, and the time when a thermocouple registered a temperature change. The events studied included sudden changes in slag bath state (composition and temperature), changes in operating setpoints (ilmenite feed rate, reductant feed rate, power input), and operational errors (complete loss of reductant or of all feed). All of the result sets showed significant lags between occurrences in the slag bath and temperature changes in the refractory wall. The delays are such that it appears impractical to rely on sidewall thermocouple signals for warning of impending damage to the refractory wall, or for purposes of actively controlling freeze lining thickness. Some measures are suggested to improve the usefulness of these signals during furnace operation.

Jan 1, 2005

By David C. Yang

A packed column (or static tube) flotation system is an innovative technology which utilizes a controlled dispersion reagent scheme and a new machine. The unique aspect of the machine is its packed-bed design permitting an unlimited froth bed height with countercurrent water washing for effective processing of fine particles. In operation, the conditioned ore slurry is fed into the middle section of the column where separation processes begin. Air, introduced at the bottom of the packed column, contacts the hydrophobic particles and floats them off continuously as the feed is added, while the gangue sinks to the base of the column. The system functions efficiently because intimate particle-bubble contact is achieved by the packing design which has no moving parts and requires no ancillary air-bubble generator. Other attractive features of the packed column flotation include high throughput, low power requirements, and simple control. Results from laboratory and pilot plant tests of this system show remarkable improvements over current industrial practices on a wide variety of ores and coals.

Jan 1, 1988

By K. R. Long

Until it was defunded in 1995, the U.S. Bureau of Mines maintained a Cost Estimating System (CES) for prefeasibility-type economic evaluations of mineral deposits and estimating costs at producing and non-producing mines. This system had a significant role in mineral resource assessments to estimate costs of developing and operating known mineral deposits and predicted undiscovered deposits. For legal reasons, the U.S. Geological Survey cannot update and maintain CES. Instead, statistical tools are under development to estimate mining costs from basic properties of mineral deposits such as tonnage, grade, mineralogy, depth, strip ratio, distance from infrastructure, rock strength, and work index. The first step was to re-estimate ?Taylor?s Rule? which relates operating rate to available ore tonnage. The second step was to estimate statistical models of capital and operating costs for open pit porphyry copper mines with flotation concentrators. For a sample of 27 proposed porphyry copper projects, capital costs can be estimated from three variables: mineral processing rate, strip ratio, and distance from nearest railroad before mine construction began. Of all the variables tested, operating costs were found to be significantly correlated only with strip ratio.

Jan 1, 2011

By J. W. Hawkins, K. B. C. Brady, K. Miller, J. Cuddeback

Remining of abandoned coal mines in Pennsylvania requires the implementation of pollution abatement and mining techniques called Best Management Practices (BMPs). Water-quality data from over 100 remining sites with more than 230 abandoned discharges were analyzed with respect to the types of BMPs employed to abate the pollution loadings of acidity, iron, manganese, aluminum and sulfate. Discharges exhibiting a significant decrease in acidity were most highly associated with sites where large volumes of alkaline materials were encountered (66.7%) or added (63.7%). The best results for iron loading were achieved with large-quantity alkaline addition (54.6%) and water handling systems (47.8%). Water handling systems (47.4%), daylighting (40.7%), and revegetation (40.2%) were associated with significantly lower manganese loadings. The decreases in acidity and sulfate loads associated with increasing the amount of alkaline material in the backfill indicates that the production of acid mine drainage can be retarded by adding large quantities of alkaline materials.

Jan 1, 2002

By R. C. Milici

Historical production data and reserve decline rates can be used both to predict future coal production rates and to estimate when the reserve will be depleted. Reserve estimates inferred herein from historical production data and decline rates are commonly lower than estimates made from geologic data. The latter include significant amounts of lower quality (deeper, thinner, higher sub) coal which may be mined when the better deposits are depleted.

Feb 24, 1997

By Howard J. Handewith

Long used in mine development in England, Europe and Russia, roadheaders are growing in size, features, productivity and application. Beginning with the basics, this paper covers the economic and the technical aspects of the new roadheaders in both mine production and development. The author explains how to choose and integrate roadheaders into ongoing operations as another step in the inexorable march from labor to capital intensive mining. Innovations now on the drawing boards are covered that are the challenge of the future.

Jan 1, 1983

By B. K. Parekh, Z. Chen

INTRODUCTION The need for cleaning and recovery of fine (minus 28 mesh or 0.5 mm) coal fraction has increased in recent years. This results from realizing a substantial recovery of ultraclean coal from the waste stream improving overall Btu (heat) recovery, providing extra revenue for the coal industry. Also the potential of using the clean coal so obtained for making coal-water mixture which could replace oil. An additional benefit of recovery clean coal from the waste stream is reducing environmental concern of burning uncleaned coal and in waste disposal. Deashing of coal by physical beneficiation processes is limited by the degree to which ash components are liberated from coal. Conventional processes have been inefficient in terms of Btu recovery, for ultrafine coal. Chemical cleaning methods, which involves leaching of ash material from coal, have provided ultraclean coal at high Btu recoveries, are more costly than the physical cleaning methods. An advanced physical separation technique that appears to address the need discussed above is selective flocculation. This technique which has been successfully utilized in iron ore beneficiation offers the potential of processing fine and ultrafine coal to produce a clean fuel. OBJECTIVES The main objective of the present study is to investigate applicability of selective flocculation technique for recovery of clean coal product from the waste coal slurry supplied by the Peabody Coal co., from their three different coal preparation plants. It is also the objective of the program to conduct preliminary economic study of the selective flocculation process.

Jan 1, 2002

By R. L. Virta

Editor?s note: Each year, the June issue of Mining Engineering features an industrial minerals review. Several people put in a fair amount of time in developing the material for this issue. Thank you to the industrial minerals annual review editor, to the technical committees chair and vice-chair, and to the authors of the individual commodity profiles. Jim Norman, member SME, of GeoTrans Inc., is the industrial minerals annual review editor. Abani Samal, member SME, of Pincock Allen & Holt, is chair of the industrial minerals technical committees. Technical committee vice chairs include: ? Abani Samal, member SME, of Pincock Allen & Holt, agricultural minerals. ? Aaron McMahon member SME, of Pincock Allen & Holt, ceramics and refractories ? Bradley S. Van Gosen, member SME, of the U.S. Geological Survey, chemical raw materials. ? Mark Zdunczyk, member SME, of Continental Placer Inc., construction materials. ? Jerry Gauntt, member SME, of Marston, fillers and pigments. ? Michael Cheshire, member SME, of Indiana University, sorbents, filters and process aids. ? Candace Trimble, Oil-Dri Corp. of America, specialty minerals. Their help makes possible this June industrial miner-als issue. On behalf of ME readers, the editors thank them. Ball Clay Four companies ? H.C. Spinks Clay (owned by Lhoist Group), Kentucky-Tennessee Clay (owned by Imerys Group), Old Hickory Clay, and Unimin Corp. ? mined ball clay in four states in 2008. Production, on the basis of preliminary data, was 964 kt (1.1 millon st) with an estimated value of $45.3 million. That was a 10- percent decrease in tonnage from 1.07 Mt (1.2 mil-lion st) with a value of $49.2 million that was produced in 2007. Tennessee was the leading producer state with 63 percent of domestic production, followed by Texas, Mississippi and Kentucky. About 73 percent of production was airfloat, 16 percent was crude and 11 percent was water-slurried.

Jan 1, 2009

By P. Massacci, F. La Marca, G. Bonifazi

Certain deposits of incoherent materials which are near the surface and exploitable by open-pit mining may be characterized in real time before they are mined through an analysis of ground-surface imagery. If the slice to be stripped is not overly thick, in fact, surface texture and color properties may be extrapolated to its entire thickness. Image analysis techniques to process ground surface images acquired in situ(or in the laboratory shortly after their acquisition) which yield pattern vectors representative of RGB color component distributions and HSB texture parameters have been developed. The techniques were applied to a mineral sandy ore deposit containing three different lithotypes. Geostatistical analyses showed that the data used to characterize the lithotypes were reliable. The correct recognition of the lithotypes was carried out using a multi-barycenter classification algorithm. Such in situ image-analysis procedures open the way to the proper selection of the ore to be mined, or the proper way for run of mine (r.o.m).processing, or the appropriate blend to be processed before or at the same time as the mining process itself is enacted.

Jan 1, 1999

By A. K. Sinha

Modern mine ventilation systems have grown rapidly in recent years both in tern of its complexities as well as its value for human health and safety. Although computer models are now available to help the design and operation of mine ventilation systems, considerable differences often exist between the computer based predictions and practical results. Research conducted to compare computer result with practical measurements made in ventilation circuits simulated in a physical model seems to confirm such differences. It is concluded that although a mine ventilation computer model is a very powerful tool, it can be utilized to its full potential only after more reliable input data are developed.

Jan 1, 1985

Electrostatically charged water droplets efficiently suppress breathable dust produced during open air rock crushing operations, according to recently completed independent tests conducted for the Environmental Protection Agency. Since a primary rock crusher produces very heavy clouds of dust, this application was selected as an appropriate test site to measure the efficiencies of new "charged fogging" equipment in mining and mineral processing operations. EPA's Industrial Environmental Research Laboratory, Research Triangle Park, NC, contracted TRC-Environmental Consultants Inc. of Wethersfield, CT, to conduct a full-scale demonstration of a recently developed electrostatic fogger, designed to project a charged fog spray at distances up to 15.2 m. Test results indicated overall fogger efficiencies of approximately 70%. The Fogger IV* employed in these tests is reportedly the largest charged logger ever made, with an extremely long operating range. The original fogger was designed for indoor dust control; this fourth generation version is designed for fugitive dusts, indoor and outdoor, and has an operating range up to 15.2 in.

Jan 6, 1981