Search Documents

By W. Basuki, B. Setyotomo, L. Hakim, R. Hendrajaya

Due to high crack sensitivity of slab product of gas and oil line pipe application, its steel making process and alloy composition were evaluated and then improved to overcome its critical solidification process and reduced surface defects. The study was conducted at Slab Steel Plant Krakatau Steel. The purpose was to improve slab surface quality by reducing surface defects so that the slab surface doesn't need to be totally repaired. The method applied was by performing plant trial process, which the secondary process parameters such as alloying method and the casting parameters such as casting powder selection, metallurgical cooling, mould level control, and superheat were continuously monitored and then adjusted to the surface quality of the product. Based on the calculation of Ferrite potential of the steel, the chemical composition was designed to achieve optimum casting parameters in order to avoid high shrinkage during solidification. The results of the study are decreased surface defect quantity, and smooth casting process. The quantity of crack decreased by almost 90%. The slab surface repairing was significantly reduced from 85. % to less than 10%. These new casting parameters and developed alloy composition are then used and standardized for the mass production of the steel.

Jan 1, 2005

To date, improved thickening of clay mineral dispersions presents major technological and environmental challenge to mining and mineral processing industry worldwide. Flocculant-assisted dewatering processes currently employed during thickening are far from being efficient, requiring further development and process optimisation for dramatic improvement. In this paper, recent studies carried out to modify (i) pulp chemistry, (ii) flocculation performance and (iii) particle interactions to significantly improve the dewatering behaviour of flocculated, model and plant smectite and kaolinite clay dispersions are presented. It is shown that pulp pH-mediated hydrolyzable metal ion hydrolysis and specific adsorption in tandem with high molecular weight flocculant and shear may synergistically act to significantly enhance the dewaterability of both clay mineral pulps. Furthermore, polymeric flocculant structure type is demonstrated to show clear links with floc shear sensitivity, and hence, flocculation performance and pulp dewaterability. The implications and relevance of the findings plant clay mineral waste tailings thickening operations are drawn.

Jan 1, 2006

By Fulchand Shende

Around the world many potash mines experience brine inflow problems. The presence of brine in underground excavations may induce structural and stability problems. A study has been carried out to simulate the effect of brine on the performance of pillar support. The testing program consisted of loading potash specimens in a creep frame, and simulating inflows by continuously pumping brine into an experimental cell. Brine temperatures and load conditions were varied to simulate several mining and inflow conditions. Specimens were fitted with acoustic emission transducers to monitor energy emissions during an eight-hour test duration. Samples of brine were also collected to provide K+ and Na+ concentration data necessary for an accurate assessment of the dissolution process. Test results indicated that dissolution rates are highly dependent on brine temperature and load conditions. Loads approaching 50% UCS tend to generate very high rates of energy emissions, often leading to the failure of the simulated pillars. This study demonstrated that acoustic emission could be effectively used for predicting the performance of pillars when exposed to inflow brine.

May 1, 2001

By Mohammad Mehdi Salarirad

Fouling of activated carbon by different organic species is a great concern in carbon in pulp and carbon in leach circuits. The rate of gold adsorption onto activated carbon from synthetic gold solutions which contained different amounts of potassium ethyl xanthate (PEX), potassium isobutyl xanthate (PIBX), and methyl isobutyl carbinol (MIBC) were evaluated through batch adsorption tests. The results of these experiments showed that the gold sorption rate rapidly decreases by increasing the concentration of collectors including PIBX and PEX up to 20 mg/L and at higher concentrations, the kinetic rate constant (i.e., k value) gradually leveled off to 53 h-1 for PIBX, which is 46% lower than the 99 h-1 for PEX. At low concentrations of up to 15 mg/L of MIBC, a gradual decrease of the rate constant was observed, while at higher concentrations, the decrease was found to be more pronounced. The gold loading capacity and the rate of gold adsorption onto activated carbon from a gold cyanidation pulp in the presence of flotation reagents were also evaluated. The results of these experiments showed that the flotation reagents have no significant effect on the gold loading capacity of activated carbon at prolong adsorption period, meanwhile the rate of gold adsorption continuously decreases by increasing the concentration of flotation reagents in the leaching solution.

Oct 1, 2011

By B. Huffman

This paper examines several new trends in the design and application of linings for copper melting shaft furnaces including the use of large shapes, monolithic back-up linings and improved refractory engineering to significantly reduce refractory installation time, diamond saw blade costs, fuel and down-time. The net results are shown to be dramatically increased refractory service life, reusable safety linings, elimination of hot spots and lower refractory disposal costs.

Jan 1, 2007

By A. Henk, C. M. Aruffo, K. Fischer

"Geomechanical reservoir modeling offers a valuable tool to predict tectonic stresses, in particular the local perturbations in orientation and/or magnitude which occur at lithological boundaries and faults. The paper presents a workflow for building and calibrating such geomechanical models. The numerical simulations are based on the Finite Element method and can range from field-scale models to smaller, highly detailed submodels of specific fault blocks. The approach considers the reservoir-specific characteristics with respect to subsurface geometry (lithostratigraphic boundaries, faults), mechanical properties and ambient stress field. During the subsequent calibration stage calculated stresses are compared to stress data actually observed in borehole data. Poorly constrained input parameters are iteratively modified within reasonable limits until a satisfactory fit between calculated and measured stresses is achieved. This validated model can then be used for stress predictions between wells and in undrilled parts of the reservoir, respectively. The workflow is applied to two case studies - a large gas field in Northern Germany and a CO2 sequestration project in Australia – to test and illustrate its practical value. INTRODUCTIONDetailed knowledge of the tectonic stress field is crucial for the optimal exploration and use not only of conventional and unconventional hydrocarbon reservoirs, but also for deep geothermal reservoirs, carbon capture and storage (CCS) projects as well as underground mining and nuclear waste repositories. Any reliable stress prediction is hindered by the observation that the magnitude and orientation of the stress field can vary significantly – not only in time, but also in space. Such spatial stress variations comprise all scales, i.e., from the scale of lithospheric plates down to the grain-scale. On the reservoir- and fault blockscale, the local stress field can be influenced by faults and different mechanical properties of lithologies (Sassi & Faure, 1997). The resulting variations in stress magnitude and/or stress orientation are commonly referred to as stress perturbations and give rise to a unique, reservoir-specific stress pattern (Yale, 2003). Thereby, local stress fields can deviate by up to 90° in orientation and several tenth of Megapascal (MPa) in magnitude from regional trends."

Jan 1, 2015

By K. Sakai, M. Miyaue, T. Aoki, T. Tani, S. Tanaka, N. Kudo

In the planning stage of a tunnel, due to limited technology in the geological survey and the financial restriction, tunnel supports are often designed from unsatisfactory information, and the tunnel construction is started. Therefore, "Information-oriented construction" is carried out in the construction stage, in which the design is rationally verified and modified by observations/measurements. Moreover, the ground conditions ahead of a tunnel face must be predicted for efficient and safe tunnel construction. The authors have examined effective prediction methods to the ground conditions ahead of a tunnel face under construction of mountain tunnels (Aoki et al., 2010) in view of the established method (Schubert et al., 1995). Though the prediction method of Schubert requires the displacement in the direction of tunnel axis, it is difficult to obtain its accurate data by the electronic distance meter. Then, we have proposed a method that uses tilt sensors installed at the tunnel crown near the face to obtain the slight tilting information. To measure inclination of the tunnel crown, this inclinometer was originally developed as a daily control measurement, such that the geological condition and its possible change behind the face could be detected early, and a steady advance and construction safety could be ensured. This paper describes the method of forward prediction mechanism and advantages of this suggested method. It then presents the typical results of a field verification test at a tunnel under construction and an example of evaluation of the ground conditions ahead of the face based on the 3D numerical analysis in three types of condition changes of ground deformation moduli.

Jan 1, 2015

By Joachim von Scheele

An oxyfuel-based technology - OXYFINES - has been introduced for in-plant recycling. It provides fines, dust, sludge (without any drying-step) and other by-products arising in the steel and metal producing industries to be recycled directly back into existing processes or a separate unit on-site. Results from full-scale installation (20,000 tpy) for dust treatment, full-scale and pilot-scale trials with dry and wet materials in the steel and ferroalloy industries are presented. Processing rates at 3.5 t/h have been demonstrated. The product is agglomerates or lumpy pieces, the latter if the product has passed an all-liquid stage and thereafter been crushed. The technology does not only provide a solution to the problems connected to dust and sludge generated in metal production. It also turns these materials into a low-cost raw material useful for the production in question, thus replacing part of the raw material input in electric arc furnaces, blast furnaces, etc. Elements harmful to re-use of the processed dust or sludge, e.g., zinc and alkaline components in steel production, are removed as secondary dust, and material yield of main components for re-use is very high, about 98%. The paper reviews the concept, the results obtained and its status; its use for sludge recycling is emphasized.

Jan 1, 2004

By K. D. Peaslee, J. M. Soto, IéDé Smith, A. D. Saikia

Spinel-forming refractories reduce penetration of metal and slags through a tightening of the lining resulting from the volume expansion associated with spinel formation. Sintered spinel is often added to reduce the overall volume increase that results. Tests were carried out to evaluate the difference between performance in spinel¬forming and spinel-containing refractory mixes. Eight refractory linings, one (1) pure magnesia, three (3) magnesia-base spinel-forming and four (4) alumina-base spinel- containing dry vibratable mixes, were tested for four hours in contact with a low-carbon, low-manganese steel in a coreless induction furnace at temperatures in excess of 1600°C. Afterwards, sample were cut, and wear and penetration were measured. For magnesia-based mixes wear was minimized using 20-30wt. spinel formation although further experiments are required to determine the optimal value. For alumina-based mixes, there seemed to be an optimal ratio of spinel added to spinel formed that minimized penetration and wear at the slag line. Sidewall accretion occurred and the accretion was the highest for the mix with the ratio of spinel formed to spinel added near the optimum value. Therefore to design an optimum refractory mix the benefits of higher ratios of spinel added to reduce penetration and wear at the slag line will need to be balanced with the tendency to form accretions on the sidewalls of the furnace.

Jan 1, 2004

By A. K. Debnath

Mining being a site specific activity, land becomes the prime requirement for starting, successful execution and closure of any mining project. Many important mining projects are not progressing satisfactorily just because land is not easily available or environmental/social issues are not addressed properly. This is especially true in the case of open-pit mining, which requires large areas for mining, dumping of waste and additional land for other mine facilities. Mine closure & post mining land use exercises, though funded generously, may not achieve their objectives owing to uneven land profile after mineral extraction is over. One of the prominent solutions to these issues is application of steep angle conveyors in large open pit mines that will result in more space for internal waste dumping and enhanced slope stability of the dump. Additionally, such applications will result in economic extraction of mineral in deep open pits. Land reclamation exercise may start concurrently during early years of mine development as mineral evacuation is limited to a specific part of the mine. Surface mining facilities can also be advanced along with the pit by using modular/portable structures. The paper presented here attempts to address specific land related issues by developing suitable schemes and plans that can be practically implemented in open pit mines using advanced technology i.e. steep angle conveyors.

Aug 1, 2013

By E. Nurminen

Thermal transport properties of copper flash smelting flue dust have been investigated. Such values of the dust are needed to correctly model the process and to optimize its heat recovery performance. Dust accretions on heat recovery boiler walls may have a significant influence on the boilers heat transfer efficiency. Measurements of the thermal transport properties have been made for industrial flue dust and for pure sulphate components. The measurements have been conducted at temperatures up to 400 °C and the effect of porosity on these properties has also been investigated. The results indicate that the flue dust and the sulphate components are effective thermal insulators and the dust build-up on the boiler walls is likely to greatly decrease the heat transfer efficiency of the boiler.

Jan 1, 2007

By A. M. Reyes

Flow field hydrodynamics of serpentine flow channels was investigated numerically using computational fluid dynamics (CFD). The velocity profile simulated by the CFD model was evaluated with respect to experimental results from the literature. Rectangular and tapered flow channels were compared with respect to mixing and water management capabilities, and pressure drop. The CFD model was further developed to account for electrochemical reaction on the cathode side to determine which channel configuration was most effective in reactant conversion. The velocity profile differences between the channels were found to impact reactant conversion, as the rectangular channel had the highest conversion. With respect to water management, although the tapered channel was found to have a higher overall pressure drop, the rectangular channel was found to have higher shear and pressure forces acting on simulated liquid water droplets in the channel.

Jan 1, 2005

By A. G. Roach

IT IS generally stated that the gold ores of Nova Scotia are free-milling, and for the most part this is true. However, there is a certain proportion of the gold finely disseminated throughout the sulphides, notably arsenopyrite, and this gold is definitely not recoverable as 'free-milling' gold by amalgamation. The proportion of free-milling gold to total gold seems to vary widely in different localities in the Province and is lowest in deposits of the fissure-vein type. The problem of recovery of these relatively recalcitrant values is usually one of economics, in some plac.es a simple gravity concentrate being of such low tenor that its extraction and subsequent disposal will not bear the costs involved. In other cases, such a high percentage of values escapes from the mortars and plates that concentration is definitely indicated. The size of the mining operation is also an important factor. In the large majority of cases, however, some concentrating step is warranted, even if the resulting concentrate is stock-piled until sufficient has accumulated to justify further treatment.

Jan 1, 1940

By T. ?kre, O. M. Dotterud, S. Haarberg, J. Thonstad, G. M. Haarberg

An electrowinning pilot plant has been constructed at Falconbridge Nikkelverk A/S, Kristiansand, Norway. The equipment consists of a mixing tank where the electrolyte composition and temperature are controlled, an electrowinning tank equipped with five cathodes and six anodes of commercial size and design and a dechlorination facility. Electrowinning experiments were carried out in this pilot plant using acid cobalt chloride solution from the cobalt tankhouse. Key parameters were varied to obtain an improved understanding of the cobalt electrowinning process, focusing on the detrimental deposition of cobalt oxide on dimensionally stable anodes. The extent of anode scaling was found to be dependent on the electrowinning conditions. Low pH, temperature and cobalt concentration resulted in less scale being formed, however at the expense of cobalt current efficiency and cell voltage, adversely affecting electrowinning production capacity and energy consumption. When operating at high acidity, pH in the anolyte was higher than in the catholyte, which is believed to be due to H+ ions taking part in the current transport across the diaphragm, migrating out of the bags surrounding each anode.

Jan 1, 2005

By J. Drenda

The model for methane removal from the workings directly behind an advancing longwall as presented in this paper may be used for U-ventilated cross or length-wise systems of longwall advance, starting from the boundaries of the extraction field. In mines with high methane concentrations, Uventilated longwall extraction from the boundary of the extraction field produces a methane risk. The risk is manifested by a higher methane concentration at the end of the longwall, upper gate and incline. The methane in increasing concentrations, which is emitted mainly from the workings with caved areas, appears towards the end of the longwall and in the upper gate. The graphical model of the longwall provided includes both the workspace of the longwall and the caved area. Based upon a model of the rock distribution in the cave, a ventilation model comprising two standard air splits and large number of crosswise air splits has been constructed. Simulations indicate that if the shearer is not present in the longwall, the air distribution in the caved area is symmetrical. The presence of the shearer, both at the bottom and the top of the longwall, causes an asymmetrical air distribution in the cave, that is the asymmetrical flows in the goaf and longwall workspace and in the inflows and outflow between those regions. This phenomenon causes an increase in methane concentration at the end of the wall and at the upper gate. The methane removal method proposed for workings with a caved area directly behind the advancing U-ventilated longwall, starting from the boundary of the field, consists of the removal of methane-air mixtures from the caved area with the boom pipes. These booms may be of several meters long and may be extended if necessary. The insertion of the boom pipes into the cave towards the end of the longwall and connecting them with the general methane removal system creates negative pressure causing a change in the depression field, which is the aerodynamic potential field in the goaf area around the ends of the boom pipes. This will promote the extraction of the methane-air mixture from voids and the goaf cracks, and the area from which methane is being extracted may extend to the side of the cave. This is a positive phenomenon, which could result in the methane flow from the goaf into the airflow in the longwall workspace decreasing or even stopping. A reduction in the methane flow into the longwall workspace with extractions booms will be advantageous for the production continuity. Based on the floor load model for the rocks in the cave and the methane-removal boom load model, the value of the force required to move the boom behind the advancing wall has been calculated. Strength calculations for the pipe were performed using a finite elements method. The analysis results, as well as the comparison of the pipe material effort to the strength parameters of steel, which can serve as piping material (for the assumed load conditions), lead to a belief that the proposed boom construction satisfies the strength requirements.

Aug 1, 2013

By Sudarshan Martins

The measurement of acoustic signals produced by a tumbling mill has been previously used to determine the operating state of the mill and correlate the variations of the sound intensity with the operating conditions of the mill. Separately, the discrete element model (DEM), a software simulation of the mill, was developed to provide insight into the operation of the mill. Presently, there has not been much work reconciling the DEM simulation of the mill with the acoustic signal. Working from basic principles of linear, time-invariant systems, agreement between an acoustic DEM simulation and the measured signal is sought. First, the impulse response function of the mill is measured. The DEM provides the forces applied to the mill shell as a function of time. A convolution of these simulated shell forces and the transfer function gives the simulated acoustic signal. This signal is compared to the measured acoustic signal, both in the time domain and the frequency domain. Finally, a discussion of the results is given.

Jan 1, 2012

By W. Gan

The interactions between bitumen and quartz sands in aqueous solutions were studied with the objective of recovering residual bitumen from Athabasca oil sands froth treatment tailings. It was observed that the presence of various multivalent metal cation (Fe3-, Fe2+, Mg2+,Ca2+, etc.) increased the mutual coagulation between quartz particles and oil or bitumen droplets within certain pH ranges. While the increased coagulation was detrimental to the recovery of the bitumen since it lowered the degree of bitumen liberation from sands, this effect could be reduced or eliminated by the addition of organic chemicals such as citric acid, oxalic acid and EDTA. Among these organic chemicals, citric acid was found particularly effective even at very low concentration.

Jan 1, 2006

By K. Ghyselbrecht, R. Swennen, Y. W. Chiang, V. Cappuyns, R. M. Santos, T. Van Gerven, B. Meesschaert

Heavy metal contamination from mining and metallurgical activities of aquatic systems poses significant risk to the environment and human populations. The investigation of the distribution and immobilization mechanisms of heavy metals in sediments and soils has recently attained high priority. Different remediation methods can be employed to suppress or eliminate these contaminants. A tailored approach using both commercially available and in-house made adsorbents to rem ediate a heavy metal contamination site due to historical metallurgical activities in north Belgium is studied in this paper.

Jan 1, 2011

By J. L. Luo, D. G. Ivey, A. H. Adeleke

Double-edge-notched flat tensile samples of X70 steel were used for both slow strain-rate testing (SSRT) and cyclic loading testing with the notch located in the zone of interest, i.e., the weld metal (WM), base metal (BM) and heat affected zone (HAZ). By using both optical and scanning electron microscopy, the stress corrosion cracking (SCC) behaviour with respect to crack morphology and various forms of microstructure was investigated. In all the samples considered, the mode of failure was predominantly transgranular with cleavage facets around the edges of the fracture surface. The BM, with a bainitic microstructure, had the highest resistance to SCC when compared with the mixed microstructures of acicular ferrite-primary ferrite and acicular ferrite-grain boundary ferrite observed in the WM and HAZ, respectively. The effect of microstructure on stress corrosion cracking behaviour is discussed based on experimental observations.

Jan 1, 2005

For the last few years, a new and innovative technique has been successfully used to determine refractory and castable thickness in various metallurgical vessels. The acousto ultrasonic-echo (AU-E) technique uses stress waves to detect metal penetration and delaminations within refractory linings. In addition, it is capable of measuring the thickness of refractory layers and build-up material. The inspection and measurements can be carried out while the furnace is in full operation. The present paper discusses the principles of the AU-E technique, and its advantages and limitations. A number of case studies are presented to demonstrate various capabilities of this new Non-Destructive Testing (NDT) technique.

Jan 1, 2005