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By Winmill T. F.

Paper presented at the at the Institution of Mining Engineers' general meeting held in London on 8th June 1916: In a previous paper it has been shown that the rate of absorption of oxygen by coal is neither directly proportional to the surface area of the coal exposed nor to the percentage of oxygen in the air. Further experiments are now described supporting this conclusion

Dec 1, 1916

By H. Le Chatelier

An evident connection exists between chemical and calorific phenomena: the most important, of our sources of heat, the combustion of coal, is nothing else than a chemical reaction. Not satisfied with this indefinite statement, investigators have attempted to establish a more precise correlation between these two orders of phenomena, and have questioned whether there be not a necessary connection between the possibility of a chemical reaction and the algebraic sign of the quantity of heat which it would call into play (i.e., liberate or absorb). This question possesses the highest interest for metallurgical chemists. But the study of it by experimental methods only could not completely elucidate it. To arrive at a definite solution, it was necessary to appeal to a science much more general than chemistry,—namely, that of energetics, which embraces all the physical sciences. We can place absolute confidence in its conclusions, because they rest upon a proposition which can scarcely be denied, namely, the impossibility of The main facts in the history of the development o‡ this field of Triassic coals have been already set before the Institute in the papers of Mr. Oswald J. Heinrich, a former member of the Institute and the superintendent of the mines at Midlothian. † From these and other references to the field, it appears that coal was known to exist here as early as 1701; for on the 10th of May that year Colonel Byrd reported to the Colonial Council of Virginia the discovery of coal. Coal was mined from 1770 to 1780; but the amount shipped is unknown. It was much used in Richmond at this early date for gratefires. In 1789 shipments were made to northern ports. During the first half of the century just passed, mining operations attained in this field their greatest development, the number and extent of the collieries and the tonnage of coal raised per annum being greater for that period than for any similar period since. The maximum annual output exceeded 100,000 tons, while in two years only since the Civil War has the amount of coal raised exceeded 50,000 tons. This field covers about 150 sq. in. Its outline and the position of the strata in which the coal-outcrops occur are shown on the accompanying map, reproduced from the latest survey by the U. S. Geological Survey. Mining has been carried on along the margins of the area, often in the primitive manner in vogue at the beginning of operations, by means of shafts and slopes, usually too small in cross-section to permit the proper working of the beds. Most of the output has been won from

Jan 1, 1902

By Christopher Mark

Perhaps the most significant development in coal mine ground control during the last century was the introduction of roof bolting during the late 1940’s and 1950’s. From an engineering standpoint, roof bolts are inherently more effective than the wood timbers they replaced. Roof bolts promised to dramatically reduce the number of roof fall accidents, which then claimed hundreds of lives each year, and they were initially hailed as “one of the great social advances of our time.” Roof bolting also emerged at a time of rapid technologic transformation of the coal industry, and greatly accelerated the transition to trackless, rubber-tired face haulage. The U.S. Bureau of Mines quickly became the new roof support’s strongest advocate. Some state agencies and miners were skeptical at first, but nearly everyone was soon won over. Case histories were reported showing that roof falls could be largely eliminated while productivity increased dramatically. Little wonder that, in the words of one contemporary observer, “roof bolting has been adopted more rapidly than any other new technology in the history of coal mine mechanization.” Yet by the end of the 1950’s, it was clear that roof fall fatality incidence rates had actually increased. It would be another decade before the superior ground support provided by roof bolts would clearly save lives. The story of how roof bolting was implemented by the mining industry, but took so long to live up to its promise, is a fascinating example of the interaction between economics, technology, regulation, and science. It still has important lessons for today.

By Fashina Olugbenga Emmanuel, Ghazali Akeem, Adegbola Adekunle Amos, Omotoyinbo Joseph Ajibade, Olaniran Oladayo

"Modern engineering materials are required to be light weight and corrosion resistant, coupled with high strength and hardness. In this work, Al formed the parent metal and alloyed with 2.03% of Copper by sand casting process. The cast product 2024 was warm worked at various temperatures ranging from 300 to 5600c at 5%, 10%, 15% and 20% deformation respectively and aged accordingly. The results showed that the mechanical properties vis-à-vis hardness, tensile improved with increasing % deformation at a higher temperature. This was due to the progressive close-up of the voids emanated from casting by increasing deformation which is evident from the micrographs. MATLAB was also adopted to generate a model capable of determining the trend of flow of stress at operating temperatures. This was of immense value due to an increasing impact at higher percentage deformation with temperatures. Hence, Al -alloys will find applications in land vehicles, ships, trains, and aircraft, at elevated temperature.INTRODUCTIONThe problem of safe vehicle design with maximum impact energy absorption is a significant subject in structural crash worthiness design [1]. All engineering designs are expected to ensure the safety of users' life. This informed several studies meant to probe the causes of component failures in equipment, vehicles, and aerospace design and decide on appropriate solutions through materials selection techniques. A common example is in the design of crankcases and heads, piston, and cylinder blocks. As with engine blocks, cylinder heads can be made of Cast Iron or Aluminium Alloy. A head made of Aluminium alloy is lighter in weight than if it were made of Cast iron [2]."

Jan 1, 2013

By T. F. Witherbee

THE following calculation of heat requirement covers the working of the furnace from January 25th to February 14th, inclusive. A short time previous to the first date the furnace had been working rather badly, so that 300 lbs. of ore and 500 lbs. of limestone were taken off. Within the time mentioned the quality of the iron passed

Jan 1, 1877

By T. F. Witherbee

The following calculation of heat requirement covers the working of the furnace from January 25th to February 14th, inclusive. A short time previous to the first date the furnace had been working rather badly, so that 300 lbs. of ore and 500 lbs. of limestone were taken off. Within the time mentioned the quality of the iron passed

By Edward Capillon

THE problem of scrap is probably of greater importance inn the production of gold, silver and other precious metal alloys than is the case for base metals and alloys. Remelting of gold and silver scrap in the shop is always a costly process because it involves losses by oxidation of the base metals in the alloy with a consequent increase in the percentage of precious metal. This is most marked in the case of alloys containing the low-boiling and easily oxidized metals zinc and cadmium. Since it is. not generally feasible to assay every shop remelt it follows that the possibilities of lost values are large. So-called rolled gold and silver plate is made by soldering or welding the precious metal alloys onto base, metal. Such plate when defective must be sent to the refinery to recover the gold and silver values, thereby involving additional expense in the form of refining charges. It is obvious therefore that gold and silver alloy scrap is an important item in manufacturing cost and must be reduced to a minimum. The amount of scrap resulting from poor metal will depend on a number of factors in the manufacturing operations, not least among which is the melting and casting practice. The notes which follow are a summary of experiments performed at various times to determine what variables in melting and casting are influential in the production of sound alloys.

Jan 1, 1930

By G. M. Dowo

The widespread environmental damage caused by slimes dam construction requires rehabilitation as one of the key management strategies towards land restoration. From the time when Mhangura Copper Mine in Zimbabwe was shut down in 2000 due to viability problems, no follow-up studies were carried out on the slimes dams to assess their development with respect to ecosystem function and longterm recovery. The ecosystem function analysis (EFA) method was thus employed to achieve this end. EFA is a monitoring procedure that establishes how well an ecosystem functions as a biophysical system through the use of rapidly assessed field indicators. The field procedure makes use of simple visual indicators that are related to various soil surface processes. Conventional sampling methods are used to collect the vegetation data. The data was first analysed using landscape function analysis (LFA) software packages and then with various multivariate statistical techniques. In total 27 species were recorded from 14 families; 21 of them occurring in the acacia woodland and only 8 on the slimes dams. Hyparrhenia sp. was the dominant grass on Dam 5 and Imperata cylindrica dominated Dam 6. Acacia saligna was the most abundant tree species on the dams. The tree layer on the slimes dams was not as developed as the grass layer. The rehabilitated slimes dams converged with the natural woodland for the LFA indices of stability, nutrient cycling, and infiltration, which suggested a high level of functionality. The main factors affecting the sustainability of the rehabilitation are postulated to be fire, grazing, and tree harvesting. The study contributed to the importance of, and methods used for, assessing ecosystem function on rehabilitated slimes dams in Zimbabwe, which are often ignored as most efforts focus on the establishment of vegetation on the dams. Keywords ecosystem function analysis, EFA, mine tailings, rehabilitation, monitoring, Mhangura Copper Mine, ecosystem function.

Dec 1, 2013

By S Graskoski

The allocation of boggers and trucks at Telfer’s sublevel cave mine is currently assigned by manual techniques, with decision-making primarily dependant on the judgement of the operators and mine control. Field observations indicate that allocation decisions could be improved by establishing a systematic approach to dispatch. An investigation into the current state of technology determined that no currently available solution would provide a tool to make optimal decisions for the Telfer dispatch challenge.In an underground sublevel cave (SLC) environment, the destination decision is fixed and the source is variable, so open pit and block cave solutions are not relevant. Newcrest underwent a development venture with an external vendor to develop a novel production dispatch algorithm and user-friendly software program to make allocation decisions in a systematic way with consideration given for the true complexity of the operation.This new production software, nicknamed Dingo (for Dispatch ‘n’ Go), is a smart way to assist forepersons and mine control operators in their day-to-day roles of planning shifts and allocating trucks and loaders to optimal locations during shifts.CITATION:S Graskoski, 2017. Dingo – an optimisation tool to solve complex short interval control at Telfer underground mine, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 261–266 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By João Paulo Meneguelli Campos

O objetivo deste trabalho foi validar o modelo proposto por Kasuya et al para prever as durezas máximas da zona termicamente afetada (ZTA) em juntas soldadas de um aço com médio teor de carbono através de ensaios empíricos. Para isto, se faz necessário o cálculo da energia de soldagem, quando foram testados modelos apresentados por Marques e Modenesi e também o modelo proposto por Perdigão. As juntas soldadas foram produzidas usando chapas de aço SAE 1045 com espessura de 12,7 mm como material base, chanfro de 70º e arame sólido do tipo ER70S-6. Para mudar as condições de resfriamento das juntas soldadas, foram testadas variações nos parâmetros de soldagem, tais como: energia de soldagem, taxa de resfriamento e temperaturas de pré-aquecimento e interpasses. Foram feitos experimentos com e sem pré-aquecimento e testados pós-aquecimento e alívio de tensões. As amostras da zona fundida e da ZTA tiveram as durezas medidas e foram analisadas por meio de microscopia eletrônica de varredura. Em linhas gerais, os resultados empíricos para a dureza na ZTA seguem a mesma tendência prevista pelo modelo de Kasuya et al, mas observam-se desvios na proporcionalidade validando a equação parcialmente para o material estudado. Também foi possível constatar que para o cálculo da energia de soldagem são adequados os modelos propostos por Perdigão e Marques e Modenesi.

Aug 17, 2017

By Katsuyasu Sugawara, Takuo Sugawara, Shin-ji Abe, Tadakazu Kagami

"In order to clarify the mechanism and to obtain the fundamental data for heavy metal recovery from an incinerator ash by chlorination, pure chemical reagents, zinc oxide and lead oxide or the fly ash blended with calcium chloride and silicon dioxide were heated up to 1000°C in a nitrogen stream. Thermogravimetric curves of the samples with the chlorinating reagents indicated that solid-liquid reactions accelerated the chlorination and release of metals from the solid phase. The formation of liquid phase of calcium chloride played an important role on effective recovery of zinc and lead at lower temperatures below 800 °C. Although zinc and lead could be decreased in the incinerator ash without chlorinating reagents, addition of chlorinating· reagents enables the removal of metals in high extent· at lower temperature.IntroductionFly ash is discharged about 3,000 tons/day (about 110 million tons/year) from incinerators of municipal solid waste in Japan and mostly fly ash is disposed in landfills. Fly ash includes heavy metals e.g. zinc and lead. Since untreated fly ash caused hazardous leaching problems, Waste Disposal and Public Cleaning Law was revised in 1992, fly ash being designated 'specially controlled' general waste. Fly ash must be disposed by the following suitable, intermediate four methods: [I] Cement- Solidified Method, [2] Immobilized Chemicals Method, [3] Melting Solidified Method, [4] Acid Leaching Method, permitted by the Ministry of Health and Welfare, Japan."

Jan 1, 2000

By R. V. Ramani

"In this paper, the current status of respirable dust control in coal mine atmospheres is presented. The advancements in the engineering control of dust generation and entrainment, and of reducing the exposures are summarized. The results of the Health Surveillance Program are briefly reviewed. The results of research conducted in the Generic Mineral Technology Center for Respirable Dust are presented. The 1995 NIOSH criteria document on respirable coal mine dust is briefly reviewed. The fundamental scientific and engineering issues in need of research are discussed. A detailed bibliography is attached.IntroductionFor coal mines in the United States, the current permissible exposure limit (PEL) of 2mg/m3MRE-equivalent concentration (an 8-hour TWA concentration measured gravimetrically) was established by Public Law 91-173: the Federal Coal Mine Health and Safety of 1969 (the 1969 Coal Act). This standard is reduced when the respirable quartz content in the dust sample exceeds 5%; the reduced standard in mglm3 is obtained by dividing 10 by the percent quartz. The OSHA and ACGIB PEL for respirable coal mine dust is also 2 mg/m3 , and OSHA PEL for respirable quartz is 100 µg/m3 . The 1969 Coal Act also prescribed two activities in the Coal Mine Respirable Dust Sampling Program and the National Coal Workers' Health Surveillance Program n to control respirable dust in mines, and the coal worker's pneumoconiosis (CWP) among the coal miners.There are three principal methods by which personal exposures to respirable dust are controlled. The first is engineering control where the aim is to reduce the concentration in the mine atmosphere to or below the mandated level. The second is the provision of personal protective devices which allow the miner to work in dusty atmospheres without increasing personal exposure. The third is the use of administrative controls where the miner's exposure is controlled through work schedules and procedures to keep miner exposure at or under the mandated levels. The 1969 Coal Act specifically prohibits the use of respirators in lieu of environmental control. The compliance sampling program essentially does not give any credit to the use of administrative controls."

Jan 1, 1998

By S. Ozbilen, B. Erdogan, M. Erdogan

To study by thermal analyses the response of precipitation hardenable alloys of Al-Cu-Mg and Al-Li-Cu-Mg system to natural and artificial ageing, a series of ternary and quaternary Al-alloys with nominal compositions of Al-l.13wt%Cu-0:65wt%Mg (alloy-I), Al-1.15wt%Cu-0.57wt%Mg-0.07wt%Li (alloy-2), Al-l.19wt%Cu-0.56wt%Mg-0.75wt%Li (alloy-3), Al-2.0lwt%Cu-0.89wt%Mg (alloy-4), Al-2.14wt%Cu"0.56wt%Mg-0.07wt%Li (alloy-5) were used in the present investigation. Samples in the form of rolled sheets are subjected to water quenching at 25EC after solution treatment at 530EC for 20 min. Alloys were aged naturally at room temperature (25EC) up to 2 months and artificially at 190EC up to 2 days. By using differential scanning calorimetry (DSC) in the temperature range of25-300EC, differential thermal analysis (DTA) in the temperature range of25-600EC together with Vicker's hardness measurements, the response to natural and artificial ageing of the alloys used in the present study were investigated. It was observed that in these alloys, GPB(Cu, Mg) zones [Guinier-Preston zones with Cu and Mg] do form during water quenching at 20EC following solutionizing heat treatment. Natural ageing of the same alloys causes formation of more GPB(Cu, Mg) zones, which results in hardening in the alloys. Artificial ageing at 190EC up to l day results in GPB zone dissolution causing preliminary decrease in hardness values while two days of artificial ageing in the alloys cause S' (Al2CuMg) precipitation confirmed by DSC/DTA analyses resulting in an increase in hardness values. Li addition up to 0.75wt% helps T1 (Al2CuLi) and T 2 (Al6CuLi3) phase formation together with S' precipitation as DSC/DTA analyses show after the same heat treatment.

Jan 1, 1998

By T. OnIin, F. F. ApIan

"A study has been made of the surface properties of coals of differing ranks, in their natural state and as modified by the addition of collectors. The evaluation of their surface properties has been done by captive bubble contact angles, water and methylene iodide sessile drop contact angles, zeta potential, point-of-zero charge (PZC) shift, and flotation. .changes in the hydrophobicity of coal is a function of both the rank of the coal and the collecting reagent.INTRODUCTIONThe chemical and physical properties of a raw coal will determine its response to a given beneficiation process. .For such processes as flotation, filtration, flocculation, dispersion, handling, dust supression and agglomeration, however, it is also necessary to consider the surface properties of the coal and mineral matter constitutents of the raw coal. In the case of a specific particle to be floated, it is also necessary to consider the properties of the coal as modified by the addition of some reagent designed to modify (usually increase) the hydrophobicity of the coal surface. General properties of the coal have been well summarized by Van Krevelen (1) and Elliott (2), while the data for the surface properties of coal are much more scattered in the literature (see, e.g.: Parekh and Aplan (3), Gutierrez-Rodrigues et al. (4), Aplan (5), Arnold and Aplan (6), Hogg and Chander (7) and Rosenbaum and Fuerstenau (8)). While a knowledge of the inherent surface properties of a sample are important, of much greater practical significance are the properties of the particle in the presence of a reagent, such as a collector, designed to enhance the hydrophobicity of the particle. This study will focus on the surface properties of coals of various ranks in the presence of a variety of collectors."

Jan 1, 1989

By Adam L. Wesner, A. C. Richardson

This paper describes the development of a continuous float-and-sink process to produce coal low enough in ash content to be suitable for production of electrodes. The cleaned coal had a combined iron and silicon content of 0.239 pct. The efficiency of recovery was 84 pct. DURING World War I1 the demand for electrode carbon was greater than could be met by the supply of petroleum coke available for this use. It was believed that coke made from an extremely low-ash coal might be a suitable substitute for petroleum coke. Requirements for electrode carbon to be used for the production of aluminum are that the silicon plus iron content shall be not more than 0.14 pct of the coke. However, during the period when petroleum coke was in short supply, it appeared that relaxations of the specifications might be allowed to permit 0.4 pct iron plus silicon in the coke. For this work, the specifications were that the coal should contain less than 1 pct of ash, and the combined iron and silicon content of the coal should not exceed 0.28 pct. Heavy-liquid separations made on a number of coals showed that if certain size fractions of some coals Were separated at low specific gravities the resulting float products would meet the required specifications. The objective of this work was to develop a continuous, commercially feasible process for producing low-ash coal. After consideration of various processes, the method chosen was a float-and-sink separation using a solution of calcium chloride as the separating medium. Eagle Seam coal was used for the experiments. The —10 +35 mesh fraction was found to be the most promising feed for producing the low-ash content coal. A batch of 30 tons of — --in. coal was screened at 10 and 35 mesh; the yield of —10 +35 mesh was 20 pct of the feed. This fraction comprised the feed for the separation tests. In spite of the fact that this portion was screened a second time at 35 mesh, the coal still contained 16 pct that was finer than 35 mesh. Three-fourths of the undersize was in the —35 +48 mesh range. A representative portion of the —10 +35 mesh fraction was subjected to batch float-and-sink separations to determine the best gravity to be used in the continuous tests to obtain a high recovery of low-ash content coal. The heavy liquid used was a mixture of carbon tetrachloride and benzene which assured complete wetting of all of the particles. As usual in batch separations, adequate time was allowed for each separation so that even the near gravity particles had ample time to separate. The separations were made at increments of 0.01 sp gr from 1.25 to 1.28 and also at 1.32 and 1.59. Each specific-gravity increment was assayed for ash content. From these data it was concluded that 1.27 sp gr was best for the continuous separation of the coal. The products from the batch separation were composited into float 1.27 and sink 1.27 sp-gr fractions; these were assayed for ash, iron, and silicon. Table I shows the results of the batch separations. The composite float 1.27 fraction contained 66.04 pct of the total weight, and had an analysis of 0.79 pct ash, 0.073 pct iron, and 0.112 pct silicon, or 0.185 pct iron and silicon combined. These data are indicative of the results possible if a perfect separation is made at 1.27 sp gr under static conditions. Inasmuch as the method under investigation is a dynamic system these results could not be obtained. It remained to be determined, however, just how close to the theoretical results the actual continuous separation would be.

Jan 1, 1953

By Adam L. Wesner, A. C. Richardson

This paper describes the development of a continuous float-and-sink process to produce coal low enough in ash content to be suitable for production of electrodes. The cleaned coal had a combined iron and silicon content of 0.239 pct. The efficiency of recovery was 84 pct. DURING World War I1 the demand for electrode carbon was greater than could be met by the supply of petroleum coke available for this use. It was believed that coke made from an extremely low-ash coal might be a suitable substitute for petroleum coke. Requirements for electrode carbon to be used for the production of aluminum are that the silicon plus iron content shall be not more than 0.14 pct of the coke. However, during the period when petroleum coke was in short supply, it appeared that relaxations of the specifications might be allowed to permit 0.4 pct iron plus silicon in the coke. For this work, the specifications were that the coal should contain less than 1 pct of ash, and the combined iron and silicon content of the coal should not exceed 0.28 pct. Heavy-liquid separations made on a number of coals showed that if certain size fractions of some coals Were separated at low specific gravities the resulting float products would meet the required specifications. The objective of this work was to develop a continuous, commercially feasible process for producing low-ash coal. After consideration of various processes, the method chosen was a float-and-sink separation using a solution of calcium chloride as the separating medium. Eagle Seam coal was used for the experiments. The —10 +35 mesh fraction was found to be the most promising feed for producing the low-ash content coal. A batch of 30 tons of — --in. coal was screened at 10 and 35 mesh; the yield of —10 +35 mesh was 20 pct of the feed. This fraction comprised the feed for the separation tests. In spite of the fact that this portion was screened a second time at 35 mesh, the coal still contained 16 pct that was finer than 35 mesh. Three-fourths of the undersize was in the —35 +48 mesh range. A representative portion of the —10 +35 mesh fraction was subjected to batch float-and-sink separations to determine the best gravity to be used in the continuous tests to obtain a high recovery of low-ash content coal. The heavy liquid used was a mixture of carbon tetrachloride and benzene which assured complete wetting of all of the particles. As usual in batch separations, adequate time was allowed for each separation so that even the near gravity particles had ample time to separate. The separations were made at increments of 0.01 sp gr from 1.25 to 1.28 and also at 1.32 and 1.59. Each specific-gravity increment was assayed for ash content. From these data it was concluded that 1.27 sp gr was best for the continuous separation of the coal. The products from the batch separation were composited into float 1.27 and sink 1.27 sp-gr fractions; these were assayed for ash, iron, and silicon. Table I shows the results of the batch separations. The composite float 1.27 fraction contained 66.04 pct of the total weight, and had an analysis of 0.79 pct ash, 0.073 pct iron, and 0.112 pct silicon, or 0.185 pct iron and silicon combined. These data are indicative of the results possible if a perfect separation is made at 1.27 sp gr under static conditions. Inasmuch as the method under investigation is a dynamic system these results could not be obtained. It remained to be determined, however, just how close to the theoretical results the actual continuous separation would be.

Jan 1, 1953

By Richard E. Hucko

The U.S. Department of Energy (DOE) Coal Preparation Program focuses on providing the technical and process-development basis that can be utilized to produce environmentally acceptable clean-coal feedstocks for use as market conditions permit. A major objective of the Coal Preparation Program is the development of physical coal-cleaning technologies capable of significant removal of mineral matter and pyritic sulfur at high energy recovery levels.

Jan 1, 1989

By Viswanathan N. Nurni

In metallurgical processes, more and more usage of hydrocarbons is encouragedto bring down the carbon emissions. In this regard, numerous investigations onreduction of oxides by C-O-H-N gas mixture have been reported. Attempts to simulatethese reduction processes using shrinking core model, one of the commonmodels used for such studies, have under predicted the reduction rates. This maybe owing to the fact that the homogeneous reaction in the gas phase is not being considered. If the reaction temperatures are above 1000K, generally so for manyreduction processes, the homogeneous gas reaction rates are expected to be sohigh that one can assume local equilibrium in the gas phase. In the present study,reduction of wustite in a C-O-H-N gas mixture has been modeled using shrinkingcore model considering the water gas shift equilibrium in the gas while it diffusesthrough the product layer.

Sep 1, 2012

By J. H. Pee, Y. J. Kim, H. U. Lee, G. H. Kim

The general recycling process of tungsten scrap to produce tungsten raw materials (tungstic acid, ammonium paratungstate (APT) and WO3) have been carried out by the oxidation, milling, sodium-fusion, dissolution, and extraction processes. Many studies on the high temperature oxidation of tungsten scrap have investigated various aspects such as swelling kinetics, fracture resistance, and the effect of alloying composition. However, the accelerating factors on the scrap oxidation rate during oxidation were not considered here. In general, oxidized products were fused with sodium carbonate or sodium hydroxide to produce Na2WO4. Later in the process, solid Na2WO4 was dissolved in water. This process required considerable reaction time and was a costly process. Therefore, the aim of this study was to increase the solubility of solid oxidized products to produce Na2WO4 solution by hydrothermal reflux method. Na2WO4 solution was used to produce CaWO4 and H2WO4 by general chemical reactions with calcium chloride and hydrochloric acid. Ammonia solution was also added to the tungstic acid to produce APT. In this study, the effect of ammonia addition on the APT precipitation process was investigated in detail.

Jan 1, 2015

By A. L. Wilder, S. N. Dixon

Introduction Coeur d'Alene Mines Corp.'s largest precious metals property is located in the historic Rochester Mining District 40 km (25 miles) northeast of Lovelock, NV. The property encountered cold weather operational problems soon after its fall start-up in 1986 due to its elevation of over 1830 m (6000 ft). The problem of ice buildup on the heaps because of sprayed solution application was faced immediately. It was felt that allowing ice to build up all winter long until a spring thaw was impractical due to the large area under leach. Further, the operating cost and delivery schedule for a solution heating system was unacceptable. The development and installation of a leach solution distribution system using drip emitters made efficient, cost-effective winter operation possible. Other benefits of this system have also been observed and are discussed here. General process description 15,422 kt/day (17,000 stpd) of - 1.27-cm (-1 /2-in) crushed ore from the three-stage crushing plant are delivered to the leach pad using 77.1 t (85 st) rear dump haul trucks. The ore is drifted into place with a D-9 bulldozer. Leach panels are contiguous and are approximately 8861 m'(90,000 square ft) in area built in 6-m (20-ft) lifts. New panels are built on top of older areas to a final height of 61 m (200 ft). Each panel is ripped and cross-ripped prior to leaching. Barren solution is distributed to the heap using drip emitters at rates of 0.02 to 0.41 L/min/m2 (0.0005 to 0.01 gpm per sq ft), depending on the age of the panels. The pH of the leach solution is 10.7 with a cyanide concentration of 0.75 kg/t (1.5 lb per st). Approximately 50% of the silver and 80% of the gold are finally recovered. Pregnant solution percolates though the heap and flows by gravity into one of two 9.46 ML (2.5 million gal) pregnant solution ponds. The solution is then pumped to a conventional Merrill-Crowe process plant. Clarification takes place in three 9464 L/min (2,500 gpm) capacity filters. The solution is then pumped to a packed vacuum deareation tower for the removal of dissolved oxygen. Typical deareated solution contains 0.7 parts per million dissolved oxygen. Precipitation of gold and silver is accomplished by adding a zinc dust slurry to the deareated solution at the suction of the filter press feed pump. Precipitated gold and silver are recovered in three recessed plate and frame filter presses. Barren solution is discharged into a 11.7 ML (3.1 million gal) pond where cyanide makeup occurs. This solution is pumped back to the heap for further leaching. The precipitate filter cake, containing approximately 75% dore (Ag + Au), is then fluxed with anhydrous borax, soda ash, sodium nitrate and fluorspar to yield a neutral, bisilicate slag. The fluxed precipitate is then charged into a propane-fired melting furnace and heated to 1150° C (2100° F) for 3 1/2 hours. Slag and dore bullion are poured into conical cast iron pots yielding buttons of 800 to 1000 troy oz. The dore typically contains 98.5% silver and 1 % gold. Slag is crushed and tabled to recover the trapped dore blebs and beads. Concentrate from the table is returned to the furnace. Table tails are sent to the crushing circuit and out to the leach pad. Solution application The area kept under leach at Rochester is approximately 130 000 m2 (1.4 million sq ft). Barren solution is delivered to the pad at 21.2 kL/min (5600 gpm) for a resultant application rate of 0.16 L/min/m2 (0.004 gpm per sq ft). A traditional solution sprinkling system using No. 12 Senninger Wobblers with individual pressure regulators was installed at the onset of leaching activities. The Wobblers were placed at 9.1-m (30¬ft) staggered centers and were fed off of a gridwork of Yellowmine plastic piping. Solution flow rates were moni¬tored to each panel. The onset of cold weather with an average nighttime temperature of -12° C (10° F) made it apparent that continual operation would not be possible with the sprinklers. A significant amount of ice was built up on top of the heap, making maintenance and pipe removal dangerous, if not impossible. Leach solution application was restricted to daylight hours to inhibit ice formation. Process plant flow rates were reduced to maintain steady-state operating conditions. However, as daylight temperatures dropped below freezing, ice continued to accumulate due to the sprays. Besides the obvious operating hazards brought on by the growing icefield, there was also the potential environmental hazard associated with an early thaw melting the ice too rapidly for the solution containment facilities. One other option for preventing ice formation was heating of the barren solution prior to spraying. Initial plant design allowed for expansion of the propane storage and distribution system as well as modification of the barren piping for a solution heater. This option was not exercised because the operating costs for an adequate system would have been prohibitive, and timely delivery of a system was not available. An investigation was conducted on the various drip irriga¬tion products available, since subsurface solution applicators would eliminate ice formation altogether. Systems utilizing external flow emitters were ruled out because of their ten¬dency to clog when buried. Emitter systems using perforated tubing were also eliminated from consideration due to their inability to adequately control flow over required lengths of tubing. An in-line emitter system was finally selected which demonstrated clog resistance and adequate flow control, enabling direct burial.

Jan 1, 1990