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By D. D. Schlepp

There is a continuing debate about the influence of circulating load and classifier efficiency on the capacity of the circuit. Specifically, the effects of preferential classification, bypassed fines, and the sharpness of classification will be examined. Horizontal cyclones have also proven to be very successful in a number of operations but their impact on the circuit capacity has not been clearly defined.

Jan 1, 1990

By Messias dos Santos Machado, Renato B. Godoy, Roberta Lima, Andressa Silva, Francisco Valenzuela-Díaz, Rene R. Oliveira, Esperidiana Moura

This work aims to incorporate the Bof White Clay, from Boa Vista, Paraiba State, Brazil, as natural nanofiller in Ehylene vinyl alcohol copolymer (EVOH) and obtain flexible films. Nanocomposite was obtained using a twin-screw extruder, and film formed using a blow extruder machine. The flexible film nanocomposite was characterized, by tensile tests, XRD, DSC and their properties were evaluated. The results showed a good interaction between the clay and the EVOH resulting in an increase of properties of films nanocomposites as compared to films neat polymer.

Jan 1, 2015

By Cristian Melipichun, Leopoldo Gutierrez

The effect of the presence of fine particles of kaolinite and montmorillonite on the induction time for attachment of bubbles to particles of a copper concentrate rich in chalcopyrite was evaluated in this study. The results obtained from induction time measurements were correlated with data of concentrate recovery achieved from micro-flotation experiments. The effect of the presence of fine clays on the stability of air-water foams was also studied through measurements of the foam volume generated in a glass column under different conditions of air flowrate and MIBC concentrations. The experimental results showed that induction time values increased under the presence of fine clays. These data agreed with results obtained from micro-flotation experiments that showed that copper concentrate recovery decreased when clay particles were added. Although a complete explanation for these results is not available, the fact that experimental observations indicated that fine clay particles tend to adsorb on gas bubbles, suggests that the interactions between fine phyllosilicate particles and air bubbles have to be taken into account when studying the effect of clays on froth flotation. Foamability tests showed that the presence of fine clay particles increased the foam volumes only at high additions of clays and low dosages of MIBC. The results obtained at higher dosages of MIBC showed that the foam volumes decreased with the addition of clays under all the experimental conditions tested.

Jan 1, 2014

By Kai Wang, Chao Xu, Qiang Fu, Tong Yang, Chunyu Zhao, Wei Zhao

The stress of a coal seam is an important factor that affects the permeability of the coal seam and then affects the coalbed methane (CBM) drainage. In China, adjacent coal seam mining is an important method to reduce stress, which increases the permeability of the coal seam. However, in the process of mining adjacent coal seams, many coal pillars remain, which causes stress concentrations and results in a decrease in permeability. Therefore, it is important to study the influence of coal pillars on the stress of adjacent layers and its distribution and evolution in the floor rock. This paper took the Shendong Baode Coal Mine as a case study and investigated the influence of the coal pillar on the stress and permeability of coal seam #11. The results show that under a coal pillar, the relationship between the vertical stress of different floor depths and the width of the coal pillar can be divided into a negative correlation zone, transition zone, and positive correlation zone. The change in the coal pillar width does not affect the pressure relief range or the degree of pressure relief in the adjacent coal seams below the goaf. The field measurements show that after the mining of panel #81,505, the permeability coefficient of coal seam #11 under the goaf increased from 0.1434 to 26.3545 m2/( MPa2*d), increasing 182.7 times, and the drainage mixing volume of boreholes #1 and #2 increased from 1.24 to 1.52 m3/ min. While the permeability coefficient of coal seam #11 from 12.5 m in the coal pillar has only increased by 2.6 times, the drainage volume of boreholes #3 and #4 did not change significantly.

Nov 19, 2022

By Tony B. Szwilski

"The efficiency of operation and life of an advancing longwall coalface depends, to a great extent. on the face-end roof strata conditions and the stability of the gateroads. The factors that influence the rate of closure of gateroads are examined, in particular the gateside pack and the coal rib (crush) pillars. The performance of mechanized packing systems is briefly discussed. Gateroad deformation surveys were carried out at two coal mines to determine the influence of the rib pillar width on gateroad stability; also, the influence of the gateside pack on the immediate roof and floor strata is analyzed based on strata bed displacement measurements from instruments installed in the gateroad and pack-hole of a longwall advancing face operating in a thick seam (7.55 m). Concluding, an evaluation of the fac e-end systems examined is given and recommendations made f or the most suitable rib pillar width. face-end geometry and roof strata reinforcement.IntroductionKevword s: Coal mining, Pillars, Rib pillars, Ground control, Longwall mining, Gateroads , Packing systems, Roof control. The face-end region of a longwall advancing face is the center of mining activity, being the turn-around point for the coal cutting machine. and the place of gateroad formation and movement of special face-end supports. The design of face-end layouts can be aided by knowledge of strata control parameters, such as the effective loading of the immediate roof strata , convergence of the roof and floor, magnitude and distribution of fractures in the roof strata around the face-end , optimum placement of supports, coal seam thickness and strength characteristics, geometry of layout and interaction from neighbouring workings. Generally, the gateroad is formed by one of three face-end methods: (a) advanced headings, (b) in-line system (gateroad formed at the face) or (c) conventional ripping with or without stable elimination (also halfheading). The quality of gateroad is influenced principally by the face-end system employed, standard of gateside pack and width of pillar. A good standard of gateroad is generally achieved by employing the half-heading face-end system, the gateside pack and coal rib pillar having comparative support/ yield (stiffness factor) characteristics. However, the halfheading is often not favoured due to face operation restrictions."

Jan 1, 1981

By S Love, M Anderson, M Boland

"The high rate of failure of new mine developments to meet feasibility study expectations has been the subject of many fine technical papers. Yet failure rates remain stubbornly high.Similarly, the common occurrence of disastrous acquisitions resulting from failed due diligence on projects is well known. Yet such mistakes continue to be made.The authors argue that project and due diligence failure are caused at least partly by cognitive biases. These biases pervade decision-making throughout project evaluations.A wider understanding of these biases (and their effects) is necessary. Only then can mitigating actions be taken.The opportunity for this wider understanding exists. A number of best-selling books have been published on the topic in recent years. With wider understanding of key concepts and terms, cognitive biases can be recognised and discussed. They can also be challenged and mitigated.The authors believe that these concepts should be entry-level, required knowledge for anyone evaluating, developing, reviewing or financing mining projects.Perhaps the most prevalent biases in project evaluation failure are the ‘over-optimism’ biases. In particular, the planning fallacy and confirmation bias.The anchoring effect is also pervasive. This bias propagates unrealistic assumptions from scoping and prefeasibility studies through to so-called definitive feasibility studies. Unrecognised anchoring biases also undermine the validity of many ‘independent’ due diligence reviews. They are also prevalent in corporate acquisitions.The availability heuristic refers to a mental shortcut that can lead to a number of biases. One of these is the narrative fallacy. The mind constructs coherent narratives and opinions, regardless of the amount and quality of the information that support them. Narrative fallacy commonly occurs in the evaluation of social and political risk. Another is disaster neglect, which is especially common in the failure to assess risks associated with tailings management.This paper outlines the relevance of these biases to mine project evaluations. It also provides examples where the authors have observed their effects.CITATION:Love, S, Boland, M and Anderson, M, 2016. Influence of cognitive biases on project evaluation, in Proceedings Project Evaluation 2016, pp 226–235 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 8, 2016

By Zhi-gang Que, Sheng-li Wu, Guo-liang Zhang, Bo Su, Chao-gang Hou

NOx released during fuel combustion is one of the major air pollutants, such as acid rain and photochemical smog. At present, still not have an economical and effective method of inhibiting NOx emission for sintering flue gas. Therefore, controlling conditions of fuel combustions to enhance the reduction of NOx is important for decreased the emission. In this study, microsintering furnace has been performed to investigate the effects of NOx emission from char-N during coke breeze combustion. The results show that the emission concentration of NOx decreased with increasing temperature when it is sinter bed temperature higher than 1000℃. The lower emission concentration of NOx was obtained when the concentration of oxygen was decreased. And the maximum concentration of NOx will be reduced with the enhanced of heating rate. If heating preservation time was prolonged, it would promote to NOx reduction with reduction substances resulted in lower NOx emissions in the combustion of coke breezes.

Jan 1, 2015

By Shengli Wu, Binbin Du, Mingyin Kou, Laixin Wang, Kai Gu, Shun Yao, Heng Zhou

Coke plays an important role on the actual blast furnace production (BF), and its quality significantly influences the BF ironmaking process. In this study, the effects of physical properties, chemical composition and high-temperature properties of coke on main technical indexes of blast furnace were investigated. Some coke indexes were defined to evaluate the coke quality. The main technical indexes of BF include production, quality of HM, and fuel consumption. The quantitative relationship between coke quality and main technical indexes of BF were obtained after a series of statistical analysis. What’s more, the effect of these coke quality indexes on blast furnace smelting process was also explored, and all the relationships obtained from the analysis will provide a theoretical basis for the appropriate use of coke in blast furnace. The most reasonable range of coke quality indexes can be determined combining with the actual production as well.

Mar 1, 2018

By Z. Huda

The effect of various percentages of cold-working and recrystallization on the microstructure and hardness of commercially-pure aluminum plate, has been studied. The 'A critical deformation for the aluminum, has been determined. Experimentation involved cold rolling and recrystallization processes followed by quantitative metallographic practice and the hardness measurements. The raw material chosen was a plate of commercial aluminum which was cold rolled to different percentage of cold-work and then recrystallized by heat treatment at 150°C. The critical deformation percentage of aluminum was computed to be around 30% of cold-worked.

Jan 1, 2007

By Francisco Morganti

This report gives in the first part the metallurgical basics for the production of AHSS grades in integrated steel plants starting at the melt shop and ending at the annealing lines of the cold mill. The corresponding process and plant technologies in each production step with its specifics and rules are explained. In the second part by way of example the practical requirements for TRIP 780 steel grade are highlighted like a recipe for process control in the steel plant, hot and cold rolling mill, annealing line and finally skin pass mill. Measuring of mechanical technological properties on samples shows that the specifications according to DIN EN 10268 are fulfilled.

Oct 30, 2017

By E. L. Chanturiya

The research and characterisation for compositional, physicochemical, structural, electrical and flotation properties of various pyrite samples for a copper-zinc sulfide ore was carried out. Various methods were used during the research, such as optical microscopy, X-ray diffraction, electron probe micro-analysis (EPMA), phase emission analysis, routine chemical analysis, auger electron spectroscopy (AES), scanning electron microscopy (SEM), back-scattered electron images (BSE), potentiometry, and instrumental neutron-activation analysis, flotation. Analysis of obtained results established the interrelation between impurity structures and concentration of electric charge carriers in minerals, Butyl xanthate sorption and flotation yield of pyrite. The research concluded that pyrite samples differ by morphology, micro defects of structure, concentration of donor and acceptor impurities (Co, As, Sb, etc.) and conductivity parameters (thermo-electrical force, specific resistance and concentration of charge carriers The peculiarity of pentagon-dodecahedral pyrite is the high concentration of electric charge carriers (electrons) and the more negative surface potential (by 25–75 mV) in comparison to cubic pyrite. The surface of cubic varieties is more active, therefore it is oxidized in alkaline lime medium much faster, than the surface of pentagon-dodecahedral varieties. This phenomenon is caused by high reaction ability, irregular jointing and defects of cubic pyrite. This promotes the increase of calcium ion sorption on its surface and the decrease of Butyl xanthate sorption. According to this, an increase in alkalinity (lime medium) from a pH of 10.0–11.5 leads to an increase of gold content reporting to the tail of bulk flotation. Gold content is increased from 0.58 g/t (?? 9.5) to 1.9 g/t (?? 11.6), which represents an increase in gold recovery of 24.68 to 79%, respectively.

Jan 1, 2016

By J. M. Jimenez, G. D. Schena, A. J. Cazorla

A full-scale Deister column was operated in parallel with the conventional cleaning bank of cells and a pilot Jameson cell in parallel with the conventional rougher cells. Flotation column performance was appreciably enhanced by use of an improved washing system and an internal launder. The performance of the rougher bank of cells, Jameson cells, cleaner cell bank and column were described by simple linear functions. These allowed calculation of overall circuit recoveries and evaluation of alternative circuits. An evaluation procedure based on a financial criterion is demonstrated with a simplified example, illustrating how revenues and operating margins are often of more concern than concentrate grade and recovery

Jun 18, 1905

By Eldon Dunlap

RECENTLY the producing branch of the petroleum industry has shown a considerable and growing interest in the quantitative determination of the water, oil, and gas content of cores as it relates to estimation of reserves, to providing a, basis for judging as to the feasibility of applying various secondary-recovery and pressure-maintenance processes, and in general to the operation of producing properties. For years it has been known that oil, gas and water coexisted in the pores of many semidepleted oil measures. It is now generally believed that oil-bearing beds contain connate water in amounts varying up to 50 per cent of the pore space. However, only lately has reliable direct evidence of the extensive occur-rence of connate water in oil sands been published. Very little work has been done to ascertain the effect of this water on the productivity and ultimate recovery of oil from wells. It was the intent of this research to study the influence of this indigenous water on the flow of oil through unconsolidated sands, with the hope that the results could be applied qualitatively to the flow of oil in underground reservoirs partly saturated with water. Obviously, ultimate recovery estimates based on the void volume of the reservoir will be in error unless a, conscious or unconscious correction is made for the volume of water occupying a portion of the effective pore volume of the reservoir- Evaluation engineers in the past have applied arbitrary saturation and recovery factors that may inadverently have compensated for the failure to consider specifically the water content. Nevertheless, the evidence available indicates that these factors need revising if each is to be independently correct and truly representative. Although the mere fact that the connate water renders part of the pore volume of the reservoir incapable of containing oil is of primary importance to the operator, it is also of interest to know whether and to what extent the presence of varying amounts of interstitial water influ-ences the permeability of the sand to oil.

Jan 1, 1938

By W. R. Reed, D. E. Pollock, T. W. Beck, J. A. Organiscak, J. D. Potts

"In underground continuous mining operations, ventilation, water sprays, and machine-mounted flooded bed scrubbers are the primary means of controlling respirable dust exposures at the working face. Changes in mining arrangements, such as, face ventilation configuration, orientation of crosscuts mined in relation to the section ventilation, and equipment operator positioning, can impact the ability of dust controls to reduce occupational respirable dust exposures. This study reports and analyzes dust concentrations measured by the Office of Mine Safety and Health Research for both remote-controlled continuous mining machine operators and haulage operators at ten U.S. underground mines. Results of these respirable dust surveys show that continuous miner exposures varied little based on depth of cut, but are significantly affected by ventilation configuration. Haulage operators experienced elevated concentrations in blowing face ventilation. The type of cut influenced exposures, with elevated exposures observed for both continuous miner operators and haulage operators when working in crosscuts driven into, or counter to, the section airflow. Individual cuts are highlighted to demonstrate instances of minimal and excessive dust exposure attributable to particular mining configurations. These findings form the basis of recommendations for lowering face worker respirable dust exposures when performing a variety of continuous mining cuts.INTRODUCTION Underground continuous coal mining operations may encounter a wide range of conditions and arrangements during production and development activities. These activities typically produce respirable coal mine dust, putting operators of continuous mining machines and coal haulers at risk for elevated exposures. In order to comply with federal regulations limiting respirable dust exposures for the duration of a working shift, mine operators typically implement ventilation, water sprays, and machine-mounted flooded-bed dust collectors (scrubbers) to dilute and control mine dusts during coal cutting. Nevertheless, changes in operational conditions can limit the ability of these controls to effectively reduce dust exposures. Some examples of conditions that can change during the course of mining include face ventilation configuration, orientation of crosscuts mined in relation to the section ventilation, and operator positioning. Because these arrangements are largely under the control of mine operators, any insight into associated exposures may inform future plans and behaviors, reducing occupational exposures to respirable dust. The objective of this OMSHR study is to evaluate respirable dust exposures associated with a range of continuous mining arrangements by comparing occupational dust concentrations measured during a series of field surveys. These comparisons consider face ventilation configurations, depths of cut, and crosscut mining practices."

Jan 1, 2015

By W. R. Reed, D. E. Pollock, T. W. Beck, J. A. Organiscak, J. D. Potts

In underground continuous mining operations, ventilation, water sprays and machine-mounted flooded-bed scrubbers are the primary means of controlling respirable dust exposures at the working face. Changes in mining arrangements — such as face ventilation configuration, orientation of crosscuts mined in relation to the section ventilation and equipment operator positioning — can have impacts on the ability of dust controls to reduce occupational respirable dust exposures. This study reports and analyzes dust concentrations measured by the Pittsburgh Mining Research Division for remotecontrolled continuous mining machine operators as well as haulage operators at 10 U.S. underground mines. The results of these respirable dust surveys show that continuous miner exposures varied little with depth of cut but are significantly higher with exhaust ventilation. Haulage operators experienced elevated concentrations with blowing face ventilation. Elevated dust concentrations were observed for both continuous miner operators and haulage operators when working in crosscuts driven into or counter to the section airflow. Individual cuts are highlighted to demonstrate instances of minimal and excessive dust exposures attributable to particular mining configurations. These findings form the basis for recommendations for lowering face worker respirable dust exposures.

Jan 1, 2016

By K. Winterton, Carruthers. J.

"Attempts have been made to produce hardened structures of a pseudomorphic type in various carbon and alloy steels. In order to obtain martensite with a fine distribution of cementite, an initial structure of fine lamellar or nodular pearlite is required; this may be obtained by conventional means. This is followed by partial austenitization and quenching.Two methods have been tried to induce partial austenitization:(a) A resistance (direct current) heating method involving rapid entry into the austenite field.(b) A new method, described as the ""threshold"" technique, involving homogenization of temperature just below A 1, followed by entry into the austenite field; two furnaces are required.The resulting structures have been examined for microstructures, hardness, tensile, and impact values. The tensile properties are comparable with those obtainable by conventional treatment methods. Impact values are disappointing, but this is explainable from the nature of the manifold changes occurring."

Jan 1, 1960

By Hong Li, Chenxiao Li, Wenwen Mao, Hua Lu

Directly charging limestone into slag in BOF is a newly emerging technique which broke through the traditional BOF slagging principle. It is necessary to study the decomposition behavior of limestone in converter slag during BOF steelmaking. FeOx, SiO2, MnOx and pre-melting slags were mixed with limestone according to different quality proportion to simulate the environment of limestone in converter slag. TG-DTA results indicated that slag with individual component, including FeOx, SiO2 and MnOx, all had obvious effects on reducing the decomposition temperature of limestone. Pre-melting slags with multiple components had further reducing effects than individual component. XRD results showed converter slag component would react with decomposition product of CaCO3 and generate solid solution or oxide, reducing the activity of CaO and the decomposition temperature of CaCO3.

Mar 1, 2017

By Ram Song, Yohei Harada, Shinji Kumai, Kazuho Otsuka

"Recently, vertical-type high-speed twin-roll casting (HSTRC) has been developed. The HSTRC shows extremely high cooling rates over 1,000 K/s even at the mid-thickness area. The fabricated strip has many metallurgical characteristics; super-saturation of alloying elements, fine solidified structure, and homogeneous distribution of fine constituent particles. In Al-Mn based alloys, the Mn alloying element can be supersaturated in the a-Al matrix and also form Mn-containing constituent particles during solidification. The Mn supersaturation and the distribution of primary/secondary particles in cast products affect the metallurgical behavior in the down-stream processing and can improve mechanical properties of the final products. In this study, Al-Mn based alloy strips were fabricated by HSTRC with various Mn contents. The solidified microstructure, constituent particles and its distribution, and Mn solubility were investigated in the as-cast condition. Due to the high cooling rate of HSTRC, fine constituent particles were homogeneously distributed, and coarse intermetallics were not observed. Mn solid solubility was estimated by electrical conductivity. The estimated Mn solubility was equivalent between strip surface and mid-thickness area.INTRODUCTION Al-Mn based alloys, as non-heat treatable wrought aluminum alloys, are widely used in packaging and heat exchanger for automobile industry. Besides Mn, Al-Mn based alloys often contain Fe and/or Si as alloying elements or natural impurities. During solidification, Mn can be super-saturated in the Al matrix, and also form Mn-containing constituent particles. Additionally, in the subsequent thermal-mechanical processes such as homogenization, rolling, and intermediate annealing, Mn in solid solution precipitates out of the Al matrix as secondary particles. The size, distribution, type, and the amount of dispersoids including constituent particles affect to texture evolution, recrystallization behavior, and final mechanical properties of wrought Al-Mn based alloys (Huang et al., 2016; Huang & Marthinsen, 2015; Engler et al., 1995; Muggerud et al., 2013). Therefore, controlling the initial level of Mn super-saturation and the distribution of constituent particles are important in the cast Al-Mn based alloys."

Jan 1, 2018

By Dong Liang, Honggang Zhong, Zhenxing Yin, Qijie Zhai

"2507 super duplex stainless steel (SDSS) has been widely applied in a marine environment, attributing to its excellent pitting corrosion resistance and mechanical properties which are particularly determined by the nitrogen precipitation behaviors and volume fraction of ferrite. In this paper, various cooling rates were obtained by applying four different moulds with the common gating system. By which the influence of cooling rates on nitrogen precipitation behaviors and the ferrite fraction in cast 2507 SDSS was comparatively investigated. The results showed that nitrogen porosity could easily precipitate in cast 2507 SDSS under standard atmospheric pressure. The number of nitrogen holes increased with decreasing the cooling rates, and the holes mainly distributed in three zones, i.e. the interface between the horizontal and vertical columnar grains, top vertical columnar grains and the final solidification region. Additionally, higher ferrite fraction was obtained with lower cooling rates.IntroductionDuplex stainless steels (DSS) have a dual-phase microstructure consisting of ferrite (d) and aus-tenite (?). Due to the combined advantageous properties of d and ? phase, their application rapid-ly increased in industry [1, 2]. Super duplex Stainless Steel (SDSS) is the third generation of du-plex stainless steels, of which the alloy elements Cr, Ni and N content are higher than the stand-ard 2205 DSS. Because it has high contents of alloy elements, the SDSS has better mechanical properties, and its pitting resistance equivalent number (PREN) reached a point 43. Hence SDSS has been used in petroleum chemical industry, the marine equipment and harsh corrosion environments [3]. SDSS contains ferrite stabilizing elements, such as Cr, Mo and Si, and austenite stabilizing elements like Ni, Mn and N [4]. Many researchers have studied the effects of these elements on the stabilization of d and ? phase and the ratio of the two phases. High nitrogen con-tent is another prominent feature of SDSS. Nitrogen addition to SDSS is very effective for improving its mechanical properties [5] and corrosion resistance [6], such as pitting resistance in NOx environment. To increase the nitrogen content in steels, a lot of work had been done. N. Nakamura and S. Takaki [7] examined the behavior of nitrogen absorption in Fe-23Cr alloy powder by sintering in nitrogen gas atmosphere, they found nitrogen content easily up to 1.0 wt. %. Using devised NH3 gas injection system, W. Park et al. [8] successfully produced austenitic Fe–23.5Cr alloys containing over 3 wt. % of nitrogen. Further-more, W.P. Tong et al. [9] stated that nitrogen percent was extraordinary high (about 10 wt. %) in pure iron plate. However, the above methods are difficult to be applied to large-scale industrial production."

Jan 1, 2012

By S. M. Khandrika

It is shown that dewatering of fine coal particles (D50 : 21 microns) is enhanced near the point of zero charge. The coal surface is modified by the addition of copper ions and adjusting pH to precipitate surface active metal hydroxy species which promote agglomeration and produce low moisture cakes. Filtration kinetics data are used in calculating filter cake parameters from an integrated form of Darcy's law. The influence of copper ions and pH on filter cake parameters and correlations among them are presented.

Jan 1, 1993