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By R. D. Russell, R. M. Farquhar

SOTOPIC tracers have become an important aid in following the progress of chemical processes in the laboratory. It has recently been found possible to utilize a system of naturally existing iso-topic tracers to obtain information about the geological history of lead ores. Common lead, such as is found in lead deposits, is a mixture of four stable isotopes having atomic weights 204, 206, 207, and 208. Of these, the last three are identical with the lead isotopes produced as stable end products of the radioactive decays of uranium and thorium: the first, lead-204, is not known to be produced on the surface of the earth by any process. Since uranium and thorium Occur in the surface regions of the earth in amounts comparable with lead, and since the half-lives of uranium and thorium isotopes are of the same order as the age of the earth, they produce the radiogenic lead isotopes in amounts comparable to the amount of nonradiogenic lead present. Every significant exposure of a sample of lead to uranium and thorium will therefore lead to the permanent alteration of the lead isotope ratios in that sample. It is this unique property of lead that serves as a means of tracing the history of a lead sample in terms of its contacts with the radioactive elements. If lead from a lead mineral has been analyzed with a mass spectrometer, the measured isotope ratios are determined entirely by the isotope ratios of primeval lead, which are identical for all minerals, and by the particular history of the sample. It follows that for samples from any particular geological area, observed differences in the isotopic composition are enough to distinguish different geological histories. An illustration of the qualitative application of this statement is given in Table I by analyses of some galenas from the western Cordillera. Samples from deposits in Pre-Cambrian sediments have very different lead isotope ratios from those of the ores in the Paleozoic sediments. Although the two types are associated closely geographically, it is apparent that they have had quite different histories and have probably been emplaced at quite different times, as the ideas outlined in the following section suggest. Even when applied quantitatively, a lead isotope analysis can never indicate a unique history of any lead sample. However, it greatly restricts the choices available and combined with other geological and geochemical data can lead to a much better understanding of the genesis of lead ores. General Character of Lead Isotope Variations: Early isotopic analyses of common leads by Nierl showed that geologically younger leads were generally richer in isotopes of masses 206, 207, and 208, with respect to that of mass 204. This regularity of measured lead isotope ratios can be easily observed by plotting each of the ratios Pb207/Pbm and Pb205/ Pb204 against the ratio Pb206/Pb204. In both graphs the points lie scattered closely about a well defined mean curve. It was immediately supposed that this regularity resulted from the growth of all leads from a common primeval lead present at some time, To, early in the earth's history. Lead in the outer part of the earth would become continually enriched in the radiogenic isotopes as a result of the uranium and thorium intimately associated with it. The subsequent extraction of some of this lead and formation of a lead mineral free of the radioactive parents provide samples of lead existing in the earth at the time of mineralization, T. Younger leads in general will be richer in the radiogenic isotopes because they have been associated with uranium and thorium for a longer time. Then lead ratios would be given by the formulae: (Pb206/Pb204)YTPb^/Pb204) +f "(u201) kdt T (Pb207Pb204)r = (Pb208/Pb204)T0 + J (U295/Pb204) k' dt T (Pb208/Pb204) t = (Pb208Pb204 + J (Th204) A." dt [1] where A, A', and A" are the decay constants of U238, U285 and Th232. Summaries of measurements of radioactivity of surface rocks, such as given by Faul,2 are of limited

Jan 1, 1958

By N. K. Chen, R. B. Pond

IN the study of slip band* formation, there have been many examples to show that they do not always appear as lines traversing the entire crystal, but as segments whose ends seem to vanish in their path through the crystal. This characteristic appearance of slip bands has been witnessed under the optical microscope at various magnifications'-' and also under the electron microscope.' A typical example of this behavior seen with the optical microscope is shown in Fig. 1. However, the slip band studies were generally conducted on polished surfaces of single or poly-crystalline metals which had been previously deformed; i.e., the load was generally released so that the observation could be made. Any picture of slip bands so obtained can represent the surface phenomenon only in a static state of the strained material. The conditions prior to their formation cannot be definitely and clearly assigned. Thus, while a segmented slip band may suggest that slip is a growth process as supposed by the theory of the nucleation of slip,V he usual appearance of suddenly and fully developed slip bands around the crystal has generally been considered as a consequence of uniform shear of the entire slip plane akin to a cataclysmic process. Little clear-cut information is available with regard to the speed at which a slip band forms, its direction of motion, the geometry of its position with regard to its neighbors, and its dependence on orientation. A description is given in this paper of experimental apparatus by which the progressive formation of slip bands can be recorded while the specimen is undergoing deformation. Qualitative and quantitative data on the dynamic formation of slip bands will be presented with special interest concerning the propagation of slip bands, the spacing of slip bands, and their relations to strain hardening. Views on the formation of slip bands are discussed and a mechanism of the unit process involved in the formation of a slip band is proposed. Preparation of Specimens Single-crystal specimens of high purity aluminum (99.997 pct), 1/8 in. square in cross-section and 1% in. long in gage length, were made by the method of gradual solidification from the liquid state. Since no machining work could be introduced in preparation of crystals of such small size, a special mold was designed for casting them to final shape. The mold consisted of two, separate, high purity graphite blocks. Generally, 20 molds were packed together in one container so that 20 specimens could be obtained by one casting operation. This was desirable since it was possible by this method to obtain groups of crystals with similar orientations. The as-cast crystals were carefully clipped from the gate, etched, and homogenized for 24 hr at 600°C. They were then very gently polished using a 4/0 paper, re-etched, and finally electrolytically polished after the method previously described by Chen and Mathewson.6 The crystallographic orientations were determined using a back-reflection, Laue method. Tensile Testing and Photographic Method The tensile testing equipment for these tests was composed of a specially designed microtensile machine, microload cell and microclip gage with necessary appurtenances. The members of the microtensile machine consisted of three parts, as shown in Fig. 2. The chassis is equipped with an oil cylinder, A, and piston, the piston being part of the movable cross-head, B. Pressure in the oil cylinder is controlled and regulated by an external pneumatic-hydraulic cell, C, which is connected to the cylinder by a Vs in. high pressure copper tube. This cell is half filled with hydraulic oil and has a needle valve, D, on the oil exit side as well as a needle valve, E, on the gas inlet side. A quick-acting valve, F, as well as a pressure gage is provided for the gas side. The oil exits into the load piston on the microtensile machine. By connecting a tank of inert gas to the gas inlet, regulated pressures were provided over the oil so that the oil would leave the cell at a rate determined by the setting of the exit needle valve, the gas pressure, and the pressure of the oil in the load piston of the microtensile machine. With this pneumatic-hydraulic appurtenance it was possible to

Jan 1, 1953

By Dirk A. Benham, William A. Warfield

INTRODUCTION Whenever a mine operator is faced with a decision between various mining methods or even equipment selection, he must be assured that his decision will have a positive effect on his economic operating goals. For instance, if a mine operator has a choice of using an LHD mining system or a slusher mining system, then his decision to use either must not only fit within the operational limitations of the mining plan (such as production requirements, physical features of the ore body, mine plant facilities, manpower requirements, etc.), but also assure that the ore is being extracted at the least possible cost. To aid in his decision making process, the operator will commonly compare acquisition costs, operating costs, maintenance costs, and the operational advantages and disadvantages of each system in addition to considering his personal observations and feelings. A decision to select a mining system using only those criteria aforementioned will not necessarily lead the operator down the path to maximizing profits. In addition, the operator should also compare the economic effects of each system upon the overall mining operation. A relatively simple method for determining the economic effects is to calculate and compare the break-even grades for each system under consideration. By implementing such an analysis, the operator can now select a mining system which can operate within the limits of the mining plan as well as extract the ores at the least possible cost, thus yielding maximum profits. This paper will present the geologic and physical conditions of a mine being operated by the Hypothetical Mining Company in the Grants Mineral District. An LHD and Blusher mining system are under consideration and are compared by examining operating costs, equipment availability, and the conventional operational advantages and disadvantages of each. Finally, the economic effects of each system upon the overall mine's operation are compared by utilizing break-even grade analysis. DESCRIPTION AND MINING METHODS The Hypothetical Mining Company has located an ore body in the Grants Mineral District. After extensive surface exploration drilling and cost considerations are evaluated, it is decided to open a mine. The following tasks must now be performed: 1. outline ore body and it's basic characteristics, 2. look at mining methods currently in use in the area, and 3. determine mining techniques and methods for exploitation of the ore body. For the sake of argument, the newly discovered ore body is located towards the western edge of the Grants Mineral Belt. The host rock for uranium mineralization is the Westwater Member of the Morrison Formation. The Westwater Canyon sands are overlain by the Brushy Basin Member of the Morrison Formation and underlain by the Recapture Member, all of Jurassic Age. Westwater Canyon sandstone is a fine to very course grained subarkosic sand with interbedded green and red mudstone. The Brushy Basin Member consists predominantly of greenish-gray mudstones and contains thin lenses of sandstone and a few thin beds of limestone. The Recapture Member consists of alternating thin beds of reddish brown, grayish red, and light gray sandstone and siltstone. The Recapture interfingers with the Cowsprings Sandstone in the area of the mine. The mineralization is based on the groundwater flow within the Morrison Formation. Primary ore distribution is based on three basic parameters: ore migration in a geochemical cell, lenticular mudstone interbedding, and enrichment along fault zones. In areas where two fault systems intersect, ore thicknesses of up to 30 m (100 ft.) are encountered. In those areas where the ore is well defined and thicknesses facilitate full face mining, the mining methods are determined more by ground or operating conditions, equipment availability, and access to working areas than they are in the fringe areas of the ore body where grade control is more important and split-shooting and break-even grade determines the mining technique. If a modified room-and-pillar mining method using systematic development is selected, better control of the ventilation, equipment utilization, and mining plan can be obtained. Figure I shows a typical mining area where the ore is thick,

Jan 1, 1982

By J. D. Testerman

A statistical technique to identify and describe naturally occurring zones in a reservoir and to correlate these zones from well to well is described. The technique is particularly useful in describing a reservoir where cross flow between adjacent strata is important in determining reservoir behavior. Although it has been used primarily for permeability zonation, the technique is general and can be used to correlate any reservoir property or related data, such as the information contained in well logs. INTRODUCTION One of the first problems encountered by the reservoir engineer in predicting or interpreting fluid displacement behavior during secondary recovery processes is that of organizing and using the large amount of data available from core analysis. Permeabilities pose particular problems in organization because they usually vary by more than an order of magnitude between different strata. Due to the sheer volume, it is almost always necessary to group data and to use an average value to represent a number of measurements. Perhaps the most common method now used to group permeability data is the capacity-fraction technique, which ranks permeabilities in order of magnitude, regardless of the physical location of the permeabilities within the reservoir. The cumulative per cent capacity is plotted against cumulative per cent thickness. This plot is divided into an arbitrary number of zones, generally of equal thickness. Five zones (or averaged groups of data) usually are obtained, each of which is treated as homogeneous in subsequent calculations. The division so obtained has no physical meaning; strata in the same zone, calculation-wise, are usually not adjacent in the reservoir. Reservoir engineering techniques being developed will handle crossflow that occurs between adjacent communicating reservoir strata because of imbibition and gravity segregation. Since crossflow occurs between physically adjacent layers within the reservoir, a new zonation technique recognizing the actual location of strata within the reservoir is necessary. Similarly, the recognition of natural zones is important for predictions of oil recovery by processes involving diffusion. One such process is miscible displacement, where predictions of lateral diffusion within the reservoir must recognize the actual location of the invaded zones in relation to the rest of the formation. Natural zones must also be adequately recognized to account for heat transfer within the reservoir during thermal exploitation. Because of the complexity of the problem, statistics appear to offer the only practical hope of dividing a reservoir into physically-meaningful natural zones. This paper presents a statistical technique for identifying these natural zones and for ascertaining which ones are likely to be continuous between adjacent wells. The zones defined have minimum variation of permeability internally and a maximum variation between zones. The technique is general and can thus be applied to reservoir properties other than permeability. The method will guide the reservoir engineer in estimating which zones are likely to be continuous between wells. However, a statistical correlation based on permeabilities in two different wells is no guarantee that the zones so defined are, in fact, continuous. Rather, the assumption of continuity must be consistent with geological data concerning the depositional environment, as well as justified on the basis of engineering judgment in combination with statistics, just as judgment is required with conventional zonation methods. CALCULATION PROCEDURE The reservoir zonation technique is a two-step operation. The steps are individually described, and a sample calculation is presented in the Appendix. ZONATION OF INDIVIDUAL WELLS First, the set of permeability data at a single well is zone, into Zones. These zones are selected so that variation is minimized within the zones and maximized between the zones. The equations4,6 used to zone the data are where B = the variance between zones, , = the number of zones, i = the summation index for the number of zones, j = the Sumation index for the number of data within the zone, mi = the number of data in the ith zone, k,. = the mean of the permeability data in the ith zone, k . = the over-all mean of the data in the well, W = the pooled variance within zones, N = the total number of

By Alan Stanley

THE Maclntyre Development of National Lead Co. is located at Tahawus, N. Y., in the heart of the Adirondack Mountains. Operations involve the mining and concentrating of a titaniferous iron ore to produce ilmenite and magnetite concentrates. A general description of the operation and metallurgy has been given by Frank R. Milliken.1 Pigment plant production demands that the MacIntyre mill produce a 44.7 pct. TiO2 ilmenite concentrate. To achieve the required ilmenite grade and tonnage it is important that the table concentrate grade be closely controlled. Unfortunately, however, the titaniferous orebody which feeds the Maclntyre mill is not uniform. Ore dressing characteristics vary from one end of the orebody to the other, and from one level to the next.. The changeable nature of the mill feed precludes a single adjustment of the equipment for long periods of time. Thus the operators must constantly watch the equipment to insure a uniform concentrate from the fine and coarse tables and Wetherills, or dry magnetic separators. Chemical assaying of mill products requires about 4 hr from the time the sample is taken until assay results are obtained, and this is available only on a two-shift basis. The ore may change rapidly, even several times during a shift, so that assay results lose most of their control value by the time they are reported to the mill operating crew. Members of the crew have therefore tried to evaluate the table and Wetherill concentrate by visual inspection, since through long experience the shift operators, under most circumstances, can gage closely the grade of the mill products. However, there are times when the, physical nature of the ore is radically different from normal. Under these conditions visual inspection is of no value, and at such times final ilmenite as low as 43 pct TiO2 has been produced and shipped before the assay results have been received. The specific gravity method of assaying for TiO2 has been attempted to eliminate the shipping of ilmenite below normal grade as well as to help control day to day and hour to hour mill production. Table I shows the minerals found in the Maclntyre ore along with their average weight proportions and specific gravities. The first two products considered for the specific gravity method were fine and coarse table concentrates. It was reasoned that these products were essentially ilmenite with the higher specific gravity gangue minerals. Since they were always produced the same way, and the desired grade of TiO2 was always constant, the specific gravity of these materials would increase or decrease as the amount of ilmenite increased or decreased. Thus for table concentrates which assayed 40 pct TiO2 a constant gravity would invariably be obtained, and as the TiO2 value changed the specific gravity would change in direct proportion. The third product considered was Wetherill ilmenite. It was assumed that a desired grade of 44.7 pct TiO2 would also always contain the same amount and type of gangue minerals along with the ilmenite, and thus would always have the same specific gravity. As the TiO2 value of the ilmenite concentrate changed so would its specific gravity. Dr. Kenneth Vincent, chief metallurgist of the Baroid Division of National Lead Co. at Magnet Grove, Ark., ran specific gravity tests on 17 samples of the desired products. The lowest specific gravity reading assayed the lowest in TiO2 and as the specific gravity increased the trend was for the TiO2 assay to increase, see Fig. 1. Since these results warranted further investigation, a 500-g capacity Torsion balance and 250 ml Le Chatelier specific gravity bottles were obtained. [ ] Shift samples of fine table concentrate, coarse table concentrate, and final ilmenite were tested. Each sample was split and 85 g weighed on the Torsion balance. The Le Chatelier bottle was filled with water to a zero mark. To avoid wetting the neck of the bottle it was found necessary to do this

Jan 1, 1952

By A. L. Bailey, B. A. Landry

All who are even generally aware of the tremendous rate of increase in coal washing operations must realize the growing importance of the float-and-sink test. I believe it is conservative to estimate that, in the past decade, the dollar volume of float-and-sink testing has increased tenfold. It is a simple matter of economy, then, to examine the factors that determine the cost of adequate float-and-sink testing. When the Coal Preparation Section of the Bureau of Mines entered upon a greatly expanded program of such work in connection with the synthetic liquid fuels investigations, it seemed advisable to examine these factors experimentally. The principal consideration that differentiates float-and-sink test sampling from general purpose sampling, is that the original particle size must be preserved. Therefore, the total cost of the test will be directly affected by any standard that might be proposed to limit sample bulk reduction at any given particle size. For this reason, the relationship of sample size to variability of results was the first factor to be studied experimentally. Of course, the matter is rendered complex by the circumstance that the float-and-sink test, not a simple analytical measurement but a process test, comprehends a number of more-or-less independent items of fundamental data; and as shown in the report, the' variability of the samples differs with respect to these different items. This condition and the wide variety of situations in which float-and-sink test data are used, in combination with other factors, to study complex process operations, indicate the difficulty of setting up fixed standards for float-and-sink sampling and testing. At this stage at least, it is the intent rather to obtain experimental data on the principal Factors involved so that the reader may arrive more intelligently at a procedure adapted to his problem. The authors of this paper have presented experimental data showing the relationship between size of sample and particle size for different variability tolerances with respect to percentage of sink. In further studies, data are being collected to appraise also the variability of the samples with respect to float-ash content and size consist. The scope of this work will be broadened to cover particle sizes up to 4 in., and a third series of tests has yielded similar data for a much cleaner type of raw coal. Thus, the further studies will make available a fairly comprehensive meas- ure of variability with respect to size consist, percentage of sink, percentage of middlings, and percentage of ash in the float, for three coals ranging from 3.87 to 17.68 pct in refuse content (heavy sink material) and from 4.18 to 17.52 pct in middlings. Introduction At present there are no published standards for float-and-sink test sampling. During the rapid expansion of float-and-sink test work, varying procedures have been based on adaptations of the ASTM standards for sampling coal for analyses. For this reason, a special study of gross sample reduction has been undertaken to determine the limits for this step in the operation where no reduction in particle size is to be made before testing. Float-and-sink tests are made whenever a thorough study of coal characteristics is desired. The tests may be made on samples from coal-cleaning units such as jigs or tables, or coal samples may be tested which are taken from a loading boom, railroad car, or the coal seam itself. The resultant gross sample may be large and pose a problem of sample reduction. The question is, then, how much can the sample be reduced and still fall within preassigned limits of accuracy of the original gross sample of coal? Coal from channel samples may be crushed to liberate impurities and then separated into various gravity fractions from which washability curves are drawn; from these curves, it is possible to determine the cleaning characteristics of the coal. However, coal samples from coal-cleaning units cannot be

Jan 1, 1950

By G. C. Rauch, T. H. Courtney, J. Wulff

The superconducting behavior of Nb-Ti alloys containing 40 and higher wt pct of Nb and variable oxygen content was studied as a function of thermomechanical processing. Critical current density (Jc) us applied transverse magnetic field (H) data were obtained for 0.010 in. diam wires at 4.2° Kin steady fields up to 120 kOe. The precipitate responsible for increase in Jc in each of the alloys studied was related to niobium and oxygen content. In alloys containing 40 to 60 wt pct Nb with less than about 1600 ppm of oxygen, w precipitation in the range 350° to 450°C appears to be responsible for the maximum value of Jc observed. In alloys of higher oxygen content (-2500 ppm), the oxygen-enriched a phase which precipitates in the temperature range 450° to 550°C is a more effective fluxoid pinner. Maximum Jc in low oxygen (350 ppm) 80 wt pct Nb alloys was achieved by 600°C aging heat treatments. Measurements of resistive critical field also reflect the changes in composition accompanying precipitation in these alloys. It is well known that the superconducting critical current density, Jc, of solid solution superconducting alloys can be increased by precipitation heat treatments.1-4 The precipitate, to serve as an effective superconzlucting fluxoid pinner and increase Jc, must be of proper size and spacing.' Its electronic properties must also be different from those of the matrix.6 As in age-hardenable systems, optimum temperature and time of aging are dictated by the composition and history of the particular solid-solution alloy under consideration. The alloy diagram of Ti-Nb7-9 shown in Fig. 1 is typical of ß-stabilized Ti alloys. Precipitation to achieve high Jc in Ti-Nb and Ti-Ta alloys is usually carried out in what is believed to be a two-phase a + ß region.1,2,4,10 Previous work on Ti-Nb4,11 and on other ß-stabilized systems such as Ti-V, Ti-Mo,12-14 has shown, however, that the first precipitate to appear is not necessarily (Y. Under specific conditions the meta-stable w phase is precipitated instead. A further complication arises in such alloys from the strong influence of contained oxygen on the phase stability and on the kinetics of precipitation.15,16 The superconducting critical current density of Nb-Ti alloy containing less than 36 wt pct Nb has been studied by Vetrano and Boom1 and Kramer and Rhodes.4 The most effective aging temperature was found to be about 425°C; fluxoid pinning was attributed to the precipita- tion of a by Vetrano and Boom and of w by Kramer and Rhodes. Although the latter workers used recrystal-lized material and the former cold-worked, studies carried out in our laboratory lead us to believe that the type of precipitate responsible for increased Jc is unaffected by prior cold-work.17 That other types of precipitates may also be effective, especially in higher oxygen-containing alloys, has been demonstrated by Reuter, et al.2 in this laboratory with the aid of electron microscopy. Reuter et al. found that at an aging temperature of 600°C, fee-TiO is precipitated, resulting in high values of Jc. Even higher values of Jc were observed after heat treatment at 500°C, but the precipitate could not be indexed as fee-TiO. Whether the precipitate was oxygen-rich w or a could not be clearly distinguished. The work nevertheless indicates that appreciable amounts of oxygen alter the nature of the phases precipitated at different temperatures, at least in alloys containing more than 36 wt pct Nb. Since such compositions are more readily worked into suitable wire than lesser niobium content alloys, it was decided to study the response to aging of the alloy compositions reported in the present paper with the hope of clarifying the effect of composition on the precipitation processes responsible for high values of Jc. I. EXPERIMENTAL Nb-Ti alloys containing 40, 50, 60, and 80 wt pct Nb were prepared by are-melting 35 g ingots of iodide crystal bar titanium and electron-beam melted niobium.

Jan 1, 1969

By H. A. Hoffman

Competition from an all-flotation plant, with demonstrated economies and efficiencies, plus a change in smelting contract and introduction of improved cyclones lead to conversion from gravity-flotation. Detailed descriptions are given of equipment installed and procedures used at St. Joseph Lead's Federal mill. Future plans include further quality control by instrumentation in all aspects of the mill operation. Also planned are improvements in materials handling systems. Competitive conditions will continue to dictate improvements and changes in the mill flowsheet. The advent of all-flotation mills in the Lead Belt was introduced by the Indian Creek mill in late 1953. This modern and efficient plant then became a pattern for the other mills in this area to re-evaluate their circuits in an effort to develop flowsheets that would improve operating conditions and metallurgy. The Indian Creek mill demonstrated that all-flotation would require considerably less operating and maintenance labor than the combination of tabling and flotation that was common in the Lead Belt at that time. Two significant changes occurred in recent years to allow all-flotation to be seriously considered in other Lead Belt mills. One was a change in the smelting contract which did not require gravity concentrate. Another was the development of cyclones which provided classification of the flotation feed in a very small space. Since the Federal mill was the largest concentrating plant in the Lead Belt it was felt that the greatest savings could be made by investigating the all-flotation possibilities at this mill. Interest was stimulated by the milling and ore dressing Depts. to determine if this mill would be converted without undue cost, provided the metallurgy could be improved. Accordingly, laboratory tests were initiated to learn what metallurgical benefit could be derived. Numerous tests were run which indicated that grinding to all-flotation would improve the tailing by as much as 0.02 pct Pb. This was quite significant when multiplied by the tonnage of ore treated. Projecting the added cost of power for extra grinding and flotation, and the additional flotation reagents required, plus additional new equipment that would have to be purchased, it would still add up to a considerable saving. The all-flotation mill would reduce man power by some 30 pct, and make a metallurgical improvement. Operating costs could be reduced bv 2$ per ton. The metallurgical improvement would amount to 4$ per ton, for a total of 6$ per ton of ore milled. An estimate of the cost of the conversion was set at $250,000. With the savings as estimated this could be paid off in about two years. On paper it therefore seemed attractive enough to justify a mill test. MILL TESTING One section of the Federal mill was made available for use as a separate test circuit. Cyclones and density controllers were borrowed from the Viburnum and Indian Creek mills. Denver flotation cells were obtained from the Desloge mill that was then shut down. Two 10-cell groups of Fagergren flotation machines, consisting of eight roughers and two cleaners in each bank, were segregated from the remainder of the plant. The 9x12-ft rod mill was continued as a primary grinding mill. The two 6%x12-ft mills on this section were converted from rods to balls, and the speed increased to 22.0 rpm. Cyclones were installed to close the circuit of these ball mills. The ground pulp from each of the ball mills was fed separately to its own bank of flotation cells so that two completely separated test circuits could be run in parallel. This test circuit operated on a three-shift basis from Dec. 22, 1959 to Mar. 21, 1960. The first few weeks were occupied in developing conditions for proper metallurgy and trouble-free operations. Results were rather erratic but as the ore dressing laboratory and the mill operators became more familiar with conditions they were able to obtain expected results, which could be duplicated day after day. The last five weeks of testing indicated the best results and are tabulated in Table I. During the first two weeks a Denver unit cell was used on No. 1 flotation circuit. Even though it recovered almost one half of

Jan 1, 1962

By H. Pew, J. H. Field

To alleviate pollution more restrictive legislation is being enacted, either limiting emission of pollutants or the type of fuel that can be utilized. The nature and magnitude of air pollution problems affecting the mining, preparation, coking and combustion of coal are described. Methods for combatting particulate emissions by use of mechanical separators and electrostatic pre-cipitors are discussed. Proposed methods to meet the problem of gaseous emissions currently receiving considerable attention are described, with special emphasis on methods to decrease pollution by sulfur oxides. Concern about air pollution goes back several centuries, but until very recently most effort has been aimed at coal smoke and other visible pollutants. The classic example of a 'successful' campaign for smoke abatement and control is the fruitful combined effort of the city of Pittsburgh and its surrounding Allegheny County, which eventually led to the reconstruction of downtown Pittsburgh at an estimated cost of one billion dollars. Historically, the city's downtown Golden Triangle district had been afflicted by pollutants evolving from steel mills, from a variety of other industries, and from railroad locomotives. Efforts to alleviate the situation prior to 1943 were virtually ineffective. In 1945, however, a comprehensive redevelopment plan was prepared and backed by state authority. Within a few years a clean, modern metropolis has evolved where once stood America's famous 'smoky city.' But the victory in Pittsburgh, as in various other American cities, has not solved the national problem. Current estimates indicate that 133 million tons annually of air pollutants from all sources still are emitted annually into the atmosphere above the United States. About 10% of this annual effluent is particulate matter so that most of the remaining pollution problems will be solved only when other effluents are reduced. Essentially, these are sulfur oxides, nitro- gen oxides, hydrocarbons, and carbon monoxide. Over the years, both states and local communities have tended to increase the restrictions on smoke and fly ash — problems mostly of concern in the combustion of coal. Prior to the middle 1950's, ordinances sometimes permitted emissions of smoke equivalent to as much as No. 3 on the Ringlemann scale. Since 1956, no ordinance has been passed which allows smoke of greater than No. 2. Under today's conditions of improved fuels, equipment and practice, a few communities have passed laws prohibiting emission of smoke of any density darker than Ringlemann No. 1. The majority of existing laws on fly ash emission in the U.S. limit emissions equivalent to 0.85 lb of fly ash per 1000 Ib of flue gas. In recent years, however, regulations which have been adopted give cognizance to the higher level of performance now obtainable with improved equipment. A comparison of the restrictions of five codes adopted since 1960 is given in Table I. The most stringent of these is the one for New York City which provides for a maximum emission of 0.6 lb fly ash per million Btu heat release (equivalent to roughly 0.51 lb/1000 lb of flue gas). The first comprehensive effort to restrict the emission of SO2 resulted from the passage of a 1937 law in St. Louis. This regulation stipulated that coal containing in excess of 23% volatile matter and 2% sulfur must be washed, thereby presumably producing some effective reduction in the input sulfur content. This was followed in 1949 by a Los Angeles County law which prohibited the emission of SO2 in concentrations greater than 0.2%. Most SO2-restrictive legislation passed since that date has been based on this limiting 0.2% SO2 by volume, although modifications are occasionally permitted under selected conditions, sometimes based on the fact that certain limiting ground concentrations are not exceeded — such as in the rules adopted by the San Francisco Bay area. To date, no legislation has been passed in the U.S. to limit the generation of nitrogen oxides from the combustion of fossil fuels. However, such oxides are considered to be of potential importance in air pollution control because of their possible detrimental effects on health and their reported role in the formation of photochemical smog. Interest in reducing oxides of nitrogen from powerplant and auto exhausts is increasing and regulations limiting their quantity can be expected in the future.

Jan 1, 1968

By John Tabor, R. B. Spivey

INTRODUCTION Shafts have been sunk in a number of ways. By and large, however, most have been sunk by drill, blast, muck, and slip form methods. Most methods have provided satisfactory means of completion. The major drawbacks to the conventional methods have been: (1) un- reliable cost estimates for completion; (2) unreliable rates of progress; and (3) unreliable integrity of the shaft lining. Recently , engineering design studies have been done that strongly indicate, that, by the use of existing proven technology, shafts can be completed faster, more cheaply, safer, and with a better lining that has been possible using conventional methods. THE METHOD The alternate method utilizes the techniques of big hole drilling, shield excavator tunnelling, and pre-cast concrete lining. Big Hole Drilling - Drilled shafts have been completed for several years and I don't intend to address the technology, only to point out the use of drilled shafts is an alternate method of shaft sinking. Ideally, in a multi-shaft mine, the first shaft would be blind bored and cased to a size, whereby it can handle the muck from the excavation of subsequent shafts. It should be an 8' to 10' completed diameter. The cost of such a shaft in sedimentary formations compares favorably with a conventional shaft. However, it is much faster. For additional shafts, the role of the drill is to complete small holes (3' to 4') to the desired horizon. This is merely a hole to allow slashing to a larger size with easier muck removal from an underground drift connected to the previously drilled shaft. The smaller holes, just as the larger one, should be cased and grouted into place so as to assure a smooth open hole. SHIELD EXCAVATOR Theory and History - Tunnelling Shields have been in common use for several decades, and steam powered shields were used in England over 100 years ago. The purpose of the shield is to provide temporary ground support, protect personnel during operation, and to house the excavating equipment. The excavating equipment approach has varied from attempts at a continuous or semi-continuous boring machine, the tunnel mole, to a mechanical or hydraulic digging arm. The shield may or may not be an active digging element. If not active, the boring tool or cutter is advanced ahead of the shield to full diameter and then the shield is moved up to the cutter, or the shield advances along with the cutter. If active, the cutter opens a conical free face, and the shield is either jacked forward so that the leading edge spalls rock to the free face or poling plates are thrust forward to spall to the free face. In either approach, various methods of muck removal are incorporated into the shield. These may be gathering arms, conveyors, or with moles, hydraulic transport, where the cuttings are sufficiently fine. The efficiency of the muck removal system is critical as excavation is rapid and the system could easily become muck-bound. Application to Shaft Sinking- Technically, the use of a shield to sink vertical shafts is no different than a tunnelling operation. It is, in fact, less complex in most respects. Muck and water removal are difficult in a blind-driven shaft. However, where an underground opening is available for handling muck and water, rapid shield sinking is possible, using a pilot hole for muck and water to fall through and be removed from below. The Tabor Mining Shield is basically a caisson approach, whereby, the ground is only seen at the face or bottom. It does have hydraulic jacks to force it downward and has segmented cutting edges which allows forepoling ahead of the shield. The hydraulic excavator allows mining in the center of the face around the previously drilled hole with the forepoling segments slabbing to this free face. First, the drilled hole is cased and grouted. The machine is a tube with an excavator. The work cycle is as follows: (1) The casing and grout are cut at predetermined intervals by shaped charges. (2) The casing is crushed by the excavator, removed from the hole and hoisted to the surface. (3) The excavator then rips out a face around the hole by digging the formation in tension and breaking the pieces

Jan 1, 1982

By G. Britsianes, T. L. Joseph

THE reduction of a lump of iron ore is a complicated sequence of up to three reactions proceeding simultaneously in a gas-solid system. As the ore moves down the blast furnace into zones of higher temperature and higher reducing power, it is successively reduced through the three oxides of iron into metallic iron. The reduction process involves much more than chemical problems. Physical factors add to the complexity of the overall process. Under optimum conditions, reduction of the ore is completed at a level about one-half way down the blast furnace stock column. At this point, the ore undergoing reduction has attained a temperature of about 1000°C and has been in the furnace for about 6 hr. On the practical side, the behavior of the ore during smelting has been of great interest to operators. Unsatisfactory blast furnace operation on burdens containing magnetite ore or badly slagged sinter has often been attributed to poor re-ducibility. The question of reducibility has also been raised in formulating quality standards for agglomerates such as nodules, briquettes, and pellets. In the present investigation, the solid phases formed during reduction were studied as a step toward a better understanding of the overall process. Equilibrium Studies The iron-oxygen equilibrium diagram shown in Fig. 1 reveal; a number of facts pertinent to the gaseous reduction of iron ores. This diagram is from the work of Darken and Gurryl, 2 and represents a correlation of the best available data. Four solid phases may exist during the complete reduction of hematite to metallic iron. These are hematite (Fe2O3), magnetite (Fe3O4), wustite (FeO), and iron (Fe). The wustite phase is a solid solution which is not stable below 570°C. At this temperature the solid solution undergoes a eutectoid-type of decomposition into the phases, magnetite and iron. Thus above 570°C, the diagram dictates that a hematitic ore should pass through a four-phase sequence on reduction to metallic iron. Below 570°C, only hematite, magnetite, and iron should appear. Information on the iron-oxygen system has been derived largely from CO and H2 reduction equilibria. The Fe-C-0 relationships have been studied extensively by R. Schenck and his coworkers and well summarized by H. Schenck.3 More recent studies have been made by Darken and Gurry.1, 2 Data from these sources have been combined and plotted in Fig. 2. With respect to the Fe-H-O system, the works of Emmett and Schultz4 seem the most reliable, and these data have also been included in Fig. 2. Certain physical properties of the solid phases of the iron-oxygen system are summarized in Table I. The crystallographic information is of special interest as much of the present work has been concerned with the X-ray analysis of the products of reduction. Reduction with Hydrogen The reduction of ore with hydrogen is the net result of two or more gas-solid reactions. Above 570°C, the reaction sequence may be represented by stoichiometric stages as follows: 3Fe203+ H2e2Fe,O, + H20 [1] 2Fe3O, + 2H2 6FeOw + 2H2O [2] 6FeOw + 6H3 ^ 6Fe + 6H=O [3] Fe2O3 + 3H2 ^ 2Fe + 3H,O. [4] These reduction reactions follow the general form: A (solid) + B (gas) e C (solid) + D (gas). This type of gas-solid reaction has been investigated by Langmuirl' who has shown that such reactions can occur only at the boundary between the two solid phases. Furthermore, a nucleus of the second phase must initiate the reaction. Once such an interface exists, the reaction proceeds through a layer of the solid reaction product (C). The specific mechanisms involved will depend a great deal on the properties and condition of this particular layer. A number of heterogeneous reactions such as the dehydration of single crystals of copper penta-hydrate and the calcination of limestone follow this type of process. It should be noted that the inter-facial type of reaction also occurs even in dense polycrystalline material which simulates a mono-crystalline behavior.

Jan 1, 1954

By O. R. Wagner, R. O. Leach, H. W. Wood, C. F. Harpke

PAN AMERICAN PETROLEUM CORP.TULSA, OKLA. CASPER, WYO A field test has been made in which additional oil recovery was obtained from a previously-waterflooded "oil-wet" sandstone reservoir. This recovery improvement was accomplished by adjusting the reservoir wettability through chemical treatment of the flood water. The test was made in the Muddy sand of the West Harrisburg Unit, Neb. The chemical used, sodium hydroxide, was injected as a slug of dilute caustic solution through a water-injection well. The natural wettability of the reservoir and the chemical requirements for reversing wettability were determined in the laboratory from contact-angle studies using field water and oil samples. Laboratory flood tests with a synthetic system had shown that reversing the wettability of an oil-wet consolidated core would lead to improved oil recovery. The field performance indicates that the mechanism by which increased oil retovery is obtained in the field is the same as that observed in the lahoratory. Laboratory studies indicate that higher ultimate recoveries and decreascd water-injection requirements result when the adjusting agent is added early in the life of the flood. However, a previously waterflooded area was intentiorzally chosen for the field test so that unambiguous conclusions could be made about the effects of chemical injection on wettability and the extent of oil-recovery improvernent afforded by wettability reversal. Forces existing at the fluid-solid and fluid-fluid interfaces in a porous medium have an important effect on oil recovery during a water flood. Modifying these interfacial forces in the reservoir to improve oil recovery has been the object of much research. Several papers' ' have discussed the use of surfactants to lower the water-oil interfacial tension. This paper describes work concerned with improving oil recovery by modifying the forces at the fluid-solid interfaces— that is, by changing the preferential wettability. An earlier paper: presented evidence to show that some reservoir systems could be changed from preferentially oil-wet to preferentially water-wet by the action of simple chemicals added to the water to increase waterflood oil recovery. The process was attractive for further study because it used only inexpensive chemicals and because it called for a gross "wettability reversal" rather than for a precise adjustment. The present paper is an extension of the earlier work. Laboratory flow tests were made using treated water and oil in a consolidated core to determine the amount of additional oil recovery and the producing performance which might be expected from reversing the wettability of an oil-wet reservoir during a flood. A contact-anglc study using water and oil from the Muddy "J" sand of the Harrisburg field, Banner County, Neb., indicated the reservoir to be preferentially oil-wet and susceptible to wettability reversal through chemical injection. Based on these studies, a field trial of wettability-reversal water flooding was initiated. in the Harrisburg field. The primary purpose of the trial was to determine if wettability-reversal flooding would improve oil recovery in an actual field situation. The field trial was also an important test of the laboratory tecnique used to determine the effect on oil recovery of certain wettability manipulation, as well as a test of the contract-angle method of determining reservoir wetra-bility. The paper is presented in two parts. The first part covers the laboratory experiments leading up to the field trial, and the second part covers the field trial. PART I—LABORATORY STUDY The laboratory experiments consisted of displacement tests using an idealized fluid system and of a contact-angle study with crude and water from the Muddy "J" sand of the West Harrisburg Unit, Banner County, Neb. The displacement tests were designed to determine the effects of a particular wettability manipulation, oil-wet to water-wet, on oil displacement in a water flood. The contact-angle measurements were made to determine the natural wettability of the reservoir and to determine if beneficial wetting changes could be brought about by a chemical addition to the flood water. PROCEDURE DISPLACEMENT TESTS The displacement tests were perfornled in a consolidated sandstone core using a refined oil and water. The wetting properties of this system could

By W. A. Hockings, M. E. Volin, A. L. Mular

Batch grinding tests at short times were made in a laboratory rod mill with 10 x 14 mesh quartzite in corn syrup-water mixtures of varying viscosity. The weight fraction broken and size modulus were found to be independent of viscosity up to 20 cp, but at higher viscosities breakage of the feed decreased while the size modulus increased. The mechanisms of the effect of viscosity are discussed on the basis of particle dynamics. The effect of viscosity of the suspending medium on grinding has not been accorded much attention, although both wet and dry grinding are used in bene-ficiation processes and the viscosities of water and air differ greatly. schweyerl investigated the rates of grinding of quartzite in a pebble mill with air, water and glycerol as the suspending media and found the rate in terms of new surface developed per thousand revolutions of the mill to be constant and dependent on viscosity up to 20,000 rev, but to decrease and become independent of viscosity for longer grinding times. Based on considerations of the drag forces exerted on suspended particles and on the grinding media under turbulent and laminar flow conditions, viscosity can be expected to inhibit the rate of grinding in a given system as it changes the flow conditions from turbulent to laminar. The objective of this study was to determine the effect of viscosity of the suspending fluid in the batch grinding of a homogeneous feed of uniform size for short residence times, a region of more practical interest than the long times investigated by Schweyer. In actual grinding operations, the viscosity of the fluid does not change, but the consistency (apparent viscosity) of the pulp increases with additions of fines. In this study the consistency of the pulp was not measured because it was thought that the grinding times were too short to alter the apparent viscosity appreciably.* *Minus 200 mesh quartz at 65% solids has an apparent viscosity of about 25 cp as measured by a simple consistometer. Personal communication from D. F. Kelsall to A. L. Mular. For the purposes of this study, the effect of viscosity on grinding can be shown sufficiently well on the basis of the cumulative weight fraction finer than the feed size at any time, and the size modulus, ku, of the finer than feed sizes. The parameter, ku, is obtained from a form of the Gaudin-Schuhmann equation. METHOD AND MATERIAL The grinding tests were accomplished in a laboratory rod mill 10-1/2 in. long and 8 in. bore with a 20-lb rod charge consisting of two 1-in., eight 3/4-in., eight 1/2-in., and eight 1/4-in. diam rods. The mill speed was 43.2 rpm. Charges of 400 g 10 x 14 mesh Wisconsin quartzite** were ground for times of 60, **Courtesy of Minnesota Mining and Mfg. Co. 120, 180 and 240 sec in 500 cc of fluid made up of corn syrup and water in measured proportions. The temperature of the pulp was measured immediately upon completion of grinding, and the size distribution of the quartzite was determined by a wash-wet-dry screening technique. Corn syrup was chosen because of its high viscosity and ideal viscous behavior, and also because its density is not greatly different from that of water. The viscosity of each fluid mixture was measured with an Ostwald viscometer at 25 C. and a correction was made for the temperature of the pulp according to tabulated values for sucrose solutions. The density differences were so small that they probably did not significantly affect breakage. RESULTS AND DISCUSSION The conditions of the grinding tests, computed viscosities, weight fractions finer than the feed size and values of a and ku are listed in Table I. The values of a and ku were taken from the linear portions of the log-log plots of cumulative weight fraction finer vs size for the various grinding times. The plots for tests in fluids of average viscosity 8.6 cp are shown in Fig. 1. In general all of the sets of curves were linear throughout most of the size

Jan 1, 1965

By Leendert de Witte

Conventional resistivity logs consisting of a short normal, a long normal, and one or more long lateral curves do not give data that allow a complete quantitative interpretation in beds thinner than 20 ft. Reservoir rocks usually exhibit zones of continuous homogeneity of quite limited thickness where the long lateral curves become useless because of adjacent bed effects and boundary phenomena. If the beds are 12 ft or thicker, the short and long normals may be used for qualitative interpretation, which can be streamlined by the application of simplified departure curves. For beds of a thickness less than twice the long normal spacing, this procedure breaks down. The combination of the limestone curve, the later-olog or guard electrode log, and the microlaterolog permit quantitative interpretation for beds that are at least 10 ft thick, provided the mud resistivity and the hole diameter are known with sufficient accuracy. For beds thinner than 10 ft, combinations of the microlaterolog with short spaced laterologs and pseudo laterologs appear to be promising. Interpretation of these curves again requires the application of simplified departure curves. Resolution of various possible combinations was analyzed using departure curve data calculated on the Whirlwind I computer at the Massachusetts Institute of Technology. A field example is shown using the microlaterolog-microlog combination, and the combination of a 6-in. modified laterolog plus a 6-in. pseudo laterolog. INTRODUCTION For the purpose of quantitative interpretation of resistivity logs in porous formations, we want to obtain two essential quantities from the logs, namely, the true resistivity of the undisturbed formation, Rt, and the resistivity of the part of the formation invaded by mud filtrate, Rt. The apparent resistivities of all conventional logging devices are functions of these two parameters and are also influenced by a third unknown parameter, the diameter of the invaded zone, d. It has been shown' that from the normal curves alone it is impossible to arrive at a unique solution for the three unknowns, Rt, R1, and d1. In very thick homogeneous beds, if invasion is not too deep, we can obtain a fair approximation to Rt from the long lateral curves and then use the two normal curves to find Rt and d1 Even under the most favorable conditions, the resolution of this system is not very good. The short normal does not give a reasonable approximation to R1 unless invasion is very deep (dl>16 hole diameters). For very deep invasion, however, the long laterals no longer approximate Rt. For bed thickness between 20 and 40 ft, the long laterals are affected appreciably by the adjacent beds; and the curves are distorted by boundary anomalies to the extent that they lose their quantitative usefulness in most cases. For the same bed thicknesses, the normal curves still function reasonably well. Although it is impossible to find unique solutions Lor R1 and Rt using the normal curves alone, we can obtain a reasonable approximation for the ratio R1/Rt through the use of simplified departure curves. This fact was brought to our attention by A. J. de Witte, geologist with Continental Oil Co. As the magnitude of Rl/Rt is a major clue to the presence of oil in formations, this method can be used to good advantage for qualitative analysis and will be discussed in somewhat greater detail. With the aid of suitable bed thickness corrections, the analysis of the normal curves may be used for bed thicknesses larger than 12 ft. For thinner beds, the method rapidly loses its resolution; and we have to resort to different types of resistivity logs if we want to attempt to analyze the curves quantitatively. The inadequacy of conventional resistivity curves in thin beds is far more serious than generally realized. Fig. 1 shows a conventional E. S. with a 16-in. and 64-in. normal and a 16-ft lateral through a section of Lansing-Kansas City lime, in comparison to a guard electrode survey through the same section in a neighboring well. The porous zones, which show up as low resistivity breaks on the guard electrode log, are completely masked by adjacent bed effects and boundary anomalies on the conventional curves. Even the short normal shows most of the porous Zones only as Vague deflections and in many cases fails to register Their

Jan 1, 1955

By Alan Stanley

THE MacIntyre Development of National Lead Co. is located at Tahawus, N. Y., in the heart of the Adirondack Mountains. Operations involve the mining and concentrating of a titaniferous iron ore to produce ilmenite and magnetite concentrates. A general description of the operation and metallurgy has been given by Frank R. Milliken.' Pigment plant production demands that the MacIntyre mill produce a 44.7 pct TiO, ilmenite concentrate. To achieve the required ilmenite grade and tonnage it is important that the table concentrate grade be closely controlled. Unfortunately, however, the titaniferous orebody which feeds the MacIntyre mill is not uniform. Ore dressing characteristics vary from one end of the orebody to the other, and from • one level to the next. The changeable nature of the mill feed precludes a single adjustment of the equipment for long periods of time. Thus the operators must constantly watch the equipment to insure a uniform concentrate from the fine and coarse tables and Wetherills, or dry magnetic separators. Chemical assaying of mill products requires about 4 hr from the time the sample is taken until assay results are obtained, and this is available only on a two-shift basis. The ore may change rapidly, even several times during a shift, so that assay results lose most of their control value by the time they are reported to the mill operating crew. Members of the crew have therefore tried to evaluate the table and Wetherill concentrate by visual inspection, since through long experience the shift operators, under most circumstances, can gage closely the grade of the mill products. However, there are times when the physical nature of the ore is radically different from normal. Under these conditions visual inspection is of no value, and at such times final ilmenite as low as 43 pct TiO, has been produced and shipped before the assay results have been received. The specific gravity method of assaying for TiO, has been attempted to eliminate the shipping of ilmenite below normal grade as well as to help control day to day and hour to hour mill production. Table I shows the minerals found in the MacIntyre ore along with their average weight proportions and specific gravities. The first two products considered for the specific gravity method were fine and coarse table concentrates. It was reasoned that these products were essentially ilmenite with the higher specific gravity gangue minerals. Since they were always produced the same way, and the desired grade of TiO, was always constant, the specific gravity of these materials would increase or decrease as the amount of ilmenite increased or decreased. Thus for table concentrates which assayed 40 pct TiOz a constant gravity would invariably be obtained, and as the TiO, value changed the specific gravity would change in direct proportion. The third product considered was Wetherill ilmenite. It was assumed that a desired grade of 44.7 pct Ti02 would also always contain the same amount and type of gangue minerals along with the ilmenite, and thus would always have the same specific gravity. As the TiO, value of the ilmenite concentrate changed so would its specific gravity. Dr. Kenneth Vincent, chief metallurgist of the Baroid Division of National Lead Co. at Magnet Grove, Ark., ran specific gravity tests on 17 samples of the desired products. The lowest specific gravity reading assayed the lowest in TiO, and as the specific gravity increased the trend was for the TiO, assay to increase, see Fig. 1. Since these results warranted further investigation, a 500-g capacity Torsion balance and 250 ml Le Chatelier specific gravity bottles were obtained. Shift samples of fine table concentrate, coarse table concentrate, and final ilmenite were tested. Each sample was split and 85 g weighed on the Torsion balance. The Le Chatelier bottle was filled with water to a zero mark. To avoid wetting the neck of the bottle it was found necessary to do this

Jan 1, 1953

By Alan Stanley

THE MacIntyre Development of National Lead Co. is located at Tahawus, N. Y., in the heart of the Adirondack Mountains. Operations involve the mining and concentrating of a titaniferous iron ore to produce ilmenite and magnetite concentrates. A general description of the operation and metallurgy has been given by Frank R. Milliken.' Pigment plant production demands that the MacIntyre mill produce a 44.7 pct TiO, ilmenite concentrate. To achieve the required ilmenite grade and tonnage it is important that the table concentrate grade be closely controlled. Unfortunately, however, the titaniferous orebody which feeds the MacIntyre mill is not uniform. Ore dressing characteristics vary from one end of the orebody to the other, and from • one level to the next. The changeable nature of the mill feed precludes a single adjustment of the equipment for long periods of time. Thus the operators must constantly watch the equipment to insure a uniform concentrate from the fine and coarse tables and Wetherills, or dry magnetic separators. Chemical assaying of mill products requires about 4 hr from the time the sample is taken until assay results are obtained, and this is available only on a two-shift basis. The ore may change rapidly, even several times during a shift, so that assay results lose most of their control value by the time they are reported to the mill operating crew. Members of the crew have therefore tried to evaluate the table and Wetherill concentrate by visual inspection, since through long experience the shift operators, under most circumstances, can gage closely the grade of the mill products. However, there are times when the physical nature of the ore is radically different from normal. Under these conditions visual inspection is of no value, and at such times final ilmenite as low as 43 pct TiO, has been produced and shipped before the assay results have been received. The specific gravity method of assaying for TiO, has been attempted to eliminate the shipping of ilmenite below normal grade as well as to help control day to day and hour to hour mill production. Table I shows the minerals found in the MacIntyre ore along with their average weight proportions and specific gravities. The first two products considered for the specific gravity method were fine and coarse table concentrates. It was reasoned that these products were essentially ilmenite with the higher specific gravity gangue minerals. Since they were always produced the same way, and the desired grade of TiO, was always constant, the specific gravity of these materials would increase or decrease as the amount of ilmenite increased or decreased. Thus for table concentrates which assayed 40 pct TiOz a constant gravity would invariably be obtained, and as the TiO, value changed the specific gravity would change in direct proportion. The third product considered was Wetherill ilmenite. It was assumed that a desired grade of 44.7 pct Ti02 would also always contain the same amount and type of gangue minerals along with the ilmenite, and thus would always have the same specific gravity. As the TiO, value of the ilmenite concentrate changed so would its specific gravity. Dr. Kenneth Vincent, chief metallurgist of the Baroid Division of National Lead Co. at Magnet Grove, Ark., ran specific gravity tests on 17 samples of the desired products. The lowest specific gravity reading assayed the lowest in TiO, and as the specific gravity increased the trend was for the TiO, assay to increase, see Fig. 1. Since these results warranted further investigation, a 500-g capacity Torsion balance and 250 ml Le Chatelier specific gravity bottles were obtained. Shift samples of fine table concentrate, coarse table concentrate, and final ilmenite were tested. Each sample was split and 85 g weighed on the Torsion balance. The Le Chatelier bottle was filled with water to a zero mark. To avoid wetting the neck of the bottle it was found necessary to do this

Jan 1, 1953

By W. W. Eckles

This paper is presented as a suniniary report of the use of well gas composition correlations obtained from mass spectrometer recordings as a means of identification and determination of reservoir continuity. Conventional methods for detecting composition differences are en-pensive, elaborate, and difficult to obtain. This excludes the use of extensive composition data for most applications. During recent years the mass spec-trometer has come into general use as an analytical tool in petroleum refineries. The use of mass spectrometer composition patterns ir~ characterizing or "finger-printing" the produced gas from a reservoir, presents a novel method for correlatitlg gas samples from well to well. The mass spectrometer provides a trace similar to an electric log. having peaks which represent the abuntlnnce of certaitz hydrocarbons in the well gas sample. Without going further into the detailed analysis the idea has been advanced that these traces or patterns could be used as a means of identifying a particular natural gas. This theory has proven to be essentially correct. The mass spectrometer pattern method is simple and cheap as COi?7pared to other standard methods. It greatly facilitates the solution of reservoir and geological problems in which correlation of well gas Com-positions is a factor. Specific field applications have been made. This paper concerns the results obtained in 465 individual gas analyses from 35 fields and 77 res- ervoirs. In a number of cases it has been found that such data have been extremely valuable in the determination of reservoir continuity. In at least one case, the method was a valuable contribution in tracing a reservoir from sand to sand in a coinplex fnulted field involving n11rnerous gas reservoirs. Field applications are presented to illustrate the possibilities of the method at the present stage of developnient and to stimulate the ernployrnent of this new approach by geologists and petroleum engineers in the industry. INTRODUCTION Identification of producing horizons and the determination of reservoir continuity are often a problem in those areas where dome structures and highly faulted sands are encountered. To complicate the picture further, there may be numerous sands, one on top of the other which dip and diverge in different directions. Even though it may be possible to develop some solutions to the preceding problems on the basis of the geological and reservoir data on hand. it is readily recognized that substantiating data based on independent methods would he extremely valuable. It has been found through field studies that correiation of well gas composition can be used to advantage in the geological and engineering study of a complex reservoir identification problem. METHOD FOR COMPARISON AND CORRELATION OF WELL GAS SAMPLES Since a large number of well gas samples are required in a gas identification or reservoir con- tinuity problem, it is necessary that a method of analysis be employed which can detect differences in composition readily and inexpensively. Although detection would be possible by means of low temperature fractional distillation (POD) analpsis, the method requires a relatively large sample and is comparatively slow and expensive to run. The mass spectrometer affords an inexpensive and precise analysis of small well gas samples taken at the surface which are about 1/300 as large as a POD sample. These samples can be obtained by regular field personnei and shipped to the spectrometer for analysis. It is, therefore, a practical approach to the problem. A typical record from the mass spectrometer is illustrated in Fig. I. The peaks on the record represent the abundance of ions produced from the different hydrocarbon molecules making up the gas sam-ple. In well gas comparisons only five peaks are employed, since the other peaks are formed from the same gas molecules and furnish no additional information. The five peaks used represent the abundance of methane, propane, ethane, butane and heavier, and oxygen. They are referred to respectively as the 16, 29, 30, 43, and 32 peaks. The oxygen peak is used to correct for air content in

Jan 1, 1958

By G. W. P. Rengstorff, H. B. Goodwin

A method is described for purifying iron in batches of 150 Ib or more. Oxygen, carbon, nitrogen, and sulphur are removed from flakes of electrolytic iron by treatment in wet and then dry hydrogen. A special consumable-electrode arc furnace is used to remove hydrogen and to melt the flakes into ingots. A LTHOUGH iron and steel have been made and used for hundreds of years, there are still wide gaps in the knowledge of these metals. One reason for this is that the true properties of the base metal, iron, are not well known, simply because really pure iron has never been readily available for research purposes. Commercial iron, and even the "pure" irons which are readily available, are really complex alloys of iron with oxygen, nitrogen, hydrogen, carbon, sulphur, silicon, and other elements. With such materials, it has not been possible to prepare steels and other iron-base alloys in which all elements are present in exactly controlled amounts. It is an almost impossible task to determine the separate effects of each element or the intereffects of several elements unless alloys can be prepared containing only the desired elements. The ability to make controlled alloys of low impurity content is of far more than academic interest. It will assist in the study of such practical problems as the brittle failure of ship hulls or high pressure gas pipelines, determination of the factors which affect the deep-drawing properties of steels, the improvement of magnetic and electrical properties, the phenomenon of aging, and many others. In 1949, the American Iron and Steel Institute asked Battelle Memorial Institute to prepare high purity iron on a larger scale than had been attempted up to that time. The work was directed toward the preparation of iron as low as possible in carbon, oxygen, nitrogen, hydrogen, and sulphur because these are the contaminating elements of major interest in many research investigations on iron-base alloys. The initial goal was to prepare iron with not more than a few thousandths of one percent of each of these impurities. The purpose was to set up a "bank" of high purity iron on which researchers could draw when a supply was needed and which could be replenished from time to time as the stock became depleted. Of several possible purification methods, heating in hydrogen was selected as the most promising for the removal of both carbon and oxygen from solid iron. Metallic impurities are not removed by hydrogen. Electrolytic iron was chosen as a starting material because it is the most readily available form of iron low in metallic impurities. Decarburization and desulphurization were obtained by annealing in wet hydrogen at relatively low temperatures. The optimum temperature, as found by previous investigators,' is about 1400°F. This treatment also removes nitrogen. Deoxidation is favored by dry hydrogen and higher temperature. There is evidence from previous work that an anneal at 2200°F in dry hydrogen will deoxidize the iron, reduce the nitrogen content, and reduce the sulphur content. These facts suggested the use of a two-stage process: treatment in wet hydrogen followed by treatment in dry hydrogen. To carry out the purification process in a reasonable time, it was necessary that the iron be in thin pieces. Flakes of electrolytic iron were used. Because most research requires that the iron be in massive form, it was nccessary to melt the purified iron to consolidate it into large pieces. For this work, it was decided to prepare ingots weighing at least 15 lb by using a cold hearth arc-melting process in which the iron was melted in an inert atmosphere of argon or helium. This method of melting was selected because the water-cooled copper crucible is not wet by the iron and does not contaminate it as a refractory crucible would. Because the crucible is also the ingot mold, contamination from mold materials was also eliminated. Contamination from electrodes was avoided by making them from purified electrolytic iron. The melting procedure finally developed was an adaptation of the Kellogg electric ingot process.' Two batches of purified iron weighing about 100 Ib each in ingot form were prepared with analyses as shown in Table I. The remainder of this paper describes the procedures in more detail. In general, the process con-

Jan 1, 1956

By E. A. Steigerwald

E. A. Steigerwald (Thompson Ramo Wooldridge, Inc.1— he authors' results clearly indicate that cracking can be produced by the hydrogen pressure developed during a charging operation. This type of cracking or blistering has also been observed in polycrystalline materials24"28 when the charging conditions are sufficiently severe and is often referred to as irreversible embrittlement since it cannot be removed by a baking treatment. There are additional data, however, which must be considered before a pressure theory can be generally employed to account for all failures which occur as a result of hydrogen. In many cases, hydrogen embrittlement in a tensile test or in delayed failures under static loads is a reversible phenomena which cannot be simply explained on the basis of preexisting cracks generated by the charging operation. It is this aspect of the problem which has prompted many investigators to seek mechanisms other than hydrogen pressure to explain their results.24'n728 Fig. 15 indicates an example where, under specific experimental circumstances, hydrogen embrittlement can occur at liquid nitrogen temperatures. In this case, which has been previously decribed,'' specimens were charged with varying quantities of hydrogen, immediately quenched, and tested in liquid nitrogen (-320°F). A companion set of identical specimens were charged, aged at 300°F to remove the hydrogen, and also tested at -320°F. When the current density was greater than lo-' amp per sq in., embrittlekent occurred in both sets of specimens, indicating that cracking had occurred during charging and the embrittlement, as in the case of Fe-Si single crystals, was irreversible. At current densities between approximately 103 and lo-' amp per sq in, the embrittlement was present only for those specimens which contained hydrogen during the testing sequence. The embrittlement was therefore reversible with respect to the aging and charging operations. Since extensive hydrogen movement would not be expected at -320°F, it is difficult to reconcile these data with a mechanism which requires pressure and pressure dependent growth of preexisting cracks. There are other features of hydrogen embrittlement such as the reversibility of the incubation time for delayed failure with respect to applied stressg0 and the influence of prestraining31 which are also difficult to explain using a pressure model. Any general mechanism of hydrogen embrittlement will have to consider the reversible aspects of the embrittlement data as well as the irreversible portion which has been clearly presented for the Fe-Si crystals and which is consistent with a pressure model. A. S. Tetelman and W. D. Robertson (authors' reply)—he authors agree with Dr. Steigerwald that a general mechanism of hydrogen embrittlement must be applicable in all cases where embrittlement occurs. Dr. Steigerwald's experiments were performed on an iron alloy which has an extremely complex microstructure, and therefore does not lend itself to the direct and detailed observations that can be made in Fe-Si. The change in the characteristics of cracks as a consequence of annealing at 300°F is not really known in detail but it is probable that stress-relaxation (blunting) occurs, dislocations produced near the crack tips will be pinned by carbon atoms, and hydrogen will be lost to the atmosphere. Any, or all of these effects of annealing will alter the ease with which a crack subsequently propagates under applied stress. A quantitative treatment of the problem must take these effects into account. Since diffusional processes are presumably eliminated at -320°F, the general mechanism proposed by Dr. Steigerwald's colleagues cannot be operative at this temperature. A detailed discussion of the general' inapplicability of this mechanism has been presented elsewhere. However, the data presented by Dr. Steigerwald in his discussion can be explained in terms of a pressure model. Crack propagation under internal pressure P and applied stress occurs when where is the total energy expended in creating new surface area and by plastic work at the crack tip. The total crack length increases with increasing current density, since we have shown that it systematically increases with hydrogen concentration and Dr. Steigerwald has shown that hydrogen concentration increases with current density. For large L (high current density) Eq. [I] can be satisfied even if P = 0 and the embrittlement process does not require the presence of hydrogen. Specimens charged at a lower current density will con-

Jan 1, 1963

By Kenneth Schellinger

THE terms surface tension and surface energy are well known when applied to liquids and are generally described by referring to the excess energy of the air: liquid interface as a result of unsaturated molecular forces surrounding the surface molecules of the liquid due to the presence of the air phase on one side. Such unbalanced forces produce the familiar water droplet of spherical form and are generally summed up as a surface tension measured in dynes per centimeter which can be shown mathematically to be equal numerically to a corresponding surface energy expressed in ergs per square centimeter. A specific surface energy, however, is best thought of as the energy necessary to produce one unit, of new surface on a substance. Hence, in producing a bubble in a flotation cell the impeller must supply surface energy corresponding to the air: liquid interfacial area on the interior of the bubble. Inasmuch as it is relatively easy to extend or contract the surface of a liquid, there are a number of successful methods for liquid surface tension, or energy, measurement based upon surface deformation. This happy state of affairs does not, however, extend to solids, which are considered to possess surface energies for the same reasons as do liquids, i.e. because of unsaturated ionic bonds at the solid: gas interface. As in the case of the flotation cell producing surface on liquids as new bubbles, it takes energy to produce new surface on solids as new particles. As every mill man knows, this surface is produced on mineral solids in a grinding mill by the action of a tumbling mass of iron balls. But here so much energy usually is wasted by the inefficient action of these balls that a large amount of heat is generated, and the surface energy production may be easily confused with the energy necessary to produce this ineffective heat. The tumbling balls and fracturing minerals ultimately take their energy from a rather large electric motor. It has been variously estimated that from 10 to 20 pct'" only of this energy from the motor does not appear as heat and may be presumed to appear as surface energy on the min- erals present. Such a production of new surface on the mineral phases is accompanied, of course, by a size reduction that is inevitable as more and more mineral interior molecules become surface molecules by the fracture exposure. This size reduction of mineral particles, although the most obvious feature and perhaps the sole object of the milling operation, is from this energy viewpoint the outward manifestation of the production of surface energy only. Measurement of the characteristic surface energies of pure minerals and their various mixtures in ores would be a step towards understanding of the energetics of the commercial grinding operation. In addition, the characteristic surface energy of a mineral is probably a physical property specific for that mineral, and therefore, from a scientific standpoint, should be measured. It is interesting to note that, in contrast to the large body of work on the surface tensions of liquid systems and biological systems, the field of solid surface energies has been neglected. Prior to 1920 it is difficult to find more than one or two references to work on solid surface energies in Chemical Abstracts. Since 1920 such references number somewhat less than 100, while those on liquid systems are numbered in the thousands. Much of this apparent neglect of the field of solid surface energies (the term is intended to be somewhat inclusive at this point and refers both to the solid: gas, and the solid:liquid interface) is because of the lack of a reliable method of measurement rather than any lack of scientific curiosity. It was, and still is, difficult to produce new surface on a solid without the simultaneous production of interior changes in the same solid which may consume part of the energy used. The extension in the surface area can be measured, but the interior crystal-

Jan 1, 1953