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By Patrick R. Taylor

In the search for the development of more "environmentally friendly" and more intensive waste disposal approaches to meet more and more stringent environmental regulations, thermal plasma-based processes are considered one of the most promising alternatives to well- established technologies such as incineration. This paper presents an overview on the research and development status of thermal plasma-based waste remediation technologies. The properties of thermal plasma are described. Due to its unique feature of high-energy intensity and super high temperature, thermal plasma is particularly capable of destroying organic- containing wastes. Its potential and promising application to waste remediation may include: treatment of incinerator ashes; metallurgical dusts (especially, electric arc furnace dust); medical wastes; radioactive wastes; and other Resource Conservation and Recovery Act (RCRA) listed hazardous wastes. Many research institutes and vendors have been involved in the development of thermal plasma-based waste treatment technology encouraged by the cleanup programs supported by the Environmental Protection Agency (EPA), the Department of Energy (DoE) and the Department of Defense (DoD). More recently, thermal plasma-based waste treatment technologies (sometimes called plasma-enhanced pyrolysis) are focused more and more on not only just destroying organic wastes but also on how to practically, and economically recover energy contained in the organic waste materials in addition to the recovery of metals in order to offset the high operating costs.

Jan 1, 2003

By Lassi Klemettinen

For better understanding and maximal value utilization of the WEEE smelting process, the behavior and distribution of different trace elements must be known. In this study, the behavior of nickel as a trace element was studied in an equilibrium system with metallic copper—spinel saturated iron silicate slag (with 3 wt-% K2O)—iron aluminous spinel—gas. The experiments were conducted in alumina crucibles at 1300 °C, in oxygen pressure range of 10−10–10−5 atm. A time series of 15–60 min experiments was also conducted for investigating the formation rate of the primary spinel phase in the system. The results show that the distribution coefficient of nickel between metallic copper and liquid slag changes from approximately 70 to 0.4 along the increasing oxygen pressure range. In addition, a significant part of the nickel deports into the spinel phase. The spinel formation was investigated based on composition analysis results and visual observations from SEM-images.

By Albert Wraith, Thomas Price, Wayne Boyd, Skip (I. E. ) Hills, Cameron Harris

Most Peirce-Smith converters inject air through tuyeres, with nitrogen representing the majority of gas passing through the process. The nitrogen controls the temperature of the vessel by carrying away heat from the reactions, both globally and locally at the tuyere tip. However, nitrogen adds energy to the bath and contributes to splashing and limits the blowing rate. High oxygen smelting has made streams of gas containing high concentrations of sulphur dioxide commonplace, which can be used to substitute SO2 for nitrogen and drastically changes Peirce- Smith converting (and all other smelting/converting processes as well). Less SO2 is required to carry away the same quantity of heat, which allows higher concentrations of oxygen and leads to the possibility of increased production. The paper investigates this substitution, its impact on converter productivity, and on the remainder of the plant. 181

Jan 1, 2009

By Patrick R. Taylor

In the search for the development of more "environmentally friendly" and more intensive waste disposal approaches to meet more and more stringent environmental regulations, thermal plasma-based processes? are considered one of the most promising alternatives to well-established technologies such as incineration. This paper presents an overview on the research and development status of thermal plasma-based waste remediation technologies. The properties of thermal plasma are described. Due to its unique feature of high-energy intensity and super high temperature, thermal plasma is particularly capable of destroying organic-containing wastes. Its potential and promising application to waste remediation may include: treatment of incinerator ashes; metallurgical dusts (especially, electric arc furnace dust); medical wastes; radioactive wastes; and other Resource Conservation and Recovery Act (RCRA) listed hazardous wastes. Many research institutes and vendors have been involved in the development of thermal plasma-based waste treatment-technology encouraged by the cleanup programs supported by the Environmental Protection Agency (EPA), the Department of Energy (DoE) and the Department of Defense (000). More recently, thermal plasma-based waste treatment technologies (sometimes called plasma-enhanced pyrolysis) are focused more and more on not only just destroying organic wastes but also on how to practically, and economically recover energy contained in the organic waste materials in addition to the recovery of metals in order to offset the high operating costs.

Jan 1, 2003

By Jerry D. St. Clair

A multidisciplinary team of scientists and engineers at Wont has been working to understand heavy metal contamination of DuPont process waste streams and technologies for abatement of these metals. As part of this effort, an extensive study was made of a specific waste stream of importance in DuPont's environmental commitment. This 200 gpm stream contains 5-5000 ppm of nickel plus a variety of inorganic and organic constituents. The chemical complexity of the waste rendered conventional. alkaline precipitation ineffective, and only through the simultaneous application of analytical characterization, fundamental chemical understanding, and process engineering did effective technical approaches emerge. In this instance, ion exchange, sulfide precipitation, and caustic digestion ultimately proved successful in reducing the nickel to below the 1 ppm target. The results of this study will be presented, along with key learnings about the process of solving heavy metal contamination problems.

Jan 1, 1994

By P. A. Rusin

Many manganiferous silver deposits remain undeveloped because standard chemical extraction methods yield poor recoveries or are ' environmentally unacceptable. Biotreatment of such ore deposits in our laboratory resulted in manganese and silver recoveries of greater than 90%. Ore and sediment samples were collected from mining sites in Colorado and Arizona. Portions of samples were incubated in a semi-solid mineral salts medium amended with 20 mM glucose mid manganese dioxide (Mn medium). The cultures were incubated at 3(fC until manganese reduction was detected by a .color change fr:om .black to clear. Bacteria from these cultures were purified on Tryptic Soy Agar and individual isolates were retested for Mn reduction by an agar overlay method. Bacteria were identified according to Bergefs Manual ?of Systematic . Bacteriology. Most of the Mn-reducing bacteria are Bacillus species. Bacterial manganese reduction kinetic experiments were performed in 52 ml mineral salts broth supplemented with manganiferous silver ore instead of manganese dioiide. These cultures were incubated with agitation for 16 d. Aliquots were removed periodically and analyzed for solubilized manganese by atoniic absorption (AA). Cyanide (1,0 M) Vias added to the remaining ore-medium mixture for a 24 h bottle roll. The supernatant was analyzed for soluble silver by AA. Similar experiments were conducted on a larger scale using 15% pulp density. After bfotreatment of the ore, standard bottle rolls were performed. The pregnant solutions and the residues were analyzed for manganese and silver?using AA or fire assay as appropriate. In sterile. controls-which received no biotreatment, manganese and silver recoveries were 0.3% and 10% respectively; During biotreatment, total manganese solubilizatiori was as high as 99.8%. The reduced manganese could . be stripped from ?the growth medium using hydrometallurgical techniques. Silver recovery vaned from 70% to 92.5%. Microbial treatment of refractory mangairlferous ores can result in high recoveries of manganese and silver. Retention time varies depending upon the relative concentrations of manganese, silver, and other metals in the ore with only two days required in some cases, The biotreatment of ore is environmentally' acceptable while the use. of chemicals such as sulfur dioxide is less so.

Jan 1, 1991

By A. Kontopoulos

The Olympias Mine in Northern Greece is producing an extremely refractory gold-bearing arsenical pyrite concentrate, containing on the average 41 3 S, 40 3 Fe, 10-12 3 As, 25 ppm Au and 35 ppm Ag. During the process selection stage, more than a dozen alternative technologies? were considered and an in-depth analysis was prepared for the three most promising, ie roasting, pressure oxidation and biological oxidation. Detailed capital and operating cost estimates were prepared, based, where appropriate, on laboratory and pilot-plant tests. A number of criteria was used for process evaluation and selection, including capital and operating costs; environmental impact, gold' recovery, stage of development, etc. Based on the above evaluation, the Sherritt Pressure Oxidation Process was finally selected. A detailed description of the process selection stage, supported with laboratory and pilot-plant test results on many of the processes considered, will be? presented.

Jan 1, 1989

By P. Halsall

Smelters of medium or low grade tin concentrates must recover a high proportion of tin from iron-bearing slags or concentrates; the volatility of tin sulphide makes possible the production of iron-free tin fume. Laboratory work defined conditions which would promote the sulphidisation of tin slags and concentrates melted with them, to result in tin recovery as fume, and a residue of less than 0.5% Sn content, which could be controlled to vary with the value of tin. Subsequently pilot-plant work on 6-tonne and 15-tonne scale led to a commercial plant of 45 tonne. capacity (1962), for melting and fuming primary and secondary low-grade tin materials by submerged combustion. Some factors contributing to the rate of Working expressed in terms of the 'half-life and the amount of work done, the 'half-life-tonne' are studied, leading to the design and operation (1972) of the 100-tonne water-jacketed unit, presently in use, treating a wide range of slags and low tin-content ores and residues.

Jan 1, 1983

By Kazutaka Kunii

It is invariably certain that after punching for IC Leadframes, scrap metal were generated. These seraps were re-dissolved and in order to use as raw material for leadframes, it is necessary to remove the Ni plating. In this study a simple method was developed for the removal of Ni plating by surface oxidation of Ni plating. For this purpose a fundamental study was carried out on the oxidation behavior of Ni plating. Results showed that by controlling the oxidation condition, a considerably high rate of Ni could be removed.

Jan 1, 1996

By Yuanbo Zhang, Bin Xu, Guanghui Li, Xiao Kang, Chen Liu, Tao Jiang

Iron-bearing dusts, containing valuable constituents such as Fe, CaO, MgO, C, etc., are generally utilized as raw material in iron ore sintering. However, the dusts characterized by low granulating and refractory performances always lead to negative effects on sintering indexes. As we know, the innovative process named composite agglomeration process (CAP) has a series of advantages compared to traditional sintering process (TSP). In CAP, part or all of the iron-bearing dusts is made into green pellets with 5-15mm in diameter, while the rest of iron-bearing dusts and all of the other fine ores is granulated after mixing with fuels, fluxes and return fines. Compared with TSP, CAP could increase the ratio of iron-bearing dusts from 5% to over 20%. Meanwhile, the yield, ISO tumbler index and productivity reached 75.82%, 65.13% and 1.531t·m-2·h -1, respectively.

Jan 1, 2015

By Fabiano A. C. M. Passos, Vanessa P. R. Silva, Lillian M. B. Domingos, Fernanda A. N. G. Silva, Zuleica C. Castilhos, Roberto B. Faria

Wastes from gold mining need to be monitored from the beginning of mining activities until to the mine closure. Wastes from tailings dam were characterized by XRD, XRF, elemental analysis of carbon and sulfur and ICP-OES. In flotation waste (FW) were observed quartz, dolomite, pyrite, muscovite and chamosite were observed. Meanwhile, in cyanidation waste (CW), besides those described in FW, minerals such as sphalerite, galena, pyrrhotite, microcline and albite were detected, indicating a higher concentration of sulfide minerals in the cyanidation waste. In relation to C and S content, to FW and CW, they were 2.5 and 0.0% and 0.64 and 15.4%, respectively, confirming the majority of sulfides at CW sample and indicating the absence of the flotation organic reagents at the cyanidation waste. The analysis by ICP-OES indicated As, Zn, Pb, Cr and Cd content for FW and CW: 13.30 and 343 mg/kg; 399 and 7,900 mg/kg; 136 and 13,000 mg/kg; 130 and 260 mg/kg; 3.60 and 84.60 mg/kg, respectively. It was also verified significant levels of heavy metals, which indicates the necessity of performing wastes toxicity tests.

Mar 1, 2017

By Kazutoshi Haga, Atsushi Shibayama, Altansukh Batnasan

This study presents a viable approach for recovery of precious metals such as gold (Au), silver (Ag), palladium (Pd), and base metals, including copper (Cu), nickel (Ni), cobalt (Co), lead (Pb) and zinc (Zn) from waste printed circuit boards (WPCBs) via iodine-iodide leaching and precipitation. The behaviours of dissolution and precipitation of precious and base metals during iodine-iodide leaching and precipitation processes were discussed. Sodium hydroxide (NaOH) was used to remove base metal impurities exist in the pregnant leach solution under alkaline conditions. Precious metals remained in the resulting solution from NaOH precipitation were recovered by reduction using ascorbic acid (L-AA) solution. Results show that under optimum leaching conditions, almost all (> 99%) of Au was dissolved in an iodine-iodide solution when the dissolution efficiencies of other precious metals (Ag, Pd) and base metals, besides calcium (leaching of 25%) were less than 1 and 6%, respectively. The study revealed that more than 95% of Cu, Ni, Pb, Zn, Fe and Mn were initially removed from the pregnant leach solution at pH of 9.3 with addition of 0.1 M NaOH. Then 99.8% Au, 81.7% Ag and 74% Pd were precipitated from the obtained solution after NaOH precipitation while L-AA dose was 0.6 ml/ml at the condition. It can be concluded that the precious and base metals could be recovered selectively and economically from WPCBs via iodine-iodide leaching followed by precipitation using NaOH and L-AA.

Mar 1, 2018

By Jinxing Ji

Several fundamental aspects related to the nickel electrowinning from chloride electrolytes have been addressed in this paper. The thermodynamic study includes the activity coefficient of the hydrogen ion and the speciation diagram of NiCI2 solutions. The activity coefficient of the hydrogen ion (YH+) was calculated and estimated experimentally using a combination glass pH electrode. It was found that YH+ was greater than one in concentrated NiCl2 solutions and increased significantly with increasing NiCl2 concentration. The speciation diagram for NiCl2 solutions was plotted with YH+ and the effect of the ionic strength on the equilibrium constants being taken into account. It was discovered that the predominant nickel species in the acidic region were Ni2+ and NiCI+ in 0.937 M NiCl2 solution at 25°C. Electrodeposition tests demonstrated that higher Nit' concentration in the electrolyte improved the current efficiency of nickel electrodeposition (CENi). The additions of H3BO3, and NH4Cl increased very little the current efficiency of nickel electrodeposition at pH 1.5 and temperature 60°C. However, the addition of sulfate decreased the current efficiency of nickel electrodeposition. Nickel electrodeposition was also found to be a steady-state process since the amount of acid added to the electrolyte at a constant pH increased linearly with time during galvanostatic electrodeposition. The cathode surface pH during nickel electrodeposition was measured using a flat-bottom combination glass pH electrode and a 500-mesh gold gauze as cathode. The cathode surface pH was found always to be higher than the pH in the bulk electrolyte, and if the current density was sufficiently large, it would eventually reach a level causing precipitation of insoluble Ni(OH)2(s) on the cathode surface. Rotating disc electrode studies revealed that the rate of nickel electrodeposition was first order with respect to the activity of nickel ion and zero order with respect to the activities of chloride and hydrogen ions. The rate of hydrogen evolution was found to be first order with respect to the activity of hydrogen ion and to be zero order with respect to the activities of nickel and chloride ions. These findings indicate that nickel deposition and hydrogen evolution proceed independently.

Jan 1, 1995

By J. Winters, L. Vos, C. Canoo

Committed to a sustainable development of zinc applications, Union Miniere is investigating processes for the minimisation of waste and residues originating from the classic hydrometallurgical zinc process. In that context, Union Miniere has developed a method for the cold inertisation and solidification of goethite, the Graveliet® process. The result is a hard and inert gravel that can be used in the building industry. During the past two years, a pilot plant for the production of Graveliet® has been built and operated. In the present paper, the Graveliet® process and the pilot plant are described after which the properties of the produced gravel are discussed, from both a mechanical and an environmental point-of-view. Graveliet fulfils the criteria for use as a secondary building material. The GravelietJ process is a viable technology to avoid stockpiling of goethite residues and it thus assures the long-term development of the hydrometallurgical zinc process.

Jan 1, 2000

By Frank A. Stephens

The process of converting iron ore (principally Fe,03 or Fe30,) into iron carbide (Fe,C) to be used as feedstock for steel-making yields complex mixtures of several Fe-containing compounds as a function of processing conditions. In addition to the above compounds (hematite, magnetite and cementite), the mixtures typically contain wustite (FeO) and metallic iron(Fe). Mossbauer spectroscopy has been developed into aquantitative analytical method for monitoring the degree of conversion to carbide from samples periodically extracted from a fluidized bed reactor type of pilot plant. Calibration of absolute quantities of the above five compounds is based on standards prepared from known mixtures of the high purity individual phases. The PC-based spectrometer allows fitting of the well-known spectral components of each of the five phases, the resulting spectral areas then being compared with the calibration curves via PC software to yield the weight fraction of each. Emphasis has been placed on standardizing and simplifying the analysis procedure for routine use in an industrial environment.

Jan 1, 1993

By Wei Gao, Qing-cai Liu, Cun-fang Lu, Huimin Zheng, Jian Yang, Chun-ling Yao

"Mercury in flue gas of coal-fired plants was concerned as another serious pollution when sulfur dioxide pollution was controlled now. The adsorbent made from fly ash by thermal precipitation sulfur to remove mercury in fuel gas from coal combustion plant, SEM, BET, TGA and other measurement methods were used to characterize the effect on surface morphology, sulfur distribution and specific surface. High temperature deposition furnace was applied to increase sulfur content in fly ash based adsorbents produced in lab. The study found that sulfur attached to the adsorbent surface, mesopore and microporous structure, increasing its sulfur content of adsorbent. Sulfur was filled in interspace as small molecule S2, S5, increased their surface area and enhanced their adsorption capacity. The specific surface area increased by thermal precipitation sulfur, and specific surface area which increased with increasing temperature.1. IntroductionThe mercury emission caused by human activity has accounted for 10%-30% of total mercury emission all over the world[11, and the emission from coal-fired power plant have a huge proportion of these emission caused by human activity. Active carbon microstructure and surface morphology play an important role in its adsorption capability, which offers the potential for controlling environmental pollutant, such as sewage, fuel gas, atmosphere and et al [2,31, because it is a material with high specific surface area that long been considered as an excellent adsorbent. At present, include activated carbon, fly ash, calcium-based sorbents and other novel adsorbents. The adsorption capacity and production cost were very important in the process of mercury removal by adsorbents, so the mercury removal has focus on developing adsorbents of highly-efficient. In particular, the waste of metallurgical from coal combustion and the others have a significant advantage about the cost, and they have the highly-efficient in mercury removal after modified to enhance their adsorption capacity, such as fly ash of coal-fired. Apart from specific surface area, element content, pore structure, and surface morphology of activated carbon have great effect on its adsorption ability. Compared to adsorbents without modification, active carbon impregnated with other elements, such as chlorine, sulfur, bromine and et al. had more excellent characteristics to remove specific pollutants."

Jan 1, 2011

By Zhuoqing An, Qi Li, Zhancheng Guo, Yanling Zhang

Fluidized bed is an important iron-making reactor, especially for the finely sized iron-bearing materials. However, defluidization caused by sticking between particles extremely limited its wide spread commercialization. In this paper, apparent viscosity was put forward to express the ability of particles to resist movement, which is reasonably considered as the comprehensive results of interaction between particles. Meanwhile, an experimental measuring method of apparent viscosity of particles was proposed, during which the torque exerted on the rotating blade in a particle layer is measured, and then the apparent viscosity is obtained based on the motion equations of powder particles. Further, the apparent viscosity of iron particles was measured by using of this method, and the effects of shape, size, and temperature were examined. The data can provide important information for understanding when and why defluidization happened.

Jan 1, 2015

By Antoine Allanore, Luis A. Ortiz, Donald R. Sadoway

"The steelmaking industry has drastically reduced its energy consumption in the last fifty years, and today’s technologies are considered to operate at their optimal efficiency with respect to energy needs. To cope with new constraints related to greenhouse gas (GHG) emissions, a change of paradigm is necessary. One of the promising technologies that could be deployed to help reach CO2 mitigation targets relies on the intensive use of electricity: molten oxide electrolysis (MOE). This paper presents the key process parameters that need to be tuned to address the practical needs for both high productivity in a steelmaking reactor and for an energy efficient process. Herein we show that contrary to common perception, the electrolysis process for ironmaking requires less energy than today’s chemical reduction route. Furthermore, we prove that most of the energy that must be provided to operate the electrolytic iron production cell is thermal energy which is readily generated by joule heating during electrolysis due to large currents being passed through the electrolyte. The energy consumption of the electrolysis cell is therefore shown to be highly dependent on the cell configuration and the chemistry of the electrolyte. As a consequence, the CO2-impact of the technology strongly depends on both the power production mode and the technological choices for design of the process, including cell configuration. Surprisingly enough, even when the electricity generation is not carbon-free, MOE still appears to be viable from the perspective of reducing GHG emissions providing sound reactor design considerations are made.IntroductionIn the context of greenhouse gas (GHG) emissions mitigation, the steelmaking industry is considering several techniques that could sustain the efforts and progress achieved by this sector in the last decades [1]. A recent report [2] on potential routes for low-CO2 steelmaking highlighted for all techniques both the strong dependency of CO2 emissions on electric power production mode and the need for a decrease in energy consumption per tonne of steel. Incited to innovate with respect to this last criterion, the steel industry considers electrolysis to be a promising technological solution, and in particular the molten oxide electrolysis (MOE) process. This process conducts electrolysis in a mixture of oxides that dissolve the iron oxide feed, which by the action of electric current is decomposed into liquid iron and oxygen gas. The opportunity for reduction in energy consumption during steelmaking by MOE is commonly attributed to the “direct” pathway from iron oxide to liquid metal offered by the use of a molten oxide melt and operation at a temperature above the melting point of iron, ideally 1600°C, to provide enough superheat for tapping the molten iron product:"

Jan 1, 2011

By Mingming Zhang, Marshall S. Coe, Marcelo W. Andrade

To supply iron units and flux burden in blast furnaces, sinter basicity is one of the vital parameters for sinter plants. The sinter basicity also plays an important role in sinter quality since it imparts the formation of different mineral phases in sinter. Pot-grate sintering tests were carried out with low and high basicity to investigate the effects of sinter basicity on sinter mineralogy, properties and productivity. It was found that with an increase in sinter basicity, both sinter productivity and reducibility (RI) increased. Tumbler index (TI) and low temperature degradation index (LTD) of high basicity sinter were comparable to low basicity sinter. Softening and melting tests showed that sinter with 3.5 C/S basicity had slightly higher softening temperature comparing to lower basicity sinter with C/S 2.6, acid and fluxed pellets. XRD analyses confirmed the formation of silico-ferrite of calcium and alumina (SFCA) and calcium ferrite (CF) in the tested sinter samples.

Jan 1, 2015

By Antoine Allanore, Guillaume Lambotte, Bradley R. Nakanishi

Current industrial methods used for rare earth element (REE) extraction involve: 1) ore enrichment, 2) separation of rare earth oxides (REOs), 3) chlorination or hydrofluorination, and 4) individual electrowinning of REEs from a molten halide electrolyte. The complexity of REE extraction is inherited from their electronic configuration. Recently, molten oxide electrolysis (MOE) has been used to produce reactive metals directly from their oxides, e.g. titanium. As a single-step alternative to processes 3) and 4), or laboratory has investigated rare earth extraction by MOE. A key challenge is to find a molten electrolyte more stable than REOs. One possibility is to use binaries of REOs directly as a solvent. We have, therefore, developed two experimental approaches for studying molten REOs at temperatures exceeding 2200oC. The present work reports the most recent experimental results obtained with La2O3-Y2O3. Those promising results demonstrate potential for operating with molten REOs and refine the underlying materials challenge for electrodes to enable metal recovery.

Jan 1, 2015