Mechanically agitated gas-liquid reactors

The values of effective interfacial area, a, and liquid side mass transfer coefficient, kLa, were obtained in 0.385, 0.57 and 1.0 m i.d. horizontal agitated contactors by using chemical methods. Propeller type of impellers were employed for agitation. Two modes of operation were studied: (i) surface aeration and (ii) sparging of gas. The impeller speed was varied from 50 to 700 rev/min, and the nozzle gas velocity was varied from 40 to 160 m/s. The effects of impeller spacing, liquid submergence and nozzle gas velocity on the values of a and kLa were investigated. A scale-up criterion is discussed.



On a obtenu, au moyen des methodes chimiques, les valeurs de la surface interfaciale effective a et du coefficient du transfert lateral de masse de liquides kLa, dans des contacteurs horizontaux et agites dont les diametres interieurs etaient respectivement 0.385, 0.57 et 1.0 metre. On a utilise, pour l'agitation, des rotors a helice. On a etudie deux modes d'operation, a savoir (i) l'aeration de la surface et (ii) le barbotage de gaz. On a fait varier la vitesse des rotors entre 50 et 700 tours a la minute et celle du gaz gicle entre 40 et 160 metres a la seconde. On a etudie les effets de l'espacement des rotors, de la submersion des liquides et de la vitesse du gaz gicle sur les valeurs de a et kLa etudiees. On discute un critere a echelle accrue.

Mass transfer characteristics of horizontal agitated contactors

In this review, the literature on surface aerators is critically analysed. In a number of studies, the critical speed for the onset of surface aeration has been correlated with the geometry of the system and the operating conditions. The studies on the rate of surface aeration, gas hold-up, mass transfer coefficients are inadequate for the design and scale-up. A comparison of the available designs, in terms of gas hold-up, and mass transfer coefficient is presented. A mathematical model has been proposed for surface aeration. Guidelines have been given for the selection of impeller configuration and overall design of surface aerators. Suggestions have been made for future studies in this area.

Design of stirred vessels with gas entrained from free liquid surface

A method of estimating the mixing time of multiple-impeller vessels from that of a single-impeller vessel was proposed According to the model assumed, the vessel has completely mixed cells separated by impellers, and the exchange flow rate of liquid across two adjacent cells controls the over-all mixing The mixing time of multiple-impeller vessels of various diameters was measured and analyzed on the basis of the model The range of application of the model was determined experimentally



On propose une methode d'estimation du temps de melange de reservoirs a turbines multiples a partir du temps de melange d'un reservoir a turbine unique Selon le modele propose, le reservoir melange completement les cellules separees par les turbines et le debit d'echange du liquide a travers les cellules adjacentes controle le melange global Le temps de melange des reservoirs a turbines multiples de diametres varies a ete mesure et analyse sur la base de ce modele La gamme d'application du modele a ete determinee de maniere experimentale

Mixing time of liquid in horizontal stirred vessels with multiple impellers

This paper presents the concept and the performances of a mini horizontal stirred tank reactor, used for hydrogenation reaction. A simple analytical model based on characteristic times of heat and mass transfer illustrates the intensification principle and shows that the relevant intensification parameter is the mass to heat transfer characteristics times ratio. The proof of concept is made through a small scale reactor named RAPTOR ® (French acronym for Reactor with Polyvalent Rectilinear Stirred Reactor with Optimised Transfer). The mass transfer performances are measured and compared to conventional stirred tank reactor and other multiple impeller continuous reactors. In a following second paper, a comparative study is proposed to evaluate the eco-efficiency and the techno-economic advantages of a continuous process involving a RAPTOR ® versus a classical batch process based on a stirred reactor.

Intensification principle of a new three-phase catalytic slurry reactor. Part I: Performance characterisation

To stabilize the flow pattern and to evaluate capability as a gas absorber, experiments were performed with baffled vessels. Apparatuses used were three geometrically similar batch horizontal stirred vessels. Studies were madeon the transfer rate of oxygen into sodium sulphite solution. Results obtained were :1) In the experiments, Froude No. was varied over a wide range to correlate the overall volumetric absorbtion coefficient KGa. The relation between KGa and Froude No. fora baffled vessel accorded with the one obtaind for a non-baffled vessel in state A1 corresponding to the limited range of Froude No., in which the liquid is splashed violently by the impeller.2) The over-all volumetric absorption coefficient KGawas approximately in proportion to power consumption per unit volume Pv. It was expressed by:KGA=KPV : Dt=10.6-18.4, e=0.3-0.7, PV=5X100-2X102: K=5.5X109 (oxygen-sodium sulphite solution system)where Dt is diameter of vessel, e is ratio of volume of liquid to volume of vessel.

Effect of baffle plate on absorption rate of gas in batch horizontal stirred vessel

幾何学的に相似な3種の横型攪絆槽を用い, タービン羽根によって攪拌し, 亜硫酸ソーダ水溶液による酸素ガス吸収速度を測定して, 以下の結果をえた。1) 槽内液の飛散が著しいA1状態においては, 総括吸収容量係数はフルード数に比例する。2) 実用的に重要なA1状態につき, 総括吸収容量係数KG・αと液単位体積当りの所要動力Pvとの関係は (酸素-亜硫酸ソーダ水溶液系) ここで, eは攪拝槽容積に対する吸収液量の割合, Dtは攪拝槽径である。

Studies on the Rate of Gas-Absorption in Batch Horizontal Stirred Vessels

Experiments were carried out to obtain basic informations on mixing rate of solid partcles by air-blending. Using a cylindrical apparatus of 12cm in diamter, Mixing rate was calculated from the variation of concentrations of marked particles sampled from the mixture. Results obtained were:1) Coefficent of Mixing rate φ was expressed by φ=k1exp [k2(u2/u1)+k3(u1/nmf)] Where, u2 is the velocity of air issured from active part of perforated plate, u1 is the velocity from non active part of perforated plate and umf is the incipient fluidization velocity measured on the condition u1=u2.2) The exchang of position of solid particles in the region above the non active part of perforated plate determines the degree of Mixing by air blending.

Koji Andou

Papers

Effect of baffle plate on absorption rate of gas in batch horizontal stirred vessel

Studies on the Rate of Gas-Absorption in Batch Horizontal Stirred Vessels

The Mixing Rate of Solid Particles by Air Blending