scholarly journals Comparison between bubbling and turbulent regime for the simulation of batch pharmaceutical powders fluidized bed drying

2018 ◽  
Author(s):  
Amel Zammouri ◽  
N. Boudhrioua Mihoubi ◽  
N. Kechaou
Keyword(s):  
Mass Transfer ◽  
Fluidized Bed ◽  
Bubble Size ◽  
Pilot Plant ◽  
Plug Flow ◽  
Pharmaceutical Powders ◽  
Turbulent Regime ◽  
Fluidised Bed ◽  
Turbulent Model ◽  
Bubble Phase

The two-phase theory has been frequently used to model fluidised bed drying. At high air velocities, a transition from the bubbling regime to the turbulent regime may occur. In this work, we compare a bubbling model and a turbulent model for the simulation of a two pharmaceutical powders drying in a pilot plant and an industrial plant fluidised bed. The bubbling model was based on a discrete variable bubble size. Heat and mass transfer coefficients were based on the Kunii and Levenspiel correlation [1]. Flow regime was supposed to be completely mixed for the emulsion phase. For the turbulent model, the bubble size is not anymore discrete but continuous and bubble phase is less distinguishable than in the bubbling regime. Heat and mass transfer were those proposed by Foka[2]. In addition, the freeboard section was considered since high entrainment is specific of this regime. Gas backmixing was taken into account by considering a plug flow with axial dispersion for the interstitial gas flow. The bubble phase being dilute,  was modeled by a plug flow. A plug flow was also considered for the freeboard gas. The solid phase was supposed to be completely mixed. The bubbling regime simulation gave good agreement with experiment in the case of the pilot plant experiment, while the turbulent model better simulated the industrial scale experiment. Key words: batch fluidized bed, pharmaceutical powder, drying, modeling, bubbling, turbulent 

scholarly journals Gas solid contacting measurements in a turbulent fluidized bed by oxidation of carbon monoxide

2019 ◽  
Vol 23 (Suppl. 5) ◽  
pp. 1413-1423
Author(s):  
Robbie Venderbosch ◽  
Wolter Prins ◽  
Swaaij van
Keyword(s):  
Mass Transfer ◽  
Fluidized Bed ◽  
Phase Model ◽  
Internal Diameter ◽  
Turbulent Regime ◽  
Dense Phase ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Fluid Bed ◽  
Real Flow

The conversion rate of the mass transfer controlled oxidation of CO over a Pt/?-alumina catalyst (d = 65 ?m) has been studied in a fluidized bed (internal diameter = 0.05 m) p operated close to and in the turbulent fluid bed regime. The objectives were to investigate the gas-solids contacting efficiency to evaluate the conversion data in terms of overall mass transfer coefficients and define the apparent contact efficiency. At high superficial gas velocities, the concept of formation of particle agglomerates and voids is more realistic than the two-phase model considering discrete bubbles and a dense phase. The two-phase model is not useless but has hardly any relation with the real flow pattern in the turbulent regime.

scholarly journals Simulation and Analysis of Plug Flow Fluidized Bed Dryer

2020 ◽  
Vol 9 (7) ◽  
pp. 805-811
Keyword(s):  
Mass Transfer ◽  
Moisture Content ◽  
Heat And Mass Transfer ◽  
Fluidized Bed ◽  
Plug Flow ◽  
Small Scale ◽  
Outlet Temperature ◽  
Drying Process ◽  
Fluidized Bed Dryer ◽  
Hot Air

Today many industries now use the dryer as a part of grain-drying process even during wet and dry seasons. This helps in reducing spoilage and wastage of paddy. Mostly the available industrial dryers are expensive to purchase and to maintain its smooth functioning. This study therefore is a step to design a simple Plug flow fluidized dryer that can lead to introduce small scale dryers to paddy process industry. The Plug flow fluidized bed dryers are designed and fabricated in this study consists of the drying chamber, hot air distributer plate, hot air inlet and exit system, paddy entry and exit system, fluidization chamber unit with temperature control unit and the centrifugal fan. The evaluation of dryer is based on drying time and reduction in moisture content and outlet temperature of paddy on quality parameters. Dryer dimensions are very important to analyze heat and mass transfer analysis of the Plug flow fluidized bed drying process of paddy grains. It was found d that heat and mass transfer properties of paddy grains in fluidized bed dryer was decreases as the time of drying passes and very rapid at the start of drying. The model present here predicts about dryer dimensions along safe zone of rough rice moisture content with other parameters. Simulation results show a good agreement between the simulation model and the existing simulation models

scholarly journals Biological treatment of water contaminated by hydrocarbons in three-phase gas-liquid-solid fluidized bed

2013 ◽  
Vol 8 (1) ◽  
pp. 9-15
Keyword(s):  
Mass Transfer ◽  
Fluidized Bed ◽  
Biological Treatment ◽  
Plug Flow ◽  
Point Of View ◽  
Operating Conditions ◽  
Solid Particles ◽  
Hydrodynamic Characteristics ◽  
Intimate Contact ◽  
Three Phase

Biological treatment has been carried out in two different systems: aerated closed and threephase fluidized bed reactors for hydrocarbons removal from refinery wastewaters. For the two systems, hydrodynamic study allowed the determination of operating conditions before treatment experiments. Then, in a second time, biological treatments have been conducted in the same operating conditions. The obtained results showed that in the three-phase fluidized bed we can degrade hydrocarbons more rapidly than in a closed aerated bioreactor. Among the different appropriate techniques available to create efficient contacts between phases, the three-phase fluidization G/L/S where carrier particles are moving inside the reactor seems very interesting. It allows an intimate contact between phases and present many advantages concerning hydrodynamic and mass transfer phenomena. In fact, depending on operating conditions and the bubble flow behaviour, the three-phase fluidized bed could display different flow regimes In these systems called bioreactors the solid particles covered with a biofilm are fluidized by two ascending flows of air and contaminated water. With favourable operating conditions, from a hydrodynamic and mass transfer point of view, the pollutant can be biologically degraded up to 90%. Until this date, the three-phase bioreactors modelling remains very complex because it required taking into account several factors: the pollutant biodegradation rate in the biofilm, the bioreactor hydrodynamic characteristics, and the reactant interfacial gas-liquid and liquidsolid mass transfer. Thus the essential purpose of modelling is to integrate the microbial kinetics with the reactor hydrodynamics. We can notice that a few models have incorporated both bioreactor hydrodynamics and microbial kinetics. For the steady state bioreactor model, we generally assume that the particles are uniform in size, the biofilm is uniform in thickness, and the biofilm can be considered as homogeneous matrix through which oxygen and substrate diffuse and are consumed by the microbes. The liquid phase in the bioreactor substrate is considered to be axially dispersed while the gas phase is assumed to be in plug flow [2]. Rittmann (1997) proposed a model based on wake theory for predicting bed expansion and phase hold-ups for three-phase fluidized bed bioreactors. In this model he modified the correlation for the computation of the bioparticles drag coefficient CD [3]. He also attempted to explain the biofilm detachment which can occur with three broad patterns: erosion, sloughing and scouring and assumed that the factors affecting detachment rates can be grouped into two categories (physical forces and microorganisms physiology in the biofilm).

INVESTIGATION ON HYDRODYNAMICS OF FLUIDIZED BED AS A COMPONENT DETERMINING HEAT AND MASS TRANSFER

1974 ◽  
Author(s):  
N. B. Kondukov ◽  
L.I. Frenkel ◽  
M. B. Kliot ◽  
B. V. Pankov ◽  
V. S. Potapochkin ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Fluidized Bed

Tertiary nitrification in pilot-plant plug-flow fixed-film reactors with long-term ammonium deficiency

1994 ◽  
Vol 29 (10-11) ◽  
pp. 61-67 ◽  
Author(s):  
M. Fruhen ◽  
K. Böcker ◽  
S. Eidens ◽  
D. Haaf ◽  
M. Liebeskind ◽  
...  
Keyword(s):  
Pilot Plant ◽  
Effective Means ◽  
Plug Flow ◽  
Nitrification Rate ◽  
Industrial Project ◽  
Transfer Processes ◽  
Fixed Film ◽  
Film Reactor ◽  
Observation Period

The objective of this study is to investigate to what extent the nitrification capacity of a pilot-plant fixed-film reactor changes during extensive periods of nutrient supply deficiency. The examined pilot-plant was an upflow reactor filled with swelling clay of medium grain size (6 to 8 mm). The experiments revealed that the maximum nitrification rate remained practically constant during the first weeks after the onset of unregulated ammonium supply. The capacity declined slowly, dropping to approximately 66% of the initial capacity after about ten weeks. Still ammonium peaks of up to 8 mg/l were readily nitrified throughout the entire period of the experiment. The reduction in nitrification capacity during the observation period did not result from decay processes of biomass but from the reactor becoming blocked and thus hampering transfer processes. It could be observed that the detached organisms attached again further up. This semi-industrial project demonstrated that a plug-flow fixed-film reactor can be used as effective means of tertiary nitrification.

Fluidized-Bed Methanation: Interaction between Kinetics and Mass Transfer

2011 ◽  
Vol 50 (5) ◽  
pp. 2781-2790 ◽  
Author(s):  
Jan Kopyscinski ◽  
Tilman J. Schildhauer ◽  
Serge M. A. Biollaz
Keyword(s):  
Mass Transfer ◽  
Fluidized Bed

Fate and abatement of mercury and other trace elements in a coal fluidised bed oxy combustion pilot plant

Fuel ◽  
2012 ◽  
Vol 95 ◽  
pp. 272-281 ◽  
Author(s):  
O. Font ◽  
P. Córdoba ◽  
C. Leiva ◽  
L.M. Romeo ◽  
I. Bolea ◽  
...  
Keyword(s):  
Trace Elements ◽  
Pilot Plant ◽  
Fluidised Bed
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