An industrial-scale annular centrifugal extractor for the TRPO process

Abstract

Annular centrifugal extractors (ACEs) offer advantages including excellent hydraulic and mass-transfer performance, small hold-up volume, short residence time, and thus low solvent degradation, high nuclear criticality, easy start-up and shut-down, high compact structure. Therefore, ACEs have attracted increasing interest for future nuclear processing schemes, including the partitioning of high-level liquid waste (HLLW). Laboratory-scale and pilot-scale ACEs have been applied in demonstration tests of the trialkyl phosphine oxide (TRPO) process for HLLW partitioning. In this study, an industrial-scale ACE (260 mm in rotor diameter) with magnetic coupling and a “hanging” rotor structure was developed for the TRPO process. Moreover, a series of hydraulic and mass-transfer tests were carried out in the industrial-scale ACE. The maximum throughput can reach 10 m3/h under suitable operation parameters when kerosene is used as the organic phase, and water is used as the aqueous phase. The influence of the total flowrate, the flow ratio (aqueous/organic, A/O), and the rotor speed on the liquid hold-up volume was determined. The extraction stage efficiency is higher than 98% under test parameters for extraction of Nd3+ and HNO3, using 30% TRPO kerosene as the extractant from an HNO3 solution containing Nd. All results show good performance of the industrial-scale ACE for the TRPO process.