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By S. S. SHINDE, P. C. JIKAR, N. B. DHOKEY

Mill scale is an oxide waste product of steel mills, containing around 70 percent iron and other allied impurities. In the present context, a dynamic prototype counter-current reactor (CCR) was used for the experimentation and simulation of a particle bed using the discrete element method (DEM). Mill scale was pulverized to ASTM mesh range 140 (106 μm)/+ 270 (53 μm) and oxidized in a CCR to make a single oxide Fe2O3 phase by maintaining the required thermodynamic conditions, such as pure oxygen at 1,100 °C. This oxidized powder was then subjected to a reduction reaction in the CCR, with gas mixture (H2:N2) ratio of 1:4 at 875±5 °C for filling degree, fd , and reactor revolution, ω, ranging from 5.38 to 16.14 percent and 2 to 5 rpm, respectively. A creeping fluid flow condition (Re < 1) and natural heat convection (Gr/Re2 >> 1) were maintained during the solid–gas reaction, and the particle-bed behavior was quantified by Froude number for the optimum operating window. The simulation was validated with the experimental results of reactor reaction product by X-ray diffraction (XRD) and scanning electron microscope (SEM) images.

By S. K. Sahoo, S. K. Sharma, U. K. Singh, G. S. P. Singh

This research focuses on the strata control issues in a Bord and Pillar depillaring working under the influence of dead load condition of voluminous and fragmented softcover of overburden dump material. It reports the modeling of a mine working through the FLAC 2D software under the Indian geo-mining conditions. The modeling results of an actual mine working under softcover were compared with that under the intact overburden condition to assess the influence of the soft overburden over the depillaring working. The modeling work involved progressive caving of the strata and the cyclic goaf filling following the modelsimulated occurrence of main fall and periodic caving. Mohr-Coulomb Failure criteria along with a simplified strain-softening (MCSS) model was used to study the failure and caving mechanism. Salamon’s compaction model was used to simulate compaction and resultant stress recovery in the goaf material. Comparison of the model findings was done in terms of load on supports, abutment stress, and convergence, apart from the stress redistribution and failure mechanism. The load transfer mechanism of the soft overburden was also studied for an overall understanding of the strata behavior in such workings.

Jun 16, 2020

By SK SAHOO, UK SINGH, SK SHARMA, GSP SINGH

Surface mining accounts for most coal production in Indian geo-mining conditions compared with underground methods, whose implementations are in deeper coal reserves and for lower stripping ratio in a congested operating space. The bord-and-pillar method is the preferred underground method in India for reasons of flexibility and investment cost. While previous researchers conducted field investigations on intact overburden conditions, this study focuses on the strata control issues in a bord-and-pillar depillaring working under the influence of the dead-load condition of voluminous and fragmented softcover of overburden dump material. The modeling results helped in ascertaining the criticality of strata behavior and rib-pillar stability in actual mining conditions when compared with the conventional intact overburden.

By Andrew Theobald, Peter Dare-Bryan, Trevor Byers

The use of advanced modelling techniques and the timing flexibility of electronic initiation systems allows for unprecedented control over blast outcomes as shown in several complex blasting problems experienced by the open pit operation Xstrata Ernest Henry Mine (EHM) in north-west Queensland, Australia.

Jan 1, 2010

By Lok M. Sharma, Deep K. Khatri, Bradfield. Brett

"A shored enclosure was required to access a control structure upstream below the dam of a deep lake. The shoring involves the interaction of the structure, soil, and water and the loads imposed include the hydrostatic forces of the water, soil pressures as well as dynamic forces due to currents and waves. Deep excavation support systems have traditionally been designed using classical methods that involve direct computations of earth pressures. However, traditional analysis does not take into account soil-structure interaction. Numerical modelling offers better means to analyze soil-structure interaction. This paper presents a 2D finite element (2D-FE) analysis of a deep excavation support structure that was required to remove and replace a control structure at the upstream toe of a dam. The sheet-piling shoring was designed to withstand the lateral pressures from 14 m deep free water and 5.5 m deep excavation below the free water to reach the required excavation level to replace the gate structure. Elastic-plastic analyses were performed to predict the stresses and deformations of the complicated shoring structure and excavation bottom. The soil parameters, procedures used to develop the 2D-FE model, and the results are discussed in this paper. The shoring system is currently under construction.INTRODUCTIONA deep shoring system enclosure is required to keep out water and soil and to provide a support for unbalanced loadings due to dewatering and/or, excavation in order to permit construction of the permanent structures in the dry. A braced shoring system consists of a single wall sheet piling which is driven into the ground to form a “box” around the excavation site and is braced on the inside. After bracing the sheet piling, seal concrete is placed into the bottom to prevent water from seeping into the open excavation from underneath the sheet piling, and the water is pumped out to provide the dry work area. The braced shoring involves the interaction of the structure, soil, and water and the loads imposed include the hydrostatic forces of the water, soil pressures as well as dynamic forces due to currents and waves. Deep excavation support systems have traditionally been designed using classical methods that involve direct computations of earth pressures, (active, passive, or apparent pressures). There have been some uncertainties regarding the actual distribution of earth pressures due to influence of the support wall flexibility, as these traditional methods do not take into account soil-structure interaction. Numerical modelling offers better means to analyze soilstructure interaction."

Jan 1, 2017

By K Koskinen, S Ronkainen

The flow field induced in an Outokumpu TankCell and by an OK rotor-stator mixing device in a laboratory and a process size flotation cell was modelled numerically using computational fluid dynamics (CFD). The primary target was to discover and reproduce the various interactions between the flow field and the flotation cell by numerical means. As power consumption depends sensitively on flow field, it can be regarded as a top-level derived quantity (or measure/metric) indicating the validity of the numerically obtained flow field. Having properly validated numerical means to produce the flow field the influence of various design parameters can be captured with certain accuracy. In addition, separate gas and solid phase models for bubbles and solids, respectively, were implemented. The comparisons between velocities and turbulence quantities measured using the laser doppler velocimetry (LDV) technique and CFD modelling were performed. The grid generation was performed with the commercial Gambit 1.3 and the subsequent integration and solving of the resulting algebraic equations with the commercial CFD-code Fluent 6.22. The computationally economic multiple reference frame method was included to model the moving rotor blades. Gas and solid phase models were modified mixture models.

Jan 1, 2005

By B BussiFre, J Molson, M Aubertin, G W. Wils

Waste rock piles containing reactive sulfide minerals can serve as long-term sources of acid mine drainage (AMD). Within these piles, many physical, geochemical and biological processes can contribute to the production of AMD. The flow of water, for example, depends on internal pile structure, which depends on the dumping methods used to construct the pile. In this paper, the internal structure and grain size distribution of typical waste rock piles are first reviewed with respect to their effect on internal water flow. A numerical model is then applied to simulate unsaturated flow within a waste pile assuming two primary waste materials, different atmospheric conditions and several geometric configurations. The simulations suggest that water movement can be controlled by introducing fine-grained material layers within the coarser host material. However, these layers should not be horizontal because they can lead to localised high-saturation regions as well as preferential flow favouring the production of AMD. A shallow slope towards the pile boundary may be introduced to force drainage to the outside while maintaining low saturation within the interior, thus reducing the production of AMD.

Jan 1, 2003

By Henry Hu, Alfred Yu

"A numerical model has been developed to simulate heat and mass transfer phenomena occurring during a novel magnesium reduction process-the vertical retort technology. The model was based on the control - volume finite difference approach. Simulations were run to determine the effect of various processing parameters on magnesium reduction cycle time. The model predicted temperature distributions, heating curves, recovery ratio of magnesium, and total process times. The predictions were used to optimize the magnesium reduction process including dimensions of the retort, geometries of the reactant compounds, and productivities. The results indicate that the implementation of the optimized processing parameters significantly decreases the reduction time, and consequently increases the production rate as well as lowers the energy consumption.IntroductionMagnesium consumption has been growing considerably in the past decade [1]. Of the total magnesium production, 30% is produced by the thermal reduction (Pidgeon) process, and it is anticipated to be still the main technology for producing magnesium in future [2]. One of the advantages of the Pidgeon process is that it is capable of producing high purity magnesium demanded by both the automotive and aerospace industries. However, the inefficiency of heat and mass transfer taking place in the horizontal Pidgeon reduction process results in low productivity, high energy consumption, labor-intensive operation, large floor space and high capital investment. This limits the production scale of a horizontal Pidgeon reduction process [3].Vertical reduction processTo overcome the shortcomings of the horizontal magnesium reduction process, a novel vertical magnesium reduction process [3] for large-scale production has been developed, in which heat and mass transfer in the retort is enhanced. The new process shortens reduction time, reduces energy consumption and increases productivity. The vertical reduction system is comprised of a vertically-placed retort, a heating furnace and a vacuum system. A section of the vertical retort is illustrated in Figure 1. Since the retort is set vertically, instead of horizontally, the entire procedure of loading the reactants material in the new process is different from the one for the horizontal reduction process."

Jan 1, 2001

By R. I. Jeffery, J. W. Summers

An account is given of the verification and calibration of a numerical modelling technique that has been developed for the prediction of subsurface strata deformation following the extraction of coal by longwall mining methods.

Jan 4, 1992

By W. M. Ma, Daniel W. H. Su, K. Centofanti, Yi Luo, W. L. Zhong, Syd S. Peng

NTRODUCTION Surface subsidence monitoring is the most effective means for investigating the nature of, and developing the techniques for pre¬dicting the surface movement and deformation process. However, because of imperfection in survey equipment and field practices, the surface movement data collected from field survey are not error-free. Also due to lack of proper numerical techniques for computing surface deformation from the measured surface move¬ment data, a relatively large portion of the subsidence data col¬lected could not provide information other than surface movement. In a paper by Luo and Peng (1992), the sources and magnitude of errors in the measured surface movements using an electronic total station in subsidence survey are discussed. If the errors in the measured surface movement components are left untreated before calculation for deformation indices (i.e., slope, strain and curva¬ture), the errors will be carried over to the deformation indices and enlarged if improper numerical procedures are used in the calcu¬lation. It should be noticed that in protecting structures affected by ground subsidence, accurate surface deformation indices are much more important than surface movement. In order to improve the accuracy of the collected surface movement data and the calcu¬lated deformation indices, a number of numerical procedures are also proposed in the same paper. The proposed techniques include: a data smoothing technique for data pre-processing; and a number of numerical methods and/or procedures for calculating surface deformation indices from the measured surface movement data. DATA SMOOTHING Because of various factors, the measured surface movement data always contain errors, small or large. In order to better utilize the collected data, a data smoothing method is proposed to correct the errors in the measured movement data. The method uses the same concept as the influence function method (e.g., Knothe, 1957) on which many existing subsidence prediction methods are based. The data smoothing method makes necessary corrections on the measured movement for the point of interest according to not only the measured movement at this point but also those at the surrounding points. The contribution of a surrounding point in making the correction for the point of interest is inversely propor¬tional, in exponential form, to the distance between them. The new magnitude of a movement component at the point of interest (Zi*) is calculated by

Jan 1, 1992

By Kathy S. Kalenchuk

Damages have been observed in shafts, backfill infrastructure and the slick line at the Leeville Mine. Shaft damage (shearing and spalling of the concrete liner) is attributed to mine-induced rock mass deformations concentrated where regional faults intersect the shafts. Aggregate bin, mixer station and conveyor drive damage (shotcrete shearing, heave of concrete floor slabs and bending of a vertical steel beams) is attributed to rock mass squeezing induced by elevated magnitudes of the vertically orientated major principal stresses. Separation of the slick line has occurred do to extension of the stressshadowed rock mass immediately above the mined out areas. Three-dimensional numerical models have been developed and calibrated to simulated rock mass deformations with magnitudes similar to those believed to have produced the observed damages. By stepping through the mine sequence, models reproduce deformations at the same mining stage as when damage has occurred. Calibrated models have been used to forward project further damage over the remaining mine life.

Jun 1, 2012

By Seyed Ahmad Jenabali-Jahromi

In this paper a meshless method called Finite Point Method (FPM) is developed to simulate the solidification process of continuously cast bloom steel in both primary and secondary cooling region. The method is based on the use of a weighted least-square interpolation procedure. A transverse slice of bloom as it moves with casting speed is considered as computational domain. The two dimensional heat transfer equation together with temperature dependent thermophysical properties is solved in the computational domain. The present work is verified in the mold region by the comparison of the surface temperature simulated by FPM and finite volume method (FVM) and also comparison of solidified shell thickness simulated by FPM and measured on a breakout bloom. For secondary cooling region the validation is done by comparison of the surface temperature simulated by FPM, FVM and thermovision measurements.

Jan 1, 2009

By S. H. Seyedein

A mathematical model was developed to study fluid flow and solidification in a single-roll casting system. Fluid flow coupled with energy equations were solved numerically using a finite volume method. A body-fitted coordinate transformation technique was adopted to handle the irregularly shaped domain. In order to couple the continuity and momentum equations, a SIMPLEC algorithm was used. A fixed-grid enthalpy method was considered to model the solidification in the system. The turbulence effect on flow field was modeled using a low-Re k-e model The model developed in this work was further run under various conditions to optimize the operating parameters of the process.

Jan 1, 2004

By Sang-Joon Kim, Hae-Geon Lee, Hyun-Jin Cho

"Decarburization phenomena on the surface of liquid iron have been simulated by numerical method and the results were compared to the experimental data. During the DeC process in a converter, a large amount of splashed droplets are generated from the top surface of the bath and consequently the reaction surface area is increasing tremendously. Since the decarburization mainly occurs at the interface, it is important to understand the reactions on the liquid iron droplets. The flow and species concentration fields around liquid droplets taking into account the reaction of carbon with oxygen at the interface were calculated by a commercial CFD code FLUENT which solving multiphase Navier-Stokes equation with Volume Of Fluid method, species transport equations and energy transport equation. The initial carbon concentration was fixed to 4 wt% and the concentrations of oxygen in the atmosphere were varied from 5 to 50 wt%. As comparing the numerical calculation with experimental data written in the reference, the results have a good agreement for decarburization rate.IntroductionIn a primary steelmaking process, one of the main functions is to decarburize from hot metal and the 4% of carbon is decreased to about 0.5% of carbon. Even though there are some possible reactions leading to the removal of carbon from hot metal, the main reaction occurs on the free surface by direct oxidation of carbon at the gas-liquid interface with producing the carbon monoxide gas. In many metallurgical processes involving a jet impinging onto a steel bath surface, especially in a Basic Oxygen Furnace (BOF) converter, it is important to understand the behavior of molten iron droplets splashing out of the steel. The iron droplets are generated by an oxygen or air jet blowing and it increases the total surface area of liquid iron tremendously. Since the decarburization reaction is mainly affected by the surface area, it is necessary to verify the decarburization phenomena around the splashed droplets from liquid iron in order to allow an analysis ofBOF process possible."

Jan 1, 2011

By K. Krishnapisharody

A mathematical model has been developed to predict the interface dynamics and droplet generation of the buoyant phase in a two-fluid system. The model employs the well-known SIMPLE algorithm for obtaining flow fields and the Volume of Fluid (VOF) method, for interface tracking. The implementation of the model in water-oil systems, where the oil layer is placed above a recirculating water bath, is discussed. The evolution of the water-oil interface leading to the formation of oil droplets is computed realistically.

Jan 1, 2008

By Guo Chen, Yifeng Shi, Xiaobiao Shang, Nanshang Shen, Bangqi Zhang, Jinhui Peng, Junruo Chen

"The energy is introduced directly into the volume of the honeycomb ceramic regenerator due to the complex interaction of microwaves with minerals in microwave gas heating system. A three-dimensional numerical model is developed to simulate the electromagnetic field by solving Maxwell's equations using finite-difference time-domain method. Computational result is presented for the microwave power absorption of the regenerator. Effects of the dielectric constant and the effective loss factor on the microwave power absorption in the regenerator are studied as well. Numerical results show that the heating pattern strongly depends on the dielectric property of the regenerator. The demonstration of the model of electromagnetic field distribution can be applied effectively and efficiently to optimize the fundamental parameters in the microwave heating processing.IntroductionIn recent years, microwave energy has been utilized in many fields, such as food processing, chemical engineering and mineral processing [l]. In contrast to conventional heating, where heat is transferred from a surface to the interior, microwave energy is introduced directly into the volume of minerals due to the complex interaction of the microwave with the mineral. Based on volumetric heating effects, microwave heating has several advantages such as pollution free, rapid heating technique, internal heating, high efficiency over conventional heating [ 1-4]."

Jan 1, 2013

By Nan Wang

Based on the commercial computational fluid dynamics software, Fluent, the fluid flow and temperature field in an iron-bath reactor were simulated numerically, and the effects of top-blown and side-blown operating parameters on the mixing time of iron bath, distribution range of oxygen in top space, and post-combustion ratio were investigated. The simulated results showed that the mixing time of iron bath increased initially and then decreased with the increase of inclined degree and immersion depth of side-blown lance. The distribution range of oxygen became wider as pulling the top lance away from the iron bath. Furthermore, post-combustion ratio was reduced given the top lance was too close the bath. The simulation results provide theoretical base for the process optimization of iron-bath reactor and further development of new type iron-bath smelting reduction process.

Jan 1, 2009

By M. K. Ameen, R. El-Hacha

This paper presents the analytical results obtained from numerical simulation of reinforced concrete slabs strengthened with various FRP systems and subjected to blast loading. A three-dimensional finite element model using AUTODYN software was used to predict the overall behavior of the slabs. The numerical results were validated by comparing with experimental results from a program carried out to investigate the efficiency of different strengthening systems on the blast resistance improvement of small-scale reinforced concrete (RC) slabs. The experimental program consisted of testing nine RC slabs strengthened with three different externally bonded (EB) FRP systems attached at the bottom side of the slabs and one RC slab tested without strengthening for comparison purposes. The EB FRP strengthening systems investigated included two layers of Carbon Fiber Reinforced Polymer (CFRP) sheets, two layers of Glass Fiber Reinforced Polymer (GFRP) sheets, and one layer of Glass-Fiber Resin Polymer (GRP) sheet. Different epoxy resin, patching mortars and impregnating epoxy adhesives were used for the slab surface preparation and FRP system application of the strengthening layers. The aim was to evaluate the residual strength of the test specimens after exposure to blast loads. The blast loading parameters were evaluated for each test using AUTODYN simulation and compared with the computer program CONWEP. All specimens were subjected to same spherical TNT charge weight and stand-off distance with the respect to the slab top surface. Extensive comparison is made between the experimental results and the AUTODYN simulations for the control unstrengthened slab and the strengthened slabs including time history records of the bottom steel strain and mid-span acceleration and the peak dynamic deflection of the slabs.

Jan 1, 2010

By Yuting Xue, Danqing Gao, Brijes Mishra

Heterogeneity and discontinuity significantly affect rockmass strength. Past studies have largely used arbitrary scaling approaches to produce rockmass strength from laboratory rock tests. This paper proposes a stochastic approach to produce rockmass strength from laboratory rock tests. Based on the laboratory data, MATLAB with an extreme value stochastic model generated a database for each physico-mechanical property of the rock. Then finite-difference software FLAC2D simulated laboratory-sized rock specimens. Random material properties in MATLAB were generated using the grids developed in the numerical model. The random properties were then applied to the final FLAC2D model. Model runs simulated the approach performed in the laboratory. The results from the model indicate that a stochastic approach produced compressive strengths that were lower than those from the deterministic approach. Failure modes for each specimen were different from those observed in the laboratory. In addition, random density also influenced the failure mode, highlighting the importance of stochastic analysis in rocks.

By Yuting Xue, Danqing Gao, Brijes Mishra

Heterogeneity and discontinuity significantly affect rock strength. For accurate stability prediction, intact rock behavior is imperatively included in rock mass behavior. However, past research largely used arbitrary scaling approaches to produce rock strength. This paper considers a stochastic approach in order to determine the strength of a rock. Based on the laboratory data, a MATLAB® with extreme value stochastic model generates a database for each physico-mechanical property. Then FLAC® simulates laboratory-sized rock specimens. The grids developed in the numerical model can in turn develop random material properties in MATLAB®, which researchers then applied to the final FLAC® model. Model runs simulate the approach performed in the laboratory. The results from the model indicate that a stochastic approach produces strengths that are lower than a deterministic approach. Failure modes for each specimen are different, similar to observations in the laboratory. In addition, random density also influences the failure mode, highlighting the importance of stochastic analysis in rocks.