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By C. M. Frost

Two Federal Bureau of Mines recycle hydrogenation experiments to prepare catalytic cracking feed stock were made at 3,000 pounds pressure with crude shale oil retorted from Green River (Colo.) shale in the gas-combustion retort. The hydrogenated product from the first experiment, made at 784° F., was used for investigating the effects of nitrogen content on catalytic cracking yields and for determining the quality of the catalytically cracked gasoline. Hydrogenated product containing 0.14 percent or more of nitrogen produced less gasoline when cracked in a CAT "A" unit than was obtained from East Texas light gas oil cracked at the same conditions; product containing 0.10 percent or less nitrogen produced a quantity of cracked gasoline equal to that obtained from the East Texas light gas oil. The catalytically cracked gasoline had research octane numbers calculated to be approximately 95 clear and 103 with 3 ml. of tetraethyl lead. The principal product from the second experiment, made at 828° F., was a low nitrogen content gas oil which was used for investigating the yields of cracked products obtained when it was catalytically cracked to different degrees of conversion. Yields of cracked products, when plotted as functions of conversion, were essentially the same, within the experimental range of the data, as published yields from catalytic cracking of East Texas heavy gas oil; however, yields from cracking the shale-oil product did not display the sensitivity to change of cracking temperature that has been found for East Texas gas oil.

Jan 1, 1960

By Patrick O. Shires, Harry W. Schnabel

With stable building sites becoming scarce in the greater San Francisco Bay Area, the new Summit Senior Care Facility is being built into the side of an unstable hillside adjacent to the San Ramon Regional Medical Center in San Ramon, California. This hillside has had a long history of instability and the site of the new Senior Care Facility required excavation into both a historic old landslide and a more recent active landslide. After a thorough geotechnical study, it was concluded that the best way to build the new facility would be to construct a tied-back retaining wall in the area of the old landslide, since it extended off-site onto two adjacent properties, and remove the active landslide and replace it with compacted fill before cutting into its toe area with an additional tied-back retaining wall. The design was further complicated by the proximity of the site to several active faults. In the area of the old landslide, the combination of an ascending slope behind the wall, landslide forces and seismic forces resulted in total design pressures between 365 to 4,575 PSF for a wall with a maximum height of 30 feet. The wall for the old landslide was constructed by first drilling and placing steel soldier piles in concrete. The tip of the soldier piles extended a minimum of 12 feet below the landslide plane that was up to 36 feet below the bottom of the wall. Permanent double corrosion protected tiebacks were then installed through the soldier beams and anchored below the slide plane. A shotcrete facing was then installed on the face of the wall. BACKGROUND The site of the Summit Senior Care Facility is located on the southwest flank of Mount Diablo adjacent to San Ramon Valley which is characterized by gently rolling hills. The San Ramon Valley Regional Medical Center, which opened in 1990, is located to the north and an existing church is located to the southwest. There are also private residences located to the southeast. The site is shown in Figure 1. Numerous faults run close to the site, the most significant of which are the Calaveras and Pleasanton faults. The site has also had a long history of slope instability and has been the subject of numerous investigations. Studies conducted in 1979 and 1984 concluded that there was a landslide in the area and recommended that a buttress shear key be constructed between the subject site and the existing church for a sewer main as well as removal and replacement of the head area of the old landslide to stabilize the hospital site. While two previous geotechnical studies in 2008 and 2016 identified slope instability, they did not recognize the genesis and limits of the old landslide on the western portion of the site or the limits of the active landslide on the eastern portion of the site.

Jan 1, 2018

By J. E. Conley

Available statistics show that the demands of the American chemical industry for sodium sulphate have been increasing slightly in recent years. The supply from domestic sources, particularly In the form of byproduct salt cake from the acid manufacturers, has been tending to decrease due to the growing manufacture of synthetic acid. Both hydrochloric and nitric acids are being synthesized from their elements. The natural result has been that a smaller amount of salt cake is available. Simultaneously, the expansion of the Kraft paper industry, especially in the South, has brought about greater demand for sodium sulphate in that section. This dean is being met by domestic byproduct salt cake, by imported German sodium sulphate made from potash waste liquors, and by favorable situated domestic deposits of Glauber salts and tile anhydrous salt, thenardite. No shortage of natural sodium sulphate exists in the United States, but usually such deposits occur in semiarid regions far removed from transportation facilities and from markets. Moreover, the major portion of the natural deposits is Glauber salt or mirabilite (Na2SO4 ? 10H20), which must be dried or dehydrated in order to meet consumer requirements. The water of hydration represents, roughly, 55 percent of tae total weight of the crude salts and therefore has a very important influence on transportation costs. In marry instances the cost of getting, even the dehydrated product to market is the deciding economic factor. Therefore, the recovery oil production of anhydrous sodium sulphate from plant-.waste liquors or from natural brines of suitable composition might be economically feasible. The U.S. Bureau of Mines, at its nonmetallic Minerals Experiment Station, New Brunswick, N. J., has, for a number of rears, been investigating the commercial possibilities of treating the complex saline mineral polyhalite (K2SO4?NgSO4?2CaSO4?2H20) for the recovery of potash and magnesia. Certain proposed processes (1, 2, 3, 4)4/ yield waste liquors that contain the bulk of the magnesium and sulphate originally combined as magnesium sulphate in the polyhalite molecule. Sodium chloride In limited concentrations is also present, as extensive beds of salt occur in strata overlying the polyhalite deposits. A typical waste liquor would contain:

Jan 1, 1936

By D. R. Flinn

A newly developed chemical conditioning technique, which greatly simplifies the preparation of plating baths for the electrodeposition of titanium diboride (TiB2) coatings, is described in this report. The new plating technique was used to prepare samples of titanium diboride (TiB2) coatings on three types of substrate materials. These samples were then evaluated in both low- and high-speed wear-test programs to determine the wear resistance, microhardness, and adhesion of the coatings. In general, it was found that the wear resistance of the coatings is independent of substrate. Scanning electron micrographs have shown that the coating wear surfaces are very smooth, suggesting slow and continuous removal of the coating during the wear test (that is, adhesive wear). Adhesion between the coating and all substrates was excellent. Microhardness results show that the TiB2 coating is harder than alumina, with a hardness value exceeding 5,000 kg/mm2 measured in one test. The results of the wear tests show that TiB2 coatings have relatively poor wear resistance compared with alumina in low-speed unlubricated sliding environments, but exhibit wear properties comparable with alumina in high-speed unlubricated sliding environments.

Jan 1, 1981

Adolph Greiner, Seraing, Belgium:—I have nothing special to add to Professor Hubert's paper except to say that there are some little things that it would be well to have corrected when the paper comes to be published. In dealing with the thermal efficiency of the engine, you will find that the 29.84 per cent. was a very high one. Professor Hubert has forgotten those engines built under the Cockerill type, but he has referred to them in Appendix 11. At our works at Cockerill we have built 63 engines, giving 63,000 h.p., and the other companies who have received licenses have built 113 engines, making 103,000 h.p., and aggregating 176 engines and 166,000 h.p. Eight years ago I had the pleasure of giving to the Institute the results obtained up to that time. Since then a good many engines have been constructed. In 1898 I thought a blast-furnace producing 100 tons of pig iron would allow 3,000 h.p. Professor Witz and Professor Hubert show that with the same production of pig the new engines take 3,800 h.p. out of the gas. At present at Cockerill we make 700 to 800 tons of pig iron per day, and we hope to have 26,000 h.p. in a few years. At present we have only half of that in gas-engines, but we hope to have in five or six years all the gas out of these furnaces to the number of 25,000 or 26,000 h.p. Tom WEstGarth, Middlesbrough, England :—My contribution is not a paper in the ordinary sense of the word, because I am sure you will agree with me that what I have written is only supplementary to the other two papers. The notes are schedules of the larger-size gas-engines built by British engine-makers, of 500 h.p. and upwards. If you look at the schedules you will find that in England gas-engines have become quite ordinary motors for a good many purposes. It was at first thought that gas-engines were troublesome, and ill-

Jan 1, 1907

By Lowell B. Moon

Concern over possible wartime shortages finally resulted in passage of the Strategic Materials Act in 1939. As authorized by one section of this legislation, the Bureau of Mines proceeded to investigate deposits of seven strategic minerals with the objective of developing tonnages of low-grade material that could be mined in an emergency. During the war, the size of the program and the number of strategic minerals were increased, and the objective was the more immediate one of aiding production. Since the war, the size of the program has been reduced, but the number of minerals on the strategic list continues to be large. The objective has returned to that of 1939. In the course of the program, more than 10,000 examinations were made and about 1,300 projects were run on deposits of 33 different commodities. A considerable contribution to war production was made in six of the commodities investigated, and a minor contribution was made in twelve others. Substantial reserves have been indicated in 19 minerals. Private interest is currently active in some of the deposits developed in 14 commodities.

Jan 1, 1950

By J. H. Nixon

A three phase program evaluated commercial proximity warning devices, developed and designed a microprocessor-based electrostatic field measurement instrument, and utilized this instrument to investigate the electro-static fields about power lines. The Phase I program consisted of test and evaluation of these commercially available proximity devices. The evaluation results were reported in the Phase I report entitled ?Evaluation of Proximity Warning Devices? dated 22 February 1980. The Phase II program resulted in the design and development of a microprocessor-based Distributed Sensor A.C. Electrometer which measures the electrostatic field present at 17 discrete locations along a crane boom. Operator control of the measurement system allows simultaneous electric field measurements from 17 probes, print out of the electric fields measured, and data archiving on magnetic tape for post measurement analysis. Under the Phase III program, electrostatic fields around a crane boom were measured by the instrument at 17 high voltage power lines of various voltages and geometries. The electric field data was processed and plotted versus boom distance from the power line. Analysis of the electric field data indicate that the distances at which a single sensor alarm will activate, vary by a factor of 3 to 1. This is due primarily to variations in boom orientation. The results also indicate that in the case of multiple power lines, a single electrostatic field sensor cannot reliably be used to determine the distance from a power line.

Jan 1, 1982

In this paper, the scientific bases of creation of simulation modelling systems of excavator-truck-conveyor complex work are represented. During the simulation modelling process of big mining and transport systems work the strict and full account of an order and sequence of all operations of simulated process is carried out. Step-by-step fixing of mining and transport system elements condition - excavators in loading and unloading points, trucks, road section, unloading points in storage bin, crushers and conveyors is conducted. Work and idle time of system elements are considered. During modelling process the information characterising system work as a whole is collected. It allows us to establish qualitative and quantitative influence of each system element on the final results of its functioning and provides to estimate rationality of a particular organisation variant of mining and transport equipment interaction from technological positions. Simulation results are: economic and technological indicators of mining and transport complex functioning of the period for each subsystem, as well as on the road, the points of loading, unloading and reloading.

Dec 6, 2010

By Charles H. Jacoby

The solution mining of evaporites has a history of approximately 5,000 years. The insitu leaching of metalliferous ore will have many of the same characteristic problems which have confronted industry for years in the production of evaporite minerals. Basically we will be converting the less soluble forms of valuable metals into their more soluble salts and producing these in much the same manner as, for example, sodium chloride. There are a number of problems which we are faced with that are more complex and complicated and, therefore, will require a higher degree of sophistication than previously employed. One of our most important undertakings will be the clearcut definition of the problems involved. While a great deal of expertise can be drawn from the solution mining of evaporites and the oil industry, problems peculiar to the hydrometallurgical field will need to be solved. One of these is the introduction of permeability into an impermeable rock so as to expose the sought after values of metals which by volume are infinitesimal when compared with sodium chloride, potash or other type water soluble mineralization. After establishing this permeability which will be miniscule when compared to a solution cavity, there will be the maintenance of this permeability. In general, salt deposits are of a somewhat uniform chemical composition and thus their chemistry was relatively simple. Each metalliferous ore body is somewhat unique in its chemistry and will need to be treated accordingly.

Jan 1, 1974

By Z Terzic, M Schult, D Chu, S Macklin

The East West Link road tunnels are proposed to provide a connection between the CityLink toll road and the Eastern Freeway north of the Melbourne CBD. The alignment passes from Moonee Ponds valley beneath the Upfield Line railway cutting, Royal Park, the historic Melbourne Cemetery and beneath Alexander Parade rising to an eastern portal at Hoddle Street. The western (Royal Park) part of the alignment passes through the folded and faulted Silurian Melbourne Formation, which has been subjected to deep weathering since the Triassic.The Melbourne Formation in the Royal Park area is mainly characterised by interbedded sequences of siltstone and fine-grained sandstone. The beds are often graded and a clear boundary between the siltstone and fine-grained sandstone rock can be difficult to distinguish. Variation in lithology and the presence of structural geological features such as folds and faults have resulted in an irregular weathering profile within the Silurian rock; nonetheless the formation typically becomes less weathered with depth.Due to difficulties in obtaining reliable laboratory strength and stiffness relationships with weathering grade, in situ testing methods such as downhole shear wave velocity and high-quality pressuremeter testing are a useful aid to assessing appropriate geotechnical parameters for design.This paper presents an analysis of the variation in shear modulus of the Melbourne Formation, determined at small-strain (from downhole seismic data) and at ‘engineering scale’ strain (from pressuremeter tests) for extremely weathered (XW), highly weathered (HW) and moderately weathered (MW) rock. Estimates of small strain shear modulus (Go) obtained a range between 400 to 3400 MPa for these weathering grades. By comparison against the pressuremeter test data, reduction factors to be applied to these Go values to estimate shear moduli at engineering strain levels typically range between 0.10 and 0.35.The downhole geophysics undertaken in the Royal Park boreholes also suggests that there is an inversion in velocity between approximately 15 and 27?m depth below the top of the formation. This is thought to be related to the effects deep Plio-Pleistocene weathering, iron cementation of joints and increasing frequency of ‘non-healed’ joints in the transition from MW to slightly weathered (SW) rock.CITATION:Macklin, S, Schult, M, Terzic, Z and Chu, D, 2014. Strain-dependent stiffness of the weathered Melbourne Formation, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 179–188 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By Frederick L. Hoffman

These extracts are sufficient for the purpose of emphasizing the practical difficulties of averaging iron-mining conditions so as to make general vital statistics concerning iron miners useful Tor scientific. purposes. It is self-evident that conclusions based upon iron miners, so called, working largely above ground and employed chiefly in open-cut blasting ~perations or the management of steam shovels, etc., can not be made to apply to miners working continuously underground with an exposure of dust and other conditions quite similar to underground mining methods in the extraction of gold, silver, copper, lead, and other ores. The so-called "milling" process as practiced on the Mesabi Range may here be referred to, the same being explained in the report of the Immigration Commission to consist "in the sinking of a shaft on the edge of the ore body from which a tunnel is run in under the ore and connected with a vertical, funnel-shaped hole from under the surface, through which the ore is 'milled' down into the tramcars placed under the opening under the tunnel. After being loaded at the bottom of the funnelshaped hole, the cars are run out to the bottom 0.£ the shaft. where the ore is dumped into skids or elevators and raised to the ~urface and unloaded into the tipple, where it is loaded into thecal'S ready for shipment." It is properly pointed out that the so-called " milling" process employs some of the features of both the open-pit and underground methods of mining. For these and many other reasons it is self-evident that general statistics concerning iron mining are quite likely to be inconclusive and possibly seriously misleading. Aside from the foregoing the problem is seriously complicated by the extensive employment of foreign labor in the iron-mining ind ustries of the Lake Superior districts and of Negro labor in iron mining in Alabama. Within recent years, according to the report of the Immigration Commission, a considerable displacement has occurred in t~e quality of labor employed in iron mining, the displacement bemg referred to as "progressive," in that one race or group of races has entered the region and taken up the work offered in the lower occupations, the race or races already holdinz such positions having. moved up in the scale of occupation leaving the field to the newcomers. This statement is quite suggestive in that it indicates a comparatively short average trade life or trade exposure, quite at variance with the relatively long average ascer- MINES, QUARRIES, ORE REDUCTION, AND SMELTING. 377 tained for the iron mines of New <Tersey. It is said in the report of the Immigration Commission that- The Scandinavians and the other northern European races have given way to the Finns and Slovenians, and in the open-pit mines the Finns and Slovenians have given way to the south Italian, Montenegrins, Croatins, and other southern European races. In the underground mines the common labor and mining is chiefly done bv Finns and Slovenians because the races from the southern countries can not stand the heavy physical work required in this kind of mining. Here, too, is found the same upward movement, for formerly the English (Cornishmen) and Scandinavians' were in the lower occupations in the underground properties, At present the south Italians, Serbians, Montenegrins, and Croatians are performing the most menial work and are the races who are now at the foot of the scale of occupations. It is a matter of conjecture on the ranges as to who will push these races up or whether they will remain the commou laborers of the region. Inquiry was made into the prevalence of diseases OIl the ranges, but more with reference to outside sanitary conditions than to occupational exposure. The most common diseases on the ranges, however, were ascertained to be pulmonary tuberculosis and typhoid fever, and to a lesser extent smallpox and venereal diseases. With -cgard to pulmonary tuberculosis it is said that the disease is most Eevalent among the Finns and the Swedes, and is chiefly imported, I'here is no reference to a possible connection between disease occur- ~ence and occupational conditions, above or below ground, but there .s no evidence that this aspect of the iron-mining industry was made .he subject of a special investigation.

Jan 1, 1918

After considerable input from the mining industry, the Canadian Securities Administrators (CSA) finalised National Instrument 43-101: Standards of Disclosure for Mineral Projects. This Instrument, which became law across Canada on 1 February 2001, applies to all technical public disclosure on mineral projects and requires all technical disclosure to be based on the work of a æqualified personÆ (QP). While the QP is quite similar to the Competent Person in Australia there are important differences when it comes to all disclosure. This paper will summarise the main areas in which the Instrument introduces major changes to Canadian disclosure standards on mineral projects including the role and responsibility of the qualified person; the increased requirements to file technical reports; the incorporation by reference of the October 2000 CIM definitions of resources and reserves and additional rules governing written disclosure of scientific and technical information. In October 2001, eight months after the implementation of NI 43-101, the CSA compiled a list of frequently asked questions (FAQs) and CSA responses to assist mining industry participants and their advisors in understanding and applying NI-43-101. This document has been well received by industry. The CSA plans to update the FAQs when further guidance is requested. Two industry committees have been established to provide the CSA with technical advice on the application of NI 43-101. As recommended by the Ontario Securities Commission/Toronto Stock Exchange Mining Standards Task Force, the CSA has established an external industry advisory committee û the Mining Technical Advisory and Monitoring Committee (MTAMC) û to monitor the application of NI 43-101 and advise the CSA on industry and professional developments. The role of the CSA-Canadian Institute of Mining, Metallurgy and Petroleum (CIM) Working Committee on Reserves and Resources is to ensure that the future changes and updates to the CIM Standards can be efficiently and effectively incorporated in NI 43-101. During this first year, the Canadian securities regulators have seen an improvement in the quality of disclosure on mineral projects, which will increase investor confidence in the industry.

Jan 1, 2002

By Thomas E. Finch

Engineering mine design encompasses a range of situations, and each situation has its own range of detail and fineness. The most time consuming, and perhaps repetitive design situation involves evaluation of new or alternate mining methods. Many man years are consumed examing alternatives conjured up at all levels of the design team, from the number crunching engineer to the engineering manager. Many alternatives are intuitively disregarded, some are briefly evaluated and thrown out, and many others are started but not completed due to time constraints. All alternatives have similar input characteristics and evaluation procedures. In the design process, production requirements are known and equipment production capabilities are generated to determine the numbers and costs of an equipment type required to match a given situation. The end result is some comparative figure, typically cost per ton or yard upon which a decision is built. The similarity of input data and problem solving techniques lends design to computer solution. Computer aided equipment evaluation is not new to the mining industry. An existing and accepted technique is exemplified with the programs used by truck manufacturers. Given a haulage profile and production requirements, the number of anyone capacity, horsepower, tire size, gear ratio or similar characteristically identified truck can be determined. This information can be outputted in varying degrees of complexity and the results used with equally varying percentages of credibility by design or production engineers. Most engineers are willing to accept-the computer&apos;s effort with relief and a desire for belief. Although inherently more complex, the ultimate end of computer manipulation should be total mine design. This is an extremely large step in the evolution of mine design, and not many engineers, including the authors, believe the results would be directly applicable or necessarily correct. As with computer simulations of an operation, total computer design of mines requires such complex and lengthy input that each mine might be manually designed more quickly and cheaply. The existence of computer programs which initially evaluate a mining system or part of the system is upon us, however.

Jan 1, 1978

By Steve Colburn

The CRITERION Survey Systems utilize both theodolite mounted and hand held reflectorless distance meters. These are eye safe, easy-to-use, and specifically designed to endure the harsh environments characteristic to the mining, quarry and explosives industries. Survey data collected by the systems is digitally stored in a ruggedized data collector and then processed with a specialized, Windows-based, interactive software program which can be run on any standard PC.

Jan 1, 1997

By T. Adamcewicz

The province's lignite resources lie mainly in the south, extensions of the much larger deposits in Montana and North Dakota. Because of planned additional capacity, conventional steam power generation will probably remain as the dominant resource usage for many decades. Conversion of coal to other energy forms is receiving emphasis and in the future will compete with steam power generation in terms of quantities used.Economic deposits, minable by present-day technology, have been generally defined. Because a large percentage of the total lignite resource is in seams containing multiple partings, future extraction will become much more difficult and capital intensive.Increased public involvement will ensure that the impacts of future coal mining and usage operations are compatible with environmental and social objectives.

Jan 1, 1982

By G. G. Morgis

A reasonably clear and broad definition of occupational disease as originated by the Supreme Court of Ohio is: "A disease contracted in the usual and ordinary course of events which from the common experience of humanity is known to be incident to a particular employment." An ailment does not become an occupational disease simply because it is contracted on the employer&apos;s premises. It must be one that is commonly regarded as natural to, inherent in, and concomitant of the work in question. The important distinction between accidental-traumatic injuries and occupational-disease injuries is that accidents occur at specific times, ordinarily are discovered readily, and usually leave no question as to the particular employer it whose development the accident occurred. On the other hand, occupational diseases may develop slowly, unknown to the employer and employee until disability occurs, and the injuries sustained are continuing disabilities over an extended period of time and may be incurred while the employee is working for one of several employers.

Jan 1, 1952

The additional information that Clarke and Taylor (1982) provide about the important but poorly documented Ardlethan deposit is, of course, very welcome. However their contention that structural considerations, in conjunction with petrology, alter the interpretation of the mineralogical and geochemical data presented previously (Scott, 1981) is not accompanied by adequate supporting evidence. Indeed characteristics of the orebodies studied invalidate their arguments.Heterogeneity between matrix and fragments is not a problem in the South Cherry and Ardwest orebodies because most samples are comprised entirely of interlocking hydrothermal assemblages with a fabric and mineralogy that is uniform through both former breccia fragments and matrix. In hand specimen, the rock superficially resembles altered granite and, as indicated by Clarke and Taylor (1982), a brecciated texture is difficult to discern. In thin section, relict brecciated textures can be observed as localized changes in the grainsize or in the distribution of minerals that outline former breccia fragments (P. J. Eadington, 1982, personal communication).Because of the intense brecciation and comminution of rocks (fragments &lt; 10 mm are usual) in the South Cherry and Ardwest breccia bodies, hydrothermal recrystallization was complete, resulting in homogenization of fragments and matrix. Furthermore, the amount of sample analysed (-100 g for drill core and 2-3 kg for hand specimens) is sufficiently large to be representative of both former breccia fragments and matrix. The Carpathia and Stackpool orebodies, with their abundance of sedimentary fragments, have alteration superimposed on a heterogeneous fabric, and were not studied. Thus the problems of differentiating between fragments and matrix (Clarke and Taylor, 1982) are irrelevant to the particular orebodies described in my paper.Within the alteration halo, which is several hundred metres wide (Paterson, 1976), the very uniformity of the alteration assemblages implies that subsequent, postmineralization brecciation is of only minor significance.Indeed tourmaline pipes in the Ardwest pit are less than several metres across (Clarke, 1979) and produce minimal alteration in the surrounding rocks. Therefore the interpretation of the mineralogical zonation is not compromised by the recognition of several periods of brecciation.

Jan 1, 1982

By L. E. Veki, S. M. Luukkanen, J. P. Karvonen, J. O. Leppinen

Today there is a consensus that xanthate adsorption on sulfide minerals is primarily controlled by redox reactions occurring at specific potentials on these semi-conductive minerals. Consequently, it is possible to control xanthate adsorption by controlling electrochemical conditions in the system by using oxidizing and reducing agents. The scope of this study was to investigate the possibilities to increase the selectivity of Cu-Fe-Zn ore flotation by applying electrochemical control in the conditioning of the flotation feed. In this work, mild steel grinding in a nitrogen atmosphere was used as the basis to provide a negative starting potential and minimize the amount of oxidation products on sulfide mineral surfaces. To study how different potential levels affect flotation results, a controlled conditioning procedure was utilized maintaining potential at a desired level by titrating the pulp with air. Xanthate adsorption kinetics during conditioning was examined by taking pulp samples for spectrophotometric analysis and laboratory flotation tests were conducted for samples that underwent the controlled conditioning procedure in the potential range of -200mV to +200mV vs. SHE. A clear correlation was detected between chalcopyrite recovery and the potential during controlled conditioning indicating that there was a constant increase in chalcopyrite recovery when the potential was shifted to more anodic values. It is possible that utilizing potential control in the conditioning stage, a smelter grade copper concentrate can be achieved directly in rougher flotation without cleaning stages. Conditioning in favorable conditions had significant positive effects on flotation selectivity of chalcopyrite. The improvement in copper concentrate grade being predominantly caused by the depression of pyrite. By applying the controlled conditioning procedure pyrite recovery in rougher flotation was reduced even low as under 1%, while in the tests without controlled conditioning, pyrite recovery varied between 7.5 – 65.7%. The result of this work indicate that affecting collector adsorption by electrochemical control in the conditioning stage can provide significant improvement in sulfide mineral flotation and industrial applications could lead to decreased chemical consumption, reduced equipment and maintenance costs.

Jan 1, 2018

By Daniel W. H. Su

The importance of incorporating fundamental principles of rock material response and failure mechanics into a pillar strength design model has been demonstrated. To accurately assess pillar strength, a model should account not only for the characteristics of the coal, but also for those of the surrounding strata. The interactions between the pillar and the surrounding roof and floor dictate ultimate pillar strength. Confinement, or the lack thereof, provided by roof and floor frictional end-constraint is one of the most significant factors in the strength of very wide pillars. The best conditions for end-constraint occur with ideally strong roof and floor. In this paper, it will be shown that weak roof and floor may decrease the ultimate pillar strength by as much as 30% compared to ideal conditions. Field observations confirm this pillar strength reduction in the presence of weak roof and floor. Furthermore, rock partings within the coal have a variable effect on pillar strength, depending on the parting strength. A competent shale parting within the coal reduces the effective pillar height, thus increasing the ultimate pillar strength; a weak claystone parting slightly decreases the strength. Imposed load distribution also has a significant effect on pillar strength, such that asymmetric pillar loading, similar to that observed in pillars adjacent to high extraction mining, reduces the ultimate pillar strength below that of equivalent pillars subject to uniform load distributions.

Jan 1, 1997

By J. Visman

"The Compound Water Cyclone is a concentrator for the wet processing, in bulk, of finely divided materials such as slack coal, fine ores and mineral sands. It was originally developed by the Fuels and Mining Practice Division of the Mines Branch, Department of Mmes and Technical Surveys, Ottawa, for the cleaning of friable slack coals and slurries.Since its introduction in the coal industry in 1962, its application to other materials has also been studied, with special emphasis on simplicity of operation and low over-all cost per ton of finished product .In this paper, a description is given of commercial two-stage units presently available for the processing of granular materials, including wastes a1:1d other low-grade products. A pneumatic control system is used for operating the cyclone under back pressure .and for automatic cut-point adjustment. An account is given of results obtained on coal mineral sands and ores in the Wes tern Regional Laboratory of the Department of Mines and Technical Surveys. Results of several industrial applications are discussed."

Jan 1, 1966