Search Documents

By L. A. Roe

Magnetic separation occupies an attractive position in the field of ore beneficiation. It is a simple yet effective method, used for some 150 years and steadily growing more important. This type of beneficiation orginated in 1792, when William Fullarton was issued a British patent covering the separation of iron ore by magnetic attraction. What is magnetism, and why are some materials capable of being magnetized and others not? The study involves many unknowns, and even a partial answer to these questions would be a dissertation in solid state physics and perhaps other fields of science. But the last two decades have revealed basic facts as to why certain materials are magnetic and what happens to them when they are magnetized.

Jan 12, 1958

By Prakash C. Kapur

Many balling and gradation system6 generate self- similar size distributions of the agglomerates. Inspection of the experimental data shows that this is also true of the steady state distributions resulting from the granulation of coarse, partially wet powders, for example, the fertilizer feeds. This result is exploited in the derivations of a number of simple and useful relationships that are pertinent to the analysis of these agglomeration systems. The bonding liquid demand of the granulating charge is a third order polynomial function of the dimensionless ratio of feed particle size to median granule diameter in the weight-fraction distribution. The median size, in turn, is the scale factor or characteristic size parameter in the similarity distribution. The granule size distribution, therefore, is completely specified by the liquid content and the similarity function, and so are the process efficiency and the ungranulated component In the product at steady state.

Jan 1, 1977

By Henry M. Howe

The death of Sir Lowthian Bell removes almost the last of the group of heroic leaders who made their age and ours the Age of Steel—a group which his luster and the luster of his peers, Bessemer, Siemens and Tunner, made one of the most brilliant, perhaps even the most brilliant, in the annals of induetry. Born on February 15th, 1816, in Newcastle-on-Tyne, he was the eldest son of Thomas Bell, an alderman of Newcastle, and of his wife Catherine Lowthian of Newbiggin, near Carlisle, in Cumberland, and was christened Isaac Lowthian, the name of his maternal grandfather. His father was born about 1788, and came in 1808 from Newbiggin to Newcastle, where he entered the office of the Cumbrian firm of Losh & Company, manufacturers of alkali and wrought-iron, at the Walker Iron and Alkali Works, at Walker, near Newcastle. Young Isaac Lowthian Bell was educated at Dr. Bruce's school in Newcastle, whence he went to Germany and Denmark, learning there German and Danish. On his return he studied at Edinburgh University, and then at the Sorbonne in Paris. As a student he already showed the remarkable character and application which later gained him such distinction. After studying the manufacture of alkali near Marseilles, he returned, and when about twenty years old (A.D. 1836) was employed in his father's firm, then called Losh, Wilson, & Bell. After spending a year in their Newcastle offices, and after visiting the important iron-making districts of France, Germany, Poland, and Austria, he took charge of their rolling-mills at. Walker, and profited so well by his opportunities, and especially by the teachings of his father and of Mr. John Vaughan (later one of the founders of the great firm of Bolckow, Vaughan & Co.), that he was made manager of the Walker works in or about

Jan 1, 1906

By John T. Dickman, Ralph E. O’Dette

Chemical Abstracts Service (CAS) is in the process of evolving a computer-based information system which will process all of the material selected for abstracting in the area of chemistry and chemical engineering and its related fields such as the earth sciences and technologies. This system is already operational to some extent and is expected to be fully utilized by 1971. The objective of CAS is to make chemical and related information more readily available, more usable and more used. Chemical Abstracts handle some 5000 abstracts weekly from 13, 000 journals and patents from 25 nations. These cover all of the 80 CA subject sections which relate to chemistry and also extend into areas of interest to geologists, mineralogists, and mining engineers. In this way, CAS fulfills its objective of complete coverage of its major fields, informative abstracting, and indexing to maximum specificity. The concept of a computer-based information system is that of a single machine-language data base into which the results of intellectual analysis of the literature are entered and from which computer programs produce a variety of publications and services applicable to the needs of a wide range of users.

Jan 1, 1969

By Keith Sutherland

AEROFLOAT 25 is a complex mixture of free cresylic acid with aryl substituted dithiophosphoric acids, sulphides, disulphides, etc. Its complete composition has not been published by the makers or patentees. It is prepared1 by the reaction between phosphorus pentasulphide and carefully selected cresylic acid. We have been informed that this acid contains no phenol and very little cresol, and that it is rich in the higher alkyl phenols, particularly the xylenols. The reaction between a phenol ROH and phosphorus pentasulphide may produce compounds of the following type:2 (i) RO S P Diaryldithiophosphoric acids RO SH (ii) R-SH Thiophenolic compounds (iii) R-S-R Diaryl sulphides (iv) R-S-S-R Diaryl disulphides (v) Substituted thianthren compounds Except for the simplest type, the thiophenols (ii), the boiling points of these compounds lie above 300° C. The amounts of the thianthren compounds formed from the five xylenols (if all these are present) will vary according to the position of the substituents. In an attempt to ascertain something of the nature of the reagent, fractional distillation under atmospheric pressure was undertaken. At the outset, hydrogen sulphide was freely evolved, and-particularly below 200° C.-the fractions had the strong odor characteristic of the

Jan 1, 1939

By F. S. Crawford

IRON and copper are mined in the Lake Superior district. The iron mines of the district have the best safety record for that industry in the country as a whole, while the copper mines of the district rank second in two of the four years recorded (Table 1). In Utah copper comes mainly from open-pit mines, which enables that state to lead easily in safety. All of the Michigan production comes from deep underground workings. About 60 per cent of the iron miners in St. Louis County, Minnesota, are employed at open-pit mines; this favorably affects the combined open-pit and underground accident-frequency rate, as this county provides most of the Minnesota-mined iron ore. In Michigan, however, there are few open-pit mines, the bulk of the production coming from underground mines, while all of the Wisconsin production, just across the state line from Michigan, is from underground mines. In spite of the fact that fewer mines in Michigan use the safer open-pit method, the iron-mining industry of that state maintained a consistently low record from 1931 to 1934; however, it was many points behind its nearest competitor, Minnesota, with its much greater production from open-pit mines.

Jan 1, 1939

By M. E. Wadsworth, R. D. Groves, B. W. Madsen

Experimental results obtained from large-scale (7 ton), long-term (500 days) leaching of low-tenor copper sulfide ores were interpreted by a geometric model involving the movement of a reaction zone through the ore fragments. The postulated leaching mechanism involved mixed kinetics and included diffusion of the reacting species through the host rock and a chemical reaction at the surface of the mineral particles. Ore properties which were considered were Ore particle size and shape, grade of ore, and mineral content. Excellent agreement between the mixed kinetic model and the laboratory leaching results was obtained when -1/2-in. ore particles were not included in the leach. Also, a satisfactory prediction of copper recovery from +1/2-in. ore with a different particle size distribution was made; however, it was necessary to modify the shape factor in the model. Prediction of copper recovery from an ore sample which included the -1/2-in. fine fraction and leaching for 460 days was 56.5%, and the recovery from leaching was 47.0%. The presence of fines caused solution channeling and a deficiency of oxygen which inhibited the leaching rate. Also, compaction of fines around coarser particles interfered with circulation around the ore particles, and bulk solution transport probably was a rate controlling factor.

Jan 1, 1976

By J. S. Seawright

Haulage is a costly feature in the operation of an open pit mine, whether it be iron, copper, or limestone. The National Iron Co. has adapted an old underground method to the open pit inclined skip haulage to bring the ore from the pit bottom to the crusher or beneficiation plant. The Rockover skip has been placed in operation where limited areas have retarded or eliminated use of long rail or road slopes. Deep and narrow orebodies subject to rapid increase in depth that discourage use of conveyor belts and necessary crushing plants are ideal for this system. The skip haulage method was developed to combine the desirable features of conveyor, truck, and rail haulage and at the same time avoid the draw- backs. The skip was designed to follow the natural angle of repose of the pit wall and can vary from 25° to 45°. Open-pit skips now in operation show that the installation is successful and provide the

Jun 1, 1955

By John A. Meech, J. G. Paterson

Activated carbon is a strong adsorbent for amyl xanthate, capable of removing from solution up to a quarter of its own weight in xanthate. In selective flotation system where depression is unstable, separation efficiency increases with activated carbon additions. The improvements observed are brought about by two mechanisms. First, by removing stripped and residual collector ions from solution, competition between depressant and xanthate is reduced and depression is stabilized. In addition, the texture of the froth phase at high pine oil concentrations is modified by activated carbon such that better drainage between the air bubbles takes place, alleviating the mechanical entrapment of depressed mineral particles. In treating a bulk copper/lead concentrate produced from GECO ore, selectively between galena and chalcopyrite is increased when activated carbon is used. Although the rate of flotation of galena is marginally lowered by activated carbon, a small extension in the duration of flotation allows the lead recovery to increase by 19% at the same recovery of copper. An addition rate of 0.75 kg/ton (1.5 lb/st) of bulk concentrate is suggested as optimum from this testwork. However, the actual level used in the mill is dependent upon the residual concentrations of collector and frother in the bulk concentrate pulp.

Jan 1, 1979

By L. D. Godshall

A great deal has been written of late regarding the loss of silver in assaying; very discordant results have been published by different writers, and much uncertainty exists concerning even approximate losses in a careful determination of silver, as represented by a fire-assay. In the present paper it has been the aim of the writer to determine as accurately as possible the losses sustained by silver, under certain specified conditions, during the process of cupellation. Such losses are well known to be due to absorption by the cupel and volatilization. The conditions, however, which govern these losses are not believed by the writer to be so well understood. The most important of these are : 1. The effect of variable quantities of silver used. 2. The temperature of cupellation. 3. The character and quantity of impurities in the lead button. 4. The weight of the lead button. 5. The nature of the cupel. The following experiments were made for the purpose of demonstrating, as nearly as possible, the total loss of silver in cupellation under the most favorable conditions to be obtained in commercial assaying. Chemically pure silver and pure lead were taken. The latter was obtained from test-lead, first melted into a bar, from which pieces of the desired weight were cut and accurately weighed. The experiments recorded in this paper were planned by the writer, but executed throughout by Mr. J. N. Walker, whose ability as an accurate, careful and painstaking assayer is too well known and recognized throughout the West to require any further endorsement from me.

Jan 1, 1897

By Basil B. Zavoico

During 1938 the Russian oil industry, while able to increase its production 4.69 per cent above the preceding year, was not successful in correcting some of its basic difficulties, and the industry's position as it entered 1939 was unsatisfactory. The internal political difficulties of 1937 and 1938 took a toll in the oil industry as they did elsewhere in the U. S. S. R., further complicating the solution of the problems facing it, most important of which still remain: lack of experienced and responsible leadership, able to make quick decisions; undisciplined and migratory labor; and insufficient and often unsatisfactory quality of the various equipment needed by the industry and its ineffective distribution. Recent developments in the U. S. S. R. suggest that during 1939 the management will be granted more latitude and hence somewhat better results may be anticipated from the executive branch, provided, however, the "purges" do not recur. The labor should be better disciplined and should not shift as easily, owing to the introduction, at the close of 1938, of individual labor passports to all workers in the country, the principal purpose of which is to correct those two deficiencies. It is not anticipated, however, that the service of supply will show any appreciable improvement in 1939, partly because of inherent difficulties and partly because the manufacturers of heavy machinery are working primarily and necessarily for munitions. Production Production of crude oil during 1938 is estimated at 224,714,000 bbl., as compared with 212,742,000 bbl. in 1937, an increase of 4.69 per cent but 12.76 per cent below the planned output. While there were no major readjustments in the source of supply of crude oil, both the older districts, Baku and Grozny, were barely able to maintain their 1937 levels of production, the increased output being supplied primarily by the fields of Maikop and Ural Permian Basin districts. While exploration work was outstandingly successful in 1937, in 1938 no discoveries of any

Jan 1, 1939

By Basil B. Zavoico

During 1938 the Russian oil industry, while able to increase its production 4.69 per cent above the preceding year, was not successful in correcting some of its basic difficulties, and the industry's position as it entered 1939 was unsatisfactory. The internal political difficulties of 1937 and 1938 took a toll in the oil industry as they did elsewhere in the U. S. S. R., further complicating the solution of the problems facing it, most important of which still remain: lack of experienced and responsible leadership, able to make quick decisions; undisciplined and migratory labor; and insufficient and often unsatisfactory quality of the various equipment needed by the industry and its ineffective distribution. Recent developments in the U. S. S. R. suggest that during 1939 the management will be granted more latitude and hence somewhat better results may be anticipated from the executive branch, provided, however, the "purges" do not recur. The labor should be better disciplined and should not shift as easily, owing to the introduction, at the close of 1938, of individual labor passports to all workers in the country, the principal purpose of which is to correct those two deficiencies. It is not anticipated, however, that the service of supply will show any appreciable improvement in 1939, partly because of inherent difficulties and partly because the manufacturers of heavy machinery are working primarily and necessarily for munitions. Production Production of crude oil during 1938 is estimated at 224,714,000 bbl., as compared with 212,742,000 bbl. in 1937, an increase of 4.69 per cent but 12.76 per cent below the planned output. While there were no major readjustments in the source of supply of crude oil, both the older districts, Baku and Grozny, were barely able to maintain their 1937 levels of production, the increased output being supplied primarily by the fields of Maikop and Ural Permian Basin districts. While exploration work was outstandingly successful in 1937, in 1938 no discoveries of any

Jan 1, 1939

By J. H. Westbrook

UNTIL very recently the development of high temperature alloys has been strictly empirical. It is, in fact, a great tribute to the intuition, perseverance, and industry of the practicing metallurgists of this country and abroad that the amazing increases in gas turbine service temperature over the past 15 years have been achieved with so little fundamental knowledge. The result of this development has been the realization of successful but highly complex alloys possessing five, six, or more alloying elements and correspondingly complex microstructures. Within the last few years, considerable effort has been devoted to the identification of the secondary phases in these alloys and to the correlation of the presence or absence of such phases with alloy properties. Little attention, however, has been given the problem of identification of the mechanism (s) by which such phases enhance the properties of the alloy and especially to the assessment of the particular properties of the secondary phase (either in- trinsic or relative to the matrix phase) which are basically responsible for the improvement. Conceivable mechanisms which might apply include dispersion hardening and precipitation hardening. In both cases geometrical factors—particle size, dispersion, volume fraction, etc.—and agglomeration re-

Jan 1, 1958

By J. Campbell

The hydrostatic tensions in pure metals and long freezing range alloys are evaluated theoretically considering the viscous flow of residual liquid and the general plastic collapse of the casting. The former mechanism operates until the radii of the remaining liquid channels are of the order of 10-3 cm radius, after which the second process limits the attainable negative pressures which range from —1500 to -4200 atm for nickel, aluminum, copper, and iron. In previous reports1'2 the maximum possible hydrostatic tensions developed during solidification have been evaluated employing spherical symmetry. This inevitably involves the concept of totally confined liquid regions, the reality of which has recently been brought into serious doubt3 following observations of the freezing of various transparent materials. Regions of interdendritic liquid which are apparently about to be isolated by the growth of dendrite arms are observed not to be cut off because the advance of the dendrite tips is arrested until the region has completely solidified. Although this may be the result of the very low melting point liquid available at this late stage in freezing, or the result of a higher rate of heat transfer to the dendrite tips because of the acceleration in liquid flow rate near the completion of solidification, this point need not concern us. In this paper an attempt is made to approximate more closely to real conditions; thus the assumption of confined liquid regions is abandoned and cylindrical symmetry adopted. It has also been necessary, therefore, to consider the viscous flow of residual liquid through the remaining channels in the pasty zone. Furthermore, the rather special conditions of spherically symmetric solidification led to extremely high solidification rates and hence unusually high tensile stresses as solidification neared completion; the cylindrical Symmetry appears to yield solidification rates and stresses which are more typical of real castings. The rate of solidification is first considered since this critically affects both the flow of the liquid and the creep of the solid.

Jan 1, 1969

By Kenneth K. Humphreys, Joseph W. Leonard, Robert L. Llewellyn, William F. Lawrence

INTRODUCTION Cleaning fine coal sizes utilizing air currents in machines as the primary separating medium is called dry concentration or pneumatic cleaning. In 1947 approximately 18 million tons (16.38 million mt) of bituminous coal were cleaned by air machines; in 1965, 25.4 million tons (23.1 14 million mt); but in 1975, only 7 million tons (6.37 million mt). Table 11-1 shows the tonnages cleaned of bituminous coal and lignite in the United States by various types of equipment from 1938-1963. Table 11-2 shows only tonnages cleaned by pneumatic methods from 1964-1975. The decrease in tonnage to approximately 7 million tons (6.3 million mt) is due to a higher moisture content in the mined coal and the greater difficulty in cleaning the coal by air. There also was a definite trend to load raw coal at the mines, especially the slack which is the most expensive to clean due to the dewatering and drying requirements. While there have not been any applications of pneumatic cleaning in the anthracite field, its use has not been fully explored. The same is true for lignite and subbituminous coals.

Jan 1, 1979

By George W. Maynard

IN the course of an examination of some of the California hydraulie mines in November last, I visited the property of the Gold Run Ditch and Mining Company, near Dutch Flat, Placer County. This is one of the most important and extensively worked mines in the district. The gold occurs in the characteristic blue gravel, which averages 175 feet in thickness, the lower 40-60 feet being made tip of cement gravel, which resists the action of water, and can only be loosened by blasting. The specimen which I have the pleasure of laying before the members was presented to me by Mr. I. L. Gould, the intelligent superintendent of the mines, who informs me that he found it in the old river channel, about twelve feet above the bedrock. The flattened water-worn nugget of gold, about the size of a kidney-bean, is imbedded in blue cement gravel, around which quartz has crystallized. When found the projecting portion of the nugget was enveloped in quartz, the core of gravel and gold having only been discovered after breaking the lump of quartz. On the quartz there is a shell of cement. The specimen is a remarkable confirmation of the theory of the deposition of quartz from solution. DISCUSSION. DR. T. STERRY HUNT, in commenting upon this occurrence, remarked that it is in accordance with what we already know of the recency of some of the quartz of this region, and cited the microscopic

Jan 1, 1880

By Jerry G. Rose, Robert C. Howell

This paper addresses a process by which both the disposal and utilization of preparation plant coal refuse can be simultaneously accomplished with an attendant benefit of significantly increasing the percentage of extractable coal. A laboratory study is described in which coal refuse was successfully utilized as an aggregate in low cost concrete (coal-crete) mixes under simulated mine environments. Coal-crete specimens with compressive strengths of 14 000 kPa (2000 psi) were consistently produced. A construction sequence and mining plans are offered for placing the low-cost coal-crete pillars in accessible areas in room and-pillar mines so that a substantial portion of the remaining coal pillars could be extracted. The method could be applicable in areas where mining procedures do not permit pillar extraction became of possible surface subsidence, roof problems, or other conditions. Possible structural difficulties with the coal- crete pillar support system are discussed. Using a discounted cash flow analysis, the economic feasibility of mining with the coal-crete pillar system is investigated. The cost of the system is compared to the cost of a mining system which would have less coal recovery. The analysis indicates that although at higher coal selling prices the coal-crete mining system may yield an acceptable rate of return, the alternative of leaving the coal pillars is more attractive at the present time.

Jan 3, 1979

By Carle Hayward

SULPHUR has long been one of the banes of the steel manufacturer and often no effort and expense have been spared in order to reduce it to a small per cent. in the finished product. This condition is clue to a general conviction that in many cases where steels have failed in service, sulphur has been the cause. But there has been a growing feeling in recent years that the verdict against sulphur has been unnecessarily severe. In cases of segregation it was present in augmented amounts along with other impurities, but it had not caused the segregation. High sulphur in pig iron is caused by poor furnace conditions and the sulphur is merely one indication of an iron that has not been properly reduced. No amount of subsequent treatment under oxidizing conditions in the open-hearth furnace can remedy the defects, although the per cent. of sulphur may be considerably reduced. In other words, the causes of bad steel can frequently be traced back to bad pig iron, and sulphur is merely one indication that the pig iron is bad. The writer recently visited a steel plant where a mass of evidence had been accumulated which substantiated this fact, and the superintendent was .emphatic in stating that high sulphur was not harmful provided the steel was not otherwise poor due to insufficient reduction in the blast furnace. The presence of a moderate amount of sulphur is desirable from the standpoint of the man who machines the steel. The low-sulphur material drags and the production of a smooth surface is very difficult. A slight increase in sulphur enables the machinist to produce a smooth surface without difficulty. Since, therefore, such large quantities of steel are subjected to machining, it becomes highly important that the sulphur controversy should be settled, and if its presence is proved to be harmless the ban on it should be lifted.

Jan 10, 1916

Under date of Sept. 30, the following open letter was addressed to the Members of the Colorado Section of the American Institute of Min-ing and Metallurgical Engineers by a Colorado Committee: At a meeting of the Colorado Section of the American Institute of Mining and Metallurgical Engineers, held on Friday, Sept. 19, a reso-lution was unanimously passed condemning the Engineers' Licensing Bill passed at the last session of the State Legislature, and requesting the Chairman to appoint a Committee to act in conjunction with the other National Engineering Societies and the Colorado Metal Mining Associa-tion, with a view to securing its repeal at the extra session of the Legis-lature which the Governor has expressed his intention of calling. It may be within your knowledge that the bill in question was passed by the Legislature and signed by the Governor without the knowledge of any of the National Societies, and of few if any of their members. Under its provisions residents of other states cannot even come into this to examine a mine without securing a license, and aliens (among whom are many honored members of, the profession in Colorado) cannot obtain such a license at all. The mining industry in this state needs the coopera-tion of outside engineers, and we should welcome any assistance from them that will tend to develop our resources. To attempt to discourage the activity of visiting engineers will inevitably react on us, and brand the state as being hostile to brains and capital from outside. The difficulty of securing a license will prove a serious handicap to young engineers starting out in the independent practice of their profession. Moreover, a license issued to au engineer qualified in one branch will entitle him to practice in any other: so that the license is apt to mislead the public.

Jan 11, 1919

By P. K. Lucke

ONE of the interesting features connected with the great continental uplift, which formed the table land of Mexico, is the great depth to which oxidation and secondary enrichment of orebOdies occurred. This table land lies at altitudes ranging from 4000 to. 7000 ft. (1219 to 2133 m.) above sea level. Several cases could be cited of oxidized zones in copper and lead mines which reached depths of upward of 1500 ft. (457 m.) below the surface, and it is universally admitted that the oxidized zone in a mine is limited by the permanent water level. FIG. 1. Mexico, however, like many other countries in which deserts occur, is visited at rare intervals by tremendous floods, which sometimes cause variable water levels over long periods. The following cases bear out the idea, and lead to interesting conclusions of commercial value. My paper demonstrates that carbonates of ores may occur below water level and sulphides above, and I will endeavor to explain the causes of the phenomena in certain specific instances.

Jan 6, 1918