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By Scott Samson, Weidong Wang, Shekhar Bhansali, Vandana Upadhyay

"We present an improved design for the two-arm polysilicon thermal actuator. The classic thermal actuator design produces a localized hot spot at approximately the center of the thin actuator arm. This phenomenon limits the actuator efficiency, lifetime, and reliability. Since the actuator deflection is based on thermal expansion of the material, advantage may be gained by making the temperature profile more uniform along the hot-arm length. In our design, the geometry of the thin arm is modified by forming a nonlinear structure near the approximate location of the original hot spot. Electromechanical simulations of this design show an increase in deflection, due to a flattening of the temperature profile along the hot arm. The solid model generation, finite element analysis and simulations are carried out using PEA software. Experimental devices are in the process of being fabricated by using a polysilicon rnicromachining process.1. IntroductionMost active MEMS devices employ some kind of actuating mechanism to increase functionality. Various actuating mechanisms like magnetic, electrostatic, thermal, magnetostatic and piezoelectric have been investigated and incorporated for actuating microstructures. The primary features required from many on-chip actuating mechanisms are large deflection (>10 µm), low actuation voltage, low power.consumption, reliability, fast response, ease of design and fabrication, and small size. Thermal actuation is an attractive mechanism for rnicromechanical devices requiring high actuation forces, large deflections, good linearity and low actuation voltage. Thermal actuators, also known as ""electrothermal actuators"", ""heatuators"" or ""U-shaped thermal actuators"", have been largely used in MEMS based devices to provide both in-plane and out-of-plane actuation [l] .Thermal actuators are also easily compatible with standard CMOS circuitry due to their low driving voltage. However, high power consumption remains a major drawback of the thermal actuation mechanism."

Jan 1, 2004

By Harold V. Pearce

THE plant of the Boston and Colorado Smelting Company, at Argo, Colo., has not received special notice in technical or scientific publications for some time past. Dr. Peters' described the development of the reverberatory furnace used at Argo, but he dealt almost exclusively with the increase in size and the corresponding gain in capacity. Since the time of his description the changed conditions have led to a modification of the former smelting practice, and this modification forms the basis of the present paper. No claim is made for personal originality in connection with these improvements, in fact, I expressly disclaim any such intention, since nearly every successful step in the development of the process now used at Argo has been suggested by Dr. Richard Pearce at various times during the past 12 years, though perhaps in a different manner of exe¬cution. These changes would undoubtedly have been made before, were it not that many problems of greater metallurgical importance and momentarily of more urgent need thus had to be solved. At the time to which I refer, economic conditions demanded mainly an increase of capacity. Moreover, the determination and placing of exact losses in smelting were not so imperative as they now are. About three years ago, the time of my appointment to the - management of. the works of the Boston and Colorado Smelting Co., the great decline in the price of copper occurred; the Argo plant, in common with all others engaged in the copper-industry, lost heavily in the market-value of the stocks on hand of ore and furnace-products. Added to this was the unfortunate circumstance that the copper-supply of the Argo plant from general sources began to dwindle; in fact, it almost entirely ceased. About this time the smelting-plants in the west-

Mar 1, 1905

By J. Drelich

An improved experimental procedure to measure contact angle has been consolidated with coal surface preparation involving polishing with abrasive paper, alumina powder, and a cloth, followed by ultrasonic and mechanical cleaning. Specifically, the captive-bubble measuring technique has been compared with the sessile-drop technique and the former has been recommended for the examination of the hydrophobic properties of coal surfaces. Results of the research program, which is currently under way, on the examination of the effect of the nature, amount, size and distribution of mineral inclusions in coal on its wettability are briefly reviewed.

Jan 1, 1999

By Soumitry J. Ray

Poor visibility of powered industrial vehicles, such as forklifts, used in industry is often the cause of accidents that include pedestrians. Current standards allow up to 20 % non-visible regions for forklifts where measurement of these regions is performed by using lamps. A collaboration of research organizations, including National Institute of Standards and Technology, Georgia Institute of Technology (NIST), and Direct Dimensions, has been evaluating advanced methods for measuring a forklift operator?s visibility. These methods can potentially improve visibility standards. They can also help forklift and sensor manufacturers to determine (1) how visibility-assist sensors and algorithms can be designed and (2) where sensors can be mounted on forklifts. This paper includes explanation of visibility measurement experiments performed and results, associated language suggested to standards organizations, and a prototype design for measuring the visibility of forklifts automatically.

Aug 1, 2013

By W. L. Dalke

The Minntac complex is a facility for production of iron ore pellets located on the Mesabi Range at mountain iron, Minnesota. It consists basically of a mine, crushing plant, concentrator, and a pelletizer producing twelve and one-half million tons of pellets annually. This paper deals with some of the aspects of the grinding circuits; but prior to that discussion, it might be well to briefly describe the flow of material in the operation. The crude ore, containing from 20% to 25% magnetic iron, is mined by 14-yard electric shovels. .the blasted ore is loaded directly into 50-yard side dump railroad cars and hauled to the crushing plant. Crushing is done in three stages, originally, two 60" primary crushers; four 7-foot standard secondary crushers; and six 7-foot short head tertiary crushers were installed, when the plant was expanded to double its capacity, five secondary and ten tertiary crushers were added. These were duplicates of the original 7-foot standard and short head crushers used in the original construction, there was no expansion of the primary crushers but a one-half-million-ton surge pile of tertiary crusher feed was added.

Jan 1, 1976

By C. D. Litton

This paper describes two new gas diagnostic techniques which have been used successfully to determine: 1) the combustion status of underground mines which have been sealed due to fire (Littol1 Ratio); and 2) the location of fires in abandoned, underground mines or waste banks (Kim Ratio). The Litton Ratio makes use of the rate of change of CO, calculated on both an air-free and methane-free basis, from mine gas samples and compares these values with those expected from a normal, combustion-free environment. The Kim Ratio uses the concentrations of total hydrocarbons, C2 ?C5, less the methane, to arrive at ratio values which increase as combustion intensity increases. The details of these two new techniques, their application to real situations, and their limitations will be discussed.

Jan 1, 1989

Improve the safety, reliability and overall effectiveness of mine stench warning systems and to provide a means of remote control stench injector operation. Approach Industrial gas odorants were analyzed for their suitability for use in mine stench warning systems. A prototype stench injector capable of precise flowrate control was designed, fabricated, and tested using the odorant chosen as having the most favorable properties. Based on the results of the field tests, a second generation injector was developed. The second generation unit features optional remote control operation, and in addition, is simpler to refill and is less expensive than the original injector. A complete second generation system, consisting of two manually operated injectors and one remote controlled injector was in-mine tested through actual mine fire drills. How It Works Ethyl mercaptan mixed with Freon is the predominant stench agent used in the U.S. underground metal and nonmetal mines. However ethyl mercaptan's toxicity,

Jan 1, 1982

By N Slade, D Kennedy

Optimal throughput is a key objective for the successful operation of any manufacturing or processing business. In the mining industry in particular, in order to obtain maximum return on the significant capital investment in the physical assets involved, ensuring continuous throughput is a major focus for the complete leadership team. Failure to meet throughput objectives becomes a major source of distraction for management which too often attempts to solve shortfalls by æforcingÆ and æenforcingÆ production targets. This focus on the short term and the lack of attention to addressing root causes frustrates operators who attempt to satisfy unattainable short-term targets and lose sight of the long-term goal. Mount Isa Copper Operations, Xstrata Copper, North Queensland, had ambitious plans to increase throughput volume by ten per cent within a four month period to allow budgets to be achieved within the financial year. To achieve this, the process had to overcome the interplay of a multi-node (æsiloedÆ) production system and its associated inventories, each node, of which on the face of it at least, had more than enough ænameplateÆ capacity to meet these plans. However, the actual volume achieved at the end point of the system was well below this nameplate capacity and the system operated with an extraordinarily high standard deviation. The key issues in terms of making or exceeding plan were: how to substantially reduce the variability of the system and managing the inventories between nodes, how to synchronise throughput between the production nodes, and how to improve the decision-making ability within the process. In this paper, the implementation team has shown that a revolutionary process view of the operation together with appropriate planning decisions allowed increased throughput to be achieved without further capital investment.

Jan 1, 2006

By R. Dawson Hall

LONG regarded as nearly worked out, the anthracite region still shows promise of a hundred years of life, for means are being found to get bottom, top, pillar, and other coal that earlier generations disregarded as too expensive to mine. Rock drivages and, still more, machinery are making it possible to get such coal. Mechanical methods enable the owner of thin beds to mine these with profit, and the miner recognizes that he must permit the use of machinery or the inexorable laws of economics will deny him opportunity to work. E. L. Dana, Jr., well outlines this situation, which in the past year became definitely established. Stripping also is recovering, safely and inexpensively, coal that past generations regarded as too hazardous and costly for mining.

Jan 1, 1935

By C Beal, S Singh

Sensor-based bulk ore sorting is a form of preconcentration that autonomously measures and physically separates discrete bulk ‘pods’ of run of mine (‘ROM’) or primary crushed material. This case study examines the results of a full scale bulk ore sorting trial undertaken at Cozamin mine in Zacatecas, Mexico in 2019. The bulk ore sorting plant comprised primarily of a mobile jaw crusher, fixed conveyor, MR analyser, and diverter gate. Results of the trial demonstrate that bulk ore sorting could deliver a net improvement in copper metal fed to the processing plant of 6-8 per cent within an equal gross tonnage of ore. Copper metal increases were the result of improvements in mining recovery, where valuable mineralisation is recovered from marginal or sub-grade material that would otherwise be discarded as waste or stockpiled as low-grade. The increase in mining recovery more than compensates for metal losses suffered in the bulk ore sorting plant.

Nov 10, 2020

By Wei Luo

Nickeliferous laterites were characterized by particle size analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX), Fourier transform infrared (FTIR) spectroscopy and thermal analysis. Results showed that the laterites consist mainly of nickel-substituted lizardite with cobble-like morphology and traces amounts of magnetite and phlogopite. As fluoride ions can react with silicon in the lizardite crystal structure and form metal-fluoride complexes, as well as increase the equilibrium constant of the lizardite dissolution in acid solution dramatically, the addition of minor fluoride salts (0.2wt.% NaF) gave a markedly enhanced metal extraction rate (Ni 81.7% and Co 52.3%) under the experi-mental conditions of particle size d50= 25 µm, 10% (v/v) H2SO4, reaction time 2 h, reaction temperature 90°C, liquid-to-solid ratio 3 mL g-1 and stirring at 500 rpm compared with H2SO4 alone (Ni 69.6% and Co 30.8%).

Jan 1, 2010

By Colleagues from Process and Operation departments, Guy Chevalier

"QCM's pellet plant, located in Port-Cartier, Quebec, produces up to 8.6 million tons of iron ore pellets annually. Four different types are produced: three for blast furnace operations and one for direct reduction furnaces. The paper presents the scientific approach that led to the installation of new process equipment to improve the reducibility of direct reduction pellets (DR pellet). The findings, the equipment selection and some post start-up modifications are presented.This low silica DR pellet is used in Midrex and HyL shaft furnaces. A good DR pellet has to meet strict chemical, physical and metallurgical specifications. An important metallurgical property is its ability to release oxygen when exposed to reducing gases. Considering that the market for DR pellets is expanding and being aware that reducibility is critical for our clients, a program to improve the latter was undertaken. Test work showed that one factor which has a negative effect on reducibility is the proportion of particles larger than 75 microns. Knowing that the best way to reduce the amount of coarse particles was to close our open grinding circuits, we began evaluating the most suitable classification equipment applicable to our process operations. We settled on hydro-classifiers based on their very sharp cut and their low operating costs. In light of the hydro-classifiers performance it was also decided to replace the hydro-cyclones of an already closed circuit.INTRODUCTIONAt the Québec Cartier Mining pellet plant, continuous improvement programs are aimed at increasing levels of consistency and improved chemical, physical and metallurgical properties. This is being accomplished while still maintaining pellet plant production volumes to satisfy market demands.QCM produces three types of pellets for blast furnace use: acid pellets, designated as ""BHF"", fluxed pellets, designated as ""BAF"", and low silica fluxed pellets, designated as ""BSA"". For direct reduction, a low silica acid pellet or DR pellet, designated as ""BBS"" is produced. This low silica DR pellet is used in Midrex and HyL shaft furnaces.The demand for DR pellets has been increasing during the last few years and is believed to continue so in the future. Wanting to be present in this growing market QCM found that it would be essential to work at improving its DR pellets quality. Efforts have been focused on improvements in three areas: SiO2 reduction, elimination of sticking and increasing reducibility. Improvement programs have begun with laboratory research followed by plant trials and full-scale implementation as a cooperative effort among QCM, COREM, and key customers."

Jan 1, 2002

By J. G. Schofield, C. G. Tan, R. J. Ord

"Most electric furnaces in the nickel and copper smelting industries are still fitted with conventional electrode holders which consist of water-cooled electrical contact clamps and a pressure ring. The water cooling exerts a significant cooling effect on the electrode column. The importance of controlling the temperature of the Soderberg electrode paste at the contact clamp area is examined, using in-plant experience and computer simulation of the paste melting and baking process. In addition to the effect of water-cooling, the effect of other variables, including the mantle air temperature, the electrode current, the furnace freeboard temperature and the electrode slipping rate are discussed. Ways in which the variable heating conditions in the paste melting zone can be controlled are outlined.IntroductionIn most non-ferrous electric smelting operations, the breakage of Soderberg electrodes is an infrequent, isolated occurrence. Occasionally, however, a rash of breakages may be experienced on a particular furnace for what appears to be no obvious reasons. The extent of the breaks may not exhibit a uniform pattern; sometimes the break may be less than half a metre above the electrode tip; at other times it may be at or just below the roof level. The latter type of break is, of course, the most dangerous since it is closest to the non-baked, weak portion of the electrode paste column. No matter where the breaks occur, they result in abnormal furnace power, charging and tapping conditions and loss of production while the new electrode section is slipped and baked. On a six-electrode furnace, breakage on one electrode has the immediate effect of reducing the total furnace power by one-third. On a three-electrode furnace, the effect is more drastic, one half of the power being lost."

Jan 1, 1995

By V. Ross

"The Upper Group 2 (UG2) reef in the Bushveld Complex in South Africa hosts an estimated 40% of the world’s Platinum Group Metal (PGM) resources. The processing of this ore via flotation poses two particular challenges: limiting the levels of chromite in the concentrate to reduce downstream smelting problems, and enhancing the recovery of ultrafine (typically -10 micron), liberated PGMs. Conventional ways of suppressing the entrained chromite, such as froth washing, is not effective in PGM operations, which are dominated by mechanical cells. The recovery of fine particles is hampered by low collision efficiencies with air bubbles, as well as oxidised surface layers especially in tailings operations. This paper documents the results of laboratory tests on a run-of-mine PGM UG2 ore, investigating the application of a pneumo-mechanical column (PMC) and its effect on PGM flotation and its selectivity with regard to chromite. A key feature of the device is the stage-wise release of aerated slurry from an agitated downcomer, thus creating conditions where the superficial velocity profiles of air and slurry change axially within the separation zone. This aids segregation of the silicates and chromite-rich fractions in the separation zone, concentrating the latter towards the bottom of the column and minimising its entrainment into the concentrate. Comparison of the performance of the PMC to that of mechanical laboratory cells under equivalent operating conditions showed improved PGM flotation kinetics and recovery. This was accompanied by a decrease in gangue recovery compared to the mechanical cells by more than 40%, thus doubling the final rougher concentrate grade from 50 to 100 g/t. Significantly, whilst the overall Cr2O3 recovery was reduced by more than 60%, the selectivity (PGM recovery vs Cr2O3 grade in the concentrate) was doubled.INTRODUCTIONThe Bushveld complex in the northern part of South Africa hosts the world’s largest reserves of Platinum Group Metals (PGMs), representing approximately 40% of the total PGE. It is characterised by three main PGM bearing reefs, namely Merensky, Upper Group 2 (UG2) and the Platreef. The Merensky and Platreef are dominated by silicates in the form of pyroxenites, and carry economically recoverable amounts of copper and nickel, in the form of chalcopyrite and pentlandite. The UG2 on the other hand is a chromitite ore with chromite as (ideally, FeO.Cr2O3) the most abundant gangue, often constituting more than 70% by mass with a PGM grade of around 4.5 g/t. Other key gangue minerals are pyroxene, feldspar and talc. The PGEs occur in a wide variety of minerals, with platinum and palladium sulphides typically accounting for about half of the total. Base metal sulphides such as chalcopyrite, pentlandite and pyrrhotite occur in only very minor amounts, accounting mostly for less than 0.1% by mass."

Jan 1, 2018

By R. Lee-Aston

HALLOWAY mine of Tennessee Copper Co. at Copperhill, Tenn., has been under development for several years. It has two shafts, the A shaft, 1336 ft deep from the surface to the 16 level, and the B shaft, lying 500 ft to the southeast and extending 1385 ft deep from the 10 level down to the 24 level. A section through the two shafts, Fig. 1, shows the development work entailed by the proposal and the area involved. The Problem: For operational reasons it was necessary to extend the B shaft from the 10 level to surface, and the pilot hole and raising method was chosen. This method had been used to extend the Company's Boyd manshaft from the 10 to the 14 level in 1954, but no satisfactory hole surveying method had been employed. In that instance, when the hole was located it was found to be about 8 ft from its calculated position. The success of this shaft extension method lies in the ability to keep the pilot hole within the proposed shaft diameter for nearly the entire length. The approximate 670 ft of extension distance in one hole was thought to be excessive because of deflection encountered locally in other core drilling. Since a connection between the two shafts, intermediate between the surface and the 10 level, would be required at some future date, the pilot hole drilling was done in two sections. This intermediate level was fixed at the 6 level and distances became 470 ft from surface to the 6 level and 230 ft from the 6 to the 10 level. A rock pentice of 25 ft was left temporarily in place just above the 10 level.

Jan 3, 1958

By John M. Hartman

THE high temperature of the blast of modern furnaces renders it desirable that the pipe conveying the blast into the furnace crucible shall transmit and radiate as little heat as possible. To accomplish this, the pipe shown in the accompanying sketch was devised and patented. It consists of a slide-valve, leg-pipe, and belly-pipe, which are held together and to the tuyere by a system of levers and links. The slide-valve is superior to the old throttle-valve. The leg-pipe is formed of two thicknesses of wrought-iron pipe, with a space of half an inch filled in with clay and brick. The belly-pipe is made in the same way as the leg-pipe, and terminates in a globe face to suit the tuyere. The quarter turn is made extra thick, of cast iron, and the cap on the end is lined with clay also. The catches, A, B, C, are merely for convenience in putting the pipe together. The joints D and E are globe faces, and allow the pipe to adjust itself to any angle. The eye-piece is made of violet glass, which cuts off the glare from the bright coals in the furnace and allows a close examination of the interior, so that any water dropping or vapor can be detected. The glass does not become coated with dirt, like mica. Since good running of furnaces is shown by a bright tuyere, it is necessary to have a good eve-piece to examine then. To detach the pipe, a man lifts the weights, the side rods are then slipped off the bell crank under the quarter turn, the link under the belly-pipe is unhooked, and the pipe carried away. The same process is reversed to put the pipe together. The nozzle is changed by taking off the cap, G, drawing the nozzle through the belly-pipe, and inserting another. In this way the change can be made quickly, without taking down the pipe. On the old tuyere pipe bolts with brass nuts were used, which burned up and gave trouble. In other cases key-bolts were used, making it difficult to adjust the pipe. Bolts make too rigid a joint, and there is no provision for movement from contraction or expansion. As the temperature of the blast increases there is more expansion, and where rigid joints are

Jan 1, 1879

The development of reliable and accurate solution sampling systems plus on-line atomic absorption spectrophotometers and voltammetric analysers at Pasminco Metals - EZ's (PMEZ) zinc refinery at Hobart, Tasmania, has led to extensive implementation of On-Stream Analysis (OSA) throughout the hydrometallurgical circuit. These systems complement industrial autotitrator and colorimetric analysers and with the comprehensive use of a powerful integrated Distributed Control System (DCS), provide extensive monitoring and control of all the important in solution' parameters for the plant. Samples can be left unaltered, or filtered or settled, to remove solids. They are then precision diluted and pneumatically transported to analyser shelters, where they are analysed for zinc, acid, copper, cadmium, lead, antimony, cobalt, nickel, mercury and ferrous, ferric and/or total iron. The range of analyses depends on the sample itself. The results are used for feed forward and/or feedback control of reagents where possible, or simple trend monitoring and out-of-specification alarming when closed loop control is not practical. The overall system reliability and accuracy is such that many daily composite plant samples are no longer analysed off-line. Operator sampling has also been reduced, and in two places, autotitrators with automatic sample pre-treatment have been installed for preparing and analysing samples collected by operators.

Jan 1, 1993

By J. L. SCHUELER

THE writer has reread Mr. Ingalls' interesting article in the July, 1923, issue of MINING AND METAL- LURGY on "The Use of Spelter in Galvanizing." It seems that most writers, in commenting upon coatings of spelter on sheets and wire, dwell upon the thin coatings which these materials carry, and rightly so. However, they seem to forget that until very recently, in the case of wire, the manufacturer did not know how to apply a heavy coating of spelter to the wire, especially if the wire was to be woven into fence or fabricated in some other manner, because heavy coatings of spelter are exceedingly brittle. This is even true in the case of high-grade spelter, but to a lesser degree than with Prime Western. Because of this brittleness, it has been necessary for wire manufacturers to smooth the coating by passing the wire through tightly compressed wiping means of some kind, usually asbestos. This removes all of the excess spelter and allows only a thin coating to remain. The latter, as a rule, is malleable and the wire can be fabricated without material injury to the coating.

Jan 1, 1924

By Ángel Ruiz-Sánchez

Ethylene glycol additions to aqueous acid solutions for leaching copper sulfides increase both copper and iron extractions compared to a conventional sulfuric acid leach with hydrogen peroxide (H2O2). The role of ethylene glycol is to prevent peroxide destruction, which normally occurs in solutions that contain both cupric and ferric ions. However, despite this improvement, ethylene glycol and sulfuric acid concentrations must be high (3.5 M and 0.7 M, respectively) to obtain satisfactory conversion levels at room temperature. In the present investigation, EDTA was used as an additive to complex the cupric and ferrous ions, lowering the requirements of ethylene glycol and H2SO4 to 0.11 M and 0.007 M, respectively, while minimizing oxidant decomposition. The experimental results for a mainly chalcopyrite, copper concentrate showed complete copper extraction in 24 h at room temperature, with the stoichiometric quantity of EDTA for the copper and iron dissolved. Tests using seawater were equally as successful.

By Dave Bulled, Jim Thompson, Tim Leriche, Mark Blake, Troy Wilkie

"A commitment to a core testing, plant modeling and reconciling technique has shown substantial economic benefits to IOC in terms of accurate production forecasting, smoother operation of the mill, improved expectations of throughput and co-operation across production departments from geology, planning, mining, and processing, to shipping of concentrate to market.This paper describes a successful seven year program of forecasting throughput of the autogenous milling circuit at the Carol Lake concentrator of IOC. Work started with audits of the grinding circuit in 2001 and benchmarking of the data collected from samples of mill feed and plant operation to the CEET mill design and throughput forecasting model.Initially 390 drill core samples were tested for SAG Power Index (SPI) to measure the energy required in milling, and the data distributed using a geostatistical technique across the two operating pits, so that hardness was estimated in each of the 40,000 blocks (or 1500 million tons) of potential ore. In 2004 a forecast of energy requirement, i.e. forecast of throughput for a given power availability at the mill, was produced for each ore block using the CEET model and used for mine planning to smooth plant throughput. The forecast for blocks mined on a monthly basis was reconciled with plant results over the next 2 years and minor changes made to the CEET model. The forecasting exercise was repeated in 2006 and in 2008 with the latest model based on the testing of almost 1300 samples of drill core at closer spacing.INTRODUCTIONThe contracting of sales to clients and the timely supply of products to meet those contracts is a cornerstone of good business practice. Ensuring the correct scheduling of production is a major concern of mining companies where the supply and qualities of the raw material is uncertain and production facilities are not flexible. This is particularly challenging when the product is of high volume and produced far from the customer, such as iron ore.Apart from the metal content of the ore being mined, the greatest impact on production scheduling is the throughput of the comminution section of the extraction plant; most notably when size reduction is achieved by autogenous grinding. The response of the mills to variability in the hardness of the ore can change throughput by as much as 50% from day to day at some plants."

Jan 1, 2009