Centrifugal contactors flowsheet, tests

Law, J.D., Wood, D.J., Herbst, R.S. 1997. Development and testing of SREX flowsheets for treatment of Idaho Chemical Processing Plant sodium-bearing waste using centrifugal contactors. Sep. Sci. Technol. 32 C1 —4) 223-240. 

As organic and aqueous phases are macroscopically separated by the membrane, HFM offer several hydrodynamic advantages over other contactors, such as the absence of flooding and entrainment, or the reduction of feed consumption (160, 161). The flowsheets tested in HFM were similar to those developed for centrifugal contactor tests. Computer codes based on equilibrium (162) and kinetics data, diffusion coefficients (in both phases and in the membrane pores), and a hydrodynamic description of the module, were established to calculate transient and steady-state effluent concentrations. It was demonstrated that, by selecting appropriate flow rates (as mass transfer is mainly controlled by diffusion), very high DFs (DI A 11 = 20,000 and DFrm = 830) could be achieved. Am(III) and Cm(III) back-extraction efficiency was up to 99.87%. 

After acquisition of experimental data, flowsheet calculations were carried out. A theoretical recovery of cesium was fixed at 99.99%. Hydraulic tests and chemical transfer tests were first carried out with centrifugal contactors, then with pulsed columns, first on simulated effluents and then on actual effluents. 

While this chapter and this applications section has focused on ANL and CINC contactors, other centrifugal contactors have been used to process nuclear materials. Some of these contactors and the flowsheets tested using them are discussed here. 

Rivalier, P. and J-Y. Lanoe. 2000. Development of a New Miniature Short-residence-time Annular Centrifugal Solvent Extraction Contactor for Tests of Process Flowsheets in Hot Cells. ATALANTE 2000, October 24—26, Avignon, France. 

Flowsheet testing and data collection were performed using the General Atomic Company solvent extraction pilot plant equipment shown in Figure 1. Included in this equipment are several 5.1 to 7.6 cm (2 to 3 in.) diameter cylindrical glass pulse columns, a 15-2 cm (6 in.) diameter annular pulse column, a centrifugal contactor (Robatel Co.) and associated tanks, feed systems and concentrators. 

In the tests carried out in centrifugal extractors, the extraction and recovery of cesium higher than 99.99% were obtained on simulated effluents, with a very good coherence between calculated flowsheets and experimental results.102 Tests confirmed the feasibility of the implementation of the cesium process in pulsed columns, the latter representing the most adapted contactors for the industrial implementation to overcome the drawback due to the presence of solid matter in waste to be treated. 

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