scholarly journals Effects of air-lift reactor dimensions on its hydrodinamic characteristics

2010 ◽  
Vol 64 (1) ◽  
pp. 35-46
Author(s):  
Milan Milivojevic ◽  
Danijela Andrejic ◽  
Branko Bugarski
Keyword(s):  
Liquid Velocity ◽  
Solid Particles ◽  
Hydrodynamic Characteristics ◽  
Solid Loading ◽  
Phase System ◽  
Two Phase ◽  
Liquid Circulation ◽  
Airlift Bioreactors ◽  
Circulation Velocity ◽  
Liquid Circulation Velocity

In this study the hydrodynamic characteristics of the external loop airlift bioreactors were investigated. The influence of reactor height and solid particles concentration on the mean liquid circulation velocity was examined. Also, the possibility of theoretical prediction of this liquid circulation velocity was assessed. The correlation originally proposed by Glennon et al. (Chem. Eng. Commun. 121 (1993) 183-192) for two phase system liquid velocity prediction was extended and corrected for application to three phase systems. The accuracy of this new correlation was tested on our experimental data. The corrected correlation shows higher accuracy than the originally proposed one. In addition, the influence of reactor geometry and solid loading on reactor working performances was established.

scholarly journals A Simple Analytical Method for Determining Basic Hydrodynamic Characteristics of Hybrid Fluidized-Bed Air-Lift Apparatae

2017 ◽  
Vol 38 (1) ◽  
pp. 121-133
Author(s):  
Bolesław Tabiś ◽  
Dominika Boroń
Keyword(s):  
Fluidized Bed ◽  
Analytical Method ◽  
Solid Particles ◽  
Hydrodynamic Characteristics ◽  
Shear Forces ◽  
Two Phase ◽  
Forced Circulation ◽  
Simple Analytical Method ◽  
Airlift Bioreactors ◽  
Air Lift

Abstract A simple analytical method for determination of basic hydrodynamic characteristics of hybrid fluidized-bed air-lift devices was presented. These devices consist of two parts: a two-phase air-lift part and a two-phase liquid-solid fluidized-bed part. Forced circulation of fluid in the air-lift part is used for fluidization of solid particles in the fluidized-bed part. According to the opinion given in the literature, if such apparatus is used for aerobic microbiological processes, its advantage is lower shear forces acting on the biofilm immobilized on fine-grained material compared with shear forces in three-phase fluidized-bed bioreactors. Another advantage is higher biomass concentration due to its immobilization on fine particles, compared with two-phase airlift bioreactors. A method of calculating gas hold-up in the air-lift part, and gas and liquid velocities in all zones of the analyzed apparatus is presented.

scholarly journals Hydrodynamic characteristics of a two-phase gas-liquid flow upward through a fixed bed of spherical particles

2001 ◽  
Vol 66 (1) ◽  
pp. 53-64 ◽  
Author(s):  
Snezana Serbula ◽  
Velizar Stankovic
Keyword(s):  
Pressure Drop ◽  
Liquid Velocity ◽  
Fixed Bed ◽  
Particle Diameter ◽  
Packed Bed ◽  
Spherical Particles ◽  
Hydrodynamic Characteristics ◽  
Phase System ◽  
Relative Pressure ◽  
Two Phase

The influence of an electrochemically generated gas phase on the hydrodynamic characteristics of a three-phase system has been examined. The two-phase fluid, (gas-liquid), in which the liquid phase is the continuous one, flows through a packed bed with glass spheres. The influence of the liquid velocity was examined, as well as the gas velocity and particle diameter on the pressure drop through the fixed bed. It was found that with increasing liquid velocity (wl = 0.0162-0.03 m/s), the relative pressure drop decreases through the fixed bed. With increasing current density, the pressure drop increases, since greater gas quantities stay behind in the fixed bed. Besides, it was found that with decreasing diameter of the glass particles, the relative pressure drop also decreases. The relationship betweeen the experimentally obtained friction factor and the Reynolds number was established.

An innovative process for waste water treatment: the circulating floating bed reactor

1996 ◽  
Vol 34 (9) ◽  
pp. 89-99 ◽  
Author(s):  
V. Lazarova ◽  
J. Manem
Keyword(s):  
Water Treatment ◽  
Waste Water Treatment ◽  
Reactor Design ◽  
Effective Control ◽  
Innovative Technology ◽  
Process Stability ◽  
Liquid Circulation ◽  
Three Phase ◽  
Circulation Velocity ◽  
Liquid Circulation Velocity

Increasing volumes of wastewater combined with limited space availability and progressively tightening European standards promote the development of new intensive biotechnologies for water treatment. Fixed biomass processes offer several advantages compared with conventional biological treatments: higher volumetric load, increased process stability and compactness of the reactors. The purpose of this paper is to present a new concept of gas-lift mobile bed, the circulating floating bed reactor (CFBR). The reactor design is simple and does not require any complex technical devices (easier effluent and air-flow distribution, no primary settling, no back-washing). This new process is studied and developed in an industrial-scale prototype. The optimum hydrodynamic characteristics of the CFBR (liquid circulation velocity 0.3-0.4 m s−1, kLa 50-300 h−1, average mixing time 85 s) were not deteriorated by the high solid hold-ups (up to 40% v/v) of the floating media. On the contrary, three-phase operating improves the local gas hold-up in the downcomer. Improved hydrodynamics in the CFBR guarantee high nitrification rates and operation stability either in tertiary (up to 2 kgN m−3 d−1) or secondary (up to 0.6 kgN m−3 d−1) nitrification. The results show that nitrification is the limiting step in simultaneous C+N treatment. The negative effect of the increasing C/N ratio is more pronounced than stepwise decreasing of the temperature. The study of the biofilm composition and activity shows an effective control of the attached biomass growth by the high liquid circulation velocity. It is concluded that this new three-phase bioreactor ensures not only an enhanced process stability and biological reaction rate through an effective biofilm control but also guarantees an excellent synergy between hydrodynamic and biological performances. These advantages are highlighted by the simplicity of the reactor design. Thus, this innovative technology will be an attractive solution for intensive wastewater treatment for nitrogen and carbon removal.

scholarly journals Mixing characteristics of draft tube airlift bioreactor using the electrical resistance tomography

2021 ◽  
Author(s):  
Farouzatu Yakubu-Gumery
Keyword(s):  
Shear Rate ◽  
Xanthan Gum ◽  
Draft Tube ◽  
Mixing Time ◽  
Airlift Bioreactor ◽  
Liquid Circulation ◽  
Mixing Characteristics ◽  
Circulation Velocity ◽  
Liquid Circulation Velocity ◽  
The Cross

In this work, mixing characteristics in terms of mixing time, hydrodynamics (liquid circulation velocity and gas hold up) and shear rate were performed in the downcomer of a draft tube airlift bioreactor with different geometries (i.e., Ad/Ar between 0.38 – 2.31 and bottom clearances between 0.003-0.00 m). Newtonian (water and 34.5% coalescing sugar solution) and on Newtonian (0.2% and 0.5% xanthan gum solutions) with different viscosities were used as the liquid phase. Compressed air was used as the gas phase which was introduced through cross and circular shaped sparger configurations at superficial velocities Ugr = 0.00165-0.00807 m/s. The combined effects of geometric parameters (Ad/Ar, bottom clearances), sparger configuration, and liquid viscosity on mixing characteristics have been presented. Results showed that the increase in superficial gas velocity (Ugr) corresponds to an increase in energy generated, and thus decreases in mixing time. However, the increase in Ugr corresponds to the increase in liquid circulation velocity, gas holdup and shear rate values. Moreover, bottom clearances and draft tube diameters show effects on flow resistance frictional losses which affect results of mixing parameters investigated. The influence of sparger configurations on mixing time and liquid circulation velocity is significant due to their effect on gas distribution. Mixing time decreased to about 40% in air-water media using the cross shaped sparger. Results obtained with cross shaped sparger showed even and uniform distribution of gas, which provided better mixing as compared to the circular shaped sparger configuration. However, the sparger configuration effect on shear rate is not as significant (about 20% reduction in shear rate values using the cross shaped sparger). The effect of fluid viscosity had a significant influence on both mixing times and circulation velocity, especially in the coalescing media of sugar and xanthan gum solutions. Results from this work will help to develop a clear pattern for operation and mixing that can help improving [sic] several industrial processes, especially the ones related to emerging fields of technology such as the biotechnology industry.

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