Gas hold‐up behavior of mechanically agitated gas‐liquid reactors using pitched blade downflow turbines

Abstract

Fractional gas holdup was measured in 0.57, 1.0, and 1.5 m i.d. vessels. Pitched blade downflow turbines (PTD) were used as the impeller. Design details of the impeller, such as the impeller diameter (0.22 T to 0.5 T) and blade width (0.25 D to 0.4 D), were studied. The effect of sparger type, geometry and size on fractional gas hold‐up has been investigated in detail. Four different types of spargers (pipe, conical, ring and concentric ring spargers) were used. Sparger location was varied for all the types studied. Further, design details of the ring sparger, which gave the highest hold‐up were then studied in detail. These included ring diameter, number of holes and hole size. All the reported correlations for fractional gas hold‐up in mechanically agitated gas‐liquid reactors were tested and compared. A better correlation has been developed for pitched blade turbines.

Hydrodynamics of a Stirred Vessel Equipped with a Gas-Inducing Impeller

“…For both designs of the lower impeller, a 1.0 m ring sparger shows higher gas hold-up as compared to a 0.4 m diameter ring sparger. In conventional stirred vessels employing a PBTD impeller, Rewatkar and Joshi (1993) have reported that a ring sparger of diameter 2D gives a slightly higher gas hold-up as compared to a ring sparger having a diameter of 0.8D. In the present work, a ring diameter of 1.0 m corresponds to 2D whereas, a 0.4 m diameter corresponds to 0.8D.…”

Experimental and Numerical Study of Multiphase Mixing Hydrodynamics in Batch Stirred Tank Applied to Ammoniacal Thiosulphate Leaching of Gold

“…Gas hold-up has linear dependence on superficial velocity as described by Rewatkar et al [39] numerically and approved experimentally experimentally later by Kraume and Zehner [40] for glass beds suspended in water and by Laakkonen [41] for Xanthan solutions. In the current study, gas holdup was measured over the range of gas flow rates from 1 to 10 L/min at constant impeller speed of 400 rpm.…”

A Review on Gas‐Liquid Reactions in Light Oil Sweetening: Kinetics and Reactor Design Aspects

“…Chakraborty et al [48] reported ceramics to be one of the most effective materials resulting into higher e g . The effect of the sparger ring diameter s has also been studied and found that spargers with 0.45d, 0.80d, 1.40d, and 2.0d dimensions are the most effective ones, where d represents impeller diameter [46,[49][50][51][52]. The effect of sparger location has also been reported in the literature.…”

“…Holland and Chapman [54] impeller and sparger also plays an important role. It has been reported that impellers placed near to spargers generate smaller bubble sizes leading to lower terminal velocity, v t with higher e g [47,50,53,55]. The diagram of a propeller type and a flat blade turbine type impeller are shown in Fig.…”

“…The effect of sparger location has also been reported in the literature. It has been found that spargers located below impeller with smaller orifice size are the most effective [50][51][52][53]. The diagram of a ring sparger is shown in Fig.…”