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By António Fiúza, Anthony Danko, Patrícia Leitão, Aurora Futuro, Cristina Vila, Lurdes Dinis

The average global recovery rates for processing scheelite ores by physical methods are normally in the range 50 to 70%, and it is problematic to attain a minimum grade of 60% WO3 in the concentrates without penalizing further this yield. Direct hydrometallurgical processing of low-grade concentrates or medium- to high-grade ores may become an interesting global economic alternative as it allows increasing the recovery rate, avoiding major penalizations due to the grade of the concentrate and increasing the added value of the final product. Leaching of scheelite by sodium carbonate presents several advantages such as its selectivity regarding the dissolution of troubling metals like iron and aluminium, allowing for a simple and flexible process diagram. However, it has the disadvantage that it is performed at high temperature and pressure with a high consumption of reagents. The feasibility of leaching is appraised by the extraction yield and selectivity, but also by the operating cost. Considering these aspects, a relevant objective of the research was to transform alkaline pressure leaching into a feasible processing alternative directly applicable to both medium- and high-grade ores and simultaneously to low- and high-grade concentrates produced by physical methods. The research used ore samples and low-grade concentrates from a typical skarn orebody as well as high-grade concentrates from a chalcopyrite-scheelite orebody. Different operating conditions were tested. Temperature, pressure and reagent concentration showed to be fundamental, but not exclusive, in determining the leaching behaviour. The operating conditions are milder than the ones generally proposed in the literature or currently in use in industry, but with higher carbonate consumptions. The research was oriented towards potential industrial implementation allowing for the application of optimization methods and straight scale-up to pilot-plan design and project.

By Raymond W. Hiteshue, Sam Friedman, Paul Dobransky, Robert Madden

A hvab coal was carbonized in a closed system at 600 ° C and 40 to 1 , 200 psig to produce a high- Btu gas and char . By retaining the volatiles within the system, it was possible to virtually eliminate production of tars and oils . Depending on pressure and residence time , yields of combustible gases (72 to 92 percent methane ) amounted to 4,000 to 6,000 cubic feet per ton of maf coal and gross heating values of these gases varied from 830 to 960 Btu per cubic foot . Yields of char (maf ) were about 1,600 pounds per ton of maf coal . Increased residence time favored production of gases but reduced their heating values , whereas increase in pressure resulted in somewhat higher heating values and lower production . Similar effects were observed from the carbonization of a low- temperature tar . If these results could be translated to an economical carbonization process for producing high- Btu gas from coal , the demand for coal could be expanded by 40 to 50 million tons per year . Because of large yields of char , a process of this type would obviously have to be integrated with coal - fired power plants . Fortunately , operations could be conducted at essentially atmospheric pressure as product gas under this condition can be obtained in satisfactory yields and with good quality .

Jan 1, 1964

By John Latilla

Exxaro Mining?s Matla Coal situated in Mpumalanga, South Africa operates two shortwall faces on the No 4 and No 2 seam while the No 5 seam has also been longwalled in the past. Severe strata loading events have lead to a number of serious roof falls on the wall face (facebreaks) resulting in safety threats as well as considerable production losses. In 2002 the No 4 seam shortwall suffered a facebreak restricted mainly to the tailgate side of the mining panel due to a thick, near surface dolerite sill not breaking properly. This was partly due to the premature suspension of longwalling in the overlying No 5 seam. The resultant overloading lead to severe pillar damage and subsequent bord collapse. Surface pre-split blasting was successfully used to relieve the pressure as well as to pre-condition the dolerite above the following two panels. The shortwall on the No 2 seam has experienced mid-face loading due to No 4 seam chain pillars lying over this area and creating a secondary cantilever effect. Pre-split blasting of the solid rock above the No 4 seam pillars has resulted in a significant reduction in the number of facebreaks. The panel layout of the No 2 seam was subsequently changed so that the chain pillars on both the No 4 and No 2 seam are superimposed whereas previously they were offset.

Jan 1, 2007

By W. R. Seyfried

The problem of extracting alumina from clay and low-grade bauxites has been the subject of considerable interest for some time. The basic reason, of course, lies in the fact that known reserves of high-grade bauxite are not inexhaustible and that the present commercial process cannot successfully cope with low-grade bauxites or clay. Ultimately it may be necessary to use these poorer raw materials for all commercial operations. An unprecedented demand for aluminum during the war emergency and the constantly threatened shortage of imported bauxite caused the United States Government to take an active role in this problem. Through the National Academy of Sciences, the War Production Board and the Defense Plant Corporation, it investigated processes and finally selected four to be used in the construction and operation of four experimental plants. Each plant was to be designed in such a way as to facilitate its incorporation into a larger commercial plant should the need arise. The Chemical Construction Corporation process, or "Chemico" ammonium sulphate process as it is better known, was one of the four selected. The extensive literature and patents on record before the war generally follow one of two process-types depending upon the extracting reagent used. One group uses an acid reagent, the other an alkali. The Chemico process uses an acid reagent. For those interested in other processes described in literature, there is a short bibliography at the end of this paper. The basic steps of all acid extraction processes are: (I) to make the aluminum silicates acid soluble, (2) to separate the released alumina from impurities and insoluble gangue, and (3) to recover the reagent for re-use. The Process as Planned In April 1941, a group of chemists and engineers of the Chemical Construction Corp. became interested in the problem of extracting alumina from clays and low-grade bauxites and, under the leadership of Mr. Blakeslee Barnes, Vice President and General Manager of the company, first drafted a process in July of that year—five months prior to Pearl Harbor. The work continued in our research laboratories and with a small pilot plant. By June 1943, the work had progressed to a point where it was possible to apply for a patent on the process which was U.S. patent 2,405,426, granted August 6, 1946. Immediately prior to the development of the Salem plant, the process was envisaged to be as follows: I. The first step was to make the aluminum silicates acid soluble. It was planned: (a) Clay or lour-grade bauxite would be roasted at 700 to 800°C (1292° to 1472°F). (b) The roasted ore would then be leached with hot aqueous ammonium bi-sulphate to form a slurry. In this way the

Jan 1, 1949

By Rafael C. Castro, Paul V. Savard, Kathleen M. Murtagh

Preliminary design is underway for the Massachusetts Water Resources Authority’s (MWRA) next major tunnel program, the Metropolitan Water Tunnel Program (MWTP). The MWTP is the latest part of MWRA’s ongoing efforts to achieve redundancy for its metropolitan water transmission system including its historic deep rock City Tunnel, City Tunnel Extension and Dorchester Tunnels. The MWTP comprises several deep rock tunnels that will be approximately 10-foot to 12-foot finished diameter totaling just over fourteen miles long and ten connections to existing large diameter surface piping and pumping stations. This paper will present an update on current engineering and permitting efforts, packaging schemes, and the schedule to complete the MWTP.

Jun 13, 2023

By M. Akser

Ilmenite, rutile, and zircon deposits of commercial importance have not been reported to-date from Turkey. However, information from recent reconnaissance activities indicates the possibility of an economically viable heavy-mineral deposit along the Black Sea coast of Turkey in the vicinity of Ormanli, northwest of Istanbul. Consequently beach and sand dune samples were collected from that area for additional analysis. Laboratory methodologies, designed to simulate standard industrial heavy-mineral plant practices, were used to analyze and evaluate the samples. Based on the analyses, and current market needs, none of the deposits in the Ormanli area qualify as a commercial heavy-mineral deposit.

Jan 1, 1995

By W. H. White, A. J. Sinclair

"Unaltered biotites from three samples of monzonite and gabbro from the Copper Mountain stock and a single sample from a pegmatic biotite-chalcopyrite vein cutting the Triassic Wolf Creek formation have a mean K-A age of 193±7 m.y. These data support a suggestion based on geological evidence that Copper Mountain ore deposits are related genetically to the Copper Mountain stock.A cogenetic mineral pair (biotite and clinopyroxene) from a sample of sericitized and chloritized monzonite of the Copper Mountain stock have identical K-A ages of 150 m.y., which probably represents a time of wide-spread, post-ore, hydrothermal alteration. This alteration is believed to be related genetically to a group of post-ore intrusions known as the ""mine dykes,"" suggesting that they also have an age of 150 m.y."

Jan 1, 1968

By L. F. Zeiler

In the past, health concerns in coal mines have primarily centered on those elements which have been essentially inherent to the mining environment. These would include respirable coal mine dust, respirable crystalline silica, excessive noise levels, and diesel exhaust particulates. Commercially-available chemical products are prevalent on mine property. These potentially toxic materials are chemical formulations that can degrease, clean, and lubricate metal parts, separate coal from rock in float/sink operations, and aid in roof consolidation, among other uses. As the general public has become more aware of the hazards of chemical exposures, miners have likewise become more concerned about working with an ever-expanding variety of chemical products on the job. Often, product or chemical specific hazard communication training is inadequate or ineffective, and miners do not know exactly what the ingredients are in the products they handle, or the health hazards involved with their use or misuse. Currently, the Mine Safety and Health Administration (MSHA), by law, enforces 1972 Threshold Limit Values (TLV). MSHA is making preparations to adopt new personal exposure limits for enforcement. The values given throughout the article are 1994 TLV's and are not enforcement standards, but are used for discussion purposes. They reflect the current scientific thinking regarding personal exposure to these chemical agents. An overview of these products is presented, and the potential health hazards associated with their use are discussed. Controls needed to prevent overexposures, such as proper handling procedures and personal protective equipment, are covered. Methods used to collect and identify contaminants are presented.

Jan 1, 1995

By R. J. Arsenault

The yield drop that occurs in tantalum, Cu-AZ. and Ag-Al was investigated as a function of strain rate and at several temperatures. From the strain-rate dependence of the yield drop an activation volume was calculated and found to agree with that obtained from differential strain-mte tests. The temperature dependence of the yield drop can he explained in terms of the parameter temperature divided by activation volume. The yield drop is attributed to the rapid multiplication of dislocations during their motion. THE yield-point or yield-drop (upper yield stress minus the lower yield stress) phenomenon has been the subject of numerous investigations1-9 in both bcc and fcc metals. Also, there is no dearth of theoretical explanations10-20 to account for the yield-point phenomenon. The present explanations can be divided into two categories: the concept of dislocation locking and subsequent unlocking and the concept of multiplication of dislocations due to their motion. The Vottrell10,11mechanism of locking and unlocking, as applied to bcc metals, is the best known of the three proposed locking mechanisms. The two additional mechanisms, short-range order (SRO)7,16,17 and Suzuki-type locking,14,15 have been employed to account for the existence of yield points in fcc metals. The experimental evidence supporting the locking of dislocations, especially in bcc metals, is well-established. The dependence of the yield point on interstitial concentrations,' the kinetics of strain aging,2 and the observations by electron-transmission microscopy18 are some of these experimental results. The number of experimental observations supporting dislocation locking in fcc metals is not as extensive as in bcc metals. The unlocking of dislocations, which actually is supposed to account for the yield drop, is by no means well-established by experimental results for either bcc or fcc metals. The similar temperature dependence6 of the yielding and plastic flow is one of the experimental factors that cannot be explained in terms of the unlocking of dislocations. The mechanism based on the rapid multiplication of dislocations has been proposed by several investigators. 18-20 Johnston and Gilman19 have proposed a detailed model of yielding, which was later employed by Hahn21 to predict quantitatively the yield drop in iron. This mechanism was discussed in a previous paper22 and several limitations were pointed out. In the same paper it was shown that an activation volume could be obtained from the strain-rate dependence of the yield drop and that a correlation existed between the activation volumes obtained from the yield-drop tests and from differen-

Jan 1, 1964

By Corby G. Anderson

In the majority of industrial operations recovering gold and silver by hydrometallurgical means, cyanide is the predominant lixiviant. However, as an economic alternative, production of massive quantifies of silver chloride was done on an industrial scale in the nitrous-sulfuric acid pressure leaching of a refractory precious metals concentrate. This proven process required no cyanide. Thus, because of the large volumes encountered during day-to-day plant operation, the need for efficient and low cost methods of silver chloride precipitation, reduction and materials handling was mandatory. As such, this paper covers the evolution of plant scale precipitation, filtration, washing, reduction and control of silver chloride processing. As well, an in-depth description of the unique leaching system is included.

Jan 1, 1998

By W. P. Campbell

Foreword At the outset, it should be stated that this paper does not pretend to present a panacea for the ills that 'frozen' wells are heir to, but rather is an attempt to bring to the attention of those whose special concern it is, a little theory and some facts, which have been brought to light recently, in connection with the problem of 'freezing' as it applies to naphtha-producing wells in the Turner Valley field, and to draw some conclusions that follow from the facts discovered. It should also be stated that the investigation is not to be regarded as in any sense complete, but in progress. Doubtless new facts will be brought to light from time to time which may modify present ideas on the subject, but whether favourable or contrary, these will be welcomed, as the purpose of the Department is to secure as complete information as possible of the factors contributing to 'freezing', since this must be the first step to an intelligent attempt to remedy or prevent its occurrence, if such can be done. It is possible, too, that the cause or causes of freezing may not be the same in all cases, but whether this be so or not will have to be determined later as new information comes to hand. Introduction One of the worries which must constantly confront the operators of gas-naphtha producing wells in Turner Valley-although all, fortunately, have not met with it-is the possibility of the occurrence of what is commonly called 'freezing' (going off production).

Jan 1, 1930

By R. Ressel

Keywords: ferrovanadium, thermodynamics, phosphorus Recyclable material is rapidly gaining in importance as a source of raw materials in industrialized countries. This is also the case in the production of ferrovanadium, where, increasingly, materials such as discarded capacitors, spent catalysts, slag, dust and sludge are used. As the V-content in the raw material varies greatly, the demands on process technology are very high. The share of perturbing elements depends very much on the source of the raw materials, which, in turn, makes a corresponding optimization of the various refining steps necessary. The raw materials are mostly available as oxides, which means that carbon, silicon or aluminium are used as reducing agents. Thermodynamic calculations were used to show especially the behavior of vanadium and phosphorus at different process conditions.

Jan 1, 2005

By L. M. Pruett

The Arizona Legislature is currently in the process of considering mined land reclamation legislation in the 1994 legislative session. A bipartisan legislative study committee has drafted proposed mined land legislation. The committee has attempted to craft legislation that is appropriate for the unique conditions in Arizona. Existing Arizona and federal laws and regulations extensively regulate the environmental performance of mines in the state to protect public health, safety and the environment. The proposed mined land reclamation legislation does not replace or duplicate these statutory provisions relating to environmental protection. Instead, the purpose of the proposed legislation is to provide for the reclamation of land that is being mined and to fill the gap in existing laws by requiring the reclamation of land that currently is being mined or that has been mined since 1986 to provide for future land use. The legislation would require an operator to submit a reclamation plan describing the exploration operations, mining operations, post-mining land use and the proposed reclamation measures for review by a state agency. Financial assurance also would be required in an amount such that a third party could complete the approved reclamation measures. Arizona's mined land reclamation legislation would recognize Arizona's leading role in hard rock mining and emphasize the mining industry's economic importance to Arizona and the nation. Because mining operations necessarily require disturbing the surface of the earth to extract valuable minerals, reclamation requirements would be adapted to different conditions and would vary depending on site-specific conditions and on the commodity being mined. The current proposal does not identify the state agency that will administer the mined land reclamation program and approve reclamation plans, substantial changes to plans, and transfers of reclamation plans to other operators.

Jan 1, 1994

By Philip C. Good

Preliminary studies showed that direct hydrolysis of H2SiF6 to SiO2 and HF at elevated temperatures was subject to many mechanical difficulties, and that corrosion of construction materials was a serious problem. Elimination of SiO2 from the HF product was generally poor. An alternative procedure, hydrolysis of lime-neutralized H2SiF6 by steam at 950° to 1,100° C, yielded a product very low in SiO2. Condensates containing up to 300 g/1 HF were prepared.

Jan 1, 1968

By A. Usov

The studies carried out by the Russian researchers and those carried out jointly within some contracts with scientific organizations and companies of other countries, show that the electric pulse disintegration of materials (ED), proposed and investigated in detail in Russia (Kalyatsky, et al, 1980; Usov et al, 1987; Semkin et al, 1995; Usov and Tsukerman, 2000; Kurets et al, 2002) has been widely recognized and developed abroad (Andres, 1995; Inoue et al, 2000; Biela et al, 2008). The Russian and international journals and the proceedings of the conferences dealing with the electric pulse disintegration pay great attention to the principal principals of selective disintegration of materials. There is no, however, any information concerning both the technical means developed to implement the technique and the assessment of their performance, which would be necessary in objective assessment of the industrial use of the technology. The results of long-term studies of the technique and technologies of electric pulse disaggregation by research institutes such as Research Institute of High Voltages (Tomsk), Kola Science Centre of RAS (Apatity), Institute "Mekhanobr"(S.Pertersburg) described. Exploratory stands and technological installations are developed to carry out pilot tests and operations under production conditions. Basic circuits and classification of technical means electric pulse disintegration of the materials are proposed, the analysis of transportation schemes and classification of the material in the disintegration apparatus are given, construction of chambers for continuous stadial disintegration of ores and materials are presented. The features and technological efficiency of electric pulse disintegration of various types of ores, and the spheres of effective use of the method have been determined. Keywords: electropulse disintegration, disintegration machines, chambers of comminution, stadial comminution.

Sep 1, 2012

By Edward Peters

Scandium (Sc) has unique properties and is one of the more valuable elements in the periodic table. Scandium can be used in solid oxide fuel cells and to produce high strength aluminium alloys of value, for example, in the aerospace industry. Scandium is often grouped together with the rare earth elements (REE). Amongst others, scandium can be found in bauxite residues, so called red mud. It is possible to extract and enrich scandium from red mud by leaching and solvent extraction. Scandium can then be recovered from the pregnant strip liquor by crystallization. The strip liquor will however still contain certain impurity elements. In the present work, a method for obtaining a pure scandium solid phase by direct crystallization from the strip liquor is evaluated. It was found that Fe and Ti co-precipitate with Sc under the conditions employed.

By Ismail Adeniyi Okewale, Hendrik Grobler

Significant factors believed to be responsible for tailings dam failure which can lead to loss of lives, destruction of properties and assets or damage to the environment are the mechanics of material characteristics and static liquefaction. It is therefore essential to understand the tendency for the likely occurrence of liquefaction in tailings dam as well as mechanics behind the behaviour of this tailing materials (inevitable products of ore mining, mineral and metallurgical processes). This study aims to present the mechanical behaviour and susceptibility to liquefaction of a gold tailings sample. Series of oedometer tests were conducted to determine the compression behaviour and the possibility of transitional behaviour or not. Index and physical tests were conducted to determine engineering grading descriptors which was directly linked to compression behaviour and comparisons made with other tailings. Microstructure was studied to understand the effects of fabric on the behaviour of samples and the chemical composition and mineralogy were also investigated. The compression paths slowly converge and the gold tailings might be said to be less transitional. The gold tailing is less dependent on initial state. The loosest gold tailing is more susceptible to liquefaction and compared to other gold tailings, this sample is less susceptible to liquefaction.

Apr 19, 2024

By Francisco A. Fonseca

The Carajás Hills are in Brazil's Eastern Amazon, between the Araguaia and Xingu rivers, and parallels 5° and 7° Latitude South. A location map is given in Fig. 1. It is an area of low mountains (maximum altitude 900 meters), covered by the Amazon rain forest. Annual average temperature is 25°C, ranging from 31°C (maximum) to 19°C (minimum). Annual rainfall averages 2,000mm. Although it rains throughout the whole year, heavy rains occur from December through March. At the beginning of the 20's, Brazilian explorationists made brief geological descriptions of the area. Due to the thick soil, scarce fresh rock outcrops and the tropical forest covering a completely unpopulated area, detailed geological studies were difficult and reconnaissance expeditions were limited to the river margins.

Jan 1, 1982

By Luis Alberto Martinez Tipe

The paper show how the inclusion of the uncertainty of the geology of the orebody into the mine planning and design process can be of great help, for the mine planner, in both assessing and quantifying the existing risk in the key project indicators such as DCF, and ore tonnage. This is achieved by using conditional simulation and Monte Carlo techniques which provide equally probable models of the original orebody model of the deposit. In this fashion, it is possible to assess the sensitivity of the pit design and related long-term production scheduling (cutbacks) to grade uncertainty.

Sep 12, 2005

By William B. Plank

AN outstanding development in the field of education for the mineral industries during the past year has been an unprecedented eagerness by young men for college training in this field. The enrollment of students in the 53 mineral technology schools in the United States in 1936-'37 reached the all- time high of 7190. This represented an increase of 43 per cent in two years and was about ten per cent of all engineering students. Of these 7190 students only 980 graduated and were available - for positions in the industry. That the supply of graduates did not equal the demand can be substantiated by every school dean and by the personnel agents of many mining, metallurgical, and petroleum companies. Some of these companies last summer inaugurated the plan of employing, for the

Jan 1, 1938