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By Xiao-hui Fan, Li-shun Yuan, Xu-ling Chen, Wei Lv, Min Gan, Yi Wang

"As the amount of ferrous scrap increases every year, it becomes more and more urgent to deal with this iron-bearing resource properly. This paper puts forward a method on resource-oriented utilization of ferrous scrap (cold-bonded pelletizing), and these cold-bonded pellets can be used as coolant in a converter. The influence on the pellets qualities by using different kinds of chloride as rust agents is studied, and results show that the strength of cold-bonded pellets increases significantly by using a combination of the three kinds of chloride -NaCl,MgClz,FeCh, their best dosages are 1.2%, 0.2%, 0.1% respectively. Other iron-bearing materials also have an effect upon the pellets strength, by adding 5% iron powder and maintaining for 48h, the compressive strength of the clumps surpass 2500N/A, dropping strength surpass 4 times/ A, and 10% iron slag or 20% steel slag can replace 5% iron powder while obtaining the comparative quality. The influence of different ratios of three ferrous scrap (converter mud, iron scale and dust) is further studied, and results show that when the ratio is 30% : 30% : 40%, the pellet strength reaches the maximum. After maintaining for 24~48h, the clumps can meet the mechanical as well as the physical-chemical requirements as BOF steelmaking refrigerant.IntroductionGreat amounts of converter mud, dust and iron scale are produced in steel production process. These materials are of great values, and their accumulation not only leads to environmental pollution, but also wastes the precious resources, which restricts the sustainable development of the steel industry [1,2] The main approach at present to dealing with the ferrous scrap is to add them into sintering. But in this way, the utilization factor of sintering and the quality of sinter decline while the energy consumption increases [3].Therefore, more advanced and efficient technology is needed to make the best of these iron resources. Cold consolidation of ferrous scrap is a simple process that has many advantages such as less investment, quicker effect, lower energy and lower cost [4-5] But the conventional maintaining period is too long, usually up to four-six weeks, and the pellet strength is low. Therefore, the key points of the cold-bonded pelletizing are to develop a new adhesive [4,5] to shorten the natural maintenance cycle and to improve the strength of the pellets. A method on resource-oriented utilization of ferrous scrap (cold-bonded pelletizing) is brought forward, and these cold-bonded pellets can be used as coolant in converter. After maintaining for 48h, these cold-bonded pellets can satisfy the mechanical requirements to replace the converter coolant [6]."

Jan 1, 2013

By W. L. Saunders, Richard T. Dana

The dynamites are graded according to the percentage of nitroglycerin that they contain. Thus a “40% powder” would be one in which the sticks, weighing one-half pound each, would include one-fifth of a pound of pure nitroglycerin. Dynamite is usually packed in paper cartridges weighing about one-half pound each which will vary in diameter. When ordering, it is customary to specify a size of cartridge that will as nearly as possible fill the drill hole, the commonest size being 1 ¼” in diameter by 8” in length. It is nearly always shipped in 50-lb. boxes, which have a volumetric capacity of 3/4 cu.ft.

Jan 1, 2013

By M. G. Maruma

The effect of the amount of cold reduction and annealing temperature on the evolution of the texture of AISI 441 steel is reported. The steel was cold rolled by 62%, 78%, and 82%, followed by isothermal annealing of each sample at 900°C, 950°C, and 1025°C for 3 minutes. The crystallographic texture was determined by Phillips X?Pert PROMPD texture diffractrometer. Microstructures were characterized using optical microscopy and scanning electron microscopy (SEM).The results show that sample that received 78% cold reduction and annealing at 1025°C presented the highest Rm-value and lowest ?R-value, which would enhance its deep-drawing capability. In addition, this sample showed the highest intensity of shifted ?-fibre, notably {554}<225> and {334}<483>. It can therefore be concluded that the ?-fibre, which favours deep drawing, is optimal after 78% cold reduction and annealing at 1025°C.

Jan 1, 2013

By S. C. Gaillard

Tailings are made of ground rock that is left over from removing valuable minerals. The tailings are usually fine particles that cause environmental issues for storage and disposal. Disposal of tailings is a growing concern, as more tailings are produced from the increasing demand for mined material (ITRC, 2008). This project proposes a way to convert the mine waste to a useful product. Tailings were selected from a South Carolina crushed stone quarry, the products of which are used for road beds, sidewalks, asphalt and driveways. These tailings were processed to generate synthetic aggregates for construction applications. The synthetic aggregate creates a product that could be used for many purposes, including aggregate for sidewalks, driveways, roads and building materials. Testing methods followed the North Carolina Department of Transportation (NCDOT) guidelines for physical testing of coarse natural aggregate, which are sieve analysis, Los Angeles abrasion, absorption, specific gravity and soundness test. The synthetic aggregate produced passed all tests for NCDOT and, in some instances, rated better than a natural aggregate. Using the tailings from the crushed stone and mining industry would convert the waste into a valuable, marketable product.

Jan 1, 2013

By James D. Pile

Following a methane ignition in the active panel of a longwall coal mine, the affected panel was successfully isolated from the rest of the mine. This allowed for the remainder of the mine to return to regular operation, and the conventional practice of having to seal the portals for a defined period of time was avoided. After the affected panel had remained isolated for a regulatorily mandated period of time, it was reopened in preparation for longwall face recovery. As it was not possible to move the shields from their existing positions to facilitate the installation of recovery mesh prior to shield recovery, alternative methods had to be considered to stabilise the gob and minimise flushing, thereby improving operator safety. The objective of the paper is to show how stabilisation of the gob was achieved during shield recovery, thereby minimising flushing, and improving operator safety. Phenolic foam was chosen and injected from between the shields into the gob behind them. This is a technique that has been used to great effect in Germany, to a lesser extent in Australia, but not knowingly to date in the United States. To ensure nothing was left to chance and thereby guarantee the project?s success, the procedure used in Germany was employed, down to the application of equivalent hardware, which was sourced through the North American supplier.

Jan 1, 2013

By Ryan Garvey

A numerical investigation is made into unstable failures of coal pillars (i.e. coal bumps) using the finite difference software FLAC3D. A static energy balance is first derived to calculate the excess energy released as a consequence of unstable failure in rock. Two- and three-dimensional mining layouts are then assessed on their bump-potential based on the magnitudes of excess energy released during simulated pillar failures. A three dimensional pillar model is developed to represent tributary area loading of an infinite room-and-pillar layout. Pillar strength and brittleness characteristics are calibrated using a Mohr-Coulomb strain-softening constitutive law to simulate width-to-height ratio coal pillars ranging from 1:1 to 5:1. Width-to-height ratio pillars 1:1 to 3:1 release large magnitudes of excess energy as the pillars fail, representing massive collapse of room-and-pillar layouts. The larger pillars maintain their residual strength during failure; however significant excess energy is still released during temporary reductions in pillar strength. A two-dimensional model is then constructed of a gate road pillar failing due to elastic rebound of the surrounding rock mass. Soft loading conditions initiate unstable failure for all pillar widths, while the total magnitudes of excess energy increase with the size of pillar being modeled. The results from these tests indicate that excess energy may be used as a direct assessment of the bump potential of simulated mine layouts.

Jan 1, 2013

By Gordon J. Hughes

The ldaho Cobalt Belt represents a unique geologic environment containing some of the largest known reserves of cobalt in the United States. Stratabound cobalt-copper-gold deposits formed within a sedimentary basin that was generated by the rifting of an Archean cratonic block. Host rocks for these deposits are the Early to Middle Proterozoic Yellowjacket Formation comprising a suite of clastic sediments, volcaniclastics, and mafic tuffs that accumulated in the intracratonic rift basin about 1.7 b.y. ago. Rifting was probably initiated during a regional heating and doming event that may date back to 1.8 b.y. ago. During this time, other rift basins were likely to have formed in the region. They probably represent the precursors of a much larger depositional environment having characteristics of an Atlantic- type or passive continental margin where younger formations of the Belt Supergroup were deposited. The Yellowjacket Formation has been subdivided in the Idaho Cobalt Belt into three genetic units representing various subenvironments of a deepwater clastic fan complex. A northwest- trending deep-basin structural trough accumulated fine-grained muddy sediments that were periodically interrupted by distal turbidites of the subaqueous fans. Subsequent progradation caused the deposition of coarser-grained clastics of the more proximal portions of the fan complexes. Submarine fan lobes were built across northwest-trending tectonically active basin growth faults. These in-basin structures caused a great deal of penecontemporaneous deformation within the Yellowjacket sequence. Northeast-trending fault zones formed an orthogonal set of fractures that controlled the shape and size of sub-basins, and were also an influence on lateral migration of dominantly fine-grained clastic material. The eruption of mafic tuffs at about 1.7 b.y. ago added a new component to the Yellowjacket sedimentary sequence. Around the Blackbird mine area these tuffs commonly occur either near the base or within some of the sandier sequences. Since most of the sand influxes were largely controlled by basinal tectonism, the tuffs were probably erupted during tectonically active periods of basin development. The dynamic nature of the sedimentary environment probably caused much of the tuffaceous component to be mixed with other clastics and even resedimented as volcaniclastic material. In time, the change to a higher energy sedimentation regime resulted in such a dramatic clastic dilution of the tuffs that they could not survive in the areas of the vents, and, if present, they must have been distributed elsewhere in the basin.

Jan 1, 2013

By M. Steyn

[Zr(C9H6NO)4]?(HCON(CH3)2)?(H2O), where (C9H6NO) = 8-hydroxy quinoline (oxH), was synthesized and characterized. This tetrakis-coordinated zirconium complex crystallized in the triclinic crystal system (Pi, Z=2) along with water and N,N?-dimethylformamide(DMF) solvate in the asymmetric unit. The metal atom is surrounded by four N,O-donating bidentate ox-ligands that are arranged around the metal centre to give a square antiprismatic coordination polyhedron with a small distortion towards a dodecahedral geometry. Crystal packing is stabilized by intermolecular interactions of adjacent oxine ring systems in neighbouring molecules, as well as hydrogen bonding of the aqua and DMF solvate molecules, linking the molecular entities into a supramolecular three-dimensional network.

Jan 1, 2013

By Robert B. Bittner

Large diameter piles (2 to 3 m diameter, both driven and drilled) are being used more frequently by designers of bridge foundations. The use of these large piles allows the pile cap to be positioned off the bottom but usually still below water. Conventional cofferdams as shown in Figure 1 below are not suited to this type of pile cap. However, float-in cofferdams offer a viable alternative. This paper describes the float-in cofferdam system, its initial development for use on the Bath-Woolwich Bridge in Maine and its most recent application on the new Carquinez Bridge in California.

Jan 1, 2013

By Hongbo Yang, Tongbo Zhang, Ting Huang, Jingshe Li, Fangfang Song

"Liquid core length is a very important parameter of the process of continuous casting, which directly reflects the cooling status in secondary cooling zone and solidification rate of the slab. In this paper, the billet caster in some steel plant in China was chosen as the prototype of simulating. A numerical simulating model for calculating the liquid core length of continuous casting billet was built by ProCAST software, which was verified reasonable and accurate by pin-shooting technique. Based on the model, the relationships between casting speed, casting temperature and liquid core length of casting billet were found, which was very practically useful for the workers on sit to improve casting billet quality. IntroductionContinuous casting process developed very rapidly because of the high metal yield, energy saving, and low-cost 111• And the quality requirements of continuous casting billet for customers became higher and higher with the fast development of economic121• Internal defect usually is the major quality problem for continuous casting billet[3•61 , which is influenced by the solidification process of casting billet, especially the solidification process of liquid core17•81 • So it is very important to study on the relationship between casting parameters and the liquid core length which means the distance between the crystallizer meniscus and the casting billet solidification end-point. In practical production process, the workers usually control the quality of casting billet according to the liquid core length."

Jan 1, 2013

By Sam X. Yao

In construction of drilled shafts under water, placing concrete in the shafts is technically demanding and involves complex construction logistics. Past construction experience has demonstrated that high quality concrete can be placed in drilled shafts under water with a proper concrete mix and proper placement techniques. However, a significant number of failures have occurred which have resulted in excessive cost overruns and delays. These problems may have occurred because proper underwater concrete construction techniques have not been widely disseminated within the industry. This is a technical area where competent design and sound construction planning can achieve a significant reduction in both risk and cost. This paper will discuss some key technical issues in the concrete mix design, concrete production and placement for the drilled shaft construction. The paper also describes two lesson-learned case histories from drilled shaft construction projects.

Jan 1, 2013

By Benjamin Cebrian

Wall control blasting is an expensive and labor intensive operation. Obtaining a good design is a first step that is not enough to ensure desired results. Experience shows that designs are not always well implemented, not only in the contour blast itself, but also in surrounding production blasts that can affect the final pit wall. In this paper techniques and reference indicators are described in order to audit and evaluate if correct implementation of designs have been done.

Jan 1, 2013

By Samuel S. Adams

The Grants uranium region of northwest New Mexico is the largest uranium district in the United States (approximately 50% of U.S. production plus reserves) and one of the largest In the world, with approximately 900 million pounds U308 production plus reserves. Deposits of the region are unusual among sandstone deposits for their high content of epigenetic carbonaceous material, generally interpreted but not proved to be of humic origin--that is, co-extensive with uranium in the primary deposits. Virtually all production in the region has been from the Jackpile Sandstone and Westwater Canyon Member of the Jurassic Morrison Formation. The tabular uranium deposits contain, in addition to humate and uranium, significant authigenic phyllosilicates, quartz overgrowths, humate-replaced detrital silicates, and a trace-metal assemblage typical of other sandstone uranium deposit types. Surrounding the deposits in the two sandstone units of the Morrison Formation is an alteration zone within which iron leaching has altered detrital ilmenite-magnetite to residual masses of titanium oxides. Feldspar alteration is locally present within this zone, below deposits in the Jackpile Sandstone, and above those in the Westwater Canyon Member. The feldspar alteration increases in inten¬sity toward the Brushy Basin Member which separates the two sandstone units, ranging from partial replacement to replacement and dissolution of plagioclase and sanidine. Spatial relations among the epigenetic humate, authigenic silicates, and the broad alteration zones that extend from the Brushy Basin Member to and including the uranium deposits suggest that (a) the organic material was involved in the unusual silicate alteration, transport, and authigenesis, and (b) that the humates originated in shales of the Brushy Basin Member. Stratigraphic relations among the Brushy Basin Member and the overlying Jackpile Sandstone and underlying Westwater Canyon Member suggest [in turn] that there was continuous, interfingering deposition controlled in part by contemporaneous basement subsidence along northwest- and northeast-trending zones. Following minor erosion of upper Jackpile Sandstone and deposition of basal organic-rich Cretaceous sediments, the silicates of the Jackpile Sandstone were once again altered by organic-bearing fluids, this time permeating down from Cretaceous sediments and partly obliterated ore-stage alteration.

Jan 1, 2013

By Mark K. Larson

Panel-scale modeling of stress changes induced by longwall coal mining is a challenging problem, particularly in deep mines of the western United States. Two common approaches to this problem are the empirical and boundary element modeling methods. One boundary element method, LaModel, was recently calibrated to field measurements at a mine in Colorado (Larson and Whyatt, 2012). However, the calibrated overburden properties were extreme, resulting in very low estimates of gob loading. Next, the empirical method was calibrated to field measurements and applied to the problem, but this approach clearly extrapolated this method well beyond the characteristics of underlying cases. This paper examines a third option, the elastic continuum boundary element program Mulsim. The program was expanded to handle LaModel-size meshes in a version dubbed Mulsim/ Large. Properties for the elastic, homogeneous overburden model in Mulsim were estimated as a thickness-weighted average of typical published elastic properties for each major stratum. These properties, along with a commonly used pillar strength equation and coal properties, produced the measured load transfer distance and reasonable gob loading without further calibration. Given the number of input parameters required for all of these methods, it is not surprising that LaModel and the empirical approach could be adjusted further to incorporate similar gob loads. However, these extraordinary measures failed to bring gate road pillar loading in line with Mulsim results. Differences in pillar load estimates continued to be significant (as large as 65% in this study). These results demonstrate that, for this particular case, the choice of analysis method impacts results in ways that cannot be removed by calibration of input parameters. Finally, the natural fit between the Mulsim model and mine conditions suggests that approximating overburden at the particular site used for this research as an elastic continuum is superior to the alternatives examined.

Jan 1, 2013

By A. R. Sorta, D. C. Sego

ABSTRACT The settling, shear strength, and index properties of oil sands fines-sand mixture tailings (FSMT) for a wide range of solids and fines content are investigated. Results indicate that the liquid limit of FSMT obeys a linear mixture law. The fines-water ratio (FWR) governs the permeability of composite tailings (CT) and CT with comparable geotechnical behaviour can be produced from the same initial FWR mixtures. A phosphogypsum (PG) dosage > 900 mg/kg does not improve the dewatering behaviour of CT. The undrained shear strength of FSMT at the liquid limit is approximately 2.4 kPa, but is dependent on fines content at the plastic limit.

Jan 1, 2013

By S. Makni, S. Koppalkar, A. Bouajila

ABSTRACT This paper briefly reviews the gravity recovery between conventional and centrifugal gravity separators. The advantages of semicontinuous gravity separators will be discussed, as will techniques for upgrading the gravity concentrates. The research efforts in optimizing semicontinuous gravity separators will be recalled. An innovative gravity circuit for eliminating or minimizing the use of complex processing schemes will be reviewed. Ongoing gold gravity research has revealed that gold particle shape transformation is one of the main factors explaining the lower recoveries of the plant units. Efforts to devise possible remedies for improving plant gravity recovery will be discussed.

Jan 1, 2013

By Bruce K. Hebblewhite

This paper provides an overview of the international ?state of the art? with respect to underground coal mining methods used in seams of thickness greater than 4.5 m, through a review of a selection of high performing thick seam mining operations around the world?both Single Pass Longwall (SPL) and Longwall Top Coal Caving (LTCC). The paper discusses the recent operational experiences from these selected faces, together with the ground control issues faced, and identifies some of the major, inherent geotechnical factors that can influence the mining method selection, design criteria, and ultimate performance, from both an operational and safety perspective. It is clear that both of these methods are developing quickly? not only from an operational and equipment perspective, but also from the understanding of critical geotechnical criteria. There is an increasing role for both methods in thick seam environments, although the higher SPL faces will only be successful in the near to mid-term under benign geotechnical environments. Regardless of the method, a thorough understanding of the critical geotechnical factors is a key to successful implementation of either method.

Jan 1, 2013

By Jason Baird, Philip Mulligan

This report details the preliminary calculations governing the underwater collapse of an oil pipe via explosive lensing. An explosive lens changes the detonation wave produced by an explosive by changing the geometric conditions of the explosive (Zukas and Walters, 1998). Multiple lenses can be focused on a central location, generating a series of precise detonation waves collapsing in on a specific point. This report will assume a spherical-shaped, single explosive charge and explain how the authors determined the explosive charge size needed to seal a metal pipe while focusing on one explosive charge acting on part of the pipe. Future calculations will analyze the combination of multiple explosive charges acting on the pipe as a whole.

Jan 1, 2013

By De-qing Zhu, Zi-fu Gao, Jian Pan

"In order to produce high quality metalized products and prevent from burden cohesion during pre-reduction, self-fluxed pellets were made for COREX process in the paper. The effects of reduction temperature and reducing gas composition on pre-reduction behaviors of self-fluxed pellets are studied. The results show that the prereduced pellets have poor quality and deposited carbon appears when the reduction temperature is between 600°C and 700°C. The metallization rate, reduction degree and compressive strength of prereduced pellets are promoted by the elevating reduction temperature and mole fraction of H2. Pellets reduced by pure H2 at 800°C have high metallization rate (96.2%), reduction degree (99.4%) and compressive strength (960N/pellet). In all tests, self-fluxed pellets display normal swelling (RSI<l5%) behavior which reveals that self-fluxed pellets are suitable for COREX process. Increasing reduction temperature and mole fraction ofH2 in reducing gas is benefit for pre-reduction of pellets.IntroductionCompared with Blast Furnace, the COREX process has advantages of short flow sheet, using non-coke coal and high-energy utilization. Acidic pellets and lump ores are the chief iron- bearing burden for COREX process which could lead to low melting point substance appearing in per-reduction process. In addition, the acidic hematite pellets tend to swell during the reduction [1-3]. This will result in decreasing compressive strength of pellets, burden cohesion, bad air permeability and poor work status in shaft furnace. Adding carbonate flux could restrain burden bonding to some extent in actual production, but decomposition of carbonate flux increases energy consumption. Worse still, weak reduction potential is unfavorable to iron material reduction [ 4, 5]."

Jan 1, 2013

By D. W. Nel

Nanofiltration (NF) has attracted much attention over the past few years due to the reduced energy consumption compared to reverse osmosis (RO) and better separation performance compared to ultrafiltration (UF). Although research has been done in the area of NF of nickel ions, sodium ions, and acid separation, not much attention has been given to the separation of high nickel concen¬trations from sulphuric acid streams. The use of NF for the separation of nickel and acid from a spent nickel electrolyte is an innovative process alternative for future industrial application within a base metal refinery. In this study, the separation performance of a composite polyamide NF membrane on a spent nickel electrolyte was investigated by varying the sodium sulphate concentration in the feed (50-150 g/l), the trans-membrane pressure (35-55 bar), and cross-flow velocity (1.5-3.5 m/s), and measuring quantities such as total permeate flux, acid rejection, nickel rejection, and sodium rejection. The nickel and acid concentration in the feed were kept constant with variations between 40-60 g/l and 25-40 g/l respectively, while the temperature of the experiments was kept constant at 50°C. The membrane was found to be very selective for nickel ions, with the rejection of nickel ions varying between 54.4% and 98.2%. The rejection of acid ions varied between -5.9% and 21.8%. The rejection of sodium ions varied between 16.6% and 72.4% at a cross-flow velocity of 2.5 m/s and sodium sulphate concentration of 50 g/l in the feed solution. An increase in trans-membrane pressure increased the rejection of nickel, sodium, and acid ions, while an increase in sodium sulphate concentration decreased the rejection of nickel and acid ions. The total permeate flux was found to increase with an increase in trans-membrane pressure and decrease with an increase in sodium sulphate concentration. The cross-flow velocity had an insignificant effect on the total permeate flux and the rejection of nickel, sodium and acid ions.

Jan 1, 2013