• Application of hydrocyclones for recovery of fine gold from placer material

      Rao, P.D.; Wolff, E.N.; Maneval, D.R. (University of Alaska Mineral Industry Research Laboratory, 1982)
      Alaska and other gold areas have seen a sharp resurgence of placer mining in the last few years. Mines using sluice boxes usually recover gold down to 100 mesh, but recovery of gold finer than this size is a function of particle shape factor, sluice box design and operating parameters. It is felt that a concentrating device is needed to recover gold finer than 100 mesh that may not be recoverable in a sluice box. The device should be capable of processing a large volume of water and solids discharged from the sluice-box. Compound water cyclones, successfully used in the coal processing industry, seem to offer solutions. A system using these devices could recover a concentrate which would be one twenty fifth the size of the original solids in a two stage process. It is not intended to produce a finished product with cyclones, but to reduce bulk so that the reduced concentrate, free of slimes, could further be treated by flotation, gravity methods, or cyanidation to isolate the gold. This report addresses only the application of hydrocyclones for concentrating gold from placer material.
    • Characteristics and utilization of fly ash

      Lu, F.C.; Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1971)
      Fly ash produced by four power plants in Fairbanks and vicinity was collected and analyzed. Current fly ash specification and potential users of fly ash in general and in the Fairbanks area in particular were evaluated. A detailed bibliography on utilization of fly ash is appended for reference by producers and potential users of fly ash.
    • Characterization and evaluation of washability of Alaskan coals

      Rao, P.D.; Wolff, E.N. (University of Alaska Mineral Industry Research Laboratory, 1980)
      This report is a result of the second part of a continuing study to obtain washability data for Alaskan coals to supplement the efforts of the U.S. Department of Energy in their ongoing studies on washability of U.S. coals.
    • Characterization and evaluation of washability of Alaskan coals - fifty selected seams from various coal fields

      Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1986)
      FINAL TECHNICAL REPORT: September 30,1976 to February 28,1986
    • Characterization and evaluation of washability of Alaskan coals - phase i - selected seams from Nenana, Jarvis Creek and Matanuska coal fields

      Rao, P.D.; Wolff, E.N. (University of Alaska Mineral Industry Research Laboratory, 1979)
      This report covers the results of a study conducted to obtain washability data for Alaskan coals to supplement the efforts of the U.S. Department of Energy (formerly U.S. Bureau of Mines) in its ongoing studies on washability of U.S. coals.
    • Characterization and evaluation of washability of Alaskan coals - phase iii, selected seams from the northern Alaska, Nulato, Eagle, Nenana, Broad Pass, Kenai, Beluga, and Chignik coal fields

      Rao, P.D.; Wolff, E.N. (University of Alaska Mineral Industry Research Laboratory, 1982)
      This report is a result of the third part of a continuing study to obtain washability date for Alaskan coals, to supplement the efforts of the U.S. Department of Energy in their ongoing studies on washability of U.S. coals. Washability characteristics were determined for fifteen coal samples from the Northern Alaska, Nulato, Eagle, Nenana, Broad Pass, Kenai, Beluga and Chignik coal fields. The raw coals were crushed to 1-1/2 inches, 2/8 inch and 14 mesh topsizes, and float-sink separations were made at 1.30, 1.40 and 1.70 specific gravities.
    • Characterization and evaluation of washability of Alaskan Coals - phase iv, selected seams from the northern Alaska, Chicago Creek, Unalakleet, Nenana, Matanuska, Beluga, Yentna, and Herendeen Bay coal fields

      Rao, P.D.; Wolff, E.N. (University of Alaska Mineral Industry Research Laboratory, 1982)
      This report is a result of the fourth and final part of a study to obtain washability data for Alaskan coals, to supplement the efforts of the U.S. Department of Energy in their ongoing studies on washability of U.S. coals. Washability characteristics were determined for fifteen coal samples from the Northern Alaska, Chicago Creek, Unalakleet, Nenana, Matanuska, Beluga, Yentna and Herendeen Bay coal fields. The raw coal was crushed to 1 1/2 inches, 3/8 inch and 14 mesh top sizes, and float-sink separations were made at 1.30, 1.40 and 1.60 specific gravities.
    • Characterization and washability studies of raw coal from the Little Tonzona Field, Alaska

      Rao, P.D.; Walsh, D.E.; Phillips, N.; Charlie, K.G. (University of Alaska Mineral Industry Research Laboratory, 1991)
      Coal occurs in an isolated exposure of Tertiary, non-marine sedimentary rocks along the southwest bank of the Little Tonzona River, near Farewell, Alaska. The Little Tonzona River coal field is located approximately 150 air miles northwest of Anchorage, Alaska, and 210 air miles southwest of Fairbanks, Alaska; near the boundaries of Denali National Park. The Alaska Railroad and the Parks Highway are approximately 100 air miles from the coal field at their nearest point. The village of McGrath, on the Kuskokwim River, is located approximately 90 miles to the west (1). An impressive outcrop of coal-bearing Tertiary sediments is exposed for a distance of more than 275 feet on the west bank of the Little Tonzona River (Figure 1). More than seven coal beds, ranging in thickness from 3 feet ta 30 feet, with a cumulative thickness of over 134 feet, are interbedded with clay beds up to 40 feet thick. The clays are fine textured, extremely plastic, light grey to nearly white bentonites andlor tonsteins. Doyon Ltd., an ANSCA Native Corporation, holds land selections covering the inferred limits of the coal field. During 1980 and 1981, Doyon entered into exploration agreements with McIntyre Mines Inc. of Nevada. The two season exploration program took place from June 1,1980 through August 22,1980 and from May 27,1981 through August 22, 1981. During the 1980 field season, geologic mapping, prospecting, stratigraphy, trenching and bulk sampling of all coal outcrops were performed. This produced a total of 34 samples, which were taken for analysis. In 1981, six diamond drill holes with a cumulative length of 2,935 feet were completed. Core recovery was close to 90%, and a total of 147 coal samples, which represented 802.8 cumulative feet of coal, were taken for analysis. The exploration program confirmed a strike length of over 3 miles to the southwest from the main river bank exposure. Northward extension is unknown at this time. Although outcrop exposure is poor away from the river banks, burnout zones resulting from past coal bed fires form a resistant, recognizable on strike feature in the relatively unindurated Tertialy sequence. The appearance of these burnout zones along strike is often the only surface indication of the buried coal-bearing strata. Well preserved plant fossil impressions in the baked clays date the deposit as probable Miocene (2). Coal characterization and washability studies were performed on all coal samples by the Mineral Industry Research Laboratory of the University of Alaska Fairbanks. This work was conducted under the direction of Dr. P.D. Rao, Professor of Coal Technology.
    • Characterization of Alaska's coals

      Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1974)
      Coal characterization is a systematic determination of those properties of coal, or of its constituents, that affect its behavior when used. It will help in planning for recovery and use of the extensive Alaskan coal deposits, which have proven reserves of 130 billion tons. This estimate is of necessity based on widely scattered outcrops and meager drill hole data, and the reserves in the Cook Inlet region and the Northern Alaska field are considered to be several fold this figure.
    • Characterization of coal products from high temperature processing of Usibelli low-rank coals

      Rao, P.D.; Walsh, D.E.; Wilson, W.; Li, YuFu (University of Alaska Mineral Industry Research Laboratory, 1991)
      This research project was conducted in association with Gilbert/Commonwealth Inc. as part of an overall techno-economic assessment of high temperature drying of low-rank coals. This report discusses the characteristics of the dried/pyrolyzed products of two high temperature, evaporative processes and the dried product from a hydrothermal process. The long term goal of this and other coal drying studies conducted at MIRL, was to define drying technologies that have significant and real potential to competitively move Alaska's, low-rank coals (LRCs) into the export, steam coal market of the Pacific Rim. In 1990, Japan imported 33 million metric tons (mt) of steam coal with an additional 39 million mt imported by other Far East nations(2). Australia dominates the export steam coal market to these Pacific Rim countries and exported 48 million mt in 1990 and an additional 61 million mt of metallurgical coal(2). The worldwide steam coal export market has been expanding rapidly, from 20 million mt in 1973 to 150 million mt in 1989, and is expected to double to nearly 300 million mt by the end of the century(3). Could Alaska capture only 3% of the projected new world steam coal market, which is not an unreasonable expectation, the value of the state's coal exports would soar from nominally $28 million per year to over $100 million per year. However, without development of economical methods for drying/stabilizing Alaskan LRCs, the only increase in export of Alaskan coals may be from the few "higher rank" coals within a "reasonable" transport range of the existing Alaska rail system or tidewater. Presently the coal from the Usibelli Coal Mine is the only low-rank coal exported internationally as a steam coal; primarily for its blending properties with other coal to improve combustion. But for Alaskan low-rank coals to truly stand on their own merits, economical drying processes must be developed that produce a physically and chemically stable dried product. The technologies that have the most potential for increasing the use of Alaskan coals are those that can reduce the moisture content of these coals economically, and produce a fuel that is accepted in the international market place. Drying technologies will no doubt differ, depending on the end use of the fuel; be it dried lump coal, briquettes or pellets for pulverized coal or stoker applications, or concentrated coal-water fuels made from hot water dried LRCs. There are a number of developing processes that may work with Alaskan coals. Some drying processes, however, have been plagued by the production of excessive amounts of coal fines, Since the demand for Alaskan coal is currently limited to lump size coal, large quantities of fines are a definite liability. In this study, two high temperature drying/pyrolysis processes and one hydrothermal process were investigated. The high temperature drying/pyrolysis processes were conducted at (1) the Western Research Institute, (WRI) an affiliate of the University of Wyoming Research Corporation, Laramie, WY, and (2) Coal Technology Corporation (CTC) of Brisol, VA. Hydrothermal processing was conducted at MIRL, University of Alaska Fairbanks. A summary of these processes and the products they produced follows.
    • Coal in Alaska requirements to enhance environmentally sound use in both domestic and Pacific Rim markets

      Wilson, W.G.; Irwin, W.; Sims, John; Rao, P.D.; Noll, Bill (University of Alaska Mineral Industry Research Laboratory, 1990)
      This document originates from three meetings held in 1989 with the leaders of the Alaskan Coal Industry and coal technologists from the U.S. Department of Energy (DOE)~ Mineral Industry Research Laboratory (MIRL) and Geophysical Institute - University of Alaska Fairbanks, the Alaska Department of Natural Resources, the Alaska Science and Technology Commission, several of the Alaska Native Corporations, and a number of coal experts from private industries. The information included is intended to illustrate the vast resource base and quality of Alaskan coals, show the projected size of the Pacific Rim steam coal market, discuss policy changes necessary to facilitate the development of an expanded coal industry, and describe the technology development needs for Alaskan coals to compete in the world market. It is aimed at increasing the general knowledge about the potential of coal in Alaska and providing data for use in marketing the resource.
    • Deadfall Syncline coal, quality and reserves

      Callahan, J.E.; Rao, P.D.; Walsh, D.E. (University of Alaska Mineral Industry Research Laboratory, 1992)
      PRESENT INVESTIGATION The purpose of the 1991 drilling program was twofold: 1. To evaluate the coal reserves in a previously identified thick coal in an area of low structural dips and dip-slope topography near the axial plunge of the west extension of the Deadfall Syncline, primarily for surface mining, and to determine the feasibility of mining additional beds in conjunction with the thick coal. (For the purposes of this investigation, this coal is designated K3 as explained below), 2. To examine a continuous and unbroken stratigraphic interval of the Corwin formation in the northeastern part of the Deadfall Syncline as an initial step toward evaluation of the whole basin. This was accomplished by drilling overlapping holes aligned generally parallel to the dip direction, and spaced in accordance with the magnitude of dip and depth capacity of the drill. About 720 feet of stratigraphic section were covered in this way. A total of fourteen exploratory holes were drilled, ranging from 116 to 426 feet in depth (Figure 2). The drill was a Mobil B-60 mounted on a Nodwell tracked vehicle. Circulation was provided by a large compressor mounted on another Nodwell. Most of the footage was drilled with an air hammer, which provided a significant improvement in drilling rates over conventional rotary drilling. Lithology of cuttings from all holes was logged continuously, and composite grab samples from each 5 or 10 foot interval were taken. Coal cuttings were collected on a (relatively) clean plastic sheet, and promptly double bagged in plastic to minimize loss of bed moisture. Cores were taken from the K3 coal at 3 drill hole locations, and the underlying K4 coal was also cored at one of these 3 holes. A comparison of core length to geophysical logs indicates essentially 100% recovery for all cores. All samples, including rock cuttings, were shipped to the Mineral Industry Research Laboratory (MIRL), University of Alaska Fairbanks, for analyses and/or storage. All holes were logged with a Gearhart-Owen GeoLogger using natural garmna and gammagamma density tools. The log response with these tools for coals is distinct and unambiguous, particularly that of the density log, and the resolution is sufficient to estimate bed thickness to within 3 to 4 inches (Figures 8 and 9).
    • Determination mercury in Alaskan coals by flameless atomic absorption

      Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1973)
      An oxygen combustion, double gold amalgamation system is constructed for the determination of mercury in Alaskan coals. Solutions have been found for certain problems in design and operation. The effect of operating variables have been thoroughly evaluated and analytical procedure is outlined. The system involves combustion of goal in an oxygen atmosphere and amalgamating mercury on gold coils. The amalgamated mercury is released by heating and measured in an atomic absorption cell.
    • Determination of molybdenum in geological materials

      Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1971-09)
      This paper will describe a method for the determination of molybdenum in geological materials. It is known that molybdenum as molybdate or phosphomolybdate ion can be extracted using the liquid ion exchanger, Aliquat 336 (methyl tricapryl ammonium chloride, available from General Mills, Inc. Kankakee, Ill.). Aliquat 336 has been used for analytical separation of gold, tungsten, and actinide-lanthanide elements.
    • The determination of titanium in titaniferous magnetite ores by atomic absorption spectrophotometry

      Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1972-03)
      Amos and Willis (1) first investigated the use of nitrous oxide for the determination of titanium. They found that the presence of HF and iron enhance the absorption of titanium. They recommended “much more extensive investigation before a practicing chemical analyst can determine this element in a routine fashion by atomic absorption.” Various authors (2, 3, 4, 5, 6) have investigated titanium by atomic absorption and have recommended a number of different procedures to remove interference. In attempting to analyze lithium metaborate fusions (7, 8) of titaniferous magnetite ores of Alaska by atomic absorption, it was found that the interferences are not completely removed by any single approach suggested in the literature. Silicon, iron and aluminum could vary widely between samples and an approach was needed that would completely eliminate interference effects of all these elements, without having to match the gross matrix composition of samples and standards.
    • Distribution of certain minor elements in Alaskan coals

      Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1968)
      Seventy-five samples of coal from Northern Alaska, Jarvis Creek, Nenana, Matanuska, Kenai and Bering River Coal Fields were analyzed by quantitative spectrochemical procedures f o r lead, gallium, copper, barium, beryllium, nickel, titanium, vanadium, zirconium, cobalt, chromium, germanium, and tin. Other elements, of significance, identified from the spectrograms were, gold and silver identified in certain Nenana coals and silver in coals from Chickaloon in the Matanuska field, in concentrations up to several parts per million of coal ash. Forty-one of the above samples were sink-floated to study the distribution of minor elements between the organic and inorganic phases of the coals. Relative affinities of the minor of the minor elements to the organic matter in the coal is discussed.
    • Distribution, analysis, and recovery of fine gold from alluvial deposits

      Cook, D.J.; Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1973)
      The United States Bureau of Mines, in its Heavy Metals Program, desired to have research performed to determine the size-frequency distribution and possible economic value of gold particles in the fine size ranges of Alaskan placer deposits. Primary interest was involved in obtaining evidence of the occurrence of fine gold and to determine the ameanability of standard sampling and production methods in the evaluation and recovery processes. A research contract between the United States Bureau of Mines and the University of Alaska was initiated in June, 1968 as the first phase of this investigation, but was subsequently modified in June, 1969 to include beneficiation processes amenable to recovery as well as evaluation methods for fine and flakey gold. In searching the literature relative to fine gold in Alaskan placer deposits, it was found that virtually no research has been devoted to determining the extent of fine gold distribution and its effect on evaluation and subsequent recovery methods. Standard evaluation techniques have relied on gravity methods of concentration and recovery of the visible gold from the concentrate. In general, this has proved satisfactory in that operational recovery methods used were probably not conducive to retaining gold particles of less than 100 mesh in size. Operators have made no attempt to obtain a size analysis of gold in a head sample, but many have kept records of the size distribution of the gold as actually recovered. A review of these records, from selected areas, indicates that the -100 mesh gold represents from 0 to 5% of the total gold recovered. Although figures of this type may point to a probably fine gold loss, the difficulties inherent in evaluating the tailng material or modifying the recovery system have usually discouraged efforts in this direction.
    • Ferric chloride leaching of the Delta sulfide ores and gold extraction from the leaching residue

      Lin, H.K.; Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1988)
      Conventional differential and bulk flotation processes have difficulties in achieving high recoveries with acceptable grades far zinc, lead and copper from the complex sulfide ores found at Tok, Alaska. Furthermore, gold and silver, which account for a significant fraction of total value of the ores, are distributed evenly in the flotation tailings and concentrate. Therefore, processing both flotation tailings and concentrate would be necessary to obtain high recoveries of gold and silver. A mineralogical study revealed that the economic sulfide minerals are interstitially associated with a large preponderance of pyrite. The economic sulfide minerals are 10 to 40 microns in size. These mineralogical facts explain the difficulties encountered in the flotation process. A hydrometallurgical method involving ferric chloride leaching and subsequent steps to recover lead, zinc, silver and copper from the leach liquor has been studied at the Mineral Industry Research Laboratory, University of Alaska Fairbanks for the treatment of Delta ores. This alternative is attractive for processing complex sulfide ores which conventional flotation and smelting cannot handle. In addition, the liberation of sulfur in the environmentally acceptable elemental form, rather than as sulfur dioxide, may prove a major advantage of this hydrometallurgical method because of stringent environmental regulations.
    • Focus on Alaska's coal '75, proceedings of the conference

      Rao, P.D.; Wolff, E.N. (University of Alaska Mineral Industry Research Laboratory, 1975)
      Interest in Alaska's coals has increased greatly in the last few years partly as a II result of the public's realization that we are in a real energy shortage and partly because the building of the Alaska pipe line has demonstrated that transportation for Alaska's raw materials can be supplied if needed. Both President Ford and Secretary of Interior Kleppe have pointedly stated that Alaska must furnish much of the nation's energy needs in the next few decades. During the years 1974 and 1975, industry also showed greater interest as indicated by the large scale exploration activities in the Nenana, Beluga and Susitna coal fields. As a result of all of this interest it was decided that the time was right for an exchange of information on Alaska's coal; to bring people together and bring them up to date, and this conference was the result. Focus on Alaska's Coal, the first conference of its kind, attracted wide participation and apparently an enthusiastic response. The papers and the audience questions showed an overriding concern for the nation's energy needs and the possibility that Alaska can help alleviate those needs with its enormous solid fuel resources along with its oil and gas resources. As a result of the conference, the following points were brought into focus: Alaska's coal deposits are much more extensive than hitherto known. The development of a coal industry in Alaska to supply west coast markets is no longer a dream, and will in fact be a reality before long. Additional research on characterization and upgrading of coals is needed to further evaluate the potential of the enormous reserves. Alaska's coals are low in sulfur and thus are environmentally more acceptable. It is hoped that this conference brought into focus the opportunities Alaska offers to the nation and as a result, that work will be stimulated leading to the further development and utilization of its coal resources.
    • Focus on Alaska's coal '80, proceedings of the conference

      Rao, P.D.; Wolff, E.N. (University of Alaska Mineral Industry Research Laboratory, 1980)
      The principal objectives of the conference were to bring together current knowledge on Alaska's coal resources, mining methods, utilization and marketing, and every interested party to share this knowledge. The excellent papers presented and the large number of participants indicates that the objectives were accomplished.