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By Susan T. Bagley, Kenneth L. Rubow, David H. Carlson, Bruce K. Cantrell, Winthrop F. Watts

Permissible exposure limits (PELs) have been established for gaseous pollutants, carbon monoxide (CO), carbon dioxide (CO2), nitric oxide (NO), nitrogen dioxide (NO2), and some gas-phase hydrocarbons emitted in diesel exhaust. There is, as yet, no PEL recommended for diesel exhaust aerosol (DEA), nor is there a standard method for sampling this aerosol. The University of Minnesota and the U.S. Bureau of Mines have collaborated to develop a personal diesel exhaust aerosol sampler (PDEAS) which utilizes size-selective inertial impaction and gravimetric analysis. During the field tests of this sampler, numerous air quality measurements were made in underground coal mines that use diesel equipment. The mine mean DEA concentrations for the five mines surveyed, determined with the PDEAS in the haulageway, was 0.89 mg/m3 with a standard deviation of 0.44 mg/m3. DEA contributed 52 % of the respirable aerosol at this location. In three of the mines filter samples were collected for DEAassociated polynuclear aromatic hydrocarbons (PAHs) and biological activity determinations. Two of the mines were also monitored for the major gaseous constituents found in diesel exhaust. In general, the PAH and biological activity levels were similar for all three mines, and indicate that up to 25 % of the haulageway concentrations may be contributed by outby diesel vehicles. Measured concentrations of CO, C02, NO, NO2, and SO2, were well below regulated levels. INTRODUCTION Diesel exhaust contains pollutant gases, such as carbon monoxide, carbon dioxide, nitric oxide, nitrogen dioxide, and gas-phase hydrocarbons, as well as DEA. Much of the health-related concern focuses on DEA and associated organic compounds (Watts, 1992a). A wide variety of these PAHs have been identified and some are known carcinogens and/or mutagens. The U.S. Mine Safety and Health Administration (MSHA) has proposed new PELs for these and other contaminants (MSHA, 1989). MSHA has also published an advance notice of proposed rulemaking to establish a separate PEL for diesel particulate (MSHA, 1992). The U.S. Bureau of Mines has collaborated with the University of Minnesota to develop and field test a PDEAS. The PDEAS is a three stage sampler based on the MSA' personal respirable dust sampler. It utilizes a respirable cyclone preclassifier followed by a 0.8 µm cut point impactor and afterfilter operating at a flow rate of 2 L/min. Respirable aerosol greater than 0.8, µm in size is collected by the impactor while DEA, less than 0.8 µm in size, is collected by the afterfilter. Hence, gravimetric analysis of the afterfilter permits measurement of DEA concentrations. This development and laboratory evaluation of the PDEAS were described previously by Cantrell (1990) and Rubow (1990). During field tests of the sampler, numerous air quality measurements were made in continuous miner sections of five underground coal mines that use diesel haulage equipment. These air quality measurements included levels of selected PAH and biological activity associated with DEA collected in the intake and haulageway areas of three of the five underground mines, and CO, CO2, NO, and NO2 in two of the mines. The objectives of this paper are to present the DEA and associated pollutant concentrations measured in these mines and to assess the impact of diesel face-haulage equipment on underground mine air quality. MINE DESCRIPTIONS The mines used for the PDEAS evaluation were designated J, K, L, N, and 0. Mines K, N, and 0 are located in the Western United States, while mines J and L are located in the East. Each mine produces high volatile, bituminous coal with shift production levels varying from 500 to 2000 tons/section. Seam heights varied from 1.5 to 3.0 m. Mines K and N use continuous mining to develop longwall panels. The others are strictly room-and-pillar operations using continuous miners. The number and types of diesel-powered vehicles used at these mines were described by Watts (1992b). Mines J, K, N, and 0 use diesel power to assist in a wide range of activities in addition to coal haulage. These included road maintenance, personnel and materials transport, lubrication, and welding. Mine L used only three diesel-powered shuttle cars to haul coal. SAMPLING AND ANALYSIS METHODS Aerosol Measurements Aerosol samples were collected in the mine portal area, the clean air intake to the continuous miner section, the haulageway one crosscut inby from the feeder breaker and belt, in the return airway, and on selected personnel. The haulageway sampling site was located near the point where the diesel-powered shuttle cars turn around to dump their loads. Additional respirable and DEA samples were collected and have been reported by Haney (1990).

Jan 1, 1993

By Y. S. Roditis

A new method for interpolating a block model is proposed, where both the diamond drill holes (DHs) and blast holes (BHs) data are used. Combining these data types poses a geostatistical "class size" problem due to the different statistical properties of the densely populated BHs and the sparsely populated DH data. This paper discusses how linear regression was used to adjust the DH values prior to the interpolation to account for the "class size" problem which is inherent to the procedure. The correlation between the BHs and the DHs is found. The DHs are then corrected based on the regression line. Each block that falls within a certain range of influence of a blast hole is assigned a different code and is interpolated with the combined BH and regressed DH data set. Blocks that fall outside the range of blast hole influence are interpolated using the original DH data set. A comparison against other methods, indicate a 12% improvement over using DHs only and a 2% improvement over using BHs only.

Jan 1, 1992

By Raymond Mancha

"Conventional" coal dryers really do not exist. What we really mean to say is that there are many and varied kinds of coal dryers -- and the "air handling problem" is really the only portion of it which has been approached for solution by conventional methods. It now appears that these conventional methods need supplementing by some new, relatively unconventional apparatus. In order to approach this matter with mutual understanding, here is a quick survey of the coal drying art. Figure #1 shows a McNally Pittsburgh Pulso Dryer, In the McNally Pulso Dryer, the coal is fed-onto the screen by a rotary feeder assuring even distribution of the coal. As the coal travels forward due to the action of the screen, it is subjected to a controlled pulsating flow of hot gases. T ese originate below the deck and are directed up through the moving bed of coal. Fines sifting through the deck are dried in the hopper below the screen as they fall through the hot gases to an evacuation screw. The coal remaining on the screen is dried to the desired degree when it reaches the discharge end. At this point, it is directed down into the evacuation screw to combine with the fines, or it may be discharged as a separate product. As the coal travel down the screen, it is subjected to intermittent upward currents of hot gases. These first distend the bed allowing the gases to come into intimate contact with the coal particles for rapid and efficient heat transfer. Then, as the flow of gas is cut off, the bed settles and the extreme fines sift through the screen preventing their being carried away into the exhaust system.

Jan 1, 1958

By Williams R. Reynolds

Studies of the northeastern Mississippi bauxites were initiated primarily for the purpose of ascertaining the quality and quantity of the ore. Subsequently, this ore was found to have a rather dubious economic value as was previously suspected but never established in earlier economic reports (1, 2, 3). However, the quality of ore was found to be higher than previously thought. Even though the ore bodies were determined during the early stages of this study to be too thin, small and widespread for commercial production a continuation of the study was not abandoned. On the contrary, the present investigation was intensified concentrating less on the economic application and more on stratigraphy and genesis. Considering the ever increasing demand for aluminum products the northeastern Mississippi bauxite district which includes portions of Tippah, Benton, Pontotoc, and Union Counties may soon become, in spite of inferior quantities of ore, an attractive area for bauxite production. Presently, however, the meager quantity of ore discourages exploitation. On the other hand, these northeastern district bauxites are facies of more extensive units of lignite bearing high aluminum clays, and considering the advances in aluminum extraction from clay these clays may in the future beckon mining interest. The bauxite of the northeastern Mississippi district, mapped as a part of the Betheden Formation (4). has an outcrop trend along the county lines of Tippah and Benton Counties and the extreme western portion of Union and Pontotoc Counties. Studies of exposures and cores stratigraphically positions the outcrop between the middle Midway Porters Creek Clay and the lower Eocene Wilcox sands and

Jan 1, 1977

By Charles M. Hauptman

The Karst asbestos deposit, discovered seventy years ago, is 32 miles south of Bozeman in southwestern Montana. The deposit is about one-half mile west of the Gallatin River which flows in a deep V-shaped valley flanked on either side by rugged mountains. The Madison range is west of the river and the Gallatin range lies to the east. A busy all-weather highway, U.S. No. 191, follows the river and is the major north-south route between Bozeman and the Gallatin valley to the north and Idaho and the west entrance of Yellowstone National Park to the south. The asbestos deposit is a large body of serpentinized peridotite in which anthophy11ite.occurs, both as distinct veins and as a disseminated mineral in the peridotite mass. The known exposures of the asbestos-bearing rock occur on a steen south slope at an "elevation of about 7000 feet, an elevation 'which is about 1200 feet above the Gallatin River. Over the years, a number of small companies have attempted to exploit the Karst asbestos deposit without continuing success. The present operator, Galaxy Mining Corporation, has attempted a systematic approach to the problem by utilizing geologic and engineering surveys to determine the economic and technical feasibility of a mine and plant to produce a finished asbestos pro-duct. The results of this work indicate a high probability of success for the project. However the company now faces that dilel1lJllB so common to the non-metallic mineral business; that is, whether to continue a research program of further mineralogical and technological studies in conjunction with detailed market surveys or to rely on the work done to date and embark on a pilot progril1n

Jan 1, 1971

By MOHAMED WAEL, ANASTASIA GOEVA, ABDULAZIZ TAWFEEQI, IHTISHAM TARIQ, S. M. ZAKIR HOSSAIN, NIAZ ALI KHAN, MUHAMMAD FAISAL IRFAN

Carbon dioxide (CO2) mineral carbonation is a carbon capture and storage (CCS) technique that can sequester CO2 permanently in the form of durable carbonate minerals. Extendable permanent storage capacity — onshore and offshore storage reservoirs — and the exothermic nature of the mineralization process make this technique attractive [1]. In the present study, maximum carbonation efficiency for aqueous mineral carbonation was achieved through two steps: optimization of calcium leaching from cement kiln dust followed by the reaction of pure CO2 with the calcium hydroxide precipitates formed by hydroxylation using sodium hydroxide (NaOH). Optimization of calcium leaching is highly important, as it is a rate-limiting reaction step in mineral carbonation and also influences and enhances the carbonation efficiency. To maximize the calcium leaching as well as carbonation efficiency, response surface methodology — with either Box-Behnken design or central composite design — was applied. It is the most well-known statistical, fully randomized and bias-free method for determining optimized conditions using quadratic regression models.

By C. R. Tinsley

Valuations can be molded, twisted and misinterpreted. Cases of spurious scope setting; limits to the information or access by the valuer; difficulties with the lack of comparative valuations; inappropriate valuation methods and outright speculations are described. None should be accepted by an experienced, independent minerals valuer. The Australasian Institute of Mining and Metallurgy (TheAusIMM) is working on a Valmin Code for which a Manual of Best Practice and Valuation Guidelines may be developed.

Jan 1, 1995

By H. Suharyono

A laboratory investigation of flocculation following polymer addition during slurry flow through pipes and in-line (static) mixers is described. Results are presented showing the effects of flow velocity, pipe length, in-line mixer elements and the use of multiple addition points on flocculation performance as measured by settling rate and supernatant turbidity. The effects of agitation and mixing time are shown to be generally consistent with the results of equivalent tests, both batch and continuous, conducted in stirred tanks.

Jan 1, 1995

By L. F. McHugh

Molybdenum conversion operations discussed in this paper encompass all major operations commercially used to upgrade molybdenite concentrates to various refined products. More emphasis is placed on discussion of key pyrometallurgical unit operations. These operations conducted at Metec include roasting, sublimation, and hydrogen reduction

Jan 1, 1986

By M. Misra

The coral contaminated with plutonium at Johnston Atoll UA) was subjected to gravity and flotation separation processes at the Soil Washing Laboratory (SWL) and also at the Johnston Atoll UA) site. Tests were conducted with the contaminated coral fractions referred to as the "HP-l" ( hot particles) and the "sludge". The gravity process tested was centrifugal gravity separation and the flotation processes were conventional Denver mechanical flotation and tall column flotation. Flotation tests were conducted using both fresh and sea water. Industrial fatty acid (anionic collector) was chosen as collector to make plutonium-enriched particles hydrophobic. The use of flurosilicic acid and sodium silicate made the clean coral hydrophilic. The results show that each of the processed when tested with appropriate size fraction and operating conditions resulted in passing the success criteria. It was possible to obtain more than 80% weight of the original coral as "clean sand" having activity below the JA site "soil screening level" of 13.5 pCi/gm. The field tests spiked with plutonium particles showed remarkable success. The effect of depressants, flotation medium and the coral pretreatmentis described. Finally, a flowsheet developed by the University of Nevada, Reno to treat 8000 tons of HP-l pile presently stored at JA is presented.

Jan 1, 1996

By R. A. Young

Effective October 1, 1958, President Eisenhower imposed, by Presidential Order, fixed import quotas on lead metal and lead concentrates and also on zinc metal and zinc concentrates. He did this in response to an escape clause case under the Trade Agreements Act filed by many of the large and small lead and zinc mining companies in September 1957. It is the purpose of this paper to give the experience of the lead-zinc industry under this order during its first two years and some observations on what might have come about under different conditions of U.S.A. consumption. Before considering these various experiences and observations, it seems wise to first outline briefly the basic problem which prompted such an order. Under the Tariff Act of 1930, the duty on pig lead was fixed at 2-l/8¢ per pound and slab zinc at 1-3/4e; per pound. The ores, concentrates and closely related products of these metals carried closely related duty rates. The Trade Agreements Act of 1934 and succeeding similar acts had given the, President the power to lower these and other duties. As a result-of various negotiations with foreign nations, by 1951 these duties had been lowered to their present day rates of 1-1/16 per pound on' pig lead and 7/10o, per pound on slab zinc. Related ores, concentrates and semi-fabricated forms of the metals received commensurate treatment. Under these acts, the Tariff Commission has the right to recommend to the President duty increases, specific quotas or both if find that imports have injured the affected industry. He has the right to accept or reject such recommendations, in whole or in part, in the light of the national interest,

Jan 1, 1961

By Rodolfo V. de la Cruz

The broad front concept is based on the principle that gasification can be achieved more efficiently and completely from a plane broad combustion front in contrast to other geometries obtainable with current methods of gasification. By restricting combustion to a plane broad front, the ideal condition for gasification is achieved. A plane broad combustion front can be developed in coal by initiating and propagating combustion from the walls of an oriented channel and collecting product gases from another similarly oriented channel. Flow will then be directed along the highest permeability of the coal bed, the available cross-sectional area for fluid flow is substantially increased and, more importantly, the increased flow will be uniformly distributed throughout the whole mass of coal. The success of the method is greatly dependent on how well an initial and rigorous permeability survey and associated corrective measures yield a well-characterized coal bed. To maintain uniform reaction rates, the advance of the combustion front is located with pressure- or mass flow-transducers. These sensors are then connected to servo-controlled mufflers for controlling segments of the fire front which are advancing ahead of others. Finally, the development of the concept to overcome problems of roof collapse, reactant and product gas leakages, and water invasion are briefly summarized.

Jan 1, 1976

By T. Karlkvist, H. R. Kota, F. Andreas, B. I. Pålsson

"Separation of different calcium minerals have long been an interesting and challenging problem. In this investigation calcium mineral separation is examined by: microflotation, zeta potential measurement and adsorption, using novel collectors having two functional groups instead of one. In theory, by varying the distance between the functional groups, it could be possible to preferentially target one calcium mineral by matching the spatial distance between the sites on the mineral surface. In this investigation two new surfactants have been tested to estimate their ability to float apatite and/or calcite. Preliminary findings show that an increase in distance between the functional groups favors one mineral over the other, and this might be due to differences in the mineral surface structure. INTRODUCTION Apatite is a strategically important mineral which has both great value for industrial use as a precursor to phosphoric acid; and in the agricultural industry as an important source of phosphorous in fertilizers. This has led both the European Union and the United States to recognize it as an important resource for the future. Currently there is no lack of apatite in the world, but it is important to develop the beneficiation to ensure future supply. A common problem in apatite flotation is the selectivity towards calcite, which it is commonly associated with. Although calcite is an important industrial mineral its abundance makes it not usually worth to extract from apatite ores unless it is easy to separate1,2. Both apatite and calcite are semi soluble minerals with calcium as one of their constituents. The most common way to separate apatite and calcite is to use flotation. A process that involves making the mineral particles to extract from the system hydrophobic by adsorbing a collector on the mineral surface. One way to study collector adsorption on a mineral surface is by zeta potential measurements. The zeta potential is the charge at a slip plane a short distance from the surface. By measuring the zeta potential with and without the presence of collector it is possible to investigate if the collector is present at the surface or not, a change is indicative of collector adsorption. The zeta potential of fluorite, apatite and calcite without collector can be seen in Figure 1. The small difference in zeta potential between apatite and calcite shows the similarity in their surface properties and gives an indication of their separation difficulty. One additional problem with semi soluble minerals is their tendency to slightly dissolve in the pulp and thereby change the ionic composition of the solution. This makes separation and research problematic as the freed ions may readsorb on the mineral surface and interfere with the collector adsorption on the mineral surfaces3–5."

Jan 1, 2016

Aqueous pressure oxidation at low temperature, although desirable from a process engineering and operating point of view, presents unique problems when temperatures approach 160°C (320°F). In developing the pressure oxidation process for the Lone Tree Mine, elemental sulfur formation and agglomeration with pyrite proved to be a problem. This paper discusses some of the unique features of the Lone Tree sulfide deposit and its amenability to low-temperature oxidation. Problems encountered during pilot plant operation and their solutions are discussed.

Jan 1, 1995

By Thomas P. Oxford

The impact of recent legislation on Florida phosphate industry operations has been dramatic. The most significant influences are described: the National Environmental Policy Act of 1969; the Federal Water Pollution Control Act Amendments of 1972; and implementation of the Florida Environmental Land and Water Management Act of 1972. Further discussion includes: critical examination of the recently completed EPA Areawide EIS; potential effects of the Resource Conservation and Recovery Act of 1976; the Surface Mining Control and Reclamation Act of 1977; current local and state laws; and summary of studies on radiochemical effects of mining, seepage from gypsum ponds, and dewatering of waste clays.

Jan 1, 1979

By H. J. Bogert

Shallow, gently dipping quartz veins at the Mineral Hill Mine are mined in room and pillar stopes. Ore zones are severely folded and fractured, thus actual pillar strength and physical properties of the rock mass deviate significantly from conventional laboratory tests and pillar theory. Laboratory specimens large enough to include pre-existing fractures proved to be representative of actual pillar strength. Further adjustment for specific pillars was based on RQD. Deformation and stress were measured in several pillars during pillar recovery. Stress data and finite element modeling were used to estimate absolute pillar stress at failure. The stress/strain relation provided an excellent indicator of pillar behavior. Good agreement between lab data and underground data was found.

Jan 1, 1995

By William E. Robinson

Our earthly treasures are being quickly depleted. We have experienced what can happen in an energy crisis. You have read and heard all kinds of stories as to what caused this crisis. On the surface it would seem that all of a sudden a situation becomes a crisis whether it be fuel, potatoes, beef or whatever. Well, of course, they don't just happen. There is always a little fore-warning here, an indicator there. Someone recognizes a sign of potential trouble but is ridiculed when he forecasts it. We are running out of sand: Producers of aggregates who can say today ... "That couldn't happen to me", can well be awakened tomorrow to the cold fact of reality. It could come from any number of directions. Depletion is mostly foreseeable but zoning isn't. Legislation can also be sudden death to availibility. With the ever growing population moving into the rural countryside, available deposits are being sold either to developers or being zoned for restricted use. The fact that a gravel pit or quarry is located on a particular plot has not fazed some of the local planning boards when they decided to place the adjoining property in a residential Zone A. Proponents of zoning preach that such use is necessary to insure that the land will be put to its best use. Planning boards establish the best places for schools, homes, shopping areas, factories, etc., so that the individuals or groups are in harmony with each other. This is usually done to date without thought or consideration to the geological importance or potential of the area. Today over half of the United States is living under some form of land use restriction. Little consideration has been given to what lies under the ground to be zoned. Fortunately, the states are slowly getting around to geological surveying. I feel that it is about time that state and federal authorities institute governmental restrictions to prohibit or control local zoning ordinances which would deplete or deny an area of its natural resources. While I could continue for the balance of my time just on this facet of our industry's problems, my point is: How sure are you of your next load of sand? I could be well laughed at by some of you for saying that there is an alarmingly rapid disappearance of "nearby" sand and gravel reserves in many areas of the country. A questionable statement, except to those producers where depletion has already taken place.

Jan 1, 1974

By K. Whiting

In October 1993, the first two of a series of full scale passive biological treatment cells were constructed to treat mine drainage from the Burleigh Mine (located approximately 48 km west of Denver, Colorado in the Clear Creek/Central City Superfund Site). The two cells are each 19-21 m long, 10.7 m wide and 1.2 m deep. Each cell contains approximately 216 cubic meters of substrate (composted manure) and is designed to treat 60 L/min of mine flow. One cell is designed as an upflow reactor and the other cell is designed as a downflow reactor. The differences in flow hydraulics and treatment efficiencies will be tested in these two cell for approximately nine months before the remaining cells are built to treat all the discharge. The substrate material was selected based on a series of bench scale tests. During the tests, the amount of metals removed was determined. The design flow rate was based on a sulfide generation rate of 400 nanomoles of sulfide generated per cubic centimeter of substrate per day. Metal removal results for the first three months of operation of the two cells will be presented and compared to results of bench and pilot studies at other sites.

Jan 1, 1994

By John S. Livermore

I feel very privileged to be added to the distinguished group that has received this award since the first recipient, Reno Sales, received it in 1954. If my research is correct, the last geologist to be honored was Bill Callahan in 1982. Perhaps the Awards Committee decided it was about time to select a geologist, and I became the beneficiary. Regarding the discovery of the Carlin ore body, it was the culmination of several studies - one going back as far as 1939 when a US Bureau of Mines engineer named W.O. Vanderberg recognized an unusual type of gold mineralization in sediments in northern Nevada. What was unusual was the fact that the gold was so fine that it would not concentrate in a pan. This, plus the study of the Roberts Mountain thrust by Ralph Roberts (1960) and conversations with Harry Bishop, manager of the Gold Acres Mine, pointed Alan Coope and me in the direction of the Lynn Window and, eventually, the Carlin discovery. There has been a great deal written about this discovery. I thought it would be interesting to discuss the evolution of Carlin gold exploration in Nevada since this time and to discuss the changes in perception of this unique type of mineralization. The method used by Coope and me in following up on Roberts' work was to map geologically the Roberts Mountain thrust and conduct geochemical sampling of favorable outcrops and float. Coope was highly experienced in geochemical exploration, as he had graduated from the Royal School of Mines in London, studying under John S. Webb, one of the pioneers of geochemistry as applied to mineral exploration. We first considered using pathfinder elements, but finally concentrated on gold analyses alone, even though the sensitivity of fire assays used at that time was only about one-half part per million. According to the spatial relationship of the mineralization to the Roberts Mountain thrust, as pointed out by Roberts (1960), we were looking for mineralization within the thrust itself. Our models were the known Gold Acres and Getchell mines, which contained reserves on the order of 0.9 to 1.8 mt (1 to 2 million st). These were not of substantial size, but I had hoped we might find more than one of these tributary to a mill that would justify an operation for our employer, Newmont Mining Corp. What we ended up with was the type of deposit we were looking for - an open pit deposit of micron gold, which the old timers had missed because the gold was not capable of being panned. But never in our wildest dreams did we think there was a chance of finding a body containing 10 mt (11 million st) of ore at 0.30 oz/st (10.3 g/t).The deposit was not in the thrust proper but was found in a favorable horizon of Roberts Mountain siltstone that was below the thrust. This is the first example of how a model should not be followed blindly. Newmont was successful in keeping this discovery quiet for some time. After a considerable amount of drilling, a rumor circulated that they had discovered a large low-grade ore body of around 1.7 to 2.1 g/t (0.05 to 0.06 oz/st), which of course would not have been economic with gold at $1.13/g ($35/oz), which was the fixed price at that time. The company, for obvious reasons, did not discourage the rumor. When, however, the true results came out there was a lot of feverish activity. Because of this new type of so-called "invisible gold," which could have been missed by the old timers, the thought was that other deposits would be discovered very soon. The Carlin and other smaller deposits, including Bootstrap, Blue Star and Gold Quarry, were in windows where the lower plate of the Roberts Mountain formation (below the thrust) had been exposed by erosion. This then became the new

Jan 1, 1997

Everyone knows the importance of careful handling of explosives. Even so, the point is on occasion all too graphically driven home. Witness the recent blast at a Utah explosives plant that killed five people. Part three of this series on explosives discusses transportation, storage, handling, and destruction. Federal, state, and sometimes local regulations govern the many steps involved in transporting, storing, and handling explosive materials. Regulations minimize personnel exposure to hazardous material and insure that the explosives remain stable and usable.

Jan 9, 1981