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By Pragna N. H. Bhakta

The minerals industry is under political and economic pressure to reduce its processing wastes and minimize their impact on the environment: Recycling is one of the means by which the minerals Industry can reduce the quantities of effluents and residues that are discharged to the environment. The wise use of available resources is not only an environmental necessity but also an economic benefit as natural mineral resources are depleted and/or become more complex. The purpose of this paper is to review the technical and regulatory issues that will help shape the future of minerals recycling over the next ten years. Research and development to address technical issues will be discussed with emphasis on the Bureau of Mines recycling research program.

Jan 1, 1992

By Kenneth S. Coley, Michael Pomeroy, Elaine Chen

Recent work on modeling of BOF steelmaking is reviewed, highlighting the critical aspects of each approach. It is concluded that the most successful models should be based on a deep understanding of the mechanisms and kinetics of the critical reactions. The importance of the decarburization mechanism is discussed with particular reference to its role in droplet swelling or bloating which has a profound influence on the droplet residence time in the slag. Conditions which cause bloating are discussed and the rate determining step is proposed to be primarily nucleation of CO bubbles inside the metal droplet with some influence from growth by reaction at the bubble/metal interface. The discrepancy in the super-saturation ratio required for classical nucleation is discussed and an approach using a surface tension modifying parameter is illustrated. Finally, the role of CO nucleation in controlling the driving force for dephosphorization is discussed.

Jan 1, 2014

By Ahmet Haxhiaj, Jaroslaw Drelich

"Both composition and porosity of pellets are the main parameters influencing the reductive melting process in water-jacket furnace during the roasting of sulfide lead concentrate. Roasting in a smelter located in Trepçë is done at about 9000C, for pellets which are composed of PbS, CaCO3, Fe2O3, and SiO2. In order to faciltiate the formation of slag in the reductive melting, the pellets must have the proper content of CaO, SiO2, and FeO, and porosity. The plant’s practice indicates that pellets with porosity of 18% do not melt adequately in the water-jacket furnace. The optimum porosity for the proper melting of pellets needs to be 32-40% and can be achieved when pellets are loaded with more than 10 wt.% CaO. Pellets with less than 10% CaO have a limited network of pores, such that reactive gases cannot reach the entire ore structure. Also, the composition of the pellets must satisfy the ratio of CaO : SiO2 : FeO = 1 : 1.2 : 1.8 to facilitate the formation of slag in the reductive melting process.IntroductionAgglomeration roasting of sulfide lead concentrate is an important phase in the production of lead by reductive melting [1-6]. The reductive melting process is a complex process with contradictory effects of several technological indexes which many times are hard to measure and determine. In this process, loading the water-jacket furnace with pellets of optimized composition and structure can reduce the consumption of coke, and achieve high level of lead recovery. Pellets (agglomerates) should be porous, but at the same time they should have necessary mechanical strength. ‘Self-melting’ ability of pellets is controlled by the types and quantities of fluxes blended into the pellet composition. Three major additives and their role are:"

Jan 1, 2011

By J. Avraamides

Some operational difficulties have been encountered in the transfer of carbon-in-pulp technology to Australian conditions. Many gold mines? are located in remote and arid areas where the available ground water is highly saline. There is a gradual depletion of free milling oxidised gold ore reserves resulting in the necessity to treat deeper primary sulphide .deposits which can be refractory. Some near-surface ore-bodies and tailing dumps are contaminated by natural vegetative matter which can interfere with the adsorption of gold from the cyanided pulp,. Advances which have been? made include potable water conservation in elution, a new type of regeneration kiln, inter-stage screens, alternative leaching systems transportable carbon-in-pulp plants and efficient open-cut mining methods. Academic and applied research is well supported by government and industry and the results are normally rapidly disseminated and put into practice by the gold mining industry.

Jan 1, 1989

By Finlay Campbell

Nickel laterite pressure acid leach plants and reduction roast plants have had a checkered history in their engineering, construction, startup and operational reliability. Many potential projects have been the subject of detailed studies over the last thirty to forty years but relatively few have advanced to commercial production. Four reduction roast plants are currently operating, an additional one was partially constructed but never completed, and another was started up in 1974 and shut down after 12 years operation. Three acid leach plants have been built and commissioned in the last five years, trying to follow the example of the Moa Nickel plant in Cuba. An additional acid leach plant project is currently on hold, following limited construction work, its future subject to review by the owner because of potential cost over-runs. This paper attempts to discuss difficulties that may be encountered as a project is developed and will address factors which may affect production ramp-up schedule, long term production performance and overall production success. Comparisons are made with ramp-up performance at other large metallurgical plants that employ some comparable unit operations. Keywords: Caron, PAL, nickel laterite ore, ramp-up, reliability, process development, equipment design, step-out, commissioning, startup.

Jan 1, 2004

By Zhihe Dou, Zimu Zhang, Guozhi Lv, Yan Liu, Xiaoli Jiang

"Cyclic heat stewed slag washing water carries high content of alkali and calcium and may cause serious tube scaling and impose an adverse impact on normal production. This study proposes a solution to utilize washing water by absorbing and mineralizing CO2, potentially restraining scaling and being able to create calcium carbonate powders. Effects of water flux on water quality, utilization ratio of CO2 and yield of calcium carbonate powder have been investigated; meanwhile, features of calcium carbonate powder are also represented. On the other hand, effects of factors such as as injection flux, pressure of CO2 on utilization ratio of CO2, morphology and purity of calcium carbonate are also investigated. The results show unambiguously that after soften injection of CO2, calcium ions were removed effectively via precipitation, alleviating the scaling problem. High purity yet fine carbonate powder could be achieved.IntroductionNowadays, 0.34 tons of blast furnace slags will be produced when producing 1 ton of pig iron; ensuing that, 0.12 tons of steel slag will be generated with 1 ton steel production while 1.57 billion tons of steel output all over the world in the year of 2012. It is therefore a critical issue to realize zero discharge of steel slags to achieve sustainable development and cyclic economy of iron and steel industry. In recent years, research institute of MCC and China JINGYE engineering company developed a heat stewed steel slag self-decomposition technology GENERATION III to solve the problem of instability of steel slags and realize the zero discharge. However, the problem of circulation line scaling which may cause the clogging, even exploding, need to be solved. The principles of the technology are: directly spraying water to the high temperature steel slag when it is poured into the hot closed pot, realizing the selfdecomposition via utilizing the waste heat of steel slag. The washing water is recycled to achieve a cyclic utilization. The process is shown in Figure 1."

Jan 1, 2014

By Cong Wang, Siyang Long, Pengcheng Zhang, Haibin Zuo

This paper introduced the research progress of microwave treatment on coal. The mechanics of microwave treatment mainly include thermal effects and non-thermal effects. Thermal effects, which lead to cracks and changes of pore structure, attribute to the selective heating of microwave. Non-thermal effects involve the removal of oxygen functional groups, improvement of coal rank and decomposition of minerals. Therefore, microwave treatment of coal has a lot of potential applications, mainly including drying, desulfurization, improvement of grindability, enhancement of coal-water slurry property and change the combustion and gasification properties.

Jan 1, 2016

Halide media are considered as suitable alternatives to cyanide for extracting gold and have received much attention lately. The extraction of gold by iodide-iodine mixture has been patented and briefly studied without much attention given to the fundamental aspects of this process. This paper reports recent studies on the kinetics of gold extraction in iodide media, using hypochlorite, iodine and hydrogen peroxide oxidants. The kinetics of dissolution was found to be dependent on the solution pH, reagent concentration and most importantly the iodide- oxidant molar ratio. Without proper control, the gold surface can be passivated due to the formation of solid products. Thermodynamic modelling was carried out to determine the equilibria governing the dissolution process. The formation of AuI solid was also identified as a possible product during the dissolution.

Jan 1, 1992

By Reimers. Jan H.

Practically all the world's lead is produced by sintering and blast furnace smelting, or the Imperial Smelting Process which is a variant of the blast furnace process. Increased coke and labour costs and strict lead emission limits have, however, made blast furnace smelting undesirable in most countries. A change-over to other lead smelting processes providing better working conditions and lower emissions is, therefore,. expected to occur once economic conditions improve and the necessary capital expenditures can be justified. The need for new lead smelting processes has long been evident and a number of new processes have been proposed 'and advanced to various stages of development. One of the new processes is already proven on commercial scale, while several others are still being tested on pilot plant scale.

Jan 1, 1983

By John D. Kinton

A patent is a right granted by the government to exclude others from making, using, selling, offering to sell, or importing a claimed invention. Once the right is granted, the patentee may use the U.S. Federal Courts to enforce that right. Reading a patent from a litigation perspective is quite different than reading it from a technical perspective. The Judge's interpretation of the claims will affect their scope, and likely the ultimate outcome of a patent case. Additionally, the patent right can be challenged. If done successfully, the patent can be rendered invalid or unenforceable. The likelihood of success, and well as the achievement of other litigation goals is often influenced by the forum where the litigation is initiated. Finally, patent litigation costs are significant, and will weigh heavily in the decision to file (or fight) a patent lawsuit.

Jan 1, 2006

By Leon E. Laforest

An early commitment by Kidd Creek Mines Ltd. (formerly Texasgulf Canada) to follow a stringent environmental control programme from the initial stages of design and development of its metallurgical facilities in Timmins, Ontario, has resulted in the on-going attainment of extremely low levels of industrial waste emissions. This paper outlines the monitoring programme initiated and maintained by the company's environmental control section. Comparative results of environmental sampling for the periods before and after the copper smelter start-up are highlighted.

Jan 1, 1983

By Bhagyadhar Bhoi, Chitta Ranjan Mishra, Pravas Ranjan Behera

Red mud of Indian origin contains around 55% plus of Fe2O3 and is considered as a hazardous waste for the alumina industry. For production of one tone of alumina employing the Bayer’s Process, around two tones of red mud is generated from three tones of Bauxite. Conventional process of steel making is not devoid of environmental pollution. In the present investigation, efforts have been made to produce steel from red mud by adopting reduction roasting, magnetic separation and hydrogen plasma smelting route. Magnetic fraction, containing enriched iron oxide and minimal content of alumina, is produced following the first two stages which is then subjected to hydrogen plasma smelting process for production of steel. This novel concept follows a green path way for production of steel free from pollution and is termed as green steel. Further, the only by-product that is produced in the process, is water, which is eco-friendly and recyclable.

Jan 1, 2015

By Fathi Habashi

Laboratory autoclaves for hydrometallurgical investigations are available in a variety of sizes, models, and materials of constructions. They vary in sizes from 25 mL to 2 liters for laboratory studies and 5 to 50 gallons for pilot plant work. They are essential tools for studying aqueous oxidation of sulfide concentrates, dissolution of oxide minerals at high temperature and pressure and hydrothermal precipitation reactions. The maximum pressure and temperature at which any pressure vessel can be used will depend upon the design of the vessel and the materials used in its construction. Since all materials lose strength at elevated temperatures, any pressure rating must be stated in terms of the temperature at which it applies. A review of existing models and their accessories will be given.

Jan 1, 2000

By F. J. Arriagada

Where gold is present in a finely disseminated form within sulfide particles, the porosity and surface area of the calcined material strongly influence leaching since they control the penetration of solution inside the gold-bearing grains. On the basis of a stability diagram for the Fe-O-S in the temperature range of 400 to 750aC, the expected sequence chemical transformations associated with the oxidation of pyrite is discus-sed. By using analytical techniques which include scanning electron microscopy, X-ray diffraction and BET gas adsorption, the chemical and structural changes experienced by auriferous pyrite-arsenopyrite concentrates and pure pyrite samples are studied under an oxidizing roasting atmosphere of com-position 80% N + 20% O2 in the temperature range of 450 to 750°C. The results indicate that as the roasting temperature increases, the surface area of the calcines decreases sharply after a maximum value attained at about 450-500°C. SEM micrographs show that the needle-shaped tips which characterize the surface of the oxide product become wider and the size of the pores between them is decreased when the roasting temperature is in-creased from 550 to 750°C. This effect suggests that the formation of a more "closed" hematite product at higher temperatures is due to sintering associated with a faster growth and crystallization of the oxide. A strong correlation is shown between increasing roasting temperature and increase in gold lost in cyanidation tailings, an effect which may be partly attributed to the loss in surface area of the calcines.

Jan 1, 1982

By Enrico Cerilli, Bryan Salt

Xstrata Nickel’s Sudbury Smelter has systematically developed its converting aisle from a single stage to a counter current multi stage converting process. This has required the development of two unique converters; the Slag Cleaning Vessel (SCV) and the Slag Make Converter (SMC). This has resulted in a unique three stage converting process that enables treatment of secondary materials and producing a slag that can be discharged without further treatment. The paper will also discuss future changes currently being considered to further improve environmental, plant hygiene and productivity performance.

Jan 1, 2009

By G. L. Peralta

Geothermal energy is an important source of power in more than 12 countries and is a potential source in 50 countries. However, the exploration and use of geothermal resources generate residues such as scale and sludge. The scale is from the steam distribution pipes while the sludge is from cooling ponds. These solids contain significant levels of elements which are of environmental importance notably, arsenic, sulfur, copper, zinc and lead that require safe treatment and disposal. The compositions, phases, textures, morphologies and size of scale and sludge particles have been studied by laser particle size analysis, light microscopy, scanning electron microscopy, X-ray microanalysis, and X-ray diffraction. In addition, their leachability was tested with protocol leaching procedures and sequential extractions. The detailed spatial relationships and speciation of the environmentally significant constituents have received particular emphasis. The information obtained is useful in understanding how the scale and sludge are formed, their leaching behavior if disposed of in a landfill and in developing appropriate treatment strategies.

Jan 1, 1994

By Kimura. E.

Continuous estimation of phosphorus content of molten copper is required to produce phosphorus deoxidized copper in a continuous casting operation. The phosphorus content of molten copper was related to its electric resistivity, which was measured by the four-probed technique with a specially-shaped cell. In a laboratory scale, the linear relationship between the above factors was confirmed in the temperature range of 1083OC through 1200°C. The phosphorus concentration range measured was from 40 to 500 ppm. The phosphorus content was monitored successfully by measuring the electric resistivity of the molten copper in the distributor of a continuous caster in an industrial scale.

Jan 1, 1992

By Renato G. Bautista

The solvent extraction separation of nickel, cobalt and their associated metals have been considered for industrial application since the early 1960's. This review of the solvent extraction processes is limited to the industrial applications, pilot plant and the more extensive bench scale studies reported in the literature. The processes with their significant chemical and technological contributions are discussed in detail whenever the information are available. The application of solvent extraction to the nickel-cobalt processing has so far been limited to the secondary separation of nickel-cobalt containing feedstocks derived from other primary nickel-cobalt separation methods.

Jan 1, 1993

By Ali Nadir Khan

Depleting copper resources and advancing technologies have challenged industries to develop more viable, adaptable and cost efficient processes using also secondary raw materials in copper production. This study is targeting to that goal by dynamic modelling of flow and heat transfer coupled with chemical kinetics in an industrial scale flash smelting furnace settler using commercial CFD software ANSYS Fluent. First, different physical phenomena occurring inside the settler, for example, settling and separation of the matte/slag phases, and heat transfer between slag/matte phases and settler walls are studied. Secondly, reaction kinetics between matte and slag, and between slag/matte and settler walls, and impurity element distribution will be studied. This would also include phase changes phenomena due to these reactions and the flow of the reaction gases inside the settler. Settling of polydispersed droplets, their coagulation, breakage, and WEEE particle behavior are further targets of the modelling work.

By Zhou Jiemin

A mathematical model is developed to determine the economic thicknesses of refractories and insulations in rectangular furnaces, Both the heat loss cost and the lining investment are taken into account to achieve a minimum operation cost. For the sake of calculating the heat flux, the paper is particularly concerned with the simulation of the three-dimensional transient heat conduction processes in the lining and a Douglas-Rachford method is used to solve the finite difference equations, The model has been used to design an industrial electric resistance furnace operated periodically. the values of temperatures and power consumption measured from the furnace correspond with the model results.

Jan 1, 1991