|Research Group and Research|
|Development of Modified Slurry Bubble Column Reactor (S. Mekala and S. K. Majumder):|
|Slurry reactors have attracted the attention of researchers over the years due to its widespread applications and importance in various processes in chemical and biochemical industries. Recently downflow slurry bubble column columns are gaining importance as a simple and inexpensive of means of achieving multiphase process yield due to its several advantages.From the literature it is found that a very few studies on hydrodynamics and transport processes in the downflow slurry bubble column reactor are available though it has several industrial applications. The present study reports on the hydrodynamic and mass transfer characteristics in an ejector induced modified slurry bubble column reactor. The completed work includes the gas holdup, bubble size distribution, the three-phase friction factor, bubble generated turbulent energy, the dispersion coefficient of bubble motion, velocity characteristic factor and mass transfer phenomena by current density method. A functional relationship between three-phase friction factor and energy loss due to wettability of liquid with the solid surface also developed. The gas holdup has been analyzed by the drift flux model and interpreted the same based on different significant dimensionless groups. The mass transfer coefficient is evaluated by using the electro-reductionof ferricyanide ions as the model reaction.|
|The effects of superficial slurry velocity, gas velocity, slurry viscosity and gas holdup on mass transfer coefficient are analyzed. Empirical correlations have been developed for the downflow slurry system with the different variables to interpret the mass transfer phenomena. The developed correlation for mass transfer efficiency as a function of quality of mixedness is also interpreted by the information entropy theory. The present study in the modified downflow system may give insight into a further understanding and modeling of flow characteristics in industrial applications.|
|Publications based on the research:|
|Development of Plant Prototype for Removal of Ammonia, Arsenic and Dyestuffs from Water by Ozone Microbubbles (S. Khuntia, S. K. M.ajumder and P. Ghosh) :|
|Ozone is applied to remove the organic and inorganic compounds present in the wastewater due to its various advantages. Many organic and inorganic compounds react with ozone or hydroxyl radicals directly or indirectly. However, it has a few disadvantages, which limit its application in water treatment. The main drawbacks of ozone are its relatively low solubility and stability in water. To alleviate some of the drawbacks of conventional ozonation processes, microbubble-aided ozonation has been successfully attempted by several scientists. Various wonderful properties of microbubbles such as large gas−liquid interfacial area, slow rising velocity with long lifetime, and small ozone requirement increase the ozonation efficiency. In addition, ozone microbubbles are also capable of generating hydroxyl radicals under certain conditions.|
|This work presents oxidation of some pollutants (e.g. ammonia, arsenic and dyestuffs) by ozone microbubbles in a pilot-plant. In-depth studies have been carried out on the change of concentration of pollutant in the reactor with time, mass transfer of ozone in water, reaction kinetics, and the effect of pH on the reactions. Adsorbents have been developed for adsorption of arsenic. Concentration of hydroxyl radicals has been measured. A mechanism has been proposed for the generation of hydroxyl radicals by ozone microbubbles.|
|Publications based on the research:|
|Mineral Benificiation by Ionic Microbubble (Rajeev Parmar and S. K. Majumder)|
|As we are leading towards our future, technology is changing day by day to more advancement than last few decades. Technologies are getting much deeper and smaller, thereby enhancing the efficiency and capacity. In every field, research has gone to higher level by exploring new areas. In chemical engineering, bubbles play an important role in various unit operations. In recent studies it has been reported that smaller bubbles give rise to larger interfacial area, which motivate the introduction of processes aided with microbubbles (Tabei et al., 2007).|
|Process for Mineral Beneficiation|
In the present scenario microbubble has got much popularity as they are being used in many chemical, biochemical, metallurgical and petrochemical industries to increase the efficiency of the process (Devatine et al., 2007). They have been used as diagnostic aids to scan the various organs of body and they are being proposed to use as a drug or gene carrier and treatment in cancer therapy (Lindner, 2004). The microbubble-aided extraction process is becoming a highly promising direction in chemical engineering (Tan et al., 2011). Microbubble aided flotation has been widely employed in the various fields for the process intensification. They have been used for recovery of proteins (Amiri and Valsaraj, 2004), recovery of microorganism (Hanotu et al., 2012), removal of heavy metal ions from water (Ciriello et al., 1982), removal of dye and pigment (Alves et al., 2006). This work aimed to explore the rheology, dispersion characteristics, and the stability of microbubble and efficiency of mineral beneficiation based on the physicochemical properties.
The terminal rise velocity of carbon dioxide microbubble is found to higher than air and lower than nitrogen microbubble. From drainage curve analysis it is observed that the stability of the microbubble can be increased by increasing surface tension The results showed that the charge on the surface of microbubble is highly promising in separating opposite charged particles. The recovery of mineral particle are found to be dependent on surfactant concentration, size of microbubble and particles, zeta potential of microbubble, nature of surface potential of bubble and microbubble-particle mixture circulation velocity. The separation efficiency of microbubble increases with increase in mixture circulation velocity and surfactant concentration. The recoveries of ZnO and Al2O3 particles are maximum with CTAB. In case of CuO particles, the SDS and Tween-20 are found to be more effective than CTAB. The rate constant found to be significantly influenced by the physicochemical properties of the liquid and particles. These results clearly indicate that presence of a hydrophobic surface forces necessarily results in particle collection by a microbubble but other surface forces also contribute to fine particle separation.
|Publications based on the research:|
|Microfluid Flow and Particle Transport in Evaporating Droplet (Ashis Kumar Thokchom, S. K. Majumder and A. Singh):|
|Pattern formation resulting from evaporation of sessile droplets containing solute particles is encountered in various applications in microfluidic devices. In this study it is observed that by controlling the heating of the substrate one can modify the convection cells and hence finally the deposition pattern of solute particles. The fluid velocity and particle concentration inside the evaporating droplet was measured using the Particle Image Velocimetry (PIV) technique. Experiments were conducted for the case of symmetric as well as asymmetric heating of the substrate from the bottom. It was observed that the flow pattern inside the droplet results from the combined effect of buoyancy driven flow and Marangoni convection. At low temperature and symmetric heating, two counter rotating vortices were observed whose direction is such that the particle deposition occurs at the pinned contact line. However, at high temperature the flow is reserved and the particles are deposited at the center of the dried droplet. In case of asymmetric heating only one convection cell was observed with asymmetric particle deposition. Analysis of various dimensionless numbers associated with convective flow showed that Marangoni convection dominated in all our experiments. Also numerical simulations carried out to solve the fluid flow and energy transport equation inside the evaporating droplets for similar conditions as the experiments. The results from the simulations are found to be in qualitative agreement with the experiments.|
|Images of Evaporating Droplet|
|Publications based on the research:|
|Flow pattern-based transport processes of air-non-newtonian flow in helical coil (Anil Kumar Thandlam, Chiranjib Das and S. K. Majumder)|
|The helical coil system is also important as a compact helical reactor to execute the gas-liquid reaction with intense mixing. The reaction performance may be significant in the helical coil due to its absence of back mixing. Now-a-days, helical coil is hence gaining importance as a simple intensified and inexpensive gas-liquid or gas-liquid-solid reactor. In literature, significant research has been reported to understand the properties of Newtonian fluids like thermodynamics, stability, thermal conductivity, thermal diffusively, viscosity and convective heat transfer coefficient in helical coil system (Zeeshan and Ellahi 2013; Ellahi 2013, Ellahi 2014).|
|Helical Coil System for Heat Transfer Operation|
|Apart from gas-Newtonian liquid reaction, there are lots of reactions with gas-non-Newtonian liquid are executed in the chemical and biochemical industries. Literature shows that there are limited works on air-non-Newtonian liquid two-phase flow through helical coils as compared to air-Newtonian fluids. This work aimed to investigate the flow characteristics and transport process of gas-non-Newtonian liquid flow through helical coil. The attention has been focused on flow patterns, hold-up, frictional two-phase pressure drop, mixing characteristics, heat transfer and mass transfer characteristics and effect of various geometrical parameters like tube diameter, coil diameter, pitch difference, particle diameter and physical properties of liquid on them.|
|Research publications from the research|
|Process intensification on liquid-liquid extraction in a modified jet- driven extraction column (Bharat K. Goshika and S. K. Majumder):|
|The vast literature on the extraction process has given a good insight into the various columns in which the extraction process can be carried out. Some of the recent work is based on developing the novel extraction systems by giving the process intensification as the reason. As per literature using gases to the liquid-liquid extraction process has given a best yield. The using of gas into the liquid–liquid mixing gives the emulsion of the mixture with fine drops by which the large interfacial area is developed for the mass transfer. The most of the extraction experiments were conducted in countercurrent flow of the liquids, there is less work done on the gas-aided concurrent liquid-liquid extraction system.
Based on this, the present research work to be performed is formulated as,
Although the non-agitated extraction columns spray column, packed column, perforated plate column, sieve plate column, etc can handle high flow rates and are simple and cheap, there have been few applications of these columns because they suffer from serious back mixing of the continuous phase. It was shown that the back mixing is reduced when the spray column is operated with dense packing of drops.
|Development of Extraction System|
|Another way of increasing the efficiency of a non-agitated extraction column is to introduce an inert gas (air, nitrogen, oxygen) as a mixing agent in the two-phase liquid-liquid (L-L) system. This method of energy introduction increases the turbulence within the new three-phase gas-liquid-liquid (G-L-L) system, which causes an improved dispersion of droplets, and, consequently, a higher dispersed phase holdup and therefore a great mass transfer area (Sohn et al. (1998), Dehkordi et al. (2002), Lu et al. (2005), Saien et al. (2006), Ferial et al. (2010), tan et al. (2013)). In the present study a jet driven down flow column is proposed. The column is procured by modifying the ejector induced downflow column which was used for studying the hydrodynamics of two and three phase flow (gas-liquid (Majumder 2008), liquid-liquid (Mukherjeee et al. 1988), and gas-liquid-solid (Sivaiah et al. 2013). Galkin et al. (1961) concluded that the extraction efficiency was nearly three times greater for conventional columns when air was introduced into the extraction column, and claimed that the process is more efficient than by the use of stirring or pulsation of the column. As the column have many advantages than other conventional reactors, it has the capability of air dispersing into the column with continuous phase without any external|
|power requirement, this column is modified to use the air-liquid-liquid three phase flow system for the applicability of extraction process. As gas aided liquid-liquid extraction process has advantages over non-gas-aided extraction, it gaining importance as a simple and inexpensive means of achieving such gas-liquid extraction in scientific and academic community.|
|Beneficiation of fine particles by micro- and macro-bubble-aided flotation (M. K. Fahad, S. K. Majumder and P Ghosh)|
|Studies on objectives:
|Mineral beneficiation by aeration by developing microstructure flotation column (Ritesh Prakash, S. K. Majumder and A. Singh)|
|The objective of the study:
|Beneficiation mineral and protein by charged microbubbles in a plant prototype (Kumari Ruby, Dhiren Boro and S. K. Majumder)|
|The objective of the study:
|Hydrodynamics, mixing and extraction of copper from particle-laden solutions in microchannel (Somen Mondal and S. K. Majumder)|
Solvent extraction is the second most important separation technique used in the industries for purification of some materials or removal of some unwanted materials from the others present in a solution. Solvent extraction is an attractive separation technique in separation of non-volatile solutes from aqueous solutions, separation of heat sensitive materials such as antibiotics (e.g., penicillin which is recovered from fermentation broth by using the solvent butyl acetate), separation of the close boiling component mixtures. The other most important use of solvent extraction for most of the chemicals, petrochemicals, refineries and other industries is the removal of organics from their waste effluent.
Solvent extraction is a two-component two phase flow process in which one is the aqueous phase and the other one is the organic phase. In two phase flow the in-situ composition is different from the inlet composition since the two fluids have different density. The lighter fluid tends to slip past the heavier one. So, in any two phase flow study, it is important to understand the flow patterns i.e., the phase distribution which occurs under specific flow conditions since the hydrodynamics and heat and mass transfer characteristics are governed by the existing flow distribution. The contact area of the extract and the raffinate phase is also different for different flow patterns. More area of contact between the extract and the raffinate phase results more mass transfer between the phases. An accurate estimation of pressure drop is also of considerable interest to estimate the required pumping power in petrochemical, chemical and other industries where two-phase mixture co-exists for different transport processes.
In the present day scenario, researchers and engineers are interested in miniaturization for process intensification of chemical processes or scaling out or numbering up approach. For such processes surface to volume ratio becomes significant and an increase in this ratio increases the reaction and transport rate.
The objectives of the present study are to perform experimental investigations and analysis on:
Prof. Subrata K. Majumder
Key Research Areas : Multiphase flow and reactor development, Hydrodynamics in multiphase flow, Mineral
processing, Process intensifications, Micro-nano bubble science and technology and
its applications, Food processing, Microchannel-based extraction, Jet driven gas-aided
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