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By M. Evertsson, M. Johansson

"In minerals processing control is vital to increasing performance and output of a plant. Model predictive control (MPC) is one of the most effective control strategies used in process industry. Sbárbaro (Sbárbaro and Del Villar, 2010), Asbjörnsson (Asbjörnsson, 2015), and Légaré (Légaré et al., 2016) have for example highlighted the possibility to simulate, develop and tune control systems using plant simulators within minerals processing. In more recent years the use of model predictive controllers have increased, and many process industries now utilize more advanced control methods to regulate their processes, raising the question regarding how to, build, test and verify a proposed control solution successfully. In this research, a linear model predictive controller is formulated and applied to a simulator of an existing tertiary crushing circuit. The circuit has in previous work by Johansson (Johansson, 2017) been modeled in MATLAB Simulink and calibrated relative plant data to an average error of less than 10% over 8 hours of production. The work demonstrates how to formulate the controller model structure to describe conveyor belts, storage components, screens, crushers, and control objectives for a minerals processing circuit. The work illustrates how to apply and successfully evaluate possible upsides in a circuit. The advantage of a crushing circuit simulator is that it can be configured, tuned and modified in any possible way, which is of great benefit to developers and engineers. Additionally, examples of how to use estimated measures to improve the performance of the plant are demonstrated. The control performance is finally evaluated for three different controller configurations."

Jan 1, 2018

By S. Amira

In the last two decades, many new creep-resistant magnesium alloys have been developed for high temperatures applications. Their mechanical performance and corrosion behaviour were reported for various experimental conditions. However, these conditions often led to uneven comparison basis. In the present study the microstructure, mechanical properties and corrosion performance of four of these newly developed creep-resistant magnesium alloys were systematically compared. Specimens were obtained from experimental box-like components that were die-cast and thixocast in comparable conditions. Their mechanical and corrosion properties were compared using similar testing conditions. Results show that the creep resistance, strength and impact resistance of specimens are comparable but systematically lower compared to specimens cast under optimized conditions. The reduced concentration of elements such as Al, Ca, Sr and Ce lead to a decrease of the corrosion resistance of the magnesium alloys in 3.5% NaCI solution.

Jan 1, 2007

By A. V. Henry

THE kaolins of the southeastern United States were known to civiliza-tion as early as the latter part of the eighteenth century-and yet the Fig. 1.-KAOLIN PRODUCTION AND IMPORTS. commercial history of Georgia kaolins may be said to begin in the year 1900. The U. S. Bureau of Mines reported for that year a production of 6885 tons of "miscellaneous" clays in Georgia. A comparison of these figures with those of 1934, when the production rose to 284,556 tons (65 per cent of the domestic production), indicates the growing economic and technologic importance of this raw material. Fig. 1 clearly shows that a part of the increase is due to a normal growth in the use of kaolinitic clays and a part is due to replacement of clays formerly imported.

Jan 1, 1937

By Euler De Souza, J. Daniel Stinnette, Julian Varaschin

"This paper outlines some of the factors that affect the airflow required for the ventilation of modern diesel-powered equipment and of electric equipment and examines how they can be applied in determining reasonable ventilation rates for Tier IV compliant diesel equipment and for electric equipment operating in mining environments. Airflow calculations for modern diesel-powered equipment and for electric equipment are more complex and must be based on a combination of factors that are unique to each mine. Methodologies for ventilation rate determinations for each case are proposed in this paper.INTRODUCTIONTraditionally, airflow requirements for production and support equipment operating in underground mines have been determined by multiplying the vehicle power by a ventilation rate that was either mandated by regulations or determined empirically from known quantities. However, in light of the drastic reductions to diesel equipment emissions mandated by the US EPA Tier IV and EURO Stage 4 regulations, there is still a great deal of uncertainty in the underground mining industry among those responsible for the ventilation of planned new mines or the expansion of current mines. The question remains, what ventilation rates should the ventilation system designer apply for modern diesel equipment?Also, given the ongoing development of grid/battery-electric equipment and active construction of fully electric mines, it has become critical to determine adequate airflow rates per brake kilowatt of electric engine power. One of the most important criteria for determining ventilation rates for electric equipment is the amount of heat they generate, as this is the most significant emission produced by electric equipment (which do not produce exhaust gases or particulates). Therefore, ventilation rates required to dissipate heat from electric equipment must be suitably determined for all electric vehicle fleets operating in underground mines."

Jan 1, 2019

By H. H. Rachford, W. P. Schultz

The use of computing machines to solve physical problems has made it imperative to represent physical data in a form computing machines can use. Although curve-fitting is an old and well-practiced art, there still seems to be some interest in questions regarding what methods can be used and why. Even though there are many good references on this subject, it may be of some value to discuss a particular method which has been found to be useful, and to make available the associated tables for its use in the hope that there can be saved a few of the tedious hours necessary to reduce many of the suggested methods to practice. Although a very brief discussion of the mathematical background of the tables is included immediately below, those interested only in their use can skip directly to the section on Use of the Tables. Direct Fit of a Set of Points A frequently encountered problem is: Given data which can be represented by a smooth curve +(x), to find an easy-to-evaluate function F(x), with only a few coefficients, which is a good approximation of +(x) on the interval 0 5 x 5 x,,. Consider F(x) as a linear combination of m + 1 arbitrary, single-valued, continuous, linearly independent functions, f,(x), Ff.r) = a,f,,(x) + a,f,(x) + . . . -+ aifi(x) + If the value of Q(x) is known or can be read from the curve at the points xj: +(x,), +(x,), . . . +(xj) . . . +(x.), and if n = m, then all the coefficients of F(x) can be determined, and F(x,) — +(x,) = 0 for j =. 0, 1, . . . n. This follows from the solution of the set of linear simultaneous equations. +(x<.) = aofu(x,) + aJI(x0) + . . . + a,,f,,(x,) =a, = f,,(x,) + a,f,(x,) + . . . + a,f,,(x,) +(x,,) = a,,f,(x,,) + a,f,(x,) + ... + a,,f.,(x,,) ...........(2) for the coefficients ai. Although the set a, from the solutions of the set of Equations 2 yields an fix) which gives an exact value of $(x,) for the n + 1 points, there is no restraint on ~(xj in the interval xi < x < xj+,. Indeed, if the points +(x,) are not sufficiently smooth, very serious differences may arise between F(x) in the interval and the smooth curve +(x). Least-Squares Fit It has been suggested&apos; that if n is made to exceed m, and the set a, is found to minimize the function the function F(x) is much less sensitive to small errors in +(xi), and usually provides a much better fit to the smooth function +(x). This is known as the best fit in the sense of the least-squares error. To minimize $, set £ = 0,i = 0,1,... iTi,.....(3) The m + 1 equations from Equation 3 are k—n k=n a.^p /,,(a) f,(xt) + a, X A: = 0 k=O k = n k = n k=0 k=0 +(x.) f,(x,),............(4) one equation being obtained for each i = 0, 1, . . . m. Inasmuch as the arbitrary functions f(x) may be evaluated for x,, k = 0, 1, . . . n, and the +(x,) are known values of the curve to be fitted, the simultaneous Equations 4 may be solved for the set a,. Particular Functions Given the functions fi(x) and the set +(xj), the solutions for require evaluating a number of sums of products as well as the solution of an m + 1 order set

Jan 1, 1956

By J. Drew Potts

The U.S. Bureau of Mines identified respirable dust sources and controls on four continuous auger mining sections, two with relatively low dust levels and two with high levels. Factors adversely affecting dust levels included auger equipment design, continuous haulage, and low seam height. Dust controls included ventilation practices and spray systems. Maximizing airflow seemed to reduce dust levels most. Air leakage and shock loss can be reduced by constructing stoppings with brushed-on mortar containing fiberglass and by keeping areas between curtains and ribs free from obstructions and storing equipment not essential for face activities in outby crosscuts. Curtain configuration, setback distance, and installation can also affect dust levels. Use of both blowing and exhausting curtains is the most effective configuration. Setbacks from the face should not exceed 15 ft. Installing brattice curtains at least 5.5 ft from ribs, when entries are 26 ft wide, minimizes velocity head. Installing curtains tightly against the mine roof and floor helps maintain a forward airflow movement in the center of the mine heading; curtain overlap can create a tighter seal. The wet-auger spray system also effectively controls dust, provided the mine is already exercising good ventilation practices.

Jan 1, 1989

By Mark Bosse

This is a paper demonstrating the use of a fixed wire and trolley system to deliver 2 or 5 lb cast primers (with 2 meter cap/fuse assemblies) deep into avalanche terrain. This avalanche terrain is mitigated using explosives prior to being opened to guests.

Feb 1, 2020

By Roger J. Berdusco

Kaiser Resources Ltd. owns and operates a 5-million-tonper- year open-pit and hydraulic coal mine near Sparwood in southeastern British Columbia. Since 1969, Kaiser has maintained a field-scale reclamation program dedicated to the reclamation of disturbances associated with past and present mining and exploration activities . Since that time, over 1400 acres have been treated using modified forestry and agricultural techniques with encouraging results.

Jan 1, 1978

THE Lehigh Valley Section is planning with a num-ber of other organizations a three-day conference, April 25, 26 and 27, with field visits to cement, slate and steel plants in the vicinity of Easton, Pa. W. B. Plank is chairman and D. Knickerbocker Boyd is sec-retary. Headquarters will be at Hotel Easton. Wednesday&apos; will be cement day. In the forenoon A. S. T. M. Committee D-16 will meet and after luncheon the delegates will visit the Martin Creek plants of the Alpha Portland Cement Co. An evening dinner and general session on cement is being arranged. Thursday morning will be devoted to a technical ses-sion on slate, and the breaking of ground for the new John Markel mining building at Lafayette College. After luncheon various slate quarries will be inspected, the visitors being guests of the companies. In the eve-ning there will be a conference dinner at Hotel Easton with a number of distinguished visitors. Friday will be given over to steel and will include a visit to Lehigh University, an inspection of the plant of the Bethlehem Steel Corp., and a luncheon as guests of the latter.

Jan 3, 1928

By Joseph A. DeCarlo

This publication presents statistical data on oven-and beehive-coke plants in the United States. Information on the carbonizing capacity of the coke industry is important because of the close relationship between the coke industry and most of the other basic industries of our country. Coke is an essential-raw material in pig-iron production; also, coal-chemical materials are used to make fertilizers, paints, plastics, synthetic rubber, explosives, detergents, nylon, pharmaceuticals, dyes, and many other useful products necessary to sustain and improve the high standards of living in our country. Oven-coke plants in the United States on December 31, 1958, are tabulated in table 1. This tabular presentation shows the location, classification, number and type of ovens, annual coke capacity, coal chemicals produced, and name and address of parent company for each individual coke plant. About 86 percent of the capacity of slot-type coke ovens in the United States is owned by iron and steel companies. In most of these plants the coke ovens are integrated with the blast furnaces to facilitate transportation of raw materials for steel making. This has resulted in large coke plants, and the average annual coke capacity of "furnace" plants in 1958 was 1.3 million tons. Nonfurnace or "merchant" plants include coke plants associated with chemical operations, gas utilities, as well as coke plants that produce metallurgical, industrial) and residential-heating grades of coke and coal-chemical materials for sale on the open market. These plants ordinarily are not as large as furnace plant~ and annual coke capacity of merchant plants in 1958 averaged only 500 thousand tons. At the end of 1958 there were 55 furnace plants and 22 merchant plants.

Jan 1, 1959

By Jinhua Wang

Based on engineering examples and theoretical analysis, the mechanism of chemical consolidation for fractured roadway surrounding rock was discussed. The chemical consolidating materials and three consolidating methods, that is, capsule, forced infusion and spraying, were introduced. Finally the application effects of the chemical consolidating technique to reinforce the fractured surrounding rock of roadways were analysed.

Jan 1, 1996

By Fuqiang Zheng, Shuai Wang, Ting Duan, Yufeng Guo, Tao Jiang, Andrew Yakovlevich Travyanov

Organic compound binder can effectively enhance the strength of green pellet and reduce the addition amount of binder during pelletizing. However, compared with traditional bentonite binder pellet, the compressive strength of the preheated and roasted pellets significantly declined. It is of significance to resolve this problem for the application of organic compound binder. In this paper, magnetite concentrate was used as raw material, carboxymethyl cellulose (CMC)- bentonite compound was used as binder, characteristics of preheated and roasted pellets and the effects of additives on that were systematically studied, The results show that sodium acetate can effectively improve the characteristics of the finished compound binder pellets. The compressive strength of the preheated and roasted pellets were increased by 52/N·p-1 and 342/N·p-1 respectively when the addition amount of sodium acetate is 2.2%wt of compound binder. Moreover, sodium acetate has no adverse effect on pelletizing process and drying characteristics of green balls.

Jan 1, 2015

By David K. Sitler

Continuing advances in manufactured diamond materials used in rock cutting tools have created a new generation of high production tools for mining. This paper will review the three major manufactured diamond products available for the mining industry as supplied by General Electric Company, Specialty Materials Department, and examine the ways in which these materials are employed. As an integral part of this examination, the economic impact of manufactured diamond tools will be evaluated. Time and again, one will find that the premium price of these tools is economically justified when compared to traditional tools.

Jan 1, 1985

By T. T. Campbell

Research conducted by the Bureau of Mines demonstrated the feasibility of preparing columbium and tantalum metals by the application of Kroll-process techniques. Yields in excess of 95 percent were obtained in a modified Kroll-process reduction apparatus constructed from nickel and Inconel.4 Operating conditions during reduction and distillation were determined. Optimum temperatures during sodium reductions ranged from 650° to 750° C and for magnesium from 700° to 800° C with retort pressures ranging from 3 to 7 psig. Undesirable vapor phase reactions occurred when temperatures exceeded 750° C during sodium reductions or 850° C with magnesium. Vacuum distillation at 850° C effectively removed volatile salts and excess reductant from the reduced metals. Calculations based on the results obtained in small scale tests indicate that reaction rates of up to 34 lb/hr could be obtained during columbium reductions and up to 60 lb/hr during tantalum reductions in production scale reac¬tors. The small, laboratory-scale techniques used in this study could be adapted to commercial practice. The reduced powder or sponge metals can be consolidated by conventional arc-melting techniques, and the arc-melted metals can be fabricated into ductile sheet at room temperature. Analyses of arc-melted buttons prepared from Kroll-process tantalum or columbium showed that tantalum of greater than 99.8-percent purity was obtained and that columbium purity exceeded 99.7 percent. A significant purification of the reduced metals occurred when they were consolidated by electron-beam melting, and the purity and ductility of electron-beam-melted Kroll-process tantalum and columbium compared favorably with the commercial metals. After electron-beam melting, the purity of the tantalum exceeded 99.95 percent, and columbium purity was approximately 99.9 percent.

Jan 1, 1962

By M. Asghari, R. Amiri, A. Haratian, S. Haji

The aim of this investigation is the evaluation of optimising the Shahroud copper ore beneficiation plant near the Iranian city of Shahroud, by means of a sensor-based ore sorter applying X-ray transmission technology. Currently, this plant’s feed capacity of 52t/h produces 0.5t/h copper concentrate with a grade of 30% and copper recovery of 85% from a feed grade of 0.36%. By applying an X-ray transmission-based (XRT) sorter, it is possible to preconcentrate the feed and remove the gangue materials before entering the plant, enabling the production rate of concentrate to be increased. In this study, the obtained representative sample from the plant was preconcentrated in particle size of - 75+10mm by using the X-ray sorter, thus the concentrate with Cu grade of 0.85% was obtained. Therefore, by using of X-ray sorter the Cu grade of plant feed was increased to 0.48%. By increasing the feed grade from 0.36% to 0.48%, and considering a Cu recovery of 85%, the production rate will be increased from 0.48t/h to 0.61t/h. Therefore, the preconcentration by using the XRT sorter increases the production rate by 27%. Keywords: Optimisation, preconcentration, copper, X-ray, sensor-based ore sorting

Jan 1, 2020

By J. G. Mieczaniec

"A key element for a successful mining operation is the grinding circuit. It must be reliable, maintainable and must perform to or above design capacities for 95% of the time. Once chosen and installed major modifications are either prohibitive or very expensive. The selection of mills and drive system is probably the single most important decision made within the concentrator complex.Economic studies revealed that the optimum expansion for Lornex was a 68070 increase in plant throughput. This indicated that the new mill would have to be larger than the existing 32-foot mills.The Lornex ore has a wide range of hardness which has a great influence on mill throughput (Table 1). To smooth out the fluctuations, a blending program ha s always been in effect at the mine, coupled with ball charge control for the primary mills. As can be appreciated, an optimum balance is difficult to achieve. A sudden change to so ft ore with a high ball charge puts the mill into jeopardy with a constant speed drive.The blending philosophy would continue after the expansion, but with the addition o f a second primary crusher, it was envisaged to have the new mill process harder ore to maintain production targets. In theory, the new mill would have a proportionally larger ball charge than the existing mills.This scheme makes the new mill vulnerable for processing so ft ore for a fixed speed mill. Thus, variable speed seemed an attractive option.In early 1979 prominent mill manufacturers were invited to submit proposals for the new mill. Fixed and variable speed mills were to be considered with mill size ranging from 32-foot to 36-foot diameter. The proposals were to include the drive, ball charge, % critical speed, couplings, gears, etc. - the complete package. The recommendations were variable with most manufacturers submitting several alternatives. Recommended mill speed varied from 68% to 78% critical. The concept of variable speed was becoming more attractive, Lornex ultimately decided on a twin DC motor drive system for a 34-foot diameter mill.After start-up it was discovered that best throughput occurred at 78% mill critical speed or top speed of the drive motors. The motor speed range was adjusted upward from 186 to 200 rpm. Today the mills operate at 79% critical or a motor speed o f 193.5 rpm.Clearly the selection of the variable speed mill allowed the flexibility to optimize throughput."

Jan 1, 1985

By Terry J. Close

In 1985, at the request of the U.S. Bureau of Land Management, the U. S. Bureau of Mines studied part of the 56,623-acre South McCullough Mountains Wilderness Study Area (NV-050-435) in order to evaluate its identified mineral resources. The area studied is located in Clark County, NV, about 30 miles southwest of Boulder City. No mineral resources were identified. The study area contains the eastern part of the unorganized McCullough Mountain (McClanahan) mining district which has had no recorded production. Between 1911 and 1982, 23 lode claims were located in the part of the mining district that is in the study area; four of these claims are currently held by assessment (1986). A total of 11 mineral sites were found and examined during the U.S. Bureau of Mines investigations; 26 mine workings were examined. Of the 11 sites, four are within the study area, and seven are nearby. Of the seven nearby sites, six are adjacent to the west boundary and consist of precious-and base-metals bearing vein occurrences in metamorphic rocks. The seventh site is near the east study area boundary, and consists of a tungsten-bearing vein occurrence that is also in metamorphic rocks. The four sites within the study area consist of vein occurrences in metamorphic rocks that contain silver, gold, arsenic, lead, zinc, and copper. The veins at these four sites are too small and low grade to be classified resources; however, there are indications that three of the sites may have silver and gold resources at depth. Detailed delineation of the veins, and determinations of tonnages and grades are needed. This would entail additional mapping and sampling, trenching and drilling, and opening inaccessible workings.

Jan 1, 1987

By Gomm SA

The Mount Tom Price Concentrator, which contains a heavy medium cyclone plant for beneficiation of the -6+0.5mm fraction of low grade iron ore, is described. Testwork was carried out on an opportune basis over a period exceeding twelve months, to evaluate the separation performance of the heavy medium cyclones. Plastic density tracers were used and ore samples were taken and analysed. The effect of operating medium specific gravity (S.G.) on the separation parameters, the iron grade of the sinks product, and the mass and iron recoveries were investigated. Also examined were the differences in perform- ance between particles of different size. The implications of the findings for plant oper- ation are discussed.

Jan 1, 1987

By Mariana Peixoto

Muitos componentes de ferro fundido ficam expostos a altas temperaturas quando em serviço, podendo ocorrer a decomposição da perlita através da difusão do carbono da cementita para as lamelas de grafita, resultando em alteração microestrutural e degradação das propriedades mecânicas. A influência que a temperatura e o tempo de exposição têm sobre a microestrutura de um ferro fundido cinzento foi avaliado em amostras de quatro ferros fundidos de mesma base, com diferentes percentuais de cromo e molibdênio. Ensaios de banho de sal a uma temperatura de 500ºC foram realizados em corpos de prova com diâmetro de 10 mm. Os ensaios foram realizados com tempos de exposição a esta temperatura, após homogeneização térmica do material, de 0, 1, 2 e 4 horas. As análises metalográficas evidenciam a ocorrência da decomposição da perlita. Adicionalmente foram realizados ensaios de microdureza, a qual se mostrou sensível às alterações microestruturais geradas pela temperatura elevada. O ferro fundido com maior percentual de cromo e molibdênio apresentou melhor estabilidade da microestrutura para as condições ensaiadas.

Aug 17, 2017

By Bernardo Martins Braga

O desgaseificador RH é um reator de refino secundário bem estabelecido. Nesse equipamento, gás inerte é usado para promover a circulação de aço entre a panela de aciaria e uma câmara de vácuo. A predição correta da dispersão de gás na perna de subida do RH é importante para a modelagem confiável do processo. O presente trabalho estudou a penetração de gás na perna de subida do RH por meio de modelos físico e matemático. No estudo, foram considerados apenas um ou dois bicos injetores e vazões de gás, por bico, entre 5l/min e 50l/min. Para as condições com um bico injetor, os resultados das duas abordagens mostraram boa concordância qualitativa. Já para as condições com dois bicos injetores, a concordância só foi satisfatória para vazões de até 30l/min por bico. Adicionalmente, os resultados obtidos indicaram que o problema de penetração de gás em modelos matemáticos de desgaseificador RH identificado na literatura está relacionado com erros numéricos e não com falhas na modelagem da física do problema.

Aug 17, 2017