Search Documents

By R. R. Beebe

Marcona Corporation produces about 3.5 million long tons of iron ore pellets annually on its two travelling grate pelletizing machines at San Nicolas, Peru. During 1969, these pellets will be shipped to customers in four marketing areas--Japan, the United States, Europe, and South America. All of these sales are on the open market, and product quality is a major concern. Typical chemical, structural, and quality test results for Marcona pellets are given in Table 1. [ ]

Jan 1, 1969

By Keith Jones, Martin Knights, Timothy Watson

In 1996 a KBR (Brown and Root) led international JV was appointed to design and supervise an underground and surface package. The design of 6 km of tunnels, plus enlargements, deep shafts in glacial and sandstone deposits for the conversion of the existing LEP underground laboratory at CERN, Geneva adjacent to the Jura Mountains/Lake Geneva had to be undertaken in an operational environment and in conjunction with other underground constructions associated with the US$3bn refurbishment.

Jan 1, 2003

By M. B. Mooiman

It has recently been discovered that the pH at which gold can be extracted from cyanide solution with primary, secondary, and tertiary amines can be increased 2 to 5 pH units by the addition of modifiers. Under these circumstances gold can be extracted at pH values from 9 to 11, commensurate with the pH range found in cyanide leach liquors. The selectivity of the amines and amine/modifier combinations for AU (CN)[-2] over other metal -cyanide complexes is presented and discussed. In addition, potential applications for the solvent extraction of gold from cyanide solutions are discussed.

Jan 1, 1983

By Gordon A. Gross

Banded siliceous manganese-iron bearing sediments recognized as distinctive facies of Algoma type iron-formation constitute low grade resources of manganese in many countries. Manganiferous facies associated with oxide and carbonate facies of iron-formation have iron to manganese ratios ranging from 0.2 to 2 and commonly about one. Manganiferous facies up to 30 meters thick occurring separately or with other iron-formation facies are associated with cherts, carbonates, shales, turbidites, tuffs and lavas. Primary cherty manganiferous facies and their gondite metamorphic equivalents represent significant manganese resources and are protores for higher grade deposits derived by secondary enrichment processes.

Jan 1, 1982

By P. R. Hervey

Quartz is the second most widely used electronic material, with approximately 3,000 tons of single crystals used each year. Virtually all of this material is synthetic; grown with a technique called hydrothermal growth. We will review the basics of hydrothermal growth, the feedstocks for these crystals, and the challenges to improving the growth process. We will also review the processing of these crystals, the markets and applications where they are used, and the global outlook for these markets.

Jan 1, 1999

By Zygmunt Sadowski

Problems encountered in barite flotation from various waste materials such as spent drilling muds are likely to be closely connected with the effect of chemical additives and metal ions present either added or present as contaminants, on the flotation. Fuerstenau and Palmer (1976) have studied in detail the adsorption of multivalent cations onto oxide and silicate minerals. It was observed that the adsorption of a multivalent metal species exhibits a sharp pH dependence which is related to the formation of hydroxy complexes of the metal ions in solution. Investigations on the recovery of barite from tailings ponds and mining wastes (Sullivan and Lamot, 1981) have shown that such barite materials can contain large quantities of carbonate and silicate minerals (including clay minerals). Also iron oxide slimes can be present. From these substances cations such as Ca2+, Mg2+, Fe2+ and A13+ can potentially dissolve and be present in the aqueous phase accompanying the various minerals. These ions and their hydrolysis products can have a substantial effect on any subsequent flotation scheme. The present study investigates the effect of the noted ions on both the stability and electrokinetic behavior of barite suspensions.

Jan 1, 1986

By Paul Schmidt, John Barber

This paper discusses the determination of cutoff grade (COG), including all revenue and cost factors and how to apply the COG in the world of engineering studies and mine planning for underground mines. It provides the engineer with important considerations and practical methods to establish COG and methods of using the COG in the work of mine planning, including the application of Mineable Stope Optimizer (MSO) software which is available on several 3D mine planning packages.

Feb 1, 2024

By James K. Gowans

The Red Dog Operation is located in northwestern Alaska at Latitude 68°, 100 miles north of the Arctic Circle and 50 miles inland from the Chukchi Sea. The orebody was acquired by the NANA Regional Corporation, (an Alaska Native Corporation established by the Alaska Native Claims Settlement Act of 1971), in 1980 in their land selection. In 1982 Cominco American and the NANA Corporation signed a development agreement and Cominco Alaska Inc., a wholly owned subsidiary of Cominco American, was formed to manage the Red Dog Project. An extensive exploration program in 1980 -1982 outlined a mineral inventory of 85 million tons, at a grade of 5.2% Pb, 17.1 % Zn, and 2.4 oz/ton Ag, which makes the Red Dog the second largest deposit ever discovered. Broken Hill, in Australia, is the only zinc orebody which was originally larger than Red Dog. The design of the facilities is to process 2.1 million tons of ore annually, which will produce 560,000 tons of zinc concentrate, 100,000 tons of lead concentrate and 50,000 tons of bulk lead/zinc concentrate.

Jan 1, 1991

By Jr. Foot

EIMCO Process Equipment Company has introduced the new SmartCell series of conventional flotation cells. The flagship of this new development is the 5000 ft3 cell that is the largest available in industry. This new series of cells includes a cylindrical tank design, a conical draft tube and froth crowder. Optional air control, wash water addition and embedded expert control are available. A discussion of the design parameters, energy efficiency, testing, and commercial plant results are presented.

Jan 1, 1997

By Anthony R. Przybylek, John M. Visnesky

INTRODUCTION Thermal dryers have been utilized for reducing moisture of bituminous coal since the late 1930's. Since that time, numerous changes in the coal industry have motivated advances in thermal drying technology. The purpose of this paper is to discuss the changes that occurred to dryer design and focus on current practices of fine coal drying. The major topics discussed in this paper are: - Early Thermal Dryer Design and Evolution - Current Drying System Design and Associated Components - Current Economics of Fine Coal Thermal Drying - Future Markets and Design Considerations EARLY THERMAL DRYER DESIGN AND EVOLUTION Background The practice of drying fine coal with heated air has been performed for more than one half century. Throughout that period, both Metallurgical and Steam coal producers have used this method for reducing the surf ace moisture content of their fine plant products. During the late 1930's and early 19401s, vibrating bed and flash dryers were used to per- form the drying duties. Closed water circuits and vacuum filtration had not yet been integrated into process circuitry and centrifugal dryers were in their early stages of development. During that same period, changes in mining practices were reshaping the distribution of coal to our processing facilities. Plants originally designed for the purpose of processing coarser fractions of coal were being burdened with additional quantities of fine coal. Those plants, unable to recover fine coal, would reject these solids to plant bleed. The higher incidences of stream pollution that resulted from these events prompted clean stream legislation and the need for new, more efficient fine coal recovery circuits. The coal processing industry responded to these needs by integrating closed water circuits and filtration into circuits. The fine coal filter cakes recovered exhibited poor handling characteristics by themselves and often required further dewatering to improve their characteristics. Flash dryers at that time were being used to dry the coarser products. For those facilities operating flash dryers, the solution to this new problem appeared to be simple. The filter cake was combined with the coarser (-1/4") coal and then introduced to the flash drying column for drying. The filter cakes, however, presented significant problems for the flash drying systems. Heavy lumps of filter cake could not be dispersed and conveyed by the rising hot air and as a result would settle out in the bottom of the column. This material, known as "drop-out", would then accumulate and require further handling. The solution to this problem was not an easy one. Sophisticated mixing equipment was employed to condition the feed to the dryers. As attempts to minimize drop-out with this approach failed, the only recourse was to collect the material with conveying systems and recycle it back to the plant or dispose of it. The additional costs of handling this material reduced the attractiveness of the flash systems and opened the door for the development of a new, more cost effective coal drying system. Due to the nature of the problems experienced by the flash systems, fluid bed systems were considered. Fluid bed dryers were being used in other industries at that time but had no operating history in the coal industry. Dorr-Oliver transferred technology from other industries and built the first fluid bed drying system for fine coal.

Jan 1, 1988

By Louis W. Cope

Placer material, regardless of the value of gold, tin, titanium, diamonds or other value mineral it contains, remains worthless until the valuable constituent is separated from the bulk of the material. This separation is no mean task when considering that a gold placer containing 0.01 to 0.03 oz/yd3 of gold, which is the range of grade of typical placer deposits; yes, 1:3,000,000! It is a miracle that gold placer mining has ever been profitable. Added to the situation of minute quantities of gold are several other problems, such as the gold often being very finely divided, the association of boulders and clay, and running and/or ground water. As each placer deposit is individual and distinctive, many factors have to be considered in planning the method for gold recovery from the alluvial deposit. Previous chapters have shown that in the exploration and sampling stage, some knowledge of the amount of each size of coarse and fine material which occurs in the deposit as well as the size distribution of the discrete gold particles is determined. Unless informed to the contrary, as a general rule of thumb, plant designers will consider that 40 percent of the material will pass through a 5/8-inch screen or punched plate hole. Also that there may be an occasional nugget and normally considerable amounts of fine gold. The designer must

Jan 1, 1992

By R. Asamoah, P. Forson, W. Skinner, M. Zanin

Despite the seeming benefits decoupling pyrite and arsenopyrite minerals present in practice, little success has been achieved. The present study presents possible process routes for attaining selective flotation broadly capitalizing on differential oxidation between these minerals, and the use of a chelating collectors. The best performance was achieved with dithionocarbamate application following copper activation, yielding 81.4% arsenopyrite and 37% pyrite recovery. Preaeration followed by staged addition of xanthate produced 76% arsenopyrite and 31% pyrite recovery while reverse flotation of pyrite after H2O2 addition gave rise to rejection of 66% pyrite accompanied with 24% arsenopyrite.

Mar 2, 2022

By M. Misra, I. A. H. Schneider

The flocculation of -38 pm calcite, hematite and kaolinite aqueous suspensions by the yeast Candida parapsilosis and products derived from rupture of the microorganism was studied. Flocculation of hematite suspensions by the microorganism and its derivatives readily takes place between pH 2.8 and 11.4. Maximum flocculation occurs at about pH 6.5. Flocculation of calcite suspensions by the microorganism and its derivatives readily takes place between pH 7.0 and 11.8. Maximum flocculation occurs at about pH 10.0. Flocculation of kaolinite suspensions was less than that for the other two minerals. However, a soluble fraction derived from the rupture of the organism functioned as a good flocculant for the mineral, albeit at an increased concentration, between pH 2.6 and 11.5. Maximum flocculation occurs between pH 6.8 and 7.2. An attempt is made to relate the behavior of the various systems to the surface characteristics of the minerals and the surface and chemical properties of microorganism and its derivatives. Experimentation used to evaluate the flocculation includes actual flocculation tests, microelectrophoresis measurements and scanning electron microscopy.

Jan 1, 1994

By L. G. Austin

The data of Dunn and Martin (1978) is reanalyzed using a rigorous application of Hertzian theory to the impact process. The Young's modulus of steel required to fit their data to the theory is a factor of about 10 3, too low compared to the values quoted for steels. Thus, doubt is thrown on the validity of their experimental technique, and it is possible that their values for maximum impact force and stress are far too low.

Jan 1, 2002

By C. A. Pickles, D. Mallette

Silicon nitride (Si3N4 ) is an advanced structural ceramic materia1 which is presently being considered for a number of potential engineering applications, particularly in heat engines, gas turbines, and electronics. With respect to other structural ceramics, silicon nitride has relatively low thermal conductivity and thermal expansion coefficients and a moderate elastic modulus. Thus, during thermal cycling the stresses developed in this material are lower than in other structural ceramics. At the present time silicon nitride is produced via three main processes: thermal decomposition of silicon imide or amide, treatment of silicon tetrachloride or silane vapour with ammonia and nitriding of silicon powder. These three methods of production are discussed with particular attention to the effect of morphology and phase content on the properties of the final product. In this work carbothermal production of silicon nitride has been studied in a high temperature resistance furnace. Compacted briquettes of silica and carbon were produced which were reacted in a nitrogen atmosphere. The optimum reaction temperature and the carbon to silica ratio were found to be 1425OC and ten to one, respectively. The presence of large amounts of ash in the reductant promoted the formation of silicon nitride. The specific surface area of the briquettes did not have a large effect over the range studied in the present work. Briquette seeding with small amounts of Si3N4 was effective in increasing the reaction rates.

Jan 1, 1990

By Mahesh C. Jha, Frank J. Smit

Column flotation and selective agglomeration are promising advanced physical cleaning processes that can be developed for preparing premium quality coal-water slurry fuel from coal fines. Such a fuel could either replace oil or natural gas in certain industrial and utility boilers or else could be burned in advanced combustors currently under development. These applications require coal cleaned to sulfur and ash contents below 258 g/GJ and 430 - 860 g/GJ (0.6 lb/million Btu and 1 - 2 lb/million Btu), respectively, to meet clean air emission requirements. A highly loaded slurry must be produced in order to avoid derating the boilers, and the total cost of the fuel must be below $2.37/GJ ($2.50/million Btu) in order to penetrate the market by the turn of the century. Achieving these technical and economic goals depend critically on the selection of suitable feed coals. This paper describes the identification and evaluation of 18 coals and final selection of six coals from different regions of the United States as potential feedstock for preparation of premium fuel. The work is being performed under a cost-shared DOE project.

Jan 1, 1995

By J. C. Judd, D. D. Harbuck, M. D. Odekirk

The US Bureau of Mines investigated germanium and gallium extraction from an ore containing 0.089% Ge and 0.036% Ga. While previous researchers concluded that a reducing agent, such as SO2 is needed to extract germanium and gallium from such ore, this research showed that high extractions (87% Ge, 97% Ga) were possible using sulfuric acid alone, if the acid concentration were properly controlled. This control was achieved using a two-stage countercurrent leach circuit. Microprobe analyses revealed that the non-extracted germanium is in solid solution with quartz, and therefore cannot be leached with SO2 or sulfuric acid.

Jan 1, 1992

By D. Lenartowicz, K. R. Alexander, M Collings

Cosmo Howley is a gold deposit in the Northern Territory of Australia. The geology is complex and the input of geological data is an important part of the grade control process. As the geology of the deposit has become better understood, grade control and mining techniques have evolved to meet the changing circumstances. Present grade control depends on the use of angled blast holes, 21/2 benches and selective mining. Data is processed on site using 2 386 PC's running Surpac software. An environmental protection programme is employed, including soil stripping and stockpiling, sulphide waste containment and water quality monitoring.

Jan 1, 1989

By D. D. Harbuck

The US Bureau of Mines investigated germanium and gallium extraction from an ore containing 0.089% Ge and 0.036% Ga. While previous researchers concluded that a reducing agent, such as SO2 is needed to extract germanium and gallium from such ore, this research showed that high extractions (87% Ge, 97% Ga) were possible using sulfuric acid alone, if the acid concentration were properly controlled. This control was achieved using a two-stage countercurrent leach circuit. Microprobe analyses revealed that the non-extracted germanium is in solid solution with quartz, and therefore cannot be leached with SO2 or sulfuric acid.

Jan 1, 1991

By H. Nematollahi

Numerous magnesite deposits are found in the south part of Khorasan state, east of Iran. During the past few years, production of high-grade magnesite ore was possible only by using selective mining method. The decreases of high-grade ore imply upgrading of the low-grade ore. To do so, the objective for the first phase is to obtain a material which contains less than 2.5% SiO2. The present study was carried out based on three different samples. The results obtained in laboratory indicate that the direct flotation of magnesite by fatty acids led to acceptable result.

Jan 1, 2003