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By J. Walter Snavely

PRESENT-DAY processing in many industries, calcining, sintering, briquetting, beneficiation and nodulizing, increasingly calls for the handling of large volumes of hot bulk materials. Various types of conveyors have been employed. This discussion will cover the factors governing their selection. For temperature ranges up to 400°F, or approximately 200 °C, a wide range of conveyors is available. Special constructions of rubber conveyor belts, steel conveyor belts, vibrating and shaker conveyors, apron conveyors, and drag chain conveyors, all are used successfully. As temperatures go well above 400 2F, however, choice of conveyors is narrowly limited. This paper will consider the problem of handling bulk materials only where the temperatures exceed 400°F. The arbitrary selection of 400 °F as a dividing point undoubtedly can be challenged, as special conveyor belting constructions are available which are suitable for temperatures in excess of 400°F. However, when the relatively short life of such belts and the cost of their replacement, with the attendant down time, are balanced against the reliability and long service life of the properly designed steel constructed units to be discussed, there is little question in any operator's mind that the special belts are more expensive to use. Because the conveyors under study are for the handling of bulk materials, inevitably including a high proportion of fines, obviously wire mesh belts cannot be included for consideration. Even though this type of conveyor is widely used at high temperatures, i.e., for carrying glassware through a lehr, it is unsuited for the conveying of bulk materials, and therefore will be excluded from further discussion in this paper. Preliminary to the study of the conveyor itself is the determination as to whether the material is to be cooled while it is being handled, or whether the processing requires retention of all heat and the maintenance of a given temperature range. In the majority of cases cooling is incidental to or part of the handling process, when the handling, for example, follows completion of sintering, roasting, calcining, refining, or some other process. To meet such operating conditions successfully, the conveying medium used must have: 1—a construction capable of withstanding maximum initial temperatures of the material being handled. 2—a construction providing efficient heat transfer for cooling. 3—a construction providing dependable operation and long life with minimum service requirements, and 4—a construction providing controlled and efficient conveying. Under the usual conditions of cooling during the handling, the construction selected to withstand the initial maximum temperatures does not necessarily involve using alloys, as excellent results can be achieved with normal carbon steels and cast irons, when they are properly applied and proportioned. The earliest and simplest type of conveyor for handling very hot materials is the cast steel drag chain conveyor, still widely used for handling hot cement clinker, as illustrated by Figs. I and 2. Because of the rugged and generous proportions of the chain link design, low carbon steels are entirely suitable for the links. The pins, however, must be alloy steel. The simple, rugged construction of this type of conveyor makes it readily capable of withstanding high initial temperatures, even though the chain is operating buried in the material. The drag-chain type of conveyor has advantages and limitations. Although the efficiency of the heat transfer is relatively poor, the life of the conveyor is reasonably long, and because of its crude simplicity it does not require much servicing. However, as a conveyor, it is limited in capacity, and largely limited to horizontal runs. Furthermore, because of the crude design, heavy weight, and the chain operating at the temperature of the material, greatly reducing permissible operating chain pulls, this type of conveyor is limited to relatively short centers. Another type of conveyor that has been used for very hot materials is the cast pan conveyor. Because of its very generous proportions the cast pan, which is made of either cast iron or malleable iron, can withstand initial maximum temperatures. It also provides efficient heat transfer for cooling. Further, it is on efficient conveyor construction, which can be used for inclines. Because the chain employs rolling friction instead of sliding friction, and is not in the maximum temperature zone, much longer centers are possible. It is this type of conveyor that is frequently used in the casting of various metal pigs, pig iron, and aluminum; it is obvious, therefore, that very high initial temperatures are being handled. With this kind of conveyor the return run is frequently sprayed with water to accelerate heat transfer. The build-up of residual heat in the very heavy cast pans is thus overcome. The outboard roller steel pan conveyor is an improved pan conveyor' which provides high rates of heat transfer and substitutes formed steel pans for the heavy cast pans. It is a very efficient conveying medium. The details of this particular construction are clearly shown in Fig. 3. An early application of this type of conveyor is shown in Fig. 4. In this case the conveyor units are handling roasted phosphate rock at average temperatures of 1000" to 1500°F, and frequent maximum temperatures as high as 1900°F. Several widths are used. The capacity of the unit at a speed of 50 fpm is approximately 30 tph per inch of width at peak loadings, average capacity being about 1/3 of peak loading. The assembled conveyor is shown in Fig. 5, with views of both the top and the underside to show all the construction details. In particular, the following general design principles were carried out in this construction:

Jan 1, 1954

By d&apos, John C. Entremont

Pure iron was inductively melted in small refractory crucibles and optical pyrometer and immersion thermocouple readings were simultmzeously taken. The resulting emissivities of the liquid iron surface obtained were found to be greatly affected by both the gaseous atmosphere and geometrical changes in the physical setup. Quantitative values for these effects are indicated. FOR many applications in both the laboratory and plant, optical pyrometry is still the best means of measuring temperatures in the incandescent range. A prerequisite in evaluating the correct temperature is a good value of the emissivity of the surface. To obtain the emissivity from the tabulated values of the literature can be very confusing and often far from correct. There are many reasons for these difficulties, and it is not within the scope of this paper either to enumerate or to discuss them all. Its purpose is to show quantitatively how several factors affect the apparent emissivities obtained from experimental measurements on liquid iron surfaces. The black body is the reference state for the quantitative values of emissivities and is defined1 as a body which absorbs all radiation incident on it, reflecting none; such a surface emits more radiation per unit area per unit time than any surface which reflects any radiation, and is given a value of unit emissivity. All bodies having reflective power thus have emissivities less than unity and are considered nonblack or grey bodies. The ratio of the radiant energy emitted by the flat, nonblack surface to that of a perfectly black surface of equal area and temperature is the emissivity of the surface. The above definitions are applied to flat, polished, opaque surfaces, very seldom encountered in actual measurements, and for this reason many authors have suggested that the word "emittance" be used for real bodies rather than emissivity. The emittance has reference to the material and its configuration rather than to its properties in the idealized state. Recent observations of molten iron in a small refractory crucible indicate that not only the configuration of its surface but the geometrical arrangement of its surrounding and the nature of the surrounding atmosphere have a pronounced effect on the emittance. Neglect of changes in such conditions may lead to errors as large as 40°C at 1600°C. Thus it is suggested that the term "apparent emissivity" be used and that it be recognized that its value pertains to a particular experimental arrangement only. As a result of not recognizing these differences in emissivities, which are obtainable from changes in the physical setup of an observation, many investigators have incorrectly quoted their values as those of the emissivities of particular materials rather than as an apparent emissivity for their particular arrangements. As a consequence, values of the emissivity of liquid iron ranging from 0.3 up to 0.55 are found in the literature. In an effort to establish an accurate optical temperature scale for liquid iron solutions in which de-oxidation studies were to be carried out, it was observed that the temperature relationship, obtained by simultaneously taking immersion thermocouple

Jan 1, 1963

By R. Lagneborg

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

Jan 1, 1968

By Margaret Dienes, Karl L. Fetters

IT is recognized that ingot structure is important in determining the quality of finished steel. Such elements of ingot structure as the size, shape and distribution of primary crystals; the size, shape and distribution of shrinkage cavities; the degree and kind of segregation (both macro and micro); the distribution of nonmetallic impurities and gas cavities are each the result of solidification phenomena. These structural features vary with variations in ingot practice: Their control requires a knowledge of their correlation with the variables of ingot practice. The structures of full-sized commercial steel ingots have been studied extensively by the Steel Ingots Committee of the Iron and Steel Institute.1 This work has contributed much to our knowledge of ingot structure and the factors that control it. These investigations of necessity have been limited in scope because of their costliness and the great amount of time required. Studies of the structure of small steel ingots have not been very satisfactory because of the rapid rate of freezing of the ingots. Their structures are thus difficult to resolve and to interpret. Medium sizes of steel ingots in the ranges of 150 to 500 lb. do offer opportunity for study, but their cost also becomes greater and their use less expeditious. Experimental models for the study of steel-ingot structure have been made of nonferrous metals. Gathmann2 used lead-tin alloys and reported that they were satisfactory for determination of the location of the major shrinkage cavities and the "planes of weakness" resulting from the pattern of crystallization. Certain features of mold design have been illustrated by these results. Bezdenezhnihk3 has used copper and aluminum ingots similarly and has shown the effect of mold-wall thickness on the depth of columnar grains. These studies of nonferrous models have been useful, but their results have been limited because the analogy with steel ingots obviously is not a close one. Model wax ingots have also been useful in pointing out important features of mold design. Gathmann4 watched the solidification of wax ingots, through a glass-walled mold, and has reported the effects of mold type on the location of the shrinkage cavities. Segregation was simulated by using a mixture of paraffin and stearine and adding a red dye that on freezing segregated preferentially to the stearine. Brearley5 also used wax models to determine .the effects of some of the principal features of mold design. Carlsson and Hultgren6 used stearic acid to show that the columnar crystals of ingots tend to slope upward progressively from the mold wall toward the center of the ingot. As with the nonferrous ingots, the wax ingots have

Jan 1, 1943

By J. W. Leonard

One of the more obvious phenomena which relate to coke formation is that soft coals of low volatile matter content tend to yield hard or high strength cokes while hard coals of high volatile matter content tend to yield soft or low strength cokes. This observation led researchers of the Coal Research Bureau of West Virginia Univ. to study the possibility of using Hardgrove grindability as a supplemental rank indicator for coking properties. Grindability has been used for many years as a means to measure the resistance of coal to comminution but it has rarely if ever been considered for evaluating coals for carbonization. The coal proper- ties which are measured by grindability are complex, but recent work with the difficult-to-correlate high volatile coals has demonstrated that a 93% correlation exists between grindability and the total petrographic rnicrinites, exinites, and resinites. This work demonstrated that inherent ash had no apparent effect on the grindability of high volatile coals, suggesting that the coal substance is apparently harder than the associated ash. These observations, together with the patented Burstlein process," indicate that the distribution of hard and soft components in the individual high volatile coals and blends of coals may be quantitatively interrelated to coke stability through selected ranges of coal volatile matter. The objective of this progress report is 1) to demonstrate the statistical relationships which exist between coal grindability and the numerous coal petrographic entities and 2) to present the results of initial studies concerning the correlation of the coke physical strength index of stability with coal volatile matter and grindability.

Jan 3, 1964

By Brian F. Osborne

A continuous on-line particle-size analysis system for solid/liquid suspensions is described. The basic sensor utilizes a centrifugal principle to separate particles according to size, the resultant separation being measured by means of beta-ray attenuation. Results obtained when analyzing a variety of materials at sizes from 65 mesh (210 µ) to 20 w are discussed in detail. Accuracies better than 2% are demonstrated. The effects of particle specific gravity, and mixtures of materials of diverse specific gravities, are discussed from both a practical and a theoretical viewpoint. It is demonstrated that particle specific gravity has a minimal effect on the size reading obtained. This renders the instrument suitable for handling materials where the ratio of light to heavy component may change. The design of the first commercial installation of this instrument is described in detail. This installation will be capable of analyzing three streams in sequence, measurement at three particle sizes being effected on each stream.

Jan 1, 1975

By C. A. Wright

Since the adoption by the U. S. Bureau of Standards several years ago of specifications for standard 100- and 200-mesh sieves, frequent requests have been received that this Bureau test and certify sieves of other sizes than these. With a view to the adoption of a series of standard testing sieves which might be of use to all industries making fineness tests, this Bureau for two years has been studying the question of such a standard screen scale. Various scales that have been proposed were considered, and information was sought of representative firms in the various industries interested as to their requirements. Manufacturers of sieves have also been consulted as to the desirability of different screen scales and the practicability of their manufacture. As a result of this study of the question, a conference was called at the Bureau of Standards, Apr. 20, 1916, of representatives of various committees of the American Society for Testing Materials, American Society of Civil Engineers, American Institute of Mining Engineers, American Foundrymen's Association, Mining and Metallurgical Society of America, American Water Works Association, American Institute of Metals and the American Spice Trade Association; also representatives of the Committee of Revision of the U. S. Pharmacopæia, the U. S. Geological Survey, the U. S. Bureau of Mines, the U. S. Office of Public Roads and Rural Engineering, the U. S. Office of Grain Standardization and the U. S. Bureau of Standards; also representatives of a number of private firms engaged in industries in which sieves are used, such as the glass, the drug milling, the abrasive, the asphalt, the mining, the spice, the chemical, and the graphite industries; also representatives of the firms in this country manufacturing wire cloth and sieves. This Conference, after considering the various screen scales either proposed or now in use, adopted as a Standard Screen Scale that given in Table 1, and recommends that it be adopted generally by scientific,

Jan 1, 1918

By S. C. Geol, C. H. Page

INTRODUCTION Mining at Mindola Mine, Rokana Division of Nchanga Consolidated Copper Mines Limited is the deepest on the Zambian Copperbelt. Mining extends to 1150 metre depth so far and the present plans extend to 1500 metres, although reserves exist below this level. Mindola Mine is the major producer of copper/cobalt ore at Rokana Division and produces approximately 200,000 tonnes of copper/cobalt ore per month. A standard open stoping method is the only method used for mining with minor variations in positioning drilling drives and other development, figure 1. The standard main haulage interval is 75m but in flat dipping areas the full stope height is split into two or three panels. In 1970 severe mining problems were experienced when mining deeper than 850111 below surface. The main problems included: - Heavy support requirements in drilling drives near stope face. - Premature closure of blast holes necessitating pre-charging of the holes with explosives immediately after drilling and well before the day of blasting. - Severe bumping and spitting due to rock movements on drive surfaces and remotely within the rock mass under high stress. - Low mining efficiency due to dilution from the waste hangingwall. - These stress related factors also caused some premature detonations of precharged but unprimed blast holes which became a serious safety hazard. A number of alternatives have been considered to overcome these problems. A search for leas sensitive explosives to avoid the premature detonation problem has been partially successful, however, the need for a method of reducing stress levels at the mining face is still considered essential as the mine goes deeper. This paper describes experiments with Regional Support Pillars as a method of reducing stresses at the mining face.

Jan 1, 1981

By W. J. Heck

The need for a better understanding of the effect of fluid pressure on the strength of intact and jointed rock has long been recognized. The behavior of pore fluid pressure was first pointed out by Terzaghi 1 who suggested the application of the effective stress concept to rock and concrete. While the effective stress concept has been used for some time in the design of mass concrete dams, it only recently has been applied to rock. Robinson 2 and Handin et al.3 evaluated the effects of pore pressure on a variety of sedimentary rocks and demonstrated the validity of the concept. Work using pore fluids other than water has been done by Boozer, et al.4 who considered strain rate and temperature as additional variables. According to the effective stress theory, the effective stress, [a], is the difference between the total stress, [a], and the pore pressure, u, and is the controlling factor influencing frictional strength of rock, other parameters remaining constant. Assuming the Mohr-Coulomb failure criteria applies, the shear strength, T, is given by the equation [r=d+ (a-u)tan ¢](1) where [~F], the angle of internal friction, and c, the cohesion intercept of "no load" shear strength, are the effective stress parameters.* Robinson,2 Handin,3 and others have demonstrated that moderately porous sand-

Jan 1, 1972

By Kerstin Malmqvist

A prospecting project for deep-seated sulphide ore bodies will be expensive and means a considerable economic risk. The high costs depend on the demand for extensive drilling. It is therefore important to find effective methods to estimate the outcome of different prospecting strategies. The results from a preliminary study of the possibility of using mathematical methods for this purpose are presented. We have found that mathematical methods, especially simulation technique, might be an important tool in such exploration work. A mathematical model of an ore field and of a drilling procedure has been constructed. A set of parameters describes the geometry, the size distribution and the intensity of ore bodies. Another set describes the geometry and the intensity of drill holes. Some preliminary results are given of Monte-Carlo simulations and probability calculations.

Jan 1, 1977

By G. Rowan, M. W. Clegg

The basic equations for the flow of gases, compressible liquids and incompressible liquids are derived and the full implications of linearising then discussed. Approximate solutions of these equations are obtained by introducing the concept of a disturbed zone around the well, which expands outwards into the reservoir as fluid is produced. Many important and well-established results are deduced in terms of simple functions rather than the infinite series, or numerical solutions normally associated with these problems. The wide range of application of this approach to transient radial flow problems is illustrated with many examples including: gravity drainage of depletion-type reservoirs; multiple well systems; well interference. INTRODUCTION A large number of problems concerning the flow of fluids in oil reservoirs have been solved by both analytical and numerical methods but in almost all cases these solutions have some disadvantages — the analytical ones usually involve rather complex functions (infinite series or infinite integrals) which are difficult to handle, and the numerical ones tend to mask the physical principles underlying the problem. It would seem appropriate, therefore, to try to find approximate analytical solutions to these problems without introducing any further appreciable errors, so that the physical nature of the problem is retained and solutions of comparable accuracy are obtained. One class of problems will be considered in this paper, namely, transient radial flow problems, and it will be shown that approximate analytical solutions of the equations governing radial flow can be obtained, and that these solutions yield comparable results to those calculated numerically and those obtained from "exact" solutions. It will also be shown that the restrictions imposed upon the dependent variable (pressure) are just those which have to be assumed in deriving the usual diffusion-type equations. The method was originally suggested by Guseinov,1 who (a) postulated a disturbed zone in the reservoir, the radius of which increases with time, and (b) replaced the time derivatives in the basic differential equation by its mean value in the disturbed zone. In this paper it is proposed to review the basic theory leading to the equations governing the flow of homogeneous fluids in porous media and to consider the full implications of the approximation introduced in linearising them. The Guseinov-type approximation will then be applied to these equations and the solutions for the flow of compressible and incompressible fluids, and gases in bounded and infinite reservoirs obtained. As an example of the application of this type of approximation, solutions to such problems as production from stratified reservoirs, radial permeability discontinuities; multiple-well systems, and well interference will be given. These solutions agree with many other published results, and in some cases they may be extended to more complex problems without the computational difficulties experienced by other authors. THEORY In order to review the basic theory from a fairly general standpoint it is proposed to limit the idealising assumptions to the minimum necessary for analytical convenience. The assumptions to be made are the following: 1. That the flow is irrotational. 2. That the formation is of constant thickness. 3. Darcy's Law is valid. 4. The formation is saturated with a single homogeneous fluid.

By AIME AIME

THE following compilation of State bureaus and officials that deal with mineral resources is compiled in part from a new "Check List of State Agencies and Officials Concerned with the Management of Natural Re- sources," compiled for the National Resources Committee, Washington, D. C., by Clifford J. Hynning. Alabama-Geological Survey of Alabama, University. Walter B. Jones, State Geologist. Chief Mine Inspector: W. B. Hill- house, 614 Lincoln Life Bldg., Birmingham.

Jan 1, 1939

By F. W. Sperr

The byproduct coke oven is the most important artificial source of fuels for metals melting. Its products are solid, liquid, and gaseous in form. The amount of coke and primary byproducts obtained per ton of coal varies with the nature of the coal. The following represents the results obtained in many plants: Metallurgical coke (over 3/4 in.).............................. 69 per cent. of coal Domestic coke (1/2 to 3/4 in.)................................ 2 per cent. of coal Breeze (under 1/2 in.)...................................... 4 per cent. of coal Surplus gas, cubic feet per net ton........................... 6600 Gas for heating ovens, cubic feet per net tor i................. 4400 Tar, gallons per net ton.................................... 9 Ammonium sulfate, pounds per net ton....................... 25 Benzols, gallolls per net ton................................. 4 All of these products, except ammonium sulfate, have important fuel value. Part or all of the metallurgical coke may be crushed or screened to furnish additional domestic coke. If producer gas is used, there will be a surplus of 11,000 cu. ft. of coke-oven gas per net ton of coal. The use of coke in the metallurgical industries has been retarded by the mental attitude of writers who disregard the dependence of coke quality on the conditions of its manufacture. Terms like "byproduct coke," ('beehive coke," "48-hour coke," and "72-hour coke" are only generally descriptive and tell nothing of the coke quality. For example, one writeri stated that in brass-foundry practice, Connellsville coke is considered rnuch superior to byproduct coke on account of the high sulfur content of the latter. Another2 says, "At equal prices for hard Connellsville coke and for byproduct coke at the foundry door, the hard coke is unquestionably cheaper. It will melt more metal per ton than the byproduct coke and requires less labor, as the byproduct coke is less dense and burns faster, thus requiring more frequent firing." A little study of the conditions under which coke is manufactured will show the error in making general statements like these. The percentage of sulfur in coke depends largely on that in the original coal, and byproduct coke from a

Jan 1, 1921

By Allan D. Taylor, Robert S. Shoemaker

Adopting as a principle the phrase "the mill of yesterday should not be built with the high cost money of today," the authors have designed a hypothetical concentrator which could be built for a typical southwestern United States (or other similar area) copper ore. Many of the design features could also be used for other ores in other climates. Functional design, large equipment, and outdoor type of construction have been combined in a concentrator (which includes all ancilliary facilities such as truck and maintenance shops, offices, warehouse, nominal tailings disposal, and water supply) which could be built today for substantially less than the cost of comparable but conventional plants.

Jan 1, 1973

By C. Perez-Rosales

A simplified method for evaluating specific surface of porous media is described. The theory takes as its point of departure a previous statistical method. Due to its simplicity, it is considered that the proposed method has certain advantages over methods currently used. By making some simplifications, the procedure for estimating specific surface is reduced to superposing, on an enlarged reproduction of a section of the sample to be analyzed, an evenly spaced grid and counting the number of intersections of the grid lines with the perimeter of pores. An indirect test of the theory is presented and the advantages of the method are discussed. INTRODUCTION The specific surface of a porous medium, defined as the surface area of the pores per unit bulk volume, is an important parameter with regard to flow of fluids through porous materials. In particular, it has long been recognized that specific surface is closely related to permeability. Since the internal surface of any porous material is extremely complex, the measurement of specific surface can only be accomplished by indirect means. It is considered that the best method' in current use for determining specific surface is the statistical method of Chalkley, Cornfield and Parka who originally applied it for estimating volume-surface ratios of morphologic components, such as cells or nuclei. This method will be outlined later. A method which has been used extensively in determining specific surface is based on the adsorption of a vapor by the internal surface of porous media. However, this method does not yield the surface pertinent to fluid flow, since it includes the tiny molecular interstices which do not influence the permeability of the porous material.' This method has been employed by Brooks and Purcell measure internal surface area of sedimentary rocks. The Kozeny equation, which relates the specific surface to the permeability of a porous medium, has found wide use in determination of specific surface. However, the KOzeny equation is not strictly correct. Large discrepancies have been found between theory and experiments.' Consequently. the specific surface estimated by this method is subject to serious uncertainties. Finally, there are other methods for specific surface measurements which are based upon a variety of physical and chemical properties: the heat conduction by a gas, ionic adsorption phenomena and direct chemical reactions of the surface with other substances. This paper describes a simplified statistical method for determining specific surface of porous materials. It is considered that, due to its simplicity, it has certain advantages over the methods presently used. For its validity, it is required that the porous structure of the material under study be of a spatially random nature. This is not a serious limitation since the naturally occurring porous media have this characteristic. THEORY The method proposed in this paper takes as its point of departure the interesting result obtained by Chalkley et al The method shows that if a line of length r is dropped repeatedly at random over a section of a porous medium, and counts are made of the number of times the two end points fall within pore areas (denoted by h for "hits") and the number of times the line intersects the perimeter of pores (denoted by c for "cuts"), then in a very large number of throws where S is the internal surface of the sample (surface of pores) and V, the volume of the pores (Fig. 1). Since the specific surface S, and the porosity 4 are given, respectively, by S. = Sl V, and 4 = V,l V,, where V, is the total volume of the sample, it follows from Eq. 1

By J. Lyndon Rosenblad

The strength of a jointed-rock mass is not well-understood. It is believed, however, that the behavior of a rock mass is governed by both the intact rock properties and the properties of the discontinuities. Rock research in the past has been concentrated on the determination of intact rock properties. Several studies are presently underway which should provide more insight into the properties of the discontinuities. Few research programs, however, have been undertaken with the intent of studying the composite rock mass behavior where either the intact rock strength or the properties of the discontinuities may control failure. There are three approaches available for studying the behavior of a rock mass, namely, field studies, mathematical models (finite element), and geomechanical models. A geomechanical model has been developed in this study where the strength and failure modes of a model rock mass are studied as a function of intact block geometry, joint orientation, joint properties, and confining pressure. The objective of this study is to gain some insight into the parameters that govern the behavior of a rock mass, which parameters are most important, and when these parameters control. This chapter describes only one phase of the study, the development of equipment for use with the rock-blocks model. The models being tested are approximately 22 x 22 x 6-in. The size varies slightly depending upon the joint orientation used. The equipment developed includes model material molds, reaction frames, loading apparatus, measuring and recording instrumentation, and other accessory equipment pertinent to the operation of a successful study. The usual problems in equipment development, such as uniformity of load application, loading capabilities, and reaction capacities are all

Jan 1, 1970

By R. B. Rosene, G. L. Foster, A. R. Hendrickson

he properties of some of the common fracturing oils, such as sand-falling rate, fluid loss and viscasity, are a function of the three major constituents of the oil. These are: asphaltic material, parafin waxes and a base oil. The base oil can be either high or low viscosity. Asphaltic material increases viscosity by thickening the oil, decreasing the rate of fall of sand through the oil. at temperatures up to 200" F. When large arnorrnts of parafin wax are present, much of the wax i.s not dissolved, but is present in the form of rnicroscopic crystals. 7'his, of course is limited to temperatures below the melting points of waxe.s. As a result, parafin waxes clo not function primarily as thickener.7, but rother as bullting materials. The functiori of wax, without asphaltic material, in a low viscosity base oil is uniquely unlike that of wax with asphalt coexistent in the oil. The resulting difierence in wax crystal size governs the sand-falling rate to a large extent. An ideal type of fracturing oil is one containing neither asphalt nor waxes. In such cases, the viscosity and resulting low sand-falling rate are apparently due to soluble resin- ous hydrocarbons, which are compatible with formation oils. INTRODUCTION Since the introduction of hydraulic fracturing as a method of stimulating production from oil and gas wells, a variety of fluids have been employed to open the fractures and carry the propping agent. Such fluids include gels, emulsions, and oils. In the latter category, the use of refined oils has increased tremendously, and it is probably safe to assume that such oils represent more than one-half of the total fluid used in fracturing. The general acceptance of refined oils for fracturing can be accounted for on the basis of their relatively low cost and general applicability. To minimize transportation costs, such refined oils are generally obtained within the local areas of operation. As a result there are several kinds of oil used in different areas, with a wide variation in the basic composition. These types may vary from a fair grade of lubricating stock to a highly viscous cut-back asphalt. or road oil. Originally, little attention was paid to the composition of the oils used for fracturing, and any oil which would carry sand was considered satisfactory. Recently, however, service companies and well operators have become more concerned with the type of oils used for fracturing. With this in mind, the present work was undertaken to evaluate and compare many widely used fracturing oils to determine which constituents were most desirable for fracturing purposes. Some of the important properties of fracturing fluids are sand-falling rate, viscosity, and fluid loss. Other properties, that are actually of no less importance, include flash point, pour point, emulsifying tendencies with formation brines, and compatability with the formation oils. This discussion has been limited, however, to the first mentioned properties in order to give some idea of the general composition of the refined oils, how they function, and why. PROPERTIES OF FRACTURING OILS The properties of fracturing oils are a function of the three major constituents of the oil. These may be designated as: (1) asphaltic material, (2) paraffin waxes and (3) a base oil, which may be of either high or low viscosity. The asphaltic material clas-

Jan 1, 1956

By Victor Phillips

Cyclone thickeners have emerged from the development stage and now can be accepted as useful tools for the recovery of fine coal from a preparation plant circulating water. As primary thickeners in a closed water circuit operation, their advantages over conventional thickening methods are twofold-the lower initial investment and reduced area requirements.

Jan 8, 1951

By F. A. Emmerton

I have used for about two years, in the laboratory of the Joliet Steel Company, a rapid method for the determination of phosphorus in iron, steel, and ores, which possesses one or two features sufficiently novel to warrant description. In general, it is the method described by Mr. Benjamin B. Wright (Transactions, vol. x., p. 197), involving the precipitation of the phosphorus by means of molybdate solution, and its estimation in the yellow precipitate by reduction of the molybdic acid, and titration of the resulting oxide with a standardized permanganate solution, according to the principles laid down by Werncke (Fres, Zeit., vol. xiv., p. 1). In the use of this method, I had difficulty at first in obtaining a yellow precipitate of reasonably uniform composition. It is a well-known fact that, to secure this result, the conditions of precipitation must not vary. The principal condition is temperature; and acidity, concentration, proportion of nitrates and chlorides, and time, are important elements. I am aware that uniformity in these conditions has been obtained to a reasonable extent by many chemists,. so that they are enabled to use with success, methods based on the

Jan 1, 1887

By R. Hogg, D. W. Fuerstenau

Based on a simplified model for the motion of particulate materials in horizontal, rotating cylinders, approximate expressions have been derived relating the power consumption of a tumbling mill to its dimensions and speed of rotation and to the amount and nature of the charge. The basic assumptions underlying the model are that there is no slip between the charge and the mill shell, that the free surface of the charge remains essentially planar during rotation, and that there is no transfer of momentum from the material flowing down the free surface back to the mill shell. The relationships formulated from this model have been shown to be in excellent agreement with experimental results taken from the literature. While the requirements of the model are most clearly met at low speeds of rotation, the results appear to be valid even for speeds up to 70-80% of the critical speed. Poorer agreement between theory and experiment is found when the charge consists of relatively large particles (balls) and when the filling of the mill exceeds 50% of the available volume. Qualitative explanations of these deviations have been offered.

Jan 1, 1973