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By Yasushi Sawada

An experimental investigation was carried out to study the rates of reduction of iron oxides dissolved in liquid Ca0-SO2-A203 slags by Fe-C droplets at temperatures ranging from 1325 OC to 1550 OC. The %FeO in the slag was varied from 5.5 to 18. Flash X-ray images were employed to observe the behavior of Fe-C droplets in the slags during the reactions and for determining the slag-gas-metal interfacial area. Effect of P205 in the slag and sulfur in the droplet was also investigated. The reduction rates were determined by measuring the volume of CO evolved as a function of time and the estimated slag-gas- metal interfacial area. The reduction rates have increased with increasing %FeO in the slag and the slag temperature. The experimentally established relationship between the reduction rates and FeO (wt%) in slag is given by

Jan 1, 1992

By Arthur B. Foote

THE ball mill has superseded stamps for the reduction of gold ores in most of the recently designed plants, partly because stamps are not suited to die fine grinding required for flotation, and partly to save space and construction cost. Experience with these new mills seems to confirm the idea that it is more difficult to recover bold from a ball-mill product than it is when stamps are used for crushing. Microscopical examination of particles of gold that have passed through a ball mill show that the gold has been pounded into exceedingly thin flakes coated with a talcy surface, making it more difficult to save by amalgamation, flotation, or concentrating. Bearing in mind that gold is extremely malleable, it seems reasonable that this should be so. Contrast the action in a stamp battery, where the crushing is by impact in the presence of mercury, to the grinding and rolling under pressure in a ball mill. It is well known that a better recovery can be obtained by panning or amalgamation from a sample of ore that has been crushed by mortar and pestle than from one reduced on a bucking board.

Jan 1, 1937

The international scientific and engineer-ing community is being challenged to take advantage of the opportunity offered by the U.N. International Decade for Natural Disaster Reduction (IDNDR) program to reduce rapid onset geological hazards along the Pacific Rim. Natural disasters observe no national boundaries; international cooperation offers the best opportunity to reduce the losses these catastrophic events create.

Jan 1, 1990

Reduction of Iron Content from Silica by Gravitational Processes In this research work, it was attempted to reduce the iron contents (Fe2O3) in silica sample which was provided from Shenin silica mine using gravitational processes including jig machine, multi gravity separator (MGS), shaking table and spiral. The silica sample contains 93.75 per cent SiO2, 0.44 per cent Fe2O3, 2.78 per cent Al2O3, and 0.08 per cent TiO2 and the Fe2O3 has to be reduced to about 0.1 per cent or less than 0.02 per cent. Mineralogical studies and XRD analysis indicated the presence of haematite, pyrite and goethite as the major iron impurity phases. Mineralogical studies of polished and thin sections yielded that the degree of freedom of silica is more than 80 per cent in the range of -300 +212 mm. After elimination of fine particles, at first nine tests were carried out on crusher product (in two size fractions), wet rod mil product and scrubber product by means of Jig Machine. The best results were obtained with about 0.15 per cent Fe2O3 on rod mill and scrubber product which was not desirable. Thereafter 7 tests were carried out using shaking table; the best results were obtained with about 0.14 per cent Fe2O3 on rod mill and scrubber product which was not desirable. MGS showed the worst result in order to iron removal from silica which was not desirable. Finally 9 testes were carried out using spiral whish is the best gravitational separator for elimination of iron impurities from silica. The best result of spiral tests were achieved on scrubber product. In this test concentrate weight percent and its Fe2O3 grade were 82.32 per cent and 0.085 per cent respectively. Finally a test was carried out using 2 stages of spiral in order to develop flow sheet. In this test concentrate weight percent and its Fe2O3 grade were 78.8 per cent and 0.1 per cent respectively. This product can be used to produce float (clear flat) glass.

Sep 13, 2010

By George Kazonich

The high costs and environmental problems associated with making iron and steel in the United States is driving the development of new technologies to replace the blast furnace. A prototype reactor incorporating rocket technology was designed and built. This rapid rate reactor was operated successfully and consistently made iron metal. Minus 325-mesh magnetite particles could be reduced to iron metal in less than 50 ms in a high temperature flow through reactor. Iron product was recovered inside the reactor and in a downstream cyclonic separator. The results of typical operation and how parametric changes affected the reduction of iron ore concentrates are discussed.

Jan 1, 1993

By Y Peng, D Wannas

In the fine particle flotation technologies being developed today the fine hydrophilic (gangue) particles are usually well dispersed. These highly dispersed fine particles can be recovered into the flotation froth product by mechanical entrainment. Flocculation of hydrophilic particles caused by polymer depressants could potentially reduce the mechanical entrainment of these particles. This paper reports testwork completed on fine particles of several solids, iron oxide, hydroxylapatite, galena and sphalerite, as well as on a relatively coarse quartz sample (-75+38 ¦m). Dodecylamine was used as a collector for the quartz, and several dispersants and polymer depressants, including sodium silicate, sodium metaphosphate, zinc sulfate, potassium dichromate, corn starch, corn dextrin and carboxymethyl celluloses (with molecular weights of both 700 000 and 80 000) were used as flotation modifiers. The major part of the testwork involved flotation tests in a 200 ml flotation column. Both water and solid recoveries were recorded. The degree of flocculation and dispersion was determined by settling tests in 250 ml graduated cylinders. It was observed that flocculation of the fine hydrophilic particles significantly reduced their mechanical entrainment, while dispersion severely aggravated it. Thus, in the flotation separation of artificial mixtures of the -75+38 ¦m quartz and fine iron oxide or hydroxylapatite, polymer depressants that caused flocculation were found to perform better than the ones that did not cause flocculation.

Jan 1, 2005

By G. Castillo, J. Mortensen

"INTRODUCTION Molybdenite is typically produced as a co-product in the copper ore flotation process. At the Rio Tinto Kennecott Concentrator (RTKC) in Copperton, Utah, the molybdenite is initially floated with copper sulfides and other value minerals producing a Cu-Mo concentrate. This is then separated in the molybdenum plant by depressing copper sulfides and pyrite and floating only molybdenite. The molybdenum plant in RTKC comprises the rougher circuit and several stages of cleaning to achieve a certain grade requirement of Mo. The rougher circuit is where the first stage of separation occurs. Cu sulfides and pyrite are depressed in the rougher circuit by adding NaSH under nitrogen and in the cleaner circuit by adding NaSH under air. The depression of Cu sulfides (and pyrite) by NaSH is related to the redox activity1. It is important therefore to maintain a reducing potential in the circuit in order to achieve effective Cu-Mo separation. If the rougher circuit is under air, like RTKC’s molybdenum cleaner circuits, it is harder to maintain the target redox potential because NaSH oxidizes rapidly in the presence of air thereby increasing NaSH consumption significantly. CU-MO SEPARATION AND ROLE OF PULP POTENTIAL The collector adsorption on copper sulfide minerals is through an electrochemical mechanism2. The collector changes the surface chemistry of the Cu mineral allowing it to float. Molybdenite, or MoS2, on the other hand, floats readily in the presence of a frother as it is naturally hydrophobic. Usually, hydrocarbon oil extenders such as diesel or burner oil are added to enhance Mo recovery. In order to effectively separate Cu from Mo, the collector complex on the copper surface needs to be destabilized or desorbed using a reducing agent such as NaSH or Nokes. As long as the circuit is under highly reducing conditions, the collector remains detached from the sulfide mineral surface allowing Cu sulfide depression. Therefore, it is important to measure the oxidation-reduction potential (ORP) continually and maintain the reducing condition with addition of NaSH. For a given collector each mineral will have a characteristic potential or electrochemical window for flotation to occur3, therefore, it is necessary to reduce the potential outside of this window in order to effectively separate Cu and Fe sulfides from MoS2 minerals2. In RTKC plant, the target reducing condition is between -450 to -550 mV to effectively destabilize the collector and depress Cu and Fe minerals. Typically the dosage of NaSH used in the molybdenum plant could range from 6 to 30 gallons/min (gpm). The high dosage of NaSH could pose risk of H2S exposure. RTKC wanted to evaluate alternatives to NaSH in order to reduce its consumption and minimize risk of H2S gas generation."

Jan 1, 2016

By Girley Ferreira Rodrigues, Crocce Denise Romano Espinosa, Victor Bridi Telles, Eduardo Junca, Jorge Alberto Soares Tenorio

"Steel sector is responsible for the generation of solid waste, liquid and gaseous effluents. The Solid waste are mainly composed of slag, dust, sludge and scrap. The industry generates approximately 650kg of solid waste per tonne of steel. Approximately 10% of this waste is in the form of dust and mud. The basic oxygen furnace dust is a waste generate by steel sector. Each tonne of produced steel generates 10 to 20 kg dust. Thus, the aim of this paper is study the reduction of pellets made with BOF dust using hydrogen and study kinetic during the reduction. The tests were performed in a netzsch thermobalance to obtain the data of lost mass. This loss mass is coming from iron oxides present in the BOF dust.IntroductionThe generation of solid waste is a problem for many companies in the steel sector. The main solid wastes generated are slag, dust, sludge and scrap [1]. Beyond solid waste liquid and gaseous effluents are also generated.The basic oxygen furnace is responsible for 60% of all steel produced. This sector is the second largest generator of solid waste from an integrated steel mill, contributing with 27% of solid waste generated in a plant ( 5-7 million tons of waste generated annually worldwide) [2,3,4]."

Jan 1, 2013

By Alain Denis, Marcelo Curtes Martins, Jeferson Rocio de Oliveira

In this work we present a study of optimization of a new inhibitor for turbulence pickling line. The efficiency of inhibition was measured and the weight of loss was evaluated in four different materials to optimize the dosage of the inhibitor. In seven months we had 8.7% of reduction in pickling losses.

Oct 1, 2019

By Jörg Wallner

In order to limit SO2 emissions, the Montanwerke Brixlegg AG has installed a desulphurisation plant with the primary aim of reducing the peak emissions from the copper converter that are of particular ecological concern. The author discusses the process requirements, the desulphurisation process selected and the results achieved.

Jan 1, 1996

By Vladimir Lobanov, Pritchinm Alexander, Nikifor Ageev

"Sulfuric anhydride is one of the most voluminous technological emissions. The possibility of high-temperature SO2 oxidations without catalyst in presence of calcium-bearing filling materials (CaO, Ca(OH)2 and CaCO3) with obtaining of binding material on the basis of waterless calcium sulfate is studied. Due to application package HSC-4 the thermodynamic analysis of the specified interactions is made and following conclusions are drawn: 1) Reactions are feasible in the all range of investigated temperatures (400 – 1000 °?); 2) The best results should be expected at use of ???; 3) The heat of reaction does possible autogenous behavior of process. The researches have shown: 1) Practical possibility of the process; 2) SO2 oxidation without the catalyst is feasible in presence of ???, Ca(OH)2 and CaCO3; 3) The optimum temperature range is 600-800 °?; 4) The content of waterless calcium sulfate in a product reaches 48% that makes it possible to use as the binding material; 5) At excess of ??? the degree of SO2 collection is nearer to 100%. Introduction At processing of sulfide raw materials in metallurgical furnaces the significant amount of sulfur, mainly in the form of sulfuric anhydride is escaped. Rich gases (SO2>3 %) are used for the sulfuric acid or element sulfur production. Chemism of sulfuric acid manufacturing is based on catalytic high-temperature oxidation of anhydride. Poor gases of metal works (SO2 =2,5 %) and power combustion units (SO2 =0,5 %) after clearing discharge into the atmosphere. Commonly, to recovery of weak sulfuric anhydride the chemical and physicochemical methods are applied. A few chemical ways of recycling sulfur dioxide are applied practically. In a number of methods for SO2 recovery a pulp of metals oxides (magnesium, zinc, etc.) with formation of sulfites is used. In other case sulfuric anhydride is catch by weak sulfuric acid in the presence of an oxidizer (pyrolusite ore). Methods of absorption SO2 by solid sorbents, (carbon fibers, silica gels, zeolites) are known and put into practice. Regeneration of the saturated sorbents is realized by thermal decomposition or extraction. Obtained as a result high-concentrated solutions are a commercial product."

Jan 1, 2008

By Robert Peretti, Antonio Zucca, Andrea Manni, Silvia Serranti, Paolo Massacci, Marcello Ghiani

"This research study aims to identify the best way of processing colemanite concentrates, which is sometimes characterised by a high content of As sulphides, finely disseminated in the matrix of the boron mineral.Scanning Electron Microscopy analyses have been carried out to identify all the mineralogical constituents and to evaluate their distribution, frequency and mutual relationships.Colemanite concentrates are mainly used by chemical plants producing boric acid and gypsum. A high As content is unacceptable for further use of tailings coming from the leaching process and is very dangerous if the tailings are released into the environment.Grinding tests were conducted under dry and wet conditions in order to assess how As sulphide minerals are released from colemanite minerals.Some of the difficulties involved in obtaining selective liberation of As sulphides from colemanite minerals were overcome, although a certain decrease in As grade in the higher size classes was registered.All comminution products have been analysed by SEM, monitoring the degree of liberation of the mineralogical constituents.Flotation tests have been carried out, following different comminution flow sheets and adopting different modulating conditions in order to evaluate the influence of the following parameters:- collector concentration versus contaminants concentration (As minerals) in the froths;- kind and quantity of the frothing agent to maximise mineral recovery in the froths;- kind and quantity of the modulating agents to maximise the selectivity of the process;- conditioning modalities in order to obtain a suitable dispersion of fines and avoid segregation of Asbearing particles together with colemanite ones;- solid/liquid ratio of the pulp to minimise the water flow into the plant.Information obtained from SEM analysis has been adopted to evaluate segregation phenomena in pulp and in flotation products."

Jan 1, 2003

Reduction of titania and ilmenite ores by Cf4-H2-Ar gas mixture was investigated in a laboratory fixed bed reactor. Titania was reduced to titanium oxycarbide in the temperature range of 12OO-1500°C. At 1400-15000C, the extent of reduction of titania to titanium oxycarbide achieved more than 85% in 90 min. Optimum conditions for titanium oxycarbide synthesis by reduction of titania include temperature in the range of 1300-1450°C, methane content 8 vol% and hydrogen content above 35 vol%. Ilmenite ore was reduced by Cf4-HrAr gas mixture to metallic iron and titanium oxycarbide. Metallic iron catalyzed methane cracking and solid carbon deposition. Titanium oxycarbide formed at temperatures as low as 950°C. The optimum temperature for reduction of ilmenite is 1200°C and the optimum methane content is 8 vol%. Increase in hydrogen content increased both rate and extent of reduction. With 5 vol% CH4-75 vol% Hr20 vol% Ar gas mixture, the reduction of ilmenite completed in 60 min. Reduction of titanium oxides to oxycarbide with following chlorination may be an efficient alternative technology for processing of titanium minerals.

Jan 1, 2001

By D. Sanguinetti, A. Consigny, M. Nodwell

"Alkali precipitation of dissolved metals is an inexpensive but non-selective means of treating mine wastewater. Alternatively, sulphide precipitation can treat to below parts-per-million concentrations while selectively recovering valuable metals. While technically feasible, sulphide treatment of dilute waste streams increases the size and cost of the plant relative to the metals loading. Ion exchange has been applied at two separate sites to pre-concentrate nickel containing wastewater prior to recovery in smaller and more cost effective sulphide precipitation circuits. The result is a dual-circuit system that can maintain high selectivity and reduce overall facility cost while meeting strict effluent regulations.INTRODUCTIONAlkali precipitation using lime is the most common method of treating mining effluents for dissolved metals removal. This method is generally sufficient for waste streams containing mixed metals of little value, and for meeting modest metal concentration limits in the final effluent. Due to the non-selective nature of the lime process, the produced metal hydroxide sludge is of little value. All metals are removed together in a sludge product which cannot be re-processed for further value recovery.By contrast, sulphide precipitation can be used to selectively remove and recover valuable base metals (such as copper, zinc, nickel and cobalt), since the sulphide will preferentially target these metals without reacting with less valuable metals (such as iron and aluminum). The low solubility of the metal sulphide solids also supports the removal of base metals to lower concentrations than can be achieved with alkali precipitation in addition to other benefits discussed more fully in a prior paper (Bratty, Lawrence, Kratochvil & Marchant, 2006). The corollary to this solubility feature is that sulphide precipitation can function on influent streams containing low (< 10 mg/L) metals concentrations to meet very low parts-perbillion final effluent concentrations. Reagent overdosing is also minimized when compared to alkali precipitation."

Jan 1, 2012

By Thomas P. Battle

Ilmenite (iron titanate) is the source of over 90% of all the titanium produced in the world today. At some point during production of titanium dioxide or titanium metal the iron impurity must be removed. Too often it becomes a waste instead of a product. DuPont and MINPRO have developed a solid-state process which separates the iron and titanium components of ilmenite into different high-purity powders, which can be separated using conventional mineral processing techniques. The main reactor in this process is a unique high-temperature ball mill, where the iron segregates from the ilmenite lattice with the assistance of catalytic quantities of He\. The results of lab, pilot plant, theoretical, and scale-up studies are presented and discussed.

Jan 1, 1996

By N. A. Jabit

The dissolution behaviour of ilmenite in acid solutions has been studied by many researchers to improve the leaching efficiency. Most studies which utilized natural ilmenite from different origins resulted in different reactivity due to the alteration caused by the weathering process. Previous researchers have suggested that the greater reactivity shown by some ilmenite samples towards sulphuric acid may be a result of the mineral being relatively unaltered. In the present study a rotating synthetic ilmenite disc of 2.2 cm diameter was subjected to leaching studies in hydrochloric acid. The dissolution rates of iron and titanium from synthetic ilmenite were determined in hydrochloric acid solutions (4 M to 9 M) over a temperature range of 50 to 80°C. Results show that the rate of dissolution of both iron and titanium increased with the increase in acid concentration. However, the rates decreased with time and obeyed a parabolic rate law indicating the blockage of the surface by an insoluble product. The rates of dissolution of both iron and titanium were higher in the presence of SnCl2 and remained unaffected with time indicating the reductive role of SnCl2 which inhibits the formation of surface blocking solids. Application to natural ilmenite is also discussed.

Jan 1, 2014

By Hugo Leandro Rosa

A CBMM aplicou aços micro ligados ao nióbio em dois tipos de caçambas de carregadeiras de rodas que operam na usina de Araxá, Brasil. O objetivo foi avaliar os benefícios destes aços relacionados com redução dos custos, aumento da produtividade e vida útil dos componentes. Uma das máquinas analisadas coleta peças quentes de ferro nióbio para carregamento dos silos do britador. O uso de um aço ferramenta de alta resistência e resistente ao desgaste solucionou os problemas de deformação, desgaste e rachaduras durante o serviço, aumentando a vida útil da caçamba em cerca de 190%. A outra máquina avaliada foi uma carregadeira de rodas que opera na mina de minério de nióbio. O novo desenho com aços de alta resistência mecânica e resistente ao desgaste reduziu o peso em 14%, correspondendo ao incremento na capacidade de carga. A carga extra possibilitou um aumento na produtividade dos caminhões de 42 toneladas. Com os novos materiais, as trincas anteriormente encontradas na caçamba da pá carregadeira foram eliminadas, enquanto foi mantida a resistência ao desgaste antes oferecida pelo aço revestido com carbeto de cromo reduzindo também os custos de investimento em 7%.

Aug 17, 2017

By Paulo Henrique da Silva Gomes

A melhoria contínua dos processos é fator fundamental para o sucesso do negócio. Avaliar as melhores práticas e propor soluções que equilibrem os custos e o uso consciente dos recursos naturais transformará o negócio sustentável e sólido. Com esse ideal, foi realizado um estudo de viabilidade econômico-financeira e operacional para a implantação de um novo modelo de peação (fixação) de cargas conteinerizadas com produtos siderúrgicos (bobinas de aço) da CSN movimentados pelo Sepetiba Tecon - Porto de Itaguaí - RJ. O processo de peação de bobinas era basicamente realizado utilizando-se de madeiras fumigadas para a fixação das bobinas dentro do contêiner. O estudo objetivou a implantação de um processo de peação utilizando cintas de poliéster, reduzindo o uso de madeira, proporcionando maior segurança pessoal e agilidade nas operações. Além disto, propôs também a utilização de um implemento para acomodações das bobinas dentro do contêiner que pode ser operado por uma empilhadeira de menor capacidade, reduzindo assim a emissão de gases poluentes e o consumo de combustíveis fósseis.

Jul 29, 2018

By Ivan Rodrigues

A eficiência operacional é um fator essencial para garantir a competitividade das empresas. O desafio é estudar os processos de forma a aumentar a sua produtividade sem necessidade de investimento, gerando valor as empresas. O equipamento estudado, a Linha de Inspeção é o gargalo na produção limitando a geração de produtos em volume ou qualidade. As etapas eleitas para estudo foram os setup’s das atividades de inicio (encaixe) e final (desencaixe) do processo, atividades não automatizadas, com maior intervenção humana que sofrem interferência direta dos tempos e métodos praticados pelos operadores. Utilizando o método dedutivo, tendo como ferramenta de apoio, a pesquisa bibliográfica para fundamentação teórica e realizadas observações de campo, determinou-se os melhores tempos para realização das atividades visando a sua otimização. O presente trabalho tem como objetivo modificar o método operacional nesta Linha de Inspeção visando o aumento da eficiência produtiva, aumentando a geração dos laminados à frio. O trabalho comprovou que a mudança do modo operacional proporciona um incremento de 8% na produção (1.800t/mes).

Aug 17, 2017

By Brian Hart, Liuyin Xia, Staman Dimov

The recovery of rare earth elements (REE) is fast becoming of significant interest globally. Modern research and development programs (outside China) towards the optimization of REE mineral recovery by flotation have been lacking. Due to the mineralogical nature of many hosting deposits, the separation and recovery flotation flowsheets can be very complex. As part of a research project, a selected suite of hydroxamic acid collectors (Naphthoyl, Cyclohexyl, Benzoyl, Octyl, Terta-butyl benzoyl, Salicylic) were tested in order to examine their potential for recovery and selectivity. Micro flotation tests were conducted on a feed sample, recovery and grade of the products were used to evaluate their relative flotation efficiency and selectivity and these results (flotation with the hydroxamate collectors) were compared to a phosphoric acid/sulphonate collector mix(shorten as "mixed"). In the testing, the flotation response with the hydroxamate collectors was significantly better than the "mixed" collectors on freshly ground (no slimes removed) samples. Furthermore the tests revealed that for most of the hydroxamate reagents tested, their dosage requirements to achieve recoveries at the same levels was less than that for the "mixed" reagents. Product assays show that recovery of both La and Ce is significantly better for using the salicylic hydroxamate and that Nb, Y and Zr recovery are favored by using octyl hydroxamate. These results indicate mineral flotation selectivity could be achieved by using selective hydroxamtes. Spectral fingerprinting by TOF-SIMS surface analysis has allowed for the identification of reagent species. TOF-SIMS surface analyses of grains analysis confirmed that REE bearing grains reporting to the concentrates are doing so in response to collector attachment whereas grains reporting to the tails are doing so in response to a lack of collector. The TOF-SIMS surface data bas been used to examine the factors promoting flotation stream partitioning.

Jan 1, 2014