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By William B. Plank

NEVER before have so many men chosen the mineral technology field for their college training. In the college year 1936-'37, 7190 such students were enrolled in the 53 schools of the United States. My last study of the mineral technology schools of the United States and Canada was made for the year -1934-'35, and the current study, as the previous one was made for the A.I.M.E. under the auspices of the Division of Mineral Industry Education. Altogether, four studies of enrollment have been made. The first three were for successive college years beginning with 1932-'33. This present one covers a two-year period, for the purpose of these studies may he served satisfactorily if they are made biannually. The data on the schools were collected in the same way as for former studies, 'namely, by questionnaire, dated in this case Nov. 18, 1936. The figures reported are therefore comparable with those of former cars.

Jan 1, 1937

By D. J. Mack, R. E. Reiswig

Six examples of the peritectoid transformation were selected from the literature and studied by the method of isothermal transformation. The kinetics and mechanisms of five of the examples are presented as TTT diagrams and photomicrographs. The exist-enc- of a peritectoid in the sixth case is doubtful. ALTHOUGH the peritectoid transformation per se has been known for many years, no precise published data exist concerning the kinetics or mechanisms involved in transformations of this type, except for the brief treatment by Rhines, et al. 1,10 Bearing in mind the fact that investigations of recent years are uncovering more and more peritectoids and suspected peritectoids, a thorough study of the well-established peritectoids appeared to be in order. It was for this reason that a study of the kinetics and morphological mechanisms of six binary peritectoids was undertaken. The six peritectoids selected from the literature for study were those reported at 7.02 wt pct Al-Ag, 26.0 wt pct Sb-Cu, 30.5 wt pct Sb-Cu, 32.3 wt pct Sn-Cu, 8.35 wt pct Si-Cu, and 21.2 wt pct Al-Cu. These selections were based on availability and purity of components, ease of preparation and heat-treatment, and estimated reliability of the available equilibrium diagrams in the regions of interest. EXPERIMENTAL PROCEDURE The alloys used in this investigation were induction melted in electrode-grade graphite and chill-cast in cast-iron split molds. In all cases, the alloys were so brittle that they could easily be broken into samples weighing 1 or 2 g. Chemical analyses showed that the alloys used were close to the respective peritectoid compositions reported in the literature and that the impurity levels were low in all cases. Metallographic examination showed uniform distributions of phases in all samples, indicating uniformity of composition in the samples studied. Isothermal transformation studies were carried out in fused-salt media, using the familiar inter-rupted-quench method. Uniformity of temperature in the salt baths was maintained by continuous stirring with a stainless-steel agitator. On the basis of actual observations of the temperature fluctuations, the estimated temperature control was + 10C for the Ag-Al and Cu-Sb alloys and ±30C for the Cu-Sn, Cu-Si, and Cu-Al alloys. The accuracy of all temperature measurements was estimated to be ±1°C. It was found necessary to mount metallographic specimens of the Ag-Al alloy in cold-curing methyl methacrylate, since the temperatures encountered in mounting in bakelite or lucite caused an appreciable degree of transformation to the ß phase. For the other alloys, wood-flour-filled bakelite mounts were used to avoid extraneous X-ray diffraction lines during the later examination of the metallographic specimens on a Norelco Geiger-counter d if f r ac tomete r. In the X-ray diffraction procedure, agreement between the published diffraction patterns and those obtained in this study was good. This was particularly important for phase identification, since the literature contained little in the way of micrograph description in some cases. Etching of the silver-aluminum alloy for metallographic examination was done by swabbing with either of the following reagents: 1) 10 g CrO3, 1 g (NH4), SO2, 0.5 g NH4NO3, 100 ml H2O, or 2) 10 ml NH4OH, 1 ml 20 pct KOH, 4 ml 3 pct H2O2, 5 ml H2O. The other alloys were etched with the usual bichromate etchant: 2 g K2Cr2O7, 1.5 g NaC1, 8 ml conc. H2SO4, 100 ml H20 (swabbed vigorously). EXPERIMENTAL RESULTS A) The Ag-Al peritectoid at 7.02 wt pct Al— The phase equilibrium involved in this peritectoid is shown in Fig. I.2 The phase boundaries in the vicinity of the peritectoid were most comprehensively established by Hume-Rothery, et al,3 who placed the equilibrium temperature at 448 °C and the equilibrium compositions of the a ß' and y phases at 6.11, 7.02, and 7.24 wt pct Al, respective The alloy used in this study analyzed4 6.95 wt pct A making it slightly hypoperitectoid according to the accepted equilibrium diagram. The rate of the transformation a+ y — ß' varies rapidly with degree of undercooling below the equilibrium temperature, passing through a maximum in the vicinity of 350°C. Thus the TTT dia-

Jan 1, 1960

By G. B. Misra

While investigating on the aerodynamic resistance of airways supported with peripheral timber sets, at regular intervals, the following theoretical equations were developed by the author to estimate the resistance coefficient of such airways: [ ] for S < 1, where f is Darcy-Weisbach resistance coefficient of the airway, C is modified drag coefficient of the supporting member, D is equivalent diameter of the bare airway, 8 is ratio of the approach velocity over the sets to the average velocity of the bare airway, A is cross-sectional area of the bare airway, a is projected frontal area of the sets, A., is cross-sectional area of the air stream at the vena contracta inside the set, S is spacing of the sets, f, is resistance coefficient of the bare airway, l is length of aerodynamic influence of sets, p is perimeter of the bare airway, p, is setted portion of the perimeter of the bare airway, pe is unsetted portion of the perimeter of the bare airway, and P shielding factor. The equations were verified experimentally in a model rectangular airway supported with one- (bars), three-, and four-piece sets of square-section timber of three different sizes and were found to hold true. The work has been further extended to one-, three-, and four-piece sets of round timber of 2.6, 3.2, and 3.8 cm diam with the same experimental set up. Tests have been carried out for spacings of 25, 50, 75, 100, 150, and 200 cm over a regime of flow defined by the Reynolds number (with respect to the equivalent diameter of the bare duct) ranging from about 1.5 X 106 to 5 X 106 using the same experimental techniques. The values of f are calculated in the manner indicated in [Ref. 1]. Unlike with square-section timber, the resistance coefficient f of the airway setted with round timber shows a distinct variation with the Reynolds number of flow. This conforms to observations made by Sales and Hinsley.2 In order to have a comparable value of f for all types of sets with all sizes of timber, it was necessary to select the value of f at a fixed Reynolds number of flow. Since f is chiefly a function of the drag coefficient of the sets, the appropriate Reynolds number RE is that with respect to the diameter of timber in the set. Considering the diameters of timber used and the regime of flow over which measurements were made, f was chosen at a value of RE = 20,000 in all cases. The f vs. S curves are maximal in nature and in conformity with theory, the f vs. 1/S curves are straight lines up to a value of S = 1 beyond which they show a distinct flexure. The observed values of 1, the length of aerodynamic influence of sets, agree with the relation 1 = 42 e, developed for square-section timber sets, thus suggesting that the shape of timber has little influence on the length of aerodynamic influence. The value of the modified drag coefficient CD for round timber was calculated in the same way as for square timber in Ref. 1, taking the contraction factor Z = 1.5 for round-edged constrictions. CD has an average value of 0.96 with a standard deviation of 6.08% as compared to the free stream drag coefficient of 1.2 at RE = 20,000 for long cylindrical obstructions The shielding factor [ ] is plotted against S/1 in [Fig. 1]. The curves are more or less independent of the size of timber, but are different for the different types of sets, possibly due to their different degree of symmetry. Values of f calculated by the author&apos;s [Eqs. 1 and 2], using experimental values of CD&apos; and [ ] and taking I = 42 e, are plotted in [Fig. 2] against experimentally measured values of f for different types of sets with different sizes of round timber. The values agree closely with a standard deviation of only 5%, thus establishing the veracity of the theoretical equations developed by the author for round timber as well. A comparison was made between the Xenofontowa4 equations (the only other reasonable relations available for the estimation of the resistance coefficient of supported airways) and the author&apos;s [Eqs. 1 and 2] by comparing in [Fig. 3] the values of the resistance coefficient f computed by the Xenofontowa relations with those experimentally measured by the author. In order to make

Jan 1, 1975

By Donald K. Weaver

THERE have been eight different oil zones identified and produced at Santa Fe Springs, of which three or four are in turn divided into two or three parts. These zones are, from top to bottom, the Foix, difference of opinion over this nomenclature, with reference to the different zones referred to as Clark, it has no particular bearing on the water problems. Each of these oil zones has had waters of varying salinity associated with it, either within or at the bottom of the &apos;zone. Table 1 is a tabulation of the zones, their maximum thicknesses, salinity and heads of various waters. Surface waters are fresh, and of high head, giving artesian flow in some instances.

Jan 1, 1930

By E. von Maltitz

IN his highly interesting paper on "Piping and Segregation in Steel Ingots,"1 Prof. Howe emphasizes the effect of successive phases of internal pressure in the ingot in the evolution of gas, and the consequent formation of blow-holes. From his statements in other places, it may be inferred that he does not here intend to ignore the other variable factor, temperature, but rather to discuss this one more particularly. At all events, it is my purpose not to engage in controversy with Prof. Howe, but rather to contribute, towards the complete elucidation of this important subject which we all desire, my own views and experience. If, in doing so, I specially emphasize other factors than pressure, I need not be understood as denying what I do not think it necessary to discuss fully. Nor, in presenting my own original conclusions, need I be understood as claiming to be the first who ever reached or announced them. Many things are asserted or suggested upon inconclusive evidence; and to confirm such tentative propositions may be as valuable a service as to overthrow them. In the following passage, Prof. Howe adduces analogies, based upon the behavior of charcoal and of water, respectively, which seem to me questionable "In general, the. solvent power falls as the pressure falls ; and in general it rises as the temperature falls. Thus, to heat a solid, for instance charcoal, may expel part of its dissolved gas ; and a tumbler of water drawn cold from the faucet gradually evolves gas, as it stands and warms up on the sideboard." (p. 238.) Charcoal is a solid body, which has the property not only of absorbing gases in large quantities, but also of expelling the thus absorbed gases upon heating. A comparison between charcoal and iron as to the absorption of gases is scientifically not possible ; the gas-content of charcoal is partly due to the

Sep 1, 1907

"WELFARE…Welfare endeavor in connection with both the metal and the coal mines of Utah has shown gratifying progress during recent years and both the operators and their employees are deserving of much credit for the efforts put forth to better living, working, educational and receational conditions in most of the mining camps of the state.In the older metal mining camps of Utah, where the towns are incorporated and independent of the mining properties operating in the vicinity, less opportunity is pre¬sented for the companies to exercise efforts looking towards improved welfare conditions than is the case of camps located on company ground and under the full control of operators.Even in such camps, however, as illustrated in Bingham, the companies can do much to better welfare conditions. In this camp the Utah Copper Company has spent $800,000 since 1 920 in the erection of modern brick cottages, apartment houses and the Gemmell Memorial Club. The cottages and apartments have every convenience to be found in up-to-date city homes. The Gemmell Memorial Club, erected and equipped at a cost of $1 75,000, was provided by the company for the benefit of the Utah Copper Company employees living in the canyon and has been made the recreational center for the camp."

Jan 1, 1925

By R. S. Shoemaker, R. M. Darrah

Expanded markets for copper in the past few years and a consequent search for new ore bodies have revitalized the widely known but seldom applied method of producing copper called heap leaching. Heap leaching is defined here as the process applied to oxide ores which have been mined solely for the purpose of leaching. In this case, all costs of mining the ore become a part (and a substantial one, as will be shown) of the cost of the copper produced, whereas in dump leaching the mining cost has already been accounted for as a stripping cost for the sulfide ore. Of course, with newly opened ore bodies, stripping costs may be divided through accounting procedures, between the copper produced by the mill and that obtained by leaching, but in general this type of operation must be economic on the basis of the sulfide ore alone. Heap Leaching Requires Low Capitalization Heap leaching, as a beneficiation method, is unique in that it is the only process used for the recovery of a metal in which the time involved from mining the ore to metal production is measured in months instead of hours or at the most, days. Then too, after the ore body has been depleted and mining has ceased, metal production will continue for some substantial period of time. Heap leaching is also unique because unlike any other method of beneficiation, metal recovery cannot be accurately forecast ahead of time and recovery will never approach that of a conventionally milled sulfide ore or even that of a vat leached oxide ore. Counter-balancing this drawback, however, is the relatively low capital expenditure necessary to put a heap leaching operation into production and the consequence that smaller ore bodies which would not support the higher capital cost involved in a vat leaching plant can be made into producers. Stated more simply, in heap leaching the operator accepts low recovery in exchange for low capital costs and low break even point. Whether the operator chooses vat leaching with its higher recovery and higher capital costs, is a mater of economics which depends in part on the nature of the ore to decide. For instance, an ore that will vat leach in 7 to 10 days using 7 pounds of sulfuric acid per pound of copper produced might use double or triple that amount of acid during the months that are required for heap leaching.

Jan 12, 1968

By AIME AIME

THIS journal is fully indexed-every issue, as soon as published-in a set of card?, which thus brings ready to your hand any article on any subject in this journal or in any one of 1700 other journals in all languages. This Engineering Index Service, instituted in January, 1928, is to be found in the Public Libraries of Newark, Cleveland, Bridgeport, Baltimore and the John Crerar Library, Chicago. Engineers in any field who live or work in New Jersey will find this mammoth index to the latest engineering literature in the Public Library of Newark, N. J.

Jan 1, 1929

By Richard W. Smith

Why are we losing our liberties? (1) . . . because our local chambers of commerce come to the National Chamber&apos;s annual meeting, vote for a policy on federal economy, and then go to Capitol Hill and ask for a federal project for their area. (2) ... because our mining men ask for a subsidy to mine submarginal deposits that can&apos;t be economically mined in a free economy. (3) . . . because 18,000 men and organizations all over the country recently wired or wrote a Congressional committee asking that the Army Engineers be exempt from the President&apos;s power to reorganize the Executive Branch of the government under the recommendations of the Hoover Commission.

Jan 1, 1949

By Henderson, Robert

A GOOD idea of the magnitude of the underground operations at Climax can be gained from the following figures. A little more than 43,000,000 tons has been drawn from the mine and of this amount, 40,500,000 tons has been drawn in the past ten years and 12,000,000 tons was drawn in two of the war years. The maximum daily average output over a period of one month was slightly more than 20,000 tons but during this period, production on certain days was 24,000 tons, and 9000 tons was produced in a single eight-hour shift. This production came chiefly from 260 draw points although all of them were never in operation at one time. The haulage system for these draw points is made up of 7.5 miles of 36-in.-gauge track, and 131,000 ft. of subsidiary drifts and 44,000 ft. of raises have been driven to develop the necessary broken ore reserves for this high production. Power consumption is often considered an index of operating efficiency. In 1943, the year of maximum production, the mine power consumption was 19,223,000 kw.-hr. or 3 kw.-hr. per ton; in 1945 it was 3.5 kw.-hr. per ton. To handle this amount of power, there are four transformer stations and one switch station in the mine. Mr. Garrabrant, the chief electrician, describes the electrical installation in this issue.

Jan 1, 1946

By Ferid Kromer

This paper is the first in a series which will describe geology, mining methods, and production costs of some, of Turkey&apos;s more important minerals. In this paper the economically significant minerals-chromite, meerschaum, and magnesite-of the Tagtepe district are described. The cost data presented are believed by the author to be the first made public on Turkish chromite mining.

Jan 1, 1950

By Robert S. Archer

THE proper material of construction for a given purpose is that material which meets the requirements satisfactorily at the lowest ultirnatc cost. It is consistent with this principle that most aluminum castings are made of an alloy containing about 8 per cent. copper. This alloy possesses mechanical properties satisfactory for general engineering purposes together with manufacturing characteristics leading to the production of finished castings at low cost. It is to the aluminum industry what gray iron is to the iron and steel industry. Just as some services require "semi-steel," malleable castings or steel castings instead of gray iron, there is a certain and growing demand for aluminum castings of superior strength or ductility, or both. Since the beginning of .the industry producers and others have sought to develop alloys or processes by which such castings could be made. Out of these efforts have emerged many alloy compositions and special processes, of which only a few have had sufficient merit to survive. It is the purpose of this paper to describe those which seem to the authors to offer the greatest promise for the production on a commercial scale of aluminum castings of superior mechanical properties, with special reference to heat-treated castings. The suitability of an alloy or process for actual manufacture is affected by so many factors that the problem of appraisal is not a simple one. Since this is such an important part of the whole subject it is proposed to discuss briefly some of the requirements. The final verdict is of course the result of commercial trial and experience. It will therefore, perhaps, be profitable to employ a somewhat historical method of treatment in discussing the subject of alloy development. The alloys or processes to be used in the production of aluminum castings are to be considered from the standpoint of their effects on both the utility and the cost of the finished casting. Specific gravity and mechanical properties come under the first head, while the properties

Jan 1, 1927

By J. B. Newsorn

VERTICAL SHAFTS in the United States have heretofore been sunk by blasting and mucking. The blasting leaves uneven, shattered walls which usually must be supported. Even though the walls will stand, shaft lining is needed to furnish supports for the cage guides, pipes, and power conduits. The lining is generally timber, and as timber can be most easily framed into rectangles, rectangular shaft openings are the rule. The timber reduces the size of the cage floor. For example, if the Idaho Maryland company had put down No. 2 shaft by blasting and mucking, the cage area would have been about thirty per cent of the total shaft area. Besides a low percentage of useful area, an ordinary shaft is subject to fire hazard and to timber maintenance charges. It is also poor for ventilation because the timber ribs cause eddies which greatly reduce the speed of the air currents. A bored shaft does not have these disadvantages. The walls are smooth, circular, and not shattered by blasting, so lining is not required in most

Jan 1, 1936

By L. R. Smith

BUTANE OPERATED drilling rigs are a recent innovation in the petroleum industry, so extensive data on their operation are not available. However, experience indicates that, within limitations, as much can he accomplished with butane as with steam, at a decided reduction .in expense of installation and cost of operation. Commercial butane is a liquid motor fuel similar to gasoline, but much more volatile, so that it has to be stored under pressure. At 10° F. it is liquid at atmospheric pressure, but at 100° it has a pressure of 70 lb. or more. As soon as the pressure is reduced, it turns to vapor and in that state is far more easily mixed with the air necessary for combustion. Butane occurs as a by-product in the absorption process of natural gasoline extraction from casing-head gas. The product has been used to some extent 10 raise the octane value of gasoline. However, because of its volatile nature, such admixture is stable only to a limited degree. Attempts also have been made to introduce the product in a gaseous form into oil- hearing formations in repressuring work. It has, however, until recently, for the most part been wasted.

Jan 1, 1937

By Stanley J. Gasior, Albert J. Forney, Joseph H. Field

Most bituminous coal mined near Eastern industrial areas requiring high-Btu pipeline gas is caking and therefore unsuitable for fixed-bed pres- sure gasification by present techniques. If the caking property of such coal can be destroyed, the resulting fuel can be gasified in a fixed bed at pressure with steam and oxygen as a preliminary step in making a high-Btu gas. To find a practical way to convert strongly caking coals of granular or small lump size to noncaking fuel was the object of this study. In previous work, strongly caking coals of 1/8- to 1½ -in. size were converted to a noncaking coal char by treatment in a static bed in about 3 hours1 and coal of 18-100 Tyler mesh in a fluidized bed in about 5 min.2 An inert gas such as steam, nitrogen, carbon dioxide or a mixture of all three with a small amount of oxygen was used in both studies. In our work a strongly caking bituminous coal from the Pittsburgh seam of 4-8 Tyler mesh size was converted to a noncaking form in free-fall in about 2 sec by dropping it through a countercurrent flow of steam containing 4% to 7% oxygen at 1150º-1200°F and 300 psig. This method should also be applicable to smaller-sized material.

Jan 3, 1965

By S. H. Ash

IN no part of the world other than a small area in Pennsylvania is anthracite mining an industry of major magnitude. As the deposits of anthracite in the United States are limited virtually to Pennsylvania, the difficulties of this industry have been commonly considered a state rather than a national problem. However, there is also national interest in the conservation and wise utilization of all the country&apos;s fuel resources and in the control of interstate waterways. The anthracite industry is confronted with a serious problem of water accumulation in many of the mines, a problem that must be solved in the near future if progressively higher mining costs are to be avoided. It cannot be solved by the operating companies without state or Federal aid, or both, owing to the magnitude of the work required, the diversity of interests of the coal and surface ownerships, the hazard to the whole mining community, and interests affected outside the mining region. &apos;The costs of abating the ever-increasing surface seepage to mine workings and of handling this seepage once it has occurred are beyond the eco¬nomic resources of the operating managements.

Jan 1, 1941

By Walter C, Smith

Metallic bismuth was known in the Middle Ages and the name is supposed to come from the German Wismut. The origin of the German name is uncertain. References to bismuth are found in the writings of Valentine, Paracelsus, and Agricola between 1450 and 1550. Early specimens of bismuth were very impure and often were confused with antimony, tin, and zinc. About the middle of the eighteenth century, J. H. Pott, C. J. Geoffroy, and Torbern Bergman succeeded in producing fairly pure bismuth and showed it to be an elementary metal similar in many respects to lead.

Jan 1, 1953

By AIME AIME

OCTOBER will be western month for the Institute. With meetings at Spokane, Tulsa, Los Angeles, and San Francisco, and with a large number of American Institute of Mining Engineers members and their families in the party sailing out through the Golden Gate to Japan on the afternoon of the tenth, the major activities of the Institute will, for this month at least, be west of the Mississippi. Despite cancellations due to necessity, most of the officers of the Institute will be present and taking part in some one or more of the Western meetings. Prof. Robert S. Richards, our senior past-president, will attend both the Spokane and San Francisco meetings and then go to Japan. President Bradley will preside at the San Francisco meeting and then head the party going to Tokyo. At Tulsa and Los Angeles, the principal officers of the Petroleum Division will be present and active and at all the meetings, directors, ex-directors and -present and past officers will be on the job and keeping things moving.

Jan 1, 1929

By E. H. Mohr

AT the McGill concentrator of the Nevada Consolidated Copper Co., all flotation operations have been carried out in Forrester cells since November, 1926. In respect to cost of operation, the new cell has proved to be superior to the Callow, which it supplanted, and its incorporation in the flow sheet has resulted in a marked improvement in the metallurgy. Before citing the advantages of the new machine over the old, it should be explained that the Forrester has not only replaced the Callow, but it has made possible the elimination of a number of tables as well. When Callow cells were in use, table concentration preceded flotation. The ball mill pulp was elevated, by means of air lifts, to roughing Wilfley tables situated two floors directly above the flotation floor. On an intermediate floor were additional tables which cleaned the concentrate from those above. The finished table concentrate constituted approximately 60 per cent. of the total mill production, and contained about 40 per cent. of the recovered copper. The table tailings were returned to the classifiers, the overflow from which went to the flotation cells and the oversize to the ball mills. As soon as the Forrester cells were installed, this tabling operation was discontinued. The ball mill pulp now discharges into the classifiers direct, without the intermediate tabling. It was impracticable to employ the present flow sheet when Callow cells were in use, for the reason that unless the greater part of the heavy mineral was first removed, it accumulated on the mats and adversely affected the flotation operation. By tabling ahead of flotation, it was practicable to maintain the concentrator at 10 to 20 per cent. greater capacity (depending upon the pyrite content of the ore) than was possible by flotation alone. This was due to the necessity for finer grinding in the latter case. Even though the table concentrates contained only 6 to 8 per cent. copper content, the low smelting costs made it advantageous to operate at high mill capacity, at the cost of low grade of product.

Jan 1, 1927

By C. E. Lesher

Two processes for agglomerating fine sized ores with low temperature coke are described. One process (Orcarb) agglomerates ores with limited amounts of carbon; the other (ore-carbon pellets) pelletizes fine sized ores, using low temperature cokes as the binder. Data are presented on the products obtained when taconite, magnetite, and hematite concentrates and several titanium oxide ores were used. REDUCTION of finely divided oxide ores has long been a major metallurgical problem. Various methods of agglomerating, notably briquetting, sintering, nodulizing, and pelletizing, have been developed and are in industrial use. Carbon is the usual reducing agent for oxide ores and attempts have been made to agglomerate fine ores with coking coal in order to get the metallurgical advantages of intimate contact and increased particle sizes suitable for subsequent smelting or reduction.1-3 For the past three years, research has been in progress on two processes for combining fine sized ores with reactive carbon in the form of low temperature coke. By one process, designated Orcarb, the ore is coated with coke carbon in amounts limited to that required for reduction and the result is an appreciable but limited increase in product particle size over that of the original ore. The second process, called ore-carbon pellets, produces pellets of fine ore bound by low temperature coke. The first objective was to develop a process for combining an oxide ore with only enough carbon for its reduction, the amount being that derived from the simple reduction equations. The carbon (that amount theoretically required for the reduction of the oxides in an agglomerate with ore), calculated to CO, ranges from 10 pct for zinc calcines Or phosphate Ores to 21 pct for rutile and 26 pct for silica. The carbon required for reducing iron oxides falls between the extremes—10 and 26 pet&apos; When the carbon in the agglomerate is low temperature coke, reduction by hydrogen may be expected to take place, thus modifying the calculated carbon require- ment. On the other hand, in practice, an excess of reducing agent over that required in theory is normally used. Screen sizes of three iron ores on which the greater part of the experimental work was performed are given in Table I. Most of the testing was done with Freeport (Renton Mine) coal, but Pittsburgh and Elkhorn bed coals were also used. The first objective was to agglomerate the ore with sufficient low temperature coke to provide carbon for reduction, i.e., in the range from 10 to 25 pct. This was accomplished by preheating the ore, mixing with pulverized coking coal, and completing the coal carbonization in a plain steel rotating retort. The pilot retort, as it is now constituted, is shown by diagram in Fig. 1 and photograph, Fig. 2. Ore is fed into the upper kiln by a screw; it is heated to 900° to 1100°F by direct flame and it is then discharged into an insulating hopper from which it goes

Jan 1, 1956