Numerical Experiments And Correlation Of Two-phase Flow In Pulsed Sieve-plate Extraction Column Based On The Euler-euler Model

Pulsed sieve-plate extraction columns (PSECs) are typical examples of multi-stage extractors. These columns have been found wide applications in petroleum, nuclear industries,metallurgy and pharmaceutical. Knowledge of the hydrodynamic characteristic of a PSEC under any operating conditions plays an important role in performents improvement,developing and/or improving design strategies and scale-up procedures, selection and optimization of operating conditions of PSEC.In this paper, computational fluid dynamics software (Fluent) is used to simulate the two-phase flow of water-dodecane system without any mass transfer in a PSEC with standard structure. The commercial grid generation tool ICEM is used to create mesh geometry and generate grids which based on a 2D planar reduced domain. Standard ?-? turbulence model for each phase is chosen to model the turbulence in the system. Schiller and Naumann model is used for the computation of the drag coefficient. In order to calculate the drag force,the diameter of the droplet is assumed constant as 0.002m for that the droplet breakage and coalescence are neglected in our simulations. Euler-Euler two-phase flow model which solves the equations for momentum conservation and mass conservation for each phase and phase coupled SIMPLE scheme for pressure-velocity are chosen for CFD simulations.Systematic CFD numerical experiments are conducted under different operating conditions (pulse velocity, the continuous phase flow rate, the dispersed phase flow rate). The CFD results shows that with increase in phase throughput for a given pulse velocity, the flow condition of PSEC transfers from stable state (dispersion regime) to unstable state (transition regime and flooding). Under the range of stable operating conditions, the holdup of dispersed phase almost linearly increases with an increase in dispersed phase flow rate and phase ratio.However, the effect of continuous phase flow rate on the holdup is found to be negligible because of there is only a slight increase in holdup with an increase in the continuous phase flow rate. The change trend of the holdup that firstly increases and then decreases with the increasing of pulse velocity is not obvious. When the PSEC operates under unstable operating conditions, the holdup fluctuates without any rules according to flow rate of both phase,phase ratio and pulse velocity.Three holdup correlations in PSEC that one proposed by Pratt and the other two based on the correlation of Pratt proposed by Jiading Wang are used to correlate the holdup obtained from CFD. The predicted values calculated by Pratt correlation are found to be more than 10%. Howere, the predicted values calculated by the two correlations proposed by Jiading Wang are in good agreement with those obtained by CFD.