Search Documents

By Lendall P. Warriner, Blandford C. Burgess

Jasper County lies just north of the geographical center of Georgia, bounded on the west and north by the Ocmulgee River. The county seat, Monticello, is approximately 65 miles east-southeast of Atlanta and 40 miles north of Macon. It is served by the Macon-Athens branch of the Central of Georgia Railway Co. and by five paved highways converging from adjoining county seats. Farming and lumbering are the principal local occupations. About half the county is covered with pine and mixed hardwoods; a large part of the forested land is owned by the Soil Conservation Service of the Department of Agriculture in its Piedmont Land Utilization Project. The topography is one of gently rolling field and forest with occasional hills rising 100 ft or: more above the creek beds. Though annual rainfall is in the neighborhood of 60 in., most of it falls in torrential downpours of short duration which tend rapidly to erode the red soil and convert the country roads to greasy tracks of red mud.

Jan 1, 1949

By V. B. Achanti

This paper deals with the effect of various bit geometric parameters on failure characteristics of rock material. Improvement of rock cutting efficiency of continuous mining machines has been an interesting research topic for the last few decades. In the current study, an automated rotary rock cutting simulator, duplicating a continuous miner, was utilized to study these parameters in the laboratory. Improvement of bit performance in terms of its life, cutting efficiency, dust production and energy consumption has drawn wide spread attention over the years. Research shows that optimizing bit parameters can result in efficient fragmentation of rock. Indiana limestone rock material was utilized in this study while bit tip angle, bit tip size, bit spacing, depth of cut and cutting velocity of rotary drum were varied to investigate the failure characteristics. The cutting pressure, penetrating pressure and the depth of cut were monitored on the simulator during the cutting process. Air borne dust and settled dust were measured for each experiment. Then, the specific airborne dust and specific energy were determined for the each type of bit. Triaxial tests were carried out to correlate the failure angle of the rock in static case to dynamic cutting process failure. The physical and mechanical properties of the rock were also determined in order to assess their influence on the wear characteristics of each bit.

Jan 1, 1998

By Ryosuke Matsuoka

Keywords: Tantalum capacitor, Scrap, Recovery, Titanium, Chlorination A recycling process for tantalum from capacitor scraps using an oxidation process followed by mechanical separation and chemical treatment was investigated. This study demonstrates that sintered tantalum electrodes inside the capacitor scraps can be mechanically collected after the oxidation of the scraps in air, and high-purity tantalum oxide powder (Ta2O5) was efficiently recovered after chemical treatment. By reducing the Ta2O5 obtained through magnesiothermic reduction, tantalum powder with 99 mass-% purity was obtained. Using the chlorination for tantalum recovery was also investigated, and the tantalum or tantalum compounds were reacted with chloride wastes such as FeClx. It was found that tantalum was effectively separated and purified when tantalum powder is reacted with FeClx at 1100 K under an argon atmosphere. This recycling process utilizing chloride scrap has now been extended to other reactive metals such as titanium.

Jan 1, 2004

By Bradley Stoughton

AT THE meeting of the Board of Directors on May 20, the resignation of Bradley Stoughton as Secretary of the Institute was presented and regretfully accepted by the Board. The letter of resignation follows : Gentlemen: About two years ago, I indicated to the President and some members of the Board my belief that the office of Secretary of the Institute should not be a permanent one. It is my observation of events, not only in our own Institute, but also in several sister societies, that too long a tenure of office by the Secretary inevitably leads to a situation which is not good either for him or for the society. After submitting this in writing to the Directors on February 17, 1920, I was overpersuaded by members of the Board to defer resignation until a more convenient time for the

Jan 1, 1921

By Blamey Stevens

(San Francisco Meeting, October, 1911.) My previous paper is entitled, The Laws of Igneous Emanation Pressure. The present paper lays no claim to the exactitude and completeness of a law, since it is of a provisional nature and may be disregarded when experiments have established a basis for more exact reasoning. The general physical states in which aqueous emanations may occur are first considered. The possible physical conditions under which the mineral elements may occur in emanations are then discussed, and a classification of deposits, dependent on emanation, is proposed. A system of scientific experimental investigation is outlined, and it is shown that the physical and chemical properties of emanation may be exactly determined thereby. The investigation is urged as feasible and simple, and not necessarily requiring large and costly apparatus. It is the only step necessary to make possible the formulation of a complete set of laws of igneous emanation. Process of Emanation. In a rising column, magma ranges in temperature from 900° to 1,200°C. Exhalation must begin at some fairly great depth. What this depth may be we can only surmise, since no experimental evidence is available. Exhalation, however, continues as the magma flows upward, until at another level the occluded gases have all escaped. This depth is probably upward of 5,000 ft. (See Fig. 1.) All exhalations must come from between these two levels. As the whole emanation is the sum of the exhalations and residues, the residues must come from below the uppermost level. They will be most abundant when coming, from those parts of the intrusion which have solidified below the lower level.

Apr 1, 1912

By BUREAU OF MINES

PLATINUM

Feb 1, 1922

By G. E. McElroy, D. Harrington

In connection with the cooperative metal-mine dust and ventilation investigations of the U. S. Bureau of Mines and the U. S. Public Health Service , some underground data have been obtained with intent to ascertain the adaptability of the katathermometer for determining the comfort of working places in mines . This preliminary study indicates that the instrument will probably be useful for making routine determinations of comfort conditions in our mines , and that it may also prove an important accessory for investigative work on problems in ventilation and kindred subjects ; in both coal and metal mines , although the instrument should probably be altered somewhat for maximum utility under the varied conditions in the mines of the United States . The katathermometer is an instrument contrived by Dr. Leonard Hill , an eminent English physiologist , and its various features have been fully described by him in his book entitled " The Science of Ventilation and Open Air Treatment . " He made exhaustive experiments and concluded that the rate of cooling of the human body was the controlling factor in determining comfort or discomfort , and then set out to make an instrument that would measure this rate of cooling . The resulting instrument the katathermometer measures its own rate of cooling when its temperature approximates that of the human body and thus serves as an index of the rate of cooling of the body itself . - The instrument consists of an alcohol thermometer having a cylindrical bulb 1 inches long and 3/4 inches in diameter, and a stem about 8 inches long graduated from 95 to 100° F. This temperature range gives a mean temperature of 97.5° F. ( 36.5° C. ) , which is approximately that of the clothed body surface . The stem terminates in a small reservoir which serves the double purpose of acting as a safety overflow in case of overheating the bulb , and of insuring a regular rate of cooling by the time the meniscus has fallen to the 1000 point .

May 1, 1922

By L. C. IlsLey, R. A. Kearns

As the use of electricity becomes more and more general in mining opera- tions, interest in regulations governing its application becomes greater. During the past year the electrical section of the Bureau of Mines has made a study of State regulations now in force relating to the use of electricity in coal mines. Technical Paper 271, entitled "State Mining Laws on the Use of Electricity in and about Coal Mines", has been published as a result of this study. The present paper represents a compilation of all laws relating to accident prevention with respect to electrical circuits. This group of regulations is perhaps the most important of any that relate to safety in coal mines. Its importance is shown by reference to accident statistics in Bulletin 115, (Fay, A.H., Coal-Mine Fatalities in United States, 1870-1914, Bureau of Mines, 1916), which show that about 77 per cent of the fatalities due to electricity in and about coal mines were caused by direct or indirect contact with trolley or other power circuits. In actual number this means that of 710 men killed by electricity, 546 were killed by contact with electric wires. Undoubtedly, a large percentage of these accidents might have been prevented had the wires been properly guarded. The compilation follows:

Mar 1, 1921

By Ludwig Hermann

"Phosphorus is required by every cell of living organisms and essential for plant growth. It is a non-renewable resource that must be mined from natural deposits, going gradually into depletion. Abundant secondary resources are available in sewage sludge and meat and bone meal, with the highest exploitable P concentrations in ashes that remain from their widely used combustion with energy recovery. ASH DEC has successfully removed heavy metals and transformed sewage sludge ash into a marketable P fertilizer by application of a thermo-chemical treatment process. Pilot scale investigations in which ash was treated proved that generally heavy metal limits required by fertilizer legislation can be attained. To achieve a high P availability for crops – an essential fertilizer quality feature – was a more challenging R&D task. Our presentation demonstrates the scientific approach and R&D results that lead from assessment of market requirements to licensed products.IntroductionPhosphorus (P) is required by every cell of living organisms. It is one of the major elements for plant nutrition and therefore essential for crop production. P supply in plant nutrition depends entirely on external inputs into soils [1]. This is achieved by P-fertilizers deriving from rock phosphate deposits that are gradually going into depletion. Serious prognoses anticipate that rock phosphate will be the first low running resource in the world [2]. In the EU, last year 2.530 kt of phosphorus (P2O5 in fertilizers) was consumed and only 313 kt (P2O5 in rock phosphate) was mined. Since 2007, rock phosphate prices have increased by 500% because of a tight supply situation [3].For these reasons, P recycling is becoming an increasingly important issue. Suitable secondary raw materials with regard to their high P-content and abundance are sewage sludge and meat and bone meal. In the EU 989 kt P2O5 are accumulated annually in theses materials, of which 632 kt P2O5 are permanently lost to landfills and other forms of disposal. The main reasons for their limited recycling are concerns on heavy metal contents and organic pollutants that may incite health hazards. As an additional shortcoming, the availability of P from these materials to plants is poor and storage and transportation are problematic issues [4, 5]."

Jan 1, 2008

By J. C. D. Gush

Paper written on project work carried out in partial fulfilment of Laboratory-scale testwork was undertaken to recover oxidic copper-cobalt minerals by froth flotation, which requires maintaining a certain sulphide level in the pulp. To improve control of the sulphide concentration, an electronic closed-loop system was designed that responds to the potential output of an ion-selective electrode. The PID control was improved by adding a pre-emptive control and a self-calibration feature; a data logging facility is also included. An inexpensive valve design was incorporated using locally available parts. The operating results of this control design are presented.

Jan 1, 2005

By Bruna Silva de Almeida

Tradicionalmente propriedades mecânicas tais como: Limite de escoamento e dureza em processos de laminação a frio são avaliadas antes e após o processo devido a dificuldade de obter estes valores após cada cadeira de laminação. Atualmente são empregadas simulações numéricas, onde inúmeros modelos usam valores de tensões antes e após laminação e obtém-se uma predição destes valores entre cadeiras, normalmente utilizando aproximações ou dados conseguidos em algum laminador piloto. A finalidade deste trabalho foi estudar uma bobina processada de um aço IF, em escala industrial, num laminador de tiras a frio de cinco cadeiras avaliando algumas propriedades mecânicas e correlacionando os aspectos microestruturais das amostras retiradas entre as cadeiras deste laminador. Para o estudo da evolução das propriedades mecânicas do início ao final do processo, foram preparadas amostras para os ensaios mecânicos e para análise das mudanças microestruturais foram preparadas amostras por técnicas de metalografia. O resultado apresentado após estas avaliações mostram o comportamento mecânico diferenciado após cada redução.

Aug 8, 2018

By Jue Kou, Fazhao Sun, Jiang Liu, Cuili Gui, Baoqiang Yu, Chunbao Sun

A novel special magnetic separator was developed based on the special properties of precious metal-bearing alloy in highgrade nickel matte. The recovery of Au, Pt, and Pd was 77.79%, 84.79%, and 81.79% respectively at optimum operation conditions of magnetic separator feed of 2.5t/h, pulp density of 45%, and flush water of 1.5t/h, and the recovery significantly improved comparing with normal magnetic separator. Magnetic field simulation of the special magnetic separator indicates that magnetic intensity of 0.6 T can be generated on the surface of magnetic drum, which can strengthen the recovery of heavy alloy that contains precious metals. The alternate strong and weak magnetic field can also make magnetic particles rolling on the surface of drum, which will reduce the generation of magnetic agglomeration to a large extent and decrease the content of impurities in magnetic concentrate.

Jun 16, 2022

By Junfu Chen, Jiann-Yang Hwang, Yong Zhou, Lijun Lu, Likun Lia, Jixiong Liu

The sheet-like NiS-ZnS heterostructured composites were prepared by the microwave hydrothermal. The fabrication of the heterojunctions broadened the range of light response of ZnS. The photoexcited electrons of ZnS migrated to the redox potential of NiS/Ni2S under visible light irradiation, which can facilitate the effective separation of photogenerated electrons and holes in space. The visible photocatalytic activity towards hydrogen production for NiS/ZnS nanosheet heterostructed composites without co-catalyst achieved 0.28 mmol h–1, and the quantum efficiency was up to 18.6% under the wavelength with 420 nm visible light irradiation.

Jan 1, 2015

By J Wheeler

The benefits of fine size separation in magnetite concentration are detailed focusing on published research from various iron ore producers. Basic principles of fine sizing and advancements in screening technology are addressed. A chronological review of research is used to show the evolution of fine sizing applications in the industry, starting with studies that demonstrated the benefit of using fine screens to produce consistent lower silica concentrates, followed by improvements in fine sizing equipment that have made effi cient screen classification in ball mill circuits practical. Case studies are used to demonstrate how positive sizing with screens can be used to significantly shift concentrate ‘grind/grade’ relationships.

Jul 11, 2011

By Francesco Toschi

The Special Bar Quality family comprises a wide range of steel grades, mainly requested by the automotive, energy and engineering sectors, for applications where significant performances are required (eg. stresses, temperatures, working cycles, etc.). To meet these requirements it is necessary to reach a precise control of both the mechanical characteristics and metallurgy structures along the whole production chain. For semi-product with large dimensions, such as equivalent diameters around 300 mm, this is traditionally obtained through a manufacturing route which comprises the casting in ingots followed by reheating, forging and rolling. After 2010, new processes were investigated and technologies developed to replace the ingot route with a continuous casting followed by controlled high-reduction rolling. In these processes a seamless integration of CCM with rolling is implemented so to obtain the precise control of material flow, applied deformation and working temperatures. By using the proper combination of rolling diameter, speed and applied reduction, a very good control of the metallurgy structure across the whole section can be obtained, so to also remove the internal discontinuities ("voids") generated during the continuous casting. These processes, which can be defined "forging-like", are applicable to several grades also with large semi-product dimensions (300 mm and more). Besides, removing the ingot route means increased yield and productivity, which is very beneficial to the economical management of the plant. An example of this "forging-like" process is represented by the high-reduction blooming stand installed by Acciaierie Venete in the Padova-Camin mill. This article describes its main concepts as well as its technology and process features.

Oct 30, 2017

By Jiang Diao, Xuan Liu, Tao Zhang, Bing Xie

In the present study, the oxidation process of vanadium and chromium bearing hot metal was investigated by using CaO-FetO-SiO2 slags at 1653K in MoSi2 furnace. The results indicated that both the vanadium distribution LV and chromium distribution LCr were of the orders of 2.2~2.4 with the basicity range of 1.32~1.78 and FeO weight percent range of 28%~45%. Both LV and LCr decreased with increasing basicity and decreasing FeO weight percent. The phosphorus distribution LP was of the order of 1.34~1.56. However, LP increased with increasing basicity and decreasing FeO weight percent. The oxidation ratio values of V and Cr in hot metal were above 84% and the values of P were nearly 50%. In other words, it means the addition of CaO in vanadium slag provided a certain ability of dephosphorization along with keeping high oxidation ratios of V and Cr.

Jan 1, 2015

By Junwei Han, Wenqing Qin, Dawei Wang, Fen Jiao, Wei Liu

The removal of iron impurity from zinc calcine was studied by magnetization roasting and magnetic separation. The effects of roasting temperature, magnetic intensity, ore grinding, and leaching pretreatment on iron grade and recovery were investigated. The results indicated that iron recovery increased with the increase of roasting temperature or magnetic intensity, while iron grade was always less than 22%, depending on the fact that the magnetite were not liberated completely. The good liberation was difficult to be achieved by ore grinding but was easier by acid leaching, since the magnetite grains were very fine. After the leaching pretreatment, the recovery of 76.31% with iron grade of 53.24% was obtained by one roughing and cleaning. The SEM/EDS analysis showed that a part of sphalerite, zinc ferrite and other gangues were mixed into the iron concentrate, while some of fine magnetite was reported to the tailing.

Jan 1, 2016

By L Dyer, G. J. Wilkie, P. Walters, B Tadesse, L. Keeney

Grade Engineering® is a term trademarked by the Cooperative Research Centre for Optimising Resource Extraction (CRC ORE) and includes five key levers for upgrading ores and rejecting waste prior to expensive downstream comminution and mineral processing. These five levers include natural deportment, induced deportment, bulk sorting, particle sorting and gravity separation. Over the past ten years, CRC ORE has progressed a range of technologies that exploit these levers from laboratory proof of concept through to large scale demonstration and validation. This paper details the work carried out by CRC ORE and Curtin University for assessing the amenability of an ore for its natural deportment and particle sorting attributes in an Integrated Screening and Particle Sorting (ISPS) Grade Engineering® process. ISPS is seen as a preferred method for Grade Engineering® as compared to individually operated unit operations as the benefits of each can be complementary. Furthermore, it is suggested that integrating the two levers has two important impacts: 1. Firstly, there is a risk that isolated particle sorting test results will be misinterpreted as being representative of the full sample without considering the mass balance impact of high-grade material that might have been lost in the fines fraction. This fine fraction will not be detected through the particle sorter. 2. Secondly, and potentially of more valuable impact, is that the opportunity may exist to upgrade the feed first through determining if there is a concentration of high grade to the fine (or coarse) fraction which can be separated through screening. Undertaking screening in the preparation stage of the particle sorting process will enable analysis and separation of the fine or coarse fractions of a rock mass. The result of this study provides the mining industry with an independent framework for undertaking an Order of Magnitude (ISPS) Grade Engineering® assessment on a range of constituent ore types. Keywords: Grade engineering, particle sorting, grade by size fractionation

Jan 1, 2020

By Felipe Darabas Rzatki

Polyether ether ketone (PEEK) is a high performance thermoplastic often selected for high temperature tribological applications under chemically aggressive environments. The present work evaluate the tribological behavior of a high performance PEEK composite under ambient and high temperature (30 and 80°C, respectively). The atmosphere was also varied (air or tetrafluorethane). An AMTI tribometer equipped with a hermetic chamber and a heating system was used to carry out sliding tests of PEEK cylinders on 304 stainless steel polished discs (Sq < 10 nm) with reciprocating movement and 175 N normal force. Surfaces roughness analyses were performed with a white light interferometer. As expected, there was a strong influence of temperature on the tribological behavior of the samples tested in ambient atmosphere (25% decrease in friction coefficient associated with a 100% increase in wear rate). On the other hand, samples tested in tetrafluorethane atmosphere showed no significant friction temperature dependence.

Jul 31, 2018

By Luis Armando Espitia

AISI 410 martensitic stainless steel specimens were low temperature plasma nitrided at 400°C in a mixture of 75%N2:25%H2, during 20 h. Active screen technic was used to avoid any edge effect The nitrided case is composed of expanded martensite (a’N) and e-Fe3N iron nitride, whilst chromium nitride precipitation was avoided. Surface hardness reached 1275 HV0.01. The transverse microhardness profile shows a gentle hardness gradient with a NHT nitrided case depth of 28 µm. Nanoindentation tests were carried out in order to assess the hardness (H), the Young modulus (E), the H/E and H3/E2 ratios and the elastic recovery (We) of both nitrided and non-nitrided specimens. The cavitation erosion mass losses were measured as a function of exposure time. The results showed a decrease of 27 times of the mass loss compared to the non-nitride specimens. Wear rate decreased from 2.56 mg/h for the non-nitrided condition to 0.085 mg/h after nitriding. The increment in the elastic recovery and the higher hardness values are responsible for the greater cavitation erosion resistance exhibited by the expanded martensite. Such results showed that low temperature plasma nitriding and the formation of expanded martensite are effective to increase cavitation erosion resistance of AISI 410 stainless steel.

Jul 31, 2018