Annular centrifugal extractors (ACE), also called annular centrifugal contactors offer several advantages over the other conventional process equipment such as low hold-up, high process throughput, low residence time, low solvent inventory and high turn down ratio. The equipment provides a very high value of mass transfer coefficient and interfacial area in the annular zone because of the high level of power consumption per unit volume and separation inside the rotor due to the high g of centrifugal field. For the development of rational and reliable design procedures, it is important to understand the flow patterns in the mixer and settler zones. Computational Fluid Dynamics (CFD) has played a major role in the constant evolution and improvements of this device. During the past thirty years, a large number of investigators have undertaken CFD simulations. All these publications have been carefully and critically analyzed and a coherent picture of the present status has been presented in this review paper. Initially, review of the single phase studies in the annular region has been presented, followed by the separator region. In continuation, the two-phase CFD simulations involving liquid-liquid and gas-liquid flow in the annular as well as separator regions have been reviewed. Suggestions have been made for the future work for bridging the existing knowledge gaps. In particular, emphasis has been given to the application of CFD simulations for the design of this equipment.
The separation efficiency/capacity of a large number of liquid−liquid dispersions has been investigated over a wide range of physical properties: 100 < Δρ < 625 kg/m 3 , 3 < σ < 58.3 mN/m, 0.3 < μ C and μ D < 12.2 mPa•s. For gravity separation, phase disengagement experiments were performed in a 100 mL measuring cylinder. The centrifugal separation was carried out in different sizes of annular centrifugal extractors (ACE) with rotor sizes ranging from 30 to 250 mm over a rotor speed of 6.28 rad/s < N < 314.15 rad/s. The rotor speed translated into power consumption over the range of 20−600 kW/m 3 . A novel data driven correlation containing physical properties and separation forces has been developed using Random Forest technique for dispersion number. The developed correlation could be used for the design of gravity or centrifugal separators.
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