Informatics Publishing Limited

Suchita B. Rai ¹, Kailas L. Wasewar ², M. J. Chaddha ¹, R. S. Mishra ¹, J. Mukhopadhyay ¹

Affiliations
1 Jawaharlal Nehru Aluminium Research Development and Design Centre, Wadi, Amravati Road, Nagpur, IN
2 Visvesaraya Institute of Technology (VNIT), Nagpur, IN

Abstract

Bauxite Residue or Red mud is the waste generated during bauxite processing for production of alumina through Bayer process. Red mud is a highly alkaline material (pH about 10.5-12.5) because of digestion of bauxite ore in caustic soda solution at elevated temperatures. The high alkalinity also limits its use for various applications such as vegetation, construction material etc. Land disposal of these materials often has negative environmental impacts such as contamination of soil and groundwater, and consumes vast areas of land. Revegetation of dewatered red mud is not possible without addition of amendments because of the high pH, high salinity, and absence of nutrients and organic constituents. Red mud ponds can be rehabilitated and abandoned bauxite mine pits can be refilled by identifying suitable amenders to ameliorate the caustic properties of red mud so that vegetation cover can be developed. Red mud from an alumina refinery situated at the eastern coast of India has been modified by adding amenders/ modifiers/ neutralizers such as coal dust, superphosphate and gypsum and their effectiveness is studied by carrying out the pH studies. The effect of addition of these neutralizers has been very well seen as the pH of red mud slurry stabilizes to a value well below 8.5-9.0 as compared to the value of above 10.5 obtained without using them. Gypsum and a combination of superphosphate and coal dust are found to be very effective as amenders as they reduce the pH of red mud to a much lower value. To study the suitability of red mud for vegetation, shrubs have been planted in red mud mixed with amenders The survival of the plants in red mud mixed with neutralizers/ amenders and their proper growth in it show that bulk utilization of red mud can be carried out in the area of vegetation by growing suitable flora and fauna.

Keywords

Amenders, pH, Red Mud, Vegetation.

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Dhaneshwar Devikar ¹, Swapnil Dharaskar ², Y. C. Bhattacharyulu ², Kailas L. Wasewar ²

Affiliations
1 Department of Chemical Engineering, Anuradha Engineering College, Chikhli (M.S), IN
2 Department of Chemical Engineering, Jawaharlal Darda Institute of Engineering & Technology, Yavatmal (M.S), IN

Abstract

Current post combustion CO₂ capture systems in power plants typically employ amine based solvent, such as monoethanolamine (MEA), to capture CO₂ from flue gas followed by a desorption (or solvent regeneration) step, usually a stripping column, to recover the captured CO₂ and regenerate the solvent. The MEA solvent has high heat of reaction with CO₂ that leads to higher stripping energy consumption during CO₂ recovery, thus making amine scrubbing an energy expensive process. The solvents suggested for CO₂ capture in this work belong to a group of compounds called ionic liquids (ILs). Many ILs have shown a remarkably good CO₂ solubility. Ionic liquids have also shown good selective CO₂ absorption, thus making ILs a potential candidate for CO₂ capture from flue gas. Since CO₂ absorption in ILs involves physisorption (physical absorption) rather than chemisorption (chemical absorption) of CO₂ in amine based solvents, there is a potential to develop energy efficient ionic liquid based absorption-stripping process. The choice of the ionic liquid, 1-hexyl-3-methylimidazolelium tetrafluoroborate (HMIM)BF₄, has not been optimized but was chosen based on chemical absorption behaviour and the desire to understand performance. Engineering design estimates indicate that the investment for the ionic liquid process will be 11% lower than the amine based process and provide a 12% reduction in equipment footprint.

Keywords

CO₂ Capture, MEA, Ionic Liquids, (HMIM)BF₄.

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