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By Irwin R. Higgins, Joseph C. Milbourne

The selection of a suitable nitrate removal process depends on a variety of site-specific chemical and environmental issues. The dominant technologies for nitrate removal include biological denitrification and continuous countercurrent ion exchange. The decision to apply either of these technologies, or both together, depends on the nature of the waste water to be treated. Factors that affect the selection of the biological system include the feed composition and feed temperature. Ion exchange nitrate removal systems ere less sensitive to the feed composition but require disposal or destruction of the concentrated pregnant eluate. The paper discusses Tetra's continuous countercurrent ion exchange technology (CCIX™) and fixed film biological reactor, Denite®. The treatment of the ion exchange pregnant eluant is also discussed.

Jan 1, 1995

By Wayne R. Charley

High operating costs and environmental restrictions have combined to increase smelting costs for precious metals to a level where many mining companies cannot afford to operate. The need for a hydro-metallurgical process to produce bullion with an efficient, economical and environmentally safe method is well recognized by the industry. This paper describes the research and development program conducted by Behrent Engineering Company in its investigation of the use of an acidic solution of thiourea for the extraction of precious metals from concentrates and high-grade ores. The areas discussed are: process design parameters, health and environmental aspects and economics of the process. The scope of this paper includes the leaching process, the recovery of precious metals from pregnant solutions and the production of dore'. Thiourea leaching offers a complete alternative to smelting and cyanidization for those concentrates and ores amenable to this process.

Jan 1, 1984

By S. W. Clark, R. Meglen

A seismic refraction survey of selected environs of Brewster Phosphate's Lonesome mine near Bradley, FL identified various layers of overburden, minable matrix (ore body) and basement (i.e., bedrock) that correlated with core logs. Bivariate correlation procedures determined that statistical relations existed between mining parameters and seismic velocities. For instance, a correlation of approximately -0.6 was inferred between P wave velocity and ore grade.

Jan 1, 1990

By Fernando Muge

A complex pyrite orebody located in the South of Portugal (MO INHO) was exploited in the past by cut and fill methods until a certain level. It was decided to design a new plant for non ferrous metal extraction and the rate of production and exploitation method was modified accordingly. So, a sub level stoping (SLS) method was en visaged for the exploitation of the deepest part of the orebody (under 265 m level). For the planning of this SLS method, it was decided to perform a geostatistical study of the orebody, on the basis of the available information, which consists mainly of channel samples assayed for Cu, S, Zn and Pb.

Jan 1, 1979

By Paul M. Godlewski, Gerry Millar, Harvey W. Parker

Recently, over 70 railroad tunnels in the western USA have been enlarged and rehabilitated "live track," utilizing modern excavation and lining methods, in most cases to clear the larger double-stack container cars. This paper presents the general conditions of the tunnels and the technical aspects and costs of the rehabilitation of approximately 40 kilometers of tunnels, which range in length from a few hundred meters to 13 kilometers. Concrete-lined tunnels were rehabilitated by grouting and rock bolting, while unlined or timber-supported tunnels were relined with shotcrete and rock bolts. High output lining methods were required because of limited track time. Enlargement has been accomplished primarily by carving notches out of the concrete linings with a roadheader, or occasionally with saws. Unlined tunnels were enlarged by drill-and-blast or roadheader excavation.

Jan 1, 1991

By N. Parra, M. N. Herrera, T. Vargas, C. González, B. Escobar

The bioleaching of mineral sulfide pulps in a bench-scale rotating-drum reactor was studied. The reactor contained horizontal paddles on the inner wall for lifting the mineral pulp. The performance of the reactor was tested by bioleaching a refractory pyritic gold concentrate in the presence of pure Thiobacillus ferrooxidans (ATCC 19859). The concentrate was efficiently bioleached at a 50% pulp density with the drum operating at from 0.5 to 1.0 rpm. Attempts at bioleaching the concentrate at the same pulp density used in a conventional stirred reactor showed severe inhibition of bacterial activity. The results demonstrated that the drum reactor allows the process to operate at much higher pulp densities than conventional stirred-tank reactors. This results in improved bacterial activity because of better attrition control of the mineral particles.

Jan 1, 1999

By K. A. Natarajan, Namita Deo

Strains of Bacillus polymyxa, preadapted and grown in the presence of corundum, were found to be capable of the efficient separation of hematite from alumina. Results of tests performed using binary hematite-corundum and ternary he- matite-quartz-corundum mixtures in the presence of cells and metabolic products separated from the adapted bacterial culture indicated that more than 99% of the hematite could be efficiently separated through selective flocculation after desliming. It was found that alumina-specific bioproteins and other nonproteinaceous compounds were secreted by bacterial cells after adaptation to the mineral. The utility of this bioprocessing is demonstrated in the removal of iron from bauxite ores through selective

Jan 1, 2000

By M. Noaparast, F. Woodcock, A. R. Laplante

A novel methodology for estimating gold recoveries in gravity-separation circuits is presented. The methodology makes use of a population-balance model. The model represents gold liberation, breakage and classification behavior and applies preconcentration and recovery performance curves to gravity-recoverable gold. The derivation of the necessary parameters is explained and demonstrated using data from an actual gravity circuit and from a projected application. The methodology makes it possible to estimate the performance of a gravity circuit having a large gold circulating load and a relatively-low unit recovery (e.g., a jig) or having a high recovery on a bleed of the circulating load (e.g., a Knelson Concentrator).

Jan 1, 1996

By Chris Chmura, Ketut Karmawan, Ian J. Duckworth

P.T. Freeport Indonesia operates a mining complex located in the highlands of West Papua, Indonesia. Present production from PTFI’s DOZ Underground Block Cave Mine is approximately 40 thousand tonnes per day (ktpd). This paper describes the design process and recommended ventilation infrastructure necessary to expand the DOZ Mine reserves and to increase sustained daily production above 50 ktpd. The enlarged footprint will feature longer production panels of up to 650 m in length, more active draw points, a second large gyratory crusher, and additional men and mobile equipment. The increased ventilation capacity will be achieved through the development of new, dedicated ventilation drifts, and primary Underground exhaust fans.

Jan 1, 2005

By D. Edward, C. Clarkson, B. A. Firth

The presence of misplaced ultrafine particles decreases the separation efficiency of unit operations used in coal preparation. Although the classification of fine coal was considered to be adequate for the needs of the coal industry during the 1970s and 1980s, it is apparent that further improvements in the yield/ash/moisture relationship achieved by coal preparation plants will require increased efficiency in this size-separation step. This paper describes the capability of current and developing techniques to address the problems that need to be overcome.

Jan 1, 1998

By Tracy E. Barnes

The process of computerized reserve estimation consists of assuming a model of the spatial continuity of a deposit and then, working within the assumed model, estimating the grade and tonnage of the deposit. The basis for geostatistical analysis is a statistical definition of this continuity or the variogram. The true variogram is essentially impossible to define. So an experimental variogram is defined from the sample data and kriging proceeds assuming that this experimental variogram is a good approximation of the true variogram. Therefore the closer the experimental variogram is to the true variogram the better the estimate will be. Realizing that the variogram is nothing more than the definition of the spatial continuity of the deposit, taking the known geologic continuity of the deposit into account will give a superior variogram. The use of known geology is a widely recognized necessity for good structural analysis of a deposit, but is rarely fully incorporated into the structural analysis.

Jan 1, 1982

By L. B. Rothfeld

Two new coal use technologies are on the verge of commercial acceptance by the utility industry: atmospheric fluidized bed combustion (AFBC) and gasification combined cycle (GCC). Generating plants under construction or in planning will replace older pulverized coal (PC) boilers or substitute for new PC boiler capacity. This paper reports recent developments in the commercialization of AFBC and GCC, emphasizing the potential impact on the coal mining industry. The influence of coal quality characteristics on fuel selection is explored by means of preliminary economic calculations for different coals and competing fuels.

Jan 1, 1987

By Arthur P. Chaves, Lauro S. Norbert Costa, Adão B. Da Luz

A series of bench-scale bleaching tests have been carried out on kaolin samples from the Rio Capim area( northern Brazil) at CETEM/CNPq. The whole sample has been homogenized and submitted to particle size separation, when the + 44 µm fraction has been discarded, prior to being bleached. The main objective of this series of tests has been to evaluate the possible effects of interactions among variables which are believed to play important roles in the bleaching operation on the efficiency of the process itself in terms of the brightness achieved in the final product The tests have been planned according to a classical four-variable, two-level factorial technique. The chosen variables have been the pH, sodium dithionite addition, aluminium sulphate addition and bleaching time. The study has shown that, apart of time, all other three variables are significant. None of the interactions among them have shown to be of significance. Brightness numbers close to 88 have been obtained in the products, which represents an improvement, since brightness for the non-bleached - 44 µm Rio Capim kaolin sample averages 83.

Jan 1, 1995

By Bruce T. Stanley

Though most porphyry-molybdenum deposits lend themselves to various reserve estimating techniques, still there must exist the constant effort to not merely obtain an estimate but rather to obtain the best estimate. To answer the challenge of a complete ore reserve estimation, one must attack the problem with the purpose of obtaining the results closest to reality. What we wish to determine is simple: metric tons (short tons), grade, and kilograms (pounds) of molybdenum contained. In order to effectively accomplish this task, further consideration must be given to the ease of using the information obtained and its inherent reliability. The only known method for ore reserve estimation that supplies the needed results along with its distribution and a measure of confidence provided by sound mathematical backup is geostatistics. The following review is an example of geostatistical application of an ore reserve estimate at the AMAX Henderson mine demonstrating technique, viability, and usefulness of results.

Jan 1, 1979

By M. S. Klima, M. Fofana

The use of a laboratory-scale magnetic fluid-based separator for coal separations was examined. A Frantz laboratory magnetic separator was modified by fabricating new pole pieces of the appropriate geometry to provide the proper magnetic field gradients. Two separation chambers, which were constructed of Plexiglas, were designed to fit between the pole pieces. A commercially available, water-based, ferromagnetic fluid was used as the separating medium. The separating density was changed by varying the current intensity of the electromagnet coil. Both batch and continuous separations were made using 0.59 x 0.50-mm and 0.18 x 0. 15-mm coal. The results are compared to those obtained using organic liquids.

Jan 1, 1998

By V. Ciribeni, R. J. Ferretti, C. de Arrieta, E. E. Rossi

The relationship between collector concentration and the solution pH at which flotation occurs is discussed for different minerals. When flotation results are plotted as log of the concentration against pH, the values define areas of total, partial or no flotation. The experiments were performed in three different conditions: a) floating with the same solution used for conditioning; b) floating with water at the same pH as the conditioning solution; and c) floating with water at pH = 7. In each case, the results obtained are quite different. It is suggested that the presence of a second layer of collector reduces flotation over some domains in the graphs. These domains are called depression areas.

Jan 1, 1992

By M. Li, J. D. Miller

It has been discovered that water insoluble alcoholic solutions of alkyl hydroxamic acids serve as selective collectors for the flotation of phosphate mineral resources (Miller et al., 2000). The effectiveness of the new collector chemistry has been demonstrated by the results from single stage bench scale flotation experiments for feed material from plants in Florida, North Carolina, and Utah. In the best case, from experiments with low grade (5% P20,) coarse feed (16 x 35 mesh), a single stage phosphate recovery of 95% was achieved with a concentrate grade of 31% P20,. Such a separation efficiency could not be achieved using the traditional fatty acid/fuel oil collectors as is evident from a comparison of the respective grade/recovery curves.

Jan 1, 2002

By Paulo Roberto, S. M. Roberto, Francisco Valadares Póvoa, Evandro C. Silva

The market of mineral goods worldwide is characterized by a growing pressure on suppliers for better quality products, lower prices and productive processes which are energetically efficient and environmentally friendly. These pressures force the mineral industry to re-think not only the present models of exploitation of natural resources and production, but also their own model of techno- logical development. This paper outlines the model and the experience of Technology Strategic Planning (TSP) adopted by CVRD to face these demands, warranting and expanding its participation in the current markets and developing new businesses.

Jan 1, 1998

By Robert A. Hains, William P. Balaz, K. Payne

Ceramics are usually used to line chutes, pipes, dust collectors, separators, cyclones or bins where abrasive or corrosive material is moving. Improvements in ceramic manufacturing methods and quality, use of other abrasion resistant materials in combination with Alumina ceramic, improved adhesives and installation methods allow the use of Alumina ceramic tile in applications with impact. This paper discusses the criteria to determine if ceramics can provide a cost effective alternative to other liners for abrasive material handling applications, design parameters for liner systems, system costs, and case histories. The goal will be to provide a practical guide for improving the performance of existing ceramic lined systems or determining if ceramics is a cost effective solution for your abrasive material handling applications.

Jan 1, 1996

By Brij M. Moudgil, Shoulian Zhu, J. L. Pinault

A new technique, prompt neutron activation probe (PNAP), for analyzing phosphate rock slurry in-situ was evaluated both in the laboratory and at the plant. The technique yielded a high precision in the analysis of Ca, Si and H using 252Cf source. Low accuracy of the direct measurement of P using 241Am/Be in the laboratory tests was attributed to the interference of rare earth elements present in the samples, particularly Gadolinium. No significant effect of variables such as solids loading, particle size distribution, and flotation reagents was observed on the probe performance. The probe can detect the compositional changes of the feed, tailings and the concentrate streams in the plant.

Jan 1, 1993