Search Documents

By Clayton Vernon Deutsch, Marcel Antônio Arcari Bassani, João Felipe Coimbra Leite Costa, Vanessa Cerqueira Koppe, Pedro Henrique Alves Campos

Traditional linear approaches oversimplify the complexities of ore blending. Adopting nonlinear blending models in mining and mineral processing is critical to enhancing prediction accuracy and allowing optimization regarding nonadditive variables, such as metallurgical recovery. This study implements a simulated annealing algorithm in short-term mine planning that seeks to optimize the metal recovery by considering how to blend the ore in the mine better. Two nonlinear metallurgical recovery models are used as inputs to the algorithm to represent synergistic and antagonistic blending. The results of the case study demonstrate that the optimized schedule exhibits improvements in both blending behaviors when contrasted with conventional linear-based scheduling plans.

Jan 1, 2025

Coal fly ash and flue gas desulfurization (FGD) sludges can be returned to mine pits, fills and revegetation zones in Virginia by regulation if (and only if) a positive beneficial use can be shown. Utilization of alkaline fly ash for control of acid drainage from pyritic coal processing waste piles, and use as a soil amendment for revegetation, are the two dominant beneficial uses proposed over time. Both applications must be controlled by the basic chemical properties of the ash proposed for utilization. Currently, public concerns over long-term As and Se leaching from various applications are increasingly driving regulatory options for mine site utilization. Many fly ash materials are relatively low in inherent alkalinity or neutralizing ability, and certain ashes are actually acidic. Failure to add sufficient total alkalinity will result in strong acidification of the ash utilization zones, stripping heavy metals like Mn, Zn and Cu from the fly ash matrix. Similarly, if alkaline ash is loaded into non-acid forming coal wastes at high rates such that leachate pH is > 9.5, significant leaching of As and Se has been documented in large scale laboratory leaching columns. Utilization of fly ash and FGD as a mine soil amendment for revegetation is based upon combined liming and water holding capacity benefits, however, levels of soluble salts (primarily sulfate and borates) limit one-time application rates to 100 Mg/ha or less.

Jan 1, 2006

By Haia Roffman, Amiram Roffman

A gas company operated more than 100 distribution stations. Mercury filled manometers were used for years in these stations to measure the flow of natural gas through the system. Use and handling of these manometers resulted in mercury spills and ground contamination. To assess the human health and environmental effects of these spills and the need of remediation, it was important to determine mercury specific species present and their concentrations. Soil samples were analyzed for total mercury, methyl mercury, inorganic mercury and elemental mercury. These analyses served as important input in the risk assessment performed for these stations.

Jan 1, 1998

By Jr. McCulloch

Mining operations of Freeport Indonesia (FI) are located approximately 4 degrees -6' south latitude, 137 -7' east longitude in Irian Jaya the eastern most state of Indonesia (Figure I). The mines are located approximately 96 km (60 miles) from coast in the Carstenz Mountain range. The ore bodies are between 2900 and 4000 meters (9500 and 13 000 ft) elevation.

Jan 1, 1989

By Wojciech Klecan, John H. Raymer

Baseline quantities of difficult ground and support types were estimated for the Chattahoochee Tunnel using the Rock Mass Rating system. RMR classifies the ground into five categories, ranging from “very good” to “very poor,” based on five main parameters: intact rock strength, RQD, joint spacing, joint condition, and groundwater inflow. For the Chattahoochee Tunnel, these parameters were independently measured in the cores and shown graphically on the boring logs. A 55 matrix was calculated to obtain the statistical distribution of RMR for the project. Three baseline ground types were defined based on the RMR. Geologic mapping inside the tunnel during construction has verified the accuracy of this method.

Jan 1, 2003

By K. A. Brame, L. G. Austin, R. S. C. Rogers

The breakage parameters of phosphate ore were determined by batch first-ordering grinding studies in a laboratory ball mill according to the Austin, Klimpel, and Luckie procedures. The results were scaled to five larger mills of 0.56, 0.82, 8.36, 4.41, and 5 m in diameter assuming equilibrium ball charges for the full-scale mills. The results were used to predict product size distributions and capacities for batch grinding in the smaller mills and open-circuit grinding in the larger mills. The predicted capacities were in approximate agreement with experimental values except for the 5-m diam mill. The Bond method gave capacity predictions that were 4570 to 150% too high.

Jan 1, 1987

By R. Worrall

The global mining industry has been proactive over the last decade in finding ways to embrace the concept of sustainability. However, legacy mine sites (which include abandoned derelict and orphan mine sites) across the world continue to present issues for the global mining community, governments, local communities and NGOs. Unfortunately there has been much less academic focus on this area of mining and sustainability. This paper seeks to address how principles of sustainable development can be used to guide the development of processes for addressing post mining landuse issues for legacy mining areas. This is being done using a case study area located near Ipswich, in southeast Queensland, Australia. This area has a 160 year history of coal mining, and was one of Queensland?s crucial early industries. Mining in the area ceased in 2003 leaving a degraded landscape covering an area in excess of two thousand hectares adjacent to one of the fastest growing urban areas in Australia. A sustainability criteria and indicators framework for post-mining landuse on legacy mined land, developed from current best practice used for measuring sustainability across a range of industries is being developed. A review of current best practice suggests the framework should: (1) consider in equal measure environmental, social and economic factors; (2) have a minimum number of indicators which should be easy to identify and measure; (3) must have indicators with a meaningful output; and overall, the framework must consider particular requirements of the site being investigated. Application of the framework to the case study area is an ongoing aspect of this research, and the results will be evaluated through the use of expert stakeholders.

Jan 1, 2007

By J. M. Tranquilla

EMR Microwave has developed several unique processes for the pretreatment of refractory gold and copper ores. This report describes a recent large scale pilot project involving a carbonaceous gold-bearing whole ore. Pilot plant testwork conducted jointly by EMR and Bateman Engineering Inc. has shown that 90+% cyanide soluble gold recovery is obtainable from refractory (sulphide and carbonaceous) Carlin, Nevada gold ores. Typical cyanide soluble gold recoveries for untreated material is 20%. AC energy consumption was found to be between 58.l kWh/ton and 15.5 kWh/t for an assumed heat recovery of 50% and 80% respectively. The plant was operated at reduced temperatures ( 400°C) from previous testwork on similar ore at 600°-700°C.

Jan 1, 2000

By William M. PhD. Schafer

The net acid generation (NAG) pH method is an important analytical tool that supplements static and kinetic tests for assessment of the acid generation risk of rock samples. This method is useful because it is simple, rapid and cost-effective; it combines features of the static and kinetic tests; and it can be conducted at mine assay labs. The NAG pH test is particularly effective for operational testing programs used to classify, selectively handle, and route potentially acid-generating waste rock. The NAG pH procedure is based on a 24 hour oxidation of a pulverized rock sample with hydrogen peroxide and subsequent measurement of the sample's pH. If the NAG pH is below a critical value, determined empirically, then the sample has the potential to generate acid in the field. The critical NAG pH value is typically within the range of 3 to 4.5, but the exact relationship between NAG pH and potential acid generation should be determined individually for each mine site, based on comparison with results of acid base accounting, humidity cell tests, and mineralogical analyses. Calibration and use of the NAG test for predicting ARD risk at several mines are described in this paper.

Jan 1, 2000

By Gregg Wilkerson

The Blind Springs Hill pumice beds are located 5 miles southwest of Benton, California in the foothills between the Benton Mountain Range and Blind Springs Valley. The best exposures of the pumice are in an area 0.75 miles west of Blind Springs Hill. The pumice is Quaternary ejecta material which came from the rhyolitic volcanoes in the Glass Mountain-Volcanic Tablelands area of Mono County. The pumice beds occur in two distinct layers separated by an unconformity. The upper layer is 0 to 11 feet thick and consists of coarse subangular pumice fragments, some of which are over 1.75 inches in diameter. The lower bed is medium to coarse grained with subangular fragments up to 1.0 inch. The lower bed is 0 to 9 feet thick. Overburden at the Blind Springs Hill deposit varies from 0 to 15 feet. There are approximately 1 million cubic yards of material in the deposit that can be mined. The size distribution in the deposit is mostly fine with only 10.6% of the pumice fragments being over 0.5 inch in diameter, the minimum size needed for stone-wash or acid-wash applications. Suitability of pumice for the textile industry is quantified by standard 15-minute abrasion and absorption tests. In the Blind Springs Hill deposit, the plus 0.5 inch fraction has an abrasion loss of 33% which is too high for stone-wash application but it has an absorption capacity of 36% which makes it suitable for acid-wash applications in the textile industry. The abrasion and absorption properties of this deposit are within the range of those which have been measured for other pumice deposits within the United States.

Jan 1, 1995

By V. Badaker, R. J. Sweigard, C. D. Barton, J. W. Stringer, J. M. Ringe, A. D. True, D. H. Graves

Field studies have demonstrated the relationship between the growth of high-value trees on surface mined land and the physical conditions of the root growth medium. Specifically, the survival and height of hardwoods grown on less compacted material are far superior to those grown on compacted material. Furthermore, studies have demonstrated that the physical condition of the root growth medium can be characterized by dry bulk density and penetrometer resistance and that these parameters are also related to tree growth measurements. Site indices are useful for evaluating and predicting the productivity and timber yield for a specific location. A method has been proposed to estimate the site indices for various tree species on reclaimed surface mined land as a function of the physical properties of the root growth medium.

Jan 1, 2005

By Holger Witthaus

Various seam conditions had been examined during longwall production at RAG German hard coal mines. Based on the field data a prediction method was developed considering separation planes as influencing factors for roof falls at the face. The characteristics, orientation, and density of separation are important factors on the occurrence of roof falls. In addition to geological influences, the performance parameters and geometry of support must be considered and optimized for the prediction and prevention of roof falls in a longwall face. Based on detailed macro- and microscopic investigations of e coal seams considering various ranks of carbonization, the origin and characteristics of separation planes are determined and a strata-specific influence on roof fall is interpreted. It was assessed that the coal face fracturing and displacement caused by the stress depend on the floor and roof strata conditions due to activation of the existing separation planes. Field studies are shown giving an idea of influences by advance rates of the longwall face, support delay and hydraulic pressure to the roof control in longwall faces in depth of more than 3000 ft. The analysis includes the application of specific software developed for longwall roof fall prediction as a result of a European research project. The software allows a laminar graphic display of roof fall probability, which is used for recognition of risk areas and risk management.

Jan 1, 2009

By C. A. Fleming, C. J. Ferron, I. Dymov

An oxidized gold/silver ore from Mexico has been evaluated at Lakefield Research in order to develop an economically viable treatment flowsheet for the recovery of gold and silver. Initial cyanidation test results indicated that at least 20 kg/t cyanide was required for maximum gold and silver extractions, due to high cyanide consumption by an oxidized zinc mineral present in the ore. A process was developed for the recovery and recirculation of the cyanide from the leach liquors. The proposed flowsheet included direct cyanidation, CCD and Merrill-Crowe, followed by precipitation of the zinc associated with cyanide with sodium sulphide and recycling of the regenerated cyanide liquor to the leach circuit. The process was demonstrated during a continuous pilot plant. A mill has been erected recently in Mexico and has been operating using this flowsheet.

Jan 1, 1997

By N. Rajmohan, K. T. Jacob

Presented is a thermodynamic feasibility analysis of extracting base metal chlorides from low-grade, multi-metallic oxide ores using CaC[1]2 as a chlorinating agent in the presence of SO2 and O2. The oxides react to form corresponding chlorides, while CaC[1]2 is converted to CaSO4. The Ellingham diagram is used for comparing the standard Gibbs' free energy change for the sulfation-chlorination reaction of a large number of oxides. Except for alumina, silica and chromia, most of the other metal oxides will be converted to their respective chlorides. The volatile chlorides can be condensed, and the chlorides present in the condensed state can be leached. A process is proposed that uses a nontoxic chlorinating agent and gives an efficient separation of the metallic values from the gangue.

Jan 1, 1993

By FJ. Johnson

Polymer utilization has increased steadily over the past several decades; however, their usefulness is sometimes limited by natural forces. For example, polymers tend to degrade when subjected to elevated temperatures. This degradation can release toxic fumes, create excess smoke, and aid in the spread of fire. For these reasons, many polymers are filled with various compounds which impart flame retardancy (FR) properties. These fillers do not make polymers non-combustible; rather, they increase resistance to ignition and reduce bum rate. Also, they suppress smoke generation, which is important as up to 80% of fire-related deaths are due to smoke inhalation [1]. Therefore, methods to impart flame retardancy in polymers are industrially important. The early flame retardants used in polymers were halogen-based, working on the principle of inhibiting free radical formation in the vapour phase thus impeding combustion propagation [2]. Usually these were combined with antimony compounds such as Sb203 to decrease loading, yet provide the same FR qualities. However, questions have arisen recently concerning toxicity of halogenated flame retardants. Possible release of toxic compounds (such as dioxins) upon combustion has been reported [3]. Fear of future regulations concerning halogen addition has led to the search for different FR fillers. Two of the more common replacements for halogen-based systems are alumina trihydrate (Al(OH)3 or ATH), and magnesium hydroxide (Mg(OH)2)' These systems impart flame retardancy through heat absorption and by release of water of hydration upon their decomposition. ATH has a low decomposition temperature (230°C), limiting its use to unsaturated polymers, epoxies, urethanes, and some wire and cable formulations. However, some advantages of ATH over halogenated FR are that it is relatively cheap, doesn't generate toxic gases, is non-volatile, and is impervious to moisture [2].

Jan 1, 1997

By Ulf Svensson, Donald E. Zipperian

This paper reviews commercial installations of FLOTAIRE Column Flotation Machines for metallic, nonmetallic, and coal flotation. Second generation FLOTAIRE Column Flotation Machines employ dual aeration systems to provide a mixture of air bubble sizes. Operating data presented in this paper shows that optimum grade and recovery relationship for each rougher, cleaner, and scavenger application are obtained by adjusting the ratio and volume of aspirator air bubbles and micro diffuser air bubbles.

Jan 1, 1988

By Michael D. Zuber

This paper discusses the use of a coalbed methane simulator that has been modified to account for the removal of grid blocks as a function of time to estimate gas emission and production for a variety of mine-associated problems. The specialized features of the simulator are presented. Example applications illustrate the models' use in estimating methane emission rates during mine roadway development, and estimation of longwall panel degasification by horizontal boreholes.

Jan 1, 1997

By H. D. R. Browner, D. A. Marsh

The need for a product dewatering step between the milling/classification and leach/carbon stages of gold plants has traditionally been performed by thickeners. Whether these be the 'conventional' or 'high-rate' types both require considerable initial capital outlay even without provision for standby facilities. In addition, their sensitivity (both mechanically and metallurgically) to changing feed conditions often results in these being considered 'high-risk' items of equipment, requiring a high degree of attention from operating personnel.

Jan 1, 1992

By Jerry L. Hodgson

This paper presents an application case history of the planning methods used for developing, costing and scheduling an underground hydro- electric pumped storage facility in weak rock. This method covers the system configuration, excavation methods and costs, initial support systems and final lining systems. This study was performed by the Omaha District, Corps of Engineers for the proposed Gregory County Hydro- electric Pumped Storage Project, and presents a synopsis and the results of the studies performed.

Jan 1, 1986

By R. W. Williams

Consequent on the development of digital computers the importance of analog simulation as a means of studying engineering problems has diminished in recent years. The general-purpose nature of a digital computer ensures its applicability to a wide range of tasks whereas an analog simulator is confined to the one specific use for which it was designed. Nevertheless the analog technique remains attractive in its application to certain aspects of the study of mine ventilation networks, for reasons which will now be developed.

Jan 1, 1980