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By R. E. Zimmerman

Wide attention is being placed upon various methods for cleaning the fine sizes of bituminous coals. The author describes and analyzes the results achieved on wet concentrating tables of modern design on unclassified feeds of —Vz in. particle sizes, including tests on high-sulphur coals. THE increased economic necessity of cleaning the small sizes of coal has forced wide attention upon various methods or processes being used. Although numerous cleaning plants in the past have been cleaning coal smaller than Vz or % in., the large quantities of higher ash fines being produced by mechanical mining and the need for cleaner coal under competitive market conditions have brought about many new installations of fine-coal cleaning plants. Of various methods used, one of the more popular types is the wet concentrating table. Approximately 525 tables have been installed in the United States in the past four years of which 320 have been installed in 20, large new plants. There are now probably 1600 tables of all types in existence in this country for cleaning coal. The purpose of this paper is to describe the cleaning of fine coal by wet concentrating tables. Its scope is confined to a discussion of the theory of tabling and some of the factors entering into tabling action, a description of the Deister SuperDuty diagonal-deck coal table and a discussion of the results of tabling various fine sizes of coals. Al- though tables have been used for cleaning coal as coarse as 2 in. and favorable results are reported, this paper is limited to reporting on the results of cleaning coal fines from 1/2 in. down. Also, although it is well known that the performance of tables is even superior under classified or closely sized feed conditions, this paper concerns itself with the results achieved by tabling unclassified feeds. History of Wet Concentrating Tables The wet concentration of minerals by some form of tabling is quite old, starting originally from fixed, smooth surfaced, tilted boards taking advantage of the laminar flow of liquid films and the separation of minerals according to specific gravity. This was followed by the development of rough deck surfaces

Jan 1, 1951

When the suggestion was made by Major General Leonard Wood that the Institute assist in the formation of a National Reserve Corps of - Engineers, Dr. Drinker's name occurred first to the Board of Directors as the man who would be most capable of carrying out the proposed plan. Dr. Drinker has long been associated with work in connection with military training and is at present the Chairman of the Governing Committee on Military Training Camps Association which is having such important results at Plattsburg and other places in this country. As Chairman of the Institute's Committee on National Reserve Corps of Engineers, Dr. Drinker was a member of the Joint Conference Committee of the National Engineering Societies .on. this subject., He was an earnest worker in the movement, which, has finally resulted in definite legislation by Congress; whereby a Reserve Corps of Engineers is authorized in the new Army Bill which became effective July 1, 1916. Notice of the results of the work was sent to all the members of the National Engineering Societies early in July, and the and the Department of the United States has recently issued a circular which has been sent to all the members of the National Engineering: Societies, as well, as to many other engineers, outlining, the line, whereby engineers may enroll themselves in the Officers Reserve Corps. Dr. Drinker has, therefore, fulfilled the mission which he undertook when assuming the Chairmanship of the Institute's Committee. He now asks the permission of the Board of Directors to withdraw as Chairman and has requested that he be replaced in this position by Mr. Arthur S. Dwight, in; the belief that the Chairmanship of the Institute's Committee and, membership on the Joint Committee should be vested in a man ,located in New York City, for the better carrying put of the important work now before the Joint Committee. We are happy to say that Dr. Drinker has consented to remain a member of the Institute's Committee; but the completion of the first phase of his work; as,Chairman, should not be allowed, to pass without an expression of appreciation on behalf of the Institute for his services.

Jan 9, 1916

By A. W. Fahrenwald, Lewis S. Prater

BY taking advantage of the fundamental difference between screening and classification-namely, that specific gravity has no effect on screening but is one of the important factors in classification-a combination of the two may be used as a process of mineral concentration. Although this fact is not new, so far as is known it has had little or no commercial application. The scheme is not presented now as a process for producing finished products but rather as a preliminary operation rejecting part of the barren material from an ore before it is subjected to more costly treatment. That is largely the function of the new heavy-media concentration processes that have been widely accepted. Original installation costs for the present sink-float processes are relatively high, however, which confines their use to operations where large tonnages are handled. Sink-float has been successful on only the relatively coarse (approximately plus 10-mesh) portion of an ore, and it is in this same range that classification screening can function most satisfactorily. Theoretically, there is no upper limit to the size of particles that can be handled in a sink-float operation, but the degree of liberation in the very large pieces usually limits this. With classification screening, particles from 3/8 to 1/2 in. would be the largest that could be handled, but the lower range could be extended somewhat below 10 mesh. In order to take full advantage of the difference in specific gravities of the minerals being separated, sorting in the classifier should be under as extreme hindered-settling conditions as possible. Laboratory tests have been made on a galena ore and on an artificial mixture of quartz and magnesite to determine the separations that may be expected. Although more than one scheme may be followed, in these tests the separations were made by cutting the underflow from the classifier as a concentrate and then screening the overflow. The screen oversize was rejected as a tailing. Classification was done in a hindered-settling teeter column and screening was done by hand, using the standard [v2]series. The accompanying flowsheet gives the testing procedure followed. [ ]

Jan 1, 1945

By John Mathews

DURING the prosecution of the aircraft-production program in 1917 and 1918, the writer visited many plants engaged in the manufacture of motors, planes and parts, in carrying out his duties as chairman of the Committee on Aircraft-engine Forgings. On several occasions, when the question of expansion was discussed, it was noted that there was confusion in the use of the terms: the true coefficient of expansion, a physical constant, and distortion in hardening. One engineer, referring to a steel shown in the accompanying table; stated that he could not consider it for crankshafts because of its excessive coefficient of expansion, while another steel, also listed in the table, as said to be especially good because it had no coefficient of expansion, since it came out of the oil bath perfectly straight. Many years ago one of our employees designed anew oil furnace; when asked what became of the products of combustion, he replied: "There ain't any, we burn them all up." While the coefficient of expansion is not without its effect in volume changes in hardened steel, it is not a determining factor in the matter of distortion and going out of shape. Irregular heating, uneven furnace bottoms, and carelessness in withdrawing the part from the furnace, as well as the manner in which the part enters the quenching bath are of greater moment. Generally speaking, also, steels of relatively low hardening temperature will distort less than those requiring higher hardening heats. The coefficient of expansion must be considered in engineering design most frequently when different metals or alloys are used in the same construction. For example, the difference of expansion between a steel crankshaft and an aluminum crank-case might be of real importance and a steel with no coefficient of expansion would be much less desirable than one with the normal coefficient. About 15 years ago, the writer made many determinations of the coefficient of expansion at low temperature ranges, usually between 20° and 100° C. Among the materials tested were: Pure forged electrolytic iron, 11.73 parts per million for 1° C.; cast aluminum (99.93 per cent. Al.),

Jan 2, 1920

By A. R. Troiano, W. J. Barnett

The existence of a grain size stabilization effect on martensitic type reactions as shown by Scheill in an iron-29 pct nickel alloy and by Troiano and Tokich2 in cobalt prompted a review of other martensitic reactions to determine if this stabilization effect is characteristic of all martensite type reactions. Preliminary work has shown this effect to be present both in the gamma —+ epsilon transformation in an iron-20 pct manganese alloy and the martensite transformation of SAE 4140 and 3 pct Cr-O.40 pct steels. No appreciable effect was found in an SAE 2340 steel. The M, temperature for the gamma —+ epsilon transformation was lowered from 380°F to about room temperature by varying the annealing treatment following cold work as shown in Table I. The effect of austenitic grain size on the M, of three steels is shown in Table 2. M, was deter- mined by the conventional quench-temper method of Greninger and Troiano. In a single crystal the change in external shape concomitant with the homogeneous shear mechanism of the martensite transformation can take place unhindered. In a polycrystalline specimen a restraint of these changes must occur at the grain boundaries. Therefore, the smaller the grain size the greater the shear strain energy necessary for the formation of a martensite crystal. The degree of lowering of M, due to the reduction of grain size is much greater when the change in crystal structure involves only a small energy change, such as face-centered cubic —+ close packed hexagonal (that is, CO and Fe-20 pct manganese alloy). The maximum lowering of M, observed in the steels investigated was 50°F with a change in the ASTM austenitic grain size of 1-2 to 8-9. In comparison, the crystal structure change face-centered cubic —+ body-centered tetragonal involves a considerable energy change. There is little doubt that with much finer grain sizes the increased grain boundary restraint would greatly enhance this stabilization effect. The implications of this phenomenon are multifold. Undoubtedly. under certain conditions it offers a method of stabilizing high temperature phases for room temperature

Jan 1, 1949

By Edgar S. Cook

At the close of the Bethlehem Meeting, the writer was experimenting with large fuel-charges, 4000 Ibs. basis, as compared with 2000 Ibs., hot had not made sufficient progress to draw any safe conclusions. Previously me had always used 2000 Ibs. fuel, the ore-burden being proportioned to this as a basis. I could never persuade myself that there was any advantage to be derived from following the more popular method of larger fuel-charges. Our men were accustomed to the old way of filling ; and we did not care to run the risk of the errors likely to follow any alteration in routine work, particulary as I could not, by my course of reasoning, discover ally compensating gain. Nevertheless, after reading Mr. Gordon's discussion of Mr. Birkinbine's paper, '' Operations of Warwick Furnace from August 27th, 1880, to September 1st, 1885" (Transactions, xiv., 833), I determined to test by actual experiment the value of large fuel-charges : the change was made in the week commencing March 28th, 1886, and continued until July 25th, about four months. The fuel and ores remained during the trial the same as had been used before, and have been used since. For the first two weeks, the furnace worked with great regularity, giving excellent results, exceeding those of the two weeks immediately preceding. But for my remembrance that the furnace had on former occasions worked with equal uniformity for longer periods without any apparent reason, I should doubtless have concluded that this improvement was due to the different method of filling and congratulated myself that a means had at last been found to prevent inconvenient "dirt" accumulations. Before abjuring my previous skepticism, however, I resolved to pursue the trial further. The fourth meek developed the peculiar conditions that had prevailed previous to the change; and these continued with more or less frequency during May, June and July. At last, finding no improvement over the smaller charges—no change in fact for better or for worse—I commenced filling the 2000 lbs. fuel-charge in the latter part of July, and have continued it up to present writing, September 4th.

Jan 1, 1887

By Frank C. Greene

Missouri has had one of the best years in history in the development of gas, the 49 completed gas wells having an average of nearly 1,000,000 cu. ft. initial open flow. Altogether 101 wells were drilled in the western part of the state, from Andrew County on the north to Vernon County on the south. Of these 49 were gas wells (including four old wells drilled deeper) with an initial open flow of 48,850,295 cu. ft., eight were oil wells (including one old well drilled deeper) with an initial capacity of 125 bbl. per day and 44 were dry holes (including five old wells drilled deeper). All the oil wells were in previously discovered pools in Jackson and Cass Counties. The outstanding discovery was a "shoestring" of a sand that is termed the Bartlesville, trending northwest and southeast across townships 48 and 49 N., R. 32 W., in central Jackson County. The sand is believed to be a narrow channel or bar, probably not over 800 ft. wide, lying at a higher horizon than the Bluejacket or true Bartlesville sand. A total of 32 wells with 47,453,080 cu. ft. initial open flow has been completed along the 6 miles of the shoestring. The largest individual well had an open flow of 4,500,000 cu. ft. The depth of these wells ranges from 350 to 635 ft., depending on surface elevation. The rock pressure ranges from 145 to 169 pounds. The Missouri Valley Gas and Oil Co. and Panhandle Eastern Pipe Line Co. have laid pipe lines into the area and most of the wells are now connected. In other parts of Jackson County and in other counties of the state there was very little activity during 1937. Of the 101 completions, 88 were in Jackson County. Cass County had five oil wells and three dry holes, Bates County one dry hole and Vernon County two dry holes. In the northern counties, Andrew and Clinton were represented by one dry hole each. At the end of 1937 drilling and leasing operations were very active and wildcatting promises to feature the coming year.

Jan 1, 1938

By F. P. Dewey

At the Wilkes-Barre Meeting of the Institute, Dr. J. Lawrence Smith, in the course of his remarks on some peculiarities in the composition of irons, alluded to the so-called " bucltshot" iron, and exhibited a specimen of this material. He said that when the small granules, or shot, were separatetl from the mass, they could be flattencd under the hammer, and inferred that these particles had been decarburized by the blast before sinking into the hearth of the furnace, and thus we had the exceptional production of wrought iron in the blast furnace. I have recently obtained a characteristic specimen of this variety of iron from one of the furnaces at Orbisona, Pa. Considerable uncertainty existed as to its true nature and the conditions of its production. Its weight seemed to preclude the idea that it containetl much or any slag, yet its lack of strength indicated that it was not homogeneous cast iron. At times considerable quantities had been produced, which could only be utilized by charging in the furnace and remelting. The specimen, on the freshly fractured surfacc, appeared to consist of flattened globules of iron cemented together by a bluish material which one would naturally suppose to be slag, and qualitative examination for lime strengthened this supposition. It was quite difficult to obtain drillings, as there was a tendency to split in several directions as soon as pressure mas applied; but enough was obtained to undertaltc quantitative determinations. They were found to consist of two portions—one attracted by the magnet, and the other not. By repeated separation the magnetic portion was found to be 94.44 per cent., and the non-magnetic 5.56 per cent. Analyses of these gave the following results: Magnetic Portion. Non-magnetic Portion. Percent, Percent. Graphite,.....3.480 Lime,. . 71.41 0 = 24.028 Combined carbon,. .. 0.260 Magnesia,. trace. Silicon,..... 2.790 Protox. of Phosphorus,.... 0.412 iron,. trace. Sulphur,.....0.292 Sulphide of Copper,.....0.110 caleium, 3.67 S= 1.72 0 = 3.440 Manganese,.... 0.500 -Iron (by dif.).,. .. . 91.206 27.468 --Silica,. 24 62 0 = 13.131 100.000 99.90

Jan 1, 1879

By H. P. Reid

Portland cement is manufactured under either of two general processes, the wet or the dry. The raw materials in general consist of limestone, shells, marl, cement rock, clay, shale, blast-furnace slag, etc., so proportioned that when calcined the desired composition will be obtained. In the wet process the combined raw materials are ground to extreme fineness in the presence of water, to a resulting slurry of from 30 to 50 per cent moisture content. The moisture of the slurry may be reduced by thickening or filtering processes for feed to the cement kiln or the slurry may be fed to the kiln with its full percentage of water. The dry process differs from the wet in that the surface moisture of the raw materials is removed prior to grinding. For the drying of these materials heat is required and in most cases is produced by burning of raw fuel either on grates or stokers before the dryers or in suspension in the form of pulverized coal, oil or gaseous fuel. The power required for making the cement is sometimes purchased from outside sources; sometimes it is generated from the heat in the waste gases leaving the cement kilns, or generated at the plants direct from raw fuel. We have, then, as the possible requirements of fuel in the cement industry: (1) fuel for power generation, (2) fuel for drying raw materials, including coal before pulverizing, and (3) fuel for burning the raw materials to cement clinker. There is no essential difference in quality required in fuel for burning the materials by the wet and,dry processes. Fuel fob Power Generation As there is nothing peculiar to steam generation in a cement mill power plant as compared with other power plants this use classification of such fuel will be found in other reports of the Technical Committee. Fuel for Drying Raw Materials and Coal Any fuels capable of producing moderate temperature gases may be used for drying raw materials. There is no problem of material contamination from fuels at this part of the cement manufacture to be guarded against.

Jan 1, 1932

THE strike of the coal miners began on April 1, as had been expected, the entire force of unionized miners-both anthracite and bituminous-going out and making this the most widespread strike of record. Up to the present writing there has been no serious inconvenience to industry in general, the accu-mulated stocks of coal being large and the non-union mines having continued to make a substantial production. However, the union labor leaders, having concentrated their efforts toward inducing the non-union miners to go out also, met with some measure of success in certain fields and created a shortage of coking coal, which caused iron makers to bank a few furnaces. The strike of textile workers in New England spread further. Here and there, throughout the country there were sporadic troubles with the builders. Rail-way labor was the subject of continued palavers, which did not get anywhere. On the whole the events of April were in line with the forecast that this would be a year of labor troubles. In domestic politics, the soldier bonus bill, having been passed by the House, went to committee consider-ation in the Senate. Public opposition to it manifestly waxed. On the floor of the Senate the tariff bill was under consideration and is drawing nigh to passage, without there being much consideration of its probable economic consequences. It is going to be a very high tariff and there is much in it that is equivalent to subsidizing small and normally unprofitable industries at the expense of the people as a whole. Abroad affairs were more quiet, superficially at least; than they were in March. In Egypt, India and South Africa things calmed, down, so far as we know, but in Ireland there was continued turmoil. The Irish, having won their freedom to the same degree as the Canadians, have entered upon violent quarrels among themselves, more over phrases than anything .else, so far as we can see. Lloyd George obtained a spectacular vote of confidence from Parliament and thus postponed, the exigency of a general election.

Jan 5, 1922

F. JOHNSON,* Birmingham, England (written discussion t).--. Mr. Skowronski's first melting experiments tend to show that ingots with a "level set" may be obtained without oxygen. Now it is characteristic of all metals which occupy a smaller volume when solid than they do when molten to "pipe." In vertical-cast ingots, this pipe resembles a horn-shaped cavity, with the wide mouth uppermost. In horizontal-cast ingots, the pipe is a longitudinal furrow along the center-line of the ingot surface. If copper be successfully deoxidized and degasified, this furrow will inevitably be produced. In the author's oxygen-free ingots, it is. clear that gases were occluded and these gases effectively opposed the formation of a pipe or furrow by shrinkage (fluid contraction). It is riot a special property of any particular gas which produces this effect. Hence it is not surprising that the author has succeeded in producing level and overpoled ingots through the agency of sulphur. dioxide gas. That he has counteracted the overpoling influence of sulphur by means of oxygen is somewhat difficult to explain, since the well known reaction between cuprous sulphide and cuprous oxide should result in the production of sulphur dioxide gas. Why the presence of excess cuprous oxide should neutralize the overpoling influence of this gas without eliminating sulphur is not at all clear. It is to be regretted that the oxygen was not determined in the bars given in Tables 3 and 4. It is by no means established that sulphur is responsible for the over, poling of ingots given in Table 4, since carbon was used for overpoling. If, however, the same kind of poling treatment was given as that applied in the case of ingots in Table 1, the responsibility of sulphur assumes more definite shape. The author rightly points out that Mr. Johnson's theory of the equilibrium between gases and cuprous oxide does not explain why a simple addition of cuprous oxide does not correct an overpoled charge. Such a charge must be re-worked to "set" copper. This re-working (rabbling) undoubtedly forcibly removes the excess gases, which are not removable by cuprous oxide.

Jan 11, 1918

By R. E. Zimmerman

Wide attention is being placed upon various methods for cleaning the fine sizes of bituminous coals. The author describes and analyzes the results achieved on wet concentrating tables of modern design on unclassified feeds of —Vz in. particle sizes, including tests on high-sulphur coals. THE increased economic necessity of cleaning the small sizes of coal has forced wide attention upon various methods or processes being used. Although numerous cleaning plants in the past have been cleaning coal smaller than Vz or % in., the large quantities of higher ash fines being produced by mechanical mining and the need for cleaner coal under competitive market conditions have brought about many new installations of fine-coal cleaning plants. Of various methods used, one of the more popular types is the wet concentrating table. Approximately 525 tables have been installed in the United States in the past four years of which 320 have been installed in 20, large new plants. There are now probably 1600 tables of all types in existence in this country for cleaning coal. The purpose of this paper is to describe the cleaning of fine coal by wet concentrating tables. Its scope is confined to a discussion of the theory of tabling and some of the factors entering into tabling action, a description of the Deister SuperDuty diagonal-deck coal table and a discussion of the results of tabling various fine sizes of coals. Al- though tables have been used for cleaning coal as coarse as 2 in. and favorable results are reported, this paper is limited to reporting on the results of cleaning coal fines from 1/2 in. down. Also, although it is well known that the performance of tables is even superior under classified or closely sized feed conditions, this paper concerns itself with the results achieved by tabling unclassified feeds. History of Wet Concentrating Tables The wet concentration of minerals by some form of tabling is quite old, starting originally from fixed, smooth surfaced, tilted boards taking advantage of the laminar flow of liquid films and the separation of minerals according to specific gravity. This was followed by the development of rough deck surfaces

Jan 1, 1951

By C. V. Milikan

Allocation of allowed production in a prorated field by the use of bottom-hole pressures is a method which is sound in theory. Thus far it has had limited application because the experience in correlating bottom-hole pressures with the depletion of wells or fields is not sufficient to interpret all the pressure changes. With additional data and more general knowledge of bottom-hole pressures their use in proration will probably become common. Bottom-hole pressure is the pressure at or near the bottom of a well. It is usually determined at the face of the producing horizon. Bottom-hole pressure measured while the well is producing, may be called the bottom-hole producing pressure or bottom-hole flowing pressure. If the well has been shut in or shut down long enough for the pressure in the producing horizon within the drainage area of the well to equalize, it may be called the reservoir pressure. The allowable production from a prorated field may be allocated to the individual wells or leases by three methods: 1. Bottom-hole producing or flowing pressures. (a) The potential capacity of a well to produce. (b) A uniform differential pressure while producing at the allowed rate. 2. Reservoir pressures. 3. A combination of bottom-hole producing pressures and reservoir pressures. In most prorated fields the allowed production is allocated to the individual wells or leases in proportion to their individual potentials. This method is based on the theory that there is a direct relationship between the permeability and the porosity of the reservoir. More directly stated it means that there is a direct relationship between the amount of oil in the reservoir and the rate at which it will move through the reservoir. While in general this relationship is true, it may vary considerably in different wells. Furthermore, in many wells the capacity of the reservoir to deliver oil to the well is greater than the capacity of the flow string to deliver oil to the surface. It is especially true where the potential is determined by flowing through tubing or by pumping.

Jan 1, 1933

G. B. WATERHOUSE,* Buffalo, N. -Y. (written discussion?).-One of the most essential features of rail manufacture is the production of rails that will give good service and be free from failures. To this end rails are made to careful specifications and their manufacture is controlled by rigid inspection on the part of both the producing mill and the railroad or its representative, such as the Hunt special inspection referred to in the paper. Captain Hunt refers to the crescent-shape base failures and describes them as ruptures in the rail flanges extending from the outside inward toward the web. This is hardly correct and may be misleading. It has been shown, over and over again, that the base breaks originating in seams invariably start at the center of the rail base; and run longitudi-nally in varying lengths from 3 to 12 in. and sometimes longer. Most of them are from 5 to 8 in. long and then curve outward to the edge of the flange. The split at the center of the base may exist for an indefinite time and not be discovered until the break shows on top of the flange or the piece of flange breaks off. The. stresses that cause the break are explained in two ways: (1) by the eccentric bearing of the rail base, that is taking contact at one side or edge and bringing excessive strain at the center of the base which starts fracture in any seam that may he present at that point; (2) the split may be due to cross strain in the base where this member is thrown into. compression, as happens where a pair of trucks are on opposite sides of the cross tie or rail-base hearing, and the head is put in tension. A careful study of "split base breaks" shows that fully 95 per cent. occur on the tie bearing, which is further evidence that the above de-scribed causes for the initial break are probably correct. These split base breaks are almost invariably progressive, but always start at the center of the rail-base running longitudinally.

Jan 12, 1919

By L. W. Jones, B. H. Bennetts

The removal and disposition of large quantities of slag from blast-furnaces is a question of great importance in the design of works, and various methods have been devised, from time to time, in order to take the best advantage of local conditions. With blast-furnaces treating copper-ores or lead-ores, it is necessary to use a fore-hearth, or matte-settler, in order to collect, if possible, every particle of valuable matte which, otherwise, would be carried away with the out-flowing slag. In all of these cases, the slag overflowing from the fore-hearth is caught in pots and then conveyed to the dump. If the slag is of no value and the necessary water-supply, grade and dumping-space be available, the disposal of the slag by granulation is by far the cheapest and best method. It involves a minimum of labor, both at the furnace and at the dump; and it permits a continuous outflow of slag from the furnace or settling-pot, thereby avoiding frequent tapping and plugging. When the conditions of water-supply, grade and dump-area will not permit slag-granulation, there are three other methods in common use. Large steel or cast-iron pots, or ladles, supported by trunnions on heavy cars which are moved by steam-, air-, or electric locomotives; some type of mechanical conveyor; and small pots or buggies moved by hand. The pots on the slag-cars are generally circular or oval in shape, and each one contains from 15 to 40 or more cu. ft. of molten material. The mechanism for tipping them is more or less elaborate; and, as a general rule, the slag is dumped alongside, and quite close to, the track. They are more or less costly to construct and to keep in repair, and, in order to use them to best advantage, it is necessary to have a good elevation of track above the dumping-ground ; furthermore, the rails must be of heavy weight, and well-supported on heavy ties. Other disadvantages of the slag-pots are—1, that the slag cannot be removed continuously

Jan 1, 1906

By R. E. Collins, Paul B. Crawford

Mathematical equations have been derived to show the effect of the slippage phenomomenon (Klinkenberg effect) on unsteady-state gas flow through porous media. The assumption is made that the slippage may be represented by an equation of the type It is pointed out that most of the existing data on unsteady gas flow may be corrected for slippage by a simple change in definition of the dimen-sionless groups. INTRODUCTION Several solutions to the various problems associated with the unsteady-state flow of gas through porous media have been recently presented in the literature.','" The cited publications have resented solutions for flow under ideal conditjons. The principal assumptions involved include: (a) the density of the gas obeys the perfect gas law; (b) the viscosity of the gas is constant; and (c) the gas permeability is constant. Few, if any, actual gases under reservoir conditions are believed to conform with the above, but the ideal solutions do provide the basis for making improved estimates on the performance of gas reservoirs. The purpose of this paper is to show the performance characteristics when assumption (c) is corrected for the slippage phenomenon or the Klinkenberg effect. This is believed to be a step nearer to reality. MATHEMATICAL DEVELOPMENT Case 1. Gas Flow — Ideal Conditions The equations describing the flow of gas under ideal conditions have been clearly presented in the cited literature; however, for completeness of this work they are repeated here. The basic differential equation describing the flow of gas is Equation (6). It may be derived as follows: The continuity equation, the perfect gas law and Darcy's law are combined to give: Manuscript received in the Petroleum Branch office Aug. 3, 1963 or If — is constant, Equation (5) is rewritten to form the basic Equation (6). or for the linear case A dimensionless equation is obtained by dividing through by (pl)z and making the substitutions shown below: The resulting equation is A similar procedure for the radial case leads to the following equations: where and Equations (11), (12), and (13) are those used by Bruce, et al., and Jenkins and Aronofsky for their computational work.

Jan 1, 1953

Dimitri Konstantinovitch Tschernoff, was horn in Petrograd, Russia, on Nov. 1, 1839, and died in Yalta (Crimea) in the south of Russia, on Jan. 2, 1921. He obtained his early education in the Russian Gymnasium, corresponding to the American high school, and in the Technologic Institute. On graduation from this Institute in 1858, he was engaged as a professor of geometry and algebra and later became a librarian and superintendent of the museum in the same Institute. He also attended lectures in the mathematical physics section at the Univrrsity of Petrograd from 1859 to 1862. In 1866, Professor Tschernoff left the Technologic Institute and entered the employ of the Obouchoff steel plant, founded in 1863 for the manufacture of guns. Here he did his most important work on the heat treatment of steel, its crystallization and metallography. In 1880, he left the Obouchoff plant and went to the south of European Russia, where he discovered and developed some rock-salt mines. This enterprise brought him a rather large fortune. In 1884, he returned to Petrograd and during the next four years held several prominent positions in government departments. In 1899, he became professor of metallurgy in the Michael Artillery Academy, and retained that position until the time of the Russian Revolution. In 1902, Professor Tschernoff was elected an honorary member of the American Institute of Mining and Metallurgical Engineers. In September, 1917, Professor Tschernoff was sponding his vacation, as usual, in the city of Yalta (Crimea) in the south of Russia, with his wife and one of his daughters. The revolution progressed so rapidly that they were unable to return to Petrograd, and were compelled to stay in Yalta without provision for the winter season. Suffering from hunger. and lack of sufficient clothing, and deprived of his books, Tschernoff nevertheless continued his studies and gave a number of lectures on steel at the Polytechnic Institute. At the same time he worked hard on some. mathematical problems. His health broke down through long-continued under-nourishment. His works in the metallurgical field are well known to the students of metallurgy; good abstracts of his most important papers were published in Revue de Metallurgie (1915, pp. 829-882) in commemoration of his 75th birthday.

Jan 1, 1922

By Franklin J. Kay

Introduction The methods used in surface, mining vary throughout the world, depending on many variables such as: the types of over- burden materials, the depth of the overburden, the thickness of the seam, and other operational choices, both financial and functional. However, the stripping machines are typically draglines, stripping shovels, excavators, scrapers, loaders, and bulldozers. In all cases the economic feasibility of mining thin seams depends on the market needs, the market location, the equipment used, the mine management, the quality of the coal, and the labor market. Slight negative combinations of these parameters have closed many mines while positive combinations allow others to exist. The limited mobility or slow movement of large stripping shovels, draglines, and bucket wheel excavators make them more economically fitted to areas where large quantities of overburden are to be moved. This is necessary to keep the transfer and setup time between pits a negligibly small percent of the total operational time. Equipment such as the scrapers, loaders, backhoes, trucks, and bulldozers that are either very mobile or can be trailered is more versatile and can be used in the smaller area mines.* Mobile equipment is also more practical in areas with shallow overburden because of the constant movement required while removing overburden. In thin coal seams the equipment is usually paired such that the operational equipment can be listed as: (1) dragline-loader, (2) shovel-truck- loader, (3) scraper-loader. (4) loader-truck-loader, or (5) loader-loader. In these operations the overburden is removed with the first machine(s) of the pairing and the loader or loaders are used for coal production. Recent articles in Coal Age (Chironis, 1978) and Mining Engineering (Wiebmer, 1978) have discussed varying philosophies in mining similar seams of coal. One operator uses draglines for competitive mining while the other uses scrapers for the same purpose. Both cite strong cases sup- porting their choice of equipment as good sound economic decisions and their success supports their choices. The drag-line operation is adding new larger draglines to decrease the cost of mining, rather than to increase coal production. The scraper operation has also gone to more and larger scrapers for basically the same reasons. These operations and all

Jan 1, 1981

By W. S. Landis

WHEN dealing with a new reagent, one is concerned with three principal factors: available supply, cost, and results. The atmosphere contains an inexhaustible supply of oxygen mechanically mixed with nitrogen (omitting rare gases and minor impurities) in the proportions of one volume of oxygen to four volumes of nitrogen. (All figures are based on slide-rule precision and minor impurities are neglected.) Expressed in terms of weight, 1 ton of oxygen represents a volume of 22,500 cu. ft. and is contained in a volume of 112,000 cu. ft. of air. Water, also an inexhaustible supply, is a chemical compound containing 89 per cent. oxygen and, 11 per cent. hydrogen. Of the hundreds of schemes proposed for the enriching of air or separation of oxygen, nothing of value has yet appeared. From the standpoint of mechanical separation, liquefaction followed by rectification is the only process that has been developed to a really commercial stage. Theoretically, it should be a .simple matter to separate the mechanical mixture of nitrogen and oxygen; but fractionation can be performed only by converting to the liquid phase and this phase can be obtained only at lower than critical temperatures. The problem, therefore, is not so simple and the cost of the actual operation bears no relationship to the theoretical simplicity of the process. The largest single unit of the required apparatus so far placed in commercial use will handle only 60,000 cu. ft. of air per hour through a compressor which operates at a little over 250 lb. per sq. in. After this apparatus has operated continuously for 14 to 18 days it must be shut down for 6 to 8 hr. to be thawed out, have accumulated impurities removed and again cooled down for production. The cost of such a unit erected in batteries, with necessary spares for maintaining production, and including prime movers, hoisting and all auxiliary equipment, will be about $125,000. To produce one ton of oxygen per hour requires two operating machines of this size; and if the production is to be absolutely continuous a spare unit must be provided. To operate a plant of two units requires 10 or 11 men, excluding boiler attendants, if steam is generated in the plant.

Jan 11, 1924

Dimitri Konstantinovitch Tschernoff, was horn in Petrograd, Russia, on Nov. 1, 1839, and died in Yalta (Crimea) in the south of Russia, on Jan. 2, 1921. He obtained his early education in the Russian Gymnasium, corresponding to the American high school, and in the Technologic Institute. On graduation from this Institute in 1858, he was engaged as a professor of geometry and algebra and later became a librarian and superintendent of the museum in the same Institute. He also attended lectures in the mathematical physics section at the Univrrsity of Petrograd from 1859 to 1862. In 1866, Professor Tschernoff left the Technologic Institute and entered the employ of the Obouchoff steel plant, founded in 1863 for the manufacture of guns. Here he did his most important work on the heat treatment of steel, its crystallization and metallography. In 1880, he left the Obouchoff plant and went to the south of European Russia, where he discovered and developed some rock-salt mines. This enterprise brought him a rather large fortune. In 1884, he returned to Petrograd and during the next four years held several prominent positions in government departments. In 1899, he became professor of metallurgy in the Michael Artillery Academy, and retained that position until the time of the Russian Revolution. In 1902, Professor Tschernoff was elected an honorary member of the American Institute of Mining and Metallurgical Engineers. In September, 1917, Professor Tschernoff was sponding his vacation, as usual, in the city of Yalta (Crimea) in the south of Russia, with his wife and one of his daughters. The revolution progressed so rapidly that they were unable to return to Petrograd, and were compelled to stay in Yalta without provision for the winter season. Suffering from hunger. and lack of sufficient clothing, and deprived of his books, Tschernoff nevertheless continued his studies and gave a number of lectures on steel at the Polytechnic Institute. At the same time he worked hard on some. mathematical problems. His health broke down through long-continued under-nourishment. His works in the metallurgical field are well known to the students of metallurgy; good abstracts of his most important papers were published in Revue de Metallurgie (1915, pp. 829-882) in commemoration of his 75th birthday.

Jan 1, 1922