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Jan 12, 1950

By Rainer M. Lotzien, Michael J. G. Battersby, Jan Kleefeld, Julian V. Brown, Rainer M. Imhof

A new flotation system has been developed to improve the generally slow separating differentials of fine bubbles and fine particle suspensions. The new technology is based on established pneumatic flotation designs called Imhoflot which use intensive in-line pre-aeration to aerate the flotation pulp prior to its introduction to the separating cell. In the new system (see figure 1) this separation is speeded up dramatically by the introduction of centrifugal motivation in the separating vessel, without the use of internal moving parts. The design focuses on providing increased differential forces on buoyant mineralised bubbles and hydrophilic fines. The commercial benefit to industry is much reduced residence time, less than 30 seconds, which offers considerable cost savings in equipment and infrastructure.

Jan 1, 2003

By D. Lelinski

Air-sparged hydrocyclone (ASH) flotation is one of the new promising technologies. Numerous applications have been successfully tested since its conception; nevertheless, research and development efforts have continued to provide for further improvements with respect to operating conditions and design considerations. Results from experimental studies on bubbles generation in the ASH system are presented in this paper. Bubble size distributions generated during ASH operation have been determined using a high-speed photographic technique. The influence of many factors including surfactant concentration, water flowrate, and porous tube pore size has been studied. Test results indicate that these process variables have a profound effect on the bubble size distribution. With an increase in surfactant concentration or water flowrate (shear field) the bubble size distributions become narrower and shift toward smaller average bubble diameters. However, the influence of pore size is more complicated. Depending on the experimental conditions the average bubble size was found to range from about 100 to 300 microns in diameter.

Jan 1, 1995

By NONE N

Jan 1, 1963

By J. M. Girard

Ground control problems at surface mining operations can occur for a variety of reasons. Stress, gravity loading, rock strength, geology, pore pressure, weather effects, underground workings, and many other factors contribute to slope instabilities that range from small rock falls to massive slides of material. While some of these failures can he predicted or controlled by preventive measures, each year many completely unexpected failures occur. Current methods for monitoring generally involve measuring displacements at a few, selected points in and around the suspected area of instability. While most of the displacements along these points will be in a downslope direction, freeze-thaw cycles of water-filled joints, horizontal stresses or pressure, buoyancy in saturated soils, human measurement errors, or other situations can produce deformation in almost any direction, even without any instability in the slope. Determination of which, if any of the observed movements represents a potential hazard is essential.

Jan 1, 1998

By J. E. Lawver, B. J. Clingan, R. E. Snow

Response surface methodology is a well-known and powerful technique for determining optimum conditions in flotation systems. One disadvantage is the onerous task of the numerical calculations and curve plotting. This paper describes a system in which the investigator simply selects the range of several flotation variables after which the design of the experiment, data analysis, generation of response surface equations, and response surface plots are automatically carried out using a digital computer and a computer-driven curve plotter. Several typical response surfaces of important variables in phosphate flotation are presented as examples.

Jan 1, 1980

It is no longer satisfactory to assess the value of a coking coal on its intrinsic properties alone, its value depends upon its behaviour as a component in a blend. No single test can be used to make this assessment, it can only be made by carrying out a suite of tests. The quality parameters which are considered desirable, and which have widespread acceptance, have been discussed and their application to the blending of coals from New South Wales and New Zealand has been reported and discussed. Blending can be utilised to offset deficiencies, or capitalise on advantages, of the individual coals making up a blend. Coals can be blended, which alone are poorly coking, but which have compensating features. Blending also allows better exploitation of coking coal Reserves..

Jan 1, 1980

By Graham A. Davis

The definition of sustainable development is often taken from the so-called ?Brundtland? report, requiring that activities of the current generation not detract from the potential welfare of future generations. Mining is often held up as unsustainable in this regard since the extracted resource is nonrenewable. Yet Brundtland?s definition of sustainable development also requires that the current generation address the disparity in welfare across the globe, a facet of Brundtland?s report that most have ignored. This paper examines the impact of mining on the welfare of the poor. It finds that poverty levels in the poorest mining and oil intensive economies are lower than expected given these economies? geographical location and level of income, and that extractive activities are therefore completely consistent with sustainable development.

May 1, 2004

By R. V. Ramani, A. S. C. Owili-eger

The rapid depletion of shallower coal reserves dictate that mining in the future will be deeper and more complex with more difficult natural conditions. Consequently, an increase in methane emission is expected. It is becoming evident that more accurate predictions and better planning are necessary to design efficient methane drainage systems. This objective can be achieved by the utilization of the knowledge of the physics of gas flow through coal seams and rock strata and by the application of digital computers in the solution of methane flow problems. Although the methane emission models described here have not been adequately applied to existing field operations, good agreement between actual field measurements reported in literature and the simulation results indicates the potential of these models for initial flow quantity approximations and ventilation planning. This report has, therefore, introduced to the mine operator yet another application of computers as a planning tool. AREAS FOR FURTHER RESEARCH The study reported here is by no means complete. Extensive research efforts should be directed to the following areas: (a) Better understanding of the physics of gas flow through porous media which exhibit fracture permeability. (b) Determination of field parameters which control gas migration. (c) Investigation of the effects of the rate of penetration on the emission rate and fracture propagation.

Jan 1, 1974

Jan 1, 1943

Jan 1, 1955

By William Watson

Coal production in the United States in 2010 increased to a level of 960 Mt (1,085.3 million st), according to preliminary data from the U.S. Energy Information Administration (EIA), an increase of 1 percent, or 9.43 Mt (10.4 million st) above the 2009 level of 975 Mt (1,074.9 million st) (Table 1). In 2010, U.S. coal consumption increased in all sectors except commercial and institutional, while total coal stocks fell slightly for the year. Coal consumption in the electric power sector in 2010 was higher by 4.5 percent, while coking coal consumption increased by 37.9 percent and the other industrial sector increased by 7.1 percent. The commercial and institutional sector, which prior to 2008 had been called the ?residential and commercial? sector and is the smallest of all the coal-consuming sectors, declined by 3.1 percent in 2010. (Note: All percentage change calculations are done at the short tons level.) U.S. coal exports increased from the 2009 levels due mostly to higher demand for metallurgical coal, while coal imports decreased for a third year in a row. The increase in coal consumption for electric generation during the year was the consequence of improving domestic economic conditions further bolstered by a cold winter and warm summer in important coal-consuming regions. Preliminary data show that total generation in the electric power sector (electric utilities and independent power producers, including useful thermal output) in the U.S. increased in 2010 by 4.2 percent. Coal-based generation also increased, resulting in a 38-Mt (42-million st) increase in coal consumed in the electric power sector. Coal use in all the sectors other than the electric power sector increased by 13.9 percent to a level of 65.9 Mt (72.7 million st).

Jan 1, 2011

By Searl. Milton F.

Introduction The urgency of further development of our domestic energy resources becomes more apparent every day. The production capability of existing facilities, taken in the aggregate, declines perhaps 10% per year; imported energy is expensive if available at all; conservation helps reduce demand but eventually will reach a point of diminishing return; new energy sources are promising but past experience, as with nuclear power, teaches us lead times are long and success is not assured. To approach the energy future rationally, it is essential to have some idea of the size of the nation's remaining energy resources, their characteristics, and the degree of uncertainty involved in their estimates. Resources are, of course, only one end of a long chain leading to energy supply to the ultimate consumer. They are an essential element, however, and the only one not under society's control. Given that the resources and a national will to produce the energy exist, it is possible to convert the resources to supply in, generally, an environmentally reasonable manner. However, the process of developing supply takes time. Government must permit access to the resource, and remunerative prices and further evolution of technology are required. This paper does not deal with these essentials, but they must not be forgotten. This discussion is limited to coal, oil, natural gas and gas liquids, uranium, and oil shale. Other energy sources are discussed elsewhere in this issue. Crude Oil Conventional crude oil resources are of greatest concern today, given our dependence on imported oil and its rapidly rising price. Estimates of oil originally in place (OOIP) range from 619 billion bbl to 1,094 billion bbl, differing by almost a factor of two (Table 1). This is surprising because the U.S. is a mature petroleum province with over 120 billion bbl produced and over 400 billion bbl OOIP discovered. Differences in the estimates involve differences in the experience of the various estimators, the interpretation of present geologic information and historical statistics, the methodology, and probably the extent (i.e., water depths) for which offshore resources are included. The range shown for the estimate of a given estimator appears to be primarily due to geologic uncertainty. This uncertainty can be measured by taking the ratio of the low and of the high estimate to the expected estimate for that information source. The low estimates range from 0.85 to 0.87 of their respective values. The high estimates range from 1.18 to 1.27 of the expected values. In all cases the high estimate is further from the expected value than the low,

Jan 9, 1980

By J. Sikamo, A. Mwanza, C. Mweemba

"The Zambian copper mining industry as we know it today had its genesis in the 1920s. Consistent private sector-driven investment in the industry over a period of over 50 years in exploration, mine development and operation, development of minerals processing facilities, building of infrastructure for pyrometallurgical and hydrometallurgical processing, with attendant support facilities, including building of whole new towns, resulted in copper production rising to a peak of 769 000 t in 1969, providingover 62 000 direct jobs. The industry was nationalized in 1973 and remained in government hands for just over 24 years. During this period, the industry experienced a serious decline in production levels, reaching the lowest level in the year 2000 when production was 250 000 t. An average of just under 2000 jobs were lost every year in the 24-year period, reaching just over 22 000 direct jobs in 2000.Following the return of Zambian politics to pluralism and liberalized economic policies, the government decided to privatize the mining industry. The process started in 1996 and by the year 2000 all the mining assets had been privatized. The new investors embarked on serious investment to upgrade the assets and to develop greenfield mining projects. Fourteen years later and after more than US$12 billion investment, production levels increased year-on-year to a peak of 763 000 t in 2013 with direct jobs reaching 90 000.This paper discusses the impact of the mining industry in Zambia on the economy in areas such as employment, support for other industries, direct contribution to the national gross domestic product (GDP), foreign exchange earnings, and social amenities. The paper also focuses on the performance of the mines during these periods vis-à-vis mineral availability, mineral grades and complexity, new technologies, and human capital. This is looked at particularly in the light of current challenges the industry is facing. Suggestions are proposed on how the industry can be nurtured to continue being a major driver for the Zambian economy and a major player in the international copper mining business."

Jan 1, 2016

By Bahram Sameit

Blast engineers have been taking advantage of image-based rock fragmentation analysis methods for the past three decades to estimate rock size distributions. These methods utilize a range of image segmentation techniques, from manual to fully-automated, to delineate the edges of rocks in images. Rock delineation results are then converted to physical rock sizes (and percentage passing curves) by scaling the image pixels to correspond to physical measurements. The size scaling process is critical for acquiring physical measurements, but specifc to the limitations of different applications. This article starts by presenting a shovel bucket-based fragmentation analysis system, where scaling is done using the known width of the shovel bucket within the image. It will then describe methods that use pictures captured by digital cameras with scaling reference objects in the view. Finally, the article presents a method that uses three-dimensional imaging to capture images without the need for scaling reference objects.

By EUGENE MCAULIFE

Jan 1, 1934

By A. H. Shapiro

A decanter centrifuge of novel design was developed for the dewatering of fine-solids slurries having micron-range particles that form paste-like, flowable, hard-to-dewater cakes. The design combines a compound beach with a cake-flow control structure that allows expressed liquid from the cake in the dry beach region to be returned back to the liquid pool while maintaining high solids throughput. In order to provide optimal performance with various operating parameters (feed rate, centrifugal gravity, pool, differential speed, concentration of feed solids, and different slurry types), the cake-flow control is adjustable. The second part of the beach is preferably at zero angle. Tests showed that the new design allows increases in both solids dryness and solids throughput.

Jan 1, 2001

By G. Demi, G. Belardi, N. Shehu, S. Cico

The physico-chemical interaction between minerals such as olivine, chromite and serpentine and the ions most commonly present in solution, like Ca and Mg and flotation reagents such as EDTA and oleic acid was investigated. The study was conducted via release tests, electrophoretic measurements and microflotation of selected minerals coming from the Kukes deposit (Albania). The results were confirmed by means of beneficiation tests on various types of ores, from the Kukes (Kalimash), from Bulquiza area and from the Rizo deposit (Greece). It has been demonstrated that when Na-K Oleate is used as collector chromite, olivine and serpentine can be separated at pH = 2.5 and/or 5.5 employing EDTA (EthyleneDiamineTetraAcetate) on previously deslimed material. This approach ensures flotation concentrates with a Cr2O3 content about 50%, at a recovery in excess of 65%.

Jan 1, 2003

A FEW nights ago while working in the small hours of the morning on a clarion message intended for this page, we repaired to the kitchen for coffee, as is our wont when the solitude of the late hour and the stillness of the night seduce thoughts from the job at hand to reminiscences. The thought occurred, as we slowly dissolved the instant coffee in boiling water, that this modern world of canned, frozen, and dried foods deprives us of some of the subtler and therefore more delightful pleasures of life. We recall the aroma of boiling coffee which greeted us on getting up in the morning before the ease of instant coffee deprived us of the aroma from the old coffees. This line of thinking led us to place the blame on our wife for taking the easy way of making coffee and thereby depriving us of some of our enjoyment. From thinking about our spouse, it is only a short step to thinking about "the boss" or bosses in general.

Jan 9, 1951

By J. R. CAIN

SAMUEL L. HOYT, ? Nela Park, Cleveland, Ohio (written discussion?). The work that Dr. Cain is doing on gases in steel should have a highly important bearing on investigational work in connection with steel-making practice. We found, for example, in our work in connection with the use of manganese in open-hearth practice that we needed expressions for the manganese efficiency and the "condition" of the steel. To get these figures we assumed that we would need to know the amount of FeO at different stages of the heat and the amounts of the gases present. This required simultaneous analyses of our samples for FeO and the gases and Dr. Cain seems to be the only investigator who has considered the analytical work from this point of view. That he has done so is very encouraging and it is to be hoped that his work will solve the mys-teries now surrounding this neglected phase of steel metallurgy. Those interested in the Ledebur method for use in connection with the efficiency of manganese as a "deoxidizing " agent will he disappointed to learn that more recent work at the Bureau indicates that Ledebur determinations are not reliable. The principal source of error seems to be due to the partial reduction of the ferrous oxide by the carbon present in the steel. However, it seems like an unnecessary criticism of the Ledebur method to state (p. 1319) that it proved of little value because it showed little differences in oxygen for a series of steels treated with ,various reagents and showing variations in physical properties and free-

Jan 12, 1919