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By J. P. Heller, H. B. Bradley, A. S. Odeh

A potentiometric model technique is presented for determining the areal sweep efficiency of a five-spot well pattern, at and beyond breakthrough. A sharp interface between displaced and displacing fluids is assumed. Although the prototype svstem is referred to as a waterflood operation, obvious changes in the notation and computations will adapt the results to other displacement processes. The results of the study include the following. 1. Areal sweep efficiencies for a five-spot well pattern, at and beyond breakthrough, for mobility ratios (displacing to displaced fluid) of 4:1, 2:1, 1:1 and 1:4. 2. Extension of potentiometric analysis to the investigation of the areal sweep efficiency beyond breakthrough in a five-spot pattern by the application of conformal mapping and conductive-solid models. 3. The use of layers of conductive fabric in representing mobility ratio changes in potentiometric models. 4. The development of a probe mechanism for probing conductive solids. The results obtained by conductive-cloth models agree with earlier areal sweep efficiencies at breakthrough obtained by Aronofsky and Ramey 1 on the potentiometric analyzer using electrolytic-tank models. Results beyond breakthrough differ from those obtained by the X-Ray Shadowgraph technique. Data from this study show that, for mobility ratios greater than one, water cut rises rapidly as fluid is produced after breakthrough. However, for mobility ratios smaller than one, a large increase in area swept resulted with only a small increase in water cut. INTRODUCTION In calculating reservoir performance of waterflood-ing operations and other fluid-injection programs, it is necesssary to estimate the areal sweep efficiency * before and after injected-fluid breakthrough into production wells. Influence of mobility ratio on oil-production history, before and after breakthrough for a five-spot well pattern, has been studied by X-Ray Shadowgraph techniques 2-5 and by gelatin models.6 In none of these investigations was the transition zone controlled experimentally. Steady-state anaiog techniques assume that a vertical and discrete interface exists between the displacing and displaced phase. Thus, when using a potentiometric analysis, it is assumed that no transition zone exists. To determine the areal sweep efficiency beyond breakthrough for a five-spot well pattern using the potentiometric analyzer, four principal problems had to be resolved. These were the following. 1. The laborious method of representing changes in mobility ratio in electrolytic tanks by means of contoured wooden blocks. 2. Vapcrization of the electrolyte solution during the study causing concentration changes and, thereby, variable conductivity. 3. The scale-limitation problem 7 that is accentuated by abrupt eiectrolyte depth changes. 4. A wellbore geometry problem. EXPERIhlENTAL EQUIPMENT AND PROCEDURES CONDUCTIVE-SOLID MODEL The theory, equipment and procedural techniques of the electrolytic-tank potentiometric model have been treaced excellently by Lee8 and by Muskat.9 By the use of a conductive solid to represent the fluid conductivity of the porous media, the need for contouring wooden blocks to represent mobility ratio was eliminated. It was found that a carbon-black coated fabric, Uskon D-16,** could be employed as a fairly uniform conductive media. This material, when stacked in appropriate layers and pressed together, can be used to represent changes in mo-

By P. J. D. Lloyd, Jill Urban, M. R. Urban

The adsorption of gold from cyanide solutions onto constituents of the reef, and its role in reducing the efficiency of the gold-recovery process by M. R. URBAN. M.Sc. (Chem. Eng.) Rand (Visitor). JILL URBAN. B.Sc. (Chem. Eng.) Rand (Visitor) and P. J. D. LLOYD. Ph.D. (Cape Town) (Fellow) Evidence for the adsorption or re-precipitation of gold from cyanide solutions onto gangue minerals of the Witwatersrand reefs has been gathered over a number of years by various investigators. The evidence from tests using radioactive tracers is conclusive and indicates thlt adsorption contributes about 0,1 g/t to the total gold loss from conventional reduction works. The loss is a function of the alkalinity and cyanide concentration of the solution, and it appears to be affected by the extent of time between milling and cyanidation. The heavy minerals appear to be the strongest adsorbers, and the clay minerals somewhat less strong adsorbers. A sensitive qualitative test based on thin-layer chromatography permits the extent of adsorption and desorption to be readily determined.

By Larissa Koroznikova, Steve Durkin, Patrick Bouwmeester, Michael Tuck

In currently used mining methods, blasting techniques often causes dilution of valuable ore and results in costly processing requirements. In the context of narrow vein mining of thin and highly concentrated orebodies there is a need of a mining method that can reduce dilution in order to remain economically viable. This research project explored the viability of a new mining technology, thermal fragmentation, in narrow vein mining. Thermal fragmentation technology uses a flame jet to produce extreme heat that spalls the surrounding rock to a strategically located drill hole, as an alternative to traditional blasting. This paper creates a net present value (NPV) model of a mining method using thermal fragmentation, as well as for an existing method used for narrow vein mining; comparisons and evaluations were made regarding the feasibility of the new technology. It was found that while overall costs for thermal fragmentation were relatively high, reductions in wages, haulage and processing costs, as well as increased productivity and ore recovery, meant that the new method would improve the financial performance of any operation. These results identify that there is an opportunity to introduce the thermal fragmentation technology to narrow vein mines within Australia, in order to lower costs and increase profit.

By Michael J. Sapko, Gregory M. Green, Harry C. Verakis, Kenneth L. Cashdollar

The National Institute for Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration (MSHA) conducted a joint survey to determine the range of coal particle sizes found in dust samples collected from intake airways of U.S. coal mines. The last comprehensive survey of this type was performed in the 1920’s. The size of the coal dust is relevant to the amount of rock dust required to inert the coal dust, with more rock dust needed to inert finer sizes of coal dust. Dust samples were collected by MSHA inspectors from several mines in each of MSHA’s ten bituminous Coal Mine Health and Safety Districts. Samples were normally collected in several intakes at each mine. The laboratory analysis procedures included acid leaching of the sample to remove the limestone rock dust, sonic sieving to determine the dust size, and low temperature ashing of the sieved fractions to correct for any remaining incombustible matter. The results indicate that particle sizes of mine coal dust in intake airways are finer than those measured in the 1920’s. The significance of these finer coal dust sizes is discussed relevant to the amount of rock dust required to prevent coal dust explosions.

By François Larouche

Since their commercialization in the early 1990s, lithium-ion batteries (LIBs) have become ubiquitous for powering a myriad of portable electronics. Their usage now extends to the automotive industry and stationary energy storage market. With an average life of 6.2 years and the strong demand, the volume of spent LIBs has increased exponentially, making recycling mandatory. Currently, recycling/ recovery of spent LIBs is limited in comparison to all other types of batteries. The current processes focus mainly on the recovery of the most valuable metals such as cobalt and nickel, leaving lithium and phosphate in a low value end-product. It is necessary that new advanced recycling technologies are developed for the recovery of spent LIBs both from an economic and environmental perspective. In this paper, the current R&D status of LIBs recycling is reviewed with the emphasis placed on hydrometallurgical processing opportunities for Li-ion and Li-solid state batteries.

By W. A. Roper

Since 1950, several papers have been published which have described various methods for studying mobility ratio effects. The methods which have been described for studying mobility ratio effects include X-ray shadowgraph techniques, stepwise potentiometric model procedures, stepwise numerical procedures, gelatin model studies and fluid mapper model studies. The purpose of this paper is to describe a procedure for using a resistance network for studying mobility effects. DESCRIPTION OF APPARATUS The basic unit of the experimental model consisted of a network of 840 resistors fastened to a sheet of black Lucite which was mounted on a wooden frame, Fig. 1. The dimensions of the Lucite sheet were 36 X 36 in. The resistors were fastened to the Lucite sheet at mesh points by means of snaps. The mesh points were arranged in a square pattern, 30 X 30 in., spaced at intervals of l1/2 in. The snap fasteners permitted several resistors to be "stacked" in parallel. By adding additional resistors to the basic unit, the specific resistance on each side of the flood front could be varied. The square network of resistors represented one of four symmetrical elements of a five-spot well pattern. The current input was analogous to an injection well and the current output was analogous to a production well." The power supply was essentially a full wave transformer-rectifier system for converting alternating-current into direct-current. The DC voltage could be varied from 41.43 to 290 v in steps of 41.43 v by selecting the proper outlet jacks. The major components of the power supply were: a Triro power transformer, R 11-A; a dual 5Y3 vacuum tube; two gas filled OD-3 tubes; and a Triplett voltmeter, model 227-1, range 0 to 500 DC v. The voltages at the mesh points were determined with a Keithley electrometer, model 210, No. 185, manufactured by Keithley Instruments, Cleveland, Ohio. A Heathkit vacuum tube volt-

By B. H. Caudle, W. J. Bernard

Factors which influence the success or failure of a waterflood can seldom be determined in the laboratory. For this reason pilot waterfloods are initiated in a repreventative portion of the oil reservoir in question. For a pilot flood to predict quantitatively the recovery to be expected in a field-wide waterflood operation, the pilot area must behave as though it were confined (surrounded by similar areas). In this study, laboratory fluid-flow models were used to determine the simplest pilot pattern, for particular conditions of mobility ratio and initial gas saturation, that would behave as though it were confined. Pilot patterns studied ranged in complexity from a single inverted five-spot to a grouping of nine regular five-spots. Only the innermost producing well in each pattern was studied. Model results showed that the optimum number of wells in the pattern depends upon the oil-water mobility ratio and the expected oil-bank size. Unfavorable mobility ratios will, in general, require more wells in the pilot pattern than will favorable mobility ratios. Pilot patterns in reservoirs which contain a dispersed, flowable, free gas saturation will require fewer wells than for the under-saturated case. The single inverted five-spot pattern was found to be unsatisfactory for predicting behavior of fully developed waterfloods. In particular, it is possible that, in reservoirs which contain a flowable, dispersed gas phase, the oil bank will never be observed at the producers due to the large amounts of free gas which continue to be produced with the oil. INTRODUCTION One method which has been used to predict the performance of a waterflood is the pilot flood. The pilot waterflood is a flood which involves only a small cluster of the reservoir wells and is located in a small, representative portion of the reservoir. The object is that oil produced from the pilot can, in some way, be related to the oil recovery to be expected from a field-wide expansion of the waterflood. However, these field pilot waterfloods have often been unreliable in the prediction of oil recovery in a fully developed waterflood. This unreliability has also been demonstrated in several laboratory studies of pilot floods. Some of the investigators have shown that there are situations in which the pilot flood oil production is far too optimistic with respect to the oil recovery in the fully de- veloped flood. Others4-G have shown that the pilot results can also be pessimistic, especially if the pilot waterflood is initiated in an oil reservoir which has been depleted by primary recovery and is at very low pressure. The major reason for this unreliability of pilot water-floods is the migration of fluids into or out of the pilot area. By the well-known method of images, if straight lines can be drawn to represent vertical planes of symmetry in a porous medium which contains pressure sources and sinks (injectors and producers), then these lines are invariant streamlines, or lines across which there is no potential gradient, and therefore no flow. In an actual reservoir, these lines of symmetry can never be established exactly because of reservoir inhomogeneities and irregular reservoir boundaries. However, if the reservoir is relatively large and contains wells in repetitive patterns, these lines of symmetry are commonly assumed to exist for the pattern units sufficiently far removed from the reservoir boundary. Lines of symmetry for the five-spot injection pattern are shown in Fig. 1. Each five-spot unit in this figure can be considered confined with respect to flow across its boundary. In pilot floods this is not the case. The lines of symmetry for the pilot patterns investigated in this study are shown in Fig. 2. It is obvious that the fluid within these pilots is not confined and is therefore able to migrate into or out of the pilot area. Intuitively, one can see that, if more wells are added to the pilot, the innermost unit tends to behave more and more like the confined pattern. However, there is a practical limit to the number of wells which should be placed in the pilot. This limit is usually determined by economic factors. It was the purpose of this study to use laboratory fluid-flow models to determine which of the previously mentioned pilot patterns will force the innermost producing well to behave as it would in a fully developed waterflood. Since fluid migration is influenced by initial saturation conditions and the mobility ratio, these factors were included in the study. The ultimate objective of this study was to develop data which would allow the operator to choose a pilot pattern and operating conditions that will yield a production history which can be applied directly as an estimate of the performance of each production well of the fully developed waterflood. BASIS FOR THE STUDY The basic problem of field pilot floods is the migration of the reservoir fluids into or out of the pilot area. This problem has been the subject of previously reported model studies on pilot floods. These studies have been concerned mainly with the development of arbitrary "correction factors" to be applied to the simple, unconfined pilot systems such as the single five-spot. The correction factors were intended to adjust the production history of the un-

By Zhi-xiang Cui

Effects of flux, vulcanizing agent and reductant on slag cleaning in new-type slag cleaning furnace (Φ3.6 × 8.1 m) were investigated under the conditions including smelting temperature of 1200 and 1250 °C, settling time of 30 and 60 min, and Fe/SiO2 of 1.7–1.9. The results show that addition of SiO2, B2O3 or CaF2 into original copper smelting slag can improve settling separation effect. Though no effect on copper recovery, addition of FeS can provide heat required by reaction with oxygen and reduce copper dissolution in spinel phase and slag. Copper content in discarded slag can be controlled at 0.26% under the optimum comprehensive conditions with ratio of oxygen to natural gas of 1.6.

By J. G. Patchett, R. W. Rausch

Fresh waters and the presence of clay in many Rocky Mountain and West Coast sands require special methods of log analysis. Archie's saturation equation requires addition of a shale correction term, and the SP equation must also be modified to account for clays. Suitable equations were developed several years ago, but have not been widely used due to the algebraic complexity. A computer-oriented method has now been developed to overcome this problem. The basic shaly sand equations are rearranged in four different ways to permit solution for various sets of available input data. Essential to application of the method is the correction of observed SP values to those that would be observed if the resistivity of the formation waters were exactly interchangeable with the activity. A graphic method for doing this is given. Where conditions require consideration of the effect of clay in the sands, the method presented has been found to improve the accuracy of water-saturation determinations. INTRODUCTION Log interpretation in many Rocky Mountain and West Coast basins is complicated by rapid vertical and lateral changes in water resistivity. Calculation of formation water resistivity from the SP curve becomes difficult in zones that contain clay, since changes in SP deflection may be due to changes in either clay content or water salinity. In hydrocarbon-producing reservoirs, the problem is further complicated because hydrocarbon saturation also reduces the SP.1 A log interpretation system using computers has been developed to provide a solution to this problem, based on equations proposed by de Witte.2 Four different simultaneous solutions of de Witte's equations have been made. Each solution method uses a different set of input data as independent variables. Thus, a choice of solution method is possible, depending upon the logs run and the availability of other data. Two of the solutions do not require a knowledge of water resistivity. This system is intended to be used primarily in multiple sandstone-shale sequences of low and moderate resistivities where the principal contaminant in the sandstones is clay. However, where sufficient regional data are available, interpretation in single-zone sandstone reservoirs can also be improved by using the method. THEORY AND HISTORY OF SHALY SAND ANALYSIS The log interpretation formula originally proposed by Archie3 in 1941 is applicable only to rock-fluid systems wherein the rock has negligible electrical conductivity. In 1949, Patnode and Wyllie4 showed that if the rock itself can be considered conductive due to the presence of clay, a different calculation approach is necessary. During the following years, this problem was investigated at great length, as was the related problem of the effect of rock conductivity on the SP.5-11 These investigations established functional relationships between SP, resistivity, water saturation and water resistivity for such a formation. Refs. 2 and 12 provide summaries of these studies. Unfortunately, practical use of these relationships required that water resistivity be known independently from the SP. Although log interpretation methods for rock systems containing clay were proposed at that time,' they were not generally accepted for routine use. There are three principal reasons for this. First, in many field situations involving high-salinity water, rock conductivity may be neglected (even if present) without introducing appreciable error. This may be seen by considering the following expression for waier-saturated rock.' 1/R2=1/R1+1/FRn....(1) where 1/R, is conductivity due to clay. As Rw becomes small, I/FRw becomes much greater than 1/R, which may be neglected. Where 1/R, may be neglected, the sandstone is called clean. If the term may not be neglected, the sandstone is termed dirty or shaly. For resistivity purposes, the classification between clean and shaly sands then depends not only upon the conductivity due to shale in the sand, but also upon the resistivity of the associated water (shale is used here to mean surface condition due to disseminated clay). A sand of given conductivity might safely be treated as clean in association with high-salinity water, but would require shaly sand methods if associated with fresher waters. Shaly sand methods are not required in many areas having saline waters; but in Rocky Mountain and West Coast sands having relatively fresh waters (often more than 0.3 ohm-m resistivity at formation conditions), the shaly sand methods are needed. Errors Rw calculations from the SP due to the presence of shale are likewise related to water salinity. In saline water formations drilled with fresh mud, the ratio of mud filtrate resistivity to water resistivity is high, the SP is large and the presence of shale can introduce large errors in water resistivity calculated by the conventional method. When the resistivity ratio is low, the errors are smaller. At zero SP, no error would result from shale. Thus, from the SP viewpoint, a given rock could be shaly if associated with a saline water, and clean in association with a fresh water, which is the opposite of the resistivity-oriented definition above.

By Jürgen F. Brune, R. Karl Zipf, Kenneth L. Cashdollar

This paper outlines the legal standards and methods for protecting underground coal mines in the United States from explosions of methane gas and coal dust. It will discuss inspection and monitoring of mine atmospheres, dilution of methane through ventilation, methane drainage prior to, during and post-mining, as well as explosion prevention through rock dusting and sealing of mined-out areas. Recent research findings of the National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory on the magnitude of pressures obtained during methane explosions from modeling and full-scale explosion tests at the NIOSH Lake Lynn Experimental Mine will be presented. This work is currently being applied to modeling the structural response of explosion-proof mine seals to pressures from gas explosions. Also, new research will be presented on the inertization of float coal dust in mines through the addition of inert stone dust and on the application of the Coal Dust Explosibility Meter (CDEM), a handheld device developed by NIOSH to directly measure the explosibility of a coal dust - limestone dust mixture based on optical reflectivity.

By Paulo Couceiro

Highly non-ideal explosives usually tend to react expressively below their ideal detonation velocities. In these cases, dimensional effects and product heterogeneities become important to proper model the detonation state. Although Direct Numerical Simulation (DNS) techniques can provide a complete and exact solution for this problem, its actual computation cost is still not practical for industrial applications. In order to minimize these constrains, a simplified two-dimensional steady non-ideal detonation model for cylindrical stick explosives is developed. Based on an ellipsoidal shock shape approach, the proposed model uses the quasi-one dimensional theory for the axial flow solution and combine the post-shock sonic flow criteria with some limiting conditions for the explosives’ unconfined radius determination. Due to its attractive fitting capability for unconfined detonation experimental data, the model offers the possibility to predict the non-ideal detonation state for any diameter, resulting in a full mapping of the diameter-effect curve of the explosive. Thus, the proposed engineering approach is used to model the main properties of some of the most common ammonium nitrate-based explosives used in mining and quarrying industries, including the complete axial flow solution.

By Frederick Prime

The Great or Cumberland Valley, which (under a variety of names) extends from Canada, through Vermont, Massachusetts, Connecticut, New York, Pennsylvania, Maryland, Virginia, and East Tennessee, to Alabama, is composed in part of limestones lying immediately above the Potsdam sandstone. Geologically, they belong to the era between the Potsdam and Trenton, and are commonly termed Calciferous. A peculiarity of these limestones is their great richness in limonite or brown hematite ores, which form a large part of the charges of the many blast-furnaces situated on their outcrops. The mines from which the ores are obtained are (properly speaking) only pits or quarries, from which 'the ore is extracted by means of picks or shovels, powder being rarely employed. The ore does not occur casually at any point in the limestone, but forms regular lines, following apparently the outcrops of certain beds. In Lehigh County, Penn., where 1 have been engaged on the Geological Survey of the State, during the past season, there are three or four of these lines. During the progress of the survey I was much struck by the fact that the two most important and promising lines of outcrop were, one at the base of the crystalline schists (forming the South or Lehigh Mountain), and overlying the Potsdam sandstone conformably; the other, near the line of junction of the calciferous limestone with the slates of the Cincinnati epoch. The mines along these two lines, following the topography of the country, were in place, richer and more permanent than those of the belts between, which were generally leaner. A peculiarity of these two lines of outcrop, and one to which I particularly desire to draw attention, is the occurrence of what I at first mistook for a highly altered slaty limestone, but which subsequent analysis proved to consist in great part of damourite (hydrated potash mica). The following are analyses of this damourite slate: I. From Fogelsville, Lehigh County, within a few hundred feet of the contact of limestone and slate, by Dr. F. A. Genth. 11. From Hensingerville, Lehigh County, within 300 feet of gneiss, by Mr. Sydney Castle, of the University of Pennsylvania. 111. From Allentown, Lehigh County, within 150 feet of con

By L. L. Handy

Two equations are compared for calculating imbibi-tion rates of water into porous media. A linear relation was found to apply when the square of the volume of water imbibed was plotted against time for water imbibing in natural rock materials. The effect of adsorbed organic materials on surface wettability was determined from measurements of rate of imbibition, water saturation and water permeability. INTRODUCTION An understanding of the mechanisms by which water displaces oil from porous media requires an understanding of the role of capillary forces in the displacement process. The capillary forces are determined by properties of the water-oil-solid surfaces. Consequently, some measure of the surface properties of reservoir rocks is necessary if displacement behavior in oil reservoirs is to be predicted from laboratory measurements. Several experimental procedures have been proposed to assign quantitative wettability indexes to reservoir rock surfaces. The most recent of these proposals are those of Bobek, Mattox and Denekas' and Amott.' These indexes are designed to show a continuous variation from the preferential oil-wet to the preferential water-wet systems. They require measuring some property of the rock which is a function of surface wettability. The quantities are measured on unaltered core material and compared with values obtained for known oil-wet and water-wet extremes on the same material. These methods are useful but are semi-empirical in nature. They have the disadvantage that the measured quantities may be functions of other variables in addition to surface wettability. Some understanding of the behavior of water-oil-rock systems may be obtained from studies of the simpler water-air-rock systems. Surfaces of a given wettability are more easily maintained for the latter. Also, certain approximations can be made for the flow of water and air which are not justified for water-oil flow. The theoretical and experimental work discussed in this paper is part of a study of the role of capillarity in the dynamic displacement of air by water. The expec- tation is that observations for the water-air system will lead to generalizations which are applicable to water-oil systems. THEORY Imbibition is defined as that process by which one fluid displaces another from a porous medium as a result of capillary forces only. Differential equations have been derived to describe the displacement of oil by water during imbibition, but these equations have not been solved.".' With certain assumptions, however, solutions are possible for water-air imbibition.

By Sean Gallagher

Study Design. A split-plot experimental design was used to evaluate the influence of posture, trunk angle, and rotational velocity on peak torque output and myoelectric activity during maximal trunk extension maneuvers. Objectives. To determine whether the kneeling posture alters extension torque capabilities in isometric and isokinetic exercises as compared with standing. Also, to ascertain whether recruitment of trunk muscles is modified by such a postural change. Summary of Background Data. Factors such as workplace geometry may force workers to adopt awkward or unusual postures in the performance of manual tasks. An understanding of the limitations placed on strength in unconventional working postures is crucial to the proper design of jobs. Methods. Twenty-one healthy male subjects (mean age = 36 years 7 SD) performed 12 trunk extension exertions in standing and kneeling postures. Isometric tests were performed at 22.5°. 45°, and 67.5° of trunk flexion. isokinetic tests were done at three velocities: 30°/sec, 60°/sec, and 90°/sec. Electromyographic data were collected from eight trunk muscles to assess muscle recruitment under each condition. A prior; orthogonal contrasts were specified for analysis of both torque and electromyographic data. Results. The kneeling posture was associated with a 15% decrease in peak torque output when contrasted with standing; however, no concomitant change in trunk muscle activity was evident. Trunk hyperflexion (isometric tests) and increasing rotational velocity (isokinetic tests) were associated with reduced torque in both postures. Trunk muscle activity was primarily affected by changes in trunk angle and velocity of contraction. Conclusions. A reduced extensor capability exists in the kneeling posture, despite equivalent trunk muscle activity. The similar activation patterns in both postures suggest that the strength deficit does not result from alterations in trunk muscle function. Rather, it may be the consequence of a reduced capability to rotate the pelvis in the kneeling posture, due to a disruption of the biornechanical linkage of the leg structures. [Key words: electromyography, isokinetic, isometric, low back pain, posture. strength1 Spine 1997;22:1864-1872

By Charles P. Williams

The determinations of the specific gravities of a number of samples of lead produced in Missouri, which form the subject of this note, were undertaken with the view of ascertaining if any approximation to the purity of such leads could be reached in this manner. The results would seem to indicate that, whatever value the method may have in the case of the crude and more impure

By J. W. Harden

AT our meeting in October last we saw in operation at Pittsburgh, the comparatively modern process of the utilization of small coal by washing, by an arrangement similar to that of Berard or Morrison. The small coal washed was that of an old pile, the refuse of the mining of the Pittsburgh bed, and which had long lain uncared for. Value was thereby restored to it when it was converted into a very good coke. This circumstance led to comments on the mountains of broken coal lying wasted, and in its present condition worse than useless, in the neighborhood of the mines of the Wyoming Valley, though they are not confined to that district. Some things were said condemning the course which produced it, some were left unsaid. Of a system that destroys one-half the coal-bed in producing the other half there can, however, be but one opinion. Schemes have been suggested for the utilization of present accumulations which, if successfully applied, would in so Far be beneficial. More than ordinary attention is now being given to the same subject in England ; a Mr. Barker has invented a means by which he amalgamates the "dust," too fine to burn in ordinary grates, with a composition he calls "diamond cement," producing blocks of coal said to resist water, both hot and cold, and which a smart blow will only break to pieces, not cause to crumble. But any scheme less than the one which will prevent the wasting of coal, which still goes on, though that involves the aban- donment of the breaker, will only be one of expediency; and the latter can only be done by the aid of the consumer. But the wasting of coal is not alone with the breaker; much is made in the mine. The cause is not far to seek ; the remedy is with capitalist and owner. Owners and consumers then are alike interested, and they have it in their power, in the one case, to mitigate, in the other, almost entirely to remove the cause of the evil. Of consumers there is one in every

By Douglas Pollock, John Organiscak

Water spray characteristics, including droplet size and velocity, airborne dust capture potential, and induced airflow quantity for various spray nozzle designs were evaluated to provide basic information for improving spray applications. Water droplet size and velocity characteristics were initially measured by a Phase Doppler Particle Analyzer (PDPA) for hollow cone, full cone, flat fan, and air atomized spray nozzles at similar operating parameters. Airflow inducement and dust capture experiments were also conducted under the same operating parameters to examine any salient features of the spray nozzle type, droplet characteristics, induced airflow, and airborne dust capture. Test results indicate that there are trade offs between airflow inducement and dust capture efficiency. A spray nozzle with a wider discharge angle was observed to induce more airflow, but at reduced dust capture efficiencies. Increasing spray nozzle fluid pressure(s) generally reduced water droplet sizes with concurrent increases in droplet velocity, airflow inducement, and airborne dust capture. Placing a three-sided barrier around the spray nozzles normally reduced spray air induction and increased dust capture efficiency. A direct relationship between airborne dust capture efficiency and spray input power normalized per unit of airflow induced was ob- served. This information can be utilized to improve the performance of water sprays for reducing airborne dust levels.

By Eckley B. Coxe

At the first meeting of the Institute, a paper was read by Mr. Rothwell, calling attention to the importance of at once considering the great waste of anthracite coal under the present system of mining and preparing that fuel for market, and a committee was appointed to examine and report upon the method now in use. About the time the committee were selected, a general resumption of work, after the long strike, took place in the coal regions, and the members of the committee have not in consequence had as much leisure to devote to the study of the question as its importance demands. In the present preliminary report we shall merely sketch out the . plan which we propose to pursue in our investigations, so that when our fellow-members are called upon to assist us in our work by furnishing statistics, etc., they may understand more clearly for what object our inquiries will be made. As one of the most practicable methods of obtaining the information requisite for an intelligent consideration of our subject, we propose to send, from time to time, to members and others interested in the mining of anthracite coal, printed sets of questions relating to points under consideration. We would here impress upon our fellow members the importance of filling up these papers as far as they can from their own knowledge. We would, of course, wish each question to be answered as fully as possible, but we do not expect every one to answer them all. One question well answered would be of more use to us than the whole paper filled up with answers, many of

By C. F. Hews

Trackless mining at the International Nickel Company of Canada, Limited by C. F. HEWS* (Visitor) An account is given of the evolution and advantages of trackless equipment in the underground operations of International Nickel's Ontario Division, with special reference to fill-method mining, development practice, sublevel caving, and induced block caving. Details of maintenance, environmental control, and operator training are also given.

By Carvalho A. Felipe de

The search for environmentally friendly and cost-effective methods for gold extraction has been undertaken in order to provide alternatives to the use of cyanide leaching in the gold industry. Among such alternative reagents is the combination of chloride and hypochlorite ions due to their oxidation of metallic gold and its complexation. Therefore, the current work aims at investigating gold leaching from an oxidized material by means of a solution comprising calcium hypochlorite and sodium chlorite. The sample used in the current research contained 66.1% Fe2O3, 20.4%SiO2, and 35.7 g/t of Au. In addition, XRD and SEM-EDS analysis revealed iron oxide, quartz and muscovite as the main crystalline phases in the sample. For comparison purposes, cyanidation of the oxidized material resulted in 90% gold extraction in 24 h. The reference conditions for the leaching tests with the chlorite-hypochlorite system were: particle size −37 μm, solid/liquid ratio of 10% (w/v), 10 g/L NaCl, 10 g/L Ca (OCl)2, pH 5–6, 3 h of leaching. The effects of the: (i) Ca(OCl)2 concentration, (ii) NaCl concentration, (iii) pHrange and (iv) the effect of pulp density in the extraction of gold were assessed. In addition, the stability of the hypochlorite solutions (OCl−) was investigated. The ideal concentrations of Ca(OCl)2 and NaCl were determined as 25 g/L and 15 g/L, respectively, whereas the optimal pH range was 4–6. Under these conditions, the final gold extraction reached approximately 84%. By varying the solids content of the pulp (10%, 20% and 30%), it was observed that the lower solids value resulted in greater gold extraction (84%). The degradation of the hypochlorite solution and the possible catalytic effect of the presence of the solid were evidenced. To sumup, in the experiment, high gold extractions were achieved in shorter periods of time (3 h), as compared to the cyanidation of the same sample. On the other hand, itwas necessary to use significant amounts of the reagent due to hypochlorite instability at the pH conditions recommended for high gold extractions.