Fluidization refers to a process by which a fluid like state is imparted to granular solid particles by the passing of a fluid upwards through the bed of particles. A semi fluidized bed is characterized by a fluidized bed and a packed bed in a series within a single contacting vessel. Gas-liquid-solid semi fluidization is defined as an operation in which a bed of solid particles is suspended in gas and/or liquid upward flowing media due to the net gravitational force on the particles and the motion of the particles is restricted by a top restraint. Such an operation generates intimate contact between the gas, liquid and solid particles in these systems and provides substantial advantages for applications in physical, Chemical and biochemical processing involving gas, liquid and solid phases. The experiments were conducted using liquid as the continuous phase and gas as the discontinuous phase. In this work air, water and dolomite (2.31mm, and 1.7mm) are used as the gas, liquid and solid phases respectively. The experiments were carried out in a 100 mm ID of 2m height vertical Plexiglas column. Knowledge of minimum liquid semi fluidization velocity is essential for the successful operation of gas-liquid-solid semi fluidized beds. Bed pressure measurements have been made to predict the values of the minimum liquid semi fluidization velocity. In the present work, hydrodynamic characteristics viz., the pressure drop, bed expansion of a co-current gas-liquid-solid semi fluidized bed has been studied. These have done in order to develop a good understanding of each of the flow regime in gas-liquid and liquid-solid semi fluidization. The effect of static bed height, particle size, liquid velocity and gas velocity on hydrodynamics parameters like minimum semi fluidization velocity, pressure drop, expansion ratio have been investigated. Experimental study based on statistical design has been made to investigate the expansion ratio of semi fluidized bed. The experimental val.

The general purpose of the experimental investigations described here has to study the hydrodynamic properties of gas-liquid fluidized beds. Gas -liquid fluidization of or three-phase fluidization is a chemical engineering operation where all the three phases are brought into contact with each other. This contact is brought about by passing the gas and liquid trough the bed of solids. The solids are said to be in a fluidized state when they are suspended in the continuous phase.Hydrodynamic properties such as gas hold-up, liquid hold-up and bed porosity have been studied. These properties depend upon certain independent variables such as gas flow rates, liquid flow rate, particle size, static bed heights, gas density, liquid density, solid density, liquid surface tension, liquid viscosity, gas viscosity and particle shape. During the course of this experimental investigation only four of these parameters have been varied, viz, gas flow rates, liquid flow rates, static bed height and particle size.The result of these experimental investigations is discussed and correlations have also been developed for the hydrodynamics properties studied.

Hydrodynamics and Transport Processes of Inverse Bubbly Flow provides the science and fundamentals behind hydrodynamic characteristics, including flow regimes, gas entrainment, pressure drop, holdup and mixing characteristics, bubble size distribution, and the interfacial area of inverse bubble flow regimes. Special attention is given to mass and heat transfer. This book is an indispensable reference for researchers in academia and industry working in chemical and biochemical engineering. Hydrodynamics and Transport Processes of Inverse Bubbly Flow helps facilitate a better understanding of the phenomena of multiphase flow systems as used in chemical and biochemical industries. - A first book in the market dedicated to the hydrodynamics of inverse bubbly flows - Includes fundamentals of conventional and inverse bubble columns for different hydrodynamic parameters - Includes recommendations for future applications of bubble flows

Useful as a reference for engineers in industry and as an advanced level text for graduate engineering students, Multiphase Flow and Fluidization takes the reader beyond the theoretical to demonstrate how multiphase flow equations can be used to provide applied, practical, predictive solutions to industrial fluidization problems. Written to help advance progress in the emerging science of multiphase flow, this book begins with the development of the conservation laws and moves on through kinetic theory, clarifying many physical concepts (such as particulate viscosity and solids pressure) and introducing the new dependent variable--the volume fraction of the dispersed phase. Exercises at the end of each chapterare provided for further study and lead into applications not covered in the text itself. - Treats fluidization as a branch of transport phenomena - Demonstrates how to do transient, multidimensional simulation of multiphase processes - The first book to apply kinetic theory to flow of particulates - Is the only book to discuss numerical stability of multiphase equations and whether or not such equations are well-posed - Explains the origin of bubbles and the concept of critical granular flow - Presents clearly written exercises at the end of each chapter to facilitate understanding and further study

A new theoretical approach to the modelling of the upward flow of gas-particle suspensions is presented. In this, the proposed theory is used to predict suspension concentration, radial gas and solids velocities, axial gas and solids velocities. This thesis provides a general expression for slip velocity between gas and solids phases. The equivalence of pressure gradient with suspension concentration is demonstrated. The experimentally observed existence of core-annulus flow structure, a rapidly- rising dilute core surrounded by a slowly-falling denser annulus adjacent to the pipe walls, in vertical risers is predicted by the theory. Sodium chloride tracer impulse injection was used to measure the longitudinal solids mixing in circulating fluidized bed risers of internal diameter 0.152 and 0.305m at superficial gas velocity from 2.8 to 5.0 m/s for mean solids circulation flux from 5.0 to 80 kg/m2s. The measured solids mixing data were satisfactorily described by a simple one-dimensional dispersion model which permits residence time distribution curves to be calculated directly from a knowledge of operating conditions. The degree of longitudinal solids mixing in the riser is found to decrease with increase in riser diameter. The measurement of instantaneous local temperature fluctuation traces and mean thermal boundary layers was conducted with a special probe for various operating conditions. A mechanism, in which eddying particle cloud swarms and gas packets are pictured as the receptors of heat, and relatively steady conduction of heat and unsteady random transport of heat play the principal roles in the wall-to-suspension heat transfer, is proposed and is analyzed mathematically. Overall heat transfer coefficients were measured on 0.180 m long heat transfer section in two scale cold model circulating fluidized bed risers at several temperature differences for ... powder at superfical gas velocity from 1.96 to 5.66 m/s, and for solids circulation fluxes up to 118.54 kg/m2s. Average heat transfer coefficients increase with suspension concentration which ranged from 0 to 86.09 kg/m3, and decrease with heat transfer temperature difference, Tw - Tb, which ranged from 12 to 121.5 degrees C Heat transfer coefficients are found to increase with riser diameter.