Study On The Performances Of The Mass Transfer And Hydrodynamics In The Φ38Pulsed Sieve-plate Column

Pulsed sieve-plate column is one of the most important extraction equipments inchemical process, widely used in nuclear fuel reprocessing. The dispersed phase drop size,holdup and overall volumetric mass transfer coefficient are the key parameters to judge theworking performance of the pulsed sieve-plate columns, and have a direct influence on theoptimization and scale-up of the extraction columns. In this article, the performance of themass transfer in the column was studied, and the hydrodynamics （the dispersed phase dropsize and holdup） were researched simultaneously under the condition of the mass transfer. Atthe same time, the flow field information in the pulsed sieve-plate column was simulatedthrough the CFD software.The experiment was carried out in a38mm inner diameter standard pulsed sieve-platecolumn with the system of30%tributyl phosphate （TBP） in kerosene-nitric acid-water （theconcentration of the nitric acid was3mol/L）. The water was set as the continuous phase,while the30%tributyl phosphate （TBP） in kerosene-nitric as the dispersed phase, the nitricacid as the solute, and the direction of the extraction was from the continuous phase to thedispersed phase. The dispersed phase drop size, holdup and overall volumetric mass transfercoefficient are measured by the photography, volume displacement method and steady-stateconcentration profiles respectively. The influence of the continuous and dispersed phasesuperficial velocities, pulse intensity, flow ratio and overall superficial velocity on the dropsize, holdup and Koxa had been analysed.It shows that the dispersed phase drop size increases with the increase of the two phasesand overall superficial velocities, and decreases with the pulse intensity; when the continuousphase superficial velocity is constant, the drop size increases with the flow ratio. Thedispersed phase holdup increases with the increase of the two phases and overall superficialvelocities and the pulse intensity; as the continuous phase superficial velocity is fixed, theincrease of the flow ratio will contribute to the increase of the holdup. The overall volumetric mass transfer coefficient increases with the increase of the pulse intensity; when thecontinuous and dispersed phases superficial velocities increase, the overall volumetric masstransfer coefficient will increase until it reaches a maximum value firstly, and then itdecreases gradually; under the condition of the constant continuous phase superficial velocity,the overerall volumetric mass transfer coefficient increases with the flow ratio firstly, anddecreases after the maximum value. In addition, it has been found the dispersed drop sizescan be described by the normal distribution, and independent of the operating conditions.According of the discussion of the factors that influence the drop size, holdup andoverall volumetric mass transfer coefficient, the three correlations concerning of the d₃₂, φand K_oxa have been concluded: d₃₂=0.0016u_x^0.97uy^1.96（Af）^-0.59（u_x+u_y）^-2.79、φ=49.71u_x^-0.42u_y⁽0.52_Af^1.35、K_oxa=5.45u_x^0.51u_y^0.71（Af）^0.07，The calculated values are compared with theexperimental data with a maximum deviation of15%,20%and35%respectively which arepractically acceptable. Through the three correlations, the performance of the hydrodynamicand mass transfer in the pulsed sieve-plate column can be predicted adequately.Compared with the hydrodynamic performances under the experimental system of30%TBP/kerosene-water in the pulsed sieve-plate column, it shows that the dispersed phase dropsize and holdup under the condition without mass transfer are slighly higher. It is not sensiblethat the conlusions concluded from the condition without mass transfer are applied to theexperimental research with the mass transfer.The simulation results showed: the continuous phase velocity increased constantly whilethe dispersed phase velocity flowed quickly firstly under the influence of pulse and thentended to be uniform when the two phases were poured into the column; the radial velocitiesof the two phases were in the certain regulations of distribution that the velocities decreasedincreasingly from the center to the wall; the distribution of the two phases was homogeneouswith a smaller volume distribution of the dispersed phase.