Search Documents

By H. W. Hitzrot, R. A. Limons, L. V. Fegan

The authors have developed and tested a new method for measuring pellet-bed temperatures in the traveling-grate or the shaft furnace. This method-using silver-palladium alloy wires as indicators-is less costly and less time-consuming than existing methods. Silver palladium wires, having specific melting points in the 2000° to 2500°F range, are enclosed in ceramic capsules. Each capsule is placed in a nichrome wire basket filled with a sample of green pellets, the baskets being the means for recovering the capsule after firing. After the encapsulated wires have been exposed to the firing cycle, the alloy wires are examined to determine the maximum temperatures attained by the pellet sample. This gives accurate, rapid determinations of maximum temperatures attained during pellet induration in either the traveling-grate or shaft furnace.

Jan 6, 1965

By A. English, M. J. Greaves

This paper is a discussion of pelletizing systems developed over the last 15 to 20 years for the agglomeration of fine iron ore concentrates. Five different pelletizing systems are now in commercial use in the U.S., and for the purposes of comparison, estimated operating costs and capital costs for the construction of four of them are included. Capacities of existing commercial plants are examined, together with the anticipated capabilities of plants presently being built or projected. In just 21 years, the art of pelletizing iron ore concentrates has reached maturity with mastery of the separation of finely divided concentrates from low-grade iron ores and their agglomeration into pellets containing about 65% iron. This accomplishment has firmly established an improved feed for the blast furnace, with resulting benefits in faster reduction of burdens and greater economy of operation. The present production capacity of pelletizing facilities in the U.S. is about 20 million tons annually, and it is expected to double by 1970. The rapid expansion of pelletizing in the U. S. has been closely observed in European countries, notably in Sweden and Germany, where pioneer agglomerating techniques were developed early in this century. PELLETIZING PLANTS AND PROCESSES Twelve commercial pelletizing plants are presently in operation in the U. S. and Canada. An equal number are in various stages of engineering and construction, and many others are being considered. The pelletizing systems currently employed include shaft furnaces, horizontal grates using three different airflow arrangements, and grate kilns. The capacity of pelletizing operations in North America is shown in Table I. All of these plants are integrated with the mine, the ore-crushing facilities and the concentrating plant and are equipped with storage and loading-out facilities for the product. Normally, a pelletizing plant is composed of a shuttle conveyor above the receiving bins; balling equipment; a heat-hardening system including the necessary auxiliaries such as furnaces, burners and controls, ducts, fans, meters and instrumentation; fines recovery equipment; and product handling equipment. Also included are the necessary auxiliaries and utilities such as boilers or power plant; oil unloading and storage facilities; coal unloading storage, grinding and distribution facilities; and bentonite or other additive storage and distribution equipment. Shaft Furnaces: Vertical shaft furnaces used in this country are limited to the treatment of natural magnetite concentrates containing minor quantities of residual fluxing elements. Fig. 1 shows a perspective view of the shaft furnace with balling, feeding and pellet-handling equipment. An elevation of a shaft furnace is shown in Fig. 2. A commercial shaft furnace unit is about 45 ft in height with a 6 x 14-ft rectangular cross section and has a nominal production rate of approximately 50 gross tons of pellets per hour. The upper portion of the furnace shaft is constructed of fire brick as protection from the high process temperatures involved. The lower portion of the shaft is lined with abrasion-resistant brick to withstand erosion from the fired pellets. Rectangular-shaped, refractory-lined and insulated combustion chambers are situated on each side of the shaft furnace. Oil or gas is burned to produce high temperature gases which are forced into the furnace through ports located near the top of the combustion chambers. The shaft furnaces operate at a pressure of approximately 6 psi. Pellets are fed into the top of the furnace by a pantographic feeder designed to produce the desired pellet stockline. The furnace is kept filled at all times and pellets are fed and discharged from the furnace at the same rate. In early development, 10 to 12 lb of solid fuel was incorporated in the pellets. However, the main source of process heat is now derived from the combustion chamber gases. In some instances no solid fuel is used. The pellet movement in the shaft furnace is counter-current to the flow of gases. Ambient air is introduced through louvers at the lower end of the furnace, at about 6 psi, cooling the fired pellets and supplementing the heat of the high temperature gases from the combustion chamber ports. The zone of maximum temperature, located above the ports of the combus-

Jan 1, 1963

By J. L. Gillson

Andre Hubaux: In the writer's opinion, more stress should be put on field and microscope observations, as J. L. Gillson does. His discovery of relics of big labra-dorite feldspars from the Marcy anorthosite in all the other rocks is proof enough that previous field observations have been inadequate. The writer's field experience with anorthositie massifs is limited to the Egersund-Sogndal district in southern Norway; however, this is a very large and well exposed area. It seems to have so many points in common with the Adirondack region that a detailed comparison should be beneficial. This comparison was not possible 20 years ago, owing to the scarcity of geological data, at least for Norway. Both regions are now far better known—the Norway district because of the work of Professors Bugge and Barth 33-35 and especially because of the extensive field and microscopic research of P. Michot,30-35 who introduced me in the field to the problems of that region. In a particular unit of the Egersund district, a sodi-fication of the plagioclase, very similar to what Gillson calls "andesinization," has taken place. 12' The percentage of anorthite in the plagioclase has dropped from 42 to 43 pct in the original norite down to 27 pct, but never below that level. This metasomatical transformation is a part of a whole series of processes of mig-matitization which have produced, above the level of granitization, concentrations of Mg, Fe, and Ti and among them, patches and parallel bands of ilmenite and magnetite. Thus both regions present somewhat comparable features and the theories to explain them have several points in common. However, as there seem to be differences between some American conceptions and the views commonly accepted at the University of Liege, I would like to make some comments about J. L. Gill-son's article. The author speaks of the garnet as being an anti-stress mineral. However, garnet may be found in schists, where its helicitic texture, when present, demonstrates its formation during differential movement. Furthermore, the whole concept of stress and anti-

Jan 1, 1959

By Albert Sauveur

As THE years go by, names of distinguished metallurgists will be added to the list of Henry Marion Howe lecturers, and now and then an illustrious one, for to be chosen to deliver the Howe lecture will be, I do not hesitate to predict, a highly coveted honor. I pray, therefore, your indulgence, if I confess to a feeling of gratification in having been appointed the first of these lecturers. It does not follow, however, that I am losing all sense of proportion and that I have an exaggerated idea of the little I have been able to contribute to our knowledge of iron and steel. Indeed, I fully realize how small were my claims to so great a distinction. I realize, also, that those entrusted with the task of selecting a lecturer were actuated, in coming to a decision, by their knowledge of the long and intimate friendship that had existed between the leader we have lost and myself. For their generous impulse, I thank them from the bottom of my heart; and with becoming modesty, I take up my task as the first Henry Marion Howe lecturer. It would be pleasant and indeed most appropriate to devote this entire lecture to a eulogy of Henry Marion Howe and his work, but how short the time for so large an undertaking and how inadequate my qualifications! On Aug. 28, Sept. 4, 11, and 18, 1875, a series of articles appeared in the Engineering & Mining Journal entitled "What is Steel?" With one exception, these constitute the first professional paper of Henry Marion Howe. That was nearly fifty years ago, three years after graduating from Harvard University. He was then but twenty-seven years old and already his keenly inquisitive mind was actively at work. There is a touch of romance in this young metallurgist who, on entering his. scientific career, destined to be so brilliant and so fruitful, on the very threshold of it, seems to have selected as his motto "What is Steel?" Like a knight-errant of science, he started on his quest for an answer to that question, a quest which was to last forty-seven years and which death only brought to an end. And while thus engaged how many wonderful messages we received from him, each one bringing us nearer to the goal! How illuminating, inspiring and encouraging were those messages! How well-equipped he was to wrench from nature some of the secrets she so jealously guards! How broad his learning and how clear his

Jan 5, 1924

By Edwin Dudley Martin

DURING the past twelve years the iron and steel industry has made a major advance through the development of the continuous wide strip rolling mill. So far-reaching have been the results that not only has a better product been sold at a lower price but this improvement in quality has permitted manufacturers of products using steel to make important savings in the cost of fabrication. The net result has been a better product at lower cost to the consumer without reduction in either employment or of wages paid within the industry. That is why the iron and steel industry is proud of its attainment. Being a basic industry of strategic importance, such an advance in technology has had its effects on our internal economy, our standard of living, and our industrial power as a nation in both peace and wartime.

Jan 1, 1939

By R. H. Ogburn

THE GROUND now being worked by the Fairbanks Exploration Co., near Fairbanks, Alaska, has been known to be gold bearing since 1901. In the early days it was worked by drift mining and other small-scale methods. In 1922, Hammond started prospecting the gold-bearing ground and obtaining options on the properties desired. Two years later the present Fairbanks Exploration Co. started taking up the options, and preparing to exploit the ground. For the prospect drilling Keystone drills were used, with holes at the points of equilateral triangles 600 ft. apart. Holes were also put down more closely spaced to determine the limits of dredging ground. In the first drilling casing was used to the bottom of the holes, but in later work the casing was put down only to the bottom of the thawed ground, and the rest of the hole put down without casing. The gold content was determined by panning, each 2 ft. of depth being determined separately. Where no casing was used the size of the hole was determined by using water to measure its volume. The greatest concentration of gold occurs at or near bedrock. All the gold-bearing streams head in one big dome. Gold, however, is not found clear to the head of the creeks, the pay being first found some distance downstream from the head.

Jan 1, 1933

By C. R. Johnson, R. A. Greenkorn, L. K. Shallenbarger

This paper describes a study, based on core data, of the directional permeability of a sandstone reservoir. Directional air permeabilities are explained and correlated with lithology by the tensor theory of permeability, which is extended to the more general case of heterogeneous anisotzopic porous media. In this case, the permeability tensor is made up of two components: (I) anisotropy (variation around a point) which correlates with bedding, and (21 heterogeneity (variation from point-to-point) which correlates with grain size. INTRODUCTION Previous studies of directional permeabilityl.5-8 have concerned themselves only with anisotropy at a point, rather than with both point-to-point differences and local anisotropies. In this paper, we present the existing tensor theory of permeability for anisotropic porous media and then extend it to the more general case of heterogeneous anisotropic porous media. The laboratory measurements of directional permeability are explained in view of this extended theory and the data are discussed in terms of the lithologic factors that correlate with it. The results show what the heterogeneity and anisotropy of the reservoir element are, and that the directional permeability correlates with lithology. Data used in this paper are measurements of air permeability in eight directions, spaced at 45° intervals, on 142 2-in. vertical plugs from 30 cores. The core data are meaningful in terms of directional permeability because the cores were oriented to within 45O during drilling and coring.3 Although we initially thought that only 60 per cent of the core material was reliable, subsequent study showed that almost all of it was reliably oriented. After determining the air permeabilities, the data were reduced to three independent variables for each plug: the major and minor permeability axes, and the direction of the major axis. These were obtained by converting the permeability data to the reciprocal square root of permeability and fitting the transformed data with ellipses according to the tensor theory of permeability.8 The point-to-point areal variation of the minimum permeability axis is related to grain size. The direction of the permeability axes, where the major axis exceeds the minor axis by at least 5 per cent (measured variation is about 4 per cent), correlates with the bedding. The permeability tensor used in this study must be considered as the sum of a scalar and a tensor, with the scalar being the minor axis permeability as a function of position, and the tensor the directional effect, which is additive permeability over the minor axis. In this case, the point-to-point variation or heterogeneity (minor axis) is substantially larger than the variation at a point or anisotropy. It may be important that this separation of "directional permeabilities" be recognized when considering migration of fluids due to permeability variation. Local migration may be due to anisotropy and point-to-point migration may be due to heterogeneity, but the direction and magnitude of these may not be the same. Furthermore, in truly heterogeneous systems, one would expect that anisotropy would be the smaller of the two effects. THEORY TENSOR THEORY OF PERMEABILITY FOR ANISOTROPIC POROUS MEDIA8 Darcy's law for flow in porous media in its usual form is where qis the flow rate vector, k is the permeability, is the viscosity, is the vector differential operator, and P is the Pressure. Consider flow, q, through a unit area in the direction of the unit vector n from elementary flow tubes parallel

Jan 1, 1965

By Reinhardt Thiessen

During the last few years a type of coal called "splint coal" has been brought to the attention of the United States Bureau of Mines, through numerous inquiries concerning its nature. Until recent years it appears to have escaped general notice. The term "splint coal" is of long standing, but was thought to be merely another expression applied by the miner to coal having certain minor characteristics. When closely examined, however, these coals were found to form a marked and distinct type, with distinctive characteristics that cannot be mistaken. Because splint coals produce a hot cheerful flame, possess a clean blocklike nature, and have a high volatile content, they have lately become much valued for domestic, gas-producer and steaming purposes, and have attracted considerable attention. Mattkohle For many years we have heard from the Germans about Mattkohle and Streifenkohle, in contradistinction to Glanzkohle, but have not realized that they were of a different type from the coals with which we were most familiar. This type of coal was first brought to general notice by Muck, in 1881, who gave a good description of it.' Because this coal is often intercalated with thin sheets of brightly shining cod, Schondorff, who was more familiar with the Saar coals, called it Streifernkohle. This term was later used by Muck also. Still later Potoné² used this term exclusively for the whole group in contradistinction to a class called Glanzkohle, and considered these coals to be composed alternately of Humuskohle and Faulkohle or Mattkohle (Pig. 20). Not knowing the nature of the German coals and not realizing that the term Streifenkohle was applied to a distinct class of coal, the terms of its components as used by Potonié and others were translated to "bright Coal" and "dull coal" and applied to the components of our

Jan 1, 1930

By C. D. Woodward

THE subject of electric signals for the despatching off mining cages through shafts has received cousiderable attention recently from various mining companies. The Anaconda Copper Mining Co. has found it necessary to develop a system that is reliable, safe and simple in operation, and easy to repair. The movement of all mine cages or skips is under the direction of a station tender, who rides on the cages when men or supplies are being lowered or raised. When ore is hoisted, he is stationed at a skip pocket for loading and despatching the skips. For the station tender's use, two signal systems are installed in each hoisting compartment, and he is the only employee authorized to use them. One system is known as the "AC" or Station bells, as it is operated from the 110-volt, 60-cycle, power service; the other system, called the "DC" or shafts bells, takes its energy from closed-circuit primary batteries. As a supplement to the two main signals, a buzzer system is installed. The general arrangement is similar to "the main signal, except that there is a mine buzzer at each station. When a signal switch connected into the buzzer system is pulled down, all buzzers are operated, thus notifying the station tender that he is wanted at some particular level. Placed on the station posts, and within easy reach of the men on the cages, are the signal pull switches for the main signals. The station, or "AC," pull switches are furnished with a short rope as shown in Fig. 1, while the shaft, or "DC," pull switches are equipped with ropes that extend down the shaft past the next station. To avoid all confusion in the use of the three signal systems, a standard arrangement has been adopted in all mines for the location of the pull switches. Fig. 2 illustrates the position of the pull switch at the various mine stations for the main signal systems, but it does not show the buzzer pull switch; this is fixed to the roof timbers about 25 ft. back from the shaft. If the skip pockets are a considerable distance below the station, a pull switch for each main shaft compartment is connected to the "AC" system and placed at this point. However, if the distance is short, a light cord is attached to the station pull switches and dropped down to the skip pocket.

Jan 2, 1922

By I. Sheinhartz, H. M. McCullough

DURING the course of a lubrication study in relation to the compacting of metal powders, it became desirable to measure the thickness of sprayed graphite coatings on steel dies for hot pressing. The thickness of these lubricant coatings ranged between 0.0001 and 0.002 in. In their particular case, the authors were interested in a method for measuring the lubricant thickness on tapered die inserts having curved surfaces. The lubricant was sprayed on the inserts at an elevated temperature and it was desirable to measure the thickness as soon as possible after application. Various standard types of commercial equipment were tried. Most of the available devices operated on either a mechanical or magnetic principle. The mechanical devices, such as micrometers, dial indi-

Jan 1, 1956

By Rztssell H. Bennett

A SURVEY of the Mesabi Range iron-ore industry demonstrates that a satisfactory degree of technical progress has been achieved in the last fifteen years. This advance has not been made over a uniform front, but, by salients and bays, according to the different initial positions, economic and technical, of the component producing companies. The producers endowed with rich ore have in general, because of natural advantages, progressed more slowly than their neighbors with leaner properties. The advance has been made step by step all along the line -blasting, loading, hauling and concentrating-and without the benefit of radical innovation. There have been, for instance, no such parallel discoveries in iron ore as leaching and flotation in copper. The much lower unit price of iron operates, of course, to bar the application of these and other practices developed for the higher-priced metals. There exists, however, a radically new concentration process whose technology is well worked out and which may become economically operative in the not too distant future; this, as so often happens in engineering advance, because of recent developments in an entirely unrelated field. First, however, let me devote a paragraph or two to the more important economies effected in mining.

Jan 1, 1932

By Alan M. Bateman

POSSIBLE postwar trends of the more important world minerals will be determined in part by their present world position and by the acts and forces that have operated during the war period, so it is desirable first to review briefly what has been happening in the foreign field of metals and minerals. When we first entered this war we of the mineral profession were all acutely conscious of our lack of strategic minerals and other materials, which had to be imported in great quantities-minerals such as manganese, chrome, tin, mercury, nickel, and antimony. But we realized also that we had to acquire vast quantities of those minerals of which we had thought we were bountifully supplied. Our assumed domestic abundances turned out to be woefully deficient, and demands also arose for new minerals never before produced in large quantities. Some threescore minerals entered the strategic list of our imports. Ores from new sources had to be sought, developed, and transported. Tonnages in the millions of such bulk materials as zinc, lead, copper, chrome, and manganese flowed to feed our war efforts. Sparsely distributed minerals such as tin, mercury, antimony, tungsten, cobalt, mica, and corundum had to be lured from their rock lairs in greatly increased quantities to feed the hungry maw of war industry, and the rare minerals such as tantalite, columbite, beryl, and quartz crystals had to be developed and procured in quantities never before dreamed of. New uses such as radio and radar created demands for many minerals formerly thought of only as adornments of museum collections and not as pressing industrial minerals. Such minerals were never before mined in quantity.

Jan 1, 1945

By Edward Judd

THE old Cerro de Pasco smelter at La Fundicion, near Tinahuarea, 9 miles. from the Cerro de Pasco. mines and at an elevation of 14,300 ft., has now been replaced by a thoroughly modern smelting plant at Oroya, the junction point of the company's private railroad with the Central Railway, of Peru. This site has the advantages of being closer to the Morochoca mines, as well as nearer to the port of Callao, and at the same time is 2000 ft. lower in elevation, which benefits not only the cost of transportation but also the tech-nical operation of blast furnaces , and converters. The Oroya smelter was designed with the idea of .smelting about 2500 tons of. ore per day, but having in mind the possibility of increasing its capacity, all departments of the plant can be extended within reasonable -limits; for instance, if it is found that reverber-atory smelting is cheapest, taking into consideration the cost of fine crushing and fuel, it is possible to extend the roaster and reverberatory plants accordingly. The ore handling system is modern, consisting of belt conveyors, reclaiming machines, and electrically driven calcine cars, all requiring the minimum of labor. Waste heat from the reverberatory furnaces is utilized in boilers for the production of power to operate the plant, and the power house is equipped with condensing units to obtain the highest economy. Shop installations for the making of all repairs required for the smelter are unusually complete, includ-ing iron foundry, steel foundry, forging and machine shops, carpenter and pattern shops, and an electrical shop. There is also a plant for the production of all clay and silica refractory brick used in the furnaces; this is situated on the smelter site and is conveniently arranged for receiving raw materials and delivering finished brick to the several departments of the smelter. The laboratory is in a wing. of the general office, which is a two-story brick structure, situated on the smel-ter site.

Jan 10, 1923

By GEORGE D. RAMSAY

ABOUT three miles west of Fontana San Bernardino County, California, and fifty miles east of Los Angeles, the Kaiser Co., Inc., has built an integrated steel plant. By integrated, I mean that from its wholly owned iron ore and coal supply, the Kaiser Co. is producing in its own mills iron and steel products. Pig iron to meet the West Coast needs has been produced at Fontana since Jan. 1, 1943; steel ingots were first poured there May 14, 1943; and steel plate for ships was first rolled Aug. 15, just sixteen months after ground was broken. Briefly, the plant consists of: (I) Two batteries of by-product coke ovens, totalling ninety ovens, carbonizing about 1740 tons of coal per day at capacity; with by-product facilities for the production of tar, ammonia, and ammonium suIphate, light oil distillates, and tar distillates. (2) One blast furnace producing at

Jan 1, 1944

By J. Norman Bulkley

As electrical power is used to a greater extent on the Rand than in any other mining center, it is thought that a short description of the methods used and results obtained may be of interest. In comparing Rand practice with that on other fields, several general factors should be borne in mind: First, the mines are all working on large tonnages of low-grade ore (average. $6.50). The annual crushing rate is about 27,000,000 tons. Second, the mines are all grouped udder the financial and engineering control of mining houses, so that the results of a group, rather than an individual mine, are open for study, and practice follows more uniform lines. Third, coal of fair quality (about 12,000 B.t.u.) can be obtained for $2 to $3 per ton., Good supplies of condensing water are, however, scarce, and have to be carefully stored. Power Supply Power is supplied by the Victoria Falls & Transvaal Power Co., Ltd., and its subsidiary, the Rand Mines Power Supply Co. Both companies, which are practically one from an engineering point of view, operate the following stations, all feeding into the same system.

Jan 2, 1916

By R. R. French

Investigations were conducted by the lndiana Geological Survey for some dry methods of bene-ficiating low-grade gypsum ore. Seventy-two batch and continuous flow tests were performed with a roller mill, rod mill, pebble mill, electronic color sorter, electrostatic separator, and an air separator. Approximately 650 size analyses and 550 chemical analyses were performed during the investigation. Batch samples were tested by the Survey, and most of the continuous flow tests were handled by com-mercial laboratories. INTRODUCTION Although many companies producing gypsum have been interested in dry beneficiation, very little information has been published in the past. One of the most comprehensive investigations was reported by the Canadian Department of Mines.5 Other reports of interest have been published by the Canadian Department of Mines,' the South Australian Department of Mines,2 and the U.S. Bureau of Mines.3 Some beneficiating practices, such as hand picking, selective mining, crushing and screening, milling, and air classifying, were already in use in the Canadian industry prior to MacPherson's investigations.5 MacPherson examined the effect of tabling, air separation, screening, flotation, electrostatic separation, calcining, washing, and various types of milling, in his efforts to eliminate dolomite, limestone, and small amounts of silica and clay from the gypsum ore. RAW MATERIAL Gypsum and anhydrite occur within the lower part of the St. Louis Limestone (Mississippian) in southwestern Indiana. Gypsum in single beds 10 or more ft thick occur at Shoals, Martin County; near Freedom, Owen County; near Bloomfield, Greene County; and in the Devonian strata of LaPorte County. Only the Shoals deposit has been exploited commercially. The western edge of the Shoals deposit is contaminated by a continuous bed of shale, about 1 1/2 to 2 ft thick, near the top of the evaporite and by thin continuous strata or irregular masses of carbonate rock. The low-grade material used in these investigations was obtained from the waste pile of the National Gypsum Co.'s plant at Shoals. The waste ore averaged about 67.4% gypsum and was contaminated by various amounts of shale, dolomite, and limestone. All the material had been previously crushed and screened to minus 1 1/4 to plus 3/8 in. X-ray analyses of powdered, sedimentated, gly-colated, and heat-treated samples of the shale showed that it was composed of slightly structurally disordered illite, Fe-rich chlorite, and very finegrained disseminated silt. The clays and silt were partly cemented with carbonate material. Light-gray argillaceous limestone and gray or brown porous dolomite made up most of the carbonate rock contamination. Crushing Characteristics: The rate unweathered gypsum, carbonate rock, and shale reduce in size was determined by crushing handpicked samples in a rod mill and screening at minus 100 mesh (.0059 in.). Fig. 1 graphically represents the data. These data indicate that carbonate rock should be relatively easy to separate from gypsum, but that shale should be difficult to separate from gypsum by differential crushing. Controlled Samples: Eight rod mill tests of hand-picked samples of mixed gypsum and shale and mixed gypsum and carbonate rock were made. Sample weight and crushing weight were standardized, but the scalping screen size was varied from 3 to 10 mesh (.265 to .0787 in.) in order to obtain the optimum purity and recovery. The data obtained from the tests (see Table I) illustrate that the relatively hard carbonate rock allows appreciable beneficiation (13.6 to 18%), but the low strength gypsum and shale allows only minimal separation (3.1 to 7.5%).* Semi control led Samples: During the investigation considerable slaking of the shale was noted when the ore was subjected to alternate wetting and drying. As demonstrated in laboratory tests, as much as 76% shale can be removed by two cycles of wetting and drying in a 48-hour period with subsequent screening at .265 in. Five ore samples, stockpiled and weathered, were screened, rod-mill crushed and rescreened at .157 or .187 in. with excellent results (Table 11).

Jan 1, 1967

By A. G. Loomis

IT is only within the past 10 years that serious attempt appears to have been made to improve rotary drilling fluids by the application of the principles of colloid chemistry, although the use of chemicals to control the rheological properties of clay slips has long been known in the ceramic industry. The main difficulty apparently lay in the lack of a complete analysis of all of the functions of a drilling fluid in the drilling of the well, together with the lack of adequate consideration of how colloid science could be applied to secure these ends, and particularly how apparent antithetical properties of the fluid could be compromised. Thus one analysis1 of the many requirements of a drilling fluid proved conclusively that the viscosity should be low, in order that cuttings and entrained gas might be eliminated effi-ciently in the settling ditch, while the loss in carrying capacity accompanying low viscosity could be regained by increasing either the density of the mud or the upward velocity of the mud stream in the annular space of the well, and the danger of sticking of the drill stem due to rapid settling in case of enforced suspension of drilling operations could be eliminated by enhancing the thixotropic properties of the fluid. The desired properties of the drilling fluid having thus been established, it was a natural step to treat the fluid with vis-cosity-reducing chemicals, such as salts of weak organic acids1,2-for example, sodium tannate or gallate-and to adjust the pH to the alkaline side to such a degree of thixo-tropy as would give low viscosity and low yield point under the conditions of flow prevailing in the settling ditch, but rapid gelation and high yield point when quiescent in the annular space during shut-downs. In fact, flow in the settling ditch should be just short of turbulent while flow in the well, together with the flow of mud past the cuttings, is practically always turbulent. The use of chemicals other than those mentioned, such as Calgon (sodium hexametaphosphate) and certain other phosphates together with sodium tannate, has now become standard practice and it is the consensus that this method of treatment has proved to be an important step in the development of the art of drilling oil wells.

Jan 1, 1940

By G. Derge, Ling Yang, John Henderson

Self-diffusion coefficients of aluminum have been measured by the capillary reservoir technique in liquids of the CaO-SiO2-Al2O3 system containirg equimolar portions of CaO and SiO2, in the temperature range 1400o to 1520oC. For the melt containing 6.0 mole pct Al2O3 the results can be expressed by the equation D = [(4.3 * 0.3) x 104] exp [(-85,000 * 17,500)/RT]cm~sec-'; for the melt containing 12.5 mole pct Al2O3, by the equation D = (5.4 i 0.2) exp [(-60,000 * 10,00O)/RT] cm2sec-: A concept of the constitution of these melts has been developed which proposes that the ratios O/(Si +Al) and Al2 O3/CaO determine the dominant species present. In recent years considerable work has been done on the system CaO-SiO2-A12O3 with a view to elucidating the structure of liquids of this system. Conductivity,' electromotive force, 3 density,4 and activity5 measurements have all contributed to an understanding of the problem, but as yet there is no entirely satisfactory theory that can account for all the observed experimental results. In principle, measurements of self-diffusion coefficients should give further information which is not obtainable in other ways. Self-diffusion coefficients for calcium, silicon,6 and oxygen7 have been measured. The present investigation extends the series of self-diffusion coefficient measurements to include aluminum and develops a concept of constitution for liquids of this system which is compatible with all the observed experimental results. EXPERIMENTAL The technique used in the measurement of the self-diffusion coefficient of aluminum was the capillary-reservoir method,8 A126 being incorporated in the melt contained in the capillary and inactive aluminum in the reservoir melt. This method was chosen because it minimizes convection currents' in the diffusion zone. It has the further advantage that the boundary conditions are such that a slight modifica- tion of Anderson and saddington's8 solution of Fick's Law yields an equation which requires measurements only of the length and the initial and final average specific activities of the solidified melt within the capillary. where t is the diffusion time, Co is the average specific activity of the melt contained in the capillary at t = O, C is the average specific activity of the melt contained in the capillary at t = t, 1is the length of the capillary, and D is the self-diffusion coefficient. The equation is of somewhat different form than those previously applied to high temperature diffusion studies because the specific activity of the melt in the reservoir was negligible both before and after diffusion. The diffusion apparatus is shown schematically in Fig. 1. It consisted of a silicon carbide resistance furnace containing the inactive melt in a graphite crucible, internal dimensions 7/8 by 4 in., enclosed in a 1 1/4- by 1 1/2- by 30-in. McDanel tube. A 3/8-in. McDanel thermocouple sheath to which graphite radiation shields and a graphite protection tube were affixed, was used to hold the capillaries. By moving this sheath through a rubber seal at the top of the McDanel tube the capillaries could be lowered into or raised out of the melt. Temperature was measured with a Pt-Pt 13 pct Rh thermocouple which was calibrated periodically against a standard couple. The furnace temperature was controlled to ± 5°C through the thermocouple immersed in the melt. Temperature variation over the depth of the melt was less than ± 3°C. The inactive melts were prepared from pure native quartz, assaying better than 99.9 pct SiO2, A.R. grade A12O3 and A.R. grade CaCO,. The same quartz and CaCO3 were used in preparing the active melts, the

Jan 1, 1962

By B. T., Colley

AS always when metallurgical operations are conducted within or close to agricultural and stock-raising regions, the question of damage due to fume and smoke presented itself when the Cerro de Pasco Copper Corporation's new smelter commenced to operate in La Oroya in 1922, For more than twenty years the Corporation had operated its old plant close to Cerro de Pasco without encountering difficulties from smoke claims, owing to the fact that it was in an open plain where more or less constant air currents carried and dissipated the smoke over large areas, affording ample dilution. But Oroya is in a deep canyon formed by four contributing valleys up and down which the smoke travels for long distances in a more or less concentrated form. Though the altitude of Oroya is more than 12,000 ft., and the surrounding country rises to much greater elevations, nevertheless there exists there a large and important stock-raising industry and also a considerable development in agriculture, consisting of the cultivation of potatoes, barley, etc.

Jan 1, 1945

By Donald B. Gillies

WE HAVE come a long way since the time of the old steel master who declared that chemistry would ultimately bring the steel business to ruin. Yet I sometimes doubt whether even now we fully recognize the great debt we owe to the institutions that today are initiating young men into the fascinating mysteries of science and training them in the art of engineering. I am not sure that we recognize the importance of the contribution that the schools of applied science and the technical colleges are making to our industrial economy. That contribution is neither narrow nor restricted. It covers the whole range of industry. Dr. Compton, himself, has shown in his survey of leading American corporations that the engineer is twelve times more likely than the nonengineer to become president, five times more likely to become treasurer, and thirty times more likely to become an officer. So the hand of the engineer not only is all-powerful in the laboratory and in the drafting room but his control is increasing in all departments of management.

Jan 1, 1940