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By Miguel Angel Banuet Rodriquez, Hector Conceso Aragon

"Construction of the longest road tunnel in Mexico is part of Acapulco’s alternate roadway to the scenic roadway project. This article provides a brief summary regarding details of the construction since the project began. Work was done by skilled engineers and Mexican workers that includes outstanding execution of the work in an urban and tourist area. This project will have a strong impact on the steady development of the port of Acapulco.Project locationAcapulco’s Alternate Roadway Project is currently under construction in the city of Acapulco, located in the Guerrero state of Mexico. It is an 8-km (5-mile) long roadway that starts at the Icacos neighborhood, heading toward Acapulco’s airport, crossing a drill-and-blast tunnel that is 3,160 m (10,350 ft) long under Veladero Park, a mountainous area. The tunnel overburden reaches a depth of 380 m (1,250 ft) approximately at the central point of the horizontal alignment, and continues with a 4-km (2.5-mile) long elevated road to connect to the existing Viaducto Diamante toll road (Fig. 1).Tunnel construction has already been finished using two portals for drilling and blasting operations; Brisamar Portal on the west side and Cayaco Portal on the east side (Fig. 2).Geometric dataOnly two main excavation cross-sections were considered in the executive design. The first one corresponds to the running tunnel for a three-lane vehicle section, with crosssection areas between 120 and 130 m2 (1,290 and 1,400 sq ft) taking into consideration different geological and geotechnical conditions to be encountered (Fig. 3).The second one corresponds to eight emergency bays, each one 50 m (164 ft) long, laid down within the tunnel outline, located at 400 m (1,312 ft) from each one with excavation cross-sections between 156 to 169 m2 (1,680 to 1,820 sq ft), in accordance to geological and geotechnical conditions to be encountered (Fig. 4).The tunnel’s horizontal alignment is completely straight, having a small curve within the vertical alignment on Cayaco portal, because there were some differences in levels when tunnel excavation started. Tunnel slopes were designed in such a way that rainwater does not run down into the tunnel at any time."

Jan 3, 2018

By M. R. Moon

The mine fire at Wilberg Mine in 1984 reached the surface resulting in the failure of the vertical ledge forming the roof and entrance for three main intake portals. The fallen material was covered with a concrete cap to seal the air from the mine. As the mine was recovered and ventilation pressure was placed on seals on the perimeter of the fire area, the concrete capped rubble proved ineffective. Due to the steep and rugged terrain and the inaccessibility to the portals from underground, horizontal holes were drilled into the portal entries and three seals were placed remotely. The seals in conjunction with pressure balancing the seals around the perimeter of the fire area resulted -in the control of the mine fire.

Jan 1, 1993

By V. Aghazadeh, E. Bidari, M. Aazami

In this study, mineralogical and microanalysis characterization, as well as diagnostic leaching and cyanidation tests, were performed to gain a better understanding of the refractory nature of the arsenical zone of a Carlin-type gold deposit and also to evaluate possible treatment routes to maximize gold recovery. The results obtained showed that only 56% of the ore’s gold content is amenable to direct cyanidation. The majority of the remaining gold was found as submicroscopic gold and in association with sulfide minerals, such as orpiment, pyrite, and sphalerite. It was also found that despite the abundance of silicate and carbonate minerals in the arsenical zone, they do not play a key role in the refractory nature of the ore, and gold can be liberated from such minerals by appropriate grinding. The analyses further revealed that orpiment dissolves readily during cyanidation, and this dissolution retards the kinetics of gold extraction. Pyrite and sphalerite were generally found to occur in fine network texture and in association with quartz. Flotation of such auriferous sulfides may be difficult due to their oxidized surface. Fine grinding (−20 μm) was found to be partially effective in improving gold extraction.

May 28, 2020

By R. K. Mehta

This paper presents the application of a simple genetic algorithm (SGA) to a coal slurry grinding process in order to find the optimum set of conditions under which the desired slurry properties can be attained. The operating parameters of the process were; slurry % solids, dispersant dosage, ball size, and mill speed. The optimization algorithm, which is based upon the mechanics of natural genetics, was used to find near-global optimum points specific to responses measured In terms of fineness, specific energy consumption, viscosity coefficient, and viscosity exponent. In order to minimize the viscosity of the slurry and simultaneously achieve a condition of maximum packing density, optimization was carried out by the penalty method using an overall objective function incorporating several responses. Computer results and analysis demonstrate the ability of the genetic algorithm to perform better than a traditional technique such as response surface methodology (RSM) and to rapidly locate "the global optimum".

Jan 1, 1992

By Juan J. Monsalve, AMAN SONI, ALEX PFREUNDSCHUH, Nino Ripepi

Ground control failures are one of the main causes of accidents in the underground stone mining industry. Some of the fundamental tools for rockfall hazard identification are related to rock mass characterization and geotechnical discontinuity mapping. Recent technological advances in these methods are related to remote sensing techniques and point cloud processing software for automated discontinuity mapping. Remote sensing techniques, such as LiDAR and photogrammetry, generate multimillion point clouds with millimetric precision, capturing the structure of the rock mass. The automated point cloud processing tools offer alternative algorithm-based methods to characterize and map these discontinuities. However, their applicability is constrained by multiple factors such as site specific conditions of the rock mass and the parameters used within the mapping algorithms. This paper evaluates the performance of automated discontinuity extraction software compared with manual virtual discontinuity mapping. Sampling windows from laser-scanned sections in an underground limestone mine are defined and mapped using discontinuity set extractor (DSE). Results from the virtual discontinuity software are compared with manually extracted fractures from I-Site based on reviewing orientation, trace length, spacing, number of extracted discontinuities, and processing time. The analysis determined that the automated mapping algorithm was able to identify the same discontinuity sets that had been manually mapped. The automated mapping software mapped an excessive amount of smaller fractures, which caused the comparison of both mapping techniques to be unsuccessful in terms of trace length and spacing.

Mar 19, 2021

By P. James

"INTRODUCTION Control of target stream pH is very important in leach mining and treatment of MIW (mining influenced water). On the production side, solution acidity can impact SX (solvent extraction) effectiveness through PLS (pregnant leach solution) and raffinate pH. Many older operations and legacy mining sites generate ARD (acid rock drainage) that is too weak for profitable metal production by conventional means and faces costly wastewater treatment for mitigation and disposal. For wastewater and environmental treatment, neutralization to precipitate and remove metal contaminants to clean the wastewater is the dominant approach. Traditional lime neutralization and precipitation is most often used but results in large amounts of mixed metal sludge requiring costly disposal. Blue Planet Strategies (BPS); which focuses on improved resource utilization targeting electrolytic treatment and waste conversion into resources, has developed a new “reagentless” neutralization process. Electricity is utilized in its proprietary DEMET™ (Dynamic Electrolytic Metal Effluent Treatment) platform capability to controllably raise target stream pH. The method offers a simple, low-cost approach yielding cleaner treatment chemistry. It can result in less sludge generation and enables possibilities to selectively recover contaminants as potentially saleable products for new revenue generation to offset further offset treatment costs. DEMET Overview BPS’s patented electrolytic DEMET platform leverages solid scientific and chemistry foundations through its advanced design to achieve capabilities and performance not previously realized. DEMET technology combines separated compartment electrolytic cell functionality with proprietary advanced dynamic electrodes and cell configurations to achieve a variety of chemistries and processing targets.[1-6] DEMET‘s unique elements can yield higher processing rates at practical efficiencies, lower energy consumption, plus improved processing stability and lower maintenance requirements due to enhanced resistance to cell fouling and shorting; while also thwarting cross stream (catholyte vs. anolyte) contamination. Consequently, DEMET can provide a superior, extremely versatile, and more cost-effective electrolytic treatment option where a multitude of FEED and PRODUCT stream combinations might be employed in comparison to traditional tankhouse electrolytic cells."

Jan 1, 2015

By I. Raposo, I. Moreno-Ventas, A. Palma, M. J. Díaz, M. Vázquez

The oxidative degradation kinetics of chalcopyrite have been studied by thermogravimetric analysis (TGA). The obtained data are necessary for the kinetic description of the flash fusion process, which can contribute to the optimization of the smelting process in copper extractive metallurgy. Activation energy (Ea) evolutions of the involved processes have been determined by several isoconversional methods; in this sense, the chalcopyrite oxidation processes could be adequately described, among studied models (E1641–16, Ozawa–Flynn–Wall, Kissinger–Akahira–Sunose and Friedman), by the Kissinger–Akahira– Sunose kinetic model. Using this method, Ea and A values are found to be very dependent on the conversion. Under lower conversion levels, higher Ea and A values have been calculated with respect to that found for medium and higher conversion levels.

By T. C. Murray

An automatic control system was recently installed to insure the continuity of operation between the ship docking and ore handling facilities and the computerized conveyor-fed sintering plants and blast furnaces. Although the basic concept for material handling has not changed, many innovations including computer control have been implemented.

Jan 1, 1978

By David R. Delling

Introduction In 1967, Tenneco acquired Kern County Land Co. The primary reason for the acquisition was to obtain Kern's agricultural, manufacturing, and oil interests. Included in the Kern portfolio were the core of Tenneco's present sodium leases in Sweetwater County, WY. This lease base has been ex¬panded and now consists of 62 km2 (24 sq miles). Beneath this property lies more than 500 Mt (550 million st) of economic trona ore. Following the Kern acquisition, Tenneco continued exploration and feasibility studies concerning the trona leases. The effort was accelerated in 1976. Tenneco was attracted to trona because of the favorable lease position it held, the growth rate of the Wyoming industry during the 1960s and 1970s, and the prospects for a long-term, stable business enterprise. The reserve picture was certainly attractive to a company long accustomed to the never-ending struggle to replace oil and gas reserves. In 1978, Wyoming was a boom area that had experienced rapid growth for a number of years. Unemployment was very low and vacant housing nonexistent. The prospects for soda ash were somewhat different in the 1970s than now. But it was recognized even then that a new producer would have a challenging task to compete in this business. Tenneco knew the capital burden required to build a grassroots facility during inflationary time, would have to be offset elsewhere Since labor and energy are the dominant direct costs in mining trona and producing soda ash these factors have always received a great deal of attention. Contracting and permits Environmental monitoring on the site began in late 1977. With the already mentioned considerations in mind, engineering began by mid-1978. Brown & Root Inc. was selected as the general contractor for the project. S. A. Scott & Co. was the engineering subcontractor for the mine shafts, hoists, ventilation system, and miscellaneous mine facilities. Frontier-Kemper was awarded the contract for sinking the two mine shafts. Acquisition of numerous federal, state, and local permits occupied all of 1978 and 1979. The Wyoming Industrial Siting Permit, which addresses socioeconomic issues, drew the most public interest. Siting issues were all satisfactorily resolved by negotiating reasonable stipulations with various local governmental units, school districts, and the like. Site location The Green River project location is not truly remote. It is located within 5 km (3 miles) of Interstate 80 and only about 32 km (20 miles) west of the city of Green River. Nevertheless, a substantial investment had to be made in communication and utility links to the site. These included: • A 14-km (8.5-mile) rail spur connecting with the Union Pacific Railroad at Bryan, WY. This spur has four bridge structures including one crossing Interstate 80. Most soda ash is shipped by rail, and coal is received over this line as well. • A paved 5-km (3-mile) roadway connecting to Interstate 80. • A powerline extension of about 27 km (16.5 miles), along with two new substations. • A 24-km (15-mile) waterline connecting the plant to a pump station on the Green River. The site is located on gently sloping terrain at an elevation of about 2.1 km (6800 ft). Ground conditions are good for construction. Weathered bedrock lies near the surface in most places. Geology The general geology of the Green River Basin has been well described previously. Tenneco's ore is in several superimposed evaporate beds. But the bulk of it is present in Bed 17, located about 457 m

Jan 10, 1985

By J. F. Colinet, W. R. Reed, J. D. Potts

Dust surveys were conducted at six underground coal mines to determine if deep-cutting practices expose face workers to higher levels of respirable dust. The surveyed mines were able to successfully mine deep cuts without significantly increasing the dust exposures of face workers. In general, all of the selected mines exercised good dust control practices by maintaining water sprays, scrubber airflows, proper curtain setback distances and providing sufficient airflow to the active faces. For exhausting face ventilation, field data indicate that scrubber airflow is the most important factor for controlling dust. Data collected for this study indicate that 20-mesh screens should be cleaned for every 12.2 m (40 ft) of advance, because 22% of the deep cuts surveyed for this study experienced a 20% to 35% decrease in scrubber airflow over the course of the cut. For blowing face ventilation, field data and past research indicate that dust control is aided by maintaining a proper curtain-to-scrubber airflow ratio of 1.0 (measured before scrubber activation), as well as a curtain setback distance that allows the miner operator to stand at the mouth of the curtain for the entire cut. Dust levels on the bolting faces did not appear to be affected by the longer cycles associated with deep-cut mining when good ventilation practices were used.

Jan 1, 2011

By G. Robson

"From monitoring gas levels and air quality in coal mines to protection from collisions for large vehicles at mine sites, SICK offers a wide range of sensors and systems to improve safety and to monitor potentially dangerous situations. SICK offers solutions for the analysis and monitoring of underground coal mining atmospheres. These systems supply the coal mine operator valuable safety and ventilation information, as well as data which identify and monitors atmospheres of those production areas within the mine which may or may not be worked, such as Goafs and sealed areas. Underground coal mines contain dangerous gases, which must be monitored and controlled in order to allow productive mining operations to take place and to minimize the risk of explosion. Underground mines are a potentially dangerous place for mine workers. These are the main reasons for using Tube bundle systems SICK has had great success in selling these systems into the Australian and New Zealand Markets and this is helped by the strong drive for mine safety from both the Mine Owners and the Regulatory bodies charged with the responsibility of ensuring Mine Regulations are met. The Australian mining industry uses Tube Bundle Systems at almost all underground sites, even after mining has ceases and the mine is placed in care and maintenance. Sick has been working in international markets for some time now but has had limited success in selling Tube bundle Systems to these markets. However in recent times there has been raised interest in Tube Bundle from China, India and Turkey as these countries strive to improve mine productivity and lessen the risk of explosion or Spontaneous Combustion. Our lack of penetration into International Coal markets has been very much based on the perceived cost of the system, not the benefits to safety and productivity. Unless a mine has had an event such as spon com or a Methane explosion they rarely consider the very low level measurement capability (20 PPM CO & 100 PPM CH4) or the long term trending benefits of the Tube Bundle system. It is only after a catastrophic event the System is considered. Real Time or electrochemical Sensors are commonly used to monitor the Mine Atmosphere, the real problems of methane build up or potential Spon Com in Goafs and sealed areas cannot be monitored using Real Time Sensors as the electrochemical cell deteriorates after approx. 12 months and in sealed areas these cells cannot be maintained or replaced. Whilst the Technique of Tube Bundle Systems is quite old SICK have spent many years redesigning the Tube Bundle System into a cost effective and real value for money product. The system uses state of the art sampling and highly accurate Infra-Red wide Spectrum Analysers."

Jan 1, 2016

By AMIT SHARMA, BIBHUTI BHUSAN MANDAL

Operators of mining vehicles are exposed to high levels of whole-body vibration (WBV) and are therefore at risk of developing vibration-related health disorders. For implementing an effective control strategy, it is imperative to locate the source(s) of vibration, and the specific changes that might occur to the vibration signals during its transmission through the seats to the recipient human body. With this objective, Seat Effective Amplitude Transmissibility (SEAT) values of seat modules used in dumpers (n = 10) and other heavy earth-moving machines (n = 11) were evaluated in an iron ore mine. Vibration was measured simultaneously on the seat and on the cabin floor beneath the seat using tri-axial and uni-axial accelerometers. The study aims at determining the quality of seat modules of the transport and non-transport vehicles from the perspective of their natural resonance frequencies and capability of any such seat in reducing harmful vibration. The highest acceleration values were observed in the z-axis for all the dumpers. SEATrms values ranged from 78 to 133% and SEATvdv values ranged from 72 to 130% for the dumpers. For other HEMMs, SEATrms values ranged from 55 to 125% and SEATvdv values ranged from 56 to 123%. Mechanical vibration contains multiple frequency components. To understand the changes taking place to the different signals at these frequencies, 1/3 octave band analysis was carried out for the signals recorded both on the seat and the floor. There was significant attenuation (38 to 57%) at 4 Hz for three Dumper seats, whereas they resonated in the range of 1.6–2.5 Hz. The transmissibility(%) in the resonating frequencies ranged from 108 to 156%. Resonance frequencies for the remaining seven dumpers ranged from 3 to 8 Hz. The spine has been reported to resonate at 4 Hz, whereas resonance at 1.6 Hz has little significance to human beings in regard to WBV of a seated person. Hence, the characteristic resonant frequency of 4 Hz of seats as observed in the present study has the potential of causing adverse impacts on spinal health. Evaluation of SEAT factors and resonance characteristics of seats are therefore recommended to be examined while selecting a mining vehicle for regular deployment in mines.

Mar 12, 2021

By Yi Luo, Jian Yang

Subsurface strata movements and deformations associated with longwall mining operations in underground coal mines could cause various disturbances to subsurface mine structures, ground water bodies, and coalbed methane reservoirs. In order to assess those disturbances correctly and to design effective and efficient mitigation measures, it is necessary to develop an accurate prediction model for subsurface strata movements and deformations. Decades of research have demonstrated that variations of stratification and lithology in the overburden have significant influence on the subsurface strata movements and deformations during ground subsidence process. The key strata theory states that the thick and hard key strata serve as the backbone of the overburden and control the movements of the thin and soft weak strata located above them. From an engineering standpoint, the overburden strata are subdivided into several individual groups by the key strata with each group consisting of a key layer at the bottom and weak layers overlying it. A new subsurface subsidence prediction model considering the key strata effects on subsurface strata movements and deformations has been proposed. In this method, elastic modulus, specific weight, tensile strength, and uniaxial compressive strength (UCS) of each layer are used to identify the key layers and to determine the needed subsurface subsidence parameters. The influence function method, proven to be accurate and versatile for surface subsidence prediction, was employed to predict the subsidence on each of the overburden layers from mining horizon progressively upward to ground surface with the assumption that the predicted subsidence on a given layer serves as the subsidence source for the layer immediately above. The enhanced subsurface subsidence prediction model has been demonstrated with an actual case to show its applicability and improvement.

Jan 25, 2021

By Subhas G. Malghan

Feldspathic deposits occur widely throughout the United States, but North Carolina, California, Connecticut and South Carolina accounted for over 80% of the total domestic feldspar output for the year 1973.1 Pegmatites and granites constitute the major feldspar reserves of the United States,2 and in addition, feldspar is produced as a by-product by firms whose major products are spodumene and mica.3 Feldspar is concentrated by hand-cobbing and flotation; the latter forms the major method of separating and concentrating feldspar. Feldspar flotation is practiced in the United States, Mexico, Finland, Norway, West Germany, Japan and the USSR. According to the U. S. Bureau of Mines estimates, the production of feldspar in the United States and rest of the world were 704,000 tons and 2,514,000 tons respectively. Feldspar is principally used as a flux in making glass, pottery, porcelain, enamel,-tile and other ceramic products. In recent years, the domestic feldspar industry is faced with a number of problems. As a result of increased cost of energy and the introduction in 1972 of new legislative programs relating to air, water, and noise pollution, land-use restrictions, and mined-land rehabilitation, the production costs have increased. Apart from the increased cost of operation, an operational problem exists with the feldspar producers in North Carolina, especially those in the Spruce Pine area. This problem is concerned with the use of hydrofluoric acid in the feldspar flotation. Feldspar producers in Spruce Pine, North Carolina have been discharging process waste water into the North Toe River. The mill waste water contains active fluoride ions. Fluoride in excessive concentrations is undesirable in waters used for drinking. It is stated that water

Jan 1, 1976

By J. A. Botín

Investment decision for large mining projects imply an enormous financial risk and therefore, require a more complex risk evaluation methodology taking into account all sources of uncertainty from each process in the project value chain. Generally, the main sources of risk are those related to uncertainty on grade and other techical variables of the orebody. In this study, conditional simulation is applied to develop a risk management model to quantify and to manage financial risk associated to uncertainty on the grade of the orebody. The model was validated in case study on a real porphyry copper orebody in Chile.

Feb 23, 2014

By M. S. Frasad

The State of Minnesota is interested in stimulating the development of clay resources and recently supported a two year project to collect data on geological, mineralogical, processing, economic and environmental aspects of such potential developments. This paper presents the .various process options adopted on the bulk samples collected from the Minnesota River Valley area which is a primary deposit and contains a major silica fraction. A standard test flowsheet involving degritting, dispersion, HGMS, and cycloning was developed and for some samples yielded an acceptable filler grade product. Secondary streams containing relatively high grade kaolin but of coarse size were also obtained. Improvement in particle size distribution and in physical properties related to paper product specifications (brightness, viscosity) were obtained by size reduction processes. Market and economic considerations for kaolin consumption in the upper Midwest are analyzed. Current markets for paper grade kaolin in Minnesota were briefly discussed.

Jan 1, 1990

By L. Wilfley, G. A. Calboreanu

"Wear resistant 25% Cr hard cast iron is a heterogeneous material containing 1,600 HV hard chromium carbides embedded into martensitic matrix. It is the most used cast alloy in wear operations of mining industry, chemical industry, fracking, etc. During the last decade the hard iron manufacturers increased wear resistance in the following ways: • Reduce / eliminate harmful retained austenite and chromium + carbon depleted areas especially within eutectic carbide cells. In Max5A the improved 25% Cr alloy brittle carbide eutectic cells are removed which increases toughness. • Delay delamination between chromium carbides and matrix particularly during sliding abrasion wear. Delamination commences at the weakest chromium carbide – matrix contact lines exposing chromium carbide to localized bending stresses which gradually chip carbides away. Once the chromium carbide base is removed accelerated wear degradation occurs. • Evenly randomize and avoid discontinuities in the chromium carbide network. When chromium carbides are perpendicularly positioned to the wear surface wear rate is minimized. On the contrary the highest wear rate takes place when 3D oriented chromium carbides are parallel with the wear surface. In this case chromium carbides cover top network discontinuities being just matrix supported which leads to rapid carbide cracking. The new hard iron discussed in this paper fulfils and exceeds the above requirements increasing the casting service life around 250% in various wear operations. Physical and mechanical properties of Max5A are compared with well manufactured Industry Standard 25% Cr hard iron. The paper presents practical accomplishments obtained in the USA, South America and India. INTRODUCTION The chemical composition of Max5A and Industry Standard 25% Cr are identical like specified by ASTM A532 Class III Type A requesting C = 2.0-3.3% and Cr = 23.0-30.0%. Manganese, silicon, nickel, molybdenum and copper contents are limited by maximum accepted quantities.[1] According to published data the eutectic chromium carbides chemical composition of 25% Cr hard iron is Cr = 54% and C = 8% which indicates strong depletion of chromium and carbon along chromium carbide - matrix interfaces. [2] The optimized Max5A microstructure has minimized retained austenite, is devoid of harmful carbide eutectic cells and has the most advantageous chromium carbide and secondary chromium carbide morphology. This favorable microstructure increases wear resistance, mechanical properties and corrosion resistance. The paper compares the Max5A microscopic features and mechanical – physical properties with similar properties of high quality Industry Standard 25% Cr."

Jan 1, 2017

By G. H. K. Pearse

Long range transport of pollutants, particularly of sulphur dioxide and the associated acidic precipitation, has received much attention in the press and in international discussion during the last few years. Studies revealing increasing acidity of lakes and the dying out of fish populations over broad regions of the eastern half of North America have created alarm. In this paper, I will not attempt a description of the acid rain phenomenon. For this r recommend the balanced treatment of the subject by Gene Likens et al (1979) in Scientific Americana For my purposes I accept that the problem is serious and direct my attention to exploring a solution. Ultimately, the key lies in the answer to the question; "What do we do with the enormous tonnages of pollution abatement byproducts, chiefly sulphur compounds, that would arise from pollution control?"' Little thought has been given to this most limiting factor to environmental clean-up. This is symptomatic of a basic flaw in the [philosphy] that under-ins environmental policy. Although this paper is to propose a solution to the abatement byproduct problem, the basic flaw - the firmly entrenched, universally adopted, 'polluter pays [philosphy] as it is currently [understood] - needs some comment.

Jan 1, 1981

By O. M. Arafat, J. A. Finch

"The Functional Performance Equation calculated from a plant grinding survey defines two distinct ball mill circuit efficiencies and how they relate to total production rate through the target grind size. The survey data are also used to calculate a complete ball mill size distribution model, represented by the energy specific grinding rates, not just through the target grind size, but through all the size classes. Cyclone separation performance is represented by individual size recoveries to underflow. When these two unit operation performances are entered into the circuit modelling program (Streamline™), along with the circuit feed rate and size distribution, all the circuit survey size distributions and mass flows are perfectly regenerated by the program. The many issues associated with the historical Epstein (breakage-selection) models are eliminated. Once the circuit program is populated, pump and cyclone performance changes can be evaluated using a step-by-step procedure in order to maximize Classification System Efficiency. Mill water use and media sizing opportunities are also diagnosed in order to maximize Mill Grinding Efficiency at the size of interest. An example is provided. This circuit analysis and modelling system, and related training, is provided through a web-based application. INTRODUCTION Since its development (McIvor, 1988), the Functional Performance Equation for ball milling has facilitated new understanding of industrial circuit cause and effect relationships, leading to significant strides in operational performance. Success stories of this refreshing approach to plant circuit performance improvement are now too numerous to list. Finch and McIvor (circa 1986) also discovered that the Functional Performance “Mill Grinding Rate” at the size of interest was the same cumulative grinding rate that is calculated from mill feed and discharge size distributions using a first-order rate equation. By calculating these cumulative grinding rates for all screen sizes, a complete ball mill model is generated (as used by Finch and Ramirez, 1981). Others in industry, Hinde and Kalala (2009), for example, have noted the same. Lacking the complexity needed to maintain their interest, most researchers have ignored this model, broadly opting instead for Epstein’s (1948) characterization of grinding as a chemical reaction, combining “selection rate” and “breakage size distribution” functions. The much simpler ball mill model presented here has previously been incorporated into a proprietary circuit modeling program (McIvor, 2005) and used for plant improvement work (for example, see McIvor and Finch, 2007, and McIvor, 2014). Now, by combining this extremely business-friendly ball mill model with optimization criteria from Functional Performance Analysis, a circuit modeling system (including the needed supplementary steps to assure successful plant implementation of circuit design changes) is at the disposal of every plant metallurgist, grinding equipment/material provider, and circuit designer."

Jan 1, 2017

By P. E. Wingrove

The Kayford, Boone and Nicholas Division of Bethlehem Mines Corporation operates a modern coal preparation plant in Van, West Virginia. Since the start-up of the Van Plant in 1976 until the summer of 1980, the refuse handling system proved to be a costly maintenance problem and a material handling bottleneck. During the 1980 two-week miner's vacation the original system, which included two screw conveyors and a drag conveyor, was replaced by an installation utilizing two Flexowall steep angle belt conveyors. This paper describes the technical and economic analysis that led to the new installation and reviews its first year operating performance. The Van facility is a heavy media plant designed to handle 127 mm x 0 raw metallurgical quality coal from the Powellton seam at a maximum feed rate of 590 TPH (metric tons per hour). Depending on mining conditions, the clean coal recovery rate averages between 50 and 65%. The plant is set up with three types of cleaning circuits. Coarse material (127 mm x 12 mm) is cleaned in heavy media baths. Intermediate size material (12 mm x .5 mm) is cleaned in heavy media cyclones. Fine coal (.5 mm x 0) is cleaned in a hydrocyclone1 froth flotation circuit.

Jan 1, 1981