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By Ernest Kirkendall

The amount of research done in the last fen years on the subject of diffusion in solid metals is significant of the importance of this problem. To review the literature dealing with diffusion is unnecessary here. Deschl in 1912 reviewed the work that had been done on diffusion in solids and gave a bibliography of the literature published before that time. Mehl's paper in 19362 is an excellent review of diffusion in metals and contains a large bibliography. Of importance also for it? review and bibliography is an article by 14. I. Krynitsky.~ While considerable material lias appeared in the literature on diffusion in brass, the amount of information is not great compared to that pertaining to some of the other alloys. Most of the information published is of a qualitative nature; that which is quantitative varies considerably. Thus the quantitative determination of the rates of diffusion of copper and zinc in alpha brass by a new method appeared worth while. In the present investigation the rate of diffusion of zinc in approximately the same composition alpha brass has been determined :it three temperatures. Procedure The method used consisted of plating copper on a beta brass, heating it, to allow diffusion to take place, and measuring the concentration of copper by determining the lattice constant of the alloy. This method is unique in that it uses a beta brass of such a composition that at the tem perature at which diffusion takes place the beta brass is saturated wit11 copper. Thus, while the beta brass supplies thc zinc, no diffusion takes

Jan 1, 1939

By Ernest Kirkendall

The amount of research done in the last fen years on the subject of diffusion in solid metals is significant of the importance of this problem. To review the literature dealing with diffusion is unnecessary here. Deschl in 1912 reviewed the work that had been done on diffusion in solids and gave a bibliography of the literature published before that time. Mehl's paper in 19362 is an excellent review of diffusion in metals and contains a large bibliography. Of importance also for it? review and bibliography is an article by 14. I. Krynitsky.~ While considerable material lias appeared in the literature on diffusion in brass, the amount of information is not great compared to that pertaining to some of the other alloys. Most of the information published is of a qualitative nature; that which is quantitative varies considerably. Thus the quantitative determination of the rates of diffusion of copper and zinc in alpha brass by a new method appeared worth while. In the present investigation the rate of diffusion of zinc in approximately the same composition alpha brass has been determined :it three temperatures. Procedure The method used consisted of plating copper on a beta brass, heating it, to allow diffusion to take place, and measuring the concentration of copper by determining the lattice constant of the alloy. This method is unique in that it uses a beta brass of such a composition that at the tem perature at which diffusion takes place the beta brass is saturated wit11 copper. Thus, while the beta brass supplies thc zinc, no diffusion takes

Jan 1, 1939

By Y. Yhang, D. C. Sego

ABSTRACT This paper evaluates the potential of freeze-thaw dewatering using Albian mature fine tailings (MFT). Freezing tests were first performed to study the effect of freezing rate on dewatering efficiency. Lower freezing rate resulted in higher thawed solids content and shear strength. Subsequently, large strain consolidation tests were conducted to investigate consolidation behaviour and how it is affected by freeze-thaw. The consolidation behaviour was presented in terms of effective stress versus void ratio and permeability versus void ratio. The results can be used to predict the field behaviour of Albian MFT and optimize the application of freeze-thaw for MFT dewatering.

Jan 1, 2014

Prof. J. C. BRanner, Stanford University, Cal. (communication to the Secretary): On p. 398, Mr. Hedburg mentions Marionite and Brannerite as ores of zinc. Neither of these has been authoritatively recognized as a distinct mineral species. Marionite, originally described by Elderhorst, was subsequently determined to be nothing else than hydrozincite. Analyses of the so-called Brannerite were sent by me to Prof. Penfield, who says it is a mixture of Smithsonite with some other mineral. On p. 398, Mr. Hedburg says the zinc-bearing formation of North Arkansas " is recognized as the Upper Silurian." So far as my observation goes, the ores occur both in Lower Carboniferous and in Ordovician or Lower Silurian rocks, but nowhere in rocks known to be of Upper Silurian age. If Mr. Hedburg has any paleontological evidence of the Upper Silurian age of these rocks, or of any of them, he will confer a favor upon geologists by making it known. On the same page is another statement in which I cannot concur. He says that in this region, " it can easily be seen that the largest fissure-deposits have been eroded and washed away, leaving here and there a few patches adhering to the hillsides." I am compelled to say that in many years' study of the geology of the region in question, I have never been able to recognize such a state of affairs as Mr. Hedburg here describes. The patches which he regards as remnants of fissure-veins, " adhering to the hillsides," I have found to be either the edges of bedded deposits, or portions of the zinc-bearing breccias, formed along old drainage-lines, and laid bare by the ordinary processes of erosion. That fissure-deposits have been partly removed by the same agency, goes without saying; but it is, in ,my judgment, no more true of North Arkansas than of any other mining-region that erosion has selected and washed away " the largest " deposits. My own views of the region in question are given in detail

Jan 1, 1902

By M. K. Matthews

The use of backfill has important environmental control implications which, although frequently overlooked, can be both beneficial and problematical. Where backfill is widely used, the reduction in stope heat load and improved air utilization influence the overall mine ventilation and refrigeration requirements significantly. A programme of work examining in detail all the environmental consequences of backfilling is currently underway at the Environmental Engineering Laboratory of the Research Organization of the Chamber of Mines. This paper gives an overview of the work and presents some findings. In so doing, the environmental implications to be considered when backfilling are highlighted.

Jan 1, 1988

Validation and Application of Filtration Theory to Plate and Frame Pressure Filtration - From Laboratory to Full Scale

Sep 13, 2010

By B T. Qin, C Zhu, Y W. Jia, Y Lu, F L. Li, Q L. Shi

Air leakage through rock fractures in coal mining is a major cause of coal spontaneous combustion. In order to overcome the deficiency of the existing fire control technology and prevent coal spontaneous combustion by isolating coal from oxygen, the article proposes a novel technology of inorganic solidified foam (ISF) with high expansion to fill fractures effectively. ISF consists of fly ash, cement, setting accelerator, redispersible polymer powder, water and aqueous foam. For preparing homogeneous and stable ISF, a preparation system with a pore type foam generator, a mixer device installed with a hollow shaft and helical blades, air compressor, slush pump and monitoring instruments was developed, and the working principles of key devices were elucidated. Based on a series of experiments on the different ratios of each component material and technological parameters of the preparation system, ISF with a foam expansion ratio of 8~10 and dry density of 250–400 kg/m3 was prepared. The relationship between elastic compressive strength, modulus of elasticity and density was summarised. Based on the injection experiment for fracture of loose coal pile with high temperature, the characteristics of sealing air leakage, compressive strength, thermal insulation, flow and cooling of ISF in the fresh state were investigated, indicating that ISF can effectively cut off the air leakage and cover the coal sample to reduce the temperature in the earlier stage, and ISF can remain stable and not crack. The ISF was applied to Luwa coalmine to seal small coal pillar pressure fractures and loose coal fractures in goaf. After press-casting the ISF in Luwa coalmine, the pressure-difference of inner-outer increased, meaning the effect of external conditions on the pressure-difference decreased, showing that it could plug the air leakage effectively.CITATION:Qin, B T, Shi, Q L, Lu, Y, Zhu, C, Li, F L and Jia, Y W, 2015. The novel technology of inorganic solidified foam with high expansion for preventing coal spontaneous combustion, in Proceedings The Australian Mine Ventilation Conference, pp 121–126 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By John C. McDonald

CONTROLLED cold work is used between solution heat treatment and precipitation heat treatment for producing certain tempers of the commercial aluminum base alloy 2219 (designation of the Aluminum Association, U.S.A.) which contains 6.3 pet Cu as the major ingredient responsible for the age hardening. The complete composition limits for this alloy are listed in Table I. The alloy has been described in detail,' and the control of the heat treatment has also been published.2 Beneficial effects of such cold work in other alloys have also been pointed out.3'4 NO data have been published on the effects of varying amounts of cold work under fixed aging conditions. In connection with an investigation of the possibility of providing the desired cold work by explosively generated shock waves, it became desirable to investigate the effect of variable cold work, and to compare the re -sults with those obtained from explosives. The general principles of explosive hardening are well-described in the literature.' All material used was guaranteed by the supplier

Jan 1, 1968

By David D. Eyer

Since the decade of the 1990s is nearly upon us, I have focused on what I see are the likely trends featured in new large underground coal mines 10 years from now. I do this from the vantage point of having been involved in the installation of large mines for more than twenty years. Little of the equipment resources we have available today was unknown when I entered the coal business in 1960. There were continuous miners, longwalls and diesel-powered equipment in Europe, monitoring systems, computers, heavy media separation systems, froth flotation and conveyors then as there are now. A substantial evolutionary process has occurred with these and other mining machines and processes. Some evolved only to die out, such as boring-type continuous miners; others, such as longwall systems, flourished. My intuition tells me that since there have been largely evolutionary rather than revolutionary developments in the near past, the same is true of the future, at least for the next 10 years. In other words, the elements of what are in the future are with US now. Some, such as computer-based applications, may evolve beyond our wildest dreams -but I doubt it.

Jan 1, 1988

By Benjamin P. Hay

Complexation of a metal ion to a ligand often results in structural changes that introduce steric strain within the ligand. A design criterior:1 for ligands that will complex metal ions more strongly is to choose Iigar:1d architecture, that minimizes this strain. This paper describes how molecular mechanics models can be used to define the degree of ligand binding site organization in terms of' ,strain energies associated with conformational reorganization and distortion of the binding conformer. This approach yields a method to predict how modifications to ligand structure will affect metal binding affinity.

Jan 1, 1999

By S. K. Dimitrov

?Ellatzite Med? is one of the biggest mining companies in Bulgaria, processing about 12,000,000 t of ore per year. Waste materials left after extraction of copper concentrate are deposited in tailings dam ?Benkovski 2?. The hydraulic structure is built according to the downstream method, through hydrocyclonization where the downstream batter and the body of the wall are formed by the separated coarse sand particles of the separated tailings. In connection with the prolonged concession of Ellatzite Med and the enlarged capacity of Benkovski 2, the tailings dam has expanded on to the surrounding terrain. To guarantee a normal hydrocyclonization and build up of a tailings wall during waste deposition from the ore mill, the technological scheme of the hydraulic transport system of Benkovski 2 has been changed.

Aug 1, 2013

By Michael K. Rhodes

A 120 tonne per day BacTech bacterial oxidation plant treating refractory gold concentrates for Gold Mines of Australia's Youanmi project in Western Australia commenced operation September 1994. This was the first commercial application of the BacTech process. A pilot plant trial on concentrates produced from Youanmi ore was carried out at BacTech's laboratory in Perth. Results and measurements from this trial were used by Signet Engineering Pty Ltd to design the commercial plant. This paper cover the results obtained from the piloting, their implementation in the plant design and the initial commissioning of the full scale plant.

Jan 1, 1995

By Terkel Rosenqvist

THE desulphurization of molten iron and steel is a very complicated process. One way to arrive at a better understanding of this process is to break it down into several simpler chemical processes that can be studied individually in the laboratory. For a study of the different factors that influence the equilibrium distribution of sulphur between liquid metals and slags, several simpler equilibria may be investigated. One very important subject is the determination of the escaping tendency of sulphur in the liquid metal and its dependency on temperature and composition of the melt. Several papers in this field have recently been published.', ' Another subject is the study of the sulphur capacity of the slag. A molten slag is indeed complex, and even if sulphur distribution data for a large variety of molten slags may give empirical data about their desulphurizing power, the importance of the individual components is still not quite clear. It is accepted generally that lime is the most important desulphurizing component in the slag. The present investigation has as its purpose to study the desulphurizing power of lime in its standard state, and to provide a basis for thermodynamic calculations of the desulphurizing power of various lime-containing slags. The standard state of lime at steelmaking temperatures is solid calcium oxide, CaO. It can react with sulphur to form solid calcium sulphide, CaS. The relative stability of calcium oxide and calcium sulphide is expressed by the free energy of the reaction: 2Ca0 (s) + S1 (g) = 2CaS (s) + O2 (g) The existing free energy data for this reaction, listed by Kelley5 nd Osborn,' are uncertain to about 10 kcal and are of limited value for a calculation of equilibrium constants. Under the conditions prevailing in a melting furnace, the sulphur pressure may be expressed conveniently by the ratio H,S/H2 and the oxygen pressure by the ratio H,O/H, (or CO,/CO). The desulphurizing power of calcium oxide may, therefore, be studied by the reaction CaO + HIS = CaS + H2O. A study of this reaction may be complicated by certain side reactions: Water vapor and hydrogen sulphide may react. to form sulphur dioxide, and calcium sulphide may be oxidized to calcium sulphate. A thermodynamic calculation shows that these side reactions will be suppressed to insignificance if the equilibrium is studied in the presence of an excess of hydrogen. The apparatus used is shown in Fig. 1. About 10 g calcium oxide and 20 g calcium sulphide (laboratory qualities) were intimately mixed, and some water was added to make a thick paste. The paste was put into a thimble of zirconium silicate, which was placed within the constant temperature zone of a furnace, and capillary refractory tubes were attached in both ends. After the mixture had been heated in dry hydrogen at 1000°C for several hours all Ca(OH), and CaCO, had decomposed and CaSO, was reduced, so only CaO and CaS remained in the thimble forming a porous plug. The mixture was examined by X-ray diffraction after the initial reduction in dry hydrogen as well as after the subsequent experimental runs up to 1425 °C. It was shown that crystalline calcium oxide and calcium sulphide were always present together in about equal amounts. The unit cell edges were found to be 4.80A for CaO and 5.68A for CaS in good agreement with existing literature values." This shows that the mutual solid solubility is very small, and that the compounds are present in their standard states. Purified hydrogen was passed through water sat-urators kept at constant temperature in a thermostat bath. The amount of water vapor saturation was checked by means of a dew point method, not shown on Fig. 1. The gas mixture was passed through the capillary inlet into the furnace, where it was sifted through the porous plug of calcium oxide and calcium sulphide. The hydrogen sulphide present in the outgoing gas was absorbed in a zinc acetate solution and the hydrogen was collected over water. When one liter of hydrogen had been collected, the amount of hydrogen sulphide was determined by iodometric titration. As one molecule of H,O is used for the formation of each molecule of H,S, the equilibrium ratio H,S/H,O would be , where (H,O) is the molar concentration in the ingoing gas, and (H,S) the molar concentration in the outgoing gas. In the present work (H,S) was always very small compared to (H20). In order for the observed H,S/H20 ratio to represent the true equilibrium ratio the gas flow has to be: 1—Sufficiently slow to give a complete establishment of equilibrium, and 2—sufficiently fast to counteract thermal diffusion. Incomplete reaction would give a value decreasing with increasing flow rate, and thermal diffusion would give a value increasing with decreasing flow rate. When inlet and outlet tubes of about 2 sq mm cross-section were used, the observed gas ratio was independent of the flow rate between 15 and 125 cc per min, Fig. 2. In this range, therefore, the observed gas ratio represents true equilibrium.* For the rest of the in-

Jan 1, 1952

By S Sokhanvaran

Electrodeposition of silicon from a cryolite based electrolyte at a relatively low temperature (1000°C) is a promising approach to generate high purity silicon. In order to obtain fundamental data pertaining to electrowinning of silicon from Cryolite?SiO2 melts, density and electrical conductivity measurements were made. A range of temperatures and SiO2 contents was studied for each property. It was found that while density has an inverse relationship with temperature, the dependence for electrical conductivity is direct. Increasing silica content up to the saturation limit (~ 5 wt%) increases the density whereas further increase in SiO2, lowers the melt density. On the other hand, the conductivity is lower for the melts with greater SiO2 content, at any temperature.

Jan 1, 2011

A Life Cycle Assessment (LCA) of stainless steel production, including that of the nickel, ferronickel, ferrochromium and iron feedstocks was carried out using inventory data derived from the literature. The environmental impact categories considered in the study were Global Warming Potential (GWP), Acidification Potential (AP) and total (or full cycle) energy consumption. The effects of different sources of electricity (black coal, natural gas and hydroelectricity) were also examined in the study. The results of the LCA showed that when ferronickel is used as the nickel source, the total energy consumption for stainless steel production is approximately 50% higher than when nickel metal is used as the nickel source (75 MJ/kg cf. 49 MJ/kg). This result comes about largely because the Fe units in ferronickel have a much higher energy intensity than do the Fe units in pig iron, and the greater the use of the former at the expense of the latter, the greater is the total energy consumption. The results also showed that the production of ferronickel made by far the largest contribution (59%) to the total energy consumption for stainless steel production when this feedstock is used as the nickel source, but when nickel metal is used as the nickel source the contributions of the various stages are more evenly distributed. It was also observed that the electricity consumption of the electric furnaces used in the production of ferronickel, ferrochromium and stainless steel contributed approximately 50% to the total energy consumed in stainless steel production. Given the relatively low efficiencies associated with electrical power generation, significant reductions in the total energy of stainless steel production could be anticipated if more direct use of thermal energy was made in the ferronickel, ferrochromium and/or stainless steel smelting stages, for example by utilising bath smelting processes.

Jan 1, 2004

By L. Lacerda

Spray-on ground support membranes (GSM) or thin support liners hold today perhaps as much potential to impact underground (u/g) ground support operations as dry and later wet-mix shotcrete when introduced to mining in the latter part of the 20th century. This emerging technology has come a long way from the time the first single component experimental coatings were tested in the mid-1980s. Due to a number of factors, including occupational health risk and mine safety regulations, it has taken quite some time for the development of non-hazardous membrane products. However, at this junction most existing u/g mines that employ more conventional forms of ground support could benefit from evaluating GSM technology as a means of improving safety and the bottom line. The same is especially true for future mine developments. This paper describes Master Builders Inc.’s CS1251 GSM product and its implementation. It discusses the situations in which GSM may replace other forms of ground support. Furthermore, it evaluates GSM costs & safety issues and looks at present applications and the potentially bright future of this technology.

Jan 1, 2002

By Scott W. Hazen, George W. Gladfelter

This report presents the results of an initial investigation into some problems resulting from the use of assays representing unequal sample interval lengths and the use of the weighted average grade of ore in evaluating bedded mineral deposits . A mathematical proof and examples are given to show that the unweighted and weighted assay averages are equivalent when there is no correlation between assay value and sample interval length but that these averages are different when there is correlation between assay value and sample interval length . The amount of this difference between estimates is a function of the degree of correlation . One set of sample and assay data , based on 11 stratigraphic sections of the Phosphoria formation in Idaho , indicates that the relationship between the amount of difference between estimates and the correlation factor is approximately linear . If this correlation relationship can be established , within acceptable limits of precision , as a consistent attribute of deposits , the estimate of weighted average grade of ore could be predicted directly from the unweighted estimate of grade of ore by using the relationship as a prediction factor . Randomness tests on the sample and assay data from the Phosphoria formation , using the mean - square - successive - difference method , indicate that correlation between assay value and sample interval length ( each sample interval length represents an individual bed or stratum of the formation ) , apparently has little effect on the independence between successive assays , between successive sample interval lengths , and between the products of assays and sample interval lengths . Therefore , these data can be analyzed statistically as long as the original sample sections have been selected at random for sampling .

Jan 1, 1964

By Grieveson P, Terry B. S

Carbothermic reduction of sulphide minerals for achieving a selective separation of metallic species from complex minerals has been discussed by considering the prevailing oxygen potential during the course of reaction. Construction of univariant plots for the reduction of sulphides with carbon monoxide gas or carbon and in the presence of either lime or anhydrous calcium sulphate is the key feature of this work. The theoretical calculations for univariants in the Cu-Fe-S-O system indicated a preferential separation of metallic copper and iron by imposing a chemical potential. This is evident from a logarithmic plot of sulphur dioxide partial pressure against reciprocal temperature. The results are compared with empirical data for the reduction equilibrium. The reduction behaviour of the constituent sulphides are also discussed together with the experimental results and theoretically predicted phase stability diagrams.

Jan 1, 1992

Bill S.1431 for the creation of a Department of Natural Resources has received a propitious hearing before the Senate Committee on Government Operations. Interior Secretary Rogers C. B. Morton was one of the prominent witnesses who testified in favor. The department had been proposed, Morton said, with "the conviction that the development of all natural resources would be harmonized with the most practicable possible means to protect and preserve the environment, consistent with the social and economic needs of the Nation." Another opinion on the pro side came from Atomic Energy Commissioner Clarence E. Larson, who said that a "total picture" had become essential to the establishment of a policy for developing energy resources in the best public interest. Commissioner James T. Ramey, on the other hand, was one of the AEC dissenters. Ramey said he believed the reorganization of resource responsibilities would hinder efforts to deal with energy-environmental problems and prevent the use of AEC "expertise and facilities" to the greatest advantage. As Arnold Weber, associated director of the Office of Management and Budget, pointed out, however, retiring AEC Chairman Glenn T. Seaborg is in favor of the new department. Another supporter, and one who can cast a vote on the bill, is Sen. Frank E. Moss. Final Standards for emissions from new stationary sources will be published by the Environmental Protection Agency on October 27. The initial proposals, appearing in the Federal Register on August 17, called for limiting emissions per million Btu of heat input (maximum 2-hr average) to 0.2 lb of particulate matter, and, where solid fuel is burned, to 1.2 lb of sulfur dioxide and 0.7 lb of nitrogen dioxide. While the new rules are mainly for new plants, the EPA is also proposing them for "existing plants which are modified in such a way as to increase or alter. . . their emissions."

Jan 1, 1971

By Richard D. Miller

The helium resources base of the United States was estimated by the U.S. Bureau of Mines (Bureau) to be 894.6 Bcf as of January 1, 1989. These resources are divided into four categories in decreasing degree of assurance of their existence: (1) helium in storage and in proved natural gas reserves, 282.4 Bcf, (2) helium in probable natural gas resources, estimated at 237.7 Bcf, (3) helium in possible natural gas resources, estimated at 263.1 Bcf and (4) helium in speculative natural gas resources, estimated at 111.4 Bef. These helium resources are further divided into depleting and nondepleting, with the helium in storage being in a classification. The depleting resources are those associated with natural gasfields that are, or will be produced for the natural gas they contain. Almost all of the helium in potential (probable, possible and speculative) natural gas resources is included in this classification. These depleting resources are estimated to contain 775 Bcf of the total helium resource base. Helium resources contained in nondepleting natural gas resources, i.e., those in shut-in, abandoned, or otherwise nonproducing natural gas fields, are estimated to total 84 Bcf There is 35 Bcf of helium in storage in the Federal Government-owned Cliffside Gasfield near Amarillo, TX.

Jan 1, 1990