Wiped film evaporator with a roller wiper and an internally mounted condenser for the recovery of TBP and n-DD from degraded PUREX solvent

Abstract

Wiped Film Evaporator (WFE) is a promising choice for processing viscous and thermally labile compounds due to its short residence time, enhanced heat transfer rates, and a high fraction of distillate yield in a single pass. This article evaluates the viability of a WFE with a roller wiper and an internally mounted condenser to recover tri-butyl phosphate (TBP) and n-dodecane (n-DD) from degraded PUREX solvent by vacuum distillation. Degraded solvents derived from different sources were purified using a combination of primary cleanup by sodium carbonate scrubbing and secondary cleanup by vacuum distillation using the WFE. Primary cleanup could efficiently remove the acidic degradation products of TBP. However, the scrubbed solvents were not of acceptable quality due to their poor physical properties. Secondary cleanup by vacuum distillation notably improved the physical properties of the solvent. A detailed quality assessment of the recovered solvents in terms of density, viscosity, interfacial tension (IFT), and phase separation time (PST) ratio showed that all the solvents recovered were of acceptable quality. The highest PST ratio and lowest IFT of the recovered solvents were 1.36 and 8.6 mN m−1, respectively. The maximum solvent recovery, TBP recovery, and n-DD recovery obtained were 93.8%, 83.8%, and 99.8%, respectively.