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By G. O. Onyedika, M. U. Obidiegwu, G. C. Onuegbu

The effect of kolanut (KN) filler and compatibilizer (maleic anhydride) contents on the transport of toluene through low density polyethylene (LDPE) and low density polyethylene composite were studied at the temperatures 40, 60 and 80 °C.The kolanut powder used was ground to 25 μm particle size. In preparation of composite 0–5 wt% of kolanut powder and 0–2.5 wt% of the compatibilizer were mixed with 200 g of low density polyethylene in an injection moulding machine. The injected polyethylene and polyethylene/kolanut composites (LDPE/KN) were taken for sorption test. The sorption data obtained for low density polyethylene and kolanut powder filled low density polyethylene at the different temperature investigated were expressed as the molar percentage uptake (% Qt) of toluene per gram of the kola nut composites. Results show that the uptake of toluene at the five filler content (0–5 wt%) generally increased with increase in sorption temperature but decreased with increase in compatibilizer and filler contents. This can be seen at 80 °C and 0, 1, 1.5 and 2.5 wt% of compatibilizer respectively. The molar percentage uptake of toluene at 1 wt% of filler yielded the following values; 8.6789, 8.4768, 8.3476 and 8.2679 respectively. At 2 wt% it yielded 8.6224, 8.1333, 7.9525 and 7.9042 respectively, at 3 wt% it gave 8.4336, 7.9450,7.8900 and 7.7823 respectively, at 4 wt% it yielded 8.0263,7.9614,7.8218 and 7.6800 respectively and at 5 wt% it gave 7.9635, 7.8630, 7.6256 and 7.5013 respectively.

Mar 1, 2017

By Guan-zhou Qiu, Shui-shi Liu, Yu-feng Guo, Tao Jiang

"The preparation of high-quality synthetic ruitle from electric furnace titanium slag was systematically investigated by activation roasting followed by acid leaching process. The results showed that impurities such as Ca and Mg in titanium slag can be effectively removed and TiO2 grade of the product was markedly improved by the process. High-quality synthetic rutile containing 88.54% TiO2, 0.42% (CaO+MgO) was obtained under the conditions that roasted with 7.5%(wt) H3PO4 at 1000 oC for 2h, followed by two-stage leaching in boiling dilute sulfuric acid for 2h. Mechanism studies showed that anosovite solid solution and silicate minerals were reacted with phosphoric acid in the roasting process. As a result, titanium components in titanium slag turned into rutile (TiO2) and impurities were transformed into acid-soluble phosphate and quartz.IntroductionWith the gradual depletion of natural rutile and the rapid development of titanium industry in China, the natural rutile reserves cannot satisfy the requirement for production of titanium pigment and titanium sponge. Ilmenite is, therefore, becoming main raw material for titanium industry. However, because of its low TiO2 grade, it generally requires preconcentration to titanium-rich material such as titanium slag or synthetic rutile [1-3].Ilmenite resources are extremely rich in Pan-xi area of China, which account for 90.54% of total ilmenite reserves in China [4]. The titanium slag produced by electric smelting of ilmenite concentrate has high contents of Ca and Mg, and is not suitable as a raw material for chloride process and titanium sponge production. Therefore, upgrading titanium slag to prepare raw material suitable for chloride process and titanium sponge production has important significance for the development of China's titanium industry."

Jan 1, 2011

By Hemraj Dangi, S. Murali, Bhisham Yadav, Mohini Saxena, P. Asokan

"Demonstration studies were carried on the use of fly ash as soil modifier and supplier of micronutrients to improve the agricultural productivity based on the process optimised at lab scale at Advanced Materials & Processes Research Institute, Bhopal. The field trials were conducted in Uttar Pradesh (North India) Orissa (South Eastern India) and Madhya Pradesh (Central India) under different soil and crop conditions. 100-650 tonnes of fly ash per hectare were applied depending upon the soil and fly ash characteristics. Both short and long term studies on impact of fly ash on soil and food quality were conducted. With the fly ash application, the edible yield of tomato, cabbage, potato, wheat, pea, onion, paddy, sunflower, maize etc., were increased from 12 - 46% as compared to the control soil where no fly ash was used. The crop response to various elements mainly heavy metals grown in soil and fly ash applied soil was found comparable to that of control, which are within the permissible limits and meet the food quality standards. The results of impact of fly ash on biotic and abiotic properties of soil, along with the quantity and quality of agricultural produces generated under pilot scale demonstrations in three different parts of India are discussed in this paper. The outcome of this work could act as guiding force for confidence building and to maximise the use of fly ash, generated from thermal power plants worldwide as one of the major mineral waste for agriculture purposes.IntroductionThe advantages of application of fly ash in terms of improvement of soil properties and crop yields have been published by various researchers in India and abroad. Attention is also given about the possible negative and beneficial impact of pond ash in agriculture due to presence of heavy elements, radioactive nuclides and plant nutrients in fly ash. It is evident from the analysis of Indian fly ash that the presence of heavy elements and radionuclides levels are comparable with normal soil. The positive impact that has been reported is with regard to germination, yield and crop growth. The significant impacts are: long term effect of heavy and toxic elements content of fly ash on soil and up take of these elements by plant. Pilot scale demonstration studies have been completed with varying soil crop-combination under different agro-climatic conditions showed considerable improvement in the productivity of cereals, oil seeds and vegetables."

Jan 1, 2008

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

By R. Escalera-Lozano, M. Herrera-Trejo, M. A. Pech-Canul, J. López-Cuevas, A. L. Leal-Cruz, M. I. Pech-Canul

"The use fly-ash (FA) and rice-hull-ash (RHA) offers the potential for the manufacture of hybrid Al/SiCp/spinel composites via reactive infiltration, both with recycled aluminum. The main reason behind this statement is the beneficial role that both waste materials play in preventing the degradation of SiCp reinforcements when the composites are processed with aluminum in molten state. Experimentally, MgAl2O4 is formed in situ during the infiltration of SiCp-preforms in the temperature range 1050-1150 oC for 50-70 min in argon atmosphere at a pressure slightly above to that of the atmospheric pressure. Results reveal that both FA and RHA help in preventing SiCp dissolution and the subsequent formation of the unwanted Al4C3; and although FA-composites still might be susceptible to corrosion via Al4C3 -by the interaction of native carbon in FA with liquid aluminum- a proper FA treatment significantly mitigates its deleterious effect. Primary corrosion mechanisms and strategies to overcome the potential degradation effects are outlined.IntroductionOwing to inherent materials characteristics and post-processing complications –such as corrosion damage- development of metal matrix composites (MMCs) from recycling/waste sources might be a challenging task. Fly-ash (FA) and rice-hull-ash (RHA) are two primary waste materials that offer excellent opportunities for the development of Al matrix composites. Due to its singular hollow-spherical shape and low density, FA has attracted the attention of many researchers. For this reason, most of the efforts to develop Al-based composites from waste materials have been centered on the use of fly ash. Extensive research efforts in the use of FA for Al-based composites have been undertaken by Rohatgi and coworkers [1-4]. In addition to lowering costs, incorporation of fly ash into aluminum has been proved to decrease the materials’ density, increase their hardness, abrasion resistance and stiffness [1]. One of the major outcomes from the mechanical evaluation of aluminum composites prepared with fly ash is that related to their compression characteristics. Typical compressive stress-strain curves form A356/hollow fly ash composites show a linear elastic region followed by a plateau (associated to the collapse of the hollow particles), and then an increase in stress, representing densification of the foam. The crushing of the cenospheres in the composites has been related to an enhancement in the energy absorption capabilities of the material and to a better damage tolerance [4]."

Jan 1, 2008

By Munyaradzi Kwatara, Ron Schonewille, Edgar Peek, Juzer Tayabally

"The potential recovery of nickel from a South-American saprolitic laterite ore using the segregation roasting technique was investigated. The ore was heated to temperatures that ranged between 900 and 1 000°C in a rotary kiln. In all the tests, the laterite ore was first mixed with a predetermined amount of calcium chloride and either coal or coke. By varying the temperature, calcium chloride and reductant in the different tests, a preliminary set of optimal conditions was established for the specific laterite ore that was tested. A combination of chemical analysis and electron-probe-micro-analysis (EPMA) were used to determine and evaluate the effectiveness of segregation roasting on the recovery of nickel. The present paper describes the test procedure and the results that were obtained.IntroductionIt is known that laterite ore resources account for an estimated 72% of the world's nickel resources, with sulfide sources accounting for the remaining 28%. Yet sulfide resources account for 58% of the world's primary nickel production while laterite resources account for the remaining 42% [I]. There are numerous reasons for this discrepancy, but the most important one is the mineralogical and compositional complexity that is associated with laterite ore deposits. For example, this complexity currently offers only limited opportunities for upgrading, thereby creating capital intensive whole ore processing facilities. It then follows logically that the identification and application of a low-cost processing option for the treatment of laterites could potentially open up an opportunity for exploiting these vast untapped laterite resources.To this end, a preliminary screening investigation was initiated by Xstrata Process Support to evaluate the potential application of the so-called (nickel) segregation process as a unit operation that could potentially be integrated into a laterite processing flow sheet. Laboratory bench tests were performed on this segregation process and this paper details some of the findings from this preliminary investigation."

Jan 1, 2011

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 Jay Black

In the thiosulfate gold leaching process gold is oxidized to Au+ by a copper(II) ammine catalyst and complexed by thiosulfate. Copper(I) complexes, formed during gold oxidation, are reoxidised to Cu(II) complexes by oxygen. In this study, we present the results of a spectrophotometric study of the Cu(I)-NH3-Cl system, which follows on from our recent investigations of speciation in the Cu(I)-Cl and Cu(I)-S2O3-Cl systems and is part of a detailed study of copper(I) speciation associated with the gold leaching process. Formation constants for Cu(I)-NH3-Cl complexes have been determined by modeling the systematic changes in the UV spectra that occur as the concentration of the components is varied. The analysis of the data indicates that three Cu(I)-ammonia complexes are present, i.e., [Cu(NH3)2]+, [Cu(NH3)Cl2]- and [Cu(NH3)2Cl] and their respective log Kf values are 11.13, 8.33 and 10.79 at 25°C. Investigations of the oxidation of Cu(I)-NH3-Cl solutions by oxygen in the atmosphere are also presented. These experiments indicate that the reaction of copper(I) complexes progresses through various intermediates. The presence of many copper(I) and copper(II) complexes in ammonia thiosulfate solutions complicates the task of determining optimal conditions for gold leaching. Further studies are needed to identify the complexes and chemical processes that are important in the Cu(I)-NH3-S2O3-Cl system.

Jan 1, 2003

By Zbigniew Zurecki

The selection of atmosphere composition is critical for controlling surface quality of reactive aluminum alloys during solution treatments. An improper selection of annealing atmosphere can result in surface blistering in AI-Mg and sub-surface depletion of lithium in AI-U ingots. To determine optimum atmosphere compositions for homogenizing A1-Mg and Al-Li alloys, Ii number of exploratory experiments were carried out in air, nitrogen, and carbon dioxide based atmospheres including reactive impurities or additive such as moisture and sulfur hexafluoride. This paper describes the influence of these atmospheres on high-temperature oxidation and sub-surface defects. The results are discussed in terms of the change in Pilling-Bedworth ratio.

Jan 1, 1996

By Itavahn Alves da Silva, Jose Dimas de Arruda, Amanda Aparecida Fátima Arruda, da Silva de Souza, Carlos Antonio da Silva, Varadarajan Seshadri, Samuel

The knowledge of the flow field inside a continuous casting mold is essential to improve operational efficiency of the process and also to achieve better inclusion control. Physical modeling, PIV technique and CFD have been employed to assess the velocity distribution in the metal- slag interface region in a slab mold. The analysis of results shows how higher casting velocity and lower immersion depth of submerged nozzle can lead to higher turbulence in the slag-metal interface. The effects of density difference between slag and metal and interfacial tension between the phases have been highlighted.

Jan 1, 2016

By Keith E. Forrester

This paper presents results of laboratory and field optimization of a proprietary processes developed by FESI for the stabilization of heavy metal bearing wastes. The specific waste studies presented within the paper include foundry ash, aluminum sweat furnace ash and a heavy metal contaminated soil. The FESI process chemistry and engineered processes were found to be the most cost efficient demonstrated and available method of stabilizing heavy metals and highly successful in passing regulatory limits.

Jan 1, 1994

By L. Escudero-Castejon, S. Sanchez-Segado, A. Jha, Y. Hara, S. Parirenyatwa

Oxidative alkali roasting of chromite is the state-of-the-art process for manufacturing chromium-containing chemicals, which involves dealing with serious environmental problems arising from handling Cr6+-containing wastes generated in this process. In this article a new method for the extraction of Cr2O3 from chromite ores is explained, based on the carbothermic reduction of concentrates in the presence of alkali investigated in the temperature range of 950–1050 °C. Under these conditions, the iron oxides present in the ore body are reduced to metallic iron and the resulting separation of chromium occurs by forming sodium chromite (NaCrO2). The reduced samples are magnetically separated for the recovery of an iron-rich fraction, and a non-magnetic fraction containing NaCrO2, MgO and other impurities. The further treatment of the non-magnetic fraction by leaching yields a Cr2O3-rich product of approximately 85% purity, with remaining alumina, alkali and magnesia. The main advantage of the process is that, under reducing atmosphere and subsequent leaching conditions, the oxidation of Cr3+ to Cr6+ is completely avoided; thereby decreasing the risk of land, air and water pollution.

Mar 1, 2017

By Gavin K. W. Freeman

The efficient separation of cobalt from nickel is a fundamental objective in the refining of cobalt. Based on recent experience at the Corefco refinery in Fort Saskatchewan, the identification of a novel process for the selective precipitation of cobalt from aqueous ammonia leach liquors is described. The addition of calcium sulphate, CaSO4.2H2O (gypsum), to an aqueous solution containing cobalt(III) hexammine sulphate, [Co(NH3)6]2(SO4)3, will result in the precipitation of a sparingly soluble double salt having the stoichiometry, [Co(NH3)6]2(SO4)3.2CaSO4.xH2O, where x = 4 or 6. Leach residues, which may contain a significant quantity of cobalt associated with the cobalt calcium double salt, can be washed with process solutions that contain ammonium carbonate. After contact with ammonium carbonate, the cobalt is recovered into solution, while the calcium is re-precipitated as the insoluble carbonate. The simplicity of this elemental separation and its high selectivity for cobalt, as well as the demonstrated usefulness in improving cobalt recoveries, are the basis for the potential applications of this process.

Jan 1, 2003

By Marcelo B. Mourao

Interactions of carbonaceous materials with liquid Fe-C melts have been investigated experimentally by determining the volatile yield due to rapid devolatilization (Flash Pyrolysis) and rates of dissolution at temperatures ranging from 1623 to 1873 K. The volatile yield increased with increasing the temperature. The comparison of results of different types of carbonaceous materials was possible by expressing the volatile yield in terms of Enhancement Factor, fE. The rates of dissolution of spectroscopic graphite and an industrial coke seemed to obey the correlation for natural convection under turbulent conditions. The experimental data for the graphite suggested that the rate of dissolution was controlled by the mass-transfer in the liquid boundary layer adjacent to the solid sample. The value for the empirical parameter correlating the dissolution coefficient and the operating variables was found to be 0.19 which was close to that reported in the literature. The comparison of the results obtained for the coke samples with those for the graphite revealed that the impurities and the porosity of the samples can effect the dissolution rates.

Jan 1, 1992

By C. Ramasamy

The tariff reductions on imports, as a part of on-going liberalisation process in India, has fueled competition within and outside India and has, in turn provided an opportunity to reach global markets. This change calls for quality upgrades and cost-competitiveness without impairing the environment. In this context, gas based processes, contributing to improvement in quality and environment as well as processes where controls are applied when gases inimical to environment are involved, are discussed in a remelt/cast-house scenario. The impact of such processes on fabrication cost of sheet ingot is seen alongwith consumption and cost of materials and compared with a world class standard plant in North America.

Jan 1, 1996

By Joner Oliveira Alves

The aim of this work was to study the use of steelmaking slag as raw material to the production of rock wool and glass wool. Firstly, the chemical composition of the slag was analyzed. These results were used to infer the amount of additives to assemble the charge for the experiments. A laboratory-scale electric furnace was used to melt the mixtures used as charge. The melt material were turned into a water filled recipient, this process was performed in order to impose a fast freezing that is a characteristic of mineral wool production. Finally, with the rest of the melt material it was performed the Herty Viscosity Test. Samples of the produced material were characterized by different analyses. The results found in this research may lead to a technological innovation, because they indicate that the use of steelmaking slag to produce rock wool and glass wool is possible.

Jan 1, 2009

By William D. Riley

The U. S. Bureau of Mines has developed technology to recover by-product materials from aluminum scrap using engineered scavenger compounds (ESC). ESCs are structural oxides with a channel or tunnel structure that allows them to hold ions of a specitksizes and charges. The scavenging reaction is easily reversible allowing the ESC to be recharged for continued use and the ion is recovered as an electro deposit. Key features of this novel technology are; a) ESC ,systems are designed to have a high degree of selectivity for a desired ionic species. b) The recovered mater.ial requires little or no additional reprocessing prior to reuse. Two current uses for the ESC technology that are described in this paper are the removal and recycle oflithium (Li) from lithium aluminum (Li-AL) alloys; and, using ESCs as a replacement for the conventional demaging (magnesium removal) technology used by the secondary casting industry. Research indicates that the ESC technology proposed for both these applications has either 'distinct economic and/or environmental advantages over previously employed methods of recovering. metal values from aluminum scrap.

Jan 1, 1995

By Rongjin Zhu, Yue Wu, Shuxing Qiu, Qingyun Zhang, Shengfu Zhang

Co-pyrolysis of biomass and coal was investigated as an effective way to reduce the greenhouse gas emission. The effects of poplar on the thermal behavior of fat coal were studied using thermogravimetric analyzer. The blended samples heated to characteristic temperature were subjected to attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to characterize the macromolecular structure. The results indicated that the synergistic effects existed in co-pyrolysis process of blends since lower char yield than calculated values, and the synergistic effects presented positive and negative trend with the increase of temperature, respectively. The carbonyl/carboxyl C=O stretching vibration functional groups and aliphatic side chain from individual fuels were decomposed in advance during co-pyrolysis. Furthermore, the hydrocarbon-generating potential (A-factor) and thermal maturity(C-factor) of the mixtures showed nonadditivity performance.

Mar 1, 2018

By Run Huang, Xuewei Lv, Lei Lei, Guibao Qiu, Chenguang Bai

"The TiO2-rich slag and pig iron can be produced from ilmenite concentrate by the electric furnace process. In this study, ilmenite concentrate was reduced in a vertical furnace equipped with a weighting data acquisition system. The effects of reducing agent (carbon) amount on the iron reduction were studied. The phase transformation, morphology and chemical compositions of reduced samples were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. It was found that the reductive degree of ilmenite concentrate increased with the increase of reducing time. The phases of reduced samples were mostly iron, rutile, Ti3O5 and Fe2TiO5. The mass loss percentage increased with increasing the carbon amount from 8% to 12%. When the carbon amount exceeded 12%, the mass loss percentage decreased with the increasing of carbon amount.IntroductionIlmenite and rutile are the main raw materials for producing titania pigment and titanium metal. With the development of the titanium industry, huge amounts of titanium resources are needed. As sources of high-grade titania mineral decrease worldwide, more attention should be paid to the processes involving low grade mineral such as ilmenite ore. In ilmenite, MgO and CaO are the gangue parts. Therefore, the ilmenite refining becomes more and more popular. In the previous studies, the methods of ilmenite refining are electric furnace smelting, direct acid leaching, selective chlorination and thermal reduction [1]. Electric furnace smelting method is widely used in the titanium industry, however, which consumes a great deal of energies and has a high CO2 emission. Its essence is to remove iron oxides and obtain a high titania slag. So the thermal reduction of ilmenite concentrate is an important step in titanium industry, which can decrease carbon reagent consumption and save energy.Over the past several decades, many studies have been carried out on the mechanism and kinetics of the reduction of different ilmenite ores, which are as follows: The carbothermal reduction of Panzhihua ilmenite initiated at about 860 oC. In the temperatures ranging from 900 oC to 1400 oC, the reaction rate was changed like a shape of “M”. That was to say that the reaction rate increased with the growth of temperature at first, then decreased, afterward increased again and at last the reaction was arrested [2]. The Mohammad A.R group [3, 4] showed that the carbothermal reduction of primary ilmenite concentrate was faster in hydrogen and initiated at a lower reduced temperature than in argon and helium. The reduction in argon and helium had about the same rate and extent. Titanium oxycarbide started at 1000°C in hydrogen. The conversion of primary ilmenite concentrate to metallic iron and titanium oxycarbide at 1200 °C was completed in 300 minutes. Monoxide as the reductant to reduce ilmenite had been studied intensively by a few research groups [5, 6]. The rate and the degree of reduction depended on the formation of a metallic shell of iron which inhibited the transfer of CO to the reaction zones; titanium had a strong effect on the mechanism and rate of reduction of iron oxides. Wang and Yuan [7] studied the reductive kinetics of the reaction between a natural ilmenite and carbon. At temperature below 1100°C, chemical reaction was the rate controlling step, at 1100 to 1250°C mixed controlling was rate controlling step, above 1250°C diffusion through the product layer controlled the reaction. Zhang [8] investigated the reduction of natural, sintered and preoxidized ilmenite concentrates in hydrogen methane mixtures. Preoxidation and sintering of ilmenite concentrates changed their phase composition and caused a sharp decrease in specific surface area of raw materials and an increase in carburization temperature. Sintering also increased the metallization temperature of iron."

Jan 1, 2011

By C. M. F. Vieira

The main characteristics and physical and mechanical properties of clays from the county of Campos dos Goytacazes, located at the northern part of the State of Rio de Janeiro, Brazil, are presented. The characterization included mineralogical composition, chemical composition and particle size distribution. The properties related to water absorption, linear shrinkage and flexural rupture strength were obtained in samples that were prepared by 20 MPa uniaxial pressing and fired at 950 and 1100oC. The results showed that the clays are predominantly kaolinitic with high percentage of clay minerals. The kaolinitic structure associated with a small amount of fluxes confers a refractory behavior which makes difficult the sinterization and impairs the ceramic consolidation.

Jan 1, 2009