Search Documents

By Paul M. Wiltcher

This paper discusses how benefits in engineering design can be achieved from combining existing GRP concrete design guidelines with carbon steel design codes primarily made possible due to the increase in the constitutive properties of modern composite rebar or GRP. It also examines the technical and practical considerations necessary to both construct and ensure the integrity of composite rebar during transportation and handling on site and the measures taken by Franki-Cementation Joint Venture to ensure the safe deployment of the GRP in the workplace on the Noord/Zuidlijn Project in Amsterdam between 2003 and 2006.

Jan 1, 2006

The roasting of sulphide ores and concentrates is often the first step in the production of metals or chemicals. In many processes, the production of sulphuric acid is viewed as a by-product, while in some plants production is an important economic factor. Regardless of the purpose, a pyrite roasting plant consists of mainly three plant sections: roasting, gas cleaning and sulphuric acid. With the addition of air, the pyrite concentrates are transformed into solid oxides and gaseous sulphur dioxide at temperatures of 600 - 1000° C. After cleaning and cooling, the sulphur dioxide in the roasting gas is further processed to sulphuric acid. Two types of reactors are used depending on the application: stationary or circulating fluid bed . For over 60 years, Outotec has progressively been developing the principle of fluidised bed technology in several different reactor types for a multitude of process applications. The versatility of the fluidised bed reactor system has manifested itself in the treatment of minerals, including solid fuels, and for metallurgical processes both in the ferrous and non-ferrous fields. Process applications have included roasting, calcining, combustion and charring of coals, as well as off-gas treatment. This paper provides a summary of the pyrite roasting technology currently used along with a simple cost comparison of pyrite roasting and sulphur burning processes.

Jan 1, 2009

The roasting of sulphide ores and concentrates is often the first step in the production of metals or chemicals. In many processes, the production of sulphuric acid is viewed as a by-product, while in some plants production is an important economic factor. Regardless of the purpose, a pyrite roasting plant consists of mainly three plant sections: roasting, gas cleaning and sulphuric acid. With the addition of air, the pyrite concentrates are transformed into solid oxides and gaseous sulphur dioxide at temperatures of 600 - 1000° C. After cleaning and cooling, the sulphur dioxide in the roasting gas is further processed to sulphuric acid. Two types of reactors are used depending on the application: stationary or circulating fluid bed . For over 60 years, Outotec has progressively been developing the principle of fluidised bed technology in several different reactor types for a multitude of process applications. The versatility of the fluidised bed reactor system has manifested itself in the treatment of minerals, including solid fuels, and for metallurgical processes both in the ferrous and non-ferrous fields. Process applications have included roasting, calcining, combustion and charring of coals, as well as off-gas treatment. This paper provides a summary of the pyrite roasting technology currently used along with a simple cost comparison of pyrite roasting and sulphur burning processes.

Jan 1, 2009

By Peter A. Oshust

The EKATI Diamond Mine has successfully completed the development and commissioning of the Panda Underground Project to extract the ore below the Panda open pit. The dominant kimberlite domain of the Panda Underground, intermixed olivine-rich and mud-rich resedimented volcaniclastic kimberlite (RVK), is very similar to the kimberlite domain characterizing the open pit portion of the pipe. A sublevel retreat mining method is in operation underground at Panda; near-vertical blast rings are drilled and blasted into an open void. Broken ore is mucked with load, haul and dump trucks (LHD?s), sized underground then moved to surface through a conveyor system to the process plant. An advanced feasibility study is in progress at the Koala Underground Project. The Koala pipe is geologically more complex than Panda. The pipe below the open pit is comprised of at least five distinct kimberlite domains. There is a 100 m thick zone of incompetent low-grade mud-rich RVK between the open pit and the stable high-grade olivine-rich primary volcaniclastic kimberlite where mining will be initiated. As a result, it is proposed that Koala will employ sublevel caving; each blast ring shot would be confined and mucked in sequence to maintain the cave of the over-lying low-grade RVK ore. The sublevel cave method seeks to safely defer the mucking of the low grade ore to the latter part of the mine life.

May 1, 2006

By M P. Cipold, J F. Bachmann, C C. Bachmann, J Ha, H B. Wurst

In washability, the objective is to establish the set of maximum possible separation performance criteria for a given mineral feed. The method of choice for this has been the conventional sink–?float analysis. Using traditional sink–float method it is not possible to sample and automatically measure. This fact, as well as time, cost and safety aspects, as well as required and manageable sample size of the sink–float method have prompted the search for a new approach for establishing separation performance criteria. This is especially important as performance levels of separator plants can be maximised if reliable information based on an analysis of washability in conjunction with particle size distribution, elemental constituency becomes available in time. The new method to establish washability and associated performance information utilises at least two measurement technologies concurrently: single energy X-ray transmission and image processing. For porous or very inhomogeneous materials the results can be refined further by using dual energy X-ray transmission and image processing.If used as a standard laboratory device the continuous build-up of the washability curve allows to evaluate the statistical significance of the sample size during measurement.The measuring method can even be improved if it is combined with an automatic sampling system that feeds a continuous and representative particle stream to the analyser. Then the value of the collected data increases considerably since the washability data are additionally available in time to be considered in the control of the process plant. The washability curve can be derived and is continuously updated based on the particles measured during the past time interval. Older curves and results are stored in a database and can be retrieved for later reference. This technology now enables automated sampling and integrated automated measurement, which was previously not possible.This incorporation of an automated washability monitor at a representative sample gives near real-time data that would impinge positively on the profitability of the plant operation. The method was extensively tested using a range of samples with different densities, varying from 1 g/cm3 (coal) to 5 g/cm3 (iron ore).CITATION:Bachmann, C C, Bachmann, J F, Cipold, M P, Wurst, H B and Ha, J, 2017. Inline analysis of washability parameters for process control, in Proceedings Eighth World Conference on Sampling and Blending , pp 213–218 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

By H. Sarvamangala

Biomineralization of manganese on titanium condenser material exposed to seawater has been illustrated. Biom-ineralization occurs when the fouling components, namely, the microbes, are able to oxidize minerals present in water and deposit them as insoluble oxides on biofilm surfaces. Extensive biofilm characterization studies showed that an alarmingly large number of bacteria in these biofilms are capable of oxidizing manganese and are, thereby, capable of causing biomineralization on the condenser material exposed to seawater. This paper addresses studies on understanding the exact role of the microbes in bringing about oxidation of manganese. The kinetics of manganese oxidation by marine Gram-positive manganese oxidizing bacterium Bacillus spp. that was isolated from the titanium surface was studied in detail. Manganese oxidation in the presence of Bacil-lus cells, by cell free extract (CFE) and heat-treated cell free extract was also studied. The study confirmed that bacteria mediate manganese oxidation and lead to the formation of biogenic oxides of MnO2, eventually leading to biomineralization on titanium surface exposed to seawater.

Jan 1, 2008

By F. Fraas, J. E. Conley

"The problem of recovering potash from the mineral polyhalite (K2SO4.MgSO4.2CaSO4.2H2O), occurring in large quantities in the salt beds of Texas and New Mexico, has been under investigation at the Nonmetallic Minerals Experiment Station of the U. S. Bureau of Mines continuously since 1928. Most of the results previously obtained have been published in technical journals and in a series of Bureau of Mines Reports of Investigations.The experiments described in the present report were performed to ascertain whether a continuous countercurrent extraction of calcined polyhalite by hot water would yield satisfactory recoveries and concentrations of sium sulphate in the top liquor. Previous investigation by Storch 4 had shown that the rate of solution of uncalcined polyhalite was too slow to be of value in an industrial process, and Storch and Clarke 5 had demonstrated that calcination of the polyhalite greatly, accelerated the rate of solution in hot water, allowing most of the potassium sulphate to be readily extracted."

Sep 1, 1933

By N. Raeis Hosseiny, S. H. Bassir

"Chador-Malu iron ore is one of the most important iron mines of Iran.About 98 percent of Fe in the ore is in shape of Magnetite, Hematite, Martite, aqua oxide of Iron and the other irons are with ferrous silicates, actinolite, cholorite and ferrous dolomites. 1% of Fe has replaced in pyrite. The phosphor distribution in the ore is non-hemogenous and its average in the whole of the deposit is 94%. It is in shape of Apatite.This mine contains considerable phosphor, which makes it useless for metallurgical uses. At this mine the phosphor is reduced in the iron ore at two steps. At the first step, magnetic part of the ore is separated from the gangues and phosphors by magnetic separator. At the second step, the ore is enriched by the flotation methods. Experimental flotation methods to obtain the optimum conditions are as follows:• Effect of Starch as Hematite depressant with ATRAC as Apatite collector• Effect of Sodium silicate as Hematite depressant with ATRAC as Apatite collector• Effect of ASAM as Apatite collector with Sodium silicate as Hematite depressant• Effect of ATRAC (BEROL) as Apatite collector with Sodium silicate as Hematite depressant• Effect of ASAM & ATRAC mixture as Apatite collector with Sodium silicate as Hematite depressant• Effect of Kcarbonate as pH-modifier• Final test to Optimize pH, Collector, DepressantAt this research we have found the optimum circumstance of the flotation of Chador-Malu iron ore in order to decreasing phosphors of iron oxide and floating of Apatite to make pure Hematite.To reach the optimum conditions, some tests were done with different amounts of pH, collector and depressant. The results are as follows:"

Jan 1, 2003

By J. R. Allsup

Air pollutants in exhaust gas produced from LP-gas (propane) were studied using both laboratory engines and vehicles. The objective of the study was to evaluate engine parameters relating to the advantageous use of propane as a low-pollution fuel. Some comparisons are made between gasoline, natural gas, and propane. Results show that engines can operate over a wider range of A/F with minimum carbon monoxide and hydrocarbon emission when using propane than when using gasoline. Mixture enrichment using propane is unnecessary during cold starts, thereby eliminating the emission penalty during warmup. Carbon monoxide and hydrocarbon emission using propane are unaffected by ambient temperature. The photochemical reactivity of hydrocarbon emission is considerably lower with propane than with gasoline.

Jan 1, 1972

By Gustavo E. Armijo

This job was done in Morristown, NJ, with mono fluid system jet grouting for the construction of a new bank building. After the demolition of the existing two story structures, an excavation in loose sandy fill materials was necessary in order to reach the new structure basement level. Due to this jet grouting was selected as a medium to provide both excavation support and permanent underpinning, minimizing the adjacent building settlements. These two adjacent buildings were partially underpinned with a "gravity wall" made with 2 and 3 rows of secant vertical and inclined jet grout columns. Besides the classical jet grouting control methods, during the jet grouting execution, all the drilling and grouting parameters were recorded by a proprietary system called "Slogger". Additionally, after the jet grouting execution, an innovative result control technique was used by means of the application of the same parameter recording system. Some of the production columns were re-drilled and a comparison was made between the obtained drilling parameters and those obtained for the same age test columns. Under the referred existing conditions and in comparison with the conventional underpinning techniques, this project demonstrated that jet grouting, with proper execution and result control, can be faster than them and can maintain the building structural stability and act, at the same time, as a retention system minimizing the existing building settlements.

Jan 1, 2002

By M Simpson

Greywackes of the greater Auckland Region (Brynderwyn Hills to Hamilton), when considered on a regional scale, have characteristic ranges of physical, mineralogical and other properties. Some properties (eg density, porosity, crushing resistance, clay index) generally cluster and correlate with the basement greywacke facies, regions and terranes recognised by geologists, and their diagenetic/metamorphic level. Other local factors, particularly variations in mineralogical composition, nature of matrix cement, grain size, and degree of weathering may produce aberrant properties. Some of these local variations, when extreme, have the potential to affect the aggregateÆs performance in roading or the concrete industries.   Smectite and the zeolite laumontite are the major deleterious minerals occurring in fresh greywacke rocks of the Auckland region, although weathered rocks may contain halloysite, an expanding member of the kaolin clay mineral group. These minerals, when found in abnormally high levels in greywackes cause expansion effects in the aggregate. Currently there are inconsistencies in the detailed correlation of shrinkage, clay index, clay mineral content and intrinsic expansion data that need further research to resolve them.  

Jan 1, 2007

By R. Karl Zipf

Multiple seam mining interactions caused by full extraction mining, whether due to undermining or overmining, frequently involve tensile failure of the affected mine roof. The adverse ground control conditions may prevent mining for both safety and economic reasons. Prior researchers have identified the geometric, geologic and mining factors controlling multiple seam mining interactions. This numerical study examines the mechanics of these interactions using a modeling procedure that 1) incorporates the essential constitutive behavior of the rock such as strain-softening of the intact rock and shear and tensile failure along bedding planes and 2) captures the geologic variability of the rock especially the layering of weak and strong rocks and weak bedding planes. Specifically, the numerical study considered the effect of vertical stress, interburden thickness, and the immediate roof quality of the affected seam in both undermining and overmining situations. The models show that for overburden-to-interburden thickness (OB/IB) ratios of less than 5, interactions do not occur, and that for OB/IB more than 50, extreme interaction is a certainty. In between, the possibility of an interaction was found to depend on gob width-to-interburden thickness ratio, site specific geology and horizontal stress to rock strength ratio in addition to the OB/IB ratio. The models also showed that horizontal stress was profoundly altered well above or below a full extraction area and that these changes are likely to influence the success or failure of multiple seam mining. The role of horizontal stress in multiple seam mining interactions has received little attention in prior investigations. Four factors control the mechanics of multiple seam mining interactions: 1. vertical stress concentration 2. horizontal stress concentration 3. stress re-direction 4. bedding plane slip bands A combination of vertical and horizontal stress increase and high stress gradients in the vicinity of full extraction areas re-orients principal stresses into a very unfavorable direction. This seemingly small stress re-orientation has a profound adverse effect on bedded rock.

By O. Mejia, J. Drozdiak

"This paper summarizes a comprehensive energy and cost study comparing an existing SAG mill based circuit at Huckleberry Mine with two proposed circuits involving comminution technologies which are associated with energy efficiency: high pressure grinding rolls (HPGR) and high speed stirred mills. The specific energy requirements expressed as kWh/t for the proposed circuits were determined from pilotscale HPGR and stirred mill testing conducted at the University of British Columbia. Samples and operating data were collected from Huckleberry’s copper-molybdenum concentrator to evaluate current mill performance for comparison. To support the base case, the SABC circuit was modeled using JK SimMet® software. The main comparison focused on the complete energy requirements for each circuit, including materials handling equipment such as conveyors, screens, feeders and pumps. This paper also provides capital and operating cost estimates for each of the comminution circuits. The results showed that the HPGR - ball mill circuit achieved a 21% reduction in energy consumption over the existing SAG - ball mill circuit at the same P80 grind size of 160 µm. At a grind of 80% passing 75 µm, the HPGR - stirred mill circuit showed a 34% reduction in energy compared to the base case. It was concluded that the energy reduction for the new flowsheets significantly improved the economics of the Huckleberry comminution duty.INTRODUCTIONUp until now, tumbling mills such as AG/SAG mills and ball mills have had a dominant bearing on the design and economics of comminution circuits. However, it is commonly agreed that the majority of employed comminution processes are energy intensive and energy inefficient, accounting for up to 80% of overall process plant energy consumption and having an efficiency of as low as 1% (Abouzeid and Fuerstenau, 2009; Fuerstenau and Abouzeid, 2002). The U.S. department of energy reported that there is a potential to reduce energy consumption in the metals industry by up to 61% from current practice to bestestimated practical minimum energy consumption; suggestions included the implementation of best practices and the adoption of energy efficient mining and mineral processing technologies such as advanced blasting techniques, high pressure grinding rolls (HPGR) and stirred mills (U.S. DOE, 2007)."

Jan 1, 2013

By Ralph J. Holmes, Victor Sharp, Steven J. Spencer, CSIRO Minerals, Kevin J. Davey, Jonathan J. Campbell, Peter L. Phillips

"Improved measurement tools for monitoring and control of AG/SAG mill performance have a high level of interest in industry. Historically, acoustic emission monitoring has been widely used on SAG/AG/ball mills and hydrocyclones to provide new information on the conditions inside these devices affecting their performance. The current work was focused on a new technique using surface vibration monitoring of a number of pilot-scale and production-scale AG/SAG mills to yield insights into the events occurring in the mills. The development of relationships between signal analysis outputs and mill operating conditions can be used for soft-sensor measurement of mill process variables. The technique used an array of accelerometers mounted on the mill lifter bolts linked to a fast data acquisition system which monitored the surface waves generated during operation. Details of the system are presented. Mill operating variables were adjusted systematically to provide a wide range of operating conditions for surface vibration signal collection. The experimental approach is discussed.The signals acquired during the experiments were analysed using a range of techniques. The results show that strong relationships exist between measured vibration power (both total power and within certain frequency bands) and mill load level/power and mill speed. A new method for extraction of power spectral density and band power information on features of interest in a mill rotation cycle is also presented."

Jan 1, 2003

By Jurgens J. Louw, Vincent C. Smith, Gareth C. Smith, Agit Singh, Dave G. Hulbert

"During 2000 Mintek Developed the PlantStar plant wide control platform for the minerals processing industry. The flexibility of the PlantStar control platform has enabled Mintek to investigate and easily develop new control strategies for both milling and flotation. This includes a Solids Feed Controller, a Safety Limit Controller, Mill Power Optimiser and Flotation Optimiser, amongst others.Processes with long dead times, like a feed belt to a mill, are difficult to control. The solids feed controller was developed for minerals processing plants using a specialised time delay compensator. Using conventional time delay compensators that are purely model based, results in robustness problems due to model uncertainties. The Mintek Solid Feeds Controller makes use of a plant model, but compensates for model inaccuracies, giving more controller stability and a more robust delay compensation algorithm.Often there are more variables on a plant that need to be controlled (process variables) than there are variables to control them with (manipulated variables). Process constraints are often reached and violated. Safety control loops are necessary to prevent constraints being reached. The safety limit controller has been developed to switch smoothly between normal and safety control loops without bumping the process. The safety loop output is chosen in accordance with a predefined list of priorities and whether the respective constraint boundaries are exceeded.The Mill Power Optimiser helps to find the power peak on the mill power curve. It continuously perturb the solids feed rate to learn ‘where’ on the curve the mill ‘was’ and then to drive it continuously toward the middle, maximum power drawn. This insures maximum grind with maximum throughput. It also prevents power dips due to mill overloads by cutting the solids feed to a minimum if the power drop below a specified threshold. Once the power rises above the threshold the solids feed is increased again to an intermediate value from where it start the perturbations again to find the maximum. This makes the milling circuit easier to operate."

Jan 1, 2003

By S. Christiansen, G. R. Winslow, R. W. Kobler

Todays End of Life vehicles are shredded and their metal components recovered and recycled by standard methods. The remaining non-metallic fraction is shredder residue, and contains vast amounts of high value engineering plastics. None are today recovered. Discussed are the developmental approaches used in the first process to recover these valuable plastics. Examined are initial laboratory studies, pilot plant design and construction, product development, results, and flowchart explanations.

Jan 1, 2001

By Jay C. Hanson

Various electrical and electromagnetic (EM) geophysical techniques are currently being evaluated by the U.S. Bureau of Mines for their effectiveness in the detection and monitoring of electrically conductive (1 to 5 S/m) lixiviant (leach solution) to depths of 600 m, either above or below the water table. These techniques include magnetotellurics (MT) , controlled source audiofrequency magnetotellurics (CSAMT), resistivity and focused resistivity, ground-penetrating radar (GPR), frequency-domain electromagnetics (FEM), and time-domain electromagnetics (TEM). Of these techniques, TEM may be the most effective, but CSAMT and focused resistivity also hold promise. Geophysical computer modeling of the borehole TEM technique was conducted based on an idealized geoelectric section (layered earth) with characteristics based on the Santa Cruz porphyry copper deposit near Cas a Grande, AZ. Layer resistivities and thicknesses were obtained from geophysical data and geologic logs available from the site. Modeling of borehole TEM in both preleach and during leach situations was conducted. Simulating the TEM method using computer modeling proved to be encouraging since there were substantial differences between leached and nonleached responses. The modeling does not prove the effectiveness of TEM in the field, but does indicate that detection of deep lixiviant zones is theoretically possible.

Jan 1, 1992

By Karina Forster

Rock mass characterisation is a critical component of effective stope design. Unexpected excessive stope dilution or uneconomic stope sizes can be the result of rock mass characterisation that is not representative of actual stope conditions. Comprehensive characterisation of the rock forming the stope hanging wall, back, ends and footwall is best done by a rock mechanics or ground control expert, however, this is time consuming and is often limited by available access. There are two general approaches for characterising a stope hanging wall for dilution estimating. Detailed classification and mapping data can be collected in local areas where good exposure is available. Personnel, exposure and time are usually not available to do a thorough analysis for all stopes. The stope hanging walls are then broken into lenses or domains and similar conditions are assumed for each area. The second approach consists of using readily available data such as RQD. Other rock mass properties which influence hanging wall behaviour are estimated based on back analysing a few case histories. Stope design is then based on the variability of the one parameter, such as RQD, that is consistently measured for the rock mass surrounding the ore body. This paper presents a third approach which looks, in depth, at the interpretation of geological core logging data for rock mass characterisation. Several rock mass properties that influence stope design, such as joint alteration, rock mass strength, joint spacing and orientations, have been linked to data collected by the mine geologists. This drill hole logging data was calibrated against underground mapping and used to back analyse the dilution prediction for mined-out stopes.

May 1, 2006

By H. Gumede

The occurrence of fracturing due to high stress levels is a major factor in hangingwall stability in deep level gold mine stopes. However, rock falls cannot be the result of these fractures alone. Rock falls can result only from the occurrence of unstable rock blocks defined by the interaction of the stress induced fractures and naturally occurring geological planes of weakness. These planes include bedding planes and joint set planes. However, there is a general lack of information on the characteristics of these planes (orientations, spacings and lengths)?it does not appear that any such systematic and quantified information, if collected, has been published. To remedy this situation to some extent, joint mapping exercises have been carried out in several geological environments in two gold mines. The data collected on joint geometry included orientation, spacing and length, and this information is included in the paper. In addition, the paper describes the use of the data collected to evaluate the potential for rock falls and the probability of failure of stope support

Jan 1, 2007

By Johan F. W. Kock

"Hearing loss due to excessive noise exposure is the most prevalent industrial disease. It is ranked on the World Health Organization’s (WHO) priority list for major work related injuries. Uncontrolled noise not only has a physical effect, but is also a psychological hazard affecting the performance and well being of man. Noise induced hearing loss (NIHL) is irreversible, yet it is preventable. The first defence against noise (noise control engineering) is a high priority in the mining industry. Second defences should be a last resort when the engineering control of noise is inadequate. Hearing conservation programs and the use of conventional hearing protection devices seem to have failed in the prevention of noise induced hearing loss. If compensation payouts that quadrupled in the past ten years are used as a barometer for the success of existing hearing conservation programs, then new strategies and technologies need to be investigated. The best practice Hearing Protection Device (HPD) may be seen as the minimum standard for second defence noise control.Conventional hearing protection is widely applied, but also misused in the industry as well as in the mining sector. Empirical research results, ownership, general attitudes of workers as well as qualitative aspects will be explored. The paper provides reasons, evidence, case studies and strategies regarding the best practice hearing protection philosophy (the Noise Clipper Model) as implemented in the Implats Mining Group. Worldwide tendencies towards custom-made HPD’s, findings that indicate improvements in hearing conservation programs and finally the successful application of Custom-made Hearing Protection Devices, will be outlined."

Jan 1, 2003