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By Al. Valero, A. Domínguez

This paper appraises the energy requirements for mineral production through an exergy approach taking into account the long-term decline in ore grades. In this context, the exergy required for restoring resources from the dispersed state of the so called Crepuscular Earth into the physical and chemical conditions in which it was delivered by the ecosystems in light of the available technology, is known as exergy cost. The exergy cost is the point of reference in order to evaluate in a single variable, characteristics such as composition, concentration (ore grade) and the state of technology. The ratio between the exergy cost and the minimum thermodynamic cost required to accomplish the same process is called unit exergy cost and provides a measure of the irreversibility of the analyzed processes. Otherwise, the ore grade is one of the main issues which affects directly the costs associated with mining the ore. Hence, the unit exergy costs to produce minerals from progressively lower ores grades by the current technology is analyzed. The unit exergy cost curves are presented for some important minerals such as aluminium, chromium, cobalt, copper, gold, lead, manganese, nickel and zinc, in order to know the trend when the ore grade decreases.

Jan 1, 2011

By Bjørn Nilsen

"INTRODUCTION/BACKGROUND Weakness zones or faults containing clay-rich gouge represent one of the most challenging rock mass conditions to be encountered during tunneling. In Norway, such conditions count for a large part of the rock support costs, and in cases where the rock support has been insufficient, serious instability and cave-in have in many cases been the result. Most commonly, such cave-in has occurred after water filling of hydropower tunnels, but in some cases it has also occurred in tunnels under excavation and in completed “dry” tunnels. To avoid instability, two important requirements have to be fulfilled: 1) The location of the weakness zone and its character have to be identified in time. 2) The rock support has to be sufficient to withstand the loading caused by the zone. An incident which really brought the problems related to swelling clay into focus was the cave-in at the Hanekleiv road tunnel in 2006. Here, rock fall from the roof as shown in Figure 1 occurred unexpectedly about 10 years after the tunnel was completed. Fortunately this happened at a time with very little traffic, and nobody was injured. This incident emphasized the significance of the issue of swelling clay, although it was found to be caused also by gravitational collapse of the clay-rich gouge material of the weakness zone, and not related to swelling only (Nilsen et al. 2007).In this paper, main focus will be on discussing the characteristic features of swelling clay, test procedures which are being used for characterizing swelling clay, and the reliability of the results from testing for use in support evaluation and design in conditions with swelling clay. It is generally well known that swelling clay may cause considerable pressure on support elements, but quantifying this pressure for reliable analysis and design of rock support is still a great challenge."

Jan 1, 2016

By Wallace N. Thomas

The present interest in large diameter grinding mills and the rapidly rising cost of the drive in proportion to the cost of the mill establishes a need to explore the drive system in detail. The drive for a seven to eight thousand horsepower mill will cost from 1350 thousand to $600 thousand which represents nearly half the total cost of the mill package, and requires as much building space as the mill proper. Some of the drive components require a longer time to manufacture and the installation time and costs are equal to those for the mill. It is apparent that the drive has become a dominant factor in the overall mill design consideration. A new plant requires a tremendous investment in both time and money. With the high degree of competition in the mining industry, low capital cost is an exceedingly important factor in the development of a project. It is just as important, however, to insure that the equipment is going to perform satisfactorily for the anticipated life of the project without adding unplanned operating, maintenance and replacement costs. This is the position in which the engineer or designer usually finds himself and is really one of his primary functions -- establishing a realistic compromise between cost and performance.

Jan 1, 1969

By Nikhil Dhawan, SHAILA MIR

Consumer preference for ever-higher laptop performance coupled with laptops’ declining lifespans make them a significant contributor to electronic waste. An in-depth evaluation of elemental composition and distribution is important for determining metal recovery potential and sustainable recovery processes. In this work, the characterization of individual components of laptops is studied for the systematic identification of important elements and for streamlined and structured recycling, to reduce processing steps and improve economics. A process flowsheet highlighting various recycling routes by targeting metals and various components is also proposed.

By S. K. Kawatra, V. Claremboux, S. Valluri

Carbon dioxide capture from coal-fired power plant flue gas and subsequent sequestration is expected to play a vital role in mitigating global climate change. To meet the growing need for CO2 capture Technology, Michigan Technological University is researching CO2 capture and Utilization. We have successfully converted CO2 into oxalic acid using an electrochemical approach. If oxalic acid can be produced in bulk from CO2, it can be used to leach rare earth minerals at low cost. Electrochemical reduction of CO2 to hydrocarbons and other chemicals is a complex multistep reaction with adsorbed intermediates. The exact reaction mechanisms leading to various products are not clear from the literature to date and will likely change over the range of conditions like pH, electrode potential, electrolyte medium, catalyst, etc. In this paper, we will present an idea of how the factors mentioned above will effect the electrochemical reduction of CO2 to Oxalic acid. INTRODUCTION. CO2 is thermodynamically quite stable, as shown by its highly negative heat of formation. Thus, it is expected that the formation of any useful chemical from CO2 will require the input of at least as much energy as geological sequestration. However, to be more effective the resulting economic value of the chemical need only pass the cost of the additional energy required beyond geological sequestration. This lends itself to two extremes: one where the quantity of energy required is low and one where the economic value of the additional energy is low. It is expected that CO2 can be reduced via electrolysis to several compounds. Of particular interest are formic acid, oxalic acid, methanol, ethanol, formaldehyde, and carbon monoxide (as a component to syn-gas). These chemicals have been reported as electrolytic products previously in literature and have considerable potential for application. EXPERIMENTAL Electrocatalytic Production of Oxalate from CO2 We are using membrane electrolysis cell to produce oxalate from CO2. A membrane electrolysis cell is a 2-chamber electrolysis cell where the chambers are separated by a selectively permeable membrane. To produce oxalate, a cation exchange membrane (which selectively exchanges cations) was used. Previous literature suggests that in the cathode chamber an organic electrolyte, such as tetraethylammonium perchlorate or tetraethylammonium bromide in dimethylformamide, are preferred3. In the anode chamber, a sodium hydroxide solution water is used. Carbon dioxide is then bubbled into the cathode chamber as a current is applied.

Jan 1, 2019

By F. Milton Lewis

In this paper an attempt has been made to review the cost trends in producing copper by conventional milling. smelting and hydro-metallurgical means during the last five years. The primary objectives of this cost analysis are to provide a base for future projections as well as to indicate which cost items are more volatile in their influence on overall cost of producing copper.

Jan 1, 1977

By Allan Breitenbach

Leaching has been used since the 1600s on unlined ore dumps and since the late 1970s on lined leach pads for the recovery of metals from mined ore, the latter typically called ?heap? leaching and the former ?dump? leaching. Modern day run-of-mine (ROM) or crushed ore heaps are stacked in controlled lifts on lined leach pads and irrigated with a solvent solution (dilute alkaline cyanide for precious meals, dilute sulfuric acid for base metals and uranium). Conventional lined leach pads store process solutions and any storm water, snow melt and cumulative wet season surplus water by gravity flow to external ponds. Impounding valley leach pads (also known as valley fill heaps) differ from conventional leach pads by storing various combinations of process liquid solution and surplus water within internal ponds by using the interstitial pore volume of the ore. While impounding liquids within the heap is simple in concept, impounding leach pads are more complicated for construction and containment compared to conventional leach pads with external ponds.

Jan 1, 2012

By F. Letowski

A column reactor was applied for leaching with simultaneous flotation a complex sulfide ore in ferric sulfate-solution under oxygen pressure. Elemental sulfur and the flotable, nonreacted sulfides were collected in the froth and separated from the insoluble, nonflotable gangue minerals and solid particles formed during pressure leaching. The two-stage laboratory unit, built from Corning-glass elements is described. Results of the continuous leaching/flotation experiments conducted under 20-40 psig of oxygen pressure are presented, as are supplementary batch leaching experiments with iron precipitation under 150 psig oxygen pressure. High zinc extraction to solution and near total accumulation of lead sulfate in the nonflotable fraction are easily attainable. Relatively poor flotation of pyrite is probably caused by the partial oxidation of its sulfidic sulfur to sulfate.

Jan 1, 1988

By W. C. Morgan

This paper discusses some of the problems involved in predicting the productivity of a shovel and truck fleet in a new set of operating conditions. More specifically, it concentrates on the problems of predicting the travel times on the haul and return portions of the truck cycle under new profile conditions and the prediction of the interaction effect between the shovel and trucks at the loading point. The ability to calculate the travel times for a new road profile is not new. Additional corrections of these calculated times for expected actual operation can be made. In considering the interaction between the loader and the hauler, there are two approaches that can be taken. Probably the most accurate method of predicting the shovel-truck interaction is a simulation of the step-by-step operation considering the variation in cycle times of the shovel and trucks. This is usually called a stochastic simulation and requires input describing how these cycle times vary. However, by understanding the causes of this shovel-truck interaction it is possible to make sufficiently accurate predictions with much simpler methods. For the purpose of this discussion let us assume that the problem involves trying to predict the productivity of a single shovel-truck fleet at some future time in an existing operation. Let us also assume for simplification that the new operation to be simulated has the same loading and pit conditions and the same dumping conditions as did the existing operation. Therefore, the only difference would be the difference in the hauling profile for the new operation. The problem then becomes one of predicting the change in the travel times on the haul and return portions of the cycle, and in determining the change in interaction between the shovel and trucks with the new truck cycle times.

Jan 1, 1968

By H. E. Goetzman

A cooperative research project supported by the taconite industry and the Minnesota DNR was undertaken to establish quality standards for carboxymethyl cellulose (CMC) based organic binders. The objective of this study was to identify the effect of CMC quality parameters such as degree of substitution, molecular weight, and purity as well as the effect of inorganic extenders such as sodium carbonate on performance. These factors have been evaluated by green-ball testing with two taconite concentrates followed by pot-grate tests. Balling tests with bentonite and Peridur were conducted to provide baseline data. At a constant DS the molecular weight as measured by viscosity had the greatest effect on green-ball drop strength. Dry-ball compression strength was most dependent on CMC addition rate and sodium carbonate content. DS was not found to have a major effect on green-ball quality for medium molecular weight CMC.

Jan 1, 1988

By H. Zhu

Qualitative and interpretative information as obtained from geological and/or geophysical studies, in addition to precise measurement, is incorporated into the estimation process through an indicator variable. The indicator conditioned estimator is formulated as a cokriging and its expression is data value dependent as opposed to that of the traditional kriging estimators. The solution of the dual cokriging system pro-vides simultaneously an estimate of the unknown and an estimate of the conditional probability that the unknown belongs to a specific population or class. Being an unbiased and minimum-error-variance estimator by construction, the indicator conditioned estimator is better in the least square sense than the ordinary kriging estimator because it uses additional information carried by the indicator data.

Jan 1, 1989

By J. S. Gardner, R. Woolacott, P. D. Robinson

In 1917, U.S. Coal and Coke Company, a subsidiary of U.S. Steel, opened Mine 31 and built the community of Lynch, Kentucky. For the time this was truly a major engineering accomplishment. It was documented in Howard N. Eavenson’s 1939 AIME paper, “Coal Through the Ages.” In 1996, Arch Coal donated the Portal 31 property to Harlan County for public use. In 2003 the Southeast Education Foundation, Inc. and the Kentucky Coal Museum plan to open the Portal 31 Exhibition Mine to the public to tell the story of Kentucky coalmining through the decades. This presentation will summarize the history of the project, efforts to bring it to reality, the engineering problems, and the challenges of providing a safe environment for visitors.

Jan 1, 2003

By Kunio Hashimoto

The conventional troughed belt conveyor system is the most widely used form of equipment for transporting bulk materials in the world today. The reason is not only because it is possible to transport a great deal over a long distance when compare to other types of equipment but also due to its greater economic efficiency and low initial and running costs. When dry, powdery materials and liquid materials are being conveyed, there are enclosed transport methods such as flow, case, air-slider and pipe line. In addition to features of the belt conveyor, a system employing a pipe line to transport dry powdery and liquid materials has always been considered an ideal method. This has been brought into reality through the Pipe Conveyor Sys tem.

Jan 1, 1984

By Russell. A. Smith

This paper describes some recent work on the identification and development of new chemical reagents aimed at improving the industrial processing of phosphate ores by froth flotation. In particular, three chemical product families which will be discussed appear to offer enhanced flexibility by: 1) utilizing a small amount of a silica control reagent which can significantly reduce the amount of anionic (carboxylic) collector required for a given P2O5 recovery level; 2) utilizing a new anionic collector family which offers high P2O5 recovery and selectivity versus standard carboxylic collectors; and 3) utilizing another new anionic collector family which has, in some tests, allowed for selective removal of dolomite from apatite. Examples and use characteristics of each of these new chemical ideas will be presented.

Jan 1, 1993

By Deepak Malhotra

Is operator training necessary for optimization of flotation plants? The answer is obvious-Yes. The author suggests a three-phase program for operators when new plants are built or new crews are hired in existing operations. Case examples are discussed to illustrate the benefits of operator training.

Jan 1, 1999

By Roy Norcross

For the past few years Caro's acid has been used for the treatment of cyanide containing slurry effluents, providing a feasible alter­ naive to other slurry treatment processes including !NCO SO2 / Arr and ferrous sulfate. Presently, mines using Caro's acid gen­erate their own Caro's acid onsite making a relatively low quali­ty product. It was at this point where we, at Degussa Corporation, decided to focus our efforts on engineering a Caro's acid genera­tor capable of cost effectively producing a high quality Caro's acid solution, thus reducing operating costs significantly. Caro's acid or peroxymonosulfuric acid is not a new chem­ical nor is it new to Degussa. The product was named after Heinrich Caro (1834-1910), a German chemist who first described its synthesis and its oxidizing properties in 1898. Degussa has been producing the potassium salt of Caro's acid as the triple salt, 2KHSO5 - 2KHSO4 - K2SO4, called Caroat®, for over 30 years. Caroat® is used for household and denture cleansers, as a bleaching agent in dish washing detergents, in printed circuit board etching and for cyanide destruction in the plating industry. From our experience in producing Caroat® Degussa developed its new Caro's acid based DegOX™ technology for the treat­ment of cyanide containing effluents from gold and silver mines.

Jan 1, 1996

By Dennis L. Boley, Francesco Gallavresi, Donald A. Bruce

The authors describe novel aspects of ground reinforcement and treatment as related to soft ground excavation for tunnels throughout the world. Insitu reinforcement for cut slopes (soil nailing), as underpinning (reticulated micropiles), and as direct tunnel support (infilaggi) is introduced. Ground treatment focuses on new aspects of permeation grouting (by the tube'a manchette system), and on jet grouting-a very powerful and positive new technique. Recent developments in equipment, materials, methods and instrumentation are reviewed, with special reference to major tunnelling projects in Italy and Singapore.

Jan 1, 1987

By James Humphrey

There is a natural resistance to change in any form. When it comes to implementing a game-changing technology like autonomous haulage on an operating mine site, the resistance can at times appear insurmountable. Whether based on real information or misguided preconceptions, it?s essential that we don?t underestimate the effort it will take to overcome this resistance, while clearly recognizing when it?s worth the effort. These realizations did not happen overnight for sites where autonomous haulage has been implemented. Nor did they happen overnight for manufacturers of autonomous mining equipment. Caterpillar, for example, began building toward autonomy more than 30 years ago and had a truck operating in the mid-1990s. Lessons learned during those early years led to the realization that there was much more to be learned ? not just about the machines themselves, but about the systems and knowledge that must be in place for a successful implementation. Working closely with customers, initiating real-life demonstrations on mine sites, having discussions with regulatory agencies and other stakeholders ? these and many other activities were necessary before autonomy could be fully and successfully launched. After decades of effort, Caterpillar?s first official commercial autonomous mine site went to work in 2011 in Farmington, NM.

By D. Corrigan, A. Ahmad, R. Sood, J. Bratt, R. Holt

Zinc oxide based electronic ceramics are being used increasingly to protect electric and electronic circuits against transient voltage surges. Varistors are produced by sintering and annealing ZnO based powder compacts through long sintering and annealing cycles. Because of the length of these cycles, a manufacturing plant is saddled with expensive high temperature equipment with low throughput. Ceramics Kingston Inc. has developed a new technology that uses 2.45 GHz microwave energy for sintering and annealing. The new technology has the potential for increasing equipment and labour productivity very considerably. Additionally, the new technology will result in appreciable energy savings and add flexibility to the manufacturing process. Microstructural examination of varistors sintered conventionally and by microwave technology showed considerably smaller grain size in the microwave sintered materials. The electrical properties of the microwave sintered ceramics compare very favorably with those of the ones sintered conventionally.

Jan 1, 1990

By Aurel Goodwin, Diann Kraft, V. S. Znamensky

This chapter deals with the Mine Safety and Health Administrations's (MSHA] concern and obligations with regard to asbestiform minerals. Asbestiform minerals are defined as the magical group of hydrated, silicate minerals that possess a fiberlike structure capable of being woven into cloth. Their unique combination of properties, such as resistance to heat and chemical attack, high tensile strength, and flexibility was recognized centuries before Christ. Pausanias, the early Greek geographer, speaks of golden lamps, made about 430 BC, with in- combustible wicks of Carpathian flax. The Ro- mans used asbestos as cremation clothes to con- serve the ashes of deceased persons of rank. Charlemagne had an asbestos table cloth that he used to pass through fire to clean (Lanza, 19381. Early recognition of the health hazards associated with exposure to asbestos was documented in the first century by Pliny the Elder, a Roman naturalist, and Strabo, a Greek geographer. Both wrote of slaves with sickness of the lungs, whose occupation was that of weaving asbestos into cloth. This concern for the health of asbestos workers disappeared over the ages. Today, with the use of modern technology, asbestos products have been greatly exploited. The asbestos output has increased over a hundredfold in the past 70 years. World production has jumped from 454 t/y (500 stpy) in 1900 to 4.5 Mt/y (5 million stpy) in 1978. An increase in health problems for asbestos workers accompanied this increased usage. However, it was not until the modern era that the association of asbestos with chronic respiratory disease was rediscovered. Reports were published at the turn of the century documenting the effects of asbestos exposure on textile workers. One such report in 1907 by H.M. Montague Murray described the post mortem findings on a 34-year- old carding machine operator. Murray de- scribed the lungs as showing extensive diffuse pulmonary fibrosis spicules of asbestos. Subsequently, more reports of pulmonary fibrosis following inhalation of asbestos were published, including an epidemiological study of asbestos miners in 1930 (Merewether and Price, 1930), at Thetford, Que., Canada. This study took place at the mine 52 years after large-scale mining of asbestos had begun. But, the cancer- producing potential of asbestos was not established until 1949 when a report by Merewether in England described an excess of cancer of the lung and pleura [the lining of the lungs) among individuals dying from asbestosis (Merewether, 1949). In the past decade much attention has been focused on asbestosis, mesothelioma, and bronchogenic carcinoma, as the three major biological effects associated with asbestos ex- posure. Parenchymal and pleural asbestosis is a fibrosis in the substance of the lung with thickening and often calcification of the membranes lining the thoracic cavity. Mesothelioma is a malignant tumor of the membranes lining the thoracic or abdominal cavities, and bronchogenic carcinoma is a cancer of the lung tissue itself. These diseases occur in various degrees and combinations. The severity and occurrence of these biological effects are directly influenced by conditions such as dose response relationships, intensity of exposure, duration of exposure, lapse of time since initial exposure, and cigarette smoking. Numerous studies indicate that the relationship between these conditions and the incidence of disease is proportional. Congress has recently concluded (Congressional Record, 1979) that, "exposure to asbestos fibers has been identified as significantly in- creasing the incidence of cancer and other severe or fatal diseases such as abestosis." Congress conveys its concerns for the safety and health of the nation's miners through the Federal Mine Safety and Health Act of 1977 in which it gave MSHA the authority to set safe

Jan 1, 1986