Search Documents

By William Schriever

The flow of a gas-free liquid through a spherical-grain sand has been investigated by S1ichter.l By theoretical considerations involving a rather large number of approximations he arrives at the following flow-formula: V = CPd2At NLB{1 - m) where V is the volume of liquid delivered in time t through a cylindrical column of sand of length L and cross-sectional area A by a pressure-drop P when the sand grains of diameter d are packed to a porosity m and the coefficient of viscosity of the liquid is n. C and B are constants which were determined from geometrical relations; B was in reality a function of . Values of B(l — m) for various values of m were given in a table. In the same Annual Report of the U. S. Geological Survey, King reported the results of his experiments on the flow of water through porous media. He found that there was a departure of about 86 per cent. from a linear relationship between rate of flow and pressure, for a specimen of Dunnville sandstone for pressure drops not exceeding 60 cm. of mercury. The specimen was approximately 4 cm. in diameter and 5.1 cm. in length. Over the same range of pressure he found a departure of 45 per cent. for a specimen of Madison sandstone. For unconsolidated sands he found departures as great as 49 per cent. for pressure drops of 70 cm. of mercury; for pressure drops not exceeding a few inches of water he obtained a close approximation to a linear relation. He also investi-

Jan 1, 1930

By C. S. Barrett

WhEN a collimated beam of protons or other energetic particles is scattered by a single crystal, the emerging particles produce patterns that contain much crystallographic information. Calculations of the trajectories of individual particles can predict with reasonable accuracy the complete pattern (which is related reciprocally to channeling, now studied in detail6) but the task is a lengthy one which has been completed for very few cases. A many-beam dynamic diffraction calculation of the patterns would be even more difficult and in some cases may be invalid. Because of these complexities, simple methods that will predict to a rough approximation the relative intensities of the lines in films of the back-scattering patterns of a given crystal are wanted. I have found a method which, although it is not a valid computation of intensities or of film darkening by either dynamic or kinematic diffraction principles or by trajectory calculations, nevertheless is found to be useful in practice. It has been tested on several crystal types,7 and is here tested on additional ones. The method consists in first calculating the structure factor F(hk1) for the (hkl) plane, of spacing d, by the familiar equation: where the summation extends over the atoms in the unit cell and fj is the atom scattering factor of the jth atom (using tables computed for electron diffraction, preferably those computed without exchange). Then the F values are squared and summed over all the orders, n, for which F2 has an appreciable value, giving a quantity: Finally, I, is expressed as a percentage of Ic for the

Jan 1, 1970

By R. Lagneborg

WhEN mechanical twins initiate cracking it has been proposed1 that the friction stress for dislocation motion, in the Cottrell criterion for brittle fracture2 should be replaced by the stress required to propagate a twin, ttp. TF is the fracture stress, d the grain diameter, ß a geometric constant, u shear modulus, and y the effective surface energy. Since TTp is likely to vary with grain size, it cannot be substituted by a constant in Eq. [I]. If an expression for the energy change caused by a twin in a stressed material could be obtained, it is in principle possible to compute the critical size of the twin, i.e., the size at which the system can decrease its energy spontaneously, as a function of applied stress, thus giving the stress required to just barely propagate the twin, i.e., TTP. Consider a circular twin disc with a radius r and having a lenticular cross section, Fig. 1. Twin dislocations3 of strength b exist in the twin boundary parallel to the twin plane, one loop on each atomic plane. Assume that the total numbers of loops, n, can be replaced by one circular loop of a multiple dislocation, nb with a radius r. The energy change of the system, AW, due to such a twin in an applied stress field can then be calculated: The first term is the total twin surface energy, the second the elastic energy due to the twin dislocations, and the third the energy released by the twin in the applied stress field. yt is the twin boundary energy, r, the radius of the dislocation core, and T the applied

Jan 1, 1968

By J. H. Ffolliott

ALL, of the prospects that later became mines in the Ducktown district were discovered prior to 1854, and most of them were exploited before the turn of the century. It is the purpose of this paper to discuss the exploration and current development of the Boyd mine, discovered in 1853. It is in the heart of the Ducktown Basin, in the extreme southeast corner of Tennessee, and is being developed by the Tennessee Copper Co. GEOLOGY The geology of the district has been fully described in many papers. Probably the most complete description is that of Emmons and Laney.1 The rocks of the district are considered to be of Lower Cambrian age and are a part of the Great Smoky formation, consisting mainly of interbedded graywacke and mica schist, in which the ore deposits occur. The ore bodies are included in an area of about 6 sq. miles, 2 miles wide and 3 miles long striking N. 45° E., and may be grouped into three general lode systems. The northeast system, including the East Tennessee, London and Burra Burra ore bodies, and the southeast group, comprising the Polk County, Mary and Calloway deposits, are all characterized by relatively high copper values. The ores of the central system, which includes the Eureka, Boyd, Old Tennessee and Cherokee ore bodies, are low in copper and high in total sulphide content. Boyd mine lies roughly halfway between the Old Tennessee and Eureka ore bodies [ ] and 2500 ft. in the hanging wall of the Burra Burra mine (Fig. 1). Elevation of the surface is about 1725 ft. above sea

Jan 1, 1942

The co-operation of the members of the Institute is earnestly sought by the Committee on Nominations, recently appointed by the Board of . Directors, in its work of formulating a ticket for officers and places falling vacant in the Board of Directors in February, 1916. The Committee must present the official ticket of nominations to the Board of Directors at its October meeting. Members are, therefore, urged to send promptly their nominations for officers and Directors in order that the Committee may have an opportunity to give them full consideration. The officers to be elected at the annual meeting in February, 1916, are: One officer, known as Director and President. Two officers, known as Director and Vice-President. Five officers, known as Director; The attention of members is called to Articles V and VII of the Constitution, and to By-Law XIII, which reads as follows: "The geographical districts to be considered by the Committee on Nominations shall he as follows, until otherwise ordered by the Board. District No. 1. New England, New York, and New Jersey, excepting New York City and district., which is provided for in the Constitution. (N. B.-New York City and district is designated District 0.) District No. 2. Pennsylvania. District No. 3. Ohio, Indiana, Illinois, Iowa, and Missouri. District No. 4. Minnesota, Wisconsin, and Michigan. District No. 5. Montana, North and South Dakota, Wyoming, Nebraska, Kansas, Washington, Oregon, Idaho, and Alaska. District No. 6. California and Nevada. District No. 7. Utah, Colorado, Arizona, and New Mexico. District No. 8. Louisiana and Texas. District No. 9. Other Southern States and District of Columbia. District No. 10. Mexico. District No. 11. Canada."

Jan 7, 1915

By R. Taggart, R. H. Ericksen, D. H. Polonis

MarTENSITIC a has been observed to form spontaneously from the retained ß phase during the preparation of thin foil specimens of metastable Ti-Cr alloys containing from 6.9 to 20 wt pet Cr. Similar spontaneous martensite reactions have been reported in thin foils of 0 brass' and other alloys.2 4 The absence of retained austenite in iron-based alloys has also been attributed to spontaneous decomposition during thinning.5 The present work indicates that a unique situation occurs during which the spontaneous transformation takes place when the transitional ? phase is present in the as-quenched or partially aged ß phase. Alloys containing 6.9, 7.0, 8.0, 12.0, and 20.0 wt pet Cr were prepared by the levitation melting of "io-chrome" chromium and iodide titanium. The 0.5-in.-diam ingots were vacuum-annealed at 1000oC, and wafers 0.020 in. thick were then cut from the ingots. These wafers were wrapped in molybdenum foil, encapsulated in Vycor under a reduced pressure of purified helium, and then held for 30 min at 1000°C. The specimens were quenched in water to retain the metastable high-temperature ß phase. The quenched alloys were thinned by mechanical grinding to about 0.005 in. thick, then electropolished in a solution of 300 ml methyl alcohol, 175 ml n-butyl alcohol, and 30 ml perchloric acid at a temperature of -40°C. Needle specimens 0.005 to 0.010 in. diam were taken from each ingot and heat-treated with the foil specimens. X-ray diffraction patterns indicated the structure of the 6.9, 7.0, and 8 wt pet alloys to be a

Jan 1, 1968

By L. W. Rowe, S. S. Cole

A laboratory bench scale unit is described whereby finely divided chlorinatable residues are held for a short period by a restraining bed of a coarse-grained ore of comparable composition to permit 'flash' chlorination of the high surface area powder. Results on chlorinating a finely divicled titania residue using rutile sand as the restraining bed showed that 92 pct utilization of chlorine and equivalent conversion of TiO2 in the fine residue to Ticl4 were attained with a dust loss of about 3 to 4 pct and an equivalent amount of ch1om'nation of the titanium values in the restraining bed. THE chlorination of coarse grain titaniferous ores; i.e., 20 to 150 mesh sizes in fluidized beds is practiced commercially.' One effective method found for the chlorination of a very fine material in a fluidized bed is the "flash" chlorination technique.' By charging the finely divided charge material into the bottom of an established bed of optimum sized rutile, ilmenite, titanium beneficiate, or even an inert material such as sand, chlorination occurs before the dust can pass through the bed. The major requirement is that the bed be less chlorinatable than the charge. In this process, the charge consists of a finely divided (between one and 50 µ) titania residue obtained from a titaniferous ore beneficiation process. The charge is blended with a 20 pct wt basis addition of 20 to 60 .mesh size low volatile coke (to minimize hydrogen chloride formation) and fed to the bottom of the bed with the chlorine gas stream. A ball check device is used to permit entry of the charge and prevent the bed from discharging when the gas flow is cut off. The coarse pieces of coke serve to reduce compaction in the charge mixture and permit sat]sfactory feeding without plugging or jamming. Feed and gas rates are adjusted to provide for complete reaction of the charge material, with 90 to 95 pct chlorine efficiency, and maintain a gas flow in the range of 0.4 to 0.6 ft per sec. The equipment consisted of a 3-in. diam mullite tube enclosed in an electric furnace. A bow-shaped 3/4 in. Saran tube fed the charge from an air lock type of feed hopper (to prevent the escape of the chlorine gas into feed bin) to the bottom of the bed. The charge rate was set by providing a small awiliary hopper below the feed hopper where a weighed portion of the charge could be discharged in a specified time interval into the main chlorine stream. The chlorine rate was measured by a flowmeter. The reaction tube was filled with a bed of Australian rutile ore, this restraining bed serving two purposes; i.e., it rapidly heated the fresh charge to the reaction temperature and retained the particles in the bed for a sufficient time for selective chlorination to proceed. Due to the fine particle size and open, porous structure of the charge, this reaction was almost instantaneous, and, with proper adjustment of feed and gas rates, very little fine material passed through the bed without reacting and only a very small fraction of the restraining bed was chlorinated. A typical reaction procedure was to fill the bench scale fluidized bed unit with a 1 kg charge of Australian rutile ore analyzing 95.5 pct TiO2, 0.6 pct FeO, a beach sand deposit 40 to 150 mesh size. When fluidized, the bed was approximately 2 ft in depth. The ore was fluidized with a 1:l mixture of chlorine and nitrogen at a rate of 0.40 ft per sec. This gas mixture was necessitated by the comparatively short bed depth; a larger unit, with a deeper bed, could be fluidized with chlorine alone without significant free chlorine loss. Feed rate was 8.0 g per min of beneficiated ilmenite analyzing 85.0 pct TiO2, 2.6 pct FeO plus 1.6 g per min of 20 to 60 mesh petroleum coke. The

Jan 1, 1962

Committee on Reduction and Refining of Copper............ 3 A.I.M.E. Officers and Directors.................... 4 Preface. By C. R. Kuzell....................... 7 Career and Achievements of James Douglas. By Arthur L. Walker. . 9 PAPERS Smelting 1. Reverberatory Smelting Practice History of Reverberatory Smelting in Montana, 1879-1933. By Frederick Laist..............................23 Reverberatory Smelting of Raw Concentrates at the International Smelter, Miami, Arizona. By P. D. I. Honeyman (With Discussion)...... 88 Development of Gun-feed Reverberatory Furnaces at Garfield Plant of American Smelting and Refining Company. By R. A. Wagstaff (With Discussion)........................99 An Experimental Combination of Shaft Roasting and Reverberatory Smelting. By Frederick Laist and J. P. Cooper (With Discussion).... 104 Forms of Copper Found in Reverberatory Slags. By Royal B. Jackman and Carle R. Hayward (With Discussion).............111 2. Converting Practice Development of Copper Converting at Butte and Anaconda. By William Kelly and Frederick Laist...................122 Developments in Converting Lead and Copper Matte at Tooele. By B. L. Sackett.............................132 Messina Stationary Basic Copper Converter. By R. G. Knickerbocker (With Discussion)........................140 Smelting Copper Concentrates in a Converter. By George E. Beavers. 149 Sulfuric Acid from Converter Gases. By George E. Beavers......151 Development of Monolithic Tamped Periclase Converter Linings at United Verde Copper Company Smelter. By F. H. Parsons (With Discussion) . 153 3. Descriptions of Plants The Noranda Smelter. By W. B. Boggs and J. N. Anderson......165 Smelting Operations at Roan Antelope Copper Mines, Limited. By Charles R. Wraith.......................202 4. Waste-heat Boiler Practice Copper-refinery Waste-heat Boilers at Great Falls Reduction Department, Anaconda Copper Mining Company. By E. S. Bardwell......225

Jan 1, 1934

By Randall L. Neal

This paper discusses the impact of taxes at the state and federal level on typical on-shore oil and gas exploration economics in the USA. Taxes considered are the windfall profits excise tax, state production (or severance) taxes, state income tax, and federal income tax. Also considered will be market prices for oil and gas in the USA. The effect of government take as a percent of revenue, on rate of return, discounted Payout, and discounted cumulative cash flow is shown on the attached tables. The conclusion drawn is that tax laws, while rarely the most important factor to be considered when drilling a well, can have significant impact on the profitability of oil and gas ventures, and should be considered when determining where to drill. Hypothetical exploration wells were analyzed for the impact of tax laws on project profitability. The results of this study show that when factors other than taxes are postulated to be the same (such as producing rate, capital, operating costs, and prices), cash flow can vary by as much as 68% due to the differences in the tax laws. Other significant findings for the cases studied include: (a) that discounted payout varied by as much as 1.8 years, (b) that rate of return differed by up to 67% and (c) the total tax rate as a percentage of revenue had a maximum variance of 33%.

Jan 1, 1982

By J. E. Willson, N. K. Bohidar

An evaluation of internal stress distribution based on photoelastic studies and destructive testing of simulation models shows that pillar failure is a function of the internal stress distribution, and that stability can be changed by altering the internal stress pattern. Induced stresses in three-dimensional epoxy disks subjected to uniaxial forces were evaluated by photoelastic studies. Stress profiles across different sections perpendicular to the loading direction revealed two maxima for each profile. Based on the stress distribution for the entire column, an attempt was made to explain pillar spalling and the hour glass pattern of failure in a mine pillar. For maximum stability and optimum design of mine pillars, it is necessary to consider the external forces, the nature and distribution of induced stresses and the characteristics of the pillar material as determined in the laboratory. This paper summarizes the research done by N. K. Bohidarl and Ben L. seegrniller2 as partial fulfilment of the requirement for Master of Science degree in Mining Engineering, University of Utah. It is an evaluation of a study to determine the stress distribution in short columns in order that regions of high stress concentration in mine pillars may be found and their effect on pillar failure be ascertained. The ratios of the dimensions of the columns studied are representative of those found in mines located in flat-bedded deposits. The weight of the overburden generally constitutes the major external force. This force is calculated by taking into account specific weight and thickness of the cover. Determination of the distribution of this force on pillars may often require a complex analytical study. There have been many investigations of the strength

Jan 1, 1968

R. W. Balluffi (Atomic Energy Div., Sylvania Electric Products Inc., Bayside, N. Y.)—Since porosity is known to form in the copper side of Cu-Ni couples during diffusion24,25 it is of importance to consider this factor in interpreting the large variations of chemical diffusivity with copper concentration reported for this system. The presence of porosity may affect the measurement of D in two ways: 1—density changes in the couple invalidate the usual solutions of the diffusion equation, and 2—the pores may act as short-circuiting paths when transport through the vapor or along internal surfaces is appreciable or else as open circuits when these effects are small. The error produced by the first effect may be estimated by a graphical analysis. Fig. 8 shows the porosity generated in the copper side of the Kirkendall interface of a pure nickel vs pure copper couple after diffusion for 350 hr at 1040°C in hydrogen. In Fig. 9 the actual diffusion curve which would be obtained by the usual slicing technique is shown as a solid line drawn to the same scale (from the data of da Silva and Mehl"). The amounts of porosity (obtained by lineal analysis) and of nickel are graphically represented by the hatched areas. The standard solutions of the diffusion equation are valid only when all volume elements of unit length and unit cross section contain equal numbers of atoms." It is possible to correct the experimental curve to satisfy this condition by shrinking the couple in the direction of diffusion in such a way as to eliminate the porosity.* The corrected diffusion curve obtained after

Jan 1, 1954

By Wayne A. Greenwalt

A method that determines venture participation when the decision maker's level of risk aversion varies according to venture profitability and risk investment is presented. The decision maker's fundamental aversion to risk is established by the selection of a desired working interest for a venture that anticipates only a discounted payout.

Jan 1, 1982

By H. J. Rose

Sixty-five million net tons of coal were carbonized in the by-product and beehive coke ovens1 of the United States during 1924. This tonnage represented 13.4 per cent. of the bituminous coal which was mined in that year. Table 1 shows production and disposition.2 Table 1.—Production and Disposition of Ocen Coke in 1924 By-product Beehive Total Coal charged into ovens, tons................ 49,061,339 15,914,310 64,975,649 Coke produced (exclusive of screenings and breeze), tons............................. 33,983,568 10,286,037 44,269,605 Average yield of coke, per cent ............. 69.3 6.46 68.9 Disposition of coke, per cent.: Blast furnace.......................... . . 82.6 Foundry............................... . 13.3 6.6 Domestic.............................. . 1.4 6.7 Water gas manufacture and all other uses.. 4.6 . 4.1 Cokes having somewhat different combinations of chemical and physical properties are desired for the various uses listed above, and these properties depend primarily upon the types of coal used. American coals have a wide range of purity and coking quality, and the chief subject of this paper will be the selection of coals for the manufacture of blast furnace, foundry, domestic, and water-gas coke, in by-product coke ovens. It will obviously be necessary to include a discussion of those physical and chemical characteristics that are generally considered essential or desirable for each type of coke. Suitable Coals The examination and development of new sources of coking coal are important because of the irregular and limited distribution of high-grade

Jan 1, 1927

By Ferit Gurses

Extensive coal and lignite deposits exist in Turkey. Bituminous coal is the nation's principal mineral resource; important not only as fuel for the industrial development of the country, but also as a means of obtaining foreign exchange. Of the electrical power generated during 1939, 82.8 per cent was derived from coal.' It is anticipated that the lignite deposits will be one of the major sources of power for the electrification of the country. Bituminous Coal The locations of the four principal bituminous-coal2 basins are indicated on Fig. 1. The Eregli-Zonguldak basin lies on the Black Sea northwest of Ankara; the Canakkale basin lies near the junction of the Dardannelles; the Trakya basin is in European Turkey northwest of the Bosphorus and the Erzurum basin lies far to the east. The Eregli-Zonguldak basin is the most important of the four. This coal basin was discovered in 1829 but did not arouse interest until 1848; up to 1865, its annual production had not exceeded 50,000 metric tons. In 1865, during the Sultanate, working of coal mines was started by the Navy department, and the annual production was 61,145 metric tons. In 1908, the Minister of Commerce and Agriculture was authorized to develop the whole coal basin. Production reached 264,397 metric tons in 1910, and during 1915-1922, preceding the revolution, the total produc- tion of the basin was' 2,676,043, or an average of 334,000 metric tons annually. The period of national revolution that followed was marked by a steady increase in coal production in Turkey, although world production decreased, because of the crisis of 1929-1932, about 52 per cent. ARea and Geology of the Coal Basin The geology of the Eregli-Zonguldak area is not yet completely known. The basin begins -at Gungazi, to the west of Eregli, and extends to Sogutozu, a distance of about 106 miles. The coal beds, however, appear only in places and the overlying Cretaceous strata hide them elsewhere. This area includes the most important centers, such as Kandilli, Alacaagzi, Teflenli, Kozlu, Gelik (see Fig. 2). The geological sequence of the district is correlated with the Cretaceous of the Balkans; which is, in turn, a prolongation of the Alpine zone. Geological surveys made by G. Ralli, R. Zeiller and P. Arni3 show that the Eregli-Zonguldak formations fall into three natural divisions. Series a, The Alacaagzi in the district of that name (Fig. 2), is of the Culm stage. The strata strike generally east-west and dip about 30" south. This series appears also around Kandilli and Camli, with a steeper angle of dip, but the deposits there lack regularity. The Alacaagzi stage appears also farther east, to the south of Kozlu and Gelik. The Alacaagzi series contains 15 seams of an average thickness of 2 ft. of good coal. Series b, the Kozlu, best represented in Zonguldak, Kilimli, Catalagzi, and between

Jan 1, 1944

By Ferit Gurses

Extensive coal and lignite deposits exist in Turkey. Bituminous coal is the nation's principal mineral resource; important not only as fuel for the industrial development of the country, but also as a means of obtaining foreign exchange. Of the electrical power generated during 1939, 82.8 per cent was derived from coal.' It is anticipated that the lignite deposits will be one of the major sources of power for the electrification of the country. Bituminous Coal The locations of the four principal bituminous-coal2 basins are indicated on Fig. 1. The Eregli-Zonguldak basin lies on the Black Sea northwest of Ankara; the Canakkale basin lies near the junction of the Dardannelles; the Trakya basin is in European Turkey northwest of the Bosphorus and the Erzurum basin lies far to the east. The Eregli-Zonguldak basin is the most important of the four. This coal basin was discovered in 1829 but did not arouse interest until 1848; up to 1865, its annual production had not exceeded 50,000 metric tons. In 1865, during the Sultanate, working of coal mines was started by the Navy department, and the annual production was 61,145 metric tons. In 1908, the Minister of Commerce and Agriculture was authorized to develop the whole coal basin. Production reached 264,397 metric tons in 1910, and during 1915-1922, preceding the revolution, the total produc- tion of the basin was' 2,676,043, or an average of 334,000 metric tons annually. The period of national revolution that followed was marked by a steady increase in coal production in Turkey, although world production decreased, because of the crisis of 1929-1932, about 52 per cent. ARea and Geology of the Coal Basin The geology of the Eregli-Zonguldak area is not yet completely known. The basin begins -at Gungazi, to the west of Eregli, and extends to Sogutozu, a distance of about 106 miles. The coal beds, however, appear only in places and the overlying Cretaceous strata hide them elsewhere. This area includes the most important centers, such as Kandilli, Alacaagzi, Teflenli, Kozlu, Gelik (see Fig. 2). The geological sequence of the district is correlated with the Cretaceous of the Balkans; which is, in turn, a prolongation of the Alpine zone. Geological surveys made by G. Ralli, R. Zeiller and P. Arni3 show that the Eregli-Zonguldak formations fall into three natural divisions. Series a, The Alacaagzi in the district of that name (Fig. 2), is of the Culm stage. The strata strike generally east-west and dip about 30" south. This series appears also around Kandilli and Camli, with a steeper angle of dip, but the deposits there lack regularity. The Alacaagzi stage appears also farther east, to the south of Kozlu and Gelik. The Alacaagzi series contains 15 seams of an average thickness of 2 ft. of good coal. Series b, the Kozlu, best represented in Zonguldak, Kilimli, Catalagzi, and between

Jan 1, 1944

By L. A. Shipman

The combustion of coal in fuel beds has been practiced as an art for many years; during the last 2 7 years a scientific approach to this subject has contributed a small amount of fundamental data. The subject is a very controversial one. Opinions regarding the performance of the same coal used in the same equipment in different plants may vary from "the best coal ever used in the plant" to "the worst coal ever tired." These opinions can all be true, owing to the various conditions under which the coal was used. Because of these differences, an attempt will be made in this paper to discuss coal facts and coal characteristics as related to the use phenomena observed during the art of firing coal in fuel beds for many years. The work of Kreisinger1 and his associates in the 1,'. S. Bureau of Mines, reported in 1916, was the first scientific attempt I know of to obtain factual data explaining the mechanism of combustion of fuel beds. They gave a chart showing an ignited fuel bed. The air passing up through the fuel bed first combined with the fuel by a reaction resulting in the complete combustion of carbon to CO2, which combined with the carbon in higher levels of the fuel bed to form CO with the absorption of heat. The fundamental facts produced in those experiments proved of much value and checked with practical experiences with hand-fired fuel beds. Hand firing was the prevailing method of stoking coal at that time. The order in which these reactions occur, as shown by Kreisinger and his associates, has been amply confirmed by repetition of this work with different fuels both her? and abroad. These experiments also showed that under their conditions the rate of burning was proportional to the air flow. These data were of practical value to a fireman and were accepted as generally true in all fuel beds. In later years many observations by myself in fuel beds of underfeed stokers and other thick fuel beds such as gas producers, where channeling. increase of particle size, or both, occur. indicated that, instead of the horizontal layers we had thought were present, perhaps the layers were vertical or irregular. Later investigations in fuel beds made by Mayers2 and Barnes3 indicated that the burning takes place in some instances along the surfaces of vertical or irregular channels or cracks in the fuel bed and that under these conditions a reaction occurs that differs from that in the old horizontal-layered handfired fuel beds. Examining the data in Kreisinger'sl experiments, and the information in different charts with different fuels, different retort positions and air admissions of Barnes3 and the gas analysis arid isotherms of Mayers,2 one can check experience observation and come to a conclusion that as particle size of the fuel increases with other conditions the same, the maximum CO2 and temperature

Jan 1, 1947

By L. A. Shipman

The combustion of coal in fuel beds has been practiced as an art for many years; during the last 2 7 years a scientific approach to this subject has contributed a small amount of fundamental data. The subject is a very controversial one. Opinions regarding the performance of the same coal used in the same equipment in different plants may vary from "the best coal ever used in the plant" to "the worst coal ever tired." These opinions can all be true, owing to the various conditions under which the coal was used. Because of these differences, an attempt will be made in this paper to discuss coal facts and coal characteristics as related to the use phenomena observed during the art of firing coal in fuel beds for many years. The work of Kreisinger1 and his associates in the 1,'. S. Bureau of Mines, reported in 1916, was the first scientific attempt I know of to obtain factual data explaining the mechanism of combustion of fuel beds. They gave a chart showing an ignited fuel bed. The air passing up through the fuel bed first combined with the fuel by a reaction resulting in the complete combustion of carbon to CO2, which combined with the carbon in higher levels of the fuel bed to form CO with the absorption of heat. The fundamental facts produced in those experiments proved of much value and checked with practical experiences with hand-fired fuel beds. Hand firing was the prevailing method of stoking coal at that time. The order in which these reactions occur, as shown by Kreisinger and his associates, has been amply confirmed by repetition of this work with different fuels both her? and abroad. These experiments also showed that under their conditions the rate of burning was proportional to the air flow. These data were of practical value to a fireman and were accepted as generally true in all fuel beds. In later years many observations by myself in fuel beds of underfeed stokers and other thick fuel beds such as gas producers, where channeling. increase of particle size, or both, occur. indicated that, instead of the horizontal layers we had thought were present, perhaps the layers were vertical or irregular. Later investigations in fuel beds made by Mayers2 and Barnes3 indicated that the burning takes place in some instances along the surfaces of vertical or irregular channels or cracks in the fuel bed and that under these conditions a reaction occurs that differs from that in the old horizontal-layered handfired fuel beds. Examining the data in Kreisinger'sl experiments, and the information in different charts with different fuels, different retort positions and air admissions of Barnes3 and the gas analysis arid isotherms of Mayers,2 one can check experience observation and come to a conclusion that as particle size of the fuel increases with other conditions the same, the maximum CO2 and temperature

Jan 1, 1947

By J. E. Burke

RECENT investigations have elucidated many of the phenomena of the grain growth process, but have also revealed some conflicting and unexplained results. Beck and his co-workers1,2,3 have shown that grain growth continues with continued heating at one temperature until the average grain size approaches the thickness of the specimen, Plotting the logarithm of the average grain diameter, D, against the logarithm of the annealing time, t, they find the straight line relationship given by the equation: [D=Ktn [11] with possible small deviations at short annealing times. K and n are constants at constant temperature. On the other hand, Walker4 finds that, in alpha brass, the rate of growth falls off more rapidly than indicated by Eq I after long annealing, so that an equilibrium grain size is approached. Burke5 showed, using Walker's data, that time and temperature for grain growth are apparently related through an activation energy, H, according to the relationship: [t, Hr i '_ III t„ = R \T, - ~) [2]] where t1 and t2 are the annealing times necessary for the average grain size to increase from Do to D at temperatures T1 and T2 and R is the gas laws constant. In the case quoted, H had the value 60,000 cal per mol. The apparent validity of this relationship, at least up to 700°C, and the approximate value of H were later confirmed by Beck.' The results obtained by Beck, Kremer, Demer and Holzworth2 for aluminum and aluminum-magnesium alloys could not be satisfied by such a relationship, since the slope of the isothermal curves increased with increasing temperature. These data indicate and Beck, Holzworth and Hu6 later demonstrated experimentally that the only apparent factor controlling the rate of grain growth at constant temperature is the grain size. While many of the phenomena have been elucidated, a reasonably quantitative explanation of the process is lacking. There exists uncertainty even as to the primary driving force for grain growth, although there is a considerable body of indirect evidence that the interfacial energy of the grain boundary is responsible.7,8,10 Making implicit use of this assumption, several authors14,15 have pointed out that grain boundaries should migrate toward their center of curvature. Harker and Parker' have advanced this concept furthest, and show that one can expect grain boundary migration to occur only when the grain faces are curved, or when they meet at non-equilibrium angles. When the face is curved toward a grain A, for example, the atoms in the surface of grain B, on the other side of the boundary, are on the average more surrounded by the atoms of their lattice than the atoms on the surface of grain A. Because of thermal motion, the atoms at the interface will sometimes be attached to grain A and

Jan 1, 1948

By Richard M. Foose

Five miles southwest of Mt. Holly Springs, Cumberland County, Pennsylvania, the Philadelphia Clay Co. has been mining and milling a white clay since 1896; for use in white cement, as a filler in rubber, pigment and paper, in the manufacture of insecticides, and for other minor purposes. Until late in 1942, when the mine was abandoned because of labor shortage, combined underground mining and surface stripping produced approximately 30,000 tons of clay a year, of which 10,000 tons were refined in the mill. Geology Lower Cambrian Antietam quartzite and the Rilontalto quartzite, stratigraphi-cally older, trend N.55°E. and make a sharp 1600-ft. anticlinal ridge of the South Mountains. The Tomstown dolomite overlies the Antietam quartzite on the southeast flank of the anticline, which is displaced near its crest by a steeply dipping oblique fault. Erosion of the less resistant Tomstown formation has resulted in a narrow valley at an elevation of 700 ft. Directly on top of the Antietam quartzite and at the base of the Tomstown formation is a zone of sandy white clay, lenticular along the strike of the formations, ranging in thickness from 10 to 300 ft. within a mile. All of the formations dip steeply to the southeast, from 65" to vertical. The clay crops out at an elevation of about 1000 feet. Origin and Character The uppermost part of the Antietam formation is sericitic and schistose at many places, and at all these places weathering is in an advanced stage. The clay is the residual product of weathering of this sericitic quartzite or sandy schist. The crude clay has the physical aspect of a sandy kaolin, but there Are large areas in the clay formation that are low in free silica, and commonly the 30 ft. adjacent to the Antietam quartzite is notably free of silica. The overlying Tomstown dolomite has been weathered almost completely to a mixed yellow and brown clay, which carries a zone of nodular and chunky limonite and manganese ore, 4 to 12 ft. thick, about loo ft. from the contact with the white clay. In mining, this zone is an important "marker," indicating where the white clay may be expected in an advancing tunnel. The contact of the white clay formation with the yellow and brown clay of the Tomstown formation is relatively sharp, although the line of contact is irregular and therefore responsible for the lenticular character of the white clay formation. Following is an analysis of the refined clay containing less than one per cent of moisture when dried at 212°F.: SiO2, 67.05 per cent; Al2O3, 22.27; Fe2O3, 0.40; CaO, 0.00; TiO2, 1.05; MgO, 0.52; Na20, 0.04; K2O, 0.88; ignition loss, 7.65; total, 99.86.

Jan 1, 1948

By Richard M. Foose

Five miles southwest of Mt. Holly Springs, Cumberland County, Pennsylvania, the Philadelphia Clay Co. has been mining and milling a white clay since 1896; for use in white cement, as a filler in rubber, pigment and paper, in the manufacture of insecticides, and for other minor purposes. Until late in 1942, when the mine was abandoned because of labor shortage, combined underground mining and surface stripping produced approximately 30,000 tons of clay a year, of which 10,000 tons were refined in the mill. Geology Lower Cambrian Antietam quartzite and the Rilontalto quartzite, stratigraphi-cally older, trend N.55°E. and make a sharp 1600-ft. anticlinal ridge of the South Mountains. The Tomstown dolomite overlies the Antietam quartzite on the southeast flank of the anticline, which is displaced near its crest by a steeply dipping oblique fault. Erosion of the less resistant Tomstown formation has resulted in a narrow valley at an elevation of 700 ft. Directly on top of the Antietam quartzite and at the base of the Tomstown formation is a zone of sandy white clay, lenticular along the strike of the formations, ranging in thickness from 10 to 300 ft. within a mile. All of the formations dip steeply to the southeast, from 65" to vertical. The clay crops out at an elevation of about 1000 feet. Origin and Character The uppermost part of the Antietam formation is sericitic and schistose at many places, and at all these places weathering is in an advanced stage. The clay is the residual product of weathering of this sericitic quartzite or sandy schist. The crude clay has the physical aspect of a sandy kaolin, but there Are large areas in the clay formation that are low in free silica, and commonly the 30 ft. adjacent to the Antietam quartzite is notably free of silica. The overlying Tomstown dolomite has been weathered almost completely to a mixed yellow and brown clay, which carries a zone of nodular and chunky limonite and manganese ore, 4 to 12 ft. thick, about loo ft. from the contact with the white clay. In mining, this zone is an important "marker," indicating where the white clay may be expected in an advancing tunnel. The contact of the white clay formation with the yellow and brown clay of the Tomstown formation is relatively sharp, although the line of contact is irregular and therefore responsible for the lenticular character of the white clay formation. Following is an analysis of the refined clay containing less than one per cent of moisture when dried at 212°F.: SiO2, 67.05 per cent; Al2O3, 22.27; Fe2O3, 0.40; CaO, 0.00; TiO2, 1.05; MgO, 0.52; Na20, 0.04; K2O, 0.88; ignition loss, 7.65; total, 99.86.

Jan 1, 1948