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By Orville R. Lyons, A. C. Richardson

DURING the past few years there has been a growing demand by coal operators for detailed information about the performance characteristics of the various dryers now being manufactured, preferably in such a form that the information could be used to determine the type of dryer best suited to a particular drying problem. A few operators have been desirous of going even further, because they are of the opinion that present-day dryers are not properly designed and that fundamental studies of dryer design should be undertaken. This growing demand for a method of dryer evaluation and the indicated need for fundamental research resulted in the sponsorship by Bituminous Coal Research, Inc. of a project at Battelle Memorial Institute to investigate the thermal drying of coal. In investigating this problem, the most feasible method of attack appeared to be a survey of active operations to determine the present status of the thermal drying of coal. Data were obtained, usually by actual plant tests with the cooperation of the various preparation engineers and their staffs, for Q screen-type dryers, 8 rotary- type dryers, 3 continuous-pallet-type dryers, 2 flash-type dryers, I tray-type dryer, and I cascade-type dryer. The testing program provided: (I) data for 24 coal- drying operations, (2) information about dried, (3) information about the previous treatment that the coal had received, and (4) information about operating costs. The data obtained through the dryer survey and relationships determined from the data make it evident that all of the types of dryers included in the survey can be operated with the same degree of effectiveness if each type of dryer is used to dry the sizes of coal for which it is best suited. It should be noted that it is usually undesirable and often impossible to dry different sizes of coal in one type of dryer. By use of the data in the report, any prospective dryer user, having determined the surface moisture percentage and screen- size analysis of the coal to be dried, the tons of water to be removed per hour, and the final surface moisture percentage desired, should be able to determine with a fair degree of accuracy: (I) the difficulty of the drying problem, (2) the approximate cost of drying, (3) the required dryer inlet gas temperature and volume and exhaust gas temperature and volume, (4) the type of dryer to use, and (5) the size of dryer required. The method of testing the dryers and determining the difficulty of drying can be used by operators already having dryers to check the performance of their particular dryer and determine whether they are operating effectively. Considerably more information was obtained from the survey of thermal drying than was anticipated when the survey was first considered. However, a great deal of work still remains to be done in the field

Jan 1, 1948

By Peter T. Luckie

Up until the past couple of years, thermal coal dryers were only used to dry midwest and eastern United States bituminous coals. These dryers were primarily installed at coal preparation plants to freeze proof the coal and lower the transportation costs per BTU. Today thermal coal dryers are being specified to dry western sub-bituminous and lignite coals for these and other reasons brought about by the intense interest in coal gasification and liquefaction. One reason for drying western coals ahead of a coal gasification plant is the elimination of surface moisture which would prevent efficient sizing of the coal, since feed material size consist is very important in most commercial coal gasification processes. Thermal dryers are being proposed for liquefaction processes because of the need for a feed material containing approximately 4% or less total moisture Future coal gasification processes may also need to reduce feed material moisture content.

Jan 1, 1975

By C. J. Hall

The simplest natural ventilation cycle is similar to a Joule or Brayton cycle. This comprises two reversible adiabatic processes in the shafts and constant pressure processes underground and on surface. The thermal efficiency of such a cycle is given by the temperature increase in the downcast shaft divided by the absolute temperature of the air at the bottom of the downcast shaft, and is independent of the temperature increase underground. This efficiency is comparable to the Carnot efficiency, which is the greatest possible value between constant temperature reservoirs, source and sink. Two variations of the Joule cycle are investigated, using numerous work examples. In the first, dry air is used as the working substance, a fan is provided at the top of the upcast shaft, and various mass rates of flow are used with frictionless shafts and a constant resistance value in the horizontal mine workings. The lost work less the fan work gives the natural ventilation work, and this divided by the enthalpy increase in the workings gives the thermal efficiency. The thermal efficiency increases dramatically with mass rate of flow, although the enthalpy increase remains constant. This appears to violate the second law of thermodynamics, since the frictionless case has a Carnot efficiency. When the lost work is added to the enthalpy increase, however, the efficiency decreases slightly from the Carnot value, to conform with the second law. This increase in efficiency with mass rate of flow is often referred to as the reheat effect, although the air is not heated. The second investigation is similar to the first, except that the air entering the downcast shaft contains a small amount of water vapor, and there is evaporation in the mine workings only, until the air entering the upcast shaft is saturated. There is, of course, condensation in the upcast shaft. In this case, it is not possible to calculate the Carnot efficiency, but the thermal efficiency is 20 to 40% of the similar dry air values. This decrease is much more than can be accounted for by the larger value of specific heat for water vapor. In addition, the natural ventilation work is almost constant with increased mass rate of flow, and the thermal efficiency based on heat addition tends to decrease. The thermal efficiency based on heat and lost work decreases in conformity with the second law. The reasons for the differences in behavior between dry and moist air are not readily apparent.

Jan 1, 1991

For the convenience of those who are unfamilar with thermodynamics, the following brief description and explanation is given of the thermodynamical terms and methods used in this book. It must, however, be strongly emphasized that the account given below is not an introduction to chemical thermodynamics; its sole purpose is to give the reader a rough understanding of the methods used in the earlier chapters. For further information, reference must be made to the standard textbooks on chemical thermodynamics by Glasstone.

Jan 1, 1953

By A. Alfantazi

Recently, titanium and its alloys have been the materials of choice for the liner and internal components of autoclaves used to extract Ni and Co from laterite ores. There have been many corrosion incidents ranging from localized attacks due to scale formation or welding, to damage caused by pockets of concentrated acid. Most of the literature focuses on methods to avoid the corrosion altogether. Little has been published to increase awareness of the chemistry at these conditions. For this paper, a literature review of the thermodynamics of titanium was undertaken to decipher the slew of information available. E-pH diagrams were constructed from select data and compared with the results of electrochemical experiments. Since nickel laterite leaching takes place in sulphuric acid, and in many cases chloride concentrations are very high, the Ti-H2O, Ti-Cl--H2O and Ti-SO4---H2O systems were considered.

Jan 1, 2004

By Horace V. Winchell

PERHAPS the matter of greatest interest to all mining men at the present time is the question of income and excess profits taxes on mines. Every producing mine in the United States is called upon to render to the government an account of its operations and to pay a graduated tax upon its earnings. It is manifestly a matter in which every mine owner, every stockholder in a mining corporation, every mining and metallurgical engineer, every person employed by a mining company and every one engaged in an industry which in any way depends upon the continued operation of our mines or who consumes their products is financially, to a greater or less extent, involved. In view of this fact it is surprising to see how little attention is paid to it and how few of our members have taken the pains to investigate and understand the provisions of recent enactments by Congress and the ways in which these enactments are being applied to mining industries.

Jan 1, 1920

By Joseph G. Selmeczi

Lime and limestone-based SO2 scrubbing processes have demonstrated reasonably good success in removing low concentrations of SO2 from flue gases. While most of the operating problems experienced in the early days of scrubbing have been worked out, problems usually increase and removal efficiency drops with increased amounts of SO2 present in the gas stream. In order to overcome these difficulties, yet still taking advantage of lime and limestone as the lowest cost neutralizing agents, a host of so-called double- alkali systems were developed. These processes take advantage of cations such as Na+ and NH4+ capable of forming highly water soluble bases or basic salts, such as hydroxide, carbonate or sulfite, which having been neutralized or acidified by the absorbed SO2 can be regenerated with a lower cost base such as lime.

Jan 1, 1974

By J. M. Floyd

"Top submerged lance furnace developments started in CSIRO in the early 1970s and was given the name Sirosmelt. In the early work the technology was developed for tin smelting and processing tin slags but once a small pilot plant was established other slag processing applications were soon recognised and evaluated for various copper, nickel, zinc and cobalt-containing slags. The process was tried for copper smelting and converting, which was proven in the small pilot plant in 1978. In the same year the first commercial application of the technology was established for the recovery of tin from slags at Associated Tin Smelters, Sydney. Work on lead smelting was initiated by the CSIRO team in the late 1970s and laboratory work led to pilot plant trials by Mount Isa Mines.In the second decade of the technology the focus of development became commercial acceptance of the technology through marketing, development and application by Ausmelt and Mount Isa Mines; the former commercialising and developing the technology for a wide range of applications, while the latter concentrated on its own commercial needs of copper and lead smelting. This decade saw a number of commercial plants built in Australia, with considerable interest becoming evident from other parts of the world. Towards the end of this decade Mount Isa also entered into the business of marketing of the technology through rights dating to the joint work with CSIRO in the late 1970s.So far, after five years, the third decade of the technology has been characterised by diversification of applications of the technology to areas outside the non-ferrous and precious metals production industry. The waste processing and recycle industry and the iron and steel industry have recognised that the top submerged lancing system is a new type of reactor with many significant features which provide new opportunities for processing a range of materials under good environmental controls in a cost effective manner.I hope this audience will excuse my boldness in talking about the third decade of the technology when we are only half way through! I am aiming in this paper to not only talk about the past, but to try illustrate the future directions which I envision."

Jan 1, 1996

By Fred C. Bond

MOST investigators are aware of the present unsatisfactory state of information concerning the fundamentals of crushing and grinding. Considerable scattered empirical data exist, which are useful for predicting machine performance and give, acceptable accuracy when the installations and materials compared are quite similar. However, there is no widely accepted unifying principle or theory that can explain satisfactorily the actual energy input necessary in commercial installations, or can greatly extend the range of empirical comparisons. Two mutually contradictory theories have long existed' in the literature, the Rittinger and Kick. They were derived from different viewpoints and logically lead to different results. The Rittinger theory is the older and more widely accepted. In its first form, as stated by P. R. Rittinger, it postulates that the useful work done in crushing and grinding is directly proportional to the new surface area produced and hence inversely proportional to the product diameter. In its second form it has been amplified and enlarged to include .the concept of surface energy; in this form it was precisely stated by A. M. Gaudin2 as follows: "The efficiency of a comminution operation is the ratio of the surface energy produced to the kinetic energy expended. According to the theory in its second form, measurements of the surface areas of the feed and product and determinations of the surface energy per unit of new surface area produced give the useful work accomplished. Computations using the best values of surface energy obtainable indicate that perhaps, 99 pct of the work input in crushing and grinding is wasted. However, no method of comminution has yet been devised which results in a reasonably high mechanical efficiency under this definition. Laboratory tests have been reported' that support the theory in its first form by indicating that the new surface produced in. different grinds is proportional to the work input. However, most of these tests employ an unnatural feed consisting either of screened particles of one sieve size or a scalped feed which has had the fines removed. In these cases the proportion of work" done on. the finer product particles is greatly increased and distorted beyond that to be expected with a normal feed containing the natural fines. Tests on pure crystallized quartz are likely to be misleading since it does not follow the regular breakage pattern of most materials but is relatively harder to grind at the finer sizes, as will be shown later. This theory appears to be indefensible mathematically, since work is the product of force multiplied by distance, and the distance factor (particle deformation before breakage) is ignored. The Kick theory' is based primarily upon the stress-strain diagram of cubes under compression, or the deformation factor. It states that the work required is proportional to the reduction in volume of the particles concerned. Where F represents the diameter of the feed particles and P is the diameter of the product particles, the reduction ratio Rr is F/P, and according to Kick the work input required for reduction to different sizes is proportional to log Rr/log 2.5 The Kick theory is mathematically more tenable than the Rittinger when cubes under compression are considered, but it obviously fails to assign a sufficient proportion of the total work in. reduction to the production of fine particles. According to the Rittinger theory as demonstrated by the theoretical breakage of cubes the new surface produced, and consequently the useful work input, is proportional to Rr-1.5 If a given reduction takes place in two or more stages, the overall reduction ratio is the product of the Rr values for each stage, and the sum of the work accomplished in all stages is proportional to the sum of each Rr-1 value multiplied by the relative surface area before each reduction stage. It appears that neither the Rittinger theory, which is concerned only with surface, nor the Kick theory, which is concerned only with volume, can be completely correct. Crushing and grinding are concerned both with surface and volume; the absorption of evenly applied stresses is proportional to the volume concerned, but breakage starts with a crack tip, usually on the surface, and the concentration of stresses on the surface motivates the formation of the crack tips. The evaluation of grinding results in terms of surface tons per kw-hr, based upon screen analysis, involves an assumption of the surface area of the subsieve product, which may cause important errors. The'evaluation in terms of kw-hr per net ton of 200 mesh produced often leads to erroneous results when grinds of appreciably different fineness are compared, since the amount of -200 mesh material produced varies with the size distribution characteristics of the feed. This paper is concerned primarily with the development, proof, and application of a new Third Theory, which should eliminate the objections to the two old theories and serve as a practical unifying principle for comminution in all size ranges. Both of the old theories have been remarkably barren of practical results when applied to actual crushing and grinding installations. The need for a new satisfactory theory is more acute than those not directly concerned, with crushing and grinding calculations can realize. In developing a new theory it is first necessary to re-examine critically the assumptions underlying

Jan 1, 1952

By S. A. TAYLOR

AN EDITORIAL on the Strike Situation in the Coal mining industry in the New York Evening Post of Nov. 4, 1919, gave what purported to be statistics of the Department of Labor, for a period of two weeks, which showed an average for the year, based on these two weeks, of 32% hours per week. This mode of arriving at the number of hours per week, while not accurate, is not so far off from the facts as to call for any special comment. The report of the U. S. Geological Survey, Department of Coal Statistics, give so the number of days worked in 1917 as 243; reducing the same to hours per week, assuming 8 hours per day, shows a weekly operation of mines at an average of 36J4 hours. But this assumption is not exactly correct, for the reason that it is not very often that the miners work the full 8 hours per day. There are many explanations for this, but it is not pertinent to this statement to discuss them now, as the important thing to consider is whether a 30-hour week would be for the best interest of not only the men themselves, but the public or country in general.

Jan 1, 1920

By Andrew J. Troop

"VAUGHAN THOMPSON designed the Thompson retrievable diamond drill wedge and reaming assembly in 1948. Since 1950, the Hudson Bay Exploration and Development Company, Limited has used the method extensively. The wedge, setting tool, and reamer have been modified slightly since they were first introduced. In 1951, Mr. Thompson designed the Thompson arc cutter. The purpose of this tool is to decrease effectively the diameter of the arc cut, using standard drilling tools. This directional drilling device is usually employed when a branch hole is desired. The Thompson arc cutter has been used with success at Birch Lake, Saskatchewan, at the property of Cuprus Mines, Limited, Manitoba, and at Thompson Lake, Manitoba.UsesThe Thompson retrievable wedge provides a simple method for:(1) Re-drilling lost core sections(2) Re-sampling sections of old holes(3) By-passing lost tools Correcting the direction of a hole(4) Drilling a branch hole to obtain intersections at a higher elevation than the original holePrevious to the spring of 1951, the wedge was used only for the first four of these purposes. Recently it has been employed extensively for drilling branch holes."

Jan 1, 1953

By Irving Hoch

INTRODUCTION The demand for tunnelling can be related to urban population size and density; often, tunnelling occurs when a certain city size and density threshold is reached, and increases thereafter as a function of those population characteristics. Subways for rail mass transit are the most notable example, of course, but tunnels for water supply and perhaps for sewerage can also be related to size and density. As cities grow large they sometimes outgrow their local water supply and have to import water from distant places via tunnels; witness New York City, Los Angeles and San Francisco. And it has been suggested that Chicago use deep tunnels for storm water storage because tertiary treatment to meet water quality standards will require treating storm water runoff.(1) Other uses of underground space also increase with urban density, e.g., underground parking, concourses and shopping centers such as Rockefeller Center in New York City and the Place Ville-Marie in Montreal. These examples can be viewed as illustrative of the central point of urban land economics. As the number of people locating in a place increase, they bid up land values and make the more intensive use of land economic, with land defined to embrace the space both above and below the surface. Hence, we are led to think about the city, and of urban land use, in three dimensions. Now, if we accept the relation of underground space use to urban size and density, recent demographic trends seem anything but hopeful for future tunnelling demand: urban density is declining, population growth is slowing down generally, and there

Jan 1, 1974

By C. O. Brawner

Approximately 7 billion tons of soil, rock and ore are currently being excavated in open pit mines and quarries on the North American continent at the present time. As the depth of excavation increases and the grade of ore being mined reduces, the safety and economy of the stability of the pit slopes becomes increasingly important. The magnitude of the potential influence on economics can be appreciated from the results of recent full scale field studies by Kennecott Copper Corporation at the Kimbley pit near Ely Nevada (Merrill, 1968). This pit was originally excavated with an average wall slope of 45°. Based on detailed studies it appeared that a slope of 610 would be stable. Subsequent excavation to this slope proved the original pit could have been steepened by 16° during production.

Jan 1, 1968

By Eugene F. Casey

The next ten to fifteen years will be exciting ones for the construction industry because three city agencies alone have started or will start, on tremendous expansion programs, the cost of which will exceed a total of four billion dollars. The major portion of this work will be done by the use of tunnelling methods. *Tunnelling is construction by any method of a covered cavity of predesigned geometry whose final location and use under the surface, whose cross-sectional area is greater than two sq. meters. The New York City Transit Authority's expansion program will provide for approximately 52 miles of new subways. The Board of Water Supply has already started on City Tunnel No. 3 which, when completed will provide the City with enough water until the year 2000, and the Board of Water Resources has embarked on a tremendous program to clean up the surrounding waters. Yes, these will be exciting years, particularly when one reads about the new novel exotic methods of rock breaking and disintegration, coupled with the new methods of soft ground tunnelling.

Jan 1, 1997

By George H. Jones

NO STRANGER phenomenon exists in the American mining industry today than the so-called bootleg anthracite industry in Pennsylvania which now produces probably close to 15 per cent of the total hard coal out- put of the State. Instead of being what - was first thought to be a temporary condition, countenanced because of the desperate condition of some of the miners at the depth of the depression. it is thriving now as never before. Re- ports of it have penetrated all over the world, as exemplified by inquiries concerning it in Durban, South Africa mentioned by John C. Cosgrove in his article in the July MINING AND META LURGY.

Jan 1, 1939

By Giorgio De Tomi, Ricardo Tichauer

Mineral exploration is a critical step for success in mining. However, small-scale mining often ignores exploration best practices. This paper introduces the Tichauer-DeTomi Matrix, a tool for assessment of geological uncertainty in small-scale mining. This matrix, which measures the level of compliance of exploration programs in small deposits with industry best practices, has been applied to three small mining projects in Brazil: an artisanal gold mine in the Amazon, a small-scale manganese mining venture in the Northeast, and a small manganese deposit in the Southeast. The application of the matrix resulted in indexes that reflect the actual level of maturity of the mineral exploration program in each project. Therefore, the matrix has shown potential to be an effective tool for assessment of the geological uncertainty remaining in small-scale mineral projects, as well as to identify priority exploration activities for reduction of risks associated with the geological uncertainty. As a risk assessment tool, the TichauerDeTomi Matrix may be helpful in promoting investment and sustained development in and around small mines.

By P. Z. Caverhill

In this section of the province only the most meagre of surveys have been made and because these are not sufficient to determine with any degree of accuracy even the total forest area, the information presented in this paper is not complete. Area: -The area south of the Canadian National, and served by the Pacific Great Eastern, is roughly 38,000. square miles, 30,000 of which is classed as productive. This is approximately equal to the productive area of Norway, or half of Finland-or of 30 per cent of Sweden. It is larger than that of either Nova Scotia or New Brunswick. Eliminating from the productive area 3600 square miles of grass-land and areas capable of agricultural development, 26,000 square miles (16,600,000 acres) remains as absolute forest-land, as compared with the 55,000,000 acres of Sweden, the 37,500,000 acres of Finland, the 17,000,000 acres of Norway, and the 7,600,000 acres of Austria.

Jan 1, 1925

By Dr. O’Neil Thomas J., Donald W. Gentry

Money is like an arm or leg-use it or lose it." -Henry Ford INTRODUCTION If it were not for the existence of interest, the analysis of investment opportunities would be greatly simplified. In the absence of interest, investors would be indifferent as to when cash outlays are made or cash benefits are received. It would, in fact, be irrelevant whether the outlays preceded or followed inflows as long as both amounts are known with certainty. Of course, it does make a considerable difference whether, for example, a firm receives $1 million now or five years from now. The reason is that money does, indeed, have a value which is a function of time. Interest is how this time value is measured. Interest is generally defined as money paid for the use of borrowed money. In other words, interest is the rental charge for using an asset over some specific time period. The rate of interest is the ratio of the interest chargeable at the end of a specific period of time to the money owed, or borrowed, at the beginning of that period. In order to understand why interest exists, it is necessary to take the lender's viewpoint. The lender can justify charging interest for several reasons: 1) Risk: The lender is faced with the possibility that the borrower will be unable to repay the loan. 2) Inflation: Money repaid in the future will be in units of lower value due to inflation. 3) Transactions Cost: There will be expense incurred in preparing the loan agreement, recording payments, collecting the loan, and other administrative tasks. 4) Opportunity Cost: By committing limited funds to one borrower, a lender is unable to take advantage of other available opportunities. 5) Postponement of Pleasure: By lending money, an individual (or organization) is postponing the pleasure which that money could purchase. Each of these is a valid reason for a lender demanding interest from a borrower. The level of interest is, like the price of other assets, determined by supply and demand. Nonetheless, from time to time various analysts have taken a then current average interest rate and broken it down into the components described previously.

Jan 1, 1984

By Neil Williams

The brecciated dolostone-hosted (Mississippi Valley-type) and associated shale-hosted stratiform Pb-Zn deposits at McArthur River occur adjacent to a major syndepositional fault, the Emu fault. Base-metal zoning, mineral parageneses, and Pb and stable isotope ratios indicate that both types of deposits formed contemporaneously from metalliferous brines that flowed into the host sediments from the Emu fault. Derivation of brines from underlying evaporitic sediments is suggested. Geochemical evidence indicates that the mechanism of ore formation was sulfate-reduction coupled with oxidation of organic matter. The textural relationships of stratiform sulfide mineralization to diagenetic dolomite concretions, chert blebs, volcanic glass shards, and inter-ore breccia beds, indicate that the reactions proceeded diagenetically within about 100 m of the sediment/water interface.

Jan 1, 1979

"THE GOLD MINING REGION of Timmins - Val d'Or, astride the Ontario-Quebec border, has long suffered the effects of rising costs during the period when the U.S. price of gold was fixed at $35 per ounce. The federal government, through such assistance programs as that set up under the Emergency Gold Mining Assistance Act (E.G.M.A. ) in 1948, has subsidized the gold mining communities of Canada for a total of over $300 million to March 31, 1972. Of this, the Timmins - Val d'Or ""gold belt"" has received more than twothirds, almost $220 million. In spite of these continuous subsidies, only 12 gold mines are still producing in the Timmins - Val d'Or belt, whereas 71 mines have received subsidies for some period since 1948. The vital question is how the communities previously supported principally by the mining of gold will survive in the long run, as many of the older mines either are already depleted or are quickly becoming so. With the rising price of gold on the 'free market in recent months, prospects look a little brighter for the time being. Even with the increased official price of U.S. $38, which made the maximum government subsidized price about $48 per ounce, gold mines have not sold any gold to the government since January 1972 and some stopped doing so months before that. The populace of the region has not been enthusiastic about relocation nor about extensive retraining programs in the past and probably will not be in the future. So, when the remaining gold mines become depleted, the old problems of community depression will remain."

Jan 1, 1973