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By A. R. Ledoux

I was wondering whether we were going to adhere to our text. It seems to me that we are having a very remarkable meeting of mining engineers this year, because no matter what the texts may be that are assigned to us, we get back toward something higher; we turn to the consideration of questions of ethics, and of applied Christianity. Yesterday we listened to the most eloquent and remarkable address by Mr. Rickard in memory of Dr. Raymond, and it was told us that he was to speak about Raymond's achievements as an engineer. He did say considerable on that subject, but he was himself carried away with the spirit of the man and moved us all by his portrayal of Dr. Raymond's continued and fruitful labors for the betterment of mankind—that is to say, his religion. Our President asked me if I would say something this afternoon and I find in the bulbtin that the text of the discourses which we are to have here this afternoon is "Internlttional Cooperation in Mining in North America." But again I find that the eloquent speaker who has just preceded me has dwelt largely on ethical and spiritual cooperation rather than upon cooperation in mining. That is, cooperation as men, rather than solely as engineers. The imaginary line dividing Canada from the United States, unmarked by fort or military post, was mentioned by a previous speaker. There are going to be in the future, I am sure, fewer entanglements of the barbed wire of tariff discrimination along our border-—to that end let us cooperate. But there has always been a reciprocity in men. A Canadian conceived and created our great transcontinental line, the Great Northern Railway; an American made the Canadian Pacific what it is. In mining and metallurgy, American engineers, backed by American capital, have built up great Canadian industries while Canadian experts have developed some of the resources on this side of the line. They have done much more than develop our resources; some of them have been our leaders in sympathy for labor. It is therefore not a question of creating a spirit of cooperation, but of giving it freer scope and a fuller realization of fraternity—or, to use the word now more common and of deeper significance—brotherhood. These are days of combination. Corporate interests in this country are now compelled, or at least encouraged, to combine in ways that

Jan 1, 1920

By David K. Mitchell

The mineral pyrite (or marcasite) occurs in coal beds as balls, lenses, veinlets and bands. Several million tons are w-asted annually on the refuse dumps from coal mining and coal-preparation activities. Sporadic attempts have been made in the United States to recover this pyrite for manufacture of sulphuric acid but only a few plants have succeeded in recovering it on a commercial scale. Shipments of pyrite from coal mines during 1941 were reported as follows: Illinois -The Midland Electric Coal Corp., Henry County, shipped 12,026 long tons containing 46 pct sulphur, at its Atkinson preparation plant. Indiana—The Snow Hill Coal Corp. produced pyrite from its Talleydalc preparation plant in Vigo County. Kansas—The Mineral Products Co. produced 3902 long tons of pyrite containing 44 pct of sulphur from picking table and washery refuse. Specifications for coal pyrite for acid manufacture rangc from 5 to 8 pct maximum carhon limit, and 42 to 45 pct minimum sulphur limit. Where flash roasting is practiced, the pyrite must be minus 100-mesh. Most companies give no size specifications. One company specifies 20- mesh or finer. Impurities in pyrite other than carbon may limit its use—for instance, arsenic, probably as arseno pyrite-—even though a concentrate can be made complying with specifications otherwise. Pyrite-recovery Plants Bradford breakers and picking tables may be used to make a marketable product where the pyrite occurs largely in sizes coarser than about I in. To make a grade of concentrate acceptable to sulphuric-acid plants the pyrite must break freely from the accompanying coal and slate, which is a rare condition to find. Most pyrite occurring in coal beds requires crushing and an abrasive type of grinding to free it of entwined coal and slate, followed by mechanical concentration by jigs, tables or other concentrating devices suitable for heavy ores, to make a satisfactory concentrate. At the Snow Hill Coal Corporation's plant in Indiana and at the Midland Electric Corporation's plant at Xtkinson, Ill., the final concentrate is made by a mechanical jig. The most recent and complete mill for concentrating pyritc from coal-mine refuse is that of the Mineral Products Co. at West Mineral, Kans., in which jigs and tables are used. Many regrinds and recirculations of products are necessary to get a concentrate of uniform grade. Trends On the whole, the economics of recovering pyritc from coal is not favorable. Cer-

Jan 1, 1948

By Ben B. Cox

During the past year considerable progress was made in the exploitation of Iraq's resources, although no new fields were discovered. The principal development was the completion of the much heralded pipe line from Kirkuk to the Mediterranean, by the Iraq Petroleum Co., Ltd., and the beginning of crude exports to Europe on the second of August. Official ceremonies for the opening of the lines took place in January, 1935. The line in itself is sufficient achievement under the existing natural handicaps to deserve a moment's attention. It is 1151 miles long, composed of two independent lines made up mostly of 12-in. with some 10-in. and 8-in. pipe, and extends from Kirkuk westward 156 miles to beyond the Euphrates River as a double line. From that point, near the village of Haditha inside the Iraq border, it bifurcates, one leg going as a single line to Haifa through the British Mandated Territories of Trans-Jordania and Palestine, and the other to Tripoli through the French Mandates of Syria and the Leban(on)ese Republics. The total length of the Tripoli line is 532 miles, of the Haifa line 619 miles. The line leaves Kirkuk at an elevation of 1013 ft., drops to 350 ft. at the Tigris, to 200 ft. at Wadi Tharthar west of the Tigris and again to 300 ft. at the Euphrates, rises to more than 3150 ft. at mile 451 on the central Arabian steppe along the south line and to more than 2500 ft. at mile 466 along the north line. On crossing the rift valley of the Jordan River south of Galilee, it drops abruptly below 850 ft. below sea level, requiring the use of extra heavy 8-in. pipe and a relief station to reduce the pressure. A picked group of American welders, under H. S. Austin, of the Ajax Pipe Line Co., laid the line. It is coated, wrapped, and buried 30 in. beneath the surface in solid rock along much of the route. It crosses four large rivers and wide stretches of alkaline soils. Twelve pumping stations are employed, three of which are double east of the bifurcation. Each single station houses three 500-hp. crude-burning deisel engines flexible-coupled to reciproratirig pumps. Each pumping unit is capable of handling a minimum of 21,000 bbl. of oil, giving the entire system a

Jan 1, 1935

. E. P. MATHEWSON, New York, N. Y.-I would like to call attention to the excellent plan for protecting the lining of the tanks from rough handling by the excavator. Many engineers, when considering mechanical excavators for lead-lined tanks, have been afraid that the machinery might get out' of order and rip out the lining. This difficulty seems to have been entirely overcome in this installation, and those who have been responsible for its success deserve a great deal of credit. A. F. CASE,* Cleveland, Ohio. (written discussion t).-The application of the automatic unloader to the copper leaching process at Ajo was a very radical departure from the common use of this machine, inasmuch as the only previous use of this device has been in connection with the unloading of coal and ore from vessels on the Great Lakes. There are many phases in connection with the unloading of ore from lake vessels that are not presented in the extraction of ore tailings from leaching vats. For instance, in unloading from boats, it is necessary to provide means to reach under the hatches to parts of the cargo hold which do not lie directly under the hatches, and to work in inaccessible places that do not exist in a leaching vat. These necessities require complications that could be very easily dispensed with in this new application. On this account the unloader, is applied to the New Cornelia, plant, represents what is probably the simplest development of the machine that has ever been produced, and, manifestly, in its simplest form it could he expected to show results corresponding to its performances when installed with all of its complications. One of the requirements of vessel unloading is extreme vertical travel, when the bucket is required to reach the bottom of the, cargo hold, often 12 or 13 ft. below water-level, and discharge into a receptacle 30 ft. above-the water. This was materially simplified at Ajo for the reason that the vertical travel was never more than 20 ft. This condition immediately resulted in the possibility of shortening the walking beam which carries the bucket leg, and, in fact, in entirely reducing the size of all the working, parts of the trolley, walking beam, and bucket leg, as far as reaches were concerned.

Jan 11, 1918

By S. D. Baumer, P. M. Hulme

B. M. Larsen (U. S. Steel Co., Kearny, N. J.)—Could we have some sort of an estimate on the cost of calcium carbide for this treatment? Also, if you used calcium carbide on carbon-saturated iron, would some effect hold back the reaction? P. M. Hulme (authors' reply)—As far as I know we have not worked on carbon-saturated iron. About 3½ pct C is the highest we have worked on. As far as cost goes, it depends on how much sulphur You have to take out. It will run anywhere from $0.75 to $2.00 a ton overall cost including the cost of carbide per ton of metal treated. That is, using the efficiencies that we show in this paper. We are getting better efficiencies now. T. L. Joseph (University of Minnesota, Minneapolis, Minn.)—Did you say 2 lb of calcium compound? Mr. Hulme—That is based on 10 lb of calcium carbide per lb of sulphur removed. D. E. Babcock (Republic Steel Corp., Youngstown, Ohio)—We have run this type of desulphurization process at the blast furnace. We have desulphurized between 100 and 200 at the blast furnace and taken the iron right out of the furnace with an injector system. The process gave us quite varied results; stratified iron, high sulphur on the top and low sulphur on the bottom, and we decided it was impractical. Mr. Hulme Just what was the type of injection equipment? Dr. Babcock—Nitrogen gas for one injection method and we used fairly large gun equipment. We followed the same general type of pattern you show only on a larger scale. Mr. Hulme—It sounds very much like what we call the gale of wind method. We have very erratic results with that. Dr. Babcock—We have tried several types, and particle sizes. The operation was not satisfactory. Mr. Hulme—Of course, we have never tried it on that scale except on a continuous basis. That is the reason we abandoned the idea of working on 35 ton ladles on a batch principle and took it as it came out of the cupola and treated it on the fly on a continuous basis. Dr. Babcock—When you compare the relative effectiveness of the process as carried out, it does not give a very favorable comparison of that process which is already developed. We did not feel it was worth the

Jan 1, 1952

By S. E. Bretherton

Most metallurgists appreciate the great need of a process for the extraction and recovery of valuable metals from complex ore, where the presence of one metal increases the cost of extracting the other rnetals to such an extent that not any of the metals can be extracted at a profit. We need only refer to some of the mines in Colorado, Utah, and New Mexico, where oxidation has taken place and the sulphur, zinc, copper, and some of the iron and other metals have been leached out, large bodies of oxidized ore remaining, rich in lead, silver, and sometimes gold. These metals have been concentrated by the removal of the other metals, leaving a very desirable ore for treatment in the blast-furnace for the production of lead bullion, and recovery of the silver and gold. If lead is not present, the gold and silver metals are usually recovered by some method of milling, or the ore is shipped to a smelter, where it is mixed with lead ore or copper-iron sulphide ore from some other mine. In these same mines, when developed to greater depth below the leached or oxidized zone, the ore is found to contain the original mixture of sulphur, zinc, copper, etc., added to, or I should say left with, the lead, silver, and gold values; but instead of adding to the value of the ore, the presence of these elements, especially zinc, makes the copper, silver, and gold of less value, and often worthlees. Such was the experience of the oldest mines in Leadville,.Colo., until methods of mechanical separation of the lead from the zinc were developed sufficiently to allow of some profit by the making of a concentrate rich in zinc to be shipped to the zinc smelter, and sometimes a lead concentrate which could be shipped to the lead smelter; but even in these cases the waste of the different metals is a very serious matter. In the very best concentrating plants some zinc will be left in the lead concentrate, to be lost and to give considerable trouble in the lead-smelting furnace. On the other hand, some of the lead, with a large percentage of the copper and silver, will follow the zinc into the zinc concentrate, to be, perhaps, recovered by smelting the cinder or clinker left in the re-

Jan 1, 1915

By Noel Stearn

WHEN the Age of Machinery was suddenly thrust upon civilization about the beginning of the nineteenth century, an unprecedented demand for mineral resources sprang up. This demand brought about the rapid development of the known ore deposits and the discovery of such other deposits as could be encountered by energetic and canny pros-pectors. Thus in the countries now reasonably ac-cessible nearly all orebodies have been located except those which are totally concealed even from the eyes and "senses" of experienced and expert prospectors. The high rate of exhaustion of known ore deposits and the necessity of looking farther and farther ahead for raw materials as a matter of insurance on the stu-pendous capital outlays involved in mining, develop-ment, and conversion operations, have resulted in excep-tional activity in three different fields of effort. The first is purely geographic. Prospectors are now pene-trating the few hitherto inaccessible regions in the hope of stumbling upon exposed ore deposits or locating visible indications of their presence. The second is chemical. Industrial chemists and metallurgists are seeking to facilitate the exploitation of lower grade ores to find methods of recovering valuable metals from common substances. In the third field of effort. lie the activities of the economic geologist and the mining engineer, who en-deavor to locate concealed ore deposits, which would remain hidden from the prospector, no matter. how expert or conscientious he might be. Obviously the task which such a man must face is both exacting and indefinite, and the tools which he has heretofore been permitted to bring to it are, for the most part, abstract-a knowledge of certain fundamental princi-ples and processes involved in the origin, occurrence, structure, and distribution of deposits. of natural re-sources and of the rocks which form the environments of those deposits, and a process-of reasoning by analogy supplemented by the .use of the diamond drill, or such artificial exposure as the test pit, trench, shaft or tunnel. His primary efforts are usually bent on acquiring a knowledge of the distribution of the rocks-as accurate -is possible-which is a natural prerequisite to any conclusion as to how they became so distributed. Over very extensive areas, however, he meets. the extreme difficulty of being unable to see the rocks, except at rare intervals, since .they have been concealed by an overburden of glacial material, of alluvium, of soil, or of other rocks.

Jan 9, 1928

By Smith, George Otis

ENGINEERING is in essence quantitative, and the engineer must deal with exact figures when he plans and, constructs. Engineering truths are not best expressed by adjectives, yet my wish, today, is not to attempt a quantitative measure of the dominant position of the mineral industry of the United States in the existing scheme of material things, but rather to seek a clualitative appraisal of what mining and metallurgical engineers are doing to promote and make secure our , national progress. Statistics help when we wish to gage material prosperity, but they fail when we desire to determine what share the engineers have in adding to the happiness and welfare of our people

Jan 1, 1928

Wartime geological studies by the U. S. Geological Survey and subsequent drilling carried on by the Bureau of Mines disclosed new ore in the Illinois-Wisconsin zinc field. As a result, several companies are carrying on drilling programs to locate and define new ore bodies. The Vinegar Hill company, which operates a custom mill to handle ores from various sources, now employs about fifty men in production at their Andrews mine. The ore is usually found in a 200-ft horizon below the surface. Water problems are not serious. Commercial-grade ore ranges up to 8 and 9 per-cent zinc and the cut off is approximately 41/2 percent.

Jan 1, 1948

By C. Gatlin, N. E. Garner

Results of impulsive wedge penetration tests on two synthetic, plastically deforming rocks are presented. Basic data obtained were force-time, displacement-time, and force-displacement curves for the impacts, plus the crater geometry. Wedge geometry and blow frequency were varied over a considerable range. The synthetic rocks consisted of wax-sand mixtures; two waxes of diflerent ductilities were used to provide variable "rock" characteristics. Conventional triaxial tests showed that these synthetic rocks exhibited force-deformation curves and Mohr envelopes quite similar to real rocks, except that strengths were much lower. Measured forces from static penetration tests agreed closely with theoretical values; however, dynamic force values were much higher than the static. These latter disparities are attributed to the viscous nature of the waxes. Thus the utility of these or similar rock models must depend on the scaling of rock viscosity, which is as yet unknown for impulsive loadings at elevated stress states. It appears, however, that some macroscopic, static phenomena may be studied with wax-sand rock models. INTRODUCTION The resistance of solid materials to indentation or perforation by projectiles or other penetrators has been studied by workers in many areas. Despite these efforts no universally accepted laws or formulas are available for describing experimental observations. In the metals field the force-deformation behavior of impacting bodies is often analyzed by the Hertz law for elastic collisions, the Meyer law if plastic deformations occur, or some combination of both.' The similarities of these expressions to empirical drilling formulas of the oil industry are apparent. Beginning with the basic contributions of Simon and co-workers at Battelle,' a number of experimental papers concerning the reaction of rocks to vertical impact have appeared in the U. S. mining and petroleum literature.'-' Most published data have, to date, been obtained at atmospheric pressure, although some early high pressure information was reported by Payne and Chippendale.8 Maurer" has recently utilized available brittle impact data to develop a drilling rate equation based on the experimentally observed proportionality between crater volume and blow energy. His result agreed with earlier efforts by both Somerton, who used dimensional analysis, and Outmans, who used plasticity theory. It has long been known that rocks exhibit different modes of failure depending on the state of stress. The literature in this area is considerable; however, papers by Bredthauer, Handin and Hager,13 nd Robinson", are adequate to illustrate the point. Since rocks flow plastically at certain triaxial stress conditions, the mathematical theory of plasticity has been used to analyze the rock drilling problem. Cheatham'" has altered the wedge identation solution of Randtl to rocks, and has developed useful equations for penetrator forces under a variety of conditions. Outmans" has utilized Hill's solution in a similar manner to develop a drilling rate equation. Both Cheatham and Outmans used the linear Mohr-Coulomb rule to relate rock strength and confining pressure. The actual stress at the hole bottom is not easily ascertained, although photoelastic studies by Galle and Wil-hoit," plus the analytical treatment of Cheatham and wilhoiti8 provide some insight. Consequently it is not clear to what extent the highly idealized rheological model of a perfectly plastic solid can be realistically applied to the rock drilling problem. This paper is the first report on a long range experimental study of crater formation in rocks at elevated stress states. The data presented here are from the first phase of the project. Data obtained from impulsive wedge impacts on two synthetic, plastically deforming rocks are presented. MODEL ROCKS Geologists have long been faced with modelling the behavior of the earth and, as a consequence, have studied scaling problems in some detail.' In general, their main problem is handling the wide disparity between laboratory and geologic time. In our studies the time effects (blow velocity or rate of loading, blow duration, etc.) were essentiafly the same for both. model and prototype, as were were geometry and tooth penetration. Thus application of available scaling laws suggests that Similarity is obtained if the stress-strain curves of model and prototype are similar." For this reason Hubbert and Willis''

By G. J. Lindenburg, T. L. Wilson

The Velvet uranium mine is located in the Big Indian district of the Colorado Plateau. The uranium ore body lies within the lower Triassic Chinle Formation, and the ore is associated with west-south- westerly trending fluvial sand systems. Exploration and mining are directed by longhole drilling and radiometric sampling. Results of the gamma probing, face scanning, and geologic mapping guide mining decisions and planning. Three people are directly involved with the geologic procedures: two geologists and a mine supervisor. The two geologists map, do rib scans, and direct longhole drilling. The third man involved, the mine supervisor, has last minute directive action based on shot hole probe data.

Jan 1, 1984

By A. P. Svenningsen

DURING the work at the test mill in Morenci, it was determined that a suitable feed for the ball mills could be made by a single pass through a short-head cone crusher. These crushers did not require a closed circuit delivering only a screen product to the mills, such as is the practice in some concentrators. By no means does this mean that the practice in these other concentrators is wrong, but just that the Morenci ore can be most economically crushed and ground in this manner. Therefore, the design of the secondary crushing plant was simply a problem of taking 25,000 tons of ore per 16 hour day from the primary crusher, this ore ranging in size from fine particles to 10 or 12 in., and reducing it to minus 3/4 in. Inasmuch as outages must be contended with in any crushing plant, it was assumed that the crusher would operate at full capacity for approximately only twleve hours per day, which is three-quarter capacity for the 16-hour shift. With this in mind, it was necessary to design a crushing plant which would average approximately 1600 tones per hour for the 16-hour day, or 2000 tons per hour for slightly over 12 hours per day.

Jan 1, 1942

By AIME

TO say that Milton Fies has been active in promoting the Southern Research Institute is a masterpiece of understatement. He is a director and trustee who was in on the ground floor when plans were first made for the Institute and since it became an actuality early in 1945 his interest and efforts continue. He talked about it at the last regional meeting of the Birmingham Section of the A.F.A. and has talked all over the South-and when he makes a speech he has really prepared it. He does not try to rival a political spellbinder, but his careful, concise English is always well thought out and to the point. Southern Research might be called his present hobby as it has been for the past two or three years. Another major interest has been his encouragement and training of engineering students. Active in the formation of the Student Chapter of the A.I.M.E. at the University of Alabama, for several years he saw to it that the students had a prominent engineer at each monthly meeting, usually taking them down to Tuscaloosa from Birmingham in his own automobile. He has also been keenly interested in the mining engineering activities at Tuscaloosa, both in the Bureau of Mines and the University.

Jan 1, 1946

ABOUT 2 lb. of alumina (aluminum oxide) of high purity is required to produce a pound of metallic aluminum. Projected production of metallic aluminum in the United States is now seven to ten times the peacetime rate a few years ago. In the past, all the alumina for aluminum production in the United States has been obtained from bauxite. Part of the bauxite was mined in the United States--chiefly in Arkansas-and part was imported from Surinam. All of it was chemically treated in the United States to separate the greater part of the aluminum oxide from the bauxite, alkaline solutions being used, in a method known as the Bayer process. The ingredients of the bauxite other than alumina, such as the compounds of iron titanium, and silicon, constitute the tailings from the Bayer-process operation. This product contains sufficient iron to give it a red color and hence it is called "red mud." Lime and soda used in the processing, are also present. Varying amounts of alumina remain in the red mud, depending upon the characteristics of the bauxite, the effectiveness of the treatment, and in particular upon the amount of silica originally present in the bauxite. High-silica bauxites result in high alumina loss in the red mud.

Jan 1, 1942

By F. D. Rosi, C. A. Dube, B. H. Alexander

The slip and twinning planes have been determined in deformed crystalsof titanium by an X-ray method of analysis. The slip planes are of the type {1010} and {1011}, while the twinning planes are of the type {1072}, {1121}, and (1122). In the case of the predominant (1010) slip, a type I digonal axis of indices <1120> was the effective slip direction. Microscopic observations on the appearance of the three twin types disclosed a distinct difference in their shapes, and an attempt was made to correlate this difference with the amount of twinning shear. The slip mechanism was discussed on the basis of the difference in c/a ratios for the common hexagonal close-packed metals. IT is a general rule that slip in metals occurs most easily on the planes of greatest atomic density and of the largest interplanar spacing, and that the direction of slip is a close-packed direction. Thus, of the hexagonal close-packed metals which have been investigated by the German school in the decade 1925 to 1935 (cadmium, zinc, and magnesium), it has been found that slip occurs on the basal plane (0001) and in a <1120> direction.&apos; In the case of magnesium above 225oC, slip occurs on a first-order pyramidal plane (1011) as well as on the basal plane.&apos; The hexagonal metals, moreover, deform in part by twinning, and, again with the exception of magnesium at elevated temperatures, the twinning plane has always been reported to be a second-order pyramidal plane {1012).&apos; In view of this consistency in the plastic behavior of these metals, it has been supposed that the same slip and twinning elements would be operative in the other important hexagonal close-packed metals (titanium, zirconium, and beryllium), although there are some reasons why this may not be so. Referring to the tabulation in Table I of the axial ratios of the important metals in this structural class, it may be seen that they can be categorized into three distinct groups depending on the value of their c/a ratios. In the first group are cadmium and zinc with large positive deviations from the ideal ratio for closest packing. This expansion in the direction of the c-axis would be such as to accentuate the basal plane as the slip plane, because it increases the interplanar spacing. The second group includes cobalt and magnesium, which closely approximate the ideal ratio. In the third group are zirconium, titanium, and beryllium whose axial ratios are decidedly less than the ideal. The lattice of the elements in this group is compressed along the c-axis which, in effect, tends to make the basal plane less favorable for slip inasmuch as it reduces the interplanar spacing and the atomic density of this plane. Thus, for metals in the third group, it may be said that there is a certain indefiniteness about the glide plane, in that planes other than the basal plane may be expected to operate. The fact that magnesium begins to exhibit planes other than the normal slip and twinning planes at elevated temperatures may indicate that this behavior will become more pronounced in metals of lower axial ratios. For this reason it might be expected that the slip and twinning behavior of zirconium, titanium, and beryllium would be different from that found in cadmium and zinc. One indication that there is a difference is reflected in the recent work which has been done on the deformation textures of these metals."&apos; As will be shown later, there is a significant difference between the rolling textures of cadmium, zinc, and magnesium on the one hand, and zirconium, titanium, and beryllium on the other, and this difference suggests that the mechanism of plastic flow is not the same in these two groups of metals. From these considerations, therefore, it may be seen that there are good reasons why it cannot be concluded that titanium will have the same crystal-lographic elements of slip and twinning as those exhibited by zinc and cadmium. For the complete determination of these elements it would be most advantageous to have single crystals. However, much valuable information can be obtained by using coarse grained polycrystalline specimens, provided the grains are sufficiently large to permit X-ray

Jan 1, 1954

By William B. Heroy

LOOKING back over the industrial and commercial progress of the United States during the last half century the outstanding influence has been the growth of the use of the fluid fuels, petroleum and natural gas. At the turn of the century these fuels supplied only 8 per cent of the energy requirements of the nation. Last year nearly 45 per cent of our heat and power supply were derived from these fuels. These figures are merely statistical reflections of the fundamental change in our national economy which has affected, in so many amazing ways, the life of this generation. The factors which have caused this change are still operative. The trend which has thus been established still continues and growth in the use of these fuels is, in all probability, still well below the peak, both for this country and for other parts of the world. Two great wars have not essentially changed this basic trend; if anything they have served to accelerate it. World War II did not alone increase our requirements for liquid fuels; it demonstrated the absolute essentially of petroleum resources to our national security. Petroleum is no longer just an important factor in our national standard of living; it is the most important single element in our national defence-

Jan 1, 1946

By Leslie W. Austen

ROTARY kiln operators will agree that some of the most severe conditions a refractory must stand occur in the hot zone of a kiln burning Portland cement, dead burn dolomite, magnesite, peri-clase, and similar materials. Frequently the operator is faced with factors beyond his control which drastically shorten the life of refractories. Shutdown due to mechanical failure can be serious if the period is of sufficiently long duration to cause the dropping of coating or the loosening of the lining. A change in slurry can affect the coating and cause ring buildup. A change in type of fuel and its effect upon the flame can cause a shift in location of the hottest zone. Weekend shutdowns or any other interruption can cause the operator trouble and may damage the refractories, since stopping and starting a rotary kiln is certainly more difficult than stopping and starting a motor. Some operators have tried to set an estimate of damage for each shutdown in equivalent days of running time. Conditions affecting the refractory may be roughly grouped in four classes: chemical attack, mechanical stress, thermal shock, and abrasion. Chemical Attack: The drive to obtain maximum production through a kiln demands maximum operating temperatures, temperatures which are limited more by the ringing up or melting of the clinker. This can cause interface temperatures at the junction of coating and refractory which require the use of a basic kiln block to withstand the chemical attack. Chemical changes take place within the refractory itself, especially in chemically bonded or unburned kiln blocks. These changes cause the formation of the ceramic or burned bond. Migrating liquids or fluxes from the kiln charge have an effect within the refractory and lead to mineral or glass formation. The alkalies, sodium and potassium, migrate into the refractory as silicates, chlorides, sulphates or other salts. They may move under capillary action or may be caused to move by volatilization with condensation in the cooler portion. Mechanical Stress: Concentrated stress may be caused by several factors or combinations thereof. I—The rings of refractories must be kept tight and rigid within the kiln, and this alone demands considerable force to hold the blocks in place. So that the force will not be concentrated, the blocks should fit the circle as perfectly as possible, with the faces in contact overall. 2—As the kiln is heated, thermal expansion takes place at the hot end of the kiln block. Since this disturbs the plane face it too can cause a concentrated stress at the two ends of the block, and shearing stress can be set up within the brick itself because of the difference in expansion between the two ends. 3—If a lining becomes loose and moves in the shell very severe stress can be set up, and as the kiln rotates this load changes and gives the effect of repeated loading. Permanent expansion of the refractory can also cause severe loading. 4—Not least important, flexing of the kiln is frequently the cause of concentrated stresses. Thermal Shock: Thermal shock, the result of heating and cooling too rapidly, occurs on starting and stopping or when a large patch of coating drops, exposing the bricks. Again, its destructive effect is often the result of phase change, liquid to solid or the reverse; dense refractories loaded with glass-forming impurities are particularly susceptible. Thermal shock is a. problem with refractories set in the wall or roof of a stationary furnace, and becomes even more serious in a rotary kiln, the tendency to spa11 being magnified with movement and concentration of stress. Uniform rate of feed and loading insures both better coating and a more uniform stress. Abrasion: If the refractories do not take a coating, abrasion can become a most destructive factor. Movement of the lining in shell or movement of loose blocks causes abrasion, which is also most destructive if the refractories do not take a coating. An analysis of the problem of basic lining for the hot zone reveals, therefore, a number of desirable characteristics: high refractoriness, basic chemical reaction, resistance to spalling, good strength at all stages, ability to take coating, true sizing, volume stability, and abrasion resistance. Increased demand

Jan 1, 1953

By Leslie W. Austen

ROTARY kiln operators will agree that some of the most severe conditions a refractory must stand occur in the hot zone of a kiln burning Portland cement, dead burn dolomite, magnesite, peri-clase, and similar materials. Frequently the operator is faced with factors beyond his control which drastically shorten the life of refractories. Shutdown due to mechanical failure can be serious if the period is of sufficiently long duration to cause the dropping of coating or the loosening of the lining. A change in slurry can affect the coating and cause ring buildup. A change in type of fuel and its effect upon the flame can cause a shift in location of the hottest zone. Weekend shutdowns or any other interruption can cause the operator trouble and may damage the refractories, since stopping and starting a rotary kiln is certainly more difficult than stopping and starting a motor. Some operators have tried to set an estimate of damage for each shutdown in equivalent days of running time. Conditions affecting the refractory may be roughly grouped in four classes: chemical attack, mechanical stress, thermal shock, and abrasion. Chemical Attack: The drive to obtain maximum production through a kiln demands maximum operating temperatures, temperatures which are limited more by the ringing up or melting of the clinker. This can cause interface temperatures at the junction of coating and refractory which require the use of a basic kiln block to withstand the chemical attack. Chemical changes take place within the refractory itself, especially in chemically bonded or unburned kiln blocks. These changes cause the formation of the ceramic or burned bond. Migrating liquids or fluxes from the kiln charge have an effect within the refractory and lead to mineral or glass formation. The alkalies, sodium and potassium, migrate into the refractory as silicates, chlorides, sulphates or other salts. They may move under capillary action or may be caused to move by volatilization with condensation in the cooler portion. Mechanical Stress: Concentrated stress may be caused by several factors or combinations thereof. I—The rings of refractories must be kept tight and rigid within the kiln, and this alone demands considerable force to hold the blocks in place. So that the force will not be concentrated, the blocks should fit the circle as perfectly as possible, with the faces in contact overall. 2—As the kiln is heated, thermal expansion takes place at the hot end of the kiln block. Since this disturbs the plane face it too can cause a concentrated stress at the two ends of the block, and shearing stress can be set up within the brick itself because of the difference in expansion between the two ends. 3—If a lining becomes loose and moves in the shell very severe stress can be set up, and as the kiln rotates this load changes and gives the effect of repeated loading. Permanent expansion of the refractory can also cause severe loading. 4—Not least important, flexing of the kiln is frequently the cause of concentrated stresses. Thermal Shock: Thermal shock, the result of heating and cooling too rapidly, occurs on starting and stopping or when a large patch of coating drops, exposing the bricks. Again, its destructive effect is often the result of phase change, liquid to solid or the reverse; dense refractories loaded with glass-forming impurities are particularly susceptible. Thermal shock is a. problem with refractories set in the wall or roof of a stationary furnace, and becomes even more serious in a rotary kiln, the tendency to spa11 being magnified with movement and concentration of stress. Uniform rate of feed and loading insures both better coating and a more uniform stress. Abrasion: If the refractories do not take a coating, abrasion can become a most destructive factor. Movement of the lining in shell or movement of loose blocks causes abrasion, which is also most destructive if the refractories do not take a coating. An analysis of the problem of basic lining for the hot zone reveals, therefore, a number of desirable characteristics: high refractoriness, basic chemical reaction, resistance to spalling, good strength at all stages, ability to take coating, true sizing, volume stability, and abrasion resistance. Increased demand

Jan 1, 1953

Data about production are practically non-existent before 1860. The Census of 1840 reported a small amount, and a number of small mines were opened in the forties, all of the coal being used locally, or hauled to consumers in wagons. Tonnages shown in Table 72 are estimated from those for which authority is given. Railroads reported coal tonnages carried in the state in 1878 and subsequent years for years ending June 30th;, it is not stated that the tonnage originated in the state. Considering this fact, and the considerable amounts used locally, the tonnages given in Table 72 are certainly not larger than the actual amounts produced.

Jan 1, 1942

By Thomas O. Breitling

The Mill Design Session at the Annual Meeting in New York next February will have a total of four papers. All of these papers will be concerned with the subject of in-plant dust in the hard-rock mining industry. The emphasis on efficient dust collection is timely, because dust is a problem not yet adequately covered in AIME papers. In general, dust collection should be the step following dust suppression. Dust collection and its return to the ore recovery circuit, or its waste to tailing are sources of added operating cost. If possible, dust should be kept in the main stream of ore flow by suppression.

Jan 1, 1970