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By H. W. McQuaid

IT IS usually assumed that chemical specifications are sufficient for steel to be used for case carburizing, and if the steel analyzes within the ordinary limits specified for steel for this purpose, no difficulty traceable to the steel used should be encountered in obtaining satisfactory results in the case carburizing and hardening. Much work has been done to determine the effect of various alloying elements on the rate of carbon penetration, etc. but, to our knowledge, little if anything has been published in regard to the effect of the quality of the steel on the final results in the hardening of case-carburized steel parts. The writers believe that the structure of the case both before and after quenching is greatly affected by the actual condition of the steel itself as made, and that for good results in the case-carburizing and hardening departments, the steel should be of the best possible quality as regards non-metallic impurities. It is the purpose of this paper to prove that the presence of excess dissolved oxides in the steel, as made in the melting furnace, affects permanently the results obtained in carburizing and hardening and that it is possible that the presence of dissolved oxide can result in total unfitness of low-carbon steel for, case hardening purposes. When races and rolls for roller bearings are made from a low-carbon steel, case carburized and hardened, it is of primary importance that the results of this treatment be of the highest quality. It is necessary, therefore, that in the case-carburizing work each detail be rigorously checked to avoid any defects which would cause the loss of much time and material. The case carburizing with which this paper deals was done in under-fired oil furnaces. The temperature of each furnace is controlled by means of a platinum platinum-rhodium thermocouple, in connection with a potentiometer indicator and potentiometer recorder. The temperature of each furnace is registered every 15 min. by an operator, who is continually checked by the automatic recorders.

Jan 2, 1922

(Under this heading will be published notes sent to the Secretary of the Institute by members or other persons introduced by members.) Engineer of many years' experience in mining engineering, construction, public works, contracting, water-power development and operation, having heretofore retired on a sufficient competence, wishes to have employment with thoroughly reputable concern where his experience would be of value; the question of remuneration is of secondary importance. A-2591. Engineer, in military service nearly two years, desires, when discharged, to secure permanent position offering future opportunities. Experienced as mechanical and metallurgical engineer, investigator, teacher. Technical graduate and post-graduate from two of best American schools. Ability as executive, organizer and industrial leader. Especially fitted for industrial position of administrative nature or as technical assistant to industrial manager. Salary expected $4500 to $5000. A-2619. Member A. I. M. E., age 36, twelve years' experience in smelting and hydrometallurgy of copper ores, desires research or works position with responsible company. Speaks fair Spanish. Can handle men. Will welcome difficult metallurgical problems. Salary $5000. A-2627. Mining engineer, recently discharged from the Army as Captain, Engineers, age 38, 15 years' experience in the Southwest and in Mexico in gold, silver and copper mining, engineering, surveying, sampling and assaying, with special training in prospect and mine examination and the development of prospects. Speaks Spanish; immediately available; references. A-2136.

Jan 6, 1919

By Martin Valeri

The operation described in-this paper will be confined to the Nemacolin Mine of The Buckeye Coal company, Nemacolin, Pennsylvania.' This mine is-located on the Monongahela River approximately sixty miles south of Pittsburgh. The mining is in the Pittsburgh seam that has an average thickness of 88 to 90 inches. The current practice is to mine approximately 80 inches, leaving 8 to 10 inches of roof coal. All of the coal produced is used solely for by-product coking by the parent Youngstown Sheet & Tube Company, Youngstown, Ohio. Eight to ten inches of top coal are left by the miners to prevent air slacking of the draw slate. In addition, this top coal which will float at the washing gravity has a very high ash and sulphur content, and when mined, seriously affects the quality of the clean coal product.

Jan 1, 1961

By L. W. Saperstein

Surface mining of coal is undoubtedly one of the more controversial aspects of the mineral industries today. There is a constant tug between the need for readily available and inexpensive energy supplies and the desire to minimize disturbance to the land. Without a doubt, surface mining severely disturbs the land surface. The duration of this disturbance, from a minimum of a few months to a maximum of infinity, however, is strictly dependent upon the mine operator's willingness to reclaim. Surface mining critics claim that it is impossible to ameliorate the detrimental effects of this mining to insignificance. The more vocal critics, indeed, are calling for complete abolition of surface mining for coal. Thus, they do not believe that it is possible to restore surface- mined land to pre-mining conditions. As a consequence of this position, an adversary relationship has developed between the operators and their critics who, simultaneously, believe they are doing their best for the United States. In a forum of mining experts, there is little need to recount the kind and amount of devastation that can result from poorly reclaimed land. This has been done numerous times, including once 1 by the author. Of particular interest to this paper, though, are the environmental hazards associated with contour strip mining. In addition to the problems of area mining: denudation of vegetation; exposure of toxic spoil; increase of erosion runoff; etc.--contour mining has the very real problem of landslide due to the outslope stacking of overburden. Contour mining is understood to be the extraction of coal from a hillside outcrop such that the resultant pit follows, or nearly follows, an elevation contour. The problem with contour mining as usually practiced is that the spoil from the cut, or the first cut if multiple cuts are made, is placed on the outslope. If this slope is steep, the resulting pile is difficult to stabilize, generally erodes swiftly, and may fail disastrously.

Jan 1, 1973

By E. P. Youngman

Gold and precious stones were mined in Egypt in prehistoric times. This mining, carried on at intervals, extended over thousands of years, until about 1300 A. D. Then ensued a dormant period of several hundred yoars. In the mean- time Europe made great rogress in mining practice, metallurgy, and geology and sent out various expeditions during the nineteenth century to investigate ancient mines. But the exploratory work produced no material results, and not until the beginning of the present century did actual mining recommence. The reopening of old gold mines in Rhodesia aroused interest in London and Paris, and these cities provided the capital necessary for the investigation of the ancient minee in West Africa and Egypt. Speculation resulted in the division of most of the uncultivated area of Egypt and the Sudan into huge concessions, and a number of expeditions were made; but after an unprecedented activity in West Africa, roaction set in, and the flow of capital ceased. The concession- aires, mostly individuals with insufficient capital and with a misconception of the initial difficulties of communication, water supply, and labor, allowed

Jan 1, 1932

By William J. Miles

The major health hazard from exposure to crystalline silica historically has been silicosis. Silicosis is the scarring of the lung from excessive exposure to crystalline silica. It has been recognized as an occupational disease for over two thousand years, since early Greek physicians noted the respiratory problems of miners, stonecutters, and quarrymen who were exposed to excessive quantities of mineral dust. During the industrial revolution, the incidence of the disease was greatly increased by the use of machinery which increased dust levels. Subsequently, the need for dust control was recognized and dust control measures were instituted. Silicosis is characterized by progressive breathlessness on exertion and develops over the course of years. X-ray images of the lungs show progressive scarring of the lungs. The symptoms are related to the amount of exposure to crystalline silica and the years of exposure.

Jan 1, 1990

By M. Laliberte

"Gold-mine effluents are often characterized by high concentrations of copper, ammonia and cyanide derivatives (mostly cyanates and thiocyanates). While not acutely toxic to birds, this water can be acutely toxic to fishes and invertebrates. In many jurisdictions, the effluent requires further treatment in order to pass a mandatory requirement to be nonlethal to species like the rainbow trout (Oncorhynchus mykiss) or Daphnia magna. Using actual mine water, it has been demonstrated that aerated moving bed biofilm reactors will biodegrade the ammonia, cyanides, cyanates and thiocyanates, thereby removing the toxicity associated with these components. By removing copper by precipitation the water can be made to pass acute toxicity tests. Tests have demonstrated that the process is stable between 4 and 25°C, with no significant changes in the treated water composition. Once the biomass is acclimatized, the process is resistant to upsets and requires very little inputs except for phosphorus and air. Furthermore, it has been demonstrated that an anoxic reactor can be added downstream of the aerated reactors to remove nitrates if required.IntroductionThis paper will demonstrate that gold-mine effluents, which are toxic to fishes and invertebrates, can be made nontoxic by using a combination of chemical precipitation and biological oxidation.The typical composition of gold-mine effluents will first be described. The applicable legislation will then be introduced, with its requirement that the treated effluent be nontoxic. The toxicity of a typical untreated effluent will then be confirmed, and the sources of the toxicity identified. After that, a number of toxicity reduction treatment methods will be presented, and the selected method will be described.The lab tests that confirmed the efficiency of the treatment method will be presented, with three phases of testing as the understanding of the process gradually improved. Toxicity test results showing that the water is nontoxic after treatment through the temperature range will be presented."

Jan 1, 2015

By Helena Byrdziak

Polish Copper Industry, located in the Lepica-Glogów region and operated since the 1970's, includes four mines and two smelters, "Legnica" and "Glogów", the latter consisting of "Glogów" I" and "Glogów II" both having different technologies. The "Legnica" and the "Glogów I" smelters using shaft furnaces, so sulfur elimination largely takes place during batchwise converting, resulting in fluctuation SO2-concentration between less than 1% up to 10% in the converter pas W the sulfuric acid plants. The ensuing difficulties of the past have now largely been overcome. Introduction of flash smelting at "Glogów II" with subsequent acid making by double SO2-conversion from the stable process gas, contributed significantly to further reduction Of SO2-emission. In 1994 a new double conversion sulfuric acid plant was installed at "Glogów l" as well as a "Solinox" desulfurisation plant at "Legnica", further reducing SO2 emission considerably, The next step towards this goal under consideration is a semi-dry desulfurization system for the "Glogów I" power station, SO2- abatement measures by KGHM and the results thereby achieved are presented.

Jan 1, 1996

By Kung-Lee Wang

This Bureau of Mines study illustrates the economic significance of the Florida phosphate industry to the State and to the Nation. Environmental considerations related to phosphate industry activity are discussed briefly. Based on forecasts of Florida phosphate production in 1975, and using 1972 dollars, regional and national output value, income, and employment created by the phosphate industry were estimated for 1975. State and Federal government tax revenues generated by the phosphate industry, are also measured. Further, the concentrated impact of the phosphate industry on certain Florida areas and on regional industries is examined. Finally, the phosphate industry's importance to the U.S. balance of payments, U.S. agricultural production, and the Frasch sulfur industry is considered, in addition to byproduct fluorine, and potential byproduct uranium from fertilizer manufacturing.

Jan 1, 1974

By J. C. Rae

A Japanese mining engineer was given a year's leave of absence by his company and dispatched on a tour of inspection of all the principal coal mining regions of the world. He visited the New Castle region of England, Wales, Scotland, France, Germany and Alsatian mines, the underseas col¬lieries at Nova Scotia and Vancouver, and our own important fields of Illinois, Pennsylvania, West Virginia, Kentucky, Colorado, Utah and Wyoming. You are probably surprised to know that after seeing all these, he pronounced the Gebo mine of the Owl Creek Coal Company as the most interesting operation he had seen. The Gebo Mine is located about three miles west of Kirby on the Chicago, Burlington & Quincy Railroad in the Big Horn Basin region of Wyoming, 500 miles north of Denver and 200 miles south of Billings, Montana. The mine is working on a coal bed five or six to eleven or twelve feet' thick, dipping 22 to 23 degrees toward the northeast. The coal occurs in what is called the Eagle formation; and is found between two massive sandstones from 25 to 65 feet thick, which, weathering into bold', gray-colored cliffs, serves as a guide to the location of the coal bed. The deepest workings have an overburden of 800 feet. Cleavage planes of the coal extend at an angle of 45 degres to the pitch, and perpendicular to roof and floor. The coal itself is generally clean and not difficult to cut. It ignites readily from spontaneous combustion, however, which circumstance makes an ever-present fire hazard which must be carefully watched and guarded against. The coal is classed as sub-bituminous with analysis about as follows: Moisture 17% Volatile Matter 33% Fixed Carbon 46% Ash 4% Sulphur, about ½ % B. t. u. value a trifle under 11,000. It is known as Owl Creek coal, is one of the best domestic and steam fuels in the West, and is very popular in Montana, Idaho, Washington, Wyoming, South Dakota and Nebraska. While the coal slacks somewhat rapidly when exposed to the weather, it stores readily for months if placed under cover. On account of the somewhat isolated position of the mine as regards manufacturing establishments, there was a decided difficulty in disposing of slack, especially during the early years of the mine (1907 to 1914), and approximately 10 per cent of the entire product had to be wasted as slack during those years. This difficulty has been largely overcome since 1914, due partly to growth of manufacturing establishments in tributary territory, and also to enlarged transportation facilities. Also largely due to its isolated position, the mine has been compelled to use an extremely large proportion of box cars, much over 50 per cent of the product (in some years 75 per cent) being shipped in box cars, which, of course, entails extensive loading equipment and increases cost of loading. The output of the Gebo Mine for 1920 was 348,000 tons, for 1921, 273,000 tons; the rate of production during the year 1922 was over 1,700 tons daily, and 2,000 tons daily in January, 1923. The mine was developed by driving three openings straight down the pitch, the main slope being 12 to 14 feet wide and 3,000 feet long. A little distance from the surface a pair of level entries were turned right and left, known as the first East and first West. From these, rooms were driven up the pitch and chute mining attempted with only indifferent success: The failure of this rise-room method of mining was attributable to several

Jan 1, 1923

By Victor F. Hollister

Introduction Trends of successful discovery technology and psychology emerge from a thoughtful study of various companies' exploration programs. These subjective patterns can be generalized into groups of factors for discussion. Here, for convenience, factors that influence exploration success are separated into management and geologic concerns. Most successful discoveries have a demonstrably favorable management combined with a technically competent geologic input. Both are required. But the management input is decisive. Management factors include the correct definition of management's role; cost of exploration; time needed for exploration; commodity selection; and the fostering of autonomy, creativity, and confidence in the geology department. Geologic factors include imaginative technical competence (field as well as academic), correct development and use of empirical exploration or prospecting models, and dedication. Success comes to those entities that are properly managed and have technological competence. A management team that directs a company's business has been compared to a dynasty. The dynasty lays out policy and follows up with appropriate action. In that management's power is pervasive, the term is appropriate. Management's role is, however, more important. Many examples can be cited where the geologic input was impeccable. But management somehow snatched defeat from the jaws of victory, and the exploration success was turned to a third party's profit. Management Factors Management's role can be broadly generalized to four parts. These are to identify the commodities it seeks, define its part in the exploration process, develop a functioning exploration department, and have the desire to succeed. It must have confidence in its geologists and delegate to them the authority and responsibility they need to operate successfully. Head office management cannot do the thinking for a field staff thousands of kilometers away. There is no substitute for confidence and delegation of authority. Successes came to those who had the freedom to act. Motivation is a management requisite. Management's role is to prevent destructive, internecine political battles within the corporate structure. Most large US mining corporations have well known histories of political strife that have damaged their exploration efforts. Management's role must, above all, include the desire to succeed. There are cases where management has been confronted with a commercial exploration success, but their reaction is to request additional study or exploration. Perhaps the problem of bringing a commercial find into production is beyond their capabilities. But a bona fide discovery sent back for additional work commonly is lost due to that management. The cost of exploration is a factor that management must accept. A variety of studies made during the past 40 years shows the cost per discovery to be $25 million, $38 million, $200 million, or even $290 million. These figures are derived by dividing the total exploration expenditure by the number of discoveries. However, successful management dynasties have a much lower cost per discovery during their management regime. Asarco, from 1948 through 1963, had one of the lowest cost discovery rates in the world. Duval Corp., from 1948 through 1968, had comparably low discovery costs. Placer Development, from 1955, was equally successful. Western Mining in Australia has had one of the longest lived dynasties associated with exploration success. Time is vital in exploration success. Most successful exploration case histories stress sufficient time in project exploration so that the target is well tested. A large target cannot always be adequately evaluated by a few holes (strat or concept testing). Serendipity helps in exploring large targets, but it best operates in a lengthy program. Numerous case histories include pleasant surprises. But these came mostly after the 10th hole. Commodity markets are important factors governing exploration success. Management's decision to explore for a specific commodity can doom its effort if that product suffers from severe oversupply. Unquestionably, progressive copper price increases from 1948 through 1968 helped convert marginal porphyry copper discoveries

Jan 8, 1985

By Roger L. Hulette

Mt. Newman Mining Co. is now completing an expansion program, begun even before initial construction was complete, which will result in facilities with the ability to ship over 30 million tons of iron ore per year by early 1973. Confidence in such rapid future growth was evidenced by careful planning for the future expansion of those facilities provided for initial operation of the project which first shipped ore on 1 April 1969. Ore sales contracts totaling more than 300 million tons have been negotiated, thus justifying the optimism which led the joint venturers to provide over $200 million in initial investment and a like amount in capital required to finance the continuing expansion program. Members of the Mt. Newman Joint Venture are: Amax Iron Ore Corporation - 25% (a subsidiary of American Metals Climax) Pilbara Iron Ltd. - 30% (a subsidiary of Colonial Sugar Refining) Dampier Mining Ltd. - 30% (a subsidiary of Broken Hill Proprietary) Seltrust Iron Ore Ltd. - 5% (a subsidiary of Selection Trust Ltd. of London) ? Mitsui C. Itoh Iron Ore Pty. Ltd. - 10% Mt. Newman Mining Co. Pty. Ltd. manages the project on behalf of the five companies which make up the joint venture.

Jan 1, 1972

By R. K. Hill

The Hidalgo Smelter successfully reduced operating costs by 25% compared to the previous two years through a focused holistic approach to development of its entire workforce. The first phase involved basic team training skills for natural work teams. The second phase provided leadership training via breakthrough education to 40 of the smelter leader-both hourly and salaried. The third phase stretched out the teams training to include rewards for performance that resulted in hourly teams converting to salaried status-part of a company wide initiative. The fourth phase saw 1998 become the "Year of Safe Cost Reduction" where 7 breakthrough projects focused on different areas of expenditure. Implementation of lean manufacturing as a tool for teams to truly get their arms around what they controlled, introduced accountability and responsibility for operating results at the team level. This will allow the release of experienced supervisors from this role, to a pool of technical expertise, where our future breakthroughs will be designed and implemented.

Jan 1, 1999

By Jay Nopola, Christopher Johnson, Matthew Minnick, Erik Hemstad, Erik Walega

Mining data collection, storage, and interpretation methods have progressively changed over time. Data collection, for the most part, has transitioned from handwritten notes and logs based on manual gauge readings to real-time data streaming through instrumentation capable of directly communicating with site-based data historians or cloud storage. Data collection and storage have had to adjust commensurately with the volume of data, leading to more complex database architecture. Geoscience interpretation methods have also changed; however, the first goals of modeling and understandings from first principles remain the same and are typically deeply rooted in historical academic work. Machine learning methods are becoming more common, available, and implemented by industry and practitioners. Despite the wide accessibility of machine learning methods, the population of geoscience subject matter experts in the underlying theory of this analysis type is limited. This form of analysis, therefore, must be conducted carefully and in conjunction with subject matter experts, on both machine learning theory and the field it is being applied to. This paper aims to provide background history on data analytics and machine learning, current methods and practices, and high-level geoscience case study examples, as well as take aways regarding the mining industry, potential pitfalls specific to geosciences, and possible perspectives on the direction of artificial intelligence in the future.

Jun 25, 2023

By R. Stenne

This paper deals with a complementary soil investigation which being part of the contract helped understand the behavior of a softened clay and adjusted the design of a retaining structure accordingly. The investigated softened clay proved to have lost its original strength but had maintained some characteristics of its stress history and in particular high horizontal stress. Pressuremeter tests and flat dilatometer tests were of interest to estimate the at rest earth pressure. A design consisting of a T-shaped slurry wall in conjunction with transverse walls was the most effective solution to cope with high active pressures and low passive pressures.

Jan 1, 2000

By Yuemin Zhao, Wenxuan Liu, Maoming Fan, Zhanyuan Long

"Coal is mainly composed of energy-producing elements carbon and hydrogen. In addition to these elements, coal usually contains many other valuable elements, including iron, aluminum, silicon, rare earth elements, lithium, gallium, germanium, vanadium, uranium, titanium, scandium and phosphorus. These coalassociated elements are significantly enriched in coal combustion byproduct fly ash because the majority of the main components, carbon and hydrogen elements, being removed. Table 1 provides the chemical composition range of the main element oxides in 12 Chinese fly ash samples collected from coal power plants located in Northeast China, Northwest China, Southwest China and Southeast China. It can be seen from Table 1 that the major mineral components of different ashes are similar, but the bulk chemistry of different fly ashes may vary due to the changes of ratios of the mineral components in different coals. The major mineral components in various Chinese coal combustion fly ash are silicates, iron oxides and unburned carbon.Chinese coal fly ash usually contains about 5 to 15 percent of unburned carbon, which are generally chars with irregular shapes and wide particle size distribution. In addition to unburned carbon, XRD analysis of four Chinese fly ash samples from Liaoning, Shanxi, Guizhou and Shandong provinces indicates that the fly ash samples are composed of minerals such as quartz (SiO2), mullite (3Al2O3.2SiO2 or 2Al2O3.SiO2), hematite (Fe2O3), maghemite (gamma form of hematite, ?-Fe2O3) and magnetite (Fe3O4). The mullite and quartz particles are usually present as spherical particles because they are formed by melting clays, feldspars, quartz, calcite and other common minerals in coal during coal combustion. The silicate particles have usually entrapped gas to yield hollow spherical particles because their lower melting point facilitates gas entrapment.The iron oxides are usually spherical also. The magnetite (Fe3O4) is derived from pyrite (FeS2), hematite (Fe2O3), siderite (FeCO3) and limonite (2Fe2O3.3H2O) in the coal. Maghemite (?-Fe2O3) is formed by dehydration of the mineral hydrohematite (?-FeO(OH)) and/or oxidation of magnetite (Fe3O4) during coal combustion. Maghemite (?-Fe2O3) and magnetite (Fe3O4) are strongly magnetic, so they are recovered from Chinese coal fly ash and widely used for coal processing in China (Fan et al., 2005, 2000)."

Jan 3, 2018

By W. S. Tremaine

When the Hedley Mascot mill was built in 1935, it was designed as a straight flotation plant. The ore to be treated at that time was a gold ore in which the gold was intimately associated with arsenopyrite and pyrrhotite in highly silicified and garnetized limestone gangue. This material was ground to 85 per cent minus 325 mesh in two-stage grinding and floated in standard flotation cells to produce about a 5-ounce concentrate, which was shipped to Tacoma smelter for refining. This arrangement gave us a recovery of about 89 per cent. Test work indicated that the best way to improve this recovery would be to build a cyanide plant to treat our flotation middling. Arrangements for the construction of this plant were finally approved and work on it was started in the spring of 1940. This plant was of the conventional type in which the flotation middlings were thickened, filtered, and then put through the usual cyanide process. Its capacity was 50 tons of middlings per day. This arrangement worked quite satisfactorily and gave us an increase in overall recovery of 4 per cent. Unfortunately, about the time the plant was completed, we developed, and started to ship to the mill, ore that differed entirely from that met with up to that time. Instead of being hard, it was very soft, the orebody from which- it came being much faulted and brecciated. In many sections, the sulphides were oxidized and the breccia was filled in with a very soft, hydrous iron silicate known as chloropal. When this new ore was mixed with the old ore and sent to the mill, the whole operation was disrupted. The chloropal slimed so badly that the classification, flotation circuits, and cyanide plant would not handle it. The difficulty in the cyanide plant was at the head end, where the 10 ft. by 20 ft. thickener and the 8 ft. by 8ft. drum filter would not handle the middlings containing a large percentage of primary slime and chloropal. This material would not thicken to more than 30 per cent solids in the thickener and, when pumped to the filter, would forma very thin, slimy cake. Overall recovery dropped to between 83 and 84 percent and it was quite apparent that some extensive changes would have to be made in our flow-sheet before this ore could be treated successfully.

Jan 1, 1947

By B J. Andrew, M R. Daley

Mount Isa Copper Mines is a world-class mining operation producing approximately six million tonnes of ore per annum. With over 50 years of mining history and over 76 million tonnes of underground resource remaining there are many challenges facing the mine technical team today and into the future. The mine consists of nine distinct areas: the Hangingwall Lens, Footwall Lens, 1100, 1900, N1100, N1900, 3000, 3500 and N3500 orebodies. Each of these areas have different characteristics, requiring varying methods of mine design and ground control for safe and efficient orebody extraction. Each of the areas operate with an independent sequence whilst interacting with the entire underground operation. Within the first five years after graduating mining engineers tend to orient their careers in either a technical or operations direction. Engineers working towards a specialised technical career will often be working as mine planning engineers, whilst others more focused in the operations stream occupy roles such as operations or project engineers. At this stage of a mining engineerÆs career they are not yet categorised into one stream or another, but career decisions made now can generally focus their ultimate career path in one direction or the other. Due to the size of the Mount Isa operations there are many opportunities for engineers pursuing both career path and plenty of room for growth forthose as yet unsure.

Jan 1, 2005

By Gregory D. Savage, Bruce M. Everett

Introduction The growing role of Colombia as a major supplier of internationally traded steam coal has been widely discussed in the industry. Although Colombian coal has been produced and exported in small quantities for a number of years, the country's position as a major coal exporter began in earnest in 1985 with the first commercial exports from the Cerrejon North Block Project. The mine is located on the Guajira peninsula in northeast Colombia, about 145 km (90 miles) from the coast (Fig. 1). In addition to the mine itself, the project involves construction of a dedicated railroad and port. This forms a modern, efficient, and integrated system. The project is embodied in a 50-50 association contract between International Colombia Resources (Intercor), a wholly-owned subsidiary of Exxon, and Carbocol, the Colombian state coal company. Intercor and Carbocol share investment and operating expenses equally. Intercor has the additional responsibility of managing operations on behalf of the partners. Each partner is entitled to 50% of the coal produced, and each markets its share separately. The project is a multi-seam, truck and shovel operation, based on large reserves (2 to 3 Gt or 2.2 to 3.3 billion st) of high quality bituminous coal. Exports began in the first quarter of 1985, at modest levels through what is called Early Coal Facilities. The permanent coal handling system began operation in February 1986. Production will increase rapidly in each of the next few years, reaching the design capacity of 15 Mt/a (16.5 million stpy) in 1989. Based on available resources, however, the resource will support expansion, and continued growth in production into the 1990s is feasible. Importance of transportation The success of a new coal export venture, such as Cerrejon, depends heavily on efficient transportation. In the international coal industry, overland and ocean transport can in some cases account for 40% to 50% of the final value of the product. Many coals, such as western US subbituminous coals, cannot reach export markets at all because of their low heat content and great distance from export markets. By the same token, low-grade resources are often commercially attractive for local markets even in the face of competition with much higher quality coals from distant sources. Figure 2 shows the growth in steam coal imports into Europe, the largest trading market. Through

Jan 6, 1986

By H. Stuart Auvil

Twelve samples of run-of-oven coke were taken at coke plants in the United States and Canada. Sampling procedure was directed toward obtaining the highest possible degree of uniformity in the gross samples, so that variations in results caused by sampling variations were at a practical minimum. Under these conditions the standard deviation of the screen analysis test on 500-pound samples is found to range from 1.2 percent for the 1-inch screen to 4.5 percent for the 5-inch screen. At present, the A.S.T.H. standard method of test requires that results be reported to the nearest 0.1 percent. This implies a higher than actual degree of precision, and revision of the report required by the method is suggested. Much larger Samples than are generally tested are required to reduce normal testing errors to a point where they are not appreciable fractions of the total variations found in a smoothly operating plant. For example, it is deduced that over 100,000 pounds of coke must be screened to determine if ordinary day-to-day variations in screen analysis have appreciable effects on the performance of a blast furnace.

Jan 1, 1950