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R. H. SWEETSER, Columbus, Ohio.-My experience with oxygen in the blast is limited to the use of one tank of oxygen in melting out a chilled anthracite furnace. The oxygen was introduced through the peephole of the tuyeres and opened them in a very short time. We could see that an intense heat was generated just as soon as the oxygen struck the fuel. I agree with the committee in respect to many. of the things that will probably happen in the iron blast furnace, particularly as to the speeding up of the operation. There will undoubtedly be changes in the shape of the blast furnace, and if I were designing one today I should hesitate about the form to give it. Mr. Kirby suggested that the proper shape might be rectangular. Some of the men of the American Rolling Mill Co. have reached the same conclusion, as a result of Royster and Joseph finding that the combustion zone in the front of the tuyeres extended into the furnace less than 40 in. If this is correct, we might build the furnace with an elongated rectangu-ular hearth having the shorter dimension a little over 80 in. and secure. a very intense temperature in the hearth. The committee's report said, "With more oxygen available in the blast, the smelting ability of the furnace will be increased beyond the' speed of the preparing zone in the shaft." This can be controlled by providing ample facilities for getting stock into the furnace, and this will be one of the biggest changes in blast-furnace construction. The question has been raised as to finding suitable refractories to withstand the increase of hearth temperature. If the furnace can be kept full, the descending column of cold material will probably take care of the increased heat from more rapid combustion of the coke. At the Cleveland meeting, in 1912, the iron blast-furnace men listened with great interest to a paper on copper slags; from Mr. Kirby's paper, it looks as though they might again have to go to the copper men, for many of the problems of the iron blast furnace of the. future that uses oxygen may be worked out on lines of the copper blast furnace.

Jan 11, 1924

By Gordon W. Hodgson, Edward Tipman

INT'RODUCTION An appreciable number of the oil fields in Western Canada are accumulations of heavy black oils in more or less unconsolidated sandstones. When the crude oils are produced by conventional means, they are frequently contaminated with both sand and oilfield water. The water is usually present as emulsified water, and the sand and other solid materials are suspended in the emulsions. The presence of the solid material in the crude oils is troublesome and, in general, little is known about the behavior of suspended solid particles in emulsions. The Stokes equation describes the behavior of suspended particles in homogeneous fluids in terms of particle size, density differential, and fluid viscosity. In the case of an emulsion, particle size and density differential introduce no difficulties, but considerable doubt centers around the viscosity term. It has been reported1 that the viscosity of an emulsion is related to the viscosity of the continuous phase by an expression of the type: n = a, (1 + a C) where n is the viscosity of the emulsion, n,, is the viscosity of the continuous phase, a is a constant, C' is the volume concentration of the disperse phase. The value of 17, the coefficient of the concentration term, has been determined for various systems, and has been found to vary from a value of 1 to 4.75. The value of 2.5 has been found to be applicable to a large number of systems, and this is the value that is widely used in the equation which then becomes the Einstein equation for the viscosity of emuls~ons. It is of considerable significance that neither the particle size nor the viscosity of the disperse phase enters the expression; the expression for the viscosity of the enlulsion is based solely upon the viscosity of the continuous phase and the concentration of the disperse phase. For crude oil emulsions the Simha equation and the data presented by Fukushima and lchimurai show a non-linear dependence of the viscosity ratio on the water concentration. While it is undoubtedly reasonable to use these data for predicting the viscosity of a specific emulsion, and while it is equally reasonable to expect the calculated viscosity to predict the settling rate of a solid spherical particle in the emulsion by means of Stokes equation, there seems to be no direct evidence that this calculation is indeed sound for describing the settling rates of solid particles in emulsions of water in crude oils. PROCEDURE A direct approach to the problem was thus indicated. Laboratory equipment was designed and built for the direct determination of the rate-of-fall characteristics of solid particles in emulsions of water in oil. Although the apparatus incorporated the basic design of conventional falling-ball viscometers, the study was concerned directly with the rate-of-fall characteristics of particles in emulsions, rather than with the viscosity of the emulsions as such. The crude oil used in this study was a very heavy black crude oil—the McMurray oil obtained from oil-soaked sands outcropping on the Athabasca River in northeastern Alberta. It was produced from the sands by strip mining followed by hot-water separation of the oil in the separation plant of the Alberta Government at Bitumount'. The primary plant product was a wet crude oil containing about 5 per cent solids and 35 per cent water. The final plant product was only slightly different from the native oil, having lost only about 4 per cent of its bulk as light ends during dehydration distillations. In the present investigation two kerosene dilutions of the McMurray oil were used in addition to the dry plant product. The McMurray oil contained 1.92 per cent solids. Analysis of the solids by X-ray diffraction showed the presence of kaolinite, pyrite, and illite as major constituents. with lesser amounts of quartz. Particle size of the pyrite and quartz was less than 10

Jan 1, 1957

By Emmanuel J. Voulgaris

The ?Milos Conferences? is an activity of the non-profit organization ?Milos Conference Center - George Eliopoulos?, located on the island of Milos, Greece. The objective of the ?Milos Conferences? is to create the conditions for interaction among different disciplines of academia and industry, and dissemination of the cutting edge between scientific and technological development. The young scientists are our special aim. The governing body of the ?Milos Conferences? is the ?Milos Conferences Council?. The president of the Council is Mrs. Kitty Kyriacopoulos - founder of the ?Milos Conference Center - George Eliopoulos?, and the members are from academia and industry. The planning and the organization of all conferences are carried out by the ?Heliotopos Professional Congress Organizers? in Athens. The venue is always the ?Milos Conference Center - George Eliopoulos? on the island of Milos. The ?Milos Conferences? comprise of different conference series, each devoted to a general subject. This book covers the proceedings of the ?International Conference on Sustainable Development Indicators in the Mineral Industries?, (SDIMI), a conference of the series under the general title ?Restoring the Natural Balance?.

Jan 1, 2003

By Jens P. Nielsen, W. H. Justice

This paper describes an improved acidizing technique which has been applied in acidizing gas wells in the La Gloria Field. Wells acidized in this manner exhibited a much greater increase in deliverahility than wells acidized in the conventional manner. The acid is injected into the well in small slugs separated by a small volume of high pressure gas. The acid and gas are displaced from the tuhing by high pressure gas to reduce the hydrostatic head on the well when the acid is recovered from the well. The well is opened for production as soon as the acid and gas are displaced. This procedure permits a very rapid recovery of the acid which results in large increases in the deliverability of the gas wells. It has been found advantageous in the acidization of gas injection wells to inject the high pressure gas directly after the acid without backflowing the acid out of the well. This practice has made it possible to inject the gas in the injection wells of this field with a much lower pressure differential. This reduces the horsepower required to inject the gas and also decrease:, the number of injection wells required per reservoir. INTRODUCTION The results obtained by acidizing gas wells ill the La Gloria Field have varied considerably in the past. For this reason. a planned study of the acidizing procedure was undertaken in order to obtain more consistent results. The Frio Sands of the La Gloria Field are rather permeable and it was not necessary to acidize many of the wells when they were originally completed. At the completion of an eight-year cycling program in several of the gas reservoirs, it became necessary to recomplete many wells in other reservoirs. It was found that the opan Flow potential of the wells recompleted in different sands was not as large as wells that were originally completted in that reservoir. A study of the drilling records of several of these wells indicated that the sands had originally been subjected to considerable hydrostatic drilling fluid overload while the well was being drilled to the deeper sands of the field. It is indicated that during this eight-year period, the drilling mud and water that were lost into the formation when the well was being drilled had formed a relatively impermeable Eone around the well bore. This impermeable zone around the well bore made it very difficult to obtain high deliverability wells when the original wells are recompleted in other zones. Muskat' has shown that in uniformly permeable and porous formations a zone of partial plugging one ft in radius around the well would drastically decrease the productivity of the well. The analysis for this problem shows that the production capacity of a well is very sensitive to the value of the permeability of the zone immediately surrounding the well bore. This is to be expected in view of the highly localized character of the pressure drop in a radial flow system about the well center. The reduction of the deliverability is not proportional to the thickness of the mud-affected zone as the major portion of the reduction in deliverahility IS caused hy the

Jan 1, 1952

By P. W. Bridgman

Flow and fracture are admittedly complicated phenomena of which we are yet only partially masters. There is not even nni-.persal agreement as to the details of the language best adapted merely to describe the phenomena, to say nothing of any theory. Certain points of view, however, are widely held, and there are certain general expectations as to what sort of procedures will prove permissible. A complete description of any situation involving fracture would demand a complete history of all the variables in the control of the experimenter. The experimenter endeavors so to choose his independent variables that they are adequate to determine completely the situation in the sense that when an experiment is repeated on the same initial material and with the independent variables running through the same sequence, all the other measurable properties of the system will also run through the same course. It is, I think, the universal conviction that when we are dealing with phenomena of flow and fracture, the most important of the necessary variables are the external forces acting on the various parts of the body; when the force history repeats, with certain obvious restrictions such as that temperature must be constant and non-mechanical forces, such as magnetic field, must be small enough to be ineffective, then the history of all measurable properties will repeat; in particular the alteration of geometrical shape due to flow will run through the same course, and when fracture comes, the character of the fracture will be reproduced. Complete mastery of merely the descriptive aspects of flow and fracture would demand the ability to predict the entire course of flow and complete characterization of the final fracture for every possible combination of forces, varying in time in all possible ways, when applied to bodies of all possible shapes. This full situation is obviously of prohibitive complexity. The first stage in reduction to manageable simplicity is to resolve the total situation into the sum of contributions made by small elements. Our thesis is that if each of the elements is adequately characterized, the behavior of the whole system is fixed. The element is usually taken of a simple geometrical shape, suggested by the mathematics best adapted to the particular situation. The forces acting across the faces of the elements are ultimately determined by the forces acting across the free faces of the whole system. The detailed process of finding the precise forces on the faces of all the elements in terms of the external forces involves the use of a special mathematical invention, the stress, a constructional quantity consisting of six components. The stress at any point in the body is determined by both the external force system and by the physical properties of the body at all points; quite different stresses prevail at the interior of bodies of the same shape under the same external forces in the elastic and plastic ranges. The forces on the faces of any element are, however, uniquely determined by the stress system at the element. Our fundamental thesis

Jan 1, 1945

By P. W. Bridgman

FLOW and fracture are admittedly complicated phenomena of which we are yet only partially masters. There is not even universal agreement as to the details of the language best adapted merely to describe the phenomena, to say nothing of any theory. Certain points of view, however, are widely held, and there are certain general expectations as to what sort of procedures will prove permissible. A complete description of any situation involving fracture would demand a complete history of all the variables in the control of the experimenter. The experimenter endeavors so to choose his independent variables that they are adequate to determine completely the situation in the sense that when an experiment is repeated on the same initial material and with the independent variables running through the same sequence, all the other measurable properties of the system will also run through the same course. It is, I think, the universal conviction that when we are dealing with phenomena of flow and fracture, the most important of the necessary variables are the external forces acting on the various parts of the body; when the force history repeats, with certain obvious restrictions such as that temperature must be constant and non- mechanical forces, such as magnetic field, must be small enough to be ineffective, then the history of all measurable properties will repeat; in particular the alteration of geometrical shape due to flow will run through the same course, and when fracture comes, the character of the fracture will be reproduced. Complete mastery of merely the descriptive aspects of flow and fracture would demand the ability to predict the entire course of flow and complete characterization of the final fracture for every possible combination of forces, varying in time in all possible ways, when applied to bodies of all possible shapes. This full situation is obviously of prohibitive complexity. The first stage in reduction to manage- able simplicity is to resolve the total situation into the sum of contributions made by small elements. Our thesis is that if each of the elements is adequately characterized, the behavior of the whole system is fixed. The element is usually taken of a simple geometrical shape, suggested by the mathematics best adapted to the particular situation. The forces acting across the faces of the elements are ultimately determined by the forces acting across the free faces of the whole system. The detailed process of finding the precise forces on the faces of all the elements in terms of the external forces involves the use of a special mathematical invention, the stress, a constructional quantity consisting of six components. The stress at any point in the body is determined by both the external force system and by the physical properties of the body at all points; quite different stresses prevail at the interior of bodies of the same shape under the same external forces in the elastic and plastic ranges. The forces on the faces of any element are, however, uniquely determined by the stress system at the element. Our fundamental thesis

Jan 1, 1944

By M. P. Tixier, K. S. Kunz

A method for the interpretation of temperature curves recorded in gas producing wells is described. One essen-tial feature of the method is a simple graphical construction which conveniently reflects the amount of gas flowing from a given producing formation. This method, applied in conjunction with the Induction Log and radioactivity logs, is valuable to determine the points of entry of gas and to estimate the over-all thickness of the producing zones and their respective contributions to the total production. The method in particular is helpful in evaluating the effect of fracturing operations. An outstanding result of the application of the method is to bring to the light the relative importance of sand-shale interfaces in the production of gas. The paper is illustrated with field examp1es. INTRODUCTION The electrical logging tools involving conventional systems are not applied in wells which do not contain water base mud (empty holes, or wells filled with oil base mud), because of the absence of electrical connection between the electrodes and the surrounding formations. It is, therefore, common practice in this case to use other methods which do not require the presence of a conductive fluid in the borehole: resistivity log with scratcher electrodes, Induction Log, radioactivity logs, temperature log. . . . Such conditions are encountered in some regions, as the San Juan Basin, N. Mex., where a technique of drilling gas wells, using gas as a drilling fluid, has been introduced in the last two years. By the middle of 1953, an appropriate method for the logging of these wells was devised on the basis of field tests and of theoretical studies. It is the purpose of the present paper to give a description of this method. In these wells the logging operations are performed during the process of gas production, so that the temperatures in the boreholes are strongly affected by the cooling due to the expansion of the gas. On the other hand, a special thermometer, with a high sensivity and a short time constant, has been recently made available, which has enabled much more detailed and accurate recordings of the borehole temperatures than with the conventional instruments. As a result of these two circumstances, the temperature log constitutes the essential element of the method, in making possible the detection of the gas producing zones, the definition of their boundaries, and the estimation of the respective contributions of each separate zone to the total production. The method also involves the radioactivity and Induction Logs, as auxiliary documents. These logs in the present instance are helpful in the determination of the reservoirs. However, the information they give in this respect is limited. This comes from the fact that, due to the absence of the MicroLog and/or MicroLaterolog and of the SP log, the estimation of formation factors and connate water salinities is somewhat conjectural. Furthermore, little help is obtained from the Neutron log for the evaluation of porosity and of formation factor because the variations of gas saturation affect the Neutron log in a way similar to the variations of porosity. It should be said also that even an exact knowledge of the gas saturation of the reservoir beds would not

Jan 1, 1956

By W. W. Loo

A REVIEW of the literature on the reduction of cassiterite showed. that scarcely any progressive changes were made in the methods of reducing cassiterite until within the last two decades, and that during that period many improvements in the metallurgy of tin have taken place. Since 1914 the world's consumption of tin has increased considerably, resulting in the exploitation of primary tin deposits such as the Bolivian lode, which has become an important source of tin. On account of the low tin content of Bolivian ore, and the presence of objectionable impurities of the reduced tin, the smelting of this ore and the refining of the tin has changed considerably from the methods formerly used. A comparative study of the methods of smelting cassiterite concentrates suggested that an investigation be planned so as. to determine what factors effect the extraction of tin from its ores by reduction with carbon. The first part of the experimental work was the determination of whether roasted cassiterite concentrates can be reduced by carbon without the use of flux, and the reduced pellets of tin be collected into a single mass separate from the dry gangue residue The second part of the experimental work was a comparison of the effect of variations of the different factors on the smelting of roasted cassiterite concentrates: first, the effect of varying the composition of the slag; second, the effect of varying the amount of reducing agent; third, the effect of varying the relative amount of the resulting slag; and fourth, the effect of different kinds of reducing agents:

Jan 1, 1928

By D. D. Smith, D. P. Squier, E. L. Dougherty

A system of differential equations describing the temperature behavior of fluid injected at constant surface temperature in a well is derived and .solved analytically. A formula for the fluid temperature at any time and depth is given, as well us a special formula valid for very large times. These formulas are used to calculate temperatures for several typical cases. The results indicate that, initially, the temperature of the water entering the formation is considerably lower than the injection temperature. This condition lasts for only a short period— less than three days for most cases of practical interest. Following this highly transient period, during which the temperature of the fluid entering the formation builds up to about 50 to 75 per cent of the injection temperature. the system enters a quasi-steady state in which the temperature changes are very slow. After severl years, the bottom-hole temperature will still be 50" to 100°F lower than the injection temperature, hilt the heat losses may he tolerable. INTRODUCTION Predicting the behavior of a hot-water flood requires that the temperature of the water entering the injection interval be estimated. This report describes the development and solution of a system of equations which describes the temperature behavior of the injected water in the wellbore with certain simplifying assumptions. The only previous means known to the authors for describing such a process is that of Moss and White.' Their results appear to be close to those obtained by our method in the practical cases which were compared; this agreement is largely due to the fact that in our method temperature soon approaches a quasi-steady state, as was assumed in their method throughout. However, our model covers all times, is continuous (whereas the Moss-White model depends on breaking the depth into discrete intervals) and. we feel. more closely describes the physical problem. FORMULATION OF THE PROBLEM PHYSICAL SYSTEM AND ASSUMPTIONS The injection procedure consists of pumping water at a fixed surface temperature T., down an infinitely long cylindrical well or tubing of inner radius Any material exterior to the water column such as mud, casing, or cement is regarded as part of the formation. The general behavior of the system may be described qualitatively as follows. When the hot water is first introduced into the system, the temperature difference between the formation and the water is large, resulting in a high rate of heat transfer. As a result, the temperature adjacent to the wellbore rises very quickly. Because the segment of the formation adjacent to the wellbore largely controls the heat transfer rate, the heat transfer rate will become relatively constant when this portion has reached a temperature close to that of the water opposite it. The temperature of the water and formation then increase very slowly with time. The length of the initial highly transient period and the temperature of the water at its conclusion will be functions of depth, injection rate, injection-string radius, surface injection temperature and the physical properties associated with the water-formation system. The following additional assumptions were made. 1. There is no heat transfer by radiation in the system. 2. There is no heat transfer by conduction in the vertical direction in either the injection stream or the formation. 3. The linear volumetric and mass flow rate of the water is constant throughout the injection stream. 4. No horizontal temperature gradient exists in the injection stream. 5. The product of density and heat capacity is constant for both the water and the formation, and the formation thermal conductivity is constant. 6. Initially, both the water in the wellbore and the reservoir are at a temperature given by the (constant) ambient surface temperature plus the product of depth and geothermal gradient (assumed constant). At large distances for the wellbore (r m), the formation will remain at this temperature. 7. The water temperature and the formation temperature at r — r,, are equal for all depths D. DERIVATION OF EQUATIONS The differential equation satisfied by the fluid temperature T,(D, t), which is obtained by writing a heat balance on a cylindrical differential of volume dV of the injection string between the depths D and D i dD, is

By David Dvorkin, Thomas C. Anderson

INTRODUCTION A major function of the Mine Safety and Health Administration (MSHA), Denver Safety and Health Technology Center (DSHTC), Ventilation Branch, is to provide engineering analyses of underground mine¬ ventilation systems for coal, metal, and nonmetal in¬spection departments in accordance with field surveys and data analyses. Health and safety problems such as the control of diesel contaminants, dust, methane, radon, and radon daughters all are dependent upon ventilation. It is necessary for the ventilation engineers at DSHTC to have a complete understanding of the various and highly complex ventilation systems used in the nation's mines. Only through the proper assembly and analysis of data can the engineer determine the causes of prob¬lems and make suitable recommendations. Furthermore, the engineer must have the ability to predict the results of any such recommendations. In the study of the ventilation system at any indi¬vidual mine, it is common practice to collect data on airflow quantities and pressures at key points throughout the mine. However, these data give only a single point¬-in-time view of the system. As the mine develops and progresses, the system undergoes numerous changes; as the mine becomes more extensive, the ventilation re¬quirements increase, and the costs rise. For proper utilization of the available resources, it is necessary for the engineer to have a sound engineering basis for deci¬sions on how best to ventilate the mine. To evaluate the system as a whole, particularly re¬garding possible system changes, it has become necessary to rely on computers to perform the calculations in¬volved in analyzing the network. This chapter sum¬marizes the implementation of such computer capabili¬ties at DSHTC, as well as the services that are available from DSHTC. ANALOG SIMULATIONS AND ANALYSES OF VENTILATION NETWORKS As early as 1954, the US Bureau of Mines (USBM) in Pittsburgh, PA, was using an analog computer as an aid in analyzing ventilation systems. The Mcllroy Fluid Network Analyzer used filament-tube resistance elements and an electrical power supply to simulate mine-ventila¬tion systems electrically. This system is shown in Fig. 1. Analog simulation has proven to be a practical tool, providing fast analyses of complicated problems after the initial setup has been completed. Advancements in electronic technology over the past 24 years have made possible the construction of an analog computer that has streamlined several operating features of the previous machines. The DSHTC Ventilation Branch now has an improved electronic analog computer to assist in the analyses of ventilation systems. General Features As shown in Fig. 2, the analog computer used at the DSHTC Ventilation Branch has three "element" cabi¬ nets, a console, and a printer. The cabinets contain the fan elements and the airway-resistance elements that are used to "program" an analysis problem; each element is independent of the others. The console contains the "patchboard" and the controls necessary to operate the analog computer. The patchboard connects the inde¬pendent elements into the circuit appropriate for simu¬lating the ventilation system. The total system is controlled from a panel on the console, while the value corresponding to each element is set on the individual controls located on the face of each element. The control panel has three visual output displays that give the quantity of flow, the pressure of the output junction with respect to a datum, and the differential pressure across each element. The control panel also allows manual selection of the element to be monitored, or automatic scanning and printing of values for the entire system. Capabilities The analog computer can simulate an existing mine¬-ventilation network. This is accomplished by collecting field data at the mine to give a complete pressure-¬quantity network. Resistance values for each airway branch may be determined from the quantity of flow in the branch and from the pressure differential between the end-point junctions of the branch. The basic rela¬tonship to determine the resistance is expressed as: H=R •Q2 where H is the pressure differential, R is the resistance, and Q is the quantity of air in the flow. After the resistance values are known for all of the airways in the circuit, the elements on the analog com¬puter can be set to the corresponding values. The elements are designed to reflect the basic relationships, with electrical potentials corresponding to pressures and

Jan 1, 1982

By Alexandre Alex) J. Bredikhin

"DISCLAIMER: the statements presented herein are those of the author and do not necessarily represent the views of US DoD or its Components.ABSTRACTProgress on the $750M lock project on the Monongahela River was derailed by discovery of large anomalies in the 6.5-7-ft dia. drilled shafts of the new river wall foundation. The anomalies were located 45 to 50’ below the top of the wall at the critical shaft-to-wall interface, and ranged in thickness from several inches to 2-plus feet. A Specialty team, comprised of representatives from the contractor, the Government, and structural design consultants, was formed to evaluate the extent of the problem and the impact on the new lock wall. With no standard method in place, the Government took the lead to develop acceptance criteria for the repairs while the contractor took the lead to identify the repair means and methods. The Government developed a detailed Quality Control plan to capture and document all of the repair data and to approve each shaft repair in a timely manner. This paper provides an overview of the anomalies encountered and the need for repairs; discusses the details of the repair plan; and provides details on the unique quality control measures employed to verify the repairs. By developing and adhering to a detailed quality control plan, the structural integrity of all of the shafts was successfully restored.INTRODUCTIONThe new Charleroi Locks Project is currently under construction by the U.S. Army Corps of Engineers (USACE) in Pittsburgh, Pennsylvania. In the region, the Corps of Engineers is modernizing the series of locks and dams on the Monongahela River. One facet of this modernization is replacement of the existing Locks #4 (aka Charleroi Locks) located upstream of Pittsburgh, Pennsylvania with new and larger capacity locks. The relative location of the project is shown on Fig. 1. The original construction of twin locks (56’x720’ & 56’x360’) and the fixed-crest dam was completed in 1932, with lock walls supported on timber pile foundations. The fixed crest dam was replaced with a gated dam in the 1960’s. The existing lock is undersized and in poor condition and thus needs to be replaced. The project requires the construction of the new river chamber adjacent to the existing land chamber which must remain operational to navigation throughout the construction. In order to accomplish this, the lock walls need to be constructed in the wet. The river wall was constructed using two construction methods referred to on the project as “cofferbox” and “non-cofferbox” construction."

Jan 1, 2017

By J. Levin

Bond's Standard Work Index (SWi) indicates the grindability of an ore, and his Operating Work Index (OWI) indicates the performance of a grinding mil or circuit. The comparison of the two indices offers a measure of the efficiency of the grinding operation. Mil (or circuit) performance, particularly on the Witwatersrand, is often indicated by the index kilowatt -hours per tonne of minus 75 µm material produced (kWh/t minus 75µm or OE75)' The paper shows that a standard kWh/t minus 75 µm index (SE75) can be obtained from the standard Bond grindability test (which provides the SWi), and asks whether the two E75 indices can be used in the various ways in which the two Work Indices are used. For the answer, the paper presents averaged values for the standard grindability indices of the gold ores of the Witwatersrand, averaged values for the performance of grinding mils operating on those ores, and the results of laboratory grinding tests on a composite of several Witwatersrand ores. The particle-size indicator for the calculation of the Wi indices, the am size, is constant in its relation to the largest particles present, whereas the percentage minus 75 µm, the indicator of size for the E75 index, varies with the degree of grinding in its relation to the size of the largest particles. Because of this difference, the standard Work Index increases as the grind becomes finer, whereas the standard kWh/t minus 75 µ value decreases. The Wi and E75 indices nevertheless serve similar purposes when applied to moderately fine grinding-finer than 70 per cent minus 75 µm. Open circuit laboratory grinding tests revealed three stages in the grinding process, and credible values for the open circuit Work Index were obtained only from the second stage. The conversion of the open circuit Work Indices to the equivalent of close circuit indices by the application of Bonds open circuit inefficiency factor (a constant for grinds indicated by the d80 size) was of limited success; however, the development of a conversion factor related to particle-size should not be difficult. Initially difficulty was experienced in the calculation of the 0E75 indices from the results of the laboratory tests, but it was eventually considered that a constant value of the index derived from the results would be close to the true open-circuit index. The open-circuit grinding test could there fore be a convenient method for the detection of differences in the grindability of ores.

Jan 1, 1992

By Sudarshan Martins

The measurement of acoustic signals produced by a tumbling mill has been previously used to determine the operating state of the mill and correlate the variations of the sound intensity with the operating conditions of the mill. Separately, the discrete element model (DEM), a software simulation of the mill, was developed to provide insight into the operation of the mill. Presently, there has not been much work reconciling the DEM simulation of the mill with the acoustic signal. Working from basic principles of linear, time-invariant systems, agreement between an acoustic DEM simulation and the measured signal is sought. First, the impulse response function of the mill is measured. The DEM provides the forces applied to the mill shell as a function of time. A convolution of these simulated shell forces and the transfer function gives the simulated acoustic signal. This signal is compared to the measured acoustic signal, both in the time domain and the frequency domain. Finally, a discussion of the results is given.

Jan 1, 2012

Lower the respirable dust exposure of longwall shearer operators by isolating and con-fining the dust cloud near the face. Approach Install conveyor belt screens at various locations on the body of the shearer to contain and hold the dust cloud toward the face side of the machine. This approach provides a cleaner air split in the walkway, over the shearer operators. How It Works On most longwall shearer sections, the dust exposure of the shearer operators is primarily attributable to the machine it-self. The dust cloud originates at the face, and the exposure of the operators depends largely on how quickly this dust spreads into the walkway. Conveyor belt screens placed on the gob side of the body of the machine can reduce the amount of dust which spreads out into the walk-way. In addition, belting may be installed over any open spaces between the shearer under-frame and the panline to prevent conveyor dust from boiling out into the operator's walkway.

Jan 1, 1981

By X. Yang, G. D. Zhai

The prop is the most important part to ensure the proper functioning of hydraulic support. When the hydraulic support is impacted by the roof, the prop is prone to extrusion deformation, expansion, and even bursting. In order to study the stress on a doubly-telescopic hydraulic support prop under impact load, an impact simulation was carried out based on the drop weight method. First, the impact model of the hydraulic system of the prop was established in AMESim software and the dynamic response curves of the bottom and middle cylinder of the prop obtained. Then, according to the conservation of energy, the pressure formulaes in the hydraulic cylinder of the prop under impact load were derived and verified by the AMESim simulation results, and the maximum pressure on the inner surface of the hydraulic cylinder of the prop obtained. Lastly, the transient dynamic simulation of a hydraulic support prop was carried out in ANSYS Workbench software, and cloud diagrams of stress and deformation of the prop obtained using Workbench simulation. The AMESim simulation process describes the change in fluid pressure in the prop, and the pressure formulae can be used to estimate the internal pressure of the prop under impact load. The finite element analysis results show that the stress of the middle hydraulic cylinder is much greater than that on the bottom hydraulic cylinder under impact load, which can provide a reference for prop design.

Jul 2, 2022

By Hongpu Kang

The fully mechanized top coal caving mining method has been the main mining approach for thick coal seams with high output and efficiency in Chinese coal mines. The gateroads for the top coal caving mining faces should be driven along the floor of the thick coal seam with a part of the seam as roof. The support of the gateroads is commonly difficult because of the low strength and broken structures of the coal seams, and the increasingly large section of gateroads meeting the need of greater and greater face coal output. Based on the analyses on the geomechanics properties and production conditions of the top coal caving mining, the influences of the top coal caving mining parameters on the stability of gateroads, including mining thickness and face length, are studied. The deformation and damage features of the rock mass surrounding the gateroads with the top coal seam as roof are investigated, the interaction of the support with the surrounding rock mass, the support theory are studied. The bolting design method and criteria, bolting forms and parameters for the gateroads with the top coal as roof are put forward. The rock bolting components, including bolt bars, face plates, cable tendons, meshes, and steel straps, are introduced. Finally, the gateroad bolting effects are evaluated through a typical case study on the basis of field monitoring data, such as the displacement of surrounding rock mass and the forces along bolts and cables.

Aug 1, 2013

By Mohab Sabry, Emre Biringen

"Over the past decades, there has been an increasing recognition of the strategic use of pile-supported rafts in design of heavily-loaded structures to reduce total and differential settlements. However, such a hybrid foundation construction method has not been widely utilized in many countries, including the U.S., due to code limitations. In current practice, the foundation design is based on either (i) the bearing capacity of the raft supported by the subgrade soils, or (ii) solely the pile capacity. This paper addresses the potential use of such hybrid piled-raft systems, where the structural load is shared by both by the piles and the subgrade soils directly beneath the raft, in foundation design of power plant structures. The study assessed some of the characteristics of piled-raft behavior by undertaking three-dimensional finite element analyses of two raft sizes, and various pile layout patterns, including the rafts with piles distributed evenly and only in the central area of the raft. The computer software PLAXIS 3D with the Mohr-Coulomb constitutive soil model was used to facilitate the modeling of such cases. The results presented in this paper indicate how strategically locating the piles could reduce the differential and total settlements.INTRODUCTIONUnder the high applied loads coming from the superstructure, the addition of piles is primarily required to improve the factor of safety against failure when a raft does not provide adequate bearing capacity. If the bearing capacity of the raft is sufficient to carry the total load with a reasonable safety margin, then the addition of piles is usually intended to reduce the settlements to an acceptable amount. In current practice, the design process for pile-supported raft foundations conservatively concentrates on providing solely the pile capacity to carry the total structural load without taking the contribution of the raft into account. This paper addresses the potential use of hybrid piled-rafts in controlling foundation settlement of power plant structures by considering the support of both the piles and the subgrade soils beneath the raft to carry the load."

Jan 1, 2017

By H. H. Schrenk, Carlton E. Brown

"INTRODUCTION The angle at which a hole is drilled has long been thought to affect the amount of dust disseminated into the air during wet drilling. The amount disseminated has been reported as increasing rapidly with the approach of the angle of the hole to the vertical (up) position. 4/ This has been explained commonly as being caused by a decrease in contact of water with the face of the drill hole; increase in amount of sludge dropping through the air; and increase in amount of sludge running down the drill steel and being thrown into the air by the rotation of the drill steel and by leakage of air from the front head of the drill.The steep up angles of the holes drilled are responsible, at least partly, for the higher dust concentrations found in such places as raises, compared with those at level faces, where most of the holes are drilled at angles farther from the vertical (up) position. The mining industry is coming to realize more and more the importance of the angle of the drill hole as a contributing cause of the high dust concentrations found in some raises. Much work is being done to counteract the effect of the angle of the drill hole on dust dissemination. The rate of rater flow through drill steels is being increased by the use of water tubes of larger diameter or by higher water pressures to obtain better contact between water and the face of the drill hole. Traps are being developed to catch the sludge from the drill hole and allow it to drain down through a special pipe before it drops through the air or runs down the drill steel. Drills that permit little or no air to leak from the front head along the drill steel are being designed and used. Care is being taken to prevent the exhaust from the drill dispersing the sludge into the air."

Feb 1, 1938

By O. Hoover, M. Herman, V. V. Damiano

The Jetter and borie' teclznique of determining textures using a spherical specimen has been applied to tlze study of compression-rolled beryllium sheet. Snzall spheres the order of 1 mm in diam cut from the beryllium sheet were autotnatically rotated about tz41o axes using the G.E. single-crystal goniometer. Quantitative pole figures were obtained without tke need to apply absorption corrections. Compression-rolled beryllium exhibited peak intensities ,for (0002) planes of positions tilted 10 deg to the rolling plane and a near random distribution of (1010) planes about the nornal to the rolling plane. TECHNIQUES for determining textures of rolled sheet material are amply described in the literature. The techniques are found to be variations of two basic methods. One due to Decker, Asp, and arker, referred to as the transmission method, utilizes a thin-sheet specimen in which the X-ray beam enters the specimen from one side and the intensity of the beam which emerges from the opposite side is measured. The second method due to chulz,3 referred to as the reflection method, utilizes a thick specimen and the intensity of the beam emerging from the same side is measured. The two rotations of the specimen in the beam are designated a and 8. In order to completely determine the texture of sheet material, it is generally necessary to use a combination of the two methods. The calculations involved in correcting the raw X-ray data for absorption effects and the combining of the data obtained by the two methods are very laborious and time consuming. To avoid the intensity corrections which arise as a result of the changing diffraction volume and path length within the sample other methods have been proposed. The Norton method utilizes a cylindrically shaped specimen cut from the sheet material. Since the rods have rotational symmetry, the absorption correction is constant for rotations about the sheet texture. Jetter and Borie' employed a spherical specimen to analyze the fiber texture of extruded aluminum rods. The spheres were rotated rapidly about the fiber axis to include a large number of grains in the X-ray beam and changes in intensity with respect to tilts of the fiber axis were measured. The absorption correction was constant for all angles and was neglected. The Jetter and Borie' technique finds excellent ap- plication to very fine-grained low-absorbing metals in which the entire sphere volume can contribute to the diffraction volume. In the case of low-absorbing metals, however, serious limitations on specimen thickness occur as demonstrated by Braggs due to de-focussing effects. Peak shifts may occur which negate the assumption that integrated intensities are proportional to peak intensities. These limitations in sphere size to the order of 0.5 to 1 mm for beryllium require that the grain size be sufficiently small to include a large enough statistical sample. The present paper describes the application of spherical specimens less than 1 mm in diam to the quantitative determination of pole figures for compression-rolled beryllium sheet having a grain size the order of 10 p. EXPERIMENTAL 1) Specimen Preparation. Two techniques for spark-machining beryllium spheres were tried. One involved the use of a hollow cylinder as a cutting tool. The tool was fed into the rotating cylindrical specimen as shown in Fig. l(a). The hollow cylinder was carefully aligned such that the axis of the cylinder and the axis of the specimen lay in the same plane and were 90 deg to each other. As the hollow cylinder was fed into the rotating cylindrical specimen, a spherical shape was formed as shown in Fig. 1. Alignment was very critical. Slight misalignment resulted in the formation of a barrel-shaped specimen instead of a sphere. A second technique involved the use of a cutting wheel shaped as shown in Fig. 2 with a groove of the desired radius. A section of the sheet specimen was first turned into a cylinder on the left part of the cutting wheel. It was then shifted to the right and a spherical specimen was turned as shown in Fig. 2. The axis of the cylinder lay in the plane of the sheet. Flats corresponding to the rolling plane of the sheet were used to grip the specimen during the machining operation and these served to identify the rolling plane of the sphere. 2) Rotation of Spec=. The spherical specimen is shown mounted on the G.E. single-crystal goniometer in Fig. 3. The knob A of the goniometer shown in Fig. 3 rotates the specimen about the pedestal axis. These angles have been designated as @ angles. The knob B rotates the specimen about an axis perpendicular to the pedestal axis. These angles have been designated as p angles. A device was made to automatically drive the single-crystal goniometer by means of two flexible shafts connected to the A and B knobs as shown in Fig. 3. The motor system was designed to rotate the knob A, thus rotating the specimen through angles of $I while the B knob remained stationary. After one complete

Jan 1, 1967

By Yves Dardel

The literature concerning the remelting of alunlinum and its alloys is very rich. Unfortunately the majority of the papers on this subject have no scientific value, for the theories or explanations are too often in opposition to the laws of physical chemistry. Furthermore only a few of the methods of purification are considered in the literature. Hence it has seemed necessary to the author to sketch a general theory of the purification of secondary aluminum. The purpose of the purification is to eliminate the impurities that the charges, and the atmosphere of the furnaces bring into the bath during the successive remelt-ings. Indeed scrap as well as metal can be used when soiled with oil, greases, water, or others, if it has been sufficiently dried and contains oxides. At the melting point of the metal, the oils and greases are decomposed into their constituent elements H², O2, H²O, co², CO, CH,, and others. These gases are added to the corresponding gases in the atmosphere of the furnace. The impurities introduced into the metal during the remelting will accordingly be the products resulting from the action of these gases on the liquid bath. The quantity of hydrogen that is soluble in aluminum and its alloys is given by the relation of sieverts3 as a function of its partial pressure PH2 in the atmosphere m = K vPH² [I] where K is a constant, which depends only upon the temperature and increases with it. The experiments of Rijntgen and Braun4, RÖntgen and M611er5, Bircum-shaw6 and Winterhagerl have rendered it possible to determine the value of K, when the temperature is less than 1.000°C. One obtains: log K = - 4,702.5T + o 238 [2] Besides its usual significance, the term Ph~ represents also the internal pressure of dissolved hydrogen, since in the equilibrium, that is1 when no gas exchange Occurs between the two phases, the Pressures of hydrogen in the metal and in the atmosphere must be equal. Eq I shows that when the partial pressure of H2 increases the amount of dissolved hydrogen in equilibrium increases, and that, if the contrary Occurs, the quantity of H² should diminish. However, if for any reason the diffusion of hydrogen is hindered and the total amount of dissolved gas remains constant while the temperature decreases, the internal pressure of H² increases until it reaches the value of the hydrostatic pressure. At this point, bubbles of hydrogen appear in the bath and escape out of it. The amount of hydrogen in the metal is then limited by a a depending On the hydro- static pressure, which is practically equal to one atmosphere. Indeed hydrogen does not accumulate in the form of a hydride appearing as a separate solid phase. However1 even the mechanism of the solubility is not yet elucidated. One does not know exactly as yet, whether the

Jan 1, 1949