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Agnihotri A.,Jawaharlal Nehru Aluminium Research Development and Design Center | Pathak S.U.,Visvesvaraya National Institute of Technology | Mukhopadhyay J.,Indian Institute of Technology Gandhinagar
Transactions of the Indian Institute of Metals | Year: 2014

Aluminium reduction process is a nonlinear, time varying electrochemical process, in which alumina (Al2O3) dissolved in cryolite (Na3AlF6) is electrolysed to produce molten aluminium. In industrial practice the term noise refers to unsteady voltage signal in the reduction cell or random and/or uncontrolled fluctuations in the cell voltage; it can be used to identify problems in the cell operation. The main objectives of the reduction process is to achieve as high a current efficiency as possible with minimum energy consumption. Noises of certain frequencies are generally considered unfavorable to cell current efficiency and energy consumption. Therefore, noise control is an important issue in commercial cell automatic control system. The present paper analyses noise from different sources during cell operation and their possible causes with help of Fast Fourier Transformation techniques in terms of frequency and amplitudes of the fluctuations. An advanced data acquisition system was used for collecting the data required for the noise studies. The characterization of the three types of noise generated is discussed. Real-time algorithms have been implemented to allow on-line estimation of the noise sources and intensities. © 2013 Indian Institute of Metals.


Agnihotri A.,Jawaharlal Nehru Aluminium Research Development and Design Center | Pathak S.U.,Visvesvaraya National Institute of Technology | Mukhopadhyay J.,Indian Institute of Technology Gandhinagar
Advanced Materials Research | Year: 2014

The Hall-Heroult process for the production of aluminium is based on the electrochemical reduction of alumina (Al2O3) dissolved in a cryolite (Na3AlF6) based electrolyte. Instability in cell voltage is referred to as noise. Normal voltage noise is inevitable due to bubble evolution and it has little effect on performance parameters such as, current efficiency and power consumption. Metal rolling noise (wavy noise) is caused by the disturbances in cell magnetic field and it affects the cell current efficiency adversely. Investigating the causes of the cell instability in the aluminium smelting cells can lead to better cell performance. Understanding the variation in cell voltage is critical for cells, because magnitude of voltage determines the energy consumption pattern in the process and hence, any saving on voltage can save energy. Voltage affects the current efficiency of the cell and an optimum cell voltage leads to higher current efficiency without compromising on energy consumption. Magnetic, current distribution, heat loss and voltage at zero current measurements along with online current and voltage signal can help to identify the problems and their combined effects on the performance of the cells. In order to estimate the loss in current efficiency of the aluminum electrolysis cells due to metal instabilities, measurements were performed and data analyzed. The present paper analyses the effect of voltage fluctuations (noise) during metal instability along with cause of instability and its effect on current efficiency of the cell. Measurements carried out to estimate the deviations from the normal cell operations are also discussed. © (2014) Trans Tech Publications, Switzerland.


Rai S.B.,Jawaharlal Nehru Aluminium Research Development and Design Center | Wasewar K.L.,Visvesvaraya National Institute of Technology | Mishra R.S.,Jawaharlal Nehru Aluminium Research Development and Design Center | Mahindran P.,Jawaharlal Nehru Aluminium Research Development and Design Center | And 3 more authors.
Desalination and Water Treatment | Year: 2013

In Bayer process of obtaining alumina from bauxite, the insoluble product generated after bauxite digestion with sodium hydroxide at elevated temperature and pressure is known as "red mud" or "bauxite residue." It is an alkaline residue with a high pH of 10.5-12.5. It is disposed as dry or semi dry material in red mud pond or abandoned bauxite mines. The environmental concerns which are related to the disposal of red mud are its large quantity and causticity resulting in soil and groundwater pollution. At present, there is no viable process developed for utilizing the bauxite residue, consequently, this large quantity of waste material is required to be disposed economically and safely to the environment. In this view, a pH-reduction processing step is incorporated to ameliorate the red mud by sequestrating it with CO2. By mixing carbon dioxide into the bauxite residue, the compound's pH level can be reduced to levels normally found in alkaline soil. It was seen that full neutralization of red mud takes place following CO2 carbonation, but the pH rebound of carbonated mixtures takes place and the pH drifts upward to a value of 9.4-9.7 with time when solution and solid remains in contact. Chemical, mineralogical, and morphological analysis of neutralized red mud is also studied in the paper. © 2013 Balaban Desalination Publications.


Rai S.,Jawaharlal Nehru Aluminium Research Development and Design Center | Wasewar K.L.,Visvesvaraya National Institute of Technology | Lataye D.H.,Visvesvaraya National Institute of Technology | Mukhopadhyay J.,Jawaharlal Nehru Aluminium Research Development and Design Center | Yoo C.K.,Kyung Hee University
International Journal of Environmental Science and Technology | Year: 2013

In this study, feasibility of using seawater to neutralize alkaline red mud for its safe disposal has been studied using Taguchi's design of experimental methodology. Parameters such as weight of red mud, volume of seawater, stirring time and temperature were tested at three levels to study their effect on response characteristic, i.e., pH of the neutralized slurry. The analysis of variance showed that volume of seawater added and quantity of red mud are the two significant parameters with 53.59 and 44.92 % contribution each, respectively. Under the optimized parameters, pH value of red mud slurry reaches to about 8.0 which is within disposable limits. When seawater or other Ca- and Mg-rich brines are added to caustic red mud, the pH of the mixture is reduced causing hydroxide, carbonate or hydroxy carbonate minerals to be precipitated. This mechanism of neutralization process has been explained with emphasis on chemical analysis, mineralogy and morphology of the neutralized red mud. The process improved the physical characteristics of red mud with entrained liquor becoming non-hazardous water with reduced alkalinity. The results would be extremely useful in the process of safe disposal of red mud. © 2012 CEERS, IAU.


Singh R.,Visvesvaraya National Institute of Technology | Khatirkar R.K.,Visvesvaraya National Institute of Technology | Chouhan R.N.,Jawaharlal Nehru Aluminium Research Development and Design Center | Sapate S.G.,Visvesvaraya National Institute of Technology
Transactions of the Indian Institute of Metals | Year: 2016

AA3004 aluminium alloy is most widely used in the beverage industry due to its excellent deep drawing properties and corrosion resistance. During deep drawing of the AA3004 sheets, the ‘earing phenomenon’ has to be minimized for economic advantage. In AA3004 and modified AA3004 alloys (like AA3104), this can be achieved by tailoring the crystallographic texture of the fully recrystallized sheet. Conventionally, AA3004 sheets are produced through direct chill (DC) casting route. In the present study, a twin roll cast AA3004 sheet is used for further processing (cold rolling and annealing). The texture comprised mainly of Cu ({112} 〈111〉), Brass ({110} 〈112〉) and S ({123} 〈634〉) orientations in the as-cast as well as cold rolled condition (Cu, Brass and S components being stronger in the cold rolled condition as compared to as-cast material). After complete recrystallization of 90 % cold rolled sheet, cube texture are deviated from ideal cube ({100} 〈001〉) (5°–10°) along with formation of Goss ({110} 〈001〉) and P{011} 〈122〉 components. This was in contrast to the DC casting route, where strong cube recrystallization texture is obtained. © 2016 The Indian Institute of Metals - IIM


Rai S.,Jawaharlal Nehru Aluminium Research Development and Design Center | Wasewar K.L.,Visvesvaraya National Institute of Technology | Lataye D.H.,Visvesvaraya National Institute of Technology | Mishra R.S.,Jawaharlal Nehru Aluminium Research Development and Design Center | And 4 more authors.
Waste Management and Research | Year: 2012

'Red mud' or 'bauxite residue', a waste generated from alumina refinery is highly alkaline in nature with a pH of 10.5-12.5. Red mud poses serious environmental problems such as alkali seepage in ground water and alkaline dust generation. One of the options to make red mud less hazardous and environmentally benign is its neutralization with acid or an acidic waste. Hence, in the present study, neutralization of alkaline red mud was carried out using a highly acidic waste (pickling waste liquor). Pickling waste liquor is a mixture of strong acids used for descaling or cleaning the surfaces in steel making industry. The aim of the study was to look into the feasibility of neutralization process of the two wastes using Taguchi's design of experimental methodology. This would make both the wastes less hazardous and safe for disposal. The effect of slurry solids, volume of pickling liquor, stirring time and temperature on the neutralization process were investigated. The analysis of variance (ANOVA) shows that the volume of the pickling liquor is the most significant parameter followed by quantity of red mud with 69.18% and 18.48% contribution each respectively. Under the optimized parameters, pH value of 7 can be achieved by mixing the two wastes. About 25-30% of the total soda from the red mud is being neutralized and alkalinity is getting reduced by 80-85%. Mineralogy and morphology of the neutralized red mud have also been studied. The data presented will be useful in view of environmental concern of red mud disposal. © The Author(s) 2012.


Mohamed Najara P.A.,Jawaharlal Nehru Aluminium Research Development and Design Center | Nimjeb M.T.,Jawaharlal Nehru Aluminium Research Development and Design Center | Chaddhac M.J.,Jawaharlal Nehru Aluminium Research Development and Design Center | Ramana Rao K.V.,Jawaharlal Nehru Aluminium Research Development and Design Center
Indian Journal of Chemical Technology | Year: 2011

Quantitative analysis of aluminium, iron, silicon and titanium present in bauxite residue (red mud) has been achieved by thin layer chromatography coupled with optical scanning densitometry. Silicon in red mud sample is detected at pH range 0.75-0.95 on chromatography plates prepared with microcrystalline cellulose modified with 10% sodium molybdate. Aluminium, iron and titanium are detected on silica gel H layers impregnated with 0.2% sodium formate and developed with mixture of 10% aqueous solutions of sodium chloride and formic acid in 8:2 v/v. The chromatograms obtained for the cations are quantitatively evaluated by optical scanning densitometry by measuring absorbance at 530-520 nm for aluminium, 660-528 nm for iron and 395-410 nm for titanium and silicon in reflectance mode. The quantitative densitometric data has been evaluated with analogous data obtained by wet analysis.


Mohamed Najar P.A.,Jawaharlal Nehru Aluminium Research Development and Design Center | Chouhan R.N.,Jawaharlal Nehru Aluminium Research Development and Design Center | Nimje M.T.,Jawaharlal Nehru Aluminium Research Development and Design Center | Ramana Rao K.V.,Jawaharlal Nehru Aluminium Research Development and Design Center
Journal of Planar Chromatography - Modern TLC | Year: 2010

A simple TLC method with scanning densitometry has been established for quantitative analysis of primary aluminum. The presence of microgram amounts of two major elements as impurities in the concentrated aluminum matrix was successfully detected. Chromatography on microcrystalline cellulose pre-developed with 10% sodium molybdate, dilute hydrochloric acid (3-5%), and sodium molybdate in specific ratios was used for the detection of silicon in smelter-grade aluminum. Silica gel H, silica gel G, and their combinations with aluminum oxide G were used for chromatographic study of iron and aluminum. Aqueous mixtures of formic acid and salt solutions of sodium chloride, sodium formate, potassium chloride, and potassium bromide were used as mobile phases for realizing ideal separation of microgram amounts of iron from milligram quantities of aluminum. Quantitative densitometric analysis of aluminum, iron, and silicon was achieved by measuring absorbance at 530-520, 628-560, and 410-395 nm, respectively, in reflectance mode. The quantitative densitometric data were compared with corresponding data obtained by optical emission spectrometric (OES) analysis of primary aluminum (1xxx series unalloyed with purity >99% Al). © Akadémiai Kiadó.


Mohamed Najar P.A.,Jawaharlal Nehru Aluminium Research Development and Design Center | Sonali R.G.,Jawaharlal Nehru Aluminium Research Development and Design Center | Nimje M.T.,Jawaharlal Nehru Aluminium Research Development and Design Center | Ramana Rao K.V.,Jawaharlal Nehru Aluminium Research Development and Design Center
Chinese Journal of Chromatography (Se Pu) | Year: 2012

Thin layer chromatography (TLC) of cobalt and nickel has been performed on silica gel layers induced with alkali mediated cellulose extract. A novel combination of 10% aqueous solutions of Tween-20 and potassium thiocyanate in 1:1 (v/v) was identified as the best mobile phase for the selective separation of Co2+ from Ni2+ on the impregnated Silica Gel G layers. The chromatographic characteristics of the cations were studied and the limits of detection as well as the limits of quantification for Co2+ and Ni2+ were determined. The quantitative estimation of the cations was achieved from the digital image analysis of respective chromatograms. The proposed quantitative method was successfully applied with 0 -0 50% error for the determination of Co2+ from Ni2+ in spiked samples of bauxite, soil and rock containing common cations such as Al3+, Fe2+, Ti4+, Zn2+, Mn2+, Cu2+, Cr6+, Mg2+, etc. under the optimized chromatographic conditions.


Bhukte P.G.,Jawaharlal Nehru Aluminium Research Development and Design Center | Chaddha M.J.,Jawaharlal Nehru Aluminium Research Development and Design Center
Journal of the Geological Society of India | Year: 2014

India is endowed with more than 3000 million tons of bauxite resources. Out of total India reserves, about 70% reserves are concentrated in Eastern Ghats (Odisha and Andhra Pradesh) region. Majority of the Eastern Ghat bauxite deposits are located at high altitude (high level type) and have been developed on khondalite and charnockite group of rocks with different geomorphological conditions. These are formed at an elevation of about 900- 1400 meter above mean sea level (msl). The physico-mechanical and technological properties of these bauxite vary widely depending upon the parent rock composition, mode of origin, geomorphological position, duration and age of bauxite formation. In the Bayer process the most important parameter that decides the economic importance is the quality of bauxite which again decides the digestion parameters for alumina extraction. Jawaharlal Nehru Aluminium Research Development and Design Centre (JNARRDC) is in process of evaluating the bauxite and laterite deposits of India for its suitability for commercial applications. The present paper highlights the geological and geomorphological features of Eastern Ghats bauxite deposits and their technological characteristics. These studies are required to evaluate the bauxite in terms of their suitability for metallurgical and non metallurgical applications. © 2014 Geological Society of India.

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