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By J. A. M. Cano

Pot Grate tests were carried out in the pilot plant at Samarco producing pellets containing SiO2 between 2.0% and 2.2% in a wide range of basicity to be used in blast furnace. These pellets were submitted to tests in Samarco's laboratory and another laboratory in Germany to evaluate the metallurgical properties. The pellets in the binary basicity range (CaO/SiO2) from 0,87 to 0,95 were those that presented the best results in the Pot Grate tests. Based on the results, these pellets are being routinely produced?on industrial-scale confirming the results observed in laboratory tests.?

Jan 1, 1994

By Jun Yuan

Kaolin clays from five different commercial deposits in Georgia were studied to understand the variations of zeta potential and related fundamental properties. The results suggest that higher negative zeta potential is related to exchangeable or soluble calcium ions in the clays.

Jan 1, 1997

By R. K. Mehta

Stirred ball mill feed used for ultra-fine grinding application requires fine size separation step in order to avoid over-grinding. This paper presents the selectivity curves obtained for oil shale and complex sulfide are using 460 mesh (30 micron) Derrick vibrating screen. Interestingly, the selectivity curves generated from the experimental data were monotonic increasing selectivity for oil shale but not monotonic increasing for sulfide ore. These non-monotonic increasing selectivity curves were similar to the mechanical air separator fishhook selectivity curves described by Luckie and Austin. A 2 stage classification in series model describing the fishhook selectivity curve has been used in proposing the classification mechanism for fine vibrating screens when heterogeneous multicomponent sulfide are undergoes size separation.

Jan 1, 1992

By B. R. Pothini, H. von Schonfeldt

In underground coal mining many excavated openings have a relatively short projected life span. To ensure safety for men and materials at a minimum cost over the projected operating life, only pillars for overburden support and roof bolts for support of the openings are used extensively. Mining activity constantly changes the geometry of the mine producing load changes on the structural support members of the openings that often induce unstable deformations which can lead to roof falls or pillar failures. The paper describes how simple deformation measurements can be used to design primary and supplementary roof supports and to predict roof falls and possibly pillar bumps. Specifically, bed separations in the roof measured directly with the help of borescopes and calculated from differential convergence data are used to optimize bolt links or support requirements for chemical stabilization of mine roofs. Roof falls are predicted on the basis of admissible values for cumulative convergence between roof and floor, convergence rate, and the change of the rate of convergence. The pillar extraction operations convergence anomalies detected from contouring identify bump prone pillars, while convergence and pillar dilation determine the yield zone in a pillar to verify pillar softening and de-stressing. Manuscript not received in time for publication.

Jan 1, 1983

By Z. Yunquan

The flocculation and dispersion behaviors of microsize wolframite and quartz are systematically studied in this paper. For synthetic mixtures, the floc separatory method on gravity units--electromagnetic vibration table (EVT) and lifting column (LC), have been approached. Satisfactory results can be obtained with a weak shearing. A better metallurgical performance can also be achieved for natural ore slimes through the combined technique. The efficiency is better than that of single gravity separation. Finally, the mechanism has been investigated.

Jan 1, 1990

By R. Xiong, A. K. Fallaw, G. Wang, L. R. Moore, S. Dobson, J. Gu

"INTRODUCTION The Central District of the Florida phosphate industry is located in southwest Polk and southeast Hillsborough Counties, with the Southern Extension lying in western Hardee, eastern Manatee and northwest De Soto Counties. (Lawver, 1983) Figure 1 shows the major phosphate formations in Florida. Almost all Florida phosphate production has been in the Central district with additional production from a mine in the Northern District. The Central District is comprised of the Bone Valley Deposit, a relatively thin layer of high grade ore which has been the main source of phosphate mining for decades, and the Hawthorn formation, a thick but low grade formation which covers most of peninsular Florida. (Lawver, 1983) Florida phosphate producers use the Crago process where calcium phosphate is floated with anionic, fatty acid type collectors followed by cationic reverse flotation of silica with amine type collectors. The phosphate matrix is put through various size separation techniques to obtain a typical -28 Mesh (< 700 µm) particle size for fine flotation and a -16 mesh (< 1190 µm) to +28 mesh (> 700 µm) particle size for coarse flotation. In some cases this coarse fraction can be sent to shipping as an intermediate product. The +16 mesh (>1190 µm) to – ¾“ (19 mm) fraction is sent to shipping as a final product called pebble. Figure 2 demonstrates a simplified diagram of the mining and processing of calcium phosphate (matrix) through a Central Florida mine. Particle size and mineralogy are important considerations in the Crago process for two main reasons, the mass of the particle and the particle surface area. Both of which are dependent on the coordination of the anionic collector to available Ca2+ sites on the minerals’ surface. The increased surface area, and available Ca2+, of the smaller apatite particles will allow for more fatty acid molecules to coordinate than the larger particles, with a lower availability of Ca2+. So, the larger particle would require more collector to be introduced in the system to sufficiently cover the apatite particles to produce a surface sufficiently hydrophobic to attach to air bubbles allowing flotation to occur. (Guan, 2009) The Bone Valley deposit has very favorable flotation characteristics when compared to other mining ores around the world. The matrix of the Bone Valley is relatively high grade, BPL (Bone Phosphate in Lime) values typically range from 6-18%, BPL recoveries, from such a matrix, can often be achieved above 85+% with fatty acid based collectors dosed below 1 #/ton. As mentioned, the sizing is an important step as there is also high grade apatite in the +16 mesh (1mm) that is screened to a final product grade, 60-65% BPL. The lack of quartz in the larger size fraction has allowed the Central District to produce high quality, low cost phosphate product, called pebble, through effective screening with no further beneficiation. (Guan, 2009)"

Jan 1, 2015

By A. Bhagwat, S. Tadolini

"Steel members of the ground support systems in underground mines are routinely exposed to corrosive environment that may range from acidic to alkaline. Corrosion of steel bolts leads to metal loss and thereby, reduction in strength and useful life. Protective coatings are commonly applied to the steel bolts to combat corrosion. However, coatings are expensive and often cumbersome in practical applications. Instead, Minova has developed an innovative technology based on sacrificial anodes. The anodes were designed from non-ferritic alloys that are inferior to steel on the Galvanic Series. This paper will present data from field testing to show significant benefit of the technology. Potential applications in current products will be discussed. INTRODUCTION Corrosion is a physical alteration of a steel material from electrochemical reaction with its environment that often results in reduction of the mechanical and physical properties of that material. Mine roof bolts, the subject of this investigation, are particularly susceptible to corrosion as they can be exposed in their working environment to ground water and air with high humidity. As other researchers have determined, corrosion increases markedly in sulfide ore bodies due to acid runoff. There are several types of corrosion that a rock bolt is likely to undergo when used for ground reinforcement in underground mines (Aziz et al., 2013). Of all the types of corrosion, pitting is particularly dangerous as it can remove capacity for the bolt to deform with subsequent strata movements. Sudden failure of a bolt is likely to occur when severe pitting corrosion is experienced. The type and nature of corrosion depend on the nature of the ground condition and bolt encapsulation. Generally, the type of corrosion and severity of the corrosion varies along the axis of bolt. Almost all of the mine roof bolts used in mines, with the exception of fiber reinforced polymers, are made from steel. The corrosion of iron is an electrochemical phenomenon with the overall equation:"

Jan 1, 2018

By C. E. Semler

A 5 year test program, involving on-line, in-vessel exposures at Barrick Goldstrike Mines. Inc. has provided valuable information and experience about the materials and designs for brickwork linings in pressure oxidation autoclaves. A variety of brick and mortar products have been evaluated. Properties before and after exposure are used to document the performance. Benefits have included the development of a new silicate mortar improved understanding of brick requirements and increased autoclave operating time between maintenance shut-downs. More improvements are expected in the future based on further information from the test program.

Jan 1, 1997

By W. A. McKinney

The U.S. Bureau of Mines, Kennecott Copper Corp., and New Mexico Institute of Mining and Technology are cooperating on a research project to improve extraction of copper from previously leached waste dumps that are in part compacted and impervious to leach solutions. The field work is being done at the "J" leach dump, Chino Mines Division, Kennecott Copper Corp., Santa Rita, N. Mex. The laboratory percolation leaching tests were made at the U.S. Bureau of Mines Salt Lake City Metallurgy Research Center on drill core samples from the "J" dump to determine how much copper might be leached if permeability could be restored by explosive heaving or other means. The core samples from nine drill holes on "J" dump contained from 0.06 to 0.14 percent copper. Copper extractions ranging from 15 to 3 percent were obtained in 75 days by percolation leaching of minus-1-inch material with dilute sulfuric acid. The tests results indicate that about 2&apos;7 percent of the copper remaining in the "J" dump could be extracted under ideal leaching conditions.

Jan 1, 1970

By S. G. Sawyer

The Pittsburgh Safety and Health Technology Center (PSHTC) of the Mine Safety and Health Administration (MSHA) provides engineering and scientific support to the inspectorate personnel of MSHA. One of the Center&apos;s myriad roles is to assist in the investigation of mining accidents, especially those involving fatalities. Center personnel utilize forensics to help uncover the causes of accidents and to make technical recommendations on the prevention of future similar mishaps. To exemplify a typical forensic investigation, this paper documents the methodology used in determining the reasons for a boat sinking, which resulted in a double fatality on a mine company pond.

Jan 1, 1997

By T. Guler

Turkey has important celestite reserves in Sivas. These reserves have gypsum and/or calcite as gangue minerals. Celestite-calcite ore cannot be concentrated by gravity methods due to the low efficiency of gravity methods in fine sizes. Research was tried to concentrate celestite to a market grade by flotation. Parameters such as pH, particle size, dosage and types of collector and depressant were examined. Cyanamid A-845 and Na-oleate combination as collector, sodium silicate as depressant, and Aerofroth-65 as frother were found as the optimum flotation reagents. By applying 3-stage cleaning, a concentrate assaying 95,34 % SrS04 was obtained with 84,93 % recovery.

Jan 1, 1999

By Robert Moore Lewis

Extensive exploration is being undertaken throughout the world in search for heavy minerals, particularly rutile and other titanium minerals. The federal government is sponsoring research involving rutile ores and recovery of stockpile-grade concentrates from domestic sources. Producers are being forced to turn to deposits with a heavy mineral content as low as 0.50% (essentially rutile and zircon). The North Carolina State University Minerals Research Laboratory investigated the possibilities of recovering heavy minerals from the amine tailings of the Texasgulf Inc.&apos;s phosphate plant at Aurora, North Carolina. One laboratory beneficiation procedure using gravity, electrostatic and magnetic processes, resulted in the recovery of 78.7% of the heavy minerals in the amine tailings. Based on this percentage recovery and the present rate of phosphate mining, approximately 13,000 tons per year of heavy minerals (principally ilmenite and zircon) with a potential value of approximately $1,045,000 (1977) could be recovered. The economic potential for recovery of these heavy minerals appears to be favorable. A flotation procedure for up-grading the heavy minerals content in the amine tailings has been developed at the Laboratory, which could allow for concentration of heavy minerals and storing them in tailings area other than main tailings for future processing.

Jan 1, 1978

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 sulfur) coal which may be mined when the better deposits are depleted.

Jan 1, 1997

By Kendall Y. Keuhey

The Mercur Mine, developed and operated by Getty Mining Company, is designed to process 3,000 tons/day of gold ore from the historical Mercur Hill mining district. The mill process involves crushing, grinding, and cyanide carbon in leach for recovery of gold ores ranging from 0.08 to 0.10 oz/ton. During the mining of normal grade ore, a substantial tonnage of material containing 0.02 to 0.05 oz/ton is mined and would be available for heap leaching. Also, Getty Mining is developing methods to test and prepare lower grade material for heap leaching by rejecting a course rock fraction from the grinding circuit SAG mill. This lower grade fraction is suitable for heap leaching, and its removal will upgrade the regular mill feed. Other test methods are directed toward leaching techniques on some 4.0 million tons of tailings that resulted from roasting and/or cyanide leaching Mercur ores in the early 1900s. The natural carbons associated with the Mercur deposits require special treatment to reduce their gold adsorption effects when leached with cyanide.

Jan 1, 1983

By M. G. Vieira

This investigation addressed the possibility of producing pellet feed at a silica content of = 1.0% using a representative sample of Samarco´s mechanical flotation tailings. This sample contained 11.0% Fe and presented an F80 = 116 µm and a d50 = 63 µm. The higher silica content was verified in the coarser fractions and the higher iron content in the fraction -37 µm. Specular hematite is the most abundant mineralogical phase in the fraction -37 µm. The technological tests used one of four methods: magnetic concentration using a wet high-intensity magnetic separator, magnetic concentration using a SLon high-gradient magnetic separator, reverse flotation or direct flotation. The methods using the magnetic concentrator SLon, reverse flotation and direct flotation did not present results meeting the target of the study: iron content in the concentrate (rougher stage) greater than 34% or iron recovery greater than 80%. Cleaner stages were not achievable with the resulting concentrates. In contrast, the most successful method consisted of using wet high-intensity magnetic separators (WHIMS) as a rougher stage and reverse flotation as a cleaner stage. Using this route, it was possible to produce a pellet feed with a silica grade of 1.0% and high specular hematite content.

Jan 1, 2010

By Robert A. Bauer

Introduction A longwall mining demonstration currently in progress in the Herrin (No.6) Coal Member near Benton, Illinois, involves the extraction of three adjacent panels by the longwall method. The first panel was completed in May, 1977. The Illinois State Geological Survey is involved in this project for two reasons: (1) to detail the geology of the roof and relate the geologic features to the behavior of the roof during mining operations, and (2) to study the nature and occurrence of coal balls (carbonate petrifactions of peat) encountered during this demonstration. General Geology of Area The stratigraphic sequence of beds immediately above the No. 6 Coal in this area, ranging from oldest to youngest, is: gray shale (Energy Shale Member), black carbonaceous shale (Anna Shale Member), and argillaceous limestone (Brereton Limestone Member) (figure 1). In some areas of the mine, where one of these units may rest directly on the coal, one or more of the members is absent from the stratigraphic sequence. The nature of roof for the area is shown in figure 2. It is greatly exaggerated in the vertical direction. The Walshville Channel, 11.3 km west of this mine, was a river at least in part deposited at the same time as the coal. The gray shale wedge on top of the coal, which thins away from the channel, is thought to represent an overbank deposit of mud from the channel. The next layer deposited on top of the gray shale, and on the coal not covered by gray shale, is the black carbonaceous shale, believed to represent a mud deposited in a brackish environment. The area where the roof lithologies change rapidly from one shale to

Jan 1, 1977

By S. P. Singh

Drifts are the nerve centre of underground mining. They provide essential communications between primary openings and production areas. In view of their strategic importance in the overall safety, economy and productivity of mines, an empirical approach for blast design during drifting has been proposed in this paper. The approach was developed with the objective of minimum blast damage and provides computerized blasthole patterns for drifting operations. The drift blasting practices and problems in Canadian mines have also been reviewed in this paper.

Jan 1, 1991

By K. T. Valsaraj

The separation process called solvent sublation for the removal of two hydrophobic compounds (penta-and tri-chlorophenols) from the aqueous phase is discussed. A steady state mathematical model for the process is discussed. The process was conducted in a continuous countercurrent mode. The underlying mechanisms, theory and experimental details on the effects of process variables on removal efficiency are reported.

Jan 1, 1992

By J. R. Carr

A crucial concern when implementing computer algorithms for geostatistical analyses on microcomputers is speed of execution. Kriging, in particular, typically relies on a Gauss elimination algorithm to solve for weights. Because such an algorithm is required for each estimate, the solution for weights can result in very slow program execution speed on a microcomputer. One approach to enhancing the efficiency of Gauss elimination is demonstrated herein. The upper triangle plus diagonal of the intersample covariance matrix is used in a modified banded Gauss elimination algorithm. Results show that such an algorithm yields approximately a two-fold reduction in execution time for kriging when the number of nearest neighbors used for estimation is large.

Jan 1, 1990

By James N. Brentz

This paper deals briefly with the problem of efficiently selecting the most cost effective haulage truck. Problems and factors are identified that effect productivity and operating cost. Despite the sophistication of computerized vehicle simulation programs, there is a wide disparity in accuracy and methodology, particularly in dealing with the various elements of cost.

Jan 1, 1984