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By T. K. Prentice

ABSTRACTED AND REVIEWED BY E. W. DAVIS,* MEMBER A.I.M.E. THE January-February number of the Journal of the Chemical Metallurgical and Mining Society of South Africa is made up entirely of a discussion of Ball Wear in Cylindrical Mills. Following the principal paper by T. K. Prentice are several remarkably pertinent and carefully prepared discussions. Few persons in this country would be likely to see this publication, and since the information presented is new and of current interest, it seems desirable to abstract and review this publication for the benefit of the members of the A.I.M.E. The purpose of the investigation is stated in the first two paragraphs of Prentice's paper, as follows: Early in 1941, The Chamber of Mines Steel Products, Limited, initiated a series of tests under semi-working scale conditions to determine, if possible, those physical and chemical properties of a ball which make it resistant to wear when used in a cylindrical mill as a grinding medium, with the primary object of incorporating those beneficial qualities in the balls being produced at their works. This paper describes the tests carried out and discusses the results obtained. From these results it was possible to formulate a new theory relating to ball wear in cylindrical mills. This theory is presented in the second portion of this paper. PRACTICAL BALL-MILL TESTS IN A CYLINDRICAL MILL Part I of the paper begins with a discussion of the methods used for the manufacture of grinding balls in South Africa. The following paragraph is of particular interest. The cast steel ingots, 4 ¼ - in. square by 3 ft. 6 in. long, are re-heated in a gas-fired sloping stationary-hearth furnace and then rolled in a six-pass continuous mill into 2 5/8 in. round billets. Some of these billets are then removed and cut into suitable lengths for forging into 4 in., 3 ½ in., 3 in. or 2 ½ in. balls by means of three Drop and two Beché hammers, but the greater number, whilst still at about 1,000 ºC., pass directly into a set of scroll rolls which produce, in an ingenious manner, finished 3 in. balls direct from the 2 5/8 in. billets. Except in special cases, all balls are allowed to cool in the atmosphere and are not water quenched. Details of the Tests In order to enable the reader to evaluate properly the results and conclusions in the rest of the paper and in the discussions following the paper, most of the information presented by the author under this heading is quoted: ….. The testing unit was a nominal 30 in. diameter and 18 in. long centre discharge Denver Ball Mill. The ore pulp to the ball mill comprised a small portion of the normal feed to one of the fourteen City Deep 5 ft. 6 in. X 22 ft. tube mills, and the grinding media consisted of the balls under test plus other balls to give the desired load. The running time of the test-mill was divided into approximately equal periods of five days 13 ½ hours each. The usual procedure was to examine and make up the load

Jan 1, 1944

By A. Bauer, P. Calder, N. H. Carr, G. R. Harris

Since both rotary and jet piercing drills are used by the Iron Ore Co. at Smallwood, it is often desirable in planning to know in which regions of the orebody or new orebodies a particular drill will be the most economic. This makes it necessary to establish a correlation between drillability and pierceability and some physical rock properties. For rotary drills a good correlation was found with penetration rate and grinding factor index. The jet piercers were found to have a reciprocal relationship in the sense that the best rotary ground was the worst jet ground and vice versa. It is also indicated how an economic comparison could be made using these penetration rate versus grinding factor index curves, the hole size distribution curves for single pass and chambered holes and the mine distribution curve for grinding factor index. A discussion is presented on the fuel oxygen ratios to be used in jet piercing and on the site gas sampling and analysis which has been used to set up the drills. The fuel has been cut back so that stoichio-metric conditions exist, carbon monoxide is drastically reduced and pop-up or exploding holes eliminated. No decrease in penetration rate has been observed contrary to the published results of previous workers. The blasting procedure and results at Smallwood are discussed and the operation of Iron Ore Co.'s slurry pump-mix truck is also described briefly. Smallwood mine is part of the Iron Ore Co.'s Carol Lake operation and is situated in Labrador, 240 miles north of Sept-Iles, Quebec. Last year 15 million tons of crude ore were crushed to yield 6.3 million tons of concentrate and pellets. This year the figures will be 17 million tons of crude and 7% million tons of concentrate and pellets which is the full plant capacity. Carol Lake ores consist primarily of specularite and magnetite mixed with quartz. For convenience the ore has been split-into the following classifications depending on the percentage of magnetics in the sample, shown in brackets: specularite (0 to 10%), specularite-magnetite (10 to 20%), magnetite- specularite (20 to 30%), magnetite (>30%). The order of classification also represents the order of increasing grinding difficulty - the specularite generally being the easiest and the magnetite the hardest. The orebody also contains a small percentage of waste materials consisting of limonite carbonate, quartz carbonate and quartz magnetite. The first two materials are among the softest in the mine, generally softer than the specularite, and the quartz magnetite is amongst the hardest. The bulk of the material in the mine is of the specularite-magnetite and magnetite-specularite classifications. As a result of test drilling at Smallwood in 1960 with rotary, jet and percussion drills, the Iron Ore Co. purchased four JPM-4 jet piercers for the bulk of production drilling and set up an oxygen plant to supply 20 tons of oxygen per day. This oxygen is sufficient for two machines operating full time and one part time. In addition, there are two 50-R, one 60-R and one 40-R machines in use. The benches are 45 ft high and 50 ft holes are generally drilled. JET DRILLING At the onset of jet drilling in the late fall of 1962, two major problems were encountered: 1) freezing due to winter operations; experience and the use of heat at more places, such as the rotary head, has eliminated this,'" and 2) exploding or "popping" drilled holes; this happened frequently (several holes "popping" each day) and was the cause of two lost time accidents. In one instance a hole was being measured with a tape which fell down the hole causing it to "pop." Safety glasses though pulverized saved the wearer's eyesight. Various methods were then employed to detonate the holes before measuring or loading (dropping lighted rags of fusees down, or sparking across a spark gap). These methods were time consuming and far from completely successful. Consideration was given to the fuel oxygen ratio on the machines and what this would produce in the way of product gases. A fuel oxygen weight ratio of 0.35 which was quite oxygen negative was being used. Theoretically appreciable carbon monoxide would be produced at this fuel oxygen ratio. On the close down procedure of the jet which calls for low oxygen after flame out, oxygen would be left in the hole along with this carbon monoxide. This is an explosive mixture. The fuel oxygen ratio was cut back to stoichiometric

Jan 1, 1967

By Charles V. Seastone

The hydro-electric plant of the Peninsular Power Co. is located at what is commonly known as Lower Twin Falls on the Menominee River. This location is about 3I/2 miles north of the city of Iron Mountain, Mich. The principal points of delivery of electric energy from this plant are in the mining regions adjacent to Florence, Wis., and Iron River, Mich., and in the cities of Iron River and Iron Mountain. The hydro-electric plant at Twin Falls and the substation of the Iron Mountain Electric Light & Power Co, are connected by a 6,600-volt transmission line carried on steel towers and steel poles, the latter being used within the city limits. The plant at Twin Falls and the substation at Iron River, about 36 miles distant, are connected by a 66,000-volt, duplicate, three-phase transmission line, supported on steel towers. At Iron River, are located a 1,500-kw. auxiliary steam plant, and the substation, from which the current is distributed to the mines in this vicinity. A description of the auxiliary plant, main and customers' substations, and of the main and secondary transmission lines, follows later in this paper. General Layout The relative location of the dam, forebay, and power house will be understood by referring to Fig. 1. The dam is constructed on a ledge of solid rock which forms Lower Twin Falls. This rock ledge offers an excellent location in that the height of the dam, and therefore the amount of concrete, are thereby reduced, and also in that practically no pumping was required in unwatering the dam site. The maximum head provided by the dam is 44 ft., with an average working head of from 40 to 42 ft. The other structures, including the substructure of the power house,

Jan 1, 1915

By P. Hudock

Thin films of PbS and CdS have been deposited on insulutiug- sapphire substrates by euzploying a subliwzation technique rising near-equilibriurum conditions in ultrahigh vacuum. Oriented polycrystalline PbS and CdS films on sapphire have mobilities approachitzg values characteristic of bulk crystals. In the case of CdS, special purification procedures were crucial in obtaining high-mobility films. By performing the depositiotz of a compound within a small chamber heated to a UNiform temperature within a Vacuum systerrz, it is possible to approach equiilibrium cod-tions r.~litl~irs the chamber. In this way; the sublimation and condensation proceed under near equilibrium co?zditions, and it was found that the properties of dePosited corrzpounds were similar to those of the source material. Oriented PbS films on sapphire have a roor?l- temperature unobility of 700 sq cm per v sec and a T-5/2 temperature dependence characteristic of bulk crrystnls. CdS layers on sapphive Izazse a resistivity ~uhich is corrlpamble to the resistivity of the souvce crystals over a range of four ordem of rrlagnitude. Irz contrast, Ihe resistivity of CdS films prepared by conventional evaporation depends largely upon the substrate terrzperat~ire and postheating treatrrletlt, vather than upon the properties of' the solirce rrraterial. In the case oj the CdS films the achievment of high carrier mobility required the cargful exclusion of cont~~~~ii~unts from the films. The steps taken to accomplish this included presublimation of the source material, performance of the deposition at a backg-m~ozd pressure less than 10-8 Torr, and a solvent extraction with liquid cadminum, similar to that described by Aven and woodbury. The deposition of ,films under near-equilibrium conditions is being op-plied to other classes oj COmpounds. II should he of 1:allce ,tor llle deposition of nny matevial that decomposes in the vapor state. THIN films of PbS and CdS have been deposited on insulating sapphire substrates by employing a sublimation technique using near-equilibrium conditions in ultrahigh vacuum. Oriented polycrystalline PbS and CdS films on sapphire have Hall mobilities approaching values characteristic of bulk crystals. In the case of CdS, special purification procedures were crucial in obtaining high-mobility films. Depositions were performed in a small quartz sublimation cell shown in Fig. 1 that contained the compound and the single-crystal sapphire substrate. The substrates were etched in tapered solutions of hot phosphoric acid, rinsed in deionized water, dried, and transferred to the cell under dry nitrogen. Graphite crucibles and substrates were used in experiments where it was necessary to provide an inert test vehicle for the analytical determination of impurities in the source crystals and deposited films. The crucibles and substrates were machined out of spectrographic-grade graphite having less than 1 ppm of impurities. A quartz mask was sometimes used to define a pattern which could be used for Hall and resistivity measurements. Close spacing between the compound and substrate was maintained to insure better transport of each component from the source material.

Jan 1, 1968

By P. E. Hildebrand, S. W. Mao, C. N. Crain

Hydrologic and economic criteria figure in many obvious ways in water resources development, but they are rarely linked quantitatively, and most of the applications are pertinent only to the case in point. In the preparation of a regional plan for the massive program of groundwater development in the Punjab, situations have arisen where the choice among two or more alternatives was made by analyzing the economic implications of critical hydrologic parameters. Two of these situations which are of more or less general interest are described herein. The first involves basic development policy, i.e., the question of whether groundwater development should be based on the demand of the economy, or the conservation concept of safe yield. The analysis demonstrated that mining of groundwater is clearly indicated for areas where alternative supplies are unavailable. The second problem involves integrating hydrologic data into an economic model to determine optimum well design. From an analysis of all pertinent factors, a simple nomograph was derived for determining well specifications on site during construction. The nomograph can be modified for use in any alluvial terrain. In the Northern Zone of the Indus Plains —the region known as the Punjab- Pakistan is proceeding with integrated development of water and land resources on a scale never before contemplated. The heart of the development plan is a massive program of groundwater development to supplement canal irrigation supplies and to provide drainage relief to the irrigated lands. By the close of 1966 about 2500 high-capacity wells were in operation and furnishing the water supply and drainage requirements for nearly two million irrigated acres. The development plan calls for the construction of a total of nearly 30,000 wells with an aggregate capacity of 120,000 cfs by 1980. This is part of an integrated program eventually affecting over 20 million acres of irrigated lands. [This development program is administered by the West Pakistan Water and Power Development Authority (WAPDA) for which the firm of Tipton and Kalm-bach, Inc. serves as regional planning consultant for the Northern Zone. The material presented herein is derived from planning studies which have been made in connection with the preparation of a regional development plan for the Northern zone.] Pakistan is proceeding with this large-scale development of land and water resources at a time when she is at the threshold of an almost calamitous population growth. Furthermore, she is attempting this development at a time when most of her usable land is already occupied and her food demands exceed current production. Here in the Northern Zone is one of the largest continuous areas of irrigated land in the world, easily irrigated, with a warm, dry climate and ample potential supplies of surface water and groundwater. Except for an abundance of land and labor, other primary resources are lacking or in very limited supply. The agriculture sector so dominates the economy that only by means of an effective development of the agricultural resources can other sectors grow and contribute to a viable economy. Because of inadequate irrigation, farming here has not effectively participated in the twentieth century revolution in agriculture, and only by means of massive development of potential supplies can Pakistan catch up. Capital for any kind of mass development must come from the outside. But the overriding restraint to development of the land and labor resources is the availability of water. ECONOMICS OF DEVELOPMENT The decision-making process in planning regional development becomes increasingly complex as the various sectors of the economy become more highly developed. Where, as in this case, one sector dominates the economy and its development can be considered the key to development of other sectors, the decision-making process is simplified and it is easier to identify alternatives and to trace the prob-

Jan 1, 1970

By A. Kelly, S. Sato

Tensile tests have been performed on aluminum single crystals of 99.99 pct purity at 196°K. The resolved shear stress when the stress-strain curve becomes concave to the strain axis depends on orientation, being always higher for crystals with an initial orientation close to the sides of the unit triangle. Observations have been made, with the optical microscope, of the appearance of slip lines on polished surfaces of the crystals. Particular attention has been paid to the first appearance of cross-slip. It is confirmed that marked cross-slip is first seen when the stress-strain curve becomes concave to the strain axis. Measurements are reported of the lengths of the slip lines observed on top and side faces of the crystals at various stages of the deformation. The lengths of the slip lines vary inversely as the flow stress for all crystals, independent of crystal orientation. From measurements of the lengths and separations of the slip traces it is possible to estimate the number of dislocations which are annihilated at each cross-slip site. It is concluded that the annihilation of screw dislocations of opposite sign is the most important cross-slip process occurring. FRIEDEL1 recently pointed out that the stress-strain curve of many pure metals of face-centered-cubic structure can be considered as composed of three stages. Plastic flow commences with a region showing a small rate of hardening which is approximately linear. This has been called "easy glide*. It is followed by a region of more rapid hardening in which the slope of the curve is again approximately constant and this, in turn, is superseded by a final part of the curve which is concave to the strain axis. Following Diehl2 we may designate these regions as stages I, II, and III respectively. The onset of stage 111 occurs at lower stresses at higher temperatures. The appearance of the slip lines formed during these various stages has been described by a number of workers?-5* The object of the present work was to make detailed observations of the lengths and separations of slip lines for a number of crystals of different orientations deformed at the same temperature and strain rate. Although much previous work has been published on the deformation of aluminum single crystals the importance of measurements of these quantities has only recently been realized—they are essential for experimental tests of recent theories of work hardening.' 9 In aluminum, deformed at room temperature, stage 11 of the stress-strain curve is very weakly marked, as the stress for the onset of stage 111 is attained soon after the end of easy glide. In the present experiments it was decided to use a temperature lower than room temperature so that stage II of the curve was better developed. However, at temperatures as low as 90°K slip lines are not measured easily with the optical microscope.5 For this reason 1960k was chosen as a suitable temperature. Even at 1960k however, stage III of the curve commences at glide strains of 6 to 10 pct and hence

Jan 1, 1960

By E. H. Citron

CLEANING fine coal in jigs is not new in Europe, where the feldspar jig is being used almost exclusively for this purpose. A feldspar jig operates with an artificial bed made up generally of feldspar or other hard rock material. Dimensions and specific gravity of this material must be of suitable values for good bedding qualities. For good efficiency, the size should range between 1x2 in. and 2x2x½ in. thick. The disadvantage of an artificial bed is that it is not mobile and must be replaced every so often with new material to obtain good cleavage characteristics. A semi-mobile bed has been developed to retain only a part of the feldspar on the sieve screen— the other part is drawn off with the refuse material, from which it is reclaimed and returned to the jig feed. Recirculating this feldspar rock offers definite advantages. However, in time it will lose its original shape because of wear, and new bed material must be added to the jig feed. The latest feldspar jigs arc generally air-pulsated, Baum-type jigs, although more than 70 pct of the feldspar jigs operating in Continental Europe are still of the piston type. These jigs are very popular in Europe, but they do require a great deal of time and attention. New Theory to Eliminate Artificial Bedding: At the preparation plants of Pittsburg & Midway Coal Mining Co. it has always been the contention that a small piston-type jig could be developed to clean fine 1/4x0-in. coal down to 28 to 60 mesh efficiently by obtaining and admitting bedding material from the present plant refuse circuit to the jig feed. This eliminates use of artificial bedding materials. The jig should incorporate these essential adjustable features as follows: Adjustable Sieve Screen A screen that can be raised and lowered to increase or decrease washing compartment depth. The sieve screen also can be set on an incline level, or decline. Adjustable Plunger Eccentric Length of stroke can be adjusted to increase or decrease pulsion and suction. Variable Plunger Speed Variable speed reducer for decreasing and increasing the number of strokes per minute. Water Distribution Adjustable baffle plate separating the plunger and sieve compartment so the water can be distributed uniformly over the entire sieve screen area. Refuse Ejector Special unique rubber-type refuse ejector gate operated by air and electrically controlled (as a conventional jig). Automatic Control Conventional float that measures the specific gravity of the coal-water refuse medium in the jig is of the submerged type. The float is mounted on a vertical stem held in position by two parallel arms. A movable weight regulates the effective specific gravity of the float. The float stem can be raised and lowered, having a graduated scale to indicate the depth of bed for the setting of the float. Hutch Drawoff Hutch material is drawn from the cell compartment to the elevator compartment by gravity. The first one-cell experimental jig incorporating all these features was built in January 1955 by Ore

Jan 1, 1959

By Nath S. Parate

Emphasis on publications related to coal mining subsidence and damages is appropriate at present in view of the energy crisis and increased coal production and public alertness. I have worked in Harrisburg with the state government Public Utilities Commission on energy-fuel matters and issues (Parate, 1978-80). I have participated in the communication on subsidence/ damage reviews and status with the Bureau of Mines Liasion Office (Kebblish, 1978-79). I have done research (Parate, 1965) and published papers (Parate, 1972; Parate, 1967) in Britain on coal mining subsidence and damages around Sheffield-Nottinghamshire coal fields. I have a few comments on the recent paper titled, "Pennsylvania Subsidence Control Guidelines," by C.J. Bise. 1) What is the basis of the empirical formula or guideline, LD _ (0.27 x D) ± 4.6, defining the support area? 2) The particular structure may not be damaged due to vertical uniform displacement caused by mining beneath unless the displacement is differential (King, 1964). 3) The author mentions the limited subsidence research in the US, and quite rightly so. But he fails to quote any work reference by continental investigators except the British or review work by the US. What are the reasons? 4) The author has not mentioned the importance and role of angle of draw for Pennsylvania, Kentucky, or Illinois coal fields. Is there any current research investigation on the relationship between subsidence research investigation, damage, and transference of strains to structures? There have been a number of newspaper reports on subsidence damage in Wilkesbarre and other areas in Pennsylvania. Is the author aware of such instances and traditional attitudes to such issues? Many times government agencies--due to lack of funds, technical expertise, and public policies--are unable or do not find it interesting to keep updates on these issues, as per the author's knowledge and experience with state governments. 5) What is the net effect and role of the D.E.R. Insurance Office on the monitoring, reducing, or controlling subsidence damage, particularly in Pennsylvania?

Jan 1, 1983

By Albert Hoskinson

PROGRESS on the earth depends to a large extent upon the rapid inter-change of ideas and commodities between the various nations of the world. The smooth flow of commerce, by which these ideas and com-modities move, is accelerated by accurate and complete maps of the various land and water areas of the earth, The production of accurate maps depends upon a complete knowledge of the figure and dimensions of the object to be charted, therefore a knowledge of the shape of the earth is a prime necessity for accurate charting purposes. Gravity observa-tions were first undertaken to aid in determining the shape of the earth so that the geodetic surveys of its land and water areas might be more accurately connected to form an undistorted map. A large part of the earth's surface is water and it is therefore necessary to get gravity values at sea as well as on land before a complete and accurate figure of the earth can be determined. Dr. F. A. Vening Meinesz, of Holland, was the first scientist to perfect a pendulum instrument that would accurately measure gravity at sea. He had previously developed a multiple pendulum apparatus for measur-ing gravity upon swampy and unstable land areas in Holland and it was therefore quite natural that he should adapt the instrument to give accurate results upon a still more unstable support, the surface of the sea. His instrument as perfected gives satisfactory results when mounted in gimbals on any vessel where the roll and pitch are not more than about 5° and where the vibrations from rotating machinery and wave action are not large enough to cause the pendulums to shift on the knife-edges. This degree of stability can be obtained on surface craft only in protected waters or on very calm days. Therefore, Dr. Meinesz mounted his instrument in a. submarine so that he could submerge below the disturbed surface waters and get the desired stability in nearly any kind of weather by simply diving to greater depths. Most of the gravity-at-sea work has been done with a Meinesz instrument and a very large number of the observations have been made by Dr. Meinesz himself. He has occupied nearly 1000 sea stations and probably has traveled as many miles by

Jan 1, 1938

By R. A. Burmeister, P. E. Greene

Two methods for the synthesis and growth of single crystals of B6 P are described: a solution-growth process employing nickel as the solvent, and a vapor-growth process employing BBr3 and pH3 as the reac-tants. Relevant portions of the Ni-B-P phase diagram have been examined and liquidus data are presented for an isobaric section at an equivalent P2 pressure of 3.8 Torr, and an isothertnal section at 1300°C. Solution-growth techniques are described and the purity and crystalline perfection of the resulting material is discussed. Epitaxial growth of BeP on &P substrates has been obtained using the vapor-phase system. Evidence is presented which supports the assignment of the stoichioknetry B6P to boron sub-plwsphide. THE B-P system differs from other III-V systems in that it contains two distinct compounds. The existence of the monophosphide (BP) has been known for some time,' whereas the subphosphide (B6P) was reported only recently.' Both of these compounds are large bandgap semiconductors (Eg = 2.0 ev for BP~ and 3.3 ev for B6P4), and are therefore of interest for optoelectronic applications. The crystal structure of B6P is quite different from those of most semiconductors, being derived from that of a-rhombohedral boron by the incorporation of the two phosphorus atoms in the intericosahedral sites of the a-boron unit cell?76 B6P also exhibits a number of unusual characteristics, including a high degree of chemical inertness, hardness, and high-temperature stability. No information concerning other physical properties is available in the literature. The present study is part of a broader investigation of the preparation and properties of B6P. This paper considers methods of growing single crystals of B6P of suitable size and quality for physical-property measurements. A detailed discussion of the electrical and optical properties of B6P will be given elsewhere.' GENERAL CONSIDERATIONS The method first used to synthesize B6P was the disproportionation of BP' according to the reaction The equilibrium P2 pressures corresponding to this reaction were also determined .'" It is therefore possible, in principle, to apply several of the reactions reported for the synthesis of BP to the synthesis of B6P merely by selecting lower phosphorus pressures or higher temperatures, in accordance with the equilibrium data. Other techniques for the direct synthesis of microcry stalline B8P have also been reported.1°

Jan 1, 1968

By D. L. Harris, A. M. Gaudin

Observations were made of the distribution of mercaptan containing S35 between aqueous solution and mineral and between aqueous solution and the gaseous phase. Although equilibrium may not have been attained, adsorption of the reagent was shown to occur reasily from air or aqueous solution on sphalerite, zincite, and willem-ite and to correspond to flotation. Adsorption on quartz did not similarly occur. THE following results, presented here in condensed form,' were obtained in a preliminary study of the adsorption of n-hexane thiol, hexyl mercaptan, on sphalerite, zincite, willemite, and quartz, from aqueous solution and from a gas. Interest in this subject was aroused by a Belgian report' of effective use of hexyl mercaptan for flotation collection of oxidized zinc minerals. The relatively low boiling point, 149°C, of the mercaptan3 suggested the desirability of extending the usual measurements of partition of collector between aqueous solution and gas and between gas and mineral. It is believed that this paper presents the first measurements of this type on a flotation system. Attempts were made to carry out the measurements at equilibrium, but as the work progressed it became increasingly doubtful that this desirable condition had been achieved. To control composition and extent of the gas phase, the apparatus was a wholly-enclosed thermally-controlled glass system. Because of these constraints and the desirability of dealing with pure minerals, a scale of operations was chosen in which a few grams of deslimed mineral were used in each test. It was also necessary to choose a particularly sensitive method for mercaptan analysis, and in fact a method that would permit the experimenters to follow the approach to equilibrium. For these reasons mercaptan marked by radiosulphur 35 was used. An analysis was made for the radiosulphur by a modification of the method of Gaudin and Carr. Coarsely-crystallized sphalerite was handpicked, stage-crushed in the dry state, wet-screened on a 200-mesh sieve, and deslimed in water at about 5 microns. Further treatment consisted of a wash in dilute aqueous hydrogen peroxide, drying, removal of the dark-colored fraction in a Frantz magnetic separator, washing in very dilute hydrochloric acid, repeated washing in distilled and conductivity water, and drying. The last washings showed a conductivity equivalent to a few ppm NaC1, that is, much more than would be provided, theoretically, by a saturated ZnS solution. The material was stored dry in sealed bottles. Analyses were as follows: Zn, 62.3 pct; Fe, 0.43 pct; Cd, 0.44 pct; S, 31.2 pct; Mn, 0.001 pct. The specific surface (BET method) was 2000 cm2/g. Zincite from Franklin furnace of the New Jersey Zinc Co. was hand-picked, dry-crushed, wet-screened at 100 mesh, and deslimed at about 10 microns. After drying, the associated zinc, manganese, calcium, and silicate minerals were removed in a Frantz magnetic separator. The purified zincite was washed in distilled water and conductivity water to a conductance of less than 2 ppm equivalent NaC1, dried, and stored. Analyses were as follows: Zn, 75.1 pct; Fe, 0.9 pct; Mn, 2.78 pct. The specific surface (BET method) was 1740 cm 2/g. Willemite, also from Franklin furnace, was purified similarly. Analyses were as follows: Zn, 52.5 pct; Fe, 0.12 pct; SiO², 27.3 pct; loss on ignition, 0.13 pct. The specific surface was 1760 cm 2/g. Conductivity water (double-distilled) and demin-eralized-distilled water were used in most of the tests. The specific resistance was not less than 600, 000 ohms, and usually above 1,000,000. Radiosulphur-marked hexyl mercaptan (1-hexane thiol) was synthesized by Tracerlab, Inc., Boston. Two lots were secured several months apart. The last lot, consisting of about 0.5 g of the mercaptan, had a total activity of about 10 millicuries. Tracerlab Co. guaranteed only the activity; hence a quasi -vapor pressure determination (based upon an S analysis) of the mercaptan was made. The calculated value, 4.2 mm of mercury at 25.5' C, has been compared with that of a sample of Highest Purity 1-hexane thiol from Fisher Scientific Co. The latter had a vapor pressure of 4.5 mm of mercury at 2.5 C. Analytical Procedures The sample containing radiosulphur-marked mercaptan was oxidized to convert the mercaptan sulphur to sulphate, carrier barium sulphate being added to provide a suitable quantity of total barium sulphate in a filter cake. The precipitate was filtered and dried, and counting was carried out either in a streaming-gas (Q-gas) counter for high sensitivity or with an end-window G-M counter for convenience. The oxidized and precipitated mercaptan gave a radioactive count of 65 counts per minute per microgram in the end-window Geiger-Mueller counter and 1100 counts per minute per microgram in a Q-gas counter. For standardization of the mercaptan solution, 15 replicate analyses were made. The average deviation per measurement was about 1600 cpm in 65,000 cpm, the probable error in the mean being 275 cpm. It

Jan 1, 1955

By David R. Maneval, W. E. Foreman, J. Richard Lucas

INTRODUCTION The objective of this chapter is to inform the industry, as well as the public, of the challenges in dealing with the problems associated with the contamination of air and water from coal preparation plants. The need for an informed industry is most important. It is hoped that some contribution may be given to a more efficient and economical approach to the problems of plant waste contaminants at individual plants. The problem has many facets, and consideration to specific area should begin early before any significant problems develop at a given plant. It is then possible to have a reasoned approach before the pressures of an emergency environment force hasty and incomplete solutions. It will be necessary to anticipate these problems in the design of new preparation plants and advance consideration should be given to all the problems concerned with contaminants. The first part of the chapter will concern itself mainly with the contamination aspects of fine-coal cleaning and "black-water" disposal. Also attention will be given to the nature and formation of water from coal-mine drainage systems and the treatment of these waters for industrial use. Some attention will be devoted to the cost of installing and operating the various beneficiation systems for the removal of suspended solids. The second part of the chapter will analyze the problems of air contaminants from coal preparation plants. The nature and the effects of these contaminants and their potential for air pollution will be examined. One of the most critical is the measurement and analysis of these contaminants. As a result of identifying and determining the extent of the problem, better control can be planned. One of the most serious contaminants in air involves the element sulfur, and its elimination as a source of air pollution is one of the most challenging areas in coal preparation today. The last part of the chapter will emphasize the long-range problem of refuse disposal and control. Minimum operating and maintenance costs are functions of the proper selection and geometry of refuse disposal areas. Disposal procedures are varied but must be rigidly pursued or difficulties will result. Maintenance of refuse areas, including monitoring of burning refuse, is critical. It should be recognized that fine-solid refuse disposal systems must be carefully designed to minimize contamination. WATER CONTAMINANTS FROM PREPARATION PLANTS Pollution Aspects of Fine-Coal Cleaning and "Black-Water" Disposal The effluents from coal washeries and waters draining from plant-site surfaces inevitably contain fine coal and coal refuse materials in suspen-

Jan 1, 1968

By N. A. Gokcen, S. Fujishiro

The dissociation pressure of Cr3C2 has been measured in the range of 1908" to 2237°K by means of graphite Knudsen effusion cells. It has been found that Cr3C2 vaporizes according to the following reaction: 1/3 Cr3C2 (s or 1) = 2/3 C (graph.) + Cr (g). The equilibrizcm pressure, P, of Cr (g) is found to be log Ps=- - (21,194/T) + 6.525 over solid Cr3C2 and estimated as log P, = - (19,535/T) + 5.76 over liquid Cr3C2. CARBIDES of chromium are of great importance in alloy steels and cemented carbides. The published data on their therm odynamic properties at high temperatures, however, are meager. The heat capacity and change in entropy of Cr3C2 were determined calorimetrically by Kelley and Moore1 in the range of approximately 50" to 300°K, and by Oriani and Murphy2 from 297" to 1188°K. The standard entropy of Cr3C2at 298.15°K, obtained by Kelley.7 was later confirmed by DeSorbo.4 Equilibrium in the reaction was investigated by Boericke.5 A recent tabular summary

Jan 1, 1962

By J. E. Pavlick, W. W. Mullins, H. W. Paxton

The growth of nitrogen-austenite during nitriding of large-gvained ferrite between 650" and 800°C has been studied as a functimz oJ time and nitrogen potential of the atmosphere for a variety of alloying elements dissolved in the ferrite. Whereas no preferential grain boundary penetration by aistenite takes place in zone-refined iron, the addition of aboit I zot pct oj' V, Ti, Cr. Si, or A1 produces significant protrusion of austenite down former 0-0 boundaries. This group of elernents also produces ragged y-0 interfaces in the a grains which advance more slozuly than those in zone-refined iron. 1 zut pct of Ni, Co, Mn, or Mo dissolved in ferrite leads to essentially smooth 7-a interfaces, which advance at rates very sinzilar to those in zone-refined iron. The reasons for this effect are not clear. Two possible limiting hypotheses, not necessarily exclusive, are discussed. One involves p.referentia1 grain bozindary diffusion of nitrogen. the other the production of a zone of ferrite, stpersatcirated with respect to nitrogen, from which austenite precipitates helerogeneozisly on the a-a gyain boundaries. In many phase transformations which occur by nu-cleation and diffusion-controlled growth, information on the parameters which control the rates of nuclea-tion and of growth is frequently not quantititative. The present work describes a continuation of efforts to obtain quantitative data on growth rates in systems where thermodynamic and kinetic factors are known independently, and thus where comparison with models of the growth process is possible. The work has been conducted on iron-base systems for two reasons. Firstly, there are several interesting transformations in this system, many of which are of practical importance. Secondly, the information on phase diagrams, activities, and diffusion coefficients is more complete in this system than in any other. These data are still inadequate to check all the effects of alloying elements, but at worst it is possible to make estimates and thus examine order-of-magni-tude agreement with proposed models. It will be necessary to do this in the present work. The problem studied was the growth of nitrogen-austenite in from the surface of large-grained columnar crystals of alloyed ferrite exposed to an NHs/Hz atmosphere. Earlier work by Grozier et al.' had suggested that growth of austenite may occur preferentially along grain boundaries of alloyed ferrite, whereas zone-refined (ZR) iron shows no such effect, Fig. 1. Growth of nitrogen-austenite into single crystals of zone-refined ferrite is planar provided sufficient nu-cleation sites for austenite are present, and is controlled by volume diffusion of nitrogen through the

Jan 1, 1967

By Northcutt Ely

International developments affecting foreign in- vestments in 1960-61 were many, varying from region to region and differing with respect to various categories of investments. Total value of U.S. private investment abroad in 1960 was approximately $32.7 billion, an increase of $2.9 billion over 1959. Production and distribution of mineral resources was, by a sizeable margin, the most important function of American capital working in foreign countries in 1960. Investment in mining or petroleum interests totaled approximately $14 billion, or 42% of all direct foreign investment. In- vestments by industry for 1960 were as follows: Petroleum-10.9 billions, Mining-3.0 billions, Manufacturing-11.2 billions, Utilities-2.5 billions, other-5.1 billions. American investors found Canada and Latin America to be most desirable in 1960 with the greatest percentage of American capital in all areas centered in the petroleum and mining industries. The areal breakdown of total American investments is as follows: Canada-$11.2 billions, Latin America-$8.4 billions, Western Europe-$6.6 billions, Middle East-$1.2 billions, Far East-$1.2 billions, Africa-$.9 billions, other areas-$3.2 billions.

Jan 3, 1962

By Thomas Fraser, H. F. Yancey

BefoRe a new coal-washing plant is installed, or an existing washery is remodelled and improved, considerable experimental work on the coal to be washed should be done. A thorough examination of a coal, to determine whether it can be washed successfully and the best and most economical process for securing a satisfactory grade of washed coal, calls for mine sampling, analytical work, and experimental coal-washing tests which may require several months' time and the expenditure of considerable money. Having collected the required data on the characteristics of the coal and the results secured with different types of machines under different sets of conditions, it is necessary to decide what method of treatment should be used. The interpretation of the experimental data is no small part of the problem. The first step in the investigative work is to determine from the characteristics of the coal and the manner of occurrence of the impurities whether it is possible to separate the dirt from the coal and produce a washed coal of the required quality. Then it is necessary to select the type of washer or the system of treatment that will produce the greatest amount of washed coal of this grade for the least cost. To secure this information, tests may be made at laboratories operated by consulting or contracting engineers, at the testing plants of machinery manufacturers, at commercial washeries, or in an experimental washery erected on the site of the proposed plant. Such tests will produce figures in which every factor, including analyses of raw coal and washed coal and yield of washed coal, may vary widely. To reduce these results to a common basis for comparison is very difficult. A number of plans

Jan 1, 1923

By Thomas Fraser, H. F. Yancey

BefoRe a new coal-washing plant is installed, or an existing washery is remodelled and improved, considerable experimental work on the coal to be washed should be done. A thorough examination of a coal, to determine whether it can be washed successfully and the best and most economical process for securing a satisfactory grade of washed coal, calls for mine sampling, analytical work, and experimental coal-washing tests which may require several months' time and the expenditure of considerable money. Having collected the required data on the characteristics of the coal and the results secured with different types of machines under different sets of conditions, it is necessary to decide what method of treatment should be used. The interpretation of the experimental data is no small part of the problem. The first step in the investigative work is to determine from the characteristics of the coal and the manner of occurrence of the impurities whether it is possible to separate the dirt from the coal and produce a washed coal of the required quality. Then it is necessary to select the type of washer or the system of treatment that will produce the greatest amount of washed coal of this grade for the least cost. To secure this information, tests may be made at laboratories operated by consulting or contracting engineers, at the testing plants of machinery manufacturers, at commercial washeries, or in an experimental washery erected on the site of the proposed plant. Such tests will produce figures in which every factor, including analyses of raw coal and washed coal and yield of washed coal, may vary widely. To reduce these results to a common basis for comparison is very difficult. A number of plans

Jan 1, 1923

By Arthur F. Taggart

Tins paper proposes two units (believed to be new) for designating, respectively, capacity and efficiency for primary and intermediate crushers. CAPACITY Operators know that the tonnage of rock that can be put through a particular crusher in a give time depends primarily upon the crusher setting (open setting for jaw and primary gyratory types; closed setting for cones and rolls), and secondarily on the lithological character of the feed, its maximum size, the amount of fines that it carries, its moisture content, and the method of feeding. The proposed capacity formula states a relationship between all of these factors in one empirical equation, as follows: TR = TR80KK'K" [I] in which Ts, called "reduction tons per hour" is the new capacity unit; T = tons of feed per hour requiring crushing; R80 = "80-per cent reduction ratio"; and K, K', and K" are constants that approximate quantitatively lithological character, moisture content and method of feeding, respectively. T is the hourly weight of material in the feed that is coarser than the coarsest discharge of the crusher. (For marked departures from the normal specific gravity range - 2.5 to 2.7 - T should. be adjusted to corresponding volumes.) In the crushers under consideration, discharge from the crushing zone is limited by the minimum dimension of a particle. Passage of the particle through a square-mesh screen is limited by its intermediate dimension. Sheppard1 has shown that the ratio of maximum: intermediate: minimum average dimensions of broken rock fragments may be taken as about 1.5 : 1 : 0.6 for nonslabby rocks such as are normally crushed, while for slabby rocks, such as thin-bedded sedimentaries, foliated schists and gneisses, and the blocky metamorphics, the ratio is of the average order I.3:I:0.3, with the possibility of an even smaller relative value for the thickness. Gaudin2 finds the corresponding ratio for 150 + 200-mesh pyrite to be 1.4: 1 : 0.6. The hourly tonnage of crusher-plant feed, therefore, should be diminished by the amount thereof that would pass a square-mesh screen of which the aperture is S times the crusher setting, where S is a shape factor with the value 1.7 for rocks that break exceptionally cubic; 2 for ores and rocks that exhibit no appreciable tendency to slabbiness; and 2.5 to 3, or, in exceptional cases, even larger, when the tendency to slabbiness is marked. R80 is the quotient of the theoretical square-mesh aperture that would pass 80 per cent of the feed, divided by the aperture that would pass 80 per cent of the product. It is best determined from screen tests.

Jan 1, 1941

By C. B. E. Douglas

The following analysis was stimulated by a previous article on evaluation of the water problem at Eureka, Nev., which describes a method using formulas especially devised to calculate flow potential of extensive aquifers characterized by relatively even porosity and permeability throughout. The present discussion submits that the method was unsuitable for solving the kind of problem occurring at Eureka, where the amount of water available, rather than the flow potential, may have been the vital factor. IN an interesting article on evaluation of the water problem at Eureka, Nev.,1 W. T. Stuart describes how a difficult water problem, or one phase of it, may be evaluated by means of a small scale test. Test data are plotted by a method rendering, under certain conditions, a straight-line graph that can be projected to show how much the water table will be lowered by pumping at any specified rate for a given time. A formula is then used to determine the size of opening, or extent of workings, necessary to provide sufficient inflow to enable pumping to be maintained at that rate. At first glance this might seem the answer to a miner's prayer, but a word of caution is in order. It may not be the whole answer. Moreover, results obtained by the method described are reliable only for conditions approximating those assumed. Even where conditions do not meet this requirement, however, it may be possible to draw helpful inferences from the results, perhaps enough to facilitate another approach to evaluation of a problem. The two formulas Mr. Stuart used, the Theis formula and the one developed from it by Cooper and Jacob, were given field checks a number of years ago in valley alluvials by the Water Supply Div. of the U. S. Geological Survey and found to be reliable when the aquifer is very large in horizontal extent and sufficiently isotropic for the test well and observation wells to be in material of the same average permeability as the saturated part of the aquifer as a whole." Extensive valley alluvials, sands, and gravels can be evaluated in this way, and there are even cases in which the method could apply to porous limestones, such as flat beds of very large areal extent that have been submerged below the water table after extensive weathering. These are sometimes prolific sources of water for towns and industries. It is necessary for them to have been above the water table for some geologically long period of time in a fairly humid climate before submergence because the necessary high porosity and permeability, and large reservoir capacity, are the result of weathering, that is, of solution by the carbonic acid (H,CO3) in rainwater formed by the absorption of CO, from the air by raindrops, and this dissolving action must cease when all the H2CO3 has been consumed by re- action with the carbonate to form the more soluble bicarbonate. Consequently this weathering process is largely restricted to a zone that does not extend much below the water level, and submergence is necessary after the weathering to provide large reservoir capacity and good hydraulic continuity. On the other hand, water courses tend to form along faults and fractures in limestone, and to become enlarged by solution, well below water level when, as often happens, fresh meteoric water is circulated rapidly through them to considerable depth by hydrostatic pressure, as through an inverted syphon. Although the reservoir capacity of such water courses is relatively small they may extend far enough to tap more prolific sources. Cavities, and sometimes caves of considerable size, are found in limestones where the acid formed by the oxidation of sulphides has attacked them. This action can take place as deep below water level as surface water is carried by syphonic or artesian circulation, because the oxygen it carries in solution will not be consumed until it reacts with some reducing agent, such as a sulphide. Moreover, the formation of acid and solution of limestone in this way is not confined to the immediate vicinity of the sulphide. Oxidation of pyrite, for example, results in formation of acid in several successive stages, each taking place as more oxygen becomes available, as by the accession of fresh water into the circulation at some place beyond the sulphides. When the acid thus formed attacks the limestone, CO, is liberated and the ultimate effect of the complete oxidation of one unit of pyrite will be the removal of six times its volume of limestone as the sulphate and bicarbonate, both of which are relatively soluble. The reaction may be continued or renewed along a water course far from the site of the sulphides, where the small electric potential produced by contact with the limestone helped to start the reaction. Mr. Stuart refers2 0 caves in the old mining area in the block of Eldorado limestone southwest of the Ruby Hill fault at Eureka, Nev., and to the cavities encountered in drillholes in the downthrown block on the other side of the fault. Although he interprets these cavities as evidence that this formation was sufficiently isotropic (evenly porous and permeable) to give reliable results by the method he describes, they may, in fact, be entirely local conditions. There is reason to think they were probably formed

Jan 1, 1956

By J. A. Putnam, A. D. K. Laird

In laboratory research on the behavior of oil, gas and water in porous materials, no direct method has been devised to measure saturation without disturbing the flow. Indirect methods involving various forms of radiation have been developed for measuring one or two components. The X-ray absorption method for two components has been described previously1-3. The possibility of three component measurement has also been mentioned1. Since two component measurement still requires considerable care to insure accuracy, the fact that three components can be measured satisfactorily is not generally appreciated. The fraction of the energy of an X-ray beam of one wavelength transmitted through a material is given by the transmission factor. in which 1 is the beam's path length through the fluid. p is the fluid density, and 1,. is its mass absorption coefficient. Eq. 1 implies that all parts of the beam pass through equal amounts of the fluid. Practical applications are, therefore, limited to systems in which the fluid is distributed so that I varies negligibly over the cross-section of the beam. Typical variations of the transmission factor with X-ray tube potential arc shown in Fig. 2 from which experimental points have been omitted for clarity. The X-ray absorption of low pressure gases in a core is practically zero so it cannot he distinguished from that a vacuum by instruments that will differentiate between liquids. The transmission factor of a gas in a core is. therefore, unity. Consequently, the saturation of only one gaseous component can be found. If two fluids completely fill a core, their two saturations add to unity and, therefore, only one value of the transmission factor, T, is needed to determine both of them. When two liquids do not completely fill the core, their saturations do not add to unity and transmission factors at two wavelengths must be measured. At one of these wavelengths, 7 for one liquid must be different from T or the other liquid. The change of T for one liquid us the wavelength is changed between the two values must be different from the corresponding change of T in the other liquid. The two values of fluid saturation will also give that of the gas because the three saturations must add to unity. In Fig. 2 it can be seen that there are many large differences of T between various oil solutions and water solutions at any one potential, and between potentials for any one solution. Consequently, conditions for optimum accuracy of measurement of the saturations of a gas and two liquids can be chosen. Once the operating potentials have been selected, however. it is more convenient to cross plot the data from Fig. 2 on transmission factor-solution concentration coordinates for the chosen potentials, as shown in Fig. 3. Fig. 3 was used to plan the experimental procedure for Core N-38-1. Since the voltage control at 45 kv was good, the slopes of the curves in Fig. 2 at this potential would cause little error. At low potentials, however, the voltage control was not good, so 33 kv was chosen because the small slopes of the curves made voltage control less critical. The lowest strength beam that could be measured reasonably at 33 kv corresponded to a minimum T factor of 0.385. Fig. 3 shows that both 4.80 weight per cent of cadmium chloride in water and 24.0 per cent of iodobenzene in crystal oil had this T value, and, consequently, were indistinguishable to the X-rays at 33 kv. Thus, at 33 kv, the liquid saturation was given by the same curve regardless of the relative amounts of oil and water solutions present. This simple calibration curve from which the gas and liquid saturation can be read, is shown in Fig. 4. Fig. 3 also shows that at 45 kv, T for the aqueous solution is 0.610. and that T for the oil solution is 0.220. These values were transferred to Fig. 4 to give the triangular calibration plot from which the brine and oil saturations can be found, after the gas saturation has been determined at 33 kv.