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By George A. Roberts, Arthur H. Grobe

Tensile, hardness and density properties are presented for a new 18-8 stainless steel powder for the —50, —100, and —140 mesh cuts and also for a prepared blend containing 62 pct —325 mesh powder. The data were obtained for sintering temperatures of 2100° to 2350°F and for compacting pressures of 30 to 50 tons per sq in. A NEED has existed for a stainless steel powder of uniform composition from particle to particle, which could be readily molded and sintered, and which would yield moderate to high strength and ductility when processed into parts by standard powder metallurgy techniques. The literature reveals that previously available powders have been lacking in one or several of these desirable characteristics. Originally attempts to produce stainless steel powder by blending and diffusing elemental metal powders were unsuccessfu1.l A truly alloyed stainless steel powder reported by Dale in 1947 yielded reasonable mechanical properties but required an exceptionally high sintering temperature of 2400°F in pure dry hydrogen.' A later development reported in 1950 by Stern provided a stainless type powder of excellent molding properties' but this powder likewise required sintering at temperatures over 2350 °F and did not yield properties as high as those previously reported. The powder was not truly alloyed prior to sintering. A prealloyed stainless steel powder has been developed that is readily moldable at 30 to 50 tons per sq in., can be sintered at low temperatures (2100" to 2300°F), and which yields compacts with both high strength and ductility. The powder is prepared by the liquid disintegration method," direct from molten metal. Early attempts to make 18 pct Cr, 8 pct Ni stainless steel powder by this method did not produce a usable powder for pressing and sintering because of a preponderance of spherical particles with relatively high, surface oxide content. It was learned that silicon additions to iron alloys, powdered by this process, gave bright powder of low-oxide content and such additions were made to 18-8 stainless with similar results. An attendant change in particle shape occurred reducing the number of spheroids materially. The optimum composition which has been studied and is reported here contains approximately 2.5 pct Si. Silicon additions to stainless steel of the 18-8 type improve the resistance to high-temperature oxidation and promote the formation of ferrite. Corrosion resistance is, however, controlled by chromium content and even though ferrite may exist the corrosion resistance is not generally impaired.4 Experimental Procedure A detailed study of the 18-8, 2.5 pct Si powder has been made in accordance with the following outline: 1. Four blends a. — 50 mesh b. —100 mesh

Jan 1, 1952

By Henry M. Howe

THE natural effect of large size should be to increase segrega¬tion. I have previously pointed' to the excessive segregation in many large ingots as tending to confirm this, but I have shown that in case of ingots less than 16 in. square this expected effect of ingot-size is liable to masked by that of other variables. Under these conditions we should expect that if large ingot-size really does tend to increase segregation, this effect would be shown by taking the average of large numbers of cases, so that the effects of these other variables might off-set and cancel each other.

Jan 10, 1909

What is your personal view and assessment of the overall health of the industry in the current global economy? The economic outlook remains soft for the near future and, although the global economy is showing signs of recovery, uncertainty has tempered the pace of recovery. In addition to uncertainty, we are still facing significant economic challenges in many parts of the world, including Europe and the United States. The rapid expansion of China?s economy has recently slowed, further contributing to the sense of uncertainty in the overall health of the global economy. This situation is both a blessing and a curse, depending on which sector of the mining industry we are considering. For example, coal, industrial minerals, aggregates, base metal and precious metals markets are impacted by different forces and drivers and will experience different outcomes within the same economic environment. Let me give a few concrete examples to illustrate this concept. The prevailing economic uncertainty that I have just described tends to drive investors toward safe havens. Gold has historically been viewed as a safe haven and as long as investors shy away from traditional investments, gold prices will remain high and gold mining companies will continue to expand and invest capital in their operations. The same sluggish economy that drives gold prices higher has the opposite effect on other segments of the minerals industry. A great example of this is industrial minerals and aggregates used in construction. The markets that consume these minerals have contracted significantly over the past five years. The outlook for this segment is poor, as the glut of available housing continues to inhibit demand for new construction and, thus, many industrial minerals. In addition to this, the federal government?s lack of political will to enact long-term legislation funding transportation and infrastructure projects continues to be a drag on the U.S. aggregates industry.

Jan 1, 2013

By J. Pinto, F. Galasso

THE current emphasis in preparing boron fibers by reduction of gaseous boron compounds on a resistively heated metal wire substrate has renewed interest in the borides of those metals which have relatively high melting points and are available as fine wires. A knowledge of the structures and properties of the borides, which are formed when boron diffuses into the metal core during boron deposition, can be of assistance in the understanding of the boron fiber formation process and the fiber properties. Many of these borides are well-known and their properties have been measured. However, when an unidentified boride is found in the core, it may be difficult to establish its composition because of the small amount of material available, the preferred orientation effects on the reflections in its X-ray pattern, and the possible overlap of X-ray reflections if several borides are present in the core. For example. the proper indexing of the X-ray pattern of WB4, which was formed in the tungsten substrate core during boron fiber formation, was accomplished only after small single crystals of this boride were grown and X-ray precession investigations were conducted.' This note presents the results of a study of the phases formed in the core when tungsten, tantalum, and molybdenum metal wires were used as substrates in the boron fiber preparation process with particular emphasis on the identification and characterization of a higher boride of molybdenum analogous to WB,. Boron was deposited on resistively heated stationary 0.0012-in.-diam tantalum, tungsten, and molybdenum wires at 1050°C for various times up to 60 sec using boron trichloride and hydrogen as the reactant gases. After 60 sec of boron deposition the fibers were approximately 0.006 in. in diam. Examination of photomicrographs of fiber cross sections showed that the boron had diffused nearly to the center of the tungsten and molybdenum cores in 15 and 30 sec, respectively, and only halfway to the center of the tantalum core in 60 sec. X-ray diffraction photographs of the fibers indicated that it was also after 15 and 30 sec deposition times that the tungsten and molybdenum metal reflections, respectively, had disappeared from the X-ray patterns of the fibers. The patterns of the boron fibers produced using tantalum wire as a substrate showed that amorphous boron, TaB2, and tantalum metal were present after a few seconds deposition time and remained even after deposition times of 60 sec. Until a deposition time of 15 sec was reached, the tungsten substrate fibers contained amorphous boron,273 6WB, W2B5, and WB4 as well as tungsten metal, while the molybdenum substrate fibers contained amorphous boron, MoBa, Mo2B5, and molybdenum metal for deposition times up to 30 sec. Just before the molybdenum metal pattern disappeared, a pattern similar to that of WB, appeared, suggesting that a phase, MOB,, isomorphous with WB,, was present in the fiber. This same pattern was obtained from the product formed by heating a mixture of molybdenum metal and excess boron powder in a boron nitride crucible at 1960°C in an argon atmosphere. As was the case with the WBn pattern, this pattern could best be indexed on the basis of a hexagonal unit cell rather than the tetragonal unit cell Chrktien and Helgorsky reported for ~0~4,~ see Table I. The unit cell parameters for MoB4 were calculated to be a, = 5.214A, co = 6.358A. Assuming the space group P63/mmc and positions5 2M01 in 2b and 2MoII in 2c found for tungsten in WB~,' a logical structure for MOB, was determined using geometrical considerations to place the boron

Jan 1, 1969

By A. T. Sutaone

"In the Dongri Buzurg Manganese Mine of M/s Manganese Ore (India) Ltd., high grade lumpy manganese ore required for iron and steel industries is produced through multi-stage crushing and screening. This has resulted in accumulation of 50,000 tonnes of low grade fines over the years. This production of such fines is still going on. The fines create environmental problems, like air and water pollution and siltation in adjoining fields. Besides containing lot of manganese values, they occupy large space which is very scare in mining area.The Indian Bureau of Mines under one of its statutory functions has suggested the company to explore the possibility of recovery of additional values under conservation and environmental aspects. Hence the company has sponsored a bulk sample for beneficiation studies in the Modern Mineral Processing Laboratory and Pilot Plant of Indian Bureau of Mines at Nagpur, India. The main manganese minerals present in these mine rejects have been identified as pyrolusite and psilomelane. The purpose of this study was to explore the possibility of evolving a suitable beneficiation flowsheet to obtain manganese concentrates assaying over 72% MnO2 to be used as raw material for the manufacture of dry cell batteries.The sample/material was subjected to characterisation studies in terms of chemical analysis, granulometry and mineralogical compositions. Based on these characterisation studies, the beneficiation process developed comprised of desliming, jigging and low intensity magnetic separation mainly to reject quartz, silicates and jacobsite. The manganese concentrate thus produced assayed 70.2% MnO2 with MnO2 recovery of 78% and weight per cent yield of 63.5. This natural concentrate could be mixed with the electrolytic manganese dioxide produced by the company and this blend can thus be used as a raw material for the manufacture of dry cell batteries by the end users. The paper deals with the details of test work carried out in evolving the process flowsheet."

Jan 1, 2003

By Charles Rich, Robert Munson, Leonard Obert

Improved methods of predicting the caving characteristics of ore bodies is discussed. Experiments were conducted at Climax mine, Climax, Colo., on varied rock compositions. The cavability of adjacent areas, as well as seismic energy absorption proved to be good factors in determining cavability. Seismic velocity, core recovery, and rock quality designation (RQD) were found to be not as reliable.

Jan 1, 1977

By Q. J. Xu

In blasting sensitive areas, the use of traditional blasting for rock fracture is restricted. Soundless cracking technology has been presented to achieve rock fracture instead of blasting. However, when the diameter of a borehole is larger than 50 mm, it is very dangerous that the soundless cracking agent (SCA) will have a tendency to gush from the borehole, which also leads to cracking failure. In this paper, a new large scale borehole soundless cracking technology is presented, using a new enlarged drill bit and mechanical plugging, which could solve the hole gush problem. Experiments were made to measure the expansive pressure of the SCA working in boreholes of F40 mm and F100 mm. The difference between two sizes of cracking phenomenon was compared and analyzed to show that large scale borehole soundless cracking has larger expansion pressure and faster reaction speed than traditional soundless cracking. Based on the experimental data, finite element analysis was utilized to study the stress concentration and stress distribution between two neighboring large boreholes in several media during the cracking process. Using the data from experiments with finite element numerical simulation, the brittle material fracture condition was analyzed to design the parameters of the borehole mesh. With the theoretical analysis, the technological process and reference parameters of large scale borehole soundless cracking were proposed, including the borehole spacing, burden distance, depth of the borehole and so on. Then a single rock was cracked with the new enlarged drill bit and new plugging, and the results proved the feasibility of the new large scale borehole soundless cracking technology, which achieved the expected goal of improving the cracking ability and reducing the cracking time. This paper presents a new efficient rock cracking method for blasting sensitive areas, and which could apply to mining engineering, demolition engineering, excavation engineering and other engineering applications where there is a demand soundless and non-vibration fracturing of rock.

Aug 1, 2013

By E. Teghtsoonian, K. G. Davis

Cobalt crystals of commercial purity have been tested in tension. Their resolved shear stress-shear strain curves are very similar in form to those for zinc, magnesium, and cadmium. There is an initial linear region for shear strains up to around 150 pct, the ratio of work hardening slope to shear modulus at room temperature being about 2 X x This is followed by an upturn, which is, PLASTIC deformation in metal single crystals with close-packed structures has been found strongly dependent on stacking-fault energy. The high stacking-fault energy hexagonal metals magnesium, zinc, and cadmium have been quite extensively tested, but up to now no data have been available for a comparable hexagonal metal with low stacking-fau1t energy' An however, smaller in magnitude for cobalt than for the other metals. Values for the critical resolved shear stress rise from 97 kg per sq cm at room temperature to approximately 170 kg per sq cm at -196 °C. The Cottrell-Stokes ratio is not constant either for variations in the strain rate or for temperature changes, its value decreasing with strain. investigation into the plastic deformation of cobalt, which has a very low stacking-fault energy, has therefore been undertaken. EXPERIMENTAL PROCEDURES Cobalt crystals in the form of rods 0.3 cm in diam were grown in an electron-beam floating-zone refiner at a rate of zone travel of 25 cm per hr. Details of the growing procedure are given in Ref. 1. The zoned cobalt rods had the following analysis:

Jan 1, 1963

By Y. J. Wang

A graphical technique by which the operating points for a two-fan ventilation system can be represented as the intersection of the modified fan curves is described. In constructing the diagram, the air quantities associated with the fans are considered to be independent variables and used as the axes of a rectangular coordinate system. The diagram may include, in addition to the modified fan curves, contour lines for resistances, pressures, and air powers. Procedures for drawing the diagram are discussed and illustrated with an example of the ventilation system.

Jan 1, 1986

By Donald V. Currie

"The Alberta and Northwest Chamber of Mines was founded in Edmonton, Alberta in 1935. The organization represented private sector mining explorers and developers in the province and north west Canada. The Chamber aided and abetted the establishment of the two territorial mining associations. Because of corporate human resource department creation by north of sixty mine operators, the Chamber refocused on Alberta and broadened its perspective to include activities beyond mining. In 1977 the name changed to the Alberta Chamber of resources. The slogan (in more modern terms vision, mandate, goal, etc) remains as Orderly Development of Canada's Resources.The sixty-three year reputation of the Chamber, built on volunteer rather than staff contribution, is the principal reason for any success. The key has truly been the reputation, not an image, as all activities have been solution oriented.This presentation provides insight into the structure and methodology applied by the organization, and reviews some of the successes and failures during the period 1985 to present. Examples discussed include:• Canada-Alberta Partnership on Minerals 1992-1995• Regional Upgrader Business Plan• National Oil Sands Task Force• Lakeland and Waterways Railway"

Jan 1, 1998

By Nathaniel Arbiter

THE separation of minerals by flotation can be regarded as a rate process, with the extraction of any one mineral determined by its flotation rate, and the grade of concentrate by the relative rates for all the minerals. So regarded, the significant variables for the process are those that control the rates. These variables are of two types, the first describing the ore and its physical and chemical treatment prior to flotation and the second characterizing the separation process in the cells. This paper will examine the variation in rates for a group of separations, will show that a simple rate law appears to govern, and will consider the relation of the control variables to the rates. The use of rate constants for evaluation of performance and efficiency will be discussed. Flotation involves the selective levitation of mineral and its transfer from cell to launder. The flotation rate is the rate of this transfer. It may be defined by the slope of a recovery-time curve for any cell in a bank, or at any time in batch operation. The objective in flotation rate study is an equation expressing the rate in terms of some measurable property of the pulp. This can be either the concentration of floatable mineral in weight per unit volume1,2 or a relative concentration, which will be a function of the recovery." A rate equation for an actual flotation pulp will contain at least two constants, both to be determined from the data. One of these, the initial concentration or proportion of floatable mineral, is not necessarily equal to the feed assay because of nonfloatable oversize or locked particles." The other, a rate constant, is a measure of proportionality between the rate and the pulp property on which the rate depends. The value of the rate constant will be determined by the values of all variables which control the process and will be changed by significant changes in any of them. It is, therefore, a direct measure of performance. Where recovery or grade change continuously with flotation time, the rate constant will be independent of time and will characterize the entire course of the separation. Development of Rate Equations Rate equations can be developed either by analysis of the mechanism of the process or by direct fitting of equations to recovery-time data. Sutherland's attempt by the first method' suggests that the effect of particle size variation on the rate complicates the derivation of a simple equation applicable to an ore pulp. A further problem with an ore is the concentrate grade requirement, which usually involves a variable rate of froth removal. Thus the final rate for any cell may depend on the froth character and froth height, as well as on the pulp composition. This does not imply that each cell cannot reach a steady state2 in which the rate will depend ultimately on pulp composition. The second method is the fitting of rate equations consistent with the necessary boundary conditions* to experimental recovery-time curves. On the assumption that under constant operating conditions the flotation rate is proportional to the actual or relative concentration of floatable mineral in the pulp, a generalized rate equation may be expressed as follows: Rate = Kcn [I] where K is the rate constant, c is some measure of the quantity of floatable mineral in the pulp at time t, and n is a positive number. In previous rate studies, the value of n has been taken as 1, either by direct assumption," or as a result of the hypothesis that bubble-particle collision is rate determining.' A first order equation results, which after integration in terms of cumulative recovery R, leads to Loge A/A-R = Kt [2] The quantity A is the maximum possible recovery with prolonged time under the conditions used. No conclusive proof for the validity of this equation in flotation has been advanced. The evidence cited in its support consists entirely in the demonstration that it appears to apply to a limited number of recovery-time curves."' It will be shown subsequently that this procedure is not sufficient to establish the order of a flotation rate equation. The possibility that the equation may be of higher order therefore requires examination. If, in particular, the exponent in eq 1 is assumed to be 2, then after integration there results R = A2Kt/1 + AKt [3] with K again a rate constant and A the maximum proportion of recoverable mineral. Eq 3 may be

Jan 1, 1952

By M Slight, H Lacy

In recent times, with the global mining industry’s focus on sustainable development there has been a significant focus on mine closure and rehabilitation performance and reporting through the development of the International Council on Mining Metals (ICMM), the Global Reporting Initiative and the Equator Principles. In addition, financial reporting obligations under International Financial Reporting Standards and the Sarbanes Oxley Act (2002) have also led to better understanding and improvements with industry closure performance, liability management and reporting.Under these sustainable development principles and financial reporting obligations, mining companies are required to consider mine closure planning and associated cost estimates across all life cycle phases of the mine. Internal processes have been developed within mining companies to better understand their closure liabilities and obligations and likely costs and cost estimating processes are generally developed for long-term life-of-mine (asset) planning and budgeting, financial reporting for corporate balance sheet provisioning purposes, and regulator reporting for environmental bonding and financial assurances.These days mining companies need to plan for, prepare and actually mine for closure right from the start of a project. This means that their closure and rehabilitation liabilities throughout each stage of the mine life cycle phases must be understood, planned for, managed and controlled.So how is the industry performing? Understanding of closure liabilities is improving and reflected in liability cost estimations that are recognising the likely issues to be faced at closure, but there is a way to go to ensure that the industry doesn’t add to the increasing legacy liabilities being passed onto the wider community.CITATION:Slight, M and Lacy, H, 2016. Closure liabilities – where are we at?, in Proceedings Life-of-Mine 2016 Conference , pp 28–30 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jun 28, 2016

Geomechanics is one of the more specialised aspects of site supervision on a major tunnell- ing project. The controlled deformation of a rock mass as a result of tunnelling and the knowledge of loading of temporary and permanent underground supports are important for safe, economic construction. These basic parameters depend on the construction method and sequence and the geological conditions through which a tunnel is driven. Thus geomechanical monitoring during the construction phase provides feedback to a design team and allows any revisions to a design to cater for local conditions not revealed by earlier investigations. Detailed geological mapping is an integral part of geomechanics in the construction phase. It serves as a monitor on pre construction predictions and also forms part of the as- constructed record. If conventional excavation-techniques are adopted, geomechanics can provide a service of blast' vibration monitoring of surface structures in urban areas.

Jan 1, 1976

By Roberts C

The satisfactory testing and characterisation of mineralisation amenable to heap leaching, is of prime importance to successful operation of a project. This paper outlines a methodology for assessing material suitability. A general model is used for classing material types for suitability for treatment and for economic analysis. The four levels of these are overburden, oxide, transitional and unoxidised materials. During exploration, reverse circulation (RC) drilling can be used effectively to define these zones by a combination of logging, analysis and provision of cuttings for column leach and bottle roll trials. RC cuttings can he used effectively for column leach trials, when calibrated against conventional processing-sized samples, obtained from surface. Tbis allows metallurgical testing to depth and definition of transitional ore types and the base of oxidation, accurately and economically with an acceptable density of samples. The accurate prediction of base of oxidation and variations in recovery with depth and ore types can be used to develop 'economic' pit designs with zones of variable recovery. Petrological studies of leaching results and examination of mineralisation types carried out on concentrates, provide information on gold distribution and physical and chemical constraints. The examination of concentrates can be particularly useful for types of mineralisation when overall gold content is frequently at or below one pan per million. Explanation of anomalous recovery of gold grains in dense goethite and solution-robbing by carbonaceous material can be identified by use of petrological and scanning electron microscope. An understanding of the role of the host rock in leaching characteristics can also he provided by petrology where siliceous or clayey materials can require significantly different treatment.

Jan 1, 1994

Develop a training program to help mine workers effectively fight small fires in underground Goal mines. Training would enable miners to make rapid judgments on whether to attempt extinguishment, and how best to use the firefighting equipment on hand. Approach Fire reports were analyzed to define and delineate physical and behavioral variables which affect firefighting activities, and to determine effective procedures for extinguishing small fires. A course was then designed to train miners in such procedures. Finally, the course was reviewed by industry experts and administered to a group of miners to determine needed revisions and to validate the course. How It Works Analysis of fire data showed that six items should be emphasized in teaching proper fire response: 1. Alertness to fire potential. 2. Immediate power cutoff. 3. Internal, external communication. 4. Teamwork in fighting fires. 5. Role of ventilation and position of men inby the fresh air side. 6. Effective use of fire suppressant materials.

Jan 1, 1983

By P. Bardzil, J. Gurland

An experimental study of the variation of transverse-rupture strength with composition Anexperimentaland grain studysize has shown that the strength reaches a maximum for values of the mean free path between carbide particles of 0.3 to 0.6 microns. The fracture oforiginates in and proceeds through the carbide grains mainly. Impact strength and hardness also were recorded. MOST of the physical properties of sintered carbides vary linearly with composition. The transverse-rupture strength, however, shows a unique behavior. As the amount of binder metal is varied from 6 to 25 pct by weight, the strength at first increases; then, between 15 and 20 pct Co, it reaches a maximum of nearly 400,000 psi, and finally decreases with further additions of binder metal. This behavior of the transverse-rupture strength has been reported, among others, by Englel and Sandford and Trent.' The significance of these observations has not been discussed in the literature. That it may be of more than specific importance is indicated by the very similar variation of strength with composition encountered in other systems sintered in the presence of a liquid phase, such as Tic-Ni3 and Fe-Cu.' Experimental Details All compacts were prepared and sintered according to normal industrial practice. The average diameter of WC grains and the mean free path between grains were measured on metallographically prepared samples by a method of linear and planar analysis sing the relations where d is the average diameter of dispersed grains; Nl is the number of noncontiguous grains intersected on a metallographic plane by a line of unit length; N, is the number of noncontiguous grains per unit area; P is the mean free path between grains of dispersed phase; and f is the volume fraction of dispersed phase. Approximately 1000 grains were counted on each sample. For each composition d2 was plotted against P, the resulting straight lines serving as a check on the measurements. The distribution curves of the WC powders of different average diameters were homologous, and no attempt was made to influence the grain size by blending powders, adjusting the sintering conditions, or otherwise altering the particle size distribution. Densities were measured by differential weighings in air and water. The degree of densification did not vary consistently with either composition or grain size. The density is influenced by slight amounts of impurities, specifically by 0.1 to 0.2 pct Fe which enters the powders during ball milling. As an illus- -tration of the experimental variations, a number of measured densities are listed in Table I. They are expressed in percentage of theoretical density, as calculated from the published X-ray densities of WC and Co.' For the purpose of determining the transverse-rupture strength, rectangular test specimens (3/16x 3/8x3/4 in.) were broken by loading at the center of a 9/16 in. span. The average strength of five or more samples is reported for each composition and grain size. The compacts were ground on two parallel surfaces only. The load was applied at an average rate of 6,800 psi per sec. Since the elongation after fracture of the alloys is very small, it was assumed that the compacts deform elastically to failure and the fracture stress was calculated by the conventional beam formula. The data for one alloy are presented in Table II as an example of the results and scattering ranges encountered. The precision of the test, as measured by the average difference between duplicates, is of the order of 15,000 psi. The results are strictly comparable only to compacts prepared and tested in the manner described and of similar chemical composition and grain size characteristics. Unnotched Charpy specimens were used for impact testing. Each point represents the average of 3 to 20 samples, the larger number being used in an attempt to determine the influence of grain size. Considerable scatter was encountered, the range from lowest to highest value often amounting to 30 pct of the impact strength. The hardness is reported as a Ra reading, using a 60 kg load with diamond brale indenter. Compositions are given in weight percent.

Jan 1, 1956

By A. Rohkohl, R. Piillenberg

The QSL plant at "BERZELIUS" Stolberg GmbH in Stolberg, Germany was commissioned in 1990, introducing a new era of lead smelting in the more than 150-year-old history of the lead smelter. The lead smelter in Stolberg has changed its appearance several times during its existence. Therefore, at many locations on the site, old and obsolete buildings and equipment parts can still be seen. They are often located side by side with new modern constructions like the QSL-plant and the mercury removal plant, and reflect the specific contrast between tradition and modern technology. After a brief description of the development of the smelter and its decision to implement the current novel plant, the most recent operating results are reported. Following some modifications to the process and equipment, which had become necessary along with the implementation of the new technology, the plant is in operation today at approximately 30% above its design capacity. These achieved production levels are not restricted by the QSL-reactor but by precedent and subsequent available equipment. The QSL-plant entirely complies with the demands of modern, energy-saving, ecologically compatible lead production technology. Stringent environmental standards are maintained on a continuing basis. The demonstrated viability and flexibility of the overall process permits the operation to adapt quickly to the prevailing economical situation worldwide.

Jan 1, 2000

By J. Menashi, D. A. Douglas, A. S. Rappas

Aqueous solutions of Na2Cr04 are reduced with CO to produce hydrous Cr2O3 and NaHCO3/Na2CO3. CH3OH, HCOO- and HCHO in the presence of CO2 also reduce Cr(VI) and yield similar products. It is shown that the rate of Cr(VI) reduction can be represented by the expression -d [Cr(VI) ]/dt = k[Cr(VI)]0.5[R], where [R] is the aqueous phase concentration of CH3OH, HCOO- or CO. With these three reductants, the activation energies for the reduction processes are comparable and are of the order of 100 kJ/mol (43,000 Btu per lb mol). Rapid reduction rates are attained at temperatures in excess of 220°C (428°F). With these three reductants, a green acid-insoluble readily filterable hydrous Cr203, is formed. With HCHO, significant reduction of Cr(VI) occurs at about 80° to 100° C (176° to 212° F). The product is an acid-soluble violet modification of hydrous Cr203. Solutions of Na2CrO4 contaminated with Mo(VI) and W(VI) can be reduced to yield a Cr2O3 product with significantly reduced contaminant levels.

Jan 1, 1986

By Maria I. De Rosa

This report analyzes mine fires for all U.S. underground and surface coal mining categories by state and 2-year time periods during 1990-1999. Risk rate values are derived, and ignition source, methods of fire detection and suppression, and other variables are examined. The data were derived from Mine Safety and Health Administration (MSHA) mine fire accident publications and verbal communications with mine personnel. The analysis will provide the National Institute for Occupational Safety and Health, MSHA, and the mining industry with a better understanding of the causes and hazards associated with mine fires and will form a basis for future fire research programs.

Jan 1, 2004

By Maria I. De Rosa

This report analyzes mobile equipment fires for all U.S. surface and underground coal and metal/nonmetal mining categories by state and 2 year time periods during 1990-1999. Risk rate values are derived, and ignition source, methods of fire detection and suppression, and other variables are examined. The data were derived from MSHA mine fire accident publications and verbal communications with mine personnel. The analyses will provide the National Institute for Occupational Safety and Health (NIOSH), the Mine Safety and Health Administration (MSHA), and the mining industry with a better understanding of the hazards associated with mobile equipment fires and will create a basis for future fire research programs.

Jan 1, 2004