Study On Axial Mixing Of Continuous Phase And Hydrodynamic Property In Pulsed Sieve-Plate Column

Pulsed sieve-plate extraction column is a key device for nuclear fuel reprocessing technology, and it is always getting' extensive attention and is being deeply investigated. Axial mixing of continuous phase, drop size and holdup of dispersed phase are parameters of fundamental importance in the design and operation of liquid-liquid extraction pulsed sieve-plate extraction columns. To improve the design of pulsed sieve-plate extraction column and make the design more normative and reliable, the study on the axial mixing, drop size and holdup performances of pulsed sieve-plate extraction column is very necessary.In this paper,the axial mixing coefficient of the continuous phase,drop size and holdup of dispersed phase have been studied in a ?38mm standard pulsed sieve-plate extraction column, in which 30% tributyl phosphate (TBP)/kerosene is used as the dispersed phase, and water is the continuous phase. The residence time distribution(RTD) curves have been measured through stimulus-response technique, and the axial mixing coefficient value Ec of the continuous phase is evaluated by the least-squares fitting method. The drop size value d32 and holdup value (p of dispersed phase are measured by the photography and volume displacement method respectively. The influence of the pulse intensity, continuous and dispersed phase superficial velocities on the axial mixing, drop size and holdup had been analysed.The results shown that the influence of concentration of tracer solution, radial sampling probe position and axial sampling probe position on the continuous phase axial mixing coefficient can be ignored. The axial mixing coefficient increases with the increase of the pulse intensity or the two phases. However, the droplet size decreases as the pulse intensity or the superficial velocities of the two phases increase. The holdup increases with the increase of the pulse intensity or the two phases. In addition, it has been found that compared with KCl solution as a tracer, the continuous phase axial mixing coefficient values Ec obtained similarly can be considered the same result when taking methylene blue solution as a tracer.According to the discussion of the factors that influence the axial mixing coefficient,drop size and holdup, the four empirical correlations including of the Ec1, Ec2,d32 and ? have been concluded: Ec1=9.45×10-2uc0.56ud0.95(Af)2.17(1-?)0.82,Ec2=3.25×10-2uc0.56ud1.06(Af)2.24?-0.36,d32=2.84uc-0.106ud-0.067(Af)-0.111 and ?=1.4×10-4uc0.505ud1.215(Af)2.097. The calculated values are compared with the experimental data with a maximum deviation of ±20%,±20%,±15% and±20% respectively which are practically acceptable. Through the above empirical correlations,the performance of the axial mixing coefficient and hydrodynamic property in the pulsed sieve-plate extraction column can be predicted adequately.