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Frank 11. Probert, Neudorf, Anhalt, Germany (communication to the Secretary): I have read with much pleasure Mr. Collier's valuable paper. But the system of timbering which he describes as used in the levels, stopes, etc., though it must be admitted to be very strong and safe, seems to me somewhat extravagant. The amount of timber required every month for such a system must be enormous; and only where suitable material could be cheaply obtained would such a plan be economically practicable. The first point which strikes me is the unusually great diameter of the timber employed. In the mines of Pfaffenberg and Meiseberg, which are under my supervision, the country-rock consists of argillaceous slates, traversed by innumerable small fissures or joints, dipping at all angles and striking to all points of the compass. Undoubtedly, this net-work has been caused by the upheaval of granite masses in the vicinity. Each fissure is accompanied by a more or less well-c1efinc.d gouge or fluccan, caused by the rubbing together of the slates at or after the original disturbance. In such

Jan 1, 1900

By W. N. Lacey, R. H. Olds, B. H. Sage

The volumetric behavior of five mixtures of black oil and natural gas and of two mixtures of condensate and natural gas from a field in the San Joaquin Valley was experimentally established. This work was carried out at roo°, I9o° and 250°F in the pressure interval between 400 and 5000 psi. The viscosity of the liquid phase of four mixtures of black oil and natural gas was experimentally measured in the above-indicated temperature and pressure intervals. The effect of methane upon the precipitation of bitumen from the black oil was studied at 230°F. Introduction The solution of a number of the economical and technological problems which arise in connection with petroleum production is dependent upon the availability of the necessary quantitative information covering the materials involved. This requires data concerning physical properties of naturally occurring hydrocarbon mixtures at the pressures and temperatures characteristic of underground petroleum reservoirs. The experimental determination of the desired data for each situation encountered is relatively time-consuming. However, it is considered to yield results sufficiently more reliable than those obtained from correlations to justify the effort. For these reasons there was undertaken a laboratory investigation of the viscosity of the liquid phase and the volu- metric and phase behavior of mixtures of oil and gas samples obtained from wells in a field located in the San Joaquin Valley. Terminology The nomenclature of petroleum engineering is not at present entirely standardized. Many commonly used technical terms are not everywhere given the same meanings. For the purposes of this paper the following definitions will be adopted: Black oil refers to the dark-colored, hydrocarbon liquid obtained when the producing horizon of the well lies partly in the condensed hydrocarbon phase of the reservoir. Condensate is the term applied to the relatively volatile, pale yellow or amber-colored hydrocarbon liquid that is often obtained from the surface separator system when the producing horizon of the well lies in the gas cap of the reservoir. The gas obtained from the surface separator system is called natural gas regardless of whether the well is producing black oil or condensate. As might be expected from the multi-component character of naturally occurring hydrocarbon materials, the compositions of black oil, condensate and natural gas are subject to considerable variation depending upon the temperatures and pressures prevailing in the surface separator system as well as upon the overall composition of the material produced from the reservoir. In order to obtain samples capable of reproducing the total hydrocarbon material produced by the well, all oil and gas mixtures used in this investigation were com-

Jan 1, 1949

By Henry M. Howe

THIS paper gives the composition of the iron and slag at different stages in the "air-furnace" process of preparing "hard metal," or white cast-iron, for conversion into malleable cast-iron by annealing. The details of the process are given in an appendix. One of us had been trying for years to work some chemist of some of our malleable-iron works up to a degree of enthusiasm which would lead him to make such au investigation. It would have had the advantage of the greater familiarity with the conditions which one habitually on the spot must have. Failing in this, he made use of an opportunity which presented itself of taking samples here represented, with such fairness as the conditions permitted, holding firmly that a rough approximation to the truth is better than the complete lack of data, or that a bird in the hand is worth two in the bush. We hope that this attempt may stimulate others effectively to duplicate this work, and thus correct or confirm it. Our results are shown in Table I. and graphically in Figs. 1 and 2. Discussion.-At the time when the first two samples were taken, the metal and slag were still too sluggish to permit fair sampling, and not until sample 6 were the conditions really favorable, because at the time of the fourth sample the metal was not fully melted, and even at the time of sample 5 it was still sluggish. Indeed, the slag was probably very heterogeneous throughout, because it took up silica and alumina rapidly from the bottom, and because it was so siliceous as to be sluggish at this relatively low temperature. This hetero-geneousness is exaggerated in the two samples of slag 8, apparently by the great viscosity due to its extraordinary acidity. Note that the manganous oxide of one sample is about two and

Mar 1, 1909

By J. L. Green

Virginia-Carolina Chemical Corp., in its Florida Operations, uses both roller mills and ball mills in dry grinding of phosphate rock. The roller mills have been in operation since 1954 in the Mining Department. The ball mills were installed and put in operation in 1960 in the Harding Concentrate Superphosphate Plant. The roller mills in the Mining Department are used to grind phosphate rock for outside customers. This involves short notice orders of varying grinds, grades and types of rock. The ball mills grind phosphate rock for use in V-C's own phosphoric acid and concentrated superphosphate plant. These mills grind generally two types of rock for one grind. In 1959, a 10% speed-up was made in the operating speed of the roller mills. This paper deals with the operational gains and resulting cost savings which evolved from this speed-up, and compares the present operations of the roller mills and of the ball mills in grinding phosphate rock. In January 1959 it was decided to determine the feasibility of reducing the grinding cost on the roller mills, per ton of rock ground, by speeding up the mill 10%. At this time, one mill was completely reconditioned so it would be in top condition. Extensive tests were then run both before and after the mill speed-up to determine the resultant cost savings. These tests showed that, due to this 10% speed-up, the mill capacity was increased approximately 20% and grinding power costs per ton were reduced approximately 10%. Table I shows the results of these tests. Each test run actually represents several of the same type rock and grind, averaged together. Each test run lasted approximately three hours. The validity of these runs has been confirmed by subsequent operation in grinding over 1,000,000 tons of phosphate rock. Accurate records have been kept on power consumption and repairs as well as tons produced. Two types of feed rock were used for the tests — pebble phosphate rock and flotation phosphate concentrate rock. The pebble phosphate rock size is approximately 80-90% plus 20 mesh. The flotation concentrate phosphate rock size is approximately 15% plus 20 mesh and 95% plus 100 mesh. The same two types of rock feed were used for all the test runs. Test Nos. 1, 2, and 3 were run at the original mill speed of 85.5 rpm on the vertical shaft. Test No. 1 was run with a feed of high grade flotation concentrates; the desired fineness attempted was 70% passing 200 mesh. Tests No. 2 and No. 3 were run with a feed of low grade pebble. Test No. 2 was run for a desired fineness of 70% passing 200 mesh. Test No. 3 was run for desired fineness of 50% passing 200 mesh.

Jan 1, 1963

By J. K. Buehler

With the rapid acceleration of the cost of shovel dippers and major standard shovel clipper rebuild components, maintenance management at Kennecott Copper Corp.'s Bingham Canyon mine initiated a dipper maintenance and rebuild program. The program focused on extending the service life of the shovel dipper, reducing field labor in maintaining dippers, and lowering shovel dipper rebuild costs. While comprehensive evaluation of the program is still underway, preliminary benefits of the program indicate: •Reduced field ,gelding for shovel dipper field maintenance, •Fewer dipper rebuild units entering the shop, and •Reduced dipper rebuild costs per unit.

Jan 1, 1979

By T. L. Joseph

Blast furnaces are most efficient thermally when the CO2 in the top gas is highest. Oxygen introduced in the air blast is converted to CO in the combustion zones. The extent to which CO, generated in front of the tuyeres, is converted later to CO2 depends upon the ratio of ore to coke in the charge and the degree to which CO2, formed by reduction of iron oxides with CO, reverts to CO by the secondary reaction C + CO2 = 2CO. About 300 to 400 lb. of carbon' per ton of pig iron is normally involved in the solution-loss reaction or direct reduction of FeO with carbon, which produces the same over-all results; that is, lower CO2 in the top gas. Rich2 has recently reported a reduction in fuel consumption at slower rates of blowing on two furnaces in spite of higher heat losses per ton of iron. Lower fuel consumption at slow operating rates was due to more complete reduction of the ore that resulted in higher CO2 in the top gas and consequently more efficient use of carbon. Kinney3 has reported substantial savings in fuel as a result of crushing and sizing the ore charge. Improvements in practice brought about by sintering magnetite concentrates, flue dust and fine ores have been due to the establishment of conditions favoring more complete reduction of the ore in the upper part of the furnace. The extent to which oxides and fluctuations in composition in pig iron affect the quality of steel and finished product needs further study. There is evidence that more thorough preheating and reduction of the ore in the upper part of the furnace tend to give a better quality of iron. Bogatzkii4 found from laboratory work that the amount of oxygen entering electrolytic iron, melted under various slags, was directly proportional to the concentration of free FeO in the slag and inversely proportional to the basicity of the slag. Herty and Gaines5 concluded that the silicate content of open-hearth steel before deoxidation is related to the concentration of silica in the pig-iron charge, indicating that most of the persistent inclusions are silica from the iron. They also found that

Jan 1, 1936

By T. L. Joseph

Blast furnaces are most efficient thermally when the CO2 in the top gas is highest. Oxygen introduced in the air blast is converted to CO in the combustion zones. The extent to which CO, generated in front of the tuyeres, is converted later to CO2 depends upon the ratio of ore to coke in the charge and the degree to which CO2, formed by reduction of iron oxides with CO, reverts to CO by the secondary reaction C + CO2 = 2CO. About 300 to 400 lb. of carbon' per ton of pig iron is normally involved in the solution-loss reaction or direct reduction of FeO with carbon, which produces the same over-all results; that is, lower CO2 in the top gas. Rich2 has recently reported a reduction in fuel consumption at slower rates of blowing on two furnaces in spite of higher heat losses per ton of iron. Lower fuel consumption at slow operating rates was due to more complete reduction of the ore that resulted in higher CO2 in the top gas and consequently more efficient use of carbon. Kinney3 has reported substantial savings in fuel as a result of crushing and sizing the ore charge. Improvements in practice brought about by sintering magnetite concentrates, flue dust and fine ores have been due to the establishment of conditions favoring more complete reduction of the ore in the upper part of the furnace. The extent to which oxides and fluctuations in composition in pig iron affect the quality of steel and finished product needs further study. There is evidence that more thorough preheating and reduction of the ore in the upper part of the furnace tend to give a better quality of iron. Bogatzkii4 found from laboratory work that the amount of oxygen entering electrolytic iron, melted under various slags, was directly proportional to the concentration of free FeO in the slag and inversely proportional to the basicity of the slag. Herty and Gaines5 concluded that the silicate content of open-hearth steel before deoxidation is related to the concentration of silica in the pig-iron charge, indicating that most of the persistent inclusions are silica from the iron. They also found that

Jan 1, 1936

By R. W. Raymond

The immense commercial value of the Gayley dry-blast process has been established beyond controversy. The testimony of practical blast-furnace managers, on both sides of the Atlantic, agrees that it reduces the cost of pig-iron about $1 per ton; but from the same testimony it appears that this direct economy does not by any means cover its commercial advantages—in fact, that under conditions frequently encountered in practice, it presents other benefits of even greater immediate financial importance. To this point I shall recur in a later part of the present paper. The history of the reception given to this invention, especially on the other side of the Atlantic, has repeated an experience familiar to American engineers. First, the reports of our practice were rejected as theoretically impossible, according to generally accepted notions and formulas; then the figures were reluctantly accepted; and finally the attempt has been made to explain how they could have been obtained. As to the Gayley dry blast, me Americans have been for several years in the last stage of the discussion, and the rest of the professional world is rapidly coming to it. Meanwhile, the remark has been repeatedly made that, whatever Mr. Gayley's process may turn out to be worth, it was not an invention on his part, but simply the energetic and persevering execution of a procedure already proposed by others. This question I wish to discuss first in the present paper. I. What Did Mr. Gayley Invent? Realizing that this is not the place for detailed argument on an issue of patent law, I shall not undertake to quote and criticise the publications prior to Mr. Gayley'a first patents. It may be admitted, without such critical analysis, that the possible advantages of removing moisture from the air forced into an iron blast-furnace were recognized and talked about a hun-

Jan 1, 1909

By E. L. BROKENSHIRE

FLUORSPAR, a little known non-metallic mineral, referred to technically as fluorite, chemically as calcium fluoride, is a compound of calcium and fluorine in the ratio of one molecule of calcium to two of fluorine. By weight it is composed of 51.3 per cent of calcium and 48.7 per cent of fluorine. Its specific gravity is 3.2. It is brittle, has a hardness of four and can be easily scratched with a knife. It weighs about 200 Ib. per cubic foot and has a melting point of 1650" F. The color of fluorspar ranges from pure white and opaque white, according to its purity, to various hues of yellow, green, pink, lavender, blue and brown, to bluish black. Although the lumps have color, when ground the fluorspar becomes pure white. The reason for this is because the mineral usually carries no fixed pigment, the color being produced by the re- fraction of light rays within the crystal structure and small quantities of organic matter which readily oxidizes. It crystallizes in the isometric system with perfect octahedral cleavages.

Jan 1, 1929

The following is a partial list of members and guests who called at Institute headquarters during the period July 10, 1917, to Aug. 10, 1917: G. A. Collins, Seattle, Wash. Norman Picot, Melbourne, Aust. A. D. R. Galloway, Komfrodua, W. Africa. W. E. Pomeroy, El Paso, Tex. F. Lynwood Garrison, Philadelphia,; Pa. Francis R. Pyne, Elizabeth, N. J. Geo. M. Henderson, Bland, N. M. W. L. Remick, W. Norfolk, Va. L. B. Herr, Jr., So, Bethlehem, Pa. M. F. Sayre, Schenectady, N. Y. Zay Jeffries, Cleveland, 0. Leighton Stewart, New York, N. Y. H. H. Lauer, Allentown, Pa. Randolph D. Talmage, Joplin, Mo. Wm. B. McKinlay, Yonkers, N. Y. H. J. Volker, Ossining, N. Y. A. N. Mackay, Republic of Colombia. Dwight E. Woodbridge, Duluth, Minn. Edmund Newton, Minneapolis, Minn. Kwong Wu, Peking, China. J. N. Acosta has resigned his position as mining engineer for the Shannon Copper Co., Gleeson, Ariz., and is now engaged as consulting engineer for Lower California, Mexico, with headquarters at San Diego, Cal. L. D. Albin, formerly assistant general sales manager of the Ingersoll-Rand Co., was appointed general sales manager on July 25,1917.

Jan 9, 1917

By Gordon MacVean

THE adoption of rock dusting, as a safety measure, has made notable progress in the West Virginia coal mines since May, 1925. At that time there were but two mines in the State that were thoroughly rock dusted, mines No. 2 and No. 12 of the Boone County Coal Corp., at Sharpless. Since then it is probable that 75 per cent of the coal operators in the State have given consideration at one time or another to rock dusting. This growth of interest followed the meetings of the various mining institutes all over the country, during the summer of 1925, at which papers were presented, drawing the attention of the coal mining operators to the merits of this safety measure. Yet outside of the experience with rock dusting at the Old Ben Coal Corp., of Southern Illinois, and the Carbon Fuel Co., of Rains, Utah, there had been no actual occurrence in the coal mines of the United States, which could be taken as positive evidence of the efficacy of rock dusting in the prevention of the propagation of coal dust explosions. The U. S. Bureau of Mines, however, had run innumerable tests under conditions which closely approximated actual coal mining conditions and had clearly shown that rock dusting was effective.

Jan 1, 1926

By C. W. Pollock

THAT a distressing explosion of some magnitude did not take place in the Berry No. 3 mine of the Ford Collieries Co. recently was solely because no source of ignition was present when the stage was set for such an occurrence. The mines of this company, which are in West Deer Township, Allegheny' County, Pa., have been operating in the double or thick Freeport seam since 1.909. During this entire period they have been classed as gaseous by the Pennsylvania Department of Mines, and some gas has been encountered from time to time almost entirely however in development work in the vicinity of clay veins or wants-and never to my knowledge on gobs or in rib work.

Jan 1, 1935

Cycle, automatic, in mine hoists, LV, 17. Cylindrical furnaces, repairing partly collapsed, XXXVI, 215-222. Dacite-porphyry, San Jose, Tamaulipas, Mex., percentage composition, XXXVI, 186. DAGGETT, ELLSWORTH: The Extraordinary Faulting at the Berlin Mine, Nev., XXXVIII, [liii], 297. Daiquiri, Cuba: geology, LIII, 3, 43. iron deposits, LIII, 40. Magdalena mine, LIII, 9, 23, 24. mines, bibliography, LIII, 59. situation of mines, LIII, 42. [ ]

Jan 1, 1918

By Noel S. Christensen

COBALT is a silvery white metal with a slight bluish cast, strongly resembling nickel in its appearance and properties, notably its resistance to corrosion, although its alloys with other metals differ quite decidedly in their properties from those of nickel. The name cobalt was derived from the German "Kobold" meaning goblin and this came to be applied to the cobalt minerals which, although they resembled ores, did not readily yield metal when smelted by the primitive processes available in the Middle Ages. Cobalt minerals were used as pigments by potters and glass workers before the Christian era. Cobalt blue glass was found in the tombs of the Egyptians and in the ruins of Troy, and many colors used by the ancient Greeks and Romans contained cobalt. The ancients were entirely unaware that the colors they used were caused by cobalt and the metal itself was only isolated about the middle of the eighteenth century by Brandt although the preparation of cobalt compounds had been carried on in a small way ever since the opening of the silver-cobalt deposits at Schneeberg, Germany, in 1470. The metal is fairly hard, with a density when pure of 8.81 in the cast state and 8.92 after working. The commercial grade of cobalt has a density of about 8.75 in the cast state. The atomic weight is 58.97. The Brinell hardness of the pure metal is 124; that of the commercial grade varies from as low as 100 to as high as 138, depend¬ing upon the impurities present. Pure cobalt has a sharp melting point at 1478°C. The tensile strength of the pure metal in the cast condition is said to be higher than that of any other pure metal. Kalmus gives it as 34,400 lb. per sq. in. for cast unannealed metal; the effect of annealing at 850 to 900°C. is to raise the strength slightly. The yield point is close to the ultimate strength and the reduction in area and elongation are both low. Mechanical working raises the tensile strength of pure cobalt rapidly and in the form of wire it will be over 100,000 lb. per sq. in. The presence of small quantities of carbon in the commercial metal raises the tensile strength to as high as 61,000 lb. per sq. in., the reduction in area and elongation being raised at the same time to approximately 20 per cent.

Jan 1, 1933

By Joklik, G. F.

Most publicity about the copper industry nowadays is focused on the adequacy of ore reserves and on excessive mining capacity. These concerns, stemming from public awareness of actual and potential shortages and oversupplies, relate to production rather than consumption. Perhaps the reason for this one-sided view is that copper is thought of as a commodity which is conspicuously traded in world markets, rather than as one of many industrial materials that serve today's rapidly changing technology. Copper differs from other widely traded commodities in that its real cost of production has progressively increased since World War 11. The reasons for the increase are identifiable by analyzing operations in one of the world's large producing centres, the copper province of Arizona. Another respect in which copper differs from some other commodities is that increases in demand occur less automatically in the case of copper than they tend to in commodities whose consumption is more directly related to population growth. The copper industry's current inability to generate and attract needed investment capital is attributable to these differences between copper and other commodities; it suggests that the concept of copper purely as a commodity is outdated. The key to the problem is better integration between the activities of copper producers and users. Depending on circumstances, integration takes various forms- for example, investment tied to long-term sales con- tracts between producers in developing countries and consumers overseas; common ownership of producing and manufacturing facilities in industrialized nations like the U.S.; and consumer-oriented research and marketing by the copper producers.

Jan 1, 1978

By C. W. Binckley, F. R. Burgess, E. R. Haymaker

A method of establishing stabilized back-pressure curves for gas wells producing from formations of extremely low permeability is presented. Actual well performance under many different operating conditions is shown by the stabilized back-pressure curve. By use of the method. it is possible to conduct back-pressure tests with a critical-flow prover on wells that stabilize slowly, and save approximately 88% of the gas ordinarily vented to obtain satisfactory test data, with a great reduction in time required for testing. INTRODUCTION The reasons for establishing dependable back-pressure curves on gas wells have been pointed out by previous publications. The publication most referred to. of course, is the United States Bureau of Mines Monograph 7, titled "Back-Pressure Data on Natural Gas Wells and Their Application to Production Practices". The technique generally established therein has been accepted and used by many engineers; and, when proper tests are conducted, the results can be used for the analysis and solution of several practical problems concerning field operation and development. Even where formations of low specific permeability are encountered, the determination of a well's actual performance by the back-pressure test method permits the engineer to analyze many problems in individual well operation and also to predict necessary future field development. Such problems as the determination of the ability of a well to produce into a pipe line at a predetermined line pressure, the design of gas gathering systems and meter settings, and the determination of the time and the number of wells required to be drilled to meet future market obligations, can be solved, in part., by the use of a reliable back-~ressure curve. In addition, the computed well delivery rates determined by data from backpressure tests ordered by state regtilatory bodies, when compared with the true back-Pressure curve, permit the operator to ascertain whether such data represent unstable or relatively stabilized delivery rates for given pressure conditions of the well. The technique of back-pressure testing, as described in this report, was developed by Phillips Petroleum Company engineers from data obtained during a testing program that started in 1944 and has been continued to date. Three hundred and eleven back-pressure tests were conducted on 299 wells located in the southern part of the Hugoton Field. The gas-bearing zone is composed of several dolomitic formations of the Permian Age; the important ones are the Herington, Upper Krider, Lower Krider, and Winfield. The average bottom-hole temperature is approximately 91 °F.. and the initial wellhead shut-in pressures range from 400 to 440 psig. The spacing pattern is 640 acres per well with each well located near the center of the section. The range of back-pressure potentials on wells tested was from 500 to 23,000 Mcfd. All gas wells were acidized, and the quantity of acid used, expressed in 1574 hydrocloric acid, varied from 12,000 to 22,000 gallons per well. The quantity and concentration of each treatment depended on the stage, the formation being treated, and experience gained from previously completed wells. The gas in the Hugoton Feld is a "dry" gas. It has a gasoline content of approximately 0.25 gallons per thousand cubic feet, as determined by charcoal test, and its specific gravity averages about 0.71 as compared to air (air = 1.00 at 60°F.). Of the wells tested, 71 were completed with 7" casing, 3 with 9 5/8" casing, and 1 with 6%" casing set on top of the upper producing formation with the well bore through the gas bearing formations being open hole. Two hundred and twenty-four were completed with 5 1/2'' O.D. casing set through the gas bearing formations and perforated. For the purpose of establishing reliable back-pressure curves in the area, Phillips Petroleum Company personnel has computed data on the basis of 24-hour flows per point. Early in the program, many tests were actually permitted to flow 24 hours to obtain data for each plotting point, at great expense in man power and time. Presently, however, such tests have been replaced by tests of short duration flows which can be made to effect results that correspond to the tests obtained by flows of much longer duration. METHOD When a gas well producing from a reservoir of low permeability is opened for production through a constant size orifice, both the rate of flow and working pressure decline. first at a high rate and later at a lower rate until after several hours the decline becomes difficult to ascertain. In this paper the rae of flow and working pressure are considered to be stabilized when it becomes difficult to observe changes in working pressure during a period of three hours by the use of a deadweight pressure gage. Stalibization of pressure in the literal sense is never obtained in a producing gas well. In formations of low permeability. such as those in the Hugo-ton Field, most wellhead working pressures approach stabilization closely enough to be used satisfactorily in the determination of a back-Pressure potential curve after flow periods of 24 hours. We shall therefore describe the backpressure curve calculated from ohserved rates of flow and working pressure at the end of 24-hour flow periods.

Jan 1, 1949

By E. R. Haymaker, C. W. Binckley, F. R. Burgess

A method of establishing stabilized back-pressure curves for gas wells producing from formations of extremely low permeability is presented. Actual well performance under many different operating conditions is shown by the stabilized back-pressure curve. By use of the method. it is possible to conduct back-pressure tests with a critical-flow prover on wells that stabilize slowly, and save approximately 88% of the gas ordinarily vented to obtain satisfactory test data, with a great reduction in time required for testing. INTRODUCTION The reasons for establishing dependable back-pressure curves on gas wells have been pointed out by previous publications. The publication most referred to. of course, is the United States Bureau of Mines Monograph 7, titled "Back-Pressure Data on Natural Gas Wells and Their Application to Production Practices". The technique generally established therein has been accepted and used by many engineers; and, when proper tests are conducted, the results can be used for the analysis and solution of several practical problems concerning field operation and development. Even where formations of low specific permeability are encountered, the determination of a well's actual performance by the back-pressure test method permits the engineer to analyze many problems in individual well operation and also to predict necessary future field development. Such problems as the determination of the ability of a well to produce into a pipe line at a predetermined line pressure, the design of gas gathering systems and meter settings, and the determination of the time and the number of wells required to be drilled to meet future market obligations, can be solved, in part., by the use of a reliable back-~ressure curve. In addition, the computed well delivery rates determined by data from backpressure tests ordered by state regtilatory bodies, when compared with the true back-Pressure curve, permit the operator to ascertain whether such data represent unstable or relatively stabilized delivery rates for given pressure conditions of the well. The technique of back-pressure testing, as described in this report, was developed by Phillips Petroleum Company engineers from data obtained during a testing program that started in 1944 and has been continued to date. Three hundred and eleven back-pressure tests were conducted on 299 wells located in the southern part of the Hugoton Field. The gas-bearing zone is composed of several dolomitic formations of the Permian Age; the important ones are the Herington, Upper Krider, Lower Krider, and Winfield. The average bottom-hole temperature is approximately 91 °F.. and the initial wellhead shut-in pressures range from 400 to 440 psig. The spacing pattern is 640 acres per well with each well located near the center of the section. The range of back-pressure potentials on wells tested was from 500 to 23,000 Mcfd. All gas wells were acidized, and the quantity of acid used, expressed in 1574 hydrocloric acid, varied from 12,000 to 22,000 gallons per well. The quantity and concentration of each treatment depended on the stage, the formation being treated, and experience gained from previously completed wells. The gas in the Hugoton Feld is a "dry" gas. It has a gasoline content of approximately 0.25 gallons per thousand cubic feet, as determined by charcoal test, and its specific gravity averages about 0.71 as compared to air (air = 1.00 at 60°F.). Of the wells tested, 71 were completed with 7" casing, 3 with 9 5/8" casing, and 1 with 6%" casing set on top of the upper producing formation with the well bore through the gas bearing formations being open hole. Two hundred and twenty-four were completed with 5 1/2'' O.D. casing set through the gas bearing formations and perforated. For the purpose of establishing reliable back-pressure curves in the area, Phillips Petroleum Company personnel has computed data on the basis of 24-hour flows per point. Early in the program, many tests were actually permitted to flow 24 hours to obtain data for each plotting point, at great expense in man power and time. Presently, however, such tests have been replaced by tests of short duration flows which can be made to effect results that correspond to the tests obtained by flows of much longer duration. METHOD When a gas well producing from a reservoir of low permeability is opened for production through a constant size orifice, both the rate of flow and working pressure decline. first at a high rate and later at a lower rate until after several hours the decline becomes difficult to ascertain. In this paper the rae of flow and working pressure are considered to be stabilized when it becomes difficult to observe changes in working pressure during a period of three hours by the use of a deadweight pressure gage. Stalibization of pressure in the literal sense is never obtained in a producing gas well. In formations of low permeability. such as those in the Hugo-ton Field, most wellhead working pressures approach stabilization closely enough to be used satisfactorily in the determination of a back-Pressure potential curve after flow periods of 24 hours. We shall therefore describe the backpressure curve calculated from ohserved rates of flow and working pressure at the end of 24-hour flow periods.

Jan 1, 1949

By A. English, M. J. Greaves

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

Jan 1, 1963

By Richard F. Link, George S. Koch

About 50,000 assays of mine samples were required in a preliminary investigation of the distribution of gold, silver, lead, copper, and zinc in two large Mexican mines, the Frisco mine at San Francisco del Oro (Chihuahua) and the Fresnillo mine at Fresnillo (Zacatecas). The feasibility of working with so many assays rests directly on the use of machine processing methods. The purpose of this article is to describe the methods used because machine (or data) processing can also be used efficiently to make the many calculations from mine assays needed in mining operations. No particular originality is claimed for these methods, which are straightforward applications of standard procedures for machine processing. Inasmuch as machine processing is essentially a routine job once it is begun, procedures must be organized more completely than is the case where human judgment can be inserted at every step. Before undertaking any work, it is necessary to decide carefully just which data must be processed as well as the exact results desired.

Jan 9, 1960

By Charles W. Frey

OF all the machinery used in mining work, mine cars are probably the most abused. They are hauled through water and muck, up hill and down grade, whipped around curves, bumped and jerked, and exposed to the ravages of the weather. However, as a general rule their lubrication is not altogether neglected. The mine operator may not heed the extra drag that a frozen conveyor bearing gives, but he is all too aware of the increased load that faulty mine car wheels put on his power plant. When the circuit breakers begin to fly, and when his mine loco- motives come out with only half the cars that they were able to carry a month before, then neglected mine car wheel lubrication becomes apparent, and woe to the person responsible.

Jan 1, 1938