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By Jiann-Yang Hwang

Microwave heating has been proved an effective method to rapidly heat iron oxide. This offers an opportunity to apply microwave heating in the steelmaking process. The reduction reaction of iron oxide is traditionally achieved at high temperature with reducing gases such as H2 and CO generated from various sources, including coke, coal, and natural gas. This study investigates the differences in iron oxide reduction using conventional and microwave heating under H2 and CO atmospheres. A special microwave thermal gravimetric device was designed and built to facilitate the investigation. With this device, iron oxides can be heated by electric resistance heating, microwave heating, or a combination of methods. The incoming CO and/or H2 also can be preheated to simulate a potential utilization of recovered heat. The iron oxide weight and temperature can be monitored during an entire reduction period. A series of reduction experiments have been conducted. The results are presented and discussed.

Jan 1, 2006

By Z. G. Song, C. Y. Sun, X. R. Zhang, Y. Yu

In skarn type scheelite deposit, there are calcium minerals with floatability similar to scheelite, such as calcite, fluorite, etc., which are difficult to separate. Heating cleaning method developed by Petrov has been widely applied in processing rough concentrate of scheelite for nearly half a century, but there exists a general lack of full understanding of the interaction between floatation reagent and mineral particles surfaces. The mechanism on separation of scheelite and calcium minerals in heating cleaning process was investigated by mineral flotation experiments, XPS analysis, as well as solution chemistry and crystal chemistry calculations. The results showed that the sequence of minerals floatability using sodium oleate as collector and a large amount of sodium silicate as modifier in heating flotation test was scheelite > calcite > fluorite, which was the same as solution chemistry calculations based on Gibbs free energy vs. pH and also the same as Ca-X intensity order by crystal chemistry analysis. There are two sides about the mechanism of heating cleaning method: one is that the adsorbed collector on calcium minerals surface is desorbed more easily than scheelite, and the other is selective dissolution of calcium ions from the mineral surface because of Ca-X intensity difference in heating and stirring process.

Jan 1, 2014

By L. Yuan

In the U.S. coal mining industry, most spontaneous combustion fires occur in longwall or worked-out gob areas. In order to reduce the fire hazard caused by spontaneous combustion, it is important to understand how ventilation and gob characteristics affect the spontaneous heating process. Given the difficulty to conduct field tests in such an environment, a computational fluid dynamics (CFD) study was conducted to investigate the effects of ventilation and gob characteristics on the spontaneous heating process in longwall gob areas. Two longwall panels with a bleeder ventilation system were simulated. The spontaneous heating is modeled as the low-temperature oxidation of coal in the gob using the Arrhenius rate law and kinetic data obtained from previous laboratory-scale studies. The heat generated from the spontaneous heating is transported by convection and conduction, and oxygen and the oxidation products are transported by convection and diffusion. Unsteady state simulations were conducted with different ventilation conditions and gob permeability distributions. The ventilation parameters varied in the simulations are the pressure at the bottom of the bleeder shaft and regulator resistance in the second entry inby the longwall face.

Jan 1, 2009

By "Andreas Steinwandter

The demand for increasing energy efficiency and CO2 reduction is one of the global megatrends of our time. Although the steel industry suffers from a volatile economic environment, the steel plants are interested to find opportunities for sustainable cost reduction and put efforts into healthy solutions for the environmental. Integrated steel plants are trying to cut electrical power and energy costs as these are among the biggest cost factors that can be influenced and taking all the advantages they can. For the integrated iron and steel making route the interaction of waste energy utilization along with process energy demand, natural and metallurgical gases, steam and heating systems as well as power generation has to be considered. Potential energy sources, such as sinter plant, basic oxygen furnace (BOF) cooling stack or reheating furnaces are considered in order to elaborate an integrated energy concept. Especially electric power generation is an attractive option for steel plant operators since it can easily be connected to the existing power grid of the steel plant. When direct local use of waste heat is limited, the best option is to convert it to mechanical/electrical power with a Rankine Cycle. A stand-alone system, compact design with minimum operational costs in order to fit into the existing steel plant layout, are the main requirements of such units. The objective of this paper is to demonstrate economic feasible opportunities for energy recovery for sinter cooler and basic oxygen furnace with focus on electric power generation via ORC modules taking at the same time advantages of CO2 reduction by utilizing waste heat from the process. Furthermore typical arrangements and layouts of such solutions as well as basic economic calculations will be presented in the paper.

Oct 30, 2017

By Walter E. Lewis

Ventilation-air-heating plants are in use at several iron mines on the Menominee Iron Range, Iron River, Mich. Many of the mines are exceptionally wet; during winter months, when fresh air is forced down the wet air shafts into the mine, it is usually necessary to heat the fresh air to above freezing so that the openings will not be closed by ice. The problem of ice closing air shafts has been solved by the practice of reversing the air current before the openings have become completely closed. This procedure involves drawing warm air from the mine up the usual down-draft air shaft. The M. A. Hanna Co. has found, at some of their mines on the Menominee Range, that it is more convenient to heat the below-freezing air rather than reverse the air current. Intermittent freezing and thawing of ice that has formed in the air shaft tends to loosen the wall rock, requiring major shaft repairs. The openings are kept free of ice the year around by heating the fresh air during periods of below-freezing weather. Table 1 shows the monthly minimum moan, maximum mean, and mean temperatures for the Iron River area. Under normal conditions of temperature, the furnaces are fired in November and usually are not allowed to go out until April of the following year.

Jan 1, 1951

By William Gleason

"It has been more than 10 years since Montana Resources’ copper/molybdenum mine has had a lost-time injury at its site in Butte, MT. With more than 350 employees and an average production of about 15.5 Mt/a (17 million stpy), which includes 29.5 kt (65 million lbs) of copper and 4 kt (9 million lbs) of molybdenum, the mine’s journey to a decade of exemplary safety is an impressive feat that has required hard work, commitment and, most of all, leadership from every level of the operation.It has not always been an easy journey, nor has it been one without scrapes and bumps along the way, but it is one that has produced stellar results. Mike McGivern, vice president of human resources, and Pete Steilman, safety manager at the mine, spoke with Mining Engineering about how the operation transformed from a site that was accustomed to collecting citations for safety violations to one that is now collecting awards for its safety record.Simply put, Montana Resources has made safety a value and the people its top priority.The operations faced many predictable challenges in 2003, when the mine was being brought back online after three years of sitting in care-and-maintenance status. It had been shuttered in 2000 because of low commodity prices and high operating costs, and, in the three years that the mine was idled, the equipment became dilapidated, and some of it was no longer in compliance. Less than half of the workforce returned to the site for the restart, and the team was challenged with getting the gears turning again to produce copper and molybdenum. But the most daunting challenge of all of was keeping the workforce safe during the transition.In the first few years of operation the mine racked up citations from the U.S. Mine Safety and Health Administration (MSHA) at an alarming pace, so much so that in May 2006, Montana Resources received a letter from the MSHA District Office informing the company that the operation was being placed on the Potential Pattern of Violations list due to its excessive citation history and high rate of significant and substantial citations. It was clear that something significant had to be done to change the course of action at the mine."

Oct 1, 2019

By J. P. Harrison, N. Bozorgzadeh, M. Dolowy-Busch

"It is common in rock engineering practice to characterize the triaxial strength of intact rock by using only data samples of small size. Practical guidelines such as ASTM support such sample sizes. In this paper, we investigate the reliability of the Hoek-Brown strength criterion estimated from such samples. For this purpose, we use an unusually large published set of triaxial strength data to randomly select a large number of data samples of small size to simulate the situation that frequently encounters in practice. The samples are generated with different arrangements with regards to the confining pressure. We fit the Hoek-Brown criterion to each of these samples, obtain estimates of strength parameters and compare them to those obtained from the complete data set. Our analysis suggests that estimates based on small samples are not reliable and can lead to both over- and under-estimation of strength.Additionally, we use these small samples to investigate the statistical methods for obtaining design values of strength as suggested by limit state design standards such as Eurocode 7. We show that, if used in conjunction with small samples, these methods do not guarantee a safe estimate of strength and in many cases lead to highly over-conservative estimates.We present a potential solution to this problem by augmenting the small data sets with Bayesian informative priors to give much more reliable estimates of strength. We conclude with suggestions for the development of informative prior distributions."

Jan 1, 2015

By S. M. Bradshaw

The principles of microwave heating are discussed with reference to dielectric properties, heating phenomena and microwave equipment. Microwave regeneration of granular activated carbon for the carbon-in-pulp process is examined on a laboratory scale, with special attention being given to highlight the problem areas and specific considerations related to microwave heating. Results indicate that microwave regeneration of carbon with 40% moisture on a wet basis by heating to 650°C with steam addition regenerates the carbon to virgin carbon activity levels but with a higher abrasion resistance. A preliminary economic assessment showed that the capital cost for 120 kg/h microwave unit would be R540 000 with an annual operating cost of R 320/t carbon. These figures yield a return on investment of 12%. The aim of this paper is to provide an introduction to microwave heating and to illustrate its application to the microwave regeneration of granular activated carbon for the carbon-in-pulp (CIP) process.

Jan 1, 1998

By H. B. Brunot

The United States Bureau of Mines under provisions of Schedule 2C4 issues approvals covering complete operating units such as loading machines, room hoists, and storage-battery locomotives. Certain manufacturers design and build entire machines. Other manufacturers purchase a part or all of the electrical accessories from manufacturers of electrical equipment and make up permissible units by assembling them. Before the assembler purchases electrical accessories for use in such contemplated units he may require certain information from the accessory manufacturer as to whether the particular accessories are suitable for assembly in his proposed permissible outfit. To aid accessory manufacturers in marketing their product, a provision was incorporated in Schedule 20 whereby tests might be made on individual accessories and reports rendered as to the suitability of a given accessory for use in permissible assemblies.

Jan 1, 1935

By D. A. Bulled

• "What does it look like?" - describes the appearance. • "How does it work?" - outlines the operation. e "Why does it work?"- explains the principles. • "What about controls?" - indicates possible automatic systems. • "How is it sized?" - discusses the necessary testwork and evaluation. • "What are the results?" - demonstrates test and operating results. • "What's the benefit?" - concludes with gains for the user.

Jan 1, 1999

By R. S. Dean

The careful work of Gross and Zimmerleyl has established the fact that the energy actually used in grinding is proportional to the new surface produced. This confirmation of Rittinger's law was made by crushing quartz in a frictionless drop-weight machine and determining the surface of the quartz by its rate of solution in hydrofluoric acid. The details of this procedure have been described adequately elsewhere and need not be repeated here. The resultant data furnish the only available basis for comparing accurately the efficiency of grinding machines. This method is so cumbersome experimentally that it has been little used. As an alternative all sorts of approximations have been proposed. The best of these is complete size analysis by sieving and elutria-tion. Such procedure is very lengthy and difficult to carry out accurately. Furthermore, any sizing method becomes very inaccurate for determining surface with very fine sizes where the ratio of surface to volume becomes very large. To avoid the lengthy and difficult technique of elutriation it has been proposed to estimate the size distribution below 200 mesh from various probability formulas. Such a procedure is at best an engineering approximation; at worst it is a mere guess. Some time ago Dr. V. H. Gottschalk2 found that the coercive forces of magnetite powders were directly proportional to the surface area, regardless of size distribution. It was at once apparent that this furnished a method for determining grinding efficiency quickly and accurately. The only requirement was a single determination of the relation between the work input of the Gross-Zimmerley drop-weight machine and the coercive force of the resultant crushed magnetite. For this purpose Ural Mountain magnetite in definite octahedra was

Jan 1, 1939

By R. S. Dean

The careful work of Gross and Zimmerleyl has established the fact that the energy actually used in grinding is proportional to the new surface produced. This confirmation of Rittinger's law was made by crushing quartz in a frictionless drop-weight machine and determining the surface of the quartz by its rate of solution in hydrofluoric acid. The details of this procedure have been described adequately elsewhere and need not be repeated here. The resultant data furnish the only available basis for comparing accurately the efficiency of grinding machines. This method is so cumbersome experimentally that it has been little used. As an alternative all sorts of approximations have been proposed. The best of these is complete size analysis by sieving and elutria-tion. Such procedure is very lengthy and difficult to carry out accurately. Furthermore, any sizing method becomes very inaccurate for determining surface with very fine sizes where the ratio of surface to volume becomes very large. To avoid the lengthy and difficult technique of elutriation it has been proposed to estimate the size distribution below 200 mesh from various probability formulas. Such a procedure is at best an engineering approximation; at worst it is a mere guess. Some time ago Dr. V. H. Gottschalk2 found that the coercive forces of magnetite powders were directly proportional to the surface area, regardless of size distribution. It was at once apparent that this furnished a method for determining grinding efficiency quickly and accurately. The only requirement was a single determination of the relation between the work input of the Gross-Zimmerley drop-weight machine and the coercive force of the resultant crushed magnetite. For this purpose Ural Mountain magnetite in definite octahedra was

Jan 1, 1939

By J. van Driel

NOx is a growing concern for acid plant operators due to recent legislation reducing the allowable stack limits, as well as continually more stringent requirements for product acid quality. NOx also causes a major problem during maintenance as NOx rich acid residues fume following exposure to moisture in the air. Until recently, the solution for NOx related issues was to treat the symptom, rather than the cause. NOx in product acid was treated using chemicals and the NOx in the plant stack was generally left untreated. As part of an environmentally driven change in concentrates, Budel Zink installed the first gas phase NOx destruction process to be incorporated into a commercial scale acid plant. Nitrogen oxides contained in the process gas are reduced selectively with ammonia over a catalyst to form nitrogen and water. As a result, the NOx reduction is in agreement with the permit requirements.

Jan 1, 2002

By Miguel N. Herrera, Abbas H. Mirza, Fiona M. Doyle

The standard test methods used to determine the pyrite content of coal and mineral wastes, and their propensity to release acidic drainage, are critically reviewed. In addition to analysis of total sulfur by combustion, test methods using selective oxidation of pyrite by HNO3 and H2O2 are available. The oxidation kinetics of pyrite vary appreciably from sample to sample, and it is difficult to ascertain whether complete dissolution has occurred in heterogeneous materials. The reliability, reproducibility and suitability of different standard test methods were studied, using well characterized ore and coal pyrite samples. The kinetics of pyrite dissolution were also investigated. The results are discussed in terms of the fundamental chemical and physical characteristics of each sample, and the implications for waste characterization are considered.

Jan 1, 1992

Fresh coal refuse was sampled at 21 US mines. Five of the sites were drilled, sampled and tested more extensively. Field tests included Standard Penetration tests, and in-situ density determinations. Laboratory testing included specific gravity, gradation, maximum, and minimum density tests, as well as 9-inch) drained triaxial tests, 9 and 10-inch, permeability tests, slake-durability tests, and accelerated slaking tests. Some refuse sites had significantly lower shear strengths and permeabilities in old, slaked or weathered material than in fresh refuse. Testing did not show useful correlations between strength and permeability changes and other material properties which could serve as "predictors". Testing of refuse under "accelerated slaking" conditions showed promise as a comparative tool and as a potential means of preparing artificially aged samples for evaluations of long-term behavior. The state-of-the-art in slaking research, and the implications of slaking on coal refuse disposal, and on practical methods of managing slaking, were also studied.

Jan 1, 1981

By Susanne Pignolet-Brandom

This paper examines the viability of using the QEM*SEM automated scanning electron microscope for the determination iron sulfide and calcite volumetric percentages. The analytical reliability was verified by comparing elemental abundances calculated for fourteen samples using the QEM*SEM volumetric percentages and appropriate mineral compositions and elemental abundances determined by standard laboratory procedures. The abundances were comparable, thus demonstrating suitability of this technique for evaluation of the acid neutralization and generation potentials of mining wastes.

Jan 1, 1990

By Fred Leighton

The least squares method of rock noise source location presented is shown to be more accurate and reliable than standard direct solution methods. This method is particularly effective in improving solutions from rock noise locations outside of geophone array boundaries. A least squares solution for a medium .in which the seismic velocity is the same in all directions is also presented. In this special case, one can solve for both the source coordinates and the velocity.

Jan 1, 1972

By Dean H. Ambrose

This Bureau of Mines publication summarizes the status of mine electrical equipment reliability research. Failure rate data were estimated from theoretical, laboratory, and field studies. Tables are presented listing reliability characteristics of molded-case circuit breakers, undervoltage relays, ground check monitors, cables, motors, and control circuitry. Application of failure rate data is shown in tables listing maintenance scheduling intervals of components and components that are most sensitive to the probability of hazardous voltages on power distribution systems in the mines. Complete, accurate, and appropriate failure rates on mine equipment are of the utmost importance for reliability evaluations.

Jan 1, 1985

By K. C. Grogan

"GeneralGIANT ORE is complex, with the gold values for the most part occurring in extremely close association with arsenopyrite, stibnite, jamesonite, and a wide group of antimonial minerals locally termed 'the grey minerals'. Pyrite is the most abundant of the sulphide minerals• and minor quantities of chalcopyrite, galena, and sphalerite also occur. Pyrrhotite has been found in some sections of the mine, but to date none of it has been nickeliferous. Native gold occurs in varying amounts throughout the ore bodies.In 1944, ore dressing investigations were commenced on diamond-drill core rejects and samples of surface outcrop ore. Results soon indicated that treatment to produce satisfactory recovery of the gold values would involve fine grinding to 80-85 per cent minus 200 mesh, recovery of free gold by jigs, followed by flotation, roasting of the flotation concentrate, and subsequent cyanidation of the calcine. Proceeding from this information, the flow-sheet was prepared, plant design worked out, equipment purchased, and construction of the treatment plant commenced in May, 1947.The crushing, grinding, and flotation units of the plant were rushed to completion and commenced operation on May 12th, l.948, at 225 tons of ore per day. This rate was maintained until January 27th, 1949, when the Allis-Chalmers roaster and cyanide plants were completed and commenced operation. During the period May 12th, 1948, to January 27th, 1949, gold recovered by amalgamation was the sole source of revenue. Flotation concentrate was stockpiled pending the completion of the Allis~Chalmers roaster and cyanide plants."

Jan 1, 1953

By Thomas O. Llewellyn

This U.S. Bureau of Mines (USBM) report presents a concise review on sources, processes, supply, and historical use patterns of domestic cadmium. It also covers a preliminary estimated cadmium material flow for the year 1989. This preliminary study contains information on cadmium and cadmium-bearing products in the United States. The data in this report were obtained from both published and/or unpublished sources of information. However, in order to estimate the fate of cadmium in each operation or application stage, some assumptions, judgments, and correlations were made by the USBM in an attempt to determine the material flows losses.

Jan 1, 1994