Search Documents

By Jim F. Lemons

INTRODUCTION A nickel doesn't buy much anymore. That's even true in the cost of recovering nickel -- the commodity. A 5[C] per pound (11 [c] per kilogram) increase in the nickel price won't cover a 10-percent increase in fuel costs for processing laterite ores, nor will it cover a 10- percent increase in wages for recovering nickel from a sulphide ore. It won't even cover a 5- percent increase in the capital cost necessary to mine and process ocean nodules. The basis for this statement and a quantitative analysis of the variations in costs to recover nickel from different types of nickel ores will be discussed in this paper. During the early part of the 1970's, the interest in nickel and its potential development was shifting from Canada to the Pacific Basin area. Canadian growth rate was slowing and each additional increase in nickel capacity was very expensive (Argall, G.O., 1970). Laterite ores were attractive to developers since they were easy to mine at a low labor cost, and technologies were being developed that would allow the recovery of nickel in marketable forms (Mohide, T.P., Warden, C.L., Mason, J.D., 1977). During the last decade, new laterite production was achieved in the Philippines and Botswana, and a significant increase in production from Indonesia and New Caledonia occurred. However, recent reports on nickel identify numerous problems plaguing the industry, i.e., high energy costs that are forcing shutdowns (INCO, 1980), (Mohide, T.P., Warden, C.L., Mason, J.D., 1977), high Canadian sulphide mining labor costs (Anon., 1976), and rapid inflation of nickel capital costs (Anon., 1981b). No definitive study has been made to determine how sensitive the total cost of production is to rising energy, labor, or capital costs, or to identify to what extent increased byproduct revenues could be used to offset these production costs. The purpose of this paper is to quantify the effects of increases in energy, labor, capital costs, and by-product credits on the future cost of production from nickel reserves and/or resources. METHODOLOGY OF ANALYSIS In order to evaluate the sensitivity of nickel production costs to changes in energy, labor, and capital costs, and in byproduct revenues, an analysis was made of existing and proposed nickel operations, their costs, and their sensitivity to change. The data for these analyses were obtained from numerous sources including international govern¬ment and university publications, professional journals, company reports, private communications, U.S. Bureau of Mines contracts, and estimates by Bureau of Mines personnel. These data were collected, in part, as an ongoing effort of the U.S. Bureau of Mines Minerals Availability System (MAS) to systematically measure and classify identified mineral resources according to their respective extraction technologies, economics, and commercial availability. The MAS Program is currently evaluating the present and potential availability of nickel to the United States in relation to mining, beneficiation, smelting, refining, leaching, transportation, infrastructure, environment, land use, labor, productivity, technology efficiencies, operating capacities, deposit life, and political factors. As a summary of this data, the following briefly describes nickel ore types as each relates to energy, labor, capital, and byproducts. Sulphide Operations Nickel is currently available from sulphide deposits. Roughly 55 percent of the current world nickel production in market economy countries is from sulphide ores, although only about 20 percent of the known land-based nickel reserves and/or resources are sulphides (INCO, 1981). In 1979, the Western World sulphide reserves were estimated at about 9.2 million metric tons of nickel (Little, A.D., 1979). Sulphide ores are typically mined underground, thus resulting in high mining costs; however, these ores can often be upgraded by flotation prior to final nickel recovery and require about one-third of the energy required to recover nickel from laterites (Anon., 1981c). In addition, nickel in sulphide ores may be associated with economically recoverable byproducts, which include copper, cobalt, gold, silver, and other precious metals. Laterite Operations Forty-five percent of current nickel production is from laterite deposits. Laterite deposits account for 80 percent of the known land-based nickel reserves and/or resources (INCO, 1981). In 1979, the Western World laterite reserves were estimated at over 35 million metric tons of nickel (Little, A.D., 1979). Nickeliferrous laterites are residual soils formed by weathering, typically under tropical or near tropical conditions. They can be easily mined by open-cut methods, but generally cannot be beneficiated; thus, recovery of nickel must entail processing of the total mined ore. Usually, these ores have high moisture content (20 to 30 percent by weight) that result in additional fuel costs to dry the ore. Nickel silicates, garnierites, are, processed by pyrometallurgical methods; limonite nickel oxides are normally leached. Byproduct cobalt is not recovered from most ferronickel operations, and is only recovered to a limited extent from many leach operations.

Jan 1, 1982

By Paul E. Rosten

Introduction This papers describes some of the latest improvements that have been incorporated or planned by the Cleveland-Cliffs Iron Co. to reduce operating costs and improve pellet quality. The Cleveland-Cliffs Iron Co. operates and manages mining, beneficiation, and pelletizing operations in Michigan, Canada, and western Australia. This paper deals with the grate-kiln pelletizing operations at Republic, Humboldt, Tilden, Empire, and Pioneer in Michigan, and the Adams and Sherman in Ontario, Canada. Table I characterizes each operation in regard to location, ore type, pellet capacity and date that pellets were first produced. All of the operations with the exception of Pioneer and Tilden, utilize downdraft-two-pass grate cycles of drying followed by preheating. Pioneer utilizes an all-downdraft, three-pass grate cycle which consists of three drying zones followed by the preheat zone. The Pioneer and Tilden cycles have been described previously (Lindroos and Koski, 1966; Villar and Dawe, 1975; Koski, 1977). Tilden utilizes a three-pass grate cycle with a stage of updraft drying, followed by two downdraft drying stages. Recuperation systems which supply hot gases to a drying zone from second stage cooling were designed and fur¬nished for Tilden I. Tilden II will be identical. Empire IV will also be furnished with a recuperation system. The Adams grate¬kiln system was retrofitted with a recuperation system. This paper will summarize some of the efforts that are in effect or planned for grate-kiln pelletizing systems to: (1) reduce operating and maintenance costs, (2) reduce energy requirements, (3) improve product quality, and (4) meet environmental standards.

Jan 1, 1981

By AIME AIME

The following financial report of the Treasurer of the United Engineering Society is published for the information of members NEW YORK, February 15, 190S. To the Board of' Trustees, United Engineering Society I beg to submit herewith the report of the Treasurer as of December 31, 1907. Your attention is called to the fact that the resources and liabilities, receipts and disbursements statements cover all the financial transactions of the United Engineering Society from its organization up to December 31, 1907. The income and expenses of operating the building during the whole operating period from December 1 to December 31, 1907, somewhat in excess of twelve months, are given. Included in the expenses, amounting in all to $52,647.11, will be found an item entitled "Building Equipment (construction account)." The expenditures under this item were not made for the operating expenses of the building, they represent a construction account, properly speaking, covering expenditures for furnishings and equipment of the building. The Founders' Agreement specifically provides for this class of expenditure under the provision that the Founder Societies shall each be liable for a charge not to exceed $200,000 of principal, which shall include the land and building completed and ready for occupancy, together with the " furnishings, equipment and personal property therein." Certain details of equipment are yet to be supplied, and it. is proposed in the near future to call upon the Founder Societies for an assessment on their respective land and building funds to cover this item of building equipment. Such action would enable the item of $10,039.85 to be transferred to the income account and reduce correspondingly the assessment

Mar 1, 1908

By E. A. Anderson, C. W. Siller, Gerald Edmunds

In the pressurc die-casting of zinc alloys it is customary to force the molten alloy under high pressure into a permanent steel die by means of a plunger moving in a bushing that has a clearance on the diameter of the order of 0.002 in. Successful operation of the plunger type of machine requires the presence in the zinc alloy of certain percentages of aluminum. Without these aluminum additions, the normal reaction of molten zinc on ferrous materials causes sticking of the plunger arid a complcte shutdown of the equipment. All of the zinc alloys used for pressure dir-rnsting today contain approximately 4 per cent of aLUminum, which is more than suffieient to make plunger opcration feasible. The clearancc bet,ween the plunger and its bushing is an important matter. As the space bccomes larger, there is a loss in effective metal pressure. Ordinary gray cast iron served fairly well and is still uscd in some machines. However, the rate at which the plunger c1earance. increases with this material is considered by many to be far too great. There is, therefore, a serious interest in finding new matcrinls more: capable of retaining the desired clearance during long periods of use. Today marly die casters are using special materials for plungers and bushings selected by the somewhat expensive and time-consuming test of actual experience. An analysis of the problem reveals two possible end points of plunger. operation: (1) the building up of zinc-alloy plunger-material reaction products in sufficient bulk to cause sticking and (2) rapid solution, wear or erosion, all of which will increase the clearance to an undesirable extent. If neither of these takes place, the pluriger will operatc for a long time, of course.. The authors have developed a laboratory apparat,us in which the action of a plunger moving in a bushing immersed in molten zinc alloy could be simulated closely. Such a machine made possible a more rapid and less expensive survey of the available construction materials and an analysis of the specific alloying reactions taking place in the clearance area.

Jan 1, 1940

By Gerald Edmunds, C. W. Siller, E. A. Anderson

In the pressurc die-casting of zinc alloys it is customary to force the molten alloy under high pressure into a permanent steel die by means of a plunger moving in a bushing that has a clearance on the diameter of the order of 0.002 in. Successful operation of the plunger type of machine requires the presence in the zinc alloy of certain percentages of aluminum. Without these aluminum additions, the normal reaction of molten zinc on ferrous materials causes sticking of the plunger arid a complcte shutdown of the equipment. All of the zinc alloys used for pressure dir-rnsting today contain approximately 4 per cent of aLUminum, which is more than suffieient to make plunger opcration feasible. The clearancc bet,ween the plunger and its bushing is an important matter. As the space bccomes larger, there is a loss in effective metal pressure. Ordinary gray cast iron served fairly well and is still uscd in some machines. However, the rate at which the plunger c1earance. increases with this material is considered by many to be far too great. There is, therefore, a serious interest in finding new matcrinls more: capable of retaining the desired clearance during long periods of use. Today marly die casters are using special materials for plungers and bushings selected by the somewhat expensive and time-consuming test of actual experience. An analysis of the problem reveals two possible end points of plunger. operation: (1) the building up of zinc-alloy plunger-material reaction products in sufficient bulk to cause sticking and (2) rapid solution, wear or erosion, all of which will increase the clearance to an undesirable extent. If neither of these takes place, the pluriger will operatc for a long time, of course.. The authors have developed a laboratory apparat,us in which the action of a plunger moving in a bushing immersed in molten zinc alloy could be simulated closely. Such a machine made possible a more rapid and less expensive survey of the available construction materials and an analysis of the specific alloying reactions taking place in the clearance area.

Jan 1, 1940

By Sydney H. Ball

AMERICAN consumption of industrial diamonds has increased five fold in the past 25 years and today accounts for 15 to 20 percent of the world's sale of rough diamonds. In another decade the value of industrial diamonds sold may well equal or exceed that of gemstones. It is generally understood that industrial diamonds are one of the strategic minerals being stocked by the Government in the present crisis to ensure rapid and efficient armament production. Diamond die making is a trade largely confined to artisans in Switzerland and in certain parts of France. Today, in addition to turning out pilots, we should train expert artisans in diamond die making, for thousands of miles of tremendously small-gauge wire will be needed to make the instruments by which the efficiency and safety of these pilots is assisted.

Jan 1, 1941

[†AARONSON, ALFRED E., Vice-Pres., Mid-Co. Petroleum Co., Mid-Co. Bldg. Tulsa, Okla. '18 ABADIE, EMILE R., Min. Engr Address wanted. '76 ¦ABADILLA, QUIRICO A. Geol. Dept. Cia. Mexicans de Petroleo "El Aguila," S. A., Edifico "El Aguila," Esq., Calles Aurora y Comercio,] [ ]

Jan 1, 1925

By E. G. Dahlgren, Dan O. Howard

THE West Edmond oil field, which covers parts of Oklahoma, Canadian, Kingfisher, and Logan Counties in the State of Oklahoma, is in geographical extent the largest single oil field found in the state. At the present time, its area of 26,800 acres is almost twice as large as the Oklahoma City field, which hitherto was the state's largest field. Many authorities believe that the West Edmond field is the most important oil pool found in the United States since Pearl Harbor. The discovery of the field without the help of geological, geophysical, or other recognized technical information, the fact that the oil and gas accumulated in a stratigraphic or wedge-type trap, and the rapid development of the productive area under wartime conditions are some of the interesting features of the field. The West Edmond field lies west of the Oklahoma City, Britton, and Edmond fields. The field is in an area that has been considered on the west flank of the Granite Ridge line of folding, on which a number of Central Oklahoma's most important oil fields are located. Over a period of years, especially since the discovery of the new pools such as Oklahoma City, Edmond, Britton, and Crescent, the general area of the West Edmond field has been explored intensively by geological and geophysical methods. This led at times to the drilling of a few dry Wilcox sand tests.

Jan 1, 1945

By E. E. Donath

Application of the coal hydrogenation process for the production of chemicals is described. It has been estimated that a plant to produce 31,090 bbl per day of chemicals and fuels would cost $326,- 000,000. These products would consist of 6.1 pct by weight tar acids, 50.8 pct aroma tics, 16.4 pct LPG, and 26.7 pct gasoline. THE coal hydrogenation process is well known as a means for the production of liquid fuels from coal. In this paper the possibilities of the coal hydrogenation process as a source of chemical raw materials will be discussed. The recovery of chemicals from coal hydrogenation products necessitates some modifications and additions to the equipment used for the production of fuels. The conversion of coal into liquid fuels such as gasoline requires two steps: liquid phase and vapor phase hydrogenation. Intermediate oils obtained in the liquid phase contain oxygen and nitrogen compounds, especially aromatic compounds, since the coal itself is composed mainly of cyclic compounds. These oils are the raw material for the separation of high molecular weight aro-matics and of tar acids and tar bases. The relative amounts of heavy and middle oil—boiling above and below, e.g., 325°C—can be influenced by temperature, residence time, and catalyst of the liquid phase hydrogenation. In the vapor phase hydrogenation a solid bed catalyst is used to convert the intermediate oil from the liquid phase operation into hydrocarbons of the gasoline boiling range. Essentially pure hydrocarbons with a low content of sulphur, oxygen, nitrogen, and olefines are obtained. Depending mainly on the catalyst, the high ring compound content of the liquid phase oil can be preserved and gasoline rich in aromatics obtained. However, with other catalysts, these ring compounds can be split into gasoline with a high content of isoparaffins.' Again, depending on the operating conditions, products of varying boiling range can be obtained. Selection of catalyst and operating conditions therefore makes possible the production of different grades of motor fuel and also variations in the relative amounts of benzene, toluene, and xylene when aromatic hydrocarbons are produced. The schematic flowsheet, Fig. 1, shows the main steps of the coal hydrogenation process, and the product streams used for the recovery of chemicals are indicated. In the liquid phase hydrogenation stage, coal is made into a paste with recycle heavy oil. The coal paste is mixed with hydrogen and preheated at a pressure of 300 to 700 atm in heat exchangers and preheaters. The coal paste and hydrogen enter high pressure converters where the liquefaction of coal, conversion of the high boiling liquid materials initially obtained, into intermediate oils is performed at a temperature around 470°C. The reaction products enter the hot catchpot in which lower boiling oil vapors are separated from the residue containing unreacted coal, ash, and heavy oil. This residue, usually called H.O.L.D. (heavy oil let down), is processed to separate solid and liquid material. By thermal treatment of the residue, e.g., a coking process, distillate oil is obtained, which can be recycled as part of the pasting oil. This stream is rich in polynuclear aromatics and can be, and has been, used for the recovery of such material. The oil vapors and hydrogen from the hot catchpot are cooled in heat exchangers and a cooler, and the condensed oil is separated from the recycle hy-

Jan 1, 1953

By E. E. Donath

Application of the coal hydrogenation process for the production of chemicals is described. It has been estimated that a plant to produce 31,090 bbl per day of chemicals and fuels would cost $326,- 000,000. These products would consist of 6.1 pct by weight tar acids, 50.8 pct aroma tics, 16.4 pct LPG, and 26.7 pct gasoline. THE coal hydrogenation process is well known as a means for the production of liquid fuels from coal. In this paper the possibilities of the coal hydrogenation process as a source of chemical raw materials will be discussed. The recovery of chemicals from coal hydrogenation products necessitates some modifications and additions to the equipment used for the production of fuels. The conversion of coal into liquid fuels such as gasoline requires two steps: liquid phase and vapor phase hydrogenation. Intermediate oils obtained in the liquid phase contain oxygen and nitrogen compounds, especially aromatic compounds, since the coal itself is composed mainly of cyclic compounds. These oils are the raw material for the separation of high molecular weight aro-matics and of tar acids and tar bases. The relative amounts of heavy and middle oil—boiling above and below, e.g., 325°C—can be influenced by temperature, residence time, and catalyst of the liquid phase hydrogenation. In the vapor phase hydrogenation a solid bed catalyst is used to convert the intermediate oil from the liquid phase operation into hydrocarbons of the gasoline boiling range. Essentially pure hydrocarbons with a low content of sulphur, oxygen, nitrogen, and olefines are obtained. Depending mainly on the catalyst, the high ring compound content of the liquid phase oil can be preserved and gasoline rich in aromatics obtained. However, with other catalysts, these ring compounds can be split into gasoline with a high content of isoparaffins.' Again, depending on the operating conditions, products of varying boiling range can be obtained. Selection of catalyst and operating conditions therefore makes possible the production of different grades of motor fuel and also variations in the relative amounts of benzene, toluene, and xylene when aromatic hydrocarbons are produced. The schematic flowsheet, Fig. 1, shows the main steps of the coal hydrogenation process, and the product streams used for the recovery of chemicals are indicated. In the liquid phase hydrogenation stage, coal is made into a paste with recycle heavy oil. The coal paste is mixed with hydrogen and preheated at a pressure of 300 to 700 atm in heat exchangers and preheaters. The coal paste and hydrogen enter high pressure converters where the liquefaction of coal, conversion of the high boiling liquid materials initially obtained, into intermediate oils is performed at a temperature around 470°C. The reaction products enter the hot catchpot in which lower boiling oil vapors are separated from the residue containing unreacted coal, ash, and heavy oil. This residue, usually called H.O.L.D. (heavy oil let down), is processed to separate solid and liquid material. By thermal treatment of the residue, e.g., a coking process, distillate oil is obtained, which can be recycled as part of the pasting oil. This stream is rich in polynuclear aromatics and can be, and has been, used for the recovery of such material. The oil vapors and hydrogen from the hot catchpot are cooled in heat exchangers and a cooler, and the condensed oil is separated from the recycle hy-

Jan 1, 1953

By W. R. Bendy

GRINDING is a large and costly part of Portland cement manufacture. Prior to clinkering in the rotary kiln, raw materials are ground to a fineness of 80 to 90 pct passing 200 mesh. Then, after burning and cooling, the resulting clinker is ground to about 92 pct passing 325 mesh. In the cement industry the most favored method of grinding has always been by impact and attrition of a ball charge in a rotating mill. Other types of mills, in which materials are ground between die rings and rollers, or between die rings and large balls, are sometimes used for single-stage grinding and often for preliminary grinding followed by grinding in ball-type mills. Their efficiency is usually high, but maintenance and repair costs are high also, and the ball-type mill continues to be the most widely used.

Jan 10, 1957

By Albert E. Wiggin, Frederick Laist

Page I. Introduction............................470 II. The Sources and Amount of Slime................470 II. The Composition of the Slime..................471 IV. The Experimental Development of the .Anaconda Slime Plant.. 471 1. The Great Falls Slime Plant and Experimental Work......471 2. The Experimental Work Done at Anaconda..........473 (a) SlimeThickening Devices.............. 474 (b) SlimeConcentrators................. 475 (c) Dewatering the Slime Plant Concentrate......... (d) The Use of Chemicals to Accelerate the Settlement of Slime........................ 478 (e) The Effect of Temperature upon the Settlement of Slime 478 V. A Description of the Anaconda Slime Plant........... 479 1. A Diagrammatic Flow Sheet of Plant............. 480 2. The Slime-Thickening Division................ 480 3. The Concentrating Division.................. 481 4. The Concentrate-Dewatering Division............. 483 5. General Data........................ 484 I. IntRoduction The new slime-concentrating plant at the Washoe Reduction Works, Anaconda, was put into operation during March, 1914. This plant, which has a capacity of 26,000,000 gal. of slime pulp carrying 2,500 tons of solid matter per day, consists of Dorr thickeners and Anaconda multiple-deck slime concentrators. This plant is the culmination of a great deal of experimental work extending over a considerable period of time, which , work will be described briefly in the following pages. II. The Sources and Amount of Slime Up to the beginning of this year, the ore from the Anaconda company's mines in Butte, Mont., has been concentrated both at the Great Falls

Jan 1, 1915

By J. C. Bradley

THE relation of annealing temperature to conductivity of copper wire has been determined. Conductivity hard was 98.26 per cent. After a 10-min. heating at 200°C. it was 98.69. By annealing 10 min. at 300° C. a large increase, to 100.93, occurred. Maximum conductivity, 101.15, was attained after a 500° C. anneal; thereafter it decreased to 100.53 after a 950° C. anneal. If copper is gassed the decrease is much more than this. Materials and Methods The work was done on high grade electrolytic copper, 99.942 per cent. copper plus silver, silver 0.0008 per cent. It was hot-rolled to >/4 in., then cold drawn to 0.080 in. The wire was cut into 25 5-ft. lengths and numbered 1 to 25 as cut. Four samples were tested hard. The others were wound into 5-in. diameter coils. For the 100° C. heating a coil was put into water, the water brought to boiling, and the wire kept at this temperature for 10 min. For the higher temperatures the coils were placed in envelopes of sheet copper, a little water added, and the envelopes sealed by folding over the edges twice, and hammering them together. This kept the air out very well. The envelope and wire 'were brought to the desired temperature; this was maintained for 10 min., then the whole was water-quenched.

Jan 1, 1927

Thomas H. Beddall, so we are informed by Major J. B. Carlock, has been promoted and is now Adjutant of the 1st Battalion, 1st Gas Regi¬ ment. He was awarded, last summer, the Croix de Guerre. R. A. Bull. See letter in Proceedings of Milwaukee Meeting. Captain Stanley C. Bullock's record since entering the service is given as follows in a letter recently received from Mrs. Bullock: Resigned position of mine manager in Chile in November, 1915, to return to England to obtain commission in Royal Engineers. Joined Officers' Training Corps, Dec. 20, 1915. Commission gazetted, Jan. 27, 1916, 2d Lieut., R. E. Landed in France, Feb. 6, 1916. Posted to 179th Tunnelling Co., R. E. Took part in following battles: Somme, 1916; Ypres;1917; Arras, 1917; Somme, March and July, 1917; Messines, 1917. Gazetted: Acting Captain, July 11, 1916; Temp.-Lieutenant, Oct. 26, 1916; Captain, Sept. 29, 1918. Awarded Military Cross, Jan. 1, 1918, for conspicuous bravery and devotion to duty under a heavy enemy gas bombardment, when, by his example and perseverance in spite of every difficulty and obstacle, mining work was successfully completed which was vital for the success of the operations. The Cross was presented to Capt. Bullock by the King, on Sept. 25, 1918. First Lieut. J. J. Cadot, in a letter sent to Mr. H. `V. Hardinge from France, says he has been at the "Front." He also mentions that the Boche "is a good sprinter."

Jan 12, 1918

Minnesota J. A. MACKILLICAN, Chairman W. W. J. CROZE, Vice-chairman T. L. JOSEPH, Vice-chairman S. E. ATKINS, Secretary-Treasurer, Alworth Bldg., Duluth, Minn. Montana MURL H. GIDEL, Chairman ALBERT E. WIGGIN, Vice-chairman ALEXANDER M. MUDONALD, Secretary-Treasurer, 101 W. Granite St. Butte, Mont. GEORGE G. GRISWOLD FRANCIS A. THOMSON

Jan 1, 1929

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 Stanley M. Moos, Richard Addison

Introduction The Pueblo Viejo gold-silver mine, located in the Dominican Republic, started production in early 1974 processing ores averaging 4 g/t gold and 20 g/t silver at a rate of 7.25 kt/d. The ore milled is a silicified siltstone with average work index of about 8 that occurs as an extensive oxide capping of a primary sulfide ore body. The sulfide ores are refractory to conventional treatment process and extensive research work is now in progress to develop a treatment process for them. The ore deposit has a long history, having been mined by the indigenous Arawak Indians for some time in the early sixteenth century prior to the arrival of the Spanish, and then by the Spaniards. In the early 1950s, Italian engineers attempted to process the sulfide ores. Mining by the Indians and Spanish was abandoned because of low grade and little coarse gold in the oxide ores and by the Italians because of the refractory nature of the sulfide ore. In 1969, Rosario Resources geologists discovered that there existed sufficient reserves of oxide ore for a viable mining operation and the plant was designed, built, and brought into production.

Jan 1, 1981

By R. F. Steigerwald

The effects of heat transfer on the corrosion behavior of type 304 stainless steel in boiling water have been studied. Heat transfer conditions increase the tendencies of the stainless steel toward stress-corrosion mucking when the water is contaminated with Cl-. Surface preparation is the most important variable in determining the severity of the stress-corrosion problem in water with a given Cl- content. Heat treatment, chemical cleaning, and degree of wet film boiling also affect the corrosion of stainless steels used as heat transfer surfaces in boiling water. An up-paratus for corrosion testing under controlled heat transfer conditions is described. THE principal objective of this investigation was to study the corrosion behavior of AISI Type 304 stainless steel in boiling high-purity water under conditions of heat transfer. The principal variables in the study were: a) boiling conditions: limited boil, agitated boil; b) metallurgical structure: annealed or sensitized; c) surface condition: rolled, pickled, or ground. The results of the study should elucidate the role of heat transfer in the corrosion of stainless steel in boiling high-purity water and provide a base line from which to assess the severity of this type of corrosion. Although there has been an investigation of the effect of heat transfer on the corrosion behavior of stainless steels in alkaline waters,' work on the corrosion of stainless steels under heat transfer has been largely confined to various acid solutions.'-4 Furthermore, the study of the corrosion of stainless steels in high-purity water has been generally restricted to auto-clave and instream testing in superheated (e.g., 300°C) water and steam.5'6 Cooling water problems led to this study of the corrosion behavior of type 304 stainless steel in high-purity water at its atmospheric boiling point. In addition to the effects of heat transfer, this study also considered the influences of the type of boiling,7 metallurgical structure, and surface condition on the corrosion behavior of stainless steel in high-purity water. Two boiling conditions were investigated in this study: a) limiting boiling, i.e., when the heat-transfer surface had just reached the boiling point and boiling nucleated randomly over the specimen surface and b) agitated boiling, i.e., when a mild degree of superheat had been achieved on the specimen surface and boiling occurred generally over the specimen surface. Both boiling conditions are broadly classified as wet-film boiling. Originally, this program included the study of a third type of boiling, dry-film conditions. At dry-film boiling the temperature of the heat transfer surface is high enough so that it is covered with a continuous film of steam. Experimental difficulties made it impossible to study this kind of boiling with the available apparatus. Since surface condition affects heat transfer rates, three typical surfaces were chosen for study: a) as-rolled, the 2B finish received from the supplier, b) as-pickled, 30 min in 8 pct HNO3-1 pct HF, and c) as-ground on 120 grit paper. In order to evaluate the effect of improper heat treatment or welding on hot wall corrosion, both annealed and sensitized mi-crostructure were included in this study. EXPERIMENTAL Test Apparatus. The particular problems of interest in this investigation required a knowledge of the thermal gradient through the test specimen. From this gradient, the heat flux to the surface and the surface temperature could be determined. In order to satisfy this need, an apparatus similar to the boiling-disk apparatus of Fisher and whitney2 was designed. The solution is contained in a thermally-insulated, steel pipe lined with TEFLON resin. A stainless steel _______;________________________________________

Jan 1, 1970

CONTENTS PAGE. WHITE, DAVID.-Environmental Conditions of Deposition of Coal. Discussed by E. C. Jeffrey, George H. Ashley, Reinhardt Thiessen, S. W. Parr, David B. Reger, Wilbur A. Nelson, James F. Kemp, E. S. Moore, Homer G. Turner, David White, A. C. Noé, W. A. I. M. van Waterschoot van der Gracht 2 THIESSEN, REINHARDT.-The Constitution of Coal. Discussed by Edward C. Jeffrey, Reinhardt Thiessen, Ralph H. Sweetser, David White 12 TURNER, HOMER G.-Microscopical Structure of Anthracite. Discussed by E. S. Moore, Edward C. Jeffrey, Reinhardt Thiessen, H. J. Rose, James F. Kemp, David White, Clarence A. Seyler, A. C. Noé 14 JEFFREY, EDWARD C.-Coal in Relation to Coke. Discussed by H. J. Rose, David White, E. S. Sinkinson, S. W. Parr, James F. Kemp, Edward C. Jeffrey, Reinhardt Thiessen, Chas. R. Fettke 17 FRANCIS, W., and WHEELER, R. V.-The Resolution of Coal by Oxidation. Discussed by Edward C. Jeffrey, S. W. Parr, E. S. Sinkinson, Reinhardt Thiessen, David White 23 TIDESWELL, F. V., and WHEELER, R. V.-The Constitution of Coal. Discussed by David White, A. C. Fieldner 24 JOLLY, J., and WHEELER, R. V.-Organic Sulfur Compounds in Coal. Discussed by S. W. Parr 25 SINNATT, F. S.-Selective Combustion in Coal. Discussed by J. D. Davis, A. C. Fieldner, Geo. S. Rice, W. M. Grant, H. J. Rose, S. W. Parr, David White 25 COBB, JOHN W.-Nitrogenous Constituents of Coal. Discussed by S. W. Parr, H. J. Rose, Reinhardt Thiessen 28 PARR, S. W., and HOBART, F. B.-Coal and Oxygen. Discussed by J. D. Davis, W. T. Thorm, Jr., S. W. Parr, H. J. Rose, A. C. Fieldner, F. F. Jorgensen, David White, W. M. Grant 30 FIELDNER, A. C., and DAVIS, J. D.-Modern Views of Chemistry of Coals of Different Ranks as Conglomerates. Discussed by S. W. Parr, David White, Reinhardt Thiessen, A. C. Fieldner, Clarence A. Seyler 32 EBY, J. BRIAN.-Contact Metamorphism of Some Colorado Coals. Discussed by Geo. C. McFarlane, W. T. Thom, Jr 35 WHITE, DAVID.-Progressive Regional Carbonization of Coals. Discussed by A. C. Fieldner, Homer G. Turner, W. A. J. M. van Waterschoot van der Gracht, A. C. Noé 37 THOM, W. T., JR.-Moisture as a Component of the Volatile Matter of Coal. Discussed by A. C. Fieldner, S. W. Parr, Clarence A. Seyler, W. T. Thom, Jr., R. D. Hall 39

Jan 7, 1925

By Edward L. Beutner, Robert M. Crump

Benson Mines low-grade iron ore reserve is a replacement deposit within the Grenville gneisses of the Adirondacks. The average grade of the crude ore is about 23 per cent iron. The iron minerals are principally magnetite and hematite disseminated throughout the gneisses as discrete grains about 1 mm in size. Both the ores that are beneficiated by magnetic means and the non-magnetic ores that are treated by a gravity method of concentration are found in stratigraphically different positions but are mined from one open pit, which is about 2.5 miles long and 800 feet wide and are treated separately. The gneisses are described and named according to the distinctive mineralogy of each. Recognition of the gneissic types permits the interpretation of the structure as a northward-plunging syncline overturned to the west. A large subsidiary anticline-syncline complex occurs on the east limb of the major syncline. Iron minerals in sufficient quantity to be considered ore are confined to areas where the footwall rock has been overturned to become the hanging wall.

Jan 1, 1968