Search Documents

By H. O. McDonald

Solutions containing Cr6+ and sulfuric acid are used in a number of surface-finishing operations. Substantial quantities of chromium and copper are lost and pollution problems are created when the spent solutions are discarded. To minimize the undesirable environmental effects while improving secondary resource recovery technology, the Bureau of Mines is conducting research to detoxify and recover metals from these solutions. Spent etchants are treated to remove copper and reduce Cr6+ to Cr 3+ in an electrolytic cell. The anodes and cathodes are granulated coke. The spent solution is continuously pumped through the electrodes. Hexavalent chromium is reduced to trivalent chromium, and copper is recovered at the cathode. Reoxidation of Cr3+ at the anode was not observed. The removal and recovery of copper reduction of Cr6+ lessen chemical demand and increase efficiency in waste in treatment operations associated with the use of these solutions.

Jan 1, 1980

By Perry Harrison

THE increased use of sintering for the beneficiation of iron ores and the reclaiming of flue dust creates a lively interest in sintering costs and, economics. The character of material sintered and geographical location of plants so radically alter sintering costs and economics that it is well to understand at least the basic elements which control such changes. The following cost factors are believed to be roughly approximated for large-scale Dwight-Lloyd 'continuously operated sinter-machine installations located anywhere. PER CRUDE TON Labor, supplies and repairs 0.15 Power 6.5¢ X kw-hr. rate ? Plant overhead and administration 0.05 Depreciation per ton annual capacity 0.05 Fuel: 6 per cent coke breeze or equivalent minimum ? 1 per cent coke breeze additional for each 5 per cent free and combined water in ore or dust ? Ignition distillate at 0.6 gal. per ton ? PER SINTER TON Royalty on Ore 0.10 Royalty on Flue Dust 0.15 PER CRUDE TON "Winter expense"; i. z., the cost of the five months enforced idle . period for plants tied in to Great Lakes transportation season 0.03 Using the foregoing data, it is possible to roughly approximate the cost of efficient sintering at any location for. any ore, viz:

Jan 1, 1932

By Charles J. Moore

It seems a duty incumbent on the older members of the Institute to set forth in permanent form some of the results of their experience for the benefit of the younger members; this is the principal object of the present paper, which is the result of a recent examination requiring somewhat unusual geologic investigation. History. The London vein mas first discovered by float and occasional outcrops in the year 1873, four years before the great lead carbonate discoveries of Leadville, but the mine was not definitely located and opened until two years later, when the present locations, Mother, Paris, London, and Hard to Beat, were surveyed for patent. Since 1875 the London mine has been worked almost continuously until 1911, when the force was reduced to a few men only. In its early life the ore was assumed to be free-milling gold-quartz, although lead was a constituent of the vein throughout, and much useless expenditure was made in the erection and operation of a free-gold stamp-mill, with plates and tables for saving concentrates. The vein then opened was in the porphyry-limestone contact, a siliceous lead-ore, clearly most amenable to reduction by lead-smelter. The losses due to this process led in time to the close of the mill. For 20 years past, the mine has been worked under lease and the ore shipped to the lead-smelters in Denver or Salida. In January, 1912,I examined the mine to ascertain whether it was advisable to run a cross-cut tunnel some 4,200 ft. in length to intersect the main vein at a depth of 650 ft. below the present lowest workings. Finding a greatly-faulted zone, a close determination of the geological conditions became necessary to the solution of the problem.

Jan 1, 1914

By S. Ivanova

The results presented in this paper show that the gold solution dilution is a key parameter to control the dispersion of gold on ?-Al2O3 the selected support. The variation of concentration leads to changes in pH which modify the nature of gold complexes from HAuCl4 formed in the solution. These complexes are presented. Some of them (AuCl3(OH)- and AuCl2(OH)2 -) react with the surface of alumina and give interesting interaction. AuCl2(OH)2 complex has been considered as an ideal complex because of the strong anchorage of a bidentate species on the alumina. This complex is formed mainly in a solution of gold with a concentration of 10-4 M giving a pH of 3.5-4.5. The nature of the anchorage and the amount of chlorine, has an influence upon the formation of Au-Cl bridges which modify the dispersion of the gold on alumina of the final catalyst as shown by TEM.

Oct 1, 2003

By J. A. H. Church

The report is too voluminous to be considered in detail within the scope of a single paper, so I will confine my consideration of it to the broader aspects, leaving other members to deal with points of particular interest. The method of presentation leaves one with an uneasy sense of prolixity and confusion of thought; the foreword by the Chairman may well be accepted as a true index of the whole. His argument amounts to this: Recognizing at the outset the futility of divided counsels, it was deemed advisable to arrive at unanimity. To this end, some members subscribed to views to which they do not whole-heartedly assent, thus giving weight to conclusions with which they were at variance. Unanimity cannot be qualified-either it exists or is absent-and, moreover, in the text of the Com-mission I can find no word that unanimity is required. Surely it would have been preferable to have a unanimous report covering such aspects as were acceptable to all members, with minority reports by individual members on such other aspects as were controversial, leaving it to the Government to give such weight to the divergent views as the personality of their sponsors might warrant. In the final analysis the value of an opinion varies directly as the personality of its exponent.

Jan 1, 1926

By Yuanbo Zhang, Helei Zhang, Heng Yu, Guanghui Li, Zhengwei Yu, Tao Jiang

"Composite agglomeration process (CAP) is an innovative method for preparing blast furnace burden. For CAP, the classified raw materials of pelletizing feeds and matrix feeds are mixed, charged and sintered. The characteristics of these two kinds of feeds obviously affect the permeability of per-ignition bed, as well as the sinter productivity and quality. In this study, the Ergun equation is proposed to predict the pressure drop of CAP bed using the particle size distribution. The calculation process indicates that the Dv and the Em are the two tuning parameters. The results show that there is a gap between the calculated values by Ergun equation and the measured results by pressure drop testing facility. Eliminated this error by modified the Ergun equation and then validated it through experimental studies using simulated CAP mix and test facility. Therefore, the modified Ergun equation can be used to predict the permeability of CAP bed.IntroductionThe sintering process is one of predominant agglomeration processes for preparing ironmaking burden from iron-bearing materials. Sinter accounts for 70-80% of the blast furnace burden in China and the continuous improvement of sinter quality provides a guarantee to anterograde production of blast furnace. Sinter productivity and quality are strongly related to the permeability of the bed during sintering, which is dependent on the structure of the bed before ignition in the early stage [l]. The size distribution, the shape of granules and the bed voidage are the primary affecting factors to pre-ignition permeability."

Jan 1, 2013

By Stephen H. Partney

Waste clay ponds are a necessary part of phosphate rock beneficiation. They are large, averaging 2.6 km2 (1 sq mile). They are unsightly in that they protrude 6 to 15 m (20 to 50 ft) above natural grade. Stabilization and reclamation is slow and they have had a history of catastrophic failure. Florida has never published a specific rule regarding the configuration or height of these ponds. But it has enforced several policies along these lines. The phosphate industry has been forced to make major monetary decisions that affect mine economics for decades. The Florida Bureau of Mine Reclamation believes that the direction of regulation has been solidified but changes are still anticipated. Phosphate rock has been mined in Florida since 1890 (Fig. 1). Three notable technological changes occurred in the industry that led to major shifts in mining technique and volume. By about 1915, hydraulic mining had been replaced by centralized washers. Hydraulic mines usually started at an outcrop in or adjacent to a stream of the pebble zone. Water was pumped out of the stream through high-pressure monitors and sand and clay were washed away from the pebble. Mobile grizzlies and screens were used in conjunction with animal and human labor to concentrate the pebble and haul it away. Populations were sparse and the clays washed into the stream were considered an acceptable price for the commerce. The clays were not voluminous because the pebble zone typically contained relatively small amounts of them. Machines largely replaced animals by 1910 and provided greater efficiency of production. Centralized washers replaced mobile trommels. They allowed greater ease of access to shipping routes by rail. Some clays were placed in mine cuts from 1915 to 1930. Some were dammed off to increase the capacity of a given site. Some of these also failed, leading to clay plumes that were visible all the way to the Gulf of Mexico. By concentrating the waste clays (slimes) in impoundments, the solids concentration had increased, making plumes persistent for long distances. There were complaints. But there was no litigation against the companies during that time. In 1930, flotation technology allowed the recovery of the phosphate from deeper zones. This was because the "concentrate" size phosphate rock was in the sand-size range and could not be screened out. Centralized beneficiation plants grew into a three-step process - washing and screening, feed preparation and flotation (Fig. 2). Reagent storage, safety and the flotation cell complex made the plants into large capital installations. Larger draglines were required to dig deeper into the matrix. These had dramatically larger production capacities, which were then figured into the overall material balance for a given plant. The number of operators shrank and the production per operator grew. Larger areas were being bermed off for waste clay storage. An economic incentive became apparent for storing as much waste clay as possible in each settling area. At the same time, the population was steadily growing and more eyes were watching the activities of the phosphate mines. Phosphate mining, focused on production and profit, was earning a bad name from its neighbors. When the subject of phosphate mining

Jan 1, 1998

By M. J. Pool

The partial molar heats of solution in liquid tin of cadmium, silver, tellurium, and zinc have been measured at 655°. 700°, and 750°K by liquid-metal solution calorimetry. Silver, cadmium, and zinc are endothermic at these temperatures while tellurium is exothermic. Only the heat of solution of silver depends on composition while all four elements show a temperature-de pendent heat of solution. The heat of solution of tellurium is constant up to 0.6 g-at. pct, becomes increasingly more exothermic, and reaches a limiting value at 1 g-at. pct Te. The limiting value has been used to calculate the heat of formation of SnTe at 750°K. The heat effects associated with the dissolution of the compounds Ag2 Te, CdTe, and ZnTe in liquid tin were measured at 750°K. These values are cotnOined with the measured hat effects at 750°Kfor silver, cadmium, tellurium, and zinc to detertrline the heats of formation of the telluride compounds. Cadmium lelluride exhibits a heat of dissolution which has a compositional dependence. THERE is a considerable amount of interest in the compounds of tellurium because of their electronic properties. Both cadmium and zinc tellurides are thermoelectric materials and considerable work has been done on their electronic properties but a limited amount of data is available on their ther-modynamic properties. This work was undertaken to elucidate the heat of formation data on cadmium and zinc telluride. Since both cadmium and zinc are in Group II it seemed to be of interest to compare the values obtained for them with the heat of formation of a Group I telluride. Silver telluride was selected for this comparison. In the course of the work it was also possible to determine the heat of formation of tin telluride and therefore to make a comparison of some of the Group I, 11, and lV tellurides with the metallic elements silver, cadmium, and tin being in the same period. There is also a great deal of interest in the energetic changes which occur upon addition of solute elements to a common solvent. This investigation provided an opportunity to study the partial molar heats of solution of silver, cadmium, tellurium, and zinc in liquid tin. The partial molar heats of solution are of theoretical interest because solute-solute interactions are a minimum in dilute solutions and application of solution models is simpli- fied. In order to complete the analysis of solute-solute and solute-solvent interactions the temperature dependence of the partial molar heats of solution was also measured. MATERIALS AND EXPERIMENTAL PROCEDURE All materials were of the highest purity available. The silver, zinc, cadmium, and tellurium were obtained from American Smelting and Refining Co. and were reported to be 99.999 pct pure. The silver telluride, zinc telluride, and cadmium telluride were obtained from Atomergic Chemetals Co., a division of Gallard-Schlesinger Chemical Manufacturing Corp., and were electronic-grade material of 99.999 pct purity. Tin used for the solvent bath and for calibration was obtained from the Vulcan Manufacturing Co. and was reported as being 99.99 pct pure. The liquid-tin solution calorimeter used in this work is similar in principle to the differential twin-type calorimeter described by K1eppa.l Two of three identical calorimeter wells are used together during any set of experiments, one well being active and the other being passive. The wells are positioned 120 deg apart in an aluminum calorimeter block. Each well contains a multijunction thermopile and a Pyrex test tube to hold the liquid metal bath. Forty-eight of the thermopile junctions are distributed over the surface of each calorimeter well adjacent to the test tube and serve to integrate the heat effects occurring. The other forty-eight are next to the aluminum calorimeter block. The thermopiles for the three wells are connected differentially so that any change in temperature at the outer junctions (which will be the same for both wells because of the high conductivity of the aluminum block) will oppose for the two wells and result in no shift of the zero. The electrical output represents the true temperature difference between the two reaction vessels. A reaction occurring in the active well gives a comparison with another body of very similar thermal properties. In this way, any spurious heat effects due to slight temperature drifts within the entire calorimeter block are eliminated. The output of the differential thermopile goes to a dc amplifier with multiple ranges of from * 10 pv to 1 30 mv. The output of the amplifier is then fed into a Leeds and Northrup strip-chart recorder. The adiabatic temperature change is then calculated using the technique of Howlett, Leach, Ticknor, and ever.' The aluminum calorimeter block is contained in a cylindrical furnace with main and control heaters

Jan 1, 1965

By M. Fujikawa

The Kamioka Zinc Smelter was converted from the jarosite process to the goethite process in the year 2000. The reasons for the conversion of the process were that the silica content of the raw material increased and the iron content decreased. The silica easily turns to a gel in sulfuric acid solutions and this causes the solid-liquid separation characteristics to deteriorate. The basic behavior of silica in sulfuric acid solution was investigated and it was found that the goethite process is the most suitable to effectively separate and remove silica from solution. Furthermore, Fe has the capability to remove elements such as Ge that have an adverse effect on zinc electrolysis. This means that, when the Fe content of the raw material decreased, the impurity removal capability also decreased and there was a risk of a build-up of impurities in the process. Iron precipitates in many forms in sulfuric acid solutions. The capability to remove elements such as Ge differs depending on the compound precipitated. Goethite has a higher capability than jarosite to remove elements such as Ge. In this report, the results of applying the process established by investigations of the basic behavior of Fe, silica and Ge in the zinc refining plant are presented.

Jan 1, 2006

By R. J. Gochin, P. Bevilacqua, G. D. Schena

This class of flowsheet-dependent simulators does not replace modular simulators, such as Modsim and Microsim, which are necessary for the assessment of different flowsheets before selection of the most desirable technical option and for investigation of the fine details of unit processes. The system presented here is regarded as complementary, serving in the early stages of feasibility studies as an aid to assessing the convenience and economics of preconcentration; the example used is of dense-medium preconcentration of a barytes-fluorite ore

Jun 13, 1905

By Nathan T. Lowe

This report updates an accounting of mines and prospects in the Seafoam mining district, Custer County, Idaho, begun during mineral appraisal of the Idaho Primitive Area. Thirty-two mine and prospect locations have been added to the Bureau's Mineral Industry Location Subsystem (MILS) data base as a result of initial phases of mineral appraisal of the River of No Return Wilderness; most previously known locations were field checked and the updated information added to the data base. The district's major deposits include polymetallic fissure veins of gold-silver-lead-zinc-copper hosted by granodiorite and quartz monzonite which have been intruded by dikes ranging in composition from rhyolite to dacite, and vein type replacements of silver-lead-zinc-copper hosted by calcareous xenoliths imbedded in major intrusives. These deposits may be related to the intrusion of the Rapid River pluton or the Casto pluton. The dominant northwest structural trend is parallel to an aeromagnetic high, a weak gravity salient, and the Blue Bunch Mountain dike swarm.

Jan 1, 1983

By III Basham

As environmental laws and regulations become more complex and the economic cost of non-compliance becomes greater, periodic assessment of environmental compliance, identification of potential liability and implementation of any necessary remedial action should be a standard part of the operational methods of any successful business. The title of this paper "Environmental Audits, A Shield, A Sword or A Trojan Horse?" is intended to draw attention to the fact that environmental audits can be used positively to shield a business operations from actual or potential environmental liability; can be used proactively as a 'sword" in both a marketing context ("do business with us because we conduct our business safely and professionally?) and as a mechanism for developing positive relationships with environmental regulators; and, used negatively, as a "Trojan horse", by developing information which those same environmental regulators (or the public) use in an enforcement context against your business or that of your clients. This paper will discuss the concept of environmental audits in general; the pros and cons of conducting the same; and the role of the attorney, as part of the "audit" team, to insure, to the greatest extent possible, that the audit process is productive from both a managerial and legal perspective.

Jan 1, 1992

By W. N. Lacey, R. H. Olds, B. H. Sage

Samules of liquid and gas were obtained from the primary separator of a well in the Paloma field. The volumetric properties of the samples and of six systematically chosen mixtures of the samples were experimentally determined at 100°, 190°, and 250°F. at pressures up to 5000 lb. per sq. inch. From these data the influence ,of pressure and temperature upon the composition and specific volume of the bubble-point liquid and of the retrograde dew-point gas was established, The formation volumes and gas-oil ratios of the rnixtures investigated were calculated on the basis of the plant-product oil, which is defined as the isobutane and less volatile portion of each mixture. The results are presented in graphical and tabular form. The volumetric behavior of the mixture corresponding to that produced by the well at the time of sampling was determined for 235ºF., the reported reservoir temperature, by graphical interpolation of the experimental data with respect to composition and temperature. The results indicate that the well-production mixture probably existed as a gas at its retrograde dew point under the conditions of temperature and pressure believed to prevail in the producing zone at the time of sampling. The effect upon the phase behavim occasioned by the omission from the well-production mixture of certain components of intermediate molecular weight was investigated. In the first case, all of the isobutane and 11-butane, and substantially all of the iso-pentane, were removed from the mixture of trap samples corresponding to the well production. In the second case, all the propane, isobutane and n-butane, and substantially all of the isopentane, were removed. Both modifications led to considerable increases in the retrograde dew-point Pressure at 235ºF.; an increase of 558 lb. Per sq. in. above that of the unmodified well-production mixture in the first case, and an increase of 1208 lb. Per sq. in. in the second. It was concluded that the material? remaining after the removal of certain components of intermediate molecular weight could not be injected back into the reservoir in the saqe proportion in which they were produced without entailing appreciable loss of liquid material through condensation within the formation. Introduction Under the usual conditions of production practice, petroleum arrives at the surface of the earth in a physical state considerably different from that in which it existed in the underground reservoir. The relative rates of production and the properties of oil and gas measured at surface conditions do not constitute, in general, even a qualitative description of the fluids existing in the reservoir. The estimation of reserves and the attainment of optimum efficiency with regard to rate, quantity, and cost of production require accurate data concerning the physical properties of petroleum throughout large changes in pressure and temperature. Many schemes have been devised for predicting the behavior of propane, as it is encountered in nature? but the experimental work upon which these predictions are based has not, for the most part, been extended to the higher pressures that occur in practice, nor do these methods permit, as yet, the estima-

Jan 1, 1945

By E. A. Mihok

A pilot plant for treating mine drainage by neutralization with limestone was designed, fabricated, and operated by the Bureau of Mines. The process consists of (1) producing a very fine (minus 400-mesh) limestone slurry, (2) mixing the slurry with the mine water, (3) aerating the resulting mixture to remove carbon dioxide and precipitate iron, and (4) separating the solids from the liquid by sedimentation. A mine discharge of pH 2.8, containing 1,700 ppm total acidity, 36 ppm ferrous iron, and 360 ppm total iron, was treated at rates from 300 to 400 gpm. The treated water ultimately reached a pH of 7.4 and contained no detectable iron. The resulting sludge compacted to approximately one-third the volume of sludge from mine water neutralized with lime. The advantages of the limestone process, compared with the conventional lime process are as follows: Widespread distribution and lower cost of run-of-mine, indigenous limestone; simplicity of plant design; reduced hazards and plant operating and maintenance costs accruing from the use of a less reactive chemical agent; higher solids concentration of the precipitated sludge; and no deleterious effect caused by accidental overtreatment. While total process costs could not be determined, it is conservatively estimated that the cost of treating mine water by the limestone process is one-third to one-half the cost of the lime process, depending on the characteristics of the water to be treated and the availability and quality of limestone used.

Jan 1, 1968

By Robert L. Frantz

The U.S. Bureau of Mines (USBM) established on August 15, 1983, a Generic Mineral f Technology Center (GTC) for Respirable Dust within the Mining and Mineral Resources Research Institutes (MRIs) at The Pennsylvania State University (PSU) and West Virginia University (WW) in association with participating MRIs at Massachusetts Institute of Technology (MIT) and the University of Minnesota (UMN). The primary goal of the Center is to reduce the incidence and severity of respirable dust disease through researching and advancing the fundamental under- standing of all aspects of respirable dust associated with mining and milling and the interaction of dust and lungs. Other Center activities include the training of engineers and scientists, graduate students and undergraduate students through their respective institutions, and the technology transfer to the industry. The Center also serves as the reference center for publications in the respirable dust area.

Jan 1, 1986

By B. J. Arnold

Utility coal specifications usually contain a requirement for a maximum moisture content in order to prevent coal handling problems and to minimize evaporative losses in the boiler. As most coal cleaning processes are water-based, dewatering and sometimes thermal drying steps are required to meet moisture specifications. Screens are often used for dewatering, with centrifuges and filters used to further reduce moisture in many cases. Algorithms to predict the performance of commercial dewatering devices were developed for the Coal Cleaning Simulator running under Aspen Plus? during a project sponsored by the U.S. Department of Energy and the Electric Power Research Institute. These algorithms include calculations for size degradation in the devices and fines loss to effluents, where appropriate, and a calculation for moisture content of the product based on particle size and specific gravity distribution. This paper discusses the algorithm for coarse and fine coal centrifuges and gives comparisons between predicted moisture and solids loss and published moisture and solids loss values for various particle size ranges.

Jan 1, 1996

By R. W. Gurry

IN the course of a series of measurements of the rate of diffusion of carbon in austenite at about 960°C. (1760°F.) and 1110°C. (2030°F.), it became necessary to determine carbon concentration when austenite is saturated with graphite, because of indications that the hitherto accepted value of the solubility of graphite in this temperature range is too low. Specimens of carbonyl iron were saturated at temperature in a hydrogen-toluene atmosphere which was in equilibrium with graphite. The carbon content of the steel was measured either by combustion or by the loss of weight after substantially complete decarburization in an atmosphere of hydrogen saturated at room temperature with water vapor. The absence of carbide or graphite as a phase at temperature was demonstrated by microscopic examination of saturated specimens that had been drastically quenched. The mean result of concordant measurements is that gamma iron saturated with respect to graphite contains 1.39 per cent carbon at 957°C. (1755°F.) and 1.89 per cent at 1110°C. (2030°F.). These two values, plotted along with what appears from the literature to be the best value (0.69 per cent) at the iron-graphite eutectoid temperature (738°C. or 1360°F.), yield a curve that is almost linear, and which, continued upward through a short interval, leads to a limiting solubility of 1.98 per cent at the iron-graphite eutectic temperature 1135°C. (2075°F.) instead of the commonly accepted value of about 1.7 per cent. EXPERIMENTAL PROCEDURE The samples of carbonyl iron, with the exception of those for microscopic examination, were cylinders 3.8 cm. long, 0.475 cm. in diameter. They were placed in a graphite holder and suspended in a vertical furnace, the temperature of which was controlled precisely by means of the resistance of the platinum winding.1 In the empty furnace the range of temperature over a distance of 4 cm. at the heat center was 9°C. (16°F.) but at a given location the temperature remained within ±0.5°C. (0.9°F.); it was measured by inserting a platinum-rhodium couple calibrated at the melting point of palladium, 1555°C. Since the presence of the sample probably improved the uniformity of temperature, it was decided to consider the average temperature of the sample to be 3°C. lower than the maximum measured in the empty furnace with the same setting of the controller. Data were obtained in the vicinity of two temperatures, 960°C. (1760°F.) and 1110°C. (2030°F.). The samples for microscopic examination, 2.2 cm. long, 0.475 cm. in diameter, were suspended individually on pure iron wire; for these no temperature correction was applied. The carburizing gas passed into the furnace was dry, oxygen-free hydrogen saturated at room temperature with

Jan 1, 1942

By C T. Dunbar, P A. Walker, G E. LeJuge

A programme of blast improvement was initiated at the Mt Whaleback iron ore mine by BHPIO management in early-1998. One component of that work was the need to improve wall control blasting practices to better achieve the designed pit slope elements. This paper describes the geological conditions in which pit walls are developed, the mine operating equipment, the blast design concepts applied to minimise blast damage, the techniques applied in an assessment of the blast performance and the operational procedures developed to ensure that the blast concepts are effectively implemented in the production environment. Substantial changes have been implemented in both technical and operational aspects of the mining operation in order to achieve the improvements in pit wall condition, in particular recognising the need for a more flexible approach to limits blasting in response to highly variable and complex geology. The benefits to the mine are not only an improved wall condition, but increased confidence on the part of mine management that mine plans may be implemented on design and on schedule.

Jan 1, 2001

By Junwei Han, Wenhua Li, Wenqing Qin, Fen Jiao, Wei Liu, Jiaqi Xu

"A novel technology was developed to study the process of recycling copper from waste printed circuit boards (WPCBs), which are the main source of metal production in the next decades. The chemical compositions of the WPCBs were investigated. The results indicated that the PCB powder was mainly composed of copper (38.5 wt.%), iron, aluminum, and non-metallic materials. Copper is mainly in the form of Cu and is the most valuable metal for the recycle of WPCBs. The concentrated WPCBs powder, obtained by the mechanical process, were pressed as the anode, which was directly electrolyzed to produce copper. The effects of H2SO4 concentration, Cu2+ concentration, current density, pole pitch, and liquid-to-solid ratio on the voltage, current efficiency, and copper extraction were investigated. The results indicated that the optimum conditions were liquid-to-solid ratio of 30 mL/g, current density of 571 A/m2, sulfuric acid concentration of 180 g/L, 50 g/L of copper ion, polar distance of 3 cm. Under the conditions, a desired current efficiency could be achieved. Meanwhile, about 95.62% Cu was recovered from the WPCBs. The experimental studies also revealed that the purity of copper obtained at the highest current efficiency was higher to 99.98%. Produced copper sheet were characterized by X-ray diffraction (XRD). XRD analysis indicated that the copper was the main phase. INTRODUCTION With the rapid development of electronic industry, more and more waste electronic and electrical equipments (WEEE) are generated every year (Fogarasi et al., 2012; Liang et al., 2013). The production of printed circuit boards (PCBs) is the base of electronic industry, because it is the essential part of all electrical and electronic equipments (Schlummer et al., 2007). As a result, a considerable amount of waste PCBs containing plenty of heavy metals have to be treated. In general, PCBs contain about 28% metals that are abundant non-ferrous metals such as Cu, Pb, and Sn. Printed circuit boards can be considered as a secondary resource for recycling rather than wasting. The contents of gold and silver respectively reach 80 g/t and 3300 g/t, which are much higher than that of primary ores. Copper is the main metal of PCB and its content is as high as 26.8% ( Zhang et al., 2009)."

Jan 1, 2018

By J. Nakayama

Down-the-hole hammer is commonly recognized as the most powerful drilling equipment for weathered to fresh rock formation including boulders. However, its drilling diameter is restricted by reasons of difficulty to actualize large diameter drillhead and to ensure discharging means of cuttings. Cuttings are usually removed by flushing i.e. uprising return air after compressed air actuates hammer, but in case of large diameter drilling, as the clearance between drill rod and surrounding wall of hole become fairly large, necessary up-hole air velocity to transport cuttings can not be maintained. In case of marine or underwater drilling or high groundwater table, orthodox down-the-hole hammer is obstructed its operation by water. This single head hammer drill combined large diameter drillhead with reverse circulation of drilling fluid enables large diameter drilling extending to 1.5 m, i.e. actualized large diameter mechanical drillhead incorporated with ensured cuttings removal means enabled this range of drilling. This paper introduces its features and actual applications to large diameter bored pile drilling for varied sorts of rocks in maritime construction projects.

Jan 1, 1996