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By Hamed Khodadadi, Hamid Ghadiri

In this study, a fuzzy logic self-tuning PID controller based on an improved disturbance observer is designed for control of the ball mill grinding circuit. The ball mill grinding circuit has vast applications in the mining, metallurgy, chemistry, pharmacy, and research laboratories; however, this system has some challenges. The grinding circuit is a multivariable system in which the high interaction between loops, the variation of the system parameters with time, and time delay are some of the problems that pose a challenge. Since the controller parameters are determined offline in classic PID control, these gains are unchangeable and cannot overcome the mentioned challenges in this system. Hence, a fuzzy logic self-tuning PID controller, which is a combination of fuzzy logic and a conventional PID controller, is proposed to control the grinding system, especially in the presence of model mismatch and disturbances. In addition, in order to solve the system challenges, a multivariable control approach based on an improved disturbance observer is proposed to suppress the effects of the disturbances. The most important feature of the algorithm proposed in this paper as the combination of fuzzy logic self-tuning PID and improved disturbance observer is its ability to eliminate system interaction, attenuate internal and external disturbances, and compensate the effect of system uncertainty on the performance of the ball mill grinding circuit. Simulation results in the cases of the set-point change in particle size and circulating load in the presence of model mismatch and external disturbances confirmed the controller performance compared to other controllers.

By Hamed Khodadadi, Hamid Ghadiri

In this study, a fuzzy logic self-tuning PID controller based on an improved disturbance observer is designed for control of the ball mill grinding circuit. The ball mill grinding circuit has vast applications in the mining, metallurgy, chemistry, pharmacy, and research laboratories; however, this system has some challenges. The grinding circuit is a multivariable system in which the high interaction between loops, the variation of the system parameters with time, and time delay are some of the problems that pose a challenge. Since the controller parameters are determined offline in classic PID control, these gains are unchangeable and cannot overcome the mentioned challenges in this system. Hence, a fuzzy logic self-tuning PID controller, which is a combination of fuzzy logic and a conventional PID controller, is proposed to control the grinding system, especially in the presence of model mismatch and disturbances. In addition, in order to solve the system challenges, a multivariable control approach based on an improved disturbance observer is proposed to suppress the effects of the disturbances. The most important feature of the algorithm proposed in this paper as the combination of fuzzy logic self-tuning PID and improved disturbance observer is its ability to eliminate system interaction, attenuate internal and external disturbances, and compensate the effect of system uncertainty on the performance of the ball mill grinding circuit. Simulation results in the cases of the set-point change in particle size and circulating load in the presence of model mismatch and external disturbances confirmed the controller performance compared to other controllers.

By PEILIN LAN, LEONARD HILL, SIMON TIMBILLAH, BERNARD FOSU, CESAR SOSA-BLANCO

The use of sodium hydrosulfide (NaHS) in most of the operations in by-product molybdenum flotation comes with safety concerns and, in some instances, a high reagent cost. Engineered solutions at the various operations where NaHS is used have reduced the possibility ofH2S gas evolution immensely. However, the threat of exposure remains, and this, coupled with the high dosages of NaHS consumed, supports the continued search for alternative depressants. This paper focuses on efforts to study the applicability of disodium carboxymethyl trithiocarbonate (DCMT), an organic depressant, as an alternative to NaHS. Benchscale rougher flotation results for samples from the Sierrita Cu–Mo plant showed the best DCMTperformance at 8 kg/t of DCMT and pH=10.5 with 30 min of shear conditioning and 10 min of flotation conditioning time. The Aminpro plant model simulation confirmed that DCMT with 4–8 kg/t under certain shearing and conditioning times achieved superior or equivalent Mo–Cu separation efficiencies when compared to NaHS.

Apr 19, 2021

By WILLARD W. CUTLER

This bulletin reviews, in the light of recent experience, the use of production-decline curves in estimating the future production of oil from wells. It deals with the estimation of the reserves of recoverable oil in properties already producing or in those adjacent to them, takes cognizance of the physical laws governing expulsion of oil from oil sands, and shows how the production-decline curve can be made to utilize these laws in estimating reserves and rates of production. The valuation of oil properties should be based on the total amount of oil recoverable from a property by the methods in use, the rate of recovery, the cost of production, and the selling price. Numerous other curves besides those for reserves and rates of production may be formed from the production-decline curve and will present desired information in a convenient time-saving form. These curves also are described. Methods developed before the production-decline curve method was used are briefly discussed in order that the principles on which estimations of oil reserves are based may be made plain. The construction of curves and tables for estimating future production of individual wells and of average wells in most of the important oil districts of the United States is described and operating problems that may be solved by the use of production-decline curves are discussed. The bulletin does not deal with costs, oil prices, or the methods of evaluating oil properties. Many engineers have amply demonstrated the value of the production- decline curve method by forecasting within reasonable limits the production of many thousands of wells and tracts. The value of similar estimates depends however, on (1) the application of trustworthy methods; (2) the care and judgment of the estimator; and (3) the length and reliability of the records and the accuracy of ofher information used in estimating future production. When adequate records and information are available, experience has shown that It qualified engineer can forecast production far more accurately than has been deemed possible, except where the usual conditions governing the expulsion of oil from a sand have been radically changed by applying compressed air or by flooding with water, or, to a less degree, by using vacuum. In general, the production-decline curve method, though there are limits to its accuracy, is far more trustworthy than any other.

Jan 1, 1924

By T. P. Mucho

Over the past several years, two types of roof control problems have been en- countered at Beth Energy's Eighty Four Complex mine in Southwestern Pennsylvania. These problems have been (1) poor roof conditions encountered while advancing submain entries and longwall panel entries and (2) deterioration and failure of long- wall gateroads, principally the tailgate entry. This paper discusses the efforts by mine personnel to analyze the origins of the various attempts to-deal with the problems, and the success (or failure) of these efforts. Highlighted are the use of various common roof Control materials, variations in mining techniques, cementatious pillars, and changes in pillar design using yield and abutment pillars to address these problems.

Jan 1, 1986

By R. F. Kehrman

Voice Frequency (VF) electromagnetic trapped miner location devices were tested for reliability and effectiveness in 93 coal mines. Tests included uplink pulsed CW, downlink pulsed OW and downlink voice evaluations. Frequencies were 630, 1050, 1950 and 3030 Hertz. Overburden depths varied from 70 feet to 1550 feet. Successful communications were established at 91 of the 93 mines. Data indicate the transmitters and receivers will operate in practically all coal mine environments. Reliability and accuracy as location devices appear to depend on noise, depth and presence of metallic objects which distort the magnetic field. In addition, theoretical models appear to define best case situations in terms of noise and conductivity. Minor hardware problems were encountered, mostly involving battery contacts, switches and antenna cables on the receivers. No hardware problems occurred with the transmitters.

Jan 1, 1978

By P. Favreau

"This paper describes the progress accomplished at the Noranda Technology Centre in the field of three-dimensional computer-aided underground blast design. Traditional methods of laying out underground blasts are reviewed, and the new computer-aided approach is described. Time savings achieved through the use of BLASTCAD can be advantageously used to better engineer blasts, using models and blast vibration analysis. Future work involving the attachment of blast models directly to the system is also addressed.IntroductionThe Noranda Technology Centre's (NTC) Environment and Mining Laboratory, in cooperation with the mining operations of the Noranda Group, is committed to the development and implementation of new technologies in the field of mineral extraction . Within the frame of its research program, the Blasting Technology Program is developing computer "" tools"" designed to assist the blasting engineer or technician. These computer "" tools"" are regrouped under a global software system called BLASTCAD.The BLASTCAD project started in 1990 at NTC. At that time computer programs designed to calculate and model various blasting parameters had been accumulated. These programs cam e from different sources and were mutually incompatible. Furthermore, they were developed as research programs with tittle effort spent on user interface. These programs are very useful, but are highly specialized, need large input files and can be quite tedious to use as ""standalone"" packages .Therefore, the situation being faced was one where all these programs were available at the Noranda Technology Centre, but not a t the operations. The two following options were then considered: 1. continue to run all the models and programs at the Noranda Technology Centre, and present results through reports to the mines, or2. regroup all the different programs under a single one that would make them share the same data base and be transported to the user. This second option is the one that was adopted; the result is BLASTCAD."

Jan 1, 1993

By Zuhair A. Nawab, Muhammad A. Al-Marhqun, Mehmet Guney

"The Atlantis-Il-Deep is a stratified metalliferous deposit located along the median valley of the Red Sea at a water depth of about 2200 m. The metal-bearing mud contains sulphides of zinc, copper and iron with significant amounts of silver, gold and cobalt. A variety of oxide, siliceous and carbonaceous gangue material is also present. Long sediment cores indicate that the thickness of the deposit may reach 25 m, but the average kriged thickness of metal-rich sediments is about 11 m.Mining geostatistics was applied to estimate the Red Sea offshore mineral resources. Experimental semi-variograms were computed along 0 ± 180 degrees and then models were fitted to analyze the mineralization phenomenon. Kriging estimates indicate that 696.330 million t of bulk sediments contain 1.891 million t of zinc, 0.425 million t of copper and 3. 75 thousand t of silver. Gold and cobalt contents were calculated from the analysis of solids in flotation concentrates as 47 t and 5368 t respectively. The significant outcome of implementing geostatistics to the Red Sea brine precipitates is not only for the evaluation of metal resources, but it also provides a useful tool in the optimization of selective dredging of appropriate areas to be mined. IntroductionThe discovery and extensive exploration of hot brines and hydrothermal sediments in the Red Sea median valley revealed the fact that the Atlantis-II-Deep is a potentially exploitable metalliferous mud in the economic sense. Sediments in the mineralized deep are composed mainly of oxides, various types of silicates and sulphides with considerable concentrations of zinc, copper, cadmium, silver and gold. The mineral-rich deposit, located at a mean water depth of about 2000 m, has an average thickness of 11 m, and is covered by a brine layer having a temperature of 60°C."

Jan 1, 1988

By Adriano Santos

O presente trabalho busca apresentar o desenvolvimento, as diferenças e os resultados dos testes de flotação em bancada em circuito fechado (locked cycle test - LCT), desenvolvidos para avaliar o circuito industrial do projeto Morro do Pilar da Manabi que foi projetado para processar um itabirito com 30% de teor de ferro. Para buscar a máxima eficiência na recuperação de ferro a rota de processo desenvolvida prevê a flotação em duas estreitas faixas de tamanho: a faixa -0,15+0,044mm será processada em células mecânicas e a fração -0,044mm em colunas de flotação. Por se tratar de um minério de baixo teor, houve a necessidade de desenvolver um teste de bancada, preciso e robusto, para avaliar o desempenho do itabirito no circuito industrial projetado, composto por etapas de flotação rougher, cleaner, recleaner e scavenger. O teste em circuito fechado desenvolvido apresentou excelentes resultados, coerentes com o desempenho de testes piloto contínuos feitos com o mesmo itabirito pobre.

Aug 2, 2018

By Michael Kukay, Paul Conrad, Cosmas Opoku-Ware

This project is exploring the potential for developing trees tolerable to degraded un-reclaimed mine site soils and tailings as a solution to re-establishing long-term tree growth on those sites. The project incorporates growing tree seedlings in an underground greenhouse grown from seeds planted in the degraded mine soils in which they will eventually be planted. The outcome of the project is expected to lead to a successful solution for re-establishing tree growth in soils and tailings containing high metal concentrations with minimal post-planting human intervention. The research is being conducted in an underground greenhouse located 100 ft below the surface in the old Orphan Boy Mine Underground Mine Education Center (UMEC) located on Montana Tech’s campus in Butte, Montana.

By A. W. Asman

The problem of balanced design in a belt conveyor has been under constant study. Increased use of this method of transport in recent years has stimulated investigations. Conveyor belt, power transmission and other machinery should be adequate to perform the required service. All components of the belt conveyor should work as an efficient unit moving its load continuously between terminals. As part of a long term research project on belt conveyors, Hewitt-Robins established in 1954 a 2-year grant at Pennsylvania State University. Under terms of the grant, certain fundamental phenomena were to be studied. This work evolved a new concept in belt conveyor power determination based on the principle of belt tension. The Penn State contract furnished the foundation for later more detailed studies. From these most recent investigations, more specific factors were defined. In the final analysis, all of the data collected has been worthwhile in belt conveyor design. Units now operate over long distances at speeds of over 800 fpm. Long high lifts are commonplace. Where vertical or inclined shafts were the rule, belt conveyors receive first consideration. Although belt conveyors have moved forward rapidly, the future will see a tremendous gain in their use. The ideal test belt conveyor would be several thousand feet in length and have a maximum tension of at least 70,000 lb., Also, this conveyor should be horizontai and have a variable feed rate of more than one material. Data from such a field belt conveyor combined with laboratory information would permit accurate analysis. Since this type of conveyor was not available, many field locations were visited: An alternate would have been to erect a closed circuit system in the laboratory. Either method had limitations and the first was selected as having the best possibilities. Manufacturers of conveyor belting and machinery basically have been using the same horsepower formula. As more information became available from field installations, factors in the basic formula were modified. Practically all conveyors are designed today by adding together the horsepowers required to move the empty belt, move the load horizontally, and elevate the load. In selecting size of drive motor, the first two elements are relatively unimportant if the last is large. However, it is the combination of

Jan 1, 1961

By F. E. Harris

The United States produces about 30 percent of the world output of salt. Numerous deposits occur in widely separated areas, but the leading producing States are California, Kansas, Louisiana, Michigan, New York, Ohio, Texas, Utah, and West Virginia. Although no great amount of salt is produced at present in Pennsylvania, the potential sources in that State recently aroused a good deal of interest. The United States salt industry is highly organized; it comprises fewer companies than when small crude works with primitive methods and equipment eked out salt for local needs, but concentration of output brought about by modern inventions and methods of production has improved the quality of the produce greatly and accelerated production.

Jan 1, 1939

By T. J. Batchler

Deformable materials are sometimes added to ventilation stopping constructions to prevent damage caused by convergence in coal mines. However, adding deformable materials can significantly reduce the capacity of a stopping to resist transverse loading. As part of its mining health and safety program, the National Institute for Occupational Safety and Health (NIOSH) has conducted research on the effect of various materials with different deformation properties on the transverse loading capability of a stopping wall. Based on a three-point hinge method of failure, a half-wall method of testing in the NIOSH Mine Roof Simulator was used to simulate full-scale wall behavior. This simulated the fracture initiation and eventual failure of the stoppings from transverse loading. The impact of the modulus of elasticity of various deformable materials was examined in this study. A polystyrene foam block with a low modulus of elasticity, which is commonly used as a deformable material, was shown to degrade the transverse load capacity of the stopping by as much 95%. Other materials with higher modulus of elasticity preserved more of the transverse load capacity of the stopping, but were not able to absorb as much convergence. This paper presents the results of a parametric study that quantifies the impact of various deformable materials in block stopping construction under transverse load conditions. Disclaimer: The findings and conclusions in this report have not been formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy.

Jan 1, 2009

By J. Durkin

The Bureau of Mines has conducted field studies in coal mines throughout the United States to determine the effectiveness of electromagnetic techniques in locating miners trapped underground following a mine accident. Data from these tests have been used to generate models of expected signal and noise distributions as found above these mines. These distributions have aided in placing the expected performance of a through-the-earth electromagnetic communications technique into a probabilistic framework. Results show that at a 10% false-alarm rate, the expected probability o detecting a miner's signal" from a depth of 1000 ft is 54% at 500 ft it is 95%. These depths exceed the actual depths of 90 and 50%, respectively, of United States coal mines. Sensitivity studies have shown that at depth of 1000 ft, the probability of detection will improve approximately 2% for each dB of increase in signal-to-noise (SNR) ratio.

By R L. Brathwaite

The gold-scheelite-quartz lodes of the Wakamarina valley were the most productive of the mesothermal gold-bearing areas in the Marlborough Schist. Most of the production came from the Empire City and Golden Bar mines which worked the Golden Bar lode. Only 134 m of its 1800 m strike length are accessible, in the No.2 level of the Golden Bar Mine. A fault has downthrown the Golden Bar Mine section by = 47 m and displaced it left-laterally by 18 m. The lode is a typical ribbon-banded mesothermal vein, averaging c. 1.75 m wide, and enclosing narrow horses of schist country rock. It is composed of bands of milky æbuckÆ quartz with thin laminae of schist. Scheelite occurs in short strings of grains within quartz on the footwall side of the lode and also in small quartz-carbonate veinlets in the foot wall and hanging wall schist. The lode quartz contains only localised traces of pyrite and arsenopyrite. They are more abundant in the wall-rock schist.   The Golden Bar lode lies within a steeply dipping normal fault, which, on its footwall side, is adjacent to a 40 m-wide, shallow-dipping mylonite shear zone. Within 1 m of the lode, the shear foliation has been dragged down to nearly parallel the lode footwall. Wall rock alteration is manifested by a marked increase in K and Rb, which correlate with abundant illite/muscovite and K-feldspar within 2 m of the footwall of the lode. Amphibole, stilpnomelane, and pumpellyite show a progressive decrease towards the lode. As and Sb increase close to the lode, but are at background levels within the lode itself. Enhanced Cr (150-430 ppm) in the quartz, relative to the schists (~40 ppm), suggests that the source hydrothermal fluids passed through and leached mafic rocks, such as the metabasites from the hanging wall of the lode (~400 ppm Cr).

Jan 1, 1995

This publication contains 10 papers presented at a symposium on ATRS systems in Charleston, WV, on June 23, 1983. Included are papers by MSHA Technical Support (Roof Control), West Virginia Institute of Technology, the Bureau of Mines, and seven roof bolter manufacturers and/or designers of ATRS systems. These papers summarize the most recent developments in ATRS technology and can serve as a guide to potential designers, developers, and users of ATRS systems.

Jan 1, 1985

By H R. Phillips

During the 1980s and early 1990s, the South African coal industry experienced a series of methane explosions in which well over 200 coal miners lost their lives. In addition, a fire and an explosion in the gold mining sector claimed a further 240 lives. These tragic incidents resulted in the establishment of a research facility at Kloppersbos dedicated to explosion and fires research and the funding of an extensive research program, and almost certainly influenced the government of the day in its decision to establish, in 1993, the Leon Commission of Enquiry into Mine Health and Safety. The results of this focused research program, the wide-ranging recommendations of the Leon Commission and the determination of the coal mining industry to improve its safety record all combined to result in the past 20 years without a major explosion.This paper lists some of the research outcomes and, through three case studies, illustrates what can be learnt from investigations following explosions. The paper concludes with an evaluation of some of the findings of the Royal Commission on the Pike River coal tragedy. Many of the Commission’s conclusions are pertinent and relevant to the coal mining industry worldwide and their implementation could significantly improve coalmine safety; however, a careful study of the available facts indicates there could well be an alternative explanation of the source of the methane, the location of the ignition and the size of the explosion at the Pike River coalmine.CITATION:Phillips, H R, 2015. Lessons learnt from mine explosions, in Proceedings The Australian Mine Ventilation Conference, pp 19–28 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By Dippenaar R, Evans T

Twin-roll continuous casting technology is rapidly approaching commercialisation. Fundamentally different than conventional continuous casting, heat transfer and hence solidification during twin-roll casting are governed by the interfacial melt/mould thermal resistance, as opposed to the resistance of the solidifying shell. Under these conditions the interface resistance is predominantly controlled by the melt/substrate wetting behaviour. The very early stages of melt/mould contact are characterised by highly transient heat transfer conditions. The overall melt cooling rates prior to the formation of the first solid are reported to be in the range of 1000 - 50000 K/s with melt undercoolings of up to 300 K. At the points of intimate melt/mould contact the thermal resistance is approaching zero, where cooling rates and undercooling much larger than those reported in the literature are probably occurring. Improved wetting will reduce the energy barrier for nucleation while at the same time increasing the cooling rate of the liquid. Since the overall nucleation rate is controlled both by the rate of cluster formation and the rate of atom transfer to the nucleus, a critical cooling rate will exist above which the nucleation rate is expected to be reduced. Under these conditions, it is possible that the first solid phase to form is a metastable glass which subsequently transforms into a crystalline phase. The implications on nucleation and early growth are also discussed.

Jan 1, 1999

Pyrometallurgy has played a very important role in southern Africa for at least four centuries. It continues to do so, and recent years have seen many exciting developments in pyrometallurgical technology. The wonderfully diverse rich mineral deposits in this area of the world have provided some unique opportunities for industrial processes to be established. The ?Southern African Pyrometallurgy 2006? conference was set up to showcase southern African pyrometallurgical operations, and to provide a forum for the exchange of ideas between people working at various types of smelters. Papers have been obtained from a wide variety of pyrometallurgical plants in southern Africa. These descriptions of plant operations (as well as some history, and highlights of current work) will provide useful reference information for some time to come. Contributions are also included from universities, research organizations, and engineering companies, so that the full spectrum of pyrometallurgical activities can be covered. The plant descriptions will be published on a website, where they can be updated as and when required, with the eventual goal of having a description of every smelter in the region. The conference venue was selected to be the 'Cradle of Humankind' world heritage area, about 40 km from Johannesburg. Not only does this keep the conference within easy reach of the city and yet far enough out into the countryside to allow people to focus on the conference, it is also within easy reach of many pyrometallurgical plants. There is a particular significance to the choice of location, in that the Swartkrans area close to the Sterkfontein Caves is the site of the earliest evidence of the deliberate controlled use of fire by human beings (about 1.3 million years ago), and this is obviously a necessary precursor to pyrometallurgy. The area also lends itself to a very wide range of outdoor, social, and cultural activities to supplement the technical content of the programme. It is hoped that activities such as a hot air balloon safari and visits to the world-renowned Sterkfontein Caves and Wonder Cave will help to make the conference a memorable one for those able to attend. I trust that the ongoing value of the papers and presentations will make all the hard work of the many contributors most worthwhile.

Jan 1, 2006

By Oliver C. Ralston

[This paper is an expmded revision of a report entitled "Froth Flota- tion and Agglomerate Tabling of Honmetdlic Idinerds, " published in Trans- actions of the Canadian Ir-stitute of Iriining and !,letdlurgy (vol. 40, November 1937, pp- 6? 1-726) and al'enared a year pr~viousl:~. Revisions en'oodied herein brinc the &ta I:T to Jn?uac"g 1, 193;. References have also been added to make the earlier paper more complete for the period it covered. This paper is an expmded revision of a report entitled "Froth Flota- tion and Agglomerate Tabling of Honmetdlic Idinerds, " published in Trans- actions of the Canadian Ir-stitute of Iriining and !,letdlurgy (vol. 40, November 1937, pp- 6? 1-726) and al'enared a year pr~viousl:~. Revisions en'oodied herein brinc the &ta I:T to Jn?uac"g 1, 193;. References have also been added to make the earlier paper more complete for the period it covered.]

Jan 1, 1938