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By A. Juganda, H. PINHEIRO, J. Brune, N. SANDOVAL, G. Bogin, K. Gallagher, F Wilson

The present work discusses the nuances of scaling and flow similarity to develop a 1/40th scale version of a longwall coal mine. Details on the geometric, kinematic, and dynamic scaling of the physical model are presented and discussed. This works also discusses using a 30% CO2 – 70% He gas mixture as a surrogate for methane. It also presents the implications of various Reynolds numbers (ranging from 7,000 to 140,000) and rotation of the shearer drums in the dynamic representation of the airflow and gas mixtures in the physical scaled model.

Mar 19, 2022

By G. Frey, D. Scott, C. Pritchard

Controlled recirculation has been used in the metal/nonmetal mining industry for energy savings when heating and cooling air, in undersea mining and for increasing airflow to mining areas. For safe and effective use of controlled district recirculation, adequate airflow to dilute contaminants must exist prior to implementation, ventilation circuit parameters must be accurately quantified, ventilation network modeling must be up to date, emergency planning scenarios must be performed and effective monitoring and control systems must be installed and used. Safety and health issues that must be considered and may be improved through the use of controlled district recirculation include blasting fumes, dust, diesel emissions, radon and contaminants from mine fires. Controlled recirculation methods are expected to become more widely used as mines reach greater working depths, requiring that these health and safety issues be well understood. The U.S. National Institute for Occupational Safety and Health (NIOSH) conducted two controlled recirculation tests over three days at a Wyoming trona mine, utilizing an inline booster fan to improve airflow to a remote and difficult-to-ventilate development section. Test results were used to determine the effect that recirculation had on air qualities and quantities measured in that section and in other adjacent areas. Pre-test conditions, including ventilation quantities and pressures, were modeled using VnetPC. During each test, ventilation quantities and pressures were measured, as well as levels of total dust. Sulfur hexafluoride (SF6) tracer gas was used to simulate a mine contaminant to monitor recirculation wave cycles. Results showed good correlation between the model results and measured values for airflows, pressure differentials, tracer gas arrival times, mine gasses and dust levels.

Jan 1, 2013

By Xuebin Liu, Yi Shang, Can Zhou, Hongqiu Zhu, Junbo Du

In the neutral leaching process of zinc hydrometallurgy, the pH value directly affects the leaching rate of zinc calcine. However, due to the complex mechanism of the leaching process and frequent fluctuation of working conditions, it is difficult to control the pH value by manual control. Therefore, this study proposes a fuzzy control method based on rule extraction under multiple working conditions, and analyzes the pH control performance. Firstly, the different operating states are classified according to process mechanisms and the Pearson method. Secondly, under the framework of the active learning algorithm, the approximate linear dependence (ALD) method is introduced to iteratively select samples with rule information in the original sample set for manual annotation. Then, the support vector machine (SVM) method is used to extract fuzzy control rules in different working conditions. Finally, a fuzzy rule set is established according to the samples mapped by the support vector. The simulation results based on industrial data show that the proposed method has better control performance than conventional fuzzy control and proportional–integral–derivative (PID) control.

Apr 1, 2024

By H. Huang, R. N. Gow

"Previously, Gibbs’ phase rule was applied to mass-balanced EH-pH diagrams for the Cu-As-S-H2O system. Diagrams were generated using the stoichiometry of enargite as a basis. In this study, the calculations were expanded to cover the stoichiometries of three other Cu-As-S minerals (tennantite, sinnerite, and lautite) and compared to enargite. Stability regions within the resulting EH-pH diagrams were found to change with stoichiometry such that a particular mineral would predominate if its stoichiometry was used in the calculation. Solution speciation was also found to vary, with thioarsenate being the best example. This stoichiometric effect helps to explain results reported in the literature and would be difficult to realize if it were not for mass-balanced calculations. INTRODUCTION A comprehensive thermodynamic review has recently been conducted on the aqueous copper-arsenic-sulfur system (Gow et al., 2014a-d). The free energies of over 100 species were collected from various authors and thermodynamic databases to produce mass-balanced EH-pH diagrams, using the thermodynamic equilibrium calculation software, STABCAL (Huang, 2014). The full database was listed and discussed by Gow et al. (2014A). Resulting diagrams were generated for enargite and confirmed with Raman spectroscopy using bulk mineral electrodes in order to identify reactions spectroelectrochemically. Theoretical calculations agreed well with the experimental results under alkaline conditions (Gow et al., 2014a), acid conditions (Gow et al., 2014b), and alkaline sulfide leaching conditions (Gow et al., 2014c). In this study, additional mass-balanced EH-pH diagrams are generated by changing the copper-arsenic-sulfur stoichiometry from enargite (Cu3AsS4) to tennantite (Cu12As4S13), sinnerite (Cu6As4S9) and lautite (CuAsS). Regions for the thermodynamically stable species are shown to change with the four different mineral compositions. Potential leach conditions, both for co-dissolution and selective dissolution techniques, were examined for differences in predominant species according to changing copper-to-arsenic ratios, sulfur compositions, and sulfur oxidation states."

Jan 1, 2015

By Mahmut Altiner

In the present study, the use of horse residue as an alternative reducing agent in the roasting of a low-grade goethite ore containing 17.60% Fe was investigated. Additional roasting experiments were carried out with corn starch and without reducing agent for comparison. Each roasted product was characterized using X-ray diffraction (XRD) and magnetic hysteresis (MH) loops analyses. The optimum roasting conditions (roasting temperature [400, 500, and 600 °C], reducing agent/ore ratio [0.04, 0.08, and 0.12], and roasting time [10, 20, and 30 min]) were investigated based on the Taguchi approach. The magnetic susceptibilities of the roasted sample with the addition of reducing agents were higher compared to that of the roasted sample in the absence of reducing agent. Experimental findings indicate that the horse residue can be used as the reducing agent. Finally, an iron ore concentrate assaying a Fe grade of 62.12% with a recovery of 56.93% was prepared using wet magnetic separation at a magnetic intensity of 0.5 T from the ore roasted under the following roasting conditions: roasting temperature of 500 °C, reducing agent/ sample ratio of 0.08, and roasting time of 30 min.

Jun 3, 2020

By H. M. Ray

The discovery of the New Lead Belt in the mid-'50s began a search for mill design criteria that is continuously updated. The opportunity to design, construct, and operate four new mills in the span of 20 years provided fertile areas for new concepts. The central theme for design parameters encompassed simplicity, functional, and economic consideration. Ore characteristics for each plant remained relatively constant, providing stable criteria for grinding circuits. Bond index nominally 10-12. Flotation circuit parameters were based upon power application with 10-20% excess capacity built-in to protect recovery. Newer equipment exhibits greater power application efficiency lowering horsepower requirements per ton. Instrumentation was installed to stabilize circuits, protect equipment, and improve products. With ever increasing requirements of higher quality products, environmental considerations, and operating cost pressures, the upgrading of operating procedures is in a constant state of flux. Installation of more efficient equipment, chemical processing, or any other technique would be considered as feasible. Current practice is for St. Joe to design and engineer in-house its own plant design. The exception being detailing of structural steel. It is felt that familiarity with past design criteria serves as a valuable foundation to incorporate changes. Also, direct contact with operator provides specific data, and feedback for constructive criticism that is utilized for defining and correcting problems. The results are in reality an operator's plant with the benefit of advancing technology that meets the demands for improved products without sacrificing the economies of throughput or recovery.

Jan 1, 1977

By Larry D. Patts

Section 317(e) of the Federal Coal Mine Health & Safety Act of 1969 directed the Secretary of the Interior to prepare standards under which all working places in a mine shall be illuminated by permissible' lighting while persons are working in such places. Section 317(e) further provides that such Working places shall be illuminated within 18 months after such standards are promulgated. In accordance with this section of the Act, there was published in the Federal Register for December 31,1970 a notice of proposed ru1emaking which prescribed the illumination to be provided in the working p1 aces of underground coal mines. In 1ight of written comments, suggestions, and objections to this proposed ru1emaking, the proposed standards were with-drawn and reproposed in the Federal Register for Wednesday, October 27, 1971. In light of further comments, suggestions, and objections, a public hearing was held on April 4, 1974 and standards were again reproposed and published in the Federal Register for April 1, 1976. Promulgation of the final lighting standards took place on October 1, 1976 which means that the underground coal mining industry must comply with face illumination requirements by April 1, 1978. As mentioned previously, the first proposed ru1emaking for illumination of underground coal mines was published in the Federal Register on October 27, 1971. In early 1972, Consolidation Coal Company (Consol) and the United States Bureau of Mines agreed to a cooperative study of underground face illumination; Conso1 felt that expertise in this field would become increasingly important. Conso1's initial efforts in illumination were aimed at investigati.ng practical lighting systems for underground face equipment. We were concerned with installing unobtrusive lights which provided sufficient face illumination for safety, but at the same time were readily maintainable, electrically reliable, and physically sheltered from damage.

Jan 1, 1977

By R. H. King

Recently, the North American mining industry experienced a severe recession, forcing managers to take dramatic steps to cut costs and compete in the difficult international market. Some of these steps were closing mines, reducing work forces, renegotiating wage agreements, and purchasing the most productive equipment. Managers are now looking beyond these traditional avenues and are focusing more on advanced technology. In the present environment, it is essential that mine operators obtain the maximum use of capital expended on equipment. However, mine workers do not obtain maximum efficiency or productivity from equipment because the adverse and hazardous mine environment impedes human performance. Also, the efficient use of large, complex machines calls for levels of precision that many times are beyond the capability of even highly trained miners. A possible solution to this problem is a machine that mines without operators - autonomous mining machines. However, numerous problems confront researchers who are attempting to develop such equipment. Some mining tasks are not always composed of a series of cyclic motions readily performed by factory floor robots. In addition, mining takes place in the geological environment where conditions are highly variable and unpredictable. As a result, these machines must be able to sense and adapt to variations in operating tasks and environment. Considerable autonomous vehicle research has been completed, especially for defense. However, autonomous vehicle (AV) technology has not advanced to practical application yet (King, 1988) and mining research is necessary in areas: representing mining specific knowledge; •analyzing and reasoning about sensor data in the mining environment; and •discovering completely new mining methods or new approaches to existing methods that become apparent when we remove the constraints imposed by the necessity of human operators. A specific machine, the LHD, can be used to show the problems for researchers who are attempting to develop autonomous machines for mining. This author chose the LHD because it can borrow concepts developed for autonomous navigation by military programs. But considerable mining research is also required. Furthermore, studies done at the Henderson mine, in Colorado, show autonomous LHD 's promise cost and safety benefits (King, 1988). At Henderson, LHDs load ore from draw points, tram to an ore pass, dump and return, or switch to another draw point. An autonomous LHD must sense vehicle position along the route, relate sensor data to stored-map information, to determine location, follow drift center lines, plan paths between dump position and initiate appropriate control commands, sense vehicle operating status and vehicle health, key on features or targets for special tasks like high speed turns, perform end of travel tasks (loading and dumping), and detect and avoid obstacles. These goals are similar to those for shuttle cars, trucks, and front-end loaders. Therefore, much of the technology is transferable. Each Henderson LHD extracts six to 40 dippers from each of a series of draw points. The LHD transports the ore to an ore pass within 55 m (180 ft) of the draw point, making the longest round trip 110 m (360 ft). The LHDs have very fast hydraulic dumping and loading systems that reduce the round trip cycle to less than one minute. Even though the LHD is capable of 500 trips per shift, the average production is 300 dippers. Man trip and lunch reduce available operating time to 6.5 hours per shift. Mucking difficulties (setting large boulders aside), operator breaks for activities like talking shop, and cleaning and smoothing roads further reduce operating time. Supervised autonomy can reduce the number of operating units by increasing operating time per shift since computer controlled machines can operate during lunch and between shifts and reduce operator errors. If dippers per shift increase from 300 to 350 (long-range goals are 500 dippers per shift), constant production requires only 10 operating LHDs and two spares. Manpower requirements drop from 24 to four by controlling five machines from one workstation. A review of technology available from the Autonomous Land Vehicle, the Advanced Ground Vehicle Technology, the Ground Surveillance Robot, and other programs, show the following differences between others work and mining industry needs: •If we focus initially on mobile haulage vehicles, we can navigate from a map. We do not need to explore. •We can modify the environment to reduce the navigation requirements. •We have a harsher environment than any of the research programs have encountered. •Our equipment must operate faster and more precisely than present AVs. •Our equipment must operate reliably over long periods of time. •We must have better onboard machine health monitoring and diagnostics. •The AV programs do not address geosensing. •The major AV programs are not cost-effective. For example, we cannot afford the computer power for robust image processing, yet. To computer control an LHD, we must replace the guidance and monitoring skills of experienced operators with sensors, computing hardware, interfaces, and several software mod¬ules. Experienced operators avoid collisions and load efficiently in piles that may contain oversize muck. Collision avoidance without an operator requires sensing all obstacles in the draw

Jan 1, 1991

By A. Lashgari, V. Kecojevic

This paper presents research on the environmental impact of digging and loading equipment used in surface coal mining. Environmental impact was assessed through the measurement of equipment exhaust and dust emissions, and sound level. In this study, exhaust emission refers to carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx) and volatile organic compounds (VOCs). Dust generation refers to fine particles (PM2.5), inhalable particles (PM10) and total suspended particulate matter (TSP). Sound level refers to the sound pressure level at different distances from the equipment. Modeling of the environmental impact of digging and loading equipment was conducted using the Microsoft Visual Studio.NET software package. This research was a part of a broader project involving the development of a software system for the selection of productive, cost-efficient and ecofriendly mining systems, sponsored by the Appalachian Research Initiatives for Environmental Sciences (ARIES). This research may assist mining professionals in quantifying the environmental impact of digging and loading equipment, and developing strategies for reducing the overall impact of such equipment in surface mining.

Jan 1, 2013

By Charles K. Presley

This paper deals with drilling large diameter shafts for the mining and construction industry with diameters in excess of 3 feet to more than 20 feet in diameter. It discusses appropriate applications of the rotary drill method, linings for large diameter shafts, circulation systems,, and the limitations of the method. Each specific rotary drill method is determined by the geology of the area, the depth to be drilled and the formation fluids encountered. Shaft lining or casing must be improved to result in lighter weight, higher strength and lower cost. All phases of rotary drilling equipment must be improved to drill shafts in excess of 10 feet in diameter. As these goals are reached, more shafts of large diameter will be drilled by the rotary method for the mining and construction industry.

Jan 1, 1967

By Bo Hyun Kim, Mark K. Larson

Although techniques and practices of mining are highly advanced, coal pillar bursts or bumps continue to occur. Many uncertainties remain because of the highly anisotropic characteristics of coal seams that are associated with geologic structure and the mining-induced spatial redistribution of stress in coal pillars. Thus, to prevent fatalities in underground coal mining, continuous efforts are required to better understand the catastrophic failure mechanisms in coal mines. In this study, 3DEC modeling in conjunction with the Discrete Fracture Networks (DFNs) technique was performed to better understand the true anisotropic behavior of the specimens acquired from a bump-prone underground coal mine. The spatial characteristics of the dis- continuities (i.e., cleats and bedding planes) as input data for the 3DEC model are estimated based on the results of the laboratory tests and field observations. The DFNs explicitly generated the coal seam that was poorly or well cleated, indicating the different spacing between cleat apertures using the probability distribution functions for fracture density (or frequency) and size. The heterogeneity of the engineering properties (i.e., cohesion and tensile strength) are also considered by Monte Carlo simulations. Simulation results of laboratory tests using the 3DEC model and DFNs technique agreed well with the results of the laboratory tests. These calibrated results can be used as we seek to evaluate bump risk by modeling at field scale.

Jun 25, 2024

By K. V. Raj, C. A. Berry, A. T. Weakley, A. L. Miller, P. R. Griffiths, D. A. Parks

Diesel particulate matter (DPM) has been classified as a carcinogen to humans by the International Agency for Research on Cancer. As a result of its potential carcinogenic nature, DPM exposure is regulated by the Mine Safety and Health Administration. Currently, diesel emissions in the workplace are monitored by collecting the aerosol onto filters, which are then sent to a laboratory for thermal-optical analysis using the NIOSH method 5040. This process can take days or even weeks, and workers can potentially be exposed to excessive levels of DPM before the problem is identified. Moreover, the delay involved in getting the loaded filter to the lab inevitably means the loss of some of the more volatile organic carbon. To remedy this delay, researchers from the National Institute for Occupational Safety and Health are seeking to develop a field-portable, real-time method for measuring elemental and organic carbons in DPM aerosols. In the current study, the use of mid-infrared spectrometry was investigated. It is believed that mid-infrared spectroscopy is more suitable for use in a real-time field-portable device than thermo-optical analysis methods. This article presents a method for measuring organic carbon (OC) and elemental carbon (EC) in DPM for a broad range of OC/EC ratios. The method has been successfully applied to laboratory-generated and mine samples.

By W. C. Shanks

The Pioche District of Lincoln County in southeastern Nevada (Figures 1 and 2) has been an historically important producer of silver, zinc, and lead. Economic geology of districts in the Pioche area is summarized most adequately in recent reports by Tschanz and Pampeyan (1) and Gemmill (2) and only a few major aspects will be discussed here. Production in the Pioche District began in 1869 and early mining concentrated on silver-bearing fissures in lower Cambrian quartzites. In the early 1870's the Pioche District was second only to the Comstock Lode in world silver production (3). More recent mining activities have centered on the other major ore type in the area, bedded replacement of lower Cambrian carbonates by Ag-Zn-Pb sulfide ore. Production of replacement ore peaked around 1950. The present study is focused on the Pan American Mine because it is an excellent example of low grade carbonate replacement deposits, because there is little structural dismemberment, and because access was readily available. Most previous workers have suggested that both the fissure vein deposits and the bedded replacement deposits of the Pioche districts are a result of spatially related Laramide igneous activity. The purpose of this study is to determine whether ore genesis is a result of igneous activity or if mineralization might be related to late diagenetic processes such as formed Mississippi Valley "type" deposits. Stable isotopes of sulfur, carbon, and oxygen in ore and gangue minerals have been studied to determine the probable isotopic composition of the ore fluid and paleomagnetic studies of the carbonate rocks have been utilized to determine timing of mineralization. Additionally, petrographic and field studies of carbonate lithologies were undertaken in an attempt to delineate non-structural controls on ore localization. These studies are still proceeding and the results presented herein are, therefore, preliminary in nature.

Jan 1, 1979

By Harry Asche

Tunnels are frequently specified by owners to be designed to a structural code, often a bridge code. In the USA, AASHTO have created a tunnel code, based on structural principles, the AASHTO LRFD Tunnel Design Specification. The Load Resistance Factor Design method (LRFD) described in the AASHTO title is an approximation to the probabilistic design of structures, based on the independence of load and resistance. This methodology is well known to be problematic in geotechnical design, but it is widely used. The paper considers the difficulties of this approach and describes alternative approaches that would result in more appropriate designs for tunnels.

Jun 13, 2021

By C. Pritchard

John Marks said in his acceptance of the Hartman Award in 2008, “I guess that without the occasional complaint, your mine is probably over-ventilated” (Marks, 2008). Miners are seldom in this situation and spend much of the time trying to find enough air to keep an operation running. With examination, there are usually changes that can be made to increase the efficiency of ventilation systems. Mine ventilation air is a costly commodity, especially by the time it has been heated or cooled and moved to the bottom of the shaft and through the mine airways. Modifications that result in surplus mine ventilation air could bring financial and environmental benefits. Some issues mine operators have needed to address recently are increased airflow requirements to dilute diesel particulates in metal and nonmetal mines, to ventilate reserves that are deeper, hotter, and further away from fans and shafts, and to meet demands from increased production. This paper discusses successful methods to find additional usable air when there is no extra ventilation capacity. Most of the options presented in this paper are useful for metal/ nonmetal operations but some may be applicable to coal as well.

Jan 1, 2009

By Ron F. Schritt

Over the many years since the development of the steam powered shovel, various powering and control techniques have been employed for the various shovel functions. While volumes have been published on this subject, this paper will be limited to a very brief discus-sion of one of the latest of these and its application to a unique machine. The evaluation of the subject machine is far beyond the scope of this discussion, which will be limited to the techniques and equipment employed, and the considerations involved in their choice. The basic requirements for any power and associated control system for any power shovel function have remained relatively un-changed over the years. To the extent possible, such an equipment grouping must be: Easy to install during fabrication Easy to maintain and repair by available personnel Life cycle cost competitive Adequately reliable Adequately responsive And as may be expected these factors are arranged in various orders of priority by different manufacturers and users. All the various time honored approaches have to some extent fulfilled these require-ments but were discarded or fell into disuse when more effective approaches were developed. The latest in this long line of develop-ments and perhaps the most promising is that of electro-hydraulic controls and hydraulic drive.

Jan 1, 1977

By Tina Živec, Žibertm Marko

"Civil design has changed in many ways using BIM (Building Information Modelling) technology in its most recent form. Such a technological breakthrough has not been successful so far in traditional oriented Engineering Geology, except in the Mining and oil exploration markets with budgets on much different scales. The fact is that paper, pencil and hand drawn sketches are still state of the art and a perfectly acceptable way of producing subjective geological interpretations.Using the technology available, we have developed a set of procedures and techniques to combine the latest surveying and remote sensing technology, GIS based tools to manage large data sets and BIM modelling techniques in a 3D geological environment.To demonstrate the concept, the forthcoming Karavanke tunnel project (Slovenia) has been chosen for testing techniques. The project, with its rich documentation from previous phases and new data available, represented a good basis for testing the possibility of digitizing geological data while communicating with Leapfrog Geo 3D modelling algorithms. This type of procedure would then allow engineers at the construction site to use the 3D model for prognosis and evaluation, while upgrading it daily with new information.INTRODUCTIONThe Karavanke tunnel crosses the mountain range on the border between Slovenia and Austria. As the geology is very complex due to its imbricate fan structure, a series of geological – geotechnical and hydrogeological investigations have been performed since the 1970s, resulting in extensive project documentation. The construction of the 7864 m long single-tube two-lane tunnel took place in the late 1980s. Currently, the tunnel represents a critical point on Pan-European Transport Corridor X (Salzburg, Austria – Thessaloniki, Greece), with insufficient safety measures. The need for improved traffic flow and enhanced road safety led the Slovenian government in 2013 to a decision to continue with activities regarding the construction of the second tunnel tube 70 m east of the existing tunnel.The extensive project documentation from previous investigation phases and construction of a new tunnel tube presented a good base for a pilot project, in order to test the emerging new technologies for data acquisition, processing and analysis in a 3D environment. Several products are available on the market for data acquisition and 3D geological modelling, but only a few can be applied in the civil design, as well. Developing a standard format and procedure for implementing the 3D geological model using new remote sensing techniques, 3D geological modelling tools, such as Leapfrog Geo and BIM (Building Information Modelling) modelling techniques would move the Engineering Geology, Geotechnics and Tunneling to a more advanced level. 3D modelling tools would therefore not only be used as a visualization tool, but would also contribute to in a more efficient communication and workflow between the professionals involved in the project."

Jan 1, 2016

By Peter G. Chamberlain

The Bureau of Mines is conducting research to boost domestic production of manganese. Virtually no mining exists in the low grade and/or small deposits that occur in this Country. One large, low-grade manganese deposit located in westcentral Arizona--The Artillery Peak district--was extensively studied and sporadically mined during the 1940's and 1950's. Although manganese mining in the district has been long dormant, recent studies indicate that the deposits may be amenable to economical production by heap and/or in situ leaching methods. A conceptual design for an in situ leaching system features undercutting and blasting a block of ore, leaching with SO2, and extracting the manganese as a sulfate or oxide. Possible applications to other manganese deposits depend upon formation permeability and specific manganese mineralogy.

Jan 1, 1981

By Louis J. Czel

Although lithium was first discovered by Arfwedson in Sweden in 1817, it did not reach any significant status in commercial application until 1908 when Thomas A. Edison received a patent covering the use of lithium hydroxide in alkaline' storage batteries. Edison's achievement can be regarded as a major breakthrough in the development of the lithium industry. In the years prior to 1908 lithium salts had found only modest applications in the pharmaceutical and pyrotechnic fields. The next important milestone in the growth of this net industry occurred in Germany in 1918 when Metallgesellschaft at its metallurgical laboratory at Frankfort-on-Main discovered that the addition of a few hundredths percent of lithium metal to aluminum and its alloys increased-the hardness. This brought into being a new commercial use of lithium in the manufacture of bearing metals. The new material, called "Bahnmetall" (railroad, metal), was widely used for, many years in the manufacture of bearings for railroad and automotive purposes. Its use continued until the early 1930's and there was a short-lived renewal of its production during World War II. Subsequent use of-the alloy was soon outmoded.

Jan 1, 1961

By H. Huang, R. N. Gow

"In Part I, Gibbs’ phase rule was applied to mass-balanced EH-pH diagrams for the Cu-As-S-H2O system. The diagrams were generated using the stoichiometry of enargite as a basis. In this study, the calculations were expanded to cover the stoichiometries of three other Cu-As-S minerals – tennantite, sinnerite and lautite – and compared with enargite. Stability regions within the resulting EH-pH diagrams were found to change with stoichiometry such that a particular mineral would predominate if its stoichiometry was used in the calculation. Solution speciation was also found to vary, with thioarsenate being the best example. This stoichiometric effect helps to explain results reported in the literature and would be difficult to realize if it were not for mass-balanced calculations. IntroductionA comprehensive thermodynamic review has been conducted on the aqueous copper-arsenic-sulfur (Cu- As-S) system (Gow et al., 2014, 2015a, 2016b; Gow, Huang and Young, 2016c). Data on the free energies of more than 100 species were collected from various authors, and thermodynamic databases collated to produce mass-balanced EH-pH diagrams using the thermodynamic equilibrium calculation software STABCAL (Huang, 2014). The full database is listed and discussed in Gow et al. (2015a). Diagrams were generated for enargite and confirmed with Raman spectroscopy using bulk mineral electrodes in order to identify reactions spectroelectrochemically. Theoretical calculations agreed well with the experimental results under alkaline conditions (Gow et al., 2015a), acid conditions (Gow et al., 2014) and alkaline sulfide leaching conditions (Gow et al., 2015b).In the present study, additional mass-balanced EH-pH diagrams were generated by changing the Cu-As-S stoichiometry from enargite (Cu3AsS4) to tennantite (Cu12As4S13), sinnerite (Cu6As4S9) and lautite (CuAsS). Regions for the thermodynamically stable species were shown to change with the four different mineral compositions. Potential leach conditions, both for co-dissolution and selective dissolution techniques, were examined for differences in predominant species according to changing copper-to-arsenic ratios, sulfur compositions and sulfur oxidation states."

Jan 1, 2016