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By E. Fockedey

he destruction of free cyanide on a Co3O4 doped carbon felt was studied. The experiments were done with an eiectrochemical filter press cell on dilute alkaline solutions containing 250 mg/l NaCN. No chloride ions were added to the solutions. The cobalt oxide protects the felt against corrosion and has a catalytic effect on the degradation of the cyanide. This kind of electrode allows working with current density as high as 1200 Aim without any visible degradation of the felt. The most interesting results were obtained with a current density of 400 Aim' at which the cyanide concentration can be lowered to 5 mg/l with a current efficiency of more than 70 % and a specific energy consumption of about 10 kWh/ kg CN.

Jan 1, 1998

By S. K. Kawatra, T. C. Eisele

"Recent advances in microbiology have made the application of biotechnology to metallurgical processes possible. Hydrometallurgy stands to gain the cost from the use of microorganisms, as they are useful for both dissolution aids and for removing metals from solution. The development of genetic engineering techniques promises to greatly increase the importance of bioprocessing of metals and minerals by the year 2000.In this paper, the basic effects of microorganisms on metallurgical processes are reviewed, and the applications which are currently either in use or near being used are presented. Representative data collected at Michigan Technological University is also given.IntroductionMany hydrometallurgical operations exist which are thermodynamically possible, but which are industrially impractical due to slow kinetics, high reagent costs, or the need for a highly corrosive environment. However, recent discoveries in microbiology indicate that in many cases these difficulties can be reduced greatly by the action of bacteria and other microorganisms (1-8).A major advantage of using living organisms in hydrometallurgy is that once the culture is established the microorganisms produce their own reagents either from the material being processed or from low-cost nutrient supplements. They thus allow extremely complex chemical reactions to be carried out at reasonable cost. The major drawback of using microorganisms is their inability to tolerate extremely high temperatures, excessive concentrations of toxic metals, or very highly acidic, alkaline, or corrosive conditions. However, the complex reactions which bacteria make possible frequently eliminate the need for such extreme conditions. Also, in recent years a number of organisms have been isolated from such exotic environments as hot springs and deep-ocean vents which can tolerate temperatures higher than was previously thought possible for any organism, and can catalyze a number of metallurgically important reactions (8)."

Jan 1, 1988

By Jyri Talja, Shaolong Chen, Hannu Mansikkaviita

"Drying (water removal) prior to smelting is always economically feasible. Unnecessary heating of vapour can thus be eliminated resulting in savings of5-15 MUSD every year.Thermodynamically removal of one ton of water out of copper concentrate at 100 °C (with 10 % moisture) requires approximately 3150 MJ/tH2o, consisting of heating of the water (377 MJ), heating of the concentrate (509 MJ) and water evaporation (2260 MJ). This is quite independent of the selected drying technology. In reality some more heat is needed as higher temperature is practiced to enhance the drying performance and to reduce the equipment size.Major nominator in drying energy efficiency is amount of gases, which depends greatly on the drying technology. Dryers based on direct heating with fossil fuels have high gas flow rates, and thus they require additional energy of about 1400-1600 MJ/tH2o, compared to indirect modemsteam drying at 250-400 MJ/tH2o.Significant benefits in energy consumption (900-1300 MJ/tH2o) with additional potential for a bonus profit of 2-4 MUSD/y year, together with full elimination of some 40 000 tpy CO2 per mid-size dryer is available by selecting sustainable, energy efficient steam drying.IntroductionRemoval of water from the concentrate is very energy intensive thus having a significant environmental impact. However, drying prior to smelting is always economically feasible and very often viable also from the perspective of process operations. This environmental impact of drying can, however, be decreased or even fully eliminated with proper selection of the drying technology.Energy incorporated in drying consists always of a number of phases like liquid (water), solids (concentrate) and gases (water vapour, purging I dilution air, combustion gases). Each phase is heated to a specific temperature during the drying process.Heating of water, heating of the concentrate and water evaporation consumes more or less the same amount of energy despite of the drying technology (3150 MJ per ton of water). In conventional drying this amount of energy is achieved by combustion of fossil fuels wirg subsequent CO2 emission. Alternatively, chemical energy derived from sulphide smelting can be utilized in a form of steam thus generating zero emission ofCO2, in modem steam drying."

Jan 1, 2012

By Yong Li, Tao Jiang, Xiangxin Xue, He Yang

"In this paper, we describe the current status and research progress on the utilization of typical industrial solid wastes in China. We propose a creative method called “eco-utilizing wastes” with an aim of both integration and increment but without second-time waste and pollution, in terms of the characteristics of typical industrial solid wastes, such as titanium-bearing blast furnace slag, high-silicon iron tailing and boron-enriched slag as well as oil shale.Situation of Typical Industrial Solid Wastes in ChinaThough mineral resources in China are abundant, most of these are low grade ores. Moreover, the distribution of mineral resources is asymmetric, which causes the increase of cost and decrease of the economic benefit. Over-exploitation of mineral resources results in a large number of solid wastes. The accumulation of solid wastes not only means the waste of valuable resources, but also causes environment deterioration. There exist some problems in the current practice of the disposal of industrial solid waste, such as only emphasizing the final results and causing new pollution and waste [1]. So the research and development of a high value-added method has a high practical relevance to our nation. Based on the present status and research progress of industrial solid wastes in China, a creative new idea and method for eco-utilization of solid wastes is proposed in this paper."

Jan 1, 2012

By Satu Strömberg

A single-particle laminar-flow technique was used to study oxidation of two nickel concentrates and a granulated nickel matte (43 wt% of Ni). Experimental conditions were: reaction gas from N2 to N2 + 75 vol% O2; gas preheating temperatures ranging from 500 to 1100°C. The major nickel-bearing minerals in the two concentrates were pentlandite and violarite, respectively. Chemical analysis of the particles was used to determine the oxidation degree of the materials, and optical and scanning electron microscopy were used to detect their morphology and mineralogy. Total desulfurization of the nickel concentrates was achieved under the most oxidizing conditions, while the sulfur removal from the nickel matte was not as efficient, especially with the coarse size fraction. Pentlandite-based concentrate was found to be less reactive than the violarite-based.

Jan 1, 1995

By R. G. Henley

Mount Isa copper concentrate was combusted in a laminar-flow furnace. The conditions simulated those likely to be encountered in flames in flash smelters of the Outokumpu (air as oxidant) and INCO (oxygen as oxidant) types. The range of conditions studied was as follows: T 400-1400°C, 02 0-100%, SO2 0-95% for residence times up to 0.23 s. The distribution of sulfur, arsenic and lead between the particles and the gas phase was studied. Combustion was very rapid provided the concentrate was adequately dispersed, i.e., no agglomerates. The importance of the latter is discussed. It was possible to oxidize 80% of the sulfur present in the con¬centrate after only 0.1 s reaction time at 1000°C in an atmosphere contain¬ing 8.5% 02 and 12.5% SO2. Best volatilizations (90% of the As, 52% of the Pb) were obtained under localized conditions attained in an air-type flame. Average volatilizations were: air-type flame, As 50%, Pb 32%; oxygen-type flame, As 40%, Pb 30%. The substitution of oxygen for air reduced the arsenic volatilization. The products of combustion were mainly cuprospinel and cuprite; small inclusions of elemental copper were found in some of the particles. At high temperatures, there was a loss of copper due to vaporization of CU( g) CuO kg) (g)

Jan 1, 1983

By Zhi-biao Yin

Copper smelter flue dusts often cannot be directly recycled to the smelting process and accumulate as hazardous wastes requiring environmentally acceptable disposal. Because of the limited amount of flue dust, a separate copper extraction process must be simple and require-a small plant investment. A flue dust process has been developed, consisting of the following steps: (1) roasting a pelletized mixture of hydrated lime and flue dust to fix arsenic and sulfur as insoluble calcium salts, (2) heap leaching the roasted pellets with a buffered ammonia/ammonium salt solution to extract copper as an ammine complex in a lined cell that is the final repository of the leached pellets, and (3) boiling ammonia from the lixiviant to precipitate copper. Condensed ammonia and the filtered solution are returned to leaching. Heap leaching in the final repository cell lowers the capital investment significantly compared with competing extraction processes. Chemistry with respect to arsenic, sulfur and copper is discussed.

Jan 1, 1992

By Joel A. Huffinan

"This presentation is being given to better inform the audience of the dependability of precious metal analysis by fire assay. A brief explanation, however, of standard fire assay exploration procedures will be given. An overview of other types of analyses by fire assay will be discussed as well, and the operation of a modern day assay laboratory.IntroductionThe use of lead oxide for the fire assay process dates back to the finds in Troy II and the Cappadocian Tablets about 3,000 B.C. Some advances have been made in the basic procedures due to instrumentation and electronics, but the fusion and cupellation procedures used in fire assay remain much the same as during this period.In 1600 AD. Agricola was the first to take a scientific approach to fire assay recording methods and procedures used (Hillerbrand and Allen, 1905) [1]. Since this period, much of the recognized research into the analysis of ores and metals was carried out in the late 1800's and early 1900's prior to World War II, and again after the deregulation of precious metals. The renewed interest in precious metals mining and metallurgy are due much to advances in precious metals heap leaching in late 1970's."

Jan 1, 1999

By K. Krishnapisharody

The phenomenon of slag droplet formation under the action of gas-stirring in steel ladles has been analyzed with experiments conducted in a thin-slice room-temperature model using water and mineral oils as the working fluids. Visual and video investigations have been performed on the interface behaviour along with measurements of liquid velocities in both phases, using the Particle Image Velocimetry (PIV) technique. The measured velocity data and observations on the interface break-up establish that the droplet formation results primarily from an instability mechanism at the interface.

Jan 1, 2008

By Jan Pan, Deqing Zhu, Xianlin Zhou, Yanhong Luo, Zixing Xue

"Magnetic roasting process, aiming at obtaining magnetite concentrate, is the principle method of exploiting siderite as a raw material in iron and steel industry. Study on preparing DRI from siderite through coal based reduction technology is sporadic. To make the process of how siderite is reduced to iron clear, roasted ore reduced from siderite by lignite under different time periods were analyzed. The results indicated that: at the temperature of 1050°C, siderite was rapidly decomposed into magnetite, and further reduced as Fe30r?FeO?Fe, the later step was slower than the previous one. A fracture of particles was found during the process of thermal decomposition and the reduction of newly formed magnetite. As the reduction proceeded, metallization rate of products increased, and the iron grain grew along with time.IntroductionWith the rapid development of economy, China demands more and more iron ores for the iron and steel industry. China has rich iron ore resources, but 97% of them are below 30% in iron grade, many are refractory and unutilized [1], therefore large quantities of imported iron ores are in a desperate need. China imported 686 million tons of iron ore in 2011 (data from the China Customs), accounting for nearly 60% of the total consumption. To guarantee the healthy development of iron and steel industry, domestic refractory iron ores have to be utilized both economically and environmentally."

Jan 1, 2013

By D. R. Kreuzer

The sulfide smelting industry is striving for up-scaling their operations by increasing the throughput and efficiencies of the furnaces. The physical phenomena related to refractory materials prevailing in smelters and furnaces are highly complex. The refractory materials are exposed to fairly high temperatures, thermo-mechanical stresses, penetration of pores, erosion and chemical corrosion. The application of numerical simulation tools is needed for the refractory engineering task to consider those phenomena and to evaluate the impact of operational regimes on the refractory design and finally on the integrity of the furnaces. The work discusses case studies of simulations addressing problems and questions related to the refractory design process. Practical simulation approaches which employ simplified models are introduced as the engineering process demands results in a reasonable time.

By Zhou Shu-cai

"A method has been proposed for the pre-treatment of high phosphorus iron ore by carbothermic reduction assisted with microwave irradiation and magnetic separation on a laboratory scale. Chemical analysis of the reduced ore sample, the metal sample and the slag sample were conducted. Based on the above research, the influences of carbon addition, microwave power and microwave irradiation time on the recovery of Fe and dephosphorization were discussed. It indicated that the increase of microwave irradiation time and power had substantial effect on the recovery of Fe while the influence of carbon addition was not obvious and the highest iron recovery ratio reaches some 95.5% when the dephosphorization ratio was 37.68%. A high iron recovery ratio and a reasonable dephosphorization rate were incompatible under the conditions investigated in this study due to the reduced iron and because unreduced P-contained gangues were not efficiently separated. This method may provide a reference for the future utilisation of high-phosphorus iron ore.IntroductionWith the rapid growth of crude steel production in China, the source of iron ore tends to become increasingly strained and is facing the risks of raw material shortage for the iron and steel industry. In order to decrease the production cost, China has to focus on the utilization of its domestic low grade iron ores for the iron and steel plants [1-2]. China has a large deposit of high phosphorous iron ore with a reserve of 7.45 billion tons which is unused in any large scale [3]. Therefore, the development of a successful and economically viable technology for high phosphorus iron ore is of profound importance. To remove phosphorus from the high phosphorus iron ore, several mineral and metallurgical processes have been proposed, such as bio-leaching [4], roasting reduction plus melting separation [5], pre-reduction and screening methods combined with mechanical crushing or air jet milling[6] selective agglomeration plus reverse flotation [7]. However these processes are not cost effective or are time consuming. The traditional pyrometallurgical process( BF+ BOF) refuse this kind of ore mainly because that molten iron is saturated with carbon or high carbon content and thus all phosphor us in the burden goes to the molten iron[8]. Therefore, it is important to exploit the cheap and abundant high phosphorus iron ore as a resource in ironmaking. In recent years, the microwave was widely introduced as a heat resource for extractive metallurgy of iron ore or other minerals. For example, microwave assisted ore milling, microwave assisted carbothermic reduction of metal oxides and microwave assisted mineral leaching issues[9-10]"

Jan 1, 2014

By Donghai Li, Cheng Pan, Xuewei Lv, Mei Liu, Enguang Guo

"Phosphorite is the main raw material for the production of phosphorus in chemical industry. More attentions have been drawn to the phosphorite concentrate beneficiated from low-grade phosphorite due to the decrease of high-grade phosphorite. For another, the agglomeration process is necessary for the phosphorite concentrate after beneficiation process. The mineralogy and sintering process of the phosphorite from Leshan, China were studied in this work. The result shows that the main phases in the phosphorite are fluorapatite (Ca3(P04)3F), hydroxylapatite (Cas(P04)3(0H)), quartz (Si02) and dolomite (CaMg(C03)2). The yield of the sinter increases with increasing the carbon dosage to 7%, and then decreases when it continuously increases. Similar regularities were found for the strength and the content of P20s of the sinter. The best strength of the sinter as well as its P205 content were discovered when the carbon dosage is 7%. Fluorapatite ((Ca5(P04)3)F) is the main phase in the sinter while fuggerite (Ca2MgSiz01) is the main binder phase.IntroductionPhosphorus is an important foundation industrial raw material of national defense industry, food industry and chemical industry, where it is used to produce red phosphorus, phosphonium hydroxide, phosphorus pentasulfide and phosphoric anhydride[l-2]."

Jan 1, 2013

By Richard A. Heckman

Destructive Thermal Technology (DTT) is used in the management of various waste streams. DTT includes Destructive Distillation, Pyrolysis and Classical Incineration. Recent work has more clearly defined the differences in these technologies based upon a more rigorous thermochemical approach. The U.S. Environmental Protection Agency (EPA) has chosen Classical Incineration as the Best Developed Available Technology (BDAT) for the management of hazardous organic wastes. Municipal Solid Wastes (MSW) and Sewage Sludges (SS) are also managed using Classical Incineration. Three environmental problems plague the use of Classical Incineration. Destructive Distillation, on the other hand, avoids these problems. It is an environmentally benign DTT for managing a wide variety of organic waste streams, including hazardous wastes. Thermochemical analysis of the available data on the performance of three types of DTT will be discussed.

Jan 1, 1994

By Sung-Joo Lee, Gi-Chon Han, Nam-Il Um, Hee-Chan Cho

"In Korea, almost all of bottom ash produced by coal power plants is disposed of in ash ponds. Ash storage areas comprise more than 80% of most coal power plant sites. This disposal method is causing environmental problems and a managerial burden for plant operators. In this study, investigations to develop a beneficiation process for separating coal pond ash into various products were undertaken. To improve efficiency of the separation, coal ash was separated by sizes and each size fraction was subject to various beneficiation processes. The separation process used were flotation (-200 mesh size), hindered settling (16x200) and tabling (16x200 and 8x16 mesh). The results showed that various marketable products, such as lightweight aggregate, sand, high-carbon fuel, could be recovered from coal pond ash using simple physical separation techniques.IntroductionDue to the increased use of coals every year, about fifty million ton of coals were used in 2007 alone. As a result, about 6 million tons of coal ash were generated. In Korea, the coal bottom ash is classified as a general industrial waste and is usually disposed of in ash ponds. The costs for this disposal method continue to increase due to rising costs of site management and development and more strict environmental regulation. Therefore, utilities are constantly looking for ways to increase utilization of coal ash. In this study, various beneficiation processes were evaluated to examine the possibility of separating coal pond ash into various products which can be used as aggregates and high-carbon fuel."

Jan 1, 2008

By Jared Ball, Darren Snashall, Paul Telford, Pengfu Tan, Ben Hogg

"The foamed converter charges were up to 3 8 per month in Xstrata Copper Smelter at Mount Isa. The issue of high converter foamover frequency had remained unsolved for many decades in Mount Isa. A thermodynamic model of copper P-S converter and a viscosity model of converter slag have been developed to simulate the slag blow and copper blow, in order to understand the mechanism of converter foamover. The model predicts the chemistry and viscosity of slag during slag blow and copper blow. The effects of oxygen potential, charge of dirty reverts, slag carryover, under-blowing, over-blowing, and temperature on the foamover and viscosity of slag in copper blow have been discussed. A theory has been developed to understand the mechanism of converter foamover. The practical solutions have also been developed and implemented in Mount Isa Copper Smelter. Some improvements of the industrial operations have been presented. After a series of improvements, the number of foamed charges per month in the converter operations has been decreased significantly from 35 in Aug 2008 to only one per month in 2009/2010.1. IntroductionThe Copper Smelter in Mount Isa receives the concentrate containing about 25% copper and produces anode copper that contains about 99% copper. There are several stages in the process. The first stage carries out in the ISASMELT™ furnace. The ISASMELT™ process produces a molten copper matte containing about 60% copper. An iron-silica slag and a sulfur dioxidebearing off-gas are the by-products of the process. The slag is taken to the slag dams for cooling before it is recycled through the Mount Isa Copper Concentrator.The matte is sent to Peirce-Smith converters. The converters further remove iron and sulphur to produce blister copper which contains about 97% copper. The anode furnaces remove any remaining sulphur and oxygen to produce anode copper that is about 99. 7% pure. This is cast into anodes and sent to the Xstrata Copper Refinery in Townsville for final refining.In the copper pyrometallurgical industrials, slag foaming is an important phenomena which occurs when the gas bubbles have stability and not rupture. Foaming greatly increases the interfacial area between matte, slag and gas and is essential for the operation of high intensity smelting processes. However, foaming or foamover is undesirable in P-S converter since it can damage the equipment and injure the operators. Figure 1 shows that the whole process of a foamover development in a converter."

Jan 1, 2011

By W. K. Tolley

The Bureau of Mines is investigating hydrometallurgical processing techniques to recycle metals from semiconductors and other advanced materials. Cadmium and tellurium were recovered from CdTe scrap produced in the manufacture of infrared optic devices. Sulfation, ferric chloride leaching, and oxygen-pressure leaching have been tested. Cadmium dissolution was achieved using oxygen-pressure leaching in dilute sulfuric acid. However, no satisfactory scheme for dissolution of the higher valued tellurium has been devised. Leaching the ground CdTe for 75 min at 110°C in 1.1M H2S0, under 120 psig 0, yielded 99.5% Cd extraction. Tellurium remained in the leach residue as TeO, and elemental tellurium; residual cadmium was less than 0.5%. The cadmium in the leach liquor was purified of coextracted metals such as gallium and iron by adjusting the pH. The cadmium was recovered as cadmium sulfate crystals by evaporating the solution. Recovery of by product metals, notably gallium, is possible.

Jan 1, 1991

By Augusto Viana Leandro Teixeira

Rare Earth Elements (REE) are fundamental for modern life products and green technologies. Supply constraints and the price peak of 2011 boosted intensive research for alternatives for processing and separation. Complex monazite- type, rare earth ores usually contain high acid consumption impurities, such as iron and aluminum, and radioactive thorium in their composition. These impurities are not removed by conventional concentration processes due to fine, micro-level association between the REE carrying minerals and the gangue minerals. This work presents a selective process route for REE extraction from iron-rich, monazite ores. The process involves sulfation by addition of concentrated sulfuric acid and pyrohydrolysis at temperatures of approximately 700–750 °C. Experimental results show REE extraction higher than 70% and low iron (below 5%) and thorium extraction (below 10%). A method based on thermogravimetric analyses was shown to be adequate to predict the behavior of a given ore sample in the sulfationselective pyrolysis-leaching process.

By Ling-yun Yi, Yuan-bo Zhang, Bing Hu, Zhu-Cheng Huang, Zhen-yuan Liao

"Nucleation and growth mechanism of iron crystal grain in coal-based shaft furnace direct reduction process by microwave heating were investigated by optical microscope, scanning electron microscope and EDX. The results indicate that microwave has selectivity on various minerals which absorb microwaves. The high temperature in certain area of pellets and thermal stress on the interface of minerals are formed, results in the wustite grain smashed along the joints, and iron crystal grains turned out a spherical shape obviously. The iron crystal nucleus is formed firstly at the edge of wustite, on the interface between grains and in the holes in pellets, and grows gradually while reduction carries on from surface layer to inner core. Microwave heating promotes the rate of transportation and accumulation of the iron crystal grain, increases growth rate of iron crystal grain and contributes to formation of dense iron-jointed crystal texture eventually.IntroductionMicrowave energy as a new energy, which selectively heating materials through internal energy dissipation, has the advantages of heating uniformity, high thermal efficiency, fast heating, clean and pollution-free compared to conventional heating motheds. Microwave energy also has obvious superiority in increasing productivity. Thus, it has been widely used in many areas, including electronics, food processing, chemical, medicine, environmental protection, and family life etc [1]. As a rapidly developed green metallurgical method, microwave heating also has been widely recognized by areas of grinding, pretreatment, pre-reduction, drying, furnacing, metal extraction, and waste materials processing and utilization. Some research achievements are gradually putting into practice, showing great potential in chemical and metallurgical industry [2-3]."

Jan 1, 2011

By J. R. Odekirk

The nature of mineral distributions and locking characteristics in mill products are important factors in understanding mill performance. Such data are obtained by microscopic point counting methods. Reduction 'of point-count data from volume to weight percentages, and reduction of data for each size fraction back to a head sample requires lengthy hand calculations. The use of computer processing for such data reduction results in obtaining information on a realistic time basis. An example of computer processed point-count data is presented.

Jan 1, 1981