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By R. A. Jankowski

Although the number of operating longwall mining systems has remained relatively consistent over the past five years, longwall production levels have increased significantly during this period. Longwall production currently accounts for approximately 50% of U.S. underground coal production. While longwalls are highly productive and offer other advantages, operations employing this method of mining continue to experience dust compliance problems. This increased longwall productivity has meant that far more dust is being produced. An improved understanding of the longwall face ventilation system and advancement of face ventilation technologies are necessary to ensure all face personnel are allowed to work in an environment that is free of excessive levels of airborne respirable coal mine dust. The Dust and Toxic Substances Control Branch of the National Institute for Occupational Safety and Health's Pittsburgh Research Laboratory has examined several basic principles of the longwall face ventilation system, and has evaluated the effectiveness of numerous improved face ventilation techniques for longwall mining systems. These include identifying improved techniques for measuring face ventilation parameters on longwall mining sections and investigating the fundamental relationship between face air flow and the entrainment and dilution of respirable coal mine dust. Studies have been completed to determine the impact on face dust levels from using belt entry air to ventilate the longwall. Novel methods have been identified to increase the amount of face air flow and to manage face air flow to most effectively minimize face workers' dust exposure. Unique systems of auxiliary face ventilation have been developed and evaluated at full-scale, simulated longwall test facilities. The theoretical and applied aspects of each of these principles and technologies are discussed. Application of these results, throughout the longwall mining industry, as documented from surveys conducted in the early 1980's and 1990's, have reduced the health hazard associated with excessive exposure to respirable coal mine dust.

Jan 1, 1998

By Gordon Cook

American Electric Power Company (AEP operates 31 coal mines in three states, and some 26 electric generating stations (19 coal-fired) located in the Ohio River Basin. Normally the system burns over 36,071,600 tonnes (40,000,000 tons) of coal and generates in excess of 3.6 X 1018 J (100 billion kwh) of electricity per year. In 1975, AEP, in response to the progressively more stringent air quality requirements of the clean air act, acquired large low-sulfur reserves in Carbon County, Utah (Figure 1. Location Map). Price River Coal Company (PRCC) is the operator OF this multi-seam complex, which is part of the Book Cliffs coalfield at an elevation exceeding 1,829 m (6,000 ft.). The topography is mountainous and divided by numerous canyons. Flat areas are at a premium (Figure 2. Castle Gate Area). Modern high production longwall mining takes in some top and bottom waste, and in this particular operation, it amounts to about 14% of the ROM tonnage.

Jan 1, 1983

By Valérie J. Bertrand, Richard W. Lawrence, Marcos G. Monroy

Two cemented paste backfill (CPB) formulations containing pyritic tailings were leached in deionized water in flooded and alternating air-flooded environments and in a simulated acid rock drainage-type (ARD) solution. Scanning Electron Microscopy (SEM), solid phase chemistry and acid-base accounting measurements documented the weathering characteristics of the CPB samples. Short-term exposures of the portland-CPB samples preferentially dissolved the cement binder to a greater extent than slag-Portland CPB mistures. In all cases, the added neutralizing potential provided to backfill by cement was short-lived and insufficient to neutralize the acid generating potential of the mixture.

Jan 1, 2000

Conventional wisdom in the mineral processing industry leads one to believe that pressure oxidation of refractory carbonaceous (preg-robbing) ores is not a practical approach to process development. Initial acid pressure oxidation testing on carbonaceous sulfide ores at the Twin Creeks Mine supported this conventional wisdom. After testing other refractory process options, including air and oxygen enriched roasting, Santa Fe Pacific Gold decided to take a second look at pressure oxidation, using conditions outside the normal range of conventional practice. A combination of very fine grinding and high operating temperature and pressure resulted in significant increases in gold extraction. This paper details the effect of operating parameters developed for Twin Creeks on gold recovery, sulfur oxidation, carbon oxidation/passivation and preg-robb through the laboratory and pilot plant investigations.

Jan 1, 1995

By D. Pearson

About 15,000 tonnes of zinc per year is present in the dusts and fumes produced in electric arc and BOS steelmaking, secondary copper refining and brass ingot making. Apart from the use of some copper-smelter fumes for zinc chemicals manufacture, zinc is not recovered and their disposal by landfill entails some risk of pollution by leach-out. The paper describes processes for recovering the zinc based on leaching and electrowinning. It was shown that the procedures normally employed for purifying zinc-electrolytes derived from primary sources are sometimes ineffective for secondary materials. Alternative process routes are proposed. Source materials were leached with acidic or alkaline reagents and solvent extraction was employed for electrolyte purification in addition to the usual techniques involving precipitation. Examples of integrated flow sheets for specific source materials are presented.

Jan 1, 1980

By William A. Gibson, Kenneth P. Neumann

In 1967, development of the Cyprus Thompson Creek molybdenum deposit began near Challis, ID. The first mining claims were staked on an intrusive rock out-crop. Exploration continued for 14 years. In 1978, the decision was made to develop the deposit. In Dec. 1980, approval was received for the environmental impact statement and facilities construction and waste rock removal began. By the middle of 1983, 126 Mt (139 million st) of rock had been removed and all facilities completed. Location The Thompson Creek project is located about 58 km (36 miles) southwest of Challis in Custer County, in south central Idaho. The mine and mill are situated between 2.2 and 2.6 km (7,217 and 8,530 ft) in elevation. The project is located in an isolated area. Surrounded by mountains, it is adjacent to the Sawtooth National Recreation Area. The Salmon river is 8 km (5 miles) south of the project. The project claim block is lo-

Jan 1, 1984

By Chengliang Jliang, B. K. Parek, Xuxin Shao

Of the impurities present in phosphate ore, dolomite is the most difficult to remove due to the similar chemical compositions of the impurities and also adsorption of dissolved species of dolomite onto phosphate. A new amphoteric surfactant was found to be a suitable collector for separation of dolomite from phosphate. Flotation results showed that the new amphoteric collector had a high flotation selectivity for dolomite in wide pH ranges. The flotation study of francolite and dolomite in each other's supernatant demonstrated that the dissolved ions had little effect on the selectivity of the new collector, but were detrimental to the flotation separation using sodium oleate as collector. A phosphate concentrate with 35.2% P2O5 with 90% recovery was obtained using 290 g/t of the amphoteric collector from a mixture of francolite and dolomite containing 26.2% P2O5. The rejection of MgO was 81.41%.

Jan 1, 1999

By S. K. Kawatra

The fly ash from coal combustion often has a high unburned-carbon content. This can make it unusable as a cement admixture, which is the major fly ash utilization market. As a result, high-carbon fly ashes currently disposed of by landfilling, at sometimes considerable expense. In this paper, the use of froth flotation to remove the unburned carbon from fly ash is described. Three different fly ashes were studied, which had Loss-on-Ignition (LOI) values of 6.79, 6.90, and 11.11 %. It was found that the use of an alkanolamide/oil mixture as a froth-conditioning reagent could greatly reduce the amount of collector needed, by increasing the affinity of the collector for oxidized carbonaceous surfaces. For each of the three fly ashes, froth flotation reduced the LOI of the ash to less than 2% which is well below the ASTM specification of no ' more than 6.0% LOI for Class F fly ash. Increasing carbon content of the ash tended to increase the quantities of reagents needed in flotation.

Jan 1, 1996

By X. Y. Yu, X. A. Wei, A. Zeng

"The flotation behaviors of diaspore and three kinds of silicate minerals - kaolinite, illite and pyrophyllite - using an organosilicon cationic surfactant as collector were investigated as functions of reagent concentration and pulp pH. The results show that the organosilicon cationic collector QAS122 is a suitable collector for the flotation of aluminosilicate minerals but has weak collecting ability with regard to diaspore, enabling the flotation separation of diaspore from silicate minerals using QAS122 as collector. The flotation of a bauxite ore was then studied in detail. Finally, a reverse flotation separation process was used to process a low-grade bauxite ore. It was concluded that use of the organosilicon cationic collector is effective. A concentrate with aluminum oxide (Al2O3) to silicon dioxide (SiO2) mass ratio, or A/S, of 9.67 was obtained from natural bauxite ore with A/S of 6.07 at pH of around 11. The Al2O3 recovery rate was 81.72 percent. IntroductionChina has abundant bauxite ore resources, but more than 98 percent of the bauxite ores are the diasporic type, with the characteristics of complex mineral composition, low aluminum oxide (Al2O3) to silicon dioxide (SiO2) mass ratio, or A/S, and difficulty of processing. The gangue minerals in bauxite ores are mainly kaolinite, pyrophyllite and illite, containing titanium and iron impurities (Zong et al., 2008). It is known that high-grade bauxite ore, with A/S greater than 8, can be processed directly by the Bayer process (Papanastassiou et al., 2002; Ma et al., 1996). However, Chinese diasporic ores have been processed mainly by the sintering process, which is environmentally damaging and energy intensive. Increasing the A/S of the diasporic ores using a flotation method is needed (Xia et al., 2010).Froth flotation is one of the most widely used processes to concentrate valuable minerals in beneficiation ores. It is particularly useful for separating finely ground ores from their associated gangue minerals. For diasporic bauxite ores, flotation is applied to obtain high-quality material for the Bayer process by increasing the A/S. Direct flotation has been shown to be an efficient method for the desilicating of diasporic bauxite ore (Wang et al., 2004; Xu et al., 2004), but reverse flotation has more advantages for this purpose, including less collector consumption, less foaming product and less effect on metallurgy (Liu et al., 2007; Hu et al., 2003; Hu, 2003; Luo et al., 2001)."

Jan 1, 2015

By Donald T. Mylar

It is axiomatic that in designing a bulk material handling system the primary consideration is the functioning of the machines. The structure is secondary -its reasons for being are to support, enclose and provide access to the machine, for servicing. This results in a wide variety of supporting structures. Other considerations are: plant layout, local soil conditions, climate, local laws and codes, and last, but by no means least, the Customer's wishes.

Jan 1, 1971

By Harry Asche

Tunnels are frequently specified by owners to be designed to a structural code, often a bridge code. In the USA, AASHTO have created a tunnel code, based on structural principles, the AASHTO LRFD Tunnel Design Specification. The Load Resistance Factor Design method (LRFD) described in the AASHTO title is an approximation to the probabilistic design of structures, based on the independence of load and resistance. This methodology is well known to be problematic in geotechnical design, but it is widely used. The paper considers the difficulties of this approach and describes alternative approaches that would result in more appropriate designs for tunnels.

Jun 13, 2021

By D. L. Stevens

Following an in-depth scenario and strategic-planning exercise in 1997, Noranda's mine production goal was set at 500 kt/a (550,000 stpy) of both copper and zinc metal in five years. There had been no recent discoveries, reserves were shrinking and things had to be done differently and quickly. Change is now continual in Noranda's program. The following steps were taken: the exploration and business development groups were combined, teams were formed to search for and respond to opportunity; geologists were coached to become more business minded and engineers were coached to become more optimistic; the company went global; clear thresholds were set, marginal properties were farmed out and other properties were fast tracked; reconnaissance exploration was focussed where there was a clear competitive advantage; and Noranda became a "flexible" partner to juniors and seniors. Is it working? A number of successes, near successes and outright failures are discussed. The main result is a much higher rate of opportunity flux, which is essential for success in the mining industry.

Jan 1, 2000

By C. Pritchard

John Marks said in his acceptance of the Hartman Award in 2008, “I guess that without the occasional complaint, your mine is probably over-ventilated” (Marks, 2008). Miners are seldom in this situation and spend much of the time trying to find enough air to keep an operation running. With examination, there are usually changes that can be made to increase the efficiency of ventilation systems. Mine ventilation air is a costly commodity, especially by the time it has been heated or cooled and moved to the bottom of the shaft and through the mine airways. Modifications that result in surplus mine ventilation air could bring financial and environmental benefits. Some issues mine operators have needed to address recently are increased airflow requirements to dilute diesel particulates in metal and nonmetal mines, to ventilate reserves that are deeper, hotter, and further away from fans and shafts, and to meet demands from increased production. This paper discusses successful methods to find additional usable air when there is no extra ventilation capacity. Most of the options presented in this paper are useful for metal/ nonmetal operations but some may be applicable to coal as well.

Jan 1, 2009

By J. D. Miller, J. Hupka

Important aspects of kerosene penetration into tar sand have been investigated. The natural tar sand porosity was measured and used to analyze the performance of the hot water process. Subsequently, pretreatment experiments, using 20-kg tar sand samples (Asphalt Ridge and Whiterocks, Utah) and kerosene as a diluent were carried out at the expected summer temperature (26°C) and the expected winter temperature (-14°C). The natural tar sand porosity accessible by diluent has a crucial impact on the reduction of bitumen viscosity and influences the penetration time required for successful bitumen separation from tar sand by hot water processing. Thus, the tar sand porosity is a critical variable that determines appropriate operating conditions. Experimental results indicate that diluent penetration into the Asphalt Ridge tar sand (high porosity) is almost complete after 30 min, whereas for the Whiterocks tar sand (low porosity) the penetration process is much slower, being still incomplete after 15 hours regardless of the ambient temperature.

Jan 1, 1994

By Mengxiong Guo, Xuxin Shao

The recent depressant research is summarized, and a new kind of depressant (SCO) has been put forward in this article. Using Na-oleate as a collector and SCO as a depressant, separation of dolomite and phosphate was studied. When SCO was added in the concentration range of 80 g/t to 2kg/t at pH 9.5 ± 0.2, dolomite was absolutely depressed, and apatite kept its floatability. Interestingly, in the mixture of phosphate and dolomite, the dolomite floated. The reasons for such a behavior are investigated through flotation and electrokinetic studies. It was found that the adsorption of dissolved species on dolomite and phosphate resulted in reverse flotation. A concentration of 31.59% P205 and 83.87% recovery of P205 was obtained from the mixture of phosphate and dolomite (2:1) with 26.6% P205 using 210 g/t SCO and Na-oleate 4.93*10-5 M at pH 9.

Jan 1, 1989

By B. R. T. Simoneit

The conversion of organic matter to petroleum by hydrothermal activity is an easy process, occurring in nature in many types of environments. Geologically immature organic matter of marine sediments is being altered by this process in Guaymas Basin (Gulf of California), Escanaba Trough and Middle Valley (northeast Pacific), Bransfield Strait (Antarctica), and Atlantis 11 and Kebrit Deeps (Red Sea). Contemporary organic detritus and viable microorganisms are also converted in part to petroleum-like products by the same process when present to become entrained, as for example on the East Pacific Rise at 13o N and 21o N and on the mid-Atlantic Ridge at 26oN. The hydrocarbon products (methane to asphalt) generated in all these areas have been elucidated in terms of composition, organic matter sources, and analogy to reservoir petroleum. This petroleum represents a major input of carbon to the primary chemosynthetic productivity of hydrothermal vent systems and may be important to interactions with metals in hydrothermal ore formation.

Jan 1, 1991

By M. Prasad, G. M. Rao, T. C. Rao, A. K. Majmudar

A two-step flotation scheme was employed to beneficiate a low-grade, cherty-calcareous rock phosphate ore from the Jhabua district, Madhya Pradesh, India. In the first stage, apatite and calcite ire floated together to remove silica, and, in the second stage, calcite is floated and apatite is depressed. The reagent scheme consists of sodium oleate, sodium silicate, orthophosphoric acid and sulfuric acid. The effect of reagent dosages on the efficiencies of separtition in each stage was studied systematically. A flowsheet was proposed for the processing of a low-grade phosphate ore containing 12.5% P2O5, 26.5% SiO2 and a CaO/P2O5 ratio of 2.64 (=32% calcite). The proposed flowsheet would produce a composite phosphate concentrate containing 27.2% P2O5, 6.37% SiO2 and a much reduced CaO/P205 ratio of 1.66. The total P2O5 recovery for the composite concentrate would be 73% .

Jan 1, 1996

By William S. Hallager

Banded ironstone and associated fine-grained carbonaceous sediments near Jardine, Montana, are enriched in gold, arsenic, and tungsten. The mineralized sediments lie within a thick sequence of quartz-mica schists cut by a 2.6 b.y, granite. Surface, underground, and drill hole mapping are used to construct structure contour maps of individual ironstone lenses. Each lens is then unfolded by triangulation of minimum surface path distances between drill hole penetration points. Major and minor element abundances in composite ironstone samples are interrelated through R-mode factor analysis. Results indicate five significant element groupings thought to reflect coarse detrital, fine detrital, sulfide-rich chemical, iron-rich chemical, and epiclastic ultramafic sediment. Ultramafic factor scores are highest in a previously undefined rock type rich in cummingtonite, biotite, and chlorite; lacking in quartz; and closely associated with at least one ore horizon. Detrital dilution of ironstone, calculated from chromium and nickel content, drops off significantly as ore-bearing ironstone is approached. This observation may indicate that centers of gold precipitation have protected themselves, either topographically or by rapid deposition, from detrital contamination. Gold mineralization correlates most strongly with the sulfide- rich factor. Gold may have been introduced through hotspring activity as a bisulfide complex.

Jan 1, 2013

By Hasan Sevim

This paper summarizes recent developments in modeling of underground coal slurry haulage networks for determination of optimum design and operating parameters. The model presented here is based on a stochastic dynamic programming formulation, applicable in any typical room-and-pillar and/or longwall mining configuration commonly practiced in the United States. The formulation and the structure of the model is general enough to handle design problems involving more than one face and mining method. Given the stochastic operating characteristics and a system layout, the model can be used to determine the equipment configuration and operating regimes that minimize the overall unit cost of coal haulage.

Jan 1, 1983

By Charles H. Rice

Coal liquefaction processes can be divided into two broad classifications - direct and indirect. Direct liquefaction processes, in general, slurry coal with a solvent and react it with hydrogen under elevated temperature and pressure. Indirect liquefaction is the term applied to processes in which coal is first gasified to generate a synthesis gas of carbon monoxide and hydrogen. The synthesis gas is then converted to various types of liquid fuels by the proper selection of catalyst and conditions. The first experiments on direct coal liquefaction were undertaken in 1933 by Bergius. Development and commercialization of the Bergius concept was accomplished mainly through the effort of I.G. Farben at the Ludwigshafen plant of its subsidiary, Badische Anilin und Soda Fabrik A.G, under the leadership of M. Pier (1). A demonstration plat having an annual capacity of 100,000 tons of coal was built in Leuna, Saxony in 1927. Six years later, Imperial Chemicals Industries, Ltd., commissioned a plant in Billingham, England (2).

Jan 1, 1981