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By G. Guzman, L. Sevilla, M. Botz

"Newmont Mining Corporation operates the Yanacocha mine in Perú and the gold milling section of the property includes a Sulfidization-Acidification-Recycle-Thickening (SART) plant to remove copper from pregnant leach solution. Since its commissioning in 2008, the plant has been intermittently operated as needed to remove copper upstream of a carbon adsorption circuit. However, starting in 2015 Newmont expects the plant to operate on a more continuous basis in response to higher copper ores that will be processed in the gold mill. In anticipation of this, Newmont conducted a campaign in May 2014 with stockpiled high-copper ore to evaluate performance of the SART plant with elevated levels of copper in feed solution. Results from the campaign demonstrated the SART plant is capable of efficiently treating high-copper leach solution. During the campaign, leach solution copper levels ranged from about 100 to 700 mg/L, and copper removals ranging from about 56% to +99% were achieved. The median copper removal efficiency observed during the campaign was about 94%. The primary plant modification determined necessary following the campaign was the need to improve consistency with sulfide dosing. INTRODUCTION Copper removal from cyanide leach solution can be affected through the addition of sulfide at acidic pH to precipitate copper sulfide as a solid. There has been renewed interest in the process in the past several years due to the increasingly common issue of high copper levels in cyanide leach solutions. The term Sulfidization- Acidification-Recycle-Thickening (SART) is used as an acronym for the process according to the primary unit operations utilized. At a pH of approximately 4.0 to 5.0, the addition of soluble sulfide to a copper-bearing leach solution will result in the precipitation of copper sulfide (Cu2S) solid. The overall acidification and sulfidization reaction is (assuming the use of sulfuric acid for pH adjustment): 2Cu(CN)3-2 + 3H2SO4 + S-2 ? Cu2S(s) + 6HCN(aq) + 3SO4-2 The above reaction is written relative to the copper-cyanide complex 2Cu(CN)3-2, though analogous reactions also take place with the other common copper-cyanide complexes Cu(CN)2- and Cu(CN)4-3. Sulfide in the above reaction (S-2) is normally supplied as sodium hydrosulfide (NaHS) purchased in solid or concentrated liquid form. Two characteristics of this reaction that are beneficial to a leaching operation are: 1. Copper is removed from solution as Cu2S (synthetic chalcocite) solid, which can then be sold to a smelter for its copper value. 2. Cyanide that is complexed with copper in the leach solution is released as free cyanide, thereby regenerating cyanide that can be recycled to the leaching operation for continued use."

Jan 1, 2015

By John B. Gustavson

The mineral deposits found in carbonate facies rocks of sedimentary basins include deposits comprised of the country rock itself such as limestone for chemical uses, dolomite for road aggregate, and a variety of other industrial uses of the sedimentary rock. Exploration for new reserves is generally conducted on basis of outcrop investigation, subsurface drilling, and facies change studies while geophysics and geochemistry are not applied. In contrast, rapid development has taken place in the application of both geophysical and geochemical techniques in exploration for stratiform deposits of zinc, lead, barite, and fluorite deposits. This paper will present case histories and show illustrations from such work in the Mid-Continent region. The Metals Division of International Oil & Gas, Inc. has gathered this experience through work over the last three years along the southern margin of the Eastern Interior platform focusing on the states of Arkansas and Tennessee. The exploration work was conducted partially for the Company's own account, partially in joint exploration ventures with mining companies including International Mogul Mines, Ltd., a Canadian company; Bear Creek Mining Company, a subsidiary of Kennecott Copper Corporation; the Mining Division of W. R. Grace and Company, and Boliden-Preussag Exploration, a Swedish-German partnership. We wish to take this opportunity to thank our venture partners for allowing presentation of the various sections of this paper.

Jan 1, 1976

By William Lodding

That grinding may change a crystalline material both in a physical and in a chemical sense has been shown by a number of authors in recent years. Thus Mackenzie (1) and Bartha (2) reported the effects of careful grinding on muscovite, quartz, gypsum, dolomite, etc. Increase in specific surface produced by grinding implies increase in total energy of a system. Newly produced surfaces are chemically more reactive; dislocations may be introduced during grinding, and existing strain may be released by the same process, as shown by Holt et el. (3) All these changes are easily detected by thermal analysis, but it is not easy to separate the multiplicity of effects registered and to arrive at quantitative interpretations. This paper is an attempt to analyze by the use of thermal analysis some effects produced in grinding. In differential thermal analysis (DTA) one measures all thermal changes occurring in a substance during heating or cooling. Chemical changes, such as decompositions, synthesis, oxidation, reduction, etc., and physical changes such as phase transformations, changes in specific surface and in thermal conductivity, strain release, etc. By thermo gradmetric analysis (TGA) on the other hand only chemical changes involving weight loss or gain are recorded. Similarly gas evolution analysis (GEA) will register only reactions involving gas evolution, including water vapor, and oxidation-reduction. By performing two or all three of these thermal methods of thermal analysis simultaneously and on the same specimen one can separate the different effects registered and by difference evaluate their magnitude.

Jan 1, 1966

By Clarence O. Babcock

Model pillars of limestone, marble, sandstone, and granite, with length-to-diameter ratios of 3, 2, 1, 0.5, and 0.25 (0.286 for granite), were broken in axial compression to determine to what extent an increase in end constraint increased compressive strength. Radial end constraints of 13 to 23 percent of the average axial stress in the pillar, produced by solid steel rings bonded with epoxy to the ends of dogbone-shaped specimens, increased compressive strength somewhat above that of cylindrical pillars without ring constraint. However, when the results were compared with those obtained by other investigators for straight specimens of several rock types taken collectively, with L/D ratios greater than 0.5, the resulting strengths were not significantly different. Thus, the amount of end constraint produced by the solid steel rings was about the same as that produced by the friction from the steel end plates. In other tests a radial prestress of 3,000 psi or 5,000 psi was applied prior to axial loading by adjustable hardened steel rings to increase the constraint above that obtained for the solid rings. The average radial constraint stress, expressed as a percentage of the average axial pillar stress at failure for the 3,000 psi prestress, was 54.3 percent for limestone, 40.3 percent for marble, 44.7 percent for sandstone, and 23.4 percent for granite. The average radial constraint stress, expressed as a percentage of the average axial pillar stress at failure for the 5,000 psi prestress, was 74.2 percent for limestone, 51.2 percent for marble, 61.6 percent for sandstone, and 29.7 percent for granite. These constraints increased the compressive strength significantly above the strength of straight specimens and solid-ring constrained specimens. These results suggest that large horizontal stresses in orebodies mined by the room and pillar method should increase the strength of the pillars and allow an increase in ore recovery by a reduction of pillar size when major structural defects are absent.

Jan 1, 1969

By Kenneth J. Edmiston

The objectives of this paper are: to review the current status of chloride leach processes for sulfide concentrates, to make an evaluation as to the applicability of chloride leaching for replacing pyrometallurgical processes and to comment on recent advances in construction materials. The paper does not delve in detail on process chemistry. Sufficient references are presented on each process to allow the interested researcher to obtain process chemistry details. GENERAL The fact that chloride oxidates can solubilize base metals from sulfide concentrates has been known since the 1880's. The work of Hoepfner in 1902 was particularly accurate for its time with regard to the chemistry of chloride solutions. Recent work has dealt with the understanding of chloride extraction thermodynamics by modelling the behavior of metal chloride complexes. In the last several years several excellent review articles and symposiums have been issued covering chloride chemistry (1 thru 6).

Jan 1, 1984

By George D. Haley

This report will be given in two sections. The first sec¬tion outlines techniques and equipment to form almond shaped fluorspar briquettes by means of briquet presses, and the second section outlines techniques of the balling disc. PART I - BRIQUET PRESSES Fluorspar has been briquetted for a number of years and the so called "peach pit" briquet is known to many steelmen. Present production is estimated at over 100,000 tons annually. Slide 1 shows an assortment of various sizes and shapes of briquettes. It is possible to form fluorspar into almost any configuration of briquet. For safety on the melting floor, pillow type briquets are preferred. Ease of mechanical handling and durability of the product are facil¬itated by an almond shape. The dimensions of the almond can vary from 1-in. to 1-1/2-in. in length, from 13/16-in. to 1-in. in width and from 1/2-in. to 1-in. in thickness. The type of equipment to pro¬duce almond shaped fluorspar briquettes is shown in Slide 2. Here we have a Komarek-Greaves and Company 300 ton briquettor equipped with almond rolls. This machine is capable of producing fluorspar briquettes at a rats of 30 tons per hour with power consumption of 35 hp per ton par hour.

Jan 1, 1969

By E. Steel

The asbestifom habit is most commonly developed in certain amphiboles and chrysotile, but other minerals may also crystallize with this unususual habit, The habit may be characterized by 1) a fibril structure, single or twinned crystals of very small widths (generally less than 0.5 inn) which have gram with a common fiber axis direction but which are disoriented in the other crystallographic directions, 2) anomalous optical properties, primarily parallel extinction, 3) unusual tensile strength, 4) high aspect ratio, and 5) flexibility. In addition, there is evidence to indicate that some amphibole asbestos may have unusual surface properties.

Jan 1, 1979

By T. T. Toomver

The evolution of Inco's Selective Reduction Smelting Process as practised today is described, beginning with the initial laboratory experiments on small samples to the processing of large bulk samples through pilot plant equipment. For both the Guatemalan and Indonesian (Soroako) ores, the initial screening tests using hydro-, vapo-, and pyro-metallurgical processes showed that the latter was the most promising both metallurgically and economically. Later, larger scale tests confirmed the earlier testwork.

Jan 1, 1979

By Steve Karl

"The global underground construction and tunneling industry is in pretty good shape. Billions are being spent in shoring up aging infrastructure in the United States and other places, and new underground projects are being put out for bid.With each new project, comes new equipment, technology and tunneling methods. So it is incumbent on tunneling professionals to constantly improve their knowledge of the profession. This is where spending a few days with other underground construction professionals can assist the tunneler in keeping up.Every two years, tunnelers and underground construction engineers, contractors, suppliers, designers and owners from around the world gather for the Rapid Excavation Tunneling Congress (RETC). The 2017 conference was held in June in San Diego, CA. The UCA of SME puts on the conference.This years’ RETC attracted 1,400 attendees. The accompanying sold-out exhibit totaled 188 service and equipment suppliers. In addition, the conference had the UCA of SME bookstore, where the new History of Tunneling in the United States book was introduced. And a short course on tunnel rehabilitation was featured.Technical programmingRETC 2017 featured nearly 100 technical presentations. Topics covered the breadth of the global underground construction industry. Here is a sampling of a few. The proceedings from the conference is available from SME, 303-948-4200, www.smenet.org.Accomplishing extraordinary tasks as a machine supplier for Metro Doha: The construction of the Metro Doha in the State of Qatar established a modern, safe, efficient and integrated public transportation network. Upon final completion of multiple phases, the network will comprise four metro lines with a length of 216 km (83 miles) and 100 stations. Phase one comprises 112 km (43 miles of underground tunnels (56 km or 22 miles of twin-tube tunnels). Twenty-one earth pressure balance tunnel boring machines (TBM) were deployed by the four different joint ventures. The project was initiated, managed and supervised by the owner, Transport Authority Qatar Rail.Phase two of the Doha Metro will start upon the completion of Phase One in 2019 (Qatar Vision 2030). The owner placed full faith in the manufacturer’s abilities to deliver equipment of high quality, state of the art standards within the given time frame. This paper focused on the manufacturer’s scope of delivery and on the supplier’s high standards of quality in production, logistics and services."

Jan 9, 2017

By Paul M. Jr. Musgrove, Donald C. Moore

Conventional Smelting Practice Conventional copper smelting practice varies from smelter to smel¬ter, but generally consists of some or all of the following unit processes: roasting, smelting, converting, and fire refining. Roasting. Copper sulfide concentrates can be smelted directly or after an initial roasting step. Roasting is used in some smelters because roasting prior to smelting increases smelting capacity, less energy is required to melt hot roaster calcines than wet sulfide concen¬trates, roaster off gases are high in Sot concentration, 5-15% SO2, and some volatile impurities are removed from the concentrate prior to smelting. However, many smelters do not use roasters, because the problems associated with handling hot dry calcines outweigh the advantages mentioned. Concentrate roasting is performed in multiple hearth or fluid bed roasters. If the moisture is low, roasting can be performed autogenously, usually at 500-600°C. High roasting temperatures are avoided because excess oxidation of the iron compounds may lead to magnetite formation. Magnetite is detrimental to reverb operation because mag¬netite can combine with refractory minerals to form a highly viscous slag. This slag prohibits efficient matte-slag separation and leads to excessive copper losses. Also, magnetite can settle through the matte layer, deposit on the furnace bottom, and consequently reduce furnace capacity. Roasting is carried out only on sulfide concentrates prior to smelt¬ing in reverb or electric furnaces. For smelting processes, such as the flash and continuous that rely on the exothermic heat of oxidation of the sulfur minerals, roasting is not practiced. Reverberatory Smelting. The predominate copper smelting fur¬nace for the past 50 years has been the reverb. These furnaces are typically 100-120 ft long, 30-35 ft wide, and 12-15 ft high. A typical furnace layout is shown in Fig. 2. Refractory brick linings cover all internal surfaces of the furnace. Originally the flame was directed to reverberate or reflect off the furnace ceiling and melt the feed material. Current practice is to direct the flame down the furnace length to melt the concentrate. A method of charging the concentrates or calcines, generally along the side walls to minimize refractory erosion, is incorporated in the furnace design. The copper concentrates, calcines, and fluxes charged into the reverb undergo a series of complicated reactions as the temperature of the mixture increases. The reaction of the iron and copper sulfides with the oxygen in the furnace produces a molten Cu25-FeS mixture called matte. Copper smelting metallurgy is based on the fact that sulfur has a greater affinity for copper than for iron and most other common metals. Therefore, in a system containing copper, the copper will preferentially remain as a sulfide compound until all of the other metals have been oxidized. The oxidized metals combine with silica to form a silicate slag that floats on the matte and is removed from the system. Reverberatory furnace smelting chemistry can be approximated by the following chemical equations: FeS2 + O2 - FeS+ SO2 (1) The formation of FeS ensures that any copper present other than as sulfides will be reduced by the relationship: CuO2 + 2FeS + O2 - CuS + 2FeO+SO2 (2) or 2Cu +FeS - Cu2S + Fe (3) As the molten charge travels down the furnace, continued oxida¬tion of the iron minerals and sulfurization of the copper minerals occurs. When all of the copper has been converted to sulfides, the iron sulfides can then be further oxidized as: FeS + (3)2 O2 FeO + SiO2 (4) The FeO reacts with the silica added as flux in the furnace charge. A simplified equation is: FeO + SiO2 -FeO SiO2 (5) The iron silicate slag formed is skimmed from the surface at the end opposite the burners. The copper content of reverb slag is usually less than 0.6% Cu and is discarded. Matte is removed along the side wall and is taken to the converter for oxidation of the remaining sulfur and iron. The main objectives in reverberatory smelting are to produce a molten Cu2S-FeS matte containing 30-60% Cu and a throwaway slag. Production of matte permits complete conversion of all copper minerals into copper sulfides, which can migrate because of specific gravity differences, through the lighter slag layer. Also, the molten matte droplets collect the noble metals, gold and silver, as the matte settles in the furnace. The large settling area of the furnace provides enough separation time to produce a low grade slag, which can be discarded without further processing. High heat losses are associated with reverberatory smelting be¬cause of the large volume of gases sweeping through the furnace. Therefore, an outside source of heat is required to keep the smelting reaction going. Natural gas, fuel oil, or pulverized coal are used as this heat source.

Jan 1, 1985

The extraction and processing of minerals from surface mines and quarries can produce significant fugitive emissions as a result of site activities such as blasting, unpaved road haulage, loading, primary crushing and stockpiling. Uncontrolled fugitive dust emissions can present serious environmental, health, safety and operational issues impacting both site personnel and the wider community. Simulation technology is finding increasing use for the purposes of advanced warning of potential problem emissions in addition to providing a basis for future planning applications where demonstrable compliance with regulatory requirements are necessary. The initial re-entrainment and subsequent dispersion of fugitive dust presents a process complicated by the combination of the in pit topography, the surrounding natural topography and the dynamic nature of emissions from these sites. These factors impact upon the accuracy and reliability of the conventional Gaussian plume based computational prediction methods employed for regulatory compliance and IPPC applications. This paper proposes that optimal modelling of open pit emissions may be more accurately achieved by the use of a multi-scale predictive modelling approach utilizing computational fluid dynamics (CFD) methods for high resolution near source dispersion and conventional Gaussian based methods for far field dispersion modeling. This paper presents a numerical based flow and dispersion analysis of a typical UK based open pit utilizing CFD in conjunction with a conventional Gaussian plume based methods. Typical operating emissions and meteorological conditions are obtained from long term data records collected at a large operating quarry extraction operation in the UK. Emissions are modelled using a Lagrangian framework within conventional atmospheric boundary layer (ABL) profiles expressed as functions of turbulence and velocity parameters under assumed neutral conditions. Results are presented in terms of the impact of site topography on in pit retention as compared to the Gaussian based method.

Jan 1, 2009

By Harvey P. Knudsen

This paper illustrates the application of geostatistics to a roll front type uranium deposit located in Wyoming. The steps involved in calculation of experimental variograms, variogram modeling and verification of the resulting models are described in detail. The resulting spherical variogram models for grade thickness and thickness show strong geometrical anisotropies. The major axis of anisotropy for both variables is approximately parallel to the axis of the roll front and the minor axis perpendicular to the roll. This model confirms the technique of drilling "fences" across the roll front, where the drilling is much closer together than the fences along the roll.

Jan 1, 1978

By Xiaojie Yang, Gang Yang, Zhenli Hao, Manchao He, Ruifeng Huang, Zheng Wang, Chaowen Hu

Preventing the spontaneous combustion of remnant coal, which is indicated by carbon monoxide (CO), is a significant issue for coal mining safety. The N00 longwall mining method with Z-type ventilation is advantageous for the prevention and control of CO; however, research regarding this topic is limited. To investigate the distribution of CO in a goaf and working face, a sealing material and technique for blocking the goaf were introduced after proposing a forming method for a Z-type ventilation system; furthermore, a monitoring method was designed and applied in the field. The results demonstrated that the CO concentration during mining in the upper corner and return airway ranged between 4–6 ppm and 3–7 ppm, respectively. More importantly, no CO was generated in the goaf. The results indicate that the advantages and mechanisms regarding the prevention of spontaneous ignition using the N00 longwall mining method with Z-type ventilation are as follows: (1) The adoption of the downward ventilation technique is not only beneficial for reducing the air pressure difference between both ends of the working face, but also prevents CO accumulation in the upper corner. (2) The basis of a spontaneous combustion disaster is eliminated owing to the absence of coal pillars reserved in the goaf. This study proposes a superior method for mitigating spontaneous combustion disasters related to remnant coal in the goaf in a coal mining field and contributes to the better understanding of the N00 longwall mining method for coal mining safety.

Nov 28, 2022

By Joseph M. Driscoll

After 30 years of successfully mining gold, Newmont Gold has temporarily ceased production from the original Carlin Pit. In late 1993, the Carlin East decline was driven and an extensive underground exploration program was started. Today, Newmont Gold produces refractory ore from the Carlin East Underground at the rate of 864 t/d (950 stpd). Annual production is more than 3.1 t (100,000 02). More than 70 underground miners will be employed during Carlin East's estimated six-year mine life. About 70% of the ore at Carlin East is mined by mechanized longhole stoping with delayed, cemented backfill. The remaining ore is mined by underhand drift and cemented fill methods.

Jan 1, 1997

By William M. Dowall

The recently completed in-pit crushing and conveying project at Phelps Dodge's Morenci Mine is rated among the world's leading materials handling projects. The operation involves the crushing and transport of more than 109 kt/ d (120,000 stpd) of copper ore, using regenerative conveyors capable of providing more than 5.5 MW (7000 hp) of equivalent electrical energy. The Morenci Mine is located 330 km (200 miles) east of Phoenix, AZ. Phelps Dodge Corp. owns an 85% interest in the mine. The remaining 15% is owned by Sumitomo Metal Mining Co., Ltd. and Sumitomo Corp. Copper has been continuously produced from the Morenci district since the late 1800s. Until 1989, run-of-mine ore was transported from active mining faces to the Morenci and Metcalf concentrators by truck and rail haulage. In that year, a system of in-pit, semi-portable crushing plants and overland conveyors was commissioned. This substantially reduced truck haulage and effectively eliminated rail haulage in the pit. The system used two semi-portable, in-pit crushing stations equipped with 60/89 gyratory crushers. The crushed ore from both plants reported to the first of two overland belt conveyors, arranged in series, for transport from the pit to a coarse ore stockpile. The system was "backed-up" by existing locomotive rail haulage.

Jan 1, 1993

By J. D. Isbister

Coal is the most abundant and most economical source of energy in the United States, however, combustion of coal results in release of pollutants to the environment. The release of sulfur dioxide and oxides of nitrogen during combustion of coal contributes to the deterioration of the environment. Energy independence in the United States must include the increased use of coal reserves. Increased reliance on coal for energy will dictate the necessity for making coal a cleaner fuel. New technologies employing a variety of techniques from harsh chemical treatment to mild physical separations to clean coal are rapidly becoming available. Success for any coal cleaning process is in economics which translate into efficient removal of sulfur with high recovery of combustibles as well as low capital and operating costs for the process. Conventional coal cleaning processes remove water soluble sulfates and a portion of the pyritic sulfur and ash from coals. Removal of additional sulfur from coals requires more advanced coal cleaning techniques. Coal contains many organic sulfur forms which are the most difficult of the sulfur types to remove from coal. The heteroaromatic sulfur species, such as the comlex thiophenes, are the most commonly found organic sulfur forms. These sulfur forms are resistant to chemical attack and are considered to be refractory compounds. Atlantic Research Corporation has developed an "unique" microorganism, CB1 (Coal Bug 1), capable of oxidizing thiophenic sulfur in coal to form water soluble sulfates.

Jan 1, 1986

By K. E. Livo, D. H. Knepper

Modern remote sensing provides a means for locating and characterizing exposed mineralized systems in many parts of the world. These capabilities are non-invasive and help target specific areas for more detailed exploration. An example of how remote sensing technology can be used is evident from a study of the Questa Mining District, New Mexico. Analysis of low spectral resolution data from the Landsat Thematic Mapper satellite system clearly shows the region-al distribution of two broad mineral groups often associated with mineralized systems: clay-carbonate-sulfate and iron oxides-iron hydroxides. Analysis of high spectral resolution data from the Airborne Visible and Infrared Imaging System (AVIRIS) shows the occurrence and distribution of many individual mineral species that characterize the pattern of hydrothermally altered rocks in the district.

Jan 1, 2004

By W. D. Delahaut

Sampling tests performed at the Paradise Peak Mine compared various blasthole samplers and reverse circulation sampling methods. Statistical analysis of the data indicates that be-low-the-deck bag sampling produced a 24 to 29 percent error when compared to bulk sampling methods. Use of a chip pile wedge sampler reduced error to 17 percent. Reverse circulation sampling upgraded over bulk blasthole sampling by 7 percent for gold and 11 percent for silver. These results indicate that bias sampling conditions exist when small volume bag sampling is employed in production blasthole drilling.

Jan 1, 1991

Arsenic (As) removal behavior from Changgoon mine tailings was investigated using Acidithiobacillus ferrooxidans (A. ferrooxidans) in well-controlled batch reactors by varying pulp density (0.5?4%, pH=1.8, temp=30oC), reaction initial pH (1.8?2.2, pulp density=0.5%, temp=30oC), and temperature (25?35oC, pulp density=0.5%, pH=1.8). The initial concentration of As in the mine tailings used for bioleaching tests was about 30000 ppm, and the size range of tailings used in this study was 63?74 µm. The reaction speed and initial cell concentration were fixed to 150 rpm and 107 cells/mL, respectively. To complement leaching experiments, pH, oxidation/reduction potential (ORP), and amount of ferrous/ferric ions in leachate were analyzed. Scanning electron microscopy and x-ray diffraction analyses were also conducted for the samples before and after leaching to see if any morphological and compositional changes in tailings took place during leaching process. The As leaching efficiency increased with decreasing pulp density, decreasing pH, and increasing temperature in the presence of A. ferrooxidans. Specifically, no significant change in As removal rate was observed when pulp density d 2% while the removal rate dramatically decreased at pulp density of 4%. Regarding pH effect, As removal rate was much more enhanced at lower pHs (i.e., 1.8 and 2.0) compared to pH 2.2. Increasing temperature was observed to tend to enhance As removal rate, showing about 20% enhanced leaching rate under 35oC compared to 25oC and 30oC at the elapsed time of 5 days. The results for As removal behavior at different conditions (i.e., pH, temperature, pulp density) were consistent with the change in pH, ORP, and ferric ion concentration in leachate, showing greater removal rate at the condition with lower pH, and higher ORP and ferric ion concentration in leachate. Furthermore, decreasing removal efficiency was likely in part due to the extent of the formation of by-product (i.e., jarosite) of ferric ions.

Feb 27, 2013

By Jacob L. Brinkman, Catherine E. Johnson

Unmanned aerial vehicles (UAVs) are being explored by researchers to measure concentrations of gas emissions in situations where such measurements are otherwise extremely difficult to obtain, such as NO and NO2 (NOx) emissions from surface mine blasting. Recently, countries have imposed or are planning to impose surface blasting gas pollution regulations, which creates a need for an improved understanding of UAV-based gas measuring systems. The experiments detailed in this paper were performed to determine if airflow generated by the rotors, also known as downwash, unnaturally alters concentration measurements. Downwash turbulence could create locations of varying pressure, which could affect concentration. A UAV fitted with gas sensors was attached to a stand in a controlled environment containing a mixture of NOx. The gas sensor measuring points were placed at various distances on and from the UAV body to evaluate downwash effects on gas concentration. Results show that the presence of downwash turbulence causes no statistically significant changes to concentration measurements at any distance or direction from the UAV. Based on these results, it is possible to use a UAV-mounted gas monitor to measure concentrations without concern for downwash interference, provided the UAV and measuring point are entirely contained within the gas cloud.

May 20, 2021