Vivek V. Buwa
Ph.D. Student

Abhijeet H. Thaker
Research Scholar
Department of Chemical Engineering
Indian Institute of Technology Delhi
Hauz Khas, New Delhi 110 016,
India
Tel: +91-11-2659 6252
Mobile: +91 96549 26889
email: abhijeet.thaker@gmail.com
         
            chz138439@chemical.iitd.ac.in
Educational Qualification
  • PhD in Chemical Engineering (Ongoing from January, 2014)                    
    • Institute: Indian Institute of Technology Delhi, New Delhi, India
    • Thesis Title: Dispersed Liquid-Liquid Flow in a Continuous Gravity Settler: Measurements and Population Balance Modeling      
    • Thesis Advisor: Prof. Vivek V. Buwa (IIT Delhi)
  • Master of Technology in Chemical Engineering (July 2011 – June 2013)
    • Institute: Sardar Vallabhabhai National Institute of Technology (NIT-Surat), Gujarat, India
    • Thesis title: Isomerization of Higher Alkanes Catalyzed by Medium Pore Zeolite
    • Thesis advisors: Prof. Parimal A. Parikh (NIT-Surat)
                                   Dr. Bharat L. Newalkar (Bharat Petroleum Corporate Research and Development Center, Greater Noida, UP, India)
  • Bachelor of Engineering (Chemical Engineering) (July 2008 – June 2011)
    • Institute: L. D. College of Engineering, Ahmedabad, Gujarat, India
  • Diploma in Chemical Engineering (Dec 2004 – Dec 2007)
    • Institute: N. G. Patel Polytechnic, Bardoli, Gujarat, India
Work Experience
  • Apprentice: Bayer Corp Science, Ankleshwar, Gujarat (March 2008 – June 2008)

Research Interests
  • Multiphase Flows
  • Population Balance Modeling
  •  Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF)
  •  Catalysis

Doctoral Dissertation Topic:
Dispersed Liquid-Liquid Flow in a Continuous Gravity Settler: Measurements and Population Balance Modeling
Several different equipment are used to disengage the liquid phases (immiscible liquids) following the solvent extraction processes. Centrifugal contactors and rotating disc contactors are preferred for phase separation when the process requires very short residence time. On the other hand, gravity settlers are used extensively for disengagement of liquid–liquid dispersions after solvent extraction process and are ideal for the processes that require longer residence time and most importantly when the dispersions are easily separable due to the difference in density. Their performance in terms of separation efficiency has a significant impact on the process economy of hydrometallurgical applications and of several other chemical processes (alkylation, sulphonation, crude desalting, etc). To improve the separation performance, the effects of settler operating parameters such as total flow rate, inlet drop size distribution, phase properties and dispersed phase volume fraction needs to be understand. It is also essential to understand the effects of design parameters such as settler size, the location of dispersion inlet/outlets, flow rates, physical properties of the fluid phases and settler internals (baffles, picket fences, end plate, etc.) on the separation performance. Therefore, the present work is focused on investigations on the effects of the aforementioned parameters on the rate of phase separation in a laboratory–scale continuous gravity settler. In addition to the large–scale investigations, understanding of binary (drop˗drop) and interfacial (drop˗interface) coalescence, which is responsible for the phase separation process, is also important.
Typical photograph of a laboratory-scale mixer-settler/span>
Inlet drop size distribution measurement by high-speed imaging Captured sample image
Drop size distribution measurement by micro-shadowgaphy technique
Dynamics of Gas-Liquid Flow and Mixing in a Shallow Vessel: PIV and LIF Measurements

Gas–liquid reactors are widely used for different applications in the chemical, metallurgical, oil and gas industries. These reactors are broadly categorized into two groups namely tall columns (with height to diameter ratio (H/D) > 5), e.g., bubble column, airlift reactor, etc., and shallow vessels (H/D < 1), e.g., Basic Oxygen Furnace (BOF), Ladle, etc. In these reactors, liquid–phase mixing is achieved either by mechanical agitation or mixing induced by gas bubbles. In the metallurgical industries, due to high temperatures and harsh environment in the molten metal baths, gas–induced mixing is used in the shallow vessels. The extent of gas–liquid mixing is closely related to the local liquid flow field induced by single/multiple bubble plumes and different bottom blowing configurations. In shallow vessels, the free gas–liquid interface influences the meandering motion of the gas plume and also the local liquid recirculation flow.

Furthermore, the top blowing intensifies the sloshing motion of the gas–liquid interface. This leads to change in the liquid flow characteristics and in turn in the overall mixing process. Therefore the primary focus of present work is to understand the effects of (i) uniform and differential flow schemes, (ii) free gas–liquid interface, (iii) combined top and bottom gas blowing configuration and bubble size on the liquid–phase velocity distribution, dynamics of gas–liquid flow and turbulent quantities (e.g., turbulent kinetic energy, rate of kinetic energy dissipation, Reynolds stresses, etc.) by Particle Image Velocimetry (PIV) and their role in liquid phase mixing by Laser Induced Fluorescence (LIF) measurements.
Schematic of PIV system
Snapshots of measured velocity contours in r-z plane   Measured time-evolution of vertical liquid velocity at location P
Flow streamlines and recirculation in rz- plane Snapshot of measured tracer distributions at 10s in rz- plane
PIV Video: Instantaneous vertical liuqid velocity processing vectors PIV Video: Instantaneous vertical liuqid velocity contours
LIF Video: Tracer distribution LIF Video: Tracer distribution (in terms of concentration distribution)
Experimental Analysis of Particle-Scale Flow and Tracer Distribution in Packed Beds

Packed beds are widely used in chemical process industries to carry out solid–catalyzed gas–phase reactions. The catalyst particle shape determines the local (particle–scale) transport phenomena which in turn contributes to the pressure drop, dispersion, heat and mass transport characteristics and therefore the reactor performance. Hence, it is imperative to understand the particle–scale flow in the packed beds. Even though a wide range of bed–scale experiments have been performed for estimation of global parameters like pressure drop, overall heat transfer coefficients etc., they do not provide detailed information on the particle–scale transport phenomena. On the other hand, particle–resolved CFD simulations can provide such detailed particle–scale information which helps to establish a relationship between the particle shape and the reactor performance. However, the CFD models lack rigorous validation due to difficulty in obtaining reliable particle–scale measurements. Therefore, the main purpose of the present work is to establish an approach measurements of the local flow field around the particle and residence time distribution (RTD) in the packed beds with the application of Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF) measurement techniques. This information will be helpful in rigorous validation of CFD models which then can be used with confidence for the development of novel particle shapes for improving the reactor performance.

Schematic of experimental set–up
  
PIV Videos:                       Rebed: 1100                                                              Rebed: 2200                                                               Rebed: 6600
  
LIF Videos:                       Rebed: 1100                                                              Rebed: 2200                                                               Rebed: 6600
Publications 
International/National Journals
  • Abhijeet H. Thaker, Mayur Darekar, K. K. Singh and Vivek V. Buwa, Experimental investigations of liquid–liquid disengagement in a continuous gravity settler, submitted to Chemical Engineering Research and Design (2018).
  • Abhijeet H. Thaker, Abdul Quiyoom and Vivek V. Buwa, Dynamics of Meandering Bubble Plumes and Their Role in Mixing in Shallow Vessel, submitted to Physics of Fluid (2018).
  • Abhijeet H. Thaker, Mathew John, Kishor Kumar, Mahesh W. Kasture, Snehalkumar Parmar, Bharat L. Newalkar and Parimal A. Parikh, Hydroisomerization of Biomass Derived n-Hexadecane Towards Diesel Pool: Effect of Selective Removal External Surface Sites from Pt/ZSM-22, Int. J. Chem. React. Eng., 14 (1) 2016, 155-165
International/National Conferences
  • Abhijeet H. Thaker, Abdul Quiyoom and Vivek V. Buwa, Dynamics of Gas-Liquid Flow and Mixing in a Ladle: PIV and LIF Measurements, Presented at 12th International Symposium on Particle Image Velocimetry (ISPIV2017), Busan, Korea.
  • Abhijeet H. Thaker, Karthik G. M. and Vivek V. Buwa, Experimental and CFD Analysis of Particle–Scale Flow and RTD in Packed Beds, 13th International Conference on Gas–Liquid and Gas–Liquid–Solid Reactor Engineering (GLS–13), Belgium, Brussels, 2017.
  • Abhijeet H. Thaker and Vivek V. Buwa, Experimental investigations of interfacial and binary coalescence of multi–layered drops, International Symposium on Chemical Reaction Engineering (ISCRE25), May 20–23 2018, Florence, Italy.
  • Sahil V. Bhujbal, Abhijeet H. Thaker, Deepak Sharma and Vivek V. Buwa, “ Effect of Free Interface on Dynamics of Gas−Liquid and Mixing in a Shallow Vessel: PIV and LIF Measurements”, 19th International Symposium on Applications of Laser and Imaging Techniques to Fluid Mechanics (LXLASER–2018), Lisbon, Portugal 16–19 July 2018.
  • Saroj K. Panda, Abhijeet H. Thaker, Vivek V. Buwa, K. K. Singh and K. T. Shenoy, Numerical Simulations of Batch Settling of Liquid-Liquid Dispersion Using OpenFOAM and Experimental Verification, CHEMCON 2015, Guwahati, India.
  • Abhijeet H. Thaker and Parimal A. Parikh, Straight Chain Paraffins’ Hydroisomerization as Green Gasoline Pool: Recent Developments, CHEMCON 2012, Jalandhar, India.
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