Search Documents

By Liguang Zhu, Yihua Han, Qingjun Zhang, Xiaoyan Wu, Pengcheng Xiao

The evolution of chemical composition, size, proportion, and morphology of the Al-Ti-Mg-O inclusions during the steelmaking process of Interstitial Free (IF) steel from the RH to the Continuous Casting (CC) slab were investigated by means of Auto-SEM. Results showed that many of Al2O3 and MgO-Al2O3 type inclusions are modified by TiOx, while most of their shapes are irregular due to the high melting temperature. The composition evolutions and melting characteristics of Al-Ti-Mg-O inclusions under different contents of [Al], [Ti] and [Mg] were estimated by using thermodynamic software Factsage 7.0. Results showed that estimated results are in good agreement with the analysis results of industrial samples. Both the Ti alloying and spontaneous enrichment would make a high Ti concentration environment that was in favor of the TiOx existence. Moreover, more TiOx component can modify MgO-Al2O3 spine inclusion into inclusions with a lower melting temperature.

Mar 1, 2018

By Kai Hu, Xuewei Lv, Run Zhang

An oxygen sensor of zirconia-based solid electrolytes for in situ measurements of oxygen potential in high titanium slag was developed in the present study. With the facility, series of measurements of electromotive force were successfully conducted for different titanium slags at 1998 K under an argon atmosphere. Oxygen potential in the slag was calculated by the measured EMF and simultaneous readings of temperature using the modified Nernst equation. In addition, the relationship between slag compositions and the oxygen potential in the slag was explored in detail. It has been found that the oxygen potential increases with increasing FeO content in the slag and decreases with the increasing Ti2O3 content in the slag. The oxygen potential in the slag has been calculated thermodynamically and compared with the experimental measurements. The results showed that oxygen potential in the slag may be controlled by FeO/Fe equilibrium reaction.

Mar 1, 2018

By V. Yahorava

Mintek has developed a non-destructive Resin-in-Leach method for the recovery of Rare Earth Elements (REE) from phosphogypsum (PG) waste dumps. However, PG from different sources was found to be highly variable in terms of REE recovery and physical properties. Development of a pre-treatment process was initiated to improve the robustness of the current REE recovery process in order to render it effective for any type of PG. Extensive research into the mineralogy of REE associations with PG revealed that the majority of REE are trapped inside phosphogypsum clusters which inhibits their recovery. Hydrothermal treatment of PG-containing slurry was found to result in re-crystallisation of gypsum with the release of REE phases encapsulated in it. This process was tested on various PG samples and subsequent REE recoveries improved from 5 to 80%. This approach carries a large potential for unlocking value associated with gypsum dumps worldwide.

By Benjamin Kohler, Amelinda Olson, Marc Snyderman, Chanaka De Alwis, Mike Lewis, James Cox, Matthew Call, Julia Kluck

UTRS Inc. has developed a novel two-step method to extract commercially viable titanium alloys (patent pending no. 20130164167[1]). This approach has proven its potential to produce a variety of titanium alloys (Ti-6Al-4V,Ti Al ,etc.,) x y and has demonstrated a number of advantages over the current commercial titanium production process. Additionally, the UTRS Process operates without producing CO2 and eliminates the use of TiCl. Step 1: Aluminothermic reduction makes available many types of ores that could otherwise not be used. Due to the aluminothermic reduction technique and the composition of the ore,metal extracted from this step will inherently contain non-titanium elements. Step 2: Electro-refining removes undesirable elements from the thermally extracted titanium. This refined metal has a dendritic morphology with a wool-like appearance that is referred to as “titanium wool”. This new morphology of titanium allows it to have a diversity of endproduct types from titanium powder to bulk titanium.

Mar 1, 2017

By Yuanbo Zhang, Zhixiong You, Daoxian Duan, Guanghui Li, Tao Jiang, Xiaohui Fan

"Presently, high-grade manganese oxide ores are usually utilized by a coal-based reduction roasting process. However, there were some obvious drawbacks, including serious environmental pollution, high energy consumption, etc. The reduction temperature is relatively high (850-900 °C). In this study, a kind of biomass, pine black charcoal, was used as a reductant to reduce low-grade manganese oxide ores. Under the optimal conditions of reduction temperature of 600~650 °C, roasting time of 30~45 min and ratio of ore to reductant 5:1, the leaching efficiency of manganese reached more than 98%. Compared with the traditional coal-based reduction process, the reduction temperature is reduced by 250-300 °C.IntroductionManganese plays a very important strategic role in the national economy, and it is widely used not only in the metallurgical industry, but also in the light industry, chemical industry, medicine, agriculture, etc [1]. The average grade of manganese ores in China is evenly about 21%, which belongs to typical low-grade manganese ores [2]. Therefore, large quantity of high-grade manganese ores is required to import in order to meet the rapid development of Chinese manganese industry. As reported, the conventional treatment of reduction roasting has been widely applied for processing manganese oxide ores, in which coals or reducing gases (CO, H2 or CHi) were usually used as reducers [3]. However, there were some insuperable problems, such as high energy consumption, poor operating conditions, serious environmental pollution, etc [ 4-9]."

Jan 1, 2013

By Huimin Lu, Lian Zhou, Qiang Li

"A three-dimensional mathematical model is developed for the regenerative rotary hearth furnace with 40 meters medium diameter. The influence of combustion switchover and outlet pressure on the fluctuation and distribution of temperature and pressure is studied with numerical simulation method. The results showed that the temperature field and flow field is suitable for requirement of industrial production; the fluctuation of the temperature field and pressure is acceptable; the influence of outlet pressure on the furnace pressure is great.IntroduceRotary hearth furnace which is originally utilized as heat treating and reheating industrial furnace, now is also used for carbon based DRl production. With the need of market and the concern of resource recycling and environmental issues, the DRl production from ore or from waste material by rotary hearth furnace attracts more and more attentions from steel industry [1,2].When rotary hearth furnace works, the feed pellets are charged on the hearth and rotate within an annular furnace chamber with the process of reduction. For the sake of rapid reduction, usually the depth of the pellet is one or two layers, accounting for less than 90% of the volume of furnace. As result, the exhaust gases carry away a lot of heat, so that energy utilization efficient is low [3]. Currently, in order to reduce the consumption of energy and improve the production efficiency, many methods have been adopted. The regenerative combustion technology is one of the most promising."

Jan 1, 2013

By Mario Sanchez, Jose Palacios, Fernando Parada

Carbon steels have less than 0.02% copper and have low atmospheric corrosion resistance. The addition of at least 0.20 wt% Cu improves this property. Also, 0.8 wt% Cu in steel shows a hardening potential for developing high strength corrosion resistant steels. Copper slags containing 42–45% of iron, silica and minor amounts of copper were used for producing Fe–Cu alloys by reducing the oxides contained in the slag to obtain a Fe-0.84 wt% Cu alloy, which could be suitable as feeding material to manufacture a corrosion resistance steel, and also would be an alternative for minimizing the copper industry ’s environmental impact, and to introduce the application of the Circular Economy concept to the natural resources exploitation, especially in countries where their economy is strongly based in mining and metallurgical extraction.

Mar 1, 2018

By Ademar B. Lugão, Sandra R. Scagliusi, Elizabeth C. L. Cardoso

When butyl rubbers are subjected to high energy radiation, they form easy free radicals that initiate various chemical reactions. These reactions alter the molecular distribution of irradiated rubbers by crosslinking or scission affect their physical and mechanical properties. This work aims to the analysis of effect induced by γ-exposure on the crosslinking density in butyl rubbers by swelling measurements accomplished before and after irradiation at 25, 50, 100 and 200 kGy, with further evaluation of crosslinking density accomplished by Flory-Rehner equation; this is a proper procedure for the qualification of radiation resistance. It can be noticed that changes in material structure was due to build-up of new three-dimensional network in studied rubbers. Changes in crosslinking density of butyl rubber compounds emphasize that degradation mechanism is strongly influenced by gamma-radiation doses higher than 50 kGy, since chain scission process predominates over crosslinking reaction.

Mar 1, 2017

By Yuanbo Zhang, Zhixiong You, Zijian Su, Bingbing Liu, Guanghui Li, Guang Yang, Tao Jiang

Sodium stannate is widely used in the electroplating and tin alloy industry. But the traditional processes for sodium stannate production are characterized by long flowsheet, high production cost and strict requirement for the equipments, etc. In this study, a novel process for sodium stannate preparation from cassiterite concentrate and sodium carbonate via roasting in CO/CO2 mixed gas then followed by leaching was developed. The effects of roasting parameters on the Sn leaching efficiency were conducted. A Sn leaching efficiency of 77.2% was obtained under the optimal conditions. Sodium stannate (Na2SnO3·3H2O) with a purity of 95.8% was produced by the new process, which is better than that specified for the industrial first-grade product.

Jan 1, 2014

By Courtney Young, Jerome Downey

"The various technologies developed for treating spent potlining (SPL) from primary aluminum smelters have been reviewed on several occasions. The technologies generally involve physical, chemical, and thermal processes, either individually or in combination, with the primary objective of total recycle, waste minimization, or complete disposal. In general, those technologies geared for recycling involve separations and are therefore subject to recovery inefficiencies that are attributed to several factors. However, the inefficiencies could be reduced or possibly eliminated if the pots were designed for recyclability. This concept is applied to SPLASH, a recently developed SPL management technology.IntroductionAluminum is produced by molten salt electrolysis via the Hall-Héroult process. The process is conducted in an electrolytic “pot,” which is comprised of a steel frame first lined with insulating refractory brick, and then conductive graphite blocks, which serves as the carbon cathode [1, 2]. These materials are collectively referred to as “potlining.” Anodes comprised of petroleum coke/pitch are suspended above the pot and extend down into the molten cryolite (Na3AlF6) electrolyte. The electrolyte temperature is maintained at approximately 980 °C by resistance heating as low voltage (4-5 volts) and high current (50,000-300,000 amps) are applied across the two electrodes.High purity alumina is added to the cryolite bath, where it dissolves and becomes amenable to aluminum reduction at the cathode:"

Jan 1, 2008

By Xia Hong-ying, Peng Jin-hui, Zheng Zhao-qiang, Zhang Li-bo

"Preparation of activated carbon from the walnut shell by microwave assisted steam activation was studied. Influences of the three parameters, activation temperature, activation duration and steam flow rate on the adsorption capacity and yield of walnut shell activated carbon(WSAC) were investigated,optimization process was obtained by the Response Surface Methodology (RSM). The optimum preparation conditions were as follows: activation temperature of 980°C, activation duration of 41 min and steam flow rate of 1.66 ml/min. The optimum conditions resulted in an activation carbon with an iodine number of 1025 mg/g and a yield of 52.17%, while the BET surface area, total pore volume and average pore diameter of WSAC were 1328m2/g, 0.72ml/g and 2.2nm respectively. The study supported the potentiality of comprehensive utilization ofWalnut shell and the benefits of the microwave heating.IntroductionActivated carbons are one of the most important adsorbent materials in modern society because of its abundantly developed pore structure, strong adsorption ability, high surface area and thermo stability. They have extensive application in many industries fields which include gas purification [1], catalyst supports [2] and other pollutants [3]. However, in recent years, the industrial production of activated carbon is facing the problem of raw material scarcity and high cost, which limit to be widely used. Therefore, the selection of an appropriate precursor plays an important role and it has become hot sport to seek cheap raw material to lower preparation cost. As a kind of reproducible resource, the waste from agriculture and forestry is a high-grade raw material for preparing activated carbon due to is high carbon content, such as palm shell [4], rice hull [5], and coconut shell [6]. At present Walnut shell is widely accepted to be a renewable source of biomass. According to statistics, there is more than 1000,000 tonnes of walnut shells are produced in China annually [7]. As a good precursor for activated carbon production, Walnut shell is a major agricultural waste, to make better use of the cheap and abundant agricultural waste, it is proposed for activated carbon production."

Jan 1, 2014

By Mairyanne S. S. Souza, Sergio Neves Monteiro, Victor Tomazinho Bartolazzi, Dienifer Daiana Konzen

Clay is used in the production and manufacture of materials for the construction of buildings from remote periods. Advances and improvements of its properties have allowed several applications to this raw material. In this work the quality of four types of ceramic tiles manufactured or used in the northwest of the state of Rio de Janeiro and in the southeastern state of Minas Gerais was evaluated. Geometric, physical and mechanical aspects were evaluated according to the Brazilian standard NBR 15310:2009. The results indicate numerous nonconfor- mities with highlights for geometric parameters, surface flatness and yield tests. The nonconformities found in the samples indicate that there was a failure in the production control of the product and in the approval of the control of the lots.

Mar 1, 2018

By Glenio F. Daniel, Vinícius O. Barbosa, André R. Gomes, Sergio N. Monteiro, Victor B. de Souza, Frederico M. Margem

Nowadays notorious technological growth is encouraging research natural materials in substitution to more usual synthetic ones. One of those initiatives is the vegetable fibers that have been studied for the replacement of glass and carbon fibers. This research addresses broadly the study of the natural fibers mechanics properties, but none study have been made with natural fabrics, such as the pure jute fabric used in Brazil to make ropes and carpets. This work aim to evaluate the mechanical behavior of jute fabric strips with different dimensions to be used as reinforcement into polymeric composites Lots of those fabric strips were subjected to tensile tests in order to obtain the tensile resistance for each strip size. The results obtained during the tests were satisfactory and indicated that 160 × 160 × 1 mm correspond to the best result and the perfect fabric strip for the composite reinforcement.

Mar 1, 2017

By Jie Li, Wenzhou Yu, Xuewei Lv

An efficient enrichment of primary silicon from the Al–Si melt can be beneficial for the Si purification and the cost reduction of the solvent refining process. In this paper, an alternating magnetic field was used to enhance the mass transfer and promote the crystal growth of primary silicon during the directional solidification of hypereutectic Al–Si alloy. The results show that the growth rate and morphologies of Si crystals changed continuously along the directional solidification direction. With the decreasing of Si content in the melt and the weakness of the electromagnetic stirring, the crystal growth rate of primary silicon gradually decreased and the Si morphologies changed from planetocellular ,cellulardendrite, and columnardendrite, respectively. This provides a deeper understanding of the Si crystal growth during the electromagnetic solidification, which will be good for achieving a high-efficiency enrichment of primary silicon in Al–Si melt.

Mar 1, 2018

By Maria das Graças da Silva-Valenzuela, Mathilde Julienne Gisele Champeau Ferreira, Simeão Lopes Ferreira, Francisco Rolando Valenzuela-Díaz

The use of clays to formulate powder coating can improve physical properties, besides a final product with more sustainable characteristics due to the elimination of some additives, which may be substituted for the clay. We investigate the use of a modified smectite clay to formulate powder coating based on polyester resin. Four compositions of incorporated claywere evaluated (0, 4, 7, and 10wt%). Powder coating were prepared in a twin-screw extruder at 105 °C, and characterized by XRD, FTIR and SEM. Tests of flexibility, adhesion and impact strength in accordance to ASTM standards were performed. Diffractograms of the samples showed the characteristic peak of the modified smectite in d(001) * 37°(2h), indicating exfoliation of the clay. Micrographs by SEM showed the presence of lamellar structure for the clay-based powder coating.Mechanical assays were found for all analyzed coatings, indicating that sample containing 7% of clay presents the best performance.

Mar 1, 2018

By John A. Clark, Danylo Oryshchyn, Casey Carney, Stephen Gerdemann, Cathy Summers, Thomas Ochs

"Limited analysis of combustion gas streams where carbon capture is not of interest is done mainly to ascertain operation parameters. Stringent regulations on acid gases and particulates promote careful flue gas analysis. Unregulated components are typically not analyzed. Typically not more than four points (two in the boiler, and one each in the flue and the stack) are sampled. A successful oxy-fuel process with carbon capture and compression is anticipated to require as many as 12 sample points with analysis for water, nitrogen, oxygen, argon, NOx, SOx, and carbon monoxide. Carbon dioxide captured for beverages produces a high value product and the cost associated with analysis is warranted. However, carbon capture for disposal must keep all costs to a minimum. This paper will compare alternative approaches for cost-effective sampling and analysis of the carbon dioxide product streams from oxy-fuel combustion, through all stages of production through compression and pipeline/vessel delivery.IntroductionAnalysis of gases in an oxy-combustion process with carbon capture is essential to the operations of the oxy-fired boiler and the subsequent collection, compression, and purification of carbon dioxide. The process is charged with pure oxygen and not-so-pure carbon in the form of coal at the front end, generating a product of mainly carbon dioxide with traces of argon, nitrogen, sulfur compounds, nitrogen compounds, oxygen, hydrogen, and mercury. It is possible that hydrogen chloride and hydrogen sulfide may also be present in trace amounts [1]. The trace components primarily come from impurities contained in coal such as water, sulfur, nitrogen, and volatile organic compounds. Coal also contains a good deal of mineral matter that is transformed into ash during combustion, becoming particulates that can complicate the analysis regimes utilizing standard analytical equipment."

Jan 1, 2010

By T. Feldmann

Despite the ubiquity of applications for germanium, there is a lack of practically useful solubility data in acidic solutions. Previous studies were done at ambient temperature and only for commonly used acids (H2SO4, HCl). Hence, an investigation of the solubility of GeO2 in different acids was undertaken. Several inorganic and organic acids were studied in the concentration range of 1–11 mol/L and at 23, 40, and 60 °C. In the case of H2SO4 and HCl previous data was confirmed. Lower acidity resulted in a higher solubility for Ge at all tested temperatures. Tests done at 40 and 60 °C and low to moderate acidity levels, gave slightly increased solubility values at higher temperatures compared to 23 °C. This wasn’t the case at higher acidity levels, i.e., the solubility curves at different temperatures converge at high acidity. Lastly, a relationship of water activity and GeO2 solubility in different acid media was established.

By B. Manana

In heap leaching, the oxidative dissolution of value minerals encapsulated deep within large particles cannot be fully understood on the basis of the bulk solution conditions relative to variable solution conditions near the mineral surface. In the present study, the diffusion of the oxidising species through inner particle pores is simulated in a model apparatus that separates an inert platinum electrode under controlled reduction potential from the bulk solution through narrow pores of varying length. The Cu-NH3 system was selected as a model system and Cu(II)/Cu (I) as the redox couple of interest. Platinum probes inserted in the pores allowed the measurement of varying redox potentials along the pore length. Results showed that in a 10 mm pore, there exists a narrow (0.5 mm) zone near the reduction surface that is depleted of the oxidant and in which its supply is strongly diffusion limited, even if it is in abundance in the bulk solution. The consistent presence of this narrow diffusion region across all experimental results indicated that the transportation of the reduced species away from the reaction surface had the most significant influence on the potential variations within the pore. This was further supported by the minimal effect of varying concentrations of both Cu(II) and dissolved oxygen on the solution potential within this region.

By Markus A. Reuter, Jacob Wood, Robert Matusewicz

Over the last 20 years, significant improvements in copper smelter productivity have been realized through the advent of continuous smelting processes. This progress has until recently however, not been carried through to copper converting. Peirce-Smith converting has been widely used by the copper industry for 100 years but is limited by its batch nature in achieving large scale of production. A logical next step is therefore copper converting on a continuous basis with its inherent environmental benefits. A number of continuous converting technologies are currently in use or being developed within the copper industry, the majority of these operating with calcium-ferrite slags. A notable exception however is the Ausmelt Continuous Copper Converting (C3) technology which has focused on operation with ferrous-calciumsilicate or loosely called olivine type slags. This paper discusses the merits of the Ausmelt C3 process and the advantages offered in terms of operational flexibility and process control arising from the use of lime modified iron silicate slags. It also examines the effects of key process variables pertinent to continuous copper converting from both a theoretical and experimental/operational perspective.

Jan 1, 2009

By Fuqiang Zheng, Yufeng Guo, Guanzhou Qiu, Tao Jiang, Xiaoming Qu

MxTi3-xO5 is the main titanium-bearing mineral in the titanium-bearing electric furnace slag (TEFS), which is produced by direct reduction-electric furnace smelting process with vanadium titanomagnetite concentrate in Panzhihua-Xichang region of China. In order to effectively utilize the titanium resource in TEFS, the thermomechanical analysis and conditions for the growing up of MxTi3-xO5 grain were investigated, which emphasized on the effects of CaF2 and cooling rate on the crystallization of MxTi3-xO5 in the melting process. The mineral phase and morphology of titanium-bearing slag were determined by XRD and electron microscope technique, respectively. The results indicated that the average grain size of MxTi3-xO5 grown up from 30 to 92 lm and the area fraction of MxTi3-xO5 reached about 66% from 61% under the conditions of 5 wt% CaF2 and cooling rate at 1 °C/min.

Mar 1, 2017