Experiments were conducted in a liquid-solid circulating fluidized bed to study the effect of liquid viscosity and solids inventory on pressure gradient, critical transitional liquid velocity, onset average solids holdup, axial solids holdup distribution, average solids holdup and solids circulation rate in circulating fluidization regime with riser operated in fixed inventory mode. The results indicate that critical transitional liquid velocity decreases with increase in liquid viscosity. The onset average solids holdup, on the other hand, increases with increase in either auxiliary liquid velocity or solids inventory. The variation of axial solids holdup distribution, average solids holdup and solids circulation rate with liquid viscosity when solid inventory was 0.15. m was dissimilar with either 0.25. m or 0.35. m solid inventory. Correlations were proposed for estimating the average solids holdup and are satisfactorily compared with experimental values. © 2010 Elsevier B.V.

P Sesha Talpa Sai

Department Of Chemical Engineering

Shilapuram Vidyasagar

K. Krishnaiah

CIRCULATING FLUIDIZED BED

SOLIDS CIRCULATION RATE

SOLIDS HOLDUPS

TRANSITIONAL VELOCITY

VISCOUS EFFECT

Fluidization

Fluidized bed process

Liquids

Pressure effects

velocity

Viscosity of liquids

Viscous flow

Fluidized beds

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Chemical Engineering and Processing: Process Intensification

We present a modeling framework for the simulation of the hydrodynamic features of a liquid solid circulating fluidized bed (LSCFB) using computational fluid dynamics (CFD). Using an Eulerian-Eulerian approach to deal with the two-phase flow aspects and the kinetic theory of granular flow (KTGF) approach to deal with the solid-fluid interaction, we simulate the complete flow loop of an LSCFB using three-dimensional, time-dependent CFD calculations. We show that the essential features of the two-phase flow in the riser, the downcomer, the liquid-solid separator at the top and in the solids return feed pipe at the bottom are captured well in these simulations. The role of the flow distributors in establishing circulation is critically analyzed with the aid of post-processing tools. Comparison with literature data shows qualitative agreement with known trends of important hydrodynamic parameters and highlights the need for calibration of the constitutive equations for LSCFB applications. © 2013 Elsevier B.V.

Powder Technology

Numerical simulation of the hydrodynamics of a liquid solid circulating fluidized bed

While the choice of the location of the liquid distributor in a liquid-solid circulating fluidized bed is application dependent, three different methods exist for operating the riser in the circulating fluidization regime. Experiments were conducted to study the effect of the location of the liquid distributor, method of operation, liquid viscosity, and solids inventory on the axial solids holdup distribution in the circulating fluidized bed regime. The results show that the location of the liquid distributor has a significant effect on axial solids holdup, and the axial solids holdups obtained by the three methods of operation are different under identical conditions. The variation of the axial solids holdup distribution with liquid viscosity with a solid inventory of 0.15 m was different from that with both 0.25 and 0.35 m solid inventories. There is significant interaction of the solids inventory and liquid viscosity on the axial solids holdup distribution. © 2012 American Chemical Society.

Industrial and Engineering Chemistry Research

Axial solids holdup distribution in a liquid-solid circulating fluidized bed: Effect of the liquid distributor, method of operation, and viscosity of the fluidizing media

Experiments were conducted in a liquid-solid circulating fluidized bed with different viscous liquids and particles to study the hydrodynamics, average solid hold up and solid circulation rate. The effects of operating parameters, i.e., primary liquid flow rate in the riser, auxiliary liquid flow rate, total liquid flow rate and viscosity of the liquid were studied for solids of different density and particle size. Results show that the circulating fluidization regime starts earlier for more viscous solutions because of the decrease in critical transitional velocity. The onset of solid holdup increases with an increase in liquid viscosity for sand and for glass beads. The solid circulation rate increases with an increase in total velocity and auxiliary velocity, and also increases with increasing viscosity.

Fulltext

Brazilian Journal of Chemical Engineering

SOLID HOLDUP AND CIRCULATION RATE IN A LIQUID-SOLID CIRCULATING FLUIDIZED BED WITH VISCOUS LIQUID MEDIUM

Average solid holdup in the axial direction was investigated in a liquid solid circulating fluidized bed riser (LSCFB), with liquids of different viscosities. The effect of operating parameters including; primary, secondary and total velocity, particle diameter and density was studied. Experiments were conducted using water and glycerol at different concentration having viscosities in the range 1-1.36 cp. The results indicated that the solid holdup in the riser was axially uniform for viscous liquids and increases with increase in auxiliary velocity. The average solid holdup decreases with increase in total velocity and increases with increase in viscosity for sand-glycerol, glass bead-glycerol system. The experimental measurements were compared with the existing holdup model prediction that varied linearly with viscosity. Further, a correlation was developed to estimate average solid holdup in the riser, and the performance of the expression was compared with the present experimental data. © 2014 Production and hosting by Elsevier B.V.

Alexandria Engineering Journal

Solid holdup in liquid solid circulating fluidized bed with viscous liquid medium

To design an industrial liquid solid circulating fluidized bed system properly, it is important that the hydrodynamics be studied first. So far investigations have been carried out in a liquid solid circulating fluidized bed (LSCFB) with tap water as the liquid phase. There is still limited understanding on how particles are circulated in LSCFB with viscous fluids. The aim of our work was to characterize the hydrodynamics in a LSCFB with varying viscosity. Experiments were conducted in a fluidized bed riser of 0.1 m diameter by 2.4 m height with different viscous liquids, to study its effects of operating parameters namely; primary velocity, secondary velocity, total velocity, on the hydrodynamics characteristics of the LSCFB in terms of solid holdup, solid circulation rate and particle velocity. Experiments were conducted using water and glycerol at different concentration. The solid particle resin of 0.5 mm diameter was used for the experiment. The results indicate that the solid hold up in the riser is axially uniform for viscous liquids and increases with increase in auxiliary velocity. The average solid holdup found to decrease with increase in total velocity and increases with increase in liquid viscosity as the critical transitional velocity decreases with the increase in viscosity. The solid circulation rate is found to increase with increase in total velocity and auxiliary velocity, and also increases with increasing viscosity. © 2013, The Institution of Engineers (India).

Journal of The Institution of Engineers (India): Series E

Hydrodynamics Studies in a Liquid Solid Circulating Fluidized Bed of Varying Liquid Viscosity

Experiments were conducted in a liquid-solid circulating fluidized bed (LSCFB) to study the flow regimes, operational instability, critical transitional velocity to circulating fluidized bed (CFB) regime, solids holdup and solids circulation rate by three experimental methods. The results indicate that the operational instabilities such as arch formation, liquid-solid separator blockage and solids return pipe blockage were observed in two of these methods at large primary and auxiliary liquid velocities. The critical transitional velocity that demarcates the expanded bed from CFB regime was observed to be different by these three methods. Each of these methods has its own merits and demerits in terms of operating range of CFB regime, solids holdup, solids circulation rate and application. © 2008 Elsevier B.V. All rights reserved.

Comparison of macroscopic flow properties obtained by three methods of operation in a liquid-solid circulating fluidized bed

Experiments were conducted in a liquid-solid circulating fluidized bed (LSCFB) of 80 mm i.d. and 2.8 m high to study the macroscopic flow structure over a wide range of liquid velocity and solids inventory in the storage vessel. The results indicate that the valve configuration (i.e. lift pot and the angle made by the solids feed pipe with the riser), solids inventory in the storage vessel and location of the primary liquid distributor were found to play an important role on the macroscopic properties of LSCFB. Dynamic leak, flow of solids from the return leg into the riser in the absence of auxiliary liquid flow, has been noticed at very high liquid velocities when the primary liquid distributor inlet (positioned at the bottom of the riser) is near to the solids feed pipe from the storage vessel. The dynamic leak was prevented by changing the position of the primary distributor inlet and the macroscopic flow behavior with and without dynamic leak was compared. The transitional liquid velocity that demarcates the conventional fluidization from the circulating fluidization was determined by three different methods and was found to be independent of solids inventory and dynamic leak. © 2007 Elsevier B.V. All rights reserved.

Chemical Engineering Journal

Hydrodynamics of a liquid-solid circulating fluidized bed: Effect of dynamic leak

Industrial & Engineering Chemistry Research

(Gas)−Liquid−Solid Circulating Fluidized Bed Reactors: Characteristics and Applications

Chemical Engineering & Technology

Studies on Regime Transition, Operating Range and System Stability in a Liquid-Solid Circulating Fluidized Bed

Asia-Pacific Journal of Chemical Engineering

Effect of various parameters on the solid circulation rate in a liquid-solid circulating fluidized bed

Macroscopic properties of liquid-solid circulating fluidized bed with viscous liquid medium

Journal	Chemical Engineering and Processing: Process Intensification
ISSN	02552701
Open Access	No