Bubble size in a forced circulation loop reactor

Abstract

BACKGROUND: The bubble size distribution in gas-liquid reactors influences gas holdup, residence time distribution, and gas-liquid interfacial area for mass transfer. This work reports on the effects of independently varied gas and liquid flow rates on steady-state bubble size distributions in a new design of forced circulation loop reactor operated with an air-water system. The reactor consisted of a cylindrical vessel (∼26 L nominal volume, gas-free aspect ratio ≈6, downcomer-to-riser cross-sectional area ratio of 0.493) with a concentric draft tube and an annular riser zone. Both gas and liquid were in forced flow through a sparger that had been designed for minimizing the bubble size.

Mixing parameters for an airlift bioreactor considering constant cross sectional area of riser to downcomer: Effect of sparging gas location

“…The friction loss of fluid in the two phase flow regime in the annulus becomes less than single phase flow and finally causes an increase in the liquid circulation velocity. Mixing in the airlift bioreactor is sometimes described in terms of a dimensionless mixing time, θ m , defined as follows: (12) The dependence of dimensionless mixing time on gas flow rate is given in Table 1, in both modes of sparging gas. The dimensionless …”

“…These parameters are sensitive to superficial gas velocity and physical properties of the fluids, gas flow rate and bioreactor geometry and have been extensively studied because of their influence on mass transfer phenomena [10]. Muthukumar et al [7], Freitas et al [11] and Fadavi et al [12] investigated the hydrodynamic behavior of concentric draft-tube type airlift bioreactors. They demonstrated that an increase in the air-flow rate decreases mixing and circulation times.…”

Experimental Study of the Mixing Time in a Jet‐Mixed Gas‐Liquid System

“…Air was also introduced through a sparger from the tank bottom. The conductivity measuring method [6,[18][19][20] was employed to obtain the mixing time. For this, after the system was established, a pulse input of a tracer (60 mL of NaCl aqueous solution with a concentration of www.cet-journal.com200 g/L) was injected by a syringe within the shortest possible time period of about 1 s. The tracer was added at the top of the tank at 1 cm under the liquid surface and at a distance of 10 cm from the center of the tank.…”

Hydrodynamic and Mass Transfer Characteristics of Annulus-Rising Airlift Reactor – The Effect of Reactor Scale

“…Huang et al [13] compared several typical mass transfer models for one ALR and recommended the one time model proposed earlier by Cocke et al [22] based on the penetration theory, as shown in Eq. (6).…”

“…A large number of studies on CR_ALRs have been reported and great achievements have been obtained with experimental [4][5][6][7][8] or simulation [9][10][11][12][13][14] methods. However, studies on AR-ALRs are quite scarce [15][16][17][18] although Koide et al.…”