Students:
Premkumar K.   
Research Scholar
Year of Registration: 2012
Email: premkumar@iitg.ernet.in
Thesis Title: Experimental and Numerical Investigation of Circulating Fluidized Bed (CFB) at Two Different Scales
Description: http://www.iitg.ernet.in/chemeng/images/premkumar.jpg
CFB has profound applications, viz., cracking, combustion, drying, gasification, etc. Even though CFB has been used commercially for more than four decades, it is not well understood. Design and scale up of CFB are still done empirically. One of the major reasons is complex interactions of particle-particle, particle-wall and particle-gas.  Due to the complex interactions, heterogeneous structures like meso-scale metastable structures (clusters) forms in CFB. Studies of these local structures are warranted as most of the reactions in CFB are fast reactions. Also, it has been reported that flow structures and regimes in CFB varies with solid flux and gas velocity. I have been working to address some of these challenges as part of my Ph.D dissertation. In this work, advantages of experimental and numerical studies are exploited to complement each other. Using non-invasive radiotracer technique, RPT (Radioactive Particle Tracking) and pressure probe, hydrodynamics of CFB are studied to understand the effect of operating conditions. Experiments are carried out in laboratory and pilot plant scale setup to understand the effect of scale. Euler-Euler and Euler-Lagrangian modelling approaches are used to simulate the CFB.
 
 
 
Figure (a) Velocity vector of solids (b) Pilot plant scale CFB (c) Lab scale CFB (d) Position track of solids (e) Mean axial velocity of solids (f) PDF of instantaneous velocities and (g) Particle track of solids showing clusters (Euler-Lagrangan simulation)
 
Richa Sharma   
Research Scholar
Year of Registration: 2012
Thesis Title: Process Intensification of Hydrogen Generation and Separation Using A Pd Membrane Reactor
Fuel is the driving source to any innovation. I target hydrogen as fuel because it is an energy carrier that drives fuel cell technology to generate electric power much more efficiency than gasoline. But H2 is a quite low density fuel such that it leads to its difficulty in storage and henceforth transportation. Thus, in order for hydrogen to be implemented as a commercial fuel, wide research work across the globe has been focused in storing hydrogen using metal hydrides. Consequently, another way to deal with hydrogen storage is, why not bypass hydrogen storage altogether by generating hydrogen in place using light weight heavy density alcohols. However, hydrogen produced from these hydrocarbons can never be pure which comprises a mixture of H2, CO2, CO, H2O and CH4. This brings to the need of separating hydrogen from the mixture gases using either of the commercialized technologies: a) pressure swing adsorption (PSA) beds with multiple water gas shift reactors or b) a H2 selective membrane as separator. Now as the market seems to aim for all in one technology, it motivates the concept of "membrane reformer" as an "On-board" H2 generator ally with fuel cells. Membrane reformer integrates steam reforming and membrane separation for a compact assembly. Further, membrane integration to steam reforming (mostly consisting of 60% H2 by volume) drives the equilibrium leading to higher conversion and higher purity H2 in the permeate side.
Through the current study, my overall objective is to experimentally demonstrate the effect of varying integration modes of reforming catalysts with dense Pd membranes on permeate hydrogen flux. In addition, high purity of hydrogen in the permeate line should be continuously checked and maintained such that it can be directly fed to a PEM-fuel cell. The global idea is to aim for 65L/min high purity hydrogen to derive 5KW power for any small scale portable generator, battery or a motor engine as well.  Research work comprise of a) preparation, characterization, testing of both catalysts and membranes; b) integration modes and designs will be tested for the optimized methanol steam reforming catalyst with dense Pd membrane and
c) comparison of the in-house membrane reformer cum test rig with a commercial in order to come up with question or solutions which can be directed towards membrane reformer's full scale commercial acceptance. The results below outline some recent works performed for membrane based as an integrated reformer and separator to compare commercial membrane performance.
bed are performed using state-of-the-art measurements techniques, radioactive particle tracking (RPT) and gamma-ray densitometry. In addition, the effect of various operating parameters like inlet velocities, bed height and particle size and type (group B and group D), column geometry and size is investigated. Some key results with experimental setup have shown here.
Figure (a) Membrane reformer conversion with feed (b) Membrane reformer permeate H2 flow rate (c) membrane separator permeate H2 flow rate
 
Lipika Kalo                       
Ph.D. Research Scholar
Year of Registration: 2012
Thesis Title: Experimental and Numerical Investigation of Liquid-Solids and Gas-Solids Cylindrical and Conical Fluidized Beds
Conical fluidized bed has wide applicability in various processes including nuclear fuel particle coating, crystallization, coal gasification and liquefaction and roasting sulphide ores etc. The flow pattern of solid and fluid in fluidized bed is largely depend on phenomena occurring at different length and time scales. However, despite having wide applicability limited studies on conical fluidized bed are reported in literature. Most of these studies are based on off-line measurements and development of empirical models for prediction of pressure drop and minimum fluidization velocities. Further, very few studies are reported on rigorous CFD modeling of these types of beds by using first principles to understand the interaction physics between fluid-solids with change in process variables and geometry. The current work aims numerical simulation of conical and cylindrical liquid-solids and gas-solids fluidized bed using both Euler-Euler and Euler-Lagrangian model. Further in-situ measurements on fluid-solids conical fluidized bed are performed using state-of-the-art measurements techniques, radioactive particle tracking (RPT) and gamma-ray densitometry. In addition, the effect of various operating parameters like inlet velocities, bed height and particle size and type (group B and group D), column geometry and size is investigated. Some key results with experimental setup have shown here.
 
Figure (a) & (b) Cylindrical setup with RPT and densitometry facility (c) & (d) Conical setup with RPT and densitometry facility (e) Glass experimental setup (f) Binary pseudo-3D DDPM simulation of cylindrical setup (g) Binary pseudo-3D DDPM simulation of conical setup (h) Mean axial velocity profile of solids in 3D binary bed.
 
Rupesh Verma                       
Research Scholar
Year of Registration: 2012
Thesis Title: Investigation of Liquid Cooled Pebble Bed Reactor: Experiments and CFD Simulations
Graphite moderated liquid cooled pebble bed reactor (PBR), which is a new generation reactor is considered very safer and economical. This reactor is also suitable for production of hydrogen as the temperature of these reactors is considerably high. These reactors are still in R&D stage and have not been commercialized till date. The critical advantage of this proposed reactor over conventional nuclear reactor is its high thermal efficiency (~45%) and reduced shut down period (due to continuous circulation of pebbles).  In the liquid cooled Pebble bed reactors, both coolant (liquid) and pebbles flow co-currently upward. The coolant gets separated from the top of the reactor and fuel pebbles are recirculated back to the system depending upon their burnup. The design of circulation mechanism of these pebbles is very critical as these pebbles are coated with graphite on top layer which is very brittle.
In this work, I am using both experimental and numerical approach to understand the flow behavior of pebbles in liquid cooled pebble bed reactor. Radioactive particle tracking (RPT) and gamma-ray densitometry technique is being used to understand the flow quantities (mean, instantaneous and fluctuation velocities, rms velocities and turbulent kinetic energy) and distribution of pebbles respectively for different operating conditions. Dense discrete phase model (DDPM) of ANSYS 14 is being used to numerically simulate the behavior of the bed. Typical results of gamma-ray densitometry and DDPM simulations with photograph of experimental setup are shown below.
 
Figure (a) Photograph of Experimental setup (b) Experimental setup with RPT facility (c) Experimental setup with gamma-ray densitometry facility (df) Pseudo - 3D CFD-DDPM simulation results: contour of pebble volume fraction (e) Mean volume fraction of pebbles at different heights (f) Flow diagram for RPT experiment.
 
Jitendra Singh Rawat       
Research Scholar
Year of Registration: 2013
Thesis Title: Investigation of Nozzle Assisted Gas-Solids Fluidized bed: Experiments and CFD Simulations
 

 

 
Nozzle assisted gas-solids fluidized bed is widely used in many industries. These side wall mounted nozzles are generally used to inject the reactant at different axial/radial locations for uniform distribution of feed. However, extra void is generated due to high velocity of injection in the vicinity of nozzle inlet which significantly changes the hydrodynamics of such gas-solids fluidized bed. In thesis work, both numerical and experimental approach is being used to quantify the change in behavior of such bed with and without nozzle presence. Further, injection geometry will be optimized in such a way that effect of injection on behavior of gas-solids fluidized bed can be minimized. Radioactive particle tracking (RPT) and gamma-ray densitometry experiments is being performed to understand the hydrodynamics of such bed experimentally. The CFD simulations are being performed in Euler-Euler and Euler-Langrange CFD-DEM) frameworks. Some typical experimental as well as simulation results with photograph of experimental setup are shown below. 
 
Figure (a) Experimental setup with gamma-ray densitometry facility (b) mesh for CFD simulations (c) RPT set up (d) Pseudo - 3D set up (e) Chordal averaged volume fraction via densitometry (f) Time averaged volume fraction of solids in 3D and (g) 2D model.
 
Endallu Leema                       
Research Scholar
Year of Registration: 2015
Thesis Title: Design of a compact membrane Reformer for production of Ultra-Pure Hydrogen through Steam Reforming of Bio-Glycerol
 
Soorya Pradeep                       
M.Tech Student
Year of Registration: 2014
Thesis Title: Study of Fluidized Systems Using Experimental Data From Radioactive Particle Tracking Technique
Gas-Solids and Liquid-Solids Fluidized beds are widely used in chemical industries as the advantages outweigh the disadvantages. The project involves deeper understanding of Fluidized bed through the time series analysis of Radioactive Particle Tracking (RPT) technique and pressure transducer data. Position time series and velocity time series data retrieved from RPT technique is processed using Applied Mathematics tools, giving Hurst exponent, autocorrelation and information entropy. Turbulence involved in system is analyzed by calculation of diffusivity and by Chaos analysis. Eddy diffusivity is calculated and analyzed in different coordinates for various operating conditions, particle type, and shape of column using both differential and integral method. Chaos analysis is initiated by study of information entropy, mutual entropy, and information loss on scale up. It further extends to reconstruction of attractors by singular value decomposition method. Further, similar analysis will be conducted with pressure transducer data and results will be matched to get the similar information at industrial scale with data obtained from pressure transducers. Typical results of Rescaled analysis and axial eddy diffusivity for liquid solids fluidized bed is shown below.
 
Priyanka Shrivastava
M.Tech Student
Year of Registration: 2014
Thesis Title: Experimental Investigation of Underground Coal Gasification
Increasing developments have been directed towards efficient energy generation from existing natural resources. Coal is one such abundant resource vastly exploited usually at the cost of life with hazardous mining trails and much of the coal in the ground is too deep or too low in quality to be mined economically. Today, less than one-sixth of the world's coal is economically accessible. However, with growing advent of clean technology, and growing hydrogen economy, improved coal extraction preparation and utilization is incurred using underground coal gasification (UCG). The process involves injection of oxygen and steam into ignited underground coal seams to produce gases that can be used as fuel, power generation or feedstock for various chemical and food industries. UCG is a clean gas technology which provides advantage of higher efficiency, higher safety, environmentally friendliness, and lower cost when compared with the surface gasification. Laboratory scale experiments are performed to investigate effect of temperature, pressure, oxygen to steam ratio, gas flow rates on product gas (which is a mixture of H_2 ,CO, CO_2 , CH_4  and some amount of volatile gases) & cavity shape . Some typical experimental results with the set up are shown below:
 
Figure (a) Experimental Set-up (b) Post combustion cavity of Bapung & Nagaland coal blocks (c) & (d) Temperature progress of Bapung & Nagaland coal blocks during gasification experiment respectively
 
Trilokpati Tribedi
M.Tech Student
Year of Registration: 2014
Thesis Title:  Insights of Circulating Fluidized Bed: Experiments and EMMS Modeling
Gas-solid reactors are critical to numerous process industries. Circulating Fluidized Bed (CFB) is finding significant applications in industry because of its efficiency, operational flexibility and profitability. In thesis work, both numerical and experimental approach is being used to understand the scale-up issues of
 
circulating fluidized bed. Solid flux is measured by measuring volume fraction and time of flight. Gamma ray tomography/densitometry is used to measure solid fraction, where Caesium-137 is used as gamma ray emitter. Solid flux measurement has been conducted in Lab scale and Pilot plant scale CFB. Simultaneously Pressure fluctuation has been recorded with Pressure Transducer at different positions of riser. Effects of solid inventory and air inlet velocity on solid flux and Pressure fluctuation are studied. The CFD simulations are being performed in Euler-Euler with Wen & Yu and EMMS drag Model.
Figure (a) Experimental setup with Pressure Transducer (b) Variation of solid flux with solid inventory and air velocity (c) Mean Solid volume fraction from CFD simulation (d) Pressure fluctuation at two positions of riser (e) Solid volume fraction from Pressure data analysis.
 
Kuldeep Singh
B.Tech Student
Year of Registration: 2012
Thesis Title: Development of Reactor Model for Cracking of Crude Oil in Gas-Solids Circulating Fluidized Bed
 
Kailash Bhakal
B.Tech Student
Year of Registration: 2012
Thesis Title: Performance study of CDU Unit Using Flue Gas as Stripping Media