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By Stephen R. Brown

The principles of quality management are well developed and, from a practical stand- point, thoroughly implemented in the process industries of Japan. Although these principles are now applied to the U.S. manufacturing industry, and as a result, the steel industry, they have been largely ignored in the non-ferrous and precious metals industries. This paper presents the concepts and practical approaches to implement a total quality management program. Contrary to the beliefs of many managers, such a program increases yields, recoveries and output while it decreases unit costs. In fact, quality management incorporating statistical process control will be an essential ingredient for metallurgical plants to effectively compete in the '90's.

Jan 1, 1991

By G. A. Rowell, T. M. Barczak, J. C. Zelanko

The US Bureau of Mines conducted a multifaceted geomechanics research project at a bump-prone longwall coal mine in eastern Kentucky. This mine presented a unique opportunity to study coal mine bumps because the problem appeared to be confined to areas beneath a sandstone channel of limited areal extent. The Bureau's research plan sought to exploit the uniqueness of the site by monitoring strata behavior and longwall support reactions as the longwall face approached and passed beneath a sandstone channel. The study incorporated static pillar stress and strata deformation measurements, shield support leg pressure measurements and microseismic monitoring, as well as geologic mapping and the collection of observational data. Data collection was underway when a major coal bump occurred on the longwall face at the mine. Pillar behavior (load and deformation), shield loading and microseismic activity were monitored prior to, during and after the bump. Observations in the tailgate indicated that these pillars were failing prior to and following the face bump. Shield load data, evaluated in an effort to identify trends that could be used to forecast coal bumps, appear to provide a measure of the effectiveness of destressing operations conducted on the face (e.g. shot firing). Analyses of microseismic data revealed anomalous values associated with microseismic "energy" prior to the face bump. In addition, microseismic source-location data and underground observations provided some insight as to the sequence of pillar and face bumps.

Jan 1, 1992

By J. B. Zachwieja, P. E. Richardson, G. W. Walker

The electrochemical nature of mineral-collector interactions and their relationship to flotation have been investigated to develop a better understanding of the factors controlling sulfide mineral beneficiation. Spectrophotometric and electrochemical techniques have been used to examine the reactions occurring on electrodes composed of a bed of bornite particles in the presence and absence of potassium ethylxanthate (KEtX) at a pH of 9.2. The combined techniques showed that KEtX sequentially reacts with bornite by (1) a chemisorption reaction forming ca hydrophobic species between --0.4 and -0.2 V (SCE), (2) an electrochemical oxidation reaction forming cuprous xanthate between -- 0.2 V and the xanthate/ dixanthogen redox potential, and (3) oxidation to dixanthogen when the potential exceeds the reversible value for the xanthate/dixanthogen couple. The flotation response of bornite closely parallels spectrophotometric and electrochemical evidence for adsorption of KEtX by the reactions listed above. The degree of surface oxidation resulting from the formation of iron oxides on the surface dictates the flotation response as evidenced by the fact that oxidized bornite floats at more anodic potentials than unoxidized bornite. The strong correlations between the flotation response, degree of oxidation, and potential indicate that chemisorbed xanthate produces a hydrophobic layer sufficient to float unoxidized bornite, but cuprous xanthate and dixanthogen arc required to float oxidized bornite.

Jan 1, 1988

By Richard R. Klimpel

This paper summarizes the author's laboratory and industrial experiences in designing and evaluating frothers for optimal coal flotation circuit performance. The key variables discussed are particle size distribution hydrocarbon addition rate, frother chemical structure, and frother dosage. A number of detailed examples will be used to illustrate the important rare/recovery/selectivity interactions that can occur.

Jan 1, 1995

By K. N. Han

The kinetics of gold dissolution in iodide solutions with oxygen in an autoclave was investigated. The leaching process was described by a gas-liquid-solid heterogeneous reaction. The effects of stirring speed, temperature, oxygen partial pressure and lixiviant, concentrations on the overall leaching rate was investigated. It was found that the dissolution of gold could be represented by a heterogeneous chemical reaction. Under the conditions studied, the apparent activation energy ranged from 34.7 to 54.3 kJ/mol. Experimental findings were in good agreement with the kinetic model proposed.

Jan 1, 1998

By P. V. R. Bhaskar Sarma, P. K. Sahoo, G. Roy Chaudhury

A process was developed to treat an ammoniacal leach liquor containing zinc using Di (2-ethyl hexyl) phosphoric acid (D2EHPA) as the extractant. The objective of this work was to develop a process package for the treatment of complex sulfide leach liquors. Zinc extraction could not be carried out directly from the ammoniacal solution in mixer-settler units because of crud formation and low extraction efficiency. After neutralizing the free ammonia with H2SO4, the extraction efficiency was only about 40%, due to the high concentration of (NH4)2SO4. To decrease the (NH4)2SO4 concentration, the free NH3 was steam stripped, and the resultant liquor was subjected to zinc solvent extraction. An extraction efficiency of 98% could be achieved by controlling the equilibrium pH. Stripping studies were also optimized after removing ammonia from the zinc-loaded organic. A continuous 100-hr operation that included extraction, scrubbing and stripping, was carried out successfully.

Jan 1, 1995

By James W. Griffith, Sarah A. Riling

Bituminous coal dust was repeatedly placed into one lung lobe of anesthetized Macaca nemestrina monkeys using a flexible fiberoptic bronchoscope. Radiographs taken at 15 day intervals showed a focal radiographic density after 90 days time when a total of 1 gram of dust had been instilled. The radiographic density progressed slightly in size until 12 months by which time 3 grams of dust had been instilled and the animals were euthanized. At necropsy, the only significant gross lesion detected was the focal black pulmonary lesion located at the dust instillation site. Histologically, the lesion was composed of coal dust laden macrophages located primarily within interstitial tissue and interspersed with a slight amount of reticulum and connective tissue fibers. The distribution of coal dust was limited to the instillation site in the right caudal lung lobe based on radiographic, gross and histologic examination. Bronchoalveolar lavage of both right and left caudal lung lobes was performed 8 times during the 12 month long experiments without significant complications. More macrophages were found in lavage fluid from the right lung than the left, and most macrophages from right lung contained coal dust particles. Based upon a limited physical examination and complete blood count at 15 day intervals the animals remained normal during the experiment. We conclude that the primate lung's response to focal experimental bituminous coal dust resulted in a marked focal increase in pulmonary alveolar macrophages, which can be recovered regularly in high numbers by bronchoalveolar lavage. The model described has significant potential for investigating the pathogenesis of various respirable dust-induced pneumoconioses, for evaluation of new therapeutic approaches, and for refining experimental and clinical diagnostic applications of bronchoalveolar lavage. Key words: Coal Workers Pneumoconiosis, Disease model; Primate, Lung Lavage Fluids

Jan 1, 1991

By Z. T. Bieniawski

In the past 15 years, rock mass classifications have experienced unprecedented development and have emerged as powerful practical methods for assessing ground conditions and tunnel support. Such methods as the RMR System (Geomechanics Classification) and the Q-System have provided many advantages over the classical Terzaghi rock-load method introduced in 1946. These new classifications have found wide applications all over the world but some doubts have been expressed and shortcomings pointed out. The author, who developed the RMR System, takes a penetrating look into the promises and the pitfalls of modern rock mass classifications. He dispels some misconceptions and shows how rock mass classifications can serve as effective and dependable design aids in tunneling.

Jan 1, 1987

By P. Somasundaran, S. E. El-Mofty

A comparison of the IMC Anionic Process and the CLDRI Process, based on pilot plant testing of waste pebble by Jacobs Engineering is presented. Estimated costs for constructing and operating a beneficiation plant utilizing dolomite flotation are given. Research to develop practical flotation processes for removing dolomite from low-grade phosphate rock has been a high priority for the Florida Institute of Phosphate Research. The Institute funded the above pilot plant programs in 1998 and 2000. The Florida Phosphate industry currently deals with the increasing dolomite content of ore reserves by practicing selective mining. Heavy media separation plants installed at two mines to remove dolomite from pebble are not being operated. The flotation separation of dolomite from waste pebble requires that the flotation feed be ground. Grinding liberates the mineral species and produces particle sizes small enough to be floated. Only two dolomite flotation processes, the IMC Anionic Process and the CLDRI Process, have been successfully demonstrated on flotation feed that has not been deslimed after grinding. Deslimed flotation feed, relative to undeslimed feed, has improved flotation performance and reduced reagent consumption. However, for the above mention processes, undeslimed ground feed increases the yield of concentrate because the phosphate desliming losses are avoided.

Jan 1, 2002

By J. D. Miller

Reaction kinetics for gold dissolution in acid thiourea solutions were investigated using formamidine disulfide as an oxidant. For the conditions studied it appears that a surface reaction limits the rate of gold dissolution. The rate was found to be first order with respect to thiourea concentration and half order with respect to the concentration of formamidine disulfide; the apparent activation energy for the reaction was 10.40 kcal/mol (43.40 kJ/mol); and the reaction rate was independent of pH for the pH range 1.0 to 3.0.

Jan 1, 1999

By R. Hogg, T. F. Dumm

Procedures for particle size analysis on respirable dust from coal mines have been evaluated. Using respirable dusts dispersed in a laboratory dust chamber, size distributions measured using cascade impactors have been com- pared with the results of a variety of laboratory sizing methods performed on samples collected on filters placed side-by-side with the impactors. The laboratory techniques included centrifugal sedimentation, laser diffraction/scattering and automatic particle counting. The general agreement among the various methods was very good, with systematic differences which can be attributed to the different definitions of size used. Simple conversion factors have been obtained which can be used to transform the laboratory data to equivalent aerodynamic sizes. Similar comparisons have been made on samples collected in underground coal mines. Again, the results are in quite good agreement although small discrepancies were observed in some cases. These have been attributed to some degree of agglomeration in the airborne dust, leading to slightly coarser apparent distributions in the impactor samples.

Jan 1, 1987

By P. H. Lu, M. J. DeMarco, J. R. Koehler

Beginning in late 1985 and continuing through 1987, US Bureau of Mines personnel investigated longwall chain pillar and entry design in two and three-entry gateroad systems at a deep underground coal mine in central Utah. To evaluate their respective stability characteristics, four chain pillars and two longwall panels within the two separate entry systems were instrumented with Bureau hydraulic borehole pressure cells to continuously monitor vertical and horizontal pillar and panel stresses through adjacent panel retreat. In addition, supplemental entry closure information was obtained from sites located in the vicinity of the instrumented pillars. The findings presented in this report demonstrate the practicality of evaluating mine pillar stability using in situ methods and support three significant conclusions regarding ground control aspects of the investigated two-entry system: (1) Total areal entry loading was considerably less for the two-entry system, as opposed to the three-entry system, (2) a smaller percentage of opened ground in the two-entry system contributed to a marked reduction in rooffalls, and (3) lower areal loading in the two-entry system suggests improved ground conditions when mining the underlying seam.

Jan 1, 1987

By Edwin Itzig-Heine, Daniel Traylor, Bernard Tarralle, Michael McKenna

This paper discusses the challenges associated with the design and construction of a dual-cell, “figure eight” shaped shaft in saturated, soft ground for the Northeast Interceptor Sewer project in Los Angeles. The shaft will be excavated to a depth of41 m and used to launch two EPB TBMs. The specifications required concrete diaphragm walls, embedded below the shaft invert, and a grout curtain beneath the wall. To control water pressure and basal stability without a grout curtain, wall panels were embedded deeper than required into a stiff, cohesive deposit. Details of wall panel excavation using a Hydrofraise are presented.

Jan 1, 2003

By Yoshiak Mizuta, Hi Keu Lee

The manuscript of this paper was not available for publication when the Proceedings went to press. Should the authors elect, they may distribute copies at the time of the Symposium

Jan 1, 1986

By Larry Taylor, Thomas Zdeb, Brian Jacobs, Dennis Jensen

Subway tunnels proposed for the Los Angeles County Metropolitan Transportation Authority (LAMTA) East Side Extension are to be excavated below the groundwater through an area of Los Angeles, California with dissolved hydrogen sulfide concentrations in excess of 200 mg/L. To address unique construction and worker safety issues, bench scale and field pilot test studies were conducted to evaluate various mitigation alternatives including in-situ oxidation by chemical injection, slurry pH adjustment to suppress H2S evolution, and chemical treatment to remove the H2S from the slurry and muck material. The results provided the basis for detailed hydrogen sulfide control specifications for the contractor.

Jan 1, 1999

By Jerry L. Hodgson

This paper presents an application case history of the planning methods used for developing, costing and scheduling an underground hydro- electric pumped storage facility in weak rock. This method covers the system configuration, excavation methods and costs, initial support systems and final lining systems. This study was performed by the Omaha District, Corps of Engineers for the proposed Gregory County Hydro- electric Pumped Storage Project, and presents a synopsis and the results of the studies performed.

Jan 1, 1986

By Q. X. Yun, S. H. Liu

This paper provides a new approach to determine the opening layout in underground mining methods by means of genetic programming. Based on a set of random combination of openings, the layout of openings will gradually improve with the help of genetic operations, including reproduction, crossover, mutation and fitness calculation. The optimal solution will finally emerge according to Darwinian principle: "the survival of the fittest ".

Jan 1, 2002

By George A. Desborough, David L. Fey, Stanley E. Church

About 100 mine-waste dumps from past metal exploration and mining in Colorado and Montana were sampled using surficial-sampling methods for laboratory studies of the minus-2-mm fraction. In the laboratory, the composite samples were split into l00g samples that were leached to assess their acid-generation potential and associated release of potentially toxic metals that may degrade water quality in the headwaters of the Animas River watershed in Colorado and the Boulder River watershed in Montana. Two leach methods were studied: a passive leach using de-ionized water, and a more aggressive leach following the EPA-1312 method. The resulting pH values of the leachates using both methods are comparable. The concentrations of sulfate and several, but not all, dissolved or water-soluble metals are higher in the EPA-1312 leachates than in the passive leachates; however, the overall trends of the data are very similar. The passive leach method is less labor intensive and may be more representative of the natural weathering process occurring on the mine-waste dumps, simulating the natural precipitation and snowmelt. Three chemical characteristics of mine wastes studied here provide a relative ranking of mine-waste dumps for the purpose of determining priority for removal or remediation. These characteristics are: net acid production (NAP), sum of dissolved toxic metals (?As+Cd+Cu+Pb+Zn), and dissolved iron in leachates. Ranking can be done evaluating plots of NAP versus the sum of dissolved toxic metals, and NAP versus dissolved iron. These two plots serve as a basis for relative ranking of polymetallic-vein and acid-sulfate mine wastes studied. This ranking scheme may apply to mine wastes from production of other deposit types in other watersheds.

Jan 1, 2000

By Alfredo Romero Quispe, Carlos Hoffman Sampaio

This work presents a study of characterization of activated carbons for the adsorption of Au(CN)2- complex. A comparative study of six samples of activated carbons, three Brazilian and three produced out of Brazil was made in order to determine their qualification for a performance in adsorption circuits in the extractive metallurgy of gold. The adsorptive capacity and the kinetics of adsorption were compared to the physical and chemical properties of each one. The influence of poluant ions on the kinetics and loading capacity of aurocianyde anion was also determined.

Jan 1, 1995

By S. R. Maynard

The Ortiz Mountains lie 25 mi (40 km) northeast of Albuquerque, New Mexico in Santa Fe County (Figure 1). Approximately 350,000 ounces (11,000 kgs) of gold have been produced from the Ortiz Mountains since the 1820s. The 100 square mile (260 square km) Ortiz Mine Grant was secured from the Mexican government in 1833 by Jose Francisco Ortiz for the purpose of mining gold. The Grant has remained more or less intact to the present. The mineral rights are currently owned by Ortiz Mines, Inc. of Joplin, Missouri and are leased to LAC Minerals, USA, Inc. (west half) and to Gold Fields Mining Corporation (east half).

Jan 1, 1989