Search Documents

By Z R. Guo, Y Qiu, X F. Wang

Mechanical damage leads to the increase of effective stress of sediments, and pore closure hinders the discharge of methane gas. Ignoring the influence of mechanical damage leads to an excessive prediction of hydrate gas production. Therefore, a fully coupled model considering mechanical damage-chemical decomposition-gas-water two-phase seepage-temperature was developed in this study, and the model was verified by Masuda experiment. Based on the fully coupled model, the temporal and spatial evolution of the whole process of hydrate decomposition under the influence of three initial absolute permeabilities, three pressure drops and three water saturations were considered. The results showed that: • The gas production rate reached the peak value in a short time after depressurisation, and the peak value increased with the increase of the absolute initial permeability. The larger the initial absolute permeability was, the faster the damage variable reached the peak value. The porosity increased gradually before the damage variable reached its peak, and the gas flowed more easily. • When the pressure drop was low, the hydrate remained stable in solid form. As the pressure drop increased, the hydrate gradually began to decompose. The greater the pressure drop was, the faster the initial decomposition rate of the hydrate was. So the damage variable increased rapidly and the porosity increased continuously, resulting in a large gas production rate at the initial stage of decomposition. • The larger the initial water saturation was, the smaller the effective stress wss, resulting in the slow growth of the damage variable and the small change of porosity.While the gas relative permeability was small, it resulted in a smaller gas production rate, and hydrate decomposition was slower. • The damage variable showed a process of rapid growth first, then slowly increased to the peak, and then gradually decreased to a stable state. When the damage was considered, the hydrate decomposition time to the steady state was longer, and the gas production was about 80.68 per cent of that without considering the damage.

Nov 29, 2022

By Mark Samonds

"Manufacturing processes which involve liquid to solid and solid state transformations in metals encompass a wide variety of physical phenomena. The past twenty years have seen a steady evolution in the complexity and scope of numerical models of these processes, beginning with thermal analyses without phase change. Recently, a few software packages have become available which have true multi-physics capabilities. This permits the treatment of thermal, fluids, stress, electromagnetic, chemical reaction and microstructure development aspects altogether in a fully coupled simulation. This paper will consider various aspects of these types of models.Coupled thermal and fluid flow analyses of continuous castings have been around for fifteen years. Coupled thermal and free surface fluid flow simulations of shape castings have been available for ten years, including view factor radiation models for investment castings. Only recently, however, have fully coupled thermal, fluid, and stress analyses become practical. This implies the reverse coupling of the mechanical deformations to the solution of the energy and momentum equations through modification to the interface heat transfer coefficients and the fluid domain geometry. This has been implemented with a combined eulerian-lagrangian finite element method. Appropriate mechanical constitutive models will also be discussed.Many types of defects need to be predicted in casting processes. Those related to stress include hot tearing, hot cracking, part distortion, and thermal fatigue in dies. Macroporosity, microporosity, and microsegregation are determined by the solidification behavior and microstructure development in a casting. In particular, microporosity is influenced by dissolved gases, the morphology of the mushy zone, the liquid to solid density change, and the local pressure conditions. Macrosegregation is caused by the partitioning of solutes during. solidification and subsequent thermo-solutal convection. An additional transport equation is required for each solute that is being tracked. Computational thermodynamics is being incorporated into these types of analyses to determine transformation temperatures, partition coefficients, densities, and enthalpies. In combination, the microstructure and microporosity models can frequently predict a variety of mechanical models, such as yield strength, tensile strength, and elongation."

Jan 1, 2001

By S. Mao

Total station has been predominantly applied in stationary survey scenarios in construction. With the moving target tracking and point survey automation functions, a robotic total station (RTS) lends itself well to more dynamic applications. Nevertheless, a RTS unit is still unable to track multiple targets simultaneously or to survey a target point when the line-of-sight is temporarily unavailable. In this paper, we propose a methodology to synchronize and automate multiple RTS units intended to address dynamic tracking and surveying applications in the construction field. By using the application programming interface (API) from the manufacturer, we implement the proposed methodology and the prototype system integrates two RTS units in regard to space and time and communicates survey command instructions among RTS units through wireless networks. The two RTS units can be operated to survey the two ends of one swinging sling concurrently in order to retrieve the actual length of the sling within several millimeters accuracy. Besides, in applications where line-of-sight between a target object and one RTS unit cannot be guaranteed all the time, continuous surveying can be materialized by automatically delegating the task to another synchronized RTS unit with clear view of the target object. A field test was conducted to demonstrate the application of the proposed automation approach in which sling length was measured of a rigging framework used for lifting industrial modules. The testing results are presented and achievable accuracy and reliability are discussed. The proposed solution overcomes the limitations of global positioning system (GPS) and laser scanning and holds high potential to provide cost effective solutions to many dynamic field applications.

Aug 1, 2013

By G. Scamans, J. Lazaro-Nebreda, Z. Fan, J. B. Patel

"Melt quality is crucial for both continuous and shape casting of light alloys and in order to improve it, removal of excessive inclusions, accumulated impurities and unwanted gases becomes necessary. To address this problem, a new multi-purpose high shear liquid metal treatment technology, based on intensive melt shearing by a rotor/stator unit, has been developed. The device ensures achieving uniform temperature and chemical composition and an efficient dispersion of gas and solid phases in the melt with minimal disturbance of melt surface, and can be used, among other things, for de-gassing and de-ironing of Al-alloy melts. Efficient degassing is achieved by dispersing each argon bubble into many small ones, which significantly increases the overall surface area of the bubbles and the time they remain in the melt capturing hydrogen before reaching the surface. This allows using much lower inert gas flow and mixing times than conventional rotary degassing. When applied to Al-alloy scrap, with accumulated iron, the high shear melt treatment speeds up the nucleation and growth of primary Fe-rich intermetallic particles, allowing a faster removal rate. Therefore it reduces processing times, increasing recycling productivity, and facilitates full metal circulation of secondary Al-alloys.INTRODUCTION Aluminium and magnesium alloys are widely considered in various industrial sectors for the purpose of weight saving (Polmear, 1995). In particular, they are used in the automotive sector, where components are mostly manufactured by high pressure die casting (HPDC) because of its simplicity and relatively low cost, but efficiency and mechanical properties are quite low compared with other processes. To date, the main focus to overcome this problem has been for improving the HPDC machinery (Dahle, 2001) but little attention has been paid to the opportunities of controlling the nature and quality of the molten metal supplied to the die. In this way, liquid metal treatment, which involves a variety of physical and/or chemical processing methods to improve melt quality prior casting, is crucial for both continuous and shape casting products."

Jan 1, 2018

By Leonard Sugin

As we approach the end-of the 20th century we are made more aware of the tremendous role that energy plays both directly and indirectly in our varied way of life. The industralized nations of the world have already established industries and economies which are greatly dependent upon the availability of energy. The underdeveloped and developing nations of the world are slowly and surely moving to the same utlimate requirements. The world wide need for distribution of energy sources is continuing to grow. At the present time there is a great imbalance between the sources of energy and the consuming economies In order to bring about greater equality between supply and demand major efforts and large capital expenditures are constantly being made. Industralized areas are seeking their own independent sources of energy whereas those areas of the world which contain great reserves of energy are limiting its export as well as developing its own industralized capacity. Nevertheless, energy bearing materials are still transported great distances in order to satiate the appetites of power hungry economies.

Jan 1, 1975

By D J. Murray

This paper outlines the principles of friction hoisting and the components involved, and gives a description of a specific mine hoist. Friction hoisting is compared with conventional drum hoisting, and the depth of shaft at which friction hoists become more economical than drum hoists, with respect to power consumption, is determined. Introduction T HE purpose of this paper is to outline the principles of friction hoisting, to describe the components and to show the advantages of multi-rope friction hoisting. Some calculations are made to show that the power requirements and the initial costs of friction hoists are less than those of conventional drum hoists, once a certain depth of shaft has been reached. The use of multi-rope friction hoists is gradually superseding the employment of the conventional drum hoist in many parts of the world. It results in heavier payloads from deeper levels, an increase in shaft safe-ty and a more compact installation for protection against adverse weather conditions. It was observed that where drums and friction sheaves exceeded 30 feet in diameter, a number of mechanical disadvantages were being experienced;

Jan 1, 1965

By Gerald L. Tiley

When payloads and hoisting distances are beyond the capacity of a single headrope, a multi-rope hoist will cost less than, and require less maintenance than, several hoists with one headrope per conveyance. This paper describes the basic type of multi-rope drum and friction hoists in use today, the types of ropes available, and the essentials of a satisfactory installation.

Jan 1, 1981

By P. K. Jimack, C. E. Goodyer, A. M. Mullis, P. C. Bollada

"We review the application of advanced numerical techniques such as adaptive mesh refmement, implicit time-stepping, multigrid solvers and massively parallel implementations as a route to obtaining solutions to the 3-dimensional phase-field problem with a domain size and interface resolution previously possible only in 2-dimensions. Using such techniques it is shown that such models are tractable even as the interface width approaches the solute capillary length.IntroductionMulti-scale modelling impinges upon many areas of science, engineering and technology where the interplay between processes occurring on disparate length and/or timescales can affect the properties of systems in a complex, and sometimes unforeseen, manner. One such is the processing of materials where interactions at the atomic scale, through the nano- and microstructural scale can have a profound affect on the macro-scale response of engineering components. Here we focus on one such problem, the crystallisation of alloy melts, to illustrate how a range of advanced numerical techniques make the modelling of such systems tractable.The modelling of solidification structures, in particular the growth of dendritic crystals, is a subject of intense and enduring interest within the scientific community, both because dendrites are a prime example of spontaneous pattern formation and they have a pervasive influence on the engineering properties of metals. For alloy systems, which form the vast majority of engineering materials, solidification involves the rejection of both solute and latent heat from the growing solid, forming a coupled diffusion problem in which both the chemical and thermal diffusion equations should be solved. The multi-scale nature of this problem arises from the disparity between the thermal and solutal diffusivities for most liquid metals, which are typically 10-5 m2 s-1 and 10-9 m2 s-1 respectively. The ratio of these two, referred to as the Lewis number (Le =Dia), is therefore typically of the order 10,000 and gives a measure of the multi-scale nature of the problem. In fact, in many cases the thermal diffusivity is so much larger than its solutal counterpart that thermal diffusion is considered instantaneous, wherein the system can be approximated as isothermal such that the multi-scale calculation does not need to be performed. This is certainly a reasonable approach in most conventional castings. However, there is a class of solidification problem in which this approach is far from satisfactory, namely Rapid Solidification (RS). The application of isothermal phase-field models in such situations are highly likely to produce spurious results or to fail totally, particularly for temperatures below To (the temperature at which the free energies of the solid and liquid phases are equal at the concentration of the bulk alloy), wherein partitionless solidification may occur."

Jan 1, 2013

"The link between ore texture and mineral liberation has previously been established at a microscopic scale. To construct ore texture models that can be used in mining applications requires this relationship to be retained at a significantly larger scale. This is initially dealt with by finding a basic set of microtextures that form the elements of the ore textures at the next larger mesoscopic scale, simulating these mesotextures at a fine scale, then changing the support of the mesotexture simulations to generate the expected mining block/stope mesotexture distributions. Thus, a mutually exclusive and exhaustive set of spatially locatable mesotextures can be used to fully characterize the metallurgical properties of in situ material.A method that generates expected distributions of mesotextures for any mining block size or shape is proposed, and includes: (1) characterizing the spatial correlation of the set of mesotextures with a single covariance function; (2) generating multiple simulations of mesotextures at a fine scale; and (3) using the simulations at a fine scale to generate the expected mining block/stope mesotexture distributions. A case study, using the George Fisher sediment-hosted base metal deposit in Queensland Queensland, Australia, is developed to demonstrate the proposed methodology as well as show the inadequacy of off-the-shelf approaches.Mining-scale texture models can be used to improve the in situ discrimination of ore from waste by exploiting the joint spatial variability of grades and textures to quantify the expected metal recovery of in situ material, then calculate local marginal cut-off grades. An artificial case study is presented to demonstrate the changes in ore/waste selection when considering ore texture models compared to constant metal recoveries."

Jan 1, 2005

By Sanat Talmaki

Construction and mining worksites pose unique challenges to workers and equipment operators due to their dynamic and unstructured nature. Narrow haul roads, crowded work spaces and presence of workers and equipment in close proximity, combined with large blind spots and overall poor visibility afforded to operators lead to collisions and run-over-type accidents between equipment, workers, and other entities that may be present on the jobsite. Operations that involve machine-infrastructure interaction, particularly in the case of concealed infrastructure such as excavation and drilling lead to unintended strikes between the equipment?s end-effect or and the infrastructure. Such accident-prone scenarios can be avoided by providing operators with real-time feedback and warnings using 3D visualization and proximity monitoring of the entities present in the equipment?s vicinity. Thus the jobsite in the real world is abstracted and represented in a 3D virtual world. However, this requires the ability to create a seamless link between real-world sensors present on the equipment and/or the jobsite and the virtual environment. This paper describes a non-restrictive acquisition allocation framework that allows position and orientation sensor streams from construction and mining job sites to be used for updating 3D virtual scenes in real-time for providing vital collision avoidance warnings to equipment operators.

Aug 1, 2013

By K L. Silversides, A Chlingaryan, A Melkumyan

Multiple data sources can be fused to improve boundary modelling in stratified deposits such as the banded iron formation (BIF) hosted deposits in the Pilbara Region of Western Australia. Accurate boundaries are essential to produce high quality geological models. Initial models are based on the widely spaced exploration hole data. This creates a high level of uncertainty in areas between the holes, with different interpretations of the boundary equally probable. Including directional information collected in these holes in the models can reduce the number of possibilities. Including data collected during mining, such as blastholes and bench measurements, can further guide the model. This research demonstrates a Gaussian Processes based method of fusing these disparate data sources to better inform the boundaries. Our results demonstrate that when only exploration points are used the model creates a smooth boundary with minimal variation between the holes. Each additional data source refined the model and added additional detail to the boundary. For the blast data, the new detail projects down to the bench below the current bench to allow for a better prediction before mining commences on that bench.

Mar 22, 2022

By S. A. Bortz

IIT Research Institute has initiated several multi-sponsored research programs. In this paper the methods for developing four of these programs are discussed. In general, a broad area of investigation must be proposed to interest a spectrum of different industries. The work must not touch upon proprietary data and will probably involve a number of scientific disciplines. Thus, the problem to be solved will attract sponsors who need to know more about the area under study but do not wish, as a single company, to commit the resources required to obtain the necessary know-how for their needs. The paper draws on the background of four IITRI multi-sponsored projects: Size Reduction, a study of grinding of material to reduce their particle size; Melt-Formed Ceramics Research, a method of producing dense, polycrystalline ceramics using glass forming methods; Binders in Ceramic Processing, which addresses the problems associated with the use of organic aids for ceramic processing; and a Study in Air Pollution Technology, a program to review and assess pollution control equipment for current and future applications.

Jan 1, 1984

By David R. Maneval

In 1956 the Legislature of the Commonwealth of Pennsylvania created a "Coal Research Board" in the Department of Mines and Mineral Industries. Over the years through amendments to the original legislation, the scope of authority for research has been expanded from the narrow area of improving and increasing the utilization of coal to covering all aspects of coal technology and any other area of interest which would be of value to the coal industry. In January of 1964, the Board commenced a vigorous program using appropriated funds and funds donated by the coal industry to finance a research program devoted to seeking solutions to the mine drainage problem. A review of published literature on the treatment of mine drainage indicated that much work done up to that point in time concerned only the mechanism of mine drainage formation and theoretical chemistry. Very few applied, developmental, or engineering studies had been devoted to finding practical solutions to the problem of polluted waters being discharged from active or abandoned mines. Projects were therefore undertaken on a wide variety of more utilitarian approaches. This paper will discuss briefly some of the pollution abatement approaches which have been funded by the Coal Research Board of this State, and will describe in some detail a multistage flash evaporator treatment plant now under construction.

Jan 1, 1970

By R Razanatsimba, A Galli

A mining company has entered into contractual commitments to supply certain quantities of its product to clients in each time period. Failure to fulfil its obligations would damage its reputation as a reliable supplier. The planned production would normally be sufficient unless major problems such as highwall failures, roof falls, natural disaster, or strikes that interrupt production or delays in obtaining environmental permits, occur. To overcome these difficulties, the company may be able to obtain more of the commodity: from its strategic stockpile (if there is sufficient there); by buying it on the spot market; or for some commodities such as gold and uranium, by leasing it. Two sources of uncertainty, the spot price of the commodity and the occurrence of serious incidents that interrupt production, are considered. For simplicity it is assumed that the commodity price follows a geometric Brownian motion, that productions incidents have a binomial distribution, that they are independent from one time period to another and that they do not affect prices. A branching tree structure is used to model the joint evolution of prices and production incidents. The aim of this research project was to evaluate the companyÆs options for fulfilling its contractual commitments. When evaluating these options, multi-stage stochastic programming with recourse was used to solve this problem because in addition to providing the dollar value of the project, it gives decision-makers the æroadmapÆ to reach the optimal value. That is, how much material should be bought/sold on the spot market, how much to add to/subtract from the stockpile, how much to lease and in the worst case what the shortfall would be, for each time period as a function of the current spot price and breakdown status. A case-study over a five-year period is used to illustrate the proposed procedure. In this study the production would be sufficient to cover the companyÆs contractual commitments unless production incidents occur. Focus is on evaluating the impact of the quantity initially in the stockpile on the value of the project when the commodity market is tight, that is, when only small quantities can be bought on the spot market or by leasing.

Sep 26, 2011

By Tianzu Yang, Weifeng Liu, Lin Chen, BOYI XIE, DUCHAO ZHANG, HUI XIAO

The oxygen-rich bath smelting process of copper dross was simulated using Factsage software. It was found that the two-step simulation results agreed better with the industrial data, especially in the speiss. Bi, Pb, Sb, As, and Cu contents in the speiss by two-step simulation differed from the industrial data by 0.6 wt.%, 0.8 wt.%, 2.6 wt.%, 7.2 wt.%, and 8.6 wt.%, respectively. Twostep simulation results indicated that the speiss partitioning of Sb, As, and Cu increased from 60.1%, 32.3%, and 27.5%to 81.6%, 67.8%, and 47.2%, respectively, with the smelting temperature increasing from 1050 °C to 1250 °C. While the metal partitioning of Sb and Cu increased from 0% and 2.7% to 15.2% and 13.3%, respectively, with the separation temperature increasing from 400 °C to 700 °C.

Oct 19, 2020

By W. J. Kogelmann

Roadheaders, also called Boom Miners or Boom-type Tunneling Machines have been in North America since 1968, when first introduced by Willy Kogelmann, the founder of Alpine Equipment Corp. (?Alpine?). Roadheaders were invented in Europe in the late 1940s. Machines with in-line, axial cutter heads were developed in the former Soviet Union. The British Dosco DRCL is based on the Russian PK-3 roadheader. Roadheaders with transverse ?ripper? cutter heads were invented in Hungary (1). The Austrian-made Alpine Miners of VOEST-Alpine, purchased by Sandvik AB, are based on a 1965 Hungarian license. Roadheaders are widely used in the mining and tunneling industries because they can excavate drifts, entries and tunnels with cross sections of any shape and size, can handle mixed faces, work on steep grades, and negotiate tight curves and cross-cuts. A roadheader?s only major limitation is the strength and abrasiveness of rock and minerals to be excavated. This paper covers roadheader selection criteria, improvements in reliability, attachments for flexibility (Multi-Tool Miner), and automated support systems for increased cutting time for increased shift production.

Jan 1, 2008

By Peter Zhang

Room and pillar mining under shallow depth is usually conducted with a high extraction ratio, which leaves small pillars with a low safety factor in some old workings in abandoned mines. Pillar sloughage, squeezing or even collapse may have occurred in those old workings with small pillars, either at the time of mining or later. The conditions of the pillars in abandoned mines can affect mining above them. Subsidence fractures and abutment pressure are indications of multi-seam interaction caused by squeezing or collapse of small pillars. To mine over areas with potentially unstable small pillars, the panel layout in the upper seam should be such that multi-seam interaction can be minimized and proper roof and rib support should be installed in the influence zones. This case study presents an example of multi-seam mining above small pillars under a shallow depth of cover. Though the interburden is relatively thick and competent, interaction is still present over the influence zones. Pillar stability and multi-seam interaction analysis, numerical modeling and in-situ monitoring are presented to demonstrate how the upper seam can be mined safely over the small pillars.

Jan 1, 2014

By Michael Murphy

A multi-stage triaxial procedure has been developed for the enhanced servo controls and feedback systems at the National Institute for Occupational Safety and Health (NIOSH) rock mechanics laboratory. Due to the difficulty of preparing multiple rock specimens for single-stage triaxial tests at different confinements, multi-stage testing provides a huge advantage if only a few samples of coal measure rocks can be prepared from the drill core. A multi-stage test can provide mechanical properties, post-failure properties, and a complete failure envelope for a single specimen. For the multi-stage test procedure, a parameter used to define the slope of the stress-radial strain curve was developed and monitored in real time in order to successfully predict peak strengths at different confining stages. For this paper, multi-stage tests have been conducted on sandstones of varying strengths, including Berea sandstone which has well-documented properties, and fine-grained and coarse sandstone from a western US coal mine. For the tests conducted on the fine-grained sandstone, it was found that the ramp rate was an important factor in the success of obtaining peak strengths during the multi-stage tests. For each rock type, a table including Young?s modulus, Poisson?s ratio, unconfined compressive strength, friction angle, cohesion, residual friction angle, and residual cohesion are reported. The values from these tables have been used as input parameters for projects at NIOSH requiring numerical model input parameters.

Jan 1, 2014

By D. M. Bodily, M. D. Deo, E. M. Whitney

Field data from coalbed methane wells indicate a significant variation in composition as a function of flow rate and time. In particular, San Juan Basin wells have displayed an increase in C02 concentration over time. Prediction of gas quality is critical to the economic evaluation of any coalbed project. Previous models have forecast only pressure and production profiles, ignoring compositional variations. In this study a multicomponent model that incorporates binary isotherms for methane and carbon dioxide has been developed. An extended Langmuir isotherm is used for the adsorption representation and a constant separation factor (similar to relative volatilities in distillation) describes the phase distribution of the species. This separation factor depends both on the surface characteristics of the coal and on the adsorbing species. The chromatographic separation equations have been superimposed on Darcy's law flow. The formulation allows decoupling of the pressure and compositional partial differential equations. The equations have been cast in dimensionless form and solved for pressures and compositions. It is observed that the composition of the preferentially adsorbed C02 increases at the wellbore as a function of dimensionless time. The dimensionless time is directly proportional to the real time and coalbed permeability and is inversely proportional to the gas viscosity, coal porosity and the square of the length of the reservoir. As the separation factor increases, the compositional variation increases. This variation in produced C02 concentration is also greater when the initial C02 concentration in the reservoir is higher. A sensitivity study has been performed to identify the effects of important parameters such as isotherm variables and reservoir characteristics on pressure and composition profiles.

Jan 1, 1993

By H. Chu

Selective Agglomeration experiments carried out to clean ultra-fine coal are examined. Effect of feed size, pulp density, coalescing agent dosage, and mixing intensity and duration on the kinetics of agglomeration are principally evaluated. A computer coded population balance model governing agglomerate size distribution and composition utilizing coalescence and breakage mechanisms is developed. Model calibration, verification and extension are analyzed.

Jan 1, 1987