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FEBRUARY GENERAL MEETING The January General Meeting of the Institute was held in Kelvin House, Johannesburg on 21st January, 1970, at 4.30 p.m. Mr V. C. Robinson (Vice-President) was in the Chair. There were also present eighteen Members, Messrs M. Barcza, A. R. C. Fowler, R. C. J. Goode, Prof J. de V. Lambrechts, Messrs T. C. A. Meyer, J. A. Nixon, V. C. Robinson and P. W. J. van Rensburg (Council Members), C. A. Border, D. F. H. Grave, S. D. Hill, A. F. Lee, W. L. le Roux, C. S. Macphail, D. L Starkey, S. G. Taussig, W. T. L Wayman and Dr A. Whillier. Three Associate Members, Dr M. I. Brittan, Messrs R. Hemp and M. J. Martinson. One Student, Mr R. P. W. Henrard. Two Visitors, Dr N. G. W. Cook and Mr J. B. Smith. Secretary, Mr D. C. Visser. Total present: Twenty-six. 1. OBITUARY The Vice-President: "It is my sad duty to announce the death of the following members of the Institute: Reginald Gordon McConnell, Member, who joined the Institute on 24th April, 1946 and passed away on 26th September, 1969. James Henry Moore, Member, who joined the Institute on 28th February, 1951 and passed away on 2nd January, 1970. As a mark of respect to the memory of the deceased and in sympathy with the bereaved I would ask those present to stand and observe a few moments silence." 2. MINUTES The Vice-President: "May we confirm the Minutes of the General Meetings held on 15th October and 19th November, 1969, as published in the December, 1969 issue of the Journal?" 3. MEMBERSHIP The Vice-President: "I have pleasure in announcing that the names of the under-mentioned candidates, having been published in accordance with By-Law 5.2.2, Council has elected them to membership of the Institute in the following grades: Member: Woodford Anson Gilbert. Associate Members: Michael John Harvey Tonking, Schalk Willem Vorster, Edward Alfred Cole, Johannes Godlieb Bosch. Graduate: Leonard Raymond Kilpatrick. Affiliates: Clive Frere Knight Pouiton, David Philip Ayliff, Kenneth Gillings, Edward Gilbert East. Students: Stirling Graham Low, Petrus Stephanus van der Merwe, Louis Johannes Fourie, Clive Maxwell Winterstein. MEMBERS TRANSFERRED TO A HIGHER GRADE From Associate Member to Member: Albert Arthur Hazell, Neville Martin Hayne. "I welcome the newly elected members to the Institute and congratulate the members who had been transferred to a higher grade. 4. GENERAL BUSINESS The Vice-President: "I wish to announce that except for the student prizes awarded at the November meeting, Council has decided to make no awards for 1969. Are there any further matters to raise under the heading of General? If not, we will proceed to the next item on the agenda which is the presentation of tonight's paper. 5. PAPER FOR PRESENTATION The Vice-President: "Professor Starfield may I call on you to deliver the paper entitled "A rapid method of calculating temperature increases along mine airways". After the presentation of the paper, the Vice-President said: The Vice-President: "Thank you very much, Professor Starfield. Gentlemen, I think that many of you here, who have to do with the design of mines in an age where costs and difficulties generally, are increasing at a rate which we find almost impossible to keep up with, I would agree with you that we are fortunate to have a band of people like Professor Starfield, and others who are dedicated to producing the tools, and methods which we need to sort out these problems. I am sure that you would agree with me, that the old rule-of-thumb methods are finished forever, that we can never go back to the methods which served us in the past, when we were close to the surface and had not met the conditions which we are meeting now, and which we are going to meet in an increasing degree in the future. It is to people like Professor Starfield, with these clear, completely logically described new methods, that we look for the solution of our problems in the future. I think the whole problem of layout of any mine, is one where you can reliably prognosticate what you are likely to find in a variety of circumstances to meet the wide range of things which must happen when you consider the costs in these modern operations. Thank you very much, Professor Starfield, for coming and giving us this paper. Thank you for making plain to me how these mathematical models of yours are used. I am sure that what you have said will be a very valuable addition to the archives of this Institution. Thank you very much, indeed, and Gentlemen, will you please show your appreciation in the normal way." (Applause). Professor J. de V. Lambrechts, Mr R. Hemp and Dr A. Whillier then contributed to the discussion. (These contributions will appear in a later issue of the Journal.) PAPERS OPEN FOR DISCUSSION The Vice-President: "Listed on the agenda are papers open for discussion. I would suggest that anyone wishing to contribute to these papers submit their contributions to the Secretary in writing." CONCLUSION The Vice-President: "I wish to thank members and visitors for their attendance, and now declare the meeting closed." The meeting closed at 5.30 p.m

By William M. Courtis

Since many accounts of Silver Islet Mine, in Lake Superior, have already been published, it is supposed that the members of the Institute are familiar with the location and character of the mine. To many, however, a more detailed account of the ore and manner of treatment will, perhaps, not be without interest. The extraordinary richness of Silver Islet ores, and the difficulty of obtaining correct assays, induced the company to erect smelting works of its own. Accordingly, ground was broken at Wyandotte; Mich., early in the spring of 1871, and the work was pressed on with indomitable energy by Captain E. B. Ward of Detroit, as president, and Mr. Thomas MacFarlane, the discoverer of Silver Islet, as superintendent of the works, so that by July 1st the works were so far completed that smelting could be commenced. The intention was to work Western ores with those from Lake Superior, since the latter contain but a small amount of lead. Hence the capacity of the works is much larger than is needed for the present yield of the mine. The planned process for treatment was smelt-

By O. Norman Lotter

The formulation and use of mixed collector suites in sulphide flotation can be traced back as far as 1957 with the work of Glembottskii and his co-workers in Moscow. The subject was reviewed by Lotter and Bradshaw in 2010, and proposed a synergy between ideally-selected different reagent types to deliver improved performance, in particular the in situ catalysis of a xanthate to dixanthogen by a dithiocarbamate. Correctly formulated for a particular application, an optimally arranged mixed collector suite delivers the following improvements to the flotation process: • An increase in the flotation kinetics • Improvement in coarse, or middling, particle recovery • Reduction in total dosage requirement • Best results are found from testing the ratios of the collectors. This is of critical importance. In all an optimally formulated mixed collector system usually delivers an increase in paymetals recovery of 1–4% absolute, with a gain in concentrate grade in the range 10–20% relative. In recent years, the addition of semi-conductor theory and associated electrochemistry has contributed significantly to this toolbox by way of identifying optimum domains of Eh and pH for the flotation of individual minerals. In the case of mixtures of minerals, this is where the mixed collector system delivers significant value by way of presenting a mixed set of collector radicals and dimers in a common Eh and pH domain for overall performance. This calls on a fundamental understanding of organic chemistry, mineralogy, semiconductor theory, and electrochemistry. Whereas the selection of grinding media type effectively influences the Eh, the pH can be easily controlled by pH modifiers. The theory of this system, and some industrial case studies, are discussed.

By John J. Sammarco

Mining, traditionally a low-tech industry, is now utilizing surprisingly complex programmable electronic (PE) systems. The functional safety of PE-based mining systems is an international issue and concern. From 1995 to 2001, there were 11 PE-related mining incidents reported in the U.S. and 71 PE-related mining incidents reported in Australia. These incidents are due, in part, to unprecedented levels of system complexity. The National Institute for Occupational Safety and Health (NIOSH) is addressing this issue of system complexity by conducting research to develop a quantitative complexity assessment methodology based on Normal Accident Theory (NAT). The methodology models the behavioral interactive complexity at the level of system requirements. A graph-theoretical approach is used for creating quantitative metrics from Software Cost Reduction (SCR) dependency graphs. This complexity assessment methodology will help realize simpler, safer systems that will be easier to validate and verify. The methodology will benefit mining and other industries as well.

By T. Egleston

During the last winter we have been actively engaged in the School of Mines in search for boracic acid. This has been owing to the fact that Mr. M. W. Iles, assistant in the qualitative laboratory, has discovered a test for that substance which makes its discovery exceedingly simple instead of being, as previously, very difficult. It consists in powdering the mineral, calcining it, then moistening it with sulphuric acid, and heating on a platinum wire until the sulphuric acid is expelled. It is then moistened with glycerin and made to take fire. If boracic acid is present it infallibly gives a green flame. It is not at all surprising, under such circumstances, the test being so easy, that boracic acid has been found by the students in a great many cases where its presence was not previously suspected, and in some where its detection was previously too difficult to warrant looking for it. We were not prepared, however, for its discovery in Lake Superior iron ores, and were disposed at first to think that a mistake had been made. After, however, it had been frequently reported in these ores it was considered worth while

The Institute was founded in 1894 as the Chemical and Metallurgical Society of South Africa. In 1904 it was reconstituted as the Chemical Metallurgical and Mining Society of South Africa and in 1956 it became the South African Institute of Mining and Metallurgy. The objects of the Institute are to advance the science and practice of mining and metallurgy, to afford opportunities for the interchange and recording of knowledge of mining and metallurgy and to ensure high standards of professional conduct and competence. Membership benefits include monthly issues of the Journal of the Institute, monthly General Meetings at which papers are read, symposia, excursions to mining and industrial concerns and the use of club facilities at Kelvin House. Technical journals received on an exchange basis are available to members at the Johannesburg Public Library. The current membership of the Institute is over 1,600. Membership applications are accepted from suitably qualified persons and the requirements for entrance to the various grades of membership are summarised below. Fellows shall not be less than 30 years of age, shall be university graduates in pure or applied science or shall produce evidence to the satisfaction of the Council that they have successfully completed a co-ordinated course of study in pure or applied science of at least three years' duration at an approved university or institution deemed by the Council to be of equivalent status. Members shall have been employed in senior technical positions in important mining or metallurgical undertakings for at least five years or they shall have practised as mining or metallurgical consultants for at least five years. They shall be practising their profession at the time of application. Entrance fee R10.00, Annual subscription RI7.00. Letters of designation: F.S.A.I.M.M. Members shall be not less than 25 years of age and shall be university graduates in pure or applied science, or shall have successfully completed co-ordinated courses of study in pure or applied science of at least three years' duration. They shall have been engaged in work of an approved technical character in the mining or metallurgical industries, of which not less than two years shall have been in positions of responsibility. A candidate shall be practising his profession at the time of his application. Entrance fee R8.00, Annual subscription RI5.00. Letters of designation: M.S.A.I.M.M. Associates shall be not less than twenty-five years of age, and shall have been engaged in positions of responsibility in, or associated with, the mining or metallurgical industries for periods of not less than three years. If, however, the candidate for admission to the higher grade of Associate, is at the time of his application, already a Student, he need satisfy the Council only that he is, at the time of his application, engaged in a position of responsibility in or associated with the mining or metallurgical industries. In all cases the applicants shall satisfy the Council that they are fit and proper persons to become Associates. Entrance fee R8.00, Annual subscription R15.00. Graduates shall be not less than 21 years of age and shall be university graduates in pure or applied science, or have completed co-ordinated courses of study in pure or applied science of at least three years' duration at an approved university or institution. They shall not remain Graduate members after attaining the age of 30 years without the permission of Council. Entrance fee R2.00, Annual subscription R10.00. Students shall be persons not less than 18 years of age who are being educated or trained in a manner approved by the Council, to occupy a technical position in or associated with the mining or metallurgical industries and who, furthermore, shall not have attained the qualification required for a higher grade of membership. They may remain Students until they have obtained the necessary qualifications for transfer to a higher grade of membership, but not after the end of the Institute's financial year in which they attain the age of 28 (twenty-eight) years. They shall then transfer to a higher grade to retain membership of the Institute. The Council may relax the provisions of this clause in such cases as it considers appropriate. Entrance fee nil; Annual subscription R3.00. Other. The Council has the power to elect to the grade of Fellow or Member, candidates who may not fulfil all the requirements for entrance to these grades but whose status, professional achievements and practical experience in mining or metallurgy justify such election. Applications. Requests for membership application forms should be addressed on the attached form to the Secretary, South African Institute of Mining and Metallurgy, P.O. Box 61019, Marshalltown, Transvaal.

By Jun Enriquez

Kennecott Utah Copper aims to extend anode furnace campaigns to more than three years. As part of that goal improvements are sought on anode-furnace tuyere-area refractory performance. Kennecott and Praxair developed high pressure nitrogen refining for the Oxidation Stage which shortened anode furnace fire refining cycles by up to two hours per cycle. Future developments include optimizing the Reduction Stage’s steam-gas reforming and achieving coherent jet tuyereless refining.

By Frederick Prime

TO an association like the one before which I read this paper, few questions can be more important and constantly recurring than the following, viz.: "What economy can be effected in the manufacture of American iron?" And it is the one with which I purpose to deal in this paper ; premising, however, that my object is merely to indicate the direction in which an answer should be sought for, rather than to give it myself. This subject may be divided into two parts, "Economy in the production of pig-iron," and "Economy in the manufacture of wrought-iron ;" but it is to the former alone that I shall confine myself this evening.

By R. Karl Zipf

Multiple seam mining interactions caused by full extraction mining, whether due to undermining or overmining, frequently involve tensile failure of the affected mine roof. The adverse ground control conditions may prevent mining for both safety and economic reasons. Prior researchers have identified the geometric, geologic and mining factors controlling multiple seam mining interactions. This numerical study examines the mechanics of these interactions using a modeling procedure that 1) incorporates the essential constitutive behavior of the rock such as strain-softening of the intact rock and shear and tensile failure along bedding planes and 2) captures the geologic variability of the rock especially the layering of weak and strong rocks and weak bedding planes. Specifically, the numerical study considered the effect of vertical stress, interburden thickness, and the immediate roof quality of the affected seam in both undermining and overmining situations. The models show that for overburden-to-interburden thickness (OB/IB) ratios of less than 5, interactions do not occur, and that for OB/IB more than 50, extreme interaction is a certainty. In between, the possibility of an interaction was found to depend on gob width-to-interburden thickness ratio, site specific geology and horizontal stress to rock strength ratio in addition to the OB/IB ratio. The models also showed that horizontal stress was profoundly altered well above or below a full extraction area and that these changes are likely to influence the success or failure of multiple seam mining. The role of horizontal stress in multiple seam mining interactions has received little attention in prior investigations. Four factors control the mechanics of multiple seam mining interactions: 1. vertical stress concentration 2. horizontal stress concentration 3. stress re-direction 4. bedding plane slip bands A combination of vertical and horizontal stress increase and high stress gradients in the vicinity of full extraction areas re-orients principal stresses into a very unfavorable direction. This seemingly small stress re-orientation has a profound adverse effect on bedded rock.

The Registrar has requested us to publish the following notices: COUNCIL'S POLICY REGARDING LATE APPLICATIONS IN TERMS OF SECTION 18(4) (b) OF THE PROFESSIONAL ENGINEERS' ACT, 1968 (ACT NO. 81 OF 1968) Laat aansoeke om registrasie as Professionele Ingenieurs Die Suid-Afrikaanse Raad vir Professionele Ingenieurs (SARPI) vestig die aandag daarop dat daar 'n mistasting bestaan oor die vraag of 'n persoon sonder erkende ingenieurskwalifikasies wat nie in 1969 aansoek gedoen het om registrasie as professionele ingenieur nie, nie meer aansoek mag doen nie. Diegene wat voor 14 Februarie 1969 minstens 3 jaar aanvaarbare ingenieurswerk gedoen het kan nog oorweeg word. Die werk moet egter voldoen aan die standaarde deur SARPI neergele: dit Suid-Afrikaanse Road vir Professionele Ingenieurs DIE WET OP PROFESSIONELE INGENIEURS, 1968 (WET NO. 81 VAN 1968): JAARGELD: 1972/73 BOEKJAAR Kragtens die bepalings van Artikel 18(9) (b) van die Wet verval die Registrasie van 'n persoon wat as 'n ingenieur of ingenieur-in-opleiding geregistreer is as sodanige persoon versuim om die voorgeskrewe jaargeld binne ses maande nadat dit betaalbaar word, te betaal. Aandag word ook vriendelik daarop gevestig dat persone wat kragtens Artikel 18(4) (b) van die Wet geregistreer is (dit wil se persone wat nie oor 'n erkende akademiese kwalifikasie beskik nie) en wat toelaat dat hulle registrasie verval, moontlik nie weer vir registrasie in aanmerking sal kan kom nie. Vir persone in hierdie kategorie is dit dus van kardinale belang om toe te sien dat hulle jaargeld binne die voorgeskrewe tydperk betaal word.

By William Gleason

The evolution of technology has made the world a more connected place. It continues to change the way we power our homes and vehicles and is leading to a future that seems to be limitless. Limitless as long as we can continue to supply the minerals necessary for technology to produce better iPhones, more efficient electric cars, better wind turbines and sophisticated national defense systems. These minerals, dubbed critical minerals, have surged in importance in every corner of the world and, on Aug. 3-4, they were topic of conversation at the Critical Minerals 2014 conference in Denver, CO. The conference, hosted by SME and the Australasian Institute of Mining and Metallurgy (AusIMM), looked at critical minerals from every angle, from where they are found to what the future might be. Among the minerals that have been called critical are rare earths, a collection of 17 minerals that have become increasingly important as technology continues to advance in everything from communications to energy to national defense. Leading off the conference, David Abraham, senior fellow at the Institute for Analysis of Global Security, explained that, like many people, he is relatively new to rare earths. Unlike most people, though, Abraham developed more than a passing interest in the minerals and has since travelled the world to understand the role of rare earths ? where they are found, how they are mined, how they get to market and, eventually, what applications they are used in. Following his travels, he said he returned concerned about the sector and how the industry will keep up with the demand that only seems to be growing in the modern world. And, Abraham noted, that it is not just the developed world that is driving demand. It stretches even to places like Indonesia, where the average annual income is about $3,000/year. Yet, the nation is one of the most active places in the world for social media with a population that is wired in with all kinds of electronics. The problem facing the sector is, and has been for a long time, and especially since 2010, supply of the minerals. At one time, China produced about 98 percent of the world?s supply and controlled the sector completely. In 2010, as the world began to demand more rare earths and develop other sources, China announced an export ban on rare earths. This changed the game completely, from the production lines all the way to the floor of the U.S. Congress.

By Youn-Bae Kang

In order to overcome weak points of steel for its engineering applications, in particular, for environmentally benign, energy-efficient, lightweight engineering systems, a number of new steels have been proposed, especially to improve strength-to-weight ratio (specific strength). Mass production of these steels, however, has encountered a serious roadblock particularly in the steel refining and casting processes. This is because their chemistries and cleanliness requirements are vastly different from those of the conventional steels, and thus an incremental improvement of the prevailing process technologies is found hard to meet the requirements. In this study, a new process is proposed, which employs inert gas bubbles in the shroud nozzle, liquid steel drops in the degassing chamber, and the siphon transport for continuous casting. The proposed process which integrates the final refining and cleaning steps prior to casting is expected to be a technologically disruptive innovation on the conventional counterpart. The effectiveness of the individual steps is discussed with experimental results.

By Elaine T. Cullen

Miners, like many skilled blue-collar workers, are not traditional learners. They have not always been successful in classroom-type settings, preferring to learn on the job in a hands-on environment. U.S. law requires that miners have a minimum of 8 hours of safety training annually, plus 40 hours for underground miners and 24 hours for surface miners when they enter the industry. However, miners rarely view this training time positively. In fact, it has been called “safety jail” by many, who regard it as a time to get a little extra sleep While mining has become far safer in the past 100 years, it is still a dangerous occupation. The Office for Mine Safety and Health Research, a part of the National Institute for Occupational Safety and Health (NIOSH), has funded a project for the past 4 years to address this challenge. The purpose of the research was to find a way to develop effective safety training for these people. Miners are born story tellers. They share “near miss” stories, stories about master miners they have known, and stories about how things used to be. These stories not only pass along information about what will happen if a miner fails to respect the mining environment, they also instruct listeners in the culture of mining and the values that it embraces. Stories, it seems, are a way to get safety messages across to miners, especially inexperienced ones, and using older, wiser miners in these stories is an obvious choice. This paper will discuss how a series of training videos was developed, how “master miners” and story lines were chosen, and how the resulting videos have been received in the mining industry.

By R. Simon

The sources of energy dissipation for concentrated loadings on rock are considered in an attempt to account for the experimentally measured magnitude of the work required to break out a unit volume of rock from the free surface of an essentially semi-infinite medium. It is concluded that most of this work probably represents the elastic strain energy developed by the loading in a much larger volume of rock beneath the loaded region than the volume of the rock fragment broken out to the side of the loaded region. This strain energy is largely dissipated in the form of stress waves generated by the high rate of unloading produced by the propagating cracks. The energies associated with the formation of the new surfaces of the cracks and with the stress waves generated directly by the loading process are computed to be negligibly small. Possibilities for improving the utilization of energy to drill rod. subject to the geometrical limitations imposed by down-hole operation, are discussed. It is pointed out that any such possible improvements would probably have to be differential ones, since each rock configuration of more favorabIe loading geometry that can be created down the hole is accompanied by a complementary configuration of less favorable loading geometry. INTRODUCTION Dislodging each cubic inch of rock from the bottom of the hole by the action of a bit requires the expenditure of an amount of energy that varies from approximately 5,000 in.-lb to approximately 100,000 in.-lb, depending on the hardness of the rock, or, more technically, upon its fragmentation strength.1 In this paper we will discuss (I) why the energy expended in drilling is so large, (2) what happens to this energy upon completion of the drilling process, and (3) what are the possibilities for reducing the magnitude of the energy required to drill rock. DETERMINATION OF ROCK DRILLING ENERGY The volume of rock removed per unit time from the bottom of a hole of diameter D is evidently (7/4)D2R, where R is the rate of penetration of the bit. If P is the rate at which work is done by the bit on the rock at the bottom of the hole, the energy required to break out a unit volume of rock is given by: Ev =(4/p) P/D2R............(i) For rotary drilling, of either the rolling-cone or drag-bit varicty, P = 2pLN, where L is the torque resistance to rotation at the bottom of the hole and N is the rate of rotation of the bit. L is essentially the same as the torque measured at the rotary table only when drilling in shallow holes. The energies expended in rotating the drill string against the frictional resistance of the walls of the hole and and against the viscous drag of the drilling fluid are extraneous to the subject under consideration, although these may be much greater in magnitude than E, when drilling in a deep hole. For percussion drilling, P = fE where f is the percussion frequency and E is the work done on the rock per impact. The latter quantity can be both computed and measured for a percussion drilling machine. 2 (Under satisfactory drilling conditions, defined in terms of ranges of numerical values of certain dimensionless parameters, E is only 30 to 50 per cent less than the impact energy of the striker.2) Alternatively, E, may be measured directly by dropping chisels shaped like bit edges, backed by rigid weights, onto the surfaces of laboratory rock samples of effectively semi-infinite extent. Under these circumstances, essentially all of the impact energy is converted to work done on the rock, and the relationships among volume of rock broken out, chisel shape, impact energy and indexing distances can be obtained.3 The values of the energy required to break out a unit volume of rock under favorable circumstances are substantially in agreement for rotary drilling, percussion drilling and drop testing at atmospheric pressure. The energy per unit volume is a quantity of the order of magnitude of roughly twice the com-pressive strength of the rock as measured by a uniaxial loading test. The phrase "order of magnitude" in this paper means from about 1/3 as much to 3 times as much; i.e., the energy per unit volume may range from roughly the same up to several times

By B. P. Spigarelli

To meet the growing need for CO2 capture and storage technology, Michigan Technological University is researching CO2 capture and storage using carbonate solutions. The objective of the present study was to increase the absorption rate of CO2 into the carbonate solution without reducing the absorption capacity of the solution. This approach used a polypropylene glycol methyl ether (PPGME) as a surfactant to chemically alter the gas bubble size. Experiments were conducted to study the absorption rate of CO2 at varying surfactant concentrations of 0, 0.12, 0.24, 0.36 and 0.48 g/L. Results showed that as the concentration of surfactant increased in solution, the absorption rate also increased. The CO2 absorption rate increased from 3.45 mmol/min CO2 at 0 g/L PPGME to 3.92 mmol/min CO2 at 0.48 g/L PPGME. This amounted to a 14% increase in the CO2 absorption rate with no decrease in absorption capacity of the solution.

By J. S. Stachulak, G. H. Schnakenberg

The objective of the Diesel Emissions Evaluation Program (DEEP)-sponsored project at Inco's Stobie mine was to conduct a long term field evaluation of diesel particulate filter (DPF) systems available to the underground mining industry. Some of the major issues studied were criteria for selecting the filter media, means of DPF regeneration, efficiency of DPF systems and the occurrence of unwanted secondary emissions, and reliability and durability of DPF systems. Nine state-of-the-art diesel particulate matter (DPM) filtration systems have been retrofitted to heavy-duty and light-duty vehicles and have been subjected to extensive long-term in-mine evaluation. Periodic efficiency tests were conducted at various stages of the study (2001, 2002 and 2004) to establish in-use efficiencies and durability of the tested DPF systems. The results were used to assess the effects of the filter systems on the concentrations of particulate matter, nitric oxide, nitrogen dioxide and carbon monoxide in the vehicle exhaust. The variety of filtration systems and regeneration concepts used in this study offered the opportunity to investigate their advantages and disadvantages. This paper also offers a review of selected experiences with the installation and operation of the DPF systems on underground mining vehicles at the Inco Stobie Mine.

By T. Sterry Hunt

THE essential principle of this new process, now in operation in Chili and in North Carolina, for the extraction of copper from its ores, is the dissolving of the oxides of copper by a hot solution of protochloride of iron and common salt. In the action which takes place, the protochloride of iron is converted into peroxide, while the oxides of copper are changed into protochloride and dichloride, the latter of which, though insoluble in water, is readily soluble in a hot strong brine. From the solution thus obtained, metallic iron throws down the copper in a metallic state, regenerating the protochloride of iron; which is then ready for the treatment of a fresh portion of oxidized copper ore. In the case of slimy ores, the contact of the bath with the ore is effected by agitation in tubs; but when the ores are granular, lixiviation in large vats is equally efficient and simpler. The hot solutions, charged with chlorides of copper, are digested in tanks with scrap-iron, or better, are made to flow through covered channels containing the scrap-iron, and in their passage lose the whole of their copper; the reaction at the same time evolving so much heat as to keep up the temperature of the liquid. In order to prevent a certain loss of chlorine, which otherwise takes place from the production of some basic ferric chloride in the reaction between the ferrous chloride and the oxides of copper (both protoxide and dinoxide being generally present in calcined ores), a portion of sulphurous fumes from the roasting is made to pass through the regenerated bath before adding it to fresh ore. This has hitherto been effected by injection, with the aid of a jet of steam.

By C. Gatlin, N. E. Garner

Results of impulsive wedge penetration tests on two synthetic, plastically deforming rocks are presented. Basic data obtained were force-time, displacement-time, and force-displacement curves for the impacts, plus the crater geometry. Wedge geometry and blow frequency were varied over a considerable range. The synthetic rocks consisted of wax-sand mixtures; two waxes of diflerent ductilities were used to provide variable "rock" characteristics. Conventional triaxial tests showed that these synthetic rocks exhibited force-deformation curves and Mohr envelopes quite similar to real rocks, except that strengths were much lower. Measured forces from static penetration tests agreed closely with theoretical values; however, dynamic force values were much higher than the static. These latter disparities are attributed to the viscous nature of the waxes. Thus the utility of these or similar rock models must depend on the scaling of rock viscosity, which is as yet unknown for impulsive loadings at elevated stress states. It appears, however, that some macroscopic, static phenomena may be studied with wax-sand rock models. INTRODUCTION The resistance of solid materials to indentation or perforation by projectiles or other penetrators has been studied by workers in many areas. Despite these efforts no universally accepted laws or formulas are available for describing experimental observations. In the metals field the force-deformation behavior of impacting bodies is often analyzed by the Hertz law for elastic collisions, the Meyer law if plastic deformations occur, or some combination of both.' The similarities of these expressions to empirical drilling formulas of the oil industry are apparent. Beginning with the basic contributions of Simon and co-workers at Battelle,' a number of experimental papers concerning the reaction of rocks to vertical impact have appeared in the U. S. mining and petroleum literature.'-' Most published data have, to date, been obtained at atmospheric pressure, although some early high pressure information was reported by Payne and Chippendale.8 Maurer" has recently utilized available brittle impact data to develop a drilling rate equation based on the experimentally observed proportionality between crater volume and blow energy. His result agreed with earlier efforts by both Somerton, who used dimensional analysis, and Outmans, who used plasticity theory. It has long been known that rocks exhibit different modes of failure depending on the state of stress. The literature in this area is considerable; however, papers by Bredthauer, Handin and Hager,13 nd Robinson", are adequate to illustrate the point. Since rocks flow plastically at certain triaxial stress conditions, the mathematical theory of plasticity has been used to analyze the rock drilling problem. Cheatham'" has altered the wedge identation solution of Randtl to rocks, and has developed useful equations for penetrator forces under a variety of conditions. Outmans" has utilized Hill's solution in a similar manner to develop a drilling rate equation. Both Cheatham and Outmans used the linear Mohr-Coulomb rule to relate rock strength and confining pressure. The actual stress at the hole bottom is not easily ascertained, although photoelastic studies by Galle and Wil-hoit," plus the analytical treatment of Cheatham and wilhoiti8 provide some insight. Consequently it is not clear to what extent the highly idealized rheological model of a perfectly plastic solid can be realistically applied to the rock drilling problem. This paper is the first report on a long range experimental study of crater formation in rocks at elevated stress states. The data presented here are from the first phase of the project. Data obtained from impulsive wedge impacts on two synthetic, plastically deforming rocks are presented. MODEL ROCKS Geologists have long been faced with modelling the behavior of the earth and, as a consequence, have studied scaling problems in some detail.' In general, their main problem is handling the wide disparity between laboratory and geologic time. In our studies the time effects (blow velocity or rate of loading, blow duration, etc.) were essentiafly the same for both. model and prototype, as were were geometry and tooth penetration. Thus application of available scaling laws suggests that Similarity is obtained if the stress-strain curves of model and prototype are similar." For this reason Hubbert and Willis''

A party of some 60 members of the Institute were welcomed at the Union Junction Works of Scaw Metals Limited on Thursday, 23rd January for a morning visit. Dr J. M. Bereza, the metallurgical Director, gave an informative introductory talk to the assembled visitors, which briefly covered the major activities of the Company. This was followed by refreshments, and the visitors were then allocated to 12 guides for the conducted tour of the Works. The progress of the Company is an impressive saga of the development of heavy industry in this country linked primarily to the expanding mining industry. Many other outlets are now available for Scaw products and the rapidly advancing techniques developed by their own chemists as well as the processes made available from overseas associates indicates the forward looking attitude of the Company. The visitors were impressed by the modern laboratory services, closely linked to rigid quality control, resulting in a high standard of final products. The most fascinating section to many of the visitors was the continuous casting machines and rolling mills recently installed, although the most lucrative section is the large steel foundry. After the tour the parties gathered in a marquee tent for liquid refreshments, followed by a lavish luncheon in the canteen. The visitors were officially welcomed by Mr Richard Boustred, the Deputy Managing Director, and Mr V. C. Robinson replied, thanking the Company on behalf of the South African Institute of Mining and Metallurgy. Arrangements were made for golf in the afternoon at the Germiston Golf Club for those who wished to play. A.E.G.

By H. T. Kennedy, S. G. Dardaganian, J. L. Clanton

This paper presents equilibrium ratios measured on oil and gas samples taken from the Kelly-Snyder field at the reservoir temperature of 128°F. From these data smoothed curves were constructed for the reservoir fluid up to the bubble-point, 1,874 psia. A material balance calculation, based on the use of equilibrium ratios instead of the usual solubility and shrinkage meayr~rements is made on the field and compared to the con\.entional method. DETERMINATION OF EQUILIBRIUM RATIOS The equilibrium ratios, or K values were obtained by recombining separator samples of oil and gas taken when the reservoir was above its bubble point, and thus represented the reservoir fluid before any change had occurred due to the evolution of gas. The well sampled had a gas-oil ratio of 617 cu ft of high pressure sepalator gas per barrel of separator oil. and a bottom-hole temperature of 128°F. Samples were brought to equilibrium by agitating for 24 hours in a thermostat, maintained at the proper temperature within 0.2ºF, mercury being added when necessary to maintain the pressure constant. Samples of oil and gas were then taken by constant pressure displacement, and analyzed by low temperature frac-tionation. Equilibrium ratios were determined at 128°F and 500, 800, 1,000 and 1,400 psig. At the latter pressure, there were indications that the gas samples were contaminated with small quantities of oil, and only data taken at the first three pressures were included in Fig. I. This figure has been extended to higher and lower pressures by the use of the Fluor charts for 3,000 psi convergence pressure, on which the experimental points fit well. MATERIAL BALANCE EQUATIONS The possible errors involved in conventional material balance equations have been analyzed by Muskat1. Where the errors occur in field measurements, or in obtaining effective averages from variables such as gas-oil ratio and pressure, they will evidently be involved in any attempt to estimate the content of the reservoir. On the other hand, substantial errors may be introduced in conventional material balance calculations by: (1) the neglect of the amount of oil dissolved in gas at high pressures and temperatures in the reservoir, but which condenses under separator conditions; (2) the assumption that the separation of oil and gas in the reservoir may be duplicated by a differential liberation in the