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By F. G. Clapp

IT is to be hoped that no casual reader will erroneously refer to the latest publication' of the Division of Public Relations of the American Petroleum Institute, as being "Petroleum Facts and Fancies." The facts are so faithfully derived and the figures are so authentically sponsored by the highest sources that no person can read this valuable volume (287 pages and numerous tables) without being convinced that every- thing therein set forth is "the truth and nothing but the truth." Yet, having read the volume from the perspective of the world's petroleum industry and with a critical attitude that comes from years of study of the subjects discussed, I find myself tempted to cogitate and to envisage a few of the fancies that come to mind as a fitting sequel.

Jan 1, 1929

By Kexin Jiao, Zhijia Zhang, Jianliang Zhang, Zhengjian Liu

Carburization behavior of molten iron in blast furnace is an essential part of BF long campaign technology. Maintaining carbon content stable is an important prerequisite to ensure the high production of the blast furnace. In this paper, the important aspects of the research progress which mainly including the study of iron carburization at the upper and the lower parts of the blast furnace was reviewed. Indirect carburizing is the main way at the top of the blast furnace. The content of carbon in metallic iron increases with the reducibility of iron ore improved. The thermodynamics and kinetics conditions are good for carburization reaction to take place at the bottom of the blast furnace. Carbon content of molten iron increased by coke carburizing. Meanwhile, the drawbacks of the existing literature on iron carburization behavior were analyzed and new research directions of iron carburization were proposed in the future.

Jan 1, 2015

By S N. Donaldson, B L. Hollis, K Wynn, L Potts, M Evans

A real-time load-haul-dump (LHD) dispatch optimisation tool has been deployed at Panel Cave 1 and Panel Cave 2 at Newcrest’s Cadia Valley Operations. The tool, known as ORB, is the first known successful implementation of an optimisation-based, autonomous, real-time dispatch tool, custombuilt for underground mining operations. ORB can co-ordinate the optimal dispatch of LHD’s in a block cave to achieve a range of objectives while adhering to draw compliance and geotechnical constraints. It is an example of highly automated short-term interval control. This paper starts by outlining the pre-existing business planning process, detailing the simple logic that produced the daily draw order. Next, the motivations for a real-time dispatch tool are presented, drawing comparison to the limitations in existing planning processes and how these can be overcome through an optimisation-based, autonomous, real-time dispatch tool. Subsequently, the paper details the Ratio Bogging Draw Strategy, through which tonnes targets are expressed continuously on draw bells or draw points as a ratio of total cumulative cave draw. This signifies artificial planning boundaries are removed and that draw targets are linked within a cave; such that tonnes are unlocked by bogging other parts of the cave, instead of as a function of time. This creates incentive within the target mechanism for fixing and bogging struggling draw areas whilst allowing uncapped progress if all draw targets are progressing within compliance. Furthermore, the optimisation tool developed is outlined, including the data it uses and the objectives it optimises. Finally, detail on the improvements to operations the implementation of this tool has brought, and the business process change it has facilitated are presented using Newcrest’s Cadia Valley Operations as a case study.

Mar 15, 2021

By Yogesh Narula

Nevis Bluff Landslide - On September 17” 2000, a rockfall measuring lO,OOOm3 at Nevis Bluff, New Zealand, triggered a loday emergency. It ended when a hazardous column of rock that towered over State Highway 6 was finally shattered. The operation called for unusual and unique solutions using aerial bombing and inverted blasting techniques, not known to have been attempted before under these conditions, anywhere in the world.

Jan 1, 2002

By Dr. Tristan Worsey, Dr. Jhon Silva-Castro

Confinement is an important aspect of blasting. Reducing and increasing confinement can determine whether a blast design performs properly. Over-confined shots usually have poor fragmentation, higher vibrations, and stemming ejection, and unconfined shots usually have a lot of air blast and fly rock. When talking about confinement in blasting, static confinement conditions are typically referenced. Static confinement conditions are ruled by free faces, shot muck, burden, spacing, stemming, hole depth, toe, etc. All these conditions exist in a static state. Static confinement conditions are generally analyzed before the shot takes place, but once the shot starts, the conditions will change according to the sequence and delay of the shot. Once the shot starts, Dynamic confinement takes place. For the authors, Dynamic confinement is the confinement conditions that exist for the charge when it fires and should account not only for the variables included for the static confinement but also for the time and sequence of the shot. The paper explores the theory of dynamic confinement and its role in influencing blast performance. Time and sequence are the main influencers of dynamic confinement and will be the focus of the paper. How to generate the appropriate timing based on blast design, dynamic confinement, static confinement, and geology will also be discussed.

Jan 21, 2025

It was Harold McMillan, Prime Minister of England 30 years ago, who used the phrase "The Wind of Change" to describe political events in Africa in his day. So well did this phrase capture the spirit of the time that it echoed around the world, and the echo has never stopped. Change is the constant factor in the society in which we live and everyone of us has had experience of the effect which it has had on our professional and personal lives.Change will not stop, it will continue at an increasing rate and the questions we must answer are how do we prepare ourselves to meet the challenge of future change and how do we take advantage of the opportunities which it will bring?It is these questions which I wish to discuss in this address.There is nothing new about change in the mineral industry, it has been happening for thousands of years and it will continue as long as civilisation exists on earth. One type of change is economic and we are all aware of the rises and falls which occur in the prices of metals and minerals (Figure 1). When these have happened in an orderly manner, and could be predicted and planned for, it has been possible to take advantage of the benefits and minimise ill-effects, but when they were sudden and precipitate, and could not be predicted, the consequences were serious. The extreme example, of course, was the oil price shock of the 1970s which had such disastrous effects on industry and society.Other types of change are social, cultural and political. They have all been important in recent years and will continue to be so in the future.But it is technological change which may well be the most important because its effects are profound and irreversible, and alter irrevocably the way in which we live. So in discussing the mineral industry in a changing world I will talk specifically about technological change.

Jan 1, 1989

By M Taylor

The Project Specification and Technical Requirements documents associated with several recent large road tunnel projects within Australia have specified the application of AS/IEC 61508 – FunctionalSafety of Electrical/Electronic/Programmable Electronic Safety Related Systems at very high performance levels for the various control and fire life safety systems associated with such facilities.This paper seeks to explore the implications of referencing this standard within the road tunnel services context in terms of practicality, complexity and cost, whilst providing some examples of how a high safety integrity level (SIL) level can theoretically be achieved given current hardware availability.

Mar 8, 2011

By B. De Paoli

At Pietrafitta, between Assisi and Perugia, ENEL (Italian National Electricity Authority) has for some time been managing a power-station operated with lignite, mined from an open mine on the way to exhaustion. A new plant is under construction which is located in the mine that was filled with tailings, mainly clays, sandy silts, lignite and ashes produced by the power-station. The soil profile is shown in Fig. 1: the thickness of the made ground is around 27 m. The foundation of the new power-station is on 320 t piles, 1.20 m diameter, embedded in the cohesive base formation at a depth of 57.5 m. 2,350 piles will be constructed for a total length of 125 km. It is therefore one of the largest pile sites at present in operation in Italy. [ ]

Jan 1, 1994

By Harper F

This paper outlines the authors' views of the methodologies which can be employed to value mineral properties at different stages of development for the purposes of project financing, mergers and public floats. This paper discusses the key issues in Discounted Cash Flow (DCF) analysis including the importance of data verification and the shortcomings in DCF analysis. Stockmarket valuation measures and valuation methodology for exploration and pre development projects are examined through examples and pitfalls are identified. The use of valuations in corporate transactions and their strategic value is also discussed.

Jan 1, 1994

By Jiachen Wang, Nan Wang, Yang Li

The energy structure and consumption ratio in China determine the practical demand for the collaborative mining of coal and co-associated resources. The multi-layer mining of coal, uranium, coalbed methane, and oil and gas co-associated resources, represented by the Ordos Basin, Junggar Basin, and Tarim Basin, faces numerous challenges. Additionally, coal has been found to coexist with various mineral resources in 33 coal-bearing basins worldwide. The scientific issues related to the multi-layer development of coal related co-associated resources urgently need to be addressed. This paper discusses the unique challenges and potential solutions in the multi-layer development of coal-related co-associated resources. The challenges include large extraction space, high mining intensity, intense overburden movement, rapid surface subsidence, and severe overburden damage due to repeated mining disturbances. Proposed solutions include the establishment of a correlation mechanism between multi-layer mining and the carrying capacity of the overburden environment, analysis of the impact characteristics of multiple field couplings, and exploration of their superposition evolution laws. The paper also proposes the development of a comprehensive evaluation and prediction system for overburden environmental capacity loss, a global sensitivity analysis model for overburden environmental capacity, and an intelligent identification and early warning system based on multi-source information fusion. These solutions aim to achieve scientific and precise mining with minimal overburden environmental capacity loss. And the multi-layer development of coal-related co-associated resources is a complex task that requires a multidisciplinary approach and innovative solutions, and further research is needed to validate these strategies and explore new methods and technologies for efficient and sustainable extraction.

Jun 25, 2024

By Gareth Barnes

Traditional approach to improvement is driven by good ideas from good people, but whilst the business case may sound good, when the project is complete, we often have not delivered on expectations.  Why not? The best way to successfully predict the outcomes of an improvement effort in a complex process is through using statistical modelling, which considers the impact of uncertainty within interacting processes.  Applying Theory of Constraints in a model helps leaders to quickly determine: Where the constraining process(es) is/are Where improvements will add the most value How much improvement should be targeted - before the next constraint takes over The confidence level of achieving a given target, which gives us a clear pathway to improvement. This paper presents an analysis of statistical modelling applications at Vale’s Manitoba Operations to achieve the 2025 targets. Using statistical modelling of the Business Structure, the team identified a series of process improvements through a Theory of Constraints Analysis. Value Stream Maps (VSMs) were used to define the required data, apply statistical modelling, and conduct training sessions enabling the Manitoba team to identify the constraining influences. Scenario testing in the Statistical models helped identify the Hierarchy of Constraints and specify the pathway to improvement. How to Improve a Business Video link https://vimeo.com/344418155

May 4, 2025

By Ian Thomson

The Social License to Operate ? We are operating in an era where social license in the resource industry is as important ? if not more important ? than mineral potential ? Concept proposed by Placer Dome executive Jim Cooney in 1997 as essential requirement for the future survival of the mining industry ? ?You don?t get your social license by going to a government ministry and making an application or simply paying a fee? It requires far more than money to truly become part of the communities in which you operate.? Pierre Lassonde, President of Newmont Mining Corporation (2003). What it is ?Granted by the local community ? Intangible, informal, non-permanent ? Has to be earned and then maintained ? Defined as ? Ongoing Acceptance (a lower level) ? Ongoing Approval (a higher level) ? Expression of the quality of the ?relationship?

Aug 1, 2013

By B. G. Agnew

In evaluating fracture treatments, the need to answer such questions as "What zone or zones were actually treated?" and "What was the vertical extent of the treatment" is necessary, since determining effectiveness of the fracture treatwrent depends on knowledge of the reservoir portions stimulated and the vertical extent of the fracture system or systems. Injection of hot or cold fluids during fracturing operations will transfer heat to the surrounding formations and fracture faces mainly by heat conduction. Once injection ceases, temperature anomalies will develop opposite the zone fractured because the rate of temperature decay is less than that opposite zones heated or cooled by flow inside the wellbore or along the cement sheath. Thus, temperature surveys can he used to determine where fractures were generated outside the wellbore and to reasonahly estimate the vertical extent of the fractrires. This technique has been used successfully to evaluate over 344 fracture treatments at depths ranging from 1,500 to 15,700 ft. Examples of actual temperature surveys are presented to show how this method of fracture treatment evaluation can be used effectively and beneficially. INTRODUCTION Stimulation of producing or injection wells by fracturing is commonplace in the industry today. In evaluating these treatments, two basic questions which arise are "What zone or zones were actually stimulated?" and "What was the vertical extent of the treatment?". Knowledge of the reservoir portions stimulated and vertical extent of the fracture system or systems is vital to effect efficient and economical well completions and to assure maximum recovery from reservoirs. Not all fracture treatments are successful and many times the desired or anticipated results are not achieved. When this occurs, it is in most cases the engineer's job to determine why. The answer to this problem forms the primary basis for deciding whether to spend more money for development drilling and/or completion attempts or to forego additional expenditures to improve the particular zone. Also, knowledge of the reservoir portion actually stimulated is invaluable in planning future workovers. This is especially true in wells producing from reservoirs containing multiple porosity stringers or zones. For various reasons, all zones within a reservoir may not be perforated on initial completion with the thought of developing remaining zones through future workover operations. Because particular zones are perforated and fracturing fluid pumped down the wellbore, it cannot be assumed that all perforated zones are stimulated, and in turn drained. Occasionally, unperforated zones which are planned for future development are actually stimulated on initial completion. eliminating the need for future recompletion attempts or all zones perforated initially are not stimulated, thus requiring additional completion work to insure that these zones are adequately drained. In most cases, it is costly. if not impossible, to determine with assurance why a fracture treatment is unsuccessful after the job has been completed and the results tested. Further, unpredictable upper and lower fracture barriers. as well as possible borehole communications (cement channels), do not permit it to be taken for granted that the formation opposite the perforations is the only zone receiving the fracture treatment. Thus. evaluation of fracture treatments is necessary for efficient and prudent well completion practices and should be done simultaneously with the fracture job. Several methods have been used to locate fractured zones, all of which are based on detection of radioactive tracer materials added to either the fracturing fluid or the propping agent. These methods have been helpful in increasing knowledge of fracturing operations; however, they are seriously limited because of cost and inability to detect accurately radioactive tracer material more than a few inches away from the borehole. To develop a better diagnostic tool to pinpoint which zone or zones had actually been fractured, temperature surveys were run after fracturing with heated and cooled fluids. Significant temperature anomalies were found to exist opposite zones suspected of receiving the fracture treatment. From the analysis and examples to be shown, it can be seen that temperature surveys run in a stabilized wellbore several hours after a fracture treatment using hot or cold fluid will yield temperature anomalies which show the actual reservoir portion stimulated, the vertical extent of the fracture system or systems and a qualitative indication of the portion of fracture-fluid volume entering a given depth interval. The experience and illustrations used in this paper are based on evaluation of over 344 fracture treatments during the past three years using this diagnostic tool at depths ranging from 1.500 to 15,700 ft and fracture volumes ranging from 2.000 to 110.000 gal. Based on analyses of these temperature surveys, analyses of fracture gradients and evaluation of several open-hole packer impressions in the West Texas area,' vertical fracturing is the predominant mechanism and horizontal fractures occurred frequently, if at all.

Jan 1, 1967

By A. W. Ambrose

The output or oil and gas rrom the producing fields in the United States is rapidly deelining. Coincident with this decline is a steadily increasing demand ror petroleum and its products, but at present there are no commercial substitutes ror gasoline and lubricating oil. Undoubtedly, many new fields will be discovered in this country during the next rew years. Indeed, there may be periods or temporary flush production that ror a rew months or a year or perhaps two years will afford a surplus. Such peaks are temporary and should not be given too much weight in considering the relation between petroleum supply and our national lire. In considering this problem we must regard a long period or time, and, ir we do that we shall see that domestic production will be unable to keep pace with consumption. Hence, the public good demands t~at the highest efficiency obtainable be practiced in the production or oil. To accomplish this end, the operator or to-day should so organize his rorces ror development and production that he recovers every barrel or oil that can be recovered at a profit. This necessarily involves the use or eeonomical and scientific methods or development a:nd production and the elimination or waste. The Bureau or Mines has ror years urged the conservation or petroleum and its products, and has pointed out that -such conservation should start before the oil is brought to the surface rather than arter it is in storage tanks. Losses or petroleum underground have undoubtedly been rar greater than losses in storage, in transportation, and in refining. The quantity lost usually is indeterminate, and hence difficult to express in terms or money, but by remembering that entire oil fields have been ruined by invadIng waters some idea may be gained or the importance or underground waste. The petroleum engineer is coming to be recognized as an extremely important aid in the intelligent development or oil fields. In this paper an effort is made to outline ror the engineer and producer a field or work whereby science and engineering not only can but have been applied practically. The mining engineer has been the direct- ing hand in the development of mines, and it is being recognized more and more that the petroleum engineer has a similar function in developing oil properties. Thispaper aims to show the general method of procedure in studying underground conditions in producing oil fields and how such study may not only correct but even prevent great unnecessary losses. Such work provides the company with maximum insurance for the field against loss and is accompliphed at minimum cost and minimum risk. Throughout the paper reference is made to oil wells and oil fields, but to a certain degree many of the suggestions relating to oil wells are applicable in the care and protection of gas wells and in solving gas problems.

Jan 1, 1921

By Edmund J. Flynn

My subject Is Industrial Relations. Thus, I may appear as an intruder at this annual meeting of the Society of Mining Engineers. But I am no more an intruder here than is Industrial Relations in the day-to-day functioning of an engineer either in a staff or a line job. Engineers deal with people, as well as with blueprints, organizational charts, production data, etc. Where you have people, you have emotions, gripes, wants - real or imagined. Or you may just need some people or, at the other end of the pole, you may want to free yourself of people. But whether it is the wants or the needs, the pleasant or the unpleasant aspects of dealing with people, an Industrial Relations Department within an organization is there to help with these human relationships. This is the point for a definition of terns. Reference has just been made to "dealing with people? and to "human relations." This is, precisely the area in which Industrial Relations operates in the western Mining Divisions of Kennecott. In other organizations, what we refer to as Industrial Relations, may be called personnel relations, personnel administration, employee relations, or labor management relations. In our opinion the term Industrial Relations is best descriptive of the activity because it embraces the broad field of human behavior, reactions and satisfactions growing out of an individual?s entire employment relationship including his hiring, his lifetime on the job, and his termination. This is an individual?s industrial life. However, despite the use of the word "industrial", we are ever conscious that Industrial Relations is limited to human relations. Operational activities and decisions relating to the mining, milling, smelting and refining processes are for the line organization. The Industrial Relations interest in these line organizations activities and decisions relates only to the impact they nay have on employees - on people generally within the organization.

Jan 1, 1959

By Walter R. Hibbard

Precipitation in the northeastern United States, Florida, California and in many industrialized areas of the world is now more acidic (lower pH) than can be accounted for by natural causes. At the same time, the acidity of many lakes and streams in the northeastern United States has been measured and found to be similar to that of actual rain. These facts have led to conclusions that the two conditions are related. Coal burning utilities, 700 to 1000 miles upwind, have been accused of being the cause, leading to proposals for strict emission controls on the alleged offenders. The costs of these controls would place an estimated $10 to $15 billion capital burden on utility customers in about 15 states plus $2 to $6 billion annual operating costs. There appears to be no direct well-established scientific evidence that the accused are guilty but that the indictment is based largely on circumstantia1 evidence. This study examines the evidence, describes the situation and proposes what must be done to reduce the acid precipitation in an orderly cost beneficial manner. It is interesting to observe that studies by the different adversaries on the acid precipitation issue come to different conclusions largely because they do not read the same literature, but selectively develop evidence to support their own points of view, This study will try to review the issues impartially and reach a position of scholarly balance.

Jan 1, 1982

By M. R. Geer

The Bureau of Mines examined the washability data for 25 Appalachian coals requiring low-density washing to reduce sulfur content to 1 percent, using the distribution-curve method. The purpose was to estimate how closely theoretical sulfur values could be approached, what yields of washed coal could be expected, and the recovery efficiencies that might be achieved. Assuming that the run-of-mine coal would be crushed to 3/8 inch and cleaned in dense-medium cyclones, the calculations indicate that theoretical sulfur contents could be approached closely when cleaning at a specific gravity of separation as low as 1.30. With coals that have favorable specific gravity compositions the recovery efficiency anticipated for cleaning at 1.30 specific gravity is surprisingly high. Similar calculations for cleaning with concentrating tables at intermediate specific gravities indicated that theoretical sulfur contents at 1.50 specific gravity could be approached closely with some coals but not with others. The calculations suggest that operating a table at a specific gravity of separation much lower than about 1.50 probably would be unsatisfactory with most coals.

Jan 1, 1968

By D. A. Peacock

"INTRODUCTION Outer space technology and exploration have reached a tipping point so that mining and mineral processing in outer space is now a certainty and not a dream. Several competing companies, worldwide, are well on the way to building spaceships to land on the Moon and eventually mine the Moon and asteroids for volatiles, rare earth metals and Helium-3. The Google Lunar XPrize offers a $30 million prize1. China has recently landed a spacecraft on the Moon. The European Space Agency, with cooperation from the United States, has landed a spacecraft, Philae, on a comet. And, Mars One is planning a one-way trip to establish a settlement of humans on Mars. How and why are the Moon and asteroids and their resources of interest to private space industry and companies? Why are the Moon and asteroids viewed as a potential business venue? GEOLOGY OF THE MOON AND ASTEROIDS –WHY DO WE WANT TO MINE THERE? Space enterprises are actively working towards establishing and operating lunar and asteroid mining locations for resource extraction, resource processing, conversion to salable products, and distribution of the products and services in space and to Earth and beyond2. Forty-five years ago, the Apollo manned missions to the Moon returned rocks and regolith to Earth, which were studied and analyzed. What they found was that the Moon contains valuable minerals and resources. These minerals are largely due to meteor and asteroid impacts, which have, over eons, created this mineral rich regolith. These impacts have occurred on Earth as well, for billions of years, particularly early on in the history of the solar system. However, on Earth, wind, water, and vegetation have erased most of these impacts. On the Moon, in contrast, the only weathering is caused by subsequent impacts and the solar wind. The Moon regolith contains valuable rare earth minerals, platinum-group minerals (particularly where the Moon has been impacted by asteroids), volatiles (useful for processing and habitation), Helium-3 and titanium. Almost non-existent on earth, Helium-3 is abundant and accessible on the Moon and can be used in nuclear fusion power plants, producing much more energy than fission reactions and with much less radioactive waste. One of the main reasons Helium-3 is sought after as a fusion fuel is because there are no neutrons generated as a reaction product. Governments and private companies focus on mining of Helium-3 on the Moon as a basis for their economic models. Moon Express, one of the private companies who is planning on mining on the Moon, will recover moon rocks to fund its early operations25. Subsequently, it will recover Helium-3, platinum, and rare earth metals, as it engages in surface mining operations."

Jan 1, 2016

By E. P. Carman

1. DAVENPORT, S. J. Bibliography of Bureau of Mines Publications Dealing With Health and Safety in the Mineral and Allied Industries, 1910--46. Tech. Paper 705, 1948, 154 pp. 30 cents. 2. FJELDNER, A. C., FISHER, P. L., AND POLLOCK, M. B. Bibliography of Bureau of Mines Investigations of Coal and Its Products, 1940 to 1945. Tech. Paper 698, 1947, 53 pp. 15 cents. 3. GOOD, J. E., ABREU, ALVARO, AND FRASER, THOMAS. The Coal Industry of Brazil. Part 1. General Economy, Production, and Marketing. Tech. Paper 713, 1949, 38 pp. 20 cents.

Jan 1, 1954

By G. E. Johnson

E. D. HYMAN*—How much sorting of scrap is done ? G. E. JOHNSON (author's reply)—We do practically no sorting. We charge "run of mine" scrap to the furnace. The unmeltables, mostly iron, are in such demand today that there is no difficulty in disposing of them. It may soon be desirable to sort out from the unmeltables as much of the brass as possible. J. J. BRUGMAN†—We have somewhat similar problems in the secondary aluminum business. What is your method of removing the unmelted material from the furnaces? Why have you such an apparently small space in which to charge your materials? Do you find that you have to seal that opening, or can you have it open and continuously charge at one end and pull out the other ? G. E. JOHNSON—Our means of melting scrap is efficient only to the extent that we use the waste heat from the vaporizing chamber to do the job. It is a batch process. We open the charge door and place the scrap on the hearth by hand shoveling. The door is then closed during the melting down period. After the melting is complete, the opposite door is opened and the unmeltables are raked out. The doors are approximately 3½ X 4½ ft and are not sealed during the process only closed. They are nominally tight. Some metal is oxidized in the process. We have visualized a means of conveying the materials through this melting unit with the metals that are melted trickling out during its travel. T. H. WELDON‡—Mr. Johnson, in line with the last question, is it necessary to seal the furnace between the melting down and the vaporizing unit, or have you got an inverted syphon in the bottom of the chamber? G. E. JOHNSON—That was one of the first things we encountered. We had to have a sealed opening, and it is a molten metal seal. You have indirectly asked me another question, which was: "Do you have to seal up the melting unit?" I would say we should exclude as much air as possible, although we are not too efficient in doing that. We allow the melting unit doors to be open when we charge and when we remove unmeltables. You can readily see that that would lead to the idea of having a controlled atmosphere in the melting unit, and I think this would do a more efficient job of melting the scrap. T. H. WELDON—How often do you charge the furnace? G. E. JOHNSON—We charge the melting unit, and rake out the unmeltables, about every hour. H. R. HANLEY*—Are any provisions made for controlling the rate of oxidation for the production of various size particles for certain characteristics of the zinc oxide product? G. E. JOHNSON—Yes, there are many. You are getting pretty much into the fine points of zinc oxide manufacture. Some of us still think we have something to learn about that. In general, this muffle furnace as I have described it to you produces a rounded particle of zinc oxide which is generally formed by a rapid oxidation of the zinc vapor, followed by rapid cooling. We have gone to the other extreme in some of our experiments. We have changed the furnace to produce a type of zinc oxide, such as we thought was peculiar to American process zinc oxide, by controlling the temperature at the point of oxidation and maintaining that temperature for a much longer period of time than we do when we make the rounded shape. There are other relationships that this furnace readily provides. One of the important factors is the ratio of air to zinc vapors. We can vary that by varying the air supply to the baghouse, or vary the rate at which we are vaporizing the zinc by the simple expedient of regulating the temperature over the carborundum arch. We have a number of variables that permit us to produce all of the grades of French process zinc oxide from lead-free up through the highest grades of seal oxides. There are many controls that we can apply to the operation. What I have said is but a brief condensation. K. MORGAN*—Can Mr. Johnson give us some idea of the fuel consumption of the furnace ? How much oil does he use per ton of zinc distilled? I am also interested to know what sort of heat transmission he gets through the arch? What is the thickness of the tiles used to construct the arch? Some time ago we built a small furnace for a different purpose, using a carborundum arch, and we found that the reflectivity of the molten zinc surface was so great we had to use a very high arch temperature. We found we made an improvement by having a layer of carbon on the surface of the zinc. Has Mr. Johnson had any experience on these points ? Does he make any sort of insolu-bles which he leaves in the furnace which he cannot tap out ? G. E. JOHNSON—I believe your first question was the fuel consumption. If I recall, somewhere in this paper there is a test that I quote. I believe we used 800 gal in a given period of time. Offhand I cannot translate that into tons of metal. I might also state that we have this understanding; that the carborundum arch, as the temperature becomes higher, becomes more efficient in heat transmission. As a matter of fact, I believe it is at about 2600°F or higher that the highest efficiency of heat transmission becomes available. We have calculations that I cannot quote from memory which indicate that the carborundum arch does a really very fine job for this type of furnace. Another point that we had considered was the fact that this furnace could be readily constructed so as to furnish an ideal source of heat for waste heat boilers. If a carborundum arch was used over the melting unit, we would have no zinc vapors in the gases at all— just clean combustion gases from which we would have removed some of the heat. L. P. DAVIDSON†— The insolubles

Jan 1, 1950