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By Bernard L. Cohen

INTRODUCTION The most serious occupational radiation episode in U.S. history was the exposure of uranium miners to radon daughters in the 1945-1968 time period. Although the maximum permissible dose at that time was 12 WLM (working level months) per year, average exposures were several times that figure, and ten times higher exposures were not uncommon. Starting in the early 1960s, mounting epidemiological evidence appeared for an excess incidence of lung cancer among these miners; up to 1974, there was an excess of 134 cases (159 observed vs 25 expected) among the 4000 in the group under study (NAS-1980). When this excess became apparent, the Federal Government took jurisdiction, greatly tightened enforcement, and in 1969 lowered the maximum permissible exposure to 4 WLM per year. These standards were met largely by a great improvement in ventilation. As a result of these measures, average miner exposures were reduced 5-fold from 1965 to 1968 and by another factor of 3 by 1970. In 1978, the 4 WLM/year maximum permissible exposure was exceeded by only 37 of 7500 underground miners, for only 16 wars it exceeded by more than 25%, and for only 8 was it exceeded by 502 (AIF-1980). The average exposures to the various groups are listed in Table 1. We see that the average exposure for all miners was 1.03 WLM, and for those who worked essentially full time underground it was 1.45 WLM. For purpose of later discussion, it will be convenient to choose a single value for average exposures. In view of the fact that employment situations and job categories are bound to vary over a lifetime of work, we take this to be 1.3 WLM/year. The purpose of this paper is not to dwell on history, but rather to address the question of whether or not this present situation is satisfactory. This question was considered recently by a study group under the auspices of National Institue of Occupational Safety and Health (NIOSH-1980) and it answered the question in the negative, concluding that the maximum permissible exposure should be substantially reduced. However, their arguments were incomplete and were lacking in perspective. The principal thrust of this paper is to provide some of the material overlooked. RISK TO URANIUM MINERS FROM RADON EXPOSURE In order to quantify the risk to uranium miners under present working conditions, it is first necessary to estimate the risk of lung cancer per WLM of exposure. The most straightforward way of doing this is to use the data on the group of uranium miners under study. These are listed in Table 2 for 8 exposure ranges and for the total group (NAS-1980). If all data are given equal weight, the risk is seen to be 3.5 x 10-6 per year per WLM. Much can be said in favor of using this value for the risk as dose independent; it is within one standard deviation (SD) of the observations in 5 of the 8 dose categories (as expected from the definition of SD), and within 2 SD for all 8, and for the three cases differing from the mean by more than one SD, two are above and one is below. However, the uranium miner exposures in the present situation will be far below those covered in Table 2, so it is worth considering the possibility that the risk differs from this at low doses. From the last column of Table 2 we see that the experience from all exposures below 600 WLM indicates a risk higher than the mean for the entire group by more than two standard deviations (the value 600 WLM in this comparison was deliberately chosen to maximize this deviation; for exposures below 360 WLM and 840 WLM, the excess is only 1.0 and 1.6 standard deviations respectively). In view of this tendency for the risk to be higher at lower dose, we will take the risk to be 5.0 x 10-6 per year per WLM in what we will refer to as model A. This risk estimate is based entirely on exposures much [higher] than those that will be experienced by

Jan 1, 1981

By T. Yukimasa

Hachinohe smelter, a zinc-lead blast furnace complex with the annual capacity of zinc plus lead of 100,000 tons, had originally treated normal zinc and lead sulfide concentrates. However, it is currently handling a great variety of raw feeds ranging from complex sulfides to oxidic recycled materials in view of resource economy, most of which are unsuitable for zinc electrolysis. This paper reports on some significant efforts recently carried out on improving sintering operation, i.e., the increasing use of secondaries against harmful ingredients like halogens, and the substantial reduction in energy use as the results of various modifications and improvements.

Jan 1, 1982

By Hiroyuki Abé

This paper is a review of research and development on geothermal energy extraction in Japan especially on hydraulic fracturing. First recent geothermal developments in Japan are outlined in Part I. An increase in the production rate of geothermal wells may be highly dependent on the geothermal well stimulation technology based on hydraulic fracturing. The hydraulic fracturing technique must be developed also for geothermal energy to be extracted from hot, dry rock masses. In Part II, the research on hydraulic fracturing and field application are reviewed.

Jan 1, 1982

By John S. Lagarias

While systems to remove sulfur oxides from flue gases have been used at coal fired power plants since 1931, critical need for flue gas desulfurization has only occurred since the late 1960s following the passage of the Clean Air Act Amendments. Commercial and advanced flue gas desulfurization processes (FGD) are reviewed. Advantages and disadvantages of the processes are discussed. Regulatory requirements leading to the development of FGD systems are identified. The location and operation of coal fired plants may be determined more and more by the regulatory requirements for sludge disposal, waste, water discharge and air emissions.

Jan 1, 1978

By J. Raatikainen, I. Auranen

"INTRODUCTION Sorting technology has advanced rapidly recently. Of the two possibilities particle sorting has advanced especially in introducing new sensors and the use of multiple sensors. The analyzing and computing lead times have also shortened. This has made it a viable technology option for many applications but not for the most important sorting task at a mine; the run-of mine ore. Bulk sorting, however, has advanced in smaller steps, even if the technology has the capability to tackle the run-of-mine ore and offers a high potential to bring mines substantial economic benefits. The sensors, which are useful are restricted by the difficult operating conditions or by the ore characteristics. One of the important features of run-of-mine sorting technology is the major material handling infrastructure required. The capital expenditure can be substantial requiring good understanding of the sortability curve (grade-recovery curve) behavior of the ore. This paper discusses one industrial case, where substantial amount of data measured from the ore feed belt has been obtained. This data was then analyzed for the grade recovery curves obtainable from that ore with sorting. EXPERIMENTAL The XRF measurement used was the FCA device from IMA Engineering (Fig.1). It is a specially built version of XRF designed to operate with coarse material. The measurement was situated at the main belt conveyor taking ore from the primary crusher to the stockpile. The crushed ore was about 80% -300 mm at a capacity of 1100-1200 tph (Fig.2). Measurement times were varied from 30 seconds to a minute. Measurements were obtained over several months.As the XRF is a surface distribution measuring technique, the measurement was first tested upon accuracy and reproducibility against plant daily wet chemical assays and against on-line Courier feed analysis. As there is a varying delay in the ore stockpile, the delay time was used as a variant in the validation. Different measurement times were tested for accuracy. A one minute measurement time gave a total measurement relative standard error, which was both for Cu and Ni below 3%. The results showed also very robust correlations; for Cu, the correlation coefficient was R > 0,94 for one minute measurements over three months and R > 0,86 for Ni respectively. Fig 3. Shows a measurement period of two hours showing substantial feed grade variations (given as relative value; 1.0 represents the mean value during the measurement month)."

Jan 1, 2018

By D. W. Gunkle

Processing of various ores and materials in a reducing atmosphere has been done for many years. However, the typical device currently used is a large, often high maintenance, expensive piece of equipment; the rotary kiln. While it is a very reliable and a proven technology, the rotary kiln also has its limitations. It is limited by its ability to process very fine materials without creating a huge dust loss to the air pollution control equipment. This leads us towards the development of an alternate technology; the Gas Suspension System. Gas suspension preheating of various materials has been in commercial use since the early 1950's, but recently has been expanded to include Gas Suspension Reduction. Laboratory experience has proven successful on several materials; Nickel Laterite Fines, Iron Ore Fines, Fluorspar, and Clays. The gas suspension reduction system has many advantages over the conventional reduction kiln when processing fines. They are; lower cost, more fuel efficient, able to process fines, less real estate required, etc.

Jan 1, 1998

By Adrian C. Dorenfeld

[Agitation and transport of slurries have been investigated intensively for the past twenty years. It has been shown (1) that slurries have the properties summarized in Figs. 1, 2, 3, 4, and S. For a detailed exposition the reader is referred to the above reference and the bibliography, which, in turn, have extensive references and bibliographies. An interesting problem with which the senior author has been concerned with is the scab up of power requirements for slurry agitators operating in the laminar region with pseudo plastic materials. Pulps of shaly ores, after various chemical reactions in aqueous leaching systems, are often difficult to settle and filter if agitation is violent. In these cases agitation must be at a minimum, yet prevent [tling] such as in copper uranium ores. This mild agitation is on the laminar region.]

Jan 1, 1967

By Jerry C. Tien

The rare earth elements (REEs) are a group of 17 chemical (metallic) elements. REEs are used widely in high-technology, clean-energy products as well as weapon systems. China's dominant position as a producer of over 95% of the world REEs output and the world's increasing reliance on REE products have highlighted concerns about the future availability of rare earths in recent years. This paper briefly reviews the REEs world reserves, production, consumption, the impact of our heavy reliance on REEs products and China's changing policies on REE export on world supply chain.

Jan 1, 2013

By L. Xiao

Using K-oleate as a collector and alizarin red S (ARS) as a modifying agent, selective depression of dolomite from francolite was achieved in alkaline medium (pH> 9.0). Interestingly. ARS was also found to depress igneous apatite in alkaline medium in oleate flotation of apatite and calcite. Adsorption of ARS alone on dolomite was found to be higher than that on francolite. Complimentary adsorption experiments of ARS and K-oleate showed that oleate adsorption was increased in the presence of ARS on francolite but not on dolomite. K-oleate adsorbs on both francolite and dolomite and causes precipitation of calcium and magnesium oleate. Such precipitates can be pre-vented when ARS is present. The results are explained in terms of competitive adsorption for the active sites on francolite and dolomite by oleate and ARS, and their interactions with dis-solved mineral species in solution.

Jan 1, 1988

This paper presents the results of an investigation of the stability of the mass flow rates and average pellet size in the different streams of an industrial-scale balling circuit. The variables in this study include water content, drum speed and fresh feed rate. It was found that both the mass flow rates and pellet diameter are greatly disturbed when a change, positive or negative, in any of the variables takes place. For most of these disturbances to be damped don, a period of one hour or so is required. When a disturbance in the feed rate was made, the transient period extended to more than one and half hours (the duration of the experiment). It was observed that there is an interaction between the drum speed and moisture needed for producing an acceptable green ball product. The moisture content of the product pellets was found to be a function of the pellet size, with the larger pellets retaining a higher moisture content.

Jan 1, 1980

By Frank Pollard

The Australian coal industry over recent years has experienced the situation whereby exploration and mine development are moving into geographical areas where the coal seams have never been mined to any extent in the past, if at all, and particularly where there is no history of experience in preparation of these seams. Additionally, the demands have been such that the development of a mine up to production stage should proceed with minimum delay. This is a situation which is of some importance and concern, in view of the coal quality requirements now experienced within world markets which can only be met, in most cases, by careful preparation. Costs are such that the preparation plant should operate as required by the situation and with maximum efficiency, which means that laboratoty information of breakage and washability characteristics which are required for preparation plant design should be accurate and available as soon as possible, even to a certain extent during the progress of the exploration.

Jan 1, 1981

By Peter N. Calder

There is little doubt that the stability of both highwalls and spoil piles is essential to efficient strip mining. Accurate determination of the appropriate geotechnical parameters will pay dividends during mining, but only if the mine operation closely follows the engineering plans which have incorporated These factors. Productivity is invariably higher in mines where failure of highwalls and spoil piles does not occur. This is the result of the reduced rehandle and better working conditions found in stable mines. Control of the waste piles and highwalls also leads to better coal recover since failures can result in the burial of uncovered coal, which is then lost to mining. Safety is an important consideration. The importance of providing a safe working place for employees and of protecting costly mining equipment is hard to overemphasize. For miners, working in areas where instability exists, the degree of hazard involved in their occupation is increased particularly where night operations are involved. It is true, too, that there have been many cases where loading equipment has been buried and severely damaged by failures.

Jan 1, 1980

By Jurgen Weissflog

Why, where and since when using shiftable conveyors? Advantages of this equipment The ever increasing demand for bulk materials such as ore, coal, lignite, oilsand, oilshale and bauxite requires mainly an opencast operation. To exploit these materials huge amounts of overburden and partings must be transportes by means of conveyors, trucks or trains. When analyzing the various opencast mines it can be established that there exist only two basic types of mining systems, i. e., the discontinuous strip mining system as used in the USA (Fig. 1) and the continuous mining system as is commonly applied in Europe. The reason why these two mining methods have been developed parallel to and independently of each other to such a high technical standard results from the varying geological conditions of the mineral deposits.

Jan 1, 1983

By Satya Harpalani

The four most important parameters controlling the flow of gas in coal are the gas content, permeability, diffusion coefficient and cleat characteristics. Estimates of these and, more importantly, a knowledge about the variation in their values over time are required for simulation of long-term gas production. This paper describes experimental techniques to determine each of these, along with their time dependency, under simulated in situ conditions. It is shown that the permeability, diffusion coefficient and the cleat aperture values are not constant as usually assumed to be. There is a significant variation in their values as a result of changes in the microstructure of coal associated with release and flow of gas.

Jan 1, 1995

By H. P. Hatch

Ash is a material that many people leave to nature to handle. Others sometimes sweep it under the rug to be disposed of by someone else. In our business we cannot do either. In fact the American Electric Power System spends many millions of dollars in plant investment costs to collect the material, and then many more millions to dispose it. In 1965 alone the coal fired steam generating plants in., the AEP System produced approximately 2,400,000 tons of ash, enough to fill 40,000 coal cars which would extend as a single train across the entire states of Ohio and Indiana. Even though our present ash production is large, this is only the beginning when we forecast the future growth of our system. By 1980 it is estimated that our generating capacity will expand to about three times its present size, and with coal as our primary source of fuel our ash production will increase proportionately to about 7 million tons a year.

Jan 1, 1966

By Norman F. Schulz

The technical excellence of separation achieved in a mineral concentration process, or any other process where two constituents of any kind are physically separated from each other, is expressed uniquely and quantitatively by the Separation Efficiency: ES = (R ? Rg) where R is the percentage of the valuable constituent and Rg the percentage of the waste appearing in the concentrate. The Separation Efficiency meets all the usual requirements of a true efficiency and is independent of the nature of the process used. It can be visualized as the percentage of the feed material that, in effect, actually undergoes complete separation while the rest of the feed is distributed randomly and unchanged into the two separation products.

Jan 1, 1969

By Michael Clar

Total suspended solids (TSS), generally referred to simply as sediment, is one of the four major parameters of water pollution associated with surface mining activities. The other three para¬meters are iron, manganese and pH. Currently the Environmental Protection Agency (EPA) is in the process of developing and implement¬ing effluent limitations for these pollutants pursuant to section 301 of the Federal Water Pollution Control Act Amendments of 1972, 33 USC 1811.1 To date, effluent guidelines for existing point sources have been published, and guidelines for new sources are forthcoming. The effluent limits which have already been developed for TSS have been subjected to some controversy.1 Some industry spokesmen have indicated that they may be unable to meet these effluent limitation guidelines for TSS. The industry claims that in certain areas the suggested limit is unattainable since high suspended solid loads already exist in streams due to numerous and various sources of nonpoint pollution which include agriculture, silviculture and urban construction for which no TSS effluent limits have been set. An opposite viewpoint asserts that the TSS limitations are too lenient since permit data from the Regions (U.S. EPA Regions) indicates present compliance for several companies under more stringent TSS limits. The experience at the Centralia mine in Washington is one example.2

Jan 1, 1977

By R. E. Musgrove

At the present time Climax Uranium Company recovers vanadium oxide from carnotite type uranium ores in the mill at Grand Junction, Colorado, The flowsheet of this mill is shown in Figure I. Vanadium is solubilized by a salt roast of the slime fraction of the ore and dissolution is accomplished by a water leach. The metal is precipitated from the pregnant liquor as sodium polyvanadate by heating to boiling and adjusting the pH to 3 with sulfuric acid. The sodium polyvanadate, commonly called, "red caken, is filtered, melted, and cast into thin flakes. This fused flaked vanadium oxide is the material which is packaged for sale. Fused vanadium oxide, marketed by Climax, contains approximately 87% V205, 7% alkali oxide, 0.08% sulfur, 0.03% phosphorus, and less than 0.5% Insoluble. This material is of a lower grade and has a higher alkali oxide content than other vanadium products offered for sale at this time. A typical analysis of a high grade vanadium oxide currently offered for sale by another company is 98% V205, 1 - 2% alkali oxide, less than 0.05% sulfur and less than 0.2% Insoluble. The only reagent consumed in the precipitation of the sodium polyvanadate is sulphuric acid. The total reagent cost is 0.58 cents per pound of vanadium oxide produced.

Jan 1, 1958

Mining steeply dipping coal seams is a difficult task. Prior to 1996, fully mechanized longwall mining methods along the seam strike direction were tried in China and other countries. Due to its larger coal reserve in steep seams, China made more, but still limited, progress on mining such seams than other major coal-mining countries. In the last two decades, accelerated research efforts have tried to improve the mining technology in steeply dipping coal seams. Based on this work, a dynamic model of a roof-support-floor (R-S-F) system under asymmetrical constraints in mining steep seams is established here, and a theory of strata control and hazard prevention is formed. The key technologies for mining steep coal seams include global and regional strata control methods in the longwall face; methods for the longwall face machines to sustain static and dynamic loads; and flexible protection technology. These theories and technologies have been successfully applied in China to the mining of steep coal seams of varying thickness and hardness, with hard and soft roof and floor, and with a high potential for spontaneous combustion. In recent years, the technology has been introduced to Russia, India, Uzbekistan and other countries where steep coal seams are mined.

Jan 1, 2013

By H. W. Breathitt

World demand for phosphate rock has increased significantly in the past fifteen years. Prior to the early 1960's, most of the world production was obtained from Florida, North Africa, and Kola. As the 1960's arrived, new mines in North Florida and Eastern North Carolina, as well as expanded production in the Western United States, .increased domestic production. Many new mines overseas have also become significant. This includes countries such as Senegal, Togo, Israel, Spanish Sahara, and Jordan. Limited production, often as by-products, has been noted in South Africa, Brazil, and other countries. In recent years, and even recent months, we have learned of many new areas being considered as potential sources of phosphate rock. This includes Australia, Saudi Arabia, Mexico, Colombia, and Brazil. Many other developing countries have discoveries and are considering their new deposits, often with difficult beneficiation problems, as potential sources of phosphate. These factors all relate to expanded world, population and the demand for more fertilizer products to produce food. In this paper, four areas of the world with different types of phosphate deposits are briefly reviewed to contrast the ore beneficiation problems to Florida procedures--long considered the "standard" of the industry, at least for most of the United States' domestic production. Agrico has three large operating mines in Florida with total production capacity exceeding seven million tons per year. Here, pebble phosphate (+14 mesh material) is produced without the use of flotation, whereas all of the material finer than 14 mesh is subjected to flotation beneficiation to upgrade into high grade concentrates.

Jan 1, 1977