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By G. E. Johnson

E. D. HYMAN*—How much sorting of scrap is done ? G. E. JOHNSON (author's reply)—We do practically no sorting. We charge "run of mine" scrap to the furnace. The unmeltables, mostly iron, are in such demand today that there is no difficulty in disposing of them. It may soon be desirable to sort out from the unmeltables as much of the brass as possible. J. J. BRUGMAN†—We have somewhat similar problems in the secondary aluminum business. What is your method of removing the unmelted material from the furnaces? Why have you such an apparently small space in which to charge your materials? Do you find that you have to seal that opening, or can you have it open and continuously charge at one end and pull out the other ? G. E. JOHNSON—Our means of melting scrap is efficient only to the extent that we use the waste heat from the vaporizing chamber to do the job. It is a batch process. We open the charge door and place the scrap on the hearth by hand shoveling. The door is then closed during the melting down period. After the melting is complete, the opposite door is opened and the unmeltables are raked out. The doors are approximately 3½ X 4½ ft and are not sealed during the process only closed. They are nominally tight. Some metal is oxidized in the process. We have visualized a means of conveying the materials through this melting unit with the metals that are melted trickling out during its travel. T. H. WELDON‡—Mr. Johnson, in line with the last question, is it necessary to seal the furnace between the melting down and the vaporizing unit, or have you got an inverted syphon in the bottom of the chamber? G. E. JOHNSON—That was one of the first things we encountered. We had to have a sealed opening, and it is a molten metal seal. You have indirectly asked me another question, which was: "Do you have to seal up the melting unit?" I would say we should exclude as much air as possible, although we are not too efficient in doing that. We allow the melting unit doors to be open when we charge and when we remove unmeltables. You can readily see that that would lead to the idea of having a controlled atmosphere in the melting unit, and I think this would do a more efficient job of melting the scrap. T. H. WELDON—How often do you charge the furnace? G. E. JOHNSON—We charge the melting unit, and rake out the unmeltables, about every hour. H. R. HANLEY*—Are any provisions made for controlling the rate of oxidation for the production of various size particles for certain characteristics of the zinc oxide product? G. E. JOHNSON—Yes, there are many. You are getting pretty much into the fine points of zinc oxide manufacture. Some of us still think we have something to learn about that. In general, this muffle furnace as I have described it to you produces a rounded particle of zinc oxide which is generally formed by a rapid oxidation of the zinc vapor, followed by rapid cooling. We have gone to the other extreme in some of our experiments. We have changed the furnace to produce a type of zinc oxide, such as we thought was peculiar to American process zinc oxide, by controlling the temperature at the point of oxidation and maintaining that temperature for a much longer period of time than we do when we make the rounded shape. There are other relationships that this furnace readily provides. One of the important factors is the ratio of air to zinc vapors. We can vary that by varying the air supply to the baghouse, or vary the rate at which we are vaporizing the zinc by the simple expedient of regulating the temperature over the carborundum arch. We have a number of variables that permit us to produce all of the grades of French process zinc oxide from lead-free up through the highest grades of seal oxides. There are many controls that we can apply to the operation. What I have said is but a brief condensation. K. MORGAN*—Can Mr. Johnson give us some idea of the fuel consumption of the furnace ? How much oil does he use per ton of zinc distilled? I am also interested to know what sort of heat transmission he gets through the arch? What is the thickness of the tiles used to construct the arch? Some time ago we built a small furnace for a different purpose, using a carborundum arch, and we found that the reflectivity of the molten zinc surface was so great we had to use a very high arch temperature. We found we made an improvement by having a layer of carbon on the surface of the zinc. Has Mr. Johnson had any experience on these points ? Does he make any sort of insolu-bles which he leaves in the furnace which he cannot tap out ? G. E. JOHNSON—I believe your first question was the fuel consumption. If I recall, somewhere in this paper there is a test that I quote. I believe we used 800 gal in a given period of time. Offhand I cannot translate that into tons of metal. I might also state that we have this understanding; that the carborundum arch, as the temperature becomes higher, becomes more efficient in heat transmission. As a matter of fact, I believe it is at about 2600°F or higher that the highest efficiency of heat transmission becomes available. We have calculations that I cannot quote from memory which indicate that the carborundum arch does a really very fine job for this type of furnace. Another point that we had considered was the fact that this furnace could be readily constructed so as to furnish an ideal source of heat for waste heat boilers. If a carborundum arch was used over the melting unit, we would have no zinc vapors in the gases at all— just clean combustion gases from which we would have removed some of the heat. L. P. DAVIDSON†— The insolubles

Jan 1, 1950

By F. P. Dewey

The most serious problem that confronts the lead-smelter is the waste caused during smelting by the volatilization of both lead and silver, which are consequently lost in the form of fume. It is not difficult to collect a portion of the solid materials passing out of the

Jan 1, 1890

By E. DeGolyer

PROSPECTING for new deposits is a part of the ordinary routine business of the petroleum industry to an extent that is not true for any other mineral industry. The health of the industry depends upon whether we are successful or unsuccessful. How many know what it costs to find oil today and what it has cost in the past? Very few, I will wager. The industry is not well informed upon this extremely important point. We cannot deal in averages for lack of information. Does it cost more or less than previously? Prospect wells are increasingly deeper and, since the introduction of the core drill, prospecting techniques have required increasingly expensive field oper-

Jan 1, 1939

By Adrian C. Dorenfeld

Factorial design is a mathematical method of drawing valid conclusions from a series of tests made in a predetermined pattern. It is applied to flotation ore testing using, in this case, five variables, each varied twice, requiring a total of 32 tests. Representative conclusions are checked by repeat testing.

Jan 12, 1951

By James B. Fletcher

Leaching of the block caved mine from 1941 through 1970 is described, and the improvements made are listed. Detailed is the increased knowledge of leaching gained through this operation, including methods used in forecasting production, prediction of the economical end point, rate of recovery, and ultimate recovery.

Jan 1, 1972

By L. O. Millard

Stockpiles in the minerals industries serve a wide variety of purposes. Usually they are for surge between stages of processing, for a dependable plant feed in anticipation of delays, or to provide for single or double shift mining in conjunction with round-the-clock milling. Often surge piles are necessary to insure a uniform feed to continuous process equipment where the material is received as an intermittent or variable flow. Extensive use is made of stockpiling for the primary purpose of blending. The significant fact about all stockpiling of bulk materials is that storing and reclaiming are two separate and distinct operations and they may present widely different problems in the selection of methods and tools.

Jan 10, 1959

By J. F. Kemp

CONTENTS. [ ] INTRODUCTION. THE saying that " of all the known regions of the universe, the most unsafe to reason about is that which is under our feet,"* might well be the motto of the present paper, in view of the writer's profound appreciation of the difficulties and uncertainties of the subject. In such a field, the temptation is very strong to announce a probable proposition, and then to defend it with a loyalty insensibly graduating into partisanship. Conscious of this danger, the writer has endeavored to maintain an impartial and candid form of statement, though others may feel that he has not been wholly successful. The subject, as here considered, falls naturally into two di-

Jan 1, 1902

By H. C. Theuerer

EVEN the highest purity silicon available for semiconductor use contains significant amounts of donors and acceptors, usually aluminum, phosphorus, and boron. Aluminum and phosphorus can be removed from silicon by adaptations of the zone refining techniques' widely used with germanium. Removal of boron, however, has been a difficult problem. The approximate distribution coefficient for boron in silicon is 0.8, so that while zone refining is possible, it is not very effective in any reasonable number of passes. It has been found, however, that boron can be effectively removed from silicon by treatment of a liquid zone with hydrogen and water vapor. Starting with 40 ohm-cm, n-type silicon, use of zone refining coupled with hydrogen

Jan 1, 1957

By J. E. Ryan

TRONA, Calif., is a miniature urban community of some 3500 people, located on the northwest shore of dry Searles Lake in the extreme northwest corner of San Bernardino County, approximately 186 miles north and east of Los Angeles. Since it is situated on the Mojave Desert, a typically desert climate prevails with wide variations in temperature between day and night, extreme daytime summer heat, and cool to cold winters. Rainfall averages somewhat less than 4 in. per year, and dust storms are common. The rate of evaporation, however, is great, amounting to 6 to 9 ft of water per year. The extremely low humidity makes the summer heat of 110°F tolerable with only a mild, temporary discomfort.

Jan 5, 1951

Dr. James Douglas, who is memorialized on another page of this Bulletin, who held a place in the affections and regard of Institute members second to that of no other living roan, left in his will the sum of $100,000 for the maintenance of the Library of the American Institute of Mining Engineers. This is in addition to the $100,000 which Dr. Douglas gave during his lifetime. We believe that it is Dr. Douglas' wish that the library, the great means by which the benefits of Institute membership may be extended to those distant from headquarters, should be maintained by the Institute at the highest possible level of efficiency and serviceability.

Jan 9, 1918

By Immo H. Redeker

Abstract-North Carolina is the leading state in the US in lithium mineral production. Spodumene is mined in open Pits and concentrated by flotation by the two companies, Lithium Corp. of America and Foote Mineral Co. North Carolina State University has a mineral research laboratory in Asheville, N. C., with trained personnel, batch and pilot plant facilities to assist in the state's mineral development. The NCSU Minerals Research Laboratory assisted both lithium-producing companies with spodumene concentration problems and has lately worked closely with Lithium Corp. of America to develop the best flowsheet for spodumene and byproduct recovery. The concentration of North Carolina spodumene and byproducts from pegmatites is presented and illustrated with figures.

Jan 4, 1979

By Gordon B. French

Occidental's in situ retorting process for oil shale has many advantages over the conventional, underground mine and surface retort. Only a portion of the oil shale is mined and transported outside where it blends with the oil-shale talus found in the area. Spent shale is retained underground without surface disposal problems. The process consumes no water from outside sources. Noise and dust levels are kept at a minimum. As many of the facilities as possible are located underground. More oil is produced from a given area than conventional surface processing. Additional energy can be recovered by using conventional turbines to generate electrical power of magnitude of three to four times required by the operation.

Jan 1, 1977

By R. H. Raring, F. E. Martin

A high speed gas quenching dilatometer useful in studying phase transformations in low alloy steels is described. Changes in specimen length are measured by means of an electrical micrometer tube. The maximum instantaneous cooling rate is approximately 5000°F per sec; the maximum average cooling rate from 1650' to 950°F is approximately 2900°F per sec. Data for steels of 0.11 pct and 0.67 pct C content are included. KNOWLEDGE of phase transformations as they occur in an alloy under conditions of continuous cooling affords valuable insight into its properties. The transformation characteristics during continuous cooling of steels of high hardenability, which decompose entirely to martensite at fairly slow cool-

Jan 1, 1957

By Milton E. Wadsworth, Edward M. Eyring

Better understanding of solid surfaces and their associated adsorption products is of both academic and practical value. The study of detergents and their behavior in cleaning surfaces is fundamentally related to the nature of the products adsorbed and their ability to compete for certain surfaces. Similarly in flotation, the nature of the adsorbate before and after adsorption is basic to clear understanding of the process. The recently developed pellet technique employing infrared spectroscopy provides a powerful tool for the study of solid surfaces. Absorption bands, which are infrared-active, may be observed for adsorbed products. Also any changes in the surface substrate that occur as a result of adsorption may be detected by means of differential spectra

May 1, 1956

By D. J. Spottiswood

The control of thickener operation has proved difficult due to a lack of understanding of thickener operation and the long retention times involved. This is particularly true in counter current decantation circuits where the interact ion between thickeners further complicates the control problem. In this paper, the control aims and controlable variables are identified, and the development of a control system is discussed. Models of the sedimentation process, as carried out in thickeners, have been primarily aimed at thickener design. These models are examined and utilized in a dynamic model development. A preliminary dynamic model of the thickener operation is discussed here with relation to control application and its use in CCD circuit control examined.

Jan 1, 1984

By John A. Church

In a recent paper read before the Institute it was said of faults that "the sensible expression of the fracture is an earthquake." This notion, which has been expressed before, though usually as a theory and not as an admitted conclusion, is based upon the early belief that faulting is a violent rupture of the earth's crust. Faults are of different kinds, from great dislocations of the earth —hundreds of miles in length—down to the still more mysterious displacements with which miners have to deal. The latter are usually quite short, from 1000 to 20,000 feet in length, but are distinguished even above their greater brethren by the excessive pro-

Jan 1, 1893

By George F. Beardsley

The silver-fields of Zeehan and Dundas are located on the "West Coast" of Tasmania, 30 miles from the port of Strahan on the Macquarie Harbor. This harbor is 17 miles long, from 4 to 5 miles wide, and completely landlocked. Its only drawback is a shallow bar with 9 feet of water on it. The hills on the western side of the harbor vary from 200 to 300 feet in height, and are all composed of quartzite or a quartz grit. From 15 to 20 miles back from the eastern shore of the harbor is a conglomerate-capped range of mountains, rising to the height of 4700 feet. The immediate eastern

Jan 1, 1893

By Wilson Blake

Rock deformation and failure taking place around underground openings is usually both accompanied and preceded by the phenomena of rock noise or microseismic activity. These small-scale releases of seismic and acoustic energy can be detected with special geophysical monitoring equipment. Use of this equipment allows one to look inside a rock mass to determine how an opening is behaving under the applied loading system. Microseismic equipment and monitoring techniques are briefly reviewed, and use of the microseismic method as an engineering tool in monitoring rock structure stability is illustrated by case histories. Examples cited range from evaluating roof stability using single-channel portable equipment, to rock burst monitoring using sophisticated computer controlled, multichannel monitoring systems.

Jan 1, 1983

By D. W. Jessup

THE handling of native labor is offering an interesting problem that requires diplomacy. It is difficult to induce many of the men to leave their villages and enter into regular work. They do not feel the necessity of manual labor other than to obtain sufficient money to pay the annual hut tax and to buy a little clothing. The ground provides mealies (corn) which means food and beer, he hunts and catches fish, so why work? But gradually, as the native becomes more civilized, his wants increase and his ideas change; he now needs money to supply his desires and eventually he must work more. So in time it is hoped that the labor market will be better supplied.

Jan 1, 1931

By P. Schwed

IN determining the mechanism responsible for sintering, the most direct procedure available is the comparison of the observed time and temperature dependence of the process with the dependence to be expected upon the basis of each conceivable mechanism. This was done by Kuczynskil who, in treating the mechanism of surface diffusion, postulated, in effect, that the concentration gradient of vacancies is different from zero only within the neck. This procedure was recently questioned by Cabrera' who assumed, on the contrary, that diffusion occurs only in the region outside the neck. In the present note, the calculations are performed without restriction on the region of diffusion. To carry out this objective it is first necessary to

Jan 1, 1952