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By B. K. Parekh

Silicon carbide (SiC) can be produced by heating rice hulls to elevated temperature, The product is a mixture of beta crystalline silicon carbide whiskers, particles and unreacted carbon. The silicon carbide whiskers are 0.5 micron in diameter and 50 to 100 micron in length and have been found useful for reinforcing metal and other composite materials. The carbon can be removed by combustion, but this makes separation of the silicon carbide whiskers from particles difficult and a high grade whisker product cannot be made. However, a clean high grade Sic whiskers product can be obtained from the pre-burned converted rice hulls using physical separation processes that are based on differential wetting. Recovery of Sic whiskers from the pre-burned material was found to exceed 90 percent. A modification of the froth flotation process developed during this study is now being used commercially to separate silicon carbide whiskers and particles and to recover a high grade whisker product.

Jan 1, 1985

By Steven Tubbs

Steven Tubbs From mine to farm is a long journey for Florida's phosphate, but it is an important one to the American farmer who uses phosphate fertilizers to replenish the soil and produce the crops which eventually wind up on the American dinner table. In this phosphate-food connection, transportation plays a vital life-giving role, a role that is unique because of the large quantities of phosphate produced and the mineral's location in relation to its markets. Florida Leads World Florida is the world's largest phosphate producer, supplying 80% of the nation's and a third of the world's annual total. About 95% of Florida's phosphate goes into agricultural chemicals, with 90% going into fertilizers. Phosphate production is primarily concentrated in west central Florida, with the exception of mining and processing in north Florida by Occidental Chemical Co. The phosphate rock is beneficiated at the mine sites and then is transported out of Florida in a raw state, or to one of the industry's 18 chemical complexes where it is processed further. In 1981, Florida produced more than 42 Mt (46 million st) of phosphate rock-a 1% decrease from 1980. The industry also produced more than 12 Mt (13 million st) of phosphate chemical products in 1981 and transported them to both domestic and foreign customers. This year, the state's phosphate production and shipments are substantially lower than recent annual levels because of a depressed worldwide phosphate market. With production down slightly in 1981, shipments declined and company inventories increased dramatically. Phosphate-related shipments through the port of Tampa alone fell 20%. As a result, in 1982, phosphate operations cut production to reduce inventories. According to the Fertilizer Institute, during the fiscal year ending June 30, 1982, phosphate rock production fell 18%; phosphate rock shipments, 28%; finished fertilizer production, 30%; finished fertilizer shipments, 25%; and phosphate rock exports declined by 20%. Despite depressed conditions, Florida phosphate production and shipments are expected to increase in the near future with more rock being processed into fertilizer products. Phosphate is one of Florida's major industries. The US Bureau of Mines estimates it contributed $3 billion to the state's economy in 1981 and an additional $1.4 billion to the US economy. In addition, phosphate exports contributed to

Jan 10, 1982

By K. V. S. Sastry, A. J. Hunt, K. D. Lofftus

Sol-gel processing is rapidly becoming an important process for producing such advanced materials as high activity catalysts, fiber optics and ceramic precursors. These materials can be tailor made with properties unique to sol particles as well as the gel aggregates by controlling production of the sol, the formation of the gel, and the removal of the interstitial fluids. This paper presents colloidal and kinetic principles of sol generation and gel formation. Hydrolysis of alkoxides provides the best means of controlling sol production and electrostatic stabilization enables the formation of the most homogeneous gels. Gelation occurs by hierarchial aggregation which produces inhomogeneities much larger than the sol particles. Colloidal and kinetic principles can be applied to reduce the size of the inhomogeneities and obtain high performance transparent insulation and new ceramic composites.

Jan 1, 1990

By K. P. Stricker, H. Keddeinis, K. Grebe

Recent investigations by Mannesmann Research have shown that disintegration of sinter with widely varying quality levels is subject to a much more complex set of influences than was previously assumed. It was confirmed that disintegration at temperatures between 300° and 600°C (570° and 1,110°F) is triggered by the degradation of hematite. The specific tendency of hematite to disintegrate is, however, not constant: sinters containing the same amount of hematite can show widely differing disintegration tendencies, depending on structural homogeneity, porosity, and gangue quantity. Sinters with heterogeneous structures transmit stress to the hematite phase and this favors disintegration. Another factor is the brittleness of the glassy silicate phase, which can be influenced even by small modifications of minor gangue constituents.

Jan 2, 1984

By S. J. Schatzel, K. M. Ajayi, E. N. Rubinstein, Z. Khademian

This study simulates the impact of a shale gas well casing breach near a longwall mine. Field studies are conducted to measure mining-induced permeability changes over the abutment pillar of a longwall mine, and a geomechanical model is developed in 3DEC, a three-dimensional numerical modeling code, to predict the aperture of fractures in the overburden at the study site. The predicted aperture values are used to determine mining-induced permeabilities, and the results are compared with the field measurements. These aperture values are provided as inputs into fracture flow code (FFC), which generates a stochastic discrete fracture network (DFN) model for the study site and predicts the potential shale gas flow to the mine. Results from 100 DFN realizations are statistically analyzed using the bootstrapping method to compensate for notable variation in fracture geometry. The results show a significant difference between the gas inflow for nearby panels due to increase in the induced permeability during mining of the second panel. The average gas flow to the mine was calculated as 4.72 × 10 m3/s (49 cfm) for a hypothetical breach at the Sewickley horizon during the first panel mining, 8.97 × 10 m3/s (19 cfm) for a hypothetical breach at the Uniontown horizon during the first panel mining, 2.16 × 10 m3/s (458 cfm) for a hypothetical breach at the Sewickley horizon during the second panel mining, and 8.07 × 10 m3/s (171 cfm) for a hypothetical breach at the Uniontown horizon during the second panel mining. Depending on the mine ventilation system, this could result in methane concentrations exceeding regulatory limits. Hence, these findings provide insights into the potential risk of an unconventional gas well casing breach near a longwall mine under shallow cover.

Feb 1, 2024

By P. J. G. du Toi

Anaconda's experience with percussion longhole drilling in Butte, Montana, has consisted of six phases: 1. Drilling horizontal blast holes in stopes with push feeds. 2. Ring and parallel blast hole drilling in longhole stopes with bar mounted as well as skid jumbo mounted longhole drifters. 3. Ring and parallel drilling in raise climber shrinkage stoping using special raise climber drilling decks designed and built in Butte, Montana. 4. Parallel longhole drilling in horizontal cut and fill stopes with monorail jumbo. 5. Drilling water drain holes between mine levels. 6. Drilling leach holes through caved zones into old stope workings for leaching purposes. 7. Sample hole drilling.

Jan 1, 1970

By D. G. Krige

I read the paper “The jackknife approach” with interest. There appears to be a widespread misunderstanding of the kriging variance as a measure of the error variance of the kriged grade estimate of an ore block. Virtually all mineral deposits display skew frequency distributions and are subject to the well-known proportional effect. Thus, it is usual to find in an ore body, when subdivided a really into subpopulations, that the variances of the grades (or the total sills of the variograms) for the subpopulations will be correlated with the corresponding mean grades (usually linearly with the squares of the mean grades). Thus, the variogram will be stationary.

Jan 1, 1996

By T. Grounds, K. Singh, W. R. Reed, R. Cross, G. Ross, S. Klima, M. Shahan

"A 2nd generation roof bolter canopy air curtain (CAC) design was tested by National Institute for Occupational Safety and Health (NIOSH) at a Midwestern underground coal mine. During the study, the roof bolter never operated downwind of the continuous miner. Using a combination of personal Data Rams (pDR) and gravimetric samplers, the dust control efficiency of the roof bolter CAC was ascertained. Performance evaluation was determined using three methods: (1) comparing roof bolter operator concentrations underneath the CAC to roof bolter concentrations outside the CAC, (2) comparing roof bolter operator concentrations underneath the CAC to the concentrations at the rear of the bolter, and finally, (3) using the gravimetric data directly underneath the CAC to correct roof bolter operator concentrations underneath the CAC and comparing them to the concentrations at the rear of the bolter. Method 1 dust control efficiencies ranged from -53.9% to 60.4%. Method 2 efficiencies ranged from -150.5% to 52.2%, and Method 3 efficiencies ranged from 40.7% to 91%. Reasons for negative and low dust control efficiencies are provided in this paper and include: incorrect sampling locations, large distance between CAC and operator, and contamination of intake air from line curtain. Low dust concentrations encountered during the testing made it difficult to discern whether differences in concentrations were due to the CAC or due to variances inherent in experimental dust measurement. However, the analyses, especially the Method 3 analysis, show that the CAC can be an effective dust control device. INTRODUCTION Canopy air curtains (CAC) have been shown to be an effective respirable coal mine dust control for roof bolters in a laboratory setting with dust control efficiencies ranging from 14% up to 75% [Goodman and Organiscak 2001, Listak and Beck 2012, Reed et al. 2017]. Unfortunately, there is limited information on their effectiveness for controlling respirable coal mine dust in the field. On continuous miners, CAC dust control efficiencies ranged from 23% to 69% [Krisko 1975]. Two underground tests of the CAC on roof bolters demonstrated dust control efficiencies of 35% and 53% [Listak and Beck 2012] before problems occurred with operation of the CAC. Since the implementation of the new respirable coal mine dust limit from 2.0 mg/m3 to 1.5 mg/m3 (Code of Federal Regulations, 30 CFR 70.100, 2015), roof bolter CACs are becoming more commonplace in underground coal mines as a dust control tool to prevent roof bolter operator overexposure to respirable coal mine dust. J.H. Fletcher & Co. has been instrumental in delivering an effective design which incorporates the filter, blower, and canopy plenum seamlessly into the design of the roof bolter, resulting in a successful operational roof bolter CAC."

Jan 1, 2018

By A. D. MacPhail

The Highland Valley Copper partnership was formed in July 1986 and was the logical result of a mine with a large ore reserve but no adequate mill, and a mine with a large, modem mill but dwindling ore reserves. The original partners -Cominco and Lornex -were joined in January 1988 by Highmont Mining Co. which contributed a two-line concentrator. During 1988/1989, the Highmont mill was moved 7.5 km to adjoin the Lornex mill, forming what is now called the Highland mill, with a current nominal capacity of 130 000 tonnes per day. The mine is located 220 km northeast of Vancouver, British Columbia and is close to four communities in which personnel make their home: Logan Lake, Merritt, Ashcroft, and Kamloops. The map in Figure 1 2.2 shows the general area. Kamloops is a major service centre and is serviced by two railways, two major roads and a regional airport.

Jan 1, 1993

By R. Raymond

The occurrence and distribution of organic sulfur in coals may be investigated using electron probe microanalysis, scanning electron microscopy, and optical petrography. A general relationship exists between macerals and organic sulfur contents in individual coals: sporinite, resinite = micrinite, vitrinite > pseudovitrinite = semifusinite = macrinite > fusinite. With increasing organic sulfur content of a coal, the total range in organic sulfur content between macerals containing high and low organic sulfur contents likewise increases. Furthermore, the organic sulfur content of the vitrinite in most coals equals the organic sulfur content of the coal. For any individual coal, organic sulfur contents of macerals correlate inversely with reflectance-in-oil measurements, but the amount the organic sulfur contents vary between macerals cannot be calculated based solely on the coal's rank. Formation of pyrite following peatification has no effect on organic sulfur contents of surrounding macerals.

Jan 1, 1986

By David H. Carlson

Mechanical sorting of "poor" rock accumulated from past native copper mining operations has been under study at the Michigan Tech's Institute of Mineral Research for several years. Prior to this work, the poor rock dumps totaling approximately 9 million tons containing an estimated 35-70 million pounds of copper (1) have been considered mainly as a local source of road aggregate used from time to time and consequently of minor value. An electro¬mechanical sorting machine developed by International Sorting Systems Corporation of Santa Barbara, California has been tested for preconcentration of the waste rock before conventional milling (2,3). The ISSC machine has possibilities for underground preconcentration of crushed mine-run native copper ores. The objective of the study described here was to provide information about limi¬tations on sortability due to characteristics of the ore and present crushing practices. When the native copper mines were in operation prior to termination in 1969, two types of ore were produced, amygdaloidal and conglomeritic. In the first type copper occurs in vesicles left by gas bubbles entrapped during rapid cooling of the tops of lava flows. The conglomeritic ore beds consist of rounded pebbles and fragments cemented together by calcite, epidote, chlorite, and feldspar; the copper occurs around pebbles, in cracks, and sometimes as partial or total re¬placements of pebbles. The copper in the conglomeritic ore usually is in finer grain sizes than that in the amygdaloidal ore, and large (plus 4 inch) copper masses are virtually absent.

Jan 1, 1970

By R. R. Fullerton

Diatomite or diatomaceous earth is composed of innumerable microscopic opaline skeletons of single-celled aquatic plants called diatoms. The unique properties of this material enable it to be used as an important filtration medium and filler. The Circumpacific contains several economic deposits of diatomite. The largest of these is located in Lompoc, Ca. This deposit is the world's largest, purest, and most uniform marine deposit currently being mined. The other Circumpacific deposits are of fresh water origin. These deposits and Lompoc's unique marine deposit are significant sources of the world's diatomite supply.

Jan 1, 1982

By K. I. Cunningham, C. S. Spirakis

Two types of native sulfur deposits have been found in Lechuguilla Cave: thin late-stage crusts and massive early- formed deposits. Most, if not all, of the crusts appear to have formed by remobilization of native sulfur contained within gypsum and sulfur masses. The process is occurring today and is slowly converting the sulfur to gypsum. The absence of primary gypsum or reductants in the cave indicates that the early-formed massive sulfur deposits did not form by in-place reduction of sulfate, which is the process that formed the commercial sulfur deposits in the Delaware basin. Instead, it appears that H2S dissolved in basinal brines was oxidized by oxygen in near-surface ground waters in the cave. Fluid- inclusion data, which suggest the presence of both fresh water and saline water as the sulfur formed, support this interpretation. Although individual sulfur deposits in Lechuguilla Cave are no more than several tens of metric tons, the abundance of secondary gypsum (as much as 10 meters thick) indicates that native sulfur may once have been much more extensive.

Jan 1, 1992

By E. J. Rorem

Rockfall and unstable rock slopes can be con-trolled by using steel wire-rope net systems as barriers or as slope draping. The chief advantage of such systems over rigid type barriers is the flexibility of wire rope netting. This flexibility and strength permits kinetic energy dissipation with low maintenance requirements. Mining activities can produce temporary or long-term unnatural slopes and unstable rock faces that may produce rockfall hazards. Such conditions can necessitate efforts to minimize the hazard to workers, structures and equipment.

Jan 1, 1996

By R. K. Singhal

Optimization of a load-haul system for a surface mine involves two processes. The first is proper selection of mining equipment compatible with the minesite job specifications and the second is an efficient utilization of this equipment. All things being equal optimal productivity and cost is achieved when the capacity of the hauling equipment is matched at all times with that of the loading equipment.

Jan 1, 1986

By H. E. Hawkes

Reconnaissance mineral exploration based on the distribution of ore metals in stream sediments has become a generally accepted method of mineral reconnaissance. This approach seems to work almost equally well in all climates and in all kinds of terrain, provided of course that the ore deposits being sought are exposed at or near the surface and are actively undergoing erosion. Nobody with any experience in the field would question the validity of the concept on which stream sediment reconnaissance is based. Considerable dispute does arise, however, when the subject of density of sample sites per unit area, or sample spacing, comes up for discussion. What is the optimum balance between completeness of coverage and cost? The tacit assumption is frequently made that a greater sample density necessarily leads to more complete coverage and hence a lower probability of missing an important discovery, without regard for the size of the stream sample or the topology of the drainage pattern. The purpose of this paper is to attempt to bring the problem of site selection in stream sediment sampling into better focus, and to present a formula that may help in planning reconnaissance programs.

Jan 1, 1976

By S. S. Peng

High horizontal stress has been well recognized as a significant factor in roof control. It can adversely affect roof stability if the panel is designed improperly. Mining experience has shown that it can cause a cutter roof. The effects of high horizontal stress on roof stability depend on many factors such as magnitude and direction of the maximum principal horizontal stress, ratio of the maximum to minimum principal horizontal stress, structure and mechanical properties of the immediate roof and mining sequence. However, little is known about the intrinsic mechanism of high horizontal stress effect on roof stability except some conceptual explanations. In order to design a stable entry, the redistribution and concentration of high horizontal stress around the openings must be fully understood. Using the 3-D finite element analysis technique, this paper presents the redistribution and concentration of high horizontal stress field for a three-entry system with different orientations of horizontal stress. Based on the horizontal stress redistribution, possible roof failure for different orientations of horizontal stress is analyzed.

Jan 1, 1996

By R. Addison, P. V. Avotins, D. W. Kestner, M. F. Dibble, L. A. Haas, M. D. Flavel, D. Halbe, D. J. Barratt, G. V. Jergenaen

Mineral processing in 1980 can be described by several key words, familiar to the industry throughout the past decade: complex, low grade, environmental, energy, high tonnage, and economics. Flowsheets have become more complex in order to treat lower-grade, finer-grained, more complex ores and still meet environmental and economic constraints. Operators and researchers have had to cope with these problems, which have resulted in marked trends in mineral processing. The use of advanced instrumentation in process monitoring, control, and modeling has been increasing to deal with fluctuating ore grades, higher plant capacities, rapidly rising operating costs, and process complexities. The industry has been presented with new generations of equipment that reportedly do the job more efficiently and at a reduced cost. The need to meet stricter air and water environmental standards has resulted in a concerted effort by the mineral industries to obtain an appropriate balance between the needs of mining and mineral processing and the requirements for proper environmental, safety, and health protection. Energy and economic considerations have led to increased equipment size, particularly in grinding, flotation, and conveying. Throughout all phases of mineral processing there has been an effort to reduce energy consumption. One avenue followed by researchers and operators was the testing and use of chemicals to reduce energy requirements.

Jan 5, 1981

By Guy Reed, Russell Frith

In situ or pre-mining horizontal stresses are arguably the least well understood of the principal inputs into underground coal mining geotechnical engineering design, whether analytical, empirical, or numerical. This is a direct result of both the cost and difficulty of obtaining meaningful stress measurements, the various limitations of the measurement method in terms of sourcing strata types that approximate the assumed conditions of the post-measurement mathematics to convert measured strains into stresses, and a common practice by some geotechnical professionals to preferentially utilise generic values rather than interrogate the available measurement data for cause and effect relationships between horizontal stress magnitudes, directions and a range of associated controls. That numerical modelling simulations attempt to mimic reality but often rely on simplified generic horizontal stress input assumptions is a particular cause for further consideratio The paper attempts to further explore the nature of in situ horizontal stresses using a range of stress measurement results from the Australian coal sector supplemented by several international studies addressing the same basic issue, the result being a number of credible and highly relevant “cause and effect" inter-relationships between the three principal in situ stresses in addition to the influence of rock properties (e. Young's Modulus and Poisson's Ratio), cover depth and the larger-scale structural geological environment. In particular, the paper demonstrates that despite being commonly overlooked as a primary rock/coal material property, Poisson's Ratio and the associated K Effect are intrinsic to understanding 3D in situ stress measurement results and therefore, predicting in situ stress magni- tudes more generally for geotechnical analyses purposes. As a fundamental question, the paper addresses whether it is necessary and of engineering value to characterise in situ horizontal stresses: according to distinct "domains," in the same way that more easily identifiable geotechnical properties such as rock mass ratings, coal seam thickness, ply splits, and cover depth are often treated.

Jun 25, 2024

By J. L. Huiatt

Kerosine, fuel oil No. 2, vapor oil, and fuel oil No. 6 were separated into general hydrocarbon fractions by ion exchange chromatography and adsorption chromatography. The collecting properties of these fractions were evaluated by flotation of molybdenum and copper minerals from a natural chalcopyrite ore. Paraffin fractions and aromatic fractions of low polarity produced the best molybdenum recoveries. Selective flotation of molybdenite from copper sulfide minerals was not possible with any of the chromatographic fractions.

Jan 1, 1972